

###Comment on semi-classical approaches to giant magnetoresistance in magnetic multilayers|Yu Shi###

Comment on semi-classical approaches to giant magnetoresistance in magnetic multilayers. Some conceptual issues in the semi-classical approaches to giant
magnetoresistance in magnetic multilayers are discussed.

###Comment on "High Field Quasiparticle Tunneling in Bi_2Sr_2CaCu_2O_{8+δ} : Negative Magnetoresistance in the Superconducting State" (N.Morozov et al, Phys.Rev. Lett. 84,1784 (2000))|V. N. Zavaritsky,M. Springford,A. S. Alexandrov###

Comment on "High Field Quasiparticle Tunneling in Bi_2Sr_2CaCu_2O_{8+δ} : Negative Magnetoresistance in the Superconducting State" (N.Morozov et al, Phys.Rev. Lett. 84,1784 (2000)). We show that the negative c-axis magnetoresistance in cuprates is the normal
state feature.

###c-Axis longitudinal magnetoresistance of the electron-doped superconductor Pr1.85Ce0.15CuO4|W. Yu,B. Liang,R. L. Greene###

c-Axis longitudinal magnetoresistance of the electron-doped superconductor Pr1.85Ce0.15CuO4. We report c-axis resistivity and longitudinal magnetoresistance measurements
of superconducting Pr1.85Ce0.15CuO4 single crystals. In the temperature range
13K<T<32K, a negative magnetoresistance is observed at fields just above Hc2.
Our studies suggest that this negative magnetoresistance is caused by
superconducting fluctuations. At lower temperatures (T<13K), a different
magnetoresistance behavior and a resistivity upturn are observed, whose origin
is still unknown.

###Local magnetoresistance in Fe/MgO/Si lateral spin valve at room temperature|Tomoyuki Sasaki,Toshio Suzuki,Yuichiro Ando,Hayato Koike,Tohru Oikawa,Yoshishige Suzuki,Masashi Shiraishi###

Local magnetoresistance in Fe/MgO/Si lateral spin valve at room temperature. Room temperature local magnetoresistance in two-terminal scheme is reported.
By employing 1.6 nm-thick MgO tunnel barrier, spin injection efficiency is
increased, resulting in large non-local magnetoresistance. The magnitude of the
non-local magnetoresistance is estimated to be 0.0057 ohm at room temperature.
As a result, a clear rectangle signal is observed in local magnetoresistance
measurement even at room temperature. We also investigate the origin of local
magnetoresistance by measuring the spin accumulation voltage of each contact
separately.

###Large rectification magnetoresistance in nonmagnetic Al/Ge/Al heterojunctions|Kun Zhang,Huan-huan Li,Peter Grünberg,Qiang Li,Sheng-tao Ye,Yu-feng Tian,Shi-shen Yan,Zhao-jun Lin,Shi-shou Kang,Yan-xue Chen,Guo-lei Liu,Liang-mo Mei###

Large rectification magnetoresistance in nonmagnetic Al/Ge/Al heterojunctions. Magnetoresistance and rectification are two fundamental physical properties
of heterojunctions and respectively have wide applications in spintronics
devices. Being different from the well known various magnetoresistance effects,
here we report a brand new large magnetoresistance that can be regarded as
rectification magnetoresistance: the application of a pure small sinusoidal
alternating-current to the nonmagnetic Al/Ge Schottky heterojunctions can
generate a significant direct-current voltage, and this rectification voltage
strongly varies with the external magnetic field. We find that the
rectification magnetoresistance in Al/Ge Schottky heterojunctions is as large
as 250% at room temperature, which is greatly enhanced as compared with the
conventional magnetoresistance of 70%. The findings of rectification
magnetoresistance open the way to the new nonmagnetic Ge-based spintronics
devices of large rectification magnetoresistance at ambient temperature under
the alternating-current due to the simultaneous implementation of the
rectification and magnetoresistance in the same devices.

###Non-monotonic magnetic field and density dependence of in-plane magnetoresistance in dilute two-dimensional holes in GaAs/AlGaAs|H. Noh,Jongsoo Yoon,D. C. Tsui,M. Shayegan###

Non-monotonic magnetic field and density dependence of in-plane magnetoresistance in dilute two-dimensional holes in GaAs/AlGaAs. We studied low temperature (T=50mK) in-plane magnetoresistance of a dilute
two-dimensional hole system in GaAs/AlGaAs heterostructure that exhibits an
apparent metal-insulator transition. We found an anisotropic magnetoresistance,
which changes dramatically at high in-plane fields ($B_{\parallel}\agt$5T) as
the hole density is varied. At high densities where the system behaves metallic
at $B_{\parallel}=0$, the transverse magnetoresistance is larger than the
longitudinal magnetoresistance. With decreasing the hole density the difference
becomes progressively smaller, and at densities near the "critical" density and
lower, the longitudinal magnetoresistance becomes larger than the transverse
magnetoresistance.

###Tunneling magnetoresistance in ensembles of ferromagnetic granules with exchange interaction and random easy axes of magnetic anisotropy|Y. M. Beltukov,V. I. Kozub,A. V. Shumilin,N. P. Stepina###

Tunneling magnetoresistance in ensembles of ferromagnetic granules with exchange interaction and random easy axes of magnetic anisotropy. We study the tunneling magnetoresistance in the ensembles of ferromagnetic
granules with random easy axes of magnetic anisotropy taking into account the
exchange interaction between granules. It is shown that due to the exchange
interaction magnetoresistance is effectively decoupled from magnetization, i.e.
the strongest negative magnetoresistance can be observed at the field where
magnetization is almost saturated. Under some conditions, the sign of
magnetoresistance can be reversed and tunneling magnetoresistance can become
positive at certain magnetic fields. Our theory agrees with measurements of
magnetoresistance in ensembles of Fe granules in SiCxNy matrix.

###Negative magnetoresistance due to conductivity fluctuations in films of the topological semimetal Cd3As2|Timo Schumann,Manik Goyal,David A. Kealhofer,Susanne Stemmer###

Negative magnetoresistance due to conductivity fluctuations in films of the topological semimetal Cd3As2. Recently discovered Dirac and Weyl semimetals display unusual
magnetoresistance phenomena, including a large, non-saturating, linear
transverse magnetoresistance and a negative longitudinal magnetoresistance. The
latter is often considered as evidence of fermions having a defined chirality.
Classical mechanisms, due to disorder or non-uniform current injection, can
however, also produce negative longitudinal magnetoresistance. Here, we report
on magnetotransport measurements performed on epitaxial thin films of Cd3As2, a
three-dimensional Dirac semimetal. Quasi-linear positive transverse
magnetoresistance and negative longitudinal magnetoresistance are observed. By
evaluating films of different thickness and by correlating the temperature
dependence of the carrier density and mobility with the magnetoresistance
characteristics, we demonstrate that both the quasi-linear positive and the
negative magnetoresistance are caused by conductivity fluctuations. Chiral
anomaly is not needed to explain the observed features.

###Percolation mechanism for Colossal Magnetoresistance|Paul J. M. Bastiaansen,Hubert J. F. Knops###

Percolation mechanism for Colossal Magnetoresistance. We argue that colossal magnetoresistance is a critical phenomenon and propose
a mechanism to describe it. The mechanism relies on the halfmetallic behavior
of the materials showing colossal magnetoresistance, and yields a correlated
percolation model that, we argue, captures all qualitative features of colossal
magnetoresistance, above as well as below the Curie temperature. The model only
serves for revealing the underlying mechanism of colossal magnetoresistance,
and does not aim to reproduce precise, numerical results.

###Comment on: Weak Anisotropy and Disorder Dependence of the In-Plane Magnetoresistance in High-Mobility (100) Si Inversion Layers|V. T. Dolgopolov,A. Gold###

Comment on: Weak Anisotropy and Disorder Dependence of the In-Plane Magnetoresistance in High-Mobility (100) Si Inversion Layers. Comment on: Weak Anisotropy and Disorder Dependence of the In-Plane
Magnetoresistance in High-Mobility (100) Si Inversion Layers

###Theory of magnetoresistance based on variable-range hopping in the presence of Hubbard interaction and spin-dynamics|M. Wohlgenannt###

Theory of magnetoresistance based on variable-range hopping in the presence of Hubbard interaction and spin-dynamics. We develop a theory of magnetoresistance based on variable-range hopping. An
exponentially large, low-field and necessarily positive magnetoresistance
effect is predicted in the presence of Hubbard interaction and spin-dynamics
under certain conditions. The theory was developed with the recently discovered
organic magnetoresistance in mind. To account for the experimental observation
that the organic magnetoresistance effect can also be negative, we tentatively
amend the theory with a mechanism of bipolaron formation.

###The Influence of Magnetic Domain Walls on Longitudinal and Transverse Magnetoresistance in Tensile Strained (Ga,Mn)As Epilayers|G. Xiang,N. Samarth###

The Influence of Magnetic Domain Walls on Longitudinal and Transverse Magnetoresistance in Tensile Strained (Ga,Mn)As Epilayers. We present a theoretical analysis of recent experimental measurements of
magnetoresistance in (Ga,Mn)As epilayers with perpendicular magnetic
anisotropy. The model reproduces the field-antisymmetric anomalies observed in
the longitudinal magnetoresistance in the planar geometry (magnetic field in
the epilayer plane and parallel to the current density), as well as the unusual
shape of the accompanying transverse magnetoresistance. The magnetoresistance
characteristics are attributed to circulating currents created by the presence
of magnetic domain walls.

###Giant magnetoresistance and extraordinary magnetoresistance in inhomogeneous semiconducting DyNiBi|Frederick Casper,Claudia Felser###

Giant magnetoresistance and extraordinary magnetoresistance in inhomogeneous semiconducting DyNiBi. The semiconducting half-Heulser compound DyNiBi shows a negative giant
magnetoresistance (GMR) below 200 K. Except for a weak deviation, this
magnetoresistance scales roughly with the square of the magnetization in the
paramagnetic state, and is related to the metal-insulator transition. At low
temperature, a positive magnetoresistance is found, which can be suppressed by
high fields. The magnitude of the positive magnetoresistance changes slightly
with the amount of impurity phase.

###Magnetoresistance in a High Mobility Two-Dimensional Electron Gas|L. Bockhorn,P. Barthold,D. Schuh,W. Wegscheider,R. J. Haug###

Magnetoresistance in a High Mobility Two-Dimensional Electron Gas. In a high mobility two-dimensional electron gas (2DEG) in a GaAs/AlGaAs
quantum well we observe a strong magnetoresistance. In lowering the electron
density the magnetoresistance gets more pronounced and reaches values of more
than 300%. We observe that the huge magnetoresistance vanishes for increasing
the temperature. An additional density dependent factor is introduced to be
able to fit the parabolic magnetoresistance to the electron-electron
interaction correction.

###Measurement and simulation of anisotropic magnetoresistance in single GaAs/MnAs core/shell nanowires|J. Liang,J. Wang,A. Paul,B. J. Cooley,D. W. Rench,N. S. Dellas,S. E. Mohney,R. Engel-Herbert,N. Samarth###

Measurement and simulation of anisotropic magnetoresistance in single GaAs/MnAs core/shell nanowires. We report four probe measurements of the low field magnetoresistance in
single core/shell GaAs/MnAs nanowires synthesized by molecular beam epitaxy,
demonstrating clear signatures of anisotropic magnetoresistance that track the
field-dependent magnetization. A comparison with micromagnetic simulations
reveals that the principal characteristics of the magnetoresistance data can be
unambiguously attributed to the nanowire segments with a zinc blende GaAs core.
The direct correlation between magnetoresistance, magnetization and crystal
structure provides a powerful means of characterizing individual hybrid
ferromagnet/semiconductor nanostructures.

###The level shifting induced negative magnetoresistance in the nearest-neighbor hopping conduction|X. R. Wang,S. C. Ma,X. C. Xie###

The level shifting induced negative magnetoresistance in the nearest-neighbor hopping conduction. We propose a new mechanism of negative magnetoresistance in non-magnetic
granular materials in which electron transport is dominated by hopping between
two nearest-neighbor clusters. We study the dependence of magnetoresistance on
temperature and separation between neighboring clusters. At a small separation
we find a negative magnetoresistance at low temperatures and it changes over to
a positive value as temperature increases. For a fixed temperature,
magnetoresistance changes from negative to positive when the cluster separation
increases. The change of magnetoresistance $\Delta R/R$ can be more than 80% at
low temperatures.

###Chemical Tuning of Positive and Negative Magnetoresistances, and Superconductivity in 1222-type Ruthenocuprates|A. C. Mclaughlin,L. Begg,C. Harrow,S. A. J. Kimber,F. Sher,J. P. Attfield###

Chemical Tuning of Positive and Negative Magnetoresistances, and Superconductivity in 1222-type Ruthenocuprates. High critical-temperature superconductivity and large (colossal)
magnetoresistances are two important electronic conducting phenomena found in
transition metal oxides. High-Tc materials have applications such as
superconducting magnets for MRI and NMR, and magnetoresistive materials may
find use in magnetic sensors and spintronic devices. Here we report chemical
doping studies of RuSr2(R2-xCex)Cu2O10-d ruthenocuprates which show that a
single oxide system can be tuned between superconductivity at high hole dopings
and varied magnetoresistive properties at low doping levels. A robust variation
of negative magnetoresistance with hole concentration is found in the
RuSr2R1.8-xY0.2CexCu2O10-d series, while RuSr2R1.1Ce0.9Cu2O10-d materials show
an unprecedented crossover from negative to positive magnetoresistance with
rare earth (R) ion radius.

###Intrinsic magnetoresistance in metal films on ferromagnetic insulators|Vahram L. Grigoryan,Wei Guo,Gerrit E. W. Bauer,Jiang Xiao###

Intrinsic magnetoresistance in metal films on ferromagnetic insulators. We predict a magnetoresistance induced by the interfacial Rashba spin-orbit
coupling in normal metal|ferromagnetic insulator bilayer. It depends on the
angle between current and magnetization directions identically to the "spin
Hall magnetoresistance" mechanism caused by a combined action of spin Hall and
inverse spin Hall effects. Due to the identical phenomenology it is not obvious
whether the magnetoresistance reported by Nakayama et al. is a bulk metal or
interface effect. The interfacial Rashba induced magnetoresistance may be
distinguished from the bulk metal spin Hall magnetoresistance by its dependence
on the metal film thickness.

###Anomalous organic magnetoresistance from competing carrier-spin-dependent interactions with localized electronic and nuclear spins|Y. Wang,N. J. Harmon,K. Sahin-Tiras,M. Wohlgenannt,M. E. Flatté###

Anomalous organic magnetoresistance from competing carrier-spin-dependent interactions with localized electronic and nuclear spins. We describe a new regime for low-field magnetoresistance in organic
semiconductors, in which the spin-relaxing effects of localized nuclear spins
and electronic spins interfere. The regime is studied by the controlled
addition of localized electronic spins to a material that exhibits substantial
room-temperature magnetoresistance ($\sim 20$\%). Although initially the
magnetoresistance is suppressed by the doping, at intermediate doping there is
a regime where the magnetoresistance is insensitive to the doping level. For
much greater doping concentrations the magnetoresistance is fully suppressed.
The behavior is described within a theoretical model describing the effect of
carrier spin dynamics on the current.

###The Effect of Dopants on the Magnetoresistance of WTe2|Steven Flynn,Mazhar Ali,R. J. Cava###

The Effect of Dopants on the Magnetoresistance of WTe2. Elucidating the nature of the large, non-saturating magnetoresistance in WTe2
is a significant step in functionalizing this phenomenon for applications.
Here, Mo, Re, and Ta doped WTe2 are compared to determine whether isovalent and
aliovalent substitutions have different effects on the large magnetoresistance.
By 1% substitution, isoelectronic doping reduces the magnetoresistance by a
factor of 1.2 with an apparent linear trend, whereas aliovalent doping reduces
the effect by over an order of magnitude while following a higher-order decay.
The apparent increased sensitivity of the magnetoresistive effect to aliovalent
doping over simple isoelectronic disorder supports the conclusion that the
large magnetoresistance in WTe2 arises from interactions between balanced hole
and electron populations.

###Helicity-protected domain-wall magnetoresistance in ferromagnetic Weyl semimetal|Koji Kobayashi,Yuya Ominato,Kentaro Nomura###

Helicity-protected domain-wall magnetoresistance in ferromagnetic Weyl semimetal. The magnetotransport properties of disordered ferromagnetic Weyl semimetals
are investigated numerically. We found an extraordinarily stable and huge
magnetoresistance effect in domain walls of Weyl semimetals. This effect
originates from the helicity mismatch of Weyl fermions and is a specific
property of Weyl semimetals. Although conventional magnetoresistance effects
are strongly suppressed in domain walls where local magnetization varies
gradually, the helicity-protected magnetoresistance in Weyl semimetals
maintains almost $100\%$ of the magnetoresistance ratio for any kind of thick
domain walls, even in the presence of disorder. The contribution of surface
Fermi arcs to the magnetoresistance is also discussed.

###Large linear magnetoresistance and magnetothermopower in layered SrZnSb$_2$|Kefeng Wang,C. Petrovic###

Large linear magnetoresistance and magnetothermopower in layered SrZnSb$_2$. We report the large linear magnetoresistance ($\sim 300\%$ in 9 T field at 2
K) and magnetothermopower in layered SrZnSb$_2$ crystal with
quasi-two-dimensional Sb layers. A crossover from the semiclassical parabolic
field dependent magnetoresistance to linear field dependent magnetoresistance
with increasing magnetic field is observed. The magnetoresistance behavior can
be described very well by combining the semiclassical cyclotron contribution
and the quantum limit magnetoresistance. Magnetic field also enhances the
thermopower. Our results can be well understood by the magnetotransport of
Dirac states in the bulk band structure.

###Rashba-Edelstein Magnetoresistance in Metallic Heterostructure|Hiroyasu Nakayama,Yusuke Kanno,Hongyu An,Takaharu Tashiro,Satoshi Haku,Akiyo Nomura,Kazuya Ando###

Rashba-Edelstein Magnetoresistance in Metallic Heterostructure. We report the observation of magnetoresistance originating from Rashba
spin-orbit coupling (SOC) in a metallic heterostructure: the Rashba-Edelstein
(RE) magnetoresistance. We show that the simultaneous action of the direct and
inverse RE effects in a Bi/Ag/CoFeB trilayer couples current-induced spin
accumulation to the electric resistance. The electric resistance changes with
the magnetic-field angle, reminiscent of the spin Hall magnetoresistance,
despite the fact that bulk SOC is not responsible for the magnetoresistance. We
further found that, even when the magnetization is saturated, the resistance
increases with increasing the magnetic-field strength, which is attributed to
the Hanle magnetoresistance in this system.

###Robust magnetotransport in disordered ferromagnetic kagome layers with quantum anomalous Hall effect|Koji Kobayashi,Masaki Takagaki,Kentaro Nomura###

Robust magnetotransport in disordered ferromagnetic kagome layers with quantum anomalous Hall effect. The magnetotransport properties of disordered ferromagnetic kagome layers are
investigated numerically. We show that a large domain-wall magnetoresistance or
negative magnetoresistance can be realized in kagome layered materials (e.g.
Fe$_3$Sn$_2$, Co$_3$Sn$_2$S$_2$, and Mn$_3$Sn), which show the quantum
anomalous Hall effect. The kagome layers show a strong magnetic anisotropy and
a large magnetoresistance depending on their magnetic texture. These
domain-wall magnetoresistances are expected to be robust against disorder and
observed irrespective of the domain-wall thickness, in contrast to conventional
domain-wall magnetoresistance in ferromagnetic metals.

###Spin-induced anomalous magnetoresistance at the (100) surface of hydrogen-terminated diamond|Yamaguchi Takahide,Yosuke Sasama,Masashi Tanaka,Hiroyuki Takeya,Yoshihiko Takano,Taisuke Kageura,Hiroshi Kawarada###

Spin-induced anomalous magnetoresistance at the (100) surface of hydrogen-terminated diamond. We report magnetoresistance measurements of hydrogen-terminated
(100)-oriented diamond surfaces where hole carriers are accumulated using an
ionic-liquid-gated field-effect-transistor technique. Unexpectedly, the
observed magnetoresistance is positive within the range of 2<T<10 K and -7<B<7
T, in striking contrast to the negative magnetoresistance previously detected
for similar devices with (111)-oriented diamond surfaces. Furthermore we find:
1) magnetoresistance is orders of magnitude larger than that of the classical
orbital magnetoresistance; 2) magnetoresistance is nearly independent of the
direction of the applied magnetic field; 3) for the in-plane field, the
magnetoresistance ratio defined as [rho(B)-rho(0)]/rho(0) follows a universal
function of B/T. These results indicate that the spin degree of freedom of hole
carriers plays an important role in the surface conductivity of
hydrogen-terminated (100) diamond.

###Including fringe fields from a nearby ferromagnet in a percolation theory of organic magnetoresistance|Nicholas J. Harmon,Ferran Macià,Fujian Wang,Markus Wohlgenannt,Andrew D. Kent,Michael E. Flatté###

Including fringe fields from a nearby ferromagnet in a percolation theory of organic magnetoresistance. Random hyperfine fields are essential to mechanisms of low-field
magnetoresistance in organic semiconductors. Recent experiments have shown that
another type of random field --- fringe fields due to a nearby ferromagnet ---
can also dramatically affect the magnetoresistance. A theoretical analysis of
the effect of these fringe fields is challenging, as the fringe field
magnitudes and their correlation lengths are orders of magnitude larger than
that of the hyperfine couplings. We extend a recent theory of organic
magnetoresistance to calculate the magnetoresistance with both hyperfine and
fringe fields present. This theory describes several key features of the
experimental fringe-field magnetoresistance, including the applied fields where
the magnetoresistance reaches extrema, the applied field range of large
magnetoresistance effects from the fringe fields, and the sign of the effect.

###Extremely large magnetoresistance in few-layer graphene/boron-nitride heterostructures|Kalon Gopinadhan,Young Jun Shin,Rashid Jalil,Thirumalai Venkatesan,Andre K. Geim,Antonio H. Castro Neto,Hyunsoo Yang###

Extremely large magnetoresistance in few-layer graphene/boron-nitride heterostructures. Understanding magnetoresistance, the change in electrical resistance upon an
external magnetic field, at the atomic level is of great interest both
fundamentally and technologically. Graphene and other two-dimensional layered
materials provide an unprecedented opportunity to explore magnetoresistance at
its nascent stage of structural formation. Here, we report an extremely large
local magnetoresistance of ~ 2,000% at 400 K and a non-local magnetoresistance
of > 90,000% in 9 T at 300 K in few-layer graphene/boron-nitride
heterostructures. The local magnetoresistance is understood to arise from large
differential transport parameters, such as the carrier mobility, across various
layers of few-layer graphene upon a normal magnetic field, whereas the
non-local magnetoresistance is due to the magnetic field induced
Ettingshausen-Nernst effect. Non-local magnetoresistance suggests the
possibility of a graphene based gate tunable thermal switch. In addition, our
results demonstrate that graphene heterostructures may be promising for
magnetic field sensing applications.

###Impurity and dispersion effects on the linear magnetoresistance in the quantum limit|Shuai Li,Hai-Zhou Lu,X. C. Xie###

Impurity and dispersion effects on the linear magnetoresistance in the quantum limit. Magnetoresistance, that is, the change of the resistance with the magnetic
field, is usually a quadratic function of the field strength. A linear
magnetoresistance usually reveals extraordinary properties of a system. In the
quantum limit where only the lowest Landau band is occupied, a quantum linear
magnetoresistance was believed to be the signature of the Weyl fermions with 3D
linear dispersion. Here, we comparatively investigate the quantum-limit
magnetoresistance of systems with different band dispersions as well as
different types of impurities. We find that the magnetoresistance can also be
linear for the quadratic energy dispersion. We show that both longitudinal and
transverse magnetoresistance can be linear if long-range-Gaussian-type
impurities dominate, but Coulomb-type impurities can only induce linear
transverse magnetoresistance. Moreover, we find a negative longitudinal
magnetoresistance in massless Dirac fermions, regardless of the impurity type,
as a result of the combined effect of the linear dispersion and the scattering
mechanism. Our findings well explain some of the linear magnetoresistance
observed in the experiments and provide insights to the understanding of
quantum-limit magnetoresistance.

###Investigation of Magnetic Proximity Effect inTa/YIG Bilayer Hall Bar Structure|Yumeng Yang,Baolei Wu,Kui Yao,Santiranjan Shannigrahi,Baoyu Zong,Yihong Wu###

Investigation of Magnetic Proximity Effect inTa/YIG Bilayer Hall Bar Structure. In this work, the investigation of magnetic proximity effect was extended to
Ta which has been reported to have a negative spin Hall angle.
Magnetoresistance and Hall measurements for in-plane and out-of-plane applied
magnetic field sweeps were carried out at room temperature. The size of the MR
ratio observed (~10-5) and its magnetization direction dependence are similar
to that reported in Pt/YIG, both of which can be explained by the spin Hall
magnetoresistance theory. Additionally, a flip of magnetoresistance polarity is
observed at 4 K in the temperature dependent measurements, which can be
explained by the magnetic proximity effect induced anisotropic
magnetoresistance at low temperature. Our findings suggest that both magnetic
proximity effect and spin Hall magnetoresistance have contribution to the
recently observed unconventional magnetoresistance effect.

###Quasilinear quantum magnetoresistance in pressure-induced nonsymmorphic superconductor CrAs|Q. Niu,W. C. Yu,K. Y. Yip,Z. L. Lim,H. Kotegawa,E. Matsuoka,H. Sugawara,H. Tou,Y. Yanase,Swee K. Goh###

Quasilinear quantum magnetoresistance in pressure-induced nonsymmorphic superconductor CrAs. In conventional metals, modification of electron trajectories under magnetic
field gives rise to a magnetoresistance that varies quadratically at low field,
followed by a saturation at high field for closed orbits on the Fermi surface.
Deviations from the conventional behaviour, e.g. the observation of a linear
magnetoresistance, or a non-saturating magnetoresistance, have been attributed
to exotic electron scattering mechanisms. Recently, linear magnetoresistance
has been observed in many Dirac materials, in which the electron-electron
correlation is relatively weak. The strongly correlated helimagnet CrAs
undergoes a quantum phase transition to a nonmagnetic superconductor under
pressure. Near the magnetic instability, we observe a large and non-saturating
quasilinear magnetoresistance from the upper critical field to 14 T at low
temperatures. We show that the quasilinear magnetoresistance arises from an
intricate interplay between a nontrivial band crossing protected by
nonsymmorphic crystal symmetry and strong magnetic fluctuations

###Intrinsic Magnetoresistance in Three-Dimensional Dirac Materials|Huan-Wen Wang,Bo Fu,Shun-Qing Shen###

Intrinsic Magnetoresistance in Three-Dimensional Dirac Materials. Recently, negative longitudinal and positive in-plane transverse
magnetoresistance have been observed in most topological Dirac/Weyl semimetals,
and some other topological materials. Here we present a quantum theory of
intrinsic magnetoresistance for three-dimensional Dirac fermions at a finite
and uniform magnetic field B. In a semiclassical regime, it is shown that the
longitudinal magnetoresistance is negative and quadratic of a weak field B
while the in-plane transverse magnetoresistance is positive and quadratic of B.
The relative magnetoresistance is inversely quartic of the Fermi wave vector
and only determined by the density of charge carriers, irrelevant to the
external scatterings in the weak scattering limit. This intrinsic anisotropic
magnetoresistance is measurable in systems with lower carrier density and high
mobility. In the quantum oscillation regime a formula for the phase shift in
Shubnikov-de Hass oscillation is present as a function of the mobility and the
magnetic field, which is useful for experimental data analysis.

###Tunneling anisotropic magnetoresistance driven by magnetic phase transition|X. Z. Chen,J. F. Feng,Z. C. Wang,J. Zhang,X. Y. Zhong,C. Song,L. Jin,B. Zhang,F. Li,M. Jiang,Y. Z. Tan,X. J. Zhou,G. Y. Shi,X. F. Zhou,X. D. Han,S. C. Mao,Y. H. Chen,X. F. Han,F. Pan###

Tunneling anisotropic magnetoresistance driven by magnetic phase transition. The independent control of two magnetic electrodes and spin-coherent
transport in magnetic tunnel junctions are strictly required for tunneling
magnetoresistance, while junctions with only one ferromagnetic electrode
exhibit tunneling anisotropic magnetoresistance dependent on the anisotropic
density of states with no room temperature performance so far. Here we report
an alternative approach to obtaining tunneling anisotropic magnetoresistance in
alfa-FeRh-based junctions driven by the magnetic phase transition of alfa-FeRh
and resultantly large variation of the density of states in the vicinity of MgO
tunneling barrier, referred to as phase transition tunneling anisotropic
magnetoresistance. The junctions with only one alfa-FeRh magnetic electrode
show a magnetoresistance ratio up to 20% at room temperature. Both the polarity
and magnitude of the phase transition tunneling anisotropic magnetoresistance
can be modulated by interfacial engineering at the alfa-FeRh/MgO interface.
Besides the fundamental significance, our finding might add a different
dimension to magnetic random access memory and antiferromagnet spintronics.

###Disentangle magnon magnetoresistance from anisotropic and spin Hall magnetoresistance in NiFe/Pt bilayers|Yanjun Xu,Yumeng Yang,Ziyan Luo,Yihong Wu###

Disentangle magnon magnetoresistance from anisotropic and spin Hall magnetoresistance in NiFe/Pt bilayers. We conducted a systematic angular dependence study of nonlinear
magnetoresistance in NiFe/Pt bilayers at variable temperature and field using
the Wheatstone bridge method. We successfully disentangled magnon
magnetoresistance from other types of magnetoresistances based on their
different temperature and field dependences. Both the spin Hall/anisotropic and
magnon magnetoresistances contain sine phi and sine 3 phi components with phi
the angle between current and magnetization, but they exhibit different field
and temperature dependence. The competition between different types of
magnetoresistances leads to a sign reversal of sine 3 phi component at a
specific magnetic field, which was not reported previously. The
phenomenological model developed is able to account for the experimental
results for both NiFe/Pt and NiFe/Ta samples with different layer thicknesses.
Our results demonstrate the importance of disentangling different types of
magnetoresistances when characterizing the charge-spin interconversion process
in magnetic heterostructures.

###Linear nonsaturating magnetoresistance in the Nowotny chimney ladder compound Ru$_2$Sn$_3$|Beilun Wu,Víctor Barrena,Federico Mompeán,Mar García-Hernández,Hermann Suderow,Isabel Guillamón###

Linear nonsaturating magnetoresistance in the Nowotny chimney ladder compound Ru$_2$Sn$_3$. We present magnetoresistivity measurements in high-quality single crystals of
the Nowotny chimney ladder compound Ru$_2$Sn$_3$. We find a linear and
nonsaturating magnetoresistance up to 20 T. The magnetoresistance changes with
the magnetic field orientation at small magnetic fields, from a positive to a
negative curvature. Above 5 T, the magnetoresistance shows no sign of
saturation up to 20 T for any measured angle. The shape of the anisotropy in
the magnetoresistance remains when increasing temperature and Kohler's rule is
obeyed. We associate the linear and nonsaturating magnetoresistance to a small
Fermi surface with hot spots, possibly formed as a consequence of the
structural transition. We discuss the relevance of electron-electron
interactions under magnetic fields and aspects of the topologically nontrivial
properties expected in Ru$_2$Sn$_3$.

###Signatures of Chiral Anomaly in the Magnetoresistance of a Quasi-3-Dimensional Electron Gas at the Interface of LaVO$_3$ and KTaO$_3$|Harsha Silotia,Anamika Kumari,Anshu Gupta,Joydip De,Santanu Kumar Pal,Ruchi Tomar,S. Chakraverty###

Signatures of Chiral Anomaly in the Magnetoresistance of a Quasi-3-Dimensional Electron Gas at the Interface of LaVO$_3$ and KTaO$_3$. In a Dirac semimetal charges flow between two Weyl nodes when electric and
magnetic fields (B||E) are parallel to each other manifesting interesting
physical properties such as negative longitudinal magnetoresistance, planar
Hall effect and anisotropic magnetoresistance. We observe a co-existence of
weak antilocalization with large negative longitudinal magnetoresistance and an
unusual Hall resistance with (B||E) configuration, at the conducting interface
of LaVO$_3$ and KTaO$_3$. The depth of the conducting channel at the interface
is estimated to be around 30 nm by using spectroscopy techniques of
photoluminescence and time-correlated single-photon counting. Both planar Hall
effect and anisotropic magnetoresistance exhibit oscillatory behaviour as a
function of the angle between E and B. A very similar temperature dependence of
negative longitudinal magnetoresistance, planar Hall effect and anisotropic
magnetoresistance suggest a strong correlation among them.

###New Mechanism of Magnetoresistance in Bulk Semiconductors: Boundary Condition Effects|G. Gonzalez de la Cruz,Yu. G. Gurevich,V. V. Prosentsov###

New Mechanism of Magnetoresistance in Bulk Semiconductors: Boundary Condition Effects. We consider the electronic transport in bounded semiconductors in the
presence of an external magnetic field. Taking into account appropriate
boundary conditions for the current density at the contacts, a change in the
magnetoresistance of bulk semiconductors is found as compared with the usual
theory of galvanomagnetic effects in boundless media. New mechanism in
magnetoresistance connected with the boundary conditions arises. In particular,
even when the relaxation time is independent of the electron energy,
magnetoresistance is not vanish.

###Weak Field Magnetoresistance in Quasi-One-Dimensional Systems|Yoshitaka Nakamura,Hidetoshi Fukuyama###

Weak Field Magnetoresistance in Quasi-One-Dimensional Systems. Theoretical studies are presented on weak localization effects and
magnetoresistance in quasi-one-dimensional systems with open Fermi surfaces.
Based on the Wigner representation, the magnetoresistance in the region of weak
field has been studied for five possible configurations of current and field
with respect to the one-dimensional axis. It has been indicated that the
anisotropy and its temperature dependences of the magnetoresistance will give
information on the degree of one-dimensionality and the phase relaxation time.

###Large magnetoresistance effect due to spin-injection into a non-magnetic semiconductor|G. Schmidt,G. Richter,P. Grabs,C. Gould,D. Ferrand,L. W. Molenkamp###

Large magnetoresistance effect due to spin-injection into a non-magnetic semiconductor. A novel magnetoresistance effect, due to the injection of a spin-polarized
electron current from a dilute magnetic into a non-magnetic semiconductor, is
presented. The effect results from the suppression of a spin channel in the
non-magnetic semiconductor and can theoretically yield a positive
magnetoresistance of 100%, when the spin flip length in the non-magnetic
semiconductor is sufficiently large. Experimentally, our devices exhibit up to
25% magnetoresistance.

###Ballistic versus diffusive magnetoresistance of a magnetic point contact|L. R. Tagirov,B. P. Vodopyanov,K. B. Efetov###

Ballistic versus diffusive magnetoresistance of a magnetic point contact. The quasiclassical theory of a nanosize point contacts (PC) between two
ferromagnets is developed. The maximum available magnetoresistance values in PC
are calculated for ballistic versus diffusive transport through the area of a
contact. In the ballistic regime the magnetoresistance in excess of few
hundreds percents is obtained for the iron-group ferromagnets. The necessary
conditions for realization of so large magnetoresistance in PC, and the
experimental results by Garcia et al are discussed

###Model for a Macroscopically Disordered Conductor with an Exactly Linear High-Field Magnetoresistance|Vishwesha Guttal,David Stroud###

Model for a Macroscopically Disordered Conductor with an Exactly Linear High-Field Magnetoresistance. We calculate the effective resistivity of a macroscopically disordered two
dimensional conductor consisting of two components in a perpendicular magnetic
field. When two components have equal area fractions, we use a duality theorem
to show that the magnetoresistance is non-saturating and at high fields varies
exactly linearly with magnetic field. At other compositions, an effective
medium calculation leads to a saturating magnetoresistance. We briefly discuss
possible connections between these results and magnetoresistance measurements
on heavily disordered chalconide semiconductors.

###Non-collinear Spin Valve Effect in Ferromagnetic Semiconductor Trilayers|G. Xiang,B. L. Sheu,M. Zhu,P. Schiffer,N. Samarth###

Non-collinear Spin Valve Effect in Ferromagnetic Semiconductor Trilayers. We report the observation of the spin valve effect in
(Ga,Mn)As/p-GaAs/(Ga,Mn)As trilayer devices. Magnetoresistance measurements
carried out in the current in plane geometry reveal positive magnetoresistance
peaks when the two ferromagnetic layers are magnetized orthogonal to each
other. Measurements carried out for different post-growth annealing conditions
and spacer layer thickness suggest that the positive magnetoresistance peaks
originate in a noncollinear spin valve effect due to spin-dependent scattering
that is believed to occur primarily at interfaces.

###Room temperature tunneling anisotropic and collinear magnetoresistance|A. N. Grigorenko,K. S. Novoselov,D. J. Mapps###

Room temperature tunneling anisotropic and collinear magnetoresistance. We report a room temperature tunneling anisotropic magnetoresistance in
Co/Al2O3/NiFe junctions containing magnetic electrodes oxidized prior to
forming the Al2O3 layer. A significant change in a tunnel magnetoresistance is
observed when the layer magnetizations are rotated collinearly in the junction
plane by an applied external field. The angular dependence of the tunneling
anisotropic magnetoresistance could be explained by the presence of an
antiferromagnetic oxide layer formed within the barrier.

###Quasi-reversible Magnetoresistance in Exchange Spring Tunnel Junctions|M. Zhu,M. J. Wilson,P. Mitra,P. Schiffer,N. Samarth###

Quasi-reversible Magnetoresistance in Exchange Spring Tunnel Junctions. We report a large, quasi-reversible tunnel magnetoresistance in
exchange-biased ferromagnetic semiconductor tunnel junctions wherein a soft
ferromagnetic semiconductor (\gma) is exchange coupled to a hard ferromagnetic
metal (MnAs). Our observations are consistent with the formation of a region of
inhomogeneous magnetization (an "exchange spring") within the biased \gma
layer. The distinctive tunneling anisotropic magnetoresistance of \gma produces
a pronounced sensitivity of the magnetoresistance to the state of the exchange
spring.

###The effects of spin-spin interactions on magnetoresistance in disordered organic semiconductors|N. J. Harmon,M. E. Flatté###

The effects of spin-spin interactions on magnetoresistance in disordered organic semiconductors. A recent theory of magnetoresistance in positionally disordered organic
semiconductors is extended to include exchange and dipolar couplings between
polarons. Analytic results are discovered when the hyperfine, exchange, and
dipolar interactions have little time to operate between hopping events. We
find an angle-of-field dependence of the magnetoresistance that agrees with
previous experiments and numerical simulations. In addition we report new
magnetoresistive behavior that critically depends upon the amount of anisotropy
in the dipolar interaction.

###Magnetoresistance Induced by Rare Strong Scatterers in a High Mobility 2DEG|L. Bockhorn,I. V. Gornyi,D. Schuh,C. Reichl,W. Wegscheider,R. J. Haug###

Magnetoresistance Induced by Rare Strong Scatterers in a High Mobility 2DEG. We observe a strong negative magnetoresistance at non-quantizing magnetic
fields in a high-mobility two-dimensional electron gas (2DEG). This strong
negative magnetoresistance consists of a narrow peak around zero magnetic field
and a huge magnetoresistance at larger fields. The peak shows parabolic
magnetic field dependence and is attributed to the interplay of smooth disorder
and rare strong scatterers. We identify the rare strong scatterers as
macroscopic defects in the material and determine their density from the peak
curvature.

###Two-Fold-Symmetric Magnetoresistance in Single Crystals of Tetragonal BiCh2-Based Superconductor LaO0.5F0.5BiSSe|Kazuhisa Hoshi,Motoi Kimata,Yosuke Goto,Tatsuma D Matsuda,Yoshikazu Mizuguchi###

Two-Fold-Symmetric Magnetoresistance in Single Crystals of Tetragonal BiCh2-Based Superconductor LaO0.5F0.5BiSSe. We have investigated the in-plane anisotropy of the c-axis magnetoresistance
for single crystals of a BiCh2-based superconductor LaO0.5F0.5BiSSe under
in-plane magnetic fields. We observed two-fold symmetry in the c-axis
magnetoresistance in the ab-plane of LaO0.5F0.5BiSSe while the crystal
possessed a tetragonal square plane with four-fold symmetry. The observed
symmetry lowering in magnetoresistance from the structural symmetry may be
related to the nematic states, which have been observed in the superconducting
states of several unconventional superconductors.

###Magnetic field dependent variable range hopping behaviour in resistivity at low temperatures in polycrystalline colossal magnetoresistive manganites: evidence of spin polarised tunnelling|P. Raychaudhuri,P. Taneja,S. Sarkar,A. K. Nigam,P. Ayyub,R. Pinto###

Magnetic field dependent variable range hopping behaviour in resistivity at low temperatures in polycrystalline colossal magnetoresistive manganites: evidence of spin polarised tunnelling. It has been observed that the low temperature magnetoresistance behaviour in
polycrystalline colossal magnetoresistive (CMR) manganites differ significantly
from the single crystals. The polycrystalline samples show large
magnetoresistance at temperatures much below the ferromagnetic transition
temperature where the magnetoresistance of single crystals is very small. This
has conventionally been attributed to spin polarised tunnelling at the grain
boundaries in polycrystalline samples. In this paper we show the existence of a
variable range hopping behaviour in resistivity at low temperatures in
polycrystalline CMR samples. This behaviour gets gradually suppressed under the
application of magnetic field. We discuss the significance of these results
with respect to spin polarised tunnelling.

###Magetoresistance of RuO_2-based resistance thermometers below 0.3 K|Michio Watanabe,Masashi Morishita,Youiti Ootuka###

Magetoresistance of RuO_2-based resistance thermometers below 0.3 K. We have determined the magnetoresistance of RuO_2-based resistors (Scientific
Instruments RO-600) between 0.05 K and 0.3 K in magnetic fields up to 8 T. The
magnetoresistance is negative around 0.5 T and then becomes positive at larger
fields. The magnitude of the negative magnetoresistance increases rapidly as
the temperature is lowered, while that of the positive magnetoresistance has
smaller temperature dependence. We have also examined the temperature
dependence of the resistance below 50 mK in zero magnetic field. It is
described in the context of variable-range-hopping conduction down to 15 mK.
Hence, the resistors can be used as thermometers down to at least 15 mK.

###Magnetic Transition in the Kondo Lattice System CeRhSn2|Z. Hossain,L. C. Gupta,C. Geibel###

Magnetic Transition in the Kondo Lattice System CeRhSn2. Our resistivity, magnetoresistance, magnetization and specific heat data
provide unambiguous evidence that CeRhSn2 is a Kondo lattice system which
undergoes magnetic transition below 4 K.

###Switching Current vs. Magnetoresistance in Magnetic Multilayer Nanopillars|S. Urazhdin,Norman O. Birge,W. P. Pratt Jr.,J. Bass###

Switching Current vs. Magnetoresistance in Magnetic Multilayer Nanopillars. We study current-driven magnetization switching in nanofabricated magnetic
trilayers, varying the magnetoresistance in three different ways. First, we
insert a strongly spin-scattering layer between the magnetic trilayer and one
of the electrodes, giving increased magnetoresistance. Second, we insert a
spacer with a short spin-diffusion length between the magnetic layers,
decreasing the magnetoresistance. Third, we vary the angle between layer
magnetizations. In all cases, we find an approximately linear dependence
between magnetoresistance and inverse switching current. We give a qualitative
explanation for the observed behaviors, and suggest some ways in which the
switching currents may be reduced.

###Negative Magnetoresistance in (In,Mn)As|S. J. May,A. J. Blattner,B. W. Wessels###

Negative Magnetoresistance in (In,Mn)As. The magnetotransport properties of an In0.95Mn0.05As thin film grown by
metal-organic vapor phase epitaxy were measured. Resistivity was measured over
the temperature range of 5 to 300 K. The resistivity decreased with increasing
temperature from 90 ohm-cm to 0.05 ohm-cm. The field dependence of the low
temperature magnetoresistance was measured. A negative magnetoresistance was
observed below 17 K with a hysteresis in the magnetoresistance observed at 5 K.
The magnetoresistance as a function of applied field was described by the
Khosla-Fischer model for spin scattering of carriers in an impurity band.

###Magnetoresistance of atomic-scale electromigrated nickel nanocontacts|Z. K. Keane,L. H. Yu,D. Natelson###

Magnetoresistance of atomic-scale electromigrated nickel nanocontacts. We report measurements of the electron transport through atomic-scale
constrictions and tunnel junctions between ferromagnetic electrodes. Structures
are fabricated using a combination of e-beam lithography and controlled
electromigration. Sample geometries are chosen to allow independent control of
electrode bulk magnetizations. As junction size is decreased to the single
channel limit, conventional anisotropic magnetoresistance (AMR) increases in
magnitude, approaching the size expected for tunneling magnetoresistance (TMR)
upon tunnel junction formation. Significant mesoscopic variations are seen in
the magnitude and sign of the magnetoresistance, and no evidence is found of
large ballistic magnetoresistance effects.

###Spin-dependent Quantum Interference in Single-Wall Carbon Nanotubes with Ferromagnetic Contacts|H. T. Man,I. J. W. Wever,A. F. Morpurgo###

Spin-dependent Quantum Interference in Single-Wall Carbon Nanotubes with Ferromagnetic Contacts. We report the experimental observation of spin-induced magnetoresistance in
single-wall carbon nanotubes contacted with high-transparency ferromagnetic
electrodes. In the linear regime the spin-induced magnetoresistance oscillates
with gate voltage in quantitative agreement with calculations based on a
Landauer-Buttiker model for independent electrons. Consistent with this
interpretation, we find evidence for bias-induced oscillation in the
spin-induced magnetoresistance signal on the scale of the level spacing in the
nanotube. At higher bias, the spin-induced magnetoresistance disappears because
of a sharp decrease in the effective spin-polarization injected from the
ferromagnetic electrodes.

###Transport in Magnetic Nanoparticles Super-Lattices : Coulomb Blockade, Hysteresis and Magnetic Field Induced Switching|Reasmey P. Tan,Julian Carrey,Celine Desvaux,Jeremie Grisolia,Philippe Renaud,Bruno Chaudret,Marc Respaud###

Transport in Magnetic Nanoparticles Super-Lattices : Coulomb Blockade, Hysteresis and Magnetic Field Induced Switching. We report on magnetotransport measurements on millimetric super-lattices of
Co-Fe nanoparticles surrounded by an organic layer. At low temperature, the
transition between the Coulomb blockade and the conductive regime becomes
abrupt and hysteretic. The transition between both regime can be induced by a
magnetic field, leading to a novel mechanism of magnetoresistance. Between 1.8
and 10 K, high-field magnetoresistance due to magnetic disorder at the surface
of the particles is also observed. Below 1.8 K, this magnetoresistance abruptly
collapses and a low-field magnetoresistance is observed.

###High-field and low field magnetoresistance of CoFe nanoparticles elaborated by organometallic chemistry|Reasmey P. Tan,Julian Carrey,Marc Respaud,Celine Desvaux,Philippe Renaud,Bruno Chaudret###

High-field and low field magnetoresistance of CoFe nanoparticles elaborated by organometallic chemistry. We report on magnetotransport measurements on CoFe nanoparticles surrounded
by an insulating organic layer. Samples were obtained by evaporating a solution
of nanoparticles on a patterned substrate. Typical behaviour of Coulomb
blockade in array of nanoparticles is observed. High and low field
magnetoresistance have been evidenced. Below 10 K, a large high-field
magnetoresistance is measured, reaching up to 500 %. Its amplitude decreases
strongly with increasing voltage. At 1.6 K, this high-field magnetoresistance
vanishes and an inverse low field tunnelling magnetoresistance is observed.

###Asymmetric Bias Dependence in Double Spin Filter Tunnel Junctions|G. X. Miao,J. S. Moodera###

Asymmetric Bias Dependence in Double Spin Filter Tunnel Junctions. In double spin filter (SF) tunnel junctions, the spin information is
generated and analyzed purely from the SF effect with nonmagnetic electrodes.
In this article we numerically evaluate the bias dependence of
magnetoresistance in such tunnel junctions (nonmagnetic metal / SF /
nonmagnetic insulator / SF / nonmagnetic metal), particularly in cases when
different SF materials are utilized. A large magnetoresistance with
nonmonotonic and asymmetric bias dependence is expected within the frame of WKB
approximation. We illustrate the systematic influence of tunnel barrier height,
tunnel barrier thickness, and exchange energy splitting on magnetoresistance,
particularly focusing on the asymmetric behavior of the magnetoresistance bias
dependence.

###Magnetotransport effects of ultrathin Ni80Fe20 films probed in-situ|Stephen Krzyk,Alexander von Schmidsfeld,Mathias Kläui,Ulrich Rüdiger###

Magnetotransport effects of ultrathin Ni80Fe20 films probed in-situ. We have investigated the magnetoresistance of Permalloy (Ni80Fe20) films with
thicknesses ranging from a single monolayer to 12 nm, grown on Al2O3, MgO and
SiO2 substrates. Growth and transport measurements were carried out under
cryogenic conditions in UHV. Applying in-plane magnetic vector fields up to 100
mT, the magnetotransport properties are ascertained during growth. With
increasing thickness the films exhibit a gradual transition from tunneling
magnetoresistance to anisotropic magnetoresistance. This corresponds to the
evolution of the film structure from separated small islands to a network of
interconnected grains as well as the transition from superparamagnetic to
ferromagnetic behavior of the film. Using an analysis based on a theoretical
model of the island growth, we find that the observed evolution of the
magnetoresistance in the tunneling regime originates from the changes in the
island size distribution during growth. Depending on the substrate material,
significant differences in the magnetoresistance response in the transition
regime between tunneling magnetoresistance and anisotropic magnetoresistance
were found. We attribute this to an increasingly pronounced island growth and
slower percolation process of Permalloy when comparing growth on SiO2, MgO and
Al2O3 substrates. The different growth characteristics result in a markedly
earlier onset of both tunneling magnetoresistance and anisotropic
magnetoresistance for SiO2. For Al2O3 in particular the growth mode results in
a structure of the film containing two different contributions to the
ferromagnetism which lead to two distinct coercive fields in the high thickness
regime.

###Magnetoresistance in nanostructures: the role of nonuniform current|Tiago S. Machado,M. Argollo de Menezes,Tatiana G. Rappoport,Luiz C. Sampaio###

Magnetoresistance in nanostructures: the role of nonuniform current. We developed a method to calculate the magnetoresistance of magnetic
nanostructures. We discretize a magnetic disk in small cells and numerically
solve the Landau-Lifshitz-Gilbert (LLG) equation in order to obtain its
magnetization profile. We consider a anisotropic magnetoresistance (AMR) that
depends on the local magnetization as the main source of the magnetoresistance.
We then use it as an input to calculate the resistance and current distribution
numerically, using a relaxation method. We show how magnetoresistance
measurements can be useful to obtain information on the magnetic structure.
Additionally, we obtain non-homogeneous current distributions for different
magnetic configurations in static and dynamical regimes.

###Absence of weak antilocalization in ferromagnetic films|Noa Kurzweil,Eugene Kogan,Aviad Frydman###

Absence of weak antilocalization in ferromagnetic films. We present magnetoresistance measurements performed on ultrathin films of
amorphous Ni and Fe. In these films the Curie temperature drops to zero at
small thickness, making it possible to study the effect of ferromagnetism on
localization. We find that non-ferromagnetic films are characterized by
positive magnetoresistance. This is interpreted as resulting from weak
antilocalization due to strong Bychkov-Rashba spin orbit scattering. As the
films become ferromagnetic the magnetoresistance changes sign and becomes
negative. We analyze our data to identify the individual contributions of weak
localization, weak antilocalization and anisotropic magnetoresistance and
conclude that the magnetic order suppresses the influence of spin-orbit effects
on localization phenomena in agreement with theoretical predictions.

###Semiclassical theory of magnetoresistance in positionally-disordered organic semiconductors|N. J. Harmon,M. E. Flatté###

Semiclassical theory of magnetoresistance in positionally-disordered organic semiconductors. A recently introduced percolative theory of unipolar organic
magnetoresistance is generalized by treating the hyperfine interaction
semiclassically for an arbitrary hopping rate. Compact analytic results for the
magnetoresistance are achievable when carrier hopping occurs much more
frequently than the hyperfine field precession period. In other regimes, the
magnetoresistance can be straightforwardly evaluated numerically. Slow and fast
hopping magnetoresistance are found to be uniquely characterized by their
lineshapes. We find that the threshold hopping distance is analogous a
phenomenological two-site model's branching parameter, and that the distinction
between slow and fast hopping is contingent on the threshold hopping distance.

###Light controlled magnetoresistance and magnetic field controlled photoresistance in CoFe film deposited on BiFeO3|B. Kundys,C. Meny,M. R. J. Gibbs,V. Da Costa,M. Viret,M. Acosta,D. Colson,B. Doudin###

Light controlled magnetoresistance and magnetic field controlled photoresistance in CoFe film deposited on BiFeO3. We present a magnetoresistive-photoresistive device based on the interaction
of a piezomagnetic CoFe thin film with a photostrictive BiFeO3 substrate that
undergoes light-induced strain. The magnitude of the resistance and
magnetoresistance in the CoFe film can be controlled by the wavelength of the
incident light on the BiFeO3. Moreover, a light-induced decrease in anisotropic
magnetoresistance is detected due to an additional magnetoelastic contribution
to magnetic anisotropy of the CoFe film. This effect may find applications in
photo-sensing systems, wavelength detectors and can possibly open a research
development in light-controlled magnetic switching properties for next
generation magnetoresistive memory devices.

###Organic magnetoresistance from deep traps|Nicholas J. Harmon,Michael E. Flatté###

Organic magnetoresistance from deep traps. We predict that singly-occupied carrier traps, produced by electrical stress
or irradiation within organic semiconductors, can cause spin blockades and the
large room-temperature magnetoresistance known as organic magnetoresistance.
The blockade occurs because many singly-occupied traps can only become doubly
occupied in a spin-singlet configuration. Magnetic-field effects on spin mixing
during transport dramatically modify the effects of this blockade and produce
magnetoresistance.We calculate the quantitative effects of these traps on
organic magnetoresistance from percolation theory and find a dramatic nonlinear
dependence of the saturated magnetoresistance on trap density, leading to
values $\sim$ 20%, within the theory's range of validity.

###Combined study of microwave-power/linear-polarization dependence of the microwave-radiation-induced magnetoresistance oscillations in GaAs/AlGaAs devices|Tianyu Ye,Han-Chun Liu,W. Wegscheider,R. G. Mani###

Combined study of microwave-power/linear-polarization dependence of the microwave-radiation-induced magnetoresistance oscillations in GaAs/AlGaAs devices. We report the results of a combined microwave polarization-dependence and
power-dependence study of the microwave-radiation-induced magnetoresistance
oscillations in high mobility GaAs/AlGaAs heterostructure devices at liquid
helium temperatures. The diagonal resistance was measured with the magnetic
field fixed at the extrema of the radiation-induced magnetoresistance
oscillations, as the microwave power was varied at a number of microwave
polarization angles. The results indicate a nonlinear relation between the
oscillatory peak or valley magnetoresistance and the microwave power, as well
as a cosine square relation between the oscillatory peak or valley
magnetoresistance and the microwave polarization angle. The main features are
briefly compared with the predictions of existing models.

###Magnetoresistance from broken spin helicity|D. P. Leusink,R. G. J. Smits,P. Ngabonziza,X. L. Wang,S. Wiedmann,U. Zeitler,A. Brinkman###

Magnetoresistance from broken spin helicity. The propensity of some materials and multilayers to have a magnetic field
dependent resistance, called magnetoresistance, has found commercial
applications such as giant magnetoresistance harddisk read heads. But
magnetoresistance can also be a powerful probe of electronic and magnetic
interactions in matter. For example, magnetoresistance can be used to analyze
multiband conductivity, conduction inhomogeneity, localized magnetic moments,
and (fractional) Landau level structure. For materials with strong spin-orbit
interaction, magnetoresistance can be used as a probe for weak antilocalization
or a nontrivial Berry phase, such as in topological insulator surface states.
For the three dimensional topological insulators a large and linear
magnetoresistance is often used as indication for underlying non-trivial
topology, although the origin of this effect has not yet been established.
Here, we observe a large magnetoresistance in the conducting bulk state of
Bi$_2$Te$_3$. We show that this type of large magnetoresistance is due to the
competition between helical spin-momentum locking (i.e. spin rotates with
momentum direction) and the unidirectional spin alignment by an applied
magnetic field. Warping effects are found to provide the (quasi) linear
dependence on magnetic field. We provide a quantitative model for the helicity
breaking induced magnetoresistance that can be applied to a vast range of
materials, surfaces or interfaces with weak to strong spin-orbit interactions,
such as the contemporary oxide interfaces, bulk Rashba systems, and topological
insulator surface states.

###Hanle Magnetoresistance in Thin Metal Films with Strong Spin-Orbit Coupling|Saül Vélez,Vitaly N. Golovach,Amilcar Bedoya-Pinto,Miren Isasa,Edurne Sagasta,Mikel Abadia,Celia Rogero,Luis E. Hueso,F. Sebastian Bergeret,Fèlix Casanova###

Hanle Magnetoresistance in Thin Metal Films with Strong Spin-Orbit Coupling. We report measurements of a new type of magnetoresistance in Pt and Ta thin
films. The spin accumulation created at the surfaces of the film by the spin
Hall effect decreases in a magnetic field because of the Hanle effect,
resulting in an increase of the electrical resistance as predicted by Dyakonov
[PRL 99, 126601 (2007)]. The angular dependence of this magnetoresistance
resembles the recently discovered spin Hall magnetoresistance in Pt/Y3Fe5O12
bilayers, although the presence of a ferromagnetic insulator is not required.
We show that this Hanle magnetoresistance is an alternative, simple way to
quantitatively study the coupling between charge and spin currents in metals
with strong spin-orbit coupling.

###Comparative study of microwave radiation-induced magnetoresistive oscillations induced by circularly- and linearly- polarized photo-excitation|Tianyu Ye,Han-Chun Liu,Zhuo Wang,W. Wegscheider,Ramesh G. Mani###

Comparative study of microwave radiation-induced magnetoresistive oscillations induced by circularly- and linearly- polarized photo-excitation. A comparative study of the radiation-induced magnetoresistance oscillations
in the high mobility GaAs/AlGaAs heterostructure two dimensional electron
system (2DES) under linearly- and circularlypolarized microwave excitation
indicates a profound difference in the response observed upon rotating the
microwave launcher for the two cases, although circularly polarized microwave
radiation induced magnetoresistance oscillations observed at low magnetic
fields are similar to the oscillations observed with linearly polarized
radiation. For the linearly polarized radiation, the magnetoresistive response
is a strong sinusoidal function of the launcher rotation (or linear
polarization) angle, {\theta}. For circularly polarized radiation, the
oscillatory magnetoresistive response is hardly sensitive to {\theta}.

###Spintronic Functionalities in Multiferroic Oxide-based Heterostructures|I. Fina,X. Martí###

Spintronic Functionalities in Multiferroic Oxide-based Heterostructures. The list of materials systems displaying both electric and magnetic long
range order is short. Oxides, however, concentrate numerous examples of
multiferroicity with, in some cases, a large magnetoelectric coupling. As a
result, a fruitful research field has emerged contemporaneously with the
consolidation of spintronic. The synergy between multiferroics and spintronics
was meant to be inevitable and hence the characterization of spintronic
functionalities in multiferroic materials is rather abundant. The aim of the
present chapter is to review the oxide heterostructures where magnetoelectric
coupling is demonstrated by means of spintronic functionalities (i.e.
magnetoresistance, anisotropic magnetoresistance, giant magnetoresistance or
tunnel magnetoresistance).

###Large magnetoresistance by Pauli blockade in hydrogenated graphene|J. Guillemette,N. Hemsworth,A. Vlasov,J. Kirman,F. Mahvash,P. L. Lévesque,M. Siaj,R. Martel,G. Gervais,S. Studenikin,A. Sachrajda,T. Szkopek###

Large magnetoresistance by Pauli blockade in hydrogenated graphene. We report the observation of a giant positive magnetoresistance in millimetre
scale hydrogenated graphene with magnetic field oriented in the plane of the
graphene sheet. A positive magnetoresistance in excess of 200\% at a
temperature of 300 mK was observed in this configuration, reverting to negative
magnetoresistance with the magnetic field oriented normal to the graphene
plane. We attribute the observed positive, in-plane, magnetoresistance to
Pauli-blockade of hopping conduction induced by spin polarization. Our work
shows that spin polarization in concert with electron-electron interaction can
play a dominant role in magnetotransport within an atomic monolayer.

###Negative Magnetoresistance in Dirac Semimetal Cd3As2|Hui Li,Hongtao He,Hai-Zhou Lu,Huachen Zhang,Hongchao Liu,Rong Ma,Zhiyong Fan,Shun-Qing Shen,Jiannong Wang###

Negative Magnetoresistance in Dirac Semimetal Cd3As2. A large negative magnetoresistance is anticipated in topological semimetals
in the parallel magnetic and electric field configuration as a consequence of
the nontrivial topological properties. The negative magnetoresistance is
believed to demonstrate the chiral anomaly, a long-sought high-energy physics
effect, in solid-state systems. Recent experiments reveal that Cd3As2, a Dirac
topological semimetal, has the record-high mobility and exhibits positive
linear magnetoresistance in the orthogonal magnetic and electric field
configuration. However, the negative magnetoresistance in the parallel magnetic
and electric field configuration remains unveiled. Here, we report the
observation of the negative magnetoresistance in Cd3As2 microribbons in the
parallel magnetic and electric field configuration as large as 66% at 50 K and
even visible at room temperatures. The observed negative magnetoresistance is
sensitive to the angle between magnetic and electrical field, robust against
temperature, and dependent on the carrier density. We have found that carrier
densities of our Cd3As2 samples obey an Arrhenius's law, decreasing from
3.0x10^17 cm^-3 at 300 K to 2.2x10^16 cm^-3 below 50 K. The low carrier
densities result in the large values of the negative magnetoresistance. We
therefore attribute the observed negative magnetoresistance to the chiral
anomaly. Furthermore, in the perpendicular magnetic and electric field
configuration a positive non-saturating linear magnetoresistance up to 1670% at
14 T and 2 K is also observed. This work demonstrates potential applications of
topological semimetals in magnetic devices.

###Extremely large and significantly anisotropic magnetoresistance in ZrSiS single crystals|Yang-Yang Lv,Bin-Bin Zhang,Xiao Li,Shu-Hua Yao,Y. B. Chen,Jian Zhou,Shan-Tao Zhang,Ming-Hui Lu,Yan-Feng Chen###

Extremely large and significantly anisotropic magnetoresistance in ZrSiS single crystals. Recently, the extremely large magnetoresistance observed in transition metal
telluride, like WTe$_2$, attracted much attention because of the potential
applications in magnetic sensor. Here we report the observation of extremely
large magnetoresistance as 3.0$\times$10$^4$ % measured at 2 K and 9 T magnetic
field aligned along [001]-ZrSiS. The significant magnetoresistance change
(~1.4$\times$10$^4$ %) can be obtained when the magnetic field is titled from
[001] to [011]-ZrSiS. These abnormal magnetoresistance behaviors in ZrSiS can
be understood by electron-hole compensation and the open orbital of Fermi
surface. Because of these superior MR properties, ZrSiS may be used in the
novel magnetic sensors.

###Valley-Contrasting Orbital Magnetic Moment Induced Negative Magnetoresistance|Hailong Zhou,Cong Xiao,Qian Niu###

Valley-Contrasting Orbital Magnetic Moment Induced Negative Magnetoresistance. The valley-contrasting orbital magnetic moment of Bloch electrons allows the
lifting of valley degeneracy by an out-of-plane magnetic field. We demonstrate
that this leads to negative magnetoresistance, utilizing a gapped
two-dimensional multi-valley model as an example. An intuitive physical picture
in terms of the increased carrier density from a magnetic gating effect is
proposed for this negative magnetoresistance. In particular, giant negative
magnetoresistance is achieved after one of the two valleys is depleted by the
magnetic field. This new mechanism of negative magnetoresistance is argued to
be relevant in ionic-liquid gated gapped graphene with small effective mass.

###Anisotropic magnetoresistance in topological insulator Bi1.5Sb0.5Te1.8Se1.2/CoFe heterostructures|B. Xia,P. Ren,Azat Sulaev,Z. P. Li,P. Liu,Z. L. Dong,L. Wang###

Anisotropic magnetoresistance in topological insulator Bi1.5Sb0.5Te1.8Se1.2/CoFe heterostructures. Topological insulator is composed of an insulating bulk state and time
reversal symmetry protected two-dimensional surface states. One of the
characteristics of the surface states is the locking between electron momentum
and spin orientation. Here, we report a novel in-plane anisotropic
magnetoresistance in topological insulator Bi1.5Sb0.5Te1.8Se1.2/CoFe
heterostructures. To explain the novel effect, we propose that the
Bi1.5Sb0.5Te1.8Se1.2/CoFe heterostructure forms a spin-valve or Giant
magnetoresistance device due to spin-momentum locking. The novel in-plane
anisotropic magnetoresistance can be explained as a Giant magnetoresistance
effect of the Bi1.5Sb0.5Te1.8Se1.2/CoFe heterostructures.

###Anomalous Hall-like transverse magnetoresistance in Au thin films on Y$_3$Fe$_5$O$_{12}$|Tobias Kosub,Saül Vélez,Juan M. Gomez-Perez,Luis E. Hueso,Jürgen Faßbender,Fèlix Casanova,Denys Makarov###

Anomalous Hall-like transverse magnetoresistance in Au thin films on Y$_3$Fe$_5$O$_{12}$. Anomalous Hall-like signals in platinum in contact with magnetic insulators
are common observations that could be explained by either proximity
magnetization or spin Hall magnetoresistance. In this work, longitudinal and
transverse magnetoresistances are measured in a pure gold thin film on the
ferrimagnetic insulator Y$_3$Fe$_5$O$_{12}$ (Yttrium Iron Garnet, YIG). We show
that both the longitudinal and transverse magnetoresistances have
quantitatively consistent scaling in YIG/Au and in a YIG/Pt reference system
when applying the Spin Hall magnetoresistance framework. No contribution of an
anomalous Hall effect due to the magnetic proximity effect is evident.

###Microstructural Changes Influencing the Magnetoresistive Behavior of Bulk Nanocrystalline Materials|Stefan Wurster,Martin Stueckler,Lukas Weissitsch,Timo Mueller,Andrea Bachmaier###

Microstructural Changes Influencing the Magnetoresistive Behavior of Bulk Nanocrystalline Materials. Bulk nanocrystalline materials of small and medium ferromagnetic content were
produced using severe plastic deformation by high-pressure torsion at
roomtemperature. Giant magnetoresistive behavior was found for as deformed
materials, which was further improved by adjusting the microstructure with
thermal treatments. The adequate range of annealing temperatures was assessed
with in-situ synchrotron diffraction measurements. Thermally treated CuCo
materials show larger giant magnetoresistance after annealing for 1 h at 300C,
while for CuFe this annealing temperature is too high and decreases the
magnetoresistive properties. The improvement of magnetoresistivity by thermal
treatments is discussed with respect to the microstructural evolution as
observed by electron microscopy and ex situ synchrotron diffraction
measurements.

###Hydrodynamic magnetoresistance in graphene Corbino devices|Alex Levchenko,Songci Li,A. V. Andreev###

Hydrodynamic magnetoresistance in graphene Corbino devices. We study hydrodynamic electron magnetotransport in graphene devices. We show
that in these systems a distinct mechanism of magnetoresistance appears, which
is absent in systems with Galilean-invariant electron liquid. The resulting
magnetoresistance depends on the intrinsic conductivity and viscosity of the
electron liquid, and becomes especially pronounced near charge neutrality. We
obtain analytic expressions for magnetoransport coefficients of Corbino
devices, and obtain estimates for the electrical and thermal magnetoresistances
for monolayer and bilayer systems at charge neutrality. Magnetoresistance
becomes strong (of order 100%) at relatively weak fields, at which the kinetic
coefficients of the electron liquid are practically unaffected by the magnetic
field.

###Activated and quantum creep of the charge-density waves in magnetic field in {\it o}-TaS$_3$|I. A. Cohn,S. V. Zaitsev-Zotov###

Activated and quantum creep of the charge-density waves in magnetic field in {\it o}-TaS$_3$. We demonstrate that magnetoresistance of creeping charge-density waves in the
quasi-one dimensional conductor {\it o}-TaS$_3$ changes its character from a
negative parabolic at $T\gtrsim 10$ K where it obeys $1/T^2$ law to a weakly
temperature dependent negative nearly linear one at lower temperatures. The
dominant contribution into the negative parabolic magnetoresistance comes from
magnetic field induced splitting of the CDW order parameter. The linear
magnetoresistance arises due to CDW quantum interference similar to the
scenario of negative linear magnetoresistance in single-electron systems.

###Coexistence of Weak Localization and a Metallic Phase in Si/SiGe Quantum Wells|V. Senz,T. Heinzel,T. Ihn,K. Ensslin,G. Dehlinger,D. Gruetzmacher,U. Gennser###

Coexistence of Weak Localization and a Metallic Phase in Si/SiGe Quantum Wells. Magnetoresistivity measurements on p-type Si/SiGe quantum wells reveal the
coexistence of a metallic behavior and weak localization. Deep in the metallic
regime, pronounced weak localization reduces the metallic behavior around zero
magnetic field without destroying it. In the insulating phase, a positive
magnetoresistivity emerges close to B=0, possibly related to spin-orbit
interactions.

###A possible role of D^- band in hopping conductivity and metal-insulator transition in 2D structures|V. I. Kozub,N. V. Agrinskaya,S. I. Khondaker,I. Shlimak###

A possible role of D^- band in hopping conductivity and metal-insulator transition in 2D structures. A simple two-band model is suggested explaining recently reported unusual
features for hopping magnetoresistance and the metal-insulator transition in 2D
structures. The model implies that the conductivity is dominated by the upper
Hubbard band (D^- band). Experimental studies of hopping magnetoresistance for
Si delta doped GaAs/AlGaAs heterostructure give additional evidences for the
model.

###Comment on "Magnetoresistance and differential conductance in mutliwalled carbon nanotubes"|C. Schonenberger,A. Bachtold###

Comment on "Magnetoresistance and differential conductance in mutliwalled carbon nanotubes". Jeong-O Lee et al. [Phy. Rev. B, 61, R16 362 (2000)] reported
magnetoresistance and differential conductance measurements of multiwalled
carbon nanotubes. The observed aperiodic conductance fluctuations and the
negative magnetoresistance was interpreted to originate exclusively from
changes in the density of states at the Fermi energy. We show that this
interpretation is questionable and not supported by their measurements.

###Classical mechanism for negative magnetoresistance in two dimensions|A. Dmitriev,M. Dyakonov,R. Jullien###

Classical mechanism for negative magnetoresistance in two dimensions. The classical two-dimensional problem of non-interacting electrons scattered
by short-range impurity centers in the presence of magnetic field is
investigated both analytically and numerically. A strong magnetoresistance
exists in such a system, due to freely circling electrons, which are not taken
into account by the Boltzmann-Drude approach. A parabolic magnetoresistance is
found at low fields.

###Anisotropic Magnetoresistance in GaMnAs films|K. Y. Wang,K. W. Edmonds,R. P. Campion,L. X. Zhao,A. C. Neumann,C. T. Foxon,B. L. Gallagher,P. C. Main###

Anisotropic Magnetoresistance in GaMnAs films. The magnetoresistance in a series of Ga1-xMnxAs samples with 0.2 =< x =< 0.8
have been measured for three mutually orthogonal orientations of the external
magnetic field. The anisotropy magnetoresistance decreases with increasing of
the Mn content, which means that the magnetic disorder or defects scattering
increases with increasing of Mn content. And also the magneto-crystalline
anisotropy increases with increasing of Mn concentration.

###Anomalous Low-Field Classical Magnetoresistance in Two Dimensions|Alexander Dmitriev,Michel Dyakonov,Remi Jullien###

Anomalous Low-Field Classical Magnetoresistance in Two Dimensions. The magnetoresistance of classical two-dimensional electrons scattered by
randomly distributed impurities is investigated by numerical simulation. At low
magnetic fields, we find for the first time a negative magnetoresistance
proportional to |B|. This unexpected behavior is shown to be due to a memory
effect specific for backscattering events, which was not considered previously.

###Linear in-plane magnetoconductance and spin susceptibility of a 2D electron gas on a vicinal silicon surface|Y. Y. Proskuryakov,Z. D. Kvon,A. K. Savchenko###

Linear in-plane magnetoconductance and spin susceptibility of a 2D electron gas on a vicinal silicon surface. In this work we have studied the parallel magnetoresistance of a 2DEG near a
vicinal silicon surface. An unusual, linear magnetoconductance is observed in
the fields up to $B = 15$ T, which we explain by the effect of spin olarization
on impurity scattering. This linear magnetoresistance shows strong anomalies
near the boundaries of the minigap in the electron spectrum of the vicinal
system.

###Exact analytical expression for magnetoresistance using quantum groups|S. A. Alavi,S. Rouhani###

Exact analytical expression for magnetoresistance using quantum groups. We obtain an exact analytical expression for magnetoresistance using
noncommutative geometry and quantum groups.Then we will show that there is a
deep relationship between magnetoresistance and the quantum group $su_{q}(2)$,
from which we understand the quantum interpretation of the quantum corrections
to the conductivity.

###Magnetic polarons and magnetoresistance in EuB6|M. J. Calderon,L. G. L. Wegener,P. B. Littlewood###

Magnetic polarons and magnetoresistance in EuB6. EuB6 is a low carrier density ferromagnet which exhibits large
magnetoresistance, positive or negative depending on temperature. The formation
of magnetic polarons just above the magnetic critical temperature has been
suggested by spin-flip Raman scattering experiments. We find that the fact that
EuB6 is a semimetal has to be taken into account to explain its electronic
properties, including magnetic polarons and magnetoresistance.

###Antilocalization and spin-orbit coupling in hole strained GaAs/InGaAs/GaAs quantum well heterostructures|G. M. Minkov,A. A. Sherstobitov,A. V. Germanenko,O. E. Rut,V. A. Larionova,B. N. Zvonkov###

Antilocalization and spin-orbit coupling in hole strained GaAs/InGaAs/GaAs quantum well heterostructures. Low-field magnetoresistance in p-type strained quantum wells is studied. It
is shown that the Rashba mechanism leads to the cubic in quasimomentum
spin-orbit splitting of the hole energy spectrum and the antilocalization
behavior of low-field magnetoresistance is well described by the
Hikami-Larkin-Nagaoka expression.

###Interlayer Aharonov-Bohm interference in tilted magnetic fields in quasi-one-dimensional layered conductors|Benjamin K. Cooper,Victor M. Yakovenko###

Interlayer Aharonov-Bohm interference in tilted magnetic fields in quasi-one-dimensional layered conductors. Different types of angular magnetoresistance oscillations in
quasi-one-dimensional layered materials, such as organic conductors (TMTSF)2X,
are explained in terms of Aharonov-Bohm interference in interlayer electron
tunneling. A two-parameter pattern of oscillations for generic orientations of
a magnetic field is visualized and compared with the experimental data.
Connections with angular magnetoresistance oscillations in other layered
materials are discussed.

###Gated Spin Transport through an Individual Single Wall Carbon Nanotube|Bhaskar Nagabhirava,Tanesh Bansal,Gamini Sumanasekera,Lei Liu,Bruce W. Alphenaar###

Gated Spin Transport through an Individual Single Wall Carbon Nanotube. Hysteretic switching in the magnetoresistance of short-channel,
ferromagnetically contacted individual single wall carbon nanotubes is
observed, providing strong evidence for nanotube spin transport. By varying the
voltage on a capacitively coupled gate, the magnetoresistance can be
reproducibly modified between +10% and -15%. The results are explained in terms
of wave vector matching of the spin polarized electron states at the
ferromagnetic / nanotube interfaces.

###High-field magnetoresistive effects in reduced-dimensionality organic metals and superconductors|J. Singleton,R. D. McDonald,N. Harrison###

High-field magnetoresistive effects in reduced-dimensionality organic metals and superconductors. The large charge-transfer anisotropy of quasi-one- and quasi-two-dimensional
crystalline organic metals means that magnetoresistance is one of the most
powerful tools for probing their bandstructure and interesting phase diagrams.
Here we review various magnetoresistance phenomena that are of interest in the
investigation of metallic, superconducting and charge-density-wave organic
systems.

###Current-induced magnetoresistance oscillations in two-dimensional electron systems|X. L. Lei###

Current-induced magnetoresistance oscillations in two-dimensional electron systems. Electric current-induced magnetoresistance oscillations recently discovered
in two-dimensional electron systems are analyzed using a microscopic scheme for
nonlinear magnetotransport direct controlled by the current. The
magnetoresistance oscillations are shown to result from drift-motion assisted
electron scatterings between Landau levels. The theoretical predictions not
only reproduce all the main features observed in the experiments but also
disclose other details of the phenomenon.

###Interlayer exchange coupling in (Ga,Mn)As based multilayers|A. D. Giddings,T. Jungwirth,B. L. Gallagher###

Interlayer exchange coupling in (Ga,Mn)As based multilayers. Exhibiting antiferromagnetic interlayer coupling in dilute magnetic
semiconductor multilayers is essential for the realisation of
magnetoresistances analogous to giant magnetoresistance in metallic multilayer
structures. In this work we use a mean-field theory of carrier induced
ferromagnetism to explore possible (Ga,Mn)As based multilayer structures that
might yield antiferromagnetic coupling.

###Oscillatory nonlinear differential magnetoresistance of highly mobile 2D electrons in high Landau levels|X. L. Lei###

Oscillatory nonlinear differential magnetoresistance of highly mobile 2D electrons in high Landau levels. We examine the current-induced magnetoresistance oscillations in
high-mobility two-dimensional electron systems using the balance-equation
scheme for nonlinear magnetotransort. The reported analytical expressions for
differential magnetoresistivity at high filling factors in the overlapping
Landau-level regime, which show good agreement with the experimental
observation and the numerical calculation, may be helpful in extracting
physical information from experiments.

###Skyrmions in a Doped Antiferromagnet|I. Raicevic,Dragana Popovic,C. Panagopoulos,L. Benfatto,M. B. Silva Neto,E. S. Choi,T. Sasagawa###

Skyrmions in a Doped Antiferromagnet. Magnetization and magnetoresistance have been measured in insulating
antiferromagnetic La_{2}Cu_{0.97}Li_{0.03}O_{4} over a wide range of
temperatures, magnetic fields, and field orientations. The magnetoresistance
step associated with a weak ferromagnetic transition exhibits a striking
nonmonotonic temperature dependence, consistent with the presence of skyrmions.

###Galvanomagnetic effects in graphene|I. I. Boiko###

Galvanomagnetic effects in graphene. Galvanomagnetic effects in graphene
  Magnetoresistivity and Hole-effect were theoretically investigated for
neutral and gated graphene. It is shown that in neutral graphene Hall-effect is
totally absent. In gated, exactly monopolar graphene effect of
magnetoresistivity vanishes; here Hall-constant does not involve any relaxation
characteristic in contrast to result obtained for popular method of relaxation
time approximation.

###Anomalous magneto-transport at the superconducting interface between LaAlO3 and SrTiO3|M. Sachs,D. Rakhmilevitch,M. Ben Shalom,S. Shefler,A. Palevski,Y. Dagan###

Anomalous magneto-transport at the superconducting interface between LaAlO3 and SrTiO3. The magnetoresistance as a function of temperature and field for atomically
flat interfaces between 8 unit cells of LaAlO3 and SrTiO3 is reported.
Anomalous anisotropic behavior of the magnetoresistance is observed below 30 K
for superconducting samples with carrier concentration of 3.5\times10^13 cm^-2
. We associate this behavior to a magnetic order formed at the interface.

###Interference oscillations of microwave photoresistance in double quantum wells|S. Wiedmann,G. M. Gusev,O. E. Raichev,T. E. Lamas,A. K. Bakarov,J. C. Portal###

Interference oscillations of microwave photoresistance in double quantum wells. We observe oscillatory magnetoresistance in double quantum wells under
microwave irradiation. The results are explained in terms of the influence of
subband coupling on the frequency-dependent photoinduced part of the electron
distribution function. As a consequence, the magnetoresistance demonstrates the
interference of magneto-intersubband oscillations and conventional microwave-
induced resistance oscillations.

###Abnormal magnetoresistance behavior in Nb thin film with rectangular antidot lattice|W. J. Zhang,S. K. He,B. H. Li,F. Cheng,B. Xu,Z. C. Wen,W. H. Cao,X. F. Han,S. P. Zhao,X. G. Qiu###

Abnormal magnetoresistance behavior in Nb thin film with rectangular antidot lattice. Abnormal magnetoresistance behavior is found in superconducting Nb films
perforated with rectangular arrays of antidots (holes). Generally
magnetoresistance were always found to increase with increasing magnetic field.
Here we observed a reversal of this behavior for particular in low temperature
or current density. This phenomenon is due to a strong 'caging effect' which
interstitial vortices are strongly trapped among pinned multivortices.

###Magnetoresistance from Fermi Surface Topology|Sheng Nan Zhang,Quan Sheng Wu,Yi Liu,Oleg V. Yazyev###

Magnetoresistance from Fermi Surface Topology. Extremely large non-saturating magnetoresistance has recently been reported
for a large number of both topologically trivial and non-trivial materials.
Different mechanisms have been proposed to explain the observed
magnetotransport properties, yet without arriving to definitive conclusions or
portraying a global picture. In this work, we investigate the transverse
magnetoresistance of materials by combining the Fermi surfaces calculated from
first principles with the Boltzmann transport theory approach relying on the
semiclassical model and the relaxation time approximation. We first consider a
series of simple model Fermi surfaces to provide a didactic introduction into
the charge-carrier compensation and open-orbit mechanisms leading to
non-saturating magnetoresistance. We then address in detail magnetotransport in
three representative materials: (i) copper, a prototypical nearly free-electron
metal characterized by the open Fermi surface that results in an intricate
angular magnetoresistance, (ii) bismuth, a topologically trivial semimetal in
which very large magnetoresistance is known to result from charge-carrier
compensation, and (iii) tungsten diphosphide WP2, a recently discovered type-II
Weyl semimetal that holds the record of magnetoresistance in compounds. In all
three cases our calculations show excellent agreement with both the field
dependence of magnetoresistance and its anisotropy measured at low
temperatures. Furthermore, the calculations allow for a full interpretation of
the observed features in terms of the Fermi surface topology. These results
will help addressing a number of outstanding questions, such as the role of the
topological phase in the pronounced large non-saturating magnetoresistance
observed in topological materials.

###Negative Magnetoresistance in Granular Bi - HTSC with Trapped Magnetic Fields|A. A. Sukhanov,V. I. Omelchenko###

Negative Magnetoresistance in Granular Bi - HTSC with Trapped Magnetic Fields. Magnetoresistive properties of granular Bi-based HTSC with trapped magnetic
fields are investigated in the temperature region near superconducting
transition . The effect of trapped field and transport current values and
orientations on the field dependence of magnetoresistance is studied. It is
found that for the magnetic field parallel and the current perpendicular to
trapping inducing field the field dependence of magnetoresistance is
nonmonotonic and magnetoresistance turns out to be negative for small fields.
The magnetoresistance sign inversion field increases roughly linear with the
trapped magnetic field and slightly decrease with transport current. The
results are explained in the framework of model of magnetic flux trapping in
granules or superconducting loops embedded in weak links matrix.

###3000 % high-field magnetoresistance in super-lattices of CoFe nanoparticles|Reasmey P. Tan,Julian Carrey,Marc Respaud,Celine Desvaux,Philippe Renaud,Bruno Chaudret###

3000 % high-field magnetoresistance in super-lattices of CoFe nanoparticles. We report on magnetotransport measurements on millimetre-large super-lattices
of CoFe nanoparticles surrounded by an organic layer. Electrical properties are
typical of Coulomb blockade in three dimensional arrays of nanoparticles. A
large high-field magnetoresistance, reaching up to 3000 %, is measured between
1.8 and 10 K. This exceeds by two orders of magnitude magnetoresistance values
generally measured in arrays of 3d metals ferromagnetic nanoparticles. The
magnetoresistance amplitude scales with the magnetic field / temperature ratio
and displays an unusual exponential dependency with the applied voltage. The
magnetoresistance abruptly disappears below 1.8 K. We propose that the
magnetoresistance is due to some individual paramagnetic moments localized
between the metallic core of the nanoparticles, the origin of which is
discussed.

###Extraordinary Magnetoresistance in Hybrid Semiconductor-Metal Systems|T. H. Hewett,F. V. Kusmartsev###

Extraordinary Magnetoresistance in Hybrid Semiconductor-Metal Systems. We show that extraordinary magnetoresistance (EMR) arises in systems
consisting of two components; a semiconducting ring with a metallic inclusion
embedded. The im- portant aspect of this discovery is that the system must have
a quasi-two-dimensional character. Using the same materials and geometries for
the samples as in experiments by Solin et al.[1;2], we show that such systems
indeed exhibit a huge magnetoresistance. The magnetoresistance arises due to
the switching of electrical current paths passing through the metallic
inclusion. Diagrams illustrating the flow of the current density within the
samples are utilised in discussion of the mechanism responsible for the
magnetoresistance effect. Extensions are then suggested which may be applicable
to the silver chalcogenides. Our theory offers an excellent description and
explanation of experiments where a huge magnetoresistance has been
discovered[2;3].

###Linear magnetoresistance in commercial n-type silicon due to inhomogeneous doping|Nicholas Porter,Christopher Marrows###

Linear magnetoresistance in commercial n-type silicon due to inhomogeneous doping. Free electron theory tells us that resistivity is independent of magnetic
field. In fact, most observations match the semiclassical prediction of a
magnetoresistance that is quadratic at low fields before saturating. However, a
non-saturating linear magnetoresistance has been observed in exotic
semiconductors such as silver chalcogenides, lightly-doped InSb, N-doped InAs,
MnAs-GaAs composites, PrFeAsO, and epitaxial graphene. Here we report the
observation of a large linear magnetoresistance in the ohmic regime in
commonplace commercial n-type silicon wafer. It is well-described by a
classical model of spatially fluctuating donor densities, and may be amplified
by altering the aspect ratio of the sample to enhance current-jetting:
increasing the width tenfold increased the magnetoresistance at 8 T from 445 %
to 4707 % at 35 K. This physical picture may well offer insights into the large
magnetoresistances recently observed in n-type and p-type Si in the non-ohmic
regime.

###Anisotropic magnetoresistance of charge-density wave in $o$-TaS$_3$|Katsuhiko Inagaki,Toru Matsuura,Masakatsu Tsubota,Shinya Uji,Tatsuya Honma,Satoshi Tanda###

Anisotropic magnetoresistance of charge-density wave in $o$-TaS$_3$. We report the magnetoresistance of a charge-density wave (CDW) in $o$-TaS$_3$
whiskers at 4.2 K under a magnetic field up to 5.2 T. An anisotropic negative
magnetoresistance is found in the nonlinear regime of current-voltage
characteristics. The angle dependence of the magnetoresistance, studied by
rotating the magnetic field upon the $c$-axis, exhibited a two-fold symmetry.
The magnetoresistance amplitude exhibits maxima when the field is parallel to
the $a$-axis, whereas it vanishes to the $b$-axis. The observed anisotropy may
come from difference in interchain coupling of adjacent CDWs along the $a$- and
$b$-axes. Comparison of the anisotropy to the scanning tunneling microscope
image of CDWs allows us to provide a simple picture to explain the
magnetoresistance in terms of delocalization of quantum interference of CDWs
extending over the $b$-$c$ plane.

###Anisotropic Magnetotransport and Exotic Longitudinal Linear Magnetoresistance in WTe2 Crystals|Yanfei Zhao,Haiwen Liu,Jiaqiang Yan,Wei An,Jun Liu,Xi Zhang,Hua Jiang,Qing Li,Yong Wang,Xin-Zheng Li,David Mandrus,X. C. Xie,Minghu Pan,Jian Wang###

Anisotropic Magnetotransport and Exotic Longitudinal Linear Magnetoresistance in WTe2 Crystals. WTe2 semimetal, as a typical layered transition-metal dichalcogenide, has
recently attracted much attention due to the extremely large, non-saturating
parabolic magnetoresistance in perpendicular field. Here, we report a
systematic study of the angular dependence of the magnetoresistance in WTe2
single crystal. The violation of the Kohler rule and a significant anisotropic
magnetotransport behavior in different magnetic field directions are observed.
Surprisingly, when the applied field is parallel to the tungsten chains of
WTe2, an exotic large longitudinal linear magnetoresistance as high as 1200% at
15 T and 2 K is identified. Violation of the Kohler rule in transverse
magnetoresistance can be understood based on a dual effect of the excitons
formation and thermal activation, while large longitudinal linear
magnetoresistance reflects perfectly the scattering and nesting of quasi-1D
nature of this balanced hole-electron system. Our work will stimulate studies
of such double-carrier correlated material and corresponding quantum physics.

###Origin of the Extremely Large Magnetoresistance in the Semimetal YSb|J. Xu,N. J. Ghimire,J. S. Jiang,Z. L. Xiao,A. S. Botana,Y. L. Wang,Y. Hao,J. E. Pearson,W. K. Kwok###

Origin of the Extremely Large Magnetoresistance in the Semimetal YSb. Electron-hole (e-h) compensation is a hallmark of multi-band semimetals with
extremely large magnetoresistance (XMR) and has been considered to be the basis
for XMR. Recent spectroscopic experiments, however, reveal that YSb with
non-saturating magnetoresistance is uncompensated, questioning the e-h
compensation scenario for XMR. Here we demonstrate with magnetoresistivity and
angle dependent Shubnikov - de Haas (SdH) quantum oscillation measurements that
YSb does have nearly perfect e-h compensation, with a density ratio of $0.95$
for electrons and holes. The density and mobility anisotropy of the charge
carriers revealed in the SdH experiments allow us to quantitatively describe
the magnetoresistance with an anisotropic multi-band model that includes
contributions from all Fermi pockets. We elucidate the role of compensated
multi-bands in the occurrence of XMR by demonstrating the evolution of
calculated magnetoresistances for a single band and for various combinations of
electron and hole Fermi pockets.

###Vertical organic spin valves in perpendicular magnetic fields|M. Grünewald,R. Göckeritz,N. Homonnay,F. Würthner,L. W. Molenkamp,G. Schmidt###

Vertical organic spin valves in perpendicular magnetic fields. We report the results of magnetoresistance measurements in vertical organic
spin valves with the magnetic field oriented perpendicular to the layer stack.
The magnetoresistance measurements were performed after carefully preparing
either parallel or antiparallel in-plane magnetization states of the magnetic
electrodes in order to observe traces of Hanle precession. Due to the low
mobility in organic semiconductors the transit time of spin polarized carriers
should allow for precession of the spins in perpendicular fields which in
statistical average would quench the magnetoresistance. However, in none of the
experiments we do observe any change in resistance while sweeping the
perpendicular field, up to the point where the electrode's magnetization starts
to reorient. This absence of Hanle type effects indicates that the
magnetoresistance is not based on the injection of spin polarized electrons
into the organic semiconductor but rather on tunneling through pinholes
superimposed with tunneling anisotropic magnetoresistance.

###Possible Scale Invariant Linear Magnetoresistance in Pyrochlore Iridates Bi$_2$Ir$_2$O$_7$|Jiun-Haw Chu,Jian Liu,Han Zhang,Kyle Noordhoek,Scott. C. Riggs,Maxwell Shapiro,Claudy Ryan Serero,Di Yi,M. Melissa,S. J. Suresha,C. Frontera,E. Arenholz,Ashvin Vishwanath,Xavi Marti,I. R. Fisher,R. Ramesh###

Possible Scale Invariant Linear Magnetoresistance in Pyrochlore Iridates Bi$_2$Ir$_2$O$_7$. We report the observation of a linear magnetoresistance in single crystals
and epitaxial thin films of the pyrochlore iridate Bi$_2$Ir$_2$O$_7$. The
linear magnetoresistance is positive and isotropic at low temperatures, without
any sign of saturation up to 35 Tesla. As temperature increases, the linear
field dependence gradually evolves to a quadratic field dependence. The
temperature and field dependence of magnetoresistance of Bi$_2$Ir$_2$O$_7$
bears strikingly resemblance to the scale invariant magnetoresistance observed
in the strange metal phase in high Tc cuprates. However, the residual
resistivity of Bi$_2$Ir$_2$O$_7$ is more than two orders of magnitude higher
than the curpates. Our results suggest that the correlation between linear
magnetoresistance and quantum fluctuations may exist beyond high temperature
superconductors.

###Giant Current-Perpendicular-to-Plane Magnetoresistance in Multilayer Graphene as Grown on Nickel|S. C. Bodepudi,A. P. Singh,Sandipan Pramanik###

Giant Current-Perpendicular-to-Plane Magnetoresistance in Multilayer Graphene as Grown on Nickel. Strong magnetoresistance effects are often observed in ferromagnet-nonmagnet
multilayers, which are exploited in state-of-the-art magnetic field sensing and
data storage technologies. In this work we report a novel
current-perpendicular-to-plane magnetoresistance effect in multilayer graphene
as grown on a catalytic nickel surface by chemical vapor deposition. A negative
magnetoresistance effect of 10^4% has been observed, which persists even at
room temperature. This effect is correlated with the shape of the 2D peak as
well as with the occurrence of D peak in the Raman spectrum of the as-grown
multilayer graphene. The observed magnetoresistance is extremely high as
compared to other known materials systems for similar temperature and field
range and can be qualitatively explained within the framework of "interlayer
magnetoresistance" (ILMR).

###Tunneling Magnetoresistance in Junctions Composed of Ferromagnets and Time-Reversal Invariant Topological Superconductors|Zhongbo Yan,Shaolong Wan###

Tunneling Magnetoresistance in Junctions Composed of Ferromagnets and Time-Reversal Invariant Topological Superconductors. Tunneling Magnetoresistance between two ferrromagnets is an issue of
fundamental importance in spintronics. In this work, we show that tunneling
magnetoresistance can also emerge in junctions composed of ferromagnets and
time-reversal invariant topological superconductors without spin-rotation
symmetry. Here the physical origin is that when the spin-polarization direction
of injected electron from the ferromagnet lying in the same plane of the
spin-polarization direction of Majorana zero modes, the electron will undergo a
perfect spin-equal Andreev reflection, while injected electrons with other
spin-polarization direction will be partially Andreev reflected and partially
normal reflected, which consequently have a lower conductance, and therefore,
the magnetoresistance effect emerges. Compared to conventional magnetic tunnel
junctions, an unprecedented advantage of the junctions studied here is that
arbitrary high tunneling magnetoresistance can be obtained even the
magnetization of the ferromagnets are weak and the insulating tunneling
barriers are featureless. Our findings provide a new fascinating mechanism to
obtain high tunneling magnetoresistance.

###Large linear magnetoresistance from neutral defects in Bi$_2$Se$_3$|Devendra Kumar,Archana Lakhani###

Large linear magnetoresistance from neutral defects in Bi$_2$Se$_3$. The chalcogenide Bi$_2$Se$_3$ can attain the three dimensional (3D) Dirac
semimetal state under the influence of strain and microstrain. Here we report
the presnece of large linear magnetoresistance in such a Bi$_2$Se$_3$ crystal.
The magnetoresistance has quadratic form at low fields which crossovers to
linear above 4 T. The temperature dependence of magnetoresistance scales with
carrier mobility and the crossover field scales with inverse of mobility. Our
analysis suggest that the linear magnetoresistance in our system has a
classical origin and arises from the scattering of high mobility 3D Dirac
electrons from crystalline inhomogeneities. We observe that the charged
selenium vacancies are strongly screened by high mobility Dirac electrons and
the neutral crystalline defects are the main scattering center for transport
mechanism. Our analysis suggests that both the resistivity and the
magnetoresistance have their origin in scattering of charge carriers from
neutral defects.

###Gate-tunable large magnetoresistance in an all-semiconductor spin-transistor-like device|Martin Oltscher,Franz Eberle,Thomas Kuczmik,Andreas Bayer,Dieter Schuh,Dominique Bougeard,Mariusz Ciorga,Dieter Weiss###

Gate-tunable large magnetoresistance in an all-semiconductor spin-transistor-like device. A large spin-dependent and electric field-tunable magnetoresistance of a
two-dimensional electron system (2DES) is a key ingredient for the realization
of many novel concepts for spin-based electronic devices. The low
magnetoresistance observed during the last decades in devices with lateral
semiconducting (SC) transport channels between ferromagnetic (FM) source (S)
and drain (D) contacts has been the main obstacle for realizing spin field
effect transistor proposals. Here, we show both, a large two terminal
magnetoresistance in lateral 2DES-based spin valve geometry, with up to 80%
resistance change, and tunability of the magnetoresistance by an electric gate.
The large magnetoresistance is due to finite electric field effects at the
FM/SC interface, which boost spin-to-charge conversion. The gating scheme we
use is based on switching between uni- and bi-directional spin diffusion,
without resorting to the spin-orbit coupling.

###Interfacial Rashba magnetoresistance of two-dimensional electron gas at LaAlO$_3$/SrTiO$_3$ interface|Kulothungasagaran Narayanapillai,Gyungchoon Go,Rajagopalan Ramaswamy,Kalon Gopinadhan,Dongwook Go,Hyun-Woo Lee,Thirumalai Venkatesan,Kyung-Jin Lee,Hyunsoo Yang###

Interfacial Rashba magnetoresistance of two-dimensional electron gas at LaAlO$_3$/SrTiO$_3$ interface. We report the angular dependence of magnetoresistance in two-dimensional
electron gas at LaAlO$_3$/SrTiO$_3$ interface. We find that this interfacial
magnetoresistance exhibits a similar angular dependence to the spin Hall
magnetoresistance observed in ferromagnet/heavy metal bilayers, which has been
so far discussed in the framework of bulk spin Hall effect of heavy metal
layer. The observed magnetoresistance is in qualitative agreement with
theoretical model calculation including both Rashba spin-orbit coupling and
exchange interaction. Our result suggests that magnetic interfaces subject to
spin-orbit coupling can generate a nonnegligible contribution to the spin Hall
magnetoresistance and the interfacial spin-orbit coupling effect is therefore
key to the understanding of various spin-orbit-coupling-related phenomena in
magnetic/non-magnetic bilayers.

###Revealing Controllable Anisotropic Magnetoresistance in Spin Orbit Coupled Antiferromagnet Sr2IrO4|Chengliang Lu,Bin Gao,Haowen Wang,Wei Wang,Songliu Yuan,Shuai Dong,Jun-Ming Liu###

Revealing Controllable Anisotropic Magnetoresistance in Spin Orbit Coupled Antiferromagnet Sr2IrO4. Antiferromagnetic spintronics actively introduces new principles of magnetic
memory, in which the most fundamental spin-dependent phenomena, i.e.
anisotropic magnetoresistance effects, are governed by an antiferromagnet
instead of a ferromagnet. A general scenario of the antiferromagnetic
anisotropic magnetoresistance effects mainly stems from the magnetocrystalline
anisotropy related to spin-orbit coupling. Here we demonstrate magnetic field
driven contour rotation of the fourfold anisotropic magnetoresistance in bare
antiferromagnetic Sr2IrO4/SrTiO3 (001) thin films hosting a strong spin-orbit
coupling induced Jeff=1/2 Mott state. Concurrently, an intriguing minimal in
the magnetoresistance emerges. Through first principles calculations, the
band-gap engineering due to rotation of the Ir isospins is revealed to be
responsible for these emergent phenomena, different from the traditional
scenario where relatively more conductive state was obtained usually when
magnetic field was applied along the magnetic easy axis. Our findings
demonstrate a new efficient route, i.e. via the novel Jeff=1/2 state, to
realize controllable anisotropic magnetoresistance in antiferromagnetic
materials.

###Extreme magnetoresistance induced by Zeeman effect-driven electron-hole compensation and topological protection in MoSi$_2$|M. Matin,R. Mondal,N. Barman,A. Thamizhavel,S. K. Dhar###

Extreme magnetoresistance induced by Zeeman effect-driven electron-hole compensation and topological protection in MoSi$_2$. The magnetoresistance is the magnetic field induced change of electrical
resistivity of a material. Recent studies have revealed extremely large
magnetoresistance in several non-magnetic semimetals, which has been explained
on the basis of either electron-hole compensation or the Fermi surface
topology, or the combination of both. Here, we present a single crystal study
on MoSi$_2$, which exhibits extremely large magnetoresistance, approaching
almost 10$^7$ % at 2 K and 14 T magnetic field. It is found that the
electron-hole compensation level in MoSi$_2$ evolves with magnetic field, which
is resulted from strong Zeeman effect, and found beneficial in boosting the
large non-saturating magnetoresistance. The non-trivial Berry phase in the de
Haas-van Alphen oscillations and the moderate suppression of backward
scattering of the charge carriers lend support for the topological nature of
this semimetal. The ultra-large carrier mobility of the topologically protected
charge carriers reinforces the magnetoresistance of MoSi2 to an unprecedented
large value.

###Spin-flip induced magnetoresistance in positionally disordered organic solids|N. J. Harmon,M. E. Flatté###

Spin-flip induced magnetoresistance in positionally disordered organic solids. A model for magnetoresistance in positionally disordered organic materials is
presented and solved using percolation theory. The model describes the effects
of spin flips on hopping transport by considering the effect of spin dynamics
on an effective density of hopping sites. Faster spin-flip transitions open up
`spin-blocked' pathways to become viable conduction channels and hence produces
magnetoresistance. The magnetoresistance can be found analytically in several
regimes, including when the spin-flip time is slower than the hopping time. The
ratio of hopping time to the hyperfine precession time is a crucial quantity in
determining the shape of magnetoresistance curves. Studies of magnetoresistance
in known systems with controllable positional disorder would provide a
stringent test of this model.

###Hopping magneto-transport via nonzero orbital momentum states and organic magnetoresistance|Alexandre S. Alexandrov,Valentin A. Dediu,Victor V. Kabanov###

Hopping magneto-transport via nonzero orbital momentum states and organic magnetoresistance. In hopping magnetoresistance of doped insulators, an applied magnetic field
shrinks the electron (hole) s-wave function of a donor or an acceptor and this
reduces the overlap between hopping sites resulting in the positive
magnetoresistance quadratic in a weak magnetic field, B. We extend the theory
of hopping magnetoresistance to states with nonzero orbital momenta. Different
from s-states, a weak magnetic field expands the electron (hole) wave functions
with positive magnetic quantum numbers, m > 0, and shrinks the states with
negative m in a wide region outside the point defect. This together with a
magnetic-field dependence of injection/ionization rates results in a negative
weak-field magnetoresistance, which is linear in B when the orbital degeneracy
is lifted. The theory provides a possible explanation of a large low-field
magnetoresistance in disordered pi-conjugated organic materials (OMAR).

###Magnetoresistance in relativistic hydrodynamics without anomalies|Andrew Baumgartner,Andreas Karch,Andrew Lucas###

Magnetoresistance in relativistic hydrodynamics without anomalies. We present expressions for the magnetoconductivity and the magnetoresistance
of a strongly interacting metal in 3+1 dimensions, derivable from relativistic
hydrodynamics. Such an approach is suitable for ultraclean metals with emergent
Lorentz invariance. When this relativistic fluid contains chiral anomalies, it
is known to exhibit longitudinal negative magnetoresistance. We show that
similar effects can arise in non-anomalous relativistic fluids due to the
distinctive gradient expansion. In contrast with a Galilean-invariant fluid,
the resistivity tensor of a dirty relativistic fluid exhibits similar angular
dependence to negative magnetoresistance, even when the constitutive relations
and momentum relaxation rate are isotropic. We further account for the effect
of magnetic field-dependent corrections to the gradient expansion and the
effects of long-wavelength impurities on magnetoresistance. We note that the
holographic D3/D7 system exhibits negative magnetoresistance.

###Magnetoresistance of semi-metals: the case of antimony|Benoît Fauqué,Xiaojun Yang,Wojciech Tabis,Mingsong Shen,Zengwei Zhu,Cyril Proust,Yuki Fuseya,Kamran Behnia###

Magnetoresistance of semi-metals: the case of antimony. Large unsaturated magnetoresistance has been recently reported in numerous
semi-metals. Many of them have a topologically non-trivial band dispersion,
such as Weyl nodes or lines. Here, we show that elemental antimony displays the
largest high-field magnetoresistance among all known semi-metals. We present a
detailed study of the angle-dependent magnetoresistance and use a
semi-classical framework invoking an anisotropic mobility tensor to fit the
data. A slight deviation from perfect compensation and a modest variation with
magnetic field of the components of the mobility tensor are required to attain
perfect fits at arbitrary strength and orientation of magnetic field in the
entire temperature window of study. Our results demonstrate that large orbital
magnetoresistance is an unavoidable consequence of low carrier concentration
and the sub-quadratic magnetoresistance seen in many semi-metals can be
attributed to field-dependent mobility, expected whenever the disorder
length-scale exceeds the Fermi wavelength.

###On the temperature scaling behaviour of the linear magnetoresistance observed in high-temperature superconductors|John Singleton###

On the temperature scaling behaviour of the linear magnetoresistance observed in high-temperature superconductors. An analytical model invoking variations in the charge-carrier density is used
to generate magnetoresistance curves that are almost indistinguishable from
those produced by sophisticated numerical models. This demonstrates that,
though disorder is pivotal in causing linear magnetoresistance, the form of the
magnetoresistance thus generated is insensitive to details of the disorder.
Taken in conjunction with the temperature ($T$) dependence of the zero-field
resistivity, realistic levels of disorder are shown to be sufficient to explain
the linear magnetoresistance and field-$T$ resistance scaling observed in
high-temperature pnictide and cuprate superconductors. Hence, though the
$T$-linear zero-field resistance is a definite signature of the "strange metal"
state of high-temperature superconductors, their linear magnetoresistance and
its scaling is unlikely to be so.

###Spin Hall Magnetoresistance in Metallic Bilayers with In-plane Magnetized Ferromagnets|Łukasz Karwacki,Krzysztof Grochot,Stanisław Łazarski,Witold Skowroński,Jarosław Kanak,Wiesław Powroźnik,Józef Barnaś,Feliks Stobiecki,Tomasz Stobiecki###

Spin Hall Magnetoresistance in Metallic Bilayers with In-plane Magnetized Ferromagnets. We revisit the theory and experiment on spin Hall magnetoresistance (SMR) in
bilayers consisting of a heavy metal (H) coupled to in-plane magnetized
ferromagnetic metal (F), and determine contributions to the magnetoresistance
due to SMR and anisotropic magnetoresistance (AMR) in four different bilayer
systems: W/$\text{Co}_{20}\text{Fe}_{60}\text{B}_{20}$, W/Co,
$\text{Co}_{20}\text{Fe}_{60}\text{B}_{20}$/Pt, and Co/Pt. To do this, the AMR
is explicitly included in the diffusion transport equations in the ferromagnet.
The results allow precise determination of different contributions to the
magnetoresistance, which can play an important role in optimizing prospective
magnetic stray field sensors. They also may be useful in the determination of
spin transport properties of metallic magnetic heterostructures in other
experiments based on magnetoresistance measurements.

###Huge linear magnetoresistance due to open orbits in $γ$-PtBi$_2$|Beilun Wu,Víctor Barrena,Hermann Suderow,Isabel Guillamón###

Huge linear magnetoresistance due to open orbits in $γ$-PtBi$_2$. Some single-crystalline materials present an electrical resistivity which
decreases between room temperature and low temperatures at zero magnetic field
as in a good metal and switches to a nearly semiconductinglike behavior at low
temperatures with the application of a magnetic field. Often, this is
accompanied by a huge and nonsaturating linear magnetoresistance which remains
difficult to explain. Here we present a systematic study of the
magnetoresistance in single-crystal $\gamma$-PtBi$_2$. We observe that the
angle between the magnetic field and the crystalline $c$ axis fundamentally
changes the magnetoresistance, going from a saturating to a nonsaturating
magnetic field dependence. In between, there is one specific angle where the
magnetoresistance is perfectly linear with the magnetic field. We show that the
linear dependence of the nonsaturating magnetoresistance is due to the
formation of open orbits in the Fermi surface of $\gamma$-PtBi$_2$.

###Anomalous linear magnetoresistance in high quality crystalline lead thin films|Yi Liu,Yue Tang,Ziqiao Wang,Chaofei Liu,Cheng Chen,Jian Wang###

Anomalous linear magnetoresistance in high quality crystalline lead thin films. Intriguing novel phenomena in lead films inspire new understanding of quantum
physics, such as quantum size effect and quantum phase transitions etc. The
improvement of the sample quality makes it even more promising to explore the
intrinsic properties in two-dimensional system. In this paper, we show that the
crystalline interfacial striped incommensurate layer can increase the quality
of the lead films and significantly enhance the magnitude of magnetoresistance.
By performing systematic transport measurement, a predominant anomalous linear
magnetoresistance is revealed, and the widely used Parish-Littlewood model and
Abrikosov's explanation fail to describe the observation. Instead, we propose a
new model of linear magnetoresistance based on linear band structure, which
shows a good agreement with the experimental results. Our studies reveal a
novel origin of linear magnetoresistance which may also be helpful to
understand the linear magnetoresistance in other materials with linear
dispersion of electronic structure.

###Anisotropic magnetotransport in LaAlO$_3$/SrTiO$_3$ nanostructures|M. S. Prasad,G. Schmidt###

Anisotropic magnetotransport in LaAlO$_3$/SrTiO$_3$ nanostructures. A number of recent studies indicate that the charge conduction of the
LaAlO$_3$/SrTiO$_3$ interface at low temperature is confined to filaments which
are linked to structural domain walls in the SrTiO$_3$ with drastic
consequences for example for the temperature dependence of local transport
properties. We demonstrate that as a consequences of this current carrying
filaments on the nano-scale the magnetotransport properties of the interface
are highly anisotropic. Our magnetoresistance measurements reveal that the
magnetoresistance in different nanostructures ($<500nm$) is random in magnitude
and sign, respectively. Warming up nanostructures above the structural phase
transition temperature (105K) results in the significant change in MR. Even a
sign change of the magnetoresistance is possible. The results suggest that
domain walls that are differently oriented with respect to the surface exhibit
different respective magnetoresistance and the total magnetoresistance is a
result of a random domain wall pattern formed during the structural phase
transition in the SrTiO$_3$ at cool down.

###Intervalley Tunneling and Crossover from the Positive to Negative Interlayer Magnetoresistance in Quasi-Two-Dimensional Dirac Fermion System with or without Mass Gap|Takao Morinari###

Intervalley Tunneling and Crossover from the Positive to Negative Interlayer Magnetoresistance in Quasi-Two-Dimensional Dirac Fermion System with or without Mass Gap. We theoretically investigate the interlayer magnetoresistance in
quasi-two-dimensional Dirac fermion systems, where the Fermi energy is at the
Dirac point. If there is an intermediate insulating layer that has an overlap
with the wave functions in the Dirac fermion layers, there appears a positive
magnetoresistance regime due to the intervalley tunneling. We show that the
interlayer magnetoresistance can be used to find whether Dirac fermions are
massive or not from the minimum in the interlayer magnetoresistance. As a
specific system, we consider \alphaI under high pressure. We also discuss that
one has to be careful in analyzing the crossover temperature from the positive
to negative magnetoresistance. A simple picture is applied to the crossover in
the zero temperature limit but it does not apply to the data at finite
temperatures. We show that the ratio of the Fermi velocity to the scattering
rate is evaluated from the zero temperature limit of the crossover temperature.

###Topological linear magnetoresistivity and thermoconductivity induced by noncentrosymmetric Berry curvature|Min-Xue Yang,Hai-Dong Li,Wei Luo,Bingfeng Miao,Wei Chen,D. Y. Xing###

Topological linear magnetoresistivity and thermoconductivity induced by noncentrosymmetric Berry curvature. The Berry curvature plays a key role in the magnetic transport of topological
materials. Yet, it is not clear whether the Berry curvature by itself can give
rise to universal transport phenomena with specific scaling behaviors. In this
work, based on the semiclassical Boltzmann formalism and the symmetry analysis,
we show that the noncentrosymmetric distribution of the Berry curvature
generally results in linear magnetoresistivity and thermoconductivity both
exhibiting the B-scaling behavior. We then study such kind of topological
linear magnetoresistivity in the 2D MnBi2Te4 flakes and the 3D
spin-orbit-coupled electron gas, the former showing good agreement with the
experimental observations. The difference between our mechanism and the
conventional anisotropic magnetoresistance is elucidated. Our theory proposes a
universal scenario for the topological linear magnetoresistivity and
thermoconductivity and predicts such effects to occur in various materials,
which also provides a reasonable explanation for the recent observations of
linear magnetoresistivity.

###Non-local magnetoresistance in YIG/Pt nanostructures|Sebastian T. B. Goennenwein,Richard Schlitz,Matthias Pernpeintner,Matthias Althammer,Rudolf Gross,Hans Huebl###

Non-local magnetoresistance in YIG/Pt nanostructures. We study the local and non-local magnetoresistance of thin Pt strips
deposited onto yttrium iron garnet. The local magnetoresistive response,
inferred from the voltage drop measured along one given Pt strip upon
current-biasing it, shows the characteristic magnetization orientation
dependence of the spin Hall magnetoresistance. We simultaneously also record
the non-local voltage appearing along a second, electrically isolated, Pt
strip, separated from the current carrying one by a gap of a few 100 nm. The
corresponding non-local magnetoresistance exhibits the symmetry expected for a
magnon spin accumulation-driven process, confirming the results recently put
forward by Cornelissen et al. [1]. Our magnetotransport data, taken at a series
of different temperatures as a function of magnetic field orientation, rotating
the externally applied field in three mutually orthogonal planes, show that the
mechanisms behind the spin Hall and the non-local magnetoresistance are
qualitatively different. In particular, the non-local magnetoresistance
vanishes at liquid Helium temperatures, while the spin Hall magnetoresistance
prevails.

###Magnetotransport properties of granular oxide-segregated CoPtCr films for applications in future magnetic memory technology|Morgan Williamson,Maxim Tsoi,Pin-Wei Huang,Ganping Ju,Cheng Wang###

Magnetotransport properties of granular oxide-segregated CoPtCr films for applications in future magnetic memory technology. Magnetotransport properties of granular oxide-segregated CoPtCr films were
studied on both macroscopic and microscopic length scales by performing bulk
and point-contact magnetoresistance measurements, respectively. Such a
perpendicular magnetic medium is used in state-of-the-art hard disc drives and
if combined with magnetoresistive phenomena (for read/write operations) may
lead to a novel concept for magnetic recording with high areal density. While
the bulk measurements on the films showed only small variations in dc
resistance as a function of applied magnetic field (magnetoresistance of less
than 0.02 %), the point-contact measurements revealed
giant-magnetoresistance-like changes in resistance with up to 50,000 % ratios.
The observed magnetorestive effect could be attributed to a tunnel
magnetoresistance between CoPtCr grains with different coercivity. The
tunneling picture of electronic transport in our granular medium was confirmed
by the observation of tunneling-like current-voltage characteristics and bias
dependence of magnetoresistance; both the point-contact resistance and
magnetoresistance were found to decrease with the applied dc bias.

###Spin-dependent scattering induced negative magnetoresistance in topological insulator Bi2Te3 nanowires|Biplab Bhattacharyya,Bahadur Singh,R. P. Aloysius,Reena Yadav,Chenliang Su,Hsin Lin,S. Auluck,Anurag Gupta,T. D. Senguttuvan,Sudhir Husale###

Spin-dependent scattering induced negative magnetoresistance in topological insulator Bi2Te3 nanowires. Studies of negative magnetoresistance in novel materials have recently been
in the forefront of spintronic research. Here, we report an experimental
observation of the temperature dependent negative magnetoresistance in Bi2Te3
topological insulator (TI) nanowires at ultralow temperatures (20 mK). We find
a crossover from negative to positive magnetoresistance while increasing
temperature under longitudinal magnetic field. We observe a large negative
magnetoresistance which reaches -22% at 8T. The interplay between negative and
positive magnetoresistance can be understood in terms of the competition
between dephasing and spin-orbit scattering time scales. Based on the
first-principles calculations within a density functional theory framework, we
demonstrate that disorder (substitutional) by Ga+ ion milling process, which is
used to fabricate nanowires, induces local magnetic moments in Bi2Te3 crystal
that can lead to spin-dependent scattering of surface and bulk electrons. These
experimental findings show a significant advance in the nanoscale spintronics
applications based on longitudinal magnetoresistance in TIs. Our experimental
results of large negative longitudinal magnetoresistance in 3D TIs further
indicate that axial anomaly is a universal phenomenon in generic 3D metals.

###Orbital Magnetoresistance in the LaSrCuO System|F. F. Balakirev,I. E. Trofimov,S. Guha,Marta Z. Cieplak,P. Lindenfeld###

Orbital Magnetoresistance in the LaSrCuO System. Measurements of resistivity, Hall effect, and magnetoresistance have been
made on seven c-axis oriented thin-film specimens of La(2-x)Sr(x)CuO(4) with
values of x from 0.048 to 0.275, and one specimen that also contains Nd. The
orbital magnetoresistance is found not to be proportional to the square of the
tangent of the Hall angle except for values of x near 0.15 above about 80K. For
smaller values of x the temperature dependence of the magnetoresistance is
different, but quite similar in the various specimens, in spite of large
differences in resistivity, Hall coefficient, and Hall angle.

###Circuit model for spin-bottleneck resistance in magnetic-tunnel-junction devices|T. Jungwirth,A. H. MacDonald###

Circuit model for spin-bottleneck resistance in magnetic-tunnel-junction devices. Spin-bottlenecks are created in magnetic-tunnel-junction devices by spatial
inhomogeneity in the relative resistances for up and down spins. We propose a
simple electrical circuit model for these devices which incorporates
spin-bottleneck effects and can be used to calculate their overall resistance
and magnetoresistance. The model permits a simple understanding of the
dependence of device magnetoresistance on spin diffusion lengths, tunneling
magnetoresistance, and majority and minority spin resistivities in the
ferromagnetic electrodes. The circuit model is in a good quantitative agreement
with detailed transport calculations.

###Evidence of Vortices on the Insulating Side of the Superconductor-Insulator Transition|N. Markovic,A. M. Mack,G. Martinez-Arizala,C. Christiansen,A. M. Goldman###

Evidence of Vortices on the Insulating Side of the Superconductor-Insulator Transition. The magnetoresistance of ultrathin insulating films of Bi has been studied
with magnetic fields applied parallel and perpendicular to the plane of the
sample. Deep in the strongly localized regime, the magnetoresistance is
negative and independent of field orientation. As film thicknesses increase,
the magnetoresistance becomes positive, and a difference between values
measured in perpendicular and parallel fields appears, which is a linear
function of the magnetic field and is positive. This is not consistent with the
quantum interference picture. We suggest that it is due to vortices present on
the insulating side of the superconductor-insulator transition.

###Spin polarized tunneling in the half-metallic ferromagnet La0.7Sr0.3MnO3: experiment and theory|P. Raychaudhuri,K. Sheshadri,P. Taneja,S. Bandyopadhyay,P. Ayyub,A. K. Nigam,R. Pinto###

Spin polarized tunneling in the half-metallic ferromagnet La0.7Sr0.3MnO3: experiment and theory. The magnetoresistance (MR) in polycrystalline colossal magnetoresistive
compounds follows a behavior different from single crystals below the
ferromagnetic transition temperature. This difference is usually attributed to
spin polarized tunneling at the grain boundaries of the polycrystalline sample.
Here we derive a theoretical expression for the contribution of spin polarized
tunneling to the magnetoresistance in granular ferromagnetic systems under the
mean field approximation. We apply this model to our experimental data on the
half metallic ferromagnet La0.7Sr0.3MnO3, and find that the theoretical
predictions agree quite well with the observed dependence of the spin polarized
MR on the spontaneous magnetization.

###The magnetoresistance in GdNi: Magnetic-polaronic-like effect near Curie temperature and low temperature sign reversal|R. Mallik,E. V. Sampathkumaran,P. L. Paulose,V. Nagarajan###

The magnetoresistance in GdNi: Magnetic-polaronic-like effect near Curie temperature and low temperature sign reversal. The results of magnetoresistance ($\Delta \rho /\rho$)measurements in GdNi,
in the temperature range 4.2 to 300 K are reported. The sign of $\Delta \rho
/\rho $ above the Curie temperature (Tc= 70 K) is negative and its magnitude in
a magnetic field of 80kOe grows with decreasing temperature below 150 K with a
peak value of about -20% at Tc. These features, qualitatively resembling those
in giant magnetoresistance systems (manganates), are attributed to the
formation of some kind of magnetic polarons induced by Gd. The
magnetoresistance changes sign below 12 K which is attributed to subtle band
structure effects.

###Magnetic Domain Walls in Double Exchange Materials|Luis Brey###

Magnetic Domain Walls in Double Exchange Materials. We study magnetic domain walls in double exchange materials. The domain wall
width is proportional to the square root of the stiffness. In the double
exchange model the stiffness has two terms: the kinetic energy and the Hartree
term. The kinetic energy term comes from the decrease of the tunneling
amplitude in the domain wall region. The Hartree term appears only in double
exchange materials and it comes from the connection between band-width and
magnetization. We also calculate the low-field magnetoresistance associated
with the existence of magnetic domains. We find a magnetoresistance of 1-2%.
The magnetoresistance c an be considerably larger in magnetically constrained
nanocontacts.

###Spin dependent scattering of a domain-wall of controlled size|J. -E. Wegrowe,A. Comment,Y. Jaccard,J. -Ph. Ansermet,N. M. Dempsey,J-P. Nozieres###

Spin dependent scattering of a domain-wall of controlled size. Magnetoresistance measurements in the CPP geometry have been performed on
single electrodeposited Co nanowires exchange biased on one side by a sputtered
amorphous GdCo layer. This geometry allows the stabilization of a single domain
wall in the Co wire, the thickness of which can be controlled by an external
magnetic field. Comparing magnetization, resistivity, and magnetoresistance
studies of single Co nanowires, of GdCo layers, and of the coupled system,
gives evidence for an additional contribution to the magnetoresistance when the
domain wall is compressed by a magnetic field. This contribution is interpreted
as the spin dependent scattering within the domain wall when the wall thickness
becomes smaller than the spin diffusion length.

###Analysis of negative magnetoresistance. Statistics of closed paths. II. Experiment|G. M. Minkov,S. A. Negashev,O. E. Rut,A. V. Germanenko,O. I. Khrykin,V. I. Shashkin,V. M. Danil'tsev###

Analysis of negative magnetoresistance. Statistics of closed paths. II. Experiment. It is shown that a new kind of information can be extracted from the Fourier
transform of negative magnetoresistance in 2D semiconductor structures. The
procedure proposed provides the information on the area distribution function
of closed paths and on the area dependence of the average length of closed
paths. Based on this line of attack the method of analysis of the negative
magnetoresistance is suggested. The method has been used to process the
experimental data on negative magnetoresistance in 2D structures with different
relations between the momentum and phase relaxation times. It is demonstrated
this fact leads to distinction in the area dependence of the average length of
closed paths.

###Negative in-plane and out-of-plane magnetoresistivities in optimally doped Bi2Sr2Ca0.8Y0.2Cu2O8+d single crystal|D. Thopart,A. Wahl,A. Maignan,Ch. Simon###

Negative in-plane and out-of-plane magnetoresistivities in optimally doped Bi2Sr2Ca0.8Y0.2Cu2O8+d single crystal. Both the in-plane and out-of-plane magnetoresistivities have been measured in
the normal state of an optimally doped Bi2Sr2Ca0.8Y0.2Cu2O8+d single crystal
with a magnetic field applied parallel and perpendicular to the CuO2 planes.
  Whatever the magnetic field and the current directions are, a negative
magnetoresistivity is obtained over a wide range of temperature above the
critical temperature Tc. For the in-plane and out-of-plane measurements, the
non-dominant orbital contribution to magnetoresistivity suggests the
substantial role played by the spin degrees of freedom.

###Response of the two-dimensional electron gas of AlGaAs/GaAs heterostructures to parallel magnetic field|V. S. Khrapai,E. V. Deviatov,A. A. Shashkin,V. T. Dolgopolov###

Response of the two-dimensional electron gas of AlGaAs/GaAs heterostructures to parallel magnetic field. We study the transport properties of the two-dimensional electron gas in
AlGaAs/GaAs heterostructures in parallel to the interface magnetic fields at
low temperatures. The magnetoresistance in the metallic phase is found to be
positive and weakly anisotropic with respect to the orientation of the in-plane
magnetic field and the current through the sample. At low electron densities
($n_s< 5\times 10^{10}$ cm$^{-2}$) the experimental data can be described
adequately within spin-related approach while at high $n_s$ the
magnetoresistance mechanism changes as inferred from $n_s$-independence of the
normalized magnetoresistance.

###C-axis negative magnetoresistance and upper critical field of Bi2Sr2CaCu2O8|V. N. Zavaritsky,M. Springford,A. S. Alexandrov###

C-axis negative magnetoresistance and upper critical field of Bi2Sr2CaCu2O8. The out-of-plane resistance and the resistive upper critical field of
BSCCO-2212 single crystals with Tc=91-93 K have been measured in magnetic
fields up to 50 T over a wide temperature range. The results are characterised
by a positive linear magnetoresistance in the superconducting state and a
negative linear magnetoresistance in the normal state. The zero field normal
state c-axis resistance, the negative linear normal state magnetoresistance,
and the divergent upper critical field Hc2(T)are explained in the framework of
the bipolaron theory of superconductivity.

###Magnetotransport in lateral superlattices with small-angle impurity scattering: Low-field magnetoresistance|A. D. Mirlin,E. Tsitsishvili,P. Woelfle###

Magnetotransport in lateral superlattices with small-angle impurity scattering: Low-field magnetoresistance. An analytical study of the low-field magnetoresistance of a two-dimensional
electron gas subject to a weak periodic modulation is presented. We assume
small-angle impurity scattering characteristic for high-mobility semiconductor
heterostructures. It is shown that the condition for existence of the strong
low-field magnetoresistance induced by so-called channeled orbits is
$\eta^{3/2}ql\gg 1$, where $\eta$ and $q$ are the strength and the wave vector
of the modulation, and $l$ is the transport mean free path. Under this
condition, the magnetoresistance scales as $\eta^{7/2}$.

###Magnetoresistance of single-domain ferromagnetic particles|J. Aumentado,V. Chandrasekhar###

Magnetoresistance of single-domain ferromagnetic particles. We have performed magnetoresistance measurements on single-domain, submicron
elliptical Ni particles using nonmagnetic probes in a four probe geometry at
liquid helium temperatures. In the smallest particles, the magnetoresistance
shows sharp jumps which are associated with the switching of individual
domains. Using an anisotropic magnetoresistance model, we can reconstruct
hysteresis loops of the normalized magnetization. The remanent magnetization in
zero applied magnetic field is typically 15 percent less than the saturation
magnetization. This relaxation of the magnetization may be due to surface
effects or crystal grain structure in the particles.

###Interlayer exchange coupling and giant magnetoresistance in Fe/V (001) superlattices|A. Broddefalk,R. Mathieu,P. Nordblad,P. Blomqvist,R. Wäppling,J. Lu,E. Olsson###

Interlayer exchange coupling and giant magnetoresistance in Fe/V (001) superlattices. Magnetization and magnetoresistivity studies of Fe/V (001) superlattices are
reported. The first giant magnetoresistance peak with respect to the vanadium
and iron layer thicknesses is investigated. The interlayer antiferromagnetic
coupling strength is found to show a peak at a vanadium layer thickness of
  13 atomic monolayers ($\approx$ 20 \AA) with a full width at half maximum of
about 2 monolayers. The antiferromagnetic coupling shows a maximum at an iron
layer thickness of about 6 monolayers ($\approx$ 9 \AA) for series of
superlattices with vanadium thicknesses around 13 monolayers. The magnitude of
the giant magnetoresistance shows a similar variation as the antiferromagnetic
coupling strength.

###Coherent vs incoherent interlayer transport in layered metals|J. Wosnitza,J. Hagel,J. S. Qualls,J. S. Brooks,E. Balthes,D. Schweitzer,J. A. Schlueter,U. Geiser,J. Mohtasham,R. W. Winter,G. L. Gard###

Coherent vs incoherent interlayer transport in layered metals. The magnetic-field, temperature, and angular dependence of the interlayer
magnetoresistance of two different quasi-two-dimensional (2D) organic
superconductors is reported. For $\kappa$-(BEDT-TTF)$_2$I$_3$ we find a
well-resolved peak in the angle-dependent magnetoresistance at $\Theta =
90^\circ$ (field parallel to the layers). This clear-cut proof for the coherent
nature of the interlayer transport is absent for
$\beta$''-(BEDT-TTF)$_2$SF$_5$CH$_2$CF$_2$SO$_3$. This and the non-metallic
behavior of the magnetoresistance suggest an incoherent quasiparticle motion
for the latter 2D metal.

###A comparative study of the magnetic and magnetotransport properties between a metallic (x=0.6) and a semiconducting (x=0.2) member of the solid solution LaNixCo1-xO3|J. Androulakis,N. Katsarakis,Z. Viskadourakis,J. Giapintzakis###

A comparative study of the magnetic and magnetotransport properties between a metallic (x=0.6) and a semiconducting (x=0.2) member of the solid solution LaNixCo1-xO3. We present a comparative study of both the magnetic and magnetotransport
properties for two members of the perovskite solid solution LaNixCo1-xO3
(x=0.2, 0.6) located on opposite sides of the chemically induced
metal-to-insulator transition. LaNi0.6Co0.4O3 exhibits metallic behavior and
small but negative magnetoresistance, whereas LaNi0.2Co0.8O3 exhibits
semiconducting behavior and giant negative magnetoresistance at low
temperatures. On the other hand, we observe pronounced similarities in the
magnetic properties of both compounds. A consistent explanation regarding the
origin of the magnetoresistance in the two members of the solid solution is
provided.

###Giant magnetoresistance in quantum magnetic contacts|L. R. Tagirov,B. P. Vodopyanov,B. M. Garipov###

Giant magnetoresistance in quantum magnetic contacts. We present calculations of quantized conductance and magnetoresistance in
nanosize point contacts between two ferromagnetic metals. When conductance is
open for only one conduction electrons spin-projection, the magnitude of
magnetoresistance is limited by the rate of conduction electron spin-reversal
processes. For the case when both spin-channels contribute to the conductance
we analyze the influence of the point contact cross-section asymmetry on the
giant megnetoresistance. Recent experiments on magnetoresistance of magnetic
point contacts are discussed in the framework of the developed theory.

###Magnetoresistance of a 2D electron gas caused by electron interactions in the transition from the diffusive to the ballistic regime|L. Li,Y. Y. Proskuryakov,A. K. Savchenko,E. H. Linfield,D. A. Ritchie###

Magnetoresistance of a 2D electron gas caused by electron interactions in the transition from the diffusive to the ballistic regime. On a high-mobility 2D electron gas we have observed, in strong magnetic
fields (omega_{c} tau > 1), a parabolic negative magnetoresistance caused by
electron-electron interactions in the regime of k_{B} T tau / hbar ~ 1, which
is the transition from the diffusive to the ballistic regime. From the
temperature dependence of this magnetoresistance the interaction correction to
the conductivity delta sigma_{xx}^{ee}(T) is obtained in the situation of a
long-range fluctuation potential and strong magnetic field. The results are
compared with predictions of the new theory of interaction-induced
magnetoresistance.

###Magnetoresistance through spin polarized p-states|Nikos Papanikolaou###

Magnetoresistance through spin polarized p-states. We present a theoretical study of the ballistic magnetoresistance in Ni
contacts using first-principles, atomistic electronic-structure calculations.
In particular we investigate the role of defects in the contact region in order
to explain the recently observed spectacular magnetoresistance ratio. Our
results predict that possible presence of spin polarized oxygen in the contact
region, could explain conductance changes by an order of magnitude. Electronic
transport essentially occurs through spin-polarized oxygen p states, and this
mechanism gives a much higher magnetoresistance than that obtained assuming
clean atomically sharp domain walls alone.

###Unconventional magnetoresistance in long InSb nanowires|S. V. Zaitsev-Zotov,Yu. A. Kumzerov,Yu. A. Firsov,P. Monceau###

Unconventional magnetoresistance in long InSb nanowires. Magnetoresistance in long correlated nanowires of degenerate semiconductor
InSb in asbestos matrix (wire diameter of around 5 nm, length 0.1 - 1 mm) is
studied over temperature range 2.3 - 300 K. At zero magnetic field the electric
conduction $G$ and the current-voltage characteristics of such wires obey the
power laws $G\propto T^\alpha$, $I\propto V^\beta$, expected for
one-dimensional electron systems. The effect of magnetic field corresponds to a
20% growth of the exponents $\alpha$, $\beta$ at H=10 T. The observed
magnetoresistance is caused by the magnetic-field-induced breaking of the
spin-charge separation and represents a novel mechanism of magnetoresistance.

###Very large magnetoresistance in lateral ferromagnetic (Ga,Mn)As wires with nanoconstrictions|C. Ruester,T. Borzenko,C. Gould,G. Schmidt,L. W. Molenkamp,X. Liu,T. J. Wojtowicz,J. K. Furdyna,Z. G. Yu,M. E. Flatte###

Very large magnetoresistance in lateral ferromagnetic (Ga,Mn)As wires with nanoconstrictions. We have fabricated (Ga,Mn)As nanostructures in which domain walls can be
pinned by sub-10 nm constrictions. Controlled by shape anisotropy, we can
switch the regions on either side of the constriction to either parallel or
antiparallel magnetization. All samples exhibit a positive magnetoresistance,
consistent with domain-wall trapping. For metallic samples we find a
magnetoresistance up to 8%, which can be understood from spin accumulation. In
samples where, due to depletion at the constriction, a tunnel barrier is
formed, we observe a magnetoresistance of up to 2000 %.

###Fourfold oscillations and anomalous magnetic irreversibility of magnetoresistance in the non-metallic regime of Pr1.85Ce0.15CuO4|P. Fournier,M. -E. Gosselin,S. Savard,J. Renaud,I. Hetel,P. Richard,G. Riou###

Fourfold oscillations and anomalous magnetic irreversibility of magnetoresistance in the non-metallic regime of Pr1.85Ce0.15CuO4. Using magnetoresistance measurements as a function of applied magnetic field
and its direction of application, we present sharp angular-dependent
magnetoresistance oscillations for the electron-doped cuprates in their
low-temperature non-metallic regime. The presence of irreversibility in the
magnetoresistance measurements and the related strong anisotropy of the field
dependence for different in-plane magnetic field orientations indicate that
magnetic domains play an important role for the determination of electronic
properties. These domains are likely related to the stripe phase reported
previously in hole-doped cuprates.

###Weak localization and antilocalization in semiconducting polymer sandwich devices|Ö. Mermer,M. Wohlgenannt,G. Veeraraghavan,T. L. Francis###

Weak localization and antilocalization in semiconducting polymer sandwich devices. We have performed magnetoresistance measurements on polyfluorene sandwich
devices in weak magnetic fields as a function of applied voltage, device
temperature (10K to 300K), film thickness and electrode materials. We observed
either negative or positive magnetoresistance, dependent mostly on the applied
voltage, with a typical magnitude of several percent. The shape of the
magnetoresistance curve is characteristic of weak localization and
antilocalization. Using weak localization theory, we find that the
phase-breaking length is relatively large even at room temperature, and
spin-orbit interaction is a function of the applied electric field.

###Spin injection across magnetic/non-magnetic interfaces with finite magnetic layers|Alexander Khaetskii,J. Carlos Egues,Daniel Loss,Charles Gould,Georg Schmidt,Laurens W. Molenkamp###

Spin injection across magnetic/non-magnetic interfaces with finite magnetic layers. We have reconsidered the problem of spin injection across
ferromagnet/non-magnetic-semiconductor (FM/NMS) and
dilute-magnetic-semiconductor/non-magnetic-semiconductor interfaces, for
structures with \textit{finite} magnetic layers (FM or DMS). By using
appropriate physical boundary conditions, we find expressions for the
resistances of these structures which are in general different from previous
results in the literature. When the magnetoresistance of the contacts is
negligible, we find that the spin-accumulation effect alone cannot account for
the $d$ dependence observed in recent magnetoresistance data. In a limited
parameter range, our formulas predict a strong $d$ dependence arising from the
magnetic contacts in systems where their magnetoresistances are sizable.

###Large negative magnetoresistance in thiospinel CuCrZrS4|Takao Furubayashi,Hiroyuki Suzuki,Nami Kobayashi,Shoichi Nagata###

Large negative magnetoresistance in thiospinel CuCrZrS4. We report on large negative magnetoresistance observed in ferromagnetic
thiospinel compound CuCrZrS$_{4}$. Electrical resistivity increased with
decreasing temperature according to the form proportional to
$\textrm{exp}(T_{0}/T)^{1/2} $, derived from variable range hopping with strong
electron-electron interaction. Resistivity under magnetic fields was expressed
by the same form with the characteristic temperature T0 decreasing with
increasing magnetic field. Magnetoresistance ratio $\rho (T,0)/\rho(T,H)$ is
1.5 at 100 K for H=90 kOe and increases divergently with decreasing temperature
reaching 80 at 16 K. Results of magnetization measurements are also presented.
Possible mechanism of the large magnetoresistance is discussed.

###Magnetoresistance of a semiconducting magnetic wire with domain wall|V. K. Dugaev,J. Barnas,J. Berakdar,V. I. Ivanov,W. Dobrowolski,V. F. Mitin###

Magnetoresistance of a semiconducting magnetic wire with domain wall. We investigate theoretically the influence of the spin-orbit interaction of
Rashba type on the magnetoresistance of a semiconducting ferromagnetic
nanostructure with a laterally constrained domain wall. The domain wall is
assumed sharp (on the scale of the Fermi wave length of the charge carriers).
It is shown that the magnetoresistance in such a case can be considerably
large, which is in a qualitative agreement with recent experimental
observations. It is also shown that spin-orbit interaction may result in an
increase of the magnetoresistance. The role of localization corrections is also
briefly discussed.

###Weak ferromagnetism of La_{1.99}Sr_{0.01}CuO_4 thin films: evidence for removal of corrugation in CuO_2 plane by epitaxial strain|I. Tsukada###

Weak ferromagnetism of La_{1.99}Sr_{0.01}CuO_4 thin films: evidence for removal of corrugation in CuO_2 plane by epitaxial strain. The weak ferromagnetism of La_{1.99}Sr_{0.01}CuO_4 epitaxial thin films is
investigated using magnetoresistance measurement. While a steplike negative
magnetoresistance associated with the weak ferromagnetic transition is clearly
observed in the films grown on YAlO_3(001), it is notably suppressed in the
films grown on SrTiO_3(100) and
(LaAlO_3)_{0.3}(SrAl_{0.5}Ta_{0.5}O_3)_{0.7}(100), and almost disappears in
films grown on LaSrAlO_4(001). The strong suppression of the steplike
magnetoresistance provides evidence that the CuO_2 planes are much less
corrugated in thin films grown on tetragonal substrates, particularly on
LaSrAlO_4(001), than in bulk crystals.

###Magnetoresistance of Junctions made of Underdoped YBCO Separated by a Ga-doped YBCO Barrier|L. Shkedy,G. Koren,E. Polturak###

Magnetoresistance of Junctions made of Underdoped YBCO Separated by a Ga-doped YBCO Barrier. We report magnetoresistance measurements of ramp type
superconductor-normal-superconductor (SNS) junctions. The junctions consist of
underdoped $YBa_{2}Cu_{3}O_y$ (YBCO) electrodes separated by a barrier of
$YBa_{2}Cu_{2.6}Ga_{0.4}O_y$. We observe a large positive magnetoresistance,
linear in the field. We suggest that this unusual magnetoresistance originates
in the field dependence of the proximity effect. Our results indicate that in
underdoped YBCO/N/YBCO SNS structures, the proximity effect does not exhibit
the anomalously long range found in optimally doped YBCO structures. From our
data we obtain the diffusion coefficient and relaxation time of quasiparticles
in underdoped YBCO.

###Giant enhancement of room temperature magnetoresistance in La_{0.67}Sr_{0.33}MnO_{3}/Nd_{0.67}Sr_{0.33}MnO_{3} multilayers|Soumik Mukhopadhyay,I. Das###

Giant enhancement of room temperature magnetoresistance in La_{0.67}Sr_{0.33}MnO_{3}/Nd_{0.67}Sr_{0.33}MnO_{3} multilayers. The metal-insulator transition temperature in CMR manganites has been altered
and brought close to the room temperature by preparing
La$_{0.67}$Sr$_{0.33}$MnO$_{3}$ (LSMO)/ Nd$_{0.67}$Sr$_{0.33}$MnO$_{3}$ (NSMO)
multilayers with ultra thin individual layers of LSMO and NSMO. The LSMO/NSMO
multilayers with ultra thin individual layers of thickness of about $10\AA$
exhibits 150% magnetoresistance at 270 K whereas LSMO/NSMO multilayers with
moderate individual layer thickness of about $40\AA$ each exhibits a mere 15%
magnetoresistance at the same temperature. We have shown that the reduction in
thickness of the individual layers leads to increased spin fluctuation which
results in the enhancement of magnetoresistance.

###Resonant tunneling magnetoresistance in epitaxial metal-semiconductor heterostructures|J. Varalda,A. J. A. de Oliveira,D. H. Mosca,J. -M. George,M. Eddrief,M. Marangolo,V. H. Etgens###

Resonant tunneling magnetoresistance in epitaxial metal-semiconductor heterostructures. We report on resonant tunneling magnetoresistance via localized states
through a ZnSe semiconducting barrier which can reverse the sign of the
effective spin polarization of tunneling electrons. Experiments performed on
Fe/ZnSe/Fe planar junctions have shown that positive, negative or even its
sign-reversible magnetoresistance can be obtained, depending on the bias
voltage, the energy of localized states in the ZnSe barrier and spatial
symmetry. The averaging of conduction over all localized states in a junction
under resonant condition is strongly detrimental to the magnetoresistance.

###Low temperature magnetoresistance of dirty thin films and quantum wires near a parallel-field-tuned superconducting quantum phase transition|N. Shah,A. V. Lopatin,V. M. Vinokur###

Low temperature magnetoresistance of dirty thin films and quantum wires near a parallel-field-tuned superconducting quantum phase transition. We study the low temperature magnetoresistance of dirty thin films and
quantum wires close to a quantum phase transition from a superconducting to
normal state, induced by applying a parallel magnetic field. We find that the
different corrections (Aslamazov-Larkin, density of states and Maki-Thompson)
to the normal state conductivity, coming from the superconducting pair
fluctuations, are of the same order at zero temperature. There are three
regimes at finite temperatures. In the "quantum" regime, which essentially
shows a zero-temperature-like behavior we find a negative magnetoresistance.
Since in the "classical" regime the correction is positive, we predict a
non-monotonic magnetoresistance at higher temperatures.

###Anomalous magnetoresistance behavior of CoFe nano-oxide spin valves at low temperatures|J. Ventura,J. B. Sousa,M. A. Salgueiro da Silva,P. P. Freitas,A. Veloso###

Anomalous magnetoresistance behavior of CoFe nano-oxide spin valves at low temperatures. We report magnetoresistance curves of CoFe nano-oxide specular spin valves of
MnIr/CoFe/nano-oxidized CoFe/CoFe/Cu/CoFe/nano-oxidized CoFe/Ta at different
temperatures from 300 to 20 K. We extend the Stoner-Wolfarth model of a common
spin valve to a specular spin valve, introducing the separation of the pinned
layer into two sublayers and their magnetic coupling across the nano-oxide. We
study the effect of different coupling/exchange (between the antiferromagnetic
layer and the bottom sublayer) field ratios on the magnetization and
magnetoresistance, corresponding with the experimentally observed anomalous
bumps in low temperature magnetoresistance curves.

###Low density spin-polarized transport in 2D semiconductor structures: The enigma of temperature dependent magnetoresistance of Si MOSFETs in an in-plane applied magnetic field|S. Das Sarma,E. H. Hwang###

Low density spin-polarized transport in 2D semiconductor structures: The enigma of temperature dependent magnetoresistance of Si MOSFETs in an in-plane applied magnetic field. The temperature dependence of 2D magnetoresistance in an applied in-plane
magnetic field is theoretically considered for electrons in Si MOSFETs within
the screening theory for long-range charged impurity scattering limited carrier
transport. In agreement with recent experimental observations we find an
essentially temperature independent magnetoresistivity for carrier densities
well into the 2D metallic regime due to the field-induced lifting of spin and,
perhaps, valley degeneracies. In particular the metallic temperature dependence
of the ballistic magnetoresistance is strongly suppressed around the
zero-temperature critical magnetic field ($B_s$) for full spin-polarization,
with the metallic temperature dependence strongest at B=0, weakest around $B
\sim B_s$, and intermediate at $B \gg B_s$.

###Classical magnetotransport of inhomogeneous conductors|Meera M. Parish,Peter B. Littlewood###

Classical magnetotransport of inhomogeneous conductors. We present a model of magnetotransport of inhomogeneous conductors based on
an array of coupled four-terminal elements. We show that this model generically
yields non-saturating magnetoresistance at large fields. We also discuss how
this approach simplifies finite-element analysis of bulk inhomogeneous
semiconductors in complex geometries. We argue that this is an explanation of
the observed non-saturating magnetoresistance in silver chalcogenides and
potentially in other disordered conductors. Our method may be used to design
the magnetoresistive response of a microfabricated array.

###A room-temperature polymeric spin-valve|Sayani Majumdar,Himadri S. Majumdar,Reino Laiho,Ronald Osterbacka###

A room-temperature polymeric spin-valve. We report giant magnetoresistance up to 150 percent at low bias current and
low temperature as well as room temperature magnetoresistance in polymeric
spin-valves having the structure LSMO/conjugated polymer/Co. The conjugated
polymers, regiorandom and regioregular P3HT were used as the spacer materials.
We observed an asymmetric bias voltage dependence of different devices and
additional, hitherto unseen, peaks in MR vs. magnetic field plot with low bias
currents measurements that we attribute to local magnetic moments due to
spin-trapping in the defects in the spacer material. Also, various spacer
thicknesses led to variation of magnetoresistance within a certain temperature
range.

###Magnetoresistance oscillations in GaAs/AlGaAs superlattices subject to in-plane magnetic fields|L. Smrčka,P. Vašek,P. Svoboda,N. A. Goncharuk,O. Pacherová,Yu. Krupko,Y. Sheikin###

Magnetoresistance oscillations in GaAs/AlGaAs superlattices subject to in-plane magnetic fields. The MBE-grown GaAs/AlGaAs superlattice with Si-doped barriers has been used
to study a 3D-2D transition under the influence of the in-plane component of
applied magnetic field. The longitudinal magnetoresistance data measured in
tilted magnetic fields have been interpreted in terms of a simple tight-binding
model. The data provide values of basic parameters of the model and make it
possible to reconstruct the superlattice Fermi surface and to calculate the
density of states for the lowest Landau subbands. Positions of van Hove
singularities in the DOS agree excellently with magnetoresistance oscillations,
confirming that the model describes adequately the magnetoresistance of
strongly coupled semiconductor superlattices.

###Negative differential conductance and magnetoresistance oscillations due to spin accumulation in ferromagnetic double-island devices|Ireneusz Weymann,Jozef Barnas###

Negative differential conductance and magnetoresistance oscillations due to spin accumulation in ferromagnetic double-island devices. Spin-dependent electronic transport in magnetic double-island devices is
considered theoretically in the sequential tunneling regime. Electric current
and tunnel magnetoresistance are analyzed as a function of the bias voltage and
spin relaxation time in the islands. It is shown that the interplay of spin
accumulation on the islands and charging effects leads to periodic modification
of the differential conductance and tunnel magnetoresistance. For a
sufficiently long spin relaxation time, the modulations are associated with
periodic oscillations of the sign of both the tunnel magnetoresistance and
differential conductance.

###Weak localisation magnetoresistance and valley symmetry in graphene|E. McCann,K. Kechedzhi,Vladimir I. Fal'ko,H. Suzuura,T. Ando,B. L. Altshuler###

Weak localisation magnetoresistance and valley symmetry in graphene. Due to the chiral nature of electrons in a monolayer of graphite (graphene)
one can expect weak antilocalisation and a positive weak-field
magnetoresistance in it. However, trigonal warping (which breaks p/-p symmetry
of the Fermi line in each valley) suppresses antilocalisation, while
inter-valley scattering due to atomically sharp scatterers in a realistic
graphene sheet or by edges in a narrow wire tends to restore conventional
negative magnetoresistance. We show this by evaluating the dependence of the
magnetoresistance of graphene on relaxation rates associated with various
possible ways of breaking a 'hidden' valley symmetry of the system.

###Magnetoresistance of UPt3|T. M. Lippman,J. P. Davis,H. Choi,J. Pollanen,W. P. Halperin###

Magnetoresistance of UPt3. We have performed measurements of the temperature dependence of the
magnetoresistance up to 9 T in bulk single crystals of UPt3 with the magnetic
field along the b axis, the easy magnetization axis. We have confirmed previous
results for transverse magnetoresistance with the current along the c axis, and
report measurements of the longitudinal magnetoresistance with the current
along the b axis. The presence of a linear term in both cases indicates broken
orientational symmetry associated with magnetic order. With the current along
the c axis the linear term appears near 5 K, increasing rapidly with decreasing
temperature. For current along the b axis the linear contribution is negative.

###Illumination-induced changes of the Fermi surface topology in three-dimensional superlattices|N. A. Goncharuk,L. Smrcka,P. Svoboda,P. Vasek,J. Kucera,Yu. Krupko,W. Wegscheider###

Illumination-induced changes of the Fermi surface topology in three-dimensional superlattices. The magnetoresistance of the MBE-grown GaAs/AlGaAs superlattice with Si-doped
barriers has been measured in tilted magnetic fields in the as-grown state, and
after brief illumination by a red-light diode at low temperature, T is
approximately 0.3 K. A remarkable illumination-induced modification of
magnetoresistance curves has been observed, which indicates a significant
change of the superlattice Fermi surface topology. Analysis of
magnetoresistance data in terms of the tight-binding model reveals that not
only electron concentration and mobility have been increased by illumination,
but also the coupling among 2D electron layers in neighboring quantum wells has
been reduced.

###Giant magnetoresistance in nanoscale ferromagnetic heterocontacts|A. N. Useinov,R. G. Deminov,L. R. Tagirov,G. Pan###

Giant magnetoresistance in nanoscale ferromagnetic heterocontacts. A quasiclassical theory of giant magnetoresistance in nanoscale point
contacts between different ferromagnetic metals is developed. The contacts were
sorted by three types of mutual positions of the conduction spin-subband
bottoms which are shifted one against another by the exchange interaction. A
model of linear domain wall has been used to account for the finite contact
length. The magnetoresistance is plotted against the size of the nanocontact.
In heterocontacts the magnetoresistance effect turned out to be not only
negative, as usual, but can be positive as well. Relevance of the results to
existing experiments on GMR in point heterocontacts is discussed.

###Hall magnetoresistivity response under Microwave excitation revisited|Jesus Inarrea###

Hall magnetoresistivity response under Microwave excitation revisited. We theoretically analyzed the microwave-induced modification of the Hall
magnetoresistivity in high mobility two-dimensional electron systems. These
systems present diagonal magnetoresistivity oscillations and zero-resistance
states when are subjected to microwave radiation. The most surprising
modification of the Hall magnetoresistivity is a periodic reduction which
correlates with a periodic increase in the diagonal resistivity. We present a
model that explains the experimental results considering that radiation affects
directly only the diagonal resistivity and the observed Hall resistivity
changes are coming from the tensor relationship between both of them.

###Size Effects in the Magnetoresistance of Graphite: Absence of Magnetoresistance in Micrometer size Samples|J. C. González,M. Muñoz,N. García,J. Barzola-Quiquia,D. Spoddig,K. Schindler,P. Esquinazi###

Size Effects in the Magnetoresistance of Graphite: Absence of Magnetoresistance in Micrometer size Samples. We present a study of the magnetoresistance of highly oriented pyrolytic
graphite (HOPG) as a function of the sample size. Our results show
unequivocally that the magnetoresistance reduces with the sample size even for
samples of hundreds of micrometers size. This sample size effect is due the
large mean free path and Fermi wavelength of carriers in graphite and may
explain the observed practically absence of magnetoresistance in micrometer
confined small graphene samples where quantum effects should be at hand. These
were not taken into account in the literature yet and ask for a revision of
experimental and theoretical work on graphite.

###Nonresonant microwave absorption in epitaxial La-Sr-Mn-O films and its relation to colossal magnetoresistance|M. Golosovsky,P. Monod,P. K. Muduli,R. C. Budhani,L. Mechin,P. Perna###

Nonresonant microwave absorption in epitaxial La-Sr-Mn-O films and its relation to colossal magnetoresistance. We study magnetic-field-dependent nonresonant microwave absorption and
dispersion in thin La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ films and show that it
originates from the colossal magnetoresistance. We develop the model for
magnetoresistance of a thin ferromagnetic film in oblique magnetic field. The
model accounts fairly well for our experimental findings, as well as for
results of other researchers. We demonstrate that nonresonant microwave
absorption is a powerful technique that allows contactless measurement of
magnetic properties of thin films, including magnetoresistance, anisotropy
field and coercive field.

###Electric Field Tuned Dimensional Crossover in Ar-Irradiated SrTiO3|J. H. Ngai,Y. Segal,F. J. Walker,S. Ismail-Beigi,K. Le Hur,C. H. Ahn###

Electric Field Tuned Dimensional Crossover in Ar-Irradiated SrTiO3. We present low temperature magnetoresistance measurements of Ar-irradiated
SrTiO3 under an applied electrostatic field. The electric field, applied
through a back gate bias, modulates both the mobility and sheet density, with a
greater effect on the former. For high mobilities, 3-dimensional orbital
magnetoresistance is observed. For low mobilities, negative magnetoresistance
that is consistent with the suppression of 2-dimensional weak-localization is
observed. The crossover from 3 to 2-dimensional transport arises from a
modulation in the carrier confinement, which is enhanced by the electric field
dependent dielectric constant of SrTiO3. The implications of our results on the
development of oxide electronic devices will be discussed.

###Influence of length and measurement geometry on magnetoimpedance in La0.7Sr0.3MnO3|A. Rebello,R. Mahendiran###

Influence of length and measurement geometry on magnetoimpedance in La0.7Sr0.3MnO3. We show that ac magnetoresistance at room temperature in La0.7Sr0.3MnO3 is
extremely high (= 47% in H = 100 mT, f = 3-5 MHz), and magnetic field
dependence of reactance exhibits a double peak behavior. However, magnitudes of
the ac magnetoresistance and magnetoreactance for a fixed length of the sample
(li) decrease with decreasing separation (lv) between voltage probes unlike the
dc magnetoresistance. On the contrary, change in li has a negligible influence
on magnetoimpedance when lv is fixed. Our results indicate that high frequency
electrical transport is sensitive to local variations in the magnetic
permeability.

###Exchange coupling and magnetoresistance in CoFe/NiCu/CoFe spin-valves near the Curie point of the spacer|S. Andersson,V. Korenivski###

Exchange coupling and magnetoresistance in CoFe/NiCu/CoFe spin-valves near the Curie point of the spacer. Thermal control of exchange coupling between two strongly ferromagnetic
layers through a weakly ferromagnetic Ni-Cu spacer and the associated
magnetoresistance is investigated. The spacer, having a Curie point slightly
above room temperature, can be cycled between its paramagnetic and
ferromagnetic states by varying the temperature externally or using joule
heating. It is shown that the giant magnetoresistance vanishes due to a strong
reduction of the mean free path in the spacer at above ~30 % Ni concentration
-- before the onset of ferromagnetism. Finally, a device is proposed and
demonstrated which combines thermally controlled exchange coupling and large
magnetoresistance by separating the switching and the read out elements.

###Theory of acoustic-phonon assisted magnetotransport in 2D electron systems at large filling factors|O. E. Raichev###

Theory of acoustic-phonon assisted magnetotransport in 2D electron systems at large filling factors. A microscopic theory of the phonon-induced resistance oscillations in weak
perpendicular magnetic fields is presented. The calculations are based on the
consideration of interaction of two-dimensional electrons with
three-dimensional (bulk) acoustic phonons and take into account anisotropy of
the phonon spectrum in cubic crystals. The magnetoresistance is calculated for
[001]-grown GaAs quantum wells. The results are in agreement with available
experimental data. Apart from the numerical results, analytical expressions for
the oscillating part of magnetoresistance are obtained. These expressions are
valid in the region of high-order magnetophonon resonances and describe the
oscillating magnetoresistance determined by several groups of phonons polarized
along certain high-symmetry directions.

###Universal Properties of Linear Magnetoresistance in Strongly Disordered Semiconductors|H. G. Johnson,S. P. Bennett,R. Barua,L. H Lewis,D. Heiman###

Universal Properties of Linear Magnetoresistance in Strongly Disordered Semiconductors. Linear magnetoresistance occurs in semiconductors as a consequence of strong
electrical disorder and is characterized by nonsaturating magnetoresistance
that is proportional to the applied magnetic field. By investigating a
disordered MnAs-GaAs composite material, it is found that the magnitude of the
linear magnetoresistance (LMR) is numerically equal to the carrier mobility
over a wide range and is independent of carrier density. This behavior is
complementary to the Hall effect that is independent of the mobility and
dependent on the carrier density. Moreover, the LMR appears to be insensitive
to the details of the disorder and points to a universal explanation of
classical LMR that can be applied to other material systems.

###Dominant role of impurity scattering over crystalline anisotropy for magnetotransport properties in the quasi-1D Hollandite Ba1.2Rh8O16|Alain Pautrat,Wataru Kobayashi###

Dominant role of impurity scattering over crystalline anisotropy for magnetotransport properties in the quasi-1D Hollandite Ba1.2Rh8O16. Angular magnetotransport measurements have been performed to tackle the
origin of the magnetoresistance in the quasi-1D Hollandite Ba1.2Rh8O16. Three
samples of different impurities amount were measured. We observe that the low
temperature resistivity upturn is not due to a charge density wave transition,
and a dominant role of impurities scattering for low temperature transport
properties is instead demonstrated. The components of magnetoresistance were
separated by using the Kohler plot and the angular dependency of the resistance
under magnetic field. It shows the major contribution of an isotropic, likely
spin driven, negative magnetoresistance. Galvanomagnetic characteristics are
then consistent with a Kondo effect and appear to be essentially 3D at low
temperature.

###Magnetic microstructure and magnetotransport in Co2FeAl Heusler compound thin films|Mathias Weiler,Franz D. Czeschka,Inga-Mareen Imort,Günter Reiss,Andy Thomas,Georg Woltersdorf,Rudolf Gross,Sebastian T. B. Goennenwein###

Magnetic microstructure and magnetotransport in Co2FeAl Heusler compound thin films. We correlate simultaneously recorded magnetotransport and spatially resolved
magneto optical Kerr effect (MOKE) data in Co2FeAl Heusler compound thin films
micropatterned into Hall bars. Room temperature MOKE images reveal the
nucleation and propagation of domains in an externally applied magnetic field
and are used to extract a macrospin corresponding to the mean magnetization
direction in the Hall bar. The anisotropic magnetoresistance calculated using
this macrospin is in excellent agreement with magnetoresistance measurements.
This suggests that the magnetotransport in Heusler compounds can be adequately
simulated using simple macrospin models, while the magnetoresistance
contribution due to domain walls is of negligible importance.

###Experimental observation of an enhanced anisotropic magnetoresistance in non-local configuration|Daniel Rüffer,Franz D. Czeschka,Rudolf Gross,Sebastian T. B. Goennenwein###

Experimental observation of an enhanced anisotropic magnetoresistance in non-local configuration. We compare non-local magnetoresistance measurements in multi-terminal Ni
nanostructures with corresponding local experiments. In both configurations,
the measured voltages show the characteristic features of anisotropic
magnetoresistance (AMR). However, the magnitude of the non-local AMR signal is
up to one order of magnitude larger than its local counterpart. Moreover, the
non-local AMR increases with increasing degree of non-locality, i.e., with the
separation between the region of the main current flow and the voltage
measurement region. All experimental observations can be consistently modeled
in terms of current spreading in a non-isotropic conductor. Our results show
that current spreading can significantly enhance the magnetoresistance signal
in non-local experiments.

###Effect of Interface Induced Exchange Fields on Cuprate-Manganite Spin Switches|Yaohua Liu,C. Visani,N. M. Nemes,M. R. Fitzsimmons,L. Y. Zhu,J. Tornos,M. Zhernenkov,A. Hoffmann,C. Leon,J. Santamaria,S. G. E. te Velthuis###

Effect of Interface Induced Exchange Fields on Cuprate-Manganite Spin Switches. We examine the anomalous inverse spin switch behavior in
La$_{0.7}$Ca$_{0.3}$MnO$_3$ (LCMO)/YBa$_2$Cu$_3$O$_{7-\delta}$ (YBCO)/LCMO
trilayers by combined transport studies and polarized neutron reflectometry.
Measuring magnetization profiles and magnetoresistance in an in-plane rotating
magnetic field, we prove that, contrary to many accepted theoretical scenarios,
the relative orientation between the two LCMO's magnetizations is not
sufficient to determine the magnetoresistance. Rather the field dependence of
magnetoresistance is explained by the interplay between the applied magnetic
field and the (exponential tail of the) induced exchange field in YBCO, the
latter originating from the electronic reconstruction at the LCMO/YBCO
interfaces.

###Influence of linearly polarized radiation on magnetoresistance in irradiated two-dimensional electron systems|Jesus Inarrea###

Influence of linearly polarized radiation on magnetoresistance in irradiated two-dimensional electron systems. We study the influence of the polarization angle of linear radiation on the
radiation-induced magnetoresistance oscillations in two-dimensional electron
systems and examine the polarization immunity on the temperature and quality of
the sample. We have applied the radiation-driven electron orbits model
obtaining that the magnetoresistance is affected by the orientation of the
electric field of linearly polarized radiation when dealing with high quality
samples and low temperatures. Yet, for lower quality samples and higher
temperature, we recover polarization immunity in the radiation driven
magnetoresistance oscillations. This could be of interest for future
photoelectronics in high quality mesoscopic devices. VC 2012 American Institute
of Physics

###High-field moment polarization in the ferromagnetic superconductor UCoGe|W. Knafo,T. D. Matsuda,D. Aoki,F. Hardy,G. W. Scheerer,G. Ballon,M. Nardone,A. Zitouni,C. Meingast,J. Flouquet###

High-field moment polarization in the ferromagnetic superconductor UCoGe. We report magnetization and magnetoresistivity measurements on the
isostructural ferromagnetic superconductors UCoGe and URhGe in magnetic fields
up to 60 T and temperatures from 1.5 to 80 K. At low-temperature, a moment
polarization in UCoGe in a field $\mu_0\mathbf{H}\parallel\mathbf{b}$ of around
50 T leads to well-defined anomalies in both magnetization and
magnetoresistivity. These anomalies vanish in temperatures higher than 30-40 K,
where maxima in the magnetic susceptibility and the field-induced variation of
the magnetoresistivity are found. A comparison is made between UCoGe and URhGe,
where a moment reorientation in a magnetic field
$\mu_0\mathbf{H}\parallel\mathbf{b}$ of 12 T leads to field-induced reentrant
superconductivity.

###Emerging Weak Localization Effects on Topological Insulator-Insulating Ferromagnet (Bi_2Se_3-EuS) Interface|Qi I. Yang,Merav Dolev,Li Zhang,Jinfeng Zhao,Alexander D. Fried,Elizabeth Schemm,Min Liu,Alexander Palevski,Ann F. Marshall,Subhash H. Risbud,Aharon Kapitulnik###

Emerging Weak Localization Effects on Topological Insulator-Insulating Ferromagnet (Bi_2Se_3-EuS) Interface. Thin films of topological insulator Bi_2Se_3 were deposited directly on
insulating ferromagnetic EuS. Unusual negative magnetoresistance was observed
near the zero field below the Curie temperature (T_C), resembling the weak
localization effect; whereas the usual positive magnetoresistance was recovered
above T_C. Such negative magnetoresistance was only observed for Bi_2Se_3
layers thinner than t~4nm, when its top and bottom surfaces are coupled. These
results provide evidence for a proximity effect between a topological insulator
and an insulating ferromagnet, laying the foundation for future realization of
the half-integer quantized anomalous Hall effect in three-dimensional
topological insulators.

###Interface-induced magnetism in perovskite quantum wells|Clayton A. Jackson,Susanne Stemmer###

Interface-induced magnetism in perovskite quantum wells. We investigate the angular dependence of the magnetoresistance of thin (< 1
nm), metallic SrTiO3 quantum wells epitaxially embedded in insulating,
ferrimagnetic GdTiO3 and insulating, antiferromagnetic SmTiO3, respectively.
The SrTiO3 quantum wells contain a high density of mobile electrons (~7x10^14
cm^-2). We show that the longitudinal and transverse magnetoresistance in the
structures with GdTiO3 are consistent with anisotropic magnetoresistance, and
thus indicative of induced ferromagnetism in the SrTiO3, rather than a
nonequilibrium proximity effect. Comparison with the structures with
antiferromagnetic SmTiO3 shows that the properties of thin SrTiO3 quantum wells
can be tuned to obtain magnetic states that do not exist in the bulk material.

###Giant magnetoresistance in single layer graphene flakes with a gate voltage tunable weak antilocalization|Kalon Gopinadhan,Young Jun Shin,Indra Yudhistira,Jing Niu,Hyunsoo Yang###

Giant magnetoresistance in single layer graphene flakes with a gate voltage tunable weak antilocalization. A clear gate voltage tunable weak antilocalization and a giant
magnetoresistance of 400 percent are observed at 1.9 K in single layer graphene
with an out-of-plane field. A large magnetoresistance value of 275 percent is
obtained even at room temperature implying potential applications of graphene
in magnetic sensors. Both the weak antilocalization and giant magnetoresistance
persists far away from the charge neutrality point in contrast to previous
reports, and both effects are originated from charged impurities.
Interestingly, the signatures of Shubnikov-de Haas oscillations and the quantum
Hall effect are also observed for the same sample.

###Electronic structure basis for the titanic magnetoresistance in WTe$_2$|I. Pletikosić,Mazhar N. Ali,A. Fedorov,R. J. Cava,T. Valla###

Electronic structure basis for the titanic magnetoresistance in WTe$_2$. The electronic structure basis of the extremely large magnetoresistance in
layered non-magnetic tungsten ditelluride has been investigated by
angle-resolved photoelectron spectroscopy. Hole and electron pockets of
approximately the same size were found at the Fermi level, suggesting that
carrier compensation should be considered the primary source of the effect. The
material exhibits a highly anisotropic, quasi one-dimensional Fermi surface
from which the pronounced anisotropy of the magnetoresistance follows. A change
in the Fermi surface with temperature was found and a high-density-of-states
band that may take over conduction at higher temperatures and cause the
observed turn-on behavior of the magnetoresistance in WTe$_2$ was identified.

###Nanosized Vertical Organic Spin-Valves|R. Göckeritz,N. Homonnay,A. Müller,T. Richter,B. Fuhrmann,G. Schmidt###

Nanosized Vertical Organic Spin-Valves. A fabrication process for vertical organic spin-valve devices has been
developed which offers the possibility to achieve active device areas of less
than 500x500 nm^2 and is flexible in terms of material choice for the active
layers. Characterization of the resulting devices shows a large
magnetoresistance of sometimes more than 100%, however with equally large
variation from device to device. Comparison with large-area spin-valves
indicates that the magnetoresistance of both, large and small devices most
likely originates from tunneling through pinholes and tunneling
magnetoresistance.

###Anomalous Quantum Transport Properties in Semimetallic Black Phosphorus|Kazuto Akiba,Astushi Miyake,Yuichi Akahama,Kazuyuki Matsubayashi,Yoshiya Uwatoko,Hayato Arai,Yuki Fuseya,Masashi Tokunaga###

Anomalous Quantum Transport Properties in Semimetallic Black Phosphorus. Magnetoresistance in single crystals of black phosphorus is studied at
ambient and hydrostatic pressures. In the semiconducting states at pressures
below 0.71 GPa, the magnetoresistance shows periodic oscillations, which can be
ascribed to the magneto-phonon resonance that is characteristic of high
mobility semiconductors. In the metallic state above 1.64 GPa, the both
transverse and longitudinal magnetoresistance show titanic increase with
exhibiting superposed Shubnikov-de Haas oscillations. The observed small Fermi
surfaces, high mobilities and light effective masses of carriers in
semimetallic black phosphorus are comparable to those in the representative
elemental semimetals of bismuth and graphite.

###Defect induced negative magnetoresistance and surface state immunity in topological insulator BiSbTeSe2|Karan Banerjee,Jaesung Son,Praveen Deorani,Peng Ren,Lan Wang,Hyunsoo Yang###

Defect induced negative magnetoresistance and surface state immunity in topological insulator BiSbTeSe2. Absence of backscattering and occurrence of weak anti-localization are two
characteristic features of topological insulators. We find that the
introduction of defects results in the appearance of a negative contribution to
magnetoresistance in the topological insulator BiSbTeSe2, at temperatures below
50 K. Our analysis shows that the negative magnetoresistance originates from an
increase in the density of defect states created by introduction of disorder,
which leaves the surface states unaffected. We find a decrease in the magnitude
of the negative magnetoresistance contribution with increasing temperature and
a robustness of the topological surface states to external disorder.

###Spin Hall Magnetoresistance in a Canted Ferrimagnet|Kathrin Ganzhorn,Joseph Barker,Richard Schlitz,Matthias Althammer,Stephan Geprägs,Hans Huebl,Benjamin A. Piot,Rudolf Gross,Gerrit E. W. Bauer,Sebastian T. B. Goennenwein###

Spin Hall Magnetoresistance in a Canted Ferrimagnet. We study the spin Hall magnetoresistance effect in ferrimagnet/normal metal
bilayers, comparing the response in collinear and canted magnetic phases. In
the collinear magnetic phase, in which the sublattice magnetic moments are all
aligned along the same axis, we observe the conventional spin Hall
magnetoresistance. In contrast, in the canted phase, the magnetoresistance
changes sign. Using atomistic spin model calculations of the magnetic
configuration, we show that the electric transport for the different magnetic
phases can be rationalized considering the individual sublattice moment
orientations. This enables a magneto-transport based investigation of
non-collinear magnetic textures.

###Photo-spin voltaic effect and photo-magnetoresistance in proximized platinum|D. Li,A. Ruotolo###

Photo-spin voltaic effect and photo-magnetoresistance in proximized platinum. Spin orbit coupling in heavy metals allows conversion of unpolarized light
into an open-circuit voltage. We experimentally prove that this photo-spin
voltaic effect is due to photo-excitation of carriers in the proximized layer
and can exist for light in the visible range. While carrying out the
experiment, we discovered that, in closed-circuit conditions, the anisotropic
magnetoresistance of the proximized metal is a function of the light intensity.
We name this effect photo-magnetoresistance. A magneto-transport model is
presented that describes the change of magnetoresistance as a function of the
light intensity.

###Magnetoresistance originated from charge-spin conversion in ferromagnet|Tomohiro Taniguchi###

Magnetoresistance originated from charge-spin conversion in ferromagnet. Transverse magnetoresistance in a ferromagnetic/nonmagnetic/ferromagnetic
trilayer originated from charge-spin conversion by anomalous Hall effect is
investigated theoretically. Solving the spin diffusion equation in bulk and
using the spin-dependent Landauer formula at the ferromagnetic/nonmagnetic
interface, an analytical formula of the transverse resistivity is obtained. The
charge-spin conversion by the anomalous Hall effect contributes to the
magnetoresistance in a manner proportional to the square of the spin anomalous
Hall angle. The angular dependence of the magnetoresistance is basically
identical to that of planar Hall effect, but has an additional term which
depends on the relative angle of the magnetizations in two ferromagnets.

###Magnetoresistance in organic semiconductors: including pair correlations in the kinetic equations for hopping transport|A. V. Shumilin,V. V. Kabanov,V. I. Dediu###

Magnetoresistance in organic semiconductors: including pair correlations in the kinetic equations for hopping transport. We derive the kinetic equations for polaron hopping in organics that
explicitly take into account the double occupation possibility and pair
intersite correlations. The equations include simplified phenomenological spin
dynamics and provide a self-consistent framework for the description of the
bipolaron mechanism of the organic magnetoresistance. At low applied voltages
the equations can be reduced to effective resistor network that generalizes the
Miller-Abrahams network and includes the effect of spin relaxation on the
system resistivity. Our theory discloses the close relationship between the
organic magnetoresistance and the intersite correlations. Moreover, in the
absence of correlations, as in ordered system with zero Hubbard energy, the
magnetoresistance vanishes.

###High magnetoresistance at room temperature in p-i-n graphene nanoribbons due to band-to-band tunneling effects|Gengchiau Liang,S. Bala kumar,M. B. A. Jalil,S. G. Tan###

High magnetoresistance at room temperature in p-i-n graphene nanoribbons due to band-to-band tunneling effects. A large magnetoresistance effect is obtained at room-temperature by using
p-i-n armchair-graphene-nanoribbon (GNR) heterostructures. The key advantage is
the virtual elimination of thermal currents due to the presence of band gaps in
the contacts. The current at B=0T is greatly decreased while the current at
B>0T is relatively large due to the band-to-band tunneling effects, resulting
in a high magnetoresistance ratio, even at room-temperature. Moreover, we
explore the effects of edge-roughness, length, and width of GNR channels on
device performance. An increase in edge-roughness and channel length enhances
the magnetoresistance ratio while increased channel width can reduce the
operating bias.

###Spin Hall Magnetoimpedance|Johannes Lotze,Hans Huebl,Rudolf Gross,Sebastian T. B. Goennenwein###

Spin Hall Magnetoimpedance. The recently discovered spin Hall magnetoresistance effect electrically
probes pure spin current flow across a ferrimagnetic insulator/normal metal
bilayer interface. While usually the DC electrical resistance of the bilayer is
measured as a function of the magnetization orientation in the magnetic
insulator, we here present magnetoimpedance measurements using bias currents
with frequencies up to several GHz. We find that the spin Hall
magnetoresistance effect persists up to frequencies of at least 4 GHz, enabling
a fast readout of the magnetization direction in magnetic insulator/normal
metal bilayers. Our data furthermore show that all interaction time constants
relevant for the spin Hall magnetoresistance effect are shorter than 40 ps.

###Effect of Interlayer Spin-Flip Tunneling for Interlayer Magnetoresistance in Multilayer Massless Dirac Fermion Systems|Kenji Kubo,Takao Morinari###

Effect of Interlayer Spin-Flip Tunneling for Interlayer Magnetoresistance in Multilayer Massless Dirac Fermion Systems. We investigate the effect of the interlayer spin-flip tunneling for the
interlayer magnetoresistance under magnetic fields in alpha-(BEDT-TTF)2I3,
which is a multilayer massless Dirac fermion system under pressure. The mean
field of the spin-flip correlation associated with the interlayer Coulomb
interaction enables the interlayer spin-flip tunneling. Assuming the
non-vertical interlayer spin-flip tunneling, we calculate the interlayer
magnetoresistance using the Kubo formula. The crossover magnetic field, at
which the interlayer magnetoresistance changes from positive to negative is
shifted by the Zeeman energy and in good agreement with the experiment.

###Observation of pseudo two dimensional electron transport in the rock salt type topological semimetal LaBi|Nitesh Kumar,Chandra Shekhar,Shu-Chun Wu,Inge Leermakers,Olga Young,Uli Zeitler,Binghai Yan,Claudia Felser###

Observation of pseudo two dimensional electron transport in the rock salt type topological semimetal LaBi. Topological insulators are characterized by an inverted band structure in the
bulk and metallic surface states on the surface. In LaBi, a semimetal with a
band inversion equivalent to a topological insulator, we observe surface state
like behavior in the magnetoresistance. The electrons responsible for this
pseudo two dimensional transport, however, originate from the bulk states
rather topological surface states, which is witnessed by the angle dependent
quantum oscillations of the magnetoresistance and ab initio calculations. As a
consequence, the magnetoresistance exhibits strong anisotropy with large
amplitude (~ 10^5 %).

###Colossal Magnetoresistance Manganites and Related Prototype Devices|Yukuai Liu,Yuewei Yin,Xiaoguang Li###

Colossal Magnetoresistance Manganites and Related Prototype Devices. We review colossal magnetoresistance in single phase manganites, as related
to the field sensitive spin charge interactions and phase separation; the
rectifying property and negative/positive magnetoresistance in
manganite/Nb:SrTiO3 pn junctions in relation to the special interface
electronic structure; magnetoelectric coupling in manganite/ferroelectric
structures that takes advantage of strain, carrier density, and magnetic field
sensitivity; tunneling magnetoresistance in tunnel junctions with dielectric,
ferroelectric, and organic semiconductor spacers using the fully spin polarized
nature of manganites; and the effect of particle size on magnetic properties in
manganite nanoparticles

###Magnetoresistance of double layer hybrid system in tilted magnetic field|Fariborz Parhizgar,Reza Asgari###

Magnetoresistance of double layer hybrid system in tilted magnetic field. Magnetoresistance and Hall coefficient of a graphene layer are investigated
in the presence of a tilted magnetic field. We consider the graphene layer is
assembled by either another graphene layer or a two-dimensional electron gas
(2DEG) and an interlayer electron-electron interaction is modeled within Random
Phase Approximation. Our calculated magnetoresistances show different
interlayer screening effects between decoupled graphene-graphene and
graphene-2DEG systems. We also analyze the dependence of dielectric materials
as well as the distance between layers on magnetoresistances. The angle
dependence of the Hall coefficient is studied and we show that a quite large
Hall resistivity occurs in the graphene layer.

###Polaronic correlations and phonon renormalization in La1-xSrxMnO3 (x = 0.2, 0.3)|M. Maschek,J. -P. Castellan,D. Lamago,D. Reznik,F. Weber###

Polaronic correlations and phonon renormalization in La1-xSrxMnO3 (x = 0.2, 0.3). According to standard theory the magnetoresistance magnitude in ferromagnetic
manganites crucially depends on the electron-phonon coupling strength. We
showed that in La0.7Sr0.3MnO3 the phonon renormalization is strong, despite its
relatively small magnetoresistance. Here, we report results of a similar
inelastic neutron scattering investigation of a closely related compound,
La0.8Sr0.2MnO3, where the magnetoresistance is enhanced. We find similar phonon
renormalization and dynamic CE-type polaron correlations as in La0.7Sr0.3MnO3.
However, quantitative comparison of the results for the two samples shows that
only polaron lifetime is well correlated with the strength of the CMR.

###Evolution of the magnetoresistance lineshape with temperature and electric field across Nb-doped SrTiO$_3$ interface|A. Das,S. T. Jousma,A. Majumdar,T. Banerjee###

Evolution of the magnetoresistance lineshape with temperature and electric field across Nb-doped SrTiO$_3$ interface. We report on the temperature and electric field driven evolution of the
magnetoresistance lineshape at an interface between Ni/AlO$_x$ and Nb-doped
SrTiO$_3$. This is manifested as a superposition of the Lorentzian lineshape
due to spin accumulation and a parabolic background related to tunneling
anisotropic magnetoresistance (TAMR). The characteristic Lorentzian line shape
of the spin voltage is retrieved only at low temperatures and large positive
applied bias. This is caused by the reduction of electric field at large
positive applied bias which results in a simultaneous reduction of the
background TAMR and a sharp enhancement in spin injection. Such mechanisms to
tune magnetoresistance are uncommon in conventional semiconductors.

###Voltage induced control and magnetoresistance of noncollinear frustrated magnets|A. Kalitsov,M. Chshiev,B. Canals,C. Lacroix###

Voltage induced control and magnetoresistance of noncollinear frustrated magnets. Noncollinear frustrated magnets are proposed as a new class of spintronic
materials with high magnetoresistance which can be controlled with relatively
small applied voltages. It is demonstrated that their magnetic configuration
strongly depends on position of the Fermi energy and applied voltage. The
voltage induced control of noncollinear frustrated materials (VCFM) can be seen
as a way to intrinsic control of colossal magnetoresistance (CMR) and is the
bulk material counterpart of spin transfer torque concept used to control giant
magnetoresistance in layered spin-valve structures.

###Superconductivity in the topological semimetal YPtBi|Nicholas P. Butch,P. Syers,Kevin Kirshenbaum,Andrew P. Hope,Johnpierre Paglione###

Superconductivity in the topological semimetal YPtBi. The noncentrosymmetric Half Heusler compound YPtBi exhibits superconductivity
below a critical temperature T_c = 0.77 K with a zero-temperature upper
critical field H_c2(0) = 1.5 T. Magnetoresistance and Hall measurements support
theoretical predictions that this material is a topologically nontrivial
semimetal having a surprisingly low positive charge carrier density of 2 x
10^18 cm^-3. Unconventional linear magnetoresistance and beating in
Shubnikov-de Haas oscillations point to spin-orbit split Fermi surfaces. The
sensitivity of magnetoresistance to surface roughness suggests a possible
contribution from surface states. The combination of noncentrosymmetry and
strong spin-orbit coupling in YPtBi presents a promising platform for the
investigation of topological superconductivity.

###Weak Localization Effects as Evidence for Bulk Quantization in Thin Films Bi2Se3|Li Zhang,Merav Dolev,Qi I. Yang,Robert H. Hammond,Bo Zhou,Alexander Palevski,Yulin Chen,Aharon Kapitulnik###

Weak Localization Effects as Evidence for Bulk Quantization in Thin Films Bi2Se3. Strong spin-orbit coupling in topological insulators results in the
ubiquitously observed weak antilocalization feature in their magnetoresistance.
Here we present magnetoresistance measurements in ultra thin films of the
topological insulator Bi_2Se_3, and show that in the 2D quantum limit, in which
the topological insulator bulk becomes quantized, an additional negative
magnetoresistance feature appears. Detailed analysis associates this feature
with weak localization of the quantized bulk channels, providing thus evidence
for this quantization. Examination of the dephasing fields at different
temperatures indicates different scattering mechanism in the bulk vs the
surface states.

###Absence of Colossal Magnetoresistance in the Oxypnictide PrMnAsO0.95F0.05|Eve. J. Wildman,Falak Sher,Abbie. C. Mclaughlin###

Absence of Colossal Magnetoresistance in the Oxypnictide PrMnAsO0.95F0.05. We have recently reported a new mechanism of colossal magnetoresistance in
electron doped Mn oxypnictides NdMnAsO1-xFx. Magnetoresistances of up to -95
percent at 3 K have been observed. Here we show that upon replacing Nd for Pr,
the CMR is surprisingly no longer present. Instead a sizeable negative
magnetoresistance is observed for PrMnAsO0.95F0.05 below 35 K (MR7T (12 K) =
-13.4 percent for PrMnAsO0.9F0.05. A detailed neutron and synchrotron X-ray
diffraction study of PrMnAsO0.95F0.05 has been performed, which shows that a
structural transition, Ts, occurs at 35 K from tetragonal P4/nmm to
orthorhombic Pmmn symmetry. The structural transition is driven by the Pr 4f
electrons degrees of freedom.

###Large Magnetoresistance at Room Temperature in Ferromagnet/Topological Insulator Contacts|Sarmita Majumder,Samaresh Guchhait,Rik Dey,Leonard Franklin Register,Sanjay K. Banerjee###

Large Magnetoresistance at Room Temperature in Ferromagnet/Topological Insulator Contacts. We report magnetoresistance for current flow through iron/topological
insulator (Fe/TI) and Fe/evaporated-oxide/TI contacts when a magnetic field is
used to initially orient the magnetic alignment of the incorporated
ferromagnetic Fe bar, at temperatures ranging from 100 K to room temperature.
This magnetoresistance is associated with the relative orientation of the Fe
bar magnetization and spin-polarization of electrons moving on the surface of
the TI with helical spin-momentum locking. The magnitude of the observed
magnetoresistance is relatively large compared to that observed in prior work.

###Linear magnetoresistance in the charge density wave state of quasi-two-dimensional rare-earth tritellurides|Alexander A. Sinchenko,Pavel D. Grigoriev,Pascal Lejay,Pierre Monceau###

Linear magnetoresistance in the charge density wave state of quasi-two-dimensional rare-earth tritellurides. We report measurements of the magnetoresistance in the charge density wave
(CDW) state of rare-earth tritellurides, namely TbTe$_3$ and HoTe$_3$. The
magnetic field dependence of magnetoresistance exhibits a temperature dependent
crossover between a conventional quadratic law at high $T$ and low $B$ and an
unusual linear dependence at low $T$ and high $B$. We present a quite general
model to explain the linear magnetoresistance taking into account the strong
scattering of quasiparticles on CDW fluctuations in the vicinity of "hot spots"
of the Fermi surface (FS) where the FS reconstruction is the strongest.

###Metal-insulator transition and giant anisotropic magnetoresistance in ultra thin (Ga,Mn)As|R. R. Gareev,A. Petukhov,M. Schlapps,M. Doeppe,J. Sadowski,M. Sperl,W. Wegscheider###

Metal-insulator transition and giant anisotropic magnetoresistance in ultra thin (Ga,Mn)As. MBE-grown, 5 nm-thick annealed Ga0.95Mn0.05As films with Tc~90K demonstrate
transition from metallic to insulating state below To~10K, where sheet
resistances Rsh~h/e2 and both longitudinal Rxx and transverse Rxy components
become comparable. Below metal-insulator transition we found giant anisotropic
magnetoresistance (GAMR), which depends on orientation of magnetization to
crystallographic axes and manifests itself in positive magnetoresistance near
50% for Rxx at T=1.7K, H//[110] crystallographic direction and parallel to
current in contrast to smaller and negative magnetoresistance for H//
direction. We connect GAMR with anisotropic spin-orbit interaction resulting in
formation of high- and low- resistance states with different localization along
non-equivalent easy axes.

###Impact of tunnel barrier strength on magnetoresistance in carbon nanotubes|Caitlin Morgan,Maciej Misiorny,Dominik Metten,Sebastian Heedt,Thomas Schäpers,Claus M. Schneider,Carola Meyer###

Impact of tunnel barrier strength on magnetoresistance in carbon nanotubes. We investigate magnetoresistance in spin valves involving CoPd-contacted
carbon nanotubes. Both temperature and bias voltage dependence clearly indicate
tunneling magnetoresistance as the origin. We show that this effect is
significantly affected by the tunnel barrier strength, which appears to be one
reason for the variation between devices previously detected in similar
structures. Modeling the data by means of the scattering matrix approach, we
find a non-trivial dependence of the magnetoresistance on the barrier strength.
Furthermore, analysis of the spin precession observed in a nonlocal Hanle
measurement yields a spin lifetime of $\tau_s = 1.1\,$ns, a value comparable
with those found in silicon- or graphene-based spin valve devices.

###Heavily $n$-doped Ge: low-temperature magnetoresistance properties|A. Ferreira da Silva,M. A. Toloza Sandoval,A. Levine,E. Levinson,H. Boudinov,B. E. Sernelius###

Heavily $n$-doped Ge: low-temperature magnetoresistance properties. We report here an experimental and theoretical study on the magnetoresistance
properties of heavily phosphorous doped germanium on the metallic side of the
metal-nonmetal transition. An anomalous regime, formed by negative values of
the magnetoresistance, was observed by performing low-temperature measurements
and explained within the generalized Drude model, due to the many-body effects.
It reveals a key mechanism behind the magnetoresistance properties at low
temperatures and, therefore, constitutes a path to its manipulation in such
materials of great interest in fundamental physics and technological
applications

###Electric current noise in mesoscopic organic semiconductors|D. S. Smirnov,A. V. Shumilin###

Electric current noise in mesoscopic organic semiconductors. We demonstrate that nuclear spin fluctuations lead to the electric current
noise in the mesoscopic samples of organic semiconductors showing the
pronounced magnetoresistance in weak fields. For the bipolaron and
electron-hole mechanisms of organic magnetoresistance, the current noise
spectrum consists of the high frequency peak related to the nuclear spin
precession in the Knight field of the charge carriers and the low frequency
peak related to the nuclear spin relaxation. The shape of the spectrum depends
on the external magnetic and radiofrequency fields, which allows one to prove
the role of nuclei in magnetoresistance experimentally.

###Linear unsaturated magnetoresistance in YSi single crystal|Vikas Saini,Souvik Sasmal,Ruta Kulkarni,Arumugam Thamizhavel###

Linear unsaturated magnetoresistance in YSi single crystal. Linear magnetoresistance is a phenomenon that has been observed in a few
topological compounds that originate from classical and quantum phenomena.
Here, we performed electrical transport measurements, in zero and applied
magnetic fields, on the YSi single crystal along all three principal
crystallographic directions of the orthorhombic crystal structure. For
$I~\parallel~[001]$ and $H~\parallel~[100]$ direction above $\approx 10$~T,
mobility fluctuation driven linear magnetoresistance is observed without any
sign of saturation up to $14$~T magnetic field. Anisotropy in the Fermi surface
is immanent from the angular dependence of the magnetoresistance. Kohler rule
violation is observed in this system and Hall data signifies multiple charge
carriers in YSi.

###Magnetoresistance and Scaling Laws in Type-II Weyl Semimetal WP_2|V. Nagpal,K. S. Jat,S. Patnaik###

Magnetoresistance and Scaling Laws in Type-II Weyl Semimetal WP_2. Topological materials with extremely large magnetoresistance exhibit a
prognostic feature of resistivity turn-on behaviour. This occurs when the
temperature dependence of resistivity changes from metallic to semiconducting
characteristics on application of external magnetic field above a threshold
value. Here, we study the magneto-transport properties of type-II Weyl
Semimetal WP2. We find that semi-classical theories of magnetoresistance are
consistent with our data without the need to invoke topological surface states.
Our findings in this work provides an alternative basis to understand the
temperature dependence of magnetoresistance in topological materials.

###Enhanced magnetoresistance in perpendicular magnetic tunneling junctions with MgAl2O4 barrier|Pravin Khanal,Bowei Zhou,Magda Andrade,Christopher Mastrangelo,Ali Habiboglu,Arthur Enriquez,Daulton Fox,Kennedy Warrilow,Wei-Gang Wang###

Enhanced magnetoresistance in perpendicular magnetic tunneling junctions with MgAl2O4 barrier. Perpendicular magnetic tunnel junction with MgAl2O4 barrier is investigated.
It is found that reactive RF sputtering with O2 is essential to obtain strong
perpendicular magnetic anisotropy and large tunneling magnetoresistance in
MgAl2O4-based junctions. An interfacial perpendicular magnetic anisotropy
energy density of 2.25 mJ/m2 is obtained for the samples annealed at 400C. An
enhanced magnetoresistance of 60% has also been achieved. The Vhalf, bias
voltage at which tunneling magnetoresistance drops to half of the zero-bias
value, is found to be about 1V, which is substantially higher than that of
MgO-based junctions.

###Temperature-driven changes in the Fermi surface of graphite|Laxman R. Thoutam,Samuel E. Pate,Tingting Wang,Yong-Lei Wang,Ralu Divan,Ivar Martin,Adina Luican-Mayer,Ulrich Welp,Wai-Kwong Kwok,Zhi-Li Xiao###

Temperature-driven changes in the Fermi surface of graphite. We report on temperature-dependent size and anisotropy of the Fermi pockets
in graphite revealed by magnetotransport measurements. The magnetoresistances
obtained in fields along the c-axis obey an extended Kohler's rule, with the
carrier density following prediction of a temperature-dependent Fermi energy,
indicating a change in the Fermi pocket size with temperature. The
angle-dependent magnetoresistivities at a given temperature exhibit a scaling
behavior. The scaling factor that reflects the anisotropy of the Fermi surface
is also found to vary with temperature. Our results demonstrate that
temperature-driven changes in Fermi surface can be ubiquitous and need to be
considered in understanding the temperature-dependent carrier density and
magnetoresistance anisotropy in semimetals.

###Impact of Boron doping to the tunneling magnetoresistance of Heusler alloy Co2FeAl|Ali Habiboglu,Yash Chandak,Pravin Khanal,Bowei Zhou,Carter Eckel,Jacob Cutshall Kennedy Warrilow,John O'Brien,John R. Schaibley,Brian J. Leroy,Wei-Gang Wang###

Impact of Boron doping to the tunneling magnetoresistance of Heusler alloy Co2FeAl. Heusler alloys based magnetic tunnel junctions can potentially provide high
magnetoresistance, small damping and fast switching. Here junctions with
Co2FeAl as a ferromagnetic electrode are fabricated by room temperature
sputtering on Si/SiO2 substrates. The doping of Boron in Co2FeAl is found to
have a large positive impact on the structural, magnetic and transport
properties of the junctions, with a reduced interfacial roughness and
substantial improved tunneling magnetoresistance. A two-level magnetoresistance
is also observed in samples annealed at low temperature, which is believed to
be related to the memristive effect of the tunnel barrier with impurities.

###Giant Microwave Absorption in Metallic Grains: Relaxation Mechanism|F. Zhou,B. Spivak,N. Taniguchi,B. L. Altshuler###

Giant Microwave Absorption in Metallic Grains: Relaxation Mechanism. We show that the low frequency microwave absorption of an ensemble of small
metallic grains at low temperatures is dominated by a mesoscopic relaxation
mechanism. Giant positive magnetoresistance and very strong temperature
dependence of the microwave conductivity is predicted.

###Quasi-linear magnetoresistance in an almost 2D band structure|A. J. Schofield,J. R. Cooper###

Quasi-linear magnetoresistance in an almost 2D band structure. We present a theoretical study of the orbital magnetoresistance in a unixial
anisotropic metal within the relaxation-time approximation. The appearance of a
new dimensionless scale, delta=4t_perp/epsilon_F, allows the possibility of a
new region at intermediate fields where the magnetoresistance is linear in
applied magnetic field for currents flowing along the unixial direction. (Here,
t_perp characterizes the bandwidth along the unixial direction.) In the limit
of large anisotropy (small delta), corresponding to a quasi-two-dimensional
metal made up of weakly coupled layers, we obtain an analytic expression for
the magnetoresistance valid for all magnetic fields. We test our analytic
results numerically and we compare our expressions with the c-axis
magnetoresistance of Sr_2RuO_4.

###Spin flip scattering in magnetic junctions|F. Guinea###

Spin flip scattering in magnetic junctions. Processes which flip the spin of an electron tunneling in a junction made up
of magnetic electrodes are studied. It is found that: i) Magnetic impurities
give a contribution which increases the resistance and lowers the
magnetoresistance, which saturates at low temperatures. The conductance
increases at high fields. ii) Magnon assisted tunneling reduces the
magnetoresistance as $T^{3/2}$, and leads to a non ohmic contribution to the
resistance which goes as $V^{3/2}$, iii) Surface antiferromagnetic magnons,
which may appear if the interface has different magnetic properties from the
bulk, gives rise to $T^2$ and $V^2$ contributions to the magnetoresistance and
resistance, respectively, and, iv) Coulomb blockade effects may enhance the
magnetoresistance, when transport is dominated by cotunneling processes.

###A phenomenological model for magnetoresistance in granular polycrystalline colossal magnetoresistive materials: the role of spin polarised tunnelling at the grain boundaries|P. Raychaudhuri,T. K. Nath,A. K. Nigam,R. Pinto###

A phenomenological model for magnetoresistance in granular polycrystalline colossal magnetoresistive materials: the role of spin polarised tunnelling at the grain boundaries. It has been observed that in bulk and polycrystalline thin films of collossal
magnetoresistive (CMR) materials the magnetoresistance follows a different
behaviour compared to single crystals or single crystalline films below the
ferromagnetic transition temperature Tc. In this paper we develop a
phenomenological model to explain the magnetic field dependence of resistance
in granular CMR materials taking into account the spin polarised tunnelling at
the grain boundaries. The model has been fitted to two systems, namely,
La0.55Ho0.15Sr0.3MnO3 and La1.8Y0.5Ca0.7Mn2O7. From the fitted result we have
separated out, in La0.55Ho0.15Sr0.3MnO3, the intrinsic contribution from the
intergranular contribution to the magnetoresistance coming from spin polarised
tunnelling at the grain boundaries. It is observed that the temperature
dependence of the intrinsic contribution to the magnetoresistance in
La0.55Ho0.15Sr0.3MnO3 follows the prediction of double exchange model for all
values of field.

###An ordered stack of spin valves in a layered magnetoresistive perovskite|T. G. Perring,G. Aeppli,T. Kimura,Y. Tokura,M. A. Adams###

An ordered stack of spin valves in a layered magnetoresistive perovskite. The layered compound La2-2xSr1+2xMn2O7 (x=0.3) consists of bilayers of
metallic MnO2 sheets separated by insulating material. The compound exhibits
markedly anisotropic magnetoresistance at temperatures well below the
three-dimensional magnetic ordering temperature TC=90 K in addition to colossal
magnetoresistance around TC. We present neutron diffraction data which show
that the magnetic structure of this material switches from antiferromagnetic
stacking of the (ferromagnetically ordered) sheets in zero field to
ferromagnetic stacking in a field of 1.5 Tesla. The data are the first to be
collected on any manganite as a function of applied field, exactly as the
magnetoresistance data themselves are collected. They provide a natural
explanation of the low-field magnetoresistance in the ordered phase in terms of
spin-polarised tunnelling between the magnetic layers and suggest that the
material is a bulk stack of spin-valve devices.

###The effect of the total density of states at Fermi level on spin polarised tunnelling in granular La0.55Ho0.15Sr0.3MnO3|P. Raychaudhuri,A. K. Nigam,R. Pinto,Sujeet Chaudhary,S. B. Roy###

The effect of the total density of states at Fermi level on spin polarised tunnelling in granular La0.55Ho0.15Sr0.3MnO3. We study the spin polarised tunnelling mechanism through magnetisation and
magnetoresistance in the granular polycrystalline colossal magnetoresistive
manganite, La0.55Ho0.15Sr0.3MnO3. This system has a ferromagnetic transition
temperature (Tc) of 255 K associated with a metal-insulator transition around
the same temperature. We have investigated dependence of the magnetoresistance
due to spin polarised tunnelling on temperature and reduced magnetisation of
the sample. We discuss the significance of our results within the realm of a
model recently proposed by us to explain the spin polarised tunnelling in
granular La0.7Sr0.3MnO3, in the light of the recent finding by A. Biswas et al.
(cond-mat/9806084) regarding the evolution of the total density of states at
Fermi level as a function of temperature in colossal magnetoresistive
materials.

###Ando, Lavrov, and Segawa Reply|Yoichi Ando,A. N. Lavrov,Kouji Segawa###

Ando, Lavrov, and Segawa Reply. Authors' Reply to the Comment by Janossy et al. [cond-mat/0005275] on our
article, "Magnetoresistance Anomalies in Antiferromagnetic
YBa_{2}Cu_{3}O_{6+x}: Fingerprints of Charged Stripes" [cond-mat/9905071, Phys.
Rev. Lett. 83, 2813 (1999)].

###Colossal Magnetoresistance using the Small Polaron Picture with Finite Bandwidth Effects|Sudhakar Yarlagadda###

Colossal Magnetoresistance using the Small Polaron Picture with Finite Bandwidth Effects. We present a small polaron picture and show that finite bandwidth effects are
important to understand colossal magnetoresistance. Besides the polaron size
parameter, we show that there is another parameter (adiabaticity parameter)
that is relevant to studying magnetoresistance. We find that for fixed values
of the polaron size parameter an increase in the adiabaticity parameter
increases the magnetoresistance. The magnetic transition is studied within a
mean field approach. We point out important oversights in the literature. We
find that for the reported values of the bandwidth (based on band structure
calculations) and for experimentally determined values of activation energy and
Debye frequency, the calculated values of the magnetoresistance compare
favorably with experimental ones. We calculate the optical conductivity too and
find that there is reasonable agreement with experiment.

###Anomalous magnetotransport in (Y$_{1-x}$Gd$_{x}$)Co$_{2}$ alloys: interplay of disorder and itinerant metamagnetism|A. T. Burkov,A. Yu. Zyuzin,T. Nakama,K. Yagasaki###

Anomalous magnetotransport in (Y$_{1-x}$Gd$_{x}$)Co$_{2}$ alloys: interplay of disorder and itinerant metamagnetism. New mechanism of magnetoresistivity in itinerant metamagnets with a
structural disorder is introduced basing on analysis of experimental results on
magnetoresistivity, susceptibility, and magnetization of structurally
disordered alloys (Y$_{1-x}$Gd$_{x}$)Co$_{2}$. In this series, YCo$_{2}$ is an
enhanced Pauli paramagnet, whereas GdCo$_{2}$ is a ferrimagnet (T$_{\rm c}$=400
K) with Gd sublattice coupled antiferromagnetically to the itinerant Co-3d
electrons. The alloys are paramagnetic for $x < 0.12$. Large positive
magnetoresistivity has been observed in the alloys with magnetic ground state
at temperatures T$<$T$_{\rm c}$. We show that this unusual feature is linked to
a combination of structural disorder and metamagnetic instability of itinerant
Co-3d electrons. This new mechanism of the magnetoresistivity is common for a
broad class of materials featuring a static magnetic disorder and itinerant
metamagnetism.

###Comment on: "Current-voltage characteristics and zero-resistance state in 2DEG"|M. V. Cheremisin###

Comment on: "Current-voltage characteristics and zero-resistance state in 2DEG". We demonstrate that N(S)-shape current-voltage characteristics proposed to
explain zero-resistance state in Corbino(Hall bar) geometry 2DEG
(cond-mat/0302063, cond-mat/0303530) cannot account essential features of
radiation-induced magnetoresistance oscillations experiments.

###High field magnetoresistivity of epitaxial La2-xSrxCuO4 thin films|J. Vanacken,L. Weckhuysen,T. Wambecq,P. Wagner,V. V. Moshchalkov###

High field magnetoresistivity of epitaxial La2-xSrxCuO4 thin films. A large positive magnetoresistivity (up to tens of percents) is observed in
both underdoped and overdoped superconducting La2-xSrxCuO4 epitaxial thin films
at temperatures far above the superconducting critical temperature Tc. For the
underdoped samples, this magnetoresistance far above Tc cannot be described by
the Kohler rule and we believe it is to be attributed to the influence of
superconducting fluctuations. In the underdoped regime, the large
magnetoresistance is only present when at low temperatures superconductivity
occurs. The strong magnetoresistivity, which persists even at temperatures far
above Tc, can be related to the pairs forming eventually the superconducting
state below Tc. Our observations support the idea of a close relation between
the pseudogap and the superconducting gap and provide new indications for the
presence of pairs above Tc.

###Ballistic magnetoresistance in nickel single-atom conductors|Matthew R. Sullivan,Douglas A. Boehm,Daniel A. Ateya,Susan Z. Hua,Harsh Deep Chopra###

Ballistic magnetoresistance in nickel single-atom conductors. Large ballistic magnetoresistance (BMR) has been measured in Ni single-atom
conductors electrodeposited between microfabricated thin films. These
measurements irrefutably eliminate any magnetostriction related artifacts in
the BMR effect.

###Low temperature charge ordering versus grain boundary effects in polycrystalline La1-xCaxMnO3 manganites|E. Rozenberg###

Low temperature charge ordering versus grain boundary effects in polycrystalline La1-xCaxMnO3 manganites. In this communication the enhancement of low temperature magnetoresistance in
polycrystalline La1-xCaxMnO3 manganites is discussed. It is shown that
so-called grain boundary effects seem to be the simplest and natural
explanation of this phenomenon.

###Large magnetoresistance in $π$-conjugated semiconductor thin film devices|Ö. Mermer,G. Veeraraghavan,T. L. Francis,Y. Sheng,D. T. Nguyen,M. Wohlgenannt,A. Köhler,M. K. Al-Suti,M. S. Khan###

Large magnetoresistance in $π$-conjugated semiconductor thin film devices. Following the recent discovery of large magnetoresistance at room temperature
in polyfluorence sandwich devices, we have performed a comprehensive
magnetoresistance study on a set of organic semiconductor sandwich devices made
from different pi-conjugated polymers and small molecules. The measurements
were performed at different temperatures, ranging from 10K to 300K, and at
magnetic fields, $B < 100mT$. We observed large negative or positive
magnetoresistance (up to 10% at 300K and 10mT) depending on material and device
operating conditions. We compare the results obtained in devices made from
different materials with the goal of providing a comprehensive picture of the
experimental data. We discuss our results in the framework of known
magnetoresistance mechanisms and find that none of the existing models can
explain our results.

###Large linear magnetoresistivity in strongly inhomogeneous planar and layered systems|S. A. Bulgadaev,F. V. Kusmartsev###

Large linear magnetoresistivity in strongly inhomogeneous planar and layered systems. Explicit expressions for magnetoresistance $R$ of planar and layered strongly
inhomogeneous two-phase systems are obtained, using exact dual transformation,
connecting effective conductivities of in-plane isotropic two-phase systems
with and without magnetic field. These expressions allow to describe the
magnetoresistance of various inhomogeneous media at arbitrary concentrations
$x$ and magnetic fields $H$. All expressions show large linear
magnetoresistance effect with different dependencies on the phase
concentrations. The corresponding plots of the $x$- and $H$-dependencies of
$R(x,H)$ are represented for various values, respectively, of magnetic field
and concentrations at some values of inhomogeneity parameter. The obtained
results show a remarkable similarity with the existing experimental data on
linear magnetoresistance in silver chalcogenides $Ag_{2+\delta}Se.$ A possible
physical explanation of this similarity is proposed. It is shown that the
random, stripe type, structures of inhomogeneities are the most suitable for a
fabrication of magnetic sensors and a storage of information at room
temperatures.

###Pinhole and tunneling conduction channels superimposed in magnetic tunnel junction: results and inferences|Soumik Mukhopadhyay,I. Das###

Pinhole and tunneling conduction channels superimposed in magnetic tunnel junction: results and inferences. The influence of ballistic channels superimposed on tunneling conduction
channels in magnetic tunnel junctions has been studied in a manganese oxide
based tunneling device. Inversion of magnetoresistance has been observed in
magnetic tunnel junctions with pinhole nanocontacts over a broad temperature
range. The tunnel magnetoresistance undergoes a change of sign at higher bias
and temperature. This phenomenon is attributed to the parallel conduction
channels consisting of spin conserved ballistic transport through the pinhole
contact where the transmission probability is close to unity and spin polarized
tunneling across the insulating spacer with weak transmittivity. The results
seem to resolve a controversy regarding ballistic magnetoresistance in
ferromagnetic nanocontacts and establishes that ballistic magnetoresistance do
exist even if the previous results are attributed to magnetostriction and
magnetostatic force related artifacts.

###Colossal Positive Magnetoresistance in a Doped Nearly Magnetic Semiconductor|Rongwei Hu,K. J. Thomas,Y. Lee,T. Vogt,E. S. Choi,V. F. Mitrovic,R. P. Hermann,F. Grandjean,P. C. Canfield,J. W. Kim,A. I. Goldman,C. Petrovic###

Colossal Positive Magnetoresistance in a Doped Nearly Magnetic Semiconductor. We report on a positive colossal magnetoresistance (MR) induced by
metallization of FeSb$_{2}$, a nearly magnetic or "Kondo" semiconductor with 3d
ions. We discuss contribution of orbital MR and quantum interference to
enhanced magnetic field response of electrical resistivity.

###Magnetoresistance in semiconductor structures with hopping conductivity: effects of random potential and generalization for the case of acceptor states|N. V. Agrinskaya,V. I. Kozub,A. V. Shumilin,E. Sobko###

Magnetoresistance in semiconductor structures with hopping conductivity: effects of random potential and generalization for the case of acceptor states. We reconsider the theory of magnetoresistance in hopping semiconductors.
First, we have shown that the random potential of the background impurities
affects significantly preexponential factor of the tunneling amplitude which
becomes to be a short-range one in contrast to the long-range one for purely
Coulomb hopping centers. This factor to some extent suppresses the negative
interference magnetoresistance and can lead to its decrease with temperature
decrease which is in agreement with earlier experimental observations. We have
also extended the theoretical models of positive spin magnetoresistance, in
particular, related to a presence of doubly occupied states (corresponding to
the upper Hubbard band) to the case of acceptor states in 2D structures. We
have shown that this mechanism can dominate over classical wave-shrinkage
magnetoresistance at low temperatures. Our results are in semi-quantitative
agreement with experimental data.

###Weak field magnetoresistance of narrow-gap semiconductors InSb|R. Yang,G. L. Yu,Yanhui Zhang,P. P. Chen###

Weak field magnetoresistance of narrow-gap semiconductors InSb. The magnetoresistance of InSb has been intensively investigated. The
experiments we perform here focus on weak field magnetoresistance of InSb thin
film. We investigate the magnetoresistance of InSb films in perpendicular,
tilted as well as parallel magnetic field. Our results verify the previous
observations concerning weak localization effect in InSb thin film. Moreover,
we systematically study the anisotropy of magnetoresistance of InSb. We find
that the existence of in-plane field can effectively suppress the weak
localization effect of InSb film. We fit the experimental data with two types
of models, the match between data and model is excellent. From the fitting
procedure, we get information about phase coherence time, spin-orbit scattering
time. The information about Zeeman effect and sample roughness are also
extracted from the fitting procedure.

###Linear magnetoresistivity in the ternary AM2B2 and A3Rh8B6 phases (A = Ca, Sr; M = Rh, Ir)|Hiroyuki Takeya,Mohammed ElMassalami###

Linear magnetoresistivity in the ternary AM2B2 and A3Rh8B6 phases (A = Ca, Sr; M = Rh, Ir). We studied the magnetoresistivity of the AM2B2 and A3Rh8B6 (A = Ca, Sr; M =
Rh, Ir) compounds within the ranges 1.8<=T<=300 K and 0<=H<=50 kOe. The
zero-field resistivity {\rho}0(T) is metallic and follows closely the
Bloch-Gr\"uneisen description. A positive, nonsaturating, and dominantly
linear-in-H magnetoresistivity was observed in all samples, including the ones
with a superconducting ground state. Such {\Delta}{\rho}T(H)/{\rho}T(0),
reaching 1200% in favorable cases, was found to be much stronger for the AM2B2
compounds and to decrease with temperature as well as when Ca is replaced by
Sr, or Rh is replaced by Ir. Finally, the general features of the observed
magnetoresistivity will be discussed in terms of the Abrikosov model for the
linear magnetoresistivity in inhomogeneous materials.

###Quantum transport of two-dimensional Dirac fermions in SrMnBi2|Kefeng Wang,D. Graf,Hechang Lei,S. W. Tozer,C. Petrovic###

Quantum transport of two-dimensional Dirac fermions in SrMnBi2. We report two-dimensional quantum transport in SrMnBi$_2$ single crystals.
The linear energy dispersion leads to the unusual nonsaturated linear
magnetoresistance since all Dirac fermions occupy the lowest Landau level in
the quantum limit. The transverse magnetoresistance exhibits a crossover at a
critical field $B^*$ from semiclassical weak-field $B^2$ dependence to the
high-field linear-field dependence. With increase in the temperature, the
critical field $B^*$ increases and the temperature dependence of $B^*$
satisfies quadratic behavior which is attributed to the Landau level splitting
of the linear energy dispersion. The effective magnetoresistant mobility
$\mu_{MR}\sim 3400$ cm$^2$/Vs is derived. Angular dependent magnetoresistance
and quantum oscillations suggest dominant two-dimensional (2D) Fermi surfaces.
Our results illustrate the dominant 2D Dirac fermion states in SrMnBi$_2$ and
imply that bulk crystals with Bi square nets can be used to study low
dimensional electronic transport commonly found in 2D materials like graphene.

###Anomalous Magnetoresistance in Fibonacci Multilayers|L. D. Machado,C. G. Bezerra,M. A. Correa,C. Chesman,J. E. Pearson,A. Hoffmann###

Anomalous Magnetoresistance in Fibonacci Multilayers. The present paper theoretically investigates magnetoresistance curves in
quasiperiodic magnetic multilayers for two different growth directions, namely
[110] and [100]. We considered identical ferromagnetic layers separated by
non-magnetic layers with two different thicknesses chosen based on the
Fibonacci sequence. Using parameters for Fe/Cr multilayers, four terms were
included in our description of the magnetic energy: Zeeman, cubic anisotropy,
bilinear and biquadratic couplings. The minimum energy was determined by the
gradient method and the equilibrium magnetization directions found were used to
calculate magnetoresistance curves. By choosing spacers with a thickness such
that biquadratic coupling is stronger than bilinear coupling, unusual behaviors
for the magnetoresistance were observed: (i) for the [110] case there is a
different behavior for structures based on even and odd Fibonacci generations;
and more interesting, (ii) for the [100] case we found magnetic field ranges
for which the magnetoresistance increases with magnetic field.

###Weak localization and magnetoresistance in a two-leg ladder model|Michael P. Schneider,Sam T. Carr,Igor V. Gornyi,Alexander D. Mirlin###

Weak localization and magnetoresistance in a two-leg ladder model. We analyze the weak localization correction to the conductivity of a spinless
two-leg ladder model in the limit of strong dephasing \tau_\phi << \tau_tr,
paying particular attention to the presence of a magnetic field, which leads to
an unconventional magnetoresistance behavior. We find that the magnetic field
leads to three different effects: (i) negative magnetoresistance due to the
regular weak localization correction (ii) effective decoupling of the two
chains, leading to positive magnetoresistance and (iii) oscillations in the
magnetoresistance originating from the nature of the low-energy collective
excitations. All three effects can be observed depending on the parameter
range, but it turns out that large magnetic fields always decouple the chains
and thus lead to the curious effect of magnetic field enhanced localization.

###Negative Magnetoresistance and Spin Filtering of Spin-Coupled Diiron-Oxo Clusters|Rui-Ning Wang,Jorge H. Rodriguez,Wu-Ming Liu###

Negative Magnetoresistance and Spin Filtering of Spin-Coupled Diiron-Oxo Clusters. Spin dependent transport has been investigated for an {\it open shell
singlet} diiron-oxo cluster. Currents and magnetoresistances have been studied,
as a function of spin state, within the non-equilibrium Green's function
approach. The applied bias can be used for tuning the sign of the observed
magnetoresistance. A colossal magnetoresistance ratio has been determined, on
the order of to 6000$%$, for hydrogen anchoring. Applied biases lower than 0.3
V, in conjunction with sulfur anchoring, induce a negative magnetoresistance
due to lowering of the anchor-scatterer tunneling barrier. In addition, the
diiron-oxo cluster displays nearly perfect spin filtering for parallel
alignment of the iron magnetic moments due to energetic proximity, relative to
the Fermi level, of its highest occupied molecular orbitals.

###Giant negative magnetoresistance driven by spin-orbit coupling at the LAO/STO interface|M. Diez,A. M. R. V. L. Monteiro,G. Mattoni,E. Cobanera,T. Hyart,E. Mulazimoglu,N. Bovenzi,C. W. J. Beenakker,A. D. Caviglia###

Giant negative magnetoresistance driven by spin-orbit coupling at the LAO/STO interface. The LAO/STO interface hosts a two-dimensional electron system that is
unusually sensitive to the application of an in-plane magnetic field.
Low-temperature experiments have revealed a giant negative magnetoresistance
(dropping by 70\%), attributed to a magnetic-field induced transition between
interacting phases of conduction electrons with Kondo-screened magnetic
impurities. Here we report on experiments over a broad temperature range,
showing the persistence of the magnetoresistance up to the 20~K range ---
indicative of a single-particle mechanism. Motivated by a striking
correspondence between the temperature and carrier density dependence of our
magnetoresistance measurements we propose an alternative explanation. Working
in the framework of semiclassical Boltzmann transport theory we demonstrate
that the combination of spin-orbit coupling and scattering from finite-range
impurities can explain the observed magnitude of the negative
magnetoresistance, as well as the temperature and electron density dependence.

###Drastic pressure effect on the extremely large magnetoresistance in WTe2: quantum oscillation study|P. L. Cai,J. Hu,L. P. He,J. Pan,X. C. Hong,Z. Zhang,J. Zhang,J. Wei,Z. Q. Mao,S. Y. Li###

Drastic pressure effect on the extremely large magnetoresistance in WTe2: quantum oscillation study. The quantum oscillations of the magnetoresistance under ambient and high
pressure have been studied for WTe$_2$ single crystals, in which extremely
large magnetoresistance was discovered recently. By analyzing the Shubnikov-de
Haas oscillations, four Fermi surfaces are identified, and two of them are
found to persist to high pressure. The sizes of these two pockets are
comparable, but show increasing difference with pressure. At 0.3 K and in 14.5
T, the magnetoresistance decreases drastically from 1.25 $\times$ $10^5$\%
under ambient pressure to 7.47 $\times$ $10^3$\% under 23.6 kbar, which is
likely caused by the relative change of Fermi surfaces. These results support
the scenario that the perfect balance between the electron and hole populations
is the origin of the extremely large magnetoresistance in WTe$_2$.

###Fourier transform analysis of irradiated Weiss oscillations|Jesús Iñarrea,Gloria Platero###

Fourier transform analysis of irradiated Weiss oscillations. We present a theoretical approach to study the effect of microwave radiation
on the magnetoresistance of a one-dimensional superlattice.
  In our proposal the magnetoresistance of a unidirectional spatial periodic
potential (superlattice), is modulated by microwave radiation due to an
interference effect between both, space and time-dependent potentials. The
final magnetoresistance will mainly depend on the spatial period of the
superlattice and the radiation frequency. %Then, by tuning either the spatial
period of the superlattice or the radiation %frequency, the magnetoresistance
can be strongly modified. We consider an approach to study these effects based
on the fast Fourier transform of the obtained magnetorresistance profiles in
function of the inverse of the magnetic field. Based on this theory we propose
the design of a novel radiation sensor for the Terahertz band.} % We first
study the FFT of the system for each potential individually. Then we study
jointly the FFT of the system when the two types of potentials are
simultaneously acting.

###Quasi-linear magnetoresistance and the violation of Kohler's rule in the quasi-one-dimensional Ta$_4$Pd$_3$Te$_{16}$ superconductor|Xiaofeng Xu,W. H. Jiao,N. Zhou,Y. Guo,Y. K. Li,Jianhui Dai,Z. Q. Lin,Y. J. Liu,Zengwei Zhu,Xin Lu,H. Q. Yuan,Guanghan Cao###

Quasi-linear magnetoresistance and the violation of Kohler's rule in the quasi-one-dimensional Ta$_4$Pd$_3$Te$_{16}$ superconductor. We report on the quasi-linear in field intrachain magnetoresistance in the
normal state of a quasi-one-dimensional superconductor Ta$_4$Pd$_3$Te$_{16}$
($T_c$$\sim$4.6 K). Both the longitudinal and transverse in-chain
magnetoresistance shows a power-law dependence, $\Delta
\rho$$\propto$B$^\alpha$, with the exponent $\alpha$ close to 1 over a wide
temperature and field range. The magnetoresistance shows no sign of saturation
up to 50 tesla studied. The linear magnetoresistance observed in
Ta$_4$Pd$_3$Te$_{16}$ is found to be overall inconsistent with the
interpretations based on the Dirac fermions in the quantum limit, charge
conductivity fluctuations as well as quantum electron-electron interference.
Moreover, it is observed that the Kohler's rule, regardless of the field
orientations, is violated in its normal state. This result suggests the loss of
charge carriers in the normal state of this chain-containing compound, due
presumably to the charge-density-wave fluctuations.

###Effect of Quantum Tunneling on Spin Hall Magnetoresistance|Seulgi Ok,Wei Chen,Manfred Sigrist,Dirk Manske###

Effect of Quantum Tunneling on Spin Hall Magnetoresistance. We present a formalism that simultaneously incorporates the effect of quantum
tunneling and spin diffusion on spin Hall magnetoresistance observed in normal
metal/ferromagnetic insulator bilayers (such as Pt/YIG) and normal
metal/ferromagnetic metal bilayers (such as Pt/Co), in which the angle of
magnetization influences the magnetoresistance of the normal metal. In the
normal metal side the spin diffusion is known to affect the landscape of the
spin accumulation caused by spin Hall effect and subsequently the
magnetoresistance, while on the ferromagnet side the quantum tunneling effect
is detrimental to the interface spin current which also affects the spin
accumulation. The influence of generic material properties such as spin
diffusion length, layer thickness, interface coupling, and insulating gap can
be quantified in a unified manner, and experiments that reveal the quantum
feature of the magnetoresistance are suggested.

###Hidden Weyl Points in Centrosymmetric Paramagnetic Metals|Dominik Gresch,QuanSheng Wu,Georg W. Winkler,Alexey A. Soluyanov###

Hidden Weyl Points in Centrosymmetric Paramagnetic Metals. The transition metal dipnictides TaAs2 , TaSb2 , NbAs2 and NbSb2 have
recently sparked interest for exhibiting giant magnetoresistance. While the
exact nature of magnetoresistance in these materials is still under active
investigation, there are experimental results indicating anisotropic negative
magnetoresistance. We study the effect of magnetic field on the band structure
topology of these materials by applying a Zeeman splitting. In the absence of
magnetic field, we find that the materials are weak topological insulators,
which is in agreement with previous studies. When the magnetic field is
applied, we find that type-II Weyl points form. This result is found first from
a symmetry argument, and then numerically for a k.p model of TaAs2 and a
tight-binding model of NbSb2. This effect can be of help in search for an
explanation of the anomalous magnetoresistance in these materials.

###Viscous magnetoresistance of correlated electron liquids|Alex Levchenko,Hong-Yi Xie,A. V. Andreev###

Viscous magnetoresistance of correlated electron liquids. We develop a theory of magnetoresistance of two-dimensional electron systems
in a smooth disorder potential in the hydrodynamic regime. Our theory applies
to two-dimensional semiconductor structures with strongly correlated carriers
when the mean free path due to electron-electron collisions is sufficiently
short. The dominant contribution to magnetoresistance arises from the
modification of the flow pattern by the Lorentz force, rather than the magnetic
field dependence of the kinetic coefficients of the electron liquid. The
resulting magnetoresistance is positive and quadratic at weak fields. Although
the resistivity is governed by both viscosity and thermal conductivity of the
electron fluid, the magnetoresistance is controlled by the viscosity only. This
enables extraction of viscosity of the electron liquid from magnetotransport
measurements.

###Spin Hall magnetoresistance in antiferromagnet/heavy-metal heterostructures|Johanna Fischer,Olena Gomonay,Richard Schlitz,Kathrin Ganzhorn,Nynke Vlietstra,Matthias Althammer,Hans Huebl,Matthias Opel,Rudolf Gross,Sebastian T. B. Goennenwein,Stephan Geprägs###

Spin Hall magnetoresistance in antiferromagnet/heavy-metal heterostructures. We investigate the spin Hall magnetoresistance in thin film bilayer
heterostructures of the heavy metal Pt and the antiferromagnetic insulator NiO.
While rotating an external magnetic field in the easy plane of NiO, we record
the longitudinal and the transverse resistivity of the Pt layer and observe an
amplitude modulation consistent with the spin Hall magnetoresistance. In
comparison to Pt on collinear ferrimagnets, the modulation is phase shifted by
90{\deg} and its amplitude strongly increases with the magnitude of the
magnetic field. We explain the observed magnetic field-dependence of the spin
Hall magnetoresistance in a comprehensive model taking into account magnetic
field induced modifications of the domain structure in antiferromagnets. With
this generic model we are further able to estimate the strength of the
magnetoelastic coupling in antiferromagnets. Our detailed study shows that the
spin Hall magnetoresistance is a versatile tool to investigate the magnetic
spin structure as well as magnetoelastic effects, even in antiferromagnetic
multidomain materials.

###Change in the order of magnetic transition in HoRhGe as probed by magnetoresistance and magnetocaloric studies|Sachin B. Gupta,K. G. Suresh,A. K. Nigam###

Change in the order of magnetic transition in HoRhGe as probed by magnetoresistance and magnetocaloric studies. Magnetoresistance and magnetocaloric properties of polycrystalline HoRhGe
have been studied. This compound orders antiferromagnetically with a Neel
temperature (TN) of 5.5 K and undergoes a first order metamagnetic transition
at 2 K. It shows a large negative magnetoresistance of 25% at TN, for a field
of 50 kOe. However, at 2 K and in lower fields, the magnetoresistance is found
to be positive with a magnitude of about 12%, which is attributed to the first
order metamagnetic transition. The compound also shows large magnetocaloric
effect near its Neel temperature. Field dependence of magnetic entropy change
also reflects the change in the nature of magnetic transition as the field is
increased. The value of magnetic entropy change (-{\Delta}SM) is found to be
11.1 J/kg K for a field change of 50 kOe. Field dependence of magnetoresistance
and magnetocaloric effect clearly shows the change in the order of the
metamagnetic transition with increase in field.

###Aharonov-Bohm effect and giant magnetoresistance in graphene nanoribbon rings|Viet-Hung Nguyen,Yann-Michel Niquet,Philippe Dollfus###

Aharonov-Bohm effect and giant magnetoresistance in graphene nanoribbon rings. We report a numerical study on Aharonov-Bohm (AB) effect and giant
magnetoresistance in rectangular rings made of graphene nanoribbons (GNRs). We
show that in low energy regime where only the first subband of contact GNRs
contributes to the transport, the transmission probability can be strongly
modulated, i.e., almost fully suppressed, when tuning a perpendicular magnetic
field. On this basis, strong AB oscillations with giant negative
magnetoresistance can be achieved at room temperature. The magnetoresistance
reaches thousands % in perfect GNR rings and a few hundred % with edge
disordered GNRs. The design rules to observe such strong effects are also
discussed. Our study hence provides guidelines for further investigations of
the AB interference and to obtain high magnetoresistance in graphene devices.

###Vortex crossing, trapping and pinning in superconducting nanowires of a NbSe$_2$ two-dimensional crystal|Shaun A. Mills,Jacob J. Wisser,Chenyi Shen,Zhuan Xu,Ying Liu###

Vortex crossing, trapping and pinning in superconducting nanowires of a NbSe$_2$ two-dimensional crystal. Nanowires of two-dimensional (2D) crystals of type-II superconductor NbSe$_2$
prepared by electron-beam lithography were studied, focusing on the effect of
the motion of Abrikosov vortices. We present magnetoresistance measurements on
these nanowires and show features related to vortex crossing, trapping, and
pinning. The vortex crossing rate was found to vary non-monotonically with the
applied field, which results in non-monotonic magnetoresistance variations in
agreement with theoretical calculations in the London approximation. Above the
lower critical field, $H_{c1}$, the crossing rate is also influenced by
vortices trapped by sample boundaries or pinning centers, leading to
sample-specific magnetoresistance patterns. We show that the local pinning
potential can be modified by intentionally introducing surface adsorbates,
making the magnetoresistance pattern a "magneto fingerprint" of the
sample-specific configuration of vortex pinning centers in a 2D crystal
superconducting nanowire.

###Features of Low Temperature Tunnel Magnetoresistance in Pressed Powder of Chromium Dioxide|V. A. Horielyi,N. V. Dalakova,E. Yu. Beliayev###

Features of Low Temperature Tunnel Magnetoresistance in Pressed Powder of Chromium Dioxide. Resistive and magnetoresistive properties of two samples of compacted powders
of ferromagnetic half-metal CrO_{2} with shape anisotropy of nanoparticles were
studied. The powders were prepared by the method of hydrothermal synthesis and
consisted of needle-like particles with average diameters 24-34 nm and mean
length of 300 nm. One of the samples has been made of compacted powder of pure
CrO_{2}, while another sample has been prepared from a substitution solid
solution Cr_{1-x}Fe_{x}O_{2}. The aim of this work was to study the effect of
Fe impurity on the value of tunnel resistance and tunnel magnetoresistance for
compacted CrO_{2} powders. It was found that the addition of Fe impurity leads
to an increase in the coercive force of the powder and reduce the tunnel
magnetoresistance. We assume resonant tunneling mechanism on the Fe impurities.
We found a strong dependence of the magnetoresistance on the spin relaxation
rate in the process of magnetization reversal. The possible reasons for such
dependence are discussed.

###Magnetoresistance evidence on surface state and field-dependent bulk gap in Kondo insulator SmB6|F. Chen,C. Shang,Z. Jin,D. Zhao,Y. P. Wu,Z. J. Xiang,Z. C. Xia,A. F. Wang,X. G. Luo,T. Wu,X. H. Chen###

Magnetoresistance evidence on surface state and field-dependent bulk gap in Kondo insulator SmB6. Recently, the resistance saturation at low temperature in Kondo insulator
SmB6, a long-standing puzzle in condensed matter physics, was proposed to
originate from topological surface state. Here,we systematically studied the
magnetoresistance of SmB6 at low temperature up to 55 Tesla. Both temperature-
and angular-dependent magnetoresistances show a similar crossover behavior
below 5 K. Furthermore, the angular-dependent magnetoresistance on different
crystal face confirms a two-dimensional surface state as the origin of
magnetoresistances crossover below 5K. Based on two-channels model consisting
of both surface and bulk states, the field-dependence of bulk gap with critical
magnetic field (Hc) of 196 T is extracted from our temperature-dependent
resistance under different magnetic fields. Our results give a consistent
picture to understand the low-temperature transport behavior in SmB6,
consistent with topological Kondo insulator scenario.

###Linear magnetoresistance in metals: guiding center diffusion in a smooth random potential|Justin C. W. Song,Gil Refael,Patrick A. Lee###

Linear magnetoresistance in metals: guiding center diffusion in a smooth random potential. We predict that guiding center (GC) diffusion yields a linear and
non-saturating (transverse) magnetoresistance in 3D metals. Our theory is
semi-classical and applies in the regime where the transport time is much
greater than the cyclotron period, and for weak disorder potentials which are
slowly varying on a length scale much greater than the cyclotron radius. Under
these conditions, orbits with small momenta along magnetic field $B$ are
squeezed and dominate the transverse conductivity. When disorder potentials are
stronger than the Debye frequency, linear magnetoresistance is predicted to
survive up to room temperature and beyond. We argue that magnetoresistance from
GC diffusion explains the recently observed giant linear magnetoresistance in
3D Dirac materials.

###Magnetoresistance and Quantum Oscillations of an Electrostatically Tuned Semimetal-to-Metal Transition in Ultra-Thin WTe2|Valla Fatemi,Quinn D. Gibson,Kenji Watanabe,Takashi Taniguchi,Robert J. Cava,Pablo Jarillo-Herrero###

Magnetoresistance and Quantum Oscillations of an Electrostatically Tuned Semimetal-to-Metal Transition in Ultra-Thin WTe2. We report on electronic transport measurements of electrostatically gated
nano-devices of the semimetal WTe\textsubscript{2}. High mobility metallic
behavior is achieved in the 2D limit by encapsulating thin flakes in an inert
atmosphere. At low temperatures, we find that a large magnetoresistance can be
turned on and off by electrostatically doping the system between a semimetallic
state and an electron-only metallic state, respectively. We confirm the nature
of the two regimes by analyzing the magnetoresistance and Hall effect with a
two-carrier model, as well as by analysis of Shubnikov-de Haas oscillations,
both of which indicate depletion of hole carriers via the electrostatic gate.
This confirms that semiclassical transport of two oppositely charged carriers
accurately describes the exceptional magnetoresistance observed in this
material. Finally, we also find that the magnetoresistance power law is
sub-quadratic and density-independent, suggesting new physics specifically in
the semimetallic regime.

###The study on quantum material WTe2|Xing-Chen Pan,Xuefeng Wang,Fengqi Song,Baigeng Wang###

The study on quantum material WTe2. WTe2 and its sister alloys have attracted tremendous attentions recent years
due to the large non-saturating magnetoresistance and topological non-trivial
properties. Herein, we briefly review the electrical property studies on this
new quantum material.

###Giant Anisotropic Magnetoresistance due to Purely Orbital Rearrangement in the Quadrupolar Heavy Fermion Superconductor PrV$_2$Al$_{20}$|Yasuyuki Shimura,Qiu Zhang,Bin Zeng,Daniel Rhodes,Rico Uwe Schonemann,Masaki Tsujimoto,Yosuke Matsumoto,Akito Sakai,Toshiro Sakakibara,Koji Araki,Wenkai Zheng,Qiong Zhou,Luis Balicas,Satoru Nakatsuji###

Giant Anisotropic Magnetoresistance due to Purely Orbital Rearrangement in the Quadrupolar Heavy Fermion Superconductor PrV$_2$Al$_{20}$. We report the discovery of giant and anisotropic magnetoresistance due to the
orbital rearrangement in a non-magnetic correlated metal. In particular, we
measured the magnetoresistance under fields up to 31.4 T in the cubic Pr-based
heavy fermion superconductor PrV$_2$Al$_{20}$ with a non-magnetic $\Gamma _3$
doublet ground state, exhibiting antiferro-quadrupole ordering below 0.7 K. For
the [100] direction, we find that the high-field phase appears between 12 T and
25 T, accompanied by a large jump at 12 T in the magnetoresistance ($\Delta MR
\sim $ 100 $\% $) and in the anisotropic magnetoresistivity (AMR) ratio by
$\sim $ 20 $\% $. These observations indicate that the strong hybridization
between the conduction electrons and anisotropic quadrupole moments leads to
the Fermi surface reconstruction upon crossing the field-induced
antiferro-quadrupole (orbital) rearrangement.

###False spin zeros in the angular dependence of magnetic quantum oscillation in quasi-two-dimensional metals|P. D. Grigoriev,T. I. Mogilyuk###

False spin zeros in the angular dependence of magnetic quantum oscillation in quasi-two-dimensional metals. The interplay between angular and quantum magnetoresistance oscillations in
quasi-two-dimensional metals leads to the angular oscillations of the amplitude
of quantum oscillations. This effect becomes pronounced in high magnetic field,
when the simple factorization of the angular and quantum oscillations is not
valid. The amplitude of quantum magnetoresistance oscillations is reduced at
the Yamaji angles, i.e. at the maxima of the angular magnetoresistance
oscillations. These angular beats of the amplitude of quantum oscillations
resemble and may be confused with the spin-zero effect, coming from the Zeeman
splitting. The proposed effect of "false spin zeros" becomes stronger in the
presence of incoherent channels of interlayer electron transport and can be
used to separate the different contributions to the Dingle temperature and to
check for violations from the standard factorization of angular and quantum
magnetoresistance oscillations.

###Giant and Linear Magnetoresistance in Liquid Metals at Ambient Temperature|Xiaolin Wang,Feixiang Xiang,David Cortie,Zengji Yue,Zhi Li,Zhidong Zhang,Lina Sang###

Giant and Linear Magnetoresistance in Liquid Metals at Ambient Temperature. Disorder-induced magnetoresistance has been reported in a range of solid
metals and semiconductors, however, the underlying physical mechanism is still
under debate because it is difficult to experimentally control. Liquid metals,
due to lack of long-range order, offers an ideal model system where many forms
of disorder can be deactivated by freezing the liquid. Here we report
non-saturating magnetoresistance discovered in the liquid state of three
metals: Ga, Ga-In-Sn and Bi-Pb-Sn-In alloys. The giant magnetoresistance
appears above the respective melting points and has a maximum of 2500% at 14
Tesla. The reduced diamagnetism in the liquid state implies that a short-mean
free path of the electron, induced by the spatial distribution of the liquid
structure, is a key factor. A potential technological merit of this
liquidtronic magnetoresistance is that it naturally operates at higher
temperatures.

###Observation of spin-orbit magnetoresistance in CoFeB/heavy metal/MgO with existence of both spin Hall effect and Edelstein effect|Haoran Ni,Shuangfeng Li,Qihan Zhang,Jiguang Yao,Yongwei Cui,Xiaolong Fan,Desheng Xue###

Observation of spin-orbit magnetoresistance in CoFeB/heavy metal/MgO with existence of both spin Hall effect and Edelstein effect. In this paper, we report the observation of spin-orbit magnetoresistance
(SOMR) in ferromagnetic metal/heavy metal/MgO system. We measure the
magnetoresistance as the function of the thickness of heavy metal (HM) for
CoFeB/HM/MgO and CoFeB/HM films where HM = Pt and Ta. Besides the conventional
spin Hall magnetoresistance (SMR) peak, the evidence of the SOMR is indicated
by another peak of the MR ratio when the thickness of HM is around 1 ~ 2 nm for
CoFeB/HM/MgO films, which is absent for CoFeB/HM films. We speculate the SOMR
observed in our experiment originates from the spin-orbit coupling at the
HM/MgO interface. We give the boundary conditions of our samples and calculate
the theoretical magnetoresistance based on spin diffusion equation. Based on
the theoretical results, we can explain the two peaks we observe separately
comes from the spin current generated by spin Hall effect and by Edelstein
effect.

###Comment on "Weak localization in GaMnAs: evidence of impurity band transport" by L. P. Rokhinson et. al. (Phys. Rev. B, 76, 161201 R; arXivCond-mat:0707.2416)|N. V. Agrinskaya,V. I. Kozub###

Comment on "Weak localization in GaMnAs: evidence of impurity band transport" by L. P. Rokhinson et. al. (Phys. Rev. B, 76, 161201 R; arXivCond-mat:0707.2416). We suggest that negative magnetoresistance in small magnetic fields at
temperatures lower than 3 K reported in the paper under discussion may be
related to superconducting transition in In leads (with Tc = 3.4 K).

###Robust scheme for magnetotransport analysis in topological insulators|G. Eguchi,S. Paschen###

Robust scheme for magnetotransport analysis in topological insulators. The recent excitement about Dirac and Weyl fermion systems has renewed
interest in magnetotransport properties of multi-carrier systems. However, the
complexity of their analysis, even in the simplest two-carrier case, has
hampered a good understanding of the underlying phenomena. Here we propose a
new analysis scheme for two independent conduction channels, that strongly
reduces previous ambiguities and allows to draw robust conclusions. This is
demonstrated explicitly for the example of three-dimensional topological
insulators. Their temperature and gate voltage-dependent Hall coefficient and
transverse magnetoresistance behavior, including the phenomenon of huge linear
transverse magnetoresistance, can be traced back to two conduction channels,
with fully determined carrier concentrations and mobilities. We further derive
an upper limit for the transverse magnetoresistance. Its violation implies
field dependences in the electronic band structure or scattering processes, or
the presence of more than two effective carrier types. Remarkably, none of the
three-dimensional topological insulators or semimetals with particularly large
transverse magnetoresistance violates this limit.

###Spin transport in antiferromagnetic NiO and magnetoresistance in Y$_3$Fe$_5$O$_{12}$/NiO/Pt structures|Yu-Ming Hung,Christian Hahn,Houchen Chang,Mingzhong Wu,Hendrik Ohldag,Andrew D. Kent###

Spin transport in antiferromagnetic NiO and magnetoresistance in Y$_3$Fe$_5$O$_{12}$/NiO/Pt structures. We have studied spin transport and magnetoresistance in yttrium iron garnet
(YIG)/NiO/Pt trilayers with varied NiO thickness. To characterize the spin
transport through NiO we excite ferromagnetic resonance in YIG with a microwave
frequency magnetic field and detect the voltage associated with the inverse
spin-Hall effect (ISHE) in the Pt layer. The ISHE signal is found to decay
exponentially with the NiO thickness with a characteristic decay length of 3.9
nm. This is contrasted with the magnetoresistance in these same structures. The
symmetry of the magnetoresistive response is consistent with spin-Hall
magnetoresistance (SMR). However, in contrast to the ISHE response, as the NiO
thickness increases the SMR signal goes towards zero abruptly at a NiO
thickness of $\simeq$ 4 nm, highlighting the different length scales associated
with the spin-transport in NiO and SMR in such trilayers.

###Nonmonotonic magnetoresistance of a two-dimensional viscous electron-hole fluid in a confined geometry|P. S. Alekseev,A. P. Dmitriev,I. V. Gornyi,V. Yu. Kachorovskii,B. N. Narozhny,M. Titov###

Nonmonotonic magnetoresistance of a two-dimensional viscous electron-hole fluid in a confined geometry. Ultra-pure conductors may exhibit hydrodynamic transport where the collective
motion of charge carriers resembles the flow of a viscous fluid. In a confined
geometry (e.g., in ultra-high quality nanostructures) the electronic fluid
assumes a Poiseuille-like flow. Applying an external magnetic field tends to
diminish viscous effects leading to large negative magnetoresistance. In
two-component systems near charge neutrality the hydrodynamic flow of charge
carriers is strongly affected by the mutual friction between the two
constituents. At low fields, the magnetoresistance is negative, however at high
fields the interplay between electron-hole scattering, recombination, and
viscosity results in a dramatic change of the flow profile: the
magnetoresistance changes its sign and eventually becomes linear in very high
fields. This novel non-monotonic magnetoresistance can be used as a fingerprint
to detect viscous flow in two-component conducting systems.

###Giant anisotropic magnetoresistance and planar Hall effect in the Dirac semimetal Cd3As2|Hui Li,Huanwen Wang,Hongtao He,Jiannong Wang,Shun-Qing Shen###

Giant anisotropic magnetoresistance and planar Hall effect in the Dirac semimetal Cd3As2. Anisotropic magnetoresistance is the change tendency of resistance of a
material on the mutual orientation of the electric current and the external
magnetic field. Here, we report experimental observations in the Dirac
semimetal Cd3As2 of giant anisotropic magnetoresistance and its transverse
version, called the planar Hall effect. The relative anisotropic
magnetoresistance is negative and up to -68% at 2 K and 10 T. The high
anisotropy and the minus sign in this isotropic and nonmagnetic material are
attributed to a field-dependent current along the magnetic field, which may be
induced by the Berry curvature of the band structure. This observation not only
reveals unusual physical phenomena in Weyl and Dirac semimetals, but also finds
additional transport signatures of Weyl and Dirac fermions other than negative
magnetoresistance.

###Non-stoichiometry effects on the extreme magnetoresistance in Weyl semimetal WTe2|J. X. Gong,J. Yang,M. Ge,Y. J. Wang,D. D. Liang,L. Luo,X. Yan,W. L. Zhen,S. R. Weng,L. Pi,C. J. Zhang,W. K. Zhu###

Non-stoichiometry effects on the extreme magnetoresistance in Weyl semimetal WTe2. Non-stoichiometry effect on the extreme magnetoresistance is systematically
investigated for the Weyl semimetal WTe2. Magnetoresistance and Hall
resistivity are measured for the as-grown samples with a slight difference in
Te vacancies and the annealed samples with increased Te vacancies. The fittings
to a two-carrier model show that the magnetoresistance is strongly dependent on
the residual resistivity ratio (i.e., the degree of non-stoichiometry), which
is eventually understood in terms of electron doping which not only breaks the
balance between electron-type and hole-type carrier densities but also reduces
the average carrier mobility. Thus, compensation effect and ultrahigh mobility
are probably the main driving force of the extreme magnetoresistance in WTe2.

###Robustness of anomaly-related magnetoresistance in doped Weyl semimetals|Hiroaki Ishizuka,Naoto Nagaosa###

Robustness of anomaly-related magnetoresistance in doped Weyl semimetals. Weyl semimetal with Weyl fermions at Fermi energy is one of the topological
materials, and is a condensed-matter realization of the relativistic fermions.
However, there are several crucial differences such as the shift of Fermi
energy, which can hinder the expected interesting physics. Chiral anomaly is a
representative nontrivial phenomenon associated with Weyl fermions, which
dictates the transfer of fermions between the Weyl fermions with opposite
chirality; it is manifested as the negative magnetoresistance. Here we
demonstrate that the magnetoresistance is robust against the deviation from the
ideal Weyl Hamiltonian such as the shifted Fermi energy and nonlinear
dispersions. We study a model with the energy dispersion containing two Weyl
nodes, and find that the magnetoresistance persists even when the Fermi level
is far away from the node, even above the saddle point that separates the two
nodes. Surprisingly, the magnetoresistance remains even after the pair
annihilation of the nodes.

###Anomalous normal state magnetotransport in an electron-doped cuprate|Nicholas R. Poniatowski,Tarapada Sarkar,Richard L. Greene###

Anomalous normal state magnetotransport in an electron-doped cuprate. We report magnetoresistance and Hall angle measurements of the electron-doped
cuprate La$_{2-x}$Ce$_x$CuO$_4$ over a wide range of dopings from $x = 0.08 -
0.17$. Above 100 K, we find an unconventional $\sim H^{3/2}$ magnetic field
dependence of the magnetoresistance observed in all samples doped within the
superconducting dome. Further, the measured magnetoresistance violates Kohler's
rule. Given the ubiquity of this anomalous magnetoresistance at high
temperatures above the superconducting dome, we speculate that the origin of
this behavior is linked to the unusual $\rho \sim T^2$ resistivity observed
over the same wide parameter range at high temperatures. We also find a strong
doping dependence of the Hall angle with an unconventional temperature
dependence of $\cot \theta_H \sim T^{4}$ ($T^{2.5}$) for samples doped below
(above) the Fermi surface reconstruction doping $x_{\text{FSR}} = 0.14$.

###Theory of unidirectional spin Hall magnetoresistance in heavy-metal/ferromagnetic-metal bilayers|Steven S. -L. Zhang,Giovanni Vignale###

Theory of unidirectional spin Hall magnetoresistance in heavy-metal/ferromagnetic-metal bilayers. Recent experiments have revealed nonlinear features of the magnetoresistance
in metallic bilayers consisting of a heavy-metal (HM) and a ferromagnetic metal
(FM). A small change in the lon- gitudinal resistance of the bilayer has been
observed when reversing the direction of either the applied in-plane current or
the magnetization. We attribute such nonlinear transport behavior to the
spin-polarization dependence of the electron mobility in the FM layer acting in
concert with the spin accumulation induced in that layer by the spin Hall
current originating in the bulk of the HM layer. An explicit expression for the
nonlinear magnetoresistance is derived based on a simple drift-diffusion model,
which shows that the nonlinear magnetoresistance appears at the first order of
spin Hall angle (SHA), and changes sign when the current is reversed, in
agreement with the experimental observations. We also discuss possible ways to
control the sign of the nonlinear magnetoresistance and to enhance the
magnitude of effect.

###Low temperature magnetoresistance of (111) (La$_{0.3}$Sr$_{0.7}$)(Al$_{0.65}$Ta$_{0.35}$)/SrTiO$_3$|V. V. Bal,Z. Huang,K. Han,Ariando,T. Venkatesan,V. Chandrasekhar###

Low temperature magnetoresistance of (111) (La$_{0.3}$Sr$_{0.7}$)(Al$_{0.65}$Ta$_{0.35}$)/SrTiO$_3$. The two dimensional conducting interfaces in SrTiO$_3$-based systems are
known to show a variety of coexisting and competing phenomena in a complex
phase space. Magnetoresistance measurements, which are typically used to
extract information about the various interactions in these systems, must be
interpreted with care, since multiple interactions can contribute to the
resistivity in a given range of magnetic field and temperature. Here we review
all the phenomena that can contribute to transport in SrTiO$_3$-based
conducting interfaces at low temperatures, and discuss possible ways to
distinguish between various phenomena. We apply this analysis to the
magnetoresistance data of (111) oriented
(La$_{0.3}$Sr$_{0.7}$)(Al$_{0.65}$Ta$_{0.35}$)/STO (LSAT/STO) heterostructures
in perpendicular field, and find an excess negative magnetoresistance
contribution which cannot be explained by weak localization alone. We argue
that contributions from magnetic scattering as well as electron-electron
interactions can provide a possible explanation for the observed
magnetoresistance.

###Anomalous Hall magnetoresistance in a ferromagnet|Yumeng Yang,Ziyan Luo,Haijun Wu,Yanjun Xu,Run-Wei Li,Stephen J. Pennycook,Shufeng Zhang,Yihong Wu###

Anomalous Hall magnetoresistance in a ferromagnet. The anomalous Hall effect, observed in conducting ferromagnets with broken
time-reversal symmetry, offers the possibility to couple spin and orbital
degrees of freedom of electrons in ferromagnets. In addition to charge, the
anomalous Hall effect also leads to spin accumulation at the surfaces
perpendicular to both the current and magnetization direction. Here we
experimentally demonstrate that the spin accumulation, subsequent spin
backflow, and spin-charge conversion can give rise to a different type of spin
current related magnetoresistance, dubbed here as the anomalous Hall
magnetoresistance, which has the same angular dependence as the recently
discovered spin Hall magnetoresistance. The anomalous Hall magnetoresistance is
observed in four types of samples: co-sputtered (Fe1-xMnx)0.6Pt0.4, Fe1-xMnx
and Pt multilayer, Fe1-xMnx with x = 0.17 to 0.65 and Fe, and analyzed using
the drift-diffusion model. Our results provide an alternative route to study
charge-spin conversion in ferromagnets and to exploit it for potential
spintronic applications.

###Extremely large magnetoresistance and the complete determination of the Fermi surface topology in the semimetal ScSb|Y. J. Hu,E. I. Paredes Aulestia,K. F. Tse,C. N. Kuo,J. Y. Zhu,C. S. Lue,K. T. Lai,Swee K. Goh###

Extremely large magnetoresistance and the complete determination of the Fermi surface topology in the semimetal ScSb. We report the magnetoresistance of ScSb, which is a semimetal with a simple
rocksalt-type structure. We found that the magnetoresistance reaches
$\sim$28000 % at 2 K and 14 T in our best sample, and it exhibits a resistivity
plateau at low temperatures. The Shubnikov-de Haas oscillations extracted from
the magnetoresistance data allow the full construction of the Fermi surface,
including the so-called $\alpha_3$ pocket which has been missing in other
closely related monoantimonides, and an additional hole pocket centered at
$\Gamma$. The electron concentration ($n$) and the hole concentration ($p$) are
extracted from our analysis, which indicate that ScSb is a nearly compensated
semimetal with $n/p\approx0.93$. The calculated band structure indicates the
absence of a band inversion, and the large magnetoresistance in ScSb can be
attributed to the nearly perfect compensation of electrons and holes, despite
the existence of the additional hole pocket.

###Sign of viscous magnetoresistance in electron fluids|Ipsita Mandal,Andrew Lucas###

Sign of viscous magnetoresistance in electron fluids. In sufficiently clean metals, it is possible for electrons to collectively
flow as a viscous fluid at finite temperature. These viscous effects have been
predicted to give a notable magnetoresistance, but whether the
magnetoresistance is positive or negative has been debated. We argue that
regardless of the strength of inhomogeneity, bulk magnetoresistance is always
positive in the hydrodynamic regime. We also compute transport in weakly
inhomogeneous metals across the ballistic-to-hydrodynamic crossover, where we
also find positive magnetoresistance. The non-monotonic temperature dependence
of resistivity in this regime (a bulk Gurzhi effect) rapidly disappears upon
turning on any finite magnetic field, suggesting that magnetotransport is a
simple test for viscous effects in bulk transport, including at the onset of
the hydrodynamic regime.

###Magnetization governed magnetoresistance anisotropy in topological semimetal CeBi|Yang-Yang Lyu,Fei Han,Zhi-Li Xiao,Jing Xu,Yong-Lei Wang,Hua-Bing Wang,Jin-Ke Bao,Duck Young Chung,Mingda Li,Ivar Martin,Ulrich Welp,Mercouri G. Kanatzidis,Wai-Kwong Kwok###

Magnetization governed magnetoresistance anisotropy in topological semimetal CeBi. Magnetic topological semimetals, the latest member of topological quantum
materials, are attracting extensive attention as they may lead to
topologically-driven spintronics. Currently, magnetotransport investigations on
these materials are focused on anomalous Hall effect. Here, we report on the
magnetoresistance anisotropy of topological semimetal CeBi, which has tunable
magnetic structures arising from localized Ce 4f electrons and exhibits both
negative and positive magnetoresistances, depending on the temperature. We
found that the angle dependence of the negative magnetoresistance, regardless
of its large variation with the magnitude of the magnetic field and with
temperature, is solely dictated by the field-induced magnetization that is
orientated along a primary crystalline axis and flops under the influence of a
rotating magnetic field. The results reveal the strong interaction between
conduction electrons and magnetization in CeBi. They also indicate that
magnetoresistance anisotropy can be used to uncover the magnetic behavior and
the correlation between transport phenomena and magnetism in magnetic
topological semimetals.

###Origin of the butterfly magnetoresistance in ZrSiS|J. A. Voerman,L. Mulder,J. C. de Boer,Y. Huang,L. M. Schoop,Chuan Li,A. Brinkman###

Origin of the butterfly magnetoresistance in ZrSiS. ZrSiS has been identified as a topological material made from non-toxic and
earth-abundant elements. Together with its extremely large and uniquely
angle-dependent magnetoresistance this makes it an interesting material for
applications. We study the origin of the so-called butterfly magnetoresistance
by performing magnetotransport measurements on four different devices made from
exfoliated crystalline flakes. We identify near-perfect electron-hole
compensation, tuned by the Zeeman effect, as the source of the butterfly
magnetoresistance. Furthermore, the observed Shubnikov-de Haas oscillations are
carefully analyzed using the Lifshitz-Kosevich equation to determine their
Berry phase and thus their topological properties. Although the link between
the butterfly magnetoresistance and the Berry phase remains uncertain, the
topological nature of ZrSiS is confirmed.

###Microscopic theory of OMAR based on kinetic equations for quantum spin correlations|A. V. Shumilin###

Microscopic theory of OMAR based on kinetic equations for quantum spin correlations. The correlation kinetic equation approach is developed that allows describing
spin correlations in a material with hopping transport. The quantum nature of
spin is taken into account. The approach is applied to the problem of the
bipolaron mechanism of organic magnetoresistance (OMAR) in the limit of large
Hubbard energy and small applied electric field. The spin relaxation that is
important to magnetoresistance is considered to be due to hyperfine interaction
with atomic nuclei. It is shown that the lineshape of magnetoresistance depends
on short-range transport properties. Different model systems with identical
hyperfine interaction but different statistics of electron hops lead to
different lineshapes of magnetoresistance including the two empirical laws
$H^2/(H^2 + H_0^2)$ and $H^2/(|H| + H_0)^2$ that are commonly used to fit
experimental results.

###Determination of spin-orbit torque efficiencies in heterostructures with in-plane magnetic anisotropy|Yan-Ting Liu,Tian-Yue Chen,Tzu-Hsiang Lo,Tsung-Yu Tsai,Shan-Yi Yang,Yao-Jen Chang,Jeng-Hua Wei,Chi-Feng Pai###

Determination of spin-orbit torque efficiencies in heterostructures with in-plane magnetic anisotropy. It has been shown that the spin Hall effect from heavy transition metals can
generate sufficient spin-orbit torque and further produce current-induced
magnetization switching in the adjacent ferromagnetic layer. However, if the
ferromagnetic layer has in-plane magnetic anisotropy, probing such switching
phenomenon typically relies on tunneling magnetoresistance measurement of
nano-sized magnetic tunnel junctions, differential planar Hall voltage
measurement, or Kerr imaging approaches. We show that in magnetic
heterostructures with spin Hall metals, there exist current-induced in-plane
spin Hall effective fields and unidirectional magnetoresistance that will
modify their anisotropic magnetoresistance behavior. We also demonstrate that
by analyzing the response of anisotropic magnetoresistance under such
influences, one can directly and electrically probe magnetization switching
driven by the spin-orbit torque, even in micron-sized devices. This pump-probe
method allows for efficient and direct determination of key parameters from
spin-orbit torque switching events without lengthy device fabrication
processes.

###Theory for the negative longitudinal magnetoresistance in the quantum limit of Kramers Weyl semimetals|Bo Wan,Frank Schindler,Ke Wang,Kai Wu,Xiangang Wan,Titus Neupert,Hai-Zhou Lu###

Theory for the negative longitudinal magnetoresistance in the quantum limit of Kramers Weyl semimetals. Negative magnetoresistance is rare in non-magnetic materials. Recently, a
negative magnetoresistance has been observed in the quantum limit of
$\beta$-Ag$_2$Se, where only one band of Landau levels is occupied in a strong
magnetic field parallel to the applied current. $\beta$-Ag$_2$Se is a material
that host a Kramers Weyl cone with band degeneracy near the Fermi energy.
Kramers Weyl cones exist at time-reversal invariant momenta in all symmorphic
chiral crystals, and at a subset of these momenta, including the $\Gamma$
point, in non-symmorphic chiral crystals. Here, we present a theory for the
negative magnetoresistance in the quantum limit of Kramers Weyl semimetals. We
show that, although there is a band touching similar to those in Weyl
semimetals, negative magnetoresistance can exist without a chiral anomaly. We
find that it requires screened Coulomb scattering potentials between electrons
and impurities, which is naturally the case in $\beta$-Ag$_2$Se.

###Quasi-isotropic orbital magnetoresistance in lightly doped SrTiO$_{3}$|Clément Collignon,Yudai Awashima,Ravi,Xiao Lin,Carl Willem Rischau,Anissa Acheche,Baptiste Vignolle,Cyril Proust,Yuki Fuseya,Kamran Behnia,Benoît Fauqué###

Quasi-isotropic orbital magnetoresistance in lightly doped SrTiO$_{3}$. A magnetic field parallel to an electrical current does not produce a Lorentz
force on the charge carriers. Therefore, orbital longitudinal magnetoresistance
is unexpected. Here we report on the observation of a large and non saturating
magnetoresistance in lightly doped SrTiO$_{3-x}$ independent of the relative
orientation of current and magnetic field. We show that this quasi-isotropic
magnetoresistance can be explained if the carrier mobility along all
orientations smoothly decreases with magnetic field. This anomalous regime is
restricted to low concentrations when the dipolar correlation length is longer
than the distance between carriers. We identify cyclotron motion of electrons
in a potential landscape tailored by polar domains as the cradle of
quasi-isotropic orbital magnetoresistance. The result emerges as a challenge to
theory and may be a generic feature of lightly-doped quantum paralectric
materials.

###Hidden low-temperature magnetic order revealed through magnetotransport in monolayer CrSBr|Evan J. Telford,Avalon H. Dismukes,Raymond L. Dudley,Ren A. Wiscons,Kihong Lee,Jessica Yu,Sara Shabani,Allen Scheie,Kenji Watanabe,Takashi Taniguchi,Di Xiao,Abhay N. Pasupathy,Colin Nuckolls,Xiaoyang Zhu,Cory R. Dean,Xavier Roy###

Hidden low-temperature magnetic order revealed through magnetotransport in monolayer CrSBr. Magnetic semiconductors are a powerful platform for understanding, utilizing
and tuning the interplay between magnetic order and electronic transport.
Compared to bulk crystals, two-dimensional magnetic semiconductors have greater
tunability, as illustrated by the gate modulation of magnetism in exfoliated
CrI$_3$ and Cr$_2$Ge$_2$Te$_6$, but their electrically insulating properties
limit their utility in devices. Here we report the simultaneous electrostatic
and magnetic control of electronic transport in atomically-thin CrSBr, an
A-type antiferromagnetic semiconductor. Through magnetotransport measurements,
we find that spin-flip scattering from the interlayer antiferromagnetic
configuration of multilayer flakes results in giant negative magnetoresistance.
Conversely, magnetoresistance of the ferromagnetic monolayer CrSBr vanishes
below the Curie temperature. A second transition ascribed to the ferromagnetic
ordering of magnetic defects manifests in a large positive magnetoresistance in
the monolayer and a sudden increase of the bulk magnetic susceptibility. We
demonstrate this magnetoresistance is tunable with an electrostatic gate,
revealing that the ferromagnetic coupling of defects is carrier mediated.

###First-principles study on the electron-phonon coupling and magnetoresistance of LaBi under pressure|Jian-Feng Zhang,Peng-Jie Guo,Miao Gao,Kai Liu,Zhong-Yi Lu###

First-principles study on the electron-phonon coupling and magnetoresistance of LaBi under pressure. The extremely large magnetoresistance (XMR) material LaBi was reported to
become superconducting under pressure accompanying with suppressed
magnetoresistance. However, the underlying mechanism is unclear. By using
first-principles electronic structure calculations in combination with a
semiclassical model, we have studied the electron-phonon coupling and
magnetoresistance of LaBi in the pressure range from 0 to 18 GPa. Our
calculations show that LaBi undergoes a structural phase transition from a
face-centered cubic lattice to a primitive tetragonal lattice at $\sim$7 GPa,
verifying previous experimental results. Meanwhile, LaBi remains topologically
nontrivial across the structural transition. Under all pressures that we have
studied, the phonon-mediated mechanism based on the weak electron-phonon
coupling cannot account for the observed superconductivity in LaBi, and the
calculated magnetoresistance for LaBi does not show a suppression. The distinct
difference between our calculations and experimental observations suggests
either the existence of extra Bi impurities in the real LaBi compound or the
possibility of other unknown mechanism.

###Large Magnetoresistance and Weak Antilocalization in V1-delta Sb2 Single Crystal|Yong Zhang,Xinliang Huang,Wenshuai Gao,Xiangde Zhu,Li Pi###

Large Magnetoresistance and Weak Antilocalization in V1-delta Sb2 Single Crystal. The binary pnictide semimetals have attracted considerable attention due to
their fantastic physical properties that include topological effects, negative
magnetoresistance, Weyl fermions and large non-saturation magnetoresistance. In
this paper, we have successfully grown the high-quality V1-deltaSb2 single
crystals by Sb flux method and investigated their electronic transport
properties. A large positive magnetoresistance that reaches 477% under a
magnetic field of 12 T at T = 1.8 K was observed. Notably, the
magnetoresistance showed a cusp-like feature at the low magnetic fields and
such feature weakened gradually as the temperature increased, which indicated
the presence of weak antilocalization effect (WAL). The angle-dependent
magnetoconductance and the ultra-large prefactor alpha extracted from the
Hikami-Larkin-Nagaoka equation revealed that the WAL effect is a 3D bulk effect
originated from the three-dimensional bulk spin-orbital coupling.

###Large positive magnetoresistance in photocarrier doping potassium tantalites in the extreme quantum limit|Ruishu Yang,Dingbang Wang,Yang Zhao,Shuanhu Wang,Kexin Jin###

Large positive magnetoresistance in photocarrier doping potassium tantalites in the extreme quantum limit. We report on a high-field magnetotransport study of KTaO3 single crystals.
This material is a promising candidate to study in the extreme quantum limit
(EQL). By photocarrier doping with 360 nm light, we have observed a significant
positive, non-saturating, and linear magnetoresistance at low temperatures
accompanied by a vanishing Hall coefficient. When cooled down to 10 K and
subjected to a magnetic field of 12 T, the value of magnetoresistance of KTaO3
(100) is increased by as much as 433%. Such behavior can be attributed to all
electrons occupying only the lowest Landau level in the EQL. In this state, a
quantum magnetoresistance is produced. This result provides novel insights into
the next generation of magnetic devices based on complex materials and adds a
new family of materials with positive magnetoresistance.

###Bilinear magnetoresistance in HgTe topological insulator: opposite signs at opposite interfaces demonstrated by gate control|Yu Fu,Jing Li,Jules Papin,Paul Noel,Salvatore Teresi,Maxen Cosset-Cheneau,Cecile Grezes,Thomas Guillet,Candice Thomas,Yann-Michel Niquet,Philippe Ballet,Tristan Meunier,Jean-Philippe Attane,Albert Fert,Laurent Vila###

Bilinear magnetoresistance in HgTe topological insulator: opposite signs at opposite interfaces demonstrated by gate control. Spin-orbit effects appearing in topological insulators (TI) and at Rashba
interfaces are currently revolutionizing how we can manipulate spins and have
led to several newly discovered effects, from spin-charge interconversion and
spin-orbit torques to novel magnetoresistance phenomena. In particular, a
puzzling magnetoresistance has been evidenced, bilinear in electric and
magnetic fields. Here, we report the observation of bilinear magnetoresistance
(BMR) in strained HgTe, a prototypical TI. We show that both the amplitude and
sign of this BMR can be tuned by controlling, with an electric gate, the
relative proportions of the opposite contributions of opposite surfaces. At
magnetic fields of 1 T, the magnetoresistance is of the order of 1 \% and has a
larger figure of merit than previously measured TIs. We propose a theoretical
model giving a quantitative account of our experimental data. This phenomenon,
unique to TI, offers novel opportunities to tune their electrical response for
spintronics.

###Anisotropic magnetotransport in the layered antiferromagnet TaFe$_{1.25}$Te$_3$|Rajeswari Roy Chowdhury,Samik DuttaGupta,Chandan Patra,Anshu Kataria,Shunsuke Fukami,Ravi Prakash Singh###

Anisotropic magnetotransport in the layered antiferromagnet TaFe$_{1.25}$Te$_3$. The discovery of fascinating ways to control and manipulate antiferromagnetic
materials have garnered considerable attention as an attractive platform to
explore novel spintronic phenomena and functionalities. Layered
antiferromagnets (AFMs) exhibiting interesting magnetic structures, can serve
as an attractive starting point to establish novel functionalities down to the
two-dimensional limit. In this work, we explore the magnetoresistive properties
of the spin-ladder AFM TaFe$_{1.25}$Te$_3$. Magnetization studies reveal an
anisotropic magnetic behavior resulting in the stabilization of a spin-flop
configuration for H $\perp$ (10-1) plane (i.e., out-of-plane direction).
Angle-dependent longitudinal and transverse magnetoresistances show an unusual
anharmonic behavior. A significant anisotropic enhancement of magnetoresistance
when H $\perp$ (10-1) plane compared to H $\parallel$ (10-1) directions has
been observed. The present results deepen our understanding of the
magnetoresistive properties of low-dimensional layered AFMs, and point towards
the possibility of utilizing these novel material systems for antiferromagnetic
spintronics.

###The out-of-plane magnetoresistance in a Van der Waals thin film of WTe2|Y. S. Liu,H. Xiao,C. Zhang,C. W. Zhang,Y. G. Shi,T. Hu,C. M. Schneider###

The out-of-plane magnetoresistance in a Van der Waals thin film of WTe2. We report the magneto-transport measurements of thin film devices of the
topological Weyl semimetal WTe2 with the applied current along and vertical to
the in-plane directions. The device is composed of a Van der Waals thin film of
WTe2 sandwiched between top and bottom Au electrodes.At low temperatures, we
found a large unsaturated in-plane magnetoresistance and a saturated
out-of-plane magnetoresistance when the external magnetic fields are applied
perpendicular to the plane. By analysis of Shubnikov-de Haas oscillations, one
oscillation peak is found in the out-of-plane magnetoresistance, in contrast to
four oscillation peaks in the in-plane magnetoresistance.Our work provides new
insight into the origin of the unsaturated magnetoresistance in WTe2 and may
inspire non-planar engineering to reach higher integration in spintronics.

###Robust negative longitudinal magnetoresistance and spin-orbit torque in sputtered Pt3Sn topological semimetal|Delin Zhang,Wei Jiang,Hwanhui Yun,Onri Jay Benally,Thomas Peterson,Zach Cresswell,Yihong Fan,Yang Lv,Guichuan Yu,Javier Garcia Barriocanal,Przemyslaw Swatek,K. Andre Mkhoyan,Tony Low,Jian-Ping Wang###

Robust negative longitudinal magnetoresistance and spin-orbit torque in sputtered Pt3Sn topological semimetal. Contrary to topological insulators, topological semimetals possess a
nontrivial chiral anomaly that leads to negative magnetoresistance and are
hosts to both conductive bulk states and topological surface states with
intriguing transport properties for spintronics. Here, we fabricate
highly-ordered metallic Pt3Sn and Pt3SnxFe1-x thin films via sputtering
technology. Systematic angular dependence (both in-plane and out-of-plane)
study of magnetoresistance presents surprisingly robust quadratic and linear
negative longitudinal magnetoresistance features for Pt3Sn and Pt3SnxFe1-x,
respectively. We attribute the anomalous negative longitudinal
magnetoresistance to the type-II Dirac semimetal phase (pristine Pt3Sn) and/or
the formation of tunable Weyl semimetal phases through symmetry breaking
processes, such as magnetic-atom doping, as confirmed by first-principles
calculations. Furthermore, Pt3Sn and Pt3SnxFe1-x show the promising performance
for facilitating the development of advanced spin-orbit torque devices. These
results extend our understanding of chiral anomaly of topological semimetals
and can pave the way for exploring novel topological materials for spintronic
devices.

###Paramagnons, weak disorder and positive giant magnetoresistance|George Kastrinakis###

Paramagnons, weak disorder and positive giant magnetoresistance. At low temperature and for finite spin scattering in a weakly disordered
metal, for a certain value, predicted from our theory, of the
material-dependent paramagnon interaction, the total conductivity becomes
highly sensitive to the orbital effects of a finite magnetic field. As a
consequence, positive giant magnetoresistance and giant corrections to the Hall
coefficient arise. We obtain very good agreement between this theory and recent
positive giant magnetoresistance experiments, while making specific
material-dependent predictions.

###Magnetoresistance of Two-Dimensional Fermions in a Random Magnetic Field|D. V. Khveshchenko###

Magnetoresistance of Two-Dimensional Fermions in a Random Magnetic Field. We perform a semiclassical calculation of the magnetoresistance of spinless
two-dimensional fermions in a long-range correlated random magnetic field. In
the regime relevant for the problem of the half filled Landau level the
perturbative Born approximation fails and we develop a new method of solving
the Boltzmann equation beyond the relaxation time approximation. In absence of
interactions, electron density modulations, in-plane fields, and Fermi surface
anisotropy we obtain a quadratic negative magnetoresistance in the weak field
limit.

###Magnetoresistance and Hall Constant of Composite Fermions|D. V. Khveshchenko###

Magnetoresistance and Hall Constant of Composite Fermions. We consider both disorder and interaction effects on the magnetoresistance
and Hall constant of composite fermions in the vicinity of half filled Landau
level. By contrast to the standard case of Coulomb interacting two-dimensional
electron gas we find logarithmic temperature corrections to the Hall
conductivity and the magnetoresistance of composite fermions whereas the Hall
constant acquires no such correction in the lowest order. The theory provides a
possible explanation of the resistivity minimum at filling factor $\nu=1/2$.

###Negative Magnetoresistance in the Nearest-neighbor Hopping Conduction|X. R. Wang,X. C. Xie###

Negative Magnetoresistance in the Nearest-neighbor Hopping Conduction. We propose a size effect which leads to the negative magnetoresistance in
granular metal-insulator materials in which the hopping between two nearest
neighbor clusters is the main transport mechanism. We show that the hopping
probability increases with magnetic field. This is originated from the level
crossing in a few-electron cluster. Thus, the overlap of electronic states of
two neighboring clusters increases, and the negative magnetoresistance is
resulted.

###Collective charge density wave motion through an ensemble of Aharonov-Bohm rings|M. I. Visscher,B. Rejaei###

Collective charge density wave motion through an ensemble of Aharonov-Bohm rings. We investigate theoretically the collective charge density wave motion
through an ensemble of small disordered Aharonov-Bohm rings. It is shown that
the magnetic flux modulates the threshold field and the magnetoresistance with
a half flux quantum periodicity $\Phi_{0}/2=h/2e$, resulting from ensemble
averaging over random scattering phases of multiple rings. The magnitude of the
magnetoresistance oscillations decreases rapidly with increasing bias. This is
consistent with recent experiments on $NbSe_3$ in presence of columnar defects
[Phys. Rev. Lett. 78, 919 (1997)].

###Weak magnetoresistance of disordered heavy fermion systems|A. Chattopadhyay,M. Jarrell,H. R. Krishnamurthy,H. K. Ng,J. Sarrao,Z. Fisk###

Weak magnetoresistance of disordered heavy fermion systems. We compare the magnetoresistance of UCu$_{3.5}$Pd$_{1.5}$ with calculations
done within the disordered heavy fermion framework of Miranda et al. using a
phenomenological spectral function for the Anderson model, calibrated against
Bethe ansatz and quantum Monte Carlo results. Both in experiment and theory, we
find a weak negative magnetoresistance. In contrast, thermodynamic quantities
have a strong field dependence. Using qualitative arguments broad distribution
of Kondo scales, we explain the different field dependence of susceptibility
and resistivity.

###Incoherent interlayer transport and angular-dependent magnetoresistance oscillations in layered metals|Ross H. McKenzie,Perez Moses###

Incoherent interlayer transport and angular-dependent magnetoresistance oscillations in layered metals. The effect of incoherent interlayer transport on the interlayer resistance of
a layered metal is considered. We find that for both quasi-one-dimensional and
quasi-two-dimensional Fermi liquids the angular dependence of the
magnetoresistance is essentially the same for coherent and incoherent
transport. Consequently, the existence of a three-dimensional Fermi surface is
not necessary to explain the oscillations in the magnetoresistance that are
seen in many organic conductors as the field direction is varied.

###Ballistic electron transport through magnetic domain walls|Jeroen B. A. N. van Hoof,Kees M. Schep,Arne Brataas,Gerrit E. W. Bauer,Paul J. Kelly###

Ballistic electron transport through magnetic domain walls. Electron transport limited by the rotating exchange-potential of domain walls
is calculated in the ballistic limit for the itinerant ferromagnets Fe, Co, and
Ni. When realistic band structures are used, the domain wall magnetoresistance
is enhanced by orders of magnitude compared to the results for previously
studied two-band models. Increasing the pitch of a domain wall by confinement
in a nano-structured point contact is predicted to give rise to a strongly
enhanced magnetoresistance.

###Anomalous magnetoconductance due to weak localization in 2D systems with anisotropic scattering: computer simulation|A. V. Germanenko,V. A. Larionova,G. M. Minkov,S. A. Negashev###

Anomalous magnetoconductance due to weak localization in 2D systems with anisotropic scattering: computer simulation. The results of computer simulation of particle motion over the plane with
randomly distributed scatters are presented. They are used to analyse the
influence of scattering anisotropy on the negative magnetoresistance due to
weak localisation. It is shown that the magnetic field dependence of
magnetoresistance in this case can be described by the well known expression,
obtained in the diffusion limit for isotropic scatternig, but with the
prefactor less than unity and breaking-phase length which differs from the true
value.

###Strong magnetoresistance induced by long-range disorder|A. D. Mirlin,J. Wilke,F. Evers,D. G. Polyakov,P. Woelfle###

Strong magnetoresistance induced by long-range disorder. We calculate the semiclassical magnetoresistivity $\rho_{xx}(B)$ of
non-interacting fermions in two dimensions moving in a weak and smoothly
varying random potential or random magnetic field. We demonstrate that in a
broad range of magnetic fields the non-Markovian character of the transport
leads to a strong positive magnetoresistance. The effect is especially
pronounced in the case of a random magnetic field where $\rho_{xx}(B)$ becomes
parametrically much larger than its B=0 value.

###Charge melting and polaron collapse in $La_{1.2}Sr_{1.8}Mn_{2}O_{7}$|L. Vasiliu-Doloc,S. Rosenkranz,R. Osborn,S. K. Sinha,J. W. Lynn,J. Mesot,O. H. Seeck,G. Preosti,A. J. Fedro,J. F. Mitchell###

Charge melting and polaron collapse in $La_{1.2}Sr_{1.8}Mn_{2}O_{7}$. X-ray and neutron scattering measurements directly demonstrate the existence
of polarons in the paramagnetic phase of optimally-doped colossal
magnetoresistive oxides. The polarons exhibit short-range correlations that
grow with decreasing temperature, but disappear abruptly at the ferromagnetic
transition because of the sudden charge delocalization. The "melting" of the
charge ordering as we cool through $T_C$ occurs with the collapse of the
quasi-static polaron scattering, and provides important new insights into the
relation of polarons to colossal magnetoresistance.

###Large Magnetoresistance Ratio in Ferromagnetic Single-Electron Transistors in the Strong Tunneling Regime|X. H. Wang,A. Brataas###

Large Magnetoresistance Ratio in Ferromagnetic Single-Electron Transistors in the Strong Tunneling Regime. We study transport through a ferromagnetic single-electron transistor. The
resistance is represented as a path integral, so that systems where the tunnel
resistances are smaller than the quantum resistance can be investigated. Beyond
the low order sequential tunneling and co-tunneling regimes, a large
magnetoresistance ratio at sufficiently low temperatures is found. In the
opposite limit, when the thermal energy is larger than the charging energy, the
magnetoresistance ratio is only slightly enhanced.

###Magnetoresistance of a two-dimensional electron gas in a parallel magnetic field|V. T. Dolgopolov,A. Gold###

Magnetoresistance of a two-dimensional electron gas in a parallel magnetic field. The conductivity of a two-dimensional electron gas in a parallel magnetic
field is calculated. We take into account the magnetic field induced
spin-splitting, which changes the density of states, the Fermi momentum and the
screening behavior of the electron gas. For impurity scattering we predict a
positive magnetoresistance for low electron density and a negative
magnetoresistance for high electron density. The theory is in qualitative
agreement with recent experimental results found for Si inversion layers and Si
quantum wells.

###Low Temperature Anomaly in Mesoscopic Kondo Wires|Pritiraj Mohanty,Richard A. Webb###

Low Temperature Anomaly in Mesoscopic Kondo Wires. We report the observation of an anomalous magnetoresistance in extremely
dilute quasi-one-dimensional AuFe wires at low temperatures, along with a
hysteretic background at low fields. The Kondo resistivity does not show the
unitarity limit down to the lowest temperature, implying uncompensated spin
states. We suggest that the anomalous magnetoresistance may be understood as
the interference correction from the accumulation of geometric phase in the
conduction electron wave function around the localized impurity spin.

###Giant Magnetoresistance at the Interface of Iron Thin Films|J. Balogh,L. F. Kiss,A. Halbritter,I. Kézsmárki,G. Mihály###

Giant Magnetoresistance at the Interface of Iron Thin Films. Ag/Fe/Ag and Cr/Fe/Cr trilayers with a single $25 nm$ thick ferromagnetic
layer exhibit giant magnetoresistance (GMR) type behavior. The resistance
decreases for parallel and transversal magnetic field alignements with a
Langevin-type magnetic field dependence up to B=12 T. The phenomenon is
explained by a granular interface structure. Results on Fe/Ag multilayers are
also interpreted in terms of a granular interface magnetoresistance.

###Electronic Structure of Novel Cation-Radical Salts in High Magnetic Fields|J. S. Brooks,L. Balicas,K. Storr,B. H. Ward,S. Uji,T. Terashima,C. Terakura,J. A. Schlueter,R. W. Winter,J. Mohtasham,G. L. Gard,G. C. Papavassiliou,M. Tokumoto###

Electronic Structure of Novel Cation-Radical Salts in High Magnetic Fields. Two organic conducting materials, where unusual aspects of their composition
play important roles, are explored: beta''-(BEDT-TTF)2SF5XSO3 which exhibits
superconductivity, or a metal-insulator transition (for X=CH2CF2 or CHF
respectively), and tau-(P-S, S -DMEDT-TTF)2 (AuBr2) (AuBr2)y which exhibits a
large, hysteretic, negative magnetoresistance. Detailed angular dependent
magnetoresistance studies that allow a tomographic view of the electronic
structure of these materials with increasing magnetic fields are presented.

###Quasiclassical negative magnetoresistance of a 2D electron gas: interplay of strong scatterers and smooth disorder|A. D. Mirlin,D. G. Polyakov,F. Evers,P. Woelfle###

Quasiclassical negative magnetoresistance of a 2D electron gas: interplay of strong scatterers and smooth disorder. We study the quasiclassical magnetotransport of non-interacting fermions in
two dimensions moving in a random array of strong scatterers (antidots,
impurities or defects) on the background of a smooth random potential. We
demonstrate that the combination of the two types of disorder induces a novel
mechanism leading to a strong negative magnetoresistance, followed by the
saturation of the magnetoresistivity $\rho_{xx}(B)$ at a value determined
solely by the smooth disorder. Experimental relevance to the transport in
semiconductor heterostructures is discussed.

###Large magnetoresistance using hybrid spin filter devices|P. LeClair,J. K. Ha,H. J. M. Swagten,C. H. van de Vin,J. T. Kohlhepp,W. J. M. de Jonge###

Large magnetoresistance using hybrid spin filter devices. A magnetic "spin filter" tunnel barrier, sandwiched between a non-magnetic
metal and a magnetic metal, is used to create a new magnetoresistive tunnel
device, somewhat analogous to an optical polarizer-analyzer configuration. The
resistance of these trilayer structures depends on the relative magnetization
orientation of the spin filter and the ferromagnetic electrode. The spin
filtering in this configuration yields a previously unobserved
magnetoresistance effect, exceeding 100%.

###Enhanced Granular Magnetoresistance due to Ferromagnetic Layers|J. Balogh,M. Csontos,D. Kaptas,G. Mihaly###

Enhanced Granular Magnetoresistance due to Ferromagnetic Layers. Giant magnetoresistance (GMR) of sequentially evaporated Fe-Ag structures
have been investigated. Direct experimental evidence is given that inserting
ferromagnetic layers into a granular structure significantly enhances the
magnetoresistance. The increase of the GMR effect is attributed to spin
polarization effects. The large enhancement (up to more than a fourfold value)
and the linear variation of the GMR in low magnetic fields are explained by
scattering of the spin polarized conduction electrons on paramagnetic grains.

###Zener Tunneling Between Landau Orbits in a High-Mobility Two-Dimensional Electron Gas|C. L. Yang,J. Zhang,R. R. Du,J. A. Simmons,J. L. Reno###

Zener Tunneling Between Landau Orbits in a High-Mobility Two-Dimensional Electron Gas. Magnetotransport in a laterally confined two-dimensional electron gas (2DEG)
can exhibit modified scattering channels owing to a tilted Hall potential.
Transitions of electrons between Landau levels with shifted guiding centers can
be accomplished through a Zener tunneling mechanism, and make a significant
contribution to the magnetoresistance. A remarkable oscillation effect in weak
field magnetoresistance has been observed in high-mobility 2DEGs in
GaAs-AlGa$_{0.3}$As$_{0.7}$ heterostructures, and can be well explained by the
Zener mechanism.

###Quantum in-plane magnetoresistance in 2D electron systems|Julia S. Meyer,Vladimir I. Fal'ko,B. L. Altshuler###

Quantum in-plane magnetoresistance in 2D electron systems. We review various aspects of magnetoresistance in (quasi-)twodimensional
systems subject to an in-plane magnetic field. Concentrating on single-particle
effects, three mechanisms leading to magnetoresistance are discussed: the
orbital effect of the magnetic field -- due to inter-subband mixing -- and the
sensitivity of this effect to the geometrical symmetry of the system, the
interplay between spin-orbit coupling and Zeeman splitting, and the influence
of the field on spin scattering at magnetic impurities.

###Magnetoresistance calculations for a two-dimensional electron gas with unilateral short-period strong modulation|Karel Vyborny,Ludvik Smrcka,Rainer A. Deutschmann###

Magnetoresistance calculations for a two-dimensional electron gas with unilateral short-period strong modulation. The linear response theory is used to describe magnetoresistance oscillations
of short-period unilateral superlattices with strong modulation (or
alternatively arrays of coupled quantum wires). The semiclassical description
of this system fails for strong magnetic fields (magnetic breakdown) and we
employ a simple fully-quantum-mechanical tight-binding model in conjunction
with Kubo's formula instead. The resulting magnetoresistance data nicely
compare to the experiments while the model opens good intuitive insight into
the effects taking place in the system.

###Ballistic Magnetoresitance over 4000% at Room Temperature in Ni-Ni Electrodeposited Nanocontacts|Hai Wang,H. Cheng,N. Garcia###

Ballistic Magnetoresitance over 4000% at Room Temperature in Ni-Ni Electrodeposited Nanocontacts. This paper reports ballistic magnetoresistance values over 4000% measured in
electrodeposited Ni-Ni nanocontacts with T geometry previously developed . Over
the time, after several magnetic field cycles, the ballistic magnetoresistance
relaxed to a 400%. While that the magnetoreistance of a contact could rise
indefinitely; relaxtion and reproducibility are, however, the main issue. We
find that the tip ending radius conforming the contacts appears not to play the
main role.

###Crossed-anisotropy films for magnetic tunnel junctions and magnetic memory applications|A. N. Grigorenko,D. J. Mapps###

Crossed-anisotropy films for magnetic tunnel junctions and magnetic memory applications. A prototype of magnetoresistive random access memory (MRAM) based on magnetic
tunnel junctions (MTJ) was fabricated with crossed-anisotropy of magnetic
layers on either side of the tunnelling barrier layer. It is demonstrated that
the introduction of crossed-anisotropy results in smaller switching fields and
better switching times compared to the conventional case of aligned
anisotropies. The magnetoresistive properties of fabricated devices are in good
agreement with the micromagnetic model.

###Anomalous Negative Magnetoresistance Caused by Non-Markovian Effects|Vadim V. Cheianov,A. P. Dmitriev,V. Yu. Kachorovskii###

Anomalous Negative Magnetoresistance Caused by Non-Markovian Effects. A theory of recently discovered anomalous low-field magnetoresistance is
developed for the system of two-dimensional electrons scattered by hard disks
of radius $a,$ randomly distributed with concentration $n.$ For small magnetic
fields the magentoresistance is found to be parabolic and inversely
proportional to the gas parameter, $ \delta \rho_{xx}/\rho \sim - (\omega_c
\tau)^2 / n a^2.$ With increasing field the magnetoresistance becomes linear
$\delta \rho_{xx}/\rho \sim - \omega_c \tau $ in a good agreement with the
experiment and numerical simulations.

###Giant Magnetoresistance in Multilayers with Noncollinear Magnetizations|S. Urazhdin,R. Loloee,W. P. Pratt Jr###

Giant Magnetoresistance in Multilayers with Noncollinear Magnetizations. We study the dependence of perpendicular-current magnetoresistance in
magnetic multilayers on the angle between the magnetizations of the layers.
This dependence varies with the thickness of one of the layers, and is
different for multilayers with two and three magnetic layers. We derive a
system of equations representing an extension of the two-current series
resistor model, and show that the angular dependence of magnetoresistance gives
information about the noncollinear spin-transport in ferromagnets.

###Stoner-Wohlfart model applied to bicrystal magnetoresistance hysteresis|R. Gunnarsson,M. Hanson,C. Dubourdieu###

Stoner-Wohlfart model applied to bicrystal magnetoresistance hysteresis. We calculate numerically the magnetization direction as function of magnetic
field in the Stoner-Wohlfart theory and are able to reproduce the shape of the
low-field magnetoresistance hysteresis observed in manganite grain boundary
junctions. Moreover, we show that it is necessary to include biaxial
magnetocrystalline anisotropy to fully describe the grain boundary
magnetoresistance in La$_{0.7}$Sr$_{0.3}$MnO$_3$/SrTiO$_3$ bicrystal tunnel
junctions.

###Large tunneling anisotropic magnetoresistance in (Ga,Mn)As nanoconstrictions|A. D. Giddings,M. N. Khalid,J. Wunderlich,S. Yasin,R. P. Campion,K. W. Edmonds,J. Sinova,T. Jungwirth,K. Ito,K. Y. Wang,D. Williams,B. L. Gallagher,C. T. Foxon###

Large tunneling anisotropic magnetoresistance in (Ga,Mn)As nanoconstrictions. We report a large tunneling anisotropic magnetoresistance (TAMR) in a thin
(Ga,Mn)As epilayer with lateral nanoconstrictions. The observation establishes
the generic nature of this effect, which originates from the spin-orbit
coupling in a ferromagnet and is not specific to a particular tunnel device
design. The lateral geometry allows us to link directly normal anisotropic
magnetoresistance (AMR) and TAMR. This indicates that TAMR may be observable in
other materials showing a comparable AMR at room temperature, such as
transition metal alloys.

###Magnetoresistance of mesoscopic granular ferromagnets|A. Y. Dokow H. Vilchik,A. Frydman###

Magnetoresistance of mesoscopic granular ferromagnets. We have performed magnetoresistance (MR) measurements of granular
ferromagnets having lateral dimensions smaller than 0.5 $\mu$m and containing a
small number of grains (down to about 100). Compared to macroscopic samples,
these granular samples exhibit unusually large saturation fields and MR
amplitudes. In addition, the evolution of the magnetoresistance curve as the
intergrain distance decreases is qualitatively different than that of large
samples. We discuss these results and suggest that they reflect a transition
from percolation to quasi single-channel dominated transport.

###Inverse Magnetoresistance of Molecular Junctions|Hugh Dalgleish,George Kirczenow###

Inverse Magnetoresistance of Molecular Junctions. We present calculations of spin-dependent electron transport through single
organic molecules bridging pairs of iron nanocontacts. We predict the
magnetoresistance of these systems to switch from positive to negative with
increasing applied bias for both conducting and insulating molecules. This
novel inverse magnetoresistance phenomenon is robust, does not depend on the
presence of impurities, and is unique to molecular and atomic nanoscale
magnetic junctions. Its physical origin is identified and its relevance to
experiment and to potential technological applications is discussed.

###Inversion of magnetoresistance in magnetic tunnel junctions : effect of pinhole nanocontacts|Soumik Mukhopadhyay,I. Das###

Inversion of magnetoresistance in magnetic tunnel junctions : effect of pinhole nanocontacts. Inverse magnetoresistance has been observed in magnetic tunnel junctions with
pinhole nanocontacts over a broad temperature range. The tunnel
magnetoresistance undergoes a change of sign at higher bias and temperature.
This phenomenon is attributed to the competition between the spin conserved
ballistic transport through the pinhole contact where the transmission
probability is close to unity and spin polarized tunneling across the
insulating spacer with weak transmittivity.

###Strong suppression of weak (anti)localization in graphene|S. V. Morozov,K. S. Novoselov,M. I. Katsnelson,F. Schedin,L. A. Ponomarenko,D. Jiang,A. K. Geim###

Strong suppression of weak (anti)localization in graphene. Low-field magnetoresistance is ubiquitous in low-dimensional metallic systems
with high resistivity and well understood as arising due to quantum
interference on self-intersecting diffusive trajectories. We have found that in
graphene this weak-localization magnetoresistance is strongly suppressed and,
in some cases, completely absent. This unexpected observation is attributed to
mesoscopic corrugations of graphene sheets which cause a dephasing effect
similar to that of a random magnetic field.

###Spin-dependent tunneling in modulated structures of (Ga,Mn)As|P. Sankowski,P. Kacman,J. A. Majewski,T. Dietl###

Spin-dependent tunneling in modulated structures of (Ga,Mn)As. A model of coherent tunneling, which combines multi-orbital tight-binding
approximation with Landauer-B\"uttiker formalism, is developed and applied to
all-semiconductor heterostructures containing (Ga,Mn)As ferromagnetic layers. A
comparison of theoretical predictions and experimental results on
spin-dependent Zener tunneling, tunneling magnetoresistance (TMR), and
anisotropic magnetoresistance (TAMR) is presented. The dependence of spin
current on carrier density, magnetization orientation, strain, voltage bias,
and spacer thickness is examined theoretically in order to optimize device
design and performance.

###Negative Hopping Magnetoresistance and Dimensional Crossover in Lightly Doped Cuprate Superconductors|Valeri N. Kotov,Oleg P. Sushkov,M. B. Silva Neto,L. Benfatto,A. H. Castro Neto###

Negative Hopping Magnetoresistance and Dimensional Crossover in Lightly Doped Cuprate Superconductors. We show that, due to the weak ferromagnetism of La$_{2-x}$Sr$_x$CuO$_4$, an
external magnetic field leads to a dimensional crossover 2D $\to$ 3D for the
in-plane transport. The crossover results in an increase of the hole's
localization length and hence in a dramatic negative magnetoresistance in the
variable range hopping regime. This mechanism quantitatively explains puzzling
experimental data on the negative magnetoresistance in the N\'eel phase of
La$_{2-x}$Sr$_x$CuO$_4$.

###Polarization immunity of magnetoresistivity response under Microwave excitation|Jesus Inarrea,Gloria Platero###

Polarization immunity of magnetoresistivity response under Microwave excitation. We analyze theoretically the dependence of the microwave polarization sate
and sense on the magnetoresistivity response of two-dimensional electron
systems. Linear and circular polarization have been considered with different
senses and directions. We discuss the polarization dependence of the
longitudinal magnetoresistivity and propose an explanation for the
experimentally observed polarization immunity, i.e., resistivity oscillations
and zero resistance state regions are unaffected by the sense of circular
polarization or by the direction of microwave electric field.

###Room-temperature magnetoresistance switching of Py thin films induced by Fe-nanoparticles grown by STM-assisted CVD|Jens Mueller,Steffen Wirth,Stephan von Molnar###

Room-temperature magnetoresistance switching of Py thin films induced by Fe-nanoparticles grown by STM-assisted CVD. Arrays of Fe-nanoparticles grown by STM-assited CVD have been placed on top
of a narrow stripe of Py. The magnetic coupling between the nanoparticles and
the underlying Py film results in distinct negative jumps of the Py
magnetoresistance. The switching of the magnetization orientation of individual
particles is clearly reflected in the Py magnetoresistance as a consequence of
AMR and DWMR, with a homogeneous particle magnetization orientation yielding
the highest resistances.

###(Ga,Mn)As based superlattices and the search for antiferromagnetic interlayer coupling|A. D. Giddings,T. Jungwirth,B. L. Gallagher###

(Ga,Mn)As based superlattices and the search for antiferromagnetic interlayer coupling. Antiferromagnetic interlayer coupling in dilute magnetic semiconductor
superlattices could result in the realisation of large magnetoresistance
effects analogous to the giant magnetoresistance seen in metallic multilayer
structures. In this paper we use a mean-field theory of carrier induced
ferromagnetism to explore the multidimensional parameter space available in
(Ga,Mn)As based superlattice systems. Based on these investigations we examine
the feasibility of creating a superlattice that exhibits antiferromagnetic
coupling and suggest potentially viable recipes.

###Higher order terms in the geometric resonance of open orbits in unidirectional lateral superlattices|Akira Endo,Yasuhiro Iye###

Higher order terms in the geometric resonance of open orbits in unidirectional lateral superlattices. The geometric resonance of open orbits in unidirectional lateral
superlattices has been examined with high magnetic-field resolution.
Magnetoresistance oscillations periodic in 1/B, analogous to the well-known
commensurability oscillations but orders of magnitude smaller both in magnitude
and in the magnetic-field scale, have been observed superposed on the low-field
positive magnetoresistance. The periodicity in 1/B can be interpreted in terms
of higher order resonances.

###Evidence for Two-Dimensional Spin-Glass Ordering in Submonolayer Fe Films on Cleaved InAs Surfaces|Toshimitsu Mochizuki,Ryuichi Masutomi,Tohru Okamoto###

Evidence for Two-Dimensional Spin-Glass Ordering in Submonolayer Fe Films on Cleaved InAs Surfaces. Magnetotransport measurements have been performed on two-dimensional electron
gases formed at InAs(110) surfaces covered with a submonolayer of Fe.
Hysteresis in the magnetoresistance, a difference in remanent magnetoresistance
between zero-field-cooling procedures and field-cooling procedures, and
logarithmic time-dependent relaxation after magnetic field sweep are clearly
observed at 1.7 K for a coverage of 0.42 monolayer. These features are
associated with spin-glass ordering in the Fe film.

###Effects of the Zero-Mode Landau Level on Inter-Layer Magnetoresistance in Multilayer Massless Dirac Fermion Systems|N. Tajima,S. Sugawara,R. Kato,Y. Nishio,K. Kajita###

Effects of the Zero-Mode Landau Level on Inter-Layer Magnetoresistance in Multilayer Massless Dirac Fermion Systems. We report on the experimental results of interlayer magnetoresistance in
multilayer massless Dirac fermion system $\alpha$-(BEDT-TTF)$_2$I$_3$ under
hydrostatic pressure and its interpretation. We succeeded in detecting the
zero-mode Landau level (n=0 Landau level) that is epected to appear at the
contact points of Dirac cones in the magnetic field normal to the
two-dimensional plane. The characteristic feature of zero-mode Landau carriers
including the Zeeman effect is clearly seen in the interlayer
magnetoresistance.

###Cr-doping effect on the orbital fluctuation of heavily doped Nd1-xSrxMnO3 (x ~ 0.625)|R. Tasaki,S. Fukushima,M. Akaki,D. Akahoshi,H. Kuwahara###

Cr-doping effect on the orbital fluctuation of heavily doped Nd1-xSrxMnO3 (x ~ 0.625). We have investigated the Cr-doping effect of Nd0.375Sr0.625MnO3 near the
phase boundary between the x2-y2 and 3z2-r2 orbital ordered states, where a
ferromagnetic correlation and concomitant large magnetoresistance are observed
owing to orbital fluctuation. Cr-doping steeply suppresses the ferromagnetic
correlation and magnetoresistance in Nd0.375Sr0.625Mn1-yCryO3 with 0 < y <
0.05, while they reappear in 0.05 < y < 0.10. Such a reentrant behavior implies
that a phase boundary is located at y = 0.05, or a phase crossover occurs
across y = 0.05.

###Correlation of the angular dependence of spin-transfer torque and giant magnetoresistance in the limit of diffusive transport in spin valves|M. Gmitra,J. Barnas###

Correlation of the angular dependence of spin-transfer torque and giant magnetoresistance in the limit of diffusive transport in spin valves. Angular variation of giant magnetoresistance and spin-transfer torque in
metallic spin-valve heterostructures is analyzed theoretically in the limit of
diffusive transport. It is shown that the spin-transfer torque in asymmetric
spin valves can vanish in non-collinear magnetic configurations, and such a
non-standard behavior of the torque is generally associated with a
non-monotonic angular dependence of the giant magnetoresistance, with a global
minimum at a non-collinear magnetic configuration.

###Magnetization driven metal - insulator transition in strongly disordered Ge:Mn magnetic semiconductors|O. Riss,A. Gerber,I. Ya. Korenblit,A. Suslov,M. Passacantando,L. Ottaviano###

Magnetization driven metal - insulator transition in strongly disordered Ge:Mn magnetic semiconductors. We report on the temperature and field driven metal-insulator transition in
disordered Ge:Mn magnetic semiconductors accompanied by magnetic ordering,
magnetoresistance reaching thousands of percents and suppression of the
extraordinary Hall effect by a magnetic field. Magnetoresistance isotherms are
shown to obey a universal scaling law with a single scaling parameter depending
on temperature and fabrication. We argue that the strong magnetic disorder
leads to localization of charge carriers and is the origin of the unusual
properties of Ge:Mn alloys.

###Finite Element Modeling of Charge and Spin-currents in Magnetoresistive Pillars with Current Crowding Effects|N. Strelkov,A. Vedyayev,D. Gusakova,L. D. Buda-Prejbeanu,M. Chshiev,S. Amara,A. Vaysset,B. Dieny###

Finite Element Modeling of Charge and Spin-currents in Magnetoresistive Pillars with Current Crowding Effects. The charge and spin diffusion equations taking into account spin-flip and
spin-transfer torque were numerically solved using a finite element method in
complex non-collinear geometry. This approach was used to study the
spin-dependent transport in giant magnetoresistance metallic pillars sandwiched
between extended electrodes as in magnetoresistive heads for hard disk drives.
The charge current crowding around the boundaries between the electrodes and
the pillar has a quite significant influence on the spin current.

###Giant magnetic broadening of ferromagnetic resonance in a GMR Co/Ag/Co/Gd quadlayer|Sezen Demirtas,Ali R. Koymen,Myron B. Salamon###

Giant magnetic broadening of ferromagnetic resonance in a GMR Co/Ag/Co/Gd quadlayer. Both magnetic-resonance damping and the giant magnetoresistance effect have
been predicted to be strongly affected by the local density of states in thin
ferromagnetic films. We employ the antiferromagnetic coupling between Co and Gd
to provide a spontaneous change from parallel to antiparallel alignment of two
Co films. A sharp increase in magnetic damping accompanies the change from
parallel to antiparallel alignment, analogous to resistivity changes in giant
magnetoresistance.

###Diameter Dependence of the Transport Properties of Antimony Telluride Nanowires|Y. M. Zuev,J. S. Lee,C. Galloy,H. Park,P. Kim###

Diameter Dependence of the Transport Properties of Antimony Telluride Nanowires. We report measurements of electronic, thermoelectric, and galvanomagnetic
properties of individual single crystal antimony telluride (Sb2Te3) nanowires
with diameters in the range of 20-100 nm. Temperature dependent resistivity and
thermoelectric power (TEP) measurements indicate hole dominant diffusive
thermoelectric generation, with an enhancement of the TEP for smaller diameter
wires up to 110 uV/K at T = 300 K. We measure the magnetoresistance, in
magnetic fields both parallel and perpendicular to the nanowire [110] axis,
where strong anisotropic positive magnetoresistance behavior was observed.

###Local spin valve effect in lateral (Ga,Mn)As/GaAs spin Esaki diode devices|Mariusz Ciorga,Christian Wolf,Andreas Einwanger,Martin Utz,Dieter Schuh,Dieter Weiss###

Local spin valve effect in lateral (Ga,Mn)As/GaAs spin Esaki diode devices. We report on a local spin valve effect observed unambiguously in lateral
all-semiconductor all-electrical spin injection devices, employing
p+-(Ga,Mn)As/n+-GaAs Esaki diode structures as spin aligning contacts. We
discuss the observed local spin-valve signal as a result of interplay between
spin-transport-related contribution and tunneling anisotropic magnetoresistance
of magnetic contacts. The magnitude of the spin-related magnetoresistance
change is equal to 30 Ohm which is twice the magnitude of the measured
non-local signal.

###Electrical spin injection and transport in Germanium|Yi Zhou,Wei Han,Li-Te Chang,Faxian Xiu,Minsheng Wang,Michael Oehme,Inga A. Fischer,Joerg Schulze,Roland. K. Kawakami,Kang L. Wang###

Electrical spin injection and transport in Germanium. We report the first experimental demonstration of electrical spin injection,
transport and detection in bulk germanium (Ge). The non-local magnetoresistance
in n-type Ge is observable up to 225K. Our results indicate that the spin
relaxation rate in the n-type Ge is closely related to the momentum scattering
rate, which is consistent with the predicted Elliot-Yafet spin relaxation
mechanism for Ge. The bias dependence of the nonlocal magnetoresistance and the
spin lifetime in n-type Ge is also investigated.

###Chiral Anomaly and Classical Negative Magnetoresistance of Weyl Metals|D. T. Son,B. Z. Spivak###

Chiral Anomaly and Classical Negative Magnetoresistance of Weyl Metals. We consider the classical magnetoresistance of a Weyl metal in which the
electron Fermi surface possess nonzero fluxes of the Berry curvature. Such a
system may exhibit large negative magnetoresistance with unusual anisotropy as
a function of the angle between the electric and magnetic fields. In this case
the system can support a new type of plasma waves. These phenomena are
consequences of chiral anomaly in electron transport theory.

###Observation of magnetocapacitance in ferromagnetic nanowires|Kulothungasagaran Narayanapillai,Mahdi Jamali,Hyunsoo Yang###

Observation of magnetocapacitance in ferromagnetic nanowires. The authors have investigated magnetic domain wall induced capacitance
variation as a tool for the detection of magnetic reversal in magnetic
nanowires for in-plane (NiFe) and out-of-plane (Co/Pd) magnetization
configurations. The switching fields in the capacitance measurements match with
that of the magnetoresistance measurements in the opposite sense. The origin of
the magnetocapacitance has been attributed to magnetoresistance. This
magnetocapacitance detection technique can be useful for magnetic domain wall
studies.

###Interaction effects and transport properties of Pt capped Co nanoparticles|A. Ludwig,L. Agudo,G. Eggeler,A. Ludwig,A. D. Wieck,O. Petracic###

Interaction effects and transport properties of Pt capped Co nanoparticles. We studied the magnetic and transport properties of Co nanoparticles (NPs)
being capped with varying amounts of Pt. Beside field and temperature dependent
magnetization measurements we performed delta-M measurements to study the
magnetic interactions between the Co NPs. We observe a transition from
demagnetizing towards magnetizing interactions between the particles for an
increasing amount of Pt capping. Resistivity measurements show a crossover from
giant magnetoresistance towards anisotropic magnetoresistance.

###Spin Hall Magnetoresistance Induced by a Non-Equilibrium Proximity Effect|H. Nakayama,M. Althammer,Y. -T. Chen,K. Uchida,Y. Kajiwara,D. Kikuchi,T. Ohtani,S. Geprägs,M. Opel,S. Takahashi,R. Gross,G. E. W. Bauer,S. T. B. Goennenwein,E. Saitoh###

Spin Hall Magnetoresistance Induced by a Non-Equilibrium Proximity Effect. We report anisotropic magnetoresistance in Pt|Y3Fe5O12 bilayers. In spite of
Y3Fe5O12 being a very good electrical insulator, the resistance of the Pt layer
reflects its magnetization direction. The effect persists even when a Cu layer
is inserted between Pt and Y3Fe5O12, excluding the contribution of induced
equilibrium magnetization at the interface. Instead, we show that the effect
originates from concerted actions of the direct and inverse spin Hall effects
and therefore call it "spin Hall magnetoresistance."

###Giant magnetoresistance for ensembles of ferromagnetic granules in variable range hopping conductivity regime|V. I. Kozub,A. V. Shumilin###

Giant magnetoresistance for ensembles of ferromagnetic granules in variable range hopping conductivity regime. We study an effect of moderate magnetic field on variable range hopping
conductivity in arrays of ferromagnetic granules separated by tunnel barriers.
It is shown that the resulting magnetoresistance can be significantly larger
than the standard "giant" magnetoresistance in Fe-N-Fe-N... multilayers. The
effect is related to a gain in densities of states available for the virtual
processes within the intermediate granules due to magnetic-field induced
alignment of the granule magnetizations.

###Chiral Anomaly and Diffusive Magnetotransport in Weyl Metals|A. A. Burkov###

Chiral Anomaly and Diffusive Magnetotransport in Weyl Metals. We present a microscopic theory of diffusive magnetotransport in Weyl metals
and clarify its relation to chiral anomaly. We derive coupled diffusion
equations for the total and axial charge densities and show that chiral anomaly
manifests as a magnetic-field-induced coupling between them. We demonstrate
that a universal experimentally-observable consequence of this coupling in
magnetotransport in Weyl metals is a quadratic negative magnetoresistance,
which will dominate all other contributions to magnetoresistance under certain
conditions.

###A brief introduction to giant magnetoresistance|Liu Chang,Min Wang,Lei Liu,Siwei Luo,Pan Xiao###

A brief introduction to giant magnetoresistance. Giant magnetoresistance (GMR) is a quantum mechanical magnetoresistance
effect observed in thin film structures composed of alternating ferromagnetic
and nonmagnetic layers. The effect manifests itself as a significant decrease
(typically 10-80%) in electrical resistance in the presence of a magnetic
field. The effect is exploited commercially by manufacturers of hard disk
drives. The 2007 Nobel Prize in physics was awarded to Albert Fert and Peter
Grunberg for the discovery of GMR.

###Linear polarization study of microwave-radiation-induced magnetoresistance oscillations: Comparison of power dependence to theory|Tianyu Ye,Jesus Inarrea,W. Wegscheider,R. G. Mani###

Linear polarization study of microwave-radiation-induced magnetoresistance oscillations: Comparison of power dependence to theory. We present an experimental study of the microwave power and the linear
polarization angle dependence of the microwave-induced magnetoresistance
oscillations in the high-mobility GaAs/AlGaAs two-dimensional electron system.
Experimental results show the sinusoidal dependence of the oscillatory
magnetoresistance extrema as a function of the polarization angle. Yet, as the
microwave power increases, the angular dependence includes additional harmonic
content, and it begins to resemble the absolute value of the cosine function.
We present a theory to explain such peculiar behavior.

###Field induced suppression of charge density wave in GdNiC$_2$|Kamil K. Kolincio,Karolina Górnicka,Michał J. Winiarski,Judyta Strychalska - Nowak,Tomasz Klimczuk###

Field induced suppression of charge density wave in GdNiC$_2$. We report the specific heat, magnetic, magnetotransport and galvanomagnetic
properties of polycrystalline GdNiC$_2$. In the intermediate temperature region
above $T_N$ = 20 K, we observe large negative magnetoresistance due to Zeeman
splitting of the electronic bands and partial destruction of a charge density
wave ground state. Our magnetoresistance and Hall measurements show that at low
temperatures a magnetic field induced transformation from antiferromagnetic
order to a metamagnetic phase results in the partial suppression of the CDW.

###Oscillating magnetoresistance in graphene p-n junctions at intermediate magnetic fields|Hiske Overweg,Hannah Eggimann,Ming-Hao Liu,Anastasia Varlet,Marius Eich,Pauline Simonet,Yongjin Lee,Kenji Watanabe,Takashi Taniguchi,Klaus Richter,Vladimir I. Fal'ko,Klaus Ensslin,Thomas Ihn###

Oscillating magnetoresistance in graphene p-n junctions at intermediate magnetic fields. We report on the observation of magnetoresistance oscillations in graphene
p-n junctions. The oscillations have been observed for six samples, consisting
of single-layer and bilayer graphene, and persist up to temperatures of 30 K,
where standard Shubnikov-de Haas oscillations are no longer discernible. The
oscillatory magnetoresistance can be reproduced by tight-binding simulations.
We attribute this phenomenon to the modulated densities of states in the n- and
p- regions.

###Magnetoresistance in an electronic cavity coupled to one-dimensional systems|Chengyu Yan,Sanjeev Kumar,Patrick See,Ian Farrer,David Ritchie,J. P. Griffiths,G. A. C. Jones,Michael Pepper###

Magnetoresistance in an electronic cavity coupled to one-dimensional systems. In this work, we performed magnetoresistance measurement in a hybrid system
consisting of an arc-shaped quantum point contact (QPC) and a flat, rectangular
QPC, both of which together form an electronic cavity between them. The results
highlight a transition between collimation-induced resistance dip to a
magnetoresistance peak as the strength of coupling between the QPC and the
electronic cavity was increased. The initial results show the promise of hybrid
quantum system for future quantum technologies.

###Linear magnetoresistance in compensated graphene bilayer|G. Yu. Vasileva,D. Smirnov,Yu. L. Ivanov,Yu. B. Vasilyev,P. S. Alekseev,A. P. Dmitriev,I. V. Gornyi,V. Yu. Kachorovskii,M. Titov,B. N. Narozhny,R. J. Haug###

Linear magnetoresistance in compensated graphene bilayer. We report a nonsaturating linear magnetoresistance in charge-compensated
bilayer graphene in a temperature range from 1.5 to 150 K. The observed linear
magnetoresistance disappears away from charge neutrality ruling out the
traditional explanation of the effect in terms of the classical random resistor
network model. We show that experimental results qualitatively agree with a
phenomenological two-fluid model taking into account electron-hole
recombination and finite-size sample geometry.

###Theory of huge tunneling magnetoresistance in graphene|F. Zhai,K. Chang###

Theory of huge tunneling magnetoresistance in graphene. We investigate theoretically the spin-independent tunneling magnetoresistance
effect in a graphene monolayer modulated by two parallel ferromagnets deposited
on a dielectric layer. For the parallel magnetization configuration, Klein
tunneling can be observed in the transmission spectrum, but at specific oblique
incident angles. For the antiparallel magnetization configuration, the
transmission can be blocked by the magnetic-electric barrier provided by the
ferromagnets. Such a transmission discrepancy results in a tremendous
magnetoresistance ratio and can be tuned by the inclusion of an electric
barrier.

###Spin-polarized electron transport in the high-pressure ferromagnetic phases (GaSb)$_2$M (M=Cr,Mn)|A. A. Pronin,M. V. Kondrin,V. R. Gizatullin,O. A. Sazanova,A. G. Lyapin,S. V. Popova###

Spin-polarized electron transport in the high-pressure ferromagnetic phases (GaSb)$_2$M (M=Cr,Mn). For the first time magnetrotransport of the ferromagnetic high-pressure
phases of (GaSb)$_2$M (M=Cr,Mn) was measured. It was found that the main
component of magnetotransport in these phases is negative and its amplitude is
increasing with temperature rising and approaching Curie temperature. Measuring
of magnetoresistance in the cycling magnetic fields demonstrated that the
Yosida component of magnetresistance is negligible and the main part of the
magnetoresistance can be attributed to the spin-polarized electron transport.

###Insulator/metal phase transition and colossal magnetoresistance in holographic model|Rong-Gen Cai,Run-Qiu Yang###

Insulator/metal phase transition and colossal magnetoresistance in holographic model. Within massive gravity, we construct a gravity dual for insulator/metal phase
transition and colossal magnetoresistance (CMR) effect found in some manganese
oxides materials. In heavy graviton limit, a remarkable
magnetic-field-sensitive DC resistivity peak appears at the Curie temperature,
where an insulator/metal phase transition happens and the magnetoresistance is
scaled with the square of field-induced magnetization. We find that metallic
and insulating phases coexist below the Curie point and the relation with the
electronic phase separation is discussed.

###Magnetotransport in Dirac metals: chiral magnetic effect and quantum oscillations|Gustavo M. Monteiro,Alexander G. Abanov,Dmitri E. Kharzeev###

Magnetotransport in Dirac metals: chiral magnetic effect and quantum oscillations. Dirac metals are characterized by the linear dispersion of fermionic
quasi-particles, with the Dirac point hidden inside a Fermi surface. We study
the magnetotransport in these materials using chiral kinetic theory to describe
within the same framework both the negative magnetoresistance caused by chiral
magnetic effect and quantum oscillations in the magnetoresistance due to the
existence of the Fermi surface. We discuss the relevance of obtained results to
recent measurements on ${\rm Cd_3As_2}$.

###Spin- and Symmetry-Filtering Combined Tunnel Magnetoresistance through Epitaxial MgO/EuS Tunnel Barriers|Zhiwei Gao,Yihang Yang,Fen Liu,Qian Xue,Guo-Xing Miao###

Spin- and Symmetry-Filtering Combined Tunnel Magnetoresistance through Epitaxial MgO/EuS Tunnel Barriers. We created epitaxial magnetic tunnel junctions of FeCo/MgO/EuS on MgO
buffered Si (100). Tunnel magnetoresistance reached up to 64% at 4.2 K. An
unexpected fast drop of magnetoresistance was recorded for MgO thickness above
1 nm, which is attributed to the forced nonspecular conductance across the EuS
conduction band minimum located at the X point, rather than the desired Delta_1
conductance centered around the Gamma point.

###Origin of magnetoresistance suppression in thin $γ$-MoTe$_2$|Shazhou Zhong,Archana Tiwari,George Nichols,Fangchu Chen,Xuan Luo,Yuping Sun,Adam W. Tsen###

Origin of magnetoresistance suppression in thin $γ$-MoTe$_2$. We use both classical magnetotransport and quantum oscillation measurements
to study the thickness evolution of the extremely large magnetoresistance (XMR)
material and type-II Weyl semimetal candidate, $\gamma$-MoTe$_2$, protected
from oxidation. We find that the magnetoresistance is systematically suppressed
with reduced thickness. This occurs concomitantly with both a decrease in
carrier mobility and increase in electron-hole imbalance. We model the two
effects separately and conclude that the XMR effect is more sensitive to the
former.

###Quantizing momentum transport in bilayer graphene|Muhammad Imran###

Quantizing momentum transport in bilayer graphene. The momentum transport in ultraclean bilayer graphene is characterized by the
viscous transport. In quantizing magnetic field the momentum current passes
through the guiding centers of cyclotron orbits. In this study we derive the
quantized Hall viscosity of bilayer graphene that is the next topological
feature after the quantum Hall effect. This can be detected in the non-local
magnetoresistivity measurements that varies with the quantized steps of
magnetoresistivity.

###Gigantic negative magnetoresistance of nanoheterostructures described by the Fivaz model|P. V. Gorskyi###

Gigantic negative magnetoresistance of nanoheterostructures described by the Fivaz model. It is shown that the negative magnetoresistance of nanoheterostructures
described by the Fivaz model can become apparent not only under strong, but
also under intermediate or weak degeneracy of free carrier gas in them. In so
doing, in the Fivaz model it becomes apparent to a larger extent than in the
case of a parabolic, though anisotropic, conduction band. The negative
magnetoresistance can be both due to spin splitting and the Landau quantization
proper.

###Transport in indium-decorated graphene|U. Chandni,Erik A. Henriksen,J. P. Eisenstein###

Transport in indium-decorated graphene. The electronic transport properties of single layer graphene having a dilute
coating of indium adatoms has been investigated. Our studies establish that
isolated indium atoms donate electrons to graphene and become a source of
charged impurity scattering, affecting the conductivity as well as
magnetotransport properties of the pristine graphene. Notably, a positive
magnetoresistance is observed over a wide density range after In doping. The
low field magnetoresistance carries signatures of quantum interference effects
which are significantly altered by the adatoms.

###Magnon contribution to the magnetoresistance of iron nanowires deposited using pulsed electrodeposition|Philip Sergelius,Josep M Montero Moreno,Martin Waleczek,Tim Böhnert,Detlef Görlitz,Kornelius Nielsch###

Magnon contribution to the magnetoresistance of iron nanowires deposited using pulsed electrodeposition. Iron nanowires with a square cross section are grown by pulsed
electrodeposition within a newly developed nanochannel template that allows for
easy characterization. Measurements of the magnetoresistance as a function of
magnetic field and temperature are performed within a large parameter window
allowing for the investigation of the magnonic contribution to the
magnetoresistance of electrodeposited iron nanowires. Values for the
temperature dependent magnon stiffness D(T) are extracted.

###Gate-Controlled Magnetoresistance of a Paramagnetic Insulator|Platinum Interface|L. Liang,J. Shan,Q. H. Chen,J. M. Lu,G. R. Blake,T. T. M. Palstra,G. E. W. Bauer,B. J. van Wees,J. T. Ye###

Gate-Controlled Magnetoresistance of a Paramagnetic Insulator|Platinum Interface. We report an electric field-induced in-plane magnetoresistance of an
atomically flat paramagnetic insulator|platinum (Pt) interface at low
temperatures with an ionic liquid gate. Transport experiments as a function of
applied magnetic field strength and direction obey the spin Hall
magnetoresistance phenomenology with perpendicular magnetic anisotropy. Our
results establish the utility of ionic gating as an alternative method to
control spintronic devices without using ferromagnets.

###Electronic transport in high magnetic fields of thin film MnSi|Nico Steinki,David Schroeter,Niels Wächter,Dirk Menzel,Hans Werner Schumacher,Ilya Sheikin,Stefan Süllow###

Electronic transport in high magnetic fields of thin film MnSi. We present a study of the magnetoresistivity of thin film MnSi in high
magnetic fields. We establish that the magnetoresistivity can be understood in
terms of spin fluctuation theory, allowing us to compare our data to studies of
bulk material. Despite of a close qualitative resemblance of bulk and thin film
data, there are clear quantitative differences. We propose that these reflect a
difference of the spin fluctuation spectra in thin film and bulk material MnSi.

###Understanding spintronics in F/N/F structures through a mechanical analogy|Ya. B. Bazaliy###

Understanding spintronics in F/N/F structures through a mechanical analogy. A mechanical equivalent system is introduced to mimic the behavior of
multilayer structures with diffusive spin transport. The analogy allows one to
use existing mechanical intuition to predict the influence of various
parameters on spin torques and spin-dependent magnetoresistance. In particular,
it provides an understanding of the sign-changing behavior of spin torque in
asymmetric F/N/F spin valves. It further helps to uncover the physical reason
behind the singular behavior of spin magnetoresistance in devices with
ultra-thin N-layers.

###Magnetoresistance of edge states of a two-dimensional topological insulator|Leonid Braginsky,M. V. Entin###

Magnetoresistance of edge states of a two-dimensional topological insulator. The theory of magnetoresistance of the edge state of a two-dimensional
topological insulator is developed. The magnetic field violates the
time-reversal invariance. Magnetoresistance arises due to the energy gap opened
by a magnetic field parallel to the sample surface. The combined action of
impurities and the magnetic field causes backscattering of edge electrons.
Although impurities are necessary for scattering, sufficiently strong
interaction with impurities leads to the suppression of backscattering.

###Positive magnetoresistance induced by hydrodynamic fluctuations in chiral media|Noriyuki Sogabe,Naoki Yamamoto,Yi Yin###

Positive magnetoresistance induced by hydrodynamic fluctuations in chiral media. We analyze the combined effects of hydrodynamic fluctuations and chiral
magnetic effect (CME) for a chiral medium in the presence of a background
magnetic field. Based on the recently developed non-equilibrium effective field
theory, we show fluctuations give rise to a CME-related positive contribution
to magnetoresistance, while the early studies without accounting for the
fluctuations find a CME-related negative magnetoresistance. At zero axial
relaxation rate, the fluctuations contribute to the transverse conductivity in
addition to the longitudinal one.

###Fluctuation theorem for spin transport at insulating ferromagnetic junctions|Tetsuya Sato,Masahiro Tatsuno,Mamoru Matsuo,Takeo Kato###

Fluctuation theorem for spin transport at insulating ferromagnetic junctions. General relations for nonequilibrium spin transport at a magnetic junction
between a normal metal and a ferromagnetic insulator are derived from the
quantum fluctuation theorem. They include the extended Onsager relations
between the spin conductance and the spin-current noise that hold for
nonequilibrium states driven by an external current. These relations, that are
valid for a general setup of spin Hall magnetoresistance, provide a
comprehensive viewpoint for understanding of unidirectional spin Hall
magnetoresistance in insulating ferromagnetic junctions.

###Spin-polarized transport in magnetic tunnel junctions with ZnTe barriers|W. G. Wang,C. Ni,A. Ozbay,L. R. Shah,X. Fan,X. M. Kou,E. R. Nowak,J. Q. Xiao###

Spin-polarized transport in magnetic tunnel junctions with ZnTe barriers. Magnetic tunnel junctions with wide band gap semiconductor ZnTe barrier were
fabricated. A very low barrier height and sizable magnetoresistance were
observed in the Fe/ZnTe/Fe junctions at room temperature. The nonlinear I-V
characteristic curve confirmed the observed magnetoresistance is due to
spin-dependent tunneling effect. Temperature dependent study indicated that the
total conductance of the junction is dominated by direct tunneling, with only a
small portion from the hopping conduction through the defect states inside the
barrier.

###Mean-free path effects in magnetoresistance of ferromagnetic nanocontacts|A. N. Useinov,L. R. Tagirov,R. G. Deminov,Y. Zhou,G. Pan###

Mean-free path effects in magnetoresistance of ferromagnetic nanocontacts. We investigated the mean-free path effects on the magnetoresistance of
ferromagnetic nanocontacts. For most combinations of parameters the
magnetoresistance monotonously decreases with increasing the contact
cross-section. However, for a certain choice of parameters the calculations
show non-monotonous behavior of the magnetoresistance in the region in which
the diameter of the contact becomes comparable with the mean-free path of
electrons. We attribute this effect to different conduction regimes in the
vicinity of the nanocontact: ballistic for electrons of one spin projection,
and simultaneously diffusive for the other. Furthermore, at certain
combinations of spin asymmetries of the bulk mean-free paths in a
heterocontact, the magnetoresistance can be almost constant, or may even grow
as the contact diameter increases. Thus, our calculations suggest a way to
search for combinations of material parameters, for which high
magnetoresistances can be achieved not only at the nanometric size of the
contact, but also at much larger cross-sections of nanocontacts which can be
easier for fabrication with current technologies. The trial calculations of the
magnetoresistance with material parameters close to those for the Mumetal-Ni
heterocontacts agree satisfactorily with the available experimental data.

###Anisotropic tunneling magnetoresistance and tunneling anisotropic magnetoresistance: spin-orbit coupling in magnetic tunnel junctions|Alex Matos-Abiague,Jaroslav Fabian###

Anisotropic tunneling magnetoresistance and tunneling anisotropic magnetoresistance: spin-orbit coupling in magnetic tunnel junctions. The effects of the spin-orbit interaction on the tunneling magnetoresistance
of ferromagnet/semiconductor/normal metal tunnel junctions are investigated.
Analytical expressions for the tunneling anisotropic magnetoresistance (TAMR)
are derived within an approximation in which the dependence of the
magnetoresistance on the magnetization orientation in the ferromagnet
originates from the interference between Bychkov-Rashba and Dresselhaus
spin-orbit couplings that appear at junction interfaces and in the tunneling
region. We also investigate the transport properties of
ferromagnet/semiconductor/ferromagnet tunnel junctions and show that in such
structures the spin-orbit interaction leads not only to the TAMR effect but
also to the anisotropy of the conventional tunneling magnetoresistance (TMR).
The resulting anisotropic tunneling magnetoresistance (ATMR) depends on the
absolute magnetization directions in the ferromagnets. Within the proposed
model, depending on the magnetization directions in the ferromagnets, the
interplay of Bychkov-Rashba and Dresselhaus spin-orbit couplings produces
differences between the rates of transmitted and reflected spins at the
ferromagnet/seminconductor interfaces, which results in an anisotropic local
density of states at the Fermi surface and in the TAMR and ATMR effects. Model
calculations for Fe/GaAs/Fe tunnel junctions are presented. Furthermore, based
on rather general symmetry considerations, we deduce the form of the
magnetoresistance dependence on the absolute orientations of the magnetizations
in the ferromagnets.

###Giant magnetoresistance in semiconductor / granular film heterostructures with cobalt nanoparticles|L. V. Lutsev,A. I. Stognij,N. N. Novitskii###

Giant magnetoresistance in semiconductor / granular film heterostructures with cobalt nanoparticles. We have studied the electron transport in SiO${}_2$(Co)/GaAs and
SiO${}_2$(Co)/Si heterostructures, where the SiO${}_2$(Co) structure is the
granular SiO${}_2$ film with Co nanoparticles. In SiO${}_2$(Co)/GaAs
heterostructures giant magnetoresistance effect is observed. The effect has
positive values, is expressed, when electrons are injected from the granular
film into the GaAs semiconductor, and has the temperature-peak type character.
The temperature location of the effect depends on the Co concentration and can
be shifted by the applied electrical field. For the SiO${}_2$(Co)/GaAs
heterostructure with 71 at.% Co the magnetoresistance reaches 1000 ($10^5$ %)
at room temperature. On the contrary, for SiO${}_2$(Co)/Si heterostructures
magnetoresistance values are very small (4%) and for SiO${}_2$(Co) films the
magnetoresistance has an opposite value. High values of the magnetoresistance
effect in SiO${}_2$(Co)/GaAs heterostructures have been explained by
magnetic-field-controlled process of impact ionization in the vicinity of the
spin-dependent potential barrier formed in the semiconductor near the
interface. Kinetic energy of electrons, which pass through the barrier and
trigger the avalanche process, is reduced by the applied magnetic field. This
electron energy suppression postpones the onset of the impact ionization to
higher electric fields and results in the giant magnetoresistance. The
spin-dependent potential barrier is due to the exchange interaction between
electrons in the accumulation electron layer in the semiconductor and
$d$-electrons of Co.

###Magnetoconductivity in Weyl semimetals: Effect of chemical potential and temperature|Xiao Xiao,K. T. Law,P. A. Lee###

Magnetoconductivity in Weyl semimetals: Effect of chemical potential and temperature. We present the detailed analyses of magneto-conductivities in a Weyl
semimetal within Born and self-consistent Born approximations. In the presence
of the charged impurities, the linear magnetoresistance can happen when the
charge carriers are mainly from the zeroth (n=0) Landau level. Interestingly,
the linear magnetoresistance is very robust against the change of temperature,
as long as the charge carriers mainly come from the zeroth Landau level. We
denote this parameter regime as the high-field regime. On the other hand, the
linear magnetoresistance disappears once the charge carriers from the higher
Landau levels can provide notable contributions. Our analysis indicates that
the deviation from the linear magnetoresistance is mainly due to the deviation
of the longitudinal conductivity from the $1/B$ behavior. We found two
important features of the self-energy approximation: 1. a dramatic jump of
$\sigma_{xx}$, when the $n=1$ Landau level begins to contribute charge
carriers, which is the beginning point of the middle-field regime, when
decreasing the external magnetic field from high field; 2. In the low-field
regime $\sigma_{xx}$ shows a $B^{-5/3}$ behavior and results the
magnetoresistance $\rho_{xx}$ to show a $B^{1/3}$ behavior. The detailed and
careful numerical calculation indicates that the self-energy approximation
(including both the Born and the self-consistent Born approximations) does not
explain the recent experimental observation of linear magnetoresistance in Weyl
semimetals.

###Colossal magnetoresistance over a wide temperature range in Eu0.99La0.01TiO3|Km Rubi,R. Mahendiran###

Colossal magnetoresistance over a wide temperature range in Eu0.99La0.01TiO3. We report occurrence of large magnetoresistance in lightly doped
antiferromagnetic paraelectric EuTiO3. Reports of magnetoresistance in
rare-earth titanates (RTiO3 oxides) are very scarce because they are highly
insulating at low temperatures. EuTiO3 is an insulator at 2.5 K and 1% La3+
substitution for Eu2+ lowers the resistivity over five orders of magnitude at
2.5 K. It is shown that Eu0.99La0.01TiO3 which is antiferromagnetic below T=
5.43 K shows large magnetoresistance over a wide temperature. At 2.5 K,
magnetoresistance is -42 % for H = 6 kOe and it increases to -75 % for H = 7 T.
Even at 50 K which is ten times higher than Neel temperature, magnetoresistance
is very significant (-20 % for H = 7 T). It is suggested that 4f spins on Eu2+
ion is strongly exchange coupled to doped electron in Ti-3d band via f-d
interation and field-induced suppression of 4f spin fluctuations decrease
spin-disorder scattering experienced by 3d electrons. In view of our results,
it will be interesting to investigate magnetoresistance of other rare earth
titanates.

###Fermi Surface and Carriers Compensation of pyrite-type PtBi$_{2}$ Revealed by Quantum Oscillations|Lingxiao Zhao,Liangcai Xu,Huakun Zuo,Xuming Wu,Guoying Gao,Zengwei Zhu###

Fermi Surface and Carriers Compensation of pyrite-type PtBi$_{2}$ Revealed by Quantum Oscillations. Large non-saturating magnetoresistance has been observed in various materials
and electron-hole compensation has been regarded as one of the main mechanisms.
Here we present a detailed study of the angle-dependent Shubnikov -de Haas
effect on large magnetoresistance material pyrite-type PtBi$_{2}$, which allows
us to experimentally reconstruct its Fermi-surface structure and extract the
physical properties of each pocket. We find its Fermi surface contains four
types of pockets in the Brillouin zone: three ellipsoid-like hole pockets
$\alpha$ with C$_4$ symmetry located on the edges (M points), one intricate
electron pocket $\beta$ merged from four ellipsoids along [111] located on the
corners (R points), two smooth and cambered octahedrons $\gamma$ (electron) and
$\delta$ (hole) on the center ($\Gamma$ point). The deduced carrier densities
of electrons and holes from the volume of pockets prove carrier compensation.
This compensation at low temperatures is also supported by fitting the field
dependence of Hall and magnetoresistance at different temperatures. We conclude
that the compensation is the main mechanism for the large non-saturating
magnetoresistance in pyrite-type PtBi$_{2}$. We found the hole pockets {\alpha}
may contribute major mobility because of their light masses and anisotropy to
relatively avoid large-angle scattering at low temperature. This may be a
common feature of semimetals with large magnetoresistance. The found
sub-quadratic magnetoresistance in high field is probably due to
field-dependent mobilities, another feature of semimetals under high magnetic
fields.

###Spin mediated enhanced negative magnetoresistance in Ni80Fe20 and p-silicon bilayer|Paul C Lou,Sandeep Kumar###

Spin mediated enhanced negative magnetoresistance in Ni80Fe20 and p-silicon bilayer. In this work, we present an experimental study of spin mediated enhanced
negative magnetoresistance in Ni80Fe20 (50 nm)/p-Si (350 nm) bilayer. The
resistance measurement shows a reduction of ~2.5% for the bilayer specimen as
compared to 1.3% for Ni80Fe20 (50 nm) on oxide specimen for an out-of-plane
applied magnetic field of 3T. In the Ni80Fe20-only film, the negative
magnetoresistance behavior is attributed to anisotropic magnetoresistance. We
propose that spin polarization due to spin-Hall effect is the underlying cause
of the enhanced negative magnetoresistance observed in the bilayer. Silicon has
weak spin orbit coupling so spin Hall magnetoresistance measurement is not
feasible. We use V2{\omega} and V3{\omega} measurement as a function of
magnetic field and angular rotation of magnetic field in direction normal to
electric current to elucidate the spin-Hall effect. The angular rotation of
magnetic field shows a sinusoidal behavior for both V2{\omega} and V3{\omega},
which is attributed to the spin phonon interactions resulting from the
spin-Hall effect mediated spin polarization. We propose that the spin
polarization leads to a decrease in hole-phonon scattering resulting in
enhanced negative magnetoresistance.

###Negative longitudinal magnetoresistance as a sign of a possible chiral magnetic anomaly in the half-Heusler antiferromagnet DyPdBi|Orest Pavlosiuk,Dariusz Kaczorowski,Piotr Wiśniewski###

Negative longitudinal magnetoresistance as a sign of a possible chiral magnetic anomaly in the half-Heusler antiferromagnet DyPdBi. Magnetotransport investigation of a half-Heusler antiferromagnet DyPdBi
revealed hallmark features of Weyl semimetal: huge negative longitudinal
magnetoresistance and planar Hall effect. Both effects have recently been
linked to chiral magnetic anomaly - axial charge pumping between Weyl nodes.
Magnetoresistance (MR) of single crystals of DyPdBi is very pronounced. In
magnetic field longitudinal to electrical current direction it reaches -80% and
its relative difference with respect to that measured in transverse field
(expressed as anisotropic magnetoresistance) is extremely strong: -60% at 10K
and 14 T. The planar Hall effect in DyPdBi depends on temperature and magnetic
field in non-monotonous way, which has not been previously reported. We compare
magnetoresistance measured with voltage contacts on mid-line of the sample with
that measured with contacts on its edge, and show that the role of
current-jetting, an extrinsic source of anisotropic negative magnetoresistance,
is marginal. We discuss that nature of the compound and sample quality exclude
intrinsic sources of negative and anisotropic magnetoresistance other than weak
localization and the chiral magnetic anomaly.

###Huge magnetoresistance and ultra-sharp metamagnetic transition in polycrystalline ${Sm_{0.5}Ca_{0.25}Sr_{0.25}MnO_3}$|Sanjib Banik,Kalipada Das,Tapas Paramanik,N. P. Lalla,Biswarup Satpati,Kalpataru Pradhan,I. Das###

Huge magnetoresistance and ultra-sharp metamagnetic transition in polycrystalline ${Sm_{0.5}Ca_{0.25}Sr_{0.25}MnO_3}$. Large magnetoresistive materials are of immense interest for a number of
spintronic applications by developing high density magnetic memory devices,
magnetic sensors and magnetic switches. Colossal magnetoresistance, for which
resistivity changes several order of magnitude (${\sim10^4 \%}$) in an external
magnetic field, occurs mainly in phase separated oxide materials, namely
manganites, due to the phase competition between the ferromagnetic metallic and
the antiferromagnetic insulating regions. Can one further enhance the
magnetoresistance by tuning the volume fraction of the two phases? In this
work, we report a huge colossal magnetoresistance along with the ultra-sharp
metamagnetic transition in half doped ${Sm_{0.5}Ca_{0.25}Sr_{0.25}MnO_3}$
manganite compound by suitably tuning the volume fraction of the competing
phases. The obtained magnetoresistance value at 10 K is as large as
$\sim10^{13}\%$ in a 30 kOe external magnetic field and $\sim10^{15}\%$ in 90
kOe external magnetic field and is several orders of magnitude higher than any
other observed magnetoresistance value reported so far. Using model Hamiltonian
calculations we have shown that the inhomogeneous disorder, deduced from
tunneling electron microscopy, suppresses the CE-type phase and seeds the
ferromagnetic metal in an external magnetic field.

###Linear magnetoresistance with a universal energy scale in a strong-coupling superconductor|W. Zhang,Y. J. Hu,C. N. Kuo,S. T. Kuo,Yue-Wen Fang,Kwing To Lai,X. Y. Liu,K. Y. Yip,D. Sun,F. F. Balakirev,C. S. Lue,Hanghui Chen,Swee K. Goh###

Linear magnetoresistance with a universal energy scale in a strong-coupling superconductor. The recent discovery of a nonsaturating linear magnetoresistance in several
correlated electron systems near a quantum critical point has revealed an
interesting interplay between the linear magnetoresistance and the zero-field
linear-in-temperature resistivity. These studies suggest a possible role of
quantum criticality on the observed linear magnetoresistance. Here, we report
our discovery of a nonsaturating, linear magnetoresistance in Mo$_8$Ga$_{41}$,
a nearly isotropic strong electron-phonon coupling superconductor with a
linear-in-temperature resistivity from the transition temperature to $\sim$55
K. The growth of the resistivity in field is comparable to that in temperature,
provided that both quantities are measured in the energy unit. Our datasets are
remarkably similar to magnetoresistance data of the optimally doped
La$_{2-x}$Sr$_x$CuO$_4$, despite the clearly different crystal and electronic
structures, and the apparent absence of quantum critical physics in
Mo$_8$Ga$_{41}$. A new empirical scaling formula is developed, which is able to
capture the key features of the low-temperature magnetoresistance data of
Mo$_8$Ga$_{41}$, as well as the data of La$_{2-x}$Sr$_x$CuO$_4$.

###Non-local magnon-based transport in yttrium iron garnet/platinum heterostructures at high temperatures|Richard Schlitz,Sergey Granovsky,Sebastian T. B. Goennenwein###

Non-local magnon-based transport in yttrium iron garnet/platinum heterostructures at high temperatures. The spin Hall effect in a heavy metal thin film allows to probe the magnetic
properties of an adjacent magnetic insulator via magnetotransport measurements.
Here, we investigate the magnetoresistive response of yttrium iron
garnet/platinum heterostructures from room temperature to beyond the Curie
temperature $T_\mathrm{C, YIG} \approx 560\,\mathrm{K}$ of the ferrimagnetic
insulator. We find that the amplitude of the (local) spin Hall
magnetoresistance decreases monotonically from $300\,\mathrm{K}$ towards
$T_\mathrm{C}$, mimicking the evolution of the saturation magnetization of
yttrium iron garnet. Interestingly, the spin Hall magnetoresistance vanishes
around $500\,\mathrm{K}$, well below $T_\mathrm{C}$, which we attribute to the
formation of a parasitic interface layer by interdiffusion. Around room
temperature the non-local magnon-mediated magnetoresistance exhibits a power
law scaling $T^{\alpha}$ with $\alpha = 3/2$, as already reported. The exponent
decreases gradually to $\alpha \sim 1/2$ at around $420\,\mathrm{K}$, before
the non-local magnetoresistance vanishes rapidly at a similar temperature as
the spin Hall magnetoresistance. We attribute the reduced $\alpha$ at high
temperatures to the increasing thermal magnon population which leads to
enhanced scattering of the non-equilibrium magnon population and a reduced
magnon diffusion length. Finally, we find a magnetic field independent offset
voltage in the non-local signal for $T > 470\,\mathrm{K}$ which we associate
with electronic leakage currents through the normally insulating yttrium iron
garnet film. Indeed, this non-local offset voltage is thermally activated with
an energy close to the band gap.

###On universal butterfly and antisymmetric magnetoresistances|H. T. Wu,Tai Min,Z. X. Guo,X. R. Wang###

On universal butterfly and antisymmetric magnetoresistances. Butterfly magnetoresistance (BMR) and antisymmetric magnetoresistance (ASMR)
are about a butterfly-cross curve and a curve with one peak and one valley when
a magnetic field is swept up and down along a fixed direction. Other than the
parallelogram-shaped magnetoresistance-curve (MR-curve) often observed in
magnetic memory devices, BMR and ASMR are two ubiquitous types of MR-curves
observed in diversified magnetic systems, including van der Waals materials,
strongly correlated systems, and traditional magnets. Here, we reveal the
general principles and the picture behind the BMR and the ASMR that do not
depend on the detailed mechanisms of magnetoresistance: 1) The systems exhibit
hysteresis loops, common for most magnetic materials with coercivities. 2) The
magnetoresistance of the magnetic structures in a large positive magnetic field
and in a large negative magnetic field is approximately the same. With the
generalized Ohm's law in magnetic materials, these principles explain why most
BMR appears in the longitudinal resistance measurements and is very rare in the
Hall resistance measurements. Simple toy models, in which the
Landau-Lifshitz-Gilbert equation governs magnetization, are used to demonstrate
the principles and explain the appearance and disappearance of BMR in various
experiments. Our finding provides a simple picture to understand
magnetoresistance-related experiments.

###Low-field magnetoresistance in GaAs 2D holes|S. J. Papadakis,E. P. De Poortere,H. C. Manoharan,J. B. Yau,M. Shayegan,S. A. Lyon###

Low-field magnetoresistance in GaAs 2D holes. We report low-field magnetotransport data in two-dimensional hole systems in
GaAs/AlGaAs heterostructures and quantum wells, in a large density range, $2.5
\times 10^{10} \leq p \leq 4.0 \times 10^{11}$ cm$^{-2}$, with primary focus on
samples grown on (311)A GaAs substrates. At high densities, $p \gtrsim 1 \times
10^{11}$ cm$^{-2}$, we observe a remarkably strong positive magnetoresistance.
It appears in samples with an anisotropic in-plane mobility and predominantly
along the low-mobility direction, and is strongly dependent on the
perpendicular electric field and the resulting spin-orbit interaction induced
spin-subband population difference. A careful examination of the data reveals
that the magnetoresistance must result from a combination of factors including
the presence of two spin-subbands, a corrugated quantum well interface which
leads to the mobility anisotropy, and possibly weak anti-localization. None of
these factors can alone account for the observed positive magnetoresistance. We
also present the evolution of the data with density: the magnitude of the
positive magnetoresistance decreases with decreasing density until, at the
lowest density studied ($p = 2.5 \times 10^{10}$ cm$^{-2}$), it vanishes and is
replaced by a weak negative magnetoresistance.

###Non-Markovian Effects on the Two-Dimensional Magnetotransport: Low-field Anomaly in Magnetoresistance|Vadim V. Cheianov,A. P. Dmitriev,V. Yu. Kachorovskii###

Non-Markovian Effects on the Two-Dimensional Magnetotransport: Low-field Anomaly in Magnetoresistance. We discuss classical magnetotransport in a two-dimensional system with strong
scatterers. Even in the limit of very low field, when $\omega_c \tau \ll 1$
($\omega_c$ is the cyclotron frequency, $\tau$ is the scattering time) such a
system demonstrates strong negative magnetoresistance caused by non-Markovian
memory effects. A regular method for the calculation of non-Markovian
corrections to the Drude conductivity is presented. A quantitative theory of
the recently discovered anomalous low-field magnetoresistance is developed for
the system of two-dimensional electrons scattered by hard disks of radius $a,$
randomly distributed with concentration $n.$ For small magnetic fields the
magentoresistance is found to be parabolic and inversely proportional to the
gas parameter, $ \delta \rho_{xx}/\rho \sim - (\omega_c \tau)^2 / n a^2.$ In
some interval of magnetic fields the magnetoresistance is shown to be linear
$\delta \rho_{xx}/\rho \sim - \omega_c \tau $ in a good agreement with the
experiment and numerical simulations. Magnetoresistance saturates for $\omega_c
\tau \gg na^2$, when the anomalous memory effects are totally destroyed by the
magnetic field. We also discuss magnetotransport at very low fields and show
that at such fields magnetoresistance is determined by the trajectories having
a long Lyapunov region.

###Effect of the four-sheet Fermi surface on magnetoresistivity of MgB2|I. Pallecchi,M. Monni,C. Ferdeghini,V. Ferrando,M. Putti,C. Tarantini,E. Galleani D'Agliano###

Effect of the four-sheet Fermi surface on magnetoresistivity of MgB2. Recent experimental data of anisotropic magnetoresistivity measured in MgB2
films have shown an intriguing behaviour: the angular dependence of
magnetoresistivity changes dramatically with temperature and disorder. In order
to explain such phenomenology, in this work, we extend our previous analyses on
multiband transverse magnetoresistivity in magnesium diboride, by calculating
its analytic expression, assuming a constant anisotropic Fermi surface mass
tensor. The calculation is done for arbitrary orientation of the magnetic field
with respect to the crystalline axes and for the current density either
perpendicular or parallel to the magnetic field. This approach allows to
extract quite univocally the values of the scattering times in the s- and p-
bands by fitting experimental data with a simple analytic expression. We also
extend the analysis to the magnetoresistivity of polycrystalline samples, with
an arbitrary angle between the current density and the magnetic field, taking
into account the anisotropy of each randomly oriented grain. Thereby, we
propose magnetoresistivity as a very powerful characterization tool to explore
the effect of disorder by irradiation or selective doping as well as of phonon
scattering in each one of the two types of bands, in single crystals and
polycrystalline samples, which is a crucial issue in the study of magnesium
diboride.

###Anomalous magnetoresistance effect in nanoengineered material|S. Dickert,D. K. Singh,R. Thantirige,M. T. Tuominen###

Anomalous magnetoresistance effect in nanoengineered material. The periodic response of magnetoresistance to an externally tunable
parameter, such as magnetic field or chemical composition, in the bulk or an
artificially designed material has been exploited for technological
applications as well as to advance our understanding of many novel effects of
solid state physics. Some notable examples are the giant magnetoresistance
effect in layered materials, the quantum hall effect in semiconductor
heterostructure and the phase coherence of electronic wave function in
disordered metals. In recent years, the ability to engineer materials at the
nanoscale has played a key role in exploring new phenomenon. Using a system
involving periodic Co dots array in direct contact with a surrounding
polycrystalline Cu film, we report the observation of giant thermal hysteresis
and an anomalous oscillatory magnetoresistance behavior. The unusual aspects of
oscillatory magnetoresistance include its observation along only one field scan
direction in an intermediate temperature range of 100 K < T < 200 K. Reducing
the thickness of the Cu film weakens the magnetoresistance oscillation. These
properties suggest a new phenomenon, which could be harnessed for future
technological applications.

###Quantum oscillations with non-zero Berry phase from a complex three dimensional Fermi surface in Bi2Te3|Sourabh Barua,K. P. Rajeev###

Quantum oscillations with non-zero Berry phase from a complex three dimensional Fermi surface in Bi2Te3. We performed angle dependent magnetoresistance study of a metallic single
crystal sample of Bi2Te3. We find that the magnetoresistance is highly
asymmetric in positive and negative magnetic fields for small angles between
the magnetic field and the direction perpendicular to the plane of the sample.
The magnetoresistance becomes symmetric as the angle approaches 90 degree. The
quantum Shubnikov de-Haas oscillations are symmetric and show signatures of
topological surface states with Dirac dispersion in the form of non-zero Berry
phase. However, the angular dependence of these oscillations suggests a complex
three dimensional Fermi surface as the source of these oscillations, which does
not exactly conform with the six ellipsoidal model of the Fermi surface of
Bi2Te3. We attribute the asymmetry in the magnetoresistance to a mixing of the
Hall voltage in the longitudinal resistance due to the comparable magnitude of
the Hall and longitudinal resistance in our samples. This provides a clue to
understanding the asymmetric magnetoresistance often seen in this and similar
materials. Moreover, the asymmetric nature evolves with exposure to atmosphere
and thermal cycling, which we believe is either due to exposure to atmosphere
or thermal cycling, or both affecting the carrier concentration and hence the
Hall signal in these samples. However, the quantum oscillations seem to be
robust against these factors which suggests that the two have different
origins.

###Magnetoresistance control in granular Zn/1-x-y/Cd/x/Mn/y/GeAs/2/ nanocomposite ferromagnetic semiconductors|L. Kilanski,I. V. Fedorchenko,M. Górska,A. Ślawska-Waniewska,N. Nedelko,A. Podgórni,A. Avdonin,E. Lahderanta,W. Dobrowolski,A. N. Aronov,S. F. Marenkin###

Magnetoresistance control in granular Zn/1-x-y/Cd/x/Mn/y/GeAs/2/ nanocomposite ferromagnetic semiconductors. We present studies of structural, magnetic and electrical properties of
Zn/1-x-y/Cd/x/Mn/y/GeAs/2/ nanocomposite ferromagnetic semiconductor samples
with changeable chemical composition. The presence of MnAs clusters induces in
the studied alloy room temperature ferromagnetism with the Curie temperature,
TC, around 305 K. The chemical composition of the chalcopyrite matrix controls
the geometrical parameters of the clusters inducing different magnetoresistance
effects in the crystals. The presence of ferromagnetic clusters in the alloy
induces either negative or positive magnetoresistance with different values.
The Cd-content allows a change of magnetoresistance sign in our samples from
negative (for x = 0.85) to positive (for x = 0.12). The negative
magnetoresistance present in the samples with x = 0.85 is observed at
temperatures T < 25 K with maximum values of about -32% at T = 1.4 K and B = 13
T, strongly depending on the Mn content, y. The positive magnetoresistance
present in the samples with x = 0.12 is observed with maximum values not
exceeding 50% at B =13 T and T = 4.3 K, changing with the Mn content, y.

###Full angular dependence of the spin Hall and ordinary magnetoresistance in epitaxial antiferromagnetic NiO(001)/Pt thin films|Lorenzo Baldrati,Andrew Ross,Tomohiko Niizeki,Christoph Schneider,Rafael Ramos,Joel Cramer,Olena Gomonay,Mariia Filianina,Tatiana Savchenko,Daniel Heinze,Armin Kleibert,Eiji Saitoh,Jairo Sinova,Mathias Kläui###

Full angular dependence of the spin Hall and ordinary magnetoresistance in epitaxial antiferromagnetic NiO(001)/Pt thin films. We report the observation of the three-dimensional angular dependence of the
spin Hall magnetoresistance (SMR) in a bilayer of the epitaxial
antiferromagnetic insulator NiO(001) and the heavy metal Pt, without any
ferromagnetic element. The detected angular-dependent longitudinal and
transverse magnetoresistances are measured by rotating the sample in magnetic
fields up to 11 T, along three orthogonal planes (xy-, yz- and xz-rotation
planes, where the z-axis is orthogonal to the sample plane). The total
magnetoresistance has contributions arising from both the SMR and ordinary
magnetoresistance. The onset of the SMR signal occurs between 1 and 3 T and no
saturation is visible up to 11 T. The three-dimensional angular dependence of
the SMR can be explained by a model considering the reversible field-induced
redistribution of magnetostrictive antiferromagnetic S- and T-domains in the
NiO(001), stemming from the competition between the Zeeman energy and the
elastic clamping effect of the non-magnetic MgO substrate. From the observed
SMR ratio, we estimate the spin mixing conductance at the NiO/Pt interface to
be greater than $2\times10^{14}$ ${\Omega}^{-1}$ $m^{-2}$. Our results
demonstrate the possibility to electrically detect the N\'eel vector direction
in stable NiO(001) thin films, for rotations in the xy- and xz- planes.
Moreover, we show that a careful subtraction of the ordinary magnetoresistance
contribution is crucial to correctly estimate the amplitude of the SMR.

###Giant magnetoresistance, three-dimensional Fermi surface and origin of resistivity plateau in YSb semimetal|Orest Pavlosiuk,Przemysław Swatek,Piotr Wiśniewski###

Giant magnetoresistance, three-dimensional Fermi surface and origin of resistivity plateau in YSb semimetal. Very strong magnetoresistance and a resistivity plateau impeding low
temperature divergence due to insulating bulk are hallmarks of topological
insulators and are also present in topological semimetals where the plateau is
induced by magnetic field, when time-reversal symmetry (protecting surface
states in topological insulators) is broken. Similar features were observed in
a simple rock-salt-structure LaSb, leading to a suggestion of the possible
non-trivial topology of 2D states in this compound. We show that its sister
compound YSb is also characterized by giant magnetoresistance exceeding one
thousand percent and low-temperature plateau of resistivity. We thus performed
in-depth analysis of YSb Fermi surface by band calculations, magnetoresistance,
and Shubnikov--de Haas effect measurements, which reveals only
three-dimensional Fermi sheets. Kohler scaling applied to magnetoresistance
data accounts very well for its low-temperature upturn behavior. The
field-angle-dependent magnetoresistance demonstrates a 3D-scaling yielding
effective mass anisotropy perfectly agreeing with electronic structure and
quantum oscillations analysis, thus providing further support for 3D-Fermi
surface scenario of magnetotransport, without necessity of invoking
topologically non-trivial 2D states. We discuss data implying that analogous
field-induced properties of LaSb can also be well understood in the framework
of 3D multiband model.

###Ultrathin All-in-one Spin Hall Magnetic Sensor with Built-in AC Excitation Enabled by Spin Current|Yanjun Xu,Yumeng Yang,Mengzhen Zhang,Ziyan Luo,Yihong Wu###

Ultrathin All-in-one Spin Hall Magnetic Sensor with Built-in AC Excitation Enabled by Spin Current. Magnetoresistance (MR) sensors provide cost-effective solutions for diverse
industrial and consumer applications, including emerging fields such as
internet-of-things (IoT), artificial intelligence and smart living.
Commercially available MR sensors such as anisotropic magnetoresistance (AMR)
sensor, giant magnetoresistance (GMR) sensor and tunnel magnetoresistance (TMR)
sensors typically require an appropriate magnetic bias for both output
linearization and noise suppression, resulting in increased structural
complexity and manufacturing cost. Here, we demonstrate an all-in-one spin Hall
magnetoresistance (SMR) sensor with built-in AC excitation and rectification
detection, which effectively eliminates the requirements of any linearization
and domain stabilization mechanisms separate from the active sensing layer.
This was made possible by the coexistence of SMR and spin-orbit torque (SOT) in
ultrathin NiFe/Pt bilayers. Despite the simplest possible structure, the
fabricated Wheatstone bridge sensor exhibits essentially zero DC offset,
negligible hysteresis, and a detectivity of around 1nT/sqrt(Hz) at 1Hz. In
addition, it also shows an angle dependence to external field similar to those
of GMR and TMR, though it does have any reference layer (unlike GMR and TMR).
The superior performances of SMR sensors are evidently demonstrated in the
proof-of-concept experiments on rotation angle measurement, and vibration and
finger motion detection.

###Evolution of the Spin Hall Magnetoresistance in Cr$_2$O$_3$/Pt bilayers close to the Néel temperature|Richard Schlitz,Tobias Kosub,Andy Thomas,Savio Fabretti,Kornelius Nielsch,Denys Makarov,Sebastian T. B. Goennenwein###

Evolution of the Spin Hall Magnetoresistance in Cr$_2$O$_3$/Pt bilayers close to the Néel temperature. We study the evolution of magnetoresistance with temperature in thin film
bilayers consisting of platinum and the antiferromagnet Cr$_2$O$_3$ with its
easy axis out of the plane. We vary the temperature from 20 - 60{\deg}C, close
to the N\'eel temperature of Cr$_2$O$_3$ of approximately 37{\deg}C. The
magnetoresistive response is recorded during rotations of the external magnetic
field in three mutually orthogonal planes. A large magnetoresistance having a
symmetry consistent with a positive spin Hall magnetoresistance is observed in
the paramagnetic phase of the Cr$_2$O$_3$, which however vanishes when cooling
to below the N\'eel temperature. Comparing to analogous experiments in a
Gd$_3$Ga$_5$O$_{12}$/Pt heterostructure, we conclude that a paramagnetic field
induced magnetization in the insulator is not sufficient to explain the
observed magnetoresistance. We speculate that the type of magnetic moments at
the interface qualitatively impacts the spin angular momentum transfer, with
the $3d$ moments of Cr sinking angular momentum much more efficiently as
compared to the more localized $4f$ moments of Gd.

###Probing the Origin of Extreme Magnetoresistance in Pr/Sm Mono-Antimonides/Bismuthides|Zhongzheng Wu,Fan Wu,Peng Li,Chunyu Guo,Yi Liu,Zhe Sun,Cheng-Maw Cheng,Tai-Chang Chiang,Chao Cao,Huiqiu Yuan,Yang Liu###

Probing the Origin of Extreme Magnetoresistance in Pr/Sm Mono-Antimonides/Bismuthides. Combining angle-resolved photoemission spectroscopy and magneto-transport
measurements, we systematically investigated the possible origin of the extreme
magnetoresistance in Pr/Sm mono-antimonides/bismuthides (PrSb, SmSb, PrBi,
SmBi). Our photoemission measurements reveal that the bulk band inversion and
surface states are absent (present) in Pr/Sm antimonides (bismuthides),
implying that topological surface states are unlikely to play an important role
for the observed extreme magnetoresistance. We found that the electron-hole
compensation is well satisfied in all these compounds and the bulk band
structure exhibits no obvious temperature dependence from 10 K up to 150 K.
Simultaneous fittings of the magnetoresistance and Hall coefficient reveal that
the carrier mobility is dramatically enhanced at low temperature, which
naturally explains the suppression of extreme magnetoresistance at high
temperatures. Our results therefore show that the extreme magnetoresistance in
these compounds can be well accounted for by the two-band model with good
electron-hole compensation. Finally, we found that both PrSb and SmSb exhibit
highly linear bulk bands near the X point and lie close to the transition point
between a topologically trivial and nontrivial phase, which might be relevant
for the observed anomalous quantum oscillations.

###Magnetotransport properties of La$_{1-x}$Ca$_x$MnO$_3$ (0.52 $\leq x \leq$ 0.75): signature of phase coexistence|M. Čulo,M. Basletić,E. Tafra,A. Hamzić,S. Tomić,F. Fischgrabe,V. Moshnyaga,B. Korin-Hamzić###

Magnetotransport properties of La$_{1-x}$Ca$_x$MnO$_3$ (0.52 $\leq x \leq$ 0.75): signature of phase coexistence. We report the temperature and magnetic field dependence of transport
properties in epitaxial films of the manganite La$_{1-x}$Ca$_{x}$MnO$_{3}$ in
the overdoped region of the phase diagram for $x > 0.5$, where a
charge--ordered (CO) and an antiferromagnetic (AF) phase are present.
Resistivity, magnetoresistance and angular dependence of magnetoresistance were
measured in the temperature interval $4.2 ~\mathrm{K} < T < 300 ~\mathrm{K}$,
for three concentrations $x = 0.52, 0.58$ and $0.75$ and in magnetic fields up
to 5 T. The semiconductor/insulator--like behavior in zero field was observed
in the entire temperature range for all three concentrations \textit{x} and the
electric conduction, at lower temperatures, in the CO state obeys 3D Mott's
variable--range hopping model. A huge negative magnetoresistance for $x = 0.52$
and $x = 0.58$, a metal--insulator transition for $B > 3 ~\mathrm{T}$ for $x =
0.52$ and the presence of anisotropy in magnetoresistance for $x = 0.52$ and $x
= 0.58$ show the fingerprints of colossal magnetoresistance (CMR) behavior
implying the existence of ferromagnetic (FM) clusters. The declining influence
of the FM clusters in the CO/AF part of the phase diagram with increasing $x$
contributes to a possible explanation that a phase coexistence is the origin of
the CMR phenomenon.

###Magnetotransport in Fe-intercalated \textit{T}S$_2$: the comparison between \textit{T} = Ti and Ta|Jesse Choe,Kyungmin Lee,C. -L. Huang,Nandini Trivedi,E. Morosan###

Magnetotransport in Fe-intercalated \textit{T}S$_2$: the comparison between \textit{T} = Ti and Ta. Sharp magnetization switching and large magnetoresistance were previously
discovered in single crystals of 2H-Fe$_x$TaS$_2$ and attributed to the Fe
superstructure and its defects. We report similar sharp switching in
1T-Fe$_x$TiS$_2$ ($0.086\;{\leq}\;x\;{\leq}0.703$) and the discovery of large
magnetoresistance. The switching field $H_s$ and magnetoresistance are similar
to 2H-Fe$_x$TaS$_2$, with a larger than expected bowtie magnetoresistance and a
sharp hysteresis loop. Despite previous reports, electron diffraction shows
only the $\sqrt{3}{\times}\sqrt{3}$ superstructure in 1T-Fe$_x$TiS$_2$. The
Curie and Weiss temperatures remain roughly constant below $x~\sim~1/3$ before
monotonically increasing for higher x. By contrast, the switching field and
magnetoresistance reach a maximum where defects in the superstructure exist,
approach a minimum near perfect superstructures, and remain constant above
$x~\sim~ 0.4$. Additionally, an increase in $H_s$ with annealing time is
reported. Glassy behavior is shown to coexist within the ferromagnetic state in
1T-Fe$_x$TiS$_2$ for compositions between $0.1$ and $0.703$. A simple model
captures the essential phenomenology and explains most similarities and
differences between 1T-Fe$_x$TiS$_2$ and 2H-Fe$_x$TaS$_2$, and provides
insights into other magnetically intercalated transition metal dichalcogenides.

###Nonsaturating large magnetoresistance in the high carrier density nonsymmorphic metal CrP|Q. Niu,W. C. Yu,E. I. Paredes Aulestia,Y. J. Hu,Kwing To Lai,H. Kotegawa,E. Matsuoka,H. Sugawara,H. Tou,D. Sun,F. F. Balakirev,Y. Yanase,Swee K. Goh###

Nonsaturating large magnetoresistance in the high carrier density nonsymmorphic metal CrP. The band structure of high carrier density metal CrP features an interesting
crossing at the Y point of the Brillouin zone. The crossing, which is protected
by the nonsymmorphic symmetry of the space group, results in a hybrid,
semi-Dirac-like energy-momentum dispersion relation near Y. The linear
energy-momentum dispersion relation along Y-$\Gamma$ is reminiscent of the
observed band structure in several semimetallic extremely large
magnetoresistance (XMR) materials. We have measured the transverse
magnetoresistance of CrP up to 14 T at temperatures as low as $\sim$ 16 mK. Our
data reveal a nonsaturating, quadratic magnetoresistance as well as the
behaviour of the so-called `turn-on' temperature in the temperature dependence
of resistivity. Despite the difference in the magnitude of the
magnetoresistance and the fact that CrP is not a semimetal, these features are
qualitatively similar to the observations reported for XMR materials. Thus, the
high-field electrical transport studies of CrP offer the prospect of
identifying the possible origin of the nonsaturating, quadratic
magnetoresistance observed in a wide range of metals.

###Observation of Large Unidirectional Rashba Magnetoresistance in Ge(111)|T. Guillet,C. Zucchetti,Q. Barbedienne,A. Marty,G. Isella,L. Cagnon,C. Vergnaud,N. Reyren,J. -M. George,A. Fert,M. Jamet###

Observation of Large Unidirectional Rashba Magnetoresistance in Ge(111). Relating magnetotransport properties to specific spin textures at surfaces or
interfaces is an intense field of research nowadays. Here, we investigate the
variation of the electrical resistance of Ge(111) grown epitaxially on
semi-insulating Si(111) under the application of an external magnetic field. We
find a magnetoresistance term which is linear in current density j and magnetic
field B, hence odd in j and B, corresponding to a unidirectional
magnetoresistance. At 15 K, for I = 10 $\mu$A (or j = 0.33 A/m) and B = 1 T, it
represents 0.5 % of the zero field resistance, a much higher value compared to
previous reports on unidirectional magnetoresistance. We ascribe the origin of
this magnetoresistance to the interplay between the externally applied magnetic
field and the current-induced pseudo-magnetic field in the spin-splitted
subsurface states of Ge(111). This unidirectional magnetoresistance is
independent of the current direction with respect to the Ge crystal axes. It
progressively vanishes, either using a negative gate voltage due to carrier
activation into the bulk (without spin-splitted bands), or by increasing the
temperature due to the Rashba energy splitting of the subsurface states lower
than $\sim$58 k$_B$. The highly developed technologies on semiconductor
platforms would allow the rapid optimization of devices based on this
phenomenon.

###Magnetoresistance in Fe$_{1-x}$Ga$_x$ thin films presenting striped magnetic pattern: the role of closure domains and domain walls|B. Pianciola,S. Flewett,E. De Biasi,C. Hepburn,L. Lounis,M. Vásquez-Mansilla,M. Granada,M. Barturen,M. Eddrief,M. Sacchi,M. Marangolo,J. Milano###

Magnetoresistance in Fe$_{1-x}$Ga$_x$ thin films presenting striped magnetic pattern: the role of closure domains and domain walls. In this work we show the existence of closure domains in Fe$_{1-x}$Ga$_x$
thin films featuring a striped magnetic pattern and study the effect of the
magnetic domain arrangement on the magnetotransport properties. By means of
X-ray resonant magnetic scattering, we experimentally demonstrate the presence
of such closure domains and estimate their sizes and relative contribution to
surface magnetization. Magnetotransport experiments show that the behavior of
the magnetoresistance depends on the measurement geometry as well as on the
temperature. When the electric current ows perpendicular to the stripe
direction, the resistivity decreases when a magnetic field is applied along the
stripe direction (negative magnetoresistance) in all the studied temperature
range, and the calculations indicate that the main source is the anisotropic
magnetoresistance. In the case of current flowing parallel to the stripe
domains, the magnetoresistance changes sign, being positive at room temperature
and negative at 100 K. To explain this behavior, the contribution to
magnetoresistance from the domain walls must be considered besides the
anisotropic one.

###Possible quantum nematic in a colossal magnetoresistance material|Gabrielle Beaudin,Lucie Maude Fournier,Michael Nicklas,Michel Kenzelmann,Mark Laver,William Witczak-Krempa,Andrea D. Bianchi###

Possible quantum nematic in a colossal magnetoresistance material. EuB6 has for a long time captured the attention of the physics community, as
it shows a ferromagnetic phase transition leading to a insulator the metal
transition together with colossal magnetoresistance (CMR). EuB6 has a very low
carrier density, which is known to drastically change the interaction between
the localized Eu moments and the conduction electrons. One of early triumphs of
the quantum theory in condensed matter was the presence of Fermi surface, which
is intimately linked to the symmetry of the underlying crystal lattice. This
symmetry can be probed by angle resolved magnetoresistance (AMRO) measurements.
Here, we present angle resolved magnetoresistance (AMRO) measurements that show
a that in EuB6 this symmetry is broken, possibly indicating the presence of a
quantum nematic phase. We identify the region in the temperature-magnetic field
phase diagram where the magnetoresistance shows two-fold oscillations instead
of the expected fourfold pattern. Quantum nematic phases are analogous to
classical liquid crystals. Like liquid crystals, which break the rotational
symmetry of space, their quantum analogs break the point-group symmetry of the
crystal due to strong electron-electron interactions, as in quantum Hall
states, Sr3Ru2O7, and high temperature superconductors. This is the same region
where magnetic polarons were previously observed, suggesting that they drive
the nematicity in EuB6. This is also the region of the phase diagram where EuB6
shows a colossal magnetoresistance (CMR). This novel interplay between magnetic
and electronic properties could thus be harnessed for spintronic applications.

###Two-carrier Magnetoresistance: Applications to Ca$_3$Ru$_2$O$_7$|Lakshmi Das,Yang Xu,Tian Shang,Alexander Steppke,Masafumi Horio,Jaewon Choi,Simon Jöhr,Karin von Arx,Jasmin Mueller,Dominik Biscette,Xiaofu Zhang,Andreas Schilling,Veronica Granata,Rosalba Fittipaldi,Antonio Vecchione,Johan Chang###

Two-carrier Magnetoresistance: Applications to Ca$_3$Ru$_2$O$_7$. Ambipolar transport is a commonly occurring theme in semimetals and
semiconductors. Here we present an analytical formulation of the conductivity
for a two-band system. Electron and hole carrier densities and their respective
conductivities are mapped into a two-dimensional unit-less phase space.
Provided that one of the carrier densities is known, the dimensionless phase
space can be probed through magnetoresistance measurements. This formulation of
the two-band model for conductivity is applied to magnetoresistance experiments
on Ca$_3$Ru$_2$O$_7$. While previous such measurements focused on the
low-temperature limit, we cover a broad temperature range and find negative
magnetoresistance in an intermediate interval below the electronic transition
at 48 K. The low-temperature magnetoresistance in Ca$_3$Ru$_2$O$_7$ is
consistent with a two-band structure. However, the model fails to describe the
full temperature and magnetic field dependence. Negative magnetoresistance
found in an intermediate temperature range is, for example, not captured by
this model. We thus conclude that the electronic and magnetic structure in this
intermediate temperature range render the system beyond the most simple
two-band model.

###Superconducting triplet pairings and anisotropic magnetoresistance effects in ferromagnet/superconductor/ferromagnet double-barrier junctions|Andreas Costa,Jaroslav Fabian###

Superconducting triplet pairings and anisotropic magnetoresistance effects in ferromagnet/superconductor/ferromagnet double-barrier junctions. Ferromagnetic spin valves offer the key building blocks to integrate giant-
and tunneling-magnetoresistance effects into spintronics devices. Starting from
a generalized Blonder-Tinkham-Klapwijk approach, we theoretically investigate
the impact of interfacial Rashba and Dresselhaus spin-orbit couplings on the
tunneling conductance, and thereby the magnetoresistance characteristics, of
ferromagnet/superconductor/ferromagnet spin-valve junctions embedding thin
superconducting spacers between the either parallel or antiparallel magnetized
ferromagnets. We focus on the unique interplay between usual electron
tunnelings-that fully determine the magnetoresistance in the normal-conducting
state-and the peculiar Andreev reflections in the superconducting state. In the
presence of interfacial spin-orbit couplings, special attention needs to be
paid to the spin-flip ("unconventional") Andreev-reflection process that is
expected to induce superconducting triplet correlations in proximitized
regions. As a transport signature of these triplet pairings, we detect
conductance double peaks around the singlet-gap energy, reflecting the
competition between the singlet and an additionally emerging triplet gap; the
latter is an effective superconducting gap that can be ascribed to the
formation of triplet Cooper pairs through interfacial spin-flip scatterings
(i.e., to the generation of an effective triplet-pairing term in the order
parameter). We thoroughly analyze the Andreev reflections' role in connection
with superconducting magnetoresistance phenomena, and eventually unravel huge
conductance and magnetoresistance magnetoanisotropies-easily exceeding their
normal-state counterparts by several orders of magnitude-as another
experimentally accessible fingerprint of unconventional Andreev reflections.

###Gate-tunable magnetoresistance in six-septuple-layer MnBi$_2$Te$_4$|Yaoxin Li,Chang Liu,Yongchao Wang,Hao Li,Yang Wu,Jinsong Zhang,Yayu Wang###

Gate-tunable magnetoresistance in six-septuple-layer MnBi$_2$Te$_4$. The recently discovered antiferromagnetic topological insulator
MnBi$_2$Te$_4$ hosts a variety of exotic topological quantum phases such as the
axion insulator and Chern insulator states. Here we report systematic gate
voltage dependent magneto transport studies in six septuple-layer
MnBi$_2$Te$_4$. In p-type carrier regime, we observe positive linear
magnetoresistance when MnBi$_2$Te$_4$ is polarized in the ferromagnetic state
by an out-of-plane magnetic field. Whereas in n-type regime, distinct negative
magnetoresistance behaviors are observed. The magnetoresistance in both regimes
is highly robust against temperature even up to the N\'eel temperature. Within
the antiferromagnetic state, the behavior of magnetoresistance exhibits a
transition from negative to positive as applying a gate voltage. The boundaries
between different magnetoresistance behaviors in the experimental phase diagram
can be explicitly characterized by the gate-voltage-independent magnetic fields
that denotes the processes of the spin-flop transition. The rich transport
phenomena demonstrate the intricate interplay between topology, magnetism and
dimensionality in MnBi$_2$Te$_4$.

###Rashba spin-orbit coupling enhanced magnetoresistance in junctions with one ferromagnet|Chenghao Shen,Ranran Cai,Alex Matos-Abiague,Wei Han,Jong E. Han,Igor Zutic###

Rashba spin-orbit coupling enhanced magnetoresistance in junctions with one ferromagnet. We explain how Rashba spin-orbit coupling (SOC) in a two-dimensional electron
gas (2DEG), or in a conventional $s$-wave superconductor, can lead to a large
magnetoresistance even with one ferromagnet. However, such enhanced
magnetoresistance is not generic and can be nonmonotonic and change its sign
with Rashba SOC. For an in-plane rotation of magnetization, it is typically
negligibly small for a 2DEG and depends on the perfect transmission which
emerges from a spin-parity-time symmetry of the scattering states, while this
symmetry is generally absent from the Hamiltonian of the system. The key
difference from considering the normal-state magnetoresistance is the presence
of the spin-dependent Andreev reflection at superconducting interfaces. In the
fabricated junctions of quasi-2D van der Waals ferromagnets with conventional
$s$-wave superconductors (Fe$_{0.29}$TaS$_2$/NbN) we find another example of
enhanced magnetoresistance where the presence of Rashba SOC reduces the
effective interfacial strength and is responsible for an equal-spin Andreev
reflection. The observed nonmonotonic trend in the out-of-plane
magnetoresistance with the interfacial barrier is an evidence for the
proximity-induced equal-spin-triplet superconductivity.

###Effect of Pt vacancies on magnetotransport of Weyl semimetal candidate GdPtSb epitaxial films|Dongxue Du,Laxman Raju Thoutam,Konrad T. Genser,Chenyu Zhang,Karin M. Rabe,Bharat Jalan,Paul M. Voyles,Jason K. Kawasaki###

Effect of Pt vacancies on magnetotransport of Weyl semimetal candidate GdPtSb epitaxial films. We examine the effects of Pt vacancies on the magnetotransport properties of
Weyl semimetal candidate GdPtSb films, grown by molecular beam epitaxy on
c-plane sapphire. Rutherford backscattering spectrometry (RBS) and x-ray
diffraction measurements suggest that phase pure GdPt$_{x}$Sb films can
accommodate up to $15\%$ Pt vacancies ($x=0.85$), which act as acceptors as
measured by Hall effect. Two classes of electrical transport behavior are
observed. Pt-deficient films display a metallic temperature dependent
resistivity (d$\rho$/dT$>$0). The longitudinal magnetoresistance (LMR, magnetic
field $\mathbf{B}$ parallel to electric field $\mathbf{E}$) is more negative
than transverse magnetoresistance (TMR, $\mathbf{B} \perp \mathbf{E}$),
consistent with the expected chiral anomaly for a Weyl semimetal. The
combination of Pt-vacancy disorder and doping away from the expected Weyl
nodes; however, suggests conductivity fluctuations may explain the negative LMR
rather than chiral anomaly. Samples closer to stoichiometry display the
opposite behavior: semiconductor-like resistivity (d$\rho$/dT$<$0) and more
negative transverse magnetoresistance than longitudinal magnetoresistance.
Hysteresis and other nonlinearities in the low field Hall effect and
magnetoresistance suggest that spin disorder scattering, and possible
topological Hall effect, may dominate the near stoichiometric samples. Our
findings highlight the complications of transport-based identification of Weyl
nodes, but point to possible topological spin textures in GdPtSb.

###Transport and magnetic properties in ferromagnetic manganese-oxide thin films|Liang-Jian Zou,X. G. Gong,Qing-Qi Zheng,C. Y. Pan###

Transport and magnetic properties in ferromagnetic manganese-oxide thin films. The transport and magnetic properties in ferromagnetic manganese-oxide thin
films are studied based on the model of the coupling between the mobile
d-electrons and the core spins in Mn ions. The spontaneous magnetization and
the resistivity are obtained for various magnetic fields and temperature. The
resistivity in absence of magnetic field and the magnetoresistance exhibit
maxima near the Curie temperature, the applied magnetic field moves the
position of the resistivity peak to high temperature and suppresses the peak
value, which agree with the experimental results. The Hall resistivity is
predicted to exhibit maximum near the Curie point. The pressure effect of the
magnetoresistance can also be explained qualitatively in this mechanism. The
colossal magnetoresistance in ferromagnetic manganese-oxide thin films is
attributed to the spin-correlation fluctuation scattering and the low
dimensional effect.

###Spin Splitting and Weak Localization in (110) GaAs/AlGaAs Quantum Wells|T. Hassenkam,S. Pedersen,K. Baklanov,A. Kristensen,C. B. Sorensen,P. E. Lindelof,F. G. Pikus,G. E. Pikus###

Spin Splitting and Weak Localization in (110) GaAs/AlGaAs Quantum Wells. We investigate experimentally and theoretically the spin-orbit effects on the
weak localization in a (110) GaAs 2-dimensional electron gas (2DEG). We analyze
the role of two different terms in the spin splitting of the conduction band:
the Dresselhaus terms, which arise due to the lack of inversion center in the
bulk GaAs, and the Rashba terms, which are caused by the asymmetry of the
quantum well. It is shown that in A3B5 quantum wells the magnetoresistance due
to the weak localization depends qualitatively on the orientation of the well.
In particular, it is demonstrated that the (110) geometry has a distinctive
feature that in the absence of the Rashba terms the ``antilocalization''
effect, i.e. the positive magnetoresistance, does not exist. Calculation of the
weak anti-localization magnetoresistance is found to be in excellent agreement
with experiments.

###Magnetic phase diagram and transport properties of FeGe_2|C. P. Adams,T. E. Mason,S. A. M. Mentink,E. Fawcett###

Magnetic phase diagram and transport properties of FeGe_2. We have used resistivity measurements to study the magnetic phase diagram of
the itinerant antiferromagnet FeGe_2 in the temperature range from 0.3->300 K
in magnetic fields up to 16 T. In contrast to theoretical predictions, the
incommensurate spin density wave phase is found to be stable at least up to 16
T, with an estimated critical field \mu _0H_c of ~ 30 T. We have also studied
the low temperature magnetoresistance in the [100], [110], and [001]
directions. The transverse magnetoresistance is well described by a power law
for magnetic fields above 1 T with no saturation observed at high fields. We
discuss our results in terms of the magnetic structure and the calculated
electronic bandstructure of FeGe_2. We have also observed, for the first time
in this compound, Shubnikov-de Haas oscillations in the transverse
magnetoresistance with a frequency of 190 +- 10 T for a magnetic field along
[001].

###Violation of Kohler's rule by the magnetoresistance of a quasi-two-dimensional organic metal|Ross H. McKenzie,J. S. Qualls,S. Y. Han,J. S. Brooks###

Violation of Kohler's rule by the magnetoresistance of a quasi-two-dimensional organic metal. The interlayer magnetoresistance of the quasi-two-dimensional metal
$\alpha$-(BEDT-TTF)$_2$KHg(SCN)$_4$ is considered. In the temperature range
from 0.5 to 10 K and for fields up to 10 tesla the magnetoresistance has a
stronger temperature dependence than the zero-field resistance. Consequently
Kohler's rule is not obeyed for any range of temperatures or fields. This means
that the magnetoresistance cannot be described in terms of semiclassical
transport on a single Fermi surface with a single scattering time. Possible
explanations for the violations of Kohler's rule are considered, both within
the framework of semi-classical transport theory and involving incoherent
interlayer transport. The issues considered are similar to those raised by the
magnetotransport of the cuprate superconductors.

###The transverse magnetoresistance of the two-dimensional chiral metal|J. T. Chalker,S. L. Sondhi###

The transverse magnetoresistance of the two-dimensional chiral metal. We consider the two-dimensional chiral metal, which exists at the surface of
a layered, three-dimensional sample exhibiting the integer quantum Hall effect.
We calculate its magnetoresistance in response to a component of magnetic field
perpendicular to the sample surface, in the low temperature, but macroscopic,
regime where inelastic scattering may be neglected. The magnetoresistance is
positive, following a Drude form with a field scale,
$B_0=\Phi_0/al_{\text{el}}$, given by the transverse field strength at which
one quantum of flux, $\Phi_0$, passes through a rectangle with sides set by the
layer-spacing, $a$, and the elastic mean free path, $l_{\text{el}}$.
Experimental measurement of this magnetoresistance may therefore provide a
direct determination of the elastic mean free path in the chiral metal.

###Large Low Temperature Magnetoresistance and Magnetic Anomalies in Tb$_2$PdSi$_3$ and Dy$_2$PdSi$_3$|R. Mallik,E. V. Sampathkumaran,P. L. Paulose###

Large Low Temperature Magnetoresistance and Magnetic Anomalies in Tb$_2$PdSi$_3$ and Dy$_2$PdSi$_3$. The results of heat-capacity, magnetic susceptibility, electrical resistivity
and magnetoresistance $(\Delta \rho/\rho)$ measurements on the compounds
Tb$_2$PdSi$_3$ and Dy$_2$PdSi$_3$, are reported. The results establish that
these compounds undergo long-range magnetic ordering (presumably with a complex
magnetic structure) below (Tc=) 23 and 8 K respectively. The $\Delta \rho/\rho
$ is negative in the vicinity of Tc and the magnitude grows as Tc is approached
from higher temperature as in the case of well-known giant magnetoresistance
systems (La manganite based perovskites); this is attributed to the formation
of some kind of magnetic polarons. The magnitude of magnetoresistance at low
temperatures is quite large, for instance, about 30% in the presence of 60 kOe
field at 5 K in the Dy sample.

###Residual resistivity ratio and its relation to the positive magnetoresistance behavior in natural multilayer LaMn2Ge2; relevance to artificial multilayer physics|S. Majumdar,R. Mallik,E. V. Sampathkumaran,P. L. Paulose###

Residual resistivity ratio and its relation to the positive magnetoresistance behavior in natural multilayer LaMn2Ge2; relevance to artificial multilayer physics. Results of low temperature magnetoresistance ($\Delta\rho/\rho$) and
isothermal magnetization (M) measurements on polycrystalline ferromagnetic (T_C
close to 300 K) natural multilayers, LaMn_{2+x}Ge_{2-y}Si_y, are reported. It
is found that the samples with large residual resistivity ratio,
$\rho(300K)/\rho(4.2K)$, exhibit large positive magnetoresistance at high
magnetic fields. The Kohler's rule is not obeyed in these alloys. In addition,
at 4.5 K, there is a tendency towards linear variation of $\Delta\rho/\rho$
with magnetic field with increasing $\rho(300K)/\rho(4.2K$); however, the field
dependence of $\Delta\rho/\rho$ does not track that of M, thereby suggesting
that the magnetoresistance originates from non-magnetic layers. It is
interesting that these experimental findings on bulk polycrystals are
qualitatively similar to what is seen in artificially grown multilayer systems
recently.

###Giant transverse magnetoresistance in an asymmetric system of three GaAs/AlGaAs quantum wells in a strong magnetic field at room temperature|V. I. Tsebro,O. E. Omel'yanovskii,V. V. Kapaev,Yu. V. Kopaev,V. I. Kadushkin###

Giant transverse magnetoresistance in an asymmetric system of three GaAs/AlGaAs quantum wells in a strong magnetic field at room temperature. The giant transverse magnetoresistance is observed in the case of
photoinduced nonequilibrium carriers in an asymmetric undoped system of three
GaAs/AlGaAs quantum wells at room temperature. In a magnetic field of 75 kOe,
the resistance of nanostructure being studied increases by a factor of 1.85.
The magnetoresistance depends quadratically on the magnetic field in low fields
and tends to saturation in high fields. This phenomenon is attributed to the
rearrangement of the electron wave function in magnetic field. Using the fact
that the incoherent part of the scattering probability for electron scattering
on impurities and bulk defects is proportional to the integral of the forth
power of the envelope wave function, the calculated field dependence of the
magnetoresistance is shown to be similar to that observed experimentally.

###Two lifetimes and the pseudogap in the orbital magnetoresistance of Zn-substituted La{1.85}Sr{0.15}CuO{4}|A. Malinowski,A. Krickser,Marta Z. Cieplak,S. Guha,K. Karpinska,M. Berkowski,P. Lindenfeld###

Two lifetimes and the pseudogap in the orbital magnetoresistance of Zn-substituted La{1.85}Sr{0.15}CuO{4}. The effect of zinc doping on the anomalous temperature dependence of the
magnetoresistance and the Hall effect in the normal state was studied in a
series of La{1.85}Sr{0.15}Cu{1-y}Zn{y}O{4} films, with values of y between zero
and 0.12. The orbital magnetoresistance at high temperatures is found to be
proportional to the square of the tangent of the Hall angle, as predicted by
the model of two relaxation rates, for all Zn-doped specimens, including
nonsuperconducting films. The proportionality constant is equal to 13.7+/-0.5
independent of doping. This is very different from the behavior observed in
underdoped La{2-x}Sr{x}CuO{4} films where a decrease of x destroys the
proportionality. In addition, the behavior of the orbital magnetoresistance at
low temperatures is found to be different depending on whether x is changed or
y. We suggest that these differences reflect a different evolution of the
pseudogap in the two cases.

###Geometric Resonance in Modulated Quantum Hall Systems Near $ ν= 1/2$|Nataliya A. Zimbovskaya,Joseph L. Birman###

Geometric Resonance in Modulated Quantum Hall Systems Near $ ν= 1/2$. We propose a theory for the new effects recently observed by Willett et al
[1] in the magnetoresistance of a weakly modulated two dimensional electron gas
near filling factor 1/2. Minima in transverse magnetoresistance and maxima in
longitudinal magnetoresistance at the same magnetic field producing the new
resonance structure are reported. The structure occurs due to geometric
resonance of the composite fermion cyclotron orbits with the modulation period
of the effective magnetic field $ B_{eff} $ due to the applied density
modulation. The transverse minimum occurs due to the inhomogeneity in the field
$ B_{eff} $ in the presence of density modulations, whereas the longitudinal
maximum can arise due to a shape-effect (distortion) of the composite fermion
Fermi surface (CF-FS). Thus the minima and maxima reflect different physical
mechanisms.
  PACS numbers 71.10 Pm, 73.40 Hm, 73.20 Dx {}

###Temperature and Angular Dependence of the Magnetoresistance in Low Dimensional Organic Metals|J. S. Qualls,J. S. Brooks,S. Uji,T. Terashima,C. Terakura,H. Aoki,L. K. Montgomery###

Temperature and Angular Dependence of the Magnetoresistance in Low Dimensional Organic Metals. Detailed studies of the magnetoresistance of alpha-(ET)2KHg(SCN)4 and
alpha-(ET)2TlHg(SCN)4 as a function of temperature, magnetic field strength,
and field orientation are reported. Below 15 K, the temperature dependence of
the magnetoresistance is metallic (dR/dT > 0) for magnetic field orientation
corresponding to an angular dependent magnetoresistance oscillation (AMRO)
minimum and nonmetallic (dR/dT < 0) at all other field orientations. We find
that this behavior can be explained in terms of semiclassical models without
the use of a non-Fermi liquid description. The alternating temperature
dependence (metallic/nonmetallic)with respect to field orientation is common to
any system with either quasi-one or two-dimensional AMRO. Furthermore, we
report a new metallic property of the high field and low temperature regime of
alpha-(ET)2MHg(SCN)4 (where M = K, Rb, or Tl) compounds.

###Temperature dependence of the interlayer magnetoresistance of quasi-one-dimensional Fermi liquids at the magic angles|Ross H. McKenzie,Perez Moses###

Temperature dependence of the interlayer magnetoresistance of quasi-one-dimensional Fermi liquids at the magic angles. The interlayer magnetoresistance of a quasi-one-dimensional Fermi liquid is
considered for the case of a magnetic field that is rotated within the plane
perpendicular to the most-conducting direction. Within semi-classical transport
theory dips in the magnetoresistance occur at integer amgic angles only when
the electronic dispersion parallel to the chains is nonlinear. If the field
direction is fixed at one of the magic angles and the temperature is varied the
resulting variation of the scattering rate can lead to a non-monotonic
variation of the interlayer magnetoresistance with temperature. Although the
model considered here gives a good description of some of the properties of the
Bechgaard salts, (TMTSF)2PF6 for pressures less than 8kbar and (TMTSF)2ClO4 it
gives a poor description of their properties when the field is parallel to the
layers and of the intralayer transport.

###Magnetoresistance of Three-Constituent Composites: Percolation Near a Critical Line|Sergey V. Barabash,David J. Bergman,D. Stroud###

Magnetoresistance of Three-Constituent Composites: Percolation Near a Critical Line. Scaling theory, duality symmetry, and numerical simulations of a random
network model are used to study the magnetoresistance of a
metal/insulator/perfect conductor composite with a disordered columnar
microstructure. The phase diagram is found to have a critical line which
separates regions of saturating and non-saturating magnetoresistance. The
percolation problem which describes this line is a generalization of
anisotropic percolation. We locate the percolation threshold and determine the
t = s = 1.30 +- 0.02, nu = 4/3 +- 0.02, which are the same as in
two-constituent 2D isotropic percolation. We also determine the exponents which
characterize the critical dependence on magnetic field, and confirm numerically
that nu is independent of anisotropy. We propose and test a complete scaling
description of the magnetoresistance in the vicinity of the critical line.

###Grain boundary effects on magnetotransport in bi-epitaxial films of La$_{0.7}$Sr$_{0.3}$MnO$_3$|R. Mathieu,P. Svedlindh,R. A. Chakalov,Z. G. Ivanov###

Grain boundary effects on magnetotransport in bi-epitaxial films of La$_{0.7}$Sr$_{0.3}$MnO$_3$. The low field magnetotransport of La$_{0.7}$Sr$_{0.3}$MnO$_3$ (LSMO) films
grown on SrTiO$_3$ substrates has been investigated. A high qualtity LSMO film
exhibits anisotropic magnetoresistance (AMR) and a peak in the
magnetoresistance close to the Curie temperature of LSMO. Bi-epitaxial films
prepared using a seed layer of MgO and a buffer layer of CeO$_2$ display a
resistance dominated by grain boundaries. One film was prepared with seed and
buffer layers intact, while a second sample was prepared as a 2D square array
of grain boundaries. These films exhibit i) a low temperature tail in the low
field magnetoresistance; ii) a magnetoconductance with a constant high field
slope; and iii) a comparably large AMR effect. A model based on a two-step
tunneling process, including spin-flip tunneling, is discussed and shown to be
consistent with the experimental findings of the bi-epitaxial films.

###Parallel magnetic field induced strong negative magnetoresistance in a wide p-Ge_{1-x}Si_x/Ge/p-Ge_{1-x}Si_x quantum well|M. V. Yakunin,G. A. Alshanskii,Yu. G. Arapov,V. N. Neverov,O. A. Kuznetsov###

Parallel magnetic field induced strong negative magnetoresistance in a wide p-Ge_{1-x}Si_x/Ge/p-Ge_{1-x}Si_x quantum well. A negative magnetoresistance under the in-plane magnetic field, reaching
maximum 30-40% of its zero-field value in fields higher than ~12 T, has been
found in wide Ge_{1-x}Si_x/Ge/p-Ge_{1-x}Si_x quantum wells (QW) containing the
quasi-two-dimensional hole gas. In the QWs of intermediate widths and hole
densities, this negative magnetoresistance may be explained as being caused by
suppression of the intersubband scattering due to the upper subband
depopulation. For the widest QWs with the highest hole densities, in which the
hole gas is divided into two sublayers, similar negative magnetoresistance was
observed and tentatively interpreted as also been due to suppression of the
intersubband scattering, but subbands are the lowest symmetric and
antisymmetric states of the double quantum well structure. These subbands shift
under the in-plane magnetic field not vertically in energy, but horizontally
along the wave vector.

###Novel critical field in magneto-resistance oscillation of 2DEG in asymmetric GaAs/AlGaAs double wells measured as a function of the in-plane magnetic field|P. Svoboda,Y. Krupko,L. Smrcka,M. Cukr,T. Jungwirth,L. Jansen###

Novel critical field in magneto-resistance oscillation of 2DEG in asymmetric GaAs/AlGaAs double wells measured as a function of the in-plane magnetic field. We have investigated the magnetoresistance of strongly asymmetric double-well
structures formed by a thin AlGaAs barrier grown far from the interface in the
GaAs buffer of standard heterostructures. In magnetic fields oriented parallel
to the electron layers, the magnetoresistance exhibits an oscillation
associated with the depopulation of the higher occupied subband and with the
field-induced transition into a decoupled bilayer. In addition, the increasing
field transfers electrons from the triangular to rectangular well and, at high
enough field value, the triangular well is emptied. Consequently, the
electronic system becomes a single layer which leads to a sharp step in the
density of electron states and to an additional minimum in the
magnetoresistance curve.

###Correlation between the residual resistance ratio and magnetoresistance in MgB2|X. H. Chen,Y. S. Wang,Y. Y. Xue,R. L. Meng,Y. Q. Wang,C. W. Chu###

Correlation between the residual resistance ratio and magnetoresistance in MgB2. The resistivity and magnetoresistance in the normal state for bulk and
thin-film MgB2 with different nominal compositions have been studied
systematically. These samples show different temperature dependences of normal
state resistivity and residual resistance ratios although their superconducting
transition temperatures are nearly the same, except for the thin-film sample.
The correlation between the residual resistance ratio (RRR) and the power law
dependence of the low temperature resistivity, rho vs. T^c, indicates that the
electron-phonon interaction is important. It is found that the
magnetoresistance (MR) in the normal state scales well with the RRR, a0(MR)
proportional to (RRR)^2.2 +/- 0.1 at 50 K. This accounts for the large
difference in magnetoresistance reported by various groups, due to different
defect scatterings in the samples.

###Unconventional spin density wave in (TMTSF)2PF6 below T* ~ 4K|Mario Basletic,Bojana Korin-Hamzic,Kazumi Maki###

Unconventional spin density wave in (TMTSF)2PF6 below T* ~ 4K. The presence of subphases in spin-density wave (SDW) phase of (TMTSF)2PF6
below T* ~ 4K has been suggested by several experiments but the nature of the
new phase is still controversial. We have investigated the temperature
dependence of the angular dependence of the magnetoresistance in the SDW phase
which shows different features for temperatures above and below T*. For T > 4K
the magnetoresistance can be understood in terms of the Landau quantization of
the quasiparticle spectrum in a magnetic field, where the imperfect nesting
plays the crucial role. We propose that below T* ~ 4K the new unconventional
SDW (USDW) appears modifying dramatically the quasiparticle spectrum. Unlike
conventional SDW the order parameter of USDW depends on the quasiparticle
momentum. The present model describes many features of the angular dependence
of magnetoresistance reasonably well. Therefore, we may conclude that the
subphase in (TMTSF)2PF6 below T* ~ 4K is described as SDW plus USDW.

###Magnetoresistance and percolation in the LaNi(1-x)Co(x)O3 solid solution|J. Androulakis,Z. Viskadourakis,N. Katsarakis,J. Giapintzakis###

Magnetoresistance and percolation in the LaNi(1-x)Co(x)O3 solid solution. A detailed study of the zero-field electrical resistivity and
magnetoresistance for the metallic members of the LaNi_{1-x}Co{x}O3 solid
solution with 0.3<=x<=0.6 is reported. The low temperature resistivity of the
compounds with 0.3<=x<=0.5 exhibits a logarithmic dependence that is
characteristic of systems with spin fluctuations. It is suggested that the
effect of the magnetic field dependence on the spin fluctuations plays a vital
role in determining the magnetoresistive behavior of these compounds. Concrete
experimental evidence that classify the chemically induced metal-to-insulator
transition (x_{c}=0.65) as a percolative phenomenon is provided. The
resistivity data for the x=0.6 metallic compound are analyzed in the framework
of cluster percolation threshold theory. The results of this analysis are
consistent with the suggestion that the growth of magnetic metallic clusters in
the presence of a magnetic field is mainly responsible for the observed giant
magnetoresistance effect at low temperatures for the compounds with x>=0.6.

###Magnetotransport in Single Crystal Half-Heusler Compounds|K. Ahilan,M. C. Bennett,M. C. Aronson,N. E. Anderson,P. C. Canfield,E. Munoz-Sandoval,T. Gortenmulder,R. Hendrixx,J. A. Mydosh###

Magnetotransport in Single Crystal Half-Heusler Compounds. We present the results of electrical resistivity and Hall effect measurements
on single crystals of HfNiSn, TiPtSn, and TiNiSn. Semiconducting behavior is
observed in each case, involving the transport of a small number of highly
compensated carriers. Magnetization measurements suggest that impurities and
site disorder create both localized magnetic moments and extended paramagnetic
states, with the susceptibility of the latter increasing strongly with reduced
temperature. The magnetoresistance is sublinear or linear in fields ranging
from 0.01 - 9 Tesla at the lowest temperatures. As the temperature increases,
the normal quadratic magnetoresistance is regained, initially at low fields,
and at the highest temperatures extending over the complete range of fields.
The origin of the vanishingly small field scale implied by these measurements
remains unknown, presenting a challenge to existing classical and quantum
mechanical theories of magnetoresistance.

###Non-saturating magnetoresistance in heavily disordered semiconductors|M. M. Parish,P. B. Littlewood###

Non-saturating magnetoresistance in heavily disordered semiconductors. The resistance of a homogeneous semiconductor increases quadratically with
magnetic field at low fields and, except in very special cases, saturates at
fields much larger than the inverse of the carrier mobility, a number typically
of order 1 Tesla. Here, we argue that a macroscopically disordered and strongly
inhomogeneous semiconductor will instead show a non-saturating
magnetoresistance, with typically a quasi-linear behaviour up to very large
fields, and possibly also extending down to very low fields, depending on the
degree of inhomogeneity. We offer this as a possible explanation of the
observed anomalously large magnetoresistance in doped silver chalcogenides.
Furthermore, our model of an inhomogeneous semiconductor can be developed into
magnetoresistive devices that possess a large, controllable, linear response.

###Extrinsic inhomogeneity effects in magnetic, transport and magnetoresistive properties of La_{1-x}Ca_{x}MnO_{3} (x\approx 0.33) crystal prepared by the floating zone method|B. I. Belevtsev,D. G. Naugle,K. D. D. Rathnayaka,A. Parasiris,J. Fink-Finowicki###

Extrinsic inhomogeneity effects in magnetic, transport and magnetoresistive properties of La_{1-x}Ca_{x}MnO_{3} (x\approx 0.33) crystal prepared by the floating zone method. The paper describes a study of the magnetic, transport and magnetoresistive
properties of La_{1-x}Ca_{x}MnO_{3} (x\approx 0.33) crystals prepared by the
floating-zone method. We found that these properties testify to rather good
crystal perfection of the sample studied. In particular, a huge
magnetoresistance ([R(0)-R(H)]/R(H) in the field H = 5 T is about 2680 %) is
found near the Curie temperature (216 K). At the same time, some distinct
features of measured properties indicate the influence of extrinsic
inhomogeneities arising due to technological factors in the sample preparation.
Analysis of the data obtained shows that these are rare grain boundaries and
twins. Specific influence of the grain-boundary-like inhomogeneities on the
transport and magnetoresistive properties are considered.

###Spin-related magnetoresistance of n-type ZnO:Al and Zn_{1-x}Mn_{x}O:Al thin films|T. Andrearczyk,J. Jaroszynski,G. Grabecki,T. Dietl,T. Fukumura,M. Kawasaki###

Spin-related magnetoresistance of n-type ZnO:Al and Zn_{1-x}Mn_{x}O:Al thin films. Effects of spin-orbit coupling and s-d exchange interaction are probed by
magnetoresistance measurements carried out down to 50 mK on ZnO and
Zn_{1-x}Mn_{x}O with x = 3 and 7%. The films were obtained by laser ablation
and doped with Al to electron concentration ~10^{20} cm^{-3}. A quantitative
description of the data for ZnO:Al in terms of weak-localization theory makes
it possible to determine the coupling constant \lambda_{so} = (4.4 +-
0.4)*10^{-11} eVcm of the kp hamiltonian for the wurzite structure, H_{so} =
\lambda_{so}*c(s x k). A complex and large magnetoresistance of
Zn_{1-x}Mn_{x}O:Al is interpreted in terms of the influence of the s-d
spin-splitting and magnetic polaron formation on the disorder-modified
electron-electron interactions. It is suggested that the proposed model
explains the origin of magnetoresistance observed recently in many magnetic
oxide systems.

###Magnetic oscillations in a two-dimensional network of compensated electron and hole orbits|Alain Audouard,David Vignolles,Evert Haanappel,Ilya Sheikin,Rustem B. Lyubovskii,Rimma N. Lyubovskaya###

Magnetic oscillations in a two-dimensional network of compensated electron and hole orbits. The FS of (ET)8Hg4Cl12(C6H5Br)2 can be regarded as a 2D network of
compensated electron and hole orbits coupled by magnetic breakthrough.
Simultaneous measurements of the interlayer magnetoresistance and magnetic
torque have been performed up to 28 T. Magnetoresistance and de dHvA
oscillations spectra exhibit frequency combinations typical of such a network.
Even though some of the observed magnetoresistance oscillations cannot be
interpreted on the basis of neither conventional SdH oscillations nor quantum
interference, the temperature and magnetic field (both orientation and
magnitude) dependence of all the Fourier components of the dHvA spectra can be
consistently accounted for by the LK formula. This behaviour is at variance
with that currently reported for compounds illustrating the linear chain of
coupled orbits model.

###Anisotropic Magneto-Thermopower: the Contribution of Interband Relaxation|J. -E. Wegrowe,Q. Anh Nguyen,M. Al-Barki,J. -F. Dayen,T. L. Wade,H. -J. Drouhin###

Anisotropic Magneto-Thermopower: the Contribution of Interband Relaxation. Spin injection in metallic normal/ferromagnetic junctions is investigated
taking into account the anisotropic magnetoresistance (AMR) occurring in the
ferromagnetic layer. It is shown, on the basis of a generalized two channel
model, that there is an interface resistance contribution due to anisotropic
scattering, beyond spin accumulation and giant magnetoresistance (GMR). The
corresponding expression of the thermopower is derived and compared with the
expression for the thermopower produced by the GMR. First measurements of
anisotropic magnetothermopower are presented in electrodeposited Ni nanowires
contacted with Ni, Au and Cu. The results of this study show that while the
giant magnetoresistance and corresponding thermopower demonstrates the role of
spin-flip scattering, the observed anisotropic magnetothermopower indicates
interband s-d relaxation mechanisms.

###Spin injection into a short DNA chain|X. F. Wang,Tapash Chakraborty###

Spin injection into a short DNA chain. Quantun spin transport through a short DNA chain connected to ferromagnetic
electrodes has been investigated by the transfer matrix method. We describe the
system by a tight-binding model where the parameters are extracted from the
experimental data and realistic metal energy bands. For ferromagnetic iron
electrodes, the magnetoresistance of a 30-basepair Poly(G)-Poly(C) DNA is found
to be lower than 10% at a bias of < 4 V, but can rach up to 20% at a bias of 5
V. In the presence of the spin-flip mechanism, the magnetoresistance is
significantly enhanced when the spin-flip coupling is weak but as the coupling
becomes stronger the decreasing magnetoresistance develops an oscillatory
behavior.

###The magnetotransport properties of La0.7Sr0.3MnO3/BaTiO3 superlattices grown by pulsed laser deposition technique|P. Murugavel,W. Prellier###

The magnetotransport properties of La0.7Sr0.3MnO3/BaTiO3 superlattices grown by pulsed laser deposition technique. We have investigated the magnetotransport properties of La0.7Sr0.3MnO3/BaTiO3
superlattices, grown on SrTiO3 substrate by pulsed laser deposition technique,
both with current-in-plane and current-perpendicular-to-the-plane directions.
Several features indicate the presence of magnetic inhomogeneities at the
interfaces which is independent of BaTiO3 layer thickness variation. First, the
magnetic property in the superlattices decreases. Second, a hysteresis in
magnetoresistance due to the relaxation of the resistive state is observed.
Third, a threshold under an applied magnetic field in the magnetoresistance is
seen. Such behaviors are in agreement with the phase separation scenario which
could be the possible reason for these magnetic inhomogeneities at the
interfaces. On the contrary, the magnetoresistance with the
current-perpendicular-to-the-plane direction is mostly attributed to the
tunneling effect along with the ordering of the spin at the interface. This
study confirms the importance of the interfaces in superlattices that can be
used to control novel physical properties in oxide materials.

###Large magnetoresistance in intermetallic compounds R2Mn3Si5 (R = Tb, Dy and Ho)|R. Nirmala,S. K. Malik,A. V. Morozkin,Y. Yamamoto,H. Hori###

Large magnetoresistance in intermetallic compounds R2Mn3Si5 (R = Tb, Dy and Ho). Magnetization (M) and magnetoresistance (MR) measurements on polycrystalline
R2Mn3Si5 (R = Tb, Dy and Ho) compounds (tetragonal, space group P4/mnc) have
been carried out in the temperature range of 2 K-300 K, in various applied
fields. Both, the rare earth and the Mn, are found to carry magnetic moments in
these compounds. Mn has two sub-lattices (Mn1 and Mn2) that order magnetically
at two different temperatures. Rare earth and Mn1 moments order
ferromagnetically at TC1 whereas Mn2 is found to magnetically order at TC2 (TC1
= 89 K, 86 K, 78 K and TC2 = 18 K, 34 K, 16 K for R = Tb, Dy and Ho compounds,
respectively). Magnetoresistance measurements reveal large negative MR values
of about 50 % near TC2 at 9 T in all these compounds. This giant
magnetoresistance is attributed to the spin-dependent scattering effects,
competing exchange interactions and the layered structure of these compounds

###Role of Fe substitution on the anomalous magnetocaloric and magnetoresistance behavior in Tb(Ni1-xFex)2 compounds|Niraj K. Singh,K. G. Suresh,D. S. Rana,A. K. Nigam,S. K. Malik###

Role of Fe substitution on the anomalous magnetocaloric and magnetoresistance behavior in Tb(Ni1-xFex)2 compounds. We report the magnetic, magnetocaloric and magnetoresistance results obtained
in Tb(Ni1-xFex)2 compounds with x=0, 0.025 and 0.05. Fe substitution leads to
an increase in the ordering temperature from 36 K for x=0 to 124 K for x=0.05.
Contrary to a single sharp MCE peak seen in TbNi2, the MCE peaks of the Fe
substituted compounds are quite broad. We attribute the anomalous MCE behavior
to the randomization of the Tb moments brought about by the Fe substitution.
Magnetic and magnetoresistance results seem to corroborate this proposition.
The present study also shows that the anomalous magnetocaloric and
magnetoresistance behavior seen in the present compounds is similar to that of
Ho(Ni,Fe)2 compounds.

###Resonant magnetoresistance in organic spin-valves|Alexandre Reily Rocha,Stefano Sanvito###

Resonant magnetoresistance in organic spin-valves. We investigate theoretically the effects of surface states over the
magnetoresistance of Ni-based organic spin-valves. In particular we perform
{\it ab initio} electronic transport calculations for a benzene-thiolate
molecule chemically attached to a Ni [001] surface and contacted either by Te
to another Ni [001] surface, or terminated by a thiol group and probed by a Ni
STM tip. In the case of S- and Te-bonded molecules we find a large asymmetry in
the spin-currents as a function of the bias, although the $I$-$V$ is rather
symmetric. This leads to a smooth although not monotonic dependence of the
magnetoresistance over the bias. In contrast, in the case of a STM-type
geometry we demonstrate that the spin-current and the magnetoresistance can be
drastically changed with bias. This is the result of a resonance between a
spin-polarized surface state of the substrate and the $d$-shell band-edge of
the tip.

###Magnetotransport of lanthanum doped RuSr2GdCu2O8 - the role of gadolinium|M. Pozek,A. Dulcic,A. Hamzic,M. Basletic,E. Tafra,G. V. M. Williams,S. Kraemer###

Magnetotransport of lanthanum doped RuSr2GdCu2O8 - the role of gadolinium. Strongly underdoped RuSr_1.9La_0.1GdCu_2O_8 has been comprehensively studied
by dc magnetization, microwave measurements, magnetoresistivity and Hall
resistivity in fields up to 9 T and temperatures down to 1.75 K. Electron
doping by La reduces the hole concentration in the CuO2 planes and completely
suppresses superconductivity. Microwave absorption, dc resistivity and ordinary
Hall effect data indicate that the carrier concentration is reduced and a
semiconductor-like temperature dependence is observed. Two magnetic ordering
transitions are observed. The ruthenium sublattice orders antiferromagnetically
at 155 K for low applied magnetic field and the gadolinium sublattice
antiferromagnetically orders at 2.8 K. The magnetoresistivity exhibits a
complicated temperature dependence due to the combination of the two magnetic
orderings and spin fluctuations. It is shown that the ruthenium magnetism
influences the conductivity in the RuO2 layers while the gadolinium magnetism
influences the conductivity in the CuO2 layers. The magnetoresistivity is
isotropic above 4 K, but it becomes anisotropic when gadolinium orders
antiferromagnetically.

###Is magnetoresistance in excess of 1,000 % possible in Ni point contacts?|A. R. Rocha,T. Archer,S. Sanvito###

Is magnetoresistance in excess of 1,000 % possible in Ni point contacts?. Electronic transport in nickel magnetic point contacts is investigated with a
combination of density functional theory and the non-equilibrium Green
functions method. In particular we address the possibility of huge ballistic
magnetoresistance in impurity-free point contacts and the effects of oxygen
impurities. On-site corrections over the local spin density approximation
(LSDA) for the exchange and correlation potential, namely the LDA+U method, are
applied in order to account for low-coordination and strong correlations. We
show that impurity-free point contacts present magnetoresistance never in
excess of 50%. This value can raise up to about 450 % in the case of oxygen
contamination. These results suggest that magnetoresistance in excess of 1,000
% can not have solely electronic origin.

###Scattering by Atomic Spins and Magnetoresistance in Dilute Magnetic Semiconductors|M. Foygel A. G. Petukhov###

Scattering by Atomic Spins and Magnetoresistance in Dilute Magnetic Semiconductors. We studied electrical transport in magnetic semiconductors, which is
determined by scattering of free carriers off localized magnetic moments. We
calculated the scattering time and the mobility of the majority and
minority-spin carriers with both the effects of thermal spin fluctuations and
of spatial disorder of magnetic atoms taken into account. These are responsible
for the magnetic-field dependence of electrical resistivity. Namely, the
application of the external magnetic field suppresses the thermodynamic spin
fluctuations thus promoting negative magnetoresistance. Simultaneously,
scattering off the built-in spatial fluctuations of the atomic spin
concentrations may increase with the magnetic field. The latter effect is due
to the growth of the magnitude of random local Zeeman splittings with the
magnetic field. It promotes positive magnetoresistance. We discuss the role of
the above effects on magnetoresistance of non-degenerate semiconductors where
magnetic impurities are electrically active or neutral.

###Spin-Polarized Tunneling as a probe of (Ga,Mn)As electronic properties|M. Elsen,H. Jaffres,R. Mattana,L. Thevenard,A. Lemaitre,J. -M. George###

Spin-Polarized Tunneling as a probe of (Ga,Mn)As electronic properties. We present magnetic and tunnel transport properties of
(Ga,Mn)As/(In,Ga)As/(Ga,Mn)As structure before and after adequate annealing
procedure. The conjugate increase of magnetization and tunnel magnetoresistance
obtained after annealing is shown to be associated to the increase of both
exchange energy $\Delta$$_{exch}$ and hole concentration by reduction of the Mn
interstitial atom in the top magnetic electrode. Through a 6x6 band k.p model,
we established general phase diagrams of tunneling magnetoresistance (TMR) and
tunneling anisotropic magnetoresistance (TAMR) \textit{vs.} (Ga,Mn)As Fermi
energy (E$_F$) and spin-splitting parameter (B$_G$). This allows to give a
rough estimation of the exchange energy $\Delta$$_{exch}$=6B$_G$$\simeq$120 meV
and hole concentration p$\simeq1.10^{20}$cm$^{-3}$ of (Ga,Mn)As and beyond
gives the general trend of TMR and TAMR \textit{vs.} the selected hole band
involved in the tunneling transport.

###Transport, magnetic and superconducting properties of RuSr2RCu2O8 (R= Eu, Gd) doped with Sn|M. Pozek,I. Kupcic,A. Dulcic,A. Hamzic,D. Paar,M. Basletic,E. Tafra,G. V. M. Williams###

Transport, magnetic and superconducting properties of RuSr2RCu2O8 (R= Eu, Gd) doped with Sn. Ru{1-x}Sn{x}Sr2EuCu2O8 and Ru{1-x}Sn{x}Sr2GdCu2O8 have been comprehensively
studied by microwave and dc resistivity and magnetoresistivity and by the dc
Hall measurements. The magnetic ordering temperature T_m is considerably
reduced with increasing Sn content. However, doping with Sn leads to only
slight reduction of the superconducting critical temperature T_c accompanied
with the increase of the upper critical field B_c2, indicating an increased
disorder in the system and a reduced scattering length of the conducting holes
in CuO2 layers. In spite of the increased scattering rate, the normal state
resistivity and the Hall resistivity are reduced with respect to the pure
compound, due to the increased number of itinerant holes in CuO2 layers, which
represent the main conductivity channel. Most of the electrons in RuO2 layers
are presumably localized, but the observed negative magnetoresistance and the
extraordinary Hall effect lead to the conclusion that there exists a small
number of itinerant electrons in RuO$_2$ layers that exhibit colossal
magnetoresistance.

###Strong spin-orbit interactions and weak antilocalization in carbon doped p-type GaAs heterostructures|Boris Grbic,Renaud Leturcq,Thomas Ihn,Klaus Ensslin,Dirk Reuter,Andreas D. Wieck###

Strong spin-orbit interactions and weak antilocalization in carbon doped p-type GaAs heterostructures. We present a comprehensive study of the low-field magnetoresistance in carbon
doped p-type GaAs/AlGaAs heterostructures aiming at the investigation of
spin-orbit interaction effects. The following signatures of exceptionally
strong spin-orbit interactions are simultaneously observed: a beating in the
Shubnikov-de Haas oscillations, a classical positive magnetoresistance due to
the presence of the two spin-split subbands, and a weak anti-localization dip
in the magnetoresistance. The spin-orbit induced splitting of the heavy hole
subband at the Fermi level is determined to be around 30% of the total Fermi
energy. The phase coherence length of holes of around 2.5 $\mu$m at a
temperature of 70 mK, extracted from weak anti-localization measurements, is
promissing for the fabrication of phase-coherent p-type nanodevices.

###Hall effect and magnetoresistance in the normal state of the superconductor LaO$_{0.9}$F$_{0.1-x}$FeAs|Huan Yang,Xiyu Zhu,Lei Fang,Gang Mu,Hai-Hu Wen###

Hall effect and magnetoresistance in the normal state of the superconductor LaO$_{0.9}$F$_{0.1-x}$FeAs. By using a two-step method, we successfully synthesized the iron based new
superconductor LaO$_{0.9}$F$_{0.1-x}$FeAs. The Hall effect and
magnetoresistance were measured in wide temperature region. A negative Hall
coefficient R_H has been found implying a dominant conduction by electron-like
charge carriers in this material. The charge carrier density determined at 100K
is about 9.8E20 cm-3, which is close to the cuprate superconductors. It is
further found that the magnetoresistance does not follow the Kohler's law.
Meanwhile, the Hall coefficient, the resistivity at 0T, and magnetoresistance
all have an anomalous property at about 240K, which may be induced by the
multi-band effect or by some exotic scattering mechanism.

###Upper critical field, Hall effect and magnetoresistance in the iron-based layered superconductor LaFeAsO_{0.9}F_{0.1-δ}|Xiyu Zhu,Huan Yang,Lei Fang,Gang Mu,Hai-Hu Wen###

Upper critical field, Hall effect and magnetoresistance in the iron-based layered superconductor LaFeAsO_{0.9}F_{0.1-δ}. By using a two-step method, we successfully synthesized the iron based new
superconductor LaFeAsO_{0.9}F_{0.1-\delta}$. The resistive transition curves
under different magnetic fields were measured, leading to the determination of
the upper critical field Hc2(T) of this new superconductor. The value of Hc2 at
zero temperature is estimated to be about 50 Tesla roughly. In addition, the
Hall effect and magnetoresistance were measured in wide temperature region. A
negative Hall coefficient R_H has been found, implying a dominant conduction
mainly by electron-like charge carriers in this material. The charge carrier
density determined at 100 K is about 9.8E20cm^{-3}, which is close to the
cuprate superconductors. It is further found that the magnetoresistance does
not follow Kohler's law. Meanwhile, the different temperature dependence
behaviors of resistivity, Hall coefficient, and magnetoresistance have
anomalous properties at about 230 K, which may be induced by some exotic
scattering mechanism.

###Effect of frequency and temperature on microwave-induced magnetoresistance oscillations in two-dimensional electron systems|Jesus Inarrea###

Effect of frequency and temperature on microwave-induced magnetoresistance oscillations in two-dimensional electron systems. Experimental results on microwave-induced magnetoresistance oscillation in
two-dimensional electron systems show a similar behavior of these systems
regarding temperature and microwave frequency. It is found that these
oscillations tend to quench when frequency or temperature increase, approaching
magnetoresistance to the response of the dark system. In this work we show that
this experimental behavior can be addressed on the same theoretical basis.
Microwave radiation forces the electron orbits to move back and forth being
damped by interaction with the lattice. We show that this damping depends
dramatically on microwave frequency and also on temperature. An increase in
frequency or temperature gives rise to an increase in the lattice damping
producing eventually a quenching effect in the magnetoresistance oscillations.

###Unusual field dependence of radio frequency magnetoimpedance in La0.67Ba0.33MnO3|A. Rebello,R. Mahendiran###

Unusual field dependence of radio frequency magnetoimpedance in La0.67Ba0.33MnO3. We have investigated magnetic field dependence of the ac magnetoresitance and
the magnetoreactance in La0.67Ba0.33MnO3 over a wide frequency range from f = 0
to 30 MHz. A huge ac magnetoresistance of 55 % at f = 15 MHz in a small
magnetic field of H = 100 mT and magnetoreactance of 80 % at 2 MHz are
reported. We show distinct field dependence of the magnetoreactance and the
magnetoresistance with increasing frequency. It is shown that while the ac
magnetoresistance is negative and shows a single peak at the origin for all
frequencies except f = 30 MHz, the single peak in the magnetoreactance
transforms into a valley at the origin and simultaneously a double peak
develops . The position of the double peak increases in field with increasing
frequency. Eventually, the sign of the magnetoreactance changes from negative
to positive. Our results indicate possible occurrence of the ferromagneic
resonance in MHz range in unsaturated manganite.

###Spin-orbit interaction and weak localization in heterostructures|M. M. Glazov,L. E. Golub###

Spin-orbit interaction and weak localization in heterostructures. Theory of weak localization in two-dimensional high-mobility semiconductor
systems is developed with allowance for the spin-orbit interaction. The
obtained expressions for anomalous magnetoresistance are valid in the whole
range of classically weak magnetic fields and for arbitrary strengths of bulk
and structural inversion asymmetry contributions to the spin splitting. The
theory serves for both diffusive and ballistic regimes of electron propagation
taking into account coherent backscattering and nonbackscattering processes.
The transition between weak localization and antilocalization regimes is
analyzed. The manifestation of the mutual compensation of Rashba and
Dresselhaus spin splittings in magnetoresistance is discussed. Perfect
description of experimental data on anomalous magnetoresistance in
high-mobility heterostructures is demonstrated. The in-plane magnetic field
dependence of the conductivity caused by an interplay of the spin-orbit
splittings and Zeeman effect is described theoretically.

###Negative and Positive Magnetoresistance in Bilayer Graphene: Effects of Weak Localization and Charge Inhomogeneity|Yung-Fu Chen,Myung-Ho Bae,Cesar Chialvo,Travis Dirks,Alexey Bezryadin,Nadya Mason###

Negative and Positive Magnetoresistance in Bilayer Graphene: Effects of Weak Localization and Charge Inhomogeneity. We report measurements of magnetoresistance in bilayer graphene as a function
of gate voltage (carrier density) and temperature. We examine multiple
contributions to the magnetoresistance, including those of weak localization
(WL), universal conductance fluctuations (UCF), and inhomogeneous charge
transport. A clear WL signal is evident at all measured gate voltages (in the
hole doped regime) and temperature ranges (from 0.25 K to 4.3 K), and the phase
coherence length extracted from WL data does not saturate at low temperatures.
The WL data is fit to demonstrate that electron-electron Nyquist scattering is
the major source of phase decoherence. A decrease in UCF amplitude with
increasing gate voltage and temperature is shown to be consistent with a
corresponding decrease in the phase coherence length. In addition, a weak
positive magnetoresistance at higher magnetic fields is observed, and
attributed to inhomogeneous charge transport.

###Colossal magnetoresistance in an ultra-clean weakly interacting 2D Fermi liquid|Xiaoqing Zhou,B. A. Piot,M. Bonin,L. W. Engel,S. Das Sarma,G. Gervais,L. N. Pfeiffer,K. W. West###

Colossal magnetoresistance in an ultra-clean weakly interacting 2D Fermi liquid. We report the observation of a new phenomenon of colossal magnetoresistance
in a 40 nm wide GaAs quantum well in the presence of an external magnetic field
applied parallel to the high-mobility 2D electron layer. In a strong magnetic
field, the magnetoresistance is observed to increase by a factor of ~300 from 0
to 45T without the system undergoing any metal-insulator transition. We discuss
how this colossal magnetoresistance effect cannot be attributed to the spin
degree-of-freedom or localization physics, but most likely emanates from strong
magneto-orbital coupling between the two-dimensional electron gas and the
magnetic field. Our observation is consistent with a field-induced 2D-to-3D
transition in the confined electronic system.

###Tunnel magnetoresistance in alumina, magnesia and composite tunnel barrier magnetic tunnel junctions|Oliver Schebaum,Volker Drewello,Alexander Auge,Günter Reiss,Markus Münzenberg,Henning Schuhmann,Michael Seibt,Andy Thomas###

Tunnel magnetoresistance in alumina, magnesia and composite tunnel barrier magnetic tunnel junctions. Using magnetron sputtering, we have prepared Co-Fe-B/tunnel barrier/Co-Fe-B
magnetic tunnel junctions with tunnel barriers consisting of alumina, magnesia,
and magnesia-alumina bilayer systems. The highest tunnel magnetoresistance
ratios we found were 73% for alumina and 323% for magnesia-based tunnel
junctions. Additionally, tunnel junctions with a unified layer stack were
prepared for the three different barriers. In these systems, the tunnel
magnetoresistance ratios at optimum annealing temperatures were found to be 65%
for alumina, 173% for magnesia, and 78% for the composite tunnel barriers. The
similar tunnel magnetoresistance ratios of the tunnel junctions containing
alumina provide evidence that coherent tunneling is suppressed by the alumina
layer in the composite tunnel barrier.

###On the resistivity at low temperatures in electron-doped cuprate superconductors|S. Finkelman,M. Sachs,J. Paglione,G. Droulers,P. Bach,R. L. Greene,Y. Dagan###

On the resistivity at low temperatures in electron-doped cuprate superconductors. We measured the magnetoresistance as a function of temperature down to 20mK
and magnetic field for a set of underdoped PrCeCuO (x=0.12) thin films with
controlled oxygen content. This allows us to access the edge of the
superconducting dome on the underdoped side. The sheet resistance increases
with increasing oxygen content whereas the superconducting transition
temperature is steadily decreasing down to zero. Upon applying various magnetic
fields to suppress superconductivity we found that the sheet resistance
increases when the temperature is lowered. It saturates at very low
temperatures. These results, along with the magnetoresistance, cannot be
described in the context of zero temperature two dimensional
superconductor-to-insulator transition nor as a simple Kondo effect due to
scattering off spins in the copper-oxide planes. We conjecture that due to the
proximity to an antiferromagnetic phase magnetic droplets are induced. This
results in negative magnetoresistance and in an upturn in the resistivity.

###The magnetoresistance and Hall effect in CeFeAsO: a high magnetic field study|H. Q. Yuan,L. Jiao,J. Singleton,F. F. Balakirev,G. F. Chen,J. L. Luo,N. L. Wang###

The magnetoresistance and Hall effect in CeFeAsO: a high magnetic field study. The longitudinal electrical resistivity and the transverse Hall resistivity
of CeFeAsO are simultaneously measured up to a magnetic field of 45T using the
facilities of pulsed magnetic field at Los Alamos. Distinct behaviour is
observed in both the magnetoresistance Rxx({\mu}0H) and the Hall resistance
Rxy({\mu}0H) while crossing the structural phase transition at Ts \approx 150K.
At temperatures above Ts, little magnetoresistance is observed and the Hall
resistivity follows linear field dependence. Upon cooling down the system below
Ts, large magnetoresistance develops and the Hall resistivity deviates from the
linear field dependence. Furthermore, we found that the transition at Ts is
extremely robust against the external magnetic field. We argue that the
magnetic state in CeFeAsO is unlikely a conventional type of spin-density-wave
(SDW).

###Magnetodielectric behavior in La2CoMnO6 nanoparticles|J. Krishna Murthy,A. Venimadhav###

Magnetodielectric behavior in La2CoMnO6 nanoparticles. We have investigated magnetic, dielectric and magnetodielectric properties of
La2CoMnO6 nanoparticles prepared by sol-gel method. Magnetization measurements
revealed two distinct ferromagnetic transitions at 218 K and 135 K that can be
assigned to ordered and disordered magnetic phases of the La2CoMnO6
nanoparticles. Two dielectric relaxations culminating around the magnetic
transitions were observed with a maximum magnetodielectric response reaching
10% and 8% at the respective relaxation peaks measured at 100 kHz under 5T
magnetic field. The dc electrical resistivity followed an insulating behavior
and showed a negative magnetoresistance; there was no noticeable anomaly in
resistivity or magnetoresistance near the magnetic ordering temperatures.
Complex impedance analysis revealed a clear intrinsic contribution to the
magnetodielectric response; however, extrinsic contribution due to
Maxwell-Wagner effect combined with magnetoresistance property dominated the
magnetodielectric effect at high temperatures.

###Giant negative magnetoresistance in high-mobility 2D electron systems|A. T. Hatke,M. A. Zudov,J. L. Reno,L. N. Pfeiffer,K. W. West###

Giant negative magnetoresistance in high-mobility 2D electron systems. We report on a giant negative magnetoresistance in very high mobility
GaAs/AlGaAs heterostructures and quantum wells. The effect is the strongest at
$B \simeq 1$ kG, where the magnetoresistivity develops a minimum emerging at $T
\lesssim 2$ K. Unlike the zero-field resistivity which saturates at $T \simeq 2
$ K, the resistivity at this minimum continues to drop at an accelerated rate
to much lower temperatures and becomes several times smaller than the
zero-field resistivity. Unexpectedly, we also find that the effect is destroyed
not only by increasing temperature but also by modest in-plane magnetic fields.
The analysis shows that giant negative magnetoresistance cannot be explained by
existing theories considering interaction-induced or disorder-induced
corrections.

###Two dimensional Dirac fermions and quantum magnetoresistance in CaMnBi$_2$|Kefeng Wang D. Graf,Limin Wang,Hechang Lei,S. W. Tozer,C. Petrovic###

Two dimensional Dirac fermions and quantum magnetoresistance in CaMnBi$_2$. We report two dimensional Dirac fermions and quantum magnetoresistance in
single crystals of CaMnBi$_2$. The non-zero Berry's phase, small cyclotron
resonant mass and first-principle band structure suggest the existence of the
Dirac fermions in the Bi square nets. The in-plane transverse magnetoresistance
exhibits a crossover at a critical field $B^*$ from semiclassical weak-field
$B^2$ dependence to the high-field unsaturated linear magnetoresistance ($\sim
120%$ in 9 T at 2 K) due to the quantum limit of the Dirac fermions. The
temperature dependence of $B^*$ satisfies quadratic behavior, which is
attributed to the splitting of linear energy dispersion in high field. Our
results demonstrate the existence of two dimensional Dirac fermions in
CaMnBi$_2$ with Bi square nets.

###Anomalous magnetic, transport and thermal properties of Gd5Ge3|Bibekananda Maji,K. G. Suresh,A. K. Nigam###

Anomalous magnetic, transport and thermal properties of Gd5Ge3. We have studied the magnetic, thermal and magnetotransport properties of
polycrystalline Gd5Ge3. It is found that the compound is a strong
antiferromagnet and does not undergo any strong metamagnetic transition even in
a field of 90 kOe. However, a small but visible ferromagnetic component is
found to coexist with the antiferromagnetic order at low temperatures, as
revealed by the anomalies in magnetization, magnetoresistance and heat capacity
data. Our data suggest that the ferromagnetic component is of magnetostructural
in origin, as evidenced by the strong field induced irreversibility of the
magnetoresistance and heat capacity isotherms. The first order like
magnetostructural distortion established in this material is found to result in
a martensitic like scenario wherein the kinetic arrest controls the
field/temperature dependence of physical properties such as heat capacity and
magnetoresistance.

###Magnetotransport and induced superconductivity in Bi based three-dimensional topological insulators|M. Veldhorst,M. Snelder,M. Hoek,C. G. Molenaar,D. P. Leusink,A. A. Golubov,H. Hilgenkamp,A. Brinkman###

Magnetotransport and induced superconductivity in Bi based three-dimensional topological insulators. The surface of a 3D topological insulator is conducting and the topologically
nontrivial nature of the surface states is observed in experiments. It is the
aim of this paper to review and analyze experimental observations with respect
to the magnetotransport in Bi-based 3D topological insulators, as well as the
superconducting transport properties of hybrid structures consisting of
superconductors and these topological insulators. The helical spin-momentum
coupling of the surface state electrons becomes visible in quantum corrections
to the conductivity and magnetoresistance oscillations. An analysis will be
provided of the reported magnetoresistance, also in the presence of bulk
conductivity shunts. Special attention is given to the large and linear
magnetoresistance. Superconductivity can be induced in topological
superconductors by means of the proximity effect. The induced supercurrents,
Josephson effects and current-phase relations will be reviewed. These materials
hold great potential in the field of spintronics and the route towards Majorana
devices.

###Longitudinal interlayer magnetoresistance in quasi-2D metals|P. D. Grigoriev###

Longitudinal interlayer magnetoresistance in quasi-2D metals. The longitudinal interlayer magnetoresistance $R_{zz}(B_{z})$ is calculated
in strongly anisotropic layered metals, when the interlayer band width $4t_{z}$
is less than the Landau level separation $\hbar \omega_{c}$. The impurity
scattering has much stronger effect in this regime than in 3D metals and leads
to a linear longitudinal interlayer magnetoresistance $R_{zz}\propto B_{z}$ in
the interval $\hbar \omega_{c}>4t_{z}>>\sqrt{\Gamma_{0}\hbar \omega_{c}}$
changing to a square-root dependence $R_{zz}\propto B_{z}^{1/2}$ at higher
field or smaller $t_{z}$. The crossover field allows to estimate the interlayer
transfer integral as $t_{z}\sim \sqrt{\Gamma_{0}\hbar \omega_{c}}$.
Longitudinal interlayer magnetoresistance, being robust to the increase of
temperature or long-range disorder, is easy for measurements and provides a
useful tool to investigate the electronic structure of quasi-two-dimensional
compounds.

###Temperature and Field Dependence of Magnetic Domains in La$_{1.2}$Sr$_{1.8}$Mn$_2$O$_7$|B. Bryant,Y. Moritomo,Y. Tokura,G. Aeppli###

Temperature and Field Dependence of Magnetic Domains in La$_{1.2}$Sr$_{1.8}$Mn$_2$O$_7$. Colossal magnetoresistance and field-induced ferromagnetism are well
documented in manganite compounds. Since domain wall resistance contributes to
magnetoresistance, data on the temperature and magnetic field dependence of the
ferromagnetic domain structure are required for a full understanding of the
magnetoresistive effect. Here we show, using cryogenic Magnetic Force
Microscopy, domain structures for the layered manganite
La$_{1.2}$Sr$_{1.8}$Mn$_2$O$_7$ as a function of temperature and magnetic
field. Domain walls are suppressed close to the Curie temperature T$_C$, and
appear either via the application of a c-axis magnetic field, or by decreasing
the temperature further. At temperatures well below T$_C$, new domain walls,
stable at zero field, can be formed by the application of a c-axis field.
Magnetic structures are seen also at temperatures above T$_C$: these features
are attributed to inclusions of additional Ruddleston-Popper manganite phases.
Low-temperature domain walls are nucleated by these ferromagnetic inclusions.

###Giant magnetoresistance and spin Seebeck coefficient in zigzag a-graphyne nanoribbons|M. X. Zhai,X. F. Wang,P. Vasilopoulos,Y. S. Liu,Y. J. Dong,L. Zhou,Y. J. Jiang,W. L. You###

Giant magnetoresistance and spin Seebeck coefficient in zigzag a-graphyne nanoribbons. We investigate the spin-dependent electric and thermoelectric properties of
ferromagnetic zigzag-graphyne nanoribbons (ZGNRs) using the density-functional
theory combined with the non-equilibrium Green's function method. A giant
magnetoresistance is obtained in the pristine even-width ZGNRs and can be as
high as 10e6 %. However, for the doped systems, a large magnetoresistance
behavior may appear in the odd-width ZGNRs rather than the even-width ones.
This suggests that the magnetoresistance can be manipulated in a wide range by
the dopants on edges of ZGNRs. Another interesting phenomenon is that in the B-
and N-doped even-width ZGNRs the spin Seebeck coefficient is always larger than
the charge Seebeck coefficient, and a pure-spin-current thermospin device can
be achieved at specific temperatures.

###Strain driven anisotropic magnetoresistance in antiferromagnetic La$_{0.4}$Sr$_{0.6}$MnO$_{3}$|A. T. Wong,C. Beekman,H. Guo,W. Siemons,Z. Gai,E. Arenholz,Y. Takamura,T. Z. Ward###

Strain driven anisotropic magnetoresistance in antiferromagnetic La$_{0.4}$Sr$_{0.6}$MnO$_{3}$. We investigate the effects of strain on antiferromagntic (AFM) single crystal
thin films of La$_{1-x}$Sr$_{x}$MnO$_{3}$ (x = 0.6). Nominally unstrained
samples have strong magnetoresistance with anisotropic magnetoresistances (AMR)
of up to 8%. Compressive strain suppresses magnetoresistance but generates AMR
values of up to 63%. Tensile strain presents the only case of a metal-insulator
transition and demonstrates a previously unreported AMR behavior. In all three
cases, we find evidence of magnetic ordering and no indication of a global
ferromagnetic phase transition. These behaviors are attributed to epitaxy
induced changes in orbital occupation driving different magnetic ordering
types. Our findings suggest that different AFM ordering types have a profound
impact on the AMR magnitude and character.

###Anisotropic transverse magnetoresistivity in alpha-YbAlB4|Yosuke Matsumoto,Jinpyo Hong,Kentaro Kuga,Satoru Nakatsuji###

Anisotropic transverse magnetoresistivity in alpha-YbAlB4. We measured the transverse magnetoresistivity of the mixed valence compound
$\alpha$-YbAlB$_4$. Two configurations were used where current was applied
along [110] direction for both and magnetic field was applied along [-110] and
$c$-axis. We found the transverse magnetoresistivity is highly anisotropic. In
the weak field below 1 T, it is consistent with stronger $c$-$f$ hybridization
in the $ab$ plane which was suggested from the previous zero field resistivity
measurements. At the higher field above 3 T, we observed a negative transverse
magnetoresistivity for the field applied along the $c$-axis. The temperature
dependences of the resistivity measured at several different fields suggest the
suppression of the heavy fermion behavior at the characteristic field of $\sim
5.5$ T.

###Superconductivity emerging from suppressed large magnetoresistant state in WTe2|Defen Kang,Yazhou Zhou,Wei Yi,Chongli Yang,Jing Guo,Youguo Shi,Shan Zhang,Zhe Wang,Chao Zhang,Sheng Jiang,Aiguo Li,Ke Yang,Qi Wu,Guangming Zhang,Liling Sun,Zhongxian Zhao###

Superconductivity emerging from suppressed large magnetoresistant state in WTe2. The recent discovery of large and non-saturating magnetoresistance (LMR) in
WTe2 provides a unique playground to find new phenomena and significant
perspective for potential applications. Here we report the first observation of
superconductivity near the proximity of suppressed LMR state in pressurized
WTe2 through high-pressure synchrotron X-ray diffraction, electrical
resistance, magnetoresistance, and ac magnetic susceptibility measurements. It
is found that the positive magnetoresistance effect can be turned off at a
critical pressure of 10.5 GPa without crystal structure change and
superconductivity emerges simultaneously. The maximum superconducting
transition temperature can be reached to 6.5 K at ~15 GPa and it decreases down
to 2.6 K at ~25 GPa. In-situ high pressure Hall coefficient measurements at 10
K demonstrate that elevating pressure decreases hole carrier's population but
increases electron carrier's population. Significantly, at the critical
pressure, we observed a sign change in the Hall coefficient, indicating a
possible Lifshitz-type quantum phase transition in WTe2.

###Low-field microwave absorption and magnetoresistance in iron nanostructures grown by electrodeposition on n-type lightly-doped silicon substrates|J. F. Felix,L. C. Figueiredo,J. B. S. Mendes,P. C. Morais,C. I. L. de Araujo###

Low-field microwave absorption and magnetoresistance in iron nanostructures grown by electrodeposition on n-type lightly-doped silicon substrates. In this study we investigate magnetic properties, surface morphology and
crystal structure in iron nanoclusters electrodeposited on lightly-doped (100)
n-type silicon substrates. Our goal is to investigate the spin injection and
detection in the Fe/Si lateral structures. The samples obtained under electric
percolation were characterized by magnetoresistive and magnetic resonance
measurements with cycling the sweeping applied field in order to understand the
spin dynamics in the as-produced samples. The observed hysteresis in the
magnetic resonance spectra, plus the presence of a broad peak in the
non-saturated regime confirming the low field microwave absorption (LFMA), were
correlated to the peaks and slopes found in the magnetoresistance curves. The
results suggest long range spin injection and detection in low resistive
silicon and the magnetic resonance technique is herein introduced as a
promising tool for analysis of electric contactless magnetoresistive samples.

###Temperature-driven transition from a semiconductor to a topological insulator|Steffen Wiedmann,Andreas Jost,Cornelius Thienel,Christoph Brüne,Philipp Leubner,Hartmut Buhmann,Laurens W. Molenkamp,J. C. Maan,Uli Zeitler###

Temperature-driven transition from a semiconductor to a topological insulator. We report on a temperature-induced transition from a conventional
semiconductor to a two-dimensional topological insulator investigated by means
of magnetotransport experiments on HgTe/CdTe quantum well structures. At low
temperatures, we are in the regime of the quantum spin Hall effect and observe
an ambipolar quantized Hall resistance by tuning the Fermi energy through the
bulk band gap. At room temperature, we find electron and hole conduction that
can be described by a classical two-carrier model. Above the onset of quantized
magnetotransport at low temperature, we observe a pronounced linear
magnetoresistance that develops from a classical quadratic low-field
magnetoresistance if electrons and holes coexist. Temperature-dependent bulk
band structure calculations predict a transition from a conventional
semiconductor to a topological insulator in the regime where the linear
magnetoresistance occurs.

###Electrical detection of magnetization reversal without auxiliary magnets|K. Olejník,V. Novák,J. Wunderlich,T. Jungwirth###

Electrical detection of magnetization reversal without auxiliary magnets. First-generation magnetic random access memories based on anisotropic
magnetoresistance required magnetic fields for both writing and reading. Modern
all-electrical read/write memories use instead non-relativistic spin-transport
connecting the storing magnetic layer with a reference ferromagnet. Recent
studies have focused on electrical manipulation of magnetic moments by
relativistic spin-torques requiring no reference ferromagnet. Here we report
the observation of a counterpart magnetoresistance effect in such a
relativistic system which allows us to electrically detect the sign of the
magnetization without an auxiliary magnetic field or ferromagnet. We observe
the effect in a geometry in which the magnetization of a uniaxial (Ga,Mn)As
epilayer is set either parallel or antiparallel to a current-induced
non-equilibrium spin polarization of carriers. In our structure, this
linear-in-current magnetoresistance reaches 0.2\% at current density of $10^6$
A cm$^{-2}$.

###The large unsaturated magnetoresistance of Weyl semimetals|Yiming Pan,Huaiqiang Wang,Pengchao Lu,Jian Sun,Baigeng Wang,D. Y. Xing###

The large unsaturated magnetoresistance of Weyl semimetals. The Weyl semimetal (WSM) is a novel topological gapless state with promises
exotic transport due to chiral anomaly. Recently, a family of nonmagnetic WSM
candidates including TaAs, NbAs, NbP etc is confirmed by first principle
calculation and experiments. The TaAs family are reported to display the large
unsaturated magnetoresistance (XMR), which have not yet been explained. Here,
we give a theoretical calculation of XMR based on the extended effective-medium
approach to Weyl semimetals. We predict the power law of XMR at high magnetic
field and the "turn-on" magnetic field, which are well in agreement with
experiments data. Furthermore, we investigate the $\theta$-dependence
magnetoresistance and find the transition between the postive XMR and the
negative magnetoresistance induced by chiral anomaly, which should be confirmed
by further experiments.

###Linear magnetoresistance and surface to bulk coupling in topological insulator thin films|Sourabh Singh,R. K. Gopal,Jit Sarkar,Atul Pandey,Bhavesh G. Patel,Chiranjib Mitra###

Linear magnetoresistance and surface to bulk coupling in topological insulator thin films. We explore the temperature dependent magnetoresistance of bulk insulating
topological insulator thin films. Thin films of Bi2Se2Te and BiSbTeSe1.6 were
grown using Pulsed Laser Deposition technique and subjected to transport
measurements. Magnetotransport measurements indicate a non-saturating linear
magnetoresistance (LMR) behavior at high magnetic field values. We present a
careful analysis to explain the origin of LMR taking into consideration all the
existing models of LMR. Here we consider that the bulk insulating states and
the metallic surface states constitute two parallel conduction channels.
Invoking this, we were able to explain linear magnetoresistance behavior as a
competition between these parallel channels. We observe that the crossover
field, where LMR sets in, decreases with increasing temperature. We propose
that this cross over field can be used phenomenologically to estimate the
strength of surface to bulk coupling.

###Relative weight of the inverse spin Hall and spin rectification effects for metallic Py,Fe/Pt and insulating YIG/Pt bilayers estimated by angular dependent spin pumping measurements|Sascha Keller,Jochen Greser,Matthias R. Schweizer,Andres Conca,Burkard Hillebrands,E. Th. Papaioannou###

Relative weight of the inverse spin Hall and spin rectification effects for metallic Py,Fe/Pt and insulating YIG/Pt bilayers estimated by angular dependent spin pumping measurements. We quantify the relative weight of inverse spin Hall and spin rectification
effects occurring in RF-sputtered polycrystalline permalloy, molecular beam
epitaxy-grown epitaxial iron and liquid phase epitaxy-grown yttrium-iron-garnet
bilayer systems with different capping materials. To distinguish the spin
rectification signal from the inverse spin Hall voltage the external magnetic
field is rotated in-plane to take advantage of the different angular
dependencies of the prevailing effects. We prove that in permalloy anisotropic
magnetoresistance is the dominant source for spin rectification while in
epitaxial iron the anomalous Hall effect has an also comparable strength. The
rectification in yttrium-iron-garnet/platinum bilayers reveals an angular
dependence imitating the one seen for anisotropic magnetoresistance caused by
spin Hall magnetoresistance.

###Current-induced magnetization switching in atom-thick tungsten engineered perpendicular magnetic tunnel junctions with large tunnel magnetoresistance|Mengxing Wang,Wenlong Cai,Kaihua Cao,Jiaqi Zhou,Jerzy Wrona,Shouzhong Peng,Huaiwen Yang,Jiaqi Wei,Wang Kang,Youguang Zhang,Jürgen Langer,Berthold Ocker,Albert Fert,Weisheng Zhao###

Current-induced magnetization switching in atom-thick tungsten engineered perpendicular magnetic tunnel junctions with large tunnel magnetoresistance. Perpendicular magnetic tunnel junctions based on MgO/CoFeB structures are of
particular interest for magnetic random-access memories because of their
excellent thermal stability, scaling potential, and power dissipation. However,
the major challenge of current-induced switching in the nanopillars with both a
large tunnel magnetoresistance ratio and a low junction resistance is still to
be met. Here, we report spin transfer torque switching in nano-scale
perpendicular magnetic tunnel junctions with a magnetoresistance ratio up to
249% and a resistance area product as low as 7.0 {\Omega}.{\mu}m2, which
consists of atom-thick W layers and double MgO/CoFeB interfaces. The efficient
resonant tunnelling transmission induced by the atom-thick W layers could
contribute to the larger magnetoresistance ratio than conventional structures
with Ta layers, in addition to the robustness of W layers against high
temperature diffusion during annealing. The switching critical current density
could be lower than 3.0 MA.cm-2 for devices with a 45 nm radius.

###Huge Positive Magnetoresistance in Antiferromagnetic Double Perovskite Metals|Viveka Nand Singh,Pinaki Majumdar###

Huge Positive Magnetoresistance in Antiferromagnetic Double Perovskite Metals. Metals with large positive magnetoresistance are rare. We demonstrate that
antiferromagnetic metallic states, as have been predicted for the double
perovskites, are excellent candidates for huge positive magnetoresistance. An
applied field suppresses long range antiferromagnetic order leading to a state
with short range antiferromagnetic correlations that generate strong electronic
scattering. The field induced resistance ratio can be more than tenfold, at
moderate field, in a structurally ordered system, and continues to be almost
twofold even in systems with upto 25 % antisite disorder. Although our explicit
demonstration is in the context of a two dimensional spin-fermion model of the
double perovskites, the mechanism we uncover is far more general, complementary
to the colossal negative magnetoresistance process, and would operate in other
local moment metals that show a field driven suppression of non-ferromagnetic
order.

###Efficient spin injection and giant magnetoresistance in Fe/MoS$_2$/Fe junctions|Kapildeb Dolui,Awadhesh Narayan,Ivan Rungger,Stefano Sanvito###

Efficient spin injection and giant magnetoresistance in Fe/MoS$_2$/Fe junctions. We demonstrate giant magnetoresistance in Fe/MoS$_2$/Fe junctions by means of
\textit{ab-initio} transport calculations. We show that junctions incorporating
either a mono- or a bi-layer of MoS$_2$ are metallic and that Fe acts as an
efficient spin injector into MoS$_2$ with an efficiency of about 45\%. This is
the result of the strong coupling between the Fe and S atoms at the interface.
For junctions of greater thickness a maximum magnetoresistance of $\sim$300\%
is obtained, which remains robust with the applied bias as long as transport is
in the tunneling limit. A general recipe for improving the magnetoresistance in
spin valves incorporating layered transition metal dichalcogenides is proposed.

###Negative magnetoresistance dynamics in expanded graphite under hydrostatic pressure up to 1.8 GPa|V. V. Slyusarev,P. I. Polyakov###

Negative magnetoresistance dynamics in expanded graphite under hydrostatic pressure up to 1.8 GPa. Basal plane resistivity of expanded graphite was studied under simultaneous
influence of hydrostatic pressure up to 1.8 GPa and magnetic field 0.8 T in the
77-300 K temperature region. Magnetic field induces negative magnetoresistance
in the sample within all temperature and pressure range studied. A change in
resistivity of the sample under maximum pressure reaches 80%. Significant
change in resistivity dependence on temperature under the pressure of 0.6 GPa
suggests for ordering transition in the sample studied. Negative
magnetoresistance in the graphite reaches about 15% at 0.6 GPa. Magnetic field
acts in the same way as pressure and potentiates the transition formation and
further magnetoresistance dynamics. The effects observed are mostly of elastic
character according to resistivity of the unloaded sample.

###Observation of large spin accumulation voltages in non-degenerate Si spin devices due to spin drift effect: Experiments and theory|Takayuki Tahara,Yuichiro Ando,Makoto Kameno,Hayato Koike,Kazuhito Tanaka,Shinji Miwa,Yoshishige Suzuki,Tomoyuki Sasaki,Tohru Oikawa,Masashi Shiraishi###

Observation of large spin accumulation voltages in non-degenerate Si spin devices due to spin drift effect: Experiments and theory. A large spin-accumulation voltage of more than 1.5 mV at 1 mA, i.e., a
magnetoresistance of 1.5 {\Omega}, was measured by means of the local
three-terminal magnetoresistance in nondegenerate Si-based lateral spin valves
(LSVs) at room temperature. This is the largest spin-accumulation voltage
measured in semiconductor-based LSVs. The modified spin drift-diffusion model,
which successfully accounts for the spin drift effect, explains the large
spin-accumulation voltage and significant bias-current-polarity dependence. The
model also shows that the spin drift effect enhances the spin-dependent
magnetoresistance in the electric two terminal scheme. This finding provides a
useful guiding principle for spin metal-oxide semiconductor field-effect
transistor (MOSFET) operations.

###Magnetoresistance oscillations and the half-flux-quantum state in spin-triplet superconductor Sr2RuO4|X. Cai,Y. A. Ying,J. E. Ortmann,W. -F. Sun,Z. -Q. Mao,Y. Liu###

Magnetoresistance oscillations and the half-flux-quantum state in spin-triplet superconductor Sr2RuO4. We report results of our low-temperature magneto electric transport
measurements on micron-sized short cylinders of odd-parity, spin-triplet
superconductor Sr$_2$RuO$_4$ with the cylinder axis along the $c$ axis. The
in-plane magnetic field and measurement current dependent magnetoresistance
oscillations were found to feature an amplitude much larger than that expected
from the conventional Little-Parks effect, suggesting that the
magnetoresistance oscillations originate from vortex crossing. The free-energy
barrier that controls the vortex crossing was modulated by the magnetic flux
enclosed in the cylinder, the in-plane field, measurement current, and
structural factors. Distinct features on magnetoresistance peaks were found,
which we argue to be related to the emergence of half-flux quantum states, but
only in samples for which the vortex crossing is confined at specific parts of
the sample.

###Transition from positive to negative magnetoresistance induced by a constriction in semiconductor nanowire|Maciej Wołoszyn,Bartłomiej J. Spisak,Paweł Wójcik,Janusz Adamowski###

Transition from positive to negative magnetoresistance induced by a constriction in semiconductor nanowire. We have studied the magnetotransport through an indium antimonide (InSb)
nanowire grown in [111] direction, with a geometric constriction and in an
external magnetic field applied along the nanowire axis. We have found that the
magnetoresistance is negative for the narrow constriction, nearly zero for the
constriction of some intermediate radius, and takes on positive values for the
constriction with the radius approaching that of the nanowire. For all
magnitudes of the magnetic field, the radius of constriction at which the
change of the magnetoresistance sign takes place has been found to be almost
the same as long as other geometric parameters of the nanowire are fixed. The
sign reversing of the magnetoresistance is explained as a combined effect of
two factors: the influence of the constriction on the transverse states and the
spin Zeeman effect.

###Polaronic metal phases in La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ uncovered by inelastic neutron and x-ray scattering|M. Maschek,D. Lamago,J. -P. Castellan,A. Bosak,D. Reznik,F. Weber###

Polaronic metal phases in La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ uncovered by inelastic neutron and x-ray scattering. Among colossal magnetoresistive manganites the prototypical ferromagnetic
manganite La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ has a relatively small
magnetoresistance, and has been long assumed to have only weak electron-lattice
coupling. Here we report that La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ has strong
electron-phonon coupling: Our neutron and x-ray scattering experiments show
strong softening and broadening of transverse acoustic phonons on heating
through the Curie temperature T$_C$ = 350 K. Simultaneously, we observe two
phases where metallic resistivity and polarons coexist. The ferromagnetic
polaronic metal phase between 200 K and T$_C$ is characterized by quasielastic
scattering from dynamic CE-type polarons with the relatively short lifetime of
$\mathbf{\tau}\approx 1\,\rm{ps}$. This scattering is greatly enhanced above
T$_C$ in the paramagnetic polaronic metal phase. Our results suggest that the
strength of magnetoresistance in manganites scales with the inverse of polaron
lifetime, not the strength of electron-phonon coupling.

###Pure spin-Hall magnetoresistance in Rh/Y3Fe5O12 hybrid|T. Shang,Q. F. Zhan,H. L. Yang,Z. H. Zuo,Y. L. Xie,H. H. Li,L. P. Liu,B. M. Wang,Y. H. Wu,S. Zhang,Run-Wei Li###

Pure spin-Hall magnetoresistance in Rh/Y3Fe5O12 hybrid. We report an investigation of anisotropic magnetoresistance (AMR) and
anomalous Hall resistance (AHR) of Rh and Pt thin films sputtered on epitaxial
Y$_3$Fe$_5$O$_{12}$ (YIG) ferromagnetic insulator films. For the Pt/YIG hybrid,
large spin-Hall magnetoresistance (SMR) along with a sizable conventional
anisotropic magnetoresistance (CAMR) and a nontrivial temperature dependence of
AHR were observed in the temperature range of 5-300 K. In contrast, a reduced
SMR with negligible CAMR and AHR was found in Rh/YIG hybrid. Since CAMR and AHR
are characteristics for all ferromagnetic metals, our results suggest that the
Pt is likely magnetized by YIG due to the magnetic proximity effect (MPE) while
Rh remains free of MPE. Thus the Rh/YIG hybrid could be an ideal model system
to explore physics and devices associated with pure spin current.

###Quasi-two-dimensional Dirac fermions and quantum magnetoresistance in LaAgBi$_2$|Kefeng Wang,D. Graf,C. Petrovic###

Quasi-two-dimensional Dirac fermions and quantum magnetoresistance in LaAgBi$_2$. We report quasi-two-dimensional Dirac fermions and quantum magnetoresistance
in LaAgBi$_2$. The band structure shows several narrow bands with nearly linear
energy dispersion and Dirac-cone-like points at the Fermi level. The quantum
oscillation experiments revealed one quasi-two-dimensional Fermi pocket and
another complex pocket with small cyclotron resonant mass. The in-plane
transverse magnetoresistance exhibits a crossover at a critical field $B^*$
from semiclassical weak-field $B^2$ dependence to the high-field unsaturated
linear magnetoresistance which is attributed to the quantum limit of the Dirac
fermions. Our results suggest the existence of quasi 2D Dirac fermions in
rare-earth based layered compounds with two-dimensional double-sized Bi square
nets, similar to (Ca,Sr)MnBi$_{2}$, irrespective of magnetic order.

###Large magnetothermopower and Fermi surface reconstruction in Sb$_2$Te$_2$Se|Kefeng Wang,D. Graf,C. Petrovic###

Large magnetothermopower and Fermi surface reconstruction in Sb$_2$Te$_2$Se. We report the magnetoresistance, magnetothermopower and quantum oscillation
study of Sb$_2$Te$_2$Se single crystal. The in-plane transverse
magnetoresistance exhibits a crossover at a critical field $B^*$ from
semiclassical weak-field $B^2$ dependence to the high-field unsaturated linear
magnetoresistance which persists up to the room temperature. The
low-temperature Seebeck coefficient is negative in zero field contrary to the
positive Hall resistivity, indicating the multiband effect. The magnetic field
induced the sign reversion of the Seebeck coefficient between 2 K and 150 K, .
The quantum oscillation of crystals reveals the quasi-two-dimensional
(quasi-2D) Fermi surface. These effects are possibly attributed to the large
Fermi surface which touches Brillouin zone boundary to becomes quasi-2D and the
variation in the chemical potential induced by the magnetic field.

###The chiral anomaly factory: Creating Weyl fermions with a magnetic field|Jennifer Cano,Barry Bradlyn,Zhijun Wang,Max Hirschberger,N. P. Ong,B. A. Bernevig###

The chiral anomaly factory: Creating Weyl fermions with a magnetic field. Weyl fermions can be created in materials with both time reversal and
inversion symmetry by applying a magnetic field, as evidenced by recent
measurements of anomalous negative magnetoresistance. Here, we do a thorough
analysis of the Weyl points in these materials: by enforcing crystal
symmetries, we classify the location and monopole charges of Weyl points
created by fields aligned with high-symmetry axes. The analysis applies
generally to materials with band inversion in the $T_d$, $D_{4h}$ and $D_{6h}$
point groups. For the $T_d$ point group, we find that Weyl nodes persist for
all directions of the magnetic field. Further, we compute the anomalous
magnetoresistance of field-created Weyl fermions in the semiclassical regime.
We find that the magnetoresistance can scale non-quadratically with magnetic
field, in contrast to materials with intrinsic Weyl nodes. Our results are
relevant to future experiments in the semi-classical regime.

###Radiation-induced resistance oscillations in 2D electron systems with strong Rashba coupling|Jesus Inarrea###

Radiation-induced resistance oscillations in 2D electron systems with strong Rashba coupling. We present a theoretical study on the effect of radiation on the
mangetoresistance of two-dimensional electron systems with strong Rashba
spint-orbit coupling. We want to study the interplay between two well-known
effects in these electron systems: the radiation-induced resistance
oscillations and the typical beating pattern of systems with intense Rashba
interaction. We analytically derive an exact solution for the electron wave
function corresponding to a total Hamiltonian with Rashba and radiation terms.
We consider a perturbation treatment for elastic scattering due to charged
impurities to finally obtain the magnetoresistance of the system. Without
radiation we recover a beating pattern in the amplitude of the Shubnikov de
Hass oscillations: a set of nodes and antinodes in the magnetoresistance. In
the presence of radiation this beating pattern is strongly modified following
the profile of radiation-induced magnetoresistance oscillations. We study their
dependence on intensity and frequency of radiation, including the teraherzt
regime.

###Unidirectional spin Hall magnetoresistance in topological insulator/ferromagnetic layer heterostructures|Yang Lv,James Kally,Delin Zhang,Joon Sue Lee,Mahdi Jamali,Nitin Samarth,Jian-Ping Wang###

Unidirectional spin Hall magnetoresistance in topological insulator/ferromagnetic layer heterostructures. The large spin orbit coupling in topological insulators results in helical
spin-textured Dirac surface states that are attractive for topological
spintronics. These states generate an efficient spin-orbit torque on proximal
magnetic moments at room temperature. However, memory or logic spin devices
based upon such switching require a non-optimal three terminal geometry, with
two terminals for the writing current and one for reading the state of the
device. An alternative two terminal device geometry is now possible by
exploiting the recent discovery of a unidirectional spin Hall magnetoresistance
in heavy metal/ferromagnet bilayers and (at low temperature) in magnetically
doped topological insulator heterostructures. We report the observation of
unidirectional spin Hall magnetoresistance in a technologically relevant device
geometry that combines a topological insulator with a conventional
ferromagnetic metal. Our devices show a figure-of-merit (magnetoresistance per
current density per total resistance) that is comparable to the highest
reported values in all-metal Ta/Co bilayers.

###Large linear magnetoresistance in a transition-metal stannide $β$-RhSn$_4$|X. Z. Xing,C. Q. Xu,N. Zhou,B. Li,Jinglei Zhang,Z. X. Shi,Xiaofeng Xu###

Large linear magnetoresistance in a transition-metal stannide $β$-RhSn$_4$. Materials exhibiting large magnetoresistance may not only be of fundamental
research interest, but also can lead to wide-ranging applications in magnetic
sensors and switches. Here we demonstrate a large linear-in-field
magnetoresistance, $\Delta \rho/\rho$ reaching as high as $\sim$600$\%$ at 2 K
under a 9 Tesla field, in the tetragonal phase of a transiton-metal stannide
$\beta$-RhSn$_4$. Detailed analyses show that its magnetic responses are
overall inconsistent with the classical model based on the multiple electron
scattering by mobility fluctuations in an inhomogenous conductor, but rather in
line with the quantum effects due to the presence of Dirac-like dispersions in
the electronic structure. Our results may help guiding the future quest for
quantum magnetoresistive materials into the family of stannides, similar to the
role played by PtSn$_4$ with topological node arcs.

###Determination of spin relaxation times in heavy metals via 2nd harmonic spin injection magnetoresistance|C. Fang,C. H. Wan,X. M. Liu,B. S. Yang,J. Y. Qin,B. S. Tao,H. Wu,X. Zhang,Z. M. Jin,A. Hoffmann,X. F. Han###

Determination of spin relaxation times in heavy metals via 2nd harmonic spin injection magnetoresistance. In tunnel junctions between ferromagnets and heavy elements with strong spin
orbit coupling the magnetoresistance is often dominated by tunneling
anisotropic magnetoresistance (TAMR). This makes conventional DC spin injection
techniques impractical for determining the spin relaxation time ($\tau_s$).
Here, we show that this obstacle for measurements of $\tau_s$ can be overcome
by 2nd harmonic spin-injection-magnetoresistance (SIMR). In the 2nd harmonic
signal the SIMR is comparable in magnitude to TAMR, thus enabling Hanle-induced
SIMR as a powerful tool to directly determine $\tau_s$. Using this approach we
determined the spin relaxation time of Pt and Ta and their temperature
dependences. The spin relaxation in Pt seems to be governed by Elliott-Yafet
mechanism due to a constant resistivity $\times$spin relaxation time product
over a wide temperature range.

###Magnetotransport properties in a noncentrosymmetric itinerant magnet Cr$_{11}$Ge$_{19}$|N. Jiang,Y. Nii,R. Ishii,Z. Hiroi,Y. Onose###

Magnetotransport properties in a noncentrosymmetric itinerant magnet Cr$_{11}$Ge$_{19}$. We have investigated anomalous Hall effect and magnetoresistance in a
noncentrosymmetric itinerant magnet Cr$_{11}$Ge$_{19}$. While the temperature-
and magnetic-field-dependent anomalous Hall conductivity is just proportional
to the magnetization above 30 K, it is more enhanced in the lower temperature
region. The magnitude of negative magnetoresistance begins to increase toward
low temperature around 30 K. The anisotropic magnetoresistance emerges at
similar temperature. Because there is no anomaly in the temperature dependence
of magnetization around 30 K, the origin of these observations in transport
properties is ascribed to some electronic structure with the energy scale of 30
K. We speculate this is caused by the spin splitting due to breaking of spatial
inversion symmetry.

###Integration of antiferromagnetic Heusler compound Ru$_2$MnGe into spintronic devices|Jan Balluff,Teodor Huminiuc,Markus Meinert,Atsufumi Hirohata,Günter Reiss###

Integration of antiferromagnetic Heusler compound Ru$_2$MnGe into spintronic devices. We report on the first integration of an antiferromagnetic Heusler compound
acting as a pinning layer into magnetic tunneling junctions. The
antiferromagnet Ru$_2$MnGe is used to pin the magnetization direction of a
ferromagnetic Fe layer in MgO based thin film tunnelling magnetoresistance
stacks. The samples were prepared using magnetron co-sputtering. We investigate
the structural properties by X-ray diffraction and reflection, as well as
atomic force and high-resolution transmission electron microscopy. We find an
excellent crystal growth quality with low interface roughnesses of 1-3 \r{A},
which is crucial for the preparation of working tunnelling barriers. Using Fe
as a ferromagnetic electrode material we prepared magnetic tunneling junctions
and measured the magnetoresistance. We find a sizeable maximum
magnetoresistance value of 135%, which is comparable to other common Fe based
MTJ systems.

###Room Temperature Magnetoresistance and Exchange Bias in "314 - type" Oxygen-Vacancy Ordered SrCo$_{0.85}$Fe$_{0.15}$O$_{2.62}$|Prachi Mohanty,Sourav Marik,Deepak Singh,Ravi P. Singh###

Room Temperature Magnetoresistance and Exchange Bias in "314 - type" Oxygen-Vacancy Ordered SrCo$_{0.85}$Fe$_{0.15}$O$_{2.62}$. Herein, we report the magneto-transport and exchange bias effect in a "314 -
type" oxygen - vacancy ordered material with composition
SrCo$_{0.85}$Fe$_{0.15}$O$_{2.62}$. This material exhibits a ferrimagnetic
transition above room temperature, at 315 K. The negative magnetoresistance
starts to appear from room temperature (-1.3 $\%$ at 295 K in 70 kOe) and
reaches a sizable value of 58 $\%$ at 4 K in 70 kOe. Large exchange bias effect
is observed below 315 K when the sample is cooled in the presence of a magnetic
field. The coexistence of nearly compensated and ferrimagnetic regions in the
layered structure originate magnetoresistance and exchange bias in this sample.
The appearance of a sizable magnetoresistance and giant exchange bias effect,
especially near room temperature indicates that "314-type" cobaltates are a
promising class of material systems for the exploration of materials with
potential applications as magnetic sensors or in the area of spintronics.

###Magnetic Proximity Effect in Pt/CoFe2O4 Bilayers|Walid Amamou,Igor V. Pinchuk,Amanda Hanks,Robert Williams,Nikolas Antolin,Adam Goad,Dante J. O'Hara,Adam S. Ahmed,Wolfgang Windl,David W. McComb,Roland K. Kawakami###

Magnetic Proximity Effect in Pt/CoFe2O4 Bilayers. We observe the magnetic proximity effect (MPE) in Pt/CoFe2O4 bilayers grown
by molecular beam epitaxy. This is revealed through angle-dependent
magnetoresistance measurements at 5 K, which isolate the contributions of
induced ferromagnetism (i.e. anisotropic magnetoresistance) and spin Hall
effect (i.e. spin Hall magnetoresistance) in the Pt layer. The observation of
induced ferromagnetism in Pt via AMR is further supported by density functional
theory calculations and various control measurements including insertion of a
Cu spacer layer to suppress the induced ferromagnetism. In addition, anomalous
Hall effect measurements show an out-of-plane magnetic hysteresis loop of the
induced ferromagnetic phase with larger coercivity and larger remanence than
the bulk CoFe2O4. By demonstrating MPE in Pt/CoFe2O4, these results establish
the spinel ferrite family as a promising material for MPE and spin manipulation
via proximity exchange fields.

###Current jetting distorted planar Hall effect in a Weyl semimetal with ultrahigh mobility|J. Yang,W. L. Zhen,D. D. Liang,Y. J. Wang,X. Yan,S. R. Weng,J. R. Wang,W. Tong,L. Pi,W. K. Zhu,C. J. Zhang###

Current jetting distorted planar Hall effect in a Weyl semimetal with ultrahigh mobility. A giant planar Hall effect (PHE) and anisotropic magnetoresistance (AMR) is
observed in TaP, a nonmagnetic Weyl semimetal with ultrahigh mobility. The
perpendicular resistivity (i.e., the planar magnetic field applied normal to
the current) far exceeds the zero-field resistivity, which thus rules out the
possible origin of negative longitudinal magnetoresistance. The giant PHE/AMR
is finally attributed to the large anisotropic orbital magnetoresistance that
stems from the ultrahigh mobility. Furthermore, the mobility-enhanced current
jetting effects are found to strongly deform the line shape of the curves, and
their evolution with the changing magnetic field and temperature is also
studied. Although the giant PHE/AMR suggests promising applications in
spintronics, the enhanced current jetting shows the other side of the coin,
which needs to be considered in the future device design.

###Spin-current-related magnetoresistance in epitaxial Pt/Co bilayers in the presence of spin Hall effect and Rashba-Edelstein effect|Ye Du,Saburo Takahashi,Junsaku Nitta###

Spin-current-related magnetoresistance in epitaxial Pt/Co bilayers in the presence of spin Hall effect and Rashba-Edelstein effect. We analyze the experimentally obtained spin-current-related magnetoresistance
in epitaxial Pt/Co bilayers by using a drift-diffusion model that incorporates
both bulk spin Hall effect and interfacial Rashba-Edelstein effect (REE). The
magnetoresistance analysis yields, for the Pt/Co interface, a
temperature-independent Rashba parameter in the order of 1e-11 eV m that agrees
with theoretical calculations, along with an effective interfacial REE
thickness of several angstroms which is in overall consistency with our
previous spin-orbit torque analysis. In particular, our results suggest that
both bulk and interface charge-spin current inter-conversions need to be taken
into account for the spin-current-related magnetoresistance analysis in
highly-conductive magnetic hetero-structures such as the epitaxial Pt/Co
bilayers.

###Focused ion beam modification of non-local magnon-based transport in yttrium iron garnet/platinum heterostructures|Richard Schlitz,Toni Helm,Michaela Lammel,Kornelius Nielsch,Artur Erbe,Sebastian T. B. Goennenwein###

Focused ion beam modification of non-local magnon-based transport in yttrium iron garnet/platinum heterostructures. We study the impact of Ga ion exposure on the local and non-local
magnetotransport response in heterostructures of the ferrimagnetic insulator
yttrium iron garnet and platinum. In particular, we cut the yttrium iron garnet
layer in between two electrically separated wires of platinum using a Ga ion
beam, and study the ensuing changes in the magnetoresistive response. We find
that the non-local magnetoresistance signal vanishes when the yttrium iron
garnet film between the Pt wires is fully cut, although the local spin Hall
magnetoresistance signal remains finite. This observation corroborates the
notion that pure spin currents carried by magnons are crucial for the non-local
magnetotransport effects observed in magnetic insulator/metal nanostructures.

###Structural, magnetostatic and magnetodynamic studies of Co/Mo-based uncompensated synthetic antiferromagnets|Piotr Ogrodnik,Jarosław Kanak,Maciej Czapkiewicz,Sławomir Ziętek,Aleksiej Pietruczik,Krzysztof Morawiec,Piotr Dłużewski,Krzysztof Dybko,Andrzej Wawro,Tomasz Stobiecki###

Structural, magnetostatic and magnetodynamic studies of Co/Mo-based uncompensated synthetic antiferromagnets. In this work, we comprehensively investigate and discuss the structural,
magnetostatic, dynamic, and magnetoresistive properties of epitaxial Co/Mo
superlattices. The magnetization of the Co sublayers is coupled
antiferromagnetically with a strength that depends on the thickness of the
nonmagnetic Mo spacer. The magnetization and magnetoresistance hysteresis loops
clearly reflect interlayer exchange coupling and the occurrence of uniaxial
magnetic anisotropy induced by the strained Co sublayers. Upon accounting for a
deviation of the sublayer thicknesses from the nominal value, theoretical
modeling, including both micromagnetic and macrospin approaches, precisely
reproduces experimental magnetic hysteresis loops, magnetoresistance curves,
and ferromagnetic resonance dispersion relations. The Mo spacer thickness as a
function of the interlayer magnetic coupling is determined as a fitting
parameter by modeling the experimental results.

###Magnetization reversal, giant exchange bias effect and magnetoresistance in oxygen vacancy ordered Sr$_{4}$Fe$_{3}$CoO$_{11}$|Prachi Mohanty,Sourav Marik,C. Madhu,D. Singh,O. Toulemonde,Ravi P. Singh###

Magnetization reversal, giant exchange bias effect and magnetoresistance in oxygen vacancy ordered Sr$_{4}$Fe$_{3}$CoO$_{11}$. We report the structural, magnetic, exchange bias and magnetotransport effect
in Sr$_{4}$Fe$_{3}$CoO$_{11}$. The material crystallizes in the orthorhombic
$\textit{Cmmm}$ space group. It shows antiferromagnetic (G-type) transition
(T$_{N}$ = 255 K) along with interesting temperature induced magnetization
reversal (T$_{Comp.}$= 47 K measured at 100 Oe). The magnetic reversal can be
elucidated considering the increased magnetocrystalline anisotropy with Co
substitution. Magnetoresistance measurements shows an interesting crossover
from negative to positive side at $\sim$ 100 K. The negative magnetoresistance
reaches 80 $\%$ at 25 K in 7 T magnetic field. Giant exchange bias effect is
observed below T$_{N}$ under field cooling condition. The origin of the
negative magnetoresistance and giant exchange bias in this sample can be
attributed to the magnetic frustration.

###Magnetoresistance effects in the metallic antiferromagnet Mn$_2$Au|S. Yu. Bodnar,Y. Skourski,O. Gomonay,J. Sinova,M. Kläui,M. Jourdan###

Magnetoresistance effects in the metallic antiferromagnet Mn$_2$Au. In antiferromagnetic spintronics, it is essential to separate the resistance
modifications of purely magnetic origin from other effects generated by current
pulses intended to switch the N\'eel vector. We investigate the
magnetoresistance effects resulting from magnetic field induced reorientations
of the staggered magnetization of epitaxial antiferromagnetic Mn2Au(001) thin
films. The samples were exposed to 60 T magnetic field pulses along different
crystallographic in-plane directions of Mn2Au(001), while their resistance was
measured. For the staggered magnetization aligned via a spin-flop transition
parallel to the easy [110]-direction, an ansiotropic magnetoresistance of -0.15
% was measured. In the case of a forced alignment of the staggered
magnetization parallel to the hard [100]-direction, evidence for a larger
anisotropic magnetoresistance effect was found. Furthermore, transient
resistance reductions of about 1 % were observed, which we associate with the
annihilation of antiferromagnetic domain walls by the magnetic field pulses.

###Crossover from Positive to Negative Interlayer Magnetoresistance in Multilayer Massless Dirac Fermion System with Non-Vertical Interlayer Tunneling|Takao Morinari,Takami Tohyama###

Crossover from Positive to Negative Interlayer Magnetoresistance in Multilayer Massless Dirac Fermion System with Non-Vertical Interlayer Tunneling. We present a theoretical description of the interlayer magnetoresistance in
the layered Dirac fermion system with the application to the organic conductor
\alpha-(BEDT-TTF)_2I_3 under pressure. Assuming a non-vertical interlayer
tunneling and including higher Landau level effects we calculate the interlayer
conductivity using the Kubo formula.We propose a physical picture of the
experimentally observed crossover from the negative interlayer
magnetoresistance, where the Dirac fermion zero-energy Landau level plays a
central role, to the positive interlayer magnetoresistance that is the
consequence of the Landau level mixing effect upon non-vertical interlayer
hopping. The crossover magnetic field depends on the Landau level broadening
factor and can be used to determine the Dirac fermion Landau level energy
spectrum.

###On the Origin of Non-Saturating Linear Magnetoresistivity|Ferdinand Kisslinger,Christian Ott,Heiko B. Weber###

On the Origin of Non-Saturating Linear Magnetoresistivity. The observation of non-saturating classical linear magnetoresistivity has
been an enigmatic phenomenon in solid state physics. We present a study of a
two-dimensional ohmic conductor, including local Hall effect and a
self-consistent consideration of the environment. An equivalent-circuit scheme
delivers a simple and convincing argument why the magnetoresistivity is linear
in strong magnetic field, provided that current and biasing electric field are
misaligned by a nonlocal mechanism. A finite-element model of a two-dimensional
conductor is suited to display the situations that create such deviating
currents. Besides edge effects next to electrodes, charge carrier density
fluctuations are efficiently generating this effect. However, mobility
fluctuations that have frequently been related to linear magnetoresistivity are
barely relevant. Despite its rare observation, linear magnetoresitivity is
rather the rule than the exception in a regime of low charge carrier densities,
misaligned current pathways and strong magnetic field.

###Sign reversal of magnetoresistance and p to n transition in Ni doped ZnO thin film|Arpana Agrawal,Tanveer A. Darb,R. J. Choudhary,Archana Lakhani,Pranay K. Sen,Pratima Sen###

Sign reversal of magnetoresistance and p to n transition in Ni doped ZnO thin film. We report the magnetoresistance and nonlinear Hall effect studies over a wide
temperature range in pulsed laser deposited Ni0.07Zn0.93O thin film. Negative
and positive contributions to magnetoresistance at high and low temperatures
have been successfully modeled by the localized magnetic moment and two band
conduction process involving heavy and light hole subbands, respectively.
Nonlinearity in the Hall resistance also agrees well with the two channel
conduction model. A negative Hall voltage has been found for T $\gte 50 K$,
implying a dominant conduction mainly by electrons whereas positive Hall
voltage for T less than 50 K shows hole dominated conduction in this material.
Crossover in the sign of magnetoresistance from negative to positive reveals
the spin polarization of the charge carriers and hence the applicability of Ni
doped ZnO thin film for spintronic applications.

###Thickness dependence of unidirectional spin-Hall magnetoresistance in metallic bilayers|Yuxiang Yin,Dong-Soo Han,Mark C. H. de Jong,Reinoud Lavrijsen,Rembert A. Duine,Henk J. M. Swagten,Bert Koopmans###

Thickness dependence of unidirectional spin-Hall magnetoresistance in metallic bilayers. A nonlinear magnetoresistance - called unidirectional spin-Hall
magnetoresistance - is recently experimentally discovered in metallic bilayers
consisting of a heavy metal and a ferromagnetic metal. To study the fundamental
mechanism of the USMR, both ferromagnetic and heavy metallic layer thickness
dependence of the USMR are presented in a Pt/Co/AlOx trilayer at room
temperature. To avoid ambiguities, second harmonic Hall measurements are used
for separating spin-Hall and thermal contributions to the non-linear
magnetoresistance. The experimental results are fitted by using a
drift-diffusion theory, with parameters extracted from an analysis of
longitudinal resistivity of the Co layer within the framework of the
Fuchs-Sondheimer model. A good agreement with the theory is found,
demonstrating that the USMR is governed by both the spin-Hall effect in the
heavy metallic layer and the metallic diffusion process in the ferromagnetic
layer.

###Magnetotransport evidence of irreversible spin reorientation in the collinear antiferromagnetic state of underdoped $\mathrm{Nd}_{2-x}\mathrm{Ce}_x\mathrm{CuO}_4$|Alma Dorantes,Ahmed Alshemi,Zengle Huang,Andreas Erb,Toni Helm,Mark Kartsovnik###

Magnetotransport evidence of irreversible spin reorientation in the collinear antiferromagnetic state of underdoped $\mathrm{Nd}_{2-x}\mathrm{Ce}_x\mathrm{CuO}_4$. We make use of the strong spin-charge coupling in the electron-doped cuprate
$\mathrm{Nd}_{2-x}\mathrm{Ce}_x\mathrm{CuO}_4$ to probe changes in its spin
system via magnetotransport measurements. We present a detailed study of the
out-of-plane magnetoresistance in underdoped single crystals of this compound,
including the nonsuperconducting, $0.05\,\leq x\,\leq 0.115$, and
superconducting, $0.12\,\leq x\,\leq 0.13$, compositions. Special focus is put
on the dependence of the magnetoresistance on the field orientation in the
plane of the CuO$_2$ layers. In addition to the kink at the field-induced
transition between the noncollinear and collinear antiferromagnetic
configurations, a sharp irreversible feature is found in the angle-dependent
magnetoresistance of all samples in the high-field regime, at field
orientations around the Cu--O--Cu direction. The obtained behavior can be
explained in terms of field-induced reorientation of Cu$^{2+}$ spins within the
collinear antiferromagnetic state. It is, therefore, considered as an
unambiguous indication of the long-range magnetic order.

###Theory of bilinear magneto-electric resistance from topological-insulator surface states|Steven S. -L. Zhang,Giovanni Vignale###

Theory of bilinear magneto-electric resistance from topological-insulator surface states. We theoretically investigate a new kind of nonlinear magnetoresistance on the
surface of three-dimensional topological insulators (TIs). At variance with the
unidirectional magnetoresistance (UMR) effect in magnetic bilayers, this
nonlinear magnetoresistance does not rely on a conducting ferromagnetic layer
and scales linearly with both the applied electric and magnetic fields; for
this reason, we name it bilinear magneto-electric resistance (BMER). We show
that the sign and the magnitude of the BMER depends sensitively on the
orientation of the current with respect to the magnetic field as well as the
crystallographic axes -- a property that can be utilized to map out the spin
texture of the topological surface states via simple transport measurement,
alternative to the angle-resolved photoemission spectroscopy (ARPES).

###Magnetoresistance of individual ferromagnetic GaAs/(Ga,Mn)As core-shell nanowires|Christian H. Butschkow,Elisabeth Reiger,Stefan Geißler,Andreas Rudolph,Marcello Soda,Dieter Schuh,Georg Woltersdorf,Werner Wegscheider,Dieter Weiss###

Magnetoresistance of individual ferromagnetic GaAs/(Ga,Mn)As core-shell nanowires. We investigate, angle dependent, the magnetoresistance (MR) of individual
self-assembled ferromagnetic GaAs/(Ga,Mn)As core-shell nanowires at cryogenic
temperatures. The shape of the MR traces and the observed strong anisotropies
in transport can be ascribed to the interplay of the negative magnetoresistance
effect and a strong uniaxial anisotropy with the magnetic easy direction
pointing along the wire axis. The magnetoresistance can be well described by a
quantitative analysis based on the concept of the effective magnetic field,
usually used to describe ferromagnetic resonance phenomena. The nanowires we
investigate exhibit a uniaxial anisotropy which is approximately 5 times larger
than the strain induced anisotropy observed in lithographically prepared
(Ga,Mn)As stripes.

###Low-temperature magnetotransport of narrow-gap semiconductor FeSb2|H. Takahashi,R. Okazaki,Y. Yasui,I. Terasaki###

Low-temperature magnetotransport of narrow-gap semiconductor FeSb2. We present a study of the magnetoresistance and Hall effect in the narrow-gap
semiconductor FeSb2 at low temperatures. Both the electrical and Hall
resistivities show unusual magnetic field dependence in the low-temperature
range where a large Seebeck coefficient was observed. By applying a two-carrier
model, we find that the carrier concentration decreases from 1 down to 10^-4
ppm/unit cell and the mobility increases from 2000 to 28000 cm2/Vs with
decreasing temperature from 30 down to 4 K. At lower temperatures, the
magnetoresistive behavior drastically changes and a negative magnetoresistance
is observed at 3 K. These low-temperature behaviors are reminiscent of the
low-temperature magnetotransport observed in doped semiconductors such as
As-doped Ge, which is well described by a weak-localization picture. We argue a
detailed electronic structure in FeSb2 inferred from our observations.

###Linear magnetoresistance induced by intra-scattering semiclassics of Bloch electrons|Cong Xiao,Hua Chen,Yang Gao,Di Xiao,Allan H. MacDonald,Qian Niu###

Linear magnetoresistance induced by intra-scattering semiclassics of Bloch electrons. The weak field magnetoresistance has seen a revived interest due to the
distinct role played by the momentum-space Berry curvature of Bloch electrons.
While most previous studies in this regard focus on the inter-scattering motion
of semiclassical Bloch electrons in electromagnetic fields, the
intra-scattering effects of the semiclassical dynamics augmented by the Berry
curvature, magnetic moment and shift vector on the magnetoresistance have been
largely overlooked. Here we uncover that these intra-scattering effects, which
are neglected in the field-independent relaxation time approximation to the
Boltzmann collision integral, can be as important as the inter-scattering ones.
Concrete calculations on the two dimensional gapped Dirac model show that the
sign of the negative linear magnetoresistance given by the Berry curvature
alone is reversed when one considers the magnetic moment and shift vector.

###Magnetoresistance generated from charge-spin conversion by anomalous Hall effect in metallic ferromagnetic/nonmagnetic bilayers|Tomohiro Taniguchi###

Magnetoresistance generated from charge-spin conversion by anomalous Hall effect in metallic ferromagnetic/nonmagnetic bilayers. A theoretical formulation of magnetoresistance effect in a metallic
ferromagnetic/nonmagnetic bilayer originated from the charge-spin conversion by
the anomalous Hall effect is presented. Analytical expressions of the
longitudinal and transverse resistivities in both nonmagnet and ferromagnet are
obtained by solving the spin diffusion equation. The magnetoresistance
generated from charge-spin conversion purely caused by the anomalous Hall
effect in the ferromagnet is found to be proportional to the square of the spin
polarizations in the ferromagnet and has fixed sign. We also find additional
magnetoresistances in both nonmagnet and ferromagnet arising from the mixing of
the spin Hall and anomalous Hall effects. The sign of this mixing resistance
depends on those of the spin Hall angle in the nonmagnet and the spin
polarizations of the ferromagnet.

###Evidence for trivial Berry phase and absence of chiral anomaly in semimetal NbP|Sudesh,P. Kumar,P. Neha,T. Das,A. K. Rastogi,S. Patnaik###

Evidence for trivial Berry phase and absence of chiral anomaly in semimetal NbP. We report a detailed magneto-transport study in single crystals of NbP. High
quality crystals were grown by vapour transport method. An exceptionally large
magnetoresistance is confirmed at low temperature which is non-saturating and
is linear at high fields. Models explaining the linear magnetoresistance are
discussed and it is argued that in NbP this is linked to charge carrier
mobility fluctuations. Negative longitudinal magnetoresistance is not seen,
unlike several other Weyl monopnictides, suggesting lack of well defined chiral
anomaly in NbP. Unambiguous Shubnikov-de-Haas oscillations are observed at low
temperatures that are correlated to Berry phases. The Landau fan diagram
indicates trivial Berry phase in NbP crystals corresponding to Fermi surface
extrema at 30.5 Tesla.

###High frequency dynamics modulated by collective magnetization reversal in artificial spin ice|Matthias B. Jungfleisch,Joseph Sklenar,Junjia Ding,Jungsik Park,John E. Pearson,Valentine Novosad,Peter Schiffer,Axel Hoffmann###

High frequency dynamics modulated by collective magnetization reversal in artificial spin ice. Spin-torque ferromagnetic resonance (ST-FMR) arises in heavy
metal/ferromagnet heterostructures when an alternating charge current is passed
through the bilayer stack. The methodology to detect the resonance is based on
the anisotropic magnetoresistance, which is the change in the electrical
resistance due to different orientations of the magnetization. In connected
networks of ferromagnetic nanowires, known as artificial spin ice, the
magnetoresistance is rather complex owing to the underlying collective behavior
of the geometrically frustrated magnetic domain structure. Here, we demonstrate
ST-FMR investigations in a square artificial spin-ice system and correlate our
observations to magnetotransport measurements. The experimental findings are
described using a simulation approach that highlights the importance of the
correlated dynamics response of the magnetic system. Our results open the
possibility of designing reconfigurable microwave oscillators and
magnetoresistive devices based on connected networks of nanomagnets.

###Finite Temperature Behavior in the Second Landau Level of the Two-dimensional Electron Gas|V. Shingla,E. Kleinbaum,A. Kumar,L. N. Pfeiffer,K. W. West,G. A. Csathy###

Finite Temperature Behavior in the Second Landau Level of the Two-dimensional Electron Gas. Reports of weak local minima in the magnetoresistance at $\nu=2+3/5$,
$2+3/7$, $2+4/9$, $2+5/9$, $2+5/7$, and $2+5/8$ in the second Landau level of
the electron gas in GaAs/AlGaAs left open the possibility of fractional quantum
Hall states at these filling factors. In a high quality sample we found that
the magnetoresistance exhibits peculiar features near these filling factors of
interest. These features, however, cannot be associated with fractional quantum
Hall states; instead they originate from magnetoresistive fingerprints of the
electronic bubble phases. We found only two exceptions: at $\nu=2+2/7$ and
$2+5/7$ there is evidence for incipient fractional quantum Hall states at
intermediate temperatures. As the temperature is lowered, these fractional
quantum Hall states collapse due to a phase competition with bubble phases.

###Linear magnetoresistance in the low-field limit in density-wave materials|Yejun Feng,Yishu Wang,D. M. Silevitch,J. -Q. Yan,Riki Kobayashi,Masato Hedo,Takao Nakama,Yoshichika Ōnuki,A. V. Suslov,B. Mihaila,P. B. Littlewood,T. F. Rosenbaum###

Linear magnetoresistance in the low-field limit in density-wave materials. The magnetoresistance (MR) of a material is typically insensitive to
reversing the applied field direction and varies quadratically with magnetic
field in the low-field limit. Quantum effects [1], unusual topological band
structures [2], and inhomogeneities that lead to wandering current paths [3, 4]
can induce a crossover from quadratic to linear magnetoresistance with
increasing magnetic field. Here we explore a series of metallic charge- and
spin-density-wave systems that exhibit extremely large positive linear
magnetoresistance. By contrast to other linear MR mechanisms, this effect
remains robust down to miniscule magnetic fields of tens of Oersted at low
temperature. We frame an explanation of this phenomenon in a semi-classical
narrative for a broad category of materials with partially-gapped Fermi
surfaces due to density waves.

###Interface spin polarization of the Heusler compound Co2MnSi probed by unidirectional spin Hall magnetoresistance|C. Lidig,J. Cramer,L. Weißhoff,T. R. Thomas,T. Kessler,M. Kläui,M. Jourdan###

Interface spin polarization of the Heusler compound Co2MnSi probed by unidirectional spin Hall magnetoresistance. Many Heusler compounds are predicted to be ferromagnetic half metals in the
bulk, which makes them promising compounds for spintronics. However, for
devices the transport spin polarization at specific interfaces requires
optimization. We show that investigations of the unidirectional
magnetoresistance provide an alternative approach to access this quantity.
Based on a Wheatstone-bridge design we probed the unidirectional
magnetoresistance of Co2MnSi/(Ag, Cu, or Cr)(0.5 nm)/Pt (or Ta) multilayers and
separate the spin-dependent unidirectional spin Hall magnetoresistance from
other contributions. We demonstrated that by the insertion of a thin epitaxial
Ag layer the spin-dependent contribution is doubled corresponding to a
significant increase of the transport spin polarization, which is discussed in
the framework of highly spin polarized interface states.

###Weak Localization in Systems with Chiral Spin Textures and Skyrmion Crystals|K. S. Denisov,L. E. Golub###

Weak Localization in Systems with Chiral Spin Textures and Skyrmion Crystals. Theory of interference-induced quantum corrections to conductivity is
developed for two dimensional systems with chiral spin textures including
skyrmions. The effect of exchange interaction between electrons and spin
textures on weak localization of electronic waves is studied. The spin
dephasing rates are calculated as functions of the spin texture size. The
anomalous magnetoresistance is shown to be governed by the size and
magnetization spatial distribution of the spin textures. The effect of average
magnetization-induced spin splitting on weak localization is analyzed. The
sign-alternating weak-antilocalization magnetoresistance is demonstrated for
skyrmion crystals. We argue that analysis of the low-field magnetoresistance
serves as an independent tool for an experimental detection of chiral spin
textures and, in particular, skyrmions.

###Composition dependence of magnetoresistance in Fe$_{1-x}$Ni$_{x}$ alloys|S. S. Acharya###

Composition dependence of magnetoresistance in Fe$_{1-x}$Ni$_{x}$ alloys. Resistance of Fe$_{1-x}$Ni$_x$(x=0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 and 0.9)
has been measured using four probe method from 5K to 300K with and without a
longitudinal magnetic field of 8T. The zero field resistivity of x=0.1 and 0.9
alloys, predominant contribution to resistivity above near room temperature is
due to electron-phonon scattering, whereas for x=05 and 0.7 alloys
electron-magnon scattering is dominant. Alloys with x=0.1 and 0.9 exhibit
positive magnetoresistance(MR) from 5K to 300K. For x=0.5 and 0.7 alloys,
magnetoresistance changes sign from positive to negative with increase in
temperature. The temperature at which sign changes increase with Ni
concentration in the alloy. The field dependent magnetoresistance is positive
for x=0.1, 0.7 and 0.9 alloys whereas it is negative for x=0.5 alloy. MR
follows linear behaviour with field for x=0.1 alloy. MR of all other alloys
follow a second order polynomial in field.

###Odd-parity linear magnetoresistance and the planar Hall effect|Yishu Wang,Patrick A. Lee,D. M. Silevitch,F. Gomez,S. E. Cooper,Y. Ren,J. -Q. Yan,D. Mandrus,T. F. Rosenbaum,Yejun Feng###

Odd-parity linear magnetoresistance and the planar Hall effect. The phenomena of odd-parity magnetoresistance and the planar Hall effect are
deeply entwined with ferromagnetism. The intrinsic magnetization of the ordered
state permits these unusual and rarely observed manifestations of Onsager's
theorem when time reversal symmetry is broken at zero applied field. Here we
study two classes of ferromagnetic materials, rare-earth magnets with high
intrinsic coercivity and antiferromagnetic pyrochlores with strongly-pinned
ferromagnetic layers at domain walls, which both exhibit odd-parity
magnetoresistive behavior. The peculiar angular variation of the response with
respect to the relative alignments of the magnetization, magnetic field, and
current reveal the two underlying microscopic mechanisms:
spin-polarization-dependent scattering of a Zeeman-shifted Fermi surface and
magnetoresistance driven by the anomalous velocity physics usually associated
with the anomalous Hall effect.

###Nonlinear magnetotransport shaped by Fermi surface topology and convexity in WTe2|Pan He,Chuang-Han Hsu,Shuyuan Shi,Kaiming Cai,Junyong Wang,Qisheng Wang,Goki Eda,Hsin Lin,Vitor M. Pereira,Hyunsoo Yang###

Nonlinear magnetotransport shaped by Fermi surface topology and convexity in WTe2. The nature of Fermi surface defines the physical properties of conductors and
many physical phenomena can be traced to its shape. Although the recent
discovery of a current-dependent nonlinear magnetoresistance in spin-polarized
non-magnetic materials has attracted considerable attention in spintronics,
correlations between this phenomenon and the underlying fermiology remain
unexplored. Here, we report the observation of nonlinear magnetoresistance at
room temperature in a semimetal WTe2, with an interesting temperature-driven
inversion. Theoretical calculations reproduce the nonlinear transport
measurements and allow us to attribute the inversion to temperature-induced
changes in Fermi surface convexity. We also report a large anisotropy of
nonlinear magnetoresistance in WTe2, due to its low symmetry of Fermi surfaces.
The good agreement between experiments and theoretical modeling reveals the
critical role of Fermi surface topology and convexity on the nonlinear
magneto-response. These results lay a new path to explore ramifications of
distinct fermiology for nonlinear transport in condensed-matter.

###Dirac state switching in transition metal diarsenides|Gyanendra Dhakal,M. Mofazzel Hosen,Wei-Chi Chu,Bahadur Singh,Klauss Dimitri,BaoKai Wang,Firoza Kabir,Christopher Sims,Sabin Regmi,William Neff,Dariusz Kaczorowski,Arun Bansil,Madhab Neupane###

Dirac state switching in transition metal diarsenides. Topological Dirac and Weyl semimetals, which support low-energy
quasiparticles in condensed matter physics, are currently attracting intense
interest due to exotic physical properties such as large magnetoresistance and
high carrier mobilities. Transition metal diarsenides such as MoAs2 and WAs2
have been reported to harbor very high magnetoresistance suggesting the
possible existence of a topological quantum state, although this conclusion
remains dubious. Here, based on systematic angle-resolved photoemission
spectroscopy (ARPES) measurements and parallel first-principles calculations,
we investigate the electronic properties of TAs2 (T = Mo, W). Importantly,
clear evidence for switching the single-Dirac cone surface state in MoAs2 with
the cleaving plane is observed, whereas a Dirac state is not observed in WAs2
despite its high magnetoresistance. Our study thus reveals the key role of the
terminated plane in a low-symmetry system, and provides a new perspective on
how termination can drive dramatic changes in electronic structures.

###Scaling Analysis of Anomalous Hall Resistivity in the Co$_{2}$TiAl Heusler Alloy|Rudra Prasad Jena,Devendra Kumar,Archana Lakhani###

Scaling Analysis of Anomalous Hall Resistivity in the Co$_{2}$TiAl Heusler Alloy. A comprehensive magnetotransport study including resistivity ($\rho_{xx}$) at
various fields, isothermal magnetoresistance and Hall resistivity ($\rho_{xy}$)
has been carried out at different temperatures on the Co$_{2}$TiAl Heusler
alloy. Co$_{2}$TiAl alloy shows a paramagnetic (PM) to ferromagnetic (FM)
transition below the curie temperature (T$_{C}$) $\sim$ 125 K. In the FM
region, resistivity and magnetoresistance reveals a spin flip electron-magnon
scattering and the Hall resistivity unveils the anomalous Hall resistivity
($\rho_{xy}^{AH}$). Scaling of anomalous Hall resistivity with resistivity
establishes the extrinsic scattering process responsible for the anomalous hall
resistivity; however Skew scattering is the dominant mechanism compared to the
side-jump contribution. A one to one correspondence between magnetoresistance
and side-jump contribution to anomalous Hall resistivity verifies the
electron-magnon scattering being the source of side-jump contribution to the
anomalous hall resistivity.

###Pressure-induced suppression of charge density wave and emergence of Superconductivity in 1T-VSe2|S. Sahoo,U. Dutta,L. Harnagea,A. K. Sood,S. Karmakar###

Pressure-induced suppression of charge density wave and emergence of Superconductivity in 1T-VSe2. We report pressure evolution of charge density wave (CDW) order and emergence
of superconductivity (SC) in 1T-VSe2 single crystal by studying resistance and
magnetoresistance behavior under high pressure. With increasing
quasi-hydrostatic pressure the CDW order enhances with increase ofthe ordering
temperature up to 240K at 12 GPa. Upon further increase of pressure, the
resistance anomaly due to CDW order gets suppressed drastically and
superconductivity emerges at ~15 GPa, with the onset critical temperature (Tc)
~ 4K. The pressure dependence of Tc is found negligible, different from the
significant increase or a dome-shape seen in iso-structural layered diselenide
superconductors. The high pressure magnetoresistance and Hall measurements
suggest successive electronic structural changes with Fermi surface
modifications at 6 GPa and 12GPa. From the observed negative magnetoresistance
in this pressure range and absence of coexisting CDW and SC phases, we propose
that intra-layer spin-fluctuation can play a role in the emergence of
superconductivity in the high pressure phase.

###Spin flop and crystalline anisotropic magnetoresistance in CuMnAs|M. Wang,C. Andrews,S. Reimers,O. J. Amin,P. Wadley,R. P. Campion,S. F. Poole,J. Felton,K. W. Edmonds,B. L. Gallagher,A. W. Rushforth,O. Makarovsky,K. Gas,M. Sawicki,D. Kriegner,J. Zubac,K. Olejnik,V. Novak,T. Jungwirth,M. Shahrokhvand,U. Zeitler,S. S. Dhesi,F. Maccherozzi###

Spin flop and crystalline anisotropic magnetoresistance in CuMnAs. Recent research works have shown that the magnetic order in some
antiferromagnetic materials can be manipulated and detected electrically, due
to two physical mechanisms: Neel-order spin-orbit torques and anisotropic
magnetoresistance. While these observations open up opportunities to use
antiferromagnets for magnetic memory devices, different physical
characterization methods are required for a better understanding of those
mechanisms. Here we report a magnetic field induced rotation of the
antiferromagnetic Neel vector in epitaxial tetragonal CuMnAs thin films. Using
soft x-ray magnetic linear dichroism spectroscopy, x-ray photoemission electron
microscopy, integral magnetometry and magneto-transport methods, we demonstrate
spin-flop switching and continuous spin reorientation in antiferromagnetic
films with uniaxial and biaxial magnetic anisotropies, respectively. From
field-dependent measurements of the magnetization and magnetoresistance, we
obtain key material parameters including the anisotropic magnetoresistance
coefficients, magnetocrystalline anisotropy, spin-flop and exchange fields.

###Resolution of spin Hall and anisotropic magnetoresistance in Pt/EuO$_{1-x}$|Kingshuk Mallick,Aditya A. Wagh,Adrian Ionescu,Crispin H. W. Barnes,P. S. Anil Kumar###

Resolution of spin Hall and anisotropic magnetoresistance in Pt/EuO$_{1-x}$. We report on the angular and field dependence of the magnetoresistance (MR)
in bilayers of Pt/EuO_{1-x} thin films, measured in both in-plane and
out-of-plane geometries at different temperatures (T). Presence of oxygen
vacancies manifested by a metal-insulator transition as well as a high-T
ferromagnet to paramagnet transition (T_P) were observed in the bilayers. The
Anisotropic Magnetoresistance (AMR) could be extracted in the entire T-range,
even above T_P, exhibiting two sign crossovers. We attribute its T-evolution to
the rotation of easy axis direction from a high-T out-of-plane to a low-T
in-plane orientation. In addition, considering MR contributions from the films'
(111) texture and interface, we identify a T-window wherein the spin Hall
effect induced spin Hall magnetoresistance (SMR) could be extracted.

###Structural and magneto-transport studies of iron intercalated Bi2Se3 single crystals|Shailja Sharma,C. S. Yadav###

Structural and magneto-transport studies of iron intercalated Bi2Se3 single crystals. A detailed investigation on the structural and magneto-transport properties
of iron intercalated Bi2Se3 single crystals have been presented. The x-ray
diffraction and Raman studies confirm the intercalation of Fe in the van der
Waals gaps between the layers. The electrical resistivity of the compounds
decreases upon intercalation, and Hall resistivity shows the enhancement of the
charge carriers upon intercalation. The magnetoresistance shows the
non-saturating linear behavior at higher magnetic field and low temperature.
Intercalation of Fe increases the onset of the linear magnetoresistance
behavior, indicating the reduction in quantum effects. The Kohler scaling
employed on the magnetoresistance data indicates single scattering process for
all these compounds in the measured temperature range of 3- 300 K.

###Giant Magnetoresistance in Boundary-Driven Spin Chains|Kasper Poulsen,Nikolaj T. Zinner###

Giant Magnetoresistance in Boundary-Driven Spin Chains. In solid state physics, giant magnetoresistance is the large change in
electrical resistance due to an external magnetic field. Here we show that
giant magnetoresistance is possible in a spin chain composed of weakly
interacting layers of strongly coupled spins. This is found for all system
sizes even down to a minimal system of four spins. The mechanism driving the
effect is a mismatch in the energy spectrum resulting in spin excitations being
reflected at the boundaries between layers. This mismatch, and thus the
current, can be controlled by external magnetic fields resulting in giant
magnetoresistance. A simple rule for determining the behavior of the spin
transport under the influence of a magnetic field is presented based on the
energy levels of the strongly coupled spins.

###Magnetic field-dependent resistance crossover and logarithmic to non-saturating magnetoresistance in topological insulator Bi$_2$Te$_3$|Anand Nivedan,Kamal Das,Sandeep Kumar,Arvind Singh,Sougata Mardanya,Amit Agarwal,Sunil Kumar###

Magnetic field-dependent resistance crossover and logarithmic to non-saturating magnetoresistance in topological insulator Bi$_2$Te$_3$. We report a metal-insulator like transition in single crystalline 3D
topological insulator Bi2Te3 at a temperature of 230K in presence of an
external magnetic field applied normal to the surface. This transition becomes
more prominent at larger magnetic field strength with the residual resistance
value increasing linearly with the magnetic field. At low temperature, the
magnetic field dependence of the magnetoresistance shows a transition from
logarithmic to linear behavior and the onset magnetic field value for this
transition decreases with increasing temperature. The logarithmic
magnetoresistance indicates the weak anti-localization of the surface Dirac
electrons while the high temperature behavior originates from the bulk carriers
due to intrinsic impurities. At even higher temperatures beyond~230 K, a
completely classical Lorentz model type quadratic behavior of the
magnetoresistance is observed. We also show that the experimentally observed
anomalies at ~230K in the magneto-transport properties do not originate from
any stacking fault in Bi2Te3.

###Metamagnetic transitions and anomalous magnetoresistance in EuAg$_4$As$_2$ single crystal|Qinqing Zhu,Liang Li,Zhihua Yang,Zhefeng Lou,Jianhua Du,Jinhu Yang,Bin Chen,Hangdong Wang,Minghu Fang###

Metamagnetic transitions and anomalous magnetoresistance in EuAg$_4$As$_2$ single crystal. In this paper, the magnetic and transport properties were systematically
studied for EuAg$_4$As$_2$ single crystals, crystallizing in a centrosymmetric
trigonal CaCu$_4$P$_2$ type structure. It was confirmed that two magnetic
transitions occur at $\textit{T}$$_{N1}$ = 10 K and $\textit{T}$$_{N2}$ = 15 K,
respectively. With the increasing field, the two transitions are noticeably
driven to lower temperature. At low temperatures, applying a magnetic field in
the $\textit{ab}$ plane induces two successive metamagnetic transitions. For
both $\textit{H}$ $\parallel$ $\textit{ab}$ and $\textit{H}$ $\parallel$
$\textit{c}$, EuAg$_4$As$_2$ shows a positive, unexpected large
magnetoresistance (up to 202\%) at low fields below 10 K, and a large negative
magnetoresistance (up to -78\%) at high fields/intermediate temperatures. Such
anomalous field dependence of magnetoresistance may have potential application
in the future magnetic sensors. Finally, the magnetic phase diagrams of
EuAg$_{4}$As$_{2}$ were constructed for both $\textit{H}$ $\parallel$
$\textit{ab}$ and $\textit{H}$ $\parallel$ $\textit{c}$.

###Cooperative orbital moments and edge magnetoresistance in monolayer WTe$_2$|Arpit Arora,Li-kun Shi,Justin C. W. Song###

Cooperative orbital moments and edge magnetoresistance in monolayer WTe$_2$. We argue that edge electrons in monolayer WTe$_2$ can possess a "cooperative"
orbital moment (COM) that critically impacts its edge magnetoresistance
behavior. Arising from the cooperative action of both Rashba and Ising spin
orbit coupling, COM quickly achieves large magnitudes (of order few Bohr
magnetons) even for relatively small spin-orbit coupling strengths. As we
explain, such large COM magnitudes arise from an unconventional cooperative
spin canting of edge spins when Rashba and Ising spin orbit coupling act
together. Strikingly, COM can compete with spin moments to produce an unusual
anisotropic edge magnetoresistance oriented at an oblique angle. In particular,
this competition produces a direction along which $\mathbf{B}$ is ineffective
at gapping out the edge spectrum leaving it nearly gapless. As a result, large
contrasts in gap sizes manifest as $\mathbf{B}$ is rotated granting giant
anisotropic magnetoresistance of 0.1-10 million % at 10 T and low temperature.

###Spin-lattice relaxation phenomena in the magnetic state of a suggested Weyl semimetal CeAlGe|Karan Singh,K. Mukherjee###

Spin-lattice relaxation phenomena in the magnetic state of a suggested Weyl semimetal CeAlGe. In this work we report the results of DC susceptibility, AC susceptibility
and related technique, resistivity, transverse and longitudinal
magnetoresistance and heat capacity on polycrystalline magnetic semimetal
CeAlGe. This compound undergoes antiferromagnetic type ordering around 5.2 K
(T1). Under application of external magnetic fields, parallel alignment of
magnetic moments is favored, above 0.5 Tesla. At low field and temperature,
frequency and AC field amplitude response of AC susceptibility indicate to the
presence of spin-lattice relaxation phenomena. The observation of spin-lattice
interaction suggests to the presence of Rashba-Dresselhaus spin-orbit
interaction which is associated with inversion and time reversal symmetry
breaking. Additionally, presence of negative and asymmetric longitudinal
magnetoresistance indicates anomalous velocity contribution to the
magnetoresistance due to Rashba-Dresselhaus spin-orbit interaction which is
further studied by heat capacity.

###Magnetoresistance scaling, disorder, `hot spots' and the origin of $T$-linear resistivity in BaFe$_2$(As$_{1-x}$P$_x$)$_2$|Nikola Maksimovic,Ian M. Hayes,Vikram Nagarajan,Alexei E. Koshelev,John Singleton,Yeonbae Lee,Thomas Schenkel,James G. Analytis###

Magnetoresistance scaling, disorder, `hot spots' and the origin of $T$-linear resistivity in BaFe$_2$(As$_{1-x}$P$_x$)$_2$. The scaling of $H$-linear magnetoresistance in field and temperature was
measured in under-doped (x = 0.19) and optimally-doped
(x=0.31)~BaFe$_2$(As$_{1-x}$P$_x$)$_2$. We analyze the data based on an orbital
model in the presence of strongly anisotropic quasiparticle spectra and
scattering time due to antiferromagnetism. The magnetoresistance is dominated
by the properties of small regions of the Fermi surface called `hot spots'
where antiferromagnetic excitations induce a large quasiparticle scattering
rate. Approximate temperature-magnetic field scaling relations are derived and
shown to be consistent with the experimental data. We argue that these results
link the origin of linear-in-temperature resistivity to hot spots arising from
an antiferromagnetic critical point, and magnetoresistance measurements provide
a route to quantify this link.

###Hysteretic magnetoresistance in nanowire devices due to stray fields induced by micromagnets|Y. Jiang,E. J. de Jong,V. van de Sande,S. Gazibegovic,G. Badawy,E. P. A. M. Bakkers,S. M. Frolov###

Hysteretic magnetoresistance in nanowire devices due to stray fields induced by micromagnets. We study hysteretic magnetoresistance in InSb nanowires due to stray magnetic
fields from CoFe micromagnets. Devices without any ferromagnetic components
show that the magnetoresistance of InSb nanowires commonly exhibits either a
local maximum or local minimum at zero magnetic field. Switching of microstrip
magnetizations then results in positive or negative hysteretic dependence as
conductance maxima or minima shift with respect to the global external field.
Stray fields are found to be in the range of tens of millitesla, comparable to
the scale over which the nanowire magnetoresistance develops. We observe that
the stray field signal is similar to that obtained in devices with
ferromagnetic contacts (spin valves). We perform micromagnetic simulations
which are in reasonable agreement with the experiment. The use of locally
varying magnetic fields may bring new ideas for Majorana circuits in which
nanowire networks require control over field orientation at the nanoscale.

###Universal Behavior of Magnetoresistance in Organic Dirac Electron Systems|Ryotaro Kobara,Shin Igarashi,Yoshitaka Kawasugi,Ryusei Doi,Toshio Naito,Masafumi Tamura,Reizo Kato,Yutaka Nishio,Koji Kajita,Naoya Tajima###

Universal Behavior of Magnetoresistance in Organic Dirac Electron Systems. In-plane magnetoresistance for organic massless Dirac electron system (OMDES)
$\alpha$-(BEDT-TTF)$_2$I$_3$ and $\theta$-(BEDT-TTF)$_2$I$_3$ in addition to
possible candidates of the OMDES $\alpha$-(BETS)$_2$I$_3$ and
$\alpha$-(BEDT-STF)$_2$I$_3$, was investigated under hydrostatic pressure. We
have found the universal behavior of the in-plane magnetoresistance under a low
magnetic field perpendicular to two-dimensional plane. As for
$\alpha$-(BEDT-TTF)$_2$I$_3$, the universality was examined with the parameters
of temperature, magnetic field and its direction. We suggest that the universal
magnetoresistance behavior is found even for the gapped state of
$\alpha$-(BEDT-TTF)$_2$I$_3$ under intermediate pressure, when the thermal
energy exceeds the gap.

###Anomalous Hall effect and negative longitudinal magnetoresistance in half-Heusler topological semimetal candidates TbPtBi and HoPtBi|Orest Pavlosiuk,Patryk Fałat,Dariusz Kaczorowski,Piotr Wiśniewski###

Anomalous Hall effect and negative longitudinal magnetoresistance in half-Heusler topological semimetal candidates TbPtBi and HoPtBi. Half-Heusler compounds have attracted significant attention because of their
topologically non-trivial electronic structure, which leads to unusual electron
transport properties. We thoroughly investigated the magnetotransport
properties of high-quality single crystals of two half-Heusler phases, TbPtBi
and HoPtBi, in pursuit of the characteristic features of topologically
non-trivial electronic states. Both studied compounds are characterized by the
giant values of transverse magnetoresistance with no sign of saturation in
magnetic field up to 14 T. HoPtBi demonstrates the Shubnikov-de Haas effect
with two principal frequencies, indicating a complex Fermi surface; the
extracted values of carrier effective masses are rather small, $0.18\,m_e$ and
$0.27\,m_e$. The investigated compounds exhibit negative longitudinal
magnetoresistance and anomalous Hall effect, which likely arise from a nonzero
Berry curvature. Both compounds show strongly anisotropic magnetoresistance,
that in HoPtBi exhibits a butterfly-like behavior.

###Anisotropic magnetoresistance and memory effect in bulk systems with extended defects|K. S. Denisov,K. A. Baryshnikov,P. S. Alekseev,N. S. Averkiev###

Anisotropic magnetoresistance and memory effect in bulk systems with extended defects. Memory effects can have a profound impact on the resistivity of semiconductor
systems, resulting in giant negative magnetoresistance and MIRO phenomena. This
work opens the discussion of the memory effects in 3D conducting systems
featured by the presence of the extended one-dimensional defects, such as screw
dislocations or static charge stripes. We demonstrate that accounting for the
memory effect, that is the capture of electrons on collisionless spiral
trajectories winding around extended defects, leads to the strong negative
magnetoresistance in case when the external magnetic field direction becomes
parallel to the defects axis. This effect gives rise to a significant
magnetoresistance anisotropy already for an isotropic Fermi surface and no
spin-orbit effects. The proposed resistivity feature can be used to detect
one-dimensional scattering defects in these systems.

###A two-terminal spin valve device controlled by spin-orbit torques with enhanced giant magnetoresistance|Can Onur Avci,Charles-Henri Lambert,Giacomo Sala,Pietro Gambardella###

A two-terminal spin valve device controlled by spin-orbit torques with enhanced giant magnetoresistance. We report on the combination of current-induced spin-orbit torques and giant
magnetoresistance in a single device to achieve all-electrical write and read
out of the magnetization. The device consists of perpendicularly magnetized
TbCo and Co layers separated by a Pt or Cu spacer. Current injection through
such layers exerts spin-orbit torques and switches the magnetization of the Co
layer while the TbCo magnetization remains fixed. Subsequent current injection
of lower amplitude senses the relative orientation of the magnetization of the
Co and TbCo layers, which results in two distinct resistance levels for
parallel and antiparallel alignment due to the current-in-plane giant
magnetoresistance effect. We further show that the giant magnetoresistance of
devices including a single TbCo/spacer/Co trilayer can be improved from 0.02%
to 6% by using a Cu spacer instead of Pt. This type of devices offers an
alternative route to a two terminal spintronic memory that can be fabricated
with moderate effort.

###Evidence of symmetry lowering in antiferromagnetic metal TmB12 with dynamic charge stripes|A. Azarevich,V. Glushkov,S. Demishev,A. Bogach,V. Voronov,S. Gavrilkin,N. Shitsevalova,V. Filipov,S. Gabani,J. Kacmarcik,K. Flachbart,N. Sluchanko###

Evidence of symmetry lowering in antiferromagnetic metal TmB12 with dynamic charge stripes. Precise angle-resolved magnetoresistance and magnetization measurements have
revealed (i) strong charge transport and magnetic anisotropy and (ii) emergence
of a huge number of magnetic phases in the ground state of TmB12
antiferromagnetic metal with fcc crystal structure and dynamic charge stripes.
By analyzing the angular H-fi magnetic phase diagrams reconstructed from
experimental angle-resolved magnetoresistance and magnetization data we argue
that the symmetry lowering is a consequence of suppression of the indirect
Ruderman- Kittel-Kasuya-Yosida (RKKY) exchange along 110 directions between
nearest neighboring magnetic moments of Tm3+ ions and subsequent redistribution
of conduction electrons to quantum fluctuations of the electron density
(stripes). Magnetoresistance components are discussed in terms of charge
scattering on the spin density wave, itinerant ferromagnetic nano-domains and
on-site Tm3+ spin fluctuations.

###Electrical detection of the spin-flop and room-temperature magnetic ordering in van der Waals CrPS$_{4}$/(Pt, Pd) heterostructures|Rui Wu,Andrew Ross,Shilei Ding,Yuxuan Peng,Fangge He,Yi Ren,Romain Lebrun,Yong Wu,Zhen Wang,Jinbo Yang,Arne Brataas,Mathias Kläui###

Electrical detection of the spin-flop and room-temperature magnetic ordering in van der Waals CrPS$_{4}$/(Pt, Pd) heterostructures. We study magneto-transport in heterostructures composed of the van der Waals
antiferromagnet CrPS$_{4}$ and the heavy metals Pt and Pd. The transverse
resistance (R$_{xy}$) signal reveals the spin-flop transition of CrPS$_{4}$ and
a strongly enhanced magnetic ordering temperature (>300 K), which might
originate from a strong spin-orbit coupling at the interface. While
CrPS$_{4}$/Pt devices allow for easy detection of the spin-flop transition,
CrPS$_{4}$/Pd devices show a more substantial enhancement in magnetic ordering
temperature and exhibit a topological Hall effect signal, possibly related to
chiral spin structures at the interface. The longitudinal magnetoresistance
(R$_{xx}$) results from a combination of spin-Hall magnetoresistance and the
negative magnetoresistance that can be explained by a field-induced change of
the electronic band structure of CrPS$_{4}$.

###Perpendicular magnetic tunnel junctions with multi-interface free layer|Pravin Khanal,Bowei Zhou,Magda Andrade,Yanliu Dang,Albert Davydov,Ali Habiboglu,Jonah Saidian,Adam Laurie,Jian-Ping Wang,Daniel B Gopman,Weigang Wang###

Perpendicular magnetic tunnel junctions with multi-interface free layer. Future generations of magnetic random access memory demand magnetic tunnel
junctions that can provide simultaneously high magnetoresistance, strong
retention, low switching energy and small cell size below 10nm. Here we study
perpendicular magnetic tunnel junctions with composite free layers where
multiple ferromagnet/nonmagnet interfaces can contribute to the thermal
stability. Different nonmagnetic materials (MgO, Ta, Mo) have been employed as
the coupling layers in these multi-interface free layers. The evolution of
junction properties under different annealing conditions is investigated. A
strong dependence of tunneling magnetoresistance on the thickness of the first
CoFeB layer has been observed. In junctions where Mo and MgO are used as
coupling layers, large tunneling magnetoresistance above 200% has been achieved
after 400{\deg}C annealing.

###Combined Magnetic Imaging and Anisotropic Magnetoresistance Detection of Dipolar Skyrmions|Jin Tang,Jialiang Jiang,Ning Wang,Yaodong Wu,Yihao Wang,Junbo Li,Y. Soh,Yimin Xiong,Lingyao Kong,Shouguo Wang,Mingliang Tian,Haifeng Du###

Combined Magnetic Imaging and Anisotropic Magnetoresistance Detection of Dipolar Skyrmions. Magnetic skyrmions are localized particle-like nontrivial swirls that are
promising in building high-performance topological spintronic devices. The
read-out functions in skyrmionic devices require the translation of magnetic
skyrmions to electrical signals. Here, we report combined real-space magnetic
imaging and anisotropic magnetoresistance studies on dipolar skyrmions. A
single skyrmion chain and single skyrmion are observed using Lorentz
transmission electron microscopy imaging. Meanwhile, the field, helicity, and
skyrmion count dependence of anisotropic magnetoresistance of the Fe3Sn2
nanostructures are obtained simultaneously. Our results demonstrate that the
anisotropic magnetoresistance of skyrmions is independent of the helicity and
proportional to the skyrmion count. Our work could promote read-out operations
in skyrmion-based spintronic devices.

###Low-temperature magnetoresistance hysteresis in Vanadium-doped Bi$_{2}$Te$_{2.4}$Se$_{0.6}$ bulk topological insulators|Birkan Düzel,Christian Riha,Karl Graser,Olivio Chiatti,Saskia F. Fischer###

Low-temperature magnetoresistance hysteresis in Vanadium-doped Bi$_{2}$Te$_{2.4}$Se$_{0.6}$ bulk topological insulators. Bi$_{2}$Te$_{2.4}$Se$_{0.6}$ single crystals show gapless topological surface
states and doping with Vanadium allows to shift the chemical potential in the
bulk band gap. Accordingly, the resistivity, carrier density, and mobility are
constant below 10 K and the magnetoresistance shows weak antilocalization as
expected for low-temperature transport properties dominated by gapless surface
states of so-called three-dimensional topological "insulators". However, the
magnetoresistance also shows a hysteresis depending on the sweep rate and the
magnetic field direction. Here, we provide evidence for
Bi$_{2-x}$Te$_{2.4}$Se$_{0.6}$ single crystals with concentrations $x$ = 0,
0.015 and 0.03 of Vanadium, that such magnetoresistance hysteresis is enhanced
if both, three-dimensional bulk states and quasi-two-dimensional topological
states contribute to the transport ($x$ = 0 and 0.03), and it is mostly
suppressed if the topological states govern transport ($x$ = 0.015). The
results are discussed in terms of spin-dependent scattering between the
different available states.

###Inverse Ising effect and Ising magnetoresistance|Duo Zhao,Jiaqian Sun,Wei Tang,Yu-Jia Zeng###

Inverse Ising effect and Ising magnetoresistance. Ising (Zeeman-type) spin-orbit coupling (SOC) generated by in-plane inverse
asymmetry has attracted considerable attention, especially in Ising
superconductors and spin-valley coupling physics. However, many unconventional
observations and emerging physical phenomena remain to be elucidated. Here, we
theoretically study the spin texture of {\sigma}_z (spin angular momentum
projection along z) induced by Ising SOC in 1Td WTe2, and propose an
unconventional spin-to-charge conversion named inverse Ising effect, in which
the directions of the spin current, spin polarization and charge current are
not orthogonal. In particular, we predict the Ising magnetoresistance, whose
resistance depends on the out-of-plane magnetic momentum in WTe2/ferromagnetic
heterostructure. The Ising magnetoresistance is believed to be an interesting
counterpart to the well studied spin Hall magnetoresistance. Our predictions
provide promising way to spin-momentum locking and spin-charge conversion based
on emerging Ising SOC.

###Quantum Interference by Vortex Supercurrents|G. P. Papari,V. M. Fomin###

Quantum Interference by Vortex Supercurrents. We analyze the origin of the parabolic background of magnetoresistance
oscillations measured in finite-width superconducting mesoscopic rings with
input and output stubs and in patterned films. The transmission model
explaining the sinusoidal oscillation of magnetoresistance is extended to
address the parabolic background as a function of the magnetic field. Apart
from the interference mechanism activated by the ring, pinned superconducting
vortices as topological defects introduce a further interference-based
distribution of supercurrents that affects, in turn, the voltmeter-sensed
quasiparticles. The onset of vortices changes the topology of the
superconducting state in a mesoscopic ring in a such a way that the full
magnetoresistance dynamics can be interpreted owing to the interference of the
constituents of the order parameter induced by both the ring with its
doubly-connected topology and the vortex lattice in it.

###Axial anomaly and longitudinal magnetoresistance of a generic three dimensional metal|Pallab Goswami,J. H. Pixley,S. Das Sarma###

Axial anomaly and longitudinal magnetoresistance of a generic three dimensional metal. We show that the emergence of the axial anomaly is a universal phenomenon for
a generic three dimensional metal in the presence of parallel electric ($E$)
and magnetic ($B$) fields. In contrast to the expectations of the classical
theory of magnetotransport, this intrinsically quantum mechanical phenomenon
gives rise to the longitudinal magnetoresistance for any three dimensional
metal. However, the emergence of the axial anomaly does not guarantee the
existence of negative longitudinal magnetoresistance. We show this through an
explicit calculation of the longitudinal magnetoconductivity in the quantum
limit using the Boltzmann equation, for both short-range neutral and long-range
ionic impurity scattering processes. We demonstrate that the ionic scattering
contributes a large positive magnetoconductivity $\propto B^2$ in the quantum
limit, which can cause a strong negative magnetoresistance for any three
dimensional or quasi-two dimensional metal. In contrast, the finite range
neutral impurities and zero range point impurities can lead to both positive
and negative longitudinal magnetoresistance depending on the underlying band
structure. In the presence of both neutral and ionic impurities, the
longitudinal magnetoresistance of a generic metal in the quantum limit
initially becomes negative, and ultimately becomes positive after passing
through a minimum. We discuss in detail the qualitative agreement between our
theory and recent observations of negative longitudinal magnetoresistance in
Weyl semimetals TaAs and TaP, Dirac semimetals Na$_3$Bi, Bi$_{1-x}$Sb$_x$, and
ZrTe$_5$, and quasi-two dimensional metals PdCoO$_2$,
$\alpha$-(BEDT-TTF)$_2$I$_3$ which do not possess any bulk three dimensional
Dirac or Weyl quasiparticles.

###Angular Dependent Magnetoresistance Oscillation of a Quasi-Two-Dimensional System in a Periodic Potential|Daijiro Yoshioka###

Angular Dependent Magnetoresistance Oscillation of a Quasi-Two-Dimensional System in a Periodic Potential. (BEDT-TTF)$_2$MHg(SCN)$_4$[M:K,Rb,Tl] shows typical two-dimensional angular
dependent magnetoresistance oscillation (ADMRO) at high temperature (T$>$8K),
but at lower temperature it shows anomalously large magnetoresistance, and the
ADMRO pattern changes. These low temperature behaviors are explained as effects
of a periodic potential. The present explanation is different from that by
Kartsovnik et al. [J. Phys. I France {\bf 3} (1993) 1187] in that
reconstruction of the cylindrical Fermi surface into an open Fermi surface is
not assumed. It is also predicted that if the periodic potential exists at
quantizing magnetic field, resistivity peak of new origin should be observed.

###Magnetoresistance in La(1-x)SrxCoO3 for 0.05 - x - 0.25|Vladimir Golovanov,Laszlo Mihaly,A. R. Moodenbaugh###

Magnetoresistance in La(1-x)SrxCoO3 for 0.05 - x - 0.25. The dc resistivity, magnetoresistance and magnetic susceptibility of
La(1-x)SrxCoO3 compounds have been investigated in the temperature range of 4K
to 300K for magnetic fields up to 7 T. In the doping range studied (0.05 - x -
0.25) the electronic properties of the material exhibit a crossover from
semiconducting to metallic behavior. The magnetoresistance is highest in the
semiconducting state. A correlation was found between the energy gap determined
from the dc conductivity and the energy scale identified from neutron
scattering data. The results are interpreted in terms of a double exchange
model.

###Polaron transport and lattice dynamics in colossal magnetoresistance manganites|J. D. Lee,B. I. Min###

Polaron transport and lattice dynamics in colossal magnetoresistance manganites. Based on the model combining the spin double exchange and the lattice
polaron, we have studied the colossal magnetoresistance phenomena observed in
perovskite manganites R_{1-x}A_xMnO_3. First, effects of both the double
exchange and the electron-phonon interaction on the transport property are
investigated. We have evaluated the temperature dependent resistance and the
magnetoresistance using the Kubo formula, and examined the crossover from
tunneling to hopping regime of small polarons. Second, effects of the double
exchange interaction on the lattice degree of freedom are explored. It is found
that both the hardening of the phonon frequency and the reduction of the phonon
damping take place with decreasing the temperature.

###Magnetoresistance in Mn pyrochlore: electrical transport in a low carrier density ferromagnet|Pinaki Majumdar,Peter Littlewood###

Magnetoresistance in Mn pyrochlore: electrical transport in a low carrier density ferromagnet. We discuss magnetotransport in a low density electron gas coupled to spin
fluctuations near and above a ferromagnetic transition. Provided the density is
low enough ($n \lesssim 1/\xi^{3}(T)$, with $\xi(T)$ the ferromagnetic
correlation length), spin polarons form in an intermediate temperature regime
above $T_c$. Both in the spin polaron regime, and in the itinerant regime
nearer $T_c$, the magnetoresistance is large. We propose that this provides a
good model for ``colossal'' magnetoresistance in the pyrochlore
Tl$_{2-x}$Sc$_x$Mn$_2$O$_7$, fundamentally different from the mechanism in the
perovskite manganites such as La$_{1-x}$Sr$_x$MnO$_3$.

###Universal Relationship Between Giant Magnetoresistance and Anisotropic Magnetoresistance in Spin Valve Multilayers|B. H. Miller,Branko P. Stojkovi'c,E. D. Dahlberg###

Universal Relationship Between Giant Magnetoresistance and Anisotropic Magnetoresistance in Spin Valve Multilayers. We measure the giant magnetoresistance (GMR) with the current both parallel
and perpendicular to the direction of the magnetization in the ferromagnetic
(FM) layers and thus probe the anisotropy of the effective mean free paths for
the spin-up and spin-down electrons, seen in the anisotropic magnetoresistance.
We find that the difference of the GMR in the two configurations, when
expressed in terms of the sheet conductance, displays a nearly universal
behavior as a function of GMR. On interpreting the results within the Boltzmann
transport formalism we demonstrate the importance of bulk scattering for GMR.

###Spin-Dependent Coulomb Blockade in Ferromagnet/Normal-Metal/Ferromagnet Double Tunnel Junctions|Hiroshi Imamura,Saburo Takahashi,Sadamichi Maekawa###

Spin-Dependent Coulomb Blockade in Ferromagnet/Normal-Metal/Ferromagnet Double Tunnel Junctions. We study theoretically the spin-dependent transport in
ferromagnet/normal-metal/ferromagnet double tunnel junctions by special
attention to cotunneling in the Coulomb blockade region. The spin accumulation
caused by cotunneling squeezes the Coulomb blockade region when the
magnetizations in the ferromagnetic electrodes are antiparallel. Outside the
squeezed Coulomb blockade region, we propose a new anomalous region, where the
sequential tunneling in one of the spin bands is suppressed by the Coulomb
blockade and that in the other is not. In this region, the tunnel
magnetoresistance oscillates as a function of bias voltage. The temperature
dependences of the tunnel magnetoresistance and the magnitude of the spin
accumulation are calculated.

###Theory of angular magnetoresistance oscillations in Tl2Ba2CuO6|Adrian Dragulescu,Victor M. Yakovenko,David J. Singh###

Theory of angular magnetoresistance oscillations in Tl2Ba2CuO6. Using the calculated electron energy band structure of Tl2Ba2CuO6, we compute
the dependence of the c axis magnetoresistance on the orientation of the
magnetic field for different magnitudes of the magnetic field. We explain the
known experimental results for the in-plane rotation of the magnetic field and
predict the shape of the magnetoresistance oscillations for the out-of-plane
rotations of the magnetic field. We show how the latter oscillations can be
utilized to reconstruct the shape of the Fermi surface and to study the
coherence of inter-plane electron tunneling.

###Negative Magnetoresistance of Granular Metals in a Strong Magnetic Field|I. S. Beloborodov,K. B. Efetov###

Negative Magnetoresistance of Granular Metals in a Strong Magnetic Field. The magnetoresistance of a granular superconductor in a strong magnetic field
destroying the gap in each grain is considered. It is assumed that the
tunneling between grains is sufficiently large such that all conventional
effects of localization can be neglected. A non-trivial sensitivity to the
magnetic field comes from superconducting fluctuations leading to the formation
of virtual Cooper pairs and reducing the density of states. At low temperature,
the pairs do not contribute to the macroscopic transport but their existence
can drastically reduce the conductivity. Growing the magnetic field one
destroys the fluctuations, which improves the metallic properties and leads to
the negative magnetoresistance.

###Observation of a temperature dependent electrical resistance minimum above the magnetic ordering temperature in Gd$_2$PdSi$_3$|R. Mallik,E. V. Sampathkumaran,M. Strecker,G. Wortmann###

Observation of a temperature dependent electrical resistance minimum above the magnetic ordering temperature in Gd$_2$PdSi$_3$. Results on electrical resistivity, magnetoresistance, magnetic Results on
electrical resistivity, magnetoresistance, magnetic susceptibility, heat
capacity and Gd Mossbauer measurements on a Gd-based intermetallic compound,
Gd$_{2}$PdSi$_{3}$ are reported. A finding of interest is that the resistivity
unexpectedly shows a well-defined minimum at about 45 K, well above the long
range magnetic ordering temperature (21 K), a feature which gets suppressed by
the application of a magnetic field. This observation in a Gd alloy presents an
interesting scenario. On the basis of our results, we propose electron
localization induced by s-f (or d-f) exchange interaction prior to long range
magnetic order as a mechanism for the electrical resistance minimum.

###Angular Dependence of C-Axis Magnetoresistance in Bi-2212 Single Crystals With Columnar Defects|N. Morozov,L. N. Bulaevskii,M. P. Maley,J. Y. Coulter,A. E. Koshelev,T. -W. Li###

Angular Dependence of C-Axis Magnetoresistance in Bi-2212 Single Crystals With Columnar Defects. We measured the angular dependence of the c-axis magnetoresistance rho_c(B)
of Bi-2212 irradiated with heavy ions. At temperatures near 68 K the scaling of
rho_c(B) with the c-axis magnetic field component B_perp is broken and the
in-plane field, B_parallel, affects rho_c. At this temperature, at a specific
field B_cr \approx B_Phi/2, magnetoresistance becomes independent of field
orientation. This crossing point allows us to estimate the correlation length L
of pancake positions along the c axis. We find L/s is about 100 at B=B_cr,
where s is the interlayer spacing. This provides evidence of strong enhancement
of pancake alignment in the vortex liquid in crystals with columnar defects.

###Field-asymmetric transverse magnetoresistance in a nonmagnetic quantum-size structure|A. A. Gorbatsevich,V. V. Kapaev,Yu. V. Kopaev,I. V. Kucherenko,O. E. Omel'yanovskii,V. I. Tsebro###

Field-asymmetric transverse magnetoresistance in a nonmagnetic quantum-size structure. A new phenomenon is observed experimentally in a heavily doped asymmetric
quantum-size structure in a magnetic field parallel to the quantum-well layers
- a transverse magnetoresistance which is asymmetric in the field (there can
even be a change in sign) and is observed in the case that the structure has a
built-in lateral electric field. A model of the effect is proposed. The
observed asymmetry of the magnetoresistance is attributed to an additional
current contribution that arises under nonequilibrium conditions and that is
linear in the gradient of the electrochemical potential and proportional to the
parameter characterizing the asymmetry of the spectrum with respect to the
quasimomentum.

###Magnetic behaviour of Eu_2CuSi_3: Large negative magnetoresistance above Curie temperature|Subham Majumdar,R. Mallik,E. V. Sampathkumaran,Kirsten Rupprecht,G. Wortmann###

Magnetic behaviour of Eu_2CuSi_3: Large negative magnetoresistance above Curie temperature. We report here the results of magnetic susceptibility,
electrical-resistivity, magnetoresistance (MR), heat-capacity and ^{151}Eu
Mossbauer effect measurements on the compound, Eu_2CuSi_3, crystallizing in an
AlB_2-derived hexagonal structure. The results establish that Eu ions are
divalent, undergoing long-range ferromagnetic-ordering below (T_C=) 37 K. An
interesting observation is that the sign of MR is negative even at temperatures
close to 3T_C, with increasing magnitude with decreasing temperature exhibiting
a peak at T_C. This observation, being made for a Cu containing magnetic
rare-earth compound for the first time, is of relevance to the field of
collosal magnetoresistance.

###Anisotropic magnetoresistive properties of La_{1-x}Ca_{x}MnO_{3} (x \approx 1/3) film at temperatures far below the Curie temperature|B. I. Belevtsev,V. B. Krasovitsky,D. G. Naugle,K. D. D. Rathnayaka,A. Parasiris###

Anisotropic magnetoresistive properties of La_{1-x}Ca_{x}MnO_{3} (x \approx 1/3) film at temperatures far below the Curie temperature. A sharp distinction between magnetoresistance (MR) behavior for the magnetic
fields applied perpendicular (H_{perp}) and parallel (H_{par}) to the film
plane is found in colossal-magnetoresistance film La_{1-x}Ca_{x}MnO_{3} (x
\approx 3). At increasing of H_{perp} the MR is first negative (at H_{perp} < 4
kOe), then positive (4 kOe < H_{perp} < 12 kOe), and then negative again
(H_{perp} > 12 kOe). At increasing of H_{par} the MR is positive below H_{par}
\simeq 6 kOe and negative above it. In both cases the magnetic field was
perpendicular to the current. The anisotropic behavior of this kind occurs only
at low temperatures (T < 18 K) and is quite different from the results of
previous studies.

###Percolative phase separation induced by nonuniformly distributed excess oxygens|Ilryong Kim,Joonghoe Dho,Soonchil Lee###

Percolative phase separation induced by nonuniformly distributed excess oxygens. The zero-field $^{139}$La and $^{55}$Mn nuclear magnetic resonances were
studied in $\rm La_{0.8}Ca_{0.2}MnO_{3+\delta}$ with different oxygen
stoichiometry $\delta$. The signal intensity, peak frequency and line
broadening of the $^{139}$La NMR spectrum show that excess oxygens have a
tendency to concentrate and establish local ferromagnetic ordering around
themselves. These connect the previously existed ferromagnetic clusters
embedded in the antiferromagnetic host, resulting in percolative conduction
paths. This phase separation is not a charge segregation type, but a
electroneutral type. The magnetoresistance peak at the temperature where
percolative paths start to form provides a direct evidence that phase
separation is one source of colossal magnetoresistance effect.

###Anisotropic magnetoresistance of GaAs two-dimensional holes|S. J. Papadakis,E. P. De Poortere,M. Shayegan,R. Winkler###

Anisotropic magnetoresistance of GaAs two-dimensional holes. Experiments on high-quality GaAs (311)A two-dimensional holes at low
temperatures reveal a remarkable dependence of the magnetoresistance, measured
with an in-plane magnetic field ($B$), on the direction of $B$ relative to both
the crystal axes and the current direction. The magnetoresistance features, and
in particular the value of $B$ above which the resistivity exhibits an
insulating behavior, depend on the orientation of $B$. To explain the data, the
anisotropic band structure of the holes and a re-population of the
spin-subbands in the presence of $B$, as well as the coupling of the orbital
motion to $B$, need to be taken into account.

###Giant AC magnetoresistance and anisotropic AC magnetoresistance in granular magnetic alloys|A. B. Pakhomov,J. C. Denardin,M. Knobel,O. F. de Lima###

Giant AC magnetoresistance and anisotropic AC magnetoresistance in granular magnetic alloys. (withdrawn)AC resistance of melt-spun granular magnetic Cu85Co15 ribbons was
measured as a function of temperature in the range 5-300 K, magnetic field Hdc
in the range -60 kOe to 60 kOe, and frequency in the range 1-1000 Hz. A sharp
peak of zero-field resistance, which scales with frequency, and an associated
isotropic giant AC magnetoresistance in small fields are observed around the
temperature of collective freezing of interacting magnetic moments. Anomalous
behavior of AC resistance in large fields (Hdc > 20 kOe) is observed in a much
broader temperature range. This effect is not only frequency- dependent, but
also highly sensitive to anisotropy. We call it anisotropic AC
magnetoresistance.

###Measuring anisotropic scattering in the cuprates|K. G. Sandeman,A. J. Schofield###

Measuring anisotropic scattering in the cuprates. A simple model of anisotropic scattering in a quasi two-dimensional metal is
studied. Its simplicity allows an analytic calculation of transport properties
using the Boltzmann equation and relaxation time approximation. We argue that
the c-axis magnetoresistance provides the key test of this model of transport.
We compare this model with experiments on overdoped Tl-2201 and find reasonable
agreement using only weak scattering anisotropy. We argue that optimally doped
Tl-2201 should show strong angular-dependent magnetoresistance within this
model and would provide a robust way of determining the in-plane scattering
anisotropy in the cuprates.

###Current induced switching of magnetic domains to a perpendicular configuration|Xavier Waintal,Piet W. Brouwer###

Current induced switching of magnetic domains to a perpendicular configuration. In a ferromagnet--normal-metal--ferromagnet trilayer, a current flowing
perpendicularly to the layers creates a torque on the magnetic moments of the
ferromagnets. When one of the contacts is superconducting, the torque not only
favors parallel or antiparallel alignment of the magnetic moments, as is the
case for two normal contacts, but can also favor a configuration where the two
moments are perpendicular. In addition, whereas the conductance for parallel
and antiparallel magnetic moments is the same, signalling the absence of giant
magnetoresistance in the usual sense, the conductance is greater in the
perpendicular configuration. Thus, a negative magnetoconductance is predicted,
in contrast with the usual giant magnetoresistance.

###Interaction effects and the metallic phase in p-SiGe|P. T. Coleridge,A. S. Sachrajda,P. Zawadzki###

Interaction effects and the metallic phase in p-SiGe. Magnetoresistance results are presented for p-SiGe samples on the metallic
side of the B=0 metal-insulator transition. The results cannot be understood
within the framework of standard theories for quantum corrections of a weakly
interacting 2- dimensional system. In particular no logarithmic dependence on
temperature is observed, at low fields, in either the longitudinal or Hall
resistivities despite evidence in the magnetoresistance of weak localisation
effects. Further, the Hall coefficient shows a strong logarithmic dependence on
field. The results are better explain by renormalisation group theories and by
an anomalous Hall effect associated with strong spin-orbit coupling in the
presence of a background spin texture.

###Field-induced metal-insulator transition in a two-dimensional organic superconductor|J. Wosnitza,S. Wanka,J. Hagel,H. v. Loehneysen,J. S. Qualls,J. S. Brooks,E. Balthes,J. A. Schlueter,U. Geiser,J. Mohtasham,R. W. Winter,G. L. Gard###

Field-induced metal-insulator transition in a two-dimensional organic superconductor. The quasi-two-dimensional organic superconductor
beta-(BEDT-TTF)_2SF_5CH_2CF_2SO_3 (T_c approx 4.4 K)shows very strong
Shubnikov-de Haas (SdH) oscillations which are superimposed on a highly
anomalous steady background magnetoresistance, R_b. Comparison with de Haas-
van Alphen oscillations allow a reliable estimate of R_b which is crucial for
the correct extraction of the SdH signal. At low temperatures and high magnetic
fields insulating behavior evolves. The magnetoresistance data violate Kohler's
rule, i.e., cannot be described within the framework of semiclassical transport
theory, but converge onto a universal curve appropriate for dynamical scaling
at a metal-insulator transition.

###Fermi-liquid behaviour of the low-density 2D hole gas in GaAs/AlGaAs heterostructure at large values of r_s|Y. Y. Proskuryakov,A. K. Savchenko,S. S. Safonov,M. Pepper,M. Y. Simmons,D. A. Ritchie###

Fermi-liquid behaviour of the low-density 2D hole gas in GaAs/AlGaAs heterostructure at large values of r_s. We examine the validity of the Fermi-liquid description of the dilute 2D hole
gas in the crossover from 'metallic'-to-'insulating' behaviour of R(T).It has
been established that, at r_s as large as 29, negative magnetoresistance does
exist and is well described by weak localisation. The dephasing time extracted
from the magnetoresistance is dominated by the T^2 -term due to Landau
scattering in the clean limit. The effect of hole-hole interactions, however,
is suppressed when compared with the theory for small r_s.

###Negative Magnetoresistance Produced by Hall Fluctuations in a Ferromagnetic Domain Structure|Sergey V. Barabash,D. Stroud###

Negative Magnetoresistance Produced by Hall Fluctuations in a Ferromagnetic Domain Structure. We present a model for a negative magnetoresistance (MR) that would develop
in a material with many ferromagnetic domains even if the individual domains
have no magnetoresistance and even if there is no boundary resistance. The
negative MR is due to a classical current-distortion effect arising from
spatial variations in the Hall conductivity, combined with a change in domain
structure due to an applied magnetic field. The negative MR can exceed 1000% if
the product of the carrier relaxation time and the internal magnetic field due
to spontaneous magnetization is sufficiently large.

###Giant Magnetoresistance by Exchange Springs in DyFe$_2$/YFe$_2$ Superlattices|S. N. Gordeev,J-M. L. Beaujour,G. J. Bowden,P. A. J. de Groot,B. D. Rainford,R. C. C. Ward,M. R . Wells,A. G. M. Jansen###

Giant Magnetoresistance by Exchange Springs in DyFe$_2$/YFe$_2$ Superlattices. Magnetization and magnetoresistance measurements are reported for
antiferromagnetically coupled DyFe$_2$/YFe$_2$ multilayers in fields up to 23
T. We demonstrate that the formation of short exchange springs (~ 2 nm) in the
magnetically soft YFe$_2$ layers results in a giant magneto-resistance as high
as 32% in the spring region. It is shown that both the magnitude of the effect,
and its dependence on magnetic field, are in good agreement with the theory of
Levy and Zhang for giant magnetoresistance due to domain wall like structures.

###Magnetic field effects on two-dimensional Kagome lattices|Takashi Kimura,Hiroyuki Tamura,Kenji Shiraishi,Hideaki Takayanagi###

Magnetic field effects on two-dimensional Kagome lattices. Magnetic field effects on single-particle energy bands (Hofstadter
butterfly), Hall conductance, flat-band ferromagnetism, and magnetoresistance
of two-dimensional Kagome lattices are studied. The flat-band ferromagnetism is
shown to be broken as the flat-band has finite dispersion in the magnetic
field. A metal-insulator transition induced by the magnetic field (giant
negative magnetoresistance) is predicted. In the half-filled flat band, the
ferromagnetic-paramagnetic transition and the metal-insulator one occur
simultaneously at a magnetic field for strongly interacting electrons. All of
the important magnetic fields effects should be observable in mesoscopic
systems such as quantum dot superlattices.

###Magnetotransport Mechanisms in Strongly Underdoped YBa_2Cu_3O_x Single Crystals|E. Cimpoiasu,G. A. Levin,C. C. Almasan,A. P. Paulikas,B. W. Veal###

Magnetotransport Mechanisms in Strongly Underdoped YBa_2Cu_3O_x Single Crystals. We report magnetoresistivity measurements on strongly underdoped YBa_2Cu_3O_x
(x=6.25, 6.36) single crystals in applied magnetic fields H || c-axis. We
identify two different contributions to both in-plane and out-of-plane
magnetoresistivities. The first contribution has the same sign as the
temperature coefficient of the resistivity \partial ln(\rho_i)/\partial T
(i={c,ab}). This contribution reflects the incoherent nature of the
out-of-plane transport. The second contribution is positive, quadratic in
field, with an onset temperature that correlates to the antiferromagnetic
ordering.

###High-Field Properties of Single-Crystalline Cavo3|M. H. Jung,I. H. Inoue,H. Nakotte,A. H. Lacerda###

High-Field Properties of Single-Crystalline Cavo3. The magnetic properties of perovskite CaVO3 single crystals have been studied
by means of magnetoresistance r(T, H) and magnetization M(H) measurements in
fields to 18T. At 2 K, the magnetoresistance is positive and a maximum value of
Dr(18T)/r(0) = 16.5% is found for H//a. The magnetization exhibits a smooth
increase at 2 K, reaching values of M(18T) = 0.03, 0.05, 0.17 mB/f.u. for H//a,
H//b, and H//c, respectively. This anisotropy found in M(H) is consistent with
that observed for Dr(H//a) > Dr(H//b) > Dr(H//c). These results can be
interpreted in terms of the field-dependent scattering mechanism of CaVO3.

###Tunnel magnetoresistance and interfacial electronic state|J. Inoue,H. Itoh###

Tunnel magnetoresistance and interfacial electronic state. We study the relation between tunnel magnetoresistance (TMR) and interfacial
electronic states modified by magnetic impurities introduced at the interface
of the ferromagnetic tunnel junctions, by making use of the periodic Anderson
model and the linear response theory. It is indicated that the TMR ratio is
strongly reduced depending on the position of the $d$-levels of impurities,
based on reduction in the spin-dependent $s$-electron tunneling in the majority
spin state. The results are compared with experimental results for Cr-dusted
ferromagnetic tunnel junctions, and also with results for metallic multilayers
for which similar reduction in giant magnetoresistance has been reported.

###Magnetoresistance in the SDW state of (TMTSF)2PF6 above T*~4K; Novel effect due to the Landau quantization|Bojana Korin-Hamzic,Mario Basletic,Kazumi Maki###

Magnetoresistance in the SDW state of (TMTSF)2PF6 above T*~4K; Novel effect due to the Landau quantization. Magnetoresistance in the spin-density wave (SDW) state of (TMTSF)2PF6 is
known to exhibit a rich variety of the angular dependencies when a magnetic
field B is rotated in the b'-c*, a-b' and a-c* planes. In the presence of a
magnetic field the quasiparticle spectrum in the SDW with imperfect nesting is
quantized. In such a case the minimum quasiparticle energy depends both on the
magnetic field strength |B| and the angle \theta between the field and the
crystal direction a, b' or c*. This approach describes rather satisfactory the
magnetoresistance above T*~4K.

###Superconductivity, incoherence and Anderson localization in the crystalline organic conductor (BEDT-TTF)_3Cl_2.2H_2O at high pressures|Paul Goddard,Stanley W. Tozer,John Singleton,Arzhang Ardavan,Adam Abate,Mohamedally Kurmoo###

Superconductivity, incoherence and Anderson localization in the crystalline organic conductor (BEDT-TTF)_3Cl_2.2H_2O at high pressures. The conducting properties of the pressure-induced, layered organic
superconductor (BEDT-TTF)_3Cl_2.2H_20 have been studied at 13.5 and 14.0 kbar
using low temperatures, high magnetic fields and two-axis rotation. An upper
critical field that is significantly larger than that expected from the Pauli
paramagnetic limit is observed when the field is applied parallel to the
conducting layers. The angle dependent magnetoresistance suggests incoherent
transport between the conducting layers at both pressures and the observed
negative magnetoresistance at 13.5 kbar can be explained by considering
Anderson localization within the layers. Further application of pressure
destroys the effects of localization.

###Spin polarization and transition from metallic to insulating behavior in 2D systems|E. Tutuc,E. P. De Poortere,S. J. Papadakis,M. Shayegan###

Spin polarization and transition from metallic to insulating behavior in 2D systems. We have made quantitative measurements of the spin polarization of
two-dimensional (2D) GaAs (100) electrons and GaAs (311)A holes, as a function
of an in-plane magnetic field. The functional form of the in-plane
magnetoresistance is shown to be intimately related to the spin polarization.
Moreover, for three different 2D systems, namely GaAs (100) electrons, GaAs
(311)A holes, and AlAs (411)B electrons, the temperature dependence of the
in-plane magnetoresistance reveals that their behavior turns from metallic to
insulating before they are fully spin polarized.

###Coexistence of glassy antiferromagnetism and giant magnetoresistance (GMR) in Fe/Cr multilayer structures|N. Theodoropoulou,A. F. Hebard,M. Gabay,A. K. Majumdar,C. Pace,J. Lannon,D. Temple###

Coexistence of glassy antiferromagnetism and giant magnetoresistance (GMR) in Fe/Cr multilayer structures. Using temperature-dependent magnetoresistance and magnetization measurements
on Fe/Cr multilayers that exhibit pronounced giant magnetoresistance (GMR), we
have found evidence for the presence of a glassy antiferromagnetic (GAF) phase.
This phase reflects the influence of interlayer exchange coupling (IEC) at low
temperature (T < 140K) and is characterized by a field-independent glassy
transition temperature, Tg, together with irreversible behavior having
logarithmic time dependence below a "de Almeida and Thouless" (AT) critical
field line. At room temperature, where the GMR effect is still robust, IEC
plays only a minor role, and it is the random potential variations acting on
the magnetic domains that are responsible for the antiparallel interlayer
domain alignment.

###Observation of minority spin character of the new electron doped manganite La_0.7Ce_0.3MnO_3 from tunneling magnetoresistance|C. Mitra,P. Raychaudhuri,K. Doerr,K. -H. Mueller,L. Schultz,P. M. Oppeneer,S. Wirth###

Observation of minority spin character of the new electron doped manganite La_0.7Ce_0.3MnO_3 from tunneling magnetoresistance. We report the magnetotransport characteristics of a trilayer ferromagnetic
tunnel junction build of an electron doped manganite (La_0.7Ce_0.3MnO_3) and a
hole doped manganite (La_0.7Ca_0.3MnO_3). At low temperatures the junction
exhibits a large positive tunneling magnetoresistance (TMR), irrespective of
the bias voltage. At intermediate temperatures below T_C the sign of the TMR is
dependent on the bias voltage across the junction. The magnetoresistive
characteristics of the junction strongly suggest that La_0.7Ce_0.3MnO_3 is a
minority spin carrier ferromagnet with a high degree of spin polarization, i.e.
a transport half metal.

###Interaction Effects in Conductivity of Si Inversion Layers at Intermediate Temperatures|V. M. Pudalov,M. E. Gershenson,H. Kojima,G. Brunthaler,A. Prinz,G. Bauer###

Interaction Effects in Conductivity of Si Inversion Layers at Intermediate Temperatures. We compare the temperature dependence of resistivity \rho(T) of Si MOSFETs
with the recent theory by Zala et al. This comparison does not involve any
fitting parameters: the effective mass m* and g*-factor for mobile electrons
have been found independently. An anomalous increase of \rho with temperature,
which has been considered a signature of the "metallic" state, can be described
quantitatively by the interaction effects in the ballistic regime. The in-plane
magnetoresistance \rho(B) is qualitatively consistent with the theory; however,
the lack of quantitative agreement indicates that the magnetoresistance is more
susceptible to the sample-specific effects than \rho(T).

###Direct observation of electron doping in La0.7Ce0.3MnO3 using x-ray absorption spectroscopy|C. Mitra,Z. Hu,P. Raychaudhuri,S. Wirth,S. I. Csiszar,H. H. Hsieh,H. J. Lin,C. T. Chen,L. H. Tjeng###

Direct observation of electron doping in La0.7Ce0.3MnO3 using x-ray absorption spectroscopy. We report on a X-ray absorption spectroscopic (XAS) study on a thin film of
La0.7Ce0.3MnO3, a manganite which was previously only speculated to be an
electron doped system. The measurements clearly show that the cerium is in the
Ce(IV) valence state and that the manganese is present in a mixture of Mn2+ and
Mn3+ valence states. These data unambiguously demonstrate that La0.7Ce0.3MnO3
is an electron doped colossal magnetoresistive manganite, a finding that may
open up new opportunities both for device applications as well as for further
basic research towards a better modelling of the colossal magnetoresistance
phenomenon in these materials.

###Tight-binding model for strongly modulated two-dimensional superlattices|Karel Vyborny,Ludvik Smrcka###

Tight-binding model for strongly modulated two-dimensional superlattices. Common models describing magnetotransport properties of periodically
modulated two--dimensional systems often either directly start from a
semiclassical approach or give results well conceivable within the
semiclassical framework. Recently, magnetoresistance oscillations have been
found on samples with strong unilateral modulation and short period (d=15 nm)
which cannot be explained on a semiclassical level (magnetic breakdown). We use
a simple fully quantum mechanical model which gives us both magnetoresistance
data nicely comparing to the experiments and a good intuitive insight into the
effects taking place in the system.

###Small-angle scattering in a marginal Fermi-liquid|E. C. Carter,A. J. Schofield###

Small-angle scattering in a marginal Fermi-liquid. We study the magnetotransport properties of a model of small-angle scattering
in a marginal Fermi liquid. Such a model has been proposed by Varma and
Abrahams [Phys. Rev. Lett. 86, 4652 (2001)] to account for the anomalous
temperature dependence of in-plane magnetotransport properties of the high-Tc
cuprates. We study the resistivity, Hall angle and magnetoresistance using both
analytical and numerical techniques. We find that small-angle scattering only
generates a new temperature dependence for the Hall angle near particle-hole
symmetric Fermi surfaces where the conventional Hall term vanishes. The
magnetoresistance always shows Kohler's rule behavior.

###Nearly total spin polarization in La2/3Sr1/3MnO3 from tunneling experiments|M. Bowen,M. Bibes,A. Barthelemy,J. -P. Contour,A. Anane,Y. Lemaitre,A. Fert###

Nearly total spin polarization in La2/3Sr1/3MnO3 from tunneling experiments. We have performed magnetotransport measurements on La2/3Sr1/3MnO3 / SrTiO3 /
La2/3Sr1/3MnO3 magnetic tunnel junctions. A magnetoresistance ratio of more
than 1800 % is obtained at 4K, from which we infer an electrode spin
polarization of at least 95 %. This result strongly underscores the
half-metallic nature of mixed-valence manganites and demonstrates its
capability as a spin analyzer. The magnetoresistance extends up to temperatures
of more than 270K. We argue that these improvements over most previous works
may result from optimizing the patterning process for oxide heterostructures.

###Structure, Magnetic Properties and Spin-glass Behavior in La$sub{0.9}Tesub{0.1}MnOsub{3}$|Guotai Tan,P. Duan,S. Y. Dai,Y. L. Zhou,H. B. Lu,Z. H. Chen###

Structure, Magnetic Properties and Spin-glass Behavior in La$sub{0.9}Tesub{0.1}MnOsub{3}$. In this study we report the structure, magnetic and electrical transport
properties of pervoskite oxide La$sub{0.9}Tesub{0.1}MnOsub{3}$. This is a novel
material with the space group R-3c, which shows the spin-glass-like feature at
low temperature and has a good colossal magnetoresistance behavior. The
magnetoresistance ratio is about 51% at 200 K in a field of 4 T. The XPS
measurement suggests that Te ions are in the Te$up{4+}$ state, while Mn ions
may be in the 2+ and 3+ valence state.

###Spin-dependent magnetoresistance and spin-charge separation in multiwall carbon nanotubes|X. Hoffer,Ch. Klinke,J. -M. Bonard,L. Gravier,J. - E. Wegrowe###

Spin-dependent magnetoresistance and spin-charge separation in multiwall carbon nanotubes. The spin-dependent transport in multiwall carbon nanotubes obtained by
chemical vapor deposition (CVD) in porous alumina membranes is studied. The
zero bias anomaly is found to verify the predicted Luttinger liquid power law.
The magnetoresistance at high fields varies in sign and amplitude from one
sample to the other, which is probably due to the presence of dopant in the
tube. In contrast, the magnetoresistance due to the spin polarized current is
destroyed in the nanotube as expected in case of spin-charge separation.

###Radiation induced zero-resistance states: a dressed electronic structure effect|P. H. Rivera,P. A. Schulz###

Radiation induced zero-resistance states: a dressed electronic structure effect. Recent results on magnetoresistance in a two dimensional electron gas under
crossed magnetic and microwave fields show a new class of oscillations,
suggesting a new kind of zero-resistance states. A complete understanding of
the effect is still lacking. We consider the problem from the point of view of
the electronic structure dressed by photons due to a in plane linearly
polarized ac field. The dramatic changes in the dressed electronic structure
lead to a interpretation of the new magnetoresistance oscillations as a
persistent-current like effect, induced by the radiation field.

###Optimization of the extraordinary magnetoresistance in semiconductor-metal hybrid structures for magnetic-field sensor applications|M. Holz,O. Kronenwerth,D. Grundler###

Optimization of the extraordinary magnetoresistance in semiconductor-metal hybrid structures for magnetic-field sensor applications. Semiconductor-metal hybrid structures can exhibit a very large geometrical
magnetoresistance effect, the so-called extraordinary magnetoresistance (EMR)
effect. In this paper, we analyze this effect by means of a model based on the
finite element method and compare our results with experimental data. In
particular, we investigate the important effect of the contact resistance
$\rho_c$ between the semiconductor and the metal on the EMR effect. Introducing
a realistic $\rho_c=3.5\times 10^{-7} \Omega{\rm cm}^2$ in our model we find
that at room temperature this reduces the EMR by 30% if compared to an analysis
where $\rho_c$ is not considered.

###Field-tuned Collapse of an Orbital Ordered and Spin-polarized State: Colossal Magnetoresistance in Bilayered Ruthenate|G. Cao,L. Balicas,X. N. Lin,S. Chikara,V. Duairaj,E. Elhami,J. W. Brill,R. C. Rai###

Field-tuned Collapse of an Orbital Ordered and Spin-polarized State: Colossal Magnetoresistance in Bilayered Ruthenate. Ca3Ru2O7 with a Mott-like transition at 48 K features different in-plane
anisotropies of magnetization and magnetoresistance. Applying magnetic field
along the magnetic easy-axis precipitates a spin-polarized state via a
first-order metamagnetic transition, but does not lead to a full suppression of
the Mott state, whereas applying magnetic field along the magnetic hard axis
does, causing a resistivity reduction of three orders of magnitude. The
colossal magnetoresistivity is attributed to the collapse of the orbital
ordered and spin-polarized state. Evidence for a density wave is also
presented.

###Crossed Andreev Reflection in Structures Consisting of a Superconductor with Ferromagnetic Leads|Taro Yamashita,Saburo Takahashi,Sadamichi Maekawa###

Crossed Andreev Reflection in Structures Consisting of a Superconductor with Ferromagnetic Leads. A theory of crossed Andreev reflection in structures consisting of a
superconductor with two ferromagnetic leads is presented. The electric current
due to the crossed Andreev reflection strongly depends on the relative
orientation of the magnetization of two ferromagnetic leads. It is shown that
the dependence of the electric current and the magnetoresistance on the
distance between two ferromagnetic leads is understood by considering the
interference between the wave functions in ferromagnets. The current and the
magnetoresistance are calculated as functions of the exchange field and the
height of the interfacial barriers.

###Temperature Dependence of Resistivity of $Sr_2CoMoO_{6-δ}$ Films|C. L. Yuan,Z. Y. Zeng,Y. Zhu,P. P. Ong,Z. X. Shen,C. K. Ong###

Temperature Dependence of Resistivity of $Sr_2CoMoO_{6-δ}$ Films. We investigate the temperature dependence of the resistivity and
magnetoresistance of a polycrystalline $Sr_2CoMoO_{6-\delta}$ film deposited on
(100)-$SrTiO_3$ substrate prepared by the pulsed laser deposition method. X-ray
diffraction, Raman and magnetoresistance results demonstrate clearly the
coexistence of a ferromagnetic metallic and an antiferromagnetic (or
paramagnetic) insulating domain. Percolative transition between these two
phases as the temperature varies, which is believed to induce a metal-insulator
transition at around $T_C$, has been directly observed in our measurements of
the temperature dependence of the sample resistivity. Thus we have provided new
direct evidence that a phase separation scenario also exists in the ordered
double-perovskite structure materials.

###Phase coherent transport in Kondo/superconducting hybrid structures|Jonghwa Eom,Yun-Sok Shin,Hu-Jong Lee,Wang-Hyun Park,Taegon Kim,Jonghan Song###

Phase coherent transport in Kondo/superconducting hybrid structures. We present measurements of the transport properties of hybrid structures
consisting of a Kondo AuFe film and a superconducting Al film. The temperature
dependence of the resistance indicates the existence of the superconducting
proximity effect in the Kondo AuFe wires over the range of $\sim0.5$ $\mu$m.
Electronic phase coherence in the Kondo AuFe wires has been confirmed by
observing the Aharanov-Bohm effect in the magnetoresistance of the loop
structure. The amplitude of the magnetoresistance oscillations shows a
reentrant behavior with a maximum at $\sim$ 870 mK, which results from an
interplay between the Kondo effect and the superconducting proximity effect.

###Nanosized Sodium-Doped Lanthanum Manganites: Role of the Synthetic Route on their Physical Properties|Lorenzo Malavasi,Maria C. Mozzati,Stefano Polizzi,Carlo B. Azzoni,Giorgio Flor###

Nanosized Sodium-Doped Lanthanum Manganites: Role of the Synthetic Route on their Physical Properties. In this paper we present the results of the synthesis and characterisation of
nanocrystalline La1-xNaxMnO3+delta samples. Two synthetic routes were employed:
polyacrylamide-based sol-gel and propellant synthesis. Pure, single phase
materials were obtained with grain size around 35 nm for the sol-gel samples
and around 55 nm for the propellant ones, which moreover present a more broaden
grain size distribution. For both series a superparamagnetic behaviour was
evidenced by means of magnetisation and EPR measurements with peculiar features
ascribable to the different grain sizes and morphology. Preliminary
magnetoresistivity measurements show enhanced low-field (< 1 T)
magnetoresistance values which suggest an interesting applicative use of these
manganites.

###Possible observation of phase coexistence of the $ν=1/3$ fractional quantum Hall liquid and a solid|G. A. Csathy,D. C. Tsui,L. N. Pfeiffer,K. W. West###

Possible observation of phase coexistence of the $ν=1/3$ fractional quantum Hall liquid and a solid. We have measured the magnetoresistance of a very low density and an extremely
high quality two-dimensional hole system. With increasing magnetic field
applied perpendicularly to the sample we observe the sequence of insulating,
$\nu=1/3$ fractional quantum Hall liquid, and insulating phases. In both of the
insulating phases in the vicinity of the $\nu=1/3$ filling the
magnetoresistance has an unexpected oscillatory behavior with the magnetic
field. These oscillations are not of the Shubnikov-de Haas type and cannot be
explained by spin effects. They are most likely the consequence of the
formation of a new electronic phase which is intermediate between the
correlated Hall liquid and a disorder pinned solid.

###High-field magnetoresistance of Fe/GaAs/Fe tunnel junctions|M. Zenger,J. Moser,W. Wegscheider,D. Weiss,T. Dietl###

High-field magnetoresistance of Fe/GaAs/Fe tunnel junctions. We investigate transport through 6 to 10 nm thin epitaxial GaAs(001) barriers
sandwiched between polycrystalline iron films. Apart from a pronounced
tunneling magnetoresistance effect (TMR) at low magnetic fields we observe a
distinct negative magnetoresistance (MR) at low and a positive MR at higher
temperatures. We show that the negative MR contribution is only observed for
the ferromagnetic iron contacts but is absent if iron is replaced by copper or
gold electrodes. Possible explanations of the negative MR involve suppression
of spin-flip scattering or Zeeman splitting of the tunneling barrier.

###New class of small amplitude low-field magnetoresistance oscillation in unidirectional lateral superlattice: Geometric resonance of Bragg-reflected cyclotron orbit|Akira Endo,Yasuhiro Iye###

New class of small amplitude low-field magnetoresistance oscillation in unidirectional lateral superlattice: Geometric resonance of Bragg-reflected cyclotron orbit. We have uncovered a new class of small amplitude magnetoresistance
oscillation in unidirectional lateral superlattice (ULSL). The oscillation is
observed in a low-field regime, typically |B| =< 0.03 T, as small undulation on
top of well-known positive magnetoresistance background. Positions of maxima of
the oscillation shift to lower field side with the increase of the electron
concentration n_e roughly proportionally to n_e^{-1/2}, and also with the
increase of period a of ULSL samples. The oscillation is attributed to
commensurability between the period a and the width of open orbits originating
from the miniband structure.

###Spin characterization and control over the regime of radiation-induced zero-resistance states|R. G. Mani###

Spin characterization and control over the regime of radiation-induced zero-resistance states. Over the regime of the radiation-induced zero-resistance states and
associated oscillatory magnetoresistance, we propose a low magnetic field
analog of quantum-Hall-limit techniques for the electrical detection of
electron spin- and nuclear magnetic- resonance, dynamical nuclear polarization
via electron spin resonance, and electrical characterization of the nuclear
spin polarization via the Overhauser shift. In addition, beats observed in the
radiation-induced oscillatory-magnetoresistance are developed into a method to
measure and control the zero-field spin splitting due to the Bychkov-Rashba and
bulk inversion asymmetry terms in the high mobility GaAs/AlGaAs system.

###1500-fold Tunneling Anisotropic Magnetoresistance in a (Ga,Mn)As stack|C. Rüster,C. Gould,T. Jungwirth,J. Sinova,G. M. Schott,R. Giraud,K. Brunner,G. Schmidt,L. W. Molenkamp###

1500-fold Tunneling Anisotropic Magnetoresistance in a (Ga,Mn)As stack. We report the discovery of a super-giant tunneling anisotropic
magnetoresistance in an epitaxially grown (Ga,Mn)As/GaAs/(Ga,Mn)As structure.
The effect arises from a strong dependence of the electronic structure of
ferromagnetic semiconductors on the magnetization orientation rather than from
a parallel or antiparallel alignment of the contacts. The key novel spintronics
features of this effect are: (i) both normal and inverted spin-valve like
signals; (ii) a large non-hysteretic magnetoresistance for magnetic fields
perpendicular to the interfaces; (iii) magnetization orientations for extremal
resistance are, in general, not aligned with the magnetic easy and hard axis.
(iv) Enormous amplification of the effect at low bias and temperatures.

###Dimensional crossover and anomalous magnetoresistivity in single crystals $Na_xCoO_2$|C. H. Wang,X. H. Chen,J. L. Luo,G. T. Liu,X. X. Lu,H. T. Zhang,G. Y. Wang,X. G. Luo,N. L. Wang###

Dimensional crossover and anomalous magnetoresistivity in single crystals $Na_xCoO_2$. The in-plane ($\rho_{ab}$) and c-axis ($\rho_c$) resistivities, and the
magnetoresistivity of single crystals $Na_xCoO_2$ with x = 0.7, 0.5 and 0.3
were studied systematically. $\rho_{ab}(T)$ shows similar temperature
dependence between $Na_{0.3}CoO_2$ and $Na_{0.7}CoO_2$, while $\rho_c(T)$ is
quite different. A dimensional crossover from two to three occurs with
decreasing Na concentration from 0.7 to 0.3. The angular dependence of in-plane
magnetoresistivity for 0.5 sample shows a \emph{"d-wave-like"} symmetry at 2K,
while the \emph{"p-wave-like"} symmetry at 20 K. These results give an evidence
for existence of a \emph{spin ordering orientation} below 20 K turned by
external field, like the stripes in cuprates.

###Low field magnetotransport in strained Si/SiGe cavities|G. Scappucci,L. Di Gaspare,F. Evangelisti,E. Giovine,A. Notargiacomo,R. Leoni,V. Piazza,P. Pingue,F. Beltram###

Low field magnetotransport in strained Si/SiGe cavities. Low field magnetotransport revealing signatures of ballistic transport
effects in strained Si/SiGe cavities is investigated. We fabricated strained
Si/SiGe cavities by confining a high mobility Si/SiGe 2DEG in a bended nanowire
geometry defined by electron-beam lithography and reactive ion etching. The
main features observed in the low temperature magnetoresistance curves are the
presence of a zero-field magnetoresistance peak and of an oscillatory structure
at low fields. By adopting a simple geometrical model we explain the
oscillatory structure in terms of electron magnetic focusing. A detailed
examination of the zero-field peak lineshape clearly shows deviations from the
predictions of ballistic weak localization theory.

###Large magnetoresistance in the magnetically ordered state as well as in the paramagnetic state near 300 K in an intermetallic compound,Gd7Rh3|Kausik Sengupta,S. Rayaprol,E. V. Sampathkumaran###

Large magnetoresistance in the magnetically ordered state as well as in the paramagnetic state near 300 K in an intermetallic compound,Gd7Rh3. We report the response of electrical resistivity $\rho$ to the application of
magnetic fields (H) up to 140 kOe in the temperature interval 1.8-300 K for the
compound, Gd7Rh3, ordering antiferromagnetically below 150 K. We find that
there is an unusually large decrease of $\rho$ for moderate values of H in the
close vicinity of room temperature uncharacteristic of paramagnets, with the
magnitude of the magnetoresistance increasing with decreasing temperature as
though the spin-order contribution to $\rho$ is temperature dependent. In
addition, this compound exhibits giant magnetoresistance behaviour at rather
high temperatures (above 77 K) in the magnetically ordered state due to a
metamagnetic transition.

###Quantitative Study of Magnetotransport through a (Ga,Mn)As Single Ferromagnetic Domain|S. T. B. Goennenwein,S. Russo,A. F. Morpurgo,T. M. Klapwijk,W. van Roy,J. de Boeck###

Quantitative Study of Magnetotransport through a (Ga,Mn)As Single Ferromagnetic Domain. We have performed a systematic investigation of the longitudinal and
transverse magnetoresistance of a single ferromagnetic domain in (Ga,Mn)As. We
find that, by taking into account the intrinsic dependence of the resistivity
on the magnetic induction, an excellent agreement between experimental results
and theoretical expectations is obtained. Our findings provide a detailed and
fully quantitative validation of the theoretical description of
magnetotransport through a single ferromagnetic domain. Our analysis
furthermore indicates the relevance of magneto-impurity scattering as a
mechanism for magnetoresistance in (Ga,Mn)As.

###Large magnetoresistance in low temperature metallic region of manganite compounds (La0.7-2xEux)(Ca0.3Srx)MnO3 (0.05<x<0.15)|D. S. Rana,C. M. Thaker,K. R. Mavani,D. G. Kuberkar,S. K. Malik###

Large magnetoresistance in low temperature metallic region of manganite compounds (La0.7-2xEux)(Ca0.3Srx)MnO3 (0.05<x<0.15). Magnetoresistance (MR) and magnetization (d.c and a.c) measurements have been
carried out on the manganites, (La0.7-2xEux)(Ca0.3Srx)MnO3 (0.05<x<0.15), in
the temperature range of 5K-320K. At 5K, an unusually large MR of almost 98% is
observed in the x=0.15 sample, nearly up to fields of 4-5 Tesla. This large
high-field MR occurs in the metallic region, far below the insulator-metal
transition temperature, and does not vary linearly with applied field. The
unusual magnetoresistance is explained the light of various possibilities of
phase segregation and cluster spin-glass behavior. Keywords: Manganites, High
field MR, Phase segregation.

###Huge Ballistic Magnetoresistance in Multiple Nanocontacts Devices|N. Garcia,M. R. Ibarra,C. Hao1,R. F. Pacheco,D. Serrate###

Huge Ballistic Magnetoresistance in Multiple Nanocontacts Devices. In this paper we report an exhaustive experimental work on magnetoresistance
effects found in a system in which a large number of nanocontacts are produced
between oxidized Fe fine particles. We have obtained the following
performances: i) Huge low field room temperature magnetoresistance (over
1000%). ii) Non-linear I-V at different applied fields and temperatures. iii)
Large thermal stability and reproducible resistance value under thermal cycles
from room temperature down to 5 K. iv) Easy to fabricate with an almost 100%
success. v) Heavy duty and transportable samples with reproducibility tested in
several laboratories. We realized that the extraordinary effect found is
related to the oxygen content at the particles surface

###Interference Effects Due to Commensurate Electron Trajectories and Topological Crossovers in (TMTSF)2ClO4|H. I. Ha,A. G. Lebed,M. J. Naughton###

Interference Effects Due to Commensurate Electron Trajectories and Topological Crossovers in (TMTSF)2ClO4. We report angle-dependent magnetoresistance measurements on (TMTSF)2ClO4 that
provide strong support for a new macroscopic quantum phenomenon, the
interference commensurate (IC) effect, in quasi-one dimensional metals. In
addition to observing rich magnetoresistance oscillations, and fitting them
with one-electron calculations, we observe a clear demarcation of
field-dependent behavior at local resistance minima and maxima (versus field
angle). Anticipated by a theoretical treatment of the IC effect in terms of
Bragg reflections in the extended Brillouin zone, this behavior results from
1D-2D topological crossovers of electron wave functions as a function of field
orientation.

###Negative magneto-resistance of electron gas in a quantum well with parabolic potential|F. M. Hashimzade,Kh. A. Hasanov,M. M. Babayev###

Negative magneto-resistance of electron gas in a quantum well with parabolic potential. We have studied the electrical conductivity of the electron gas in parallel
electric and magnetic fields directed along the plane of a parabolic quantum
well (across the profile of the potential). We found a general expression for
the electrical conductivity applicable for any magnitudes of the magnetic field
and the degree of degeneration of the electron gas. A new mechanism of
generation of the negative magnetoresistance has been revealed. It has been
shown that in a parabolic quantum well with a non-degenerated electron gas the
negative magnetoresistance results from spin splitting of the levels of the
size quantization.

###Half-metallic ferromagnets for magnetic tunnel junctions|Phivos Mavropoulos,Marjana Lezaic,Stefan Bluegel###

Half-metallic ferromagnets for magnetic tunnel junctions. Using theoretical arguments, we show that, in order to exploit half-metallic
ferromagnets in tunneling magnetoresistance (TMR) junctions, it is crucial to
eliminate interface states at the Fermi level within the half-metallic gap;
contrary to this, no such problem arises in giant magnetoresistance elements.
Moreover, based on an a priori understanding of the electronic structure, we
propose an antiferromagnetically coupled TMR element, in which interface states
are eliminated, as a paradigm of materials design from first principles. Our
conclusions are supported by ab-initio calculations.

###Unusual transport properties of ferromagnetic Heusler alloy Co$_2$TiSn|S. Majumdar,M. K. Chattopadhyay,V. K. Sharma,K. J. S. Sokhey,S. B. Roy,P. Chaddah###

Unusual transport properties of ferromagnetic Heusler alloy Co$_2$TiSn. We report results of magnetization, zero field resistivity and
magnetoresistance measurements in ferromagnetic Heusler alloy Co$_2$TiSn. There
is a striking change in the character of electron transport as the system
undergoes the paramagnetic to ferromagnetic transition. In the paramagnetic
state the nature of the electron transport is like that of a semiconductor and
this changes abruptly to metallic behaviour at the onset of ferromagnetic
ordering. Application of external magnetic field tends to suppress this
semiconducting like transport leading to a negative magnetoresistance which
reaches a peak in the vicinity of Curie temperature. Comparison is made with
the similar unusual behaviour observed in other systems including UNiSn and
manganites.

###Separating spin and charge transport in single wall carbon nanotubes|N. Tombros,S. J. van der Molen,B. J. van Wees###

Separating spin and charge transport in single wall carbon nanotubes. We demonstrate spin injection and detection in single wall carbon nanotubes
using a 4-terminal, non-local geometry. This measurement geometry completely
separates the charge and spin circuits. Hence all spurious magnetoresistance
effects are eliminated and the measured signal is due to spin accumulation
only. Combining our results with a theoretical model, we deduce a spin
polarization at the contacts of approximately 25 %. We show that the
magnetoresistance changes measured in the conventional two-terminal geometry
are dominated by effects not related to spin accumulation.

###Tunneling magnetoresistance in devices based on epitaxial NiMnSb with uniaxial anisotropy|J. Liu,E. Girgis,P. Bach,C. Ruester,C. Gould,G. Schmidt,L. W. Molenkamp###

Tunneling magnetoresistance in devices based on epitaxial NiMnSb with uniaxial anisotropy. We demonstrate tunnel magnetoresistance (TMR) junctions based on a tri layer
system consisting of an epitaxial NiMnSb, aluminum oxide and CoFe tri layer.
The junctions show a tunnelling magnetoresistance of Delta R/R of 8.7% at room
temperature which increases to 14.7% at 4.2K. The layers show clear separate
switching and a small ferromagnetic coupling. A uniaxial in plane anisotropy in
the NiMnSb layer leads to different switching characteristics depending on the
direction in which the magnetic field is applied, an effect which can be used
for sensor applications.

###Origin of positive magnetoresistance in small-amplitude unidirectional lateral superlattices|Akira Endo,Yasuhiro Iye###

Origin of positive magnetoresistance in small-amplitude unidirectional lateral superlattices. We report quantitative analysis of positive magnetoresistance (PMR) for
unidirectional-lateral-superlattice samples with relatively small periods
(a=92-184 nm) and modulation amplitudes (V_0=0.015-0.25 meV). By comparing
observed PMR's with ones calculated using experimentally obtained mobilities,
quantum mobilities, and V_0's, it is shown that contribution from streaming
orbits (SO) accounts for only small fraction of the total PMR. For small V_0,
the limiting magnetic field B_e of SO can be identified as an inflection point
of the magnetoresistance trace. The major part of PMR is ascribed to drift
velocity arising from incompleted cyclotron orbits obstructed by scatterings.

###Negative Giant Longitudinal Magnetoresistance in NiMnSb/InSb: An interface effect|S. Gardelis,J. Androulakis,Z. Viskadourakis,E. L. Papadopoulou,J. Giapintzakis###

Negative Giant Longitudinal Magnetoresistance in NiMnSb/InSb: An interface effect. We report on the electrical and magneto-transport properties of the contact
formed between polycrystalline NiMnSb thin films grown using pulsed laser
deposition (PLD) and n-type degenerate InSb (100) substrates. A negative giant
magnetoresistance (GMR) effect is observed when the external magnetic field is
parallel to the surface of the film and to the current direction. We attribute
the observed phenomenon to magnetic precipitates formed during the magnetic
film deposition and confined to a narrow layer at the interface. The effect of
these precipitates on the magnetoresistance depends on the thermal processing
of the system.

###Crossed Andreev reflection-induced magnetoresistance|F. Giazotto,F. Taddei,R. Fazio,F. Beltram###

Crossed Andreev reflection-induced magnetoresistance. We show that very large negative magnetoresistance can be obtained in
magnetic trilayers in a current-in-plane geometry owing to the existence of
crossed Andreev reflection. This spin-valve consists of a thin superconducting
film sandwiched between two ferromagnetic layers whose magnetization is allowed
to be either parallelly or antiparallelly aligned. For a suitable choice of
structure parameters and nearly fully spin-polarized ferromagnets the
magnetoresistance can exceed -80%. Our results are relevant for the design and
implementation of spintronic devices exploiting ferromagnet-superconductor
structures.

###Radiation-induced oscillatory-magnetoresistance in a tilted magnetic field in $GaAs/Al_{x}Ga_{1-x}As$ devices|R. G. Mani###

Radiation-induced oscillatory-magnetoresistance in a tilted magnetic field in $GaAs/Al_{x}Ga_{1-x}As$ devices. We examine the microwave-photoexcited magnetoresistance oscillations in a
tilted magnetic field in the high mobility two-dimensional electron system. In
analogy to the 2D Shubnikov-de Haas effect, the characteristic field, $B_{f}$,
and the period of the radiation-induced magnetoresistance oscillations appears
dependent upon the component of the applied magnetic field that is
perpendicular to the plane of the 2DES. In addition, we find that a parallel
component, $B_{//}$, in the range of $0.6 < B_{//} < 1.2$ Tesla, at a tilt
angle of $\theta = 80^{0}$, leaves the oscillatory pattern essentially
unchanged.

###Mesoscopic anisotropic magnetoconductance fluctuations in ferromagnets|Shaffique Adam,Markus Kindermann,Saar Rahav,Piet W. Brouwer###

Mesoscopic anisotropic magnetoconductance fluctuations in ferromagnets. The conductance of a ferromagnetic particle depends on the relative
orientation of the magnetization with respect to the direction of current flow.
This phenomenon is known as "anisotropic magnetoresistance". Quantum
interference leads to an additional, random dependence of the conductance on
the magnetization direction. These "anisotropic magnetoresistance fluctuations"
are caused by spin-orbit scattering, which couples the electron motion to the
exchange field in the ferromagnet. We report a calculation of the dependence of
the conductance autocorrelation function on the rotation angle of the
magnetization direction.

###Magnetism, Upper critical field and Thermoelectric power of Magneto-Superconductor RuSr2Eu1.5Ce0.5Cu2O10|R. Lal,V. P. S. Awana,H. Kishan,Rajeev Rawat,V. Ganesan,A. V. Narlikar,M. Peurla,R. Laiho###

Magnetism, Upper critical field and Thermoelectric power of Magneto-Superconductor RuSr2Eu1.5Ce0.5Cu2O10. Magnetic susceptibility, M-H plot, magnetoresistance and thermoelectric power
of the RuSr2Eu1.5Ce0.5Cu2O10 superconductor are measured. Values of the
magnetic transition temperature Tmag, superconductivity transition temperature
Tc, upper critical field Hc2, chemical potential mu, and energy width for
electric conduction W(sigma) are obtained from these measurements. It has been
found that Tmag = 140 K, Tc = 25 K (33 K) from susceptibility
(magnetoresistance) measurements, Hc2 (0) > 32 T, mu = 8 meV, and W(sigma) =
58.5 meV. These values are compared with other ruthenate superconductors, and
resulting physical information is discussed.

###Giant Magnetoresistance in an all-oxide spacerless junction|Mangala Prasad Singh,Baptiste Carvello,Laurent Ranno###

Giant Magnetoresistance in an all-oxide spacerless junction. We report the fabrication of an oxide-specific type of magnetoresistive
junction, which is a ferromagnetic bilayer. Both electrodes are high
spin-polarization oxides: magnetite (Fe3O4) and manganite (La0.7Sr0.3MnO3).
Negligible magnetic coupling between both ferromagnetic electrodes is realised,
which allows to obtain parallel and antiparallel magnetic configurations of the
electrodes when sweeping the applied magnetic field. The structure exhibits
negative giant magnetoresistance (GMR) at low temperatures. This negative MR
shows that both electrodes stay spin-polarized at the interface and have
opposite spin polarizations, i.e. the Fe3O4 layer has a negative spin
polarization at low temperature. Maximum GMR (-5%) is obtained at 55K.

###Anisotropic Magnetoresistance in Charge-Ordering $Na_{0.34}(H_3O)_{0.15}CoO_2$:Strong Spin-Charge Coupling and Spin Ordering|C. H. Wang,X. H. Chen,G. Wu,T. Wu,H. T. Zhang,J. L. Luo,G. T. Liu,N. L. Wang###

Anisotropic Magnetoresistance in Charge-Ordering $Na_{0.34}(H_3O)_{0.15}CoO_2$:Strong Spin-Charge Coupling and Spin Ordering. Angular-dependent in-plane magnetoresistance (AMR) for single crystal
$Na_{0.34}(H_3O)_{0.15}CoO_2$ with charge ordering is studied systematically.
The anisotropic magnetoresistance shows a twofold symmetry at high temperature
with rotating H in the Co-O plane, while a sixfold symmetry below a certain
temperature ($T_\rho$). At $T_\rho$, the symmetry of AMR changes from twofold
to fourfold with rotating magnetic field (H) in the plane consisting of the
current and c-axis. The variation of AMR symmetry with temperature arises from
the subtle changes of the spin structure. These results give a direct evidence
for the itinerant electrons directly coupled to the localized spins.

###Direct Correlation between 1/f-magneto-noise and magnetoresistance in La0.7Sr0.3MnO3 and (La0.5Pr0.2)Ba0.3MnO3 manganites|D. S. Rana,M. Ziese,S. K. Malik###

Direct Correlation between 1/f-magneto-noise and magnetoresistance in La0.7Sr0.3MnO3 and (La0.5Pr0.2)Ba0.3MnO3 manganites. Temperature- and magnetic field-dependent electrical noise and electrical
resistivity measurements were carried out on epitaxial thin films of a large
bandwidth La0.7Sr0.3MnO3 and a disordered intermediate bandwidth
(La0.5Pr0.2)Ba0.3MnO3 manganite system. The power spectraldensity was dominated
by 1/f-noise. This 1/f-noise was observed to follow the overall temperature
dependence of the resistivity. Moreover, in these compounds the magneto-noise
effect was found to be of nearly the same magnitude as the magnetoresistance.
This direct correlation between magneto-noise and magnetoresistance suggests
that the enhanced 1/f-noise has its origin in intrinsic charge-carrier density
fluctuations.

###Electron transport through antidot superlattices in $Si/SiGe$ heterostructures: new magnetoresistance resonances in lattices with large diameter antidots|E. B. Olshanetsky,Vincent Thomas Francois Renard,Z. D. Kvon,J. -C. Portal,J. -M. Hartmann###

Electron transport through antidot superlattices in $Si/SiGe$ heterostructures: new magnetoresistance resonances in lattices with large diameter antidots. In the present work we have investigated the transport properties in a number
of Si/SiGe samples with square antidot lattices of different periods. In
samples with lattice periods equal to 700 nm and 850 nm we have observed the
conventional low-field commensurability magnetoresistance peaks consistent with
the previous observations in GaAs/AlGaAs and Si/SiGe samples with antidot
lattices. In samples with a 600 nm lattice period a new series of
well-developed magnetoresistance oscillations has been found beyond the last
commensurability peak which are supposed to originate from periodic skipping
orbits encircling an antidot with a particular number of bounds.

###Flux-flow induced giant magnetoresistance in all-amorphous superconductor-ferromagnet hybrids|C. Bell,S. Tursucu,J. Aarts###

Flux-flow induced giant magnetoresistance in all-amorphous superconductor-ferromagnet hybrids. We present magnetoresistance measurements on all-amorphous ferromagnet (F) /
superconductor (S) heterostructures. The F/S/F trilayers show large
magnetoresistance peaks in a small field range around the coercive field of the
F layers, at temperatures within and below the superconducting transition. This
is interpreted as flux flow of weakly pinned vortices induced by the stray
field of Bloch magnetic domains in the F layers. Bilayers show much smaller
effects, implying that the Bloch walls of the F-layers in the trilayer line up
and focus the stray fields. The data are used to discuss the expected minimum
F-layer thickness needed to nucleate vortices.

###Local Hall effect in hybrid ferromagnetic/semiconductor devices|Jinki Hong,Sungjung Joo,Tae-Suk Kim,Kungwon Rhie,K. H. Kim,S. U. Kim,B. C. Lee,Kyung-Ho Shin###

Local Hall effect in hybrid ferromagnetic/semiconductor devices. We have investigated the magnetoresistance of ferromagnet-semiconductor
devices in an InAs two-dimensional electron gas system in which the magnetic
field has a sinusoidal profile. The magnetoresistance of our device is large.
The longitudinal resistance has an additional contribution which is odd in
applied magnetic field. It becomes even negative at low temperature where the
transport is ballistic. Based on the numerical analysis, we confirmed that our
data can be explained in terms of the local Hall effect due to the profile of
negative and positive field regions. This device may be useful for future
spintronic applications.

###Spin-orbit induced anisotropy in the tunneling magnetoresistance of magnetic tunnel junctions|A. Matos-Abiague,J. Fabian###

Spin-orbit induced anisotropy in the tunneling magnetoresistance of magnetic tunnel junctions. The effects of the spin-orbit interaction on the tunneling magnetoresistance
of magnetic tunnel junctions are investigated. A model in which the
experimentally observed two-fold symmetry of the anisotropic tunneling
magnetoresistance (TAMR) originates from the interference between Dresselhaus
and Bychkov-Rashba spin-orbit couplings is formulated. Bias induced changes of
the Bychkov-Rashba spin-orbit coupling strength can result in an inversion of
the TAMR. The theoretical calculations are in good agreement with the TAMR
experimentally observed in epitaxial Fe/GaAs/Au tunnel junctions.

###High-field Hall resistivity and magnetoresistance in electron-doped Pr_2-xCe_xCuO_{4-δ}|Pengcheng Li,F. F. Balakirev,R. L. Greene###

High-field Hall resistivity and magnetoresistance in electron-doped Pr_2-xCe_xCuO_{4-δ}. We report resistivity and Hall effect measurements in electron-doped
Pr$_{2-x}$Ce$_{x}$CuO$_{4-\delta}$ films in magnetic field up to 58 T. In
contrast to hole-doped cuprates, we find a surprising non-linear magnetic field
dependence of Hall resistivity at high field in the optimally doped and
overdoped films. We also observe a crossover from quadratic to linear field
dependence of the positive magnetoresistance in the overdoped films. A spin
density wave induced Fermi surface reconstruction model can be used to
qualitatively explain both the Hall effect and magnetoresistance.

###Device-spectroscopy of magnetic field effects in a polyfluorene organic light-emitting diode|T. D. Nguyen,J. Rybicki,Y. Sheng,M. Wohlgenannt###

Device-spectroscopy of magnetic field effects in a polyfluorene organic light-emitting diode. We perform charge-induced absorption and electroluminescence spectroscopy in
a polyfluorene organic magnetoresistive device. Our experiments allow us to
measure the singlet exciton, triplet exciton and polaron densities in a live
device under an applied magnetic field, and to distinguish between three
different models that were proposed to explain organic magnetoresistance. These
models are based on different spin-dependent interactions, namely exciton
formation, triplet exciton-polaron quenching and bipolaron formation. We show
that the singlet exciton, triplet exciton and polaron densities and
conductivity all increase with increasing magnetic field. Our data are
inconsistent with the exciton formation and triplet-exciton polaron quenching
models.

###Anharmonic behavior in Microwave-driven resistivity oscillations in Hall bars|Jesus Inarrea###

Anharmonic behavior in Microwave-driven resistivity oscillations in Hall bars. We analyzed the magnetoresistivity of a two-dimensional electron system
excited by microwave radiation in a regime of high intensities and low
frequencies. In such a regime, recent experiments show that different features
appear in the magnetoresistivity response which suggest an anharmonic behavior.
These features consist mainly in distorted oscillations and new resonance peaks
at the subharmonics of the cyclotron frequency. We follow the model of
microwave-driven electron orbits motion which become anharmonic when the ratio
of microwave intensity to microwave frequency is large enough.

###Influence of magnetic field offsets on the resistance of magnetic barriers in two-dimensional electron gases|S. Hugger,M. Cerchez,H. Xu,T. Heinzel###

Influence of magnetic field offsets on the resistance of magnetic barriers in two-dimensional electron gases. Magnetic barriers in two-dimensional electron gases are shifted in B space by
homogeneous, perpendicular magnetic fields. The magnetoresistance across the
barrier shows a characteristic asymmetric dip in the regime where the polarity
of the homogeneous magnetic field is opposite to that one of the magnetic
barrier. The measurements are in quantitative agreement with semiclassical
simulations, which reveal that the magnetoresistance originates from the
interplay of snake orbits with E x B drift at the edges of the Hall bar and
with elastic scattering.

###Origin of ferromagnetism in (Zn,Co)O from magnetization and spin-dependent magnetoresistance|T. Dietl,T. Andrearczyk,A. Lipińska,M. Kiecana,Maureen Tay,Yihong Wu###

Origin of ferromagnetism in (Zn,Co)O from magnetization and spin-dependent magnetoresistance. In order to elucidate the nature of ferromagnetic signatures observed in
(Zn,Co)O we have examined experimentally and theoretically magnetic properties
and spin-dependent quantum localization effects that control low-temperature
magnetoresistance. Our findings, together with a through structural
characterization, substantiate the model assigning spontaneous magnetization of
(Zn,Co)O to uncompensated spins at the surface of antiferromagnetic nanocrystal
of Co-rich wurtzite (Zn,Co)O. The model explains a large anisotropy observed in
both magnetization and magnetoresistance in terms of spin hamiltonian of Co
ions in the crystal field of the wurtzite lattice.

###Microwave photovoltage and photoresistance effects in ferromagnetic microstrips|N. Mecking,Y. S. Gui,C. -M. Hu###

Microwave photovoltage and photoresistance effects in ferromagnetic microstrips. We investigate the dc electric response induced by ferromagnetic resonance in
ferromagnetic Permalloy (Ni80Fe20) microstrips. The resulting magnetization
precession alters the angle of the magnetization with respect to both dc and rf
current. Consequently the time averaged anisotropic magnetoresistance (AMR)
changes (photoresistance). At the same time the time-dependent AMR oscillation
rectifies a part of the rf current and induces a dc voltage (photovoltage). A
phenomenological approach to magnetoresistance is used to describe the distinct
characteristics of the photoresistance and photovoltage with a consistent
formalism, which is found in excellent agreement with experiments performed on
in-plane magnetized ferromagnetic microstrips. Application of the microwave
photovoltage effect for rf magnetic field sensing is discussed.

###Theory of shot noise in single-walled metallic carbon nanotubes weakly coupled to nonmagnetic and ferromagnetic leads|I. Weymann,J. Barnas,S. Krompiewski###

Theory of shot noise in single-walled metallic carbon nanotubes weakly coupled to nonmagnetic and ferromagnetic leads. We present theoretical study of shot noise in single wall metallic carbon
nanotubes weakly coupled to either nonmagnetic or ferromagnetic leads. Using
the real-time diagrammatic technique, we calculate the current, Fano factor and
tunnel magnetoresistance in the sequential tunneling regime. It is shown that
the differential conductance displays characteristic four-fold periodicity,
indicating single-electron charging. Such a periodicity is also visible in
tunnel magnetoresistance of the system as well as in the Fano factor. The
present studies elucidate the impact of ferromagnetic (vs. nonmagnetic)
contacts on the transport characteristics under consideration.

###Induced antiferromagnetism and large magnetoresistances in RuSr2(Nd,Y,Ce)2Cu2O10-d ruthenocuprates|A. C. Mclaughlin,F. Sher,S. A. J. Kimber,J. P. Attfield###

Induced antiferromagnetism and large magnetoresistances in RuSr2(Nd,Y,Ce)2Cu2O10-d ruthenocuprates. RuSr2(Nd,Y,Ce)2Cu2O10-d ruthenocuprates have been studied by neutron
diffraction, magnetotransport and magnetisation measurements and the electronic
phase diagram is reported. Separate Ru and Cu spin ordering transitions are
observed, with spontaneous Cu antiferromagnetic order for low hole doping
levels p, and a distinct, induced-antiferromagnetic Cu spin phase in the 0.02 <
p < 0.06 pseudogap region. This ordering gives rise to large negative
magnetoresistances which vary systematically with p in the
RuSr2Nd1.8-xY0.2CexCu2O10-d series. A collapse of the magnetoresistance (MR)
and magnetisation in the pre-superconducting region may signify the onset of
superconducting fluctuations.

###Magnetic phase transition and magnetocaloric effect in PrCo9Si4 and NdCo9Si4|Niharika Mohapatra,E. V. Sampathkumaran###

Magnetic phase transition and magnetocaloric effect in PrCo9Si4 and NdCo9Si4. The compounds, PrCo9Si4 and NdCo9Si4, have been recently reported to exhibit
first-order ferromagnetic transitions near 24 K. We have subjected this
compound for further characterization by magnetization, heat-capacity and
electrical resistivity measurements at low temperatures in the presence of
magnetic fields, particularly to probe magnetocaloric effect and
magnetoresistance. The compounds are found to exhibit rather modest
magnetocaloric effect at low temperatures peaking at Curie temperature,
tracking the behavior of magnetoresistance. The magnetic transition does not
appear to be first order in its character.

###Voltage control of magnetocrystalline anisotropy in ferromagnetic - semiconductor/piezoelectric hybrid structures|A. W. Rushforth,E. De Ranieri,J. Zemen,J. Wunderlich,K. W. Edmonds,C. S. King,E. Ahmad,R. P. Campion,C. T. Foxon,B. L. Gallagher,K. Vyborny,J. Kucera,T. Jungwirth###

Voltage control of magnetocrystalline anisotropy in ferromagnetic - semiconductor/piezoelectric hybrid structures. We demonstrate dynamic voltage control of the magnetic anisotropy of a
(Ga,Mn)As device bonded to a piezoelectric transducer. The application of a
uniaxial strain leads to a large reorientation of the magnetic easy axis which
is detected by measuring longitudinal and transverse anisotropic
magnetoresistance coefficients. Calculations based on the mean-field
kinetic-exchange model of (Ga,Mn)As provide microscopic understanding of the
measured effect. Electrically induced magnetization switching and detection of
unconventional crystalline components of the anisotropic magnetoresistance are
presented, illustrating the generic utility of the piezo voltage control to
provide new device functionalities and in the research of micromagnetic and
magnetotransport phenomena in diluted magnetic semiconductors.

###Spin-valve effect and magnetoresistivity in single crystalline Ca3Ru2O7|Wei Bao,Z. Q. Mao,Z. Qu,J. W. Lynn###

Spin-valve effect and magnetoresistivity in single crystalline Ca3Ru2O7. The laminar perovskite Ca3Ru2O7 naturally forms ferromagnetic double-layers
of alternating moment directions, as in the spin-valve superlattices. The
mechanism of huge magnetoresistive effect in the material has been
controversial due to a lack of clear understanding of various magnetic phases
and phase-transitions. In this neutron diffraction study in a magnetic field,
we identify four different magnetic phases in Ca3Ru2O7 and determine all
first-order and second-order phase transitions between them. The spin-valve
mechanism then readily explains the dominant magnetoresistive effect in
Ca3Ru2O7.

###Quantum effects for ballistic transport in spintronic devices|H. G. Silva,Y. G. Pogorelov###

Quantum effects for ballistic transport in spintronic devices. Recent fabrication of atomic precision nanodevices for spintronics greatly
boosted their performance and also revealed new interesting features, as
oscillating magnetoresistance with number of atomic layers in a multilayered
structure. This motivates the need to go beyond the usual theoretical approach
of semi-classical continuous layers. Here the simple tight-binding dynamics is
used to describe quantum conduction in a multicomponent system with
spin-polarized electrodes separated by an ultrathin and atomically coherent
non-magnetic spacer (either metallic or insulating). A possibility is indicated
for obtaining a huge resonant enhancement of magnetoresistance in such device
by a special choice of gate voltage on the spacer element.

###High Bias Voltage Effect on Spin-Dependent Conductivity and Shot Noise in Carbon-doped Fe(001)/MgO(001)/Fe(001) Magnetic Tunnel Junctions|R. Guerrero,D. Herranz,F. G. Aliev,F. Greullet,C. Tiusan,M. Hehn,F. Montaigne###

High Bias Voltage Effect on Spin-Dependent Conductivity and Shot Noise in Carbon-doped Fe(001)/MgO(001)/Fe(001) Magnetic Tunnel Junctions. Low temperature (10K) high voltage bias dynamic conductivity (up to 2.7V) and
shot noise (up to 1V) were studied in epitaxial Fe(100)/Fe-C/MgO(100)/Fe(100)
magnetic tunnel junctions, as a function of the magnetic state. The junctions
show large tunnel magnetoresistance (185% at 300K and 330% at 4K). Multiple
sign inversion of the magnetoresistance is observed for bias polarity when the
electrons scan the electronic structure of the bottom Fe-C interface. The
shot-noise shows a Poissonian character. This demonstrates a pure spin
dependent direct tunneling mechanism and validates the high structural quality
of the MgO barrier.

###Observation of large $h/2e$ and $h/4e$ oscillations in a proximity dc superconducting quantum interference device|Jian Wei,Paul Cadden-Zimansky,Venkat Chandrasekhar###

Observation of large $h/2e$ and $h/4e$ oscillations in a proximity dc superconducting quantum interference device. We have measured the magnetoresistance of a dc superconducting quantum
interference device in the form of an interrupted mesoscopic normal-metal loop
in contact with two superconducting electrodes. Below the transition
temperature of the superconducting electrodes, large $h/2e$ periodic
magnetoresistance oscillations are observed. By adding a small dc bias to the
ac measurement current, $h/4e$ oscillations can be produced. Lowering the
temperature further leads to even larger oscillations, and eventually to sharp
switching from the superconducting state to the normal state. This
flux-dependent resistance could be utilized to make highly sensitive flux
detector.

###Spin-polarized tunneling through randomly transparent magnetic junctions: Reentrant magnetoresistance approaching the Julliere limit|Grigory Tkachov,Klaus Richter###

Spin-polarized tunneling through randomly transparent magnetic junctions: Reentrant magnetoresistance approaching the Julliere limit. Electron conductance in planar magnetic tunnel junctions with long-range
barrier disorder is studied within Glauber-eikonal approximation enabling exact
disorder ensemble averaging by means of the Holtsmark-Markov method. This
allows us to address a hitherto unexplored regime of the tunneling
magnetoresistance effect characterized by the crossover from
momentum-conserving to random tunneling as a function of the defect
concentration. We demonstrate that such a crossover results in a reentrant
magnetoresistance: It goes through a pronounced minimum before reaching
disorder- and geometry-independent Julliere's value at high defect
concentrations.

###Origin of resistivity minima at low temperature in ferromagnetic metallic manganites|P. R. Sagdeo,R. J. Choudhary,D. M. Phase###

Origin of resistivity minima at low temperature in ferromagnetic metallic manganites. The resistivity and magnetoresistance measurements were carried out on thin
film of La0.7Ca0.3MnO3 to investigate the possible origin of low temperature
resistivity minimum observed in these samples. We observed large hysteresis in
the magnetoresistance at low temperature; 5K and the sample current I has large
effect on resistivity minima temperature. The observation of hysteresis at low
temperatures suggests the presence of inhomogeneity at low temperatures. These
in-homogeneities consist of regions of different resistive phases. It appears
that the high resistive phase prevents the tunneling of charge carriers between
two low resistive regions and thus giving rise to the resistivity minimum in
these samples.

###Surface magnetic phase transition of the double-exchange ferromagnet: Schwinger-boson mean-field study|Satoshi Okamoto###

Surface magnetic phase transition of the double-exchange ferromagnet: Schwinger-boson mean-field study. The surface magnetic phase transition of a double-exchange model for metallic
manganites is studied using a Schwinger-boson mean-field method. About three
unit-cells wide surface layers are identified. The magnetic moment in these
layers decreases more rapidly than that in the bulk when the temperature is
increased. This behavior is consistent with experimental observations. We also
discuss the implication of this behavior on the tunneling magnetoresistance
effect using manganites and possible improvement of the magnetoresistance
effect near the bulk Curie temperature.

###Asymmetric Magnetization Reversal in a Single Exchange-Biased Micro Bar|T. Gredig,M. Tondra###

Asymmetric Magnetization Reversal in a Single Exchange-Biased Micro Bar. The asymmetric magnetization reversal is studied in a single exchange-biased
microbar of 1.5 x 13 micrometer with anisotropic magnetoresistance and magnetic
force microscopy. The particle has a moment of less than 10^-9 emu and is not
accessible with standard magnetometry. The asymmetric hysteresis loop of
CoFe/CrMnPt shows a repeatable rotation process, followed by an irreversible
nucleation process that is marked by jumps in the magnetoresistance. The
induced unidirectional anisotropy enhances the rotation process in one branch
of the hysteresis loop, followed by a sped up nucleation process. Imprinted
ferromagnetic domain patterns left behind by the antiferromagnet are observed
after the nucleation process occurred but before complete saturation is
reached.

###The precursor state to superconductivity in CeIrIn${_5}$: Unusual scaling of magnetotransport|Sunil Nair,M. Nicklas,F. Steglich,J. L. Sarrao,J. D. Thompson,A. J. Schofield,S. Wirth###

The precursor state to superconductivity in CeIrIn${_5}$: Unusual scaling of magnetotransport. We present an analysis of the normal-state Hall effect and magnetoresistance
in the heavy fermion superconductor CeIrIn${_5}$. It is demonstrated that the
modified Kohler's scaling--which relates the magnetoresistance to the Hall
angle--breaks down prior to the onset of superconductivity due to the presence
of a precursor state to superconductivity in this system. A model-independent,
single-parameter scaling of the Hall angle governed solely by this precursor
state is observed. Neither the Hall coefficient nor the resistivity exhibit
this scaling implying that this precursor state preferentially influences the
Hall channel.

###The magnetoresistance tensor of La(0.8)Sr(0.2)MnO(3)|Y. Bason,J. Hoffman,C. H. Ahn,L. Klein###

The magnetoresistance tensor of La(0.8)Sr(0.2)MnO(3). We measure the temperature dependence of the anisotropic magnetoresistance
(AMR) and the planar Hall effect (PHE) in c-axis oriented epitaxial thin films
of La(0.8)Sr(0.2)MnO(3), for different current directions relative to the
crystal axes, and show that both AMR and PHE depend strongly on current
orientation. We determine a magnetoresistance tensor, extracted to 4th order,
which reflects the crystal symmetry and provides a comprehensive description of
the data. We extend the applicability of the extracted tensor by determining
the bi-axial magnetocrystalline anisotropy in our samples.

###Giant magnetoresistance in ultra-small Graphene based devices|F. Muñoz-Rojas,J. Fernandez-Rossier,J. J. Palacios###

Giant magnetoresistance in ultra-small Graphene based devices. By computing spin-polarized electronic transport across a finite zigzag
graphene ribbon bridging two metallic graphene electrodes, we demonstrate, as a
proof of principle, that devices featuring 100% magnetoresistance can be built
entirely out of carbon. In the ground state a short zig-zag ribbon is an
antiferromagnetic insulator which, when connecting two metallic electrodes,
acts as a tunnel barrier that suppresses the conductance. Application of a
magnetic field turns the ribbon ferromagnetic and conducting, increasing
dramatically the current between electrodes. We predict large magnetoresistance
in this system at liquid nitrogen temperature and 10 Tesla or at liquid helium
temperature and 300 Gauss.

###Probing Magnetic Configurations in Co/Cu Multilayered Nanowires|Jared Wong,Peter Greene,Randy K. Dumas,Kai Liu###

Probing Magnetic Configurations in Co/Cu Multilayered Nanowires. Magnetic configurations in heterostructures are often difficult to probe when
the magnetic entities are buried inside. In this study we have captured
magnetic and magnetoresistance "fingerprints" of Co nanodiscs embedded in Co/Cu
multilayered nanowires using a first-order reversal curve method. In 200nm
diameter nanowires, the magnetic configurations can be tuned by adjusting the
Co nanodisc aspect ratio. Nanowires with the thinnest Co nanodiscs exhibit
single domain behavior, while those with thicker Co reverse via vortex states.
A superposition of giant and anisotropic magnetoresistance is observed, which
corresponds to the different magnetic configurations of the Co nanodiscs.

###Tunneling magnetoresistance in (La,Pr,Ca)MnO3 nanobridges|G. Singh-Bhalla,A. Biswas,A. F. Hebard###

Tunneling magnetoresistance in (La,Pr,Ca)MnO3 nanobridges. The manganite (La,Pr,Ca)MnO3 is well known for its micrometer scale phase
separation into coexisting ferromagnetic metallic and antiferromagnetic
insulating (AFI) regions. Fabricating bridges with widths smaller than the
phase separation length scale has allowed us to probe the magnetic properties
of individual phase separated regions. We observe tunneling magnetoresistance
across naturally occurring AFI tunnel barriers separating adjacent
ferromagnetic regions spanning the width of the bridges. Further, near the
Curie temperature, a magnetic field induced metal-to-insulator transition among
a discrete number of regions within the narrow bridges gives rise to abrupt and
colossal low-field magnetoresistance steps at well defined switching fields.

###Carbon nanoelectronics: unzipping tubes into graphene ribbons|H. Santos,L. Chico,L. Brey###

Carbon nanoelectronics: unzipping tubes into graphene ribbons. We report on the transport properties of novel carbon nanostructures made of
partially unzipped carbon nanotubes, which can be regarded as a seamless
junction of a tube and a nanoribbon. We find that graphene nanoribbons act at
certain energy ranges as a perfect valley filters for carbon nanotubes, with
the maximum possible conductance. Our results show that a partially unzipped
carbon nanotube is a magnetoresistive device, with a very large value of the
magnetoresistance. We explore the properties of several structures combining
nanotubes and graphene nanoribbons, demonstrating that they behave as optimal
contacts for each other, and opening a new route for the design of mixed
graphene/nanotube devices.

###Tunneling anisotropic magnetoresistance in organic spin valves|M. Gruenewald,M. Wahler,M. Michelfeit,C. Gould,R. Schmidt,F. Wuerthner,G. Schmidt,L. W. Molenkamp###

Tunneling anisotropic magnetoresistance in organic spin valves. We report the observation of tunneling anisotropic magnetoresistance (TAMR)
in an organic spin-valve-like structure with only one ferromagnetic electrode.
The device is based on a new high mobility perylene diimide-based n-type
organic semiconductor. The effect originates from the tunneling injection from
the LSMO contact and can thus occur even for organic layers which are too thick
to support the assumption of tunneling through the layer. Magnetoresistance
measurements show a clear spin-valve signal, with the typical two step
switching pattern caused by the magnetocrystalline anisotropy of the epitaxial
magnetic electrode.

###Magnetoresistance Oscillations in Granular Superconducting Niobium Nitride Nanowires|U. Patel,Z. L. Xiao,A. Gurevich,S. Avci,J. Hua,R. Divan,U. Welp,W. K. Kwok###

Magnetoresistance Oscillations in Granular Superconducting Niobium Nitride Nanowires. We report on magnetoresistance oscillations in superconducting NbNx nanowires
synthesized through ammonia gas annealing of NbSe3 precursor nanostructures.
Even though the transverse dimensions of the nanowires are much larger than the
superconducting coherence length, the voltage-current characteristics of these
nanowires at low temperatures are reminiscent of one-dimensional
superconductors where quantum phase slips are associated with the origin of
dissipation. We show that both the magnetoresistance oscillations and
voltage-current characteristics observed in this work result from the granular
structure of our nanowires.

###Magnetoresistive junctions based on epitaxial graphene and hexagonal boron nitride|Oleg V. Yazyev,Alfredo Pasquarello###

Magnetoresistive junctions based on epitaxial graphene and hexagonal boron nitride. We propose monolayer epitaxial graphene and hexagonal boron nitride (h-BN) as
ultimate thickness covalent spacers for magnetoresistive junctions. Using a
first-principles approach, we investigate the structural, magnetic and spin
transport properties of such junctions based on structurally well defined
interfaces with (111) fcc or (0001) hcp ferromagnetic transition metals. We
find low resistance area products, strong exchange couplings across the
interface, and magnetoresistance ratios exceeding 100% for certain chemical
compositions. These properties can be fine tuned, making the proposed junctions
attractive for nanoscale spintronics applications.

###Simulation of the Spin Field Effect Transistors: Effects of Tunneling and Spin Relaxation on its Performance|Yunfei Gao,Tony Low,Mark S. Lundstrom,Dmitri E. Nikonov###

Simulation of the Spin Field Effect Transistors: Effects of Tunneling and Spin Relaxation on its Performance. A numerical simulation of spin-dependent quantum transport for a spin field
effect transistor (spinFET) is implemented in a widely used simulator nanoMOS.
This method includes the effect of both spin relaxation in the channel and the
tunneling barrier between the source/drain and the channel. Account for these
factors permits setting more realistic performance limits for the transistor,
especially the magnetoresistance, which is found to be lower compared to
earlier predictions. The interplay between tunneling and spin relaxation is
elucidated by numerical simulation. Insertion of the tunneling barrier leads to
an increased magnetoresistance. Numerical simulations are used to explore the
tunneling barrier design issues.

###Magnetoresistance studies of $La_{2/3} Sr_{1/3} MnO_3$ - $YBa_2 Cu_3 O_7$ - $La_{2/3} Sr_{1/3} Mn O_3$ trilayers with ferromagnetic coupling along the nodal direction of $YBa_2 Cu_3 O_7$|Soumen Mandal###

Magnetoresistance studies of $La_{2/3} Sr_{1/3} MnO_3$ - $YBa_2 Cu_3 O_7$ - $La_{2/3} Sr_{1/3} Mn O_3$ trilayers with ferromagnetic coupling along the nodal direction of $YBa_2 Cu_3 O_7$. I have successfully prepared (110) trilayers of \LSMO-\YBCO-\LSMO.
Magnetization measurements on these samples reveal a stronger coupling between
the ferromagnetic layers. The coupling is an order of magnitude higher than
that seen in the case of (001) trilayers. Magnetoresistance measurements show a
first order transition in the data coinciding with the antiferromagnetic regime
deduced from the magnetization measurements. I have also measured the
anisotropic magnetoresistance (AMR) of these samples revealing an unusually
high AMR ($\sim 72000%$). I attribute such a high AMR to the pair breaking
effects in these films.

###Nonlinear magnetotransport in dual spin valves|P. Balaz,J. Barnas###

Nonlinear magnetotransport in dual spin valves. Recent experimental measurements of magnetoresistance in dual spin valves [A.
Aziz et al., Phys. Rev. Lett. 103, 237203 (2009)] reveal some nonlinear
features of transport, which have not been observed in other systems. We
propose a phenomenological model describing current-dependent resistance (and
giant magnetoresistance) in double spin valves. The model is based on a
modified Valet-Fert approach, and takes into account the dependence of
bulk/interface resistance and bulk/interface spin asymmetry parameters for the
central magnetic layer on spin accumulation, and consequently on charge
current. Such a nonlinear model accounts for recent experimental observations.

###Theory of inplane magnetoresistance in two-dimensional massless Dirac fermion system|Takao Morinari,Takami Tohyama###

Theory of inplane magnetoresistance in two-dimensional massless Dirac fermion system. We present the theory of the inplane magnetoresistance in two-dimensional
massless Dirac fermion systems including the Zeeman splitting and the
electron-electron interaction effect on the Landau level broadening within a
random phase approximation. With the decrease in temperature, we find a
characteristic temperature dependence of the inplane magnetoresistance showing
a minimum followed by an enhancement with a plateau. The theory is in good
agreement with the experiment of the layered organic conductor
\alpha-(BEDT-TTF)_2I_3 under pressure. In-plane magnetoresistsnce of graphene
is also discussed based on this theory.

###Colossal negative magnetoresistance in dilute fluorinated graphene|X. Hong,S. -H. Cheng,C. Herding,J. Zhu###

Colossal negative magnetoresistance in dilute fluorinated graphene. Adatoms offer an effective route to modify and engineer the properties of
graphene. In this work, we create dilute fluorinated graphene using a clean,
controlled and reversible approach. At low carrier densities, the system is
strongly localized and exhibits an unexpected, colossal negative
magnetoresistance. The zero-field resistance is reduced by a factor of 40 at
the highest field of 9 T and shows no sign of saturation. Unusual "staircase"
field dependence is observed below 5 K. The magnetoresistance is highly
anisotropic. We discuss possible origins, considering quantum interference
effects and adatom-induced magnetism in graphene.

###Hydrodynamic description of transport in strongly correlated electron systems|A. V. Andreev,Steven A. Kivelson,B. Spivak###

Hydrodynamic description of transport in strongly correlated electron systems. We develop a hydrodynamic description of the resistivity and
magnetoresistance of an electron liquid in a smooth disorder potential. This
approach is valid when the electron-electron scattering length is sufficiently
short. In a broad range of temperatures, the dissipation is dominated by heat
fluxes in the electron fluid, and the resistivity is inversely proportional to
the thermal conductivity, $\kappa$. This is in striking contrast with the
Stokes flow, in which the resistance is independent of $\kappa$ and
proportional to the fluid viscosity. We also identify a new hydrodynamic
mechanism of spin magnetoresistance.

###Functionalized Graphene for High Performance Two-dimensional Spintronics Devices|Linze Li,Rui Qin,Hong Li,Lili Yu,Qihang Liu,Guangfu Luo,Jing Lu,Zhengxiang Gao###

Functionalized Graphene for High Performance Two-dimensional Spintronics Devices. Using first-principles calculations, we explore the possibility of
functionalized graphene as high performance two-dimensional spintronics device.
Graphene functionalized with O on one side and H on the other side in the chair
conformation is found to be a ferromagnetic metal with a spin-filter efficiency
up to 85% at finite bias. The ground state of graphene semi-functionalized with
F in the chair conformation is an antiferromagnetic semiconductor, and we
construct a magnetoresistive device from it by introducing a magnetic field to
stabilize its ferromagnetic metallic state. The resulting room-temperature
magnetoresistance is up to 5400%, which is one order of magnitude larger than
the available experimental values.

###Weak Antilocalization and Conductance Fluctuation in a Sub-micrometer-sized Wire of Epitaxial Bi2Se3|Sadashige Matsuo,Tomohiro Koyama,Kazutoshi Shimamura,Tomonori Arakawa,Yoshitaka Nishihara,Daichi Chiba,Kensuke Kobayashi,Teruo Ono,Cui-Zu Chang,Ke He,Xu-Cun Ma,Qi-Kun Xue###

Weak Antilocalization and Conductance Fluctuation in a Sub-micrometer-sized Wire of Epitaxial Bi2Se3. In this study, we address the phase coherent transport in a
sub-micrometer-sized Hall bar made of epitaxial Bi2Se3 thin film by probing the
weak antilocalization (WAL) and the magnetoresistance fluctuation below 22 K.
The WAL effect is well described by the Hikami-Larkin-Nagaoka model, where the
temperature dependence of the coherence length indicates that electron
conduction occurs quasi-one-dimensionally in the narrow Hall bar. The
temperature-dependent magnetoresistance fluctuation is analyzed in terms of the
universal conductance fluctuation, which gives a coherence length consistent
with that derived from the WAL effect.

###Magnetoresistance Relaxation in (La0.5Eu0.5)0.7Pb0.3MnO3 Single Crystals under the Action of a Pulse Magnetic Field|A. A. Bykov,S. I. Popkov,K. A. Shaykhutdinov,K. A. Sablina###

Magnetoresistance Relaxation in (La0.5Eu0.5)0.7Pb0.3MnO3 Single Crystals under the Action of a Pulse Magnetic Field. Magnetoresistance of substituted lanthanum manganite (La0.5Eu0.5)0.7Pb0.3MnO3
in the pulse magnetic field H = 25 T was measured at different temperatures.
Magnetoresistance relaxation with a characteristic time of 10 -3 s was found.
It has been established that the temperature dependence of the relaxation
parameter {\tau}(t) at different temperatures correlates with the temperature
dependence of electrical resistance R(T). The proposed relaxation mechanism is
related to relaxation of conducting and dielectric phases in the sample volume
under phase stratification conditions. It is shown that relaxation parameter
{\tau} reflects the number of boundaries in the volume and not the ratio
between phase fractions.

###High-field magnetoresistance revealing scattering mechanisms in graphene|Andreas Uppstu,Ari Harju###

High-field magnetoresistance revealing scattering mechanisms in graphene. We show that the type of charge carrier scattering significantly affects the
high-field magnetoresistance of graphene nanoribbons. This effect has potential
to be used in identifying the scattering mechanisms in graphene. The results
also provide an explanation for the experimentally found, intriguing
differences in the behavior of the magnetoresistance of graphene Hall bars
placed on different substrates. Additionally, our simulations indicate that the
peaks in the longitudinal resistance tend to become pinned to fractionally
quantized values, as different transport modes have very different scattering
properties.

###Doping effects of Co, Ni, and Cu in FeTe0.65Se0.35 single crystals|V. L. Bezusyy,D. J. Gawryluk,M. Berkowski,M. Z. Cieplak###

Doping effects of Co, Ni, and Cu in FeTe0.65Se0.35 single crystals. The resistivity, magnetoresistance, and magnetic susceptibility are measured
in single crystals of FeTe0.65Se0.35 with Cu, Ni, and Co substitutions for Fe.
The crystals are grown by Bridgman's method. The resistivity measurements show
that superconductivity disappears with the rate which correlates with the
nominal valence of the impurity. From magnetoresistance we evaluate doping
effect on the basic superconducting parameters, such as upper critical field
and coherence length. We find indications that doping leads to two component
superconducting behavior, possibly because of local charge depression around
impurities.

###Magnetotransport effects in polar versus non-polar SrTiO3 based heterostructures|E. Flekser,M. Ben Shalom,M. Kim,C. Bell,Y. Hikita,H. Y. Hwang,Y. Dagan###

Magnetotransport effects in polar versus non-polar SrTiO3 based heterostructures. Anisotropic magnetoresistance and negative magnetoresistance for in-plane
fields are compared for the LaAlO3 /SrTiO3 interface and the symmetric Nb-doped
SrTiO3 heterostructure. Both effects are exceptionally strong in LaAlO3 /SrTiO3
. We analyze their temperature, magnetic field and gate voltage dependencies
and find them to arise from a Rashba type spin-orbit coupling with magnetic
scatterers that have two contributions to their potential: spin exchange and
Coulomb interaction. Atomic spin-orbit coupling is sufficient to explain the
small effects observed in Nb-doped SrTiO3 . These results clarify contradicting
transport interpretations in SrTiO3 -based heterostructures.

###Domain-wall induced large magnetoresistance effects at zero applied field in ballistic nanocontacts|Arndt von Bieren,Ajit K. Patra,Stephen Krzyk,Jan Rhensius,Robert M. Reeve,Laura J. Heyderman,Regina Hoffmann-Vogel,Mathias Kläui###

Domain-wall induced large magnetoresistance effects at zero applied field in ballistic nanocontacts. We determine magnetoresistance effects in stable and clean permalloy
nanocontacts of variable cross-section, fabricated by UHV deposition and
in-situ electromigration. To ascertain the magnetoresistance (MR) effects
originating from a magnetic domain wall, we measure the resistance values with
and without such a wall at zero applied field. In the ballistic transport
regime, the MR ratio reaches up to 50% and exhibits a previously unobserved
sign change. Our results can be reproduced by recent atomistic calculations for
different atomic configurations of the nanocontact, highlighting the importance
of the detailed atomic arrangement for the MR effect.

###Linear magnetoresistance on the topological surface|C. M. Wang,X. L. Lei###

Linear magnetoresistance on the topological surface. A positive, non-saturating and dominantly linear magnetoresistance is
demonstrated to occur in the surface state of a topological insulator having a
wavevector-linear energy dispersion together with a finite positive Zeeman
energy splitting. This linear magnetoresistance shows up within quite wide
magnetic-field range in a spatially homogenous system of high carrier density
and low mobility in which the conduction electrons are in extended states and
spread over many smeared Landau levels, and is robust against increasing
temperature, in agreement with recent experimental findings in Bi$_2$Se$_3$
nanoribbons.

###Observation of linear-polarization-sensitivity in the microwave-radiation-induced magnetoresistance oscillations|R. G. Mani,A. N. Ramanayaka,W. Wegscheider###

Observation of linear-polarization-sensitivity in the microwave-radiation-induced magnetoresistance oscillations. In the quasi two-dimensional GaAs/AlGaAs system, we investigate the effect of
rotating \textit{in-situ} the electric field of linearly polarized microwaves
relative to the current, on the microwave-radiation-induced magneto-resistance
oscillations. We find that the frequency and the phase of the photo-excited
magneto-resistance oscillations are insensitive to the polarization. On the
other hand, the amplitudes of the magnetoresistance oscillations are remarkably
responsive to the relative orientation between the microwave antenna and the
current-axis in the specimen. The results suggest a striking
linear-polarization-sensitivity in the radiation-induced magnetoresistance
oscillations.

###Effects of interface resistance asymmetry on local and non-local magnetoresistance structures|Tetsufumi Tanamoto,Hideyuki Sugiyama,Tomoaki Inokuchi,Mizue Ishikawa,Yoshiaki Saito###

Effects of interface resistance asymmetry on local and non-local magnetoresistance structures. Spin injection and detection are very sensitive to the interface properties
between ferromagnet and semiconductor. Because the interface properties such as
a tunneling resistance can be chosen independently between the injection and
detection sides, the magnetic transport properties are considered to depend on
the asymmetry of the two interfaces. We theoretically investigate the effect of
the asymmetric interfaces of the injection side and the detection side on both
the local and non-local magnetoresistance measurements. The results show the
magnetoresistance ratio of local measurement structure has its maximum at the
symmetric structure, and the effect of the asymmetry is very weak for the
non-local measurement structure.

###Electrostatic Tuning of the Properties of Disordered Indium Oxide Films near the Superconductor-Insulator Transition|Yeonbae Lee,Aviad Frydman,Tianran Chen,Brian Skinner,A. M. Goldman###

Electrostatic Tuning of the Properties of Disordered Indium Oxide Films near the Superconductor-Insulator Transition. The evolution with carrier concentration of the electrical properties of
amorphous indium oxide (InO) thin films has been studied using electronic
double layer transistor configurations. Carrier variations of up to 7 X 10^(14)
carriers/cm^2 were achieved using an ionic liquid as a gate dielectric. The
superconductor-insulator transition was traversed and the magnitude and
position of the large magnetoresistance peak found in the insulating regime
were modified. The systematic variation of the magnetoresistance peak with
charge concentration was found to be qualitatively consistent with a simulation
based on a model involving granularity.

###Linear magnetoresistance in HgTe quantum wells|G. M. Gusev,E. B Olshanetsky,Z. D. Kvon,N. N. Mikhailov,S. A. Dvoretsky###

Linear magnetoresistance in HgTe quantum wells. We report magnetotransport measurements in a HgTe quantum well with an
inverted band structure, which is expected to be a two-dimensional (2D)
topological insulator. A small magnetic field perpendicular the 2D layer breaks
the time reversal symmetry and thereby, suppresses the edge state transport. A
linear magnetoresistance is observed in low magnetic fields, when the chemical
potential moves through the the bulk gap. That magnetoresistance is well
described by numerical calculations of the edge states magnetotransport in the
presence of nonmagnetic disorder. With magnetic field increasing the
resistance, measured both in the local and nonlocal configurations first
sharply decreases and then increases again in disagreement with the existing
theories.

###Shubnikov de Haas quantum oscillation of the surface states in the metallic Bismuth Telluride sheets|Taishi Chen,Junhao Han,Zhaoguo Li,Fengqi Song,Bo Zhao,Xuefeng Wang,Baigeng Wang,Jianguo Wan,Min Han,Rong Zhang,Guanghou Wang###

Shubnikov de Haas quantum oscillation of the surface states in the metallic Bismuth Telluride sheets. Metallic Bi2Te3 crystalline sheets with the room-temperature resistivity of
above 10 m{\Omega} cm were prepared and their magnetoresistive transport was
measured in a field of up to 9 Tesla. The Shubnikov de Haas oscillations were
identified from the secondly-derived magnetoresistance curves. While changing
the angle between the field and normal axis of the sheets, we find that the
oscillation periods present a cosine dependence on the angle. This indicates a
two-dimensional transport due to the surface state. The work reveals a
resolvable surface contribution to the overall conduction even in a metallic
topological insulator.

###Signatures of the Berry curvature in the frequency dependent interlayer magnetoresistance in tilted magnetic fields|Anthony R. Wright,Ross H. McKenzie###

Signatures of the Berry curvature in the frequency dependent interlayer magnetoresistance in tilted magnetic fields. We show that in a layered metal, the angle dependent, finite frequency,
interlayer magnetoresistance is altered due to the presence of a non-zero Berry
curvature at the Fermi surface. At zero frequency, we find a conservation law
which demands that the `magic angle' condition for interlayer magnetoresistance
extrema as a function of magnetic field tilt angle is essentially both field
and Berry curvature independent. In the finite frequency case, however, we find
that surprisingly large signatures of a finite Berry curvature occur in the
periodic orbit resonances. We outline a method whereby the presence and
magnitude of the Berry curvature at the Fermi surface can be extracted.

###Characteristic Sign Change of the Magnetoresistance of Strongly Correlated GaAs Two-dimensional Holes|Jian Huang,L. N. Pfeiffer,K. W. West###

Characteristic Sign Change of the Magnetoresistance of Strongly Correlated GaAs Two-dimensional Holes. High quality strongly correlated two-dimensional (2D) electron systems at low
temperatures $T\rightarrow 0$ exhibits an apparent metal-to-insulator
transition (MIT) at a large $r_s$ value around 40. We have measured the
magnetoresistance of 2D holes in weak perpendicular magnetic field in the
vicinity of the transition for a series of carrier densities ranging from
$0.2-1.5\times10^{10}$ $cm^{-2}$. The sign of the magnetoresistance is found to
be charge density dependent: in the direction of decreasing density, the sign
changes from being positive to negative across a characteristic value that
coincides with the critical density of MIT.

###Phase Transition to Insulating State from Quantum Hall State by Current-Induced Nuclear Spin Polarization|Shibun Tsuda,Minh-Hai Nguyen,Daiju Terasawa,Akira Fukuda,Anju Sawada###

Phase Transition to Insulating State from Quantum Hall State by Current-Induced Nuclear Spin Polarization. We investigate the resistance enhancement state (RES) where the
magnetoresistance of the $\nu = 2/3$ fractional quantum Hall state (FQHS) is
increased with dynamic nuclear spin polarization (DNP) induced by a large
electric current. After inducing DNP, we measure the temperature dependence of
the magnetoresistance by a small current over a short period of time. We find
that the FQHS makes a phase transition to an insulating state. By measuring the
Hall resistance in the insulating state, we find that the RES exhibits a
quantized Hall resistance. We discuss the RES in association with the Anderson
localization.

###Engineered spin-valve type magnetoresistance in Fe$_3$O$_4$-CoFe$_2$O$_4$ core-shell nanoparticles|P. Anil Kumar,Sugata Ray,S. Chakraverty,D. D. Sarma###

Engineered spin-valve type magnetoresistance in Fe$_3$O$_4$-CoFe$_2$O$_4$ core-shell nanoparticles. Naturally occurring spin-valve-type magnetoresistance (SVMR), recently
observed in Sr2FeMoO6 samples, suggests the possibility of decoupling the
maximal resistance from the coercivity of the sample. Here we present the
evidence that SVMR can be engineered in specifically designed and fabricated
core-shell nanoparticle systems, realized here in terms of soft magnetic Fe3O4
as the core and hard magnetic insulator CoFe2O4 as the shell materials. We show
that this provides a magnetically switchable tunnel barrier that controls the
magnetoresistance of the system, instead of the magnetic properties of the
magnetic grain material, Fe3O4, and thus establishing the feasibility of
engineered SVMR structures.

###Giant magnetothermopower in charge ordered Nd0.75Na0.25MnO3|D. V. Maheswar Repaka,R. Mahendiran###

Giant magnetothermopower in charge ordered Nd0.75Na0.25MnO3. We report magnetization, resistivity and thermopower in the charge-orbital
ordered antiferromagnet Nd0.75Na0.25MnO3. Magnetic-field induced collapse of
antiferromagnetism is found to be accompanied by a giant negative
magnetothermopower (= 80-100% for a field change of 5T) over a wide temperature
(T = 60-225K) and giant magnetoresistance. While the field-induced metamagnetic
transition in magnetization is reversible upon field-cycling at T > 40 K, it is
irreversible at lower temperatures and this has impact on magnetoresistance,
magnetothermopower as well as change in the temperature of the sample. Our
results indicate high sensitivity of thermopower to changes in the magnetic
state of the sample.

###First Principles Study of the Magnetic Properties of LaOMnAs|Shuai Dong,Wei Li,Xin Huang,Elbio Dagotto###

First Principles Study of the Magnetic Properties of LaOMnAs. Recent experiments reported giant magnetoresistance at room temperature in
LaOMnAs. Here a density functional theory calculation is performed to
investigate magnetic properties of LaOMnAs. The ground state is found to be the
G-type antiferromagnetic order within the $ab$ plane but coupled
ferromagnetically between planes, in agreement with recent neutron
investigations. The electronic band structures suggest an insulating state
which is driven by the particular G-type magnetic order, while a metallic state
accompanies the ferromagnetic order. This relation between magnetism and
conductance may be helpful to qualitatively understand the giant
magnetoresistance effects.

###Magnetoresistive property study of direct and indirect band gap thermoelectric Bi-Sb alloys|Diptasikha Das,K. Malik,S. Bandyopadhyay,D. Das,S. Chatterjee,Aritra Banerjee###

Magnetoresistive property study of direct and indirect band gap thermoelectric Bi-Sb alloys. We report magnetoresistive properties of direct and indirect band gap
Bismuth-Antimony (Bi-Sb) alloys. Band gap increases with magnetic field. Large
positive magnetoresistance (MR) approaching to 400 % is observed. Low field MR
experiences quadratic growth and at high field it follows a nearly linear
behavior without sign of saturation. Carrier mobility extracted from low field
MR data, depicts remarkable high value. Correlation between MR and mobility is
revealed. We demonstrate that the strong nearly linear MR at high field can be
well understood by classical method, co-build by Parish and Littlewood.

###Nonlinear transport in 2D electron gas exhibiting colossal negative magnetoresistance|Q. Shi,M. A. Zudov,L. N. Pfeiffer,K. W. West###

Nonlinear transport in 2D electron gas exhibiting colossal negative magnetoresistance. We report on nonlinear transport measurements in a GaAs/AlGaAs quantum well
exhibiting a colossal negative magnetoresistance effect. Under applied dc bias,
the magnetoresistance becomes nonmonotonic, exhibiting distinct extrema that
move to higher magnetic fields with increasing current. In the range of
magnetic fields corresponding to the resistivity minimum at zero bias, the
resistivity increases linearly with current and the rate of this increase
scales with the inverse magnetic field. The latter observation is consistent
with the theory, proposed more than 35 years ago, considering classical memory
effects in the presence of strong, dilute scatterers.

###A comparative study of HoSn1.1Ge0.9 and DySn1.1Ge0.9 compounds using magnetic, magneto-thermal and magneto-transport measurements|Sachin Gupta,V. R. Reddy,G. S. Okram,K. G. Suresh###

A comparative study of HoSn1.1Ge0.9 and DySn1.1Ge0.9 compounds using magnetic, magneto-thermal and magneto-transport measurements. Polycrystalline HoSn1.1Ge0.9 and DySn1.1Ge0.9 compounds have been studied by
means of different experimental probes. Both the compounds are
antiferromagnetic and show metamagnetic transition at low temperatures.
HoSn1.1Ge0.9 shows a sign change in magnetocaloric effect (MCE) and
magnetoresistance (MR) with field, which is attributed to the metamagnetic
transition. DySn1.1Ge0.9 shows characteristics of a typical antiferromagnet, as
evidenced by magnetization, MCE and MR data. 119Sn M\"ossbauer studies show
hyperfine splitting at low temperatures, consistent with magnetization data.
Thermoelectric power and resistivity measurements reveal metallic behavior in
these compounds. Magnetic, magnetocaloric and the magnetoresistance data
clearly show that the antiferromagnetic coupling in DySn1.1Ge0.9 is stronger
than in HoSn1.1Ge0.9.

###Observation of Devil's Staircase in the Novel Spin Valve System SrCo$_6$O$_{11}$|T. Matsuda,S. Partzsch,T. Tsuyama,E. Schierle,E. Weschke,J. Geck,T. Saito,S. Ishiwata,Y. Tokura,H. Wadati###

Observation of Devil's Staircase in the Novel Spin Valve System SrCo$_6$O$_{11}$. Using resonant soft x-ray scattering as a function of both temperature and
magnetic field, we reveal a large number of almost degenerate magnetic orders
in SrCo6O11. The Ising-like spins in this frustrated material in fact exhibit a
so-called magnetic devil's staircase. It is demonstrated how a magnetic field
induces transitions between different microscopic spin configurations, which is
responsible for the magnetoresistance of SrCo6O11. This material therefore
constitutes a unique combination of a magnetic devil's staircase and spin valve
effects, yielding a novel type of magnetoresistance system.

###Spin Hall magnetoresistance and spin Nernst magnetothermopower: role of the inverse spin galvanic effect|Sebastian Tölle,Michael Dzierzawa,Ulrich Eckern,Cosimo Gorini###

Spin Hall magnetoresistance and spin Nernst magnetothermopower: role of the inverse spin galvanic effect. In ferromagnet/normal-metal bilayers, the sensitivity of the spin Hall
magnetoresistance and the spin Nernst magnetothermopower to the boundary
conditions at the interface is of central importance. In general, such boundary
conditions can be substantially affected by current-induced spin polarizations.
In order to quantify the role of the latter, we consider a Rashba
two-dimensional electron gas with a ferromagnet attached to one side of the
system. The geometry of such a system maximizes the effect of current-induced
spin polarization on the boundary conditions, and the spin Hall
magnetoresistance is shown to acquire a non-trivial and asymmetric dependence
on the magnetization direction of the ferromagnet.

###Biaxial magnetic field setup for angular magnetic measurements of thin films and spintronic nanodevices|Piotr Rzeszut,Witold Skowroński,Sławomir Ziętek,Piotr Ogrodnik,Tomasz Stobiecki###

Biaxial magnetic field setup for angular magnetic measurements of thin films and spintronic nanodevices. The biaxial magnetic-field setup for angular magnetic measurements of thin
film and spintronic devices is designed and presented. The setup allows for
application of the in-plane magnetic field using a quadrupole electromagnet,
controlled by power supply units and integrated with an electromagnet biaxial
magnetic field sensor. In addition, the probe station is equipped with a
microwave circuitry, which enables angle-resolved spin torque oscillation
measurements. The angular dependencies of magnetoresistance and spin diode
effect in a giant magnetoresistance strip are shown as an operational
verification of the experimental setup. We adapted an analytical macrospin
model to reproduce both the resistance and spin-diode angular dependency
measurements.

###Classical effects in the weak-field magnetoresistance of InGaAs/InAlAs quantum wells|M. Yu. Melnikov,A. A. Shashkin,V. T. Dolgopolov,G. Biasiol,S. Roddaro,L. Sorba###

Classical effects in the weak-field magnetoresistance of InGaAs/InAlAs quantum wells. We observe an unusual behavior of the low-temperature magnetoresistance of
the high-mobility two-dimensional electron gas in InGaAs/InAlAs quantum wells
in weak perpendicular magnetic fields. The observed magnetoresistance is
qualitatively similar to that expected for the weak localization and
anti-localization but its quantity exceeds significantly the scale of the
quantum corrections. The calculations show that the obtained data can be
explained by the classical effects in electron motion along the open orbits in
a quasiperiodic potential relief manifested by the presence of ridges on the
quantum well surface.

###Electronic phase separation in insulating (Ga,Mn)As with low compensation: Super-paramagnetism and hopping conduction|Ye Yuan,Mao Wang,Chi Xu,René Hübner,Roman Böttger,Rafal Jakiela,Manfred Helm,Maciej Sawicki,Shengqiang Zhou###

Electronic phase separation in insulating (Ga,Mn)As with low compensation: Super-paramagnetism and hopping conduction. In the present work, low compensated insulating (Ga,Mn)As with 0.7% Mn is
obtained by ion implantation combined with pulsed laser melting. The sample
shows variable-range hopping transport behavior with a Coulomb gap in the
vicinity of the Fermi energy, and the activation energy is reduced by an
external magnetic field. A blocking super-paramagnetism is observed rather than
ferromagnetism. Below the blocking temperature, the sample exhibits a colossal
negative magnetoresistance. Our studies confirm that the disorder-induced
electronic phase separation occurs in (Ga,Mn)As samples with a Mn concentration
in the insulator-metal transition regime, and it can account for the observed
superparamagnetism and the colossal magnetoresistance.

###Emergent antiferromagnetism of YTiO3 in YTiO3-CaTiO3 superlattices|P. Pal,X. Liu,M. Kareev,D. Choudhury,J. Chakhalian###

Emergent antiferromagnetism of YTiO3 in YTiO3-CaTiO3 superlattices. Transport and magnetoresistance measurements are performed on metallic,
high-carrier density YTiO3-CaTiO3 superlattices as a probe towards the
investigation of an emergent magnetic order of YTiO3. On varying the thickness
of YTiO3 while keeping the CaTiO3 layer thickness constant in the
superlattices, a low-temperature upturn in sheet-resistance, a non-Fermi
liquid-like charge transport and positive magnetoresistance are observed.
Analyses of the origin of such effects suggest that a unique antiferromagnetic
order is realized in the ultra-thin, epitaxially strained YTiO3 layers, which
corroborates well with some recent theoretical predictions in this regard.

###Spin Relaxation in Weak Localization Regime in Multilayer Graphene Spin Valves|Takehiro Yamaguchi,Rai Moriya,Satoru Masubuchi,Kazuyuki Iguchi,Tomoki Machida###

Spin Relaxation in Weak Localization Regime in Multilayer Graphene Spin Valves. The temperature dependence of the spin relaxation time in multilayer graphene
(MLG) spin valve devices was measured using a non-local magnetoresistance
(NLMR) measurement. A weak localization (WL) was observed from
magnetoresistance (MR) measurements below 70 K, suggesting coherent transport
of the charge carriers. Within the same temperature range, we observed a large
increase in the spin relaxation time and spin diffusion length even though the
diffusion constant Ds was suppressed by the WL. This demonstrated that the spin
relaxation time in MLG could be significantly extended when the charge
experiences quantum interference effect in the coherent charge transport
regime.

###Indications of the topological transport by the universal conductance fluctuations in the Bi2Te2Se microflakes|Zhaoguo Li,Yuze Meng,Jian Pan,Taishi Chen,Xiaochen Hong,Shiyan Li,Xuefeng Wang,Fengqi Song,Baigeng Wang###

Indications of the topological transport by the universal conductance fluctuations in the Bi2Te2Se microflakes. Universal conductance fluctuations (UCFs) are extracted in the
magnetoresistance responses in the bulk-insulating Bi2Te2Se microflakes. Its
two-dimensional character is demonstrated by the field-tilting
magnetoresistance measurements. Its origin from the surface electrons is
determined by the fact that the UCF amplitudes keep unchanged while applying an
in-plane field to suppress the coherence of bulk electrons. After considering
the ensemble average in a batch of micrometer-sized samples, the intrinsic UCF
magnitudes of over 0.37 e2/h is obtained. This agrees with the theoretical
prediction on topological surface states. All the evidence point to the
successful observation of the UCF of topological surface states.

###Angular variation of the magnetoresistance of the superconducting ferromagnet UCoGe|T. V. Bay,A. M. Nikitin,T. Naka,A. McCollam,Y. K. Huang,A. de Visser###

Angular variation of the magnetoresistance of the superconducting ferromagnet UCoGe. We report a magnetoresistance study of the superconducting ferromagnet UCoGe.
The data, taken on single-crystalline samples, show a pronounced structure at
$B^* = 8.5$~T for a field applied along the ordered moment $m_0$. Angle
dependent measurements reveal this field-induced phenomenon has an uniaxial
anisotropy. Magnetoresistance measurements under pressure show a rapid increase
of $B^*$ to 12.8~T at 1.0~GPa. We discuss $B^*$ in terms of a field induced
polarization change. Upper critical field measurements corroborate the unusual
S-shaped $B_{c2}(T)$-curve for a field along the $b$-axis of the orthorhombic
unit cell.

###Theoretical model for negative giant magnetoresistance in ultra-high-mobility 2D electron systems|Jesús Inarrea###

Theoretical model for negative giant magnetoresistance in ultra-high-mobility 2D electron systems. We report on theoretical studies of the recently discovered negative giant
magnetoresistance in ultraclean two-dimensional electron systems at low
temperatures. We adapt a transport model to a ultraclean scenario and calculate
the elastic scattering rate (electron-charged impurity) in a regime where the
Landau level width is much smaller than the cyclotron energy. We obtain that
for low magnetic fields the scattering rate and, as a consequence, the
longitudinal magnetoresistance dramatically drop because of the small density
of states between Landau levels. We also study the dependence of this striking
effect on temperature and an in-plane magnetic field.

###Boltzmann theory of magnetoresistance due to a spin spiral|Tomohiro Taniguchi,Hiroshi Imamura###

Boltzmann theory of magnetoresistance due to a spin spiral. We studied the magnetoresistance due to a spin spiral by solving the
Boltzmann equation. The scattering rates of conduction electrons are calculated
by using the non-perturbative wave function of the conduction electrons and the
non-equilibrium distribution function is obtained by numerically solving the
Boltzmann equation. These enable us to calculate the resistivity of a
sufficiently thin spin spiral. A magnetoresistance ratio of more than 50% is
predicted for a spin spiral with high spin polarization (>0.8) and a small
period (about 1-2 nm).

###Competition between Superconductivity and Weak Localization in Metal-Mixed Ion-Implanted Polymers|Andrew P. Stephenson,Adam P. Micolich,Ujjual Divakar,Paul Meredith,B. J. Powell###

Competition between Superconductivity and Weak Localization in Metal-Mixed Ion-Implanted Polymers. We study the effects of varying the pre-implant film thickness and implant
temperature on the electrical and superconducting properties of metal-mixed
ion-implanted polymers. We show that it is possible to drive a
superconductor-insulator transition in these materials via control of the
fabrication parameters. We observe peaks in the magnetoresistance and
demonstrate that these are caused by the interplay between superconductivity
and weak localization in these films, which occurs due to their granular
structure. We compare these magnetoresistance peaks with those seen in
unimplanted films and other organic superconductors, and show that they are
distinctly different.

###Exponential suppression of interlayer conductivity in very anisotropic quasi-two-dimensional compounds in high magnetic field|Pavel D. Grigoriev###

Exponential suppression of interlayer conductivity in very anisotropic quasi-two-dimensional compounds in high magnetic field. It is shown that in rather strong magnetic field the interlayer electron
conductivity is exponentially damped by the Coulomb barrier arising from the
formation of polaron around each localized electron state. The theoretical
model is developed to describe this effect, and the calculation of the
temperature and field dependence of interlayer magnetoresistance is performed.
The results obtained agree well with the experimental data in GaAs/AlGaAs
heterostructures and in strongly anisotropic organic metals. The proposed
theory allows to use the experiments on interlayer magnetoresistance to
investigate the electron states, localized by magnetic field and disorder.

###Microscopic theory of the magnetoresistance of disordered superconducting films|G. J. Conduit,Yigal Meir###

Microscopic theory of the magnetoresistance of disordered superconducting films. Experiments on disordered superconducting thin films have revealed a
magnetoresistance peak of several orders of magnitude. Starting from the
disordered negative-U Hubbard model, we employ an ab initio approach that
includes thermal fluctuations to calculate the resistance, and fully reproduces
the experimental phenomenology. Maps of the microscopic current flow and local
potential allow us to pinpoint the source of the magnetoresistance peak -- the
conducting weak links change from normal on the low-field side of the peak to
superconducting on the high-field side. Finally, we formulate a simple
one-dimensional model to demonstrate how small superconducting regions will act
as weak links in such a disordered thin film.

###Induced magneto-transport properties at palladium/yttrium iron garnet interface|Tao Lin,Chi Tang,Jing Shi###

Induced magneto-transport properties at palladium/yttrium iron garnet interface. As a thin layer of palladium (Pd) is directly deposited on an yttrium iron
garnet or YIG (Y3Fe5O12) magnetic insulator film, Pd develops both low- and
high-field magneto-transport effects that are absent in standalone Pd or thick
Pd on YIG. While the low-field magnetoresistance peak of Pd tracks the coercive
field of the YIG film, the much larger high-field magnetoresistance and the
Hall effect do not show any obvious relationship with the bulk YIG
magnetization. The distinct high-field magneto-transport effects in Pd are
shown to be caused by interfacial local moments in Pd.

###Giant magnetoresistance in the junction of two ferromagnets on the surface of diffusive topological insulators|Katsuhisa Taguchi,Takehito Yokoyama,Yukio Tanaka###

Giant magnetoresistance in the junction of two ferromagnets on the surface of diffusive topological insulators. We reveal the giant magnetoresistance induced by the spin-polarized current
in the ferromagnet (F_1)/topological insulator (TI)/ferromagnet (F_2) junction,
where two ferromagnets are deposited on the diffusive surface of the TI. We can
increase and reduce the value of the giant magnetoresistance by tuning the
spin-polarized current, which is controlled by the magnetization
configurations. The property is intuitively understood by the non-equilibrium
spin-polarized current, which plays the role of an effective electrochemical
potential on the surface of the TI.

###Molecular Anisotropic Magnetoresistance|Fabian Otte,Stefan Heinze,Yuriy Mokrousov###

Molecular Anisotropic Magnetoresistance. Using density functional theory calculations, we demonstrate that the effect
of anisotropic magnetoresistance (AMR) can be enhanced by orders of magnitude
with respect to conventional bulk ferromagnets in junctions containing
molecules sandwiched between ferromagnetic leads. We study ballistic transport
in metal-benzene complexes contacted by $3d$ transition-metal wires. We show
that the gigantic AMR can arise from spin-orbit coupling effects in the leads,
drastically enhanced by orbital-symmetry filtering properties of the molecules.
We further discuss how this molecular anisotropic magnetoresistance (MAMR) can
be tuned by proper choice of materials and their electronic properties.

###Negative and nonlinear magnetoresistance effect in silicon strip|Fangcong Wang,Haixia Li,Hui Guo,Xiaolong Fan,Zhankui Li###

Negative and nonlinear magnetoresistance effect in silicon strip. Both negative magnetoresistance and nonlinear magnetoresisitance were
observed in silicon strip nuclear radiation detector in room temperature if we
applied high magnetic field intensity in different direction. This result is
different with former report. We believe this is the result of coaction of high
electric field (Gunn effect) and high magnetic field, or because of the
variation of number of carriers and the carriers mobility. The weak
localization and Landau energy levels also affect the magnetoresistance.
Different crystal orientations have different energy band structures. Complex
band structures lead complex carriers mobility plus Landau energy levels. So
the magnetoresisitance effect is anisotropy.

###Six-fold crystalline anisotropic magnetoresistance in the (111) LaAlO$_3$/SrTiO$_3$ oxide interface|P. K. Rout,I. Agireen,E. Maniv,M. Goldstein,Y. Dagan###

Six-fold crystalline anisotropic magnetoresistance in the (111) LaAlO$_3$/SrTiO$_3$ oxide interface. We measured the magnetoresistance of the 2D electron liquid formed at the
(111) LaAlO$_3$/SrTiO$_3$ interface. The hexagonal symmetry of the interface is
manifested in a six-fold crystalline component appearing in the anisotropic
magnetoresistance (AMR) and planar Hall data, which agree well with symmetry
analysis we performed. The six-fold component increases with carrier
concentration, reaching 15% of the total AMR signal. Our results suggest the
coupling between higher itinerant electronic bands and the crystal as the
origin of this effect and demonstrate that the (111) oxide interface is a
unique hexagonal system with tunable magnetocrystalline effects.

###Magnetic and magnetotransport properties of ThCr2Si2-type Ce2O2Bi composed of conducting Bi2- square net and magnetic Ce-O layer|Shunsuke Shibata,Ryosuke Sei,Tomoteru Fukumura,Tetsuya Hasegawa###

Magnetic and magnetotransport properties of ThCr2Si2-type Ce2O2Bi composed of conducting Bi2- square net and magnetic Ce-O layer. ThCr2Si2-type Ce2O2Bi epitaxial thin films were grown by recently developed
multilayer solid phase epitaxy. The ionic state of Ce was confirmed to be 3+ by
x-ray photoelectron spectroscopy, corresponding to the electronic configuration
of [Xe]4f1. Electrical resistivity showed the nonmonotonic temperature
dependence with a sharp resistivity maximum, concomitant with a magnetization
kink at 10 K, suggesting antiferromagnetic transition. In addition,
magnetoresistance showed a large angular-dependent magnetoresistance. These
results imply that carrier transport in the Bi2- square net could be influenced
by magnetic ordering in the Ce-O layer owing to its unique layered structure
[Bi2-/(Ce2O2)2+], particularly in the form of epitaxial thin films.

###Unusual anisotropy of inplane field magnetoresistance in ultra-high mobility SiGe/Si/SiGe quantum wells|M. Yu. Melnikov,V. T. Dolgopolov,A. A. Shashkin,S. -H. Huang,C. W. Liu,S. V. Kravchenko###

Unusual anisotropy of inplane field magnetoresistance in ultra-high mobility SiGe/Si/SiGe quantum wells. We find an unusual anisotropy of the inplane field magnetoresistance in
ultra-high mobility SiGe/Si/SiGe quantum wells. The anisotropy depends on the
orientation between the inplane field, $B_\parallel$, and current, $I$,
relative to the crystallographic axes of the sample and is a consequence of the
intrinsic ridges on the quantum well surface. For the simplest orientations
between current and crystallographic axes, a method of recalculating the
magnetoresistance measured at $I\perp B_\parallel$ into the one measured at
$I\parallel B_\parallel$ is suggested and is shown to yield results that agree
with the experiment.

###Quantum linear magnetoresistance in NbTe2|Hongxiang Chen,Zhilin Li,Xiao Fan,Liwei Guo,Xiaolong Chen###

Quantum linear magnetoresistance in NbTe2. NbTe2 crystal is quasi-2D layered semimetal with charge density wave ground
state showing a distorted-1T structure at room temperature. Here we report the
anisotropic magneto-transport properties of NbTe2. An anomalous linear
magnetoresistance up to 30% at 3 K in 9 T was observed, which can be well
explained by quantum linear magnetoresistance model. Our results reveal that a
large quasi-2D Fermi surface and small Fermi pockets with linearly dispersive
bands coexist in NbTe2. The comparison with the isostructural material TaTe2
provides more information about the electronic structure evolution with charge
density wave transitions in NbTe2 and TaTe2.

###Spin-Hall and Anisotropic Magnetoresistance in Ferrimagnetic Co-Gd / Pt layers|W. Zhou,T. Seki,T. Kubota,G. E. W. Bauer,K. Takanashi###

Spin-Hall and Anisotropic Magnetoresistance in Ferrimagnetic Co-Gd / Pt layers. We present the Co-Gd composition dependence of the spin-Hall
magnetoresistance (SMR) and anisotropic magnetoresistance (AMR) for
ferrimagnetic Co100-xGdx / Pt bilayers. With Gd concentration x, its magnetic
moment increasingly competes with the Co moment in the net magnetization. We
find a nearly compensated ferrimagnetic state at x = 24. The AMR changes sign
from positive to negative with increasing x, vanishing near the magnetization
compensation. On the other hand, the SMR does not vary significantly even where
the AMR vanishes. These experimental results indicate that very different
scattering mechanisms are responsible for AMR and SMR. We discuss a possible
origin for the alloy composition dependence.

###Quantum Interference Theory of Magnetoresistance in Dirac Materials|Bo Fu,Huan-Wen Wang,Shun-Qing Shen###

Quantum Interference Theory of Magnetoresistance in Dirac Materials. Magnetoresistance in many samples of Dirac semimetal and topological
insulator displays non-monotonic behaviors over a wide range of magnetic field.
Here a formula of magnetoconductivity is presented for massless and massive
Dirac fermions in Dirac materials due to quantum interference in scalar
impurity scattering potentials. It reveals a striking crossover from positive
to negative magnetoresistivity, uncovering strong competition between weak
localization and weak antilocalization in multiple Cooperon modes at different
chemical potentials, effective masses and finite temperatures. The work sheds
light on the important role of strong coupling of the conduction and valence
bands in the quantum interference transport in topological nontrivial and
trivial Dirac materials.

###Magnetothermal cooling with a phase separated manganite|A. Rebello,R. Mahendiran###

Magnetothermal cooling with a phase separated manganite. We show that temperature of a current (I = 20 mA) carrying manganite
(Nd0.5Ca0.5Mn0.93Ni0.07O3) in presence of a magnetic field (H) decreases
abruptly as much as deltaT = 45 K (7 K) accompanied by a step like decrease in
magnetoresistance at a critical value of H when the base temperature is 40 K
(100 K). The magnitude of deltaT and the position of magnetoresistance step
decrease towards lower H with decreasing amplitude of the current. We discuss
possible origins of the current and magnetic- field driven temperature change
which may find applications in magnetothermal refrigeration besides
magnetocaloric effect.

###Spin Hall magnetoresistance at Pt/CoFe2O4 interfaces and texture effects|Miren Isasa,Amilcar Bedoya-Pinto,Saül Vélez,Federico Golmar,Florencio Sánchez,Luis E. Hueso,Josep Fontcuberta,Fèlix Casanova###

Spin Hall magnetoresistance at Pt/CoFe2O4 interfaces and texture effects. We report magnetoresistance measurements on thin Pt bars grown on epitaxial
(001) and (111) CoFe2O4 (CFO) ferrimagnetic insulating films. The results can
be described in terms of the recently discovered spin Hall magnetoresistance
(SMR). The magnitude of the SMR depends on the interface preparation
conditions, being optimal when Pt/CFO samples are prepared in situ, in a single
process. The spin-mixing interface conductance, the key parameter governing SMR
and other relevant spin-dependent phenomena such as spin pumping or spin
Seebeck effect, is found to be different depending on the crystallographic
orientation of CFO, highlighting the role of the composition and density of
magnetic ions at the interface on spin mixing.

###Temperature dependent spin transport properties of Platinum inferred from spin Hall magnetoresistance measurements|Sibylle Meyer,Matthias Althammer,Stephan Geprägs,Matthias Opel,Rudolf Gross,Sebastian T. B. Goennenwein###

Temperature dependent spin transport properties of Platinum inferred from spin Hall magnetoresistance measurements. We study the temperature dependence of the spin Hall magnetoresistance (SMR)
in yttrium iron garnet/platinum hybrid structures via magnetization orientation
dependent magnetoresistance measurements. Our experiments show a decrease of
the SMR magnitude with decreasing temperature. Using the sensitivity of the SMR
to the spin transport properties of the normal metal, we interpret our data in
terms of a decrease of the spin Hall angle in platinum from 0.11 at room
temperature to 0.075 at 10K, while the spin diffusion length and the spin
mixing conductance of the ferrimagnetic insulator/normal metal interface remain
almost constant.

###Large linear magnetoresistance in a new Dirac material BaMnBi2|Yi-Yan Wang,Qiao-He Yu,Tian-Long Xia###

Large linear magnetoresistance in a new Dirac material BaMnBi2. We report the synthesis of high quality single crystals of BaMnBi2 and
investigate the transport properties of the samples. The Hall data reveals
electron-type carriers and a mobility mu(5K) =1500cm2/Vs. The temperature
dependence of magnetization displays behavior that is different from CaMnBi2 or
SrMnBi2 , which suggests the possible different magnetic structure of BaMnBi2.
Angle-dependent magnetoresistance reveals the quasi-two-dimensional Fermi
surface. A crossover from semiclassical MR-H2 dependence in low field to MR-H
dependence in high field is observed in transverse magnetoresistance. Our
results indicate the anisotropic Dirac fermion states in BaMnBi2.

###Spin Hall magnetoresistance in antiferromagnet/normal metal bilayers|A. Manchon###

Spin Hall magnetoresistance in antiferromagnet/normal metal bilayers. We predict the emergence of spin Hall magnetoresistance in a magnetic bilayer
composed of a normal metal adjacent to an antiferromagnet. Based on a recently
derived drift-diffusion equation, we show that the resistance of the bilayer
depends on the relative angle between the direction transverse to the current
flow and the N\'eel order parameter. Although this effect presents striking
similarities with the spin Hall magnetoresistance recently reported in
ferromagnetic bilayers, in the present case its physical origin is attributed
to the anisotropic spin relaxation of itinerant spins in the antiferromagnet.

###Unsaturated magnetoconductance of epitaxial La0.7Sr0.3MnO3 thin films in pulsed magnetic fields up to 60 T|Wei Niu,Xuefeng Wang,Ming Gao,Zhengcai Xia,Jun Du,Yuefeng Nie,Fengqi Song,Yongbing Xu,Rong Zhang###

Unsaturated magnetoconductance of epitaxial La0.7Sr0.3MnO3 thin films in pulsed magnetic fields up to 60 T. We report on the temperature and field dependence of resistance of
La0.7Sr0.3MnO3 thin films over a wide temperature range and in pulsed magnetic
fields up to 60 T. The epitaxial La0.7Sr0.3MnO3 thin films were deposited by
laser molecular beam epitaxy. High magnetic field magnetoresistance curves were
fitted by the Brillouin function, which indicated the existence of magnetically
polarized regions and the underlying hopping mechanism. The unsaturated
magnetoconductance was the most striking finding observed in pulsed magnetic
fields up to 60 T. These observations can deepen the fundamental understanding
of the colossal magnetoresistance in manganites with strong correlation of
transport properties and magnetic ordering.

###Pressure Tuning of Collapse of Helimagnetic Structure in Au$_2$Mn|I-Lin Liu,Maria J. Pascale,Juscelino B. Leao,Craig M. Brown,William D. Ratcliff,Qingzhen Huang,Nicholas P. Butch###

Pressure Tuning of Collapse of Helimagnetic Structure in Au$_2$Mn. We identify the phase boundary between spiral spin and ferromagnetic phases
in Au$_2$Mn at a critical pressure of 16.4 kbar, as determined by neutron
diffraction, magnetization and magnetoresistance measurements. The
temperature-dependent critical field at a given pressure is accompanied by a
peak in magnetoresistance and a step in magnetization. The critical field
decreases with increasing temperature and pressure. The critical pressure
separating the spiral phase and ferromagnetism coincides with the disappearance
of the magnetroresistance peak, where the critical field goes to zero. The
notable absence of an anomalous Hall effect in the the ferromagnetic phase is
attributable to the high conductivity of this material.

###Coexistence of surface and bulk state and negative magnetoresistance in Sulfur doped Bi2Se3|Rahul Singh,Vinod K. Gangwar,D. D. Daga,Mahima Singh,A. K. Ghosh,Manoranjan Kumar,A. Lakhani,Rajeev Singh,Sandip Chatterjee###

Coexistence of surface and bulk state and negative magnetoresistance in Sulfur doped Bi2Se3. The magneto-transport properties in Sulfur doped Bi2Se3 are investigated. The
magnetoresistance (MR) decreases with increase of S content and finally for 7%
(i.e. y=0.21) S doping the magnetoresistance becomes negative. This negative MR
is unusual as it is observed when magnetic field is applied with the
perpendicular direction to the plane of the sample. The magneto-transport
behavior shows the shubnikov-de hass (SdH) oscillation indicating the
coexistence of both surface and bulk states. The negative MR has been
attributed to the bulk conduction.

###Suppression of the fieldlike spin-orbit torque efficiency due to the magnetic proximity effect in ferromagnet/platinum bilayers|T. A. Peterson,A. P. McFadden,C. J. Palmstrøm,P. A. Crowell###

Suppression of the fieldlike spin-orbit torque efficiency due to the magnetic proximity effect in ferromagnet/platinum bilayers. Current-induced spin-orbit torques in Co$_2$FeAl/Pt ultrathin bilayers are
studied using a magnetoresistive harmonic response technique, which
distinguishes the dampinglike and fieldlike contributions. The presence of a
temperature-dependent magnetic proximity effect is observed through the
anomalous Hall and anisotropic magnetoresistances, which are enhanced at low
temperatures for thin platinum thicknesses. The fieldlike torque efficiency
decreases steadily as the temperature is lowered for all Pt thicknesses
studied, which we propose is related to the influence of the magnetic proximity
effect on the fieldlike torque mechanism.

###Enhanced spin-orbit coupling in a heavy metal via molecular coupling|Satam Alotibi,B. J. Hickey,Gilberto Teobaldi,Mannan Ali,Joseph Barker,Quentin Ramasse,Gavin Burnell,Mohammed Alyami,Timothy Moorsom,Oscar Cespedes###

Enhanced spin-orbit coupling in a heavy metal via molecular coupling. Heavy metals are key to spintronics because of their high spin-orbit coupling
(SOC) leading to efficient spin conversion and strong magnetic interactions.
When C60 is deposited on Pt, the molecular interface is metallised and the spin
Hall angle in YIG/Pt increased, leading to an enhancement of up to 600% in the
spin Hall magnetoresistance and 700% for the anisotropic magnetoresistance.
This correlates with Density Functional Theory simulations showing changes of
0.46 eV/C60 in the SOC of Pt. This effect opens the possibility of gating the
molecular hybridisation and SOC of metals.

###Anomalous Anisotropic Magnetoresistance in Heavy-Fermion PrFe4P12|H. Sugawara,E. Kuramochi,T. Namiki,T. D. Matsuda,Y. Aoki,H. Sato###

Anomalous Anisotropic Magnetoresistance in Heavy-Fermion PrFe4P12. We have investigated the anisotropy of the magnetoresistance in the Pr-based
HF compound PrFe4P12. The large anisotropy of effective mass and its strong
field dependence have been confirmed by resistivity measurements. Particularly
for H||[111], where the effective mass is most strongly enhanced, the non-Fermi
liquid behavior has been observed. Also, we have found the angular dependence
of the magnetoresistance sharply enhanced at H||[111], which is evidently
correlated with both the non-Fermi liquid behavior and the high-field ordered
state (B-phase).

###Effect of half-quantum vortices on magnetoresistance of perforated superconducting films|Victor Vakaryuk,Valerii Vinokur###

Effect of half-quantum vortices on magnetoresistance of perforated superconducting films. Recent cantilever magnetometry measurements of annular micron-size samples of
Sr2RuO4 have revealed evidence for the existence of half-quantum vortices
(HQVs) in this material [Jang et al. 2011]. We propose to look for HQVs in
transport measurements and calculate magnetoresistance of a perforated
superconducting film close to the transition temperature in the presence of
HQVs. We analyze the dependence of magnetoresistance on the thermodynamic
stability of HQVs which according to [Jang et al. 2011] can be varied by the
application of an in-plane magnetic field and point out features which may help
to identify them.

###Giant Planar Hall Effect in Topological Metals|A. A. Burkov###

Giant Planar Hall Effect in Topological Metals. Much excitement has been generated recently by the experimental observation
of the chiral anomaly in condensed matter physics. This manifests as strong
negative longitudinal magnetoresistance and has so far been clearly observed in
Na$_3$Bi, ZrTe$_5$, and GdPtBi. In this work we point out that the chiral
anomaly must lead to another effect in topological metals, that has been
overlooked so far: Giant Planar Hall Effect (GPHE), which is the appearance of
a large transverse voltage when the in plane magnetic field is not aligned with
the current. Moreover, we demonstrate that the GPHE is closely related to the
angular narrowing of the negative longitudinal magnetoresistance signal,
observed experimentally.

###Giant Magnetoresistance in Hubbard Chains|Jian Li,Chen Cheng,Thereza Paiva,Hai-Qing Lin,Rubem Mondaini###

Giant Magnetoresistance in Hubbard Chains. We use numerically unbiased methods to show that the one-dimensional Hubbard
model with periodically distributed on-site interactions already contains the
minimal ingredients to display the phenomenon of magnetoresistance; i.e., by
applying an external magnetic field, a dramatic enhancement on the charge
transport is achieved. We reach this conclusion based on the computation of the
Drude weight and of the single-particle density of states, applying twisted
boundary condition averaging to reduce finite-size effects. The known picture
that describes the giant magnetoresistance, by interpreting the scattering
amplitudes of parallel or antiparallel polarized currents with local
magnetizations, is obtained without having to resort to different entities;
itinerant and localized charges are indistinguishable.

###Anomalous Hall effect induced spin Hall magnetoresistance in an antiferromagnetic Cr2O3/Ta bilayer|Yang Ji,J. Miao,K. K. Meng,X. G. Xu,J. K. Chen,Y. Wu,Y. Jiang###

Anomalous Hall effect induced spin Hall magnetoresistance in an antiferromagnetic Cr2O3/Ta bilayer. The spin Hall magnetoresistance (SMR) and anomalous Hall effect (AHE) are
observed in a Cr2O3/Ta structure. The structural and surface morphology of
Cr2O3/Ta bilayers have been investigated. Temperature dependence of
longitudinal and transverse resistances measurements confirm the relationship
between SMR and AHE signals in Cr2O3/Ta structure. By means of temperature
dependent magnetoresistance measurements, the physical origin of SMR in the
Cr2O3/Ta structure is revealed, and the contribution to the SMR from the spin
current generated by AHE has been proved. The so-called boundary magnetization
due to the bulk antiferromagnetic order in Cr2O3 film may be responsible for
the relationship of SMR and AHE in the Cr2O3/Ta bilayer.

###Negative magnetoresistance suppressed through topological phase transition in (Cd1-xZnx)3As2 films|S. Nishihaya,M. Uchida,Y. Nakazawa,K. Akiba,M. Kriener,Y. Kozuka,A. Miyake,Y. Taguchi,M. Tokunaga,M. Kawasaki###

Negative magnetoresistance suppressed through topological phase transition in (Cd1-xZnx)3As2 films. The newly discovered topological Dirac semimetals host the possibilities of
various topological phase transitions through the control of spin-orbit
coupling as well as symmetries and dimensionalities. Here, we report a
magnetotransport study of high-mobility (Cd1-xZnx)3As2 films, where the
topological Dirac semimetal phase can be turned into a trivial insulator via
chemical substitution. By high-field measurements with a Hall-bar geometry,
magnetoresistance components ascribed to the chiral charge pumping have been
distinguished from other extrinsic effects. The negative magnetoresistance
exhibits a clear suppression upon Zn doping, reflecting decreasing Berry
curvature of the band structure as the topological phase transition is induced
by reducing the spin-orbit coupling.

###Consequences of the CMR effect on EELS in TEM|Wolfgang Wallisch,Michael Stöger-Pollach,Edvinas Navickas###

Consequences of the CMR effect on EELS in TEM. Double perovskite oxides have gained in importance and exhibit negative
magnetoresistance, which is known as colossal magnetoresistance (CMR) effect.
Using a La$_2$CoMnO$_6$ (LCM) thin film we prove that the physical consequences
of the CMR effect do also influence the electron energy loss spectrometry
(EELS) signal. We observe a change of the band gap at low energy losses and are
able to study the magnetisation with chemical sensitivity by employing energy
loss magnetic chiral dichroism (EMCD) below the Curie temperature T$_C$ where
the CMR effect becomes significant.

###Domain wall resistance in CoFeB-based heterostructures with interface Dzyaloshinskii-Moriya interaction|Yuto Ishikuro,Masashi Kawaguchi,Yong-Chang Lau,Yoshinobu Nakatani,Masamitsu Hayashi###

Domain wall resistance in CoFeB-based heterostructures with interface Dzyaloshinskii-Moriya interaction. We have studied the domain wall resistance in W/Ta/CoFeB/MgO
heterostructures. The Ta layer thickness is varied to control the type of
domain walls via changes in the interfacial Dzyaloshinskii Moriya interaction.
We find a nearly constant domain wall resistance against the Ta layer
thickness. Adding contributions from the anisotropic magnetoresistance, spin
Hall magnetoresistance and anomalous Hall effect describe well the domain wall
resistance of the thick Ta layer films. However, a discrepancy remains for the
thin Ta layer films wherein chiral N\'eel-like domain walls are found. These
results show the difficulty of studying the domain wall type from resistance
measurements.

###Anisotropic Magnetoresistance and Nontrivial Spin Hall Magnetoresistance in Pt/$α$-Fe$_2$O$_3$ Bilayers|Yang Cheng,Sisheng Yu,Adam S. Ahmed,Menglin Zhu,Jinwoo Hwang,Fengyuan Yang###

Anisotropic Magnetoresistance and Nontrivial Spin Hall Magnetoresistance in Pt/$α$-Fe$_2$O$_3$ Bilayers. To date, magnetic proximity effect (MPE) has only been conclusively observed
in ferromagnet (FM) based systems. We report the observation of anomalous Hall
effect and anisotropic magnetoresistance in angular dependent magnetoresistance
(ADMR) measurements in Pt on antiferromagnetic (AF) $\alpha$-Fe$_2$O$_3$(0001)
epitaxial films at 10 K, which provide evidence for the MPE. The N\'eel order
of $\alpha$-Fe$_2$O$_3$ and the induced magnetization in Pt show a unique ADMR
compared with all other FM and AF systems. A macrospin response model is
established and can explain the AF spin configuration and all main ADMR
features in the Pt/$\alpha$-Fe$_2$O$_3$ bilayers.

###Detection of the Orbital Hall Effect by the Orbital-Spin Conversion|Jiewen Xiao,Yizhou Liu,Binghai Yan###

Detection of the Orbital Hall Effect by the Orbital-Spin Conversion. The intrinsic orbital Hall effect (OHE), the orbital counterpart of the spin
Hall effect, was predicted and studied theoretically for more than one decade,
yet to be observed in experiments. Here we propose a strategy to convert the
orbital current in OHE to the spin current via the spin-orbit coupling from the
contact. Furthermore, we find that OHE can induce large nonreciprocal
magnetoresistance when employing magnetic contact. Both the generated spin
current and the orbital Hall magnetoresistance can be applied to probe the OHE
in experiments and design orbitronic devices.

###Negative Magneto-Resistance in a Long Superconducting Wires: Theory and Experiments|Boris Ya. Shapiro###

Negative Magneto-Resistance in a Long Superconducting Wires: Theory and Experiments. The effect of negative magnetoresistance for thin superconducting wire was
considered in a simple model. These phenomena originated from competition of
two mechanism: fluctuations of the order parameter and quasiparticles charge
imbalance which accompanies each phase slip event. First process results in
conventional positive magnetoresistance while the second mechanism gives the
negative contributions. Simple analytical formula is obtained for the negative
magnetic resistance caused by both the thermodynamics (TAPS) and quantum
fluctuations. Theoretical results are compared with experimental data and
demonstrate good agreement between theory and experiment.

###Bloch-Lorentz magnetoresistance oscillations in delafossites|Kostas Vilkelis,Lin Wang,Anton Akhmerov###

Bloch-Lorentz magnetoresistance oscillations in delafossites. Recent measurements of the out-of-plane magnetoresistance of delafossites
(PdCoO$_2$ and PtCoO$_2$) observed oscillations closely resembling the
Aharonov-Bohm effect. Here, we show that the magnetoresistance oscillations are
explained by the Bloch-like oscillations of the out-of-plane electron
trajectories. We develop a semiclassical theory of these Bloch-Lorentz
oscillations and show that they are a consequence of the ballistic motion and
quasi-2D dispersion of delafossites. Our model identifies the sample wall
scattering to be the most likely factor limiting the visibility of these
Bloch-Lorentz oscillations in existing experiments.

###Jump of tunneling magnetoresistance in magnetic nanocontacts with mismatched cross section|V. L. Katkov,V. A. Osipov###

Jump of tunneling magnetoresistance in magnetic nanocontacts with mismatched cross section. We have studied the influence of the transverse size of a magnetic tunnel
nanojunction on the magnitude of the magnetoresistance. During modeling, the
size of the right contact was fixed, while the size of the left one gradually
changed until they coincided. We found a sharp drop in the tunneling
magnetoresistance (TMR) in nanocontacts with mismatched cross section. This can
be explained by the peculiarities of the spatial distribution of the electron
density, which is different for majority and minority-spin states. The
discovered effect must be taken into account in the design of TMR-based
nanodevices.

###Gigantic tunneling magnetoresistance in magnetic Weyl semimetal tunnel junctions|D. J. P. de Sousa,C. O. Ascencio,P. M. Haney,J. P. Wang,Tony Low###

Gigantic tunneling magnetoresistance in magnetic Weyl semimetal tunnel junctions. We investigate the tunneling magnetoresistance in magnetic tunnel junctions
(MTJs) comprised of Weyl semimetal contacts. We show that
chirality-magnetization locking leads to a gigantic tunneling magnetoresistance
ratio, an effect that does not rely on spin filtering by the tunnel barrier.
Our results indicate that the conductance in the anti-parallel configuration is
more sensitive to magnetization fluctuations than in MTJs with normal
ferromagnets, and predicts a TMR as large as 10^4 % when realistic
magnetization fluctuations are accounted for. In addition, we show that the
Fermi arc states give rise to a non-monotonic dependence of conductance on the
misalignment angle between the magnetizations of the two contacts.

###Hysteretic effects and magnetotransport of electrically switched CuMnAs|Jan Zubáč,Zdeněk Kašpar,Filip Krizek,Tobias Förster,Richard P. Campion,Vít Novák,Tomáš Jungwirth,Kamil Olejník###

Hysteretic effects and magnetotransport of electrically switched CuMnAs. Antiferromagnetic spintronics allows us to explore storing and processing
information in magnetic crystals with vanishing magnetization. In this
manuscript, we investigate magnetoresistance effects in antiferromagnetic
CuMnAs upon switching into high-resistive states using electrical pulses. By
employing magnetic field sweeps up to 14 T and magnetic field pulses up to
$\sim$ 60 T, we reveal hysteretic phenomena and changes in the
magnetoresistance, as well as the resilience of the switching signal in CuMnAs
to the high magnetic field. These properties of the switched state are
discussed in the context of recent studies of antiferromagnetic textures in
CuMnAs.

###Antiferromagnetic Hysteresis above the Spin Flop Field|M. J. Grzybowski,C. F. Schippers,O. Gomonay,K. Rubi,M. E. Bal,U. Zeitler,A. Kozioł-Rachwał,M. Szpytma,W. Janus,B. Kurowska,S. Kret,M. Gryglas-Borysiewicz,B. Koopmans,H. J. M. Swagten###

Antiferromagnetic Hysteresis above the Spin Flop Field. Magnetocrystalline anisotropy is essential in the physics of antiferromagnets
and commonly treated as a constant, not depending on an external magnetic
field. However, we demonstrate that in CoO the anisotropy should necessarily
depend on the magnetic field, which is shown by the spin Hall magnetoresistance
of the CoO $|$ Pt device. Below the N\'eel temperature CoO reveals a spin-flop
transition at 240 K at 7.0 T, above which a hysteresis in the angular
dependence of magnetoresistance unexpectedly persists up to 30 T. This behavior
is shown to agree with the presence of the unquenched orbital momentum, which
can play an important role in antiferromagnetic spintronics.

###Planar Hall effect in Cu intercalated PdTe$_2$|Sonika,M. K. Hooda,Shailja Sharma,C. S. Yadav###

Planar Hall effect in Cu intercalated PdTe$_2$. We present the Planar Hall effect studies on the Cu intercalated type-II
Dirac semimetal PdTe$_{2}$. The electrical resistivity exhibits a positive
field dependence both in perpendicular and parallel field directions, causing
non-zero anisotropy. The longitudinal magnetoresistance shows almost linear
field dependence at low temperatures. A tilted prolate spheroid shaped orbits
are observed in parametric plot between transverse and longitudinal
resistivities. Our study suggest that for the type-II Dirac semimetal materials
with positive longitudinal magnetoresistance, the origin of Planar Hall effect
cannot be asserted with certainty to the topological or non-topological without
taking into account the anisotropy of Fermi surface.

###Current-in-plane magnetoresistance in chiral-molecule/ferromagnetic metal bilayer due to thermally induced spin polarization|Kouta Kondou,Masanobu Shiga,Shoya Sakamoto,Hiroyuki Inuzuka,Atsuko Nihonyanagi,Fumito Araoka,Masaki Kobayashi,Shinji Miwa,Daigo Miyajima,YoshiChika Otani###

Current-in-plane magnetoresistance in chiral-molecule/ferromagnetic metal bilayer due to thermally induced spin polarization. We report chirality-induced current-in-plane magnetoresistance (CIP-MR) in
chiral molecule/ferromagnetic metal bilayer at room temperature. The previously
reported chiralityinduced current-perpendicular-to-plane magnetoresistance
(CPP-MR) originates from the chiral induced spin-selectivity (CISS) effect that
needs charge-current passing through the molecule. In contrast, the observed
CIP-MR in the present study requires no bias charge current through the
molecule. The temperature dependence of CIP-MR suggests thermally induced
spin-polarization in the chiral molecules is the key for the observed MR.

###Disorder-induced linear magnetoresistance in Sr-doped Bi2Se3 thin films|Jiayuan Hu,Wenxiang Jiang,Guohua Wang,Yunlong Li,Jiangtao Wang,Jinlong Jiao,Qi Lu,Chenhang Xu,Wentao Zhang,Jie Ma,Dong Qian###

Disorder-induced linear magnetoresistance in Sr-doped Bi2Se3 thin films. Sr-doped Bi2Se3 thin films was known as a potential candidate of topological
superconductor. The magnetoresistance (MR) of SrxBi2Se3 films with various
doping concentrations x were found to be dominated by weak antilocalization
(WAL) at low magnetic fields, whereas the classical MR, which originally
dominated the MR, was almost completely suppressed. In contrast, the MR of all
samples has been observed to be dominated by linear magnetoresistance (LMR) at
high magnetic fields. The LMR, having the linear dependence on carrier
mobility, can be successfully explained by the Parish-Littlewood model. This
indicates that LMR originates from mobility fluctuation induced by Sr dopant
atoms in doped Bi2Se3 films.

###Bilinear magnetoresistance in topological insulators: role of magnetic disorder|A. N. Zarezad,A. Dyrdał###

Bilinear magnetoresistance in topological insulators: role of magnetic disorder. Bilinear magnetoresistance is a nonlinear transport phenomenon that scales
linearly with the electric and magnetic fields, and appears in nonmagnetic
systems with strong spin-orbit coupling, such as topological insulators (TIs).
Using the semiclassical Boltzmann theory and generalized relaxation time
approximation, we consider in detail the bilinear magnetoresistance in an
effective model describing surface states of three-dimensional topological
insulators. We show that the presence of magnetic impurities remarkably
modifies the BMR signal. In general, scattering on magnetic impurities reduces
magnitude of BMR. Apart from this, an additional modulation of the angular
dependence of BMR appears when the spin-dependent component of the impurity
potential dominates the scalar one.

###Magnetotransport due to conductivity fluctuations in non-magnetic ZrTe2 nanoplates|Jie Wang,Yihao Wang,Min Wu,Junbo Li,Shaopeng Miao,Qingyi Hou,Yun Li,Jianhui Zhou,Xiangde Zhu,Yimin Xiong,Wei Ning,Mingliang Tian###

Magnetotransport due to conductivity fluctuations in non-magnetic ZrTe2 nanoplates. Transition metal dichalcogenides with nontrivial band structures exhibit
various fascinating physical properties and have sparked intensively research
interest. Here, we performed systematic magnetotransport measurements on
mechanical exfoliation prepared ZrTe2 nanoplates. We revealed that the negative
longitudinal magnetoresistivity observed at high field region in the presence
of parallel electric and magnetic fields could stem from the conductivity
fluctuations due to the excess Zr in the nanoplates. In addition, the
parametric plot, the planar Hall resistivity as function of the in-plane
anisotropic magnetoresistivity, has an ellipse-shaped pattern with shifted
orbital center, which further strengthen the evidence for the conductivity
fluctuations. Our work provides some useful insights into transport phenomena
in topological materials.

###Interplay of symmetry-conserved tunneling, interfacial oxidation and perpendicular magnetic anisotropy in CoFeB/MgO-based junctions|Pravin Khanal,Bowei Zhou,Hamid Almasi,Ali Habiboglu,Magda Andrade,Jack O'Brien,Arthur Enriquez,Carter Eckel,Christopher Mastrangelo,Wei-Gang Wang###

Interplay of symmetry-conserved tunneling, interfacial oxidation and perpendicular magnetic anisotropy in CoFeB/MgO-based junctions. The interfacial oxidation level and thermodynamic properties of the MgO-based
perpendicular magnetic tunneling junctions are investigated. The
symmetry-conserved tunneling effect depends sensitively on the MgO adatom
energy during the RF sputtering, as well as the thermal stability of the
structure during the post-growth thermal annealing. Two different failure modes
of the magnetoresistance are highlighted, involving with the decay of
perpendicular magnetic anisotropy and destruction of coherent tunneling
channels, respectively. Through the careful control of interfacial oxidation
level and proper selection of the heavy metal layers, both perpendicular
magnetic anisotropy and tunneling magnetoresistance of the junctions can be
increased.

###Observation of the unidirectional magnetoresistance in antiferromagnetic insulator Fe2O3/Pt bilayers|Yihong Fan,Pengxiang Zhang,Jiahao Han,Yang Lv,Luqiao Liu,Jian-Ping Wang###

Observation of the unidirectional magnetoresistance in antiferromagnetic insulator Fe2O3/Pt bilayers. Unidirectional magnetoresistance (UMR) has been observed in a variety of
stacks with ferromagnetic/spin Hall material bilayer structures. In this work,
we reported UMR in antiferromagnetic insulator Fe2O3/Pt structure. The UMR has
a negative value, which is related to interfacial Rashba coupling and band
splitting. Thickness-dependent measurement reveals a potential competition
between UMR and the unidirectional spin Hall magnetoresistance (USMR). This
work revealed the existence of UMR in antiferromagnetic insulators/heavy metal
bilayers and broadens the way for the application of antiferromagnet-based
spintronic devices.

###Electronic Transport in a Topological Semimetal WTe2 Single Crystal|A. N. Perevalova,S. V. Naumov,V. V. Chistyakov,E. B. Marchenkova,B. M. Fominykh,V. V. Marchenkov###

Electronic Transport in a Topological Semimetal WTe2 Single Crystal. Electrical resistivity, magnetoresistivity, and the Hall effect have been
studied in a topological semimetal WTe2 single crystal in the temperature range
from 12 to 200 K under magnetic fields up to 9 T. It has been found that
quadratic temperature dependences of the electrical resistivity in the absence
of a magnetic field and the conductivity in a magnetic field are observed at
low temperatures, which is apparently associated with contributions from
various scattering mechanisms. Single-band and two-band models were used to
analyze data on the Hall effect and magnetoresistivity. These results indicate
electron-hole compensation with a slight predominance of electron charge
carriers.

###Modulation of Hanle magnetoresistance in an ultrathin platinum film by ionic gating|Yuu Maruyama,Ryo Ohshima,Ei Shigematsu,Yuichiro Ando,Masashi Shiraishi###

Modulation of Hanle magnetoresistance in an ultrathin platinum film by ionic gating. Hanle magnetoresistance (HMR) is a type of magnetoresistance where interplay
of the spin Hall effect, Hanle-type spin precession, and spin-dependent
scattering at the top/bottom surfaces in a heavy metal controls the effect. In
this study, we modulate HMR in ultrathin Pt by ionic gating, where the surface
Rashba field created by a strong electric field at the interface between the
ionic gate and Pt plays the dominant role in the modulation. This finding can
facilitate investigations of gate-tunable, spin-related effects and fabrication
of spin devices.

###Transport properties of very overdoped nonsuperconducting Bi2Sr2CuO6+d thin films|H. Raffy,Z. Z. Li,P. Auban-Senzier###

Transport properties of very overdoped nonsuperconducting Bi2Sr2CuO6+d thin films. The transport properties, resistance, Hall effect, and low T
magnetoresistance for very oxygen overdoped nonsuperconducting Bi2Sr2CuO6+d
(Bi2201) thin films are reported. From 20 to 300K, the temperature dependence
of the resistance is well described by a law of the form a+bT4/3, theoretically
predicted to occur in the presence of ferromagnetic fluctuations. In addition,
this prediction is reinforced by the analysis of the transverse and the
longitudinal low T magnetoresistance. Interestingly, the presence of a weak
disorder causing low T electronic localization allows us to evidence very short
diffusion lengths, as observed in other systems with ferromagnetic
fluctuations.

###Transport across junctions of altermagnets with normal metals and ferromagnets|Sachchidanand Das,Dhavala Suri,Abhiram Soori###

Transport across junctions of altermagnets with normal metals and ferromagnets. Altermagnet (AM) is a novel time reversal symmetry broken magnetic phase with
$d$-wave order. We discuss theoretical models of altermagnet based systems on
lattice and in continuum that are amenable to experimental measurements and
show equivalence between the two models. We study (i) altermagnet-normal metal
(NM) and (ii) altermagnet-ferromagnet (FM) junctions, with the aim to quantify
transport properties such as conductivity and magnetoresistance. We find that a
spin current accompanies charge current when a bias is applied. The
magnetoresistance of the AM-FM junction switches sign when AM is rotated by
$90^{\circ}$, -a feature unique to the altermagnetic phase.

###Magnetic properites of the Heavy Fermion Antiferromagnets YbNiAl and YbPtAl|J. Diehl,H. Davideit,S. Klimm,S. Horn,U. Tegel,C. Geibel,F. Steglich###

Magnetic properites of the Heavy Fermion Antiferromagnets YbNiAl and YbPtAl. Measurements of electrical resistivity and Hall effect as a function of
magnetic field on the Heavy Fermion Systems YbNiAl and YbPtAl are presented.
Both compounds order antiferro magnetically and show metamagnetic behavior in a
magnetic field. Scaling behavior of the magnetoresistance above TN suggests
that the paramagnetic regime for YbNiAl can be described in terms of a single
ion Kondo effect.

###Magnetoresistance of the Double-Exchange Model in Infinite Dimension|Nobuo Furukawa###

Magnetoresistance of the Double-Exchange Model in Infinite Dimension. Double-exchange model in infinite dimension is studied as the strong Hund's
coupling limit $J\to\infty$ of the Kondo lattice model. Several quantities such
as Green's function and the d.c.\ conductivity are calculated in analytical
forms. Magnetoresistance in lightly doped (La,Sr)MnO$_3$ is reproduced very
well.

###Universal Spin-Induced Magnetoresistance in the Variable-Range Hopping Regime|Yigal Meir###

Universal Spin-Induced Magnetoresistance in the Variable-Range Hopping Regime. The magnetoresistance in the variable-range hopping regime due to Zeeman
spin-splitting and intra-impurity interactions is calculated analytically and
shown to be a universal function of $\mu H / kT \log R$. Good agreement with
numerical calculations in one and two dimensions is observed. With the
inclusion of quantum interference effects, excellent agreement with recent
experiments is obtained.

###Magnetic and Transport Properties of (La,Sr)MnO$_3$|Nobuo Furukawa###

Magnetic and Transport Properties of (La,Sr)MnO$_3$. Magnetic and transport properties of the perovskite-type $3d$
transition-metal oxide (La,Sr)MnO$_3$ are theoretically studied using the
double-exchange model in infinite dimension. Magnetoresistance properties as
well as the magnetic transition temperatures are in good agreement with the
experimental data.

###Nonequilibrium spin distribution in single-electron transistor|Alexander N. Korotkov,V. I. Safarov###

Nonequilibrium spin distribution in single-electron transistor. Single-electron transistor with ferromagnetic outer electrodes and
nonmagnetic island is studied theoretically. Nonequilibrium electron spin
distribution in the island is caused by tunneling current. The dependencies of
the magnetoresistance ratio $\delta$ on the bias and gate voltages show the
dips which are directly related to the induced separation of Fermi levels for
electrons with different spins. Inside a dip $\delta$ can become negative.

###Spin excitations in ferromagnetic manganites|J. Loos,H. Fehske###

Spin excitations in ferromagnetic manganites. An effective one-band Hamiltonian for colossal-magnetoresistance (CMR)
manganites is constructed and the spin excitations are determined. Fitting the
experimental data by the derived spin-wave dispersion gives an e_g -electron
hopping amplitude of about 0.2 eV in agreement with LDA band calculations.

###Influence of disorder on the perpendicular magnetoresistance of magnetic multilayers|Patrick Bruno,Hiroyoshi Itoh,Junichiro Inoue,Shinji Nonoyama###

Influence of disorder on the perpendicular magnetoresistance of magnetic multilayers. The effect of disorder on the perpendicular magnetoresistance of magnetic
multilayers is investigated theoretically. Various kinds of disorder are
considered: (i) interface substitutional disorder and (ii) bulk disorder in the
various layers and in the leads. The calculations are based upon the
non-equilibrium Green's function formalism, together with the recursion method
for calculating the real-space Green's function.

###Spin effects in single-electron tunneling in magnetic junctions|J. Martinek,J. Barnas,G. Michalek,B. R. Bulka,A. Fert###

Spin effects in single-electron tunneling in magnetic junctions. Spin dependent single electron tunneling in ferromagnetic double junctions is
analysed theoretically in the limit of sequential tunneling. The influence of
discrete energy spectrum of the central electrode (island)on the spin
accumulation, spin fluctuations and tunnel magnetoresistance is analysed
numerically in the case of a nonmagnetic island. It is shown that spin
fluctuations are significant in magnetic as well as in nonmagnetic junctions.

###Positive magnetoresistance and orbital ordering in La(1-x)Sr(x)MnO(3)|M. Paraskevopoulos,J. Hemberger,A. Loidl,A. A. Mukhin,V. Yu. Ivanov,A. M. Balbashov###

Positive magnetoresistance and orbital ordering in La(1-x)Sr(x)MnO(3). We report on detailed transprort measurements of single crystalline
La(1-x)Sr(x)MnO(3) (x<=0.2). We have found a giantpositive magnetoresistance in
the compositions range between 0.1<=x<=0.125 and give an explaination in terms
of orbital ordering due to the interplay between superexchange interactions and
Jahn-Teller distortions.

###Large Thermopower in a Layered Oxide NaCo_2O_4|I. Terasaki,Y. Sasago,K. Uchinokura###

Large Thermopower in a Layered Oxide NaCo_2O_4. A transition-metal oxide NaCo_2O_4 is a layered oxide in which CoO_2 and Na
alternately stack along the c axis. Recently we have found that this compound
shows unusually large thermopower with low resistivity, which is comparable to
those of Bi_2Te_3. The negative transverse magnetoresistance and the strongly
temperature-dependent Hall coefficient suggest that electron correlation
dominates the conduction mechanism in NaCo_2O_4.

###Anisotropic Transport of Two-Dimensional Holes in High Landau Levels|M. Shayegan,H. C. Manoharan,S. J. Papadakis,E. P. DePoortere###

Anisotropic Transport of Two-Dimensional Holes in High Landau Levels. Magnetoresistance data taken along $[\bar{2}33]$ and $[01\bar{1}]$ directions
in a GaAs/AlGaAs two-dimensional hole sample with van der Pauw geometry exhibit
significant anisotropy at half-integer filling factors. The anisotropy appears
to depend on both the density and symmetry of the hole charge distribution.

###Orbital Dynamics: The Origin of Anomalous Magnon Softening in Ferromagnetic Manganites|G. Khaliullin,R. Kilian###

Orbital Dynamics: The Origin of Anomalous Magnon Softening in Ferromagnetic Manganites. We study the renormalization of magnons by charge and coupled orbital-lattice
fluctuations in colossal magnetoresistance compounds. The model considered is
an orbitally degenerate double-exchange system coupled to Jahn-Teller active
phonons. The modulation of ferromagnetic bonds by low-energy orbital
fluctuations is identified as the main origin of the unusual softening of the
zone-boundary magnons observed experimentally in manganites.

###Theory of Dephasing by External Perturbation in Open Quantum Dots|M. G. Vavilov,I. L. Aleiner###

Theory of Dephasing by External Perturbation in Open Quantum Dots. We propose a random matrix theory describing the influence of a time
dependent external field on the average magnetoresistance of open quantum dots.
The effect is taken into account in all orders of perturbation theory, and the
result is applicable to both weak and strong external fields.

###Universal Behaviour of Metal-Insulator Transitions in the p-SiGe System|P. T. Coleridge,P. Zawadzki,A. S. Sachrajda,R. L. Williams,Y. Feng###

Universal Behaviour of Metal-Insulator Transitions in the p-SiGe System. Magnetoresistance measurements are presented for a strained p-SiGe quantum
well sample where the density is varied through the B=0 metal-insulator
transition. The close relationship between this transition, the high field Hall
insulator transition and the filling factor $\nu$=3/2 insulating state is
demonstrated.

###Characterisation, Raman, Magnetic and Resistivity measurements in polycrystalline samples of LaMnO3 doped with Cd|J. Lopez,V. Dediu,P. Nozar,G. Ruani,C. Dionigi,F. C. Matacotta,C. Ferdeghini,G. Calestani###

Characterisation, Raman, Magnetic and Resistivity measurements in polycrystalline samples of LaMnO3 doped with Cd. We report a study of polycrystalline samples of the family La1-xCdxMnO3+dwith
different percentage of Mn4+ ions. X-rays diffraction, Iodometric titration,
Raman, Magnetic and Electrical Resistivity measurements provide a general
characterisation of the physical properties. Results are qualitatively similar
to the ones found in Ca doped manganese perovskites.
  Key words: Cd, manganese perovskites, magnetoresistance, Raman, magnetic,
resistivity

###Magnetotransport in an array of magnetic antidots|L. Solimany###

Magnetotransport in an array of magnetic antidots. Classical transport properties of an electron, moving in plain, in an array
of magnetic antidot has been calculated. The homogeneous magnetic field in
z-direction fills the whole space except of cylinders of radius r_0. The
magnetoresistance shows additional peak and minimum according to pinned orbits
at antidots and to propagating orbits in transport direction, respectively.

###First observation of Aharonov-Bohm cages in 2-D normal metal networks|Cecile Naud,Giancarlo Faini,Dominique Mailly###

First observation of Aharonov-Bohm cages in 2-D normal metal networks. We report on magnetoresistance transport measurements performed on a
bipartite tiling of rhombus in the GaAs/GaAlAs system. We observe for the first
time large amplitude $h/e$ oscillations in this network as compared to the one
measured in square lattices of similar size. These oscillations are the
signature of a recently predicted localization phenomenon induced by
Aharonov-Bohm interferences in this peculiar network.

###Terahertz radiation from magnetoresistive Pr$_{\text{0.7}}$Ca$_{\text{0.3}}$MnO$_{\text3}$ thin films|N. Kida,M. Tonouchi###

Terahertz radiation from magnetoresistive Pr$_{\text{0.7}}$Ca$_{\text{0.3}}$MnO$_{\text3}$ thin films. Terahertz (THz) radiation with its spectrum extending up to 1 THz has been
observed by an illumination of femtosecond optical pulses to optical switching
devices fabricated on magnetoresistive manganite thin films;
Pr$_{0.7}$Ca$_{0.3}$MnO$_3$. The THz radiation strongly depends on temperature
$T$ and its $T$ trend reverses sign across charge-orbital and spin ordering
$T$'s.

###Effective Lorentz Force due to Small-angle Impurity Scattering: Magnetotransport in High-Tc Superconductors|C. M. Varma,Elihu Abrahams###

Effective Lorentz Force due to Small-angle Impurity Scattering: Magnetotransport in High-Tc Superconductors. We show that a scattering rate which varies with angle around the Fermi
surface has the same effect as a periodic Lorentz force on magnetotransport
coefficients. This effect, together with the marginal Fermi liquid inelastic
scattering rate gives a quantitative explanation of the temperature dependence
and the magnitude of the observed Hall effect and magnetoresistance with just
the measured zero-field resistivity as input.

###Considerations on the quantum double-exchange Hamiltonian|A. Weisse,J. Loos,H. Fehske###

Considerations on the quantum double-exchange Hamiltonian. Schwinger bosons allow for an advantageous representation of quantum
double-exchange. We review this subject, comment on previous results, and
address the transition to the semiclassical limit. We derive an effective
fermionic Hamiltonian for the spin-dependent hopping of holes interacting with
a background of local spins, which is used in a related publication within a
two-phase description of colossal magnetoresistant manganites.

###Theory of Angular Magnetoresistance in CPP spin valves|Daniel Huertas-Hernando,Gerrit E. W. Bauer,Yu. V. Nazarov###

Theory of Angular Magnetoresistance in CPP spin valves. The resistance of CPP spin valve is a continuous function of the angle
$\theta $ between the magnetizations of both ferromagnets. We use the cicuit
theory for non-collinear magnetoelectronics to compute the angular
magnetoresistance of CPP spin valves taking the spin accumulation in the
ferromagnetic layers into account.

###Superconducting Fluctuations in Granular Metals with a Large Coupling Between the Grains|B. S. Skrzynski,I. S. Beloborodov,K. B. Efetov###

Superconducting Fluctuations in Granular Metals with a Large Coupling Between the Grains. We study the fluctuation conductivity of superconducting granular metals at
low temperatures and strong magnetic field destroying the Cooper pairs.
Explicit calculations are performed for larger values of the coupling between
the grains than those considered in previous works. We show that in a broad
region of the coupling constants the superconducting fluctuations still
significantly reduce the conductivity leading to a negative magnetoresistance.

###Magnetic polarons in Ca_(1-x)Y_xMnO_3|H. Aliaga,M. T. Causa,M. Tovar,B. Alascio###

Magnetic polarons in Ca_(1-x)Y_xMnO_3. Experimental evidence show that in the magnetoresistive manganite Ca_(1-x)
Y_xMnO_3, ferromagnetic (FM) polarons arises in an antiferromagnetic (AF)
background, as a result of the doping with Yttrium. This hypothesis is
supported in this work by classical Monte Carlo (MC) calculations performed on
a model where FM Double Exchange (DE) and AF Superexhange (SE) compite.

###Effects of Spin Polarization on Electron Transport in Modulation Doped Cd(1-x)Mn(x)Te/Cd(1-y)Mg(y)Te:I Heterostructures|T. Andrearczyk,J. Jaroszynski,G. Karczewski,J. Wrobel,T. Wojtowicz,T. Dietl,E. Papis,E. Kami'nska,A. Piotrowska###

Effects of Spin Polarization on Electron Transport in Modulation Doped Cd(1-x)Mn(x)Te/Cd(1-y)Mg(y)Te:I Heterostructures. We examine and identify magnetoresistance mechanisms in 2D system containing
a sizable concentration of magnetic ions. We argue that some of these
mechanisms can serve as a tool to measure spin polarization. Lack of spin
degeneracy and enhanced localization make it possible to detect an additional
QHE plateau associated with extended states floating-up in vanishing magnetic
field.

###On the magnetotransport of 3D systems in quantizing magnetic field|M. V. Cheremisin###

On the magnetotransport of 3D systems in quantizing magnetic field. The resistivity components of 3D electron gas placed in quantizing magnetic
field are calculated taking into account the correction caused by combined
action of the Peltier and Seebeck thermoelectric effects. The longitudinal,
transverse and the Hall magnetoresistivities exhibit familiar 1/H-period
oscillations being universal functions of magnetic field and temperature.

###Spin-dependent electron transport through a ferromagnetic domain wall|J. Ohe,M. Yamamoto,T. Ohtsuki,K. Slevin###

Spin-dependent electron transport through a ferromagnetic domain wall. We present a theoretical study of spin-dependent transport through a
ferromagnetic domain wall. With an increase of the number of components of the
exchange coupling, we have observed that the variance of the conductance
becomes half. As the strength of the domain wall magnetization is increased,
negative magnetoresistance is also observed.

###Radiation-induced oscillatory magnetoresistance as a sensitive probe of the zero-field spin splitting in high mobility GaAs/AlGaAs devices|R. G. Mani,J. H. Smet,K. von Klitzing,V. Narayanamurti,W. B. Johnson,V. Umansky###

Radiation-induced oscillatory magnetoresistance as a sensitive probe of the zero-field spin splitting in high mobility GaAs/AlGaAs devices. We suggest an approach for characterizing the zero-field spin splitting of
high mobility two-dimensional electron systems, when beats are not readily
observable in the Shubnikov-de Haas effect. The zero-field spin splitting and
the effective magnetic field seen in the reference frame of the electron is
evaluated from a quantitative study of beats observed in radiation-induced
magnetoresistance oscillations.

###Lattice and superexchange effects in doped CMR manganites|Alexander Weisse,Holger Fehske###

Lattice and superexchange effects in doped CMR manganites. We report on the influence of the lattice degrees of freedom on charge,
orbital and spin correlations in colossal magnetoresistance (CMR) manganites.
For the weakly doped compounds we demonstrate that the electron-phonon coupling
promotes the trapping of charge carriers, the disappearance of the orbital
polaron pattern and the breakdown of ferromagnetism at the CMR transition. The
role of different superexchange interactions is explored.

###Randomness Effect on Multicritical Phenomena in Double-Exchange Systems|Yukitoshi Motome,Nobuo Furukawa,Naoto Nagaosa###

Randomness Effect on Multicritical Phenomena in Double-Exchange Systems. Double-exchange model interacting with adiabatic phonons is studied in the
presence of randomness by using the Monte-Carlo method and the systematic
size-scaling analysis. A bicritical behavior is found between the ferromagnetic
metal and the charge-ordered insulator. We find the distinct response to the
randomness between these two states, which agrees well with the experimental
results in the colossal magnetoresistance manganites.

###Giant magnetoresistance oscillations caused by cyclotron resonance harmonics|S. I. Dorozhkin###

Giant magnetoresistance oscillations caused by cyclotron resonance harmonics. For high-mobility two-dimensional electrons at a GaAs/AlGaAs heterojunction,
we have studied, both experimentally and theoretically, the recently discovered
giant magnetoresistance oscillations with nearly zero resistance in the
oscillation minima which appear under microwave radiation. We have proposed a
model based on nonequilibrium occupation of Landau levels caused by radiation
which describes the oscillation picture.

###Shot noise in a diffusive F-N-F spin valve|E. G. Mishchenko###

Shot noise in a diffusive F-N-F spin valve. Fluctuations of electric current in a spin valve consisting of a diffusive
conductor connected to ferromagnetic leads and operated in the giant
magnetoresistance regime are studied. It is shown that a new source of
fluctuations due to spin-flip scattering enhances strongly shot noise up to a
point where the Fano factor approaches the full Poissonian value.

###Strain selection of charge and orbital ordering patterns in half-doped manganites|M. J. Calderon,A. J. Millis,K. H. Ahn###

Strain selection of charge and orbital ordering patterns in half-doped manganites. Theoretical and computational results are presented clarifying the role of
long-ranged strain interactions in determining the charge and orbital ordering
in colossal magnetoresistance manganites. The strain energy contribution is
found to be of order 20-30 meV/Mn and in particular stabilizes the anomalous
'zig-zag chain' order observed in many half-doped manganites.

###Clustered States as a New Paradigm of Condensed Matter Physics|G. Alvarez,E. Dagotto###

Clustered States as a New Paradigm of Condensed Matter Physics. We argue that several materials of much current interest in condensed matter
physics share common phenomenological aspects that only very recent
investigations are unveiling. The list includes colossal magnetoresistance
manganites, high temperature superconducting cuprates, diluted magnetic
semiconductors, and others. The common aspect is the relevance of intrinsic
inhomogeneities in the form of "clustered states", as explained in the text.

###Magnetotransport Coefficients of Sm0.55Sr0.45MnO3|R Suryanarayanan,V Gasumyants###

Magnetotransport Coefficients of Sm0.55Sr0.45MnO3. Measurements of Seebeck effect in 0 and 1.5 T and Nernst coefficient in
0.3,0.9 and 1.8 T as a function of temperature on a polycrystalline sample
Sm0.55Sr0.45MnO3 are presented. The data point out conclusively that an
increase inboth the carrier density and the mobility of the charge carriers is
responsible for the observed colossal magnetoresistance

###Non-monotonic angular magnetoresistance in asymmetric spin valves|Jan Manschot,Arne Brataas,Gerrit E. W. Bauer###

Non-monotonic angular magnetoresistance in asymmetric spin valves. The electric resistance of ferromagnet/normal-metal/ferromagnet perpendicular
spin valves depends on the relative angle between the magnetization directions.
In contrast to common wisdom, this angular magnetoresistance is found to be not
necessarily a monotone function of the angle. The parameter dependence of the
global resistance minimum at finite angles is studied and the conditions for
experimental observation are specified.

###Metal-insulator transition in EuO|P. Sinjukow,W. Nolting###

Metal-insulator transition in EuO. It is shown that the spectacular metal-insulator transition in Eu-rich EuO
can be simulated within an extended Kondo lattice model. The different orders
of magnitude of the jump in resistivity in dependence on the concentration of
oxygen vacancies as well as the low-temperature resistance minimum in
high-resistivity samples are reproduced quantitatively. The huge colossal
magnetoresistance (CMR) is calculated and discussed.

###Magnetism, Charge Order and Giant Magnetoresistance in SrFeO$_{3-δ}$ Single Crystals|A. Lebon,P. Adler,C. Bernhard,A. V. Boris,A. V. Pimenov,A. Maljuk,C. T. Lin,C. Ulrich,B. Keimer###

Magnetism, Charge Order and Giant Magnetoresistance in SrFeO$_{3-δ}$ Single Crystals. The electronic and magnetic properties of SrFeO$_{3-\delta}$ single crystals
with controlled oxygen content ($0 \leq \delta \leq 0.19$) have been studied
systematically by susceptibility, transport and spectroscopic techniques. An
intimate correlation between the spin-charge ordering and the electronic
transport behavior is found. Giant negative as well as positive
magnetoresistance are observed.

###On the origin of magnetoresistance in Sr$_2$FeMoO$_6$|D. D. Sarma,Sugata Ray,K. Tanaka,A. Fujimori###

On the origin of magnetoresistance in Sr$_2$FeMoO$_6$. We report detailed magnetization ($M$) and magnetoresistance ($MR$) studies
on a series of Sr$_2$FeMoO$_6$ samples with independent control on anti-site
defect and grain boundary densities. These results, exhibiting a switching-like
behavior of $MR$ with $M$, establish that the $MR$ is controlled by the
magnetic polarization of grain boundary regions, rather than of the grains
within a resonant tunnelling mechanism.

###Observation of a node in the quantum oscillations induced by microwave radiation|Alexey E. Kovalev,Sergey A. Zvyagin,Clifford R. Bowers,John L. Reno,Jerry A. Simmons###

Observation of a node in the quantum oscillations induced by microwave radiation. The microwave induced magnetoresistance in GaAs/AlGaAs heterostructure was
studied at temperatures below 1K and frequencies in the range of 150-400 GHz. A
distinct node in the Shubnikov- de Haas oscillations, induced by the microwave
radiation, is clearly observed. The node position coincides with the position
of the cyclotron resonance on the carriers with effective mass (0.068 +/-
0.005) m0.

###Anomalous Parallel Field Negative Magnetoresistance in Ultrathin Films Near the Superconductor-Insulator Transition|Kevin A. Parendo,L. M. Hernandez,A. Bhattacharya,A. M. Goldman###

Anomalous Parallel Field Negative Magnetoresistance in Ultrathin Films Near the Superconductor-Insulator Transition. A parallel field negative magnetoresistance has been found in
quench-condensed ultrathin films of amorphous bismuth in the immediate vicinity
of the thickness-tuned superconductor-insulator transition. The effect appears
to be a signature of quantum fluctuations of the order parameter associated
with the quantum critical point.

###Entropy-Driven Reentrant Behavior in CMR Manganites|Nobuo Furukawa,Yukitoshi Motome,Naoto Nagaosa###

Entropy-Driven Reentrant Behavior in CMR Manganites. We discuss the origin of the reentrant behaviors of insulating states above
the Curie temperature of the colossal magnetoresistance manganites. We consider
a system where charge ordering and ferromagnetism compete with each other. In
the presence of randomness which pins charge order fluctuations, entropy-driven
reentrant behaviors will appear, which explains the typical temperature
dependence of the resistivity for CMR manganites.

###Magnetoresistance in metals with embedded magnetic nano-clusters|O. Tsyplyatyev,Vladimir I. Fal'ko###

Magnetoresistance in metals with embedded magnetic nano-clusters. We propose a kinetic theory of transport in metals embedded with
ferromagnetic nanoclusters, describing the dependence of the form of
magnetoresistance on anisotropy characteristics of the ensemble of clusters and
the influence of the electron spin depolarisation by clusters. We note that
this effect is strongest when all the clusters have the same intrinsic
easy-axis anisotropy.

###The Role of Grain Boundaries in Determining the Transport Properties in Magnetite|David C. Mertens,W. Montfrooij,R. J. McQueeney,M. Yethiraj,J. M. Honig###

The Role of Grain Boundaries in Determining the Transport Properties in Magnetite. We present magnetoresistance and Hall-effect measurements on single crystal
magnetite Fe3O4 close to the Verwey transition Tv = 123.8 K. We show that the
formation of grain boundaries accompanying the reduction in crystal symmetry
plays a significant role in the electron scattering mechanism, and that grain
boundaries can account for the apparent change in sign of the charge carriers
below Tv.

###Anisotropic positive magnetoresistance of a nonplanar 2D electron gas in a parallel magnetic field|A. V. Goran,A. A. Bykov,A. K. Bakarov,J. C. Portal###

Anisotropic positive magnetoresistance of a nonplanar 2D electron gas in a parallel magnetic field. We study the transport properties of a 2D electron gas in narrow GaAs quantum
wells with AlAs/GaAs superlattice barriers. It is shown that the anisotropic
positive magnetoresistance observed in selectively doped semiconductor
structures in a parallel magnetic field is caused by the spatial modulation of
the 2D electron gas.

###Planar Hall Effect MRAM|Y. Bason,L. Klein,J. -B. Yau,X. Hong,J. Hoffman,C. H. Ahn###

Planar Hall Effect MRAM. We suggest a new type of magnetic random access memory (MRAM) that is based
on the phenomenon of the planar Hall effect (PHE) in magnetic films, and we
demonstrate this idea with manganite films. The PHE-MRAM is structurally
simpler than currently developed MRAM that is based on magnetoresistance tunnel
junctions (MTJ), with the tunnel junction structure being replaced by a single
layer film.

###An Intermediate Phase at the Metal-Insulator Boundary in a Magnetically Doped Two-Dimensional Electron System|J. Jaroszynski,T. Andrearczyk,G. Karczewski,J. Wróbel,T. Wojtowicz,Dragana Popovic,T. Dietl###

An Intermediate Phase at the Metal-Insulator Boundary in a Magnetically Doped Two-Dimensional Electron System. A magnetotransport study in magnetically doped (Cd,Mn)Te 2D quantum wells
reveals an apparent metal-insulator transition as well as an anomalous
intermediate phase just on its metallic side. This phase is characterized by
colossal magnetoresistance-like phenomena, which are assigned to the phase
separation of the electron fluid and the associated emergence of ferromagnetic
bubbles.

###Negative differential resistance in single crystal La_{2}CuO_{4} at low temperature|B. I. Belevtsev,N. V. Dalakova###

Negative differential resistance in single crystal La_{2}CuO_{4} at low temperature. A current-controlled negative differential resistance has been revealed in
the I-V characteristics of single crystal La$_{2}$CuO$_{4+\delta}$ in the low
temperature region. The non-linear behavior of conductivity is accompanied by a
transition from positive to negative magnetoresistance when the current is
growing. Possible reasons for the effect observed are discussed.

###Magnetotransport in d-wave density waves|Balázs Dóra,Kazumi Maki,Attila Virosztek###

Magnetotransport in d-wave density waves. Angle dependent magnetoresistance (ADMR) and giant Nernst effect are
hallmarks of unconventional density waves (UDW). Here these transport
properties for d-wave density wave (d-DW) are computed for
quasi-two-dimensional systems. The present theory describes ADMR observed in
the pseudogap phase of Y_0.68Pr_0.32Ba_2Cu_3O_7 and CeCoIn_5 single crystals
very satisfactorily.

###Charge-transfer polaron induced negative differential resistance and giant magnetoresistance in organic spintronics: A Su-Schrieffer-Heeger model study|J. H. Wei,S. J. Xie,L. M. Mei,J. Berakdar,YiJing Yan###

Charge-transfer polaron induced negative differential resistance and giant magnetoresistance in organic spintronics: A Su-Schrieffer-Heeger model study. Combining the Su-Schrieffer-Heeger model and the non-equilibrium Green's
function formalism, we investigate the negative differential resistance effect
in organic spintronics at low temperature and interprete it with a self-doping
picture. A giant negative magnetoresistance exceeding 300% is theoretically
predicted as the results of the negative differential resistance effects.

###Magnetoresistance Anomalies in Ce-based Heavy Fermion Compounds|N E Sluchanko,A V Bogach,V V Glushkov,S V Demishev,N A Samarin,G S Burhanov,O D Chistiakov,D N Sluchanko###

Magnetoresistance Anomalies in Ce-based Heavy Fermion Compounds. The work presents experimental results of precision magnetoresistance dr(H,T)
measurements obtained for canonical heavy fermion compounds CeAl2, CeAl3, CeCu6
and substitutional solid solutions CeCu6-xAux (x=0.1 and 0.2) and
Ce(Al0.95M0.05)2 (M - Co, Ni). The research was performed in a wide range of
temperatures (1.8-30K) and magnetic fields (up to 80 kOe). The data analysis
indicates that the most consistent interpretation of magnetoresistance of both
paramagnetic and magnetically ordered Ce-based systems with strong electron
correlations can be obtained through the approach developed by K.Yosida
(Phys.Rev., 107, 396(1957)) that considers charge carrier scattering on
localized magnetic moments in metallic matrix. Within this approach local
magnetic susceptibility hiloc(H,T0)=(1/H d(dr/r)/dH)1/2 has been estimated
directly from the magnetoresistance data dr/r=f(H,T0). As a result, two
additional contributions to magnetoresistance in Ce-based magnetic
intermetallides have been established and classified. The procedure allowed to
determine the peculiarities of magnetic phase ht diagram as well as to reveal
the electron density of states renormalization effects in a wide vicinity of
quantum critical point in the archetypal Ce-based systems with strong electron
correlations.

###Spin injection in a single metallic nanoparticle: a step towards nanospintronics|A. Bernand-Mantel,P. Seneor,N. Lidgi,M. Munoz,V. Cros,S. Fusil,K. Bouzehouane,C. Deranlot,A. Vaures,F. Petroff,A. Fert###

Spin injection in a single metallic nanoparticle: a step towards nanospintronics. We have fabricated nanometer sized magnetic tunnel junctions using a new
nanoindentation technique in order to study the transport properties of a
single metallic nanoparticle. Coulomb blockade effects show clear evidence for
single electron tunneling through a single 2.5 nm Au cluster. The observed
magnetoresistance is the signature of spin conservation during the transport
process through a non magnetic cluster.

###Design and Properties of a scanning EMR probe Microscope|S. A. Solin###

Design and Properties of a scanning EMR probe Microscope. The design, fabrication, and predicted performance of a new type of magnetic
scanning probe microscope based on the newly discovered phenomenon of
extraordinary magnetoresistance (EMR) is described. It is shown that the new
probe should advance the state of the art of both sensitivity and spatial
resolution by an order of magnitude or more.

###Comments on "Giant Dielectric Response in the One-Dimensional Charge-Ordered Semiconductor (NbSe_{4})_{3}I" and "Colossal Magnetocapacitance and Colossal Magnetoresistance in HgCr_{2}S_{4}"|Gustau Catalan,James F. Scott###

Comments on "Giant Dielectric Response in the One-Dimensional Charge-Ordered Semiconductor (NbSe_{4})_{3}I" and "Colossal Magnetocapacitance and Colossal Magnetoresistance in HgCr_{2}S_{4}". Comments on "Giant Dielectric Response in the One-Dimensional Charge-Ordered
Semiconductor (NbSe_{4})_{3}I" (D. Staresinic et al., Phys. Rev. Lett. 96,
046402 (2006)) and "Colossal Magnetocapacitance and Colossal Magnetoresistance
in HgCr_{2}S_{4}" (S. Weber et al., Phys. Rev. Lett. 96, 157202 (2006))

###Effect of Ge substitution for Si on the anomalous magnetocaloric and magnetoresistance properties of GdMn2Si2 compounds|Pramod Kumar,Niraj K. Singh,K. G. Suresh,A. K. Nigam,S. K. Malik###

Effect of Ge substitution for Si on the anomalous magnetocaloric and magnetoresistance properties of GdMn2Si2 compounds. The effect of Ge substitution on the magnetization, heat capacity,
magnetocaloric effect and magnetoresistance of GdMn2Si2-xGex (x=0, 1, and 2)
compounds has been studied. The magnetic transition associated with the Gd
ordering is found to change from second order to first order on Ge
substitution. Magnetic contributions to the total heat capacity and the entropy
have been estimated. Magnetocaloric effect has been calculated in terms of
adiabatic temperature change (deltaTad) as well as isothermal magnetic entropy
change (deltaSM) using the heat capacity data. The temperature dependence of
the magnetocaloric effect in all the three compounds have shown broad peaks.
The maximum values of deltaSM and deltaTad for GdMn2Ge2 are found to be 5.9
J/kgK and 1.2 K, respectively. The magnetoresistance is found to be very large
and positive with a maximum value of about 22% in the case of GdMn2Ge2. In the
other two compounds also, the magnetoresistance is predominantly positive,
except in the vicinity of the Gd ordering temperature. The anomalous nature of
the magnetocaloric effect and the magnetoresistance has been attributed to the
canted magnetic structure of these compounds.

###Is La1.85Y0.15CuO4 an oxygen-doped cuprate superconductor?|W. Yu,B. Liang,P. Li,S. Fujino,T. Murakami,I. Takeuchi,R. L. Greene###

Is La1.85Y0.15CuO4 an oxygen-doped cuprate superconductor?. We report resistivity, Hall effect, Nernst effect, and magnetoresistance
measurements on T'-phase La1.85Y0.15CuO (LYCO) films prepared by pulsed laser
deposition under different oxygen conditions. Our results show that
superconductivity in LYCO originates from an oxygen-doped Mott-like insulator
and not from a weakly correlated, half-filled band metal as proposed
previously.

###Spin transport through a single self-assembled InAs quantum dot with ferromagnetic leads|K. Hamaya,S. Masubuchi,M. Kawamura,T. Machida,M. Jung,K. Shibata,K. Hirakawa,T. Taniyama,S. Ishida,Y. Arakawa###

Spin transport through a single self-assembled InAs quantum dot with ferromagnetic leads. We have fabricated a lateral double barrier magnetic tunnel junction (MTJ)
which consists of a single self-assembled InAs quantum dot (QD) with
ferromagnetic Co leads. The MTJ shows clear hysteretic tunnel magnetoresistance
(TMR) effect, which is evidence for spin transport through a single
semiconductor QD. The TMR ratio and the curve shapes are varied by changing the
gate voltage.

###Tunneling anisotropic magnetoresistance and spin-orbit coupling in Fe/GaAs/Au tunnel junctions|J. Moser,A. Matos-Abiague,D. Schuh,W. Wegscheider,J. Fabian,D. Weiss###

Tunneling anisotropic magnetoresistance and spin-orbit coupling in Fe/GaAs/Au tunnel junctions. We report the observation of tunneling anisotropic magnetoresistance effect
(TAMR) in the epitaxial metal-semiconductor system Fe/GaAs/Au. The observed
two-fold anisotropy of the resistance can be switched by reversing the bias
voltage, suggesting that the effect originates from the interference of the
spin-orbit coupling at the interfaces. Corresponding model calculations
reproduce the experimental findings very well.

###Anisotropic magnetoresistance contribution to measured domain wall resistances of in-plane magnetised (Ga,Mn)As|H. G. Roberts,S. Crampin,S. J. Bending###

Anisotropic magnetoresistance contribution to measured domain wall resistances of in-plane magnetised (Ga,Mn)As. We demonstrate the presence of an important anisotropic magnetoresistance
contribution to the domain wall resistance recently measured in thin-film
(Ga,Mn)As with in-plane magnetic anisotropy. Analytic results for simple domain
wall orientations supplemented by numerical results for more general cases show
this previously omitted contribution can largely explain the observed negative
resistance.

###Enhanced Spin Dependent Shot Noise in Magnetic Tunnel Barriers|S. Garzon,Y. Chen,R. A. Webb###

Enhanced Spin Dependent Shot Noise in Magnetic Tunnel Barriers. We report the observation of enhanced spin dependent shot noise in magnetic
tunnel barriers, suggesting transport through localized states within the
barrier. This is supported by the existence of negative magnetoresistance and
structure in the differential conductance curves. A simple model of tunneling
through two interacting localized states with spin dependent tunneling rates is
used to explain our observations.

###Genetic Algorithms and Critical Phenomena|A. Barrañón,J. A. López,C. O. Dorso###

Genetic Algorithms and Critical Phenomena. Genetic algorithms based on natural selection and minimal fluctuations have
been applied to model physical and biological systems. Critical exponents have
been extracted via computational simulations of nucleation for colossal
magnetoresistance, heavy ions liquid-gas phase transitions and HIV to AIDS
transition.

###Implementation of a non-equilibrium Green's function method to calculate spin transfer torque|Christian Heiliger,Michael Czerner,Bogdan Yu. Yavorsky,Ingrid Mertig,Mark D. Stiles###

Implementation of a non-equilibrium Green's function method to calculate spin transfer torque. We present an implementation of the steady state Keldysh approach in a
Green's function multiple scattering scheme to calculate the non-equilibrium
spin density. This density is used to obtain the spin transfer torque in
junctions showing the magnetoresistance effect. We use our implementation to
study the spin transfer torque in metallic Co/Cu/Co junctions.

###Magnetotransport of electrons in quantum Hall systems|I. A. Dmitriev,F. Evers,I. V. Gornyi,A. D. Mirlin,D. G. Polyakov,P. Wölfle###

Magnetotransport of electrons in quantum Hall systems. Recent theoretical results on magnetotransport of electrons in a 2D system in
the range of moderately strong transverse magnetic fields are reviewed. The
phenomena discussed include: quasiclassical memory effects in systems with
various types of disorder, transport in lateral superlattices,
interaction-induced quantum magnetoresistance, quantum magnetooscillations in
dc and ac transport, and oscillatory microwave photoconductivity.

###Large magnetocaloric effect in Gd4Co3|Niharika Mohapatra,Kartik K Iyer,E. V. Sampathkumaran###

Large magnetocaloric effect in Gd4Co3. We report a large entropy change (DeltaS) below 300 K, peaking near TC= 220
K, due to isothermal change of magnetic field, for Gd4Co3, with a refrigeration
capacity higher than that of Gd. Notably, the isothermal magnetization is
nonhysteretic - an important criterion for magnetic refrigeration without loss.
DeltaS behavior is also compared with that of magnetoresistance.

###Voltage and Temperature Dependence of High-Field Magnetoresistance in Arrays of Magnetic Nanoparticles|Reasmey P. Tan,Julian Carrey,Marc Respaud###

Voltage and Temperature Dependence of High-Field Magnetoresistance in Arrays of Magnetic Nanoparticles. Huge values of high field magnetoresistance have been recently reported in
large arrays of CoFe nanoparticles embedded in an organic insulating lattice in
the Coulomb blockade regime. An unusual exponential decrease of
magnetoresistance with increasing voltage was observed, as well as a
characteristic scaling of the magnetoresistance amplitude versus the
field-temperature ratio. We propose a model which takes into account the
influence of paramagnetic impurities on the transport properties of the system
to describe these features. It is assumed that the non-colinearity between the
core spins inside the nanoparticles and the paramagnetic impurities can be
modelled by an effective tunnel barrier, the height of which depends on the
relative angle between the magnetization of both kind of spins. The influence
on the magnetotransport properties of the height and the thickness of the
effective tunnel barrier of the magnetic moment of the impurity, as well as the
bias voltage are studied. This model allows us to reproduce the large
magnetoresistance magnitude observed and its strong voltage dependence, with
realistic parameters.

###Boundary-mediated electron-electron interactions in quantum point contacts|Vincent Thomas Francois Renard,O. A. Tkachenko,V. A. Tkachenko,T. Ota,N. Kumada,J. -C. Portal,Y. Hirayama###

Boundary-mediated electron-electron interactions in quantum point contacts. An unusual increase of the conductance with temperature is observed in clean
quantum point contacts for conductances larger than 2e^2/h. At the same time a
positive magnetoresistance arises at high temperatures. A model accounting for
electron-electron interactions mediated by bound- aries (scattering on Friedel
oscillations) qualitatively describes the observation. It is supported by
numerical simulation at zero magnetic field.

###Spin-transfer switching and thermal stability in an FePt/Au/FePt nanopillar prepared by alternate monatomic layer deposition|Kay Yakushiji,Shinji Yuasa,Taro Nagahama,Akio Fukushima,Hitoshi Kubota,Toshikazu Katayama,Koji Ando###

Spin-transfer switching and thermal stability in an FePt/Au/FePt nanopillar prepared by alternate monatomic layer deposition. We fabricated a current-perpendicular-to-plane giant magnetoresistance
(CPP-GMR) nanopillar with a 1-nm-thick FePt free layer having perpendicular
anisotropy using the alternate monatomic layer deposition method. Nanopillars
consisting of [Fe (1 monolayer (ML))/Pt (1 ML)]n (n: the number of the
alternation period) ferromagnetic layers and an Au spacer layer showed
spin-transfer induced switching at room temperature.

###Lateral magnetic anisotropy superlattice out of a single (Ga,Mn)As layer|R. G. Dengel,C. Gould,J. Wenisch,K. Brunner,G. Schmidt,L. W. Molenkamp###

Lateral magnetic anisotropy superlattice out of a single (Ga,Mn)As layer. We use lithographically induced strain relaxation to periodically modulate
the magnetic anisotropy in a single (Ga,Mn)As layer. This results in a lateral
magnetoresistance device where two non-volatile magnetic states exist at zero
external magnetic field with resistances resulting from the orientation of two
lithographically defined regions in a single and contiguous layer.

###Anisotropic Magnetoresistance in Manganites: Model and Experiment|Javier D. Fuhr,Mara Granada,Laura B. Steren,Blas Alascio###

Anisotropic Magnetoresistance in Manganites: Model and Experiment. We present measurements of anisotropic magnetoresistance of
La_{0.75}Sr_{0.25}MnO_3 films deposited on (001) SrTiO_3 substrates, and
develop a model to describe the low temperature AMR in manganites. We measure
an AMR of the order of 10^{-3} for the current I parallel to the [100] axis of
the crystal and vanishing AMR for I//[110], in agreement with the model
predictions.

###Magnetic order in Graphite: Experimental evidence, intrinsic and extrinsic difficulties|P. Esquinazi,J. Barzola-Quiquia,D. Spemann,M. Rothermel,H. Ohldag,N. García,A. Setzer,T. Butz###

Magnetic order in Graphite: Experimental evidence, intrinsic and extrinsic difficulties. We discuss recently obtained data using different experimental methods
including magnetoresistance measurements that indicate the existence of
metal-free high-temperature magnetic order in graphite. Intrinsic as well as
extrinsic difficulties to trigger magnetic order by irradiation of graphite are
discussed in view of recently published theoretical work.

###Ferromagnetic- and superconducting-like behavior of the electrical resistance of inhomogeneous graphite flake|J. Barzola-Quiquia,P. Esquinazi###

Ferromagnetic- and superconducting-like behavior of the electrical resistance of inhomogeneous graphite flake. We have measured the magnetic field and temperature dependence of the
resistivity of several micrometers long and heterogeneously thick graphite
sample. The magnetoresistance results for fields applied nearly parallel to the
graphene planes show both a granular superconducting behavior as well as the
existence of magnetic order in the sample.

###Role of electron-electron interactions in nonlinear transport in 2D electron systems|A. T. Hatke,M. A. Zudov,L. N. Pfeiffer,K. W. West###

Role of electron-electron interactions in nonlinear transport in 2D electron systems. We study the temperature evolution of the non-linear oscillatory
magnetoresistance in a high-mobility two-dimensional electron system subject to
a strong dc electric field. We find that the decay of the oscillation amplitude
with increasing temperature originates primarily from increasing quantum
scattering rate entering the Dingle factor. We attribute this behavior to
electron-electron interaction effects.

###Elucidating the role of hyperfine interactions on organic magnetoresistance using deuterated aluminium tris(8-hydroxyquinoline)|N. J. Rolfe,M. Heeney,P. B. Wyatt,A. J. Drew,T. Kreouzis,W. P. Gillin###

Elucidating the role of hyperfine interactions on organic magnetoresistance using deuterated aluminium tris(8-hydroxyquinoline). Measurements of the effect of a magnetic field on the light output and
current through an organic light emitting diode made with deuterated aluminium
tris(8-hydroxyquinoline) have shown that hyperfine coupling with protons is not
the cause of the intrinsic organic magnetoresistance. We suggest that
interactions with unpaired electrons in the device may be responsible.

###In-Plane Magnetoresistance on the Surface of Topological Insulator|Morteza Salehi,Mohammad Alidoust,Yousef Rahnavard,Gholamreza Rashedi###

In-Plane Magnetoresistance on the Surface of Topological Insulator. We study the tunneling magneto-transport properties of the Ferromagnetic
Insulator-Normal Insulator-Ferromagnetic Insulator(F$\mid$N$\mid$F) and
Ferromagnetic Insulator-Barrier Insulator-Ferromagnetic Insulator
(F$\mid$B$\mid$F) junctions on the surface of topological insulator in which
in-plane magnetization directions of both ferromagnetic sides can be parallel
and antiparallel. We derive analytical expressions for electronic conductances
of the two mentioned junctions with both parallel and antiparallel directions
of magnetization and using them calculate magnetoresistance of the two
junctions. We use thin barrier approximation for investigating the
F$\mid$B$\mid$F junction. We find that although magnetoresistance of the
F$\mid$N$\mid$F and F$\mid$B$\mid$F junctions are tunable by changing the
strength of magnetization texture, they show different behaviors with variation
of magnetization. In contrast to the magnetoresistance of F$\mid$N$\mid$F,
magnetoresistance of F$\mid$B$\mid$F junctions shows very smooth enhance by
increasing the strength of magnetization. We suggest an experimental set up to
detect our predicted effects.

###Colossal enhancement of magnetoresistance in La$_{0.67}$Sr$_{0.33}$MnO$_{3}$ / Pr$_{0.67}$Ca$_{0.33}$MnO$_{3}$ multilayers: reproducing the phase-separation scenario|Soumik Mukhopadhyay,I. Das###

Colossal enhancement of magnetoresistance in La$_{0.67}$Sr$_{0.33}$MnO$_{3}$ / Pr$_{0.67}$Ca$_{0.33}$MnO$_{3}$ multilayers: reproducing the phase-separation scenario. Colossal enhancement of magnetoresistance has been achieved over a broad
temperature range which extends upto the room temperature, in ferromagnetic
metal-charge ordered insulator manganite multi-layers. The artificially created
phase coexistence in the multilayers reproduce the characteristic signatures of
metastability in the magnetotransport properties commonly observed in
electronically phase-separated manganites.

###Influence of Mutual Drag of Light and Heavy Holes on Magnetoresistivity and Hall-effect of p-Silicon and p-Germanium|I. I. Boiko###

Influence of Mutual Drag of Light and Heavy Holes on Magnetoresistivity and Hall-effect of p-Silicon and p-Germanium. Hall-effect and magnetoresistivity of holes in silicon and germanium are
considered with due regard for mutual drag of light and heavy band carriers.
Search of contribution of this drag shows that this interaction has a
sufficient and non-trivial influence on both effects.

###Tunnel magnetoresistance of Fe3O4/MgO/Fe nanostructures|S. G. Chigarev,E. M. Epshtein,I. V. Malikov,G. M. Mikhailov,P. E. Zilberman###

Tunnel magnetoresistance of Fe3O4/MgO/Fe nanostructures. A magnetic tunnel junction Fe3O4/MgO/Fe with (001) layer orientation is
considered. The junction magnetic energy is analyzed as a function of the angle
between the layer magnetization vectors under various magnetic fields. The
tunnel magnetoresistance is calculated as a function of the external magnetic
field. In contrast with junctions with unidirectional anisotropy, a
substantially lower magnetic field is required for the junction switching.

###Spin-thermo-electronic oscillator based on inverse giant magnetoresistance|A. M. Kadigrobov,S. Andersson,Hee Chul Park,D. Radic,R. I. Shekhter,M. Jonson,V. Korenivski###

Spin-thermo-electronic oscillator based on inverse giant magnetoresistance. A spin-thermo-electronic valve with the free layer of exchange-spring type
and inverse magnetoresistance is investigated. The structure has S-shaped
current-voltage characteristics and can exhibit spontaneous oscillations when
integrated with a conventional capacitor within a resonator circuit. The
frequency of the oscillations can be controlled from essentially dc to the GHz
range by the circuit capacitance.

###Weak localization of Dirac fermions in graphene beyond the diffusion regime|M. O. Nestoklon,N. S. Averkiev,S. A. Tarasenko###

Weak localization of Dirac fermions in graphene beyond the diffusion regime. We develop a microscopic theory of the weak localization of two-dimensional
massless Dirac fermions which is valid in the whole range of classically weak
magnetic fields. The theory is applied to calculate magnetoresistance caused by
the weak localization in graphene and conducting surfaces of bulk topological
insulators.

###Tailoring magnetoresistance through rotating Ni particles|Steven Achilles,Michael Czerner,Ingrid Mertig###

Tailoring magnetoresistance through rotating Ni particles. We present \textit{ab initio} studies for different Ni nanocontacts and show
changes in the conductance of such constrictions due to atomic rearrangements
in the contact. In particular we consider a Ni particle and show that the
magnetoresistance can change from a few to 50% and can even reverse sign as a
function of the contact area formed between the particle and the leads.

###Weak Localization and Antilocalization in Topological Insulator Thin Films with Coherent Bulk-Surface Coupling|Ion Garate,Leonid Glazman###

Weak Localization and Antilocalization in Topological Insulator Thin Films with Coherent Bulk-Surface Coupling. We evaluate quantum corrections to conductivity in an electrically gated thin
film of a three-dimensional (3D) topological insulator (TI). We derive
approximate analytical expressions for the low-field magnetoresistance as a
function of bulk doping and bulk-surface tunneling rate. Our results reveal
parameter regimes for both weak localization and weak antilocalization, and
include diffusive Weyl semimetals as a special case.

###Surface-induced Magnetism Fluctuations in Single Crystal of NiBi3 Superconductor|Xiangde Zhu,Hechang Lei,C. Petrovic,Yuheng Zhang###

Surface-induced Magnetism Fluctuations in Single Crystal of NiBi3 Superconductor. We report anistropy in superconducting and normal state of NiBi3 single
crystals with Tc = 4.06 K. The magnetoresistance results indicate the absence
of scattering usually associated with ferromagnetic metals, suggesting the
absence of bulk long range magnetic order below 300 K. However, the electron
spin resonance results demonstrate that ferromagnetism fluctuations exist on
the surface of the crystal below 150K.

###Electrical spin injection into graphene through monolayer hexagonal boron nitride|Takehiro Yamaguchi,Yoshihisa Inoue,Satoru Masubuchi,Sei Morikawa,Masahiro Onuki,Kenji Watanabe,Takashi Taniguchi,Rai Moriya,Tomoki Machida###

Electrical spin injection into graphene through monolayer hexagonal boron nitride. We demonstrate electrical spin injection from a ferromagnet to a bilayer
graphene (BLG) through a monolayer (ML) of single-crystal hexagonal boron
nitride (h-BN). A Ni81Fe19/ML h-BN/BLG/h-BN structure is fabricated using a
micromechanical cleavage and dry transfer technique. The transport properties
across the ML h-BN layer exhibit tunnel barrier characteristics. Spin injection
into BLG has been detected through non local magnetoresistance measurements.

###Influence of the magnetic material on tunneling magnetoresistance and spin-transfer torque in tunnel junctions: Ab initio studies|Christian Franz,Michael Czerner,Christian Heiliger###

Influence of the magnetic material on tunneling magnetoresistance and spin-transfer torque in tunnel junctions: Ab initio studies. The dependence of tunneling magnetoresistance and spin-transfer torque in
FeCo/MgO/FeCo tunnel junctions on the Co concentration and the bias voltage are
investigated ab initio. We find that the tunneling magnetoresistance decreases
with the Co concentration in contradiction with previous calculations but in
agreement with recent experiments. This dependence is explained from bulk
properties of the alloys. By using a realistic description of the disorder in
the alloys we can show that even small amounts of disorder lead to a drastic
drop in the tunneling magnetoresistance. This provides a quantitative
explanation of the difference between calculated and measured values.
  The spin-transfer torque shows a linear voltage dependence for the in-plane
component and a quadratic for the out-of-plane component for all concentrations
at small bias voltages. In particular, the linear slope of the in-plane torque
is independent of the concentration. For high bias voltages the in-plane torque
shows a strong nonlinear deviation from the linear slope for high Co
concentrations. This is explained from the same effects which govern the
tunneling magnetoresistance.

###Spin diffusion and magnetoresistance in ferromagnet/topological-insulator junctions|Takehito Yokoyama,Yaroslav Tserkovnyak###

Spin diffusion and magnetoresistance in ferromagnet/topological-insulator junctions. We study spin and charge diffusion in
metallic-ferromagnet/topological-insulator junctions. The coupled diffusion
equations are derived perturbatively with respect to the strength of the
interlayer tunneling. We calculate spin accumulation in the ferromagnet and
junction magnetoresistance associated with a current bias along the interface.

###Fundamental limitations of half-metallicicity in spintronic materials|A. Solontsov###

Fundamental limitations of half-metallicicity in spintronic materials. Zero-point spin fluctuations are shown to strongly influence the ground state
of ferromagnetic metals and to impose limitations for the fully spin polarized
state assumed in half-metallic ferromagnets, which may influence their
applications in spintronics. This phenomenon leads to the low-frequency Stoner
excitations and cause strong damping and softening of magnons in
magnetoresistive manganites observed experimentally.

###Superconducting nanowire quantum interference device based on Nb ultrathin films deposited on self-assembled porous Si templates|C. Cirillo,S. L. Prischepa,M. Trezza,V. P. Bondarenko,C. Attanasio###

Superconducting nanowire quantum interference device based on Nb ultrathin films deposited on self-assembled porous Si templates. Magnetoresistance oscillations were observed on networks of superconducting
ultrathin Nb nanowires presenting evidences of either thermal or quantum
activated phase slips. The magnetic transport data, discussed in the framework
of different scenarios, reveal that the system behaves coherently in the
temperature range where the contribution of the fluctuations is important.

###Magnetoresistance in multilayer fullerene spin valves: a first-principles study|Deniz Çakır,Diana M. Otálvaro,Geert Brocks###

Magnetoresistance in multilayer fullerene spin valves: a first-principles study. Carbon-based molecular semiconductors are explored for application in
spintronics because their small spin-orbit coupling promises long spin life
times. We calculate the electronic transport from first principles through spin
valves comprising bi- and tri-layers of the fullerene molecules C60 and C70,
sandwiched between two Fe electrodes. The spin polarization of the current, and
the magnetoresistance depend sensitively on the interactions at the interfaces
between the molecules and the metal surfaces. They are much less affected by
the thickness of the molecular layers. A high current polarization (CP > 90%)
and magnetoresistance (MR > 100%) at small bias can be attained using C70
layers. In contrast, the current polarization and the magnetoresistance at
small bias are vanishingly small for C60 layers. Exploiting a generalized
Julli`ere model we can trace the differences in spin-dependent transport
between C60 and C70 layers to differences between the molecule-metal interface
states. These states also allow one to interpret the current polarization and
the magnetoresistance as a function of the applied bias voltage.

###Vortex crossing and trapping in doubly connected mesoscopic loops of a single-crystal type II superconductor|Shaun A. Mills,Chenyi Shen,Zhuan Xu,Ying Liu###

Vortex crossing and trapping in doubly connected mesoscopic loops of a single-crystal type II superconductor. Numerical calculations on a mesoscopic ring of a type II superconductor in
the London limit suggest that an Abrikosov vortex can be trapped in such a
structure above a critical magnetic field and generate a phase shift in the
magnetoresistance oscillations. We prepared submicron-sized superconducting
loops of single-crystal, type II superconductor NbSe$_2$ and measured
magnetoresistance oscillations resulting from vortices crossing the loops. The
free energy barrier for vortex crossing determines the crossing rate and is
periodically modulated by the external magnetic flux threading the loop. We
demonstrated experimentally that the crossing of vortices can be directed at a
pair of constrictions in the loop, leading to more pronounced magnetoresistance
oscillations than those in a uniform ring. The vortex trapping in both a simple
ring and a ring featuring two constrictions was found to result in a phase
shift in the magnetoresistance oscillations as predicted in the numerical
calculations. The controlled crossing and trapping of vortices demonstrated in
our NbSe$_2$ devices provide a starting point for the manipulation of
individual Abrikosov vortices, which is useful for future technologies.

###Calculation method of spin accumulations and spin signals in nanostructures using spin resistors|W. Savero Torres,A. Marty,P. Laczkowski,L. Vila,M. Jamet,J-P. Attané###

Calculation method of spin accumulations and spin signals in nanostructures using spin resistors. The understanding and calculation of spin transport are essential elements
for the development of spintronics devices. Here, we propose a simple method to
calculate analytically the spin accumulations, spin currents and
magnetoresistances in complex systems. This can be used both for CPP
experiments in multilayers and for multiterminal nanostructures made of
semiconductors, oxides, metals and carbon allotropes.

###Magnetoresistance of doped silicon|Antonio Ferreira da Silva,Alexandre Levine,Zahra Sadre Momtaz,Henri Boudinov,Bo E. Sernelius###

Magnetoresistance of doped silicon. We have performed longitudinal magnetoresistance measurements on heavily
n-doped silicon for donor concentrations exceeding the critical value for the
metal-non-metal transition. The results are compared to those from a many-body
theory where the donor-electrons are assumed to reside at the bottom of the
many-valley conduction band of the host. Good qualitative agreement between
theory and experiment is obtained.

###Longitudinal magnetoconductivity and magnetodielectric effect in bilayer graphene|U. Zülicke,R Winkler###

Longitudinal magnetoconductivity and magnetodielectric effect in bilayer graphene. It was recently shown that a finite imbalance between electron densities in
the $\mathbf{K}$ and $\mathbf{K}'$ valleys of bilayer graphene induces a
magnetoelectric coupling. Here we explore ramifications of this electronically
tunable magnetoelectric effect for the optical conductivity and dielectric
permittivity of this material. Our results augment current understanding of
longitudinal magnetoresistance and magnetocapacitance in unconventional
materials.

###Magnetoresistance of compensated semimetals in confined geometries|P. S. Alekseev,A. P. Dmitriev,I. V. Gornyi,V. Yu. Kachorovskii,B. N. Narozhny,M. Schütt,M. Titov###

Magnetoresistance of compensated semimetals in confined geometries. Two-component conductors -- e.g., semi-metals and narrow band semiconductors
-- often exhibit unusually strong magnetoresistance in a wide temperature
range. Suppression of the Hall voltage near charge neutrality in such systems
gives rise to a strong quasiparticle drift in the direction perpendicular to
the electric current and magnetic field. This drift is responsible for a strong
geometrical increase of resistance even in weak magnetic fields. Combining the
Boltzmann kinetic equation with sample electrostatics, we develop a microscopic
theory of magnetotransport in two and three spatial dimensions. The compensated
Hall effect in confined geometry is always accompanied by electron-hole
recombination near the sample edges and at large-scale inhomogeneities. As the
result, classical edge currents may dominate the resistance in the vicinity of
charge compensation. The effect leads to linear magnetoresistance in two
dimensions in a broad range of parameters. In three dimensions, the
magnetoresistance is normally quadratic in the field, with the linear regime
restricted to rectangular samples with magnetic field directed perpendicular to
the sample surface. Finally, we discuss the effects of heat flow and
temperature inhomogeneities on the magnetoresistance.

###Magnetothermopower and magnetoresistance of single Co-Ni/Cu multilayered nanowires|Tim Böhnert,Anna Corinna Niemann,Ann-Kathrin Michel,Svenja Bäßler,Johannes Gooth,Bence G. Tóth,Katalin Neuróhr,László Péter,Imre Bakonyi,Victor Vega,Victor M. Prida,Kornelius Nielsch###

Magnetothermopower and magnetoresistance of single Co-Ni/Cu multilayered nanowires. The magnetothermopower and the magnetoresistance of single Co Ni/Cu
multilayered nan-owires with various thicknesses of the Cu spacer are
investigated. Both kinds of measurement have been performed as a function of
temperature (50 K to 325 K) and under applied magnetic fields perpendicular to
the nanowire axis, with magnitudes up to 15 % at room temperature. A linear
relation between thermopower S and electrical conductivity {\sigma} of the
nanowires is found, with the magnetic field as an implicit variable. Combining
the linear behavior of the S vs. {\sigma} and the Mott formula, the energy
derivative of the resistivity has been determined. In order to extract the true
nanowire materials parameters from the measured thermopower, a simple model
based on the Mott formula is employed to distinguish the individual thermopower
contributions of the sample. By assuming that the non-diffusive thermopower
contributions of the nanowire can be neglected, it was found that the magnetic
field induced changes of thermopower and resistivity are equivalent. The
emphasis in the present paper is on the comparison of the magnetoresistance and
magnetothermopower results and it is found that the same correlation is valid
between the two sets of data for all samples, irrespective of the relative
importance of the giant magnetoresistance or anisotropic magnetoresistance
contributions in the various individual nanowires.

###Impact of the interface quality of Pt/YIG(111) hybrids on their spin Hall magnetoresistance|Sabine Pütter,Stephan Geprägs,Richard Schlitz,Matthias Althammer,Andreas Erb,Rudolf Gross,Sebastian T. B. Goennenwein###

Impact of the interface quality of Pt/YIG(111) hybrids on their spin Hall magnetoresistance. We study the influence of the interface quality of
Pt/Y$_3$Fe$_5$O$_{12}$(111) hybrids on their spin Hall magnetoresistance. This
is achieved by exposing Y$_3$Fe$_5$O$_{12}$(111) single crystal substrates to
different well-defined surface treatments prior to the Pt deposition. The
quality of the Y$_3$Fe$_5$O$_{12}$(YIG) surface, the Pt/YIG interface and the
Pt layer is monitored \textit{in-situ} by reflection high-energy electron
diffraction and Auger electron spectroscopy as well as \textit{ex-situ} by
atomic force microscopy and x-ray diffraction. To identify the impact of the
different surface treatments on the spin Hall magnetoresistance,
angle-dependent magnetoresistance measurements are carried out at room
temperature. The largest spin Hall magnetoresistance is found in Pt/YIG
fabricated by a two-step surface treatment consisting of a "piranha" etch
process followed by an annealing step at $500^\circ$C in pure oxygen
atmosphere. Our data suggest that the small SMR in Pt/YIG without any surface
treatments of the YIG substrate prior to Pt deposition is caused by a
considerable carbon agglomeration at the Y$_3$Fe$_5$O$_{12}$ surface.

###Evidence of Electron-Hole Imbalance in WTe2 from High-Resolution Angle-Resolved Photoemission Spectroscopy|Chenlu Wang,Yan Zhang,Jianwei Huang,Guodong Liu,Aiji Liang,Yuxiao Zhang,Bing Shen,Jing Liu,Cheng Hu,Ying Ding,Defa Liu,Yong Hu,Shaolong He,Lin Zhao,Li Yu,Jin Hu,Jiang Wei,Zhiqiang Mao,Youguo Shi,Xiaowen Jia,Fengfeng Zhang,Shenjin Zhang,Feng Yang,Zhimin Wang,Qinjun Peng,Zuyan Xu,Chuangtian Chen,X. J. Zhou###

Evidence of Electron-Hole Imbalance in WTe2 from High-Resolution Angle-Resolved Photoemission Spectroscopy. WTe2 has attracted a great deal of attention because it exhibits extremely
large and nonsaturating magnetoresistance. The underlying origin of such a
giant magnetoresistance is still under debate. Utilizing laser-based
angle-resolved photoemission spectroscopy with high energy and momentum
resolutions, we reveal the complete electronic structure of WTe2. This makes it
possible to determine accurately the electron and hole concentrations and their
temperature dependence. We find that, with increasing the temperature, the
overall electron concentration increases while the total hole concentration
decreases. It indicates that the electron-hole compensation, if it exists, can
only occur in a narrow temperature range, and in most of the temperature range
there is an electron-hole imbalance. Our results are not consistent with the
perfect electron-hole compensation picture that is commonly considered to be
the cause of the unusual magnetoresistance in WTe2. We identified a flat band
near the Brillouin zone center that is close to the Fermi level and exhibits a
pronounced temperature dependence. Such a flat band can play an important role
in dictating the transport properties of WTe2. Our results provide new insight
on understanding the origin of the unusual magnetoresistance in WTe2.

###Observation of transverse spin Nernst magnetoresistance induced by thermal spin current in ferromagnet/non-magnet bilayers|Dong-Jun Kim,Chul-Yeon Jeon,Jong-Guk Choi,Jae Wook Lee,Srivathsava Surabhi,Jong-Ryul Jeong,Kyung-Jin Lee,Byong-Guk Park###

Observation of transverse spin Nernst magnetoresistance induced by thermal spin current in ferromagnet/non-magnet bilayers. Electric generation of spin current via spin Hall effect is of great interest
as it allows an efficient manipulation of magnetization in spintronic devices.
Theoretically, spin current can be also created by a temperature gradient,
which is known as spin Nernst effect. Here, we report spin Nernst
effect-induced transverse magnetoresistance in ferromagnet (FM)/non-magnetic
heavy metal (HM) bilayers. We observe that the magnitude of transverse
magnetoresistance (i.e., planar Nernst signal) in FM/HM bilayers is
significantly modified by HM and its thickness. This strong dependence of
transverse magnetoresistance on HM evidences the spin Nernst effect in HM; the
generation of thermally-induced spin current in HM and its subsequent
reflection at the FM/HM interface. Our analysis of transverse magnetoresistance
shows that the spin Nernst angles of W and Pt have the opposite sign to their
spin Hall angles. Moreover, our estimate implies that the magnitude of the spin
Nernst angle would be comparable to that of the spin Hall angle, suggesting an
efficient generation of spin current by the spin Nernst effect.

###Spin-Hall-Active Platinum Thin Films Grown Via Atomic Layer Deposition|Richard Schlitz,Akinwumi Abimbola Amusan,Michaela Lammel,Stefanie Schlicht,Tommi Tynell,Julien Bachmann,Georg Woltersdorf,Kornelius Nielsch,Sebastian T. B. Goennenwein,Andy Thomas###

Spin-Hall-Active Platinum Thin Films Grown Via Atomic Layer Deposition. We study the magnetoresistance of yttrium iron garnet/Pt heterostructures in
which the Pt layer was grown via atomic layer deposition (ALD).
Magnetotransport experiments in three orthogonal rotation planes reveal the
hallmark features of spin Hall magnetoresistance. We estimate the spin
transport parameters by comparing the magnitude of the magnetoresistance in
samples with different Pt thicknesses. We compare the spin Hall angle and the
spin diffusion length of the ALD Pt layers to the values reported for
high-quality sputter-deposited Pt films. The spin diffusion length of 1.5nm
agrees well with platinum thin films reported in the literature, whereas the
spin Hall magnetoresistance $\Delta \rho / \rho = 2.2\times 10^{-5}$ is
approximately a factor of 20 smaller compared to that of our sputter-deposited
films. Our results demonstrate that ALD allows fabricating spin-Hall-active Pt
films of suitable quality for use in spin transport structures. This work
provides the basis to establish conformal ALD coatings for arbitrary surface
geometries with spin-Hall-active metals and could lead to 3D spintronic devices
in the future.

###Carrier localization and out of plane anisotropic magnetoresistance in $Nd_{0.55-x} Sm_x Sr_{0.45} Mn O_3$ thin films|M. K. Srivastava,A. Kaur,H. K. Singh###

Carrier localization and out of plane anisotropic magnetoresistance in $Nd_{0.55-x} Sm_x Sr_{0.45} Mn O_3$ thin films. The impact of carrier localization on the anisotropic magnetoresistance (AMR)
has been investigated in NSSMO thin films. Carrier localization is caused by
the reduced average radius of the A-site of the perovskite lattice and enhanced
size disorder due to substitution of smaller cations for larger.

###Temperature dependent nonlinear Hall effect in macroscopic Si-MOS antidot array|A. Yu. Kuntsevich,A. V. Shupltetsov,M. S. Nunuparov###

Temperature dependent nonlinear Hall effect in macroscopic Si-MOS antidot array. By measuring magnetoresistance and Hall effect in classically moderate
perpendicular magnetic field in Si-MOSFET-type macroscopic antidot array we
found a novel effect: nonlinear with field, temperature- and density-dependent
Hall resistivity. We discuss qualitative explanation of the phenomenon and
suggest that it might originate from strong temperature dependence of the
resistivity and mobility in the shells of the antidots.

###Temperature-field phase diagram of extreme magnetoresistance in lanthanum monopnictides|F. F. Tafti,Q. D. Gibson,S. K. Kushwaha,J. W. Krizan,N. Haldolaarachchige,R. J. Cava###

Temperature-field phase diagram of extreme magnetoresistance in lanthanum monopnictides. The recent discovery of extreme magnetoresistance in LaSb introduced
lanthanum monopnictides as a new platform to study topological semimetals
(TSMs). In this work we report the discovery of extreme magnetoresistance in
LaBi, confirming lanthanum monopnictides as a promising family of TSMs. These
binary compounds with the simple rock-salt structure are ideal model systems to
search for the origin of extreme magnetoresistance. Through a comparative study
of magnetotransport effects in LaBi and LaSb, we construct a triangular
temperature-field phase diagram that illustrates how a magnetic field tunes the
electronic behavior in these materials. We show that the triangular phase
diagram can be generalized to other topological semimetals with different
crystal structures and different chemical compositions. By comparing our
experimental results to band structure calculations, we suggest that extreme
magnetoresistance in LaBi and LaSb originates from a particular orbital texture
on their qasi-2D Fermi surfaces. The orbital texture, driven by spin-orbit
coupling, is likely to be a generic feature of various topological semimetals.

###Effect of spin diffusion on spin torque in magnetic nanopillars|Sergei Urazhdin,Scott Button###

Effect of spin diffusion on spin torque in magnetic nanopillars. We present systematic magnetoelectronic measurements of magnetic nanopillars
with different structures of polarizing magnetic layers. The magnetic reversal
at small magnetic field, the onset of magnetic dynamics at larger field, and
the magnetoresistance exhibit a significant dependence on the type of the
polarizing layer. We performed detailed quantitative modeling showing that the
differences can be explained by the effects of spin-dependent electron
diffusion.

###EDEPR of impurity centers embedded in silicon microcavities|N. T. Bagraev,W. Gehlhoff,D. S. Gets,L. E. Klyachkin,A. A. Kudryavtsev,A. M. Malyarenko,V. A. Mashkov,V. V. Romanov###

EDEPR of impurity centers embedded in silicon microcavities. We present the first findings of the new electrically-detected EPR (EDEPR)
technique which reveal different shallow and deep centers without using the
external cavity as well as the hf source and recorder, with measuring the only
magnetoresistance of the Si-QW confined by the superconductor delta-barriers.

###Rippled Graphene in an In-Plane Magnetic Field: Effects of a Random Vector Potential|Mark B. Lundeberg,Joshua A. Folk###

Rippled Graphene in an In-Plane Magnetic Field: Effects of a Random Vector Potential. We report measurements of the effects of a random vector potential generated
by applying an in-plane magnetic field to a graphene flake. Magnetic flux
through the ripples cause orbital effects: phase-coherent weak localization is
suppressed, while quasi-random Lorentz forces lead to anisotropic
magnetoresistance. Distinct signatures of these two effects enable an
independent estimation of the ripple amplitude and correlation length.

###Hysteretic phenomena in a 2DEG in quantum Hall effect regime studied in a transport experiment|M. V. Budantsev,D. A. Pokhabov,A. G. Pogosov,E. Yu. Zhdanov,A. K. Bakarov,A. I. Toropov###

Hysteretic phenomena in a 2DEG in quantum Hall effect regime studied in a transport experiment. We investigated experimentally non-equilibrium state of a two-dimensional
electron gas (2DEG) in the quantum Hall effect (QHE) regime, studying the
hysteresis of magnetoresistance of a 2DEG with a constriction. The large
amplitude of the hysteresis enabled us to make the consistent phenomenological
description of the hysteresis. We studied the dependence on the magnetic field
sweep prehistory (minor loop measurements), recovered the anhysteretic curve,
and studied the time dependence of the magnetoresistance. We showed that the
hysteresis of magnetoresistance of a 2DEG in the QHE regime has significant
phenomenological similarities with the hysteresis of magnetization of
ferromagnetic materials, showing multistability, jumps of relaxation, and
having the anhysteretic curve. Nevertheless, we revealed the crucial
difference, manifested itself in an unusual inverted (anti-coercive) behavior
of the magnetoresistance hysteresis. The time relaxation of the hysteresis has
fast and slow regimes, similar to that of non-equilibrium magnetization of a
2DEG in QHE regime pointing to their common origin. We studied the dependence
of the hysteresis loop area on the lithographic width of the constriction and
found the threshold value of width $\sim$1.35 $\mu$m beyond which the
hysteresis is not observed. This points to the edge nature of the
non-equilibrium currents (NECs) and allows us to determine the width of the
NECs area ($\sim$0.5 $\mu$m). We suggest the qualitative picture of the
observed hysteresis, based on non-equilibrium redistribution of the electrons
among the Landau level states and assuming huge imbalance between the
population of bulk and edge electronic states.

###Magnetoresistance peculiarities and magnetization of materials with two kinds of superconducting inclusions|Oksana N. Shevtsova###

Magnetoresistance peculiarities and magnetization of materials with two kinds of superconducting inclusions. Low-temperature properties of a crystal containing superconducting inclusions
of two different materials have been studied. In the approximation that the
size of inclusions is much smaller than the coherence length/penetration depth
of the magnetic field the theory for magnetoresistance of a crystal containing
spherical superconducting inclusions of two different materials has been
developed, and magnetization of crystals has been calculated.

###Absence of magnetic proximity effects in magnetoresistive Pt/CoFe2O4 hybrid interfaces|M. Valvidares,N. Dix,M. Isasa,K. Ollefs,F. Wilhelm,A. Rogalev,F. Sánchez,E. Pellegrin,A. Bedoya-Pinto,P. Gargiani,L. E. Hueso,F. Casanova,J. Fontcuberta###

Absence of magnetic proximity effects in magnetoresistive Pt/CoFe2O4 hybrid interfaces. Ultra-thin Pt films grown on insulating ferrimagnetic CoFe2O4 (111) epitaxial
films display a magnetoresistance upon rotating the magnetization of the
magnetic layer. We report here X-ray magnetic circular dichroism (XMCD)
recorded at Pt-L2,3 and Pt-M3 edges. The results indicate that the Pt magnetic
moment, if any, is below the detection limit (< 0.001 {\mu}$_B$/Pt), thus
strongly favoring the view that the presence of CoFe2O4 does not induce the
formation of magnetic moments in Pt. Therefore, the observed magnetoresistance
cannot be attributed to some sort of proximity-induced magnetic moments at Pt
ions and subsequent magnetic-field dependent scattering. It thus follows that
either bulk (spin Hall and Inverse spin Hall Effects) or interface (Rashba)
spin-orbit related effects dominate the observed magnetoresistance.
Furthermore, comparison of bulk magnetization and XMCD data at (Fe,Co)-L2,3
edges suggests the presence of some spin disorder in the CoFe2O4 layer which
may be relevant for the observed anomalous non-saturating field-dependence of
spin Hall magnetoresistance.

###Anomalous oscillatory magnetoresistance in superconducting transitions|Milind N. Kunchur,Charles L. Dean,Boris I. Ivlev###

Anomalous oscillatory magnetoresistance in superconducting transitions. We have discovered an oscillatory magnetoresistance phenomenon in a wide
range of superconducting systems, with a periodicity that is essentially
independent of temperature, transport current, magnetic field, and even
material parameters. The nearly universal period points to a possible
fundamental mechanism deeper than superconductivity itself, and may result from
intrinsic pair-breaking mechanisms at sub-atomic length scales.

###Magnetoresistance of heavy and light metal/ferromagnet bilayers|Can Onur Avci,Kevin Garello,Johannes Mendil,Abhijit Ghosh,Nicolas Blasakis,Mihai Gabureac,Morgan Trassin,Manfred Fiebig,Pietro Gambardella###

Magnetoresistance of heavy and light metal/ferromagnet bilayers. We studied the magnetoresistance of normal metal (NM)/ferromagnet (FM)
bilayers in the linear and nonlinear (current-dependent) regimes and compared
it with the amplitude of the spin-orbit torques and thermally induced electric
fields. Our experiments reveal that the magnetoresistance of the heavy NM/Co
bilayers (NM = Ta, W, Pt) is phenomenologically similar to the spin Hall
magnetoresistance (SMR) of YIG/Pt, but has a much larger anisotropy, of the
order of 0.5%, which increases with the atomic number of the NM. This SMR-like
behavior is absent in light NM/Co bilayers (NM = Ti, Cu), which present the
standard AMR expected of polycrystalline FM layers. In the Ta, W, Pt/Co
bilayers we find an additional magnetoresistance, directly proportional to the
current and to the transverse component of the magnetization. This so-called
unidirectional SMR, of the order of 0.005%, is largest in W and correlates with
the amplitude of the antidamping spin-orbit torque. The unidirectional SMR is
below the accuracy of our measurements in YIG/Pt.

###Synchronization of spin torque oscillators through spin Hall magnetoresistance|Tomohiro Taniguchi###

Synchronization of spin torque oscillators through spin Hall magnetoresistance. Spin torque oscillators placed onto a nonmagnetic heavy metal show
synchronized auto-oscillations due to the coupling originating from spin Hall
magnetoresistance effect. Here, we study a system having two spin torque
oscillators under the effect of the spin Hall torque, and show that switching
the external current direction enables us to control the phase difference of
the synchronization between in-phase and antiphase.

###Extremely large magnetoresistance and Kohler's rule in PdSn4: a complete study of thermodynamic, transport and band structure properties|Na Hyun Jo,Yun Wu,Lin-Lin Wang,Peter P. Orth,Savannah S. Downing,Soham Manni,Dixiang Mou,Duane D. Johnson,Adam Kaminski,Sergey L. Bud'ko,Paul C. Canfield###

Extremely large magnetoresistance and Kohler's rule in PdSn4: a complete study of thermodynamic, transport and band structure properties. The recently discovered material PtSn$_4$ is known to exhibit extremely large
magnetoresistance (XMR) that also manifests Dirac arc nodes on the surface.
PdSn$_4$ is isostructure to PtSn$_4$ with same electron count. We report on the
physical properties of high quality single crystals of PdSn$_4$ including
specific heat, temperature and magnetic field dependent resistivity and
magnetization, and electronic band structure properties obtained from angle
resolved photoemission spectroscopy (ARPES). We observe that PdSn$_4$ has
physical properties that are qualitatively similar to those of PtSn$_4$, but
find also pronounced differences. Importantly, the Dirac arc node surface state
of PtSn$_4$ is gapped out for PdSn$_4$. By comparing these similar compounds,
we address the origin of the extremely large magnetoresistance in PdSn$_4$ and
PtSn$_4$; based on detailed analysis of the magnetoresistivity, $\rho(H,T)$, we
conclude that neither carrier compensation nor the Dirac arc node surface state
are primary reason for the extremely large magnetoresistance. On the other
hand, we find that surprisingly Kohler's rule scaling of the
mangnetoresistance, which describes a self-similarity of the field induced
orbital electronic motion across different length scales and is derived for a
simple electronic response of metals to applied in a magnetic field is obeyed
over the full range of temperatures and field strengths that we explore.

###Non-saturating large magnetoresistance in semimetals|Ian A. Leahy,Yu-Ping Lin,Peter E. Siegfried,Andrew C. Treglia,Justin C. W. Song,Rahul M. Nandkishore,Minhyea Lee###

Non-saturating large magnetoresistance in semimetals. The rapidly expanding class of quantum materials known as {\emph{topological
semimetals}} (TSM) display unique transport properties, including a striking
dependence of resistivity on applied magnetic field, that are of great interest
for both scientific and technological reasons. However, experimental signatures
that can identify or discern the dominant mechanism and connect to available
theories are scarce. Here we present the magnetic susceptibility ($\chi$), the
tangent of the Hall angle ($\tan\theta_H$) along with magnetoresistance in four
different non-magnetic semimetals with high mobilities, NbP, TaP, NbSb$_2$ and
TaSb$_2$, all of which exhibit non-saturating large MR. We find that the
distinctly different temperature dependences, $\chi(T)$ and the values of
$\tan\theta_H$ in phosphides and antimonates serve as empirical criteria to
sort the MR from different origins: NbP and TaP being uncompensated semimetals
with linear dispersion, in which the non-saturating magnetoresistance arises
due to guiding center motion, while NbSb$_2$ and TaSb$_2$ being {\it
compensated} semimetals, with a magnetoresistance emerging from nearly perfect
charge compensation of two quadratic bands. Our results illustrate how a
combination of magnetotransport and susceptibility measurements may be used to
categorize the increasingly ubiquitous non-saturating large magnetoresistance
in TSMs.

###Spin Hall magnetoresistance in heterostructures consisting of noncrystalline paramagnetic YIG and Pt|Michaela Lammel,Richard Schlitz,Kevin Geishendorf,Denys Makarov,Tobias Kosub,Savio Fabretti,Helena Reichlova,Rene Huebner,Kornelius Nielsch,Andy Thomas,Sebastian T. B. Goennenwein###

Spin Hall magnetoresistance in heterostructures consisting of noncrystalline paramagnetic YIG and Pt. The spin Hall magnetoresistance (SMR) effect arises from spin-transfer
processes across the interface between a spin Hall active metal and an
insulating magnet. While the SMR response of ferrimagnetic and
antiferromagnetic insulators has been studied extensively, the SMR of a
paramagnetic spin ensemble is not well established. Thus, we investigate herein
the magnetoresistive response of as-deposited yttrium iron garnet/platinum thin
film bilayers as a function of the orientation and the amplitude of an
externally applied magnetic field. Structural and magnetic characterization
show no evidence for crystalline order or spontaneous magnetization in the
yttrium iron garnet layer. Nevertheless, we observe a clear magnetoresistance
response with a dependence on the magnetic field orientation characteristic for
the SMR. We propose two models for the origin of the SMR response in
paramagnetic insulator/Pt heterostructures. The first model describes the SMR
of an ensemble of non-interacting paramagnetic moments, while the second model
describes the magnetoresistance arising by considering the total net moment.
Interestingly, our experimental data are consistently described by the net
moment picture, in contrast to the situation in compensated ferrimagnets or
antiferromagnets.

###Large magnetoresistance in an electric field controlled antiferromagnetic tunnel junction|Yurong Su,Jia Zhang,Jing-Tao Lü,Jeongmin Hong,Long You###

Large magnetoresistance in an electric field controlled antiferromagnetic tunnel junction. Large magnetoresistance effect controlled by electric field rather than
magnetic field or electric current is a preferable routine for designing low
power consumption magnetoresistance-based spintronic devices. Here we propose
an electric-field controlled antiferromagnetic (AFM) tunnel junction with
structure of piezoelectric substrate/Mn3Pt/SrTiO3/Pt operating by the magnetic
phase transition (MPT) of antiferromagnet Mn3Pt through its magneto-volume
effect. The transport properties of the proposed AFM tunnel junction have been
investigated by employing first-principles calculations. Our results show that
a magnetoresistance over hundreds of percent is achievable when Mn3Pt undergoes
MPT from a collinear AFM state to a non-collinear AFM state. Band structure
analysis based on density functional calculations shows that the large TMR can
be attributed to the joint effect of significant different Fermi surface of
Mn3Pt at two AFM phases and the band symmetry filtering effect of the SrTiO3
tunnel barrier. In addition, other than single-crystalline tunnel barrier, we
also discuss the robustness of the proposed magnetoresistance effect by
considering amorphous AlOx barrier. Our results may open perspective way for
effectively electrical writing and reading of the AFM state and its application
in energy efficient magnetic memory devices.

###Quantum Transport in Topological Semimetals under Magnetic Fields|Hai-Zhou Lu,Shun-Qing Shen###

Quantum Transport in Topological Semimetals under Magnetic Fields. Topological semimetals are three-dimensional topological states of matter, in
which the conduction and valence bands touch at a finite number of points,
i.e., the Weyl nodes. Topological semimetals host paired monopoles and
antimonopoles of Berry curvature at the Weyl nodes and topologically protected
Fermi arcs at certain surfaces. We review our recent works on quantum transport
in topological semimetals, according to the strength of the magnetic field. At
weak magnetic fields, there are competitions between the positive
magnetoresistivity induced by the weak anti-localization effect and negative
magnetoresistivity related to the nontrivial Berry curvature. We propose a
fitting formula for the magnetoconductivity of the weak anti-localization. We
expect that the weak localization may by induced by inter- alley effects and
interaction effect, and occur in double-Weyl semimetals. For the negative
magnetoresistance induced by the nontrivial Berry curvature in topological
semimetals, we show the dependence of the negative magnetoresistance on the
carrier density. At strong magnetic fields, specifically, in the quantum limit,
the magnetoconduction depends on the type and range of the scattering potential
of disorder. The high-field positive magnetoconductivity may not be a
compelling signature of the chiral anomaly. For long-range Gaussian scattering
potential and half filling, the magnetoconductivity can be linear in the
quantum limit. A minimal conductivity is found at the Weyl nodes although the
density of states vanishes there.

###Equivalence of Effective Medium and Random Resistor Network models for disorder-induced unsaturating linear magnetoresistance|Navneeth Ramakrishnan,Ying Tong Lai,Silvia Lara,Meera M. Parish,Shaffique Adam###

Equivalence of Effective Medium and Random Resistor Network models for disorder-induced unsaturating linear magnetoresistance. A linear unsaturating magnetoresistance at high perpendicular magnetic
fields, together with a quadratic positive magnetoresistance at low fields, has
been seen in many different experimental materials, ranging from silver
chalcogenides and thin films of InSb to topological materials like graphene and
Dirac semimetals. In the literature, two very different theoretical approaches
have been used to explain this classical magnetoresistance as a consequence of
sample disorder. The phenomenological Random Resistor Network model constructs
a grid of four-terminal resistors, each with a varying random resistance. The
Effective Medium Theory model imagines a smoothly varying disorder potential
that causes a continuous variation of the local conductivity. Here, we
demonstrate numerically that both models belong to the same universality class
and that a restricted class of the Random Resistor Network is actually
equivalent to the Effective Medium Theory. Both models are also in good
agreement with experiments on a diverse range of materials. Moreover, we show
that in both cases, a single parameter, i.e. the ratio of the fluctuations in
the carrier density to the average carrier density, completely determines the
magnetoresistance profile.

###Multiband ballistic transport and anisotropic commensurability magnetoresistance in antidot lattices of AB-stacked trilayer graphene|Shingo Tajima,Ryoya Ebisuoka,Kenji Watanabe,Takashi Taniguchi,Ryuta Yagi###

Multiband ballistic transport and anisotropic commensurability magnetoresistance in antidot lattices of AB-stacked trilayer graphene. Ballistic transport was studied in a multiple-band system consisting of an
antidot lattice of AB-stacked trilayer graphene. The low temperature
magnetoresistance showed commensurability peaks arising from matching of the
antidot lattice period and radius of cyclotron orbits for each mono- and
bilayer-like band in AB stacked trilayer graphene. The commensurability peak of
the monolayer-like band appeared at a lower magnetic field than that of the
bilayer-like band, which reflects the fact that the Fermi surface of the
bilayer-like band is larger than that of monolayer-like band. Rotation of the
antidot lattice relative to the crystallographic axes of graphene resulted in
anisotropic magnetoresistance, which reflects the trigonally warped Fermi
surface of the bilayer-like band. Numerical simulations of magnetoresistance
that assumed ballistic transport in the mono- and bilayer-like bands
approximately reproduced the observed magnetoresistance features. It was found
that the monolayer-like band significantly contributes to the conductivity even
though its carrier density is an order smaller than that of the bilayer-like
band. These results indicate that ballistic transport experiments could be used
for studying the anisotropic band structure of multiple-band systems.

###Extreme Magnetoresistance in Magnetic Rare Earth Monopnictides|Linda Ye,Takehito Suzuki,Christina R. Wicker,Joseph G. Checkelsky###

Extreme Magnetoresistance in Magnetic Rare Earth Monopnictides. The acute sensitivity of the electrical resistance of certain systems to
magnetic fields known as extreme magnetoresistance (XMR) has recently been
explored in a new materials context with topological semimetals. Exemplified by
WTe$_{2}$ and rare earth monopnictide La(Sb,Bi), these systems tend to be
non-magnetic, nearly compensated semimetals and represent a platform for large
magnetoresistance driven by intrinsic electronic structure. Here we explore
electronic transport in magnetic members of the latter family of semimetals and
find that XMR is strongly modulated by magnetic order. In particular, CeSb
exhibits XMR in excess of $1.6 \times 10^{6}$ % at fields of 9 T while the
magnetoresistance itself is non-monotonic across the various magnetic phases
and shows a transition from negative magnetoresistance to XMR with field above
magnetic ordering temperature $T_{N}$. The magnitude of the XMR is larger than
in other rare earth monopnictides including the non-magnetic members and
follows an non-saturating power law to fields above 30 T. We show that the
overall response can be understood as the modulation of conductivity by the Ce
orbital state and for intermediate temperatures can be characterized by an
effective medium model. Comparison to the orbitally quenched compound GdBi
supports the correlation of XMR with the onset of magnetic ordering and
compensation and highlights the unique combination of orbital inversion and
type-I magnetic ordering in CeSb in determining its large response. These
findings suggest a paradigm for magneto-orbital control of XMR and are relevant
to the understanding of rare earth-based correlated topological materials.

###Magnetoresistance in Hybrid Pt/CoFe2O4 Bilayers Controlled by Competing Spin Accumulation and Interfacial Chemical Reconstruction|Hari Babu Vasili,Matheus Gamino,Jaume Gazquez,Florencio Sanchez,Manuel Valvidares,Pierluigi Gargiani,Eric Pellegrin,Josep Fontcuberta###

Magnetoresistance in Hybrid Pt/CoFe2O4 Bilayers Controlled by Competing Spin Accumulation and Interfacial Chemical Reconstruction. Pure spin currents hold promises for an energy-friendlier spintronics. They
can be generated by a flow of charge along a non-magnetic metal having a large
spin-orbit coupling. It produces a spin accumulation at its surfaces,
controllable by the magnetization of an adjacent ferromagnetic layer.
Paramagnetic metals typically used are close to a ferromagnetic instability and
thus magnetic proximity effects can contribute to the observed
angular-dependent magnetoresistance (ADMR). As interface phenomena govern the
spin conductance across the metal/ferromagnetic-insulator heterostructures,
unraveling these distinct contributions is pivotal to full understanding of
spin current conductance. We report here x-ray absorption and magnetic circular
dichroism (XMCD) at Pt-M and (Co,Fe)-L absorption edges and atomically-resolved
energy loss electron spectroscopy (EELS) data of Pt/CoFe2O4 bilayers where
CoFe2O4 layers have been capped by Pt grown at different temperatures. It turns
out that the ADMR differs dramatically, being either dominated by spin Hall
magnetoresistance (SMR) associated to spin Hall effect or anisotropic
magnetoresistance (AMR). The XMCD and EELS data indicate that the Pt layer
grown at room temperature does not display any magnetic moment, whereas when
grown at higher temperature it is magnetic due to interfacial Pt-(Co,Fe)
alloying. These results allow disentangling spin accumulation from interfacial
chemical reconstructions and for tailoring the angular dependent
magnetoresistance.

###Tilted Dirac Cone Effect on Interlayer Magnetoresistance in α-(BEDT-TTF)$_2$I$_3$|Naoya Tajima,Takao Morinari###

Tilted Dirac Cone Effect on Interlayer Magnetoresistance in α-(BEDT-TTF)$_2$I$_3$. We report the effect of Dirac cone tilting on interlayer magnetoresistance in
\alpha-(BEDT-TTF)$_2$I$_3$, which is a Dirac semimetal under pressure. Fitting
of the experimental data by the theoretical formula suggests that the system is
close to a type-II Dirac semimetal.

###Fermi surface properties of the bifunctional organic metal $κ$-(BETS)$_2$Mn[N(CN)$_2$]$_3$ near the metal--insulator transition|V. N. Zverev,W. Biberacher,S. Oberbauer,I. Sheikin,P. Alemany,E. Canadell,M. V. Kartsovnik###

Fermi surface properties of the bifunctional organic metal $κ$-(BETS)$_2$Mn[N(CN)$_2$]$_3$ near the metal--insulator transition. We present detailed studies of the high-field magnetoresistance of the
layered organic metal $\kappa$-(BETS)$_2$\-Mn\-[N(CN)$_2$]$_3$ under a pressure
slightly above the insulator-metal transition. The experimental data are
analysed in terms of the Fermi surface properties and compared with the results
of first-principles band structure calculations. The calculated size and shape
of the inplane Fermi surface are in very good agreement with those derived from
Shubnikov-de Haas oscillations as well as the classical angle-dependent
magnetoresistance oscillations. A comparison of the experimentally obtained
effective cyclotron masses with the calculated band masses reveals electron
correlations significantly dependent on the electron momentum. The momentum- or
band-dependent mobility is also reflected in the behavior of the classical
magnetoresistance anisotropy in a magnetic field parallel to layers. Other
characteristics of the conducting system related to interlayer charge transfer
and scattering mechanisms are discussed based on the experimental data. Besides
the known high-field effects associated with the Fermi surface geometry, new
pronounced features have been found in the angle-dependent magnetoresistance,
which might be caused by coupling of the metallic charge transport to a
magnetic instability in proximity to the metal-insulator phase boundary.

###Engineering Large Anisotropic Magnetoresistance in La0.7Sr0.3MnO3 Films at Room Temperature|Paolo Perna,Davide Maccariello,Fernando Ajejas,Ruben Guerrero,Laurence Méchin,Stephane Flament,Jacobo Santamaria,Rodolfo Miranda,Julio Camarero###

Engineering Large Anisotropic Magnetoresistance in La0.7Sr0.3MnO3 Films at Room Temperature. The magnetoresistance (MR) effect is widely employed in technologies that
pervade our world from magnetic reading heads to sensors. Diverse contributions
to MR, such as anisotropic, giant, tunnel, colossal, and spin-Hall, are
revealed in materials depending on the specific system and measuring
configuration. Half-metallic manganites hold promise for spintronic
applications but the complexity of competing interactions has not permitted the
understanding and control of their magnetotransport properties to enable the
realization of their technological potential. Here we report on the ability to
induce a dominant switchable magnetoresistance in La0.7Sr0.3MnO3 epitaxial
films, at room temperature (RT). By engineering an extrinsic magnetic
anisotropy, we show a large enhancement of anisotropic magnetoresistance (AMR)
which leads to, at RT, signal changes much larger than the other contributions
such as the colossal magnetoresistance (CMR). The dominant extrinsic AMR
exhibits large variation in the resistance in low field region, showing high
sensitivity to applied low magnetic fields. These findings have a strong impact
on the real applications of manganite based devices for the high-resolution low
field magnetic sensors or spintronics.

###Giant gate-controlled proximity magnetoresistance in semiconductor-based ferromagnetic/nonmagnetic bilayers|Kosuke Takiguchi,Le Duc Anh,Takahiro Chiba,Tomohiro Koyama,Daichi Chiba,Masaaki Tanaka###

Giant gate-controlled proximity magnetoresistance in semiconductor-based ferromagnetic/nonmagnetic bilayers. The evolution of information technology has been driven by the discovery of
new forms of large magnetoresistance (MR), such as giant magnetoresistance
(GMR) and tunnelling magnetoresistance (TMR) in magnetic multilayers. Recently,
new types of MR have been observed in much simpler bilayers consisting of
ferromagnetic (FM)/nonmagnetic (NM) thin films; however, the magnitude of MR in
these materials is very small (0.01 ~ 1%). Here, we demonstrate that NM/FM
bilayers consisting of a NM InAs quantum well conductive channel and an
insulating FM (Ga,Fe)Sb layer exhibit giant proximity magnetoresistance (PMR)
(~80% at 14 T). This PMR is two orders of magnitude larger than the MR observed
in NM/FM bilayers reported to date, and its magnitude can be controlled by a
gate voltage. These results are explained by the penetration of the InAs
two-dimensional-electron wavefunction into (Ga,Fe)Sb. The ability to strongly
modulate the NM channel current by both electrical and magnetic gating
represents a new concept of magnetic-gating spin transistors.

###Thermal transport driven by charge imbalance in graphene in magnetic field, close to the charge neutrality point at low temperature: Non local resistance|A. Tagliacozzo,G. Campagnano,D. Giuliano,P. Lucignano,B. Jouault###

Thermal transport driven by charge imbalance in graphene in magnetic field, close to the charge neutrality point at low temperature: Non local resistance. Graphene grown epitaxially on SiC, close to the charge neutrality point
(CNP), in an orthogonal magnetic field shows an ambipolar behavior of the
transverse resistance accompanied by a puzzling longitudinal magnetoresistance.
When injecting a transverse current at one end of the Hall bar, a sizeable non
local transverse magnetoresistance is measured at low temperature. While Zeeman
spin effect seems not to be able to justify these phenomena, some dissipation
involving edge states at the boundaries could explain the order of magnitude of
the non local transverse magnetoresistance, but not the asymmetry when the
orientation of the orthogonal magnetic field is reversed. As a possible
contribution to the explanation of the measured non local magnetoresistance
which is odd in the magnetic field, we derive a hydrodynamic approach to
transport in this system, which involves particle and hole Dirac carriers, in
the form of charge and energy currents. We find that thermal diffusion can take
place on a large distance scale, thanks to long recombination times, provided a
non insulating bulk of the Hall bar is assumed, as recent models seem to
suggest in order to explain the appearance of the longitudinal resistance. In
presence of the local source, some leakage of carriers from the edges generates
an imbalance of carriers of opposite sign, which are separated in space by the
magnetic field and diffuse along the Hall bar generating a non local transverse
voltage.

###Quantum magnetoresistive (hc/2e)/m periodic oscillations in a superconducting ring|V. I. Kuznetsov,O. V. Trofimov###

Quantum magnetoresistive (hc/2e)/m periodic oscillations in a superconducting ring. It was experimentally found that quantum magnetoresistive hc/2e periodic
oscillations of the Little-Parks type in a superconducting mesoscopic ring with
decreasing temperature and increasing applied dc current are modified to the
sum of harmonic (hc/2e)/m periodic oscillations. Multiple Andreev reflection
can be a possible cause of this effect.

###Spin-flop transition in atomically thin MnPS$_3$ crystals|Gen Long,Hugo Henck,Marco Gibertini,Dumitru Dumcenco,Zhe Wang,Takashi Taniguchi,Kenji Watanabe,Enrico Giannini,Alberto F. Morpurgo###

Spin-flop transition in atomically thin MnPS$_3$ crystals. The magnetic state of atomically thin semiconducting layered antiferromagnets
such as CrI$_3$ and CrCl$_3$ can be probed by forming tunnel barriers and
measuring their resistance as a function of magnetic field ($H$) and
temperature ($T$). This is possible because the tunneling magnetoresistance
originates from a spin-filtering effect sensitive to the relative orientation
of the magnetization in different layers, i.e., to the magnetic state of the
multilayers. For systems in which antiferromagnetism occurs within an
individual layer, however, no spin-filtering occurs: it is unclear whether this
strategy can work. To address this issue, we investigate tunnel transport
through atomically thin crystals of MnPS$_3$, a van der Waals semiconductor
that in the bulk exhibits easy-axis antiferromagnetic order within the layers.
For thick multilayers below $T\simeq 78$ K, a $T$-dependent magnetoresistance
sets-in at $\sim 5$ T, and is found to track the boundary between the
antiferromagnetic and the spin-flop phases known from bulk magnetization
measurements. The magnetoresistance persists down to individual MnPS$_3$
monolayers with nearly unchanged characteristic temperature and magnetic field
scales, albeit with a different dependence on $H$. We discuss the implications
of these finding for the magnetic state of atomically thin MnPS$_3$ crystals,
conclude that antiferromagnetic correlations persist down to the level of
individual monolayers, and that tunneling magnetoresistance does allow
magnetism in 2D insulating materials to be detected even in the absence of
spin-filtering.

###Reply to "Comment on 'Spin-dependent electron transmission model for chiral molecules in mesoscopic devices'"|Xu Yang,Caspar H. van der Wal,Bart J. van Wees###

Reply to "Comment on 'Spin-dependent electron transmission model for chiral molecules in mesoscopic devices'". Here we emphasize once more the distinction between generating CISS
(spin-charge current conversion) in a chiral system and detecting it as
magnetoresistance in two-terminal electronic devices. We also highlight
important differences between electrical measurement results obtained in the
linear response regime and those obtained in the nonlinear regime.

###Absence of Spin Hall Magnetoresistance in Pt/(CoNi)n multilayers|Yongwei Cui,Xiaoyu Feng,Qihan Zhang,Hengan Zhou,Wanjun Jiang,Jiangwei Cao,Desheng Xue,Xiaolong Fan###

Absence of Spin Hall Magnetoresistance in Pt/(CoNi)n multilayers. We systematically studied the magnetoresistance effect in a Pt/(CoNi)n
multilayer system with perpendicular magnetic anisotropy and the fcc (111)
texture. The angular dependence of magnetoresistance, including high-order
cosine terms, was observed in a plane perpendicular to the electrical current;
this was attributed to the geometrical-size effects caused by crystal symmetry,
the ordered arrangement of grains, and the anisotropic interface
magnetoresistance effect caused by the breaking of the symmetry at interfaces.
Based on the accuracy of our experimental results, the magnitude of spin Hall
magnetoresistance (SMR) in Pt/(CoNi)n was expected to be below
$1\times10^{-4}$. However, on evaluating the spin Hall angle of $\geq$ 0.07 for
Pt using spin-torque ferromagnetic resonance measurements, the theoretical
magnitude of SMR in our samples was estimated to exceed $7\times10^{-4}$. This
absence of SMR in the experimental results can be explained by the
Elliott-Yafet spin relaxation of itinerant electrons in the ferromagnetic
metal, which indicates that the boundary conditions of the spin current in the
heavy metal/ferromagnetic insulator may not be applicable to all-metallic
heterostructures.

###Anisotropic and extreme magnetoresistance in the magnetic semimetal candidate Erbium monobismuthide|L. - Y. Fan,F. Tang,W. Z. Meng,W. Zhao,L. Zhang,Z. D. Han,B. Qian,X. -F. Jiang,X. M. Zhang,Y. Fang###

Anisotropic and extreme magnetoresistance in the magnetic semimetal candidate Erbium monobismuthide. Rare-earth monopnictides display rich physical behaviors, featuring most
notably spin and orbital orders in their ground state. Here, we grow ErBi
single crystal and study its magnetic, thermal and electrical properties. An
analysis of the magnetic entropy and magnetization indicates that the weak
magnetic anisotropy in ErBi possibly derives from the mixing effect, namely the
anisotropic ground state of Er3+ (4f11) mingles with the isotropic excited
state through exchange interaction. At low temperature, an extremely large
magnetoresistance (~104%) with a parabolic magnetic-field dependence is
observed, which can be ascribed to the nearly perfect electron-hole
compensation and ultrahigh carrier mobility. When the magnetic field is rotated
in the ab (ac) plane and the current flows in the b axis, the angular
magnetoresistance in ErBi shows a twofold (fourfold) symmetry. Similar case has
been observed in LaBi where the anisotropic Fermi surface dominates the
low-temperature transport. Our theoretical calculation suggests that near the
Fermi level ErBi shares similarity with LaBi in the electronic band structures.
These findings indicate that the angular magnetoresistance of ErBi could be
mainly determined by its anisotropic Fermi surface topology. Besides,
contributions from several other possibilities, including the spin-dependent
scattering, spin-orbit scattering, and demagnetization correlation to the
angular magnetoresistance of ErBi are also discussed.

###Large magnetoresistance in the iron-free pnictide superconductor LaRu$_2$P$_2$|Marta Fernández-Lomana,Víctor Barrena,Beilun Wu,Sara Delgado,Federico Mompeán,Mar García-Hernández,Hermann Suderow,Isabel Guillamón###

Large magnetoresistance in the iron-free pnictide superconductor LaRu$_2$P$_2$. The magnetoresistance of iron pnictide superconductors is often dominated by
electron-electron correlations and deviates from the H$^2$ or saturating
behaviors expected for uncorrelated metals. Contrary to similar Fe-based
pnictide systems, the superconductor LaRu$_2$P$_2$ (T$_c$ = 4 K) shows no
enhancement of electron-electron correlations. Here we report a non-saturating
magnetoresistance deviating from the H$^2$ or saturating behaviors in
LaRu$_2$P$_2$. We have grown and characterized high quality single crystals of
LaRu$_2$P$_2$ and measured a magnetoresistance following H$^{1.3}$ up to 22 T.
We discuss our result by comparing the bandstructure of LaRu$_2$P$_2$ with Fe
based pnictide superconductors. The different orbital structures of Fe and Ru
leads to a 3D Fermi surface with negligible bandwidth renormalization in
LaRu$_2$P$_2$, that contains a large open sheet over the whole Brillouin zone.
We show that the large magnetoresistance in LaRu$_2$P$_2$ is unrelated to the
one obtained in materials with strong electron-electron correlations and that
it is compatible instead with conduction due to open orbits on the rather
complex Fermi surface structure of LaRu$_2$P$_2$.

###Static magnetic proximity effects and spin Hall magnetoresistance in Pt/Y$_{3}$Fe$_{5}$O$_{12}$ and inverted Y$_{3}$Fe$_{5}$O$_{12}$/Pt bilayers|Stephan Geprägs,Christoph Klewe,Sibylle Meyer,Dominik Graulich,Felix Schade,Marc Schneider,Sonia Francoual,Stephen P. Collins,Katharina Ollefs,Fabrice Wilhelm,Andrei Rogalev,Yves Joly,Sebastian T. B. Goennenwein,Matthias Opel,Timo Kuschel,Rudolf Gross###

Static magnetic proximity effects and spin Hall magnetoresistance in Pt/Y$_{3}$Fe$_{5}$O$_{12}$ and inverted Y$_{3}$Fe$_{5}$O$_{12}$/Pt bilayers. The magnetic state of heavy metal Pt thin films in proximity to the
ferrimagnetic insulator Y$_{3}$Fe$_{5}$O$_{12}$ has been investigated
systematically by means of x-ray magnetic circular dichroism and x-ray resonant
magnetic reflectivity measurements combined with angle-dependent
magnetotransport studies. To reveal intermixing effects as the possible cause
for induced magnetic moments in Pt, we compare thin film heterostructures with
different order of the layer stacking and different interface properties. For
standard Pt layers on Y$_{3}$Fe$_{5}$O$_{12}$ thin films, we do not detect any
static magnetic polarization in Pt. These samples show an angle-dependent
magnetoresistance behavior, which is consistent with the established spin Hall
magnetoresistance. In contrast, for the inverted layer sequence,
Y$_{3}$Fe$_{5}$O$_{12}$ thin films grown on Pt layers, Pt displays a finite
induced magnetic moment comparable to that of all-metallic Pt/Fe bilayers. This
magnetic moment is found to originate from finite intermixing at the
Y$_{3}$Fe$_{5}$O$_{12}$/Pt interface. As a consequence, we found a complex
angle-dependent magnetoresistance indicating a superposition of the spin Hall
and the anisotropic magnetoresistance in these type of samples. Both effects
can be disentangled from each other due to their different angle dependence and
their characteristic temperature evolution.

###Berry curvature induced magnetotransport in 3D noncentrosymmetric metals|Ojasvi Pal,Bashab Dey,Tarun Kanti Ghosh###

Berry curvature induced magnetotransport in 3D noncentrosymmetric metals. We study the magnetoelectric and magnetothermal transport properties of
noncentrosymmetric metals using semiclassical Boltzmann transport formalism by
incorporating the effects of Berry curvature and orbital magnetic moment. These
effects impart quadratic-B dependence to the magnetoelectric and magnetothermal
conductivities, leading to intriguing phenomena such as planar Hall effect,
negative magnetoresistance, planar Nernst effect and negative Seebeck effect.
The transport coefficients associated with these effects show the usual
oscillatory behavior with respect to the angle between the applied electric
field and magnetic field. The bands of noncentrosymmetric metals are split by
Rashba spin-orbit coupling except at a band touching point. For Fermi energy
below (above) the band touching point, giant (diminished) negative
magnetoresistance is observed. This difference in the nature of
magnetoresistance is related to the magnitudes of the velocities, Berry
curvature and orbital magnetic moment on the respective Fermi surfaces, where
the orbital magnetic moment plays the dominant role. The absolute
magnetoresistance and planar Hall conductivity show a decreasing (increasing)
trend with Rashba coupling parameter for Fermi energy below (above) the band
touching point.

###Magnetohydrodynamics and electro-electron interaction of massless Dirac fermions|D. A. Khudaiberdiev,G. M. Gusev,E. B. Olshanetsky,Z. D. Kvon,N. N. Mikhailov###

Magnetohydrodynamics and electro-electron interaction of massless Dirac fermions. The magnetotransport properties of massless Dirac fermions in a gapless HgTe
quantum well are investigated. In samples with narrow channels, a large
negative magnetoresistance with a Lorentzian profile is observed, which is
interpreted as a manifestation of electron viscosity due to electron-electron
interaction. Comparison of experiment with theory yields the shear stress
relaxation time of the Dirac fermions caused by electron-electron scattering.

###Current-Perpendicular-to-Plane Giant Magnetoresistance Effect in van der Waals Heterostructures|Xinlu Li,Yurong Su,Meng Zhu,Fanxing Zheng,Peina Zhang,Jia Zhang,Jing-Tao Lü###

Current-Perpendicular-to-Plane Giant Magnetoresistance Effect in van der Waals Heterostructures. Spin-dependent transport in a full van der Waals (vdW) giant
magnetoresistance (GMR) junctions with the structure of Fe3GeTe2/XTe2/Fe3GeTe2
(X = Pt, Pd) has been investigated by using first-principles calculations. The
ballistic conductance, magnetoresistance (MR) and resistance-area product (RA)
have been calculated in a current-perpendicular-to-plane (CPP) geometry. A
giant magnetoresistance of around 2000% and RA less than 0.3 {\Omega} {\mu}m2
have been found in the proposed vdW CPP GMR. In addition, the spin-orbit
coupling effect on transport and anisotropy magnetoresistance (AMR) has also
been investigated. The calculated AMR is found to be around 20% in
Fe3GeTe2/trilayer-PdTe2/Fe3GeTe2 CPP GMR. Both GMR and AMR in the proposed vdW
CPP GMR mainly originate from the bulk electronic structure properties of
Fe3GeTe2. This work demonstrates a vdW CPP GMR with superior advantages
including perpendicular magnetic anisotropy, large GMR, low RA as well as
sizable AMR may stimulate future experimental explorations and should be
appealing for their applications in spintronic devices including magnetic
sensor and memory.

###Crossover behavior in the magnetoresistance of thin flakes of the topological material ZrTe5|Zhijian Xie,Xinjian Wei,Xiaobin Qiang,Yu Zhang,Shili Yan,Shimin Cao,Congkuan Tian,Peipei Wang,Liyuan Zhang,G. D. Gu,Haizhou Lu,Jian-Hao Chen###

Crossover behavior in the magnetoresistance of thin flakes of the topological material ZrTe5. ZrTe5 is a layered material that exhibits intricate topological effects.
Intensive theoretically and experimental efforts have been devoted to try to
understand the physics in this materials. In this paper the temperature
dependent magneto-transport properties of ZrTe5 thin flakes are investigated. A
characteristic temperature T* is observed in the temperature dependence of
three different types of magnetoresistance simultaneously, which are the
saturated Hall anomaly, the chiral anomaly and the longitudinal
magnetoresistance. Furthermore, the value of T* decreases monotonically from
200K to 160K with increasing thickness of the ZrTe5 thin flakes from 42nm to
89nm. Temperature induced topological phase transitions are attributed to the
cause of such anomaly in the three types of magnetoresistance at T*. Our
findings provide a multi-parameter indicator for the emergence of topological
phase transition in ZrTe5 and could be extended to the study of other
topological materials. The temperature dependence of the three types of
magnetoresistance also shed light on the role of anomalous Hall Effect in the
transport properties of ZrTe5.

###Narrow Zero Mode in Organic Massless Dirac Electron System $α$-(BEDT-TTF)$_2$I$_3$|A. Mori,Y. Kawasugi,R. Doi,T. Naito,R. Kato,Y. Nishio,N. Tajima###

Narrow Zero Mode in Organic Massless Dirac Electron System $α$-(BEDT-TTF)$_2$I$_3$. We investigated the interlayer magnetoresistance in an organic massless Dirac
electron system $\alpha$-(BEDT-TTF)$_2$I$_3$ under pressure. We experimentally
demonstrate that the width of the zero mode owing to carrier scattering is much
narrower than that of the other Landau levels.

###One Analytical Approach of Rashba-Edelstein Magnetoresistance in 2D Materials|Wibson W. G. Silva,José Holanda###

One Analytical Approach of Rashba-Edelstein Magnetoresistance in 2D Materials. We study analytically the Rashba-Edelstein magnetoresistance (REMR) in a
structure made from an insulator ferromagnet, such as yttrium iron garnet
(YIG), and a 2D material (2DM) with direct and inverse Rashba-Edelstein
effects, such as SLG and MoS$_2$. Our results represent an efficient way of
analyzing the Rashba-Edelstein effects.

###Extraordinary magnetometry -- a review on extraordinary magnetoresistance|Thierry Desire Pomar,Ricci Erlandsen,Bowen Zhou,Leonid Iliushyn,Rasmus Bjørk,Dennis Valbjørn Christensen###

Extraordinary magnetometry -- a review on extraordinary magnetoresistance. Extraordinary magnetoresistance (EMR) is a geometric magnetoresistance effect
occurring in hybrid devices consisting of a high-mobility material joined by a
metal. The change in resistance can exceed 107% at room temperature when a
magnetic field of 5 T is applied. Magnetic field sensors based on EMR hold the
potential formeasuring weak magnetic fields with an unprecedented sensitivity,
yet, to date this potential is largely unmet. In this work, we provide an
extensive review of the current state-of-the-art in EMR sensors with a focus on
the hybrid device geometries, the constituent material properties and
applications of EMR. We present a direct comparison of the best devices in
literature across magnetoresistance, sensitivity and noise equivalent field for
different materials and geometric designs. The compilation of studies collected
in this review illustrates the extremely rich possibilities for tuning the
magnetoresistive behavior varying the device geometry and material properties.
In addition, we aim to improve the understanding of the EMR effect and its
interplay with geometry and material properties. Finally, we discuss recent
trends in the field and future perspectives for EMR.

###Fractional focusing peaks and collective dynamics in two-dimensional Fermi liquids|Adbhut Gupta,Gitansh Kataria,Mani Chandra,Siddhardh C. Morampudi,Saeed Fallahi,Geoff C. Gardner,Michael J. Manfra,Ravishankar Sundararaman,Jean J. Heremans###

Fractional focusing peaks and collective dynamics in two-dimensional Fermi liquids. Carrier transport in materials is often diffusive due to momentum-relaxing
scattering with phonons and defects. Suppression of momentum-relaxing
scattering can lead to the ballistic and hydrodynamic transport regimes,
wherein complex non-Ohmic current flow patterns, including current vortices,
can emerge. In the ballistic regime addressed here, transverse magnetic
focusing is habitually understood in a familiar single-particle picture of
carriers injected from a source, following ballistic cyclotron orbits and
reaching a detector. We report on a distinctive nonlocal magnetoresistance
phenomenon exclusive to fermions, in an enclosed mesoscopic geometry wherein
transverse focusing magnetoresistance peaks also occur at values of the
cyclotron diameter that are incommensurate with the distance between the source
and detector. In low-temperature experiments and simulations using GaAs/AlGaAs
heterostructures with high electron mobility, we show that the peaks occur
independently of the location of the detector, and only depend on the
source-drain separation. We reproduce the experimental findings using
simulations of ballistic transport in both semiclassical and quantum-coherent
transport models. The periodicity of magnetic field at which the peaks occur is
matched to the lithographically defined device scale. It is found that, unlike
in transverse magnetic focusing, the magnetoresistance structure cannot be
attributed to any set of ordered single-particle trajectories but instead
requires accounting for the collective dynamics of the fermion distribution and
of all particle trajectories. The magnetoresistance is further associated with
current flow vorticity, a collective phenomenon.

###Giant magnetoresistance of Dirac plasma in high-mobility graphene|Na Xin,James Lourembam,P. Kumaravadivel,A. E. Kazantsev,Zefei Wu,Ciaran Mullan,Julien Barrier,Alexandra A. Geim,I. V. Grigorieva,A. Mishchenko,A. Principi,V. I. Falko,L. A. Ponomarenko,A. K. Geim,Alexey I. Berdyugin###

Giant magnetoresistance of Dirac plasma in high-mobility graphene. The most recognizable feature of graphene's electronic spectrum is its Dirac
point around which interesting phenomena tend to cluster. At low temperatures,
the intrinsic behavior in this regime is often obscured by charge inhomogeneity
but thermal excitations can overcome the disorder at elevated temperatures and
create electron-hole plasma of Dirac fermions. The Dirac plasma has been found
to exhibit unusual properties including quantum critical scattering and
hydrodynamic flow. However, little is known about the plasma's behavior in
magnetic fields. Here we report magnetotransport in this quantum-critical
regime. In low fields, the plasma exhibits giant parabolic magnetoresistivity
reaching >100% in 0.1 T even at room temperature. This is orders of magnitude
higher than magnetoresistivity found in any other system at such temperatures.
We show that this behavior is unique to monolayer graphene, being underpinned
by its massless spectrum and ultrahigh mobility, despite frequent
(Planckian-limit) scattering. With the onset of Landau quantization in a few T,
where the electron-hole plasma resides entirely on the zeroth Landau level,
giant linear magnetoresistivity emerges. It is nearly independent of
temperature and can be suppressed by proximity screening, indicating a
many-body origin. Clear parallels with magnetotransport in strange metals and
so-called quantum linear magnetoresistance predicted for Weyl metals offer an
interesting playground to further explore relevant physics using this
well-defined quantum-critical 2D system.

###Comparison of coherent and weakly incoherent transport models for the interlayer magnetoresistance of layered Fermi liquids|Perez Moses,Ross H. McKenzie###

Comparison of coherent and weakly incoherent transport models for the interlayer magnetoresistance of layered Fermi liquids. The interlayer magnetoresistance of layered metals in a tilted magnetic field
is calculated for two distinct models for the interlayer transport. The first
model involves coherent interlayer transport and makes use of results of
semi-classical or Bloch-Boltzmann transport theory. The second model involves
weakly incoherent interlayer transport where the electron is scattered many
times within a layer before tunneling into the next layer. The results are
relevant to the interpretation of experiments on angular-dependent
magnetoresistance oscillations (AMRO) in quasi-one- and quasi-two-dimensional
metals. We find that the dependence of the magnetoresistance on the direction
of the magnetic field is identical for both models except when the field is
almost parallel to the layers. An important implication of this result is that
a three-dimensional Fermi surface is not necessary for the observation of the
Yamaji and Danner oscillations seen in quasi-two- and quasi-one-dimensional
metals, respectively. A universal expression is given for the dependence of the
resistance at AMRO maxima and minima on the magnetic field and scattering time
(and thus the temperature). We point out three distinctive features of coherent
interlayer transport: (i) a beat frequency in the magnetic oscillations of
quasi-two-dimensional systems, (ii) a peak in the angular-dependent
magnetoresistance when the field is sufficiently large and parallel to the
layers, and (iii) a crossover from a linear to a quadratic field dependence for
the magnetoresistance when the field is parallel to the layers. Properties (i)
and (ii) are compared with published experimental data for a range of
quasi-two-dimensional organic metals and for Sr2RuO4.

###Hall effect and magnetoresistance in single crystals of NdFeAsO$_{1-x}$F$_{x}$|Peng Cheng,Huan Yang,Ying Jia,Lei Fang,Xiyu Zhu,Gang Mu,Hai-Hu Wen###

Hall effect and magnetoresistance in single crystals of NdFeAsO$_{1-x}$F$_{x}$. Hall effect and magnetoresistance have been measured on single crystals of
$NdFeAsO_{1-x}F_{x}$ with x = 0 ($T_c$ = 0 $ $K) and x = 0.18 ($T_c$ = 50 $
$K). For the undoped samples, strong Hall effect and magnetoresistance with
strong temperature dependence were found below about 150 K. The
magnetoresistance was found to be as large as 30% at 15 K at a magnetic field
of 9 T. From the transport data we found that the transition near 155 K was
accomplished in two steps: first one occurs at 155 K which may be associated
with the structural transition, the second one takes place at about 140 K which
may correspond to the spin-density wave like transition. In the superconducting
sample with $T_c$ = 50 $ $K, it is found that the Hall coefficient also reveals
a strong temperature dependence with a negative sign. But the magnetoresistance
becomes very weak and does not satisfy the Kohler's scaling law. These
dilemmatic results (strong Hall effect and very weak magnetoresistance) prevent
to understand the normal state electric conduction by a simple multi-band model
by taking account the electron and hole pockets. Detailed analysis further
indicates that the strong temperature dependence of $R_H$ cannot be easily
understood with the simple multi-band model either. A picture concerning a
suppression to the density of states at the Fermi energy in lowering
temperature is more reasonable. A comparison between the Hall coefficient of
the undoped sample and the superconducting sample suggests that the doping may
remove the nesting condition for the formation of the SDW order, since both
samples have very similar temperature dependence above 175 K.

###Weak Localization and Negative Magnetoresistance in Wurtzite-type Crystals|F. G. Pikus,G. E. Pikus###

Weak Localization and Negative Magnetoresistance in Wurtzite-type Crystals. We have developed a theory of the negative magnetoresistance due to the weak
localization in uniaxial wurtzite-type crystals, in which the spin splitting of
the conduction band is linear in the wave vector, unlike the cubic ${\rm A_3
B_5}$ crystals. Unlike earlier theories, we take into account the correlation
between the electron motion in spin and co-ordinate spaces. It is shown that as
a result of this correlation the magnetoresistance depends on the orientation
of the magnetic field with respect to the main axis of the crystal even if the
effective mass is isotropic. The new theory allows to accurately determine the
value of the spin splitting constant in uniaxial crystals.

###CPP- Giant Magnetoresistance and Thermo-Electric Power of multilayers|S. Krompiewski,U. Krey###

CPP- Giant Magnetoresistance and Thermo-Electric Power of multilayers. Oscillations of magnetoresistance and thermo-electric power (TEP) vs. both
nonmagnetic spacer as well as ferromagnetic slab thicknesses are studied in the
current-perpendicular-to-plane (CPP) geometry, in terms of a single-band
tight-binding model. The spin-dependent conductance has been calculated from
the Kubo formula by means of a recursion Green's function technique, and the $
TEP $ directly from the well-known Onsager relations.
  In general, the observed oscillations may have either just one or two
periods. In the latter case the long period of oscillations, related to
spectacular beats, is apparently of non-RKKY type.
  The relative TEP oscillations are strongly enhanced in comparison with those
of the giant magnetoresistance, have the same periods, but different phases and
a negative bias.

###Anisotropic strains and magnetoresistance of La_{0.7}Ca_{0.3}MnO_{3}|T. Y. Koo,S. H. Park,K. B. Lee,Y. H. Jeong###

Anisotropic strains and magnetoresistance of La_{0.7}Ca_{0.3}MnO_{3}. Thin films of perovskite manganite La_{0.7}Ca_{0.3}MnO_{3} were grown
epitaxially on SrTiO_3(100), MgO(100) and LaAlO_3(100) substrates by the pulsed
laser deposition method. Microscopic structures of these thin film samples as
well as a bulk sample were fully determined by x-ray diffraction measurements.
The unit cells of the three films have different shapes, i.e., contracted
tetragonal, cubic, and elongated tetragonal for SrTiO_3, MgO, and LaAlO_3
cases, respectively, while the unit cell of the bulk is cubic. It is found that
the samples with cubic unit cell show smaller peak magnetoresistance than the
noncubic ones do. The present result demonstrates that the magnetoresistance of
La_{0.7}Ca_{0.3}MnO_{3} can be controlled by lattice distortion via externally
imposed strains.

###Magnetoresistance of the double-tunnel-junction Coulomb Blockade with magnetic metals|Kingshuk Majumdar,Selman Hershfield###

Magnetoresistance of the double-tunnel-junction Coulomb Blockade with magnetic metals. We have studied the Junction Magnetoresistance (JMR) and the Differential
junction magnetoresistance (DJMR) for double tunnel junctions with magnetic
metals in the Coulomb Blockade regime. Spikes are seen in both the JMR and the
DJMR vs. voltage curves. They occur at those places where the current increases
by a step. In all cases the large bias limit can be obtained by adding the
resistances of each of the junctions in series. The JMR is positive in all the
cases we studied, whereas the DJMR can be positive or negative as a function of
the voltage. Moreover, the relative variation of the DJMR as a function of the
voltage is larger than the variation of the JMR with the voltage.

###2D Lattice of coupled Sinai billiards: metal or insulator at g<<1|M. V. Budantsev,Z. D. Kvon,A. G. Pogosov,G. M. Gusev,J. C. Portal,D. K. Maude,N. T. Moshegov,A. I. Toropov###

2D Lattice of coupled Sinai billiards: metal or insulator at g<<1. We investigate the transport in a two-dimensional (2D) lattice of coupled
Sinai billiards fabricated on the basis of a high-mobility 2D electron gas in
GaAs/AlGaAs heterojunction. For the states with low reduced conductivity g<<1
an anomalously weak temperature dependence of g was found. The large negative
magnetoresistance described by the Lorentz line-shape of the width
corresponding to the half magnetic flux quantum through the area of the
billiard is observed. In going from g>1 to g<<1 it strongly increases. The
Shubnikov-de Haas oscillations and commensurability magnetoresistance peak are
preserved at g<<1. The data suggest that the system studied behaves more like a
metal than an insulator at g<<1 and is not described by the generally accepted
picture of Anderson localization.

###Impurities and Inelastic Processes in Magnetic Tunnel Junctions|A. M. Bratkovsky,J. H. Nickel###

Impurities and Inelastic Processes in Magnetic Tunnel Junctions. We have studied tunnel magnetoresistance (TMR) in junctions with 3d
ferromagnetic electrodes. Previously we predicted that defects in the barrier
would result in reduced effective polarization P of the impurity assisted
current. This is confirmed experimentally in the present work: introductions of
defects into the barrier drastically decreases the TMR. The degradation of
magnetoresistance with bias has also been studied and shows universal features,
attributed to effects of tunneling assisted by magnons and phonons, whose
different role is described. Details of the bias dependence of the TMR depend
on preparation procedures and well described by the model which includes
assisted tunneling. Non-linear features, seen at low biases, are related to
excitation of bulk modes by tunneling electrons. The analysis of factors
resulting in fall-off of the TMR with bias is presented.

###Spin Dynamics of the Magnetoresistive Pyrochlore Tl_2Mn_2O_7|J. W. Lynn,L. Vasiliu-Doloc,M. A. Subramanian###

Spin Dynamics of the Magnetoresistive Pyrochlore Tl_2Mn_2O_7. Neutron scattering has been used to study the magnetic order and spin
dynamics of the colossal magnetoresistive pyrochlore Tl_2Mn_2O_7. On cooling
from the paramagnetic state, magnetic correlations develop and appear to
diverge at T_C (123 K). In the ferromagnetic phase well defined spin waves are
observed, with a gapless ($\Delta <0.04$ meV) dispersion relation E=Dq^{2} as
expected for an ideal isotropic ferromagnet. As T approaches T_C from low T,
the spin waves renormalize, but no significant central diffusive component to
the fluctuation spectrum is observed in stark contrast to the
La$_{1-x}$(Ca,Ba,Sr)$_x$MnO$_3$ system. These results argue strongly that the
mechanism responsible for the magnetoresistive effect has a different origin in
these two classes of materials.

###Characterization of transport and magnetic properties in thin film La(0.67)(Ca(x)Sr(1-x))(0.33)MnO(3) mixtures|P. R. Broussard,S. B. Qadri,V. M. Browning,V. C. Cestone###

Characterization of transport and magnetic properties in thin film La(0.67)(Ca(x)Sr(1-x))(0.33)MnO(3) mixtures. We have grown thin films of (100) oriented
La_{0.67}(Ca_{x}Sr_{1-x})_{0.33}MnO_{3} on (100) NdGaO_{3} substrates by
off-axis sputtering. We have looked at the changes in the resistivity and
magnetoresistance of the samples as the Ca/Sr ratio was varied. We find that as
the calcium fraction is decreased, the lattice match to the substrate
decreases, and the films become more disordered, as observed in transport
measurements and the variation in Curie and peak resistance temperatures. We
find a correlation between the temperature independent and T^2 terms to the low
temperature resistivity. The room temperature magnetoresistance exhibits a
maximum as the peak temperature is increased by the substitution of Sr for Ca,
and a change in the field dependence to the resistivity at room temperature is
observed.

###Theory of magnetoresistance in films of dilute magnetic alloys|L. Borda,A. Zawadowski###

Theory of magnetoresistance in films of dilute magnetic alloys. Earlier a magnetic anisotropy for magnetic impurities nearby the surface of
non-magnetic host was proposed in order to explain the size dependence of the
Kondo effect in dilute magnetic alloys. Recently Giordano has measured the
magnetoresistance of dilute Au(Fe) films for different thicknesses well above
the Kondo temperature $T_K$. In this way he verified the existence of that
anisotropy even for such a case where the Kondo effect is not dominating. For
detailed comparison of that suggestion with experiments, the magnetic field
dependence of the magnetoresistance is calculated in the lowest approximation,
thus in the second order of the exchange coupling. The strength of the
anisotropy is very close to earlier estimates deduced from the size dependence
of the Kondo resistivity amplitude.

###Hall effect of epitaxial double-perovskite Sr_2FeMoO_6 thin films|W. Westerburg,F. Martin,G. Jakob###

Hall effect of epitaxial double-perovskite Sr_2FeMoO_6 thin films. We prepared high epitaxial thin films of the compound Sr_2FeMoO_6 with narrow
rocking curves by pulsed laser deposition. The diagonal and nondiagonal
elements of the resistivity tensor were investigated at temperatures from 4 K
up to room temperature in magnetic fields up to 8 T. An electronlike ordinary
Hall effect and a holelike anomalous Hall contribution are observed. Both
coefficients have reversed sign compared to the colossal magnetoresistive
manganites. We found at 300 K an ordinary Hall coefficent of -1.87x10^{-10}
m^3/As, corresponding to a nominal charge carrier density of four electrons per
formula unit. At low temperature only a small negative magnetoresistance is
observed which vanishes at higher temperatures. The temperature coefficient of
the resistivity is negative over the whole temperature range. A Kondo like
behavior is observed below 30 K while above 100 K variable range hopping like
transport occurs.

###Magnetoresistance of Granular Superconducting Metals in a Strong Magnetic Field|I. S. Beloborodov,K. B. Efetov,A. I. Larkin###

Magnetoresistance of Granular Superconducting Metals in a Strong Magnetic Field. The magnetoresistance of a granular superconductor in a strong magnetic field
is considered. It is assumed that this field destroys the superconducting gap
in each grain, such that all interesting effects considered in the paper are
due to superconducting fluctuations. The conductance of the system is assumed
to be large, which allows us to neglect all localization effects as well as the
Coulomb interaction. It is shown that at low temperatures the superconducting
fluctuations reduce the one-particle density of states but do not contribute to
transport. As a result, the resistivity of the normal state exceeds the
classical resistivity approaching the latter only in the limit of extremely
strong magnetic fields, and this leads to a negative magnetoresistance. We
present detailed calculations of physical quatities relevant for describing the
effect and make a comparison with existing experiments.

###An electron correlation originated negative magnetoresistance in a system having a partly flat band|Ryotaro Arita,Kazuhiko Kuroki,Hideo Aoki###

An electron correlation originated negative magnetoresistance in a system having a partly flat band. Inspired from an experimentally examined organic conductor, a novel mechanism
for negative magnetoresistance is proposed for repulsively interacting
electrons on a lattice whose band dispersion contains a flat portion (a flat
bottom below a dispersive part here). When the Fermi level lies in the flat
part, the electron correlation should cause ferromagnetic spin fluctuations to
develop with an enhanced susceptibility. A relatively small magnetic field will
then shift the majority-spin Fermi level to the dispersive part, resulting in a
negative magnetoresistance. We have actually confirmed the idea by calculating
the conductivity in magnetic fields, with the fluctuation exchange
approximation, for the repulsive Hubbard model on a square lattice having a
large second nearest-neighbor hopping.

###Influence of high-energy electron irradiation on the transport properties of La_{1-x}Ca_{x}MnO_{3} films (x \approx 1/3)|B. I. Belevtsev,V. B. Krasovitsky,V. V. Bobkov,D. G. Naugle,K. D. D. Rathnayaka,A. Parasiris###

Influence of high-energy electron irradiation on the transport properties of La_{1-x}Ca_{x}MnO_{3} films (x \approx 1/3). The effect of crystal lattice disorder on the conductivity and colossal
magnetoresistance in La_{1-x}Ca_{x}MnO_{3} (x \approx 0.33) films has been
examined. The lattice defects are introduced by irradiating the film with
high-energy (\simeq 6 MeV) electrons with a maximal fluence of about 2\times
10^{17} cm^{-2}. This comparatively low dose of irradiation produces rather
small radiation damage in the films. The number of displacements per atom (dpa)
in the irradiated sample is about 10^{-5}. Nethertheless, this results in an
appreciable increase in the film resistivity. The percentage of resistivity
increase in the ferromagnetic metallic state (below the Curie tempetature
T_{c}) was much greater than that observed in the insulating state (above
T_{c}). At the same time irradiation has much less effect on T_{c} or on the
magnitude of the colossal magnetoresistance. A possible explanation of such
behavior is proposed.

###The effect of the annealing temperature on the local distortion of La$_{0.67}$Ca$_{0.33}$MnO$_3$ thin films|D. Cao,F. Bridges,D. Worledge,C. Booth,T. Geballe###

The effect of the annealing temperature on the local distortion of La$_{0.67}$Ca$_{0.33}$MnO$_3$ thin films. Mn $K$-edge fluorescence data are presented for thin film samples (3000~\AA)
of Colossal Magnetoresistive (CMR) La$_{0.67}$Ca$_{0.33}$MnO$_3$: as-deposited,
and post-annealed at 1000 K and 1200 K. The local distortion is analyzed in
terms of three contributions: static, phonon, and an extra,
temperature-dependent, polaron term. The polaron distortion is very small for
the as-deposited sample and increases with the annealing temperature. In
contrast, the static distortion in the samples decreases with the annealing
temperature. Although the local structure of the as-deposited sample shows very
little temperature dependence, the change in resistivity with temperature is
the largest of these three thin film samples. The as-deposited sample also has
the highest magnetoresistance (MR), which indicates some other mechanism may
also contribute to the transport properties of CMR samples. We also discuss the
relationship between local distortion and the magnetization of the sample.

###The theory of GMR and TMR in segmented magnetic nanowires|M. Ye. Zhuravlev,H. O. Lutz,A. V. Vedyayev###

The theory of GMR and TMR in segmented magnetic nanowires. We calculate the resistivity and Giant Magnetoresistance (GMR) of a segmented
nanowire consisting of two ferromagnetic segments separated by a thin
paramagnetic spacer. The quantization of the electron motion due to the small
nanowire cross-section is taken into account; s-d electron scattering gives
rise to different mean free paths for spin-up and spin-down s-electrons. The
calculated resistivity and GMR oscillate as a function of nanowire
cross-section due to the difference in Fermi momenta of d-electrons with
opposite spins. The GMR can reach values much higher than those which are
obtained for "wires" of infinite cross-section (i.e., a multilayer). Similarly
we have calculated the Tunneling Magnetoresistance (TMR) by replacing the
paramagnetic spacer with an insulator spacer.

###Magnetoresistance in ordered and disordered double perovskite oxide, Sr$_2$FeMoO$_6$|D. D. Sarma,E. V. Sampathkumaran,Sugata Ray,R. Nagarajan,Subham Majumdar,Ashwani Kumar,G. Nalini,T. N. GuruRow###

Magnetoresistance in ordered and disordered double perovskite oxide, Sr$_2$FeMoO$_6$. We have prepared crystallographically ordered and disorder specimens of the
double perovskite, Sr$_2$FeMoO$_6$ and investigated their magnetoresistance
behaviour. The extent of ordering between the Fe and Mo sites in the two
samples is determined by Rietveld analysis of powder x-ray diffraction patterns
and reconfirmed by M\"{o}ssbauer studies. While the ordered sample exhibits the
sharp low-field response, followed by moderate changes in the magnetoresistance
at higher fields, the disordered sample is characterised by the absence of the
spectacular low-field response. We argue that the low field response depends
crucially on the half-metallic ferromagnetism, while the high-field response
follows from the overall magnetic nature of the sample, even in absence of the
half-metallic state.

###Weak anisotropy and disorder dependence of the in-plane magnetoresistance in high mobility (100) Si-inversion layers|V. M. Pudalov,G. Brunthaler,A. Prinz,G. Bauer###

Weak anisotropy and disorder dependence of the in-plane magnetoresistance in high mobility (100) Si-inversion layers. We report studies of the magnetoresistance (MR) in a two-dimensional electron
system in (100) Si-inversion layers, for perpendicular and parallel
orientations of the current with respect to the magnetic field in the 2D-plane.
The magnetoresistance is almost isotropic; this result does not support the
suggestion of the orbital origin of the MR in Si-inversion layer. In the
hopping regime, however, the MR contains a weak anisotropic component that is
non-monotonic in magnetic field. We found that the field, at which the MR
saturates, for different samples varies by a factor of two, being lower or
higher than the field of complete spin polarization of free carriers.
Therefore, the saturation of the MR can not be identified with the spin
polarization of free carriers.

###Resistance effects due to magnetic guiding orbits|J. Reijniers,F. M. Peeters###

Resistance effects due to magnetic guiding orbits. The Hall and magnetoresistance of a two dimensional electron gas subjected to
a magnetic field barrier parallel to the current direction is studied as
function of the applied perpendicular magnetic field. The recent experimental
results of Nogaret {\em et al.} [Phys. Rev. Lett. {\bf 84}, 2231 (2000)] for
the magneto- and Hall resistance are explained using a semi-classical theory
based on the Landauer-B\"{u}ttiker formula. The observed positive
magnetoresistance peak is explained as due to a competition between a decrease
of the number of conducting channels as a result of the growing magnetic field,
from the fringe field of the ferromagnetic stripe as it becomes magnetized, and
the disappearance of snake orbits and the subsequent appearance of cycloidlike
orbits.

###Ferromagnetism and large negative magnetoresistance in Pb doped Bi-Sr-Co-O misfit-layer compound|I. Tsukada,T. Yamamoto,M. Takagi,T. Tsubone,S. Konno,K. Uchinokura###

Ferromagnetism and large negative magnetoresistance in Pb doped Bi-Sr-Co-O misfit-layer compound. Ferromagnetism and accompanying large negative magnetoresistance in
Pb-substituted Bi-Sr-Co-O misfit-layer compound are investigated in detail.
Recent structural analysis of (Bi,Pb)${}_2$Sr${}_{3}$Co${}_2$O${}_9$, which has
been believed to be a Co analogue of
Bi${}_2$Sr${}_2$CaCu${}_2$O${}_{8+\delta}$, revealed that it has a more complex
structure including a CoO${}_2$ hexagonal layer [T. Yamamoto {\it et al.}, Jpn.
J. Appl. Phys. {\bf 39} (2000) L747]. Pb substitution for Bi not only
introduces holes into the conducting CoO${}_2$ layers but also creates a
certain amount of localized spins. Ferromagnetic transition appears at $T$ =
3.2 K with small spontaneous magnetization along the $c$ axis, and around the
transition temperature large and anisotropic negative magnetoresistance was
observed. This compound is the first example which shows ferromagnetic
long-range order in a two-dimensional metallic hexagnonal CoO${}_2$ layer.

###Weak localization in ferromagnets with spin-orbit interaction|V. K. Dugaev,P. Bruno,J. Barnas###

Weak localization in ferromagnets with spin-orbit interaction. Weak localization corrections to conductivity of ferromagnetic systems are
studied theoretically in the case when spin-orbit interaction plays a
significant role. Two cases are analyzed in detail: (i) the case when the
spin-orbit interaction is due to scattering from impurities, and (ii) the case
when the spin-orbit interaction results from reduced dimensionality of the
system and is of the Bychkov-Rashba type. Results of the analysis show that the
localization corrections to conductivity of ferromagnetic metals lead to a
negative magnetoresistance -- also in the presence of the spin-orbit
scattering. Positive magnetoresistance due to weak antilocalization, typical of
nonmagnetic systems, does not occur in ferromagnetic systems. In the case of
two-dimensional ferromagnets, the quantum corrections depend on the
magnetization orientation with respect to the plane of the system.

###Dynamical mean-field theory of a double-exchange model with diagonal disorder|B. M. Letfulov,J. K. Freericks###

Dynamical mean-field theory of a double-exchange model with diagonal disorder. We present a simplified model for the colossal magnetoresistance in doped
manganites by exactly solving a double-exchange model (with Ising-like local
spins) and quenched binary disorder within dynamical mean field theory. We
examine the magnetic properties and the electrical and thermal transport. Our
solution illustrates three different physical regimes: (i) a weak-disorder
regime, where the system acts like a renormalized double-exchange system (which
is insufficient to describe the behavior in the manganites); (ii) a
strong-disorder regime, where the system is described by strong-coupling
physics about an insulating phase (which is the most favorable for large
magnetoresistance); and (iii) a transition region of moderate disorder, where
both double-exchange and strong-coupling effects are important. We use the
thermopower as a stringent test for the applicability of this model to the
manganites and find that the model is unable to properly account for the sign
change of the thermopower seen in experiment.

###Thermopower and thermal conductivity of superconducting perovskite $MgCNi_3$|S. Y. Li,W. Q. Mo,M. Yu,W. H. Zheng,C. H. Wang,Y. M. Xiong,R. Fan,H. S. Yang,B. M. Wu,L. Z. Cao,X. H. Chen###

Thermopower and thermal conductivity of superconducting perovskite $MgCNi_3$. The thermopower and thermal conductivity of superconducting perovskite
$MgCNi_3$ ($T_c \approx$ 8 K) have been studied. The thermopower is negative
from room temperature to 10 K. Combining with the negative Hall coefficient
reported previously, the negative thermopower definetly indicates that the
carrier in $MgCNi_3$ is electron-type. The nonlinear temperature dependence of
thermopower below 150 K is explained by the electron-phonon interaction
renormalization effects. The thermal conductivity is of the order for
intermetallics, larger than that of borocarbides and smaller than $MgB_2$. In
the normal state, the electronic contribution to the total thermal conductivity
is slightly larger than the lattice contribution. The transverse
magnetoresistance of $MgCNi_3$ is also measured. It is found that the classical
Kohler's rule is valid above 50 K. An electronic crossover occures at $T^* \sim
50 K$, resulting in the abnormal behavior of resistivity, thermopower, and
magnetoresistance below 50 K.

###Lattice coupled first order magnetoresistance transition in an A-type antiferromagnet: Pr$_{0.46}$Sr$_{0.54}$MnO$_3$|R. Mahendiran,C. Martin,A. Maignan,M. Hervieu,B. Raveau,L. Morellon,C. Marquina,B. Garcia-Landa,M. R. Ibarra###

Lattice coupled first order magnetoresistance transition in an A-type antiferromagnet: Pr$_{0.46}$Sr$_{0.54}$MnO$_3$. We investigated magnetic, magnetotransport and magnetostriction properties of
the A-type antiferromagnet Pr$_{0.46}$Sr$_{0.54}$MnO$_3$ which undergoes a
first order paramagnetic-antiferromagnetic transition below T$_N$ = 210 K while
cooling and T$_N$ = 215 K while warming. The zero field ($\mu_0$H = 0 T)
resistivity shows a sudden jump at T$_N$ and a small bump around T$_{max}$ =
220 K (\TEXTsymbol{>} T$_N$). T$_N$ shifts down and T$_{max}$ shifts up with
increasing $\mu_0$H. Magnetoresistance as high as -45-57 % at 7 T is found in
the temperature range 180 K-230 K. Isothermal measurements indicate that the
field induced antiferromagnetic to ferromagnetic transition below T$_N$ is
accompanied by a rapid decrease of the resistivity but increase of volume
($\Delta $V/V = +0.25 % at 180 K and 13.7 T). This lattice coupled
magnetoresistance transition is suggested due to the field induced structural
transition from the low volume orthorhombic to the high volume tetragonal
structure.

###Martensitic accommodation strain and the metal-insulator transition in manganites|V. Podzorov,B. G. Kim,V. Kiryukhin,M. E. Gershenson,S-W. Cheong###

Martensitic accommodation strain and the metal-insulator transition in manganites. In this paper, we report polarized optical microscopy and electrical
transport studies of manganese oxides that reveal that the charge ordering
transition in these compounds exhibits typical signatures of a martensitic
transformation. We demonstrate that specific electronic properties of
charge-ordered manganites stem from a combination of martensitic accommodation
strain and effects of strong electron correlations. This intrinsic strain is
strongly affected by the grain boundaries in ceramic samples. Consistently, our
studies show a remarkable enhancement of low field magnetoresistance and the
grain size effect on the resistivity in polycrystalline samples and suggest
that the transport properties of this class of manganites are governed by the
charge-disordered insulating phase stabilized at low temperature by virtue of
martensitic accommodation strain. High sensitivity of this phase to strains and
magnetic field leads to a variety of striking phenomena, such as unusually high
magnetoresistance (10^10 %) in low magnetic fields.

###Magnetotransport in a bi-crystal film of La_0.7Sr_0.3MnO_3|R. Mathieu,P. Svedlindh,R. Chakalov,Z. G. Ivanov###

Magnetotransport in a bi-crystal film of La_0.7Sr_0.3MnO_3. Transport properties of an epitaxial film of La_0.7Sr_0.3MnO_3 (LSMO),
deposited epitaxially on a LaAlO_3 bi-crystal substrate having a misorientation
angle of 9.2 deg., have been studied.
  The film was patterned into a meander containing 100 grain boundaries. The
resistivity of the sample exhibits two components; one originating from the
grain boundary regions, and one from the LSMO elements in the meander; the
latter contribution is similar to the resistivity of a reference epitaxial LSMO
film. The low (<0.5 T) and high (up to 6 T) field magnetoresistance was also
studied. The meander show a large low field magnetoresistance, increasing with
decreasing temperature, and a constant high field slope of the
magnetoconductance, results that are well explained by a two-step spin
polarized tunneling model.

###Two band transport and the question of a metal-insulator transition in GaAs/GaAlAs two dimensional holes|Yuval Yaish,Oleg Prus,Evgeny Buchstab,Gidi Ben Yoseph,Uri Sivan,Iddo Ussishkin,Ady Stern###

Two band transport and the question of a metal-insulator transition in GaAs/GaAlAs two dimensional holes. The magnetotransport of two dimensional holes in a GaAs/AlGaAs
heterostructure is studied experimentally and theoretically. Spin-orbit
splitting of the heavy hole band is manifested at high carrier densities in two
Shubnikov-de Haas frequencies, classical positive magnetoresistance, and weak
antilocalization. The latter effect combined with inelastic scattering between
the spin-orbit split bands lead to metallic characteristics, namely resistance
increase with temperature. At lower densities, when splitting is smaller than
the inverse elastic scattering time, the two bands effectively merge to yield
the expected insulating characteristics and negative magnetoresistance due to
weak localization and interaction corrections to the conductivity. The "metal
to insulator" transition at intermediate densities is found to be a smooth
crossover between the two regimes rather than a quantum phase transition. Two
band calculations of conventional interference and interaction effects account
well for the data in the whole parameter range.

###Dipolar interactions and anisotropic magnetoresistance in metallic granular systems|J. Viana Lopes,J. M. B. Lopes dos Santos,Yu. G. Pogorelov###

Dipolar interactions and anisotropic magnetoresistance in metallic granular systems. We revisit the theory of magnetoresistance for a system of nanoscopic
magnetic granules in metallic matrix. Using a simple model for the spin
dependent perturbation potential of the granules, we solve Boltzmann equation
for the spin dependent components of the non equilibrium electronic
distribution function. For typical values of the geometric parameters in
granular systems, we find a peculiar structure of the distribution function of
conduction electrons, which is at variance with the two-current model of
conduction in inhomogeneous systems. Our treatment explicitly includes the
effects of dipolar correlations yielding a magnetoresistance ratio which
contains, in addition to the term proportional to the square of uniform
magnetization (< {\boldsymbol \mu} >), a weak anisotropic contribution
depending on the angle between electric and magnetic fields, and arising from
the anisotropic character of dipolar interactions.

###A model for spin-polarized transport in perovskite manganite bi-crystal grain boundaries|R. Gunnarsson,A. Kadigrobov,Z. Ivanov###

A model for spin-polarized transport in perovskite manganite bi-crystal grain boundaries. We have studied the temperature dependence of low-field magnetoresistance and
current-voltage characteristics of a low-angle bi-crystal grain boundary
junction in perovskite manganite La_{2/3}Sr_{1/3}MnO_3 thin film. By gradually
trimming the junction we have been able to reveal the non-linear behavior of
the latter. With the use of the relation M_{GB} \propto M_{bulk}\sqrt{MR^*} we
have extracted the grain boundary magnetization. Further, we demonstrate that
the built-in potential barrier of the grain boundary can be modelled by
V_{bi}\propto M_{bulk}^2 - M_{GB}^2. Thus our model connects the
magnetoresistance with the potential barrier at the grain boundary region. The
results indicate that the band-bending at the grain boundary interface has a
magnetic origin.

###Structural transformation induced by magnetic field and colossal magnetoresistance response above 313 K in MnAs|J. Mira,F. Rivadulla,J. Rivas,A. Fondado,R. Caciuffo,F. Carsughi,T. Guidi,J. B. Goodenough###

Structural transformation induced by magnetic field and colossal magnetoresistance response above 313 K in MnAs. MnAs exhibits a first-order phase transition from a ferromagnetic, high-spin
metal NiAs-type hexagonal phase to a paramagnetic, lower-spin insulator
MnP-type orthorhombic phase at T_C = 313 K. Here, we report the results of
neutron diffraction experiments showing that an external magnetic field, B,
stabilizes the hexagonal metallic phase above T_C. The phase transformation is
reversible and constitutes the first demonstration of a bond-breaking
transition induced by a magnetic field. At 322 K the hexagonal structure is
restored for B > 4 tesla. The field-induced phase transition is accompanied by
an enhanced magnetoresistance of about 17 % at 310 K. We discuss the origin of
this phenomenon, which appears to be similar to that of the colossal
magnetoresistance response observed in some members of the manganese perovskite
family.

###Ferromagnetism and giant magnetoresistance in the rare earth fullerides Eu6-xSrxC60|Kenji Ishii,Akihiko Fujiwara,Hiroyoshi Suematsu,Yoshihiro Kubozono###

Ferromagnetism and giant magnetoresistance in the rare earth fullerides Eu6-xSrxC60. We have studied crystal structure, magnetism and electric transport
properties of a europium fulleride Eu6C60 and its Sr-substituted compounds,
Eu6-xSrxC60. They have a bcc structure, which is an isostructure of other M6C60
(M represents an alkali atom or an alkaline earth atom). Magnetic measurements
revealed that magnetic moment is ascribed to the divalent europium atom with S
= 7/2 spin, and a ferromagnetic transition was observed at TC = 10 - 14 K. In
Eu6C60, we also confirm the ferromagnetic transition by heat capacity
measurement. The striking feature in Eu6-xSrxC60} is very large negative
magnetoresistance at low temperature; the resistivity ratio \rho(H = 9
T)/\rho(H = 0 T) reaches almost 10^{-3} at 1 K in Eu6C60. Such large
magnetoresistance is the manifestation of a strong pi-f interaction between
conduction carriers on C60 and 4f electrons of Eu.

###Martensitic transition and magnetoresistance in a Cu-Al-Mn shape memory alloy. Influence of aging|Jordi Marcos,Antoni Planes,Lluís Mañosa,Amílcar Labarta,Bart Jan Hattink###

Martensitic transition and magnetoresistance in a Cu-Al-Mn shape memory alloy. Influence of aging. We have studied the effect of ageing within the miscibility gap on the
electric, magnetic and thermodynamic properties of a non-stoichiometric Heusler
Cu-Al-Mn shape-memory alloy, which undergoes a martensitic transition from a
$bcc$-based ($\beta$-phase) towards a close-packed structure ($M$-phase).
Negative magnetoresistance which shows an almost linear dependence on the
square of magnetization with different slopes in the $M$- and $\beta$-phases,
was observed. This magnetoresistive effect has been associated with the
existence of Mn-rich clusters with the Cu$_2$AlMn-structure. The effect of an
applied magnetic field on the martensitic transition has also been studied. The
entropy change between the $\beta$- and $M$-phases shows negligible dependence
on the magnetic field but it decreases significantly with annealing time within
the miscibility gap. Such a decrease is due to the increasing amount of
Cu$_2$MnAl-rich domains that do not transform martensitically.

###Electromodulation of the Magnetoresistance in Diluted Magnetic Semiconductors Based Heterostructures|M. P. López-Sancho,M. C. Muñoz,L. Brey###

Electromodulation of the Magnetoresistance in Diluted Magnetic Semiconductors Based Heterostructures. We study the properties of heterostructures formed by two layers of diluted
magnetic semiconductor separated by a nonmagnetic semiconductor layer. We find
that there is a RKKY-type exchange coupling between the magnetic layers that
oscilles between ferromagnetic and antiferromagnetic as a function of the
different parameters in the problem. The different transport properties of
these phases make that this heterostructure presents strong magnetoresistive
effects. The coupling can be also modified by an electric field. We propose
that it is possible to alter dramatically the electrical resistance of the
heterostructure by applying an electric field. Our results indicate that in a
single gated sample the magnetoresistance could be modulated by with an
electrical bias voltage.

###Effect of Contact Interfaces on Quantum Conductance of Armchair Nanotubes|S. Krompiewski###

Effect of Contact Interfaces on Quantum Conductance of Armchair Nanotubes. Effect of contact interfaces, between metallic single-wall carbon nanotubes
(SWCNT) and external electrodes made also of nanotubes, on the electrical
conductance is studied. A tight-binding model with both diagonal and
off-diagonal disorder, a recursive Green function technique as well as the
Landauer formalism are used. The studies are carried out within the coherent
transport regime and are focused on: (i) evolution from conductance
quantization to resonant tunneling, (ii) SWCNT's length effects and (iii)
magnetoresistance. It is shown that the so-called on-resonance devices, i.e.
nanotubes having a conductance peak at the Fermi energy, occur with a period of
3 carbon inter-ring spacings. Additionally, the present approach provides an
insight into magnetoresistance dependence of SWCNTs on conditions at the
contact interface.

###Magnetic Flux Trapping in Granular HTSC near Superconducting Transition|A. A. Sukhanov,V. I. Omelchenko,G. A. Orlova###

Magnetic Flux Trapping in Granular HTSC near Superconducting Transition. The temperature and field dependences of the trapped magnetic fields and of
the frozen magnetoresistance of (Pb)Bi-Sr-Ca-Cu-O ceramics and Bi-based
magnetron films are investigated. It is found that in the resistive transition
region of granular Bi-HTSC the trapped magnetic fields become highly
inhomogeneous and alternating in sign at scale of less than 50 microns. Unlike
ceramic the films have critical temperature of trapping lower than the upper
temperature of magnetoresistance disappearance. The experimental results are
explained by a model in which the magnetic fields are trapped in
superconducting loops embedded in Josephson weak links medium. The loops nature
which is essentially different for films and ceramics is discussed. Observed
temperature and field dependences of trapped field are in good agreement with
those calculated for normal law of the loops distribution on critical fields.

###Anomalous Hall Effect of Calcium-doped Lanthanum Cobaltite Films|S. A. Baily,M. B. Salamon###

Anomalous Hall Effect of Calcium-doped Lanthanum Cobaltite Films. The Hall resistivity, magnetoresistance, and magnetization of
La_{1-x}Ca_{x}CoO_{3} epitaxial films with x between 0.25 and 0.4 grown on
lanthanum aluminate were measured in fields up to 7 T. The x=1/3 film, shows a
reentrant metal insulator transition. Below 100 K, the x=1/3 and 0.4 films have
significant coercivity which increases with decreasing temperature. At low
temperature the Hall resistivity remains large and essentially field
independent in these films, except for a sign change at the coercive field that
is more abrupt than the switching of the magnetization. A unique
magnetoresistance behavior accompanies this effect. These results are discussed
in terms of a percolation picture and the mixed spin state model for this
system. We propose that the low-temperature Hall effect is caused by
spin-polarized carriers scattering off of orbital disorder in the spin-ordered
clusters.

###Low frequency 1/f noise in doped manganite grain-boundary junctions|J. B. Philipp,L. Alff,A. Marx,R. Gross###

Low frequency 1/f noise in doped manganite grain-boundary junctions. We have performed a systematic analysis of the low frequency 1/f-noise in
single grain boundary junctions in the colossal magnetoresistance material
La_{2/3}Ca_{1/3}MnO_{3-delta}. The grain boundary junctions were formed in
epitaxial La_{2/3}Ca_{1/3}MnO_{3-delta} films deposited on SrTiO_3 bicrystal
substrates and show a large tunneling magnetoresistance of up to 300% at 4.2 K
as well as ideal, rectangular shaped resistance versus applied magnetic field
curves. Below the Curie temperature T_C the measured 1/f noise is dominated by
the grain boundary. The dependence of the noise on bias current, temperature
and applied magnetic field gives clear evidence that the large amount of low
frequency noise is caused by localized sites with fluctuating magnetic moments
in a heavily disordered grain boundary region. At 4.2 K additional temporally
unstable Lorentzian components show up in the noise spectra that are most
likely caused by fluctuating clusters of interacting magnetic moments. Noise
due to fluctuating domains in the junction electrodes is found to play no
significant role.

###Structure, electric and magnetic properties of the electron-doped manganese oxide: La{sub(1-x)}Te{sub(x)}MnO{sub(3)}(x=0.1, 0.15)|Guotai Tan,Shouyu Dai,Ping Duan,Huibin Lu,Yueliang Zhou,Zhenghao Chen###

Structure, electric and magnetic properties of the electron-doped manganese oxide: La{sub(1-x)}Te{sub(x)}MnO{sub(3)}(x=0.1, 0.15). In this letter, the electrical and magnetic properties of
La{sub(1-x)}Te{sub(x)}MnO{sub(3)}(x=0.1, 0.15), which is a new material and
shows good colossal magnetoresistance (CMR) behavior, have been investigated.
These compounds have rhombohedral structure. In this materical, Te replaced a
part of La ions, which induced the lattice cell constriction and Mn-O-Mn bond
angle widening. X-ray photoemission spectroscopy (XPS) measurement revealed
that the Te ions were in the tetravalent state and the manganese ions could be
considered as in a mixture state of Mn{sup(2+)} and Mn{Sup(3+)}. Thus the
material could be viewed as an electron-doped compound. The Curie temperature
(Tc) was about 240 K and 255 K for x=0.1, 0.15, respectively. The maximum
magnetoresistance ratio MR=[r(0)-r(H)]/r(0) was about 51% at 200 K and in the
applied magnetic field of 40 kOe.

###Griffiths singularities and magnetoresistive manganites|M. B. Salamon,S. H. Chun###

Griffiths singularities and magnetoresistive manganites. The large, so-called colossal, magnetoresistivity of doped manganese oxides
based on LaMnO3 has attracted considerable attention, but only one unusual
feature of the ferromagnetic transition in these compounds. We examine in this
paper the progression of magnetic and thermodynamic behavior as the transition
temperature is made to vary from 360 K to 218 K by changing the divalent
dopant. Single crystals of La_{0.7}Sr_{0.3}MnO3, as is well known, show modest
magnetoresistivity and conventional critical behavior. La$_{0.7}$Pb$_{0.3}$
Mn$O_3$, and to an even greater extent, La$_{0.7}$Ca$_{0.3}$MnO$_3$, have
unusual magnetic properties extending more than 100 K above the transition. We
treat the properties of the latter samples in the context of a Griffiths phase
in which the transition temperature is depressed from its maximum value T_{G}
by random bond-angle bending.

###Structural Aspects of Magnetic Coupling in CaCu3Mn4O12 and CaCu3Ti4O12|M. D. Johannes,W. E. Pickett,R. Weht###

Structural Aspects of Magnetic Coupling in CaCu3Mn4O12 and CaCu3Ti4O12. Two perovskite-derived materials, CaCu3Mn4O12 and CaCu3Ti4O12, have drawn
much recent interest due to their magnetoresistive, dielectric, and
magnetoelectronic characteristics. Here we present initial theoretical insights
into each of these points, based on first principles, density functional based
calculations. Our results predict CCMO to have a spin-asymmetric energy gap,
which leads to distinct temperature- and magnetic field-dependent changes in
properties, and helps to account for its observed negative magnetoresistivity.
We have studied CCTO primarily to gain insight into the exchange coupling in
both these compounds, where the conventional superexchange coupling vanishes by
symmetry for both nearest and next nearest Cu-Cu neighbors, a consequence of
the structure. In CCTO, it is necessary to go to 5th Cu-Cu neighbors to obtain
a (superexchange) coupling that can provide the coupling necessary to give
three dimensional order. Non-superexchange mechanisms may be necessary to
describe the magnetic coupling in this structural class.

###Magnetic field and pressure effects on charge density wave, superconducting, and magnetic states in Lu$_5$Ir$_4$Si$_{10}$ and Er$_5$Ir$_4$Si$_{10}$|M. H. Jung,H. C. Kim,F. Galli,J. A. Mydosh###

Magnetic field and pressure effects on charge density wave, superconducting, and magnetic states in Lu$_5$Ir$_4$Si$_{10}$ and Er$_5$Ir$_4$Si$_{10}$. We have studied the charge-density-wave (CDW) state for the superconducting
Lu$_5$Ir$_4$Si$_{10}$ and the antiferromagnetic Er$_5$Ir$_4$Si$_{10}$ as
variables of temperature, magnetic field, and hydrostatic pressure. For
Lu$_5$Ir$_4$Si$_{10}$, the application of pressure strongly suppresses the CDW
phase but weakly enhances the superconducting phase. For Er$_5$Ir$_4$Si$_{10}$,
the incommensurate CDW state is pressure independent and the commensurate CDW
state strongly depends on the pressure, whereas the antiferromagnetic ordering
is slightly depressed by applying pressure. In addition, Er$_5$Ir$_4$Si$_{10}$
shows negative magnetoresistance at low temperatures, compared with the
positive magnetoresistance of Lu$_5$Ir$_4$Si$_{10}$.

###Quantum Oscillations, Colossal Magnetoresistance and Magnetoelastic Interaction in Bilayered Ca3Ru2O7|G. Cao,L. Balicas,Y. Xin,J. E. Crow,C. S. Nelson###

Quantum Oscillations, Colossal Magnetoresistance and Magnetoelastic Interaction in Bilayered Ca3Ru2O7. We report magnetic and inter-plane transport properties of Ca3Ru2O7 at high
magnetic fields and low temperatures. Ca3Ru2O7 with a bilayered orthorhombic
structure is a Mott-like system with a narrow charge gap of 0.1eV. Of a host of
unusual physical phenomena revealed in this study, a few are particularly
intriguing: (1) a collapse of the c-axis lattice parameter at a metal-nonmetal
transition, TMI (=48 K), and a rapid increase of TMI with low uniaxial pressure
applied along the c-axis; (2) quantum oscillations in the gapped, nonmetallic
state for 20 mK<T<6.5 K; (3) tunneling colossal magnetoresistance, which yields
a precipitate drop in resistivity by as much as three orders of magnitude; (4)
different in-plane anisotropies of the colossal magnetoresistance and
magnetization. All results appear to indicate a highly anisotropic ground state
and a critical role of coupling between lattice and magnetism. The implication
of these phenomena is discussed.

###Room temperature domain wall pinning in bent ferromagnetic nanowires|D. M. Silevitch,M. Tanase,C. L. Chien,D. H. Reich###

Room temperature domain wall pinning in bent ferromagnetic nanowires. Mechanically bent nickel nanowires show clear features in their room
temperature magnetoresistance when a domain wall is pinned at the location of
the bend. By varying the direction of an applied magnetic field, the wire can
be prepared either in a single-domain state or a two-domain state. The presence
or absence of the domain wall acts to shift the switching fields of the
nanowire. In addition, a comparison of the magnetoresistance of the nanowire
with and without a domain wall shows a shift in the resistance correlated with
the presence of a wall. The resistance is decreased by 20-30 milli-Ohms when a
wall is present, compared to an overall resistance of 40-60 Ohms. A model of
the magnetization was developed that allowed calculation of the magnetostatic
energy of the nanowires, giving an estimate for the nucleation energy of a
domain wall.

###The Silicon Inversion Layer With A Ferromagnetic Gate: A Novel Spin Source|J. P. McGuire,C. Ciuti,L. J. Sham###

The Silicon Inversion Layer With A Ferromagnetic Gate: A Novel Spin Source. Novel spin transport behavior is theoretically shown to result from replacing
the usual metal (or poly-silicon) gate in a silicon field-effect transistor
with a ferromagnet, separated from the semiconductor by an ultra-thin oxide.
The spin-dependent interplay between the drift current (due to a source-drain
bias) and the diffusion current (due to carrier leakage into the ferromagnetic
gate) results in a rich variety of spin dependence in the current that flows
through such a device. We examine two cases of particular interest: (1)
creating a 100% spin-polarized electrical current and (2) creating a pure spin
current without a net electrical current. A spin-valve consisting of two
sequential ferromagnetic gates is shown to exhibit magnetoresistance dependent
upon the relative orientations of the magnetization of the two ferromagnets.
The magnetoresistance ratio grows to arbitrarily large values in the regime of
low source-drain bias, and is limited only by the spin-flip time in the
channel.

###Measuring Magnetostriction with an Atomic Force Microscope: Application to Wires in Ballistic Magnetoresistance|A. C. Papageorgopoulos,H. Wang,C. Guerrero,N. Garcia###

Measuring Magnetostriction with an Atomic Force Microscope: Application to Wires in Ballistic Magnetoresistance. In this study we present a new method of measuring magnetostriction with an
atomic force microscope adapted for the application magnetic fields. The
experiment allows us to visualise, in an elegant and educational way how the
lateral magnetoelastic shape changes take place on the sample surface when a
magnetic field is applied. We have, furthermore, used this technique to observe
magnetically induced strains as small as 5*10-8, and have measured Ni,
permalloy and commercial Cu wires and films, as well as pure Cu and Pt wires,
where results are in agreement with other methods of measurement. The
applications are, moreover, relevant to studies of ballistic magnetoresistance,
where we can draw conclusions involving the effect of the magnetically induced
strains on magnetoresistance measured at the same time as magnestostriction.

###Angle Dependent Magnetoresistance of the Layered Organic Superconductor κ-(ET)2Cu(NCS)2: Simulation and Experiment|P. A. Goddard,S. J. Blundell,J. Singleton,R. D. McDonald,A. Ardavan,A. Narduzzo,J. A. Schlueter,A. M. Kini,T. Sasaki###

Angle Dependent Magnetoresistance of the Layered Organic Superconductor κ-(ET)2Cu(NCS)2: Simulation and Experiment. The angle-dependences of the magnetoresistance of two different isotopic
substitutions (deuterated and undeuterated) of the layered organic
superconductor \kappa-(ET)2Cu(NCS)2 are presented. The angle dependent
magnetoresistance oscillations (AMRO) arising from the quasi-one-dimensional
(Q1D) and quasi-two-dimensional (Q2D) Fermi surfaces in this material are often
confused. By using the Boltzman transport equation extensive simulations of the
AMRO are made that reveal the subtle differences between the different species
of oscillation. No significant differences are observed in the electronic
parameters derived from quantum oscillations and AMRO for the two isotopic
substitutions. The interlayer transfer integrals are determined for both
isotopic substitutions and a slight difference is observed which may account
for the negative isotope effect previously reported [1]. The success of the
semi-classical simulations suggests that non-Fermi liquid effects are not
required to explain the interlayer-transport in this system.

###Current induced magnetization dynamics in current perpendicular to the plane spin valves|M. Covington,M. AlHajDarwish,Y. Ding,N. J. Gokemeijer,M. A. Seigler###

Current induced magnetization dynamics in current perpendicular to the plane spin valves. We observe magnetization dynamics induced by spin momentum transfer in the
noise spectra of current perpendicular to the plane giant magnetoresistance
spin valves. The dynamics are observable only for those combinations of current
direction and magnetic configuration in which spin transfer acts to reorient
the free layer magnetization away from the direction set by the net magnetic
field. Detailed measurements as a function of magnetic configuration reveal an
evolution of the noise spectra, going from a spectrum with a well-defined noise
peak when the free layer is roughly collinear with the pinned layer to a
spectrum dominated by 1/f noise when the free layer is in an orthogonal
configuration. Finally, the amplitude of the corresponding resistance noise
increases rapidly with increasing current until it saturates at a value that is
a substantial fraction of the magnetoresistance between parallel and
antiparallel states.

###Ferromagnetic tunneling junctions at low voltages: elastic versus inelastic scattering at $T=0 K$|C. A. Dartora,G. G. Cabrera###

Ferromagnetic tunneling junctions at low voltages: elastic versus inelastic scattering at $T=0 K$. In this paper we analyze different contributions to the magnetoresistance of
magnetic tunneling junctions at low voltages. A substantial fraction of the
resistance drop with voltage can be ascribed to variations of the density of
states and the barrier transmission with the bias. However, we found that the
anomaly observed at zero bias and the magnetoresistance behavior at very small
voltages, point to the contribution of inelastic magnon-assisted tunneling. The
latter is described by a transfer parameter $T^{J}$, which is one or two orders
of magnitude smaller than $T^{d}$, the direct transmission for elastic
currents. Our theory is in excellent agreement with experimental data, yielding
estimated values of $T^{J}$ which are of the order of $T^{d}$ / $T^{J}$ ~ 40.

###Effects of the On-Site Coulomb Repulsion in Double Exchange Magnets|D. I. Golosov###

Effects of the On-Site Coulomb Repulsion in Double Exchange Magnets. We investigate the zero-temperature phase diagram and spin-wave properties of
a double exchange magnet with on-site Hubbard repulsion. It is shown that even
within a simple Hartree -- Fock approach this interaction (which is often
omitted in theoretical treatments) leads to qualitatively important effects
which are highly relevant in the context of experimental data for the colossal
magnetoresistance compounds. These include the asymmetry of the doping
dependence of spin stiffness, and the zone-boundary ``softening'' of spin wave
dispersion. Effects of Hubbard repulsion on phase separation are analyzed as
well. We also show that in the ferromagnetic phase, an unusual
temperature-dependent effective electron-electron interaction arises at finite
T. The mean-field scheme, however, does not yield the experimentally observed
density of states depletion near the Fermi level. We speculate that proper
treatment of electron-electron interactions may be necessary for understanding
both this important feature and more generally the physics of colossal
magnetoresistance phenomenon.

###An Origin of CMR: Competing Phases and Disorder-Induced Insulator-to-Metal Transition in Manganites|Yukitoshi Motome,Nobuo Furukawa,Naoto Nagaosa###

An Origin of CMR: Competing Phases and Disorder-Induced Insulator-to-Metal Transition in Manganites. We theoretically explore the mechanism of the colossal magnetoresistance in
manganese oxides by explicitly taking into account the phase competition
between the double-exchange ferromagnetism and the charge-ordered insulator. We
find that quenched disorder causes a drastic change of the multicritical phase
diagram by destroying the charge-ordered state selectively. As a result, there
appears a nontrivial phenomenon of the disorder-induced insulator-to-metal
transition in the multicritical regime. On the contrary, the disorder induces a
highly-insulating state above the transition temperature where charge-ordering
fluctuations are much enhanced. The contrasting effects provide an
understanding of the mechanism of the colossal magnetoresistance. The obtained
scenario is discussed in comparison with other theoretical proposals such as
the polaron theory, the Anderson localization, the multicritical-fluctuation
scenario, and the percolation scenario.

###Colossal magnetoresistance without phase separation: Disorder-induced spin glass state and nanometer scale orbital-charge correlation in half doped manganites|R. Mathieu,D. Akahoshi,A. Asamitsu,Y. Tomioka,Y. Tokura###

Colossal magnetoresistance without phase separation: Disorder-induced spin glass state and nanometer scale orbital-charge correlation in half doped manganites. The magnetic and electrical properties of high quality single crystals of
$A$-site disordered (solid solution) Ln$_{0.5}$Ba$_{0.5}$MnO$_3$ are
investigated near the phase boundary between the spin glass insulator and
colossal-magnetoresistive ferromagnetic metal, locating near Ln = Sm. The
temperature dependence of the ac-susceptibility and the x-ray diffuse
scattering of Eu$_{0.5}$Ba$_{0.5}$MnO$_3$ are analyzed in detail. The
uniformity of the random potential perturbation in Ln$_{0.5}$Ba$_{0.5}$MnO$_3$
crystals with small bandwidth yields, rather than the phase separation, an
homogeneous short ranged charge/orbital order which gives rise to a
nearly-atomic spin glass state. Remarkably, this microscopically disordered
``CE-glass'' state alone is able to bring forth the colossal magnetoresistance.

###The effect of grain size on electrical transport and magnetic properties of La0.9Te0.1MnO3|J. Yang,B. C. Zhao,R. L. Zhang,Y. Q. Ma,Z. G. Sheng,W. H. Song,Y. P. Sun###

The effect of grain size on electrical transport and magnetic properties of La0.9Te0.1MnO3. The effect of grain size on structural, magnetic and transport properties in
electron-doped manganites La0.9Te0.1MnO3 has been investigated. All samples
show a rhombohedral structure with the space group at room temperature. It
shows that the Mn-O-Mn bond angle decreases and the Mn-O bond length increases
with the increase of grain size. All samples undergo paramagnetic
(PM)-ferromagnetic (FM) phase transition and an interesting phenomenon that
both magnetization and the Curie temperature decrease with increasing grain
size is observed, which is suggested to mainly originate from the increase of
the Mn-O bond length . Additionally, obviously increases with decreasing grain
size due to the increase of both the height and width of tunneling barriers
with decreasing the grain size. The results indicate that both the intrinsic
colossal magnetoresistance (CMR) and the extrinsic the extrinsic interfacial
magnetoresistance (IMR) can be effectively tuned in La0.9Te0.1MnO3 by changing
grain size.

###In-plane magnetodrag in dilute bilayer two-dimensional systems: a Fermi liquid theory|S. Das Sarma,E. H. Hwang###

In-plane magnetodrag in dilute bilayer two-dimensional systems: a Fermi liquid theory. Motivated by recent experimental results reporting anomalous drag resistance
behavior in dilute bilayer two-dimensional (2D) hole systems in the presence of
a magnetic field parallel to the 2D plane, we have carried out a many-body
Fermi liquid theory calculation of bilayer magnetodrag comparing it to the
corresponding single layer magnetoresistance. In qualitative agreement with
experiment we find relatively similar behavior in our calculated magnetodrag
and magnetoresistance arising from the physical effects of screening being
similarly modified ("suppressed") by carrier spin polarization (at "low" field)
and the conductivity effective mass being similarly modified ("enhanced") by
strong magneto-orbital correction (at "high" fields) in both cases. We
critically discuss agreement and disagreement between our theory and the
experimental results, concluding that the magnetodrag data are qualitatively
consistent with the Fermi liquid theory.

###Magnetotransport properties of ferromagnetic Pr0.85Ca0.15MnO3/ferroelectric Ba0.6Sr0.4TiO3 superlattice films|P. Murugavel,P. Padhan,W. Prellier###

Magnetotransport properties of ferromagnetic Pr0.85Ca0.15MnO3/ferroelectric Ba0.6Sr0.4TiO3 superlattice films. Artificial superlattices designed with ferromagnetic Pr0.85Ca0.15MnO3
insulating layer and ferroelectric Ba0.6Sr0.4TiO3 layer were grown on (100)
SrTiO3 substrates. The magnetotransport properties were measured with the
current perpendicular to the plane geometry. An increase in magnetoresistance
(MR), with no significant low field effect, was observed as the number of
ferroelectric Ba0.6Sr0.4TiO3 layer thickness increases even up to 9 unit cells.
For example, the superlattice [(Pr0.85Ca0.15MnO3)10(Ba0.6Sr0.4TiO3)9]25 shows
35 % MR at 100 K, though the Pr0.85Ca0.15MnO3 film was a robust insulator with
negligible MR even at high applied magnetic field. This observed large MR
cannot be explained by simple interfacial ferromagnetism or by the tunneling
magnetoresistance. One possible explanation could be the effect due to the
ferroelectric spacer layer and the associated magnetoelectric coupling.

###Uncorrelated and correlated nanoscale lattice distortions in the paramagnetic phase of magnetoresistive manganites|V. Kiryukhin,A. Borissov,J. S. Ahn,Q. Huang,J. W. Lynn,S-W. Cheong###

Uncorrelated and correlated nanoscale lattice distortions in the paramagnetic phase of magnetoresistive manganites. Neutron scattering measurements on a magnetoresistive manganite
La$_{0.75}$(Ca$_{0.45}$Sr$_{0.55}$)$_{0.25}$MnO$_3$ show that uncorrelated
dynamic polaronic lattice distortions are present in both the orthorhombic (O)
and rhombohedral (R) paramagnetic phases. The uncorrelated distortions do not
exhibit any significant anomaly at the O-to-R transition. Thus, both the
paramagnetic phases are inhomogeneous on the nanometer scale, as confirmed
further by strong damping of the acoustic phonons and by the anomalous
Debye-Waller factors in these phases. In contrast, recent x-ray measurements
and our neutron data show that polaronic correlations are present only in the O
phase. In optimally doped manganites, the R phase is metallic, while the O
paramagnetic state is insulating (or semiconducting). These measurements
therefore strongly suggest that the {\it correlated} lattice distortions are
primarily responsible for the insulating character of the paramagnetic state in
magnetoresistive manganites.

###Magnetoresistive Effects in Ferromagnet-Superconductor Multilayers|E. M. Stoudenmire,C. A. R. Sá de Melo###

Magnetoresistive Effects in Ferromagnet-Superconductor Multilayers. We consider a nanoscale system consisting of Manganite-ferromagnet and
Cuprate-superconductor multilayers in a spin valve configuration. The
magnetization of the bottom Manganite-ferromagnet is pinned by a
Manganite-antiferromagnet. The magnetization of the top Manganite-ferromagnet
is coupled to the bottom one via indirect exchange through the superconducting
layers. We study the behavior of the critical temperature and the
magnetoresistance as a function of an externally applied parallel magnetic
field, when the number of Cuprate-superconductor layers are changed. There are
two typical behaviors in the case of a few monolayers of the Cuprates: a) For
small magnetic fields, the critical temperature and the magnetoresistance
change abruptly when the flipping field of the top Manganite-ferromagnet is
reached. b) For large magnetic fields, the multilayered system re-enters the
zero-resistance (superconducting) state after having become resistive (normal).

###Spin-dependent transport through magnetic nanojunctions|Kamil Walczak,Gloria Platero###

Spin-dependent transport through magnetic nanojunctions. Coherent electronic transport through a molecular device is studied using
non-equilibrium Green's function (NEGF) formalism. Such device is made of a
carbon nanowire which is connected to ferromagnetic electrodes. The molecule
itself is described with the help of Hubbard model (Coulomb interactions are
treated by means of the Hartree-Fock approximation), while the coupling to the
electrodes is modeled through the use of a broad-band theory. It was shown that
magnetoresistance varies periodically with increasing the length of atomic wire
(in the linear response regime) and oscillates with increasing of bias voltage
(in the nonlinear response regime). Since the TMR effect for analyzed
structures is predicted to be large (tens of percentage), considered junctions
seem to be suitable for application as a magnetoresistive elements in the
future electronic circuits.

###Magnetization and magnetoresistance in insulating phases of SrFeO3-d|S. Srinath,M. Mahesh Kumar,M. L. Post,H. Srikanth###

Magnetization and magnetoresistance in insulating phases of SrFeO3-d. We report the synthesis and properties of two new insulating phases of
SrFeO3-d with introduction of oxygen deficiencies in metallic SrFeO3 ; one with
0.15 < d < 0.19 (sample A)and the other above d = 0.19 (sample B). Sample A
shows large negative magnetoresistance around the charged ordering (CO)
temperature with magnetic anomalies seen in the temperature dependent
resistivity,magnetization and M-H hysteresis loops. Sample B shows a smooth
insulating behavior with no thermal hysteresis in the resistivity and with a
small positive magnetoresistance. cac and cdc show multiple features associated
with a frustrated magnetic order (helical) due to competing ferro- and
antiferromagnetic interactions. The competing effects of ferro- and
antiferromagnetic phases extend up to T ~ 230 K revealing a new high
temperature scale in this system. These observations are discussed in the
context of magnetic interactions associated with the varying Fe4+/Fe3+ ratio.

###Heat capacity and magnetoresistance in Dy(Co,Si)2 compounds|Niraj K. Singh,K. G. Suresh,A. K. Nigam,S. K. Malik###

Heat capacity and magnetoresistance in Dy(Co,Si)2 compounds. Magnetocaloric effect and magnetoresistance have been studied in
Dy(Co1-xSix)2 [x=0, 0.075 and 0.15] compounds. Magnetocaloric effect has been
calculated in terms of adiabatic temperatue change (Delta Tad) as well as
isothermal magnetic entropy change (Delta SM) using the heat capacity data. The
maximum values of DeltaSM and DeltaTad for DyCo2 are found to be 11.4 JKg-1K-1
and 5.4 K, respectively. Both DSM and DTad decrease with Si concentration,
reaching a value of 5.4 JKg-1K-1 and 3 K, respectively for x=0.15. The maximum
magnetoresistance is found to about 32% in DyCo2, which decreases with increase
in Si. These variations are explained on the basis of itinerant electron
metamagnetism occurring in these compounds.

###Colossal magnetoresistance and quenched disorder in manganese oxides|Nobuo Furukawa,Yukitoshi Motome###

Colossal magnetoresistance and quenched disorder in manganese oxides. We give an overview on several recent topics of colossal magnetoresistive
manganites in both experiments and theories, focusing on the effect of quenched
disorder. The disorder is intrinsically involved since the compounds are solid
solutions, and its importance has been pointed out in several experiments of
transport and magnetic properties. Recent progress in the experimental control
of the strength of disorder is also reviewed. Theoretically, the effect of the
disorder has been explored within the framework of the double-exchange
mechanism. Several efforts to understand the phase diagram and the electronic
properties are reviewed. We also briefly discuss a recent topic on the effect
of disorder on competing phases and the origin of colossal magnetoresistance.

###Colossal Magnetoresistance by Avoiding a Ferromagnetic State in the Mott System Ca3Ru2O7|X. N. Lin,Z. X. Zhou,V. Durairaj,P. Schlottmann,G. Cao###

Colossal Magnetoresistance by Avoiding a Ferromagnetic State in the Mott System Ca3Ru2O7. Transport and magnetic studies of Ca3Ru2O7 for temperatures ranging from 0.4
K to 56 K and magnetic fields, B, up to 45 T leads to strikingly different
behavior when the field is applied along the different crystal axes. A
ferromagnetic (FM) state with full spin polarization is achieved for B||a-axis,
but colossal magnetoresistance is realized only for B||b-axis. For B||c-axis,
Shubnikov-de Haas oscillations are observed and followed by a less resistive
state than for B||a. Hence, in contrast to standard colossal magnetoresistive
materials, the FM phase is the least favorable for electron hopping. These
properties together with highly unusual spin-charge-lattice coupling near the
Mott transition (48 K) are driven by the orbital degrees of freedom.

###Magnetoresistance Anomalies in (Ga,Mn)As Epilayers with Perpendicular Magnetic Anisotropy|G. Xiang,A. W. Holleitner,B. L. Sheu,F. M. Mendoza,O. Maksimov,P. Schiffer,D. D. Awschalom,N. Samarth###

Magnetoresistance Anomalies in (Ga,Mn)As Epilayers with Perpendicular Magnetic Anisotropy. We report the observation of anomalies in the longitudinal magnetoresistance
of tensile-strained (Ga,Mn)As epilayers with perpendicular magnetic anisotropy.
Magnetoresistance measurements carried out in the planar geometry (magnetic
field parallel to the current density) reveal "spikes" that are antisymmetric
with respect to the direction of the magnetic field. These anomalies always
occur during magnetization reversal, as indicated by a simultaneous change in
sign of the anomalous Hall effect. The data suggest that the antisymmetric
anomalies originate in anomalous Hall effect contributions to the longitudinal
resistance when domain walls are located between the voltage probes. This
interpretation is reinforced by carrying out angular sweeps of $\vec{H}$,
revealing an antisymmetric dependence on the helicity of the field sweep.

###Magneto-transport characteristics of La1.4Ca1.6Mn2O7 thin film deposited by spray pyrolysis|P. K. Siwach,H. K. Singh,O. N. Srivastava###

Magneto-transport characteristics of La1.4Ca1.6Mn2O7 thin film deposited by spray pyrolysis. Polycrystalline thin films of double layer manganite La_1.4Ca_1.6Mn_2O_7
(DLCMO) have been deposited by nebulized spray pyrolysis on single crystal
LaAlO_3 substrates. These single phase films having grain size in the range
70-100 nm exhibit ferromagnetic transition at T_C ~ 107K. The short range
ferromagnetic ordering due to in plane spin coherence is evidenced to occur at
a higher temperature around 225 K. Insulator/semiconductor to metal transition
occurs at a lower temperature T_P ~ 55K. The transport mechanism above T_C is
of Mott`s variable range hopping type. Below T_C the current-voltage
characteristics show non-linear behaviour that becomes stronger with decreasing
temperature. At low temperatures below T_CA ~ 30K a magnetically frustrated
spin canted state is observed. The DLCMO films exhibit resonable low field
magnetoresistance and at 77K the magnetoresistance ratio is ~ 5% at 0.6 kOe and
\~ 13% at 3 kOe.

###The inelastic relaxation time due to electron-electron collisions in high-mobility two-dimensional systems under microwave radiations|X. L. Lei,S. Y. Liu###

The inelastic relaxation time due to electron-electron collisions in high-mobility two-dimensional systems under microwave radiations. In some theoretical analyses of microwave-induced magnetoresistance
oscillations in high-mobility two-dimensional systems, the "inelastic
relaxation time" $\tau_{in}$ due to electron-electron scattering is evaluated
using an equilibrium distribution function $f^0$ in the absence of radiation,
and it is concluded that $\tau_{in}$ is much larger than $\tau_{q}$, the
single-particle relaxation time due to impurity scattering. However, under the
irradiation of a microwave capable of producing magnetoresistance oscillation,
the distribution function of the high-mobility electron gas deviates remarkably
from $f^0$ at low temperatures. Estimating $\tau_{in}$ using an approximate
nonequilibrium distribution function rather than using $f^0$, one will find the
system to be in the opposite limit $1/\tau_{in}\ll 1/\tau_{q}$ even for T=0 K.
Therefore, models which depend on the assumption $1/\tau_{in}\gg 1/\tau_{q}$
may not be justifiable.

###Radiation-induced magnetotransport in high-mobility two-dimensional systems: Role of electron heating|X. L. Lei,S. Y. Liu###

Radiation-induced magnetotransport in high-mobility two-dimensional systems: Role of electron heating. Effects of microwave radiation on magnetoresistance are analyzed in a
balance-equation scheme that covers regimes of inter- and intra-Landau level
processes and takes account of photon-asissted electron transitions as well as
radiation-induced change of the electron distribution for high mobility
two-dimensional systems. Short-range scatterings due to background impurities
and defects are shown to be the dominant direct contributors to the
photoresistance oscillations. The electron temperature characterizing the
system heating due to irradiation, is derived by balancing the energy
absorption from the radiation field and the energy dissipation to the lattice
through realistic electron-phonon couplings, exhibiting resonant oscillation.
Microwave modulations of Shubnikov de Haas oscillation amplitude are produced
together with microwave-induced resistance oscillations, in agreement with
experimental findings. In addition, the suppression of the magnetoresistance
caused by low-frequency radiation in the higher magnetic field side is also
demonstrated.

###Magnetoresistivity in MgB2 as a probe of disorder in p- and s-bands|I. Pallecchi,V. Ferrando,E. Galleani D'Agliano,D. Marre',M. Monni,M. Putti,C. Tarantini,F. Gatti,H. U. Aebersold,E. Lehmann,X. X. Xi,E. G. Haanappel,C. Ferdeghini###

Magnetoresistivity in MgB2 as a probe of disorder in p- and s-bands. In this paper we present normal state magnetoresistivity data of magnesium
diboride epitaxial thin films with different levels of disorder, measured at
42K in magnetic fields up to 45 Tesla. Disorder was introduced in a controlled
way either by means of neutron irradiation or by carbon doping. From a
quantitative analysis of the magnetoresistivity curves with the magnetic field
either parallel or perpendicular to the plane of the film, we extract the ratio
of the scattering times in p- and s-bands. We demonstrate that the undoped
unirradiated thin film has p scattering times smaller than s ones; upon
irradiation, both bands become increasingly more disordered; eventually the
highly irradiated sample (neutron fluence 7.7X1017 cm-2) and the C-doped sample
have comparable scattering times in the two types of bands. This description of
the effect of disorder in the two kinds of bands on transport is consistent
with the residual resistivity values and with the temperature dependence of the
resistivity.

###Effect of charge state in nearby quantum dots on quantum Hall effect|K. Takehana,T. Takamasu,G. Kido,H. Henini###

Effect of charge state in nearby quantum dots on quantum Hall effect. Magnetoresistance measurements have been performed on a gated two-dimensional
electron system (2DES) separated by a thin barrier layer from a layer of InAs
self-assembled quantum dots (QDs). Clear features of the quantum Hall effect
were observed despite the proximity of the QDs layer to the 2DES. However, the
magnetoresistance ($\rho_{xx}$) and Hall resistance ($\rho_{xy}$) are
suppressed significantly in the magnetic field range of filling factor $\nu<1$
when a positive voltage is applied to the front gate. The influence of the
charge state in QDs was observed on the transport properties of the nearby 2DES
only in the field range of $\nu < 1$. It is proposed that the anomalous
suppression of $\rho_{xx}$ and $\rho_{xy}$ is related to spin excitation, which
is induced by spin-flip processes involving electrons in the QDs and the 2DES.

###Effect of electric/magnetic field on pinned/biased moments at the interfaces of magnetic superlattices|P. Padhan,W. Prellier###

Effect of electric/magnetic field on pinned/biased moments at the interfaces of magnetic superlattices. We have observed the pinned/biased moments in the superlattices consisting of
ferromagnetic (FM) SrRuO3 (SRO) and antiferromagnetic (AFM) SrMnO3
(SMO)bilayer. The alternate stacking of SRO and SMO leading to a low field
positive magnetoresistance with enhanced hysteretic field dependent
magnetoresistance under the application of the out-of-plane magnetic field. We
attribute these effects to the observed biased/pinned magnetic moments in the
SRO layer in the vicinity of the interfaces. In addition, the biased/pinned
moments can be oriented under the application of either the out-of-plane
magnetic field or a combination of out-of-plane magnetic field and in-plane
electric field. These results will bring new insights in the understanding of
the coupling at the AFM/FM interface which can be useful for creating new
exotic phenomena at the interfaces of the multilayer.

###Dependence of tunnel magnetoresistance in MgO based magnetic tunnel junctions on Ar pressure during MgO sputtering|Shoji Ikeda,Jun Hayakawa,Young Min Lee,Ryutaro Sasaki,Toshiyasu Meguro,Fumihiro Matsukura,Hideo Ohno###

Dependence of tunnel magnetoresistance in MgO based magnetic tunnel junctions on Ar pressure during MgO sputtering. We investigated dependence of tunnel magnetoresistance effect in
CoFeB/MgO/CoFeB magnetic tunnel junctions on Ar pressure during MgO-barrier
sputtering. Sputter deposition of MgO-barrier at high Ar pressure of 10 mTorr
resulted in smooth surface and highly (001) oriented MgO. Using this MgO as a
tunnel barrier, tunnel magnetoresistance (TMR) ratio as high as 355% at room
temperature (578% at 5K) was realized after annealing at 325 C or higher, which
appears to be related to a highly (001) oriented CoFeB texture promoted by the
smooth and highly oriented MgO. Electron-beam lithography defined
deep-submicron MTJs having a low-resistivity Au underlayer with the
high-pressure deposited MgO showed high TMR ratio at low resistance-area
product (RA) below 10 ohm-um^2 as 27% at RA = 0.8 ohm-um^2, 77% at RA = 1.1
ohm-um^2, 130% at RA = 1.7 ohm-um^2, and 165% at RA = 2.9 ohm-um^2.

###Magnetoresistance in granular CrO2 : influence of crystallographic and magnetic microstructure|A. Bajpai,A. K. Nigam###

Magnetoresistance in granular CrO2 : influence of crystallographic and magnetic microstructure. We report magnetotransport measurements on high purity sintered samples of
spintronic CrO2 in an unexplored crystallographic regime between 5-300 K. The
negative magnetoresistance (MR) as derived from RH isotherms is observed to be
unhysteretic up to temperatures as high as 200 K. Between 240-290 K, RH
isotherms exhibit some unusual features including a positive MR and strong
pinning effects. These feature disappear above 290 K and is apparently related
with the antiferromagnetic ordering of the insulating grain boundary.
Qualitatively similar features with significantly enhanced MR are also observed
when the GB density is increased. These results bring out the role played by
the magnetic and crystallographic microstructure on the magnitude, sign and
hysteresis of the magnetoresistance in this technologically important material.

###Observation of fluctuation induced tunneling conductance in polycrystalline CrO2|A. Bajpai,A. K. Nigam###

Observation of fluctuation induced tunneling conductance in polycrystalline CrO2. Intergranular conduction in half metallic CrO2 is known to occur through a
combination of spin dependent tunneling (driven by Coulomb Blockade (CB)
effects) together with certain spin independent (SI) hopping processes. We
present evidence that in polycrystalline CrO2 with enhanced grain size, both
these process (CB effect and SI Hopping) are suppressed and the functional form
of conductance is best described by Fluctuation Induced Tunneling (FIT) in a
wide temperature range. Similar features are observed when grain boundary
density is increased by Cr2O3 or Cr2O5.The spin dependent tunneling driven by
FIT results in the observation of significant enhancement and monotonic
temperature dependence of magnetoresistance. Overall, the magnetotransport
measurements in a thus far unexplored crystallographic regime of CrO2 reveal
that the functional form of conductance strongly influences its
magnetoresistive properties.

###Inelastic transport in molecular spin valves|N. Jean,S. Sanvito###

Inelastic transport in molecular spin valves. We present a study of the effects of inelastic scattering on the transport
properties of various nanoscale devices, namely H$_2$ molecules sandwiched
between Pt contacts, and a spin-valve made by an organic molecule attached to
model half-metal ferromagnetic current/voltage probes. In both cases we use a
tight-binding Su-Schrieffer-Heeger Hamiltonian and the inelastic effects are
treated with a multi-channel method, including Pauli exclusion principle. In
the case of the H$_2$ molecule, we find that inelastic backscattering is
responsible for the drop of the differential conductance at biases larger than
the excitation energy of the lower of the molecular phonon modes. In the case
of the spin-valve, we investigate the different spin-currents and the
magnetoresistance as a function of the position of the Fermi level with respect
to the spin-polarized band edges. In general inelastic scattering reduces the
spin-polarization of the current and consequently the magnetoresistance.

###Hall coefficient and magnetoresistance of 2D spin-polarized electron systems|E. H. Hwang,S. Das Sarma###

Hall coefficient and magnetoresistance of 2D spin-polarized electron systems. Recent measurements of the 2D Hall resistance show that the Hall coefficient
is independent of the applied in-plane magnetic field, i.e., the
spin-polarization of the system. We calculate the weak-field Hall coefficient
and the magnetoresistance of a spin polarized 2D system using the
semi-classical transport approach based on the screening theory. We solve the
coupled kinetic equations of the two carrier system including electron-electron
interaction. We find that the in-plane magnetic field dependence of the Hall
coefficient is suppressed by the weakening of screening and the
electron-electron interaction. However, the in-plane magnetoresistance is
mostly determined by the change of the screening of the system, and can
therefore be strongly field dependent.

###Ballistic magnetoresistance in small-size carbon nanotubes devices|S. Krompiewski,Gianaurelio Cuniberti###

Ballistic magnetoresistance in small-size carbon nanotubes devices. We theoretically study the magnetoresistance of single wall carbon nanotubes
(SWCNTs) in the ballistic transport regime, using a standard tight-binding
approach. The main attention is directed to spin-polarized electrical transport
in the presence of either axial or perpendicular magnetic field. The method
takes into account both Zeeman splitting as well as size and chirality effects.
These factors (along with a broadening of energy levels due to a strong
nanotube/electrode coupling) lead, in ultra small SWCNTs, to serious
modifications in profile of the Aharonov-Bohm oscillations. Other noteworthy
findings are that in the parallel configuration (axial magnetic field) the
ballistic magnetoconductance is negative (positive) for armchair
(semiconducting zigzag) nanotubes, whereas in the perpendicular configuration
the magnetoresistance is nearly zero both for armchair and zigzag SWCNTs.

###Persistence to high temperatures of interlayer coherence in an organic superconductor|John Singleton,PA Goddard,A Ardavan,AI Coldea,SJ Blundell,RD McDonald,S Tozer,JA Schlueter###

Persistence to high temperatures of interlayer coherence in an organic superconductor. The interlayer magnetoresistance $\rho_{zz}$ of the organic metal \cuscn is
studied in fields of up to 45 T and at temperatures $T$ from 0.5 K to 30 K. The
peak in $\rho_{zz}$ seen in in-plane fields, a definitive signature of
interlayer coherence, remains to $T$s exceeding the Anderson criterion for
incoherent transport by a factor $\sim 30$. Angle-dependent magnetoresistance
oscillations are modeled using an approach based on field-induced quasiparticle
paths on a 3D Fermi surface, to yield the $T$ dependence of the scattering rate
$\tau^{-1}$. The results suggest that $\tau^{-1}$ does not vary strongly over
the Fermi surface, and that it has a $T^2$ dependence due to electron-electron
scattering.

###Inelastic scattering in ferromagnetic and antiferromagnetic metal spintronics|R. A. Duine,P. M. Haney,A. S. Nunez,A. H. MacDonald###

Inelastic scattering in ferromagnetic and antiferromagnetic metal spintronics. We use a ferromagnetic voltage probe model to study the influence of
inelastic scattering on giant magnetoresistance and current-induced torques in
ferromagnetic and antiferromagnetic metal spin valves. The model is based on
the Green's function formulation of transport theory and represents
spin-dependent and spin-independent inelastic scatterers by interior voltage
probes that are constrained to carry respectively no charge current and no spin
or charge current. We find that giant magnetoresistance and spin transfer
torques in ferromagnetic metal spin valve structures survive arbitrarily strong
spin-independent inelastic scattering, while the recently predicted analogous
phenomena in antiferromagnetic metal spin valves are partially suppressed. We
use toy-model numerical calculations to estimate spacer layer thickness
requirements for room temperature operation of antiferromagnetic metal spin
valves.

###Magnetoresistance of Pr$_{1-x}$La$_x$Os$_4$Sb$_{12}$: Disentangling local crystalline-electric-field physics and lattice effects|C. R. Rotundu,K. Ingersent,B. Andraka###

Magnetoresistance of Pr$_{1-x}$La$_x$Os$_4$Sb$_{12}$: Disentangling local crystalline-electric-field physics and lattice effects. Resistivity measurements were performed on Pr$_{1-x}$La$_x$Os$_4$Sb$_{12}$
single crystals at temperatures down to 20 mK and in fields up to 18 T. The
results for dilute-Pr samples ($x=0.3$ and 0.67) are consistent with model
calculations performed assuming a singlet crystalline-electric-field (CEF)
ground state. The residual resistivity of these crystals features a smeared
step centered around 9 T, the predicted crossing field for the lowest CEF
levels. The CEF contribution to the magnetoresistance has a
weaker-than-calculated dependence on the field direction, suggesting that
interactions omitted from the CEF model lead to avoided crossing in the
effective levels of the Pr$^{3+}$ ion. The dome-shaped magnetoresistance
observed for $x = 0$ and 0.05 cannot be reproduced by the CEF model, and likely
results from fluctuations in the field-induced antiferroquadrupolar phase.

###Point contact spectroscopy of hopping transport: effects of a magnetic field|V. I. Kozub,A. A. Zyuzin,O. Entin-Wohlman,A. Aharony,Y. M. Galperin,V. Vinokur###

Point contact spectroscopy of hopping transport: effects of a magnetic field. The conductance of a point contact between two hopping insulators is expected
to be dominated by the individual localized states in its vicinity. Here we
study the additional effects due to an external magnetic field. Combined with
the measured conductance, the measured magnetoresistance provides detailed
information on these states (e.g. their localization length, the energy
difference and the hopping distance between them). We also calculate the
statistics of this magnetoresistance, which can be collected by changing the
gate voltage in a single device. Since the conductance is dominated by the
quantum interference of particular mesoscopic structures near the point
contact, it is predicted to exhibit Aharonov-Bohm oscillations, which yield
information on the geometry of these structures. These oscillations also depend
on local spin accumulation and correlations, which can be modified by the
external field. Finally, we also estimate the mesoscopic Hall voltage due to
these structures.

###Sharp switching of the magnetization in Fe1/4TaS2|E. Morosan,H. W. Zandbergen,Lu Li,Minhyea Lee,J. G. Checkelsky,M. Heinrich,T. Siegrist,N. P. Ong,R. J. Cava###

Sharp switching of the magnetization in Fe1/4TaS2. Anisotropic magneto-transport measurements are reported on Fe1/4TaS2 single
crystals grown by vapor transport. Both the magnetization and resistivity are
extremely anisotropic, with the magnetic moments aligned parallel to the c
crystallographic direction. Fe1/4TaS2 orders ferromagnetically below TC = 160 K
and displays very sharp hysteresis loops in the ordered state for H||c. The
corresponding magnetoresistance is negative, and it qualitatively reproduces
the features observed in the M(H) data, by showing a sharp drop around the
critical field Hs for the moment reversal. The magnetization switching time
shows an unusual increase with increasing temperature. For field applied within
the ab plane, the magnetization remains small and linear in field up to 5 T,
and the magnetoresistance is positive and quadratic in field, with no visible
hysteresis. The squareness of the H||c M(H) loops and the high critical field
for the magnetization switch (Hs = 3.7 T at T = 2 K) allow us to classify
Fe1/4TaS2 as a strong ferromagnet.

###Intervalley scattering and weak localization in Si-based two-dimensional structures|A. Yu. Kuntsevich,N. N. Klimov,S. A. Tarasenko,N. S. Averkiev,V. M. Pudalov,H. Kojima,M. E. Gershenson###

Intervalley scattering and weak localization in Si-based two-dimensional structures. We have measured the weak localization magnetoresistance in (001)-oriented Si
MOS structures with a wide range of mobilities. For the quantitative analysis
of the data, we have extended the theory of weak-localization corrections in
the ballistic regime to the system with two equivalent valleys in electron
spectrum. This theory describes the observed magnetoresistance and allows the
extraction of the phase breaking time tau_phi and the intervalley scattering
time tau_v. The temperature dependences tau_phi(T) for all studied structures
are in good agreement with the theory of electron-electron interaction effects
in two-dimensional systems. The intervalley scattering is elastic and rather
strong: tau_v is typically only an order of magnitude greater than the
transport time, tau. It is found that the intervalley scattering rate is
temperature-independent and the ratio tau_v/tau decreases with increasing the
electron density. These observations suggest that the roughness of the Si-SiO2
interface plays the major role in intervalley scattering.

###Crossover from weak localization to Shubnikov-de Haas oscillations in a high mobility 2D electron gas|T. A. Sedrakyan,M. E. Raikh###

Crossover from weak localization to Shubnikov-de Haas oscillations in a high mobility 2D electron gas. We study the magnetoresistance, \delta\rho_{xx}(B)/\rho_0, of a high-mobility
2D electron gas in the domain of magnetic fields, B, intermediate between the
weak localization and the Shubnikov-de Haas oscillations, where
\delta\rho_{xx}(B)/\rho_0 is governed by the interaction effects. Assuming
short-range impurity scattering, we demonstrate that in the {\em second order}
in the interaction parameter, $\lambda$, a {\em linear} B-dependence,
\delta\rho_{xx}(B)/\rho_0\sim \lambda^2\omega_c/E_F with {\em
temperature-independent} slope emerges in this domain of B (here \omega_c and
E_F are the cyclotron frequency and the Fermi energy, respectively). Unlike
previous mechanisms, the linear magnetoresistance is {\em unrelated} to the
electron executing the full Larmour circle, but rather originates from the
impurity scattering via the B-dependence of the {\em phase} of the
impurity-induced Friedel oscillations.

###Theory of New Quantum Oscillations in the Magnetoresistance of Graphene Layers|N. Garcia###

Theory of New Quantum Oscillations in the Magnetoresistance of Graphene Layers. We present a theory presenting new quantum oscillations in the
magnetoresistance that are revealed as fine structures superimposed to the
Schubnikov-de-Haas oscillations. They may be observed in experiments on
graphene layers as fine structures that until now seem to have been overseen or
considered to be noise. These oscillations appear also in the behaviour of the
resistance as a function of the gate voltage that changes the number of
carriers or Fermi level. Experimental studies of these resonances should give
information of the uniformity and defects of the samples and represent a new
fine structure spectroscopy. Also the lateral sample size and quantum effects
may explain the absence of magnetoresistance in a few grapheme layers.
Experiments are proposed.

###Quenched magnetic moment in Mn-doped amorphous Si (\textit{a}-Mn$_{x}$Si$_{1-x}$) across the metal-insulator transition|Li Zeng,E. Helgren,R. Islam,B. J. Wilkens,R. J. Culbertson,David J. Smith,F. Hellman###

Quenched magnetic moment in Mn-doped amorphous Si (\textit{a}-Mn$_{x}$Si$_{1-x}$) across the metal-insulator transition. The magnetic and electrical transport properties of Mn-doped amorphous
silicon (\textit{a-}Mn$_{x}$Si$_{1-x}$) thin films have been measured. The
magnetic susceptibility obeys the Curie-Weiss law for a wide range of $x$
(0.005-0.175) and the saturation moment is small. While all Mn atoms contribute
to the electrical transport, only a small fraction (interstitial Mn$^{2+}$
states with $J$=$S$=5/2) contribute to the magnetization. The majority of the
Mn atoms do not possess any magnetic moment, contrary to what is predicted by
the Ludwig-Woodbury model for Mn in crystalline silicon. Unlike
\textit{a-}Gd$_{x}$Si$_{1-x}$ films which have an enormous \textit{negative}
magnetoresistance, \textit{a-}Mn$_{x}$Si$_{1-x}$ films have only a small
\textit{positive} magnetoresistance, which can be understood by this quenching
of the Mn moment.

###Negative magnetoresistance of ultra-narrow superconducting nanowires in the resistive state|K. Yu. Arutyunov###

Negative magnetoresistance of ultra-narrow superconducting nanowires in the resistive state. We present a phenomenological model qualitatively explaining negative
magnetoresistance in quasi-one-dimensional superconducting channels in the
resistive state. The model is based on the assumption that fluctuations of the
order parameter (phase slips) are responsible for the finite effective
resistance of a narrow superconducting wire sufficiently close to the critical
temperature. Each fluctuation is accompanied by an instant formation of a
quasi-normal region of the order of the non-equilibrium quasiparticle
relaxation length 'pinned' to the core of the phase slip. The effective
time-averaged voltage measured in experiment is a sum of two terms. First one
is the conventional contribution linked to the rate of the fluctuations via the
Josephson relation. Second term is the Ohmic contribution of this quasi-normal
region. Depending on material properties of the wire, there might be a range of
magnetic fields where the first term is not much affected, while the second
term is effectively suppressed contributing to the experimentally observed
negative magnetoresistance.

###Magneto-optical behaviour of EuIn_2P_2|F. Pfuner,L. Degiorgi. H. R. Ott,A. D. Bianchi,Z. Fisk###

Magneto-optical behaviour of EuIn_2P_2. We report results of a magneto-optical investigation of the Zintl-phase
compound EuIn$_2$P$_2$. The compound orders magnetically at $T_C$=24 K and
exhibits concomitant large magnetoresistance effects. For $T\le$50 K and
increasing magnetic fields we observe a transfer of spectral weight in
$\sigma_1(\omega)$ from energies above 1 eV into the low-energy metallic
component as well as into a mid-infrared signal centered at about 600
cm$^{-1}$. This latter absorption is reminiscent to what has been seen in a
large variety of so-called Kondo materials and ascribed to excitations across
the hybridization gap. The observed gain of Drude weight upon increasing
magnetic field suggests an enhancement of the itinerant charge-carrier
concentration due to the increasing magnetization, a phenomenon that was
previously observed in other compounds which exhibit colossal magnetoresistive
effects.

###Giant Magnetoresistance in Nanogranular Magnets|A. Glatz,I. S. Beloborodov,V. M. Vinokur###

Giant Magnetoresistance in Nanogranular Magnets. We study the giant magnetoresistance of nanogranular magnets in the presence
of an external magnetic field and finite temperature. We show that the
magnetization of arrays of nanogranular magnets has hysteretic behaviour at low
temperatures leading to a double peak in the magnetoresistance which coalesces
at high temperatures into a single peak. We numerically calculate the
magnetization of magnetic domains and the motion of domain walls in this system
using a combined mean-field approach and a model for an elastic membrane moving
in a random medium, respectively. From the obtained results, we calculate the
electric resistivity as a function of magnetic field and temperature. Our
findings show excellent agreement with various experimental data.

###MagnetoResistance of graphene-based spin valves|L. Brey,H. A. Fertig###

MagnetoResistance of graphene-based spin valves. We study the magnetoresistance of spin-valve devices using graphene as a
non-magnetic material to connect ferromagnetic leads. As a preliminary step we
first study the conductivity of a graphene strip connected to metallic contacts
for a variety of lead parameters, and demonstrate that the resulting
conductivity is rather insensitive to them. We then compute the conductivity of
the spin-valve device in the parallel and antiparallel spin polarization
configurations, and find that it depends only weakly on the relative spin
orientations of the leads, so that the magnetoresistance $MR$ of the system is
very small. The smallness of $MR$ is a consequence of the near independence of
the graphene conductivity from the electronic details of the leads. Our results
indicate that, although graphene has properties that make it attractive for
spintronic devices, the performance of an graphene-based spin-valve is likely
to be poor.

###Spintronics with NSN Junction of one-dimensional quantum wires : A study of Pure Spin Current and Magnetoresistance|Sourin Das,Sumathi Rao,Arijit Saha###

Spintronics with NSN Junction of one-dimensional quantum wires : A study of Pure Spin Current and Magnetoresistance. We demonstrate possible scenarios for production of pure spin current and
large tunnelling magnetoresistance ratios from elastic co-tunnelling and
crossed Andreev reflection across a superconducting junction comprising of
normal metal-superconductor-normal metal, where, the normal metal is a
one-dimensional interacting quantum wire. We show that there are fixed points
in the theory which correspond to the case of pure spin current. We analyze the
influence of electron-electron interaction and see how it stabilizes or
de-stabilizes the production of pure spin current. These fixed points can be of
direct experimental relevance for spintronics application of normal
metal-superconductor-normal metal junctions of one-dimensional quantum wires.
We also calculate the power law temperature dependence of the crossed Andreev
reflection enhanced tunnelling magnetoresistance ratio for the normal
metal-superconductor-normal metal junction.

###Interplay between carrier localization and magnetism in diluted magnetic and ferromagnetic semiconductors|Tomasz Dietl###

Interplay between carrier localization and magnetism in diluted magnetic and ferromagnetic semiconductors. The presence of localized spins exerts a strong influence on quantum
localization in doped semiconductors. At the same time carrier-mediated
interactions between the localized spins are modified or even halted by
carriers' localization. The interplay of these effects is discussed for II-VI
and III-V diluted magnetic semiconductors. This insight is exploited to
interpret the complex dependence of resistance on temperature, magnetic field,
and concentration of valence-band holes in (Ga,Mn)As. In particular, high field
negative magnetoresistance results from the orbital weak localization effect.
The resistance maximum and the associated negative magnetoresistance near the
Curie temperature are assigned to the destructive influence of preformed
ferromagnetic bubbles on the "antilocalization" effect driven by
disorder-modified carrier-carrier interactions. These interactions account also
for the low-temperature increase of resistance. Furthermore, the sensitivity of
conductance to spin splitting and to scattering by spin disorder may explain
resistance anomalies at coercive fields, where relative directions of external
and molecular fields change.

###Metastability and magnetic memory effect in Ni-Mn-Sn alloy|S. Chatterjee,S. Giri,S. Majumdar,S. K. De###

Metastability and magnetic memory effect in Ni-Mn-Sn alloy. Magneto-structural instability in the ferromagnetic shape memory alloy of
composition Ni$_2$Mn$_{1.4}$Sn$_{0.6}$ is investigated by transport and
magnetic measurements. Large negative magnetoresistance is observed around the
martensitic transition temperature (90-210 K). Both magnetization and
magnetoresistance data indicate that upon the application of an external
magnetic field at a constant temperature, the sample attains a field-induced
arrested state which persists even when the field is withdrawn. We observe an
intriguing behavior of the arrested state that it can remember the last highest
field it has experienced. The field-induced structural transition plays the key
role for the observed anomaly and the observed irreversibility can be accounted
by the Landau-type free energy model for the first order phase transition.

###Two-Fluid Behaviour at the Origin of the Resistivity Peak in Doped Manganites|D. I. Golosov,N. Ossi,A. Frydman,I. Felner,I. Nowik,M. I. Tsindlekht,Y. M. Mukovskii###

Two-Fluid Behaviour at the Origin of the Resistivity Peak in Doped Manganites. We report a series of magnetic and transport measurements on high-quality
single crystal samples of colossal magnetoresistive manganites, La_{0.7}
Ca_{0.3} Mn O_3 and Pr_{0.7} Sr_{0.3} Mn O_3. 1 % Fe doping allows a Moessbauer
spectroscopy study, which shows (i) unusual line broadening within the
ferromagnetic phase and (ii) a coexistence of ferro- and paramagnetic
contributions in a region, T_1<T<T_2, around the Curie point T_C. In the case
of Pr_{0.7} Sr_{0.3} Mn O_3, the resistivity peak occurs at a considerably
higher temperature, T_{MI}>T_2. This shows that phase separation into metallic
(ferromagnetic) and insulating (paramagnetic) phases cannot be generally
responsible for the resistivity peak (and hence for the associated colossal
magnetoresistance). Our results can be understood phenomenologically within the
two-fluid approach, which also allows for a difference between T_C and T_{MI}.
Our data indeed imply that while magnetic and transport properties of the
manganites are closely interrelated, the two transitions at T_C and T_{MI} can
be viewed as distinct phenomena.

###Fully Band Resolved Scattering Rate in MgB2 Revealed by Nonlinear Hall Effect and Magnetoresistance Measurements|Huan Yang,Yi Liu,Chenggang Zhuang,Junren Shi,Yugui Yao,Sandro Massidda,Marco Monni,Ying Jia,Xiaoxing Xi,Qi Li,Zi-Kui Liu,Qingrong Feng,Hai-Hu Wen###

Fully Band Resolved Scattering Rate in MgB2 Revealed by Nonlinear Hall Effect and Magnetoresistance Measurements. We have measured the normal state temperature dependence of the Hall effect
and magnetoresistance in epitaxial MgB2 thin films with variable disorders
characterized by the residual resistance ratio RRR ranging from 4.0 to 33.3. A
strong nonlinearity of the Hall effect and magnetoresistance have been found in
clean samples, and they decrease gradually with the increase of disorders or
temperature. By fitting the data to the theoretical model based on the
Boltzmann equation and ab initio calculations for a four-band system, for the
first time, we derived the scattering rates of these four bands at different
temperatures and magnitude of disorders. Our method provides a unique way to
derive these important parameters in multiband systems.

###Transport through single-wall metallic carbon nanotubes in the cotunneling regime|I. Weymann,J. Barnas,S. Krompiewski###

Transport through single-wall metallic carbon nanotubes in the cotunneling regime. Using the real-time diagrammatic technique and taking into account both the
sequential and cotunneling processes, we analyze the transport properties of
single-wall metallic carbon nanotubes coupled to nonmagnetic and ferromagnetic
leads in the full range of parameters. In particular, considering the two
different shell filling schemes of the nanotubes, we discuss the behavior of
the differential conductance, tunnel magnetoresistance and the shot noise. We
show that in the Coulomb diamonds corresponding to even occupations, the shot
noise becomes super-Poissonian due to bunching of fast tunneling processes
resulting from the dynamical channel blockade, whereas in the other diamonds
the noise is roughly Poissonian, in agreement with recent experiments. The
tunnel magnetoresistance is very sensitive to the number of electrons in the
nanotube and exhibits a distinctively different behavior depending on the shell
filling sequence of the nanotube.

###Anomalous magnetic and transport properties of La(0.8-x)Eu(x)Sr0.2MnO3 (0.04 l.e. x l.e. 0.36) compounds|Rakesh Kumar,C. V. Tomy,P. L. Paulose,R. Nagarajan,S. K. Malik###

Anomalous magnetic and transport properties of La(0.8-x)Eu(x)Sr0.2MnO3 (0.04 l.e. x l.e. 0.36) compounds. Anomalous magnetic and transport properties observed in the
La0.8-xEuxSr0.2MnO3 (0.04 l.e x l.e. 0.36) compounds are presented in this
paper. The Curie temperature (TC) decreases from 260 K for x = 0.04 to 188 K
for x = 0.16 and surprisingly thereafter increases for higher Eu concentrations
(x > 0.16) and becomes nearly constant ~230 K. Resistivity increases with Eu
concentration up to x = 0.16 but decreases for higher Eu concentration (x >
0.16). In the magnetoresistance data, in addition to a peak corresponding to
the insulator-metal transition at (TI-M1), a second peak is also observed at a
relatively lower temperature, (TI-M2). Both TI-M1 and TI-M2 follow the same
trend as TC. The unique variation of TC and magnetoresistance is explained on
the basis of structure and disorder correlated to microscopic electronic phase
segregation. The studies with the existing studies also point to the
universibility of this consideration.

###Measuring entropy generated by spin-transfer|J. -E. Wegrowe,Q. Anh Nguyen,T. L. Wade###

Measuring entropy generated by spin-transfer. An experimental protocol is presented that allows the entropy generated by
spin-transfer to be measured. The effect of a strong spin-polarized current
injected on a ferromagnetic nanostructure is investigated with focusing on the
quasi-static equilibrium states of a ferromagnetic single domain. The samples
are single contacted Ni nanowires obtained by electrodeposition in a nanoporous
template. The thermal susceptibility of the magnetoresistance is measured as a
function of the magnetic field for different values of the current injected
through the wire. This quantity is related to the thermal magnetic
susceptibility of the ferromagnetic wire through the anisotropic
magnetoresistance. The ferromagnetic entropy generated by the current injection
is deduced thanks to a thermodynamic Maxwell relation. This study shows that
the effect of the spin-transfer in our samples results in the generation of
incoherent excitations instead of rotation of the magnetization.

###I-V curves of Fe/MgO (001) single- and double-barrier tunnel junctions|J. Peralta-Ramos,A. M. Llois,I. Rungger,S. Sanvito###

I-V curves of Fe/MgO (001) single- and double-barrier tunnel junctions. In this work, we calculate with ab initio methods the current-voltage
characteristics for ideal single- and double-barrier Fe/MgO (001) magnetic
tunnel junctions. The current is calculated in the phase-coherent limit by
using the recently developed SMEAGOL code, combining the nonequilibrium Green
function formalism with density-functional theory. In general we find that
double-barrier junctions display a larger magnetoresistance, which decays with
bias at a slower pace than their single-barrier counterparts. This is explained
in terms of enhanced spin filtering from the middle Fe layer sandwiched in
between the two MgO barriers. In addition, for double-barrier tunnel junctions,
we find a well defined peak in the magnetoresistance at a voltage of V=0.1 V.
This is the signature of resonant tunneling across a majority quantum well
state. Our findings are discussed in relation to recent experiments.

###Driving Weiss oscillations to Zero Resistance States by Microwave Radiation|Jesus Inarrea,Gloria Platero###

Driving Weiss oscillations to Zero Resistance States by Microwave Radiation. In this work we present a theoretical model to study the effect of microwave
radiation on Weiss oscillations. In our proposal Weiss oscillations, produced
by an spatial periodic potential, are modulated by microwave radiation due to
an interference effect between both, space and time-dependent, potentials. The
final magnetoresistance depends mainly on the spatial period of the spatial
potential and the frequency of radiation. Depending on the values of these
parameters, we predict that Weiss oscillations can reach zero resistance
states. On the other hand, these dissipationless transport states, created just
by radiation, can be destroyed by the additional presence of a periodic
space-dependent potential. Then by tuning the spatial period or the radiation
frequency, the magnetoresistance can be strongly modified.

###Magnetic order in Pr2Pd3Ge5 and possible heavy fermion behavior in Pr2Rh3Ge5|V. K. Anand,Z. Hossain,C. Geibel###

Magnetic order in Pr2Pd3Ge5 and possible heavy fermion behavior in Pr2Rh3Ge5. We report our results on two new ternary intermetallic compounds
Pr$_{2}$Pd$_{3}$Ge$_{5}$ and Pr$_{2}$Rh$_{3}$Ge$_{5}$ based on magnetic
susceptibility, magnetization, specific heat, resistivity and magnetoresistance
data. These compounds form in U$_{2}$Co$_{3}$Si$_{5}$-type orthorhombic
structure (space group \textit{Ibam}). Pr$_{2}$Pd$_{3}$Ge$_{5}$ exhibits two
magnetic transitions at T$_{N1}$ = 7.5 K and T$_{N2}$ = 8.3 K. In the
magnetically ordered state Pr$_{2}$Pd$_{3}$Ge$_{5}$ exhibits a field induced
metamagnetic transition and unusually large magnetoresistance.
Pr$_{2}$Rh$_{3}$Ge$_{5}$ does not show any phase transition down to 0.5 K. It
has a CEF singlet ground state, separated from the first excited state by about
10 K. The low lying crystal field excitations lead to exciton mediated
electronic mass enhancement as evidenced by large Sommerfeld coefficient
($\gamma$ $\sim$ 80 mJ/mol K$^2$) in Pr$_{2}$Rh$_{3}$Ge$_{5}$.

###Magnetic-field induced superconductor-antiferromagnet transition in lightly doped RBa_2Cu_3O_{6+x} (R = Lu, Y) crystals|A. N. Lavrov,L. P. Kozeeva,M. R. Trunin,V. N. Zverev###

Magnetic-field induced superconductor-antiferromagnet transition in lightly doped RBa_2Cu_3O_{6+x} (R = Lu, Y) crystals. The remarkable sensitivity of the c-axis resistivity and magnetoresistance in
cuprates to the spin ordering is used to clarify the doping-induced
transformation from an antiferromagnetic (AF) insulator to a superconducting
(SC) metal in RBa_2Cu_3O_{6+x} (R = Lu, Y) single crystals. The established
phase diagram demonstrates that the AF and SC regions apparently overlap: the
superconductivity in RBa_2Cu_3O_{6+x}, in contrast to La_{2-x}Sr_xCuO_4, sets
in before the long-range AF order is completely destroyed by hole doping.
Magnetoresistance measurements of superconducting crystals with low T_c<15-20 K
give a clear view of the magnetic-field induced superconductivity suppression
and recovery of the long-range AF state. What still remains to be understood is
whether the AF order actually persists in the SC state or just revives when the
superconductivity is suppressed, and, in the former case, whether the
antiferromagnetism and superconductivity reside in nanoscopically separated
phases or coexist on an atomic scale.

###Semiclassical framework for the calculation of transport anisotropies|Karel Vyborny,Alexey A. Kovalev,Jairo Sinova,T. Jungwirth###

Semiclassical framework for the calculation of transport anisotropies. We present a procedure for finding the exact solution to the linear-response
Boltzmann equation for two-dimensional anisotropic systems and demonstrate it
on examples of non-crystalline anisotropic magnetoresistance in a system with
spin-orbit interaction. We show that two decoupled integral equations must be
solved in order to find the non-equilibrium distribution function up to linear
order in the applied electric field. The examples are all based on the Rashba
system with charged magnetic scatterers, a system where the non-equilibrium
distribution function and anisotropic magnetoresistance can be evaluated
analytically. Exact results are compared to earlier widely-used approximative
approaches. We find circumstances under which approximative approaches may
become unreliable even on a qualitative level.

###Magnetoresistance in Spin-Polarized Transport through a Carbon Nanotube|Tae-Suk Kim,Choong-Ki Lee,Hyun-Woo Lee,B. C. Lee,K. Rhie###

Magnetoresistance in Spin-Polarized Transport through a Carbon Nanotube. We report on our theoretical study of the magnetoresistance in spin polarized
transport through a finite carbon nanotube (CNT). Varying the Fermi energy of a
CNT and the relative strength of couplings to two ferromagnetic (FM)
electrodes, we studied the conductance as well as the magnetoresistance (MR).
Due to resonant transport through discrete energy levels in a finite CNT, the
conductance and MR are oscillating as a function of the CNT Fermi energy. The
MR is peaked at the conductance valleys and dipped close to the conductance
peaks. When couplings to two FM electrodes are asymmetric, the MR dips become
negative under a rather strong asymmetry. When couplings are more or less
symmetric, the MR dips remain positive except for a very strong coupling case.
Under strong coupling case, the line broadening is significant and transport
channels through neighboring energy levels in a CNT interfere with each other,
leading to the negative MR.

###Magnetoresistance and Hall effect in e-doped superconducting SrLaCuO thin films|V. Jovanovic,Z. Z. Li,F. Bouquet,L. Fruchter,H. Raffy###

Magnetoresistance and Hall effect in e-doped superconducting SrLaCuO thin films. We have epitaxially grown c-axis oriented SrxLa1-xCuO2 thin films by rf
sputtering on KTaO3 substrates with x = 0.12. The as-grown deposits are
insulating and a series of superconducting films with various Tc(R=0) up to 26
K have been obtained by in-situ oxygen reduction. Transport measurements in the
ab plane of these samples have been undertaken. We report original results on
the temperature dependence of the Hall effect and on the anisotropic
magnetoresistance (T > Tc). We discuss the magnitude of upper critical fields
and anisotropy, the Hall effect, which presents changes of sign indicative of
the existence of two types of carriers, the normal state magnetoresistance,
negative in parallel magnetic field, a possible signature of spin scattering.
These properties are compared to those of hole-doped cuprates, such as
BiSr(La)CuO with comparable Tc.

###Theory of Weak Localization in Ferromagnetic (Ga,Mn)As|Ion Garate,Jairo Sinova,T. Jungwirth,A. H. MacDonald###

Theory of Weak Localization in Ferromagnetic (Ga,Mn)As. We study quantum interference corrections to the conductivity in (Ga,Mn)As
ferromagnetic semiconductors using a model with disordered valence band holes
coupled to localized Mn moments through a p-d kinetic-exchange interaction. We
find that at Mn concentrations above 1% quantum interference corrections lead
to negative magnetoresistance, i.e. to weak localization (WL) rather than weak
antilocalization (WAL). Our work highlights key qualitative differences between
(Ga,Mn)As and previously studied toy model systems, and pinpoints the mechanism
by which exchange splitting in the ferromagnetic state converts valence band
WAL into WL. We comment on recent experimental studies and theoretical analyses
of low-temperature magnetoresistance in (Ga,Mn)As which have been variously
interpreted as implying both WL and WAL and as requiring an impurity-band
interpretation of transport in metallic (Ga,Mn)As.

###Graphene magnetoresistance in a parallel magnetic field: Spin polarization effect|E. H. Hwang,S. Das Sarma###

Graphene magnetoresistance in a parallel magnetic field: Spin polarization effect. We develop a theory for graphene magnetotransport in the presence of carrier
spin polarization as induced, for example, by the application of an in-plane
magnetic field ($B$) parallel to the 2D graphene layer. We predict a negative
magnetoresistance $\sigma \propto B^2$ for intrinsic graphene, but for
extrinsic graphene we find a non-monotonic magnetoresistance which is positive
at lower magnetic fields (below the full spin-polarization) and negative at
very high fields (above the full spin-polarization). The conductivity of the
minority spin band $(-)$ electrons does not vanish as the minority carrier
density ($n_-$) goes to zero. The residual conductivity of $(-)$ electrons at
$n_- = 0$ is unique to graphene. We discuss experimental implications of our
theory.

###Coherent Oscillations and Giant Edge Magnetoresistance in Singly Connected Topological Insulators|Rui-Lin Chu,Jian Li,J. K. Jain,Shun-Qing Shen###

Coherent Oscillations and Giant Edge Magnetoresistance in Singly Connected Topological Insulators. The topological insulators have a gap in the bulk but extended states at the
edge that can carry current. We study a geometry in which such edge states will
manifest themselves through periodic oscillations in the magnetoconductance of
a singly connected sample coupled to leads through narrow point contacts. The
oscillations occur due to quantum interference of helical edge states of
electrons traveling along the circumference of the sample, and have a period of
B_0=h/eA_{eff}, where A_{eff} is the effective area enclosed by the edge states
of the sample. Our calculation indicates the possibility of a large change in
the magnetoresistance at small B, termed giant edge magnetoresistance, which
can have potential for application. The zero field conductance also exhibits
oscillations as a function of the Fermi energy due to interference between edge
states. The amplitude of the oscillations is governed by, and therefore can be
used to investigate, the transverse width of the edge channels.

###Huge ac magnetoresistance in La0.7Sr0.3MnO3 in sub- kilo gauss magnetic fields|A. Rebello,V. B. Naik,R. Mahendiran###

Huge ac magnetoresistance in La0.7Sr0.3MnO3 in sub- kilo gauss magnetic fields. We report dynamical magnetotransport in a ferromagnetic metallic oxide,
La0.7Sr0.3MnO3 using the ac impedance technique. The temperature dependence of
the ac resistance(R) and the inductive reactance (X) of the complex impedance
(Z = R+jX) under different dc bias magnetic fields (Hdc = 0-1 kOe) were studied
for different frequencies f = 0.1 to 5 MHz of alternating current. The zero
field R, which decreases smoothly around the Curie temperature TC for f = 100
kHz, transforms into a peak for f = 0.5-5 MHz. The peak decreases in amplitude,
broadens and shifts downward in temperature as the bias field increases. A huge
ac magnetoresistance (= 45 % at f = 2 MHz) in a field of Hdc = 1 kOe is found
and we attribute it to the magnetic field- induced enhancement in the skin
depth and concomitant suppression of magnetic fluctuations near TC. Our study
suggests that radio frequency magnetotransport provides an alternative strategy
to enhance the magnetoresistance and probe the spin-charge coupling in
manganites.

###Effect of pressure on transport and magnetotransport properties in CaFe2As2 single crystals|M. S. Torikachvili,S. L. Bud'ko,N. Ni,P. C. Canfield,S. T. Hannahs###

Effect of pressure on transport and magnetotransport properties in CaFe2As2 single crystals. The effects of pressure generated in a liquid medium, clamp, pressure cell on
the in-plane and c-axis resistance, temperature-dependent Hall coefficient and
low temperature, magnetoresistance in CaFe2As2 are presented. The T - P phase
diagram, including the observation of a complete superconducting transition in
resistivity, delineated in earlier studies is found to be highly reproducible.
The Hall resistivity and low temperature magnetoresistance are sensitive to
different states/phases observed in CaFe2As2. Auxiliary measurements under
uniaxial, c-axis, pressure are in general agreement with the liquid medium
clamp cell results with some difference in critical pressure values and
pressure derivatives. The data may be viewed as supporting the potential
importance of non-hydrostatic components of pressure in inducing
superconductivity in CaFe2As2.

###Anomalous properties in the low-carrier ordered phase of PrRu4P12: Consequence of hybridization between conduction and Pr 4f electrons|S. R. Saha,H. Sugawara,T. Namiki,Y. Aoki,H. Sato###

Anomalous properties in the low-carrier ordered phase of PrRu4P12: Consequence of hybridization between conduction and Pr 4f electrons. The low-carrier ordered phase below the metal-non-metal transition
temperature T_MI ~ 63 K of PrRu4P12 is explored by probing magnetoresistance,
magnetic susceptibility, thermoelectric power, and Hall effect on high quality
single crystals. All the measured properties exhibit the signature of
decimation of the Fermi surface below T_MI and anomalous behaviors below 30 K
including a large thermoelectric power ~-200 uV/K and a giant negative
magnetoresistance (93% at ~0.4 K). The results indicate an additional structure
below 30 K and a semimetal-like ground state. The observed anomalous behaviors
are most likely associated with the novel role of c-f hybridization between
conduction electrons and Pr 4f electrons, whose crystalline electric field
level schemes show drastic change below T_MI.

###Negative tunnel magnetoresistance and differential conductance in transport through double quantum dots|Piotr Trocha,Ireneusz Weymann,Jozef Barnas###

Negative tunnel magnetoresistance and differential conductance in transport through double quantum dots. Spin-dependent transport through two coupled single-level quantum dots weakly
connected to ferromagnetic leads with collinear magnetizations is considered
theoretically. Transport characteristics, including the current, linear and
nonlinear conductance, and tunnel magnetoresistance are calculated using the
real-time diagrammatic technique in the parallel, serial, and intermediate
geometries. The effects due to virtual tunneling processes between the two dots
via the leads, associated with off-diagonal coupling matrix elements, are also
considered. Negative differential conductance and negative tunnel
magnetoresistance have been found in the case of serial and intermediate
geometries, while no such behavior has been observed for double quantum dots
coupled in parallel. It is also shown that transport characteristics strongly
depend on the magnitude of the off-diagonal coupling matrix elements.

###Microwave-induced magnetoresistance of two-dimensional electrons interacting with acoustic phonons|O. E. Raichev###

Microwave-induced magnetoresistance of two-dimensional electrons interacting with acoustic phonons. The influence of electron-phonon interaction on magnetotransport in
two-dimensional electron systems under microwave irradiation is studied
theoretically. Apart from the phonon-induced resistance oscillations which
exist in the absence of microwaves, the magnetoresistance of irradiated samples
contains oscillating contributions due to electron scattering on both
impurities and acoustic phonons. The contributions due to electron-phonon
scattering are described as a result of the interference of phonon-induced and
microwave-induced resistance oscillations. In addition, microwave heating of
electrons leads to a special kind of phonon-induced oscillations. The relative
strength of different contributions and their dependence on parameters are
discussed. The interplay of numerous oscillating contributions suggests a
peculiar magnetoresistance picture in high-mobility layers at the temperatures
when electron-phonon scattering becomes important.

###Angular dependence of magnetoresistance and Fermi-surface shape in quasi-2D metals|P. D. Grigoriev###

Angular dependence of magnetoresistance and Fermi-surface shape in quasi-2D metals. The analytical and numerical study of the angular dependence of
magnetoresistance in layered quasi-two-dimensional (Q2D) metals is performed.
The harmonic expansion analytical formulas for the angular dependence of
Fermi-surface cross-section area in external magnetic field are obtained for
various typical crystal symmetries. The simple azimuth-angle dependence of the
Yamaji angles is derived for the elliptic in-plane Fermi surface. These
formulas correct some previous results and allow the simple and effective
interpretation of the magnetic quantum oscillations data in cuprate
high-temperature superconducting materials, in organic metals and other Q2D
metals. The relation between the angular dependence of magnetoresistance and of
Fermi-surface cross-section area is derived. The applicability region of all
results obtained and of some previous widely used analytical results is
investigated using the numerical calculations.

###Slow relaxations of magnetoresistance in AlGaAs-GaAs quantum well structures quenched in a magnetic field|N. V. Agrinskaya,V. I. Kozub,D. V. Shamshur,A. V. Shumilin,Y. M. Galperin###

Slow relaxations of magnetoresistance in AlGaAs-GaAs quantum well structures quenched in a magnetic field. We observed a slow relaxation of magnetoresistance in response to applied
magnetic field in selectively doped p-GaAs-AlGaAs structures with partially
filled upper Hubbard band. We have paid a special attention to exclude the
effects related to temperature fluctuations. Though this effect is important,
we have found that the general features of slow relaxation still persist. This
behavior is interpreted as related to the properties of the Coulomb glass
formed by charged centers with account of spin correlations, which are
sensitive to an external magnetic field. Variation of the magnetic field
changes numbers of impurity complexes of different types. As a result, it
effects the shape and depth of the polaron gap formed at the states belonging
to the percolation cluster responsible for the conductance. The suggested model
explains both the qualitative behavior and the order of magnitude of the slowly
relaxing magnetoresistance.

###Negative c-axis magnetoresistance in graphite|Y. Kopelevich,R. R. da Silva,J. C. Medina Pantoja,A. M. Bratkovsky###

Negative c-axis magnetoresistance in graphite. We have studied the c-axis interlayer magnetoresistance (ILMR), R_c(B) in
graphite. The measurements have been performed on strongly anisotropic highly
oriented pyrolytic graphite (HOPG) samples in magnetic field up to B = 9 T
applied both parallel and perpendicular to the sample c-axis in the temperature
interval 2 K < T < 300 K. We have observed negative magnetoresistance, dR_c/dB
< 0, for B || c-axis above a certain field B_m(T) that reaches its minimum
value B_m = 5.4 T at T = 150 K. The results can be consistently understood
assuming that ILMR is related to a tunneling between zero-energy Landau levels
of quasi-two-dimensional Dirac fermions, in a close analogy with the behavior
reported for alpha-(BEDT-TTF)2I3 [N. Tajima et al., Phys. Rev. Lett. 102,
176403 (2009)], another multilayer Dirac electron system.

###Unravelling the role of the interface for spin injection into organic semiconductors|Clément Barraud,Pierre Seneor,Richard Mattana,Stéphane Fusil,Karim Bouzehouane,Cyrile Deranlot,Patrizio Graziosi,Luis Hueso,Ilaria Bergenti,Valentin Dediu,Frédéric Petroff,Albert Fert###

Unravelling the role of the interface for spin injection into organic semiconductors. Whereas spintronics brings the spin degree of freedom to electronic devices,
molecular/organic electronics adds the opportunity to play with the chemical
versatility. Here we show how, as a contender to commonly used inorganic
materials, organic/molecular based spintronics devices can exhibit very large
magnetoresistance and lead to tailored spin polarizations. We report on giant
tunnel magnetoresistance of up to 300% in a (La,Sr)MnO3/Alq3/Co nanometer size
magnetic tunnel junction. Moreover, we propose a spin dependent transport model
giving a new understanding of spin injection into organic materials/molecules.
Our findings bring a new insight on how one could tune spin injection by
molecular engineering and paves the way to chemical tailoring of the properties
of spintronics devices.

###Low temperature hopping magnetotransport in paramagnetic single crystals of cobalt doped ZnO|N. Sharma,S. Granville,S. C. Kashyap,J. -Ph. Ansermet###

Low temperature hopping magnetotransport in paramagnetic single crystals of cobalt doped ZnO. Long needle-shaped single crystals of Zn1-xCoxO were grown at low
temperatures using a molten salt solvent technique, up to x=0.10. The
conduction process at low temperatures is determined to be by Mott variable
range hopping. Both pristine and cobalt doped crystals clearly exhibit a
crossover from negative to positive magnetoresistance as the temperature is
decreased. The positive magnetoresistance of the Zn1-xCoxO single crystals
increases with increased Co concentration and reaches up to 20% at low
temperatures (2.5 K) and high fields (>1 T). SQUID magnetometry confirms that
the Zn1-xCoxO crystals are predominantly paramagnetic in nature and the
magnetic response is independent of Co concentration. The results indicate that
cobalt doping of single crystalline ZnO introduces localized electronic states
and isolated Co2+ ions into the host matrix, but that the magnetotransport and
magnetic properties are decoupled.

###Multi-band effect in the noncentrosymmetric superconductors Mg_{12-δ}Ir_{19}B_{16} revealed by Hall effect and magnetoresistance measurements|Gang Mu,Huan Yang,Hai-Hu Wen###

Multi-band effect in the noncentrosymmetric superconductors Mg_{12-δ}Ir_{19}B_{16} revealed by Hall effect and magnetoresistance measurements. We report the longitudinal resistivity and Hall effect measurements on the
noncentrosymmetric superconducting Mg$_{12-\delta}$Ir$_{19}$B$_{16}$ samples
with different critical transition temperatures. A strong temperature
dependence of the Hall coefficient $R_H$ and nonlinear magnetic field
dependence of the Hall resistivity $\rho_{xy}$ in wide temperature region are
observed, suggesting a strong multi-band effect in this system. Moreover, a
large magnetoresistance up to 20% is found at the field of 9 T. We also observe
the violation of the Kohler's rule from our magnetoresistance data, further
confirming the presence of multi-band effect in our samples. A detailed
analysis shows that the data can't be simply described within the two-band
scenario at low temperatures, so we argue that there may be more than two bands
contributing to the conduction of the samples.

###Unveiling First Order CMR Transitions in the Two-Orbital Model for Manganites|Cengiz Şen,Gonzalo Alvarez,Elbio Dagotto###

Unveiling First Order CMR Transitions in the Two-Orbital Model for Manganites. Large scale Monte Carlo simulation results for the two-orbital model for
manganites, including Jahn-Teller lattice distortions, are here presented. At
hole density x=1/4 and in the vicinity of the region of competition between the
ferromagnetic metallic and spin-charge-orbital ordered insulating phases, the
colossal magnetoresistance (CMR) phenomenon is observed with a
magnetoresistance ratio ~10,000% Our main result is that this CMR transition is
found to be of first order in some portions of the phase diagram, in agreement
with early results from neutron scattering, specific heat, and magnetization,
thus solving a notorious discrepancy between experiments and previous
theoretical studies. The first-order characteristics of the transition survive,
and are actually enhanced, when weak quenched disorder is introduced.

###Anomalous scattering in superconducting indium-doped tin telluride|A. S. Erickson,T. H. Geballe,I. R. Fisher,Y. Q. Wu,M. J. Kramer###

Anomalous scattering in superconducting indium-doped tin telluride. Results of resistivity, Hall effect, magnetoresistance, susceptibility and
heat capacity measurements are presented for single crystals of indium-doped
tin telluride with compositions Sn$_{.988-x}$In$_x$Te where $0 \leq x \leq 8.4
%$, along with microstructural analysis based on transmission electron
microscopy. For small indium concentrations, $x \leq 0.9 %$ the material does
not superconduct above 0.3 K, and the transport properties are consistent with
simple metallic behavior. For $x \geq 2.7 %$ the material exhibits anomalous
low temperature scattering and for $x \geq 6.1 %$ bulk superconductivity is
observed with critical temperatures close to 2 K. Intermediate indium
concentrations $2.7% \leq x \leq 3.8%$ do not exhibit bulk superconductivity
above 0.7 K. Susceptibility data indicate the absence of magnetic impurities,
while magnetoresistance data are inconsistent with localization effects,
leading to the conclusion that indium-doped SnTe is a candidate charge Kondo
system, similar to thallium-doped PbTe.

###Antisite Domains in Double Perovskite Ferromagnets: Impact on Magnetotransport and Half-metallicity|Viveka Nand Singh,Pinaki Majumdar###

Antisite Domains in Double Perovskite Ferromagnets: Impact on Magnetotransport and Half-metallicity. Several double perovskite materials of the form A_2BB'O_6 exhibit high
ferromagnetic T_c, and significant low field magnetoresistance. They are also a
candidate source of spin polarized electrons. The potential usefulness of these
materials is, however, frustrated by mislocation of the B and B' ions, which do
not organise themselves in the ideal alternating structure. The result is a
strong dependence of physical properties on preparative conditions, reducing
the magnetization and destroying the half-metallicity. We provide the first
results on the impact of spatially correlated antisite disorder, as observed
experimentally, on the ferromagnetic double perovskites. The antisite domains
suppress magnetism and half-metallicity, as expected, but lead to a dramatic
enhancement of the low field magnetoresistance.

###Permalloy-based carbon nanotube spin-valve|H. Aurich,A. Baumgartner,F. Freitag,A. Eichler,J. Trbovic,C. Schoenenberger###

Permalloy-based carbon nanotube spin-valve. In this Letter we demonstrate that Permalloy (Py), a widely used Ni/Fe alloy,
forms contacts to carbon nanotubes (CNTs) that meet the requirements for the
injection and detection of spin-polarized currents in carbon-based spintronic
devices. We establish the material quality and magnetization properties of Py
strips in the shape of suitable electrical contacts and find a sharp
magnetization switching tunable by geometry in the anisotropic
magnetoresistance (AMR) of a single strip at cryogenic temperatures. In
addition, we show that Py contacts couple strongly to CNTs, comparable to Pd
contacts, thereby forming CNT quantum dots at low temperatures. These results
form the basis for a Py-based CNT spin-valve exhibiting very sharp resistance
switchings in the tunneling magnetoresistance, which directly correspond to the
magnetization reversals in the individual contacts observed in AMR experiments.

###Superconductor-Insulator Magneto-Oscillations in Superconducting Strips|Yeshayahu Atzmon,Efrat Shimshoni###

Superconductor-Insulator Magneto-Oscillations in Superconducting Strips. The magnetoresistance of thin superconducting strips subject to a
perpendicular magnetic field B and low temperatures T manifests a sequence of
alternating superconductor-insulator transitions (SIT). We study this
phenomenon within a quasi one-dimensional (1D) model for the quantum dynamics
of vortices in a line-junction between coupled parallel SC wires, at parameters
close to their SIT. Mapping the vortex system to 1D Fermions at a chemical
potential dictated by B, we find that a quantum phase transition of the Ising
type occurs at critical values of the vortex filling, from a SC phase near
integer filling to an insulator near 1/2-filling. For T->0, the resulting
magnetoresistance R(B) exhibits oscillations similar to the experimental
observation.

###Weakly incoherent magnetotransport in layered metals|Pavel D. Grigoriev###

Weakly incoherent magnetotransport in layered metals. We investigate the conductivity in layered metals in magnetic field in the
weakly incoherent limit, when the interlayer transfer integral is smaller than
the Landau level broadening due to the impurity potential, but the interlayer
electron tunnelling conserves the intralayer momentum. It is shown that the
impurity potential has much stronger effect in this regime, than in the
quasi-2D metals in the coherent limit. The weakly incoherent regime has several
new qualitative features, not found in the previous theoretical approaches. The
background interlayer magnetoresistance in this regime monotonically grows with
increasing of magnetic field perpendicular to the conducting layers. The
effective electron mean free time is considerably shorter than in the coherent
regime and decreases with magnetic field. This enhances the role of higher
harmonics in the angular magnetoresistance oscillations and increases the
Dingle temperature, which damps the magnetic quantum oscillations.

###Imaging Coulomb Islands in a Quantum Hall Interferometer|B. Hackens,F. Martins,S. Faniel,C. A. Dutu,H. Sellier,S. Huant,M. Pala,L. Desplanque,X. Wallart,V. Bayot###

Imaging Coulomb Islands in a Quantum Hall Interferometer. In the Quantum Hall regime, near integer filling factors, electrons should
only be transmitted through spatially-separated edge states. However, in
mesoscopic systems, electronic transmission turns out to be more complex,
giving rise to a large spectrum of magnetoresistance oscillations. To explain
these observations, recent models put forward that, as edge states come close
to each other, electrons can hop between counterpropagating edge channels, or
tunnel through Coulomb islands. Here, we use scanning gate microscopy to
demonstrate the presence of quantum Hall Coulomb islands, and reveal the
spatial structure of transport inside a quantum Hall interferometer. Electron
islands locations are found by modulating the tunneling between edge states and
confined electron orbits. Tuning the magnetic field, we unveil a continuous
evolution of active electron islands. This allows to decrypt the complexity of
high magnetic field magnetoresistance oscillations, and opens the way to
further local scale manipulations of quantum Hall localized states.

###Spin effects in transport through single-molecule magnets in the sequential and cotunneling regimes|Maciej Misiorny,Ireneusz Weymann,Jozef Barnas###

Spin effects in transport through single-molecule magnets in the sequential and cotunneling regimes. We analyze the stationary spin-dependent transport through a single-molecule
magnet weakly coupled to external ferromagnetic leads. Using the real-time
diagrammatic technique, we calculate the sequential and cotunneling
contributions to current, tunnel magnetoresistance and Fano factor in both
linear and nonlinear response regimes. We show that the effects of cotunneling
are predominantly visible in the blockade regime and lead to enhancement of
tunnel magnetoresistance (TMR) above the Julliere value, which is accompanied
with super-Poissonian shot noise due to bunching of inelastic cotunneling
processes through different virtual spin states of the molecule. The effects of
external magnetic field and the role of type and strength of exchange
interaction between the LUMO level and the molecule's spin are also considered.
When the exchange coupling is ferromagnetic, we find an enhanced TMR, while in
the case of antiferromagnetic coupling we predict a large negative TMR effect.

###Effect Of Weak Magnetic Field ($\sim $\,300 Gs) On the Intensity of Terahertz Emission of Hot Electrons in $n$-Ge at Helium Temperatures|V. M. Bondar,P. M. Tomchuk,G. A. Shepel'skii###

Effect Of Weak Magnetic Field ($\sim $\,300 Gs) On the Intensity of Terahertz Emission of Hot Electrons in $n$-Ge at Helium Temperatures. Experimental results of studying the effect of a weak magnetic field ($\sim
$300 Gs) on the intensity of the terahertz emission ($\lambda \approx $100 $\mu
$m) of hot electrons in $n$-Ge (crystallographic orientation $< 1,0,0 >)$ at
helium temperatures ($T\sim $5 K) are presented and discussed. It is shown that
the strong influence of this field (decrease of the emission intensity by
500$\div $1000{%}) is related to a decrease of the carrier concentration at
weak electric fields and the appearance of the magnetoresistance at stronger
fields. The longitudinal magnetoresistance becomes significant due to the
anisotropy of the energy dispersion law of electrons and a strong deformation
of the electron velocity distribution function by the electric field (which is
beyond the framework of the diffusion approximation).

###Orthorhombic to tetragonal transition of SrRuO3 layers in Pr0.7Ca0.3MnO3/SrRuO3 superlattices|M. Ziese,I. Vrejoiu,E. Pippel,E. Nikulina,D. Hesse###

Orthorhombic to tetragonal transition of SrRuO3 layers in Pr0.7Ca0.3MnO3/SrRuO3 superlattices. High-quality Pr0.7Ca0.3MnO3/SrRuO3 superlattices with ultrathin layers were
fabricated by pulsed laser deposition on SrTiO3 substrates. The superlattices
were studied by atomically resolved scanning transmission electron microscopy,
high-resolution transmission electron microscopy, resistivity and
magnetoresistance measurements. The superlattices grew coherently without
growth defects. Viewed along the growth direction, SrRuO3 and Pr0.7Ca0.3MnO3
layers were terminated by RuO2 and MnO2, respectively, which imposes a unique
structure to their interfaces. Superlattices with a constant thickness of the
SrRuO3 layers, but varying thickness of the Pr0.7Ca0.3MnO3 layers showed a
change of crystalline symmetry of the SrRuO3 layers. At a low Pr0.7Ca0.3MnO3
layer thickness of 1.5 nm transmission electron microscopy proved the SrRuO3
layers to be orthorhombic, whereas these were non-orthorhombic for a
Pr0.7Ca0.3MnO3 layer thickness of 4.0 nm. Angular magnetoresistance
measurements showed orthorhombic (with small monoclinic distortion) symmetry in
the first case and tetragonal symmetry of the SrRuO3 layers in the second case.
Mechanisms driving this orthorhombic to tetragonal transition are briefly
discussed.

###Negative tunneling magnetoresistance by canted magnetization in MgO/NiO tunnel barriers|Hyunsoo Yang,See-Hun Yang,Dong-Chen Qi,Andrivo Rusydi,Hiroyo Kawai,Mark Saeys,Titus Leo,David J. Smith,Stuart S. P. Parkin###

Negative tunneling magnetoresistance by canted magnetization in MgO/NiO tunnel barriers. The influence of insertion of an ultra-thin NiO layer between the MgO barrier
and ferromagnetic electrode in magnetic tunnel junctions has been investigated
by measuring the tunneling magnetoresistance and the X-ray magnetic circular
dichroism (XMCD). The magnetoresistance shows a high asymmetry with respect to
bias voltage, giving rise to a negative value of -16% at 2.8 K. We attribute
this to the formation of non-collinear spin structures in the NiO layer as
observed by XMCD. The magnetic moments of the interface Ni atoms tilt from the
easy axis due to exchange interaction and the tilting angle decreases with
increasing the NiO thickness. The experimental observations are further support
by non-collinear spin density functional theory.

###Unusual magnetoresistance in a topological insulator with a single ferromagnetic barrier|B. D. Kong,Y. G. Semenov,C. Krowne,K. W. Kim###

Unusual magnetoresistance in a topological insulator with a single ferromagnetic barrier. Tunneling surface current through a thin ferromagnetic barrier in a
three-dimensional topological insulator is shown to possess an extraordinary
response to the orientation of barrier magnetization. In contrast to
conventional magnetoresistance devices that are sensitive to the relative
alignment of two magnetic layers, a drastic change in the transmission current
is achieved by a single layer when its magnetization rotates by 90 degrees.
Numerical estimations predict a giant magnetoresistance as large as 800 % at
room temperature and the proximate exchange interaction of 40 meV in the
barrier. When coupled with electrical control of magnetization direction, this
phenomenon may be used to enhance the gating function with potentially sharp
turn-on/off for low power applications.

###Anisotropic hysteretic Hall-effect and magnetic control of chiral domains in the chiral spin states of Pr$_2$Ir$_2$O$_7$|L. Balicas,S. Nakatsuji,Y. Machida,S. Onoda###

Anisotropic hysteretic Hall-effect and magnetic control of chiral domains in the chiral spin states of Pr$_2$Ir$_2$O$_7$. We uncover a strong anisotropy in both the anomalous Hall effect (AHE) and
the magnetoresistance of the chiral spin states of Pr$_2$Ir$_2$O$_7$. The AHE
appearing below 1.5 K at zero magnetic field shows hysteresis which is most
pronounced for fields cycled along the [111] direction. This hysteresis is
compatible with the field-induced growth of domains composed by the 3-in 1-out
spin states which remain coexisting with the 2-in 2-out spin ice manifold once
the field is removed. Only for fields applied along the [111] direction, we
observe a large positive magnetoresistance and Shubnikov de Haas oscillations
above a metamagnetic critical field. These observations suggest the
reconstruction of the electronic structure of the conduction electrons by the
field-induced spin-texture.

###Interference mechanism of magnetoresistance in variable range hopping conduction: the effect of paramagnetic electron spins and continuous spectrum of scatterer energies|A. V. Shumilin,V. I. Kozub###

Interference mechanism of magnetoresistance in variable range hopping conduction: the effect of paramagnetic electron spins and continuous spectrum of scatterer energies. Despite the fact that the problem of interference mechanism of
magnetoresistance in semiconductors with hopping conductivity was widely
discussed, most of existing studies were focused on the model of spinless
electrons. This model can be justified only when all electron spins are frozen.
However there is always an admixture of free spins in the semiconductor.
  This study presents the theory of interference contribution to
magnetoresistance that explicitly includes effects of both frozen and free
electron spins. We consider the cases of small and large number of scatterers
in the hopping event. For the case of large number of scatterers the approach
is used that takes into account the dispersion of the scatterer energies. We
compare our results with existing experimental data.

###Magnetic-field-induced dimensional crossover in the organic metal $α$-(BEDT-TTF)$_{2}$KHg(SCN)$_{4}$|P. D. Grigoriev,M. V. Kartsovnik,W. Biberacher###

Magnetic-field-induced dimensional crossover in the organic metal $α$-(BEDT-TTF)$_{2}$KHg(SCN)$_{4}$. The field dependence of interlayer magnetoresistance of the pressurized (to
the normal state) layered organic metal $\alpha
$-(BEDT-TTF)$_{2}$KHg(SCN)$_{4}$ is investigated. The high
quasi-two-dimensional anisotropy, when the interlayer hopping time is longer
than the electron mean-free time and than the cyclotron period, leads to a
dimensional crossover and to strong violations of the conventional
three-dimensional theory of magnetoresistance. The monotonic field dependence
is found to change from the conventional behavior at low magnetic fields to an
anomalous one at high fields. The shape of Landau levels, determined from the
damping of magnetic quantum oscillations, changes from Lorentzian to Gaussian.
This indicates the change of electron dynamics in the disorder potential from
the usual coherent three-dimensional regime to a new regime, which can be
referred to as weakly coherent.

###Anisotropic magnetoresistance of bulk carbon nanotube sheets|E. Cimpoiasu,G. A. Levin,B. White,D. Lashmore###

Anisotropic magnetoresistance of bulk carbon nanotube sheets. We have measured the magnetoresistance of stretched sheets of carbon
nanotubes in temperatures ranging from 2 K to 300 K and in magnetic fields up
to 9 T, oriented either perpendicular or parallel to the plane of the sheets.
The samples have been partially aligned by post-fabrication stretching, such
that the direction of stretching was either parallel or perpendicular to the
direction of applied electric current. We have observed large differences
between the magnetoresistance measured under the two field orientations, most
pronounced at the lowest temperatures, highest fields, and for the
laterally-aligned sample. Treatment of the sheets with nitric acid affects this
anisotropy. We analyzed the results within the theoretical framework of weak
and strong localization and concluded that the anisotropy bears the mark of a
more unusual phenomenon, possibly magnetically-induced mechanical strain.

###Colossal non-saturating linear magnetoresistance in two-dimensional electron systems at a GaAs/AlGaAs heterointerface|M. A. Aamir,Srijit Goswami,Matthias Baenninger,Vikram Tripathi,Michael Pepper,Ian Farrer,David A. Ritchie,Arindam Ghosh###

Colossal non-saturating linear magnetoresistance in two-dimensional electron systems at a GaAs/AlGaAs heterointerface. Engineering devices with a large electrical response to magnetic field is of
fundamental importance for a range of applications such as magnetic field
sensing and magnetic read-heads. We show that a colossal non-saturating linear
magnetoresistance (NLMR) arises in two-dimensional electron systems hosted in a
GaAs/AlGaAs heterostructure in the strongly insulating regime. When operated at
high source-drain bias, the magnetoresistance of our devices increases almost
linearly with magnetic field reaching nearly 10,000% at 8 Tesla, thus
surpassing many known non-magnetic materials that exhibit giant NLMR. The
temperature dependence and mobility analysis indicate that the NLMR has a
purely classical origin, driven by nanoscale inhomogeneities. A large NLMR
combined with small device dimensions makes these systems a new and attractive
candidate for on-chip magnetic field sensing.

###Vortex kinks in superconducting films with periodically modulated thickness|Jorge I. Facio,Anabella Abate,J. Guimpel,Pablo S. Cornaglia###

Vortex kinks in superconducting films with periodically modulated thickness. We report magnetoresistance measurements through Nb films having a periodic
thickness modulation. The cylinder shaped large-thickness regions of the
sample, which form a square lattice, act as repulsive centers for the
superconducting vortices. For low driving currents along one of the axes of the
square lattice, the resistivity $\rho$ increases monotonously with increasing
magnetic field $B$ and the $\rho$--$B$ characteristics are approximately
piecewise linear. The linear $\rho$ vs $B$ segments change their slope at
matching fields where the number of vortices is an integer or a half integer
times the number of protruding cylinders in the sample. Numerical simulations
allow us to associate the different segments of linear magnetoresistance to
different vortex-flow regimes, some of which are dominated by the propagation
of discommensurations (kinks).

###Linear polarization dependence of microwave-induced magnetoresistance oscillations in high-mobility two-dimensional systems|X. L. Lei,S. Y. Liu###

Linear polarization dependence of microwave-induced magnetoresistance oscillations in high-mobility two-dimensional systems. We examine the effect of changing the linear polarization angle $\theta$ of
incident microwaves with respect to the dc current on radiation-induced
magnetoresistance oscillations in a two-dimensional (2D) system within the
balance-equation formulation of the photon-assisted magnetotransport model,
considering the radiative decay as the sole damping mechanism. At an extremum
the amplitude of oscillatory magnetoresistance $R_{xx}$ exhibits a sinusoidal,
up to a factor of 5, magnitude variation with rotating the polarization angle
$\theta$. The maximal amplitude shows up generally at a nonzero $\theta$, which
is dependent upon the extremum in question, the 2D electron setup, the
radiation frequency and the magnetic field orientation. These results provide a
natural explanation for the experimental observations by Mani {\it et al.}
[Phys. Rev. B {\bf 84}, 085308 (2011)], and Ramanayaka {\it et al.} [Phys. Rev.
B {\bf 85}, 205315 (2012)].

###Scaling of Non-Saturating MR and quantum oscillations in pristine and ion-implanted HOPG|Nicholas Cornell,M. B. Salamon,A. Zakhidov###

Scaling of Non-Saturating MR and quantum oscillations in pristine and ion-implanted HOPG. A wide variety of resistive and field dependent behaviors have been
previously observed in both doped and non-doped Highly Oriented Pyrolytic
Graphite (HOPG). We find HOPG samples to vary significantly in their
temperature dependent resistances, even between portions taken from the same
sample, yet they exhibit consistent non-saturating magnetoresistance (MR). The
scaling behavior of the MR is shown to be characteristic of a model based on
the Hall effect in granular materials. In addition to the large, field-linear
MR, all samples exhibit Shubnikov-de Haas (SdH) oscillations. Additional
samples were doped via ion-implantation by boron and phosphorous, but show no
signs of superconductivity nor any systematic change in their magnetoresistive
behavior. Analysis of the SdH data gives a 2D carrier density in agreement with
previous results, and a large mean-free path relative to crystallite size, even
in samples with thin ion-implanted surface layers.

###Theory of spin Hall magnetoresistance|Yan-Ting Chen,Saburo Takahashi,Hiroyasu Nakayama,Matthias Althammer,Sebastian T. B. Goennenwein,Eiji Saitoh,Gerrit E. W. Bauer###

Theory of spin Hall magnetoresistance. We present a theory of the spin Hall magnetoresistance (SMR) in multilayers
made from an insulating ferromagnet F, such as yttrium iron garnet (YIG), and a
normal metal N with spin-orbit interactions, such as platinum (Pt). The SMR is
induced by the simultaneous action of spin Hall and inverse spin Hall effects
and therefore a non-equilibrium proximity phenomenon. We compute the SMR in
F$|$N and F$|$N$|$F layered systems, treating N by spin-diffusion theory with
quantum mechanical boundary conditions at the interfaces in terms of the
spin-mixing conductance. Our results explain the experimentally observed spin
Hall magnetoresistance in N$|$F bilayers. For F$|$N$|$F spin valves we predict
an enhanced SMR amplitude when magnetizations are collinear. The SMR and the
spin-transfer torques in these trilayers can be controlled by the magnetic
configuration.

###Comparative Measurements of Inverse Spin Hall and Magnetoresistance in YIG|Pt and YIG|Ta|Christian Hahn,Grégoire De Loubens,Olivier Klein,Michel Viret,Vladimir V. Naletov,J. Ben Youssef###

Comparative Measurements of Inverse Spin Hall and Magnetoresistance in YIG|Pt and YIG|Ta. We report on a comparative study of spin Hall related effects and
magnetoresistance in YIG|Pt and YIG|Ta bilayers. These combined measurements
allow to estimate the characteristic transport parameters of both Pt and Ta
layers juxtaposed to YIG: the spin mixing conductance $G_{\uparrow \downarrow}$
at the YIG$|$normal metal interface, the spin Hall angle $\Theta_{SH}$, and the
spin diffusion length $\lambda_{sd}$ in the normal metal. The inverse spin Hall
voltages generated in Pt and Ta by the pure spin current pumped from YIG
excited at resonance confirm the opposite signs of spin Hall angles in these
two materials. Moreover, from the dependence of the inverse spin Hall voltage
on the Ta thickness, we extract the spin diffusion length in Ta, found to be
$\lambda_{sd}^\text{Ta}=1.8\pm0.7$ nm. Both the YIG|Pt and YIG|Ta systems
display a similar variation of resistance upon magnetic field orientation,
which can be explained in the recently developed framework of spin Hall
magnetoresistance.

###Giant magnetoresistance in the variable range hopping regime|L. B. Ioffe,B. Z. Spivak###

Giant magnetoresistance in the variable range hopping regime. We predict the universal power law dependence of localization length on
magnetic field in the strongly localized regime. This effect is due to the
orbital quantum interference. Physically, this dependence shows up in an
anomalously large negative magnetoresistance in the hopping regime. The reason
for the universality is that the problem of the electron tunneling in a random
media belongs to the same universality class as directed polymer problem even
in the case of wave functions of random sign. We present numerical simulations
which prove this conjecture. We discuss the existing experiments that show
anomalously large magnetoresistance. We also discuss the role of localized
spins in real materials and the spin polarizing effect of magnetic field.

###Nonlinear magnetotransport in a dc-current-biased graphene|C. M. Wang,X. L. Lei###

Nonlinear magnetotransport in a dc-current-biased graphene. A balance-equation scheme is developed to investigate the magnetotransport in
a dc-current-biased graphene. We examine the Shubnikov-de Haas oscillation
under a nonzero bias current. With an increase in the current density, the
oscillatory differential resistivity exhibits phase inversion, in agreement
with recent experimental observation. In the presence of surface optical
phonons, a second phase inversion may occur at higher dc bias, due to the
reduced influence of electron-heating and the enhanced direct effect of current
on differential magnetoresistivity. We also predict the appearance of
current-induced magnetoresistance oscillation in suspended graphene at lower
magnetic fields and larger current densities. For the graphene mobility
currently available ($\approx 20\,{\rm m^2/Vs}$), the oscillatory behavior may
be somewhat altered by magnetophonon resonance arising from intrinsic acoustic
phonon under finite bias current condition.

###Transport properties of Ag5Pb2O6: a three-dimensional electron-gas-like system with low-carrier-density|Shingo Yonezawa,Yoshiteru Maeno###

Transport properties of Ag5Pb2O6: a three-dimensional electron-gas-like system with low-carrier-density. We report normal-state transport properties of the single-crystalline samples
of the silver-lead oxide superconductor Ag5Pb2O6, including the electrical
resistivity, magnetoresistance, and Hall coefficient. From the Hall coefficient
measurement, we confirmed that the carrier density of this oxide is as low as
5x10^{21} cm^{-3}, one order of magnitude smaller than those for ordinary
alkali metals and noble metals. The magnetoresistance behavior is well
characterized by the axial symmetry of the Fermi surface and by a single
relaxation time. The T^2 term of the resistivity is scaled with the specific
heat coefficient, based on the recent theory for the electron-electron
scattering. The present results provide evidence that Ag5Pb2O6 is a
low-carrier-density three-dimensional electron-gas-like system with enhanced
electron-electron scatterings.

###Magnetic quantum oscillations in the charge-density-wave state of the organic metals $α$-(BEDT-TTF)$_2$MHg(SCN)$_4$ with M = K and Tl|M. V. Kartsovnik,V. N. Zverev,D. Andres,W. Biberacher,T. Helm,P. D. Grigoriev,R. Ramazashvili,N. D. Kushch,H. Müller###

Magnetic quantum oscillations in the charge-density-wave state of the organic metals $α$-(BEDT-TTF)$_2$MHg(SCN)$_4$ with M = K and Tl. The low-temperature charge-density-wave (CDW) state in the layered organic
metals $\alpha $-(BEDT-TTF)$_2$MHg(SCN)$_4$ has been studied by means of the
Shubnikov -- de Haas and de Haas -- van Alphen effects. In addition to the
dominant alpha-frequency, which is also observed in the normal state, both the
magnetoresistance and magnetic torque possess a slowly oscillating component.
These slow oscillations provide a firm evidence for the CDW-induced
reconstruction of the original cylindrical Fermi surface. The
alpha-oscillations of the interlayer magnetoresistance exhibit an anomalous
phase inversion in the CDW state, whereas the de Haas -- van Alphen signal
maintains the normal phase. We argue that the anomaly may be attributed to the
magnetic-breakdown origin of the alpha-oscillations in the CDW state. A
theoretical model illustrating the possibility of a phase inversion in the
oscillating interlayer conductivity in the presence of a spatially fluctuating
magnetic breakdown gap is proposed.

###Thermally excited multi-band conduction in LaAlO3/SrTiO3 heterostructures exhibiting magnetic scattering|V. K. Guduru,A. McCollam,A. Jost,S. Wenderich,H. Hilgenkamp,J. C. Maan,A. Brinkman,U. Zeitler###

Thermally excited multi-band conduction in LaAlO3/SrTiO3 heterostructures exhibiting magnetic scattering. Magnetotransport measurements of charge carriers at the interface of a
LaAlO3/SrTiO3 heterostructure with 26 unit cells of LaAlO3 show Hall resistance
and magnetoresistance which at low and high temperatures is described by a
single channel of electron-like charge carriers. At intermediate temperatures,
we observe non-linear Hall resistance and positive magnetoresistance,
establishing the presence of at least two electron-like channels with
significantly different mobilities and carrier concentrations. These channels
are separated by 6 meV in energy and their temperature dependent occupation and
mobilities are responsible for the observed transport properties of the
interface. We observe that one of the channels has a mobility that decreases
with decreasing temperature, consistent with magnetic scattering in this
channel.

###Tuning of quantum interference in top-gated graphene on SiC|Andrea Iagallo,Shinichi Tanabe,Stefano Roddaro,Makoto Takamura,Hiroki Hibino,Stefan Heun###

Tuning of quantum interference in top-gated graphene on SiC. We report on quantum-interference measurements in top-gated Hall bars of
monolayer graphene epitaxially grown on the Si face of SiC, in which the
transition from negative to positive magnetoresistance was achieved varying
temperature and charge density. We perform a systematic study of the quantum
corrections to the magnetoresistance due to quantum interference of
quasiparticles and electron-electron interaction. We analyze the contribution
of the different scattering mechanisms affecting the magnetotransport in the
$-2.0 \times 10^{10}$ cm$^{-2}$ to $3.75 \times 10^{11}$ cm$^{-2}$ density
region and find a significant influence of the charge density on the
intravalley scattering time. Furthermore, we observe a modulation of the
electron-electron interaction with charge density not accounted for by present
theory. Our results clarify the role of quantum transport in SiC-based devices,
which will be relevant in the development of a graphene-based technology for
coherent electronics.

###From spin-polarized interfaces to giant magnetoresistance in organic spin valves|Deniz Çakır,Diana M. Otálvaro,Geert Brocks###

From spin-polarized interfaces to giant magnetoresistance in organic spin valves. We calculate the spin-polarized electronic transport through a molecular
bilayer spin valve from first principles, and establish the link between the
magnetoresistance and the spin-dependent inter- actions at the metal-molecule
interfaces. The magnetoresistance of a Fe|bilayer-C70|Fe spin valve attains a
high value of 70% in the linear response regime, but it drops sharply as a
function of the applied bias. The current polarization has a value of 80% in
linear response, and also decreases as a function of bias. Both these trends
can be modelled in terms of prominent spin-dependent Fe|C70 interface states
close to the Fermi level, unfolding the potential of spinterface science to
control and optimize spin currents.

###Half-metallic magnetism and the search for better spin valves|Karin Everschor-Sitte,Matthias Sitte,Allan H. MacDonald###

Half-metallic magnetism and the search for better spin valves. We use a previously proposed theory for the temperature dependence of
tunneling magnetoresistance to shed light on ongoing efforts to optimize spin
valves. First we show that a mechanism in which spin valve performance at
finite temperatures is limited by uncorrelated thermal fluctuations of
magnetization orientations on opposite sides of a tunnel junction is in good
agreement with recent studies of the temperature-dependent magnetoresistance of
high quality tunnel junctions with MgO barriers. Using this insight, we propose
a simple formula which captures the advantages for spin-valve optimization of
using materials with a high spin polarization of Fermi-level tunneling
electrons, and of using materials with high ferromagnetic transition
temperatures. We conclude that half-metallic ferromagnets can yield better
spin-value performance than current elemental transition metal ferromagnet/MgO
systems only if their ferromagnetic transition temperatures exceed $\sim
950~\mathrm{K}$.

###Room temperature giant baroresistance and magnetoresistance and its tunability in Pd doped FeRh|Pallavi Kushwaha,Pallab Bag,R. Rawat###

Room temperature giant baroresistance and magnetoresistance and its tunability in Pd doped FeRh. We report room temperature giant baro-resistance ($\approx$128\%) in
$Fe_{49}(Rh_{0.93}Pd_{0.07})_{51}$. With the application of external pressure
and magnetic field the temperature range of giant baro-resistance
($\approx$600\% at 5K and 19.9 kbar and 8 Tesla) and magnetoresistance
($\approx$-85\% at 5K and 8 tesla) can be tuned from 5 K to well above room
temperature. As the AFM state is stabilized at room temperature under external
pressure, it shows giant room temperature magnetoresistance ($\approx$-55\%)
with magnetic field. Due to coupled magnetic and latticel changes, the
isothermal change in room temperature resistivity with pressure (in the absence
of applied magnetic field) as well as magnetic field (under various constant
pressure) can be scaled together to a single curve when plotted as a function
of X = T + 12.8*H - 7.2*P.

###Spin-dependent ballistic transport properties and electronic structures of pristine and edge-doped zigzag silicene nanoribbons: large magnetoresistance|A. B. Chen,X. F. Wang,P. Vasilopoulos,M. X. Zhai,Y. S. Liu###

Spin-dependent ballistic transport properties and electronic structures of pristine and edge-doped zigzag silicene nanoribbons: large magnetoresistance. The electronic structure and conductance of substitutionally edge-doped
zigzag silicene nanoribbons (ZSiNRs) are investigated using the nonequilibrium
Green's function method combined with the density functional theory. Two-probe
systems of ZSiNRs in both ferromagnetic and antiferromagnetic states are
considered. Doping effects of elements from groups III and V, in a parallel or
antiparallel magnetic configuration of the two electrodes, are discussed.
Switching on and off the external magnetic field, we may convert the metallic
ferromagnetic ZSiNRs into insulating antiferromagnetic ZSiNRs. In the
ferromagnetic state, even- or odd-width ZSiNRs exhibit a drastically different
magnetoresistance. In an odd-width edge-doped ZSiNR a large magnetoresistance
occurs compared to that in a pristine ZSiNR. The situation is reversed in
even-width ZSiNRs. These phenomena result from the drastic change of the
conductance in the antiparallel configuration.

###Vacancy Effects on Electric and Thermoelectric Properties of Zigzag Silicene Nanoribbons|R. L. An,X. F. Wang,P. Vasilopoulos,Y. S. Liu,A. B. Chen,Y. J. Dong,M. X. Zhai###

Vacancy Effects on Electric and Thermoelectric Properties of Zigzag Silicene Nanoribbons. We study the crystal reconstruction in the presence of monovacancies (MVs),
divacancies (DVs) and linear vacancies (LVs) in a zigzag silicene nanoribbon
(ZSiNR) with transversal symmetry. Their influence on the electric and
thermoelectric properties is assessed by the density functional theory combined
with the nonequilibrium Green's functions. In particular, we focus on the spin
resolved conductance, magnetoresistance and current-voltage curves. A
5-atom-ring is formed in MVs, a 5-8-5 ring structure in DVs, and a 8-4-8-4 ring
structure in LVs. The linear conductance becomes strongly spin dependent when
the transversal symmetry is broken by vacancies especially if they are located
on the ribbon's edges. The giant magnetoresistance can be smeared by asymmetric
vacancies. Single spin negative differential resistance may appear in the
presence of LVs and asymmetric MVs or DVs. A strong spin Seebeck effect is
expected at room temperature in ZSiNRs with LVs.

###Experimental evidence and control of the bulk-mediated intersurface coupling in topological insulator Bi2Te2Se nanoribbons|Zhaoguo Li,Ion Garate,Jian Pan,Xiangang Wan,Taishi Chen,Wei Ning,Xiaoou Zhang,Fengqi Song,Yuze Meng,Xiaochen Hong,Xuefeng Wang,Li Pi,Xinran Wang,Baigeng Wang,Shiyan Li,Leonid Glazman,Guanghou Wang###

Experimental evidence and control of the bulk-mediated intersurface coupling in topological insulator Bi2Te2Se nanoribbons. Nearly a decade after the discovery of topological insulators (TIs), the
important task of identifying and characterizing their topological surface
states through electrical transport experiments remains incomplete. The
interpretation of these experiments is made difficult by the presence of
residual bulk carriers and their coupling to surface states, which is not yet
well understood. In this work, we present the first evidence for the existence
and control of bulk-surface coupling in Bi2Te2Se nanoribbons, which are
promising platforms for future TI-based devices. Our magnetoresistance
measurements reveal that the number of coherent channels contributing to
quantum interference in the nanoribbons changes abruptly when the film
thickness exceeds the bulk phase relaxation length. We interpret this
observation as an evidence for bulk-mediated coupling between metallic states
located on opposite surfaces. This hypothesis is supported by additional
magnetoresistance measurements conducted under a set of gate voltages and in a
parallel magnetic field, the latter of which alters the intersurface coupling
in a controllable way.

###Sr$_{0.9}$K$_{0.1}$Zn$_{1.8}$Mn$_{0.2}$As$_{2}$: a ferromagnetic semiconductor with colossal magnetoresistance|Xiaojun Yang,Qian Chen,Yupeng Li,Zhen Wang,Jinke Bao,Yuke Li,Qian Tao,Guanghan Cao,Zhu-An Xu###

Sr$_{0.9}$K$_{0.1}$Zn$_{1.8}$Mn$_{0.2}$As$_{2}$: a ferromagnetic semiconductor with colossal magnetoresistance. A bulk diluted magnetic semiconductor (Sr,K)(Zn,Mn)$_{2}$As$_{2}$ was
synthesized with decoupled charge and spin doping. It has a hexagonal
CaAl$_{2}$Si$_{2}$-type structure with the (Zn,Mn)$_{2}$As$_{2}$ layer forming
a honeycomb-like network. Magnetization measurements show that the sample
undergoes a ferromagnetic transition with a Curie temperature of 12 K and
\revision{magnetic moment reaches about 1.5 $\mu_{B}$/Mn under $\mu_0H$ = 5 T
and $T$ = 2 K}. Surprisingly, a colossal negative magnetoresistance, defined as
$[\rho(H)-\rho(0)]/\rho(0)$, up to $-$38\% under a low field of $\mu_0H$ = 0.1
T and to $-$99.8\% under $\mu_0H$ = 5 T, was observed at $T$ = 2 K. The
colossal magnetoresistance can be explained based on the Anderson localization
theory.

###Transverse anisotropy effects on spin-resolved transport through large-spin molecules|Maciej Misiorny,Ireneusz Weymann###

Transverse anisotropy effects on spin-resolved transport through large-spin molecules. The transport properties of a large-spin molecule strongly coupled to
ferromagnetic leads in the presence of transverse magnetic anisotropy are
studied theoretically. The relevant spectral functions, linear-response
conductance and the tunnel magnetoresistance are calculated by means of the
numerical renormalization group method. We study the dependence of transport
characteristics on orbital level position, uniaxial and transverse
anisotropies, external magnetic field and temperature. It is shown that while
uniaxial magnetic anisotropy leads to the suppression of the Kondo effect,
finite transverse anisotropy can restore the Kondo resonance. The effect of
Kondo peak restoration strongly depends on the magnetic configuration of the
device and leads to nontrivial behavior of the tunnel magnetoresistance. We
show that the temperature dependence of the conductance at points where the
restoration of the Kondo effect occurs is universal and shows a scaling typical
for usual spin-one-half Kondo effect.

###Large magnetoresistance from long-range interface coupling in armchair graphene nanoribbon junctions|Suchun Li,Young-Woo Son,Su Ying Quek###

Large magnetoresistance from long-range interface coupling in armchair graphene nanoribbon junctions. In recent years, bottom-up synthesis procedures have achieved significant
advancements in atomically-controlled growth of several-nanometer-long graphene
nanoribbons with armchair-shaped edges (AGNRs). This greatly encourages us to
explore the potential of such well-defined AGNRs in electronics and
spintronics. Here, we propose an AGNR based spin valve architecture that
induces a large magnetoresistance up to 900%. We find that, when an AGNR is
connected perpendicularly to zigzag-shaped edges, the AGNR allows for
long-range extension of the otherwise localized edge state. The huge
magnetoresistance is a direct consequence of the coupling of two such extended
states from both ends of the AGNR, which forms a perfect transmission channel.
By tuning the coupling between these two spin-polarized states with a magnetic
field, the channel can be destroyed, leading to an abrupt drop in electron
transmission.

###Revealing surface states in In-doped SnTe superconducting nanoplates with low bulk mobility|Jie Shen,Yujun Xie,Judy J. Cha###

Revealing surface states in In-doped SnTe superconducting nanoplates with low bulk mobility. Indium (In) doping in topological crystalline insulator SnTe induces
superconductivity, making In-doped SnTe a candidate for a topological
superconductor. SnTe nanostructures offer well-defined nanoscale morphology and
high surface-to-volume ratios to enhance surface effects. Here, we study
In-doped SnTe nanoplates, InxSn1-xTe, with x ranging from 0 to 0.1 and show
they superconduct. More importantly, we show that In doping reduces the bulk
mobility of InxSn1-xTe such that the surface states are revealed in
magnetotransport despite the high bulk carrier density. This is manifested by
two-dimensional linear magnetoresistance in high magnetic fields, which is
independent of temperature up to 10 K. Aging experiments show that the linear
magnetoresistance is sensitive to ambient conditions, further confirming its
surface origin. We also show that the weak antilocalization observed in
InxSn1-xTe nanoplates is a bulk effect. Thus, we show that nanostructures and
reducing the bulk mobility are effective strategies to reveal the surface
states and test for topological superconductors.

###Magnetoresistance in two-component systems|P. S. Alekseev,A. P. Dmitriev,I. V. Gornyi,V. Yu. Kachorovskii,B. N. Narozhny,M. Schuett,M. Titov###

Magnetoresistance in two-component systems. Two-component systems with equal concentrations of electrons and holes
exhibit non-saturating, linear magnetoresistance in classically strong magnetic
fields. The effect is predicted to occur in finite-size samples at charge
neutrality in both disorder- and interaction-dominated regimes. The phenomenon
originates in the excess quasiparticle density developing near the edges of the
sample due to the compensated Hall effect. The size of the boundary region is
of the order of the electron-hole recombination length that is inversely
proportional to the magnetic field. In narrow samples and at strong enough
magnetic fields, the boundary region dominates over the bulk leading to linear
magnetoresistance. Our results are relevant for semimetals and narrow-band
semiconductors including most of the topological insulators.

###Rectification of radio frequency current in giant magnetoresistance spin valve|Sławomir Ziętek,Piotr Ogrodnik,Marek Frankowski,Jakub Chęciński,Piotr Wiśniowski,Witold Skowroński,Jerzy Wrona,Tomasz Stobiecki,Antoni Żywczak,Józef Barnaś###

Rectification of radio frequency current in giant magnetoresistance spin valve. We report on a highly efficient spin diode effect in an exchange-biased
spin-valve giant magnetoresistance (GMR) strips. In such multilayer structures,
symmetry of the current distribution along the vertical direction is broken
and, as a result, a non-compensated Oersted field acting on the magnetic free
layer appears. This field, in turn, is a driving force of magnetization
precessions. Due to the GMR effect, resistance of the strip oscillates
following the magnetization dynamics. This leads to rectification of the
applied radio frequency current and induces a direct current voltage $V_{DC}$.
We present a theoretical description of this phenomenon and calculate the spin
diode signal, $V_{DC}$, as a function of frequency, external magnetic field,
and angle at which the external field is applied. A satisfactory quantitative
agreement between theoretical predictions and experimental data has been
achieved. Finally, we show that the spin diode signal in GMR devices is
significantly stronger than in the anisotropic magnetoresistance
permalloy-based devices.

###Magnetoresistance of layered conductors under conditions of topological phase transition|O. Galbova,V. Peschansky###

Magnetoresistance of layered conductors under conditions of topological phase transition. The resistance of layered conductors with a multisheet Fermi surface (FS), in
a high magnetic field, in the immediate vicinity of Lifshic's topological
transition when the separate FS sheets are drown together by an external
action, pressure in part (and eventual change of the FS connectivity) is
studied theoretically. Analysis of magnetoresistance near topological
transition is illustrated for the case of FS in the shape of lightly corrugated
cylinder and two corrugated planes distributed with a repeated period in the
pulse space. It yields, that as the FS plane sheets approach sufficiently the
cylinder, the charge carriers produce a magnetic breakdown of one FS sheet to
another, decreasing a sharp anisotropy of magnetoresistance to the in-plane
current. Instead of square increase with a magnetic field, the slower
resistance growth remains linear in the field within a broad magnetic-field
range. In the intimate vicinity of topological transition, when the energy gap
between FS layers is negligibly small, the resistance is saturated.

###Hydrodynamics in graphene: Linear-response transport|B. N. Narozhny,I. V. Gornyi,M. Titov,M. Schütt,A. D. Mirlin###

Hydrodynamics in graphene: Linear-response transport. We develop a hydrodynamic description of transport properties in
graphene-based systems which we derive from the quantum kinetic equation. In
the interaction-dominated regime, the collinear scattering singularity in the
collision integral leads to fast unidirectional thermalization and allows us to
describe the system in terms of three macroscopic currents carrying electric
charge, energy, and quasiparticle imbalance. Within this "three-mode"
approximation we evaluate transport coeffcients in monolayer graphene as well
as in double-layer graphene-based structures. The resulting classical
magnetoresistance is strongly sensitive to the interplay between the sample
geometry and leading relaxation processes. In small, mesoscopic samples the
macroscopic currents are inhomogeneous which leads to linear magnetoresistance
in classically strong fields. Applying our theory to double-layer
graphene-based systems, we provide microscopic foundation for phenomenological
description of giant magnetodrag at charge neutrality and find magnetodrag and
Hall drag in doped graphene.

###Multiband character of $β$-FeSe: Angular dependence of the magnetoresistance and upper critical field|M. L. Amigó,V. Ale Crivillero,D. G. Franco,G. Nieva###

Multiband character of $β$-FeSe: Angular dependence of the magnetoresistance and upper critical field. We studied $ab$-plane transport properties in single crystals of the
superconductor $\beta$-FeSe up to 16 T. In the normal state, below 90 K, the
crystals present a strongly anisotropic positive magnetoresistance that becomes
negligible above that temperature. In the superconducting state (T$_c$=8.87(5)
K) the upper critical field anisotropy $H$$_{c2}$$\parallel$$ab$ /
$H$$_{c2}$$\parallel$$c$ changes with temperature and the angular dependence of
the dissipation for fixed temperatures and fields reflects a strongly
anisotropic behavior. Our results make evident that multiband effects are
needed to describe the measured transport properties. We model the
magnetoresistance and upper critical field behavior with a two-band model
showing that the diffusivities ratio parameter remains unchanged going from the
normal to the superconducting state.

###Evolution of the linear-polarization-angle-dependence of the radiation-induced magnetoresistance-oscillations with microwave power|Tianyu Ye,W. Wegscheider,R. G. Mani###

Evolution of the linear-polarization-angle-dependence of the radiation-induced magnetoresistance-oscillations with microwave power. We examine the role of the microwave power in the linear polarization angle
dependence of the microwave radiation induced magnetoresistance oscillations
observed in the high mobility GaAs/AlGaAs two dimensional electron system.
Diagonal resistance $R_{xx}$ was measured at fixed magnetic fields
corresponding to the photo-excited oscillatory extrema of $R_{xx}$ as a
function of both the microwave power, $P$, and the linear polarization angle,
$\theta$. Color contour plots of such measurements demonstrate the evolution of
the $R_{xx}$ versus $\theta$ line shape with increasing microwave power. We
report that the non-linear power dependence of the amplitude of the
radiation-induced magnetoresistance oscillations distorts the cosine-square
relation between $R_{xx}$ and $\theta$ at high power.

###Quantum oscillations of magnetoresistance of the submicrometer thick bismuth telluride-based films|L. N. Lukyanova,Yu. A. Boikov,V. A. Danilov,O. A. Usov,M. P. Volkov,V. A. Kutasov###

Quantum oscillations of magnetoresistance of the submicrometer thick bismuth telluride-based films. Hetero-epitaxial films based on bismuth telluride with excess of Te were
grown by hat wall technique at the surface of the mica (muscovite).
Galvanomagnetic properties of the thin films were measured, and quantum
oscillations of the magnetoresistance were found at the temperatures below 10 K
in the magnetic field from 6 to 14 T. From analysis of magnetoresistance
oscillations the main surface state parameters of the films were determined.
Expementally obtained Landau level index shift and its temperature dependence
are consistent with Berry phase specific for topological Dirac surface states.
The estimated parameters of electronic topological surface states of the
bismuth telluride-based films are of special interest because of possible usage
of them in micro generators and micro coolers, and also for other device
applications.

###Linear magnetoresistance caused by mobility fluctuations in the n-doped Cd3As2|A. Narayanan,M. D. Watson,S. F. Blake,Y. L. Chen,D. Prabhakaran,B. Yan,N. Bruyant,L. Drigo,I. I. Mazin,C. Felser,T. Kong,P. C. Canfield,A. I. Coldea###

Linear magnetoresistance caused by mobility fluctuations in the n-doped Cd3As2. Cd3As2 is a candidate three-dimensional Dirac semi-metal which has
exceedingly high mobility and non-saturating linear magnetoresistance that may
be relevant for future practical applications. We report magnetotransport and
tunnel diode oscillation measurements on Cd3As2, in magnetic fields up to 65 T
and temperatures between 1.5K to 300K. We find the non-saturating linear
magnetoresistance persist up to 65T and it is likely caused by disorder effects
as it scales with the high mobility, rather than directly linked to Fermi
surface changes even when approaching the quantum limit. From the observed
quantum oscillations, we determine the bulk three-dimensional Fermi surface
having signatures of Dirac behaviour with non-trivial Berry's phase shift, very
light effective quasiparticle masses and clear deviations from the
band-structure predictions. In very high fields we also detect signatures of
large Zeeman spin-splitting (g~16).

###Magnetization reversal assisted by half antivortex states in nanostructured circular cobalt disks|Antonio Lara,Oleksandr V. Dobrovolskiy,José L. Prieto,Michael Huth,Farkhad G. Aliev###

Magnetization reversal assisted by half antivortex states in nanostructured circular cobalt disks. The half antivortex, a fundamental topological structure which determines
magnetization reversal of submicron magnetic devices with domain walls, has
been suggested also to play a crucial role in spin torque induced vortex core
reversal in circular disks. Here we report on magnetization reversal in
circular disks with nanoholes through consecutive metastable states with half
antivortices. In-plane anisotropic magnetoresistance and broadband
susceptibility measurements accompanied by micromagnetic simulations reveal
that cobalt disks with two and three linearly arranged nanoholes directed at 45
and 135 degrees with respect to the external magnetic field show reproducible
step-like changes in the anisotropic magnetoresistance and magnetic
permeability due to transitions between different intermediate states mediated
by vortices and half antivortices confined to the dot nanoholes and edges,
respectively. Our findings are relevant for the development of multi-hole based
spintronic and magnetic memory devices.

###Unidirectional spin Hall magnetoresistance in ferromagnet/normal metal bilayers|Can Onur Avci,Kevin Garello,Abhijit Ghosh,Mihai Gabureac,Santos F. Alvarado,Pietro Gambardella###

Unidirectional spin Hall magnetoresistance in ferromagnet/normal metal bilayers. Magnetoresistive effects are usually invariant upon inversion of the
magnetization direction. In noncentrosymmetric conductors, however, nonlinear
resistive terms can give rise to a current dependence that is quadratic in the
applied voltage and linear in the magnetization. Here we demonstrate that such
conditions are realized in simple bilayer metal films where the spin-orbit
interaction and spin-dependent scattering couple the current-induced spin
accumulation to the electrical conductivity. We show that the longitudinal
resistance of Ta|Co and Pt|Co bilayers changes when reversing the polarity of
the current or the sign of the magnetization. This unidirectional
magnetoresistance scales linearly with current density and has opposite sign in
Ta and Pt, which we associate with the modification of the interface scattering
potential induced by the spin Hall effect in these materials. Our results
suggest a route to control the resistance and detect magnetization switching in
spintronic devices using a two-terminal geometry, which applies also to
heterostructures including topological insulators.

###Multiple Fermi pockets revealed by Shubnikov-de Haas oscillations in WTe2|Fei-Xiang Xiang,Menno Veldhorst,Shi-Xue Dou,Xiao-Lin Wang###

Multiple Fermi pockets revealed by Shubnikov-de Haas oscillations in WTe2. We use magneto-transport measurements to investigate the electronic structure
of WTe2 single crystals. A non-saturating and parabolic magnetoresistance is
observed in the temperature range between 2.5 to 200 K and magnetic fields up
to 8 T. Shubnikov - de Haas oscillations with beating patterns are observed.
The fast Fourier transform of the SdH oscillations reveals three oscillation
frequencies, corresponding to three pairs of Fermi pockets with comparable
effective masses , m* ~ 0.31 me. By fitting the Hall resistivity, we infer the
presence of one pair of electron pockets and two pairs of hole pockets,
together with nearly perfect compensation of the electron-hole carrier
concentration. These magnetotransport measurements reveal the complex
electronic structure in WTe2, explaining the nonsaturating magnetoresistance.

###Radiation-induced resistance oscillations in a 2D hole gas: a demonstration of a universal effect|Jesús Iñarrea,Gloria Platero###

Radiation-induced resistance oscillations in a 2D hole gas: a demonstration of a universal effect. We report on a theoretical insight about the microwave-induced resistance
oscillations and zero resistance states when dealing with p-type semiconductors
and holes instead of electrons. We consider a high-mobility two-dimensional
hole gas hosted in a pure Ge/SiGe quantum well. Similarly to electrons we
obtain radiation-induce resistance oscillations and zero resistance states. We
analytically deduce a universal expression for the irradiated
magnetoresistance, explaining the origin of the minima positions and their
$1/4$ cycle phase shift. The outcome is that these phenomena are universal and
only depend on radiation and cyclotron frequencies. We also study the
possibility of having simultaneously two different carriers driven by
radiation: light and heavy holes. As a result the calculated magnetoresistance
reveals an interference profile due to the different effective masses of the
two types of carriers.

###Room-temperature chiral charge pumping in Dirac semimetals|Cheng Zhang,Enze Zhang,Weiyi Wang,Yanwen Liu,Zhi-Gang Chen,Shiheng Lu,Sihang Liang,Junzhi Cao,Xiang Yuan,Lei Tang,Qian Li,Chao Zhou,Teng Gu,Yizheng Wu,Jin Zou,Faxian Xiu###

Room-temperature chiral charge pumping in Dirac semimetals. Chiral anomaly, a non-conservation of chiral charge pumped by the topological
nontrivial gauge fields, has been predicted to exist in Weyl semimetals.
However, until now, the experimental signature of this effect exclusively
relies on the observation of negative longitudinal magnetoresistance at low
temperatures. Here, we report the field-modulated chiral charge pumping process
and valley diffusion in Cd3As2. Apart from the conventional negative
magnetoresistance, we observe an unusual nonlocal response with negative field
dependence up to room temperature, originating from the diffusion of valley
polarization. Furthermore, a large magneto-optic Kerr effect generated by
parallel electric and magnetic fields is detected. These new experimental
approaches provide a quantitative analysis of the chiral anomaly phenomenon
which is inaccessible previously. The ability to manipulate the valley
polarization in topological semimetal at room temperature opens up a brand-new
route towards understanding its fundamental properties and utilizing the chiral
fermions.

###Fermi surface of three-dimensional La1-xSrxMnO3 explored by soft-X-ray ARPES: Rhombohedral lattice distortion and its effect on magnetoresistance|L. L. Lev,J. Krempaský,U. Staub,V. A. Rogalev,T. Schmitt,M. Shi,P. Blaha,A. S. Mishchenko,A. A. Veligzhanin,Y. V. Zubavichus,M. B. Tsetlin,H. Volfová,J. Braun,J. Minár,V. N. Strocov###

Fermi surface of three-dimensional La1-xSrxMnO3 explored by soft-X-ray ARPES: Rhombohedral lattice distortion and its effect on magnetoresistance. Electronic structure of the three-dimensional colossal magnetoresistive
perovskite La1-xSrxMnO3 has been established using soft-X-ray ARPES with its
intrinsically sharp definition of three-dimensional electron momentum. The
experimental results show much weaker polaronic coupling compared to the
bilayer manganites and are consistent with the GGA+U band structure. The
experimental Fermi surface unveils the canonical topology of alternating
three-dimensional electron spheres and hole cubes, with their shadow contours
manifesting the rhombohedral lattice distortion. This picture has been
confirmed by one-step photoemission calculations including displacement of the
apical oxygen atoms. The rhombohedral distortion is neutral to the Jahn-Teller
effect and thus polaronic coupling, but affects the double-exchange electron
hopping and thus the colossal magnetoresistance effect.

###Ultrafast Carrier Dynamics in the Large Magnetoresistance Material WTe$_{2}$|Y. M. Dai,J. Bowlan,H. Li,H. Miao,S. F. Wu,W. D. Kong,Y. G. Shi,S. A. Trugman,J. -X. Zhu,H. Ding,A. J. Taylor,D. A. Yarotski,R. P. Prasankumar###

Ultrafast Carrier Dynamics in the Large Magnetoresistance Material WTe$_{2}$. Ultrafast optical pump-probe spectroscopy is used to track carrier dynamics
in the large magnetoresistance material WTe$_{2}$. Our experiments reveal a
fast relaxation process occurring on a sub-picosecond time scale that is caused
by electron-phonon thermalization, allowing us to extract the electron-phonon
coupling constant. An additional slower relaxation process, occurring on a time
scale of $\sim$5-15 picoseconds, is attributed to phonon-assisted electron-hole
recombination. As the temperature decreases from 300 K, the timescale governing
this process increases due to the reduction of the phonon population. However,
below $\sim$50 K, an unusual decrease of the recombination time sets in, most
likely due to a change in the electronic structure that has been linked to the
large magnetoresistance observed in this material.

###Hall effect in the extremely large magnetoresistance semimetal WTe$_2$|Yongkang Luo,H. Li,Y. M. Dai,H. Miao,Y. G. Shi,H. Ding,A. J. Taylor,D. A. Yarotski,R. P. Prasankumar,J. D. Thompson###

Hall effect in the extremely large magnetoresistance semimetal WTe$_2$. We systematically measured the Hall effect in the extremely large
magnetoresistance semimetal WTe$_2$. By carefully fitting the Hall resistivity
to a two-band model, the temperature dependencies of the carrier density and
mobility for both electron- and hole-type carriers were determined. We observed
a sudden increase of the hole density below $\sim$160~K, which is likely
associated with the temperature-induced Lifshitz transition reported by a
previous photoemission study. In addition, a more pronounced reduction in
electron density occurs below 50~K, giving rise to comparable electron and hole
densities at low temperature. Our observations indicate a possible electronic
structure change below 50~K, which might be the direct driving force of the
electron-hole ``compensation'' and the extremely large magnetoresistance as
well. Numerical simulations imply that this material is unlikely to be a
perfectly compensated system.

###Bulk and surface electronic structure of trigonal structured PtBi2 studied by angle-resolved photoemission spectroscopy|Q. Yao,Y. P. Du,X. J. Yang,Y. Zheng,D. F. Xu,X. H. Niu,H. F. Yang,P. Dudin,T. K. Kim,M. Hoesch,I. Vobornik,Z. -A. Xu,X. G. Wan,D. L. Feng,D. W. Shen###

Bulk and surface electronic structure of trigonal structured PtBi2 studied by angle-resolved photoemission spectroscopy. PtBi2 with a layered trigonal crystal structure was recently reported to
exhibit an unconventional large linear magnetoresistance, while the mechanism
involved is still elusive. Using high resolution angle-resolved photoemission
spectroscopy, we present a systematic study on its bulk and surface electronic
structure. Through careful comparison with first-principle calculations, our
experiment distinguishes the low-lying bulk bands from entangled surface
states, allowing the estimation of the real stoichiometry of samples. We find
significant electron doping in PtBi2, implying a substantial Bi deficiency
induced disorder therein. We discover a Dirac-cone-like surface state on the
boundary of the Brillouin zone, which is identified as an accidental Dirac band
without topological protection. Our findings exclude quantum-limit-induced
linear band dispersion as the cause of the unconventional large linear
magnetoresistance.

###Tuning the electronic and the crystalline structure of LaBi by pressure|F. F. Tafti,M. S. Torikachvili,R. L. Stillwell,B. Baer,E. Stavrou,S. T. Weir,Y. K. Vohra,H. -Y. Yang,E. F. McDonnell,S. K. Kushwaha,Q. D. Gibson,R. J. Cava,J. R. Jeffries###

Tuning the electronic and the crystalline structure of LaBi by pressure. Extreme magnetoresistance (XMR) in topological semimetals is a recent
discovery which attracts attention due to its robust appearance in a growing
number of materials. To search for a relation between XMR and
superconductivity, we study the effect of pressure on LaBi taking advantage of
its simple structure and simple composition. By increasing pressure we observe
the disappearance of XMR followed by the appearance of superconductivity at
P=3.5 GPa.The suppression of XMR is correlated with increasing zero-field
resistance instead of decreasing in-field resistance. At higher pressures, P=11
GPa, we find a structural transition from the face center cubic lattice to a
primitive tetragonal lattice in agreement with theoretical predictions. We
discuss the relationship between extreme magnetoresistance, superconductivity,
and structural transition in LaBi.

###Super-giant magnetoresistance at room-temperature in copper nanowires due to magnetic field modulation of potential barrier heights at nanowire-contact interfaces|Md. I. Hossain,M. Maksud,N. K. R. Palapati,A. Subramanian,J. Atulasimha,S. Bandyopadhyay###

Super-giant magnetoresistance at room-temperature in copper nanowires due to magnetic field modulation of potential barrier heights at nanowire-contact interfaces. We have observed a super-giant (~10,000,000%) negative magnetoresistance at
39 mT field in Cu nanowires contacted with Au contact pads. In these nanowires,
potential barriers form at the two Cu/Au interfaces because of Cu oxidation
that results in an ultrathin copper oxide layer forming between Cu and Au.
Current flows when electrons tunnel through, and/or thermionically emit over,
these barriers. A magnetic field applied transverse to the direction of current
flow along the wire deflects electrons toward one edge of the wire because of
the Lorentz force, causing electron accumulation at that edge and depletion at
the other. This lowers the potential barrier at the accumulated edge and raises
it at the depleted edge, causing a super-giant magnetoresistance at room
temperature.

###Investigation of the tunnel magnetoresistance in junctions with a strontium stannate barrier|Matthias Althammer,Amit Vikam Singh,Sahar Keshavarz,Mehmet Kenan Yurtisigi,Rohan Mishra,Albina Borisevich,Patrick LeClair,Arunava Gupta###

Investigation of the tunnel magnetoresistance in junctions with a strontium stannate barrier. We experimentally investigate the structural, magnetic and electrical
transport properties of La$_{0.67}$Sr$_{0.33}$MnO$_{3}$ based magnetic tunnel
junctions with a SrSnO$_3$ barrier. Our results show that despite the large
number of defects in the strontium stannate barrier, due to the large lattice
mismatch, the observed tunnel magnetoresistance is comparable to tunnel
junctions with a better lattice matched STiO$_3$ barrier, reaching values of up
to 350% at T=5 K. Further analysis of the current-voltage characteristics of
the junction and the bias voltage dependence of the observed tunnel
magnetoresistance show a decrease of the TMR with increasing bias voltage. In
addition, the observed TMR vanishes for T>200 K. Our results suggest that by
employing a better lattice matched ferromagnetic electrode and thus reducing
the structural defects in the strontium stannate barrier even larger TMR ratios
might be possible in the future.

###Possible Weyl fermions in the magnetic Kondo system CeSb|C. Y. Guo,C. Cao,M. Smidman,F. Wu,Y. J. Zhang,F. Steglich,F. C. Zhang,H. Q. Yuan###

Possible Weyl fermions in the magnetic Kondo system CeSb. Materials where the electronic bands have unusual topologies allow for the
realization of novel physics and have a wide range of potential applications.
When two electronic bands with linear dispersions intersect at a point, the
excitations could be described as Weyl fermions which are massless particles
with a particular chirality. Here we report evidence for the presence of Weyl
fermions in the ferromagnetic state of the low-carrier density, strongly
correlated Kondo lattice system CeSb, from electronic structure calculations
and angle-dependent magnetoresistance measurements. When the applied magnetic
field is parallel to the electric current, a pronounced negative
magnetoresistance is observed within the ferromagnetic state, which is
destroyed upon slightly rotating the field away. These results give evidence
for CeSb belonging to a new class of Kondo lattice materials with Weyl fermions
in the ferromagnetic state.

###First-principles spin-transfer torque in CuMnAs$|$GaP$|$CuMnAs junctions|Maria Stamenova,Razie Mohebbi,Jamileh Seyedyazdi,Ivan Rungger,Stefano Sanvito###

First-principles spin-transfer torque in CuMnAs$|$GaP$|$CuMnAs junctions. We demonstrate that an all-antiferromagnetic tunnel junction with current
perpendicular to the plane geometry can be used as an efficient spintronics
device with potential high frequency operation. By using state-of-the-art
density functional theory combined with quantum transport, we show that the
N\'eel vector of the electrodes can be manipulated by spin-transfer torque.
This is staggered over the two different magnetic sublattices and can generate
dynamics and switching. At the same time the different magnetization states of
the junction can be read by standard tunnelling magnetoresistance. Calculations
are performed for CuMnAs$|$GaP$|$CuMnAs junctions with different surface
terminations between the anti-ferromagnetic CuMnAs electrodes and the
insulating GaP spacer. In particular we find that the torque remains staggered
regardless of the termination, while the magnetoresistance depends on the
microscopic details of the interface.

###Anisotropic magneto-transport and magnetic properties of low temperature phase of TaTe2|Hongxiang Chen,Zhilin Li,Liwei Guo,Xiaolong Chen###

Anisotropic magneto-transport and magnetic properties of low temperature phase of TaTe2. TaTe2 is a quasi-2D charge density wave (CDW) compound with distorted-1T type
structure exhibiting double-zigzag chains. Here we report the Fermi surface
topology of low temperature phase of TaTe2 (LT-TaTe2) by anisotropic
magneto-transport and magnetic measurements on high-quality single crystals. An
anomalous large linear magnetoresistance up to 140% at 3 K in 9 T was observed,
suggesting the existence of a small Fermi pocket in Dirac cone state in quantum
transport models. Meanwhile, strong magnetic anisotropy was observed for B
(001) and B//(001). Angle-dependent magnetoresistance and de Hass-van Alphen
oscillations suggest the anisotropy of the normal Fermi surface and the small
Fermi pocket in Dirac cone state.

###Unusual magneto-transport from Si-square nets in topological semimetal HfSiS|Nitesh Kumar,Kaustuv Manna,Yanpeng Qi,Shu-Chun Wu,Lei Wang,Binghai Yan,Claudia Felser,Chandra Shekhar###

Unusual magneto-transport from Si-square nets in topological semimetal HfSiS. The class of topological semimetals comprises a large pool of compounds.
Together they provide a wide platform to realize exotic quasiparticles for
example Dirac, nodal line Dirac and Weyl fermions. In this letter, we report
the Berry phase, Fermi surface topology and anisotropic magnetoresistance of
HfSiS which has recently been predicted to be a nodal line semimetal. This
compound contains large carrier density, higher than most of the known
semimetals. Massive amplitudes of de Haas-van Alphen and Shubnikov-de Haas
oscillations up to 20 K in 7 T assist us in witnessing nontrivial pi-Berry
phase which is a consequence of topological Dirac-type dispersion of bands
originating from the hybridization of px + py and dx2-y2 orbitals of square-net
plane of Si and Hf atoms, respectively. Furthermore, we establish the 3D
Fermi-surface which consists of very asymmetric water caltrop-like electron and
barley seed-like hole pockets which account for the anisotropic
magnetoresistance in HfSiS.

###Magnon Planar Hall Effect and Anisotropic Magnetoresistance in a Magnetic Insulator|J. Liu,L. J. Cornelissen,J. Shan,T. Kuschel,B. J. van Wees###

Magnon Planar Hall Effect and Anisotropic Magnetoresistance in a Magnetic Insulator. Electrical resistivities can be different for charge currents travelling
parallel or perpendicular to the magnetization in magnetically ordered
conductors or semiconductors, resulting in the well-known planar Hall effect
and anisotropic magnetoresistance. Here, we study the analogous anisotropic
magnetotransport behavior for magnons in a magnetic insulator
Y$_{3}$Fe$_{5}$O$_{12}$. Electrical and thermal magnon injection, and
electrical detection methods are used at room temperature with transverse and
longitudinal geometries to measure the magnon planar Hall effect and
anisotropic magnetoresistance, respectively. We observe that the relative
difference between magnon current conductivities parallel and perpendicular to
the magnetization, with respect to the average magnon conductivity, i.e.
$|(\sigma_{\parallel}^{\textrm{m}}-\sigma_{\perp}^{\textrm{m}})/\sigma_{0}^{\textrm{m}}|$
, is approximately 5% with the majority of the measured devices showing
$\sigma_{\perp}^{\textrm{m}}>\sigma_{\parallel}^{\textrm{m}}$.

###Surface charge conductivity of topological insulator in a magnetic field: effect of hexagonal warping|R. S. Akzyanov,A. L. Rakhmanov###

Surface charge conductivity of topological insulator in a magnetic field: effect of hexagonal warping. We investigate the influence of the hexagonal warping on the transport
properties of the topological insulators. We study the charge conductivity
within Kubo formalism in the first Born approximation using low energy
expansion of the Hamiltonian near the Dirac point. The effects of disorder,
magnetic field and chemical potential value are analyzed in details. We found
that the presence of the hexagonal warping effects significantly the
conductivity of the topological insulator. In particular, it gives rise to the
growth of the longitudinal conductivity with the increase of the disorder and
anisotropic anomalous in-plane magnetoresistance. The hexagonal warping also
affects the quantum anomalous Hall effect and anomalous out-of-plane
magnetoresistance. The obtained results are consistent with the experimental
data.

###Strong magnetic field induces superconductivity in Weyl semi - metal|Baruch Rosenstein,B. Ya. Shapiro,Dingping Li,I. Shapiro###

Strong magnetic field induces superconductivity in Weyl semi - metal. Microscopic theory of the normal-to-superconductor coexistence line of a 2D
two-band Weyl superconductor subjected to magnetic field is constructed. It is
shown that a Weyl semi-metal that is nonsuperconducting or having a small
critical temperature $T_{c}$ at zero field, might become a superconductor at
higher temperature when the magnetic field is tuned to a series of quantized
values $H_{n}$. The pairing occurs on Landau levels. It is argued that the
phenomenon is much easier detectable in Weyl semi - metals than in parabolic
band metals since the quantum limit already has been approaches in several Weyl
materials.. An experimental signature of the superconductivity on Landau levels
is the reduction of magnetoresistivity. This has already been observed in
$Cd_{3}As_{2}$ and several other compounds. The novel kind of quantum
oscillations of magnetoresistance detected in $ZrTe_{5}$ is discussed along
these lines.

###Enhanced superconductivity and anisotropy of FeTe0.6Se0.4 single crystals with Li-NH3 intercalation|Chenghe Li,Shanshan Sun,Shaohua Wang,Hechang Lei###

Enhanced superconductivity and anisotropy of FeTe0.6Se0.4 single crystals with Li-NH3 intercalation. We report a systematic study of anisotropy resistivity, magnetoresistance and
Hall effect of Li0.32(NH3)yFe2Te1.2Se0.8 single crystals. When compared to the
parent compound FeTe0.6Se0.4, the Li-NH3 intercalation not only increases the
superconducting transition temperature, but also enhances the electronic
anisotropy in both normal and superconducting states. Moreover, in contrast to
the parent compound, the Hall coefficient RH becomes negative at low
temperature, indicating electron-type carriers are dominant due to Li doping.
On the other hand, the sign reverse of RH at high temperature and the failure
of scaling behavior of magnetoresistance imply that hole pockets may be still
crossing or just below the Fermi energy level, leading to the multiband
behavior in Li0.32(NH3)yFe2Te1.2Se0.8.

###Magnetic-field driven ambipolar quantum Hall effect in epitaxial graphene close to the charge neutrality point|A. Nachawaty,M. Yang,W. Desrat,S. Nanot,B. Jabakhanji,D. Kazazis,R. Yakimova,A. Cresti,W. Escoffier,B. Jouault###

Magnetic-field driven ambipolar quantum Hall effect in epitaxial graphene close to the charge neutrality point. We have investigated the disorder of epitaxial graphene close to the charge
neutrality point (CNP) by various methods: i) at room temperature, by analyzing
the dependence of the resistivity on the Hall coefficient ; ii) by fitting the
temperature dependence of the Hall coefficient down to liquid helium
temperature; iii) by fitting the magnetoresistances at low temperature. All
methods converge to give a disorder amplitude of $(20 \pm 10)$ meV. Because of
this relatively low disorder, close to the CNP, at low temperature, the sample
resistivity does not exhibit the standard value $\simeq h/4e^2$ but diverges.
Moreover, the magnetoresistance curves have a unique ambipolar behavior, which
has been systematically observed for all studied samples. This is a signature
of both asymmetry in the density of states and in-plane charge transfer. The
microscopic origin of this behavior cannot be unambiguously determined.
However, we propose a model in which the SiC substrate steps qualitatively
explain the ambipolar behavior.

###Large magnetoresistance in type-II Weyl semimetal WP$_2$|Aifeng Wang,D. Graf,Yu Liu,Qianheng Du,Jiabao Zheng,Hechang Lei,C. Petrovic###

Large magnetoresistance in type-II Weyl semimetal WP$_2$. We report magnetotransport study on type-II Weyl semimetal WP$_2$ single
crystals. Magnetoresistance (MR) exhibits a nonsaturating $H^{n}$ field
dependence (14,300\% at 2 K and 9 T) whereas systematic violation of Kohler's
rule was observed. Quantum oscillations reveal a complex multiband electronic
structure. The cyclotron effective mass close to the mass of free electron
m$_e$ was observed in quantum oscillations along $b$-axis, while reduced
effective mass of about 0.5$m_e$ was observed in $a$-axis quantum oscillations,
suggesting Fermi surface anisotropy. Temperature dependence of the resistivity
shows a large upturn that cannot be explained by the multi-band
magnetoresistance of conventional metals. Even though crystal structure of
WP$_{2}$ is not layered as in transition metal dichalcogenides, quantum
oscillations suggest partial two-dimensional character.

###Magnetoresistive sensors based on the elasticity of domain walls|Xueying Zhang,Nicolas Vernier,Zhiqiang Cao,Qunwen Leng,Anni Cao,Dafine Ravelosona,Weisheng Zhao###

Magnetoresistive sensors based on the elasticity of domain walls. Magnetic sensors based on the magnetoresistance effects have a promising
application prospect due to their excellent sensitivity and advantages in terms
of the integration. However, competition between higher sensitivity and larger
measuring range remains a problem. Here, we propose a novel mechanism for the
design of magnetoresistive sensors: probing the perpendicular field by
detecting the expansion of the elastic magnetic Domain Wall (DW) in the free
layer of a spin valve or a magnetic tunnel junction. Performances of devices
based on this mechanism, such as the sensitivity and the measuring range can be
tuned by manipulating the geometry of the device, without changing the
intrinsic properties of the material, thus promising a higher integration level
and a better performance. The mechanism is theoretically explained based on the
experimental results. Two examples are proposed and their functionality and
performances are verified via micromagnetic simulation.

###A classical mechanism for negative magnetoresistance in two-dimensional systems in the ballistic regime|P. S. Alekseev,M. A. Semina###

A classical mechanism for negative magnetoresistance in two-dimensional systems in the ballistic regime. In ultra-high quality two-dimensional (2D) materials the mean free paths of
phonons and electrons relative to all mechanisms of scattering can be much
greater than a size of a sample. In this case the most intensive type of
scattering of particles is their collisions with sample edges and the ballistic
regime of heat and charge transport is realized. We study the ballistic
transport of classical interacting 2D particles in a long narrow sample. We
show that the inter-particle scattering conserving momentum leads to a positive
hydrodynamic correction to the ballistic conductance, which is a precursor of
the viscous Poiseuille flow. We examine the effect of weak magnetic field on
the electron ballistic conductance and predict a novel classical ballistic
mechanism for negative magnetoresistance. Our analysis demonstrates that,
apparently, such mechanism explains the temperature-independent part of the
giant negative magnetoresistance recently observed in the ultra-high mobility
GaAs quantum wells.

###Strain induced changes of electronic properties of B-site ordered double perovskite Sr$_2$CoIrO$_6$ thin films|S. Esser,C. F. Chang,C. -Y. Kuo,S. Merten,V. Roddatis,T. D. Ha,A. Jesche,V. Moshnyaga,H. -J. Lin,A. Tanaka,C. T. Chen,L. H. Tjeng,P. Gegenwart###

Strain induced changes of electronic properties of B-site ordered double perovskite Sr$_2$CoIrO$_6$ thin films. B-site ordered thin films of double perovskite Sr$_2$CoIrO$_6$ were
epitaxially grown by a metal-organic aerosol deposition technique on various
substrates, actuating different strain states. X-ray diffraction, transmission
electron microscopy and polarized far-field Raman spectroscopy confirm the
strained epitaxial growth on all used substrates. Polarization dependent Co
$L_{2,3}$ X-ray absorption spectroscopy reveals a change of the magnetic easy
axis of the antiferromagnetically ordered (high-spin) Co$^{3+}$ sublattice
within the strain series. By reversing the applied strain direction from
tensile to compressive, the easy axis changes abruptly from in-plane to
out-of-plane orientation. The low-temperature magnetoresistance changes its
sign respectively and is described by a combination of weak anti-localization
and anisotropic magnetoresistance effects.

###Very Large Tunneling Magnetoresistance in Layered Magnetic Semiconductor CrI$_3$|Zhe Wang,Ignacio Gutiérrez-Lezama,Nicolas Ubrig,Martin Kroner,Marco Gibertini,Takashi Taniguchi,Kenji Watanabe,Ataç Imamoğlu,Enrico Giannini,Alberto F. Morpurgo###

Very Large Tunneling Magnetoresistance in Layered Magnetic Semiconductor CrI$_3$. Magnetic layered van der Waals crystals are an emerging class of materials
giving access to new physical phenomena, as illustrated by the recent
observation of 2D ferromagnetism in Cr2Ge2Te6 and CrI3. Of particular interest
in semiconductors is the interplay between magnetism and transport, which has
remained unexplored. Here we report first magneto-transport measurements on
exfoliated CrI3 crystals. We find that tunneling conduction in the direction
perpendicular to the crystalline planes exhibits a magnetoresistance as large
as 10 000 %. The evolution of the magnetoresistance with magnetic field and
temperature reveals that the phenomenon originates from multiple transitions to
different magnetic states, whose possible microscopic nature is discussed on
the basis of all existing experimental observations. This observed dependence
of the conductance of a tunnel barrier on its magnetic state is a new
phenomenon that demonstrates the presence of a strong coupling between
transport and magnetism in magnetic van der Waals semiconductors.

###Giant Tunneling Magnetoresistance in Spin-Filter van der Waals Heterostructures|Tiancheng Song,Xinghan Cai,Matisse Wei-Yuan Tu,Xiaoou Zhang,Bevin Huang,Nathan P. Wilson,Kyle L. Seyler,Lin Zhu,Takashi Taniguchi,Kenji Watanabe,Michael A. McGuire,David H. Cobden,Di Xiao,Wang Yao,Xiaodong Xu###

Giant Tunneling Magnetoresistance in Spin-Filter van der Waals Heterostructures. Magnetic multilayer devices that exploit magnetoresistance are the backbone
of magnetic sensing and data storage technologies. Here we report novel
multiple-spin-filter magnetic tunnel junctions (sf-MTJs) based on van der Waals
(vdW) heterostructures in which atomically thin chromium triiodide (CrI3) acts
as a spin-filter tunnel barrier sandwiched between graphene contacts. We
demonstrate tunneling magnetoresistance which is drastically enhanced with
increasing CrI3 layer thickness, reaching a record 19,000% for magnetic
multilayer structures using four-layer sf-MTJs at low temperatures. These
devices also show multiple resistance states as a function of magnetic field,
suggesting the potential for multi-bit functionalities using an individual vdW
sf-MTJ. Using magnetic circular dichroism measurements, we attribute these
effects to the intrinsic layer-by-layer antiferromagnetic ordering of the
atomically thin CrI3. Our work reveals the possibility to push magnetic
information storage to the atomically thin limit, and highlights CrI3 as a
superlative magnetic tunnel barrier for vdW heterostructure spintronic devices.

###Two-dimensional Mott variable-range hopping transport in a disordered MoS$_2$ nanoflake|Jianhong Xue,Shaoyun Huang,Ji-Yin Wang,H. Q. Xu###

Two-dimensional Mott variable-range hopping transport in a disordered MoS$_2$ nanoflake. The transport characteristics of a disordered MoS$_2$ nanoflake in the
insulator regime are studied by electrical and magnetotransport measurements.
The layered MoS$_2$ nanoflake is exfoliated from a bulk MoS$_2$ crystal and the
conductance $G$ and magnetoresistance are measured in a four-probe setup over a
wide range of temperatures. At high temperatures, we observe that $\log_{10}G$
exhibits a $-T^{-1}$ temperature dependence and the transport in the nanoflake
dominantly arises from thermal activation. At low temperatures, where the
transport in the nanoflake dominantly takes place via variable-range hopping
(VRH) processes, we observe that $\log_{10}G$ exhibits a $-T^{-1/3}$
temperature dependence, an evidence for the two-dimensional (2D) Mott VRH
transport. The measured low-field magnetoresistance of the nanoflake in the
insulator regime exhibits a quadratic magnetic field dependence $\sim \alpha
B^2$ with $\alpha\sim T^{-1}$, fully consistent with the 2D Mott VRH transport
in the nanoflake.

###Negative longitudinal magnetoresistance in the density wave phase of Y$_2$Ir$_2$O$_7$|Abhishek Juyal,Amit Agarwal,Soumik Mukhopadhyay###

Negative longitudinal magnetoresistance in the density wave phase of Y$_2$Ir$_2$O$_7$. The ground state of nanowires of single crystalline Pyrochlore
Y$_2$Ir$_2$O$_7$ is a density wave. Application of a {\it transverse} magnetic
field increases the threshold electric field for the collective de-pinning of
the density wave state at low temperature, leading to colossal
magnetoresistance for voltages around the de-pinning threshold. This is in
striking contrast to the case where even a vanishingly small {\it longitudinal}
magnetic field sharply reduces the de-pinning threshold voltage resulting in
{\it negative} magnetoresistance. Ruling out several other possibilities we
argue that this phenomenon is likely to be a consequence of the chiral anomaly
in the gapped out Weyl semimetal phase in Y$_2$Ir$_2$O$_7$.

###High-Field Magnetoresistance of Organic Semiconductors|G. Joshi,M. Y. Teferi,S. Jamali,M. Groesbeck,J. van Tol,R. McLaughlin,Z. V. Vardeny,J. M. Lupton,H. Malissa,C. Boehme###

High-Field Magnetoresistance of Organic Semiconductors. The magneto-electronic field effects in organic semiconductors at high
magnetic fields are described by field-dependent mixing between singlet and
triplet states of weakly bound charge carrier pairs due to small differences in
their Land\'e g-factors that arise from the weak spin-orbit coupling in the
material. In this work, we corroborate theoretical models for the high-field
magnetoresistance of organic semiconductors, in particular of diodes made of
the conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate)
(PEDOT:PSS) at low temperatures, by conducting magnetoresistance measurements
along with multi-frequency continuous-wave electrically detected magnetic
resonance experiments. The measurements were performed on identical devices
under similar conditions in order to independently assess the magnetic
field-dependent spin-mixing mechanism, the so-called {\Delta}g mechanism, which
originates from differences in the charge-carrier g-factors induced by
spin-orbit coupling.

###Spin-Polarized Tunneling through Chemical Vapor Deposited Multilayer Molybdenum Disulfide|André Dankert,Parham Pashaei,M. Venkata Kamalakar,Anand P. S. Gaur,Satyaprakash Sahoo,Ivan Rungger,Awadhesh Narayan,Kapildeb Dolui,Anamul Hoque,Michel P. de Jong,Ram S. Katiyar,Stefano Sanvito,Saroj P. Dash###

Spin-Polarized Tunneling through Chemical Vapor Deposited Multilayer Molybdenum Disulfide. The two-dimensional (2D) semiconductor molybdenum disulfide (MoS2) has
attracted widespread attention for its extraordinary electrical, optical, spin
and valley related properties. Here, we report on spin polarized tunneling
through chemical vapor deposited (CVD) multilayer MoS2 (~7 nm) at room
temperature in a vertically fabricated spin-valve device. A tunnel
magnetoresistance (TMR) of 0.5 - 2 % has been observed, corresponding to spin
polarization of 5 - 10 % in the measured temperature range of 300 - 75 K. First
principles calculations for ideal junctions results in a tunnel
magnetoresistance up to 8 %, and a spin polarization of 26 %. The detailed
measurements at different temperatures and bias voltages, and density
functional theory calculations provide information about spin transport
mechanisms in vertical multilayer MoS2 spin-valve devices. These findings form
a platform for exploring spin functionalities in 2D semiconductors and
understanding the basic phenomenon that control their performance.

###Magnetotransport in phase-separated (Ga,Fe)N with $γ$'-Ga$_y$Fe$_{4-y}$N nanocrystals|A. Navarro-Quezada,M. Aiglinger,B. Faina,K. Gas,M. Matzer,Tian Li,R. Adhikari,M. Sawicki,A. Bonanni###

Magnetotransport in phase-separated (Ga,Fe)N with $γ$'-Ga$_y$Fe$_{4-y}$N nanocrystals. The magnetotransport in phase-separated (Ga,Fe)N containing
$\gamma$'-Ga$_y$Fe$_{4-y}$N (0\,$<$\,y\,$<$1) nanocrystals (NCs) is studied in
the temperature range between 2\,K and 300\,K. The evolution of the resistivity
and of the magnetoresistance (MR) as a function of temperature points at two
conduction mechanisms: namely a conventional Arrhenius-type one down to 50\,K,
and Mott variable range hopping at lower temperatures, where the spin-polarized
current is transported between NCs in a regime in which phonon-scattering
effects are not dominant. Below 25\,K, the MR shows a hysteretic contribution
at magnetic fields $<$1\,T and proportional to the coercive field. Anisotropic
magnetoresistance with values one order of magnitude greater than those
previously reported for $\gamma$'-Fe$_4$N thin films over the whole considered
temperature range, confirms that the observed MR in these layers is determined
by the embedded nanocrystals.

###Asymmetry-induced effects in Kondo quantum dots coupled to ferromagnetic leads|K. P. Wojcik,I. Weymann,J. Barnas###

Asymmetry-induced effects in Kondo quantum dots coupled to ferromagnetic leads. We study the spin-resolved transport through single-level quantum dots
strongly coupled to ferromagnetic leads in the Kondo regime, with a focus on
contact and material asymmetry-related effects. By using the numerical
renormalization group method, we analyze the dependence of relevant spectral
functions, linear conductance and tunnel magnetoresistance on the system
asymmetry parameters. In the parallel magnetic configuration of the device the
Kondo effect is generally suppressed due to the presence of exchange field,
irrespective of system's asymmetry. In the antiparallel configuration, on the
other hand, the Kondo effect can develop if the system is symmetric. We show
that even relatively weak asymmetry may lead to the suppression of the Kondo
resonance in the antiparallel configuration and thus give rise to nontrivial
behavior of the tunnel magnetoresistance. In addition, by using the
second-order perturbation theory we derive general formulas for the exchange
field in both magnetic configurations of the system.

###Observation of the ghost critical field for superconducting fluctuations in a disordered TaN thin film|Nicholas P. Breznay,Aharon Kapitulnik###

Observation of the ghost critical field for superconducting fluctuations in a disordered TaN thin film. We experimentally study the ghost critical field (GCF), a magnetic field
scale for the suppression of superconducting fluctuations, using Hall effect
and magnetoresistance measurements on a disordered superconducting thin film
near its transition temperature $T_c$. We observe an increase in the Hall
effect with a maximum in field that tracks the upper critical field below
$T_c$, vanishes near $T_c$, and returns to higher fields above $T_c$. Such a
maximum has been observed in studies of the Nernst effect and identified as the
GCF. Magnetoresistance measurements near $T_c$ indicate quenching of
superconducting fluctuations, agree with established theoretical descriptions,
and allow us to extract the GCF and other parameters. Above $T_c$ the Hall peak
field is quantitatively distinct from the GCF, and we contrast this finding
with ongoing studies of the Nernst effect and superconducting fluctuations in
unconventional and thin-film superconductors.

###Half-metallicity and anisotropy magnetoresistance properties of Heusler alloys Fe2Co1-xCrxSi|Y. Du,G. Z. Xu,E. K. Liu,G. J. Li,H. G. Zhang,S. Y. Yu,W. H. Wang,G. H. Wu###

Half-metallicity and anisotropy magnetoresistance properties of Heusler alloys Fe2Co1-xCrxSi. In this paper, we investigate the half-metallicity of Heusler alloys
Fe2Co1-xCrxSi by first principles calculations and anisotropy magnetoresistance
measurements. It is found that, with the increase of Cr content x, the Fermi
level of Fe2Co1-xCrxSi moves from the top of valence band to the bottom of
conduction band, and a large half-metallic band gap of 0.75 eV is obtained for
x=0.75. We then successfully synthesized a series Heusler Fe2Co1-xCrxSi
polycrystalline ribbon samples. The results of X-ray diffraction indicate that
the Fe2Co1-xCrxSi series of samples are pure phase with a high degree of order
and the saturation magnetic moment follows half-metallic Slater-Pauling rule.
Except for the two end members, Fe2CoSi and Fe2CrSi, the anisotropic
magnetoresistance of Fe2Co1-xCrxSi (x=0.25, 0.5, 0.75) show a negative value
suggesting they are stable half-metallic ferromagnets.

###Large Tunneling Anisotropic Magneto-Seebeck Effect in a CoPt|MgO|Pt Tunnel Junction|V. P. Amin,J. Zemen,J. Železný,T. Jungwirth,Jairo Sinova###

Large Tunneling Anisotropic Magneto-Seebeck Effect in a CoPt|MgO|Pt Tunnel Junction. We theoretically investigate the Tunneling Anisotropic Magneto-Seebeck effect
in a realistically-modeled CoPt|MgO|Pt tunnel junction using coherent transport
calculations. For comparison we study the tunneling magneto-Seebeck effect in
CoPt|MgO|CoPt as well. We find that the magneto-Seebeck ratio of CoPt|MgO|Pt
exceeds that of CoPt|MgO|CoPt for small barrier thicknesses, reaching 175% at
room temperature. This result provides a sharp contrast to the
magnetoresistance, which behaves oppositely for all barrier thicknesses and
differs by one order of magnitude between devices. Here the magnetoresistance
results from differences in transmission brought upon by changing the tunnel
junction's magnetization configuration. The magneto-Seebeck effect results from
variations in asymmetry of the energy-dependent transmission instead. We report
that this difference in origin allows for CoPt|MgO|Pt to possess strong thermal
magnetic-transport anisotropy.

###Magnetoresistance of disordered graphene: from low to high temperatures|B. Jabakhanji,D. Kazazis,W. Desrat,A. Michon,M. Portail,B. Jouault###

Magnetoresistance of disordered graphene: from low to high temperatures. We present the magnetoresistance (MR) of highly doped monolayer graphene
layers grown by chemical vapor deposition on 6H-SiC. The magnetotransport
studies are performed on a large temperature range, from $T$ = 1.7 K up to room
temperature. The MR exhibits a maximum in the temperature range $120-240$ K.
The maximum is observed at intermediate magnetic fields ($B=2-6$ T), in between
the weak localization and the Shubnikov-de Haas regimes. It results from the
competition of two mechanisms. First, the low field magnetoresistance increases
continuously with $T$ and has a purely classical origin. This positive MR is
induced by thermal averaging and finds its physical origin in the energy
dependence of the mobility around the Fermi energy. Second, the high field
negative MR originates from the electron-electron interaction (EEI). The
transition from the diffusive to the ballistic regime is observed. The
amplitude of the EEI correction points towards the coexistence of both long and
short range disorder in these samples.

###Temperature-dependent disorder and magnetic field driven disorder: experimental observations for doped GaAs/AlGaAs quantum well structures|N. V. Agrinskaya,V. A. Berezovets,V. I. Kozub###

Temperature-dependent disorder and magnetic field driven disorder: experimental observations for doped GaAs/AlGaAs quantum well structures. We report experimental studies of conductance and magnetoconductance of
GaAs/AlGaAs quantum well structures where both wells and barriers are doped by
acceptor impurity Be. Temperature dependence of conductance demonstrate a
non-monotonic behavior at temperatures around 100 K. At small temperatures
(less than 10 K) we observed strong negative magnetoresistance at moderate
magnetic field which crossed over to positive magnetoresistance at very strong
magnetic fields and was completely suppressed with an increase of temperature.
We ascribe these unusual features to effects of temperature and magnetic field
on a degree of disorder. The temperature dependent disorder is related to
charge redistribution between different localized states with an increase of
temperature. The magnetic field dependent disorder is also related by charge
redistribution between different centers, however in this case an important
role is played by the doubly occupied states of the upper Hubbard band, their
occupation being sensitive to magnetic field due to on-site spin correlations.
The detailed theoretical model is present.

###Nonequilibrium spin injection in monolayer black phosphorus|Mingyan Chen,Zhizhou Yu,Yin Wang,Yiqun Xie,Jian Wang,Hong Guo###

Nonequilibrium spin injection in monolayer black phosphorus. Monolayer black phosphorus (MBP) is an interesting emerging electronic
material with a direct band gap and relatively high carrier mobility. In this
work we report a theoretical investigation of nonequilibrium spin injection and
spin-polarized quantum transport in MBP from ferromagnetic Ni contacts, in
two-dimensional magnetic tunneling structures. We investigate physical
properties such as the spin injection efficiency, the tunnel magnetoresistance
ratio, spin-polarized currents, charge currents and transmission coefficients
as a function of external bias voltage, for two different device contact
structures where MBP is contacted by Ni(111) and by Ni(100). While both
structures are predicted to give respectable spin-polarized quantum transport,
the Ni(100)/MBP/Ni(100) trilayer has the superior properties where the spin
injection and magnetoresistance ratio maintains almost a constant value against
the bias voltage. The nonequilibrium quantum transport phenomenon is understood
by analyzing the transmission spectrum at nonequilibrium.

###Signatures of the Adler-Bell-Jackiw chiral anomaly in a Weyl Fermion semimetal|Chenglong Zhang,Su-Yang Xu,Ilya Belopolski,Zhujun Yuan,Ziquan Lin,Bingbing Tong,Nasser Alidoust,Chi-Cheng Lee,Shin-Ming Huang,Tay-Rong Chang,Horng-Tay Jeng,Hsin Lin,Madhab Neupane,Daniel S. Sanchez,Hao Zheng,Guang Bian,Junfeng Wang,Chi Zhang,Hai-Zhou Lu,Shun-Qing Shen,Titus Neupert,M. Zahid Hasan,Shuang Jia###

Signatures of the Adler-Bell-Jackiw chiral anomaly in a Weyl Fermion semimetal. Weyl semimetals provide the realization of Weyl fermions in solid-state
physics. Among all the physical phenomena that are enabled by Weyl semimetals,
the chiral anomaly is the most unusual one. Here, we report signatures of the
chiral anomaly in the magneto-transport measurements on the first Weyl
semimetal TaAs. We show negative magnetoresistance under parallel electric and
magnetic fields, that is, unlike most metals whose resistivity increases under
an external magnetic field, we observe that our high mobility TaAs samples
become more conductive as a magnetic field is applied along the direction of
the current for certain ranges of the field strength. We present systematically
detailed data and careful analyses, which allow us to exclude other possible
origins of the observed negative magnetoresistance. Our transport data,
corroborated by photoemission measurements, first-principles calculations and
theoretical analyses, collectively demonstrate signatures of the Weyl fermion
chiral anomaly in the magneto-transport of TaAs.

###Giant semiclassical magnetoresistance in high mobility TaAs2 semimetal|Desheng Wu,Jian Liao,Wei Yi,Xia Wang,Peigang Li,Hongming Weng,Youguo Shi,Yongqing Li,Jianlin Luo,Xi Dai,Zhong Fang###

Giant semiclassical magnetoresistance in high mobility TaAs2 semimetal. We report the observation of colossal positive magnetoresistance (MR) in
single crystalline, high mobility TaAs2 semimetal. The excellent fit of MR by a
single quadratic function of the magnetic field B over a wide temperature range
(T = 2-300 K) suggests the semiclassical nature of the MR. The measurements of
Hall effect and Shubnikov-de Haas oscillations, as well as band structure
calculations suggest that the giant MR originates from the nearly perfectly
compensated electrons and holes in TaAs2. The quadratic MR can even exceed
1,200,000% at B = 9 T and T = 2 K, which is one of the largest values among
those of all known semi-metallic compounds including the very recently
discovered WTe2 and NbSb2. The giant positive magnetoresistance in TaAs2, which
not only has a fundamentally different origin from the negative colossal MR
observed in magnetic systems, but also provides a nice complemental system that
will be beneficial for applications in magnetoelectronic devices

###Fermi surface topology and negative longitudinal magnetoresistance observed in centrosymmetric NbAs2 semimetal|Bing Shen,Xiaoyu Deng,Gabriel Kotliar,Ni Ni###

Fermi surface topology and negative longitudinal magnetoresistance observed in centrosymmetric NbAs2 semimetal. We report transverse and longitudinal magneto-transport properties of NbAs2
single crystals. Attributing to the electron-hole compensation, non-saturating
large transverse magnetoresistance reaches up to 8000 at 9 T at 1.8 K with
mobility around 1 to 2 m^2V^-1S^-1. We present a thorough study of
angular-dependent Shubnikov-de Haas (SdH) quantum oscillations of NbAs2. Three
distinct oscillation frequencies are identified. First-principles calculations
reveal four types of Fermi pockets: electron alpha pocket, hole beta pocket,
hole gamma pocket and small electron delta pocket. Although the angular
dependence of alpha, beta and delta agree well with the SdH data, it is unclear
why the gamma pocket is missing in SdH. Negative longitudinal magnetoresistance
is observed which may be linked to novel topological states in this material,
although systematic study is necessary to ascertain its origin.

###Subatomic mechanism of the oscillatory magnetoresistance in superconductors|Boris I. Ivlev###

Subatomic mechanism of the oscillatory magnetoresistance in superconductors. In the recent experiments the unusual oscillatory magnetoresistance in
superconductors was discovered with a periodicity essentially independent on
magnetic field direction and even material parameters. The nearly universal
period points to a subatomic mechanism of the phenomenon. This mechanism is
related to formation inside samples of subatomically thin ($10^{-11}cm$)
threads in the form of rings of the interatomic radius. Electron states of
rings go over into conduction electrons which carry the same spin imbalance in
energy as rings. The imbalance occurs due to spin interaction with the orbital
momentum of the ring. The conductivity near $T_c$ is determined by fluctuating
Cooper pairs consisting of electrons with shifted energies. Due to different
angular momenta of rings these energies periodically depend on magnetic field
resulting in the observed oscillatory magnetoresistance. Calculated universal
positions of peaks $(n+1/2)\Delta H$ ($\Delta H\simeq 0.18T$ and $n=0,1,2...$)
on the $R(H)$ curve are in a good agreement with experiments.

###Fourier analyses of commensurability oscillations in Fibonacci lateral superlattices|Akira Endo,Yasuhiro Iye###

Fourier analyses of commensurability oscillations in Fibonacci lateral superlattices. Magnetotransport measurements have been performed on Fibonacci lateral
superlattices (FLSLs) -- two-dimensional electron gases subjected to a weak
potential modulation arranged in the Fibonacci sequence, LSLLSLS..., with
L/S=tau (the golden ratio). Complicated commensurability oscillation (CO) is
observed, which can be accounted for as a superposition of a series of COs each
arising from a sinusoidal modulation representing the characteristic length
scale of one of the self-similar generations in the Fibonacci sequence.
Individual CO components can be separated out from the magnetoresistance trace
by performing a numerical Fourier band-pass filter. From the analysis of the
amplitude of a single-component CO thus extracted, the magnitude of the
corresponding Fourier component in the potential modulation can be evaluated.
By examining all the Fourier contents observed in the magnetoresistance trace,
the profile of the modulated potential seen by the electrons can be
reconstructed with some remaining ambiguity about the interrelation of the
phase between different components.

###Growth of (Ge,Mn) nanocolumns on GaAs(100): the role of morphology and co-doping on magnetotransport|Matthieu Jamet,Ing-Song Yu,Thibaut Devillers,André Barski,Pascale Bayle-Guillemaud,Cyrille Beigne,Johan Rothman,Vincent Baltz,Joel Cibert###

Growth of (Ge,Mn) nanocolumns on GaAs(100): the role of morphology and co-doping on magnetotransport. Changing the morphology of the growing surface and the nature of residual
impurities in (Ge,Mn) layers - by using different substrates - dramatically
changes the morphology of the ferromagnetic Mn-rich inclusions and the
magnetotransport properties. We obtained p-type layers with nanocolumns, either
parallel or entangled, and n-type layers with spherical clusters. Holes exhibit
an anomalous Hall effect, and electrons exhibit a tunneling magnetoresistance,
both with a clear dependence on the magnetization of the Mn-rich inclusions;
holes exhibit orbital MR, and electrons show only the normal Hall effect, and
an additional component of magnetoresistance due to weak localization, all
three being independent of the magnetic state of the Mn rich inclusions.
Identified mechanisms point to the position of the Fermi level of the Mn-rich
material with respect to the valence band of germanium as a crucial parameter
in such hybrid layers.

###Tailoring tunnel magnetoresistance by ultrathin Cr and Co interlayers: A first-principles investigation of Fe/MgO/Fe junctions|P. Bose,P. Zahn,J. Henk,I. Mertig###

Tailoring tunnel magnetoresistance by ultrathin Cr and Co interlayers: A first-principles investigation of Fe/MgO/Fe junctions. We report on systematic ab-initio investigations of Co and Cr interlayers
embedded in Fe(001)/MgO/Fe(001) magnetic tunnel junctions, focusing on the
changes of the electronic structure and the transport properties with
interlayer thickness. The results of spin-dependent ballistic transport
calculations reveal options to specifically manipulate the tunnel
magnetoresistance ratio. The resistance area products and the tunnel
magnetoresistance ratios show a monotonous trend with distinct oscillations as
a function of the Cr thickness. These modulations are directly addressed and
interpreted by means of magnetic structures in the Cr films and by complex band
structure effects. The characteristics for embedded Co interlayers are
considerably influenced by interface resonances which are analyzed by the local
electronic structure.

###Conductance in Co/Al2O3/Si/Al2O3 permalloy with asymmetrically doped barrier|R. Guerrero,F. G. Aliev,R. Villar,T. Santos,J. Moodera,V. K. Dugaev,J. Barnas###

Conductance in Co/Al2O3/Si/Al2O3 permalloy with asymmetrically doped barrier. Permalloy magnetic tunnel junctions. Complementary low frequency noise
measurements are used to understand the conductance results. The obtained data
indicate the breakdown of the Coulomb blockade for thickness of the asymmetric
silicon layer exceeding 1.2\AA . The crossover in the conductance, the
dependence of the tunnelling magnetoresistance with the bias voltage and the
noise below 80K correspond to 1 monolayer coverage. Interestingly, the zero
bias magnetoresistance remains nearly unaffected by the presence of the silicon
layer. The proposed model uses Larkin-Matveev approximation of tunnelling
through a single impurity layer generalized to 3D and takes into account the
variation of the barrier shape with the bias voltage. The main difference is
the localization of all the impurity levels within a single atomic layer. In
the high thickness case, up to 1.8\AA, we have introduced a phenomenological
parameter, which reflects the number of single levels on the total density of
silicon atoms.

###High pressure transport properties of the topological insulator Bi2Se3|J. J. Hamlin,J. R. Jeffries,N. P. Butch,P. Syers,D. A. Zocco,S. T. Weir,Y. K. Vohra,J. Paglione,M. B. Maple###

High pressure transport properties of the topological insulator Bi2Se3. We report x-ray diffraction, electrical resistivity, and magnetoresistance
measurements on Bi2Se3 under high pressure and low temperature conditions.
Pressure induces profound changes in both the room temperature value of the
electrical resistivity as well as the temperature dependence of the
resistivity. Initially, pressure drives Bi2Se3 towards increasingly insulating
behavior and then, at higher pressures, the sample appears to enter a fully
metallic state coincident with a change in the crystal structure. Within the
low pressure phase, Bi2Se3 exhibits an unusual field dependence of the
transverse magnetoresistance that is positive at low fields and becomes
negative at higher fields. Our results demonstrate that pressures below 8 GPa
provide a non-chemical means to controllably reduce the bulk conductivity of
Bi2Se3.

###Multidimensional Nature of Molecular Organic Conductors Revealed by Angular Magnetoresistance Oscillations|Pashupati Dhakal,Harukazu Yoshino,Jeong-Il Oh,Koichi Kikuchi,Michael J. Naughton###

Multidimensional Nature of Molecular Organic Conductors Revealed by Angular Magnetoresistance Oscillations. Angle dependent magnetoresistance experiments on organic conductors exhibit a
wide range of angular oscillations associated with the dimensionality and
symmetry of the crystal structure and electron energy dispersion. In
particular, characteristics associated with 1, 2, and 3 dimensional electronic
motion are separately revealed when a sample is rotated through different
crystal planes in a magnetic field. Originally discovered in the TMTSF based
conductors, these effects are particularly pronounced in the related system
(DMET)2I3. Here, experimental and computational results for magnetoresistance
oscillations in this material, over a wide range of magnetic field
orientations, are presented in such a manner as to uniquely highlight this
multidimensional behavior.The calculations employ the Boltzmann transport
equation that incorporates the systems triclinic crystal structure, which
allows for accurate estimates of the transfer integrals along the
crystallographic axes, verifying the 1d, 2d and 3d nature of (DMET)2I3, as well
as crossovers between dimensions in the electronic behavior.

###Magnetotransport through graphene nanoribbons at high magnetic fields|S. Minke,S. H. Jhang,J. Wurm,Y. Skourski,J. Wosnitza,C. Strunk,D. Weiss,K. Richter,J. Eroms###

Magnetotransport through graphene nanoribbons at high magnetic fields. We have investigated the magnetoresistance of lithographically prepared
single-layer graphene nanoribbons in pulsed, perpendicular magnetic fields up
to 60 T and performed corresponding transport simulations using a tight-binding
model and several types of disorder. In experiment, at high carrier densities
we observe Shubnikov-de Haas oscillations and the quantum Hall effect, while at
low densities the oscillations disappear and an initially negative
magnetoresistance becomes strongly positive at high magnetic fields. The strong
resistance increase at very high fields and low carrier densities is
tentatively ascribed to a field-induced insulating state in the bulk graphene
leads. Comparing numerical results and experiment, we demonstrate that at least
edge disorder and bulk short-range impurities are important in our samples.

###Anisotropic magneto-Coulomb effect versus spin accumulation in a ferromagnetic single-electron device|A. Bernand-Mantel,P. Seneor,K. Bouzehouane,S. Fusil,C. Deranlot,F. Petroff,A. Fert###

Anisotropic magneto-Coulomb effect versus spin accumulation in a ferromagnetic single-electron device. We investigate the magneto-transport characteristics of nanospintronics
single-electron devices. The devices consist of single non-magnetic
nano-objects (nanometer size nanoparticles of Al or Cu) connected to Co
ferromagnetic leads. The comparison with simulations allows us attribute the
observed magnetoresistance to either spin accumulation or anisotropic
magneto-Coulomb effect (AMC), two effects with very different origins. The fact
that the two effects are observed in similar samples demonstrates that a
careful analysis of Coulomb blockade and magnetoresistance behaviors is
necessary in order to discriminate them in magnetic single-electron devices. As
a tool for further studies, we propose a simple way to determine if spin
transport or AMC effect dominates from the Coulomb blockade I-V curves of the
spintronics device.

###Isothermal magnetic entropy behavior in Tb5Si3: Sign reversal and non-monotonic variation with temperature, and implications|Niharika Mohapatraa,Sitikantha D. Das,K. Mukherjee,E. V. Sampathkumaran###

Isothermal magnetic entropy behavior in Tb5Si3: Sign reversal and non-monotonic variation with temperature, and implications. The magnetic entropy change (\DeltaS), a measure of the magnetocaloric
effect, in Tb5Si3, a compound exhibiting unusual positive magnetoresistance
following a magnetic-field-induced transition below magnetic transition
temperature (~ 69 K), has been investigated. We found that \DeltaS is negative
in the paramagnetic state. At the magnetic transition temperature, \DeltaS
shows sign reversal from negative (in the paramagnetic state) to positive value
in the magnetically ordered state. The high-field state which is interestingly
the high resistive state is found to be associated with higher entropy i.e.
large positive \DeltaS, behaving like a paramagnet. On the basis of this
observation, we conclude that the magnetic field induces magnetic fluctuations
in the system resulting in positive magnetoresistance, thereby rendering
support to the idea of 'inverse metamagnetism' in this compound. In addition,
we note that Arrott plots present an interesting scenario.

###Theory of the ac spin-valve effect|Denis Kochan,Martin Gmitra,Jaroslav Fabian###

Theory of the ac spin-valve effect. The spin-valve complex magnetoimpedance of symmetric ferromagnet/normal
metal/ferromagnet junctions is investigated within the drift-diffusion
(standard) model of spin injection. The ac magnetoresistance---the real part
difference of the impedances of the parallel and antiparallel magnetization
configurations---exhibits an overall damped oscillatory behavior, as an
interplay of the diffusion and spin relaxation times. In wide junctions the ac
magnetoresistance oscillates between positive and negative values, reflecting
resonant amplification and depletion of the spin accumulation, while the line
shape for thin tunnel junctions is predicted to be purely Lorentzian. The ac
spin-valve effect could be a technique to extract spin transport and spin
relaxation parameters in the absence of a magnetic field and for a fixed sample
size.

###High-field magnetization and magnetoresistance of the $A$-site ordered perovskite oxide CaCu$_{3}$Ti$_{4-x}$Ru$_{x}$O$_{12}$~($0 \le x \le 4$)|T. Kida,R. Kammuri,M. Hagiwara,S. Yoshii,W. Kobayashi,M. Iwakawa,I. Terasaki###

High-field magnetization and magnetoresistance of the $A$-site ordered perovskite oxide CaCu$_{3}$Ti$_{4-x}$Ru$_{x}$O$_{12}$~($0 \le x \le 4$). We have measured high-field magnetization and magnetoresistance of
polycrystalline samples of the A-site ordered perovskite CaCu3Ti4-xRuxO12 (x=0
- 4) utilizing a non-destructive pulsed magnet. We find that the magnetization
for x=0.5, 1.0 and 1.5 is nonlinear, and tends to saturate in high fields. This
is highly nontrivial because the magnetization for x=0 and 4 is linear in
external field up to the highest one. We have analyzed this field dependence
based on the thermodynamics of magnetic materials, and propose that the
external fields delocalize the holes on the Cu2+ ions in order to maximize the
entropy. This scenario is qualitatively consistent with a large
magnetoresistance of -70% observed at 4.2 K at 52 T for x=1.5.

###Highly Dispersive Electron Relaxation and Colossal Thermoelectricity in the Correlated Semiconductor FeSb$_2$|Peijie Sun,Wenhu Xu,Jan M. Tomczak,Gabriel Kotliar,Martin Sondergaard,Bo B. Iversen,Frank Steglich###

Highly Dispersive Electron Relaxation and Colossal Thermoelectricity in the Correlated Semiconductor FeSb$_2$. We show that the colossal thermoelectric power, $S(T)$, observed in the
correlated semiconductor FeSb$_2$ below 30\,K is accompanied by a huge Nernst
coefficient $\nu(T)$ and magnetoresistance MR$(T)$. Markedly, the latter two
quantities are enhanced in a strikingly similar manner. While in the same
temperature range, $S(T)$ of the reference compound FeAs$_2$, which has a
seven-times larger energy gap, amounts to nearly half of that of FeSb$_2$, its
$\nu(T)$ and MR$(T)$ are intrinsically different to FeSb$_2$: they are smaller
by two orders of magnitude and have no common features. With the charge
transport of FeAs$_2$ successfully captured by the density functional theory,
we emphasize a significantly dispersive electron-relaxation time
$\tau(\epsilon_k)$ due to electron-electron correlations to be at the heart of
the peculiar thermoelectricity and magnetoresistance of FeSb$_2$.

###Epitaxial stabilization of ultra thin films of electron doped manganites|S. Middey,M. Kareev,D. Meyers,X. Liu,Y. Cao,S. Tripathi,P. Ryan,J. W. Freeland,J. Chakhalian###

Epitaxial stabilization of ultra thin films of electron doped manganites. Ultra-thin films of the electron doped manganite La$_{0.8}$Ce$_{0.2}$MnO$_3$
were grown in a layer-by-layer growth mode on SrTiO$_3$ (001) substrates by
pulsed laser interval deposition. High structural quality and surface
morphology was confirmed by a combination of synchrotron based x-ray
diffraction and atomic force microscopy. Resonant X-ray absorption spectroscopy
measurements confirm the presence of Ce$^{+4}$ and Mn$^{+2}$ ions. In addition,
the electron doping signature was corroborated by Hall effect measurements. All
grown films show ferromagnetic ground state as revealed by both XMCD and
magnetoresistance measurements and remain insulating contrary to earlier
reports of metal-insulator transition. Our results hint at the possibility of
electron-hole asymmetry in the colossal magnetoresistive (CMR) manganite phase
diagram akin to high-$T_c$ cuprates.

###Anisotropic giant magnetoresistance in NbSb2|Kefeng Wang,D. Graf,Lijun Li,C. Petrovic###

Anisotropic giant magnetoresistance in NbSb2. The extremely large transverse magnetoreistance (the magnetoresistant ratio
$\sim 1.3\times10^5\%$ in 2 K and 9 T field, and $4.3\times 10^6\%$ in 0.4 K
and 32 T field, without saturation), and the metal-semiconductor crossover
induced by magnetic field, are reported in NbSb$_2$ single crystal with
electric current parallel to the $b$-axis. The metal-semiconductor crossover is
preserved when the current is along the $ac$-plane but the magnetoresistant
ratio is significantly suppressed. The sign reversal of the Hall resistivity in
the field close to the crossover point, and the electronic structure
calculation reveals the coexistence of a small number of holes with very high
mobility and a large number of electrons with low mobility. These effects are
attributed to the change of the Fermi surface induced by the magnetic field.

###Large linear magnetoresistance in Dirac semi-metal Cd3As2 with Fermi surfaces close to the Dirac points|Junya Feng,Yuan Pang,Desheng Wu,Zhijun Wang,Hongming Weng,Jianqi Li,Xi Dai,Zhong Fang,Youguo Shi,Li Lu###

Large linear magnetoresistance in Dirac semi-metal Cd3As2 with Fermi surfaces close to the Dirac points. We have investigated the magnetoresistive behavior of Dirac semi-metal Cd3As2
down to low temperatures and in high magnetic fields. A positive and linear
magnetoresistance (LMR) as large as 3100% is observed in a magnetic field of 14
T, on high-quality single crystals of Cd3As2 with ultra-low electron density
and large Lande g factor. Such a large LMR occurs when the magnetic field is
applied perpendicular to both the current and the (100) surface, and when the
temperature is low such that the thermal energy is smaller than the Zeeman
splitting energy. Tilting the magnetic field or raising the temperature all
degrade the LMR, leading to a less pronounced quadratic behavior. We propose
that the phenomenon of LMR is related to the peculiar field-induced
shifting/distortion of the helical electrons' Fermi surfaces in momentum space.

###Transversal magnetoresistance in Weyl semimetals|J. Klier,I. V. Gornyi,A. D. Mirlin###

Transversal magnetoresistance in Weyl semimetals. We explore theoretically the magnetoresistvity of three-dimensional Weyl and
Dirac semimetals in transversal magnetic fields within two alternative models
of disorder: (i) short-range impurities and (ii) charged (Coulomb) impurities.
Impurity scattering is treated using the self-consistent Born approximation. We
find that an unusual broadening of Landau levels leads to a variety of regimes
of the resistivity scaling in the temperature-magnetic field plane. In
particular, the magnetoresitance is non-monotonous for the white-noise disorder
model. For $H\to 0$ the magnetoresistance for short-range impurities vanishes
in a non-analytic way as $H^{1/3}$. In the limits of strongest magnetic fields
$H$, the magnetoresistivity vanishes as $1/H$ for pointlike impurities, while
it is linear and positive in the model with Coulomb impurities.

###Electrical detection of magnetic skyrmions by non-collinear magnetoresistance|Christian Hanneken,Fabian Otte,André Kubetzka,Bertrand Dupé,Niklas Romming,Kirsten von Bergmann,Roland Wiesendanger,Stefan Heinze###

Electrical detection of magnetic skyrmions by non-collinear magnetoresistance. Magnetic skyrmions are localised non-collinear spin textures with high
potential for future spintronic applications. Skyrmion phases have been
discovered in a number of materials and a focus of current research is the
preparation, detection, and manipulation of individual skyrmions for an
implementation in devices. Local experimental characterization of skyrmions has
been performed by, e.g., Lorentz microscopy or atomic-scale tunnel
magnetoresistance measurements using spin-polarised scanning tunneling
microscopy. Here, we report on a drastic change of the differential tunnel
conductance for magnetic skyrmions arising from their non-collinearity: mixing
between the spin channels locally alters the electronic structure, making a
skyrmion electronically distinct from its ferromagnetic environment. We propose
this non-collinear magnetoresistance (NCMR) as a reliable all-electrical
detection scheme for skyrmions with an easy implementation into device
architectures.

###Pi Berry phase and Zeeman splitting of TaP probed by high field magnetotransport measurements|J. Hu,J. Y. Liu,D. Graf,S. M. A Radmanesh,D. J. Adams,A. Chuang,Y. Wang,I. Chiorescu,J. Wei,L. Spinu,Z. Q. Mao###

Pi Berry phase and Zeeman splitting of TaP probed by high field magnetotransport measurements. The chiral anomaly-induced negative magnetoresistance and non-trivial Berry
phase are two fundamental transport properties associated with the topological
properties of Weyl fermions. In this work, we report the quantum transport of
TaP single crystals in magnetic field up to 31T. Through the analyses of our
magnetotransport data, we show TaP has the signatures of a Weyl state,
including light effective quasiparticle masses, ultrahigh carrier mobility, as
well as negative longitudinal magnetoresistance. Furthermore, we have
generalized the Lifshitz-Kosevich formula for Shubnikov-de Haas (SdH)
oscillations with multi-frequencies, and determined the non-trivial Berry phase
of Pi for multiple Fermi pockets in TaP through the direct fitting of the
quantum oscillations. In high fields, we also probed signatures of Zeeman
splitting, from which the Land\'e g-factor is extracted.

###Magneto-transport behaviour of Bi2Se3-xTex: Role of disorder|E. P. Amaladass,T. R. Devidas,Shilpam Sharma,C. S. Sundar,A. Bharathi,Awadhesh Mani###

Magneto-transport behaviour of Bi2Se3-xTex: Role of disorder. Magnetoresistance and Hall resistance measurements have been carried out in
fastcooled single crystals of Bi2Se3-xTex (x: 0 to 2) in 4 to 300 K temperature
range, under magnetic fields up to 15 T. The variation of resistivity with
temperature that points to a metallic behaviour in Bi2Se3, shows an upturn at
low temperatures in the Te doped samples. Magnetoresistance measurements in
Bi2Se3 show clear signatures of Shubnikov de Hass oscillations that gets
suppressed in the Te doped samples. In the Bi2SeTe2 sample, the
magneto-resistance shows a cusp like positive magneto-resistance at low
magnetic fields and low temperatures, a feature associated with weak
antilocalisation (WAL), that crosses over to negative magneto-resistance at
higher fields. The qualitatively different magnetotransport behaviour seen in
Bi2SeTe2 as compared to Bi2Se3 is rationalised in terms of the disorder,
through an estimate of the carrier density, carrier mobility and an analysis in
terms of the Ioffe Regel criterion with support from Hall Effect measurements.

###Multiband effects and the possible Dirac states in LaAgSb$_2$|Kefeng Wang,C. Petrovic###

Multiband effects and the possible Dirac states in LaAgSb$_2$. Here we report the possible signature of Dirac fermions in the
magnetoresistance, Hall resistivity and magnetothermopower of LaAgSb$_2$. The
opposite sign between Hall resistivity and Seebeck coefficient indicates the
multiband effect. Electronic structure calculation reveals the existence of the
linear bands and the parabolic bands crossing the Fermi level. The large linear
magnetoresistance was attributed to the quantum limit of the possible Dirac
fermions or the breakdown of weak-field magnetotransport at the charge density
wave phase transition. Analysis of Hall resistivity using two-band model
reveals that Dirac holes which dominate the electronic transport have much
higher mobility and larger density than conventional electrons. Magnetic field
suppresses the apparent Hall carrier density, and also induces the sign change
of the Seebeck coefficient from negative to positive. These effects are
possibly attributed to the magnetic field suppression of the density of states
at the Fermi level originating from the quantum limit of the possible Dirac
holes.

###Low-frequency noise characterization of a magnetic field monitoring system using an anisotropic magnetoresistance|I. Mateos,J. Ramos-Castro,A. Lobo###

Low-frequency noise characterization of a magnetic field monitoring system using an anisotropic magnetoresistance. A detailed study about magnetic sensing techniques based on anisotropic
magnetoresistive sensors shows that the technology is suitable for
low-frequency space applications like the eLISA mission. Low noise magnetic
measurements at the sub-millihertz frequencies were taken by using different
electronic noise reduction techniques in the signal conditioning circuit. We
found that conventional modulation techniques reversing the sensor bridge
excitation do not reduce the potential $1/f$ noise of the magnetoresistors, so
alternative methods such as flipping and electro-magnetic feedback are
necessary. In addition, a low-frequency noise analysis of the signal
conditioning circuits has been performed in order to identify and minimize the
different main contributions from the overall noise. The results for chip-scale
magnetoresistances exhibit similar noise along the eLISA bandwidth ($0.1\,{\rm
mHz}-1\,{\rm Hz}$) to the noise measured by means of the voluminous fluxgate
magnetometers used in its precursor mission, known as LISA Pathfinder.

###Observation, Evidence and Origin of Room Temperature Magnetodielectric Effect in Mn doped LaGaO3|Hari Mohan Rai,Shailendra K. Saxena,Vikash Mishra,Rajesh Kumar,Pankaj R. Sagdeo###

Observation, Evidence and Origin of Room Temperature Magnetodielectric Effect in Mn doped LaGaO3. We report an observation of room temperature magnetodielectric (RTMD) effect
in Mn doped LaGaO3. Results of frequency dependent magnetoresistance (FDMR)
measurements discards the possibility of any magnetoresistive contribution in
the observed MD effect. The intrinsic nature of MD coupling has been
validated/evidenced by means of magnetic field dependent Raman spectroscopy and
explained in terms of modified volume strain governed by magnetic field induced
rerotation of spin coupled Mn-orbitals. Ultimately, present RTMD effect is
attributed to magneto-compression/magnetostriction associated with spin-phonon
coupling as evidenced in the form of magnetic field induced hardening of
symmetric stretching (SS) MnO6 octahedral Raman modes. Presently studied Mn
doped LaGaO3 can be a candidate for magnetodielectric applications.

###Magnetoresistance in copper at high frequency and high magnetic fields|Saebyeok Ahn,Sung Woo Youn,Jonghee Yoo,Dong Lak Kim,Junu Jeong,Moohyun Ahn,Jongkuk Kim,Doyu Lee,Jiyoung Lee,Taehyeon Seong,Yannis K. Semertzidis###

Magnetoresistance in copper at high frequency and high magnetic fields. In halo dark matter axion search experiments, cylindrical microwave cavities
are typically employed to detect signals from the axion-photon conversion. To
enhance the conversion power and reduce the noise level, cavities are placed in
strong solenoid magnetic fields at sufficiently low temperatures. Exploring
high mass regions in cavity-based axion search experiments requires high
frequency microwave cavities and thus understanding cavity properties at high
frequencies in extreme conditions is deemed necessary. We present a study of
the magnetoresistance of copper using a cavity with a resonant frequency of
12.9 GHz at the liquid helium temperature in magnetic fields up to 15 T
utilizing a second generation high temperature superconducting magnet. The
observations are interpreted to be consistent with the anomalous skin effect
and size effect. This is the first measurement of magnetoresistance at a high
frequency (> 10 GHz) in high magnetic fields (> 10 T).

###Transverse Magnetoresistance of Zn$_{0.9}$Co$_{0.1}$O:Al Thin Films|R. Martínez-Valdez,H. J. Jiménez-González,L. Angelats-Silva,M. Tomar###

Transverse Magnetoresistance of Zn$_{0.9}$Co$_{0.1}$O:Al Thin Films. The transverse magnetoresistance of thin films of the Diluted Magnetic
Semiconductor Zn$_{1-x}$Co$_{x}$O:Al on glass was studied for temperatures in
the range of 5 to 100 K. Measurements were made on thin films grown by rf
magnetron sputtering, with a thickness of approximately 200 nm. ZnO was alloyed
with Co to a concentration $x$ of 0.1 and co-doped with a 5.5% wt concentration
of Al. The electrical resistivity was measured along the sample surface by the
four-point probe method with a magnetic field of up to 4 T applied
perpendicular to the surface of the film. The experimental results of the
magnetoresistance have been interpreted by means of a semiclassical model that
combines a relaxation-time approximation to describe scattering processes in
ZnO and a phenomenological approach to the spin-disorder scattering due to the
indirect exchange interaction of the magnetic impurities.

###Magnetotransport properties of the new-type topological semimetal ZrTe|W. L. Zhu,J. B. He,S. Zhang,D. Chen,L. Shan,Z. A. Ren,G. F. Chen###

Magnetotransport properties of the new-type topological semimetal ZrTe. We report the first experimental results of the magnetoresistance, Hall
effect, and quantum Shubnikov-de Haas oscillations on single crystals of ZrTe,
which was recently predicted to be a new type of topological semimetal hosting
both triply degenerate crossing points and Weyl fermion state. The analysis of
Hall effect and quantum oscillations indicate that ZrTe is a multiband system
with low carrier density, high carrier mobility, small cross-sectional area of
Fermi surface, and light cyclotron effective mass, as observed in many
topological semimetals. Meanwhile, the angular dependence of the
magnetoresistance and the quantum-oscillation frequencies further suggest that
ZrTe possesses a three-dimensional Fermi surface that is rather complex. Our
results provide a new platform to realize exotic quantum phenomena related to
the new three-component fermions distinct from Dirac and Weyl fermions.

###Extremely large magnetoresistance and Fermi surface topology of PrSb|F. Wu,C. Y. Guo,M. Smidman,J. L. Zhang,H. Q. Yuan###

Extremely large magnetoresistance and Fermi surface topology of PrSb. We report magnetotransport measurements of PrSb in high magnetic fields. Our
results show that PrSb exhibits extremely large magnetoresistance(XMR) at low
temperatures. Meanwhile angle-dependent magnetoresistance measurements were
used to probe the Fermi surface via Shubnikov-de Haas (SdH) oscillations. The
angular dependence of the frequencies of the $\alpha$-branch indicate a
two-dimensional character for this Fermi surface sheet, while the effective
mass of this branch as a function of angle shows a four-fold signature. The
evolution of the Fermi surface with field was also studied up to 32~T. An
enlargement of the Fermi surface up to 14~T is observed, before the oscillation
frequencies become constant at higher fields. Meanwhile our analysis of the
residual Landau index from the high field data reveals a zero Berry phase and
therefore trivial topology of the Fermi surface.

###Spin superfluid Josephson oscillator|Yizhou Liu,Igor Barsukov,Ilya Krivorotov,Yafis Barlas,Roger K. Lake###

Spin superfluid Josephson oscillator. The magnetic analogue of the Josephson effect can be exploited to develop a
new class of nano-spin oscillators that we denote as spin superfluid Josephson
oscillators. Such a device, consisting of two exchange coupled easy-plane
metallic ferromagnets separated by a thin normal metal spacer, is proposed and
analyzed. A spin chemical potential difference drives a $2\pi$ precession of
the in-plane magnetization of each ferromagnet. The $2 \pi$ precession angle
gives maximum values of the giant magnetoresistance, resulting in large output
power compared to conventional spin Hall oscillators. An applied ac current
results in a time-averaged magnetoresistance with Shapiro-like steps. The
multistate mode-locking behavior exhibited by the spin Shapiro steps may be
explored for applications in neuromorphic computing. As an experimental
characterization method, electrical measurements of spin superfluid Josephson
junctions can provide additional signatures of spin superfluidity.

###Tunable superconductivity in parent cuprate Pr$_{2}$CuO$_{4\pmδ}$ thin films|Xinjian Wei,Ge He,Wei Hu,Xu Zhang,Mingyang Qin,Jie Yuan,Beiyi Zhu,Yuan Lin,Kui Jin###

Tunable superconductivity in parent cuprate Pr$_{2}$CuO$_{4\pmδ}$ thin films. In this article, we studied the role of oxygen in Pr$_{2}$CuO$_{4\pm\delta}$
thin films fabricated by polymer assisted deposition method. The
magnetoresistance and Hall resistivity of Pr$_{2}$CuO$_{4\pm\delta}$ samples
were systematically investigated. It is found that with decreasing the oxygen
content, the low-temperature Hall coefficient ($R_H$) and magnetoresistance
change from negative to positive, similar to those with the increase of
Ce-doped concentration in R$_{2-x}$Ce$_{x}$CuO$_{4}$ (R= La, Nd, Pr, Sm, Eu).
In addition, $T_c$ versus $R_H$ for both Pr$_{1-x}$LaCe$_{x}$CuO$_{4}$ and
Pr$_{2}$CuO$_{4\pm\delta}$ samples can coincide with each other. We conclude
that the doped electrons induced by the oxygen removal are responsible for the
superconductivity of $T^\prime$-phase parent compounds.

###Effect of B-site bismuth doping on magnetic and transport properties of La0.5Ca0.5Mn1-xBixO3 thin films|Himanshu Sharma,Deepak Kumar,Ashwin Tulapurkar,C. V. Tomy###

Effect of B-site bismuth doping on magnetic and transport properties of La0.5Ca0.5Mn1-xBixO3 thin films. The magnetic properties in manganite have been found to be highly sensitive
to the doping and structural manipulations. Here, we report the effect of
B-site bismuth doping on the magnetic and transport properties in
La0.5Ca0.5Mn1-xBixO3 (LCMBO) thin films (for x = 0, 0.02 and 0.05) for
high-efficiency spintronics devices. For thin film of LCMBO (with x = 0.02), a
significant increase in the magnetization and ferromagnetic ordering
temperature (TC) are observed. Also, about 98% magnetoresistance (MR) and
unusually large (~ 42%) anisotropic magnetoresistance (AMR) is observed at 50 K
in the same LCMBO (for x = 0.02) thin film. This observed improvement in TC, MR
and AMR in LCMBO (with x = 0.02) thin film may be attributed to the modulation
of the trapped electrons through JT-distortions due to the replacement of Mn+3
ions by larger Bi+3 ions. With further increase in bismuth doping (for x =
0.05) at the B-site, a significant decrease in magnetization and TC have been
observed.

###Magnetic oscillations of in-plane conductivity in quasi-two-dimensional metals|T. I. Mogilyuk,P. D. Grigoriev###

Magnetic oscillations of in-plane conductivity in quasi-two-dimensional metals. We develop the theory of transverse magnetoresistance in layered
quasi-two-dimensional metals. Using the Kubo formula and harmonic expansion, we
calculate intralayer conductivity in a magnetic field perpendicular to
conducting layers. The analytical expressions for the amplitudes and phases of
magnetic quantum oscillations (MQO) and of the so-called slow oscillations
(SlO) are derived and applied to analyze their behavior as a function of
several parameters: magnetic field strength, interlayer transfer integral and
the Landau-level width. Both the MQO and SlO of intralayer and interlayer
conductivities have approximately opposite phase in weak magnetic field and the
same phase in strong field. The amplitude of SlO of intralayer conductivity
changes sign at $\omega_c\tau_0=\sqrt{3}$. There are several other qualitative
difference between magnetic oscillations of in-plane and out-of-plane
conductivity. The results obtained are useful to analyze experimental data on
magnetoresistance oscillations in various strongly anisotropic quasi-2D metals.

###Magnetotransport properties and giant anomalous Hall angle in half-Heusler compound TbPtBi|Ratnadwip Singha,Shubhankar Roy,Arnab Pariari,Biswarup Satpati,Prabhat Mandal###

Magnetotransport properties and giant anomalous Hall angle in half-Heusler compound TbPtBi. Magnetic lanthanide half-Heuslers ($R$PtBi; $R$ being the lanthanide)
represent an attractive subgroup of the Heusler family and have been identified
as ideal candidates for time reversal symmetry breaking topological Weyl
semimetals. In this paper, we present the detailed analysis of the
magnetotransport properties of frustrated antiferromagnet TbPtBi. This material
shows large, non-saturating magnetoresistance (MR) with unusual magnetic field
dependence. The MR of TbPtBi is significantly anisotropic with respect to the
magnetic field, applied along different crystallographic directions and
indicates the anisotropic nature of the Fermi surface. The chiral anomaly
induced negative longitudinal magnetoresistance confirms the presence of Weyl
fermions. At low temperature, Berry phase driven large anomalous Hall
conductivity has been observed. The calculated anomalous Hall angle is the
largest reported so far.

###Magnetic-field control of topological electronic response near room temperature in correlated Kagome magnets|Yangmu Li,Qi Wang,Lisa DeBeer-Schmitt,Zurab Guguchia,Ryan D. Desautels,Jiaxin Yin,Qianheng Du,Weijun Ren,Xinguo Zhao,Zhidong Zhang,Igor A. Zaliznyak,Cedomir Petrovic,Weiguo Yin,M. Zahid Hasan,Hechang Lei,John M. Tranquada###

Magnetic-field control of topological electronic response near room temperature in correlated Kagome magnets. Strongly correlated Kagome magnets are promising candidates for achieving
controllable topological devices owing to the rich interplay between inherent
Dirac fermions and correlation-driven magnetism. Here we report tunable local
magnetism and its intriguing control of topological electronic response near
room temperature in the Kagome magnet Fe3Sn2 using small angle neutron
scattering, muon spin rotation, and magnetoresistivity measurement techniques.
The average bulk spin direction and magnetic domain texture can be tuned
effectively by small magnetic fields. Magnetoresistivity, in response, exhibits
a measurable degree of anisotropic weak localization behavior, which allows the
direct control of Dirac fermions with strong electron correlations. Our work
points to a novel platform for manipulating emergent phenomena in
strongly-correlated topological materials relevant to future applications.

###Image of dynamic local exchange interactions in the dc magnetoresistance of spin-polarized current through a dopant|Stephen R. McMillan,Nicholas J. Harmon,Michael E. Flatté###

Image of dynamic local exchange interactions in the dc magnetoresistance of spin-polarized current through a dopant. We predict strong, dynamical effects in the dc magnetoresistance of current
flowing from a spin-polarized electrical contact through a magnetic dopant in a
nonmagnetic host. Using the stochastic Liouville formalism we calculate
clearly-defined resonances in the dc magnetoresistance when the applied
magnetic field matches the exchange interaction with a nearby spin. At these
resonances spin precession in the applied magnetic field is canceled by spin
evolution in the exchange field, preserving a dynamic bottleneck for spin
transport through the dopant. Similar features emerge when the dopant spin is
coupled to nearby nuclei through the hyperfine interaction. These features
provide a precise means of measuring exchange or hyperfine couplings between
localized spins near a surface using spin-polarized scanning tunneling
microscopy, without any ac electric or magnetic fields, even when the exchange
or hyperfine energy is orders of magnitude smaller than the thermal energy.

###Large negative magnetoresistance in the new antiferromagnetic rare-earth dichalcogenide EuTe$_2$|Junjie Yin,Changwei Wu,Lisi Li,Jia Yu,Hualei Sun,Bing Shen,Benjamin A. Frandsen,Dao-Xin Yao,Meng Wang###

Large negative magnetoresistance in the new antiferromagnetic rare-earth dichalcogenide EuTe$_2$. We report the synthesis and characterization of a rare-earth dichalcogenide
EuTe$_2$. An antiferromagnetic transition was found at T$_M$ = 11 K. The
antiferromagnetic order can be tuned by an applied magnetic field to access a
first-order spin flop transition and a spin flip transition. These transitions
are associated with a giant negative magnetoresistance with a value of nearly
100\%. Heat capacity measurements reveal strong electronic correlations and a
reduced magnetic entropy. Furthermore, density functional theory calculations
demonstrate that the electrons near the Fermi surface mainly originate from the
Te 5$p$ orbitals and the magnetism is dominated by localized electrons from the
Eu 4$f$ orbitals. These results suggest that both the RKKY and Kondo
interactions between the local moments and itinerant electrons play crucial
roles in the magnetism and large negative magnetoresistance of EuTe$_2$.

###Quenching of an antiferromagnet into high resistivity states using electrical or ultrashort optical pulses|Zdeněk Kašpar,Miloslav Surýnek,Jan Zubáč,Filip Krizek,Vít Novák,Richard P. Campion,Martin S. Wörnle,Pietro Gambardella,Xavier Marti,Petr Němec,K. W. Edmonds,S. Reimers,O. J. Amin,F. Maccherozzi,S. S. Dhesi,Peter Wadley,Jörg Wunderlich,Kamil Olejník,Tomáš Jungwirth###

Quenching of an antiferromagnet into high resistivity states using electrical or ultrashort optical pulses. Ultra-fast dynamics, insensitivity to external magnetic fields, or absence of
magnetic stray fields are examples of properties that make antiferromagnets of
potential use in the development of spintronic devices. Similar to their
ferromagnetic counterparts, antiferromagnets can store information in the
orientations of the collective magnetic order vector. However, also in analogy
to ferromagnets, the readout magnetoresistivity signals in simple
antiferromagnetic films have been weak and the extension of the electrical
reorientation mechanism to optics has not been achieved. Here we report
reversible and reproducible quenching of an antiferromagnetic CuMnAs film by
either electrical or ultrashort optical pulses into nano-fragmented domain
states. The resulting resistivity changes approach 20\% at room temperature,
which is comparable to the giant magnetoresistance ratios in ferromagnetic
multilayers. We also obtain a signal readout by optical reflectivity. The
analog time-dependent switching and relaxation characteristics of our devices
can mimic functionality of spiking neural network components.

###Experimental evidence of spin-orbit torque from metallic interfaces|A. Anadón,R. Guerrero,J. A. Jover-Galtier,A. Gudín,J. M. Díez,P. Olleros-Rodríguez,R. Miranda,J. Camarero,P. Perna###

Experimental evidence of spin-orbit torque from metallic interfaces. Spin currents can modify the magnetic state of ferromagnetic ultrathin films
through spin-orbit torque. They may be generated by means of spin-orbit
interaction by either bulk or interfacial phenomena. Electrical transport
measurements reveal a six-fold increase of the spin-orbit torque accompanied by
a drastic reduction of the spin Hall magnetoresistance upon the introduction of
a Cu interlayer in a Pt/Cu/Co/Pt structure with perpendicular magnetic
anisotropy. We analyze the dependence of the spin Hall magnetoresistance with
the thickness of the interlayer in the frame of a drift diffusion model that
provides information on the expected spin currents and spin accumulations in
the system. The results demonstrate that the major responsible of both effects
is spin memory loss at the interface. The enhancement of the spin-orbit torque
when introducing an interlayer opens the possibility to design more effient
spintronic devices based on materials that are cheap and abundant such as
copper.

###Field-dependent anisotropic magnetoresistance and planar Hall effect in epitaxial magnetite thin films|N. Naftalis,A. Kaplan,M. Schultz,C. A. F. Vaz,J. A. Moyer,C. H. Ahn,L. Klein###

Field-dependent anisotropic magnetoresistance and planar Hall effect in epitaxial magnetite thin films. A systematic study of the temperature and magnetic field dependence of the
longitudinal and transverse resistivities of epitaxial thin films of magnetite
(Fe3O4) is reported. The anisotropic magnetoresistance (AMR) and the planar
Hall effect (PHE) are sensitive to the in-plane orientation of current and
magnetization with respect to crystal axes in a way consistent with the cubic
symmetry of the system. We also show that the AMR exhibit sign reversal as a
function of temperature, and that it shows significant field dependence without
saturation up to 9 T. Our results provide a unified description of the
anisotropic magnetoresistance effects in epitaxial magnetite films and
illustrate the need for a full determination of the resistivity tensor in
crystalline systems.

###Magnetic order and superconductivity observed in bundles of Double-Wall Carbon Nanotubes|J. Barzola-Quiquia,P. Esquinazi,M. Lindel,D. Spemann,M. Muallem,G. D. Nessim###

Magnetic order and superconductivity observed in bundles of Double-Wall Carbon Nanotubes. The magnetotransport properties were studied in hundreds of micrometer length
double-wall carbon nanotubes (DWCNT) bundles. Above 15 K the resistance shows
an ohmic behavior and its temperature dependence is well described using the
variable-range hopping for one-dimensional system. The magnetoresistance is
negative and can be explained using an empirical model based on spin-scattering
processes indicating the existence of magnetic order up to room temperature. At
temperatures between 2 K and 15 K the resistance is non-ohmic and the
current-voltage characteristics reveal the appearance of a potential, which can
be well described by a fluctuation-induced tunneling conduction model. In this
low temperature range and at low enough input current, a positive
magnetoresistance appears - in addition to the negative one - with an
extraordinary hysteresis in field and vanishes at $T \sim 15 $K, suggesting the
existence of a superconducting state. Magnetization results partially support
the existence of both phenomena in the DWCNT bundles.

###Commensurability resonances in two-dimensional magneto-electric lateral superlattices|J. Schluck,S. Fasbender,T. Heinzel,K. Pierz,H. W. Schumacher,D. Kazazis,U. Gennser###

Commensurability resonances in two-dimensional magneto-electric lateral superlattices. Hybrid lateral superlattices composed of a square array of antidots and a
periodic one-dimensional magnetic modulation are prepared in
$\mathrm{Ga[Al]As}$ heterostructures. The two-dimensional electron gases
exposed to these superlattices are characterized by magnetotransport
experiments in vanishing average perpendicular magnetic fields. Despite the
absence of closed orbits, the diagonal magnetoresistivity in the direction
perpendicular to the magnetic modulation shows pronounced classical resonances.
They are located at magnetic fields where snake trajectories exist which are
quasi-commensurate with the antidot lattice. The diagonal magnetoresistivity in
the direction of the magnetic modulation increases sharply above a threshold
magnetic field and shows no fine structure. The experimental results are
interpreted with the help of numerical simulations based on the semiclassical
Kubo model.

###Superconductor-insulator transitions: Phase diagram and magnetoresistance|I. S. Burmistrov,I. V. Gornyi,A. D. Mirlin###

Superconductor-insulator transitions: Phase diagram and magnetoresistance. Influence of disorder-induced Anderson localization and of electron-electron
interaction on superconductivity in two-dimensional systems is explored. We
determine the superconducting transition temperature $T_c$, the temperature
dependence of the resistivity, the phase diagram, as well as the
magnetoresistance. The analysis is based on the renormalization group (RG) for
a nonlinear sigma model. Derived RG equations are valid to the lowest order in
disorder but for arbitrary electron-electron interaction strength in
particle-hole and Cooper channels. Systems with preserved and broken
spin-rotational symmetry are considered, both with short-range and with
long-range (Coulomb) interaction. In the cases of short-range interaction, we
identify parameter regions where the superconductivity is enhanced by
localization effects. Our RG analysis indicates that the
superconductor-insulator transition is controlled by a fixed point with a
resistivity $R_c$ of the order of the quantum resistance $R_q = h/ 4e^2$. When
a transverse magnetic field is applied, we find a strong nonmonotonous
magnetoresistance for temperatures below $T_c$.

###Nature of magnetotransport in metal/insulating-ferromagnet heterostructures: Spin Hall magnetoresistance or magnetic proximity effect|Xiang Zhou,Li Ma,Zhong Shi,Wei-Jia Fan,Jian-Guo Zheng,R. F. L. Evans,Shi-Ming Zhou###

Nature of magnetotransport in metal/insulating-ferromagnet heterostructures: Spin Hall magnetoresistance or magnetic proximity effect. We study the anomalous Hall-like effect (AHLE) and the effective anisotropic
magnetoresistance (EAMR) in antiferromagnetic {\gamma} -IrMn3/Y3Fe5O12(YIG) and
Pt/YIG heterostructures. For {\gamma} -IrMn3/YIG, the EAMR and the AHLE
resistivity change sign with temperature due to the competition between the
spin Hall magnetoresistance (SMR) and the magnetic proximity effect (MPE)
induced by the interfacial antiferromagnetic uncompensated magnetic moment. In
contrast, for Pt/YIG the AHLE resistivity changes sign with temperature whereas
no sign change is observed in the EAMR. This is because the MPE and the SMR
play a dominant role in the AHLE and the EAMR, respectively. As new types of
galvanomagnetic property, the AHLE and the EAMR have proved vital in
disentangling the MPE and the SMR in metal/insulating-ferromagnet
heterostructures.

###Negative magnetoresistance in viscous flow of two-dimensional electrons|P. S. Alekseev###

Negative magnetoresistance in viscous flow of two-dimensional electrons. At low temperatures, in very clean two-dimensional (2D) samples the electron
mean free path for collisions with static defects and phonons becomes greater
than the sample width. Under this condition, the electron transport occurs by
formation of a viscous flow of an electron fluid. We study the viscous flow of
2D electrons in a magnetic field perpendicular to the 2D layer. We calculate
the viscosity coefficients as the functions of magnetic field and temperature.
The off-diagonal viscosity coefficient determines the dispersion of the 2D
hydrodynamic waves. The decrease of the diagonal viscosity in magnetic field
leads to negative magnetoresistance which is temperature- and size dependent.
Our analysis demonstrates that the viscous mechanism is responsible for the
giant negative magnetoresistance recently observed in the ultra-high-mobility
GaAs quantum wells. We conclude that 2D electrons in that structures in
moderate magnetic fields should be treated as a viscous fluid.

###Anisotropic Ginzburg-Landau scaling of Hc2 and transport properties of 112-type Ca0.8La0.2Fe0.98Co0.02As2 single crystal|Xiangzhuo Xing,Wei Zhou,Nan Zhou,Feifei Yuan,Yongqiang Pan,Haijun Zhao,Xiaofeng Xu,Zhixiang Shi###

Anisotropic Ginzburg-Landau scaling of Hc2 and transport properties of 112-type Ca0.8La0.2Fe0.98Co0.02As2 single crystal. High-quality single crystal of Ca0.8La0.2Fe0.98Co0.02As2 has been
successfully synthesized using a self-flux method. The magnetization
measurement reveals a second peak effect and high critical current density
exceeding 2*10^6 A/cm2 at 5 K(self-field). The upper critical field anisotropy
was systematically studied by measuring the electrical resistivity under
various magnetic fields and angles. The angle dependent magnetoresistance, by
choosing an appropriate anisotropy parameter within the framework of the
anisotropic Ginzburg Landau (AGL) theory, can be scaled onto one single curve.
In the normal state, the negative Hall coefficient shows strong but
nonmonotonic T-dependence through a minimum at 175 K. Moreover, it is shown
that the magnetoresistance apparently violates the semiclassical Kohler's rule
below 175 K but can be well scaled by the Hall angle instead. This suggests
either the change of carriers with T or the exotic anisotropic scattering in
the system.

###Electrical Writing of Magnetic and Resistive Multistates in CoFe Films Deposited onto Pb[Zr$_x$Ti$_{1-x}$]O$_3$|V. Iurchuk,B. Doudin,J. Bran,B. Kundys###

Electrical Writing of Magnetic and Resistive Multistates in CoFe Films Deposited onto Pb[Zr$_x$Ti$_{1-x}$]O$_3$. Electric control of magnetic properties is an important challenge for modern
magnetism and spintronic development. In particular, an ability to write
magnetic state electrically would be highly beneficial. Among other methods,
the use of electric field induced deformation of piezoelectric elements is a
promising low-energy approach for magnetization control. We investigate the
system of piezoelectric substrate Pb[Zr$_x$Ti$_{1-x}$]O$_3$ with CoFe
overlayers, extending the known reversible bistable electro-magnetic coupling
to surface and multistate operations, adding the initial state reset
possibility. Increasing the CoFe thickness improves the magnetoresistive
sensitivity, but at the expenses of decreasing the strain-mediated coupling,
with optimum magnetic thin film thickness of the order of 100 nm. The simplest
resistance strain gauge structure is realized and discussed as a multistate
memory cell demonstrating both resistive memory (RRAM) and magnetoresistive
memory (MRAM) functionalities in a single structure.

###Extremely large magnetoresistance in a topological semimetal candidate pyrite PtBi2|Wenshuai Gao,Ningning Hao,Fa-Wei Zheng,Wei Ning,Min Wu,Xiangde Zhu,Guolin Zheng,Hongwei Zhang,Jinglei Zhang,Chuanying Xi,Jiyong Yang,Haifeng Du,Ping Zhang,Yuheng Zhang,Mingliang Tian###

Extremely large magnetoresistance in a topological semimetal candidate pyrite PtBi2. While pyrite-type PtBi2 with face-centered cubic structure has been predicted
to be a three-dimensional (3D) Dirac semimetal, experimental study on its
physical properties remains absent. Here we report the angular-dependent
magnetoresistance (MR) measurements of PtBi2 single-crystal under high magnetic
fields. We observed extreme large unsaturated magnetoresistance (XMR) up to
11.2 million percent at T = 1.8 K in a magnetic field of 33 T, which surpasses
the previously reported Dirac materials, such as WTe2, LaSb and NbP. The
crystals exhibit an ultrahigh mobility and significant Shubnikov-de Hass (SdH)
quantum oscillations with nontrivial Berry's phase. Analysis of Hall
resistivity indicates that the XMR can be ascribed to the nearly compensated
electron and hole. Our experimental results associated with the ab initio
calculations suggest that pyrite PtBi2 is a topological semimetal candidate
which might provide a platform for exploring topological materials with XMR in
noble metal alloys.

###Temperature effect on lattice and electronic structures of WTe$_2$ from first-principles study|Gang Liu,Huimei Liu,Jian Zhou,Xiangang Wan###

Temperature effect on lattice and electronic structures of WTe$_2$ from first-principles study. Tungsten ditelluride (WTe$_2$) exhibits extremely large and unsaturated
magnetoresistance (MR). Due to the large spatially extensions of Te-5p and W-5d
orbitals, the electronic properties of WTe$_2$ are sensitive to the lattice
structures, which can probably affect the strongly temperature dependent MR
found in experiment. Based on first-principle calculations, we investigate the
temperature effect on the lattice and electronic structures of WTe$_2$. Our
numerical results show that the thermal expansion coefficients of WTe$_2$ are
highly anisotropic and considerably large. However, the temperature (less than
300 K) has ignorable effect on the Fermi surface of WTe$_2$. Our theoretical
results clarify that the thermal expansion is not the main reason of the
temperature-induced rapid decrease of magnetoresistance.

###Thickness dependence of spin Hall magnetoresistance in FeMn/Pt bilayers|Yumeng Yang,Yanjun Xu,Kui Yao,Yihong Wu###

Thickness dependence of spin Hall magnetoresistance in FeMn/Pt bilayers. We investigated spin Hall magnetoresistance in FeMn/Pt bilayers, which was
found to be one order of magnitude larger than that of heavy metal and
insulating ferromagnet or antiferromagnet bilayer systems, and comparable to
that of NiFe/Pt bilayers. The spin Hall magnetoresistance shows a non-monotonic
dependence on the thicknesses of both FeMn and Pt. The former can be accounted
for by the thickness dependence of net magnetization in FeMn thin films,
whereas the latter is mainly due to spin accumulation and diffusion in Pt.
Through analysis of the Pt thickness dependence, the spin Hall angle, spin
diffusion length of Pt and the real part of spin mixing conductance were
determined to be 0.2, 1.1 nm, and $5.5 * 10^{14} {\Omega}^{-1} m^{-2}$,
respectively. The results corroborate the spin orbit torque effect observed in
this system recently.

###Structural-transition-induced quasi two-dimensional Fermi surface in FeSe|Yue Sun,Tatsuhiro Yamada,Sunseng Pyon,Tsuyoshi Tamegai###

Structural-transition-induced quasi two-dimensional Fermi surface in FeSe. We report detailed study of angular-dependent magnetoresistance (AMR) with
tilting angel $\theta$ from $c$-axis ranging from 0$^\circ$ to 360$^\circ$ on a
high-quality FeSe single crystal. A pronounced AMR with twofold symmetry is
observed, which is caused by the quasi two-dimensional (2D) Fermi surface. The
pronounced AMR is observed only in the orthorhombic phase, indicating that the
quasi-2D Fermi surface is induced by the structural transition. Details about
the influence of the multiband effect to the AMR are also discussed. Besides,
the angular response of a possible Dirac-cone-like band structure is
investigated by analyzing the detailed magnetoresistance at different $\theta$.
The obtained characteristic field ($B^*$) can be also roughly scaled in the 2D
approximation, which indicates that the Dirac-cone-like state is also 2D in
nature.

###Giant Positive Magnetoresistance and field-induced metal insulator transition in Cr2NiGa|S. Pramanick,P. Dutta,S. Chatterjee,S. Giri,S. Majumdar###

Giant Positive Magnetoresistance and field-induced metal insulator transition in Cr2NiGa. We report here the magneto-transport properties of the newly synthesized
Heusler compound Cr2NiGa which crystallizes in a disordered cubic B2 structure
belonging to Pm-3m space group. The sample is found to be paramagnetic down to
2 K with metallic character. On application of magnetic field, a significantly
large increase in resistivity is observed which corresponds to
magnetoresistance as high as 112% at 150 kOe of field at the lowest
temperature. Most remarkably, the sample shows negative temperature coefficient
of resistivity below about 50 K under the application of field gretare than or
equal to 80 kOe, signifying a field-induced metal to `insulating' transition.
The observed magnetoresistance follows Kohler's rule below 20 K indicating the
validity of the semiclassical model of electronic transport in metal with a
single relaxation time. A multi-band model for electronic transport, originally
proposed for semimetals, is found to be appropriate to describe the
magneto-transport behavior of the sample.

###Resistive Switching and Voltage Induced Modulation of Tunneling Magnetoresistance in Nanosized Perpendicular Organic Spin Valves|Robert Göckeritz,Nico Homonnay,Alexander Müller,Bodo Fuhrmann,Georg Schmidt###

Resistive Switching and Voltage Induced Modulation of Tunneling Magnetoresistance in Nanosized Perpendicular Organic Spin Valves. Nanoscale multifunctional perpendicular organic spin valves have been
fabricated. The devices based on an La$_{0.7}$Sr$_{0.3}$MnO$_3$/Alq$_3$/Co
trilayer show resistive switching of up to 4-5 orders of magnitude and
magnetoresistance as high as -70% the latter even changing sign when voltage
pulses are applied. This combination of phenomena is typically observed in
multiferroic tunnel junctions where it is attributed to magnetoelectric
coupling between a ferromagnet and a ferroelectric material. Modeling indicates
that here the switching originates from a modification of the
La$_{0.7}$Sr$_{0.3}$MnO$_3$ surface. This modification influences the tunneling
of charge carriers and thus both the electrical resistance and the tunneling
magnetoresistance which occurs at pinholes in the organic layer.

###Controlled Electrode Magnetization Alignment in Planar Elliptical Ferromagnetic Break Junction Devices|Gavin D. Scott,Ting-Chen Hu###

Controlled Electrode Magnetization Alignment in Planar Elliptical Ferromagnetic Break Junction Devices. Controlling the magnetization reversal process of magnetic elements is
important for a wide range of applications that make use of magnetoresistive
effects, but is difficult to achieve for devices that require adjacent thin
film structures capable of contacting an individual molecule or quantum dot. We
report on the fabrication and measurement of ferromagnetic break junction
devices with planar, elliptical leads to address the particular challenge of
controlling the relative magnetization alignment between neighboring
electrodes. Low temperature transport measurements, supported by finite-element
micromagnetic simulations, are used to characterize the magnetoresistance
response across a range of conductance levels. We demonstrate that an in-plane
external field applied parallel to the hard axis of the ellipses may be used to
controllably switch the magnetization of the source and drain electrodes
between monodomain-like parallel and antiparallel configurations for devices in
the tunneling regime.

###Impact of Anisotropy on Antiferromagnet Rotation in Heusler-type Ferromagnet/Antiferromagnet Epitaxial Bilayers|T. Hajiri,M. Matsushita,Y. Z. Ni,H. Asano###

Impact of Anisotropy on Antiferromagnet Rotation in Heusler-type Ferromagnet/Antiferromagnet Epitaxial Bilayers. We report the magnetotransport properties of ferromagnet (FM)/antiferromagnet
(AFM) Fe$_2$CrSi/Ru$_2$MnGe epitaxial bilayers using current-in-plane
configurations. Above the critical thickness of the Ru$_2$MnGe layer to induce
exchange bias, symmetric and asymmetric curves were observed in response to the
direction of FM magnetocrystalline anisotropy. Because each magnetoresistance
curve showed full and partial AFM rotation, the magnetoresistance curves imply
the impact of the Fe$_2$CrSi magnetocrystalline anisotropy to govern the AFM
rotation. The maximum magnitude of the angular-dependent resistance-change
ratio of the bilayers is more than an order of magnitude larger than that of
single-layer Fe$_2$CrSi films, resulting from the reorientation of AFM spins
via the FM rotation. These results highlight the essential role of controlling
the AFM rotation and reveal a facile approach to detect the AFM moment even in
current-in-plane configurations in FM/AFM bilayers.

###Strong Electron-Phonon Interaction and Colossal Magnetoresistance in EuTiO$_3$|Ruofan Chen,Ji-Chang Ren,Km Rubi,R. Mahendiran,Jian-Sheng Wang###

Strong Electron-Phonon Interaction and Colossal Magnetoresistance in EuTiO$_3$. At low temperatures, EuTiO$_3$ system has very large resistivities and
exhibits colossal magnetoresistance. Based on a first principle calculation and
the dynamical mean-field theory for small polaron we have calculated the
transport properties of EuTiO$_3$. It is found that due to electron-phonon
interaction the conduction band may form a tiny subband which is close to the
Fermi level. The tiny subband is responsible for the large resistivity.
Besides, EuTiO$_3$ is a weak antiferromagnetic material and its magnetization
would slightly shift the subband via exchange interaction between conduction
electrons and magnetic atoms. Since the subband is close to the Fermi level, a
slight shift of its position gives colossal magnetoresistance.

###Extremely high magnetoresistance and conductivity in the type-II Weyl semimetals WP2 and MoP2|Nitesh Kumar,Yan Sun,Nan Xu,Kaustuv Manna,Mengyu Yao,Vicky Suess,Inge Leermakers,Olga Young,Tobias Foerster,Marcus Schmidt,Binghai Yan,Uli Zeitler,Ming Shi,Claudia Felser,Chandra Shekhar###

Extremely high magnetoresistance and conductivity in the type-II Weyl semimetals WP2 and MoP2. The peculiar band structure of semimetals exhibiting Dirac and Weyl crossings
can lead to spectacular electronic properties such as large mobilities
accompanied by extremely high magnetoresistance. In particular, two closely
neighbouring Weyl points of the same chirality are protected from annihilation
by structural distortions or defects, thereby significantly reducing the
scattering probability between them. Here we present the electronic properties
of the transition metal diphosphides, WP2 and MoP2, that are type-II Weyl
semimetals with robust Weyl points. We present transport and angle resolved
photoemission spectroscopy measurements, and first principles calculations. Our
single crystals of WP2 display an extremely low residual low-temperature
resistivity of 3 nohm-cm accompanied by an enormous and highly anisotropic
magnetoresistance above 200 million % at 63 T and 2.5 K. These properties are
likely a consequence of the novel Weyl fermions expressed in this compound. We
observe a large suppression of charge carrier backscattering in WP2 from
transport measurements.

###Chiral magnetoresistance in Pt/Co/Pt zigzag wires|Yuxiang Yin,Dong-Soo Han,June-Seo Kim,Reinoud Lavrijsen,Kyung-Jin Lee,Seo-Won Lee,Kyoung-Whan Kim,Hyun-Woo Lee,Henk J. M. Swagten,Bert Koopmans###

Chiral magnetoresistance in Pt/Co/Pt zigzag wires. The Rashba effect leads to a chiral precession of the spins of moving
electrons while the Dzyaloshinskii-Moriya interaction (DMI) generates
preference towards a chiral profile of local spins. We predict that the
exchange interaction between these two spin systems results in a 'chiral'
magnetoresistance depending on the chirality of the local spin texture. We
observe this magnetoresistance by measuring the domain wall (DW) resistance in
a uniquely designed Pt/Co/Pt zigzag wire, and by changing the chirality of the
DW with applying an in-plane magnetic field. A chirality-dependent DW
resistance is found, and a quantitative analysis shows a good agreement with a
theory based on the Rashba model. Moreover, the DW resistance measurement
allows us to independently determine the strength of the Rashba effect and the
DMI simultaneously, and the result implies a possible correlation between the
Rashba effect, the DMI, and the symmetric Heisenberg exchange.

###Negative to Positive Magnetoresistance transition in Functionalization of Carbon nanotube and Polyaniline Composite|Krishna Prasad Maity,Narendra Tanty,Ananya Patra,V Prasad###

Negative to Positive Magnetoresistance transition in Functionalization of Carbon nanotube and Polyaniline Composite. Electrical resistivity and magnetoresistance(MR) in polyaniline(PANI) with
carbon nanotube(CNT) and functionalized carbon nanotube(fCNT) composites have
been studied for different weight percentage down to the temperature 4.2K and
up to magnetic field 5T. Resistivity increases significantly in composite at
low temperature due to functionalization of CNT compare to only CNT.
Interestingly transition from negative to positive magnetoresistance has been
observed for 10wt% of composite as the effect of disorder is more in fCNT/PANI.
This result depicts that the MR has strong dependency on disorder in the
composite system. The transition of MR has been explained in the basis of
polaron-bipolaron model. The long range Coulomb interaction between two
polarons screened by disorder in the composite of fCNT/PANI, increases the
effective on-site Coulomb repulsion energy to form bipolaron which leads to
change the sign of MR from negative to positive.

###Planar Hall effect in the Weyl semimetal GdPtBi|Nitesh Kumar,Satya N. Guin,Claudia Felser,Chandra Shekhar###

Planar Hall effect in the Weyl semimetal GdPtBi. Observation of Weyl and Dirac Fermions in condensed matter systems is one of
the most important discoveries. Among the very few available tools to
characterize Weyl semimetals through electrical transport, negative
magnetoresistance is most commonly used. Considering shortcomings of this
method, new tools to characterize chiral anomaly in Weyl semimetals are
desirable. We employ planar Hall effect as an effective technique in half
Heusler Weyl semimetal GdPtBi to study chiral anomaly. This compound exhibits a
large value of 1.5 mohm cm planar Hall resistivity at 2 K and in 9 T. Our
analysis reveals that the observed amplitude is dominated by Berry curvature
and chiral anomaly contributions. Through the angle dependent transport studies
we establish that GdPtBi with relatively small orbital magnetoresistance is an
ideal candidate to observe large planar Hall effect .

###Unusual magnetoresistance oscillations in preferentially oriented p-type polycrystalline ZrTe5|M. K. Hooda,C. S. Yadav###

Unusual magnetoresistance oscillations in preferentially oriented p-type polycrystalline ZrTe5. Recently H. Wang et al. (arXiv 1704.00995) have reported quantum oscillation
in magnetoresistance with the periodicity in logarithmic of magnetic field (B)
for the p-type ZrTe5. They have ascribed this type of behavior to the discrete
scale invariance, resulting from Effimov bound states. We have prepared high
quality stoichiometric (p-type) ZrTe5 polycrystals and observed
magnetoresistance (MR) oscillations, which are periodic in B. These
oscillations are in contrast to usual SdH oscillations or log B dependent
oscillations as observed for tellurium deficient and stoichiometric ZrTe5
respectively. The MR follows the three dimensional Weyl semimetal like
behavior, and Kohler's rule is obeyed at low temperatures. We obtained small
cyclotron effective mass (m* = 0.05 m_e), very high mobility of 2.2 X 10^4
cm^2/V.s and the signature of topological protected surface states in the
compound. The magnetic data shows zero cusp paramagnetic susceptibility which
supports the existence of topological surface states in ZrTe5.

###Novel magnetoresistance features in HgSe single crystal with low electron concentration|A. T. Lonchakov,S. B. Bobin,V. V. Deryushkin,V. I. Okulov,T. E. Govorkova,V. N. Neverov###

Novel magnetoresistance features in HgSe single crystal with low electron concentration. For the first time, magnetoresistive properties of the single crystal of HgSe
with a low electron concentration were studied in wide range of temperature and
magnetic field. Some fundamental parameters of spectrum and scattering of
electrons were experimentally determined. Two important features of magnetic
transport were found - strong transverse magnetoresistance (MR) and negative
longitudinal MR, which can indicate the existence of the topological phase of
the Weyl semimetal (WSM) in HgSe. Taking this hypothesis into account we
suggest a modified band diagram of the mercury selenide at low electron
energies. The obtained results are essential for the deeper understanding of
both physics of gapless semiconductors and WSMs - promising materials for
various applications in electronics, spintronics, computer and laser
technologies.

###Observation of spin-orbit magnetoresistance in metallic thin films on magnetic insulators|Lifan Zhou,Hongkang Song,Kai Liu,Zhongzhi Luan,Peng Wang,Lei Sun,Shengwei Jiang,Hongjun Xiang,Yanbin Chen,Jun Du,Haifeng Ding,Ke Xia,Jiang Xiao,Di Wu###

Observation of spin-orbit magnetoresistance in metallic thin films on magnetic insulators. A magnetoresistance effect induced by the Rashba spin-orbit interaction was
predicted, but not yet observed, in bilayers consisting of normal metal and
ferromagnetic insulator. Here, we present an experimental observation of this
new type of spin-orbit magnetoresistance (SOMR) effect in a bilayer structure
Cu[Pt]/Y3Fe5O12 (YIG), where the Cu/YIG interface is decorated with nanosize Pt
islands. This new MR is apparently not caused by the bulk spin-orbit
interaction because of the negligible spin-orbit interaction in Cu and the
discontinuity of the Pt islands. This SOMR disappears when the Pt islands are
absent or located away from the Cu/YIG interface, therefore we can
unambiguously ascribe it to the Rashba spin-orbit interaction at the interface
enhanced by the Pt decoration. The numerical Boltzmann simulations are
consistent with the experimental SOMR results in the angular dependence of
magnetic field and the Cu thickness dependence. Our finding demonstrates the
realization of the spin manipulation by interface engineering.

###Dynamical Negative Differential Resistance in Antiferromagnetically Coupled Few-Atom Spin-Chains|Steffen Rolf-Pissarczyk,Shichao Yan,Luigi Malavolti,Jacob A. J. Burgess,Gregory McMurtrie,Sebastian Loth###

Dynamical Negative Differential Resistance in Antiferromagnetically Coupled Few-Atom Spin-Chains. We present the appearance of negative differential resistance (NDR) in
spin-dependent electron transport through a few-atom spin-chain. A chain of
three antiferromagnetically coupled Fe atoms(Fe trimer) was positioned on a
Cu2N/Cu(100) surface and contacted with the spin-polarized tip of a scanning
tunneling microscope, thus coupling the Fe trimer to one non-magnetic and one
magnetic lead. Pronounced NDR appears at the low bias of 7 mV where inelastic
electron tunneling dynamically locks the atomic spin in a long-lived excited
state. This causes a rapid increase of the magnetoresistance between
spin-polarized tip and Fe trimer and quenches elastic tunneling. By varying the
coupling strength between tip and Fe trimer we find that in this transport
regime the dynamic locking of the Fe trimer competes with magnetic exchange
interaction, which statically forces the Fe trimer into the
high-magnetoresistance state and removes the NDR.

###Magnetoresistance in YBi and LuBi semimetals due to nearly perfect carrier compensation|Orest Pavlosiuk,Przemysław Swatek,Dariusz Kaczorowski,Piotr Wiśniewski###

Magnetoresistance in YBi and LuBi semimetals due to nearly perfect carrier compensation. Monobismuthides of yttrium and lutetium are shown as new representatives of
materials which exhibit extreme magnetoresistance and magnetic-field-induced
resistivity plateau. At low temperatures and in magnetic field of 9T the
magnetoresistance attains the order of magnitude of 10,000% and 1,000%, on YBi
and LuBi, respectively. Our thorough examination of electron transport
properties of both compounds show that observed features are the consequence of
nearly perfect carrier compensation rather than of possible nontrivial topology
of electronic states. The field-induced plateau of electrical resistivity can
be explained with Kohler scaling. Anisotropic multi-band model of electronic
transport describes very well the magnetic field dependence of electrical
resistivity and Hall resistivity. Data obtained from the Shubnikov-de Haas
oscillations analysis also confirm that Fermi surface of each compound contains
almost equal amounts of holes and electrons. First-principle calculations of
electronic band structure are in a very good agreement with the experimental
data.

###Longitudinal and transverse magnetoresistance in films with tilted out-of-plane magnetic anisotropy|Noga Eden,Gregory Kopnov,Shachar Fraenkel,Moshe Goldstein,Alexander Gerber###

Longitudinal and transverse magnetoresistance in films with tilted out-of-plane magnetic anisotropy. Tilted off-plane magnetic anisotropy induces two unusual characteristic
magnetotransport phenomena: extraordinary Hall effect in the presence of an
in-plane magnetic field, and non-monotonic anisotropic magnetoresistance in the
presence of a field normal to the sample plane. We show experimentally that
these effects are generic, appearing in multiple ferromagnetic systems with
tilted anisotropy introduced either by oblique deposition from a single source
or in binary systems co-deposited from separate sources. We present a
theoretical model demonstrating that these observations are natural results of
the standard extraordinary Hall effect and anisotropic magnetoresistance, when
the titled anisotropy is properly accounted for. Such a scenario may help
explaining various previous intriguing measurements by other groups.

###Magnetotransport studies of optimally doped Sr(Fe${_{1-x}}$Co${_x}$)${_2}$As${_2}$|Rohit Kumar,Luminita Harnagea,Archana Lakhani,Sunil Nair###

Magnetotransport studies of optimally doped Sr(Fe${_{1-x}}$Co${_x}$)${_2}$As${_2}$. We report magnetotransport measurements and its scaling analysis for the
optimally electron doped Sr(Fe${_{0.88}}$Co${_{0.12}}$)${_2}$As${_2}$ system.
We pbserve that both the Kohler's and modified Kohler's scalings are violated.
Interestingly, the Hall angle displays a quadratic temperature dependence
similar to many cuprates and heavy fermion systems. The fact that this
temperature dependence is seen in spite of the violation of modified Kohler's
scaling suggests that the Hall angle and the magnetoresistance are not governed
by the same scattering mechanism. We also observe a linear magnetoresistance in
this system, which does not harbor a spin density wave ground state.
Implcations of our observations are discussed in the context of spin
fluctuations in strongly correlated electron systems.

###Weak antilocalization in quasi-two-dimensional electronic states of epitaxial LuSb thin films|Shouvik Chatterjee,Shoaib Khalid,Hadass S. Inbar,Aranya Goswami,Felipe Crasto de Lima,Abhishek Sharan,Fernando P. Sabino,Tobias L. Brown-Heft,Yu-Hao Chang,Alexei V. Fedorov,Dan Read,Anderson Janotti,Christopher J. Palmstrøm###

Weak antilocalization in quasi-two-dimensional electronic states of epitaxial LuSb thin films. Observation of large non-saturating magnetoresistance in rare-earth
monopnictides has raised enormous interest in understanding the role of its
electronic structure. Here, by a combination of molecular-beam epitaxy,
low-temperature transport, angle-resolved photoemssion spectroscopy, and hybrid
density functional theory we have unveiled the bandstructure of LuSb, where
electron-hole compensation is identified as a mechanism responsible for large
magnetoresistance in this topologically trivial compound. In contrast to bulk
single crystal analogues, quasi-two-dimensional behavior is observed in our
thin films for both electron and holelike carriers, indicative of dimensional
confinement of the electronic states. Introduction of defects through growth
parameter tuning results in the appearance of quantum interference effects at
low temperatures, which has allowed us to identify the dominant inelastic
scattering processes and elucidate the role of spin-orbit coupling. Our
findings open up new possibilities of band structure engineering and control of
transport properties in rare-earth monopnictides via epitaxial synthesis.

###Nonintrinsic origin of the magnetic-field-induced metal-insulator and electronic phase transitions in graphite|José Barzola-Quiquia,Pablo D. Esquinazi,Christian E. Precker,Markus Stiller,Mahsa Zoraghi,Tobias Förster,Thomas Herrmannsdörfer,William A. Coniglio###

Nonintrinsic origin of the magnetic-field-induced metal-insulator and electronic phase transitions in graphite. A detailed magnetoresistance study of bulk and microflake samples of highly
oriented pyrolytic graphite with a thickness of 25 $\mu$m to 23~nm reveals that
the usually observed field-induced metal-insulator and electronic phase
transitions vanish in thinner samples. The observed suppression is accompanied
by orders of magnitude decrease of the magnetoresistance and of the amplitude
of the Shubnikov-de-Haas oscillations. The overall behavior is related to the
decrease in the quantity of two-dimensional interfaces between crystalline
regions of the same and different stacking orders present in graphite samples.
Our results indicate that these field-induced transitions are not intrinsic to
the ideal graphite structure and, therefore, a relevant portion of the
published interpretations should be reconsidered.

###Pressure-induced superconductivity and structural transition in ferromagnetic Cr2Si2Te6|Wanping Cai,Hualei Sun,Wei Xia,Changwei Wu,Ying Liu,Jia Yu,Junjie Yin,Hui Liu,Yu Gong,Dao-Xin Yao,Yanfeng Guo,Meng Wang###

Pressure-induced superconductivity and structural transition in ferromagnetic Cr2Si2Te6. The discovery of intrinsic magnetism in atomically thin two-dimensional
transition-metal trichalcogenides has attracted intense research interest due
to the exotic properties of magnetism and potential applications in devices.
Pressure has proven to be an effective tool to manipulate the crystal and
electronic structures of the materials. Here, we report investigations on
ferromagnetic van der Waals Cr2Si2Te6 via high-pressure synchrotron x-ray
diffraction, electrical resistance, Hall resistance, and magnetoresistance
measurements. Under compression, Cr2Si2Te6 simultaneously undergoes a
structural transition, emergence of superconductivity at 3 K, sign change of
the magnetoresistance, and dramatic change of the Hall coefficient at ~8 GPa.
The superconductivity persists up to the highest measured pressure of 47.1 GPa
with a maximum Tc = 4.5 K at ~30 GPa. The discovery of superconductivity in the
two-dimensional van der Waals ferromagnetic Cr-based Cr2Si2Te6 provides new
perspectives to explore superconductivity and the interplay between
superconductivity and magnetism.

###Non-quadratic transverse magnetoresistance of the nodal line Dirac semimetal InBi|S. V. Zaitsev-Zotov,I. A. Cohn###

Non-quadratic transverse magnetoresistance of the nodal line Dirac semimetal InBi. The transverse magnetoresistance of a nodal line Dirac semi-metal InBi has
been studied. It is found that the magnetoresistance is not quadratic. In the
region of small magnetic fields $ B\lesssim 0.1$~T, it is characterized by high
curvature, in the region of medium magnetic fields it is described by the sum
of linear and quadratic contributions, and in the region of large magnetic
fields $ B\gtrsim 1$~T, it approaches a quadratic law with a curvature several
times smaller its zero field value. A phenomenological equation is proposed
that allows to describe the entire dependence of the resistance on the magnetic
field with an error not exceeding the measurement error of several percent.

###Giant Magnetoresistance Effect in Organic Material and Its Potential for Magnetic Sensor|Mitra Djamal,Ramli,Sparisoma Viridi,Khairurrijal###

Giant Magnetoresistance Effect in Organic Material and Its Potential for Magnetic Sensor. Giant magnetoresistance (GMR) material has great potential as next generation
magnetic field sensing devices, have magnetic properties and high electrical
potential to be developed into various applications such as: magnetic field
sensor measurements, current measurements, linear and rotational position
sensor, data storage, head recording, and non-volatile magnetic random access
memory (MRAM). Today, the new GMR materials based on organic material obtained
after allowing for Organic Magnetoresistance (OMAR) was found in OLEDs (organic
light-emitting diodes). This organic material is used as a spacer layer in GMR
devices with spin-valve structures. Traditionally, metals and semiconductors
are used as a spacer layer in spin-valve. However, several factors such as spin
scattering caused by large atoms of the spacer material and the interface
scattering of ferromagnetic with a spacer, will limit the efficiency of
spin-valve. In this paper, we describe a new GMR materials based on organic
material that we have developed.

###Spin Transfer from a Ferromagnet into a Semiconductor through an Oxide barrier|C. I. L. de Araujo,M. A. Tumelero,A. D. C. Viegas,N. Garcia,A. A. Pasa###

Spin Transfer from a Ferromagnet into a Semiconductor through an Oxide barrier. We present results on the magnetoresistance of the system Ni/Al203/n-doped
Si/Al2O3/Ni in fabricated nanostructures. The results at temperature of 14K
reveal a 75% magnetoresistance that decreases in value up to approximately 30K
where the effect disappears. We observe minimum resistance in the antiparallel
configurations of the source and drain of Ni. As a possibility, it seems to
indicate the existence of a magnetic state at the Si/oxide interface. The
average spin diffusion length obtained is of 650 nm approximately. Results are
compared to the window of resistances that seems to exist between the tunnel
barrier resistance and two threshold resistances but the spin transfer seems to
work in the range and outside the two thresholds.

###Large low-field positive magnetoresistance in nonmagnetic half-Heusler ScPtBi single crystal|Zhipeng Hou,Yue Wang,Enke Liu,Hongwei Zhang,Wenhong Wang,Guangheng Wu###

Large low-field positive magnetoresistance in nonmagnetic half-Heusler ScPtBi single crystal. High-quality nonmagnetic half-Heusler ScPtBi single crystals were synthesized
by a Bi self-flux method. This compound was revealed to be a hole-dominated
semimetal with a large low-field magnetoresistance up to 240% at 2K in a
magnetic field of 1T. Magneto-transport measurements demonstrated that the
large low-field magnetoresistance effect resulted from the coexistence of
field-induced metal-semiconductor transition and weak-antilocalization effect.
Moreover, Hall measurements indicated that ScPtBi single crystal showed a high
mobility over a wide temperature region even up to room temperature (4050
cm2V-1s-1 at 2K - 2016 cm2V-1s-1 at 300K). These findings not only suggest the
nonmagnetic ScPtBi semimetal a potential material candidate for applications in
high-sensitivity magnetic sensors, but also are of great significance to
comprehensively understand the rare-earth based half-Heusler compounds.

###Resonance spin-charge phenomena and mechanism of magnetoresistance anisotropy in manganite/metal bilayer structures|V. A. Atsarkin,B. V. Sorokin,I. V. Borisenko,V. V. Demidov,G. A. Ovsyannikov###

Resonance spin-charge phenomena and mechanism of magnetoresistance anisotropy in manganite/metal bilayer structures. The dc voltage generated under ferromagnetic resonance has been studied in
bilayer structures based on manganite thin epitaxial films La0.67Sr0.33MnO3
(LSMO) and non-magnetic metals (Au, Pt, and SrRuO3) in the temperature range up
to the Curie point. The effect is shown to be caused by two different
phenomena: (1) the resonance dc electromotive force related to anisotropic
magnetoresistance (AMR) in the manganite film and (2) pure spin current (spin
pumping) registered by means of the inverse spin Hall effect in normal metal.
The two phenomena were separated using the angular dependence of the effect,
the external magnetic field H0 being rotated in the film plane. It was found
that the AMR mechanism in the manganite films differs substantially from that
in traditional ferromagnetic metals being governed by the colossal
magnetoresistance together with the in-plane magnetic anisotropy. The spin
pumping effect registered in the bilayers was found to be much lower than that
reported for common ferromagnets; possible reasons are discussed.

###Multi-band superconductivity and large anisotropy in FeS crystals|Hai Lin,Yufeng Li,Qiang Deng,Jie Xing,Jianzhong Liu,Xiyu Zhu,Huan Yang,Hai-Hu Wen###

Multi-band superconductivity and large anisotropy in FeS crystals. By using a hydrothermal method, we have successfully grown crystals of the
newly discovered superconductor FeS, which has an isostructure of the iron
based superconductor FeSe. The superconductivity appears at about 4.5K, as
revealed by both resistive and magnetization measurements. It is found that the
upper critical field is relatively low, with however an rather large anisotropy
$\Gamma=[(dH_{c2}^{ab}/dT)/(dH_{c2}^{c}/dT)]_{T_c}\approx5.8$. A huge
magnetoresistivity (290$\%$ at 9T and 10K, ${H}$ $\parallel$ c-axis) together
with a non-linear behavior of Hall resistivity vs. external field are observed.
A two-band model is applied to fit the magnetoresistance and non-linear
transverse resistivity, yielding the basic parameters of the electron and hole
bands.

###Anisotropic physical properties and pressure dependent magnetic ordering of CrAuTe$_4$|Na Hyun Jo,Udhara S. Kaluarachchi,Yun Wu,Daixiang Mou,Lunan Huang,Valentin Taufour,Adam Kaminski,Sergey L. Bud'ko,Paul C. Canfield###

Anisotropic physical properties and pressure dependent magnetic ordering of CrAuTe$_4$. Systematic measurements of temperature dependent magnetization, resistivity
and angle-resolved photoemission spectroscopy (ARPES) at ambient pressure as
well as resistivity under pressures up to 5.25 GPa were conducted on single
crystals of CrAuTe$_4$. Magnetization data suggest that magnetic moments are
aligned antiferromagnetically along the crystallographic $c$-axis below
$T_\textrm{N}$ = 255 K. ARPES measurements show band reconstruction due to the
magnetic ordering. Magnetoresistance data show clear anisotropy, and, at high
fields, quantum oscillations. The Neel temperature decreases monotonically
under pressure, decreasing to $T_\textrm{N}$ = 236 K at 5.22 GPa. The pressure
dependencies of (i) $T_\textrm{N}$, (ii) the residual resistivity ratio, and
(iii) the size and power-law behavior of the low temperature magnetoresistance
all show anomalies near 2 GPa suggesting that there may be a phase transition
(structural, magnetic, and/or electronic) induced by pressure. For pressures
higher than 2 GPa a significantly different quantum oscillation frequency
emerges, consistent with a pressure induced change in the electronic states.

###Crystallographic dependent transport properties and oxygen issue in superconducting LiTi2O4 thin films|Yanli Jia,Ge He,Heshan Yu,Wei Hu,Zhenzhong Yang,Jinan Shi,Zefeng Lin,Jie Yuan,Beiyi Zhu,Kai Liu,Lin Gu,Hong Li,Kui Jin###

Crystallographic dependent transport properties and oxygen issue in superconducting LiTi2O4 thin films. A systematic study is performed on the spinel oxide, i.e. LiTi2O4 thin films
oriented along [111]-, [110]-, and [001]-directions, to reveal the
crystallographic dependence of transport properties. With decreasing
temperature, the LiTi2O4 displays roughly identical onset temperatures of
twofold symmetry of in-plane angular dependent magnetoresistivity (AMR) (at ~
100 K), crossover from negative- to positive- magnetoresistance (at ~ 50 K),
and coherence length in the superconducting state. While, the twofold symmetry
in AMR itself suggests anisotropic electron scattering. The superconducting
transition temperature (Tc) seems insensitive to the lattice parameter.
Moreover, the spherical aberration-corrected scanning transmission electron
microscopy (Cs-STEM) discloses that oxygen vacancies exist in the LiTi2O4
films. These oxygen vacancies cause the change of lattice but show little
influence on superconductivity, differing from high-Tc cuprates where subtle
variation of oxygen way lead to a significant change in superconductivity.

###Ultraquantum magnetoresistance in Kramers Weyl semimetal candidate $β$-Ag2Se|Cheng-Long Zhang,Frank Schindler,Haiwen Liu,Tay-Rong Chang,Su-Yang Xu,Guoqing Chang,Wei Hua,Hua Jiang,Zhujun Yuan,Junliang Sun,Horng-Tay Jeng,Hai-Zhou Lu,Hsin Lin,M. Zahid Hasan,X. C. Xie,Titus Neupert,Shuang Jia###

Ultraquantum magnetoresistance in Kramers Weyl semimetal candidate $β$-Ag2Se. The topological semimetal $\beta$-Ag2Se features a Kramers Weyl node at the
origin in momentum space and a quadruplet of spinless Weyl nodes, which are
annihilated by spin-orbit coupling. We show that single crystalline
$\beta$-Ag2Se manifests giant Shubnikov-de Haas oscillations in the
longitudinal magnetoresistance which stem from a small electron pocket that can
be driven beyond the quantum limit by a field less than 9 T. This small
electron pocket is a remainder of the spin-orbit annihilatedWeyl nodes and thus
encloses a Berry-phase structure. Moreover, we observed a negative longitudinal
magnetoresistance when the magnetic field is beyond the quantum limit. Our
experimental findings are complemented by thorough theoretical band structure
analyses of this Kramers Weyl semimetal candidate, including first-principle
calculations and an effective k*p model.

###Giant Planar Hall Effect in the Dirac Semimetal ZrTe5|Peng Li,Chenhui Zhang,Junwei Zhang,Yan Wen,Xi-xiang Zhang###

Giant Planar Hall Effect in the Dirac Semimetal ZrTe5. Recently, giant planar Hall effect originating from chiral anomaly has been
predicted in nonmagnetic Dirac/Weyl semimetals. ZrTe5 is considered to be an
intriguing Dirac semimetal at the boundary of weak topological insulators and
strong topological insulators, though this claim still remains controversial.
Here, we report the observation in ZrTe5 of the giant planar Hall resistivity
that shows two different magnetic-field dependences as predicted by theory and
a maximum at the Lifshitz transition temperature. We found that the giant
planar Hall resistivity fades out with decreasing the thickness of ZrTe5
nanoplates, which may be ascribed to the vanishing of the 3D nature of the
samples. In addition, we have observed a nontrivial Berry phase,
chiral-anomaly-induced negative longitudinal magnetoresistance, and a giant
in-plane anisotropic magnetoresistance in these ZrTe5 nanoplates. All the
experimental observations demonstrated coherently that ZrTe5 is a Dirac
semimetal.

###Studies of non-trivial band topology and electron-hole compensation in YSb|Payal Wadhwa,Shailesh Kumar,Alok Shukla,Rakesh Kumar###

Studies of non-trivial band topology and electron-hole compensation in YSb. In this article, we study non-trivial topological phase and electron-hole
compensation in extremely large magnetoresistance (XMR) material YSb under
hydrostatic pressure using first-principles calculations. YSb is topologically
trivial at ambient pressure, but undergoes a reentrant topological phase
transition under hydrostatic pressure. The reentrant behavior of topological
quantum phase is then studied as a function of charge density ratio under
pressure. From the detailed investigation of Fermi surfaces, it is found that
electron to hole densities ratio increases with pressure, however a non-trivial
topological phase appears without perfect electron-hole compensation. The
results indicate that the non-trivial topological phase under hydrostatic
pressure may not have maximal influence on the magnetoresistance, and need
further investigations through experiments to determine the exact relationship
between topology and XMR effect.

###Room temperature biaxial magnetic anisotropy in La0.67Sr0.33MnO3 thin films on SrTiO3 buffered MgO (001) substrates for spintronic applications|Sandeep Kumar Chaluvadi,Fernando Ajejas,Pasquale Orgiani,Olivier Rousseau,Giovanni Vinai,Aleksandr Yu Petrov,Piero Torelli,Alain Pautrat,Julio Camarero,Paolo Perna,Laurence Mechin###

Room temperature biaxial magnetic anisotropy in La0.67Sr0.33MnO3 thin films on SrTiO3 buffered MgO (001) substrates for spintronic applications. Spintronics exploits the magnetoresistance effects to store or sense the
magnetic information. Since the magnetoresistance strictly depends on the
magnetic anisotropy of the system, it is fundamental to set a defined
anisotropy to the system. Here, we investigate by means of vectorial
Magneto-Optical Kerr Magnetometry (v-MOKE), half-metallic La0.67Sr0.33MnO3
(LSMO) thin films that exhibit at room temperature pure biaxial magnetic
anisotropy if grown onto MgO (001) substrate with a thin SrTiO3 (STO) buffer.
In this way, we can avoid unwanted uniaxial magnetic anisotropy contributions
that may be detrimental for specific applications. The detailed study of the
angular evolution of the magnetization reversal pathways, critical fields
(coercivity and switching) allows for disclosing the origin of the magnetic
anisotropy, which is magnetocrystalline in nature and shows four-fold symmetry
at any temperature.

###Enhancement of spin Hall magnetoresistance effect in CoFe2O4/Pt/CoFe2O4 trilayers|Takumi Yamamoto,Takashi Yanase,Toshihiro Shimada,Taro Nagahama###

Enhancement of spin Hall magnetoresistance effect in CoFe2O4/Pt/CoFe2O4 trilayers. The spin Hall magnetoresistance (SMR) phenomenon includes the fundamental
physics of spin current, and originates from spin accumulation at an interface
owing to the spin Hall effect. Although bilayers are the simplest structure
exhibiting SMR, these exploit spin accumulation at only one side of a layer.
Herein, trilayers of CoFe2O4/Pt/CoFe2O4 were fabricated and their spin Hall
magnetoresistance was investigated. The trilayer structure featuring a thin Pt
layer exhibited an SMR ratio four times that of a CoFe2O4/Pt bilayer. Further,
the SMR ratio exhibited a dependence on Pt layer thickness that can be
attributed to interference of the spin accumulations at both sides. Herein,
several parameters such as spin diffusion length and mixing conductance were
derived using the theory of Chen et al.

###Quantum Transport in Topological Semimetals under Magnetic Fields (II)|Hai-Peng Sun,Hai-Zhou Lu###

Quantum Transport in Topological Semimetals under Magnetic Fields (II). We review our recent works on the quantum transport, mainly in topological
semimetals and also in topological insulators, organized according to the
strength of the magnetic field. At weak magnetic fields, we explain the
negative magnetoresistance in topological semimetals and topological insulators
by using the semiclassical equations of motion with the nontrivial Berry
curvature. We show that the negative magnetoresistance can exist without the
chiral anomaly. At strong magnetic fields, we establish theories for the
quantum oscillations in topological Weyl, Dirac, and nodal-line semimetals. We
propose a new mechanism of 3D quantum Hall effect, via the "wormhole" tunneling
through the Weyl orbit formed by the Fermi arcs and Weyl nodes in topological
semimetals. In the quantum limit at extremely strong magnetic fields, we find
that an unexpected Hall resistance reversal can be understood in terms of the
Weyl fermion annihilation. Additionally, in parallel magnetic fields,
longitudinal resistance dips in the quantum limit can serve as signatures for
topological insulators.

###Synchronized, periodic, and chaotic dynamics in spin torque oscillator with two free layers|Tomohiro Taniguchi###

Synchronized, periodic, and chaotic dynamics in spin torque oscillator with two free layers. A phase diagram of the magnetization dynamics is studied by numerically
solving the Landau-Lifshitz-Gilbert (LLG) equation in a spin torque oscillator
consisting of asymmetric two free layers that are magnetized in in-plane
direction. We calculated the dynamics for a wide range of current density for
both low and high field cases, and found many dynamical phases such as
synchronization, auto-oscillation with different frequencies, and chaotic
dynamics. The observation of the synchronization indicates the presence of a
dynamical phase which has not been found experimentally by using the
conventional electrical detection method. The auto-oscillations with different
frequencies lead to an oscillation of magnetoresistance with a high frequency,
which can be measured experimentally. The chaotic and/or periodic behavior of
magnetoresistance in a high current region, on the other hand, leads to a
discontinuous change of the peak frequency in Fourier spectrum.

###Theory of Spin Hall Magnetoresistance from a Microscopic Perspective|X. P. Zhang,F. S. Bergeret,V. N. Golovach###

Theory of Spin Hall Magnetoresistance from a Microscopic Perspective. We present a theory of the spin Hall magnetoresistance of metals in contact
with magnetic insulators. We express the spin-mixing conductances, which govern
the phenomenology of the effect, in terms of the microscopic parameters of the
interface and the spin-spin correlation functions of the local moments on the
surface of the magnetic insulator. The magnetic field and temperature
dependence of the spin-mixing conductances leads to a rich behaviour of the
resistance due to an interplay between the Hanle effect and spin mixing at the
interface. Our theory provides a useful tool for understanding the experiments
on heavy metals in contact with magnetic insulators of different kinds, and it
predicts striking behaviours of magnetoresistance.

###Dynamics of Phase Separated States in the Double Exchange Model|Jing Luo,Gia-Wei Chern###

Dynamics of Phase Separated States in the Double Exchange Model. We present extensive large-scale dynamical simulations of phase-separated
states in the double exchange model. These inhomogeneous electronic states that
play a crucial role in the colossal magnetoresistance phenomenon are composed
of ferromagnetic metallic clusters embedded in an antiferromagnetic insulating
matrix. We compute the dynamical structure factor of these nanoscale textures
using an efficient real-space formulation of coupled spin and electron
dynamics. Dynamical signatures of the various underlying magnetic structures
are identified. At small hole doping, the structure factor exhibits a
dominating signal of magnons from the background N\'eel order and localized
modes from magnetic polarons. A low-energy continuum due to large-size
ferromagnetic clusters emerges at higher doping levels. Implications for
experiments on magnetoresistive manganites are discussed.

###Origin of the butterfly magnetoresistance in a Dirac nodal-line system|Y. -C. Chiu,K. -W. Chen,R. Schönemann,V. L. Quito,S. Sur,Q. Zhou,D. Graf,E. Kampert,T. Förster,K. Yang,G. T. McCandless,Julia Y. Chan,R. E. Baumbach,M. D. Johannes,L. Balicas###

Origin of the butterfly magnetoresistance in a Dirac nodal-line system. We report a study on the magnetotransport properties and on the Fermi
surfaces (FS) of the ZrSi(Se,Te) semimetals. Density Functional Theory (DFT)
calculations, in absence of spin orbit coupling (SOC), reveal that both the Se
and the Te compounds display Dirac nodal lines (DNL) close to the Fermi level
$\varepsilon_F$ at symmorphic and non-symmorphic positions, respectively. We
find that the geometry of their FSs agrees well with DFT predictions. ZrSiSe
displays low residual resistivities, pronounced magnetoresistivity, high
carrier mobilities, and a butterfly-like angle-dependent magnetoresistivity
(AMR), although its DNL is not protected against gap opening. As in
Cd$_3$As$_2$, its transport lifetime is found to be 10$^2$ to 10$^3$ times
larger than its quantum one. ZrSiTe, which possesses a protected DNL, displays
conventional transport properties. Our evaluation indicates that both compounds
most likely are topologically trivial. Nearly angle-independent effective
masses with strong angle dependent quantum lifetimes lead to the butterfly AMR
in ZrSiSe.

###Tailored tunnel magnetoresistance response in three ultrathin chromium trihalides|Hyun Ho Kim,Bowen Yang,Shangjie Tian,Chenghe Li,Guo-Xing Miao,Hechang Lei,Adam W. Tsen###

Tailored tunnel magnetoresistance response in three ultrathin chromium trihalides. Materials that demonstrate large magnetoresistance have attracted significant
interest for many decades. Recently, extremely large tunnel magnetoresistance
(TMR) has been reported by several groups across ultrathin CrI$_3$ by
exploiting the weak antiferromagnetic coupling between adjacent layers. Here,
we report a comparative study of TMR in all three chromium trihalides (CrX$_3$,
X= Cl, Br, or I) in the two-dimensional limit. As the materials exhibit
different transition temperatures and interlayer magnetic ordering in the
ground state, tunneling measurements allow for an easy determination of the
field-temperature phase diagram for the three systems. By changing sample
thickness and biasing conditions, we then demonstrate how to maximize and
further tailor the TMR response at different temperatures for each material. In
particular, near the magnetic transition temperature, TMR is non-saturating up
to the highest fields measured for all three compounds owing to the large,
field-induced exchange coupling.

###Chiral anisotropic magnetoresistance of ferromagnetic helices|Henrik Maurenbrecher,Johannes Mendil,George Chatzipirpiridis,Michael Mattmann,Salvador Pané,Bradley J. Nelson,Pietro Gambardella###

Chiral anisotropic magnetoresistance of ferromagnetic helices. We investigate the anisotropic magnetoresistance (AMR) of ferromagnetic CoNi
microhelices fabricated by electrodeposition and laser printing. We find that
the geometry of the three-dimensional winding determines a characteristic
angular and field-dependence of the AMR due to the competition between helical
shape anisotropy and external magnetic field. Moreover, we show that there is
an additional contribution to the AMR that scales proportionally to the applied
current and depends on the helix chirality. We attribute this contribution to
the self magnetic field induced by the current, which modifies the orientation
of the magnetization relative to the current flow along the helix. Our results
underline the interest of three-dimensional curved geometries to tune the AMR
and realize tubular magnetoresistive devices.

###Investigation of domain wall pinning by square anti-notches and its applications in three terminals MRAM|C. I. L. de Araujo,J. C. S. Gomes,D. Toscano,E. L. M. Paixao,P. Z. Coura,F. Sato,D. V. P. Massote,S. A. Leonel###

Investigation of domain wall pinning by square anti-notches and its applications in three terminals MRAM. In this work we perform investigations of the competition between domain-wall
pinning and attraction by anti-notches and finite device borders. The
conditions for optimal geometries, which can attain a stable domain-wall
pinning, are presented. This allow us the proposition of a three-terminals
device based on domain-wall pinning. We obtain, with very small pulses of
current applied parallel to the nanotrack, a fast motion of the domain-wall
between anti-notches. In addition to this, a swift stabilization of the pinned
domain-wall is observed with a high percentage of orthogonal magnetization,
enabling high magnetoresistive signal measurement. Thus, our proposed device is
a promising magnetoresistive random access memories with good scalability,
duration, and high speed information storage.

###Orbital-flop Induced Magnetoresistance Anisotropy in Rare Earth Monopnictide CeSb|Jing Xu,Fengcheng Wu,Jin-Ke Bao,Fei Han,Zhi-Li Xiao,Ivar Martin,Yang-Yang Lyu,Yong-Lei Wang,Duck Young Chung,Mingda Li,Wei Zhang,John E. Pearson,Jidong S. Jiang,Mercouri G. Kanatzidis,Wai-Kwong Kwok###

Orbital-flop Induced Magnetoresistance Anisotropy in Rare Earth Monopnictide CeSb. The charge and spin of the electrons in solids have been extensively
exploited in electronic devices and in the development of spintronics. Another
attribute of electrons - their orbital nature - is attracting growing interest
for understanding exotic phenomena and in creating the next-generation of
quantum devices such as orbital qubits. Here, we report on orbital-flop induced
magnetoresistance anisotropy in CeSb. In the low temperature high
magnetic-field driven ferromagnetic state, a series of additional minima appear
in the angle-dependent magnetoresistance. These minima arise from the
anisotropic magnetization originating from orbital-flops and from the enhanced
electron scattering from magnetic multidomains formed around the first-order
orbital-flop transition. The measured magnetization anisotropy can be accounted
for with a phenomenological model involving orbital-flops and a spin-valve-like
structure is used to demonstrate the viable utilization of orbital-flop
phenomenon. Our results showcase a contribution of orbital behavior in the
emergence of intriguing phenomena.

###Resummation for the Field-theoretical Derivation of the Negative Magnetoresistance|Kenji Fukushima,Yoshimasa Hidaka###

Resummation for the Field-theoretical Derivation of the Negative Magnetoresistance. We show detailed derivation of the electric conductivity of quark matter at
finite temperature and density under a magnetic field. We especially focus on
the longitudinal electric conductivity along the magnetic direction and
establish the field-theoretical description of the negative magnetoresistance
as observed in chiral materials. With increasing magnetic field our microscopic
calculation leads to changing behavior from approximately quadratic to
asymptotically linear dependence of the electric conductivity, while the
magnetic dependence is quadratic in the conventional relaxation time
approximation. The presented formulation founds a firm basis for the physical
interpretation of the negative magnetoresistance as manifestation of the chiral
anomaly, as well as it offers general methodology applicable for various
transport coefficients.

###Defect-implantation for the all-electrical detection of non-collinear spin-textures|Imara Lima Fernandes,Mohammed Bouhassoune,Samir Lounis###

Defect-implantation for the all-electrical detection of non-collinear spin-textures. The viability of past, current and future devices for information technology
hinges on their sensitivity to the presence of impurities. The latter can lead
to resistivity anomalies, the so-called Kondo effect, reshape extrinsically
Hall effects or reduce the efficiency of magnetoresistance effects essential in
spintronics. Here we demonstrate that atomic defects enable highly efficient
all-electrical detection of spin-swirling textures, in particular magnetic
skyrmions, which are promising bits candidates in future spintronics devices.
Impurities amplify the bare transport signal and can alter significantly the
spin-mixing magnetoresistance (XMR) depending on their chemical nature. Both
effects are monitored in terms of the defect-enhanced XMR (DXMR) as shown for
3d and 4d transition metal defects implanted at the vicinity of skyrmions
generated in PdFe bilayer deposited on Ir(111). The ineluctability of
impurities in devices promotes the implementation of DXMR in reading
architectures with immediate implications in magnetic storage technologies.

###Interfacial contributions to spin-orbit torque and magnetoresistance in ferromagnet/heavy-metal bilayers|K. D. Belashchenko,Alexey A. Kovalev,M. van Schilfgaarde###

Interfacial contributions to spin-orbit torque and magnetoresistance in ferromagnet/heavy-metal bilayers. The thickness dependence of spin-orbit torque and magnetoresistance in
ferromagnet/heavy-metal bilayers is studied using the first-principles
non-equilibrium Green's function formalism combined with the Anderson disorder
model. A systematic expansion in orthogonal vector spherical harmonics is used
for the angular dependence of the torque. The damping-like torque in Co/Pt and
Co/Au bilayers can be described as a sum of the spin-Hall contribution, which
increases with thickness in agreement with the spin-diffusion model, and a
comparable interfacial contribution. The magnetoconductance in the plane
perpendicular to the current in Co/Pt bilayers is of the order of a conductance
quantum per interfacial atom, exceeding the prediction of the spin-Hall model
by more than an order of magnitude. This suggests that the "spin-Hall
magnetoresistance," similarly to the damping-like torque, has a large
interfacial contribution unrelated to the spin-Hall effect.

###Observation of Shubnikov-de Haas Oscillations, Non-trivial Berry Phase, Planar Hall and Anisotropic Magnetoresistance at the conducting interface of EuO-KTaO$_3$|Nand Kumar,Neha Wadehra,Ruchi Tomar,Sushanta Dattagupta,Sanjeev Kumar,S. Chakraverty###

Observation of Shubnikov-de Haas Oscillations, Non-trivial Berry Phase, Planar Hall and Anisotropic Magnetoresistance at the conducting interface of EuO-KTaO$_3$. The momentum dependent splitting of spin-bands in an electronic system is
known as the "Rashba effect". Systems with the "Rashba effect" possess a Dirac
point in momentum space. An electron in a cyclotron orbit enclosing that Dirac
point in the reciprocal space gains a "Berry phase". We report here the
Shubnikov-de-Haas oscillations (SdH) at the conducting interface of
EuO-KTaO$_3$ (KTO). Observed SdH oscillations suggest the presence of two Fermi
surfaces. For both the Fermi surfaces, we have seen the presence of a
non-trivial "Berry phase" suggesting that the surfaces enclose the "Dirac
point". Thus the Berry phase originates from the inner and outer Fermi surfaces
of the Rashba spin-split bands. As in topological insulators, two fold planar
Hall and anisotropic magnetoresistance have also been observed in EuO-KTO.
Analyzing the SdH, Hall and magnetoresistance data, we have drawn a possible
band diagram near the Fermi surface.

###Integration of the Noncollinear Antiferromagnetic Metal Mn3Sn onto Ferroelectric Oxides for Electric-Field Control|Xiaoning Wang,Zexin Feng,Peixin Qin,Han Yan,Xiaorong Zhou,Huixin Guo,Zhaoguogang Leng,Weiqi Chen,Qiannan Jia,Zexiang Hu,Haojiang Wu,Xin Zhang,Chengbao Jiang,Zhiqi Liu###

Integration of the Noncollinear Antiferromagnetic Metal Mn3Sn onto Ferroelectric Oxides for Electric-Field Control. Non-collinear antiferromagnetic materials have received dramatically
increasing attention in the field of spintronics as their exotic topological
features such as the Berry-curvature-induced anomalous Hall effect and possible
magnetic Weyl states could be utilized in future topological antiferromagnetic
spintronic devices. In this work, we report the successful integration of the
antiferromagnetic metal Mn3Sn thin films onto ferroelectric oxide PMN-PT. By
optimizing growth, we realized the large anomalous Hall effect with small
switching magnetic fields of several tens mT fully comparable to those of bulk
Mn3Sn single crystals, anisotropic magnetoresistance and negative parallel
magnetoresistance in Mn3Sn thin films with antiferromagnetic order, which are
similar to the signatures of the Weyl state in bulk Mn3Sn single crystals. More
importantly, we found that the anomalous Hall effect in antiferromagnetic Mn3Sn
thin films can be manipulated by electric fields applied onto the ferroelectric
materials, thus demonstrating the feasibility of Mn3Sn-based topological
spintronic devices operated in an ultralow power manner.

###Transport evidence of triply degenerate nodal semimetal YRh6Ge4|Yanglin Zhu,Xin Gui,Yu Wang,David Graf,Weiwei Xie,Zhiqiang Mao###

Transport evidence of triply degenerate nodal semimetal YRh6Ge4. We have investigated magnetotransport properties of YRh6Ge4, which was
recently predicted to be a triply degenerate nodal semimetal. We find it
exhibits remarkable signatures of a chiral anomaly, manifested by large
negative longitudinal magnetoresistance, quadratic field dependence of
magnetoconductance and planar Hall effect. Furthermore, we have also observed
Shubnikov-de Haas (SdH) quantum oscillations in the magnetoresistivity
measurements on this material. The analyses of the SdH data reveal two
point-like Fermi surfaces and these pockets are found to host nearly massless
fermions. The small size of these Fermi pockets is in a good agreement with the
theoretical prediction that the triply degenerate point in YRh6Ge4 is much
closer to the Fermi level than previously demonstrated triply degenerate nodal
semimetals such as MoP and WC. These results suggest YRh6Ge4 may serve as a
model system to probe exotic properties of three-component fermions and
understand their underlying physics.

###Anomalous Magnetoresistance due to Longitudinal Spin Fluctuations in a Jeff = 1/2 Mott Semiconductor|Lin Hao,Zhentao Wang,Junyi Yang,D. Meyers,Joshua Sanchez,Gilberto Fabbris,Yongseong Choi,Jong-Woo Kim,Daniel Haskel,Philip J. Ryan,Kipton Barros,Jiun-Haw Chu,M. P. M. Dean,Cristian D. Batista,Jian Liu###

Anomalous Magnetoresistance due to Longitudinal Spin Fluctuations in a Jeff = 1/2 Mott Semiconductor. As a hallmark of electronic correlation, spin-charge interplay underlies many
emergent phenomena in doped Mott insulators, such as high-temperature
superconductivity, whereas the half-filled parent state is usually
electronically frozen with an antiferromagnetic order that resists external
control. We report on the observation of a new positive magnetoresistance that
probes the staggered susceptibility of a pseudospin-half square-lattice Mott
insulator built as an artificial SrIrO3/SrTiO3 superlattice. Its size is
particularly large in the high-temperature insulating paramagnetic phase near
the N\'eel transition. This novel magnetoresistance originates from a
collective charge response to the large longitudinal spin fluctuations under a
linear coupling between the external magnetic field and the staggered
magnetization enabled by strong spin-orbit interaction. Our results demonstrate
a magnetic control of the binding energy of the fluctuating particle-hole pairs
in the Slater-Mott crossover regime analogous to the BCS-to-Bose-Einstein
condensation crossover of ultracold-superfluids.

###Giant unidirectional magnetoresistance in topological insulator -- ferromagnetic semiconductor heterostructures|Nguyen Huynh Duy Khang,Pham Nam Hai###

Giant unidirectional magnetoresistance in topological insulator -- ferromagnetic semiconductor heterostructures. The unidirectional magnetoresistance (UMR) is one of the most complex
spin-dependent transport phenomena in ferromagnet/non-magnet bilayers, which
involves spin injection and accumulation due to the spin Hall effect (SHE) or
Rashba-Edelstein effect (REE), spin-dependent scattering, and magnon scattering
at the interface or in the bulk of the ferromagnet. While UMR in metallic
bilayers has been studied extensively in very recent years, its magnitude is as
small as 10$^-$$^5$, which is too small for practical applications. Here, we
demonstrate a giant UMR effect in a heterostructure of BiSb topological
insulator -- GaMnAs ferromagnetic semiconductor. We obtained a large UMR ratio
of 1.1%, and found that this giant UMR is governed not by the giant
magnetoresistance (GMR)-like spin-dependent scattering, but by magnon
emission/absorption and strong spin-disorder scattering in the GaMnAs layer.
Our results provide new insight into the complex physics of UMR, as well as a
strategy for enhancing its magnitude for device applications.

###Atomic Origin of Spin-Valve Magnetoresistance at the SrRuO3 Grain Boundary|Xujing Li,Li Yin,Zhengxun Lai,Mei Wu,Yu Sheng,Lei Zhang,Yuanwei Sun,Shulin Chen,Xiaomei Li,Jingmin Zhang,Yuehui Li,Kaihui Liu,Kaiyou Wang,Dapeng Yu,Xuedong Bai,Wenbo Mi,Peng Gao###

Atomic Origin of Spin-Valve Magnetoresistance at the SrRuO3 Grain Boundary. Defects ubiquitously exist in crystal materials and usually exhibit a very
different nature than the bulk matrix, and hence, their presence can have
significant impacts on the properties of devices. Although it is well accepted
that the properties of defects are determined by their unique atomic
environments, the precise knowledge of such relationships is far from clear for
most oxides due to the complexity of defects and difficulties in
characterization. Here, we fabricate a 36.8{\deg} SrRuO3 grain boundary of
which the transport measurements show a spin-valve magnetoresistance. We
identify its atomic arrangement, including oxygen, using scanning transmission
electron microscopy and spectroscopy. Based on the as-obtained atomic
structure, the density functional theory calculations suggest that the
spin-valve magnetoresistance is because of the dramatically reduced magnetic
moments at the boundary. The ability to manipulate magnetic properties at the
nanometer scale via defect control allows new strategies to design
magnetic/electronic devices with low-dimensional magnetic order.

###Spin-torque memristors based on perpendicular magnetic tunnel junctions with a hybrid chiral texture|Xueying Zhang,Wenlong Cai,Mengxing Wang,Kaihua Cao,Tianrui Zhang,Houyi Cheng,Shaoxin Li,Daoqian Zhu,Weisheng Zhao###

Spin-torque memristors based on perpendicular magnetic tunnel junctions with a hybrid chiral texture. Spin-torque memristors were proposed in 2009, which could provide fast,
low-power and infinite memristive behavior for large-density non-volatile
memory and neuromorphic computing. However, the strict requirements of
combining high magnetoresistance, stable intermediate states and spin-polarized
current switching in a single device pose difficulties in physical
implementation. Here, we experimentally demonstrate a nanoscale spin-torque
memristor based on a perpendicular-anisotropy magnetic tunnel junction with a
CoFeB/W/CoFeB composite free layer structure. Its tunneling magnetoresistance
is higher than 200%, and memristive behavior can be realized by spin-transfer
torque switching. Memristive states are maintained by robust domain wall
pinning around clusters of W atoms, where nanoscale vertical chiral spin
textures could be formed through the competition between opposing
Dzyaloshinskii-Moriya interactions and the fluctuating interlayer coupling
caused by the Ruderman-Kittel-Kasuya-Yosida interaction between the two CoFeB
free layers. Spike-timing-dependent plasticity is also demonstrated in this
device.

###Observation of Yamaji magic angles in bismuth surfaces|Tito Huber,Scott Johnson,Leonid Konopko,Albina Nikolaeva###

Observation of Yamaji magic angles in bismuth surfaces. Bismuth consist of bismuth bilayers that are two-dimensional topological
insulators and correspondingly, the surface is an array of edge states.
Moreover, topological models, including second order topologic order, predict
an interlayer electrical coupling mediated by hinge states. Here we report that
angle dependent magnetoresistance measurements of small diameter single-crystal
bismuth nanowires exhibit the sequence of magnetoresistance (MR) peaks at
Yamaji magic angles and a peak for B//bilayer, indicating coherent transport
between layers, and showing that the Fermi surface of surface electrons is a
warped cylinder. The MR peaks are associated with magnetic field induced flat
bands that are reminiscent of the well-known flat bands in bilayer graphene.
Coherent transport across layers is interpreted in term of transport by
topological hinge states.

###Extremely large linear magnetoresistance in Antimony crystal|Mukesh Kumar Dasoundhi,Indu Rajput,Devendra Kumar,Archana Lakhani###

Extremely large linear magnetoresistance in Antimony crystal. In this letter we report the observation of extremely large non-saturating
linear magnetoresistance (MR) in Antimony(Sb) crystal. An extremely large
magnetoresistance (XMR) of 43000% at 2K and large unsaturating MR$\sim\ $70% at
room temperature is observed at the magnetic field of 9T. Hall measurements
reveal a very high mobility $\sim\ $3.8 x 10$^{4}$ cm$^{2}$/Vs of charge
carriers and strong temperature dependence of carrier concentration and
mobility. The respective scaling of MR and crossover field (B$_{c}$) from
quadratic to linear MR with mobility and inverse of mobility describes the
classical origin of large linear MR in this crystal as suggested by Parish and
Littlewood (PL) model for disordered systems.

###Electrical transport properties of bulk tetragonal CuMnAs|J Volny,D. Wagenknecht,J Zelezny,P Harcuba,E Duverger-Nedellec,R H Colman,J Kudrnovsky,I Turek,K Uhlirova,K Vyborny###

Electrical transport properties of bulk tetragonal CuMnAs. Temperature-dependent resistivity and magnetoresistance are measured in bulk
tetragonal phase of antiferromagnetic CuMnAs and the latter is found to be
anisotropic both due to structure and magnetic order. We compare these findings
to model calculations with chemical disorder and finite-temperature phenomena
included. The finite-temperature ab initio calculations are based on the alloy
analogy model implemented within the coherent potential approximation and the
results are in fair agreement with experimental data. Regarding the anisotropic
magnetoresistance (AMR) which reaches a modest magnitude of 0.12%, we
phenomenologically employ the Stoner-Wohlfarth model to identify
temperature-dependent magnetic anisotropy of our samples and conclude that the
field-dependence of AMR is more similar to that of antiferromagnets than
ferromagnets, suggesting that the origin of AMR is not related to isolated Mn
magnetic moments.

###Anisotropic magnetoresistance in spin-orbit semimetal SrIrO3|Dirk J. Groenendijk,Nicola Manca,Joeri de Bruijckere,Ana Mafalda R. V. L. Monteiro,Rocco Gaudenzi,Herre S. J. van der Zant,Andrea D. Caviglia###

Anisotropic magnetoresistance in spin-orbit semimetal SrIrO3. SrIrO3, the three-dimensional member of the Ruddlesden-Popper iridates, is a
paramagnetic semimetal characterised by a the delicate interplay between
spin-orbit coupling and Coulomb repulsion. In this work, we study the
anisotropic magnetoresistance (AMR) of SrIrO3 thin films, which is closely
linked to spin-orbit coupling and probes correlations between electronic
transport, magnetic order and orbital states. We show that the low-temperature
negative magnetoresistance is anisotropic with respect to the magnetic field
orientation, and its angular dependence reveals the appearance of a fourfold
symmetric component above a critical magnetic field. We show that this AMR
component is of magnetocrystalline origin, and attribute the observed
transition to a field-induced magnetic state in SrIrO3.

###Controlling magnetoresistance by tuning semimetallicity through dimensional confinement and heteroepitaxy|Shouvik Chatterjee,Shoaib Khalid,Hadass S. Inbar,Taozhi Guo,Yu-Hao Chang,Elliot Young,Alexei V. Fedorov,Dan Read,Anderson Janotti,Christopher J. Palmstrøm###

Controlling magnetoresistance by tuning semimetallicity through dimensional confinement and heteroepitaxy. Controlling the electronic properties via bandstructure engineering is at the
heart of modern semiconductor devices. Here, we extend this concept to
semimetals where, utilizing LuSb as a model system, we show that quantum
confinement lifts carrier compensation and differentially affects the mobility
of the electron and hole-like carriers resulting in a strong modification in
its large, non-saturating magnetoresistance behavior. Bonding mismatch at the
heteroepitaxial interface of a semimetal (LuSb) and a semiconductor (GaSb)
leads to the emergence of a novel, two-dimensional, interfacial hole gas and is
accompanied by a charge transfer across the interface that provides another
avenue to modify the electronic structure and magnetotransport properties in
the ultra-thin limit. Our work lays out a general strategy of utilizing
confined thin film geometries and heteroepitaxial interfaces to engineer
electronic structure in semimetallic systems, which allows control over their
magnetoresistance behavior and simultaneously, provides insights into its
origin.

###Spin Hall magnetoresistance in Pt/YIG bilayers via varying magnon excitation|Q. B. Liu,K. K. Meng,S. Q. Zheng,Y. C. Wu,J. Miao,X. G. Xu,Y. Jiang###

Spin Hall magnetoresistance in Pt/YIG bilayers via varying magnon excitation. Spin Hall magnetoresistance (SMR) and magnon excitation magnetoresistance
(MMR) that all generate via the spin Hall effect and inverse spin Hall effect
in a nonmagnetic material are always related to each other. However, the
influence of magnon excitation for SMR is often overlooked due to the
negligible MMR. Here, we investigate the SMR in Pt/Y3Fe5O12 (YIG) bilayers from
5 to 300K, in which the YIG are treated after Ar+-ion milling. The SMR in the
treated device is smaller than in the non-treated. According to theoretical
simulation, we attribute this phenomenon to the reduction of the interfacial
spin-mixing conductance at the treated Pt/YIG interface induced by the magnon
suppression. Our experimental results point out that the SMR and the MMR are
inter-connected, and the former could be modulated via magnon excitation. Our
findings provide a new approach for separating and clarifying the underlying
mechanisms.

###Large spin-Hall effect in Si at room temperature|Paul C. Lou,Anand Katailiha,Ravindra G. Bhardwaj,Tonmoy Bhowmick,W. P. Beyermann,Roger K. Lake,Sandeep Kumar###

Large spin-Hall effect in Si at room temperature. Silicon's weak intrinsic spin-orbit coupling and centrosymmetric crystal
structure are a critical bottleneck to the development of Si spintronics,
because they lead to an insignificant spin-Hall effect (spin current
generation) and inverse spin-Hall effect (spin current detection). Here, we
undertake current, magnetic field, crystallography dependent magnetoresistance
and magneto thermal transport measurements to study the spin transport behavior
in freestanding Si thin films. We observe a large spin-Hall magnetoresistance
in both p-Si and n-Si at room temperature and it is an order of magnitude
larger than that of Pt. One explanation of the unexpectedly large and efficient
spin-Hall effect is spin-phonon coupling instead of spin-orbit coupling. The
macroscopic origin of the spin-phonon coupling can be large strain gradients
that can exist in the freestanding Si films. This discovery in a light, earth
abundant and centrosymmetric material opens a new path of strain engineering to
achieve spin dependent properties in technologically highly-developed
materials.

###Tunable giant magnetoresistance in a single-molecule junction|Kai Yang,Hui Chen,Thomas Pope,Yibin Hu,Liwei Liu,Dongfei Wang,Lei Tao,Wende Xiao,Xiangmin Fei,Yu-Yang Zhang,Hong-Gang Luo,Shixuan Du,Tao Xiang,Werner A. Hofer,Hong-Jun Gao###

Tunable giant magnetoresistance in a single-molecule junction. Controlling electronic transport through a single-molecule junction is
crucial for molecular electronics or spintronics. In magnetic molecular
devices, the spin degree-of-freedom can be used to this end since the magnetic
properties of the magnetic ion centers fundamentally impact the transport
through the molecules. Here we demonstrate that the electron pathway in a
single-molecule device can be selected between two molecular orbitals by
varying a magnetic field, giving rise to a tunable anisotropic
magnetoresistance up to 93%. The unique tunability of the electron pathways is
due to the magnetic reorientation of the transition metal center, resulting in
a re-hybridization of molecular orbitals. We obtain the tunneling electron
pathways by Kondo effect, which manifests either as a peak or a dip line shape.
The energy changes of these spin-reorientations are remarkably low and less
than one millielectronvolt. The large tunable anisotropic magnetoresistance
could be used to control electronic transport in molecular spintronics.

###Resonant Tunneling Anisotropic Magnetoresistance Induced by Magnetic Proximity|Chenghao Shen,Timothy Leeney,Alex Matos-Abiague,Benedikt Scharf,Jong E. Han,Igor Zutic###

Resonant Tunneling Anisotropic Magnetoresistance Induced by Magnetic Proximity. We reveal that the interplay between Rashba spin-orbit coupling and
proximity-induced magnetization in a two-dimensional electron gas leads to
peculiar transport properties and large anisotropy of magnetoresistance. While
the related tunneling anisotropic magnetoresistance (TAMR) has been extensively
studied before, we predict an effect with a different origin arising from the
evolution of a resonant condition with the in-plane rotation of magnetization
and having a much larger magnitude. The resonances in the tunneling emerge from
a spin-parity-time symmetry of the scattering states. However, such a symmetry
is generally absent from the system itself and only appears for certain
parameter values. Without resonant behavior in the topological surface states
of a proximitized three-dimensional topological insulator (TI), TAMR
measurements can readily distinguish them from often misinterpreted trivial
Rashba-like states inherent to many TIs.

###Anomalous Hall Effect in Layered Ferrimagnet MnSb2Te4|Gang Shi,Mingjie Zhang,Dayu Yan,Honglei Feng,Meng Yang,Youguo Shi,Yongqing Li###

Anomalous Hall Effect in Layered Ferrimagnet MnSb2Te4. We report on low-temperature electron transport properties of MnSb2Te4, a
candidate of ferrimagnetic Weyl semimetal. Long -range magnetic order is
manifested as a nearly square-shaped hysteresis loop in the anomalous Hall
resistance, as well as sharp jumps in the magnetoresistance. At temperatures
below 4 K, a lnT-type upturn appears in the temperature dependence of
longitudinal resistance, which can be attributed to the electron-electron
interaction (EEI), since the weak localization can be excluded by the
temperature dependence of magnetoresistance. Although the anomalous Hall
resistance exhibits a similar lnT-type upturn in the same temperature range,
such correction is absent in the anomalous Hall conductivity. Our work
demonstrates that MnSb2Te4 microflakes provide an ideal system to test the
theory of EEI correction to the anomalous Hall effect.

###Modulation of anisotropic magnetoresistance by anomalous Hall signal and its application to real-time domain wall velocity measurement|Ramesh Chandra Bhatt,Yo-Yu Cheng,Lin-Xiu Ye,Ngo Trong Hai,Jong-Ching Wu,Te-ho Wu###

Modulation of anisotropic magnetoresistance by anomalous Hall signal and its application to real-time domain wall velocity measurement. We present here a way to modulate the anisotropic magnetoresistance (AMR) by
anomalous Hall signal and thus measure the domain wall (DW) motion velocity at
near-coercivity. We study the magnetization relaxation at the constant field in
the longitudinal (Rxx) Hall geometry. We observed asymmetric Rxx peaks that
appear at the DW pinning fields. This unusual magnetoresistance behavior is
explained by considering the AMR modulation by the anomalous Hall voltage. In
the proposed method, using the magnetization relaxation, the real-time DW
velocity measurement is much easier in comparison to the other microscopy
methods. Moreover, the additional signal from anomalous Hall voltage makes this
technique simpler and sensitive for DW velocity measurements, which can be
useful for various spintronic sensing applications.

###Nonconventional magnetic phenomena in neodymium thin film|G. Yumnam,J. Guo,Y. Chen,V. Lauter,D. K. Singh###

Nonconventional magnetic phenomena in neodymium thin film. Neodymium is a remarkable active component in numerous magnetic alloys that
are used in various applications. However, the application of bare neodymium
thin film is limited due to the lack of information about its electrical and
magnetic properties. We report synergistic study of Nd thin film using
experimental and theoretical techniques of polarized neutron reflectometry,
magnetoresistance measurement and density functional theory. Unlike bulk Nd,
thin film specimen is a very poor electrical conductor. Also, as grown thin
film on silicon substrate does not exhibit any magnetism in zero field.
However, moderate inplane field application of $H$ = 1.2 T tends to induce weak
magnetism in the system at low temperature of $T$ $<$ 18 K, which coincides
with an unusual cross-over behavior in magnetoresistance. The study provides
important insight in the physical characteristics of Nd thin film that are
atypical for a magnetic system.

###Multifunctional behavior of Mn-site doped antiferromagnetic Mn$_5$Si$_3$ alloys|S. C. Das,S. Pramanick,S. Chatterjee###

Multifunctional behavior of Mn-site doped antiferromagnetic Mn$_5$Si$_3$ alloys. Present work reports a detailed investigation on the magnetoresistance and
magnetocaloric behavior of Ni and Cr-doped Mn$_5$Si$_3$ alloys with general
formula Mn$_{5-x}$A$_x$Si$_3$ (where A = Ni/Cr; $x$ = 0, 0.05, 0.1 and 0.2).
Both pure (undoped) and doped alloys show a reasonably large amount of
magnetoresistance (MR). Doping at Mn-site, both by Ni and Cr, results in a
monotonic decrease in MR values. Magnetocaloric effect (MCE), on the other
hand, is found to be interesting, and all the alloys show both conventional and
inverse MCE around the magneto-structural transition temperature. Among the two
types of MCE observed, the inverse MCE is found to decrease with increasing
doping concentration and consistent with the MR behavior, whereas doping
results in a significant increase in conventional MCE values.

###Magnetoresistance in quasi-one dimensional Weyl semimetal (TaSe$_4$)$_2$I|I. A. Cohn,S. G. Zybtsev,A. P. Orlov,S. V. Zaitsev-Zotov###

Magnetoresistance in quasi-one dimensional Weyl semimetal (TaSe$_4$)$_2$I. Magnetic field effect on linear and nonlinear conductivity in a
quasi-one-dimensional Weyl semimetal with a charge density wave (CDW)
(TaSe$_4$)$_2$I is studied. Longitudinal magnetoresistance in all known regimes
of CDW motion (linear conduction, creep, sliding, "Fr\"ohlich
superconductivity") is small, positive and do not exceed a fraction of per
cent. Similar magnetotransport measurements were performed in samples profiled
by focused ion beams is such a way that motion of the CDW in them is
accompanied by phase slip of the CDW. In such samples, a peak-like
non-parabolic negative magnetoresistance is observed in relatively small
magnetic fields $B \lesssim 4$ T in the nonlinear conduction regime in both
longitudinal and transverse geometries. Our results differ significantly from
ones obtained earlier and raise the question concerning conditions for
observing the axion anomaly in Weyl semimetals in the Peierls state.

###Manifestations of classical size effect and electronic viscosity in the magnetoresistance of narrow two-dimensional conductors: Theory and experiment|O. E. Raichev,G. M. Gusev,A. D. Levin,A. K. Bakarov###

Manifestations of classical size effect and electronic viscosity in the magnetoresistance of narrow two-dimensional conductors: Theory and experiment. We develop a classical kinetic theory of magnetotransport of 2D electrons in
narrow channels with partly diffusive boundary scattering and apply it to
description of magnetoresistance measured in the temperature interval 4.2-30 K
in long mesoscopic bars fabricated from high-purity GaAs quantum well
structures. Both experiment and theory demonstrate a number of characteristic
features in the longitudinal and Hall resistances caused by the size effect in
two dimensions owing to the high ballisticity of the transport. In addition to
the features described previously, we also reveal a change in the slope of the
first derivative of magnetoresistance when the cyclotron orbit diameter equals
to half of the channel width. These features are suppressed with increasing
temperature as a result of the electronic viscosity due to electron-electron
interaction. By comparing theory and experiment, we determine the
characteristic time of relaxation of angular distribution of electrons caused
by electron-electron scattering.

###Giant Thermal Magnetoresistance Driven by Graphene Magnetoplasmon|Ming-Jian He,Hong Qi,Yan-Xiong Su,Ya-Tao Ren,Yi-Jun Zhao,Mauro Antezza###

Giant Thermal Magnetoresistance Driven by Graphene Magnetoplasmon. In this work, we have predicted a giant thermal magnetoresistance for the
thermal photon transport based on the tunable magnetoplasmon of graphene. By
applying an external magnetic field, we find that the heat flux can be
modulated by approximately three orders of magnitude. Accordingly, negative and
giant relative thermal magnetoresistance ratios are both achieved for magnetic
fields with a maximum strength of 4 Tesla. This effect is mainly caused by the
suppression and enhancement of scattering interactions mediated by graphene
magnetoplasmon. Specifically, it has never been achieved before for
nanoparticles, which have no response to magnetic fields. The effect is
remarkable at these reasonable strengths of fields, and thus has considerable
significance for the real-life applications. It is also expected to enable
technological advances for the thermal measurement-based magnetic sensor and
magnetically thermal management.

###Magnetic, transport, and thermal properties of $δ$-phase UZr$_2$|Xiaxin Ding,Tiankai Yao,Lyuwen Fu,Zilong Hua,Jason Harp,Chris Marianetti,Madhab Neupane,Michael E. Manley,David Hurley,Krzysztof Gofryk###

Magnetic, transport, and thermal properties of $δ$-phase UZr$_2$. Alloys of hexagonal $\delta$-phase UZr$_2$ have been synthesized and studied
by means of heat capacity, magnetic susceptibility, magnetization, electrical
resistivity, magnetoresistance, thermoelectric power, thermal conductivity
measurements, for the first time, at temperatures from 1.8 to 300 K and in
magnetic fields up to 8 T. The weak temperature dependence of the magnetic
susceptibility and the small value of both Seebeck (0.75 $\mu$V/K at room
temperature) and of the Sommerfeld coefficient (13.5 mJ mol$^{-1}$ K$^{-2}$)
point to 5$f$-electrons in this material having a delocalized nature. The
electrical resistivity and magnetoresistance indicate the presence of
significant electronic disorder in $\delta$-UZr$_2$, consistent with the
disorder in its crystal structure. Density functional theory calculations have
been performed and compared to experimental results.

###Weak localization and anti-localization in rare earth doped topological insulators|Zengji Yue,Kirrily Rule,Zhi Li,Weiyao Zhao,Lina Sang,Guangsai Yang,Cheng Tan,Lan Wang,Abuduliken Bake,Xiaolin Wang###

Weak localization and anti-localization in rare earth doped topological insulators. We study magneto-transport phenomena in two rare-earth doped topological
insulators, SmxFexSb2-2xTe3 and SmxBi2-xTe2Se single crystals. The
magneto-transport behaviours in both compounds exhibit a systematic crossover
between weak anti-localization (positive magnetoresistance) and weak
localization (negative magnetoresistance) with changes in temperatures and
magnetic fields. The weak localization is caused by rare-earth-doping induced
magnetization, and the weak anti-localization originates from topologically
protected surface states. The transition between weak localization and weak
anti-localization demonstrates a gap opening at the Dirac point of surface
states in the quantum diffusive regime. This work demonstrates an effective way
to manipulate the magneto-transport properties of the topological insulators by
rare-earth element doping. Magnetometry measurements indicate that the
Sm-dopant alone is paramagnetic, whereas the co-doped Fe-Sm state has
short-range antiferromagnetic order. Our results hold potential for the
realization of exotic topological effects in gapped topological insulator
surface states.

###Tunnel magnetoresistance in scandium nitride magnetic tunnel junctions using first principles|Suyogya Karki,Vivian Rogers,Priyamvada Jadaun,Daniel S. Marshall,Jean Anne C. Incorvia###

Tunnel magnetoresistance in scandium nitride magnetic tunnel junctions using first principles. The magnetic tunnel junction is a cornerstone of spintronic devices and
circuits, providing the main way to convert between magnetic and electrical
information. In state-of-the-art magnetic tunnel junctions, magnesium oxide is
used as the tunnel barrier between magnetic electrodes, providing a uniquely
large tunnel magnetoresistance at room temperature. However, the wide bandgap
and band alignment of magnesium oxide-iron systems increases the
resistance-area product and causes challenges of device-to-device variability
and tunnel barrier degradation under high current. Here, we study using first
principles narrower-bandgap scandium nitride tunneling properties and transport
in magnetic tunnel junctions in comparison to magnesium oxide. These
simulations demonstrate a high tunnel magnetoresistance in Fe/ScN/Fe MTJs via
{\Delta}_1 and {\Delta}_2' symmetry filtering with low wavefunction decay
rates, allowing a low resistance-area product. The results show that scandium
nitride could be a new tunnel barrier material for magnetic tunnel junction
devices to overcome variability and current-injection challenges.

###Butterfly-like anisotropic magnetoresistance and angle-dependent Berry phase in Type-II Weyl semimetal WP2|Kaixuan Zhang,Yongping Du,Pengdong Wang,Laiming Wei,Lin Li,Qiang Zhang,Wei Qin,Zhiyong Lin,Bin Cheng,Yifan Wang,Han Xu,Xiaodong Fan,Zhe Sun,Xiangang Wan,Changgan Zeng###

Butterfly-like anisotropic magnetoresistance and angle-dependent Berry phase in Type-II Weyl semimetal WP2. Weyl semimetal emerges as a new topologically nontrivial phase of matter,
hosting low-energy excitations of massless Weyl fermions. Here, we present a
comprehensive study of the type-II Weyl semimetal WP2. Transport studies show a
butterfly-like magnetoresistance at low temperature, reflecting the anisotropy
of the electron Fermi surfaces. The four-lobed feature gradually evolves into a
two-lobed one upon increasing temperature, mainly due to the reduced relative
contribution of electron Fermi surfaces compared to hole Fermi surfaces for the
magnetoresistance. Moreover, angle-dependent Berry phase is further discovered
from the quantum oscillations, which is ascribed to the effective manipulation
of the extremal Fermi orbits by the magnetic field to feel the nearby
topological singularities in the momentum space. The revealed topological
characters and anisotropic Fermi surfaces of WP2 substantially enrich the
physical properties of Weyl semimetals and hold great promises in topological
electronic and Fermitronic device applications.

###Angular dependence of magnetoresistance and planar Hall effect in semimetals in strong magnetic fields|Akiyoshi Yamada,Yuki Fuseya###

Angular dependence of magnetoresistance and planar Hall effect in semimetals in strong magnetic fields. The semiclassical transport theory is especially powerful for investigating
galvanomagnetic effects. Generally, the semiclassical theory is applicable only
in weak fields because it does not consider Landau quantization. Herein, we
extend the conventional semiclassical theory by considering Landau quantization
through the field dependence of carrier density in semimetals. The extended
semiclassical theory is applicable even in strong fields, where Landau
quantization is noticeable. Using this new approach, we explain the qualitative
change in the angular dependence of transverse magnetoresistance (TMR),
anisotropic magnetoresistance (AMR), and planar Hall effect (PHE) in bismuth
with an increase in the magnetic field. This unveils the puzzle of nontrivial
field-induced changes in TMR, AMR, and PHE observed recently in semimetal
bismuth.

###Determination of the spin orientation of helical electrons in monolayer WTe2|Cheng Tan,Ming-Xun Deng,Feixiang Xiang,Guolin Zheng,Sultan Albarakati,Meri Algarni,James Partridge,Alex R. Hamilton,Rui-Qiang Wang,Lan Wang###

Determination of the spin orientation of helical electrons in monolayer WTe2. Monolayer WTe2 is predicted to be a quantum spin Hall insulator (QSHI) and
electron transport along its edges has been experimentally observed. However,
the 'smoking gun' of QSHI, spin momentum locking of the edge electrons, has not
been experimentally demonstrated. We propose a model to establish the
relationship between the anisotropic magnetoresistance (AMR) and spin
orientation of the helical electrons in WTe2. Based on the predictions of the
model, angular dependent magnetoresistance measurements were carried out. The
experimental results fully supported the model and the spin orientation of the
helical edge electrons was determined. Our results not only demonstrate that
WTe2 is indeed a QSHI, but also suggest a convenient method to determine the
spin orientation of other QSHIs.

###Investigation of superconducting properties and possible nematic superconductivity in self-doped BiCh2-based superconductor CeOBiS1.7Se0.3|Ryosuke Kiyama,Kazuhisa Hoshi,Yosuke Goto,Yoshikazu Mizuguchi###

Investigation of superconducting properties and possible nematic superconductivity in self-doped BiCh2-based superconductor CeOBiS1.7Se0.3. We investigate the superconducting properties and possible nematic
superconductivity of self-doped BiCh2-based (Ch: S, Se) superconductor
CeOBiS1.7Se0.3 through the measurements of in-plane anisotropy of
magnetoresistance. Single crystals of CeOBiS1.7Se0.3 were grown using a flux
method. Single-crystal structural analysis revealed that the crystal structure
at room temperature is tetragonal (P4/nmm). Bulk superconductivity with a
transition temperature of 3.3 K was observed through electrical resistivity and
magnetization measurements. Investigation of anisotropy of upper critical field
suggested relatively low anisotropy in the crystal as compared to other
BiCh2-based superconductors. In the superconducting states of CeOBiS1.7Se0.3,
two-fold symmetric in-plane anisotropy of magnetoresistance was observed, which
indicates the in-plane rotational symmetry breaking in the tetragonal structure
and hence the possibility of nematic superconductivity in CeOBiS1.7Se0.3.

###Magnetotransport signatures of chiral magnetic anomaly in the half-Heusler phase ScPtBi|Orest Pavlosiuk,Andrzej Jezierski,Dariusz Kaczorowski,Piotr Wiśniewski###

Magnetotransport signatures of chiral magnetic anomaly in the half-Heusler phase ScPtBi. Study of magnetotransport properties of ScPtBi revealed simultaneously: a
negative contribution to the longitudinal magnetoresistance, the planar Hall
effect, and distinct angular narrowing of the longitudinal magnetoresistance {
three hallmarks of chiral magnetic anomaly (pumping of axial charge between
Weyl nodes), a distinct property of topological semimetals. Electronic
structure calculations show that structural defects, such as antisites and
vacancies, bring substantial density of states at the Fermi level of ScPtBi,
indicating that it is a semimetal, not a zero-gap semiconductor, as predicted
earlier. This is in accord with electrical resistivity in ScPtBi, showing no
characteristics of semiconductor. Moreover, below 0.7K we observed an onset of
a superconducting transition, with the resistivity disappearing completely
below 0.23 K.

###Magnetotransport in semiconductors and two-dimensional materials from first principles|Dhruv C. Desai,Bahdan Zviazhynski,Jin-Jian Zhou,Marco Bernardi###

Magnetotransport in semiconductors and two-dimensional materials from first principles. We demonstrate a first-principles method to study magnetotransport in
materials by solving the Boltzmann transport equation (BTE) in the presence of
an external magnetic field. Our approach employs ab initio electron-phonon
interactions and takes spin-orbit coupling into account. We apply our method to
various semiconductors (Si and GaAs) and two-dimensional (2D) materials
(graphene) as representative case studies. The magnetoresistance, Hall mobility
and Hall factor in Si and GaAs are in very good agreement with experiments. In
graphene, our method predicts a large magnetoresistance, consistent with
experiments. Analysis of the steady-state electron occupations in graphene
shows the dominant role of optical phonon scattering and the breaking of the
relaxation time approximation. Our work provides a detailed understanding of
the microscopic mechanisms governing magnetotransport coefficients,
establishing the BTE in a magnetic field as a broadly applicable
first-principles tool to investigate transport in semiconductors and 2D
materials.

###Magnetoresistive Sensor Detectivity: A Comparative Analysis|J. E. Davies,J. D. Watts,J. Novotny,D. Huang,P. G. Eames###

Magnetoresistive Sensor Detectivity: A Comparative Analysis. We report on the noise performance characteristics of magnetic sensors using
both magnetic tunnel junction (MTJ) and giant magnetoresistance (GMR) elements.
Each sensor studied has a notably different noise and detectivity. Of the
sensors we measured, those based on GMR multilayers have the lowest noise and
detectivity. However, the GMR sensor also has a significantly smaller linear
range. To make a direct comparison between sensors we scale the linear
operating ranges of each sensor to be the same. This is the phenomenological
equivalent of modifying the flux concentration. Upon scaling the low frequency
detectivity of the TMR sensors becomes essentially equal to that of the GMR
sensor. Using the scaling approach we are able to place the detectivity in the
context of other key parameters, namely size and power consumption. Lastly, we
use this technique to examine the upper limit for magnetoresistive sensor
performance based on a notional MTJ sensor using present record setting TMR
values.

###Double magnetic phase transitions and magnetotransport anomalies in a new compound Gd$_\textbf{2}$AgSi$_\textbf{3}$|Baidyanath Sahu###

Double magnetic phase transitions and magnetotransport anomalies in a new compound Gd$_\textbf{2}$AgSi$_\textbf{3}$. Dc and ac-magnetic susceptibility ($\chi$), specific heat ($C_\mathrm{P}$),
electrical resistivity ($\rho$) and magnetoresistance measurements performed on
the new polycrystalline compound $\mathrm{Gd_2AgSi_3}$, crystallizing in the
$\alpha$-$\mathrm{ThSi_2}$ tetragonal structure, are reported. Two magnetic
phase transitions were observed in dc and ac susceptibility, specific heat, and
resistivity measurements at temperatures $\mathrm{T_{N_1}} = 11$ K and
$\rm{T_{N_2}} = 20$ K, despite a single site occupied by Gd atom, which is an
indication of the complex magnetic behavior. $\mathrm{Gd_2AgSi_3}$ turns out to
be one of the rare Gd compound in which a minimum is observed in the
temperature dependence of resistivity in the paramagnetic state and also
negative magnetoresistance over a wide temperature range (above
$\rm{T_{N_2}}$), mimicking the behavior of exotic $\mathrm{Gd_2PdSi_3}$, in
this ternary family. The isothermal magnetic entropy and adiabatic temperature
changes reach a value of 9.5 J/kg-K and 7.5 K respectively for the field change
of 9 T.

###Quantifying the spin mixing conductance of EuO/W heterostructures by spin Hall magnetoresistance experiments|Paul Rosenberger,Matthias Opel,Stephan Geprägs,Hans Huebl,Rudolf Gross,Martina Müller,Matthias Althammer###

Quantifying the spin mixing conductance of EuO/W heterostructures by spin Hall magnetoresistance experiments. The spin Hall magnetoresistance (SMR) allows to investigate the magnetic
textures of magnetically ordered insulators in heterostructures with normal
metals by magnetotransport experiments. We here report the observation of the
SMR in in-situ prepared ferromagnetic EuO/W thin film bilayers with
magnetically and chemically well-defined interfaces. We characterize the
magnetoresistance effects utilizing angle-dependent and field-dependent
magnetotransport measurements as a function of temperature. Applying the
established SMR model, we derive and quantify the real and imaginary parts of
the complex spin mixing interface conductance. We find that the imaginary part
is by one order of magnitude larger than the real part. Both decrease with
increasing temperature. This reduction is in agreement with thermal
fluctuations in the ferromagnet.

###Giant and tunneling magnetoresistance effects from anisotropic and valley-dependent spin-momentum interactions in antiferromagnets|Libor Šmejkal,Anna Birk Hellenes,Rafael González-Hernández,Jairo Sinova,Tomáš Jungwirth###

Giant and tunneling magnetoresistance effects from anisotropic and valley-dependent spin-momentum interactions in antiferromagnets. Giant or tunneling magnetoresistance are physical phenomena used for reading
information in commercial spintronic devices. The effects rely on a conserved
spin current passing between a reference and a sensing ferromagnetic electrode
in a multilayer structure. Recently, we have proposed that these fundamental
spintronic effects can be realized in collinear antiferromagnets with staggered
spin-momentum exchange interaction, which generates conserved spin currents in
the absence of a net equilibrium magnetization. Here we elaborate on the
proposal by presenting archetype model mechanisms for the antiferromagnetic
giant and tunneling magnetoresistance effects. The models are based,
respectively, on anisotropic and valley-dependent forms of the non-relativistic
staggered spin-momentum interaction. Using first principles calculations we
link these model mechanisms to real antiferromagnetic materials and predict a
$\sim$100\% scale for the effects. We point out that besides the GMR/TMR
detection, our models directly imply the possibility of spin-transfer-torques
excitation of the antiferromagnets.

###Extremely large magnetoresistance from electron-hole compensation in the nodal loop semimetal ZrP$_2$|J. Bannies,E. Razzoli,M. Michiardi,H. -H. Kung,I. S. Elfimov,M. Yao,A. Fedorov,J. Fink,C. Jozwiak,A. Bostwick,E. Rotenberg,A. Damascelli,C. Felser###

Extremely large magnetoresistance from electron-hole compensation in the nodal loop semimetal ZrP$_2$. Several early transition metal dipnictides have been found to host
topological semimetal states and exhibit large magnetoresistance. In this
study, we use angle-resolved photoemission spectroscopy (ARPES) and
magneto-transport to study the electronic properties of a new transition metal
dipnictide ZrP$_2$. We find that ZrP$_2$ exhibits an extremely large and
unsaturated magnetoresistance of up to 40,000 % at 2 K, which originates from
an almost perfect electron-hole compensation. Our band structure calculations
further show that ZrP$_2$ hosts a topological nodal loop in proximity to the
Fermi level. Based on the ARPES measurements, we confirm the results of our
calculations and determine the surface band structure. Our study establishes
ZrP$_2$ as a new platform to investigate near-perfect electron-hole
compensation and its interplay with topological band structures.

###Topological quantum phase transition in the magnetic semimetal HoSb|Jian-Min Zhang,Fang Tang,Yurong Ruan,Y. Chen,Runwu Zhang,Wenti Guo,Shuiyuan Chen,Jianping Li,Weiyao Zhao,W. Zhou,Lei Zhang,Zhida Han,Bin Qian,Xuefan Jiang,Zhigao Huang,Dong Qian,Yong Fang###

Topological quantum phase transition in the magnetic semimetal HoSb. Magnetic topological semimetals, a novel state of quantum matter with
nontrivial band topology, have emerged as a new frontier in physics and
materials science. An external stimulus like temperature or magnetic field
could be expected to alter their spin states and thus the Fermi surface
anisotropies and topological features. Here, we perform the angular
magnetoresistance measurements and electronic band structure calculations to
reveal the evolution of HoSb's Fermi surface anisotropies and topological
nature in different magnetic states. The angular magnetoresistance results
manifest that its Fermi surface anisotropy is robust in the paramagnetic state
but is significantly modulated in the antiferromagnetic and ferromagnetic
states. More interestingly, a transition from the trivial (nontrivial) to
nontrivial (trivial) topological electronic phase is observed when HoSb
undergoes a magnetic transition from the paramagnetic (antiferromagnetic) to
antiferromagnetic (ferromagnetic) state induced by temperature (applied
magnetic field). Our studying suggests that HoSb provides an archetype platform
to study the correlations between magnetism and topological states of matter.

###Unusual magnetotransport in twisted bilayer graphene|Joe Finney,Aaron L. Sharpe,Eli J. Fox,Connie L. Hsueh,Daniel E. Parker,Matthew Yankowitz,Shaowen Chen,Kenji Watanabe,Takashi Taniguchi,Cory R. Dean,Ashvin Vishwanath,Marc Kastner,David Goldhaber-Gordon###

Unusual magnetotransport in twisted bilayer graphene. We present transport measurements of bilayer graphene with 1.38{\deg}
interlayer twist and apparent additional alignment to its hexagonal boron
nitride cladding. As with other devices with twist angles substantially larger
than the magic angle of 1.1{\deg}, we do not observe correlated insulating
states or band reorganization. However, we do observe several highly unusual
behaviors in magnetotransport. For a large range of densities around half
filling of the moir\'e bands, magnetoresistance is large and quadratic. Over
these same densities, the magnetoresistance minima corresponding to gaps
between Landau levels split and bend as a function of density and field. We
reproduce the same splitting and bending behavior in a simple tight-binding
model of Hofstadter's butterfly on a square lattice with anisotropic hopping
terms. These features appear to be a generic class of experimental
manifestations of Hofstadter's butterfly and may provide insight into the
emergent states of twisted bilayer graphene.

###Flat Band Induced Negative Magnetoresistance in Multi-Orbital Kagome Metal|Jie Zhang,T. Yilmaz,J. W. R. Meier,J. Y. Pai,J. Lapano,H. X. Li,K. Kaznatcheev,E. Vescovo,A. Huon,M. Brahlek,T. Z. Ward,B. Lawrie,R. G. Moore,H. N. Lee,Y. L. Wang,H. Miao,B. Sales###

Flat Band Induced Negative Magnetoresistance in Multi-Orbital Kagome Metal. Electronic flat band systems are a fertile platform to host
correlation-induced quantum phenomena such as unconventional superconductivity,
magnetism and topological orders. While flat band has been established in
geometrically frustrated structures, such as the kagome lattice, flat
band-induced correlation effects especially in those multi-orbital bulk systems
are rarely seen. Here we report negative magnetoresistance and signature of
ferromagnetic fluctuations in a prototypical kagome metal CoSn, which features
a flat band in proximity to the Fermi level. We find that the magnetoresistance
is dictated by electronic correlations via Fermi level tuning. Combining with
first principles and model calculations, we establish flat band-induced
correlation effects in a multi-orbital electronic system, which opens new
routes to realize unconventional superconducting and topological states in
geometrically frustrated metals.

###Linear-response magnetoresistance effects in chiral systems|Xu Yang,Bart J. van Wees###

Linear-response magnetoresistance effects in chiral systems. The chirality-induced spin selectivity (CISS) effect enables the detection of
chirality as electrical charge signals. It is often studied using a
two-terminal circuit geometry where a ferromagnet is connected to a chiral
component, and a change of electrical resistance is reported upon magnetization
reversal. This is however not expected in the linear response regime because of
compensating reciprocal processes, limiting the interpretation of experimental
results. Here we show that magnetoresistance effects can indeed appear even in
the linear response regime, either by changing the magnitude or the direction
of the magnetization or an applied magnetic field. We illustrate this in a
spin-valve device and in a chiral thin film as the CISS-induced Hanle
magnetoresistance (CHMR) effect. This effect helps to distinguish
spin-transport-related effects from other effects, and can thereby provide
further insight into the origin of CISS.

###SrPd, a candidate material with extremely large magnetoresistance|Xiao-Qin Lu,Peng-Jie Guo,Jian-Feng Zhang,Kai Liu,Zhong-Yi Lu###

SrPd, a candidate material with extremely large magnetoresistance. The extremely large magnetoresistance (XMR) effect in nonmagnetic semimetals
have attracted intensive attention recently. Here we propose an XMR candidate
material SrPd based on first-principles electronic structure calculations in
combination with a semi-classical model. The calculated carrier densities in
SrPd indicate that there is a good electron-hole compensation, while the
calculated intrinsic carrier mobilities are as high as 10$^5$
cm$^2$V$^{-1}$s$^{-1}$. There are only two doubly degenerate bands crossing the
Fermi level for SrPd, thus a semi-classical two-band model is available for
describing its transport properties. Accordingly, the magnetoresistance of SrPd
under a magnetic field of $4$ Tesla is predicted to reach ${10^5} \%$ at low
temperature. Furthermore, the calculated topological invariant indicates that
SrPd is topologically trivial. Our theoretical studies suggest that SrPd can
serve as an ideal platform to examine the charge compensation mechanism of the
XMR effect.

###Nature of electrons from oxygen vacancies and polar catastrophe at LaAlO3/SrTiO3 interfaces|Xiaorong Zhou,Zhiqi Liu###

Nature of electrons from oxygen vacancies and polar catastrophe at LaAlO3/SrTiO3 interfaces. The relative significance of quantum conductivity correction and magnetic
nature of electrons in understanding the intriguing low-temperature resistivity
minimum and negative magnetoresistance of the two-dimensional electron gas at
LaAlO3/SrTiO3 interfaces has been a long outstanding issue since its discovery.
Here we report a comparative magnetotransport study on amorphous and
oxygen-annealed crystalline LaAlO3/SrTiO3 heterostructures at a relatively
high-temperature range, where the orbital scattering is largely suppressed by
thermal fluctuations. Despite of a predominantly negative out-of-plane
magnetoresistance effect for both, the magnetotransport is isotropic for
amorphous LaAlO3/SrTiO3 while strongly anisotropic and well falls into a
two-dimensional quantum correction frame for annealed crystalline
LaAlO3/SrTiO3. These results clearly indicate that a large portion of electrons
from oxygen vacancies are localized at low temperatures, serving as magnetic
centers, while the electrons from the polar field are only weakly localized due
to constructive interference between time-reversed electron paths in the clean
limit and no signature of magnetic nature is visible.

###Quantum oscillations in an optically-illuminated two-dimensional electron system at the LaAlO$_3$/SrTiO$_3$ interface|I. Leermakers,K. Rubi,M. Yang,B. Kerdi,M. Goiran,W. Escoffier,A. S. Rana,A. E. M. Smink,A. Brinkman,H. Hilgenkamp,J. C. Maan,U. Zeitler###

Quantum oscillations in an optically-illuminated two-dimensional electron system at the LaAlO$_3$/SrTiO$_3$ interface. We have investigated the illumination effect on the magnetotransport
properties of a two-dimensional electron system at the LaAlO$_3$/SrTiO$_3$
interface. The illumination significantly reduces the zero-field sheet
resistance, eliminates the Kondo effect at low-temperature, and switches the
negative magnetoresistance into the positive one. A large increase in the
density of high-mobility carriers after illumination leads to quantum
oscillations in the magnetoresistance originating from the Landau quantization.
The carrier density ($\sim 2 \times 10^{12}$ cm$^{-2}$) and effective mass
($\sim 1.7 ~m_e$) estimated from the oscillations suggest that the
high-mobility electrons occupy the d$_{xz/yz}$ subbands of Ti:t$_{2g}$ orbital
extending deep within the conducting sheet of SrTiO$_3$. Our results
demonstrate that the illumination which induces additional carriers at the
interface can pave the way to control the Kondo-like scattering and study the
quantum transport in the complex oxide heterostructures.

###Quantum unidirectional magnetoresistance|M. Mehraeen,Pengtao Shen,Steven S. -L. Zhang###

Quantum unidirectional magnetoresistance. We predict a unidirectional magnetoresistance effect arising in a bilayer
composed of a nonmagnetic metal and a ferromagnetic insulator, whereby both
longitudinal and transverse resistances vary when the direction of the applied
electric field is reversed or the magnetization of the ferromagnetic layer is
rotated. In the presence of spin-orbit coupling, an electron wave incident on
the interface of the bilayer undergoes a spin rotation and a momentum-dependent
phase shift. Quantum interference between the incident and reflected waves
furnishes the electron with an additional velocity that is even in the in-plane
component of the electron's wavevector, giving rise to the unidirectional
magnetoresistance - a nonlinear magnetotransport effect that is rooted in the
wave nature of electrons.

###Non-reciprocal magnetoresistance, directional inhomogeneity and mixed symmetry Hall devices|Gregory Kopnov,Alexander Gerber###

Non-reciprocal magnetoresistance, directional inhomogeneity and mixed symmetry Hall devices. Phenomenology similar to the nonreciprocal charge transport violating
Onsagers reciprocity relations can develop in directionally inhomogeneous
conducting films with nonuniform Hall coefficient along the current trajectory.
The effect is demonstrated in ferromagnetic CoPd films and analyzed in
comparison with the unidirectional magnetoresistance phenomena. We suggest to
use an engineered inhomogeneity for spintronics applications and present the
concept of mixed symmetry Hall devices in which transverse to current Hall
signal is measured in a longitudinal contacts arrangement. Magnetization
reversal and memory detection is demonstrated in the three terminal and the
partitioned normal metal-ferromagnet (NM - FM) device designs. Multi-bit memory
is realized in the partitioned FM-NM-FM structure. The relative amplitude of
the antisymmetric signal in the engineered ferromagnetic devices is few percent
which is 10 to 1000 times higher than in their unidirectional magnetoresistance
analogues.

###Experimental study of transport properties of Weyl semimetal LaAlGe thin films grown by molecular beam epitaxy|Niraj Bhattarai,Andrew W. Forbes,Christopher Gassen,Raghad S. H. Saqat,Ian L. Pegg,John Philip###

Experimental study of transport properties of Weyl semimetal LaAlGe thin films grown by molecular beam epitaxy. Rare earth compounds display diverse electronic, magnetic, and
magneto-transport properties. Recently these compounds of the type RAlGe (R =
La, Ce, Pr) have been shown to exhibit Weyl semimetallic behavior. In this
work, we have investigated the crystal structure, electronic, and
magneto-transport properties of the Weyl semimetal LaAlGe thin films grown by
molecular beam epitaxy. The temperature dependence of longitudinal resistivity
at different magnetic fields is discussed. Observations of magnetoresistances
and Hall effect at different temperatures and their evolution with magnetic
field up to 6 T are also discussed with relevant mechanisms. We have observed
positive unsaturated magnetoresistances, with a small quadratic contribution at
low temperatures, which tends to saturate at higher fields. The Hall
measurements confirm the electron-dominated semimetallic conduction with an
average charge carrier density of ~ 9.68*10^21 cm^(-3) at room temperature.

###Evidence for anisotropic spin-triplet Andreev reflection at the 2D van der Waals ferromagnet/superconductor interface|Ranran Cai,Yunyan Yao,Peng Lv,Yang Ma,Wenyu Xing,Boning Li,Yuan Ji,Huibin Zhou,Chenghao Shen,Shuang Jia,X. C. Xie,Igor Zutic,Qing-Feng Sun,Wei Han###

Evidence for anisotropic spin-triplet Andreev reflection at the 2D van der Waals ferromagnet/superconductor interface. Fundamental symmetry breaking and relativistic spin-orbit coupling give rise
to fascinating phenomena in quantum materials. Of particular interest are the
interfaces between ferromagnets and common s-wave superconductors, where the
emergent spin-orbit fields support elusive spin-triplet superconductivity,
crucial for superconducting spintronics and topologically-protected Majorana
bound states. Here, we report the observation of large magnetoresistances at
the interface between a quasi-two-dimensional van der Waals ferromagnet
Fe0.29TaS2 and a conventional s-wave superconductor NbN, which provides the
possible experimental evidence for the spin triplet Andreev reflection and
induced spin-triplet superconductivity at ferromagnet/superconductor interface
arising from Rashba spin-orbit coupling. The temperature, voltage, and
interfacial barrier dependences of the magnetoresistance further support the
induced spin-triplet superconductivity and spin-triplet Andreev reflection.
This discovery, together with the impressive advances in two-dimensional van
der Waals ferromagnets, opens an important opportunity to design and probe
superconducting interfaces with exotic properties.

###Fractional magnetoresistance oscillations in spin-triplet superconducting rings|Gábor B. Halász###

Fractional magnetoresistance oscillations in spin-triplet superconducting rings. Half-quantum vortices in spin-triplet superconductors are predicted to host
Majorana zero modes and may provide a viable platform for topological quantum
computation. Recent works also suggested that, in thin mesoscopic rings, the
superconducting pairing symmetry can be probed via Little-Parks-like
magnetoresistance oscillations of periodicity $\Phi_0 = h / 2e$ that persist
below the critical temperature. Here we use the London limit of Ginzburg-Landau
theory to study these magnetoresistance oscillations resulting from thermal
vortex tunneling in spin-triplet superconducting rings. For a range of
temperatures in the presence of disorder, we find novel oscillations with an
emergent fractional periodicity $\Phi_0 / n$, where the integer $n \geq 3$ is
entirely determined by the ratio of the spin and charge superfluid densities.
These fractional oscillations can unambiguously confirm the spin-triplet nature
of superconductivity and directly reveal the tunneling of half-quantum vortices
in candidate materials such as Sr$_2$RuO$_4$ and UTe$_2$.

###Magnetic sensitivity distribution of Hall devices in antiferromagnetic switching experiments|F. Schreiber,H. Meer,C. Schmitt,R. Ramos,E. Saitoh,L. Baldrati,M. Kläui###

Magnetic sensitivity distribution of Hall devices in antiferromagnetic switching experiments. We analyze the complex impact of the local magnetic spin texture on the
transverse Hall-type voltage in device structures utilized to measure
magnetoresistance effects. We find a highly localized and asymmetric magnetic
sensitivity in the eight-terminal geometries that are frequently used in
current-induced switching experiments, for instance to probe antiferromagnetic
materials. Using current-induced switching of antiferromagnetic NiO/Pt as an
example, we estimate the change in the spin Hall magnetoresistance signal
associated with switching events based on the domain switching patterns
observed via direct imaging. This estimate correlates with the actual
electrical data after subtraction of a non-magnetic contribution. Here, the
consistency of the correlation across three measurement geometries with
fundamentally different switching patterns strongly indicates a magnetic origin
of the measured and analyzed electrical signals.

###Spin valve effect in two-dimensional VSe$_2$ system|M. A. Jafari,M. Wawrzyniak-Adamczewska,S. Stagraczyński,A. Dyrdal,J. Barnaś###

Spin valve effect in two-dimensional VSe$_2$ system. Vanadium based dichalcogenides, VSe$_2$, are two-dimensional materials in
which magnetic Vanadium atoms are arranged in a hexagonal lattice and are
coupled ferromagnetically within the plane. However, adjacent atomic planes are
coupled antiferromagnetically. This provides new and interesting opportunities
for application in spintronics and data storage and processing technologies. A
spin valve magnetoresistance may be achieved when magnetic moments of both
atomic planes are driven to parallel alignment by an external magnetic field.
The resistance change associated with the transition from antiparallel to the
parallel configuration is qualitatively similar to that observed in
artificially layered metallic magnetic structures. Detailed electronic
structure of VSe$_2$ was obtained from DFT calculations. Then, the ballistic
spin-valve magnetoresistance was determined within the Landauer formalism. In
addition, we also analyze thermal and thermoelectric properties. Both phases of
VSe$_2$, denoted as H and T, are considered.

###Emergence of Intergranular Tunneling Dominated Negative Magnetoresistance in Helimagnetic Manganese Phosphide Nanorod Thin Films|B. Muchharla,R. P. Madhogaria,D. DeTellem,C. M. Hung,A. Chanda,A. T. Duong,P. T. Huy,M. T. Trinh,S. Cho,S. Witanachchi,M. H. Phan###

Emergence of Intergranular Tunneling Dominated Negative Magnetoresistance in Helimagnetic Manganese Phosphide Nanorod Thin Films. Helical magnets are emerging as a novel class of materials for spintronics
and sensor applications; however, research on their charge and spin transport
properties in a thin film form is less explored. Herein, we report the
temperature and magnetic field dependent charge transport properties of a
highly crystalline MnP nanorod thin film over a wide temperature range (2-350
K). The MnP nanorod films of 100 nm thickness were grown on Si substrates at
500 oC using molecular beam epitaxy. The temperature dependent resistivity data
exhibits a metallic behavior over the entire measured temperature range.
However, large negative magnetoresistance of up to 12% is observed below 50 K
at which the system enters a stable helical (screw) magnetic state. In this
temperature regime, the MR(H,T) dependence seems to show a magnetic field
manipulated phase coexistence. The observed magnetoresistance is dominantly
governed by the intergranular spin dependent tunneling mechanism. These
findings pinpoint a correlation between the transport and magnetism in this
helimagnetic system.

###Unusual Magnetotransport from two dimensional Dirac Fermions in Pd$_{3}$Bi$_{2}$Se$_{2}$|Shama,Dinesh Kumar,Goutam Sheet,Yogesh Singh###

Unusual Magnetotransport from two dimensional Dirac Fermions in Pd$_{3}$Bi$_{2}$Se$_{2}$. Pd$_{3}$Bi$_{2}$Se$_{2}$ has been proposed to be topologically non-trivial in
nature. However, evidence of its non-trivial behavior is still unexplored. We
report the growth and magneto-transport study of Pd$_{3}$Bi$_{2}$Se$_{2}$ thin
films, revealing for the first time the contribution of two-dimensional (2D)
topological surface states. We observe exceptional non-saturated linear
magnetoresistance which results from Dirac fermions inhabiting the lowest
Landau level in the quantum limit. The transverse magnetoresistance changes
from a semi-classical weak-field $B^{2}$ dependence to a high-field $B$
dependence at a critical field $B^{\star}$. It is found that $B^{\star} \propto
T^2$, which is expected from the Landau level splitting of a linear energy
dispersion. In addition, the magnetoconductivity shows signatures of 2D weak
anti-localization (WAL). These novel magnetotransport signatures evince the
presence of 2D Dirac fermions in Pd$_{3}$Bi$_{2}$Se$_{2}$ thin films.

###Magnetotransport in overdoped La$_{2-x}$Sr$_x$CuO$_4$: Effect of anisotropic scattering|Rui-Ying Mao,Da Wang,Qiang-Hua Wang###

Magnetotransport in overdoped La$_{2-x}$Sr$_x$CuO$_4$: Effect of anisotropic scattering. We revisit the Hall effect and magnetoresistivity by incorporating the
anisotropic scattering caused by apical oxygen vacancies in overdoped La-based
cuprates. The theoretical calculations within the Fermi liquid picture agree
well with a handful of anomalous magneto-transport data, better than the
results using an isotropic scattering rate alone. In particular, we obtain the
upturn of Hall coefficient $R_H$ with decreasing temperature $T$, the initial
drop of $R_H$ in magnetic field $B$ in all overdoped regimes, the linear
resistivity $\rho$ versus $B$ near the van Hove doping level, the temperature
dependence of the magnetoresistivity ratio, and the violation of Kohler's law.
These results suggest that many of the anomalous transport behaviors in
overdoped La$_{2-x}$Sr$_x$CuO$_4$ could actually be understood within the Fermi
liquid picture.

###Berry-curvature-induced linear magnetotransport in magnetic Weyl semimetals|Zetao Zhang,Yizhou Liu,Wenhui Duan###

Berry-curvature-induced linear magnetotransport in magnetic Weyl semimetals. Magnetotransport such as the giant magnetoresistance and Hall effect lies at
the heart of fundamental physics and technologies. Recently, some experiments
have clearly demonstrated linear magnetotransport (LMT) proportional to
magnetic field but the underlying physical mechanism is still unclear. In this
work, we show that Berry curvature effect is a new mechanism dominating the
LMT. The Berry-curvature-induced LMT widely exists in 66 out of 122 magnetic
point groups. For typical magnetic Weyl semimetals Co$_3$Sn$_2$S$_2$ and
ferromagnetic MnBi$_2$Te$_4$, Berry curvature induces LMT conductivities
reaching orders of $10^4$ and $10^2$ ${\rm \Omega^{-1}m^{-1}}$ per tesla,
respectively, which are tunable through magnetization canting induced by
moderate magnetic fields. We further reveal that Berry-curvature-induced LMT
can be detected by Hall effect and especially intrinsic magnetoresistance
exceeding $100\%$ per tesla insensitive to the sample quality. Our results
agree with recent experiments and uncover the important role of Berry curvature
in LMT.

###Large nonsaturating magnetoresistance, weak anti-localization and non-trivial topological states in SrAl$_2$Si$_2$|Sudip Malick,A. B. Sarkar,Antu Laha,M. Anas,V. K. Malik,Amit Agarwal,Z. Hossain,J. Nayak###

Large nonsaturating magnetoresistance, weak anti-localization and non-trivial topological states in SrAl$_2$Si$_2$. We explore the electronic and topological properties of single crystal
SrAl$_2$Si$_2$ using magnetotransport experiments in conjunction with
first-principle calculations. We find that the temperature-dependent
resistivity shows a pronounced peak near 50 K. We observe several remarkable
features at low temperatures, such as large non-saturating magnetoresistance,
Shubnikov-de Haas oscillations and cusp-like magneto-conductivity. The maximum
value of magnetoresistance turns out to be 459\% at 2 K and 12 T. The analysis
of the cusp-like feature in magneto-conductivity indicates a clear signature of
weak anti-localization. Our Hall resistivity measurements confirm the presence
of two types of charge carriers in SrAl$_2$Si$_2$, with low carrier density.

###Giant chirality-induced spin-selectivity of polarons|Dan Klein,Karen Michaeli###

Giant chirality-induced spin-selectivity of polarons. The chirality-induced spin selectivity (CISS) effect gives rise to strongly
spin-dependent transport through many organic molecules and structures. Its
discovery raises fascinating fundamental questions as well as the prospect of
possible applications. The basic phenomenology, a strongly asymmetric
magnetoresistance despite the absence of magnetism, is now understood to result
from the combination of spin-orbit coupling and chiral geometry. However,
experimental signatures of electronic helicity were observed at room
temperature, i.e., at an energy scale that exceeds the typical spin-orbit
coupling in organic systems by several orders of magnitude. This work shows
that a new energy scale for CISS emerges for currents carried by polarons,
i.e., in the presence of strong electron-phonon coupling. In particular, we
found that polaron fluctuations play a crucial role in the two manifestations
of CISS in transport measurements -- the spin-dependent transmission
probability through the system and asymmetric magnetoresistance.

###Possible origin of extremely large magnetoresistance in the topological insulator CaBi2 single crystal|Yuzhe Ma,Yulong Wang,Gang Wang###

Possible origin of extremely large magnetoresistance in the topological insulator CaBi2 single crystal. CaBi2 has been experimentally found to be a superconductor with a transition
temperature of 2 K and identified as a topological insulator via spin- and
angle-resolved photoemission spectroscopy, which makes it a possible platform
to study the interplay between superconductivity and topology. But the detailed
transport properties for CaBi2 single crystal remain unexplored in experiments.
Here, we systematically studied the magneto-transport properties of CaBi2
single crystal grown by a flux method. CaBi2 shows a magnetic-field-induced
upturn behavior with a plateau in resistivity at low temperature. An extremely
large and non-saturating magnetoresistance up to ~15000% at 3 K and 12 T was
achieved. The possible reason for the magnetic field and temperature dependence
of resistivity and extremely large magnetoresistance at low temperature was
discussed by adopting the Kohler's scaling law, which can be understood by the
compensation effect confirmed by the Hall Effect measurement.

###Nonreciprocal Charge Transport in Topological Kagome Superconductor CsV$_{3}$Sb$_{5}$|Yueshen Wu,Qi Wang,Xiang Zhou,Jinghui Wang,Peng Dong,Jiadian He,Yifan Ding,Bolun Teng,Yiwen Zhang,Yifei Li,Chenglong Zhao,Hongti Zhang,Jianpeng Liu,Yanpeng Qi,Kenji Watanabe,Takashi Taniguchi,Jun Li###

Nonreciprocal Charge Transport in Topological Kagome Superconductor CsV$_{3}$Sb$_{5}$. Nonreciprocal charge transport phenomena are widely studied in
two-dimensional superconductors, which demonstrate unidirectional-anisotropy
magnetoresistances as a result of symmetry breaking. Here, we report a strong
nonreciprocal transport phenomenon in superconducting CsV$_{3}$Sb$_{5}$ thin
flakes. The second harmonic voltages, mainly originating from the rectification
effect of vortex motion, are unambiguously developed with in-plane and
out-of-plane magnetic fields, and their magnitudes are comparable to those in
noncentrosymmetric superconductors. The second harmonic magnetoresistances
split into several peaks and some of them reverse their signs by ramping the
magnetic field or the current within the superconducting transition. The
nonreciprocity suggests a strong asymmetry in CsV$_{3}$Sb$_{5}$. The
centrosymmetric structure and symmetric electronic phases in CsV$_{3}$Sb$_{5}$
can hardly induce the distinct nonreciprocal transport phenomenon, which could
be correlated to a symmetry breaking from an unconventional superconducting
order parameter symmetry.

###Spin filtering effect in intrinsic 2D magnetic semiconductor Cr2Ge2Te6|Honglei Feng,Gang Shi,Dayu Yan,Yong Li,Youguo Shi,Yang Xu,Peng Xiong,Yongqing Li###

Spin filtering effect in intrinsic 2D magnetic semiconductor Cr2Ge2Te6. All van der Waals (vdW) Fe3GeTe2/Cr2Ge2Te6/graphite magnetic heterojunctions
have been fabricated via mechanical exfoliation and stacking, and their
magnetotransport properties are studied in detail. At low bias voltages large
negative junction magnetoresistances have been observed and are attributed to
spin-conserving tunneling transport across the insulating Cr2Ge2Te6 layer. With
increasing bias, a crossover to Fowler-Nordheim tunneling takes place. The
negative sign of the tunneling magnetoresistance (TMR) suggests that the bottom
of conduction band in Cr2Ge2Te6 belongs to minority spins, opposite to the
findings of some first-principles calculations. This work shows that the vdW
heterostructures based on 2D magnetic insulators are a valuable platform to
gain further insight into spin polarized tunneling transport, which is the
basis for pursuing high performance spintronic devices and a large variety of
quantum phenomena.

###Perpendicular magnetic anisotropy, tunneling magnetoresistance and spin-transfer torque effect in magnetic tunnel junctions with Nb layers|Bowei Zhou,Pravin Khanal,Onri Jay Benally,Deyuan Lyu,Daniel B. Gopman,Arthur Enriquez,Ali Habiboglu,Kennedy Warrilow,Jian-Ping Wang,Wei-Gang Wang###

Perpendicular magnetic anisotropy, tunneling magnetoresistance and spin-transfer torque effect in magnetic tunnel junctions with Nb layers. Nb and its compounds are widely used in quantum computing due to their high
superconducting transition temperatures and high critical fields. Devices that
combine superconducting performance and spintronic non-volatility could deliver
unique functionality. Here we report the study of magnetic tunnel junctions
with Nb as the heavy metal layers. An interfacial perpendicular magnetic
anisotropy energy density of 1.85 mJ/m2 was obtained in Nb/CoFeB/MgO
heterostructures. The tunneling magnetoresistance was evaluated in junctions
with different thickness combinations and different annealing conditions. An
optimized magnetoresistance of 120% was obtained at room temperature, with a
damping parameter of 0.011 determined by ferromagnetic resonance. In addition,
spin-transfer torque switching has also been successfully observed in these
junctions with a quasistatic switching current density of 7.3*10^5 A/cm2.

###Linear nonsaturating magnetoresistance in kagome superconductor CsV3Sb5 thin flakes|Xinjian Wei,Congkuan Tian,Hang Cui,Yongkai Li,Shaobo Liu,Ya Feng,Jian Cui,Yuanjun Song,Zhiwei Wang,Jian-Hao Chen###

Linear nonsaturating magnetoresistance in kagome superconductor CsV3Sb5 thin flakes. Linear nonsaturating magnetoresistance (LMR) represents a class of anomalous
resistivity response to external magnetic field that has been observed in a
variety of materials including but not limited to topological semi-metals,
high-Tc superconductors and materials with charge/spin density wave (CDW/SDW)
orders. Here we report the observation of LMR in layered kagome superconductor
and CDW material CsV3Sb5 thin flakes, as well as the dimensional crossover and
temperature (T) crossover of such LMR. Specifically, in ultrathin CsV3Sb5
crystals, the magnetoresistance (MR) exhibits a crossover from LMR at low T to
quadratic B dependence above the CDW transition temperature; the MR also
exhibits a crossover from LMR to sublinear MR for sample thickness at around
~20 nm at low T. We discuss several possible origins of the LMR and attribute
the effect to two-dimensional (2D) CDW fluctuations. Our results may provide a
new perspective for understanding the interactions between competing orders in
kagome superconductors.

###Anomalous transport in pseudospin-1 fermions|Adesh Singh,G. Sharma###

Anomalous transport in pseudospin-1 fermions. Electronic transport in the $\alpha-\mathcal{T}_3$ model of pseudospin-1
fermions with a finite gap is studied within the semiclassical Boltzmann
approximation. We show that coupling of the orbital magnetic moment to the
external magnetic field, which is otherwise absent in the massless model,
breaks valley symmetry, results in finite and measurable corrections to the
longitudinal and Hall conductivity, and yields anomalous Hall conductivity due
to the Berry curvature. We also show that, remarkably, magnetoresistance
induced by the orbital magnetic moment can be either positive or negative; the
sign depends on the amount of disorder, and is different for both conventional
and anomalous contributions to the magnetoresistance. Recent material advances
and upcoming experiments on cold atoms that may realize pseudospin-1 fermions
makes our study timely and appropriate.

###Pressure-Induced Insulator-to-Metal Transition in van der Waals compound CoPS$_3$|Takahiro Matsuoka,Rahul Rao,Michael A. Susner,Benjamin S. Conner,Dongzhou Zhang,David Mandrus###

Pressure-Induced Insulator-to-Metal Transition in van der Waals compound CoPS$_3$. We have studied the insulator-to-metal transition and crystal structure
evolution under high pressure in the van der Waals compound CoPS$_3$ through
$\textit{in-situ}$ electrical resistance, Hall resistance, magnetoresistance,
X-ray diffraction, and Raman scattering measurements. CoPS$_3$ exhibits a
$C2/m$ $\rightarrow$ $P\overline{3}$ structural transformation at 7 GPa
accompanied by a 2.9$\%$ reduction in the volume per formula unit.
Concomitantly, the electrical resistance decreases significantly, and CoPS$_3$
becomes metallic. This metallic CoPS$_3$ is a hole-dominant conductor with
multiple conduction bands. The linear magnetoresistance and the small volume
collapse at the metallization suggest the incomplete high-spin $\rightarrow$
low-spin transition in the metallic phase. Thus, the metallic CoPS$_3$ possibly
possesses an inhomogeneous magnetic moment distribution and short-range
magnetic ordering. This report summarizes the comprehensive phase diagram of
$M$PS$_3$ ($M$ = V, Mn, Fe, Co, Ni, and Cd) that metalize under pressures.

###Tremendous tunneling magnetoresistance effects based on van der Waals room-temperature ferromagnet Fe$_3$GaTe$_2$ with highly spin-polarized Fermi surfaces|Xinlu Li,Meng Zhu,Yaoyuan Wang,Fanxing Zheng,Jianting Dong,Ye Zhou,Long You,Jia Zhang###

Tremendous tunneling magnetoresistance effects based on van der Waals room-temperature ferromagnet Fe$_3$GaTe$_2$ with highly spin-polarized Fermi surfaces. Recently, van der Waals (vdW) magnetic heterostructures have received
increasing research attention in spintronics. However, the lack of
room-temperature magnetic order of vdW material has largely impedes its
development in practical spintronics devices. Inspired by the recently
discovered vdW ferromagnet Fe3GaTe2, which has been shown to have magnetic
order above room temperature and sizable perpendicular magnetic anisotropy, we
investigate the basic electronic structure and magnetic properties of Fe3GaTe2
as well as tunneling magnetoresistance effect in magnetic tunnel junctions
(MTJs) with structure of Fe3GaTe2/Insulator/Fe3GaTe2 by using first-principles
calculations. It is found that Fe3GaTe2 with highly spin-polarized Fermi
surface ensures that such magnetic tunnel junctions may have prominent
tunneling magnetoresistance effect at room temperature even comparable to
existing conventional AlOx and MgO-based MTJs. Our results suggest that
Fe3GaTe2-based MTJs may be the promising candidate for realizing long-waiting
full magnetic vdW spintronic devices.

###Observation of an unexpected negative magnetoresistance in magnetic Weyl semimetal Co$_3$Sn$_2$S$_2$|Ali G. Moghaddam,Kevin Geishendorf,Richard Schlitz,Jorge I. Facio,Praveen Vir,Chandra Shekhar,Claudia Felser,Kornelius Nielsch,Sebastian T. B. Goennenwein,Jeroen van den Brink,Andy Thomas###

Observation of an unexpected negative magnetoresistance in magnetic Weyl semimetal Co$_3$Sn$_2$S$_2$. Time-reversal symmetry breaking allows for a rich set of magneto-transport
properties related to electronic topology. Focusing on the magnetic Weyl
semimetal Co$_3$Sn$_2$S$_2$, we prepared micro-ribbons and investigated their
transverse and longitudinal transport properties from 100 K to 180 K in
magnetic fields $\mu_0 H$ up to 2T. We establish the presence of a
magnetoresistance (MR) up to 1 % with a strong anisotropy depending the
projection of $H$ on the easy-axis magnetization, which exceeds all other
magnetoresistive effects. Based on detailed phenomenological modeling, we
attribute the observed results with unexpected form of anisotropy to magnon MR
resulting from magnon-electron coupling. Moreover, a similar angular dependence
is also found in the transverse resistivity which we show to originate from the
combination of ordinary Hall and anomalous Hall effects. Thus the interplay of
magnetic and topological properties governs the magnetotransport features of
this magnetic Weyl system.

###Impact of a ferromagnetic insulating barrier in magnetic tunnel junctions|M. Abbasi Eskandari,S. Ghotb,P. Fournier###

Impact of a ferromagnetic insulating barrier in magnetic tunnel junctions. We investigate spin-dependent conductance across a magnetic tunnel junction
(MTJ) including a ferromagnetic insulating barrier. The MTJ consists of two
half-metallic ferromagnetic La2/3Sr1/3MnO3 (LSMO) manganites as electrodes and
La2NiMnO6 (LNMO) double perovskite as a ferromagnetic insulating barrier. The
resistance of the junction is strongly dependent not only on the orientation of
the magnetic moments in LSMO electrodes, but also on the direction of the
magnetization of the LNMO barrier with respect to that of LSMO. The ratio of
tunnel magnetoresistance reaches a maximum value of 24% at 10 K, and it
decreases with temperature until it completely disappears above the critical
temperature of LNMO at 280 K. The tunneling process is described using a
mechanism which involves both empty and filled eg states of the LNMO barrier
acting as a spin-filter. A magnetic insulating barrier is an interesting path
for achieving room temperature magnetoresistance in oxide-based
heterostructures.

###Unusual anisotropic magnetoresistance due to magnetization-dependent spin-orbit interactions|M. Q. Dong,Zhi-Xin Guo,X. R. Wang###

Unusual anisotropic magnetoresistance due to magnetization-dependent spin-orbit interactions. One of recent surprising discoveries is the unusual anisotropic
magnetoresistance (UAMR) that depends on two magnetization components
perpendicular to the current differently, in contrast to the conventional
anisotropic magnetoresistance (AMR) that predicts no change in resistance when
the magnetization varies in the plane perpendicular to the current. Using
density functional theory and Boltzmann transport equation calculations for bcc
Fe, hcp Co, and bcc FeCo alloys, we show that UAMR can be accounted by the
magnetization-dependent spin-orbit interactions (SOI): Magnetization-dependent
SOI modifies electron energy bands that, in turn, changes resistance. A
phenomenological model reveals the intrinsic connection between SOI and
order-parameters. Such a mechanism is confirmed by the strong biaxial stain
effect on UAMR. Our findings provide an efficient way of searching and
optimizing materials with large UAMR, important in the design of
high-performance spintronic devices.

###A strain-controlled magnetostrictive pseudo spin valve|Vadym Iurchuk,Julien Bran,Manuel Acosta,Bohdan Kundys###

A strain-controlled magnetostrictive pseudo spin valve. Electric-field control of magnetism via inverse magnetostrictive effect is an
efficient path towards improving energy-efficient storage and sensing devices
based on giant magnetoresistance effect. In this letter, we report on lateral
electric-field driven strain-mediated modulation of magnetic properties in
Co$/$Cu$/$Py pseudo spin valve grown on ferroelectric PMN-PT substrate. We show
a decrease of the giant magnetoresistance ratio of the pseudo spin valve with
increasing electric field, which is attributed to the deviation of the Co layer
magnetization from the initial direction due to strain-induced magnetoelastic
anisotropy contribution. Additionally, we demonstrate that strain-induced
magnetic anisotropy effectively shifts the switching field of the
magnetostrictive Co layer, while keeping the switching field of the nearly
zero-magnetostrictive Py layer unaffected due to its negligible
magnetostriction constant. We argue that magnetostrictively optimized magnetic
films in properly engineered multilayered structures can offer a path to
enhancing the selective magnetic switching in spintronic devices.

###Theoretical model for the extreme positive magnetoresistance|George Kastrinakis###

Theoretical model for the extreme positive magnetoresistance. We present a model for the positive extreme magnetoresistance (XMR), recently
observed in a plethora of metallic systems, such as PtSn$_4$, PtBi$_2$,
PdCoO$_2$, WTe$_2$, NbSb$_2$, NbP, TaSb$_2$, LaSb, LaBi, ZrSiS and MoTe$_2$.
The model is an extension of our earlier work on positive giant
magnetoresistance, and uses an elaborate diagrammatic formulation. XMR is a
bulk effect (not a surface effect), due to the dramatic sensitivity of the
conductivity to the finite magnetic field $H$. This is possible at low
temperatures, in the presence of finite disorder elastic spin scattering, and
for a special value, predicted from the theory, of the material-dependent
effective Coulomb repulsion. Good agreement with experiments is obtained.
According to our model XMR is higher in cleaner samples, and anisotropic with
regards to the direction of $H$. We discuss in particular compounds containing
the elements Pt, Sc, and Rh.

###Magnetoresistance of a 2-dimensional electron gas in a random magnetic field|Anders Smith,Rafael Taboryski,Luise Theil Hansen,Claus B. Sorensen,Per Hedegard,P. E. Lindelof###

Magnetoresistance of a 2-dimensional electron gas in a random magnetic field. We report magnetoresistance measurements on a two-dimensional electron gas
(2DEG) made from a high mobility GaAs/AlGaAs heterostructure, where the
externally applied magnetic field was expelled from regions of the
semiconductor by means of superconducting lead grains randomly distributed on
the surface of the sample. A theoretical explanation in excellent agreement
with the experiment is given within the framework of the semiclassical
Boltzmann equation.

###Ballistic Composite Fermions in Semiconductor Nanostructures|J. E. F. Frost,C. -T. Liang,D. R. Mace,M. Y. Simmons,D. A. Ritchie,M. Pepper###

Ballistic Composite Fermions in Semiconductor Nanostructures. We report the results of two fundamental transport measurements at a Landau
level filling factor $\nu$ of 1/2. The well known ballistic electron transport
phenomena of quenching of the Hall effect in a mesoscopic cross-junction and
negative magnetoresistance of a constriction are observed close to B~=~0 and
$\nu~=~ 1/2$. The experimental results demonstrate semi-classical charge
transport by composite fermions, which consist of electrons bound to an even
number of flux quanta.

###Theory of colossal magnetoresistance|Alan R. Bishop,Heinrich Röder###

Theory of colossal magnetoresistance. The history and recent developments in studying (colossal) magnetoresistance
in perovskite manganese oxides is reviewed. We emphasize the growing evidence
for strongly coupled spin, charge and lattice degrees of freedom. Together with
disorder, these provide the microscopic driving forces for local and
inhomogeneous textures. The modeling and experimental probes for localized
charge-spin-lattice (polaron) structures, and their multiscale ordering, is
discussed in terms of a growing synergy of solid state physics and materials
science perspectives.

###The influence of crystal-field effects on the electronic transport properties of heavy-fermion systems: a semiphenomenological approach|M. Huth,F. B. Anders###

The influence of crystal-field effects on the electronic transport properties of heavy-fermion systems: a semiphenomenological approach. The electronic transport properties of heavy-fermion systems were calculated
based on a semiphenomenological approach to the lattice non-crossing
approximation in the limit of infinite local correlations augmented by
crystal-field effects. Within the scope of this calculation using the
linearized Boltzmann theory in the relaxation time approximation the
qualitative features of the temperature-dependent resistivity, the
magnetoresistivity and the thermoelectric power can be successfully reproduced;
this is exemplified by a comparison with experimental results on CeCu_2Si_2.

###Conductivity and Atomic Structure of Isolated Multiwalled Carbon Nanotubes|A. Yu. Kasumov,H. Bouchiat,B. Reulet,O. Stephan,I. I. Khodos,Yu. B. Gorbatov,C. Colliex###

Conductivity and Atomic Structure of Isolated Multiwalled Carbon Nanotubes. We report associated high resolution transmission electron microscopy (HRTEM)
and transport measurements on a series of isolated multiwalled carbon
nanotubes. HRTEM observations, by revealing relevant structural features of the
tubes, shed some light on the variety of observed transport behaviors, from
semiconducting to quasi-metallic type. Non Ohmic behavior is observed for
certain samples which exhibit "bamboo like" structural defects. The resistance
of the most conducting sample, measured down to 20 mK, exhibits a pronounced
maximum at 0.6 K and strong positive magnetoresistance.

###Shadow Bands and Tunneling Magnetoresistance in Itinerant Electron Ferromagnets|A. H. MacDonald,T. Jungwirth,M. Kasner###

Shadow Bands and Tunneling Magnetoresistance in Itinerant Electron Ferromagnets. In itinerant electron ferromagnets spectral weight is transferred at finite
temperatures from quasiparticle peaks located at majority and minority-spin
band energies to shadow-band peaks. For a given Bloch wavevector and band
index, the majority-spin shadow-band peak is located near the minority-spin
quasiparticle energy and the minority-spin shadow-band peak is located near the
majority-spin quasiparticle energy. This property can explain much of the
temperature dependence seen in the magnetoresistance of magnetic tunnel
junctions.

###``Cold spots'': a new model for transport in high $T_c$ cuprates|L. B. Ioffe,A. J. Millis###

``Cold spots'': a new model for transport in high $T_c$ cuprates. We present a Boltzmann equation analysis of the transport properties of a
model of electrons with a lifetime which is short everywhere except near the
Brillouin zone diagonals. The anomalous lifetime is directly implied by
photoemission and c-axis transport data. We find quantitative agreement between
calculations and ac and dc longitudinal and Hall resistivity, but the predicted
longitudinal magnetoresistance disagrees with experiment. A possible
microscopic origin of the anomalous lifetime is discussed

###Weiss oscillations in the presence of small-angle impurity scattering|A. D. Mirlin,P. Woelfle###

Weiss oscillations in the presence of small-angle impurity scattering. We calculate the magnetoresistivity of a two-dimensional electron gas in the
presence of a periodic potential within classical transport theory, using
realistic models of impurity scattering. The magnetooscillations induced by
geometric resonance of the cyclotron orbits in the periodic grating, known as
Weiss oscillations, are shown to be affected strongly by the small-angle
scattering processes dominant in conventional semiconductor heterostructures.
Our results are in full agreement with experimental findings.

###Suppression of hole-hole scattering in GaAs/AlGaAs heterostructures under uniaxial compression|V. Kravchenko,N. Minina,A. Savin,C. B. Sorensen,O. P. Hansen,W. Kraak###

Suppression of hole-hole scattering in GaAs/AlGaAs heterostructures under uniaxial compression. Resistance, magnetoresistance and their temperature dependencies have been
investigated in the 2D hole gas at a [001] p-GaAs/Al$_{0.5}$Ga$_{0.5}$As
heterointerface under [110] uniaxial compression. Analysis performed in the
frame of hole-hole scattering between carriers in the two spin splitted
subbands of the ground heavy hole state indicates, that h-h scattering is
strongly suppressed by uniaxial compression. The decay time $\tau_{01}$ of the
relative momentum reveals 4.5 times increase at a uniaxial compression of 1.3
kbar.

###Magnetoresistance due to Domain Walls in Micron Scale Fe Wires with Stripe Domains|A. D. Kent,U. Ruediger,J. Yu,S. Zhang,P. M. Levy,Y. Zhong,S. S. P. Parkin###

Magnetoresistance due to Domain Walls in Micron Scale Fe Wires with Stripe Domains. The magnetoresistance (MR) associated with domain boundaries has been
investigated in microfabricated bcc Fe (0.65 to 20 $\mu$m linewidth) wires with
controlled stripe domains. Domain configurations have been characterized using
magnetic force microscopy. MR measurements as a function of field angle,
temperature and domain configuration are used to estimate MR contributions due
to resistivity anisotropy and domain walls. Evidence is presented that domain
boundaries enhance the conductivity in such microstructures over a broad range
of temperatures (1.5 K to 80 K).

###The Effects of Resonant Tunneling on Magnetoresistance through a Q uantum Dot|Tetsufumi Tanamoto,Shinobu Fujita###

The Effects of Resonant Tunneling on Magnetoresistance through a Q uantum Dot. The effect of resonant tunneling on magnetoresistance (MR) is studied
theoretically in a double junction system. We have found that the ratio of the
MR of the resonant peak current is reduced more than that of the single
junction, whereas that of the valley current is enhanced depending on the
change of the discrete energy-level under the change of magnetic field. We also
found that the peak current-valley current (PV) ratio decreases when the
junction conductance increases.

###Anomalous spin-splitting of two-dimensional electrons in an AlAs Quantum Well|S. J. Papadakis,E. P. De Poortere,M. Shayegan###

Anomalous spin-splitting of two-dimensional electrons in an AlAs Quantum Well. We measure the effective Lande g-factor of high-mobility two-dimensional
electrons in a modulation-doped AlAs quantum well by tilting the sample in a
magnetic field and monitoring the evolution of the magnetoresistance
oscillations. The data reveal that |g| = 9.0, which is much enhanced with
respect to the reported bulk value of 1.9. Surprisingly, in a large range of
magnetic field and Landau level fillings, the value of the enhanced g-factor
appears to be constant.

###Small Magnetic Polaron Picture of Colossal Magnetoresistance in Manganites|Sudhakar Yarlagadda###

Small Magnetic Polaron Picture of Colossal Magnetoresistance in Manganites. We present a small-but-sizeable magnetic polaron picture where transport at
high temperatures is activated while at low temperatures it is band-like. We
show that both double exchange and finite bandwidth effects are important to
understand colossal magnetoresistance as well as the coincidence of the
metal-insulator and the ferromagnetic transitions in manganites. The magnetic
transition is explained using band-like motion of the polarons.

###Interlayer coupling in ferromagnetic semiconductor superlattices|T. Jungwirth,W. A. Atkinson,B. H. Lee,A. H. MacDonald###

Interlayer coupling in ferromagnetic semiconductor superlattices. We develop a mean-field theory of carrier-induced ferromagnetism in diluted
magnetic semiconductors. Our approach represents an improvement over standard
RKKY model allowing spatial inhomogeneity of the system, free-carrier spin
polarization, finite temperature, and free-carrier exchange and correlation to
be accounted for self-consistently. As an example, we calculate the electronic
structure of a Mn$_x$Ga$_{1-x}$As/GaAs superlattice with alternating
ferromagnetic and paramagnetic layers and demonstrate the possibility of
semiconductor magnetoresistance systems with designed properties.

###Spin-accumulation in small ferromagnetic double barrier junctions|Arne Brataas,Yu. V. Nazarov,J. Inoue,Gerrit E. W. Bauer###

Spin-accumulation in small ferromagnetic double barrier junctions. The non-equilibrium spin accumulation in ferromagnetic double barrier
junctions is shown to govern the transport in small structures. Transport
properties of such systems are described by a generalization of the theory of
the Coulomb blockade. The spin accumulation enhances the magnetoresistance. The
transient non-linear transport properties are predicted to provide a unique
experimental evidence of the spin-accumulation in the form of a reversed
current on time scales of the order of the spin-flip relaxation time.

###Fermi surface of the colossal magnetoresistance perovskite La_{0.7}Sr_{0.3}MnO_{3}|E. A. Livesay,R. N. West,S. B. Dugdale,G. Santi,T. Jarlborg###

Fermi surface of the colossal magnetoresistance perovskite La_{0.7}Sr_{0.3}MnO_{3}. Materials that exhibit colossal magnetoresistance (CMR) are currently the
focus of an intense research effort, driven by the technological applications
that their sensitivity lends them to. Using the angular correlation of photons
from electron-positron annihilation, we present a first glimpse of the Fermi
surface of a material that exhibits CMR, supported by ``virtual crystal''
electronic structure calculations. The Fermi surface is shown to be
sufficiently cubic in nature that it is likely to support nesting.

###Normal-state magnetotransport in La_{1.905}Ba_{0.095}CuO_{4} single crystals|Yasushi Abe,Yoichi Ando,J. Takeya,H. Tanabe,T. Watauchi,I. Tanaka,H. Kojima###

Normal-state magnetotransport in La_{1.905}Ba_{0.095}CuO_{4} single crystals. The normal-state magnetotransport properties of La_{2-x}Ba_{x}CuO_{4} single
crystals with x=0.095 are measured; at this composition, a structural
transition to a low-temperature-tetragonal (LTT) phase occurs without
suppression of superconductivity. None of the measured properties (in-plane and
out-of-plane resistivity, magnetoresistance, and Hall coefficient) shows any
sudden change at the LTT phase transition, indicating that the occurrence of
the LTT phase does not necessarily cause an immediate change in the electronic
state such as the charge-stripe stabilization.

###Infinite magnetoresistance of magnetic multilayers|R. Seviour,S. Sanvito,C. J. Lambert,J. H. Jefferson###

Infinite magnetoresistance of magnetic multilayers. We examine transport properties of a magnetic superlattice with current
perpendicular to the planes. In the limit that the phase-breaking and spin flip
scattering lengths are greater than the system size, a multiple-scattering
approach is used to calculate the 4-probe conductance. We show that by tuning
the strength of tunnel barriers placed between the current and voltage probes
giant magnetoresistance ratios of arbitrary strength and size are achievable.

###Isotope effects and the charge gap formation in the charge ordered phase of colossal magnetoresistance manganites|Unjong Yu,Yu. V. Skrypnyk,B. I. Min###

Isotope effects and the charge gap formation in the charge ordered phase of colossal magnetoresistance manganites. Giant oxygen isotope effects observed in colossal magnetoresistance
manganites are investigated by employing the combined model of the double
exchange and interacting lattice polaron mechanism. We have shown that the
isotope effects on $ T_C$ in the metallic phase and $ T_{CO}$ in the charge
ordered phase of manganites can be explained well in terms of the double
exchange and polaron narrowing factors with reasonable physical parameters.

###Magnon Broadening Effect by Magnon-Phonon Interaction in Colossal Magnetoresistance Manganites|Nobuo Furukawa###

Magnon Broadening Effect by Magnon-Phonon Interaction in Colossal Magnetoresistance Manganites. In order to study the magnetic excitation behaviors in colossal
magnetoresistance manganites, a magnon-phonon interacting system is
investigated. Sudden broadening of magnon linewidth is obtained when a magnon
branch crosses over an optical phonon branch. Onset of the broadening is
approximately determined by the magnon density of states. Anomalous magnon
damping at the brillouine zone boundary observed in low Curie temperature
manganites is explained.

###Positive Magnetoresistance of Composite Fermions in Laterally Modulated Structures|S. D. M. Zwerschke,R. R. Gerhardts###

Positive Magnetoresistance of Composite Fermions in Laterally Modulated Structures. Adopting the mean-field composite fermion picture, we describe the
magneto-transport properties of a two-dimensional electron gas with laterally
modulated density around filling factor 1/2. The occurrence of a strong
positive magnetoresistance at low effective magnetic fields as well as Weiss
oscillations, which were observed in recent experiments in such systems, can be
explained within a semi-classical Boltzmann equation approach, provided one
goes beyond a second order approximation in the modulation strength.

###Conductance Quantization and Magnetoresistance in Magnetic Point Contacts|Hiroshi Imamura,Nobuhiko Kobayashi,Saburo Takahashi,Sadamichi Maekawa###

Conductance Quantization and Magnetoresistance in Magnetic Point Contacts. We theoretically study the electron transport through a magnetic point
contact (PC) with special attention to the effect of an atomic scale domain
wall (DW). The spin precession of a conduction electron is forbidden in such an
atomic scale DW and the sequence of quantized conductances depends on the
relative orientation of magnetizations between left and right electrodes. The
magnetoresistance is strongly enhanced for the narrow PC and oscillates with
the conductance.

###Self-similar magnetoresistance of Fibonacci ultrathin magnetic films|C. G. Bezerra,J. M. de Araujo,C. Chesman,E. L. Albuquerque###

Self-similar magnetoresistance of Fibonacci ultrathin magnetic films. We study numerically the magnetic properties (magnetization and
magnetoresistance) of ultra-thin magnetic films (Fe/Cr) grown following the
Fibonacci sequence. We use a phenomenological model which includes Zeeman,
cubic anisotropy, bilinear and biquadratic exchange energies. Our physical
parameters are based on experimental data recently reported, which contain
biquadratic exchange coupling with magnitude comparable to the bilinear
exchange coupling. When biquadratic exchange coupling is sufficiently large a
striking self-similar pattern emerges.

###Linear Field Dependence of the Normal-State In-Plane Magnetoresistance of Sr2RuO4|R. Jin,Y. Liu,F. Lichtenberg###

Linear Field Dependence of the Normal-State In-Plane Magnetoresistance of Sr2RuO4. The transverse and longitudinal in-plane magnetoresistances in the normal
state of superconducting Sr2RuO4 single crystals have been measured. At low
temperatures, both of them were found to be positive with a linear
magnetic-field dependence above a threshold field, a result not expected from
electronic band theory. We argue that such behavior is a manifestation of a
novel coherent state characterized by a spin pseudo gap in the quasi-particle
excitation spectrum in Sr2RuO4.

###Observation of Magnetic Fingerprints in Superconducting Au_0.7In_0.3 Cylinders|Yu. Zadorozhny,D. R. Herman,Y. Liu###

Observation of Magnetic Fingerprints in Superconducting Au_0.7In_0.3 Cylinders. Reproducible, sample-specific magnetoresistance fluctuations (magnetic
fingerprints) have been observed experimentally in the low-temperature part of
the superconducting transition regime of disordered superconducting
Au_0.7In_0.3 cylinders. The amplitude of the fluctuation was found to exceed
that of the universal conductance fluctuation in normal metals by several
orders of magnitude. The physical origin of these observations is discussed in
the context of mesoscopic fluctuations of the superconducting condensation
energy in disordered superconductors.

###Electronic Correlations in Manganites|K. Held,D. Vollhardt###

Electronic Correlations in Manganites. The influence of local electronic correlations on the properties of colossal
magnetoresistance manganites is investigated. To this end, a ferromagnetic
two-band Kondo lattice model is supplemented with the local Coulomb repulsion
missing in this model, and is analyzed within dynamical mean-field theory.
Results for the spectral function, optical conductivity, and the
paramagnetic-to-ferromagnetic phase transition show that electronic
correlations have drastic effects and may explain some experimental
observations.

###Parallel magnetic field induced giant magnetoresistance in low density {\it quasi}-two dimensional layers|S. Das Sarma,E. H. Hwang###

Parallel magnetic field induced giant magnetoresistance in low density {\it quasi}-two dimensional layers. We provide a possible theoretical explanation for the recently observed giant
positive magnetoresistance in high mobility low density {\it quasi}-two
dimensional electron and hole systems. Our explanation is based on the strong
coupling of the parallel field to the {\it orbital} motion arising from the
{\it finite} layer thickness and the large Fermi wavelength of the {\it
quasi}-two dimensional system at low carrier densities.

###Magnetoresistance and conductivity exponents of quench-condensed ultra-thin films of Bi|K. Das Gupta,G. Sambandamurthy,V. H. S. Moorthy,N. Chandrasekhar###

Magnetoresistance and conductivity exponents of quench-condensed ultra-thin films of Bi. We have studied the magnetoresistance (MR) and evolution of conductivity with
thickness of quench-condensed Bismuth films on substrates of various dielectric
constants. Our results indicate a negative intial MR proportional to the square
of the magnetic field. The conductance shows a power-law kind of dependence on
thickness, with an exponent close to 1.33, characterisitic of a 2-D percolating
system, only when the films are grown on a thin ($\sim 10${\rm \AA} Germanium
underlayer but not otherwise.

###Anisotropic effect of field on the orthorhombic-to-tetragonal transition in the striped cuprate (La,Nd)_{2-x}Sr_xCuO_4|Z. A. Xu,N. P. Ong,T. Noda,H. Eisaki,S. Uchida###

Anisotropic effect of field on the orthorhombic-to-tetragonal transition in the striped cuprate (La,Nd)_{2-x}Sr_xCuO_4. The Nd-doped cuprate La_{2-y-x}Nd_ySr_xCuO_4 displays a first-order phase
transition at T_d (= 74 K for x=0.10, y = 0.60) to a low-temperature tetragonal
(LTT) phase. A magnetic field H applied || the a-axis leads to an increase in
T_d, whereas T_d is decreased when H || c. These effects show that magnetic
ordering involving both Nd and Cu spins plays a key role in driving the LTO-LTT
transition. Related anisotropic effects are observed in the uniform
susceptibility and the in-plane magnetoresistance.

###Charge transport along the c-axis in high-T_c cuprates|Yoichi Ando###

Charge transport along the c-axis in high-T_c cuprates. Using 61-T pulsed magnetic fields, the normal-state \rho_{ab} and \rho_{c}
are measured in Bi-2201 system down to 0.66 K, and the coexistence of the
"metallic" \rho_{ab} and the "semiconducting" \rho_{c}, usually called the
charge confinement behavior, was confirmed to extend far below T_c. Recent
measurement of the c-axis magnetoresistance under 16 T dc magnetic field in
heavily underdoped Y-123 crystals revealed that the peculiar c-axis charge
transport, and thus the charge confinement, is fundamentally related to the
antiferromagnetic spin fluctuations.

###Two-dimensional quantum interference contributions to the magnetoresistance of Nd{2-x}Ce{x}CuO{4-d} single crystals|G. I. Harus,A. N. Ignatenkov,A. I. Ponomarev,L. D. Sabirzyanova,N. G. Shelushinina,N. A. Babushkina###

Two-dimensional quantum interference contributions to the magnetoresistance of Nd{2-x}Ce{x}CuO{4-d} single crystals. The 2D weak localization effects at low temperatures T = (0.2-4.2)K have been
investigated in nonsuperconducting sample Nd{1.88}Ce{0.12}CuO{4-d} and in the
normal state of the superconducting sample Nd{1.82}Ce{0.18}CuO{4-d} for B>B_c2.
The phase coherence time and the effective thickness $d$ of a conducting CuO_2
layer have been estimated by the fitting of 2D weak localization theory
expressions to the magnetoresistivity data for the normal to plane and the
in-plane magnetic fields.

###Magnetotransport in the low carrier density ferromagnet EuB_6|S. Suellow,I. Prasad,S. Bogdanovich,M. C. Aronson,J. L. Sarrao,Z. Fisk###

Magnetotransport in the low carrier density ferromagnet EuB_6. We present a magnetotransport study of the low--carrier density ferromagnet
EuB_6. This semimetallic compound, which undergoes two ferromagnetic
transitions at T_l = 15.3 K and T_c = 12.5 K, exhibits close to T_l a colossal
magnetoresistivity (CMR). We quantitatively compare our data to recent
theoretical work, which however fails to explain our observations. We attribute
this disagreement with theory to the unique type of magnetic polaron formation
in EuB_6.

###3D-melting features of the irreversibility line in overdoped Bi$_2$Sr$_2$CuO$_6$ at ultra-low temperature and high magnetic field|A. Morello,A. G. M. Jansen,R. S. Gonnelli,S. I. Vedeneev###

3D-melting features of the irreversibility line in overdoped Bi$_2$Sr$_2$CuO$_6$ at ultra-low temperature and high magnetic field. We have measured the irreversible magnetization of an overdoped
Bi$_2$Sr$_2$CuO$_6$ single crystal up to B=28 T and down to T=60 mK, and
extracted the irreversibility line $B_{\rm irr}(T)$: the data can be
interpreted in the whole temperature range as a 3D-anisotropic vortex lattice
melting line with Lindemann number $c_{\rm L}=0.13$. We also briefly discuss
the applicability of alternative models such as 2D- and quantum melting, and
the connection with magnetoresistance experiments.

###Semi-classical magnetoresistance in weakly modulated magnetic fields|A. Matulis,F. M. Peeters###

Semi-classical magnetoresistance in weakly modulated magnetic fields. The semi-classical conductance of a two-dimensional electron gas is
calculated in the presence of a one-dimensional modulated magnetic field with
zero average. In the limit of small magnetic field amplitudes (B) the
contribution of the magnetic modulation to the magnetoresistance increases as
$B^{3/2}$ in the diffusive limit, while the increase is linear in $B$ in the
ballistic regime. Temperature does not influence the power law behavior but it
decreases the prefactor of this functional behavior.

###Skyrmion Strings and Anomalous Hall Effect in Double Exchange Systems|M. J. Calderon,L. Brey###

Skyrmion Strings and Anomalous Hall Effect in Double Exchange Systems. We perform Monte Carlo simulations to obtain quantitative results for the
anomalous Hall resistance, R_A, observed in colossal magnetoresistance
manganites. R_A arises from the interaction between the spin magnetization and
topological defects via spin-orbit coupling. We study these defects and how
they are affected by the spin-orbit coupling within the framework of the double
exchange model. The obtained anomalous Hall resistance is, in sign, order of
magnitude and shape, in agreement with experimental data.

###Field-Induced Crossover and Colossal Magnetoresistance in La(0.7)Pb(0.3)MnO(3)|Y. Y. Xue,B. Lorenz,A. K. Heilman,M. Gospodinov,S. G. Dobreva,C. W. Chu###

Field-Induced Crossover and Colossal Magnetoresistance in La(0.7)Pb(0.3)MnO(3). A field-induced crossover is observed in the resistivity and magnetization
(M) of a La(0.7)Pb(0.3)MnO(3) single crystal. The field-dependence of the
resistivity and M suggests that a small spin-canted species with
mean-field-like interactions dominates at low fields (H), whereas, individual
spins and 3D Ising/Heisenberg models describe the high-H behavior rather well.
Around the ferromagnetic transition, an H-induced destruction of the small
spin-canted magnetic polarons is accompanied by large magnetoresistance.

###Low field negative magnetoresistance in double layer structures|G. M. Minkov,A. V. Germanenko,O. E. Rut,O. I. Khrykin,V. I. Shashkin,V. M. Danil'tsev###

Low field negative magnetoresistance in double layer structures. The weak localization correction to the conductivity in coupled double layer
structures is studied both experimentally and theoretically. Statistics of
closed paths has been obtained from the analysis of magnetic field and
temperature dependencies of negative magnetoresistance for magnetic field
perpendicular and parallel to the structure plane. The comparison of
experimental data with results of computer simulation of carrier motion over
two 2D layers with scattering shows that inter-layers transitions play decisive
role in the weak localization.

###Oscillatory Exchange Coupling and Positive Magnetoresistance in Epitaxial Oxide Heterostructures|K. R. Nikolaev,A. Yu. Dobin,I. N. Krivorotov,W. K. Cooley,A. Bhattacharya,A. L. Kobrinskii,L. I. Glazman,R. M. Wentzcovitch,E. Dan Dahlberg,A. M. Goldman###

Oscillatory Exchange Coupling and Positive Magnetoresistance in Epitaxial Oxide Heterostructures. Oscillations in the exchange coupling between ferromagnetic
$La_{2/3}Ba_{1/3}MnO_3$ layers with paramagnetic $LaNiO_3$ spacer layer
thickness has been observed in epitaxial heterostructures of the two oxides.
This behavior is explained within the RKKY model employing an {\it ab initio}
calculated band structure of $LaNiO_3$, taking into account strong electron
scattering in the spacer. Antiferromagnetically coupled superlattices exhibit a
positive current-in-plane magnetoresistance.

###Electron Transport in Hybrid Ferromagnetic/Superconducting Nanostructures|V. T. Petrashov,I. A. Sosnin,C. Troadec,I. Cox,A. Parsons###

Electron Transport in Hybrid Ferromagnetic/Superconducting Nanostructures. We observe large amplitude changes in the resistance of ferromagnetic (F)
wires at the onset of superconductivity of adjacent superconductors (S). New
sharp peaks of large amplitude are found in the magnetoresistance of the
F-wires. We discuss a new mechanism for the long-range superconducting
proximity effect in F/S nanostructures based on the analysis of the topologies
of actual Fermi-surfaces in ferromagnetic metals.

###True Superconductivity in a 2D "Superconducting-Insulating" System|Nadya Mason,Aharon Kapitulnik###

True Superconductivity in a 2D "Superconducting-Insulating" System. We present results on disordered amorphous films which are expected to
undergo a field-tuned Superconductor-Insulator Transition. Based on low-field
data and I-V characteristics, we find evidence of a low temperature
Metal-to-Superconductor transition. This transition is characterized by
hysteretic magnetoresistance and discontinuities in the I-V curves. The
metallic phase just above the transition is different from the "Fermi Metal"
before superconductivity sets in.

###Mesoscopic Tunneling Magnetoresistance|Gonzalo Usaj,Harold. U. Baranger###

Mesoscopic Tunneling Magnetoresistance. We study spin-dependent transport through
ferromagnet/normal-metal/ferromagnet double tunnel junctions in the mesoscopic
Coulomb blockade regime. A general transport equation allows us to calculate
the conductance in the absence or presence of spin-orbit interaction and for
arbitrary orientation of the lead magnetizations. The tunneling
magnetoresistance (TMR), defined at the Coulomb blockade conductance peaks, is
calculated and its probability distribution presented. We show that mesoscopic
fluctuations can lead to the optimal value of the TMR.

###Competition of charge, orbital, and ferromagnetic correlations in layered manganites|D. B. Romero,Y. Moritomo,J. F. Mitchell,H. D. Drew###

Competition of charge, orbital, and ferromagnetic correlations in layered manganites. The competition of charge, orbital, and ferromagnetic interactions in layered
manganites is investigated by magneto-Raman scattering spectroscopy. We find
that the colossal magnetoresistance effect in the layered compounds results
from the interplay of the orbital and ferromagnetic double-exchange
correlations. Inelastic scattering by charge-order fluctuations dominates the
quasiparticle dynamics in the ferromagnetic-metal state. The scattering is
suppressed at low frequencies, consistent with the opening of a charge-density
wave pseudogap.

###Phenomenological model for magnetotransport in a multi-orbital system|Canio Noce,Mario Cuoco###

Phenomenological model for magnetotransport in a multi-orbital system. By means of the Boltzmann equation, we have calculated some magnetotransport
quantities for the layered multi-orbital compound Sr$_2$RuO$_4$. The Hall
coefficient, the magnetoresistance and the in-plane resistivity have been
determined taking into account the Fermi surface curvature and different time
collisions for the electrons in the $t_{2g}$ bands. A consistent explanation of
the experimental results has been obtained assuming different relaxation rates
for the in-plane transport with and without an applied magnetic field,
respectively.

###c(2x2) Interface Alloys in Co/Cu Multilayers - Influence on Interlayer Exchange Coupling and GMR|Peter Zahn,Ingrid Mertig###

c(2x2) Interface Alloys in Co/Cu Multilayers - Influence on Interlayer Exchange Coupling and GMR. The influence of a c(2x2) ordered interface alloy of 3d transition metals at
the ferromagnet/nonmagnet interface on interlayer exchange coupling (IXC), the
formation of quantum well states (QWS) and the phenomenon of Giant
MagnetoResistance is investigated. We obtained a strong dependence of IXC on
interface alloy formation. The GMR ratio is also strongly influenced. We found
that Fe, Ni and Cu alloys at the interface enhance the GMR ratio for in-plane
geometry by nearly a factor of 2.

###Ab initio description of tunnel junctions|Peter Zahn,Ingrid Mertig###

Ab initio description of tunnel junctions. Based on spin-density functional theory we calculate the electronic structure
of a tunnel junction consisting of two magnetic Fe layers separated by an
insulating vacuum barrier selfconsistently. For the conductance the Landauer
formula is evaluated in the ballistic limit as function of the magnetic
configuration. Based on these conductances the tunnel magnetoresistance (TMR)
ratio is obtained. We investigate the relation between TMR ratio and spin
polarization of the electronic structure at the metal/insulator interface.

###Giant negative magnetoresistance in semiconductors doped by multiply charged deep impurities|S. D. Ganichev,H. Ketterl,W. Prettl,I. A. Merkulov,V. I. Perel,I. N. Yassievich,A. V. Malyshev###

Giant negative magnetoresistance in semiconductors doped by multiply charged deep impurities. A giant negative magnetoresistance has been observed in bulk germanium doped
with multiply charged deep impurities. Applying a magnetic field the resistance
may decrease exponentially at any orientation of the field. A drop of the
resistance as much as about 10000% has been measured at 6 T. The effect is
attributed to the spin splitting of impurity ground state with a very large
g-factor in the order of several tens depending on impurity.

###Magnetic Fingerprints in Superconducting Au$_{0.7}$In$_{0.3}$ Cylinders|Yu. Zadorozhny,D. R. Herman,Y. Liu###

Magnetic Fingerprints in Superconducting Au$_{0.7}$In$_{0.3}$ Cylinders. Reproducible, sample-specific magnetoresistance fluctuations (magnetic
fingerprints) were observed in the low-temperature part of the superconducting
transition regime of hollow Au$_{0.7}$In$_{0.3}$ cylinders of submicron
diameter. The amplitude of the fluctuations was found to exceed that of the
universal conductance fluctuation in normal metals by several orders of
magnitude. The physical origin of these observations is related to mesoscopic
fluctuations of the superconducting order parameter.

###Inhomogeneous Charge State in HTSC Cuprates and CMR Manganites|T. Egami###

Inhomogeneous Charge State in HTSC Cuprates and CMR Manganites. Recent measurements of neutron elastic and inelastic scattering suggest that
the charge states are spatially inhomogeneous at two lengthscales, atomic and
nanometer scales, in both the high-temperature superconducting (HTSC) cuprates
and colossal magnetoresistive (CMR) manganites. We suggest that the two-phonon
mechanism that controls the charge localization in CMR manganites is also at
work in HTSC cuprates, and may hold a key to understanding the mechanism of
superconductivity.

###Probing the p-Ge_{1-x}Si_x/Ge/p-Ge_{1-x}Si_x quantum well by means of the quantum Hall effect|M. V. Yakunin,G. A. Alshanskii,Yu. G. Arapov,G. I. Harus,V. N. Neverov,N. G. Shelushinina,O. A. Kuznetsov###

Probing the p-Ge_{1-x}Si_x/Ge/p-Ge_{1-x}Si_x quantum well by means of the quantum Hall effect. We have measured the temperature (0.1 < T < 15 K) and magnetic field (0 < B <
32 T) dependences of longitudinal and Hall resistivities for the
p-Ge_{1-x}Si_x/Ge, x=~0.07, multilayers with different Ge layer widths 10 < d_w
< 38 nm and hole densities p_s = (1-5)x10^{15} m^{-2}. An extremely high
sensitivity of the experimental data [the structure of magnetoresistance
traces, relative values of the inter-Landau-level (LL) gaps deduced from the
activated magnetotransport etc] to the quantum well (QW) characteristics has
been revealed in the cases when the Fermi level reaches the second confinement
subband. The background density of states (5-10)x10^{14} m^{-2}meV^{-1} deduced
from the activation behavior of the magnetoresistance is too high to be
attributed to the LL tails, but may be accounted for within a smooth random
potential model. The hole gas in the Ge QW has been found to separate into two
sublayers for d_w > ~35 nm and p_s = ~5x10^{15} m^{-2}. A dramatic indication
to this separation is the disappearance of the quantum Hall (QH) plateau for
the filling factor nu = 1 as calculated for the whole Ge layer. Concomitantly a
positive magnetoresistance emerges in the weakest fields, from which about a
factor of two different mobilities in the sublayers have been deduced. A model
is suggested to explain the existence of the QH plateaux close to the
fundamental values in a system of two parallel layers with different
mobilities. A comparison of the simulated structure of the QH
magnetoresistivity with the experimental one indicates that the hole densities
in the sublayers are not much different. Thus, the different mobilities are due
to different quality of the normal and inverted interfaces of the Ge QW.

###Spin filtering and magnetoresistance in ballistic tunnel junctions|J. C. Egues,C. Gould,G. Richter,L. W. Molenkamp###

Spin filtering and magnetoresistance in ballistic tunnel junctions. We theoretically investigate magnetoresistance (MR) effects in connection
with spin filtering in quantum-coherent transport through tunnel junctions
based on non-magnetic/semimagnetic heterostructures. We find that spin
filtering in conjunction with the suppression/enhancement of the spin-dependent
Fermi seas in semimagnetic contacts gives rise to (i) spin-split kinks in the
MR of single barriers and (ii) a robust beating pattern in the MR of double
barriers with a semimagnetic well. We believe these are unique signatures for
quantum filtering.

###Weak localization in macroscopically inhomogeneous two-dimensional systems: a simulation approach|A. V. Germanenko,G. M. Minkov,O. E. Rut###

Weak localization in macroscopically inhomogeneous two-dimensional systems: a simulation approach. A weak-localization effect has been studied in macroscopically inhomogeneous
2D system. It is shown, that although the real phase breaking length tends to
infinity when the temperature tends to zero, such a system can reveal a
saturated behavior of the temperature dependence of that parameter, which is
obtained from the standard analysis of the negative magnetoresistance and
usually identified by experimentalists with the phase braking length.

###Rhodium Doped Manganites : Ferromagnetism and Metallicity|Bernard Raveau,Sylvie Hebert,Antoine Maignan,Raymond Fresard,Maryvonne Hervieu,Daniel Khomskii###

Rhodium Doped Manganites : Ferromagnetism and Metallicity. The possibility to induce ferromagnetism and insulator to metal transitions
in small A site cation manganites Ln_{1-x}Ca_xMnO_3 by rhodium doping is shown
for the first time. Colossal magnetoresistance (CMR) properties are evidenced
for a large compositional range (0.35 \leq x < 0.60). The ability of rhodium to
induce such properties is compared to the results obtained by chromium and
ruthenium doping. Models are proposed to explain this behavior.

###Two-Carrier Transport in Epitaxially Grown MnAs|J. J. Berry,S. J. Potashnik,S. H. Chun,K. C. Ku,P. Schiffer,N. Samarth###

Two-Carrier Transport in Epitaxially Grown MnAs. Magneto-transport measurements of ferromagnetic MnAs epilayers grown by
molecular beam epitaxy reveal the presence of both positive and negative charge
carriers. Electrical transport at high temperatures is dominated by holes, and
at low temperatures by electrons. We also observe distinct changes in the
magnetoresistance associated with the transition between the electron- and
hole-dominated transport regimes. These results are of direct relevance to
MnAs/semiconductor hybrid heterostructures and their exploitation in electronic
and optical spin injection experiments.

###Spin-polarized transport in inhomogeneous magnetic semiconductors: theory of magnetic/nonmagnetic p-n junctions|Igor Zutic,Jaroslav Fabian,S. Das Sarma###

Spin-polarized transport in inhomogeneous magnetic semiconductors: theory of magnetic/nonmagnetic p-n junctions. A theory of spin-polarized transport in inhomogeneous magnetic semiconductors
is developed and applied to magnetic/nonmagnetic p-n junctions. Several
phenomena with possible spintronic applications are predicted, including
spinvoltaic effect, spin valve effect, and giant magnetoresistance. It is
demonstrated that only nonequilibrium spin can be injected across the
space-charge region of a p-n junction, so that there is no spin injection (or
extraction) at low bias.

###Oscillating magnetoresistance in diluted magnetic semiconductor barrier structures|Kai Chang,J. B. Xia,F. M. Peeters###

Oscillating magnetoresistance in diluted magnetic semiconductor barrier structures. Ballistic spin polarized transport through diluted magnetic semiconductor
(DMS) single and double barrier structures is investigated theoretically using
a two-component model. The tunneling magnetoresistance (TMR) of the system
exhibits oscillating behavior when the magnetic field are varied. An
interesting beat pattern in the TMR and spin polarization is found for
different NMS/DMS double barrier structures which arises from an interplay
between the spin-up and spin-down electron channels which are splitted by the
s-d exchange interaction.

###Spin-relaxation and magnetoresistance in FM/SC/FM tunnel junctions|Saburo Takahashi,Taro Yamashita,Hiroshi Imamura,Sadamichi Maekawa###

Spin-relaxation and magnetoresistance in FM/SC/FM tunnel junctions. The effect of spin relaxation on tunnel magnetoresistance (TMR) in a
ferromagnet/superconductor/ferromagnet (FM/SC/FM) double tunnel junction is
theoretically studied. The spin accumulation in SC is determined by balancing
of the spin-injection rate and the spin-relaxation rate. In the superconducting
state, the spin-relaxation time becomes longer with decreasing temperature,
resulting in a rapid increase of TMR. The TMR of FM/SC/FM junctions provides a
useful probe to extract information about spin-relaxation in superconductors.

###Electronic properties of antidot lattices fabricated by atomic force lithography|A. Dorn,A. Fuhrer,T. Ihn,T. Heinzel,K. Ensslin,W. Wegscheider,M. Bichler###

Electronic properties of antidot lattices fabricated by atomic force lithography. Antidot lattices were fabricated by atomic force lithography using local
oxidation. High quality finite 20 x20 lattices are demonstrated with periods of
300 nm. The low temperature magnetoresistance shows well developed
commensurability oscillations as well as a quenching of the Hall effect around
zero magnetic field. In addition, we find B periodic oscillations superimposed
on the classical commensurability peaks at temperatures as high as 1.7 K. These
observations indicate the high electronic quality of our samples.

###Sweeping of Lattice Disorder and Associated Phenomena in Colossal Magnetoresistance Compounds|Evgenii E. Narimanov,Chandra M. Varma###

Sweeping of Lattice Disorder and Associated Phenomena in Colossal Magnetoresistance Compounds. We show through a variational calculation that in a large range of parameters
the paramagnetic to ferromagnetic transition in colossal magnetoresistance
compounds is accompanied by a collapse of polaronic lattice disorder in
addition to that of spin disorder. The spin-lattice disordered state is shown
to be localized and the ordered state itinerant as observed. The observed
dramatic change in the diffuse scattering at the transition as well as the
isotope effect are also explained.

###Non-collinear spin transfer in Co/Cu/Co multilayers|M. D. Stiles,A. Zangwill###

Non-collinear spin transfer in Co/Cu/Co multilayers. This paper has two parts. The first part uses a single point of view to
discuss the reflection and averaging mechanisms of spin-transfer between
current-carrying electrons and the ferromagnetic layers of
magnetic/non-magnetic heterostructures. The second part incorporates both
effects into a matrix Boltzmann equation and reports numerical results for
current polarization, spin accumulation, magnetoresistance, and spin-transfer
torques for Co/Cu/Co multilayers. When possible, the results are compared
quantitatively with relevant experiments.

###Anisotropic strains, metal-insulator transition, and magnetoresistance of La$_{0.7}$Ca$_{0.3}$MnO$_{3}$ films|J. H. Song,J. H. Park,Y. H. Jeong,T. Y. Koo###

Anisotropic strains, metal-insulator transition, and magnetoresistance of La$_{0.7}$Ca$_{0.3}$MnO$_{3}$ films. Thin films of perovskite manganite La$_{0.7}$Ca$_{0.3}$MnO$_{3}$ were grown
epitaxially on various substrates by either the pulsed laser deposition method
or laser molecular beam epitaxy. The substrates change both the volume and
symmetry of the unit cell of the films. It is revealed that the symmetry as
well as the volume of the unit cell have strong influence on the
metal-insulator transition temperature and the size of magnetoresistance.

###Colossal Magnetoresistance is a Griffiths Singularity|M. B. Salamon,P. Lin,S. H. Chun###

Colossal Magnetoresistance is a Griffiths Singularity. It is now widely accepted that the magnetic transition in doped manganites
that show large magnetoresistance is a type of percolation effect. This paper
demonstrates that the transition should be viewed in the context of the
Griffiths phase that arises when disorder suppresses a magnetic transition.
This approach explains unusual aspects of susceptibility and heat capacity data
from a single crystal of La$_{0.7}$Ca$_{0.3}$MnO$_{3}.$

###Ferromagnetism in Diluted Magnetic Semiconductor Heterojunction Systems|Byounghak Lee,T. Jungwirth,A. H. MacDonald###

Ferromagnetism in Diluted Magnetic Semiconductor Heterojunction Systems. Diluted magnetic semiconductors (DMSs), in which magnetic elements are
substituted for a small fraction of host elements in a semiconductor lattice,
can become ferromagnetic when doped. In this article we discuss the physics of
DMS ferromagnetism in systems with semiconductor heterojunctions. We focus on
the mechanism that cause magnetic and magnetoresistive properties to depend on
doping profiles, defect distributions, gate voltage, and other system
parameters that can in principle be engineered to yield desired results.

###The second phase transition in the pyrochlore oxide Cd2Re2O7|Zenji Hiroi,Jun-Ichi Yamaura,Yuji Muraoka,Masafumi Hanawa###

The second phase transition in the pyrochlore oxide Cd2Re2O7. Evidence for another phase transition at 120 K in the metallic pyrochlore
oxide Cd2Re2O7, following the structural transition at 200 K and followed by
the superconducting transition at 1.0 K, is given through resistivity,
magnetoresistance, specific heat, and X-ray diffraction measurements. The
results indicate unique successive structural and electronic transitions
occurring in the pyrochlore compound, revealing an interesting interplay
between the crystal and electronic structures on the itinerant electron system
in the pyrochlore lattice.

###On the Theory of Magnetotransport in a Periodically Modulated Two-Dimensional Electron Gas|Natalya A. Zimbovskaya###

On the Theory of Magnetotransport in a Periodically Modulated Two-Dimensional Electron Gas. A semiclassical theory based on the Boltzmann transport equation for a
two-dimensional electron gas modulated along one direction with weak
electrostatic or magnetic modulations is proposed. It is shown that
oscillations of the magnetoresistivity $ \rho_{||} $ corresponding to the
current driven along the modulation lines observed at moderately low magnetic
fields, can be explained as classical geometric resonances reflecting the
commensurability of the period of spatial modulations and the cyclotron radius
of electrons.

###Universal angular magnetoresistance and spin torque in ferromagnetic/normal metal hybrids|Gerrit E. W. Bauer,Yaroslav Tserkovnyak,Daniel Huertas-Hernando,Arne Brataas###

Universal angular magnetoresistance and spin torque in ferromagnetic/normal metal hybrids. The electrical resistance of ferromagnetic/normal-metal (F/N)
heterostructures depends on the nature of the junctions which may be tunnel
barriers, point contacts, or intermetallic interfaces. For all junction types,
the resistance of disordered F/N/F perpendicular spin valves as a function of
the angle between magnetization vectors is shown to obey a simple universal
law. The spin-current induced magnetization torque can be measured by the
angular magnetoresistance of these spin valves. The results are generalized to
arbitrary magnetoelectronic circuits.

###Conduction Anisotropy, Hall Effect, and Magnetoresistance of (TMTSF)2ReO4 at High Temperatures|Bojana Korin-Hamzic,Emil Tafra,Mario Basletic,Amir Hamzic,Gabriele Untereiner,Martin Dressel###

Conduction Anisotropy, Hall Effect, and Magnetoresistance of (TMTSF)2ReO4 at High Temperatures. We investigated the transport properties of the quasi one-dimensional organic
metal (TMTSF)2ReO4 above the anion-ordering metal-insulator transition (T_{AO}
\approx 180K). The pronounced conductivity anisotropy, a small and smoothly
temperature dependent Hall effect, and a small, positive and temperature
dependent magnetoresistance are analyzed within the existing Fermi-liquid and
non-Fermi liquid models. We propose that the transport properties of quasi
one-dimensional Bechgaard salts at high temperatures can be described within
the Fermi liquid description.

###Theoretical Studies of Quantum Interference in Electronic Transport Through Carbon Nanotubes|W. Iwo Babiaczyk,Bogdan. R. Bulka###

Theoretical Studies of Quantum Interference in Electronic Transport Through Carbon Nanotubes. We performed studies of coherent electronic transport through a single walled
carbon nanotube. In the calculations multiple scattering on the contacts and
interference processes were taken into account. Conductance is a composition of
contributions from different channels. We studied also spin--dependent
transport in the system with ferromagnetic electrodes.
  The magnetoresistance is large and shows large oscillations, it can be even
negative in some cases.

###A key to room-temperature ferromagnetism in Fe-doped ZnO: Cu|S-J. Han,J. W. Song,C. -H. Yang,S. H. Park,J. -H. Park,Y. H. Jeong###

A key to room-temperature ferromagnetism in Fe-doped ZnO: Cu. Successful synthesis of room-temperature ferromagnetic semiconductors,
Zn$_{1-x}$Fe$_{x}$O, is reported. The essential ingredient in achieving
room-temperature ferromagnetism in bulk Zn$_{1-x}$Fe$_{x}$O was found to be
additional Cu doping. A transition temperature as high as 550 K was obtained in
Zn$_{0.94}$Fe$_{0.05}$Cu$_{0.01}$O; the saturation magnetization at room
temperature reached a value of $0.75 \mu_{\rm B}$ per Fe. Large
magnetoresistance was also observed below $100 $K.

###Magnetic phase diagram of doped CMR manganites|Unjong Yu,Yookyung Jo,B. I. Min###

Magnetic phase diagram of doped CMR manganites. The magnetic phase diagram of the colossal magnetoresistance (CMR) manganites
is determined based on the Hamiltonian incorporating the double-exchange (DE)
interaction between degenerate Mn $e_g$ orbitals and the antiferromagnetic (AF)
superexchange interaction between Mn $t_{2g}$ spins. We have employed the
rigorous quantum mechanical formalism and obtained the finite temperature phase
diagram which describes well the commonly observed features in CMR manganites.
We have also shown that the CE-type AF structure cannot be stabilized at
$x$=0.5 in this model.

###Current and Noise in a FM/quantum dot/FM System|F. M. Souza,J. C. Egues,A. P. Jauho###

Current and Noise in a FM/quantum dot/FM System. Using the Keldysh nonequilibrium technique we calculate current, noise and
Fano factor in a ferromagnetic(FM)-quantum dot-ferromagnetic(FM) system with
Coulomb interaction and spin-flip scattering in the dot. The lead polarizations
are considered in both parallel P and antiparallel AP alignments. We show that
spin-flip can increase both AP-current and AP-noise, while the P-current and
P-noise are almost insensible to it. This fact leads to a suppression of the
tunnelling magnetoresistance with increasing spin-flip rate.

###Electron space charge effect on spin injection into semiconductors|Yue Yu,Jinbin Li,S. T. Chui###

Electron space charge effect on spin injection into semiconductors. We consider spin polarized transport in a
ferromagnet-insulator/semiconductor/insulator-ferromagnet (F1-I-S-I-F2)
junction. We find that the spin current is strongly dependent on the spin
configurations, the doping and space charge distribution in the semiconductor.
When the ferromagnet-semiconductor interface resistance is comparable to the
semiconductor resistance, the magnetoresistance ratio of this junction can be
greatly enhanced under appropriate doping when the space charge effect in the
nonequilibrium transport processes is taken into consideration.

###Intrinsic Inhomogeneities in Manganite Thin Films Investigated with Scanning Tunneling Spectroscopy|T. Becker,C. Streng,Y. Luo,V. Moshnyaga,B. Damaschke,Nic Shannon,K. Samwer###

Intrinsic Inhomogeneities in Manganite Thin Films Investigated with Scanning Tunneling Spectroscopy. Thin films of La0.7Sr0.3MnO3 on MgO show a metal insulator transition and
colossal magnetoresistance. The shape of this transition can be explained by
intrinsic spatial inhomogeneities, which give rise to a domain structure of
conducting and insulating domains at the submicrometer scale. These domains
then undergo a percolation transition. The tunneling conductance and tunneling
gap measured by scanning tunneling spectroscopy were used to distinguish and
visualize these domains.

###Effect of annealing on carrier density and Curie temperature in epitaxial (Ga,Mn)As thin films|B. Sorensen,J. Sadowski,R. Mathieu,P. Svedlindh,P. E. Lindelof###

Effect of annealing on carrier density and Curie temperature in epitaxial (Ga,Mn)As thin films. We report a clear correspondence between changes in the Curie temperature and
carrier density upon annealing in epitaxially grown (Ga,Mn)As layers with
thicknesses in the range between 5 nm and 20 nm. The changes are dependent on
the layer thickness, indicating that the (Ga,Mn)As - GaAs interface has
importance for the physical properties of the (Ga,Mn)As layer. The
magnetoresistance shows additional features when compared to thick (Ga,Mn)As
layers, that are at present of unknown origin.

###The magnetoresistive behavior of Cr-doped manganites Pr0.44Sr0.56MnO3|Z. Jirak,J. Hejtmanek,K. Knizek,M. Marysko,C. Martin,A. Maignan,M. Hervieu###

The magnetoresistive behavior of Cr-doped manganites Pr0.44Sr0.56MnO3. A complex structural, magnetic and electric transport investigation shows
that the Cr doping on Mn sites in the A-type antiferromagnet Pr0.44Sr0.56MnO3
provokes a non-uniform magnetic state with coexisting FM and AFM regions.
Irrespective of the ratio of magnetic phases, the samples exhibit a
non-metallic behavior of resistivity and thermopower, pointing to the
nanoscopic nature of the phase separation. A particularly large
magnetoresistance encountered in a broad range of temperatures for samples with
Cr doping of 4 - 6 % supports such idea.

###In-Plane Magnetodrag between Dilute Two-Dimensional Systems|R. Pillarisetty,Hwayong Noh,E. Tutuc,E. P. De Poortere,D. C. Tsui,M. Shayegan###

In-Plane Magnetodrag between Dilute Two-Dimensional Systems. We performed in-plane magnetodrag measurements on dilute double layer
two-dimensional hole systems, at in-plane magnetic fields that suppress the
apparent metallic behavior, and to fields well above those required to fully
spin polarize the system. When compared to the single layer magnetoresistance,
the magnetodrag exhibits exactly the same qualitative behavior. In addition, we
have found that the enhancement to the drag from the in-plane field exhibits a
strong maximum when both layer densities are matched.

###Proximity Effect and Spontaneous Vortex Phase in Planar SF-Structures|V. V. Ryazanov,V. A. Oboznov,A. S. Prokofiev,S. V. Dubonos###

Proximity Effect and Spontaneous Vortex Phase in Planar SF-Structures. The proximity effect in SF structures was examined. It is shown that, due to
the oscillations of the induced superconducting order parameter in a
ferromagnet, the critical temperature of an SF-bilayer becomes minimal when the
thickness of the ferromagnetic layer is close to a quarter of the period of
spatial oscillations. It is found that the spontaneous vortex state arisen in
the superconductor due to the proximity of the magnetic domain structure of a
ferromagnet brings about noticeable magnetoresistive effects.

###New collective zero-resistance states in GaAs/AlGaAs heterostructures|J. C. Phillips###

New collective zero-resistance states in GaAs/AlGaAs heterostructures. Exponentially small resistance in crossed static magnetic and microwave
fields occurs in ultrapure two dimensional electron gases (2DEG), while in less
pure systems the magnetoresistance oscillates but is always positive. A
non-perturbative theory of self-organization explains the new collective states
in terms of open orbits. There are analogies to many other anomalous physical
phenomena, as well as to scaling and evolutionary principles of biophysics.

###Suppression of 2D superconductivity by the magnetic field: quantum corrections vs superconductor-insulator transition|V. F. Gantmakher,S. N. Ermolov,G. E. Tsydynzhapov,A. A. Zhukov,T. I. Baturina###

Suppression of 2D superconductivity by the magnetic field: quantum corrections vs superconductor-insulator transition. Magnetotransport of superconducting Nd_{2-x}Ce_xCuO_{4+y} (NdCeCuO) films is
studied in the temperature interval 0.3-30 K. The microscopic theory of the
quantum corrections to conductivity, both in the Cooper and in the diffusion
channels, qualitatively describes the main features of the experiment including
the negative magnetoresistance in the high field limit. Comparison with the
model of the field-induced superconductor-insulator transition (SIT) is
included and a crossover between these two theoretical approaches is discussed.

###Competing Ground States in Triple-layered Sr4Ru3O10: Verging on Itinerant Ferromagnetism with Critical Fluctuations|G. Cao,L. Balicas,W. H. Song,Y. P. Sun,Y. Xin,V. A. Bondarenko,J. W. Brill,S. Parkin###

Competing Ground States in Triple-layered Sr4Ru3O10: Verging on Itinerant Ferromagnetism with Critical Fluctuations. Sr4Ru3O10 is characterized by a sharp metamagnetic transition and
ferromagnetic behavior occurring within the basal plane and along the c-axis,
respectively. Resistivity at magnetic field, B, exhibits low-frequency quantum
oscillations when B||c-axis and large magnetoresistivity accompanied by
critical fluctuations driven by the metamagnetism when B^c-axis. The complex
behavior evidenced in resistivity, magnetization and specific heat presented is
not characteristic of any obvious ground states, and points to an exotic state
that shows a delicate balance between fluctuations and order.

###Effect of annealing on magnetic and magnetotransport properties of Ga1-xMnxAs epilayers|I. Kuryliszyn-Kudelska,T. Wojtowicz,X. Liu,J. K. Furdyna,W. Dobrowolski,J. Z. Domagala,E. Lusakowska,M. Goiran,E. Haanappel,O. Portugall###

Effect of annealing on magnetic and magnetotransport properties of Ga1-xMnxAs epilayers. High-field magnetic measurements performed with the use of magnetooptical
Kerr effect (MOKE) in the polar configuration as well as high-field and
low-field magnetotransport studies were carried out on Ga1-xMnxAs epilayers
grown by low temperature molecular beam epitaxy, and subsequently annealed
under various conditions. The structural investigations by means of high
resolution XRD were also performed. We observe significant changes in
magnetoresistivity curves, magnetization and strain introduced by the
annealing.

###Magnetic Interactions in Transition-Metal Oxides|I. V. Solovyev###

Magnetic Interactions in Transition-Metal Oxides. This a review article, which presents a general framework for the analysis of
interatomic magnetic interactions in the spin-density-functional theory, which
is based on the magnetic force theorem, make a link with the models for
transition-metal oxides, and gives several examples of how this strategy can be
used for the analysis of magnetic properties of colossal-magnetoresistive
perovskite manganites, double perovskite and pyrochlore compounds.

###Giant positive magnetoresistance in metallic VOx thin films|A. D. Rata,V. Kataev,D. Khomskii,T. Hibma###

Giant positive magnetoresistance in metallic VOx thin films. We report on giant positive magnetoresistance effect observed in VOx thin
films, epitaxially grown on SrTiO3 substrate. The MR effect depends strongly on
temperature and oxygen content and is anisotropic. At low temperatures its
magnitude reaches 70% in a magnetic field of 5 T. Strong electron-electron
interactions in the presence of strong disorder may qualitatively explain the
results. An alternative explanation, related to a possible magnetic
instability, is also discussed.

###Orange Peel coupling in granular ferromagnetic films|D. Barness,A. Frydman###

Orange Peel coupling in granular ferromagnetic films. We present magnetoresistance (MR) measurements performed on magnetic tunnel
junctions in which one of the electrodes is a granular ferromagnetic film.
These junctions exhibit a zero field resistance dip. The dip magnitude depends
on the size of the grains. We interpret these results as a consequence of the
orange peel effect between the continuous ferromagnetic film and the magnetic
grains. The coupling is found to be much stronger than that between continuous
ferromagnetic layers.

###Anisotropic magnetoresistance in a 2DEG in a quasi-random magnetic field|A. W. Rushforth,B. L. Gallagher,P. C. Main,A. C. Neumann,M. Henini,C. H. Marrows,B. J. Hickey###

Anisotropic magnetoresistance in a 2DEG in a quasi-random magnetic field. We present magnetotransport results for a 2D electron gas (2DEG) subject to
the quasi-random magnetic field produced by randomly positioned sub-micron Co
dots deposited onto the surface of a GaAs/AlGaAs heterostructure. We observe
strong local and non-local anisotropic magnetoresistance for external magnetic
fields in the plane of the 2DEG. Monte-Carlo calculations confirm that this is
due to the changing topology of the quasi-random magnetic field in which
electrons are guided predominantly along contours of zero magnetic field.

###Magnetoresistance of nondegenerate quantum electron channels formed on the surface of superfluid helium|Yu. P. Monarkha,S. S. Sokolov,G. Q. Hai,Nelson Studart###

Magnetoresistance of nondegenerate quantum electron channels formed on the surface of superfluid helium. Transport properties of quasi-one-dimensional nondegenerate quantum wires
formed on the surface of liquid helium in the presence of a normal magnetic
field are studied using the momentum balance equation method and the memory
function formalism. The interaction with both kinds of scatterers available
(vapor atoms and capillary wave quanta) is considered. We show that unlike
classical wires, quantum nondegenerate channels exhibit strong
magnetoresistance which increases with lowering the temperature.

###Remote-doping scattering and the local field corrections in the 2D electron system in a modulation-doped Si/SiGe quantum well|V. T. Dolgopolov,E. V. Deviatov,A. A. Shashkin,U. Wieser,U. Kunze,G. Abstreiter,K. Brunner###

Remote-doping scattering and the local field corrections in the 2D electron system in a modulation-doped Si/SiGe quantum well. The small, about 30% magnetoresistance at the onset of full spin polarization
in the 2D electron system in a modulation-doped Si/SiGe quantum well gives
evidence that it is the remote doping that determines the transport scattering
time. Measurements of the mobility in this strongly-interacting electron system
with remote-doping scattering allow us to arrive at a conclusion that the
Hubbard form underestimates the local field corrections by about a factor of 2.

###Demonstration of a 1/4 cycle phase shift in the radiation-induced oscillatory-magnetoresistance in GaAs/AlGaAs devices|R. G. Mani,J. H. Smet,K. von Klitzing,V. Narayanamurti,W. B. Johnson,V. Umansky###

Demonstration of a 1/4 cycle phase shift in the radiation-induced oscillatory-magnetoresistance in GaAs/AlGaAs devices. We examine the phase and the period of the radiation-induced
oscillatory-magnetoresistance in GaAs/AlGaAs devices utilizing in-situ magnetic
field calibration by Electron Spin Resonance of DiPhenyl-Picryl-Hydrazal. The
results confirm a $f$-independent 1/4 cycle phase shift with respect to the $hf
= j\hbar\omega_{c}$ condition for $j \geq 1$, and they also suggest a small
($\approx$ 2%) reduction in the effective mass ratio, $m^{*}/m$, with respect
to the standard value for GaAs/AlGaAs devices.

###Dynamic Kerr Effect and Spectral Weight Transfer in the Manganites|S. A. McGill,R. I. Miller,O. N. Torrens,A. Mamchik,I-Wei Chen,J. M. Kikkawa###

Dynamic Kerr Effect and Spectral Weight Transfer in the Manganites. We perform pump-probe Kerr spectroscopy in the colossally magnetoresistive
manganite Pr0.67Ca0.33MnO3. Kerr effects uncover surface magnetic dynamics
undetected by established methods based on reflectivity and optical spectral
weight transfer. Our findings indicate the connection between spin and charge
dynamics in the manganites may be weaker than previously thought. Additionally,
important differences between this system and conventional ferromagnetic metals
manifest as long-lived, magneto-optical coupling transients, which may be
generic to all manganites.

###Interplay between the orbital quantization and Pauli effect in a charge-density-wave organic conductor|M. Kartsovnik,D. Andres,P. Grigoriev,W. Biberacher,H. Mueller###

Interplay between the orbital quantization and Pauli effect in a charge-density-wave organic conductor. The interlayer magnetoresistance of the low-dimensional organic metal
\alpha-(BEDT-TTF)2KHg(SCN)4 under pressure shows features which are likely
associated with theoretically predicted field-induced charge-density-wave
(FICDW) transitions. At ambient pressure, a magnetic field strongly tilted
towards the conducting layers induces a series of hysteretic anomalies. We
attribute these anomalies to a novel kind of FICDW originating from a
superposition of the orbital quantization of the nesting vector and Pauli
effect on the charge-density wave.

###Controlled normal and inverse magnetoresistance and current-driven magnetization switching in magnetic nanopillars|M. AlHajDarwish,H. Kurt,S. Urazhdin,A. Fert,R. Loloee,W. P. Pratt Jr.,J. Bass###

Controlled normal and inverse magnetoresistance and current-driven magnetization switching in magnetic nanopillars. Combining pairs of ferromagnetic metals with different signs of scattering
anisotropies, let us independently invert the magnetoresistance and the
direction of current-driven switching in
ferromagnetic/non-magnetic/ferromagnetic metal nanopillars. We show all four
combinations of normal and inverse behaviors, at both room temperature and
4.2K. In all cases studied, the direction of switching is set by the net
scattering anisotropy of the fixed (polarizing) ferromagnet. We provide simple
arguments for what we see.

###Sodium Doped LaMnO3 Thin Films: Influence of Substrate and Thickness on Physical Properties|Lorenzo Malavasi,Maria Cristina Mozzati,Ivano Alessandri,Laura Depero,Carlo B. Azzoni,Giorgio Flor###

Sodium Doped LaMnO3 Thin Films: Influence of Substrate and Thickness on Physical Properties. In this paper we report the results about the synthesis and characterization
of optimally doped La1-xNaxMnO3 thin films grown onto SrTiO3 (100), NdGaO3
(100) and NdGaO3 (110) for thickness ranging from 11 to 82 nm. The effect of
substrate nature and orientation, film thickness and annealing procedure was
investigated in order to optimize their magnetoresistance (MR). We obtained
very smooth films displaying MR values greater than 70%, near to room
temperature.

###Direct Observation of High-Temperature Polaronic Behavior In Colossal Magnetoresistive Manganites|N. Mannella,A. Rosenhahn,C. H. Booth,S. Marchesini,B. S. Mun,S. -H. Yang,K. Ibrahim,Y. Tomioka,C. S. Fadley###

Direct Observation of High-Temperature Polaronic Behavior In Colossal Magnetoresistive Manganites. The temperature dependence of the electronic and atomic structure of the
colossal magnetoresistive oxides $La_{1-x}Sr_{x}MnO_{3}$ (x = 0.3, 0.4) has
been studied using core and valence level photoemission, x-ray absorption and
emission, and extended x-ray absorption fine structure spectroscopy. A dramatic
and reversible change of the electronic structure is observed on crossing the
Curie temperature, including charge localization and spin moment increase of
Mn, together with Jahn-Teller distortions, both signatures of polaron
formation. Our data are also consistent with a phase-separation scenario.

###Oscillations of magnetoresistance of 2DEG in a weak magnetic field under microwave irradiation|A. E. Patrakov,I. I. Lyapilin###

Oscillations of magnetoresistance of 2DEG in a weak magnetic field under microwave irradiation. Under microwave irradiation, in 2D electron systems with high filling factors
oscillations of longitudinal magnetoresistance appear in the range of magnetic
fields where ordinary SdH oscillations are suppressed. An unusual beat-like
behaviour of these oscillations in weak magnetic fields (B < 0.02 T) was
attributed to the zero spin splitting previously. We propose an alternate
explanation of this beat-like structure on the basis of the Boltzmann kinetic
equation, without any reference to the spin-orbit interaction.

###Atomically Resolved Spin-Dependent Tunnelling on the Oxygen-Terminated Fe3O4 (111)|N. Berdunov,S. Murphy,G. Mariotto,I. V. Shvets###

Atomically Resolved Spin-Dependent Tunnelling on the Oxygen-Terminated Fe3O4 (111). We employ spin-polarized (SP) STM to study the spin-dependent tunneling
between a magnetite (111) sample and an antiferromagnetic tip through a vacuum
barrier at room temperature. Atomic scale STM images show significant magnetic
contrast corresponding to variations in the local surface states induced by
oxygen vacancies. The estimated variations in tunneling magnetoresistance (TMR)
of 250% suggest that the spin-transport properties are significantly altered
locally by the presence of surface defects.

###Current-driven Magnetization Reversal in a Ferromagnetic Semiconductor (Ga,Mn)As/GaAs/(Ga,Mn)As Tunnel Junction|D. Chiba,Y. Sato,T. Kita,F. Matsukura,H. Ohno###

Current-driven Magnetization Reversal in a Ferromagnetic Semiconductor (Ga,Mn)As/GaAs/(Ga,Mn)As Tunnel Junction. Current-driven magnetization reversal in a ferromagnetic semiconductor based
(Ga,Mn)As/GaAs/(Ga,Mn)As magnetic tunnel junction is demonstrated at 30 K.
Magnetoresistance measurements combined with current pulse application on a
rectangular 1.5 x 0.3 um^2 device revealed that magnetization switching occurs
at low critical current densities of 1.1 - 2.2 x 10^5 A/cm^2 despite the
presence of spin-orbit interaction in the p-type semiconductor system. Possible
mechanisms responsible for the effect are discussed.

###Spin-Transfer Effects in Nanoscale Magnetic Tunnel Junctions|G. D. Fuchs,N. C. Emley,I. N. Krivorotov,P. M. Braganca,E. M. Ryan,S. I. Kiselev,J. C. Sankey,J. A. Katine,D. C. Ralph,R. A. Buhrman###

Spin-Transfer Effects in Nanoscale Magnetic Tunnel Junctions. We report measurements of magnetic switching and steady-state magnetic
precession driven by spin-polarized currents in nanoscale magnetic tunnel
junctions with low-resistance, < 5 Ohm-micron-squared, barriers. The current
densities required for magnetic switching are similar to values for
all-metallic spin-valve devices. In the tunnel junctions, spin-transfer-driven
switching can occur at voltages that are high enough to quench the tunnel
magnetoresistance, demonstrating that the current remains spin-polarized at
these voltages.

###Oscillations of 2DEG thermoelectric coefficients in magnetic field under microwave irradiation|A. E. Patrakov,I. I. Lyapilin###

Oscillations of 2DEG thermoelectric coefficients in magnetic field under microwave irradiation. It is known that under microwave irradiation, in 2D electron systems with
high filling factors oscillations of longitudinal magnetoresistance appear in
the range of magnetic fields where ordinary SdH oscillations are suppressed. In
the present paper we propose a simple quasiclassical model of these new
oscillations based on the Boltzmann kinetic equation. Our model also predicts
similar oscillations in diffusion component of thermoelectric coefficients,
which should be observable at low temperatures.

###Propagation of a magnetic domain wall in magnetic wires with asymmetric notches|A. Himeno,T. Okuno,S. Kasai,T. Ono,S. Nasu,K. Mibu,T. Shinjo###

Propagation of a magnetic domain wall in magnetic wires with asymmetric notches. The propagation of a magnetic domain wall (DW) in a submicron magnetic wire
consisting of a magnetic/nonmagnetic/magnetic trilayered structure with
asymmetric notches was investigated by utilizing the giant magnetoresistance
effect. The propagation direction of a DW was controlled by a pulsed local
magnetic field, which nucleates the DW at one of the two ends of the wire. It
was found that the depinning field of the DW from the notch depends on the
propagation direction of the DW.

###Magnetic tunneling junctions with the Heusler compound Co_2Cr_{0.6}Fe_{0.4}Al|A. Conca,S. Falk,G. Jakob,M. Jourdan,H. Adrian###

Magnetic tunneling junctions with the Heusler compound Co_2Cr_{0.6}Fe_{0.4}Al. The Heusler alloy is used as an electrode of magnetic tunneling junctions.
The junctions are deposited by magnetron dc sputtering using shadow mask
techniques with AlO_{x} as a barrier and cobalt as counter electrode.
Measurements of the magnetoresistive differential conductivity in a temperature
range between 4K and 300K are shown. An analysis of the barrier properties
applying the Simmons model to the bias dependent junction conductivity is
performed. VSM measurements were carried out to examine the magnetic properties
of the samples.

###Field-induced spin density wave in (TMTSF)$_2$NO$_3$|David Vignolles,Alain Audouard,Marc Nardone,Luc Brossard,Sabrina Bouguessa,Jean-Marc Fabre###

Field-induced spin density wave in (TMTSF)$_2$NO$_3$. Interlayer magnetoresistance of the Bechgaard salt (TMTSF)$_2$NO$_3$ is
investigated up to 50 teslas under pressures of a few kilobars. This compound,
the Fermi surface of which is quasi two-dimensional at low temperature, is a
semi metal under pressure. Nevertheless, a field-induced spin density wave is
evidenced at 8.5 kbar above $\sim$ 20 T. This state is characterized by a
drastically different spectrum of the quantum oscillations compared to the low
pressure spin density wave state.

###Unconventional density wave in CeCoIn_5?|Balázs Dóra,Kazumi Maki,Attila Virosztek,András Ványolos###

Unconventional density wave in CeCoIn_5?. Very recently large Nernst effect and Seebeck effect were observed above the
superconducting transition temperature 2.3K in a heavy fermion superconductor
CeCoIn_5. We shall interpret this large Nernst effect in terms of
unconventional density wave (UDW), which appears around T=18K. Also the
temperature dependence of the Seebeck coefficient below T=18K is described in
terms of UDW. Another hallmark for UDW is the angular dependent
magnetoresistance, which should be readily accessible experimentally.

###Large Magnetoresistance Induced by Quantum Charge Fluctuations in Magnetic Double Dots|L. Sheng,D. Y. Xing,D. N. Sheng###

Large Magnetoresistance Induced by Quantum Charge Fluctuations in Magnetic Double Dots. We study electron tunneling through two small ferromagnetic dots. Quantum
charge fluctuations and interdot coupling make each Coulomb peak of the
conductance at zero interdot coupling split across. The interdot tunnel
coupling is determined by the relative orientation of magnetizations of the two
dots, leading to different splitting energies of the Coulomb peaks in parallel
and antiparallel magnetization alignments. As a result, a very large tunneling
magnetoresistance occurs near the Coulomb peaks, and its sign may be either
positive or negative.

###Current-Induced Magnetization Switching in Permalloy-based Nanopillars with Cu, Ag, and Au|H. Kurt,R. Loloee,W. P. Pratt Jr.,J. Bass###

Current-Induced Magnetization Switching in Permalloy-based Nanopillars with Cu, Ag, and Au. We compare magnetoresistances (MR) and switching currents (I_s) at room
temperature (295K) and 4.2K for Permalloy/N/Permalloy nanopillars undergoing
current-induced magnetization switching (CIMS), with non-magnetic metals N =
Cu, Ag, and Au. The N-metal thickness is held fixed at 10 nm. Any systematic
differences in MR and I_s for the different N-metals are modest, suggesting
that Ag and Au represent potentially viable alternatives for CIMS studies and
devices to the more widely used Cu.

###Manipulating Current-Induced Magnetization Switching|S. Urazhdin,H. Kurt,M. AlHajDarwish,Norman O. Birge,W. P. Pratt Jr.,J. Bass###

Manipulating Current-Induced Magnetization Switching. We summarize our recent findings on how current-driven magnetization
switching and magnetoresistance in nanofabricated magnetic multilayers are
affected by varying the spin-scattering properties of the non-magnetic spacers,
the relative orientations of the magnetic layers, and spin-dependent scattering
properties of the interfaces and the bulk of the magnetic layers. We show how
our data are explained in terms of current-dependent effective magnetic
temperature.

###Magnetotransport and Domain Wall in Nanoconstriction of Ferromagnetic Semiconductor (Ga,Mn)As|T. Figielski,T. Wosinski,O. Pelya,J. Sadowski,A. Morawski,A. Makosa,W. Dobrowolski,R. Szymczak,J. Wrobel###

Magnetotransport and Domain Wall in Nanoconstriction of Ferromagnetic Semiconductor (Ga,Mn)As. We studied magnetoresistance (MR) of nanoconstrictions created in (Ga,Mn)As
epilayers by O+ ion implantation. Original layers exhibit a negative MR that is
plausibly caused by weak localization (WL) effects at the lowest temperatures.
In constricted samples, additionally, jumps of an enhanced conductance appear
on the background of the negative MR, whose positions reflect the hysteresis of
magnetization. We argue that they are manifestation of a suppression of WL due
to the nucleation of a domain wall in the constriction

###First-principles generation of Stereographic Maps for high-field magnetoresistance in normal metals: an application to Au and Ag|Roberto De Leo###

First-principles generation of Stereographic Maps for high-field magnetoresistance in normal metals: an application to Au and Ag. About thirty high-field magnetoresistance Stereographic Maps have been
measured for metals between Fifties and Seventies but no way was known till now
to compare these complex experimental data with first-principles computations.
We present here the method we developed to generate Stereographic Maps directly
from a metal's Fermi Surface, based on the Lifshitz model and the recent
advances by S.P. Novikov and his pupils. As an application, we test the method
with an interesting toy model and then with Au and Ag.

###Oscillatory and Vanishing Resistance States in Microwave Irradiated 2D Electron Systems|R. R. Du,M. A. Zudov,C. L. Yang,Z. Q. Yuan,L. N. Pfeiffer,K. W. West###

Oscillatory and Vanishing Resistance States in Microwave Irradiated 2D Electron Systems. Giant-amplitude oscillations in dc magnetoresistance of a high-mobility
two-dimensional electron system can be induced by millimeterwave irradiations,
leading to zero-resistance states at the oscillation minima. Following a brief
overview of the now well-known phenomenon, this paper reports on aspects of
more recent experiments on the subject. These are: new zero-resistance states
associated with multi-photon processes; suppression of Shubnikov-de Haas
oscillations by high-frequency microwaves; and microwave photoconductivity of a
high-mobility two-dimensional hole system.

###Searching for a magnetic proximity effect in magnetite-carbon structures|R. Höhne,M. Ziese,P. Esquinazi###

Searching for a magnetic proximity effect in magnetite-carbon structures. In order to study a possible magnetic proximity effect in magnetite-carbon
structures, we have performed magnetization measurements of graphite-magnetite
composites with different mass ratios as well as the measurement of the
magnetoresistance of one of them and of the magnetization of a magnetite-carbon
bilayer. The overall results do not indicate the induction of bulk
ferromagnetism in graphite and disordered carbon structures through their
contact with magnetite.

###Angular Magnetoresistance Oscillations in Organic Conductors|A. G. Lebed,Heon-Ick Ha,M. J. Naughton###

Angular Magnetoresistance Oscillations in Organic Conductors. We demonstrate that electron wave functions change their dimensionality at
some commensurate directions of a magnetic field in conductors with open
[quasi-one-dimensional (Q1D)] sheets of Fermi surface. These 1D -> 2D
dimensional crossovers lead to delocalization of wave functions and are
responsible for angular magnetoresistance oscillations. As an example, we show
that suggested theory is in qualitative and quantitative agreements with the
recent experimental data obtained on (TMTSF)2ClO4 conductor.

###Microwave modulation of electron temperature and Shubnikov-de Haas oscillation in two-dimensional electron systems|X. L. Lei,S. Y. Liu###

Microwave modulation of electron temperature and Shubnikov-de Haas oscillation in two-dimensional electron systems. Recently discovered modulations of Shubnikov-de Haas oscillations in
microwave-irradiated two-dimensional electron systems are shown to arise from
electron heating induced by the radiation. The electron temperature, obtained
by balancing the energy absorption from the microwave field and the energy
dissipation to the lattice through realistic electron-phonon couplings,
exhibits resonance. The modulation of the Shubnikov de Haas oscillation and the
suppression of magnetoresistance are demonstrated together with
microwave-induced resistance oscillation, in agreement with experimental
findings.

###Magnetoresistance in the s-d Model with Arbitrary Impurity Spin|Kaihe Ding,Bao-Heng Zhao###

Magnetoresistance in the s-d Model with Arbitrary Impurity Spin. The magnetoresistance, the number of the localized electrons, and the s-wave
scattering phase shift at the Fermi level for the s-d model with arbitrary
impurity spin are obtained in the ground state. To obtain above results some
known exact results of the Bethe ansatz method are used. As the impurity spin S
= 1/2, our results coincide with those obtained by Ishii \textit{et al%}. The
compairsion between the theoretical and experimental magneticresistence for
impurity S = 1/2 is re-examined.

###Radiation-induced zero-resistance states with resolved Landau levels|R. G. Mani###

Radiation-induced zero-resistance states with resolved Landau levels. The microwave-photoexcited high mobility GaAs/AlGaAs two-dimensional electron
system exhibits an oscillatory-magnetoresistance with vanishing resistance in
the vicinity of magnetic fields $B = [4/(4j+1)] B_{f}$, where $B_{f} =
2\pi\textit{f}m^{*}/e$, m$^{*}$ is an the effective mass, e is the charge,
\textit{f} is the microwave frequency, and $j$ =1,2,3... Here, we report
transport with well-resolved Landau levels, and some transmission
characteristics.

###Microwave spectroscopy on magnetization reversal dynamics of nanomagnets with electronic detection|J. Grollier,M. V. Costache,C. H. van der Wal,B. J. van Wees###

Microwave spectroscopy on magnetization reversal dynamics of nanomagnets with electronic detection. We demonstrate a detection method for microwave spectroscopy on magnetization
reversal dynamics of nanomagnets. Measurement of the nanomagnet anisotropic
magnetoresistance was used for probing how magnetization reversal is resonantly
enhanced by microwave magnetic fields. We used Co strips of 2 um x 130 nm x 40
nm, and microwave fields were applied via an on-chip coplanar wave guide. The
method was applied for demonstrating single domain-wall resonance, and studying
the role of resonant domain-wall dynamics in magnetization reversal.

###Enhancement of low field magnetoresistance at room temperature in La$_{0.67}$Sr$_{0.33}$MnO$_{3}$/Al$_{2}$O$_{3}$ nanocomposite|Soumik Mukhopadhyay,I. Das###

Enhancement of low field magnetoresistance at room temperature in La$_{0.67}$Sr$_{0.33}$MnO$_{3}$/Al$_{2}$O$_{3}$ nanocomposite. Magnetotransport properties in a nanocrystalline
La$_{0.67}$Sr$_{0.33}$MnO$_{3}$/micron sized Al$_{2}$O$_{3}$ granular composite
with different concentrations of Al$_{2}$O$_{3}$ have been studied. The
resistivity curves in absence of magnetic field and the various transport
mechanisms which might account for the upturn in resistivity at low
temperature, has been discussed. Enhancement of low field magnetoresistance at
room temperature with the introduction of Al$_{2}$O$_{3}$ has been observed.

###Sharp magnetization step across the ferromagnetic to antiferromagnetic transition in doped-CeFe$_2$ alloys|S. B. Roy,M. K. Chattopadhyay,P. Chaddah,A. K. Nigam###

Sharp magnetization step across the ferromagnetic to antiferromagnetic transition in doped-CeFe$_2$ alloys. Very sharp magnetization step is observed across the field induced
antiferromagnetic to ferromagnetic transition in various doped-CeFe$_2$ alloys,
when the measurement is performed below 5K. In the higher temperature regime
(T$>$5K) this transition is quite smooth in nature. Comparing with the recently
observed similar behaviour in manganites showing colossal magnetoresistance and
magnetocaloric material Gd$_5$Ge$_4$ we argue that such magnetization step is a
generalized feature of a disorder influenced first order phase transition.

###Magnetic and Transport Properties of Fe-Ag granular multilayers|M. Csontos,J. Balogh,D. Kaptas,L. F. Kiss,G. Mihaly###

Magnetic and Transport Properties of Fe-Ag granular multilayers. Results of magnetization, magnetotransport and Mossbauer spectroscopy
measurements of sequentially evaporated Fe-Ag granular composites are
presented. The strong magnetic scattering of the conduction electrons is
reflected in the sublinear temperature dependence of the resistance and in the
large negative magnetoresistance. The simultaneous analysis of the magnetic
properties and the transport behavior suggests a bimodal grain size
distribution. A detailed quantitative description of the unusual features
observed in the transport properties is given.

###Rashba spin-orbit coupling and spin precession in carbon nanotubes|A. De Martino,R. Egger###

Rashba spin-orbit coupling and spin precession in carbon nanotubes. The Rashba spin-orbit coupling in carbon nanotubes and its effect on
spin-dependent transport properties are analyzed theoretically. We focus on
clean non-interacting nanotubes with tunable number of subbands $N$. The
peculiar band structure is shown to allow in principle for Datta-Das
oscillatory behavior in the tunneling magnetoresistance as a function of gate
voltage, despite the presence of multiple bands. We discuss the conditions for
observing Datta-Das oscillations in carbon nanotubes.

###Tunnel magnetoresistance of quantum dots coupled to ferromagnetic leads in the sequential and cotunneling regimes|Ireneusz Weymann,Jürgen König,Jan Martinek,Józef Barnas,Gerd Schön###

Tunnel magnetoresistance of quantum dots coupled to ferromagnetic leads in the sequential and cotunneling regimes. We study electronic transport through quantum dots weakly coupled to
ferromagnetic leads with collinear magnetization directions. Tunneling
contributions of first and second order in the tunnel-coupling strength are
taken into account. We analyze the tunnel magnetoresistance (TMR) for all
combinations of linear and nonlinear response, at or off resonance, with an
even or odd dot-electron number. Different mechanisms for transport and spin
accumulation the various regimes give rise to different TMR behavior.

###Continuous Evolution of the Fermi Surface of CeRu2Si2 across the Metamagnetic Transition|R. Daou,C. Bergemann,S. R. Julian###

Continuous Evolution of the Fermi Surface of CeRu2Si2 across the Metamagnetic Transition. We present new, high resolution Hall effect and magnetoresistance
measurements across the metamagnetic transition in the heavy fermion compound
CeRu2Si2. The results force us to rethink the notion that the transition is
accompanied by an abrupt f-electron localisation. Instead, we explain our data
assuming a continuous change of the Fermi surface. We also point out
ambiguities in the interpretation of dHvA data and give a possible solution to
the problem of the "missing mass".

###Experimental search for anisotropic flux flow resistivity in the a-b plane of optimally doped epitaxial thin films of YBCO|G. Koren,P. Aronov,E. Polturak###

Experimental search for anisotropic flux flow resistivity in the a-b plane of optimally doped epitaxial thin films of YBCO. Transport measurements along the node and anti-node directions in the a-b
plane of optimally doped and epitaxial thin films of YBCO are reported. Low
bias magnetoresistance measurements near and below T_c show that the flux flow
resistivity along the node and anti-node directions versus magnetic field are
indistinguishable. This result suggests that within the experimental error of
our measurements, no correspondence is found between the flux pinning
properties in YBCO and the d-wave nature of the order parameter.

###Insulating state of granular superconductors in a strong-coupling regime|I. S. Beloborodov,Ya. V. Fominov,A. V. Lopatin,V. M. Vinokur###

Insulating state of granular superconductors in a strong-coupling regime. We analyze the possibility of the formation of a magnetic-field-induced
insulating state in a two-dimensional granular superconductor with relatively
strong intergranular coupling and show that such a state appears in a model
with spatial variations of the single-grain critical magnetic field. This model
describes realistic granular samples with the dispersion in grain sizes and
explains the mechanism leading to a giant peak in the magnetoresistance.

###Tight-binding model of spin-polarized tunnelling in (Ga,Mn)As-based structures|P. Sankowski,P. Kacman,J. Majewski,T. Dietl###

Tight-binding model of spin-polarized tunnelling in (Ga,Mn)As-based structures. The Landauer-Buettiker formalism combined with the tight-binding transfer
matrix method is used to describe the results of recent experiments: the high
tunneling magnetoresistance (TMR) in (Ga,Mn)As-based trilayers and highly
polarized spin injection in p-(Ga,Mn)As/n-GaAs Zener diode. For both TMR and
Zener spin current polarization, the calculated values agree well with those
observed experimentally. The role played in the spin dependent tunneling by
carrier concentration and magnetic ion content is also studied.

###Magnetodielectric effect without multiferroic coupling|G. Catalan###

Magnetodielectric effect without multiferroic coupling. The existence of a magnetodielectric (magnetocapacitance) effect is often
used as a test for multiferroic behavior in new material systems. However,
strong magnetodielectric effects can also be achieved through a combination of
magnetoresistance and the Maxwell-Wagner effect, unrelated to multiferroic
coupling. The fact that this resistive magnetocapacitance does not require
multiferroic materials may be advantageous for some practical applications.
Conversely, it also implies that magnetocapacitance per se is not sufficient to
establish multiferroic coupling.

###Intrinsic vs. Extrinsic Spin Currents. Old Ideas in a New Light|Alexander Khaetskii###

Intrinsic vs. Extrinsic Spin Currents. Old Ideas in a New Light. We have described the electron spin dynamics in the presence of Rashba spin-
orbit interaction and disorder using the spin-density matrix method. We showed
that in the Born approximation in the scattering amplitude the spin current is
zero for an arbitrary ratio of the spin-orbit splitting and the scattering rate
and for an arbitrary disorder potential. We also describe some magnetotransport
phenomena such as negative magnetoresistance and a negative charge Hall effect
which occur in the presence of spin-orbit coupling.

###Influence of Roughness and Disorder on Tunneling Magnetoresistance|P. X. Xu,V. M. Karpan,K. Xia,M. Zwierzycki,I. Marushchenko,P. J. Kelly###

Influence of Roughness and Disorder on Tunneling Magnetoresistance. A systematic, quantitative study of the effect of interface roughness and
disorder on the magnetoresistance of FeCo$|$vacuum$|$FeCo magnetic tunnel
junctions is presented based upon parameter-free electronic structure
calculations. Surface roughness is found to have a very strong effect on the
spin-polarized transport while that of disorder in the leads (leads consisting
of a substitutional alloy) is weaker but still sufficient to suppress the huge
tunneling magneto-resistance (TMR) predicted for ideal systems.

###Domain-wall resistance in ferromagnetic (Ga,Mn)As|D. Chiba,M. Yamanouchi,F. Matsukura,T. Dietl,H. Ohno###

Domain-wall resistance in ferromagnetic (Ga,Mn)As. A series of microstructures designed to pin domain-walls (DWs) in (Ga,Mn)As
with perpendicular magnetic anisotropy has been employed to determine extrinsic
and intrinsic contributions to DW resistance. The former is explained
quantitatively as resulting from a polarity change in the Hall electric field
at DW. The latter is one order of magnitude greater than a term brought about
by anisotropic magnetoresistance and is shown to be consistent with
disorder-induced misstracing of the carrier spins subject to spatially varying
magnetization.

###Interplay of Rashba and Dresselhaus spin splittings in 2D weak localization|M. M. Glazov,L. E. Golub###

Interplay of Rashba and Dresselhaus spin splittings in 2D weak localization. The effects of structural (Rashba) and bulk (Dresselhaus) spin-orbit
interaction terms on the low-field magnetoresistance are investigated in
high-quality two dimensional systems. The weak localization theory accounting
for both of these terms valid in the whole range of magnetic fields is
proposed. The suppresion of antilocalization correction as Rashba and
Dresselhaus terms strengths approach each other is demonstrated. The effect of
cubic in the wavevector spin-splitting term is analyzed.

###Two-subband quantum Hall effect in parabolic quantum wells|C. Ellenberger,B. Simovic,R. Leturcq,T. Ihn,S. E. Ulloa,K. Ensslin,D. C. Driscoll,A. C. Gossard###

Two-subband quantum Hall effect in parabolic quantum wells. The low-temperature magnetoresistance of parabolic quantum wells displays
pronounced minima between integer filling factors. Concomitantly the Hall
effect exhibits overshoots and plateau-like features next to well-defined
ordinary quantum Hall plateaus. These effects set in with the occupation of the
second subband. We discuss our observations in the context of single-particle
Landau fan charts of a two-subband system empirically extended by a density
dependent subband separation and an enhanced spin-splitting g*.

###Two Types of Microwave-Induced Magnetoresistance Oscillations in a 2D Electron Gas at Large Filling Factors|A. A. Bykov,A. V. Goran,D. R. Islamov,A. K. Bakarov,Jing-qiao Zhang,Sergey Vitkalov###

Two Types of Microwave-Induced Magnetoresistance Oscillations in a 2D Electron Gas at Large Filling Factors. The influence of microwave radiation (1.2-140 GHz) on resistance of
high-mobility two-dimensional electron gas in GaAs quantum wells is studied.
Two series of microwave-induced magnetoresistance oscillations periodic in 1/B
were observed under microwave radiation. The periods of oscillations are
determined by the microwave frequency and power, correspondingly. The
experimental data is qualitatively explained by photon-assisted transport and
Zener tunneling between Landau orbits.

###Localization of strongly correlated electrons as Jahn-Teller polarons in manganites|Y. -F. Yang,K. Held###

Localization of strongly correlated electrons as Jahn-Teller polarons in manganites. A realistic modeling of manganites should include the Coulomb repulsion
between $e_g$ electrons, the Hund's rule coupling to $t_{2g}$ spins, and
Jahn-Teller phonons. Solving such a model by dynamical mean field theory, we
report large magnetoresistances and spectra in good agreement with experiments.
The physics of the unusual, insulating-like paramagnetic phase is determined by
correlated electrons which are-due to strong correlations-easily trapped as
Jahn-Teller polarons.

###Huge nonequilibrium magnetoresistance in hybrid superconducting spin valves|F. Giazotto,F. Taddei,Rosario Fazio,F. Beltram###

Huge nonequilibrium magnetoresistance in hybrid superconducting spin valves. A hybrid ferromagnet-superconductor spin valve is proposed. Its operation
relies on the interplay between nonequilibrium transport and proximity-induced
exchange coupling in superconductors. Huge tunnel magnetoresistance values as
large as some 10^6% can be achieved in suitable ferromagnet-superconductor
combinations under proper voltage biasing. The controllable spin-filter nature
of the structure combined with its intrinsic simplicity make this setup
attractive for low-temperature spintronic applications where reduced power
dissipation is an additional requirement.

###Selective transmission of Dirac electrons and ballistic magnetoresistance of \textit{n-p} junctions in graphene|Vadim V. Cheianov,Vladimir I. Fal'ko###

Selective transmission of Dirac electrons and ballistic magnetoresistance of \textit{n-p} junctions in graphene. We show that an electrostatically created n-p junction separating the
electron and hole gas regions in a graphene monolayer transmits only those
quasiparticles that approach it almost perpendicularly to the n-p interface.
Such a selective transmission of carriers by a single n-p junction would
manifest itself in non-local magnetoresistance effect in arrays of such
junctions and determines the unusual Fano factor in the current noise universal
for the n-p junctions in graphene.

###Fractional quantum Hall effect without energy gap|S. S. Murzin,S. I. Dorozhkin,G. E. Tsydynzhapov,V. N. Zverev###

Fractional quantum Hall effect without energy gap. In the fractional quantum Hall effect regime we measure diagonal
($\rho_{xx}$) and Hall ($\rho_{xy}$) magnetoresistivity tensor components of
two-dimensional electron system (2DES) in gated GaAs/Al$_{x}$Ga$_{1-x}$As
heterojunctions, together with capacitance between 2DES and the gate. We
observe 1/3- and 2/3-fractional quantum Hall effect at rather low magnetic
fields where corresponding fractional minima in the thermodynamical density of
states have already disappeared manifesting complete suppression of the
quasiparticle energy gaps.

###Magnetoresistance in Thin Permalloy Film (10nm-thick and 30-200nm-wide) Nanocontacts Fabricated by e-Beam Lithography|Nicolas Garcia,Cheng Hao,Lu Yonghua,Manuel. Munoz,Yifang Chen,Zhengqi Lu,Yun Zhou,Genhua Pan,Zheng Cui,A. A. Pasa###

Magnetoresistance in Thin Permalloy Film (10nm-thick and 30-200nm-wide) Nanocontacts Fabricated by e-Beam Lithography. In this paper we show spin dependent transport experiments in
nanoconstrictions ranging from 30 to 200nm. These nanoconstrictions were
fabricated combining electron beam lithography and thin film deposition
techniques. Two types of geometries have been fabricated and investigated. We
compare the experimental results with the theoretical estimation of the
electrical resistance. Finally we show that the magnetoresistance for the
different geometries does not scale with the resistance of the structure and
obtain drops in voltage of 20mV at 20Oe.

###Bias dependent inversion of tunneling magnetoresistance in Fe/GaAs/Fe tunnel junctions|J. Moser,M. Zenger,C. Gerl,D. Schuh,R. Meier,P. Chen,G. Bayreuther,W. Wegscheider,D. Weiss,C. -H. Lai,R. -T. Huang,M. Kosuth,H. Ebert###

Bias dependent inversion of tunneling magnetoresistance in Fe/GaAs/Fe tunnel junctions. We investigated spin dependent transport through Fe/GaAs/Fe tunnel junctions.
The tunneling magnetoresistance effect (TMR) was probed for different types of
Fe/GaAs interfaces. For interfaces cleaned by hydrogen plasma the TMR effect is
increased and observable at room temperature. If an epitaxial Fe/GaAs(001)
interface is involved, the tunnel junction exhibits a bias dependent inversion
of the TMR effect. This is a first experimental signature for band structure
effects at a Fe/GaAs interface and relevant for spin injection experiments.

###Screening Model of Magnetotransport Hysteresis Observed in Bilayer Quantum Hall Systems|Afif Siddiki,Stefan Kraus,Rolf R. Gerhardts###

Screening Model of Magnetotransport Hysteresis Observed in Bilayer Quantum Hall Systems. We report on theoretical and experimental investigations of a novel
hysteresis effect that has been observed on the magnetoresistance of
quantum-Hall bilayer systems. Extending to these system a recent approach,
based on the Thomas-Fermi-Poisson nonlinear screening theory and a local
conductivity model, we are able to explain the hysteresis as being due to
screening effects such as the formation of ``incompressible strips'', which
hinder the electron density in a layer within the quantum Hall regime to reach
its equilibrium distribution.

###Quantum-size effect and tunneling magnetoresistance in ferromagnetic-semiconductor quantum heterostructures|S. Ohya,P. N. Hai,Y. Mizuno,M. Tanaka###

Quantum-size effect and tunneling magnetoresistance in ferromagnetic-semiconductor quantum heterostructures. We report on the resonant tunneling effect and the increase of tunneling
magnetoresistance (TMR) induced by it in ferromagnetic-semiconductor GaMnAs
quantum-well heterostructures. The observed quantum levels of the GaMnAs
quantum well were successfully explained by the valence-band kp model with the
p-d exchange interaction. It was also found that the Fermi level of the
electrode injecting carriers is important to observe resonant tunneling in this
system.

###All-electrical measurement of spin injection in a magnetic $p$-$n$ junction diode|Peifeng Chen,Juergen Moser,Philipp Kotissek,Janusz Sadowski,Marcus Zenger,Dieter Weiss,Werner Wegscheider###

All-electrical measurement of spin injection in a magnetic $p$-$n$ junction diode. Magnetic $p$-$n$ junction diodes are fabricated to investigate spin-polarized
electron transport. The injection of spin-polarized electrons in a
semiconductor is achieved by driving a current from a ferromagnetic injector
(Fe), into a bulk semiconductor ($n$-GaAs) via schottky contact. For detection,
a diluted magnetic semiconductor ($p$-GaMnAs) layer is used. Clear
magnetoresistance was observed only when a high forward bias was applied across
the $p$-$n$ junction.

###Microwave induced magnetoresistance oscillations at the subharmonics of the cyclotron resonance|S. I. Dorozhkin,J. H. Smet,K. von Klitzing,L. N. Pfeiffer,K. W. West###

Microwave induced magnetoresistance oscillations at the subharmonics of the cyclotron resonance. The magnetoresistance oscillations, which occur in a two-dimensional electron
system exposed to strong microwave radiation when the microwave frequency
$\omega$ coincides with the n-th subharmonic of the cyclotron frequency
$\omega_c$ have been investigated for n = 2, 3 and 4. It is shown that these
subharmonic features can be explained within a non-equilibrium energy
distribution function picture without invoking multi-photon absorption
processes. The existence of a frequency threshold above which such oscillations
disappear lends further support to this explanation.

###Dirac and Normal Fermions in Graphite and Graphene: Implications to the Quantum Hall Effect|Igor A. Luk'yanchuk,Yakov Kopelevich###

Dirac and Normal Fermions in Graphite and Graphene: Implications to the Quantum Hall Effect. Spectral analysis of Shubnikov de Haas (SdH) oscillations of
magnetoresistance and of Quantum Hall Effect (QHE) measured in quasi-2D highly
oriented pyrolytic graphite (HOPG) [Phys. Rev. Lett. 90, 156402 (2003)] reveals
two types of carriers: normal (massive) electrons with Berry phase 0 and
Dirac-like (massless) holes with Berry phase pi. We demonstrate that recently
reported integer- and semi-integer QHE for bi-layer and single-layer graphenes
take place simultaneously in HOPG samples.

###Interface Magnetoresistance in Manganite-Titanate Heterojunctions|T. Susaki,N. Nakagawa,H. Y. Hwang###

Interface Magnetoresistance in Manganite-Titanate Heterojunctions. We have found that the current- voltage characteristics of
La0.7Sr0.3MnO3(-delta)/Nb:SrTiO3 rectifying junctions are quantitatively
well-described by (thermally-assisted) tunneling with an effectively
temperature-independent Schottky barrier under no magnetic field, while those
of the oxygen deficient junction remarkably deviate from such a simple behavior
as magnetic field is applied. These results indicate a new form of
magnetoresistance arising from magnetic field changes of the interface band
diagram via the strong electron-spin coupling in manganites.

###Anomalous asymmetry of magnetoresistance in NbSe$_3$ single crystals|A. A. Sinchenko,Yu. I. Latyshev,A. P. Orlov,P. Monceau###

Anomalous asymmetry of magnetoresistance in NbSe$_3$ single crystals. A pronounced asymmetry of magnetoresistance with respect to the magnetic
field direction is observed for NbSe$_3$ crystals placed in a magnetic field
perpendicular to their conducting planes. It is shown that the effect persists
in a wide temperature range and manifests itself starting from a certain
magnetic induction value $B_0$, which at $T=4.2$ K corresponds to the
transition to the quantum limit, i.to the state where the Landay level
splitting exceeds the temperature.

###Intergrain connectivity and resistive broadening in vortex state: a comparison between MgB2, NbSe2 and Bi2Sr2Ca2Cu3O10 superconductors|S. D. Kaushik,S. Patnaik###

Intergrain connectivity and resistive broadening in vortex state: a comparison between MgB2, NbSe2 and Bi2Sr2Ca2Cu3O10 superconductors. Magnetoresistance and radio frequency penetration depth techniques are used
to study grain connectivity and broadening of superconducting transition. We
study and compare these issues in clean polycrytalline samples of three
different superconducting systems e.g. MgB2, NbSe2 and Bi2Sr2Ca2Cu3O10. From
the rf response, the bulk pinning force constant is evaluated. From high field
transport measurements, H-T phase diagram is ascertained for the three systems
with varying degrees of fluctuation and connectivity.

###AMR and magnetometry studies of ultra thin GaMnAs films|A. W. Rushforth,A. D. Giddings,K. W. Edmonds,R. P. Campion,C. T. Foxon,B. L. Gallagher###

AMR and magnetometry studies of ultra thin GaMnAs films. We have measured the Anisotropic Magnetoresistance (AMR) of ultra thin (5nm)
Ga(0.95)Mn(0.05)As films. We find that the sign of the AMR can be positive or
negative, which may depend on the direction of the current with respect to the
crystal. At low temperatures, transport measurements and SQUID magnetometry
suggest that the magnetisation has a component pointing out of the plane of the
film.

###Ab-initio GMR and current-induced torques in Au/Cr multilayers|P. M. Haney,D. Waldron,R. A. Duine,A. S. Nunez,H. Guo,A. H. MacDonald###

Ab-initio GMR and current-induced torques in Au/Cr multilayers. We report on an {\em ab-initio} study of giant magnetoresistance (GMR) and
current-induced-torques (CITs) in Cr/Au multilayers that is based on
non-equilibrium Green's functions and spin density functional theory. We find
substantial GMR due primarily to a spin-dependent resonance centered at the
Cr/Au interface and predict that the CITs are strong enough to switch the
antiferromagnetic order parameter at current-densities $\sim 100$ times smaller
than typical ferromagnetic metal circuit switching densities.

###Vortex motion in chilarity-controlled pair of magnetic disks|H. Masaki,T. Ishida,R. Antos,J. Shibata,T. Kimura,Y. Otani###

Vortex motion in chilarity-controlled pair of magnetic disks. We investigate the influence of the vortex chirality on the magnetization
processes of a magnetostatically coupled pair of magnetic disks. The magnetic
vortices with opposite chiralities are realized by introducing asymmetry into
the disks. The motion of the paired vortices are studied by measuring the
magnetoresistance with lock-in resistance bridge technique. The vortex
annihilation process is found to depend on the moving directions of the
magnetic vorticies. The experimental results are well reproduced by the
micromagnetic simulation.

###Formation of a Nematic Fluid at High Fields in Sr3Ru2O7|R. A. Borzi,S. A. Grigera,J. Farrell,R. S. Perry,S. J. S. Lister,S. L. Lee,D. A. Tennant,Y. Maeno,A. P. Mackenzie###

Formation of a Nematic Fluid at High Fields in Sr3Ru2O7. In principle, a complex assembly of strongly interacting electrons can
self-organise into a wide variety of collective states, but relatively few such
states have been identified in practice. We report that, in the close vicinity
of a metamagnetic quantum critical point, high purity Sr3Ru2O7 possesses a
large magnetoresistive anisotropy, consistent with the existence of an
electronic nematic fluid. We discuss a striking phenomenological similarity
between our observations and those made in high purity two-dimensional electron
fluids in GaAs devices.

###Weak localisation in bilayer graphene|R. V. Gorbachev,F. V. Tikhonenko,A. S. Mayorov,D. W. Horsell,A. K. Savchenko###

Weak localisation in bilayer graphene. We have performed the first experimental investigation of quantum
interference corrections to the conductivity of a bilayer graphene structure. A
negative magnetoresistance - a signature of weak localisation - is observed at
different carrier densities, including the electro-neutrality region. It is
very different, however, from the weak localisation in conventional
two-dimensional systems. We show that it is controlled not only by the
dephasing time, but also by different elastic processes that break the
effective time-reversal symmetry and provide invervalley scattering.

###Enhanced magneto-transport at high bias in quasi-magnetic tunnel junctions with EuS spin-filter barriers|T. Nagahama,T. S. Santos,J. S. Moodera###

Enhanced magneto-transport at high bias in quasi-magnetic tunnel junctions with EuS spin-filter barriers. In quasi-magnetic tunnel junctions (QMTJs) with a EuS spin filter tunnel
barrier between Al and Co electrodes, we observed large magnetoresistance (MR).
The bias dependence shows an abrupt increase of MR ratio in high bias voltage,
which is contrary to conventional magnetic tunnel junctions (MTJs). This
behavior can be understood as due to Fowler-Nordheim tunneling through the
fully spin-polarized EuS conduction band. The I-V characteristics and bias
dependence of MR calculated using tunneling theory shows excellent agreement
with experiment.

###Giant asymmetry of the longitudinal magnetoresistance in high-mobility two-dimensional electron gas on a cylindrical surface|A. B. Vorob'ev,K. -J. Friedland,H. Kostial,R. Hey,U. Jahn,E. Wiebicke,Ju. S. Yukecheva,V. Ya. Prinz###

Giant asymmetry of the longitudinal magnetoresistance in high-mobility two-dimensional electron gas on a cylindrical surface. A giant asymmetry in the magnetoresistance was revealed in high-mobility,
two-dimensional electron gas on a cylindrical surface. The longitudinal
resistance along the magnetic-field gradient impressed by the surface curvature
was found to vanish if measured along one of the edges of the curved Hall bar.
If the external magnetic field is reversed, then the longitudinal resistance
vanishes at the opposite edge of the Hall bar. This asymmetry is analyzed
quantitatively in terms of the Landauer-Buettiker formalism.

###Numerical analysis of the Novikov problem of a normal metal in a strong magnetic field|Roberto De Leo###

Numerical analysis of the Novikov problem of a normal metal in a strong magnetic field. We present the results of our numerical exploration of the fractal structure
found by S.P. Novikov in the problem of the behviour of magnetoresistance in a
normal metal under a strong magnetic field. The case we discuss in this paper
is the simplest non-trivial one, namely the case of 2 Fermi Surfaces that cut
the brillouin zone along of the coordinate axes (i.e. Fermi surfaces have genus
3).

###Electron Transport in Nanogranular Ferromagnets|I. S. Beloborodov,A. Glatz,V. M. Vinokur###

Electron Transport in Nanogranular Ferromagnets. We study electronic transport properties of ferromagnetic nanoparticle arrays
and nanodomain materials near the Curie temperature in the limit of weak
coupling between the grains. We calculate the conductivity in the Ohmic and
non-Ohmic regimes and estimate the magnetoresistance jump in the resistivity at
the transition temperature. The results are applicable for many emerging
materials, including artificially self-assembled nanoparticle arrays and a
certain class of manganites, where localization effects within the clusters can
be neglected.

###Stray-fields-based magnetoresistance mechanism in Ni80Fe20-Nb-Ni80Fe20 trilayers|D. Stamopoulos,E. Manios,M. Pissas###

Stray-fields-based magnetoresistance mechanism in Ni80Fe20-Nb-Ni80Fe20 trilayers. We report on the transport and magnetic properties of hybrid trilayers and
bilayers that consist of low spin-polarized Ni80Fe20 exhibiting in-plane but no
uniaxial anisotropy and low-Tc Nb. We reveal a magnetoresistance effect that is
pronounced. In our trilayers the magnetoresistance exhibits an increase of two
orders of magnitude when the superconducting state is reached: from the
conventional normal-state values 0.6 % it goes up to 1000 % for temperatures
below Tc. In contrast, in the bilayers the effect is only minor since from 3%
in the normal state increases only to 70 % for temperatures below Tc.
Magnetization data of both the longitudinal and transverse magnetic components
are presented. Most importantly, we present data not only for the normal state
of Nb but also in its superconducting state. Strikingly, these data show that
below its Tc SC the Nb interlayer under the influence of the outer Ni80Fe20
layers attains a magnetization component transverse to the external field. By
comparing the transport and magnetization data we propose a candidate mechanism
that could motivate the pronounced magnetoresistance effect observed in the
trilayers. Adequate magnetostatic coupling of the outer Ni80Fe20 layers is
motivated by stray fields that emerge naturally in their whole surface due to
the multidomain magnetic structure that they attain near coercivity. Atomic
force microscopy is employed in order to examine the possibility that such
magnetostatic coupling could be promoted by interface roughness. Referring to
the bilayers, although out-of-plane rotation of the magnetization of the single
Ni80Fe20 layer is still observed, in these structures magnetostatic coupling
does not occur due to the absence of a second Ni80Fe20 one so that the observed
magnetoresistance peaks are only modest.

###Magnetoresistance due to edge spin accumulation|M. I. Dyakonov###

Magnetoresistance due to edge spin accumulation. Because of spin-orbit interaction, an electrical current is accompanied by a
spin current resulting in spin accumulation near the sample edges. Due again to
spin-orbit interaction this causes a small decrease of the sample resistance.
An applied magnetic field will destroy the edge spin polarization leading to a
positive magnetoresistance. This effect provides means to study spin
accumulation by electrical measurements. The origin and the general properties
of the phenomenological equations describing coupling between charge and spin
currents are also discussed.

###Electric-field control of tunneling magnetoresistance effect in a Ni/InAs/Ni quantum-dot spin valve|K. Hamaya,M. Kitabatake,K. Shibata,M. Jung,M. Kawamura,K. Hirakawa,T. Machida,S. Ishida,Y. Arakawa###

Electric-field control of tunneling magnetoresistance effect in a Ni/InAs/Ni quantum-dot spin valve. We demonstrate an electric-field control of tunneling magnetoresistance (TMR)
effect in a semiconductor quantum-dot (QD) spin-valve device. By using
ferromagnetic Ni nano-gap electrodes, we observe the Coulomb blockade
oscillations at a small bias voltage. In the vicinity of the Coulomb blockade
peak, the TMR effect is significantly modulated and even its sign is switched
by changing the gate voltage, where the sign of the TMR value changes at the
resonant condition.

###Random resistor network model of minimal conductivity in graphene|V. V. Cheianov,V. I. Falko,B. L. Altshuler,I. L. Aleiner###

Random resistor network model of minimal conductivity in graphene. Transport in undoped graphene is related to percolating current patterns in
the networks of {\em N-} and {\em P}-type regions reflecting the strong bipolar
charge density fluctuations. Transmissions of the {\em P-N} junctions, though
small, are vital in establishing the macroscopic conductivity. We propose a
random resistor network model to analyze scaling dependencies of the
conductance on the doping and disorder, the quantum magnetoresistance and the
corresponding dephasing rate.

###Theory of the fractional microwave-induced resistance oscillations|I. A. Dmitriev,A. D. Mirlin,D. G. Polyakov###

Theory of the fractional microwave-induced resistance oscillations. We develop a systematic theory of microwave-induced oscillations in
magnetoresistivity of a 2D electron gas in the vicinity of fractional harmonics
of the cyclotron resonance, observed in recent experiments. We show that in the
limit of well-separated Landau levels the effect is dominated by a change of
the distribution function induced by multiphoton processes. At moderate
magnetic field, a single-photon mechanism originating from the
microwave-induced sidebands in the density of states of disorder-broadened
Landau levels becomes important.

###Coarse grained models in Coulomb-frustrated phase separation|C. Ortix,J. Lorenzana,C. Di Castro###

Coarse grained models in Coulomb-frustrated phase separation. Competition between interactions on different length scales leads to
self-organized textures in classical as well as quantum systems. This pattern
formation phenomenon has been invoked to explain some intriguing properties of
a large variety of strongly correlated electronic systems that includes for
example high temperature superconductors and colossal magnetoresistance
manganites. We classify the more common situations in which Coulomb frustrated
phase separation can occur and review their properties.

###Correlation between $T_c$ and anisotropic scattering in Tl$_2$Ba$_2$CuO$_{6+δ}$|M. Abdel-Jawad,J. G. Analytis,L. Balicas,A. Carrington,J. P. H. Charmant,M. M. J. French,N. E. Hussey###

Correlation between $T_c$ and anisotropic scattering in Tl$_2$Ba$_2$CuO$_{6+δ}$. Angle-dependent magnetoresistance measurements are used to determine the
isotropic and anisotropic components of the transport scattering rate in
overdoped Tl$_2$Ba$_2$CuO$_{6+\delta}$ for a range of $T_c$ values between 15K
and 35K. The size of the anisotropic scattering term is found to scale linearly
with $T_c$, establishing a link between the superconducting and normal state
physics. Comparison with results from angle resolved photoemission spectroscopy
indicates that the transport and quasiparticle lifetimes are distinct.

###Spin-dependent tunneling and Coulomb blockade in ferromagnetic nanoparticles|Kay Yakushiji,Franck Ernult,Seiji Mitani,Koki Takanashi,Hiroyasu Fujimori###

Spin-dependent tunneling and Coulomb blockade in ferromagnetic nanoparticles. We review studies on spin-dependent tunneling phenomena in systems containing
ferromagnetic nanoparticles. We discuss preparation methods of assembling
nanoparticles as well as the mechanisms and results of spin-dependent transport
properties. The emphasis of this review is on characteristic spin-dependent
tunneling phenomena such as enhanced tunnel magnetoresistance (TMR) due to
co-tunneling in the Coulomb blockade regime and sign changes of the TMR due to
spin accumulation in nanoparticles.

###Magnetoresistance in an all-manganite heterostructure|J. Salafranca,M. J. Calderon,L. Brey###

Magnetoresistance in an all-manganite heterostructure. We study the magnetic and transport properties of all-manganite
heterostructures consisting of ferromagnetic metallic electrodes separated by
an antiferromagnetic barrier. We find that the magnetic ordering in the barrier
is influenced by the relative orientation of the electrodes magnetization
producing a large difference in resistance between the parallel and
antiparallel orientations of the ferromagnetic layers. The external application
of a magnetic field in a parallel configuration also leads to large
magnetoresistance.

###Detection of nuclear magnetic resonance with an anisotropic magnetoresistive sensor|F. Verpillat,M. P. Ledbetter,D. Budker,S. Xu,D. Michalak,C. Hilty,S. Antonijevic,A. Pines,L. -S. Bouchard###

Detection of nuclear magnetic resonance with an anisotropic magnetoresistive sensor. We report detection of nuclear magnetic resonance (NMR) using an anisotropic
magnetoresistive (AMR) sensor. A ``remote-detection'' arrangement was used, in
which protons in flowing water were pre-polarized in the field of a
superconducting NMR magnet, adiabatically inverted, and subsequently detected
with an AMR sensor situated downstream from the magnet and the adiabatic
inverter. AMR sensing is well suited for NMR detection in microfluidic
``lab-on-a-chip'' applications.

###Plasmon phenomena as origin of DC-current induced resistivity oscillations in two-dimensional electron systems|Jesus Inarrea###

Plasmon phenomena as origin of DC-current induced resistivity oscillations in two-dimensional electron systems. We analyze theoretically the oscillations that the magnetoresistivity of
two-dimensional electron systems present when a high intensity direct current
is applied. In the model presented here we suggest that a plasma wave is
excited in the system producing an oscillating motion of the whole
two-dimensional electron gas at the plasma frequency. This scenario affects
dramatically the way that electrons interact with scatterers giving rise to
oscillations in the longitudinal resistivity. With this theoretical model
experimental results are well reproduced and explained.

###Anisotropy in magnetic and transport properties of Fe1-xCoxSb2|Rongwei Hu,V. F. Mitrovic,C. Petrovic###

Anisotropy in magnetic and transport properties of Fe1-xCoxSb2. Anisotropic magnetic and electronic transport measurements were carried out
on large single crystals of Fe1-xCoxSb2 (0<= x <=1). The semiconducting state
of FeSb2 evolves into metallic and weakly ferromagnetic by substitution of Fe
with Co for x<0.5. Further doping induces structural transformation from
orthorhombic Pnnm structure of FeSb2 to monoclinic P21/c structure of CoSb2
where semiconducting and diamagnetic ground state is restored again. Large
magnetoresistance and anisotropy in electronic transport were observed.

###Tunneling Anisotropic Magnetoresistance in Co/AlOx/Au Tunnel Junctions|R. S. Liu,L. Michalak,C. M. Canali,L. Samuelson,H. Pettersson###

Tunneling Anisotropic Magnetoresistance in Co/AlOx/Au Tunnel Junctions. We observe spin-valve-like effects in nano-scaled thermally evaporated
Co/AlOx/Au tunnel junctions. The tunneling magnetoresistance is anisotropic and
depends on the relative orientation of the magnetization direction of the Co
electrode with respect to the current direction. We attribute this effect to a
two-step magnetization reversal and an anisotropic density of states resulting
from spin-orbit interaction. The results of this study points to future
applications of novel spintronics devices involving only one ferromagnetic
layer.

###Limited local electron-lattice coupling in manganites|D. Sanchez,M. J. Calderon,J. Sanchez-Benitez,A. J. Williams,J. P. Attfield,P. A. Midgley,N. D. Mathur###

Limited local electron-lattice coupling in manganites. (Pr,Ca)MnO3 is the archetypal charge-ordered manganite, but in
Pr0.48Ca0.52MnO3 we find (using convergent-beam electron diffraction and
dark-field images) that the superlattice period is locally incommensurate with
respect to the parent lattice, and that the superlattice orientation possesses
significant local variations. This suggests that local electron-lattice
coupling never overwhelmingly dominates the rich physics of manganites, even in
the most extreme scenarios that produce the largest colossal magnetoresistance
effects.

###Probing Landau quantisation with the presence of insulator-quantum Hall transition in a GaAs two-dimensional electron system|Kuang Yao Chen,Y. H. Chang,C. -T. Liang,N. Aoki,Y. Ochiai,C. F. Huang,Li-Hung Lin,K. A. Cheng,H. H. Cheng,H. H. Lin,Jau-Yang Wu,Sheng-Di Lin###

Probing Landau quantisation with the presence of insulator-quantum Hall transition in a GaAs two-dimensional electron system. Magneto-transport measurements are performed on the two-dimensional electron
system (2DES) in an AlGaAs/GaAs heterostructure. By increasing the magnetic
field perpendicular to the 2DES, magnetoresistivity oscillations due to Landau
quantisation can be identified just near the direct insulator-quantum Hall
(I-QH) transition. However, different mobilities are obtained from the
oscillations and transition point. Our study shows that the direct I-QH
transition does not always correspond to the onset of strong localisation.

###Kondo effect in quantum dots coupled to ferromagnetic leads with noncollinear magnetizations: effects due to electron-phonon coupling|R. Swirkowicz,M. Wilczynski,J. Barnas###

Kondo effect in quantum dots coupled to ferromagnetic leads with noncollinear magnetizations: effects due to electron-phonon coupling. Spin-polarized transport through a quantum dot strongly coupled to
ferromagnetic electrodes with non-collinear magnetic moments is analyzed
theoretically in terms of the non-equilibrium Green function formalism.
Electrons in the dot are assumed to be coupled to a phonon bath. The influence
of electron-phonon coupling on tunnelling current, linear and nonlinear
conductance, and on tunnel magnetoresistance is studied in detail. Variation of
the main Kondo peaks and phonon satellites with the angle between magnetic
moments of the leads is analyzed.

###Spin transfer torques in nonlocal lateral spin valve|Yuan Xu,Ke Xia,Zhongshui Ma###

Spin transfer torques in nonlocal lateral spin valve. We report a theoretical study on the spin and electron transport in the
nonlocal lateral spin valve with non-collinear magnetic configuration. The
nonlocal magnetoresistance, defined as the voltage difference on the detection
lead over the injected current, is derived analytically. The spin transfer
torques on the detection lead are calculated. It is found that spin transfer
torques are symmetrical for parallel and antiparallel magnetic configurations,
which is different from that in conventional sandwiched spin valve.

###Resonance oscillations of magnetoresistance in double quantum wells|N. C. Mamani,G. M. Gusev,T. E. Lamas,A. K. Bakarov,O. E. Raichev###

Resonance oscillations of magnetoresistance in double quantum wells. We present experimental and theoretical studies of the magnetoresistance
oscillations induced by resonance transitions of electrons between
tunnel-coupled states in double quantum wells. The suppression of these
oscillations with increasing temperature is irrelevant to the thermal
broadening of the Fermi distribution and reflects the temperature dependence of
the quantum lifetime of electrons. The gate control of the period and amplitude
of the oscillations is demonstrated.

###GdI_2: A New Ferromagnetic Excitonic Solid?|A. Taraphder,M. S. Laad,L. Craco,A. N. Yaresko###

GdI_2: A New Ferromagnetic Excitonic Solid?. The two-dimensional, colossal magnetoresistive system GdI_2 develops an
unusual metallic state below its ferromagnetic transition and becomes
insulating at low temperatures. It is argued that this geometrically
frustrated, correlated poor metal is a possible candidate for a ferromagnetic
excitonic liquid. The renormalized Fermi surface supports a further breaking of
symmetry to a charge ordered, excitonic solid ground state at lower
temperatures via order by disorder mechanism. Several experimental predictions
are made to investigate this unique orbitally correlated ground state.

###Superconductivity in nickel-based compound GdONiBi and hole doped Gd0.9Sr0.1ONiBi|Junyi Ge,Shixun Cao,Jincang Zhang###

Superconductivity in nickel-based compound GdONiBi and hole doped Gd0.9Sr0.1ONiBi. We successfully synthesized the nickel-based compound GdONiBi with
superconducting transition temperature about 4.5 K. By partially substituting
the element Gd with Sr to introduce holes into the material, we got new
superconductor Gd0.9Sr0.1ONiBi with critical temperature about 4.7 K. The
normal state resistivity in nickel-based samples shows a metallic behavior. The
magnetoresistance measurements show a different behavior compared to those in
iron-based compounds which indicates that the mechanism in the two kinds of
superconductors maybe different.

###Canted Magnetization Texture in Ferromagnetic Tunnel Junctions|Igor Kuzmenko,Vladimir Fal'ko###

Canted Magnetization Texture in Ferromagnetic Tunnel Junctions. We study the formation of inhomogeneous magnetization texture in the vicinity
of a tunnel junction between two ferromagnetic wires nominally in the
antiparallel configuration and its influence on the magnetoresistance of such a
device. The texture, dependent on magnetization rigidity and crystalline
anisotropy energy in the ferromagnet, appears upon an increase of ferromagnetic
inter-wire coupling above a critical value and it varies with an external
magnetic field.

###Adsorbate-limited conductivity of graphene|John P. Robinson,Henning Schomerus,Laszlo Oroszlany,Vladimir I. Fal'ko###

Adsorbate-limited conductivity of graphene. We present a theory of electronic transport in graphene in the presence of
randomly placed adsorbates. Our analysis predicts a marked asymmetry of the
conductivity about the Dirac point, as well as a negative weak-localization
magnetoresistivity. In the region of strong scattering, renormalization group
corrections drive the system further towards insulating behavior. These results
explain key features of recent experiments, and are validated by numerical
transport computations.

###Bulk superconductivity and disorder in single crystals of LaFePO|James G. Analytis,Jiun-Haw Chu,Ann S. Erickson,Chris Kucharczyk,Alessandro Serafin,Antony Carrington,Catherine Cox,Susan M. Kauzlarich,Hakon Hope,I. R. Fisher###

Bulk superconductivity and disorder in single crystals of LaFePO. We have studied the intrinsic normal and superconducting properties of the
oxypnictide LaFePO. These samples exhibit bulk superconductivity and the
evidence suggests that stoichiometric LaFePO is indeed superconducting, in
contrast to other reports. We find that superconductivity is independent of the
interplane residual resistivity $\rho_0$ and discuss the implications of this
on the nature of the superconducting order parameter. Finally we find that,
unlike $T_c$, other properties in single-crystal LaFePO including the
resistivity and magnetoresistance, can be very sensitive to disorder.

###Slow relaxation of magnetoresistance in doped p -GaAs/AlGaAs layers with partially filled upper Hubbard band|N. V. Agrinskaya,V. I. Kozub,D. V. Shamshur,A. Shumilin###

Slow relaxation of magnetoresistance in doped p -GaAs/AlGaAs layers with partially filled upper Hubbard band. We observed slow relaxation of magnetoresistance in quantum well structures
GaAs-AlGaAs with a selective doping of both wells and barrier regions which
allowed partial filling of the upper Hubbard band. Such a behavior is explained
as related to magnetic-field driven redistribution of the carriers between
sites with different occupation numbers due to spin correlation on the doubly
occupied centers. This redistribution, in its turn, leads to slow
multi-particle relaxations in the Coulomb glass formed by the charged centers.

###A new temperature scale T* in lead-based relaxor systems|B. Dkhil,P. Gemeiner,A. Al-Barakaty,L. Bellaiche,E. Dulkin,E. Mojaev,M. Roth###

A new temperature scale T* in lead-based relaxor systems. Via a combination of various experimental and theoretical techniques, a
peculiar, identical temperature scale T* is found to exist in all complex
lead-based relaxor ferroelectrics. T* corresponds to a nanoscale phase
transition due to random fields. Interestingly, T* also exists in other oxides
with extraordinary properties, such as giant magnetoresistivity or
superconductivity. By analogy with such latter systems, the giant
piezoelectricity related to relaxors might originate from proximity competing
states effect.

###Current-perpendicular-to-plane magnetoresistance of a domain wall confined in a nano-oxide-layer|Jun Sato,Katsuyoshi Matsushita,Hiroshi Imamura###

Current-perpendicular-to-plane magnetoresistance of a domain wall confined in a nano-oxide-layer. We theoretically study the current-perpendicular-to-plane magnetoresistance
of a domain wall confined in a current-confined-path (CCP) structure made of a
nano-oxide-layer (NOL). In order to calculate the MR ratio of the system, the
continuity equations for charge and spin currents are numerically solved with
the three-dimensional CCP geometry by use of finite element method. It is
confirmed that the MR ratio is enhanced by the CCP structure, which is
consistent with the experimental results.

###Spin susceptibility and polarization field in a dilute two-dimensional electron system in (111) silicon|A. A. Kapustin,A. A. Shashkin,V. T. Dolgopolov,M. Goiran,H. Rakoto*,Z. D. Kvon###

Spin susceptibility and polarization field in a dilute two-dimensional electron system in (111) silicon. We find that the polarization field, B_chi, obtained by scaling the
weak-parallel-field magnetoresistance at different electron densities in a
dilute two-dimensional electron system in (111) silicon, corresponds to the
spin susceptibility that grows strongly at low densities. The polarization
field, B_sat, determined by resistance saturation, turns out to deviate to
lower values than B_chi with increasing electron density, which can be
explained by filling of the upper electron subbands in the fully spin-polarized
regime.

###Anisotropic magneto-transport effects at SrTiO3\LaAlO3 interfaces|M. Ben Shalom,C. W. Tai,Y. Lereah,M. Sachs,E. Levy,D. Rakhmilevitch,A. Palevski,Y. Dagan###

Anisotropic magneto-transport effects at SrTiO3\LaAlO3 interfaces. The resistivity as a function of temperature, magnetic field and its
orientation for atomically flat SrTiO3\LaAlO3 interfaces with carrier densities
of ~3*10^13 cm^-2 is reported. At low magnetic fields superconductivity is
observed below 130mK. The temperature dependence of the high field
magnetoresistance and its strong anisotropy suggest possible magnetic ordering
below 35K. The origin of this ordering and its possible relation to
superconductivity are discussed.

###Thickness dependence of the mobility at the LaAlO_3 / SrTiO_3 interface|C. Bell,S. Harashima,Y. Hikita,H. Y. Hwang###

Thickness dependence of the mobility at the LaAlO_3 / SrTiO_3 interface. The electronic transport properties of a series of LaAlO_3 / SrTiO_3
interfaces were investigated, and a systematic thickness dependence of the
sheet resistance and magnetoresistance was found for constant growth
conditions. This trend occurs above the critical thickness of four unit cells,
below which the LaAlO_3 / SrTiO_3 interface is not conducting. A dramatic
decrease in mobility of the electron gas of nearly two orders of magnitude was
observed with increasing LaAlO_3 thickness from five to 25 unit cells.

###Characterisation of Ferromagnetic Contacts to Carbon Nanotubes|D. Preusche,S. Schmidmeier,E. Pallecchi,Ch. Dietrich,A. K. Huettel,J. Zweck,Ch. Strunk###

Characterisation of Ferromagnetic Contacts to Carbon Nanotubes. We present an investigation of different thin-film evaporated ferromagnetic
materials for their suitability as electrodes in individual single-wall and
multi-wall carbon nanotube-based spin devices. Various electrode shapes made
from permalloy (Ni_{81}Fe_{19}), the diluted ferromagnet PdFe, and PdFe/Fe
bilayers are studied for both their micromagnetic properties and their contact
formation to carbon nanotubes. Suitable devices are tested in low-temperature
electron transport measurements, displaying the typical tunneling
magnetoresistance of carbon nanotube pseudo spin valves.

###Superconducting double spin valve with extraordinary large tunable magnetoresistance|Francesco Giazotto###

Superconducting double spin valve with extraordinary large tunable magnetoresistance. A superconducting double spin valve device is proposed. Its operation takes
advantage of the interplay between the spin-filtering effect of ferromagnetic
insulators and superconductivity-induced out-of-equilibrium transport.
Depending on the degree of nonequilibrium, extraordinary large tunnel
magnetoresistance as large as 10^2...10^6% can be obtained for realistic
material parameters, and it can be tuned over several orders of magnitude under
proper voltage biasing and temperature. The relevance of this setup for
low-temperature applications is further discussed.

###High order fractional microwave induced resistance oscillations in 2D systems|S. Wiedmann,G. M. Gusev,O. E. Raichev,A. K. Bakarov,J. C. Portal###

High order fractional microwave induced resistance oscillations in 2D systems. We report on the observation of microwave-induced resistance oscillations
associated with the fractional ratio n/m of the microwave irradiation frequency
to the cyclotron frequency for m up to 8 in a two-dimensional electron system
with high electron density. The features are quenched at high microwave
frequencies independent of the fractional order m. We analyze temperature,
power, and frequency dependencies of the magnetoresistance oscillations and
discuss them in connection with existing theories.

###New Correlated Model of Colossal Magnetoresistive Manganese Oxides|D. I. Golosov###

New Correlated Model of Colossal Magnetoresistive Manganese Oxides. A new minimal model is constructed for the doped manganese oxides which
exhibit colossal magnetoresistance (CMR), involving broad spin-majority
conduction band as well as nearly localised spin-minority electron states. A
simple mean field analysis yields a temperature-dependent hybridised band
structure with suppressed carrier weight at the Fermi level. Spin stiffness is
complex, indicating unusually strong spin wave damping. Experimental and
theoretical investigations are needed to further verify the relevance of the
proposed model.

###Geometrical and orbital effects in a quasi-one dimensional conductor|D. Graf,J. S. Brooks,E. S. Choi,M. Almeida,R. T. Henriques,J. C. Dias,S. Uji###

Geometrical and orbital effects in a quasi-one dimensional conductor. The angular dependent magnetoresistance of (Per)2[Au(mnt)2] under pressure
has revealed geometrical effects associated with the crystallographic
parameters. Pressure suppresses the charge density wave ground state of the
material, and in the metallic state both geometrical and orbital quantum
interference effects appear. Through magnetic field dependence and orientation,
the orbital and geometrical effects are independently identified. We compare
the results from (Per)2[Au(mnt)2] with previous studies of the well-known
Bechgaard salts.

###Role of anion size, magnetic moment, and disorder on the properties of the organic conductor kappa-(BETS)_2Ga_{1-x}Fe_{x}Cl_{4-y}_Br_{y}|E. Steven,H. B. Cui,A. Kismarahardja,J. S. Brooks,D. Graf,H. Kobayashi###

Role of anion size, magnetic moment, and disorder on the properties of the organic conductor kappa-(BETS)_2Ga_{1-x}Fe_{x}Cl_{4-y}_Br_{y}. Shubnikov-de Haas and angular dependent magnetoresistance oscillations have
been used to explore the role of anion size, magnetic moment, and disorder in
the organic conductors kappa-(BETS)_2GaBr_{4} and kappa-(BETS)_2FeCl_{2}_Br_{2}
in the isomorphic class kappa-(BETS)_2Ga_{1-x}Fe_{x}Cl_{4-y}_Br_{y}. The
results, combined with previous work, show correlations between the anion
composition (Ga_{1-x}Fe_{x}Cl_{4-y}_Br_{y}) and the superconducting transition
temperature, effective mass, Fermi surface topology, and the mean free path.

###Electron-electron scattering and magnetoresistance of ballistic microcontacts|K. E. Nagaev,T. V. Kostyuchenko###

Electron-electron scattering and magnetoresistance of ballistic microcontacts. Using a semiclassical Boltzmann equation, we calculate corrections to the
Sharvin conductance of a wide 2DEG ballistic contact that result from an
electron--electron scattering in the leads. These corrections are dominated by
collisions of electrons with nearly opposite momenta that come from different
reservoirs. They are positive, increase with temperature, and are strongly
suppressed by a magnetic field. We argue that this suppression may be
responsible for an anomalous positive magnetoresistance observed in a recent
experiment.

###Tunneling Anisotropic Magnetoresistance of Helimagnet Tunnel Junctions|Chenglong Jia,Jamal Berakdar###

Tunneling Anisotropic Magnetoresistance of Helimagnet Tunnel Junctions. We theoretically investigate the angular and spin dependent transport in
normal-metal/helical-multiferroic/ferromagnetic heterojunctions. We find a
tunneling anisotropic magnetoresistance (TAMR) effect due to the spiral
magnetic order in the tunnel junction and to an effective spin-orbit coupling
induced by the topology of the localized magnetic moments in the multiferroic
spacer.
  The predicted TAMR effect is efficiently controllable by an external electric
field due to the magnetoelectric coupling.

###A comparative study of angle dependent magnetoresistance in [001] and [110] $La_{2/3}Sr_{1/3}MnO_3$|Soumen Mandal###

A comparative study of angle dependent magnetoresistance in [001] and [110] $La_{2/3}Sr_{1/3}MnO_3$. The angle dependent magnetoresistance study on [001] and [110] La$_{2 /
3}$Sr$_{1 / 3}$MnO$_{3}$ thin films show that the anisotropy energy of [110]
films is higher when compared with a [001] oriented La$_{2 / 3}$Sr$_{1 /
3}$MnO$_{3}$ film of similar thickness. The data has been analyzed in the light
of multidomain model and it is seen that this model correctly explains the
observed behavior.

###Superconducting Behavior of Interfaces in Graphite: Transport Measurements of Micro-constrictions|S. Dusari,J. Barzola-Quiquia And P. Esquinazi###

Superconducting Behavior of Interfaces in Graphite: Transport Measurements of Micro-constrictions. We have studied the magnetoresistance (MR) of thin highly oriented pyrolytic
graphite mesoscopic samples without and with micro-constrictions of different
widths between the voltage electrodes. The MR for fields parallel to the c-axis
shows an anomalous hysteresis loop compatible with the behavior expected for
granular superconductors. The smaller the constriction width the larger is the
anomalous hysteresis and the higher the temperature for its observation. Our
results support the existence of granular superconductivity probably embedded
at interfaces between crystalline graphite regions.

###Spin and Valley Splittings in Multilayered Massless Dirac Fermion System|N. Tajima,M. Sato,S. Sugawara,R. Kato,Y. Nishio,K. Kajita###

Spin and Valley Splittings in Multilayered Massless Dirac Fermion System. The inter-layer magnetoresistance in a multilayered massless Dirac fermion
system, $\alpha$-(BEDT-TTF)$_2$I$_3$, under hydrostatic pressure was
investigated. We succeeded in detecting the zero-mode (n=0) Landau level and
its spin splitting in the magnetic field normal to the 2D plane. We
demonstrated that the effective Coulomb interaction in the magnetic field
intensifies the spin splitting of zero-mode Landau carriers. At temperatures
below 2K, magnetic fields above several Tesla break the twofold valley
degeneracy.

###Magnetotransport studies of EuFe$_2$As$_2$: the influence of the Eu$^{2+}$ magnetic moments|Taichi Terashima,Nobuyuki Kurita,Akiko Kikkawa,Hiroyuki S. Suzuki,Takehiko Matsumoto,Keizo Murata,Shinya Uji###

Magnetotransport studies of EuFe$_2$As$_2$: the influence of the Eu$^{2+}$ magnetic moments. We report resistivity $\rho$ and Hall effect measurements on EuFe$_2$As$_2$
at ambient pressure and 28 kbar and magnetization measurements at ambient
pressure. We analyze the temperature and magnetic-field dependence of $\rho$
and the Hall effect using a molecular-field theory for magnetoresistance and an
empirical formula for the anomalous Hall effect and find that electron
scattering due to the Eu$^{2+}$ local moments plays only a minor role in
determining electronic transport properties of EuFe$_2$As$_2$.

###Thermoelectric Properties of Electrostatically Tunable Antidot Lattices|Srijit Goswami,Christoph Siegert,Saquib Shamim,Michael Pepper,Ian Farrer,David A. Ritchie,Arindam Ghosh###

Thermoelectric Properties of Electrostatically Tunable Antidot Lattices. We report on the fabrication and characterization of a device which allows
the formation of an antidot lattice (ADL) using only electrostatic gating. The
antidot potential and Fermi energy of the system can be tuned independently.
Well defined commensurability features in magnetoresistance as well as
magnetothermopower are obsereved. We show that the thermopower can be used to
efficiently map out the potential landscape of the ADL.

###Anomalous behavior of the Hall effect in electron-doped superconductor $Nd_{2-x}$Ce_{x}Cu$O_{4+δ} with nonstoichiometric disorder|T. B. Charikova,N. G. Shelushinina,G. I. Harus,V. N. Neverov,D. S. Petukhov,O. E. Sochinskaya,A. A. Ivanov###

Anomalous behavior of the Hall effect in electron-doped superconductor $Nd_{2-x}$Ce_{x}Cu$O_{4+δ} with nonstoichiometric disorder. Magnetoresistivity and Hall effect measured in magnetic fields up to B=9T
(B||c, J||ab) in electron-doped $Nd_{2-x}$Ce_{x}Cu$O_{4+{\delta}} single
crystal films with x = 0.14; 0.15; 0.18 and different oxygen content ({\delta})
were studied in a temperature range of 0.4-4.2 K. The resistivity and Hall
coefficient behaviors in the mixed state are discussed in the framework of
flux-flow model with the inclusion of the back-flow of vortices owing to the
pinning forces.

###Coulomb Oscillations of Indium-doped ZnO Nanowire Transistors in a Magnetic Field|Xiulai Xu,Andrew C. Irvine,Yang Yang,Xitian Zhang,David A. Williams###

Coulomb Oscillations of Indium-doped ZnO Nanowire Transistors in a Magnetic Field. We report on the observation of Coulomb oscillations from localized quantum
dots superimposed on the normal hopping current in ZnO nanowire transistors.
The Coulomb oscillations can be resolved up to 20 K. Positive anisotropic
magnetoresistance has been observed due to the Lorentz force on the carrier
motion. Magnetic field-induced tunneling barrier transparency results in an
increase of oscillation amplitude with increasing magnetic field. The energy
shift as a function of magnetic field indicates electron wavefunction
modification in the quantum dots.

###Experimental evidence on the Altshuler-Aronov-Spivak interference of the topological surface states in the exfoliated Bi2Te3 nanoflakes|Yuyuan Qin,Zhaoguo Li,Fengqi Song,Qianghua Wang,Wangfeng Ding,Xuefeng Wang,Haifeng Ding,Baigeng Wang,Chris Van Haesondonck,Jianguo Wan,Min Han,Y. H. Zhang,Guanghou Wang###

Experimental evidence on the Altshuler-Aronov-Spivak interference of the topological surface states in the exfoliated Bi2Te3 nanoflakes. Here we demonstrate the Altshuler-Aronov-Spivak (AAS) interference of the
topological surface states on the exfoliated Bi2Te3 microflakes by a flux
period of h/2e in their magnetoresistance oscillations and its weak field
character. Both the osillations with the period of h/e and h/2e are observed.
The h/2e-period AAS oscillation gradually dominates with increasing the sample
widths and the temperatures. This reveals the transition of the Dirac Fermions'
transport to the diffusive regime.

###Conduction Electron Spin-Flipping at Sputtered Co(90)Fe(10)/Cu Interfaces|H. Y. T. Nguyen,R. Acharyya,W. P. Pratt Jr.,J. Bass###

Conduction Electron Spin-Flipping at Sputtered Co(90)Fe(10)/Cu Interfaces. From measurements of the current-perpendicular-to-plane (CPP)
magnetoresistance of ferromagnetically coupled [Co(90)Fe(10)/Cu]xn multilayers,
within sputtered Permalloy-based double exchange biased spin-valves, we
determine the parameter delta[(Co(90)Fe(10))/Cu] = 0.19 +/- 0.04 that sets the
probability P of spin-flipping at a Co(90)Fe(10)/Cu interface via the equation
P = 1 - exp(-delta).

###Enhancement of the ferromagnetic order of graphite after sulphuric acid treatment|J. Barzola-Quiquia,W. Böhlmann,P. Esquinazi,A. Schadewitz,A. Ballestar,S. Dusari,L. Schultze-Nobre,B. Kersting###

Enhancement of the ferromagnetic order of graphite after sulphuric acid treatment. We have studied the changes in the ferromagnetic behavior of graphite powder
and graphite flakes after treatment with diluted sulphuric acid. We show that
this kind of acid treatment enhances substantially the ferromagnetic
magnetization of virgin graphite micrometer size powder as well as in graphite
flakes. The anisotropic magnetoresistance (AMR) amplitude at 300 K measured in
a micrometer size thin graphite flake after acid treatment reaches values
comparable to polycrystalline cobalt.

###Effects of Annealing Conditions on the Microstructure and Magnetic Properties of the Perovskite Manganite, La0.75Sr0.25MnO3|D. O. J. Green,K-U. Neumann###

Effects of Annealing Conditions on the Microstructure and Magnetic Properties of the Perovskite Manganite, La0.75Sr0.25MnO3. The effects of annealing conditions upon the microstructure and the magnetic
properties of the colossal magnetoresistive manganite La0.75Sr0.25MnO3 have
been investigated. Increasing the annealing temperature and time of annealing
is seen to increase the size of crystallites within the samples. The
spontaneous magnetic moment per formula unit and the Curie temperature, as
obtained from Arrott plot analysis, are observed to depend upon the average
size of crystallites.

###Pressure effects on Dirac fermions in α-(BEDT-TTF)2I3|Takahiro Himura,Takao Morinari,Takami Tohyama###

Pressure effects on Dirac fermions in α-(BEDT-TTF)2I3. We investigate the pressure effect on the layered Dirac fermion system, which
is realized in quasi-two-dimensional organic compound {\alpha}-(BEDT-TTF)2I3.
The trajectory of the contact points is investigated using the tight-binding
model with the transfer integrals determined by X-ray diffraction experiments.
Vanishing of the Dirac fermion spectrum, opening of the gap, and pressure
dependence of inter-layer magnetoresistance are discussed.

###Sub-Poissonian shot noise in CoFeB/MgO/CoFeB-based magnetic tunneling junctions|Tomonori Arakawa,Koji Sekiguchi,Shuji Nakamura,Kensaku Chida,Yoshitaka Nishihara,Daichi Chiba,Kensuke Kobayashi,Akio Fukushima,Shinji Yuasa,Teruo Ono###

Sub-Poissonian shot noise in CoFeB/MgO/CoFeB-based magnetic tunneling junctions. We measured the shot noise in the CoFeB/MgO/CoFeB-based magnetic tunneling
junctions with a high tunneling magnetoresistance ratio (over 200% at 3 K).
Although the Fano factor in the anti-parallel configuration is close to unity,
it is observed to be typically 0.91\pm0.01 in the parallel configuration. It
indicates the sub-Poissonian process of the electron tunneling in the parallel
configuration due to the relevance of the spin-dependent coherent transport in
the low bias regime.

###Diffusive model of current-in-plane-tunneling in double magnetic tunnel junctions|Pierre-Yves Clément,Clarisse Ducruet,Claire Baraduc,Mair Chshiev,Bernard Diény###

Diffusive model of current-in-plane-tunneling in double magnetic tunnel junctions. We propose a model that describes current-in-plane tunneling transport in
double barrier magnetic tunnel junctions in diffusive regime. Our study shows
that specific features appear in double junctions that are described by
introducing two typical length scales. The model may be used to measure the
magnetoresistance and the resistance area product of both barriers in
unpatterned stacks of double barrier magnetic tunnel junctions.

###Ballistic transport of (001) GaAs 2D holes through a strain-induced lateral superlattice|D. Kamburov,H. Shapourian,M. Shayegan,L. N. Pfeiffer,K. W. West,K. W. Baldwin,R. Winkler###

Ballistic transport of (001) GaAs 2D holes through a strain-induced lateral superlattice. We report the observation of ballistic commensurability oscillations and
positive magnetoresistance in a high-mobility, (001) GaAs two-dimensional hole
system with a unidirectional, surface-strain-induced, periodic potential
modulation. The positions of the resistivity minima agree well with the
electrostatic commensurability condition. From an analysis of the amplitude of
the oscillations we deduce a ballistic scattering time and an effective
magnitude for the induced periodic potential seen by the two-dimensional holes.

###Proposal of an experimental scheme for determination of penetration depth of transverse spin current by a nonlocal spin valve|Tomohiro Taniguchi,Hiroshi Imamura###

Proposal of an experimental scheme for determination of penetration depth of transverse spin current by a nonlocal spin valve. We theoretically propose an experiment to determine the penetration depth of
a transverse spin current using a nonlocal spin valve with three ferromagnetic
(F) layers, where the F_1, F_2, and F_3 layers act as the spin injector,
detector, and absorber, respectively. We show that the penetration depth can be
evaluated by measuring the dependence of the spin signal (magnetoresistance) on
the thickness of the F_3 layer.

###Structural, magnetic, magnetocaloric and magneto-transport properties in Ge doped Ni-Mn-Sb Heusler Alloys|Roshnee Sahoo,Ajaya K. Nayak,K. G. Suresh,A. K. Nigam###

Structural, magnetic, magnetocaloric and magneto-transport properties in Ge doped Ni-Mn-Sb Heusler Alloys. The effect of Ge substitution on the magnetic, magnetocaloric and transport
properties of Ni45Co5Mn38Sb12-xGex (x=0-3) has been investigated. The decrease
in the exchange interaction brought by Ge substitution can be seen from the
reduction in the magnetization of austenite phase and the increase in the
martensitic transition temperature. Large magnetocaloric effect and
magnetoresistance have been observed at room temperature, making it a potential
material system for various applications.

###Hanle effect missing in a prototypical organic spintronic device|Alberto Riminucci,Mirko Prezioso,Chiara Pernechele,Patrizio Graziosi,Ilaria Bergenti,Raimondo Cecchini,Marco Calbucci,Massimo Solzi,Alek Dediu###

Hanle effect missing in a prototypical organic spintronic device. We investigate spin precession (Hanle effect) in the prototypical organic
spintronic giant magnetoresistance (GMR) device
La0.7Sr0.3MnO3(LSMO)/tris(8-hydroxyquinoline)(Alq3)/AlOx/Co. The Hanle effect
is not observed in measurements taken by sweeping a magnetic field at different
angles from the plane of the device. As possible explanations we discuss the
tilting out of plane of the magnetization of the electrodes, exceptionally high
mobility or hot spots. Our results call for a greater understanding of spin
injection and transport in such devices.

###Theory of giant magnetoresistance at misfit interfaces|Daichi Asahi,Naoto Nagaosa###

Theory of giant magnetoresistance at misfit interfaces. We study theoretically the resistance at the interface between the two planar
systems with different lattice constants a and b. The resistance and the effect
of the magnetic field depends sensitively on the ratio a/b. The size of the
enlarged unit cell $\lambda = n_Aa = n_Bb$ ($n_A$, $n_B$: integers) is the
crucial quantity, and the magnetic flux penetrating this enlarged unit cell
determines the oscillation of the resistance. Therefore, the magnetoresistance
is very much enhanced at (nearly) incommensurate relation between a and b.

###Transport anomalies due to anisotropic interband scattering|Maxim Breitkreiz,P. M. R. Brydon,Carsten Timm###

Transport anomalies due to anisotropic interband scattering. Unexpected transport behavior can arise due to anisotropic single-particle
scattering in multiband systems. Specifically, we show within a semiclassical
Boltzmann approach beyond the relaxation-time approximation that anisotropic
scattering between electronlike and holelike Fermi surfaces generically leads
to negative transport times, which in turn cause negative magnetoresistance, an
extremum in the Hall coefficient, and a reduction of the resistivity. The
anisotropy required for this to occur decreases with increasing mismatch
between the Fermi-surface radii.

###High TMR ratio in Co2FeSi and Fe2CoSi based magnetic tunnel junctions|Christian Sterwerf,Markus Meinert,Jan-Michael Schmalhorst,Günter Reiss###

High TMR ratio in Co2FeSi and Fe2CoSi based magnetic tunnel junctions. Magnetic tunnel junctions with Fe1+xCo2-xSi (0 < x < 1) electrodes and MgO
barrier were prepared on MgO substrates by magnetron co-sputtering. Maximum
tunnel magnetoresistance (TMR) ratios of 262 % at 15 K and 159 % at room
temperature were observed for x=0.75. Correlations of the annealing temperature
dependent atomic ordering and TMR amplitude are discussed. The high TMR for an
intermediate stoichiometry is ascribed to the adjustment of the Fermi energy
within a minority spin pseudo gap.

###Crossover from the weak to strong-field behavior of the longitudinal interlayer magnetoresistance in quasi-two-dimensional conductors|Alexej D. Grigoriev,Pavel D. Grigoriev###

Crossover from the weak to strong-field behavior of the longitudinal interlayer magnetoresistance in quasi-two-dimensional conductors. We investigate the monotonic growth of longitudinal interlayer
magnetoresistance $\bar{R}_{zz}(B_z) $, analytically and numerically in the
self-consistent Born approximation. We show that in a weak magnetic field the
monotonic part of $\bar{R}_{zz}(B_z)$ is almost constant and starts to grow
only above the crossover field $B_{c}$, when the Landau levels (LL) become
isolated, i.e. when the LL separation becomes greater than the LL broadening.
In higher field $B_{z}>>B_{c}$, $\bar{R}_{zz}(B_{z}) \propto B_{z}^{1/2}$ in
agreement with previous works.

###Formation and anisotropic magnetoresistance of Co/Pt nano-contacts through aluminum oxide barrier|Muftah Al-Mahdawi,Masashi Sahashi###

Formation and anisotropic magnetoresistance of Co/Pt nano-contacts through aluminum oxide barrier. We report on the observation of anisotropic magnetoresistance (AMR) in
vertical asymmetric nano-contacts (NCs) made through AlO$_x$ nano-oxide layer
(NOL) formed by ion-assisted oxidation method in the film stack of
Co/AlO$_x$-NOL/Pt. Analysis of NC formation was based on \emph{in situ}
conductive atomic force microscopy and transmission electron microscopy.
Depending on the purity of NCs from Al contamination, we observed up to 29% AMR
ratio at room temperature.

###Spin-memory effect and negative magnetoresistance in hopping conductivity|Oded Agam,Igor L. Aleiner,Boris Spivak###

Spin-memory effect and negative magnetoresistance in hopping conductivity. We propose a mechanism for negative isotropic magnetoresistance in the
hopping regime. It results from a memory effect encrypted into spin
correlations that are not taken into account by the conventional theory of
hopping conductivity. The spin correlations are generated by the nonequilibrium
electric currents and lead to the decrease of the conductivity. The application
of the magnetic field destroys the correlations thus enhancing the conductance.
This effect can occur even at magnetic fields as small as a few gauss.

###Magnetoresistance due to Broken C4 Symmetry in Cubic B20 Chiral Magnets|S. X. Huang,Fei Chen,Jian Kang,Jiadong Zang,G. J. Shu,F. C. Chou,C. L. Chien###

Magnetoresistance due to Broken C4 Symmetry in Cubic B20 Chiral Magnets. The B20 chiral magnets with broken inversion symmetry and C4 rotation
symmetry have attracted much attention. The broken inversion symmetry leads to
the Dzyaloshinskii-Moriya that gives rise to the helical and Skyrmion states.
We report the unusual magnetoresistance (MR) of B20 chiral magnet
Fe0.85Co0.15Si that directly reveals the broken C4 rotation symmetry. We
present a microscopic theory, a minimal theory with two spin-orbit terms, that
satisfies all the symmetry requirements and accounts for the transport
experiments.

###Current-driven spin orbit field in LaAlO3/SrTiO3 heterostructures|Kulothungasagaran Narayanapillai,Kalon Gopinadhan,Xuepeng Qiu,Anil Annadi,Ariando,Thirumalai Venkatesan,Hyunsoo Yang###

Current-driven spin orbit field in LaAlO3/SrTiO3 heterostructures. We demonstrate a current tunable Rashba spin orbit interaction in
LaAlO3/SrTiO3 (LAO/STO) quasi two dimensional electron gas (2DEG) system.
Anisotropic magnetoresistance (AMR) measurements are employed to detect and
understand the current-induced Rashba field. The effective Rashba field scales
with the current and a value of 2.35 T is observed for a dc-current of 200 uA.
The results suggest that LAO/STO heterostructures can be considered for spin
orbit torque based magnetization switching.

###Voltage-controlled inversion of tunnel magnetoresistance in epitaxial Nickel/Graphene/MgO/Cobalt junctions|F. Godel,M. Venkata Kamalakar,B. Doudin,Y. Henry,D. Halley,J. -F. Dayen###

Voltage-controlled inversion of tunnel magnetoresistance in epitaxial Nickel/Graphene/MgO/Cobalt junctions. We report on the fabrication and characterization of vertical spin-valve
structures using a thick epitaxial MgO barrier as spacer layer and a
graphene-passivated Ni film as bottom ferromagnetic electrode. The devices show
robust and scalable tunnel magnetoresistance, with several changes of sign upon
varying the applied bias voltage. These findings are explained by a model of
phonon-assisted transport mechanisms that relies on the peculiarity of the band
structure and spin density of states at the hybrid graphene|Ni interface.

###Little-Parks Oscillations in a Single Ring in the vicinity of the Superconductor-Insulator Transition|Doron Gurovich,Konstantin S. Tikhonov,Diana Mahalu,Dan Shahar###

Little-Parks Oscillations in a Single Ring in the vicinity of the Superconductor-Insulator Transition. We present results of measurements obtained from a mesoscopic ring of a
highly disordered superconductor. Superimposed on a smooth magnetoresistance
background we find periodic oscillations with a period that is independent of
the strength of the magnetic field. The period of the oscillations is
consistent with charge transport by Cooper pairs. The oscillations persist
unabated for more than 90 periods, through the transition to the insulating
phase, up to our highest field of 12 T.

###Crystal growth, resistivity and Hall effect of the delafossite metal PtCoO$_2$|Pallavi Kushwaha,Philip J. W. Moll,Nabhanila Nandi,Andrew P. Mackenzie###

Crystal growth, resistivity and Hall effect of the delafossite metal PtCoO$_2$. We report single crystal growth of the delafossite oxide PtCoO$_2$, and basic
transport measurements on single crystals etched to well-defined geometries
using focused ion beam techniques. The room temperature resistivity is 2.1
$\mu\Omega$ cm, and the Hall coefficient is consistent with the existence of
one free electron per Pt. Although the residual resistivity ratio is greater
than fifty, a slight upturn of resistivity is seen below 15 K. The angle
dependence of the in-plane magnetoresistance is also reported.

###Scaling theory of the cuprate strange metals|Sean A. Hartnoll,Andreas Karch###

Scaling theory of the cuprate strange metals. We show that the anomalous temperature scaling of five distinct transport
quantities in the strange metal regime of the cuprate superconductors can be
reproduced with only two nontrivial critical exponents. The quantities are: (i)
the electrical resistivity, (ii) the Hall angle, (iii) the Hall Lorenz ratio,
(iv) the magnetoresistance and (v) the thermopower. The exponents are the
dynamical critical exponent z = 4/3 and an anomalous scaling dimension Phi =
-2/3 for the charge density operator.

###Current dependence of the huge negative magnetoresistance in high-mobility two-dimensional electron gases|L. Bockhorn,J. Inarrea,R. J. Haug###

Current dependence of the huge negative magnetoresistance in high-mobility two-dimensional electron gases. In high-mobility two-dimensional electron gases Landau levels are already
formed at very small magnetic field values. Such two-dimensional electron gases
show a huge negative magnetoresistance at low temperatures and an unexpected
and very strong non-linear behavior with the applied current. This
non-linearity depends on carrier concentration and is explained by the subtle
interplay of elastic scattering within Landau levels and in between Landau
levels.

###Fork stamping of pristine carbon nanotubes onto ferromagnetic contacts for spin-valve devices|J. Gramich,A. Baumgartner,M. Muoth,C. Hierold,C. Schönenberger###

Fork stamping of pristine carbon nanotubes onto ferromagnetic contacts for spin-valve devices. We present a fabrication scheme called 'fork stamping' optimized for the dry
transfer of individual pristine carbon nanotubes (CNTs) onto ferromagnetic
contact electrodes fabricated by standard lithography. We demonstrate the
detailed recipes for a residue-free device fabrication and in-situ current
annealing on suspended CNT spin-valve devices with ferromagnetic Permalloy (Py)
contacts and report preliminary transport characterization and
magnetoresistance experiments at cryogenic temperatures. This scheme can
directly be used to implement more complex device structures, including
multiple gates or superconducting contacts.

###Construction of van der Waals magnetic tunnel junction using ferromagnetic layered dichalcogenide|Miho Arai,Rai Moriya,Naoto Yabuki,Satoru Masubuchi,Keiji Ueno,Tomoki Machida###

Construction of van der Waals magnetic tunnel junction using ferromagnetic layered dichalcogenide. We investigate the micromechanical exfoliation and van der Waals (vdW)
assembly of ferromagnetic layered dichalcogenide Fe0.25TaS2. The vdW interlayer
coupling at the Fe-intercalated plane of Fe0.25TaS2 allows exfoliation of
flakes. A vdW junction between the cleaved crystal surfaces is constructed by
dry transfer method. We observe tunnel magnetoresistance in the resulting
junction under an external magnetic field applied perpendicular to the plane,
demonstrating spin-polarized tunneling between the ferromagnetic layered
material through the vdW junction.

###Multi-Fields Modulation of Physical Properties of Oxide Thin Films|Huali Yang,Baomin Wang,Xiaojian Zhu,Jie Shang,Bin Chen,Run-Wei Li###

Multi-Fields Modulation of Physical Properties of Oxide Thin Films. Oxide thin films exhibit versatile physical properties such as magnetism,
ferroelectricity, piezoelectricity, metal-insulator transition (MIT),
multiferroicity, colossal magnetoresistivity, switchable resistivity, etc. More
importantly, the exhibited multifunctionality could be tuned by various
external fields, which has enabled demonstration of novel electronic devices.
In this article, recent studies of the multi-fields modulation of physical
properties in oxide thin films have been reviewed. Some of the key issues and
prospects about this field are also addressed.

###Giant thermal magnetoresistance in plasmonic structures|Ivan Latella,Philippe Ben-Abdallah###

Giant thermal magnetoresistance in plasmonic structures. A giant thermal magnetoresistance is predicted for the electromagnetic
transport of heat in magneto-optical plasmonic structures. In chains of InSb-Ag
nanoparticles at room temperature, we found that the resistance can be
increased by almost a factor of 2 with magnetic fields of 2 T. We show that
this important change results from the strong spectral dependence of localized
surface waves on the magnitude of the magnetic field.

###Topological semimetal state and field-induced Fermi surface reconstruction in antiferromagnetic monopnictide NdSb|Yongjian Wang,J. H. Yu,Y. Q. Wang,C. Y. Xi,L. S. Ling,S. L. Zhang,J. R. Wang,Y. M. Xiong,Tao Han,Hui Han,Jun Yang,Jixiang Gong,Lei Luo,W. Tong,Lei Zhang,Zhe Qu,Y. Y. Han,W. K. Zhu,Li Pi,X. G. Wan,Changjin Zhang,Yuheng Zhang###

Topological semimetal state and field-induced Fermi surface reconstruction in antiferromagnetic monopnictide NdSb. We report the experimental realization of Dirac semimetal state in NdSb, a
material with antiferromagnetic ground state. The occurrence of topological
semimetal state has been well supported by our band structure calculations and
the experimental observation of chiral anomaly induced negative
magnetoresistance. A field-induced Fermi surface reconstruction is observed, in
response to the change of spin polarization. The observation of topological
semimetal state in a magnetic material provides an opportunity to investigate
the magneto-topological phenomena.

###Large Tunneling Anisotropic Magnetoresistance mediated by Surface States|Marie Hervé,Timofey Balashov,Arthur Ernst,Wulf Wulfhekel###

Large Tunneling Anisotropic Magnetoresistance mediated by Surface States. We investigated the tunneling anisotropic magnetoresistance (TAMR) in thick
hcp Co films at cryogenic temperatures using scanning tunneling microscopy. At
around -350 mV, a strong TAMR up to 30\% is found with a characteristic voltage
dependence and a reversal of sign. With the help of \textit{ab initio}
calculations the TAMR can be traced back to a spin-polarized occupied surface
states that experience a strong spin-orbit interaction leading to a
magnetization direction depending hybridization with bulk states.

###Unconventional magneto-transport in ultrapure PdCoO2 and PtCoO2|Nabhanila Nandi,Thomas Scaffidi,Pallavi Kushwaha,Seunghyun Khim,Mark E. Barber,Veronika Sunko,Federico Mazzola,Philip D. C. King,Helge Rosner,Philip J. W. Moll,Markus König,Joel E. Moore,Sean Hartnoll,Andrew P. Mackenzie###

Unconventional magneto-transport in ultrapure PdCoO2 and PtCoO2. We have studied magneto transport in the single-band, quasi-two-dimensional
metals PdCoO2 and PtCoO2, which have extremely long mean free paths. We
observer a strong temperature dependence of the Hall resistivity in small
applied, fields, linked to a large violation of Kohler's rule in the
magnetoresistance. We discuss the extent to which these observations can be
accounted for by standard transport theory, and describe other possible,
unconventional contributions to magnetotransport in very high purity metals.

###Tuning effective hyperfine fields in PEDOT:PSS thin films by doping|M. Y. Teferi,J. Ogle,G. Joshi,H. Malissa,S. Jamali,D. L. Baird,J. M. Lupton,L. Whittaker Brooks,C. Boehme###

Tuning effective hyperfine fields in PEDOT:PSS thin films by doping. Using electrically detected magnetic resonance spectroscopy, we demonstrate
that doping the conducting polymer
poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) with
ethylene glycol allows for the control of effective local charge carrier
hyperfine fields through motional narrowing. These results suggest that doping
of organic semiconductors could enable the tuning of macroscopic material
properties dependent on hyperfine fields such as magnetoresistance, the
magneto-optical responses and spin-diffusion.

###Spin Polarization Phenomena and Pseudospin Quantum Hall Ferromagnetism in the HgTe Quantum Well|M. V. Yakunin,A. V. Suslov,S. M. Podgornykh,S. A. Dvoretsky,N. N. Mikhailov###

Spin Polarization Phenomena and Pseudospin Quantum Hall Ferromagnetism in the HgTe Quantum Well. The parallel field of a full spin polarization of the electron gas in a
\Gamma8 conduction band of the HgTe quantum well was obtained from the
magnetoresistance by three different ways in a zero and quasi-classical range
of perpendicular field component Bper. In the quantum Hall range of Bper the
spin polarization manifests in anticrossings of magnetic levels, which were
found to strongly nonmonotonously depend on Bper.

###Intrinsic Spin Seebeck Effect in Au/YIG|D. Qu,S. Y. Huang,Jun Hu,Ruqian Wu,C. L. Chien###

Intrinsic Spin Seebeck Effect in Au/YIG. The acute magnetic proximity effects in Pt/YIG compromise the suitability of
Pt as a spin current detector. We show that Au/YIG, with no anomalous Hall
effect and a negligible magnetoresistance, allows the measurements of the
intrinsic spin Seebeck effect with a magnitude much smaller than that in
Pt/YIG. The experiment results are consistent with the spin-polarized
density-functional calculations for Pt with a sizable and Au with a negligible
magnetic moment near the interface with YIG.

###Pauli spin blockade and the ultrasmall magnetic field effect|Jeroen Danon,Xuhui Wang,Aurélien Manchon###

Pauli spin blockade and the ultrasmall magnetic field effect. Based on the spin-blockade model for organic magnetoresistance we present an
analytic expression for the polaron-bipolaron transition rate, taking into
account the effective nuclear fields on the sites. We reveal the physics
producing qualitatively different magnetoconductance line shapes as well as the
ultrasmall magnetic field effect, and we study the role of the ratio between
the intersite hopping rate and the typical magnitude of the nuclear fields. Our
findings are in agreement with recent experiments and numerical simulations.

###Linear magnetoresistance from Dirac-like fermions in graphite|Hridis K. Pal,Dmitrii L. Maslov###

Linear magnetoresistance from Dirac-like fermions in graphite. We show that magnetoresistance of Bernal-stacked graphite (with the magnetic
field ${\bf B}$ parallel to the c-axis and the current in the ab plane) scales
linearly with the magnetic field over an interval of classically weak fields.
The linearity is related to the presence of extremely light, Dirac-like
carriers near the $H$ ($H^{\prime}$)- points of the Brillouin zone. The Hall
resistivity in this interval also shows a non-analytic, $B\ln |B|$ behavior,
and is dominated by holes.

###Signature of chiral fermion instability in the Weyl semimetal TaAs above the quantum limit|Cheng-Long Zhang,Bingbing Tong,Zhujun Yuan,Ziquan Lin,Junfeng Wang,Jinglei Zhang,Chuan-Ying Xi,Zhong Wang,Shuang Jia,Chi Zhang###

Signature of chiral fermion instability in the Weyl semimetal TaAs above the quantum limit. We report the electrical transport properties for Weyl semimetal TaAs in an
intense magnetic field. Series of anomalies occur in the longitudinal
magnetoresistance and Hall signals at ultra-low temperatures when the Weyl
electrons are confined into the lowest Landau level. These strongly
temperature-dependent anomalies are ascribed to the electron-hole pairing
instability. Our measurements show that the Weyl semimetal TaAs in the
ultraquantum regime provides a good platform for studying electron-electron
interaction in topological nontrivial semimetals.

###Frequency-dependent polarization-angle-phase-shift in the microwave-induced magnetoresistance oscillations|Han-Chun Liu,Tianyu Ye,W. Wegscheider,R. G. Mani###

Frequency-dependent polarization-angle-phase-shift in the microwave-induced magnetoresistance oscillations. Linear polarization angle, $\theta$, dependent measurements of the microwave
radiation-induced oscillatory magnetoresistance, $R_{xx}$, in high mobility
GaAs/AlGaAs 2D electron devices have shown a $\theta$ dependence in the
oscillatory amplitude along with magnetic field, frequency, and
extrema-dependent phase shifts, $\theta_{0}$. Here, we suggest a microwave
frequency dependence of $\theta_{0} (f)$ using an analysis that averages over
other smaller contributions, when those contributions are smaller than
estimates of the experimental uncertainty.

###Superconducting-contact-induced resistance-anomalies in the 3D topological insulator Bi2Te3|Zhuo Wang,Tianyu Ye,R. G. Mani###

Superconducting-contact-induced resistance-anomalies in the 3D topological insulator Bi2Te3. This study examines the magnetotransport response observed in flakes of the
3D topological insulator (TI) Bi2Te3, including indium superconducting
electrodes, and demonstrates two critical transitions in the magnetoresistive
response with decreasing temperatures below T = 3.4K. The first transition is
attributed to superconductivity in the indium electrodes, and the second
transition, with a critical field exceeding the transition field of indium, is
attributed to a proximity effect at the 2D planar interface of this hybrid
TI/superconductor structure.

###Microscopic Evidence of Spin State Order and Spin State Phase Separation in Layered Cobaltites RBaCo2O5.5 with R=Y, Tb, Dy, and Ho|H. Luetkens,M. Stingaciu,Yu. G. Pashkevich,K. Conder,E. Pomjakushina,A. A. Gusev,K. V. Lamonova,P. Lemmens,H. -H. Klauss###

Microscopic Evidence of Spin State Order and Spin State Phase Separation in Layered Cobaltites RBaCo2O5.5 with R=Y, Tb, Dy, and Ho. We report muon spin relaxation measurements on the magnetic structures of
RBaCo_2O_5.5 with R=Y, Tb, Dy, and Ho. Three different phases, one
ferrimagnetic and two antiferromagnetic, are identified below 300 K. They
consist of different ordered spin state arrangements of high-, intermediate-,
and low-spin Co^3+ of CoO_6 octahedra. Phase separation into well separated
regions with different spin state order is observed in the antiferromagnetic
phases. The unusual strongly anisotropic magnetoresistance and its onset at the
FM-AFM phase boundary is explained.

###Domain wall displacement in Py square ring for single nanometric magnetic bead detection|P. Vavassori,V. Metlushko,M. Gobbi,M. Donolato,M. Cantoni,R. Bertacco###

Domain wall displacement in Py square ring for single nanometric magnetic bead detection. A new approach based on the domain wall displacement in confined
ferromagnetic nanostructures for attracting and sensing a single nanometric
magnetic particles is presented. We modeled and experimentally demonstrated the
viability of the approach using an anisotropic magnetoresistance device made by
a micron-size square ring of Permalloy designed for application in magnetic
storage. This detection concept can be suitable to biomolecular recognition,
and in particular to single molecule detection.

###Novel Radiation-induced Magnetoresistance Oscillations in a Nondegenerate 2DES on Liquid Helium|Denis Konstantinov,Kimitoshi Kono###

Novel Radiation-induced Magnetoresistance Oscillations in a Nondegenerate 2DES on Liquid Helium. We report the observation of novel magnetoresistance oscillations induced by
the resonant inter-subband absorption in nondegenerate 2D electrons bound to
the surface of liquid helium. The oscillations are periodic in 1/B and
originate from the scattering-mediated transitions of the excited electrons
into the Landau states of the first subband. The structure of the oscillations
is affected by the collision broadening of the Landau levels and by
many-electron effects.

###Spin-current vortices in current-perpendicular-to-plane nanoconstricted spin-valves|N. Strelkov,A. Vedyayev,N. Ryzhanova,D. Gusakova,L. D. Buda-Prejbeanu,M. Chshiev,S. Amara,N. de Mestier,C. Baraduc,B. Dieny###

Spin-current vortices in current-perpendicular-to-plane nanoconstricted spin-valves. The charge and spin diffusion equations taking into account spin-flip and
spin-transfer torque were numerically solved using a finite element method in
complex non-collinear geometry with strongly inhomogeneous current flow. As an
illustration, spin-dependent transport through a non-magnetic nanoconstriction
separating two magnetic layers was investigated. Unexpected results such as
vortices of spin-currents in the vicinity of the nanoconstriction were
obtained. The angular variations of magnetoresistance and spin-transfer torque
are strongly influenced by the structure geometry.

###Field-Induced Magnetostructural Transitions in Antiferromagnetic Fe1+yTe1-xSx|Masashi Tokunaga,Takumi Kihara,Yoshikazu Mizuguchi,Yoshihiko Takano###

Field-Induced Magnetostructural Transitions in Antiferromagnetic Fe1+yTe1-xSx. The transport and structural properties of Fe1+yTe1-xSx (x=0, 0.05, and 0.10)
crystals were studied in pulsed magnetic fields up to 65 T. The application of
high magnetic fields results in positive magnetoresistance effect with
prominent hystereses in the antiferromagnetic state. Polarizing microscope
images obtained at high magnetic fields showed simultaneous occurrence of
structural transitions. These results indicate that magnetoelastic coupling is
the origin of the bicollinear magnetic order in iron chalcogenides.

###Giant electroresistance and tunable magnetoelectricity in a multiferroic junction|Francesco Ricci,Alessio Filippetti,Vincenzo Fiorentini###

Giant electroresistance and tunable magnetoelectricity in a multiferroic junction. First-principles density functional calculations show that the
$\textrm{SrRuO}_{3}/\textrm{PbTiO}_{3}/\textrm{SrRuO}_{3}$ multiferroic
junction with asymmetric (RuO$_{2}$/PbO and TiO$_{2}$/SrO) interfaces has a
large ferroelectric depolarizing field, whose switching changes the interface
transmission probabilities for tunneling electrons, leading to
electroresistance modulation over several orders of magnitude. The switching
further affects the interface spin density, naturally driving magnetoresistance
as well as modulated spin-dependent in-plane resistivity, which may be
exploited in field-effect devices.

###Field induced large magnetocaloric effect and magnetoresistance in ErNiSi|Sachin Gupta,R. Rawat,K. G. Suresh###

Field induced large magnetocaloric effect and magnetoresistance in ErNiSi. Large magnetocaloric effect (MCE) and magnetoresistance (MR) together with
negligible hysteresis loss has been observed in ErNiSi compound, which
undergoes metamagnetic transition at low temperatures. Magnetization, heat
capacity and resistivity measurements confirm the metamagnetic transition. The
maximum value of isothermal entropy change and MR for a field change of 50 kOe
are found to be 19.1 J/kg K and -34 %. Large MCE with negligible magnetic
hysteresis loss could make this material promising for low temperature magnetic
refrigeration.

###Titanic Magnetoresistance in WTe2|Mazhar N. Ali,Jun Xiong,Steven Flynn,Quinn Gibson,Leslie Schoop,Neel Haldolaarachchige,N. P. Ong,Jing Tao,R. J. Cava###

Titanic Magnetoresistance in WTe2. Magnetoresistance is the change of a material's electrical resistance in
response to an applied magnetic field. In addition to its intrinsic scientific
interest, it is a technologically important property, placing it in "Pasteur's
quadrant" of research value: materials with large magnetorsistance have found
use as magnetic sensors 1, in magnetic memory 2, hard drives 3, transistors 4,
and are the subject of frequent study in the field of spintronics 5, 6. Here we
report the observation of an extremely large one-dimensional positive
magnetoresistance (XMR) in the layered transition metal dichalcogenide (TMD)
WTe2; 452,700 percent at 4.5 Kelvin in a magnetic field of 14.7 Tesla, and 2.5
million percent at 0.4 Kelvin in 45 Tesla, with no saturation. The XMR is
highly anisotropic, maximized in the crystallographic direction where small
pockets of holes and electrons are found in the electronic structure. The
determination of the origin of this effect and the fabrication of
nanostructures and devices based on the XMR of WTe2 will represent a
significant new direction in the study and uses of magnetoresistivity.
  *The published version of the paper includes co-authors Tian Liang and Max
Hirschberger.
  **This paper has been published with new MR data to 60T where the MR of WTe2
reaches 13 million percent (at 0.5K) and still shows no signs of saturation. We
also have new electron diffraction patterns to lower temperature (10K). We
discuss the possible origin of the MR as coming from an electron-hole
'resonance' condition established by a perfect n/p ratio of 1 (more details in
a new "extended data" section). This makes WTe2, possibly, the first
realization of a perfectly balanced semimetal.
  ***The paper is published as "Large non-saturating magnetoresistance in WTe2"
in Nature (2014), DOI:10.1038/nature13763

###Proximity Effect in Periodic Arrays of Superconducting Nanoislands on Thin Graphite Layer|Yu. I. Latyshev,A. M. Smolovich,A. P. Orlov,A. V. Frolov,V. S. Vlasenko###

Proximity Effect in Periodic Arrays of Superconducting Nanoislands on Thin Graphite Layer. The regular structure of superconducting nanoislands of alloy W-Ga-C was
fabricated on nanothin graphite using focused ion beam. The resistance vs
temperature dependence down to 1.7K and the magnetoresistance in field up to
24T were measured both for the bridge containing nanoislands and for the
reference bridge without islands. The difference between those measurements
demonstrates the proximity effect on a regular structure of superconducting
W-Ga-C nanoislands on nanothin graphite layer.

###Spin Texture in Type-II Weyl Semimetal WTe2|Baojie Feng,Yang-Hao Chan,Ya Feng,Ro-Ya Liu,Mei-Yin Chou,Kenta Kuroda,Koichiro Yaji,Ayumi Harasawa,Paolo Moras,Alexei Barinov,Walid G. Malaeb,Cedric Bareille,Takeshi Kondo,Shik Shin,Fumio Komori,Tai-Chang Chiang,Youguo Shi,Iwao Matsuda###

Spin Texture in Type-II Weyl Semimetal WTe2. We determine the band structure and spin texture of WTe2 by spin- and
angle-resolved photoemission spectroscopy (SARPES). With the support of
first-principles calculations, we reveal the existence of spin polarization of
both the Fermi arc surface states and bulk Fermi pockets. Our results support
WTe2 to be a type-II Weyl semimetal candidate and provide important information
to understand its extremely large and nonsaturating magnetoresistance.

###Response of a spin valve to a spin battery|Khuôn-Viêt Pham###

Response of a spin valve to a spin battery. It is shown that spin valves under suitable symmetry conditions exhibit an
ON-OFF response to a spin battery, and are therefore perfect spin transistors.
While a spin valve driven by a charge battery displays the usual GMR (Giant
Magneto-Resistance), this means that a pure spin current or pure spin
accumulation can generate an infinite magnetoresistance (IMR). Magnetic tunnel
junctions as well as CPP (current perpendicular to plane) or CIP (current in
plane) metallic trilayers are discussed.

###Theory of magnon-mediated tunnel magneto-Seebeck effect|Benedetta Flebus,Gerrit E. W. Bauer,Rembert A. Duine,Yaroslav Tserkovnyak###

Theory of magnon-mediated tunnel magneto-Seebeck effect. The tunnel magneto-Seebeck effect is the dependence of the thermopower of
magnetic tunnel junctions on the magnetic configuration. It is conventionally
interpreted in terms of a thermoelectric generalization of the tunnel
magnetoresistance. Here, we investigate the heat-driven electron transport in
these junctions associated with electron-magnon scattering, using stochastic
Landau-Lifshitz phenomenology and quantum kinetic theory. Our findings
challenge the widely accepted single-electron picture of the tunneling
thermopower in magnetic junctions.

###Low-Temperature Conductivity of Weakly Interacting Quantum Spin Hall Edges in Strained-Layer InAs/GaInSb|Tingxin Li,Pengjie Wang,Gerard Sullivan,Xi Lin,Rui-Rui Du###

Low-Temperature Conductivity of Weakly Interacting Quantum Spin Hall Edges in Strained-Layer InAs/GaInSb. We report low-temperature transport measurements in strained
InAs/Ga0.68In0.32Sb quantum wells, which supports time-reversal
symmetry-protected helical edge states. The temperature and bias voltage
dependence of the helical edge conductance for devices of various sizes are
consistent with the theoretical expectation of a weakly interacting helical
edge state. Moreover, we found that the magnetoresistance of the helical edge
states is related to the edge interaction effect and the disorder strength.

###Skyrmion meets magnetic tunnel junction: an efficient way for electrical skyrmion detection investigated by ab initio theory|Jonas Friedrich Schäfer-Richarz,Philipp Risius,Michael Czerner,Christian Heiliger###

Skyrmion meets magnetic tunnel junction: an efficient way for electrical skyrmion detection investigated by ab initio theory. In our proof-of-principle study we examine the influence of skyrmions on
magnetoresistive transport. In particular, we show that magnetic tunnel
junctions are a technologically appealing and promising way for electrical
detection of non-collinear magnetic structures. The calculated effect is shown
to originate from scattering between different k-states and cannot be
identified through densities of states alone. Our results suggest that the
detection efficiency strongly depends on the utilized materials.

###Vertical transport and tunnelling in rare-earth nitride heterostructures|Jackson D. Miller,Felicia H. Ullstad,H. Joe Trodahl,Ben. J. Ruck,Franck Natali###

Vertical transport and tunnelling in rare-earth nitride heterostructures. We report an investigation of the ferromagnetic semiconductor rare earth
nitrides (RENs) for their potential for cryogenic-temperature electronics and
spintronics application. We have indentified ohmic contacts suitable for the
device structures that demand electron transport through interface layers, and
grown REN/insulator/REN heterostructures that display tunnelling
characteristics, an enormous 400% tunneling magnetoresistance and a hysteresis
promising their exploitation in non-volatile magnetic random access memory.

###Magnetic Doublon Bound States in the Kondo Lattice Model|Roman Rausch,Michael Potthoff,Norio Kawakami###

Magnetic Doublon Bound States in the Kondo Lattice Model. We present a novel pairing mechanism for electrons, mediated by magnons.
These paired bound states are termed "magnetic doublons". Applying numerically
exact techniques (full diagonalization and the density-matrix renormalization
group, DMRG) to the Kondo lattice model at strong exchange coupling $J$ for
different fillings and magnetic configurations, we demonstrate that magnetic
doublon excitations exist as composite objects with very weak dispersion. They
are highly stable, support a novel "inverse" colossal magnetoresistance and
potentially other effects.

###Crossover of the Hall-voltage distribution in AC quantum Hall effect|Hiroshi Akera###

Crossover of the Hall-voltage distribution in AC quantum Hall effect. The distribution of the Hall voltage induced by low-frequency AC current is
studied theoretically in the incoherent linear transport of quantum Hall
systems. It is shown that the Hall-voltage distribution makes a crossover from
the uniform distribution to a concentrated-near-edges distribution as the
frequency is increased or the diagonal conductivity is decreased. This
crossover is also reflected in the frequency dependence of AC
magnetoresistance.

###Sources of negative tunneling magneto-resistance in multilevel quantum dots with ferromagnetic contacts|S. Koller,J. Paaske,M. Grifoni###

Sources of negative tunneling magneto-resistance in multilevel quantum dots with ferromagnetic contacts. We analyze distinct sources of spin-dependent energy level shifts and their
impact on the tunneling magnetoresistance (TMR) of interacting quantum dots
coupled to collinearly polarized ferromagnetic leads. Level shifts due to
virtual charge fluctuations can be quantitatively evaluated within a
diagrammatic representation of our transport theory. The theory is valid for
multilevel quantum dot systems and we exemplarily apply it to carbon nanotube
quantum dots, where we show that the presence of many levels can qualitatively
influence the TMR effect.

###Current-biased Andreev interferometer|A. V. Galaktionov,A. D. Zaikin###

Current-biased Andreev interferometer. We theoretically investigate the behavior of Andreev interferometers with
three superconducting electrodes in the current-biased regime. Our analysis
allows to predict a number of interesting features of such devices, such as
both hysteretic and non-hysteretic behavior, negative magnetoresistance and two
different sets of singularities of the differential resistance at subgap
voltages. In the non-hysteretic regime we find a pronounced voltage modulation
with the magnetic flux which can be used for improving sensitivity of Andreev
interferometers.

###Multiple magnetic states within the A-phase determined by field-orientation dependence of Mn0.9Fe0.1Si|Peter E. Siegfried,Alexander C. Bornstein,Andrew C. Treglia,Thomas Wolf,Minhyea Lee###

Multiple magnetic states within the A-phase determined by field-orientation dependence of Mn0.9Fe0.1Si. We report three distinct regions within the A-phase in Fe-doped MnSi, based
on the evolution of magnetoresistance and the Hall effect as a function of
orientation of applied field. Fe impurities as pinning centers and crystalline
anisotropy are found non-negligible only at the boundary of the A-phase.
Electrical transport characteristics unique to the A-phase not only remain
robust, but also indicate a freely rotating skyrmion lattice, decoupled from
underlying crystal structure or impurity pinning.

###Angle-dependent Weiss oscillations in a nanocorrugated two-dimensional electron gas|Ching Hao Chang,Carmine Ortix###

Angle-dependent Weiss oscillations in a nanocorrugated two-dimensional electron gas. We investigate the diffusive magnetotransport properties of a two-dimensional
electron gas residing in a wrinkled nanostructure. The curved geometry of the
nanostructure renders an effective inhomogeneous magnetic field which, in
turns, yields Weiss oscillations. Since the relative strength of the effective
inhomogeneous magnetic field can be tailored by changing the direction of the
externally applied magnetic field, these Weiss oscillations exhibit a strong
directional dependence. For large external magnetic fields we also find an
anisotropic positive magnetoresistance.

###Half-Metallic Ferromagnets and Spin Gapless Semiconductors|V. V. Marchenkov,N. I. Kourov,V. Yu. Irkhin###

Half-Metallic Ferromagnets and Spin Gapless Semiconductors. A brief review of experimental and theoretical studies of half-metallic
ferromagnets (HMF) and spin gapless semiconductors (SGS) is given. The data on
resistivity and magnetoresistivity are presented. An important role of
non-quasiparticle states owing to electron-magnon scattering in transport
properties is discussed. The problem of low-temperature resistivity in HMF is
treated in terms of one-magnon and two-magnon scattering processes.

###Geometrical control of the magnetization direction in high aspect-ratio PdNi ferromagnetic nano-electrodes|J. J. Gonzalez-Pons,J. J. Henderson,E. del Barco,B. Ozyilmaz###

Geometrical control of the magnetization direction in high aspect-ratio PdNi ferromagnetic nano-electrodes. We present a study of electron-beam evaporated Pd0.4Ni0.6 alloy thin films by
means of ferromagnetic resonance measurements on extended films of varying
thickness and anisotropic magnetoresistance measurements of lithographically
patterned high aspect-ratio ferromagnetic electrodes, respectively. The results
reveal that the direction of the magnetization strongly depends on the
electrode lateral dimensions, transitioning from in-plane magnetization for
extended films to out-of-the-plane magnetization for electrode widths below 2-3
microns, reaching 58 degrees off-plane for 100 nm-wide nanoelectrodes.

###Evidence of Klein tunneling in graphene p-n junctions|N. Stander,B. Huard,D. Goldhaber-Gordon###

Evidence of Klein tunneling in graphene p-n junctions. Transport through potential barriers in graphene is investigated using a set
of metallic gates capacitively coupled to graphene to modulate the potential
landscape. When a gate-induced potential step is steep enough, disorder becomes
less important and the resistance across the step is in quantitative agreement
with predictions of Klein tunneling of Dirac fermions up to a small correction.
We also perform magnetoresistance measurements at low magnetic fields and
compare them to recent predictions.

###Diffusion based degradation mechanisms in giant magnetoresistive spin valves|M. Hawraneck,J. Zimmer,W. Raberg,K. Pruegl,S. Schmitt,T. Bever,S. Flege,L. Alff###

Diffusion based degradation mechanisms in giant magnetoresistive spin valves. Spin valve systems based on the giant magnetoresistive (GMR) effect as used
for example in hard disks and automotive applications consist of several
functional metallic thin film layers. We have identified by secondary ion mass
spectrometry (SIMS) two main degradation mechanisms: One is related to oxygen
diffusion through a protective cap layer, and the other one is interdiffusion
directly at the functional layers of the GMR stack. By choosing a suitable
material as cap layer (TaN), the oxidation effect can be suppressed.

###Small scale lateral superlattices in two-dimensional electron gases prepared by diblock copolymer masks|S. Hugger,T. Heinzel,T. Thurn-Albrecht###

Small scale lateral superlattices in two-dimensional electron gases prepared by diblock copolymer masks. A poly(styrene-block-methylmethacrylate) diblock copolymer in the hexagonal
cylindrical phase has been used as a mask for preparing a periodic gate on top
of a Ga[Al]As-heterostructure. A superlattice period of 43 nm could be imposed
onto the two-dimensional electron gas. Transport measurements show a
characteristic positive magnetoresistance around zero magnetic field which we
interpret as a signature of electron motion guided by the superlattice
potential.

###Magnetoresistance oscillations and relaxation effects at the SrTiO3-LaAlO3 interface|M. van Zalk,J. Huijben,A. J. M. Giesbers,M. Huijben,U. Zeitler,J. C. Maan,W. G. van der Wiel,G. Rijnders,D. H. A. Blank,H. Hilgenkamp,A. Brinkman###

Magnetoresistance oscillations and relaxation effects at the SrTiO3-LaAlO3 interface. We present low-temperature and high-field magnetotransport data on
SrTiO3-LaAlO3 interfaces. The resistance shows hysteresis in magnetic field and
a logarithmic relaxation as a function of time. Oscillations in the
magnetoresistance are observed, showing a square root periodicity in the
applied magnetic field, both in large-area unstructured samples as well as in a
structured sample. An explanation in terms of a commensurability condition of
edge states in a highly mobile two-dimensional electron gas between substrate
step edges is suggested.

###Electric spectroscopy of vortex states and dynamics in magnetic disks|Minori Goto,Hiroshi Hata,Akinobu Yamaguchi,Yoshinobu Nakatani,Takehiro Yamaoka,Yukio Nozaki,Hideki Miyajima###

Electric spectroscopy of vortex states and dynamics in magnetic disks. Spin-polarized radio frequency (RF) currents and RF-Oersted fields resonantly
excite a magnetic vortex core confined in a micron-scale soft magnetic disk. In
this study, we measured the rectifying voltage spectra caused by the
anisotropic magnetoresistance oscillation due to the gyration of the vortex
with different polarity and chirality. The measured spectra are presented such
that we can determine the vortex properties and strength of the spin torques
and Oersted field accurately and directly through analytical calculation.

###Competition between Thickness and Electrical Conditioning Influence in Enhancing Giant Magnetoresistance Ratio for NiCoFe/Alq3/NiCoFe Spin Valve|Mitra Djamal,Ramli,Sparisoma Viridi,Khairurrijal###

Competition between Thickness and Electrical Conditioning Influence in Enhancing Giant Magnetoresistance Ratio for NiCoFe/Alq3/NiCoFe Spin Valve. Spacer thickness and electrical conditioning have their own influence in
enhancing giant magnetoresistance (GMR) ratio. At some condition one factor can
override the other as reported by experiment results. An empiric model about
competition about these two factors is discussed in this work. Comparison from
experiment results to validate the model are also shown and explained. A
formulation is proposed to extend the existing one that now accommodates both
spacer thickness and electrical conditioning in one form.

###Evidence for the Collective Nature of the Reentrant Integer Quantum Hall States of the Second Landau Level|N. Deng,A. Kumar,M. J. Manfra,L. N. Pfeiffer,K. W. West,G. A. Csáthy###

Evidence for the Collective Nature of the Reentrant Integer Quantum Hall States of the Second Landau Level. We report an unexpected sharp peak in the temperature dependence of the
magnetoresistance of the reentrant integer quantum Hall states in the second
Landau level. This peak defines the onset temperature of these states. We find
that in different spin branches the onset temperatures of the reentrant states
scale with the Coulomb energy. This scaling provides direct evidence that
Coulomb interactions play an important role in the formation of these reentrant
states evincing their collective nature.

###Slow in-plane magnetoresistance oscillations in multiband quasi-two-dimensional metals|P. D. Grigoriev,M. M. Korshunov,T. I. Mogilyuk###

Slow in-plane magnetoresistance oscillations in multiband quasi-two-dimensional metals. Slow oscillations (SlO) of magnetoresistance is a convenient tool to measure
electronic structure parameters in quasi-two-dimensional metals. We study the
possibility to apply this method to multi-band conductors, e.g. to iron-based
high-temperature superconducting materials. We show that SlO can be used to
measure the interlayer transfer integral in multi-band conductors similar to
single-band metals. In addition, the SlO allow to measure and compare the
effective masses or the electron scattering rates in various bands.

###Low Frequency Noise in Randomly Stimulated Asymmetric Oscillators|Andrzej Stankiewicz###

Low Frequency Noise in Randomly Stimulated Asymmetric Oscillators. A new mechanism of low frequency (1/f-like) noise generation is described and
analyzed. It is attributed to higher frequency asymmetric resonance modes,
which are stimulated by a random factor, e.g. due to thermal excitation.
One-dimensional models of bi-harmonic and non-linear asymmetric oscillators are
presented to prove the concept, and a method of detecting the effect is
developed. The method is then applied to experimental data, in order to show
that the effect exists in magnetoresistive readers.

###Mechanism of Néel order switching in antiferromagnetic thin films revealed by magnetotransport and direct imaging|Lorenzo Baldrati,Olena Gomonay,Andrew Ross,Mariia Filianina,Romain Lebrun,Rafael Ramos,Cyril Leveille,Felix Fuhrmann,Thomas Forrest,Francesco Maccherozzi,Sergio Valencia,Florian Kronast,Eiji Saitoh,Jairo Sinova,Mathias Kläui###

Mechanism of Néel order switching in antiferromagnetic thin films revealed by magnetotransport and direct imaging. We probe the current-induced magnetic switching of insulating
antiferromagnet/heavy metals systems, by electrical spin Hall magnetoresistance
measurements and direct imaging, identifying a reversal occurring by domain
wall (DW) motion. We observe switching of more than one third of the
antiferromagnetic domains by the application of current pulses. Our data reveal
two different magnetic switching mechanisms leading together to an efficient
switching, namely the spin-current induced effective magnetic anisotropy
variation and the action of the spin torque on the DWs.

###Deterministic magnetization switching by voltage-control of magnetic anisotropy and Dzyaloshinskii-Moriya interaction under in-plane magnetic field|Hiroshi Imamura,Takayuki Nozaki,Shinji Yuasa,Yoshishige Suzuki###

Deterministic magnetization switching by voltage-control of magnetic anisotropy and Dzyaloshinskii-Moriya interaction under in-plane magnetic field. Based on the micromagnetic simulations the magnetization switching in a
triangle magnetic element by voltage-control of magnetic anisotropy and
Dzyaloshinskii-Moriya interaction under in-plane magnetic field is proposed.
The proposed switching scheme is not the toggle switching but the deterministic
switching where the magnetic state is determined by the polarity of the applied
voltage pulse. The mechanism and conditions for the switching are clarified.
The results provide a fast and low-power writing method for magnetoresistive
random access memories.

###Role of orbital hybridization in anisotropic magnetoresistance|Hye-Won Ko,Hyeon-Jong Park,Gyungchoon Go,Jung Hyun Oh,Kyoung-Whan Kim,Kyung-Jin Lee###

Role of orbital hybridization in anisotropic magnetoresistance. We theoretically and numerically show that longitudinal orbital currents in
ferromagnets depend on the magnetization direction, which contribute to the
anisotropic magnetoresistance (AMR). This orbital contribution to AMR arises
from the momentum-dependent orbital splitting, which is generally present in
multi-orbital systems through the orbital anisotropy and the orbital
hybridization. We highlight the latter orbital hybridization as an unrecognized
origin of AMR and also as a common origin of AMR and orbital Hall effect.

###Dimensionality of the superconductivity in the transition metal pnictide WP|Angela Nigro,Giuseppe Cuono,Pasquale Marra,Antonio Leo,Gaia Grimaldi,Ziyi Liu,Zhenyu Mi,Wei Wu,Guangtong Liu,Carmine Autieri,Jianlin Luo,Canio Noce###

Dimensionality of the superconductivity in the transition metal pnictide WP. We report theoretical and experimental results on the transition metal
pnictide WP. The theoretical outcomes based on tight-binding calculations and
density functional theory indicate that WP is a three-dimensional
superconductor with an anisotropic electronic structure and nonsymmorphic
symmetries. On the other hand, magnetoresistance experimental data and the
analysis of superconducting fluctuations of the conductivity in external
magnetic field indicate a weakly anisotropic three-dimensional superconducting
phase.

###Large magnetoresistance observed in α-Sn/InSb heterostructures|Yuanfeng Ding,Huanhuan Song,Junwei Huang,Jinshan Yao,Yu Gu,Lian Wei,Yu Deng,Hongtao Yuan,Hong Lu,Yan-Feng Chen###

Large magnetoresistance observed in α-Sn/InSb heterostructures. In this study, we report the epitaxial growth of a series of {\alpha}-Sn
films on InSb substrate by molecular beam epitaxy (MBE) with thickness varying
from 10 nm to 400 nm. High qualities of the {\alpha}-Sn films are confirmed. An
enhanced large magnetoresistance (MR) over 450,000% has been observed compared
to that of the bare InSb substrate. Thickness, angle and temperature dependent
MR are used to demonstrate the effects of {\alpha}-Sn films on the electrical
transport properties.

###Activation of magnetic moments in CVD-grown graphene by annealing|Hyungki Shin,Ebrahim Sajadi,Ali Khademi,Silvia Lüscher,Joshua A. Folk###

Activation of magnetic moments in CVD-grown graphene by annealing. Effects of annealing on chemical vapor deposited graphene are investigated
via a weak localization magnetoresistance measurement. Annealing at
\SI{300}{\celsius} in inert gases, a common cleaning procedure for graphene
devices, is found to raise the dephasing rate significantly above the rate from
electron-electron interactions, which would otherwise be expected to dominate
dephasing at 4 K and below. This extra dephasing is apparently induced by local
magnetic moments activated by the annealing process, and depends strongly on
the backgate voltage applied.

###Magnetotransport in Fe3O4 nanoparticle arrays dominated by non-collinear surface spins|Seongjin Jang,Wenjie Kong,Hao Zeng###

Magnetotransport in Fe3O4 nanoparticle arrays dominated by non-collinear surface spins. Magnetotransport in arrays of monodisperse magnetite nanoparticles has been
studied as a function of annealing temperatures. Charge transport mechanisms
change from thermally assisted interparticle tunneling to hopping between
Fe-sites within the particle as the interparticle spacing is decreased. Despite
this difference, magnetoresistance (MR) as a function of field shows a
ubiquitous behavior dominated by non-collinear surface spins. All MR as a
function of field can be fitted accurately by a Langevin-like function.

###Semiclassical magnetotransport including the effects of the Berry curvature and Lorentz force|Seungchan Woo,Brett Min,Hongki Min###

Semiclassical magnetotransport including the effects of the Berry curvature and Lorentz force. In topological semimetals and insulators, negative longitudinal
magnetoresistance and angle-dependent planar Hall effect have been reported
arising from the Berry curvature. Using the Boltzmann transport theory, we
present a closed-form expression for the nonequilibrium distribution function
which includes both the effects of the Berry curvature and Lorentz force. Using
this formulation, we obtain analytical expressions for conductivity and
resistivity tensors in Weyl semimetals demonstrating a non-monotonic field
dependence arising from the competition between the two effects.

###Computational Study of Magnetic Switching Mechanism and Magnetoresistive Behaviour of Nanoscale Spin Valve Elements|Swapnil Barman###

Computational Study of Magnetic Switching Mechanism and Magnetoresistive Behaviour of Nanoscale Spin Valve Elements. Investigation of the magnetic switching and magnetoresistive behaviour of
nanoscale spin valve elements of different sizes, shapes and arrays is of vital
importance for their application in future magnetic memory and storage devices.
To this end, we have inspected the magnetic switching mechanism and
magnetoresistive behaviour of nanoscale spin valve (Co/Cu/Ni80Fe20) elements of
two different shapes with varying lateral aspect ratios (ARs) by computational
micromagnetic simulation. Further, we have inspected the same for 2x2 and 3x3
arrays of the elliptical elements with AR = 1.25 of varying interelement
spacing. We have analysed how the shape of the hysteresis loop and its various
parameters such as the coercive field, remanence, saturation field were altered
by the variation in magnetic field. The magnetization reversal states were
simulated to explore the spatial coherence of magnetization switching. We
observe that the elements with higher AR show the Ni80Fe20 and Co layers
forming antiparallel states in the plateau similar to synthetic
antiferromagnets. As we reduce the AR, more complex quasi-uniform magnetic
states are observed which are even more complicated for elliptical elements.
The elliptical elements with the aspect ratio of 1.25 shows coherent and
predictable switching behaviour, showing its suitability for the application in
magnetic memory elements. We observe a gradual increase in magnetoresistance
(MR%) with the increase in AR of the spin valve elements, and the decrease in
interelement spacing between the spin valve elements in their arrays. The
magnetic flux density decreases, as we increase the cell spacing between the
elements. The magnetic hysteresis loops, magnetoresistance and spatial
coherence of magnetic switching give a guiding principle for selection of
geometric parameters of nanoscale spin valve arrays towards their application
in magnetic memory devices.

###A comprehensive simulation package for analysis of multilayer spintronic devices|Jakub Mojsiejuk,Sławomir Ziętek,Krzysztof Grochot,Witold Skowroński,Tomasz Stobiecki###

A comprehensive simulation package for analysis of multilayer spintronic devices. We present cmtj - a comprehensive simulation package that allows large-scale
macrospin simulations for a variety of multilayer spintronics devices. Apart
from conventional static simulations, such as magnetoresistance and
magnetisation hysteresis loops, cmtj implements a mathematical model of dynamic
experimental techniques commonly used for spintronics devices characterisation,
for instance: spin diode ferromagnetic resonance, pulse-induced microwave
magnetometry, or harmonic Hall voltage measurements. We demonstrate the
accuracy of the macrospin simulations on a variety of examples, accompanied by
some experimental results.

###Spin-Hall magnetoresistance in quasi-two-dimensional antiferromagnetic insulator/metal bilayer systems|Takuto Ishikawa,Mamoru Matsuo,Takeo Kato###

Spin-Hall magnetoresistance in quasi-two-dimensional antiferromagnetic insulator/metal bilayer systems. We study the temperature dependence of spin Hall magnetoresistance (SMR) in
antiferromagnetic insulator (AFI)/metal bilayer systems. We calculate the
amplitude of the SMR signal by using a quantum Monte Carlo simulation and
examine how the SMR depends on the amplitude of the spin, thickness of the AFI
layer, and randomness of the exchange interactions. Our results for simple
quantum spin models provide a useful starting point for understanding SMR
measurements on atomic layers of magnetic compounds.

###High field magnetotransport in composite conductors: the effective medium approximation revisited|David J. Bergman,David G. Stroud###

High field magnetotransport in composite conductors: the effective medium approximation revisited. The self consistent effective medium approximation (SEMA) is used to study
three-dimensional random conducting composites under the influence of a strong
magnetic field {\bf B}, in the case where all constituents exhibit isotropic
response. Asymptotic analysis is used to obtain almost closed form results for
the strong field magnetoresistance and Hall resistance in various types of two-
and three-constituent isotropic mixtures for the entire range of compositions.
Numerical solutions of the SEMA equations are also obtained, in some cases, and
compared with those results. In two-constituent
free-electron-metal/perfect-insulator mixtures, the magnetoresistance is
asymptotically proportional to $|{\bf B}|$ at {\em all concentrations above the
percolation threshold}. In three-constituent metal/insulator/superconductor
mixtures a line of critical points is found, where the strong field
magnetoresistance switches abruptly from saturating to non-saturating
dependence on $|{\bf B}|$, at a certain value of the
insulator-to-superconductor concentration ratio. This transition appears to be
related to the phenomenon of anisotropic percolation.

###Magnetoresistance in quasi-one-dimensional metals due to Fermi surface cold spots|Perez Moses,Ross H. McKenzie###

Magnetoresistance in quasi-one-dimensional metals due to Fermi surface cold spots. In a number of quasi-one-dimensional organic metals the dependence of the
magnetoresistance on the direction of the magnetic field is quite different
from the predictions of Boltzmann transport theory for a Fermi liquid with a
scattering rate that is independent of momentum. We consider a model in which
there are large variations in the scattering rate over the Fermi surface. The
model is the quasi-one-dimensional version of the ``cold spots'' model
introduced by Ioffe and Millis to explain anomalous transport properties of the
metallic phase of the cuprate superconductors. The dependence of the
resistance, in the most and least conducting directions, on the direction and
magnitude of the magnetic field are calculated. The calculated
magnetoresistance has a number of properties that are quite distinct from
conventional transport theory such as magic angle effects a significant
magnetoresistance when the field and current are both in the least conducting
direction. However, the model cannot give a complete description of the unusual
properties of (TMTSF)2PF6 at pressures of 8-11 kbar.

###Magnetotransport in 2D lateral superlattices with smooth disorder: Quasiclassical theory of commensurability oscillations|A. D. Mirlin,E. Tsitsishvili,P. Woelfle###

Magnetotransport in 2D lateral superlattices with smooth disorder: Quasiclassical theory of commensurability oscillations. Commensurability oscillations in the magnetoresistivity of a two-dimensional
electron gas in a two-dimensional lateral superlattice are studied in the
framework of quasiclassical transport theory. It is assumed that the impurity
scattering is of small-angle nature characteristic for currently fabricated
high-mobility heterostructures. The shape of the modulation-induced
magnetoresistivity $\Delta\rho_{xx}$ depends on the value of the parameter
$\gamma\equiv \eta^2 ql/4$, where $\eta$ and $q$ are the strength and the wave
vector of the modulation, and $l$ is the transport mean free path. For
$\gamma\ll 1$, the oscillations are described, in the regime of not too strong
magnetic fields $B$, by perturbation theory in $\eta$ as applied earlier to the
case of one-dimensional modulation. At stronger fields, where $\Delta\rho_{xx}$
becomes much larger than the Drude resistivity, the transport takes the
advection-diffusion form (Rayleigh-B\'enard convection cell) with a large
P\'eclet number, implying a much slower ($\propto B^{3/4}$) increase of the
oscillation amplitude with $B$. If $\gamma\gg 1$, the transport at low $B$ is
dominated by the modulation-induced chaos (rather than by disorder). The
magnetoresistivity drops exponentially and the commensurability oscillations
start to develop at the magnetic fields where the motion takes the form of the
adiabatic drift. Conditions of applicability, the role of the type of disorder,
and the feasibility of experimental observation are discussed.

###Anisotropic Colossal Magnetoresistance Effects in Fe_{1-x}Cu_xCr_2S_4|V. Fritsch,J. Deisenhofer,R. Fichtl,J. Hemberger,H. -A. Krug von Nidda,M. Muecksch,M. Nicklas,D. Samusi,J. D. Thompson,R. Tidecks,V. Tsurkan,A. Loidl###

Anisotropic Colossal Magnetoresistance Effects in Fe_{1-x}Cu_xCr_2S_4. A detailed study of the electronic transport and magnetic properties of
Fe$_{1-x}$Cu$_x$Cr$_2$S$_4$ ($x \leq 0.5$) on single crystals is presented. The
resistivity is investigated for $2 \leq T \leq 300$ K in magnetic fields up to
14 Tesla and under hydrostatic pressure up to 16 kbar. In addition
magnetization and ferromagnetic resonance (FMR) measurements were performed.
FMR and magnetization data reveal a pronounced magnetic anisotropy, which
develops below the Curie temperature, $T_{\mathrm{C}}$, and increases strongly
towards lower temperatures. Increasing the Cu concentration reduces this
effect. At temperatures below 35 K the magnetoresistance, $MR = \frac{\rho(0) -
\rho(H)}{\rho(0)}$, exhibits a strong dependence on the direction of the
magnetic field, probably due to an enhanced anisotropy. Applying the field
along the hard axis leads to a change of sign and a strong increase of the
absolute value of the magnetoresistance. On the other hand the
magnetoresistance remains positive down to lower temperatures, exhibiting a
smeared out maximum with the magnetic field applied along the easy axis. The
results are discussed in the ionic picture using a triple-exchange model for
electron hopping as well as a half-metal utilizing a band picture.

###Multi-scale Phase Modulations in Colossal Magnetoresistance Manganites|K. H. Kim,M. Uehara,V. Kiryukhin,S. -W. Cheong###

Multi-scale Phase Modulations in Colossal Magnetoresistance Manganites. Extensive experimental results are presented on the multi-scale phase
modulation phenomena observed in colossal magnetoresistance manganites. Two key
types of phase inhomogeneities directly relevant to the colossal
magnetoresistance (CMR) are discussed. The first type involves micrometer-scale
coexistence of structurally and electronically different phases. We present
extensive experimental data for a prototypical system exhibiting such a phase
coexistence, (La,Pr)$_{5/8}$Ca$_{3/8}$MnO$_{3}$. These data reveal that
percolative transport phenomena play the key role in the metal-insulator
transition in this system, and are largely responsible for the significant
magnitude of the magnetoresistance. The phase composition of the multiphase
states is governed by both the electron correlations and the effects of
martensitic accommodation strain. The second type of an inhomogeneous state is
realized in the paramagnetic state commonly found in manganites at
high-temperatures. In this state, nanometer-scale structural correlations
associated with nanoscale charge/orbital ordered regions are observed.
Experimental investigation of numerous manganite systems indicates that these
correlations are generic in orthorhombic mixed-valent manganites, and that the
correlated regions play an essential role in the CMR effect.

###Large magnetoresistance in bcc Co/MgO/Co and FeCo/MgO/FeCo tunneling junctions|X. -G. Zhang,W. H. Butler###

Large magnetoresistance in bcc Co/MgO/Co and FeCo/MgO/FeCo tunneling junctions. By use of first-principles electronic structure calculations, we predict that
the magnetoresistance of the bcc Co(100)/MgO(100)/bcc Co(100) and
FeCo(100)/MgO(100)/FeCo(100) tunneling junctions can be several times larger
than the very large magnetoresistance predicted for the
Fe(100)/MgO(100)/Fe(100) system. The origin of this large magnetoresistance can
be understood using simple physical arguments by considering the electrons at
the Fermi energy travelling perpendicular to the interfaces. For the minority
spins there is no state with $\Delta_1$ symmetry whereas for the majority spins
there is only a $\Delta_1$ state. The $\Delta_1$ state decays much more slowly
than the other states within the MgO barrier. In the absence of scattering
which breaks the conservation of momentum parallel to the interfaces, the
electrons travelling perpendicular to the interfaces undergo total reflection
if the moments of the electrodes are anti-parallel. These arguments apply
equally well to systems with other well ordered tunnel barriers and for which
the most slowly decaying complex energy band in the barrier has $\Delta_1$
symmetry. Examples include systems with (100) layers constructed from Fe, bcc
Co, or bcc FeCo electrodes and Ge, GaAs, or ZnSe barriers.

###From the second magnetization peak to peak effect. A study of superconducting properties in Nb films and MgB2 bulk samples|Dimosthenis Stamopoulos,Athanasios Speliotis,Dimitris Niarchos###

From the second magnetization peak to peak effect. A study of superconducting properties in Nb films and MgB2 bulk samples. We report on magnetic and magnetoresistance measurements in two categories of
superconducting Nb films grown via magnetron sputtering and MgB2 bulk samples.
In the first category, films of Tc = 9.25 K were produced by annealing during
deposition. In these films, the magnetic measurements exhibited the so-called
second magnetization peak (SMP), which is accompanied by thermomagnetic
instabilities (TMI). The characteristic field Hfj, where the first flux jump
occurs, has been studied as a function of the sweep rate of the magnetic field.
Interestingly, in the regime T < 6.4 K, the respective line Hfj(T) is constant,
Hfj(T < 6.4 K) = 40 Oe. A comparison to TMI observed in MgB2 bulk samples is
also performed. Our experimental findings cannot be described accurately by
current theories on TMI. In the second category, films of Tc = 8.3 K were
produced without annealing during deposition. In such films, we observed a peak
effect (PE). In high magnetic fields the PE is accompanied by a sharp drop and
a narrow hysteretic behaviour in the measured magnetoresistance. In contrast to
experimental works presented in the past, the comparison of our magnetic
measurements with the magnetoresistance data suggests that the appearance of
surface superconductivity rather than the melting transition of vortex matter
is the cause of the observed behaviour.

###Low Field Magnetotransport in Manganites|P. K. Siwach,H. K. Singh,O. N. Srivastava###

Low Field Magnetotransport in Manganites. The perovskite manganites of general formula RE_1-xAe_xMnO_3 (RE= rare
earth,AE=Ca, Sr, Ba and Pb)have drawn considerable attention, especially
following the discovery of colossal magnetoresistance (CMR). They exhibit
extraordinary large magnetoresistance pronounced as CMR in the vicinity of
insulator-metal/paramagnetic-ferromagnetic transition at a relatively large
applied magnetic fields. However, for applied aspectes, occurence of
significant CMR at low applied magnetic fields would be required. This review
consists of of two sections: In the first section we have extensively reviewed
the salient features e.g. structure, phase diagram, double exchange mechansim,
Jahn Teller effect, different types of ordering and phase separation of CMR
mangnaites. The second is devoted to an overview of experimental results on CMR
and related magnetotransport characteristics at low magnetic fields for doped
manganites such as polycrystalline La_0.67Ca_0.33MnO_3 films, Ag admixed
La_0.67Ca_0.33MnO_3 films, polycrystalline (La_0.7Ca_0.2Ba_0.1MnO_3)and
epitaxial (La_0.67Ca_0.33MnO_3) films on different substrates, nanophasic
La_0.7Ca_0.3MnO_3, mangnaite-polymer composites (La_0.7Ba_0.2Sr_0.1MnO_3-PMMA
and La_0.67Ca_0.33MnO_3-PMMA)and double layered polycrystalline
(La_1.4Ca_1.6-xBa_xMn_2O_7) and films (La_1.4Ca_1.6Mn_2O_7). Some other
potential magnetoresistive materials e.g. pyrochlores, chalcogenides,
ruthenates, diluted magnetic semiconductors, magnetic tunnel junctions,
nanocontacts etc have aslo been briefly dealt with. The review concludes with
the summary of results for low field magnetotransport behaviour and prospectes
for applications.

###Study of the One- and Two-Band Models for Colossal Magnetoresistive Manganites Using the Truncated Polynomial Expansion Method|C. Sen,G. Alvarez,Y. Motome,N. Furukawa,I. A. Sergienko,T. Schulthess,A. Moreo,E. Dagotto###

Study of the One- and Two-Band Models for Colossal Magnetoresistive Manganites Using the Truncated Polynomial Expansion Method. Considerable progress has been recently made in the theoretical understanding
of the colossal magnetoresistance (CMR) effect in manganites. The analysis of
simple models with two competing states and a resistor network approximation to
calculate conductances has confirmed that CMR effects can be theoretically
reproduced using non-uniform clustered states. In this paper, the recently
proposed Truncated Polynomial Expansion method (TPEM) for spin-fermion systems
is tested using the double-exchange one-band, with finite Hund coupling $J_{\rm
H}$, and two-band, with infinite $J_{\rm H}$, models. Two dimensional lattices
as large as 48$\times$48 are studied, far larger than those that can be handled
with standard exact diagonalization (DIAG) techniques for the fermionic sector.
The clean limit (i.e. without quenched disorder) is here analyzed in detail.
Phase diagrams are obtained, showing first-order transitions separating
ferromagnetic metallic from insulating states. A huge magnetoresistance is
found at low temperatures by including small magnetic fields, in excellent
agreement with experiments. However, at temperatures above the Curie transition
the effect is much smaller confirming that the standard finite-temperature CMR
phenomenon cannot be understood using homogeneous states. By comparing results
between the two methods, TPEM and DIAG, on small lattices, and by analyzing the
systematic behavior with increasing cluster sizes, it is concluded that the
TPEM is accurate to handle realistic manganite models on large systems. Our
results pave the way to a frontal computational attack of the colossal
magnetoresistance phenomenon using double-exchange like models, on large
clusters, and including quenched disorder.

###Non-Fermi liquid behavior in the magnetotransport of CeMIn5 (M: Co and Rh): Striking similarity between quasi 2D heavy fermion and high-Tc cuprates|Y. Nakajima,H. Shishido,H. Nakai,T. Shibauch,K. Behnia,K. Izawa,M. Hedo,Y. Uwatoko,T. Matsumoto,R. Settai,Y. Onuki,H. Kontani,Y. Matsuda###

Non-Fermi liquid behavior in the magnetotransport of CeMIn5 (M: Co and Rh): Striking similarity between quasi 2D heavy fermion and high-Tc cuprates. We present a systematic study of the dc-resistivity, Hall effect, and
magnetoresistance in the normal state of quasi 2D heavy fermion superconductors
CeMIn5 (M: Rh and Co) under pressure. Here the electronic system evolves with
pressure from an antiferromagnetic (AF) metal, through a highly unconventional
non-Fermi liquid, and finally into a Fermi-liquid state. The amplitude of the
Hall coefficient increases dramatically with decreasing T, reaching at low
temperatures a value significantly larger than 1/ne. Furthermore, the
magnetoresistance is characterized by T- and H-dependence which clearly violate
Kohler's rule. We found that the Hall angle cot\Theta varies as T^2, and the
magnetoresistance is well scaled by the Hall angle as \Delta
\rho_{xx}/\rho_{xx}\propto \tan^2\Theta. These non-Fermi liquid properties in
the electron transport are remarkably pronounced when the AF fluctuations are
enhanced in the vicinity of the QCP. We lay particular emphasis on the striking
resemblance of these anomalous magnetotransport with those of the high-Tc
cuprates. We argue that features commonly observed in quasi 2D heavy fermion
and cuprates very likely capture universal features of strongly correlated
electron systems.

###Magnetic and magnetoresistance behavior of Tb7Rh3, an intermetallic compound with a negative temperature coefficient of electrical resistivity in the paramagnetic state, and Paramagnetic Giant Magnetoresistance Phenomenon|Kausik Sengupta,Kartik K Iyer,E. V. Sampathkumaran###

Magnetic and magnetoresistance behavior of Tb7Rh3, an intermetallic compound with a negative temperature coefficient of electrical resistivity in the paramagnetic state, and Paramagnetic Giant Magnetoresistance Phenomenon. The results of dc magnetization, electrical and magnetoresistance and heat
capacity measurements (2-300 K) on Tb7Rh3, crystallizing in Th7Fe3-type
hexagonal structure, are reported. In this compound, magnetic ordering sets in
around 90 K with additional transitions at low temperatures and the temperature
coefficient of resistivity (R), dR/dT, is negative over a wide temperature
range in the paramagnetic state. The present magnetization results reveal that
this compound is apparently characterized by rich features in the
magnetic-field-temperature phase diagram. A point of major emphasis is that the
sign of dR/dT in the paramagnetic state can be gradually changed by the
application of magnetic field. As a result, the magnitude of the
magnetoresistance (MR) is rather large even in the vicinity of room temperature
(far above magnetic ordering temperature), in addition to giant MR behavior in
the magnetically ordered state. Viewed together With similar behavior for other
heavy rare-earth members of this series, this class of compounds can be
classified as Paramagnetic Giant Magnetoresistance Systems. A new theoretical
approach is warranted to understand this phenomenon.

###Electronic measurement and control of spin transport in Silicon|Ian Appelbaum,Biqin Huang,Douwe Monsma###

Electronic measurement and control of spin transport in Silicon. The electron spin lifetime and diffusion length are transport parameters that
define the scale of coherence in spintronic devices and circuits. Since these
parameters are many orders of magnitude larger in semiconductors than in
metals, semiconductors could be the most suitable for spintronics. Thus far,
spin transport has only been measured in direct-bandgap semiconductors or in
combination with magnetic semiconductors, excluding a wide range of
non-magnetic semiconductors with indirect bandgaps. Most notable in this group
is silicon (Si), which (in addition to its market entrenchment in electronics)
has long been predicted a superior semiconductor for spintronics with enhanced
lifetime and diffusion length due to low spin-orbit scattering and lattice
inversion symmetry. Despite its exciting promise, a demonstration of coherent
spin transport in Si has remained elusive, because most experiments focused on
magnetoresistive devices; these methods fail because of universal impedance
mismatch obstacles, and are obscured by Lorentz magnetoresistance and Hall
effects. Here we demonstrate conduction band spin transport across 10 microns
undoped Si, by using spin-dependent ballistic hot-electron filtering through
ferromagnetic thin films for both spin-injection and detection. Not based on
magnetoresistance, the hot electron spin-injection and detection avoids
impedance mismatch issues and prevents interference from parasitic effects. The
clean collector current thus shows independent magnetic and electrical control
of spin precession and confirms spin coherent drift in the conduction band of
silicon.

###The nanoscale phase separation in hole-doped manganites|R. Mathieu,Y. Tokura###

The nanoscale phase separation in hole-doped manganites. A macroscopic phase separation, in which ferromagnetic clusters are observed
in an insulating matrix, is sometimes observed, and believed to be essential to
the colossal magnetoresistive (CMR) properties of manganese oxides. The
application of a magnetic field may indeed trigger large magnetoresistance
effects due to the percolation between clusters allowing the movement of the
charge carriers. However, this macroscopic phase separation is mainly related
to extrinsic defects or impurities, which hinder the long-ranged charge-orbital
order of the system. We show in the present article that rather than the
macroscopic phase separation, an homogeneous short-ranged charge-orbital order
accompanied by a spin glass state occurs, as an intrinsic result of the
uniformity of the random potential perturbation induced by the solid solution
of the cations on the $A$-sites of the structure of these materials. Hence the
phase separation does occur, but in a more subtle and interesting nanoscopic
form, here referred as ``homogeneous''. Remarkably, this ``nanoscale phase
separation'' alone is able to bring forth the colossal magnetoresistance in the
perovskite manganites, and is potentially relevant to a wide variety of other
magnetic and/or electrical properties of manganites, as well as many other
transition metal oxides, in bulk or thin film form as we exemplify throughout
the article.

###Half Metallicity in Pr$_{0.75}$Sr$_{0.25}$MnO$_3$: A first Principle study|M. Chakraborty,P. Pal,B. R. Sekhar###

Half Metallicity in Pr$_{0.75}$Sr$_{0.25}$MnO$_3$: A first Principle study. In this communication we present a first principle study of
Pr$_{1-x}$Sr$_{x}$MnO$_3$ with $x = 0.25$. While the parent compounds of this
system are antiferromagnetic insulators with different structural and magnetic
ground states, the $x = 0.25$ is in the colossal magnetoresistance regime of
the Pr$_{1-x}$Sr$_{x}$MnO$_3$ phase diagram [C. Martin, A. Maignan, M. Hervieu,
B. Raveau, Phys. Rev. B 60 (1999) 12191]. Our band structure calculations for
the end-point compounds matches well with the existing theoretical and
experimental results [C. Martin, A. Maignan, M. Hervieu, B. Raveau, Phys. Rev.
B 60 (1999) 12191; Rune Sondena, P. Ravindran, Svein Stolen, Tor Grande,
Michael Hanfland, Phys. Rev. B 74 (2006) 144102]. Interestingly, our
calculations show that the Pr$_{0.75}$Sr$_{0.25}$MnO$_3$ has a half-metallic
character with a huge band gap of 2.8 eV in the minority band. We believe this
result would fuel further interest in some of these special compositions of
colossal magnetoresistive manganites as they could be potential candidates for
spintronic devices. We discuss the half-metallicity of the
Pr$_{0.75}$Sr$_{0.25}$MnO$_3$ in the light of changes in the orbital
hybridization as a result of Sr doping in PrMnO$_3$. Further, we highlight the
importance of half-metallicity for a consolidated understanding of colossal
magnetoresistance effect.

###Possible magnetoelectric coupling in the half doped charge ordered manganite, Pr_0.5Ca_0.5MnO_3-d|A. Karmakar,S. Majumdar,A. K. Singh,S. Patnaik,S. Giri###

Possible magnetoelectric coupling in the half doped charge ordered manganite, Pr_0.5Ca_0.5MnO_3-d. Magnetization, magnetoresistance, and magnetodielectric measurements have
been carried out on the half doped charge ordered manganite, Pr_0.5Ca_0.5MnO_3.
The low temperature state is found to be strongly dependent on the oxygen
stoichiometry whereas the high temperature state remains almost unaltered. A
disorder driven phase separation in the low temperature state is noticed in the
magnetic, magnetoresistance, and dielectric measurements which is attributed to
the oxygen deficiency in the compound. A considerable magnetodielectric (MD)
effect is noticed close to room temperature at 280 K which is fascinating for
technological applications. The strongest MD effect observed in between 180 K
and 200 K is found to be uncorrelated with magnetoresistance but it is
suggested to be due to a number of intricate processes occuring in this
temperature range which includes paramagnetic to antiferromagnetic transition,
incommensurate to commensurate charge ordering and orbital ordering. The
strongest MD effect seems to emerge from the high sensitivity of the
incommensurate state to the external perturbation such as external magnetic
field. The results propose the possible magnetoelectric coupling in the charge
ordered compound.

###Spin-Transfer Torque and Magnetoresistance in Superconducting Spin-Valves|J. Linder,T. Yokoyama,A. Sudbø###

Spin-Transfer Torque and Magnetoresistance in Superconducting Spin-Valves. We study the spin-transfer torque and magnetoresistance of a
ferromagnet$\mid$superconductor$\mid$ferromagnet spin-valve, allowing for an
arbitrary magnetization misorientation and treating both s-wave and d-wave
symmetries of the superconductor. We take fully into account Andreev reflection
and also the spin-triplet correlations that are generated when the
magnetizations are non-collinear. It is found that the torque and
magnetoresistance are both strongly enhanced when topological zero-energy
states are present at the interfaces, which is the case for d-wave
superconductors with a crystallographic orientation of [110] relative to the
interface ($d_{xy}$-wave symmetry). Moreover, we find that the
magnetoresistance displays a strong oscillatory and non-monotonous behavior as
a function of $d_S/\xi$ where $d_S$ and $\xi$ are the interlayer width of the
superconducting region and the superconducting coherence length, respectively.
This feature is also attributed to the crossover from layers of size $d_S\sim
2\xi$ to layers of size $d_S\gg 2\xi$, where the contribution to transport from
zero-energy states gradually vanishes.

###Anisotropy of the in-plane angular magnetoresistance of electron-doed Sr1-xLaxCuO2 thin films|V. P. Jovanović,L. Fruchter,Z. Z. Li,H. Raffy###

Anisotropy of the in-plane angular magnetoresistance of electron-doed Sr1-xLaxCuO2 thin films. Signatures of antiferromagnetism (AF) in the underdoped Ln2-xCexCuO4 (Ln =
Nd, Pr,...) family are observed even for doping levels for which
superconductivity exists. We have looked for a similar property in a different
electron-doped cuprate family, Sr1-xLaxCuO2, which consists of CuO2 planes
separated by Sr/La atoms, and is exempt of the possible influence of magnetic
rare earth ions. We report in-plane magnetoresistance measurements in the
normal state of underdoped, superconducting, c-axis oriented, epitaxial
Sr1-xLaxCuO2 thin films. This probe is sensitive to spin arrangement and we
find that the in-plane magnetoresistance, which is negative and does not
saturate for T, exhibits an angular dependence when measured upon rotating a
magnetic field within the CuO2 planes. The analysis reveals a superposition of
fourfold and twofold angular oscillations. Both of these increase in amplitude
with increasing field and decreasing and appear below a temperature, which gets
higher with decreasing doping levels. Our results demonstrate that these
magnetoresistance oscillations, also observed for the Ln2-xCexCuO4 (Ln = Nd,
Pr,...) family and attributed to an AF signature, are, without ambiguity, a
property of CuO2 planes. Besides, these oscillations vary with doping in an
unusual way compared to previous results: fourfold oscillations are essentially
present in the more underdoped samples while only twofold oscillations are
visible in the less underdoped ones. This intriguing observation appears to be
a consequence of spin dilution with increasing doping level.

###Localized and itinerant dichotomy of electrons in Ba(Fe,Co)2As2|H. Q. Yuan,L. Jiao,F. F. Balakirev,J. Singleton,C. Setty,J. P. Hu,T. Shang,L. J. Li,G. H. Cao,Z. A. Xu,B. Shen,H. H. Wen###

Localized and itinerant dichotomy of electrons in Ba(Fe,Co)2As2. Variant approaches, either based on the Fermi surface nesting or started from
the proximity to a Mott-insulator, were proposed to elucidate the physics in
iron pnictides, but no consensus has been reached. A fundamental problem
concerns the nature of their 3d electrons. Here we report the
magnetoresistivity (\rho_xx) and the Hall resistivity (\rho_xy) of
Ba(Fe1-xCox)2As2 (x=0 and 0.05) in a magnetic field of up to 55T. The magnetic
transition is extremely robust against magnetic field, giving strong evidence
that the magnetic ordering is formed by local moments. The magnetic state is
featured with a huge magnetoresistance and a distinguished Hall resistivity,
\rho_xy(H), which shows a pronounced parabolic field dependence, while the
paramagnetic state shows little magnetoresistance and follows a simple linear
magnetic field dependence on the Hall resistivity. Analyses of our data, based
on a two-carrier model, demonstrate that the electron carriers in the magnetic
state rapidly increase upon applying a magnetic field, partially compensating
the loss of electron carriers at T_M. We argue that the 3d-electrons in
Ba(Fe1-xCox)2As2 are divided into those who are close to forming localized
moments controlling the magnetic transition and the others giving rise to
complex transport properties through their interaction with the former.

###Domain - wall - induced magnetoresistance in pseudo spin-valve/superconductor hybrid structures|A. K. Suszka,F. S. Bergeret,A. Berger###

Domain - wall - induced magnetoresistance in pseudo spin-valve/superconductor hybrid structures. We have studied the interaction between magnetism and superconductivity in a
pseudo-spin-valve structure consisting of a Co/Cu/Py/Nb layer sequence. We are
able to control the magnetization reversal process and monitor it by means of
the giant magnetoresistance effect during transport measurements. By placing
the superconducting Nb-film on the top of the permalloy (Py) electrode instead
of putting it in between the two ferromagnets, we minimize the influence of
spin scattering or spin accumulation onto the transport properties of Nb.
Magnetotransport data reveal clear evidence that the stray fields of domain
walls (DWs) in the pseudo-spin-valve influence the emerging superconductivity
close to the transition temperature by the occurrence of peak-like features in
the magneto-resistance characteristic. Direct comparison with magnetometry data
shows that the resistance peaks occur exactly at the magnetization reversal
fields of the Co and Py layers, where DWs are generated. For temperatures near
the superconducting transition the amplitude of the DW-induced
magnetoresistance increases with decreasing temperature, reaching values far
beyond the size of the giant magnetoresistive response of our structure in the
normal state.

###Large Magnetoresistance and Jahn Teller effect in Sr$_2$FeCoO$_6$|R. Pradheesh,Harikrishnan S. Nair,V. Sankaranarayanan,K. Sethupat###

Large Magnetoresistance and Jahn Teller effect in Sr$_2$FeCoO$_6$. Neutron diffraction measurement on the spin glass double perovskite
Sr$_2$FeCoO$_6$ reveals site disorder as well as Co$^{3+}$ intermediate spin
state. In addition, multiple valence states of Fe and Co are confirmed through
M\"{o}ssbauer and X-ray photoelectron spectroscopy. The structural disorder and
multiple valence lead to competing ferromagnetic and antiferromagnetic
interactions and subsequently to a spin glass state, which is reflected in the
form of an additional $T$-linear contribution at low temperatures in specific
heat. A clear evidence of Jahn-Teller distortion at the Co$^{3+}$-O$_6$ complex
is observed and incorporating the physics of Jahn-Teller effect, the presence
of localized magnetic moment is shown. A large, negative and anomalous
magnetoresistance of $\approx$ 63% at 14K in 12T applied field is observed for
Sr$_2$FeCoO$_6$. The observed magnetoresistance could be explained by applying
a semi-empirical fit consisting of a negative and a positive contribution and
show that the negative magnetoresistance is due to spin scattering of carriers
by localized magnetic moments in the spin glass phase.

###Weak antilocalization and disorder-enhanced electron interactions in crystalline GeSbTe|Nicholas P. Breznay,Hanno Volker,Alexander Palevski,Riccardo Mazzarello,Aharon Kapitulnik,Matthias Wuttig###

Weak antilocalization and disorder-enhanced electron interactions in crystalline GeSbTe. Phase change materials can be reversibly switched between amorphous and
crystalline states and often show strong contrast in the optical and electrical
properties of these two phases. They are now in widespread use for optical data
storage, and their fast switching and a pronounced change of resistivity upon
crystallization are also very attractive for nonvolatile electronic data
storage. Nevertheless there are still several open questions regarding the
electronic states and charge transport in these compounds. In this work we
study electrical transport in thin metallic films of the disordered,
crystalline phase change material Ge$_1$Sb$_2$Te$_4$. We observe weak
antilocalization and disorder enhanced Coulomb interaction effects at low
temperatures, and separate the contributions of these two phenomena to the
temperature dependence of the resistivity, Hall effect, and magnetoresistance.
Strong spin-orbit scattering causes positive magnetoresistance at all
temperatures, and a careful analysis of the low-field magnetoresistance allows
us to extract the temperature dependent electron dephasing rate and study other
scattering phenomena. We find electron dephasing due to inelastic
electron-phonon scattering at higher temperatures, electron-electron scattering
dephasing at intermediate temperatures, and a crossover to weak temperature
dependence below 1 K.

###Revealing the origin of the vertical hysteresis loop shifts in an exchange biased Co/YMnO$_3$ bilayer|J. Barzola-Quiquia,A. Lessig,A. Ballestar,C. Zandalazini,G. Bridoux,F. Bern,P. Esquinazi###

Revealing the origin of the vertical hysteresis loop shifts in an exchange biased Co/YMnO$_3$ bilayer. We have investigated exchange bias effects in bilayers composed by the
antiferromagnetic o-YMnO$_3$ and ferromagnetic Co thin film by means of SQUID
magnetometry, magnetoresistance, anisotropic magnetoresistance and planar Hall
effect. The magnetization and magnetotransport properties show pronounced
asymmetries in the field and magnetization axes of the field hysteresis loops.
Both exchange bias parameters, the exchange bias field $H_{E}(T)$ as well as
the magnetization shift $M_E(T)$, vanish around the N\'eel temperature $T_N
\simeq 45$ K. We show that the magnetization shift $M_E(T)$ is also measured by
a shift in the anisotropic magnetoresistance and planar Hall resistance having
those a similar temperature dependence as the one obtained from magnetization
measurements. Because the o-YMnO$_3$ film is highly insulating, our results
demonstrate that the $M_E(T)$ shift originates at the interface within the
ferromagnetic Co layer. To show that the main results obtained are general and
not because of some special characteristics of the o-YMO$_3$ layer, similar
measurements were done in Co/CoO micro-wires. The transport and magnetization
characterization of the micro-wires supports the main conclusion that these
effects are related to the response of the ferromagnetic Co layer at the
interface.

###Magneto-Transport Properties of Single Crystalline LaFeAsO|C. A. McElroy,J. J. Hamlin,B. D. White,M. A. McGuire,B. C. Sales,M. B. Maple###

Magneto-Transport Properties of Single Crystalline LaFeAsO. Measurements of magnetization, specific heat, electrical resistivity, Hall
effect, and magnetoresistance on single crystalline samples of LaFeAsO grown in
a NaAs flux are reported. While this material is known to be a semimetal, the
temperature dependence of the electrical resistivity data presented herein is
reminiscent of semiconducting behavior and exhibits distinct features
associated with a structural transition and spin density wave (SDW) order.
Magnetoresistance and Hall coefficient measurements were performed in magnetic
fields up to 9 T applied perpendicular to the basal plane using a van der Pauw
configuration. The charge carrier density and mobility indicate that electrons
are the majority charge carriers and exhibit features indicative of the
structural transition and SDW formation. Low temperature X-ray diffraction
measurements have confirmed that the structural transition in these samples
occurs near 140 K, compared to a transition temperature of 156 K observed in
polycrystalline samples. Isotherms of magnetoresistivity measured as a function
of magnetic field can be scaled onto a single curve in which the scaling field
is a linear function of temperature between 2.2 K and 180 K.

###Recent Progress in III-V based ferromagnetic semiconductors: Band structure, Fermi level, and tunneling transport|Masaaki Tanaka,Shinobu Ohya,Pham Nam Hai###

Recent Progress in III-V based ferromagnetic semiconductors: Band structure, Fermi level, and tunneling transport. Spin-based electronics or spintronics is an emerging field, in which we try
to utilize spin degrees of freedom as well as charge transport in materials and
devices. While metal-based spin-devices, such as magnetic-field sensors and
magnetoresistive random access memory using giant magnetoresistance and
tunneling magnetoresistance, are already put to practical use,
semiconductor-based spintronics has greater potential for expansion because of
good compatibility with existing semiconductor technology. Many
semiconductor-based spintronics devices with useful functionalities have been
proposed and explored so far. To realize those devices and functionalities, we
definitely need appropriate materials which have both the properties of
semiconductors and ferromagnets. Ferromagnetic semiconductors (FMS), which are
alloy semiconductors containing magnetic atoms such as Mn and Fe, are one of
the most promising classes of materials for this purpose, and thus have been
intensively studied for the past two decades. Here, we review the recent
progress in the studies of the most prototypical III-V based FMS, p-type
(GaMn)As, and its heterostructures with focus on tunneling transport, Fermi
level, and bandstructure. Furthermore, we cover the properties of a new n-type
FMS, (InFe)As, which shows electron-induced ferromagnetism. These FMS materials
having zinc-blende crystal structure show excellent compatibility with
well-developed III-V heterostructures and devices.

###Interference-induced magnetoresistance in HgTe quantum wells|I. V. Gornyi,V. Yu. Kachorovskii,P. M. Ostrovsky###

Interference-induced magnetoresistance in HgTe quantum wells. We study the quantum interference correction to the conductivity in HgTe
quantum wells using the Bernevig-Hughes-Zhang model. This model consists of two
independent species (blocks) of massive Dirac fermions. We describe the
crossover between the orthogonal and symplectic classes with the increasing the
carrier concentration and calculate, respectively, weak localization and
antilocalization corrections in the absence of the block mixing and assuming
the white-noise disorder within each block. We have calculated the
interference-induced magnetoresistance in a wide interval of magnetic fields,
in particular, beyond the diffusion regime. Remarkably, each Dirac cone taken
separately gives a linear contribution to the low-field magnetoresistance,
which turns out to be asymmetric in magnetic field $B$. We present an
interpretation of this result in terms of the Berry phase formalism.
  The contributions of the two blocks are related to each other by replacing
$B$ to $-B$, so that the total magnetoresistance is symmetric and parabolic in
the limit $B\to 0$. However, in some range of parameters field dependence turns
out to be strongly non-monotonous.
  We also demonstrate that block mixing gives rise to additional singular
diffusive modes which do not show up in the absence of mixing.

###Negative magnetoresistivity in chiral fluids and holography|Karl Landsteiner,Yan Liu,Ya-Wen Sun###

Negative magnetoresistivity in chiral fluids and holography. In four dimensions Weyl fermions possess a chiral anomaly which leads to
several special features in the transport phenomena, such as the negative
longitudinal magnetoresistivity. In this paper, we study its inverse, the
longitudinal magnetoconductivity, in the case of a chiral anomalous system with
a background magnetic field B using the linear response method in the
hydrodynamic limit and from holography. Our hydrodynamic results show that in
general we need to have energy, momentum and charge dissipations to get a
finite DC longitudinal magnetoconductivity due to the existence of the chiral
anomaly. Applying the formula that we get from hydrodynamics to the holographic
system in the probe limit, we find that the result in the hydrodynamic regime
matches that calculated from holography via Kubo formula. The holographic
result shows that in an intermediate regime of B there is naturally a negative
magnetoresistivity which decreases as 1/B. At small B direct calculations in
the holographic system suggest that holography provides a new explanation for
the small B positive magnetoresistivity behavior seen in experiment, i.e. the
small B behavior comes from the quantum critical conductivity being affected by
the chiral anomaly.

###Spin transfer torques generated by the anomalous Hall effect and anisotropic magnetoresistance|Tomohiro Taniguchi,J. Grollier,M. D. Stiles###

Spin transfer torques generated by the anomalous Hall effect and anisotropic magnetoresistance. Spin-orbit coupling in ferromagnets gives rise to the anomalous Hall effect
and the anisotropic magnetoresistance, both of which can be used to create
spin-transfer torques in a similar manner as the spin Hall effect. In this
paper we show how these effects can be used to reliably switch perpendicularly
magnetized layers and to move domain walls. A drift-diffusion treatment of the
anomalous Hall effect and the anisotropic magnetoresistance describes the spin
currents that flow in directions perpendicular to the electric field. In
systems with two ferromagnetic layers separated by a spacer layer, an in-plane
electric field cause spin currents to be injected from one layer into the
other, creating spin transfer torques. Unlike the related spin Hall effect in
non-magnetic materials, the anomalous Hall effect and the anisotropic
magnetoresistance allow control of the orientation of the injected spins, and
hence torques, by changing the direction of the magnetization in the injecting
layer. The torques on one layer show a rich angular dependence as a function of
the orientation of the magnetization in the other layer. The control of the
torques afforded by changing the orientation of the magnetization in a fixed
layer makes it possible to reliably switch a perpendicularly magnetized free
layer. Our calculated critical current densities for a representative
CoFe/Cu/FePt structure show that the switching can be efficient for appropriate
material choices. Similarly, control of the magnetization direction can drive
domain wall motion, as shown for NiFe/Cu/NiFe structures.

###Robust Surface States indicated by Magnetotransport in SmB6 Thin Films|Jie Yong,Yeping Jiang,Xiaohang Zhang,Jongmoon Shin,Ichiro Takeuchi,Richard L. Greene###

Robust Surface States indicated by Magnetotransport in SmB6 Thin Films. SmB6 has been predicted and verified as a prototype of topological Kondo
insulators (TKIs). Here we report longitudinal magnetoresistance and Hall
coefficient measurements on co-sputtered nanocrystalline SmB6 films and try to
find possible signatures of their topological properties. The magnetoresistance
(MR) at 2 K is positive and linear (LPMR) at low field and becomes negative and
quadratic at higher field. While the negative part is known from the reduction
of the hybridization gap due to Zeeman splitting, the positive dependence is
similar to what has been observed in other topological insulators (TI). We
conclude that the LPMR is a characteristic feature of TI and is related to the
linear dispersion near the Dirac cone. The Hall resistance shows a sign change
around 50 K. It peaks and becomes nonlinear at around 10 K then decreases below
10 K. This indicates that carriers with opposite signs emerge below 50 K. Two
films with different geometries (thickness and lateral dimension) show
contrasting behavior below and above 50K, which proves the surface origin of
the low temperature carriers in these films. The temperature dependence of
magnetoresistance and the Hall data indicates that the surface states are
likely non-trivial.

###Magnetoresistance in organic spintronic devices: the role of nonlinear effects|A. V. Shumilin,V. V. Kabanov,V. A. Dediu###

Magnetoresistance in organic spintronic devices: the role of nonlinear effects. We derive kinetic equations describing injection and transport of spin
polarized carriers in organic semiconductors with hopping conductivity via an
impurity level. The model predicts a strongly voltage dependent
magnetoresistance, defined as resistance variation between devices with
parallel and antiparallel electrode magnetizations (spin valve effect). The
voltage dependence of the magnetoresistance splits into three distinct regimes.
The first regime matches well known inorganic spintronic regimes, corresponding
to barrier controlled spin injection or the well known conductivity mismatch
case. The second regime at intermediate voltages corresponds to strongly
suppressed magnetoresistance. The third regime develops at higher voltages and
accounts for a novel paradigm. It is promoted by the strong non-linearity in
the charge transport which strength is characterized by the dimensionless
parameter $eU/k_BT$. This nonlinearity, depending on device conditions, can
lead to both significant enhancement or to exponential suppression of the spin
valve effect in organic devices. We believe that these predictions are valid
beyond the case of organic semiconductors and should be considered for any
material characterized by strongly non-linear charge transport.

###Role of spin-orbit coupling and evolution of the electronic structure of WTe$_2$ under an external magnetic field|D. Rhodes,S. Das,Q. R. Zhang,B. Zeng,N. R. Pradhan,N. Kikugawa,E. Manousakis,L. Balicas###

Role of spin-orbit coupling and evolution of the electronic structure of WTe$_2$ under an external magnetic field. Here, we present a detailed study on the temperature and angular dependence
of the Shubnikov-de-Haas (SdH) effect in the semi-metal WTe$_2$. This compound
was recently shown to display a very large non-saturating magnetoresistance
which was attributed to nearly perfectly compensated densities of electrons and
holes. We observe four fundamental SdH frequencies and attribute them to
spin-orbit split, electron- and hole-like, Fermi surface (FS) cross-sectional
areas. Their angular dependence seems consistent with ellipsoidal FSs with
volumes suggesting a modest excess in the density of electrons with respect to
that of the holes. We show that density functional theory (DFT) calculations
fail to correctly describe the FSs of WTe$_2$. When their cross-sectional areas
are adjusted to reflect the experimental data, the resulting volumes of the
electron/hole FSs obtained from the DFT calculations would imply a pronounced
imbalance between the densities of electrons and holes. We find evidence for
field-dependent Fermi surface cross-sectional areas by fitting the oscillatory
component superimposed onto the magnetoresistivity signal to several
Lifshitz-Kosevich components. We also observe a pronounced field-induced
renormalization of the effective masses. Taken together, our observations
suggest that the electronic structure of WTe$_2$ evolves with the magnetic
field. This evolution might be a factor contributing to its pronounced
magnetoresistivity.

###Temperature dependent three-dimensional anisotropy of the magnetoresistance in WTe$_2$|L. R. Thoutam,Y. L. Wang,Z. L. Xiao,S. Das,A. Luican-Mayer,R. Divan,G. W. Crabtree,W. K. Kwok###

Temperature dependent three-dimensional anisotropy of the magnetoresistance in WTe$_2$. Extremely large magnetoresistance (XMR) was recently discovered in WTe$_2$,
triggering extensive research on this material regarding the XMR origin. Since
WTe$_2$ is a layered compound with metal layers sandwiched between adjacent
insulating chalcogenide layers, this material has been considered to be
electronically two-dimensional (2D). Here we report two new findings on
WTe$_2$: (1) WTe$_2$ is electronically 3D with a mass anisotropy as low as $2$,
as revealed by the 3D scaling behavior of the resistance
$R(H,\theta)=R(\varepsilon_\theta H)$ with $\varepsilon_\theta =(\cos^2 \theta
+ \gamma^{-2}\sin^2 \theta)^{1/2}$, $\theta$ being the magnetic field angle
with respect to c-axis of the crystal and $\gamma$ being the mass anisotropy;
(2) the mass anisotropy $\gamma$ varies with temperature and follows the
magnetoresistance behavior of the Fermi liquid state. Our results not only
provide a general scaling approach for the anisotropic magnetoresistance but
also are crucial for correctly understanding the electronic properties of
WTe$_2$, including the origin of the remarkable 'turn-on' behavior in the
resistance versus temperature curve, which has been widely observed in many
materials and assumed to be a metal-insulator transition.

###Magnetic and magnetotransport behavior of RFe5Al7 (R= Gd and Dy): Observation of re-entrant inverse-magnetocaloric phenomenon and asymmetric magnetoresistance behavior|Venkatesh Chandragiri,Kartik K Iyer,E. V. Sampathkumaran###

Magnetic and magnetotransport behavior of RFe5Al7 (R= Gd and Dy): Observation of re-entrant inverse-magnetocaloric phenomenon and asymmetric magnetoresistance behavior. We have compared and contrasted magnetic, magnetocaloric and magnetoresistive
properties of Gd and Dy members of the rare-earth (R) series RFe5Al7,
crystallizing in ThMn12 structure, known to order antiferromagnetically. Among
other observations, we would like to emphasize on the following novel findings:
(i) There are multiple sign-crossovers in the temperature (T) dependence of
isothermal entropy change (DeltaS) in the case of Dy compound; in addition to
nil DeltaS at the magnetic compensation point known for two-magnetic-sublattice
systems, there is an additional sign-crossover at low temperatures, as though
there is a re-entrant inverse magnetocaloric phenomenon. Corresponding sign
reversals could also be observed in the magnetoresistance data. (ii) The plots
of magnetoresistance versus magnetic field are found to be highly asymmetric
with the reversal of the direction of magnetic-field (H) well below TN for both
compounds, similar to that known for an antiferromagnetic tunnel junctions. We
attribute these to subtle changes in spin orientations of R and Fe moments
induced by T and H.

###Negative magnetoresistance without well-defined chirality in the Weyl semimetal TaP|Frank Arnold,Chandra Shekhar,Shu-Chun Wu,Yan Sun,Ricardo Donizeth dos Reis,Nitesh Kumar,Marcel Naumann,Mukkattu O. Ajeesh,Marcus Schmidt,Adolfo G. Grushin,Jens H. Bardarson,Michael Baenitz,Dmitry Sokolov,Horst Borrmann,Michael Nicklas,Claudia Felser,Elena Hassinger,Binghai Yan###

Negative magnetoresistance without well-defined chirality in the Weyl semimetal TaP. Weyl semimetals (WSMs) are topological quantum states wherein the electronic
bands linearly disperse around pairs of nodes, the Weyl points, of fixed (left
or right) chirality. The recent discovery of WSM materials triggered an
experimental search for the exotic quantum phenomenon known as the chiral
anomaly. Via the chiral anomaly nonorthogonal electric and magnetic fields
induce a chiral density imbalance that results in an unconventional negative
longitudinal magnetoresistance, the chiral magnetic effect. Recent theoretical
work suggests that this effect does not require well-defined Weyl nodes.
Experimentally however, it remains an open question to what extent it survives
when chirality is not well-defined, for example when the Fermi energy is far
away from the Weyl points. Here, we establish the detailed Fermi surface
topology of the recently identified WSM TaP via a combination of angle-resolved
quantum oscillation spectra and band structure calculations. The Fermi surface
forms spin-polarized banana-shaped electron and hole pockets attached to pairs
of Weyl points. Although the chiral anomaly is therefore ill-defined, we
observe a large negative magnetoresistance (NMR) appearing for collinear
magnetic and electric fields as observed in other WSMs. In addition, we show
experimental signatures indicating that such longitudinal magnetoresistance
measurements can be affected by an inhomogeneous current distribution inside
the sample in a magnetic field. Our results provide a clear framework how to
detect the chiral magnetic effect.

###Linear magnetotransport in monolayer MoS$_2$|C. M. Wang,X. L. Lei###

Linear magnetotransport in monolayer MoS$_2$. A momentum balance equation is developed to investigate the magnetotransport
properties in monolayer molybdenum disulphide when a strong perpendicular
magnetic field and a weak in-plane electric field are applied simultaneously.
At low temperature, in the presence of intravalley impurity scattering
Shubnikov de Haas oscillation shows up accompanying by a beating pattern
arising from large spin splitting and its period may halve due to high-order
oscillating term at large magnetic field for samples with ultrahigh mobility.
In the case of intervalley disorders, there exists a magnetic-field range where
the magnetoresistivity almost vanishes. For low-mobility layer, a
phase-inversion of oscillating peaks is acquired in accordance with recent
experiment. At high temperature when Shubnikov de Haas oscillation is
suppressed, the magnetophonon resonances induced by both optical phonons
(mainly due to homopolar and Fr\"ohlich modes) and acoustic phonons (mainly due
to intravalley transverse and longitudinal acoustic modes) emerge for suspended
system with high mobility. For the single layer on a substrate, another
resonance due to surface optical phonons may occur, resulting in a complex
behavior of the total magnetoresistance. The beating pattern of magnetophonon
resonance due to optical phonons can also be observed. However, for
nonsuspended layer with low mobility, the magnetoresistance oscillation almost
disappears and the resistivity increases with field monotonously.

###Breakdown of compensation and persistence of non-saturating magnetoresistance in WTe2 thin flakes|Yilin Wang,Kefeng Wang,Janice Reutt-Robey,Johnpierre Paglione,Michael S. Fuhrer###

Breakdown of compensation and persistence of non-saturating magnetoresistance in WTe2 thin flakes. We present a detailed study of magnetoresistance \r{ho}xx(H), Hall effect
\r{ho}xy(H), and electrolyte gating effect in thin (<100 nm) exfoliated
crystals of WTe2. We observe quantum oscillations in H of both \r{ho}xx(H) and
\r{ho}xy(H), and identify four oscillation frequencies consistent with previous
reports in thick crystals. \r{ho}xy(H) is linear in H at low H consistent with
near-perfect electron-hole compensation, however becomes nonlinear and changes
sign with increasing H, implying a breakdown of compensation. A field-dependent
ratio of carrier concentrations p/n can consistently explain \r{ho}xx(H) and
\r{ho}xy(H) within a two-fluid model. We also employ an electrolytic gate to
highly electron-dope WTe2 with Li. The non-saturating \r{ho}xx(H) persists to H
= 14 T with magnetoresistance ratio exceeding 2 x 104 %, even with significant
deviation from perfect electron-hole compensation (p/n = 0.84), where the
two-fluid model predicts a saturating \r{ho}xx(H). Our results suggest
electron-hole compensation is not the mechanism for extremely large
magnetoresistance in WTe2, other alternative explanations need to be
considered.

###Extraordinary Hall resistance and unconventional magnetoresistance in Pt/LaCoO3 hybrids|T. Shang,Q. F. Zhan,H. L. Yang,Z. H. Zuo,Y. L. Xie,Y. Zhang,L. P. Liu,B. M. Wang,Y. H. Wu,S. Zhang,Run-Wei Li###

Extraordinary Hall resistance and unconventional magnetoresistance in Pt/LaCoO3 hybrids. We report an investigation of transverse Hall resistance and longitudinal
resistance on Pt thin films sputtered on epitaxial LaCoO$_3$ (LCO)
ferromagnetic insulator films. The LaCoO$_3$ films were deposited on several
single crystalline substrates [LaAlO$_3$ (LAO), (La,Sr)(Al,Ta)O$_3$ (LSAT), and
SrTiO$_3$ (STO)] with (001) orientation. The physical properties of LaCoO$_3$
films were characterized by the measurements of magnetic and transport
properties. The LaCoO$_3$ films undergo a paramagnetic to ferromagnetic (FM)
transition at Curie temperatures ranging from 40 K to 85 K, below which the
Pt/LCO hybrids exhibit significant extraordinary Hall resistance (EHR) up to 50
m$\Omega$ and unconventional magnetoresistance (UCMR) ratio
$\Delta$$\rho$/$\rho_0$ about $1.2 \times 10^{-4}$, accompanied by the
conventional magnetoresistance (CMR). The observed spin transport properties
share some common features as well as some unique characteristics when compared
with well-studied Y$_3$Fe$_5$O$_{12}$-based Pt thin films. Our findings call
for new theories since the extraordinary Hall resistance and magnetoresistance
cannot be consistently explained by the existing theories.

###Isothermal anisotropic magnetoresistance in antiferromagnetic metallic IrMn|R. Galceran,I. Fina,J. Cisneros-Fernández,B. Bozzo,C. Frontera,L. López-Mir,H. Deniz,K. -W. Park,B. -G. Park,Ll. Balcells,X. Martí,T. Jungwirth,B. Martínez###

Isothermal anisotropic magnetoresistance in antiferromagnetic metallic IrMn. Antiferromagnetic spintronics is an emerging field; antiferromagnets can
improve the functionalities of ferromagnets with higher response times, and
having the information shielded against external magnetic field. Moreover, a
large list of aniferromagnetic semiconductors and metals with N\'eel
temperatures above room temperature exists. In the present manuscript, we
persevere in the quest for the limits of how large can anisotropic
magnetoresistance be in antiferromagnetic materials with very large spin-orbit
coupling. We selected IrMn as a prime example of first-class moment (Mn) and
spin-orbit (Ir) combination. Isothermal magnetotransport measurements in an
antiferromagnetic-metal(IrMn)/ferromagnetic-insulator thin film bilayer have
been performed. The metal/insulator structure with magnetic coupling between
both layers allows the measurement of the modulation of the transport
properties exclusively in the antiferromagnetic layer. Anisotropic
magnetoresistance as large as 0.15 % has been found, which is much larger than
that for a bare IrMn layer. Interestingly, it has been observed that
anisotropic magnetoresistance is strongly influenced by the field cooling
conditions, signaling the dependence of the found response on the formation of
domains at the magnetic ordering temperature.

###A magnetic skyrmion as a non-linear resistive element - a potential building block for reservoir computing|Diana Prychynenko,Matthias Sitte,Kai Litzius,Benjamin Krüger,George Bourianoff,Mathias Kläui,Jairo Sinova,Karin Everschor-Sitte###

A magnetic skyrmion as a non-linear resistive element - a potential building block for reservoir computing. Inspired by the human brain, there is a strong effort to find alternative
models of information processing capable of imitating the high energy
efficiency of neuromorphic information processing. One possible realization of
cognitive computing are reservoir computing networks. These networks are built
out of non-linear resistive elements which are recursively connected. We
propose that a skyrmion network embedded in frustrated magnetic films may
provide a suitable physical implementation for reservoir computing
applications. The significant key ingredient of such a network is a
two-terminal device with non-linear voltage characteristics originating from
single-layer magnetoresistive effects, like the anisotropic magnetoresistance
or the recently discovered non-collinear magnetoresistance. The most basic
element for a reservoir computing network built from "skyrmion fabrics" is a
single skyrmion embedded in a ferromagnetic ribbon. In order to pave the way
towards reservoir computing systems based on skyrmion fabrics, here we simulate
and analyze i) the current flow through a single magnetic skyrmion due to the
anisotropic magneto-resistive effect and ii) the combined physics of local
pinning and the anisotropic magneto-resistive effect.

###Three-Dimensional Anisotropic Magnetoresistance in the Dirac Node-Line Material ZrSiSe|Haiyang Pan,Bingbing Tong,Jihai Yu,Jue Wang,Dongzhi Fu,Shuai Zhang,Bin Wu,Xiangang Wan,Chi Zhang,Xuefeng Wang,Fengqi Song###

Three-Dimensional Anisotropic Magnetoresistance in the Dirac Node-Line Material ZrSiSe. The family of materials defined as ZrSiX (X = S, Se, Te) has been established
as Dirac node-line semimetals, and subsequent study is urgent to exploit the
promising application of unusual magnetoresistance property. In this work, we
systematically investigated the anisotropic magnetoresistance in the
newly-discovered Dirac node-line material ZrSiSe. By applying a magnetic field
of 3 T by a vector field, the three-dimensional (3D) magnetoresistance (MR)
shows strong anisotropy. The MR ratio of maximum and minimum directions can
reach 7 at 3 T and keeps increasing at the higher magnetic field. The
anisotropic MR forms a butterfly-shaped curve, which indicates the quasi-2D
electronic structures. This is further confirmed by the angular-dependent
Shubnikov-de Haas (SdH) oscillations. The first-principles calculations
establish the quasi-2D tubular-shaped Fermi surface near the X point in the
Brillouin zone. Our findings shed light on the 3D mapping of MR and the
potential applications in magnetic sensors based on ZrSiSe Dirac materials.

###Observation of Dirac surface states in the hexagonal PtBi2, a possible origin of the linear magnetoresistance|S. Thirupathaiah,Y. Kushnirenko,E. Haubold,A. V. Fedorov,E. D. L. Rienks,T. K. Kim,A. N. Yaresko,C. G. F. Blum,S. Aswartham,B. Büchner,S. V. Borisenko###

Observation of Dirac surface states in the hexagonal PtBi2, a possible origin of the linear magnetoresistance. The nonmagnetic compounds showing extremely large magnetoresistance are
attracting a great deal of research interests due to their potential
applications in the field of spintronics. PtBi$_2$ is one of such interesting
compounds showing large linear magnetoresistance (MR) in its both the hexagonal
and pyrite crystal structure. We use angle-resolved photoelectron spectroscopy
(ARPES) and density functional theory (DFT) calculations to understand the
mechanism of liner MR observed in the hexagonal PtBi$_2$. Our results uncover
for the first time linear dispersive surface Dirac states at the
$\bar{\Gamma}$-point, crossing Fermi level with node at a binding energy of
$\approx$ 900 meV, in addition to the previously reported Dirac states at the
$\bar{M}$-point in the same compound. We further notice from our dichroic
measurements that these surface states show an asymmetric spectral intensity
when measured with left and right circularly polarized light, hinting at a
substantial spin polarization of the bands. Following these observations, we
suggest that the linear dispersive Dirac states at the $\bar{\Gamma}$ and
$\bar{M}$-points are likely to play a crucial role for the linear field
dependent magnetoresistance recorded in this compound.

###Separation of Electron and Hole Dynamics in the Semimetal LaSb|F. Han,J. Xu,A. S. Botana,Z. L. Xiao,Y. L. Wang,W. G. Yang,D. Y. Chung,M. G. Kanatzidis,M. R. Norman,G. W. Crabtree,W. K. Kwok###

Separation of Electron and Hole Dynamics in the Semimetal LaSb. We report investigations on the magnetotransport in LaSb, which exhibits
extremely large magnetoresistance (XMR). Foremost, we demonstrate that the
resistivity plateau can be explained without invoking topological protection.
We then determine the Fermi surface from Shubnikov - de Haas (SdH) quantum
oscillation measurements and find good agreement with the bulk Fermi pockets
derived from first principle calculations. Using a semiclassical theory and the
experimentally determined Fermi pocket anisotropies, we quantitatively describe
the orbital magnetoresistance, including its angle dependence. We show that the
origin of XMR in LaSb lies in its high mobility with diminishing Hall effect,
where the high mobility leads to a strong magnetic field dependence of the
longitudinal magnetoconductance. Unlike a one-band material, when a system has
two or more bands (Fermi pockets) with electron and hole carriers, the added
conductance arising from the Hall effect is reduced, hence revealing the latent
XMR enabled by the longitudinal magnetoconductance. With diminishing Hall
effect, the magnetoresistivity is simply the inverse of the longitudinal
magnetoconductivity, enabling the differentiation of the electron and hole
contributions to the XMR, which varies with the strength and orientation of the
magnetic field. This work demonstrates a convenient way to separate the
dynamics of the charge carriers and to uncover the origin of XMR in multi-band
materials with anisotropic Fermi surfaces. Our approach can be readily applied
to other XMR materials.

###Signatures of the Kondo effect in VSe2|Sourabh Barua,M. Ciomaga Hatnean,M. R. Lees,G. Balakrishnan###

Signatures of the Kondo effect in VSe2. VSe2 is a transition metal dichaclogenide which has a charge-density wave
transition that has been well studied. We report on a low-temperature upturn in
the resistivity and, at temperatures below this resistivity minimum, an unusual
magnetoresistance which is negative at low fields and positive at higher
fields, in single crystals of VSe2. The negative magnetoresistance has a
parabolic dependence on the magnetic field and shows little angular dependence.
The magnetoresistance at temperatures above the resistivity minimum is always
positive. We interpret these results as signatures of the Kondo effect in VSe2.
An upturn in the susceptibility indicates the presence of interlayer V ions
which can provide the localized magnetic moments required for scattering the
conduction electrons in the Kondo effect. The low-temperature behaviour of the
heat capacity, including a high value of gamma, along with a deviation from a
Curie-Weiss law observed in the low-temperature magnetic susceptibility, are
consistent with the presence of magnetic interactions between the paramagnetic
interlayer V ions and a Kondo screening of these V moments.

###Tunneling magnetoresistance of perpendicular CoFeB-based junctions with exchange bias|Orestis Manos,Alexander Böhnke,Panagiota Bougiatioti,Robin Klett,Karsten Rott,Alessia Niesen,Jan-Michael Schmalhorst,Günter Reiss###

Tunneling magnetoresistance of perpendicular CoFeB-based junctions with exchange bias. Recently, magnetic tunnel junctions with perpendicular magnetized electrodes
combined with exchange bias films have attracted large interest. In this paper
we examine the tunnel magnetoresistance of
Ta/Pd/IrMn/Co-Fe/Ta/Co-Fe-B/MgO/Co-Fe-B/capping/Pd magnetic tunnel junctions in
dependence on the capping layer, i.e., Hf or Ta. In these stacks perpendicular
exchange bias fields of -500\,Oe along with perpendicular magnetic anisotropy
are combined. A tunnel magnetoresistance of $(47.2\pm 1.4)\%$ for the Hf-capped
sample was determined compared to the Ta one $(42.6\pm 0.7)\%$ at room
temperature. Interestingly, this observation is correlated to the higher boron
absorption of Hf compared to Ta which prevents the suppression of
$\Delta_{\textrm{1}}$ channel and leads to higher tunnel magnetoresistance
values. Furthermore, the temperature dependent coercivities of the soft
electrodes of both samples are mainly described by the Stoner-Wohlfarth model
including thermal fluctuations. Slight deviations at low temperatures can be
attributed to a torque on the soft electrode that is generated by the pinned
magnetic layer system.

###Correlation of tunnel magnetoresistance with the magnetic properties in perpendicular CoFeB-based junctions with exchange bias|Orestis Manos,Panagiota Bougiatioti,Denis Dyck,Torsten Huebner,Karsten Rott,Jan-Michael Schmalhorst,Günter Reiss###

Correlation of tunnel magnetoresistance with the magnetic properties in perpendicular CoFeB-based junctions with exchange bias. We investigate the dependence of magnetic properties on the post-annealing
temperature/time, the thickness of soft ferromagnetic electrode and Ta dusting
layer in the pinned electrode as well as their correlation with the tunnel
magnetoresistance ratio, in a series of perpendicular magnetic tunnel junctions
of materials sequence
Ta/Pd/IrMn/CoFe/Ta$(\textit{x})$/CoFeB/MgO$(\textit{y})$/CoFeB$(\textit{z})$/Ta/Pd.
We obtain a large perpendicular exchange bias of 79.6$\,$kA/m for $x=0.3\,$nm.
For stacks with $z=1.05\,$nm, the magnetic properties of the soft electrode
resemble the characteristics of superparamagnetism. For stacks with
$x=0.4\,$nm, $y=2\,$nm, and $z=1.20\,$nm, the exchange bias presents a
significant decrease at post annealing temperature
$T_\textrm{ann}=330\,^{\circ}$C for 60 min, while the interlayer exchange
coupling and the saturation magnetization per unit area sharply decay at
$T_\textrm{ann}=340\,^{\circ}$C for 60 min. Simultaneously, the tunnel
magnetoresistance ratio shows a peak of $65.5\%$ after being annealed at
$T_\textrm{ann}=300\,^{\circ}$C for 60 min, with a significant reduction down
to $10\%$ for higher annealing temperatures
($T_\textrm{ann}\geq330\,^{\circ}$C) and down to $14\%$ for longer annealing
times ($T_\textrm{ann}=300\,^{\circ}$C for 90 min). We attribute the large
decrease of tunnel magnetoresistance ratio to the loss of exchange bias in the
pinned electrode.

###One-dimensional ferromagnetic edge contacts to two-dimensional graphene/h-BN heterostructures|Bogdan Karpiak,André Dankert,Aron W. Cummings,Stephen R. Power,Stephan Roche,Saroj P. Dash###

One-dimensional ferromagnetic edge contacts to two-dimensional graphene/h-BN heterostructures. We report the fabrication of one-dimensional (1D) ferromagnetic edge contacts
to two-dimensional (2D) graphene/h-BN heterostructures. While aiming to study
spin injection/detection with 1D edge contacts, a spurious magnetoresistance
signal was observed, which is found to originate from the local Hall effect in
graphene due to fringe fields from ferromagnetic edge contacts and in the
presence of charge current spreading in the nonlocal measurement configuration.
Such behavior has been confirmed by the absence of a Hanle signal and
gate-dependent magnetoresistance measurements that reveal a change in sign of
the signal for the electron- and hole-doped regimes, which is in contrast to
the expected behavior of the spin signal. Calculations show that the
contact-induced fringe fields are typically on the order of hundreds of mT, but
can be reduced below 100 mT with careful optimization of the contact geometry.
There may be additional contribution from magnetoresistance effects due to
tunneling anisotropy in the contacts, which need to be further investigated.
These studies are useful for optimization of spin injection and detection in 2D
material heterostructures through 1D edge contacts.

###Quantitative study of the spin Hall magnetoresistance in ferromagnetic insulator/normal metal hybrids|Matthias Althammer,Sibylle Meyer,Hiroyasu Nakayama,Michael Schreier,Stephan Altmannshofer,Mathias Weiler,Hans Huebl,Stephan Geprägs,Matthias Opel,Rudolf Gross,Daniel Meier,Christoph Klewe,Timo Kuschel,Jan-Michael Schmalhorst,Günter Reiss,Liming Shen,Arunava Gupta,Yan-Ting Chen,Gerrit E. W. Bauer,Eiji Saitoh,Sebastian T. B. Goennenwein###

Quantitative study of the spin Hall magnetoresistance in ferromagnetic insulator/normal metal hybrids. We experimentally investigate and quantitatively analyze the spin Hall
magnetoresistance effect in ferromagnetic insulator/platinum and ferromagnetic
insulator/nonferromagnetic metal/platinum hybrid structures. For the
ferromagnetic insulator we use either yttrium iron garnet, nickel ferrite or
magnetite and for the nonferromagnet copper or gold. The spin Hall
magnetoresistance effect is theoretically ascribed to the combined action of
spin Hall and inverse spin Hall effect in the platinum metal top layer. It
therefore should characteristically depend upon the orientation of the
magnetization in the adjacent ferromagnet, and prevail even if an additional,
nonferromagnetic metal layer is inserted between Pt and the ferromagnet. Our
experimental data corroborate these theoretical conjectures. Using the spin
Hall magnetoresistance theory to analyze our data, we extract the spin Hall
angle and the spin diffusion length in platinum. For a spin mixing conductance
of $4\times10^{14}\;\mathrm{\Omega^{-1}m^{-2}}$ we obtain a spin Hall angle of
$0.11\pm0.08$ and a spin diffusion length of $(1.5\pm0.5)\;\mathrm{nm}$ for Pt
in our thin film samples.

###Supramolecular Spin Valves|Matias Urdampilleta,Svetlana Klyatskaya,Jean-Pierre Cleuziou,Mario Ruben,Wolfgang Wernsdorfer###

Supramolecular Spin Valves. Magnetic molecules possess a high potential as building blocks for the design
of spintronic devices. Moreover, the use of molecular materials opens the way
for the controlled use of bottom-up, e.g. supramolecular, processing techniques
combining massively parallel self-fabrication with conventional top-down
nanostructuring techniques. The development of solid state spintronic devices
based on the giant magnetoresistance (GMR), tunnel magnetoresistance (TMR), and
spin valve effects has revolutionized the field of magnetic memory
applications. Recently, organic semiconductors were inserted into nanometer
sized tunnel junctions allowing enhancement of spin reversal, giant
magneto-resistance behaviour was observed in single non-magnetic molecules
coupled to magnetic electrodes, and the use of the quantum tunnelling
properties of single-molecule magnets (SMMs) in hybrid devices was proposed.
Herein, we present an original device in which a non-magnetic molecular quantum
dot, made of a single-wall carbon nanotube (SWCNT) contacted with non-magnetic
electrodes, is laterally coupled via supramolecular interactions to a TbPc2-SMM
(Pc = phthalocyanine), which provides a localized magnetic moment. The
conductance through the SWCNT is modulated by sweeping the magnetic field,
exhibiting magnetoresistance ratios up to 300% between fully polarized and
non-polarized SMMs below 1 K. We thus demonstrate the functionality of a
supramolecular spin valve without magnetic leads. Our results open up prospects
of circuit-integration and implementation of new device capabilities.

###Interlayer magnetoresistance in multilayer Dirac electron systems: motion and merging of Dirac cones|Mohamed Assili,Sonia Haddad###

Interlayer magnetoresistance in multilayer Dirac electron systems: motion and merging of Dirac cones. We theoretically study the effect of the motion and the merging of Dirac cone
on the interlayer magnetoresistance in multilayer graphene like systems. This
merging, which could be induced by a uniaxial strain, gives rise in monolayer
Dirac electron system to a topological transition from a semi-metallic phase to
an insulating phase where Dirac points disappear. Based on a universal
Hamiltonian proposed to describe the motion and the merging of Dirac points in
two dimensional Dirac electron crystals, we calculate the interlayer
conductivity of a stack of deformed graphene like layers using Kubo formula in
the quantum limit where only the contribution of the $n=0$ Landau level is
relevant. A crossover from a negative to a positive interlayer
magnetoresistance is found to take place as the merging is approached. This
sign change of the magnetoresistance could also result from a coupling between
the Dirac valleys which is enhanced as the magnetic field amplitude increases.
Our results may describe the behavior of the magnetotransport in the organic
conductor $\alpha$-(BEDT)$_2$I$_3$ at high pressure where the merging of Dirac
cones could be observed.

###Cluster Altered Magnetic and Transport Properties in Eu Co-Doped Ge(1-x)Mn(x)Te|L. Kilanski,M. Górska,R. Szymczak,W. Dobrowolski,A. Podgórni,A. Avdonin,V. Domukhovski,V. E. Slynko,E. I. Slynko###

Cluster Altered Magnetic and Transport Properties in Eu Co-Doped Ge(1-x)Mn(x)Te. Magnetic and transport properties of Ge(1-x-y)Mn(x)Eu(y)Te crystals with
chemical compositions 0.041 < x < 0.092 and 0.010 < y < 0.043 are studied.
Ferromagnetic order is observed at 150 < T < 160 K. Aggregation of magnetic
ions into clusters is found to be the source of almost constant, composition
independent Curie temperatures in our samples. Magnetotransport studies show
the presence of both negative (at T < 25 K) and linear positive (for 25<T <200
K) magnetoresistance effects (with amplitudes not exceeding 2%) in the studied
alloy. Negative magnetoresistance detected at T < 25 K is found to be due to a
tunneling of spin-polarized electrons between ferromagnetic clusters. A linear
positive magnetoresistance is identified to be geometrical effect related with
the presence of ferromagnetic clusters inside semiconductor matrix. The product
of the polarization constant and the inter-grain exchange constant, J_P, varies
between about 0.13 meV and 0.99 meV. Strong anomalous Hall effect (AHE) is
observed for T < T_C with coefficients R_S independent of temperature. The
scaling analysis of the AHE leads to a conclusion that this effect is due to a
skew scattering mechanism.

###Anomalous electronic structure and magnetoresistance in TaAs$_2$|Yongkang Luo,R. D. McDonald,P. F. S. Rosa,B. Scott,N. Wakeham,N. J. Ghimire,E. D. Bauer,J. D. Thompson,F. Ronning###

Anomalous electronic structure and magnetoresistance in TaAs$_2$. The resistance of a metal in a magnetic field can be very illuminating about
its ground state. Some famous examples include the integer and fractional
quantum Hall effects\cite{Klitzing-QHE,Tsui-FQHE}, Shubnikov-de Haas
oscillations\cite{SdH}, and weak localization\cite{Lee-WL} \emph{et al}. In
non-interacting metals the resistance typically increases upon the application
of a magnetic field\cite{Pippard-MR}. In contrast, in some special
circumstances metals, with anisotropic Fermi surfaces\cite{Kikugawa-PdCoO2LMR}
or a so-called Weyl semimetal for instance\cite{Nielsen-ABJ,Son-ChirAnom}, may
have negative magnetoresistance. Here we show that semimetallic TaAs$_2$
possesses a gigantic negative magnetoresistance ($-$98\% in a field of 3 T at
low temperatures), with an unknown mechanism. Density functional calculations
illustrate that TaAs$_2$ is a new topological semimetal [$\mathbb{Z}_2$
invariant (0;111)] without a Dirac dispersion. This demonstrates that the
presence of negative magnetoresistance in non-magnetic semimetals cannot be
uniquely attributed to the Adler-Bell-Jackiw anomaly of bulk Dirac/Weyl
fermions. Our results also imply that the OsGe$_2$-type monoclinic dipnictides
are likely a material basis where unconventional topological semimetals may be
found.

###Second order anisotropy contribution in perpendicular magnetic tunnel junctions|A. A. Timopheev,R. Sousa,M. Chshiev,T. Nguyen,B. Dieny###

Second order anisotropy contribution in perpendicular magnetic tunnel junctions. Magnetoresistance loops under in-plane applied field were measured on
perpendicularly magnetized magnetic tunnel junction (pMTJ) pillars with nominal
diameters ranging from 50 to 150 nm. By fitting the hard-axis magnetoresistance
loops to an analytical model, the effective anisotropy fields in both free and
reference layers were derived and their variations in temperature range between
340K and 5K were determined. It is found that an accurate fitting is possible
only if a second-order anisotropy term of the form $-K_{2}cos^4{\theta}$, is
added to the fitting model. This higher order contribution exists both in the
free and reference layers and its sign is opposite to that of the first order
anisotropy constant, $K_{1}$. At room temperatures the estimated $-K_{2}/K_{1}$
ratios are 0.1 and 0.24 for the free and reference layers, respectively. The
ratio is more than doubled at low temperatures altering the ground state of the
reference layer from 'easy-axis' to 'easy-cone' regime. Easy-cone state has
clear signatures in the shape of the hard-axis magnetoresistance loops. The
same behavior was observed in all measured devices regardless of their
diameter. The existence of this higher order anisotropy was confirmed
experimentally on FeCoB/MgO sheet films by ferromagnetic resonance technique.
It is of interfacial nature and is believed to be linked to spatial
fluctuations at the nanoscale of the anisotropy parameter at the FeCoB/MgO
interface, in agreement with Dieny-Vedyayev model.

###Universal behavior of magnetoresistance in quantum dot arrays with different degree of disorder|N. P. Stepina,E. S. Koptev,A. G. Pogosov,A. V. Dvurechenskii,A. I. Nikiforov,E. Yu. Zhdanov,Y. M. Galperin###

Universal behavior of magnetoresistance in quantum dot arrays with different degree of disorder. Magnetoresistance in two-dimensional array of Ge/Si quantum dots was studied
in a wide range of zero-magnetic field conductances, where the transport regime
changes from hopping to diffusive one. The behavior of magnetoresistance is
found to be similar for all samples - it is negative in weak fields and becomes
positive with increase of magnetic field. The result apparently contradicts to
existing theories. To explain experimental data we suggest that clusters of
overlapping quantum dots are formed. These clusters are assumed to have
metal-like conductance, the charge transfer taking place via hopping between
the clusters. Relatively strong magnetic field shrinks electron wave functions
decreasing inter-cluster hopping and, therefore, leading to a positive
magnetoresistance. Weak magnetic field acts on "metallic" clusters destroying
interference of electron wave function corresponding to different paths (weak
localization) inside clusters. The interference may be restricted either by
inelastic processes, or by the cluster size. Taking into account WL inside
clusters and hopping between them within the effective medium approximation we
extract effective parameters characterizing charge (magneto) transport.

###Spin-dependent conductivity of iron-based superconductors in a magnetic field|M. O. Dzyuba,Yu. N. Chiang,D. A. Chareev,A. N. Vasiliev###

Spin-dependent conductivity of iron-based superconductors in a magnetic field. We report the results of a study of magnetic field features of electron
transport in heterojunctions with NS boundary inside iron-based
superconductors, represented by a binary phase of $\alpha$ - FeSe and
oxyarsenide pnictide LaO(F)FeAs. We used the ability of self magnetic field of
the transport current to partially destroy superconductivity, no matter how low
the field may be, in the NS interface area, where, due to the proximity effect,
the superconducting order parameter, $\Delta$, disperses from 1 to 0 within the
scale of the Ginzburg-Landau coherence length. The following features of
transport were found:(i) at $T<T_{c}$, magnetoresistance in systems with
different superconductors has different sign;(ii) sign and magnitude of the
magnetoresistance depend on the magnitude of current and temperature, and (iii)
in all operating modes where the contribution from Andreev reflection is
suppressed ($(T + eV) \gtrsim \Delta$),the hysteresis of the magnetoresistance
is present. Based on the results of the experiment and analysis it has been
concluded that there is along-range magnetic order in th eground normal state
of the iron-based superconductors studied, in the presence of itinerant
magnetism of conduction electrons which determines the possibility of
anisotropic spin-dependent exchange interaction with the local magnetic moments
of the ions.

###Spin Hall magnetoresistance as a probe for surface magnetization in Pt/CoFe$_2$O$_4$ bilayers|Miren Isasa,Saül Vélez,Edurne Sagasta,Amilcar Bedoya-Pinto,Nico Dix,Florencio Sánchez,Luis E. Hueso,Josep Fontcuberta,Fèlix Casanova###

Spin Hall magnetoresistance as a probe for surface magnetization in Pt/CoFe$_2$O$_4$ bilayers. We study the spin Hall magnetoresistance (SMR) in Pt grown $\textit{in situ}$
on CoFe$_2$O$_4$ (CFO) ferrimagnetic insulating (FMI) films. A careful analysis
of the angle-dependent and field-dependent longitudinal magnetoresistance
indicates that the SMR contains a contribution that does not follow the bulk
magnetization of CFO but it is a fingerprint of the complex magnetism at the
surface of the CFO layer, thus signaling SMR as a tool for mapping surface
magnetization. A systematic study of the SMR for different temperatures and CFO
thicknesses gives us information impossible to obtain with any standard
magnetometry technique. On one hand, surface magnetization behaves
independently of the CFO thickness and does not saturate up to high fields,
evidencing that the surface has its own anisotropy. On the other hand,
characteristic zero-field magnetization steps are not present at the surface
while they are relevant in the bulk, strongly suggesting that antiphase
boundaries are the responsible of such intriguing features. In addition, a
contribution from ordinary magnetoresistance of Pt is identified, which is only
distinguishable due to the low resistivity of the $\textit{in-situ}$ grown Pt.

###Suppression of magnetoresistance in thin $WTe_2$ flakes by surface oxidation|J. M. Woods,J. Shen,P. Kumaravadivel,Y. Pang,Y. Xie,G. A. Pan,M. Li,E. I. Altman,L. Lu,J. J. Cha###

Suppression of magnetoresistance in thin $WTe_2$ flakes by surface oxidation. Recent renewed interest in layered transition metal dichalcogenides stems
from the exotic electronic phases predicted and observed in the single- and
few-layer limit. Realizing these electronic phases requires preserving the
desired transport properties down to a monolayer, which is challenging. Here,
using semimetallic $WTe_2$ that exhibits large magnetoresistance, we show that
surface oxidation and Fermi level pinning degrade the transport properties of
thin $WTe_2$ flakes significantly. With decreasing $WTe_2$ flake thickness, we
observe a dramatic suppression of the large magnetoresistance. This is
explained by fitting a two-band model to the transport data, which shows that
mobility of the electron and hole carriers decreases significantly for thin
flakes. The microscopic origin of this mobility decrease is attributed to a ~ 2
nm-thick amorphous surface oxide layer that introduces disorder. The oxide
layer also shifts the Fermi level by ~ 300 meV at the $WTe_2$ surface. However,
band bending due to this Fermi level shift is not the dominant cause for the
suppression of magnetoresistance as the electron and hole carrier densities are
balanced down to ~ 13 nm based on the two-band model. Our study highlights the
critical need to investigate often unanticipated and sometimes unavoidable
extrinsic surface effects on the transport properties of layered
dichalcogenides and other 2D materials.

###Weak antilocalization effect due to topological surface states in Bi$_2$Se$_{2.1}$Te$_{0.9}$|K. Shrestha,D. Graf,V. Marinova,B. Lorenz,C. W. Chu###

Weak antilocalization effect due to topological surface states in Bi$_2$Se$_{2.1}$Te$_{0.9}$. We have investigated the weak antilocalization (WAL) effect in the p-type
Bi$_2$Se$_{2.1}$Te$_{0.9}$ topological system. The magnetoconductance shows a
cusp-like feature at low magnetic fields, indicating the presence of the WAL
effect. The WAL curves measured at different tilt angles merge together when
they are plotted as a function of the normal field components, showing that
surface states dominate the magnetoconductance in the
Bi$_2$Se$_{2.1}$Te$_{0.9}$ crystal. We have calculated magnetoconductance per
conduction channel and applied the Hikami-Larkin-Nagaoka formula to determine
the physical parameters that characterize the WAL effect. The number of
conduction channels and the phase coherence length do not change with
temperature up to T=5 K. In addition, the sample shows a large positive
magnetoresistance that reaches 1900% under a magnetic field of 35 T at T=0.33K
with no sign of saturation. The magnetoresistance value decreases with both
increasing temperature and tilt angle of the sample surface with respect to the
magnetic field. The large magnetoresistance of topological insulators can be
utilized in future technology such as sensors and memory devices.

###Magnetoresistance in the superconducting state at the (111) LaAlO$_3$/SrTiO$_3$ interface|S. Davis,Z. Huang,K. Han,Ariando,T. Venkatesan,V. Chandrasekhar###

Magnetoresistance in the superconducting state at the (111) LaAlO$_3$/SrTiO$_3$ interface. Condensed matter systems that simultaneously exhibit superconductivity and
ferromagnetism are rare due the antagonistic relationship between conventional
spin-singlet superconductivity and ferromagnetic order. In materials in which
superconductivity and magnetic order is known to coexist (such as some
heavy-fermion materials), the superconductivity is thought to be of an
unconventional nature. Recently, the conducting gas that lives at the interface
between the perovskite band insulators LaAlO$_3$ (LAO) and SrTiO$_3$ (STO) has
also been shown to host both superconductivity and magnetism. Most previous
research has focused on LAO/STO samples in which the interface is in the (001)
crystal plane. Relatively little work has focused on the (111) crystal
orientation, which has hexagonal symmetry at the interface, and has been
predicted to have potentially interesting topological properties, including
unconventional superconducting pairing states. Here we report measurements of
the magnetoresistance of (111) LAO/STO heterostructures at temperatures at
which they are also superconducting. As with the (001) structures, the
magnetoresistance is hysteretic, indicating the coexistence of magnetism and
superconductivity, but in addition, we find that this magnetoresistance is
anisotropic. Such an anisotropic response is completely unexpected in the
superconducting state, and suggests that (111) LAO/STO heterostructures may
support unconventional superconductivity.

###Anomalous spin Hall magnetoresistance in Pt/Co bilayers|Masashi Kawaguchi,Daiki Towa,Yong-Chang Lau,Saburo Takahashi,Masamitsu Hayashi###

Anomalous spin Hall magnetoresistance in Pt/Co bilayers. We have studied the spin Hall magnetoresistance (SMR), the magnetoresistance
within the plane transverse to the current flow, of Pt/Co bilayers. We find
that the SMR increases with increasing Co thickness: the effective spin Hall
angle for bilayers with thick Co exceeds the reported values of Pt when a
conventional drift-diffusion model is used. An extended model including spin
transport within the Co layer cannot account for the large SMR. To identify its
origin, contributions from other sources are studied. For most bilayers, the
SMR increases with decreasing temperature and increasing magnetic field,
indicating that magnon-related effects in the Co layer play little role.
Without the Pt layer, we do not observe the large SMR found for the Pt/Co
bilayers with thick Co. Implementing the effect of the so-called interface
magnetoresistance and the textured induced anisotropic scattering cannot
account for the Co thickness dependent SMR. Since the large SMR is present for
W/Co but its magnitude reduces in W/CoFeB, we infer its origin is associated
with a particular property of Co.

###Quasiclassical theory of the spin-orbit magnetoresistance of three-dimensional Rashba metals|Sebastian Tölle,Michael Dzierzawa,Ulrich Eckern,Cosimo Gorini###

Quasiclassical theory of the spin-orbit magnetoresistance of three-dimensional Rashba metals. The magnetoresistance of a three-dimensional Rashba material placed on top of
a ferromagnetic insulator is theoretically investigated. In addition to the
intrinsic Rashba spin-orbit interaction, we also consider extrinsic spin-orbit
coupling via side-jump and skew scattering, and the Elliott-Yafet spin
relaxation mechanism. The latter is anisotropic due to the mass anisotropy
which reflects the noncentrosymmetric crystal structure of three-dimensional
Rashba metals. A quasiclassical approach is employed to derive a set of coupled
spin-diffusion equations, which are supplemented by boundary conditions that
account for the spin-transfer torque at the interface of the bilayer. The
magnetoresistance is fully determined by the current-induced spin polarization,
i.e., it cannot in general be ascribed to a single (bulk) spin Hall angle. Our
theoretical results reproduce several features of the experiments, at least
qualitatively, and contain established phenomenological results in the relevant
limiting cases. In particular, the anisotropy of the Elliott-Yafet spin
relaxation mechanism plays a major role for the interpretation of the observed
magnetoresistance.

###Ballistic transport experiment detects Fermi surface anisotropy of graphene|Takushi Oka,Shingo Tajima,Ryoya Ebisuoka,Taiki Hirahara,Kenji Watanabe,Takashi Taniguchi,Ryuta Yagi###

Ballistic transport experiment detects Fermi surface anisotropy of graphene. Monolayer graphene and bilayer graphene have strikingly different properties.
One such difference is the shape of the Fermi surface. Although anisotropic
band structures can be detected in optical measurements, they have so far been
difficult to detect in transport experiments on twodimensional materials. Here
we describe a ballistic transport experiment using high-quality graphene that
revealed Fermi surface anisotropy in the magnetoresistance. The shape of the
Fermi surface is closely related with the cyclotron orbit in real space.
Electron trajectories in samples with triangular lattices of holes depend on
the anisotropy of the Fermi surface. We found that this results in the
magnetoresistance which are dependent on crystallographic orientation of the
antidot lattice, which indicates the anisotropic Fermi surface of bilayer
graphene which is a trigonally-warped circle in shape. While in monolayer,
shape of magnetoresistance was approximately independent of the orientation of
antidot lattice, which indicates that the Fermi surface is a circle in shape.
The ballistic transport experiment is a new method of detecting anisotropic
electronic band structures in two-dimensional electron systems.

###Shubnikov-de Haas oscillations, weak antilocalization effect and large linear magnetoresistance in the putative topological superconductor LuPdBi|Orest Pavlosiuk,Dariusz Kaczorowski,Piotr Wiśniewski###

Shubnikov-de Haas oscillations, weak antilocalization effect and large linear magnetoresistance in the putative topological superconductor LuPdBi. We present electronic transport and magnetic properties of single crystals of
semimetallic half-Heusler phase LuPdBi, having theoretically predicted band
inversion requisite for nontrivial topological properties. The compound
exhibits superconductivity below a critical temperature $T_{\rm c}=1.8\,$K,
with a zero-temperature upper critical field $B_{\rm c2}\approx2.3\,$T.
Although superconducting state is clearly reflected in the electrical
resistivity and magnetic susceptibility data, no corresponding anomaly can be
seen in the specific heat. Temperature dependence of the electrical resistivity
suggests existence of two parallel conduction channels: metallic and
semiconducting, with the latter making negligible contribution at low
temperatures. The magnetoresistance is huge and clearly shows a weak
antilocalization effect in small magnetic fields. Above about 1.5 T, the
magnetoresistance becomes linear and does not saturate in fields up to 9 T. The
linear magnetoresistance is observed up to room temperature. Below 10 K, it is
accompanied by Shubnikov-de Haas oscillations. Their analysis reveals charge
carriers with effective mass of $0.06\,m_e$ and a Berry phase very close to
$\pi$, expected for Dirac-fermion surface states, thus corroborating
topological nature of the material.

###Topological phase transition induced extreme magnetoresistance in TaSb$_{2}$|Zheng Wang,Yupeng Li,Yunhao Lu,Zhixuan Shen,Feng Sheng,Chunmu Feng,Yi Zheng,Zhuan Xu###

Topological phase transition induced extreme magnetoresistance in TaSb$_{2}$. We report extremely large positive magnetoresistance of 1.72 million percent
in single crystal TaSb$_{2}$ at moderate conditions of 1.5 K and 15 T. The
quadratic growth of magnetoresistance (MR $\propto\,B^{1.96}$) is not
saturating up to 15 T, a manifestation of nearly perfect compensation with
$<0.1\%$ mismatch between electron and hole pockets in this semimetal. The
compensation mechanism is confirmed by temperature-dependent MR, Hall and
thermoelectric coefficients of Nernst and Seebeck, revealing two pronounced
Fermi surface reconstruction processes without spontaneous symmetry breaking,
\textit{i.e.} Lifshitz transitions, at around 20 K and 60 K, respectively.
Using quantum oscillations of magnetoresistance and magnetic susceptibility,
supported by density-functional theory calculations, we determined that the
main hole Fermi surface of TaSb$_{2}$ forms a unique shoulder structure along
the $F-L$ line. The flat band top of this shoulder pocket is just a few meV
above the Fermi level, leading to the observed topological phase transition at
20 K when the shoulder pocket disappears. Further increase in temperature
pushes the Fermi level to the band top of the main hole pocket, induced the
second Lifshitz transition at 60 K when hole pocket vanishes completely.

###Negative magnetoresistivity in holography|Ya-Wen Sun,Qing Yang###

Negative magnetoresistivity in holography. Negative magnetoresistivity is a special magnetotransport property associated
with chiral anomaly in four dimensional chiral anomalous systems, which refers
to the transport behavior that the DC longitudinal magnetoresistivity decreases
with increasing magnetic field. We calculate the longitudinal
magnetoconductivity in the presence of backreactions of the magnetic field to
gravity in holographic zero charge and axial charge density systems with and
without axial charge dissipation. In the absence of axial charge dissipation,
we find that the quantum critical conductivity grows with increasing magnetic
field when the backreaction strength is larger than a critical value, in
contrast to the monotonically decreasing behavior of quantum critical
conductivity in the probe limit. With axial charge dissipation, we find the
negative magnetoresistivity behavior. The DC longitudinal magnetoconductivity
scales as $B$ in the large magnetic field limit, which deviates from the exact
$B^2$ scaling of the probe limit result. In both cases, the small frequency
longitudinal magnetoconductivity still agrees with the formula obtained from
the hydrodynamic linear response theory, even in the large magnetic field
limit.

###Investigation of anomalous-Hall and spin-Hall effects of antiferromagnetic IrMn sandwiched by Pt and YIG layers|T. Shang,H. L. Yang,Q. F. Zhan,Z. H. Zuo,Y. L. Xie,L. P. Liu,S. L. Zhang,Y. Zhang,H. H. Li,B. M. Wang,Y. H. Wu,S. Zhang,Run-Wei Li###

Investigation of anomalous-Hall and spin-Hall effects of antiferromagnetic IrMn sandwiched by Pt and YIG layers. We report an investigation of temperature and IrMn layered thickness
dependence of anomalous-Hall resistance (AHR), anisotropic magnetoresistance
(AMR), and magnetization on Pt/Ir20Mn80/Y3Fe5O12 (Pt/IrMn/YIG)
heterostructures. The magnitude of AHR is dramatically enhanced compared with
Pt/YIG bilayers. The enhancement is much more profound at higher temperatures
and peaks at the IrMn thickness of 3 nm. The observed spin-Hall
magnetoresistance (SMR) in the temperature range of 10-300 K indicates that the
spin current generated in the Pt layer can penetrate the entire thickness of
the IrMn layer to interact with the YIG layer. The lack of conventional
anisotropic magnetoresistance (CAMR) implies that the insertion of the IrMn
layer between Pt and YIG efficiently suppresses the magnetic proximity effect
(MPE) on induced Pt moments by YIG. Our results suggest that the dual roles of
the InMn insertion in Pt/IrMn/YIG heterostructures are to block the MPE and to
transport the spin current between Pt and YIG layers. We discuss possible
mechanisms for the enhanced AHR.

###Transport evidence for the three-dimensional Dirac semimetal phase in ZrTe5|Guolin Zheng,Jianwei Lu,Xiangde Zhu,Wei Ning,Yuyan Han,Hongwei Zhang,Jinglei Zhang,Chuanying Xi,Jiyong Yang,Haifeng Du,Kun Yang,Yuheng Zhang,Mingliang Tian###

Transport evidence for the three-dimensional Dirac semimetal phase in ZrTe5. Topological Dirac semimetal is a newly discovered class of materials and has
attracted intense attentions. This material can be viewed as a
three-dimensional (3D) analogue of graphene and has linear energy dispersion in
bulk, leading to a range of exotic transport properties. Here we report direct
quantum transport evidence of 3D Dirac semimetal phase of layered material
ZrTe5 by angular dependent magnetoresistance measurements under high magnetic
fields up to 31 Tesla. We observed very clear negative longitudinal
magnetoresistance induced by chiral anomaly under the condition of the magnetic
field aligned only along the current direction. Pronounced Shubnikov-de Hass
(SdH) quantum oscillations in both longitudinal magnetoresistance and
transverse Hall resistance were observed, revealing anisotropic light cyclotron
masses and high mobility of the system. In particular, a nontrivial {\pi}-Berry
phase in the SdH gives clear evidence for 3D Dirac semimetal phase.
Furthermore, we observed clear Landau Level splitting under high magnetic
field, suggesting possible splitting of Dirac point into Weyl points due to
broken time reversal symmetry. Our results indicate that ZrTe5 is an ideal
platform to study 3D massless Dirac and Weyl fermions in a layered compound.

###Electron trajectories and magnetotransport in nanopatterned graphene under commensurability conditions|Stephen R. Power,Morten Rishøj Thomsen,Antti-Pekka Jauho,Thomas Garm Pedersen###

Electron trajectories and magnetotransport in nanopatterned graphene under commensurability conditions. Commensurability oscillations in the magnetotransport of periodically
patterned systems, emerging from the interplay of cyclotron orbit and the
pattern periodicity, are a benchmark of mesoscopic physics in electron gas
systems. Exploiting similar effects in 2D materials would allow exceptional
control of electron behaviour, but is hindered by the requirement to maintain
ballistic transport over large length scales. Recent experiments have overcome
this obstacle and observed distinct magnetoresistance commensurability peaks
for perforated graphene sheets (antidot lattices). Interpreting the exact
mechanisms behind these peaks is of key importance, particularly in graphene
where a range of regimes are accessible by varying the electron density. In
this work a fully atomistic, device-based simulation of magnetoresistance
experiments allows us to analyse both the resistance peaks and the current flow
at commensurability conditions. Magnetoresistance spectra are found in
excellent agreement with experiment, but we show that a semi-classical
analysis, in terms of simple skipping or pinned orbits, is insufficient to
fully describe the corresponding electron trajectories. Instead, a generalised
mechanism in terms of states bound to individual antidots, or to groups of
antidots, is required. Commensurability features are shown to arise when
scattering between such states is enhanced. The emergence and suppression of
commensurability peaks is explored for different antidot sizes, magnetic field
strengths and electron densities. The insights gained from our study will guide
the design and optimization of future experiments with nanostructured graphene.

###Topologically Protected Vortex Structures to Realize Low-Noise Magnetic Sensors|Dieter Suess,Anton Bachleitner-Hofmann,Armin Satz,Herbert Weitensfelder,Christoph Vogler,Florian Bruckner,Claas Abert,Klemens Prügl,Jürgen Zimmer,Christian Huber,Sebastian Luber,Wolfgang Raberg,Thomas Schrefl,Hubert Brückl###

Topologically Protected Vortex Structures to Realize Low-Noise Magnetic Sensors. Micromagnetic sensors play a major role towards the miniaturization in the
industrial society. The adoption of new and emerging sensor technologies like
anisotropic magnetoresistance (AMR), giant magnetoresistance (GMR) and tunnel
magnetoresistance (TMR) sensors are mainly driven by their integrability and
enhanced sensitivity. At the core of such sensors, a microstructured
ferromagnetic thin film element transduces the magnetic signal. Such elements
usually switch via multi-domain, C- or S-shaped magnetization states and,
therefore, often exhibit an open non-linear hysteresis curve. Linearity and
hysteretic effects, as well as magnetic noise are key features in the
improvement of such sensors. Here, we report on the physical origin of these
disturbing factors and the inherent connection of noise and hysteresis.
Critical noise sources are identified by means of analytic and micromagnetic
models. The dominant noise source is due to irreproducible magnetic switching
of the transducer element at external fields close to the Stoner Wohlfarth
switching field. Furthermore, a solution is presented to overcome these
limiting factors: a disruptive sensor design is proposed and analyzed which
realizes a topologically protected magnetic vortex state in the transducer
element. Compared to state of the art sensors the proposed sensor layout has
negligible hysteresis, a linear regime about an order of magnitude higher and
lower magnetic noise making the sensor ideal candidate for applications ranging
from automotive industry to biological application.

###Magnetoresistance in the in-plane magnetic field induced semi-metallic phase of inverted HgTe quantum wells|T. Khouri,S. Pezzini,M. Bendias,P. Leubner,U. Zeitler,N. E. Hussey,H. Buhmann,L. W. Molenkamp,M. Titov,S. Wiedmann###

Magnetoresistance in the in-plane magnetic field induced semi-metallic phase of inverted HgTe quantum wells. In this study we have measured the magnetoresistance response of inverted
HgTe quantum wells in the presence of a large parallel magnetic field up to 33
T is applied. We show that in quantum wells with inverted band structure a
monotonically decreasing magnetoresistance is observed when a magnetic field up
to order 10 T is applied parallel to the quantum well plane. This feature is
accompanied by a vanishing of non-locality and is consistent with a predicted
modification of the energy spectrum that becomes gapless at a critical in-plane
field $B_{c}$. Magnetic fields in excess of $B_c$ allow us to investigate the
evolution of the magnetoresistance in this field-induced semi-metallic region
beyond the known regime. After an initial saturation phase in the presumably
gapless phase, we observe a strong upturn of the longitudinal resistance. A
small residual Hall signal picked up in non-local measurements suggests that
this feature is likely a bulk phenomenon and caused by the semi-metallicity of
the sample. Theoretical calculations indeed support that the origin of these
features is classical and a power law upturn of the resistance can be expected
due to the specifics of two-carrier transport in thin (semi-)metallic samples
subjected to large magnetic fields.

###Bulk Fermi surface of the type-II Weyl semimetal candidate NbIrTe$_{4}$|Rico Schönemann,Yu-Che Chiu,Wenkai Zheng,Victor Quito,Shouvik Sur,Gregory T. McCandless,Julia Y. Chan,Luis Balicas###

Bulk Fermi surface of the type-II Weyl semimetal candidate NbIrTe$_{4}$. Recently, a new group of layered transition-metal tetra-chalcogenides were
proposed, via first principles calculations, to correspond to a new family of
Weyl type-II semimetals with promising topological properties in the bulk as
well as in the monolayer limit. In this article, we present measurements of the
Shubnikov-de Haas (SdH) and de Haas-van Alphen effects under high magnetic
fields for the type-II Weyl semimetallic candidate NbIrTe$_{4}$. We find that
the angular dependence of the observed Fermi surface extremal cross-sectional
areas agree well with our DFT calculations supporting the existence of Weyl
type-II points in this material. Although we observe a large and non-saturating
magnetoresistivity in NbIrTe$_{4}$ under fields all the way up to 35 T,
Hall-effect measurements indicate that NbIrTe$_{4}$ is not a compensated
semimetal. The transverse magnetoresistivity displays a four-fold angular
dependence akin to the so-called butterfly magnetoresistivity observed in nodal
line semimetals. However, we conclude that its field and this unconventional
angular-dependence are governed by the topography of the Fermi-surface and the
resulting anisotropy in effective masses and in carrier mobilities.

###Negative to Positive Crossover of Magnetoresistance in Layered WS2 with Ohmic Contact|Yangwei Zhang,Honglie Ning,Yanan Li,Yanzhao Liu,Jian Wang###

Negative to Positive Crossover of Magnetoresistance in Layered WS2 with Ohmic Contact. The discovery of graphene has ignited intensive investigation on two
dimensional (2D) materials. Among them, transition metal dichalcogenide (TMDC),
a typical representative, attracts much attention due to the excellent
performance in field effect transistor (FET) related measurements and
applications. Particularly, when TMDC eventually reaches few-layer dimension, a
wide range of electronic and optical properties, in striking contrast to bulk
samples, are detected. In this Letter, we synthesized single crystalline WS2
nanoflakes by physical vapor deposition (PVD) method and carried out a series
of transport measurements of contact resistance and magnetoresistance. Focused
ion beam (FIB) technology was applied to deposit Pt electrodes on WS2 flakes.
Different from the electron beam lithography (EBL) fabricated electrodes,
FIB-deposited leads exhibited ohmic contact, resolving the dilemma of Schottky
barrier. Furthermore, a temperature-modulated negative-to-positive transition
of magnetoresistance (MR) associated with a crossover of carrier type at
similar temperature was demonstrated. Our work offers a pathway to optimize the
contact for TMDC and reveals the magnetoresistance characteristics of WS2
flakes, which may stimulate further studies on TMDC and corresponding potential
electronic and optoelectronic applications.

###A variety of elastic anomalies in orbital-active nearly-itinerant cobalt vanadate spinel|Tadataka Watanabe,Shogo Yamada,Rui Koborinai,Takuro Katsufuji###

A variety of elastic anomalies in orbital-active nearly-itinerant cobalt vanadate spinel. We perform ultrasound velocity measurements on a single crystal of
nearly-metallic spinel Co$_{1.21}$V$_{1.79}$O$_4$ which exhibits a
ferrimagnetic phase transition at $T_C \sim$ 165 K. The experiments reveal a
variety of elastic anomalies in not only the paramagnetic phase above $T_C$ but
also the ferrimagnetic phase below $T_C$, which should be driven by the
nearly-itinerant character of the orbitally-degenerate V 3$d$ electrons. In the
paramagnetic phase above $T_C$, the elastic moduli exhibit
elastic-mode-dependent unusual temperature variations, suggesting the existence
of a dynamic spin-cluster state. Furthermore, above $T_C$, the sensitive
magnetic-field response of the elastic moduli suggests that, with the negative
magnetoresistance, the magnetic-field-enhanced nearly-itinerant character of
the V 3$d$ electrons emerges from the spin-cluster state. This should be
triggered by the inter-V-site interactions acting on the orbitally-degenerate
3$d$ electrons. In the ferrimagnetic phase below $T_C$, the elastic moduli
exhibit distinct anomalies at $T_1\sim$ 95 K and $T_2\sim$ 50 K, with a sign
change of the magnetoresistance at $T_1$ (positive below $T_1$) and an
enhancement of the positive magnetoresistance below $T_2$, respectively. These
observations below $T_C$ suggest the successive occurrence of an orbital glassy
order at $T_1$ and a structural phase transition at $T_2$, where the rather
localized character of the V 3$d$ electrons evolves below $T_1$ and is further
enhanced below $T_2$.

###Magnetoresistance in Co-hBN-NiFe tunnel junctions enhanced by resonant tunneling through single defects in ultrathin hBN barriers|Pablo U. Asshoff,Jose L. Sambricio,Sergey Slizovskiy,Aidan P. Rooney,Takashi Taniguchi,Kenji Watanabe,Sarah J. Haigh,Vladimir Fal'ko,Irina V. Grigorieva,Ivan J. Vera-Marun###

Magnetoresistance in Co-hBN-NiFe tunnel junctions enhanced by resonant tunneling through single defects in ultrathin hBN barriers. Hexagonal boron nitride (hBN) is a prototypical high-quality two-dimensional
insulator and an ideal material to study tunneling phenomena, as it can be
easily integrated in vertical van der Waals devices. For spintronic devices,
its potential has been demonstrated both for efficient spin injection in
lateral spin valves and as a barrier in magnetic tunnel junctions (MTJs). Here
we reveal the effect of point defects inevitably present in mechanically
exfoliated hBN on the tunnel magnetoresistance of Co-hBN-NiFe MTJs. We observe
a clear enhancement of both the conductance and magnetoresistance of the
junction at well-defined bias voltages, indicating resonant tunneling through
magnetic (spin-polarized) defect states. The spin polarization of the defect
states is attributed to exchange coupling of a paramagnetic impurity in the
few-atomic-layer thick hBN to the ferromagnetic electrodes. This is confirmed
by excellent agreement with theoretical modelling. Our findings should be taken
into account in analyzing tunneling processes in hBN-based magnetic devices.
More generally, our study shows the potential of using atomically thin hBN
barriers with defects to engineer the magnetoresistance of MTJs and to achieve
spin filtering, opening the door towards exploiting the spin degree of freedom
in current studies of point defects as quantum emitters.

###Distinguishing antiferromagnetic spin sublattices via the spin Seebeck effect|Yongming Luo,Changjiang Liu,Hilal Saglam,Yi Li,Wei Zhang,Steven S. -L. Zhang,John E. Pearson,Brandon Fisher,Anand Bhattacharya,Axel Hoffmann###

Distinguishing antiferromagnetic spin sublattices via the spin Seebeck effect. Antiferromagnets are beneficial for future spintronic applications due to
their zero magnetic moment and ultrafast dynamics. But gaining direct access to
their antiferromagnetic order and identifying the properties of individual
magnetic sublattices, especially in thin films and small-scale devices, remains
a formidable challenge. So far, the existing read-out techniques such as
anisotropic magnetoresistance, tunneling anisotropic magnetoresistance, and
spin-Hall magnetoresistance, are even functions of sublattice magnetization and
thus allow us to detect different orientations of the N\'eel order for
antiferromagnets with multiple easy axes. In contrast direct electrical
detection of oppositely oriented spin states along the same easy axes (e.g., in
uniaxial antiferromagnets) requires sensitivity to the direction of individual
sublattices and thus is more difficult. In this study, using spin Seebeck
effect, we report the electrical detection of the two sublattices in a uniaxial
antiferromagnet Cr2O3. We find the rotational symmetry and hysteresis behavior
of the spin Seebeck signals measured at the top and bottom surface reflect the
dierction of the surface sublattice moments, but not the N\'eel order or the
net moment in the bulk. Our results demonstrate the important role of interface
spin sublattices in generating the spin Seebeck voltages, which provide a way
to access each sublattice independently, enables us to track the full rotation
of the magnetic sublattice, and distinguish different and antiparallel
antiferromagnetic states in uniaxial antiferromagnets.

###Effects of transition-metal spacers on the spin-orbit torques, spin Hall magnetoresistance, and magnetic anisotropy of Pt/Co bilayers|Can Onur Avci,Geoffrey S. D. Beach,Pietro Gambardella###

Effects of transition-metal spacers on the spin-orbit torques, spin Hall magnetoresistance, and magnetic anisotropy of Pt/Co bilayers. We studied the effect of inserting 0.5 nm-thick spacer layers (Ti, V, Cr, Mo,
W) at the Pt/Co interface on the spin-orbit torques, Hall effect,
magnetoresistance, saturation magnetization, and magnetic anisotropy. We find
that the damping-like spin-orbit torque decreases substantially for all samples
with a spacer layer compared to the reference Pt/Co bilayer, consistently with
the opposite sign of the atomic spin-orbit coupling constant of the spacer
elements relative to Pt. The reduction of the damping-like torque is monotonic
with atomic number for the isoelectronic 3d, 4d, and 5d elements, with the
exception of V that has a stronger effect than Cr. The field-like spin-orbit
torque almost vanishes for all spacer layers irrespective of their composition,
suggesting that this torque predominantly originates at the Pt/Co interface.
The anomalous Hall effect, magnetoresistance, and saturation magnetization are
also all reduced substantially, whereas the sheet resistance is increased in
the presence of the spacer layer. Finally, we evidence a correlation between
the amplitude of the spin-orbit torques, the spin Hall-like magnetoresistance,
and the perpendicular magnetic anisotropy. These results highlight the
significant influence of ultrathin spacer layers on the magnetotransport
properties of heavy metal/ferromagnetic systems.

###Sharp steps in magnetization, magnetoresistance and magnetostriction in Pr0.6Sr0.4Co1-yGayO3|A. Chanda,R. Mahendiran###

Sharp steps in magnetization, magnetoresistance and magnetostriction in Pr0.6Sr0.4Co1-yGayO3. We report the effect of Ga substitution on magnetization, magnetoresistance,
and magnetostriction in polycrystalline Pr0.6Sr0.4Co1-yGayO3 (y=0.0-0.3)
samples. Upon substitution of the non-magnetic Ga3+ cation for magnetic Co3+,
the low-temperature ground state transforms from ferromagnetic metallic for y =
0 to cluster glass semiconductor for y = 0.2. Magnetoresistance at 7T is
negative and its magnitude increases from 2 percentage for y = 0 to 30
percentage for y = 0.3 at 10 K. On the other hand, magnetostriction at 10 K is
positive and its value decreases with increasing y. Interestingly, the
field-dependent magnetization, magnetoresistance, and magnetostriction for y
greater than or equal to 0.2 and at T less than or equal to 3 K show reversible
abrupt steps for both positive and negative magnetic field whereas all these
quantities vary smoothly with the magnetic field above 4 K. Such steps in all
three distinct physical quantities were never reported earlier in perovskite
cobaltites and they differ from observations made in manganites and
intermetallic alloys. It is suggested that field-induced avalanche flipping of
ferromagnetic clusters could be the origin of observed steps in all these three
quantities.

###Effect of disorder on the transverse magnetoresistance of Weyl semimetals|Ya. I. Rodionov,K. I. Kugel,B. A. Aronzon,Franco Nori###

Effect of disorder on the transverse magnetoresistance of Weyl semimetals. We study the effect of random potential created by different types of
impurities on the transverse magnetoresistance of Weyl semimetals. It is shown
that the magnetic field and temperature dependence of magnetoresistance is
strongly affected by the type of impurity potential. Two limiting cases are
analyzed in detail: ($i$) the ultra-quantum limit, when the applied magnetic
field is so high that only the zeroth and first Landau levels contribute to the
magnetotransport, and ($ii$) the semiclassical situation, for which a large
number of Landau levels comes into play. A formal diagrammatic approach allowed
us to obtain expressions for the components of the electrical conductivity
tensor in both limits. In contrast to the oversimplified case of the
$\delta$-correlated disorder, the long-range impurity potential (including that
of Coulomb impurities) introduces an additional length scale, which changes the
geometry and physics of the problem. It is shown that the magnetoresistance can
deviate from the linear behavior as a function of magnetic field for a certain
class of impurity potentials.

###Anomalous planar Hall effect in a kagome ferromagnet|Neeraj Kumar,Y. Soh,Yihao Wang,Junbo Li,Y. Xiong###

Anomalous planar Hall effect in a kagome ferromagnet. The macroscopic signature for Weyl nodes so far has been the negative
longitudinal magnetoresistance arising from the chiral anomaly. However,
negative longitudinal magnetoresistance is not unique to chiral anomaly and can
arise due to completely different mechanisms such as current jetting or in
ferromagnetic systems due to the suppression of scattering with magnons.
Therefore, a macroscopic effect that can be uniquely attributed to the presence
of Weyl nodes is desirable. Here we show that the planar Hall effect could be a
hallmark for Weyl nodes. We investigated the anisotropic magnetoresistance and
planar Hall effect in Fe$_3$Sn$_2$, which has a kagome lattice and has been
predicted to be a type II Weyl metal. We discover that the planar Hall effect
contains a field antisymmetric contribution in addition to the ordinary field
symmetric contribution. The field antisymmetric planar Hall effect has a 3-fold
rotational symmetry, distinctively different from the symmetric planar Hall
effect, but consistent with the 3-fold rotational degeneracy of the
magnetization in Fe$_3$Sn$_2$. The temperature and field dependence of the
antisymmetric planar Hall effect rules out an interpretation based on
contribution from the anomalous Hall effect and is different from the symmetric
planar Hall effect, pointing to a different origin. We attribute the
antisymmetric planar Hall effect to the topological nature of Fe$_3$Sn$_2$ due
to the presence of Weyl II nodes. Our finding offers a promising route for
macroscopically probing Weyl systems.

###Observation of plateau-like magnetoresistance in twisted Fe3GeTe2/Fe3GeTe2 junction|Junghyun Kim,Suhan Son,Matthew. J. Coak,Inho Hwang,Youjin Lee,Kaixuan Zhang,Je-Geun Park###

Observation of plateau-like magnetoresistance in twisted Fe3GeTe2/Fe3GeTe2 junction. Controlling the stacking of van der Waals (vdW) materials is found to produce
exciting new findings, since hetero- or homo- structures have added the diverse
possibility of assembly and manipulated functionalities. However, so far, the
homostructure with a twisted angle based on the magnetic vdW materials remains
unexplored. Here, we achieved a twisted magnetic vdW Fe3GeTe2/Fe3GeTe2 junction
with broken crystalline symmetry. A clean and metallic vdW junction is
evidenced by the temperature-dependent resistance and the linear I-V curve.
Unlike the pristine FGT, a plateau-like magnetoresistance (PMR) is observed in
the magnetotransport of our homojunction due to the antiparallel magnetic
configurations of the two FGT layers. The PMR ratio is found to be ~0.05% and
gets monotonically enhanced as temperature decreases like a metallic giant
magnetoresistance (GMR). Such a tiny PMR ratio is at least three orders of
magnitude smaller than the tunneling magnetoresistance (TMR) ratio, justifying
our clean metallic junction without a spacer. Our findings demonstrate the
feasibility of the controllable homostructure and shed light on future
spintronics using magnetic vdW materials.

###Tuneable Magneto-Resistance by Severe Plastic Deformation|Stefan Wurster,Lukas Weissitsch,Martin Stueckler,Peter Knoll,Heinz Krenn,Reinhard Pippan,Andrea Bachmaier###

Tuneable Magneto-Resistance by Severe Plastic Deformation. Bulk metallic samples were synthesized from different binary powder mixtures
consisting of elemental Cu, Co, and Fe using severe plastic deformation. Small
particles of the ferromagnetic phase originate in the conductive Cu phase,
either by incomplete dissolution or by segregation phenomena during the
deformation process. These small particles are known to give rise to granular
giant magnetoresistance. Taking advantage of the simple production process, it
is possible to perform a systematic study on the influence of processing
parameters and material compositions on the magneto-resistance. Furthermore, it
is feasible to tune the magnetoresistive behavior as a function of the
specimens chemical composition. It was found that specimens of low
ferromagnetic content show an almost isotropic drop in resistance in a magnetic
field. With increasing ferromagnetic content, percolating ferromagnetic phases
cause an anisotropy of the magnetoresistance. By changing the parameters of the
high pressure torsion process, i.e., sample size, deformation temperature, and
strain rate, it is possible to tailor the magnitude of giant
magneto-resistance. A decrease in room temperature resistivity of approx. 3.5%
was found for a bulk specimen containing an approximately equiatomic fraction
of Co and Cu.

###Incoherent transport across the strange metal regime of highly overdoped cuprates|J. Ayres,M. Berben,M. Culo,Y. -T. Hsu,E. van Heumen,Y. Huang,J. Zaanen,T. Kondo,T. Takeuchi,J. R. Cooper,C. Putzke,S. Friedemann,A. Carrington,N. E. Hussey###

Incoherent transport across the strange metal regime of highly overdoped cuprates. Strange metals possess highly unconventional transport characteristics, such
as a linear-in-temperature ($T$) resistivity, an inverse Hall angle that varies
as $T^2$ and a linear-in-field ($H$) magnetoresistance. Identifying the origin
of these collective anomalies has proved profoundly challenging, even in
materials such as the hole-doped cuprates that possess a simple band structure.
The prevailing dogma is that strange metallicity in the cuprates is tied to a
quantum critical point at a doping $p*$ inside the superconducting dome. Here,
we study the high-field in-plane magnetoresistance of two superconducting
cuprate families at doping levels beyond $p*$. At all dopings, the
magnetoresistance exhibits quadrature scaling and becomes linear at high $H/T$
ratios. Moreover, its magnitude is found to be much larger than predicted by
conventional theory and insensitive to both impurity scattering and magnetic
field orientation. These observations, coupled with analysis of the zero-field
and Hall resistivities, suggest that despite having a single band, the cuprate
strange metal phase hosts two charge sectors, one containing coherent
quasiparticles, the other scale-invariant `Planckian' dissipators.

###Unidirectional magnetoresistance and spin-orbit torque in NiMnSb|J. Železný,Z. Fang,K. Olejník,J. Patchett,F. Gerhard,C. Gould,L. W. Molenkamp,C. Gomez-Olivella,J. Zemen,T. Tichý,T. Jungwirth,C. Ciccarelli###

Unidirectional magnetoresistance and spin-orbit torque in NiMnSb. Spin-dependent transport phenomena due to relativistic spin-orbit coupling
and broken space-inversion symmetry are often difficult to interpret
microscopically, in particular when occurring at surfaces or interfaces. Here
we present a theoretical and experimental study of spin-orbit torque and
unidirectional magnetoresistance in a model room-temperature ferromagnet NiMnSb
with inversion asymmetry in the bulk of this half-heusler crystal. Besides the
angular dependence on magnetization, the competition of Rashba and
Dresselhaus-like spin-orbit couplings results in the dependence of these
effects on the crystal direction of the applied electric field. The
phenomenology that we observe highlights potential inapplicability of commonly
considered approaches for interpreting experiments. We point out that, in
general, there is no direct link between the current-induced non-equilibrium
spin polarization inferred from the measured spin-orbit torque and the
unidirectional magnetiresistance. We also emphasize that the unidirectional
magnetoresistance has not only longitudinal but also transverse components in
the electric field -- current indices which complicates its separation from the
thermoelectric contributions to the detected signals in common experimental
techniques. We use the theoretical results to analyze our measurements of the
on-resonance and off-resonance mixing signals in microbar devices fabricated
from an epitaxial NiMnSb film along different crystal directions. Based on the
analysis we extract an experimental estimate of the unidirectional
magnetoresistance in NiMnSb.

###Strange electrical transport: Colossal magnetoresistance via avoiding fully polarized magnetization in ferrimagnetic insulator Mn3Si2Te6|Yifei Ni,Hengdi Zhao,Yu Zhang,Bing Hu,Itamar Kimchi,Gang Cao###

Strange electrical transport: Colossal magnetoresistance via avoiding fully polarized magnetization in ferrimagnetic insulator Mn3Si2Te6. Colossal magnetoresistance is of great fundamental and technological
significance and exists mostly in the manganites and a few other materials.
Here we report colossal magnetoresistance that is starkly different from that
in all other materials. The stoichiometric Mn3Si2Te6 is an insulator featuring
a ferrimagnetic transition at 78 K. The resistivity drops by 7 orders of
magnitude with an applied magnetic field above 9 Tesla, leading to an
insulator-metal transition at up to 130 K. However, the colossal
magnetoresistance occurs only when the magnetic field is applied along the
magnetic hard axis and is surprisingly absent when the magnetic field is
applied along the magnetic easy axis where magnetization is fully saturated.
The anisotropy field separating the easy and hard axes is 13 Tesla, unexpected
for the Mn ions with nominally negligible orbital momentum and spin-orbit
interactions. Double exchange and Jahn-Teller distortions that drive the
hole-doped manganites do not exist in Mn3Si2Te6. The phenomena fit no existing
models, suggesting a unique, intriguing type of electrical transport.

###Strong magnetoresistance in a graphene Corbino disk at low magnetic fields|Masahiro Kamada,Vanessa Gall,Jayanta Sarkar,Manohar Kumar,Antti Laitinen,Igor Gornyi,Pertti Hakonen###

Strong magnetoresistance in a graphene Corbino disk at low magnetic fields. We have measured magnetoresistance of suspended graphene in the Corbino
geometry at magnetic fields up to $B=0.15\,$T, i.e., in a regime uninfluenced
by Shubnikov-de Haas oscillations. The low-temperature relative
magnetotoresistance $[R(B)-R(0)]/R(0)$ amounts to $4000 B^2\% $ at the Dirac
point ($B$ in Tesla), with a quite weak temperature dependence below $30\,$K. A
decrease in the relative magnetoresistance by a factor of two is found when
charge carrier density is increased to $|n| \simeq 3 \times 10^{-10}$
cm$^{-2}$. The gate dependence of the magnetoresistance allows us to
characterize the role of scattering on long-range (Coulomb impurities, ripples)
and short-range potential, as well as to separate the bulk resistance from the
contact one. Furthermore, we find a shift in the position of the charge
neutrality point with increasing magnetic field, which suggests that magnetic
field changes the screening of Coulomb impurities around the Dirac point. The
current noise of our device amounts to $10^{-23}$ A$^2$/$\sqrt{\textrm{Hz}}$ at
$1\,$kHz at $4\,$K, which corresponds to a magnetic field sensitivity of $60$
nT/$\sqrt{\textrm{Hz}}$ in a background field of $0.15\,$T.

###Observation of the Orbital Rashba-Edelstein Magnetoresistance|Shilei Ding,Zhongyu Liang,Dongwook Go,Chao Yun,Mingzhu Xue,Zhou Liu,Sven Becker,Wenyun Yang,Honglin Du,Changsheng Wang,Yingchang Yang,Gerhard Jakob,Mathias Kläui,Yuriy Mokrousov,Jinbo Yang###

Observation of the Orbital Rashba-Edelstein Magnetoresistance. We report the observation of magnetoresistance (MR) originating from the
orbital angular momentum transport (OAM) in a Permalloy (Py) / oxidized Cu
(Cu*) heterostructure: the orbital Rashba-Edelstein magnetoresistance. The
angular dependence of the MR depends on the relative angle between the induced
OAM and the magnetization in a similar fashion as the spin Hall
magnetoresistance (SMR). Despite the absence of elements with large spin-orbit
coupling, we find a sizable MR ratio, which is in contrast to the conventional
SMR which requires heavy elements. By varying the thickness of the Cu* layer,
we confirm that the interface is responsible for the MR, suggesting that the
orbital Rashba-Edelstein effect is responsible for the generation of the OAM.
Through Py thickness-dependence studies, we find that the effective values for
the spin diffusion and spin dephasing lengths of Py are significantly larger
than the values measured in Py / Pt bilayers, approximately by the factor of 2
and 4, respectively. This implies that another mechanism beyond the
conventional spin-based scenario is responsible for the MR observed in Py / Cu*
structures originated in a sizeable transport of OAM. Our findings not only
unambiguously demonstrate the current-induced torque without using any heavy
element via the OAM channel but also provide an important clue towards the
microscopic understanding of the role that OAM transport can play for
magnetization dynamics.

###Extended Kohler$^,$s Rule of Magnetoresistance|Jing Xu,Fei Han,Ting-Ting Wang,Laxman R. Thoutam,Samuel E. Pate,Mingda Li,Xufeng Zhang,Yong-Lei Wang,Roxanna Fotovat,Ulrich Welp,Xiuquan Zhou,Wai-Kwong Kwok,Duck Young Chung,Mercouri G. Kanatzidis,Zhi-Li Xiao###

Extended Kohler$^,$s Rule of Magnetoresistance. A notable phenomenon in topological semimetals is the violation of
Kohler$^,$s rule, which dictates that the magnetoresistance $MR$ obeys a
scaling behavior of $MR = f(H/\rho_0$), where $MR = [\rho_H-\rho_0]/\rho_0$ and
$H$ is the magnetic field, with $\rho_H$ and $\rho_0$ being the resistivity at
$H$ and zero field, respectively. Here we report a violation originating from
thermally-induced change in the carrier density. We find that the
magnetoresistance of the Weyl semimetal, TaP, follows an extended Kohler$^,$s
rule $MR = f[H/(n_T\rho_0)]$, with $n_T$ describing the temperature dependence
of the carrier density. We show that $n_T$ is associated with the Fermi level
and the dispersion relation of the semimetal, providing a new way to reveal
information on the electronic bandstructure. We offer a fundamental
understanding of the violation and validity of Kohler$^,$s rule in terms of
different temperature-responses of $n_T$. We apply our extended Kohler$^,$s
rule to BaFe$_2$(As$_{1-x}$P$_x$)$_2$ to settle a long-standing debate on the
scaling behavior of the normal-state magnetoresistance of a superconductor,
namely, $MR$ ~ $tan^2\theta_H$, where $\theta_H$ is the Hall angle. We further
validate the extended Kohler$^,$s rule and demonstrate its generality in a
semiconductor, InSb, where the temperature-dependent carrier density can be
reliably determined both theoretically and experimentally.

###Proposal for a solid-state magnetoresistive Larmor quantum clock|Amal Mathew,Kerem Y Camsari,Bhaskaran Muralidharan###

Proposal for a solid-state magnetoresistive Larmor quantum clock. We propose a solid-state implementation of the Larmor clock that exploits
tunnel magnetoresistance to distill information on how long itinerant spins
take to traverse a barrier embedded in it. Keeping in mind that the tunnelling
time innately involves pristine pre-selection and post-selection, our proposal
takes into account the detrimental aspects of multiple reflections by
incorporating multiple contacts, multiple current measurements and suitably
defined magnetoresistance signals. Our analysis provides a direct mapping
between the magnetoresistance signals and the tunneling times and aligns well
with the interpretation in terms of generalized quantum measurements and
quantum weak values. By means of an engineered pre-selection in one of the
ferromagnetic contacts, we also elucidate how one can make the measurement
"weak" by minimizing the back-action, while keeping the tunneling time
unchanged. We then analyze the resulting interpretations of the tunneling time
and the measurement back action in the presence of phase breaking effects that
are intrinsic to solid state systems. We unravel that while the time-keeping
aspect of the Larmor clock is reasonably undeterred due to momentum and phase
relaxation processes, it degrades significantly in the presence of
spin-dephasing. We believe that the ideas presented here also open up a
fructuous solid state platform to encompass emerging ideas in quantum
technology such as quantum weak values and its applications, that are currently
exclusive to quantum optics and cold atoms.

###Spin anomalous-Hall unidirectional magnetoresistance|M. Mehraeen,Steven S. -L. Zhang###

Spin anomalous-Hall unidirectional magnetoresistance. We predict a spin anomalous-Hall unidirectional magnetoresistance (AH-UMR) in
conducting bilayers composed of a ferromagnetic layer and a nonmagnetic layer,
which does $\textit{not}$ rely on the spin Hall effect in the normal metal
layer$-$in stark contrast to the well-studied unidirectional spin-Hall
magnetoresistance$-$but, instead, arises from the spin anomalous Hall effect in
the ferromagnetic layer. Physically, it is the charge-spin conversion induced
by the spin anomalous Hall effect that conspires with the structural inversion
asymmetry to generate a net nonequilibrium spin density in the ferromagnetic
layer, which, in turn, modulates the resistance of the bilayer when the
direction of the applied current or the magnetization is reversed. The
dependences of the spin AH-UMR effect on materials and geometric parameters are
analyzed and compared with other nonlinear magnetoresistances. In particular,
we show that, in magnetic bilayers where spin anomalous Hall and spin Hall
effects are comparable, the overall UMR may undergo a sign change when the
thickness of either layer is varied, suggesting a scheme to quantify the spin
Hall or spin anomalous Hall angle via a nonlinear transport measurement.

###$B^2$ to $B$-linear magnetoresistance due to impeded orbital motion|R. D. H. Hinlopen,F. A. Hinlopen,J. Ayres,N. E. Hussey###

$B^2$ to $B$-linear magnetoresistance due to impeded orbital motion. Strange metals exhibit a variety of anomalous magnetotransport properties,
the most striking of which is a resistivity that increases linearly with
magnetic field $B$ over a broad temperature and field range. The ubiquity of
this behavior across a spectrum of correlated metals - both single- and
multi-band, with either dominant spin and/or charge fluctuations, of varying
levels of disorder or inhomogeneity and in proximity to a quantum critical
point or phase - obligates the search for a fundamental underlying principle
that is independent of the specifics of any material. Strongly anisotropic
(momentum-dependent) scattering can generate $B$-linear magnetoresistance but
only at intermediate field strengths. At high enough fields, the
magnetoresistance must eventually saturate. Here, we consider the ultimate
limit of such anisotropy, a region or regions on the Fermi surface that impede
all orbital (cyclotron) motion through them, but whose imposition can be
modelled nonetheless through a modified Boltzmann theoretical treatment.
Application of the proposed theorem suggests that the realization of
quadratic-to-linear magnetoresistance requires the presence of a bounded sector
on the Fermi surface possibly separating two distinct types of carriers. While
this bounded sector may have different origins or manifestations, we expect its
existence to account for the anomalous magnetotransport found in a wide range
of correlated materials.

###Spin Hall magnetoresistance in paramagnetic NdGaO3|V. Eswara Phanindra,A. Das,J. J. L. van Rijn,S. Chen,B. J. van Wees,T. Banerjee###

Spin Hall magnetoresistance in paramagnetic NdGaO3. In recent years, spin Hall magnetoresistance (SMR) has emerged as an
efficient way to probe the spontaneous magnetization state in ordered magnetic
systems, by electrical current. Less known is its versatility as a probe of
materials that do not possess spontaneous magnetization such as in paramagnets.
In this work, SMR is used to probe paramagnetic NdGaO3 (NGO), a rare earth
oxide, possessing a sizable spin orbit interaction (L=6). NGO has not been
investigated earlier for its efficiency in propagating spins. We have performed
extensive temperature and angle dependent-magnetoresistance (ADMR) studies
along dissimilar crystallographic axes in NGO, using platinum (Pt) as spin
injector and detector and utilizing (inverse) spin Hall effect. We find a close
correlation between the temperature dependence of the ADMR response with
magnetization in NGO and a linear current bias dependence of the ADMR
amplitudes. These are chacteristics of SMR effect in Pt/NGO, arising from the
torque acting on localized moments in NGO and considering crystal field induced
intermultiplet transitions with temperature. Control experiments on Pt/SrTiO3
and Pt/SiO2 devices were also carried out in order to validate the observed SMR
response in Pt/NGO bilayer and to rule out magnetoresistive contributions from
Pt.

###Fe- and Co-based magnetic tunnel junctions with AlN and ZnO spacers|Gokaran Shukla,Stefano Sanvito,Geunsik Lee###

Fe- and Co-based magnetic tunnel junctions with AlN and ZnO spacers. AlN and ZnO, two wide band-gap semiconductors extensively used in the display
industry, crystallise in the wurtzite structure, which can favour the formation
of epitaxial interfaces to close-packed common ferromagnets. Here we explore
these semiconductors as material for insulating barriers in magnetic tunnel
junctions. In particular, the {\it ab initio} quantum transport code {\it
Smeagol} is used to model the $X$[111]/$Y$[0001]/$X$[111] ($X=$ Co and Fe, $Y=$
AlN and ZnO) family of junctions. Both semiconductors display a valance-band
top with $p$-orbital character, while the conduction band bottom exhibits
$s$-type symmetry. The smallest complex-band decay coefficient in the forbidden
energy-gap along the [0001] direction is associated with the $\Delta_1$
symmetry, and connects across the band gap at the $\Gamma$ point in 2D
Brillouin zones. This feature enables spin filtering and may result in a large
tunnelling magnetoresistance. In general, we find that Co-based junctions
present limited spin filtering and little magnetoresistance at low bias, since
both spin sub-bands cross the Fermi level with $\Delta_1$ symmetry. This
contrasts the situation of Fe, where only the minority $\Delta_1$ band is
available. However, even in the case of Fe the magnitude of the
magnetoresistance at low bias remains relatively small, mostly due to
conduction away from the $\Gamma$ point and through complex bands with symmetry
different than $\Delta_1$. The only exception is for the Fe/AlN/Fe junction,
where we predict a magnetoresitance of around 1,000\% at low bias.

###Spin-orbit enabled all-electrical readout of chiral spin-textures|Imara Lima Fernandes,Stefan Blügel,Samir Lounis###

Spin-orbit enabled all-electrical readout of chiral spin-textures. Chirality and topology are intimately related fundamental concepts, which are
heavily explored to establish spin-textures as potential magnetic bits in
information technology. However, this ambition is inhibited since electrical
reading of chiral attributes is highly non-trivial with conventional current
perpendicular-to-plane (CPP) sensing devices. Here we demonstrate from
extensive first-principles simulations and multiple scattering expansion the
emergence of the chiral spin-mixing magnetoresistance (C-XMR) enabling highly
efficient all-electrical readout of the chirality and helicity of respectively
one- and two-dimensional magnetic states of matter. It is linear with
spin-orbit coupling in contrast to the quadratic dependence associated with the
newly unveiled non-local spin-mixing anisotropic MR (X-AMR). Such transport
effects are systematised on various non-collinear magnetic states --
spin-spirals and skyrmions -- and compared to the uncovered
spin-orbit-independent multi-site magnetoresistances. Owing to their simple
implementation in readily available reading devices, the proposed
magnetoresistances offer exciting and decisive ingredients to explore with
all-electrical means the rich physics of topological and chiral magnetic
objects.

###Spin-orbit-derived giant magnetoresistance in a layered magnetic semiconductor AgCrSe2|Hidefumi Takahashi,Tomoki Akiba,Alex Hiro Mayo,Kazuto Akiba,Atsushi Miyake,Masashi Tokunaga,Hitoshi Mori,Ryotaro Arita,Shintaro Ishiwata###

Spin-orbit-derived giant magnetoresistance in a layered magnetic semiconductor AgCrSe2. Two-dimensional magnetic materials have recently attracted great interest due
to their unique functions as the electric field control of a magnetic phase and
the anomalous spin Hall effect. For such remarkable functions, a spin-orbit
coupling (SOC) serves as an essential ingredient. Here we report a giant
positive magnetoresistance in a layered magnetic semiconductor AgCrSe2, which
is a manifestation of the subtle combination of the SOC and Zeeman-type spin
splitting. When the carrier concentration approaches the critical value of
2.5\times10^18 cm^-3, a sizable positive magnetoresistance of ~400 % emerges
upon the application of magnetic fields normal to the conducting layers. Based
on the magneto-Seebeck effect and the first-principles calculations, the
unconventional magnetoresistance is ascribable to the enhancement of effective
carrier mass in the SOC induced J = 3/2 state, which is tuned to the Fermi
level through the Zeeman splitting enhanced by the p-d coupling. This study
demonstrates a new aspect of the SOC-derived magnetotransport in
two-dimensional magnetic semiconductors, paving the way to novel spintronic
functions.

###Direct link between disorder, mobility and magnetoresistance in topological semimetals|Jocienne N. Nelson,Anthony D. Rice,Chase Brooks,Ian A. Leahy,Glenn Teeter,Mark Van Schilfgaarde,Stephan Lany,Brian Fluegel,Minhyea Lee,Kirstin Alberi###

Direct link between disorder, mobility and magnetoresistance in topological semimetals. The extent to which disorder influences the properties of topological
semimetals remains an open question and is relevant to both the understanding
of topological states and the use of topological materials in practical
applications. Here, we achieve unmatched and systematic control of point defect
concentrations in the prototypical Dirac semimetal Cd$_3$As$_2$ to gain
important insight into the role of disorder on electron transport behavior. We
find that arsenic vacancies introduce localized states near the Fermi level and
strongly influence the electron mobility. Reducing arsenic vacancies by
changing the As/Cd flux ratio used during deposition results in an increase in
the magnetoresistance from 200%-1000% and an increase in mobility from
5000-18,000 cm$^2$/Vs. However, the degree of linear magnetoresistance, which
has previously been linked to disorder, is found here to correlate inversely
with measures of disorder, including disorder potential and disorder
correlation lengths. This finding yields important new information in the quest
to identify the origin of linear magnetoresistance in a wider range of
materials.

###Field-Induced Magnetic States in the Metallic Rare-Earth Layered Triangular Antiferromagnet TbAuAl$_4$Ge$_2$|Ian A. Leahy,Keke Feng,Roei Dey,Ryan Baumbach,Minhyea Lee###

Field-Induced Magnetic States in the Metallic Rare-Earth Layered Triangular Antiferromagnet TbAuAl$_4$Ge$_2$. Magnetic frustration in metallic rare earth lanthanides ($Ln$) with
$4f$-electrons is crucial for producing interesting magnetic phases with high
magnetic anisotropy where intertwined charge and spin degrees of freedom lead
to novel phenomena. Here we report on the magnetic, thermodynamic, and
electrical transport properties of TbAuAl$_4$Ge$_2$. Tb ions form 2-dimensional
triangular lattice layers which stack along the crystalline $c$-axis. The
magnetic phase diagram reveals multiple nearly degenerate ordered states upon
applying field along the magnetically easy $ab$-plane before saturation. The
magnetoresistance in this configuration exhibits intricate field dependence
that closely follows that of the magnetization while the specific heat reveals
a region of highly enhanced entropy, suggesting the possibility of a
non-trivial spin textured phase. For fields applied along the $c$-axis (hard
axis), we find linear magnetoresistance over a wide range of fields. We compare
the magnetic properties and magnetoresistance with an isostructral
GdAuAl$_4$Ge$_2$ single crystals. These results identify TbAuAl$_4$Ge$_2$ as an
environment for complex quantum spin states and pave the way for further
investigations of the broader $Ln$AuAl$_4$Ge$_2$ family of materials.

###On the origin of Abrikosov's quantum linear magnetoresistance|Alexander Kazantsev,Alexey Berdyugin,Andre Geim,Alessandro Principi###

On the origin of Abrikosov's quantum linear magnetoresistance. Compensated semimetals with Weyl spectra are predicted to exhibit unsaturated
linear growth of their resistivity in quantizing magnetic fields. This
so-called quantum linear magnetoresistance was introduced by Abrikosov, but
approximations used in the theory remained poorly specified, often causing a
confusion about experimental situations in which the analysis is applicable.
Here we derive Abrikosov's exact result using an alternative formalism based on
diffusion of cyclotron orbits in a random potential. We show that both Weyl
spectrum and a disorder smooth on the scale of the magnetic length are
essential conditions for the validity of the theory, and the linear
magnetoresistance appears in the extreme quantum limit where only the zeroth
Landau level is half filled. It is the interplay between the relativistic-like
nature of Weyl fermions and the classical dynamics of their cyclotron centers,
which leads to the linear magnetoresistance. We also derive an analogous result
in two dimensions, which has been missing in the literature and is relevant for
numerous graphene-based systems.

###Weyl nodal ring states and Landau quantization with very large magnetoresistance in square-net magnet EuGa$_4$|Shiming Lei,Kevin Allen,Jianwei Huang,Jaime M. Moya,Tsz Chun Wu,Brian Casas,Yichen Zhang,Ji Seop Oh,Makoto Hashimoto,Donghui Lu,Jonathan Denlinger,Chris Jozwiak,Aaron Bostwick,Eli Rotenberg,Luis Balicas,Robert Birgeneau,Matthew S. Foster,Ming Yi,Yan Sun,Emilia Morosan###

Weyl nodal ring states and Landau quantization with very large magnetoresistance in square-net magnet EuGa$_4$. Magnetic topological semimetals (TSMs) allow for an effective control of the
topological electronic states by tuning the spin configuration, and therefore
are promising materials for next-generation electronic and spintronic
applications. Of magnetic TSMs, Weyl nodal-line (NL) semimetals likely have the
most tunability, and yet they are the least experimentally studied so far due
to the scarcity of material candidates. Here, using a combination of
angle-resolved photoemission spectroscopy and quantum oscillation measurements,
together with density functional theory calculations, we identify the
square-net compound EuGa4 as a new magnetic Weyl nodal ring (NR) semimetal, in
which the line nodes form closed rings in the vicinity of the Fermi level.
Remarkably, the Weyl NR states show distinct Landau quantization with clear
spin splitting upon application of a magnetic field. At 2 K in a field of 14 T,
the transverse magnetoresistance of EuGa4 exceeds 200,000%, which is more than
two orders of magnitude larger than that of other known magnetic TSMs. High
field magnetoresistance measurements indicate no saturation up to 40 T. Our
theoretical model indicates that the nonsaturating MR naturally arises as a
consequence of the Weyl NR state. Our work thus point to the realization of
Weyl NR states in square-net magnetic materials, and opens new avenues for the
design of magnetic TSMs with very large magnetoresistance.

###Observation of Fermi liquid phase with broken symmetry in a single crystalline nanorod of Pr$_2$Ir$_2$O$_7$|Bikash Ghosh,Abhishek Juyal,Sourav Biswas,R. Rawat,Arijit Kundu,Soumik Mukhopadhyay###

Observation of Fermi liquid phase with broken symmetry in a single crystalline nanorod of Pr$_2$Ir$_2$O$_7$. We report experimental evidence of emergent broken symmetry Fermi liquid
state in an isolated single crystalline nanorod of $\rm Pr_2 Ir_2 O_7$. We find
clear signature of the onset of the Fermi liquid behavior at low temperature
marked by the sign inversion of magnetoresistance from negative at high
temperature, characteristic of incoherent Kondo scattering, to positive as well
as a $\rm T^2$ dependence of resistivity at low temperature. A resistive
anomaly is observed, which is accompanied by thermal hysteresis in the presence
of magnetic field, suggesting itinerant metamagnetism. The observed high field
negative magnetoresistance with quadratic field dependence at low temperature,
which is most likely due to suppression of itinerant spin fluctuation, and the
irreversibility of the magneto-resistive properties in the Fermi liquid regime
suggest existence of an unusual state with broken spin rotation and time
reversal symmetry, hallmark of `hastatic' order. The major features of such
temperature dependence of resistivity and magnetoresistance can be explained in
a phenomenological model incorporating two distinct hybridization channels,
which is physically consistent with the possibility of the formation of the
`hastatic' Fermi liquid phase.

###Spin mixing conductance and spin magnetoresistance of iridate/manganite interface|G. A. Ovsyannikov,K. Y. Constantinian,V. A. Shmakov,A. L. Klimov,E. A. Kalachev,A. V. Shadrin,N. V. Andreev,F. O. Milovich,A. P. Orlov,P. V. Lega###

Spin mixing conductance and spin magnetoresistance of iridate/manganite interface. We present results on experimental studies of spin current, measured under
spin pumping at ferromag-netic resonance in wide frequency band 2-20 GHz for
SrIrO3/La0.7Sr0.3MnO3 heterostructures fabricated by RF magnetron sputtering at
high temperature. The epitaxial growth of the thin film in heterostructure by a
cube-on-cube mechanism was confirmed by XRD and TEM analysis. Taking into
account the con-tribution of anisotropic magnetoresistance the spin current was
estimated as 1/3 of the total response. We show that both real and imaginary
parts of spin mixing conductance are valuable for heterostructures with strong
spin-orbit interaction in SrIrO3. Imaginary part of spin mixing conductance was
estimated by means of shift of ferromagnetic resonance field of La0.7Sr0.3MnO3
layer in heterostructure. The spin mag-netoresistance was evaluated from
angular dependencies of magnetoresistance measured in planar Hall
configuration. In order to extract the influence of anisotropic
magnetoresistance a La0.7Sr0.3MnO3 film was measured as well. The spin Hall
angle for heterostructure was found higher than for interface Pt/
La0.7Sr0.3MnO3.

###Quantum magnetoresistance of Weyl semimetals with strong Coulomb disorder|Ya. I. Rodionov,K. I. Kugel,B. A. Aronzon###

Quantum magnetoresistance of Weyl semimetals with strong Coulomb disorder. We study the effects a strong Coulomb disorder on the transverse
magnetoresistance in Weyl semimetals at low temperatures. Using the
diagrammatic technique and the Keldysh model to sum up the leading terms in the
diagrammatic expansion, we find that the linear magnetoresistance exhibits a
strong renormalization due to the long-range nature of the Coulomb interaction
$\rho_{xx} \propto H\ln(eH\hbar v^2/cT^2_{\rm imp}),\ \ \Omega\alpha^{-1/6}\ll
T_{\rm imp}\ll \Omega/\alpha^{-3/4}$, where $\Omega = v\sqrt{2eH\hbar/c}$ is
the distance between the zeroth and the first Landau levels, $T_{\rm imp}=\hbar
vn^{1/3}_{\rm imp}$ measures the strength of the impurity potential in terms of
the impurity concentration $n$ and the Fermi velocity $v$, and $\alpha =
e^2/\hbar v$ is the effective fine structure constant of the material. As
disorder becomes even stronger (but still in the parametric range, where the
Coulomb interaction can be treated as a long-range one), we find that the
magnetoresistivity becomes quadratic in the magnetic field $\rho_{xx}\propto
H^2$.

###Unreliability of two-band model analysis of magnetoresistivities in unveiling temperature-driven Lifshitz transition|Jing Xu,Yu Wang,Samuel E. Pate,Yanglin Zhu,Zhiqiang Mao,Xufeng Zhang,Xiuquan Zhou,Ulrich Welp,Wai-Kwong Kwok,Duck Young Chung,Mercouri G. Kanatzidis,Zhi-Li Xiao###

Unreliability of two-band model analysis of magnetoresistivities in unveiling temperature-driven Lifshitz transition. Recently, anomalies in the temperature dependences of the carrier density
and/or mobility derived from analysis of the magnetoresistivities using the
conventional two-band model have been used to unveil intriguing
temperature-induced Lifshitz transitions in various materials. For instance,
two temperature-driven Lifshitz transitions were inferred to exist in the Dirac
nodal-line semimetal ZrSiSe, based on two-band model analysis of the Hall
magnetoconductivities where the second band exhibits a change in the carrier
type from holes to electrons when the temperature decreases below T = 106 K and
a dip is observed in the mobility versus temperature curve at T = 80 K. Here,
we revisit the experiments and two-band model analysis on ZrSiSe. We show that
the anomalies in the second band may be spurious, because the first band
dominates the Hall magnetoconductivities at T > 80 K, making the carrier type
and mobility obtained for the second band from the two-band model analysis
unreliable. That is, care must be taken in interpreting these anomalies as
evidences for temperature-driven Lifshitz transitions. Our skepticism on the
existence of such phase transitions in ZrSiSe is further supported by the
validation of the Kohler's rule for magnetoresistances at temperatures below
180 K. This work showcases potential issues in interpreting anomalies in the
temperature dependence of the carrier density and mobility derived from the
analysis of magnetoconductivities or magnetoresistivities using the
conventional two-band model.

###Magnetotransport on quantum spin Hall edge coupled to bulk midgap states|Youjian Chen,Wenjin Zhao,Elliott Runburg,David Cobden,D. A. Pesin###

Magnetotransport on quantum spin Hall edge coupled to bulk midgap states. We consider magnetotransport on a helical edge of a quantum spin Hall
insulator, in the presence of bulk midgap states ``side-coupled" to the edge.
In the presence of a magnetic field, the midgap levels are spin-split, and
hybridization of these levels with the itinerant edge states leads to
backscattering, and the ensuing increase in the resistance. We show that there
is a singular cusp-like contribution to the positive magnetoresistance stemming
from resonant midgap states weakly coupled to the edge. The singular behavior
persists for both coherent and incoherent edge transport regimes. We use the
developed theory to fit the experimental data for the magnetoresistance for
monolayer WTe$_2$ at liquid helium temperatures. The results of the fitting
suggest that the cusp-like behavior of the resistance in weak magnetic fields
observed in experiments on monolayer WTe$_2$ with long edge channels might
indeed be explained by hybridization of the helical edge states with spin-split
bulk midgap states. In particular, the dependence of the magnetoresistance on
the direction of the external magnetic field is well described by the
incoherent edge transport theory, at the same time being quite distinct from
the one expected for a magnetic-field-induced edge gap.

###Magnetoresistance in Noncentrosymmetric Two-dimensional Systems|Azadeh Faridi,Reza Asgari###

Magnetoresistance in Noncentrosymmetric Two-dimensional Systems. The valley-contrasting geometric features of electronic wave functions
manifested in Berry curvature and orbital magnetic moment have profound
consequences on magnetotransport properties in both three- and two-dimensional
systems. Although the importance of employing
beyond-relaxation-time-approximation methods and intervalley scatterings in
collision integral has been confirmed in three dimensions, they have been
widely overlooked in previous studies on two-dimensional multi-valley systems.
Here, we revisit the issue of weak-field magnetoresistance in two-dimensional
multi-valley systems with broken inversion symmetry. We provide an exact
solution to the Boltzmann equation and demonstrate that the inclusion of
in-scattering terms in the collision integral can change the sign of the
magnetoresistance in high-density regime. With an initial valley polarization,
we also predict an orbital magnetic moment-induced intrinsic contribution to
Hall conductivity in the time-reversal-broken situation, which is consistently
negative, and in contrast to the anomalous Hall term, it does not depend on the
polarization sign. Depending on which valley has the excess charge, our
calculations show that a completely various behavior is exhibited in the
magnetoresistance which can be considered as a valley-polarization probe in the
experiment.

###Planar Hall effect, Anisotropic magnetoresistance and thermal transport studies of Ag doped PdTe$_2$|Sonika,Sunil Gagwar,C. S. Yadav###

Planar Hall effect, Anisotropic magnetoresistance and thermal transport studies of Ag doped PdTe$_2$. Observation of planar Hall effect (PHE) in topological materials has been a
subject of great interest in the recent years, owing to its intriguing origin
because of the observation of chiral anomaly and anisotropic orbital
magnetoresistance (MR). Here, we report the planar Hall effect,
magnetoresistance and thermal transport properties (Seebeck and Nernst
coefficients) on the Ag intercalated PdTe$_2$. We observed positive
longitudinal magnetoresistance, linear field dependence of the amplitude of PHE
($\Delta\rho$), and the absence of electric and chiral charge coupling. Our
observations alongwith prolate pattern in the parametric plot ($\rho_{xy}$ vs.
$\rho_{xx}$) suggest the absence of chiral anomaly. These results in congruence
with the results on PdTe$_2$ and Cu$_{0.05}$PdTe$_2$ point towards the
importance of Fermi surface anisotropies in understanding the origin of PHE.
Further, we have shown the Seebeck ($\it{S}$) and Nernst ($\nu$) coefficients
for PdTe$_2$ and Cu and Ag intercalated compounds. We observed two phonon drag
peaks (at $\sim{9}$ K, and $\sim{50}$ K) for these compounds. The estimated
value of Fermi energy for Ag$_{0.05}$PdTe$_2$ is $\sim$ 3 times that of
PdTe$_2$.

###High magnetic field evolution of the in-plane angular magnetoresistance of electron-doped Sr1-xLaxCuO2 in the normal state|V. P. Jovanović,H. Raffy,Z. Z. Li,G. Reményi,P. Monceau###

High magnetic field evolution of the in-plane angular magnetoresistance of electron-doped Sr1-xLaxCuO2 in the normal state. We studied the in-plane angular magnetoresistance (AMR), in the normal state,
of underdoped superconducting Sr1-xLaxCuO2 , which has the simplest crystal
structure among cuprates. The measurements of two underdoped thin films with
different dopings were performed in intense magnetic field H (up to 22 T). The
longitudinal magnetoresistance at temperature T is negative and scales with
H/T. For both samples, the AMR is anisotropic and shows an unexpected
dependence on H intensity. While at the low magnetic field, one observes
essentially twofold AMR oscillations for the more doped sample, fourfold ones
start to grow under the high magnetic field, resulting in the coexistence of
the two. For the less doped film at the low magnetic field, both twofold and
fourfold AMR components exist. With the increase of the magnetic field, the
fourfold component survives a pi/4 phase shift, during which its amplitude
vanishes, at a magnetic field Hc such as: 16 T < Hc < 17 T. As a result, at the
high magnetic field above Hc, the angular dependence of the in-plane
magnetoresistance turns out to be the same for both samples. We tentatively
ascribe the above features to the presence of anti-ferromagnetism in the CuO2
planes of underdoped Sr1-xLaxCuO2.

###Ambient and high-pressure electrical transport and structural investigations of magnetic Weyl semimetal PrAlGe|U. Dutta,P. Král,M. Míšek,B. Joseph,J. Kaštil###

Ambient and high-pressure electrical transport and structural investigations of magnetic Weyl semimetal PrAlGe. We present ambient and high-pressure electrical transport and structural
properties of recently discovered magnetic Weyl semimetal PrAlGe. Electrical
resistivity at ambient pressure shows an anomaly at $T_C$ = 15.1 K related to
the ferromagnetic transition. Anomalous Hall effect (AHE) is observed below
$T_C$. We observe a 1.4 K/GPa increase of $T_C$ with pressure, resulting in
$T_C$ $\approx$ 47 K at 23.0 GPa. Strong competition between Lorentz force and
spin-scattering mechanisms suppressed by magnetic field is deduced from the
magnetoresistance measurements under pressure. As in the ambient pressure case,
the AHE is found to be present below $T_C$ up to the highest applied pressure.
We observe a clear anomaly in the pressure dependence of $T_C$,
magnetoresistance and Hall effect at 12.5 GPa suggesting the occurrence of a
pressure-induced electronic transition at this pressure. X-ray diffraction
(XRD) experiment under pressure revealed the lattice structure to be stable up
to $\sim$19.6 GPa with the absence of any symmetry changing structural phase
transition from the initial $I4_1md$ structure. Careful analysis of the
pressure dependent XRD data reveal an isostructural transition near 11 GPa.
Observed isostructural transition may be related to the pressure-induced
electronic transition deduced from the magnetoresistance and Hall effect data.

###Magneto-electrodynamics at high frequencies in the antiferromagnetic and superconducting states of DyNi_2B_2C|Durga P. Choudhury,H. Srikanth,S. Sridhar,; P. C. Canfield###

Magneto-electrodynamics at high frequencies in the antiferromagnetic and superconducting states of DyNi_2B_2C. We report the observation of novel behaviour in the radio frequency (rf) and
microwave response of DyNi_2B_2C over a wide range of temperature (T) and
magnetic field (H) in the antiferromagnetic (AFM) and superconducting (SC)
states. At microwave frequencies of 10 GHz, the T dependence of the surface
impedance Z_s=R_s+iX_s was measured which yields the T dependence of the
complex conductivity \sigma_1-i\sigma_2 in the SC and AFM states. At radio
frequencies (4 MHz), the H and T dependence of the penetration depth
\lambda(T,H) were measured. The establishment of antiferromagnetic order at
T_N=10.3 K results in a marked decrease in the scattering of charge carriers,
leading to sharp decreases in R_s and X_s. However, R_s and X_s differ from
each other in the AFM state. We show that the results are consistent with
conductivity relaxation whence the scattering rate becomes comparable to the
microwave frequency. The rf measurements yield a rich dependence of the
scattering on the magnetic field near and below T_N. Anomalous decrease of
scattering at moderate applied fields is observed at temperatures near and
above T_N, and arises due to a crossover from a negative magnetoresistance
state, possibly associated with a loss of spin disorder scattering at low
fields, to a positive magnetoresistance state associated with the metallic
nature. The normal state magnetoresistance is positive at all temperatures for
\mu_0H>2T and at all fields for T>15K. Several characteristic field and
temperature scales associated with metamagnetic transitions (H_M1(T), H_M2(T))
and onset of spin disorder H_D(T), in addition to T_c, T_N and H_c2(T) are
observed in the rf measurements.

###Magnetic field-dependent interplay between incoherent and Fermi liquid transport mechanisms in low-dimensional tau phase organic conductors|K. Storr,L. Balicas,J. S. Brooks,D. Graf,G. C. Papavassiliou###

Magnetic field-dependent interplay between incoherent and Fermi liquid transport mechanisms in low-dimensional tau phase organic conductors. We present an electrical transport study of the 2-dimensional (2D) organic
conductor tau-(P-(S,S)-DMEDT-TTF)_2(AuBr)_2(AuBr_2)_y (y = 0.75) at low
temperatures and high magnetic fields. The inter-plane resistivity rho_zz
increases with decreasing temperature, with the exception of a slight anomaly
at 12 K. Under a magnetic field B, both rho_zz and the in-plane resistivity
plane rho_xx show a pronounced negative and hysteretic magnetoresistance with
Shubnikov de Haas (SdH)oscillations being observed in some (high
quality)samples above 15 T. Contrary to the predicted single, star-shaped,
closed orbit Fermi surface from band structure calculations (with an expected
approximate area of 12.5% of A_FBZ), two fundamental frequencies F_l and F_h
are detected in the SdH signal. These orbits correspond to 2.4% and 6.8% of the
area of the first Brillouin zone(A_FBZ), with effective masses F_l = 4.0 +/-
0.5 and F_h = 7.3 +/- 0.1. The angular dependence, in tilted magnetic fields of
F_l and F_h, reveals the 2D character of the FS and Angular dependent
magnetoresistance (AMRO) further suggests a FS which is strictly 2-D where the
inter-plane hopping t_c is virtually absent or incoherent. The Hall constant
R_xy is field independent, and the Hall mobility increases by a factor of 3
under moderate magnetic fields. Our observations suggest a unique physical
situation where a stable 2D Fermi liquid state in the molecular layers are
incoherently coupled along the least conducting direction. The magnetic field
not only reduces the inelastic scattering between the 2D metallic layers, but
it also reveals the incoherent nature of interplane transport in the AMRO
spectrum. The apparent ferromagnetism of the hysteretic magnetoresistance
remains an unsolved problem.

###Evidence and Characterization of a SDW Transition in Na0.75CoO2 Single Crystals|B. C. Sales,R. Jin,K. A. Affholter,P. Khalifah,G. M. Veith,D. Mandrus###

Evidence and Characterization of a SDW Transition in Na0.75CoO2 Single Crystals. The magnetic, thermal and transport properties of Na0.75CoO2 single crystals
grown by the floating zone (FZ) method are reported. Magnetic susceptibility,
resistivity, magnetoresistance, and heat capacity data from these crystals
indicate a bulk phase transition at T1 = 22 K. These data are most consistent
with the formation of an antiferromagnet spin-density-wave (SDW) at 22 K with
the easy axis for magnetization nearly along the c axis. Weak and soft
ferromagnetism is observed for applied magnetic fields less than 0.5 T, which
suggests a slight canting of the SDW magnetization with respect to the c axis.
The jump in the heat capacity at the SDW transition is 0.45 J/K-mole-Co or
about 50% of the value expected from mean-field weak-coupling theory. The
reduced jump and the decrease in the resistivity below T1 are consistent with a
gap for only part of the Fermi surface. The magnetoresistance is small at the
SDW transition but increases in both directions reaching a value of 100% at 2 K
for applied fields of 8 Tesla. The magnetoresistance data imply that the
mobility of the remaining carriers is large and increases below T1. The
observation of a SDW transition in this material is found to be sensitive to
the preparation conditions and the degree of order in the Na layers. No SDW
transition is observed in our polycrystalline powder with the same nominal
composition (Na0.75CoO2) and lattice constants. Differential scanning
calorimetry data, however, show distinct differences between the powder and
crystal, suggesting a higher degree of order in the Na layers within the
crystal. The crystal exhibits a sharp phase transition at T2 = 340 K while for
the powder this transition is smeared over the temperature range from 250 to
310 K.

###Magnetoresistance and collective Coulomb blockade in super-lattices of ferromagnetic CoFe nanoparticles|R. P. Tan,J. Carrey,C. Desvaux,L. -M. Lacroix,P. Renaud,B. Chaudret,M. Respaud###

Magnetoresistance and collective Coulomb blockade in super-lattices of ferromagnetic CoFe nanoparticles. We report on transport properties of millimetric super-lattices of CoFe
nanoparticles surrounded by organic ligands. R(T)s follow R(T) =
R_0.exp(T/T_0)^0.5 with T_0 ranging from 13 to 256 K. At low temperature I(V)s
follow I=K[(V-V_T)/V_T]^ksi with ksi ranging 3.5 to 5.2. I(V) superpose on a
universal curve when shifted by a voltage proportional to the temperature.
Between 1.8 and 10 K a high-field magnetoresistance with large amplitude and a
strong voltage-dependence is observed. Its amplitude only depends on the
magnetic field/temperature ratio. Its origin is attributed to the presence of
paramagnetic states present at the surface or between the nanoparticles. Below
1.8 K, this high-field magnetoresistance abruptly disappears and inverse
tunnelling magnetoresistance is observed, the amplitude of which does not
exceed 1%. At this low temperature, some samples display in their I(V)
characteristics abrupt and hysteretic transitions between the Coulomb blockade
regime and the conductive regime. The increase of the current during these
transitions can be as high as a factor 30. The electrical noise increases when
the sample is near the transition. The application of a magnetic field
decreases the voltage at which these transitions occur so magnetic-field
induced transitions are also observed. Depending on the applied voltage, the
temperature and the amplitude of the magnetic field, the magnetic-field induced
transitions are either reversible or irreversible. These abrupt and hysteretic
transitions are also observed in resistance-temperature measurements. They
could be the soliton avalanches predicted by Sverdlov et al. [Phys. Rev. B 64,
041302 (R), 2001] or could also be interpreted as a true phase transition
between a Coulomb glass phase to a liquid phase of electrons.

###Evidence of electronic phase arrest and glassy ferromagnetic behaviour in (Nd0.4Gd0.3)Sr0.3MnO3 manganite : Comparative study between bulk and nanometric samples|S. Kundu,T. K. Nath###

Evidence of electronic phase arrest and glassy ferromagnetic behaviour in (Nd0.4Gd0.3)Sr0.3MnO3 manganite : Comparative study between bulk and nanometric samples. The effect of doping of rare earth Gd 3+ ion replacing Nd 3+ in
Nd0.7Sr0.3MnO3 is investigated in details. Measurements of resistivity,
magnetoresistance, magnetization, linear and non linear ac magnetic
susceptibility on chemically synthesized (Nd0.7-xGdx)Sr0.3MnO3 shows various
interesting features with doping level x=0.3. Comparative study has been
carried out between a bulk and a nanometric sample (grain size ~ 60 nm)
synthesized from the same as prepared powder to maintain identical
stoichiometry. Resistivity of the samples shows strong dependence on the
magnetic field - temperature history. The magnetoresistance of the samples also
show strong irreversibility with respect to sweeping of the field between
highest positive and negative values. Moreover, resistivity is found to
increase with time after field cooling and then switching off the field. All
these phenomena have been attributed to phase separation effect and arrest of
phases in the samples. Furthermore, the bulk sample displays a spin glass like
behaviour as evident from frequency dependence of linear ac magnetic
susceptibility and critical divergence of the nonlinear ac magnetic
susceptibility. The experimentally obtained characteristic time t after
dynamical scaling analysis of the frequency dependence of the ac susceptibility
is found to be t=10-17 s which implies that the system is different from a
canonical spin glass. An unusual frequency dependence of the second harmonic of
ac susceptibility around the magnetic transition temperature led us to
designate the magnetic state of the sample to be glassy ferromagnetic. On
reduction of grain size low field magnetoresistance and phase arrest phenomena
are found to enhance but the glassy state is observed to be destabilized in the
nanometric sample.

###Charge transport in Ho$_x$Lu$_{1-x}$B$_{12}$: Separating Positive and Negative Magnetoresistance in Metals with Magnetic Ions|N. E. Sluchanko,A. L. Khoroshilov,M. A. Anisimov,A. N. Azarevich,A. V. Bogach,V. V. Glushkov,S. V. Demishev,V. N. Krasnorussky,V. V. Voronov,N. Yu. Shitsevalova,V. B. Filippov,A. V. Levchenko,G. Pristas,S. Gabani,K. Flachbart###

Charge transport in Ho$_x$Lu$_{1-x}$B$_{12}$: Separating Positive and Negative Magnetoresistance in Metals with Magnetic Ions. The magnetoresistance (MR) $\Delta \rho/\rho$ of cage-glass compound
Ho$_x$Lu$_{1-x}$B$_{12}$ with various concentration of magnetic holmium ions
($x$$\leq$0.5) has been studied in detail concurrently with magnetization M(T)
and Hall effect investigations on high quality single crystals at temperatures
1.9-120 K and in magnetic field up to 80 kOe. The undertaken analysis of
$\Delta\rho/\rho$ allows us to conclude that the large negative
magnetoresistance (nMR) observed in vicinity of Neel temperature is caused by
scattering of charge carriers on magnetic clusters of Ho$^{3+}$ ions, and that
these nanosize regions with AF exchange inside may be considered as short range
order AF domains. It was shown that the Yosida relation $-\Delta
\rho/\rho$$\sim$$M^2$ provides an adequate description of the nMR effect for
the case of Langevin type behavior of magnetization. Moreover, a reduction of
Ho-ion effective magnetic moments in the range 3-9$\mu_B$ was found to develop
both with temperature lowering and under the increase of holmium content. A
phenomenological description of the large positive quadratic contribution
$\Delta \rho/\rho$$\sim$$\mu_D^2 H^2$ which dominates in
Ho$_x$Lu$_{1-x}$B$_{12}$ in the intermediate temperature range 20-120 K allows
to estimate the drift mobility exponential changes $\mu_D$$\sim$$T^{-a}$ with
$a$=1.3-1.6 depending on Ho concentration. An even more comprehensive behavior
of magnetoresistance has been found in the AF state of Ho$_x$Lu$_{1-x}$B$_{12}$
where an additional linear positive component was observed and attributed to
charge carriers scattering on the spin density wave (SDW). High precision
measurements of $\Delta\rho/\rho=f(H,T)$ have allowed us also to reconstruct
the magnetic H-T phase diagram of Ho$_{0.5}$Lu$_{0.5}$B$_{12}$ and to resolve
its magnetic structure as a superposition of 4f (based on localized moments)
and 5d (based on SDW) components.

###Giant magnetoresistance in electrodeposited Co-Cu/Cu multilayers: origin of absence of oscillatory behaviour|I. Bakonyi,E. Simon,B. G. Tóth,L. Péter,L. F. Kiss###

Giant magnetoresistance in electrodeposited Co-Cu/Cu multilayers: origin of absence of oscillatory behaviour. A detailed study of the evolution of the magnetoresistance was performed on
electrodeposited Co/Cu multilayers with Cu layer thicknesses ranging from 0.5
nm to 4.5 nm. For thin Cu layers (up to 1.5 nm), anisotropic magnetoresistance
(AMR) was observed whereas multilayers with thicker Cu layers exhibited clear
giant magnetoresistance (GMR) behaviour. The GMR magnitude increased up to
about 3.5 to 4 nm Cu layer thickness and slightly decreased afterwards.
According to magnetic measurements, all samples exhibited ferromagnetic (FM)
behaviour. The relative remanence turned out to be about 0.75 for both AMR and
GMR type multilayers. This clearly indicates the absence of an
antiferromagnetic (AF) coupling between adjacent magnetic layers for Cu layers
even above 1.5 nm where the GMR effect occurs. The AMR behaviour at low spacer
thicknesses indicates the presence of strong FM coupling (due to, e.g.,
pin-holes in the spacer and/or areas of the Cu layer where the layer thickness
is very small). With increasing spacer thickness, the pin-hole density reduces
and/or the layer thickness uniformity improves which both lead to a weakening
of the FM coupling. This improvement in multilayer structure quality results in
a better separation of magnetic layers and the weaker coupling (or complete
absence of interlayer coupling) enables a more random magnetization orientation
of adjacent layers, all this leading to an increase of the GMR. Coercive field
and zero-field resistivity measurements as well as the results of a structural
study reported earlier on the same multilayers provide independent evidence for
the microstructural features established here. The large GMR reported
previously on such Co/Cu multilayers at Cu layer thicknesses around 1 nm can be
attributed to the presence of a fairly large superparamagnetic (SPM) fraction
rather than being due to a strong AF coupling.

###Planar Hall-effect, Anomalous planar Hall-effect, and Magnetic Field-Induced Phase Transitions in TaAs|Q. R. Zhang,B. Zeng,Y. C. Chiu,R. Schoenemann,S. Memaran,W. Zheng,D. Rhodes,K. -W. Chen,T. Besara,R. Sankar,F. Chou,G. T. McCandless,J. Y. Chan,N. Alidoust,S. -Y. Xu,I. Belopolski,M. Z. Hasan,F. F. Balakirev,L. Balicas###

Planar Hall-effect, Anomalous planar Hall-effect, and Magnetic Field-Induced Phase Transitions in TaAs. We evaluate the topological character of TaAs through a detailed study of the
angular, magnetic-field and temperature dependence of its magnetoresistivity
and Hall-effect(s), and of its bulk electronic structure through quantum
oscillatory phenomena. At low temperatures, and for fields perpendicular to the
electrical current, we extract an extremely large Hall angle $\Theta_H$ at
higher fields, that is $\Theta_H \sim 82.5^{\circ}$, implying a very pronounced
Hall signal superimposed into its magnetoresistivity. For magnetic fields and
electrical currents perpendicular to the \emph{c}-axis we observe a very
pronounced planar Hall-effect, when the magnetic field is rotated within the
basal plane. This effect is observed even at higher temperatures, i.e. as high
as $T = 100$ K, and predicted recently to result from the chiral anomaly among
Weyl points. Superimposed onto this planar Hall, which is an even function of
the field, we observe an anomalous planar Hall-signal akin to the one reported
for that is an odd function of the field. Below 100 K, negative longitudinal
magnetoresistivity (LMR), initially ascribed to the chiral anomaly and
subsequently to current inhomogeneities, is observed in samples having
different geometries and contact configurations, once the large Hall signal is
subtracted. Our measurements reveal a phase transition upon approaching the
quantum limit that leads to the reconstruction of the FS and to the concomitant
suppression of the negative LMR indicating that it is intrinsically associated
with the Weyl dispersion at the Fermi level. For fields along the \emph{a}-axis
it also leads to a pronounced hysteresis pointing to a field-induced electronic
phase-transition. This collection of unconventional tranport observations
points to the prominent role played by the axial anomaly among Weyl nodes.

###Spin transport in Si-based spin metal-oxide-semiconductor field-effect transistors: Spin drift effect in the inversion channel and spin relaxation in the n+-Si source/drain regions|Shoichi Sato,Masaaki Tanaka,Ryosho Nakane###

Spin transport in Si-based spin metal-oxide-semiconductor field-effect transistors: Spin drift effect in the inversion channel and spin relaxation in the n+-Si source/drain regions. We have experimentally and theoretically investigated the electron spin
transport and spin distribution at room temperature in a Si two-dimensional
(2D) inversion channel of back-gate-type spin metal-oxide-semiconductor
field-effect transistors (spin MOSFETs). The magnetoresistance ratio of the
spin MOSFET with a channel length of 0.4$\mu$m was increased by a factor of 6
from that in our previous paper [Phys. Rev. B 99, 165301 (2019)] by lowering
the parasitic resistances at the source/drain junctions with
highly-phosphorus-doped n+-Si regions and by increasing the lateral electric
field in the channel along the electron transport, called "spin drift". Clear
Hanle signals with some oscillation peaks were observed for the spin MOSFET
with a channel length of 10 $\mu$ m under the lateral electric field,
indicating that the effective spin diffusion length is dramatically enhanced by
the spin drift. By taking into account the n+-Si regions and the spin drift in
the channel, one-dimensional analytic functions were derived for analyzing the
effect of the spin drift on the spin transport through the channel and these
functions were found to explain almost all the experimental results. From the
calculated spin current and spin distribution, it was revealed that almost all
the spins are unflipped during the spin-drift-assisted transport through the
0.4-$\mu$m-long inversion channel, but the most part of the injected spins from
the source electrode are relaxed in the n+-Si regions of both the source and
drain junctions. This means that the spin drift is useful and precise design of
the device structure is essential to obtain a higher magnetoresistance ratio.
Furthermore, we showed that the effective spin resistances that are introduced
in this study are very helpful to understand how to improve the
magnetoresistance ratio of spin MOSFETs for practical use.

###Magnetotransport in a model of a disordered strange metal|Aavishkar A. Patel,John McGreevy,Daniel P. Arovas,Subir Sachdev###

Magnetotransport in a model of a disordered strange metal. Despite much theoretical effort, there is no complete theory of the 'strange'
metal state of the high temperature superconductors, and its
linear-in-temperature, $T$, resistivity. Recent experiments showing an
unexpected linear-in-field, $B$, magnetoresistivity have deepened the puzzle.
We propose a simple model of itinerant electrons, interacting via random
couplings with electrons localized on a lattice of quantum 'dots' or 'islands'.
This model is solvable in a large-$N$ limit, and can reproduce observed
behavior. The key feature of our model is that the electrons in each quantum
dot are described by a Sachdev-Ye-Kitaev model describing electrons without
quasiparticle excitations. For a particular choice of the interaction between
the itinerant and localized electrons, this model realizes a controlled
description of a diffusive marginal-Fermi liquid (MFL) without momentum
conservation, which has a linear-in-$T$ resistivity and a $T \ln T$ specific
heat as $T\rightarrow 0$. By tuning the strength of this interaction relative
to the bandwidth of the itinerant electrons, we can additionally obtain a
finite-$T$ crossover to a fully incoherent regime that also has a linear-in-$T$
resistivity. We show that the MFL regime has conductivities which scale as a
function of $B/T$; however, its magnetoresistance saturates at large $B$. We
then consider a macroscopically disordered sample with domains of MFLs with
varying densities of electrons. Using an effective-medium approximation, we
obtain a macroscopic electrical resistance that scales linearly in the magnetic
field $B$ applied perpendicular to the plane of the sample, at large $B$. The
resistance also scales linearly in $T$ at small $B$, and as $T f(B/T)$ at
intermediate $B$. We consider implications for recent experiments reporting
linear transverse magnetoresistance in the strange metal phases of the
pnictides and cuprates.

###Magnetoresistance of a three-dimensional Dirac gas|Viktor Könye,Masao Ogata###

Magnetoresistance of a three-dimensional Dirac gas. We study the transversal magnetoconductivity and magnetoresistance of a
massive Dirac fermion gas. This can be used as a simple model for gapped Dirac
materials. In the zero-mass limit, the case of gapless Dirac semimetals is also
studied. In the case of Weyl semimetals, to reproduce the nonsaturating linear
magnetoresistance seen in experiments, the use of screened charged impurities
is inevitable. In this paper, these are included using the first Born
approximation for the self-energy. The screening wave number is calculated
using the random phase approximation with the polarization function taking into
account the electron-electron interaction. The Hall conductivity is calculated
analytically in the case of no impurities and is shown to be perfectly
inversely proportional to the magnetic field. Thus the magnetic field
dependence of the magnetoresistance is mainly determined by $\sigma_{xx}$. We
show that in the extreme quantum limit at very high magnetic fields the gapped
Dirac materials are expected to have $\sigma_{xx}\propto B^{-3}$ leading to
$\varrho_{xx}\propto B^{-1}$, in contrast with the gapless case where
$\sigma_{xx}\propto B^{-1}$ and $\varrho_{xx}\propto B$. At lower fields, we
find that the effect of the mass term is negligible and in the region of the
Shubnikov-de Haas oscillations the two systems behave almost identically. We
suggest a phenomenological scattering rate that is able to reproduce the linear
behavior at the oscillating region. We show that in the case of the scattering
rate calculated using the Born approximation, the strength of the relative
permittivity and the density of impurities affects the magnetic field
dependence of the conductivity significantly.

###Role of f-d exchange interaction and Kondo scattering in Nd doped pyrochlore Iridate (Eu1-xNdx)2Ir2O7|Sampad Mondal,M. Modak,B. Maji,M. K. Ray,S. Mandal,Swapan K. Mandal,M. Sardar,S. Banerjee###

Role of f-d exchange interaction and Kondo scattering in Nd doped pyrochlore Iridate (Eu1-xNdx)2Ir2O7. We report study of magnetization, resistivity, magnetoresistance and specific
heat of the pyrochlore Iridate (Eu1-xNdx)2Ir2O7 with x=0.0, 0.5 and 1.0, where
spin orbit coupling, electronic correlation, magnetic frustration and Kondo
scattering coexists. Metal insulator transition temperature (T_MI) decrease
with increase in Nd content but always coincides with magnetic irreversibility
temperature (field induced moment). Resistivity below T_MI do not fit with
either activated (gap) or to any power law (gapless) dependence. The Curie
constant show surprising result, that Nd induces singlet correlation (reduction
of para-moment) in Ir sublattice. Magnetoresistance is negative at low
temperatures below 10 K and increases strongly with increase in x and vary
quadratically with field switching over to linear dependence above 50 kOe. Low
temperature specific heat shows Schottky peak, coming from Nd moments, showing
existence of doublet split in Nd energy level, arising from f-d exchange
interaction. All materials show presence of a linear specific heat in the
insulating region. The coefficient of linear specific heat for x= 0.0 does not
vary with external magnetic field but varies superlinearly for x = 1.0
materials. We argue that linear specific heat probably rules out weakly
correlated phases like Weyl fermions. We propose that with the introduction of
Nd at Eu site the system evolves from chiral spin liquid with gapless spinon
excitations with a very small charge gap to Kondo type interaction superposed
on chiral spin liquid coexisting with long range antiferromagnetic ordering.
Huge increase of magnetoresistance with increase in Nd concentrations shows
importance of Kondo scattering in the chiral spin liquid material by rare earth
moments.

###Magnetic frustration and paramagnetic state transport anomalies in Ho4RhAl and Er4RhAl: Possible test cases for newly identified roles of itinerant electrons|Ram Kumar,E. V. Sampathkumaran###

Magnetic frustration and paramagnetic state transport anomalies in Ho4RhAl and Er4RhAl: Possible test cases for newly identified roles of itinerant electrons. We report the results of magnetic, heat-capacity, electrical and
magnetoresistance measurements on Ho4RhAl and Er4RhAl, characterized by 3 sites
for rare-earths (R). Antiferromagnetic ordering sets in at (T_N =) about 8.8
and 4.0 K respectively. While Ho compound appears to enter into a complex
spin-glass phase at T less thanT_N (at nearly 5 K), spin-glass component
appears to set in essentially almost at T_N for the Er case. The loss of the
spin-disorder contribution in the magnetically ordered state is not pronounced,
mimicking that in Gd2PdSi3, a compound which now attracts interest in the area
of topological Hall effect and magnetic skyrmions, indicating complex Fermi
surface. There is a minimum in the temperature dependence of electrical
resistivity in the case of only Ho above T_N, but significant negative
magnetoresistance is observed over a wide temperature range in the paramagnetic
state increasing with decreasing temperature for both the cases. This finding
establishes that these compounds belong to a select group of intermetallics in
which spin-disorder contribution apparently increases gradually as one
approaches respective TN with decreasing temperature. This could be an
experimental signature for the effect due to classical spin-liquid above T_N.
In view of these properties analogous to those of Gd2PdSi3, it is of interest
to investigate these 4:1:1 compounds further to understand possible
unconventional roles of itinerant electrons, not only in the magnetically
ordered state but also in the paramagnetic state, predicted by some theories in
recent years for which this Gd compound is considered to be a classic
example.Besides, magnetoresistance and isothermal entropy change
(magnetocaloric effect) track each other.

###Transport Properties of the Kondo Lattice Model in the Limit $S=\infty$ and $D=\infty$|Nobuo Furukawa###

Transport Properties of the Kondo Lattice Model in the Limit $S=\infty$ and $D=\infty$. The Kondo lattice model with Hund's ferromagnetic spin coupling is
investigated as a microscopic model of the perovskite-type 3d transition-metal
oxide La$_{1-x}$Sr$_x$MnO$_3$. In the classical spin limit $S=\infty$ and the
infinite-dimensional limit $D=\infty$, the one-body Green's function is
calculated exactly. Transport properties of the system in the presence of
magnetic fields are calculated. The giant magnetoresistance of this model,
which is in a good agreement with the experimental data of
La$_{1-x}$Sr$_x$MnO$_3$, is explained by the spin disorder scattering process.

###The Anomalous Hall Effect in YBa$_2$Cu$_3$O$_7$|Branko P. Stojkovic,David Pines###

The Anomalous Hall Effect in YBa$_2$Cu$_3$O$_7$. The temperature dependence of the normal state Hall effect and
magnetoresistance in YBa$_2$Cu$_3$O$_7$ is investigated using the Nearly
Antiferromagnetic Fermi Liquid description of planar quasiparticles. We find
that highly anisotropic scattering at different regions of the Fermi surface
gives rise to the measured anomalous temperature dependence of the resistivity
and Hall coefficient while yielding the universal temperature dependence of the
Hall angle observed for both clean and dirty samples. This universality is
shown to arise from the limited momentum transfers available for the anomalous,
spin fluctuation scattering and is preserved for any system with strong
antiferromagnetic correlations.

###Magnetic and Transport Properties of the Kondo Lattice Model with Ferromagnetic Exchange Coupling|Nobuo Furukawa###

Magnetic and Transport Properties of the Kondo Lattice Model with Ferromagnetic Exchange Coupling. The Kondo lattice model with Hund's ferromagnetic spin coupling is
investigated as a microscopic model of the perovskite-type $3d$ manganese oxide
(R,A)MnO$_3$ where $R$ and $A$ are rare earth element and alkaline earth
element, respectively. We take the classical spin limit $S=\infty$ for the
simplicity of the calculation, since the quantum exchange process seems to be
irrelevant in the high temperature paramagnetic phase. Magnetic and transport
properties of the system are calculated. In the hole doped systems,
ferromagnetic instabilities are observed as the temperature is lowered. The
giant magnetoresistance of this model is in excellent agreement with the
experimental data of (La,Sr)MnO$_3$.

###Double Degeneracy and Jahn-Teller Effects in CMR Perovskites|Jun Zang,A. R. Bishop,H. Roder###

Double Degeneracy and Jahn-Teller Effects in CMR Perovskites. Jahn-Teller (JT) electron-phonon coupling effects in the colossal
magnetoresistance perovskite compounds $La_{1-x}A_xMnO_3$ are investigated.
Electron-electron correlations between two degenerate Mn $e_g$ orbitals are
studied in the Gutzwiller approximation. The static JT distortion and
antiadiabatic polaron effects are studied in a modified Lang-Firsov
approximation. We find that (i) the electron or hole character of the charge
carrier depends on the static JT distortion, and (ii) due to the two-component
nature of the JT coupling, fluctuations in the JT distortion direction
contribute to the charge transport in similar fashion as the local spins.

###Theory on the Temperature Dependence of Giant Magnetoresistance|Hideo Hasegawa###

Theory on the Temperature Dependence of Giant Magnetoresistance. The temperature dependence of the giant magnetoresistance (GMR) for currents
parallel and perpendicular to the multilayer plane, is discussed by taking
account of the random exchange potentials, phonon scatterings and spin
fluctuations. The effect of spin fluctuations, which plays an important role at
finite temperatures, is included by means of the static functional-integral
method developed previously by the present author. Our model calculations well
explain the observed features of the parallel and perpendicular GMR of Fe/Cr
and Co/Cu multilayers recently reported by Gijs {\it et al}.

###Nonlinear Dynamics of Composite Fermions in Nanostructures|R. Fleischmann,T. Geisel,C. Holzknecht,R. Ketzmerick###

Nonlinear Dynamics of Composite Fermions in Nanostructures. We outline a theory describing the quasi-classical dynamics of composite
fermions in the fractional quantum Hall regime in the potentials of arbitrary
nanostructures. By an appropriate parametrization of time we show that their
trajectories are independent of their mass and dispersion. This allows to study
the dynamics in terms of an effective Hamiltonian although the actual
dispersion is as yet unknown. The applicability of the theory is verified in
the case of antidot arrays where it explains details of magnetoresistance
measurements and thus confirms the existence of these quasiparticles.

###On the Fermi Liquid to Polaron Crossover II: Double Exchange and the Physics of "Colossal" Magnetoresistance|A. J. Millis,R. Mueller,Boris I. Shraiman###

On the Fermi Liquid to Polaron Crossover II: Double Exchange and the Physics of "Colossal" Magnetoresistance. We use the dynamical mean field method to study a model of electrons
Jahn-Teller coupled to localized classical oscillators and ferromagnetically
coupled to ``core spins'', which, we argue, contains the essential physics of
the ``colossal magnetoresistance'' manganites $Re_{1-x} A_x MnO_3$. We
determine the different regimes of the model and present results for the
temperature and frequency dependence of the conductivity, the electron spectral
function and the root mean square lattice parameter fluctuations. We compare
our results to data, and give a qualitative discussion of important physics not
included in the calculation. Extensive use is made of results from a companion
paper titled: ``On the Fermi Liquid to Polaron Crossover I: General Results''.

###Unconventional Ferromagnetic Transition in La1-xCaxMnO3|J. W. Lynn,R. W. Erwin,J. A. Borchers,Q. Huang,A. Santoro,J-L. Peng,Z. Y. Li###

Unconventional Ferromagnetic Transition in La1-xCaxMnO3. Neutron scattering has been used to study the magnetic correlations and long
wavelength spin dynamics of La1-xCaxMnO3 in the ferromagnetic regime
(0<=x<1/2). For x=1/3 (Tc=250K) where the magnetoresistance effects are largest
the system behaves as an ideal isotropic ferromagnet at low T, with a gapless
(<0.04meV) dispersion relation E=Dq^2 and D(T=0)~170 meV-A-1. However, an
anomalous strongly-field-dependent diffusive component develops above ~200K and
dominates the fluctuation spectrum as T approaches Tc. This component is not
present at lower x.

###Electronic and Magnetic States in the Giant Magneto-resistive Compounds|C. M. Varma###

Electronic and Magnetic States in the Giant Magneto-resistive Compounds. The paramagnetic insulator to ferromagnetic metal transition in Lanthanum
manganites and the associated magnetoresistive phenomena is treated by
considering the localization due to random hopping induced by slowly
fluctuating spin configurations and electron-electron interactions. The
transition temperature and its variation with composition is derived. The
primary effect of the magnetic field on transport is to alter the localization
length, an effect which is enhanced as the magnetic susceptibility increases.
Expressions for the conductivity, its variation with magnetic field, and its
connection with magnetic susceptibility in the paramagnetic phase are given and
can be tested with further experiments.

###Resistive transport in a mesoscopic proximity superconductor|P. Charlat,H. Courtois,Ph. Gandit,D. Mailly,A. F. Volkov,B. Pannetier###

Resistive transport in a mesoscopic proximity superconductor. We review transport measurements in a normal metal (N) in contact with one or
two superconducting (S) islands. From the experiment, we distinguish the
Josephson coupling, the mesoscopic fluctuations and the proximity effect. In a
loop-shaped N conductor, we observe large h/2e-periodic magnetoresistance
oscillations that decay with temperature T with a 1/T power-law. This behaviour
is the signature of the long-range coherence of the low-energy electron pairs
induced by the Andreev reflection at the S interface. At temperature and
voltage below the Thouless energy $\hbar D / L^2$, we observe the re-entrance
of the metallic resistance. Experimental results agree with the linearized
quasiclassical theory.

###Charge Localization in Disordered Colossal-Magnetoresistance Manganites|Qiming Li,Jun Zang,A. R. Bishop,C. M. Soukoulis###

Charge Localization in Disordered Colossal-Magnetoresistance Manganites. The metallic or insulating nature of the paramagnetic phase of the
colossal-magnetoresistance manganites is investigated via a double exchange
Hamiltonian with diagonal disorder. Mobility edge trajectory is determined with
the transfer matrix method. Density of states calculations indicate that random
hopping alone is not sufficient to induce Anderson localization at the Fermi
level with 20-30% doping. We argue that the metal-insulator transtion is likely
due to the formation of localized polarons from nonuniform extended states as
the effective band width is reduced by random hoppings and electron-electron
interactions.

###Intermediate Valence Model for Tl_{2}Mn_{2}O_{7}|C. I. Ventura,B. R. Alascio###

Intermediate Valence Model for Tl_{2}Mn_{2}O_{7}. There have been speculations about the need to find a new mechanism to
explain the colossal magnetoresistance exhibited by this material, having
pyrochlore structure and thus differing structurally and electronically from
the manganites. We will report here our transport results based on a two band
model, with conduction electrons and intermediate valence ions fluctuating
between two magnetic configurations. The model has been previously employed to
understand transport and thermodynamical properties of intermediate valence Tm
compounds and, in its periodic version, to analize the phase diagram. The
results obtained with this model for the transport properties of
Tl_{2}Mn_{2}O_{7} are in good qualitative agreement with the experimental
results.

###Evidence for Kondo Effect in Au80Co20 Ribbons|D. S. Geoghegan,A. Huetten,K. -H. Mueller,L. Schultz###

Evidence for Kondo Effect in Au80Co20 Ribbons. A minimum in resistivity as a function of temperature for an as-quenched
Au80Co20 ribbon prepared by melt-spinning using a wheel surface speed of 20 m
s^{-1} is found at 25 K. No resistivity minimum is found for an as-quenched
ribbon using a wheel surface speed of 60 m s^{-1}, however, upon heat treatment
of this ribbon a resistivity minimum is recovered. The temperature of the
minimum decreases with increasing total time of heat treatment. These
observations are interpretted as evidence for the microstructural control of
the Kondo effect typically found in dilute magnetic alloys in a giant
magnetoresistance granular material.

###Magnetoresistance of composite fermions at ν=1/2|L. P. Rokhinson,V. J. Goldman###

Magnetoresistance of composite fermions at ν=1/2. We have studied temperature dependence of both diagonal and Hall resistivity
in the vicinity of $\nu=1/2$. Magnetoresistance was found to be positive and
almost independent of temperature: temperature enters resistivity as a
logarithmic correction. At the same time, no measurable corrections to the Hall
resistivity has been found. Neither of these results can be explained within
the mean-field theory of composite fermions by an analogy with conventional
low-field interaction theory. There is an indication that interactions of
composite fermions with fluctuations of the gauge field may reconcile the
theory and experiment.

###Magnetic-Field Induced Localization in the Normal State of Superconducting La_2-xSr_xCuo_4|A. Malinowski,Marta Z. Cieplak,A. S. van Steenbergen,J. A. A. J. Perenboom,K. Karpinska,M. Berkowski,S. Guha,P. Lindenfeld###

Magnetic-Field Induced Localization in the Normal State of Superconducting La_2-xSr_xCuo_4. Magnetoresistance measurements of highly underdoped superconducting
La_{2-x}Sr_xCuO_4 films with $x = 0.051$ and $x = 0.048$, performed in dc
magnetic fields up to 20 T and at temperatures down to 40 mK, reveal a
magnetic-field induced transition from weak to strong localization in the
normal state. The normal-state conductances per CuO_2--plane, measured at
different fields in a single specimen, are found to collapse to one curve with
the use of a single scaling parameter that is inversely proportional to the
localization length. The scaling parameter extrapolates to zero near zero field
and possibly at a finite field, suggesting that in the zero-field limit the
electronic states may be extended.

###Anomalous Shift of Chemical Potential in the Double-Exchange Systems|Nobuo Furukawa###

Anomalous Shift of Chemical Potential in the Double-Exchange Systems. Double-exchange system is investigated by the dynamical mean-field theory. We
show that the chemical potential shifts as a function of temperature and
magnetization, which is anomalously large. We also discuss the influences of
dynamic Jahn-Teller effect to the shift of the chemical potential. Measurement
of the shift of the chemical potential casts a constraint to theoretical
approaches for the magnetoresistance phenomena in ($R$,$A$)MnO$_3$ such as
double-exchange effects and dynamic Jahn-Teller effects. We also propose a
method to measure the shift of $\mu$.

###Instability of the Two-Dimensional Metallic Phase to Parallel Magnetic Field|V. M. Pudalov,G. Brunthaler,A. Prinz,G. Bauer###

Instability of the Two-Dimensional Metallic Phase to Parallel Magnetic Field. We report on magnetotransport studies of the unusual two-dimensional metallic
phase in high mobility Si-MOS structures. We have observed that the magnetic
field applied in the 2D plane suppresses the metallic state, causing the
resistivity to increase dramatically by more than 30 times. Over the total
existence range of the metallic state, we have found three distinct types of
the magnetoresistance, related to the corresponding quantum corrections to the
conductivity. Our data suggest that the unusual metallic state is a consequence
of both spin- and Coulomb-interaction effects.

###h/2e oscillations and quantum chaos in ballistic Aharonov-Bohm billiards|Shiro Kawabata,Katsuhiro Nakamura###

h/2e oscillations and quantum chaos in ballistic Aharonov-Bohm billiards. We study the quantum interference effect for the single ballistic
Aharonov-Bohm billiard in the presence of a weak magnetic field B. The diagonal
part of the wave-number averaged reflection coefficient $\delta {\cal R}_D$ is
calculated by use of semi-classical scattering theory. In addition to the
appearance of "h/2e oscillation" that are caused by interference between
time-reversed coherent backscattering classical trajectories, B in the
conducting region leads to negative magnetoresistance and dampening of the h/2e
oscillation amplitude. The B dependence of the results reflects the underlying
classical (chaotic and regular) dynamics.

###Magnetoresistance of a two-dimensional electron gas with spatially periodic lateral modulations: Exact consequences of Boltzmann's equation|Rolf Menne,Rolf R. Gerhardts###

Magnetoresistance of a two-dimensional electron gas with spatially periodic lateral modulations: Exact consequences of Boltzmann's equation. On the basis of Boltzmann's equation, and including anisotropic scattering in
the collision operator, we investigate the effect of one-dimensional
superlattices on two-dimensional electron systems. In addition to superlattices
defined by static electric and magnetic fields, we consider mobility
superlattices describing a spatially modulated density of scattering centers.
We prove that magnetic and electric superlattices in $x$-direction affect only
the resistivity component $\rho_{xx}$ if the mobility is homogeneous, whereas a
mobility lattice in $x$-direction in the absence of electric and magnetic
modulations affects only $\rho_{yy}$. Solving Boltzmann's equation numerically,
we calculate the positive magnetoresistance in weak magnetic fields and the
Weiss oscillations in stronger fields within a unified approach.

###High field study of normal state magneto-transport in the thallium cuprate Tl-2201|A. W. Tyler,Yoichi Ando,F. F. Balakirev,A. Passner,G. S. Boebinger,A. J. Schofield,A. P. Mackenzie,O. Laborde###

High field study of normal state magneto-transport in the thallium cuprate Tl-2201. We present a study of in-plane normal state magneto-transport in single
crystal Tl-2201 in 60T pulsed magnetic fields. In optimally doped samples (Tc ~
80K) the weak-magnetic-field regime extends to fields as high as 60T, but in
overdoped samples (Tc ~ 30K) we are able to leave the weak field regime, as
shown by the behavior of both the magnetoresistance and the Hall resistance.
Data from samples of both dopings provide constraints on the class of model
necessary to describe normal state transport in the cuprates.

###Suppression of the Coulomb interaction contribution to the conductance by a parallel magnetic field|S. G. den Hartog,S. J. van der Molen,B. J. van Wees,T. M. Klapwijk,G. Borghs###

Suppression of the Coulomb interaction contribution to the conductance by a parallel magnetic field. The Coulomb interaction contribution to the conductance is investigated in a
phase-coherent disordered 2-dimensional electron gas, which resistance can be
varied by an overall gate electrode. Its magnitude of dGeei=-0.3 e^2/h is
obtained by applying a bias voltage to suppress the Coulomb anomaly. In
contrast to theoretical predictions, dGeei is suppressed by a parallel magnetic
field. The zero-bias magnetoresistance exhibits reproducible fluctuations in
perpendicular magnetic fields on a field scale much larger than that expected
for universal conductance fluctuations, which might be attributed to
fluctuations in the Coulomb interaction contribution.

###Magnetotransport in Cuprates: a Test of the Spin Fluctuation Model|Branko Stojkovic,David Pines###

Magnetotransport in Cuprates: a Test of the Spin Fluctuation Model. We report on a simple calculation of the magnetotransport in cuprate
superconductors, based on the nearly antiferromagnetic Fermi liquid (spin
fluctuation) model. We find that the model explains all important features seen
experimentally: the violation of K"ohler's rule, the close relationship between
the Hall angle and the magnetoresistance, the temperature dependence of the
first high field correction to MR and the doping dependence of the low field MR
data. In addition, the estimated values of omega_c tau, calculated using
parameters obtained from the NMR measurements, yield values in close agreement
with those found experimentally for overdoped and optimally doped cuprates.

###Neutron scattering investigation of magnetic bilayer correlations in $La_{1.2}Sr_{1.8}Mn_2O_7$|R. Osborn,S. Rosenkranz,D. N. Argyriou,L. Vasiliu-Doloc,J. W. Lynn,S. K. Sinha,J. F. Mitchell,K. E. Gray,S. D. Bader###

Neutron scattering investigation of magnetic bilayer correlations in $La_{1.2}Sr_{1.8}Mn_2O_7$. Neutron scattering investigations of the paramagnetic correlations in the
layered manganite La$_{1.2}$Sr$_{1.8}$Mn$_{2}$O$_{7}$, which exhibits colossal
magnetoresistance above the Curie transition at T$_C$ = 112 K, show that spins
in neighboring layers within each bilayer are strongly canted at an average
angle that is dependent on both the magnetic field and temperature, as
predicted by de Gennes. The in-plane correlation length does not diverge at
T$_C$, although the magnetic Bragg intensity obeys critical scaling below
T$_C$, with the same temperature dependence as the zero-field electrical
conductance.

###Negative Domain Wall Contribution to the Resistivity of Microfabricated Fe Wires|U. Ruediger,J. Yu,S. Zhang,A. D. Kent,S. S. P. Parkin###

Negative Domain Wall Contribution to the Resistivity of Microfabricated Fe Wires. The effect of domain walls on electron transport has been investigated in
microfabricated Fe wires (0.65 to 20 $\mu m$ linewidths) with controlled stripe
domains. Magnetoresistance (MR) measurements as a function of domain wall
density, temperature and the angle of the applied field are used to determine
the low field MR contributions due to conventional sources in ferromagnetic
materials and that due to the erasure of domain walls. A negative domain wall
contribution to the resistivity is found. This result is discussed in light of
a recent theoretical study of the effect of domain walls on quantum transport.

###Anomalous Hall Effect in Double Exchange Magnets|Yong Baek Kim,Pinaki Majumdar,A. J. Millis,Boris I. Shraiman###

Anomalous Hall Effect in Double Exchange Magnets. We investigate the possible origin of anomalous Hall effect in the CMR
(colossal magnetoresistance) materials - the doped rare earth manganites -
observed recently by Matl et al. It is demonstrated that the spin-orbit
interaction in the double exchange model couples magnetization to the Berry
phase associated with three dimensional spin textures and induces a non-zero
average topological flux which in turn generates an anomalous contribution to
transverse resistivity. The same effect, but involving the orbital Berry phase,
occurs in the model with orbital degeneracy and Coulomb repulsion.

###reentrance effect in normal-metal/superconducting hybrid loops|C. -J. Chien,V. Chandrasekhar###

reentrance effect in normal-metal/superconducting hybrid loops. We have measured the transport properties of two mesoscopic hybrid loops
composed of a normal-metal arm and a superconducting arm. The samples differed
in the transmittance of the normal/superconducting interfaces. While the low
transmittance sample showed monotonic behavior in the low temperature
resistance, magnetoresistance and differential resistance, the high
transmittance sample showed reentrant behavior in all three measurements. This
reentrant behavior is due to coherent Andreev reflection at the
normal/superconducting interfaces. We compare the reentrance effect for the
three different measurements and discuss the results based on the theory of
quasiclassical Green's functions.

###Carrier Density Collapse and Colossal Magnetoresistance in Doped Manganites|A. S. Alexandrov,A. M. Bratkovsky###

Carrier Density Collapse and Colossal Magnetoresistance in Doped Manganites. A novel ferromagnetic transition, accompanied by carrier density collapse, is
found in doped charge-transfer insulators with strong electron-phonon coupling.
  The transition is driven by an exchange interaction of polaronic carriers
with localized spins; the strength of the interaction determines whether the
transition is first or second order. A giant drop in the number of current
carriers during the transition, which is a consequence of bound pairs formation
in the paramagnetic phase close to the transition, is extremely sensitive to an
external magnetic field. This carrier density collapse describes the
resistivity peak and the colossal magnetoresistance of doped manganites.

###Temperature- and Bias-dependence of magnetoresistance in doped manganite thin film trilayer junctions|J. Z. Sun,D. W. Abraham,K. Roche,S. S. P. Parkin###

Temperature- and Bias-dependence of magnetoresistance in doped manganite thin film trilayer junctions. Thin film trilayer junction of La$%_{0.67}$Sr$_{0.33}$MnO$_3$ - SrTiO$_3$ -
La$_{0.67}$Sr$_{0.33}$MnO$_3$ shows a factor of 9.7 change in resistance, in a
magnetic field around 100 Oe at 14K. The junction magnetoresistance is bias and
temperature dependent. The energy scales associated with bias and temperature
dependence are an order of magnitude apart. The same set of energies also
determine the bias and temperature dependence of the differential conductance
of the junction. We discuss these results in terms of metallic cluster
inclusions at the junction-barrier interface.

###Thin-Film Trilayer Manganate Junctions|Jonathan Z. Sun###

Thin-Film Trilayer Manganate Junctions. Spin-dependent conductance across a manganate-barrier-manganate junction has
recently been demonstrated. The junction is a La$_{0.67}$Sr$_{0.33}$MnO$_3$%
-SrTiO$_3$-La$_{0.67}$ Sr$_{0.33}$MnO$_3$ trilayer device supporting
current-perpendicular transport. Large magnetoresistance of up to a factor of
five change was observed in these junctions at 4.2K in a relatively low field
of the order of 100 Oe. Temperature and bias dependent studies revealed a
complex junction interface structure whose materials physics has yet to be
understood.

###Destruction of localized electron pairs above the magnetic-field-driven superconductor-insulator transition in amorphous InO films|V. F. Gantmakher,M. V. Golubkov,V. T. Dolgopolov,G. E. Tsydynzhapov,A. A. Shashkin###

Destruction of localized electron pairs above the magnetic-field-driven superconductor-insulator transition in amorphous InO films. We have investigated the field-induced superconductivity-destroying quantum
transition in amorphous indium oxide films at low temperatures down to 30 mK.
It has been found that, on the high-field side of the transition, the
magnetoresistance reaches a maximum and the phase can be insulating as well as
metallic. With further increasing magnetic field the film resistance drops and
approaches in the high-field limit the resistance value at transition point so
that at high fields the metallic phase occurs for both cases. We give a
qualitative account of this behavior in terms of field-induced destruction of
localized electron pairs.

###Scaling relations in charge and spin excitations for (La,Sr)MnO3|Nobuo Furukawa,Yutaka Moritomo,K. Hirota,Y. Endoh###

Scaling relations in charge and spin excitations for (La,Sr)MnO3. Scaling relations in the charge and spin excitations of (La,Sr)MnO3 are
studied from both theoretical and experimental points of view. In the
ferromagnetic metal phase, we investigate optical conductivity and neutron
inelastic scattering, and compare with a theoretical calculation based on the
dynamical mean-field theory of the double-exchange hamiltonian. Spin and charge
dynamics of (La,Sr)MnO3 exhibit typical behaviors of half metals. In these
manganite compounds with high Curie temperature, various behaviors in spin and
charge properties are explained by the double-exchange hamiltonian alone.
Magnetoresistance of these compounds as well as other compounds with lower
Curie temperature are also discussed.

###Comment on "Quantum Decoherence in Disordered Mesoscopic Systems"|I. L. Aleiner,B. L. Altshuler,M. E. Gershenson###

Comment on "Quantum Decoherence in Disordered Mesoscopic Systems". In a recent paper, Phys. Rev. Lett. 81, 1074 (1998), Golubev and Zaikin (GZ)
found that ``zero-point fluctuations of electrons'' contribute to the dephasing
rate extracted from the magnetoresistance. As a result, the dephasing rate
remains finite at zero temperature. GZ claimed that their results ``agree well
with the experimental data''. We point out that the GZ results are incompatible
with (i) conventional perturbation theory of the effects of interaction on weak
localization (WL), and (ii) with the available experimental data. More detailed
criticism of GZ findings can be found in cond-mat/9808053.

###Transport in two dimensional periodic magnetic fields|Junji Yoshida,Tomi Ohtsuki,Yoshiyuki Ono###

Transport in two dimensional periodic magnetic fields. Ballistic transport properties in a two dimensional electron gas are studied
numerically, where magnetic fields are perpendicular to the plane of two
dimensional electron systemsand periodically modulated both in $x$ and $y$
directions. We show that there are three types of trajectories of classical
electron motions in this system; chaotic, pinned and runaway trajectories. It
is found that the runaway trajectories can explain the peaks of
magnetoresistance as a function of external magnetic fields, which is believed
to be related to the commensurability effect between the classical cyclotron
diameter and the period of magnetic modulation. The similarity with and
difference from the results in the antidot lattice are discussed.

###Thickness dependent magnetotransport in ultra-thin manganite films|J. Z. Sun,D. W. Abraham,R. A. Rao,C. B. Eom###

Thickness dependent magnetotransport in ultra-thin manganite films. To understand the near-interface magnetism in manganites, uniform, ultra-thin
films of La_{0.67}Sr_{0.33}MnO_3 were grown epitaxially on single crystal (001)
LaAlO_3 and (110) NdGaO_3 substrates. The temperature and magnetic field
dependent film resistance is used to probe the film's structural and magnetic
properties. A surface and/or interface related dead-layer is inferred from the
thickness dependent resistance and magnetoresistance. The total thickness of
the dead layer is estimated to be $\sim 30 \AA$ for films on NdGaO_3 and $\sim
50 \AA$ for films on LaAlO_3.

###Magnetotransport in the doped Mott insulator|Ekkehard Lange,Gabriel Kotliar###

Magnetotransport in the doped Mott insulator. We investigate the Hall effect and the magnetoresistance of strongly
correlated electron systems using the dynamical mean-field theory. We treat the
low- and high-temperature limits analytically and explore some aspects of the
intermediate-temperature regime numerically. We observe that a
bipartite-lattice condition is responsible for the high-temperature result
$\sigma_{xy}\sim 1/T^2$ obtained by various authors, whereas the general
behavior is $\sigma_{xy}\sim 1/T$, as for the longitudinal conductivity. We
find that Kohler's rule is neither obeyed at high nor at intermediate
temperatures.

###Hall-effect in LuNi_2B_2C in normal and superconducting mixed states|V. N. Narozhnyi,J. Freudenberger,V. N. Kochetkov,K. A. Nenkov,G. Fuchs,K. -H. Müller###

Hall-effect in LuNi_2B_2C in normal and superconducting mixed states. The Hall resistivity rho_{xy} of LuNi_2B_2C is negative in the normal as well
as in the mixed state and has no sign reversal typical for high-T_c
superconductors. A distinct nonlinearity in the rho_{xy} dependence on field H
was found in the normal state for T < 40K, accompanied by a large
magnetoresistance reaching +90% for mu_0H=16T at T=20K. The scaling relation
rho_{xy} ~ \rho_{xx}^\beta (\rho_{xx} is the longitudinal resistivity) was
found in the mixed state, the value of \beta being dependent on the degree of
disorder.

###Strongly Anisotropic Transport in Higher Two-Dimensional Landau Levels|R. R. Du,D. C. Tsui,H. L. Stormer,L. N. Pfeiffer,K. W. Baldwin,K. W. West###

Strongly Anisotropic Transport in Higher Two-Dimensional Landau Levels. Low-temperature, electronic transport in Landau levels N>1 of a
two-dimensional electron system is strongly anisotropic. At half-filling of
either spin level of each such Landau level the magnetoresistance either
collapses to form a deep minimum or is peaked in a sharp maximum, depending on
the in-plane current direction. Such anisotropies are absent in the N=0 and N=1
Landau level, which are dominated by the states of the fractional quantum Hall
effect. The transport anisotropies may be indicative of a new many particle
state, which forms exclusively in higher Landau levels.

###Thermodynamics of the Double Exchange Systems|N. Furukawa###

Thermodynamics of the Double Exchange Systems. This article gives a comprehensive review on the recent studies of the double
exchange systems using non-perturbative approaches; the dynamical mean-field
theory and the Monte Carlo method. Investigations beyond mean-field type
treatments are described. Taking into account strong spin fluctuations which
create large changes in conduction electron structure, finite temperature
properties as well as dynamics of the system are calculated. Comparisons with
experimental data for colossal magnetoresistance manganites are made. We show
that high Curie temperature (Tc) compounds, e.g. (La,Sr)MnO3, are canonical
double-exchange systems. Properties of other compounds with lower Tc are
discussed in relation to inhomogeneities of the system including the issue of
phase separation.

###Magnetoresistance, Micromagnetism and Domain Wall Effects in Epitaxial Fe and Co Structures with Stripe Domains|Andrew D. Kent,Ulrich Rüdiger,Jun Yu,Luc Thomas,Stuart S. P. Parkin###

Magnetoresistance, Micromagnetism and Domain Wall Effects in Epitaxial Fe and Co Structures with Stripe Domains. We review our recent magnetotransport and micromagnetic studies of
lithographically defined epitaxial thin film structures of bcc Fe and hcp Co
with stripe domains. Micromagnetic structure and resistivity anisotropy are
shown to be the predominant sources of low field magnetoresistance (MR) in
these microstructures, with domain wall (DW) effects smaller but observable
(DW-MR $\lesssim 1 %$). In Fe, at low temperature, in a regime in which fields
have a significant effect on electron trajectories, a novel negative DW
contribution to the resistivity is observed. In hcp Co microstructures,
temperature dependent transport measurements for current perpendicular and
parallel to walls show that any additional resistivity due to DW scattering is
very small.

###Non-equilibrium spin accumulation in ferromagnetic single-electron transistors|Arne Brataas,Yu. V. Nazarov,J. Inoue,G. E. W. Bauer###

Non-equilibrium spin accumulation in ferromagnetic single-electron transistors. We study transport in ferromagnetic single-electron transistors. The non-
equilibrium spin accumulation on the island caused by a finite current through
the system is described by a generalized theory of the Coulomb blockade. It
enhances the tunnel magnetoresistance and has a drastic effect on the time-
dependent transport properties. A transient decay of the spin accumulation may
reverse the electric current on time scales of the order of the spin-flip
relaxation time. This can be used as an experimental signature of the non-
equilibrium spin accumulation.

###The Kronig-Penney-Ising picture of the colossal magnetoresistance|N. Vandewalle,M. Ausloos,R. Cloots###

The Kronig-Penney-Ising picture of the colossal magnetoresistance. From general arguments, it is shown that a magnetic Kronig-Penney model based
on the thermodynamics of an Ising model can be used for describing the Colossal
Magnetoresistance (CMR) phenomenon. The model considers a tunneling-like
transmission process of hopping electrons through a dynamic lattice
characterized by evolving magnetic clusters. In this model, correlations
between the magnetic states are considered to be more relevant than the lattice
strain effects for obtaining the CMR features. Physical arguments lead to the
theoretical description of the intrinsic temperature and field dependences of
the CMR observed in typical manganite materials.

###On the magnetoresistance anisotropy of a 2-dimensional electron gas with large half-integer filling factors|Herbert Kroemer###

On the magnetoresistance anisotropy of a 2-dimensional electron gas with large half-integer filling factors. The unsymmetric confinement of the electrons in a typical 2-dimensional
electron gas (2DEG) breaks the full cubic symmetry of the in-plane transport
properties. A rigorous invariance of the transport under rotation by pi/2 about
the cubic axis perpendicular to the plane of the gas no longer holds, even for
structurally perfect samples, and asymmetries under rotation by pi/2 are
allowed. It is proposed that this symmetry breaking plays a role in the recent
observation, by Little et al., of the pronounced anisotropy of the
magnetoresistance of a 2DEG at very low temperatures, at large half-integer
filling factors of the Landau levels in such a system.

###Magnetoresistance, Micromagnetism, and Domain Wall Scattering in Epitaxial hcp Co Films|U. Ruediger,J. Yu,L. Thomas,S. S. P. Parkin,A. D. Kent###

Magnetoresistance, Micromagnetism, and Domain Wall Scattering in Epitaxial hcp Co Films. Large negative magnetoresistance (MR) observed in transport measurements of
hcp Co films with stripe domains were recently reported and interpreted in
terms of a novel domain wall (DW) scattering mechanism. Here detailed MR
measurements, magnetic force microscopy, and micromagnetic calculations are
combined to elucidate the origin of MR in this material. The large negative
room temperature MR reported previously is shown to be due to ferromagnetic
resistivity anisotropy. Measurements of the resistivity for currents parallel
(CIW) and perpendicular to DWs (CPW) have been conducted as a function of
temperature. Low temperature results show that any intrinsic effect of DWs
scattering on MR of this material is very small compared to the anisotropic MR.

###Spin-Imbalance and Magnetoresistance in Ferromagnet/Superconductor/Ferromagnet Double Tunnel Junctions|S. Takahashi,H. Imamura,S. Maekawa###

Spin-Imbalance and Magnetoresistance in Ferromagnet/Superconductor/Ferromagnet Double Tunnel Junctions. We theoretically study the spin-dependent transport in a ferromagnet/super-
conductor/ferromagnet double tunnel junction. The tunneling current in the
antiferromagnetic alignment of the magnetizations gives rise to a spin
imbalance in the superconductor. The resulting nonequilibrium spin density
strongly suppresses the superconductivity with increase of bias voltage and
destroys it at a critical voltage Vc. The results provide a new method not only
for measuring the spin polarization of ferromagnets but also for controlling
superconductivity and tunnel magnetoresistance (TMR) by applying the bias
voltage.

###Suppression of Giant Magnetoresistance by a superconducting contact|F. Taddei,S. Sanvito,J. H. Jefferson,C. J. Lambert###

Suppression of Giant Magnetoresistance by a superconducting contact. We predict that current perpendicular to the plane (CPP) giant
magnetoresistance (GMR) in a phase-coherent magnetic multilayer is suppressed
when one of the contacts is superconducting. This is a consequence of a
superconductivity-induced magneto-resistive (SMR) effect, whereby the
conductance of the ferromagnetically aligned state is drastically reduced by
superconductivity. To demonstrate this effect, we compute the GMR ratio of
clean (Cu/Co)_nCu and (Cu/Co)_nPb multilayers, described by an ab-initio spd
tight binding Hamiltonian. By analyzing a simpler model with two orbitals per
site, we also show that the suppression survives in the presence of elastic
scattering by impurities.

###The new line of attack of analyses of NMR in 2D structures|G. M. Minkov,S. A. Negashev,O. E. Rut,A. V. Germanenko,O. I. Khrykin,V. I. Shashkin,V. M. Danil'tsev###

The new line of attack of analyses of NMR in 2D structures. There was shown that Fourier transform of the negative magnetoresistance
(NMR) which is due to interference correction to the conductivity contains the
information about the area distribution function of the closed paths and about
area dependence of the mean length of closed paths \bar{L}(S). Based on this
line of attack we suggest the method of analysis of NMR and use it for data
treatment of the NMR in 2D structure with doped barrier. There was shown that
in structure investigated \bar{L}(S)dependence is determined by the scattering
anisotropy.

###Spin Dynamical Properties of the Layered Perovskite La1.2Sr1.8Mn2O7|H. Fujioka,M. Kubota,K. Hirota,H. Yoshizawa,Y. Moritomo,Y. Endoh###

Spin Dynamical Properties of the Layered Perovskite La1.2Sr1.8Mn2O7. Inelastic neutron-scattering measurements were performed on a single crystal
of the layered colossal magnetoresistance (CMR) material La1.2Sr1.8Mn2O7 (Tc ~
120K). We found that the spin wave dispersion is almost perfectly
two-dimensional with the in-plane spin stiffness constant D ~ 151meVA. The
value is similar to that of similarly doped La1-xSrxMnO3 though its Tc is three
times higher, indicating a large renormalization due to low dimensionality.
There exist two branches due to a coupling between layers within a
double-layer. The out-of-plane coupling is about 30% of the in-plane coupling
though the Mn-O bond lengths are similar.

###Dephasing Effects by Ferromagnetic Boundary on Resistivity in Disordered Metallic Layer|Gen Tatara,Hidetoshi Fukuyama###

Dephasing Effects by Ferromagnetic Boundary on Resistivity in Disordered Metallic Layer. The resistivity of disordered metallic layer sandwiched by two ferromagnetic
layers at low-temperature is investigated theoretically. It is shown that the
magnetic field acting at the interface does not affect the classical Boltzmann
resistivity but causes a dephasing among electrons in the presence of the
spin-orbit interaction, suppressing the anti-localization due to the spin-orbit
interaction. The dephasing turns out to be stronger in the case where the
magnetization of the two layers is parallel, contributing to a positive
magnetoresistance close to a switching field at low temperature.

###Colossal magnetooptical conductivity in doped manganites|A. S. Alexandrov,A. M. Bratkovsky###

Colossal magnetooptical conductivity in doped manganites. We show that the current carrier density collapse in doped manganites, which
results from bipolaron formation in the paramagnetic phase, leads to a colossal
change of the optical conductivity in an external magnetic field at
temperatures close to the ferromagnetic transition. As with the colossal
magnetoresistance (CMR) itself, the corresponding magnetooptical effect is
explained by the dissociation of localized bipolarons into mobile polarons
owing to the exchange interaction with the localized Mn spins in the
ferromagnetic phase. The effect is positive at low frequencies and negative in
the high-frequency region. The present results agree with available
experimental observations.

###Perpendicular transport and magnetization processes in magnetic multilayers with strongly and weakly coupled magnetic layers|M. Zwierzycki,S. Krompiewski###

Perpendicular transport and magnetization processes in magnetic multilayers with strongly and weakly coupled magnetic layers. Within the framework of a two-band tight-binding model, we have performed
calculations of giant magnetoresistance, exchange coupling and thermoelectric
power (TEP) for a system consisting of three magnetic layers separated by two
non-magnetic spacers with the first two magnetic layers strongly
antiferromagnetically exchange-coupled. We have shown how does the GMR relate
with the corresponding regions of magnetic structure phase diagrams and
computed some relevant hysteresis loops, too. The GMR may take negative values
for specific layers thicknesses, and the TEP reveals quite pronounced
oscillations around a negative bias.

###Electrodynamics of Nd0.7Sr0.3MnO3 Single Crystal investigated by Optical Conductivity Analyses|H. J. Lee,J. H. Jung,Y. S. Lee,J. S. Ahn,T. W. Noh,K. H. Kim,S-W. Cheong###

Electrodynamics of Nd0.7Sr0.3MnO3 Single Crystal investigated by Optical Conductivity Analyses. We investigated temperature dependent optical conductivity spectra of
Nd0.7Sr0.3MnO3 single crystal. We found that polishing and surface scattering
effects on the Nd0.7Sr0.3MnO3 crystal surfaces could significantly distort the
optical responses, especially in the mid-infrared region. However, oxygen
annealing and gold normalization processes seemed to remedy the distortions. We
found that the spectral weight of Nd0.7Sr0.3MnO3 in the metallic state might be
composed of a Drude carrier term and a strong incoherent mid-infrared
absorptions. The temperature dependence of the spectral weight suggests that
the electron-lattice coupling should be important in optical properties of
colossal magnetoresistance manganites.

###Geometrically constrained magnetic wall|Patrick Bruno###

Geometrically constrained magnetic wall. The structure and properties of a geometrically constrained magnetic wall in
a constriction separating two wider regions are investigated theoretically.
They are shown to differconsiderably from those of an unconstrained wall, so
that the geometrically constrained magnetic wall truly constitutes a new kind
of magnetic wall, besides the well known Bloch and Neel walls. In particular,
the width of a constrained wall cann become very small if the characteristic
length of the constriction is small, as is actually the case in an atomic point
contact. This provides a simple, natural explanation for the large
magnetoresistance observed in ferromagnetic atomic point contacts.

###Berry Phase Theory of Anomalous Hall Effect: Application to Colossal Magnetoresistance Manganites|Jinwu Ye,Yong Baek Kim,A. J. Millis,P. Majumdar,Z. Tesanovic###

Berry Phase Theory of Anomalous Hall Effect: Application to Colossal Magnetoresistance Manganites. We show that the Anomalous Hall Effect (AHE) observed in Colossal
Magnetoresistance Manganites is a manifestation of Berry phase effects caused
by carrier hopping in a non-trivial spin background.
  We determine the magnitude and temperature dependence of the Berry phase
contribution to the AHE, finding that it increases rapidly in magnitude as the
temperature is raised from zero through the magnetic transition temperature
T_c, peaks at a temperature $T_{max} > T_c$ and decays as a power of T, in
agreement with experimental data. We suggest that our theory may be relevant to
the anomalous hall effect in conventional ferromagnets as well.

###Magnetoresistance Anomalies in Antiferromagnetic YBa_2Cu_3O_{6+x}: Fingerprints of Charged Stripes|Yoichi Ando,A. N. Lavrov,Kouji Segawa###

Magnetoresistance Anomalies in Antiferromagnetic YBa_2Cu_3O_{6+x}: Fingerprints of Charged Stripes. We report novel features in the in-plane magnetoresistance (MR) of heavily
underdoped YBa_2Cu_3O_{6+x}, which unveil a developed ``charged stripe''
structure in this system. One of the striking features is an anisotropy of the
MR with a "d-wave" symmetry upon rotating the magnetic field H within the ab
plane, which is caused by the rotation of the stripes with the external field.
With decreasing temperature, a hysteresis shows up below ~20 K in the MR curve
as a function of H and finally below 10 K the magnetic-field application
produces a persistent change in the resistivity. This "memory effect" is caused
by the freezing of the directionally-ordered stripes.

###Interesting history effect in the magnetotransport properies of La0.55Ho0.15Sr0.3MnOz films on LaAlO3|P Raychaudhuri,A E P de Araujo,F L A Machado,A K Nigam,R Pinto###

Interesting history effect in the magnetotransport properies of La0.55Ho0.15Sr0.3MnOz films on LaAlO3. We report the magnetoresistance measurements of a highly oriented
La0.55Ho0.15Sr0.3MnOz film on LaAlO3 substrate. The film has a metal-insulator
transition around 200 K and shows pronounced thermomagnetic history effect in
its transport properties below 45 K at 7 Tesla. The irreversibility temperature
shifts to lower temperatures when the field is reduced. This behaviour is
opposite to the thermomagnetic history effect observed in the magnetisation. At
2.8 K one also observes a significant hysteresis in the resistance versus field
curve. We propose a qualitative explanation for these observations.

###The small polaron crossover transition in colossal magnetoresistance (CMR) manganites|Unjong Yu,B. I. Min###

The small polaron crossover transition in colossal magnetoresistance (CMR) manganites. Based on the combined model of the double exchange and the polaron, we have
studied the small-to-large polaron crossover transition and explored its
effects on the magnetic and transport properties in colossal magnetoresistance
(CMR) manganites. We have used the variational Lang-Firsov canonical
transformation, and shown that the magnetic and transport properties of both
high and low $T_C$ manganites are well described in terms of a single
formalism. We have reproduced the rapid resistivity drop below $T_C$, a
realistic CMR ratio, and the {\it first-order-like} sharp magnetic phase
transition, which are observed in low $T_C$ manganites.

###Transport and magnetic properties of La_(1-x)Ca_xMnO_3-films (0.1<x<0.9)|G. Jakob,F. Martin,S. Friedrich,W. Westerburg,M. Maier###

Transport and magnetic properties of La_(1-x)Ca_xMnO_3-films (0.1<x<0.9). By laser ablation we prepared thin films of the colossal magnetoresistive
compound La_(1-x)Ca_xMnO_3 with doping levels 0.1<x<0.9 on MgO substrates.
X-ray diffraction revealed epitaxial growth and a systematic decrease of the
lattice constants with doping. The variation of the transport and magnetic
properties in this doping series was investigated by SQUID magnetization and
electrical transport measurements. For the nonmetallic samples resistances up
to 10^13 Ohm have been measured with an electrometer setup. While the transport
data indicate polaronic transport for the metallic samples above the Curie
temperature the low doped ferromagnetic insulating samples show a variable
range hopping like transport at low temperature.

###Interface resistance in ferromagnet/superconductor junctions|A. A. Golubov###

Interface resistance in ferromagnet/superconductor junctions. Results of theoretical study of spin-polarized tunneling in
ferromagnet/superconductor junctions are presented. Spin and charge currents
are calculated as a function of applied voltage and spin polarization in a
ferromagnet. The model takes into account the splitting of different spin
subbands in a ferromagnet and impurity scattering in the contact. The excess
resistance of an FS contact due to the charge-imbalance in a superconductor is
calculated for the first time. The results have implications for spin-coupled
magnetoresistance in ferromagnet/superconductor contacts and for measuring spin
polarization in ferromagnets.

###ESR study in lightly doped La_(1-x)Sr_(x)MnO_(3)|V. A. Ivanshin,J. Deisenhofer,H. -A. Krug von Nidda,A. Loidl,A. A. Mukhin,A. M. Balbashov,M. V. Eremin###

ESR study in lightly doped La_(1-x)Sr_(x)MnO_(3). This is the first systematic ESR investigation of La_(1-x)Sr_(x)MnO_(3)
single crystals for Sr concentrations x < 0.2. The rich phase diagram of this
compound, which is dominated by the Jahn-Teller effect of Mn^(3+), is a matter
of actual interest in connection with giant magnetoresistance phenomena. The
ESR signal, which is due to both Mn^(3+) and Mn^(4+), directely probes the
suppression of the Jahn-Teller distortion with increasing Sr concentration and
reveals all characteristic structural and magnetic phase transitions.

###Magnetic anisotropy, first-order-like metamagnetic transitions and large negative magnetoresistance in the single crystal of Gd$_{2}$PdSi$_3$|S. R. Saha,H. Sugawara,T. D. Matsuda,H. Sato,R. Mallik,E. V. Sampathkumaran###

Magnetic anisotropy, first-order-like metamagnetic transitions and large negative magnetoresistance in the single crystal of Gd$_{2}$PdSi$_3$. Electrical resistivity ($\rho$), magnetoresistance (MR), magnetization,
thermopower and Hall effect measurements on the single crystal
Gd$_{2}$PdSi$_3$, crystallizing in an AlB$_2$-derived hexagonal structure are
reported. The well-defined minimum in $\rho$ at a temperature above N\'eel
temperature (T$_N$= 21 K) and large negative MR below $\sim$ 3T$_N$, reported
earlier for the polycrystals, are reproducible even in single crystals. Such
features are generally uncharacteristic of Gd alloys. In addition, we also
found interesting features in other data, e.g., two-step first-order-like
metamagnetic transitions for the magnetic field along [0001] direction. The
alloy exhibits anisotropy in all these properties, though Gd is a S-state ion.

###Spin Wave Theory of Double Exchange Ferromagnets|D. I. Golosov###

Spin Wave Theory of Double Exchange Ferromagnets. We construct the 1/S spin-wave expansion for double exchange ferromagnets at
T=0. It is assumed that the value of Hund's rule coupling, J_H, is sufficiently
large, resulting in a fully saturated, ferromagnetic half-metallic ground
state. We evaluate corrections to the magnon dispersion law, and we also find
that, in contrast to earlier statements in the literature, magnon-electron
scattering does give rise to spin wave damping. We analyse the momentum
dependence of these quantities and discuss the experimental implications for
colossal magnetoresistance compounds.

###Theory of anomalous magnon softening in ferromagnetic manganites|G. Khaliullin,R. Kilian###

Theory of anomalous magnon softening in ferromagnetic manganites. In metallic manganites with low Curie temperatures, a peculiar softening of
the magnon spectrum close to the magnetic zone boundary has experimentally been
observed. Here we present a theory of the renormalization of the magnetic
excitation spectrum in colossal magnetoresistance compounds. The theory is
based on the modulation of magnetic exchange bonds by the orbital degree of
freedom of double-degenerate e_g electrons. The model considered is an
orbitally degenerate double-exchange system coupled to Jahn-Teller active
phonons which we treat in the limit of strong onsite repulsions. Charge and
coupled orbital-lattice fluctuations are identified as the main origin of the
unusual softening of the magnetic spectrum.

###Influence of parallel magnetic fields on a single-layer two-dimensional electron system with a hopping mechanism of conductivity|I. Shlimak,S. I. Khondaker,M. Pepper,D. A. Ritchie###

Influence of parallel magnetic fields on a single-layer two-dimensional electron system with a hopping mechanism of conductivity. Large positive (P) magnetoresistance (MR) has been observed in parallel
magnetic fields in a single 2D layer in a delta-doped GaAs/AlGaAs
heterostructure with a variable-range-hopping (VRH) mechanism of conductivity.
Effect of large PMR is accompanied in strong magnetic fields by a substantial
change in the character of the temperature dependence of the conductivity. This
implies that spins play an important role in 2D VRH conductivity because the
processes of orbital origin are not relevant to the observed effect. A possible
explanation involves hopping via double occupied states in the upper Hubbard
band, where the intra-state correlation of spins is important.

###Electronic Transport in a Three-dimensional Network of 1-D Bismuth Quantum Wires|T. E. Huber,M. J. Graf###

Electronic Transport in a Three-dimensional Network of 1-D Bismuth Quantum Wires. The resistance R of a high density network of 6 nm diameter Bi wires in
porous Vycor glass is studied in order to observe its expected semiconductor
behavior. R increases from 300 K down to 0.3 K. Below 4 K, where R varies
approximately as ln(1/T), the order-of-magnitude of the resistance rise, as
well as the behavior of the magnetoresistance are consistent with localization
and electron-electron interaction theories of a one-dimensional disordered
conductor in the presence of strong spin-orbit scattering. We show that this
behaviour and the surface-enhanced carrier density may mask the proposed
semimetal-to-semiconductor transition for quantum Bi wires.

###Manifestations of the Charged Stripes in the Magnetoresistance of Heavily Underdoped YBa_2Cu_3O_{6+x}|A. N. Lavrov,Yoichi Ando,Kouji Segawa###

Manifestations of the Charged Stripes in the Magnetoresistance of Heavily Underdoped YBa_2Cu_3O_{6+x}. We present a study of the in-plane and out-of-plane magnetoresistance (MR) in
heavily-underdoped, antiferromagnetic YBa_2Cu_3O_{6+x}, which reveals a variety
of striking features. The in-plane MR demonstrates a "d-wave"-like anisotropy
upon rotating the magnetic field H within the ab plane. With decreasing
temperature below 20-25 K the system acquires memory: exposing a crystal to the
magnetic field results in a persistent in-plane resistivity anisotropy. The
overall features can be explained by assuming that the CuO_2 planes contain a
developed array of stripes accommodating the doped holes, and that the MR is
associated with the field-induced topological ordering of the stripes.

###Weak localisation, hole-hole interactions and the "metal"-insulator transition in two dimensions|M. Y. Simmons,A. R. Hamilton,M. Pepper,E. H. Linfield,P. D. Rose,D. A. Ritchie,.###

Weak localisation, hole-hole interactions and the "metal"-insulator transition in two dimensions. A detailed investigation of the metallic behaviour in high quality
GaAs-AlGaAs two dimensional hole systems reveals the presence of quantum
corrections to the resistivity at low temperatures. Despite the low density
($r_{s}>10$) and high quality of these systems, both weak localisation
(observed via negative magnetoresistance) and weak hole-hole interactions
(giving a correction to the Hall constant) are present in the so-called
metallic phase where the resistivity decreases with decreasing temperature. The
results suggest that even at high $r_{s}$ there is no metallic phase at T=0 in
two dimensions.

###Two-phase behavior in strained thin films of hole-doped manganites|Amlan Biswas,M. Rajeswari,R. C. Srivastava,Y. H. Li,T. Venkatesan,R. L. Greene,A. J. Millis###

Two-phase behavior in strained thin films of hole-doped manganites. We present a study of the effect of biaxial strain on the electrical and
magnetic properties of thin films of manganites. We observe that manganite
films grown under biaxial compressive strain exhibit island growth morphology
which leads to a non-uniform distribution of the strain. Transport and magnetic
properties of these films suggest the coexistence of two different phases, a
metallic ferromagnet and an insulating antiferromagnet. We suggest that the
high strain regions are insulating while the low strain regions are metallic.
In such non-uniformly strained samples, we observe a large magnetoresistance
and a field-induced insulator to metal transition.

###Weak localization in the 2D metallic regime of Si-MOS|G. Brunthaler,A. Prinz,G. Bauer,V. M. Pudalov,E. M. Dizhur,J. Jaroszynski,P. Glod,T. Dietl###

Weak localization in the 2D metallic regime of Si-MOS. The negative magnetoresistance due to weak localization is investigated in
the two-dimensional metallic state of Si-MOS structures for high conductance
values between 35 and 120 e^2/h. The extracted phase coherence time is equal to
the momentum relaxation time at 10 K but nearly 100 times longer at the lowest
temperature. Nevertheless, only weak logarithmic corrections to the
conductivity are present in the investigated temperature and concentration
range thus proving the absence of strong quantum effects due to
electron-electron interaction. From saturation effects of the phase coherence
time a lower boundary for spin-orbit scattering of about 200 ps is estimated.

###Nanoconstriction Microscopy of the Giant Magnetoresistance in Cobalt/Copper Spin Valves|S. J. C. H. Theeuwen,J. Caro,K. P. Wellock,S. Radelaar,C. H. Marrows,B. J. Hickey,V. I. Kozub###

Nanoconstriction Microscopy of the Giant Magnetoresistance in Cobalt/Copper Spin Valves. We use nanometer-sized point contacts to a Co/Cu spin valve to study the
giant magnetoresistance (GMR) of only a few Co domains. The measured data show
strong device-to-device differences of the GMR curve, which we attribute to the
absence of averaging over many domains. The GMR ratio decreases with increasing
bias current. For one particular device, this is accompanied by the development
of two distinct GMR plateaus, the plateau level depending on bias polarity and
sweep direction of the magnetic field. We attribute the observed behavior to
current-induced changes of the magnetization, involving spin transfer due to
incoherent emission of magnons and self-field effects.

###Metallic nonsuperconducting phase and d-wave superconductivity in Zn-substituted LaSrCuO|K. Karpinska,Marta Z. Cieplak,S. Guha,A. Malinowski,T. Skoskiewicz,W. Plesiewicz,M. Berkowski,B. Boyce,Thomas R. Lemberger,P. Lindenfeld###

Metallic nonsuperconducting phase and d-wave superconductivity in Zn-substituted LaSrCuO. Measurements of the resistivity, magnetoresistance and penetration depth were
made on films of LaSrCuO with up to 12 at.% of Zn substituted for the Cu. The
results show that the quadratic temperature dependence of the inverse square of
the penetration depth, indicative of d-wave superconductivity, is not affected
by doping. The suppression of superconductivity leads to a metallic
nonsuperconducting phase, as expected for a pairing mechanism related to spin
fluctuations. The metal-insulator transition occurs in the vicinity of kFl~1,
and appears to be disorder-driven, with the carrier concentration unaffected by
doping.

###Anomaly of AC resistance in magnetic nanoparticle alloys at spin-glass-like transition|A. B. Pakhomov,J. C. Denardin,M. Knobel,O. F. de Lima###

Anomaly of AC resistance in magnetic nanoparticle alloys at spin-glass-like transition. (withdrawn) A combined study of magnetic susceptibility and AC resistance was
performed on melt-spun Cu-Co granular magnetic ribbons. The AC resistance as a
function of temperature has a sharp maximum. We associate it with a diverging
correlation length at the temperature of collective freezing of magnetic
moments via increasing magnetic losses in the induced non-uniform field.
Application of this model to the experimental data allows a direct
determination of the critical exponent of correlation length on both sides of
the transition. Giant AC magnetoresistance is observed at the freezing
temperature.

###Weak localisation, interaction effects and the metallic phase in p-SiGe|P. T. Coleridge,A. S. Sachrajda,P. Zawadzki###

Weak localisation, interaction effects and the metallic phase in p-SiGe. Magnetoresistance results are presented for p-SiGe samples on the metallic
side of the B=0 metal-insulator transition. It was possible to separate the
weak localisation and Zeeman interaction effects but the results could not be
explained quantitatively within the framework of standard theories for quantum
corrections of a weakly interacting 2-dimensional system. Analysis using a
theory for interaction corrections at intermediate temperatures, recently
proposed by Zala, Narozhny and Aleiner, provided values of the Fermi liquid
parameter $F_0^{\sigma}$ of order -0.5. Similar values also explain the linear
increase of resistance with temperature characteristic of the metallic phase. e

###Various regimes of flux motion in Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$ single crystals|Weimin Chen,J. P. Franck,J. Jung###

Various regimes of flux motion in Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$ single crystals. Four regimes of vortex motion were identified in the magnetoresistance of
Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ single crystals: (1) thermally activated
flux flow (TAFF) in samples with surface defects caused by thermal annealing;
(2) TAFF-like plastic motion of highly entangled vortex liquid at low
temperatures, with $U_{pl} \sim (1-T/T_c)/H^{1/2}$; (3) pure free flux flow
above the region of (2) in clean and optimally doped samples; or, in its place,
(4) a combination of (2) and (3). This analysis gives an overall picture of
flux motion in Bi cuprates.

###Non-Fermi-Liquid Scaling in Ce(Ru_{0.5}Rh_{0.5})_2Si_2|Y. Tabata,D. R. Grempel,M. Ocio,T. Taniguchi,Y. Miyako###

Non-Fermi-Liquid Scaling in Ce(Ru_{0.5}Rh_{0.5})_2Si_2. We study the temperature and field dependence of the magnetic and transport
properties of the non-Fermi-liquid compound Ce(Ru_{1-x}Rh_x)_2Si_2 at x=0.5.
For fields $\lesssim $0.1T the experimental results show signatures of the
presence of Kondo-disorder, expected to be large at this concentration. For
larger fields, however, magnetic and transport properties are controlled by the
coupling of the conduction electrons to critical spin-fluctuations. The
temperature dependence of the susceptibility as well as the scaling properties
of the magnetoresistance are in very good agreement with the predictions of
recent dynamical mean-field theories of Kondo alloys close to a spin-glass
quantum critical point.

###Enhancement of GMR due to spin-mixing in magnetic multilayers with a superconducting contact|F. Taddei,S. Sanvito,C. J. Lambert###

Enhancement of GMR due to spin-mixing in magnetic multilayers with a superconducting contact. We study the Giant Magnetoresistance (GMR) ratio in magnetic multiayers with
a single superconducting contact in the presence of spin-mixing processes. It
has been recently shown that the GMR ratio of magnetic multilayers is strongly
suppressed by the presence of a superconducting contact when spin-flipping is
not allowed. In this Letter we demonstrate that the GMR ratio can be
dramatically enhanced by spin-orbit interaction and/or non-collinear magnetic
moments. The system is described using a tight-binding model with either s-p-d
or s-d atomic orbitals per site.

###Current and power spectrum in a magnetic tunnel device with an atomic size spacer|Bogdan R. Bulka###

Current and power spectrum in a magnetic tunnel device with an atomic size spacer. Current and its noise in a ferromagnetic double tunnel barrier device with a
small spacer particle were studied in the framework of the sequential tunneling
approach. Analytical formulae were derived for electron tunneling through the
spacer particle containing only a single energy level. It was shown that
Coulomb interactions of electrons with a different spin orientation lead to an
increase of the tunnel magnetoresistance. Interactions can also be responsible
for the negative differential resistance. A current noise study showed, which
relaxation processes can enhance or reduce fluctuations leading either to a
super-Poissonian or a sub-Poissonian shot noise.

###Resistance Jumps and Hysteresis in Ferromagnetic Wires|Tohru Koma,Masanori Yamanaka###

Resistance Jumps and Hysteresis in Ferromagnetic Wires. A phenomenological approach based on the principle of minimum heat generation
is proposed for understanding experiments for metallic wires with a
ferromagnetic domain wall controlled by a magnetic field. This approach
elucidates the origin of negative jump and of hysteresis in the
magnetoresistance experiments. To justify our approach, we computed the
transmission probability of a single electron through a wire. Under certain
conditions, the presence of a domain wall enhances the transmission through an
impurity potential. Combining this result with the principle of minimum heat
generation explains the counterintuitive negative resistance jump.

###Magnetotransport study of the charged stripes in high-T_c cuprates|Yoichi Ando,A. N. Lavrov,Kouji Segawa###

Magnetotransport study of the charged stripes in high-T_c cuprates. We present a study of the in-plane and out-of-plane magnetoresistance (MR) in
heavily-underdoped, antiferromagnetic YBa_{2}Cu_{3}O_{6+x}, which reveals a
variety of striking features. The in-plane MR demonstrates a "d-wave"-like
anisotropy upon rotating the magnetic field H within the ab plane. With
decreasing temperature below 20-25 K, the system acquires memory: exposing a
crystal to the magnetic field results in a persistent in-plane resistivity
anisotropy. The overall features can be explained by assuming that the CuO_2
planes contain a developed array of stripes accommodating the doped holes, and
that the MR is associated with the field-induced topological ordering of the
stripes.

###Kondo effect in a magnetic field and the magnetoresistivity of Kondo alloys|T. A. Costi###

Kondo effect in a magnetic field and the magnetoresistivity of Kondo alloys. The effect of a magnetic field on the spectral density of a $\rm{S=1/2}$
Kondo impurity is investigated at zero and finite temperatures by using
Wilson's numerical renormalization group method. A splitting of the total
spectral density is found for fields larger than a critical value
$H_{c}(T=0)\approx 0.5 T_{K}$, where $T_{K}$ is the Kondo scale. The splitting
correlates with a peak in the magnetoresistivity of dilute magnetic alloys
which we calculate and compare with the experiments on
$\rm{Ce_{x}La_{1-x}Al_{2}}, x=0.0063$. The linear magnetoconductance of quantum
dots exhibiting the Kondo effect is also calculated.

###Magnetoresistance and electronic structure of asymmetric GaAs/AlGaAs double quantum wells in the in-plane/tilted magnetic field|O. N. Makarovskii,L. Smrcka,P. Vasek,T. Jungwirth,M. Cukr,L. Jansen###

Magnetoresistance and electronic structure of asymmetric GaAs/AlGaAs double quantum wells in the in-plane/tilted magnetic field. Bilayer two-dimensional electron systems formed by a thin barrier in the GaAs
buffer of a standard heterostructure were investigated by magnetotransport
measurements. In magnetic fields oriented parallel to the electron layers, the
magnetoresistance exhibits an oscillation associated with the depopulation of
the higher occupied subband and the field-induced transition into a decoupled
bilayer. Shubnikov-de Haas oscillations in slightly tilted magnetic fields
allow to reconstruct the evolution of the electron concentration in the
individual subbands as a function of the in-plane magnetic field. The
characteristics of the system derived experimentally are in quantitative
agreement with numerical self-consistent-field calculations of the electronic
structure.

###Spectacular decrease of the melting magnetic field in the charge-ordered state of tensile Pr0.5Ca0.5MnO3 films|W. Prellier,A. M. Haghiri-Gosnet,B. Mercey,Ph. Lecoeur,M. Hervieu,Ch. Simon,B. Raveau###

Spectacular decrease of the melting magnetic field in the charge-ordered state of tensile Pr0.5Ca0.5MnO3 films. An insulator to metal transition below 240K is induced by applying a 7T
magnetic field in Pr0.5Ca0.5MnO3 thin films grown by the Pulsed Laser
Deposition technique on (100) SrTiO3 substrates. This value of the melting
magnetic field, much lower that the one required in bulk (20T), is assumed to
be an effect of the tensile stress. These results confirm the importance of the
bandwidth in the control of the physical properties of this compound and open
the route to get colossal magnetoresistive properties by using strain effects.

###A proper ballistic calculation of tunneling conductance for real junctions|P. M. Levy,K. Wang,P. H. Dederichs,C. Heide,S. Zhang,L. Szunyogh,P. Weinberger###

A proper ballistic calculation of tunneling conductance for real junctions. Employing an ab initio Screened Korringa-Kohn-Rostoker (SKKR) band structure
method for a metal-vacuum-metal junction, we find that the tunnel conductance
is different when it is calculated across the barrier and far from it. We
attribute this difference to an artefact of the ballistic approach which
overestimates the role of specular reflections, and its inability to pick up
contributions from localized interface states. To reconcile the ballistic
approach with experiment, we propose that the tunnel conductance should be
calculated as if it is measured directly across the barrier. In this case the
predicted tunneling magnetoresistance is larger.

###Impurity Scattering from $δ$-layers in Giant Magnetoresistance Systems|C. H. Marrows,B. J. Hickey###

Impurity Scattering from $δ$-layers in Giant Magnetoresistance Systems. The properties of the archetypal Co/Cu giant magnetoresistance (GMR)
spin-valve structure have been modified by the insertion of very thin
(sub-monolayer) $\delta$-layers of various elements at different points within
the Co layers, and at the Co/Cu interface. Different effects are observed
depending on the nature of the impurity, its position within the periodic
table, and its location within the spin-valve. The GMR can be strongly enhanced
or suppressed for various specific combinations of these parameters, giving
insight into the microscopic mechanisms giving rise to the GMR.

###Comment on ``Magnetoresistance Anomalies in Antiferromagnetic YBa$_2$Cu$_3$O$_{6+x}$: Fingerprints of Charged Stripes''|Andras Janossy,Ferenc Simon,Titusz Feher###

Comment on ``Magnetoresistance Anomalies in Antiferromagnetic YBa$_2$Cu$_3$O$_{6+x}$: Fingerprints of Charged Stripes''. In a recent Letter Ando et al (cond-mat/9905071) discovered an anomalous
magnetoresistance(MR) in hole doped antiferromagnetic YBa$_2$Cu$_3$O$_{6+x}$,
which they attributed to charged stripes, i.e., to segregation of holes into
lines. In this Comment we show that the experiments, albeit being interesting,
do not prove the existence of stripes. In our view the anomalous behavior is
due to an (a,b) plane anisotropy of the resistivity in the bulk and to a
magnetic field dependent antiferromagnetic (AF) domain structure. It is
unlikely that domain walls are charged stripes.

###Evidence for the immobile bipolaron formation in the paramagnetic state of the magnetoresistive manganites|G. M. Zhao,Y. S. Wang,D. J. Kang,W. Prellier,M. Rajeswari,H. Keller,T. Venkatesan,C. W. Chu,R. L. Greene###

Evidence for the immobile bipolaron formation in the paramagnetic state of the magnetoresistive manganites. Recent research suggests that the charge carriers in the paramagnetic state
of the magnetoresistive manganites are small polarons. Here we report studies
of the oxygen-isotope effects on the intrinsic resistivity and thermoelectric
power in several ferromagnetic manganites. The precise measurements of these
isotope effects allow us to make a quantitative data analysis. Our results do
not support a simple small-polaron model, but rather provide compelling
evidence for the presence of small immobile bipolarons, i.e., pairs of small
polarons. Since the bipolarons in the manganites are immobile, the present
result alone appears not to give a positive support to the bipolaronic
superconductivity theory for the copper-based perovskites.

###Detecting Gapless Excitations above Ferromagnetic Domain Walls|Tohru Koma,Masanori Yamanaka###

Detecting Gapless Excitations above Ferromagnetic Domain Walls. In a two or three dimensional ferromagnetic XXZ model, a low energy
excitation mode above a magnetic domain wall is gapless, whereas all of the
usual spin wave excitations moving around the whole crystal are gapful.
Although this surprising fact was already proved in a mathematically rigorous
manner, the gapless excitations have not yet been detected experimentally. For
this issue, we show theoretically that the gapless excitations appear as the
dynamical fluctuations of the experimental observable, magnetoresistance, in a
ferromagnetic wire. We also discuss other methods (e.g., ferromagnetic
resonance and neutron scattering) to detect the gapless excitations
experimentally.

###Mesoscale magnetism at the grain boundaries in colossal magnetoresistive films|Yeong-Ah Soh,G. Aeppli,N. D. Mathur,M. G. Blamire###

Mesoscale magnetism at the grain boundaries in colossal magnetoresistive films. We report the discovery of mesoscale regions with distinctive magnetic
properties in epitaxial La$_{1-x}$Sr$_{x}$MnO$_{3}$ films which exhibit
tunneling-like magnetoresistance across grain boundaries. By using
temperature-dependent magnetic force microscopy we observe that the mesoscale
regions are formed near the grain boundaries and have a different Curie
temperature (up to 20 K {\it higher}) than the grain interiors. Our images
provide direct evidence for previous speculations that the grain boundaries in
thin films are not magnetically and electronically sharp interfaces. The size
of the mesoscale regions varies with temperature and nature of the underlying
defect.

###Exclusion of quantum coherence as the origin of the 2D metallic state in high-mobility silicon inversion layers|G. Brunthaler,A. Prinz,G. Bauer,V. M. Pudalov###

Exclusion of quantum coherence as the origin of the 2D metallic state in high-mobility silicon inversion layers. The temperature and density dependence of the phase coherence time
$\tau_\phi$ in high-mobility silicon inversion layers was determined from the
magnetoresistivity due to weak localization. The upper temperature limit for
single-electron quantum interference effects was delineated by comparing
$\tau_\phi$ with the momentum relaxation time $\tau$. A comparison between the
density dependence of the borders for quantum interference effects and the
strong resistivity drop reveals that theses effects are not related to each
other. As the strong resistivity drop occurs in the Drude regime, the apparent
metallic behavior can not be caused by quantum coherent effects.

###A nature of low-temperature resistivity minimum in ceramic manganites|E. Rozenberg,M. Auslender,I. Felner,G. Gorodetsky###

A nature of low-temperature resistivity minimum in ceramic manganites. Measurements of magnetoresistance and magnetization were carried out on
ceramic samples of La_{0.5}Pb_{0.5}MnO_{3} and La_{0.5}Pb_{0.5}MnO_{3},
containing 10 at. % Ag in a dispersed form. The results obtained for the
resistivity at zero applied magnetic field exhibit a shallow minimum at
temperatures T about 25 K - 30 K, which shifts towards lower temperatures upon
applying magnetic field and disappears at a certain (rather low) field. Also
the resistivity at helium temperature decreases upon applying magnetic fields.
It is shown that the model of spin-dependent carrier tunneling between
antiferromagnetically coupled grains may account for the results observed.

###Critical Temperature of Ferromagnetic Transition in Three-Dimensional Double-Exchange Models|Yukitoshi Motome,Nobuo Furukawa###

Critical Temperature of Ferromagnetic Transition in Three-Dimensional Double-Exchange Models. Ferromagnetic transition in three-dimensional double-exchange models is
studied by the Monte Carlo method. Critical temperature $T_{\rm c}$ is
precisely determined by finite-size scaling analysis. Strong spin fluctuations
in this itinerant system significantly reduce $T_{\rm c}$ from mean-field
estimates. By choosing appropriate parameters, obtained values of $T_{\rm c}$
quantitatively agree with experiments for the ferromagnetic metal regime of
(La,Sr)MnO$_{3}$, which is a typical perovskite manganite showing colossal
magnetoresistance. This indicates that the double-exchange mechanism alone is
sufficient to explain $T_{\rm c}$ in this material. Critical exponents are also
discussed.

###Origin of Magnetoresistance Anomalies in Antiferromagnetic YBa_{2}Cu_{3}O_{6+x}|A. S. Moskvin,Yu. D. Panov###

Origin of Magnetoresistance Anomalies in Antiferromagnetic YBa_{2}Cu_{3}O_{6+x}. Specific d-wave angular dependence of the in-plane magnetoresistence in
antiferromagnetic tetragonal YBa_{2}Cu_{3}O_{6+x} (x~0.3) on orientation of the
external magnetic field in (a,b) plane is assigned to the effective hole
transport through low lying excited purely oxygen doublet O2pe_u state, not the
ground b_{1g}(d_{x^2-y^2}) state. External magnetic field determines the
orientation of the strong exchange field for the spin-triplet
b_{1g}e_u:{}^{3}E_u state of the hole CuO_4 center and due to the spin-orbital
coupling results in either orbital polarization of the E_u doublet giving rise
to the spatial anisotropy of the hole transport. Experimental data allow to
estimate parameter of the effective spin Hamiltonian.

###Magnetoresistance induced by low-field control of phase separation in La0.5Ca0.5MnO3|F. Parisi,P. Levy,L. Ghivelder,G. Polla,D. Vega###

Magnetoresistance induced by low-field control of phase separation in La0.5Ca0.5MnO3. The effect of low magnetic fields on the transport properties of a manganite
compound with magnetic phase separation is studied. The different behavior
obtained in samples of La0.5Ca0.5MnO3 related to the way in which the low field
is applied is consistent with a picture of changes in the metallic fraction
induced by the magnetic field in a field-cooled cycle. Using a simple model of
conduction through a binary mixture, the interrelation between
magnetoresistance, metallic fraction and percolation temperature is accounted
for. A new physical coefficient relating magnetic field and metallic fraction
emerges as the relevant parameter in the description of phase separated
manganites.

###Large two-level magnetoresistance effect in doped manganite grain boundary junctions|J. B. Philipp,C. Hoefener,S. Thienhaus,J. Klein,L. Alff,R. Gross###

Large two-level magnetoresistance effect in doped manganite grain boundary junctions. We performed a systematic analysis of the tunneling magnetoresistance (TMR)
effect in single grain boundary junctions formed in epitaxial
La(2/3)Ca(1/3)MnO(3) films deposited on SrTiO(3) bicrystals. For magnetic
fields H applied parallel to the grain boundary barrier, an ideal two-level
resistance switching behavior with sharp transitions is observed with a TMR
effect of up to 300% at 4.2 K and still above 100% at 77 K. Varying the angle
between H and the grain boundary results in differently shaped resistance vs H
curves. The observed behavior is explained within a model of magnetic domain
pinning at the grain boundary interface.

###The effect of a parallel magnetic field on the Boltzmann conductivity and the Hall coefficient of a disordered two dimensional Fermi liquid|Igor F. Herbut###

The effect of a parallel magnetic field on the Boltzmann conductivity and the Hall coefficient of a disordered two dimensional Fermi liquid. Screening of an external random potential by a two dimensional (2D) Fermi
liquid may be strongly dependent on the degree of its polarization. This is
considered as a possible mechanism for the observed strong magnetoresistance of
the 2D electron liquid in the magnetic field parallel to the electron plane. A
Hartree-Fock calculation for the weakly disordered Hubbard model which
qualitatively describes the experiments on the diagonal and the Hall
resisitivity in the finite-temperature metallic state in the high mobility Si
inversion layers is presented.

###Quantum Hall Ferromagnetism in a Two-Dimensional Electron System|J. Eom,H. Cho,W. Kang,K. L. Campman,A. C. Gossard,M. Bichler,W. Wegscheider###

Quantum Hall Ferromagnetism in a Two-Dimensional Electron System. Experiments on a nearly spin degenerate two-dimensional electron system
reveals unusual hysteretic and relaxational transport in the fractional quantum
Hall effect regime. The transition between the spin-polarized (with fill
fraction $\nu = 1/3$) and spin-unpolarized ($\nu = 2/5$) states is accompanied
by a complicated series of hysteresis loops reminiscent of a classical
ferromagnet. In correlation with the hysteresis, magnetoresistance can either
grow or decay logarithmically in time with remarkable persistence and does not
saturate. In contrast to the established models of relaxation, the relaxation
rate exhibits an anomalous divergence as temperature is reduced. These results
indicate the presence of novel two-dimensional ferromagnetism with a
complicated magnetic domain dynamic.

###Current-induced conductance switching in epitaxial La0.7Sr0.3MnO3/SrTiO3 multilayers|K. Doerr,K. -H. Mueller,T. Walter,M. Sahana,D. Eckert,K. Nenkov,L. Schultz,K. Brand,M. Lehmann###

Current-induced conductance switching in epitaxial La0.7Sr0.3MnO3/SrTiO3 multilayers. We report on the non-linear in-plane electrical transport in coherently grown
[La0.7Sr0.3MnO3/SrTiO3] multilayers with ultrathin (< 3 nm) single layers.
Current-induced switching of the conductance, with low conductance at larger
currents, is demonstrated. The conductance switching is modified under a
magnetic field, resulting in an extremely large magnetoresistance of negative,
or in a special case even positive, sign. Our results suggest a percolative
nature of transport where a large local current density gives rise to a
spin-polarizing and a thermal effect of current.

###Tunneling magnetoresistance in diluted magnetic semiconductor tunnel junctions|Pin Lyu,Kyungsun Moon###

Tunneling magnetoresistance in diluted magnetic semiconductor tunnel junctions. Using the spin-polarized tunneling model and taking into account the basic
physics of ferromagnetic semiconductors, we study the temperature dependence of
the tunneling magnetoresistance (TMR) in the diluted magnetic semiconductor
(DMS) trilayer heterostructure system (Ga,Mn)As/AlAs/(Ga,Mn)As. The
experimentally observed TMR ratio is in reasonable agreement with our result
based on the typical material parameters. It is also shown that the TMR ratio
has a strong dependence on both the itinerant-carrier density and the magnetic
ion density in the DMS electrodes. This can provide a potential way to achieve
larger TMR ratio by optimally adjusting the material parameters.

###Competition of Zener and polaron phases in doped CMR manganites|A. Weisse,J. Loos,H. Fehske###

Competition of Zener and polaron phases in doped CMR manganites. Inspired by the strong experimental evidence for the coexistence of localized
and itinerant charge carriers close to the metal-insulator transition in the
ferromagnetic phase of colossal magnetoresistive manganese perovskites, for a
theoretical description of the CMR transition we propose a two-phase scenario
with percolative characteristics between equal-density polaron and Zener
band-electron states. We find that the subtle balance between these two states
with distinctly different electronic properties can be readily influenced by
varying physical parameters, producing various ``colossal'' effects, such as
the large magnetization and conductivity changes in the vicinity of the
transition temperature.

###Width of the Zero-Field Superconducting Resistive Transition in the Vicinity of the Localization Threshold|V. F. Gantmakher,M. V. Golubkov###

Width of the Zero-Field Superconducting Resistive Transition in the Vicinity of the Localization Threshold. Resistive superconducting zero-field transition in amorphous In-O films in
states from the vicinity of the insulator-superconductor transition is analyzed
in terms of two characteristic temperatures: the upper one, $T_{c0}$, where the
finite amplitude of the order parameter is established and the lower one,
$T_c$, where the phase ordering takes place. It follows from the
magnetoresistance measurements that the resistance in between, $T_c<T<T_{c0}$,
cannot be ascribed to dissipation by thermally dissociated vortex pairs. So, it
is not Kosterlitz-Thouless-Berezinskii transition that happens at $T_c$.

###Percolative conductivity and critical exponents in mixed-valent manganites|Ye Xiong,Shun-Qing Shen,X. C. Xie###

Percolative conductivity and critical exponents in mixed-valent manganites. Recent experiments have shown that some colossal magnetoresistance (CMR)
materials exhibit a percolation transition. The conductivity exponent varies
substantially with or without an external magnetic field. This finding prompted
us to carry out theoretical studies of percolation transition in CMR systems.
We find that the percolation transition coincides with the magnetic transition
and this causes a large effect of a magnetic field on the percolation
transition. Using real-space-renormalization method and numerical calculations
for two-dimensional (2D) and three-dimensional (3D) models, we obtain the
conductivity exponent $t$ to be 5.3 (3D) and 3.3 (2D) without a magnetic field,
and 1.7 (3D) and 1.4 (2D) with a magnetic field.

###Metal-insulator crossover in superconducting cuprates in strong magnetic fields|P. A. Marchetti,Zhao-bin Su,Lu Yu###

Metal-insulator crossover in superconducting cuprates in strong magnetic fields. The metal-insulator crossover of the in-plane resistivity upon temperature
decrease, recently observed in several classes of cuprate superconductors, when
a strong magnetic field suppresses the superconductivity, is explained using
the $U(1)\times SU(2)$ Chern-Simons gauge field theory. The origin of this
crossover is the same as that for a similar phenomenon observed in heavily
underdoped cuprates without magnetic field. It is due to the interplay between
the diffusive motion of the charge carriers and the ``peculiar'' localization
effect due to short-range antiferromagnetic order. We also calculate the
in-plane transverse magnetoresistance which is in a fairly good agreement with
available experimental data.

###Substrate-effect on the magnetic microstructure of La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ thin films studied by magnetic force microscopy|R. Desfeux,S. Bailleul,A. Da Costa,W. Prellier,A. M. Haghiri-Gosnet###

Substrate-effect on the magnetic microstructure of La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ thin films studied by magnetic force microscopy. Colossal magnetoresistive (CMR) La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ (LSMO) thin
films have been grown under tensile strains on (100)-SrTiO$_{3}$ substrates and
compressive strains on (100)-LaAlO$_{3}$ and (110)-NdGaO$_{3}$ substrates by
pulsed laser deposition.
  Using magnetic force microscopy (MFM), a "feather-like" magnetic pattern,
characteristic of films with an in-plane magnetization, is observed for films
deposited on both SrTiO$_{3}$ and NdGaO$_{3}$ while a "bubble" magnetic
pattern, typical of films with an out-of plane magnetization, is recorded for
LaAlO$_{3}$. We show that the shape of the magnetic pattern imaged by MFM is
fully correlated to the easy direction of the magnetization in the film.

###A new class of magnetic materials: Sr2FeMoO6 and related compounds|D. D. Sarma###

A new class of magnetic materials: Sr2FeMoO6 and related compounds. Ordered double perovskite oxides of the general formula, A2BB'O6, have been
known for several decades to have interesting electronic and magnetic
properties. However, a recent report of a spectacular negative
magnetoresistance effect in a specific member of this family, namely Sr2FeMoO6,
has brought this class of compounds under intense scrutiny. It is now believed
that the origin of magnetism in this class of compounds is based on a novel
kinetically-driven mechanism. This new mechanism is also likely to be
responsible for the unusually high temperature ferromagnetism in several other
systems, such as dilute magnetic semiconductors, as well as in various
half-metallic ferromagnetic systems, such as Heussler alloys.

###Strong ferromangnetism and weak antiferroamgnetism in double perovskites: Sr$_2$Fe{/it M}O$_6$ ({/it M}=Mo, W and Re)|Z. Fang,K. Terakura,J. Kanamori###

Strong ferromangnetism and weak antiferroamgnetism in double perovskites: Sr$_2$Fe{/it M}O$_6$ ({/it M}=Mo, W and Re). Double perovskites Sr$_2$FeMO$_6$ (M=Mo and Re) exhibit significant colossal
magnetoresistance even at room temperature due to the high Curie Temperature
(419K and 401K). However, such a high Curie Temperature is puzzling, given the
large separation between magnetic elements (Fe). Moreover, with M=W, the
electronic and magnetic properties suddenly change to insulating and
antiferromagnetic with the N{\'e}el temperature of only 16$\sim$37 K. Based on
detailed electronic structure calculations, a new mechanism is proposed which
stabilizes the strong ferromagnetic state for M=Mo and Re and is passivated for
M=W.

###Thermal magnetization fluctuations in thin films and a new physical form for magnetization damping|Vladimir L. Safonov,H. Neal Bertram###

Thermal magnetization fluctuations in thin films and a new physical form for magnetization damping. The effect of thermal fluctuations on a thin film magnetoresistive element
has been calculated. The technique involves adding to the basic spin dynamics a
general form of interaction with a thermal bath. For a general anisotropic
magnetic system the resulting equation can be written as a Langevin equation
for a harmonic oscillator. Our approach predicts two times smaller noise power
at low frequencies than the conventional stochastic Landau-Lifshitz-Gilbert
equation. It is shown that equivalent results can be obtained by introducing a
tensor phenomenological damping term to the gyromagnetic dynamics driven by a
thermal fluctuating field.

###Orbital effects in manganites|D. I. Khomskii###

Orbital effects in manganites. In this paper I give a short review of some properties of the colossal
magnetoresistance manganites, connected with the orbital degrees of freedom.
Ions Mn{3+}, present in most of these compounds, have double orbital degeneracy
and are strong Jahn-Teller ions, causing structural distortions and orbital
ordering. Mechanisms leading to such ordering are shortly discussed, and the
role of orbital degrees of freedom in different parts of the phase diagram of
manganites is described. Special attention is paid to the properties of
low-doped systems (doping 0.1 - 0.25), to overdoped systems (x > 0.5), and to
the possibility of a novel type of orbital ordering in optimally doped
ferromagnetic metallic manganites.

###Test for interlayer coherence in a quasi-two-dimensional superconductor|John Singleton,P. A. Goddard,A. Ardavan,N. Harrison,S. J. Blundell,J. A. Schlueter,A. M. Kini###

Test for interlayer coherence in a quasi-two-dimensional superconductor. Peaks in the magnetoresistivity of the layered superconductor
$\kappa$-(BEDT-TTF)$_2$Cu(NCS)$_2$, measured in fields $\leq 45$ T applied
within the layers, show that the Fermi surface is extended in the interlayer
direction and enable the interlayer transfer integral ($t_{\perp} \approx 0.04$
meV) to be deduced. However, the quasiparticle scattering rate $\tau^{-1}$ is
such that $\hbar/\tau \sim 6t_{\perp}$, implying that
$\kappa$-(BEDT-TTF)$_2$Cu(NCS)$_2$ meets the criterion used to identify
interlayer incoherence. The applicability of this criterion to anisotropic
materials is thus shown to be questionable.

###Spectacular doping dependence of interlayer exchange and other results on spin waves in bilayer manganites|T. G. Perring,D. T. Adroja,G. Chaboussant,G. Aeppli,T. Kimura,Y. Tokura###

Spectacular doping dependence of interlayer exchange and other results on spin waves in bilayer manganites. We report the measurement of spin waves in the bilayer colossal
magnetoresistive manganites La(2-2x)Sr(1+2x)Mn2O7 with x=0.30, 0.35 and 0.40.
For x=0.35 and 0.40 the entire acoustic and optic dispersion relations are
reasonably well described by those for a bilayer Heisenberg Hamiltonian with
nearest neighbour exchange only. The in-plane coupling is only weakly dependent
on x, but the coupling between the planes of a bilayer changes by a factor of
four. The results directly reveal the change from mixed and character of the
orbitals to mostly character with increasing hole concentration.

###Magnetic Diode Effect in Double Barrier Tunnel Junctions|M. Chshiev,D. Stoeffler,A. Vedyayev,K. Ounadjela###

Magnetic Diode Effect in Double Barrier Tunnel Junctions. A quantum statistical theory of spin-dependent tunneling through asymmetric
magnetic double barrier junctions is presented which describes $both$ ballistic
and diffuse tunneling by a single analytical expression. It is evidenced that
the key parameter for the transition between these two tunneling regimes is the
electron scattering. For these junctions a strong asymmetric behaviour in the
I-V characteristics and the tunnel magnetoresistance (TMR) is predicted which
can be controlled by an applied magnetic field. This phenomenon relates to the
quantum well states in the middle metallic layer. The corresponding resonances
in the current and the TMR are drastically phase shifted under positive and
negative voltage.

###Low Voltage I-V Characteristics in Magnetic Tunnel Junctions|G. G. Cabrera,N. Garcia###

Low Voltage I-V Characteristics in Magnetic Tunnel Junctions. We show that elastic currents that take into account variations of the tunnel
transmitivity with voltage and a large ratio of majority to minority spin
densities of states of the $s$ band, can account for the low voltage current
anomalies observed in magnet-oxide-magnet junctions. The anomalies can be
positive, negative or have a mixed form, depending of the position of the Fermi
level in the $s$ band, in agreement with observations. Magnon contribution is
negligible small to account for the sharp drop of the magnetoresistance with
the voltage bias.

###Effect of intersubband scattering on weak localization in 2D systems|N. S. Averkiev,L. E. Golub,S. A. Tarasenko,M. Willander###

Effect of intersubband scattering on weak localization in 2D systems. The theory of weak localization is generalized for multilevel 2D systems
taking into account intersubband scattering. It is shown that weak intersubband
scattering which is negligible in a classical transport, affects strongly the
weak-localization correction to conductivity. The anomalous magnetoresistance
is calculated in the whole range of classically low magnetic fields. This
correction to conductivity is shown to depend strongly on the ratios of
occupied level concentrations. It is demonstrated that at relatively low
population of the excited subband, it is necessary to use the present theory
because the high-field limit asimptotics is shown to be achieved only in
classical magnetic fields.

###Electron scattering on circular symmetric magnetic profiles in a two-dimensional electron gas|J. Reijniers,F. M. Peeters,A. Matulis###

Electron scattering on circular symmetric magnetic profiles in a two-dimensional electron gas. The quasi-bound and scattered states in a 2DEG subjected to a circular
symmetric steplike magnetic profile with zero average magnetic field are
studied. We calculate the effect of a random distribution of such identical
profiles on the transport properties of a 2DEG. We show that a nonzero Hall
resistance can be obtained, although $<B_{z} >=0$, and that in some cases it
can even change sign as function of the Fermi energy or the magnetic field
strength. The Hall and magnetoresistance show pronounced resonances apart from
the Landau states of the inner core, corresponding to the so-called quasi-bound
snake orbit states.

###Spin state and phase competition in TbBaCo_{2}O_{5.5} and the lanthanide series LnBaCo_{2}O_{5+δ} (0<=δ<=1)|Hua Wu###

Spin state and phase competition in TbBaCo_{2}O_{5.5} and the lanthanide series LnBaCo_{2}O_{5+δ} (0<=δ<=1). A clear physics picture of TbBaCo$_{2}$O$_{5.5}$ is revealed on the basis of
density functional theory calculations. An antiferromagnetic (AFM)
superexchange coupling between the almost high-spin Co$^{3+}$ ions competes
with a ferromagnetic (FM) interaction mediated by both p-d exchange and double
exchange, being responsible for the observed AFM-FM transition. And the
metal-insulator transition is accompanied by an xy/xz orbital-ordering
transition. Moreover, this picture can be generalized to the whole lanthanide
series, and it is predicted that a few room-temperature magnetoresistance
materials could be found in LnBa$_{1-x}$A$_{x}$Co$_{2}$O$_{5+\delta}$
(Ln=Ho,Er,Tm,Yb,Lu; A=Sr,Ca,Mg).

###Magnetization Distribution in the layered CMR Manganite La1.2Sr1.8Mn2O7 from Polarized Neutron Diffraction|D. N. Argyriou,P. J. Brown,J. S. Gardner,R. H. Heffner###

Magnetization Distribution in the layered CMR Manganite La1.2Sr1.8Mn2O7 from Polarized Neutron Diffraction. In the ferromagnetic metallic state of the colossal magnetoresistive (CMR)
manganite La1.2Sr1.8Mn2O7, the spin density distribution is essentially in
agreement with the standard picture in which the unpaired electrons occupy the
three t2g orbitals, dxy, dyz, and dxz. However we find a small spin density ~4%
of the total Mn spin) on the apical O(2) oxygen atom at both 100 K and 220 K
and we suggest that this is due to covalency effects. Surprisingly we find no
evidence of spin on the other apical oxygen O(1) suggesting that the Mn eg
electron distribution along the c-axis is highly anisotropic.

###The Structure of Nanoscale Polaron Correlations in La1.2Sr1.8Mn2O7|B. J. Campbell,R. Osborn,D. N. Argyriou,L. Vasiliu-Doloc,J. F. Mitchell,S. K. Sinha,U. Ruett,C. D. Ling,Z. Islam,J. W. Lynn###

The Structure of Nanoscale Polaron Correlations in La1.2Sr1.8Mn2O7. A system of strongly-interacting electron-lattice polarons can exhibit charge
and orbital order at sufficiently high polaron concentrations. In this study,
the structure of short-range polaron correlations in the layered colossal
magnetoresistive perovskite manganite, La1.2Sr1.8Mn2O7, has been determined by
a crystallographic analysis of broad satellite maxima observed in diffuse X-ray
and neutron scattering data. The resulting q=(0.3,0,1) modulation is a
longitudinal octahedral-stretch mode, consistent with an incommensurate
Jahn-Teller-coupled charge-density-wave fluctuations, that implies an unusual
orbital-stripe pattern parallel to the <100> directions.

###Zn-doping effect on the magnetotransport properties of Bi_{2}Sr_{2-x}La_{x}CuO_{6+δ} single crystals|Y. Hanaki,Yoichi Ando,S. Ono,J. Takeya###

Zn-doping effect on the magnetotransport properties of Bi_{2}Sr_{2-x}La_{x}CuO_{6+δ} single crystals. We report the magnetotransport properties of
Bi_{2}Sr_{2-x}La_{x}Cu_{1-z}Zn_{z}O_{6+\delta} (Zn-doped BSLCO) single crystals
with z of up to 2.2%. Besides the typical Zn-doping effects on the in-plane
resistivity and the Hall angle, we demonstrate that the nature of the
low-temperature normal state in the Zn-doped samples is significantly altered
from that in the pristine samples under high magnetic fields. In particular, we
observe nearly-isotropic negative magnetoresistance as well as an increase in
the Hall coefficient at very low temperatures in non-superconducting Zn-doped
samples, which we propose to be caused by the Kondo scattering from the local
moments induced by Zn impurities.

###Low density approach to the Kondo-lattice model|W. Nolting,G. G. Reddy,A. Ramakanth,D. Meyer###

Low density approach to the Kondo-lattice model. We propose a new approach to the (ferromagnetic) Kondo-lattice model in the
low density region, where the model is thought to give a reasonable frame work
for manganites with perovskite structure exhibiting the "colossal
magnetoresistance" -effect. Results for the temperature- dependent
quasiparticle density of states are presented. Typical features can be
interpreted in terms of elementary spin-exchange processes between itinerant
conduction electrons and localized moments. The approach is exact in the zero
bandwidth limit for all temperatures and at T=0 for arbitrary bandwidths,
fulfills exact high-energy expansions and reproduces correctly second order
perturbation theory in the exchange coupling.

###Critical Exponents for the Ferromagnetism in Colossal Magnetoresistance Manganites|Nobuo Furukawa,Yukitoshi Motome###

Critical Exponents for the Ferromagnetism in Colossal Magnetoresistance Manganites. Critical phenomena of ferromagnetic transition in colossal magnetoresistance
manganites are theoretically studied. Concerning the critical exponents for
this transition, there still remains controversy among experimental results. In
order to clarify intrinsic physics of the manganites through a comparison with
theoretical prediction, we investigate the critical phenomena of
double-exchange models by using finite-size scaling analysis on unbiased
numerical results. As a result, we show that the critical exponents of the
ferromagnetic transition of the three-dimensional double-exchange model is
consistent with those of the Heisenberg model, but are distinct from the
mean-field one.

###Colossal Effects in Transition Metal Oxides Caused by Intrinsic Inhomogeneities|J. Burgy,M. Mayr,V. Martin-Mayor,A. Moreo,E. Dagotto###

Colossal Effects in Transition Metal Oxides Caused by Intrinsic Inhomogeneities. The influence of quenched disorder on the competition between ordered states
separated by a first-order transition is investigated. A phase diagram with
features resembling quantum-critical behavior is observed, even using classical
models. The low-temperature paramagnetic regime consists of coexisting ordered
clusters, with randomly oriented order parameters. Extended to manganites, this
state is argued to have a colossal magnetoresistance effect. A scale T* for
cluster formation is discussed. This is the analog of the Griffiths
temperature, but for the case of two competing orders, producing a strong
susceptibility to external fields. Cuprates may have similar features,
compatible with the large proximity effect of the very underdoped regime.

###Two energy scales and slow crossover in YbAl3|J. M. Lawrence,T. Ebihara,P. S. Riseborough,C. H. Booth,M. F. Hundley,P. G. Pagliuso,J. L. Sarrao,J. D. Thompson,M. H. Jung,A. H. Lacerda,G. H. Kwei###

Two energy scales and slow crossover in YbAl3. Experimental results for the susceptibility, specific heat, 4f occupation
number, Hall effect and magnetoresistance for single crystals of YbAl$_{3}$
show that, in addition to the Kondo energy scale $k_{B}T_{K}$ $% \sim $ 670K,
there is a low temperature scale $T_{coh}<50$K for the onset of coherence.
Furthermore the crossover from the low temperature Fermi liquid regime to the
high temperature local moment regime is slower than predicted by the Anderson
impurity model. These effects may reflect the behavior of the Anderson Lattice
in the limit of low conduction electron density.

###Magnetoresistance of Untwinned YBa_{2}Cu_{3}O_{y} Single Crystals in a Wide Range of Doping: Anomalous Hole-Doping Dependence of the Coherence Length|Yoichi Ando,Kouji Segawa###

Magnetoresistance of Untwinned YBa_{2}Cu_{3}O_{y} Single Crystals in a Wide Range of Doping: Anomalous Hole-Doping Dependence of the Coherence Length. Magnetoresistance (MR) in the a-axis resistivity of untwinned
YBa_{2}Cu_{3}O_{y} single crystals is measured for a wide range of doping (y =
6.45 - 7.0). The y-dependence of the in-plane coherence length \xi_{ab}
estimated from the fluctuation magnetoconductance indicates that the
superconductivity is anomalously weakened in the 60-K phase; this gives
evidence, together with the Hall coefficient and the a-axis thermopower data
that suggest the hole doping to be 12% for y = 6.65, that the origin of the
60-K plateau is the 1/8 anomaly. At high temperatures, the normal-state MR data
show signatures of the Zeeman effect on the pseudogap in underdoped samples.

###Studies on the Anisotropic Properties of MgB2|O. F. de Lima###

Studies on the Anisotropic Properties of MgB2. This paper presents a brief review on the reported anisotropic properties of
MgB2, in the superconducting state (e.g. upper critical field Hc2, field
penetration depth, coherence length, energy gap) as well as in the normal state
(e.g., magnetoresistance, compressibility, thermal expansion). So far, the
reported results have been obtained using aligned crystallites, c-axis oriented
thin films and sub-millimeter crystals. Since impurity scattering affects
directly the gap anisotropy it could be one of the main reasons for the
different values observed in the Hc2 anisotropy ratio, ranging between 1.3 and
2.6.

###Prediction of Orbital Ordering in Single-Layered Ruthenates|Takashi Hotta,Elbio Dagotto###

Prediction of Orbital Ordering in Single-Layered Ruthenates. The key role of the orbital degree of freedom to understand the magnetic
properties of layered ruthenates is here discussed. In the G-type
antiferromagnetic phase of Ca$_2$RuO$_4$, recent X-ray experiments reported the
presence of 0.5 hole per site in the $d_{xy}$ orbital, while the $d_{\rm yz}$
and $d_{zx}$ orbitals contain 1.5 holes. This unexpected $t_{2g}$ hole
distribution is explained by a novel state with orbital ordering (OO),
stabilized by a combination of Coulomb interactions and lattice distortions. In
addition, the rich phase diagram presented here suggests the possibility of
large magnetoresistance effects, and predicts a new ferromagnetic OO phase in
ruthenates.

###Hole-Hole Interaction Effect in the Conductance of the Two-Dimensional Hole Gas in the Ballistic Regime|Y. Y. Proskuryakov,A. K. Savchenko,S. S. Safonov,M. Pepper,M. Y. Simmons,D. A. Ritchie###

Hole-Hole Interaction Effect in the Conductance of the Two-Dimensional Hole Gas in the Ballistic Regime. On a high mobility two-dimensional hole gas (2DHG) in a GaAs/GaAlAs
heterostructure we study the interaction correction to the Drude conductivity
in the ballistic regime, $k_BT\tau /\hbar $ $>1$. It is shown that the
'metallic' behaviour of the resistivity ($d\rho /dT>0$) of the low-density 2DHG
is caused by hole-hole interaction effect in this regime. We find that the
temperature dependence of the conductivity and the parallel-field
magnetoresistance are in agreement with this description, and determine the
Fermi-liquid interaction constant $F_0^\sigma $ which controls the sign of
$d\rho /dT$.

###Transport signatures of correlated disorder in a two-dimensional electron gas|T. Heinzel,R. D. Jaeggi,E. Ribeiro,M. v. Waldkirch,K. Ensslin,S. E. Ulloa,G. Medeiros-Ribeiro,P. M. Petroff###

Transport signatures of correlated disorder in a two-dimensional electron gas. We report electronic transport measurements on two-dimensional electron gases
in a Ga[Al]As heterostructure with an embedded layer of InAs self-assembled
quantum dots. At high InAs dot densities, pronounced Altshuler-Aronov-Spivak
magnetoresistance oscillations are observed, which indicate short-range
ordering of the potential landscape formed by the charged dots and the strain
fields. The presence of these oscillations coincides with the observation of a
metal-insulator transition, and a maximum in the electron mobility as a
function of the electron density. Within a model based on correlated disorder,
we establish a relation between these effects.

###Magnetic-field-induced collapse of charge-ordered nanoclusters and the Colossal Magnetoresistance effect in Nd(0.3)Sr(0.3)MnO(3)|T. Y. Koo,V. Kiryukhin,P. A. Sharma,J. P. Hill,S-W. Cheong###

Magnetic-field-induced collapse of charge-ordered nanoclusters and the Colossal Magnetoresistance effect in Nd(0.3)Sr(0.3)MnO(3). We report synchrotron x-ray scattering studies of charge/orbitally ordered
(COO) nanoclusters in Nd$_{0.7}$Sr$_{0.3}$MnO$_3$. We find that the COO
nanoclusters are strongly suppressed in an applied magnetic field, and that
their decreasing concentration follows the field-induced decrease of the sample
electrical resistivity. The COO nanoclusters, however, do not completely
disappear in the conducting state, suggesting that this state is inhomogeneous
and contains an admixture of an insulating phase. Similar results were also
obtained for the zero-field insulator-metal transition that occurs as
temperature is reduced. These observations suggest that these correlated
lattice distortions play a key role in the Colossal Magnetoresistance effect in
this prototypical manganite.

###Long-Range Coherence in a Mesoscopic Metal near a Superconducting Interface|H. Courtois,Ph. Gandit,D. Mailly,B. Pannetier###

Long-Range Coherence in a Mesoscopic Metal near a Superconducting Interface. We identify the different contributions to quantum interference in a
mesoscopic metallic loop in contact with two superconducting electrodes. At low
temperature, a flux-modulated Josephson coupling is observed with strong
damping over the thermal length L_{T}. At higher temperature, the
magnetoresistance exhibits large h/2e-periodic oscillations with 1/T power law
decay. This flux-sensitive contribution arises from coherence of low-energy
quasiparticles states over the phase-breaking length L_{\phi}. Mesoscopic
fluctuations contribute as a small h/e oscillation, resolved only in the purely
normal state.

###Microscopic spin interactions in the CMR manganites|J. A. Fernandez-Baca,Pengcheng Dai,H. Kawano-Furukawa,H. Yoshizawa,E. W. Plummer,S. Katano,Y. Tomioka,Y. Tokura###

Microscopic spin interactions in the CMR manganites. Using inelastic neutron scattering we measured the microscopic magnetic
coupling associated with the ferromagnetic (FM) clusters of the ``colossal
magnetoresistance'' (CMR) compound Pr$_{0.70}$Ca$_{0.30}$MnO$_3$. When the
insulating to metal (I-M) transition is induced by an external magnetic field
there is a discontinuous change in the spin-wave stiffness constant. This
result indicates that the probed regions undergo a first-order transition from
an insulating to a metallic state, and that there are no FM metallic domains in
the insulating region. We argue that the I-M transition in the CMR manganites
is more complex than the simple percolation of large FM metallic clusters.

###Two mechanisms of pseudogap formation in Bi-2201: Evidence from the c-axis magnetoresistance|A. N. Lavrov,Yoichi Ando,S. Ono###

Two mechanisms of pseudogap formation in Bi-2201: Evidence from the c-axis magnetoresistance. Measurements of the c-axis resistivity and magnetoresistance have been used
to investigate the pseudogap (PG) behavior in Bi_{2+z}Sr_{2-x-z}La_xCuO_y
(Bi-2201) crystals at various hole densities. While the PG opening temperature
T* increases with decreasing hole doping, the magnetic-field sensitivity of the
PG is found to have a very different trend: it appears at lower temperatures in
more underdoped samples and vanishes in non-superconducting samples. These data
suggest that besides the field-insensitive pseudogap emerging at T*, a distinct
one is formed above T_c as a precursor to superconductivity.

###Phase Transitions in the Bilayer $ν=2/3$ Quantum Hall Effect|N. Kumada,D. Terasawa,Y. Shimoda,H. Azuhata,A. Sawada,Z. F. Ezawa,K. Muraki,T. Saku,Y. Hirayama###

Phase Transitions in the Bilayer $ν=2/3$ Quantum Hall Effect. We measured the magnetoresistance of bilayer quantum Hall (QH) effects at the
fractional filling factor $\nu =2/3$ by changing the total electron density and
the density difference between two layers. Three different QH states were
separated by two types of phase transition: One is the spin transition and the
other is the pseudospin transition. In addition, two different hystereses were
detected, one of which is specific to bilayer systems. The phase transitions
and the hystereses are described well by a composite fermion model extended to
a bilayer system.

###Magnetocrystalline Anisotropy in a Single Crystal of CeNiGe2|M. H. Jung,N. Harrison,A. H. Lacerda,P. G. Pagliuso,J. L. Sarrao,J. D. Thompson###

Magnetocrystalline Anisotropy in a Single Crystal of CeNiGe2. We report measurements on single crystals of orthorhombic CeNiGe2, which is
found to exhibit highly anisotropic magnetic and transport properties. The
magnetization ratio M(H//b)/M(H^b) at 2 K is observed to be about 18 at 4 T and
the electrical resistivity ratio r//b/r^b is about 70 at room temperature. It
is confirmed that CeNiGe2 undergoes two-step antiferromagnetic transition at 4
and 3 K, as reported for polycrystalline samples. The application of magnetic
field along the b axis (the easy magnetization axis) stabilizes a ferromagnetic
correlation between the Ce ions and enhances the hopping of carriers. This
results in large negative magnetoresistance along the b axis.

###A Theoretical Search for the Optimum Giant Magnetoresistance|Tat-Sang Choy,Jian Chen,Selman Hershfield###

A Theoretical Search for the Optimum Giant Magnetoresistance. The maximum current-perpendicular-to-plane giant magnetoresistance is
searched for in magnetic multilayers made of Co, Ni, and Cu with disorder
levels similar to those found in room temperature experiments. The calculation
is made possible by a highly optimized linear response code, which uses the
impurity averaged Green's function technique and a 9-band per spin tight
binding model. Using simulated annealing, hundreds of different configurations
of the atomic layers are examined to find a maximum GMR of 450% in ultrathin
Ni/Cu superlattices.

###Resistivity extrema in double exchange ferromagnetic nondegenerate semiconductors|E. L. Nagaev,A. I. Podel'shchikov,V. E. Zil'bervarg###

Resistivity extrema in double exchange ferromagnetic nondegenerate semiconductors. A version of the magnetoimpurity theory of the colossal magnetoresistance
materials suitable for the double exchange ferromagnetic nondegenerate
semiconductors is presented. It provides an explanation of the nonmonotonic
temperature dependence for the charge carrier density in them when it displays
first a maximum and then a minimum, on increase in temperature. Respectively,
the resistivity displays first a minimum and then a maximum. The theory is
based on the relation between the charge carrier activation energy and the
change in the magnon free energy caused by the ionization of an impurity. This
is tantamount to the relation between the charge carrier density and the so
called giant red shift of the optical absorption edge.

###Field Suppression of the Density-of-States: A Mechanism for Large Linear Magnetoresistance|D. P. Young,J. F. DiTusa,R. G. Goodrich,D. Hall,J. Anderson,S. Guo,Julia Y. Chan,P. W. Adams###

Field Suppression of the Density-of-States: A Mechanism for Large Linear Magnetoresistance. Hall, resistivity, magnetization, and thermoelectric power measurements were
performed on single crystals of the highly anisotropic layered metal LaSb2. A
100-fold linear magnetoresistance (MR) was observed in fields up to 45 T, with
no indication of saturation. We show that the MR is associated with a
magnetic-field-dependent holelike carrier density, n(H) \propto 1/H. The effect
is orbital, depending upon the component of the magnetic field normal to the
layers. At low temperature, a field of 9 T reduces the carrier density by more
than an order of magnitude.

###Spin polarization of strongly interacting 2D electrons: the role of disorder|S. A. Vitkalov,M. P. Sarachik,T. M. Klapwijk###

Spin polarization of strongly interacting 2D electrons: the role of disorder. In high-mobility silicon MOSFET's, the $g^*m^*$ inferred indirectly from
magnetoconductance and magnetoresistance measurements with the assumption that
$g^*\mu_BH_s=2E_F$ are in surprisingly good agreement with $g^*m^*$ obtained by
direct measurement of Shubnikov-de Haas oscillations. The enhanced
susceptibility $\chi^* \propto (g^*m^*)$ exhibits critical behavior of the form
$\chi^* \propto (n - n_0)^{-\alpha}$. We examine the significance of the field
scale $H_s$ derived from transport measurements, and show that this field
signals the onset of full spin polarization only in the absence of disorder.
Our results suggest that disorder becomes increasingly important as the
electron density is reduced toward the transition.

###Electrical and magnetic properties of the new Kondo-lattice compound Ce3Pd4Ge4|H. J. Im,Y. S. Kwon,M. H. Jung###

Electrical and magnetic properties of the new Kondo-lattice compound Ce3Pd4Ge4. We have measured the electric resistivity, magnetoresistance, magnetic
susceptibility and magnetization of the new Kondo-lattice compound Ce3Pd4Ge4.
The electrical resistivity exhibits a rapid drop at temperatures below 6 K,
while the magnetic susceptibility does not show any corresponding anomaly at
that temperature. This phenomenon is similar to that of Ce3Pd20Ge6 which shows
quadrupolar interation. We suggest that there is the possibility of quadrupolar
interaction in the orthorhombic 4f-electron system Ce3Pd4Ge4. In addition, it
is realized that the spin-dependent scattering effect is responsible for the
magnetotransport.

###Anomaly in Spin Excitation Spectrum of Double-Exchange Systems with Randomness|Yukitoshi Motome,Nobuo Furukawa###

Anomaly in Spin Excitation Spectrum of Double-Exchange Systems with Randomness. Spin excitation spectrum of the double-exchange model is studied in the
presence of randomness. Spin wave approximation in the ground state shows that
the randomness significantly modifies the spectrum from the cosine-like one in
the pure system to that with anomalies such as broadening, anti-crossing and
gap opening. The origin of anomalies is speculated to be modulation of
effective ferromagnetic coupling by the Friedel oscillation. These anomalies
qualitatively reproduce the spin excitation spectrum in colossal
magnetoresistance manganites whose Curie temperatures are relatively low. Our
results suggest that randomness control is an important notion to understand
effects of the A-site substitution which has previously been understood as the
bandwidth control.

###Slow oscillations of magnetoresistance in quasi-two-dimensional metals|M. V. Kartsovnik,P. D. Grigoriev,W. Biberacher,N. D. Kushch,P. Wyder###

Slow oscillations of magnetoresistance in quasi-two-dimensional metals. Slow oscillations of the interlayer magnetoresistance observed in the layered
organic metal $\beta $-(BEDT-TTF)$_2$IBr$_2$ are shown to originate from the
slight warping of its Fermi surface rather than from independent small
cyclotron orbits. Unlike the usual Shubnikov-de Haas effect, these oscillations
are not affected by the temperature smearing of the Fermi distribution and can
therefore become dominant at high enough temperatures. We suggest that the slow
oscillations are a general feature of clean quasi-two-dimensional metals and
discuss possible applications of the phenomenon.

###Parabolic negative magnetoresistance in p-Ge/Ge1-xSix heterostructures|Yu. G. Arapov,G. I. Harus,O. A. Kuznetsov,V. N. Neverov,N. G. Shelushinina###

Parabolic negative magnetoresistance in p-Ge/Ge1-xSix heterostructures. Quantum corrections to the conductivity due to the weak localization (WL) and
the disorder-modified electron-electron interaction (EEI) are investigated for
the high-mobility multilayer p-Ge/Ge1-xSix heterostructures at T = (0.1 -
20.0)K in magnetic field B up to 1.5T. Negative magnetoresistance with
logarithmic dependence on T and linear in B^2 is observed for B >= 0.1T. Such a
behavior is attributed to the interplay of the classical cyclotron motion and
the EEI effect. The Hartree part of the interaction constant is estimated
(F_/sigma = 0.44) and the WL and EEI contributions to the total quantum
correction /Delta /sigma at B = 0 are separated (/Delta /sigma_{WL} ~ 0.3/Delta
/sigma; /Delta /sigma_{EEI} ~ 0.7/Delta /sigma).

###Field-induced metal-insulator Field-induced metal-insulator transition in the c-axis resistivity of graphite|H. Kempa,P. Esquinazi,Y. Kopelevich###

Field-induced metal-insulator Field-induced metal-insulator transition in the c-axis resistivity of graphite. We show that the resistivity perpendicular $\rho_c$ and parallel $\rho_a$ to
the basal planes of different graphite samples show similar
magnetic-field-driven metal-insulator-transitions at a field $B_c \sim 0.1 T$
applied parallel to the c-axis. Our results demonstrate the universality of the
recently found scaling in $\rho_a$ of graphite and indicate that the
metallic-like temperature dependence of $\rho_c$ is directly correlated to that
of $\rho_a$. The similar magnetoresistance found for both resistivities, the
violation of Kohler's rule and the field-induced transition indicate that the
semiclassical transport theory is inadecuate to understand the transport
properties of graphite.

###Temperature dependences of resistivity and magnetoresistivity for half-metallic ferromagnets|V. Yu. Irkhin,M. I. Katsnelson###

Temperature dependences of resistivity and magnetoresistivity for half-metallic ferromagnets. Peculiarities of transport properties of three- and two-dimensional
half-metallic ferromagnets are investigated, which are connected with the
absence of spin-flip scattering processes. The temperature and magnetic field
dependences of resistivity in various regimes are calculated. The resistivity
is proportional to T^{9/2} for T<T* and to T^{7/2} for T>T*, T* being the
crossover temperature for longitudinal scattering processes. The latter scale
plays also an important role in magnetoresistance. The contribution of
non-quasiparticle (incoherent) states to the transport properties is discussed.
It is shown that they can dominate in the temperature dependence of the
impurity-induced resistivity and in the tunnel junction conductivity.

###The angular dependent magnetoresistance in alpha-(BEDT-TTF)_2KHg(SCN)_4|Balázs Dóra,Kazumi Maki,Bojana Korin-Hamzic,Mario Basletic,Attila Virosztek,Mark V. Kartsovnik,Harald Müller###

The angular dependent magnetoresistance in alpha-(BEDT-TTF)_2KHg(SCN)_4. In spite of extensive experimental studies of the angular dependent
magnetoresistance (ADMR) of the low temperature phase (LTP) of
alpha-(BEDT-TTF)_2KHg(SCN)_4 about a decade ago, the nature of LTP remains
elusive. Here we present a new study of ADMR of LTP in alpha-(ET)_2 salts
assuming that LTP is unconventional charge density wave (UCDW). In the presence
of magnetic field the quasiparticle spectrum in UCDW is quantized, which gives
rise to striking ADMR in UCDW. The present model appears to account for many
existing ADMR data of alpha-(BEDT-TTF)_2KHg(SCN)_4 remarkably well.

###Complex Quantum Phenomena in a Bilayered Calcium Ruthenate|G. Cao,L. Balicas,Y. Xin,E. Dagotto,J. E. Crow,C. S. Nelson,J. P. Hill###

Complex Quantum Phenomena in a Bilayered Calcium Ruthenate. Ca$_3$Ru$_2$O$_7$ undergoes an antiferromagnetic transition at
$T_{\text{N}}=56 $K, followed by a Mott-like (MI) transition at
$T_{\text{MI}}=48$ K. This nonmetallic ground state, with a charge gap of 0.1
eV, is suppressed by a highly anisotropic metamagnetic transition that leads to
a fully spin-polarized metallic state. We report the observation of
Shubnikov-de Haas oscillations in the \textit{gapped} state, colossal
magnetoresistance in the inter-plane resistivity with a large anisotropy
different from that observed in the magnetization, and non-Fermi liquid
behavior in the metallic state at high magnetic fields.

###Quantum oscillation of magnetoresistance in tunneling junctions with a nonmagnetic spacer|H. Itoh,J. Inoue A. Umerski,J. Mathon###

Quantum oscillation of magnetoresistance in tunneling junctions with a nonmagnetic spacer. We make a theoretical study of the quantum oscillations of the tunneling
magnetoresistance (TMR) as a function of the spacer layer thickness. Such
oscillations were recently observed in tunneling junctions with a nonmagnetic
metallic spacer at the barrier-electrode interface. It is shown that momentum
selection due to the insulating barrier and conduction via quantum well states
in the spacer, mediated by diffusive scattering caused by disorder, are
essential features required to explain the observed period of oscillation in
the TMR ratio and its asymptotic value for thick nonmagnetic spacer.

###Ising Quantum Hall Ferromagnet in Magnetically Doped Quantum Wells|J. Jaroszynski,T. Andrearczyk,G. Karczewski,J. Wrobel,T. Wojtowicz,E. Papis,E. Kaminska,A. Piotrowska,Dragana Popovic,T. Dietl###

Ising Quantum Hall Ferromagnet in Magnetically Doped Quantum Wells. We report on the observation of the Ising quantum Hall ferromagnet with Curie
temperature $T_C$ as high as 2 K in a modulation-doped (Cd,Mn)Te
heterostructure. In this system field-induced crossing of Landau levels occurs
due to the giant spin-splitting effect. Magnetoresistance data, collected over
a wide range of temperatures, magnetic fields, tilt angles, and electron
densities, are discussed taking into account both Coulomb electron-electron
interactions and s$-$d coupling to Mn spin fluctuations. The critical behavior
of the resistance ``spikes'' at $T \to T_C$ corroborates theoretical
suggestions that the ferromagnet is destroyed by domain excitations.

###Parity Effect and Tunnel Magnetoresistance of Ferromagnet / Superconductor / Ferromagnet Single-Electron Tunneling Transistors|Hiroshi Imamura,Yasuhiro Utsumi,Hiromichi Ebisawa###

Parity Effect and Tunnel Magnetoresistance of Ferromagnet / Superconductor / Ferromagnet Single-Electron Tunneling Transistors. We theoretically study the tunnel magnetoresistance(TMR) of ferromagnet /
superconductor / ferromagnet single-electron tunneling transistors with a
special attention to the parity effect. It is shown that in the plateau region,
there is no spin accumulation in the island even at finite bias voltage.
However, the information of the injected spin is carried by the excess electron
and thus the TMR exists. The spin relaxation rate of the excess electron can be
estimated from the TMR. We also show that the TMR increases with decreasing the
size of the superconducting island.

###Spin-dependent properties of a two-dimensional electron gas with ferromagnetic gates|C. Ciuti,J. P. McGuire,L. J. Sham###

Spin-dependent properties of a two-dimensional electron gas with ferromagnetic gates. A theoretical prediction of the spin-dependent electron self-energy and
in-plane transport of a two-dimensional electron gas in proximity with a
ferromagnetic gate is presented. The application of the predicted
spin-dependent properties is illustrated by the proposal of a device
configuration with two neighboring ferromagnetic gates which produces a
magnetoresistance effect on the channel current generated by nonmagnetic source
and drain contacts. Specific results are shown for a silicon inversion layer
with iron gates. The gate leakage current is found to be beneficial to the spin
effects.

###Anisotropy and large magnetoresistance in narrow gap semiconductor FeSb2|C. Petrovic,J. W. Kim,S. L. Bud'ko,A. I. Goldman,P. C. Canfield,W. Choe,G. J. Miller###

Anisotropy and large magnetoresistance in narrow gap semiconductor FeSb2. A study of the anisotropy in magnetic, transport and magnetotransport
properties of FeSb2 has been made on large single crystals grown from Sb flux.
Magnetic susceptibility of FeSb2 shows diamagnetic to paramagnetic crossover
around 100K. Electrical transport along two axes is semiconducting whereas the
third axis exhibits a metal - semiconductor crossover at temperature Tmin which
is sensitive to current alignment and ranges between 40 and 80K. In H=70kOe
semiconducting transport is restored for T<300K, resulting in large
magnetoresistance [rho(70kOe)-rho(0)]/rho(0)=2200% in the crossover temperature
range

###Boltzmann theory of engineered anisotropic magnetoresistance in (Ga,Mn)As|T. Jungwirth,M. Abolfath,Jairo Sinova,J. Kucera,A. H. MacDonald###

Boltzmann theory of engineered anisotropic magnetoresistance in (Ga,Mn)As. We report on a theoretical study of dc transport coefficients in (Ga,Mn)As
diluted magnetic semiconductor ferromagnets that accounts for quasiparticle
scattering from ionized Mn$^{2+}$ acceptors with a local moment $S=5/2$ and
from non-magnetic compensating defects. In metallic samples Boltzmann transport
theory with Golden rule scattering rates accounts for the principle trends of
the measured difference between resistances for magnetizations parallel and
perpendicular to the current. We predict that the sign and magnitude of the
anisotropic magnetoresistance can be changed by strain engineering or by
altering chemical composition.

###Absence of Metal-Insulator-Transition and Coherent Interlayer Transport in oriented graphite in parallel magnetic fields|H. Kempa,H. C. Semmelhack,P. Esquinazi,Y. Kopelevich###

Absence of Metal-Insulator-Transition and Coherent Interlayer Transport in oriented graphite in parallel magnetic fields. Measurements of the magnetoresistivity of graphite with a high degree of
control of the angle between the sample and magnetic field indicate that the
metal-insulator transition (MIT), shown to be induced by a magnetic field
applied perpendicular to the layers, does not appear in parallel field
orientation. Furthermore, we show that interlayer transport is coherent in less
ordered samples and high magnetic fields, whereas appears to be incoherent in
less disordered samples. Our results demonstrate the two-dimensionality of the
electron system in ideal graphite samples.

###Spin Diffusion in Double-Exchange Manganites|A. L. Chernyshev,R. S. Fishman###

Spin Diffusion in Double-Exchange Manganites. The theoretical study of spin diffusion in double-exchange magnets by means
of dynamical mean-field theory is presented. We demonstrate that the
spin-diffusion coefficient becomes independent of the Hund's coupling JH in the
range of parameters JH*S >> W >> T, W being the bandwidth, relevant to colossal
magnetoresistive manganites in the metallic part of their phase diagram. Our
study reveals a close correspondence as well as some counterintuitive
differences between the results on Bethe and hypercubic lattices. Our results
are in accord with neutron scattering data and with previous theoretical work
for high temperatures.

###Magnetoresistance and magnetic anisotropy in La$_{0.5}$Sr$_{0.5}$CoO$_{3-δ}$ film|B. I. Belevtsev,V. B. Krasovitsky,A. S. Panfilov,I. N. Chukanova###

Magnetoresistance and magnetic anisotropy in La$_{0.5}$Sr$_{0.5}$CoO$_{3-δ}$ film. The magnetic and transport properties of La$_{0.5}$Sr$_{0.5}$CoO$_{3-\delta}$
film grown on a LaAlO$_3$ substrate by pulsed-laser deposition are studied. The
properties are found to be influenced by a combined influence of the magnetic
anisotropy and inhomogeneity. Magnetoresistance anisotropy is determined by the
shape anisotropy and the strain-induced magnetic anisotropy due to the
film-substrate lattice interaction. Indications of the temperature-driven spin
reorientation transition from an out-of plane orderded state at low
temperatures to an in-plane ordered state at high temperatures as a result of
competition between the mentioned anisotropy sources are found.

###Interaction-induced magnetoresistance: From the diffusive to the ballistic regime|I. V. Gornyi,A. D. Mirlin###

Interaction-induced magnetoresistance: From the diffusive to the ballistic regime. We study interaction-induced quantum correction to the conductivity tensor of
electrons in two dimensions for arbitrary T tau, where T is the temperature and
tau the transport mean free time. A general formula is derived, expressing the
correction in terms of classical propagators ("ballistic diffusons"). The
formalism is used to calculate the interaction contribution to the
magnetoresistance in a classically strong transverse field and smooth disorder
in the whole range of temperatures from the diffusive (T tau<<1) to the
ballistic (T tau>1) regime.

###Multivalued dependence of the magnetoresistance on the quantized conductance in nanosize magnetic contacts|L. R. Tagirov,B. P. Vodopyanov,K. B. Efetov###

Multivalued dependence of the magnetoresistance on the quantized conductance in nanosize magnetic contacts. We calculate the quantized conductance of nanosize point contacts between two
ferromagnets for different mutual orientations of the magnetic moments. It is
found that the magnetoresistance MR is a multivalued function of the quantized
conductance at the parallel alignment of the magnetizations sigma^F. This leads
us to the conclusion that experimentally observed large fluctuations of MR
versus sigma^F are rather due to the conductance quantization than to
measurement errors or a poor reproducibility of the results. Using the results
of the calculations we are able to understand experimental data obtained by
Garcia et al for MR of the magnetic nanocontacts.

###Magnetic Miniband Structure and Quantum Oscillations in Lateral Semiconductor Superlattices|M. Langenbuch,M. Suhrke,U. Roessler###

Magnetic Miniband Structure and Quantum Oscillations in Lateral Semiconductor Superlattices. We present fully quantum-mechanical magnetotransport calculations for
short-period lateral superlattices with one-dimensional electrostatic
modulation. A non-perturbative treatment of both magnetic field and modulation
potential proves to be necessary to reproduce novel quantum oscillations in the
magnetoresistance found in recent experiments in the resistance component
parallel to the modulation potential. In addition, we predict oscillations of
opposite phase in the component perpendicular to the modulation not yet
observed experimentally. We show that the new oscillations originate from the
magnetic miniband structure in the regime of overlapping minibands.

###Even-odd effects in magnetoresistance of ferromagnetic domain walls|M. Dzero,L. P. Gor'kov,A. K. Zvezdin,K. A. Zvezdin###

Even-odd effects in magnetoresistance of ferromagnetic domain walls. Difference in density of states for the spin's majority and minority bands in
a ferromagnet changes the electrostatic potential along the domains,
introducing the discontinuities of the potential at domain boundaries. The
value of discontinuity oscillates with number of domains. Discontinuity depends
on the positions of domain walls, their motion or collapse of domain walls in
applied magnetic field. Large values of magnetoresistance are explained in
terms of spin-accumulation. We suggest a new type of domain walls in nanowires
of itinerant ferromagnets, in which the magnetization vector changes without
rotation. Absence of transverse magnetization components allows considerable
spin accumulation assuming the spin relaxation length, L_S, is large enough.

###Nickel Antidot Arrays on Anodic Alumina Substrates|Z. L. Xiao,Catherine Y. Han,U. Welp,H. H. Wang,V. K. Vlasko-Vlasov,W. K. Kwok,D. J. Miller,J. M. Hiller,R. E. Cook,G. A. Willing,G. W. Crabtree###

Nickel Antidot Arrays on Anodic Alumina Substrates. Large area nickel antidot arrays with density up to 10^10 /cm^2 have been
fabricated by depositing nickel onto anodic aluminum oxide membranes that
contain lattices of nanopores. Electron microscopy images show a high degree of
order of the antidot arrays. Various sizes and shapes of the antidots were
observed with increasing thickness of the deposited nickel. New features appear
in the antidot arrays in both magnetization and transport measurements when the
external magnetic field is parallel to the current direction, including an
enhancement and a nonmonotonous field dependence of the magnetoresistance,
larger values of the coercive field and remanence moment, and smaller
saturation field.

###Colossal magnetoresistance in manganites as a multicritical phenomenon|Shuichi Murakami,Naoto Nagaosa###

Colossal magnetoresistance in manganites as a multicritical phenomenon. The colossal magnetoresistance in manganites AMnO_3 is studied from the
viewpoint of multicritical phenomena. To understand the complicated interplay
of various phases, we study the Ginzburg-Landau theory in terms of both the
mean-field approximation and the renormalization-group analysis to compare with
the observed phase diagram. Several novel features, such as the first-order
ferromagnetic transition, and the dip in the transition temperature near the
multicritical point, can be understood as driven by enhanced fluctuations near
the multicritical point. Furthermore, we obtain a universal scaling relation
for the H/M-M^2 plot (Arrott plot), which fits rather well with the
experimental data, providing the further evidence for the enhanced fluctuation.

###Dephasing by extremely dilute magnetic impurities revealed by Aharonov-Bohm oscillations|F. Pierre,Norman O. Birge###

Dephasing by extremely dilute magnetic impurities revealed by Aharonov-Bohm oscillations. We have probed the magnetic field dependence of the electron phase coherence
time $\tau_\phi$ by measuring the Aharonov-Bohm conductance oscillations of
mesoscopic Cu rings. Whereas $\tau_\phi$ determined from the low-field
magnetoresistance saturates below 1 K, the amplitude of Aharonov-Bohm $h/e$
oscillations increases strongly on a magnetic field scale proportional to the
temperature. This provides strong evidence that a likely explanation for the
frequently observed saturation of $\tau_\phi$ at low temperature in weakly
disordered metallic thin films is the presence of extremely dilute magnetic
impurities.

###Role of density imbalance in an interacting bilayer hole system|E. Tutuc,S. Melinte,E. P. De Poortere,R. Pillarisetty,M. Shayegan###

Role of density imbalance in an interacting bilayer hole system. We study interacting GaAs hole bilayers in the limit of zero tunneling. When
the layers have equal densities, we observe a phase coherent bilayer quantum
Hall (QH) state at total filling factor $\nu=1$, flanked by insulating phases
at nearby fillings which suggest the formation of a pinned, bilayer Wigner
crystal. As we transfer charge from one layer to another, the insulating phases
disappear while, surprisingly, the $\nu=1$ QH state becomes stronger.
Concomitantly, a pronounced hysteresis develops in the longitudinal
magnetoresistance at higher fillings, indicative of a first-order quantum phase
transition.

###Magnetotransport properties of a polarization-doped three-dimensional electron slab|D. Jena,S. Heikman,J. S. Speck,A. C. Gossard,U. K. Mishra,A. Link,O. Ambacher###

Magnetotransport properties of a polarization-doped three-dimensional electron slab. We present evidence of strong Shubnikov-de-Haas magnetoresistance
oscillations in a polarization-doped degenerate three-dimensional electron slab
in an Al$_{x}$Ga$_{1-x}$N semiconductor system. The degenerate free carriers
are generated by a novel technique by grading a polar alloy semiconductor with
spatially changing polarization. Analysis of the magnetotransport data enables
us to extract an effective mass of $m^{\star}=0.19 m_{0}$ and a quantum
scattering time of $\tau_{q}= 0.3 ps$. Analysis of scattering processes helps
us extract an alloy scattering parameter for the Al$_{x}$Ga$_{1-x}$N material
system to be $V_{0}=1.8eV$.

###Andreev Reflection in Ferromagnet/Superconductor/Ferromagnet Double Junction Systems|Taro Yamashita,Hiroshi Imamura,Saburo Takahashi,Sadamichi Maekawa###

Andreev Reflection in Ferromagnet/Superconductor/Ferromagnet Double Junction Systems. We present a theory of Andreev reflection in a
ferromagnet/superconductor/ferromagnet double junction system. The spin
polarized quasiparticles penetrate to the superconductor in the range of
penetration depth from the interface by the Andreev reflection. When the
thickness of the superconductor is comparable to or smaller than the
penetration depth, the spin polarized quasiparticles pass through the
superconductor and therefore the electric current depends on the relative
orientation of magnetizations of the ferromagnets. The dependences of the
magnetoresistance on the thickness of the superconductor, temperature, the
exchange field of the ferromagnets and the height of the interfacial barriers
are analyzed. Our theory explains recent experimental results well.

###High-field side of Superconductor-Insulator Transition|Tatyana I. Baturina,D. R. Islamov,Z. D. Kvon,M. R. Baklanov,A. Satta###

High-field side of Superconductor-Insulator Transition. We report the experimental observation of a magnetic-field-tuned
superconductor-insulator transition (SIT) in ultrathin TiN films. The low
temperature transport properties of these films show scaling behavior
consistent with a transition driven by quantum phase fluctuations in
two-dimensional superconductor. The magnetoresistance reveals peak and a
subsequent decrease in fields higher than the critical field. The temperature
dependences of the isomagnetic resistance data on the high-field side of the
SIT have been analyzed and the transition from insulating to metallic phase is
found, with at high fields the zero-temperature asymptotic value of the
resistance being equal to h/e^2.

###Unconventional charge density wave in the organic conductor alpha-(BEDT-TTF)_2KHg(SCN)_4|Kazumi Maki,Balázs Dóra,Mark Kartsovnik,Attila Virosztek,Bojana Korin-Hamzic,Mario Basletic###

Unconventional charge density wave in the organic conductor alpha-(BEDT-TTF)_2KHg(SCN)_4. The low temperature phase (LTP) of alpha-(BEDT-TTF)_2KHg(SCN)_4 salt is known
for its surprising angular dependent magnetoresistance (ADMR), which has been
studied intensively in the last decade. However, the nature of the LTP has not
been understood until now. Here we analyse theoretically ADMR in unconventional
(or nodal) charge density wave (UCDW). In magnetic field the quasiparticle
spectrum in UCDW is quantized, which gives rise to spectacular ADMR. The
present model accounts for many striking features of ADMR data in
alpha-(BEDT-TTF)_2KHg(SCN)_4.

###Low Temperature Metallic State of Ultrathin Films of Bismuth|L. M. Hernandez,Kevin A. Parendo,A. M. Goldman###

Low Temperature Metallic State of Ultrathin Films of Bismuth. Measurements of resistance vs. temperature have been carried out on a
sequence of quench-condensed ultrathin films of amorphous bismuth (a-Bi). The
resistance below about 0.1K was found to be temperature independent in a range
of films with thicknesses spanning the superconductor-to-insulator transition
that would be inferred by analyzing data obtained above 0.14K. Film
magnetoresistance was temperature dependent in the same temperature range over
which the resistance was temperature independent. This implies that the low
temperature metallic regime is intrinsic, and not a consequence of failure to
cool the electrons.

###Indications of coherence-incoherence crossover in layered transport|Urban Lundin,Ross H. McKenzie###

Indications of coherence-incoherence crossover in layered transport. For many layered metals the temperature dependence of the interlayer
resistance has a different behavior than the intralayer resistance. In order to
better understand interlayer transport we consider a concrete model which
exhibits this behavior. A small polaron model is used to illustrate how the
interlayer transport is related to the coherence of quasi-particles within the
layers. Explicit results are given for the electron spectral function,
interlayer optical conductivity and the interlayer magnetoresistance. All these
quantities have two contributions: one coherent (dominant at low temperatures)
and one incoherent (dominant at high temperatures).

###Unconventional magnetic transition and transport behavior in Na0.75CoO2|T. Motohashi,R. Ueda,E. Naujalis,T. Tojo,I. Terasaki,T. Atake,M. Karppinen,H. Yamauchi###

Unconventional magnetic transition and transport behavior in Na0.75CoO2. Here we report an unconventional magnetic and transport phenomenon in a
layered cobalt oxide, NaxCoO2. Only for x = 0.75, a magnetic transition of the
second order was clearly detected at Tm ~ 22 K where an apparent specific-heat
jump, an onset of extremely small spontaneous magnetization, and a kink in
resistivity came in. Moreover large positive magnetoresistance effect was
observed below Tm. These features of the transition strongly indicate the
appearance of an unusual electronic state that may be attributed to the
strongly-correlated electrons in Na0.75CoO2.

###Magneto-transport properties of dilute granular ferromagnets|A. Cohen,A. Frydman,R. Berkovits###

Magneto-transport properties of dilute granular ferromagnets. We present magnetoresistance (MR) measurements performed on quench condensed
granular Ni thin films which are on the verge of electric continuity. In these
systems the electric conductivity is believed to be governed by the resistance
between a very small number of grains. The films exihibit sharp resistance
jumps as a function of magnetic field. We interpret these findings as being the
result of magneto-mechanical distortions that occour in single grains which act
as bottlenecks in the dilute percolation network. The observed features provide
a unique measure of magnetostriction effects in nano-grain structures as well
as being able to shed light on some of the properties of regular granular
magnetic films.

###Screening and inplane magnetoresistance of anisotropic two-dimensional gas|V. S. Khrapai###

Screening and inplane magnetoresistance of anisotropic two-dimensional gas. In order to split the influence of the orbital and spin effects on the
inplane magnetoresistance of a quasi two-dimensional gas we derive its linear
response function and dielectric function for the case of anisotropic effective
mass. This result is used for the calculation of elastic transport relaxation
time of a quasi two dimensional system in a parallel magnetic field. The
relaxation time is proved to be isotropic in the low density limit for the case
of charged impurity scattering, allowing to separate the two contributions.

###Current-Induced Magnetization Reversal in High Magnetic Fields in Co/Cu/Co Nanopillars|B. Oezyilmaz,A. D. Kent,D. Monsma,J. Z. Sun,M. J. Rooks,R. H. Koch###

Current-Induced Magnetization Reversal in High Magnetic Fields in Co/Cu/Co Nanopillars. Current-induced magnetization dynamics in Co/Cu/Co trilayer nanopillars
(~100nm in diameter) has been studied experimentally for large applied fields
perpendicular to the layers. An abrupt and hysteretic increase in dynamic
resistance is observed at high current densities for one polarity of the
current, comparable to the giant magnetoresistance effect observed at low
fields. A micromagnetic model, that includes a spin-transfer torque, suggests
that the current induces a complete reversal of the thin Co layer to alignment
antiparallel to the applied field-that is, to a state of maximum magnetic
energy.

###Radiation-Induced Magnetoresistance Oscillations in a 2D Electron Gas|Adam C. Durst,Subir Sachdev,N. Read,S. M. Girvin###

Radiation-Induced Magnetoresistance Oscillations in a 2D Electron Gas. Recent measurements of a 2D electron gas subjected to microwave radiation
reveal a magnetoresistance with an oscillatory dependence on the ratio of
radiation frequency to cyclotron frequency. We perform a diagrammatic
calculation and find radiation-induced resistivity oscillations with the
correct period and phase. Results are explained via a simple picture of current
induced by photo-excited disorder-scattered electrons. The oscillations
increase with radiation intensity, easily exceeding the dark resistivity and
resulting in negative-resistivity minima. At high intensity, we identify
additional features, likely due to multi-photon processes, which have yet to be
observed experimentally.

###DC-transport properties of ferromagnetic (Ga,Mn)As semiconductors|T. Jungwirth,Jairo Sinova,K. Y. Wang,K. W. Edmonds,R. P. Campion,B. L. Gallagher,C. T. Foxon,Qian Niu,A. H. MacDonald###

DC-transport properties of ferromagnetic (Ga,Mn)As semiconductors. We study the dc transport properties of (Ga,Mn)As diluted magnetic
semiconductors with Mn concentration varying from 1.5% to 8%. Both diagonal and
Hall components of the conductivity tensor are strongly sensitive to the
magnetic state of these semiconductors. Transport data obtained at low
temperatures are discussed theoretically within a model of band-hole
quasiparticles with a finite spectral width due to elastic scattering from Mn
and compensating defects. The theoretical results are in good agreement with
measured anomalous Hall effect and anisotropic longitudinal magnetoresistance
data. This quantitative understanding of dc magneto-transport effects in
(Ga,Mn)As is unparalleled in itinerant ferromagnetic systems.

###Nonequilibrium spintronic transport through an artificial Kondo impurity: Conductance, magnetoresistance and shot noise|Rosa Lopez,David Sanchez###

Nonequilibrium spintronic transport through an artificial Kondo impurity: Conductance, magnetoresistance and shot noise. We investigate the nonequilibrum transport properties of a quantum dot when
spin flip processes compete with the formation of a Kondo resonance in the
presence of ferromagnetic leads. Based upon the Anderson Hamiltonian in the
strongly interacting limit, we predict a splitting of the differential
conductance when the spin flip scattering amplitude is of the order of the
Kondo temperature. We discuss how the relative orientation of the lead
magnetizations strongly influences the electronic current and the shot noise in
a nontrivial way. Furthermore, we find that the zero-bias tunneling
magnetoresistance becomes negative with increasing spin flip scattering
amplitude.

###Crossover from 2D to 3D magnetic disorder in sub-mono-atomic ferromagnetic layers|A. frydman,R. C. Dynes###

Crossover from 2D to 3D magnetic disorder in sub-mono-atomic ferromagnetic layers. We present transport and magnetoresistance (MR) measurements performed on
quench condensed ultrathin films of Gd evaporated on an amorphous Ge or Sb
layer. These films show a large negative MR accompanied by a hysteretic
superimposed structure. When the film is coated by an overlayer of Ge or Sb the
magnitude of the MR increases and the hysteretic structure disappears. We
speculate that the findings are a result of a crossover from a 2D magnetic
disorder in the uncoated layers of Gd to a 3D magnetic disorder as the Gd film
is coated by a semiconducting layer.

###Co-ordination between Rashba spin-orbital interaction and space charge effect and enhanced spin injection into semiconductors|Wei Wu,Jinbin Li,Yue Yu,S. T. Chui###

Co-ordination between Rashba spin-orbital interaction and space charge effect and enhanced spin injection into semiconductors. We consider the effect of the Rashba spin-orbital interaction and space
charge in a ferromagnet-insulator/semiconductor/insulator-ferromagnet junction
where the spin current is severely affected by the doping, band structure and
charge screening in the semiconductor. In diffusion region, if the the
resistance of the tunneling barriers is comparable to the semiconductor
resistance, the magnetoresistance of this junction can be greatly enhanced
under appropriate doping by the co-ordination between the Rashba effect and
screened Coulomb interaction in the nonequilibrium transport processes within
Hartree approximation.

###Spin-Voltaic Effect and its Implications|Igor Zutic,Jaroslav Fabian###

Spin-Voltaic Effect and its Implications. In an inhomogeneously doped magnetic semiconductor, an interplay between an
equilibrium magnetization and injected nonequilibrium spin leads to the
spin-voltaic effect--a spin analogue of the photo-voltaic effect. By reversing
either the sign of the equilibrium magnetization or the direction of injected
spin polarization it is possible to switch the direction of charge current in a
closed circuit or, alternatively, to switch the sign of the induced
open-circuit voltage. Properties of the spin-voltaic effect can be used to
perform all-electrical measurements of spin relaxation time and injected spin
polarization, as well as to design devices with large magnetoresistance and
spin-controlled amplification.

###Competing Orders and Disorder-induced Insulator to Metal Transition in Manganites|Yukitoshi Motome,Nobuo Furukawa,Naoto Nagaosa###

Competing Orders and Disorder-induced Insulator to Metal Transition in Manganites. Effects of disorder on the two competing phases, i.e., the ferromagnetic
metal and the commensurate charge/lattice ordered insulator, are studied by
Monte Carlo simulation. The disorder suppresses the charge/lattice ordering
more strongly than the ferromagnetic order, driving the commensurate insulator
to the ferromagnetic metal near the phase boundary in the pure case. Above the
ferromagnetic transition temperature, on the contrary, the disorder makes the
system more insulating, which might cause an enhanced colossal
magnetoresistance as observed in the half-doped or Cr-substituted manganites.
No indication of the percolation or the cluster formation is found, and there
remain the charge/lattice fluctuations instead which are enhanced toward the
transition temperature.

###Ising-like Spin Anisotropy and Competing Antiferromagnetic - Ferromagnetic Orders in GdBaCo_{2}O_{5.5} Single Crystals|A. A. Taskin,A. N. Lavrov,Yoichi Ando###

Ising-like Spin Anisotropy and Competing Antiferromagnetic - Ferromagnetic Orders in GdBaCo_{2}O_{5.5} Single Crystals. In RBaCo_{2}O_{5+x} compounds (R is rare earth), a
ferromagnetic-antiferromagnetic competition is accompanied by a giant
magnetoresistance. We study the magnetization of detwinned GdBaCo_{2}O_{5.5}
single crystals, and find a remarkable uniaxial anisotropy of Co^{3+} spins
which is tightly linked with the chain oxygen ordering in GdO_{0.5} planes.
Reflecting the underlying oxygen order, CoO_2 planes also develop a spin-state
order consisting of Co^{3+} ions in alternating rows of S=1 and S=0 states. The
magnetic structure appears to be composed of weakly coupled ferromagnetic
ladders with Ising-like moments, which gives a simple picture for
magnetotransport phenomena.

###Radiation-induced magnetoresistance oscillation in a two-dimensional electron gas in Faraday geometry|X. L. Lei,S. Y. Liu###

Radiation-induced magnetoresistance oscillation in a two-dimensional electron gas in Faraday geometry. Microwave-radiation induced giant magnetoresistance oscillations recently
discovered in high-mobility two-dimensional electron systems in a magnetic
field, are analyzed theoretically. Multiphoton-assisted impurity scatterings
are shown to be the primary origin of the oscillation. Based on a model which
considers the interaction of electrons with the electromagnetic fields in
Faraday geometry, we are able not only to reproduce the correct period, phase
and the negative resistivity of the main oscillation, but also to obtain
secondary peaks and additional maxima and minima in the resistivity curve, some
of which were already observed in the experiments.

###Monte Carlo Study of Doping Change and Disorder Effect on Double Exchange Ferromagnetism|Yukitoshi Motome,Nobuo Furukawa###

Monte Carlo Study of Doping Change and Disorder Effect on Double Exchange Ferromagnetism. Phase diagram and critical properties are studied for three-dimensional
double exchange model with and without quenched disorder. Employing the Monte
Carlo method and the systematic analysis on the finite-size effect, we estimate
the Curie temperature and the critical exponent as functions of the doping
concentration and the strength of the random potential. The Curie temperature
well scales to the kinetic energy of electrons in the ground state as expected
for this kinetics-driven ferromagnetism. The universality class of this
transition is described by the short-range Heisenberg fixed point. The results
are compared with the experimental results in the colossal magnetoresistance
manganites.

###Kondo effect in a quantum dot coupled to ferromagnetic leads: A numerical renormalization group analysis|Mahn-Soo Choi,David Sanchez,Rosa Lopez###

Kondo effect in a quantum dot coupled to ferromagnetic leads: A numerical renormalization group analysis. We investigate the effects of spin-polarized leads on the Kondo physics of a
quantum dot using the numerical renormalization group method. Our study
demonstrates in an unambiguous way that the Kondo effect is not necessarily
suppressed by the lead polarization: While the Kondo effect is quenched for the
asymmetric Anderson model, it survives even for finite polarizations in the
regime where charge fluctuations are negligible. We propose the linear
tunneling magnetoresistance as an experimental signature of these behaviors. We
also report on the influence of spin-flip processes.

###High Magnetic Field Sensor Using LaSb2|D. P. Young,R. G. Goodrich,J. F. DiTusa,S. Guo,J. Chan,D. Hall,P. W. Adams###

High Magnetic Field Sensor Using LaSb2. The magnetotransport properties of single crystals of the highly anisotropic
layered metal LaSb2 are reported in magnetic fields up to 45 T with fields
oriented both parallel and perpendicular to the layers. Below 10 K the
perpendicular magnetoresistance of LaSb2} becomes temperature independent and
is characterized by a 100-fold linear increase in resistance between 0 and 45 T
with no evidence of quantum oscillations down to 50 mK. The Hall resistivity is
hole-like and gives a high field carrier density of n ~ 3x10^20 cm^-3. The
feasibility of using LaSb2 for magnetic field sensors is discussed.

###Anisotropic Magnetoresistance in Lightly Doped La_{2-x}Sr_{x}CuO_{4}: Impact of Anti-Phase Domain Boundaries on the Electron Transport|Yoichi Ando,A. N. Lavrov,Seiki Komiya###

Anisotropic Magnetoresistance in Lightly Doped La_{2-x}Sr_{x}CuO_{4}: Impact of Anti-Phase Domain Boundaries on the Electron Transport. Detailed behavior of the magnetoresistance (MR) is studied in lightly doped
antiferromagnetic La_{1.99}Sr_{0.01}CuO_{4}, where, thanks to the weak
ferromagnetic moment due to spin canting, the antiferromagnetic (AF) domain
structure can be manipulated by the magnetic field. The MR behavior
demonstrates that CuO_2 planes indeed contain anti-phase AF domain boundaries
in which charges are confined, forming anti-phase stripes. The data suggest
that a high magnetic field turns the anti-phase stripes into in-phase stripes,
and the latter appear to give better conduction than the former, which
challenges the notion that the anti-phase character of stripes facilitates
charge motion.

###Inhomogeneous Ferromagnetism and Unconventional Charge Dynamics in Disordered Double Exchange Magnets|Sanjeev Kumar,Pinaki Majumdar###

Inhomogeneous Ferromagnetism and Unconventional Charge Dynamics in Disordered Double Exchange Magnets. We solve the double exchange model in the presence of arbitrary
substitutional disorder by using a self consistently generated effective
Hamiltonian for the spin degrees of freedom. The magnetic properties are
studied through classical Monte Carlo while the effective exchange, $D_{ij}$,
are calculated by solving the disordered fermion problem, and renormalised
self-consistently with increasing temperature. We present exact results on the
conductivity, magnetoresistance, optical response and `real space' structure of
the inhomogeneous ferromagnetic state, and compare our results with charge
dynamics in disordered La_{1-x}Sr_xMnO_3. The large sizes, ${\cal O} (10^3)$,
accessible within our method allows a complete, controlled calculation on the
disordered strongly interacting problem.

###Weak Localization in an Ultradense 2D Electron Gas in $δ$-doped Silicon|M. A. Zudov,C. L. Yang,R. R. Du,T. -C. Shen,J. -Y. Ji,J. S. Kline,J. R. Tucker###

Weak Localization in an Ultradense 2D Electron Gas in $δ$-doped Silicon. An ultradense 2D electron system can be realized by adsorbing PH$_3$
precursor molecules onto an atomically clean Si surface, followed by epitaxial
Si overgrowth. By controlling the PH$_3$ coverage the carrier density of such
system can easily reach $\sim 10^{14}$ cm$^{-2}$, exceeding that typically
found in GaAs/AlGaAs structures by more than two-three orders of magnitude. We
report on a first systematic characterization of such novel system by means of
standard magnetotransport. The main findings include logarithmic temperature
dependence of zero-field conductivity and logarithmic negative
magnetoresistance. We analyzed the results in terms of scaling theory of
localization in two dimensions.

###Variable-range-hopping conductivity of half-doped bilayer manganite LaSr$_{2}$Mn$_{2}$O$_{7}$|X. J. Chen,C. L. Zhang,J. S. Gardner,J. L. Sarrao,C. C. Almasan###

Variable-range-hopping conductivity of half-doped bilayer manganite LaSr$_{2}$Mn$_{2}$O$_{7}$. We report measurements of in-plane $\rho_{ab}$ and out-of-plane $\rho_{c}$
resistivities on a single crystal of the half-doped bilayer manganite
LaSr$_{2}$Mn$_{2}$O$_{7}$. In the temperature $T$ range 220 to 300 K, the
resistive anisotropy $\rho_{c}/\rho_{ab}=A+B/T$ ($A$ and $B$ constants), which
provides evidence for the variable-range-hopping conduction in the presence of
a Coulomb gap. This hopping mechanism also accounts for the quadratic magnetic
field $H$ and $\sin^{2}\phi$ dependences of the negative magnetoresistivity
$\ln [\rho_{i}(T,H,\phi)/\rho_{i}(T,H=0)]$ ($i=ab,c$), where $\phi$ is the
in-plane angle between the magnetic field and the current.

###In-plane Magnetic Field Dependent Magnetoresistance of Gated Asymmetric Double Quantum Wells|Yu. Krupko,L. Smrcka,P. Vasek,P. Svoboda,M. Cukr,L. Jansen###

In-plane Magnetic Field Dependent Magnetoresistance of Gated Asymmetric Double Quantum Wells. We have investigated experimentally the magnetoresistance of strongly
asymmetric double-wells. The structures were prepared by inserting a thin
Al$_{0.3}$Ga$_{0.7}$As barrier into the GaAs buffer layer of a standard
modulation-doped GaAs/Al$_{0.3}$Ga$_{0.7}$As heterostructure. The resulting
double-well system consists of a nearly rectangular well and of a triangular
well coupled by tunneling through the thin barrier. With a proper choice of the
barrier parameters one can control the occupancy of the two wells and of the
two lowest (bonding and antibonding) subbands. The electron properties can be
further influenced by applying front- or back-gate voltage.

###Magnetoresistance of Si(001) MOSFETs with high concentration of electrons|L. Smrcka,O. N. Makarovsky,S. G. Schemenchinskii,P. Vasek,V. Jurka###

Magnetoresistance of Si(001) MOSFETs with high concentration of electrons. We present an experimental study of electron transport in inversion layers of
high-mobility Si(001) samples with occupied excited subbands. The second series
of oscillations, observed in addition to the main series of Shubnikov-de Hass
oscillations, is tentatively attributed to the occupation of a subband
associated with the $E_{0'}$ level. Besides, a strong negative
magnetoresistance and nonlinear field dependence of the Hall resistance
accompany the novel oscillations at high carrier concentrations. The heating of
the 2D electron layers leads to suppression of the observed anomalies.

###Point Contact Spin Spectroscopy of Ferromagnetic MnAs Epitaxial Films|R. Panguluri,G. Tsoi,B. Nadgorny,S. H. Chun,N. Samarth,I. I. Mazin###

Point Contact Spin Spectroscopy of Ferromagnetic MnAs Epitaxial Films. We use point contact Andreev reflection spin spectroscopy to measure the
transport spin polarization of MnAs epitaxial films grown on (001) GaAs. By
analyzing both the temperature dependence of the contact resistance and the
phonon spectra of lead acquired simultaneously with the spin polarization
measurements, we demonstrate that all the point contacts are in the ballistic
limit. A ballistic transport spin polarization of approximately 49% and 44% is
obtained for the type A and type B orientations of MnAs, respectively. These
measurements are consistent with our density functional calculations, and with
recent observations of a large tunnel magnetoresistance in MnAs/AlAs/(Ga,Mn)As
tunnel junctions.

###Anisotropic magnetoresistive and magnetic properties of La_{0.5}Sr_{0.5}CoO_{3-δ} film|B. I. Belevtsev,V. B. Krasovitsky,A. S. Panfilov,I. N. Chukanova###

Anisotropic magnetoresistive and magnetic properties of La_{0.5}Sr_{0.5}CoO_{3-δ} film. The magnetic and transport properties of La_{0.5}Sr_{0.5}CoO_{3-\delta} film
grown on a LaAlO_3 substrate by pulsed-laser deposition are studied. The
properties are found to be influenced by the magnetic anisotropy and
inhomogeneity. Magnetoresistance anisotropy is determined by the shape
anisotropy of the magnetization and the strain-induced magnetic anisotropy due
to the film-substrate lattice interaction. Indications of the
temperature-driven spin reorientation transition from an out-of plane orderded
state at low temperatures to an in-plane ordered state at high temperatures as
a result of competition between the mentioned sources of magnetic anisotropy
are found.

###Spin states and phase separation in La_{1-x}Sr_{x}CoO_3 (x=0.15, 0.25, 0.35) films: optical, magneto-optical and magneto-transport studies|N. N. Loshkareva,E. A. Gan'shina,B. I. Belevtsev,Yu. P. Sukhorukov,E. V. Mostovshchikova,A. N. Vinogradov,V. B. Krasovitsky,I. N. Chukanova###

Spin states and phase separation in La_{1-x}Sr_{x}CoO_3 (x=0.15, 0.25, 0.35) films: optical, magneto-optical and magneto-transport studies. Optical absorption and transverse Kerr effect spectra, resistivity and
magnetoresistance of La$_{1-x}$Sr$_{x}$CoO$_3$ ($x=0.15, 0.25, 0.35$) films
have been studied. The temperature dependencies of the optical and
magneto-optical properties of the films exhibit features, which can be
attributed to the transition of the Co$^{3+}$ ions from the low-spin state
(S=0) to the intermediate-spin state (S=1) and to orbital ordering of the
Co$^{3+}$ ions in the latter state. The evolution of the properties influenced
by doping with Sr is interpreted on the basis of the phase separation model.

###Detecting percolative metal-insulator transition in manganites by resistive relaxation|X. J. Chen,H. -U. Habermeier,C. C. Almasan###

Detecting percolative metal-insulator transition in manganites by resistive relaxation. We report an experimental study of the time dependence of resistivity of a
La$_{0.9}$Sr$_{0.1}$MnO$_{3}$ ultrathin film in order to elucidate the
underlying mechanism for metal-insulator transition and colossal
magnetoresistance CMR effect. There is a clear change of sign in the resistive
relaxation rate across the metal-insulator transition driven by temperature or
magnetic field. When measuring in increasing temperature or decreasing magnetic
field, the resistivity increases with time in the metallic state but decreases
with time in the insulating state. These relaxation processes indicate that the
metal-insulator transition and the associated CMR are a direct result of phase
separation and of percolation of the metallic phase.

###Spin polarization and metallic behavior of a silicon two-dimensional electron system|Tohru Okamoto,Mitsuaki Ooya,Kunio Hosoya,Shinji Kawaji###

Spin polarization and metallic behavior of a silicon two-dimensional electron system. We have studied the magnetic and transport properties of an
ultra-low-resistivity two-dimensional electron system in a Si/SiGe quantum
well. The spin polarization increases linearly with the in-plane magnetic field
and the enhancement of the spin susceptibility is consistent with that in
Si-MOS structures. Temperature dependence of resistivity remains metallic even
in strong magnetic fields where the spin degree of freedom is frozen out. We
also found a magnetoresistance anisotropy with respect to an angle between the
current and the in-plane magnetic field.

###Mössbauer Effect Probe of Local Jahn-Teller distortion in Fe-doped Colossal Magnetoresistive Manganites|Zhao-hua Cheng,Zhi-hong Wang,Nai-li Di,Zhi-qi Kou,Guang-jun Wang,Rui-wei Li,Yi Lu,Qing-an Li,Bao-gen Shen,R. A. Dunlap###

Mössbauer Effect Probe of Local Jahn-Teller distortion in Fe-doped Colossal Magnetoresistive Manganites. Local structure of the Fe-doped La$_{1-x}$Ca$_{x}$MnO$_{3}$ (x=0.00-1.00)
compounds has been investigated by means of M\"{o}ssbauer spectroscopy.
$^{57}$Fe M\"{o}ssbauer spectra provide a direct evidence of Jahn-Teller
distortion in these manganites. On the basis of M\"{o}ssbauer results, the
Jahn-Teller coupling was estimated. It is noteworthy that Ca-concentration
dependence of Jahn-Teller coupling strength is very consistent with the
magnetic phase diagram. Our results reveal that M\"{o}ssbauer spectroscopy can
not only detect the local structural distortion, but also provide a technique
to investigate Jahn-Teller coupling of Fe-doped La$_{1-x}$Ca$_{x}$MnO$_{3}$
colossal magnetoresistive perovskites.

###Reflection of electrons from a domain wall in magnetic nanojunctions|V. K. Dugaev,J. Berakdar,J. Barnas###

Reflection of electrons from a domain wall in magnetic nanojunctions. Electronic transport through thin and laterally constrained domain walls in
ferromagnetic nanojunctions is analyzed theoretically. The description is
formulated in the basis of scattering states. The resistance of the domain wall
is calculated in the regime of strong electron reflection from the wall. It is
shown that the corresponding magnetoresistance can be large, which is in a
qualitative agreement with recent experimental observations. We also calculate
the spin current flowing through the wall and the spin polarization of electron
gas due to reflections from the domain wall.

###Physical properties of single-crystalline fibers of the colossal-magnetoresistance manganite La0.7Ca0.3MnO3|C. A. Cardoso,F. M. Araujo-Moreira,M. R. B. Andreeta,A. C. Hernandes,E. R. Leite,O. F. de Lima,A. W. Mombru,R. Faccio###

Physical properties of single-crystalline fibers of the colossal-magnetoresistance manganite La0.7Ca0.3MnO3. We have grown high-quality single crystals of the colossal-magnetoresistance
(CMR) material La0.7Ca0.3MnO3 by using the laser heated pedestal growth (LHPG)
method. Samples were grown as fibers of different diameters, and with lengths
of the order of centimeters. Their composition and structure were verified
through X-ray diffraction, scanning electron microcopy with EDX (Energy
Dispersive X-ray Analysis) and by Rietveld analysis. The quality of the
crystalline fibers was confirmed by Laue and EBSD (Electron Backscatter
Diffraction) patterns. Rocking curves performed along the fiber axis revealed a
half-height width of 0.073 degrees. The CMR behavior was confirmed by
electrical resistivity and magnetization measurements as a function of
temperature.

###'Giant' normal state magnetoresistances of Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+δ}$|V. N. Zavaritsky,J. Vanacken,V. V. Moshchalkov,A. S. Alexandrov###

'Giant' normal state magnetoresistances of Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+δ}$. Magnetoresistance (MR) of Bi-2212 single crystals with T$_{c}$ $\approx 87-92
K$ is studied in pulsed magnetic fields up to 50T along the c-axis in a wide
temperature range. The negative out-of-plane and the positive in-plane MRs are
measured in the normal state. Both MRs have similar magnitudes, exceeding any
orbital contribution by two orders in magnitude. These are explained as a
result of the magnetic pair-breaking of preformed pairs. Resistive upper
critical fields H$_{c2}$(T) determined from the in-- and out-of-plane MRs are
about the same. They show non-BCS temperature dependences compatible with the
Bose-Einstein condensation field of preformed charged bosons.

###Magnetothermopower and Nernst effect in unconventional charge density waves|Balázs Dóra,Kazumi Maki,András Ványolos,Attila Virosztek###

Magnetothermopower and Nernst effect in unconventional charge density waves. Recently we have shown that the striking angular dependent magnetoresistance
in the low temperature phase (LTP) of alpha-(BEDT-TTF)_2KHg(SCN)_4 is
consistently described in terms of unconventional charge density wave (UCDW).
Here we investigate theoretically the thermoelectric power and the Nernst
effect in UDW. The present results account consistently for the recent data of
magnetothermopower in alpha-(BEDT-TTF)_2KHg(SCN)_4 obtained by Choi et al.
(Phys. Rev. B, 65, 205119 (2002)). This confirms further our identification of
LTP in this salt as UCDW. We propose also that the Nernst effect provides a
clear signature of UDW.

###Field Dependence of the Interface Energy in Af/FM Bilayers|J. R. L. de Almeida,J. R. Steiner,S. M. Rezende###

Field Dependence of the Interface Energy in Af/FM Bilayers. In the investigations of antiferromagnetic (AF)/ ferromagnetic (FM) bilayer
samples, often distinct experimental techniques yield different values for the
measured exchange anisotropy field (HE). Using a simple microscopic model for
representing the AF/FM interface, which incorporates the effect of interface
roughness, we propose that the observed discrepancy may be accounted for by the
dependence of the interface energy between the AF and FM layers with the value
of the external applied field (H) as recently observed in anisotropic
magnetoresistance measurements, lending support to our proposal.

###Theory of Insulator Metal Transition and Colossal Magnetoresistance in Doped Manganites|T. V. Ramakrishnan,H. R. Krishnamurthy,S. R. Hassan,G. V. Pai###

Theory of Insulator Metal Transition and Colossal Magnetoresistance in Doped Manganites. The persistent proximity of insulating and metallic phases, a puzzling
characterestic of manganites, is argued to arise from the self organization of
the twofold degenerate e_g orbitals of Mn into localized Jahn-Teller(JT)
polaronic levels and broad band states due to the large electron - JT phonon
coupling present in them. We describe a new two band model with strong
correlations and a dynamical mean-field theory calculation of equilibrium and
transport properties. These explain the insulator metal transition and colossal
magnetoresistance quantitatively, as well as other consequences of two state
coexistence.

###Relevance of Cooperative Lattice Effects and Correlated Disorder in Phase-Separation Theories for CMR Manganites|Jan Burgy,Adriana Moreo,Elbio Dagotto###

Relevance of Cooperative Lattice Effects and Correlated Disorder in Phase-Separation Theories for CMR Manganites. Previous theoretical investigations of colossal magnetoresistance (CMR)
materials explain this effect using a ``clustered'' state with preformed
ferromagnetic islands that rapidly align their moments with increasing external
magnetic fields. While qualitatively successful, explicit calculations indicate
drastically different typical resistivity values in two- and three-dimensional
lattices, contrary to experimental observations. This conceptual bottleneck in
the phase-separated CMR scenario is resolved here considering the cooperative
nature of the Mn-oxide lattice distortions. This induces power-law correlations
in the quenched random fields used in toy models with phase competition. When
these effects are incorporated, resistor-network calculations reveal very
similar results in two and three dimensions, solving the puzzle.

###High-frequency spin valve effect in ferromagnet-semiconductor-ferromagnet structure based on precession of injected spins|A. M. Bratkovsky,V. V. Osipov###

High-frequency spin valve effect in ferromagnet-semiconductor-ferromagnet structure based on precession of injected spins. New mechanism of magnetoresistance, based on tunneling-emission of spin
polarized electrons from ferromagnets (FM) into semiconductors (S) and
precession of electron spin in the semiconductor layer under external magnetic
field, is described. The FM-S-FM structure is considered, which includes very
thin heavily doped (delta-doped) layers at FM-S interfaces. At certain
parameters the structure is highly sensitive at room-temperature to variations
of the field with frequencies up to 100 GHz. The current oscillates with the
field, and its relative amplitude is determined only by the spin polarizations
of FM-S junctions at relatively large bias voltage.

###On the Field Dependence of the Interface Energy in Af/FM Bilayers|J. R. L. de Almeida,J. R. Steiner,S. M. Rezende###

On the Field Dependence of the Interface Energy in Af/FM Bilayers. In the investigations of antiferromagnetic (AF)/ ferromagnetic (FM) bilayer
samples, often distinct experimental techniques yield different values for the
measured exchange anisotropy field (HE). We propose that the observed
discrepancy may be accounted in part by the dependence of the unidirectional
anisotropy with the value of the external applied field (h). Using a simple
microscopic model for representing the AF/FM interface, which incorporates the
effect of interface roughness, we show that the interface energy between the AF
and FM layer indeed varies with h, as recently observed in anisotropic
magnetoresistance measurements, lending support to our proposal.

###Domain wall scattering in an interacting one-dimensional electron gas|R. G. Pereira,E. Miranda###

Domain wall scattering in an interacting one-dimensional electron gas. We study the transport in a Luttinger liquid coupled to a magnetic chain
containing a Bloch domain wall. We compute the leading correction to the
adiabatic limit of a long domain wall, which causes no scattering. We show that
the problem is reminiscent of an impurity in a Luttinger liquid, but with a
different dependence on the interaction parameters due to spin-flip scattering.
For repulsive interactions, we find that the domain wall resistance diverges
with decreasing temperature. This may be relevant for the design of
one-dimensional systems with large magnetoresistance at low temperatures.

###Spin-filter magnetoresistance in magnetic barrier junctions|Alireza Saffarzadeh###

Spin-filter magnetoresistance in magnetic barrier junctions. The tunnel current and magnetoresistance (TMR) are investigated in magnetic
tunnel junctions consisting of a spin-filter tunnel barrier, sandwiched between
a ferromagnetic (FM) electrode and a nonmagnetic (NM) electrode. The
investigations are based on the transfer matrix method and the free-electron
approximation. The numerical results show that the spin transport depends on
the relative magnetization orientation of the FM electrode and the spin-filter
barrier, such that the tunnel current reaches its maximum when the magnetic
moments of the FM electrode and the magnetic barrier are parallel. It is also
found that the TMR increases with increasing the applied voltage.

###Transverse negative magnetoresistance of 2D structures in the presence of strong in-plane magnetic field: weak localization as a probe of interface roughness|G. M. Minkov,O. E. Rut,A. V. Germanenko,A. A. Sherstobitov,B. N. Zvonkov,D. O. Filatov###

Transverse negative magnetoresistance of 2D structures in the presence of strong in-plane magnetic field: weak localization as a probe of interface roughness. The interference induced transverse negative magnetoresistance of
GaAs/InGaAs/GaAs quantum well heterostructures has been studied in the presence
of strong in-plane magnetic field. It is shown that effect of in-plane magnetic
field is determined by the interface roughness and strongly depends on the
relationship between mean free path, phase breaking length and roughness
correlation length. Analysis of the experimental results allows us to estimate
parameters of short- and long-range correlated roughness which have been found
in a good agreement with atomic force microscopy data obtained for just the
same samples.

###Dephasing in disordered metals with superconductive grains|M. A. Skvortsov,A. I. Larkin,M. V. Feigel'man###

Dephasing in disordered metals with superconductive grains. Temperature dependence of electron dephasing time $\tau_\phi(T)$ is
calculated for a disordered metal with small concentration of superconductive
grains. Above the macroscopic superconducting transition line, when electrons
in the metal are normal, Andreev reflection from the grains leads to a nearly
temperature-independent contribution to the dephasing rate. In a broad
temperature range $1/\tau_phi(T)$ strongly exceeds the prediction of the
classical theory of dephasing in normal disordered conductors, whereas
magnetoresistance is dominated (in two dimensions) by the Maki-Tompson
correction and is positive.

###A Magnetic-Field-Effect Transistor and Spin Transport|R. N. Gurzhi,A. N. Kalinenko,A. I. Kopeliovich,A. V. Yanovsky,E. N. Bogachek,Uzi Landman###

A Magnetic-Field-Effect Transistor and Spin Transport. A magnetic-field-effect transistor is proposed that generates a
spin-polarized current and exhibits a giant negative magnetoresitance. The
device consists of a nonmagnetic conducting channel (wire or strip) wrapped, or
sandwiched, by a grounded magnetic shell. The process underlying the operation
of the device is the withdrawal of one of the spin components from the channel,
and its dissipation through the grounded boundaries of the magnetic shell,
resulting in a spin-polarized current in the nonmagnetic channel. The device
may generate an almost fully spin-polarized current, and a giant negative
magnetoresistance effect is predicted.

###Large anisotropy in the paramagnetic susceptibility of SrRuO3 films|Yevgeny Kats,Isaschar Genish,Lior Klein,James W. Reiner,M. R. Beasley###

Large anisotropy in the paramagnetic susceptibility of SrRuO3 films. By using the extraordinary Hall effect in SrRuO3 films we performed sensitive
measurements of the paramagnetic susceptibility in this itinerant ferromagnet,
from Tc (~ 150 K) to 300 K. These measurements, combined with measurements of
magnetoresistance, reveal that the susceptibility, which is almost isotropic at
300 K, becomes highly anisotropic as the temperature is lowered, diverging
along a single crystallographic direction in the vicinity of Tc. The results
provide a striking manifestation of the effect of exceptionally large
magnetocrystalline anisotropy in the paramagnetic state of a 4d itinerant
ferromagnet.

###Spin-dependent transport in phase-separated manganites|K. I. Kugel,A. L. Rakhmanov,A. O. Sboychakov,M. Yu. Kagan,I. V. Brodsky,A. V. Klaptsov###

Spin-dependent transport in phase-separated manganites. Starting from the assumption that ferromagnetically correlated regions exist
in manganites even in the absence of long-range magnetic order, we construct a
model of charge transfer due to the spin-dependent tunnelling of charge
carriers between such regions. This model allows us to analyze the temperature
and magnetic field dependence of resistivity, magnetoresistance, and magnetic
susceptibility of phase-separated manganites in the temperature range
corresponding to non-metallic behavior. The comparison of theoretical and
experimental results reveals the main characteristics of the phase-separated
state.

###Role of Inter-site Hybrid Interactions in Itinerant Ferromagnetism|Piyush Dua,Sunil Panwar,Ishwar Singh###

Role of Inter-site Hybrid Interactions in Itinerant Ferromagnetism. We study role of inter-site hybrid interactions in deciding ferromagnetic
state in the itinerant electron (narrow band) systems like some of the
transition metals. We have considered Hubbard like tight binding model
alongwith exchange and hybrid interactions. All interactions have been treated
within mean-field approximation. It is found here that hybrid interactions play
significant role at zero as well as infinite temperatures in deciding on-set of
ferromagnetic state. We have studied variation of effective mass of up and down
spin electrons in ferromagnetic state as a function of temperature. Also
studied are magnetic susceptibility, optical conductivity and magnetoresistance
as a function of temperature.

###Magnetoresistance Effect in Spin-Polarized Junctions of Ferromagnetically Contacting Multiple Conductive Paths: Applications to Atomic Wires and Carbon Nanotubes|Satoshi Kokado,Kikuo Harigaya###

Magnetoresistance Effect in Spin-Polarized Junctions of Ferromagnetically Contacting Multiple Conductive Paths: Applications to Atomic Wires and Carbon Nanotubes. For spin-polarized junctions of ferromagnetically contacting multiple
conductive paths, such as ferromagnet (FM)/atomic wires/FM and FM/carbon
nanotubes/FM junctions, we theoretically investigate spin-dependent transport
to elucidate the intrinsic relation between the number of paths and conduction,
and to enhance the magnetoresistance (MR) ratio. When many paths are randomly
located between the two FMs, electronic wave interference between the FMs
appears, and then the MR ratio increases with increasing number of paths.
Furthermore, at each number of paths, the MR ratio for carbon nanotubes becomes
larger than that for atomic wires, reflecting the characteristic shape of
points in contact with the FM.

###Impurity-induced tuning of quantum well states in spin-dependent resonant tunneling|A. Kalitsov,A. Coho,N. Kioussis,A. Vedyayev,M. Chshiev,A. Granovsky###

Impurity-induced tuning of quantum well states in spin-dependent resonant tunneling. We report exact model calculations of the spin-dependent tunneling in double
magnetic tunnel junctions in the presence of impurities in the well. We show
that the impurity can tune selectively the spin channels giving rise to a wide
variety of interesting and novel transport phenomena. The tunneling
magnetoresistance, the spin polarization and the local current can be
dramatically enhanced or suppressed by impurities. The underlying mechanism is
the impurity-induced shift of the quantum well states (QWS) which depends on
the impurity potential, impurity position and the symmetry of the QWS.

###Spin-polaron model: transport properties of EuB$_6$|Jayita Chatterjee,Unjong Yu,B. I. Min###

Spin-polaron model: transport properties of EuB$_6$. To understand anomalous transport properties of EuB$_6$, we have studied the
spin-polaron Hamiltonian incorporating the electron-phonon interaction.
Assuming a strong exchange interaction between the carriers and the localized
spins, the electrical conductivity is calculated. The temperature and magnetic
field dependence of the resistivity of EuB$_6$ are well explained. At low
temperature, magnons dominate the conduction process, whereas the lattice
contribution becomes significant at very high temperature due to the scattering
with the phonons. Large negative magnetoresistance near the ferromagnetic
transition is also reproduced as observed in EuB$_6$.

###Electrical transport and magnetic properties of nanostructured La0.67Ca0.33MnO3|Y. G. Zhao,W. Cai,X. S. Wu,X. P. Zhang,K. Wang,S. N. Gao,L. Lu###

Electrical transport and magnetic properties of nanostructured La0.67Ca0.33MnO3. Nanostructured La0.67Ca0.33MnO3 (NS-LCMO) was formed by pulsed-laser
deposition on the surface of porous Al2O3. The resistance peak temperature (Tp)
of the NS-LCMO increases with increasing average thickness of the films, while
their Curie temperatures (Tc) remain unchanged. The coercive field of the
samples increases with decreasing film thickness and its temperature dependence
can be well described by Hc(T) = Hc(0)[1-(T/TB)1/2]. A large magnetoresistance
and strong memory effect were observed for the NS-LCMO. The results are
discussed in terms of the size effect, Coulomb blockade and magnetic tunneling
effect. This work also demonstrates a new way to get nanostructured manganites.

###Localization and Interaction Effects in Strongly Underdoped La2-xSrxCuO4|Marta Z. Cieplak,A. Malinowski,S. Guha,M. Berkowski###

Localization and Interaction Effects in Strongly Underdoped La2-xSrxCuO4. The in-plane magnetoresistance (MR) in La2-xSrxCuO4 films with 0.03 < x <
0.05 has been studied in the temperature range 1.6 K to 100 K, and in magnetic
fields up to 14 T, parallel and perpendicular to the CuO2 planes. The behavior
of the MR is consistent with a predominant influence of interaction effects at
high temperatures, switching gradually to a regime dominated by spin scattering
at low T. Weak localization effects are absent. A positive orbital MR appears
close to the boundary between the antiferromagnetic and the spin-glass phase,
suggesting the onset of Maki-Thompson superconducting fluctuations deep inside
the insulating phase.

###"Spin-Flop" Transition and Anisotropic Magnetoresistance in Pr_{1.3-x}La_{0.7}Ce_{x}CuO_{4}: Unexpectedly Strong Spin-Charge Coupling in Electron-Doped Cuprates|A. N. Lavrov,H. J. Kang,Y. Kurita,T. Suzuki,Seiki Komiya,J. W. Lynn,S. -H. Lee,Pengcheng Dai,Yoichi Ando###

"Spin-Flop" Transition and Anisotropic Magnetoresistance in Pr_{1.3-x}La_{0.7}Ce_{x}CuO_{4}: Unexpectedly Strong Spin-Charge Coupling in Electron-Doped Cuprates. We use transport and neutron-scattering measurements to show that a
magnetic-field-induced transition from noncollinear to collinear spin
arrangement in adjacent CuO_{2} planes of lightly electron-doped
Pr_{1.3-x}La_{0.7}Ce_{x}CuO_{4} (x=0.01) crystals affects significantly both
the in-plane and out-of-plane resistivity. In the high-field collinear state,
the magnetoresistance (MR) does not saturate, but exhibits an intriguing
four-fold-symmetric angular dependence, oscillating from being positive at
B//[100] to being negative at B//[110]. The observed MR of more than 30% at low
temperatures induced by a modest modification of the spin structure indicates
an unexpectedly strong spin-charge coupling in electron-doped cuprates.

###Intensity of Coulomb Interaction between quasiparticles in diffusive metallic wires|B. Huard,A. Anthore,F. Pierre,H. Pothier,Norman O. Birge,D. Esteve###

Intensity of Coulomb Interaction between quasiparticles in diffusive metallic wires. The energy dependence and intensity of Coulomb interaction between
quasiparticles in metallic wires is obtained from two different methods:
determination of the temperature dependence of the phase coherence time from
the magnetoresistance, and measurements of the energy distribution function in
out-of-equilibrium situations. In both types of experiment, the energy
dependence of the Coulomb interaction is found to be in excellent agreement
with theoretical predictions. In contrast, the intensity of the interaction
agrees closely with theory only with the first method, whereas an important
discrepancy is found using the second one. Different explanations are proposed,
and results of a test experiment are presented.

###Andreev reflection at high magnetic fields: Evidence for electron and hole transport in edge states|J. Eroms,D. Weiss,J. De Boeck,G. Borghs,U. Zülicke###

Andreev reflection at high magnetic fields: Evidence for electron and hole transport in edge states. We have studied magnetotransport in arrays of niobium filled grooves in an
InAs/AlGaSb heterostructure. The critical field of up to 2.6 T permits to enter
the quantum Hall regime. In the superconducting state, we observe strong
magnetoresistance oscillations, whose amplitude exceeds the Shubnikov-de Haas
oscillations by a factor of about two, when normalized to the background.
Additionally, we find that above a geometry-dependent magnetic field value the
sample in the superconducting state has a higher longitudinal resistance than
in the normal state. Both observations can be explained with edge channels
populated with electrons and Andreev reflected holes.

###Effect of Zeeman splitting on magnetoresistivity of 2D hole gas in a Ge_{1-x}Si_x/Ge/Ge_{1-x}Si_x quantum well|Yu. G. Arapov,V. N. Neverov,G. I. Harus,N. G. Shelushinina,M. V. Yakunin,O. A. Kuznetsov,A. de Visser,L. Ponomarenko###

Effect of Zeeman splitting on magnetoresistivity of 2D hole gas in a Ge_{1-x}Si_x/Ge/Ge_{1-x}Si_x quantum well. For a two-dimensional (2D) hole system (confined within Ge layers of a
multilayered p-Ge/Ge_{1-x}Si_x heterostructure) described by Luttinger
Hamiltonian with the g-factor highly anisotropic for orientations of magnetic
field perpendicular and parallel to the 2D plane (g_perp >> g_par), reported is
an observation of low-temperature transition from metallic (dR/dT > 0) to
insulator (dR/dT < 0) behavior of resistivity R(T) induced by a perpendicular
magnetic field B. The revealed positive magnetoresistance scales as a function
of B/T. We attribute this finding to a suppression of the triplet channel of
electron-electron (hole-hole) interaction due to Zeeman splitting in the hole
spectrum.

###Changes in magnetic scattering anisotropy at a ferromagnetic/superconducting interface|K. Eid,H. Kurt,W. P. Pratt Jr.,J. Bass###

Changes in magnetic scattering anisotropy at a ferromagnetic/superconducting interface. We show that some metals and alloys (X = Cu, Ag, FeMn, or Cu and Ag combined
with each other), sputtered between ferromagnetic Co and superconducting Nb,
produce no change in current-perpendicular-to-plane magnetoresistance (CPP-MR)
in a carefully designed CPP-spin-valve. In contrast, other metals (Ru or Au) or
combinations (Cu or Ag combined with Au, Ru, or FeMn) change the CPP-MR, in
some cases even reversing its sign. We ascribe these changes to activation of
magnetic scattering anisotropies at a ferromagnetic/superconducting interface,
apparently by strong spin-flipping between the Co and Nb layers.

###Berry's phase contribution to the anomalous Hall effect of gadolinium|S. A. Baily,M. B. Salamon###

Berry's phase contribution to the anomalous Hall effect of gadolinium. When conduction electrons are forced to follow the local spin texture, the
resulting Berry phase can induce an anomalous Hall effect (AHE). In gadolinium,
as in double-exchange magnets, the exchange interaction is mediated by the
conduction electrons and the AHE may therefore resemble that of chromium
dioxide and other metallic double-exchange ferromagnets. The Hall resistivity,
magnetoresistance, and magnetization of single crystal gadolinium were measured
in fields up to 30 T. Measurements between 2 K and 400 K are consistent with
previously reported data. A scaling analysis for the Hall resistivity as a
function of the magnetization suggests the presence of a Berry's-phase
contribution to the anomalous Hall effect.

###Pseudogap formation and superconductivity of Bi$_{1.74}$Pb$_{0.38}$Sr$_{1.88}$CuO$_{6+δ}$ by studies of out-of-plane resistivity in magnetic fields|K. Kudo,Y. Miyoshi,T. Sasaki,N. Kobayashi###

Pseudogap formation and superconductivity of Bi$_{1.74}$Pb$_{0.38}$Sr$_{1.88}$CuO$_{6+δ}$ by studies of out-of-plane resistivity in magnetic fields. We report the out-of-plane resistivity in the systematically
oxygen-controlled single crystals
Bi$_{1.74}$Pb$_{0.38}$Sr$_{1.88}$CuO$_{6+\delta}$ in magnetic fields parallel
to the c-axis. Two characteristic temperatures $T^*$ and $T^{**}$ are found at
which a semiconductor-like upturn starts to develop and the magnetoresistance
changes its sign from positive to negative at lower temperature, respectively.
The obtained phase diagram strongly suggests that the pseudogap temperature
correlating to the superconducting gap is not $T^{*}$ but $T^{**}$. The gap
opened at $T^*$ may relate to another phenomenon with the different energy
scale such as the antiferromagnetic excitation due to the exchange interaction
between Cu$^{2+}$ spins.

###Coherence of polaronic transport in layered metals|Urban Lundin,Ross H. McKenzie###

Coherence of polaronic transport in layered metals. Layered systems shows anisotropic transport properties. The interlayer
conductivity show a general temperature dependence for a wide class of
materials. This can be understood if conduction occurs in two different
channels activated at different temperatures. We show that the characteristic
temperature dependence can be explained using a polaron model for the
transport. The results show an intuitive interpretation in terms of coherent
and incoherent quasi-particles within the layers. Further, we extract results
for the magnetoresistance, thermopower, spectral function and optical
conductivity for the model and discuss application to experiments.

###Magnetothermopower and Magnetoresistivity of RuSr2Gd1-xLaxCu2O8 (x=0, 0.1)|C. -J. Liu,C. -S. Sheu,T. -W. Wu,L. -C. Huang,F. H. Hsu,H. D. Yang,G. V. M. Williams,Chia-Jung C. Liu###

Magnetothermopower and Magnetoresistivity of RuSr2Gd1-xLaxCu2O8 (x=0, 0.1). We report measurements of magnetothermopower and magnetoresistivity as a
function of temperature on RuSr2Gd1-xLaxCu2O8 (x = 0, 0.1). The normal-state
thermopower shows a dramatic decrease after applying a magnetic field of 5 T,
whereas the resistivity shows only a small change after applying the same
field. Our results suggest that RuO2 layers are conducting and the magnetic
field induced decrease of the overall thermopower is caused by the decrease of
partial thermopower decrease associated with the spin entropy decrease of the
carriers in the RuO2 layers.

###Re-entrant Behavior and Gigantic Response in Disordered Spin-Peierls System|Hitoshi Seo,Yukitoshi Motome,Naoto Nagaosa###

Re-entrant Behavior and Gigantic Response in Disordered Spin-Peierls System. Effects of disorder and external field on the competing spin-Peierls and
antiferromagnetic states are studied theoretically in terms of the numerical
transfer matrix method applied to a quasi one-dimensional spin 1/2 Heisenberg
model coupled to the lattice degree of freedom. We show that, at temperatures
above the impurity-induced antiferromagnetic phase, inhomogeneous spin-Peierls
lattice distortions remain to exist showing a re-entrant behavior. This feature
can be drastically altered by very weak perturbations, e.g., the staggered
magnetic field or the change in interchain exchange coupling $J_\perp$, leading
to a huge response, which is analogous to the colossal magnetoresistance
phenomenon in perovskite manganese oxides.

###Unusual Oscillation in Tunneling Magnetoresistance near a Quantum Critical Point in Sr$_3$Ru$_2$O$_7$|Joe Hooper,Zhiqiang Mao,Robin Perry,Yoshiteru Maeno###

Unusual Oscillation in Tunneling Magnetoresistance near a Quantum Critical Point in Sr$_3$Ru$_2$O$_7$. We performed single electron tunneling measurements on bilayer ruthenate
Sr$_3$Ru$_2$O$_7$. We observe an unusual oscillation in tunneling
magnetoresistance near the metamagnetic quantum phase transition at
temperatures below 7 K. The characteristic features of this oscillation suggest
that it is unrelated to traditional quantum oscillations caused by orbit
quantization. In addition, tunneling spectra are found to change sharply in the
low bias voltage range of $V$ $<$ 2mV near the transition field. These
observations reveal that the Fermi surface of Sr$_3$Ru$_2$O$_7$ changes in a
surprising way as the system undergoes strong critical fluctuations.

###Magneto-transport studies on (Pr1/3Sm2/3)2/3A1/3MnO3 (A = Ca, Sr and Ba) compounds|Saket Asthana,D. Bahadur,A. K. Nigam,S. K. Malik###

Magneto-transport studies on (Pr1/3Sm2/3)2/3A1/3MnO3 (A = Ca, Sr and Ba) compounds. Magnetic and transport properties of (Pr1/3Sm2/3)2/3A1/3MnO3 (A = Ca, Sr and
Ba) compounds, prepared by the citrate gel route, have been investigated. These
compounds are found to crystallize in the orthorhombic structure. Charge
ordering transport behavior is indicated only in Ca-substituted compound. The
Sr- and Ba-substituted compounds show metal-insulator transition and
semiconducting-like behavior, respectively. The magnetoresistance is highest in
the Ba substituted compound. All the three samples show irreversibility in
magnetization as a function of temperature in zero-field cooled (ZFC) and field
cooled (FC) plots. The non-saturating magnetization, even at 5K and 4 Tesla
field, are observed in Ca as well Ba-substituted compounds.

###Anomalous bias dependence of tunnel magnetoresistance in a magnetic tunnel junction|Soumik Mukhopadhyay,I. Das,S. P. Pai,P. Raychaudhuri###

Anomalous bias dependence of tunnel magnetoresistance in a magnetic tunnel junction. We have fabricated a spin-polarized tunneling device based on half metallic
manganites incorporating $Ba_{2}LaNbO_{6}$ as insulating barrier. An anomalous
bias dependence of tunnel magnetoresistance (TMR) has been observed, the first
of its kind in a symmetric electrode tunnel junction with single insulating
barrier. The bias dependence of TMR shows an extremely sharp zero bias anomaly,
which can be considered as a demonstration of the drastic density of states
variation around the Fermi level of the half metal. This serves as a strong
evidence for the existence of minority spin tunneling states at the half-metal
insulator interface.

###Detecting domain wall trapping and motion at a constriction in narrow ferromagnetic wires using perpendicular-current giant magnetoresistance|A. J. Zambano,W. P. Pratt Jr###

Detecting domain wall trapping and motion at a constriction in narrow ferromagnetic wires using perpendicular-current giant magnetoresistance. We present a versatile method for detecting the presence and motion of a
trapped domain wall in a narrow ferromagnetic layer using
current-perpendicular-to-plane (CPP) giant magnetoresistance (MR). The CPP-MR
response to small motions of the trapped domain wall is enhanced because the
CPP current is restricted to the region of wall trapping. We use a
Permalloy/Cu/Permalloy spin valve in the shape of a long, ~500-nm-wide wire
with a constriction (notch) near its middle that acts as a trapping site for a
head-to-head domain wall. Two different notch shapes were studied, mostly at
4.2 K but also at 295K.

###Orbitally-driven Behavior: Mott Transition, Quantum Oscillations and Colossal Magnetoresistance in Bilayered Ca3Ru2O7|G. Cao,X. N. Lin,L. Balicas,S. Chikara,J. E. Crow,P. Schlottmann###

Orbitally-driven Behavior: Mott Transition, Quantum Oscillations and Colossal Magnetoresistance in Bilayered Ca3Ru2O7. We report recent transport and thermodynamic experiments over a wide range of
temperatures for the Mott-like system Ca3Ru2O7 at high magnetic fields, B, up
to 30 T. This work reveals a rich and highly anisotropic phase diagram, where
applying B along the a-, b-, and c-axis leads to vastly different behavior. A
fully spin-polarized state via a first order metamagnetic transition is
obtained for B||a, and colossal magnetoresistance is seen for B||b, and quantum
oscillations in the resistivity are observed for B||c, respectively. The
interplay of the lattice, orbital and spin degrees of freedom are believed to
give rise to this strongly anisotropic behavior.

###Phenomenology of Conduction in Incoherent Layered Crystals|George A. Levin###

Phenomenology of Conduction in Incoherent Layered Crystals. A novel phenomenological approach to the analysis of the conductivities of
incoherent layered crystals is presented. It is based on the fundamental
relationship between the resistive anisotropy $\sigma_{ab}/\sigma_c$ and the
ratio of the phase coherence lengths in the respective directions. We explore
the model-independent consequences of a general assumption that the
out-of-plane phase coherence length of single electrons is a short fixed
distance of the order of interlayer spacing. Several topics are discussed:
application of the scaling theory, magnetoresistivity, the effects of
substitutions and the intermediate regime of conduction when both coherence
lengths change with temperature, but at different rate.

###Origin of the anomalous low temperature upturn in resistivity in the electron-doped cuprates|Y. Dagan,A. Biswas,M. C. Barr,W. M. Fisher,R. L. Greene###

Origin of the anomalous low temperature upturn in resistivity in the electron-doped cuprates. The temperature, doping and field dependences of the magnetoresistance (MR)
in Pr_(2-x)Ce_(x)CuO_(4-delta) films are reported. We distinguish between
orbital MR, found when the magnetic field is applied perpendicular to the ab
planes, and the nearly isotropic spin MR. The latter, the major MR effect in
the superconducting samples, appears in the region of the doping-temperature
phase diagram where d(rho)/dT<0, or an upturn in the resistivity appears. We
conclude that the upturn originates from spin scattering processes.

###Magnetically-controlled impurities in quantum wires with strong Rashba coupling|R. G. Pereira,E. Miranda###

Magnetically-controlled impurities in quantum wires with strong Rashba coupling. We investigate the effect of strong spin-orbit interaction on the electronic
transport through non-magnetic impurities in one-dimensional systems. When a
perpendicular magnetic field is applied, the electron spin polarization becomes
momentum-dependent and spin-flip scattering appears, to first order in the
applied field, in addition to the usual potential scattering. We analyze a
situation in which, by tuning the Fermi level and the Rashba coupling, the
magnetic field can suppress the potential scattering. This mechanism should
give rise to a significant negative magnetoresistance in the limit of large
barriers.

###Tailoring of ferromagnetic Pr0.85Ca0.15MnO3/ferroelectric Ba0.6Sr0.4TiO3 superlattices for multiferroic properties|P. Murugavel,D. Saurel,W. Prellier,Ch. Simon,B. Raveau###

Tailoring of ferromagnetic Pr0.85Ca0.15MnO3/ferroelectric Ba0.6Sr0.4TiO3 superlattices for multiferroic properties. Superlattices composed of ferromagnetic Pr0.85Ca0.15MnO3 and ferroelectric
Ba0.6Sr0.4TiO3 layers were fabricated on (100) SrTiO3 substrates by a
pulsed-laser deposition method. The capacitance and resistive parts of the
samples were analyzed from the complex impedance measurements, performed on the
samples using a special experimental set-up. The superlattice with larger
ferroelectric thickness shows unique characteristics which are not present in
the parent ferromagnetic thin film. The superlattice show both ferromagnetic
and ferroelectric transitions which is an evidence for the coexistence of both
the properties. The high magnetoresistance (40 % at 80K) shown by the
superlattice can be attributed to the coupling between ferromagnetic and
ferroelectric layers, i.e, to the magnetoelectric effect.

###Microwave photoresponse in the 2D electron system caused by intra-Landau level transitions|S. I. Dorozhkin,J. H. Smet,V. Umansky,K. von Klitzing###

Microwave photoresponse in the 2D electron system caused by intra-Landau level transitions. The influence of microwave radiation on the DC-magnetoresistance of
2D-electrons is studied in the regime beyond the recently discovered zero
resistance states when the cyclotron frequency exceeds the radiation frequency.
Radiation below 30 GHz causes a strong suppression of the resistance over a
wide magnetic field range, whereas higher frequencies produce a non-monotonic
behavior in the damping of the Shubnikov-de Haas oscillations. These
observations are explained by the creation of a non-equilibrium electron
distribution function by microwave induced intra-Landau level transitions.

###Magnetocapacitance and exponential magnetoresistance in manganite-titanate heterojunctions|N. Nakagawa,M. Asai,Y. Mukunoki,T. Susaki,H. Y. Hwang###

Magnetocapacitance and exponential magnetoresistance in manganite-titanate heterojunctions. We present a rectifying manganite-titanate heterojunction exhibiting a
magnetic field tunable depletion layer. This creates a large positive
magnetocapacitance, a direct measure of the field-induced reduction of the
effective depletion width across the junction. Furthermore, the reduction of
the junction barrier shifts the forward bias characteristics, giving
exponentially-enhanced differential magnetoresistance, occurring despite the
absence of a spin filter. These results provide a unique probe of a Mott
insulator/band insulator interface, and further suggest new electronic devices
incorporating the magnetic field sensitivity of these strongly correlated
electron materials.

###Large magnetoresistance at room-temperature in semiconducting polymer sandwich devices|T. L. Francis,Ö. Mermer,G. Veeraraghavan,M. Wohlgenannt###

Large magnetoresistance at room-temperature in semiconducting polymer sandwich devices. We report on the discovery of a large, room temperature magnetoresistance
(MR) effect in polyfluorene sandwich devices in weak magnetic fields. We
characterize this effect and discuss its dependence on voltage, temperature,
film thickness, electrode materials, and (unintentional) impurity
concentration. We usually observed negative MR, but positive MR can also be
achieved under high applied electric fields. The MR effect reaches up to 10% at
fields of 10mT at room temperature. The effect shows only a weak temperature
dependence and is independent of the sign and direction of the magnetic field.
We find that the effect is related to the hole current in the devices.

###Effect of Ga$^{+}$ irradiation on magnetic and magnetotransport properties in (Ga,Mn)As epilayers|H. Kato,K. Hamaya,Y. Kitamoto,T. Taniyama,H. Munekata###

Effect of Ga$^{+}$ irradiation on magnetic and magnetotransport properties in (Ga,Mn)As epilayers. We report on the magnetic and magnetotransport properties of ferromagnetic
semiconductor (Ga,Mn)As modified by Ga$^{+}$ ion irradiation using focused ion
beam. A marked reduction in the conductivity and the Curie temperature is
induced after the irradiation. Furthermore, an enhanced negative
magnetoresistance (MR) and a change in the magnetization reversal process are
also demonstrated at 4 K. Raman scattering spectra indicate a decrease in the
concentration of hole carriers after the irradiation, and a possible origin of
the change in the magnetic properties is discussed.

###Tunnel magnetoresistance of polymeric chains|Kamil Walczak###

Tunnel magnetoresistance of polymeric chains. Coherent spin-dependent electronic transport is investigated in a molecular
junction made of polymeric chain attached to ferromagnetic electrodes (Ni and
Co, respectively). Molecular system is described by a simple Huckel model,
while the coupling to the electrodes is treated through the use of a broad-band
theory. The current flowing through the device is calculated within
non-equilibrium Green's function approach. It is shown that tunnel
magnetoresistance of molecular junction can be quite large (over 100 %)and
strongly depends on: (i) the lenght of the polymeric chain and (ii) the
strength of the molecule-to-electrodes coupling.

###Electronic transport through a quantum dot network|August Dorn,Thomas Ihn,Klaus Ensslin,Werner Wegscheider,Max Bichler###

Electronic transport through a quantum dot network. The conductance through a finite quantum dot network is studied as a function
of inter-dot coupling. As the coupling is reduced, the system undergoes a
transition from the antidot regime to the tight binding limit, where Coulomb
resonances with on average increasing charging energies are observed.
Percolation models are used to describe the conduction in the open and closed
regime and contributions from different blockaded regions can be identified. A
strong negative average magnetoresistance in the Coulomb blockade regime is in
good quantitative agreement with theoretical predictions for magnetotunneling
between individual quantum dots.

###Magnetic tunnel junctions with impurities|F. Kanjouri,N. Ryzhanova,B. Dieny,N. Strelkov,A. Vedyayev###

Magnetic tunnel junctions with impurities. The influence of impurities, embedded into the isolating spacer (I) between
two ferromagnetic electrodes (F), on the I-V curve and tunnel magnetoresistance
(TMR), is theoretically investigated. It is shown, that the current and TMR are
strongly enhanced in the vicinity of the impurity under the condition that the
energy of the electron's bound state on the impurity is close to the Fermi
energy. If the position of the impurity inside the barrier is asymmetric, e.g.
closer to the one of the interfaces F/I the I-V curve exhibits quasidiode
behavior.

###An Interesting Magnetoresistive System: Sr2FeMoO6|Sugata Ray,D. D. Sarma###

An Interesting Magnetoresistive System: Sr2FeMoO6. Ordered double perovskite oxides of the general formula, A2BB'O6, have been
known for several decades to have interesting electronic and magnetic
properties. However, a recent report of a spectacular negative
magnetoresistance effect in a specific member of this family, namely Sr2FeMoO6,
has brought this class of compounds under intense scrutiny. In this small
review, we present few theoretical and experimental results, describing mainly
the effects of Fe/Mo antisite defects on the properties of this compound and
also briefly discuss few other puzzling facts about this fascinating compound

###Weak antilocalization in high-mobility two-dimensional systems|L. E. Golub###

Weak antilocalization in high-mobility two-dimensional systems. Theory of weak antilocalization is developed for high-mobility
two-dimensional systems. Spin-orbit interaction of Rashba and Dresselhaus types
is taken into account. Anomalous magnetoresistance is calculated in the whole
range of classically weak magnetic fields and for arbitrary strength of
spin-orbit splitting. Obtained expressions are valid for both ballistic and
diffusive regimes of weak localization. Proposed theory includes both
backscattering and nonbackscattering contributions to the conductivity. It is
shown that magnetic field dependence of conductivity in high-mobility
structures is not described by earlier theories.

###Antisymmetric magnetoresistance in magnetic multilayers with perpendicular anisotropy|X. M. Cheng,S. Urazhdin,O. Tchernyshyov,C. L. Chien,V. I. Nikitenko,A. J. Shapiro,R. D. Shull###

Antisymmetric magnetoresistance in magnetic multilayers with perpendicular anisotropy. While magnetoresistance (MR) has generally been found to be symmetric in
applied field in non-magnetic or magnetic metals, we have observed
antisymmetric MR in Co/Pt multilayers. Simultaneous domain imaging and
transport measurements show that the antisymmetric MR is due to the appearance
of domain walls that run perpendicular to both the magnetization and the
current, a geometry existing only in materials with perpendicular magnetic
anisotropy. As a result, the extraordinary Hall effect (EHE) gives rise to
circulating currents in the vicinity of the domain walls that contributes to
the MR. The antisymmetric MR and EHE have been quantitatively accounted for by
a theoretical model.

###Diode effect in magnetic tunnel junctions|F. Kanjouri,N. Ryzhanova,B. Dieny,N. Strelkov,A. Vedyaev###

Diode effect in magnetic tunnel junctions. The influence on the I-V characteristics and tunnel magnetoresistance (TMR),
of impurities embedded into the insulating barrier I separating the two
ferromagnetic electrodes F of a magnetic tunnel junction, was theoretically
investigated. When the energy of the electron's bound state at the impurity
site is close to the Fermi energy, it is shown that the current and TMR are
strongly enhanced in the vicinity of the impurity. If the position of the
impurity inside the barrier is asymmetric, e.g. closer to one of the interfaces
F/I, the I-V characteristic exhibits a quasidiode behavior. The case of a
single impurity and of a random distribution of impurities within a plane were
both studied.

###Hysteretic resistance spikes in quantum Hall ferromagnets without domains|Henrique J. P. Freire,J. Carlos Egues###

Hysteretic resistance spikes in quantum Hall ferromagnets without domains. We use spin-density-functional theory to study recently reported hysteretic
magnetoresistance \rho_{xx} spikes in Mn-based 2D electron gases
[Jaroszy\'{n}ski et al. Phys. Rev. Lett. (2002)]. We find hysteresis loops in
our calculated Landau fan diagrams and total energies signaling
quantum-Hall-ferromagnet phase transitions. Spin-dependent exchange-correlation
effects are crucial to stabilize the relevant magnetic phases arising from
distinct symmetry-broken excited- and ground-state solutions of the Kohn-Sham
equations. Besides hysteretic spikes in \rho_{xx}, we predict hysteretic dips
in the Hall resistance \rho_{xy}. Our theory, without domain walls,
satisfactorily explains the recent data.

###Spin dependent transport of ``nonmagnetic metal/zigzag nanotube encapsulating magnetic atoms/nonmagnetic metal'' junctions|Satoshi Kokado,Kikuo Harigaya###

Spin dependent transport of ``nonmagnetic metal/zigzag nanotube encapsulating magnetic atoms/nonmagnetic metal'' junctions. Towards a novel magnetoresistance (MR) device with a carbon nanotube, we
propose ``nonmagnetic metal/zigzag nanotube encapsulating magnetic
atoms/nonmagnetic metal'' junctions. We theoretically investigate how
spin-polarized edges of the nanotube and the encapsulated magnetic atoms
influence on transport. When the on-site Coulomb energy divided by the
magnitude of transfer integral, $U/|t|$, is larger than 0.8, large MR effect
due to the direction of spins of magnetic atoms, which has the magnitude of the
MR ratio of about 100%, appears reflecting such spin-polarized edges.

###Ballistic anisotropic magnetoresistance|J. Velev,R. F. Sabirianov,S. S. Jaswal,E. Y. Tsymbal###

Ballistic anisotropic magnetoresistance. Electronic transport in ferromagnetic ballistic conductors is predicted to
exhibit ballistic anisotropic magnetoresistance (BAMR) - a change in the
ballistic conductance with the direction of magnetization. This phenomenon
originates from the effect of the spin-orbit interaction on the electronic band
structure which leads to a change in the number of bands crossing the Fermi
energy when the magnetization direction changes. We illustrate the significance
of this phenomenon by performing ab-initio calculations of the ballistic
conductance in ferromagnetic Ni and Fe nanowires which display a sizable BAMR
when the magnetization changes direction from parallel to perpendicular to the
wire axis.

###Large negative magnetoresistance in a ferromagnetic shape memory alloy : Ni_{2+x}Mn_{1-x}Ga|C. Biswas,R. Rawat,S. R. Barman###

Large negative magnetoresistance in a ferromagnetic shape memory alloy : Ni_{2+x}Mn_{1-x}Ga. 5% negative magnetoresistance (MR) at room temperature has been observed in
bulk Ni_{2+x}Mn_{1-x}Ga. This indicates the possibility of using
Ni_{2+x}Mn_{1-x}Ga as magnetic sensors. We have measured MR in the
ferromagnetic state for different compositions (x=0-0.2) in the austenitic,
pre-martensitic and martensitic phases. MR is found to increase with x. While
MR for x=0 varies almost linearly in the austenitic and pre-martensitic phases,
in the martensitic phase it shows a cusp-like shape. This has been explained by
the changes in twin and domain structures in the martensitic phase. In the
austenitic phase, which does not have twin structure, MR agrees with theory
based on s-d scattering model.

###Tunable spin transport in CrAs: role of correlation effects|L. Chioncel,M. I. Katsnelson,G. A. de Wijs,R. A. de Groot,A. I. Lichtenstein###

Tunable spin transport in CrAs: role of correlation effects. Correlation effects on the electronic structure of half-metallic CrAs in
zinc-blende structure are studied for different substrate lattice constants.
Depending on the substrate the spectral weight of the non-quasiparticle states
might be tuned from a well developed value in the case of InAs substrate to an
almost negligible contribution for the GaAs one. A piezoelectric material that
would allow the change in the substrate lattice parameters opens the
possibility for practical investigations of the switchable (tunable)
non-quasiparticle states. Since the latter are important for the tunneling
magnetoresistance and related phenomena it creates new opportunities in
spintronics.

###Spin transport and magnetoresistance in F/S/F spin valves|Jan Petter Morten,Arne Brataas,Wolfgang Belzig###

Spin transport and magnetoresistance in F/S/F spin valves. We consider spin transport and spin relaxation in superconductors using the
quasiclassical theory of superconductivity. We include spin relaxation due to
spin-orbit interaction as well as magnetic impurities, and show that the energy
dependence of the spin-flip rate is different for these two mechanisms. In
ferromagnet-superconductor-ferromagnet systems made of Co and Al, interface
resistances can be small compared to bulk resistances. This simplifies the
description of transport in Co/Al/Co spin valves, for which we numerically
calculate the temperature and Al length dependence of the magnetoresistance.

###Spin-Polarized Electron Transport through Nanometer-Scale Al Grains|L. Y. Zhang,C. Y. Wang,Y. G. Wei,X. Y. Liu,D. Davidovic###

Spin-Polarized Electron Transport through Nanometer-Scale Al Grains. We investigate spin-polarized electron tunnelling through ensembles of
nanometer scale Al grains embedded between two Co-reservoirs at 4.2K, and
observe tunnelling-magnetoresistance (TMR) and effects from spin-precession in
the perpendicular applied magnetic field (the Hanle effect). The spin-coherence
time ($T_2^\star$) measured using the Hanle effect is of order $ns$. The
dephasing is attributed to electron spin-precession in local magnetic fields.
Dephasing process does not destroy $TMR$, which is strongly asymmetric with
bias voltage. The asymmetric TMR is explained by spin relaxation in Al grains
and asymmetric electron dwell times.

###Variable range cotunneling and conductivity of a granular metal|M. V. Feigel'man,A. S. Ioselevich###

Variable range cotunneling and conductivity of a granular metal. The Efros-Shklovskii law for the conductivity of granular metals is
interpreted as a result of a variable range cotunneling process. The
cotunneling between distant resonant grains is predominantly elastic at low T
<< T_c, while it is inelastic (i.e., accompanied by creation of electron-hole
pairs on a string of intermediate non-resonant grains) at T > T_c. The
corresponding E-S temperature T_ES in the latter case is slightly
(logarithmically) T-dependent. The magnetoresistance in the two cases is
different: it may be relatively strong and negative at T much below T_c, while
at T>T_c it is suppressed due to inelastic processes which destroy the
interference.

###The role of ferroelectric-ferromagnetic layers on the properties of superlattice-based multiferroics|P. Murugavel,M. P. Singh,W. Prellier,B. Mercey,Ch. Simon,B. Raveau###

The role of ferroelectric-ferromagnetic layers on the properties of superlattice-based multiferroics. A series of superlattices and trilayers composed of ferromagnetic and
ferroelectric or paraelectric layers were grown on (100) SrTiO3 by the pulsed
laser deposition technique. Their structural and magneto-electric properties
were examined. The superlattices made of ferromagnetic Pr0.85Ca0.15MnO3 (PCMO)
and a ferroelectric, namely Ba0.6Sr0.4TiO3 (BST) or BaTiO3, showed enhanced
magnetoresistance (MR) at high applied magnetic field, whereas such enhancement
was absent in Pr0.85Ca0.15MnO3/SrTiO3 superlattices, which clearly demonstrates
the preponderant role of the ferroelectric layers in this enhanced MR.
Furthermore, the absence of enhanced MR in trilayers of PCMO/BST indicates that
the magneto-electric coupling which is responsible for MR in these systems is
stronger in multilayers than in their trilayer counterparts.

###Dependence of Giant Tunnel Magnetoresistance of Sputtered CoFeB/MgO/CoFeB Magnetic Tunnel Junctions on MgO Barrier Thickness and Annealing Temperatur|Jun Hayakawa,Shoji Ikeda,Fumihiro Matsukura,Hiromasa Takahashi,Hideo Ohno###

Dependence of Giant Tunnel Magnetoresistance of Sputtered CoFeB/MgO/CoFeB Magnetic Tunnel Junctions on MgO Barrier Thickness and Annealing Temperatur. We investigated the dependence of giant tunnel magnetoresistance (TMR) on the
thickness of an MgO barrier and on the annealing temperature of sputtered
CoFeB/MgO/CoFeB magnetic tunnel junctions deposited on SiO2/Si wafers. The
resistance-area product exponentially increases with MgO thickness, indicating
that the quality of MgO barriers is high in the investigated thickness range of
1.15-2.4 nm. High-resolution transmission electron microscope images show that
annealing at 375 C results in the formation of crystalline CoFeB/MgO/CoFeB
structures, even though CoFeB electrodes are amorphous in the as-sputtered
state. The TMR ratio increases with annealing temperature and is as high as
260% at room temperature and 403% at 5 K.

###Current oscillation and low-field colossal magnetoresistance effect in phase-separated manganites|M. Tokunaga,H. Song,Y. Tokunaga,T. Tamegai###

Current oscillation and low-field colossal magnetoresistance effect in phase-separated manganites. Current-induced switching from metallic to insulating state is observed in
phase-separated states of (La_{1-y}Pr_y)_{0.7}Ca_{0.3}MnO_3 (y=0.7) and
Nd_{0.5}Ca_{0.5}Mn_{1-z}Cr_zO_3 (z=0.03) crystals. Application of magnetic
fields to this current-induced insulating state causes pronounced low-field
negative magnetoresistance effect [r(H)/r(0)=10^{-3} at H=1kOe]. Application of
a constant voltage also causes breakdown of ohmic relation above a threshold
voltage. At voltages higher than this threshold value, oscillations in currents
are observed. This oscillation is well reproduced by a simple model of local
switching of a percolative conduction path.

###Spin and orbital ferromagnetism in strongly correlated itinerant electron systems|V. Yu. Irkhin,M. I. Katsnelson###

Spin and orbital ferromagnetism in strongly correlated itinerant electron systems. Spectra of one-electron and collective excitations in narrow-band
ferromagnets with unquenched orbital moments are calculated in various
theoretical models. The interaction of spin and orbital excitations with
conduction electrons results in the damping of the former which, however, turns
out to be rather small; therefore, apart from usual spin waves, well-defined
orbitons can exist. Non-quasiparticle states occur in the electron energy
spectrum near the Fermi energy due to this interaction. The criteria of
stability of the saturated spin and orbital ferromagnetic ordering are
considered. Possible effects of orbital ordering in magnetite and in colossal
magnetoresistance manganites are discussed.

###The impact of niobium doping upon the magnetotransport properties of the oxygen-deficient perovskite SrCo1-xNbxO3-d|T. Motohashi,V. Caignaert,V. Pralong,M. Hervieu,A. Maignan,B. Raveau###

The impact of niobium doping upon the magnetotransport properties of the oxygen-deficient perovskite SrCo1-xNbxO3-d. The oxygen-deficient perovskite cobaltite SrCo1-xNbxO3-d was synthesized by
direct solid-state reaction and its magnetotransport properties were
investigated. This cobaltite exhibits an unusual ferromagnetic behavior with a
transition temperature Tm = 130-150 K and a spin glass like behavior below Tm.
Importantly, this phase reaches a large magnetoresistance (MR) value, MR = -(rH
- r0) / r0 = 30% at 5 K in 7 T. The large MR effect is believed to be related
to the disordered magnetic state induced by the Nb-for-Co substitution.

###Perpendicular spin valves with ultra-thin ferromagnetic layers|Alexey A. Kovalev,Gerrit E. W. Bauer,Arne Brataas###

Perpendicular spin valves with ultra-thin ferromagnetic layers. We address two finite size effects in perpendicular transport through
magnetic multilayers. When the magnetic layer thickness in spin valves becomes
of the order or smaller than the spin-flip diffusion length, structural
asymmetries affect the transport properties. A magnetic layer with thickness
approaching the magnetic coherence length becomes transparent for spin currents
polarized perpendicular to the magnetization. We use the generalized
magnetoelectronic circuit theory to investigate both effects on the angular
magnetoresistance (aMR) and spin transfer torque. We analyze recent aMR
experiments to determine the spin-flip diffusion length in the ferromagnet as
well as the interface spin-mixing conductance and propose a method to measure
the ferromagnetic coherence length.

###New possibility of the ground state of quarter-filled one-dimensional strongly correlated electronic system interacting with localized spins|Chisa Hotta,Masao Ogata,Hidetoshi Fukuyama###

New possibility of the ground state of quarter-filled one-dimensional strongly correlated electronic system interacting with localized spins. We study numerically the ground state properties of the one-dimensional
quarter-filled strongly correlated electronic system interacting
antiferromagnetically with localized $S=1/2$ spins. It is shown that the
charge-ordered state is significantly stabilized by the introduction of
relatively small coupling with the localized spins. When the coupling becomes
large the spin and charge degrees of freedom behave quite independently and the
ferromagnetism is realized. Moreover, the coexistence of ferromagnetism with
charge order is seen under strong electronic interaction. Our results suggest
that such charge order can be easily controlled by the magnetic field, which
possibly give rise to the giant negative magnetoresistance, and its relation to
phthalocyanine compounds is discussed.

###Simultaneous electric and magnetic field induced nonvolatile memory|M. Quintero,A. G. Leyva,P. Levy###

Simultaneous electric and magnetic field induced nonvolatile memory. We investigate the electric field induced resistive switching effect and
magnetic field induced fraction enlargement on a polycrystalline sample of a
colossal magnetoresistive compound displaying intrinsic phase coexistence. Our
data show that the electric effect (presumably related to the presence of
inhomogeinities) is present in a broad temperature range(300 to 20 K), being
observable even in a mostly homogeneous ferromagnetic state. In the temperature
range in which low magnetic field determines the phase coexistence fraction,
both effects, though related to different mechanisms, are found to determine
multilevel nonvolatile memory capabilities simultaneously.

###Spin-polarized quasiparticle injection effects in YBCO thin films|S. Soltan,J. Albrecht,H. -U. Habermeier###

Spin-polarized quasiparticle injection effects in YBCO thin films. We report detailed transport studies on ferromagnet-superconductor
heterostructures. Epitaxial heterostructures of half-metal colossal
magnetoresistive La2/3Ca1/3MnO3 (HM-CMR) and high Tc superconducting YBa2Cu3O7
(YBCO) are grown on SrTiO3 (100) single crystal substrates by pulsed laser
deposition. Using the HM--CMR layer as source for spin-polarized
quasiparticles, we show the effect of injection of spin-polarized
quasiparticles into the ab-plane and along the c-axis of YBCO. The results show
a drop in the ab-plane resistance Rab (T) in the case of injection along the
c-axis that is discussed to be related to the opening of a pseudogap.

###Effect of interface states on spin-dependent tunneling in Fe/MgO/Fe tunnel junctions|K. D. Belashchenko,J. Velev,E. Y. Tsymbal###

Effect of interface states on spin-dependent tunneling in Fe/MgO/Fe tunnel junctions. The electronic structure and spin-dependent tunneling in epitaxial
Fe/MgO/Fe(001) tunnel junctions are studied using first-principles
calculations. For small MgO barrier thickness the minority-spin resonant bands
at the two interfaces make a significant contribution to the tunneling
conductance for the antiparallel magnetization, whereas these bands are, in
practice, mismatched by disorder and/or small applied bias for the parallel
magnetization. This explains the experimentally observed decrease in tunneling
magnetoresistance (TMR) for thin MgO barriers. We predict that a monolayer of
Ag epitaxially deposited at the interface between Fe and MgO suppresses
tunneling through the interface band and may thus be used to enhance the TMR
for thin barriers.

###Cotunneling through a quantum dot coupled to ferromagnetic leads with noncollinear magnetizations|I. Weymann,J. Barnas###

Cotunneling through a quantum dot coupled to ferromagnetic leads with noncollinear magnetizations. Spin-dependent electronic transport through a quantum dot has been analyzed
theoretically in the cotunneling regime by means of the second-order
perturbation theory. The system is described by the impurity Anderson
Hamiltonian with arbitrary Coulomb correlation parameter $U$. It is assumed
that the dot level is intrinsically spin-split due to an effective molecular
field exerted by a magnetic substrate. The dot is coupled to two ferromagnetic
leads whose magnetic moments are noncollinear. The angular dependence of
electric current, tunnel magnetoresistance, and differential conductance are
presented and discussed. The evolution of a cotunneling gap with the angle
between magnetic moments and with the splitting of the dot level is also
demonstrated.

###Metal-insulator transition in manganites: mixture of oxygen isotopes versus magnetic field|A. Taldenkov,N. Babushkina,A. Inyushkin,O. Nikolaeva,O. Gorbenko,A. Kaul###

Metal-insulator transition in manganites: mixture of oxygen isotopes versus magnetic field. We have investigated the effect of oxygen isotope substitution on the
metal-insulator transition temperature and the resistivity of the narrow band
manganite (La0.25Pr0.75)0.7Ca0.3MnO3 in a constant magnetic field. A set of 16
samples having different mixtures of 16O, 17O and 18O isotopes with average
mass varying from 16.0 to 17.8 a.m.u. was studied. We have found that the
magnetoresistance and the isotope effect can be linked together with a single
parameter - effective magnetic field, which decreases linearly with an increase
of average oxygen mass with a slope of -2 T/a.m.u. The applicability of the
small polaron model is discussed.

###Magnetic scattering of spin polarized carriers in (In,Mn)Sb dilute magnetic semiconductor|M. Csontos,T. Wojtowicz,X. Liu,M. Dobrowolska B. Jankó,J. K. Furdyna,G. Mihály###

Magnetic scattering of spin polarized carriers in (In,Mn)Sb dilute magnetic semiconductor. Magnetoresistance measurements on the magnetic semiconductor (In,Mn)Sb
suggest that magnetic scattering in this material is dominated by isolated
Mn$^{2+}$ ions located outside the ferromagnetically-ordered regions when the
system is below $T_{c}$. A model is proposed, based on the $p$-$d$ exchange
between spin-polarized charge carriers and localized Mn$^{2+}$ ions, which
accounts for the observed behavior both below and above the ferromagnetic phase
transition. The suggested picture is further verified by high-pressure
experiments, in which the degree of magnetic interaction can be varied in a
controlled way.

###Al-Substitution Effects on Physical Properties of the Colossal Magnetoresistance Compouns La0.67ca0.33mno3|I. G. Deac,L. Giurgiu,A. Darabont,R. V. Tetean,M. Miron,E. Burzo###

Al-Substitution Effects on Physical Properties of the Colossal Magnetoresistance Compouns La0.67ca0.33mno3. We present a detailed study of the polycrystalline perovskite manganites
La0.67Ca0.33AlxMn1-xO3 (x = 0, 0.1, 0.15, 0.5) at low temperatures and high
magnetic fields, including electrical resistance, magnetization, ac
susceptibility. The static magnetic susceptibility was also measured up to 1000
K. All the samples show colossal magnetoresistance behavior and the Curie
temperatures decrease with Al doping. The data suggest the presence of
correlated magnetic clusters near by the ferromagnetic transition. This appears
to be a consequence of the structural and magnetic disorder created by the
random distribution of Al atoms.

###Magnetic field asymmetry of nonlinear transport in carbon nanotubes|J. Wei,M. Shimogawa,Z. Wang,I. Radu,R. Dormaier,D. H. Cobden###

Magnetic field asymmetry of nonlinear transport in carbon nanotubes. We demonstrate that nonlinear transport through a two-terminal nanoscale
sample is not symmetric in magnetic field B. More specifically, we have
measured the lowest order B-asymmetric terms in single-walled carbon nanotubes.
Theoretically, the size of these terms can be used to infer both the strength
of electron-electron interactions and the handedness of the nanotube.
Consistent with theory, we find that at high temperatures the B-linear term is
small and has a constant sign independent of Fermi energy, while at low
temperatures it develops mesoscopic fluctuations. We also find significant
magnetoresistance of nanotubes in the metallic regime which is unexplained.

###Non-linear effects and Joule heating in I-V curves in manganites|Silvana Mercone,Raymond Fresard,Vincent Caignaert,Christine Martin,Damien Saurel,Charles Simon,Gilles Andre,Philippe Monod,Francois Fauth###

Non-linear effects and Joule heating in I-V curves in manganites. We study the influence of the Joule effect on the non-linear behavior of the
transport I-V curves in polycrystalline samples of the manganite Pr0.8Ca0.2MnO3
by using the crystalline unit cell parameters as an internal thermometer in
X-ray and neutron diffraction. We develop a simple analytical model to estimate
the temperature profile in the samples. Under the actual experimental
conditions we show that the internal temperature gradient or the difference
between the temperature of the sample and that of the thermal bath are at the
origin of the non-linearity observed in the I-V curves. Consequences on other
compounds with colossal magnetoresistance are also discussed.

###Angular magnetoresistance oscillations in bilayers in tilted magnetic fields|Victor M. Yakovenko,Benjamin K. Cooper###

Angular magnetoresistance oscillations in bilayers in tilted magnetic fields. Angular magnetoresistance oscillations (AMRO) were originally discovered in
organic conductors and then found in many other layered metals. It should be
possible to observe AMRO to semiconducting bilayers as well. Here we present an
intuitive geometrical interpretation of AMRO as the Aharonov-Bohm interference
effect, both in real and momentum spaces, for balanced and imbalanced bilayers.
Applications to the experiments with bilayers in tilted magnetic fields in the
metallic state are discussed. We speculate that AMRO may be also observed when
each layer of the bilayer is in the composite-fermion state.

###A ferromagnetic oxide semiconductor as spin injection electrode in magnetic tunnel junction|H. Toyosaki,T. Fukumura,K. Ueno,M. Nakano,M. Kawasaki###

A ferromagnetic oxide semiconductor as spin injection electrode in magnetic tunnel junction. A magnetic tunnel junctions composed of room temperature ferromagnetic
semiconductor rutile Ti1-xCoxO2-d and ferromagnetic metal Fe0.1Co0.9 separated
by AlOx barrier showed positive tunneling magnetoresistance (TMR) with a ratio
of ~11 % at 15 K, indicating that Ti1-xCoxO2-d can be used as a spin injection
electrode. The TMR decreased with increasing temperature and vanished above 180
K. TMR action at high temperature is likely prohibited by the inelastic
tunneling conduction due to the low quality of the amorphous barrier layer
and/or the junction interface.

###Spin-dependent tunneling through high-k LaAlO3|V. Garcia,M. Bibes,J. -L. Maurice,E. Jacquet,K. Bouzehouane,J. -P. Contour,A. Barthelemy###

Spin-dependent tunneling through high-k LaAlO3. We report on the use of the LaAlO3 (LAO) high-k dielectric as a tunnel
barrier in magnetic tunnel junctions. From tunnel magnetoresistance (TMR)
measurements on epitaxial La2/3Sr1/3MnO3/LAO/La2/3Sr1/3MnO3 junctions, we
estimate a spin polarization of 77% at low temperature for the
La2/3Sr1/3MnO3/LAO interface. Remarkably, the TMR of La2/3Sr1/3MnO3/LAO/Co
junctions at low bias is negative, evidencing a negative spin polarization of
Co at the interface with LAO, and its bias dependence is very similar to that
of La2/3Sr1/3MnO3/STO/Co junctions. We discuss possible reasons for this
behaviour.

###Physical Meaning of the Current Vertex Corrections: DC and AC Transport Phenomena in High-Tc Superconductors|Hiroshi Kontani###

Physical Meaning of the Current Vertex Corrections: DC and AC Transport Phenomena in High-Tc Superconductors. Famous non-Fermi liquid-like behaviors of the transport phenomena in high-Tc
cuprates (Hall coefficient, magnetoresistance, thermoelectric power, Nernst
coefficient, etc) are caused by the current vertex corrections in neary
antiferromagnetic (AF) Fermi liquid, which was called the backflow by Landau.
We present a simple explaination why the backflow is prominent in strongly
correlated systems. In nearly AF Fermi liquid, R_H is enhanced by the backflow
because it changes the effective curvature of the Fermi surfaces. Therefore,
the relaxation time approximation is not appricalbe to a system near a magnetic
quantum critical point (QCP).

###Orbital polaron lattice formation in lightly doped La1-xSrxMnO3|J. Geck,P. Wochner,S. Kiele,R. Klingeler,P. Reutler,A. Revcolevschi,B. Buechner###

Orbital polaron lattice formation in lightly doped La1-xSrxMnO3. By resonant x-ray scattering at the Mn K-edge on La7/8Sr1/8MnO3, we show that
an orbital polaron lattice (OPL) develops at the metal-insulator transition of
this compound. This orbital reordering explains consistently the unexpected
coexistence of ferromagnetic and insulating properties at low temperatures, the
quadrupling of the lattice structure parallel to the MnO2-planes, and the
observed polarization and azimuthal dependencies. The OPL is a clear
manifestation of strong orbital-hole interactions, which play a crucial role
for the colossal magnetoresistance effect and the doped manganites in general.

###Neutron scattering study of novel magnetic order in Na0.5CoO2|G. Gasparovic,R. A. Ott,J. -H. Cho,F. C. Chou,Y. Chu,J. W. Lynn,Y. S. Lee###

Neutron scattering study of novel magnetic order in Na0.5CoO2. We report polarized and unpolarized neutron scattering measurements of the
magnetic order in single crystals of Na0.5CoO2. Our data indicate that below
T_N=88 K the spins form a novel antiferromagnetic pattern within the CoO2
planes, consisting of alternating rows of ordered and non-ordered Co ions. The
domains of magnetic order are closely coupled to the domains of Na ion order,
consistent with such a two-fold symmetric spin arrangement. Magnetoresistance
and anisotropic susceptibility measurements further support this model for the
electronic ground state.

###Co-doped (La,Sr)TiO3-d: a high-Curie temperature diluted magnetic system with large spin-polarization|G. Herranz,R. Ranchal,M. Bibes,H. Jaffres,E. Jacquet,J. L. Maurice,K. Bouzehouane,F. Wyczisk,E. Tafra,M. Basletic,A. Hamzic,C. Colliex,J. -P. Contour,A. Barthelemy,A. Fert###

Co-doped (La,Sr)TiO3-d: a high-Curie temperature diluted magnetic system with large spin-polarization. We report on tunneling magnetoresistance (TMR) experiments that demonstrate
the existence of a significant spin polarization in Co-doped (La,Sr)TiO3-d
(Co-LSTO), a ferromagnetic diluted magnetic oxide system (DMOS) with high Curie
temperature. These TMR experiments have been performed on magnetic tunnel
junctions associating Co-LSTO and Co electrodes. Extensive structural analysis
of Co-LSTO combining high-resolution transmission electron microscopy and Auger
electron spectroscopy excluded the presence of Co clusters in the Co-LSTO layer
and thus, the measured ferromagnetism and high spin polarization are intrinsic
properties of this DMOS. Our results argue for the DMOS approach with complex
oxide materials in spintronics.

###Conductance switching, hysteresis, and magnetoresistance in organic semiconductors|J. H. Wei,S. J. Xie,L. M. Mei,YiJing Yan###

Conductance switching, hysteresis, and magnetoresistance in organic semiconductors. The controllability of charge transport through an organic molecular
spin-valve system is theoretically investigated on the basis of a
Su-Schrieffer-Heeger model combined with the non-equilibrium Green's function
formalism. We show how the formation of polaron in the organic sub-structure
leads to a hysteretic conductance switching, via sweeping either the bias
voltage or the electrochemical potential. We further obtain an exponential
dependence of the magnetoresistance as a function of the applied bias voltage.
The implications of calculated results in relation to experiments and device
applications are addressed and commented.

###Spin-polarized tunneling spectroscopy in tunnel junctions with half-metallic electrodes|M. Bowen,A. Barthélémy,M. Bibes,E. Jacquet,J. -P. Contour,A. Fert,F. Ciccacci,L. Dùo,R. Bertacco###

Spin-polarized tunneling spectroscopy in tunnel junctions with half-metallic electrodes. We have studied the magnetoresistance (TMR) of tunnel junctions with
electrodes of La2/3Sr1/3MnO3 and we show how the variation of the conductance
and TMR with the bias voltage can be exploited to obtain a precise information
on the spin and energy dependence of the density of states. Our analysis leads
to a quantitative description of the band structure of La2/3Sr1/3MnO3 and
allows the determination of the gap delta between the Fermi level and the
bottom of the t2g minority spin band, in good agreement with data from
spin-polarized inverse photoemission experiments. This shows the potential of
magnetic tunnel junctions with half-metallic electrodes for spin-resolved
spectroscopic studies.

###Large magnetoresistance and magnetocaloric effect above 70 K in Gd2Co2Al, Gd2Co2Ga and Gd7Rh3|Kausik Sengupta,Kartik K. Iyer,E. V. Sampathkumaran###

Large magnetoresistance and magnetocaloric effect above 70 K in Gd2Co2Al, Gd2Co2Ga and Gd7Rh3. The electrical resistivity, magnetization and heat-capacity behavior of the
Gd-based compounds, Gd2Co2Al, Gd2Co2Ga and Gd7Rh3, ordering magnetically at TC=
78 K, TC= 76 K and TN= 140 K have been investigated as a function of
temperature and magnetic field. All these compounds are found to show large
magnetoresistance (with a negative sign) in the paramagnetic state at rather
high temperatures with the magnitude peaking at respective magnetic ordering
temperatures. There is a corresponding behavior in the magnetocaloric effect as
inferred from the entropy derived from these data.

###Spin-Polarized Transport in Ferromagnet-Marginal Fermi Liquid Systems|Hai-Feng Mu,Gang Su,Qing-Rong Zheng,Biao Jin###

Spin-Polarized Transport in Ferromagnet-Marginal Fermi Liquid Systems. Spin-polarized transport through a marginal Fermi liquid (MFL) which is
connected to two noncollinear ferromagnets via tunnel junctions is discussed in
terms of the nonequilibrium Green function approach. It is found that the
current-voltage characteristics deviate obviously from the ohmic behavior, and
the tunnel current increases slightly with temperature, in contrast to those of
the system with a Fermi liquid. The tunnel magnetoresistance (TMR) is observed
to decay exponentially with increasing the bias voltage, and to decrease slowly
with increasing temperature. With increasing the coupling constant of the MFL,
the current is shown to increase linearly, while the TMR is found to decay
slowly. The spin-valve effect is observed.

###Spin transport in disordered single-wall carbon nanotubes contacted to ferromagnetic leads|S. Krompiewski,N. Nemec,G. Cuniberti###

Spin transport in disordered single-wall carbon nanotubes contacted to ferromagnetic leads. Recent conductance measurements on multi-wall carbon nanotubes (CNTs) reveal
an effective behavior similar to disordered single-wall CNTs. This is due to
the fact that electric current flows essentially through the outermost shell
and is strongly influenced by inhomogeneous electrostatic potential coming from
the inner tubes. Here, we present theoretical studies of spin-dependent
transport through disorder-free double-wall CNTs as well as single-wall CNTs
with Anderson-type disorder. The CNTs are end-contacted to ferromagnetic
electrodes modelled as fcc (111) surfaces. Our results shed additional light on
the giant magnetoresistance effect in CNTs. Some reported results concern
realistically long CNTs, up to several hundred nanometers.

###Suppression of Ferromagnetic Double Exchange by Vibronic Phase Segregation|F. Rivadulla,M. Otero-Leal,A. Espinosa,A. de Andres,C. Ramos,J. Rivas,J. B. Goodenough###

Suppression of Ferromagnetic Double Exchange by Vibronic Phase Segregation. From Raman spectroscopy, magnetization, and thermal-expansion on the system
La2/3(Ca1-xSrx)1/3MnO3, we have been able to provide a quantitative basis for
the heterogeneous electronic model for manganites exhibiting colossal
magnetoresistance (CMR). We construct a mean-field model that accounts
quantitatively for the measured deviation of TC(x) from the TC predicted by de
Gennes double exchange in the adiabatic approximation, and predicts the
occurrence of a first order transition for a strong coupling regime, in
accordance with the experiments. The existence of a temperature interval
TC<T<T* where CMR may be found is discussed, in connection with the occurrence
of an idealized Griffiths phase.

###Spin Dependent Tunneling in FM|semiconductor|FM structures|S. Vutukuri,M. Chshiev,W. H. Butler###

Spin Dependent Tunneling in FM|semiconductor|FM structures. Here we show that ordinary band structure codes can be used to understand the
mechanisms of coherent spin-injection at interfaces between ferromagnets and
semiconductors. This approach allows the screening of different material
combinations for properties useful for obtaining high tunneling
magnetoresistance (TMR). We used the Vienna Ab-initio Simulation Code (VASP) to
calculate the wave function character of each band in periodic epitaxial
Fe(100)|GaAs(100) and Fe(100)|ZnSe(100) structures. It is shown that Fe wave
functions of different symmetry near Fermi energy decay differently in the GaAs
and ZnSe.

###Magnetic field induced band depopulation in intrinsic InSb: A revisit|Bhavtosh Bansal,V Venkataraman###

Magnetic field induced band depopulation in intrinsic InSb: A revisit. The effect of Landau level formation on the population of intrinsic electrons
in InSb is probed near room temperature in magnetic fields upto 16 Tesla.
Although the measured magnetic field dependence of the Hall coefficient is
qualitatively similar to published results, it is shown that the data may also
be explained by simply including ambipolar conduction. Thus the inference on
band depopulation drawn from previous measurements on InSb is inconclusive
unless both the Hall and the magnetoresistive components of the resistivity
tensor are simultaneously measured and modelled. When the model includes both
depopulation and ambipolar conduction, a reasonable agreement with theory can
be established.

###Thermoelectric effects in strongly interacting quantum dot coupled to ferromagnetic leads|M. Krawiec,K. I. Wysokinski###

Thermoelectric effects in strongly interacting quantum dot coupled to ferromagnetic leads. We study thermoelectric effects in Kondo correlated quantum dot coupled to
ferromagnetic electrodes by calculating conductance, thermopower and thermal
conductance in the Kondo regime. We also study the effect of the asymmetry in
the coupling to the leads, which has important consequences for anti-parallel
magnetization configuration. We discuss the thermoelectric figure of merit,
tunnel magnetoresistance and violation of the Wiedemann-Franz law in this
system. The results agree with recently measured thermopower of the quantum dot
defined in a two dimensional electron gas.

###From ballistic transport to tunneling in electromigrated ferromagnetic breakjunctions|Kirill I. Bolotin,F. Kuemmeth,Abhay N. Pasupathy,D. C. Ralph###

From ballistic transport to tunneling in electromigrated ferromagnetic breakjunctions. We fabricate ferromagnetic nanowires with constrictions whose cross section
can be reduced gradually from 100 nm to the atomic scale and eventually to the
tunneling regime by means of electromigration. These devices are mechanically
stable against magnetostriction and magnetostatic effects. We measure
magnetoresistances ~ 0.3% for 100*30 nm^2 constrictions, increasing to a
maximum of 80% for atomic-scale widths. These results are consistent with a
geometrically-constrained domain wall trapped at the constriction. For the
devices in the tunneling regime we observe large fluctuations in MR, between
-10 and 85%.

###Origin of Rapid Oscillations in Low Dimensional (TMTSF)2PF6|A. V. Kornilov,V. M. Pudalov,A. -K. Klehe,A. Ardavan,J. S. Qualls,J. Singleton###

Origin of Rapid Oscillations in Low Dimensional (TMTSF)2PF6. In order to clarify the origin of the "Rapid Oscillation" (RO) in
(TMTSF)2PF6, we studied the magnetoresistance anisotropy in the Field Induced
Spin Density Wave (FISDW) phase. We have found that in the FISDW insulating
state, the Fermi surface is not totally gapped; the remaining 2D metallic
pockets are quantized in magnetic field and give rise to the RO. Decreasing
temperature does not change the size and orientation of the closed pockets,
rather, it causes depopulation of the delocalized states in favor of the
localized ones, resulting in the disappearance of the RO.

###Spin torque, tunnel-current spin polarization and magnetoresistance in MgO magnetic tunnel junctions|G. D. Fuchs,J. A. Katine,S. I. Kiselev,D. Mauri,K. S. Wooley,D. C. Ralph,R. A. Buhrman###

Spin torque, tunnel-current spin polarization and magnetoresistance in MgO magnetic tunnel junctions. We examine the spin torque (ST) response of magnetic tunnel junctions (MTJs)
with ultra-thin MgO tunnel barrier layers to investigate the relationship
between the spin-transfer torque and the tunnel magnetoresistance (TMR) under
finite bias. We find that the spin torque per unit current exerted on the free
layer decreases by less than 10% over a bias range where the TMR decreases by
over 40%. We examine the implications of this result for various spin-polarized
tunneling models and find that it is consistent with magnetic-state-dependent
effective tunnel decay lengths.

###Out of equilibrium electronic transport properties of a misfit cobaltite thin film|A. Pautrat,H. W Eng,W. Prellier###

Out of equilibrium electronic transport properties of a misfit cobaltite thin film. We report on transport measurements in a thin film of the 2D misfit Cobaltite
$Ca_{3}Co_{4}O_{9}$. Dc magnetoresistance measurements obey the modified
variable range hopping law expected for a soft Coulomb gap. When the sample is
cooled down, we observe large telegraphic-like fluctuations. At low
temperature, these slow fluctuations have non Gaussian statistics, and are
stable under a large magnetic field. These results suggest that the low
temperature state is a glassy electronic state. Resistance relaxation and
memory effects of pure magnetic origin are also observed, but without aging
phenomena. This indicates that these magnetic effects are not glassy-like and
are not directly coupled to the electronic part.

###Current-induced switching in single ferromagnetic layer nanopillar junctions|Barbaros Oezyilmaz,Andrew D. Kent###

Current-induced switching in single ferromagnetic layer nanopillar junctions. Current induced magnetization dynamics in asymmetric Cu/Co/Cu single magnetic
layer nanopillars has been studied experimentally at room temperature and in
low magnetic fields applied perpendicular to the thin film plane. In sub-100 nm
junctions produced using a nanostencil process a bistable state with two
distinct resistance values is observed. Current sweeps at fixed applied fields
reveal hysteretic and abrupt transitions between these two resistance states.
The current induced resistance change is 0.5%, a factor of 5 greater than the
anisotropic magnetoresistance (AMR) effect. We present an experimentally
obtained low field phase diagram of current induced magnetization dynamics in
single ferromagnetic layer pillar junctions.

###Laser microscopy of tunneling magnetoresistance in manganite grain-boundary junctions|M. Wagenknecht,H. Eitel,T. Nachtrab,J. B. Philipp,R. Gross,R. Kleiner,D. Koelle###

Laser microscopy of tunneling magnetoresistance in manganite grain-boundary junctions. Using low-temperature scanning laser microscopy we directly image electric
transport in a magnetoresistive element, a manganite thin film intersected by a
grain boundary (GB). Imaging at variable temperature allows reconstruction and
comparison of the local resistance vs temperature for both, the manganite film
and the GB. Imaging at low temperature also shows that the GB switches between
different resistive states due to the formation and growth of magnetic domains
along the GB. We observe different types of domain wall growth; in most cases a
domain wall nucleates at one edge of the bridge and then proceeds towards the
other edge.

###Upper critical field from normal state fluctuations in Bi$_2$Sr$_2$CuO$_{6+δ}$|F. Bouquet,L. Fruchter,I. Sfar,Z. Z. Li,H. Raffy###

Upper critical field from normal state fluctuations in Bi$_2$Sr$_2$CuO$_{6+δ}$. The in-plane magnetoresistance of an epitaxial Bi$_2$Sr$_2$CuO$_{6+\delta}$
thin film was systematically investigated as a function of doping, above $T_c$.
The orbital magnetoconductance is used to extract the crossover field line
$H_{c2}^*(T)$ in the fluctuation regime. This field is found in good agreement
with the upper critical field obtained from resistivity data below $T_c$, and
exhibits a similar upward curvature, thus pointing toward the existence of a
critical correlation length. The consequences regarding the nature of the
resistive transition are discussed.

###Controlling spin in an electronic interferometer with spin-active interfaces|A. Cottet,T. Kontos,W. Belzig,C. Schonenberger,C. Bruder###

Controlling spin in an electronic interferometer with spin-active interfaces. We consider electronic current transport through a ballistic one-dimensional
quantum wire connected to two ferromagnetic leads. We study the effects of the
spin-dependence of interfacial phase shifts (SDIPS) acquired by electrons upon
scattering at the boundaries of the wire. The SDIPS produces a spin splitting
of the wire resonant energies which is tunable with the gate voltage and the
angle between the ferromagnetic polarizations. This property could be used for
manipulating spins. In particular, it leads to a giant magnetoresistance effect
with a sign tunable with the gate voltage and the magnetic field applied to the
wire.

###Angle-dependent magnetoresistance in the weakly incoherent interlayer transport regime|M. V. Kartsovnik,D. Andres,S. V. Simonov,W. Biberacher,I. Sheikin,N. D. Kushch,H. Müller###

Angle-dependent magnetoresistance in the weakly incoherent interlayer transport regime. We present comparative studies of the orientation effect of a strong magnetic
field on the interlayer resistance of $\alpha$-(BEDT-TTF)$_2$KHg(SCN)$_4$
samples characterized by different crystal quality. We find striking
differences in their behavior which is attributed to the breakdown of the
coherent charge transport across the layers in the lower quality sample. In the
latter case, the nonoscillating magnetoresistance background is essentially a
function of only the out-of-plane field component, in contradiction to the
existing theory.

###Vortex-like excitations in a non-superconducting single-layer compound Bi$_{2+x}$Sr$_{2-x}$CuO$_{6+δ}$ single crystal in high magnetic fields|S. I. Vedeneev,D. K. Maude###

Vortex-like excitations in a non-superconducting single-layer compound Bi$_{2+x}$Sr$_{2-x}$CuO$_{6+δ}$ single crystal in high magnetic fields. The in-plane $\rho_{ab}(H,T)$ and the out-of-plane $\rho_c(H,T)$
magneto-transport in magnetic fields up to 28 T has been investigated in high
quality non-superconducting (down to 20 mK) La-free
Bi$_{2+x}$Sr$_{2-x}$CuO$_{6+\delta}$ single crystal. By measuring the angular
dependence of the in-plane and out-of-plane magnetoresistivities at
temperatures from 1 K down to 30 mK, we present evidence for the presence of
vortex-like excitations in a non-superconducting cuprate in the insulating
state. Such excitations have previously been observed by the detection of a
Nernst signal in superconducting cuprates at $T>T_c$ in magnetic fields.

###In-plane ferromagnetism in charge-ordering $Na_{0.55}CoO_2$|C. H. Wang,X. H. Chen,T. Wu,X. G. Luo,G. Y. Wang,J. L. Luo###

In-plane ferromagnetism in charge-ordering $Na_{0.55}CoO_2$. The magnetic and transport properties are systematically studied on the
single crystal $Na_{0.55}CoO_2$ with charge ordering and divergency in
resistivity below 50 K. A long-range ferromagnetic ordering is observed in
susceptibility below 20 K with the magnetic field parallel to Co-O plane, while
a negligible behavior is observed with the field perpendicular to the Co-O
plane. It definitely gives a direct evidence for the existence of in-plane
ferromagnetism below 20 K. The observed magnetoresistance (MR) of 30 % at the
field of 6 T at low temperatures indicates an unexpectedly strong spin-charge
coupling in triangle lattice systems.

###Resistance scaling for Composite Fermions in the presence of a density gradient|W. Pan,H. L. Stormer,D. C. Tsui,L. N. Pfeiffer,K. W. Baldwin,K. W. West###

Resistance scaling for Composite Fermions in the presence of a density gradient. The magnetoresistance, Rxx, at even-denominator fractional fillings, of an
ultra high quality two-dimensional electron system at T ~ 35 mK is observed to
be strictly linear in magnetic field, B. While at 35mK Rxx is dominated by the
integer and fractional quantum Hall states, at T~1.2K an almost perfect linear
relationship between Rxx vs B emerges over the whole magnetic field range
except for spikes at the integer quantum Hall states. This linear Rxx cannot be
understood within the Composite Fermion model, but can be explained through the
existence of a density gradient in our sample.

###Phase coexistence and resistivity near the ferromagnetic transition of manganites|A. S. Alexandrov,A. M. Bratkovsky,V. V. Kabanov###

Phase coexistence and resistivity near the ferromagnetic transition of manganites. Pairing of oxygen holes into heavy bipolarons in the paramagnetic phase and
their magnetic pair-breaking in the ferromagnetic phase [the so-called
current-carrier density collapse (CCDC)] has accounted for the first-order
ferromagnetic phase transition, colossal magnetoresistance (CMR), isotope
effect, and pseudogap in doped manganites. Here we propose an explanation of
the phase coexistence and describe the magnetization and resistivity of
manganites near the ferromagnetic transition in the framework of CCDC. The
present quantitative description of resistivity is obtained without any fitting
parameters by using the experimental resistivities far away from the transition
and the experimental magnetization, and essentially model independent.

###Colossal magnetocapacitance and colossal magnetoresistance in HgCr2S4|S. Weber,P. Lunkenheimer,R. Fichtl,J. Hemberger,V. Tsurkan,A. Loidl###

Colossal magnetocapacitance and colossal magnetoresistance in HgCr2S4. We present a detailed study of the dielectric and charge transport properties
of the antiferromagnetic cubic spinel HgCr2S4. Similar to the findings in
ferromagnetic CdCr2S4, the dielectric constant of HgCr2S4 becomes strongly
enhanced in the region below 60 - 80 K, which can be ascribed to polar
relaxational dynamics triggered by the onset of ferromagnetic correlations. In
addition, the observation of polarization hysteresis curves indicates the
development of ferroelectric order below about 70 K. Moreover, our
investigations in external magnetic fields up to 5 T reveal the simultaneous
occurrence of magnetocapacitance and magnetoresistance of truly colossal
magnitudes in this material.

###Anisotropic magnetoresistance and anisotropic tunneling magnetoresistance due to quantum interference in ferromagnetic metal break junctions|Kirill I. Bolotin,Ferdinand Kuemmeth,D. C. Ralph###

Anisotropic magnetoresistance and anisotropic tunneling magnetoresistance due to quantum interference in ferromagnetic metal break junctions. We measure the low-temperature resistance of permalloy break junctions as a
function of contact size and the magnetic field angle, in applied fields large
enough to saturate the magnetization. For both nanometer-scale metallic
contacts and tunneling devices we observe large changes in resistance with
angle, as large as 25% in the tunneling regime. The pattern of
magnetoresistance is sensitive to changes in bias on a scale of a few mV. We
interpret the effect as a consequence of conductance fluctuations due to
quantum interference.

###Hyperfine interaction and magnetoresistance in organic semiconductors|Y. Sheng,D. T. Nguyen,G. Veeraraghavan,Ö. Mermer,M. Wohlgenannt,U. Scherf###

Hyperfine interaction and magnetoresistance in organic semiconductors. We explore the possibility that hyperfine interaction causes the recently
discovered organic magnetoresistance (OMAR) effect. Our study employs both
experiment and theoretical modelling. An excitonic pair mechanism model based
on hyperfine interaction, previously suggested by others to explain magnetic
field effects in organics, is examined. Whereas this model can explain a few
key aspects of the experimental data, we, however, uncover several fundamental
contradictions as well. By varying the injection efficiency for minority
carriers in the devices, we show experimentally that OMAR is only weakly
dependent on the ratio between excitons formed and carriers injected, likely
excluding any excitonic effect as the origin of OMAR.

###Effect of the shape anisotropy on the magnetic configuration of (Ga,Mn)As and its evolution with temperature|K. Hamaya,T. Taniyama,T. Koike,Y. Yamazaki###

Effect of the shape anisotropy on the magnetic configuration of (Ga,Mn)As and its evolution with temperature. We study the effect of the shape anisotropy on the magnetic domain
configurations of a ferromagnetic semiconductor (Ga,Mn)As/GaAs(001) epitaxial
wire as a function of temperature. Using magnetoresistance measurements, we
deduce the magnetic configurations and estimate the relative strength of the
shape anisotropy compared with the intrinsic anisotropies. Since the intrinsic
anisotropy is found to show a stronger temperature dependence than the shape
anisotropy, the effect of the shape anisotropy on the magnetic domain
configuration is relatively enhanced with increasing temperature. This
information about the shape anisotropy provides a practical means of designing
nanostructured spin electronic devices using (Ga,Mn)As.

###Integer Quantum Hall Effect in Graphite|H. Kempa,P. Esquinazi,Y. Kopelevich###

Integer Quantum Hall Effect in Graphite. We present Hall effect measurements on highly oriented pyrolytic graphite
that indicate the occurrence of the integer quantum-Hall-effect. The evidence
is given by the observation of regular plateau-like structures in the field
dependence of the transverse conductivity obtained in van der Pauw
configuration. Measurements with the Corbino-disk configuration support this
result and indicate that the quasi-linear and non-saturating longitudinal
magnetoresistance in graphite is governed by the Hall effect in agreement with
a recent theoretical model for disordered semiconductors.

###Quantum dot with ferromagnetic leads: a density-matrix renormalization group study|C. J. Gazza,M. E. Torio,J. A. Riera###

Quantum dot with ferromagnetic leads: a density-matrix renormalization group study. A quantum dot coupled to ferromagnetically polarized one-dimensional leads is
studied numerically using the density matrix renormalization group method.
Several real space properties and the local density of states at the dot are
computed. It is shown that this local density of states is suppressed by the
parallel polarization of the leads. In this case we are able to estimate the
length of the Kondo cloud, and to relate its behavior to that suppression.
Another important result of our study is that the tunnel magnetoresistance as a
function of the quantum dot on-site energy is minimum and negative at the
symmetric point.

###Emergence of half-metallicity in suspended NiO chains|David Jacob,J. Fernández-Rossier,J. J. Palacios###

Emergence of half-metallicity in suspended NiO chains. Contrary to the antiferromagnetic and insulating character of bulk NiO,
one-dimensional chains of this material can become half-metallic due to the
lower coordination of their atoms. Here we present ab initio electronic
structure and quantum transport calculations of ideal infinitely long NiO
chains and of more realistic short ones suspended between Ni electrodes. While
infinite chains are insulating, short suspended chains are half-metallic
minority-spin conductors which display very large magnetoresistance and a
spin-valve behaviour controlled by a single atom.

###Visualizing high-temperature spin dynamics in La1-xCaxMnO3 from a mapping of EPR linewidth and g factor|Y. Liu,S. L. Wan,X. G. Li###

Visualizing high-temperature spin dynamics in La1-xCaxMnO3 from a mapping of EPR linewidth and g factor. This paper presents an analysis of electron paramagnetic resonance
parameters, i.e., g factor, linewidth, and intensity on powder samples of
La1-xCaxMnO3 at the commensurate carrier concentrations of x = N/8 (N = 1, 2,
3, 4, 5, 6, and 7). We demonstrate that the mapping of EPR parameters offers a
powerful tool to investigate high-temperature spin dynamics in the phase
diagram of colossal magnetoresistance (CMR) manganites. Our results convince
that the spin-spin relaxation mechanism should dominate the high-temperature
paramagnetic regime in CMR manganites.

###Suppression of superconductivity due to non-perturbative saddle points in the nonlinear $σ$-model|D. A. Pesin,A. V. Andreev###

Suppression of superconductivity due to non-perturbative saddle points in the nonlinear $σ$-model. We study superconductivity suppression due to thermal fluctuations in
disordered wires using the replica nonlinear $\sigma$-model ($NL\sigma M$). We
show that in addition to the thermal phase slips there is another type of
fluctuations that result in a finite resistivity. These fluctuations are
described by saddle points in $NL\sigma M$ and cannot be treated within the
Ginzburg-Landau approach. The contribution of such fluctuations to the wire
resistivity is evaluated with exponential accuracy. The magnetoresistance
associated with this contribution is negative.

###Quantum Transport with Spin Dephasing: A Nonequilibrium Green's Function Approach|Ahmet Ali Yanik,Gerhard Klimeck,Supriyo Datta###

Quantum Transport with Spin Dephasing: A Nonequilibrium Green's Function Approach. A quantum transport model incorporating spin scattering processes is
presented using the non-equilibrium Green's function (NEGF) formalism within
the self-consistent Born approximation. This model offers a unified approach by
capturing the spin-flip scattering and the quantum effects simultaneously. A
numerical implementation of the model is illustrated for magnetic tunnel
junction devices with embedded magnetic impurity layers. The results are
compared with experimental data, revealing the underlying physics of the
coherent and incoherent transport regimes. It is shown that small variations in
magnetic impurity spin-states/concentrations could cause large deviations in
junction magnetoresistances.

###Scaling of THz-conductivity at metal-insulator transition in doped manganites|A. Pimenov,M. Biberacher,D. Ivannikov,A. Loidl,A. A. Mukhin,Yu. G. Goncharov,A. M. Balbashov###

Scaling of THz-conductivity at metal-insulator transition in doped manganites. Magnetic field and temperature dependence of the Terahertz conductivity and
permittivity of the colossal magnetoresistance manganite
Pr_{0.65}Ca_{0.28}Sr_{0.07}MnO_3 (PCSMO) is investigated approaching the
metal-to-insulator transition (MIT) from the insulating side. In the
charge-ordered state of PCSMO both conductivity and dielectric permittivity
increase as function of magnetic field and temperature. Universal scaling
relationships between the changes in permittivity and conductivity are observed
in a broad range of temperatures and magnetic fields. Similar scaling is also
seen in La_{1-x}Sr_xMnO_3 for different doping levels. The observed
proportionality points towards the importance of pure ac-conductivity and
phononic energy scale at MIT in manganites.

###Magnetoresistance in a soft billiard: giant peak near the percolation threshold|Michel Dyakonov,Remi Jullien###

Magnetoresistance in a soft billiard: giant peak near the percolation threshold. By numerical simulation, we study the classical magnetoresistance of
two-dimensional electrons in the presence of weak short range scattering. A
critical magnetic field defines the percolation threshold, above which the
longitudinal resistance vanishes. Unexpectedely, just below this threshold we
find a shrp narrow peak, where the resistance may increase 15 times compared to
its zero-field value. By considering the complex topology of the effective
potential landscape for the center of the cyclotron circle, we show that this
phenomenon is related to infinite equipotential lines, which exists only in a
narrow magnetic field interval below the percolation threshold

###Electronic Aharonov-Bohm Effect Induced by Quantum Vibrations|R. I. Shekhter,L. Y. Gorelik,L. I. Glazman,M. Jonson###

Electronic Aharonov-Bohm Effect Induced by Quantum Vibrations. Mechanical displacements of a nanoelectromechanical system (NEMS) shift the
electron trajectories and hence perturb phase coherent charge transport through
the device. We show theoretically that in the presence of a magnetic feld such
quantum-coherent displacements may give rise to an Aharonov-Bohm-type of
effect. In particular, we demonstrate that quantum vibrations of a suspended
carbon nanotube result in a positive nanotube magnetoresistance, which
decreases slowly with the increase of temperature. This effect may enable one
to detect quantum displacement fluctuations of a nanomechanical device.

###Giant tunnel magnetoresistance and high annealing stability in CoFeB/MgO/CoFeB magnetic tunnel junctions with synthetic pinned layer|Young Min Lee,Jun Hayakawa,Shoji Ikeda,Fumihiro Matsukura,Hideo Ohno###

Giant tunnel magnetoresistance and high annealing stability in CoFeB/MgO/CoFeB magnetic tunnel junctions with synthetic pinned layer. We investigated the relationship between tunnel magnetoresistance (TMR) ratio
and the crystallization of CoFeB layers through annealing in magnetic tunnel
junctions (MTJs) with MgO barriers that had CoFe/Ru/CoFeB synthetic ferrimagnet
pinned layers with varying Ru spacer thickness (tRu). The TMR ratio increased
with increasing annealing temperature (Ta) and tRu, reaching 361% at Ta = 425C,
whereas the TMR ratio of the MTJs with pinned layers without Ru spacers
decreased at Ta over 325C. Ruthenium spacers play an important role in forming
an (001)-oriented bcc CoFeB pinned layer, resulting in a high TMR ratio through
annealing at high temperatures.

###Bandwidth-disorder phase diagram of half doped layered manganites|R. Mathieu,M. Uchida,Y. Kaneko,J. P. He,X. Z. Yu,R. Kumai,T. Arima,Y. Tomioka,A. Asamitsu,Y. Matsui,Y. Tokura###

Bandwidth-disorder phase diagram of half doped layered manganites. Phase diagrams in the plane of $r_A$ (the average ionic radius, related to
one-electron bandwidth $W$) and $\sigma^2$ (the ionic radius variance,
measuring the quenched disorder), or ``bandwidth-disorder phase diagrams'',
have been established for perovskite manganites, with three-dimensional (3$D$)
Mn-O network. Here we establish the intrinsic bandwidth-disorder phase diagram
of half-doped layered manganites with the two-dimensional (2$D$) Mn-O network,
examining in detail the ``mother state'' of the colossal magnetoresistance
(CMR) phenomenon in crystals without ferromagnetic instability. The
consequences of the reduced dimensionality, from 3$D$ to 2$D$, on the
order-disorder phenomena in the charge-orbital sectors are also highlighted.

###Tunnel magnetoresistance and robust room temperature exchange bias with multiferroic BiFeO3 epitaxial thin films|H. Bea,M. Bibes,S. Cherifi,F. Nolting,B. Warot-Fonrose,S. Fusil,G. Herranz,C. Deranlot,E. Jacquet,K. Bouzehouane,A. Barthelemy###

Tunnel magnetoresistance and robust room temperature exchange bias with multiferroic BiFeO3 epitaxial thin films. We report on the functionalization of multiferroic BiFeO3 epitaxial films for
spintronics. A first example is provided by the use of ultrathin layers of
BiFeO3 as tunnel barriers in magnetic tunnel junctions with La2/3Sr1/3MnO3 and
Co electrodes. In such structures, a positive tunnel magnetoresistance up to
30% is obtained at low temperature. A second example is the exploitation of the
antiferromagnetic spin structure of a BiFeO3 film to induce a sizeable (~60 Oe)
exchange bias on a ferromagnetic film of CoFeB, at room temperature.
Remarkably, the exchange bias effect is robust upon magnetic field cycling,
with no indications of training.

###Quantum theory of tunneling magnetoresistance in GaMnAs/GaAs/GaMnAs heterostructures|Alireza Saffarzadeh,Ali A. Shokri###

Quantum theory of tunneling magnetoresistance in GaMnAs/GaAs/GaMnAs heterostructures. Using a quantum theory including spin-splitting effect in diluted magnetic
semiconductors, we study the dependence of tunneling magnetoresistance (TMR) on
barrier thickness, temperature and applied voltage in GaMnAs/GaAs/GaMnAs
heterostructures. TMR ratios more than 65% are obtained at zero temperature,
when one GaAs monolayer ($\approx$ 0.565 nm) is used as a tunnel barrier. It is
also shown that the TMR ratio decreases rapidly with increasing the barrier
thickness and applied voltage, however at high voltages and low thicknesses,
the TMR first increases and then decreases. Our model calculations well explain
the main features of the recent experimental observations.

###From semiclassical transport to quantum Hall effect under low-field Landau quantization|D. R. Hang,C. F. Huang,Y. W. Zhang,H. D. Yeh,J. C. Hsiao,H. L. Pang###

From semiclassical transport to quantum Hall effect under low-field Landau quantization. The crossover from the semiclassical transport to quantum Hall effect is
studied by examining a two-dimensional electron system in an AlGaAs/GaAs
heterostructure. By probing the magneto-oscillations, it is shown that the
semiclassical Shubnikov-de Haas (SdH) formulation can be valid even when the
minima of the longitudinal resistivity approach zero. The extension of the
applicable range of the SdH theory could be due to the damping effects
resulting from disorder and temperature. Moreover, we observed plateau-plateau
transition like behavior with such an extension. From our study, it is
important to include the positive magnetoresistance to refine the SdH theory.

###Electron-electron interaction in carbon nanostructures|A. I. Romanenko,O. B. Anikeeva,T. I. Buryakov,E. N. Tkachev,A. V. Okotrub,V. L. Kuznetsov,A. N. Usoltseva,A. S. Kotosonov###

Electron-electron interaction in carbon nanostructures. The electron-electron interaction in carbon nanostructures was studied. A new
method which allows to determine the electron-electron interaction constant
$\lambda_c$ from the analysis of quantum correction to the magnetic
susceptibility and the magnetoresistance was developed. Three types of carbon
materials: arc-produced multiwalled carbon nanotubes (arc-MWNTs), CVD-produced
catalytic multiwalled carbon nanotubes (c-MWNTs) and pyrolytic carbon were used
for investigation. We found that $\lambda_c$=0.2 for arc-MWNTs (before and
after bromination treatment); $\lambda_c$ = 0.1 for pyrolytic graphite;
$\lambda_c >$ 0 for c-MWNTs. We conclude that the curvature of graphene layers
in carbon nanostructures leads to the increase of the electron-electron
interaction constant $\lambda_c$.

###Dependence of tunnel magnetoresistance on ferromagnetic electrode materials in MgO-barrier magnetic tunnel junctions|Shoji Ikeda,Jun Hayakawa,Young Min Lee,Fumihiro Matsukura,Hideo Ohno###

Dependence of tunnel magnetoresistance on ferromagnetic electrode materials in MgO-barrier magnetic tunnel junctions. We investigated the relationship between the tunnel magnetoresistance (TMR)
ratio and the electrode structure in MgO-barrier magnetic tunnel junctions
(MTJs). The TMR ratio in a MTJ with Co40Fe40B20 reference and free layers
reached 355% at the post-deposition annealing temperature of Ta=400 degree C.
When Co50Fe50 or Co90Fe10 is used for the reference layer material, no high TMR
ratio was observed. The key to have high TMR ratio is to have highly oriented
(001) MgO barrier/CoFeB crystalline electrodes. The highest TMR ratio obtained
so far is 450% at Ta = 450 degree C in a pseudo spin-valve MTJ.

###Magnetoresistance oscillations in two-dimensional electron systems under monochromatic and bichromatic radiations|X. L. Lei,S. Y. Liu###

Magnetoresistance oscillations in two-dimensional electron systems under monochromatic and bichromatic radiations. The magnetoresistance oscillations in high-mobility two-dimensional electron
systems induced by two radiation fields of frequencies 31 GHz and 47 GHz, are
analyzed in a wide magnetic-field range down to 100 G, using the
balance-equation approach to magnetotransport for high-carrier-density systems.
The frequency mixing processes are shown to be important. The predicted peak
positions, relative heights, radiation-intensity dependence and their relation
with monochromatic resistivities are in good agreement with recent experimental
finding [M. A. Zudov {\it et al.} Phys. Rev. Lett. 96, 236804 (2006)].

###Thermally excited spin-current in metals with embedded ferromagnetic nanoclusters|O. Tsyplyatyev,O. Kashuba,V. I. Fal'ko###

Thermally excited spin-current in metals with embedded ferromagnetic nanoclusters. We show that a thermally excited spin-current naturally appears in metals
with embedded ferromagnetic nanoclusters. When such materials are subjected to
a magnetic field, a spin current can be generated by a temperature gradient
across the sample as a signature of electron-hole symmetry breaking in a metal
due to the electron spin-flip scattering from polarised magnetic moments. Such
a spin current can be observed via a giant magneto-thermopower which tracks the
polarisation state of the magnetic subsystem and is proportional to the
magnetoresistance. Our theory explains the recent experiment on Co clusters in
copper by S. Serrano-Guisan \textit{et al} [Nature Materials AOP,
doi:10.1038/nmat1713 (2006)]

###Multi-photon structures in the sub-cyclotron-frequency range in microwave photoresistance of a two-dimensional electron system|X. L. Lei,S. Y. Liu###

Multi-photon structures in the sub-cyclotron-frequency range in microwave photoresistance of a two-dimensional electron system. The frequency dependence of the peak-valley pairs occurring in the
magnetoresistivity of a two-dimensional electron system under enhanced
microwave irradiation, which are considered to associate with multiphoton
processes, is examined in the sub-cyclotron-frequency range, based on a
theoretical treatment with photon-assisted electron transitions due to impurity
scattering. It is shown that with equivalent radiation power (producing the
same height of the main oscillation peak), much more and stronger multi-photon
structures show up at lower frequency, and when frequency increases all these
structures rapidly weaken, diminish and finally disappear completely. These are
in agreement with the recent experimental observation [cond-mat/0608633].

###Large cone angle magnetization precession of an individual nanomagnet with dc electrical detection|M. V. Costache,S. M. Watts,M. Sladkov,C. H. van der Wal,B. J. van Wees###

Large cone angle magnetization precession of an individual nanomagnet with dc electrical detection. We demonstrate on-chip resonant driving of large cone-angle magnetization
precession of an individual nanoscale permalloy element. Strong driving is
realized by locating the element in close proximity to the shorted end of a
coplanar strip waveguide, which generates a microwave magnetic field. We used a
microwave frequency modulation method to accurately measure resonant changes of
the dc anisotropic magnetoresistance. Precession cone angles up to $9^{0}$ are
determined with better than one degree of resolution. The resonance peak shape
is well-described by the Landau-Lifshitz-Gilbert equation.

###Magnetoresistivity Modulated Response in Bichromatic Microwave Irradiated Two Dimensional Electron Systems|Jesus Inarrea,Gloria Platero###

Magnetoresistivity Modulated Response in Bichromatic Microwave Irradiated Two Dimensional Electron Systems. We analyze the effect of bichromatic microwave irradiation on the
magnetoresistivity of a two dimensional electron system. We follow the model of
microwave driven Larmor orbits in a regime where two different microwave lights
with different frequencies are illuminating the sample ($w_{1}$ and $w_{2}$).
Our calculated results demonstrate that now the electronic orbit centers are
driven by the superposition of two harmonic oscillatory movements with the
frequencies of the microwave sources. As a result the magnetoresisitivity
response presents modulated pulses in the amplitude with a frequency of
$\frac{w_{1}-w_{2}}{2}$, whereas the main response oscillates with
$\frac{w_{1}+w_{2}}{2}$.

###Tunneling anisotropic magnetoresistance driven by resonant surface states: First-principles calculations of Fe(001) surface|Athanasios N. Chantis,Kirill D. Belashchenko,Evgeny Y. Tsymbal,Mark van Schilfgaarde###

Tunneling anisotropic magnetoresistance driven by resonant surface states: First-principles calculations of Fe(001) surface. Fully-relativistic first-principles calculations of the Fe(001) surface
demonstrate that resonant surface (interface) states may produce sizeable
tunneling anisotropic magnetoresistance in magnetic tunnel junctions with a
single magnetic electrode. The effect is driven by the spin-orbit coupling. It
shifts the resonant surface band via the Rashba effect when the magnetization
direction changes. We find that spin-flip scattering at the interface is
controlled not only by the strength of the spin-orbit coupling, but depends
strongly on the intrinsic width of the resonant surface states.

###Unconventional spin density wave in Bechgaard salt (TMTSF)2NO3|Mario Basletic,Bojana Korin-Hamzic,Kazumi Maki,Silvija Tomic###

Unconventional spin density wave in Bechgaard salt (TMTSF)2NO3. Among many Bechgaard salts, TMTSF2NO3 exhibits very anomalous low temperature
properties. Unlike conventional spin density wave (SDW), TMTSF2NO3 undergoes
the SDW transition at $\T_SDW\approx 9.5$ K and the low temperature
quasiparticle excitations are gapless. Also, it is known that TMTSF2NO3 does
not exhibit superconductivity even under pressure, while FISDW is found in
TMTSF2NO3 only for P=8.5 kbar and B>20 T. Here we shall show that both the
angle dependent magnetoresistance data and the nonlinear Hall resistance of
TMTSF2NO3 at ambient pressure are interpreted satisfactory in terms of
unconventional spin density wave (USDW). Based on these facts, we propose a new
phase diagram for Bechgaards salts.

###Transmission of correlated electrons through sharp domain walls in magnetic nanowires: a renormalization group approach|M. A. N. Araujo,V. K. Dugaev,V. R. Vieira,J. Berakdar,J Barnas###

Transmission of correlated electrons through sharp domain walls in magnetic nanowires: a renormalization group approach. The transmission of correlated electrons through a domain wall in a
ferromagnetic one dimensional system is studied theoretically in the limit of a
domain wall width smaller or comparable to the electron Fermi wavelength. The
domain wall gives rise to both potential and spin dependent scattering of the
charge carriers. Using a poor man's renormalization group approach for the
electron-electron interactions, we obtain the low temperature behavior of the
reflection and transmission coefficients. The results show that the
low-temperature conductance is governed by the electron correlations, which may
suppress charge transport without suppressing spin current. The results may
account for a huge magnetoresistance associated with a domain wall in ballistic
nanocontacs.

###Effect of high annealing temperature on giant tunnel magnetoresistance ratio of CoFeB/MgO/CoFeB magnetic tunnel junctions|Jun Hayakawa,Shoji Ikeda,Young Min Lee,Fumihiro Matsukura,Hideo Ohno###

Effect of high annealing temperature on giant tunnel magnetoresistance ratio of CoFeB/MgO/CoFeB magnetic tunnel junctions. We report tunnel magnetoresistance (TMR) ratios as high as 472% at room
temperature and 804% at 5 K in pseudo-spin valve (SV) CoFeB/MgO/CoFeB magnetic
tunnel junctions (MTJs) annealed at 450oC, which is approaching the
theoretically predicted value. By contrast, the TMR ratios for exchange-biased
(EB) SV MTJs with a MnIr antiferromagnetic layer are found to drop when they
are annealed at 450oC. Energy dispersive X-ray analysis shows that annealing at
450oC induces interdiffusion of Mn and Ru atoms into the MgO barrier and
ferromagnetic layers in EB-SV MTJs. Mechanisms behind the different annealing
behavior are discussed.

###Proposal for a digital converter of analog magnetic signals|Christian Ertler,Jaroslav Fabian###

Proposal for a digital converter of analog magnetic signals. A device which converts analog magnetic signals directly into digital
information is proposed. The device concept is based on the monostable-bistable
transition logic element, which consists of two resonant tunneling diodes (load
and driver) connected in series and employs the monostable to bistable working
point transition of the circuit. Using a magnetic resonant tunneling diode as
the driver allows to control the resulting working point of the bistable region
by an external magnetic field leading either to high or low output voltage of
the circuit, effectively realizing what could be called digital
magnetoresistance.

###Charge and spin transport in spin valves with anisotropic spin relaxation|H. Saarikoski,W. Wetzels,G. E. W. Bauer###

Charge and spin transport in spin valves with anisotropic spin relaxation. We investigate effects of spin-orbit splitting on electronic transport in a
spin valve consisting of a large quantum dot defined on a two-dimensional
electron gas with two ferromagnetic contacts. In the presence of both structure
inversion asymmetry (SIA) and bulk inversion asymmetry (BIA) a giant anisotropy
in the spin-relaxation times has been predicted. We show how such an anisotropy
affects the electronic transport properties such as the angular
magnetoresistance and the spin-transfer torque. Counterintuitively, anisotropic
spin-relaxation processes sometimes enhance the spin accumulation.

###A hidden constant in the anomalous Hall effect of a high-purity magnet MnSi|Minhyea Lee,Y. Onose,Y. Tokura,N. P. Ong###

A hidden constant in the anomalous Hall effect of a high-purity magnet MnSi. Measurements of the Hall conductivity in MnSi can provide incisive tests of
theories of the anomalous Hall (AH) effect, because both the mean-free-path and
magnetoresistance (MR) are unusually large for a ferromagnet. The large MR
provides an accurate way to separate the AH conductivity $\sigma_{xy}^A$ from
the ordinary Hall conductivity $\sigma_{xy}^N$. Below the Curie temperature
$T_C$, $\sigma_{xy}^A$ is linearly proportional to $ M$ (magnetization) with a
proportionality constant $S_H$ that is independent of both $T$ and $H$. In
particular, $S_H$ remains a constant while $\sigma_{xy}^N$ changes by a factor
of 100 between 5 K and $T_C$. We discuss implications of the hidden constancy
in $S_H$.

###Total suppression of superconductivity by high magnetic fields in YBa2 Cu3O6.6|F. Rullier-Albenque,H. Alloul,Cyril Proust,P. Lejay,A. Forget,D. Colson###

Total suppression of superconductivity by high magnetic fields in YBa2 Cu3O6.6. We have studied in fields up to 60T the variation of the transverse
magnetoresistance (MR) of underdoped YBCO6.6 crystals either pure or with Tc
reduced down to 3.5K by electron irradiation. We evidence that the normal state
MR is restored above a threshold field H'c(T), which is found to vanish at
T'c>>Tc. In the pure YBCO6.6 sample a 50 Tesla field is already required to
completely suppress the superconducting fluctuations at Tc. While disorder does
not depress the pseudogap temperature, it reduces drastically the phase
coherence established at Tc and weakly H'c(0), T'c and the onset Tnu of the
Nernst signal which are more characteristic of the 2D local pairing.

###Infrared probe of the anomalous magnetotransport of highly oriented pyrolytic graphite in the extreme quantum limit|Z. Q. Li,S. -W. Tsai,W. J. Padilla,S. V. Dordevic,K. S. Burch,Y. J. Wang,D. N. Basov###

Infrared probe of the anomalous magnetotransport of highly oriented pyrolytic graphite in the extreme quantum limit. We present a systematic investigation of the magnetoreflectance of highly
oriented pyrolytic graphite in magnetic field B up to 18 T . From these
measurements, we report the determination of lifetimes tau associated with the
lowest Landau levels in the quantum limit. We find a linear field dependence
for inverse lifetime 1/tau(B) of the lowest Landau levels, which is consistent
with the hypothesis of a three-dimensional (3D) to 1D crossover in an
anisotropic 3D metal in the quantum limit. This enigmatic result uncovers the
origin of the anomalous linear in-plane magnetoresistance observed both in bulk
graphite and recently in mesoscopic graphite samples.

###Antinodal quasiparticles below and above T_Curie in the CMR oxide La_(2-2x)Sr_(1+2x)Mn_(2)O_(7) with x=0.36|S. de Jong,Y. Huang,I. Santoso,F. Massee,W. K. Siu,A. Mans,R. Follath,O. Schwartzkopf,M. S. Golden###

Antinodal quasiparticles below and above T_Curie in the CMR oxide La_(2-2x)Sr_(1+2x)Mn_(2)O_(7) with x=0.36. In light of recent conflicting angle resolved photoemission studies on the
bilayered colossal magnetoresistant (CMR) manganite
La_{2-2x}Sr_{1+2x}Mn_{2}O_{7} (0.36< x< 0.40), new ARPES data are presented for
x=0.36 and 0.40, showing only for the former clear quasiparticle-like features
at and around the (pi, 0)-point in k-space. The electronic states are clearly
renormalised, both as regards their dispersion relation and lifetime due to
coupling to bosonic degrees of freedom. Importantly, both the existence of
quasiparticles and their renormalisation survive well into the paramagnetic
state, up to 50 K above T_Curie. This argues against strong coupling to spin
modes and raises questions regarding the nature of the paramagnetic insulating
phase.

###Quantum size effects in a one-dimensional semimetal|Shadyar Farhangfar###

Quantum size effects in a one-dimensional semimetal. We study theoretically the quantum size effects in a one-dimensional
semimetal by a Boltzmann transport equation. We derive analytic expressions for
the electrical conductivity, Hall coefficient, magnetoresistance, and the
thermoelectric power in a nanowire. The transport coefficients of semimetal
oscillate as the size of the sample shrinks. Below a certain size the semimetal
evolves into a semiconductor. The semimetal-semiconductor transition is
discussed quantitatively. The results should make a theoretical ground for
better understanding of transport phenomena in low-dimensional semimetals. They
can also provide useful information while studying low-dimensional
semiconductors in general.

###Strong magnetic scattering from TiO$_{x}$ adhesion layers|A. Trionfi,S. Lee,D. Natelson###

Strong magnetic scattering from TiO$_{x}$ adhesion layers. Electronic phase coherence in normal metals is incredibly sensitive to
magnetic scattering. As a result, the weak localization magnetoresistance and
time-dependent universal conductance fluctuations are powerful probes of
magnetic impurities. We report measurements of these effects in Au and Ag
nanowires with a 1.5 nm thick Ti adhesion layer underneath the deposited metal.
The results indicate an anomalously large magnetic impurity concentration due
to the Ti layer. Results suggest that this magnetic scattering and its
evolution are related to the oxidation state of the Ti.

###Large inverse tunneling magnetoresistance in Co$_2$Cr$_{0.6}$Fe$_{0.4}$Al/MgO/CoFe magnetic tunnel junctions|A. D. Rata,H. Braak,D. E. Buergler,C. M. Schneider###

Large inverse tunneling magnetoresistance in Co$_2$Cr$_{0.6}$Fe$_{0.4}$Al/MgO/CoFe magnetic tunnel junctions. Magnetic tunnel junctions with the layer sequence
Co$_2$Cr$_{0.6}$Fe$_{0.4}$Al/MgO/CoFe were fabricated by magnetron sputtering
at room temperature (RT). The samples exhibit a large inverse tunneling
magnetoresistance (TMR) effect of up to -66% at RT. The largest value of -84%
at 20 K reflects a rather weak influence of temperature. The dependence on the
voltage drop shows an unusual behavior with two almost symmetric peaks at
$\pm600$ mV with large inverse TMR ratios and small positive values around zero
bias.

###Magnetic characterization and switching of Co nano-rings in current-perpendicular-to-plane configuration|T. Yang,M. Hara,A. Hirohata,T. Kimura,Y. Otani###

Magnetic characterization and switching of Co nano-rings in current-perpendicular-to-plane configuration. We fabricated Co nano-rings incorporated in the vertical pseudo-spin-valve
nanopillar structures with deep submicron lateral sizes. It is shown that the
current-perpendicular-to-plane giant magnetoresistance can be used to
characterize a very small magnetic nano-ring effectively. Both the onion state
and the flux-closure vortex state are observed. The Co nano-rings can be
switched between the onion states as well as between onion and vortex states
not only by the external field but also by the perpendicularly injected dc
current.

###Magnetic field tuning of the low temperature state in YbNiSi3|Sergey L. Bud'ko,Paul C. Canfield,Marcos A. Avila,Toshiro Takabatake###

Magnetic field tuning of the low temperature state in YbNiSi3. We present detailed, low temperature, magnetoresistance and specific heat
data of single crystal YbNiSi3 measured in magnetic field applied along the
easy magnetic axis, H || b. An initially antiferromagnetic ground state changes
into a field-induced metamagnetic phase at ~16 kOe (T -> 0). On further
increase of magnetic field, magnetic order is suppressed at ~85 kOe. The
functional behaviors of the resistivity and specific heat are discussed in
comparison with those of the few other stoichiometric, heavy fermion compounds
with established field-induced quantum critical point.

###Critical behavior of transport and magnetotransport in 2D electron system in Si in the vicinity of the metal-insulator transition|D. A. Knyazev,O. E. Omelyanovskii,V. M. Pudalov,I. S. Burmistrov###

Critical behavior of transport and magnetotransport in 2D electron system in Si in the vicinity of the metal-insulator transition. We report on studies of the magnetoresistance in strongly correlated 2D
electron system in Si in the critical regime, in the close vicinity of the 2D
metal-insulator transition. We performed self-consistent comparison of our data
with solutions of two equations of the cross-over renormalization group (CRG)
theory which describes temperature evolutions of the resistivity and
interaction parameters for 2D electron system. We found a good agreement
between the \rho(T,B) data and the RG theory in a wide range of the in-plane
fields, 0-2.1 T. This agreement supports the interpretation of the observed 2D
MIT as the true quantum phase transition.

###Steplike Lattice Deformation of Single Crystalline (La$_{0.4}$Pr$_{0.6}$)$_{1.2}$Sr$_{1.8}$Mn$_{2}$O$_{7}$ Bilayered Manganite|M. Matsukawa,Y. Yamato,T. Kumagai,R. Suryanarayanan,S. Nimori###

Steplike Lattice Deformation of Single Crystalline (La$_{0.4}$Pr$_{0.6}$)$_{1.2}$Sr$_{1.8}$Mn$_{2}$O$_{7}$ Bilayered Manganite. We report a steplike lattice transformation of single crystalline
(La$_{0.4}$Pr$_{0.6}$)$_{1.2}$Sr$_{1.8}$Mn$_{2}$O$_{7}$bilayered manganite
accompanied by both magnetization and magnetoresistive jumps, and examine the
ultrasharp nature of the field-induced first-order transition from a
paramagnetic insulator to a ferromagnetic metal phase accompanied by a huge
decrease in resistance. Our findings support that the abrupt magnetostriction
is closely related to an orbital frustration existing in the inhomogeneous
paramagnetic insulating phase rather than a martensitic scenario between
competing two phases.

###First-principles prediction of high Curie temperature for ferromagnetic bcc-Co and bcc-FeCo alloys and its relevance to tunneling magnetoresistance|Marjana Lezaic,Phivos Mavropoulos,Stefan Blügel###

First-principles prediction of high Curie temperature for ferromagnetic bcc-Co and bcc-FeCo alloys and its relevance to tunneling magnetoresistance. We determine from first-principles the Curie temperature Tc for bulk Co in
the hcp, fcc, bcc, and tetragonalized bct phases, for FeCo alloys, and for bcc
and bct Fe. For bcc-Co, Tc=1420 K is predicted. This would be the highest Curie
temperature among the Co phases, suggesting that bcc-Co/MgO/bcc-Co tunnel
junctions offer high magnetoresistance ratios even at room temperature. The
Curie temperatures are calculated by mapping ab initio results to a Heisenberg
model, which is solved by a Monte Carlo method.

###Electric field effects on magnetotransport properties of multiferroic Py/YMnO3/Pt heterostructures|V. Laukhin,X. Marti,V. Skumryev,D. Hrabovsky,F. Sanchez,M. V. Garcia-Cuenca,C. Ferrater,M. Varela,U. Luders,J. F. Bobo,J. Fontcuberta###

Electric field effects on magnetotransport properties of multiferroic Py/YMnO3/Pt heterostructures. We report on the exchange bias between antiferromagnetic and ferroelectric
hexagonal YMnO3 epitaxial thin films sandwiched between a metallic electrode
(Pt) and a soft ferromagnetic layer (Py). Anisotropic magnetoresistance
measurements are performed to monitor the presence of an exchange bias field.
When the heteroestructure is biased by an electric field, it turns out that the
exchange bias field is suppressed. We discuss the dependence of the observed
effect on the amplitude and polarity of the electric field. Particular
attention is devoted to the role of current leakage across the ferroelectric
layer.

###Current-induced vortex-vortex switching in a nanopillar comprising two Co nano-rings|T. Yang,A. Hirohata,M. Hara,T. Kimura,Y. Otani###

Current-induced vortex-vortex switching in a nanopillar comprising two Co nano-rings. We fabricated a current-perpendicular-to-plane pseudo-spin-valve nanopillar
comprising a thick and a thin Co rings with deep submicron lateral sizes. The
dc current can effectively induce the flux-closure vortex states in the rings
with desired chiralities. Abrupt transitions between the vortex states are also
realized by the dc current and detected with the giant magnetoresistance
effect. Both Oersted field and spin-transfer torque are found important to the
magnetic transitions, but the former is dominant. They can be designed to
cooperate with each other in the vortex-to-vortex transitions by carefully
setting the chirality of the vortex state in the thick Co ring.

###Influence of trigonal warping on interference effects in bilayer graphene|K. Kechedzhi,Vladimir I. Fal'ko,E. McCann,B. L. Altshuler###

Influence of trigonal warping on interference effects in bilayer graphene. Bilayer graphene (two coupled graphitic monolayers arranged according to
Bernal stacking) is a two-dimensional gapless semiconductor with a peculiar
electronic spectrum different from the Dirac spectrum in the monolayer
material. In particular, the electronic Fermi line in each of its valleys has a
strong p -> -p asymmetry due to a trigonal warping, which suppresses the weak
localization effect. We show that weak localisation in bilayer graphene may be
present only in devices with pronounced intervalley scattering, and we evaluate
the corresponding magnetoresistance.

###Hidden symmetries in Bechgaard salt (TMTSF)2NO3|Kazumi Maki,Mario Basletic,Bojana Korin-Hamzic,Silvia Tomic###

Hidden symmetries in Bechgaard salt (TMTSF)2NO3. Among known Bechgaard and Fabre salts (TMTSF)2NO3 is unique since it never
becomes superconducting even under pressure. Also, though (TMTSF)2NO3 undergoes
the spin density wave (SDW) transition, the low temperature transport is
semimetallic and gapless. We propose: a) the absence of the superconductivity
is due to the inverse symmetry breaking associated with the anion ordering at
45K; b) the SDW state below 9K should be unconventional as seen from the angle
dependent magnetoresistance oscillation (AMRO); c) a new phase diagram for
Bechgaard salts, where unconventional spin density wave (USDW) occupies the
prominent space.

###Microcracks and inhomogeneously distributed defects in solids|Yuri Kornyushin###

Microcracks and inhomogeneously distributed defects in solids. A conception of inhomogeneous locally random distribution of microdefects in
crystalline solids is proposed. A method to calculate some physical properties
of solids, containing inhomogeneously distributed defects, is developed. A
contribution of this inhomogeneity to a series of physical properties is
calculated and discussed. This contribution exceeds that of homogeneously
distributed defects by the orders of magnitude. A contribution of the
inhomogeneity to electric conductivity, Hall effect and magnetoresistance is
calculated. Elastic energy and volume of inhomogeneously dislocated crystal are
regarded. It was shown that the relaxation of the elastic energy of random
dislocations during propagation of a crack facilitates the process. These
results explained a phenomenon of lamination of overdeformed metals.

###Spin-dependent transport properties in GaMnAs-based spin hot-carrier transistors|Yosuke Mizuno,Shinobu Ohya,Pham Nam Hai,Masaaki Tanaka###

Spin-dependent transport properties in GaMnAs-based spin hot-carrier transistors. We have investigated the spin-dependent transport properties of GaMnAs-based
three-terminal semiconductor spin hot-carrier transistor (SSHCT) structures.
The emitter-base bias voltage VEB dependence of the collector current IC,
emitter current IE, and base current IB shows that the current transfer ratio
alpha (= IC / IE) and the current gain beta (= IC / IB) are 0.8-0.95 and 1-10,
respectively, which means that GaMnAs-based SSHCTs have current amplifiability.
In addition, we observed an oscillatory behavior of the tunneling
magnetoresistance (TMR) ratio with the increasing bias, which can be explained
by the resonant tunneling effect in the GaMnAs quantum well.

###Large Magnetoresistance in Co/Ni/Co Ferromagnetic Single Electron Transistors|R. S. Liu,H. Pettersson,L. Michalak,C. M. Canali,D. Suyatin,L. Samuelson###

Large Magnetoresistance in Co/Ni/Co Ferromagnetic Single Electron Transistors. We report on magnetotransport investigations of nano-scaled ferromagnetic
Co/Ni/Co single electron transistors. As a result of reduced size, the devices
exhibit single electron transistor characteristics at 4.2K. Magnetotransport
measurements carried out at 1.8K reveal tunneling magnetoresistance (TMR)
traces with negative coercive fields, which we interpret in terms of a
switching mechanism driven by the shape anisotropy of the central wire-like Ni
island. A large TMR of about 18% is observed within a finite source-drain bias
regime. The TMR decreases rapidly with increasing bias, which we tentatively
attribute to excitation of magnons in the central island.

###Competing Ferromagnetic and Charge-Ordered States in Models for Manganites: the Origin of the CMR Effect|Cengiz Sen,Gonzalo Alvarez,Elbio Dagotto###

Competing Ferromagnetic and Charge-Ordered States in Models for Manganites: the Origin of the CMR Effect. The one-orbital model for manganites with cooperative phonons and
superexchange coupling $J_{\rm AF}$ has been investigated via large-scale Monte
Carlo (MC) simulations. Results for two-orbitals are also briefly discussed.
Focusing on electronic density $n$=0.75, a regime of competition between
ferromagnetic (FM) metallic and charge-ordered (CO) insulating states was
identified. In the vicinity of the associated bicritical point, colossal
magnetoresistance (CMR) effects were observed. The CMR is associated with the
development of short-distance correlations among polarons, above the spin
ordering temperatures, resembling the charge arrangement of the low-temperature
CO state.

###Angle-dependent magnetoresistance oscillations due to magnetic breakdown orbits|A. F. Bangura,P. A. Goddard,J. Singleton,S. W. Tozer,A. I. Coldea,A. Ardavan,R. D. McDonald,S. J. Blundell,J. A. Schlueter###

Angle-dependent magnetoresistance oscillations due to magnetic breakdown orbits. We present experimental evidence for a hitherto unconfirmed type of
angle-dependent magnetoresistance oscillation caused by magnetic breakdown. The
effect was observed in the organic superconductor
kappa-(BEDT-TTF)$_2$Cu(NCS)$_2$ using hydrostatic pressures of up to 9.8 kbar
and magnetic fields of up to 33 T. In addition, we show that similar
oscillations are revealed in ambient pressure measurements, provided that the
Shubnikov-de Haas oscillations are suppressed either by elevated temperatures
or filtering of the data. These results provide a compelling validation of
Pippard's semiclassical picture of magnetic breakdown.

###Uniaxial magnetocrystalline anisotropy in ${\rm CaRuO_3}$|Moty Schultz,Lior Klein,J. W. Reiner,M. R. Beasley###

Uniaxial magnetocrystalline anisotropy in ${\rm CaRuO_3}$. ${\rm CaRuO_3}$ is a paramagnetic metal and since its low temperature
resistivity is described by $\rho=\rho_0+AT^\gamma $ with $\gamma \sim 1.5$, it
is also considered a non-Fermi liquid (NFL) metal. We have performed extensive
magnetoresistance and Hall effect measurements of untwinned epitaxial films of
${\rm CaRuO_3}$. These measurements reveal that ${\rm CaRuO_3}$ exhibits
uniaxial magnetocrystalline anisotropy. In addition, the low-temperature NFL
behavior is most effectively suppressed when a magnetic field is applied along
the easy axis, suggesting that critical spin fluctuations, possibly due to
proximity of a quantum critical phase transition, are related to the NFL
behavior.

###Observation of Spin-Orbit Berry's Phase in Magnetoresistance of a Two-Dimensional Hole Anti-dot System|Ning Kang,Eisuke Abe,Yoshiaki Hashimoto,Yasuhiro Iye,Shingo Katsumoto###

Observation of Spin-Orbit Berry's Phase in Magnetoresistance of a Two-Dimensional Hole Anti-dot System. We report observation of spin-orbit Berry's phase in the Aharonov-Bohm (AB)
type oscillation of weak field magnetoresistance in an anti-dot lattice (ADL)
of a two-dimensional hole system. An AB-type oscillation is superposed on the
commensurability peak, and the main peak in the Fourier transform is clearly
split up due to variation in Berry's phase originating from the spin-orbit
interaction. A simulation considering Berry's phase and the phase arising from
the spin-orbit shift in the momentum space shows qualitative agreement with the
experiment.

###Two-Staged Magnetoresistance Driven by Ising-like Spin Sublattice in SrCo6O11|S. Ishiwata,I. Terasaki,F. Ishii,N. Nagaosa,H. Mukuda,Y. Kitaoka,T. Saito,M. Takano###

Two-Staged Magnetoresistance Driven by Ising-like Spin Sublattice in SrCo6O11. A two-staged, uniaxial magnetoresistive effect has been discovered in
SrCo6O11 having a layered hexagonal structure. Conduction electrons and
localized Ising spins are in different sublattices but their interpenetration
makes the conduction electrons sensitively pick up the stepwise
field-dependence of magnetization. The stepwise field-dependence suggests two
competitive interlayer interactions between ferromagnetic Ising-spin layers,
i.e., a ferromagnetic nearest-layer interaction and an antiferromagnetic
next-nearest-layer interaction. This oxide offers a unique opportunity to study
nontrivial interplay between conduction electrons and Ising spins, the coupling
of which can be finely controlled by a magnetic field of a few Tesla.

###Optically tuned dimensionality crossover in photocarrier-doped SrTiO$_3$: onset of weak localization|Y. Kozuka,Y. Hikita,T. Susaki,H. Y. Hwang###

Optically tuned dimensionality crossover in photocarrier-doped SrTiO$_3$: onset of weak localization. We report magnetotransport properties of photogenerated electrons in undoped
SrTiO$_3$ single crystals under ultraviolet illumination down to 2 K. By tuning
the light intensity, the steady state carrier density can be controlled, while
tuning the wavelength controls the effective electronic thickness by modulating
the optical penetration depth. At short wavelengths, when the sheet conductance
is close to the two-dimensional Mott minimum conductivity we have observed
critical behavior characteristic of weak localization. Negative
magnetoresistance at low magnetic field is highly anisotropic, indicating
quasi-two-dimensional electronic transport. The high mobility of photogenerated
electrons in SrTiO$_3$ allows continuous tuning of the effective electronic
dimensionality by photoexcitation.

###Theory of a Magnetically-Controlled Quantum-Dot Spin Transistor|Daniel Urban,Matthias Braun,Jürgen König###

Theory of a Magnetically-Controlled Quantum-Dot Spin Transistor. We examine transport through a quantum dot coupled to three ferromagnetic
leads in the regime of weak tunnel coupling. A finite source-drain voltage
generates a nonequilibrium spin on the otherwise non-magnetic quantum dot. This
spin accumulation leads to magnetoresistance. A ferromagnetic but current-free
base electrode influences the quantum-dot spin via incoherent spin-flip
processes and coherent spin precession. As the dot spin determines the
conductance of the device, this allows for a purely magnetic transistor-like
operation. We analyze the effect of both types of processes on the electric
current in different geometries.

###Spin Injection into a Graphene Thin Film at Room Temperature|Megumi Ohishi,Masashi Shiraishi,Ryo Nouchi,Takayuki Nozaki,Teruya Shinjo,Yoshishige Suzuki###

Spin Injection into a Graphene Thin Film at Room Temperature. We demonstrate spin injection into a graphene thin film with high reliability
by using non-local magnetoresistance (MR) measurements, in which the electric
current path is completely separated from the spin current path. Using these
non-local measurements, an obvious MR effect was observed at room temperature;
and the MR effect was ascribed to magnetization reversal of ferromagnetic
electrodes. This result is a direct demonstration of spin injection into a
graphene thin film. Furthermore, this is the first report of spin injection
into molecules at room temperature.

###Magnetic fingerprint in a ferromagnetic wire: Spin torque diode effect and induction of the DC voltage spectrum inherent in the wire under application for RF current|A. Yamaguchi,T. Ono,Y. Suzuki,S. Yuasa,H. Miyajima###

Magnetic fingerprint in a ferromagnetic wire: Spin torque diode effect and induction of the DC voltage spectrum inherent in the wire under application for RF current. We report the rectifying effect of a constant-wave radio frequency (RF)
current by a magnetic domain wall (DW) on a single-layered ferromagnetic wire.
A direct-current (DC) voltage is generated by the spin torque diode effect,
which is a consequence of magnetoresistance oscillation due to the resonant
spin wave excitation induced by the spin-polarized RF current. The DC voltage
spectrum strongly depends on the internal spin structure in the DW, which
corresponds to the magnetic fingerprint of the spin structure in the
ferromagnetic wire.

###The Lorenz number in CeCoIn$_5$ inferred from the thermal and charge Hall currents|Y. Onose,N. P. Ong,C. Petrovic###

The Lorenz number in CeCoIn$_5$ inferred from the thermal and charge Hall currents. The thermal Hall conductivity $\kappa_{xy}$ and Hall conductivity
$\sigma_{xy}$ in CeCoIn$_5$ are used to determine the Lorenz number ${\cal
L}_H$ at low temperature $T$. This enables the separation of the observed
thermal conductivity into its electronic and non-electronic parts. We uncover
evidence for a charge-neutral, field-dependent thermal conductivity, which we
identify with spin excitations. At low $T$, these excitations dominate the
scattering of charge carriers. We show that suppression of the spin excitations
in high fields leads to a steep enhancement of the electron mean-free-path,
which leads to an interesting scaling relation between the magnetoresistance,
thermal conductivity and $\sigma_{xy}$.

###Direct-current control of radiation-induced differential magnetoresistance oscillations in two-dimensional electron systems|X. L. Lei###

Direct-current control of radiation-induced differential magnetoresistance oscillations in two-dimensional electron systems. Magnetoresistance oscillations in two-dimensional electron systems driven
simultaneously by a strong direct current and a microwave irradiation, are
analyzed within a unified microscopic scheme treating both excitations on an
equal footing. The microwave-induced resistance oscillations are described by a
parameter $\epsilon_\omega$ proportional to the radiation frequency, while the
dc-induced resistance oscillations are governed by a parameter $\epsilon_j$
proportional to the current density. In the presence of both a microwave
radiation and a strong dc, the combined parameter $\epsilon_\omega+\epsilon_j$
is shown to control the main resistance oscillations, in agreement with the
recent measurement [Zhang {\it et al.} Phys. Rev. Lett. {\bf 98}, 106804
(2007)]

###Probing the electron-phonon coupling in MgB2 through magnetoresistance measurements in neutron irradiated thin films|M. Monni,I. Pallecchi,C. Ferdeghini,V. Ferrando,A. Floris,E. Galleani d'Agliano,E. Lehmann,I. Sheikin,C. Tarantini,X. X. Xi,S. Massidda,M. Putti###

Probing the electron-phonon coupling in MgB2 through magnetoresistance measurements in neutron irradiated thin films. We report magnetoresistance (MR) measurements on MgB2 and the corresponding
full account from ab-initio calculations; we suggest that this combination can
be a useful tool to probe electron- phonon coupling. We obtain good
quantitative agreement between high field measurements on neutron irradiated
epitaxial thin films and calculations within Bloch-Boltzmann transport theory
over a wide range of magnetic fields (0-28 T) and temperatures (40-300 K), and
as a function of the field orientation. The crossovers between in-plane and
out-of-plane MR, experimentally observed as a function of either disorder or
temperature are well reproduced indicating that disorder and interaction with
phonons strongly affect the scattering rate of s-carriers.

###Anomalous giant piezoresistance in AlAs 2D electrons with anti-dot lattices|O. Gunawan,T. Gokmen,Y. P. Shkolnikov,E. P. De Poortere,M. Shayegan###

Anomalous giant piezoresistance in AlAs 2D electrons with anti-dot lattices. An AlAs two-dimensional electron system patterned with an anti-dot lattice
exhibits a giant piezoresistance (GPR) effect, with a sign opposite to the
piezoresistance observed in the unpatterned region. We trace the origin of this
anomalous GPR to the non-uniform strain in the anti-dot lattice and the
exclusion of electrons occupying the two conduction band valleys from different
regions of the sample. This is analogous to the well-known giant
magnetoresistance (GMR) effect, with valley playing the role of spin and strain
the role of magnetic field.

###Anomalous exchange coupling in transition-metal-oxide based superlattices with antiferromagnetic spacer layers|P. Padhan,W. Prellier,R. C. Budhani###

Anomalous exchange coupling in transition-metal-oxide based superlattices with antiferromagnetic spacer layers. A direct correlation is seen between the coercive field (HC) and the
magnetic-field-dependent resistivity (MR) in SrMnO3/SrRuO3 superlattices of
perpendicular magnetic anisotropy. The magnetoresistance shows a sharp jump at
Hc for in-plane current and the out-of-plane magnetic field. Both HC and
high-field MR also oscillate with the thickness of the SrMnO3 spacer layers
separating the metallic ruthenate. Since the spacer in these superlattices has
no mobile carriers to facilitate an oscillatory coupling, we attribute the
observed behavior to the spin-polarized quantum tunneling of electrons between
the ferromagnetic layers and antiferromagnetically ordered t2g spins of SrMnO3.

###Weak localization in GaMnAs: evidence of impurity band transport|L. P. Rokhinson,Y. Lyanda-Geller,Z. Ge,S. Shen,X. Liu,M. Dobrowolska,J. K. Furdyna###

Weak localization in GaMnAs: evidence of impurity band transport. We report the observation of negative magnetoresistance in the ferromagnetic
semiconductor GaMnAs at low temperatures ($T<3$ K) and low magnetic fields ($0<
B <20$ mT). We attribute this effect to weak localization. Observation of weak
localization provides a strong evidence of impurity band transport in these
materials, since for valence band transport one expects either weak
anti-localization due to strong spin-orbit interactions or total suppression of
interference by intrinsic magnetization. In addition to the weak localization,
we observe Altshuler-Aronov electron-electron interactions effect in this
material.

###Quantum vortex tunneling in $YBa_2Cu_3O_{7-δ}$ thin films|G. Koren,Y. Mor,A. Auerbach,E. Polturak###

Quantum vortex tunneling in $YBa_2Cu_3O_{7-δ}$ thin films. Cuprate films offer a unique opportunity to observe vortex tunneling effects,
due to their unusually low superfluid density and short coherence length. Here,
we measure the magnetoresistance (\textit{MR}) due to vortex motion of a long
meander line of a superconducting film made of underdoped
$YBa_2Cu_3O_{7-\delta}$. At low temperatures (\textit{T}), the \textit{MR}
shows a significant deviation from Arrhenius activation. The data is consistent
with two dimensional Variable Range Hopping (VRH) of single vortices, i.e.
$MR\propto exp[-(T_0/T)^{1/3}]$. The VRH temperature scale $T_0$ depends on the
vortex tunneling rates between pinning sites. We discuss its magnitude with
respect to estimated parameters of the meander thin film.

###Spin-locking effect in the nanoscale ordered perovskite cobaltite LaBaCo2O6|Asish K. Kundu,E. -L. Rautama,Ph. Boullay,V. Caignaert,V. Pralong,B. Raveau###

Spin-locking effect in the nanoscale ordered perovskite cobaltite LaBaCo2O6. A new nanoscale ordered perovskite cobaltite, which consists of 90 degree
ordered domains of the layered-112 LaBaCo2O6 has been evidenced by high
resolution- transmission electron microscopy. This new form, like the
disordered La0.5Ba0.5CoO3 and ordered LaBaCo2O6, exhibits a ferromagnetic
transition at TC around 179 K. However, it differs from the two previous forms
by its strong magnetic anisotropy, and correlatively by its high value of
coercivity (0.42 Tesla) at low temperature. We suggest that this behaviour
originates from the locking of magnetic spins in the 90 degree oriented
nano-domain. Moreover, one observes a semi-metal/semi-metal transition at TC
with a maximum magnetoresistance of 6.5 % at this temperature.

###Reversal of spin polarization in Fe/GaAs (001) driven by resonant surface states: First-principles calculations|Athanasios N. Chantis,Kirill D. Belashchenko,Darryl L. Smith,Evgeny Y. Tsymbal,Mark van Schilfgaarde,Robert C. Albers###

Reversal of spin polarization in Fe/GaAs (001) driven by resonant surface states: First-principles calculations. A minority-spin resonant state at the Fe/GaAs(001) interface is predicted to
reverse the spin polarization with voltage bias of electrons transmitted across
this interface. Using a Green's function approach within the local spin density
approximation we calculate spin-dependent current in a Fe/GaAs/Cu tunnel
junction as a function of applied bias voltage. We find a change in sign of the
spin polarization of tunneling electrons with bias voltage due to the interface
minority-spin resonance. This result explains recent experimental data on spin
injection in Fe/GaAs contacts and on tunneling magnetoresistance in Fe/GaAs/Fe
magnetic tunnel junctions.

###Electron magnetotransport in GaAs/AlGaAs superlattices with weak and strong inter-well coupling|L. Smrcka,N. A. Goncharuk,P. Svoboda,P. Vasek,Yu. Krupko,W. Wegscheider###

Electron magnetotransport in GaAs/AlGaAs superlattices with weak and strong inter-well coupling. We report on magnetotransport measurements in two MBE-grown GaAs/AlGaAs
superlattices formed by wide and narrow quantum wells and thin Si-doped
barriers subject to tilted magnetic fields. It has been shown that illumination
of the strongly coupled superlattice with narrow wells leads to reduction of
its dimensionality from the 3D to 2D. The illumination-induced transition is
revealed by remarkable change of magnetoresistance curves as compared to those
measured before illumination. The experimental data along with tight-binding
model calculations indicate that the illumination not only enhances the
electron concentration but also suppresses the electron tunneling through the
barriers.

###Spin valve effect by ballistic transport in ferromagnetic metal (MnAs) / semiconductor (GaAs) hybrid heterostructures|Pham Nam Hai,Yusuke Sakata,Masafumi Yokoyama,Shinobu Ohya,Masaaki Tanaka###

Spin valve effect by ballistic transport in ferromagnetic metal (MnAs) / semiconductor (GaAs) hybrid heterostructures. We demonstrate the spin valve effect by ballistic transport in fully
epitaxial MnAs ferromagnetic metal / GaAs semiconductor / GaAs:MnAs granular
hybrid heterostructures. The GaAs:MnAs material contains ferromagnetic MnAs
nanoparticles in a GaAs matrix, and acts as a spin injector and a spin
detector. Although the barrier height of the GaAs/MnAs interface was found to
be very small, relatively large magnetoresistance was observed. This result
shows that by using ballistic transport, we can realize a large spin valve
effect without inserting a high tunnel barrier at the ferromagnetic metal /
semiconductor interface.

###Superconducting islands, phase fluctuations and the superconductor-insulator transition|Y. Dubi,Y. Meir,Y. Avishai###

Superconducting islands, phase fluctuations and the superconductor-insulator transition. Properties of disordered thin films are discussed based on the viewpoint that
superconducting islands are formed in the system. These lead to superconducting
correlations confined in space, which are known to form spontaneously in thin
films. Application of a perpendicular magnetic field can drive the system from
the superconducting state (characterized by phase-rigidity between the sample
edges) to an insulating state in which there are no phase-correlations between
the edges of the system. On the insulating side the existence of
superconducting islands leads to a non-monotonic magnetoresistance. Several
other features seen in experiment are explained.

###Spin Valve Effect in Self-exchange Biased Ferromagnetic Metal/Semiconductor Bilayers|M. Zhu,M. J. Wilson,B. L. Sheu,P. Mitra,P. Schiffer,N. Samarth###

Spin Valve Effect in Self-exchange Biased Ferromagnetic Metal/Semiconductor Bilayers. We report magnetization and magetoresistance measurements in hybrid
ferromagnetic metal/semiconductor heterostructures comprised of MnAs/(Ga,Mn)As
bilayers. Our measurements show that the (metallic) MnAs and (semiconducting)
(Ga,Mn)As layers are exchange coupled, re- sulting in an exchange biasing of
the magnetically softer (Ga,Mn)As layer that weakens with layer thickness.
Magnetoresistance measurements in the current-perpendicular-to-the-plane
geometry show a spin valve effect in these self-exchange biased bilayers.
Similar measurements in MnAs/p- GaAs/(Ga,Mn)As trilayers show that the exchange
coupling diminishes with spatial separation between the layers.

###Anisotropic magnetoresistance in nanocontacts|D. Jacob,J. Fernandez-Rossier,J. J. Palacios###

Anisotropic magnetoresistance in nanocontacts. We present ab initio calculations of the evolution of anisotropic
magnetoresistance (AMR) in Ni nanocontacts from the ballistic to the tunnel
regime. We find an extraordinary enhancement of AMR, compared to bulk, in two
scenarios. In systems without localized states, like chemically pure break
junctions, large AMR only occurs if the orbital polarization of the current is
large, regardless of the anisotropy of the density of states. In systems that
display localized states close to the Fermi energy, like a single electron
transistor with ferromagnetic electrodes, large AMR is related to the variation
of the Fermi energy as a function of the magnetization direction.

###Possible co-existence of local itinerancy and global localization in a quasi-one-dimensional conductor|A. Narduzzo A. Enayati-Rad,S. Horii,N. E. Hussey###

Possible co-existence of local itinerancy and global localization in a quasi-one-dimensional conductor. In the chain compound PrBa$_2$Cu$_4$O$_8$ localization appears simultaneously
with a dimensional crossover in the electronic ground state when the scattering
rate in the chains exceeds the hopping rate between the chains. Here we report
the discovery of a large, transverse magnetoresistance in PrBa$_2$Cu$_4$O$_8$
in the localized regime. This result suggests a novel form of localization
whereby electrons retain their metallic (quasi-one-dimensional) character over
a microscopic length scale despite the fact that macroscopically, they exhibit
localized (one-dimensional) behavior.

###An analytically solvable model of the effect of magnetic breakdown on angle-dependent magnetoresistance in a quasi-two-dimensional metal|Andrzej Nowojewski,Paul A. Goddard,Stephen J. Blundell###

An analytically solvable model of the effect of magnetic breakdown on angle-dependent magnetoresistance in a quasi-two-dimensional metal. We have developed an analytical model of angle-dependent magnetoresistance
oscillations (AMROs) in a quasi-two-dimensional metal in which magnetic
breakdown occurs. The model takes account of all the contributions from
quasiparticles undergoing both magnetic breakdown and Bragg reflection at each
junction and allows extremely efficient simulation of data which can be
compared with recent experimental results on the organic metal
kappa-ET2Cu(NCS)2. AMROs resulting from both closed and open orbits emerge
naturally at low field, and the model enables the transition to breakdown-AMROs
with increasing field to be described in detail.

###A precursor state to unconventional superconductivity in CeIrIn${_5}$|Sunil Nair,S. Wirth,M. Nicklas,J. L. Sarrao,J. D. Thompson,Z. Fisk,F. Steglich###

A precursor state to unconventional superconductivity in CeIrIn${_5}$. We present sensitive measurements of the Hall effect and magnetoresistance in
CeIrIn${_5}$ down to temperatures of 50 mK and magnetic fields up to 15 T. The
presence of a low temperature coherent Kondo state is established. Deviations
from Kohler's rule and a quadratic temperature dependence of the cotangent of
the Hall angle are reminiscent of properties observed in the high temperature
superconducting cuprates. The most striking observation pertains to the
presence of a \textit{precursor} state--characterized by a change in the Hall
mobility--that appears to precede the superconductivity in this material, in
similarity to the pseudogap in the cuprate high $T_c$ superconductors.

###Thermoelectrical manipulation of nano-magnets|A. M. Kadigrobov,R. I. Shekhter,M. Jonson,V. Korenivski###

Thermoelectrical manipulation of nano-magnets. We propose a device that can operate as a magneto-resistive switch or
oscillator. The device is based on a spin-thermo-electronic control of the
exchange coupling of two strong ferromagnets through a weakly ferromagnetic
spacer. We show that the local Joule heating due to a high concentration of
current in a magnetic point contact or a nanopillar can be used to reversibly
drive the weak ferromagnet through its Curie point and thereby
exchange-decouple the strongly ferromagnetic layers, which have an antiparallel
ground state. Such a spin-thermionic parallel-to-antiparallel switching causes
magnetoresistance oscillations where the frequency can be controlled by proper
biasing from essentially DC to GHz.

###Intrinsic Superconductivity at 25 K in Highly Oriented Pyrolytic Graphite|P. Esquinazi,N. García,J. Barzola-Quiquia,J. C. González,M. Muñoz,P. Rödiger,K. Schindler,J. -L. Yao,M. Ziese###

Intrinsic Superconductivity at 25 K in Highly Oriented Pyrolytic Graphite. High resolution magnetoresistance data in highly oriented pyrolytic graphite
thin samples manifest non-homogenous superconductivity with critical
temperature $T_c \sim 25 $K. These data exhibit: i) hysteretic loops of
resistance versus magnetic field similar to Josephson-coupled grains, ii)
quantum Andreev's resonances and iii) absence of the Schubnikov-de Haas
oscillations. The results indicate that graphite is a system with
non-percolative superconducting domains immersed in a semiconducting-like
matrix. As possible origin of the superconductivity in graphite we discuss
interior-gap superconductivity when two very different electronic masses are
present.

###Dicke-like effect in spin-polarized transport through coupled quantum dots|Piotr Trocha,Józef Barnaś###

Dicke-like effect in spin-polarized transport through coupled quantum dots. Spin-dependent electronic transport through a quantum dot side-coupled to two
quantum dots and attached to ferromagnetic leads with collinear (parallel and
antiparallel) magnetizations is analyzed theoretically. The intra-dot Coulomb
correlations are taken into account, whereas the inter-dot ones are neglected.
Transport characteristics, i.e. conductance and tunnel magnetoresistance
associated with the magnetization rotation from parallel to antiparallel
configurations, are calculated by the noneqiulibrium Green function technique.
The Green functions are derived by the equation of motion method in the
Hartree-Fock approximation. The conductance spectra are shown to reveal
features similar to the Dicke resonance in atomic physics.

###Fractional microwave-induced resistance oscillations|I. A. Dmitriev,A. D. Mirlin,D. G. Polyakov###

Fractional microwave-induced resistance oscillations. We develop a systematic theory of microwave-induced oscillations in
magnetoresistivity of a 2D electron gas in the vicinity of fractional harmonics
of the cyclotron resonance, observed in recent experiments. We show that in the
limit of well-separated Landau levels the effect is dominated by the
multiphoton inelastic mechanism. At moderate magnetic field, two single-photon
mechanisms become important. One of them is due to resonant series of multiple
single-photon transitions, while the other originates from microwave-induced
sidebands in the density of states of disorder-broadened Landau levels.

###Evidence for Two Current Conduction in Iron|I. A. Campbell,A. Fert,A. R. Pomeroy###

Evidence for Two Current Conduction in Iron. Measurements of resistivities of dilute iron based alloys show strong
deviations from Matthiessen's rule. These deviations can be explained by a
model in which spin up and spin down electrons conduct in parallel. The results
are consistent with the theory of impurity shielding in these alloys. [This
1967 paper provides the first experimental demonstration of two current
conduction at low temperatures in a ferromagnetic metal. One direct consequence
of this property is the Giant Magnetoresistance discovered in 1988 by the
groups of Albert Fert and of Peter Gr\"unberg].

###Magnetic domain wall propagation in a submicron spin-valve stripe: influence of the pinned layer|J. Briones,F. Montaigne,Daniel Lacour,M. Hehn,M. J. Carey,J. R. Childress###

Magnetic domain wall propagation in a submicron spin-valve stripe: influence of the pinned layer. The propagation of a domain wall in a submicron ferromagnetic spin-valve
stripe is investigated using giant magnetoresistance. A notch in the stripe
efficiently traps an injected wall stopping the domain propagation. The authors
show that the magnetic field at which the wall is depinned displays a
stochastic nature. Moreover, the depinning statistics are significantly
different for head to head and tail-to-tail domain walls. This is attributed to
the dipolar field generated in the vicinity of the notch by the pinned layer of
the spin-valve.

###Broadband ferromagnetic resonance of Ni81Fe19 wires using a rectifying effect|A. Yamaguchi,K. Motoi,H. Miyajima,Y. Miyashita,Y. Sanada###

Broadband ferromagnetic resonance of Ni81Fe19 wires using a rectifying effect. The broadband ferromagnetic resonance measurement using the rectifying effect
of Ni81Fe19 wire has been investigated. One wire is deposited on the center
strip line of the coplanar waveguide (CPW) and the other one deposited between
two strip lines of CPW. The method is based on the detection of the
magnetoresistance oscillation due to the magnetization dynamics induced by the
radio frequency field. The magnetic field dependences of the resonance
frequency and the rectification spectrum are presented and analytically
interpreted on the standpoint of a uniform magnetization precession model.

###Quantum fluctuations in ultranarrow superconducting nanowires|M. Zgirski,K. -P. Riikonen,V. Touboltsev,K. Yu. Arutyunov###

Quantum fluctuations in ultranarrow superconducting nanowires. Progressive reduction of the effective diameter of a nanowire is applied to
trace evolution of the shape of superconducting transition $R(T)$ in
quasi-one-dimensional aluminum structures. In nanowires with effective diameter
$\leq$ 15 nm the $R(T)$ dependences are much wider than predicted by the model
of thermally activated phase slips. The effect can be explained by quantum
fluctuations of the order parameter. Negative magnetoresistance is observed in
the thinest samples. Experimental results are in reasonable agreement with
existing theoretical models. The effect should have a universal validity
indicating a breakdown of zero resistance state in a superconductor below a
certain scale.

###Electronic Conductivity Upturn of HOPG Contrast to Transport Properties of Polycrystal Graphite|Zhiming Wang,Feng Xu,Chao Lu,He Zhang,Qingyu Xu,Jinan Zhu###

Electronic Conductivity Upturn of HOPG Contrast to Transport Properties of Polycrystal Graphite. The transport properties of highly oriented pyrolitic graphite (HOPG) and
polycrystal graphite have been studied. The electric conductivity of HOPG is
several times larger than that of the polycrystal graphite. Along with the
large magnetoresistances (MR), the polycrystal graphite show the accordant
semiconductor-like character in a wide temperature (roughly range from 20K to
120K) under 0, 4, 8, 12 T applied magnetic field, while the
magnetic-field-induced metal-semiconductor-like transition was only found in
HOPG. The difference of transport properties originates from the Coulomb
interaction quasipartical in HOPG graphite layers in contrast with the grain
boundary scattering in the polycrystal graphite.

###Magnetocapacitive La0.6Sr0.4MnO3 0.7Pb(Mg0.33Nb0.67)O3 0.3PbTiO3 epitaxial heterostructures|Ayan Roy Chaudhuri,S. B. Krupanidhi,P. Mandal,A. Sundaresan###

Magnetocapacitive La0.6Sr0.4MnO3 0.7Pb(Mg0.33Nb0.67)O3 0.3PbTiO3 epitaxial heterostructures. Epitaxial heterostructures of La0.6Sr0.4MnO3 0.7Pb(Mg0.33Nb0.67)O3 0.3PbTiO3
were fabricated on LaNiO3 coated LaAlO3 (100) substrates by pulsed laser
ablation. Ferromagnetic and ferroelectric hysteresis established their
biferroic nature. Dielectric behviour studied under different magnetic fields
over a wide range of frequency and temperatures revealed that the capacitance
in these heterostructures varies with the applied magnetic field. Appearance of
magnetocapacitance and its dependence on magnetic fields, magnetic layer
thickness, temperature and frequency indicated a combined contribution of
strain mediated magnetoelectric coupling, magnetoresistance of the magnetic
layer and Maxwell Wagner effect on the observed properties.

###A Nuclear Magnetic Resonance Study on Rubrene-cobalt Nano-composites|Masashi Shiraishi,Haruka Kusai,Ryo Nouchi,Takayuki Nozaki,Teruya Shinjo,Yoshishige Suzuki,Makoto Yoshida,Masashi Takigawa###

A Nuclear Magnetic Resonance Study on Rubrene-cobalt Nano-composites. We implemented a nuclear magnetic resonance (NMR) study on rubrene(C42H28)-Co
nano-composites that exhibit an enhanced magnetoresistance (MR) ratio of 80%.
The 59Co NMR spin echo experiment enabled clarification of the hyperfine field
of Co at the interface between the ferromagnet and the molecules, which has not
been investigated for molecular spintronics. An enhanced hyperfine field of the
Co was observed in the rubrene-Co nano-composites, which may be related to the
enhancement of the MR ratio. This study demonstrates the importance of
microscopic investigation of the interface between molecules and ferromagnets
that governs spin-dependent transport in molecular spin devices.

###Unusual temperature dependence of the oxygen-isotope effect on the exchange-energy of $La_{1-x}Ca_xMnO_3$ at high temperatures|Guo-meng Zhao,John Mann###

Unusual temperature dependence of the oxygen-isotope effect on the exchange-energy of $La_{1-x}Ca_xMnO_3$ at high temperatures. We report magnetic susceptibility $\chi(T)$ measurements on oxygen-isotope
exchanged La$_{1-x}$Ca$_{x}$MnO$_{3+y}$ up to 700 K. The $1/\chi(T)$ data show
that the ferromagnetic exchange-energy $J$ depends strongly on the
oxygen-isotope mass. The isotope effect on $J$ decreases with temperature up to
400 K and then increases again with temperature above 400 K. This unusual
temperature dependence of the isotope effect cannot be explained by existing
theories of the colossal magnetoresistance effect for doped manganites. The
present results thus provide essential constraints on the physics of
manganites.

###Vanishing Hall Coefficient in the Extreme Quantum Limit in Photocarrier-Doped SrTiO3|Y. Kozuka,T. Susaki,H. Y. Hwang###

Vanishing Hall Coefficient in the Extreme Quantum Limit in Photocarrier-Doped SrTiO3. We have investigated the extreme quantum limit of photogenerated electrons in
quantum paraelectric SrTiO3. This regime is distinct from conventional
semiconductors, due to the large electron effective mass and large lattice
dielectric constant. At low temperature, the magnetoresistance and Hall
resistivity saturate at high magnetic field, deviating from conventional
behavior. As a result, the Hall coefficient vanishes on the scale of the ratio
of the Landau level splitting to the thermal energy, indicating the essential
role of lowest Landau level occupancy, as limited by thermal broadening.

###Magnetic states and spin-glass properties in Bi0.67Ca0.33MnO3: macroscopic ac measurements and neutron scattering|M. Giot,A. Pautrat,G. Andre,D. Saurel,M. Hervieu,J. Rodriguez-Carvajal###

Magnetic states and spin-glass properties in Bi0.67Ca0.33MnO3: macroscopic ac measurements and neutron scattering. We report on the magnetic properties of the manganite Bi_{1-x}Ca_{x}MnO_3
(x=0.33) at low temperature. The analysis of the field expansion of the ac
susceptibility and the observation of aging properties make clear that a spin
glass phase appears below T = 39K, in the presence of magnetic order. Neutron
scattering shows both magnetic Bragg scattering and magnetic diffusion at small
angles, and confirms this coexistence. In contrast to Pr_{1-x}Ca_{x}MnO_3
(x=0.3-0.33) which exhibits a mesoscopic phase separation responsible for a
field driven percolation, the glassy and short range ferromagnetic order
observed here does not cause colossal magnetoresistance (CMR).

###Magnetoresistance and spin-transfer torque in magnetic tunnel junctions|J. Z. Sun,D. C. Ralph###

Magnetoresistance and spin-transfer torque in magnetic tunnel junctions. We comment on both recent progress and lingering puzzles related to research
on magnetic tunnel junctions (MTJs). MTJs are already being used in
applications such as magnetic-field sensors in the read heads of disk drives,
and they may also be the first device geometry in which spin-torque effects are
applied to manipulate magnetic dynamics, in order to make nonvolatile magnetic
random access memory. However, there remain many unanswered questions about
such basic properties as the magnetoresistance of MTJs, how their properties
change as a function of tunnel-barrier thickness and applied bias, and what are
the magnitude and direction of the spin-transfer-torque vector induced by a
tunnel current.

###Huge tunnelling anisotropic magnetoresistance in (Ga,Mn)As nanoconstrictions|A. D. Giddings,O. N. Makarovsky,M. N. Khalid,S. Yasin,K. W. Edmonds,R. P. Campion,J. Wunderlich,T. Jungwirth,D. A. Williams,B. L. Gallagher,C. T. Foxon###

Huge tunnelling anisotropic magnetoresistance in (Ga,Mn)As nanoconstrictions. We report large anisotropic magnetoresistance (AMR) behaviours in single
lateral (Ga,Mn)As nanoconstriction of up to 1300%, along with large multistable
telegraphic switching. The nanoconstriction devices are fabricated using
high-resolution electron beam lithography of a 5 nm thick (Ga,Mn)As epilayer.
The unusual behaviour exhibited by these devices is discussed in the context of
existing theories for enhanced AMR ferromagnetic semiconductor nanoscale
devices, particularly with regard to the dependence on the magnetotransport of
the bulk material. We conclude that our results are most consistent with the
Coulomb blockade AMR mechanism.

###On the electronic structure of the charge-ordered phase in epitaxial and polycrystalline La1-xCaxMnO3 (x = 0.55, 0.67) perovskite manganites|Rainer Schmidt###

On the electronic structure of the charge-ordered phase in epitaxial and polycrystalline La1-xCaxMnO3 (x = 0.55, 0.67) perovskite manganites. In this work the charge transport properties of charge ordered (CO)
La1-xCaxMnO3 (LCMO) (x= 0.55, 0.67) epitaxial thin films and polycrystals are
discussed following the recent controversy of localised electron states vs.
weakly or de- localised charge density wave (CDW) states in CO manganites. The
transport properties were investigated by current vs. voltage, direct current
resistivity vs. temperature, local activation energy vs. temperature,
magnetoresistance and admittance spectroscopy measurements, which all indicated
a localised electronic structure in the single CO phase. Delocalised charge
anomalies observed previously may be restricted to phase separated materials.

###First Principle Noncollinear Transport Calculation and Interfacial Spin-flipping of Cu/Co Multilayers|Ling Tang,Shuai Wang###

First Principle Noncollinear Transport Calculation and Interfacial Spin-flipping of Cu/Co Multilayers. In this paper the first principle noncollinear transport calculation for
Cu/Co(111) including interfacial spin-flipping was performed. We modeled
spin-flipping at the interface by assuming a noncollinear magnetic structure
with random magnetization orientation which satisfied Gaussian distribution
along average magnetization direction. The relationship between spin-dependent
conductance including interfacial spin-flipping and random magnetization
orientation distribution width was obtained. For certain distribution width,
our defined spin-flipping ratio coincides with the range of experimental
spin-flipping probability $P=1-e^{-\delta}$, where $\delta=0.25\pm0.1$. The
magnetoresistance in Co/Cu/Co spin valve system including interfacial
spin-flipping has also been calculated.

###Quantized spin waves and perpendicular standing spin waves stimulated by current in a single-layered ferromagnetic wire|A. Yamaguchi,K. Motoi,H. Miyajima###

Quantized spin waves and perpendicular standing spin waves stimulated by current in a single-layered ferromagnetic wire. The rectifying effect of radio-frequency (RF) current is highly sensitive in
terms of the spatial spin distribution and dynamics. It emerged that an
additional spin wave mode was stimulated by the direct-current (DC) current and
that this spin wave was detectable via rectification of the RF current. A
phenomenological model to describe the time-dependent anisotropic
magnetoresistance or time-dependent planer Hall effect is proposed and found to
correlate well to the experimental results. The nonlinear spin dynamics
accompanying additional spin waves are studied as functions of the RF and DC
currents, the external magnetic field, and the applied field direction.

###Non-equilibrium Green's function based single-band tight-binding model for Fe-MgO-Fe magnetic tunnel junction devices|Tehseen Raza,Hassan Raza###

Non-equilibrium Green's function based single-band tight-binding model for Fe-MgO-Fe magnetic tunnel junction devices. Motivated by observation of very high tunnel magnetoresistance (TMR) in
Fe-MgO-Fe magnetic tunnel junction devices, we propose a theoretical model for
these devices based on a single-band tight-binding approximation. An effort is
made to capture the band dispersions over the two dimensional transverse
Brillouin zone. In the transport direction, spin dependent Hamiltonian is
prescribed for Delta_1 and Delta_5 bands. Non-equilibrium Green's function
formalism is then used to calculate transport. Features like voltage dependence
of TMR are captured quantitatively within this simple model and the trends
match well with the ones predicted by ab-initio methods and experiments.

###Non-linear magnetotransport in microwave-illuminated two-dimensional electron systems|A. T. Hatke,H. -S. Chiang,M. A. Zudov,L. N. Pfeiffer,K. W. West###

Non-linear magnetotransport in microwave-illuminated two-dimensional electron systems. We study magnetoresistivity oscillations in a high-mobility two-dimensional
electron system subject to both microwave and dc electric fields. First, we
observe that the oscillation amplitude is a periodic function of the inverse
magnetic field and is strongly suppressed at microwave frequencies near
half-integers of the cyclotron frequency. Second, we obtain a complete set of
conditions for the differential resistivity extrema and saddle points. These
findings indicate the importance of scattering without microwave absorption and
a special role played by microwave-induced scattering events antiparallel to
the electric field.

###Studies of Effects of Current on Exchange-Bias: A Brief Review|J. Bass,A. Sharma,Z. Wei,M. Tsoi###

Studies of Effects of Current on Exchange-Bias: A Brief Review. MacDonald and co-workers recently predicted that high current densities could
affect the magnetic order of antiferromagnetic (AFM) multilayers, in ways
similar to those that occur in ferromagnetic (F) multilayers, and that changes
in AFM magnetic order can produce an antiferromagnetic Giant Magnetoresistance
(AGMR). Four groups have now studied current-driven effects on exchange bias at
F/AFM interfaces. In this paper, we first briefly review the main predictions
by MacDonald and co-workers, and then the results of experiments on exchange
bias that these predictions stimulated.

###Current-induced domain-wall motion in synthetic antiferromagnets|D. Herranz,R. Guerrero,R. Villar,F. G. Aliev,A. C. Swaving,R. A. Duine,C. van Haesendonck,I. Vavra###

Current-induced domain-wall motion in synthetic antiferromagnets. Domain-wall magnetoresistance and low-frequency noise have been studied in
epitaxial antiferromagnetically-coupled [Fe/Cr(001)]_10 multilayers and
ferromagnetic Co line structures as a function of DC current intensity. In
[Fe/Cr(001)]_10 multilayers a transition from excess to suppressed domain-wall
induced 1/f noise above current densities of j_c ~ 2*10^5 A/cm^2 has been
observed. In ferromagnetic Co line structures the domain wall related noise
remains qualitatively unchanged up to current densities exceeding 10^6A/cm^2.
Theoretical estimates of the critical current density for a synthetic Fe/Cr
antiferromagnet suggest that this effect may be attributed to current-induced
domain-wall motion that occurs via spin transfer torques.

###Current induced resistance change of magnetic tunnel junctions with ultra-thin MgO tunnel barriers|Patryk Krzysteczko,Xinli Kou,Karsten Rott,Andy Thomas,Günter Reiss###

Current induced resistance change of magnetic tunnel junctions with ultra-thin MgO tunnel barriers. Ultra-thin magnetic tunnel junctions with low resistive MgO tunnel barriers
are prepared to examine their stability under large current stress. The devices
show magnetoresistance ratios of up to 110 % and an area resistance product of
down to 4.4 ohm micrometer squared. If a large current is applied, a reversible
resistance change is observed, which can be attributed to two different
processes during stressing and one relaxation process afterwards. Here, we
analyze the time dependence of the resistance and use a simple model to explain
the observed behavior. The explanation is further supported by numerical fits
to the data in order to quantify the timescales of the involved phenomena.

###High-output CPP-GMR sensor with synthetic-ferrimagnet free layer and enhanced spin-torque critical currents|M. J. Carey,Neil Smith,S. Maat,J. R. Childress###

High-output CPP-GMR sensor with synthetic-ferrimagnet free layer and enhanced spin-torque critical currents. It is shown that the maximum stable output of a CPP-GMR sensor is increased
significantly by using a synthetic ferrimagnet free layer, provided the
electron current flows from free layer to reference layer. This free layer
allows a larger magnetoresistance ratio for a given free layer magnetic moment,
and in addition results in a greater than three-fold increase in the critical
current above which spin-torque instability of the free layer occurs. In read
heads with net free layer moments equivalent to only 4.5nm of Ni80Fe20, this
effect is shown to result in sustainable sense current densities above 2e8
A/cm2.

###Correlation between extrinsic electroresistance and magnetoresistance in fine-grained La0.7Ca0.3MnO3|P. Sujatha Devi,A. Kumar,Dipten Bhattacharya,Shilpi Karmakar,B. K. Chaudhuri###

Correlation between extrinsic electroresistance and magnetoresistance in fine-grained La0.7Ca0.3MnO3. We report our observation of a correlation between the extrinsic
electroresistance (EER) and magnetoresistance (EMR) via grain size in
fine-grained La0.7Ca0.3MnO3. The nature of dependence of EER and EMR on grain
size (~0.2-1.0 micron) indicates that for finer grains with low-resistive
boundaries both of them follow similar trend whereas they differ for coarser
grains with high-resistive boundaries. This could be due to a crossover in the
mechanism of charge transport across the grain boundaries - from spin-depedent
scattering process to spin-polarized tunneling one - as a function of grain
size.

###Tunneling magnetoresistance of Fe/ZnSe (001) single- and double-barrier junctions as a function of interface structure|J. Peralta-Ramos,A. M. Llois###

Tunneling magnetoresistance of Fe/ZnSe (001) single- and double-barrier junctions as a function of interface structure. In this contribution, we calculate the spin-dependent ballistic and coherent
transport through epitaxial Fe/ZnSe (001) simple and double magnetic tunnel
junctions with two different interface terminations: Zn-terminated and
Se-terminated. The electronic structure of the junctions is modeled by a
second-nearest neighbors {\it spd} tight-binding Hamiltonian parametrized to
{\it ab initio} calculated band structures, while the conductances and the
tunneling magnetoresistance are calculated within Landauer's formalism. The
calculations are done at zero bias voltage and as a function of energy. We show
and discuss the influence of the interface structure on the spin-dependent
transport through simple and double tunnel junctions.

###Huge anisotropic magneto-resistance in iridium atomic chains|V. M. Garcia-Suarez,D. Zs. Manrique,C. J. Lambert,J. Ferrer###

Huge anisotropic magneto-resistance in iridium atomic chains. We analyze in this article the magneto-resistance ratio of finite and
infinite iridium and platinum chains. Our calculations, that are based on a
combination of non equilibrium Green function techniques and density functional
theory, include a fully self-consistent treatment of non-collinear magnetism
and of the spin-orbit interaction. They indicate that, in addition to having an
extremely large magnetic anisotropy that may overcome the super-paramagnetic
limit, infinite and also realistic finite-length iridium chains show sizeable
anisotropic magnetoresistance ratios. We therefore propose iridium
nanostructures as promising candidates for nanospintronics logic devices.

###Polaron formation in the optimally doped ferromagnetic manganites La0.7Ba0.3MnO3 and La0.7Ba0.3MnO3|Y. Chen,B. G. Ueland,J. W. Lynn,G. L. Bychkov,S. N. Barilo,Y. M. Mukovskii###

Polaron formation in the optimally doped ferromagnetic manganites La0.7Ba0.3MnO3 and La0.7Ba0.3MnO3. The nature of the polarons in the optimally doped colossal magnetoresistive
(CMR) materials La0.7Ba0.3MnO3 (LBMO) and La0.7Sr0.3MnO3 (LSMO) is studied by
elastic and inelastic neutron scattering. In both materials, dynamic nanoscale
polaron correlations develop abruptly in the ferromagnetic state. However, the
polarons are not able to lock-in to the lattice and order, in contrast to the
behavior of La0.7Ca0.3MnO3. Therefore ferromagnetic order in LBMO and LSMO
survives their formation, explaining the conventional second order nature of
the ferromagnetic--paramagnetic transition. Nevertheless, the results
demonstrate that the fundamental mechanism of polaron formation is a universal
feature of these ferromagnetic perovskite manganites.

###Analysis of the normal state magnetotransport in CeIrIn${_5}$|Sunil Nair,M. Nicklas,J. L. Sarrao,J. D. Thompson,F. Steglich,S. Wirth###

Analysis of the normal state magnetotransport in CeIrIn${_5}$. We present an analysis of the normal state magnetotransport in the heavy
fermion superconductor CeIrIn${_5}$. The Hall effect and the transverse
magnetoresistance in this material do not appear to be uniquely correlated, as
inferred from the field dependence of the current ratio ($R_{\sigma} =
\sigma_{xy} / \sigma_{xx}^2 H$). The Hall coefficient is seen to satisfy a
scaling equation of the form $R_H = f [H / (a + b T^c)]$. These results are
compared to those observed earlier in CeCoIn$_5$, and are discussed in terms of
the contrasting phase diagram which the CeIrIn$_5$ system exhibits in relation
to its Co counterpart.

###Interactions Between Mn_12-ac and Thin Gold Films: Using Mn_12-ac as Scattering Centers|Joel Means,Winfried Teizer###

Interactions Between Mn_12-ac and Thin Gold Films: Using Mn_12-ac as Scattering Centers. We explore the electronic interactions between a thin gold film and a surface
layer of the molecular magnet Mn_12-acetate. Magnetoresistance measurements of
the gold allow characterization of the interactions by comparison with the
theoretical predictions of weak localization. We find that the presence of
Mn_12-acetate on the surface of the gold film leads to a reduction in elastic
scattering while increasing the spin scattering of the conduction electrons.
This is the first experimental evidence of molecular magnets being used as
scattering centers for an adjacent metallic film.

###Itinerant Ferromagnetism in the electronic localization limit|N. Kurzweil,E. Kogan,A. Frydman###

Itinerant Ferromagnetism in the electronic localization limit. We present Hall effect, $R_{xy}(H)$, and magnetoresistance, $R_{xx}(H)$,
measurements of ultrathin films of Ni, Co and Fe with thicknesses varying
between 0.2-8 nm and resistances between 1 M$\Omega$ - 100 $\Omega.$ Both
measurements show that films having resistance above a critical value, $R_{C}$,
(thickness below a critical value, $d_{C}$) show no signs for ferromagnetism.
Ferromagnetism appears only for films with $R<R_{C}$, where $R_{C}$ is material
dependent. We raise the possibility that the reason for the absence of
spontaneous magnetization is suppression of itinerant ferromagnetism by
electronic disorder in the strong localization regime.

###Dual electronic states in thermoelectric cobalt oxide|Patrice Limelette,Sylvie Hebert,Herve Muguerra,Raymond Fresard,Charles Simon###

Dual electronic states in thermoelectric cobalt oxide. We investigate the low temperature magnetic field dependence of the
resistivity in the thermoelectric misfit cobalt oxide [Bi1.7Ca2O4]0.59CoO2 from
60 K down to 3 K. The scaling of the negative magnetoresistance demonstrates a
spin dependent transport mechanism due to a strong Hund's coupling. The
inferred microscopic description implies dual electronic states which explain
the coexistence between localized and itinerant electrons both contributing to
the thermopower. By shedding a new light on the electronic states which lead to
a high thermopower, this result likely provides a new potential way to optimize
the thermoelectric properties.

###Magnetoresistance scaling in the layered cobaltate Ca3Co4O9|P. Limelette,J. C. Soret,H. Muguerra,D. Grebille###

Magnetoresistance scaling in the layered cobaltate Ca3Co4O9. We investigate the low temperature magnetic field dependences of both the
resistivity and the magnetization in the misfit cobaltate Ca3Co4O9 from 60 K
down to 2 K. The measured negative magnetoresistance reveals a scaling behavior
with the magnetization which demonstrates a spin dependent diffusion mechanism.
This scaling is also found to be consistent with a shadowed metalliclike
conduction over the whole temperature range. By explaining the observed
transport crossover, this result shed a new light on the nature of the
elementary excitations relevant to the transport.

###Superconductivity induced by phosphorus doping and its coexistence with ferromagnetism in EuFe$_{2}$(As$_{0.7}$P$_{0.3}$)$_{2}$|Zhi Ren,Qian Tao,Shuai Jiang,Chunmu Feng,Cao Wang,Jianhui Dai,Guanghan Cao,Zhu'an Xu###

Superconductivity induced by phosphorus doping and its coexistence with ferromagnetism in EuFe$_{2}$(As$_{0.7}$P$_{0.3}$)$_{2}$. We have studied EuFe$_{2}$(As$_{0.7}$P$_{0.3}$)$_{2}$ by the measurements of
x-ray diffraction, electrical resistivity, thermopower, magnetic
susceptibility, magnetoresistance and specific heat. Partial substitution of As
with P results in the shrinkage of lattice, which generates chemical pressure
to the system. It is found that EuFe$_{2}$(As$_{0.7}$P$_{0.3}$)$_{2}$ undergoes
a superconducting transition at 26 K, followed by ferromagnetic ordering of
Eu$^{2+}$ moments at 20 K. This finding is the first observation of
superconductivity stabilized by internal chemical pressure, and supplies a rare
example showing coexistence of superconductivity and ferromagnetism in the
ferro-arsenide family.

###Possible Verification of Tilted Anisotropic Dirac Cone in α-(BEDT-TTF)_2 I_3 Using Interlayer Magnetoresistance|Takao Morinari,Takahiro Himura,Takami Tohyama###

Possible Verification of Tilted Anisotropic Dirac Cone in α-(BEDT-TTF)_2 I_3 Using Interlayer Magnetoresistance. It is proposed that the presence of a tilted and anisotropic Dirac cone can
be verified using the interlayer magnetoresistance in the layered Dirac fermion
system, which is realized in quasi-two-dimensional organic compound
\alpha-(BEDT-TTF)_2 I_3. Theoretical formula is derived using the analytic
Landau level wave functions and assuming local tunneling of electrons. It is
shown that the resistivity takes the maximum in the direction of the tilt if
anisotropy of the Fermi velocity of the Dirac cone is small. The procedure is
described to determine the parameters of the tilt and anisotropy.

###Anisotropic, Intermediate Coupling Superconductivity in Cu0.03TaS2|X. D. Zhu,Y. P. Sun,S. H. Zhang,J. L. Wang,L. J. Zou,L. E. Delong,G. Cao,X. B. Zhu,X. Luo,B. S. Wang,G. Li,Z. R. Yang,W. H. Song,J. M. Dai###

Anisotropic, Intermediate Coupling Superconductivity in Cu0.03TaS2. The anisotropic superconducting state properties in Cu0.03TaS2 have been
investigated by magnetization, magnetoresistance, and specific heat
measurements. It clearly shows that Cu0.03TaS2 undergoes a superconducting
transition at TC = 4.03 K. The obtained superconducting parameters demonstrate
that Cu0.03TaS2 is an anisotropic type-II superconductor. Combining specific
heat jump = 1.6(4), gap ratio 2/kBTC = 4.0(9) and the estimated electron-phonon
coupling constant ~ 0.68, the superconductivity in Cu0.03TaS2 is explained
within the intermediate coupling BCS scenario. First-principles electronic
structure calculations suggest that copper intercalation of 2H-TaS2 causes a
considerable increase of the Fermi surface volume and the carrier density,
which suppresses the CDW fluctuation and favors the raise of TC.

###Spin transport properties of a quantum dot coupled to ferromagnetic leads with noncollinear magnetizations|Hao Zhang,Guang-Ming Zhang,Lu Yu###

Spin transport properties of a quantum dot coupled to ferromagnetic leads with noncollinear magnetizations. A correct general formula for the spin current through an interacting quantum
dot coupled to ferromagnetic leads with magnetization at an arbitrary angle
$\theta$ is derived within the framework of the Keldysh formalism. Under
asymmetric conditions, the spin current component J_{z} may change sign for
$0<\theta<\pi$. It is shown that the spin current and spin tunneling
magnetoresistance exhibit different angle dependence in the free and Coulomb
blockade regimes. In the latter case, the competition of spin precession and
the spin-valve effect could lead to an anomaly in the angle dependence of the
spin current.

###Magnetic Field Induced Coherence-Incoherence Crossover in the Interlayer Conductivity of a Layered Organic Metal|M. V. Kartsovnik,P. D. Grigoriev,W. Biberacher,N. D. Kushch###

Magnetic Field Induced Coherence-Incoherence Crossover in the Interlayer Conductivity of a Layered Organic Metal. The angle-dependent interlayer magnetoresistance of the layered organic metal
$\alpha$-(BEDT-TTF)$_2$KHg(SCN)$_4$ is found to undergo a dramatic change from
the classical conventional behavior at low magnetic fields to an anomalous one
at high fields. This field-induced crossover and its dependence on the sample
purity and temperature imply the existence of two parallel channels in the
interlayer transport: a classical Boltzmann conductivity $\sigma_{c}$ and an
incoherent channel $\sigma_{i}$. We propose a simple model for $\sigma_{i}$
explaining its metallic temperature dependence and low sensitivity to the
inplane field component.

###Anisotropic magnetoresistance in ferromagnetic atomic-sized metal contacts|M. Häfner,J. K. Viljas,J. C. Cuevas###

Anisotropic magnetoresistance in ferromagnetic atomic-sized metal contacts. Recent experiments in ferromagnetic atomic-sized contacts have shown that the
anisotropic magnetoresistance (AMR) is greatly enhanced and has an asymmetric
angular dependence as compared with that of bulk samples. The origin of these
effects is still under debate. In this work we present a theoretical analysis
of the AMR in atomic contacts of the 3d ferromagnetic materials. Our results
strongly suggest that the anomalous AMR stems from the reduced symmetry of the
atomic contact geometries. We also present calculations supporting the idea
that the pronounced voltage- and temperature dependence in some experiments can
be attributed to impurities near the constrictions.

###Nonlinear transport and oscillating magnetoresistance in double quantum wells|N. C. Mamani,G. M. Gusev,O. E. Raichev,T. E. Lamas,A. K. Bakarov###

Nonlinear transport and oscillating magnetoresistance in double quantum wells. We study the evolution of low-temperature magnetoresistance in double quantum
wells in the region below 1 Tesla as the applied current density increases. A
flip of the magneto-intersubband oscillation peaks, which occurs as a result of
the current-induced inversion of the quantum component of resistivity, is
observed. We also see splitting of these peaks as another manifestation of
nonlinear behavior, specific for the two-subband electron systems. The
experimental results are quantitatively explained by the theory based on the
kinetic equation for the isotropic non-equilibrium part of electron
distribution function. The inelastic scattering time is determined from the
dependence of the inversion magnetic field on the current.

###Fermi Liquid Model of Radiation Induced Magnetoresistance Oscillations in GaAs/Al$_x$Ga$_{1-x}$As Heterostructure Two-Dimensional Electron System: Theoretical Evidence of an Electron Reservoir|Tadashi Toyoda###

Fermi Liquid Model of Radiation Induced Magnetoresistance Oscillations in GaAs/Al$_x$Ga$_{1-x}$As Heterostructure Two-Dimensional Electron System: Theoretical Evidence of an Electron Reservoir. The magnetoresistance oscillations in GaAs/Al$_x$Ga$_{1-x}$As
heterostructures induced by millimeterwave radiation recently observed by Zudov
et al. [Phys. Rev. B {\bf 64}, 201311 (2001)] is theoretically reproduced by
introducing a model based on the finite temperature Fermi liquid theory of dc
conductivity and the electron reservoir hypothesis. The obtained oscillation
patterns show excellent agreement with the experimental result by Zudov et al.
and are independent of the polarization of the radiation field in accordance
with the experimental observation by Smet et al. [Phys. Rev. Lett. {\bf 95},
116804 (2005)].

###Colossal electroresistance and colossal magnetoresistive step in paramagnetic insulating phase of single crystalline bilayered manganite(La$_{0.4}$Pr$_{0.6}$)$_{1.2}$Sr$_{1.8}$Mn$_{2}$O$_{7}$|Y. Yamato,M. Matsukawa,R. Suryanarayanan,S. Nimori,M. Apostu,A. Revcolevschi,K. Koyama,N. Kobayashi###

Colossal electroresistance and colossal magnetoresistive step in paramagnetic insulating phase of single crystalline bilayered manganite(La$_{0.4}$Pr$_{0.6}$)$_{1.2}$Sr$_{1.8}$Mn$_{2}$O$_{7}$. We report a significant decrease in the low-temperature resistance induced by
the application of an electric current on the $ab$-plane in the paramagnetic
insulating (PMI) state of
(La$_{0.4}$Pr$_{0.6}$)$_{1.2}$Sr$_{1.8}$Mn$_{2}$O$_{7}$. A colossal
electroresistance effect attaining -95% is observed at lower temperatures. A
colossal magnetoresistive step appears near 5T at low temperatures below 10K,
accompanied by an ultrasharp width of the insulator-metal transition. Injection
of higher currents to the crystal causes a disappearance of the steplike
transition. These findings have a close relationship with the presence of the
short-range charge-ordered clusters pinned within the PMI matrix of the crystal
studied.

###Tunnel Magnetoresistance of a Single-Molecule Junction|Alireza Saffarzadeh###

Tunnel Magnetoresistance of a Single-Molecule Junction. Based on the non-equilibrium Green's function (NEGF) technique and the
Landauer-B\"{u}ttiker theory, the possibility of a molecular spin-electronic
device, which consists of a single C$_{60}$ molecule attached to two
ferromagnetic electrodes with finite cross sections, is investigated. By
studying the coherent spin-dependent transport through the energy levels of the
molecule, it is shown that the tunnel magnetoresistance (TMR) of the molecular
junction depends on the applied voltages and the number of contact points
between the device electrodes and the molecule. The TMR values more than 60%
are obtained by adjusting the related parameters.

###Distinct Signatures For Coulomb Blockade and Aharonov-Bohm Interference in Electronic Fabry-Perot Interferometers|Yiming Zhang,D. T. McClure,E. M. Levenson-Falk,C. M. Marcus,L. N. Pfeiffer,K. W. West###

Distinct Signatures For Coulomb Blockade and Aharonov-Bohm Interference in Electronic Fabry-Perot Interferometers. Two distinct types of magnetoresistance oscillations are observed in two
electronic Fabry-Perot interferometers of different sizes in the integer
quantum Hall regime. Measuring these oscillations as a function of magnetic
field and gate voltages, we observe three signatures that distinguish the two
types. The oscillations observed in a 2.0 square micron device are understood
to arise from the Coulomb blockade mechanism, and those observed in an 18
square micron device from the Aharonov-Bohm mechanism. This work clarifies,
provides ways to distinguish, and demonstrates control over, these distinct
physical origins of resistance oscillations seen in electronic Fabry-Perot
interferometers.

###Possible Kondo effect in the iron arsenides|Jianhui Dai,Guanghan Cao,Hai-Hu Wen,Zhuan Xu###

Possible Kondo effect in the iron arsenides. The normal state of the iron arsenides shows the poor metallic behavior mixed
with strong magnetic fluctuations. In particular, some FeAs-1111 and FeAs-122
compounds show the linear-T dependence of susceptibility above the spin-density
wave (SDW) transition and the logarithmic upturn of resistivity at low
temperatures. We suggest that this is due to the spin-flip scattering between
the charge carriers and the local moments in the undoped FeAs layer where Kondo
effect coexists with the SDW. This scenario is also accounted for the change of
the magnetoresistance from positive to negative in the Sr3Sc2O5Fe2As2 compound.

###Magnetic Field Induced Superconductivity in Out-of-Equilibrium Nanowires|Yu Chen,S. Snyder,A. M. Goldman###

Magnetic Field Induced Superconductivity in Out-of-Equilibrium Nanowires. Four-terminal resistance measurements have been carried out on Zn nanowires
formed using electron-beam lithography. When driven resistive by current, these
wires re-enter the superconducting state upon application of small magnetic
fields. The data are qualitatively different from those of previous experiments
on superconducting nanowires, which revealed either negative magnetoresistance
near T_{c} or magnetic field enhanced critical currents. We suggest that our
observations are associated with the damping of phase slip processes by the
enhancement of dissipation by the quasiparticle conductance channel resulting
from the application of a magnetic field.

###Non-monotonic magnetoresistance of two-dimensional electron systems in the ballistic regime|A. Yu. Kuntsevich,G. M. Minkov,A. A. Sherstobitov,V. M. Pudalov###

Non-monotonic magnetoresistance of two-dimensional electron systems in the ballistic regime. We report experimental observations of a novel magnetoresistance (MR)
behavior of two-dimensional electron systems in perpendicular magnetic field in
the ballistic regime, for k_BT\tau/\hbar>1. The MR grows with field and
exhibits a maximum at fields B>1/\mu, where \mu is the electron mobility. As
temperature increases the magnitude of the maximum grows and its position moves
to higher fields. This effect is universal: it is observed in various Si- and
GaAs- based two-dimensional electron systems. We compared our data with recent
theory based on the Kohn anomaly modification in magnetic field, and found
qualitative similarities and discrepancies.

###Electron-Hole Asymmetry of Spin Injection and Transport in Single-Layer Graphene|Wei Han,W. H. Wang,K. Pi,K. M. McCreary,W. Bao,Yan Li,F. Miao,C. N. Lau,R. K. Kawakami###

Electron-Hole Asymmetry of Spin Injection and Transport in Single-Layer Graphene. Spin-dependent properties of single-layer graphene (SLG) have been studied by
non-local spin valve measurements at room temperature. Gate voltage dependence
shows that the non-local magnetoresistance (MR) is proportional to the
conductivity of the SLG, which is the predicted behavior for transparent
ferromagnetic/nonmagnetic contacts. While the electron and hole bands in SLG
are symmetric, gate voltage and bias dependence of the non-local MR reveal an
electron-hole asymmetry in which the non-local MR is roughly independent of
bias for electrons, but varies significantly with bias for holes.

###Competition and coexistence of antiferromagnetism and superconductivity in RBa_2Cu_3O_{6+x} (R = Lu, Y) single crystals|A. N. Lavrov,L. P. Kozeeva,M. R. Trunin,V. N. Zverev###

Competition and coexistence of antiferromagnetism and superconductivity in RBa_2Cu_3O_{6+x} (R = Lu, Y) single crystals. We use c-axis resistivity and magnetoresistance measurements to study the
interplay between antiferromagnetic (AF) and superconducting (SC) ordering in
underdoped RBa_2Cu_3O_{6+x} (R = Lu, Y) single crystals. Both orders are found
to emerge from an anisotropic 3D metallic state, upon which antiferromagnetism
opposes superconductivity by driving the doped holes towards localization.
Despite the competition, the superconductivity sets in before the AF order is
completely destroyed and coexists with latter in a certain range of hole
doping. We find also that strong magnetic fields affect the AF-SC interplay by
both suppressing the superconductivity and stabilizing the Neel order.

###Weak localization in monolayer and bilayer graphene|K. Kechedzhi,E. McCann,Vladimir I. Fal'ko,H. Suzuura,T. Ando,B. L. Altshuler###

Weak localization in monolayer and bilayer graphene. We describe the weak localization correction to conductivity in ultra-thin
graphene films, taking into account disorder scattering and the influence of
trigonal warping of the Fermi surface. A possible manifestation of the chiral
nature of electrons in the localization properties is hampered by trigonal
warping, resulting in a suppression of the weak anti-localization effect in
monolayer graphene and of weak localization in bilayer graphene. Intervalley
scattering due to atomically sharp scatterers in a realistic graphene sheet or
by edges in a narrow wire tends to restore weak localization resulting in
negative magnetoresistance in both materials.

###Structural stability, magnetic and electronic properties of Co2MnSi(001)/MgO heterostructures: A density functional theory study|B. Hülsen,M. Scheffler,P. Kratzer###

Structural stability, magnetic and electronic properties of Co2MnSi(001)/MgO heterostructures: A density functional theory study. A computational study of the epitaxial Co2MnSi(001)/MgO(001) interface
relevant to tunneling magnetoresistive (TMR) devices is presented. Employing ab
initio atomistic thermodynamics, we show that the Co- or MnSi-planes of
bulk-terminated Co2MnSi form stable interfaces, while pure Si or pure Mn
termination requires non-equilibrium conditions. Except for the pure Mn
interface, the half-metallic property of bulk Co2MnSi is disrupted by interface
bands. Even so, at homogeneous Mn or Co interfaces these bands contribute
little to the minority-spin conductance through an MgO barrier, and hence such
terminations could perform strongly in TMR devices.

###Proximity-induced superconductivity in nanowires: Mini-gap state and differential magnetoresistance oscillations|Jian Wang,Chuntai Shi,Mingliang Tian,Qi Zhang,Nitesh Kumar,J. K. Jain,T. E. Mallouk,M. H. W. Chan###

Proximity-induced superconductivity in nanowires: Mini-gap state and differential magnetoresistance oscillations. We study proximity-induced superconductivity in gold nanowires as a function
of the length of the nanowire, magnetic field, and excitation current. Short
nanowires exhibit a sharp superconducting transition, whereas long nanowires
show nonzero resistance. At intermediate lengths, however, we observe two sharp
transitions; the normal and superconducting regions are separated by what we
call the mini-gap phase. Additionally, we detect periodic oscillations in the
differential magnetoresistance. We provide a theoretical model for the mini-gap
phase as well as the periodic oscillations in terms of the coexistence of
proximity-induced superconductivity with a normal region near the center of the
wire, created either by temperature or application of a magnetic field.

###A high resolution, hard x-ray photoemission investigation of La_(2-2x)Sr_(1+2x)Mn_2O_7 (0.30<x<0.50): on microscopic phase separation and the surface electronic structure of a bilayered CMR manganite|S. de Jong,F. Massee,Y. Huang,M. Gorgoi,F. Schaefers,J. Fink,A. T. Boothroyd,D. Prabhakaran,J. B. Goedkoop,M. S. Golden###

A high resolution, hard x-ray photoemission investigation of La_(2-2x)Sr_(1+2x)Mn_2O_7 (0.30<x<0.50): on microscopic phase separation and the surface electronic structure of a bilayered CMR manganite. Photoemission data taken with hard x-ray radiation on cleaved single crystals
of the bilayered, colossal magnetoresistant manganite La_(2-2x)Sr_(1+2x)Mn_2O_7
(LSMO) with 0.30<x<0.50 are presented. Making use of the increased
bulk-sensitivity upon hard x-ray excitation it is shown that the core level
footprint of the electronic structure of the LSMO cleavage surface is identical
to that of the bulk. Furthermore, by comparing the core level shift of the
different elements as a function of doping level x, it is shown that
microscopic phase separation is unlikely to occur for this particular manganite
well above the Curie temperature.

###Aharonov-Bohm effect in a side-gated graphene ring|Magdalena Huefner,Françoise Molitor,Arnhild Jacobsen,Alessandro Pioda,Christoph Stampfer,Klaus Ensslin,Thomas Ihn###

Aharonov-Bohm effect in a side-gated graphene ring. We investigate the magnetoresistance of a side-gated ring structure etched
out of single-layer graphene. We observe Aharonov-Bohm oscillations with about
5% visibility. We are able to change the relative phases of the wave functions
in the interfering paths and induce phase jumps of pi in the Aharonov-Bohm
oscillations by changing the voltage applied to the side gate or the back gate.
The observed data can be well interpreted within existing models for 'dirty
metals' giving a phase coherence length of the order of 1 micrometer at a
temperature of 500mK.

###Strongly correlated Fermi-systems: non-Fermi liquid behavior, quasiparticle effective mass and their interplay|V. R. Shaginyan,M. Ya. Amusia,K. G. Popov###

Strongly correlated Fermi-systems: non-Fermi liquid behavior, quasiparticle effective mass and their interplay. Basing on the density functional theory of fermion condensation, we analyze
the non-Fermi liquid behavior of strongly correlated Fermi-systems such as
heavy-fermion metals. When deriving equations for the effective mass of
quasiparticles, we consider solids with a lattice and homogeneous systems. We
show that the low-temperature thermodynamic and transport properties are formed
by quasiparticles, while the dependence of the effective mass on temperature,
number density, magnetic fields, etc gives rise to the non-Fermi liquid
behavior. Our theoretical study of the heat capacity, magnetization, energy
scales, the longitudinal magnetoresistance and magnetic entropy are in good
agreement with the remarkable recent facts collected on the heavy-fermion metal
YbRh2Si2.

###Asymmetric field dependence of magnetoresistance in magnetic films|A. Segal,O. Shaya,M. Karpovski,A. Gerber###

Asymmetric field dependence of magnetoresistance in magnetic films. We study an asymmetric in field magnetoresistance that is frequently observed
in magnetic films and, in particular, the odd longitudinal voltage peaks that
appear during magnetization reversal in ferromagnetic films, with out-of-plane
magnetic anisotropy. We argue that the anomalous signals result from small
variation of magnetization and Hall resistivity along the sample. Experimental
data can be well described by a simple circuit model, the latter being
supported by analytic and numerical calculations of current and electric field
distribution in films with a gradual variation of the magnetization and Hall
resistance.

###Tunneling anisotropic magnetoresistance in Fe/GaAs/Au junctions: orbital effects|M. Wimmer,M. Lobenhofer,J. Moser,A. Matos-Abiague,D. Schuh,W. Wegscheider,J. Fabian,K. Richter,D. Weiss###

Tunneling anisotropic magnetoresistance in Fe/GaAs/Au junctions: orbital effects. We report experiments on epitaxially grown Fe/GaAs/Au tunnel junctions
demonstrating that the tunneling anisotropic magnetoresistance (TAMR) effect
can be controlled by a magnetic field. Theoretical modelling shows that the
interplay of the orbital effects of a magnetic field and the Dresselhaus
spin-orbit coupling in the GaAs barrier leads to an independent contribution to
the TAMR effect with uniaxial symmetry, whereas the Bychkov-Rashba spin-orbit
coupling does not play a role. The effect is intrinsic to barriers with bulk
inversion asymmetry.

###Green-Function-Based Monte Carlo Method for Classical Fields Coupled to Fermions|Alexander Weiße###

Green-Function-Based Monte Carlo Method for Classical Fields Coupled to Fermions. Microscopic models of classical degrees of freedom coupled to non-interacting
fermions occur in many different contexts. Prominent examples from solid state
physics are descriptions of colossal magnetoresistance manganites and diluted
magnetic semiconductors, or auxiliary field methods for correlated electron
systems. Monte Carlo simulations are vital for an understanding of such
systems, but notorious for requiring the solution of the fermion problem with
each change in the classical field configuration. We present an efficient,
truncation-free O(N) method on the basis of Chebyshev expanded local Green
functions, which allows us to simulate systems of unprecedented size N.

###Directional field-induced metallization of quasi-one-dimensional Li$_{0.9}$Mo$_6$O$_{17}$|X. Xu,A. F. Bangura,J. G. Analytis,J. D. Fletcher,M. M. J. French,N. Shannon,J. He,S. Zhang,D. Mandrus,R. Jin,N. E. Hussey###

Directional field-induced metallization of quasi-one-dimensional Li$_{0.9}$Mo$_6$O$_{17}$. We report a detailed magnetotransport study of the highly anisotropic
quasi-one-dimensional oxide Li$_{0.9}$Mo$_6$O$_{17}$ whose in-chain electrical
resistivity diverges below a temperature $T_{\rm min} \sim$ 25 K. For $T <
T_{\rm min}$, a magnetic field applied parallel to the conducting chain induces
a large negative magnetoresistance and ultimately, the recovery of a metallic
state. We show evidence that this insulator/metal crossover is a consequence of
field-induced suppression of a density-wave gap in a highly one-dimensional
conductor. At the highest fields studied, there is evidence for the possible
emergence of a novel superconducting state with an onset temperature $T_c >$ 10
K.

###Electrical Spin Injection into Silicon using MgO Tunnel Barrier|Tomoyuki Sasaki,Tohru Oikawa,Toshio Suzuki,Masashi Shiraishi,Yoshishige Suzuki,Katsumichi Tagami###

Electrical Spin Injection into Silicon using MgO Tunnel Barrier. We observed spin injection into silicon through Fe/MgO tunnel barrier by
using non-local magnetoresistance measurement technique. Fe/MgO tunnel barrier
contacts with a lateral spin valve structure were fabricated on phosphorous
doped silicon-on-insulator substrate. Spin injection signals in the non-local
scheme were observed up to 120K, which is the highest value where band
transferred spins in Si have ever been reported, and spin diffusion length was
estimated to be about 2.25um at 8K. Temperature dependence and injection
current dependence of the non-local voltage were also investigated. It is
clarified that MgO tunnel barrier is effective for the spin injection into
silicon.

###Hysteretic magnetoresistance in polymeric diodes|Sayani Majumdar,Himadri S. Majumdar,Harri Aarnio,Ronald Osterbacka###

Hysteretic magnetoresistance in polymeric diodes. We report on hysteretic organic magnetoresistance (OMAR) in polymeric diodes.
We found that magnitude and lineshape of OMAR depends strongly on the scan
speed of the magnetic field and on the time delay between two successive
measurements. The time-dependent OMAR phenomenon is universal for diodes made
with various polymers. However, the width and magnitude of OMAR varied with the
polymeric material. The suggestive reason for this hysteretic behavior are
trapped carriers, which in presence of a magnetic field changes the
ferromagnetic ground-state of the polymer leading to long spin relaxation time.
These experimental observations are significant for clarification of the OMAR
phenomenon.

###Electrical Detection of Spin Precession in Single Layer Graphene Spin Valves with Transparent Contacts|Wei Han,K. Pi,W. Bao,K. M. McCreary,Yan Li,W. H. Wang,C. N. Lau,R. K. Kawakami###

Electrical Detection of Spin Precession in Single Layer Graphene Spin Valves with Transparent Contacts. Spin accumulation and spin precession in single-layer graphene are studied by
non-local spin valve measurements at room temperature. The dependence of the
non-local magnetoresistance on electrode spacing is investigated and the
results indicate a spin diffusion length of ~1.6 microns and a spin
injection/detection efficiency of 0.013. Electrical detection of the spin
precession confirms that the non-local signal originates from spin injection
and transport. Fitting of the Hanle spin precession data yields a spin
relaxation time of ~84 ps and a spin diffusion length of ~1.5 microns, which is
consistent with the value obtained through the spacing dependence.

###Current-driven vortex oscillations in metallic nanocontacts: Zero-field oscillations and training effects|M. van Kampen,L. Lagae,G. Hrkac,T. Schrefl,Joo-Von Kim,T. Devolder,C. Chappert###

Current-driven vortex oscillations in metallic nanocontacts: Zero-field oscillations and training effects. We present an experimental and theoretical study of the low-field dynamics of
current-driven vortex oscillations in nanocontacts based on spin-valve
multilayers. These oscillations appear as low-frequency (250-500 MHz)
excitations in the electrical power spectrum which arise from to variations in
the giant-magnetoresistance. We show that the vortex oscillations, once
nucleated at large fields applied perpendicular to the film plane, persist at
zero applied magnetic fields. Some training effects on the oscillation
frequency and linewidth also observed for small in-plane magnetic fields.

###Fermi Surface Evolution in an Electron-Doped High-Tc Superconductor Revealed by Magnetic Quantum Oscillations|T. Helm,M. V. Kartsovnik,M. Bartkowiak,N. Bittner,M. Lambacher,A. Erb,J. Wosnitza,R. Gross###

Fermi Surface Evolution in an Electron-Doped High-Tc Superconductor Revealed by Magnetic Quantum Oscillations. We report on the direct probing of the Fermi surface in the bulk of the
electron-doped superconductor Nd$_{2-x}$Ce$_x$CuO$_4$ at different doping
levels by means of magnetoresistance quantum oscillations. Our data reveal a
sharp qualitative change in the Fermi surface topology, due to translational
symmetry breaking in the electronic system which occurs at a critical doping
level significantly exceeding the optimal doping. This result implies that the
$(\pi/a,\pi/a)$ ordering, known to exist at low doping levels, survives up to
the overdoped superconducting regime.

###Magnetism and magnetotransport in disordered graphene|T. G. Rappoport,Bruno Uchoa,A. H. Castro Neto###

Magnetism and magnetotransport in disordered graphene. We perform Monte Carlo simulations to study the interplay of structural and
magnetic order in single layer graphene covered with magnetic adatoms. We
propose that the presence of ripples in the graphene structure can lead to
clustering of the adatoms and to a variety of magnetic states such as
super-paramagnetism, antiferromagnetism, ferromagnetism and spin glass
behavior. We derive the magnetization hysteresis and also the magnetoresistance
curves in the variable range hopping regime, which can provide experimental
signatures for ripple induced clustering and magnetism. We propose that the
magnetic states in graphene can be controlled by gate voltage and coverage
fraction.

###Quantum criticality in Yb(Rh0.97Co0.03)2Si2 probed by low-temperature resistivity|Sven Friedemann,Niels Oeschler,Cornelius Krellner,Christoph Geibel,Frank Steglich###

Quantum criticality in Yb(Rh0.97Co0.03)2Si2 probed by low-temperature resistivity. Quantum criticality in Yb(Rh0.97Co0.03)2Si2 is investigated by means of
resistivity and magnetoresistance. The partial substitution of Co leads to a
stabilization of the magnetism as expected according to the application of
chemical pressure for Yb systems. However, the signature of the Kondo-breakdown
remains at the same position in the temperature-magnetic field phase diagram
compared to stoichiometric YbRh2Si2. As a consequence, the Kondo-breakdown is
situated within the antiferromagnetic phase. These results fit well within the
global phase diagram under chemical pressure [1].

###Robust coupling of superconducting order parameter in a mesoscale NbN-Fe-NbN epitaxial structure|S. K. Bose,R. C. Budhani###

Robust coupling of superconducting order parameter in a mesoscale NbN-Fe-NbN epitaxial structure. We report an unconventional and promising route to self-assemble distributed
superconductor-ferromagnet-superconductor (S-F-S) Josephson Junctions on single
crystal [100] MgO. These structures consist of [110] epitaxial nano-plaquettes
of Fe covered with superconducting NbN films of varying thickness. The S-F-S
structures are characterized by strong magnetoresistance (MR) anisotropy for
the in-plane and out-of-plane magnetic fields. The stronger in-plane MR
suggests decoherence of S-F-S junctions whose critical current follows a
(1-T/Tc) and (1-T/Tc)1/2 dependence for T Tc and T<<Tc respectively, in
accordance with the theory of supercurrent transport in such junctions.

###Anomalous magnetoresistance on the topological surface|Takehito Yokoyama,Yukio Tanaka,Naoto Nagaosa###

Anomalous magnetoresistance on the topological surface. We investigate charge transport in two-dimensional ferromagnet/feromagnet
junction on a topological insulator. The conductance across the interface
depends sensitively on the directions of the magnetizations of the two
ferromagnets, showing anomalous behaviors compared with the conventional
spin-valve. It is found that the conductance depends strongly on the in-plane
direction of the magnetization. Moreover, in sharp contrast to the conventional
magnetoresistance effect, in the p-n junction, the conductance at the parallel
configuration is much smaller than that at the antiparallel configuration. This
stems from the way how the wavefunctions connect between both sides.

###Top and side gated epitaxial graphene field effect transistors|Xuebin Li,Xiaosong Wu,Mike Sprinkle,Fan Ming,Ming Ruan,Yike Hu,Claire Berger,Walt A. de Heer###

Top and side gated epitaxial graphene field effect transistors. Three types of first generation epitaxial graphene field effect transistors
(FET) are presented and their relative merits are discussed. Graphene is
epitaxially grown on both the carbon and silicon faces of hexagonal silicon
carbide and patterned with electron beam lithography. The channels have a Hall
bar geometry to facilitate magnetoresistance measurements. FETs patterned on
the Si-face exhibit off-to-on channel resistance ratios that exceed 30. C-face
FETs have lower off-to-on resistance ratios, but their mobilities (up to 5000
cm2/Vs) are much larger than that for Si-face transistors. Initial
investigations into all-graphene side gate FET structures are promising.

###Spin-dependent transport in nanocomposite C:Co films|Shengqiang Zhou,Markus Berndt,Danilo Buerger,Viton Heera,Kay Potzger,Gintautas Abrasonis,Gyoergy Radnoczi,Gyoergy J. Kovacs,Andreas Kolitsch,Manfred Helm,Juergen Fassbender,Wolfhard Moeller,Heidemarie Schmidt###

Spin-dependent transport in nanocomposite C:Co films. The magneto-transport properties of nanocomposite C:Co (15 and 40 at.% Co)
thin films are investigated. The films were grown by ion beam co-sputtering on
thermally oxidized silicon substrates in the temperature range from 200 to 500
degC. Two major effects are reported: (i) a large anomalous Hall effect
amounting to 2 \mu ohm cm, and (ii) a negative magnetoresistance. Both the
field-dependent resistivity and Hall resistivity curves coincide with the
rescaled magnetization curves, a finding that is consistent with spin-dependent
transport. These findings suggest that C:Co nanocomposites are promising
candidates for carbon-based Hall sensors and spintronic devices.

###Mechanisms of the microwave photoconductivity in 2D electron systems with mixed disorder|I. A. Dmitriev,M. Khodas,A. D. Mirlin,D. G. Polyakov,M. G. Vavilov###

Mechanisms of the microwave photoconductivity in 2D electron systems with mixed disorder. We present a systematic study of the microwave-induced oscillations in the
magnetoresistance of a 2D electron gas for mixed disorder including both
short-range and long-range components. The obtained photoconductivity tensor
contains contributions of four distinct transport mechanisms. We show that the
photoresponse depends crucially on the relative weight of the short-range
component of disorder. Depending on the properties of disorder, the theory
allows one to identify the temperature range within which the photoresponse is
dominated by one of the mechanisms analyzed in the paper.

###Spinel ferrite nanocrystals embedded inside ZnO: magnetic, electronic and magneto-transport properties|Shengqiang Zhou,K. Potzger,Qingyu Xu,K. Kuepper,G. Talut,D. Marko,A. Muecklich,M. Helm,J. Fassbender,E. Arenholz,H. Schmidt###

Spinel ferrite nanocrystals embedded inside ZnO: magnetic, electronic and magneto-transport properties. In this paper we show that spinel ferrite nanocrystals (NiFe2O4, and CoFe2O4)
can be texturally embedded inside a ZnO matrix by ion implantation and
post-annealing. The two kinds of ferrites show different magnetic properties,
e.g. coercivity and magnetization. Anomalous Hall effect and positive
magnetoresistance have been observed. Our study suggests a
ferrimagnet/semiconductor hybrid system for potential applications in
magneto-electronics. This hybrid system can be tuned by selecting different
transition metal ions (from Mn to Zn) to obtain various magnetic and electronic
properties.

###Modeling Antiferromagnetic Phase in Iron Pnictides: Weakly Ordered State|E. Kaneshita,T. Morinari,T. Tohyama###

Modeling Antiferromagnetic Phase in Iron Pnictides: Weakly Ordered State. We examine electronic states of antiferromagnetic phase in iron pnictides by
mean-field calculations of the optical conductivity. We find that a five-band
model exhibiting a small magnetic moment, inconsistent with the
first-principles calculations, reproduces well the excitation spectra
characterized by a multi-peak structure emerging below the N\'{e}el temperature
at low energy, together with an almost temperature-independent structure at
high energy. Investigating the interlayer magnetoresistance for this model, we
also predict its characteristic field dependence reflecting the Fermi surface.

###A large magnetoinductance effect in La0.67Ba0.33MnO3|V. B. Naik,A. Rebello,R. Mahendiran###

A large magnetoinductance effect in La0.67Ba0.33MnO3. We report four probe impedance of La0.67Ba0.33MnO3 at f = 100 kHz under
different dc bias magnetic fields. The ac resistance (R) exhibits a peak around
Tp = 325 K which is accompanied by a rapid increase and a peak in the reactance
(X) in a zero field. The magnetoreactance exhibits a sharp peak close to Tp and
its magnitude (= 60% in H = 1 kG) exceeds that of the ac magnetoresistance (= 5
% inH = 1 kG). It is suggested that the magnetoreactance arises from changes in
the self inductance of the sample rather than the capacitance.

###Perfect spin-fillter and spin-valve in carbon atomic chains|M. G. Zeng,L. Shen,Y. Q. Cai,Z. D. Sha,Y. P. Feng###

Perfect spin-fillter and spin-valve in carbon atomic chains. We report ab initio calculations of spin-dependent transport in single atomic
carbon chains bridging two zigzag graphene nanoribbon electrodes. Our
calculations show that carbon atomic chains coupled to graphene electrodes are
perfect spin-filters with almost 100 % spin polarization. Moreover, carbon
atomic chains can also show a very large bias-dependent magnetoresistance up to
1000000 % as perfect spin-valves. These two spin-related properties are
independent on the length of carbon chains. Our report, the spin-filter and
spin-valve are conserved in a single device simultaneously, opens a new way to
the application of all-carbon composite spintronics.

###Nonvanishing anisotropic magnetoresistance in Rashba two-dimensional electron systems with nonmagnetic disorders|C. M. Wang,M. Q. Pang###

Nonvanishing anisotropic magnetoresistance in Rashba two-dimensional electron systems with nonmagnetic disorders. We study anisotropic magnetoresistance (AMR) in a spin-polarized
two-dimensional electron gas with Rashba spin-orbit coupling and nonmagnetic
disorder collision. We show that AMR exists, arising from the combined effect
of in-plane magnetization, spin-orbit coupling, and nonmagnetic remote disorder
scattering. Further, numerical evaluation demonstrates that the smoothness of
the remote disorder can strongly affect AMR, and this AMR is sensitive to the
electron density. Large magnitude of AMR ($\approx24%$) is obtained for low
density system with strong spin-orbit splitting.

###Anisotropy of the Spin Density Wave Onset for (TMTSF)_2PF_6 in Magnetic Field|Ya. A. Gerasimenko,V. A. Prudkoglyad,A. V. Kornilov,V. M. Pudalov,V. N. Zverev,A. -K. Klehe,J. S. Qualls###

Anisotropy of the Spin Density Wave Onset for (TMTSF)_2PF_6 in Magnetic Field. In order to study the spin density wave transition temperature (T_SDW) in
(TMTSF)_2PF_6 as a function of magnetic field, we measured the
magnetoresistance R_zz in fields up to 19 T. Measurements were performed for
three field orientations B||a, b' and c* at ambient pressure and at P = 5 kbar,
that is nearly the critical pressure. For B||c* orientation we observed
quadratic field dependence of T_SDW in agreement with theory and with previous
experiments. For B||b' and B||a orientations we have found no shift in T_SDW
within 0.05 K, both at P=0 and P=5 kbar. This result is also consistent with
theoretical predictions.

###In-plane electronic anisotropy in underdoped Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ revealed by detwinning in a magnetic field|Jiun-Haw Chu,James G. Analytis,David Press,Kristiaan De Greve,Thaddeus D. Ladd,Yoshihisa Yamamoto,Ian R. Fisher###

In-plane electronic anisotropy in underdoped Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ revealed by detwinning in a magnetic field. We present results of angle-dependent magnetoresistance measurements and
direct optical images of underdoped Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ which reveal
partial detwinning by action of a 14T magnetic field. Driven by a substantial
magneto-elastic coupling, this result provides evidence for an electronic
origin of the lattice distortion in underdoped iron pnictides. The observed
anisotropy in these partially detwinned samples implies a substantial in-plane
electronic anisotropy in the broken symmetry state, with a smaller resistivity
along the antiferromagnetic ordering direction.

###Pseudo Spin Valves Using a (112)-textured DO_22 MnGa Fixed Layer|C. L. Zha,R. K. Dumas,J. Persson,S. M. Mohseni,J. Nogués,Johan Åkerman###

Pseudo Spin Valves Using a (112)-textured DO_22 MnGa Fixed Layer. We demonstrate pseudo spin valves with a (112)-textured DO_22 MnGa (MnGa)
tilted magnetization fixed layer and an in-plane CoFe free layer. Single D0_22
MnGa films exhibit a small magnetoresistance (MR) typically observed in metals.
In MnGa/Cu/ CoFe spin valves a transition from a negative (-0.08%) to positive
(3.88%) MR is realized by introducing a thin spin polarizing CoFe insertion
layer at the MnGa/Cu interface and tailoring the MnGa thickness. Finally, the
exchange coupling between the MnGa and CoFe insertion layer is studied using a
first-order reversal curve (FORC) technique.

###Current driven discontinuous insulator-metal transition and colossal low-field magnetoresistance in Sm0.6Sr0.4MnO3|A. Rebello,R. Mahendiran###

Current driven discontinuous insulator-metal transition and colossal low-field magnetoresistance in Sm0.6Sr0.4MnO3. It is shown that with increasing magnitude of current (I), resistivity of
Sm0.6Sr0.4MnO3 transforms from a smooth to a discontinuous insulator-metal
transition which is also accompanied by an abrupt decrease in temperature of
the sample. We report colossal low-field magnetoresistance under a high current
bias (-99% at H = 0.5 T and 70 K) and electroresistance (-8000 % at H = 0 T and
60 K) for I = 11 mA. We interpret our observations in terms of current induced
supercooling of the high temperature paramagnetic phase and enlargement of
volume fraction of the ferromagnetic phase under a magnetic field.

###Magnetoresistance of a spin MOSFET with ferromagnetic MnAs source and drain contacts|Ryosho. Nakane,Tomoyuki Harada,Kuniaki Sugiura,Satoshi Sugahara,Masaaki Tanaka###

Magnetoresistance of a spin MOSFET with ferromagnetic MnAs source and drain contacts. Spin-dependent transport was investigated in a spin metal-oxide-semiconductor
field-effect transistors (spin MOSFET) with ferromagnetic MnAs source and drain
(S/D) contacts. The spin MOSFET of bottom-gate type was fabricated by
photolithography using an epitaxial MnAs film grown on a silicon-on-insulator
(SOI) substrate. In-plane magnetoresistance showed spin-valve-type hysteretic
behavior, when the measurements were performed with constant source-drain and
source-gate biases. By comparing with the magnetization-related resistance
change resulting from the MnAs contacts, we conclude that the spin-polarized
electrons are injected from the MnAs source into the Si MOS inversion channel,
and detected by the MnAs drain.

###Thermoelectrically Controlled Spin-Switch|S. Andersson,V. Korenivski###

Thermoelectrically Controlled Spin-Switch. The search for novel spintronic devices brings about new ways to control
switching in magnetic thin-films. In this work we experimentally demonstrate a
device based on thermoelectrically controlled exchange coupling. The read out
signal from a giant magnetoresistance element is controlled by exchange
coupling through a weakly ferromagnetic Ni-Cu alloy. This exchange coupling is
shown to vary strongly with changes in temperature, and both internal Joule
heating and external heating is used to demonstrate magnetic switching. The
device shows no degradation upon thermal cycling. Ways to further optimize the
device performance are discussed. Our experimental results show a new way to
thermoelectrically control magnetic switching in multilayers.

###Crossover between distinct mechanisms of microwave photoresistance in bilayer systems|S. Wiedmann,G. M. Gusev,O. E. Raichev,A. K. Bakarov,J. C. Portal###

Crossover between distinct mechanisms of microwave photoresistance in bilayer systems. We report on temperature-dependent magnetoresistance measurements in balanced
double quantum wells exposed to microwave irradiation for various frequencies.
We have found that the resistance oscillations are described by the
microwave-induced modification of electron distribution function limited by
inelastic scattering (inelastic mechanism), up to a temperature of T*~4 K. With
increasing temperature, a strong deviation of the oscillation amplitudes from
the behavior predicted by this mechanism is observed, presumably indicating a
crossover to another mechanism of microwave photoresistance, with similar
frequency dependence. Our analysis shows that this deviation cannot be fully
understood in terms of contribution from the mechanisms discussed in theory.

###Spin-Orbit Coupling and Anomalous Angular-Dependent Magnetoresistance in the Quantum Transport Regime of PbS|Kazuma Eto,A. A. Taskin,Kouji Segawa,Yoichi Ando###

Spin-Orbit Coupling and Anomalous Angular-Dependent Magnetoresistance in the Quantum Transport Regime of PbS. We measured magnetotransport properties of PbS single crystals which exhibit
the quantum linear magnetoresistance (MR) as well as the static skin effect
that creates a surface layer of additional conductivity. The Shubnikov-de Haas
oscillations in the longitudinal MR signify the peculiar role of spin-orbit
coupling. In the angular-dependent MR, sharp peaks are observed when the
magnetic field is slightly inclined from the longitudinal configuration, which
is totally unexpected for a system with nearly spherical Fermi surface and
points to an intricate interplay between the spin-orbit coupling and the
conducting surface layer in the quantum transport regime.

###Spin-torque driven magnetic vortex self-oscillations in perpendicular magnetic fields|G. Finocchio,V. S. Pribiag,L. Torres,R. A. Buhrman,B. Azzerboni###

Spin-torque driven magnetic vortex self-oscillations in perpendicular magnetic fields. We have employed complete micromagnetic simulations to analyze dc current
driven self-oscillations of a vortex core in a spin-valve nanopillar in a
perpendicular field by including the coupled effect of the spin-torque and the
magnetostatic field computed self-consistently for the entire spin-valve. The
vortex in the thicker nanomagnet moves along a quasi-elliptical trajectory that
expands with applied current, resulting in blue-shifting of the frequency,
while the magnetization of the thinner nanomagnet is non-uniform due to the
bias current. The simulations explain the experimental magnetoresistance-field
hysteresis loop and yield good agreement with the measured frequency vs.
current behavior of this spin-torque vortex oscillator.

###Signatures of pressure induced superconductivity in insulating Bi2212|T. Cuk,D. A. Zocco,H. Eisaki,V. Struzhkin,M. Grosche,M. B. Maple,Z. -X. Shen###

Signatures of pressure induced superconductivity in insulating Bi2212. We have performed several high pressure electrical resistance experiments on
Bi1.98Sr2.06Y0.68Cu2O8, an insulating parent compound of the high-Tc Bi2212
family of copper oxide superconductors. We find a resistive anomaly, a downturn
at low temperature, that onsets with applied pressure in the 20-40 kbar range.
Through both resistance and magnetoresistance measurements, we identify this
anomaly as a signature of induced superconductivity. Resistance to higher
pressures decreases Tc, giving a maximum of 10 K. The higher pressure
measurements exhibit a strong sensitivity to the hydrostaticity of the pressure
environment. We make comparisons to the pressure induced superconductivity now
ubiquitous in the iron arsenides.

###Colossal Electroresistance and Colossal Magnetoresistance in Spinel Multiferroic CdCr2S4|C. P. Sun,C. L. Huang,C. C. Lin,J. L. Her,C. J. Ho,J. -Y. Lin,H. Berger,H. D. Yang###

Colossal Electroresistance and Colossal Magnetoresistance in Spinel Multiferroic CdCr2S4. Colossal magnetoresistance (CMR) and electroresistance (CER) induced by the
electric field in spinel multiferroic CdCr2S4 are reported. It is found that a
metal-insulator transition (MIT) in CdCr2S4 is triggered by the electrical
field. In magnetic fields, the resistivity of CdCr2S4 responds similarly to
that of CMR manganites. Combing previous reports, these findings make CdCr2S4
the unique compound to possess all four properties of the colossal
magnetocapacitive (CMC), colossal electrocapacitive (CEC), CER, and CMR. The
present results open a new venue for searching new materials to show CMR by
tuning electric and magnetic fields.

###Spin polarized current and shot noise in carbon nanotube quantum dot in the Kondo regime|Stanislaw Lipinski,Damian Krychowski###

Spin polarized current and shot noise in carbon nanotube quantum dot in the Kondo regime. Using nonequilibrium Green functions and several complementary many-body
approximations we calculate shot noise and spin dependent conductance in carbon
nanotube semiconducting quantum dot in spin-orbital Kondo regime. We point out
on the possibility of reaching giant values of tunnel magnetoresistance in this
range and discuss a prospect of its gate control. We also analyze the influence
of symmetry breaking perturbations on the shot noise with special emphasis on
spin dependent effects. The gate and bias dependencies of noise Fano factors
influenced by magnetic field, polarization of electrodes and spin-flip
processes are presented.

###Temperature dependence of spin diffusion length in silicon by Hanle-type spin precession|T. Sasaki,T. Oikawa,T. Suzuki,M. Shiraishi,Y. Suzuki,K. Noguchi###

Temperature dependence of spin diffusion length in silicon by Hanle-type spin precession. The Hanle-type spin precession method was carried out associated with
non-local magnetoresistance measurement using a highly doped (5\times10^19)
silicon channel. The spin diffusion length obtained by the Hanle-method is in
good agreement with that by the gap dependence of non-local signals. We have
evaluated the interface and bulk channel effects separately, and it was
demonstrated that the major source of temperature dependence of non-local
signals originates from the spin polarization reduction at interface between
the tunnel barrier and silicon.

###Tunneling Spin Injection into Single Layer Graphene|Wei Han,K. Pi,K. M. McCreary,Yan Li,Jared J. I. Wong,A. G. Swartz,R. K. Kawakami###

Tunneling Spin Injection into Single Layer Graphene. We achieve tunneling spin injection from Co into single layer graphene (SLG)
using TiO2 seeded MgO barriers. A non-local magnetoresistance ({\Delta}RNL) of
130 {\Omega} is observed at room temperature, which is the largest value
observed in any material. Investigating {\Delta}RNL vs. SLG conductivity from
the transparent to the tunneling contact regimes demonstrates the contrasting
behaviors predicted by the drift-diffusion theory of spin transport.
Furthermore, tunnel barriers reduce the contact-induced spin relaxation and are
therefore important for future investigations of spin relaxation in graphene.

###Strong carrier-scattering in iron-pnictide superconductors with highest Tc obtained from charge transport experiments|S. Ishida,M. Nakajima,Y. Tomioka,T. Ito,K. Miyazawa,H. Kito,C. H. Lee,M. Ishikado,S. Shamoto,A. Iyo,H. Eisaki,K. M. Kojima,S. Uchida###

Strong carrier-scattering in iron-pnictide superconductors with highest Tc obtained from charge transport experiments. Characteristic normal-state charge transport is found in the oxygen-deficient
iron-arsenides LnFeAsO1-y (Ln: La and Nd) with the highest Tc's among known
Fe-based superconductors. The effect of "doping" in this system is mainly on
the carrier scattering, quite distinct from that in high-Tc cuprates. In the
superconducting regime of the La system with maximum Tc = 28 K, the
low-temperature resistivity is dominated by a T^2 term. On the other hand, in
the Nd system with Tc higher than 40 K, the carriers are subject to stronger
scattering showing T-linear resistivity and small magnetoresistance. Such
strong scattering appears crucial for high-Tc superconductivity in the
iron-based system.

###Comment on "Isoelectronic Ru substitution at Fe-site in Sm(Fe$_{1-x}$Ru$_x$)AsO$_{0.85}$F$_{0.15}$ compound and its effects on structural, superconducting and normal state properties" (arXiv:1004.1978)|Hiroshi Kontani,Masatoshi Sato###

Comment on "Isoelectronic Ru substitution at Fe-site in Sm(Fe$_{1-x}$Ru$_x$)AsO$_{0.85}$F$_{0.15}$ compound and its effects on structural, superconducting and normal state properties" (arXiv:1004.1978). Based on the five-orbital model, we derive the reduced impurity scattering
rate $g=z\gamma/2\pi T_{c0}$ in Sm(Fe$_{1-x}$Ru$_{x}$)AsO$_{0.85}$F$_{0.15}$
from the residual resistivity. At $x=0$, the transition temperature is
$T_{c0}=50$ K. For $0.05<x<0.36$ ($0.84>T_{c}/T_{c0}>0.3$) the obtained value
of $g$ ranges from 1.5 to 2.9, which suggests that the $s_\pm$-wave state
cannot survive. We point out that the magnetoresistance frequently gives an
underestimated value of $g$ in correlated electron systems.

###Metastable magnetization behavior in magnetocaloric R6Co1.67Si3 (R=Tb and Nd) compounds|Arabinda Haldar,Niraj K. Singh,K. G. Suresh,A. K. Nigam###

Metastable magnetization behavior in magnetocaloric R6Co1.67Si3 (R=Tb and Nd) compounds. Magnetic field and time induced steps have been observed in the recently
discovered ternary silicide R6Co1.67Si3. Huge relaxation steps are observed
across different loops in the low temperature magnetization isotherms. Giant
relaxation present in this system indicates the existence of incubation time to
get the saturated moment at a certain field. Measurement protocol sensitive
magnetization behavior observed in this system may arise from the strong
magnetostructural coupling and/or magnetic frustration. Electrical resistivity
and magnetoresistance also reflect the magnetic state of the compound.
Magnetocaloric effect is found to be large at temperatures close to the
magnetic transition temperature.

###Hall carrier density and magnetoresistance measurements in thin film vanadium dioxide across the metal-insulator transition|Dmitry Ruzmetov,Don Heiman,Bruce B. Claflin,Venkatesh Narayanamurti,Shriram Ramanathan###

Hall carrier density and magnetoresistance measurements in thin film vanadium dioxide across the metal-insulator transition. Temperature dependent magneto-transport measurements in magnetic fields of up
to 12 Tesla were performed on thin film vanadium dioxide (VO2) across the
metal-insulator transition (MIT). The Hall carrier density increases by 4
orders of magnitude at the MIT and accounts almost entirely for the resistance
change. The Hall mobility varies little across the MIT and remains low,
~0.1cm2/V sec. Electrons are found to be the major carriers on both sides of
the MIT. Small positive magnetoresistance in the semiconducting phase is
measured.

###A theory for magnetic-field effects of nonmagnetic organic semiconducting materials (Revised)|X. R. Wang,S. J. Xie###

A theory for magnetic-field effects of nonmagnetic organic semiconducting materials (Revised). A universal mechanism for strong magnetic-field effects of nonmagnetic
organic semiconductors is presented. A weak magnetic field (less than hundreds
mT) can substantially change the charge carrier hopping coefficient between two
neighboring organic molecules when the two hopping states are not too
symmetric. Under the illumination of lights or under a high electric field, the
change of hopping coefficients leads also to the change of polaron density so
that photocurrent, photoluminescence, electroluminescence, magnetoresistance
and electrical-injection current become sensitive to a weak magnetic field. The
present theory can not only explain all observed features, but also provide a
solid theoretical basis for the widely used empirical fitting formulas.

###Observation and Simulation of All Angular Magnetoresistance Oscillation Effects in the Quasi-One Dimensional Organic Conductor (DMET)2I3|Pashupati Dhakal,Harukazu Yoshino,Jeong Il Oh,Koichi Kikuchi,Michael J. Naughton###

Observation and Simulation of All Angular Magnetoresistance Oscillation Effects in the Quasi-One Dimensional Organic Conductor (DMET)2I3. Measurements and calculations of magnetotransport in the molecular organic
conductor (DMET)2I3 detect and simulate all known angular magnetoresistance
oscillation (AMRO) phenomena for quasi-one dimensional (Q1D) systems. Employing
the true triclinic crystal structure in the calculations, these results address
the mystery of the putative vanishing of the primary AMRO phenomenon, the Lebed
magic angle effect, for orientations in which it was expected to be strongest.
They also show a common origin for Lebed and so-called "LN" oscillations, and
confirm the generalized nature of AMRO in Q1D systems.

###Strongly suppressed 1/f noise and enhanced magnetoresistance in epitaxial Fe-V/MgO/Fe magnetic tunnel junctions|D. Herranz,F. Bonell,A. Gomez-Ibarlucea,S. Andrieu,F. Montaigne,R. Villar1,C. Tiusan,F. G. Aliev###

Strongly suppressed 1/f noise and enhanced magnetoresistance in epitaxial Fe-V/MgO/Fe magnetic tunnel junctions. Alloying Fe electrodes with V, through reduced FeV/MgO interface mismatch in
epitaxial magnetic tunnel junctions with MgO barriers, notably suppresses both
nonmagnetic (parallel) and magnetic (antiparallel) state 1/f noise and enhances
tunnelling magnetoresistance (TMR). A comparative study of the room temperature
electron transport and low frequency noise in Fe1-xVx/MgO/Fe and Fe/MgO/Fe1-xVx
MTJs with 0 <= x <= 0.25 reveals that V doping of the bottom electrode for x <
0.1 reduces in nearly 2 orders of magnitude the normalized nonmagnetic and
magnetic 1/f noise. We attribute the enhanced TMR and suppressed 1/f noise to
strongly reduced misfit and dislocation density.

###Tunneling Spin Injection into Single Layer Graphene (Supplementary Information)|Wei Han,K. Pi,K. M. McCreary,Yan Li,Jared J. I. Wong,A. G. Swartz,R. K. Kawakami###

Tunneling Spin Injection into Single Layer Graphene (Supplementary Information). We achieve tunneling spin injection from Co into single layer graphene (SLG)
using TiO2 seeded MgO barriers. A non-local magnetoresistance ({\Delta}RNL) of
130 {\Omega} is observed at room temperature, which is the largest value
observed in any material. Investigating {\Delta}RNL vs. SLG conductivity from
the transparent to the tunneling contact regimes demonstrates the contrasting
behaviors predicted by the drift-diffusion theory of spin transport.
Furthermore, tunnel barriers reduce the contact-induced spin relaxation and are
therefore important for future investigations of spin relaxation in graphene.

###Magnetic Breakdown in the electron-doped cuprate superconductor Nd$_{2-x}$Ce$_x$CuO$_4$: the reconstructed Fermi surface survives in the strongly overdoped regime|T. Helm,M. V. Kartsovnik,I. Sheikin,M. Bartkowiak,F. Wolff-Fabris,N. Bittner,W. Biberacher,M. Lambacher,A. Erb,J. Wosnitza,R. Gross###

Magnetic Breakdown in the electron-doped cuprate superconductor Nd$_{2-x}$Ce$_x$CuO$_4$: the reconstructed Fermi surface survives in the strongly overdoped regime. We report on semiclassical angle-dependent magnetoresistance oscillations
(AMRO) and the Shubnikov-de Haas effect in the electron-overdoped cuprate
superconductor Nd$_{2-x}$Ce$_x$CuO$_4$. Our data provide convincing evidence
for magnetic breakdown in the system. This shows that a reconstructed
multiply-connected Fermi surface persists, at least at strong magnetic fields,
up to the highest doping level of the superconducting regime. Our results
suggest an intimate relation between translational symmetry breaking and the
superconducting pairing in the electron-doped cuprate superconductors.

###Unification Theory of Angular Magnetoresistance Oscillations in Quasi-One-Dimensional Conductors|Si Wu,A. G. Lebed###

Unification Theory of Angular Magnetoresistance Oscillations in Quasi-One-Dimensional Conductors. We present a unification theory of angular magnetoresistance oscillations,
experimentally observed in quasi-one-dimensional organic conductors, by solving
the Boltzmann kinetic equation in the extended Brillouin zone. We find that, at
commensurate directions of a magnetic field, resistivity exhibits strong
minima. In two limiting cases, our general solution reduces to the results,
previously obtained for the Lebed Magic Angles and Lee-Naughton-Lebed
oscillations. We demonstrate that our theoretical results are in good
qualitative and quantitative agreement with the existing measurements of
resistivity in (TMTSF)$_2$ClO$_4$ conductor.

###Two distinct quasiparticle inelastic scattering rates in the $t-J$ model and their relevance for high-$T_c$ cuprates superconductors|Guillermo Buzon,Andrés Greco###

Two distinct quasiparticle inelastic scattering rates in the $t-J$ model and their relevance for high-$T_c$ cuprates superconductors. The recent findings about two distinct quasiparticle inelastic scattering
rates in angle-dependent magnetoresistance (ADMR) experiments in overdoped
high-$T_c$ cuprates superconductors have motivated many discussions related to
the link between superconductivity, pseudogap, and transport properties in
these materials. After computing dynamical self-energy corrections in the
framework of the $t-J$ model the inelastic scattering rate was introduced as
usual. Two distinct scattering rates were obtained showing the main features
observed in ADMR experiments. Predictions for underdoped cuprates are
discussed. The implicances of these two scattering rates on the resistivity
were also studied as a function of doping and temperature and confronted with
experimental measurements.

###Additional Evidence for the Surface Origin of the Peculiar Angular-Dependent Magnetoresistance Oscillations Discovered in a Topological Insulator Bi_{1-x}Sb_{x}|A. A. Taskin,Kouji Segawa,Yoichi Ando###

Additional Evidence for the Surface Origin of the Peculiar Angular-Dependent Magnetoresistance Oscillations Discovered in a Topological Insulator Bi_{1-x}Sb_{x}. We present detailed data on the unusual angular-dependent magnetoresistance
oscillation phenomenon recently discovered in a topological insulator
Bi_{0.91}Sb_{0.09}. Direct comparison of the data taken before and after
etching the sample surface gives compelling evidence that this phenomenon is
essentially originating from a surface state. The symmetry of the oscillations
suggests that it probably comes from the (111) plane, and obviously a new
mechanism, such as a coupling between the surface and the bulk states, is
responsible for this intriguing phenomenon in topological insulators.

###Origin of the hysteresis in bilayer 2D systems in the quantum Hall regime|L. H. Ho,L. J. Taskinen,A. P. Micolich,A. R. Hamilton,P. Atkinson,D. A. Ritchie###

Origin of the hysteresis in bilayer 2D systems in the quantum Hall regime. The hysteresis observed in the magnetoresistance of bilayer 2D systems in the
quantum Hall regime is generally attributed to the long time constant for
charge transfer between the 2D systems due to the very low conductivity of the
quantum Hall bulk states. We report electrometry measurements of a bilayer 2D
system that demonstrate that the hysteresis is instead due to non-equilibrium
induced current. This finding is consistent with magnetometry and electrometry
measurements of single 2D systems, and has important ramifications for
understanding hysteresis in bilayer 2D systems.

###Large bias-dependent magnetoresistance in all-oxide magnetic tunnel junctions with a ferroelectric barrier|Nuala M. Caffrey,Thomas Archer,Ivan Rungger,Stefano Sanvito###

Large bias-dependent magnetoresistance in all-oxide magnetic tunnel junctions with a ferroelectric barrier. All-oxide magnetic tunnel junctions (MTJs) incorporating functional materials
as insulating barriers have the potential of becoming the founding technology
for novel multi-functional devices. We investigate, by first-principles density
functional theory, the bias-dependent transport properties of an all-oxide
SrRuO3/BaTiO3/SrRuO3 MTJ. This incorporates a BaTiO3 barrier which can be found
either in a non-ferroic or in a ferroelectric state. In such an MTJ not only
can the tunneling magnetoresistance reach enormous values, but also, for
certain voltages, its sign can be changed by altering the barrier electric
state. These findings pave the way for a new generation of
electrically-controlled magnetic sensors.

###Single-ion anisotropy, Dzyaloshinskii-Moriya interaction and negative magnetoresistance of the spin-1/2 pyrochlores R2V2O7|H. J. Xiang,E. J. Kan,M. -H. Whangbo,C. Lee,Su-Huai Wei,X. G. Gong###

Single-ion anisotropy, Dzyaloshinskii-Moriya interaction and negative magnetoresistance of the spin-1/2 pyrochlores R2V2O7. The electronic and magnetic properties of spin-1/2 pyrochlores R2V2O7 were
investigated on the basis of density-functional calculations. Contrary to the
common belief, the spin-1/2 V4+ ions are found to have a substantial easy-axis
single-ion anisotropy. The |D/J| ratio deduced from the magnon quantum Hall
effect of Lu2V2O7, where J is the nearest-neighbor spin exchange and D is the
Dzyaloshinskii-Moriya parameter, is much greater than the value estimated from
our calculations (i.e., 0.32 vs. 0.05). We show that this discrepancy is due to
the neglect of the single-ion anisotropy of the V4+ ions, and the negative
magnetoresistance observed for R2V2O7 arises from a new mechanism.

###Interplay of the Kondo Effect and Spin-Polarized Transport in Magnetic Molecules, Adatoms and Quantum Dots|Maciej Misiorny,Ireneusz Weymann,Jozef Barnas###

Interplay of the Kondo Effect and Spin-Polarized Transport in Magnetic Molecules, Adatoms and Quantum Dots. We study the interplay of the Kondo effect and spin-polarized tunneling in a
class of systems exhibiting uniaxial magnetic anisotropy, such as magnetic
molecules, magnetic adatoms, or quantum dots coupled to a single localized
magnetic moment. Using the numerical renormalization group method we calculate
the spectral functions and linear conductance in the Kondo regime. We show that
the exchange coupling between conducting electrons and localized magnetic core
generally leads to suppression of the Kondo effect. We also predict a
nontrivial dependence of the tunnel magnetoresistance on the strength of
exchange coupling and on the anisotropy constant.

###Field-tunable stochasticity in the magnetization reversal of a cylindrical nanomagnet|Soumik Mukhopadhyay,Amrita Singh,Arindam Ghosh###

Field-tunable stochasticity in the magnetization reversal of a cylindrical nanomagnet. The nature of magnetization reversal in an isolated cylindrical nanomagnet
has been studied employing time-resolved magnetoresistance measurement. We find
that the reversal mode is highly stochastic, occurring either by multimode or
single-step switching. Intriguingly, the stochasticity was found to depend on
the alignment of the driving magnetic field to the long axis of the nanowires,
where predominantly multimode switching gives way to single-step switching
behavior as the field direction is rotated from parallel to transverse with
respect to the nanowire axis.

###Quasi-Two-Dimensional Fermi Surfaces and Coherent Interlayer Transport in KFe$_2$As$_2$|M. Kimata,T. Terashima,N. Kurita,H. Satsukawa,A. Harada,K. Kodama,A. Sato,M. Imai,K. Kihou,C. H. Lee,H. Kito,H. Eisaki,A. Iyo,T. Saito,H. Fukazawa,Y. Kohori,H. Harima,S. Uji###

Quasi-Two-Dimensional Fermi Surfaces and Coherent Interlayer Transport in KFe$_2$As$_2$. We report the results of the angular-dependent magnetoresistance oscillations
(AMROs), which can determine the shape of bulk Fermi surfaces in
quasi-two-dimensional (Q2D) systems, in a highly hole-doped Fe-based
superconductor KFe$_2$As$_2$ with $T_c \approx$ 3.7 K. From the AMROs, we
determined the two Q2D FSs with rounded-square cross sections, corresponding to
12% and 17% of the first Brillouin zone. The rounded-squared shape of the FS
cross section is also confirmed by the analyses of the interlayer transport
under in-plane fields. From the obtained FS shape, we infer the character of
the 3d orbitals that contribute to the FSs.

###Nonlinear growth with the microwave intensity in radiation-induced magnetoresistance oscillations|R. G. Mani,C. Gerl,S. Schmult,W. Wegscheider,V. Umansky###

Nonlinear growth with the microwave intensity in radiation-induced magnetoresistance oscillations. We report the observation of inverse-magnetic-field-periodic,
radiation-induced magnetoresistance oscillations in GaAs/AlGaAs
heterostructures prepared in W. Wegscheider's group, compare their
characteristics with similar oscillations in V. Umansky's material, and
describe the lineshape variation vs. the radiation power, $P$, in the two
systems. We find that the radiation-induced oscillatory $\Delta R_{xx}$, in
both materials, can be described by $\Delta R_{xx} = -A exp(-\lambda/B)sin(2
\pi F/B)$, where $A$ is the amplitude, $\lambda$ is the damping parameter, and
$F$ is the oscillation frequency. Both $\lambda$ and $F$ turn out to be
insensitive to $P$. On the other hand, $A$ grows nonlinearly with $P$.

###First Observation of Quantum Oscillations in the Ferromagnetic Superconductor UCoGe|Dai Aoki,Ilya Sheikin,Tatsuma D. Matsuda,Valentin Taufour,Georg Knebel,Jacques Flouquet###

First Observation of Quantum Oscillations in the Ferromagnetic Superconductor UCoGe. We succeeded in growing high quality single crystals of the ferromagnetic
superconductor UCoGe and measured the magnetoresistance at fields up to 34T.
The Shubnikov-de Haas signal was observed for the first time in a U-111 system
(UTGe, UTSi, T: transition metal). A small pocket Fermi surface (F~1kT) with
large cyclotron effective mass 25m0 was detected at high fields above 22T,
implying that UCoGe is a low carrier system accompanyed with heavy
quasi-particles. The observed frequency decreases with increasing fields,
indicating that the volume of detected Fermi surface changes nonlinearly with
field. The cyclotron mass also decreases, which is consistent with the decrease
of the A coefficient of resistivity.

###Intricacies of Strain and Magnetic Field Induced Charge Order Melting in Pr0.5Ca0.5MnO3 Thin Films|Dipak Kumar Baisnab,T. Geetha Kumary,A. T. Satya,Awadhesh Mani,J. Janaki,R. Nithya,L. S. Vaidhyanathan,M. P. Janawadkar,A. Bharathi###

Intricacies of Strain and Magnetic Field Induced Charge Order Melting in Pr0.5Ca0.5MnO3 Thin Films. Thin films of the half doped manganite Pr0.5Ca0.5MnO3 were grown on (100)
oriented MgO substrates by pulsed laser deposition technique. In order to study
the effect of strain on the magnetic field induced charge order melting, films
of different thicknesses were prepared and their properties were studied by
x-ray diffraction, electrical resistivity and magnetoresistance measurements. A
field induced charge order melting is observed for films with very small
thicknesses. The charge order transition temperature and the magnetic filed
induced charge order melting are observed to depend on the nature of strain
that is experienced by the film.

###Sub-linear radiation power dependence of photo-excited resistance oscillations in two-dimensional electron systems|Jesus Inarrea,R. G. Mani,W. Wegscheider###

Sub-linear radiation power dependence of photo-excited resistance oscillations in two-dimensional electron systems. We find that the amplitude of the $R_{xx}$ radiation-induced
magnetoresistance oscillations in GaAs/AlGaAs system grows nonlinearly as $A
\propto P^{\alpha}$ where $A$ is the amplitude and the exponent $\alpha < 1$.
%, with $\alpha \rightarrow 1/2$ in %the low temperature limit. This striking
result can be explained with the radiation-driven electron orbits model, which
suggests that the amplitude of resistance oscillations depends linearly on the
radiation electric field, and therefore on the square root of the power, $P$.
We also study how this sub-linear power law varies with lattice temperature and
radiation frequency.

###Magnetoresistivity and Acoustoelectronic Effects in a Tilted Magnetic Field in $p$-Si/SiGe/Si Structures with an Anisotropic $g$ Factor|I. L. Drichko,I. Yu. Smirnov,A. V. Suslov,O. A. Mironov,D. R. Leadley###

Magnetoresistivity and Acoustoelectronic Effects in a Tilted Magnetic Field in $p$-Si/SiGe/Si Structures with an Anisotropic $g$ Factor. Magnetoresistivity $\rho _{xx}$ and $\rho _{xy}$ and the acoustoelectronic
effects are measured in $p$-Si/SiGe/Si with an impurity concentration $p$ = 2
$\times $ 10$^{11}$ cm$^{-2}$ in the temperature range 0.3-2.0 K and an tilted
magnetic field up to 18 T. The dependence of the effective $g$-factor on the
angle of magnetic field tilt $\theta $ to the normal to the plane of a two
dimensional $p$-Si/SiGe/Si channel is determined. A first order
ferromagnet-paramagnet phase transition is observed in the magnetic fields
corresponding to a filling factor $\nu $ = 2 at $\theta \approx $
59$^\textrm{o}$-60$^\textrm{o}$.

###Magneto-transport of large CVD-grown graphene|Eric Whiteway,Victor Yu,Josianne Lefebvre,Robert Gagnon,Michael Hilke###

Magneto-transport of large CVD-grown graphene. We present magnetoresistance measurements on large scale monolayer graphene
grown by chemical vapor deposition (CVD) on copper. The graphene layer was
transferred onto SiO2/Si via PMMA and thermal release tape for transport
measurements. The resulting centimeter-sized graphene samples were measured at
temperatures down to 30mK in a magnetic field. We observe a very sharp peak in
resistance at zero field, which is well fitted by weak localization theory. The
samples exhibit conductance fluctuations symmetric in field, which are
attributed to ensemble averaged conductance fluctuations due to large scale
inhomogeneities consistent with the grain boundaries of copper during the CVD
growth.

###Weak field magnetoresistance of narrow-gap semiconductor InSb|R. Yang,K. H. Gao,Y. H. Zhang,P. P. Chen,G. Yu,L. M. Wei,T. Lin,N. Dai,J. H. Chu###

Weak field magnetoresistance of narrow-gap semiconductor InSb. The weak antilocalization effect of InSb film in perpendicular as well as
tilted magnetic field is investigated. It is found that the InSb film has
quasi-two-dimensional feature and the Nyquist mechanism dominates decoherence.
The two dimensionality is also verified further and the influence of roughness
effect and Zeeman effect on weak antilocalization effect is studied by
systematically investigating the anisotropy of weak field magnetoresistance
with respect to magnetic field. It is also found that the existence of in-plane
field can effectively suppress the weak antilocalization effect of InSb film
and the roughness effect plays an important role in the anisotropy.

###Superconductivity at 32 K in single crystal Rb$_{0.78}$Fe$_2$Se$_{1.78}$}|A. F. Wang,J. J. Ying,Y. J. Yan,R. H. Liu,X. G. Luo,Z. Y. Li,X. F. Wang,M. Zhang,G. J. Ye,P. Cheng,Z. J. Xiang,X. H. Chen###

Superconductivity at 32 K in single crystal Rb$_{0.78}$Fe$_2$Se$_{1.78}$}. We successfully grew the high-quality single crystal of
Rb$_{0.78}$Fe$_2$Se$_{1.78}$, which shows sharp superconducting transition in
magnetic susceptibility and electrical resistivity. Resistivity measurements
show the onset superconducting transition ($T_{\rm c}$) at 32.1 K and zero
resistivity at 30 K. From the low-temperature iso-magnetic-field
magnetoresistance, large upper critical field $H_{\rm c2}$(0) has been
estimated as high as 180 T for in-plane field and 59 T for out-of-plane field.
The anisotropy $H^{ab}_{\rm c2}$(0)/$H^{c}_{\rm c2}$(0) is around 3.0, right
lying between those observed in K$_x$Fe$_2$Se$_2$ and Cs$_x$Fe$_2$Se$_2$.

###Topological Aspect and Quantum Magnetoresistance of $β$-Ag$_2$Te|Wei Zhang,Rui Yu,Wanxiang Feng,Yugui Yao,Hongming Weng,Xi Dai,Zhong Fang###

Topological Aspect and Quantum Magnetoresistance of $β$-Ag$_2$Te. To explain the unusual non-saturating linear magnetoresistance observed in
silver chalcogenides, the quantum scenario has been proposed based on the
assumption of gapless linear energy spectrum. Here we show, by first principles
calculations, that $\beta$-Ag$_2$Te with distorted anti-fluorite structure is
in fact a topological insulator with gapless Dirac-type surface states. The
characteristic feature of this new binary topological insulator is the highly
anisotropic Dirac cone, in contrast to known examples, such as Bi$_2$Te$_3$ and
Bi$_2$Se$_3$. The Fermi velocity varies an order of magnitude by rotating the
crystal axis.

###Hidden Fermi Liquid: Self-Consistent Theory for the Normal State of High-Tc Superconductors|Philip A. Casey,Philip W. Anderson###

Hidden Fermi Liquid: Self-Consistent Theory for the Normal State of High-Tc Superconductors. Hidden Fermi liquid theory explicitly accounts for the effects of Gutzwiller
projection in the t-J Hamiltonian, widely believed to contain the essential
physics of the high-Tc superconductors. We derive expressions for the entire
"strange metal", normal state relating angle-resolved photoemission,
resistivity, Hall angle, and by generalizing the formalism to include the Fermi
surface topology - angle-dependent magnetoresistance. We show this theory to be
the first self-consistent description for the normal state of the cuprates
based on transparent, fundamental assumptions. Our well-defined formalism also
serves as a guide for further experimental confirmation.

###Metal-insulator transition in ultrathin LaNiO3 films|R. Scherwitzl,S. Gariglio,M. Gabay,P. Zubko,M. Gibert,J. -M. Triscone###

Metal-insulator transition in ultrathin LaNiO3 films. Transport in ultrathin films of LaNiO3 evolves from a metallic to a strongly
localized character as the film's thickness is reduced and the sheet resistance
reaches a value close to h/e2, the quantum of resistance in two dimensions. In
the intermediate regime, quantum corrections to the Drude low- temperature
conductivity are observed; they are accurately described by weak localization
theory. Remarkably, the negative magnetoresistance in this regime is isotropic,
which points to magnetic scattering associated with the proximity of the system
to either a spin glass state or the charge ordered antiferromagnetic state
observed in other rare earth nickelates.

###Superconducting Vortices induced Periodic Magnetoresistance Oscillations in Single Crystal Au Nanowires|Lin He,Jian Wang###

Superconducting Vortices induced Periodic Magnetoresistance Oscillations in Single Crystal Au Nanowires. We show in this paper that it is possible to induce superconducting vortices
in a gold nanowire connected to superconducting electrodes. The gold nanowire
acquires superconductivity by the proximity effect. The differential
magnetoresistance of the nanowire beyond a critical magnetic field shows
uniform oscillations with increasing field with a period of \phi0/(2\pir^2)
(\phi0 = h/2e is the superconducting flux quantum, r = 35 nm is the radius of
the nanowire). We demonstrate that these periodic oscillations are the
signatures of the sequential generation and moving of vortices across the gold
nanowire.

###Anomalous-Nernst and anisotropic magnetoresistive heating in a lateral spin valve|A. Slachter,F. L. Bakker,B. J. van Wees###

Anomalous-Nernst and anisotropic magnetoresistive heating in a lateral spin valve. We measured the anomalous-Nernst effect and anisotropic magnetoresistive
heating in a lateral multiterminal Permalloy/Copper spin valve using
all-electrical lock-in measurements. To interpret the results, a
three-dimensional thermoelectric finite-element-model is developed. Using this
model, we extract the heat profile which we use to determine the anomalous
Nernst coefficient of Permalloy Rn=0.13 and also determine the maximum angle of
theta=8 degrees of the magnetization prior to the switching process when an
opposing non-collinear 10$^{\circ}$ magnetic field is applied.

###Ferromagnetic Enhancement of CE-type Spin Ordering in (Pr,Ca)MnO$_3$|S. Y. Zhou,Y. Zhu,M. C. Langner,Y. -D. Chuang,P. Yu,W. L. Yang,A. G. Cruz Gonzalez,N. Tahir,M. Rini,Y. -H. Chu,R. Ramesh,D. -H. Lee,Y. Tomioka,Z. Hussain,R. W. Schoenlein###

Ferromagnetic Enhancement of CE-type Spin Ordering in (Pr,Ca)MnO$_3$. We present resonant soft X-ray scattering (RSXS) results from small band
width manganites (Pr,Ca)MnO$_3$, which show that the CE-type spin ordering (SO)
at the phase boundary is stabilized only below the canted antiferromagnetic
transition temperature and enhanced by ferromagnetism in the macroscopically
insulating state (FM-I). Our results reveal the fragility of the CE-type
ordering that underpins the colossal magnetoresistance (CMR) effect in this
system, as well as an unexpected cooperative interplay between FM-I and CE-type
SO which is in contrast to the competitive interplay between the ferromagnetic
metallic (FM-M) state and CE-type ordering.

###Improved tunneling magnetoresistance at low temperature in manganite junctions grown by molecular beam epitaxy|Robert Werner,Alexandr Yu. Petrov,Lucero Alvarez Mino,Reinhold Kleiner,Dieter Koelle,Bruce A. Davidson###

Improved tunneling magnetoresistance at low temperature in manganite junctions grown by molecular beam epitaxy. We report resistance versus magnetic field measurements for a
La0.65Sr0.35MnO3/SrTiO3/La0.65Sr0.35MnO3 tunnel junction grown by
molecular-beam epitaxy, that show a large field window of extremely high
tunneling magnetoresistance (TMR) at low temperature. Scanning the in-plane
applied field orientation through 360^/circ, the TMR shows 4-fold symmetry,
i.e. biaxial anisotropy, aligned with the crystalline axes but not the junction
geometrical long axis. The TMR reaches ~ 1900% at 4K, corresponding to an
interfacial spin polarization of > 95% assuming identical interfaces. These
results show that uniaxial anisotropy is not necessary for large TMR, and lay
the groundwork for future improvements in TMR in manganite junctions.

###Interplay between interferences and electron-electron interactions in epitaxial graphene|B. Jouault,B. Jabakhanji,N. Camara,W. Desrat,C. Consejo,J. Camassel###

Interplay between interferences and electron-electron interactions in epitaxial graphene. We separate localization and interaction effects in epitaxial graphene
devices grown on the C-face of a 4H-SiC substrate by analyzing the low
temperature conductivities. Weak localization and antilocalization are
extracted at low magnetic fields, after elimination of a geometric
magnetoresistance and subtraction of the magnetic field dependent Drude
conductivity. The electron electron interaction correction is extracted at
higher magnetic fields, where localization effects disappear. Both phenomena
are weak but sizable and of the same order of magnitude. If compared to
graphene on silicon dioxide, electron electron interaction on epitaxial
graphene are not significantly reduced by the larger dielectric constant of the
SiC substrate.

###Quantm Magnetoresistance of the PrFeAsO oxypnictides|D. Bhoi,P. Mandal,P. Choudhury,S. Pandya,V. Ganesan###

Quantm Magnetoresistance of the PrFeAsO oxypnictides. We report the observation of an unusual $B$ dependence of transverse
magnetoresistance (MR) in the PrFeAsO, one of the parent compound of pnictide
superconductors. Below the spin density wave transition, MR is large, positive
and increases with decreasing temperature. At low temperatures, MR increases
linearly with $B$ up to 14 T. For $T$$\geq$40 K, MR vs $B$ curve develops a
weak curvature in the low-field region which indicates a crossover from $B$
linear to $B^2$ dependence as $B$$\rightarrow$0. The $B$ linear MR originates
from the Dirac cone states and has been explained by the quantum mechanical
model proposed by Abrikosov.

###Upper critical fields and superconducting anisotropy of K0.70Fe1.55Se1.01S0.99 and K0.76Fe1.61Se0.96S1.04 single crystals|Hechang Lei,C. Petrovic###

Upper critical fields and superconducting anisotropy of K0.70Fe1.55Se1.01S0.99 and K0.76Fe1.61Se0.96S1.04 single crystals. We have investigated temperature and angular dependence of resistivity of
K0.70(7)Fe1.55(7)Se1.01(2)S0.99(2) and K0.76(5)Fe1.61(5)Se0.96(4)S1.04(5)
single crystals. The upper critical fields Hc2(T) for both field directions
decrease with the increase in S content. On the other hand, the angle-dependent
magnetoresistivity for both compounds can be scaled onto one curve using the
anisotropic Ginzburg-Landau theory. The obtained anisotropy of Hc2(T) increases
with S content, implying that S doping might decrease the dimensionality of
certain Fermi surface parts, leading to stronger two dimensional character.

###Spin-memory loss at Co/Ru interfaces|Mazin A. Khasawneh,Carolin Klose,W. P. Pratt, Jr.,Norman O. Birge###

Spin-memory loss at Co/Ru interfaces. We have determined the spin-memory-loss parameter, $\delta_{Co/Ru}$, by
measuring the transmission of spin-triplet and spin-singlet Cooper pairs across
Co/Ru interfaces in Josephson junctions and by Current-Perpendicular-to-Plane
Giant Magnetoresistance (CPP-GMR) techniques. The probability of spin-memory
loss at the Co/Ru interface is $(1-exp(-\delta_{Co/Ru}))$. From the CPP-MR, we
obtain $\delta_{Co/Ru} = 0.34^{+0.04}_{-0.02}$ that is in good agreement with
$\delta_{Co/Ru} = 0.35 \pm 0.08$ obtained from spin-triplet transmission. For
spin-singlet transmission, we have $\delta_{Co/Ru} = 0.64 \pm 0.05$ that is
different from that obtained from CPP-GMR and spin-triplet transmission. The
source of this difference is not understood.

###Tunable magnetoresistance behavior in suspended graphitic multilayers through ion implantation|Carlos Diaz-Pinto,Xuemei Wang,Sungbae Lee,Viktor G. Hadjiev,Debtanu De,Wei-Kan Chu,Haibing Peng###

Tunable magnetoresistance behavior in suspended graphitic multilayers through ion implantation. We report a tunable magnetoresistance (MR) behavior in suspended graphitic
multilayers through point defect engineering by ion implantation. We find that
ion implantation drastically changes the MR behavior: the linear positive MR in
pure graphitic multilayers transforms into a negative MR after introducing
significant short-range disorders (implanted boron or carbon atoms), consistent
with recent non-Markovian transport theory. Our experiments suggest the
important role of the non-Markovian process in the intriguing MR behavior for
graphitic systems, and open a new window for understanding transport phenomena
beyond the Drude-Boltzmann approach and tailoring the electronic properties of
graphitic layers.

###Interplay between the Kondo effect and randomness: Griffiths phase in MxTiSe2 (M = Co, Ni, and Fe) single crystals|Minoru Sasaki,Akimasa Ohnishi,Takemasa Kikuchi,Mamoru Kitaura,Ki-Seok Kim,Heon-Jung Kim###

Interplay between the Kondo effect and randomness: Griffiths phase in MxTiSe2 (M = Co, Ni, and Fe) single crystals. We investigate the interplay between the Kondo effect and randomness in
MxTiSe2 (M = Co, Ni, and Fe) single crystals. Although the typical low-T upturn
of resistivity implies the Kondo effect around the single-ion Kondo temperature
\overline{T}_{K}, positive magnetoresistance linearly proportional to the
magnetic field and the power-law scaling of magnetization suggest the forbidden
coexistence between Kondo effect and time reversal symmetry breaking. This
puzzling result is resolved by the Griffiths scenario - disorder-induced
distribution of the Kondo temperature produces an effective Kondo temperature
(\overline{T}_{K}) much lower than \overline{T}_{K}, allowing unscreened local
moments above \overline{T}_{K} and resulting in non-Fermi liquid properties in
MxTiSe2 below the percolation threshold (x<xc).

###Magnetoresistance and Magnetic Ordering Fingerprints in Hydrogenated Graphene|David Soriano,Nicolas Leconte,Pablo Ordejón,Jean-Christophe Charlier,Juan José Palacios,Stephan Roche###

Magnetoresistance and Magnetic Ordering Fingerprints in Hydrogenated Graphene. Spin-dependent features in the conductivity of graphene, chemically modified
by a random distribution of hydrogen adatoms, are explored theoretically. The
spin effects are taken into account using a mean-field self-consistent Hubbard
model derived from first-principles calculations. A Kubo-Greenwood transport
methodology is used to compute the spin-dependent transport fingerprints of
weakly hydrogenated graphene-based systems with realistic sizes. Conductivity
responses are obtained for paramagnetic, antiferromagnetic, or ferromagnetic
macroscopic states, constructed from the mean-field solutions obtained for
small graphene supercells. Magnetoresistance signals up to $\sim 7%$ are
calculated for hydrogen densities around 0.25%. These theoretical results could
serve as guidance for experimental observation of induced magnetism in
graphene.

###Mapping Colossal Magnetoresistance Phase Transitions with the Charge-Carrier Density Collapse Model|D. O. J. Green###

Mapping Colossal Magnetoresistance Phase Transitions with the Charge-Carrier Density Collapse Model. We explain the observed specific heat anomaly (and hence entropy change) in
the colossal magnetoresistive manganite Sm0.55Sr0.45MnO3, by introducing phase
separation into the current carrier density collapse theory via the notion of
the ferromagnetic volume fraction. Within the same framework, we have also been
able to explain the observed electrical resistivity of Sm0.55Sr0.45MnO3 by
using appropriate expressions governing the scattering mechanisms far away from
the transition. Fitting specific heat and resistivity results has allowed us to
separate the hopping activation energy of polaronic carriers and the bipolaron
binding energy contributions to the exponential behaviour of resistivity in the
paramagnetic phase.

###Electrolyte gate-controlled Kondo effect in SrTiO3|Menyoung Lee,J. R. Williams,Sipei Zhang,C. Daniel Frisbie,D. Goldhaber-Gordon###

Electrolyte gate-controlled Kondo effect in SrTiO3. We report low-temperature, high-field magnetotransport measurements of SrTiO3
gated by an ionic gel electrolyte. A saturating resistance upturn and negative
magnetoresistance that signal the emergence of the Kondo effect appear for
higher applied gate voltages. This observation, enabled by the wide tunability
of the ionic gel-applied electric field, promotes the interpretation of the
electric field-effect induced 2D electron system in SrTiO3 as an admixture of
magnetic Ti3+ ions, i.e. localized and unpaired electrons, and delocalized
electrons that partially fill the Ti 3d conduction band.

###Enhancement of Spin Injection into Graphene by Water Dipping|K. M. McCreary,Hua Wen,H. Yu,Wei Han,E. Johnston-Halperin,R. K. Kawakami###

Enhancement of Spin Injection into Graphene by Water Dipping. We immerse single layer graphene spin valves into purified water for a short
duration (<1 min) and investigate the effect on spin transport. Following water
immersion, we observe an enhancement in nonlocal magnetoresistance.
Additionally, the enhancement of spin signal is correlated with an increase in
junction resistance, which produces an increase in spin injection efficiency.
This study provides a simple way to improve the signal magnitude and
establishes the robustness of graphene spin valves to water exposure, which
enables future studies involving chemical functionalization in aqueous
solution.

###Switching magnetoresistance in vertically interfaced Pr0.5Ca0.5MnO3 grown on ZnO nanowires|R. V. K. Mangalam,Z. Zhang,T. Wu,W. Prellier###

Switching magnetoresistance in vertically interfaced Pr0.5Ca0.5MnO3 grown on ZnO nanowires. The synthesis, morphology and magneto-transport properties of
nanostructure-engineered charge-ordered Pr0.5Ca0.5MnO3 grown on ZnO nanowires
are reported. The stability of the charge-ordering can be tuned, but more
interestingly the sign of the magnetoresistance is inverted at low
temperatures. Coexistence of ferromagnetic clusters on the surface and
antiferromagnetic phase in the core of the grains were considered in order to
understand these features. This work suggests that such a process of growing on
nanowires network can be readily extended to other transition metal oxides and
open doors towards tailoring their functionalities.

###Local Tunneling Magnetoresistance probed by Low-Temperature Scanning Laser Microscopy|Robert Werner,Mathias Weiler,Aleksandr Yu. Petrov,Bruce A. Davidson,Rudolf Gross,Reinhold Kleiner,Sebastian T. B. Goennenwein,Dieter Koelle###

Local Tunneling Magnetoresistance probed by Low-Temperature Scanning Laser Microscopy. Tunneling magnetoresistance (TMR) in a vertical manganite junction was
investigated by low-temperature scanning laser microscopy (LTSLM) allowing to
determine the local relative magnetization M orientation of the two electrodes
as a function of magnitude and orientation of the external magnetic field H.
Sweeping the field amplitude at fixed orientation revealed magnetic domain
nucleation and propagation in the junction electrodes. For the high-resistance
state an almost single-domain antiparallel magnetization configuration was
achieved, while in the low-resistance state the junction remained in a
multidomain state. Calculated resistance $R_\mathrm{calc}(H)$ based on the
local M configuration obtained by LTSLM is in quantitative agreement with R(H)
measured by magnetotransport.

###Microwave-induced DC Signal in a Permalloy Thin Strip at Low Applied Magnetic Field|Ziqian Wang,Lujun Huang,Xiaofeng Zhu,Xiaoshuang Chen,Wei Lu###

Microwave-induced DC Signal in a Permalloy Thin Strip at Low Applied Magnetic Field. We investigated the ferromagnetic resonance signals in a polycrystalline
permalloy thin strip under in-plane low static magnetic field. A series of DC
voltages, which contain ferromagnetic resonance or spin wave resonance signals,
were measured by inducing microwave frequencies greater than 10 gigahertz. The
resonant signals measured in low magnetic field show different properties from
those detected in high field condition. Based on the theory of DC effects in
ferromagnetic resonance and the experimental data of anisotropic
magnetoresistance, a quantitative model was proposed. We found that the shape
anisotropy significantly affects magnetization, and distorts the resonant
signals in low field condition.

###A Superconducting Gap in an Insulator|D. Sherman,G. Kopnov,D. Shahar,A. Frydman###

A Superconducting Gap in an Insulator. We present tunneling spectroscopy and transport measurements on disordered
indium oxide films that reveal the existence of a superconducting gap in an
insulating state. Two films on both sides of the disorder induced
superconductor to insulator transition (SIT) show the same energy gap scale at
low temperatures. This energy gap persists up to relatively high magnetic
fields and is observed across the magnetoresistance peak typical of disordered
superconductors. The results provide useful information for understanding the
nature of the insulating state in the disorder induced SIT.

###Spintronic devices on the base of magnetic nanostructures|L. V. Lutsev,A. I. Stognij,N. N. Novitskii,A. S. Shulenkov###

Spintronic devices on the base of magnetic nanostructures. Two types of spintronic devices on the base of magnetic nanostructures
containing silicon dioxide films with cobalt nanoparticles SiO2(Co) on GaAs
substrate - magnetic sensors and field-effect transistor governed by applied
magnetic field - are studied. Magnetic sensors are based on the injection
magnetoresistance effect. This effect manifests itself in avalanche suppression
by the magnetic field in GaAs near the SiO2(Co)/GaAs interface. Field-effect
transistor contains the SiO2(Co) film under gate. It is found that the magnetic
field action leads to great changes in electron mobility in the channel due to
the interaction between spins of Co nanoparticles and electron spins.

###Spin polarized tunneling in MgO-based tunnel junctions with superconducting electrodes|Oliver Schebaum,Jagadeesh S. Moodera,Andy Thomas###

Spin polarized tunneling in MgO-based tunnel junctions with superconducting electrodes. We prepared magnetic tunnel junctions with one ferromagnetic and one
superconducting Al-Si electrode. Pure cobalt electrodes were compared with a
Co-Fe-B alloy and the Heusler compound Co2FeAl. The polarization of the
tunneling electrons was determined using the Maki-Fulde-model and is discussed
along with the spin-orbit scattering and the total pair-breaking parameters.
The junctions were post-annealed at different temperatures to investigate the
symmetry filtering mechanism responsible for the giant tunneling
magnetoresistance ratios in Co-Fe-B/ MgO/ Co-Fe-B junctions.

###Phase of phonon-induced resistance oscillations in a high-mobility two-dimensional electron gas|A. T. Hatke,M. A. Zudov,L. N. Pfeiffer,K. W. West###

Phase of phonon-induced resistance oscillations in a high-mobility two-dimensional electron gas. We report on experimental studies of magnetoresistance oscillations that
originate from the resonant interaction of two-dimensional electrons with
thermal transverse-acoustic phonons in very high-mobility GaAs/AlGaAs quantum
wells. We find that the oscillation maxima consistently occur when a frequency
of a phonon with twice the Fermi momentum exceeds an integer multiple of the
cyclotron frequency. This observation is in contrast to to all previous
experiments associating resistance maxima with magnetophonon resonance and its
harmonics. Our experimentally obtained resonant condition is in excellent
quantitative agreement with recent theoretical proposals.

###Memory Effects in the Charge Response of Lightly Doped La_{2-x}Sr_{x}CuO_{4}|I. Raičević,Dragana Popović,C. Panagopoulos,T. Sasagawa###

Memory Effects in the Charge Response of Lightly Doped La_{2-x}Sr_{x}CuO_{4}. The in-plane magnetoresistance (MR) of a single crystal
La_{1.97}Sr_{0.03}CuO_{4} has been studied at low temperatures T using several
experimental protocols. At T well below the spin-glass transition temperature,
the MR becomes positive and exhibits several glassy features, such as history
dependence, memory and hysteresis. These observations are qualitatively similar
to the previously reported behavior of the out-of-plane resistance. The results
suggest that the memory effects in the MR are related to the onset of
glassiness in the dynamics of doped holes.

###History dependent magnetoresistance in lightly doped La_{2-x}Sr_{x}CuO_{4} thin films|Xiaoyan Shi,Dragana Popović,C. Panagopoulos,G. Logvenov,A. T. Bollinger,I. Božović###

History dependent magnetoresistance in lightly doped La_{2-x}Sr_{x}CuO_{4} thin films. The in-plane magnetoresistance (MR) in atomically smooth
La_{2-x}Sr_{x}CuO_{4} thin films grown by molecular-beam-epitaxy was measured
in magnetic fields B up to 9 T over a wide range of temperatures T. The films,
with x=0.03 and x=0.05, are insulating, and the positive MR emerges at T<4 K.
The positive MR exhibits glassy features, including history dependence and
memory, for all orientations of B. The results show that this behavior, which
reflects the onset of glassiness in the dynamics of doped holes, is a robust
feature of the insulating state.

###Training and recovery behaviours of exchange bias in FeNi/Cu/Co/FeMn spin valves at high field sweep rates|D. Z. Yang,A. Kapelrud,M. Saxegaard,E. Wahlstrom###

Training and recovery behaviours of exchange bias in FeNi/Cu/Co/FeMn spin valves at high field sweep rates. Training and recovery of exchange bias in FeNi/Cu/Co/FeMn spin valves have
been studied by magnetoresistance curves with field sweep rates from 1000 to
4800 Oe/s. It is found that training and recovery of exchange field are
proportional to the logarithm of the training cycles and recovery time,
respectively. These behaviours are explained within the model based on thermal
activation. For the field sweep rates of 1000, 2000 and 4000 Oe/s, the
relaxation time of antiferromagnet spins are 61.4, 27.6, and 11.5 in the unit
of $ms$ respectively, much shorter than the long relaxation time (~10^2 s) in
conventional magnetometry measurements.

###Paramagnetic Spin Correlations in Colossal Magnetoresistive La0.7Ca0.3MnO3|Joel S. Helton,Matthew B. Stone,Dmitry A. Shulyatev,Yakov M. Mukovskii,Jeffrey W. Lynn###

Paramagnetic Spin Correlations in Colossal Magnetoresistive La0.7Ca0.3MnO3. Neutron spectroscopy measurements reveal dynamic spin correlations throughout
the Brillouin zone in the colossal magnetoresistive material La0.7Ca0.3MnO3 at
265 K (approximately 1.03 Tc). The long-wavelength behavior is consistent with
spin diffusion, yet an additional and unexpected component of the scattering is
also observed in low-energy constant-E measurements, which takes the form of
ridges of strong quasielastic scattering running along (H 0 0) and equivalent
directions. Well-defined Q-space correlations are observed in constant-E scans
at energies up to at least 28 meV, suggesting robust short-range spin
correlations in the paramagnetic phase.

###Anomalous magnetotransport in the heavy-fermion superconductor Ce2PdIn8|Daniel Gnida,Marcin Matusiak,Dariusz Kaczorowski###

Anomalous magnetotransport in the heavy-fermion superconductor Ce2PdIn8. The normal state behavior in the heavy-fermion superconductor Ce2PdIn8 has
been probed by means of Hall coefficient (RH) and transverse magnetoresistivity
(MR) measurements. The results indicate the predominance of contributions from
antiferromagnetic spin fluctuations at low temperatures. Anomalous
non-Fermi-liquid-like features, observed below 8 K in both RH(T) and MR(T), are
related to underlying quantum critical point, evidenced before in the specific
heat and the electrical resistivity data. The magnetotransport in Ce2PdIn8 is
shown to exhibit specific types of scaling that may appear universal for
similar systems at the verge of magnetic instability.

###Angular Dependence of the High-Magnetic-Field Phase Diagram of URu2Si2|Gernot W. Scheerer,William Knafo,Dai Aoki,Jacques Flouquet###

Angular Dependence of the High-Magnetic-Field Phase Diagram of URu2Si2. We present measurements of the magnetoresistivity RHOxx of URu2Si2 single
crystals in high magnetic fields up to 60 T and at temperatures from 1.4 K to
40 K. Different orientations of the magnetic field have been investigated
permitting to follow the dependence on Q of all magnetic phase transitions and
crossovers, where Q is the angle between the magnetic field and the easy-axis
c. We find out that all magnetic transitions and crossovers follow a simple
1/cos(Q) -law, indicating that they are controlled by the projection of the
field on the c-axis.

###Dirac semimetal and topological phase transitions in A3Bi (A=Na, K, Rb)|Zhijun Wang,Yan Sun,Xingqiu Chen,Cesare Franchini,Gang Xu,Hongming Weng,Xi Dai,Zhong Fang###

Dirac semimetal and topological phase transitions in A3Bi (A=Na, K, Rb). The three-dimensional (3D) Dirac point, where two Weyl points overlap in
momentum space, is usually unstable and hard to realize. Here we show, based on
the first-principles calculations and effective model analysis, that
crystalline $A_3$Bi ($A$=Na, K, Rb) are Dirac semimetals with bulk 3D Dirac
points protected by crystal symmetry. They possess non-trivial Fermi arcs on
the surfaces, and can be driven into various topologically distinct phases by
explicit breaking of symmetries. Giant diamagnetism, linear quantum
magnetoresistance, and quantum spin-Hall effect will be expected for such
compounds.

###Effect of interfacial strain on spin injection and spin polarization of Co2CrAl/NaNbO3/Co2CrAl magnetic tunneling junction|Yongqing Cai,Zhaoqiang Bai,Ming Yang,Yuan Ping Feng###

Effect of interfacial strain on spin injection and spin polarization of Co2CrAl/NaNbO3/Co2CrAl magnetic tunneling junction. First-principles calculations were carried out to investigate interfacial
strain effects on spin injection and spin polarization of a magnetic tunnel
junction consisting of half-metallic full-Heusler alloy Co2CrAl and
ferroelectric perovskite NaNbO3. Spin-dependent coherent tunneling was
calculated within the framework of non-equilibrium Green's function technique.
Both spin polarization and tunnel magnetoresistance (TMR) are affected by the
interfacial strain but their responses to compressive and tensile strains are
different. Spin polarization across the interface is fully preserved under a
compressive strain due to stronger coupling between interfacial atoms, whereas
a tensile strain significantly enhances interface states and lead to
substantial drops in spin polarization and TMR.

###Manifestation of the shape and edge effects in spin-resolved transport through graphene quantum dots|I. Weymann,J. Barnas,S. Krompiewski###

Manifestation of the shape and edge effects in spin-resolved transport through graphene quantum dots. We report on theoretical studies of transport through graphene quantum dots
weakly coupled to external ferromagnetic leads. The calculations are performed
by exact diagonalization of a tight-binding Hamiltonian with finite Coulomb
correlations for graphene sheet and by using the real-time diagrammatic
technique in the sequential and cotunneling regimes. The emphasis is put on the
role of graphene flake shape and spontaneous edge magnetization in transport
characteristics, such as the differential conductance, tunneling
magnetoresistance (TMR) and the shot noise. It is shown that for certain shapes
of the graphene dots a negative differential conductance and nontrivial
behavior of the TMR effect can occur.

###Spin transport and spin dephasing in zinc oxide|Matthias Althammer,Eva-Maria Karrer-Müller,Sebastian T. B. Goennenwein,Matthias Opel,Rudolf Gross###

Spin transport and spin dephasing in zinc oxide. The wide bandgap semiconductor ZnO is interesting for spintronic applications
because of its small spin-orbit coupling implying a large spin coherence
length. Utilizing vertical spin valve devices with ferromagnetic electrodes
(TiN/Co/ZnO/Ni/Au), we study the spin-polarized transport across ZnO in
all-electrical experiments. The measured magnetoresistance agrees well with the
prediction of a two spin channel model with spin-dependent interface
resistance. Fitting the data yields spin diffusion lengths of 10.8nm (2K),
10.7nm (10K), and 6.2nm (200K) in ZnO, corresponding to spin lifetimes of 2.6ns
(2K), 2.0ns (10K), and 31ps (200K).

###Tunneling anisotropic magnetoresistance in single-molecule magnet junctions|Haiqing Xie,Qiang Wang,Hujun Jiao,J. -Q. Liang###

Tunneling anisotropic magnetoresistance in single-molecule magnet junctions. We theoretically investigate quantum transport through single-molecule magnet
(SMM) junctions with ferromagnetic and normal-metal leads in the sequential
regime. The current obtained by means of the rate-equation gives rise to the
tunneling anisotropic magnetoresistance (TAMR), which varies with the angle
between the magnetization direction of ferromagnetic lead and the easy axis of
SMM. The angular dependence of TAMR can serve as a probe to determine
experimentally the easy axis of SMM. Moreover, it is demonstrated that both the
magnitude and sign of TAMR are tunable by the bias voltage, suggesting a
promising TAMR based spintronic molecule-device.

###Linear magnetoresistance in topological insulators: Quantum phase coherence effects at high temperatures|Badih A. Assaf,Thomas Cardinal,Peng Wei,Ferhat Katmis,Jagadeesh S. Moodera,Don Heiman###

Linear magnetoresistance in topological insulators: Quantum phase coherence effects at high temperatures. In addition to the weak antilocalization cusp observed in the
magnetoresistance (MR) of topological insulators at low temperatures and low
magnetic fields, we find that the high-field MR in Bi2Te2Se is linear in field.
At fields up to B=14T the slope of this linear-like MR is nearly independent of
temperature over the range T=7 to 150K. We find that the linear MR arises from
the competition between a logarithmic phase coherence component and a quadratic
component. The quantum phase coherence dominates up to high temperatures, where
the coherence length remains longer than the mean free path of electrons.

###Boundary Scattering in Ballistic Graphene|Satoru Masubuchi,Kazuyuki Iguchi,Takehiro Yamaguchi,Masahiro Onuki,Miho Arai,Kenji Watanabe,Takashi Taniguchi,Tomoki Machida###

Boundary Scattering in Ballistic Graphene. We report magnetotransport measurements in ballistic graphene/hexagonal boron
nitride mesoscopic wires where the charge carrier mean free path is comparable
to wire width $W$. Magnetoresistance curves show characteristic peak structures
where the peak field scales with the ratio of cyclotron radius $R_\textrm{c}$
and wire width $W$ as $W/R_\textrm{c} = 0.9 \pm 0.1$, due to diffusive boundary
scattering. The obtained proportionality constant between $R_\textrm{c}$ and
$W$ differs from that of a classical semiconductor 2D electron system where
$W/R_\textrm{c} = 0.55$.

###Colossal Magnetoresistance in the Mn2+ Oxypnictides NdMnAsO1-xFx|E. J. Wildman,J. M. S. Skakle,N. Emery,A. C. Mclaughlin###

Colossal Magnetoresistance in the Mn2+ Oxypnictides NdMnAsO1-xFx. Colossal magnetoresistance (CMR) is a rare phenomenon in which the electronic
resistivity of a material can be decreased by orders of magnitude upon
application of a magnetic field. Such an effect could be the basis of the next
generation of magnetic memory devices. Here we report CMR in the
antiferromagnetic oxypnictide NdMnAsO1-xFx as a result of competition between
an antiferromagnetic insulating phase with strong electron correlations and a
paramagnetic semiconductor upon application of a magnetic field. The discovery
of CMR in antiferromagnetic Mn2+ oxypnictide materials could open up an array
of materials for further investigation and optimisation for technological
applications.

###Magnetoresistance from quenching of spin quantum correlation in organic semiconductors|Wei Si,Yao Yao,Xiaoyuan Hou,Chang-Qin Wu###

Magnetoresistance from quenching of spin quantum correlation in organic semiconductors. We present a theory of organic magnetoresistance (OMR) based on the quenching
of the quantum correlation between the carrier's spin and its local environment
when the incoherent hopping takes place. We prove that this process contributes
a spin-dependent prefactor to the attempt-to-escape frequency in the hopping
rate, with its value modulated by the magnetic field. The resulting OMR
exhibits a positive Lorentzian saturation component and a negative small-field
component, which are independent of model parameters. These behaviors, with
their isotope effects, are in good agreement with experimental results.

###Symmetries and weak (anti)localization of Dirac fermions in HgTe quantum wells|P. M. Ostrovsky,I. V. Gornyi,A. D. Mirlin###

Symmetries and weak (anti)localization of Dirac fermions in HgTe quantum wells. We perform a symmetry analysis of a 2D electron system in HgTe/HgCdTe quantum
wells in the situation when the chemical potential is outside of the gap, so
that the bulk of the quantum well is conducting. In order to investigate
quantum transport properties of the system, we explore symmetries of the
low-energy Hamiltonian which is expressed in terms of two flavors of Dirac
fermions, and physically important symmetry-breaking mechanisms. This allows us
to predict emerging patterns of symmetry breaking that control the weak
localization and antilocalization showing up in transverse-field
magnetoresistance.

###Multi-Band Exotic Superconductivity in the New Superconductor Bi4O4S3|Sheng Li,Huan Yang,Jian Tao,Xiaxin Ding,Hai-Hu Wen###

Multi-Band Exotic Superconductivity in the New Superconductor Bi4O4S3. Resistivity, Hall effect and magnetization have been investigated on the new
superconductor Bi4O4S3. A weak insulating behavior has been induced in the
normal state when the superconductivity is suppressed. Hall effect measurements
illustrate clearly a multiband feature dominated by electron charge carriers,
which is further supported by the magnetoresistance data. Interestingly, a kink
appears on the temperature dependence of resistivity at about 4 K at all high
magnetic fields when the bulk superconductivity is completely suppressed. This
kink can be well traced back to the upper critical field Hc2(T) in the low
field region, and is explained as the possible evidence of residual Cooper
pairs on the one dimensional chains.

###Spin-orbit-coupling induced domain-wall resistance in diffusive ferromagnets|Zhe Yuan,Yi Liu,Anton A. Starikov,Paul J. Kelly,Arne Brataas###

Spin-orbit-coupling induced domain-wall resistance in diffusive ferromagnets. We investigate diffusive transport through a number of domain wall (DW)
profiles of the important magnetic alloy Permalloy taking into account
simultaneously noncollinearity, alloy disorder, and spin-orbit coupling fully
quantum mechanically, from first principles. In addition to observing the known
effects of magnetization mistracking and anisotropic magnetoresistance, we
discover a not-previously identified contribution to the resistance of a DW
that comes from spin-orbit-coupling-mediated spin-flip scattering in a textured
diffusive ferromagnet. This adiabatic DW resistance, which should exist in all
diffusive DWs, can be observed by varying the DW width in a systematic fashion
in suitably designed nanowires.

###Transversal Magnetic Anisotropy in Nanoscale PdNi-Strips|D. Steininger,A. K. Huettel,M. Ziola,M. Kiessling,M. Sperl,G. Bayreuther,Ch. Strunk###

Transversal Magnetic Anisotropy in Nanoscale PdNi-Strips. We investigate submicron ferromagnetic PdNi thin-film strips intended as
contact electrodes for carbon nanotube-based spintronic devices. The magnetic
anisotropy and micromagnetic structure are measured as function of temperature
and aspect ratio. Contrary to the expectation from shape anisotropy, magnetic
hysteresis measurements of Pd0.3Ni0.7 on arrays containing strips of various
width point towards a magnetically easy axis in the sample plane, but
transversal to the strip direction. Anisotropic magnetoresistance measured on
individual Pd0.3Ni0.7 contact strips and magnetic force microscopy images
substantiate that conclusion.

###Biaxial strain effect of spin dependent tunneling in MgO magnetic tunnel junctions|Ajeesh M. Sahadevan,Ravi K. Tiwari,Gopinadhan Kalon,Charanjit S. Bhatia,Mark Saeys,Hyunsoo Yang###

Biaxial strain effect of spin dependent tunneling in MgO magnetic tunnel junctions. We study the effect of strain on magnetic tunnel junctions (MTJ) induced by a
diamond like carbon (DLC) film. The junction resistance as well as the tunnel
magnetoresistance (TMR) reduces with the DLC film. Non-equilibrium Green's
function quantum transport calculations show that the application of biaxial
strain increases the conductance for both the parallel and anti-parallel
configurations. However, the conductance for the minority channel and for the
anti-parallel configuration is significantly more sensitive to strain, which
drastically increases transmission through a MgO tunnel barrier, therefore, the
TMR ratio decreases with biaxial strain.

###Geometric resonances in the magnetoresistance of hexagonal lateral superlattices|Yuto Kato,Akira Endo,Shingo Katsumoto,Yasuhiro Iye###

Geometric resonances in the magnetoresistance of hexagonal lateral superlattices. We have measured magnetoresistance of hexagonal lateral superlattices. We
observe three types of oscillations engendered by periodic potential modulation
having hexagonal-lattice symmetry: amplitude modulation of the Shubnikov-de
Haas oscillations, commensurability oscillations, and the geometric resonances
of open orbits generated by Bragg reflections. The latter two reveal the
presence of two characteristic periodicities, sqrt{3} a / 2 and a / 2, inherent
in a hexagonal lattice with the lattice constant a. The formation of the
hexagonal-superlattice minibands manifested by the observation of open orbits
marks the first step toward realizing massless Dirac fermions in semiconductor
2DEGs.

###Quantum oscillations and optical conductivity in Rashba spin-splitting BiTeI|C. Martin,E. D. Mun,H. Berger,V. S. Zapf,D. B. Tanner###

Quantum oscillations and optical conductivity in Rashba spin-splitting BiTeI. We report the observation of Shubnikov-de Haas (SdH) oscillations in single
crystals of the Rashba spin-splitting compound BiTeI, from both longitudinal
($R_{xx}(B)$) and Hall ($R_{xy}(B)$) magnetoresistance. Under magnetic field up
to 65 T, we resolved unambiguously only one frequency $F = 284.3\pm 1.3$ T,
corresponding to a Fermi momentum $k_{F} = 0.093\pm 0.002$\AA$^{-1}$.The
amplitude of oscillations is strongly suppressed by tilting magnetic field,
suggesting a highly two-dimensional Fermi surface. Combining with optical
spectroscopy, we show that quantum oscillations may be consistent with a bulk
conduction band having a Rashba splitting momentum $k_{R}=0.046\pm$\AA$^{-1}$.

###Critical role of next-nearest-neighbor interlayer interaction in magnetic behavior of magnetic/nonmagnetic multilayers|Sunjae Chung,Sangyep Lee,Taehee Yoo,Hakjoon Lee,J. -H. Chung,M. S. Choi,Sanghoon Lee,X. Liu,J. K. Furdyna,Jae-Ho Han,Hyun-Woo Lee,Kyung-Jin Lee###

Critical role of next-nearest-neighbor interlayer interaction in magnetic behavior of magnetic/nonmagnetic multilayers. We report magnetoresistance data in magnetic semiconductor multilayers, which
exhibit a clear step-wise behavior as a function of external field. We
attribute this highly non-trivial step-wise behavior to next-nearest-neighbor
interlayer exchange coupling. Our microscopic calculation suggests that this
next-nearest-neighbor coupling can be as large as 24% of the nearest-neighbor
coupling. It is argued that such unusually long-range interaction is made
possible by the quasi-one-dimensional nature of the system and by the long
Fermi wavelength characteristic of magnetic semiconductors.

###Effect of rotation of the polarization of linearly polarized microwaves on the radiation-induced magnetoresistance oscillations|A. N. Ramanayaka,R. G. Mani,J. Iñarrea,W. Wegscheider###

Effect of rotation of the polarization of linearly polarized microwaves on the radiation-induced magnetoresistance oscillations. Light-matter coupling is investigated by rotating, by an angle \theta, the
polarization of linearly polarized microwaves with respect to the long-axis of
GaAs/AlGaAs Hall-bar electron devices. At low microwave power, P, experiments
show a strong sinusoidal variation in the diagonal resistance R_{xx} vs. \theta
at the oscillatory extrema, indicating a linear polarization sensitivity in the
microwave radiation-induced magnetoresistance oscillations. Surprisingly, the
phase shift \theta_{0} for maximal oscillatory R_{xx} response under
photoexcitation appears dependent upon the radiation-frequency f, the extremum
in question, and the magnetic field orientation or sgn(B).

###Theory of Strain-Controlled Magnetotransport and Stabilization of the Ferromagnetic Insulating Phase in Manganite Thin Films|Anamitra Mukherjee,William S. Cole,Patrick Woodward,Mohit Randeria,Nandini Trivedi###

Theory of Strain-Controlled Magnetotransport and Stabilization of the Ferromagnetic Insulating Phase in Manganite Thin Films. We show that applying strain on half-doped manganites makes it possible to
tune the system to the proximity of a metal-insulator transition and thereby
generate a colossal magnetoresistance (CMR) response. This phase competition
not only allows control of CMR in ferromagnetic metallic manganites but can be
used to generate CMR response in otherwise robust insulators at half-doping.
Further, from our realistic microscopic model of strain and magnetotransport
calculations within the Kubo formalism, we demonstrate a striking result of
strain engineering that, under tensile strain, a ferromagnetic charge-ordered
insulator, previously inaccessible to experiments, becomes stable.

###Fabrication and characterization of the gapless half-Heusler YPtSb thin films|Wenhong Wang,Yin Du,Enke Liu,Zhongyuan Liu,Guangheng Wu###

Fabrication and characterization of the gapless half-Heusler YPtSb thin films. Half-Heusler YPtSb thin films were fabricated by magnetron co-sputtering
method on MgO-buffered SiO2/Si(001) substrates. X-ray diffraction pattern and
Energy dispersive X-ray spectroscopy confirmed the high-quality growth and
stoichiometry. The temperature dependence of the resistivity shows a
semiconducting-type behavior down to low temperature. The Hall mobility was
determined to be 450 cm2/Vs at 300K, which is much higher than the bulk value
(300 cm2/Vs). In-plane magnetoresistance (MR) measurements with fields applied
along and perpendicular to the current direction show opposite MR signs, which
suggests the possible existence of the topological surface states.

###Exchange Field-Mediated Magnetoresistance in the Correlated Insulator Phase of Be Films|T. J Liu,J. C. Prestigiacomo,Y. M. Xiong,P. W. Adams###

Exchange Field-Mediated Magnetoresistance in the Correlated Insulator Phase of Be Films. We present a study of the proximity effect between a ferromagnet and a
paramagnetic metal of varying disorder. Thin beryllium films are deposited onto
a 5 nm-thick layer of the ferromagnetic insulator EuS. This bilayer arrangement
induces an exchange field, $H_{ex}$, of a few tesla in low resistance Be films
with sheet resistance $R\ll R_Q$, where $R_Q=h/e^2$ is the quantum resistance.
We show that $H_{ex}$ survives in very high resistance films and, in fact,
appears to be relatively insensitive to the Be disorder. We exploit this fact
to produce a giant low-field magnetoresistance in the correlated insulator
phase of Be films with $R\gg R_Q$.

###Magnetic Mn5Ge3 nanocrystals embedded in crystalline Ge: a magnet/semiconductor hybrid synthesized by ion implantation|Shengqiang Zhou,Wenxu Zhang,A. Shalimov,Yutian Wang,Zhisuo Huang,D. Buerger,A. Mücklich,Wanli Zhang,H. Schmidt,M. Helm###

Magnetic Mn5Ge3 nanocrystals embedded in crystalline Ge: a magnet/semiconductor hybrid synthesized by ion implantation. The integration of ferromagnetic Mn5Ge3 with the Ge matrix is promising for
spin injection in a silicon-compatible geometry. In this paper, we report the
preparation of magnetic Mn5Ge3 nanocrystals embedded inside the Ge matrix by Mn
ions implantation at elevated temperature. By X-ray diffraction and
transmission electron microscopy, we observe crystalline Mn5Ge3 with variable
size depending on the Mn ion fluence. The electronic structure of Mn in Mn5Ge3
nanocrystals is 3d6 configuration, the same as in bulk Mn5Ge3. A large positive
magnetoresistance has been observed at low temperatures. It can be explained by
the conductivity inhomogeneity in the magnetic/semiconductor hybrid system.

###Spin polarization and magnetoresistance through a ferromagnetic barrier in bilayer graphene|Hosein Cheraghchi,Fatemeh Adinehvand###

Spin polarization and magnetoresistance through a ferromagnetic barrier in bilayer graphene. We study spin dependent transport through a magnetic bilayer graphene
nanojunction configured as two dimensional normal/ferromagnetic/normal
structure where the gate-voltage is applied on the layers of ferromagnetic
graphene. Based on the fourband Hamiltonian, conductance is calculated by using
Landauer Butikker formula at zero temperature. For parallel configuration of
the ferromagnetic layers of bilayer graphene, the energy band structure is
metallic and spin polarization reaches to its maximum value close to the
resonant states, while for antiparallel configuration, the nanojunction behaves
as a semiconductor and there is no spin filtering. As a result, a huge
magnetoresistance is achievable by altering the configurations of ferromagnetic
graphene especially around the band gap.

###Parallel-leaky capacitance equivalent circuit model for MgO magnetic tunnel junctions|Ajeesh M. Sahadevan,Kalon Gopinadhan,Charanjit S. Bhatia,Hyunsoo Yang###

Parallel-leaky capacitance equivalent circuit model for MgO magnetic tunnel junctions. The capacitance of MgO based magnetic tunnel junctions (MTJs) has been
observed to be magnetic field dependent. We propose an equivalent circuit for
the MTJs with a parallel-leaky capacitance (Cl) across the series combination
of geometric and interfacial capacitance. The analysis of junctions with
different tunneling magnetoresistance values suggests higher Cl for low TMR
junctions. Using Cole-Cole plots the capacitive nature of MTJs is manifested.
Fitting with Maxwell-Wagner capacitance model validates the RC parallel network
model for MTJs and the extracted field dependent parameters match with the
experimental values.

###Nonlinear anomalous Hall effect and negative magnetoresistance in a system with random Rashba field|V. K. Dugaev,M. Inglot,E. Ya. Sherman,J. Berakdar,J. Barnas###

Nonlinear anomalous Hall effect and negative magnetoresistance in a system with random Rashba field. We predict two spin-dependent transport phenomena in two-dimensional electron
systems, which are induced by spatially fluctuating Rashba spin-orbit
interaction. When the electron gas is magnetized, the random Rashba interaction
leads to the anomalous Hall effect. An example of such a system is a narrow-gap
magnetic semiconductor-based symmetric quantum well. We show that the anomalous
Hall conductivity reveals a strongly nonlinear dependence on the magnetization,
decreasing exponentially at large spin density. We also show that electron
scattering from a fluctuating Rashba field in a two-dimensional nonmagnetic
electron system leads to a negative magnetoresistance arising solely due to
spin-dependent effects.

###Characterization of InSb quantum wells with atomic layer deposited gate dielectrics|M. M. Uddin,H. W. Liu,K. F. Yang,K. Nagase,T. D. Mishima,M. B. Santos,Y. Hirayama###

Characterization of InSb quantum wells with atomic layer deposited gate dielectrics. We report magnetotransport measurements of a gated InSb quantum well (QW)
with high quality Al2O3 dielectrics (40 nm thick) grown by atomic layer
deposition. The magnetoresistance data demonstrate a parallel conduction
channel in the sample at zero gate voltage (Vg). A good interface between Al2O3
and the top InSb layer ensures that the parallel channel is depleted at
negative Vg and the density of two-dimensional electrons in the QW is tuned by
Vg with a large ratio of 6.5x1014 m-2V-1 but saturates at large negative Vg.
These findings are closely related to layer structures of the QW as suggested
by self-consistent Schrodinger-Poisson simulation and two-carrier model.

###Magneto-resistance up to 60 Tesla in Topological Insulator Bi2Te3 Thin Films|S. X. Zhang,R. D. McDonald,A. Shekhter,Z. X. Bi,Y. Li,Q. X. Jia,S. T. Picraux###

Magneto-resistance up to 60 Tesla in Topological Insulator Bi2Te3 Thin Films. We report magneto-transport studies of topological insulator Bi_{2}Te_{3}
thin films grown by pulsed laser deposition. A non-saturating linear-like
magneto-resistance (MR) is observed at low temperatures in the magnetic field
range from a few Tesla up to 60 Tesla. We demonstrate that the strong
linear-like MR at high field can be well understood as the weak
antilocalization phenomena described by Hikami-Larkin-Nagaoka theory. Our
analysis suggests that in our system, a topological insulator, the elastic
scattering time can be longer than the spin-orbit scattering time. We briefly
discuss our results in the context of Dirac Fermion physics and 'quantum linear
magnetoresistance'.

###Annealing induced colossal magnetocapacitance and colossal magnetoresistance in In-doped CdCr2S4|Y. M. Xie,Z. R. Yang,L. Li,L. H. Yin,X. B. Hu,Y. L. Huang,H. B. Jian,W. H. Song,Y. P. Sun,S. Q. Zhou,Y. H. Zhang###

Annealing induced colossal magnetocapacitance and colossal magnetoresistance in In-doped CdCr2S4. The correlation between colossal magnetocapacitance (CMC) and colossal
magnetoresistance (CMR) in CdCr2S4 system has been revealed. The CMC is induced
in polycrystalline Cd0.97In0.03Cr2S4 by annealing in cadmium vapor. At the same
time, an insulator-metal transition and a concomitant CMR are observed near the
Curie temperature. In contrast, after the same annealing treatment, CdCr2S4
displays a typical semiconductor behavior and does not show magnetic field
dependent dielectric and electric transport properties. The simultaneous
occurrence or absence of CMC and CMR effects implies that the CMC in the
annealed Cd0.97In0.03Cr2S4 could be explained qualitatively by a combination of
CMR and Maxwell-Wagner effect.

###Evolution of variable range hopping in strongly localized two dimensional electron gas at NdAlO3/SrTiO3 (100) heterointerfaces|A. Annadi,A. Putra,A. Srivastava,X. Wang,Z. Huang,Z. Q. Liu,T. Venkatesan,Ariando###

Evolution of variable range hopping in strongly localized two dimensional electron gas at NdAlO3/SrTiO3 (100) heterointerfaces. We report evolution of the two-dimensional electron gas behavior at the
NdAlO3/SrTiO3 heterointerfaces with varying thicknesses of the NdAlO3
overlayer. The samples with a thicker NdAlO3 show strong localizations at low
temperatures and the degree of localization is found to increase with the
NdAlO3 thickness. The T -1/3 temperature dependence of the sheet resistance at
low temperatures and the magnetoresistance study reveal that the conduction is
governed by a two-dimensional variable range hopping mechanism in this strong
localized regime. We attribute this thickness dependence of the transport
properties of the NdAlO3/SrTiO3 interfaces to the interface strain induced by
the overlayers.

###Spin Caloritronics in graphene with Mn|Alberto Torres,Matheus P. Lima,A. Fazzio,Antônio J. R. da Silva###

Spin Caloritronics in graphene with Mn. We show that graphene with Mn adatoms trapped at single vacancies feature
spin-dependent Seebeck effect, thus enabling the use of this material for spin
caloritronics. A gate potential can be used to tune its thermoelectric
properties in a way it presents either a total spin polarized current, flowing
in one given direction, or currents for both spins flowing in opposite
directions without net charge transport. Moreover, we show that the thermal
magnetoresistance can be tuned between $-100\%$ and $+100\%$ by varying agate
potential.

###Anisotropic Magnetoresistance Effect: General Expression of AMR Ratio and Intuitive Explanation for Sign of AMR Ratio|Satoshi Kokado,Masakiyo Tsunoda###

Anisotropic Magnetoresistance Effect: General Expression of AMR Ratio and Intuitive Explanation for Sign of AMR Ratio. We derive the general expression of the anisotropic magnetoresistance (AMR)
ratio of ferromagnets for a relative angle between the magnetization direction
and the current direction. We here use the two-current model for a system
consisting of a spin-polarized conduction state (s) and localized d states (d)
with spin-orbit interaction. Using the expression, we analyze the AMR ratios of
Ni and a half-metallic ferromagnet. These results correspond well to the
respective experimental results. In addition, we give an intuitive explanation
about a relation between the sign of the AMR ratio and the s-d scattering
process.

###Discrete helicoidal states in chiral magnetic thin films|M. N. Wilson,E. A. Karhu,D. P. Lake,A. S. Quigley,A. N. Bogdanov,U. K. Rößler,T. L. Monchesky###

Discrete helicoidal states in chiral magnetic thin films. Magnetometry and magnetoresistance measurements in MnSi thin films and
rigorous analytical solutions of the micromagnetic equations show that the
field-induced unwinding of confined helicoids occurs via discrete steps. A
comparison between the magnetometry data and theoretical results shows that
finite size effects confine the wavelength and lead to a quantization of the
number of turns in the helicoid. We demonstrate a prototypical spintronic
device where the magnetic field can push or pull individual turns into a
magnetic spring that can be read by electrical means.

###Three Dimensional Dirac Semimetal and Quantum Transports in Cd3As2|Zhijun Wang,Hongming Weng,Quansheng Wu,Xi Dai,Zhong Fang###

Three Dimensional Dirac Semimetal and Quantum Transports in Cd3As2. Based on the first-principles calculations, we recover the silent topological
nature of Cd3As2, a well known semiconductor with high carrier mobility. We
find that it is a symmetry-protected topological semimetal with a single pair
of three-dimensional (3D) Dirac points in the bulk and non-trivial Fermi arcs
on the surfaces. It can be driven into a topological insulator and a Weyl
semi-metal state by symmetry breaking, or into a quantum spin Hall insulator
with gap more than 100meV by reducing dimensionality. We propose that the 3D
Dirac cones in the bulk of Cd3As2 can support sizable linear quantum
magnetoresistance even up to room temperature.

###Angular Preisach analysis of Hysteresis loops and FMR lineshapes of ferromagnetic nanowire arrays|C. Tannous,A. Ghaddar,J. Gieraltowski###

Angular Preisach analysis of Hysteresis loops and FMR lineshapes of ferromagnetic nanowire arrays. Preisach analysis is applied to the study of hysteresis loops measured for
different angles between the applied magnetic field and the common axis of
ferromagnetic Nickel nanowire arrays. When extended to Ferromagnetic Resonance
(FMR) lineshapes, with same set of parameters extracted from the corresponding
hysteresis loops, Preisach analysis shows that a different distribution of
interactions or coercivities ought to be used in order to explain experimental
results. Inspecting the behavior of hysteresis loops and FMR linewidth versus
field angle, we infer that angular dependence might be exploited in angle
sensing devices that could compete with Anisotropic (AMR) or Giant
Magnetoresistive (GMR) based devices.

###Experimental test of the spin mixing interface conductivity concept|Mathias Weiler,Matthias Althammer,Michael Schreier,Johannes Lotze,Matthias Pernpeintner,Sibylle Meyer,Hans Huebl,Rudolf Gross,Akashdeep Kamra,Jiang Xiao,Yan-Ting Chen,HuJun Jiao,Gerrit E. W. Bauer,Sebastian T. B. Goennenwein###

Experimental test of the spin mixing interface conductivity concept. We perform a quantitative, comparative study of the spin pumping, spin
Seebeck and spin Hall magnetoresistance effects, all detected via the inverse
spin Hall effect in a series of over 20 yttrium iron garnet/Pt samples. Our
experimental results fully support present, exclusively spin current-based,
theoretical models using a single set of plausible parameters for spin mixing
conductance, spin Hall angle and spin diffusion length. Our findings establish
the purely spintronic nature of the aforementioned effects and provide a
quantitative description in particular of the spin Seebeck effect.

###Spintronics and Pseudospintronics in Graphene and Topological Insulators|D. A. Pesin,A. H. MacDonald###

Spintronics and Pseudospintronics in Graphene and Topological Insulators. The two-dimensional electron systems in graphene and in topological
insulators are described by massless Dirac equations. Although the two systems
have similar Hamiltonians, they are polar opposites in terms of spin-orbit
coupling strength. We briefly review the status of efforts to achieve long spin
relaxation times in graphene with its weak spin-orbit coupling, and to achieve
large current-induced spin polarizations in topological-insulator surface
states that have strong spin-orbit coupling. We also comment on differences
between the magnetic responses and dilute-moment coupling properties of the two
systems, and on the pseudospin analog of giant magnetoresistance in bilayer
graphene.

###Electrically-Detected ESR in Silicon Nanostructures Inserted in Microcavities|Nikolay Bagraev,Eduard Danilovskii,Wolfgang Gehlhoff,Dmitrii Gets,Leonid Klyachkin,Andrey Kudryavtsev,Roman Kuzmin,Anna Malyarenko,Vladimir Mashkov,Vladimir Romanov###

Electrically-Detected ESR in Silicon Nanostructures Inserted in Microcavities. We present the first findings of the new electrically-detected electron spin
resonance technique (EDESR), which reveal the point defects in the ultra-narrow
silicon quantum wells (Si-QW) confined by the superconductor delta-barriers.
This technique allows the ESR identification without application of an external
cavity, as well as a high frequency source and recorder, and with measuring the
only response of the magnetoresistance, with internal GHz Josephson emission
within frameworks of the normal-mode coupling (NMC) caused by the microcavities
embedded in the Si-QW plane.

###Effects of interface electric field on the magnetoresistance in spin device|T. Tanamoto,M. Ishikawa,T. Inokuchi,H. Sugiyama,Y. Saito###

Effects of interface electric field on the magnetoresistance in spin device. An extension of the standard spin diffusion theory is presented by
introducing a density-gradient (DG) term that is suitable for describing
interface quantum tunneling phenomena. The magnetoresistance (MR) ratio is
modified by the DG term through an interface electric field. We have also
carried out spin injection and detection measurements using four-terminal Si
devices. The local measurement shows that the MR ratio changes depending on the
current direction. We show that the change of the MR ratio depending on the
current direction comes from the DG term regarding the asymmetry of the two
interface electronic structures.

###Unveiling the Origin of the Insulating Ferromagnetism in LaMnO3 Thin Film|Yusheng Hou,Hongjun Xiang,Xingao Gong###

Unveiling the Origin of the Insulating Ferromagnetism in LaMnO3 Thin Film. By combining genetic algorithm optimizations, first-principles calculations
and the double-exchange model studies, we have unveiled that the exotic
insulating ferromagnetism in LaMnO3 thin film originates from the previously
unreported G-type d_{3z^2-r^2}/d_{x^2-y^2} orbital ordering. An insulating gap
opens as a result of both the orbital ordering and the strong electron-phonon
coupling. Therefore, there exist two strain induced phase transitions in the
LaMnO3 thin film, from the insulating A-type antiferromagnetic phase to the
insulating ferromagnetic phase and then to the metallic ferromagnetic phase.
These phase transitions may be exploited in tunneling magnetoresistance and
tunneling electroresistance related devices.

###Magnetization Characteristic of Ferromagnetic Thin Strip by Measuring Anisotropic Magnetoresistance and Ferromagnetic Resonance|Ziqian Wang,Guolin Yu,Xinzhi Liu,Bo Zhang,Xiaoshuang Chen,Wei Lu###

Magnetization Characteristic of Ferromagnetic Thin Strip by Measuring Anisotropic Magnetoresistance and Ferromagnetic Resonance. The magnetization characteristic in a permalloy thin strip is investigated by
electrically measuring the anisotropic magnetoresistance and ferromagnetic
resonance in in-plane and out-of-plane configurations. Our results indicate
that the magnetization vector can rotate in the film plane as well as out of
the film plane by changing the intensity of external magnetic field of certain
direction. The magnetization characteristic can be explained by considering
demagnetization and magnetic anisotropy. Our method can be used to obtain the
demagnetization factor, saturated magnetic moment and the magnetic anisotropy.

###Spin Excitations in Half-Doped Manganites|Ivon R. Buitrago,C. I. Ventura###

Spin Excitations in Half-Doped Manganites. We investigate magnetic excitations in half-doped colossal magnetoresistance
manganites. In particular, we focus on spin excitations in the CE phase
originally proposed by Goodenough (Phys. Rev. 100, 564 (1955)). Using a
localized spin model we calculated magnons for 3D-perovskite compounds such as
La$_{1-x}$M$_x$MnO$_3$, where M=Ca,Sr,Ba, and for their 2D-laminar
counterparts. We compared them with predictions for the spin excitations
corresponding to other phases proposed. For the laminar half-doped manganite
La$_{0.5}$Sr$_{1.5}$MnO$_4$, for which magnon measurements by inelastic neutron
scattering exist, as well as an estimation of the magnetic couplings, our
calculations agree well with the experimental data.

###Spin-orbit-torque magnetization switching of a three terminal perpendicular magnetic tunnel junction|Murat Cubukcu,Olivier Boulle,Marc Drouard,Kevin Garello,Can Onur Avci,Ioan Mihai Miron,Juergen Langer,Berthold Ocker,Pietro Gambardella,Gilles Gaudin###

Spin-orbit-torque magnetization switching of a three terminal perpendicular magnetic tunnel junction. We report on the current-induced magnetization switching of a three-terminal
perpendicular magnetic tunnel junction by spin-orbit torque and the read-out
using the tunnelling magnetoresistance (TMR) effect. The device is composed of
a perpendicular Ta/FeCoB/MgO/FeCoB stack on top of a Ta current line. The
magnetization of the bottom FeCoB layer can be switched reproducibly by the
injection of current pulses with density $5\times10^{11}$ A/m$^2$ in the Ta
layer in the presence of an in-plane bias magnetic field, leading to the
full-scale change of the TMR signal. Our work demonstrates the proof of concept
of a perpendicular spin-orbit torque magnetic memory cell.

###The Vortex Signature of Discrete Ferromagnetic Dipoles at the LaAlO$_3$/SrTiO$_3$ Interface|A. P. Petrović,A. Paré,T. R. Paudel,K. Lee,S. Holmes,C. H. W. Barnes,A. David,T. Wu,E. Y. Tsymbal,C. Panagopoulos###

The Vortex Signature of Discrete Ferromagnetic Dipoles at the LaAlO$_3$/SrTiO$_3$ Interface. A hysteretic in-plane magnetoresistance develops below the superconducting
transition of LaAlO$_3$/SrTiO$_3$ interfaces for $\left|H_{/\!/}\right|<$ 0.15
T, independently of the carrier density or oxygen annealing. We show that this
hysteresis arises from vortex depinning within a thin superconducting layer, in
which the vortices are created by discrete ferromagnetic dipoles located solely
above the layer. We find no evidence for finite-momentum pairing or bulk
magnetism and hence conclude that ferromagnetism is strictly confined to the
interface, where it competes with superconductivity.

###Remotely sensed transport in microwave photoexcited GaAs/AlGaAs two-dimensional electron system|Tianyu Ye,Ramesh Mani,Werner Wegscheider###

Remotely sensed transport in microwave photoexcited GaAs/AlGaAs two-dimensional electron system. We demonstrate a strong correlation between the magnetoresistive and the
concurrent microwave reflection from the microwave photo-excited GaAs/AlGaAs
two-dimensional electron system (2DES). These correlations are followed as a
function of the microwave power, the microwave frequency, and the applied
current. Notably, the character of the reflection signal remains unchanged even
when the current is switched off in the GaAs/AlGaAs Hall bar specimen. The
results suggest a perceptible microwave-induced change in the electronic
properties of the 2DES, even in the absence of an applied current.

###Remote sensor response study in the regime of the microwave radiation-induced magnetoresistance oscillations|Tianyu Ye,Ramesh Mani,Werner Wegscheider###

Remote sensor response study in the regime of the microwave radiation-induced magnetoresistance oscillations. A concurrent remote sensing and magneto-transport study of the microwave
excited two dimensional electron system (2DES) at liquid Helium temperatures
has been carried out using a carbon detector to remotely sense the microwave
activity of the 2D electron system in the GaAs/AlGaAs heterostructure during
conventional magnetotransport measurements. Various correlations are observed
and reported between the oscillatory magnetotransport and the remotely sensed
reflection. In addition, the oscillatory remotely sensed signal is shown to
exhibit a power law type variation in its amplitude, similar to the
radiation-induced magnetoresistance oscillations.

###Impact of lattice strain on the tunnel magneto-resistance in Fe/Insulator/Fe and Fe/Insulator/La$_{0.67}$Sr$_{0.33}$MnO$_{3}$ magnetic tunnel junctions|Y. Saeed,N. Singh,N. Useinov,U. Schwingenschlögl###

Impact of lattice strain on the tunnel magneto-resistance in Fe/Insulator/Fe and Fe/Insulator/La$_{0.67}$Sr$_{0.33}$MnO$_{3}$ magnetic tunnel junctions. The objective of this work is to describe the tunnel electron current in
single barrier magnetic tunnel junctions within a new approach that goes beyond
the single-band transport model. We propose a ballistic multi-channel electron
transport model that can explain the influence of in-plane lattice strain on
the tunnel magnetoresistance as well as the asymmetric voltage behavior. We
consider as an example single crystal magnetic Fe(110) electrodes for
Fe/Insulator/Fe and Fe/Insulator/La$_{0.67}$Sr$_{0.33}$MnO$_{3}$ tunnel
junctions, where the electronic band structures of Fe and
La$_{0.67}$Sr$_{0.33}$MnO$_{3}$ are derived by \it{ab-initio} calculations.

###Anisotropic magneto-thermal transport and Spin-Seebeck effect|J. -E. Wegrowe,H. -J. Drouhin,D. Lacour###

Anisotropic magneto-thermal transport and Spin-Seebeck effect. The angular dependence of the thermal transport in insulating or conducting
ferromagnets is derived on the basis of the Onsager reciprocity relations
applied to a magnetic system. It is shown that the angular dependence of the
temperature gradient takes the same form as that of the anisotropic
magnetoresistance, including anomalous and planar Hall contributions. The
measured thermocouple generated between the extremities of the non-magnetic
electrode in thermal contact to the ferromagnet follows this same angular
dependence. The sign and amplitude of the magneto-voltaic signal is controlled
by the difference of the Seebeck coefficients of the thermocouple.

###K and Mn co-doped BaCd2As2: a hexagonal structured bulk diluted magnetic semiconductor with large magnetoresistance|Xiaojun Yang,Yuke Li,Pan Zhang,Hao Jiang,Yongkang Luo,Qian Chen,Chunmu Feng,Chao Cao,Jianhui Dai,Qian Tao,Guanghan Cao,Zhu-an Xu###

K and Mn co-doped BaCd2As2: a hexagonal structured bulk diluted magnetic semiconductor with large magnetoresistance. A bulk diluted magnetic semiconductor was found in the K and Mn co-doped
BaCd2As2 system. Different from recently reported tetragonal
ThCr2Si2-structured II-II-V based(Ba,K)(Zn,Mn)2As2, the Ba1-yKyCd2-xMnxAs2
system has a hexagonal CaAl2Si2-type structure with the Cd2As2 layer forming a
honeycomb-like network. The Mn concentration reaches up to its x ? 0.4.
Magnetization measurements show that the samples undergo ferromagnetic
transitions with Curie temperature up to 16 K. With low coercive field less
than 10 Oe and large magnetoresistence of about -70%, the hexagonal structured
Ba1-yKyCd2-xMnxAs2 can be served as a promising candidate for spin
manipulations.

###Giant magnetoresistance and perfect spin filter in silicene, germanene, and stanene|Stephan Rachel,Motohiko Ezawa###

Giant magnetoresistance and perfect spin filter in silicene, germanene, and stanene. Silicene, germanene and stanene are two-dimensional topological insulators
exhibiting helical edge states. We investigate global and local manipulations
at the edges by exposing them to (i) a charge-density-wave order, (ii) a
superconductor, (iii) an out-of-plane antiferromagnetic, and (iv) an in-plane
antiferromagnetic field. We show that these perturbations affect the helical
edge states in a different fashion. As a consequence one can realize quantum
spin-Hall effect without edge states. In addition, these edge manipulations
lead to very promising applications: a giant magnetoresistance and a perfect
spin filter. We also investigate the effect of manipulations on a very few
edge-sites of a topological insulator nanodisk.

###Validity of Kohler's rule in the pseudogap phase of the cuprate superconductors|M. K. Chan,M. J. Veit,C. J. Dorow,Y. Ge,Y. Li,W. Tabis,Y. Tang,X. Zhao,N. Barišić,M. Greven###

Validity of Kohler's rule in the pseudogap phase of the cuprate superconductors. We report in-plane resistivity ($\rho$) and transverse magnetoresistance (MR)
measurements in underdoped HgBa$_2$CuO$_{4+\delta}$ (Hg1201). Contrary to the
longstanding view that Kohler's rule is strongly violated in underdoped
cuprates, we find that it is in fact satisfied in the pseudogap phase of
Hg1201. The transverse MR shows a quadratic field dependence,
$\delta\rho/\rho_o=a H^{2}$, with $a(T)\propto T^{-4}$. In combination with the
observed $\rho\propto T^2$ dependence, this is consistent with a single
Fermi-liquid quasiparticle scattering rate. We show that this behavior is
universal, yet typically masked in cuprates with lower structural symmetry or
strong disorder effects.

###Non-diffusion theory of weak localization in graphene|M. O. Nestoklon,N. S. Averkiev###

Non-diffusion theory of weak localization in graphene. We put forward a theory of the weak localization in two dimensional graphene
layers which explains experimentally observable transition between positive and
negative magnetoresistance. Calculations are performed for the whole range of
classically weak magnetic field with account on intervalley transitions.
Contribution to the quantum correction which stems from closed trajectories
with few scatterers is carefully taken into account. We show that intervalley
transitions lead not only to the transition from weak antilocalization to the
weak localization, but also to the non-monotonous dependence of the
conductivity on the magnetic field.

###A 4-fold-symmetry hexagonal ruthenium for magnetic heterostructures exhibiting enhanced perpendicular magnetic anisotropy and tunnel magnetoresistance|Zhenchao Wen,Hiroaki Sukegawa,Takao Furubayashi,Jungwoo Koo,Koichiro Inomata,Seiji Mitani,Jason Paul Hadorn,Tadakatsu Ohkubo,Kazuhiro Hono###

A 4-fold-symmetry hexagonal ruthenium for magnetic heterostructures exhibiting enhanced perpendicular magnetic anisotropy and tunnel magnetoresistance. An unusual crystallographic orientation of hexagonal Ru with a 4-fold
symmetry emerging in epitaxial MgO/Ru/Co2FeAl/MgO heterostructures is reported,
in which an approximately Ru(02-23) growth attributes to the lattice matching
among MgO, Ru, and Co2FeAl. Perpendicular magnetic anisotropy of the
Co2FeAl/MgO interface is substantially enhanced as compared with those with a
Cr(001) layer. The MTJs incorporating this structure gave rise to the largest
tunnel magnetoresistance for perpendicular MTJs using low damping Heusler
alloys. The 4-fold-symmetry hexagonal Ru arises from an epitaxial growth with
an unprecedentedly high crystal index, opening a unique pathway for the
development of perpendicular anisotropy films of cubic and tetragonal
ferromagnetic alloys.

###Circular single domains in hemispherical small size Permalloy clusters|Clodoaldo I. L. de Araujo,Jakson M. Fonseca,João P. Sinnecker,Rafael G. Delatorre,Nicolas G. Garcia,André A. Pasa###

Circular single domains in hemispherical small size Permalloy clusters. We have studied ferromagnetic Permalloy clusters obtained by
electrodeposition on n-type silicon. Magnetization measurements reveal
hysteresis loops almost independent on temperature and very similar in shape to
those obtained in nanodisks with diameter bigger than 150nm. The spin
configuration for the ground state, obtained by micromagnetic simulation, shows
topological vortices with random chirality and polarization. This behaviour in
the small diameter clusters (~80nm), is attributed to the Dzyaloshinskii-Moriya
interaction that arises in its hemispherical geometries. This magnetization
behaviour can be utilized to explain the magnetoresistance measured with
magnetic field in plane and out of sample plane.

###Spin-valve effects in point contacts to exchange biased Co40Fe40B20 films|O. P. Balkashin,V. V. Fisun,L. Yu. Triputen,S. Andersson,V. Korenivski,Yu. G. Naidyuk###

Spin-valve effects in point contacts to exchange biased Co40Fe40B20 films. Nonlinear current-voltage characteristics and magnetoresistance of point
contacts between a normal metal (N) and films of amorphous ferromagnet (F)
Co40Fe40B20 of different thickness, exchange-biased by antiferromagnetic
Mn80Ir20 are studied. A surface spin valve effect in the conductance of such
F-N contacts is observed. The effect of exchange bias is found to be inversely
proportional to the Co40Fe40B20 film thickness. This behavior as well as other
magneto-transport effects we observe on single exchange-pinned ferromagnetic
films are similar in nature to those found in conventional three-layer
spin-valves.

###Effects of impurity on tunnel magnetoresistance in a ferromagnetic electrode/carbon nanotube/ferromagnetic electrode junctio|A. Ahmadi Fouladi,J. Vahedi,M. Soleymani###

Effects of impurity on tunnel magnetoresistance in a ferromagnetic electrode/carbon nanotube/ferromagnetic electrode junctio. Effects of impurity on the spin-dependent transport in a single wall carbon
nanotube spin-valve, as ferromagnetic electrode/carbon nanotube/ferromagnetic
electrode model junction is numerically investigated. Using a generalized
Green's function method and the Landauer-Buttiker formalism, the impurity
conditions are determined by randomly substitution of carbon atoms in the
honeycomb carbon nanotube lattice by nitrogen and boron atoms. We have found
that transport characteristics, including the spin-dependent current and tunnel
magnetoresistance are strongly influenced by the impurity effects. We think
that the results of the present report could be useful for designing the future
spintronic devices.

###Evidence of a small crystal field anisotropy in GdCoIn$_5$|Diana Betancourth,Victor F. Correa,Daniel J. García###

Evidence of a small crystal field anisotropy in GdCoIn$_5$. We investigate the effects of an applied magnetic field on the magnetic
properties of the antiferromagnet GdCoIn$_5$. The prominent anisotropy observed
in the susceptibility below $T_N$ is rapidly suppressed by a field of just a
few Tesla. Further evidence of this low energy-scale is obtained from
magnetoresistance and magnetostriction experiments. The lattice lenght,
particulary, shows a sudden change below 2 Tesla when the magnetic field is
applied perpendicular to the crystallographic $\hat{c}$-axis. The experimental
results as a whole can be attributed to a small but non negligible higher-order
crystalline electric field.

###Quantum interference in HgTe structures|I. V. Gornyi,V. Yu. Kachorovskii,A. D. Mirlin,P. M. Ostrovsky###

Quantum interference in HgTe structures. We study quantum transport in HgTe/HgCdTe quantum wells under the condition
that the chemical potential is located outside of the bandgap. We first analyze
symmetry properties of the effective Bernevig-Hughes-Zhang Hamiltonian and the
relevant symmetry-breaking perturbations. Based on this analysis, we overview
possible patterns of symmetry breaking that govern the quantum interference
(weak localization or weak antilocalization) correction to the conductivity in
two dimensional HgTe/HgCdTe samples. Further, we perform a microscopic
calculation of the quantum correction beyond the diffusion approximation.
Finally, the interference correction and the low-field magnetoresistance in a
quasi-one-dimensional geometry are analyzed.

###Detection of the dc inverse spin Hall effect due to spin pumping in a novel meander-stripline geometry|Mathias Weiler,Justin M. Shaw,Hans T. Nembach,Thomas J. Silva###

Detection of the dc inverse spin Hall effect due to spin pumping in a novel meander-stripline geometry. The dc voltage obtained from the inverse spin Hall effect (iSHE) due to spin
pumping in ferromagnet/normal-metal (NM) bilayers can be unintentionally
superimposed with magnetoresistive rectification of ac charge currents in the
ferromagnetic layer. We introduce a geometry in which these spurious
rectification voltages vanish while the iSHE voltage is maximized. In this
geometry, a quantitative study of the dc iSHE is performed in a broad frequency
range for Permalloy/NM multilayers with NM={Pt, Ta, Cu/Au, Cu/Pt}. The
experimentally recorded voltages can be fully ascribed to the iSHE due to spin
pumping. Furthermore we measure a small iSHE voltage in single CoFe thin films.

###Sign Reversal of anisotropic magnetoresistance in La0.7Ca0.3MnO3/STO ultrathin films|Himanshu Sharma,A. Tulapurkar,C. V. Tomy###

Sign Reversal of anisotropic magnetoresistance in La0.7Ca0.3MnO3/STO ultrathin films. We present the observation of strain induced sign reversal of anisotropic
magnetoresistance (AMR) in LCMO (LCMO) ultrathin films (thickness 4 nm)
deposited on STO (001) substrate (STO). We have also observed unusually large
AMR in LCMO/STO thin films with thickness of 6 nm below but close to its Curie
temperature (TC) which decrease as the film thickness increases. The sign
reversal of AMR (with a maximum value of - 6) with magnetic field or
temperature for the 4 nm thin film may be attributed to the increase in tensile
strain in the plane of the thin film which in turn facilitates the rotation of
the magnetization easy axis.

###Absence of a transport signature of spin-orbit coupling in graphene with indium adatoms|Zhenzhao Jia,Baoming Yan,Jingjing Niu,Qi Han,Rui Zhu,Xiaosong Wu,Dapeng Yu###

Absence of a transport signature of spin-orbit coupling in graphene with indium adatoms. Enhancement of the spin-orbit coupling in graphene may lead to various
topological phenomena and also find applications in spintronics. Adatom
absorption has been proposed as an effective way to achieve the goal. In
particular, great hope has been held for indium in strengthening the spin-orbit
coupling and realizing the quantum spin Hall effect. To search for evidence of
the spin-orbit coupling in graphene absorbed with indium adatoms, we carry out
extensive transport measurements, i.e., weak localization magnetoresistance,
quantum Hall effect and non-local spin Hall effect. No signature of the
spin-orbit coupling is found. Possible explanations are discussed.

###Spin Hall noise|Akashdeep Kamra,Friedrich P. Witek,Sibylle Meyer,Hans Huebl,Stephan Geprägs,Rudolf Gross,Gerrit E. W. Bauer,Sebastian T. B. Goennenwein###

Spin Hall noise. We measure the low-frequency thermal fluctuations of pure spin current in a
Platinum film deposited on yttrium iron garnet via the inverse spin Hall effect
(ISHE)-mediated voltage noise as a function of the angle $\alpha$ between the
magnetization and the transport direction. The results are consistent with the
fluctuation dissipation theorem in terms of the recently discovered spin Hall
magnetoresistance (SMR). We present a microscopic description of the $\alpha$
dependence of the voltage noise in terms of spin current fluctuations and ISHE.

###Magnetoresistance Anisotropy in Amorphous Superconducting Thin Films: A Site-Bond Percolation Approach|Elkana Porat,Yigal Meir###

Magnetoresistance Anisotropy in Amorphous Superconducting Thin Films: A Site-Bond Percolation Approach. Recent measurements of the magnetoresistance (MR) of amorphous
superconducting thin films in tilted magnetic fields have displayed several
surprising experimental details, in particular a strong dependence of the MR on
field angle at low magnetic fields, which diminishes and then changes sign at
large fields. Using a generalized site-bond percolation model, that takes into
account both the orbital and Zeeman effects of the magnetic field, we show that
the resulting MR curves reproduce the main experimental features. Such
measurements, accompanied by the corresponding theory, may be crucial in
pinpointing the correct theory of the superconductor-insulator transition and
of the MR peak in thin disordered films.

###Quantification of the spin-Hall anti-damping torque with a resonance spectrometer|Satoru Emori,Tianxiang Nan,Trevor M. Oxholm,Carl T. Boone,John G. Jones,Brandon M. Howe,Gail J. Brown,David E. Budil,Nian X. Sun###

Quantification of the spin-Hall anti-damping torque with a resonance spectrometer. We present a simple technique using a cavity-based resonance spectrometer to
quantify the anti-damping torque due to the spin Hall effect. Modification of
ferromagnetic resonance is observed as a function of small DC current in
sub-mm-wide strips of bilayers, consisting of magnetically soft FeGaB and
strong spin-Hall metal Ta. From the detected current-induced linewidth change,
we obtain an effective spin Hall angle of 0.08-0.09 independent of the magnetic
layer thickness. Our results demonstrate that a sensitive resonance
spectrometer can be a general tool to investigate spin Hall effects in various
material systems, even those with vanishingly low conductivity and
magnetoresistance.

###Electrical detection of the spin polarization due to charge flow in the surface state of the topological insulator Bi_1.5 Sb_0.5 Te_1.7 Se_1.3|Yuichiro Ando,Takahiro Hamasaki,Takayuki Kurokawa,Kouki Ichiba,Fan Yang,Mario Novak,Satoshi Sasaki,Kouji Segawa,Yoichi Ando,Masashi Shiraishi###

Electrical detection of the spin polarization due to charge flow in the surface state of the topological insulator Bi_1.5 Sb_0.5 Te_1.7 Se_1.3. We detected the spin polarization due to charge flow in the spin
non-degenerate surface state of a three dimensional topological insulator by
means of an all-electrical method. The charge current in the bulk-insulating
topological insulator Bi1.5Sb0.5Te1.7Se1.3 (BSTS) was injected/extracted
through a ferromagnetic electrode made of Ni80Fe20, and an unusual
current-direction-dependent magnetoresistance gives evidence for the appearance
of spin polarization which leads to a spin-dependent resistance at the
BSTS/Ni80Fe20 interface. In contrast, our control experiment on Bi2Se3 gave
null result. These observations demonstrate the importance of the Fermi-level
control for the electrical detection of the spin polarization in topological
insulators.

###Fractional Quantum Hall Effect at Landau Level Filling nu=4/11|W. Pan,K. W. Baldwin,K. W. West,L. N. Pfeiffer,D. C. Tsui###

Fractional Quantum Hall Effect at Landau Level Filling nu=4/11. We report low temperature electronic transport results on the fractional
quantum Hall effect of composite fermions at Landau level filling nu = 4/11 in
a very high mobility and low density sample. Measurements were carried out at
temperatures down to 15mK, where an activated magnetoresistance Rxx and a
quantized Hall resistance Rxy, within 1% of the expected value of h/(4/11)e^2,
were observed. The temperature dependence of the Rxx minimum at 4/11 yields an
activation energy gap of ~ 7 mK. Developing Hall plateaus were also observed at
the neighboring states at nu = 3/8 and 5/13.

###Perfect charge compensation in WTe2 for the extraordinary magnetoresistance: From bulk to monolayer|H. Y. Lv,W. J. Lu,D. F. Shao,Y. Liu,S. G. Tan,Y. P. Sun###

Perfect charge compensation in WTe2 for the extraordinary magnetoresistance: From bulk to monolayer. The electronic structure of WTe2 bulk and layers are investigated by using
the first principles calculations. The perfect electron-hole (n-p) charge
compensation and high carrier mobilities are found in WTe2 bulk, which may
result in the large and non-saturating magnetoresistance (MR) observed very
recently in the experiment [Ali et al., Nature 514, 205 (2014)]. The monolayer
and bilayer of WTe2 preserve the semimetallic property, with the equal hole and
electron carrier concentrations. Moreover, the very high carrier mobilities are
also found in WTe2 monolayer, indicating that the WTe2 monolayer would have the
same extraordinary MR effect as the bulk, which could have promising
applications in nanostructured magnetic devices.

###The Electronic and Magnetic Properties of Magnetoresistant Nd1-xSrxMnAsO Oxyarsenides|E. J. Wildman,N. Emery,A. C. Mclaughlin###

The Electronic and Magnetic Properties of Magnetoresistant Nd1-xSrxMnAsO Oxyarsenides. The oxypnictides Nd1-xSrxMnAsO have been successfully synthesised with x up
to 0.1. A synchrotron X-ray diffraction study demonstrates that there is no
change in crystal symmetry upon doping with Sr. An expansion of the inter-layer
distance between Nd-O-Nd and As-Mn-As blocks is observed with increasing x.
Results from variable temperature neutron diffraction and resistivity
measurements show that the local moment antiferromagnetic order of the Mn spins
is preserved as the [MnAs]- layers are hole doped and the materials are driven
metallic for x > 0.05. A sizeable positive magnetoresistance is observed at low
temperature which demonstrates that multiple MR mechanisms are possible in
LnMnAsO oxypnictides.

###Aharonov Bohm effect in 2D topological insulator|G. M. Gusev,Z. D. Kvon,O. A. Shegai,N. N. Mikhailov,S. A. Dvoretsky###

Aharonov Bohm effect in 2D topological insulator. We present magnetotransport measurements in HgTe quantum well with inverted
band structure, which expected to be a two-dimensional topological insulator
having the bulk gap with helical gapless states at the edge. The negative
magnetoresistance is observed in the local and nonlocal resistance
configuration followed by the periodic oscillations damping with magnetic
field. We attribute such behaviour to Aharonov-Bohm effect due to magnetic flux
through the charge carrier puddles coupled to the helical edge states. The
characteristic size of these puddles is about 100 nm.

###Magnetic Coupling in Ferromagnetic Semiconductor GaMnAs/AlGaMnAs Bilayer Devices|Y. F. Cao,Yanyong Li,Yuanyuan Li,G. N. Wei,Y. Ji,K. Y. Wang###

Magnetic Coupling in Ferromagnetic Semiconductor GaMnAs/AlGaMnAs Bilayer Devices. We carefully investigated the ferromagnetic coupling in the as-grown and
annealed ferromagnetic semiconductor GaMnAs/AlGaMnAs bilayer devices. We
observed that the magnetic interaction between the two layers strongly affects
the magnetoresistance of the GaMnAs layer with applying out of plane magnetic
field. After low temperature annealing, the magnetic easy axis of the AlGaMnAs
layer switches from out of plane into in-plane and the interlayer coupling
efficiency is reduced from up to 0.6 to less than 0.4. However, the magnetic
coupling penetration depth for the annealed device is twice that of the
as-grown bilayer device.

###Raman scattering investigation of large positive magnetoresistance material WTe$_2$|W. -D. Kong,S. -F. Wu,P. Richard,C. -S. Lian,J. -T. Wang,C. -L. Yang,Y. -G. Shi,H. Ding###

Raman scattering investigation of large positive magnetoresistance material WTe$_2$. We have performed polarized Raman scattering measurements on WTe$_2$, for
which an extremely large positive magnetoresistance has been reported recently.
We observe 5 A$_1$ phonon modes and 2 A$_2$ phonon modes out of 33 Raman active
modes, with frequencies in good accordance with first-principles calculations.
The angular dependence of the intensity of the peaks observed is consistent
with the Raman tensors of the $C_{2v}$ point group symmetry attributed to
WTe$_2$. Although the phonon spectra suggest neither strong electron-phonon nor
spin-phonon coupling, the intensity of the A$_1$ phonon mode at 160.6 cm$^{-1}$
shows an unconventional decrease with temperature decreasing, for which the
origin remains unclear.

###Change in sign of the Hall coefficient from Fermi surface curvature in underdoped high Tc copper oxide superconductors|N. Harrison,S. E. Sebastian###

Change in sign of the Hall coefficient from Fermi surface curvature in underdoped high Tc copper oxide superconductors. It has recently been proposed that the Fermi surface of underdoped high Tc
copper oxide materials within the charge-ordered regime consists of a
diamond-shaped electron pocket constructed from arcs connected at vertices. We
show here that on modeling the in-plane magnetotransport of such a Fermi
surface using the Shockley-Chambers tube integral approach and a uniform
scattering time, several key features of the normal state in-plane transport of
the underdoped copper oxide systems can be understood. These include the sign
reversal in the Hall coefficient, the positive magnetoresistance and magnetic
quantum oscillations in the Hall coefficient.

###Surface-state-dominated transport in crystals of the topological crystalline insulator In-doped Pb$_{1-x}$Sn$_x$Te|Ruidan Zhong,Xugang He,John A. Schneeloch,Cheng Zhang,Tiansheng Liu,Ivo Pletikosic,Qiang Li,Wei Ku,Tonica Valla,J. M. Tranquada,Genda Gu###

Surface-state-dominated transport in crystals of the topological crystalline insulator In-doped Pb$_{1-x}$Sn$_x$Te. Three-dimensional topological insulators and topological crystalline
insulators represent new quantum states of matter, which are predicted to have
insulating bulk states and spin-momentum-locked gapless surface states.
Experimentally, it has proven difficult to achieve the high bulk resistivity
that would allow surface states to dominate the transport properties over a
substantial temperature range. Here we report a series of indium-doped
Pb$_{1-x}$Sn$_x$Te compounds that manifest huge bulk resistivities together
with strong evidence of topological surface states, based on
thickness-dependent transport studies and magnetoresistance measurements. For
these bulk-insulating materials, the surface states determine the resistivity
for temperatures approaching 30 K.

###Bulk crystal growth and electronic characterization of the 3D Dirac Semimetal Na3Bi|Satya K. Kushwaha,Jason W. Krizan,Benjamin E. Feldman,Andras Gyenis,Mallika T. Randeria,Jun Xiong,Su-Yang Xu,Nasser Alidoust,Ilya Belopolski,Tian Liang,M. Zahid Hasan,N. P. Ong,A. Yazdani,R. J. Cava###

Bulk crystal growth and electronic characterization of the 3D Dirac Semimetal Na3Bi. High quality hexagon plate-like Na3Bi crystals with large (001) plane
surfaces were grown from a molten Na flux. The freshly cleaved crystals were
analyzed by low temperature scanning tunneling microscopy (STM) and
angle-resolved photoemission spectroscopy (ARPES), allowing for the
characterization of the three-dimensional (3D) Dirac semimetal (TDS) behavior
and the observation of the topological surface states. Landau levels (LL) were
observed, and the energy-momentum relations exhibited a linear dispersion
relationship, characteristic of the 3D TDS nature of Na3Bi. In transport
measurements on Na3Bi crystals the linear magnetoresistance and Shubnikov-de
Haas (SdH) quantum oscillations are observed for the first time.

###Observation of quantum transport features in graphene devices fabricated utilizing a nano-manipulating probe technique|Christopher Coleman,Davie Mtsuko,Chris Botha,Somnath Bhattacharyyaa###

Observation of quantum transport features in graphene devices fabricated utilizing a nano-manipulating probe technique. A novel method for fast fabrication of mesoscopic multilayered graphene
electronic devices utilizing nanoprobes to exfoliate graphite flakes is
developed. The magnetoresistance of these devices exhibit pronounced
Shubnikov-de Haas oscillations at magnetic fields above 4 T and at temperatures
below 30 K. From the analysis of the SdH oscillations we show that multilayer
graphene devices have a carrier density and effective mass (m*= 0.042me -
0.083me) comparable to those of bilayer and trilayer graphene. The quantum
lifetime in this multilayered graphene is in the range 22 to 90 fs
corresponding to a disorder-broadening of 5 to 15 meV.

###Anisotropic magnetoresistance driven by surface spin orbit scattering|Steven S. -L. Zhang,Giovanni Vignale,Shufeng Zhang###

Anisotropic magnetoresistance driven by surface spin orbit scattering. In a bilayer consisting of an insulator (I) and a ferromagnetic metal (FM),
interfacial spin orbit scattering leads to spin mixing of the two conducting
channels of the FM, which results in an unconventional anisotropic
magnetoresistance (AMR). We theoretically investigate the magnetotransport in
such bilayer structures by solving the spinor Boltzmann transport equation with
generalized Fuchs-Sondheimer boundary condition that takes into account the
effect of spin orbit scattering at the interface. We find that the new AMR
exhibits a peculiar angular dependence which can serve as a genuine
experimental signature. We also determine the dependence of the AMR on film
thickness as well as spin polarization of the FM.

###Electron degeneracy and intrinsic magnetic properties of epitaxial Nb:SrTiO$_3$ thin-films controlled by defects|A. Sarantopoulos,E. Ferreiro-Vila,V. Pardo,C. Magen,M. H. Aguirre,F. Rivadulla###

Electron degeneracy and intrinsic magnetic properties of epitaxial Nb:SrTiO$_3$ thin-films controlled by defects. We report thermoelectric power experiments in e-doped thin films of SrTiO$_3$
(STO) which demonstrate that the electronic band degeneracy can be lifted
through defect management during growth. We show that even small amounts of
cationic vacancies, combined with epitaxial stress, produce a homogeneous
tetragonal distortion of the films, resulting in a Kondo-like resistance upturn
at low temperature, large anisotropic magnetoresistance, and non-linear Hall
effect. Ab-initio calculations confirm a different occupation of each band
depending on the degree of tetragonal distortion. The phenomenology reported in
this paper for tetragonally distorted e-doped STO thin films, is similarto that
observed in LaAlO$_3$/STO interfaces and magnetic STO quantum wells.

###Slow oscillations of in-plane magnetoresistance in strongly anisotropic quasi-two-dimensional rare-earth tritellurides|P. D. Grigoriev,A. A. Sinchenko,P. Lejay,O. Leynaud,V. N. Zverev,P. Monceau###

Slow oscillations of in-plane magnetoresistance in strongly anisotropic quasi-two-dimensional rare-earth tritellurides. Slow oscillations of the in-plane magnetoresistance are observed in the
rare-earth tritellurides and proposed as an effective tool to determine the
parameters of electronic structure in various strongly anisotropic
quasi-two-dimensional compounds. These oscillations do not originate from the
small Fermi surface pockets, as revealed usually by the Shubnikov-de-Haas
oscillations, but from the entanglement of close frequencies due to a finite
interlayer transfer integral $t_z$, which allows to estimate its value. For
TbTe$_3$ and GdTe$_3$ we obtain the estimate $t_z\approx 1$ meV.

###Zero-field dissipationless chiral edge transport and the nature of dissipation in the quantum anomalous Hall state|Cui-Zu Chang,Weiwei Zhao,Duk Y. Kim,Peng Wei,J. K. Jain,Chaoxing Liu,Moses H. W. Chan,Jagadeesh S. Moodera###

Zero-field dissipationless chiral edge transport and the nature of dissipation in the quantum anomalous Hall state. The quantum anomalous Hall (QAH) effect is predicted to possess, at zero
magnetic field, chiral edge channels that conduct spin polarized current
without dissipation. While edge channels have been observed in previous
experimental studies of the QAH effect, their dissipationless nature at a zero
magnetic field has not been convincingly demonstrated. By a comprehensive
experimental study of the gate and temperature dependences of local and
nonlocal magnetoresistance, we unambiguously establish the dissipationless edge
transport. By studying the onset of dissipation, we also identify the origin of
dissipative channels and clarify the surprising observation that the critical
temperature of the QAH effect is two orders of magnitude smaller than the Curie
temperature of ferromagnetism.

###Negative Magnetoresistance in Amorphous Indium Oxide Wires|Sreemanta Mitra,Girish C Tewari,Diana Mahalu,Dan Shahar###

Negative Magnetoresistance in Amorphous Indium Oxide Wires. We study magneto-transport properties of several amorphous Indium oxide
nanowires of different widths. The wires show superconducting transition at
zero magnetic field, but, there exist a finite resistance at the lowest
temperature. The $R(T)$ broadening was explained by available phase slip
models. At low field, and far below the superconducting critical temperature,
the wires with diameter equal to or less than 100 nm, show negative
magnetoresistance (nMR). The magnitude of nMR and the crossover field are found
to be dependent on both temperature and the cross-sectional area. We find that
this intriguing behavior originates from the interplay between two field
dependent contributions.

###Chiral anomaly induced negative magnetoresistance in topological Weyl semimetal NbAs|Xiaojun Yang,Yupeng Liu,Zhen Wang,Yi Zheng,Zhu-an Xu###

Chiral anomaly induced negative magnetoresistance in topological Weyl semimetal NbAs. In this paper, we report the intercone transport of Weyl fermions in NbAs
with external magnetic field in parallel to electric field, a quantum
phenomenon known as the Adler-Bell-Jackiw anomaly. Surprisingly, the resulting
negative magnetoresistance (MR) in NbAs shows significant difference from NbP.
The observed low-field positive MR dip, which is missing in NbP at low
temperatures, indicates that the spin-orbital coupling (SOC) is significantly
stronger in NbAs than in the former. The results imply that the contribution of
arsenic to SOC in TaAs and NbAs is not negligible.

###Formation of In-plane Skyrmions in Epitaxial MnSi Thin Films as Revealed by Planar Hall Effect|T. Yokouchi,N. Kanazawa,A. Tsukazaki,Y. Kozuka,A. Kikkawa,Y. Taguchi,M. Kawasaki,M. Ichikawa,F. Kagawa,Y. Tokura###

Formation of In-plane Skyrmions in Epitaxial MnSi Thin Films as Revealed by Planar Hall Effect. We investigate skyrmion formation in both a single crystalline bulk and
epitaxial thin films of MnSi by measurements of planar Hall effect. A prominent
stepwise field profile of planar Hall effect is observed in the
well-established skyrmion phase region in the bulk sample, which is assigned to
anisotropic magnetoresistance effect with respect to the magnetic modulation
direction. We also detect the characteristic planar Hall anomalies in the thin
films under the in-plane magnetic field at low temperatures, which indicates
the formation of skyrmion strings lying in the film plane. Uniaxial magnetic
anisotropy plays an important role in stabilizing the in-plane skyrmions in the
MnSi thin film.

###Thermally-Activated Phase Slips in Superfluid Spin Transport in Magnetic Wires|Se Kwon Kim,So Takei,Yaroslav Tserkovnyak###

Thermally-Activated Phase Slips in Superfluid Spin Transport in Magnetic Wires. We theoretically study thermally-activated phase slips in superfluid spin
transport in easy-plane magnetic wires within the stochastic
Landau-Lifshitz-Gilbert phenomenology, which runs parallel to the
Langer-Ambegaokar-McCumber-Halperin theory for thermal resistances in
superconducting wires. To that end, we start by obtaining the exact solutions
for free-energy minima and saddle points. We provide an analytical expression
for the phase-slip rate in the zero spin-current limit, which involves detailed
analysis of spin fluctuations at extrema of the free energy. An experimental
setup of a magnetoeletric circuit is proposed, in which thermal phase slips can
be inferred by measuring nonlocal magnetoresistance.

###Kondo effect goes anisotropic in vanadate oxide superlattices|Hélène Rotella,Alain Pautrat,Olivier Copie,Philippe Boullay,Adrian David,Bernard Mercey,Magali Morales,Wilfrid Prellier###

Kondo effect goes anisotropic in vanadate oxide superlattices. We study the transport properties in SrVO3/LaVO3 (SVO/LVO) superlattices
deposited on SrTiO3 (STO) substrates. We show that the electronic conduction
occurs in the metallic LVO layers with a galvanomagnetism typical of a 2D Fermi
surface. In addition, a Kondo-like component appears in both the thermal
variation of resistivity and the magnetoresistance. Surprisingly, in this
system where the STO interface does not contribute to the measured conduction,
the Kondo correction is strongly anisotropic. We show that the growth
temperature allows a direct control of this contribution. Finally, the key role
of vanadium mixed valency stabilized by oxygen vacancies is enlightened.

###Spin injection into multilayer graphene from highly spin-polarized Co2FeSi Heusler alloy|Takehiro Yamaguchi,Rai Moriya,Yoichiro Oki,Shinya Yamada,Satoru Masubuchi,Kohei Hamada,Tomoki Machida###

Spin injection into multilayer graphene from highly spin-polarized Co2FeSi Heusler alloy. We demonstrate electrical spin injection into multilayer graphene (MLG) in a
lateral spin valve device from a highly spin-polarized Co2FeSi (CFS) Huesler
electrode. Exfoliated MLG was transferred onto pre-patterned epitaxial CFS
wires grown on an Si(111) substrate by a polymer-based transfer method. This
method enabled us to fabricate multiple single-crystal CFS electrodes in
contact with MLG. Electrical spin injection from CFS to MLG was detected
through non-local magnetoresistance (MR) measurement. A non-local spin signal
of 430 ohm was observed; this is the largest value among all reported non-local
MR values in graphene-based devices.

###Low temperature Hall effect in bismuth chalcogenides thin films|A. Yu. Kuntsevich,A. A. Gabdullin,V. A. Prudkogliad,Yu. G. Selivanov,E. G. Chizhevskii,V. M. Pudalov###

Low temperature Hall effect in bismuth chalcogenides thin films. Bismuth chalcogenides are the most studied 3D topological insulators. As a
rule, at low temperatures thin films of these materials demonstrate positive
magnetoresistance due to weak antilocalization. Weak antilocalization should
lead to resistivity decrease at low temperatures; in experiments, however,
resistivity grows as temperature decreases. From transport measurements for
several thin films (with various carrier density, thickness, and carrier
mobility), and by using purely phenomenological approach, with no microscopic
theory, we show that the low temperature growth of the resistivity is
accompanied by growth of the Hall coefficient, in agreement with diffusive
electron-electron interaction correction mechanism. Our data reasonably explain
the low-temperature resistivity upturn.

###Distinct Electronic Structure for the Extreme Magnetoresistance in YSb|Junfeng He,Chaofan Zhang,Nirmal J. Ghimire,Tian Liang,Chunjing Jia,Juan Jiang,Shujie Tang,Sudi Chen,Yu He,S. -K. Mo,C. C. Hwang,M. Hashimoto,D. H. Lu,B. Moritz,T. P. Devereaux,Y. L. Chen,J. F. Mitchell,Z. -X. Shen###

Distinct Electronic Structure for the Extreme Magnetoresistance in YSb. An extreme magnetoresistance (XMR) has recently been observed in several
non-magnetic semimetals. Increasing experimental and theoretical evidence
indicates that the XMR can be driven by either topological protection or
electron-hole compensation. Here, by investigating the electronic structure of
a XMR material, YSb, we present spectroscopic evidence for a special case which
lacks topological protection and perfect electron-hole compensation. Further
investigations reveal that a cooperative action of a substantial difference
between electron and hole mobility and a moderate carrier compensation might
contribute to the XMR in YSb.

###Anisotropic magnetotransport in Dirac-Weyl magnetic junctions|Yuya Ominato,Koji Kobayashi,Kentaro Nomura###

Anisotropic magnetotransport in Dirac-Weyl magnetic junctions. We theoretically study the anisotropic magnetotransport in Dirac-Weyl
magnetic junctions where a doped ferromagnetic Weyl semimetal is sandwiched
between doped Dirac semimetals. We calculate the conductance using the Landauer
formula and find that the system exhibits extraordinarily large anisotropic
magnetoresistance (AMR). The AMR depends on the ratio of the Fermi energy and
the strength of the exchange interaction. The origin of the AMR is the shift of
the Fermi surface in the Weyl semimetal and the mechanism is completely
different from the conventional AMR originating from the spin dependent
scattering and the spin-orbit interaction.

###Electrical Detection of Spin Backflow from an Antiferromagnetic Insulator/Y3Fe5O12 Interface|Weiwei Lin,C. L. Chien###

Electrical Detection of Spin Backflow from an Antiferromagnetic Insulator/Y3Fe5O12 Interface. Spin Hall magnetoresistance (SMR) has been observed in Pt/NiO/Y3Fe5O12 (YIG)
heterostructures with characteristics very different from those in Pt/YIG. We
show that the SMR in Pt/NiO/YIG strongly correlates with spin conductance, both
sharing very strong temperature dependence due to antiferromagnetic magnons and
spin fluctuation. This phenomenon indicates that spin current generated by spin
Hall effect in the Pt transmits through the insulating NiO and is reflected
from the NiO/YIG interface. Inverted SMR has been observed below a temperature
which increases with the NiO thickness, suggesting spin-flip reflection from
the antiferromagnetic NiO exchange coupled with the YIG.

###Signature of surface state coupling in thin films of the topological Kondo insulator SmB$_6$ from anisotropic magnetoresistance|M. Shaviv Petrushevsky,P. K. Rout,G. Levi,A. Kohn,Y. Dagan###

Signature of surface state coupling in thin films of the topological Kondo insulator SmB$_6$ from anisotropic magnetoresistance. The temperature and thickness dependencies of the in-plane anisotropic
magnetoresistance (AMR) of SmB$_6$ thin films are reported. We find that the
AMR changes sign from negative ($\rho_{||}<\rho_{\perp}$) at high temperatures
to positive ($\rho_{||}>\rho_{\perp}$) at low temperatures. The temperature,
T$_s$, at which this sign change occurs, decreases with increasing film
thickness $t$ and T$_s$ vanishes for $t$ $>$ 30 nm. We interpret our results in
the framework of a competition between two components: a negative bulk
contribution and a positive surface AMR.

###Impurity-limited quantum transport variability in magnetic tunnel junctions|Jianing Zhuang,Yin Wang,Yan Zhou,Jian Wang,Hong Guo###

Impurity-limited quantum transport variability in magnetic tunnel junctions. We report an extensive first-principles investigation of impurity-induced
device-to-device variability of spin-polarized quantum tunneling through
Fe/MgO/Fe magnetic tunnel junctions (MTJ). In particular, we calculated the
tunnel magnetoresistance ratio (TMR) and the average values and variances of
the currents and spin transfer torque (STT) of an interfacially doped Fe/MgO/Fe
MTJ. Further, we predicted that N-doped MgO can improve the performance of a
doped Fe/MgO/Fe MTJ. Our first-principles calculations of the fluctuations of
the on/off currents and STT provide vital information for future predictions of
the long-term reliability of spintronic devices, which is imperative for
high-volume production.

###Gate-tunable strong-weak localization transition in few-layer black phosphorus|Gen Long,Shuigang Xu,Xiangbin Cai,Zefei Wu,Tianyi Han,Jiangxiazi Lin,Yuanwei Wang,Liheng An,Yuan Cai,Xinran Wang,Ning Wang###

Gate-tunable strong-weak localization transition in few-layer black phosphorus. Atomically thin black phosphorus (BP) field-effect transistors show
strong-weak localization transition which is tunable through gate voltages.
Hopping transports through charge impurity induced localized states are
measured at low-carrier density regime. Variable-range hopping model is applied
to simulate the charge carrier scattering behavior. In the high-carrier
concentration regime, a negative magnetoresistance signals the weak
localization effect. The extracted phase coherence length is power-law
temperature dependent ($\sim T^{-0.48\pm0.03}$) and demonstrates
electron-electron interactions in few-layer BP. The competition between the
Strong localization length and phase coherence length is proposed and discussed
based on the observed gate tunable strong-weak localization transition in
few-layer BP.

###Full Electroresistance Modulation in a Mixed-Phase Metallic Alloy|Z. Q. Liu,L. Li,Z. Gai,J. D. Clarkson,S. L. Hsu,A. T. Wong,L. S. Fan,M. -W. Lin,C. M. Rouleau,T. Z. Ward,H. N. Lee,A. S. Sefat,H. M. Christen,R. Ramesh###

Full Electroresistance Modulation in a Mixed-Phase Metallic Alloy. We report a giant, ~22%, electroresistance modulation for a metallic alloy
above room temperature. It is achieved by a small electric field of 2 kV/cm via
piezoelectric strain-mediated magnetoelectric coupling and the resulting
magnetic phase transition in epitaxial FeRh/BaTiO3 heterostructures. This work
presents detailed experimental evidence for an isothermal magnetic phase
transition driven by tetragonality modulation in FeRh thin films, which is in
contrast to the large volume expansion in the conventional temperature-driven
magnetic phase transition in FeRh. Moreover, all the experimental results in
this work illustrate FeRh as a mixed-phase model system well similar to
phase-separated colossal magnetoresistance systems with phase instability
therein.

###Magneto-transport and Electronic Structures of BaZnBi$_2$|Yi-Yan Wang,Peng-Jie Guo,Qiao-He Yu,Sheng Xu,Kai Liu,Tian-Long Xia###

Magneto-transport and Electronic Structures of BaZnBi$_2$. We report the magneto-transport properties and electronic structures of
BaZnBi$_2$. BaZnBi$_2$ is a quasi-two-dimensional (2D) material with metallic
behavior. The transverse magnetoresistance (MR) depends on magnetic field
linearly and exhibits Shubnikov-de Haas (SdH) oscillation at low temperature
and high field. The observed linear MR may originate from the disorder in
samples or the edge conductivity in compensated two-component systems. The
first-principles calculations reveal the absence of stable gapless Dirac
fermion. Combining with the trivial Berry phase extracted from SdH oscillation,
BaZnBi$_2$ is suggested to be a topologically trivial semimetal. Nearly
compensated electron-like Fermi surfaces (FSs) and hole-like FSs coexist in
BaZnBi$_2$.

###Anisotropic thermal magnetoresistance for an active control of radiative heat transfer|R. M. Abraham Ekeroth,Philippe Ben-Abdallah,Juan Carlos Cuevas,Antonio García-Martín###

Anisotropic thermal magnetoresistance for an active control of radiative heat transfer. We predict a huge anisotropic thermal magnetoresistance (ATMR) in the
near-field radiative heat transfer between magneto-optical particles when the
direction of an external magnetic field is changed with respect to the heat
current direction. We illustrate this effect with the case of two InSb
spherical particles where we find that the ATMR amplitude can reach values of
up to 800% for a magnetic field of 5 T, which is many orders of magnitude
larger than its spintronic analogue in electronic devices. This thermomagnetic
effect could find broad applications in the fields of ultrafast thermal
management as well as magnetic and thermal remote sensing.

###Asymmetric Electron-Hole Decoherence in Ion-Gated Epitaxial Graphene|Kil-Joon Min,Jaesung Park,Wan-Seop Kim,Dong-Hun Chae###

Asymmetric Electron-Hole Decoherence in Ion-Gated Epitaxial Graphene. We report on asymmetric electron-hole decoherence in epitaxial graphene gated
by an ionic liquid. The observed negative magnetoresistance near zero magnetic
field for different gate voltages, analyzed in the framework of weak
localization, gives rise to distinct electron-hole decoherence. The hole
decoherence rate increases prominently with decreasing negative gate voltage
while the electron decoherence rate does not exhibit any substantial gate
dependence. Quantitatively, the hole decoherence rate is as large as the
electron decoherence rate by a factor of two. We discuss possible microscopic
origins including spin-exchange scattering consistent with our experimental
observations.

###Transversal magnetotransport in Weyl semimetals: Exact numerical approach|Jan Behrends,Flore K. Kunst,Björn Sbierski###

Transversal magnetotransport in Weyl semimetals: Exact numerical approach. Magnetotransport experiments on Weyl semimetals are essential for
investigating the intriguing topological and low-energy properties of Weyl
nodes. If the transport direction is perpendicular to the applied magnetic
field, experiments have shown a large positive magnetoresistance. In this work,
we present a theoretical scattering matrix approach to transversal
magnetotransport in a Weyl node. Our numerical method confirms and goes beyond
the existing perturbative analytical approach by treating disorder exactly. It
is formulated in real space and is applicable to mesoscopic samples as well as
in the bulk limit. In particular, we study the case of clean and strongly
disordered samples.

###Topological Phase Transition-Induced Tri-Axial Vector Magnetoresistance in (Bi1-xInx)2Se3 Nanodevices|Minhao Zhang,Huaiqiang Wang,Kejun Mu,Pengdong Wang,Wei Niu,Shuai Zhang,Guiling Xiao,Yequan Chen,Tong Tong,Dongzhi Fu,Xuefeng Wang,Haijun Zhang,Fengqi Song,Feng Miao,Zhe Sun,Zhengcai Xia,Xinran Wang,Yongbing Xu,Baigeng Wang,Dingyu Xing,Rong Zhang###

Topological Phase Transition-Induced Tri-Axial Vector Magnetoresistance in (Bi1-xInx)2Se3 Nanodevices. We report the study of a tri-axial vector magnetoresistance (MR) in
nonmagnetic (Bi1-xInx)2Se3 nanodevices at the composition of x = 0.08. We show
a dumbbell-shaped in-plane negative MR up to room temperature as well as a
large out-of-plane positive MR. MR at three directions is about in a -3%: -1%:
225% ratio at 2 K. Through both the thickness and composition-dependent
magnetotransport measurements, we show that the in-plane negative MR is due to
the topological phase transition enhanced intersurface coupling near the
topological critical point. Our devices suggest the great potential for
room-temperature spintronic applications, for example, vector magnetic sensors.

###Heat capacity evidence for conventional superconductivity in the Type-II Dirac semi-metal PdTe$_2$|Amit,Yogesh Singh###

Heat capacity evidence for conventional superconductivity in the Type-II Dirac semi-metal PdTe$_2$. We use electrical transport, magnetoresistance, and heat capacity
measurements on high quality single crystals of the recently discovered
superconducting Type-II Dirac semi-metal PdTe$_2$, to probe the nature of it's
superconducting phase. The magnitude of the electronic heat capacity anomaly at
$T_c$, the low temperature exponential $T$ dependence of the heat capacity, and
a conventional $H - T$ phase diagram establish that the superconductivity in
PdTe$_2$ is conventional in nature despite the presence of a topologically
non-trivial Fermi surface band which contributes to the electrical conduction.

###Planar Hall effect in type-II Weyl semimetal WTe2|Y. J. Wang,J. X. Gong,D. D. Liang,M. Ge,J. R. Wang,W. K. Zhu,C. J. Zhang###

Planar Hall effect in type-II Weyl semimetal WTe2. Adler-Bell-Jackiw chiral anomaly is a representative feature arising from the
topological nature in topological semimetal. We report the first experimental
observation of giant planar Hall effect in type-II Weyl semimetal WTe2. Our
comprehensive analyes of the experimental data demonstrate that the detected
planar Hall effect is originated from the chiral anomaly of Weyl fermions.
Unlike the somewhat elusive negative magnetoresistance, the planar Hall effect
is robust and easy to be detected in type-II Weyl semimetal. This work reveals
that the planar Hall effect is an effective transport probe to determine the
topological nature of topological semimetals, especially in type-II Weyl
semimetals.

###Shubnikov-de Haas-like Quantum Oscillations in Artificial One-Dimensional LaAlO3/SrTiO3 Electron Channels|Guanglei Cheng,Anil Annadi,Shicheng Lu,Hyungwoo Lee,Jung-Woo Lee,Mengchen Huang,Chang-Beom Eom,Patrick Irvin,Jeremy Levy###

Shubnikov-de Haas-like Quantum Oscillations in Artificial One-Dimensional LaAlO3/SrTiO3 Electron Channels. The widely reported magnetoresistance oscillations in LaAlO3/SrTiO3
heterostructures have invariably been attributed to the Shubnikov-de Haas (SdH)
effect, despite a pronounced inconsistency with low-field Hall resistance
measurements. Here we report SdH-like resistance oscillations in quasi-1D
electron waveguides created at the LaAlO3/SrTiO3 interface by conductive atomic
force microscopy lithography. These oscillations can be directly attributed to
magnetic depopulation of magnetoelectric subbands. Our results suggest that the
SdH oscillations in 2D SrTiO3-based systems may originate from naturally
forming quasi-1D channels.

###Pure spin current transport in a SiGe alloy|T. Naito,M. Yamada,M. Tsukahara,S. Yamada,K. Sawano,K. Hamaya###

Pure spin current transport in a SiGe alloy. Using four-terminal nonlocal magnetoresistance measurements in lateral
spin-valve devices with Si$_{\rm 0.1}$Ge$_{\rm 0.9}$, we study pure spin
current transport in a degenerate SiGe alloy ($n \sim$ 5.0 $\times$ 10$^{18}$
cm$^{-3}$). Clear nonlocal spin-valve signals and Hanle-effect curves,
indicating generation, manipulation, and detection of pure spin currents, are
observed. The spin diffusion length and spin lifetime of the Si$_{\rm
0.1}$Ge$_{\rm 0.9}$ layer at low temperatures are reliably estimated to be
$\sim$ 0.5 $\mu$m and $\sim$ 0.2 ns, respectively. This study demonstrates the
possibility of exploring physics and developing spintronic applications using
SiGe alloys.

###A new route to negative refractive index from topological metals|Tomoya Hayata###

A new route to negative refractive index from topological metals. We theoretically discuss the possibility of realizing the negative refractive
index in Weyl/Dirac semimetals. We consider the Maxwell equations with the
plasma gap and the chiral magnetic effect. We study the dispersion relations of
electromagnetic waves, and show that the refractive index becomes negative at
frequencies (just) below the plasma frequency. We find that axial anomaly, or
more specifically, negative magnetoresistance (electric current parallel to
magnetic fields) opens a new route to realize the negative refractive index.
Reflection and transmission coefficients are computed in a slab of Weyl/Dirac
semimetals.

###Angle-dependent magnetoresistance as a probe of Fermi surface warping in HgBa$_2$CuO$_{4+δ}$|Sylvia K. Lewin,James G. Analytis###

Angle-dependent magnetoresistance as a probe of Fermi surface warping in HgBa$_2$CuO$_{4+δ}$. We develop a model for the angle-dependent magnetoresistance of
HgBa$_2$CuO$_{4+\delta}$ in the underdoped regime where the Fermi surface is
thought to be reconstructed by an ordered state such as a charge density wave.
We show that such measurements can be employed to unambiguously distinguish the
form of the Fermi surface's interlayer warping, placing severe contraints on
the symmetry and nature of the reconstructing order. We describe experimentally
accessible conditions in which our calculations can be put to the test.

###One million percent tunnel magnetoresistance in a magnetic van der Waals heterostructure|Hyun Ho Kim,Bowen Yang,Tarun Patel,Francois Sfigakis,Chenghe Li,Shangjie Tian,Hechang Lei,Adam W. Tsen###

One million percent tunnel magnetoresistance in a magnetic van der Waals heterostructure. We report the observation of a very large negative magnetoresistance effect
in a van der Waals tunnel junction incorporating a thin magnetic semiconductor,
CrI3, as the active layer. At constant voltage bias, current increases by
nearly one million percent upon application of a 2 Tesla field. The effect
arises from a change between antiparallel to parallel alignment of spins across
the different CrI3 layers. Our results elucidate the nature of the magnetic
state in ultrathin CrI3 and present new opportunities for spintronics based on
two-dimensional materials.

###Magnetic Tunnel Junction Performance Under Mechanical Strain|Niklas Roschewsky,Sebastian Schafer,Frances Hellman,Vladimir Nikitin###

Magnetic Tunnel Junction Performance Under Mechanical Strain. In this work we investigate the effect of the mechanical stress on the
performance of magnetic tunnel junctions (MTJ) with perpendicular magnetic
anisotropy. We developed a 4-point bending setup, that allows us to apply a
constant stress over a large substrate area with access to electrical
measurements and external magnetic field. This setup enables us to measure key
device performance parameters, such as tunnel magnetoresistance (TMR),
switching current ($I_c^{50\%}$) and thermal stability ($\Delta$), as a
function of applied stress. We find that variations in these parameters are
negligible: less than $\SI{2}{\percent}$ over the entire measured range between
the zero stress condition and the maximum stress at the point of wafer
breakage.

###Quantum oscillations from the reconstructed Fermi surface in electron-doped cuprate superconductors|J S Higgins,M K Chan,Tarapada Sarkar,R D McDonald,R L Greene,N P Butch###

Quantum oscillations from the reconstructed Fermi surface in electron-doped cuprate superconductors. We have studied the electronic structure of electron-doped cuprate
superconductors via measurements of high-field Shubnikov-de Haas oscillations
in thin films. In optimally doped Pr$_{2-x}$Ce$_{x}$CuO$_{4\pm\delta}$ and
La$_{2-x}$Ce$_{x}$CuO$_{4\pm\delta}$, quantum oscillations indicate the
presence of a small Fermi surface, demonstrating that electronic reconstruction
is a general feature of the electron-doped cuprates, despite the location of
the superconducting dome at very different doping levels. Negative high-field
magnetoresistance is correlated with an anomalous low-temperature change in
scattering that modifies the amplitude of quantum oscillations. This behavior
is consistent with effects attributed to spin fluctuations.

###Comparison of Sensitivity and Low Frequency Noise Contributions in GMR and TMR Spin Valve Sensors with a Vortex State Free Layer|Herbert Weitensfelder,Hubert Brueckl,Armin Satz,Klemens Pruegl,Juergen Zimmer,Sebastian Luber,Wolfgang Raberg,Claas Abert,Florian Bruckner,Anton Bachleitner-Hofmann,Roman Windl,Dieter Suess###

Comparison of Sensitivity and Low Frequency Noise Contributions in GMR and TMR Spin Valve Sensors with a Vortex State Free Layer. Magnetoresistive spin valve sensors based on the giant- (GMR) and tunnelling-
(TMR) magnetoresisitve effect with a flux-closed vortex state free layer design
are compared by means of sensitivity and low frequency noise. The vortex state
free layer enables high saturation fields with negligible hysteresis, making it
attractive for applications with a high dynamic range. The measured GMR devices
comprise lower pink noise and better linearity in resistance but are less
sensitive to external magnetic fields than TMR sensors. The results show a
comparable detectivity at low frequencies and a better performance of the TMR
minimum detectable field at frequencies in the white noise limit.

###Electric and Magnetic Gating of Rashba-Active Weak Links|A. Aharony,O. Entin-Wohlman,M. Jonson,R. I. Shekhter###

Electric and Magnetic Gating of Rashba-Active Weak Links. In a one-dimensional weak-link wire the spin-orbit interaction (SOI) alone
cannot generate a nonzero spin current. We show that a Zeeman field acting in
the wire in conjunction with the Rashba SOI there does yield such a current,
whose magnitude and direction depend on the direction of the field. When this
field is not parallel to the effective field due to the SOI, both the charge
and the spin currents oscillate with the length of the wire. Measuring the
oscillating anisotropic magnetoresistance can thus yield information on the SOI
strength. These features are tuned by applying a magnetic and/or an electric
field, with possible applications to spintronics.

###Scattering theory of magnetic/superconducting junctions with spin active interfaces|F. Romeo,R. Citro###

Scattering theory of magnetic/superconducting junctions with spin active interfaces. We formulate a generalized scattering field theory a la Buttiker describing
particles transport in magnetic/superconducting heterostructures. The proposed
formalism, characterized by a four- component spinorial wavefunction of the
Bogoliubov de Gennes theory, allows to describe the spin flipping phenomena
induced by noncollinear magnetizations in the scattering region. As a specific
application of the theory, we analyze the conductance, the magnetoresistance
and the generation of spin-torque produced by an applied voltage in a
spin-valve system. Quantum size effects and quantum beating patterns both in
the conductance and in the spin-torque are carefully described.

###Exchange bias effect in alloys and compounds|S Giri,M Patra,S Majumdar###

Exchange bias effect in alloys and compounds. The phenomenology of exchange bias effects observed in structurally
single-phase alloys and compounds but composed of a variety of coexisting
magnetic phases such as ferromagnetic, antiferromagnetic, ferrimagnetic,
spin-glass, cluster-glass and disordered magnetic states are reviewed. The
investigations on exchange bias effects are discussed in diverse types of
alloys and compounds where qualitative and quantitative aspects of magnetism
are focused based on macroscopic experimental tools such as magnetization and
magnetoresistance measurements. Here, we focus on improvement of fundamental
issues of the exchange bias effects rather than on their technological
importance.

###Thermal spin transport and spin-orbit interaction in ferromagnetic/non-magnetic metals|A. Slachter,F. L. Bakker,B. J. van Wees###

Thermal spin transport and spin-orbit interaction in ferromagnetic/non-magnetic metals. In this article we extend the currently established diffusion theory of
spin-dependent electrical conduction by including spin-dependent
thermoelectricity and thermal transport. Using this theory, we propose new
experiments aimed at demonstrating novel effects such as the spin-Peltier
effect, the reciprocal of the recently demonstrated thermally driven spin
injection, as well as the magnetic heat valve. We use finite-element methods to
model specific devices in literature to demonstrate our theory. Spin-orbit
effects such as anomalous-Hall, -Nernst, anisotropic magnetoresistance and
spin-Hall are also included in this model.

###The role of elastic and inelastic processes in the temperature dependence of Hall induced resistance oscillations in strong magnetic fields|Alejandro Kunold,Manuel Torres###

The role of elastic and inelastic processes in the temperature dependence of Hall induced resistance oscillations in strong magnetic fields. We develop a model of magnetoresistance oscillations induced by the Hall
field in order to study the temperature dependence observed in recent
experiments. The model is based on the solution of the von Neumann equation
incorporating the exact dynamics of two-dimensional damped electrons in the
presence of arbitrarily strong magnetic and dc electric fields, while the
effects of randomly distributed neutral and charged impurities are
perturbatively added. Both the effects of elastic impurity scattering as well
as those related to inelastic processes play an important role. The theoretical
predictions correctly reproduce the main experimental features provided that
the inelastic scattering rate obeys a $T^2$ temperature dependence, consistent
with electron-electron interaction effects.

###First-principles study of metal-induced gap states in metal/oxide interfaces and their relation with the complex band structure|Pablo Aguado-Puente,Javier Junquera###

First-principles study of metal-induced gap states in metal/oxide interfaces and their relation with the complex band structure. We develop a simple model to compute the energy-dependent decay factors of
metal-induced gap states in metal/insulator interfaces considering the
collective behaviour of all the bulk complex bands in the gap of the insulator.
The agreement between the penetration length obtained from the model
(considering only bulk properties) and full first-principles simulations of the
interface (including explicitly the interfaces) is good. The influence of the
electrodes and the polarization of the insulator is analyzed. The method
simplifies the process of screening materials to be used in Schootky barriers
or in the design of giant tunneling electroresistance and magnetoresistance
devices.

###Study of the electronic nematic phase of Sr$_3$Ru$_2$O$_7$ with precise control of the applied magnetic field vector|J. A. N. Bruin,R. A. Borzi,S. A. Grigera,A. W. Rost,R. S. Perry,A. P. Mackenzie###

Study of the electronic nematic phase of Sr$_3$Ru$_2$O$_7$ with precise control of the applied magnetic field vector. We report a study of the magnetoresistivity of high purity Sr$_3$Ru$_2$O$_7$,
in the vicinity of its electronic nematic phase. By employing a triple-axis
(9/1/1T) vector magnet, we were able to precisely tune both the magnitude and
direction of the in-plane component of the magnetic field (H$_\parallel$). We
report the dependence of the resistively determined anisotropy on H$_\parallel$
in the phase, as well as across the wider temperature-field region. Our
measurements reveal a high-temperature anisotropy which mimics the behaviour of
fluctuations from the underlying quantum critical point, and suggest the
existence of a more complicated phase diagram than previously reported.

###Current-induced spin torque resonance of magnetic insulators|Takahiro Chiba,Gerrit E. W. Bauer,Saburo Takahashi###

Current-induced spin torque resonance of magnetic insulators. We formulate a theory of the AC spin Hall magnetoresistance (SMR) in a
bilayer system consisting of a magnetic insulator such as yttrium iron garnet
(YIG) and a heavy metal such as platinum (Pt). We derive expressions for the DC
voltage generation based on the drift-diffusion spin model and quantum
mechanical boundary condition at the interface that reveal a spin torque
ferromagnetic resonance (ST-FMR). We predict that ST-FMR experiments will
reveal valuable information on the current-induced magnetization dynamics of
magnetic insulators and AC spin Hall effect.

###Interface-dependent magnetotransport properties for thin Pt films on ferrimagnetic Y3Fe5O12|Y. Shiomi,T. Ohtani,S. Iguchi,T. Sasaki,Z. Qiu,H. Nakayama,K. Uchida,E. Saitoh###

Interface-dependent magnetotransport properties for thin Pt films on ferrimagnetic Y3Fe5O12. We have studied magnetoresistance and Hall effects for 1.8-nm-thick Pt films
grown on a ferrimagnetic insulator Y3Fe5O12 in a wide temperature (0.46-300 K)
and magnetic-field (-15-15 T) region. In the low-temperature regime where
quantum corrections to conductivity are observed, weak antilocalization
behavior observed in Pt films is critically suppressed when the film is
attached to Y3Fe5O12. Hall resistance in the Pt film is also affected by
Y3Fe5O12, and it exhibits logarithmic temperature dependence in a broad
temperature range. The magnetotransport properties in the high-field range are
significantly influenced by the interface between Pt and Y3Fe5O12.

###Competition between covalent bonding and charge transfer at complex-oxide interfaces|Juan Salafranca,Julian Rincon,Javier Tornos,Carlos León,Jacobo Santamaria,Elbio Dagotto,Stephen J. Pennycook,Maria Varela###

Competition between covalent bonding and charge transfer at complex-oxide interfaces. Here we study the electronic properties of cuprate/manganite interfaces. By
means of atomic resolution electron microscopy and spectroscopy, we produce a
subnanometer scale map of the transition metal oxidation state profile across
the interface between the high $T_c$ superconductor YBa$_2$Cu$_3$O$_{7-\delta}$
and the colossal magnetoresistance compound (La,Ca)MnO$_3$. A net transfer of
electrons from manganite to cuprate with a peculiar non-monotonic charge
profile is observed. Model calculations rationalize the profile in terms of the
competition between standard charge transfer tendencies (due to band mismatch),
strong chemical bonding effects across the interface, and Cu substitution into
the Mn lattice, with different characteristic length scales.

###Magnetoresistance of monolayer graphene with short-range scattering|G. Yu. Vasileva,P. S. Alekseev,Yu. B. Vasilyev,Yu. L. Ivanov,D. Smirnov,H. Schmidt,R. J. Haug###

Magnetoresistance of monolayer graphene with short-range scattering. We present magnetotransport measurements at classical magnetic fields for
three graphene monolayers with various levels of disorder. A square root
magnetoresistance (SRMR) behavior is observed in one sample which has the
characteristic sub-linear conductivity signaling on the presence of short-range
disorder in this sample. No square root MR was observed in other samples where
short-range scattering is inessential as it is evident from the gate voltage
dependences of their conductivities. Comparing our experimental data for the
sample with theoretical calculations we found a good qualitative agreement and
established the conditions which should be fulfilled in graphene to observe the
SRMR experimentally.

###Normal state magnetotransport properties of $β$-FeSe superconductors|J. D. Querales-Flores,M. L. Amigó,G. Nieva,C. I. Ventura###

Normal state magnetotransport properties of $β$-FeSe superconductors. We present $\beta$-FeSe magnetotransport data, and describe them
theoretically. Using a simplified microscopic model with two correlated
effective orbitals, we determined the normal state electrical conductivity and
Hall coefficient, using Kubo formalism. With model parameters relevant for
Fe-chalcogenides, we describe the observed effect of the structural transition
on the ab-plane electrical resistivity, as well as on the magnetoresistance.
Temperature-dependent Hall coefficient data were measured at 16 Tesla, and
their theoretical description improves upon inclusion of moderate electron
correlations. We confirm the effect of the structural transition on the
electronic structure, finding deformation-induced band splittings comparable to
those reported in angle-resolved photoemission.

###Violation of Kohler rule in Ta2PdTe6 and absence of same in Nb2PdS5- A high field magneto transport study|Reena Goyal,Rajveer Jha,V. P. S. Awana###

Violation of Kohler rule in Ta2PdTe6 and absence of same in Nb2PdS5- A high field magneto transport study. Here, we present the comparative study of magnetotransport properties of
recently discovered Ta2PdTe6 and Nb2PdS5 superconductors. The XRD and
magnetotransport measurements are performed on these samples to investigate
structure and superconducting properties as well as normal state transport
properties of these compounds. Both the compounds are crystallized in
monoclinic structure within space group C2m. Here, we observe superconductivity
in both the compounds Ta2PdTe6 (Tc =4.4 K) and Nb2PdS5 (Tc =6.6 K). We see a
linear magnetoresistance in Ta2PdTe6 as well as violation of Kohler rule in
same compound. On the other hand, we find the absence of same in Nb2PdS5
compound.

###Magnetoquantum oscillations in the resistance of metallic point contacts: Influence of nonequilibrium phonons|N. L. Bobrov,J. A. Kokkedee,N. N. Gribov,I. K. Yanson,A. G. M. Jansen,P. Wyder###

Magnetoquantum oscillations in the resistance of metallic point contacts: Influence of nonequilibrium phonons. The amplitude of magnetoresistance quantum oscillations of Al and Be point
contacts in a magnetic field parallel to the contact axis has been studied as a
function of voltage applied over the contact. It was found that for one group
of contacts the oscillation amplitude nonmonotonously increases with the bias
voltage increase, while for the other part of the contacts a decrease of
amplitude was observed. The scattering of electrons with nonequilibrium phonons
and also phonon-phonon collisions will be discussed as the possible reasons of
the observed effects.

###Dynamic Feedback in Ferromagnet/Spin Hall Metal Heterostructures|Ran Cheng,Jian-Gang Zhu,Di Xiao###

Dynamic Feedback in Ferromagnet/Spin Hall Metal Heterostructures. In ferromagnet/normal metal heterostructures, spin pumping and spin-transfer
torques are two reciprocal processes that occur concomitantly. Their interplay
introduces a dynamic feedback effect interconnecting energy dissipation
channels of both magnetization and current. By solving the spin diffusion
process in the presence of the spin Hall effect in the normal metal, we show
that the dynamic feedback gives rise to: (i) a nonlinear magnetic damping that
is crucial to sustain uniform steady-state oscillations of a spin Hall
oscillator at large angles. (ii) a frequency dependent spin Hall
magnetoimpedance that reduces to the spin Hall magnetoresistance in the dc
limit.

###The effect of interface roughness on exchange bias in La0.7Sr0.3MnO3 - BiFeO3 heterostructures|Mehran Vafaee,Simone Finizio,Hakan Deniz,Dietrich Hesse,Hartmut Zabel,Gerhard Jakob,Mathias Kläui###

The effect of interface roughness on exchange bias in La0.7Sr0.3MnO3 - BiFeO3 heterostructures. We characterized the interfaces of heterostructures with different stack
sequences of La0.7Sr0.3MnO3/BiFeO3 (LSMO/BFO) and BFO/LSMO using TEM revealing
sharp and rough interfaces, respectively. Magnetometry and magnetoresistance
measurements do not show a detectable exchange bias coupling for the multistack
with sharp interface. Instead, the heterostructures with rough and chemically
intermixed interfaces exhibit a sizable exchange bias coupling. Furthermore, we
find a temperature-dependent irreversible magnetization behavior and an
exponential decay of coercive and exchange bias field with temperature
suggesting a possible spin-glass-like state at the interface of both stacks.

###Hysteretic magnetoresistance and unconventional anomalous Hall effect in the frustrated magnet TmB_4|Sai Swaroop Sunku,Tai Kong,Toshimitsu Ito,Paul C. Canfield,B. Sriram Shastry,Pinaki Sengupta,Christos Panagopoulos###

Hysteretic magnetoresistance and unconventional anomalous Hall effect in the frustrated magnet TmB_4. We study TmB_4, a frustrated magnet on the Archimedean Shastry-Sutherland
lattice, through magnetization and transport experiments. The lack of
anisotropy in resistivity shows that TmB_4 is an electronically
three-dimensional system. The magnetoresistance (MR) is hysteretic at
low-temperature even though a corresponding hysteresis in magnetization is
absent. The Hall resistivity shows unconventional anomalous Hall effect (AHE)
and is linear above saturation despite a large MR. We propose that complex
structures at magnetic domain walls may be responsible for the hysteretic MR
and may also lead to the AHE.

###Uniaxial pressure induced half-metallic ferromagnetic phase transition in LaMnO$_3$|Pablo Rivero,Vincent Meunier,William Shelton###

Uniaxial pressure induced half-metallic ferromagnetic phase transition in LaMnO$_3$. We use first-principles theory to predict that the application of uniaxial
compressive strain leads to a transition from an antiferromagnetic insulator to
a ferromagnetic half-metal phase in LaMnO$_3$. We identify the Q2 Jahn-Teller
mode as the primary mechanism that drives the transition, indicating that this
mode can be used to tune the lattice, charge, and spin coupling. Applying
$\simeq$ 6 GPa of uniaxial pressure along the [010] direction activates the
transition to a half-metallic $\textit{pseudo-cubic}$ state. The
half-metallicity opens the possibility of producing colossal magnetoresistance
in the stoichiometric LaMnO$_3$ compound at significantly lower pressure
compared to recently observed investigations using hydrostatic pressure.

###Comparative Studies on Giant Magnetoresistance in Carbon Nanotubes and Graphene Nanoribbons with Ferromagnetic Contacts|S. Krompiewski###

Comparative Studies on Giant Magnetoresistance in Carbon Nanotubes and Graphene Nanoribbons with Ferromagnetic Contacts. This contribution reports on comparative studies on giant magnetoresistance
(GMR) in carbon nanotubes (CNTs) and graphene nanoribbons of similar aspect
ratios (i.e perimeter/length and width/length ratios, for the former and the
latter, respectively). The problem is solved at zero temperature in the
ballistic transport regime, by means of the Green's functions technique within
the tight-binding model and with the so-called wide band approximation for
electrodes. The GMR effect in graphene is comparable to that of CNTs, it
depends strongly on the chirality and only slightly on the aspect ratio. It
turns out that graphene, analogously to CNTs may be quite an interesting
material for spintronic applications.

###Voltage Asymmetry of Spin-Transfer Torques|Deepanjan Datta,Behtash Behin-Aein,Sayeef Salahuddin,Supriyo Datta###

Voltage Asymmetry of Spin-Transfer Torques. We present a Non-Equilibrium Green's Function based model for spin torque
transfer (STT) devices which provides quantitative agreement with
experimentally measured (1) differential resistances, (2) Magnetoresistance
(MR), (3) In-plane torque and (4) out-of-plane torque over a range of bias
voltages, using a single set of three adjustable parameters. We believe this is
the first theoretical model that is able to cover this diverse range of
experiments and a key aspect of our model is the inclusion of multiple
transverse modes. We also provide a simple explanation for the asymmetric bias
dependence of the in-plane torque, based on the polarization of the two
contacts in energy range of transport.

###Magnetoresistance in Single Layer Graphene: Weak Localization and Universal Conductance Fluctuation Studies|Yung-Fu Chen,Myung-Ho Bae,Cesar Chialvo,Travis Dirks,Alexey Bezryadin,Nadya Mason###

Magnetoresistance in Single Layer Graphene: Weak Localization and Universal Conductance Fluctuation Studies. We report measurements of magnetoresistance in single-layer graphene as a
function of gate voltage (carrier density) at 250 mK. By examining signatures
of weak localization (WL) and universal conductance fluctuations (UCF), we find
a consistent picture of phase coherence loss due to electron-electron
interactions. The gate-dependence of the elastic scattering terms suggests that
the effect of trigonal warping, i.e., the non-linearity of the dispersion
curves, may be strong at high carrier densities, while intra-valley scattering
may dominate close to the Dirac point. In addition, a decrease in UCF amplitude
with decreasing carrier density can be explained by a corresponding loss of
phase coherence.

###Direct determination of the surface termination in full Heusler alloys by means of low energy electron diffraction|Jan-Peter Wüstenberg,Takayuki Ishikawa,Masafumi Yamamoto,Christian Herbort,Martin Jourdan,Martin Aeschlimann,Mirko Cinchetti###

Direct determination of the surface termination in full Heusler alloys by means of low energy electron diffraction. The performance of Heusler based magnetoresistive multilayer devices depends
crucially on the spin polarization and thus on the structural details of the
involved surfaces. Using low energy electron diffraction (LEED), one can
non-destructively distinguish between important surface terminations of Co2XY
full-Heusler alloys. We present an analysis of the LEED patterns of the Y-Z
,the vacancy-Z, the Co and the disordered B2 and A2 terminations. As an
example, we show that the surface geometries of bulk L21 ordered Co2MnSi and
bulk B2 disordered Co2Cr0.6Fe0.4Al can be determined by comparing the
experimental LEED patterns with the presented reference patterns.

###Oscillatory angular dependence of the magnetoresistance in a topological insulator Bi_{1-x}Sb_{x}|A. A. Taskin,Kouji Segawa,Yoichi Ando###

Oscillatory angular dependence of the magnetoresistance in a topological insulator Bi_{1-x}Sb_{x}. The angular-dependent magnetoresistance and the Shubnikov-de Haas
oscillations are studied in a topological insulator Bi_{0.91}Sb_{0.09}, where
the two-dimensional (2D) surface states coexist with a three-dimensional (3D)
bulk Fermi surface (FS). Two distinct types of oscillatory phenomena are
discovered in the angular-dependence: The one observed at lower fields is shown
to originate from the surface state, which resides on the (2\bar{1}\bar{1})
plane, giving a new way to distinguish the 2D surface state from the 3D FS. The
other one, which becomes prominent at higher fields, probably comes from the
(111) plane and is obviously of unknown origin, pointing to new physics in
transport properties of topological insulators.

###Resistivity saturation in a weakly interacting 2D Fermi liquid at intermediate temperatures|Xiaoqing Zhou,B. Schmidt,L. W. Engel,G. Gervais,L. N. Pfeiffer,K. W. West,S. Das Sarma###

Resistivity saturation in a weakly interacting 2D Fermi liquid at intermediate temperatures. We report a highly unusual temperature dependence in the magnetoresistance of
a weakly interacting high mobility 2D electron gas (2DEG) under a parallel
magnetic field and when the current is perpendicular to the field. While the
linear temperature dependence below 10 K and the exponential temperature
dependence above 40 K agree with existing theory of electron-phonon scattering,
a field induced resistivity saturation behaviour characterized by an almost
complete suppression of the temperature dependence is observed from
approximately 20 to 40 K, which is in sharp contrast to the phenomenology
observed when the current is parallel to the field. Possible origins of this
intriguing intermediate temperature phenomenon are discussed.

###Large amplitude microwave emission and reduced nonlinear phase noise in Co2Fe(Ge0.5Ga0.5) Heusler alloy based pseudo spin valve nanopillars|Jaivardhan Sinha,Masamitsu Hayashi,Yukiko K. Takahashi,Tomohiro Taniguchi,Maksim Drapeko,Seiji Mitani,Kazuhiro Hono###

Large amplitude microwave emission and reduced nonlinear phase noise in Co2Fe(Ge0.5Ga0.5) Heusler alloy based pseudo spin valve nanopillars. We have studied microwave emission from a current-perpendicular-to-plane
pseudo spin valve nanopillars with Heusler alloy Co2Fe(Ga0.5Ge0.5) electrodes.
Large emission amplitude exceeding 150 nV/Hz^0.5, partly owing to the large
magnetoresistance, and narrow generation linewidth below 10 MHz are observed.
We also find that the linewidth shows significant dependence on the applied
field magnitude and its angle within the film plane. A minimum in the linewidth
is observed when the slope of the frequency versus current becomes near zero.
This agrees with theoretical prediction that takes into account non-linear
phase noise as a source for linewidth broadening.

###Transport Measurements on Nano-engineered Two Dimensional Superconducting Wire Networks|W. J. Zhang,S. K. He,H. Xiao,G. M. Xue,Z. C. Wen,X. F. Han,S. P. Zhao,C. Z. Gu,X. G. Qiu###

Transport Measurements on Nano-engineered Two Dimensional Superconducting Wire Networks. Superconducting triangular Nb wire networks with high normal-state resistance
are fabricated by using a negative tone hydrogen silsesquioxane (HSQ) resist.
Robust magnetoresistance oscillations are observed up to high magnetic fields
and maintained at low temperatures, due to the eective reduction of wire
dimensions. Well-defined dips appear at integral and rational values (1/2, 1/3,
1/4) of the reduced flux f = Phi/Phi_0, which is the first observation in the
triangular wire networks. These results are well consistent with theoretical
calculations for the reduced critical temperature as a function of f.

###Novel Giant Magnetoresistance Model using Multiple Barrier Potential|Christian Naa,Suprijadi,Sparisoma Viridi,Mitra Djamal###

Novel Giant Magnetoresistance Model using Multiple Barrier Potential. This paper proposes a new model for Giant Magnetoresistance (GMR) and
calculates its typical graph qualitatively. The model foundation is the
microscopic mechanism in GMR, where the GMR effect can be explained by
intrinsic and extrinsic potential. The potentials are spin-dependent. The
potentials determine the transmission probability then it will give conductance
value. Here, the multiple barrier potential model is proposed as the new GMR
model. The transmission probability is determined using transfer matrix method.
It was found that this model is fit qualitatively with the typical GMR graph.

###Galvanomagnetic effects and manipulation of antiferromagnetic interfacial uncompensated magnetic moment in exchange-biased bilayers|X. Zhou,L. Ma,Z. Shi,W. J. Fan,R. F. L. Evans,R. W. Chantrell,S. Mangin,H. W. Zhang,S. M. Zhou###

Galvanomagnetic effects and manipulation of antiferromagnetic interfacial uncompensated magnetic moment in exchange-biased bilayers. In this work, IrMn$_{3}$/insulating-Y$_{3}$Fe$_{5}$O$_{12}$ exchange-biased
bilayers are studied. The behavior of the net magnetic moment $\Delta m_{AFM}$
in the antiferromagnet is directly probed by anomalous and planar Hall effects,
and anisotropic magnetoresistance. The $\Delta m_{AFM}$ is proved to come from
the interfacial uncompensated magnetic moment. We demonstrate that the exchange
bias and rotational hysteresis are induced by the irreversible switching of the
$\Delta m_{AFM}$. In the training effect, the $\Delta m_{AFM}$ changes
continuously. This work highlights the fundamental role of the $\Delta m_{AFM}$
in the exchange bias and facilitates the manipulation of antiferromagnetic
spintronic devices.

###Exchange-driven magnetoresistance in silicon facilitated by electrical spin injection|Yuichiro Ando,Lan Qing,Yang Song,Shinya Yamada,Kenji Kasahara,Kentarou Sawano,Masanobu Miyao,Hanan Dery,Kohei Hamaya###

Exchange-driven magnetoresistance in silicon facilitated by electrical spin injection. We use electrical spin injection to probe exchange interactions in phosphorus
doped silicon (Si:P). The detection is enabled by a magnetoresistance effect
that demonstrates the efficiency of exchange in imprinting spin information
from the magnetic lead onto the localized moments in the Si:P region. A unique
Lorentzian-shaped signal existing only at low temperatures ($\lesssim 25 K$) is
observed experimentally and analyzed theoretically in electrical Hanle effect
measurement. It stems from spin-dependent scattering of electrons by neutral
impurities in Si:P. The shape of this signal is not directly related to spin
relaxation but to exchange interaction between spin-polarized electrons that
are localized on adjacent impurities.

###Electrical tuning of spin current in a boron nitride nanotube quantum dot|Kamal B Dhungana,Ranjit Pati###

Electrical tuning of spin current in a boron nitride nanotube quantum dot. Controlling spin current and magnetic exchange coupling by applying an
electric field and achieving high spin injection efficiency at the same time in
a nanostructure coupled to ferromagnetic electrodes have been the outstanding
challenges in nanoscale spintronics. A relentless quest is going on to find new
low dimensional materials with tunable spin dependent properties to address
these challenges. Herein, we predict, from first principles, the transverse
electric field induced switching in the sign of exchange coupling and tunnel
magnetoresistance in a boron nitride nanotube quantum dot attached to
ferromagnetic nickel contacts.

###Resolving the Dirac Cone on the Surface of Bi2Te3 Topological Insulator Nanowires by Field-Effect Measurements|Johannes Gooth,Bacel Hamdou,August Dorn,Robert Zierold,Kornelius Nielsch###

Resolving the Dirac Cone on the Surface of Bi2Te3 Topological Insulator Nanowires by Field-Effect Measurements. We validate the linear dispersion relation and resolve the Dirac cone on the
surface of a single Bi2Te3 nanowire via a combination of field-effect and
magnetoresistance measurements by which we unambiguously prove the topological
insulator nature of the nanowire surface states. Moreover we show that the
experimentally determined carrier concentration, mobility and cyclotron mass of
the surface states are in excellent agreement with relativistic models. Our
method provides a facile way to identify topological insulators that too small
for angle-resolved photo emission spectroscopy.

###Inelastic electron tunneling spectroscopy of local "spin accumulation" devices|Holly N. Tinkey,Pengke Li,Ian Appelbaum###

Inelastic electron tunneling spectroscopy of local "spin accumulation" devices. We investigate the origin of purported "spin accumulation" signals observed
in local "three-terminal" (3T) measurements of ferromagnet/insulator/n-Si
tunnel junctions using inelastic electron tunneling spectroscopy (IETS).
Voltage bias and magnetic field dependences of the IET spectra were found to
account for the dominant contribution to 3T magnetoresistance signals, thus
indicating that it arises from inelastic tunneling through impurities and
defects at junction interfaces and within the barrier, rather than from spin
accumulation due to pure elastic tunneling into bulk Si as has been previously
assumed.

###Single atom anisotropic magnetoresistance on a topological insulator surface|Awadhesh Narayan,Ivan Rungger,Stefano Sanvito###

Single atom anisotropic magnetoresistance on a topological insulator surface. We demonstrate single atom anisotropic magnetoresistance on the surface of a
topological insulator, arising from the interplay between the helical
spin-momentum-locked surface electronic structure and the hybridization of the
magnetic adatom states. Our first-principles quantum transport calculations
based on density functional theory for Mn on Bi$_2$Se$_3$ elucidate the
underlying mechanism. We complement our findings with a two dimensional model
valid for both single adatoms and magnetic clusters, which leads to a proposed
device setup for experimental realization. Our results provide an explanation
for the conflicting scattering experiments on magnetic adatoms on topological
insulator surfaces, and reveal the real space spin texture around the magnetic
impurity.

###Room temperature write-read operations in antiferromagnetic memory|Takahiro Moriyama,Noriko Matsuzaki,Kab-Jin Kim,Ippei Suzuki,Tomoyasu Taniyama,Teruo Ono###

Room temperature write-read operations in antiferromagnetic memory. B2-ordered FeRh has been known to exhibit antiferromagnetic-ferromagnetic
(AF-F) phase transitions in the vicinity of room temperature. Manipulation of
the N\'eel order via AF-F phase transition and recent experimental observation
of the anisotropic magnetoresistance in antiferromagnetic FeRh has proven that
FeRh is a promising candidate for antiferromagnetic memory material. In this
work, we demonstrate sequential write and read operations in antiferromagnetic
memory resistors made of B2-orderd FeRh thin films by a magnetic field and
electric current only. Our demonstration of writing and reading at ambient room
temperature opens a realistic pathway towards operational antiferromagnetic
memory devices.

###Studying angle-dependent magnetoresistance oscillations of cuprate superconductors in a model with antiferromagnetic reconstruction and magnetic breakdown|Sylvia K. Lewin,James G. Analytis###

Studying angle-dependent magnetoresistance oscillations of cuprate superconductors in a model with antiferromagnetic reconstruction and magnetic breakdown. We calculate angle-dependent magnetoresistance oscillations (AMRO) for
interlayer transport of cuprate superconductors in the presence of ($\pi,\pi$)
order. The order reconstructs the Fermi surface, creating magnetic breakdown
junctions; we show how such magnetic breakdown effects can be incorporated into
calculations of interlayer conductivity for this system. We successfully fit
experimental data with our model, and these fits suggest a connection between
($\pi,\pi$) order and the anisotropic scattering observed in overdoped
cuprates. This work paves the way for the use of AMRO as a tool to distinguish
different kinds of ordered states.

###New Galvanomagnetic Effects of Polycrystalline Magnetic Films|Y. Zhang,H. W. Zhang,X. R. Wang###

New Galvanomagnetic Effects of Polycrystalline Magnetic Films. Within the linear response of polycrystalline magnetic films to electric
currents, a general analysis predicts three new galvanomagnetic effects
originated from the two-dimensional nature of the films. These new
galvanomagnetic effects, which differ from the conventional extraordinary Hall
effect and anisotropic magnetoresistance, are follows. 1) The longitudinal
resistivity depends linearly on the magnetization component perpendicular to a
film. 2) A current parallel to the magnetization can generate an electric field
in the vertical direction of a film. 3) A current perpendicular to a film can
generate an electric field along the magnetization direction.

###Evidence of both surface and bulk Dirac bands in ZrSiS and the unconventional magnetoresistance|Xuefeng Wang,Xingchen Pan,Ming Gao,Jihai Yu,Juan Jiang,Junran Zhang,Huakun Zuo,Minhao Zhang,Zhongxia Wei,Wei Niu,Zhengcai Xia,Xiangang Wan,Yulin Chen,Fengqi Song,Yongbing Xu,Baigeng Wang,Guanghou Wang,Rong Zhang###

Evidence of both surface and bulk Dirac bands in ZrSiS and the unconventional magnetoresistance. The unconventional magnetoresistance of ZrSiS single crystals is found
unsaturated till the magnetic field of 53 T with the butterfly shaped angular
dependence. Intense Shubnikov-de Haas oscillations resolve a bulk Dirac cone
with a nontrivial Berry phase, where the Fermi surface area is 1.80*10^-3
{\AA}-2 and reaches the quantum limit before 20 T. Angle resolved photoemission
spectroscopy measurement reveals an electronic state with the two-dimensional
nature around the X point of Brillouin zone boundary. By integrating the
density functional theory calculations, ZrSiS is suggested to be a Dirac
material with both surface and bulk Dirac bands.

###High field magneto-transport in two-dimensional electron gas LaAlO3/SrTiO3|Ming Yang,Mathieu Pierre,Olivier Toressin,Michel Goiran,Walter Escoffier,Shengwei Zeng,Zhen Huang,Han Kun,Thirumalai Venkatesan,Ariando,Michael Coey###

High field magneto-transport in two-dimensional electron gas LaAlO3/SrTiO3. Transport properties of the complex oxide LaAlO3/SrTiO3 interface are
investigated under high magnetic field (55T). By rotating the sample with
respect to the magnetic field, the two-dimensional nature of charge transport
is clearly established. Small oscillations of the agnetoresistance with altered
periodicity are observed when plotted versus inverse magnetic field. We
attribute this effect to Rashba spin-orbit coupling which remains consistent
with large negative magnetoresistance when the field is parallel to the sample
plane. A large inconsistency between the carrier density extracted from
Shubnikov-de Haas analysis and from the Hall effect is explained by the
contribution to transport of at least two bands with different mobility.

###Resonant TMR inversion in LiF/EuS based spin-filter tunnel junctions|Fen Liu,Yihang Yang,Qian Xue,Zhiwei Gao,Aixi Chen,Guo-Xing Miao###

Resonant TMR inversion in LiF/EuS based spin-filter tunnel junctions. Resonant tunneling can lead to inverse tunnel magnetoresistance when impurity
levels rather than direct tunneling dominate the transport process. We
fabricated hybrid magnetic tunnel junctions of CoFe/LiF/EuS/Ti, with an
epitaxial LiF energy barrier joined with a polycrystalline EuS spin-filter
bar-rier. Due to the water solubility of LiF, the devices were fully packaged
in situ. The devices showed sizeable positive TMR up to 16% at low bias
voltages but clearly inverted TMR at higher bias voltages. The TMR inversion
depends sensitively on the thickness of LiF, and the tendency of inversion
disap-pears when LiF gets thick enough and recovers its intrinsic properties.

###Hydrodynamic theory of thermoelectric transport and negative magnetoresistance in Weyl semimetals|Andrew Lucas,Richard A. Davison,Subir Sachdev###

Hydrodynamic theory of thermoelectric transport and negative magnetoresistance in Weyl semimetals. We present a theory of thermoelectric transport in weakly disordered Weyl
semimetals where the electron-electron scattering time is faster than the
electron-impurity scattering time. Our hydrodynamic theory consists of
relativistic fluids at each Weyl node, coupled together by perturbatively small
inter-valley scattering, and long-range Coulomb interactions. The conductivity
matrix of our theory is Onsager reciprocal and positive-semidefinite. In
addition to the usual axial anomaly, we account for the effects of a distinct,
axial-gravitational anomaly expected to be present in Weyl semimetals. Negative
thermal magnetoresistance is a sharp, experimentally accessible signature of
this axial-gravitational anomaly, even beyond the hydrodynamic limit.

###High-Speed Magnetoresistive Random-Access Memory Random Number Generator Using Error-Correcting Code|Tetsufumi Tanamoto,Naoharu Shimomura,Sumio Ikegawa,Mari Matsumoto,Shinobu Fujita,Hiroaki Yoda###

High-Speed Magnetoresistive Random-Access Memory Random Number Generator Using Error-Correcting Code. A high-speed random number generator (RNG) circuit based on magnetoresistive
random-access memory (MRAM) using an error-correcting code (ECC) post
processing circuit is presented. ECC post processing increases the quality of
randomness by increasing the entropy of random number. { We experimentally show
that a small error-correcting capability circuit is sufficient for this post
processing. It is shown that the ECC post processing circuit powerfully
improves the quality of randomness with minimum overhead, ending up with
high-speed random number generation. We also show that coupling with a linear
feedback shift resistor is effective for improving randomness

###Longitudinal negative magnetoresistance and magneto-transport phenomena in conventional and topological conductors|A. V. Andreev,B. Z. Spivak###

Longitudinal negative magnetoresistance and magneto-transport phenomena in conventional and topological conductors. Recently a large negative longitudinal (parallel to the magnetic field)
magnetoresistance was observed in Weyl and Dirac semimetals. It is believed to
be related to the chiral anomaly associated with topological electron band
structure of these materials. We show that in a certain range of parameters
such a phenomenon can also exist in conventional centrosymmetric and time
reversal conductors, lacking topological protection of the electron spectrum
and the chiral anomaly. We also discuss the magnetic field enhancement of the
longitudinal components of the thermal conductivity and thermoelectric tensors.

###Angular dependence of magnetization reversal in epitaxial chromium telluride thin films with perpendicular magnetic anisotropy|Tanmoy Pramanik,Anupam Roy,Rik Dey,Amritesh Rai,Samaresh Guchhait,Hema CP Movva,Cheng-Chih Hsieh,Sanjay K Banerjee###

Angular dependence of magnetization reversal in epitaxial chromium telluride thin films with perpendicular magnetic anisotropy. We investigate magnetic anisotropy and magnetization reversal mechanism in
chromium telluride thin films grown by molecular beam epitaxy. We report
existence of strong perpendicular anisotropy in these thin films, along with a
relatively strong second order anisotropy contribution. The angular variation
of the switching field observed from the magnetoresistance measurement is
explained quantitatively using a one-dimensional defect model. The model
reveals the relative roles of nucleation and pinning in the magnetization
reversal, depending on the applied field orientation. Micromagnetic simulations
are performed to visualize the domain structure and switching process.

###Influence of nonequilibrium phonons on the amplitude of magnetoquantum oscillations in the point-contact resistance|N. L. Bobrov,J. A. Kokkedee,N. N. Gribov,I. K. Yanson,A. G. M. Jansen###

Influence of nonequilibrium phonons on the amplitude of magnetoquantum oscillations in the point-contact resistance. For metallic point contacts with Be and Al the magnetoquantum oscillations in
the contact resistance have been investigated as a function of the applied
voltage over the contact. For one set of point contacts the oscillation
amplitude is found to vary nonmonotonously with the applied voltage with
similarities to the point-contact spectrum of the electron-phonon interaction.
The other part of the investigated point contacts shows a decrease of the
oscillation amplitude with increasing bias voltage. For the understanding of
the voltage dependence of the amplitude of the point-contact magnetoresistance
oscillations the influence of nonequilibrium phonons generated by the
ballistically injected electrons will be discussed.

###Spin-filter effect at the interface of magnetic/non-magnetic homojunctions in Li doped ZnO nanostructures|L. Botsch,I. Lorite,Y. Kumar,P. Esquinazi,T. Michalsky,J. Zajadacz,K. Zimmer###

Spin-filter effect at the interface of magnetic/non-magnetic homojunctions in Li doped ZnO nanostructures. After more than a decade of extensive research on the magnetic order
triggered by lattice defects in a wide range of nominally non-magnetic
materials, we report its application in a spintronic device. This device is
based on a spin-filter phenomenon we discovered at the interfaces between
defect-induced magnetic and non-magnetic regions, produced at the surface of a
Li doped ZnO microwire by low-energy proton implantation. Positive
magnetoresistance is observed at 300~K and scales with the number of interfaces
introduced along the wire.

###Origin of threshold current density for asymmetric magnetoresistance in Pt/Py bilayers|Tian Li,Sanghoon Kim,Seung-Jae Lee,Seo-Won Lee,Tomohiro Koyama,Daichi Chiba,Takahiro Moriyama,Kyung-Jin Lee,Kab-Jin Kim,Teruo Ono###

Origin of threshold current density for asymmetric magnetoresistance in Pt/Py bilayers. An asymmetric magnetoresistance (MR) is investigated in Py/Pt bilayers. The
asymmetric MR linearly increases with current density up to a threshold, and
increases more rapidly above the threshold. To reveal the origin of threshold
behavior, we investigate the magnetic field dependence of the asymmetric MR. It
is found that the magnetic field strongly suppresses the asymmetric MR only
above the threshold current density. Micromagnetic simulation reveals that the
reduction of magnetization due to the spin-torque oscillation can be the origin
of the threshold behavior of asymmetric MR.

###Anisotropic electronic transport of the two-dimensional electron system in Al2O3/SrTiO3 heterostructures|K. Wolff,R. Schäfer,M. Meffert,D. Gerthsen,R. Schneider,D. Fuchs###

Anisotropic electronic transport of the two-dimensional electron system in Al2O3/SrTiO3 heterostructures. Transport measurements on the two dimensional electron system in Al2O3 SrTiO3
heterostructures indicate significant noncrystalline anisotropic behavior below
T = 30 K. Lattice dislocations in SrTiO3 and interfacial steps are suggested to
be the main sources for electronic anisotropy. Anisotropic defect scattering
likewise alters magnetoresistance at low temperature remarkably and influences
spin-orbit coupling significantly by the Elliot Yafet mechanism of spin
relaxation resulting in anisotropic weak localization. Applying a magnetic
field parallel to the interface results in an additional field induced
anisotropy of the conductance, which can be attributed to Rashba spin orbit
interaction. Compared to LaAlO3 SrTiO3, Rashba coupling seems to be reduced
indicating a weaker polarity in Al2O3 SrTiO3 heterostructures.

###Magnetism and charge density waves in RNiC$_2$ (R = Ce, Pr, Nd)|Kamil K. Kolincio,Marta Roman,Michał J. Winiarski,Judyta Strychalska - Nowak,Tomasz Klimczuk###

Magnetism and charge density waves in RNiC$_2$ (R = Ce, Pr, Nd). We have compared the magnetic, transport, galvanomagnetic and specific heat
properties of CeNiC$_2$, PrNiC$_2$ and NdNiC$_2$ to study the interplay between
charge density waves and magnetism in these compounds. The negative
magnetoresistance in NdNiC$_2$ is discussed in terms of the partial destruction
of charge density waves and an irreversible phase transition stabilized by the
field induced ferromagnetic transformation is reported. For PrNiC$_2$ we
demonstrate that the magnetic field initially weakens the CDW state, due to the
Zeeman splitting of conduction bands. However, the Fermi surface nesting is
enhanced at a temperature related to the magnetic anomaly.

###Pressure-induced topological phase transition in LaSb: First-principles study|Peng-Jie Guo,Huan-Cheng Yang,Kai Liu,Zhong-Yi Lu###

Pressure-induced topological phase transition in LaSb: First-principles study. By using first-principles electronic structure calculations, we predict that
the extreme magnetoresistance (XMR) material LaSb takes a topological phase
transition without breaking any symmetry under a hydrostatic pressure applied
between 3 and 4 GPa, meanwhile the electron-hole compensation remains in its
electronic band structure. Thus LaSb provides an ideal platform for studying
the individual role of topological property playing in the XMR phenomenon, in
addition to the electron-hole compensation. This has general implication to the
relationship of XMR effect and topological property in topological materials.

###Evidence for a Dirac nodal-line semimetal in SrAs$_{3}$|Shichao Li,Zhaopeng Guo,Dongzhi Fu,Xing-Chen Pan,Jinghui Wang,Kejing Ran,Song Bao,Zhen Ma,Zhengwei Cai,Rui Wang,Rui Yu,Jian Sun,Fengqi Song,Jinsheng Wen###

Evidence for a Dirac nodal-line semimetal in SrAs$_{3}$. Dirac nodal-line semimetals with the linear bands crossing along a line or
loop, represent a new topological state of matter. Here, by carrying out
magnetotransport measurements and performing first-principle calculations, we
demonstrate that such a state has been realized in high-quality single crystals
of SrAs3. We obtain the nontrivial pi Berry phase by analysing the Shubnikov-de
Haas quantum oscillations. We also observe a robust negative longitudinal
magnetoresistance induced by the chiral anomaly. Accompanying first-principles
calculations identify that a single hole pocket enclosing the loop nodes is
responsible for these observations.

###Singlet superconductivity in single-crystal NiBi3 superconductor|G. J. Zhao,X. X. Gong,P. C. Xu,B. C. Li,Z. Y. Huang,X F. Jin,X. D. Zhu,T. Y. Chen###

Singlet superconductivity in single-crystal NiBi3 superconductor. Andreev reflection spectroscopy with unpolarized and highly spin-polarized
currents has been utilized to study an intermetallic single-crystal
superconductor NiBi3. Magnetoresistance at zero bias voltage of point contacts
shows the occurrence and suppression of Andreev reflection by unpolarized and
polarized current, respectively. The gap value, its symmetry and temperature
dependence have been determined using an unpolarized current. The spin state in
the NiBi3 sample is determined to be antiparallel using a highly spin-polarized
current. The gap value 2Delta/kBT, gap symmetry and its temperature dependence,
combined with the antiparallel spin state show that the bulk NiBi3 is a singlet
s-wave superconductor.

###Theory of Cross-correlated Electron-Magnon Transport Phenomena: Case of Magnetic Topological Insulator|Yusuke Imai,Hiroshi Kohno###

Theory of Cross-correlated Electron-Magnon Transport Phenomena: Case of Magnetic Topological Insulator. We study transport phenomena cross-correlated among the heat and electric
currents of magnons and Dirac electrons on the surface of ferromagnetic
topological insulators. For a perpendicular magnetization, we calculate magnon-
(electron-) drag anomalous Nernst/Seebeck (anomalous Ettingshausen/Peltier)
effects and magnon-/electron-drag thermal Hall effects. The magnon-drag
thermoelectric effects are interpreted to be caused by magnon-induced
electromotive force. When the magnetization has in-plane components, there
arise thermal/thermoelectric analogs of anisotropic magnetoresistance (AMR). In
the insulating state, the thermal AMR is realized as a magnonic analog of AMR.

###Giant anisotropy of Gilbert damping in epitaxial CoFe films|Yi Li,Fanlong Zeng,Steven S. -L. Zhang,Hyeondeok Shin,Hilal Saglam,Vedat Karakas,Ozhan Ozatay,John E. Pearson,Olle G. Heinonen,Yizheng Wu,Axel Hoffmann,Wei Zhang###

Giant anisotropy of Gilbert damping in epitaxial CoFe films. Tailoring Gilbert damping of metallic ferromagnetic thin films is one of the
central interests in spintronics applications. Here we report a giant Gilbert
damping anisotropy in epitaxial Co$_{50}$Fe$_{50}$ thin film with a
maximum-minimum damping ratio of 400 \%, determined by broadband spin-torque as
well as inductive ferromagnetic resonance. We conclude that the origin of this
damping anisotropy is the variation of the spin orbit coupling for different
magnetization orientations in the cubic lattice, which is further corroborate
from the magnitude of the anisotropic magnetoresistance in Co$_{50}$Fe$_{50}$.

###Importance sampling for thermally induced switching and non-switching probabilities in spin-torque magnetic nanodevices|YiMing Yu,Cyrill B. Muratov,Richard O. Moore###

Importance sampling for thermally induced switching and non-switching probabilities in spin-torque magnetic nanodevices. Spin-transfer torque magnetoresistive random access memory is a potentially
transformative technology in the non-volatile memory market. Its viability
depends, in part, on one's ability to predictably induce or prevent switching;
however, thermal fluctuations cause small but important errors in both the
writing and reading processes. Computing these very small probabilities for
magnetic nanodevices using naive Monte Carlo simulations is essentially
impossible due to their slow statistical convergence, but variance reduction
techniques can offer an effective way to improve their efficiency. Here, we
provide an illustration of how importance sampling can be efficiently used to
estimate low read and write soft error rates of macrospin and coupled-spin
systems.

###Highly Mobile Carriers in a Candidate of Quasi-Two-Dimensional Topological Semimetal AuTe$_2$Br|Zeji Wang,Shuyu Cheng,Tay-Rong Chang,Wenlong Ma,Xitong Xu,Huibin Zhou,Guangqiang Wang,Xin Gui,Haipeng Zhu,Zhen Zhu,Hao Zheng,Jinfeng Jia,Junfeng Wang,Weiwei Xie,Shuang Jia###

Highly Mobile Carriers in a Candidate of Quasi-Two-Dimensional Topological Semimetal AuTe$_2$Br. We report the crystal and electronic structures of a non-centrosymmetric
quasi-two-dimensional (2D), candidate of topological semimetal AuTe2Br. The
Fermi surface of this layered compound consists of 2D-like, topological trivial
electron and non-trivial hole pockets which host a Dirac cone along the kz
direction. Our transport measurements on the single crystals show highly
anisotropic, compensated low-density electrons and holes, both of which exhibit
ultrahigh mobility at a level of 10^5cm^2V^-1s^-1 at low temperature. The
highly mobile, compensated carriers lead a non-saturated, parabolic
magnetoresistance as large as 3*10^5 in single-crystalline AuTe2Br in a
magnetic field up to 58 T.

###Optimizing magnetoresistive sensor signal-to-noise via pinning field tuning|J. Moulin,A. Doll,E. Paul,M. Pannetier-Lecoeur,C. Fermon,N. Sergeeva-Chollet,A. Solignac###

Optimizing magnetoresistive sensor signal-to-noise via pinning field tuning. The presence of magnetic noise in magnetoresistive-based magnetic sensors
degrades their detection limit at low frequencies. In this paper, different
ways of stabilizing the magnetic sensing layer to suppress magnetic noise are
investigated by applying a pinning field, either by an external field,
internally in the stack or by shape anisotropy. We show that these three
methods are equivalent, could be combined and that there is a competition
between noise suppression and sensitivity reduction, which results in an
optimum total pinning field, for which the detection limit of the sensor is
improved up to a factor of ten.

###Quantum Diffusive Magneto-transport in Massive Dirac Materials with Chiral Symmetry Breaking|Bo Fu,Huan-Wen Wang,Shun-Qing Shen###

Quantum Diffusive Magneto-transport in Massive Dirac Materials with Chiral Symmetry Breaking. Massive Dirac fermions break the chiral symmetry explicitly and also make the
Berry curvature of the band structure non-Abelian. By utilizing the Green's
function technique, we develop a microscopic theory to establish a set of
quantum diffusive equations for massive Dirac materials in the presence of
electric and magnetic fields. It is found that the longitudinal
magnetoresistance is always negative and quadratic in the magnetic field, and
decays quickly with the mass. The theory is applicable to the systems with
non-Abelian Berry curvature and resolves the puzzles of anomalous
magnetotransport properties measured in topological materials.

###Thermally driven two-magnet nano-oscillator with large spin-charge conversion|Bassim Arkook,Christopher Safranski,Rodolfo Rodriguez,Ilya N. Krivorotov,Tobias Schneider,Kilian Lenz,Jürgen Lindner,Houchen Chang,Mingzhong Wu,Yaroslav Tserkovnyak,Igor Barsukov###

Thermally driven two-magnet nano-oscillator with large spin-charge conversion. Next-generation spintronic applications require material properties that can
be hardly met by one material candidate. Here we demonstrate that by combining
insulating and metallic magnets, enhanced spin-charge conversion and
energy-efficient thermal spin currents can be realized. We develop a nanowire
device consisting of an yttrium iron garnet and permalloy bi-layer. An
interfacial temperature gradient drives the nanowire magnetization into
auto-oscillations at gigahertz frequencies. Interfacial spin coupling and
magnetoresistance of the permalloy layer translate spin dynamics into sizable
microwave signals. The results show prospect for energy-efficient spintronic
devices and present an experimental realization of magnon condensation in a
heterogeneous magnetic system.

###Large Magnetoresistance in Topological Insulator Candidate TaSe3|Yong Zhang,Tongshuai Zhu,Haijun Bu,Zixiu Cai,Chuanying Xi,Bo Chen,Boyuan Wei,Dongjing Lin,Hangkai Xie,Muhammad Naveed,Xiaoxiang Xi,Fucong Fei,Haijun Zhang,Fengqi Song###

Large Magnetoresistance in Topological Insulator Candidate TaSe3. Large unsaturated magnetoresistance (XMR) with magnitude about 1000% is
observed in topological insulator candidate TaSe3 from our high field (up to 38
T) measurements. Two oscillation modes, associated with one hole pocket and two
electron pockets in the bulk, respectively, are detected from our Shubnikov-de
Hass (SdH) measurements, consistent with our first-principles calculations.
With the detailed Hall measurements performed, our two-band model analysis
exhibits an imperfect density ratio n_h/n_e closing 0.9 at T< 20 K , which
suggests that the carrier compensations account for the XMR in TaSe3.

###Highly Tunable Spin-Orbit Torque and Anisotropic Magnetoresistance in a Topological Insulator Thin Film Attached to Ferromagnetic Layer|Ali G. Moghaddam,Alireza Qaiumzadeh,Anna Dyrdał,Jamal Berakdar###

Highly Tunable Spin-Orbit Torque and Anisotropic Magnetoresistance in a Topological Insulator Thin Film Attached to Ferromagnetic Layer. We investigate spin-charge conversion phenomena in hybrid structures of
topological insulator (TI) thin films and magnetic insulators. We find an
anisotropic inverse spin-galvanic effect (ISGE) that yields a highly tunable
spin-orbit torque (SOT). Concentrating on the quasiballistic limit, we also
predict a giant anisotropic magnetoresistance (AMR) at low dopings. These
effects, which have no counterparts in thick TIs, depend on the simultaneous
presence of the hybridization between the surface states and the in-plane
magnetization. Both the ISGE and AMR exhibit a strong dependence on the
magnetization and the Fermi level position and can be utilized for spintronics
and SOT-based applications at the nanoscale.

###Superconductor-Insulator Transition and the Crossover to Non Equilibrium in two-dimensional Indium - Indium-Oxide composite|Bar Hen,Xinyang Zhang,Victor Shelukhin,Aharon Kapitulnik,Alexander Palevski###

Superconductor-Insulator Transition and the Crossover to Non Equilibrium in two-dimensional Indium - Indium-Oxide composite. Magnetic-field tuned superconductor to insulator transition was observed in a
novel hybrid system of granular superconducting indium, deposited on indium
oxide thin film, which exhibits global superconductivity at low magnetic
fields. We have used annealing to tune the coupling to lie just at the
borderline where superconductivity in the underlying InOx is suppressed, which
is also close to the metal-insulator transition of the InOx. The hybrid system
exhibits a "giant" magnetoresistance above the H-SIT, with critical behavior
that manifests the duality between Cooper pairs and vortices.

###Efficient spin torques in antiferromagnetic CoO/Pt quantified by comparing field- and current- induced switching|Lorenzo Baldrati,Christin Schmitt,Olena Gomonay,Romain Lebrun,Rafael Ramos,Eiji Saitoh,Jairo Sinova,Mathias Kläui###

Efficient spin torques in antiferromagnetic CoO/Pt quantified by comparing field- and current- induced switching. We achieve current-induced switching in collinear insulating
antiferromagnetic CoO/Pt, with fourfold in-plane magnetic anisotropy. This is
measured electrically by spin Hall magnetoresistance and confirmed by the
magnetic field-induced spin-flop transition of the CoO layer. By applying
current pulses and magnetic fields, we quantify the efficiency of the acting
current-induced torques and estimate a current-field equivalence ratio of
$4x10^{-11} T A^{-1} m^2$. The N\'eel vector final state ($n \perp j$) is in
line with a thermomagnetoelastic switching mechanism for a negative
magnetoelastic constant of the CoO.

###Fermi-surface reconstruction and two-carrier model for the Hall effect in YBa2Cu4O8|P. M. C. Rourke,A. F. Bangura,C. Proust,J. Levallois,N. Doiron-Leyraud,D. LeBoeuf,L. Taillefer,S. Adachi,M. L. Sutherland,N. E. Hussey###

Fermi-surface reconstruction and two-carrier model for the Hall effect in YBa2Cu4O8. Pulsed field measurements of the Hall resistivity and magnetoresistance of
underdoped YBa2Cu4O8 are analyzed self-consistently using a simple model based
on coexisting electron and hole carriers. The resultant mobilities and Hall
numbers are found to vary markedly with temperature. The conductivity of the
hole carriers drops by one order of magnitude below 30 K, explaining the
absence of quantum oscillations from these particular pockets. Meanwhile the
Hall coefficient of the electron carriers becomes strongly negative below 50 K.
The overall quality of the fits not only provides strong evidence for
Fermi-surface reconstruction in Y-based cuprates, it also strongly constrains
the type of reconstruction that might be occurring.

###Tunnel magnetoresistance due to Coulomb blockade effects in quasi-one dimensional polymer nanofibers|H. J. Lee,A. N. Aleshin,S. H. Jhang,H. S. Kim,M. J. Goh,K. Akagi,J. S. Brooks,Y. W. Park###

Tunnel magnetoresistance due to Coulomb blockade effects in quasi-one dimensional polymer nanofibers. We report on the low temperature tunnel magnetoresistance (MR) in quasi
one-dimensional (1D) nanofibers made of conjugated polymers. The MR voltage
bias dependence reveals an enhancement (at low biases) and the oscillatory
behavior at temperatures below 10 K. The low temperature isotropic MR behavior
has been attributed to the charging effects in the polymer nanofiber which
considered as an array of small conducting regions separated by nano barriers.
These effects at low temperatures lead to the single electron tunneling
represented by the Coulomb blockade regime as well as to an enhancement and
oscillation of the tunnel MR.

###STS study of the CMR effect of a manganite thin film in an external magnetic field|B. Damaschke,T. Mildner,V. Moshnyaga,K. Samwer###

STS study of the CMR effect of a manganite thin film in an external magnetic field. A La0.75Ca0.25MnO3-film grown by metalorganic aerosol deposition technique
was investigated by scanning tunnelling microscopy and spectroscopy. A small
spot was found on the surface which exhibits the expected magnetic field
dependence of the tunnelling conductivity giving the opportunity for a local
spectroscopic study of the intrinsic colossal magnetoresistance (CMR) behavior.
The tunnelling conductivity is strongly enhanced in an external magnetic field
of 4 T and the CMR behavior can be interpreted in terms of a redistribution of
occupied electronic states torwards the Fermi energy.

###GaMnAs-based magnetic tunnel junctions with an AlMnAs barrier|Shinobu Ohya,Iriya Muneta,Pham Nam Hai,Masaaki Tanaka###

GaMnAs-based magnetic tunnel junctions with an AlMnAs barrier. We investigate the spin-dependent transport of GaMnAs-based magnetic tunnel
junctions (MTJs) containing a paramagnetic AlMnAs barrier with various
thicknesses. The barrier height of AlMnAs with respect to the Fermi level of
GaMnAs is estimated to be 110 meV. We observe tunneling magnetoresistance (TMR)
ratios up to 175% (at 2.6 K), which is higher than those of the GaMnAs-based
MTJs with other barrier materials in the same temperature region. These high
TMR ratios can be mainly attributed to the relatively high crystal quality of
AlMnAs and the suppression of the tunneling probability near at the in-plane
wave-vector k||=0.

###Fano Mechanism of the Giant Magnetoresistance Formation in a Spin Nanostructure|Valery V. Val'kov,Sergey V. Aksenov###

Fano Mechanism of the Giant Magnetoresistance Formation in a Spin Nanostructure. It is shown that, upon the electron quantum transport via the nanostructure
containing a spin dimer, the spin-flip processes caused by the s-f exchange
interaction between electron and dimer spins lead to the Fano resonance
effects. An applied magnetic field eliminates degeneracy of the upper triplet
states of the dimer, changes the conditions for implementation of the Fano
resonances and antiresonances, and induces the new Fano resonance and
antiresonance. It results in the occurrence of a sharp peak and dip in the
energy dependence of transmittance. These effects strongly modify the
current--voltage characteristic of the spin-dimer structure in a magnetic field
and form giant magnetoresistance.

###Large Magnetoresistance Effects in $Ln$CoAsO with a Ferromagnetic-Antiferromagnetic Transition|Hiroto Ohta,Chishiro Michioka,Kazuyoshi Yoshimura###

Large Magnetoresistance Effects in $Ln$CoAsO with a Ferromagnetic-Antiferromagnetic Transition. A large magnetoresistance (MR) effect was observed in the layered compounds
NdCoAsO and SmCoAsO, in which ferromagnetically ordered itinerant-electrons of
Co are sandwiched by localized 4$f$-electrons of $Ln^{3+}$, below
ferromagnetic-antiferromagnetic transition (FAFT) temperature $T_\mathrm{N}$ as
observed in other FAFT compounds. In SmCoAsO, the large MR effect is also
observed up to the Curie temperature $T_\mathrm{C}$, and it is found to be
originating in the presence of another antiferromagnetic phase in the
low-magnetic field region of the ferromagnetic phase.

###Lifshitz transitions and quasiparticle de-renormalization in YbRh$_2$Si$_2$|H. R. Naren,S. Friedemann,G. Zwicknagl,C. Krellner,C. Geibel,F. Steglich,S. Wirth###

Lifshitz transitions and quasiparticle de-renormalization in YbRh$_2$Si$_2$. We study the effect of magnetic fields up to 15 T on the heavy fermion state
of YbRh$_2$Si$_2$ via Hall effect and magnetoresistance measurements down to 50
mK. Our data show anomalies at three different characteristic fields. We
compare our data to renormalized band structure calculations through which we
identify Lifshitz transitions associated with the heavy fermion bands. The Hall
measurements indicate that the de-renormalization of the quasiparticles, {\it
i.e} the destruction of the local Kondo singlets, occurs smoothly while the
Lifshitz transitions occur within rather confined regions of the magnetic
field.

###Reversal mode instability and magnetoresistance in perpendicular (Co/Pd)/Cu/(Co/Ni) pseudo-spin-valves|J. E. Davies,D. A. Gilbert,S. M. Mohseni,R. K. Dumas,J. Åkerman,Kai Liu###

Reversal mode instability and magnetoresistance in perpendicular (Co/Pd)/Cu/(Co/Ni) pseudo-spin-valves. We have observed distinct temperature-dependent magnetization reversal modes
in a perpendicular (Co/Pd)4/Co/Cu/(Co/Ni)4/Co pseudo-spin-valve, which are
correlated with spin-transport properties. At 300 K, magnetization reversal
occurs by vertically correlated domains. Below 200 K the hysteresis loop
becomes bifurcated due to laterally correlated reversal of the individual
stacks. The magnetic configuration change also leads to higher spin disorders
and a significant increase in the giant magnetoresistance effect. First order
reversal curve measurements reveal that the coupled state can be re-established
through field cycling, and allow direct determination of the interlayer
coupling strength as a function of temperature.

###RF amplification property of the MgO-based magnetic tunnel junction using field-induced ferromagnetic resonance|K. Konishi,D. K. Dixit,A. A. Tulapurkar,S. Miwa,T. Nozaki,H. Kubota,A. Fukushima,S. Yuasa,Y. Suzuki###

RF amplification property of the MgO-based magnetic tunnel junction using field-induced ferromagnetic resonance. The radio-frequency (RF) voltage amplification property of a tunnel
magnetoresistance device driven by an RF external-magnetic-field-induced
ferromagnetic resonance was studied. The proposed device consists of a magnetic
tunnel junction (MTJ) and an electrically isolated coplanar waveguide. The
input RF voltage applied to the waveguide can excite the resonant dynamics in
the free layer magnetization, leading to the generation of an output RF voltage
under a DC bias current. The dependences of the RF voltage gain on the static
external magnetic field strength and angle were systematically investigated.
The design principles for the enhancement of the gain factor are also
discussed.

###Kondo-like mass enhancement of Dirac fermion in iron pnictides Ba(Fe$_{1-x}$Mn$_x$As)$_2$|T. Urata,Y. Tanabe,K. K. Huynh,H. Oguro,K. Watanabe,S. Heguri,K. Tanigaki###

Kondo-like mass enhancement of Dirac fermion in iron pnictides Ba(Fe$_{1-x}$Mn$_x$As)$_2$. The effect of Mn substitution, acting as a magnetic impurity for Fe, on the
Dirac cone was investigated in Ba(Fe$_{1-x}$Mn$_x$As)$_2$. Both
magnetoresistance and Hall resistivity studies clearly indicate that the
cyclotron effective mass ($m^{\ast}$) of the Dirac cone is anomalously enhanced
at low temperatures by the impurity, although its evolution as a function of
carrier number proceeds in a conventional manner at higher temperatures.
Kondo-like band renormalization induced by the magnetic impurity scattering is
suggested as an explanation for this, and the anomalous mass enhancement of the
Dirac fermions is discussed.

###Two-dimensional electron gas in a modulation-doped SrTiO3/Sr(Ti,Zr)O3 heterostructure|Adam P. Kajdos,Daniel G. Ouellette,Tyler A. Cain,Susanne Stemmer###

Two-dimensional electron gas in a modulation-doped SrTiO3/Sr(Ti,Zr)O3 heterostructure. A two-dimensional electron gas (2DEG) in SrTiO3 is created via modulation
doping by interfacing undoped SrTiO3 with a wider-band-gap material,
SrTi1-xZrxO3, that is doped n-type with La. All layers are grown using hybrid
molecular beam epitaxy. Using magnetoresistance measurements, we show that
electrons are transferred into the SrTiO3, and a 2DEG is formed. In particular,
Shubnikov-de Haas oscillations are shown to depend only on the perpendicular
magnetic field. Experimental Shubnikov-de Haas oscillations are compared with
calculations that assume multiple occupied subbands.

###Emergent Spin-Filter at the interface between Ferromagnetic and Insulating Layered Oxides|Yaohua Liu,F. A. Cuellar,Z. Sefrioui,J. W. Freeland,M. R. Fitzsimmons,C. Leon,J. Santamaria,S. G. E. te Velthuis###

Emergent Spin-Filter at the interface between Ferromagnetic and Insulating Layered Oxides. We report a strong effect of interface-induced magnetization on the transport
properties of magnetic tunnel junctions consisting of ferromagnetic manganite
La$_{0.7}$Ca$_{0.3}$MnO$_{3}$ and insulating cuprate PrBa$_{2}$Cu$_{3}$O$_{7}$.
Contrary to the typically observed steady increase of the tunnel
magnetoresistance with decreasing temperature, this system exhibits a sudden
anomalous decrease at low temperatures. Interestingly, this anomalous behavior
can be attributed to the competition between the positive spin polarization of
the manganite contacts and the negative spin-filter effect from the
interface-induced Cu magnetization.

###Role of Dirac cones in magnetotransport properties of REFeAsO (RE=rare earth) oxypnictides|I. Pallecchi,F. Bernardini,F. Caglieris,A. Palenzona,S. Massidda,M. Putti###

Role of Dirac cones in magnetotransport properties of REFeAsO (RE=rare earth) oxypnictides. In this work we study the effect of the rare earth element in iron
oxypnictides of composition REFeAsO (RE=rare earth). On one hand we carry out
Density Functional Theory calculations of the band structure, which evidence
the multiband character of these compounds and the presence of Dirac cones
along the Y-{\Gamma} and Z-R directions of the reciprocal space. On the other
hand, we explore transport behavior by means of resistivity, Hall resistance
and magnetoresistance measurements, which confirm the dominant role of Dirac
cones. By combining our theoretical and experimental approaches, we extract
information on effective masses, scattering rates and Fermi velocities for
different rare earth elements.

###Extremely Large Magnetoresistance in the Nonmagnetic Metal PdCoO2|Hiroshi Takatsu,Jun J. Ishikawa,Shingo Yonezawa,Harukazu Yoshino,Tatsuya Shishidou,Tamio Oguchi,Keizo Murata,Yoshiteru Maeno###

Extremely Large Magnetoresistance in the Nonmagnetic Metal PdCoO2. Extremely large magnetoresistance is realized in the nonmagnetic layered
metal PdCoO2. In spite of a highly conducting metallic behavior with a simple
quasi-two-dimensional hexagonal Fermi surface, the interlayer resistance
reaches up to 35000% for the field along the [1-10] direction. Furthermore, the
temperature dependence of the resistance becomes nonmetallic for this field
direction, while it remains metallic for fields along the [110] direction. Such
severe and anisotropic destruction of the interlayer coherence by a magnetic
field on a simple Fermi surface is ascribable to orbital motion of carriers on
the Fermi surface driven by the Lorentz force, but seems to have been largely
overlooked until now.

###Parallel field magnetoresistance in topological insulator thin films|C. J. Lin,X. Y. He,J. Liao,X. X. Wang,V. Sacksteder IV,W. M. Yang,T. Guan,Q. M. Zhang,L. Gu,G. Y. Zhang,C. G. Zeng,X. Dai,K. H. Wu,Y. Q. Li###

Parallel field magnetoresistance in topological insulator thin films. We report that the finite thickness of three-dimensional topological
insulator (TI) thin films produces an observable magnetoresistance (MR) in
phase coherent transport in parallel magnetic fields. The MR data of Bi2Se3 and
(Bi,Sb)2Te3 thin films are compared with existing theoretical models of
parallel field magnetotransport. We conclude that the TI thin films bring
parallel field transport into a unique regime in which the coupling of surface
states to bulk and to opposite surfaces is indispensable for understanding the
observed MR. The {\beta} parameter extracted from parallel field MR can in
principle provide a figure of merit for searching TI compounds with more
insulating bulk than existing materials.

###Disorder induced magnetoresistance in a two dimensional electron system|Jinglei Ping,Indra Yudhistira,Navneeth Ramakrishnan,Sungjae Cho,Shaffique Adam,Michael S. Fuhrer###

Disorder induced magnetoresistance in a two dimensional electron system. We predict and demonstrate that a disorder induced carrier density
inhomogeneity causes magnetoresistance (MR) in a two-dimensional electron
system. Our experiments on graphene show a quadratic MR persisting far from the
charge neutrality point. Effective medium calculations show that for charged
impurity disorder, the low-field MR is a universal function of the ratio of
carrier density to fluctuations in carrier density, a power-law when this ratio
is large, in excellent agreement with experiment. The MR is generic and should
occur in other materials with large carrier density inhomogeneity.

###Quantum Interference Noise Near the Dirac Point in Graphene|Atikur Rahman,Janice Wynn Guikema,Nina Markovic###

Quantum Interference Noise Near the Dirac Point in Graphene. Effects of disorder on the electronic transport properties of graphene are
strongly affected by the Dirac nature of the charge carriers in graphene. This
is particularly pronounced near the Dirac point, where relativistic charge
carriers cannot efficiently screen the impurity potential. We have studied
time-dependent conductance fluctuations and magnetoresistance in graphene in
the close vicinity of the Dirac point. We show that the fluctuations are due to
the quantum interference effects due to scattering on impurities, and find an
unusually large reduction of the relative noise power in magnetic field,
possibly indicating that an additional symmetry plays an important role in this
regime.

###Micromagnetic study of electrical-field-assisted magnetization switching in MTJ devices|M. Carpentieri,R. Tomasello,M. Ricci,P. Burrascano,G. Finocchio###

Micromagnetic study of electrical-field-assisted magnetization switching in MTJ devices. Perpendicular MgO-based Magnetic Tunnel Junctions are optimal candidates as
building block of Spin Transfer Torque (STT) magnetoresistive memories.
However, up to now, the only STT is not enough to achieve switching current
density below 106 A/cm2. A recent work [Wang et al., Nature Mater., vol. 11, pp
64-68, Jan. 2012] has experimentally demonstrated the possibility to perform
magnetization switching assisted by an electric-field at ultra-low current
density. Theoretically, this switching has been studied by using a macrospin
approach only. Here, we show a full micromagnetic study. We found that the
switching occurs via a complex nucleation process including the nucleation of
magnetic vortexes.

###Emergent Transition for Superconducting Fluctuations in Antiferromagnetic Ruthenocuprates|A. C. Mclaughlin,J. P. Attfield###

Emergent Transition for Superconducting Fluctuations in Antiferromagnetic Ruthenocuprates. The emergence of carrier-pairing from the electronically inhomogeneous phase
of lightly hole-doped copper oxides has been investigated through
magnetoresistance measurements on 1222-type ruthenocuprates
RuSr2(R,Ce)2Cu2O10-d, principally with R = Gd, Sm, Nd. A well-defined
transition at which superconducting fluctuations emerge is discovered at a
remarkably low critical doping, pc = 0.0084, deep within the antiferromagnetic
phase. Systematic variations of the low temperature fluctuation density with
doping and cell volume demonstrate the intrinsic nature of the electronic
inhomogeneity and provide new support for bosonic models of the superconducting
mechanism.

###Cooperative Multiscale Aging in a Ferromagnet/Antiferromagnet Bilayer|Sergei Urazhdin###

Cooperative Multiscale Aging in a Ferromagnet/Antiferromagnet Bilayer. We utilize anisotropic magnetoresistance to study temporal evolution of the
magnetization state in epitaxial Ni$_{80}$Fe$_{20}$/Fe$_{50}$Mn$_{50}$
ferromagnet/antiferromagnet bilayers. The resistance exhibits power-law
evolution over a wide range of temperatures and magnetic fields, indicating
that aging is characterized by a wide range of activation time scales. We show
that aging is a cooperative process, i.e. the magnetic system is not a
superposition of weakly interacting subsystems characterized by simple
Arrhenius activation. The observed effects are reminiscent of avalanches in
granular materials, providing a conceptual link to a broad class of critical
phenomena in other complex condensed matter systems.

###Surface superconductivity as the primary cause of broadening of superconducting transition in Nb-films|A. Zeinali,V. M. Krasnov###

Surface superconductivity as the primary cause of broadening of superconducting transition in Nb-films. We study the origin of broadening of superconducting transition in sputtered
Nb films. From simultaneous tunneling and transport measurements we conclude
that the upper critical field Hc2 always corresponds to the bottom of
transition R~0, while the top R~Rn occurs close to the critical field for
destruction of surface superconductivity Hc3 ~ 1.7 Hc2. The two-dimensional
nature of superconductivity at H>Hc2 is confirmed by cusp-like angular
dependence of magnetoresistance. Our data indicates that surface
superconductivity is remarkably robust even in disordered polycrystalline films
and, surprisingly, even in perpendicular magnetic fields.

###Interlayer electronic transport in CaMnBi$_{2}$ antiferromagnet|Aifeng Wang,D. Graf,Lijun Wu,Kefeng Wang,E. Bozin,Yimei Zhu,C. Petrovic###

Interlayer electronic transport in CaMnBi$_{2}$ antiferromagnet. We report interlayer electronic transport in CaMnBi$_{2}$ single crystals.
Quantum oscillations and angular magnetoresistance suggest coherent electronic
conduction and valley polarized conduction of Dirac states. Small cyclotron
mass, large mobility of carriers and nontrivial Berry's phase are consistent
with the presence of Dirac fermions on the side wall of the warped cylindrical
Fermi surface. Similar to SrMnBi$_{2}$ that features an anisotropic Dirac cone,
our results suggest that magnetic field-induced changes in the interlayer
conduction are also present in layered bismuth-based materials with zero-energy
line in momentum space created by the staggered alkaline earth atoms.

###Large Unidirectional Magnetoresistance in a Magnetic Topological Insulator|K. Yasuda,A. Tsukazaki,R. Yoshimi,K. S. Takahashi,M. Kawasaki,Y. Tokura###

Large Unidirectional Magnetoresistance in a Magnetic Topological Insulator. We report current-direction dependent or unidirectional magnetoresistance
(UMR) in magnetic/nonmagnetic topological insulator (TI) heterostructures,
Cr$_x$(Bi$_{1-y}$Sb$_y$)$_{2-x}$Te$_3$/(Bi$_{1-y}$Sb$_y$)$_2$Te$_3$, that is
several orders of magnitude larger than in other reported systems. From the
magnetic field and temperature dependence, the UMR is identified to originate
from the asymmetric scattering of electrons by magnons. In particular, the
large magnitude of UMR is an outcome of spin-momentum locking and a small Fermi
wavenumber at the surface of TI. In fact, the UMR is maximized around the Dirac
point with the minimal Fermi wavenumber.

###Giant tunable magnetoresistance of electrically gated graphene ribbon with lateral interface under magnetic field|A. M. Kadigrobov###

Giant tunable magnetoresistance of electrically gated graphene ribbon with lateral interface under magnetic field. Quantum dynamics and kinetics of electrically gated graphene ribbons with
lateral n-p and e-n-p junctions under magnetic field are investigated. It is
shown that the snake-like states of quasiparticles skipping along the n-p
interface do not manifest themselve in the main semiclassical part of the
ribbon conductance. Giant oscillations of the conductance of a ribbon with an
n-p-n junction are predicted and analytically calculated. Depending on the
number of junctions inside the ribbon its magnetoresistance may be controllably
changed by 50% - 90% by an extremely small change of the magnetic field or the
gate voltage.

###Lifshitz Transitions in the Ferromagnetic Superconductor UCoGe|Gaël Bastien,Adrien Gourgout,Dai Aoki,Alexandre Pourret,Ilya Sheikin,Gabriel Seyfarth,Jacques Flouquet,Georg Knebel###

Lifshitz Transitions in the Ferromagnetic Superconductor UCoGe. We present high field magnetoresistance, Hall effect and thermopower
measurements in the Ising-type ferromagnetic superconductor UCoGe. Magnetic
field is applied along the easy magnetization $c$ axis of the orthorhombic
crystal. In the different experimental probes we observed five successive
anomalies at $H \approx 4$, 9, 12, 16, and 21~T. Magnetic quantum oscillations
were detected both in resistivity and thermoelectric power. At most of the
anomalies, significant changes of the oscillation frequencies and the effective
masses have been observed indicating successive Fermi surface instabilities
induced by the strong magnetic polarization under magnetic field.

###Ballistic Anisotropic Magnetoresistance in Core Shell Nanowires and Rolled-up Nanotubes|Ching Hao Chang,Carmine Ortix###

Ballistic Anisotropic Magnetoresistance in Core Shell Nanowires and Rolled-up Nanotubes. In ferromagnetic nanostructures, the ballistic anisotropic magnetoresistance
(BAMR) is a change in the ballistic conductance with the direction of
magnetization due to spin-orbit interaction. Very recently, a directional
dependent ballistic conductance has been predicted to occur in a number of
newly synthesized nonmagnetic semiconducting nanostructures subject to
externally applied magnetic fields, without necessitating spin-orbit coupling.
In this article, we review past works on the prediction of this BAMR effect in
core-shell nanowires and rolled-up nanotubes. This is complemented by new
results we establish for the transport properties of tubular nanosystems
subject to external magnetic fields.

###Electronic transport and scattering times in tungsten-decorated graphene|Jamie A. Elias,Erik A. Henriksen###

Electronic transport and scattering times in tungsten-decorated graphene. The electronic transport properties of monolayer graphene have been studied
before and after the deposition of a dilute coating of tungsten adatoms on the
surface. For coverages up to 2.5\% of a monolayer, we find tungsten adatoms
simultaneously donate electrons to graphene and reduce the carrier mobility,
impacting the zero- and finite-field transport properties. Two independent
transport analyses suggest the adatoms lie nearly 1 nm above the surface. The
presence of adatoms is also seen to impact the low field magnetoresistance,
altering the signatures of weak localization.

###Pressure induced change in the electronic state of Ta$_4$Pd$_3$Te$_{16}$|Na Hyun Jo,Li Xiang,Udhara S. Kaluarachchi,Morgan Masters,Kathryn Neilson,Savannah S. Downing,Paul C. Canfield,Sergey L. Bud'ko###

Pressure induced change in the electronic state of Ta$_4$Pd$_3$Te$_{16}$. We present measurements of superconducting transition temperature,
resistivity, magnetoresistivity and temperature dependence of the upper
critical field of Ta$_4$Pd$_3$Te$_{16}$ under pressures up to 16.4 kbar. All
measured properties have an anomaly at $\sim 2 - 4$ kbar pressure range, in
particular there is a maximum in $T_c$ and upper critical field, $H_{c2}(0)$,
and minimum in low temperature, normal state resistivity. Qualitatively, the
data can be explained considering the density of state at the Fermi level as a
dominant parameter.

###Large polaron evolution in anatase TiO2 due to carrier and temperature dependence of electron-phonon coupling|B. X. Yan,D. Y. Wan,X. Chi,C. J. Li,M. R. Motapothula,S. Hooda,P. Yang,Z. Huang,S. W. Zeng,A. Gadekar,S. J. Pennycook,A. Rusydi,Ariando,J. Martin,T. Venkatesan###

Large polaron evolution in anatase TiO2 due to carrier and temperature dependence of electron-phonon coupling. The electronic and magneto transport properties of reduced anatase TiO2
epitaxial thin films are analyzed considering various polaronic effects.
Unexpectedly, with increasing carrier concentration, the mobility increases,
which rarely happens in common metallic systems. We find that the screening of
the electron-phonon (e-ph) coupling by excess carriers is necessary to explain
this unusual dependence. We also find that the magnetoresistance (MR) could be
decomposed into a linear and a quadratic component, separately characterizing
the transport and trap behavior of carriers as a function of temperature. The
various transport behaviors could be organized into a single phase diagram
which clarifies the nature of large polaron in this material.

###Effect of Image Potential on Spin Polarized Transport through Magnetic Tunnel Junctions|Tehseen Zahra Raza,Hassan Raza###

Effect of Image Potential on Spin Polarized Transport through Magnetic Tunnel Junctions. We study the effect of image potential on spin polarized transport through
Fe/MgO/Fe magnetic tunnel junctions in the presence of symmetry filtering. The
image potential is included within the Simmon's model coupled with the
non-equilibrium Green's function formalism to calculate the quantum transport.
The increase in the current densities for the $\Delta_1$ symmetry and the
$\Delta_5$ symmetry bands due to the image potential is more pronounced at
higher bias, whereas, the increase in the magnitude of the tunnel
magnetoresistance ratio is more prominent at lower bias for various barrier
thicknesses.

###Extremely large magnetoresistance and high-density Dirac-like fermions in ZrB2|Qi Wang,Peng-Jie Guo,Shanshan Sun,Chenghe Li,Kai Liu,Zhong-Yi Lu,Hechang Lei###

Extremely large magnetoresistance and high-density Dirac-like fermions in ZrB2. We report the detailed study on transport properties of ZrB2 single crystal,
a predicted topological nodal-line semimetal. ZrB2 exhibits extremely large
magnetoresistance as well as field-induced resistivity upturn and plateau.
These behaviors can be well understood by the two-band model with the perfect
electron - hole compensation and high carrier mobilities. More importantly, the
electrons with small effective masses and nontrivial Berry phase have
significantly high density when compared to those in known topological
semimetals. It strongly suggests that ZrB2 hosts Dirac-like nodal-line
fermions.

###Magnetoresistance based determination of basic parameters of minority charge carriers in solid matter|Y. O. Uhryn,R. M. Peleshchak,V. B. Brytan,A. A. Velchenko###

Magnetoresistance based determination of basic parameters of minority charge carriers in solid matter. Magnetoresistance as a tool of basic parameters determination of minority
charge carriers and the ratio of minority charge carriers conductivity to
majority ones in solid matter has been considered within the framework of the
phenomenological two-band model. The criterion of the application of this model
has been found. As examples of these equations usage the conductor,
semiconductor and superconductor have been introduced. From the obtained
temperature dependences of the aforementioned values in superconductor, a
supposition of a deciding role of minority charge carriers in the emergence of
superconductivity state has been made.

###Interfacial exchange coupling induced chiral symmetry-breaking of Spin-Orbit effects|P. Perna,F. Ajejas,D. Maccariello,J. L. Fernandez Cuñado,R. Guerrero,M. A. Niño,A. Bollero,R. Miranda,J. Camarero###

Interfacial exchange coupling induced chiral symmetry-breaking of Spin-Orbit effects. We demonstrate that the interfacial exchange coupling in
ferromagnetic/antiferromagnetic (FM/AFM) systems induces symmetry-breaking of
the Spin-Orbit (SO) effects. This has been done by studying the field and angle
dependencies of anisotropic magnetoresistance and vectorialresolved
magnetization hysteresis loops, measured simultaneously and reproduced with
numerical simulations. We show how the induced unidirectional magnetic
anisotropy at the FM/AFM interface results in strong asymmetric transport
behaviors, which are chiral around the magnetization hard-axis direction.
Similar asymmetric features are anticipated in other SO-driven phenomena.

###Prediction of Extraordinary Magnetoresistance in Janus Monolayer MoTeB2|Shijun Yuan,Hui Ding,Jinlan Wang,Zhongfang Chen###

Prediction of Extraordinary Magnetoresistance in Janus Monolayer MoTeB2. Based on first-principles calculations, we studied the geometric
configuration, stability and electronic structure of the two-dimensional Janus
MoTeB2. The MoTeB2 monolayer is semimetal, and its attractive electronic
structure reveals the perfect electron-hole compensation. Moreover, the
electron-type and hole-type bands of the MoTeB2 monolayer are easily adjustable
by external stain and charge doping, such as the switch of carrier polarity by
charge doping, and the metal-semiconductor transition under tensile stain.
These properties allow the MoTeB2 monolayer to be a controllable
two-dimensional material with extraordinary large magnetoresistance in magnetic
field.

###Antiferromagnetic Single-layer Spin-Orbit Torque Oscillators|Roberto E. Troncoso,Karsten Rode,Plamen Stamenov,J. Michael D. Coey,Arne Brataas###

Antiferromagnetic Single-layer Spin-Orbit Torque Oscillators. We show how a charge current through a single antiferromagnetic layer can
excite and control self-oscillations. Sustained oscillations with tunable
amplitudes and frequencies are possible in a variety of geometries using
certain classes of non-centrosymmetric materials that exhibit finite
dissipative spin-orbit torque. We compute the steady-state phase diagram as a
function of the current and spin-orbit torque magnitude. The anisotropic
magnetoresistance causes the conversion of the resulting AF oscillations to a
terahertz AC output voltage. These findings provide an attractive and novel
route to design terahertz antiferromagnetic spin-orbit torque oscillators in
simple single-layer structures.

###Engineering magnetoresistance: A new perspective|Moumita Patra,Santanu K. Maiti,Shreekantha Sil###

Engineering magnetoresistance: A new perspective. A new proposal is given to achieve high degree of magnetoresistance (MR) in a
magnetic quantum device where two magnetic layers are separated by a
non-magnetic (NM) quasiperiodic layer that acts as a spacer. The NM spacer is
chosen in the form of well-known Aubry-Andr\'{e} or Harper (AAH) model which
essentially gives the non-trivial features in MR due to its gaped spectrum and
yields the opportunities of controlling MR selectively by tuning the AAH phase
externally. We also explore the role of dephasing on magnetotransport to make
the model more realistic. Finally, we illustrate the experimental possibilities
of our proposed quantum system.

###Bilayer splitting and c-axis coupling in bilayer manganites showing colossal magnetoresistance|C. Jozwiak,J. Graf,S. Y. Zhou,A. Bostwick,Eli Rotenberg,H. Zheng,J. F. Mitchell,A. Lanzara###

Bilayer splitting and c-axis coupling in bilayer manganites showing colossal magnetoresistance. By performing angle-resolved photoemission spectroscopy of the bilayer
colossal magnetoresistive (CMR) manganite, $La_{2-2x}Sr_{1+2x}Mn_{2}O_{7}$, we
provide the complete mapping of the Fermi level spectral weight topology. Clear
and unambiguous bilayer splitting of the in-plane 3d$_{x^2-y^2}$ band, mapped
throughout the Brillouin zone, and the full mapping of the 3d$_{3z^2-r^2}$ band
are reported. Peculiar doping and temperature dependencies of these bands imply
that as transition from the ferromagnetic metallic phase approaches, either as
a function of doping or temperature, coherence along the c-axis between planes
within the bilayer is lost, resulting in reduced interplane coupling. These
results suggest that interplane coupling plays a large role in the CMR
transition.

###Unusual giant magnetoresistance effect in heterojunction structure of ultra-thin single-crystal Pb film on silicon substrate|Jian Wang,Xu-Cun Ma,Yun Qi,Ying-Shuang Fu,Shuai-hua Ji,Li Lu,X. C. Xie,Jin-Feng Jia,Xi Chen,Qi-Kun Xue###

Unusual giant magnetoresistance effect in heterojunction structure of ultra-thin single-crystal Pb film on silicon substrate. Superconductor films on semiconductor substrates draw much attention recently
since the derived superconductor-based electronics have been shown promising
for future data process and storage technologies. By growing atomically uniform
single-crystal epitaxial Pb films of several nanometers thick on Si wafers to
form a sharp superconductor-semiconductor heterojunction, we have obtained an
unusual giant magnetoresistance effect when the Pb film is superconducting. In
addition to the great fundamental interest of this effect, the simple structure
and compatibility and scalability with current Si-based semiconductor
technology offer a great opportunity for integrating superconducting circuits
and detectors in a single chip.

###Effective Resistance Mismatch and Magnetoresistance of a CPP-GMR system with Current-Confined-Paths|Jun Sato,Katsuyoshi Matsushita,Hiroshi Imamura###

Effective Resistance Mismatch and Magnetoresistance of a CPP-GMR system with Current-Confined-Paths. We theoretically study the magnetoresistance of a CPP-GMR system with current
confined paths (CCP) in the framework of Valet-Fert theory. The continuity
equations for charge and spin currents are numerically solved with the
three-dimensional CCP geometry by use of finite element method. It is confirmed
that the MR ratio is enhanced by the CCP structure, which is consistent with
the experimental results. Moreover, we find that there exists a certain contact
width which maximize the MR ratio. We show that the contact width which
maximize the MR ratio is well described by the effective resistance matching.

###Diverging Giant Magnetoresistance in the Limit of Infinitely Conducting Spacer|Soumen Mandal,R. C. Budhani,Jiaqing He,Y. Zhu###

Diverging Giant Magnetoresistance in the Limit of Infinitely Conducting Spacer. The relevance of pair-breaking by exchange and dipolar fields, and by
injected spins in a low carrier density cuprate
Y$_{1-x}$Pr$_x$Ba$_2$Cu$_3$O$_7$ sandwiched between two ferromagnetic La$_{2 /
3}$Sr$_{1 / 3}$MnO$_{3}$ layers is examined. At low external field ($H_{ext}$),
the system shows a giant magnetoresistance(MR), which diverges deep in the
superconducting state. We establish a distinct dipolar contribution to MR near
the switching field(H$_c$) of the magnetic layers. At H$_{ext} \gg$ H$_c$, a
large positive MR, resulting primarily from the motion of Josephson vortices
and pair breaking by the in-plane field, is seen.

###Spin polarized transport driven by square voltage pulses in a quantum dot system|F. M. Souza,J. A. Gomez###

Spin polarized transport driven by square voltage pulses in a quantum dot system. We calculate current, spin current and tunnel magnetoresistance (TMR) for a
quantum dot coupled to ferromagnetic leads in the presence of a square wave of
bias voltage. Our results are obtained via time-dependent nonequilibrium Green
function. Both parallel and antiparallel lead magnetization alignments are
considered. The main findings include a wave of spin accumulation and spin
current that can change sign as the time evolves, spikes in the TMR signal and
a TMR sign change due to an ultrafast switch from forward to reverse current in
the emitter lead.

###Coexistence of Dirac-Cone States and Superconductivity in Iron Pnictide Ba(Fe$_{1-x}$Ru$_x$As)$_2$|Y. Tanabe,K. K. Huynh,S. Heguri,G. Mu,T. Urata,J. Xu,R. Nouchi,N. Mitoma,K. Tanigaki###

Coexistence of Dirac-Cone States and Superconductivity in Iron Pnictide Ba(Fe$_{1-x}$Ru$_x$As)$_2$. The Ru doping effect on the Dirac cone states is investigated in iron
pnictide superconductors Ba(Fe$_{1-x}$Ru$_x$As)$_2$ using the transverse
magnetoresistance (MR) measurements as a function of temperature. The linear
development of MR against magnetic field $B$ is observed for $x$ = 0 - 0.244 at
low temperatures below the antiferromagnetic transition. The $B$-linear MR is
interpreted in terms of the quantum limit of the Dirac cone states by using the
model proposed by Abrikosov. An intriguing evidence is shown that the Dirac
cone state persists on the electronic phase diagram where the
antiferromagnetism and the superconductivity coexist.

###Strong quantum interference in strongly disordered bosonic insulators|S. V. Syzranov,A. Moor,K. B. Efetov###

Strong quantum interference in strongly disordered bosonic insulators. We study the variable-range hopping (VRH) of bosons in an array of sites with
short-range interactions and a large characteristic coordination number. The
latter leads to strong quantum interference phenomena yet allows for their
analytical study. We develop a functional renormalization group scheme that
repeatedly eliminates high-energy sites properly renormalizing the tunnelling
between the low-energy ones. Using this approach we determine the temperature
and magnetic field dependence of the hopping conductivity and find a large
positive magnetoresistance. With increasing magnetic field the behaviour of the
conductivity crossovers from the Mott's law to an activational behaviour with
the activation gap proportional to the magnetic field.

###Enhancement of the upper critical field in codoped iron-arsenic high-temperature superconductors|F. Weickert,M. Nicklas,W. Schnelle,J. Wosnitza,A. Leithe-Jasper,H. Rosner###

Enhancement of the upper critical field in codoped iron-arsenic high-temperature superconductors. We present the first study of codoped iron-arsenide superconductors of the
122 family (Sr/Ba)_(1-x)K_xFe_(2-y)Co_yAs_2 with the purpose to increase the
upper critical field H_c2 compared to single doped (Sr/Ba)Fe_2As_2 materials.
H_c2 was investigated by measuring the magnetoresistance in high pulsed
magnetic fields up to 64 T. We find, that H_c2 extrapolated to T = 0 is indeed
enhanced significantly to ~ 90 T for polycrystalline samples of
Ba_0.55K_0.45Fe_1.95Co_0.05As_2 compared to ~75 T for Ba_0.55K_0.45Fe_2As_2 and
BaFe_1.8Co_0.2As_2 single crystals. Codoping thus is a promising way for the
systematic optimization of iron-arsenic based superconductors for
magnetic-field and high-current applications.

###Influence of anisotropic magnetoresistance on nonlocal signals in Si-based multi-terminal devices with Fe electrodes|Ryosho Nakane,Shoichi Sato,Shun Kokutani,Masaaki Tanaka###

Influence of anisotropic magnetoresistance on nonlocal signals in Si-based multi-terminal devices with Fe electrodes. We have investigated the influence of anisotropic magnetoresistance (AMR) on
nonlocal signals in Si-based multi-terminal devices with ferromagnetic Fe
electrodes. The AMR of the Fe electrodes was found to have a significant
influence on nonlocal signals when the in-plane device structure is not
optimized. Moreover, realization of a pure spin current by spin diffusion was
found to be virtually impossible because of the electric potential distribution
in the depth direction in the Si channel. Although apparent signals indicating
the spin-valve effect were not detected, we mainly present structural influence
on the electric potential distribution which is indispensable for the analyses
of spin-dependent transport.

###Tunnel spin injection into graphene using Al2O3 barrier grown by atomic layer deposition on functionalized graphene surface|Takehiro Yamaguchi,Satoru Masubuchi,Kazuyuki Iguchi,Rai Moriya,Tomoki Machida###

Tunnel spin injection into graphene using Al2O3 barrier grown by atomic layer deposition on functionalized graphene surface. We demonstrate electrical tunnel spin injection from a ferromagnet to
graphene through a high-quality Al2O3 grown by atomic layer deposition (ALD).
The graphene surface is functionalized with a self-assembled monolayer of
3,4,9,10-perylene tetracarboxylic acid (PTCA) to promote adhesion and growth of
Al2O3 with a smooth surface. Using this composite tunnel barrier of ALD-Al2O3
and PTCA, a spin injection signal of 30 ohm has been observed from non-local
magnetoresistance measurements at 45 K, revealing potentially high performance
of ALD-Al2O3/PTCA tunnel barrier for spin injection into graphene.

###Non-linear transport phenomena in a two-subband system|S. Wiedmann,G. M. Gusev,O. E. Raichev,A. K. Bakarov,J. C. Portal###

Non-linear transport phenomena in a two-subband system. We study non-linear transport phenomena in a high-mobility bilayer system
with two closely spaced populated electronic subbands in a perpendicular
magnetic field. For a moderate direct current excitation, we observe
zero-differential-resistance states with a characteristic 1/B periodicity. We
investigate, both experimentally and theoretically, the Hall field-induced
resistance oscillations which modulate the high-frequency magneto-intersubband
oscillations in our system if we increase the current. We also observe and
describe the influence of direct current on the magnetoresistance in the
presence of microwave irradiation.

###Controlled formation of high-mobility shallow electron gases in SrTiO3 single crystal|Jung-Won Chang,Joon Sung Lee,Tae Ho Lee,Jinhee Kim,Yong-Joo Doh###

Controlled formation of high-mobility shallow electron gases in SrTiO3 single crystal. We report controlled formation of sub-100 nm-thin electron channels in
SrTiO$_3$ by doping with oxygen vacancies induced by Ar$^+$-ion irradiation.
The conducting channels exhibit a consistent high electron mobility (~15,000
cm$^2$V$^{-1}$s$^{-1}$), which enables clear observation of magnetic quantum
oscillations, and gate-tunable linear magnetoresistance. Near the onset of
electrical conduction, the metal-insulator transition is induced by the
mobility suppression. With the high electron mobility and the ease of
controlled channel formation, this ion-irradiation doping method may provide an
excellent basis for developing oxide electronics.

###Topological Effects on Quantum Phase Slips in Superfluid Spin Transport|Se Kwon Kim,Yaroslav Tserkovnyak###

Topological Effects on Quantum Phase Slips in Superfluid Spin Transport. We theoretically investigate effects of quantum fluctuations on superfluid
spin transport through easy-plane quantum antiferromagnetic spin chains in the
large-spin limit. Quantum fluctuations give rise to decaying of spin
supercurrent by unwinding the magnetic order parameter within the easy plane,
which is referred to as phase slips. We show that the topological term in the
nonlinear sigma model for the spin chains qualitatively differentiates decaying
rate of the spin supercurrent between integer spin and half-odd-integer spin
chains. An experimental setup for a magnetoelectric circuit is proposed, in
which the dependence of the decaying rate on constituent spins can be verified
by measuring nonlocal magnetoresistance.

###Temperature and thickness dependence of tunneling anisotropic magnetoresistance in exchange-biased Py/IrMn/MgO/Ta stacks|H. Reichlova,V. Novak,Y. Kurosaki,M. Yamada,H. Yamamoto,A. Nishide,J. Hayakawa,H. Takahashi,M. Marysko,J. Wunderlich,X. Marti,T. Jungwirth###

Temperature and thickness dependence of tunneling anisotropic magnetoresistance in exchange-biased Py/IrMn/MgO/Ta stacks. We investigate the thickness and temperature dependence of a series of
Ni0:8Fe0:2/Ir0:2Mn0:8 bilayer samples with varying thickness ratio of the
ferromagnet/antiferromagnet (tFM/tAFM) in order to explore the exchange
coupling strengths in tunneling anisotropic magnetoresistance (TAMR) devices.
Specific values of tFM/tAFM lead to four distinct scenarios with specific
electric responses to moderate magnetic fields. The characteristic dependence
of the measured TAMR signal on applied voltage allows us to confirm its
persistence up to room temperature despite an overlapped contribution by a
thermal magnetic noise.

###Magnetotransport signatures of the proximity exchange and spin-orbit couplings in graphene|Jeongsu Lee,Jaroslav Fabian###

Magnetotransport signatures of the proximity exchange and spin-orbit couplings in graphene. Graphene on an insulating ferromagnetic substrate---ferromagnetic insulator
or ferromagnetic metal with a tunnel barrier---is expected to exhibit giant
proximity exchange and spin-orbit couplings. We use a realistic transport model
of charge-disorder scattering and solve the linearized Boltzmann equation
numerically exactly for the anisotropic Fermi contours of modified Dirac
electrons to find magnetotransport signatures of these proximity effects:
proximity anisotropic magnetoresistance, inverse spin-galvanic effect, and the
planar Hall resistivity. We establish the corresponding anisotropies due to the
exchange and spin-orbit couplings, with respect to the magnetization
orientation. We also present parameter maps guiding towards optimal regimes for
observing transport magnetoanisotropies in proximity graphene.

###Giant Magnetoresistance in Bilayer Graphene Nanoflakes|R. Farghadan,M. Farekiyan###

Giant Magnetoresistance in Bilayer Graphene Nanoflakes. Coherent spin transport through bilayer graphene (BLG) nanoflakes sandwiched
between two electrodes made of single-layer zigzag graphene nanoribbon was
investigated by means of Landauer-Buttiker formalism. Application of a magnetic
field only on BLG structure as a channel produces a perfect spin polarization
in a large energy region. Moreover, the conductance could be strongly modulated
by magnetization of the zigzag edge of AB-stacked BLG, and the junction,
entirely made of carbon, produces a giant magnetoresistance (GMR) up to
$10^6\%$. Intestinally, GMR and spin polarization could be tuned by varying BLG
width and length. Generally, MR in a AB-stacked BLG strongly increases
(decreases) with length (width).

###Spin polarization ratios of resistivity and density of states estimated from anisotropic magnetoresistance ratio for nearly half-metallic ferromagnets|Satoshi Kokado,Yuya Sakuraba,Masakiyo Tsunoda###

Spin polarization ratios of resistivity and density of states estimated from anisotropic magnetoresistance ratio for nearly half-metallic ferromagnets. We derive a simple relational expression between the spin polarization ratio
of resistivity, $P_\rho$, and the anisotropic magnetoresistance ratio $\Delta
\rho/\rho$, and that between the spin polarization ratio of the density of
states at the Fermi energy, $P_{\rm DOS}$, and $\Delta \rho/\rho$ for nearly
half-metallic ferromagnets. We find that $P_\rho$ and $P_{\rm DOS}$ increase
with increasing $|\Delta \rho/\rho|$ from 0 to a maximum value. In addition, we
roughly estimate $P_\rho$ and $P_{\rm DOS}$ for a Co$_2$FeGa$_{0.5}$Ge$_{0.5}$
Heusler alloy by substituting its experimentally observed $\Delta \rho/\rho$
into the respective expressions.

###Discovery of Log-Periodic Oscillations in Ultra-Quantum Topological Materials|Huichao Wang,Haiwen Liu,Yanan Li,Yongjie Liu,Junfeng Wang,Jun Liu,Jiyan Dai,Yong Wang,Liang Li,Jiaqiang Yan,David Mandrus,X. C. Xie,Jian Wang###

Discovery of Log-Periodic Oscillations in Ultra-Quantum Topological Materials. Quantum oscillations are usually the manifestation of the underlying physical
nature in condensed matter systems. Here we report a new type of log-periodic
quantum oscillations in ultra-quantum three-dimensional topological materials.
Beyond the quantum limit (QL), the log-periodic oscillations involving up to
five oscillating cycles (5 peaks and 5 dips) are observed on the
magnetoresistance (MR) of high quality single-crystal ZrTe5, virtually showing
the clearest feature of discrete scale invariance (DSI). Further theoretical
analyses show that the two-body quasi-bound states can be responsible for the
DSI feature. Our work provides a new perspective on the ground state of
topological materials beyond the QL.

###Spin Fluctuation Induced Linear Magnetoresistance in Ultrathin Superconducting FeSe Films|Qingyan Wang,Wenhao Zhang,Weiwei Chen,Ying Xing,Yi Sun,Ziqiao Wang,Jia-Wei Mei,Zhengfei Wang,Lili Wang,Xu-Cun Ma,Feng Liu,Qi-Kun Xue,Jian Wang###

Spin Fluctuation Induced Linear Magnetoresistance in Ultrathin Superconducting FeSe Films. The discovery of high-temperature superconductivity in FeSe/STO has trigged
great research interest to reveal a range of exotic physical phenomena in this
novel material. Here we present a temperature dependent magnetotransport
measurement for ultrathin FeSe/STO films with different thickness and
protection layers. Remarkably, a surprising linear magnetoresistance (LMR) is
observed around the superconducting transition temperatures but absent
otherwise. The experimental LMR can be reproduced by magnetotransport
calculations based on a model of magnetic field dependent disorder induced by
spin fluctuation. Thus, the observed LMR in coexistence with superconductivity
provides the first magnetotransport signature for spin fluctuation around the
superconducting transition region in ultrathin FeSe/STO films.

###Magnon spin Hall magnetoresistance of a gapped quantum paramagnet|Camilo Ulloa,R. A. Duine###

Magnon spin Hall magnetoresistance of a gapped quantum paramagnet. Motivated by recent experimental work, we consider spin transport between a
normal metal and a gapped quantum paramagnet. We model the latter as the
magnonic Mott-insulating phase of an easy-plane ferromagnetic insulator. We
evaluate the spin current mediated by the interface exchange coupling between
the ferromagnet and the adjacent normal metal. For the strongly interacting
magnons that we consider, this spin current gives rise to a spin Hall
magnetoresistance that strongly depends on the magnitude of the magnetic field,
rather than its direction. This Letter may motivate electrical detection of the
phases of quantum magnets and the incorporation of such materials into
spintronic devices.

###Angle Dependent Interlayer Magnetoresistance (ILMR) in Multilayer Graphene Stacks|S. C. Bodepudi,Xiao Wang,Sandipan Pramanik###

Angle Dependent Interlayer Magnetoresistance (ILMR) in Multilayer Graphene Stacks. Interlayer magnetoresistance (ILMR) effect is explored in a vertical stack of
weakly coupled multilayer graphene as grown by chemical vapor deposition (CVD).
This effect has been characterized as a function of temperature and tilt angle
of the magnetic field with respect to the interlayer current. To our knowledge,
this is the first experimental report on angle dependent ILMR effect in
graphitic systems. Our data agrees qualitatively with the existing theories of
ILMR in multilayer massless Dirac Fermion systems. However, a sharper change in
ILMR has been observed as the tilt angle of the magnetic field is varied. A
physical explanation of this effect is proposed, which is consistent with our
experimental scenario.

###Comparative study on magnetoresistance of carbon-cobalt nanocomposite thin films grown by pulsed laser deposition|S. Sergeenkov,C. Cordova,L. Cichetto Jr,O. F. de Lima,E. Longo,F. M. Araujo-Moreira,C. Furtado###

Comparative study on magnetoresistance of carbon-cobalt nanocomposite thin films grown by pulsed laser deposition. We present a comparative study on the influence of applied magnetic field on
the resistance of $C_{1-x}Co_x$ thin films (with $x=0.1$, $0.15$ and $0.2$)
grown on $Si$ substrate by pulsed laser deposition technique. It is found that
the behavior of magnetoresistance (MR) drastically depends on the temperature.
Namely, at low temperatures MR is positive and its behavior is governed by the
field mediated weak localization scenario. While at high temperatures MR turns
negative and its behavior is dominated by electron scattering on ferromagnetic
cobalt atoms.

###Skyrmions in magnetic tunnel junctions|Xueying Zhang,Wenlong Cai,Xichao Zhang,Zilu Wang,Zhi Li,Yu Zhang,Kaihua Cao,Na Lei,Wang Kang,Yue Zhang,Haiming Yu,Yan Zhou,Weisheng Zhao###

Skyrmions in magnetic tunnel junctions. In this work, we demonstrate that skyrmions can be nucleated in the free
layer of a magnetic tunnel junction (MTJ) with Dzyaloshinskii-Moriya
interactions (DMI) by a spin-polarized current with the assistance of stray
fields from the pinned layer. The size, stability and number of created
skyrmions can be tuned by either the DMI strength or the stray field
distribution. The interaction between the stray field and the DMI effective
field is discussed. A device with multi-level tunneling magnetoresistance is
proposed, which could pave the ways for skyrmion-MTJ-based multi-bit storage
and artificial neural network computation. Our results may facilitate the
efficient nucleation and electrical detection of skyrmions.

###Coupling of magnetic order and charge transport in the candidate Dirac semimetal EuCd$_2$As$_2$|M. C. Rahn,J. -R. Soh,S. Francoual,L. S. I. Veiga,J. Strempfer,J. Mardegan,D. Y. Yan,Y. F. Guo,Y. G. Shi,A. T. Boothroyd###

Coupling of magnetic order and charge transport in the candidate Dirac semimetal EuCd$_2$As$_2$. We use resonant elastic x-ray scattering to determine the evolution of
magnetic order in EuCd$_2$As$_2$ below $T_\textrm{N}=9.5$\,K, as a function of
temperature and applied magnetic field. We find an A-type
antiferromagneticstructure with in-plane magnetic moments, and observe dramatic
magnetoresistive effects associated with field-induced changes in the magnetic
structure and domain populations. Our \textit{ab initio} electronic structure
calculations indicate that the Dirac dispersion found in the nonmagnetic Dirac
semimetal Cd$_3$As$_2$ is also present in EuCd$_2$As$_2$, but is gapped for $T
< T_\textrm{N}$ due to the breaking of $C_3$ symmetry by the magnetic
structure.

###Negative thermal magnetoresistivity as a signature of chiral anomaly in Weyl superconductors|Takuro Kobayashi,Taiki Matsushita,Takeshi Mizushima,Atsushi Tsuruta,Satoshi Fujimoto###

Negative thermal magnetoresistivity as a signature of chiral anomaly in Weyl superconductors. We propose that chiral anomaly of Weyl superconductors gives rise to negative
thermal magnetoresistivity induced by emergent magnetic fields, which are
generated by vortex textures of order parameters or lattice strain. We
establish this scenario by combining the argument based on Berry curvatures,
and the quasi-classical theory of the Eilenberger equation with quantum
corrections arising from inhomogeneous structures. It is found that the chiral
anomaly contribution of the thermal conductivity exhibits characteristic
temperature dependence, which can be a smoking-gun signature of this effect.

###Origins of the unidirectional spin Hall magnetoresistance in metallic bilayers|Can Onur Avci,Johannes Mendil,Geoffrey S. D. Beach,Pietro Gambardella###

Origins of the unidirectional spin Hall magnetoresistance in metallic bilayers. Recent studies evidence the emergence of asymmetric electron transport in
layered conductors owing to the interplay between electrical conductivity,
magnetization, and the spin Hall or Rashba- Edelstein effects. Here, we
investigate the unidirectional magnetoresistance (UMR) caused by the
current-induced spin accumulation in Co/Pt and CoCr/Pt bilayers. We identify
three competing mechanisms underpinning the resistance asymmetry, namely
interface and bulk spin-dependent electron scattering and electron-magnon
scattering. Our measurements provide a consistent description of the current,
magnetic field, and temperature dependence of the UMR and show that both
positive and negative UMR can be obtained by tuning the interface and bulk
spin-dependent scattering terms relative to the magnon population.

###Relation between unidirectional spin Hall magnetoresistance and spin current-driven magnon generation|I. V. Borisenko,V. E. Demidov,S. Urazhdin,A. B. Rinkevich,S. O. Demokritov###

Relation between unidirectional spin Hall magnetoresistance and spin current-driven magnon generation. We perform electronic measurements of unidirectional spin Hall
magnetoresistance (USMR) in a Permalloy/Pt bilayer, in conjunction with
magneto-optical Brillouin light spectroscopy of spin current-driven magnon
population. We show that the current dependence of USMR closely follows the
dipolar magnon density, and that both dependencies exhibit the same scaling
over a large temperature range of 80-400 K. These findings demonstrate a close
relationship between spin current-driven magnon generation and USMR, and
indicate that the latter is likely dominated by the dipolar magnons.

###Probing the Relationship between Anisotropic Magnetoresistance and Magnetization of ferromagnetic films|Wanli Zhang,Jing Chen,Wenxu Zhang###

Probing the Relationship between Anisotropic Magnetoresistance and Magnetization of ferromagnetic films. The anisotropic magnetoresistance (AMR) in thin permalloy strips was
calculated at each steps during magnetization by the finite element method. The
magnetization at equilibrium under different external fields was obtained by
micromagnetic simulations, while the resistance with different magnetization
was obtained by solving the Poisson equations iteratively until
self-consistence. We find that the relation between magnetization and AMR
deviates from the Stoner-Wohlfarth prediction when the magnetization is reduced
from saturation. The reason is that the demagnetization is not necessarily from
coherent rotation of the magnetic moment. We conclude that it is necessary to
use numeric simulations to optimize the responses of AMR sensors.

###Growth and Magnetotransport in Thin Film α-Sn on CdTe|Owen Vail,Patrick Taylor,Patrick Folkes,Barbara Nichols,George de Coster###

Growth and Magnetotransport in Thin Film α-Sn on CdTe. We report growth and characterization of epitaxial $\alpha$-Sn thin films
grown on CdTe(111)B. Noninvasive techniques verify the film's pseduomorphic
growth before fabrication of magnetotransport devices, overcoming ex-situ
obstacles on uncapped films for measurement in the Hall bar geometry. We
identify a transition to metallic behavior at low temperature with large
magnetoresistance, high mobility, and quantum oscillations tentatively
suggesting an n-type Dirac semimetallic channel. A parallel p-type dopant
channel with high carrier density is seen to dominate at thinner film
thicknesses. Careful preparation of the CdTe surface before growth is
considered crucial to attain a low dopant density and accessible topological
states on an insulating substrate.

###Anisotropic Landau level splitting and Lifshitz transition induced magnetoresistance enhancement in ZrTe5 crystals|L. Zhou,A. Ramiere,P. B. Chen,J. Y. Tang,Y. H. Wu,X. Lei,G. P. Guo,J. Q. He,H. T. He###

Anisotropic Landau level splitting and Lifshitz transition induced magnetoresistance enhancement in ZrTe5 crystals. Magneto-transport study has been performed in ZrTe5 single crystals. The
observed Shubnikov-de Hass quantum oscillation at low temperature clearly
demonstrates the existence of a nontrivial band with small effective mass in
ZrTe5. Furthermore, we also revealed the 3D anisotropic nature of high-field
Landau level splitting in ZrTe5, very different from the 2D behavior measured
in previous transport studies. Besides these, an abnormal large enhancement of
magnetoresistance appears at high temperatures, which is believed to arise from
the Lifshitz transition induced two-carrier transport in ZrTe5. Our study
provides more understanding of the physical properties of ZrTe5 and sheds light
on potential application of ZrTe5 in spintronics.

###Iterative path-integral summations for the tunneling magnetoresistance in interacting quantum-dot spin valves|S. Mundinar,P. Stegmann,J. König,S. Weiss###

Iterative path-integral summations for the tunneling magnetoresistance in interacting quantum-dot spin valves. We report on the importance of resonant-tunneling processes on quantum
transport through interacting quantum-dot spin valves. To include Coulomb
interaction in the calculation of the tunneling magnetoresistance (TMR), we
reformulate and generalize the recently-developed, numerically-exact method of
iterative summation of path integrals (ISPI) to account for spin-dependent
tunneling. The ISPI scheme allows us to investigate weak to intermediate
Coulomb interaction in a wide range of gate and bias voltage and down to
temperatures at which a perturbative treatment of tunneling severely fails.

###Magnetic phase diagram, magnetotransport and inverse magnetocaloric effect in the noncollinear antiferromagnet Mn$_5$Si$_3$|Roberto F. Luccas,Gabriel Sánchez-Santolino,Alex Correa-Orellana,Federico J. Mompean,Mar García-Hernández,Hermann Suderow###

Magnetic phase diagram, magnetotransport and inverse magnetocaloric effect in the noncollinear antiferromagnet Mn$_5$Si$_3$. The antiferromagnet Mn$_5$Si$_3$ has recently attracted attention because a
noncollinear spin arrangement has been shown to produce a topological anomalous
Hall effect and an inverse magnetocaloric effect. Here we synthesize single
crystals of Mn$_5$Si$_3$ using flux growth. We determine the phase diagram
through magnetization and measure the magnetoresistance and the Hall effect. We
find the collinear and noncollinear antiferromagnetic phases at low
temperatures and, in addition, a third magnetic phase, in between the two
antiferromagnetic phases which has ferromagnetic character. The latter magnetic
phase might be caused by strain produced by Cu inclusions that lead to quenched
fluctuations of the mixed character magnetic ordering in this compound.

###Impact of spin transfer torque on the write error rate of a voltage-torque-based magnetoresistive random access memory|Hiroshi Imamura,Rie Matsumoto###

Impact of spin transfer torque on the write error rate of a voltage-torque-based magnetoresistive random access memory. Impact of spin transfer torque (STT) on the write error rate of a
voltage-torque-based magnetoresistive random access memory is theoretically
analyzed by using the macrospin model. During the voltage pulse the STT assists
or suppresses the precessional motion of the magnetization depending on the
initial magnetization direction. The characteristic value of the current
density is derived by balancing the STT and the external-field torque, which is
about 5$\times$ 10$^{11}$ A/m$^{2}$. The results show that the write error rate
is insensitive to the STT below the current density of $10^{10}$ A/m$^{2}$.

###Lattice study of electromagnetic conductivity of quark-gluon plasma in external magnetic field|Nikita Yu. Astrakhantsev,Victor V. Braguta,Massimo D'Elia,Andrey Yu. Kotov,Aleksandr A. Nikolaev,Francesco Sanfilippo###

Lattice study of electromagnetic conductivity of quark-gluon plasma in external magnetic field. We study the electromagnetic (e.m.) conductivity of QGP in a magnetic
background by lattice simulations with $N_f = 2+1$ dynamical rooted staggered
fermions at the physical point. We study the correlation functions of the
e.m.~currents at $T=200,\,250$\,MeV and use the Tikhonov approach to extract
the conductivity. This is found to rise with the magnetic field in the
direction parallel to it and to decrease in the transverse direction, giving
evidence for both the Chiral Magnetic Effect and the magnetoresistance
phenomenon in QGP. We also estimate the chiral charge relaxation time in QGP.

###Disclosing antiferromagnetism in tetragonal Cr2O3 by electrical measurements|M. Asa,C. Autieri,C. Barone,C. Mauro,S. Picozzi,S. Pagano,M. Cantoni###

Disclosing antiferromagnetism in tetragonal Cr2O3 by electrical measurements. The tetragonal phase of chromium (III) oxide, although unstable in the bulk,
can be synthesized in epitaxial heterostructures. The theoretical investigation
by density functional theory predicts an antiferromagnetic ground state for
this compound. We demonstrate experimentally antiferromagnetism up to 40 K in
ultrathin films of t-Cr2O3 by electrical measurements exploiting interface
effect within a neighboring ultrathin Pt layer. We show that magnetotransport
in Pt is affected by both spin-Hall magnetoresistance and magnetic proximity
effect while we exclude any role of magnetism for the low-temperature
resistance anomaly observed in Pt.

###Record-Breaking Magnetoresistance at the Edge of a Microflake of Natural Graphite|Christian E. Precker,Jose Barzola-Quiquia,Pablo D. Esquinazi,Markus Stiller,Mun K. Chan,Marcelo Jaime,Zhipeng Zhang,Marius Grundmann###

Record-Breaking Magnetoresistance at the Edge of a Microflake of Natural Graphite. Placing several electrodes at the edge of a micrometer-size Sri Lankan
natural graphite sample at distances comparable to the size of the internal
crystalline regions, we found record values for the change of the resistance
with magnetic field. At low temperatures and at $B \sim 21$T the
magnetoresistance (MR) reaches $\sim 10^7$%. The MR values exceed by far all
earlier reported ones for graphite and they are comparable or even larger (at
$T > 50$K) than the largest reported in solids including the Weyl semimetals.
The origin of this large MR lies in the existence of highly conducting 2D
interfaces aligned parallel to the graphene planes.

###Large magnetoresistance and spin-dependent output voltage in a lateral MnGa/GaAs/MnGa spin-valve device|Koki Chonan,Nguyen Huynh Duy Khang,Masaaki Tanaka,Pham Nam Hai###

Large magnetoresistance and spin-dependent output voltage in a lateral MnGa/GaAs/MnGa spin-valve device. We investigated the spin-dependent transport properties of a lateral
spin-valve device with a 600 nm-long GaAs channel and ferromagnetic MnGa
electrodes with perpendicular magnetization. Its current-voltage
characteristics show nonlinear behavior below 50 K, indicating that tunnel
transport through the MnGa/GaAs Schottky barrier is dominant at low
temperatures. We observed clear magnetoresistance (MR) ratio up to 12% at 4 K
when applying a magnetic field perpendicular to the film plane. Furthermore, a
large spin-dependent output voltage of 33 mV is obtained. These values are the
highest in lateral ferromagnetic metal / semiconductor / ferromagnetic metal
spin-valve devices reported so far.

###Transport characteristics of type II Weyl semimetal MoTe2 thin films grown by chemical vapor deposition|Niraj Bhattarai,Andrew W. Forbes,Rajendra P. Dulal,Ian L. Pegg,John Philip###

Transport characteristics of type II Weyl semimetal MoTe2 thin films grown by chemical vapor deposition. Theoretical calculations and experimental observations show MoTe2 is a type
II Weyl semimetal, along with many members of transition metal dichalcogenides
family. We have grown highly crystalline large-area MoTe2 thin films on Si/SiO2
substrates by chemical vapor deposition. Very uniform, continuous, and smooth
films were obtained as confirmed by scanning electron microscopy and atomic
force microscopy analyses. Measurements of the temperature dependence of
longitudinal resistivity and current-voltage characteristics at different
temperature are discussed. Unsaturated, positive quadratic magnetoresistance of
the as-grown thin films has been observed from 10 K to 200 K. Hall resistivity
measurements confirm the majority charge carriers are hole.

###Structural sensitivity of the spin Hall magnetoresistance in antiferromagnetic thin films|Andrew Ross,Romain Lebrun,Camilo Ulloa,Daniel A. Grave,Asaf Kay,Lorenzo Baldrati,Florian Kronast,Sergio Valencia,Avner Rothschild,Mathias Kläui###

Structural sensitivity of the spin Hall magnetoresistance in antiferromagnetic thin films. Reading the magnetic state of antiferromagnetic (AFM) thin films is key for
AFM spintronic devices. We investigate the underlying physics behind the spin
Hall magnetoresistance (SMR) of bilayers of platinum and insulating AFM
hematite ({\alpha}-Fe2O3) and find an SMR efficiency of up to 0.1%, comparable
to ferromagnetic based structures. To understand the observed complex SMR field
dependence, we analyse the effect of misalignments of the magnetic axis that
arise during growth of thin films, by electrical measurements and direct
magnetic imaging, and find that a small deviation can result in significant
signatures in the SMR response. This highlights the care that must be taken
when interpreting SMR measurements on AFM spin textures.

###Interface-driven giant tunnel magnetoresistance in (111)-oriented junctions|Keisuke Masuda,Hiroyoshi Itoh,Yoshio Miura###

Interface-driven giant tunnel magnetoresistance in (111)-oriented junctions. We theoretically study the tunnel magnetoresistance (TMR) effect in
(111)-oriented junctions Co/MgO/Co(111) and Ni/MgO/Ni(111). The Co-based
junction is shown to have a TMR ratio over 2000$\%$, which is one order higher
than that of the Ni-based one. The high TMR ratio is attributed to the
interfacial resonance effect: The interfacial $d$-$p$ antibonding states are
formed close to the Fermi level in the majority-spin channel and these states
in both interfaces resonate with each other. This differs essentially from the
conventional coherent tunneling mechanism of high TMR ratios in
Fe(Co)/MgO/Fe(Co)(001).

###Theory of Domain-Wall Magnetoresistance in Metallic Antiferromagnets|Jun-Hui Zheng,Arne Brataas,Mathias Kläui,Alireza Qaiumzadeh###

Theory of Domain-Wall Magnetoresistance in Metallic Antiferromagnets. We develop a theory to compute the domain-wall magnetoresistance (DWMR) in
antiferromagnetic (AFM) metals with different spin structures. In the diffusive
transport regime, the DWMR can be either {\it negative} or positive depending
on the domain-wall orientation and spin structure. In contrast, when the
transport is in the ballistic regime, the DWMR is always positive, and the
magnitude depends on the width and orientation of the domain wall. Our results
pave the way of using electrical measurements for probing the internal spin
structure in antiferromagnetic metals.

###Suppression of indirect exchange and symmetry breaking in antiferromagnetic metal with dynamic charge stripes|K. Krasikov,V. Glushkov,S. Demishev,A. Khoroshilov,A. Bogach,V. Voronov,N. Shitsevalova,V. Filipov,S. Gabani,K. Flachbart,K. Siemensmeyer,N. Sluchanko###

Suppression of indirect exchange and symmetry breaking in antiferromagnetic metal with dynamic charge stripes. Precise angle-resolved magnetoresistance (ARM) measurements are applied to
reveal the origin for the lowering of symmetry in electron transport and the
emergence of a huge number of magnetic phases in the ground state of
antiferromagnetic metal HoB12 with fcc crystal structure. By analyzing of the
polar H-theta-phi magnetic phase diagrams of this compound reconstructed from
the experimental ARM data we argue that non-equilibrium electron density
oscillations (dynamic charge stripes) are responsible for the suppression of
the indirect RKKY exchange along <110> directions between the nearest
neighboring magnetic moments of Ho3+ ions in this strongly correlated electron
system.

###Electron-Electron Interactions in 2D Semiconductor InSe|Arvind Shankar Kumar,Kasun Premasiri,Min Gao,U. Rajesh Kumar,Raman Sankar,Fang-Cheng Chou,Xuan P. A. Gao###

Electron-Electron Interactions in 2D Semiconductor InSe. Electron-electron interactions (EEIs) in 2D van der Waals structures is one
of the topics with high current interest in physics. We report the observation
of a negative parabolic magnetoresistance (MR) in multilayer 2D semiconductor
InSe beyond the low-field weak localization/antilocalization regime, and
provide evidence for the EEI origin of this MR behavior. Further, we analyze
this negative parabolic MR and other observed quantum transport signatures of
EEIs (temperature dependent conductance and Hall coefficient) within the
framework of Fermi liquid theory and extract the gate voltage tunable Fermi
liquid parameter $F_0^\sigma$ which quantifies the electron spin-exchange
interaction strength.

###Concurrent magneto-optical imaging and magneto-transport readout of electrical switching of insulating antiferromagnetic thin films|Felix Schreiber,Lorenzo Baldrati,Christin Schmitt,Rafael Ramos,Eiji Saitoh,Romain Lebrun,Mathias Kläui###

Concurrent magneto-optical imaging and magneto-transport readout of electrical switching of insulating antiferromagnetic thin films. We demonstrate stable and reversible current induced switching of large-area
($> 100\;\mu m^2$) antiferromagnetic domains in NiO/Pt by performing concurrent
transport and magneto-optical imaging measurements in an adapted Kerr
microscope. By correlating the magnetic images of the antiferromagnetic domain
changes and magneto-transport signal response in these current-induced
switching experiments, we disentangle magnetic and non-magnetic contributions
to the transport signal. Our table-top approach establishes a robust procedure
to subtract the non-magnetic contributions in the transport signal and extract
the spin-Hall magnetoresistance response associated with the switching of the
antiferromagnetic domains enabling one to deduce details of the
antiferromagnetic switching from simple transport measurements.

###Tuning of charge density wave transitions in LaAu$_x$Sb$_2$ by pressure and Au-stoichiometry|Li Xiang,Dominic H. Ryan,Warren E. Straszheim,Paul C. Canfield,Sergey L. Bud'ko###

Tuning of charge density wave transitions in LaAu$_x$Sb$_2$ by pressure and Au-stoichiometry. Two charge density wave transition can be detected in LaAu$_x$Sb$_2$ at ~ 110
and ~ 90 K by careful electrical transport measurements. Whereas control of the
Au site occupancy in LaAu$_x$Sb$_2$ (for 0.9 < x < 1.0) can suppress each of
these transitions by ~ 80 K, the application of hydrostatic pressure can
completely suppress the lower transition by ~ 10 kbar and the upper transition
by ~ 17 kbar. Clear anomalies in the resistance as well as the
magnetoresistance are observed to coincide with the pressures at which the
charge density wave transitions are driven to zero.

###Tunnel Magnetoresistance in Self-Assemblies of Exchange Coupled Core/Shell Nanoparticles|Fernando Fabris,Enio Lima Jr.,Cynthia Quinteros,Lucas Nener,Mara Granada,Martín Sirena,Roberto D. Zysler,Horacio E. Troiani,Víctor Leborán,Francisco Rivadulla,Elin L. Winkler###

Tunnel Magnetoresistance in Self-Assemblies of Exchange Coupled Core/Shell Nanoparticles. We report the precise control of tunneling magnetoresistance (TMR) in devices
of self-assembled core/shell Fe$_3$O$_4$/Co$_{1-x}$Zn$_x$Fe$_2$O$_4$
nanoparticles ($0\leq x\leq 1$). Adjusting the magnetic anisotropy through the
content of Co$^{2+}$ in the shell, provides an accurate tool to control the
switching field between the bistable states of the TMR. In this way, different
combinations of soft/hard and hard/soft core/shell configurations can be
envisaged for optimizing devices with the required magnetotransport response.

###Large longitudinal magnetoresistance of multivalley systems|Yuki Mitani,Yuki Fuseya###

Large longitudinal magnetoresistance of multivalley systems. The longitudinal magnetoresistance (MR) is assumed to be hardly realized as
the Lorentz force does not work on electrons when the magnetic field is
parallel to the current. However, in some cases, longitudinal MR becomes large,
which exceeds the transverse MR. To solve this problem, we have investigated
the longitudinal MR considering multivalley contributions based on the
classical MR theory. We have showed that the large longitudinal MR is caused by
off-diagonal components of a mobility tensor. Our theoretical results agree
with the experiments of large longitudinal MR in IV-VI semiconductors,
especially in PbTe, for a wide range of temperatures, except for linear MR at
low temperatures.

###Signatures of non-trivial band topology in LaAs/LaBi heterostructure|Payal Wadhwa,T. J. Dhilip Kumar,Alok Shukla,Rakesh Kumar###

Signatures of non-trivial band topology in LaAs/LaBi heterostructure. In this article, we investigate non-trivial topological features in a
heterostructure of extreme magnetoresistance (XMR) materials LaAs and LaBi
using density functional theory (DFT). The proposed heterostructure is found to
be dynamically stable and shows bulk band inversion with non-trivial Z_{2}
topological invariant and a Dirac cone at the surface. In addition, its
electron and hole carrier densities ratio is also calculated to investigate the
possibility to possess XMR effect. Electrons and holes in the heterostructure
are found to be nearly compensated, thereby facilitating it to be a suitable
candidate for XMR studies.

###Electrical and Thermal Transport in Antiferromagnet-Superconductor Junctions|Martin F. Jakobsen,Kristian B. Naess,Paramita Dutta,Arne Brataas,Alireza Qaiumzadeh###

Electrical and Thermal Transport in Antiferromagnet-Superconductor Junctions. We demonstrate that antiferromagnet-superconductor (AF-S) junctions show
qualitatively different transport properties than normal metal-superconductor
(N--S) and ferromagnet-superconductor (F-S) junctions. We attribute these
transport features to presence of two new scattering processes in AF--S
junctions, i.e., specular reflection of holes and retroreflection of electrons.
Using the Blonder-Tinkham-Klapwijk formalism, we find that the electrical and
thermal conductance depend nontrivially on antiferromagnetic exchange strength.
Furthermore, we show that the interplay between the N\'eel vector direction and
the interfacial Rashba spin-orbit coupling leads to a large anisotropic
magnetoresistance. The unusual transport properties make AF--S interfaces
unique among the traditional condensed-matter-system-based superconducting
junctions.

###Intrinsic mechanism for anisotropic magnetoresistance and experimental confirmation in Co$_x$Fe$_{1-x}$ single-crystal films|F. L. Zeng,Z. Y. Ren,Y. Li,J. Y. Zeng,M. W. Jia,J. Miao,A. Hoffmann,W. Zhang,Y. Z. Wu,Z. Yuan###

Intrinsic mechanism for anisotropic magnetoresistance and experimental confirmation in Co$_x$Fe$_{1-x}$ single-crystal films. Using first-principles transport calculations, we predict that the
anisotropic magnetoresistance (AMR) of single-crystal Co$_x$Fe$_{1-x}$ alloys
is strongly dependent on the current orientation and alloy concentration. An
intrinsic mechanism for AMR is found to arise from the band crossing due to
magnetization-dependent symmetry protection. These special $k$-points can be
shifted towards or away from the Fermi energy by varying the alloy composition
and hence the exchange splitting, thus allowing AMR tunability. The prediction
is confirmed by delicate transport measurements, which further reveal a
reciprocal relationship of the longitudinal and transverse resistivities along
different crystal axes.

###High-Mobility Carriers Induced by Chemical Doping in the Candidate Nodal-Line Semimetal CaAgP|Yoshihiko Okamoto,Kazushige Saigusa,Taichi Wada,Youichi Yamakawa,Ai Yamakage,Takao Sasagawa,Naoyuki Katayama,Hiroshi Takatsu,Hiroshi Kageyama,Koshi Takenaka###

High-Mobility Carriers Induced by Chemical Doping in the Candidate Nodal-Line Semimetal CaAgP. We report the electronic properties of single crystals of candidate
nodal-line semimetal CaAgP. The transport properties of CaAgP are understood
within the framework of a hole-doped nodal-line semimetal. In contrast,
Pd-doped CaAgP shows a drastic increase of magnetoresistance at low magnetic
fields and a strong decrease of electrical resistivity at low temperatures
probably due to weak antilocalization. Hall conductivity data indicated that
the Pd-doped CaAgP has not only hole carriers induced by the Pd doping, but
also high-mobility electron carriers in proximity of the Dirac point.
Electrical resistivity of Pd-doped CaAgP also showed a superconducting
transition with onset temperature of 1.7-1.8 K.

###Over 1% magnetoresistance ratio at room temperature in non-degenerate silicon-based lateral spin valves|H. Koike,S. Lee,R. Ohshima,E. Shigematsu,M. Goto,S. Miwa,Y. Suzuki,T. Sasaki,Y. Ando,M. Shiraishi###

Over 1% magnetoresistance ratio at room temperature in non-degenerate silicon-based lateral spin valves. To augment the magnetoresistance (MR) ratio of n-type non-degenerate Si-based
lateral spin valves (Si-LSVs), we modify the doping profile in the Si layer and
introduce a larger local strain into the Si channel by changing a capping
insulator. The highest MR ratio of 1.4% is achieved in the Si-LSVs through
these improvements, with significant roles played by a reduction in the
resistance-area product of the ferromagnetic contacts and an enhancement of the
momentum relaxation time in the Si channel.

###Pseudo spin-valve switch based on ferromagnet/superconductor/ferromagnet trilayer microbridge|L. N. Karelina,V. V. Bol'ginov,Sh. A. Erkenov,S. V. Egorov,I. A. Golovchanskiy,V. I. Chichkov,A. ben Hamida,V. V. Ryazanov###

Pseudo spin-valve switch based on ferromagnet/superconductor/ferromagnet trilayer microbridge. A noticeable magnetoresistive effect has been observed on
ferromagnet/superconductor/ferromagnet (FSF) microbridges based on diluted
ferromagnetic PdFe alloy containing as small as 1% magnetic atoms.
Microstructuring of the FSF trilayers does not destroy the effect: the most
pronounced curves were obtained on the smallest bridges of 6-8 um wide and
10-15 um long. Below the superconducting transition we are able to control the
critical current of microbridges by switching between P and AP orientations of
magnetizations of PdFe layers. The operation of FSF-bridge as a magnetic switch
is demonstrated in several regimes providing significant voltage discrimination
between digital states or remarkably low bit error rate.

###Quantum criticality and multiple crossing points in the magnetoresistance of thin TiN-films|K. Kronfeldner,T. I. Baturina,C. Strunk###

Quantum criticality and multiple crossing points in the magnetoresistance of thin TiN-films. We have measured $R(T,B)$ of a TiN thin-film very close to the
disorder-driven superconductor-insulator transition but still superconducting
at zero field and low temperatures. In a magnetic field we find three distinct
crossing point of the magnetoresistance isotherms occur at magnetic fields
$B_{cX}$ in three different temperature regions. Each crossing point in
$R(T,B)$ corresponds to a plateau in $R(T,B_{cX})$. We systematically study the
evolution of these crossing point near the disorder-induced
superconductor/insulator transition, identify the most promising candidate for
a quantum phase transition, and provide estimates for the two critical
exponents $z$ and $\nu$.

###Dependency of high-speed write properties on external magnetic field in spin-orbit torque in-plane magnetoresistance devices|Yohei Shiokawa,Eiji Komura,Yugo Ishitani,Atsushi Tsumita,Keita Suda,Kosuke Hamanaka,Tomohiro Taniguchi,Tomoyuki Sasaki###

Dependency of high-speed write properties on external magnetic field in spin-orbit torque in-plane magnetoresistance devices. Spin-orbit torque (SOT) magnetoresistance (MR) devices have attracted
attention for use in next-generation MR devices. The SOT devices are known to
exhibit different write properties based on the relative angle between the
magnetization direction of the free layer and the write-current direction.
However, few studies that compare the write properties of each type have been
reported. In this study, we measured the external perpendicular-magnetic field
dependence of the threshold write current density and the write current
switching probability using two types of in-plane magnetization SOT-MR devices.

###Interplay between strong correlations and electronic topology in the underlying kagome lattice of Na2/3CoO2|I. F. Gilmutdinov,R. Schönemann,D. Vignolles,C. Proust,I. R. Mukhamedshin,L. Balicas,H. Alloul###

Interplay between strong correlations and electronic topology in the underlying kagome lattice of Na2/3CoO2. Electronic topology in metallic kagome compounds is under intense scrutiny.
We present transport experiments in Na2/3CoO2 in which the Na order
differentiates a Co kagome sub-lattice in the triangular CoO2 layers. Hall and
magnetoresistance (MR) data under high fields give evidence for the coexistence
of light and heavy carriers. At low temperatures, the dominant light carrier
conductivity at zero field is suppressed by a B-linear MR suggesting Dirac like
quasiparticles. Lifshitz transitions induced at large B and T unveil the lower
mobility carriers. They display a negative B^2 MR due to scattering from
magnetic moments likely pertaining to a flat band. We underline an analogy with
heavy Fermion physics.

###Experimental Confirmation of Massive Dirac Fermions in Weak Charge-Ordering State in α-(BEDT-TTF)_2I_3|Kenta Yoshimura,Mitsuyuki Sato,Toshihito Osada###

Experimental Confirmation of Massive Dirac Fermions in Weak Charge-Ordering State in α-(BEDT-TTF)_2I_3. The electronic structure of weak charge-ordering (CO) state just below the
critical pressure in an organic conductor \alpha-(BEDT-TTF)_2I_3 was
experimentally investigated using peak structure in the temperature dependence
of interlayer magnetoresistance (MR). Based on a minimal model considering
multiple Landau levels (LLs), we discuss herein the MR peak as characteristic
to multilayer massless/massive Dirac fermion (DF) systems. MR measured in the
weak CO state exhibited a clear MR peak, and its magnetic-field dependence was
consistent with the LL behavior of a massive DF with a small gap. Results
indicate that the weak CO state in \alpha-(BEDT-TTF)_2I_3 is a massive DF
state.

###Voltage-controlled antiferromagnetism in magnetic tunnel junctions|Meng Xu,Mingen Li,Pravin Khanal,Ali Habiboglu,Blake Insana,Yuzan Xiong,Thomas Peterson,Jason C. Myers,Deborah Ortega,Hongwei Qu,C. L. Chien,Wei Zhang,Jian-Ping Wang,W. G. Wang###

Voltage-controlled antiferromagnetism in magnetic tunnel junctions. We demonstrate a voltage-controlled exchange bias effect in CoFeB/MgO/CoFeB
magnetic tunnel junctions that is related to the interfacial Fe(Co)Ox formed
between the CoFeB electrodes and the MgO barrier. The unique combination of
interfacial antiferromagnetism, giant tunneling magnetoresistance, and sharp
switching of the perpendicularly-magnetized CoFeB allows sensitive detection of
the exchange bias. It is found that the exchange bias field can be isothermally
controlled by magnetic fields at low temperatures. More importantly, the
exchange bias can also be effectively manipulated by the electric field applied
to the MgO barrier due to the voltage-controlled antiferromagnetic anisotropy
in this system.

###Flexible antiferromagnetic FeRh tapes as memory elements|Ignasi Fina,Nico Dix,Enric Menéndez,Anna Crespi,Michael Foerster,Lucia Aballe,Florencio Sánchez,Josep Fontcuberta###

Flexible antiferromagnetic FeRh tapes as memory elements. The antiferromagnetic to ferromagnetic transition occurring above room
temperature in FeRh is attracting interest for applications in spintronics,
with perspectives for robust and untraceable data storage. Here, we show that
FeRh films can be grown on a flexible metallic substrate (tape shaped), coated
with a textured rock-salt MgO layer, suitable for large scale applications. The
FeRh tape displays a sharp antiferromagnetic to ferromagnetic transition at
about 90 oC. Its magnetic properties are preserved by bending (radii of 300
mm), and their anisotropic magnetoresistance (up to 0.05 %) is used to
illustrate data writing/reading capability.

###Pauli spin blockade with site-dependent g-tensors and spin-polarized leads|Philipp M. Mutter,Guido Burkard###

Pauli spin blockade with site-dependent g-tensors and spin-polarized leads. Pauli spin blockade (PSB) in double quantum dots (DQDs) has matured into a
prime technique for precise measurements of nanoscale system parameters. In
this work we demonstrate that systems with site-dependent g-tensors and
spin-polarized leads allow for a complete characterization of the g-tensors in
the dots by magnetotransport experiments alone. Additionally, we show that
special polarization configurations can enhance the often elusive
magnetotransport signal, rendering the proposed technique robust against noise
in the system, and inducing a giant magnetoresistance effect. Finally, we
incorporate the effects of the spin-orbit interaction (SOI) and show that in
this case the leakage current contains information about the degree of spin
polarization in the leads.

###Surface Acoustic Wave induced modulation of tunneling magnetoresistance in magnetic tunnel junctions|Dhritiman Bhattacharya,Peng Sheng,Md Ahsanul Abeed,Zhengyang Zhao,Hongshi Li,Jian-Ping Wang,Supriyo Bandyopadhyay,Bin Ma,Jayasimha Atulasimha###

Surface Acoustic Wave induced modulation of tunneling magnetoresistance in magnetic tunnel junctions. We show that a surface acoustic wave (SAW) applied across the terminals of a
magnetic tunnel junction (MTJ) decreases both the (time-averaged) parallel and
antiparallel resistances of the MTJ, with the latter decreasing much more than
the former. This results in a decrease of the tunneling magnetoresistance (TMR)
ratio. The coercivities of the free and fixed layer of the MTJ, however, are
not affected significantly, suggesting that the SAW does not cause large-angle
magnetization rotation in the magnetic layers through the inverse
magnetostriction (Villari) effect at the power levels used. This study sheds
light on the dynamical behavior of an MTJ under periodic compressive and
tensile strain.

###Coherent Hopping Transport and Giant Negative Magnetoresistance in Epitaxial CsSnBr$_{3}$|Liangji Zhang,Isaac King,Kostyantyn Nasyedkin,Pei Chen,Brian Skinner,Richard R. Lunt,Johannes Pollanen###

Coherent Hopping Transport and Giant Negative Magnetoresistance in Epitaxial CsSnBr$_{3}$. Single-crystal inorganic halide perovskites are attracting interest for
quantum device applications. Here we present low-temperature quantum
magnetotransport measurements on thin film devices of epitaxial single-crystal
CsSnBr$_{3}$, which exhibit two-dimensional Mott variable range hopping (VRH)
and giant negative magnetoresistance. These findings are described by a model
for quantum interference between different directed hopping paths and we
extract the temperature-dependent hopping length of charge carriers, their
localization length, and a lower bound for their phase coherence length of ~100
nm at low temperatures. These observations demonstrate that epitaxial halide
perovskite devices are emerging as a material class for low-dimensional quantum
coherent transport devices.

###Thickness Dependence of Magneto-transport Properties in Tungsten Ditelluride|Xurui Zhang,Vivek Kakani,John M. Woods,Judy J. Cha,Xiaoyan Shi###

Thickness Dependence of Magneto-transport Properties in Tungsten Ditelluride. We investigate the electronic structure of tungsten ditelluride (WTe$_2$)
flakes with different thicknesses in magneto-transport studies. The
temperature-dependent resistance and magnetoresistance (MR) measurements both
confirm the breaking of carrier balance induced by thickness reduction, which
suppresses the `turn-on' behavior and large positive MR. The Shubnikov-de-Haas
oscillation studies further confirm the thickness-dependent change of
electronic structure of WTe$_2$ and reveal a possible temperature-sensitive
electronic structure change. Finally, we report the thickness-dependent
anisotropy of Fermi surface, which reveals that multi-layer WTe$_2$ is an
electronic 3D material and the anisotropy decreases as thickness decreases.

###Coherent epitaxy of trilayer nickelate (Nd0.8Sr0.2)4Ni3O10 films by high-pressure magnetron sputtering|Jiachang Bi,Yujuan Pei,Ruyi Zhang,Shaoqin Peng,Xinming Wang,Jie Sun,Jiagui Feng,Jingkai Yang,Yanwei Cao###

Coherent epitaxy of trilayer nickelate (Nd0.8Sr0.2)4Ni3O10 films by high-pressure magnetron sputtering. Rare-earth (R) nickelates (such as perovskite RNiO3, trilayer R4Ni3O10, and
infinite layer RNiO2) have attracted tremendous interest very recently.
However, unlike widely studied RNiO3 and RNiO2 films, the synthesis of trilayer
nickelate R4Ni3O10 films is rarely reported. Here, single-crystalline
(Nd0.8Sr0.2)4Ni3O10 epitaxial films were coherently grown on SrTiO3 substrates
by high-pressure magnetron sputtering. The crystal and electronic structures of
(Nd0.8Sr0.2)4Ni3O10 films were characterized by high-resolution X-ray
diffraction and X-ray photoemission spectroscopy, respectively. The electrical
transport measurements reveal a metal-insulator transition near 82 K and
negative magnetoresistance in (Nd0.8Sr0.2)4Ni3O10 films. Our work provides a
novel route to synthesize high-quality trilayer nickelate R4Ni3O10 films.

###Antisymmetric magnetoresistance due to domain wall tilting in perpendicular magnetized films|Yangtao Su,Yang Meng,Haibin Shi,Li Wang,Xinyu Cao,Ying Zhang,Runwei Li,Hongwu Zhao###

Antisymmetric magnetoresistance due to domain wall tilting in perpendicular magnetized films. We report the observation of the antisymmetric magnetoresistance (MR) in
perpendicular magnetized CoTb films with inhomogeneous magnetization
distribution driven by gradient magnetic field. By synchronously charactering
the domain pattern evolution during transport measurements, we demonstrate that
the nonequilibrium currents in the vicinity of tilting domain walls give rise
to such anomalous MR. Moreover, theoretical calculation and analysis reveal
that the geometry factor of the multidomain texture plays a dominant role in
generating the nonequilibrium current. The explicitly established interplay
between the anomalous transport behaviors and the particular domain wall
geometry is essential to deepening understanding of the antisymmetric MR, and
pave a new way for designing novel domain wall electronic devices.

###Robust spin-transfer torque and magnetoresistance in non-collinear antiferromagnetic junctions|Srikrishna Ghosh,Aurelien Manchon,Jakub Železný###

Robust spin-transfer torque and magnetoresistance in non-collinear antiferromagnetic junctions. Ferromagnetic spin-valves and tunneling junctions are crucial for spintronics
applications and are one of the most fundamental spintronics devices. Motivated
by the potential unique advantages of antiferromagnets for spintronics, we
theoretically study here junctions built out of non-collinear antiferromagnets.
We demonstrate a large and robust magnetoresistance and spin-transfer torque
capable of ultrafast switching between parallel and anti-parallel states of the
junction. In addition, we show that the non-collinear order results in a
spin-transfer torque that is in several key aspects different from the
spin-transfer torque in ferromagnetic junctions.

###Anomalous chiral magnetic effect in time reversal symmetry breaking Weyl semimetals|Long Liang###

Anomalous chiral magnetic effect in time reversal symmetry breaking Weyl semimetals. We propose a mechanism to generate dissipationless current in time reversal
symmetry breaking Weyl semimetals through the anomalous chiral magnetic effect
(ACME). The ACME current is induced by chiral imbalance and flows along the
direction of the Weyl nodes separation in momentum space. In contrast to the
chiral magnetic effect, the ACME is not related to the chiral anomaly and does
not require external magnetic field. In the presence of parallel electric and
magnetic fields, the ACME gives rise to an antisymmetric linear
magnetoresistance and a planar Hall conductivity, which we estimate to be
observable.

###Berry curvature induced nonlinear magnetoresistivity in two dimensional systems|Shibalik Lahiri,Tanmay Bhore,Kamal Das,Amit Agarwal###

Berry curvature induced nonlinear magnetoresistivity in two dimensional systems. The band geometric properties of quantum materials play an elemental role in
the linear and nonlinear transport of electrons. In this paper, we propose that
the interplay of the Berry curvature, the orbital magnetic moment and the
Lorentz force can induce a finite nonlinear resistivity in two dimensional
systems in presence of a perpendicular magnetic field. The induced nonlinear
magnetoresistivity scales linearly with the magnetic field and is purely
quantum mechanical in origin. This novel transport signature can be used as an
additional experimental probe for the geometric quantities in intrinsically
time reversal symmetric systems.

###Nonreciprocal transport in a Rashba ferromagnet, delafossite PdCoO$_2$|Jin Hong Lee,Takayuki Harada,Felix Trier,Lourdes Marcano,Florian Godel,Sergio Valencia,Atsushi Tsukazaki,Manuel Bibes###

Nonreciprocal transport in a Rashba ferromagnet, delafossite PdCoO$_2$. Rashba interfaces yield efficient spin-charge interconversion and give rise
to nonreciprocal transport phenomena. Here, we report magnetotransport
experiments in few-nanometer-thick films of PdCoO$_2$, a delafossite oxide
known to display a large Rashba splitting and surface ferromagnetism. By
analyzing the angle dependence of the first- and second-harmonic longitudinal
and transverse resistivities, we identify a Rashba-driven unidirectional
magnetoresistance that competes with the anomalous Nernst effect below the
Curie point. We estimate a Rashba coefficient of 0.75 {\pm} 0.3 eV {\AA} and
argue that our results qualify delafossites as a new family of oxides for
nano-spintronics and spin-orbitronics, beyond perovskite materials.

###Electrical conductivity in helical and conical magnetic states|Shun Okumura,Takahiro Morimoto,Yasuyuki Kato,Yukitoshi Motome###

Electrical conductivity in helical and conical magnetic states. We theoretically study the electrical conductivity in a one-dimensional
helimagnet whose spin texture changes from helimagnetic to conical magnetic,
and to forced ferromagnetic state while increasing the magnetic field along the
helical axis. We find that the conductivity in the helimagnetic state at zero
field depends on the electron filling and the coefficient of the spin-charge
coupling. We also find that the conductivity in the conical magnetic state
changes nonlinearly to the applied field, and the magnetoresistance becomes
negative and positive depending on the model parameters.

###An innovative eye-tracker. Main features and demonstrative tests|Lorenzo Bellizzi,Giuseppe Bevilacqua,Valerio Biancalana,Mario Carucci,Roberto Cecchi,Piero Chessa,Aniello Donniacuo,Marco Mandalà,Leonardo Stiaccini###

An innovative eye-tracker. Main features and demonstrative tests. We present a set of results obtained with an innovative eye-tracker based on
magnetic dipole localization by means of an array of magnetoresistive sensors.
The system tracks both head and eye movements with a high rate (100-200 Sa/s)
and in real time. A simple setup is arranged to simulate head and eye motions
and to test the tracker performance under realistic conditions. Multimedia
material is provided to substantiate and exemplify the results. A comparison
with other available technologies for eye tracking is drawn, discussing
advantages (e.g. precision) and disadvantages (e.g. invasivity) of the diverse
approaches, the presented method standing out for low cost, robustness and
relatively low invasivity.

###Negative magnetoresistance and sign change of the planar Hall effect due to the negative off-diagonal effective-mass in Weyl semimetals|Akiyoshi Yamada,Yuki Fuseya###

Negative magnetoresistance and sign change of the planar Hall effect due to the negative off-diagonal effective-mass in Weyl semimetals. We theoretically investigated the magnetoresistance (MR) and planar Hall
effect (PHE) in Weyl semimetals based on the semiclassical Boltzmann theory,
focusing on the fine structure of the band dispersion. We identified that the
negative longitudinal MR and sign change in the PHE occur because of the
negative off-diagonal effective-mass with no topological effects or chiral
anomaly physics. Our results highlight the crucial role of the off-diagonal
effective-mass, which can cause anomalous galvanomagnetic effects. We propose
that the PHE creates a dip in their temperature dependence, which enables the
experimental detection of the Weyl point.

###Impact of Kondo correlations and spin-orbit coupling on spin-polarized transport in carbon nanotube quantum dot|D. Krychowski,S. Lipiński###

Impact of Kondo correlations and spin-orbit coupling on spin-polarized transport in carbon nanotube quantum dot. Spin polarized transport through a quantum dot coupled to ferromagnetic
electrodes with noncollinear magnetizations is discussed in terms of
nonequilibrium Green functions formalism in the finite-U slave boson mean field
approximation. The difference of orientations of the magnetizations of
electrodes opens off-diagonal spin-orbital transmission and apart from spin
currents of longitudinal polarization also spin-flip currents appear. We also
study equilibrium pure spin current at zero bias and discuss its dependence on
magnetization orientation, spin-orbit coupling strength and gate voltage.
Impact of these factors on tunneling magnetoresistance (TMR) is also
undertaken. In general spin-orbit coupling weakens TMR, but it can change its
sign.

###Dynamic spin polarization in organic semiconductors with intermolecular exchange interaction|A. V. Shumilin###

Dynamic spin polarization in organic semiconductors with intermolecular exchange interaction. It is shown that in organic semiconductors where organic magnetoresistance
(OMAR) is observed, the exchange interaction between electrons and holes
localized at different molecules leads to dynamic spin polarization in the
direction of the applied magnetic field. The polarization appears even at room
temperature due to the non-equilibrium conditions. The strong spin polarization
requires exchange energy to be comparable with Zeeman energy in the external
field and be larger or comparable with the energy of hyperfine interaction of
electron and nuclear spins. The exchange interaction also modifies the
lineshape of OMAR.

###Synchronous Unsupervised STDP Learning with Stochastic STT-MRAM Switching|Peng Zhou,Julie A. Smith,Laura Deremo,Stephen K. Heinrich-Barna,Joseph S. Friedman###

Synchronous Unsupervised STDP Learning with Stochastic STT-MRAM Switching. The use of analog resistance states for storing weights in neuromorphic
systems is impeded by fabrication imprecision and device stochasticity that
limit the precision of synapse weights. This challenge can be resolved by
emulating analog behavior with the stochastic switching of the binary states of
spin-transfer torque magnetoresistive random-access memory (STT-MRAM). However,
previous approaches based on STT-MRAM operate in an asynchronous manner that is
difficult to implement experimentally. This paper proposes a synchronous
spiking neural network system with clocked circuits that perform unsupervised
learning leveraging the stochastic switching of STT-MRAM. The proposed system
enables a single-layer network to achieve 90% inference accuracy on the MNIST
dataset.

###Origins of transverse voltages generated by applied thermal gradients and applied electric fields in ferrimagnetic-insulator/heavy-metal bilayers|Arnab Bose,Rakshit Jain,Jackson J. Bauer,Robert A. Buhrman,Caroline A. Ross,Daniel C. Ralph###

Origins of transverse voltages generated by applied thermal gradients and applied electric fields in ferrimagnetic-insulator/heavy-metal bilayers. We compare thermal-gradient-driven transverse voltages in
ferrimagnetic-insulator/heavy-metal bilayers (Tm3Fe5O12/W and Tm3Fe5O12/Pt) to
corresponding electrically-driven transverse resistances at and above room
temperature. We find for Tm3Fe5O12/W that the thermal and electrical effects
can be explained by a common spin-current detection mechanism, the physics
underlying spin Hall magnetoresistance (SMR). However, for Tm3Fe5O12/Pt the
ratio of the electrically-driven transverse voltages (planar Hall
signal/anomalous Hall signal) is much larger than the ratio of corresponding
thermal-gradient signals, a result which is very different from expectations
for a SMR-based mechanism alone. We ascribe this difference to a
proximity-induced magnetic layer at the Tm3Fe5O12/Pt interface.

###Theory of spin-polarized current flow through a localized spin triplet state|Stephen R. McMillan,Michael E. Flatté###

Theory of spin-polarized current flow through a localized spin triplet state. We derive a formalism describing quantum-coherent features of spin-polarized
charge current through a partially-polarized spin triplet defect in a
$\textit{transverse}$ magnetic field. We predict distinct few-milli-tesla-dc
magnetoresistance signatures that identify a $\textit{single}$ spin-triplet
center's character and reveal the orientation of the spin triplet's zero-field
splitting axis relative to the magnetic contact's polarization. For example, in
4H-SiC the single $(hh)$, $(kk)$, $(hk)$, and $(kh)$ divacancies are all
distinct. Spin-polarized current flow efficiently polarizes the spin,
potentially electrically initializing spin-triplet-based qubits.

###Modulation of Spin Seebeck Effect by Hydrogenation|K. Ogata,T. Kikkawa,E. Saitoh,Y. Shiomi###

Modulation of Spin Seebeck Effect by Hydrogenation. We demonstrate the modulation of spin Seebeck effect (SSE) by hydrogenation
in Pd/YIG bilayers. In the presence of 3% hydrogen gas, SSE voltage decreases
by more than 50% from the magnitude observed in pure Ar gas. The modulation of
the SSE voltage is reversible, but the recovery of the SSE voltage to the
prehydrogenation value takes a few days because of a long time constant of
hydrogen desorption. We also demonstrate that the spin Hall magnetoresistance
of the identical sample reduces significantly with hydrogen exposure,
supporting that the observed modulation of spin current signals originates from
hydrogenation of Pd/YIG.

###Growth, structure, micro-structure and magneto transport of an easy route synthesized bulk polycrystalline TiSe2|Abhilasha Saini,Kapil Kumar,M. M. Sharma,R. P. Aloysius,V. P. S. Awana###

Growth, structure, micro-structure and magneto transport of an easy route synthesized bulk polycrystalline TiSe2. This article reports an easy route synthesis of bulk polycrystalline TiSe2.
Phase purity and microstructure are determined through powder X-ray diffraction
(PXRD) and field emission scanning electron microscopy (FESEM) respectively.
Vibrational modes of TiSe2 as being analyzed by Raman spectroscopy, show the
occurrence of both Ag and Eg modes. Charge density wave (CDW) is observed in
transport measurements of TiSe2 with hysteresis in cooling and warming
measurements at around 180K. Further, studied TiSe2 showed negative
magnetoresistance (MR) below the CDW and a small positive MR above the CDW.

###Dual-gated hBN/bilayer-graphene superlattices and the transitions between the insulating phases at the charge neutrality point|Takuya Iwasaki,Yoshifumi Morita,Kenji Watanabe,Takashi Taniguchi###

Dual-gated hBN/bilayer-graphene superlattices and the transitions between the insulating phases at the charge neutrality point. We report on transport properties in dual-gated hexagonal boron nitride
(hBN)/bilayer-graphene (BLG) superlattices. Here, BLG is nontwisted, i.e.,
plain. This paper focuses on the charge neutrality point (CNP) for a plain BLG.
Under a perpendicular magnetic field, transitions between two insulating phases
at the CNP are detected by varying a displacement field with the study on the
resistance-temperature characteristics and the magnetoresistance. This work
opens avenues for exploring the global phase diagram of the hBN/BLG
superlattices beyond the CNP.

###Frequency-dependent Phonon-mediated Unidirectional Magnetoresistance in a Metal on an Insulator with Highly Nonequilibrium Magnons|Sean E. Sullivan,Hwijong Lee,Annie Weathers,Li Shi###

Frequency-dependent Phonon-mediated Unidirectional Magnetoresistance in a Metal on an Insulator with Highly Nonequilibrium Magnons. Heavy metal (HM)/magnet bilayers host many magnetoresistances (MR) and spin
caloritronic effects. Here we show that the spin Peltier effect and
electron-phonon scattering produce much larger unidirectional MR of an HM on a
magnetic insulator than existing theories that neglect the interplay between MR
and spin caloritronic effects. By accounting for local nonequilibrium in both
the magnon chemical potential and temperature, our analytical model attributes
the observed frequency dependence of the spin Peltier MR and the spin Seebeck
effect to the reduction of the thermal penetration depth, which approaches the
1 micron scale magnon spin diffusion length at high frequencies.

###The origin of enhanced interfacial perpendicular magnetic anisotropy in LiF-inserted Fe/MgO interface|Shoya Sakamoto,Takayuki Nozaki,Shinji Yuasa,Kenta Amemiya,Shinji Miwa###

The origin of enhanced interfacial perpendicular magnetic anisotropy in LiF-inserted Fe/MgO interface. The Fe/MgO interface is an essential ingredient in spintronics as it shows
giant tunneling magnetoresistance and strong perpendicular magnetic anisotropy
(PMA). A recent study demonstrated that the insertion of an ultra-thin LiF
layer between the Fe and MgO layers enhances PMA significantly. In this study,
we perform x-ray magnetic circular dichroism measurements on Fe/LiF/MgO
multilayers to reveal the origin of the PMA enhancement. We find that the LiF
insertion increases the orbital-magnetic-moment anisotropy and thus the
magnetic anisotropy energy. We attribute the origin of this
orbital-magnetic-moment-anisotropy enhancement to the stronger electron
localization and electron-electron correlation or the better interface quality
with fewer defects.

###Magnetoresistance and Kohler rule in the topological chiral semimetals CoSi|A. E. Petrova,O. A. Sobolevskii,S. M. Stishov###

Magnetoresistance and Kohler rule in the topological chiral semimetals CoSi. The transverse and longitudinal magnetoresistance (MR) of two samples of the
topological chiral semimetal CoSi with different RRR was studied. It is shown
that the Kohler rule works for the transverse MR. The Kohler rule is also
fulfilled in the case of longitudinal MR at a low reduced magnetic field. A
sharp deviation of longitudinal MR curve for sample with low RRR from the
Kohler prediction at high fields reveals its tendency to a sign change at
higher magnetic fields. The Shubnikov de Haas quantum oscillations were
observed and analyzed in both perpendicular and parallel configurations of the
current and magnetic field in sample CoSi 1 with RRR 9.33 at low temperatures.

###Large Rashba parameter for 4d strongly correlated perovskite oxide SrNbO3 ultrathin films|Hikaru Okuma,Yumiko Katayama,Kazunori Ueno###

Large Rashba parameter for 4d strongly correlated perovskite oxide SrNbO3 ultrathin films. To elucidate the spin relaxation mechanism of SrNbO3 (SNO) ultrathin films,
the transport properties of a series of SNO films with various thicknesses were
measured on both sides of the metal insulator transition. The spin orbit
scattering time was deduced from the analysis of the magnetoresistance with
weak antilocalization theory, and it was found that the spin orbit scattering
time was inversely proportional to the momentum scattering time. This result
was explained in terms of the D`Yakonov Perel` mechanism, indicative of the
dominant Rashba effect. The values of the Rashba parameter were largest in the
values reported for other ultrathin films of metallic oxides.

###Nonequilibrium Green's function approach to multi-band Cooper-pair transport: linear magnetoresistance effect due to nonunitary superconductivity|G. Tkachov###

Nonequilibrium Green's function approach to multi-band Cooper-pair transport: linear magnetoresistance effect due to nonunitary superconductivity. Many-body transport has emerged as an efficient tool for understanding
interaction effects in quantum materials with a multi-band electronic
structure. This paper proposes a formula for the two-particle transmission
coefficient for Cooper-pair transport between multi-band normal and
superconducting materials. The approach employs a tight-binding nonequilibrium
Green's function technique, allowing a direct calculation of the two-particle
current, without invoking the paradigm of Andreev reflection. As an application
of the theory, we demonstrate a low-field linear magnetoresistance effect for
superconductors with an induced nonunitary order parameter. These results
uncover an unexplored route for detecting unconventional nonunitary
superconductivity in quantum materials of current theoretical and experimental
interest.

###Negative GMR Effect in current perpendicular-to-plane (Zn,Cr)Te/Cu/Co spin salves|W. G. Wang,C. Ni,L. R. Shah,X. M. Kou,J. Q. Xiao###

Negative GMR Effect in current perpendicular-to-plane (Zn,Cr)Te/Cu/Co spin salves. Magnetic and transport properties are explored in the current
perpendicular-to-plane (CPP) spin salves with Cr doped wide band gap
semiconductor ZnTe as one of the ferromagnetic electrodes. A negative
magnetoresistance is observed in these CPP spin valves at low temperature, with
a strong temperature dependence. This effect can be explained by the large
difference of spin scattering asymmetry coefficients in (Zn,Cr)Te and Cobalt,
due to the very different spin polarizations of the two materials as revealed
by the DFT calculation.

###Corbino magnetoresistance in neutral graphene|Vanessa Gall,Boris N. Narozhny,Igor V. Gornyi###

Corbino magnetoresistance in neutral graphene. We explore the magnetohydrodynamics of Dirac fermions in neutral graphene in
the Corbino geometry. Based on the fully consistent hydrodynamic description
derived from a microscopic framework and taking into account all peculiarities
of graphene-specific hydrodynamics, we report the results of a comprehensive
study of the interplay of viscosity, disorder-induced scattering,
recombination, energy relaxation, and interface-induced dissipation. In the
clean limit, magnetoresistance of a Corbino sample is determined by viscosity.
Hence the Corbino geometry could be used to measure the viscosity coefficient
in neutral graphene.

###Evidence for three-dimensional Dirac semimetal state in strongly correlated organic quasi-two-dimensional material|Naoya Tajima,Yoshitaka Kawasugi,Takao Morinari,Ryuhei Oka,Toshio Naito,Reizo Kato###

Evidence for three-dimensional Dirac semimetal state in strongly correlated organic quasi-two-dimensional material. The three-dimensional Dirac semimetal is distinct from its two-dimensional
counterpart due to its dimensionality and symmetry. Here, we observe that
molecule-based quasi-two-dimensional Dirac fermion system,
$\alpha$-(BEDT-TTF)$_2$I$_3$, exhibits chiral anomaly-induced negative
magnetoresistance and planar Hall effect upon entering the coherent inter-layer
tunneling regime under high pressure. Time-reversal symmetry is broken due to
the strong electronic correlation effect, while the spin-orbit coupling effect
is negligible. The system provides an ideal platform for investigating the
chiral anomaly physics by controlling dimensionality and strong electronic
correlation.

###Electronic Transport Studies of Ag-doped Bi2Se3 Topological Insulator|Shailja Sharma,Shiv Kumar,Amit Kumar,Kenya Shimada,C. S. Yadav###

Electronic Transport Studies of Ag-doped Bi2Se3 Topological Insulator. The structural, magnetotransport, and angle-resolved photoemission
spectroscopy (ARPES) of Ag-doped Bi2Se3 single crystals are presented.
Temperature dependent resistivity exhibits metallic behavior with a slope
change above 200 K for Ag-doped Bi2Se3. The magnetoresistance shows positive
quadratic dependence at low fields satisfying Kohler's rule. Hall resistivity
measurement shows that electrons are dominant charge carriers. Furthermore,
these results agree well with the ARPES spectra observed at T = 20 K, where the
Fermi level lies inside the bulk conduction band. The Dirac point of the
topological surface states is shifted toward higher binding energy (~ 0.12 eV)
for Ag-doped samples as compared to pristine Bi2Se3.

###Negative transverse magnetoresistance due to negative off-diagonal mass in linear dispersion materials|Yudai Awashima,Yuki Fuseya###

Negative transverse magnetoresistance due to negative off-diagonal mass in linear dispersion materials. This study calculated the magnetoresistance (MR) in the Dirac electron
system, Dressellhaus-Kip-Kittel (DKK) model, and nodal-line semimetals based on
the semiclassical Boltzmann theory, with particular focus on the detailed
energy dispersion structure. The negative off-diagonal effective-mass was found
to induce negative transverse MR owing to the energy dispersion effect. The
impact of the off-diagonal mass was more prominent in case of a linear energy
dispersion. Further, Dirac electron systems could realize negative MR even if
the Fermi surface was perfectly spherical. The obtained negative MR in the DKK
model may explain the long-standing mystery in p-type Si.

###Anapole, chiral and orbital states in Mn3Si2Te6|Stephen W. Lovesey###

Anapole, chiral and orbital states in Mn3Si2Te6. The ferrimagnet Mn3Si2Te6 attracts attention because of a recently discovered
colossal magnetoresistance (CMR) with unique magnetic field properties. An
improved magnetic structure for the material has emerged from a neutron
diffraction study linked to understanding the CMR. A deeper theoretical
investigation of the magnetic structure has now revealed anapole, chiral and
orbital states of manganese ions not previously mentioned. Moreover, it is
shown that existence of these states in the low temperature form of Mn3Si2Te6,
with a magnetic field applied, can be tested by neutron and resonant x-ray
diffraction.

###Observations of $ν=1$ Quantum Hall Effect and Inter-Band Effects of Magnetic fields on Hall Conductivity in Organic Massless Dirac Fermion System $α$-(BETS)$_2$I$_3$ under Pressure|K. Iwata,A. Koshiba,Y. Kawasugi,R. Kato,N. Tajima###

Observations of $ν=1$ Quantum Hall Effect and Inter-Band Effects of Magnetic fields on Hall Conductivity in Organic Massless Dirac Fermion System $α$-(BETS)$_2$I$_3$ under Pressure. We investigated the magnetoresistance and the Hall effect in an organic
massless Dirac fermion system $\alpha$-(BETS)$_2$I$_3$ under pressure. The
Fermi energy of this system is slightly far away from the Dirac points, and
thus the $\nu =1$ quantum Hall state is realized in a low magnetic field at low
temperatures. Moreover, the experimental formula for chemical potential as a
function of temperature is clarified. We succeeded in detecting the inter-band
effects of the magnetic field on the Hall conductivity when the chemical
potential passes the Dirac points.

###Wide Range Thin-FIlm Ceramic Metal-Alloy Thermometers with Low Magnetoresistance|N. A. Fortune,J. E. Palmer-Fortune,A. Trainer,A. Bangura,N. Kondedan,A. Rydh###

Wide Range Thin-FIlm Ceramic Metal-Alloy Thermometers with Low Magnetoresistance. Many thermal measurements in high magnetic fields require thermometers that
are sensitive over a wide temperature range, are low mass, have a rapid thermal
response, and have a minimal, easily correctable magnetoresistance. Here we
report the development of a new granular-metal oxide ceramic composite (cermet)
for this purpose formed by co-sputtering of the metallic alloy nichrome
Ni$_{0.8}$Cr$_{0.2}$ and the insulator silcon dioxide SiO$_2$. The resulting
thin films are sensitive enough to be used from room temperature down to below
100 mK in magnetic fields up to at least 35 tesla.

###Transverse Magnetoresistance of GaAs/AlGaAs Heterojunctions in the Presence of Parallel Magnetic Fields|J. M. Heisz,E. Zaremba###

Transverse Magnetoresistance of GaAs/AlGaAs Heterojunctions in the Presence of Parallel Magnetic Fields. We have calculated the resistivity of a GaAs\slash AlGaAs heterojunction in
the presence of both an in--plane magnetic field and a weak perpendicular
component using a semiclassical Boltzmann transport theory. These calculations
take into account fully the distortion of the Fermi contour which is induced by
the parallel magnetic field. The scattering of electrons is assumed to be due
to remote ionized impurities. A positive magnetoresistance is found as a
function of the perpendicular component, in good qualitative agreement with
experimental observations. The main source of this effect is the strong
variation of the electronic scattering rate around the Fermi contour which is
associated with the variation in the mean distance of the electronic states
from the remote impurities. The magnitude of the positive magnetoresistance is
strongly correlated with the residual acceptor impurity density in the GaAs
layer. The carrier lifetime anisotropy also leads to an observable anisotropy
in the resistivity with respect to the angle between the current and the
direction of the in--plane magnetic field.

###Vertical transport in superlattices|Daniel L. Miller###

Vertical transport in superlattices. All the principal results of this work concern the vertical transport in
generic three dimensional superlattices. In the 1st chapter we make an
historical introduction, then we discuss the geometry of the problem, and the
physical parameters associated with structure of electron minibands and
strength of external fields. We found the effect of collisionless transverse
magnetoresistance, and we discuss it in the 2nd chapter. This effect is similar
to collisionless Landau damping in a plasma and we utilize the same name. In
the 3rd chapter we provide quantum mechanical reasons for the above effect; we
show how a magnetic field bends narrow superlattice minibands, and we classify
the states into Landau-type and Stark-type. In the 4th chapter we compute
longitudinal magnetoresistance of superlattices due to the imperfections of the
interfaces. Correlation length of the interface roughness can be measured
independently by this method. In the 5th chapter we discuss the current-voltage
characteristic of superlattice when an electric field destroys the one-miniband
transport. We found that the structure of the high-field domains in the
superlattices is complicated, but can be described analytically with great
accuracy. This structure reveals itself in the details of the current-voltage
characteristics. All our results are consistent with existing experiments, and
we make careful comparison of theoretical predictions and experimental results
in all chapters.

###Phase Relaxation of Electrons in Disordered Conductors|B. L. Altshuler,M. E. Gershenson,I. L. Aleiner###

Phase Relaxation of Electrons in Disordered Conductors. Conduction electrons in disordered metals and heavily doped semiconductors at
low temperatures preserve their phase coherence for a long time: phase
relaxation time $\tau_\phi$ can be orders of magnitude longer than the momentum
relaxation time. The large difference in these time scales gives rise to well
known effects of weak localization, such as anomalous magnetoresistance. Among
other interesting characteristics, study of these effects provide quantitative
information on the dephasing rate $1/\tau_\phi$. This parameter is of
fundamental interest: the relation between $\hbar/\tau_\phi$ and the
temperature $T$ (a typical energy scale of an electron) determines how well a
single electron state is defined. We will discuss the basic physical meaning of
$1/\tau_\phi$ in different situations and its difference from the energy
relaxation rate. At low temperatures, the phase relaxation rate is governed by
collisions between electrons. We will review existing theories of dephasing by
these collisions or (which is the same) by electric noise inside the sample. We
also discuss recent experiments on the magnetoresistance of 1D systems: some of
them show saturation of $1/\tau_\phi$ at low temperatures, the other do not. To
resolve this contradiction we discuss dephasing by an external microwave field
and by nonequilibrium electric noise.

###Assisted Tunneling in Ferromagnetic Junctions and Half-Metallic Oxides|A. M. Bratkovsky###

Assisted Tunneling in Ferromagnetic Junctions and Half-Metallic Oxides. Different mechanisms of spin-dependent tunneling are analyzed with respect to
their role in tunnel magnetoresistance (TMR). Microscopic calculation within a
realistic model shows that direct tunneling in iron group systems leads to
about a 30% change in resistance, which is close but lower than experimentally
observed values. The larger observed values of the tunnel magnetoresistance
(TMR) might be a result of tunneling involving surface polarized states. It is
found that tunneling via resonant defect states in the barrier radically
decreases the TMR by order of magnitude. One-magnon emission is shown to reduce
the TMR, whereas phonons increase the effect. The inclusion of both magnons and
phonons reasonably explains an unusual bias dependence of the TMR. The model
presented here is applied qualitatively to half-metallics with 100% spin
polarization, where one-magnon processes are suppressed and the change in
resistance in the absence of spin-mixing on impurities may be arbitrarily
large. Even in the case of imperfect magnetic configurations, the resistance
change can be a few 1000 percent. Examples of half-metallic systems are
CrO2/TiO2 and CrO2/RuO2.

###Strong localization of electrons in quasi-one-dimensional conductors|Yu. B. Khavin,M. E. Gershenson,A. L. Bogdanov###

Strong localization of electrons in quasi-one-dimensional conductors. We report on the experimental study of electron transport in sub-micron-wide
''wires'' fabricated from Si $\delta $-doped GaAs. These quasi-one-dimensional
(Q1D) conductors demonstrate the crossover from weak to strong localization
with decreasing the temperature. On the insulating side of the crossover, the
resistance has been measured as a function of temperature, magnetic field, and
applied voltage for different values of the electron concentration, which was
varied by applying the gate voltage. The activation temperature dependence of
the resistance has been observed with the activation energy close to the mean
energy spacing of electron states within the localization domain. The study of
non-linearity of the current-voltage characteristics provides information on
the distance between the critical hops which govern the resistance of Q1D
conductors in the strong localization (SL) regime. We observe the exponentially
strong negative magnetoresistance; this orbital magnetoresistance is due to the
universal magnetic-field dependence of the localization length in Q1D
conductors. The method of measuring of the single-particle density of states
(DoS) in the SL regime has been suggested. Our data indicate that there is a
minimum of DoS at the Fermi level due to the long-range Coulomb interaction.

###Diamagnetic Effects, Spin Dependent Fermi Surfaces, and the Giant Magnetoresistance in Metallic Multilayers|W. Tavera,G. G. Cabrera###

Diamagnetic Effects, Spin Dependent Fermi Surfaces, and the Giant Magnetoresistance in Metallic Multilayers. We study the role of diamagnetic effects on the transport properties of
metallic magnetic multilayers to elucidate whether they can explain the Giant
Magnetoresistance (GMR) effect observed in those systems. Realistic Fermi
surface topologies in layered ferromagnets are taken into account, with the
possibilities of different types of orbits depending on the electron spin. Both
configurations, with ferromagnetic and anti-ferromagnetic couplings between
magnetic layers, are considered and the transmission coefficient for scattering
at the interface boundary is modelled to include magnetic and roughness
contributions. We assume that scattering processes conserve the electron spin,
due to large spin diffusion lengths in multilayer samples. Scattering from the
spacer mixes different orbit topologies in a way similar to magnetic
`breakdown' phenomena. For antiferromagnetic coupling, majority and minority
spins are interchanged from one magnetic layer to the next. Cyclotron orbits
are also traveled in opposite directions, producing a compensation-like effect
that yields a huge GMR, particularly for closed orbits. For open orbits, one
may get the `inverse' magnetoresistance effect along particular directions.

###Interaction effects and phase relaxation in disordered systems|I. L. Aleiner,B. L. Altshuler,M. E. Gershenson###

Interaction effects and phase relaxation in disordered systems. This paper is intended to demonstrate that there is no need to revise the
existing theory of the transport properties of disordered conductors in the
so-called weak localization regime. In particular, we demonstrate explicitly
that recent attempts to justify theoretically that the dephasing rate
(extracted from the magnetoresistance) remains finite at zero temperature are
based on the profoundly incorrect calculation. This demonstration is based on a
straightforward evaluation of the effect of the electron-electron interaction
on the weak localization correction to the conductivity of disordered metals.
Using well-controlled perturbation theory with the inverse conductance $g$ as
the small parameter, we show that this effect consists of two contributions.
First contribution comes from the processes with energy transfer smaller than
the temperature. This contribution is responsible for setting the energy scale
for the magnetoresistance. The second contribution originates from the virtual
processes with energy transfer larger than the temperature. It is shown that
the latter processes have nothing to do with the dephasing, but rather manifest
the second order (in $1/g$) correction to the conductance. This correction is
calculated for the first time. The paper also contains a brief review of the
existing experiments on the dephasing of electrons in disordered conductors and
an extended qualitative discussion of the quantum corrections to the
conductivity and to the density of electronic states in the weak localization
regime.

###Critical point for the strong field magnetoresistance of a normal conductor/perfect insulator/perfect conductor composite with a random columnar microstructure|David J. Bergman###

Critical point for the strong field magnetoresistance of a normal conductor/perfect insulator/perfect conductor composite with a random columnar microstructure. A recently developed self-consistent effective medium approximation, for
composites with a columnar microstructure, is applied to such a
three-constituent mixture of isotropic normal conductor, perfect insulator, and
perfect conductor, where a strong magnetic field {\bf B} is present in the
plane perpendicular to the columnar axis. When the insulating and perfectly
conducting constituents do not percolate in that plane, the
microstructure-induced in-plane magnetoresistance is found to saturate for
large {\bf B}, if the volume fraction of the perfect conductor $p_S$ is greater
than that of the perfect insulator $p_I$. By contrast, if $p_S<p_I$, that
magnetoresistance keeps increasing as ${\bf B}^2$ without ever saturating. This
abrupt change in the macroscopic response, which occurs when $p_S=p_I$, is a
critical point, with the associated critical exponents and scaling behavior
that are characteristic of such points. The physical reasons for the singular
behavior of the macroscopic response are discussed. A new type of percolation
process is apparently involved in this phenomenon.

###Spin-splitting in GaAs 2D holes|S. J. Papadakis,E. P. De Poortere,M. Shayegan,R. Winkler###

Spin-splitting in GaAs 2D holes. We present quantitative measurements and calculations of the spin-orbit
induced zero-magnetic-field spin-splitting in two-dimensional (2D) hole systems
in modulation-doped GaAs (311)A quantum wells. The results show that the
splitting is large and tunable. In particular, via a combination of back- and
front-gate biases, we can tune the splitting while keeping the 2D hole density
constant. The data also reveal a surprising result regarding the
magnetoresistance (Shubnikov-de Haas) oscillations in a 2D system with
spin-split energy bands: the frequencies of the oscillations are {\it not}
simply related to the population of the spin-subbands. Next we concentrate on
the metallic-like behavior observed in these 2D holes and its relation to
spin-splitting. The data indicate that the metallic behavior is more pronounced
when two spin-subbands with unequal populations are occupied. Our measurements
of the magnetoresistance of these 2D hole systems with an in-plane magnetic
field corroborate this conclusion: while the system is metallic at zero
magnetic field, it turns insulating when one of the spin-subbands is
depopulated at high magnetic field.

###Quasiclassical magnetotransport in a random array of antidots|D. G. Polyakov,F. Evers,A. D. Mirlin,P. Woelfle###

Quasiclassical magnetotransport in a random array of antidots. We study theoretically the magnetoresistance $\rho_{xx}(B)$ of a
two-dimensional electron gas scattered by a random ensemble of impenetrable
discs in the presence of a long-range correlated random potential. We believe
that this model describes a high-mobility semiconductor heterostructure with a
random array of antidots. We show that the interplay of scattering by the two
types of disorder generates new behavior of $\rho_{xx}(B)$ which is absent for
only one kind of disorder. We demonstrate that even a weak long-range disorder
becomes important with increasing $B$. In particular, although $\rho_{xx}(B)$
vanishes in the limit of large $B$ when only one type of disorder is present,
we show that it keeps growing with increasing $B$ in the antidot array in the
presence of smooth disorder. The reversal of the behavior of $\rho_{xx}(B)$ is
due to a mutual destruction of the quasiclassical localization induced by a
strong magnetic field: specifically, the adiabatic localization in the
long-range Gaussian disorder is washed out by the scattering on hard discs,
whereas the adiabatic drift and related percolation of cyclotron orbits
destroys the localization in the dilute system of hard discs. For intermediate
magnetic fields in a dilute antidot array, we show the existence of a strong
negative magnetoresistance, which leads to a nonmonotonic dependence of
$\rho_{xx}(B)$.

###Distinct origins of magnetic -field -induced resistivity irreversibility in two manganites with similar ground states : Pr$_{0.5}$Sr$_{0.41}$Ca$_{0.09}$MnO$_{3}$ and La$_{0.5}$Ca$_{0.5}$MnO$_{3}$|R. Mahendiran,A. Maignan,C. Martin,M. Hervieu,B. Raveau###

Distinct origins of magnetic -field -induced resistivity irreversibility in two manganites with similar ground states : Pr$_{0.5}$Sr$_{0.41}$Ca$_{0.09}$MnO$_{3}$ and La$_{0.5}$Ca$_{0.5}$MnO$_{3}$. Our investigation of the magnetotransport in two charge ordered manganites
with similar magnetic ground states reveals that the origin of
magnetoresistance can not be concluded from the isofield resistivity, $\rho
$(T, constant H), measurements alone. Both
Pr$_{0.5}$Sr$_{0.41}$Ca$_{0.09}$MnO$_{3}$ (PrSrCa) and
La$_{0.5}$Ca$_{0.5}$MnO$_{3}$ (LaCa) show a ferromagnetic transition (T$_{C}$ =
260 K for PrSrCa, 230 K for LaCa) followed by an antiferromagnetic transition
(T$_{N}$ = 170 K for PrSrCa, 140 K for LaCa). These compounds show
qualitatively similar magnetotransport : Below the irreversibility temperature
T$_{IR}$, field cooled (FC) resistivity is lower than zero field cooled (ZFC)
and decreases continuously with T, whereas the ZFC $\rho $(T, H) resembles $\
$the behavior of $\rho $(T, H = 0 T). The value of $\rho $(ZFC)/$\rho $(FC) is
$\approx $ 10$^{4}$ at 5 K and $\mu_{0}$H = 7 T in both compounds. However,
isothermal magnetic measurements suggest distinct origins of magnetoresistance
: Field cooling enhances ferromagnetic phase fraction in LaCa whereas it drives
PrSrCa into a metastable state with high magnetization. The distinct origins of
magnetotransport is also reflected in other magnetic history dependent
properties.

###Hysteresis and Fractional Matching in Thin Nb Films with Rectangular Arrays of Nanoscaled Magnetic Dots|O. M. Stoll,M. I. Montero,J. Guimpel,Johan J. Akerman,Ivan K. Schuller###

Hysteresis and Fractional Matching in Thin Nb Films with Rectangular Arrays of Nanoscaled Magnetic Dots. We have investigated the periodic pinning of magnetic flux quanta in thin Nb
films with rectangular arrays of magnetic dots. In this type of pinning
geometry, a change in the periodicity and shape of the minima in the
magnetoresistance occurs for magnetic fields exceeding a certain threshold
value. This has been explained recently in terms of a reconfiguration
transition of the vortex lattice due to an increasing vortex-vortex interaction
with increasing magnetic field. In this picture the dominating elastic energy
at high fields forces the vortex lattice to form a square symmetry rather than
being commensurate to the rectangular geometry of the pinning array. In this
paper we present a comparative study of rectangular arrays with Ni-dots,
Co-dots and holes. In the magnetic dot arrays, we found a strong fractional
matching effect up to the second order matching field. In contrast, no clear
fractional matching is seen after the reconfiguration. Additionally, we
discovered the existence of hysteresis in the magnetoresistance in the
crossover between the low and the high field regime. We found evidence that
this effect is correlated to the reconfiguration phenomenon rather than to the
magnetic state of the dots. The temperature and angular dependences of the
effect have been measured and possible models are discussed to explain this
behavior.

###Magnetotransport in the Normal State of La1.85Sr0.15Cu(1-y)Zn(y)O4 Films|A. Malinowski,Marta Z. Cieplak,S. Guha,Q. Wu,B. Kim,A. Krickser,A. Perali,K. Karpinska,M. Berkowski,C. H. Shang,P. Lindenfeld###

Magnetotransport in the Normal State of La1.85Sr0.15Cu(1-y)Zn(y)O4 Films. We have studied the magnetotransport properties in the normal state for a
series of La1.85Sr0.15Cu(1-y)Zn(y)O4 films with values of y, between 0 and
0.12. A variable degree of compressive or tensile strain results from the
lattice mismatch between the substrate and the film, and affects the transport
properties differently from the influence of the zinc impurities. In
particular, the orbital magnetoresistance (OMR) varies with y but is
strain-independent. The relations for the resistivity and the Hall angle and
the proportionality between the OMR and tan^2 theta are followed about 70 K. We
have been able to separate the strain and impurity effects by rewriting the
above relations, where each term is strain-independent and depends on y only.
We also find that changes in the lattice constants give rise to closely the
same fractional changes in other terms of the equation.The OMR is more strongly
supressed by the addition of impurities than tan^2 theta. We conclude that the
relaxation ratethat governs Hall effect is not the same as for the
magnetoresistance. We also suggest a correspondence between the transport
properties and the opening of the pseudogap at a temperature which changes when
the La-sr ratio changes, but does not change with the addition of the zinc
impurities.

###Magnetotransport of CeRhIn5|A. D. Christianson,A. Lacerda,M. F. Hundley,P. G. Pagliuso,J. L. Sarrao###

Magnetotransport of CeRhIn5. We report measurements of the temperature-dependent anisotropic resistivity
and in-plane magnetoresistance on single crystals of the tetragonal
heavy-fermion antiferromagnet (TN = 3.8 K) CeRhIn5. The measurements are
reported in the temperature range 1.4 K to 300 K and in magnetic fields to 18
tesla. The resistivity is moderately anisotropic, with a room-temperature
c-axis to in-plane resistivity ratio rho_c/rho_a(300 K) = 1.7. rho(T)
measurements on the non-magnetic analog LaRhIn5 indicate that the anisotropy in
the CeRhIn5 resistivity stems predominately from anisotropy in Kondo-derived
magnetic scattering. In the magnetically ordered regime an applied field H
reduces TN only slightly due to the small ordered moment (0.37mu_B) and
magnetic anisotropy. The magnetoresistance (MR) below TN is positive and varies
linearly with H. In the paramagnetic state a positive MR is present below 7.5
K, while a high-field negative contribution is evident at higher temperatures.
The positive contribution decreases in magnitude with increasing temperature.
Above 40 K the positive contribution is no longer observable, and the MR is
negative. The low-T positive MR results from interactions with the
Kondo-coherent state, while the high-T negative MR stems from single-impurity
effects. The H and T-dependent magnetotransport reflects the magnetic
anisotropy and Kondo interactions at play in CeRhIn5.

###Weak localization in InSb thin films heavily doped with lead|M. Oszwaldowski,T. Berus,V. K. Dugaev###

Weak localization in InSb thin films heavily doped with lead. The paper reports on the investigations of the weak localization (WL) effects
in 3D polycrystalline thin films of InSb. The films are closely compensated
showing the electron concentration n>10^{16} cm^{-3} at the total concentration
of the donor and acceptor type structural defects >10^{18} cm^{-3}. Unless
Pb-doped, the InSb films do not show any measurable or show very small WL
effect at 4.2 K. The Pb-doping to the concentration of the order of 10^{18}
cm^{-3} leads to pronounced WL effects below 7 K. In particular, a clearly
manifested SO scattering is observed. From the comparison of the experimental
data on temperature dependence of the magnetoresistivity and sample resistance
with the WL theory, the temperature dependence of the phase destroying time is
determined. The determination is performed by fitting theoretical terms
obtained from Kawabata's theory to experimental data on magnetoresistance. It
is concluded that the dephasing process is connected to three separate
interaction processes. The first is due to the SO scatterings and is
characterized by temperature-independent relaxation time. The second is
associated with the electron-phonon interaction. The third dephasing process is
characterized by independent on temperature relaxation time tau_c. This
relaxation time is tentatively ascribed to inelastic scattering at extended
structural defects, like grain boundaries. The resulting time dephasing time
shows saturation in its temperature dependence. The temperature dependence of
the resistance of the InSb<Pb> films can be explained by the electron-electron
interaction for T<1 K, and by the WL effect for T>2 K.

###Decoupled CuO_2 and RuO_2 layers in superconducting and magnetically ordered RuSr_2GdCu_2O_8|M. Pozek,A. Dulcic,D. Paar,A. Hamzic,M. Basletic,E. Tafra,G. V. M. Williams,S. Kramer###

Decoupled CuO_2 and RuO_2 layers in superconducting and magnetically ordered RuSr_2GdCu_2O_8. Comprehensive measurements of dc and ac susceptibility, dc resistance,
magnetoresistance, Hall resistivity, and microwave absorption and dispersion in
fields up to 8 T have been carried out on RuSr_2GdCu_2O_8 with the aim to
establish the properties of RuO_2 and CuO_2 planes. At ~130 K, where the
magnetic order develops in the RuO_2 planes, one observes a change in the slope
of dc resistance, change in the sign of magnetoresistance, and the appearance
of an extraordinary Hall effect. These features indicate that the RuO_2 planes
are conducting. A detailed analysis of the ac susceptibility and microwave data
on both, ceramic and powder samples show that the penetration depth remains
frequency dependent and larger than the London penetration depth even at low
temperatures. We conclude that the conductivity in the RuO_2 planes remains
normal even when superconducting order is developed in the CuO_2 planes below
\~45 K. Thus, experimental evidence is provided in support of theoretical
models which base the coexistence of superconductivity and magnetic order on
decoupled CuO_2 and RuO_2 planes.

###Magnetoresistances observed by decomposition of the magnetic moment in La1-xCaxMnO3 films|Hyun-Tak Kim,Kwang-Yong Kang,Eun-Hee Lee###

Magnetoresistances observed by decomposition of the magnetic moment in La1-xCaxMnO3 films. A ferromagnetic phase, characterized by electron carriers and a high
temperature colossal magnetoresistance (HTCMR) dependent on the magnetic
moment, and a semiconducting phase, characterized by hole carriers and a low
temperature CMR (LTCMR), are observed in La$_{1-x}$Ca$_{x}$MnO$_3$ thin films
by the van der Pauw method. The LTCMR is much more sensitive to the magnetic
field than the HTCMR. In the ferromagnetic phase for films with anisotropic
moments in two dimensions, a remnant resistivity of the order of 10$^{-8}
\~{\Omega}m$ is observed up to 100 K and increases exponentially with both a
temperature up to $T_c$ and a magnetic field above one Tesla (a positive
magnetoresistivity). We found that the ferromagnetic phase below $T_c$ is in a
polaronic state with a polaronic mobile conduction, and the carrier density
dips near $T_c$. For resistances measured by the four-probe method with line
electrodes, low temperature information of the HTCMR is not revealed. The van
der Pauw method is more effective for the resistance measurement of a magnetic
material than the four-probe method.

###Angular dependence of magnetoresistivity in c-oriented MgB2 thin film|C. Ferdeghini,V. Braccini,M. R. Cimberle,D. Marre,P. Manfrinetti,V. Ferrando,M. Putti,A. Palenzona###

Angular dependence of magnetoresistivity in c-oriented MgB2 thin film. The anisotropy of MgB2 is still under debate: its value, strongly dependent
on the sample and on the measuring method, ranges between 1.2 and 13. In this
work we present our results on a MgB2 c-oriented superconducting thin film. To
evaluate the anisotropy, we followed two different approaches. Firstly,
magnetoresistivity was measured as a function of temperature at selected
magnetic fields applied both parallel and perpendicular to the c-axis;
secondly, we measured magnetoresistivity at selected temperatures and magnetic
fields, varying the angle q between the magnetic field and the c-axis. The
anisotropy estimated from the ratio between the upper critical fields parallel
and perpendicular to the c-axis and the one obtained in the framework of the
scaling approach within the anisotropic Ginzburg-Landau theory are different
but show a similar trend in the temperature dependence. The obtained results
are compared and discussed in the light of the two-band nature of MgB2. A
comparison between critical fields in thin films and single crystal is also
performed.

###Experimental study of weak antilocalization effect in a high mobility InGaAs/InP quantum well|S. A. Studenikin,P. T. Coleridge,N. Ahmed,P. Poole,A. Sachrajda###

Experimental study of weak antilocalization effect in a high mobility InGaAs/InP quantum well. The magnetoresistance associated with quantum interference corrections in a
high mobility, gated InGaAs/InP quantum well structure is studied as a function
of temperature, gate voltage, and angle of the tilted magnetic field.
Particular attention is paid to the experimental extraction of phase-breaking
and spin-orbit scattering times when weak anti- localization effects are
prominent. Compared with metals and low mobility semiconductors the
characteristic magnetic field $B_{tr} = \hbar/4eD \tau$ in high mobility
samples is very small and the experimental dependencies of the interference
effects extend to fields several hundreds of times larger. Fitting experimental
results under these conditions therefore requires theories valid for arbitrary
magnetic field. It was found, however, that such a theory was unable to fit the
experimental data without introducing an extra, empirical, scale factor of
about 2. Measurements in tilted magnetic fields and as a function of
temperature established that both the weak localization and the weak
anti-localization effects have the same, orbital origin. Fits to the data
confirmed that the width of the low field feature, whether a weak localization
or a weak anti-localization peak, is determined by the phase-breaking time and
also established that the universal (negative) magnetoresistance observed in
the high field limit is associated with a temperature independent spin-orbit
scattering time.

###Open Questions in CMR Manganites, Relevance of Clustered States, and Analogies with other Compounds|Elbio Dagotto###

Open Questions in CMR Manganites, Relevance of Clustered States, and Analogies with other Compounds. This is an informal paper that contains a list of ``things we know'' and
``things we do not know'' in manganites. It is adapted from the conclusions
chapter of a recent book by the author, {\it Nanoscale Phase Separation and
Colossal Magnetoresistance. The Physics of Manganites and Related Compounds},
Springer-Verlag, Berlin, November 2002. The main new result of recent manganite
investigations is the discovery of tendencies toward inhomogeneous states, both
in experiments and in simulations of models. The colossal magnetoresistance
effect appears to be closely linked to these mixed-phase tendencies, although
considerably more work is needed to fully confirm these ideas. The paper also
includes information on cuprates, diluted magnetic semiconductors, relaxor
ferroelectrics, cobaltites, and organic and heavy fermion superconductors.
These materials potentially share some common phenomenology with the
manganites, such as a temperature scale $T^*$ above the ordering temperature
where anomalous behavior starts. Many of these materials also present
low-temperature phase competition. The possibility of colossal-like effects in
compounds that do not involve ferromagnets is briefly discussed. Overall, it is
concluded that inhomogeneous ``clustered'' states should be considered a new
paradigm in condensed matter physics, since their presence appears to be far
more common than previously anticipated.

###Conductivity of a 2DEG in Si/SiGe heterostructure near metal- insulator transition: role of the short and long range scattering potential|E. B. Olshanetsky,V. Renard,Z. D. Kvon,J. C. Portal,N. J. Woods,J. Zhang,J. J Harris###

Conductivity of a 2DEG in Si/SiGe heterostructure near metal- insulator transition: role of the short and long range scattering potential. We report the observation of a metal-insulator transition (MIT) in a two-
dimensional electron gas (2DEG) in a Si/SiGe heterostructure at zero magnetic
field. On going through the MIT we observe the corresponding evolution of the
magnetic field induced transition between the insulating phase and the quantum
Hall (QH) liquid state in the QH regime. Similar to the previous reports for a
GaAs sample, we find that the critical magnetic field needed to produce the
transition becomes zero at the critical electron density corresponding to the
zero field MIT. The temperature dependence of the conductivity in a
metallic-like state at zero field is compared with the theory of the
interaction corrections at intermediate and ballistic regimes
$k_{B}T\tau/\hbar\geq1$. The theory yields a good fit for the linear part of
the curve. However the slope of that part of $\sigma_{xx}(T)$ is about two
times smaller than that reported in other 2D systems with similar values of
$r_s$. At the same time, the recent theory of magnetoresistance due to
electron-electron interaction in the case of arbitrary $k_{B}T\tau/\hbar$,
smooth disorder and classically strong fields does not seem to be quite
adequate for the description of the parabolic magnetoresistance observed in our
samples. We attribute these results to the fact that neither of these theories
deals with the whole scattering potential in a sample but leaves either its
long range or its short range component out of consideration.

###Suppression of charge-ordering and appearance of magnetoresistance in a spin-cluster glass manganite La0.3Ca0.7Mn0.8Cr0.2O3|T Sudyoadsuk,R Suryanarayanan,P Winotai,L. E. Wenger###

Suppression of charge-ordering and appearance of magnetoresistance in a spin-cluster glass manganite La0.3Ca0.7Mn0.8Cr0.2O3. The magnetic properties of electron-doped manganite La0.3Ca0.7MnO3 and
La0.3Ca0.7Mn0.8Cr0.2O3 polycrystalline samples prepared by sol-gel technique
have been investigated between 5 and 300 K in magnetic fields ranging from 0 to
5 T. The transition at 260 K, attributed to charge ordering in La0.3Ca0.7MnO3,
is completely suppressed in the Cr-substituted sample while the onset of a
magnetic remanence followed by the appearance of a magnetic irreversibility at
lower temperatures is observed in both samples. These features indicate that
ferromagnetic clusters coexist with either an antiferromagnetic phase for
La0.3Ca0.7MnO3 or a spin-cluster glass phase for La0.3Ca0.7Mn0.8Cr0.2O3 at the
lowest temperatures. The exponential temperature dependence of the resistivity
for the Cr-substituted sample is consistent with the small polaron hopping
model for 120 K < T < 300 K, while the data are better described by Mott's
hopping mechanism for T < 120 K. Whereas the parent compound La0.3Ca0.7MnO3 is
known to show no magnetoresistance, a large negative magnetoresistance is
observed in the La0.3Ca0.7Mn0.8Cr0.2O3 sample below 120 K. The appearance of
the CMR is attributed to spin dependent hopping between spin clusters and/or
between ferromagnetic domains.

###Radiation-intensity and temperature dependence of microwave-induced magnetoresistance oscillations in high-mobility two-dimensional electron systems|X. L. Lei###

Radiation-intensity and temperature dependence of microwave-induced magnetoresistance oscillations in high-mobility two-dimensional electron systems. We present a detailed theoretical investigation on the radiation induced
giant magnetoresistance oscillations recently discovered in high-mobility
two-dimensional electron gas. Electron interactions with impurities, transverse
and longitudinal acoustic phonons in GaAs-based heterosystems are considered
simultaneously. Multiphoton-assisted impurity scatterings are shown to be the
primary origin of the resistance oscillation. Based on the balance-equation
theory developed for magnetotransport in Faraday geometry, we are able not only
to reproduce the observed period, phase and the negative resistivity of the
main oscillations, but also to predict the secondary peak/valley structures
relating to two-photon and three-photon processes. The dependence of the
magnetoresistance oscillation on microwave intensity, the role of dc bias
current and the effect of elevated electron temperature are discussed.
Furthermore, we propose that the temperature-dependence of the resistance
oscillation stems from the growth of the Landau level broadening due to the
enhancement of acoustic phonon scattering with increasing lattice temperature.
The calculated temperature-variation of the oscillation agrees well with
experimental observations.

###Electronic transport in EuB$_6$|G. A. Wigger,R. Monnier,H. R. Ott,D. P. Young,Z. Fisk###

Electronic transport in EuB$_6$. EuB$_6$ is a magnetic semiconductor in which defects introduce charge
carriers into the conduction band with the Fermi energy varying with
temperature and magnetic field. We present experimental and theoretical work on
the electronic magnetotransport in single-crystalline EuB$_6$. Magnetization,
magnetoresistance and Hall effect data were recorded at temperatures between 2
and 300 K and in magnetic fields up to 5.5 T. The negative magnetoresistance is
well reproduced by a model in which the spin disorder scattering is reduced by
the applied magnetic field. The Hall effect can be separated into an ordinary
and an anomalous part. At 20 K the latter accounts for half of the observed
Hall voltage, and its importance decreases rapidly with increasing temperature.
As for Gd and its compounds, where the rare-earth ion adopts the same Hund's
rule ground state as Eu$^{2+}$ in EuB$_{6}$, the standard antisymmetric
scattering mechanisms underestimate the $size$ of this contribution by several
orders of magnitude, while reproducing its $shape$ almost perfectly. Well below
the bulk ferromagnetic ordering at $T_C$ = 12.5 K, a two-band model
successfully describes the magnetotransport. Our description is consistent with
published de Haas van Alphen, optical reflectivity, angular-resolved
photoemission, and soft X-ray emission as well as absorption data, but requires
a new interpretation for the gap feature deduced from the latter two
experiments.

###Magnons in CMR pyrochlore Tl2Mn2O7|C. I. Ventura,M. Acquarone###

Magnons in CMR pyrochlore Tl2Mn2O7. Well defined spin waves were observed when the spin dynamics of Tl2Mn2O7, the
first pyrochlore compound found to exhibit colossal magnetoresistance, was
measured [J.W.Lynn et al., Phys.Rev.Lett. 80,4582(1998)], in stark contrast
with the experimental results on the larger family of magnetoresistive
manganites with perovskite structure. In this work, we present our calculation
for the spin waves in Tl2Mn2O7, which we described using the microscopic
generic model proposed recently for this compound [C.I.Ventura and M.A.Gusmao,
Phys.Rev.B 65, 14422(2002)]. We have employed a canonical transformation to
determine perturbatively the effective spin-wave Hamiltonian, obtaining
therefrom the renormalization of the ferromagnetic spin waves related to the
localized Mn$^{4+}$ spins, due to their coupling with the conduction electrons
present. We have calculated the magnon dispersion relations along different
paths in the first Brillouin zone, comparing them with those which are obtained
for an ideal isotropic ferromagnet. This comparison evidences an agreement
between the ferromagnetic magnons obtained from the generic model and the bare
spin waves, such as had been found in neutron scattering experiments.

###Suppression of a charge density wave ground state in high magnetic fields: spin and orbital mechanisms|D. Graf,J. S. Brooks,E. S. Choi,S. Uji,J. C. Dias,M. Almeida,M. Matos###

Suppression of a charge density wave ground state in high magnetic fields: spin and orbital mechanisms. The charge density wave (CDW) transition temperature in the quasi-one
dimensional (Q1D) organic material of (Per)$_2$Au(mnt)$_2$ is relatively low
(TCDW = 12 K). Hence in a mean field BCS model, the CDW state should be
completely suppressed in magnetic fields of order 30 - 40 T. To explore this
possibility, the magnetoresistance of (Per)$_2$Au(mnt)$_2$ was investigated in
magnetic fields to 45 T for 0.5 K < T < 12 K. For fields directed along the Q1D
molecular stacking direction, TCDW decreases with field, terminating at about ~
37 T for temperatures approaching zero. Results for this field orientation are
in general agreement with theoretical predictions, including the field
dependence of the magnetoresistance and the energy gap, $\Delta_{CDW}$.
However, for fields tilted away from the stacking direction, orbital effects
arise above 15 T that may be related to the return of un-nested Fermi surface
sections that develop as the CDW state is suppressed. These findings are
consistent with expectations that quasi-one dimensional metallic behavior will
return outside the CDW phase boundary.

###Magnetotransport and Superconductivity of Alpha-Uranium|G. M. Schmiedeshoff,D. Dulguerova,J. Quan,S. Touton,C. H. Mielke,A. D. Christianson,A. H. Lacerda,E. Palm,S. T. Hannahs,T. Murphy,E. C. Gay,C. C. McPheeters,D. J. Thoma,W. L. Hults,J. C. Cooley,A. M. Kelly,R. J. Hanrahan, Jr.,J. L. Smith###

Magnetotransport and Superconductivity of Alpha-Uranium. We have measured the electrical resistivity, magnetoresistance, and Hall
effect on several new single crystal samples and one polycrystalline sample of
alpha-uranium. The residual resistivity ratios of these samples vary from 13 to
315. Matthiessen's law appears to hold above the onset of the charge density
wave phase transitions that begin near 43 K, but not below this temperature.
Sharp features at all three charge density wave transitions are observed and
the effects of high magnetic fields on them are presented and discussed. The
magnetoresistance is anisotropic, reaches 1000% at 2 K and 18 T, and does not
exhibit Kohler scaling. The Hall coefficient is positive, independent of
magnetic field, and slightly temperature dependent above about 40 K in
agreement with earlier studies. Below 40 K the Hall coefficient changes sign as
the temperature falls, varies with field, and becomes much more strongly
negative at the lowest temperatures than has been reported. Some of our results
suggest that a spin density wave may coexist with the charge density wave
states. Superconductivity is observed in two of our samples, we argue that it
is intrinsic to alpha-uranium and suggest that it is consistent with a two-band
model. Several parameters characterizing the transport and superconductivity of
alpha-uranium are estimated.

###Kubo formula for Floquet states and photoconductivity oscillations in a 2D electron gas|Manuel Torres,Alejandro Kunold###

Kubo formula for Floquet states and photoconductivity oscillations in a 2D electron gas. The recent discovery of the microwave induced vanishing resistance states in
a two dimensional electron system (2DES) is an unexpected and surprising
phenomena. In these experiments the magnetoresistance of a high mobility 2DES
under the influence of microwave radiation of frequency $\omega$ at moderate
values of the magnetic field, exhibits strong oscillations with zero-resistance
states (ZRS) governed by the ratio $\omega /\omega_c$, where $\omega_c$ is the
cyclotron frequency. In this work we present a model for the photoconductivity
of a two dimensional electron system (2DES) subjected to a magnetic field. The
model includes the microwave and Landau contributions in a non-perturbative
exact way, impurity scattering effects are treated perturbatively. In our
model, the Landau-Floquet states act coherently with respect to the oscillating
field of the impurities, that in turn induces transitions between these levels.
Based on this formalism, we provide a Kubo-like formula that takes into account
the oscillatory Floquet structure of the problem. We study the effects of both
short-range and long-range disorder on the photoconductivity. Our calculation
yields a magnetoresistance oscillatory behavior with the correct period and
phase. It is found that, in agreement with experiment, negative dissipation can
only be induced in very high mobility samples. We analyze the dependence of the
results on the microwave power and polarization. For high-intensity radiation
multi-photon processes take place predicting new negative-resistance states
centered at $ \omega / \omega_c=1/2$, and $ \omega / \omega_c= 3/2$.

###Two-dimensional metal-insulator transition and in-plane magnetoresistance in a high mobility strained Si quantum well|K. Lai,W. Pan,D. C. Tsui,S. A. Lyon,M. Muhlberger,F. Schaffler###

Two-dimensional metal-insulator transition and in-plane magnetoresistance in a high mobility strained Si quantum well. The apparent metal-insulator transition is observed in a high quality
two-dimensional electron system (2DES) in the strained Si quantum well of a
Si/Si_{1-x}Ge_x heterostructure with mobility \mu=1.9 x 10^5 cm^2/Vs at density
n=1.45 x 10^{11} cm^{-2}. The critical density, at which the thermal
coefficient of low T resistivity changes sign, is ~ 0.32 x 10^{11} cm^{-2}, so
far the lowest observed in the Si 2D systems. In-plane magnetoresistance study
was carried out in the higher density range where the 2DES shows the
metallic-like behavior. It is observed that the in-plane magnetoresistance
first increases as ~ B_{ip}^2 and then saturates to a finite value \rho(B_c)
for B_{ip} > B_c. The full spin-polarization field B_c decreases monotonically
with n but appears to saturate to a finite value as n approaches zero.
Furthermore, \rho(B_c)/\rho(0) ~ 1.8 for all the densities ranging from 0.35 x
10^{11} to 1.45 x 10^{11} cm^{-2} and, when plotted versus B_{ip}/B_c,
collapses onto a single curve.

###Classical Hall transition and magnetoresistance in strongly inhomogeneous planar systems|S. A. Bulgadaev###

Classical Hall transition and magnetoresistance in strongly inhomogeneous planar systems. The magneto-transport properties of planar and layered strongly inhomogeneous
two-phase systems are investigated, using the explicit expressions for the
effective conductivities and resistivities obtained by the exact dual
transformation, connecting effective conductivities of in-plane isotropic
two-phase systems with and without magnetic field. These expressions allow to
describe the effective resistivity of various inhomogeneous media at arbitrary
concentrations $x$ and magnetic fields $H$. The corresponding plots of the
$x$-dependence of the Hall constant $R_H(x,H)$ and the magnetoresistance
$R(x,H)$ are constructed for various values of magnetic field at some values of
inhomogeneity parameters. These plots for strongly inhomogeneous systems at
high magnetic fields show a sharp transition between partial Hall resistivities
(or Hall conductivities) with different dependencies of $R_H$ on the phase
concentrations. It is shown that there is a strong correlation between large
linear magnetoresistance effect and this sharp Hall transition. Both these
effects are a consequence of the exact duality symmetry. A possible physical
explanation of these effects and their correlation is proposed.

###Resistivity memory effect in La(1-x)Sr(x)MnO(3)|E. P. Khlybov,R. A. Sadykov,I. J. Kostyleva,W. I. Nizhankovskij,A. J. Zaleski,D. Wlosewicz,A. W. Giulitin###

Resistivity memory effect in La(1-x)Sr(x)MnO(3). During the study of magnetoresistivity in La(1-x)Ca(x)MnO(3) it was found
that after cycling of the magnetic field, some kind of magnetic field memory
effect was observed. For La0.5Ca0.5MnO3 after cycling of the magnetic field to
13T and back to zero, "frozen" magnetoresistivity decreases about 20 times
comparing to zero field value, while for La(0.47)Ca(0.53)MnO(3) it is already
about four orders of magnitude. This effect can be observed only for
concentration region 0.45 < x < 0.55. In zero magnetic field, temperature
dependence of resistivity ro(T) shows semiconducting-like behavior, while after
magnetic field cycling it becomes metal-like. So it looks as we are dealing
with magnetic field induced semiconductor (or dielectric) to metal transition.
Such effect can be explained within phase-separation picture. In zero magnetic
field material consists of antiferromagnetic matrix (insulating phase) and
coexisting ferromagnetic, conducting phase. Magnetic field application causes
ferromagnetic phase to form some kind of conducting channels which shunts
semiconducting matrix phase. Such structure is preserved after reduction of
magnetic field, leaving the material conducting.

###Magnetoresistance, specific heat and magnetocaloric effect of equiatomic rare-earth transition-metal magnesium compounds|H. Hartmann,K. Berggold,S. Jodlauk,I. Klassen,K. Kordonis,T. Fickenscher,R. Poettgen,A. Freimuth,T. Lorenz###

Magnetoresistance, specific heat and magnetocaloric effect of equiatomic rare-earth transition-metal magnesium compounds. We present a study of the magnetoresistance, the specific heat and the
magnetocaloric effect of equiatomic $RET$Mg intermetallics with $RE = {\rm
La}$, Eu, Gd, Yb and $T = {\rm Ag}$, Au and of GdAuIn. Depending on the
composition these compounds are paramagnetic ($RE = {\rm La}$, Yb) or they
order either ferro- or antiferromagnetically with transition temperatures
ranging from about 13 to 81 K. All of them are metallic, but the resistivity
varies over 3 orders of magnitude. The magnetic order causes a strong decrease
of the resistivity and around the ordering temperature we find pronounced
magnetoresistance effects. The magnetic ordering also leads to well-defined
anomalies in the specific heat. An analysis of the entropy change leads to the
conclusions that generally the magnetic transition can be described by an
ordering of localized $S=7/2$ moments arising from the half-filled $4f^7$
shells of Eu$^{2+}$ or Gd$^{3+}$. However, for GdAgMg we find clear evidence
for two phase transitions indicating that the magnetic ordering sets in
partially below about 125 K and is completed via an almost first-order
transition at 39 K. The magnetocaloric effect is weak for the antiferromagnets
and rather pronounced for the ferromagnets for low magnetic fields around the
zero-field Curie temperature.

###Domain imaging, MOKE and magnetoresistance studies of CoFeB films for MRAM applications|J. M. Teixeira,R. F. A. Silva,J. Ventura,A. M. Pereira,F. Carpinteiro,J. P. Araujo,J. B. Sousa,S. Cardoso,R. Ferreira,P. P. Freitas###

Domain imaging, MOKE and magnetoresistance studies of CoFeB films for MRAM applications. We present a detailed study on domain imaging, Kerr effect magnetometry
(MOKE) and magnetoresistance (MR), for a series of 20 nm
Co$_{73.8}$Fe$_{16.2}$B$_{10}$ thin films, both as-deposited (amorphous) and
annealed (crystalline). By considering the two different (orthogonal) in-plane
magnetization components, obtained by MOKE measurements, we were able to study
the uniaxial anisotropy induced during CoFeB-deposition and to discriminate the
magnetization processes under a magnetic field parallel and perpendicular to
such axis. MOKE magnetic imaging enabled us to observe the dominant
magnetization processes, namely domain wall motion and moment rotation. These
processes were correlated with the behavior of the magnetoresistance, which
depends both on short-range spin disorder electron scattering and on the angle
between the electrical current and the spontaneous magnetization
($\emph{\textbf{M}}_{S}$). A simple numerical treatment based on
Stoner-Wolfarth model enables us to satisfactorily predict the magnetization
behaviour observed in these films. A comparison between the results in
Co$_{73.8}$Fe$_{16.2}$B$_{10}$ films and the previous ones obtained in annealed
Co$_{80}$Fe$_{20}$ films, show that the introduction of boron in CoFe reduces
significatively the coercive and saturation fields along the easy axis (e.g.
$H_{c}$ from $\sim$ 2 down to $\sim$ 0.5 kAm$^{-1}$). Also, the magnetization
along the hard axis saturates at lower fields. We conclude that amorphous and
nanocrystalline CoFeB films show low coercive fields and abrupt switching, as
well as absence of short range spin disorder effects after switching when
compared with Co$_{80}$Fe$_{20}$.

###M-I Transition in a-Conducting Carbon Films Induced by Boron Doping|P. N. Vishwakarma,S. V. Subramanyam###

M-I Transition in a-Conducting Carbon Films Induced by Boron Doping. The amorphous conducting carbon films have been prepared at three different
preparation temperatures with different boron-doping levels. The structural and
transport properties of the same have been studied. X-ray diffraction
measurements show that the 'd' value of the carbon depends both on atomic
percentage of B in the carbon network and also on the preparation temperature.
Doping of boron increases the structural graphitic ordering of the films
prepared at lower temperatures. On the contrary for the films prepared at
higher temperatures the ordering deteriorates as the boron content increases.
The d.c electrical transport measurements on these amorphous conducting carbon
films show, doping induced metal-insulator transition via critical regime, in
the temperature interval of 1.3 K to 300K. Also the films in the insulating
regime show a crossover from Mott to ES VRH for T < 55K. Additional support to
this transition is evident from negative magnetoresistance in VRH regime when
the sample is deep inside the insulating side of MI transition. The calculated
value of density of states at Fermi level shows a gradual change with
corresponding variation in boron doping level, indicating a change in the
number of conducting pi electrons due to substitutional doping of boron in the
carbon network. However for the films exhibiting critical behaviour, the
magnetic field dependence of magnetoresistance was not as predicted by the
available theoretical models. Various calculated parameters like localization
length, density of states at the Fermi level and coulomb gap for insulating
samples were calculated from the experimental data.

###Magnetic Inhomogeneity and Magnetotransport in Electron-Doped Ca(1-x)La(x)MnO(3) (0<=x<=0.10)|C. Chiorescu,J. J. Neumeier,J. L. Cohn###

Magnetic Inhomogeneity and Magnetotransport in Electron-Doped Ca(1-x)La(x)MnO(3) (0<=x<=0.10). The dc magnetization (M) and electrical resistivity (\rho) as functions of
magnetic field and temperature are reported for a series of lightly electron
dopedCa(1-x)La(x)MnO(3) (0<=x<=0.10) specimens for which magnetization [Phys.
Rev. B {\bf 61}, 14319 (2000)] and scattering studies [Phys. Rev. B {\bf 68},
134440 (2003)] indicate an inhomogeneous magnetic ground state composed of
ferromagnetic (FM) droplets embedded in a G-type antiferromagnetic matrix. A
change in the magnetic behavior near x=0.02 has been suggested to be the
signature of a crossover to a long-ranged spin-canted phase. The data reported
here provide further detail about this crossover in the magnetization, and
additional insight into the origin of this phenomenon through its manifestation
in the magnetotransport. In the paramagnetic phase (T>=125 K) we find a
magnetoresistance =-C(M/M_S)^2 (M_S is the low-T saturation magnetization), as
observed in many manganites in the ferromagnetic (FM), colossal
magnetoresistance (CMR) region of the phase diagram, but with a value of C that
is two orders of magnitude smaller than observed for CMR materials. The doping
behavior C(x) follows that of M_S(x), indicating that electronic inhomogeneity
associated with FM fluctuations occurs well above the magnetic ordering
transition.

###Transformation of spin information into large electrical signals via carbon nanotubes|Luis E. Hueso,Jose M. Pruneda,Valeria Ferrari,Gavin Burnell,Jose P. Valdes-Herrera,Benjamin D. Simons,Peter B. Littlewood,Emilio Artacho,Albert Fert,Neil D. Mathur###

Transformation of spin information into large electrical signals via carbon nanotubes. Spin electronics (spintronics) exploits the magnetic nature of the electron,
and is commercially exploited in the spin valves of disc-drive read heads.
There is currently widespread interest in using industrially relevant
semiconductors in new types of spintronic devices based on the manipulation of
spins injected into a semiconducting channel between a spin-polarized source
and drain. However, the transformation of spin information into large
electrical signals is limited by spin relaxation such that the magnetoresistive
signals are below 1%. We overcome this long standing problem in spintronics by
demonstrating large magnetoresistance effects of 61% at 5 K in devices where
the non-magnetic channel is a multiwall carbon nanotube that spans a 1.5 micron
gap between epitaxial electrodes of the highly spin polarized manganite
La0.7Sr0.3MnO3. This improvement arises because the spin lifetime in nanotubes
is long due the small spin-orbit coupling of carbon, because the high nanotube
Fermi velocity permits the carrier dwell time to not significantly exceed this
spin lifetime, because the manganite remains highly spin polarized up to the
manganite-nanotube interface, and because the interfacial barrier is of an
appropriate height. We support these latter statements regarding the interface
using density functional theory calculations. The success of our experiments
with such chemically and geometrically different materials should inspire
adventure in materials selection for some future spintronics

###Magnetic field dependence of the magnetic phase separation in Pr1-xCaxMnO3 manganites studied by small-angle neutron scattering|Damien Saurel,Annie Brulet,Andre Heinemann,Christine Martin,Silvana Mercone,Charles Simon###

Magnetic field dependence of the magnetic phase separation in Pr1-xCaxMnO3 manganites studied by small-angle neutron scattering. Transport properties of manganese oxides suggest that their colossal
magnetoresistance (CMR) is due to percolation between ferromagnetic metallic
(FM) clusters in an antiferromagnetic insulating (AFI) matrix. We have studied
small-angle neutron scattering under applied magnetic field in CMR Pr1-xCaxMnO3
crystals for x around 0.33. Quantitative analysis of the small-angle magnetic
neutron scattering shows that the magnetic heterogeneities take place at
different scales. At the mesoscopic scale (200nm), the inhomogeneities
correspond to the percolation of the conducting ferromagnetic phase into the
insulating phases. It is at the origin of the colossal magnetoresistance of the
compound. The other inhomogeneities are nanoscopic: inside the
antiferromagnetic phase (AFI), there exist small ferromagnetic clusters. Inside
the ferromagnetic phase which exists in absence of magnetic field in some
compounds and is in fact insulating (FI), there also exist small non
ferromagnetic objects. No evolution of this nanostructure is observed when the
magnetic field is applied. The existence of such nanoscale objects is discussed
in relation to the cationic disorder of these compounds.

###Colossal Magnetoresistance Observed in Monte Carlo Simulations of the One- and Two-Orbital Models for Manganites|C. Şen,G. Alvarez,H. Aliaga,E. Dagotto###

Colossal Magnetoresistance Observed in Monte Carlo Simulations of the One- and Two-Orbital Models for Manganites. The one- and two-orbital double-exchange models for manganites are studied
using Monte Carlo computational techniques in the presence of a robust
electron-phonon coupling (but neglecting the antiferromagnetic exchange $J_{\rm
AF}$ between the localized spins). The focus in this effort is on the analysis
of charge transport. Our results for the one-orbital case confirm and extend
previous recent investigations that showed the presence of robust peaks in the
resistivity vs. temperature curves for this model. Quenched disorder
substantially enhances the magnitude of the effect, while magnetic fields
drastically reduce the resistivity. A simple picture for the origin of these
results is presented. It is also shown that even for the case of just one
electron, the resistance curves present metallic and insulating regions by
varying the temperature, as it occurs at finite electronic density. Moreover,
in the present study these investigations are extended to the more realistic
two-orbital model for manganites. The transport results for this model show
large peaks in the resistivity vs. temperature curves, located at approximately
the Curie temperature, and with associated large magnetoresistance factors.
Overall, the magnitude and shape of the effects discussed here closely resemble
experiments for materials such as $\rm La_{0.70} Ca_{0.30} Mn O_{3}$, and they
are in qualitative agreement with the current predominant theoretical view that
competition between a metal and an insulator, enhanced by quenched disorder, is
crucial to understand the colossal magnetoresistance (CMR) phenomenon.

###Theoretical studies of spin-dependent electrical transport through carbon nanotbes|S. Krompiewski###

Theoretical studies of spin-dependent electrical transport through carbon nanotbes. Spin-dependent coherent quantum transport through carbon nanotubes (CNT) is
studied theoretically within a tight-binding model and the Green's function
partitioning technique. End-contacted metal/nanotube/metal systems are modelled
and next studied in the magnetic context, i.e. either with ferromagnetic
electrodes or at external magnetic fields. The former case shows that quite a
substantial giant magnetoresistance (GMR) effect occurs ($\pm 20%$) for
disorder-free CNTs. Anderson-disorder averaged GMR, in turn, is positive and
reduced down to several percent in the vicinity of the charge neutrality point.
At parallel magnetic fields, characteristic Aharonov-Bohm-type oscillations are
revealed with pronounced features due to a combined effect of:
length-to-perimeter ratio, unintentional electrode-induced doping, Zeeman
splitting, and energy-level broadening. In particular, a CNT is predicted to
lose its ability to serve as a magneto-electrical switch when its length and
perimeter become comparable. In case of perpendicular geometry, there are
conductance oscillations approaching asymptotically the upper theoretical limit
to the conductance, $4 e^2/h$. Moreover in the ballistic transport regime,
initially the conductance increases only slightly with the magnetic field or
remains nearly constant because spin up- and spin down-contributions to the
total magnetoresistance partially compensate each other.

###Dipolar interaction effects in the magnetic and magnetotransport properties of ordered nanoparticle arrays|D. Kechrakos,K. N. Trohidou###

Dipolar interaction effects in the magnetic and magnetotransport properties of ordered nanoparticle arrays. Assemblies of magnetic nanoparticles exhibit interesting physical properties
arising from the competition of intraparticle dynamics and interparticle
interactions. In ordered arrays of magnetic nanoparticles magnetostatic
interparticle interactions introduce collective dynamics acting competitively
to random anisotropy. Basic understanding, characterization and control of
dipolar interaction effects in arrays of magnetic nanoparticles is an issue of
central importance. To this end, numerical simulation techniques offer an
indispensable tool. We report on Monte Carlo studies of the magnetic hysteresis
and spin-dependent transport in thin films formed by ordered arrays of magnetic
nanoparticles. Emphasis is given to the modifications of the single-particle
behavior due to interparticle dipolar interactions as these arise in quantities
of experimental interest, such as, the magnetization, the susceptibility and
the magnetoresistance. We investigate the role of the structural parameters of
an array (interparticle separation, number of stacked monolayers) and the role
of the internal structure of the nanoparticles (single phase, core-shell).
Dipolar interactions are responsible for anisotropic magnetic behavior between
the in-plane and out-of-plane directions of the sample, which is reflected on
the investigated magnetic properties (magnetization, transverse susceptibility
and magnetoresistance) and the parameters of the array (remanent magnetization,
coercive field, and blocking temperature). Our numerical results are compared
to existing measurements on self-assembled arrays of Fe-based and Co
nanoparticles is made.

###An anomalous magnetic phase transition at 10 K in Nd7Rh3|Kausik Sengupta,E. V. Sampathkumaran###

An anomalous magnetic phase transition at 10 K in Nd7Rh3. The compound, Nd7Rh3, crystallizing in Th7Fe3-type hexagonal structure, has
been shown recently by us to exhibit a signature of magnetic phase-coexistence
phenomenon below 10 K after a field cycling, uncharacteristic of stoichiometric
intermetallic compounds, bearing a relevance to the trends in the field of
electronic phase-separation. In order to characterize this compound further, we
have carried out dc magnetic susceptibility (chi), electrical resistivity,
magnetoresistance and heat-capacity measurements as a function temperature (T=
1.8 to 300 K). The results reveal that this compound exhibits another unusual
finding at the 10K-transition in the sense that the plot of chi(T) shows a
sharp increase in the field-cooled cycle, whereas the zero-field-cooled curve
shows a downturn below the transition. In addition, the sign of
magnetoresistance is negative and the magnitude is large over a wide
temperature range in the vicinity of magnetic ordering temperature, with a
sharp variation at 10 K. The results indicate that the transition below 10 K is
first-order in its character.

###Peculiarities of the transport properties of InMnAs layers, produced by the laser deposition, in strong magnetic fields|V. V. Rylkov,A. S. Lagutin,B. A. Aronzon,V. V. Podolskii,V. P. Lesnikov,M. Goiran,J. Galibert,B. Raquet,J. Leotin###

Peculiarities of the transport properties of InMnAs layers, produced by the laser deposition, in strong magnetic fields. Magnetotransport properties of p-InMnAs layers are studied in pulsed magnetic
fields up to 30 T. Samples were prepared by the laser deposition and annealed
by ruby laser pulses. Well annealed samples show p-type conductivity while they
were n-type before the annealing. Surprisingly the anomalous Hall effect
resistance in paramagnetic state (T>40 K) and in strong magnetic fields (B > 20
T) appears to be greater than that in ferromagnetic state (T <= 40 K), while
the longitudinal resistance rises with the temperature decrease. The negative
magnetoresistance saturates in magnetic fields higher then 10T at T near 4 K
only, whereas the saturation fields of the anomalous Hall effect resistance are
much less (around 2 T at 30K). The total reduction of resistance exceeds 10
times in magnetic fields around of 10T. The obtained results are interpreted on
the base of the assumptions of the non-uniform distribution of Mn atoms acting
as acceptors, the local ferromagnetic transition and the percolation-like
character of the film conductivity, which prevailed under conditions of the
strong fluctuations of the exchange interaction. Characteristic scales of the
magneto-electric nonuniformity are estimated using analysis of the mesoscopic
fluctuations of the non-diagonal components of the magnetoresistivity tensor.

###Influence of Point-like Disorder on the Guiding of Vortices and the Hall Effect in a Washboard Planar Pinning Potential|Valerij A. Shklovskij,Oleksandr V. Dobrovolskiy###

Influence of Point-like Disorder on the Guiding of Vortices and the Hall Effect in a Washboard Planar Pinning Potential. Explicit current-dependent expressions for anisotropic longitudinal and
transverse nonlinear magnetoresistivities are represented and analyzed on the
basis of a Fokker-Planck approach for two-dimensional single-vortex dynamics in
a washboard pinning potential in the presence of point-like disorder. Graphical
analysis of the resistive responses is presented both in the current-angle
coordinates and in the rotating current scheme. The model describes nonlinear
anisotropy effects caused by the competition of point-like (isotropic) and
anisotropic pinning. Nonlinear guiding effects are discussed and the critical
current anisotropy is analyzed. Gradually increasing the magnitude of isotropic
pinning force this theory predicts a gradual decrease of the anisotropy of the
magnetoresistivities. The physics of transition from the new scaling relations
for anisotropic Hall resistance in the absence of point-like pins to the
well-known scaling relations for the point-like disorder is elucidated. This is
discussed in terms of a gradual isotropizaton of the guided vortex motion,
which is responsible for the existence in a washboard pinning potential of new
(with respect to magnetic field reversal) Hall voltages. It is shown that
whereas the Hall conductivity is not changed by pinning, the Hall resistivity
can change its sign in some current-angle range due to presence of the
competition between i- and a-pins.

###Peculiarities in the properties of some rare-earth compounds with orthorhombic structures|V. Lovchinov,A. Apostolov,D. Dimitrov,I. Radulov,Ph. Vanderbemden###

Peculiarities in the properties of some rare-earth compounds with orthorhombic structures. Rare-earth manganites are fascinating, because they display a wide variety of
fundamental properties from magnetism to ferroelectricity, from colossal
magnetoresistance to semi-metallicity, and because they can be used in a number
of important technological applications such as controlling a magnetic memory
by an electric field or vice versa, new types of attenuators or transducers
etc. In this paper, we present our investigation on monocrystal samples with an
orthorhombic structure, grown in two different space groups: D2h(16) for
La0.78Pb0.22MnO3 and Pr0.7Sr0.3MnO3 and D2h(9) for HoMn2O5 and TbMn2O5. The
doped perovskite manganites Ln1-x Ax MnO3 (where Ln is a rare-earth ion and A
is a divalent ion) from the group D2h(16), which crystallized in different
modifications of the perovskite structure, characterized by the parameter
deformation of the type c/&#8730;2<b<a. Many properties of these compounds
(especially the giant magnetoresistance GMR, being interesting for practical
applications) depend strongly on the carrier density, on the specific zone
structure, on the type and the quantity of dopants, on the defects of the
crystal and their magnetic structure, or on the applied magnetic fields.

###Influence of chemical and magnetic interface properties of Co-Fe-B / MgO / Co-Fe-B tunnel junctions on the annealing temperature dependence of the magnetoresistance|J. Schmalhorst,A. Thomas,G. Reiss,X. Kou,E. Arenholz###

Influence of chemical and magnetic interface properties of Co-Fe-B / MgO / Co-Fe-B tunnel junctions on the annealing temperature dependence of the magnetoresistance. The knowledge of chemical and magnetic conditions at the Co40Fe40B20 / MgO
interface is important to interpret the strong annealing temperature dependence
of tunnel magnetoresistance of Co-Fe-B / MgO / Co-Fe-B magnetic tunnel
junctions, which increases with annealing temperature from 20% after annealing
at 200C up to a maximum value of 112% after annealing at 350C. While the well
defined nearest neighbor ordering indicating crystallinity of the MgO barrier
does not change by the annealing, a small amount of interfacial Fe-O at the
lower Co-Fe-B / MgO interface is found in the as grown samples, which is
completely reduced after annealing at 275C. This is accompanied by a
simultaneous increase of the Fe magnetic moment and the tunnel
magnetoresistance. However, the TMR of the MgO based junctions increases
further for higher annealing temperature which can not be caused by Fe-O
reduction. The occurrence of an x-ray absorption near-edge structure above the
Fe and Co L-edges after annealing at 350C indicates the recrystallization of
the Co-Fe-B electrode. This is prerequisite for coherent tunneling and has been
suggested to be responsible for the further increase of the TMR above 275C.
Simultaneously, the B concentration in the Co-Fe-B decreases with increasing
annealing temperature, at least some of the B diffuses towards or into the MgO
barrier and forms a B2O3 oxide.

###Quantum interference of surface states in bismuth nanowires probed by the Aharonov-Bohm oscillatory behavior of the magnetoresistance|A. Nikolaeva,D. Gitsu,L. Konopko,M. J. Graf,T. E. Huber###

Quantum interference of surface states in bismuth nanowires probed by the Aharonov-Bohm oscillatory behavior of the magnetoresistance. We report the observation of a dependence of the low temperature resistance
of individual single-crystal bismuth nanowires on the Aharonov-Bohm phase of
the magnetic flux threading the wire. 55 and 75-nm wires were investigated in
magnetic fields of up to 14 T. For 55 nm nanowires, longitudinal
magnetoresistance periods of 0.8 and 1.6 T that were observed at magnetic
fields over 4 T are assigned to h/2e to h/e magnetic flux modulation. The same
modes of oscillation were observed in 75-nm wires. The observed effects are
consistent with models of the Bi surface where surface states give rise to a
significant population of charge carriers of high effective mass that form a
highly conducting tube around the nanowire. In the 55-nm nanowires, the Fermi
energy of the surface band is estimated to be 15 meV. An interpretation of the
magnetoresistance oscillations in terms of a subband structure in the surface
states band due to quantum interference in the tube is presented.

###Oxide spintronics|Manuel Bibes,Agnes Barthelemy###

Oxide spintronics. Concomitant with the development of metal-based spintronics in the late
1980's and 1990's, important advances were made on the growth of high-quality
oxide thin films and heterostructures. While this was at first motivated by the
discovery of high-temperature superconductivity in perovskite Cu oxides, this
technological breakthrough was soon applied to other transition metal oxides,
and notably mixed-valence manganites. The discovery of colossal
magnetoresistance in manganite films triggered an intense research activity on
these materials, but the first notable impact of magnetic oxides in the field
of spintronics was the use of such manganites as electrodes in magnetic tunnel
junctions, yielding tunnel magnetoresistance ratios one order of magnitude
larger than what had been obtained with transition metal electrodes. Since
then, the research on oxide spintronics has been intense with the latest
developments focused on diluted magnetic oxides and more recently on
multiferroics. In this paper, we will review the most important results on
oxide spintronics, emphasizing materials physics as well as spin-dependent
transport phenomena, and finally give some perspectives on how the flurry of
new magnetic oxides could be useful for next-generation spintronics devices.

###Diffusive and ballistic current spin-polarization in magnetron-sputtered L1o-ordered epitaxial FePt|K. M. Seemann,V. Baltz,M. MacKenzie,J. N. Chapman,B. J. Hickey,C. H. Marrows###

Diffusive and ballistic current spin-polarization in magnetron-sputtered L1o-ordered epitaxial FePt. We report on the structural, magnetic, and electron transport properties of a
L1o-ordered epitaxial iron-platinum alloy layer fabricated by
magnetron-sputtering on a MgO(001) substrate. The film studied displayed a long
range chemical order parameter of S~0.90, and hence has a very strong
perpendicular magnetic anisotropy. In the diffusive electron transport regime,
for temperatures ranging from 2 K to 258 K, we found hysteresis in the
magnetoresistance mainly due to electron scattering from magnetic domain walls.
At 2 K, we observed an overall domain wall magnetoresistance of about 0.5 %. By
evaluating the spin current asymmetry alpha = sigma_up / sigma_down, we were
able to estimate the diffusive spin current polarization. At all temperatures
ranging from 2 K to 258 K, we found a diffusive spin current polarization of >
80%. To study the ballistic transport regime, we have performed point-contact
Andreev-reflection measurements at 4.2 K. We obtained a value for the ballistic
current spin polarization of ~42% (which compares very well with that of a
polycrystalline thin film of elemental Fe). We attribute the discrepancy to a
difference in the characteristic scattering times for oppositely spin-polarized
electrons, such scattering times influencing the diffusive but not the
ballistic current spin polarization.

###Modelling colossal magnetoresistance manganites|T. V. Ramakrishnan###

Modelling colossal magnetoresistance manganites. I briefly survey here attempts to model the rich and strange behaviour of
colossal magnetoresistance manganites, after outlining some of the phenomena
observed in them, and describing the three relevant strong local interactions
of the e_g electrons (in two different orbital states at each site), namely
with Jahn-Teller phonon modes (strength g), with resident t_2g spins
(ferromagnetic Hund's rule coupling J_H) and amongst each other (the Mott
Hubbard correlation U) . A new two fluid model of nearly localized l polarons
and band (b) electrons for low energy behaviour emerges for large g; some of
its applications are mentioned here. I describe some results of strong coupling
U, J_H calculations in single site DMFT (Dynamical Mean Field Theory), and show
that in the wide orbital liquid regime many characteristic manganite phenomena
such as an insulating ferromagnetic ground state, thermal insulator metal
transition, colossal magnetoresistance (cmr), materials systematics and the
observed low effective carrier density can all be understood qualitatively and
quantitatively. We also discuss the two 'phase' coexistence frequently found in
these systems, and show that electrostatic coulomb interactions mute lb phase
separation into nanoscale electronic inhomogeneity with l regions and b
puddles. Finally, some problems of current interest as well as general ones
arising, eg polarons and the physics of large electron phonon coupling g in the
adiabatic regime, are mentioned.

###Point-contact search for antiferromagnetic giant magnetoresistance|Z. Wei,A. Sharma,J. Bass,M. Tsoi###

Point-contact search for antiferromagnetic giant magnetoresistance. We report the first measurements of effects of large current densities on
current-perpendicular-to-plane magnetoresistance (MR) of magnetic multilayers
containing two antiferromagnetic layers separated by a non-magnetic layer.
These measurements were intended to search for a recently predicted
antiferromagnetic giant magnetoresistance (AGMR) similar to GMR seen in
multilayers containing two ferromagnetic layers separated by a non-magnetic
layer. We report on MR measurements for current injected from point contacts
into sandwiches containing different combinations of layers of F = CoFe and AFM
= FeMn. In addition to: AFM/N/AFM, F/AFM/N/AFM, and F/AFM/N/AFM/F structures,
initial results led us to examine also AFM/F/N/AFM, F/AFM, and single F- and
AFM-layer structures. At low currents, no MR was observed in any samples, and
no MR was observed at any current densities in samples containing only AFMs.
Together, these results indicate that no AGMR is present in these samples. In
samples containing F-layers, high current densities sometimes produced a small
positive MR - largest resistance at high fields. For a given contact
resistance, this MR was usually larger for thicker F-layers, and for a given
current, it was usually larger for larger contact resistances (smaller
contacts). We tentatively attribute this positive MR to suppression at high
currents of spin accumulation induced around and within the F-layers.

###Impact of in-plane currents on magnetoresistance properties of an exchange-biased spin-valve with insulating antiferromagnetic layer|D. N. H. Nam,N. C. Thuan,L. V. Hong,N. X. Phuc,S. A. Wolf,N. V. Dai,Y. P. Lee###

Impact of in-plane currents on magnetoresistance properties of an exchange-biased spin-valve with insulating antiferromagnetic layer. The impact of in-plane alternating currents on the exchange bias, resistance,
and magnetoresistance of a CoFe/NiCoO/CoFe/Cu/CoFe spin-valve is studied. With
increasing current, the resistance is increased while the maximum
magnetoresistance ratio decreases. Noticeably, the reversal of the pinned layer
is systematically suppressed in both field sweeping directions. Since the NiCoO
oxide is a good insulator, it is expected that the ac current flows only in the
CoFe/Cu/CoFe top layers, thus ruling out any presence of spin-transfer torque
acting on the spins in the antiferromagnetic layer. Instead, our measurements
show clear evidences for the influence of Joule heating caused by the current.
Moreover, results from temperature-dependent measurements very much resemble
those of the current dependence, indicating that the effect of Joule heating
plays a major role in the current-in-plane spin-valve configurations. The
results also suggest that spin-transfer torques between ferromagnetic layers
might still exist and compete with the exchange bias at sufficiently high
currents.

###Cationic Ordering and Microstructural Effects in the Ferromagnetic Perovskite La0.5Ba0.5CoO3: Impact upon Magnetotransport Properties|Eeva Leena Rautama,Philippe Boullay,Asish K. Kundu,Vincent Caignaert,Valerie Pralong,Maarit Karppinen,Bernard Raveau###

Cationic Ordering and Microstructural Effects in the Ferromagnetic Perovskite La0.5Ba0.5CoO3: Impact upon Magnetotransport Properties. The synthesis and structural study of the stoichiometric perovskite
La0.5Ba0.5CoO3 have allowed three forms to be isolated. Besides the disordered
La0.5Ba0.5CoO3 and the perfectly ordered layered LaBaCo2O6, a third form called
nanoscale-ordered LaBaCo2O6, is obtained. As evidenced by transmission electron
microscopy investigations, the latter consists of 112-type 90 degree oriented
domains fitted into each other at a nanometer scale which induce large strains
and consequently local atomic scale lattice distortions. These three
ferromagnetic perovskites exhibit practically the same Tc (174-179 K), but
differently from the other phases, the nanoscale-ordered LaBaCo2O6 is a hard
ferromagnet, with Hc = 4.2 kOe, due to the strains which may pin domain walls,
preventing the reversal of the spins in a magnetic field. The magnetotransport
properties of these phases show that all of them exhibit a maximum intrinsic
magnetoresistance, close to 6-7 % around Tc under 70 kOe but that the ordered
phase exhibits a much higher tunnelling magnetoresistance effect at low
temperature of about 15 % against 4 % due to the grain boundary effects.

###Electron transport and thermoelectric properties of layered perovskite LaBaCo2O5.5|Asish K. Kundu,B. Raveau,V. Caignaert,E. -L. Rautama,V. Pralong###

Electron transport and thermoelectric properties of layered perovskite LaBaCo2O5.5. We have investigated the systematic transport properties of the layered
112-type cobaltite LaBaCo2O5.5 by means of electrical resistivity,
magnetoresistance, electroresistance and thermoelectric measurements in various
conditions. In order to understand the complex conduction mechanism of
LaBaCo2O5.5, the transport data have been analyzed using different theoretical
models. The system shows semiconductor-semiconductor like transition (TSC)
around 326K, corresponding to ferromagnetic transition and in the low
temperature region resistivity data follows the Motts variable range hopping
model. Interestingly, near and below the room temperature this compound depicts
significant change in electro- and magnetoresistance behavior, the latter one
is noteworthy near the magnetic phase boundary. The temperature dependence of
thermopower, S(T), exhibits p-type polaronic conductivity in the temperature
range of 60-320K and reaches a maximum value of 303 uV/K (at 120K). In the low
temperature AFM region, the unusual S(T) behavior, generally observed for the
cobaltite series LnBaCo2O5.5 (Ln = Rare Earth), is explained by the electron
magnon scattering mechanism as previously described for perovskite manganites.

###Magneto-transport properties governed by the antiferromagnetic fluctuations in heavy fermion superconductor CeIrIn$_{5}$|Y. Nakajima,H. Shishido,H. Nakai,T. Shibauchi,M. Hedo,Y. Uwatoko,T. Matsumoto,R. Settai,Y. Onuki,H. Kontani,Y. Matsuda###

Magneto-transport properties governed by the antiferromagnetic fluctuations in heavy fermion superconductor CeIrIn$_{5}$. In quasi-two dimensional Ce(Ir,Rh)In$_5$ system, it has been suggested that
the phase diagram contains two distinct domes with different heavy fermion
superconducting states. We here report the systematic pressure dependence of
the electron transport properties in the normal state of
CeRh$_{0.2}$Ir$_{0.8}$In$_{5}$ and CeIrIn$_{5}$, which locates in first and
second superconducting dome, respectively. We observed non-Fermi liquid
behavior at low temperatures in both compounds, including non-quadratic
$T-$dependence of the resistivity, large enhancement of the Hall coefficient,
and the violation of the Kohler's rule in the magnetoresistance. We show that
the cotangent of Hall angle $\cot \Theta_H$ varies as $T^2$, and the
magnetoresistance is quite well scaled by the Hall angle as $\Delta
\rho_{xx}/\rho_{xx}\propto \tan^2\Theta_H$. The observed transport anomalies
are common features of Ce$M$In$_{5}$ ($M$=Co, Rh, and Ir) and high-$T_c$
cuprates, suggesting that the anomalous transport properties observed in
CeIrIn$_{5}$ are mainly governed by the antiferromagnetic spin fluctuations,
not by the Ce-valence fluctuations which has been proposed to be the possible
origin for the second superconducting dome.

###Metamagnetic transition in EuFe$_2$As$_2$ single crystals|Shuai Jiang,Yongkang Luo,Zhi Ren,Zengwei Zhu,Cao Wang,Xiangfan Xu,Qian Tao,Guanghan Cao,Zhu'an Xu###

Metamagnetic transition in EuFe$_2$As$_2$ single crystals. We report the measurements of anisotropic magnetization and magnetoresistance
on single crystals of EuFe$_2$As$_2$, a parent compound of ferro-arsenide
high-temperature superconductor. Apart from the antiferromagnetic (AFM)
spin-density-wave transition at 186 K associated with Fe moments, the compound
undergoes another magnetic phase transition at 19 K due to AFM ordering of
Eu$^{2+}$ spins ($J=S=7/2$). The latter AFM state exhibits metamagnetic
transition under magnetic fields. Upon applying magnetic field with $H\parallel
c$ at 2 K, the magnetization increases linearly to 7.0 $\mu_{B}$/f.u. at
$\mu_{0}H$=1.7 T, then keeps at this value of saturated Eu$^{2+}$ moments under
higher fields. In the case of $H\parallel ab$, the magnetization increases
step-like to 6.6 $\mu_{B}$/f.u. with small magnetic hysteresis. A metamagnetic
phase was identified with the saturated moments of 4.4 $\mu_{B}$/f.u. The
metamagnetic transition accompanies with negative in-plane magnetoresistance,
reflecting the influence of Eu$^{2+}$ moments ordering on the electrical
conduction of FeAs layers. The results were explained in terms of
spin-reorientation and spin-reversal based on an $A$-type AFM structure for
Eu$^{2+}$ spins. The magnetic phase diagram has been established.

###The magnetic state of 1212-type ruthenocuprate in magnetocaloric and magnetoresistivity measurements of polycrystalline samples of RuSr2Gd1-xCexCu2O8 and Ru1-xSr2GdCu2O8|Piotr W Klamut,Tomasz Plackowski###

The magnetic state of 1212-type ruthenocuprate in magnetocaloric and magnetoresistivity measurements of polycrystalline samples of RuSr2Gd1-xCexCu2O8 and Ru1-xSr2GdCu2O8. The magnetic properties of superconducting Ru1-xSr2GdCu2O8 (x=0, 0.02) and
non-superconducting RuSr2Gd1-xCexCu2O8 (x=0.07, 0.1) were investigated by means
of magnetocaloric experiments with complementary magnetoresistivity and ac
susceptibility measurements. The isothermal magnetocaloric coefficient M_{T}(B)
assumes positive values in a broad range of temperatures (20K<T<231 K) and
magnetic fields (0<B<13 T), i.e. also in the magnetically ordered state
(T_{m}=132 K for RuSr2GdCu2O8 and T_{m}=150 K for RuSr2Gd0.93Ce0.07Cu2O8),
which indicates no gain in the system's magnetic entropy with increasing
magnetic field. The maximum in the M_{T}(B) dependence was observed for
RuSr2GdCu2O8 in a temperature vicinity of T_{m}, which indicates a
ferromagnetic character of the accessed magnetic correlations. No spontaneous
ferromagnetic order was revealed as the M_{T} assumes limiting zero values at
zero magnetic field for the whole range of investigated temperatures.
Temperature dependencies of the specific heat reveal the magnetic-field-induced
positive temperature shift of the anomaly associated with the magnetic
transition in the Ru spin system. The M_{T}(B) dependencies and the
magnetoresistivity data suggest that the magnetic system may be inhomogeneous.

###Perspectives in spintronics: magnetic resonant tunneling, spin-orbit coupling, and GaMnAs|C. Ertler,A. Matos-Abiague,M. Gmitra,M. Turek,J. Fabian###

Perspectives in spintronics: magnetic resonant tunneling, spin-orbit coupling, and GaMnAs. Spintronics has attracted wide attention by promising novel functionalities
derived from both the electron charge and spin. While branching into new areas
and creating new themes over the past years, the principal goals remain the
spin and magnetic control of the electrical properties, essentially the I-V
characteristics, and vice versa. There are great challenges ahead to meet these
goals. One challenge is to find niche applications for ferromagnetic
semiconductors, such as GaMnAs. Another is to develop further the science of
hybrid ferromagnetic metal/semiconductor heterostructures, as alternatives to
all-semiconductor room temperature spintronics. Here we present our
representative recent efiorts to address such challenges. We show how to make a
digital magnetoresistor by combining two magnetic resonant diodes, or how
introducing ferromagnetic semiconductors as active regions in resonant
tunneling diodes leads to novel efiects of digital magnetoresistance and of
magnetoelectric current oscillations. We also discuss the phenomenon of
tunneling anisotropic magnetoresistance in Fe/GaAs junctions by introducing the
concept of the spin-orbit coupling field, as an analog of such fields in
all-semiconductor junctions. Finally, we look at fundamental electronic and
optical properties of GaMnAs by employing reasonable tight-binding models to
study disorder efiects.

###Influence of the rare-earth element on the effects of the structural and magnetic phase transitions in CeFeAsO, PrFeAsO, and NdFeAsO|Michael A. McGuire,Raphael P. Hermann,Athena S. Sefat,Brian C. Sales,Rongying Jin,David Mandrus,Fernande Grandjean,Gary J. Long###

Influence of the rare-earth element on the effects of the structural and magnetic phase transitions in CeFeAsO, PrFeAsO, and NdFeAsO. We present results of transport and magnetic properties and heat capacity
measurements on polycrystalline CeFeAsO, PrFeAsO, and NdFeAsO. These materials
undergo structural phase transitions, spin density wave-like magnetic ordering
of small moments on iron, and antiferromagnetic ordering of rare earth moments.
The temperature dependence of the electrical resistivity, Seebeck coefficient,
thermal conductivity, Hall coefficient, and magnetoresistance are reported. The
magnetic behavior of the materials have been investigated using Mossbauer
spectroscopy and magnetization measurements. Transport and magnetic properties
are affected strongly by the structural and magnetic transitions, suggesting
significant changes in the band structure and/or carrier mobilities occur, and
phonon-phonon scattering is reduced upon transformation to the low temperature
structure. Results are compared to recent reports for LaFeAsO, and systematic
variations in properties as the identity of Ln is changed are observed and
discussed. As Ln progresses across the rare-earth series from La to Nd, an
increase in the hole contributions to Seebeck coefficient, and increases in
magnetoresistance and the Hall coefficient are observed in the low temperature
phase. Analysis of hyperfine fields at the iron nuclei determined from
Mossbauer spectra indicates that the moment on Fe in the orthorhombic phase is
nearly independent of the identity of Ln, in apparent contrast to reports of
powder neutron diffraction refinements.

###Stray-fields based features observed for low and high magnetic fields in Ni$_{80}$Fe$_{20}$-Nb-Ni$_{80}$Fe$_{20}$ trilayers|D. Stamopoulos,E. Manios,N. Papachristos,I. Aristomenopoulou###

Stray-fields based features observed for low and high magnetic fields in Ni$_{80}$Fe$_{20}$-Nb-Ni$_{80}$Fe$_{20}$ trilayers. We report on the influence of stray fields for both low and high magnetic
fields applied parallel to trilayers consisting of a low-T Nb interlayer and
two outer Ni Fe layers having in-plane anisotropy. At low magnetic fields these
trilayers exhibit a pronounced magnetoresistance effect. Its dynamic transport
behavior is presented through detailed I-V characteristics. More importantly,
the detailed evolution of the longitudinal and transverse magnetic components
of the trilayers is presented from close to well below T . These data clearly
show that below T and for low magnetic fields the transport properties of the
Nb interlayer are influenced by transverse stray-fields that motivate
subsequent transverse magnetic coupling of the outer Ni Fe layers. By
generalizing this experimental finding we propose that the generic prerequisite
for the occurrence of intense magnetoresistance effects in relative trilayers
is that the coercive fields of the outer ferromagnetic layers should almost
coincide since the simultaneous occurrence of magnetic domains all over their
surface will promote a transverse magnetic coupling mediated by the
accompanying transverse stray fields. Finally, the trilayer's upper-critical
field exhibits a pronounced suppression for low magnetic fields indicative of a
behavior, while for high values the conventional behavior is recovered. A
similar process is observed in both Nb-Ni Fe bilayers and Nb single layers.
However, significant qualitative and quantitative differences exist between
these samples. Based on a mechanism that is motivated by longitudinal
stray-fields existing exclusively in the high-field regime we propose a
possible interpretation for this experimental finding.

###Oxide layer boron leads to reduced symmetry spin filtering magnetic tunnel junctions|Derek A. Stewart###

Oxide layer boron leads to reduced symmetry spin filtering magnetic tunnel junctions. Experimental studies of FeCoB/MgO/FeCoB tunnel junctions indicate that boron
diffuses into MgO during rf-sputtering and forms polycrystalline Mg-B-O
regions. These tunnel junctions provide high tunneling magnetoresistance values
and low RA products. However the crystal structure of the Mg-B-O region remains
unknown. Using density functional techniques, I examine three potential Mg(B)
oxides including Mg$_{2}$B$_{2}$O$_{5}$ (monoclinic and triclinic) and the
orthorhombic mineral Kotoite (Mg$_3$B$_2$O$_6$). Kotoite is the best candidate
for formation in magnetic tunnel junctions. The (100) surface of Kotoite has a
good lattice match with (001) MgO and could template neighboring FeCo into bcc
layers during annealing. Complex band structure analysis of Kotoite shows that
the C$_{2v}$ $\tilde{\Delta}_1$ band has a much smaller imaginary k component
than the C$_{2v}$ $\tilde{\Delta}_4$ band. Based on symmetry analysis, the
majority spin $\Delta_1$ band in FeCo should couple well with the Kotoite
$\tilde{\Delta}_1$ band, while the minority FeCo $\Delta_5$ will couple
partially with the $\tilde{\Delta}_4$ band. Kotoite provides a new route to
high tunneling magnetoresistance based on spin filtering by a lower symmetry
oxide region.

###Magnetotransport in polycrystalline La$_{2/3}$Sr$_{1/3}$MnO$_{3}$ thin films of controlled granularity|P. K. Muduli,Gyanendra Singh,R. Sharma,R. C. Budhani###

Magnetotransport in polycrystalline La$_{2/3}$Sr$_{1/3}$MnO$_{3}$ thin films of controlled granularity. Polycrystalline La$_{2/3}$Sr$_{1/3}$MnO$_{3}$ (LSMO) thin films were
synthesized by pulsed laser ablation on single crystal (100) yttria-stabilized
zirconia (YSZ) substrates to investigate the mechanism of magneto-transport in
a granular manganite. Different degrees of granularity is achieved by using the
deposition temperature (T$_{D}$) of 700 and 800 $^{0}$C. Although no
significant change in magnetic order temperature (T$_C$) and saturation
magnetization is seen for these two types of films, the temperature and
magnetic field dependence of their resistivity ($\rho$(T, H)) is strikingly
dissimilar. While the $\rho$(T,H) of the 800 $^{0}$C film is comparable to that
of epitaxial samples, the lower growth temperature leads to a material which
undergoes insulator-to-metal transition at a temperature (T$_{P}$ $\approx$ 170
K) much lower than T$_C$. At T $\ll$ T$_P$, the resistivity is characterized by
a minimum followed by ln $\emph{T}$ divergence at still lower temperatures. The
high negative magnetoresistance ($\approx$ 20$%$) and ln $\emph{T}$ dependence
below the minimum are explained on the basis of Kondo-type scattering from
blocked Mn-spins in the intergranular material. Further, a striking feature of
the T$_D$ = 700 $^{0}$C film is its two orders of magnitude larger anisotropic
magnetoresistance (AMR) as compared to the AMR of epitaxial films. We attribute
it to unquenching of the orbital angular momentum of 3d electrons of Mn ions in
the intergranular region where crystal field is poorly defined.

###Anomalous transport properties of the halfmetallic ferromagnets Co2TiSi, Co2TiGe, and Co2TiSn|Joachim Barth,Gerhard H. Fecher,Benjamin Balke,Tanja Graf,Claudia Felser,Andrey Shkabko,Anke Weidenkaff###

Anomalous transport properties of the halfmetallic ferromagnets Co2TiSi, Co2TiGe, and Co2TiSn. In this work the theoretical and experimental investigations of Co2TiZ (Z =
Si, Ge, or Sn) compounds are reported. Half-metallic ferromagnetism is
predicted for all three compounds with only two bands crossing the Fermi energy
in the majority channel. The magnetic moments fulfill the Slater-Pauling rule
and the Curie temperatures are well above room temperature. All compounds show
a metallic like resistivity for low temperatures up to their Curie temperature,
above the resistivity changes to semiconducting like behavior. A large negative
magnetoresistance of 55% is observed for Co2TiSn at room temperature in an
applied magnetic field of 4T which is comparable to the large negative
magnetoresistances of the manganites. The Seebeck coefficients are negative for
all three compounds and reach their maximum values at their respective Curie
temperatures and stay almost constant up to 950 K. The highest value achieved
is -52muV/K m for Co2TiSn which is large for a metal. The combination of
half-metallicity and the constant large Seebeck coefficient over a wide
temperature range makes these compounds interesting materials for
thermoelectric applications and further spincaloric investigations.

###Measurement of spin memory lengths in PdNi and PdFe ferromagnetic alloys|H. Arham,T. S. Khaire,R. Loloee,W. P. Pratt, Jr.,Norman O. Birge###

Measurement of spin memory lengths in PdNi and PdFe ferromagnetic alloys. Weakly ferromagnetic alloys are being used by several groups in the study of
superconducting/ferromagnetic hybrid systems. Because spin-flip and spin-orbit
scattering in such alloys disrupt the penetration of pair correlations into the
ferromagnetic material, it is desirable to have a direct measurement of the
spin memory length in such alloys. We have measured the spin memory length at
4.2 K in sputtered Pd0.88Ni0.12 and Pd0.987Fe0.013 alloys using methods based
on current-perpendicular-to-plane giant magnetoresistance. The alloys are
incorporated into hybrid spin valves of various types, and the spin memory
length is determined by fits of the Valet-Fert spin-transport equations to data
of magnetoresistance vs. alloy thickness. For the case of PdNi alloy, the
resulting values of the spin memory length are lsf(PdNi) = 2.8 +/- 0.5 nm and
5.4 +/- 0.6 nm, depending on whether or not the PdNi is exchange biased by an
adjacent Permalloy layer. For PdFe, the spin memory length is somewhat longer,
lsf(PdFe) = 9.6 +/- 2 nm, consistent with earlier measurements indicating lower
spin-orbit scattering in that material. Unfortunately, even the longer spin
memory length in PdFe may not be long enough to facilitate observation of
spin-triplet superconducting correlations predicted to occur in
superconducting/ferromagnetic hybrid systems in the presence of magnetic
inhomogeneity.

###Dephasing time and magnetoresistance of two-dimensional electron gas in spatially modulated magnetic fields|A. S. Melnikov,S. V. Mironov,S. V. Sharov###

Dephasing time and magnetoresistance of two-dimensional electron gas in spatially modulated magnetic fields. The effect of a spatially modulated magnetic field on the weak localization
phenomenon in two-dimensional electron gas (2DEG) is studied. Both the
dephasing time $\tau_H$ and magnetoresistance are shown to reveal a nontrivial
behavior as functions of the characteristics of magnetic field profiles. The
magnetic field profiles with rather small spatial scales $d$ and modulation
amplitudes $H_0$ such that $H_0d^2\ll\hbar c/e$ are characterized by the
dephasing rate $\tau_H^{-1}\propto H_0^2d^2$. The increase in the flux value
$H_0d^2$ results in a crossover to a standard linear dependence
$\tau_H^{-1}\propto H_0$. Applying an external homogeneous magnetic field $H$
one can vary the local dephasing time in the system and affect the resulting
average transport characteristics. We have investigated the dependence of the
average resistance vs the field $H$ for some generic systems and predict a
possibility to observe a positive magnetoresistance at not too large $H$
values. The resulting dependence of the resistance vs $H$ should reveal a peak
at the field values $H\sim H_0$.

###Ferromagnetic Clusters in the Brownmillerite Bilayered Compounds Ca2.5-xLaxSr0.5GaMn2O8: An Approach to Achieve Layered Spintronics Materials|A. K. Bera,S. M. Yusuf###

Ferromagnetic Clusters in the Brownmillerite Bilayered Compounds Ca2.5-xLaxSr0.5GaMn2O8: An Approach to Achieve Layered Spintronics Materials. We report the effect of La-substitution on the magnetic and magnetotransport
properties of Brownmillerite-like bilayered compounds Ca2.5-xLaxSr0.5GaMn2O8 (x
= 0, 0.05, 0.075, and 0.1) by using dc-magnetization, resistivity and
magnetoresistance techniques. The Rietveld analysis of the room temperature
x-ray diffraction patterns confirms no observable change of average crystal
structure with the La-substitution. Both magnetic and magnetotransport
properties are found to be very sensitive to the La-substitution.
Interestingly, the La-substituted compounds show ferromagnetic-like behavior
(due to the occurrence of a double exchange mechanism) whereas, the parent
compound is an antiferromagnet (TN 150 K). All compounds show an insulating
behavior, in the measured temperature range of 100 - 300 K, with an overall
decrease in the resistivity with the substitution. A higher value of
magnetoresistance has been successfully achieved by the La-substitution. We
have proposed an electronic phase separation model, considering the formation
of ferromagnetic clusters in the antiferromagnetic matrix, to interpret the
observed magnetization and magnetotransport results for the La-substituted
samples. The present study demonstrates an approach to achieve new functional
materials, based on naturally occurring layered system like
Ca2.5-xLaxSr0.5GaMn2O8, for possible spintronics applications.

###Magnetoresistance and transistor-like behavior of double quantum dots connected to ferromagnetic and superconductor leads|E. C. Siqueira,G. G. Cabrera###

Magnetoresistance and transistor-like behavior of double quantum dots connected to ferromagnetic and superconductor leads. The electric current and the magnetoresistance effect are studied in a double
quantum-dot system, where one of the dots QDa is coupled to two ferromagnetic
electrodes (F1,F2), while the second QDb is connected to a superconductor S.
For energy scales within the superconductor gap, electric conduction is allowed
by Andreev reflection processes. Due to the presence of two ferromagnetic
leads, non-local crossed Andreev reflections are possible. We found that the
magnetoresistance sign can be changed by tuning the external potential applied
to the ferromagnets. In addition, it is possible to control the current of the
first ferromagnet (F1) through the potential applied to the second one (F2). We
have also included intradot interaction and gate voltages at each quantum dot
and analyzed their influence through a mean field approximation. The
interaction reduces the current amplitudes with respect to the non-interacting
case, but the switching effect still remains as a manifestation of quantum
coherence, in scales of the order of the superconductor coherence length.

###Structural Modification and Metamagnetic Anomaly in the Ordered State of CeOs2Al10|Y. Muro,J. Kajino,K. Umeo,K. Nishimoto,R. Tamura,T. Takabatake###

Structural Modification and Metamagnetic Anomaly in the Ordered State of CeOs2Al10. A caged compound CeOs2Al10, crystallizing in the orthorhombic YbFe2Al10-type
structure, undergoes a mysterious phase transition at T_0=29 K. We report the
results of electron diffraction, magnetization, and magnetoresistance for
single crystals. Superlattice reflections characterized by a wave vector q =
(0, -2/3, 2/3) observed at 15 K indicate a structural modification in the
ordered state. Activation-type behavior of the electrical resistivity along the
three principal axes below 50 K suggests gap opening in the conduction band.
The magnetic susceptibility \chi = M/B is highly anisotropic,
\chi_a>\chi_c>\chi_b, all of which sharply decrease on cooling below T_0.
Furthermore, a metamagnetic anomaly in the magnetization and a step in the
magnetoresistance occur at B=6-8 T only when the magnetic field is applied
parallel to the orthorhombic c axis. However, T_0 hardly changes under magnetic
fields up to 14 T, irrespective of the field direction. By using these data, we
present a B-T phase diagram and discuss several scenarios for the mysterious
transition.

###Structural, Magnetic and Electron Transport Properties of Ordered-Disordered Perovskite Cobaltites|Asish K. Kundu,B. Raveau###

Structural, Magnetic and Electron Transport Properties of Ordered-Disordered Perovskite Cobaltites. Rare earth perovskite cobaltites are increasingly recognized as materials of
importance due to rich physics and chemistry in their ordered-disordered
structure for the same composition. Apart from colossal magnetoresistance
effect, like manganites, the different forms of cobaltites exhibit interesting
phenomena including spin, charge and orbital ordering, electronic phase
separation, insulator-metal transition, large thermoelectric power at low
temperature. Moreover, the cobaltites which display colossal magnetoresistance
effect could be used as read heads in magnetic data storage and also in other
applications depending upon their particular properties. The A-site
ordereddisordered cobaltites exhibit ferromagnetism and metal-insulator
transitions as well as other properties depending on the composition, size of
A-site cations and various external factors such as pressure, temperature,
magnetic field etc. Ordered cobaltites, having a 112-type layered structure,
are also reported to have an effectively stronger electron coupling due to
layered A-site cationic ordering. Most importantly for the present article we
focus on La-Ba-Co-O based ordered-disordered perovskite phases, which exhibit
interesting magnetic and electron transport properties with ferromagnetic
transition, TC ~ 177K, and it being the first member of lanthanide series.
Zener double exchange mechanism considered to be crucial for understanding
basic physics of the ferromagneticmetallic phase, yet does not explain clearly
the insulating-type phase. In terms of electron transport the
ferromagnetic-metallic or insulating/semiconducting states have been discussed
in the present article with different types of hopping model.

###Creation and control of a two-dimensional electron liquid at the bare SrTiO3 surface|W. Meevasana,P. D. C. King,R. H. He,S. -K. Mo,M. Hashimoto,A. Tamai,P. Songsiriritthigul,F. Baumberger,Z. -X. Shen###

Creation and control of a two-dimensional electron liquid at the bare SrTiO3 surface. Many-body interactions in transition-metal oxides give rise to a wide range
of functional properties, such as high-temperature superconductivity, colossal
magnetoresistance, or multiferroicity. The seminal recent discovery of a
two-dimensional electron gas (2DEG) at the interface of the insulating oxides
LaAlO3 and SrTiO3 represents an important milestone towards exploiting such
properties in all-oxide devices. This conducting interface shows a number of
appealing properties, including a high electron mobility, superconductivity,
and large magnetoresistance and can be patterned on the few-nanometer length
scale. However, the microscopic origin of the interface 2DEG is poorly
understood. Here, we show that a similar 2DEG, with an electron density as
large as 8x10^13 cm^-2, can be formed at the bare SrTiO3 surface. Furthermore,
we find that the 2DEG density can be controlled through exposure of the surface
to intense ultraviolet (UV) light. Subsequent angle-resolved photoemission
spectroscopy (ARPES) measurements reveal an unusual coexistence of a light
quasiparticle mass and signatures of strong many-body interactions.

###Long electron dephasing length and disorder-induced spin-orbit coupling in indium tin oxide nanowires|Yao-Wen Hsu,Shao-Pin Chiu,An-Shao Lien,Juhn-Jong Lin###

Long electron dephasing length and disorder-induced spin-orbit coupling in indium tin oxide nanowires. We have measured the quantum-interference magnetoresistances in two single
indium tin oxide (ITO) nanowires between 0.25 and 40 K, by using the four-probe
configuration method. The magnetoresistances are compared with the
one-dimensional weak-(anti)localization theory to extract the electron
dephasing length $L_\phi$. We found, in a 60-nm diameter nanowire with a low
resistivity of $\rho$(10 K) = 185 $\mu \Omega$ cm, that $L_\phi$ is long,
increasing from 150 nm at 40 K to 520 nm at 0.25 K. Therefore, the nanowire
reveals strict one-dimensional weak-localization effect up to several tens of
degrees of Kelvin. In a second 72-nm diameter nanowire with a high resistivity
of $\rho$(10 K) = 1030 $\mu \Omega$ cm, the dephasing length is suppressed to
$L_\phi$(0.26 K) = 200 nm, and thus a crossover of the effective device
dimensionality from one to three occurs at about 12 K. In particular,
disorder-induced spin-orbit coupling is evident in the latter sample,
manifesting weak-antilocalization effect at temperatures below $\sim$ 4 K.
These observations demonstrate that versatile quantum-interference effects can
be realized in ITO nanowires by controlling differing levels of atomic defects
and impurities.

###Tunneling anisotropic magnetoresistance of NiFe/IrMn/MgO/Pt stack: An antiferromagnet based spin-valve|B. G. Park,J. Wunderlich,X. Marti,V. Holy,Y. Kurosaki,M. Yamada,H. Yamamoto,A. Nishide,J. Hayakawa,H. Takahashi,A. B. Shick,T. Jungwirth###

Tunneling anisotropic magnetoresistance of NiFe/IrMn/MgO/Pt stack: An antiferromagnet based spin-valve. Spin-valve is a microelectronic device in which high and low resistance
states are realized by utilizing both charge and spin of carriers. Spin-valve
structures used in modern hard drive read-heads and magnetic random access
memories comprise two ferromagnetic (FM) electrodes whose relative
magnetization orientations can be switched between parallel and antiparallel
configurations, yielding the desired giant or tunneling magnetoresistance
effect. In this paper we demonstrate >100$% spin-valve-like signal in a
NiFe/IrMn/MgO/Pt stack with an antiferromagnet (AFM) on one side and a
non-magnetic metal on the other side of the tunnel barrier. FM moments in NiFe
are reversed by external fields <50mT and the exchange-spring effect of NiFe on
IrMn induces rotation of AFM moments in IrMn which is detected by the measured
tunneling anisotropic magnetoresistance (TAMR). Our work demonstrates a
spintronic element whose transport characteristics are governed by an AFM. It
demonstrates that sensitivity to low magnetic fields can be combined with
large, spin-orbit coupling induced magneto-transport anisotropy using a single
magnetic electrode. The AFM-TAMR provides means to study magnetic
characteristics of AFM films by an electronic transport measurement.

###Magnetization and Magnetoresistance of CeRu2Al10 under High Magnetic Fields along c-Axis|Akihiro Kondo,Junfeng Wang,Koichi Kindo,Tomoaki Takesaka,Yuta Ogane,Yukihiro Kawamura,Takashi Nishioka,Daiki Tanaka,Hiroshi Tanida,Masafumi Sera###

Magnetization and Magnetoresistance of CeRu2Al10 under High Magnetic Fields along c-Axis. We have studied the magnetization and magnetoresistance of CeRu2Al10 in the
applied magnetic field H along the c-axis up to ~ 55 T. The magnetization M at
low temperatures shows an H-linear increase with a small slope of M/H than that
for H // a-axis up to ~ 55 T after showing a small anomaly at H ~ 4 T, which
indicates that the critical field to the paramagnetic phase H_c^p is higher
than 55 T for H // c-axis. The magnetization curves for H // a- and c-axes
below the antiferro magnetic (AFM) transition temperature T0 behave as if the
magnetic anisotropy in the AFM-ordered phase is small, although there exists a
large magnetic anisotropy in the paramagnetic phase, which favors the easy
magnetization axis along the a-axis. On the other hand, very recently,
Khalyavin et al. have reported that the AFM order where the magnetic moment is
parallel to the c-axis takes place below T0. These results indicate that the
AFM order in this compound is not a simple one. The longitudinal
magnetoresistance for H // c-axis at low temperatures shows no anomaly
originating from the phase transition, but shows oscillations below 4.2 K. This
oscillatory behavior below 4.2 K originates from the Shubnikov-de Haas
oscillations, from which the cross section of the Fermi surface normal to the
c-axis is estimated to be 1.0*10^14 cm-2, with no large effective mass. This is
the first direct evidence of the existence of the Fermi surface below T0.

###Can layered-structure effects be observed, if the Fermi surface is closed?|P. V. Gorskyi###

Can layered-structure effects be observed, if the Fermi surface is closed?. By analyzing the longitudinal conductivity in a quantizing magnetic field
directed perpendicularly to the crystal lattice layers, it has been
demonstrated that the layered-structure effects can be observed not only in
crystals with highly open Fermi surfaces, as was conventionally believed
earlier, but also in crystals with closed ones. The calculations were carried
out in the constant-relaxation-time approximation. In weak magnetic fields,
layered-structure effects manifest themselves as a phase retardation of
Shubnikov--de Haas oscillations and a certain increase of the relative
contribution made by the latter. In the range of high magnetic fields, there
exists an optimal interval, in which the layered-structure effects reveal
themselves in the form of a sharp non-monotonous dependence of conductivity on
the magnetic field. In addition, it has been shown that the layered-structure
effects result in a decrease of the proportionality factor between the
magnetoresistance and the magnetic induction in the longitudinal Kapitsa
effect. The longitudinal conductivity of layered crystals in ultra-quantum
magnetic fields has also been analyzed. It is shown that the following
dependences of the magnetoresistance on the magnetic field can be obtained,
depending on the model used for the filling of the single Landau subband and on
whether the longitudinal conductivity is considered to be of either the drift
or diffusion type: $\rho_{zz}\propto TB^{2}$,\ $\rho_{zz}\propto B^{3}$, and
$\rho_{zz}\propto B^{4}$.

###Magnetoresistance through a single molecule|Stefan Schmaus,Alexei Bagrets,Yasmine Nahas,Toyo K. Yamada,Annika Bork,Martin Bowen,Eric Beaurepaire,Ferdinand Evers,Wulf Wulfhekel###

Magnetoresistance through a single molecule. The use of single molecules to design electronic devices is an extremely
challenging and fundamentally different approach to further downsizing
electronic circuits. Two-terminal molecular devices such as diodes were first
predicted [1] and, more recently, measured experimentally [2]. The addition of
a gate then enabled the study of molecular transistors [3-5]. In general terms,
in order to increase data processing capabilities, one may not only consider
the electron's charge but also its spin [6,7]. This concept has been pioneered
in giant magnetoresistance (GMR) junctions that consist of thin metallic films
[8,9]. Spin transport across molecules, i.e. Molecular Spintronics remains,
however, a challenging endeavor. As an important first step in this field, we
have performed an experimental and theoretical study on spin transport across a
molecular GMR junction consisting of two ferromagnetic electrodes bridged by a
single hydrogen phthalocyanine (H2Pc) molecule. We observe that even though
H2Pc in itself is nonmagnetic, incorporating it into a molecular junction can
enhance the magnetoresistance by one order of magnitude to 52%.

###Stray field and superconducting surface spin valve effect in La$_{0.7}$Ca$_{0.3}$MnO$_3$/YBa$_2$Cu$_3$O$_{7-δ}$ bilayers|T. Hu,H. Xiao,C. Visani,J. Santamaria,C. C. Almasan###

Stray field and superconducting surface spin valve effect in La$_{0.7}$Ca$_{0.3}$MnO$_3$/YBa$_2$Cu$_3$O$_{7-δ}$ bilayers. Electronic transport and magnetization measurements were performed on
La$_{0.7}$Ca$_{0.3}$MnO$_3$/YBa$_2$Cu$_3$O$_{7-\delta}$ (LCMO/YBCO) bilayers
below the superconducting transition temperature in order to study the
interaction between magnetism and superconductivity. This study shows that a
substantial number of weakly pinned vortices are induced in the YBCO layer by
the large out-of-plane stray field in the domain walls. Their motion gives rise
to large dissipation peaks at the coercive field. The angular dependent
magnetoresistance (MR) data reveal the interaction between the stripe domain
structure present in the LCMO layer and the vortices and anti-vortices induced
in the YBCO layer by the out-of-plane stray field. In addition, this study
shows that a superconducting surface spin valve effect is present in these
bilayers as a result of the relative orientation between the magnetization at
the LCMO/YBCO interface and the magnetization in the interior of the LCMO layer
that can be tuned by the rotation of a small $H$. This latter finding will
facilitate the development of superconductive magnetoresistive memory devices.
These low-magnetic field MR data, furthermore, suggest that triplet
superconductivity is induced in the LCMO layer, which is consistent with recent
reports of triplet superconductivity in LCMO/YBCO/LCMO trilayers and LCMO/YBCO
bilayers.

###Fermi Surface of the Electron-doped Cuprate Superconductor Nd_{2-x}Ce_xCuO_{4} Probed by High-Field Magnetotransport|M. V. Kartsovnik,T. Helm,C. Putzke,F. Wolff-Fabris,I. Sheikin,S. Lepault,C. Proust,D. Vignolles,N. Bittner,W. Biberacher,A. Erb,J. Wosnitza,R. Gross###

Fermi Surface of the Electron-doped Cuprate Superconductor Nd_{2-x}Ce_xCuO_{4} Probed by High-Field Magnetotransport. We report on the study of the Fermi surface of the electron-doped cuprate
superconductor Nd$_{2-x}$Ce$_x$CuO$_{4}$ by measuring the interlayer
magnetoresistance as a function of the strength and orientation of the applied
magnetic field. We performed experiments in both steady and pulsed magnetic
fields on high-quality single crystals with Ce concentrations of $x=0.13$ to
0.17. In the overdoped regime of $x > 0.15$ we found both semiclassical
angle-dependent magnetoresistance oscillations (AMRO) and Shubnikov-de Haas
(SdH) oscillations. The combined AMRO and SdH data clearly show that the
appearance of fast SdH oscillations in strongly overdoped samples is caused by
magnetic breakdown. This observation provides clear evidence for a
reconstructed multiply-connected Fermi surface up to the very end of the
overdoped regime at $x\simeq 0.17$. The strength of the superlattice potential
responsible for the reconstructed Fermi surface is found to decrease with
increasing doping level and likely vanishes at the same carrier concentration
as superconductivity, suggesting a close relation between translational
symmetry breaking and superconducting pairing. A detailed analysis of the
high-resolution SdH data allowed us to determine the effective cyclotron mass
and Dingle temperature, as well as to estimate the magnetic breakdown field in
the overdoped regime.

###Comparative analysis of tunneling magnetoresistance in low-$T_c$ Nb/AlAlOx/Nb and high-$T_c$ Bi$_{2-y}$Pb$_y$Sr$_2$CaCu$_2$O$_{8+δ}$ intrinsic Josephson junctions|V. M. Krasnov,H. Motzkau,T. Golod,A. Rydh,S. O. Katterwe,A. B. Kulakov###

Comparative analysis of tunneling magnetoresistance in low-$T_c$ Nb/AlAlOx/Nb and high-$T_c$ Bi$_{2-y}$Pb$_y$Sr$_2$CaCu$_2$O$_{8+δ}$ intrinsic Josephson junctions. We perform a detailed comparison of magnetotunneling in conventional
low-$T_c$ Nb/AlAlOx/Nb junctions with that in slightly overdoped
Bi$_{2-y}$Pb$_y$Sr$_2$CaCu$_2$O$_{8+\delta}$ [Bi(Pb)-2212] intrinsic Josephson
junctions and with microscopic calculations. It is found that both types of
junctions behave in a qualitatively similar way. Both magnetic field and
temperature suppress superconductivity in the state-conserving manner. This
leads to the characteristic sign-change of tunneling magnetoresistance from the
negative at the sub-gap to the positive at the sum-gap bias. We derived
theoretically and verified experimentally scaling laws of magnetotunneling
characteristics and employ them for accurate extraction of the upper critical
field $H_{c2}$. For Nb an extended region of surface superconductivity at
$H_{c2}<H<H_{c3}$ is observed. The parameters of Bi(Pb)-2212 were obtained from
self-consistent analysis of magnetotunneling data at different levels of bias,
dissipation powers and for different mesa sizes, which precludes the influence
of self-heating. It is found that $H_{c2}(0)$ for Bi(Pb)-2212 is $\simeq 70$ T
and decreases significantly at $T\rightarrow T_c$. The amplitude of sub-gap
magnetoresistance is suppressed exponentially at $T>T_c/2$, but remains
negative, although very small, above $T_c$. This may indicate existence of an
extended fluctuation region, which, however, does not destroy the general
second-order type of the phase transition at $T_c$.

###Multiple photoexcitation of two-dimensional electron systems: bichromatic magnetoresistance oscillations revisited|Jesus Inarrea###

Multiple photoexcitation of two-dimensional electron systems: bichromatic magnetoresistance oscillations revisited. We analyze theoretically magnetoresistance of high mobility two-dimensional
electron systems being illuminated by multiple radiation sources. In
particular, we study the influence on the striking effect of microwave-induced
resistance oscillations. We consider moderate radiation intensities without
reaching the zero resistance states regime. We use the model of
radiation-driven Larmor orbits extended to several light sources. First, we
study the case of two different radiations polarized in the same direction with
different or equal frequencies. For both cases we find a regime of
superposition or interference of harmonic motions. When the frequencies are
different, we obtain a modulated magnetoresistance response with pulses and
beats. On the other hand, when the frequencies are the same, we find that the
final result will depend on the phase difference between both radiation fields
going from an enhanced response to a total collapse of oscillations, reaching
an outcome similar to darkness. Finally, we consider a multiple photoexcitation
case (three different frquencies) where we propose the two-dimensional electron
system as a potential nanoantenna device for microwaves.

###Alternating Superconductor--Insulator Transport Characteristics in a Quantum Vortex Chain|Yeshayahu Atzmon,Efrat Shimshoni###

Alternating Superconductor--Insulator Transport Characteristics in a Quantum Vortex Chain. Experimental studies of magnetoresistance in thin superconducting strips
subject to a perpendicular magnetic field B exhibit a multitude of transitions,
from superconductor to insulator and vice versa alternately. Motivated by this
observation, we study a theoretical model for the transport properties of a
ladder--like superconducting device close to a superconductor--insulator
transition. In this regime, strong quantum fluctuations dominate the dynamics
of the vortex chain forming along the device. Utilizing a mapping of the vortex
system at low energies to one-dimensional (1D) Fermions at a chemical potential
dictated by B, we find that a quantum phase transition of the Ising type occurs
at critical values of the vortex filling, from a superconducting phase near
integer filling to an insulator near 1/2-filling. The current--voltage (I-V)
characteristics of the weakly disordered device in the presence of a d.c.
current bias I is evaluated, and investigated as a function of B, I, the
temperature T and the disorder strength. In the Ohmic regime (I/e << T), the
resulting magnetoresistance R(B) exhibits oscillations similar to the
experimental observation. More generally, we find that the I-V characteristics
of the system manifests a dramatically distinct behavior in the superconducting
and insulating regimes.

###Magnetic Field Effects on Transport Properties of PtSn4|Eundeok Mun,Hyunjin Ko,Gordon J. Miller,German D. Samolyuk,Sergey L. Bud'ko,Paul. C. Canfield###

Magnetic Field Effects on Transport Properties of PtSn4. The anisotropic physical properties of single crystals of orthorhombic PtSn4
are reported for magnetic fields up to 140 kOe, applied parallel and
perpendicular to the crystallographic b-axis. The magnetic susceptibility has
an approximately temperature independent behavior and reveals an anisotropy
between ac-plane and b-axis. Clear de Haas-van Alphen oscillations in fields as
low as 5 kOe and at temperatures as high as 30 K were detected in magnetization
isotherms. The thermoelectric power and resistivity of PtSn4 show the strong
temperature and magnetic field dependencies. A change of the thermoelectric
power at H = 140 kOe is observed as high as ~ 50 mu-V/K. Single crystals of
PtSn4 exhibit very large transverse magnetoresistance of ~ 5x10^5% for the
ac-plane and of ~ 1.4x10^5% for the b-axis resistivity at 1.8 K and 140 kOe, as
well as pronounced Shubnikov-de Haas oscillations. The magnetoresistance of
PtSn4 appears to obey Kohler's rule in the temperature and field range
measured. The Hall resistivity shows a linear temperature dependence at high
temperatures followed by a sign reversal around 25 K which is consistent with
thermoelectric power measurements. The observed quantum oscillations and band
structure calculations indicate that PtSn4 has three dimensional Fermi
surfaces.

###Unconventional quantum oscillations in mesoscopic rings of spin-triplet superconductor Sr2RuO4|X. Cai,Y. A. Ying,N. E. Staley,Y. Xin,D. Fobes,T. J. Liu,Z. Q. Mao,Y. Liu###

Unconventional quantum oscillations in mesoscopic rings of spin-triplet superconductor Sr2RuO4. Odd-parity, spin-triplet superconductor Sr2RuO4 has been found to feature
exotic vortex physics including half-flux quanta trapped in a doubly connected
sample and the formation of vortex lattices at low fields. The consequences of
these vortex states on the low-temperature magnetoresistive behavior of
mesoscopic samples of Sr2RuO4 were investigated in this work using ring device
fabricated on mechanically exfoliated single crystals of Sr2RuO4 by
photolithography and focused ion beam. With the magnetic field applied
perpendicular to the in-plane direction, thin-wall rings of Sr2RuO4 were found
to exhibit pronounced quantum oscillations with a conventional period of the
full-flux quantum even though the unexpectedly large amplitude and the number
of oscillations suggest the observation of vortex-flow-dominated
magnetoresistance oscillations rather than a conventional Little-Parks effect.
For rings with a thick wall, two distinct periods of quantum oscillations were
found in high and low field regimes, respectively, which we argue to be
associated with the "lock-in" of a vortex lattice in these thick-wall rings. No
evidence for half-flux-quantum resistance oscillations were identified in any
sample measured so far without the presence of an in-plane field.

###Field-induced high coercive ferromagnetic state and magnetoresistance in the antiferromagnetically ordered compound Fe0.5TiS2|N. V. Baranov,E. M. Sherokalova,A. S. Volegov,A. V. Proshkin,N. V. Selezneva,E. P. Proskurina###

Field-induced high coercive ferromagnetic state and magnetoresistance in the antiferromagnetically ordered compound Fe0.5TiS2. The measurements of the magnetic susceptibility, magnetization, electrical
resistivity and magnetoresistance have been performed for the Fe intercalated
compound Fe0.5TiS2. According to X-ray diffraction measurements the Fe0.5TiS2
compound synthesized in the present work has a monoclinic crystal structure
(space group I12/m1) which results from the ordering of Fe ions and vacancies
between S-Ti-S tri-layres. The changes in the heat-treatment conditions at
temperatures below 1100 Celsius degrees do not lead to an order-disorder
transition within the subsystem of intercalated Fe ions. It has been shown that
this compound exhibits an antiferromagnetic (AF) ground state below the Neel
temperature TN = 140 K. Application of the magnetic field at T < TN induces a
metamagnetic phase transition to the ferromagnetic (F) state, which is
accompanied by the large magnetoresistance effect (up to 27 %). The
field-induced AF-F transition is found to be irreversible below ~ 100 K. The
magnetization reversal in the metastable F state at low temperatures is
accompanied by substantial hysteresis (~ 100 kOe) which is associated with the
Ising character of Fe ions.

###Long-range transfer of electron-phonon coupling in oxide superlattices|N. Driza,S. Blanco-Canosa,M. Bakr,S. Soltan,M. Khalid,L. Mustafa,K. Kawashima,G. Christiani,H. -U. Habermeier,G. Khaliullin,C. Ulrich,M. Le Tacon,B. Keimer###

Long-range transfer of electron-phonon coupling in oxide superlattices. The electron-phonon interaction is of central importance for the electrical
and thermal properties of solids, and its influence on superconductivity,
colossal magnetoresistance, and other many-body phenomena in
correlated-electron materials is currently the subject of intense research.
However, the non-local nature of the interactions between valence electrons and
lattice ions, often compounded by a plethora of vibrational modes, present
formidable challenges for attempts to experimentally control and theoretically
describe the physical properties of complex materials. Here we report a Raman
scattering study of the lattice dynamics in superlattices of the
high-temperature superconductor $\bf YBa_2 Cu_3 O_7$ and the
colossal-magnetoresistance compound $\bf La_{2/3}Ca_{1/3}MnO_{3}$ that suggests
a new approach to this problem. We find that a rotational mode of the MnO$_6$
octahedra in $\bf La_{2/3}Ca_{1/3}MnO_{3}$ experiences pronounced
superconductivity-induced lineshape anomalies, which scale linearly with the
thickness of the $\bf YBa_2 Cu_3 O_7$ layers over a remarkably long range of
several tens of nanometers. The transfer of the electron-phonon coupling
between superlattice layers can be understood as a consequence of long-range
Coulomb forces in conjunction with an orbital reconstruction at the interface.
The superlattice geometry thus provides new opportunities for controlled
modification of the electron-phonon interaction in complex materials.

###IrSr_2Sm_{1.15}Ce_{0.85}Cu_{2.175}O_{10}: A Novel Reentrant Spin-Glass Material|R. H. Colman,A. C. Mclaughlin###

IrSr_2Sm_{1.15}Ce_{0.85}Cu_{2.175}O_{10}: A Novel Reentrant Spin-Glass Material. A new iridium containing layered cuprate material,
IrSr_2Sm_{1.15}Ce_{0.85}Cu_{2.175}O_{10, has been synthesized by conventional
ambient-pressure solid-state techniques. The material's structure has been
fully characterized by Rietveld refinement of high resolution synchrotron X-ray
diffraction data; tilts and rotations of the IrO_6 octahedra are observed as a
result of a bond mismatch between in-plane Ir-O and Cu-O bond lengths.
DC-susceptibility measurements evidence a complex set of magnetic transitions
upon cooling that are characteristic of a reentrant spin-glass ground-state.
The glassy character of the lowest temperature, Tg=10 K, transition is further
confirmed by AC-susceptibility measurements, showing a characteristic frequency
dependence that can be well fitted by the Vogel-Fulcher law and yields a value
of \Delta_(T_f)/[T_f \Delta log({\omega})] =0.015(1), typical of dilute
magnetic systems. Electronic transport measurements show the material to be
semiconducting at all temperatures with no transition to a superconducting
state. Negative magnetoresistance is observed when the material is cooled below
25 K, and the magnitude of this magnetoresistance is seen to increase upon
cooling to a value of MR = -9 % at 8 K.

###Quantum phase slip phenomenon in superconducting nanowires with low-Ohmic environment|Janne Lehtinen,Konstantin Arutyunov###

Quantum phase slip phenomenon in superconducting nanowires with low-Ohmic environment. In a number of recent experiments it has been demonstrated that in
ultra-narrow superconducting channels quantum fluctuations of the order
parameter, alternatively called quantum phase slips, are responsible for the
finite resistance well below the critical temperature. The acceptable agreement
between those experiments and the models describing quantum fluctuations in
quasi-one-dimensional superconductors has been established. However the very
concept of the phase slip is justified when these fluctuations are the
relatively rare events, meaning that the effective resistance of the system
should be much smaller than the normal state equivalent. In this paper we study
the limit of the strong quantum fluctuations where the existing models are not
applicable. In particular case of ultra-thin titanium nanowires it is
demonstrated that below the expected critical temperature the resistance does
not demonstrate any trend towards the conventional for a superconductor
zero-resistivity state even at negligibly small measuring currents. Application
of a small magnetic field leads to an unusual negative magnetoresistance, which
becomes more pronounced at lower temperatures. The origin of the negative
magnetoresistance effect is not clear.

###Half-Metallic Ferromagnetism in the Heusler Compound Co$_2$FeSi revealed by Resistivity, Magnetoresistance, and Anomalous Hall Effect measurements|Dirk Bombor,Christian G. F. Blum,Oleg Volkonskiy,Steven Rodan,Sabine Wurmehl,Christian Hess,Bernd Büchner###

Half-Metallic Ferromagnetism in the Heusler Compound Co$_2$FeSi revealed by Resistivity, Magnetoresistance, and Anomalous Hall Effect measurements. We present electrical transport data for single-crystalline Co$_2$FeSi which
provide clear-cut evidence that this Heusler compound is truly a half-metallic
ferromagnet, i.e. it possesses perfect spin-polarization. More specifically,
the temperature dependence of $\rho$ is governed by electron scattering off
magnons which are thermally excited over a sizeable gap $\Delta\approx 100 K$
($\sim 9 meV$) separating the electronic majority states at the Fermi level
from the unoccupied minority states. As a consequence, electron-magnon
scattering is only relevant at $T\gtrsim\Delta$ but freezes out at lower
temperatures, i.e., the spin-polarization of the electrons at the Fermi level
remains practically perfect for $T\lesssim\Delta$. The gapped magnon population
has a decisive influence on the magnetoresistance and the anomalous Hall effect
(AHE): i) The magnetoresistance changes its sign at $T\sim 100 K$, ii) the
anomalous Hall coefficient is strongly temperature dependent at $T\gtrsim 100
K$ and compatible with Berry phase related and/or side-jump electronic
deflection, whereas it is practically temperature-independent at lower
temperatures.

###Magnetic phase transitions in single crystals of the chiral helimagnet Cr1/3NbS2|N. J. Ghimire,M. A. McGuire,D. S. Parker,B. Sipos,S. Tang,J. -Q. Yan,B. C. Sales,D. Mandrus###

Magnetic phase transitions in single crystals of the chiral helimagnet Cr1/3NbS2. The chiral helimagnet Cr1/3NbS2 has been investigated by magnetic, transport
and thermal properties measurements on single crystals and by first principles
electronic structure calculations. From the measured field and temperature
dependence of the magnetization for fields applied perpendicular to the c axis,
the magnetic phase diagram has been constructed in the vicinity of the phase
transitions. A transition from a paramagnetic to a magnetically ordered phase
occurs near 120 K. With increasing magnetic field and at temperatures below 120
K, this material undergoes transitions from a helimagnetic to a soliton-lattice
phase near 900 Oe, and then to a ferromagnetic phase near 1300 Oe. The
transitions are found to strongly affect the electrical transport. The
resistivity decreases sharply upon cooling near 120 K, and the spin
reorientation from the helimagnetic ground state to the commensurate
ferromagnetic state is evident in the magnetoresistance. At high fields a large
magnetoresistance (55 % at 140 kOe) is observed near the magnetic transition
temperature. Heat capacity and electronic structure calculations show the
density of states at the Fermi level is low in the magnetically ordered state.
Effects of spin fluctuations are likely important in understanding the behavior
of Cr1/3NbS2 near and above the magnetic ordering transitions.

###Hard X-ray photoelectron spectroscopy on buried, off-stoichiometric CoxMnyGez (x : z = 2 : 0.38) Heusler thin films|Siham Ouardi,Gerhard H. Fecher,Stanislav Chadov,Claudia Felser,Benjamin Balke,Xenia Kozina,Tomoyuki Taira,Masafumi Yamamoto###

Hard X-ray photoelectron spectroscopy on buried, off-stoichiometric CoxMnyGez (x : z = 2 : 0.38) Heusler thin films. Fully epitaxial magnetic tunnel junctions (MTJs) with off-stoichiometric
Co2-based Heusler alloy shows a intense dependency of the tunnel
magnetoresistance (TMR) on the Mn composition, demonstrating giant TMR ratios
of up to 1995% at 4.2 K for 1. This work reports on the electronic structure of
non-stoichiometric CoxMnyGez thin films with a fixed Co/Ge ratio of x : z = 2 :
0.38. The electronic structure was investigated by high energy, hard X-ray
photoelectron spectroscopy combined with first-principles calculations. The
high-resolution measurements of the valence band of the non-stoichiometric
CoxMnyGez films close to the Fermi energy indicate a shift of the spectral
weight compared to bulk Co2MnGe. This is in agreement with the changes in the
density of states predicted by the calculations. Furthermore it is shown that
the co-sputtering of Co2MnGe together with additional Mn is an appropriate
technique to adjust the stoichiometry of the CoxMnyGez film composition. The
resulting changes of the electronic structure within the valence band will
allow to tune the magnetoresistive characteristics of CoxMnyGez based tunnel
junctions as verified by the calculations and photoemission experiments.

###Magnetocaloric effect and Magnetothermopower in the room temperature ferromagnet Pr0.6Sr0.4MnO3|D. V. Maheshwar Repaka,T. S. Tripathi,M. Aparnadevi,R. Mahendiran###

Magnetocaloric effect and Magnetothermopower in the room temperature ferromagnet Pr0.6Sr0.4MnO3. We have investigated magnetization(M), magnetocaloric effect(MCE) and
magnetothermopower(MTEP) in polycrystalline Pr0.6Sr0.4MnO3, which shows a
second-order paramagnetic to ferromagnetic transition near room temperature (TC
= 305 K). However, field-cooled M(T) within the long range ferromagnetic state
shows an abrupt decrease at TS = 86 K for H < 3 T. The low temperature
transition is first-order in nature as suggested by the hysteresis in M(T) and
exothermic/endothermic peaks in differential thermal analysis for cooling and
warming cycles. The anomaly at TS is attributed to a structural transition from
orthorhombic to monoclinic phase. The magnetic entropy change is negative at TC
but changes to positive at TS. Thermopower (Q) is negative from 350 K to 20 K,
shows a rapid decrease at TC and a small cusp around TS in zero field. The MTEP
reaches a maximum value of 25% for deltaH = 3 T around TC which is much higher
than 15% dc magnetoresistance for the same field change. A linear relation
between MTEP and magnetoresistance, and between delta Sm and Delta Q are found
near TC. Further, ac magnetotransport in low dc magnetic fields (H less than or
equal to 1 kOe), critical analysis of the paramagnetic to ferromagnetic
transition and scaling behavior of the magnetic entropy change versus a reduced
temperature under different magnetic fields are also reported.

###Height correlation of rippled graphene and Lundeberg-Folk formula for magnetoresistance|Kazuyuki Genma,Makoto Katori###

Height correlation of rippled graphene and Lundeberg-Folk formula for magnetoresistance. Application of an in-plane magnetic field to rippled graphene will make the
system be a plane with randomly distributed vector potentials. Massless Dirac
fermions carrying charges on graphene are scattered by the vector potentials
and magnetoresistance is induced proportional to the square of amplitude of
in-plane magnetic field $B_{\parallel}^2$. Recently, Lundeberg and Folk
proposed a formula showing dependence of the magnetoresistance on carrier
density, in which the coefficient of $B_{\parallel}^2$ is given by a functional
of the height-correlation function $c(r)$ of ripples. In the present paper, we
give exact and explicit expressions of the coefficient for the two cases such
that $c(r)$ is (i) exponential and (ii) Gaussian. The results are given using
well-known special functions. Numerical fitting of our solutions to
experimental data were performed. It is shown that the experimental data are
well-described by the formula for the Gaussian height-correlation of ripples in
the whole region of carrier density. The standard deviation $Z$ of ripple
height and the correlation length $R$ of ripples are evaluated, which can be
compared with direct experimental measurements.

###Effects of Spin Polarization in the HgTe Quantum Well|M. V. Yakunin,A. V. Suslov,S. M. Podgornykh,S. A. Dvoretsky,N. N. Mikhailov###

Effects of Spin Polarization in the HgTe Quantum Well. Magnetoresistivity features connected with the spin level coincidences under
tilted fields in a $\Gamma_8$ conduction band of the HgTe quantum well were
found to align along straight trajectories in a $(B_\bot,B_{||})$ plane between
the field components perpendicular and parallel to the layer meaning a linear
spin polarization dependence on magnetic field. Among the trajectories is a
noticeable set of lines descending from a single point on the $B_{||}$ axis,
which is shown to yield a field of the full spin polarization of the electronic
system, in agreement with the data on the electron redistribution between spin
subbands obtained from Fourier transforms of oscillations along circle
trajectories in the $(B_\bot,B_{||})$ plane and with the point on the
magnetoresistivity under pure $B_{||}$ separating a complicated weak field
dependence from the monotonous one. The whole picture of coincidences is well
described by the isotropic $g$-factor although its value is twice as small as
that obtained from oscillations under pure perpendicular fields. The
discrepancy is attributed to different manifestations of spin polarization
phenomena in the coincidences and within the exchange enhanced spin gaps. In
the quantum Hall range of $B_\bot$, the spin polarization manifests in
anticrossings of magnetic levels, which were found to depend dramatically
nonmonotonously on $B_\bot$.

###Electrical and magnetic transport study on strain driven ferromagnetic insulating thin film of low doped manganite|Rajib Nath,Sudeshna Samanta,A. K. Raychaudhuri###

Electrical and magnetic transport study on strain driven ferromagnetic insulating thin film of low doped manganite. In this paper we have created a strain driven single crystal like
ferromagnetic insulating (FMI) state in a PLD grown thin film of low doped
LCMO(X = 0.15)on NGO(100) substrate and make a thorough study of strain effects
on the electric and magnetic transport of this film. We have studied and
compared the FMI state, ferromagnetic transition temperature (TC),
ferromagnetic insulating temperature (TFMI) and the resistivity of the film in
details with bulk single crystals of X=0.18 to 0.22 doping region. We have
found that TFMI and the localisation length of the carriers are increased and
there is also a decrease in the Coulomb gap. The magneto transport behavior of
the film also differs from the bulk single crystals and the magnetoresistance
of the sample is nearly 20 to 75% with the application of the applied field(0
to 10 T) and it falls up to 5 to 40% below a certain temperature and the TC of
the film increases to higher temperature with the increasing field. The film
also shows anisotropic magnetoresistance as large as 20% depending on applied
magnetic field direction.

###Aharonov-Bohm rings with strong spin-orbit interaction: the role of sample-specific properties|Fabrizio Nichele,Yashar Komijani,Szymon Hennel,Thomas Ihn,Klaus Ensslin,Christian Gerl,Werner Wegscheider,Dirk Reuter,Andreas D. Wieck###

Aharonov-Bohm rings with strong spin-orbit interaction: the role of sample-specific properties. We present low-temperature transport experiments on Aharonov-Bohm (AB) rings
fabricated from two-dimensional hole gases in p-type GaAs/AlGaAs
heterostructures. Highly visible h/e (up to 15%) and h/2e oscillations, present
for different gate voltages, prove the high quality of the fabricated devices.
Like in previous work, a clear beating pattern of the h/e and h/2e oscillations
is present in the magnetoresistance, producing split peaks in the Fourier
spectrum. The magnetoresistance evolution is presented and discussed as a
function of temperature and gate voltage. It is found that sample specific
properties have a pronounced influence on the observed behavior. For example,
the interference of different transverse modes or the interplay between h/e
oscillations and conductance fluctuations can produce the features mentioned
above. In previous work they have occasionally been interpreted as signatures
of spin-orbit interaction (SOI)-induced effects. In the light of these results,
the unambiguous identification of SOI-induced phase effects in AB rings remains
still an open and challenging experimental task.

###Scattering mechanisms in textured FeGe thin films: magnetoresistance and the anomalous Hall effect|N. A. Porter,J. C. Gartside,C. H. Marrows###

Scattering mechanisms in textured FeGe thin films: magnetoresistance and the anomalous Hall effect. A textured thin film of FeGe was grown by magnetron sputtering with a
helimagnetic ordering temperature of TN = 276 +/- 2 K. From 5 K to room
temperature a variety of scattering processes contribute towards the overall
longitudinal and Hall resistivities. These were studied by combining
magnetometry and magnetotransport measurements. The high-field
magnetoresistance (MR) displays three clear temperature regimes: Lorentz force
MR dominates at low temperatures, above T ~ 80 K scattering from spin-waves
predominates, whilst finally for T > 200 K scattering from fluctuating local
moments describes the MR. At low fields, where the magnetisation is no longer
technically saturated, we find a scaling of magnetoresistance with the square
of the magnetisation, indicating that the MR due to the unwinding of spins in
the conical phase arises from a similar mechanism to that in magnetic domain
walls. This MR is only visible up to a temperature of about 200 K. No features
can be found in the temperature or field dependence of the longitudinal
resistivity that belie the presence of the underlying magnetic phase transition
at TN: the marked changes in behavior are at much lower temperatures. The
anomalous Hall effect has a dramatic temperature dependence in which the
anomalous Hall resistivity scales quadratically with the longitudinal
resistivity: comparison with anomalous Hall scaling theory shows that our
system is in the intrinsic 'moderately dirty' regime. Lastly, we find evidence
of a topological Hall effect of size 100 ~Ohm cm.

###Quantum and Classical Magnetoresistance in Ambipolar Topological Insulator Transistors with Gate-tunable Bulk and Surface Conduction|Jifa Tian,Cuizu Chang,Helin Cao,Ke He,Xucun Ma,Qikun Xue,Yong P. Chen###

Quantum and Classical Magnetoresistance in Ambipolar Topological Insulator Transistors with Gate-tunable Bulk and Surface Conduction. Weak antilocalization (WAL) and linear magnetoresistance (LMR) are two most
commonly observed magnetoresistance (MR) phenomena in topological insulators
(TIs) and often attributed to the Dirac topological surface states (TSS).
However, ambiguities exist because these phenomena could also come from bulk
states (often carrying significant conduction in many TIs) and are observable
even in non-TI materials. Here, we demonstrate back-gated ambipolar TI
field-effect transistors in (Bi0.04Sb0.96)2Te3 thin films grown by molecular
beam epitaxy on SrTiO3(111), exhibiting a large carrier density tunability (by
nearly 2 orders of magnitude) and a metal-insulator transition in the bulk
(allowing effectively switching off the bulk conduction). Tuning the Fermi
level from bulk band to TSS strongly enhances both the WAL (increasing the
number of quantum coherent channels from one to peak around two) and LMR
(increasing its slope by up to 10 times). The SS-enhanced LMR is accompanied by
a strongly nonlinear Hall effect, suggesting important roles of charge
inhomogeneity (and a related classical LMR), although existing models of LMR
cannot capture all aspects of our data. Our systematic gate and temperature
dependent magnetotransport studies provide deeper insights into the nature of
both MR phenomena and reveal differences between bulk and TSS transport in TI
related materials.

###Effect of Eu magnetism on the electronic properties of the candidate Dirac material EuMnBi2|Andrew F. May,Michael A. McGuire,Brian C. Sales###

Effect of Eu magnetism on the electronic properties of the candidate Dirac material EuMnBi2. The crystal structure and physical properties of the layered material EuMnBi2
have been characterized by measurements on single crystals. EuMnBi2 is
isostructural with the Dirac material SrMnBi2 based on single crystal x-ray
diffraction, crystallizing in the I4/mmm space group (No. 139). Magnetic
susceptibility measurements suggest antiferromagnetic (AFM) ordering of moments
on divalent Eu ions near T_N=22K. For low fields, the ordered Eu moments are
aligned along the c-axis, and a spin-flop is observed near 5.4T at 5K. The
moment is not saturated in an applied field of 13T at 5K, which is uncommon for
compounds containing Eu^{2+}. The magnetic behavior suggests an anisotropy
enhancement via interaction between Eu and the Mn moments that appear to be
order antiferromagnetically below approximately 310K. A large increase in the
magnetoresistance is observed across the spin-flop, with absolute
magnetoresistance reaching approximately 650% at 5K and 12T. Hall effect
measurements reveal a decrease in the carrier density below T_N, which implies
a manipulation of the Fermi surface by magnetism on the sites surrounding the
Bi square nets that lead to Dirac cones in this family of materials.

###Evidence for topological surface states in metallic single crystals of Bi2Te3|Sourabh Barua,K. P. Rajeev,Anjan K. Gupta###

Evidence for topological surface states in metallic single crystals of Bi2Te3. Bi2Te3 is a member of a new class of materials known as topological
insulators which are supposed to be insulating in the bulk and conducting on
the surface. However experimental verification of the surface states has been
difficult in electrical transport measurements due to a conducting bulk. We
report low temperature magnetotransport measurements on single crystal samples
of Bi2Te3. We observe metallic character in our samples and large and linear
magnetoresistance from 1.5 K to 290 K with prominent Shubnikov-de Haas (SdH)
oscillations whose traces persist upto 20 K. Even though our samples are
metallic we are able to obtain a Berry phase close to the value of {\pi}
expected for Dirac fermions of the topological surface states. This indicates
that we might have obtained evidence for the topological surface states in
metallic single crystals of Bi2Te3. Other physical quantities obtained from the
analysis of the SdH oscillations are also in close agreement with those
reported for the topological surface states. The linear magnetoresistance
observed in our sample, which is considered as a signature of the Dirac
fermions of the surface states, lends further credence to the existence of
topological surface states.

###Anisotropic magnetoresistance in antiferromagnetic Sr2IrO4|Cheng Wang,Heidi Seinige,Gang Cao,Jian-Shi Zhou,John B. Goodenough,Maxim Tsoi###

Anisotropic magnetoresistance in antiferromagnetic Sr2IrO4. We report point-contact measurements of anisotropic magnetoresistance (AMR)
in a single crystal of antiferromagnetic (AFM) Mott insulator Sr2IrO4. The
point-contact technique is used here as a local probe of magnetotransport
properties on the nanoscale. The measurements at liquid nitrogen temperature
revealed negative magnetoresistances (MRs) (up to 28%) for modest magnetic
fields (250 mT) applied within the IrO2 a-b plane and electric currents flowing
perpendicular to the plane. The angular dependence of MR shows a crossover from
four-fold to two-fold symmetry in response to an increasing magnetic field with
angular variations in resistance from 1-14%. We tentatively attribute the
four-fold symmetry to the crystalline component of AMR and the field-induced
transition to the effects of applied field on the canting of AFM-coupled
moments in Sr2IrO4. The observed AMR is very large compared to the crystalline
AMRs in 3d transition metal alloys/oxides (0.1-0.5%) and can be associated with
the large spin-orbit interactions in this 5d oxide while the transition
provides evidence of correlations between electronic transport, magnetic order
and orbital states. The finding of this work opens an entirely new avenue to
not only gain a new insight into physics associated with spin-orbit coupling
but also better harness the power of spintronics in a more technically
favorable fashion.

###Kinetic properties of the two-dimensional conducting system formed by CrSi2 nanocrystallites in plane (111) of silicon|V. V. Andrievskii,Yu. F. Komnik,I. B. Berkutov,I. G. Mirzoiev,N. G. Galkin,D. L. Goroshko###

Kinetic properties of the two-dimensional conducting system formed by CrSi2 nanocrystallites in plane (111) of silicon. The behaviors of resistance, magnetoresistance (up to 5 T), and Hall
electromotive force (EMF) with varying temperature (from 10 to 300 K) and
measuring current (from 10 mkA to 10 mA) are studied for the Si sample with
CrSi2 nanocrystallites (NC) in the plane (111). The conduction in such
heterostructure proceeds in the plane with the NC and is the conduction of a
two-dimensional system of charge carriers that shows some unusual effects. The
temperature variation of resistivitymaybe treated as the result of the effect
of thermal activation but in this case it is characterized by a low activation
energy different in value in different temperature ranges. This suggests that
the mechanism of conduction is more complex. It is found that the conduction is
determined by the effect of temperature variation not only on carrier
concentration but also on its mobility. Magnetoresistivity is also of different
shape in different temperature ranges. All the above features are treated in
terms of the proposed model of electron hopping through the conduction band (or
hole hopping through the valence band). A peculiar effect of giant reduction in
resistivity with increasing the measuring current has been revealed. Discussed
are some possible factors responsible for this effect.

###Inter-planar coupling dependent magnetoresistivity in high purity layered metals|N. Kikugawa,P. Goswami,A. Kiswandhi,E. S. Choi,D. Graf,R. E. Baumbach,J. S. Brooks,K. Sugii,Y. Iida,M. Nishio,S. Uji,T. Terashima,P. M. C. Rourke,N. E. Hussey,H. Takatsu,S. Yonezawa,Y. Maeno,L. Balicas###

Inter-planar coupling dependent magnetoresistivity in high purity layered metals. The magnetic field-induced changes in the conductivity of metals are the
subject of intense interest, both for revealing new phenomena and as a valuable
tool for determining their Fermi surface. Here, we report a hitherto unobserved
magnetoresistive effect in ultra-clean layered metals, namely a negative
longitudinal magnetoresistance that is capable of overcoming their very
pronounced orbital one. This effect is correlated with the inter-layer coupling
disappearing for fields applied along the so-called Yamaji angles where the
inter-layer coupling vanishes. Therefore, it is intrinsically associated with
the Fermi points in the field-induced quasi-one-dimensional electronic
dispersion, implying that it results from the axial anomaly among these Fermi
points. In its original formulation, the anomaly is predicted to violate
separate number conservation laws for left- and right-handed chiral- (e.g.
Weyl) fermions. Its observation in PdCoO$_2$, PtCoO$_2$ and Sr$_2$RuO$_4$
suggests that the anomaly affects the transport of clean conductors,
particularly near the quantum limit.

###Defect-Induced Kondo Effect in graphene: Role of Localized State of $π$ Electrons|Taro Kanao,Hiroyasu Matsuura,Masao Ogata###

Defect-Induced Kondo Effect in graphene: Role of Localized State of $π$ Electrons. We discuss a role of the localized $\pi$ orbital, which exists around the
defect, on the defect-induced Kondo effect in graphene by a numerical
renormalization group study. We find that the localized $\pi$ orbital assists
this Kondo effect, and the Kondo temperature is sensitive to the broadening of
the localized $\pi$ orbital. Secondly, we focus on the negative
magnetoresistance of this Kondo effect. In the experimental result, it has been
shown that the negative magnetoresistance is ten times larger than the usual
Kondo effect. In order to clarify the mechanism of the "magnetic sensitive"
Kondo effect, as a first step, we study an orbital magnetic field dependence of
the localized $\pi$ orbital by a tight-binding model with a Peierls phase. We
find that as the magnetic field increases, the spectral width of the localized
$\pi$ orbital increases and the local DOS at the Fermi level decreases. Since
the Kondo temperature is strongly dependent of the broadening of the localized
$\pi$ orbital, it is expected that this Kondo effect is sensitive to the
orbital magnetic field as observed in the experiment.

###Extremely large magnetoresistance and ultrahigh mobility in the topological Weyl semimetal NbP|Chandra Shekhar,Ajaya K. Nayak,Yan Sun,Marcus Schmidt,Michael Nicklas,Inge Leermakers,Uli Zeitler,Zhongkai Liu,Yulin Chen,Walter Schnelle,Juri Grin,Claudia Felser,Binghai Yan###

Extremely large magnetoresistance and ultrahigh mobility in the topological Weyl semimetal NbP. Recent experiments have revealed spectacular transport properties of
conceptually simple semimetals. For example, normal semimetals (e.g. WTe$_2$)
have started a new trend to realize a large magnetoresistance, which is the
change of electrical resistance by an external magnetic field. Weyl semimetal
(WSM) is a topological semimetal with massless relativistic electrons as the
three-dimensional analogue of graphene and promises exotic transport properties
and surface states, which are different from those of the famous topological
insulators (TIs). In this letter, we choose to utilize NbP in magneto-transport
experiments because its band structure is on assembly of a WSM and a normal
semimetal. Such a combination in NbP indeed leads to the observation of
remarkable transport properties, an extremely large magnetoresistance of
850,000 % at 1.85 K (250 % at room temperature) in a magnetic field of 9 T
without any signs of saturation, and ultrahigh carrier mobility of
5$\times$10$^6$ cm$^2$ V$^{-1}$ s$^{-1}$ accompanied by strong Shubnikov-de
Hass (SdH) oscillations. NbP presents a unique example to consequent design the
functionality of materials by combining the topological and conventional
phases.

###Chiral anomaly and transport in Weyl metals|A. A. Burkov###

Chiral anomaly and transport in Weyl metals. We present an overview of our recent work on transport phenomena in Weyl
metals, which may be connected to their nontrivial topological properties,
particularly to chiral anomaly. We argue that there are two basic phenomena,
which are related to chiral anomaly in Weyl metals: Anomalous Hall Effect (AHE)
and Chiral Magnetic Effect (CME). While AHE is in principle present in any
ferromagnetic metal, we demonstrate that a magnetic Weyl metal is distinguished
from an ordinary ferromagnetic metal by the absence of the extrinsic and the
Fermi surface part of the intrinsic contributions to the AHE, as long as the
Fermi energy is sufficiently close to the Weyl nodes. The AHE in a Weyl metal
is thus shown to be a purely intrinsic, universal property, fully determined by
the location of the Weyl nodes in the first Brillouin zone. In other words, a
ferromagnetic Weyl metal may be thought of as the only example of a
ferromagnetic metal with a purely intrinsic AHE. We further develop a fully
microscopic theory of diffusive magnetotransport in Weyl metals. We derive
coupled diffusion equations for the total and axial (i.e. node-antisymmetric)
charge densities and show that chiral anomaly manifests as a
magnetic-field-induced coupling between them. We demonstrate that an
experimentally-observable consequence of CME in magnetotransport in Weyl metals
is a quadratic negative magnetoresistance, which will dominate all other
contributions to magnetoresistance under certain conditions and may be regarded
as a smoking-gun transport characteristic, unique to Weyl metals.

###Pressure-induced Lifshitz transition in black phosphorus|Z. J. Xiang,G. J. Ye,C. Shang,B. Lei,N. Z. Wang,K. S. Yang,D. Y. Liu,F. B. Meng,X. G. Luo,L. J. Zou,Z. Sun,Y. B. Zhang,X. H. Chen###

Pressure-induced Lifshitz transition in black phosphorus. In a semimetal, both electron and hole carriers contribute to the density of
states at the Fermi level. The small band overlaps and multi-band effects give
rise to many novel electronic properties, such as relativistic Dirac fermions
with linear dispersion, titanic magnetoresistance and unconventional
superconductivity. Black phosphorus has recently emerged as an exceptional
semiconductor with high carrier mobility and a direct, tunable bandgap. Of
particular importance is the search for exotic electronic states in black
phosphorus, which may amplify the material's potential beyond semiconductor
devices. Here we show that a moderate hydrostatic pressure effectively
suppresses the band gap and induces a Lifshitz transition from semiconductor to
semimetal in black phosphorus; a colossal magnetoresistance is observed in the
semimetallic phase. Quantum oscillations in high magnetic field reveal the
complex Fermi surface topology of the semimetallic black phosphorus. In
particular, a Dirac-like fermion emerges at around 1.2 GPa, which is
continuously tuned by external pressure. The observed semi-metallic behavior
greatly enriches black phosphorus's material property, and sets the stage for
the exploration of novel electronic states in this material. Moreover, these
interesting behaviors make phosphorene a good candidate for the realization of
a new two-dimensional relativistic electron system, other than graphene.

###Brillouin zone spin filtering mechanism of enhanced TMR and correlation effects in Co(0001)/h-BN/Co(0001) magnetic tunnel junction|Sergey V. Faleev,Stuart S. P. Parkin,Oleg N. Mryasov###

Brillouin zone spin filtering mechanism of enhanced TMR and correlation effects in Co(0001)/h-BN/Co(0001) magnetic tunnel junction. The 'Brillouin zone spin filtering' mechanism of enhanced tunneling
magnetoresistance (TMR) is described for magnetic tunnel junctions (MTJ) and
studied on an example of the MTJ with hcp Co electrodes and hexagonal BN (h-BN)
spacer. Our calculations based on local density approximation of density
functional theory (LDA-DFT) for Co(0001)/h-BN/Co(0001) MTJ predict high TMR in
this device due to Brillouin zone filtering mechanism. Owning to the specific
complex band structure of the h-BN the spin-dependent tunneling conductance of
the system is ultra-sensitive to small variations of the Fermi energy position
inside the BN band gap. Doping of the BN and, consequentially, changing the
Fermi energy position could lead to variation of the TMR by several orders of
magnitude. We show also that taking into account correlation effects on beyond
DFT level is required to accurately describe position of the Fermi level and
thus transport propertied of the system. Our study suggests that new MTJ based
on hcp Co-Pt or Co-Pd disordered alloy electrodes and p-doped hexagonal BN
spacer is a promising candidate for the spin-transfer torque magnetoresistive
random-access memory (STT-MRAM).

###Large spin Hall magnetoresistance and its correlation to the spin-orbit torque in W/CoFeB/MgO structures|Soonha Cho,Seung-heon Chris Baek,Younghun Jo,Byong-Guk Park###

Large spin Hall magnetoresistance and its correlation to the spin-orbit torque in W/CoFeB/MgO structures. The spin-orbit interaction in heavy metal/ferromagnet/oxide structures has
been extensively investigated because it can be employed in manipulation of the
magnetization direction by in-plane current. This implies the existence of an
inverse effect, in which the conductivity in such structures should depend on
the magnetization orientation. In this work, we report a systematic study of
the magnetoresistance (MR) of the W/CoFeB/MgO structures and its correlation to
the current-induced torque to the magnetization. We observe that the MR is
independent of the angle between magnetization and current direction, but is
determined by the relative magnetization orientation with respect to the spin
direction accumulated by spin Hall effect, which is the same symmetry of
so-called spin Hall magnetoresistance. The MR of ~1% in W/CoFeB/MgO samples is
considerably larger than those in other structures of Ta/CoFeB/MgO or
Pt/Co/AlOx, which indicates a larger spin Hall angle of W. Moreover, the
similar W thickness dependence of the MR and the current-induced magnetization
switching efficiency demonstrates that they share the same underlying physics,
which allows one to utilize the MR in non-magnet/ferromagnet structure in order
to understand closely related other spin-orbit coupling effects such as inverse
spin Hall effect, spin-orbit spin transfer torques, etc.

###Negative longitudinal magnetoresistance in Dirac and Weyl metals|A. A. Burkov###

Negative longitudinal magnetoresistance in Dirac and Weyl metals. It has recently been found that Dirac and Weyl metals are characterized by an
unusual weak-field longitudinal magnetoresistance: large, negative, and
quadratic in the magnetic field. This has been shown to arise from chiral
anomaly, i.e. nonconservation of the chiral charge in the presence of external
electric and magnetic fields, oriented collinearly. In this paper we report on
a theory of this effect in both Dirac and Weyl metals. We demonstrate that this
phenomenon contains two important ingredients. One is the
magnetic-field-induced coupling between the chiral and the total (or vector, in
relativistic field theory terminology) charge densities. This arises from the
Berry curvature and is present in principle whenever the Berry curvature is
nonzero, i.e. is nonspecific to Dirac and Weyl metals. This coupling, however,
leads to a large negative quadratic magnetoresistance only when the second
ingredient is present, namely when the chiral charge density is a nearly
conserved quantity with a long relaxation time. This property is specific to
Dirac and Weyl metals and is realized only when the Fermi energy is close to
Dirac or Weyl nodes, expressing an important low-energy property of these
materials, emergent chiral symmetry.

###Nonlocal Magnetoresistance Mediated by Spin Superfluidity|So Takei,Yaroslav Tserkovnyak###

Nonlocal Magnetoresistance Mediated by Spin Superfluidity. The electrical response of two diffusive metals is studied when they are
linked by a magnetic insulator hosting a topologically stable (superfluid) spin
current. We discuss how charge currents in the metals induce a spin
supercurrent state, which in turn generates a magnetoresistance that depends on
the topology of the electrical circuit. This magnetoresistance relies on phase
coherence over the entire magnet and gives direct evidence for spin
superfluidity. We show that driving the magnet with an ac current allows
coherent spin transport even in the presence of U(1)-breaking magnetic
anisotropy that can preclude dc superfluid transport. Spin transmission in the
ac regime shows a series of resonance peaks as a function of frequency. The
peak locations, heights, and widths can be used to extract static interfacial
properties, e.g., the spin-mixing conductance and effective spin Hall angle,
and to probe dynamic properties such as the spin-wave dispersion. Thus, ac
transport may provide a simpler route to realizing nonequilbrium coherent spin
transport and a useful way to characterize the magnetic system, serving as a
precursor to the realization of dc superfluid spin transport.

###Semimetal-semiconductor transition and giant linear magnetoresistances in three-dimensional Dirac semimetal Bi0.96Sb0.04 single crystals|Z. J. Yue,X. L. Wang,S. S. Yan###

Semimetal-semiconductor transition and giant linear magnetoresistances in three-dimensional Dirac semimetal Bi0.96Sb0.04 single crystals. Three-dimensional (3D) Dirac semimetals are new quantum materials and can be
viewed as 3D analogues of graphene. Many fascinating electronic properties have
been proposed and realized in 3D Dirac semimetals, which demonstrates their
potential applications in next generation quantum devices. Bismuth-antimony
Bi1-xSbx can be tuned from a topological insulator to a band insulator through
a quantum critical point at x ~ 4%, where 3D Dirac fermions appear. Here, we
report on a magnetotransport study of Bi1-xSbx at such a quantum critical
point. An unusual magnetic-field induced semimetal-semiconductor phase
transition was observed in the Bi0.96Sb0.04 single crystals. In a magnetic
field of 8 T, Bi0.96Sb0.04 single crystals show giant magnetoresistances of up
to 6000% at low-temperature, 5 K, and 300% at room-temperature, 300 K. The
observed magnetoresistances keep linear down to approximate zero-field when the
temperature is below 200 K. Our experimental results are not only interesting
for the fundamental physics of 3D Dirac semimetals, but also for potential
applications of 3D Dirac semimetals in magnetoelectronic devices.

###Microscopic theory of the residual surface resistivity of Rashba electrons|Juba Bouaziz,Samir Lounis,Stefan Blügel,Hiroshi Ishida###

Microscopic theory of the residual surface resistivity of Rashba electrons. A microscopic expression of the residual electrical resistivity tensor is
derived in linear response theory for Rashba electrons scattering at a magnetic
impurity with cylindrical or non-cylindrical potential. The behavior of the
longitudinal and transversal residual resistivity is computed for an Fe
impurity at the Au(111) surface. We studied the evolution of the resistivity
tensor elements as function of the Rashba spin-orbit strength and the
magnetization direction of the impurity. We found that the absolute values of
longitudinal resistivity reduces with increasing spin-orbit strength of the
substrate and that the scattering of the conduction electrons at magnetic
impurities with magnetic moments pointing in directions not perpendicular to
the surface plane produce a planar Hall effect and an anisotropic
magnetoresistance even if the impurity carries no spin-orbit interaction.
Functional forms are provided describing the anisotropy of the planar Hall
effect and the anisotropic magnetoresistance with respect to the direction of
the impurity moment. In the limit of no spin-orbit interaction and a
non-magnetic impurity of cylindrical symmetry, the expression of the residual
resistivity of a two-dimensional electron-gas has the same simplicity and form
as for the three-dimensional electron gas [J. Friedel, NuovoCimento Suppl. 7,
287 (1958)] and can also be expressed in terms of scattering phase shifts.

###Two-parameter scaling theory of the longitudinal magnetoconductivity in a Weyl metal phase: Chiral anomaly, weak disorder, and finite temperature|Kyoung-Min Kim,Dongwoo Shin,M. Sasaki,Heon-Jung Kim,Jeehoon Kim,Ki-Seok Kim###

Two-parameter scaling theory of the longitudinal magnetoconductivity in a Weyl metal phase: Chiral anomaly, weak disorder, and finite temperature. It is at the heart of modern condensed matter physics to investigate the role
of a topological structure in anomalous transport phenomena. In particular,
chiral anomaly turns out to be the underlying mechanism for the negative
longitudinal magnetoresistivity in a Weyl metal phase. Existence of a
dissipationless current channel causes enhancement of electric currents along
the direction of a pair of Weyl points or applied magnetic fields ($B$).
However, temperature ($T$) dependence of the negative longitudinal
magnetoresistivity has not been understood yet in the presence of disorder
scattering since it is not clear at all how to introduce effects of disorder
scattering into the "topological-in-origin" transport coefficient at finite
temperatures. The calculation based on the Kubo formula of the current-current
correlation function is simply not known for this anomalous transport
coefficient. Combining the renormalization group analysis with the Boltzmann
transport theory to encode the chiral anomaly, we reveal how disorder
scattering renormalizes the distance between a pair of Weyl points and such a
renormalization effect modifies the topological-in-origin transport coefficient
at finite temperatures. As a result, we find breakdown of $B/T$ scaling, given
by $B/T^{1 + \eta}$ with $0 < \eta < 1$. This breakdown may be regarded to be a
fingerprint of the interplay between disorder scattering and topological
structure in a Weyl metal phase.

###Magnetic behavior of Gd3Ru4Al12, a layered compound with a distorted Kagome net|Venkatesh Chandragiri,Kartik K Iyer,E. V. Sampathkumaran###

Magnetic behavior of Gd3Ru4Al12, a layered compound with a distorted Kagome net. The magnetic behavior of the compound, Gd3Ru4Al12, which has been reported to
crystallize in a hexagonal structure about two decades ago, had not been
investigated in the past literature despite interesting structural features
(that is, magnetic layers and triangles as well as Kagome-lattice features
favouring frustrated magnetism) characterizing this compound. We report here
the results of magnetization, heat-capacity, and magnetoresistance studies in
the temperature (T) range 1.8-300 K. The results establish that there is a
long-range magnetic order of an antiferromagnetic type below (TN= ) 18.5 K,
despite a much large value (about 80 K) of paramagnetic Curie temperature with
a positive sign characteristic of ferromagnetic interaction. We attribute this
to geometric frustration. The most interesting finding is that there is an
additional magnetic anomaly below about 55 K before the onset of long range
order in the magnetic susceptibility data. Concurrent with this observation,
the sign of isothermal entropy change remains positive above TN with a broad
peak above TN. This observation indicates the presence of ferromagnetic
clusters before the onset of long range magnetic order. Thus, this compound may
serve as an example for a situation in which magnetic frustration due to
geometrical reasons is faced by competition with such precursor effects. There
is also a reversal of the sign of entropy-change in the curves for lower final
fields (for H less than 30 kOe) on entering into magnetically ordered state
consistent with the entrance into antiferromagnetic state. The
magnetoresistance behavior is consistent with above conclusions.

###Magnetoresistance of vertical Co-graphene-NiFe junctions controlled by charge transfer and proximity-induced spin splitting in graphene|P. U. Asshoff,J. L. Sambricio,A. P. Rooney,S. Slizovskiy,A. Mishchenko,A. M. Rakowski,E. W. Hill,A. K. Geim,S. J. Haigh,V. I. Fal'ko,I. J. Vera-Marun,I. V. Grigorieva###

Magnetoresistance of vertical Co-graphene-NiFe junctions controlled by charge transfer and proximity-induced spin splitting in graphene. Graphene is hailed as an ideal material for spintronics due to weak intrinsic
spin-orbit interaction that facilitates lateral spin transport and tunability
of its electronic properties, including a possibility to induce magnetism in
graphene. Another promising application of graphene is related to its use as a
spacer separating ferromagnetic metals (FMs) in vertical magnetoresistive
devices, the most prominent class of spintronic devices widely used as magnetic
sensors. In particular, few-layer graphene was predicted to act as a perfect
spin filter. Here we show that the role of graphene in such devices (at least
in the absence of epitaxial alignment between graphene and the FMs) is
different and determined by proximity-induced spin splitting and charge
transfer with adjacent ferromagnetic metals, making graphene a weak FM
electrode rather than a spin filter. To this end, we report observations of
magnetoresistance (MR) in vertical Co-graphene-NiFe junctions with 1 to 4
graphene layers separating the ferromagnets, and demonstrate that the
dependence of the MR sign on the number of layers and its inversion at
relatively small bias voltages is consistent with spin transport between weakly
doped and differently spin-polarized layers of graphene. The proposed
interpretation is supported by the observation of an MR sign reversal in biased
Co-graphene-hBN-NiFe devices and by comprehensive structural characterization.
Our results suggest a new architecture for vertical devices with electrically
controlled MR.

###Field induced topological phase transition from a three-dimensional Weyl semimetal to a two-dimensional massive Dirac metal in ZrTe5|Guolin Zheng,Xiangde Zhu,Yequn Liu,Jianwei Lu,Wei Ning,Hongwei Zhang,Wenshuai Gao,Yuyan Han,Jiyong Yang,Haifeng Du,Kun Yang,Yuheng Zhang,Mingliang Tian###

Field induced topological phase transition from a three-dimensional Weyl semimetal to a two-dimensional massive Dirac metal in ZrTe5. Symmetry protected Dirac semimetals can be transformed into Weyl semimetals
by breaking the protecting symmetry, leading to many exotic quantum phenomena
such as chiral anomaly and anomalous Hall effect. Here we show that, due to the
large Zeeman g factor and small band width along b-axis in Dirac semimetal
ZrTe5, a magnetic field of about 8 T along b-axis direction may annihilate the
Weyl points and open up a two-dimensional (2D) Dirac mass gap, when the Zeeman
splitting exceeds the band width along b-axis. This is manifested by a sharp
drop of magnetoresistance (MR) above 8 T, which is probably due to additional
carriers induced by the orbital splitting of the zeroth Landau level associated
with the 2D Dirac point, which is descendant of the original Weyl points.
Further evidence of the additional carriers is provided by the Hall effect and
different anisotropic magnetoresistance (AMR) in low and high field regions.
Our experiment reveals a probable topological quantum phase transition of field
induced Weyl points annihilation in Dirac semimetal ZrTe5 and gives an
alternative explanation for the drop of MR at high field.

###Magnetotransport properties of the type II Weyl semimetal candidate Ta3S2|D. Chen,L. X. Zhao,J. B. He,H. Liang,S. Zhang,C. H. Li,L. Shan,C. Ren,S. C. Wang,Z. A. Ren,G. F. Chen###

Magnetotransport properties of the type II Weyl semimetal candidate Ta3S2. We have investigated the magnetoresistance (MR) and Hall resistivity
properties of the single crystals of tantalum sulfide, Ta3S2, which was
recently predicted to be a new type II Weyl semimetal. Large MR (up to ~8000%
at 2 K and 16 T), field-induced metal-insulator-like transition and nonlinear
Hall resistivity are observed at low temperatures. The large MR shows a strong
dependence on the field orientation, leading to a giant anisotropic
magnetoresistance (AMR) effect. For the field applied along the b-axis (B//b),
MR exhibits quadratic field dependence at low fields and tends towards
saturation at high fields; while for B//a, MR presents quadratic field
dependence at low fields and becomes linear at high fields without any trend
towards saturation. The analysis of the Hall resistivity data indicates the
coexistence of a large number of electrons with low mobility and a small number
of holes with high mobility. Shubnikov-de Haas (SdH) oscillation analysis
reveals three fundamental frequencies originated from the three-dimensional
(3D) Fermi surface (FS) pockets. We find that the semi-classical multiband
model is sufficient to account for the experimentally observed MR in Ta3S2.

###The Spin Nernst effect in Tungsten|Peng Sheng,Yuya Sakuraba,Yong-Chang Lau,Saburo Takahashi,Seiji Mitani,Masamitsu Hayashi###

The Spin Nernst effect in Tungsten. The spin Hall effect allows generation of spin current when charge current is
passed along materials with large spin orbit coupling. It has been recently
predicted that heat current in a non-magnetic metal can be converted into spin
current via a process referred to as the spin Nernst effect. Here we report the
observation of the spin Nernst effect in W. In W/CoFeB/MgO heterostructures, we
find changes in the longitudinal and transverse voltages with magnetic field
when temperature gradient is applied across the film. The field-dependence of
the voltage resembles that of the spin Hall magnetoresistance. A comparison of
the temperature gradient induced voltage and the spin Hall magnetoresistance
allows direct estimation of the spin Nernst angle. We find the spin Nernst
angle of W to be similar in magnitude but opposite in sign with its spin Hall
angle. Interestingly, under an open circuit condition, such sign difference
results in spin current generation larger than otherwise. These results
highlight the distinct characteristics of the spin Nernst and spin Hall
effects, providing pathways to explore materials with unique band structures
that may generate large spin current with high efficiency.

###Different approaches to generate matching effects using arrays in contact with superconducting films|J. del Valle,A. Gomez,J. Luis- Hita,V. Rollano,E. M. Gonzalez,J. L. Vicent###

Different approaches to generate matching effects using arrays in contact with superconducting films. Superconducting films in contact with non-superconducting regular arrays can
exhibit commensurability effects between the vortex lattice and the unit cell
of the pinning array. These matching effects yield a slowdown of the vortex
flow and the corresponding dissipation decrease. The superconducting samples
are Nb films grown on Si substrates. We have studied these matching effects
with the array on top, embedded or threading the Nb superconducting films and
using different materials (Si, Cu, Ni, Py dots and dots fabricated with Co/Pd
multilayers). These hybrids allow studying the contribution of different
pinning potentials to the matching effects. The main findings are: i) Periodic
roughness induced in the superconducting film is enough to generate resistivity
minima; ii) A minor effect is achieved by magnetic pinning from periodic
magnetic field potentials obtained by dots with out of plane magnetization
grown on top of the superconducting film, iii) In the case of array of magnetic
dots embedded in the films vortex flow probes the magnetic state; i.e.
magnetoresistance measurements detect the magnetic state of very small
nanomagnets. In addition, we have studied the role played by the local order in
the commensurability effects. This was attained using an array that mimics a
smectic crystal. We have found that preserving the local order is crucial. If
the local order is not retained the magnetoresistance minima vanish.

###Weiss oscillations and particle-hole symmetry at the half-filled Landau level|Alfred K. C. Cheung,S. Raghu,Michael Mulligan###

Weiss oscillations and particle-hole symmetry at the half-filled Landau level. Particle-hole symmetry in the lowest Landau level of the two-dimensional
electron gas requires the electrical Hall conductivity to equal $\pm e^2/2h$ at
half-filling. We study the consequences of weakly broken particle-hole symmetry
for magnetoresistance oscillations about half-filling in the presence of an
applied periodic one-dimensional electrostatic potential using the Dirac
composite fermion theory proposed by Son. At fixed electron density, the
oscillation minima are asymmetrically biased towards higher magnetic fields,
while at fixed magnetic field, the oscillations occur symmetrically as the
electron density is varied about half-filling. We find an approximate "sum
rule" obeyed for all pairs of oscillation minima that can be tested in
experiment. The locations of the magnetoresistance oscillation minima for the
composite fermion theory of Halperin, Lee, and Read (HLR) and its particle-hole
conjugate agree exactly. Within the current experimental resolution, the
locations of the oscillation minima produced by the Dirac composite fermion
coincide with those of HLR. These results may indicate that all three composite
fermion theories describe the same long wavelength physics.

###Microscopic theory for radiation-induced Zero-Resistance States in 2D electron systems: Franck-Condon blockade|Jesus Inarrea###

Microscopic theory for radiation-induced Zero-Resistance States in 2D electron systems: Franck-Condon blockade. We present a microscopic model on radiation-induced zero resistance states
according to a novel approach: Franck-Condon physics and blockade. Zero
resistance states rise up from radiation-induced magnetoresistance oscillations
when the light intensity is strong enough. The theory starts off with the {\it
radiation-driven electron orbit model} that proposes an interplay of the
swinging nature of the radiation-driven Landau states and the presence of
charged impurity scattering. When the intensity of radiation is high enough it
turns out that the driven-Landau states (vibrational states) involved in the
scattering process are spatially far from each other and the corresponding
electron wave functions do not longer overlap. As a result, it takes place a
drastic suppression of the scattering probability and then current and
magnetoresistance exponentially drop. Finally zero resistance states rise up.
This is an application to magnetotransport in two dimensional electron systems
of the Franck-Condon blockade, based on the Franck-Condon physics which in turn
stems from molecular vibrational spectroscopy.

###Millimeter-scale layered MoSe2 grown on sapphire and evidence for negative magnetoresistance|M. T. Dau,C. Vergnaud,A. Marty,F. Rortais,C. Beigné,H. Boukari,E. Bellet-Amalric,V. Guigoz,O. Renault,C. Alvarez,H. Okuno,P. Pochet,M. Jamet###

Millimeter-scale layered MoSe2 grown on sapphire and evidence for negative magnetoresistance. Molecular beam epitaxy technique has been used to deposit a single layer and
a bilayer of MoSe 2 on sapphire. Extensive characterizations including in-situ
and ex-situ measurements show that the layered MoSe 2 grows in a scalable
manner on the substrate and reveals characteristics of a stoichiometric
2H-phase. The layered MoSe 2 exhibits polycrystalline features with domains
separated by defects and boundaries. Temperature and magnetic field dependent
resistivity measurements unveil a carrier hopping character described within
two-dimensional variable range hopping mechanism. Moreover, a negative
magnetoresistance was observed, stressing a fascinating feature of the charge
transport under the application of a magnetic field in the layered MoSe 2
system. This negative magnetoresistance observed at millimeter-scale is similar
to that observed recently at room temperature inWS2 flakes at a micrometer
scale [Zhang et al., Appl. Phys. Lett. 108, 153114 (2016)]. This scalability
highlights the fact that the underlying physical mechanism is intrinsic to
these two-dimensional materials and occurs at very short scale.

###Gate Tunable Magneto-resistance of Ultra-Thin WTe2 Devices|Xin Liu,Zhiran Zhang,Chaoyi Cai,Shibing Tian,Satya Kushwaha,Hong Lu,Takashi Taniguchi,Kenji Watanabe,Robert J. Cava,Shuang Jia,Jian-Hao Chen###

Gate Tunable Magneto-resistance of Ultra-Thin WTe2 Devices. In this work, the magneto-resistance (MR) of ultra-thin WTe2/BN
heterostructures far away from electron-hole equilibrium is measured. The
change of MR of such devices is found to be determined largely by a single
tunable parameter, i.e. the amount of imbalance between electrons and holes. We
also found that the magnetoresistive behavior of ultra-thin WTe2 devices is
well-captured by a two-fluid model. According to the model, the change of MR
could be as large as 400,000%, the largest potential change of MR among all
materials known, if the ultra-thin samples are tuned to neutrality when
preserving the mobility of 167,000 cm2V-1s-1 observed in bulk samples. Our
findings show the prospects of ultra-thin WTe2 as a variable magnetoresistance
material in future applications such as magnetic field sensors, information
storage and extraction devices, and galvanic isolators. The results also
provide important insight into the electronic structure and the origin of the
large MR in ultra-thin WTe2 samples.

###Electric-field-induced extremely large change in resistance in graphene ferromagnets|Yu Song###

Electric-field-induced extremely large change in resistance in graphene ferromagnets. A colossal magnetoresistance ($\sim 100\times10^3\%$) and an extremely large
magnetoresistance ($\sim 1\times10^6\%$) have been previously explored in
manganite perovskites and Dirac materials, respectively. However, the
requirement of an extremely strong magnetic field (and an extremely low
temperature) makes them not applicable for realistic devices. In this work, we
propose a device that can generate even larger changes in resistance in a
zero-magnetic field and at a high temperature. The device is composed of a
graphene under two strips of yttrium iron garnet (YIG), where two gate voltages
are applied to cancel the heavy charge doping in the YIG-induced half-metallic
ferromagnets. By calculations using the Landauer-B\"{u}ttiker formalism, we
demonstrate that, when a proper gate voltage is applied on the free
ferromagnet, changes in resistance up to $305\times10^6\%$ ($16\times10^3\%$)
can be achieved at the liquid helium (nitrogen) temperature and in a zero
magnetic field. We attribute such a remarkable effect to a gate-induced
full-polarization reversal in the free ferromagnet, which results in a
metal-state to insulator-state transition in the device. We also find that, the
proposed effect can be realized in devices using other magnetic insulators such
as EuO and EuS. Our work should be helpful for developing a realistic switching
device that is energy saving and CMOS-technology compatible.

###Tailoring tricolor structure of magnetic topological insulator for robust axion insulator|M. Mogi,M. Kawamura,A. Tsukazaki,R. Yoshimi,K. S. Takahashi,M. Kawasaki,Y. Tokura###

Tailoring tricolor structure of magnetic topological insulator for robust axion insulator. Exploration of novel electromagnetic phenomena is a subject of great interest
in topological quantum materials. One of the unprecedented effects to be
experimentally verified is topological magnetoelectric (TME) effect originating
from an unusual coupling of electric and magnetic fields in materials. A
magnetic heterostructure of topological insulator (TI) hosts such an exotic
magnetoelectric coupling and can be expected to realize the TME effect as an
axion insulator. Here we designed a magnetic TI with tricolor structure where a
non-magnetic layer of (Bi, Sb)2Te3 is sandwiched by a soft ferromagnetic
Cr-doped (Bi, Sb)2Te3 and a hard ferromagnetic V-doped (Bi, Sb)2Te3.
Accompanied by the quantum anomalous Hall (QAH) effect, we observe zero Hall
conductivity plateaus, which are a hallmark of the axion insulator state, in a
wide range of magnetic field between the coercive fields of Cr- and V-doped
layers. The resistance of the axion insulator state reaches as high as 10^9
ohm, leading to a gigantic magnetoresistance ratio exceeding 10,000,000% upon
the transition from the QAH state. The tricolor structure of TI may not only be
an ideal arena for the topologically distinct phenomena, but also provide
magnetoresistive applications for advancing dissipationless topological
electronics.

###Large magnetoresistance dips and perfect spin-valley filter induced by topological phase transitions in silicene|Worasak Prarokijjak,Bumned Soodchomshom###

Large magnetoresistance dips and perfect spin-valley filter induced by topological phase transitions in silicene. Spin-valley transport and magnetoresistance are investigated in
silicene-based N/TB/N/TB/N junction where N and TB are normal silicene and
topological barriers. The topological phase transitions in TB's are controlled
by electric, exchange fields and circularly polarized light. As a result, we
find that by applying electric and exchange fields, four groups of spin-valley
currents are perfectly filtered, directly induced by topological phase
transitions. Control of currents, carried by single, double and triple channels
of spin-valley electrons in silicene junction, may be achievable by adjusting
magnitudes of electric, exchange fields and circularly polarized light. We may
identify that the key factor behind the spin-valley current filtered at the
transition points may be due to zero and non-zero Chern numbers. Electrons that
are allowed to transport at the transition points must obey zero-Chern number
which is equivalent to zero mass and zero-Berry's curvature, while electrons
with non-zero Chern number are perfectly suppressed. Very large
magnetoresistance dips are found directly induced by topological phase
transition points. Our study also discusses the effect of spin-valley dependent
Hall conductivity at the transition points on ballistic transport and reveals
the potential of silicene as a topological material for spin-valleytronics.

###Giant tunnel magnetoresistance with a single magnetic phase-transition electrode|Jia Zhang,X. Z. Chen,C. Song,J. F. Feng,H. X. Wei,Jing-Tao Lü###

Giant tunnel magnetoresistance with a single magnetic phase-transition electrode. Magnetic phase transition tunnel magnetoresistance (MPT-TMR) effect with a
single magnetic electrode has been investigated by first-principles
calculations. The calculations show that the MPT-TMR of FeRh/MgO/Cu tunnel
junction can be as high as hundreds of percent when the magnetic structure of
FeRh changes from G-type antiferromagnetic (GAFM) to ferromagnetic order. This
new type of MPT-TMR may be superior to the tunnel anisotropic magnetoresistance
because of its huge magneto-resistance effect and similar structural
simplicity. The main mechanism for the giant MPT-TMR can be attributed to the
formation of interface resonant states at GAFM-FeRh/MgO interface. A direct
FeRh/MgO interface is found to be necessary for achieving high MPT-TMR
experimentally. Moreover, we find the FeRh/MgO interface with FeRh in
ferromagnetic phase has nearly full spin-polarization due to the negligible
majority transmission and significantly different Fermi surface of two spin
channels. Thus, it may act as a highly efficient and tunable spin-injector. In
addition, electric field driven MPT of FeRh-based hetero-magnetic
nanostructures can be utilized to design various energy efficient tunnel
junction structures and the corresponding lower power consumption devices. Our
results will stimulate further experimental investigations of MPT-TMR and other
fascinating phenomenon of FeRh-based tunnel junctions that may be promising in
antiferromagnetic spintronics.

###Transversal magnetoresistance and Shubnikov-de Haas oscillations in Weyl semimetals|J. Klier,I. V. Gornyi,A. D. Mirlin###

Transversal magnetoresistance and Shubnikov-de Haas oscillations in Weyl semimetals. We explore theoretically the magnetoresistance of Weyl semimetals in
transversal magnetic fields away from charge neutrality. The analysis within
the self-consistent Born approximation is done for the two different models of
disorder: (i) short-range impurties and (ii) charged (Coulomb) impurities. For
these models of disorder, we calculate the conductivity away from charge
neutrality point as well as the Hall conductivity, and analyze the transversal
magnetoresistance (TMR) and Shubnikov-de Haas oscillations for both types of
disorder. We further consider a model with Weyl nodes shifted in energy with
respect to each other (as found in various materials) with the chemical
potential corresponding to the total charge neutrality. In the experimentally
most relevant case of Coulomb impurities, we find in this model a large TMR in
a broad range of quantizing magnetic fields. More specifically, in the
ultra-quantum limit, where only the zeroth Landau level is effective, the TMR
is linear in magnetic field. In the regime of moderate (but still quantizing)
magnetic fields, where the higher Landau levels are relevant, the rapidly
growing TMR is supplemented by strong Shubnikov-de Haas oscillations,
consistent with experimental observations.

###Quantum Oscillations and Magnetoresistance in Type-II Weyl Semimetals - Effect of a Field Induced Charge Density Wave|Maximilian Trescher,Emil J. Bergholtz,Johannes Knolle###

Quantum Oscillations and Magnetoresistance in Type-II Weyl Semimetals - Effect of a Field Induced Charge Density Wave. Recent experiments on type-II Weyl semimetals such as WTe$_2$, MoTe$_2$,
Mo$_x$W$_{1-x}$Te$_2$ and WP$_2$ reveal remarkable transport properties in
presence of a strong magnetic field, including an extremely large
magnetoresistance and an unusual temperature dependence. Here, we investigate
magnetotransport via the Kubo formula in a minimal model of a type-II Weyl
semimetal taking into account the effect of a charge density wave (CDW)
transition, which can arise even at weak coupling in the presence of a strong
magnetic field because of the special Landau level dispersion of type-II Weyl
systems. Consistent with experimental measurements we find an extremely large
magnetoresistance with close to $B^2$ scaling at particle-hole compensation,
while in the extreme quantum limit there is a transition to a qualitatively new
scaling with approximately $B^{0.75}$. We also investigate the Shubnikov-de
Haas effect and find that the amplitude of the resistivity quantum oscillations
are greatly enhanced below the CDW transition temperature which is accompanied
by an unusual non-monotonous (non-Lifshitz-Kosevich) temperature dependence.

###Engineering and improving the magnetic properties of thin Fe layers through exchange coupling with hard magnetic Dysprosium layers|M. Ehlert,H. S. Körner,T. Hupfauer,M. Schitko,G. Bayreuther,D. Weiss###

Engineering and improving the magnetic properties of thin Fe layers through exchange coupling with hard magnetic Dysprosium layers. We report on a comprehensive study of the magnetic coupling between soft
magnetic Fe layers and hard magnetic Dysprosium (Dy) layers at low temperatures
(4.2 - 120K). For our experiments we prepared thin films of Fe and Dy and
multilayers of Fe/Dy by ultra-high vacuum sputtering. The magnetic properties
of each material were determined with a superconducting quantum interference
device. Furthermore, we performed magnetoresistance measurements with similarly
grown, microstructured devices, where the anisotropic magnetoresistance (AMR)
effect was used to identify the magnetization state of the samples. By
analyzing and comparing the corresponding data of Fe and Dy, we show that the
presence of a Dy layer on top of the Fe layer significantly influences its
magnetic properties and makes it magnetically harder. We perform a systematic
evaluation of this effect and its dependence on temperature and on the
thickness of the soft magnetic layer. All experimental results can consistently
be explained with exchange coupling at the interface between the Fe and the Dy
layer. Our experiments also yield a negative sign of the AMR effect of thin Dy
films, and an increase of the Dy films' Curie temperature, which is due to
growth conditions.

###Spin colossal magnetoresistance in an antiferromagnetic insulator|Zhiyong Qiu,Dazhi Hou,Joseph Barker,Kei Yamamoto,Olena Gomonay,Eiji Saitoh###

Spin colossal magnetoresistance in an antiferromagnetic insulator. Colossal magnetoresistance (CMR) refers to a large change in electrical
conductivity induced by a magnetic field in the vicinity of a metal-insulator
transition and has inspired extensive studies for decades\cite{Ramirez1997,
Tokura2006}. Here we demonstrate an analogous spin effect near the N\'eel
temperature $T_{\rm{N}}$=296 K of the antiferromagnetic insulator \CrO. Using a
yttrium iron garnet \YIG/\CrO/Pt trilayer, we injected a spin current from the
YIG into the \CrO layer, and collected via the inverse spin Hall effect the
signal transmitted in the heavy metal Pt. We observed a change by two orders of
magnitude in the transmitted spin current within 14 K of the N\'eel
temperature. This transition between spin conducting and nonconducting states
could be also modulated by a magnetic field in isothermal conditions. This
effect, that we term spin colossal magnetoresistance (SCMR), has the potential
to simplify the design of fundamental spintronics components, for instance
enabling the realization of spin current switches or spin-current based
memories.

###Collapse of the Cooper pair phase coherence length at a superconductor to insulator transition|S. M. Hollen,G. E. Fernandes,J. M. Xu,J. M. Valles Jr###

Collapse of the Cooper pair phase coherence length at a superconductor to insulator transition. We present investigations of the superconductor to insulator transition (SIT)
of uniform a-Bi films using a technique sensitive to Cooper pair phase
coherence. The films are perforated with a nanohoneycomb array of holes to form
a multiply connected geometry and subjected to a perpendicular magnetic field.
Film magnetoresistances on the superconducting side of the SIT oscillate with a
period dictated by the superconducting flux quantum and the areal hole density.
The oscillations disappear close to the SIT critical point to leave a
monotonically rising magnetoresistance that persists in the insulating phase.
These observations indicate that the Cooper pair phase coherence length, which
is infinite in the superconducting phase, collapses to a value less than the
interhole spacing at this SIT. This behavior is inconsistent with the gradual
reduction of the phase coherence length expected for a bosonic, phase
fluctuation driven SIT. This result starkly contrasts with previous
observations of oscillations persisting in the insulating phase of other films
implying that there must be at least two distinct classes of disorder tuned
SITs.

###Asymmetric scattering of Dirac electrons and holes in graphene|Atikur Rahman,Janice Wynn Guikema,Nina Markovic###

Asymmetric scattering of Dirac electrons and holes in graphene. The relativistic nature of Dirac electrons and holes in graphene profoundly
affects the way they interact with impurities. Signatures of the relativistic
behavior have been observed recently in scanning tunneling measurements on
individual impurities, but the conductance measurements in this regime are
typically dominated by electron and hole puddles. Here we present measurements
of quantum interference noise and magnetoresistance in graphene pn junctions.
Unlike the conductance, the quantum interference noise can provide access to
the scattering at the Dirac point:it is sensitive to the motion of a single
impurity, it depends strongly on the fundamental symmetries that describe the
system and it is determined by the phase-coherent phenomena which are not
necessarily obscured by the puddles. The temperature and the carrier density
dependence of resistance fluctuations and magnetoresistance in graphene p-n
junctions at low temperatures suggest that the noise is dominated by the
quantum interference due to scattering on impurities and that the noise minimum
could be used to determine the point where the average carrier density is zero.
At larger carrier densities, the amplitude of the noise depends strongly on the
sign of the impurity charge, reflecting the fact that the electrons and the
holes are scattered by the impurity potential in an asymmetric manner.

###Tunable excitonic insulator in quantum limit graphite|Z. Zhu,R. D. McDonald,A. Shekhter,B. J. Ramshaw,K. A. Modic,F. F. Balakirev,N. Harrison###

Tunable excitonic insulator in quantum limit graphite. Half a century ago, Mott noted that tuning the carrier density of a semimetal
towards zero produces an insulating state in which electrons and holes form
bound pairs. It was later argued that such pairing persists even if a
semiconducting gap opens in the underlying band structure, giving rise to what
has become known as the strong coupling limit of an `excitonic insulator.'
While these `weak' and `strong' coupling extremes were subsequently proposed to
be manifestations of the same excitonic state of electronic matter, the
predicted continuity of such a phase across a band gap opening has not been
realized experimentally in any material. Here we show the quantum limit of
graphite, by way of temperature and angle-resolved magnetoresistance
measurements, to host such an excitonic insulator phase that evolves
continuously between the weak and strong coupling limits. We find that the
maximum transition temperature T_EI of the excitonic phase is coincident with a
band gap opening in the underlying electronic structure at B_0= 46 +/- 1 T,
which is evidenced above T_EI by a thermally broadened inflection point in the
magnetoresistance. The overall asymmetry of the observed phase boundary around
B_0 closely matches theoretical predictions of a magnetic field-tuned excitonic
insulator phase in which the opening of a band gap marks a crossover from
predominantly momentum-space pairing to real-space pairing.

###Spin-resolved Andreev transport through double-quantum-dot Cooper pair splitters|Piotr Trocha,Ireneusz Weymann###

Spin-resolved Andreev transport through double-quantum-dot Cooper pair splitters. We investigate the Andreev transport through double-quantum-dot Cooper pair
splitters with ferromagnetic leads. The analysis is performed with the aid of
the real-time diagrammatic technique in the sequential tunneling regime. We
study the dependence of the Andreev current, the differential conductance, and
the tunnel magnetoresistance on various parameters of the model in both the
linear and nonlinear response regimes. In particular, we analyze the
spin-resolved transport in the crossed Andreev reflection regime, where a
blockade of the current occurs due to enhanced occupation of the triplet state.
We show that in the triplet blockade, finite intradot correlations can lead to
considerable leakage current due to direct Andreev reflection processes.
Furthermore, we find additional regimes of current suppression resulting from
enhanced occupation of singlet states, which decreases the rate of crossed
Andreev reflection.We also study how the splitting of Andreev bound states,
triggered by either dot level detuning, finite hopping between the dots, or
finite magnetic field, affects the Andreev current. While in the first two
cases the number of Andreev bound states is doubled, whereas transport
properties are qualitatively similar, in the case of finite magnetic field
further level splitting occurs, leading to a nontrivial behavior of
spin-resolved transport characteristics, and especially that of tunneling
magnetoresistance. Finally, we discuss the entanglement fidelity between split
Cooper pair electrons and show that by tuning the device parameters, fidelity
can reach unity.

###Topological end states in two-orbital double-exchange model for colossal magnetoresistive manganites|Yang Li,Shuai Dong,Su-Peng Kou###

Topological end states in two-orbital double-exchange model for colossal magnetoresistive manganites. Manganites are famous mostly for the colossal magnetoresistive effect, which
involves the phase separation between ferromagnetic phase and charge-ordered
CE-type antiferromagnetic phases. Furthermore, manganites contain some typical
magnetic ferroelectrics, e.g. E-type antiferromagnetic $o$-HoMnO$_3$. Here we
re-examined these zigzag-winding antiferromagnetic phases (CE-type and E-type
antiferromagnets) from the topological perspective. Our theoretical analysis
proved that the E-type phase is a weak topological insulator belonging to the
$\mathbb{Z}$ class. In momentum space, we classify the symmetries of this
phase, and find the three symmetry operators for the chiral, particle-hole, and
time-reversal symmetry. The CE-type phase can be described by the
Duffin-Kemmer-Petiau algebra, implying that it is a new class of topological
insulator and hence extends the existing classification. The corresponding
topological end states are demonstrated via numerical calculations, which may
implicate the experimental observed ferromagnetic edge states in manganite
strips (Nat. Commun. 6, 6179 (2015)) and may play a crucial role in the
colossal magnetoresistive effect.

###Sample Size Effects on the Transport Characteristics of Mesoscopic Graphite Samples|J. Barzola-Quiquia,J. -L. Yao,P. Rödiger,K. Schindler,P. Esquinazi###

Sample Size Effects on the Transport Characteristics of Mesoscopic Graphite Samples. In this work we investigated correlations between the internal microstructure
and sample size (lateral as well as thickness) of mesoscopic, tens of nanometer
thick graphite (multigraphene) samples and the temperature $(T)$ and field
$(B)$ dependence of their electrical resistivity $\rho(T,B)$. Low energy
transmission electron microscopy reveals that the original highly oriented
pyrolytic graphite material -- from which the multigraphene samples were
obtained by exfoliation -- is composed of a stack of $\sim 50 $nm thick and
micrometer long crystalline regions separated by interfaces running parallel to
the graphene planes. We found a qualitative and quantitative change in the
behavior of $\rho(T,B)$ upon thickness of the multigraphene samples, indicating
that their internal microstructure is important.} {The overall results indicate
that the metallic-like behavior of $\rho(T)$ at zero field measured for bulk
graphite samples is not intrinsic of ideal graphite. The results suggest that
the interfaces between crystalline regions may be responsible for the
superconducting-like properties observed in graphite. Our transport
measurements also show that reducing the sample lateral size as well as the
length between voltage electrodes decreases the magnetoresistance, in agreement
with recently published results. The magnetoresistance of the multigraphene
samples shows a scaling of the form ($(R(B) - R(0))/R(0))/T^\alpha = f(B/T)$
with a sample dependent exponent $\alpha \sim 1$, which applies in the whole
temperature 2 K $\le T \le 270$K and magnetic field range $B \le 8 $T.

###Magnetoresistance in Dilute $p$-Si/SiGe in Parallel and Tilted Magnetic Fields|I. L. Drichko,I. Yu. Smirnov,A. V. Suslov,O. A. Mironov,D. R. Leadley###

Magnetoresistance in Dilute $p$-Si/SiGe in Parallel and Tilted Magnetic Fields. We report the results of an experimental study of the magnetoresistance
$\rho_{xx}$ and $\rho_{xy}$ in two samples of $p$-Si/SiGe with low carrier
concentrations $p$=8.2$\times10^{10}$ cm$^{-2}$ and $p$=2$\times10^{11}$
cm$^{-2}$. The research was performed in the temperature range of 0.3-2 K and
in the magnetic fields of up to 18 T, parallel or tilted with respect to the
two-dimensional (2D) channel plane. The large in-plane magnetoresistance can be
explained by the influence of the \textit{in-plane} magnetic field on the
orbital motion of the charge carriers in the quasi-2D system. The measurements
of $\rho_{xx}$ and $\rho_{xy}$ in the tilted magnetic field showed that the
anomaly in $\rho_{xx}$, observed at filling factor $\nu$=3/2 is practically
nonexistent in the conductivity $\sigma_{xx}$. The anomaly in $\sigma_{xx}$ at
$\nu$=2 might be explained by overlapping of the levels with different spins
0$\uparrow$ and 1$\downarrow$ when the tilt angle of the applied magnetic field
is changed. The dependence of g-factor $g^*(\Theta)/g^*(0^0)$ on the tilt angle
$\Theta$ was determined.

###Magnetocrystalline anisotropy in RAu_{2}Ge_{2} (R = La, Ce and Pr) single crystals|Devang A. Joshi,A. K. Nigam,S. K. Dhar,A. Thamizhavel###

Magnetocrystalline anisotropy in RAu_{2}Ge_{2} (R = La, Ce and Pr) single crystals. Anisotropic magnetic properties of single crystalline RAu_{2}Ge_{2} (R = La,
Ce and Pr) compounds are reported. LaAu_{2}Ge_{2} exhibit a Pauli-paramagnetic
behavior whereas CeAu_{2}Ge_{2} and PrAu_{2}Ge_{2} show an antiferromagnetic
ordering with N\grave{e}el temperatures T_{N} = 13.5 and 9 K, respectively. The
anisotropic magnetic response of Ce and Pr compounds establishes [001] as the
easy axis of magnetization and a sharp spin-flip type metamagnetic transition
is observed in the magnetic isotherms. The resistance and magnetoresistance
behavior of these compounds, in particular LaAu_{2}Ge_{2}, indicate an
anisotropic Fermi surface. The magnetoresistivity of CeAu_{2}Ge_{2} apparently
reveals the presence of a residual Kondo interaction. A crystal electric field
analysis of the anisotropic susceptibility in conjunction with the
experimentally inferred Schottky heat capacity enables us to propose a crystal
electric field level scheme for Ce and Pr compounds. For CeAu_{2}Ge_{2} our
values are in excellent agreement with the previous reports on neutron
diffraction. The heat capacity data in LaAu_{2}Ge_{2} show clearly the
existence of Einstein contribution to the heat capacity.

###Interplay of magnetism, Fermi surface reconstructions, and hidden-order in the heavy-fermion material URu$_2$Si$_2$|G. W. Scheerer,W. Knafo,D. Aoki,G. Ballon,A. Mari,D. Vignolles,J. Flouquet###

Interplay of magnetism, Fermi surface reconstructions, and hidden-order in the heavy-fermion material URu$_2$Si$_2$. URu$_2$Si$_2$ is surely one of the most mysterious of the heavy-fermion
compounds. Despite more than twenty years of experimental and theoretical
works, the order parameter of the transition at $T_0 = 17.5$ K is still
unknown. The state below $T_0$ remains called "hidden-order phase" and the
stakes are still to identify the energy scales driving the system to this
phase. We present new magnetoresistivity and magnetization measurements
performed on very-high-quality single crystals in pulsed magnetic fields up to
60 T. We show that the transition to the hidden-order state in URu$_2$Si$_2$ is
initially driven by a high-temperature crossover at around 40-50 K, which is a
fingerprint of inter-site electronic correlations. In a magnetic field
$\mathbf{H}$ applied along the easy-axis $\bf{c}$, the vanishing of this
high-temperature scale precedes the polarization of the magnetic moments, as
well as it drives the destabilization of the hidden-order phase. Strongly
impurity-dependent magnetoresistivity confirms that the Fermi surface is
reconstructed below $T_0$ and is strongly modified in a high magnetic field
applied along $\mathbf{c}$, i.e. at a sufficiently-high magnetic polarization.
The possibility of a sharp crossover in the hidden-order state controlled by a
field-induced change of the Fermi surface is pointed out.

###Tunnelling anisotropic magnetoresistance effect of single adatoms on a noncollinear magnetic surface|Nuala M. Caffrey,Silke Schröder,Paolo Ferriani,Stefan Heinze###

Tunnelling anisotropic magnetoresistance effect of single adatoms on a noncollinear magnetic surface. The tunnelling anisotropic magnetoresistance (TAMR) effect describes the
sensitivity of spin-polarized electron transport to the orientation of the
magnetization with respect to the crystallographic axes. As the TAMR effect
requires only a single magnetic electrode, in contrast to the tunnelling
magnetoresistance effect, it offers an attractive route towards alternative
spintronics applications. In this work we consider the TAMR effect at the
single-atom limit by investigating the anisotropy of the local density of
states in the vacuum above transition-metal adatoms adsorbed on a noncollinear
magnetic surface, the monolayer of Mn on W(110). This surface presents a
cycloidal spin spiral ground state with an angle of 173$^\circ$ between
neighbouring spins and thus allows a quasi-continuous exploration of the
angular dependence of the TAMR of adsorbed adatoms using scanning tunnelling
microscopy. Using first-principles calculations, we investigate the TAMR of Co,
Rh and Ir adatoms on Mn/W(110) and relate our results to magnetization
direction dependent changes in the local density of states. The anisotropic
effect is found to be enhanced dramatically on the adsorption of heavy
transition-metal atoms, with values of up to 50% predicted from our
calculations. This effect will be measurable even with a non-magnetic STM tip.

###Tunable magnetoresistance in an asymmetrically coupled single molecule junction|Ben Warner,Fadi El Hallak,Henning Prüser,John Sharp,Mats Persson,Andrew J. Fisher,Cyrus F. Hirjibehedin###

Tunable magnetoresistance in an asymmetrically coupled single molecule junction. Phenomena that are highly sensitive to magnetic fields can be exploited in
sensors and non-volatile memories. The scaling of such phenomena down to the
single molecule level may enable novel spintronic devices. Here we report
magnetoresistance in a single molecule junction arising from negative
differential resistance that shifts in a magnetic field at a rate two orders of
magnitude larger than Zeeman shifts. This sensitivity to the magnetic field
produces two voltage-tunable forms of magnetoresistance, which can be selected
via the applied bias. The negative differential resistance is caused by
transient charging of an iron phthalocyanine (FePc) molecule on a single layer
of copper nitride (Cu2N) on a Cu(001) surface, and occurs at voltages
corresponding to the alignment of sharp resonances in the filled and empty
molecular states with the Cu(001) Fermi energy. An asymmetric voltage-divider
effect enhances the apparent voltage shift of the negative differential
resistance with magnetic field, which inherently is on the scale of the Zeeman
energy. These results illustrate the impact that asymmetric coupling to
metallic electrodes can have on transport through molecules, and highlight how
this coupling can be used to develop molecular spintronic applications.

###Tuning Magnetotransport in a Compensated Semimetal at the Atomic Scale|Lin Wang,Ignacio Gutiérrez-Lezama,Céline Barreteau,Nicolas Ubrig,Enrico Giannini,A. F. Morpurgo###

Tuning Magnetotransport in a Compensated Semimetal at the Atomic Scale. Either in bulk form, or when exfoliated into atomically thin crystals,
layered transition metal dichalcogenides are continuously leading to the
discovery of new phenomena. The latest example is provided by 1T'-WTe$_2$, a
semimetal recently found to exhibit the largest known magnetoresistance in bulk
crystals, and predicted to become a two-dimensional topological insulator in
strained monolayers. Here, we show that reducing the thickness through facile
exfoliation provides an effective experimental knob to tune the electronic
properties of WTe$_2$, which allows us to identify the microscopic mechanisms
responsible for the observed classical and quantum magnetotransport down to the
ultimate atomic scale. We find that the longitudinal resistance and the very
unconventional B-dependence of the Hall resistance are reproduced
quantitatively in terms of a classical two-band model for crystals as thin as
six monolayers, and that for thinner crystals a crossover to an insulating,
Anderson-localized state occurs. Besides establishing the origin of the very
large magnetoresistance of bulk WTe$_2$, our results represent the first,
complete validation of the classical theory for two-band electron-hole
transport, and indicate that atomically thin WTe$_2$ layers remain gapless
semimetals, from which we conclude that searching for a topological insulating
state by straining monolayers is a challenging, but feasible experiment.

###Large magnetoresistance in the antiferromagnetic semi-metal NdSb|N. Wakeham,E. D. Bauer,M. Neupane,F. Ronning###

Large magnetoresistance in the antiferromagnetic semi-metal NdSb. There has been considerable interest in topological semi-metals that exhibit
extreme magnetoresistance (XMR). These have included materials lacking
inversion symmetry such as TaAs, as well Dirac semi-metals such as Cd3As2.
However, it was reported recently that LaSb and LaBi also exhibit XMR, even
though the rock-salt structure of these materials has inversion symmetry, and
the band-structure calculations do not show a Dirac dispersion in the bulk.
Here, we present magnetoresistance and specific heat measurements on NdSb,
which is isostructural with LaSb. NdSb has an antiferromagnetic groundstate,
and in analogy with the lanthanum monopnictides, is expected to be a
topologically non-trivial semi-metal. We show that NdSb has an XMR of 10^4 %,
even within the AFM state, illustrating that XMR can occur independently of the
absence of time reversal symmetry breaking in zero magnetic field. The
persistence of XMR in a magnetic system offers promise of new functionality
when combining topological matter with electronic correlations. We also find
that in an applied magnetic field below the Neel temperature there is a first
order transition, consistent with evidence from previous neutron scattering
work.

###Gate-voltage response of a one-dimensional ballistic spin valve without spin-orbit interaction|Maciej Misiorny,Carola Meyer###

Gate-voltage response of a one-dimensional ballistic spin valve without spin-orbit interaction. We show that engineering of tunnel barriers forming at the interfaces of a
one-dimensional spin valve provides a viable path to a strong gate-voltage
tunability of the magnetoresistance effect. In particular, we investigate
theoretically a carbon nanotube (CNT) spin valve in terms of the influence of
the CNT-contact interface on the performance of the device. The focus is on the
strength and the spin selectivity of the tunnel barriers that are modelled as
Dirac-delta potentials. The scattering matrix approach is used to derive the
transmission coefficient that yields the tunneling magnetoresistance (TMR). We
find a strong non-trivial gate-voltage response of the TMR in the absence of
spin-orbit coupling when the energy of the incident electrons matches the
potential energy of the barrier. Analytic expressions for the TMR in various
limiting cases are derived. These are used to explain previous experimental
results, but also to predict parameters for device optimization with respect to
size and tunability of the TMR effect in the ballistic transport regime.

###Disruption of the accidental Dirac semimetal state in ZrTe$_{5}$ under hydrostatic pressure|J. L. Zhang,C. Y. Guo,X. D. Zhu,L. Ma,G. L. Zheng,Y. Q. Wang,L. Pi,Y. Chen,H. Q. Yuan,M. L. Tian###

Disruption of the accidental Dirac semimetal state in ZrTe$_{5}$ under hydrostatic pressure. We study the effect of hydrostatic pressure on the magnetotransport
properties of the zirconium pentatelluride. The magnitude of resistivity
anomaly gets enhanced with increasing pressure, but the transition temperature
$T^{\ast}$ is almost independent of it. In the case of H $\parallel$ $b$, the
quasi-linear magnetoresistance decreases drastically from 3300$\%$ (9 T) at
ambient pressure to 400$\%$ (14 T) at 2.5 GPa. Besides, the change of the
quantum oscillation phase from topological nontrivial to trivial is revealed
around 2 GPa. Both demonstrate that the pressure breaks the accidental Dirac
node in ZrTe$_{5}$. For H $\parallel$ $c$, in contrast, subtle changes can be
seen in the magnetoresistance and quantum oscillations. In the presence of
pressure, ZrTe$_{5}$ evolves from a highly anisotropic to a nearly isotropic
electronic system, which accompanies with the disruption of the accidental
Dirac semimetal state. It supports the assumption that ZrTe$_{5}$ is a semi-3D
Dirac system with linear dispersion along two directions and a quadratic one
along the third.

###Giant magnetoresistance and anomalous transport in phosphorene-based multilayers with noncollinear magnetization|Moslem Zare,Leyla Majidi,Reza Asgari###

Giant magnetoresistance and anomalous transport in phosphorene-based multilayers with noncollinear magnetization. We theoretically investigate the unusual features of the magnetotransport in
a monolayer phosphorene ferromagnetic/normal/ferromagnetic (F/N/F) hybrid
structure. We find that the charge conductance can feature a minimum at
parallel (P) configuration and a maximum near the antiparallel (AP)
configuration of magnetization in the F/N/F structure with $n$-doped F and
$p$-doped N regions and also a finite conductance in the AP configuration with
the N region of $n$-type doping. In particular, the proposed structure exhibits
giant magnetoresistance, which can be tuned to unity. This perfect switching is
found to show strong robustness with respect to increasing the contact length
and tuning the chemical potential of the N region with a gate voltage. We also
explore the oscillatory behavior of the charge conductance or magnetoresistance
in terms of the size of the N region. We further demonstrate the penetration of
the spin-transfer torque into the right F region and show that, unlike graphene
structure, the spin-transfer torque is very sensitive to the chemical potential
of the N region as well as the exchange field of the F region.

###Magnetic behavior of metallic kagome lattices, Tb3Ru4Al12 and Er3Ru4Al12|Sanjay Kumar Upadhyay,Kartik K Iyer,E. V. Sampathkumaran###

Magnetic behavior of metallic kagome lattices, Tb3Ru4Al12 and Er3Ru4Al12. We report magnetic behavior of two intermetallics-based kagome lattices,
Tb3Ru4Al12 and Er3Ru4Al12, crystallizing in the Gd3Ru4Al12-type hexagonal
crystal structure, by measurements in the range 1.8-300 K with bulk
experimental techniques (ac and dc magnetization, heat-capacity and
magnetoresistance). The main finding is that the Tb compound, known to order
antiferromagnetically below (T_N=) 22 K, shows glassy characteristics at lower
temperatures (<15K), thus characterizing this compound as a re-entrant
spin-glass. The data reveal that glassy phase is quite complex and is of a
cluster type. Since the glassy behavior was not seen for the Gd analogue in the
past literature, this finding for the Tb compound emphasizes that this kagome
family could provide an opportunity to explore the role of higher order (such
as quadrupole) in bringing out magnetic frustration. Additional findings
reported here for this compound are: (i) The temperature dependence of magnetic
susceptibility and electrical resistivity in the range 12 - 20 K are found to
be hysteretic leading to a magnetic phase in this temperature range, mimicking
disorder-induced first-order magnetic phase-transition. (ii) Features
attributable to an interesting magnetic phase co-existence phenomenon in the
magnetoresistance in zero field, after cycling across metamagnetic transition
fields, are observed. With respect to the Er compound, we do not find any
evidence for long-range magnetic ordering down to 2 K, but this appears to be
on the verge of magnetic order at 2 K.

###Scale-invariant magnetoresistance in a cuprate superconductor|P. Giraldo-Gallo,J. A. Galvis,Z. Stegen,K. A. Modic,F. F Balakirev,J. B. Betts,X. Lian,C. Moir,S. C. Riggs,J. Wu,A. T. Bollinger,X. He,I. Bozovic,B. J. Ramshaw,R. D. McDonald,G. S. Boebinger,A. Shekhter###

Scale-invariant magnetoresistance in a cuprate superconductor. The anomalous metallic state in high-temperature superconducting cuprates is
masked by the onset of superconductivity near a quantum critical point. Use of
high magnetic fields to suppress superconductivity has enabled a detailed study
of the ground state in these systems. Yet, the direct effect of strong magnetic
fields on the metallic behavior at low temperatures is poorly understood,
especially near critical doping, $x=0.19$. Here we report a high-field
magnetoresistance study of thin films of \LSCO cuprates in close vicinity to
critical doping, $0.161\leq x\leq0.190$. We find that the metallic state
exposed by suppressing superconductivity is characterized by a
magnetoresistance that is linear in magnetic field up to the highest measured
fields of $80$T. The slope of the linear-in-field resistivity is
temperature-independent at very high fields. It mirrors the magnitude and
doping evolution of the linear-in-temperature resistivity that has been
ascribed to Planckian dissipation near a quantum critical point. This
establishes true scale-invariant conductivity as the signature of the strange
metal state in the high-temperature superconducting cuprates.

###Static and Dynamic Magnetic Properties of FeMn/Pt Multilayers|Ziyan Luo,Yumeng Yang,Yanjun Xu,Mengzhen Zhang,Baoxi Xu,Jingsheng Chen,Yihong Wu###

Static and Dynamic Magnetic Properties of FeMn/Pt Multilayers. Recently we have demonstrated the presence of spin-orbit toque in FeMn/Pt
multilayers which, in combination with the anisotropy field, is able to rotate
its magnetization consecutively from 0o to 360o without any external field.
Here, we report on an investigation of static and dynamic magnetic properties
of FeMn/Pt multilayers using combined techniques of magnetometry, ferromagnetic
resonance, inverse spin Hall effect and spin Hall magnetoresistance
measurements. The FeMn/Pt multilayer was found to exhibit ferromagnetic
properties, and its temperature dependence of saturation magnetization can be
fitted well using a phenomenological model by including a finite distribution
in Curie temperature due to subtle thickness variations across the multilayer
samples. The non-uniformity in static magnetic properties is also manifested in
the ferromagnetic resonance spectra, which typically exhibit a broad resonance
peak. A damping parameter of around 0.106 is derived from the frequency
dependence of ferromagnetic resonance linewidth, which is comparable to the
reported values for other types of Pt-based multilayers. Clear inverse spin
Hall signals and spin Hall magnetoresistance have been observed in all samples
below the Curie temperature, which corroborate the strong spin-orbit torque
effect observed previously.

###Writing and Reading antiferromagnetic Mn$_2$Au: Néel spin-orbit torques and large anisotropic magnetoresistance|S. Yu. Bodnar,L. Šmejkal,I. Turek,T. Jungwirth,O. Gomonay,J. Sinova,A. A. Sapozhnik,H. -J. Elmers,M. Kläui,M. Jourdan###

Writing and Reading antiferromagnetic Mn$_2$Au: Néel spin-orbit torques and large anisotropic magnetoresistance. Antiferromagnets are magnetically ordered materials which exhibit no net
moment and thus are insensitive to magnetic fields. Antiferromagnetic
spintronics aims to take advantage of this insensitivity for enhanced
stability, while at the same time active manipulation up to the natural THz
dynamic speeds of antiferromagnets is possible, thus combining exceptional
storage density and ultra-fast switching. However, the active manipulation and
read-out of the N\'eel vector (staggered moment) orientation is challenging.
Recent predictions have opened up a path based on a new spin-orbit torque,
which couples directly to the N\'eel order parameter. This N\'eel spin-orbit
torque was first experimentally demonstrated in a pioneering work using
semimetallic CuMnAs. Here we demonstrate for Mn$_2$Au, a good conductor with a
high ordering temperature suitable for applications, reliable and reproducible
switching using current pulses and readout by magnetoresistance measurements.
The symmetry of the torques agrees with theoretical predictions and a large
read-out magnetoresistance effect of more than $\simeq 6$~$\%$ is reproduced by
ab initio transport calculations.

###Thermal activation energy of 3D vortex matter in NaFe1-xCoxAs (x=0.01, 0.03 and 0.07) single crystals|W. J. Choi,Y. I. Seo,D. Ahmad,Yong Seung Kwon###

Thermal activation energy of 3D vortex matter in NaFe1-xCoxAs (x=0.01, 0.03 and 0.07) single crystals. We report on the thermally activated flux flow dependency on the doping
dependent mixed state in NaFe1-xCoxAs (x=0.01, 0.03, and 0.07) crystals using
the magnetoresistivity in the case of B//c-axis and B//ab-plane. It was found
clearly that irrespective of the doping ratio, magnetoresistivity showed a
distinct tail just above the Tc, offset associated with the thermally activated
flux flow (TAFF) in our crystals. Furthermore, in TAFF region the temperature
dependence of the activation energy follows the relation U(T, B)=U_0 (B)
(1-T/T_c )^q with q=1.5 in all studied crystals. The magnetic field dependence
of the activation energy follows a power law of U_0 (B)~B^(-{\alpha}) where the
exponent {\alpha} is changed from a low value to a high value at a crossover
field of B=~2T, indicating the transition from collective to plastic pinning in
the crystals. Finally, it is suggested that the 3D vortex phase is the dominant
phase in the low-temperature region as compared to the TAFF region in our
series samples.

###Berry phase theory of planar Hall effect in Topological Insulators|S. Nandy,A. Taraphder,Sumanta Tewari###

Berry phase theory of planar Hall effect in Topological Insulators. Negative longitudinal magnetoresistance, in the presence of an external
magnetic field parallel to the direction of an applied current, has recently
been experimentally verified in Weyl semimetals and topological insulators in
the bulk conduction limit. The appearance of negative longitudinal
magnetoresistance in topological semimetals is understood as an effect of
chiral anomaly, whereas it is not well-defined in topological insulators.
Another intriguing phenomenon, planar Hall effect - appearance of a transverse
voltage in the plane of applied co-planar electric and magnetic fields not
perfectly aligned to each other, a configuration in which the conventional Hall
effect vanishes, has recently been suggested to exist in Weyl semimetals. In
this paper we present a quasi-classical theory of planar Hall effect of a
three-dimensional topological insulator in the bulk conduction limit. Starting
from Boltzmann transport equations we derive the expressions for planar Hall
conductivity and longitudinal magnetoconductivity in topological insulators and
show the important roles played by the orbital magnetic moment for the
appearance of planar Hall effect. Our theoretical results predict specific
experimental signatures for topological insulators that can be directly checked
in experiments.

###Splitting efficiency and interference effects in a Cooper pair splitter based on a triple quantum dot with ferromagnetic contacts|K. Bocian,W. Rudzinski,I. Weymann###

Splitting efficiency and interference effects in a Cooper pair splitter based on a triple quantum dot with ferromagnetic contacts. We theoretically study the spin-resolved subgap transport properties of a
Cooper pair splitter based on a triple quantum dot attached to superconducting
and ferromagnetic leads. Using the Keldysh Green's function formalism, we
analyze the dependence of the Andreev conductance, Cooper pair splitting
efficiency, and tunnel magnetoresistance on the gate and bias voltages applied
to the system. We show that the system's transport properties are strongly
affected by spin dependence of tunneling processes and quantum interference
between different local and nonlocal Andreev reflections. We also study the
effects of finite hopping between the side quantum dots on the Andreev current.
This allows for identifying the optimal conditions for enhancing the Cooper
pair splitting efficiency of the device. We find that the splitting efficiency
exhibits a nonmonotonic dependence on the degree of spin polarization of the
leads and the magnitude and type of hopping between the dots. An almost perfect
splitting efficiency is predicted in the nonlinear response regime when the
energies of the side quantum dots are tuned to the energies of the
corresponding Andreev bound states. In addition, we analyzed features of the
tunnel magnetoresistance (TMR) for a wide range of the gate and bias voltages,
as well as for different model parameters, finding the corresponding sign
changes of the TMR in certain transport regimes. The mechanisms leading to
these effects are thoroughly discussed.

###Singular nonlinear response in metals due to divergent Berry curvature: application to magneto-resistance in metals with type-II Weyl nodes|Hiroaki Ishizuka,Naoto Nagaosa###

Singular nonlinear response in metals due to divergent Berry curvature: application to magneto-resistance in metals with type-II Weyl nodes. The physical properties of metals are often given by the sum of the
contributions from the electrons consisting the Fermi surface (FS), and
therefore, fine structures of the electronic bands and Bloch functions are
often masked by the integral over FS. As a consequence, usually, the singular
structures in the electronic bands are often not reflected to the macroscopic
quantities. In this work, we investigate the anomaly-related magnetoresistance
in metals with type-II Weyl nodes close to the FS, and find that the
anomaly-related current increases divergently, showing a singular structure.
Detailed analysis on a simple model with multiple Weyl nodes shows that the
contribution to the magnetoresistance is dominated by the electrons in the
vicinity of the Weyl nodes; this is related to the fact that the current is
given by the square of the Berry curvature, which enhances the contribution
from the electrons around the Weyl nodes. The above results potentially allows
an estimate of the anomaly-induced current without precise information of the
entire Band structure.

###Quadratic to linear magnetoresistance tuning in TmB4|Sreemanta Mitra,Jeremy Goh Swee Kang,John Shin,Jin Quan Ng,Sai Swaroop Sunku,Tai Kong,Paul C. Canfield,B. Sriram Shastry,Pinaki Sengupta,Christos Panagopoulos###

Quadratic to linear magnetoresistance tuning in TmB4. The change of a material's electrical resistance (R) in response to an
external magnetic field (B) provides subtle information for the
characterization of its electronic properties and has found applications in
sensor and storage related technologies. In good metals, Boltzmann's theory
predicts a quadratic growth in magnetoresistance (MR) at low B, and saturation
at high fields. On the other hand, a number of nonmagnetic materials with weak
electronic correlation and low carrier concentration for metallicity, such as
inhomogeneous conductors, semimetals, narrow gap semiconductors and topological
insulators, two-dimensional electron gas (2DEG) show positive, non-saturating
linear magnetoresistance (LMR). However, observation of LMR in single crystals
of a good metal is rare. Here we present low-temperature, angle dependent
magnetotransport in single crystals of the antiferromagnetic metal, TmB4. We
observe large, positive and anisotropic MR(B), which can be tuned from
quadratic to linear by changing the direction of the applied field. In view of
the fact that isotropic, single crystalline metals with large Fermi surface
(FS) are not expected to exhibit LMR, we attribute our observations to the
anisotropic FS topology of TmB4. Furthermore, the linear MR is found to be
temperature-independent, suggestive of quantum mechanical origin.

###Damping and softening of transverse acoustic phonons in colossal magnetoresistive La$_{0.7}$Ca$_{0.3}$MnO$_3$ and La$_{0.7}$Sr$_{0.3}$MnO$_3$|Joel S. Helton,Yang Zhao,Dmitry A. Shulyatev,Jeffrey W. Lynn###

Damping and softening of transverse acoustic phonons in colossal magnetoresistive La$_{0.7}$Ca$_{0.3}$MnO$_3$ and La$_{0.7}$Sr$_{0.3}$MnO$_3$. Neutron spectroscopy is used to probe transverse acoustic phonons near the
(2, 2, 0) Bragg position in colossal magnetoresistive La0.7Ca0.3MnO3 and
La0.7Sr0.3MnO3. Upon warming to temperatures near Tc = 257 K the phonon peaks
in La0.7Ca0.3MnO3 soften and damp significantly with the phonon half width at
half maximum approaching 2.5 meV for phonons at a reduced wave vector of q =
(0.2, 0.2, 0). Concurrently a quasielastic component develops that dominates
the spectrum near the polaron position at high temperatures. This quasielastic
scattering is ~5 times more intense near Tc than in La0.7Sr0.3MnO3 despite
comparable structural distortions in the two. The damping becomes more
significant near the polaron position with a temperature dependence similar to
that of polaron structural distortions. An applied magnetic field of 9.5 T only
partially reverses the damping and quasielastic component, despite smaller
fields being sufficient to drive the colossal magnetoresistive effect. The
phonon energy, on the other hand, is unaffected by field. The damping in
La0.7Sr0.3MnO3 near Tc at a reduced wave vector of q = (0.25, 0.25, 0) is
significantly smaller but displays a similar trend with an applied magnetic
field.

###Spin filtering in CrI$_3$ tunnel junctions|Tula R. Paudel,Evgeny Y. Tsymbal###

Spin filtering in CrI$_3$ tunnel junctions. The recently discovered magnetism of two-dimensional (2D) van der Waals
crystals have attracted a lot of attention. Among these materials is CrI$_3$ -
a magnetic semiconductor exhibiting transitions between antiferromagnetic and
ferromagnetic orderings under the influence of an applied magnetic field. Here,
using first-principles methods based on density functional theory, we explore
spin-dependent transport in tunnel junctions formed of fcc Cu (111) electrodes
and a CrI$_3$ tunnel barrier. We find about 100% spin polarization of the
tunneling current for a ferromagnetically-ordered four-monolayer CrI$_3$ and
tunneling magnetoresistance of about 3,000% associated with a change of
magnetic ordering in CrI$_3$. This behavior is understood in terms of the spin
and wave-vector dependent evanescent states in CrI$_3$ which control the
tunneling conductance. We find a sizable charge transfer from Cu to CrI$_3$
which adds new features to the mechanism of spin-filtering in CrI$_3$-based
tunnel junctions. Our results elucidate the mechanisms of spin filtering in
CrI3 tunnel junctions and provide important insights for the design of
magnetoresistive devices based on 2D magnetic crystals.

###Reentrant spin-glass and transport behavior of Gd4PtAl, a compound with three sites for Gd|Ram Kumar,Jyoti Sharma,Kartik K Iyer,E. V. Sampathkumaran###

Reentrant spin-glass and transport behavior of Gd4PtAl, a compound with three sites for Gd. We report temperature (T) dependence (2-330 K) of DC and AC magnetization
(M), isothermal remnant magnetization (M_IRM), heat capacity (C), electrical
resistivity (rho), and magnetoresistance (MR) of a ternary intermetallic
compound, Gd4PtAl, crystallizing in a cubic (space group F-43m) structure. In
this structure, there are three sites for the rare-earth. The magnetization
data reveal that, in addition to a magnetic transition at 64 K, there is
another magnetic feature below 20 K. The C(T) data reveal an upturn below 64 K,
shifting to a lower temperature with increasing field, which establishes that
the onset of magnetic order is of an antiferromagnetic type. However, there is
no worthwhile feature near 20 K in the C(T) curve. AC susceptibility peak
undergoes an observable change with frequency and, in particular, the peak
around 20 K gets suppressed with the application of a dc magnetic field; in
addition, M_IRM undergoes a slow decay with time and isothermal M exhibits
low-field hysteresis below 20 K only, which is typical of spin-glasses. The
results overall suggest that this compound is a reentrant spin-glass in
zero-field. There are experimental signatures pointing to the existence of both
antiferromagnetic and ferromagnetic components, competing with the variation of
temperature and magnetic field, as a result of which electrical and
magnetoresistance behaviors are peculiar. The results overall suggest this
compound exhibits interesting magnetic and transport properties.

###Spin structure and spin Hall magnetoresistance of epitaxial thin films of the insulating non-collinear antiferromagnet SmFeO$_3$|T Hajiri,L. Baldrati,R. Lebrun,M. Filianina,A. Ross,N. Tanahashi,M. Kuroda,W. L. Gan,T. O. Menteş,F. Genuzio,A. Locatelli,H Asano,M. Kläui###

Spin structure and spin Hall magnetoresistance of epitaxial thin films of the insulating non-collinear antiferromagnet SmFeO$_3$. We report a combined study of imaging the antiferromagnetic (AFM) spin
structure and measuring the spin Hall magnetoresistance (SMR) in epitaxial thin
films of the insulating non-collinear antiferromagnet SmFeO$_3$. X-ray magnetic
linear dichroism photoemission electron microscopy measurements reveal that the
AFM spins of the SmFeO$_3$(110) align in the plane of the film. Angularly
dependent magnetoresistance measurements show that SmFeO$_3$/Ta bilayers
exhibit a positive SMR, in contrast to the negative SMR expected in previously
studied collinear AFMs. The SMR amplitude increases linearly with increasing
external magnetic field at higher magnetic field, suggesting that field-induced
canting of the AFM spins plays an important role. In contrast, around the
coercive field, no detectable SMR signal is observed, indicating that SMR of
AFM and canting magnetization components cancel out. Below 50~K, the SMR
amplitude increases sizably by a factor of two as compared to room temperature,
which likely correlates with the long-range ordering of the Sm ions. Our
results show that the SMR is a sensitive technique for non-equilibrium spin
system of non-collinear AFM systems.

###Spin-transfer dynamics in MgO-based magnetic tunnel junctions with an out-of-plane magnetized free layer and an in-plane polarizer|Ewa Kowalska,Volker Sluka,Attila Kákay,Ciarán Fowley,Jürgen Lindner,Jürgen Fassbender,Alina M. Deac###

Spin-transfer dynamics in MgO-based magnetic tunnel junctions with an out-of-plane magnetized free layer and an in-plane polarizer. Here, we present an analytical and numerical model describing the
magnetization dynamics in MgO-based spin-torque nano-oscillators with an
in-plane magnetized polarizer and an out-of-plane free layer. We introduce the
spin-transfer torque asymmetry by considering the cosine angular dependence of
the resistance between the two magnetic layers in the stack. For the analytical
solution, dynamics are determined by assuming a circular precession trajectory
around the direction perpendicular to the plane, as set by the effective field,
and calculating the energy integral over a single precession period. In a more
realistic approach, we include the bias dependence of the tunnel
magnetoresistance, which is assumed empirically to be a piecewise linear
function of the applied voltage. The dynamical states are found by solving the
stability condition for the Jacobian matrix for out-of-plane static states. We
find that the bias dependence of the tunnel magnetoresistance, which is an
inseparable effect in every tunnel junction, exhibits drastic impact on the
spin-torque nano-oscillator phase diagram, mainly by increasing the critical
current for dynamics and quenching the oscillations at high currents. The
results are in good agreement with our experimental data published elsewhere.

###Quantum effects in graphitic materials: Colossal magnetoresistance, Andreev reflections, Little-Parks effect, ferromagnetism, and granular superconductivity|Nadina Gheorghiu,Charles R. Ebbing,Benjamin T. Pierce,Timothy J. Haugan###

Quantum effects in graphitic materials: Colossal magnetoresistance, Andreev reflections, Little-Parks effect, ferromagnetism, and granular superconductivity. Unlike the more common local conductance spectroscopy, nonlocal conductance
can differentiate between nontopological zero-energy modes localized around
inhomogeneities, and true Majorana edge modes in the topological phase. In
particular, negative nonlocal conductance is dominated by the crossed Andreev
reflection. In graphene, the Andreev reflection and the inter-band Klein
tunneling couple electron-like and hole-like states through the action of
either a superconducting (SC) pair potential or an electrostatic potential. We
are here probing quantum phenomena in modified graphitic samples. Four-point
contact transport measurements at cryogenic to room temperatures were conducted
using a Quantum Design Physical Property Measurement System. The observed
negative nonlocal differential conductance Gdiff probes the Andreev reflection
at the walls of the SC grains coupled by Josephson effect through the
semiconducting matrix. In addition, Gdiff shows the butterfly shape that is
characteristic to resistive random-access memory devices. In a magnetic field,
the Andreev reflection counters the effect of the otherwise lowered conduction.
At low temperatures, the magnetoresistance shows irreversible yet strong
colossal oscillations that are known to be quantum in nature. In addition, we
have found evidence for seemingly granular SC as well as ferromagnetism.
Moreover, the Little-Parks effect is revealed in both the classical
small-amplitude and the phase-slip driven large-amplitude oscillations in the
magnetoresistance. Thus, graphitic materials show potential for quantum
electronics applications, including rectification and topological states.

###Origins of magnetic field-dependent open-circuit voltage hysteresis driven by transverse charge current in ferromagnet/normal metal structures|Christos Tengeris###

Origins of magnetic field-dependent open-circuit voltage hysteresis driven by transverse charge current in ferromagnet/normal metal structures. Recent experimental work on Au thin films demonstrated signs of charge
current-induced spin polarization through open circuit voltage measurements. In
this study, we are investigating the underlying mechanism(s) that induces this
measured signal in the Au devices. We determine the theoretically expected spin
polarization from both Rashba-Edelstein effect and bulk spin Hall effect. The
discrepancy in the scaling of the measured signal as a function of the
thickness of the Au thin film in the two cases is our key to differentiate
between the two effects when compared to experimental data. Experiments show
reversal of spin polarization at a critical thickness which reveals the
presence of multiple spin polarization mechanisms. Characteristics of both
RashbaEdelstein and spin Hall effects are observed in different thickness
regimes. In addition, we study the magnetoresistance of the same Au samples,
which reveal the presence of weak anti-localization (WAL) at low temperatures
for the low-thickness samples. More interestingly, it is revealed that the open
circuit voltage difference and magnetoresistance due to WAL have very similar
scaling with film thickness and temperature, suggesting the crucial importance
of spin-orbit interaction in understanding the phenomenon.

###Magnetic-field-induced FM-AFM metamagnetic transition and strong negative magnetoresistance in Mn$_{1/4}$NbS$_2$ under pressure|S. Polesya,S. Mankovsky,P. G. Naumov,M. A. ElGhazali,W. Schnelle,S. Medvedev,S. Mangelsen,W. Bensch,H. Ebert###

Magnetic-field-induced FM-AFM metamagnetic transition and strong negative magnetoresistance in Mn$_{1/4}$NbS$_2$ under pressure. Transition metal dichalcogenides (TMDC) stand out with their high chemical
stability and the possibility to incorporate a wide range of magnetic species
between the layers. The behavior of conduction electrons in such materials
intercalated by 3d-elements is closely related to their magnetic properties and
can be sensitively controlled by external magnetic fields. Here, we study the
magnetotransport properties of NbS$_2$ intercalated with Mn, Mn$_{1/4}$NbS$_2$,
demonstrating a complex behavior of the magnetoresistance and of the ordinary
and anomalous Hall resistivities. Application of pressure as tuning parameter
leads to the drastic changes of the magnetotransport properties of
Mn$_{1/4}$NbS$_2$ exhibiting large negative magnetoresistance up to $65 \%$ at
7.1 GPa. First-principles electronic structure calculations indicates
pressure-induced transition from ferromagnetic to antiferromagnetic state.
Theoretical calculations accounting for the finite temperature magnetic
properties of Mn$_{1/4}$NbS$_2$ suggest a field-induced metamagnetic
ferromagnetic-antiferromagnetic transition as an origin of the large negative
magentoresistance. These results inspire the development of materials for
spintronic applications based on intercalated TMDC with a well controllable
metamagnetic transition.

###Interaction and temperature effects on the magneto-optical conductivity of Weyl liquids|S. Acheche,R. Nourafkan,J. Padayasi,N. Martin,A. -M. S. Tremblay###

Interaction and temperature effects on the magneto-optical conductivity of Weyl liquids. Negative magnetoresistance is one of the manifestations of the chiral anomaly
in Weyl semimetals. The magneto-optical conductivity also shows transitions
between Landau levels that are not spaced as in an ordinary electron gas. How
are such topological properties modified by interactions and temperature? We
answer this question by studying a lattice model of Weyl semimetals with an
on-site Hubbard interaction. Such an interacting Weyl semimetal, dubbed as Weyl
liquid, may be realized in Mn$_3$Sn. We solve that model with single-site
dynamical mean-field theory. We find that in a Weyl liquid, quasiparticles can
be characterized by a quasiparticle spectral weight $Z$, although their
lifetime increases much more rapidly as frequency approaches zero than in an
ordinary Fermi liquid. The negative magnetoresistance still exists, even though
the slope of the linear dependence of the DC conductivity with respect to the
magnetic filed is decreased by the interaction. At elevated temperatures, a
Weyl liquid crossesover to bad metallic behavior where the Drude peak becomes
flat and featureless.

###Magnetoresistance oscillations in multilayer systems - triple quantum wells|S. Wiedmann,N. C. Mamani,G. M. Gusev,O. E. Raichev,A. K. Bakarov,J. C. Portal###

Magnetoresistance oscillations in multilayer systems - triple quantum wells. Magnetoresistance of two-dimensional electron systems with several occupied
subbands oscillates owing to periodic modulation of the probability of
intersubband transitions by the quantizing magnetic field. In addition to
previous investigations of these magneto-intersubband (MIS) oscillations in
two-subband systems, we report on both experimental and theoretical studies of
such a phenomenon in three-subband systems realized in triple quantum wells. We
show that the presence of more than two subbands leads to a qualitatively
different MIS oscillation picture, described as a superposition of several
oscillating contributions. Under a continuous microwave irradiation, the
magnetoresistance of triple-well systems exhibits an interference of MIS
oscillations and microwaveinduced resistance oscillations. The theory
explaining these phenomena is presented in the general form, valid for an
arbitrary number of subbands. A comparison of theory and experiment allows us
to extract temperature dependence of quantum lifetime of electrons and to
confirm the applicability of the inelastic mechanism of microwave
photoresistance for the description of magnetotransport in multilayer systems.

###The tunnel magnetoresistance in chains of quantum dots weakly coupled to external leads|Ireneusz Weymann###

The tunnel magnetoresistance in chains of quantum dots weakly coupled to external leads. We analyze numerically the spin-dependent transport through coherent chains
of three coupled quantum dots weakly connected to external magnetic leads. In
particular, using the diagrammatic technique on the Keldysh contour, we
calculate the conductance, shot noise and tunnel magnetoresistance (TMR) in the
sequential and cotunneling regimes. We show that transport characteristics
greatly depend on the strength of the interdot Coulomb correlations, which
determines the spacial distribution of electron wave function in the chain.
When the correlations are relatively strong, depending on the transport regime,
we find both negative TMR as well as TMR enhanced above the Julliere value,
accompanied with negative differential conductance (NDC) and super-Poissonian
shot noise. This nontrivial behavior of tunnel magnetoresistance is associated
with selection rules that govern tunneling processes and various high-spin
states of the chain that are relevant for transport. For weak interdot
correlations, on the other hand, the TMR is always positive and not larger than
the Julliere TMR, although super-Poissonian shot noise and NDC can still be
observed.

###Inverse Spin Hall Effect in NiFe / Normal Metal Bilayers|M. Obstbaum,M. Härtinger,T. Meier,F. Swientek,C. H. Back,G. Woltersdorf###

Inverse Spin Hall Effect in NiFe / Normal Metal Bilayers. Spin pumping in ferromagnets provides a source of pure spin currents. Via the
inverse spin Hall effect a spin current is converted into a charge current and
a corresponding detectable DC-voltage. The ratio of injected spin current to
resulting charge current is given by the spin Hall angle. However, the number
of experiments more or less equals the number of different values for spin Hall
angles, even for the most studied normal metal platinum. This publication
provides a full study of inverse spin Hall effect and anisotropic
magnetoresistance for different NiFe(Py) / normal metal bilayers using a
coplanar waveguide structure. Angle and frequency dependent measurements
strongly suggest that spin pumping and inverse spin Hall effect can be used to
quantify spin Hall angles only if certain conditions are met. Ruling out the
anisotropic magnetoresistance as a parasitic voltage generating effect
measurements of the inverse spin Hall effect in Py/Pt and Py/Au yield spin Hall
angles of 0.09 and 0.008 respectively. Furthermore, DC-voltages at
ferromagnetic resonance for Py/Pt are studied as a function of temperature and
the results are compared to theoretical models.

###Comment on "Pt magnetic polarization on Y3Fe5O12 and magnetotransport characteristics"|Stephan Geprägs,Sebastian T. B. Goennenwein,Marc Schneider,Fabrice Wilhelm,Katharina Ollefs,Andrei Rogalev,Matthias Opel,Rudolf Gross###

Comment on "Pt magnetic polarization on Y3Fe5O12 and magnetotransport characteristics". In a recent Letter [Y.M. Lu et al., Phys. Rev. Lett. 110, 147207 (2013)], Lu
et al. reported on "ferromagneticlike transport properties" of thin films of
Pt, deposited ex situ via sputtering on the ferrimagnetic insulator Y3Fe5O12.
The authors found a magnetoresistance in Pt displaying a hysteresis
corresponding to the coercive field of Y3Fe5O12, consistent with the findings
of other groups. While the latter interpreted their data in terms of the
recently proposed spin-Hall magnetoresistance, Lu et al. attributed their
observation to a magnetic proximity effect. To support this interpretation,
they measured the X-ray magnetic circular dichroism (XMCD) at the Pt L2,3 edges
from a Pt/Y3Fe5O12 sample with a Pt thickness of 1.5 nm and derived an average
induced magnetic moment of 0.054 Bohr magnetons per Pt atom. This is
contradictory to the results of our previous comprehensive XMCD study of three
different Pt/Y3Fe5O12 samples with Pt thicknesses of 3, 7, and 10 nm from which
we identified an upper limit of (0.003 +/- 0.001) Bohr magnetons per Pt
[Gepr\"ags et al., Appl. Phys. Lett. 101, 262407 (2012), arXiv:1211.0916].

###Anisotropic Electronic Mobilities in the Nematic State of the Parent Phase NaFeAs|Qiang Deng,Jie Xing,Jianzhong Liu,Huan Yang,Hai-Hu Wen###

Anisotropic Electronic Mobilities in the Nematic State of the Parent Phase NaFeAs. Hall effect and magnetoresistance have been measured on single crystals of
the parent phase NaFeAs under a uniaxial pressure. Although significant
difference of the in-plane resistivity $\rho_{xx}(I\parallel a)$ and
$\rho_{xx}(I\parallel b)$ with the uniaxial pressure along $b$-axis was
observed, the transverse resistivity $\rho_{xy}$ shows a surprisingly isotropic
behavior. Detailed analysis reveals that the Hall coefficient $R_\mathrm{H}$
measured in the two orthogonal configurations ($I\parallel a$-axis and
$I\parallel b$-axis) coincide very well and exhibit a deviation from the high
temperature background at around the structural transition temperature
$T_{\mathrm{s}}$. Furthermore, the magnitude of $R_\mathrm{H}$ increases
remarkably below the structural transition temperature. This enhanced Hall
coefficient is accompanied by the non-linear transverse resistivity versus
magnetic field and enhanced magnetoresistance, which can be explained very well
by the two band model with anisotropic mobilities of each band. Our results
together with the two band model analysis clearly show that the anisotropic
in-plane resistivity in the nematic state is closely related to the distinct
quasiparticle mobilities when they are moving parallel or perpendicular to the
direction of the uniaxial pressure.

###Negative Magnetoresistance in Topological Semimetals of Transition-Metal Dipnictides with Nontrivial Z2 Indices|Yupeng Li,Zhen Wang,Yunhao Lu,Xiaojun Yang,Zhixuan Shen,Feng Sheng,Chunmu Feng,Yi Zheng,Zhu-An Xu###

Negative Magnetoresistance in Topological Semimetals of Transition-Metal Dipnictides with Nontrivial Z2 Indices. Negative magnetoresistance (NMR) induced by the Adler-Bell-Jackiw anomaly is
regarded as the most prominent quantum signature of Weyl semimetals when
electrical field $E$ is collinear with the external magnetic field $B$. In this
article, we report universal NMR in nonmagnetic, centrosymmetric transition
metal dipnictides MPn$_{2}$ (M=Nb and Ta; Pn=As and Sb), in which the existence
of Weyl fermions can be explicitly excluded. Using temperature-dependent
magnetoresistance, Hall and thermoelectric coefficients of Nernst and Seebeck
effects, we determine that the emergence of the NMR phenomena in MPn$_{2}$ is
coincident with a Lifshitz transition, corresponding to the formation of unique
electron-hole-electron ($e$-$h$-$e$) pockets along the $I-L-I'$ direction.
First-principles calculations reveal that, along the $I-L-I'$ line, the
$d_{xy}$ and $d_{x^{2}-y^{2}}$ orbitals of the transition metal form tilted
nodal rings of band crossing well below the Fermi level. Strong spin-orbital
coupling gaps all the crossing points and creates the characteristic
$e$-$h$-$e$ structure, making MPn$_{2}$ a topological semimetal with
$\mathbb{Z}_2$ indices of [0;(111)]. By excluding the weak localization
contribution of the bulk states, we conclude that the universal NMR in
MPn$_{2}$ may have an exotic origin in topological surface states, which
appears in pairs with opposite spin-momentum locking on nontrivial surfaces.

###Butterfly Magnetoresistance, Quasi-2D Dirac Fermi Surfaces, and a Topological Phase Transition in ZrSiS|Mazhar N. Ali,Leslie M. Schoop,Chirag Garg,Judith M. Lippmann,Eric Lara,Bettina Lotsch,Stuart Parkin###

Butterfly Magnetoresistance, Quasi-2D Dirac Fermi Surfaces, and a Topological Phase Transition in ZrSiS. Magnetoresistance (MR), the change of a material's electrical resistance in
response to an applied magnetic field, is a technologically important property
that has been the topic of intense study for more than a quarter century. Here
we report the observation of an unusual "butterfly" shaped titanic angular
magnetoresistance (AMR) in the non-magnetic, Dirac material, ZrSiS. The MR is
large and positive, reaching nearly 1.8 x 10^5 percent at 9 T and 2 K at an
angle of 45o between the applied current (along the a-axis) and the applied
field (90o is H parallel to the c-axis). Approaching 90o, a "dip" is seen in
the AMR which can be traced to an angle dependent deviation from the H^2 law.
By analyzing the SdH oscillations at different angles, we find that ZrSiS has a
combination of 2D and 3D Dirac pockets comprising its Fermi surface and that
the anomalous transport behavior coincides with a topological phase transition
whose robust signature is evident despite transport contributions from other
parts of the Fermi surface. We also find that as a function of angle, the
temperature dependent resistivity in high field displays a broad peak-like
behavior, unlike any known Dirac/Weyl material. The combination of very high
mobility carriers and multiple Fermi surfaces in ZrSiS allow for large bulk
property changes to occur as a function of angle between applied fields makes
it a promising platform to study the physics stemming from the coexistence of
2D and 3D Dirac electrons.

###Semiclassical theory of anisotropic transport at LaAlO3/SrTiO3 interfaces under in-plane magnetic field|N. Bovenzi,M. Diez###

Semiclassical theory of anisotropic transport at LaAlO3/SrTiO3 interfaces under in-plane magnetic field. The unconventional magnetotransport at the interface between transition-metal
oxides $LaAlO_3$ (LAO) and $SrTiO_3$ (STO) is frequently related to mobile
electrons interacting with localized magnetic moments. However nature and
properties of magnetism at this interface are not well understood so far. In
this paper, we focus on transport effects driven by spin-orbit coupling and
intentionally neglect possible strong correlations. The electrical resistivity
tensor is calculated as a function of the magnitude and orientation of an
external magnetic field parallel to the interface. The semiclassical Boltzmann
equation is solved numerically for the two-dimensional system of spin-orbit
coupled electrons accelerated by an electric field and scattered by
spatially-correlated impurities. At temperatures of a few Kelvin and densities
such that the chemical potential crosses the second pair of spin-orbit split
bands, we find a strongly anisotropic modulation of the (negative)
magnetoresistance above 10 T, characterized by multiple maxima and minima away
from the crystalline axes. Along with the drop of the magnetoresistance, an
abrupt enhancement of the transverse resistivity occurs. The angular modulation
of the latter considerably deviates from a (low-field) sinusoidal dependence to
a (high-field) step-like behaviour. These peculiar features are the
consequences of the anisotropy of both (intra-band and inter-band )
scattering-amplitudes in the Brillouin zone when the relevant energy scales in
the system - chemical potential, spin-orbit interaction and Zeeman energy - are
all comparable to each other. The theory provides good qualitative agreement
with experimental data in the literature.

###Preparation, structure and giant magnetoresistance of electrodeposited Fe Co/Cu multilayers|B. G. Tóth,L. Péter,L. Pogány,Á. Révész,I. Bakonyi###

Preparation, structure and giant magnetoresistance of electrodeposited Fe Co/Cu multilayers. No systematic studies have been carried out on the giant magnetoresistance
(GMR) of electrodeposited (ED) Fe-Co/Cu multilayers since the elaboration of a
method for the optimization of the Cu layer deposition potential. In this
paper, we present results on the electrochemical optimization of the Cu layer
deposition potential which was found to depend on the relative iron
concentration in the bath. An X-ray diffraction study of ED Fe5Co95(1.5
nm)/Cu(dCu) multilayers with dCu ranging from 0.8 nm to 10 nm revealed an fcc
structure. For most of the multilayers, a weak superlattice satellite
reflection could be identified. The room-temperature magnetoresistance was
studied in detail as a function of the individual layer thicknesses.
Multilayers with Cu layer thicknesses above about 1.5 nm were found to exhibit
a GMR behavior with a maximum GMR of about 5 % and a typical saturation field
of 1 kOe. The GMR magnitude decreased with increasing Fe-content in the
magnetic layer. The spacer layer thickness evolution of the MR data was
established in detail after separating the ferromagnetic and superparamagnetic
GMR contributions and no oscillatory GMR was found. A comparison with
literature data on both physically deposited and ED Fe-Co/Cu multilayers is
also made.

###The role of magnetic excitations in magnetoresistance and Hall effect of slightly TM-substituted BaFe$_{2}$As$_2$ compounds (TM = Mn, Cu, Ni)|J. P. Peña,M. M. Piva,C. B. R. Jesus,G. G. Lesseux,T. M. Garitezi,D. Tobia,P. F. S. Rosa,T. Grant,Z. Fisk,C. Adriano,R. R. Urbano,P. G. Pagliuso,P. Pureur###

The role of magnetic excitations in magnetoresistance and Hall effect of slightly TM-substituted BaFe$_{2}$As$_2$ compounds (TM = Mn, Cu, Ni). We report on electrical resistivity, magnetoresistance (MR) and Hall effect
measurements in four non-superconducting BaFe$_{2-x}$TM$_x$As$_2$ (TM = Mn, Cu
and Ni) single crystals with small values of the chemical substitution $x$. The
spin density wave (SDW) ordering that occurs in these systems at temperatures
$T\sim$ (120 - 140) K, in close vicinity to a tetragonal/orthorhombic
transition, produces significant modifications in their magneto-transport
properties. While in the magnetically ordered phase the MR is positive and its
magnitude increases with decreasing temperatures, in the paramagnetic regime
the MR becomes vanishingly small. Above the spin density wave transition
temperature ($T_{\text{SDW}}$) the Hall coefficient $R_H$ is negative, small
and weakly temperature dependent, but a remarkable change of slope occurs in
the $R_H$ versus $T$ curves at $T = T_{\text{SDW}}$. The Hall coefficient
amplitude, while remaining negative, increases steadily and significantly as
the temperature is decreased below $T_{\text{SDW}}$ and down to $T =$ 20 K. The
qualitative behavior of both MR and Hall coefficient is weakly dependent on the
chemical substitution in the studied limit. The experiments provide strong
evidence that scattering of charge carriers by magnetic excitations has to be
taken into account to explain the behavior of the resistivity,
magnetoresistance and Hall effect in the ordered phase of the studied
compounds. Effects of multiple band conduction also must be considered for a
complete interpretation of the results.

###Symmetry-enforced Fermi degeneracy in topological semimetal RhSb$_3$|Kefeng Wang,Limin Wang,I-Lin Liu,F. Boschini,M. Zonno,M. Michiardi,E. Rotenberg,A. Bostwick,D. Graf,B. J. Ramshaw,A. Damascelli,J. Paglione###

Symmetry-enforced Fermi degeneracy in topological semimetal RhSb$_3$. Predictions of a topological electronic structure in the skutterudite TPn$_3$
family (T=transition metal, Pn=pnictogen) are investigated via
magnetoresistance, quantum oscillations and angle-resolved photoemission
experiments of RhSb$_3$, an unfilled skutterudite semimetal with low carrier
density. Electronic band structure calculations and symmetry analysis of
RhSb$_3$ indicate this material to be a zero-gap semimetal protected by
symmetry with inverted valence/conduction bands that touch at the $\Gamma$
point close to the Fermi level. Transport experiments reveal an unsaturated
linear magnetoresistance that approaches a factor of 200 at 60~T magnetic
fields, and quantum oscillations observable up to 150~K that are consistent
with a large Fermi velocity ($\sim 1.3\times 10^6$ m/s), high carrier mobility
($\sim 14$ m$^2$/Vs), and the existence of a small three dimensional hole
pocket. A very small, sample-dependent effective mass falls to values as low as
$0.018(2)$ of the bare electron mass and scales with Fermi wavevector. This,
together with a non-zero Berry's phase and location of the Fermi level in the
linear region of the valence band, suggests RhSb$_3$ as representative of a new
class of toplogical semimeals with symmetry-enforced Fermi degeneracy at the
high symmetry points.

###Fermi surface topology and signature of surface Dirac nodes in LaBi|Ratnadwip Singha,Biswarup Satpati,Prabhat Mandal###

Fermi surface topology and signature of surface Dirac nodes in LaBi. Novel topological state of matter is one of the rapidly growing fields in
condensed matter physics research in recent times. While these materials are
fascinating from the aspect of fundamental physics of relativistic particles,
their exotic transport properties are equally compelling due to the potential
technological applications. Extreme magnetoresistance and ultrahigh carrier
mobility are two such major hallmarks of topological materials and often used
as primary criteria for identifying new compounds belonging to this class.
Recently, LaBi has emerged as a new system, which exhibits the above mentioned
properties. However, the topological nature of its band structure remains
unresolved. Here, using the magnetotransport and magnetization measurements, we
have probed the bulk and surface states of LaBi. Similar to earlier reports,
extremely large magnetoresistance and high carrier mobility have been observed
with compensated electron and hole density. The Fermi surface properties have
been analyzed from both Shubnikov-de Haas and de Haas-van Alphen oscillation
techniques. In the magnetization measurement, a prominent paramagnetic
singularity has been observed, which demonstrates the non-trivial nature of the
surface states in LaBi. Our study unambiguously confirms that LaBi is a
three-dimensional topological insulator with possible linear dispersion in the
gapped bulk band structure.

###Magnetization reversal in Py/Gd heterostructures|Pavel N. Lapa,Junjia Ding,John E. Pearson,Valentine Novosad,J. S. Jiang,Axel Hoffmann###

Magnetization reversal in Py/Gd heterostructures. Using a combination of magnetometry and magnetotransport techniques, we
studied temperature and magnetic field behavior of magnetization in Py/Gd
heterostructures. It was shown quantitatively that proximity with Py enhances
magnetic order of Gd. Micromagnetic simulations demonstrate that a spin-flop
transition observed in a Py/Gd bilayer is due to exchange-spring rotation of
magnetization in the Gd layer. Transport measurements show that the
magnetoresistance of a [Py(2 nm)/Gd(2 nm)]25 multilayer changes sign at the
compensation temperature and below 20 K. The positive magnetoresistance above
the compensation temperature can be attributed to an in-plane domain-wall,
which appears because of the structural inhomogeneity of the film over its
thickness. By measuring the angular dependence of resistance we are able to
determine the angle between magnetizations in the multilayer and the magnetic
field at different temperatures. The measurement reveals that due to a change
of the chemical thickness profile, a non-collinear magnetization configuration
is only stable in magnetic fields above 10 kOe.

###Scaling Projections on Spin Transfer Torque Magnetic Tunnel Junctions|Debasis Das,Ashwin Tulapurkar,Bhaskaran Muralidharan###

Scaling Projections on Spin Transfer Torque Magnetic Tunnel Junctions. We investigate scaling of technologically relevant magnetic tunnel junction
devices in the trilayer and pentalayer configurations by varying the
cross-sectional area along the transverse direction using the non-equilibrium
Green's function spin transport formalism. We study the geometry dependence by
considering square and circular cross-sections. As the transverse dimension in
each case reduces, we demonstrate that the transverse mode energy profile plays
a major role in the resistance-area product. Both types of devices show
constant tunnel magnetoresistance at larger cross-sectional areas but achieve
ultra-high magnetoresistance at small cross-sectional areas, while maintaining
low resistance-area products. We notice that although the critical switching
voltage for switching the magnetization of the free layer nanomagnet in the
trilayer case remains constant at larger areas, it needs more energy to switch
at smaller areas. In the pentalayer case, we observe an oscillatory behavior at
smaller areas as a result of double barrier tunneling. We also describe how
switching characteristics of both kinds of devices are affected by the scaling.

###Signatures of long-range-correlated disorder in the magnetotransport of ultrathin topological insulators|D. Nandi,B. Skinner,G. H. Lee,K. -F. Huang,K. Shain,Cui-Zu Chang,Y. Ou,S. -P. Lee,J. Ward,J. S. Moodera,P. Kim,B. I. Halperin,A. Yacoby###

Signatures of long-range-correlated disorder in the magnetotransport of ultrathin topological insulators. In an ultrathin topological insulator (TI) film, a hybridization gap opens in
the TI surface states, and the system is expected to become either a trivial
insulator or a quantum spin Hall insulator when the chemical potential is
within the hybridization gap. Here we show, however, that these insulating
states are destroyed by the presence of a large and long-range-correlated
disorder potential, which converts the expected insulator into a metal. We
perform transport measurements in ultrathin, dual-gated topological insulator
films as a function of temperature, gate voltage, and magnetic field, and we
observe a metallic-like, non-quantized conductivity, which exhibits a weak
antilocalization-like cusp at the low magnetic field and gives way to a
nonsaturating linear magnetoresistance at large field. We explain these results
by considering the disordered network of electron- and hole-type puddles
induced by charged impurities. We argue theoretically that such disorder can
produce an insulator-to-metal transition as a function of increasing disorder
strength, and we derive a condition on the band gap and the impurity
concentration necessary to observe the insulating state. We also explain the
linear magnetoresistance in terms of strong spatial fluctuations of the local
conductivity, using both numerical simulations and a theoretical scaling
argument.

###Tunable magnetoresistance in spin-orbit coupled graphene junctions|Razieh Beiranvand,Hossein Hamzehpour###

Tunable magnetoresistance in spin-orbit coupled graphene junctions. Using the Landauer-B\"utikker formalism, we study the graphene
magneto-transport in the presence of Rashba spin-orbit interaction (RSOI). We
show that the angle resolved transmission probability in the proposed
structures can be tuned by the RSOI strength. The transmission spectrum show
Klein tunneling in the parallel (P) magnetization configuration which can be
blocked by the RSOI. This effect is also observable for the anti-parallel (AP)
magnetization configuration in different incident angle. The numerical results
shows that the spin-polarized conductance strongly depends on the strength of
the RSOI and can be generated by tuning the magnetic exchange field and RSOI
strength. This spin-polarized conductance is a sensitive oscillatory function
of the thickness of the RSO region. Because of the spin-flip effect, the
junction shows a spin-valve effect with large and negative magnetoresistance
(MR) and spin-magnetoresistance (SMR) in the presence of RSOI. When the RSOI is
on, the frequency and amplitude of shot-noise and Fano factor's oscillations
are also increased. These results can provide a way to extending the
application of graphene-based junctions in spintronics.

###Mechanically tunable spontaneous vertical charge redistribution in few-layer WTe2|Zeyuan Ni,Emi Minamitani,Kazuaki Kawahara,Ryuichi Arafune,Chun-Liang Lin,Noriaki Takagi,Satoshi Watanabe###

Mechanically tunable spontaneous vertical charge redistribution in few-layer WTe2. Broken symmetry is the essence of exotic properties in condensed matters.
Tungsten ditelluride, WTe$_2$, exceptionally takes a non-centrosymmetric
crystal structure in the family of transition metal dichalcogenides, and
exhibits novel properties$^{1-4}$, such as the nonsaturating
magnetoresistance$^1$ and ferroelectric-like behavior$^4$. Herein, using the
first-principles calculation, we show that unique layer stacking in WTe$_2$
generates surface dipoles with different strengths on the top and bottom
surfaces in few-layer WTe$_2$. This leads to a layer-dependence for
electron/hole carrier ratio and the carrier compensation responsible for the
unusual magnetoresistance. The surface dipoles are tunable and switchable using
the interlayer shear displacement. This could explain the ferroelectric-like
behavior recently observed in atomically thin WTe$_2$ films$^4$. In addition,
we reveal that exfoliation of the surface layer flips the out-of-plane spin
textures. The presented results will aid in the deeper understanding,
manipulation, and further exploration of the physical properties of WTe$_2$ and
related atom-layered materials, for applications in electronics and spintronic
devices.

###Tunnel magnetoresistance angular and bias dependence enabling tuneable wireless communication|Ewa Kowalska,Akio Fukushima,Volker Sluka,Ciarán Fowley,Attila Kákay,Yuriy Aleksandrov,Jürgen Lindner,Jürgen Fassbender,Shinji Yuasa,Alina M. Deac###

Tunnel magnetoresistance angular and bias dependence enabling tuneable wireless communication. Spin-transfer torques (STTs) can be exploited in order to manipulate the
magnetic moments of nanomagnets, thus allowing for new consumer-oriented
devices to be designed. Of particular interest here are tuneable
radio-frequency (RF) oscillators for wireless communication. Currently, the
structure that maximizes the output power is an Fe/MgO/Fe-type magnetic tunnel
junction (MTJ) with a fixed layer magnetized in the plane of the layers and a
free layer magnetized perpendicular to the plane. This structure allows for
most of the tunnel magnetoresistance (TMR) to be converted into output power.
Here, we experimentally and theoretically demonstrate that the main mechanism
sustaining steady-state precession in such structures is the angular dependence
of the magnetoresistance. The TMR of such devices is known to exhibit a
broken-linear dependence versus the applied bias. Our results show that the TMR
bias dependence effectively quenches spin-transfer-driven precession and
introduces a non-monotonic frequency dependence at high applied currents. Thus
we expect the bias dependence of the TMR to have an even more dramatic effect
in MTJs with Mn-Ga-based free layers, which could be used to design wireless
oscillators extending towards the THz gap, but have been experimentally shown
to exhibit a non-trivial TMR bias dependence.

###The upper critical field and its anisotropy in RbCr$_{3}$As$_{3}$|Qimei Liang,Tong Liu,Chuanying Xi,Yuyan Han,Gang Mu,Li Pi,Zhi-An Ren,Zhaosheng Wang###

The upper critical field and its anisotropy in RbCr$_{3}$As$_{3}$. The temperature dependence of the upper critical field ($H_{c2}$) in RbCr$%
_{3}$As$_{3}$ single crystals ($T_{c}\approx $ 7.3 K) has been determined by
means of magnetoresistance measurements with temperature down to 0.35 K in
static magnetic fields up to 38 T. The magnetic field was applied both for
directions parallel ($H\parallel c $, $H_{c2}^{\parallel c}$) and perpendicular
($H\perp c$, $H_{c2}^{\perp c}$) to the Cr chains. The curves
$H_{c2}^{\parallel c}(T)$ and $H_{c2}^{\perp c}(T)$ cross at $\sim $ 5.5 K. As
a result, the anisotropy parameter $\gamma (T)=H_{c2}^{\perp
c}/H_{c2}^{\parallel c}(T)$ increases from 0.5 near $T_{c}$ to 1.6 at low
temperature. Fitting with the Werthamer-Helfand-Hohenberg (WHH) model yields
zero-temperature critical fields of $\mu_0H_{c2}^{\parallel c}(0)\approx $ 27.2
T and $\mu_0H_{c2}^{\perp c}(0)\approx $ 43.4 T, both exceeding the BCS
weak-coupling Pauli limit $\mu_0H_{p}=1.84T_{c}=13.4$ T. The results indicate
that the paramagnetic pair breaking effect is strong for $H \parallel c$ but
absent for $H \perp c$, which was further confirmed by the angle dependent
magnetoresistance and $H_{c2}$ measurements.

###Quantum oscillations and electronic structures in large Chern number semimetal RhSn|Sheng Xu,Liqin Zhou,Huan Wang,Xiao-Yan Wang,Yuan Su,Peng Cheng,Hongming Weng,Tian-Long Xia###

Quantum oscillations and electronic structures in large Chern number semimetal RhSn. We report the magnetoresistance, Hall effect, de Haas-van Alphen (dHvA)
oscillations and the electronic structures of single crystal RhSn, which is a
typical material of CoSi family holding a large Chern number. The large
unsaturated magnetoresistance is observed with B//[001]. The Hall resistivity
curve indicates that RhSn is a multi-band system with high mobility. Evident
quantum oscillations have been observed, from which the light effective masses
are extracted. Ten fundamental frequencies are extracted after the fast Fourier
transform analysis of the dHvA oscillations with B//[001] configuration. The
two low frequencies F$_1$ and F$_2$ do not change obviously and the two high
frequencies F$_9$ and F$_{10}$ evolve into four when B rotates from B//[001] to
B//[110], which is consistent with the band structure in the first-principles
calculations with spin-orbit coupling (SOC). The extracted Berry phases of the
relative pockets show a good agreement with the Chern number $\pm4$ (with SOC)
in the first-principles calculations. Above all, our studies indicate that RhSn
is an ideal platform to study the unconventional chiral fermions and the
surface states.

###Spin effects in single electron tunneling|J. Barnas,I. Weymann###

Spin effects in single electron tunneling. An important consequence of the discovery of giant magnetoresistance in
metallic magnetic multilayers is a broad interest in spin dependent effects in
electronic transport through magnetic nanostructures. An example of such
systems are tunnel junctions -- single-barrier planar junctions or more complex
ones. In this review we present and discuss recent theoretical results on
electron and spin transport through ferromagnetic mesoscopic junctions
including two or more barriers. Such systems are also called ferromagnetic
single-electron transistors. We start from the situation when the central part
of a device has the form of a magnetic (or nonmagnetic) metallic nanoparticle.
Transport characteristics reveal then single-electron charging effects,
including the Coulomb staircase, Coulomb blockade, and Coulomb oscillations.
Single-electron ferromagnetic transistors based on semiconductor quantum dots
and large molecules (especially carbon nanotubes) are also considered. The main
emphasis is placed on the spin effects due to spin-dependent tunnelling through
the barriers, which gives rise to spin accumulation and tunnel
magnetoresistance. Spin effects also occur in the current-voltage
characteristics, (differential) conductance, shot noise, and others. Transport
characteristics in the two limiting situations of weak and strong coupling are
of particular interest. In the former case we distinguish between the
sequential tunnelling and cotunneling regimes. In the strong coupling regime we
concentrate on the Kondo phenomenon, which in the case of transport through
quantum dots or molecules leads to an enhanced conductance and to a pronounced
zero-bias Kondo peak in the differential conductance.

###Magnetotransport in La(Fe,Ru)AsO as a probe of band structure and mobility|I. Pallecchi,F. Bernardini,M. Tropeano,A. Palenzona,A. Martinelli,C. Ferdeghini,M. Vignolo,S. Massidda,M. Putti###

Magnetotransport in La(Fe,Ru)AsO as a probe of band structure and mobility. In this work we investigate the Ru substituted LaFeAsO compound, by studying
the magnetotransport behaviour and its relationship with the band structure, in
different regimes of temperature, magnetic field and Ru content. In particular
we analyse the magnetoresistance of LaFe1-xRuxAsO (0 <= x <= 0.6) samples with
the support of ab initio calculations and we find out that in the whole series:
(i) the transport is dominated by electron bands only; (ii) the
magnetoresistance exhibits distinctive features related to the presence of
Dirac cones; indeed, ab initio calculations confirm the presence of anisotropic
Dirac cones in the band structure; (iii) the low temperature mobility is
exceptionally high and reaches 18.6 m2/(Vs) in the Ru-free sample at T=2K, in
the extreme limit of a single Landau level occupied in the Dirac cones; (iv)
the mobility drops abruptly above 10K-15K; (v) the disorder has a very weak
effect on the band mobilities and on the transport properties; (vi) there
exists a correlation between the temperature ranges of Dirac cones and SDW
carrier condensation. These findings may be of crucial importance in the
investigation of the pairing mechanism in the F-doped superconducting
La(Fe,Ru)As(O,F) compounds related to this series of parent compounds.

###Transport properties and asymmetric scattering in Ba$_{1-x}$K$_x$Fe$_2$As$_2$ single crystals compared to the electron doped counterparts Ba(Fe$_{1-x}$Co$_{x}$)$_{2}$As$_{2}$}|Bing Shen,Huan Yang,Zhao-Sheng Wang,Fei Han,Bin Zeng,Lei Shan,Cong Ren,Hai-Hu Wen###

Transport properties and asymmetric scattering in Ba$_{1-x}$K$_x$Fe$_2$As$_2$ single crystals compared to the electron doped counterparts Ba(Fe$_{1-x}$Co$_{x}$)$_{2}$As$_{2}$}. Resistivity, Hall effect and magnetoresistance have been investigated
systematically on single crystals of Ba$_{1-x}$K$_x$Fe$_2$As$_2$ ranging from
undoped to optimally doped regions. A systematic evolution of the quasiparticle
scattering has been observed. It is found that the resistivity in the normal
state of Ba$_{1-x}$K$_x$Fe$_2$As$_2$ is insensitive to the potassium doping
concentration, which is very different from the electron doped counterpart
Ba(Fe$_{1-x}$Co$_{x}$)$_{2}$As$_{2}$, where the resistivity at 300 K reduces to
half value of the undoped one when the system is optimally doped. In stark
contrast, the Hall coefficient R$_H$ changes suddenly from a negative value in
the undoped sample to a positive one with slight K-doping, and it keeps
lowering with further doping. We interpret this dichotomy due to the asymmetric
scattering rate in the hole and the electron pockets with much higher mobility
of the latter. The magnetoresistivity shows also a non-monotonic doping
dependence indicating an anomalous feature at about 80 K to 100 K, even in the
optimally doped sample, which is associated with a possible pseudogap feature.
In the low temperature region, it seems that the resistivity has the similar
values when superconductivity sets in disregarding the different T$_c$ values,
which indicates a novel mechanism of the superconductivity. A linear feature of
resistivity $\rho_{ab}$ vs. $T$ was observed just above $T_c$ for the optimally
doped sample, suggesting a quantum criticality.

###Hydrogen-induced ferromagnetism in ZnO single crystals investigated by Magnetotransport|M. Khalid,P. Esquinazi###

Hydrogen-induced ferromagnetism in ZnO single crystals investigated by Magnetotransport. We investigated the electrical and magnetic properties of low-energy
hydrogen-implanted ZnO single crystals with hydrogen concentrations up to 3
at.% in the first 20 nm surface layer between 10 K and 300 K. All samples
showed clear ferromagnetic hysteresis loops at 300 K with a saturation
magnetization up to 4 emu/g. The measured anomalous Hall effect agrees with the
hysteresis loops measured by superconducting quantum interferometer device
magnetometry. All the H-treated ZnO crystals exhibited a negative
magnetoresistance up to the room temperature. The relative magnitude of the
anisotropic magnetoresistance reaches 0.4 % at 250 K and 2 % at 10 K,
exhibiting an anomalous, non-monotonous behavior and a change of sign below 100
K. All the experimental data indicate that hydrogen atoms alone in a few
percent range trigger a magnetic order in a ZnO crystalline state. Hydrogen
implantation turns out to be a simpler and effective method to generate a
magnetic order in ZnO, which provides interesting possibilities for future
applications due to the strong reduction of the electrical resistance.

###Emergence of the stripe-domain phase in patterned Permalloy films|S. Voltan,C. Cirillo,H. J. Snijders,K. Lahabi,A. Garcia-Santiago,J. M. Hernandez,C. Attanasio,J. Aarts###

Emergence of the stripe-domain phase in patterned Permalloy films. The occurrence of stripe domains in ferromagnetic Permalloy
(Py=Fe$_{20}$Ni$_{80}$) is a well known phenomenon which has been extensively
observed and characterized. This peculiar magnetic configuration appears only
in films with a thickness above a critical value ($d_{cr}$), which is strongly
determined by the sputtering conditions (i.e. deposition rate, temperature,
magnetic field). So far, $d_{cr}$ has usually been presented as the boundary
between the homogeneous (H) and stripe-domains (SD) regime, respectively below
and above $d_{cr}$. In this work we study the transition from the H to the SD
regime in thin films and microstructured bridges of Py with different
thicknesses. We find there is an intermediate regime, over a quite significant
thickness range below d$_{cr}$, which is signaled in confined structures by a
quickly changing domain-wall configuration and by a broadening of the
magnetoresistance dip at the coercive field. We call this the emerging
stripe-domains (ESD) regime. The transition from the ESD to the SD regime is
accompanied by a sharp increase of the magnetoresistance ratio at the thickness
where stripes appear in MFM.

###Magnetoresistance and surface roughness study of the initial growth of electrodeposited Co/Cu multilayers|B. G. Tóth,L. Péter,I. Bakonyi###

Magnetoresistance and surface roughness study of the initial growth of electrodeposited Co/Cu multilayers. The giant magnetoresistance (GMR) effect has been widely investigated on
electrodeposited ferromagnetic/non-magnetic (FM/NM) multilayers generally
containing a large number of bilayers. In most applications of the GMR effect,
layered structures consisting of a relatively small number of consecutive FM
and NM layers are used. It is of great interest, therefore, to investigate the
initial stages of GMR multilayer film growth by electrodeposition. In the
present work we have extended our previous studies on ED GMR multilayers to
layered structures with a total thickness ranging from a few nanometers up to
70 nm. The evolution of the surface roughness and electrical transport
properties of such ultrathin ED Co/Cu layered structures was investigated.
Various layer combinations were produced including both Co and Cu either as
starting or top layers in order (i) to see differences in the nucleation of the
first layer and (ii) to trace out the effect of the so called exchange
reaction. Special attention was paid to measure the field dependence of the
magnetoresistance, MR(H) in order to derive information for the appearance of
superparamagnetic regions in the magnetic layers. This proved to be helpful for
monitoring the evolution of the layer microstructure at each step of the
deposition sequence.

###Unusual interlayer quantum transport behavior caused by the zeroth Landau level in YbMnBi2|J. Y. Liu,J. Hu,D. Graf,T. Zou,M. Zhu,Y. Shi,S. Che,S. M. A. Radmanesh,C. N. Lau,L. Spinu,H. B. Cao,X. Ke,Z. Q. Mao###

Unusual interlayer quantum transport behavior caused by the zeroth Landau level in YbMnBi2. Relativistic fermions in topological quantum materials are characterized by
linear energy-momentum dispersion near band crossing points. Under magnetic
field, relativistic fermions acquire Berry phase of {\pi} in cyclotron motion,
leading to a zeroth Landau level (LL) at the crossing point. Such
field-independent zeroth LL, which distinguishes relativistic fermions from
conventional electron systems, is hardly probed in transport measurements since
the Fermi energy (EF) is usually not right at the band crossing points in most
topological materials. Here we report the observation of exotic quantum
transport behavior resulting from the zeroth LL in a multiband topological
semimetal YbMnBi2 which possesses linear band crossings both at and away from
the Fermi level (FL). We show that the Dirac bands with the crossing points
being above or below the FL leads to Shubnikov de-Haas oscillations in the
in-plane magnetoresistance, whereas the Dirac bands with the crossing points
being at the FL results in unusual angular dependences of the out-of-plane
magnetoresistance and in-plane Hall resistivity due to the dependence of the
zeroth LL's degeneracy on field orientation. Our results shed light on the
transport mechanism of the zeroth LL's relativistic fermions in layered
materials.

###Extremely large non-saturating magnetoresistance and ultrahigh mobility due to topological surface states in metallic Bi2Te3 topological insulator|K. Shrestha,M. Chou,D. Graf,H. D. Yang,B. Lorenz,C. W. Chu###

Extremely large non-saturating magnetoresistance and ultrahigh mobility due to topological surface states in metallic Bi2Te3 topological insulator. Weak antilocalization (WAL) effects in Bi2Te3 single crystals have been
investigated at high and low bulk charge carrier concentrations. At low charge
carrier density the WAL curves scale with the normal component of the magnetic
field, demonstrating the dominance of topological surface states in
magnetoconductivity. At high charge carrier density the WAL curves scale with
neither the applied field nor its normal component, implying a mixture of bulk
and surface conduction. WAL due to topological surface states shows no
dependence on the nature (electrons or holes) of the bulk charge carriers. The
observations of an extremely large, non-saturating magnetoresistance, and
ultrahigh mobility in the samples with lower carrier density further support
the presence of surface states. The physical parameters characterizing the WAL
effects are calculated using the Hikami-Larkin-Nagaoka formula. At high charge
carrier concentrations, there is a greater number of conduction channels and a
decrease in the phase coherence length compared to low charge carrier
concentrations. The extremely large magnetoresistance and high mobility of
topological insulators have great technological value and can be exploited in
magneto-electric sensors and memory devices.

###Strongly angle-dependent magnetoresistance in Weyl semimetals with long-range disorder|Jan Behrends,Jens H. Bardarson###

Strongly angle-dependent magnetoresistance in Weyl semimetals with long-range disorder. The chiral anomaly in Weyl semimetals states that the left- and right-handed
Weyl fermions, constituting the low energy description, are not individually
conserved, resulting, for example, in a negative magnetoresistance in such
materials. Recent experiments see strong indications of such an anomalous
resistance response; however, with a response that at strong fields is more
sharply peaked for parallel magnetic and electric fields than expected from
simple theoretical considerations. Here, we uncover a mechanism, arising from
the interplay between the angle-dependent Landau level structure and long-range
scalar disorder, that has the same phenomenology. In particular, we ana-
lytically show, and numerically confirm, that the internode scattering time
decreases exponentially with the angle between the magnetic field and the Weyl
node separation in the large field limit, while it is insensitive to this angle
at weak magnetic fields. Since, in the simplest approximation, the internode
scattering time is proportional to the anomaly-related conductivity, this
feature may be related to the experimental observations of a sharply peaked
magnetoresistance.

###Electronic structure of RSb (R = Y, Ce, Gd, Dy, Ho, Tm, Lu) studied by angle-resolved photoemission spectroscopy|Yun Wu,Yongbin Lee,Tai Kong,Daixiang Mou,Rui Jiang,Lunan Huang,S. L. Bud'ko,P. C. Canfield,Adam Kaminski###

Electronic structure of RSb (R = Y, Ce, Gd, Dy, Ho, Tm, Lu) studied by angle-resolved photoemission spectroscopy. We use high resolution angle-resolved photoemission spectroscopy (ARPES) and
electronic structure calculations to study the electronic properties of
rare-earth monoantimonides RSb (R = Y, Ce, Gd, Dy, Ho, Tm, Lu). The
experimentally measured Fermi surface (FS) of RSb consists of at least two
concentric hole pockets at the $\Gamma$ point and two intersecting electron
pockets at the $X$ point. These data agree relatively well with the electronic
structure calculations. Detailed photon energy dependence measurements using
both synchrotron and laser ARPES systems indicate that there is at least one
Fermi surface sheet with strong three-dimensionality centered at the $\Gamma$
point. Due to the "lanthanide contraction", the unit cell of different
rare-earth monoantimonides shrinks when changing rare-earth ion from CeSb to
LuSb. This results in the differences in the chemical potentials in these
compounds, which is demonstrated by both ARPES measurements and electronic
structure calculations. Interestingly, in CeSb, the intersecting electron
pockets at the $X$ point seem to be touching the valence bands, forming a
four-fold degenerate Dirac-like feature. On the other hand, the remaining
rare-earth monoantimonides show significant gaps between the upper and lower
bands at the $X$ point. Furthermore, similar to the previously reported results
of LaBi, a Dirac-like structure was observed at the $\Gamma$ point in YSb,
CeSb, and GdSb, compounds showing relatively high magnetoresistance. This
Dirac-like structure may contribute to the unusually large magnetoresistance in
these compounds.

###Absence of Metallic Behavior in Epitaxial NiCo2O4 Thin Films: Role of Microstructural Disorder|Congmian Zhen,XiaoZhe Zhang,Wengang Wei,Wenzhe Guo,Ankit Pant,Xiaoshan Xu,Jian Shen,Li Ma,Denglu Hou###

Absence of Metallic Behavior in Epitaxial NiCo2O4 Thin Films: Role of Microstructural Disorder. Despite the low resistivity (~ 1 mohm cm), the metallic electrical transport
has not been commonly observed in the inverse spinel NiCo2O4, except in certain
epitaxial thin films. Previous studies have stressed the effect of valence
mixing and degree of spinel inversion on the electric conduction of NiCo2O4
films. In this work, we have studied the effect of microstructure by comparing
the NiCo2O4 epitaxial films grown on MgAl2O4 (111) and on Al2O3 (0001)
substrates. Although the optimal growth condition and the magnetic properties
are similar for the NiCo2O4/MgAl2O4 and the NiCo2O4/Al2O3, they show metallic
and semiconducting electrical transport respectively. Despite similar
temperature and field dependence of magnetization, the NiCo2O4/Al2O3 show much
larger magnetoresistance at low temperature. Post-growth annealing decreases
the resistivity of NiCo2O4/Al2O3, but the annealed films are still
semiconducting. The correlation between the structural correlation length and
the resistivity suggests that the microstructural disorder, generated by the
dramatic mismatch between the NiCo2O4 and Al2O3 crystal structures, may be the
origin of the absence of the metallic electrical transport in NiCo2O4. These
results reveal microstructural disorder as another key factor in controlling
the electrical transport of NiCo2O4, with potentially large magnetoresistance
for spintronics application.

###Spin-transfer Antiferromagnetic Resonance|Øyvind Johansen,Hans Skarsvåg,Arne Brataas###

Spin-transfer Antiferromagnetic Resonance. Currents can induce spin excitations in antiferromagnets, even when they are
insulating. We investigate how spin transfer can cause antiferromagnetic
resonance in bilayers and trilayers that consist of one antiferromagnetic
insulator and one or two metals. An ac voltage applied to the metal generates a
spin Hall current that drives the magnetic moments in the antiferromagnet. We
consider excitation of the macrospin mode and of transverse standing-spin-wave
modes. By solving the Landau-Lifshitz-Gilbert equation in the antiferromagnetic
insulator and the spin-diffusion equation in the normal metal, we derive
analytical expressions for the spin-Hall-magnetoresistance and spin-pumping
inverse-spin-Hall dc voltages. In bilayers, the two contributions compensate
each other and cannot easily be distinguished. We present numerical results for
a MnF$_2|$Pt bilayer. Trilayers facilitate separation of the
spin-Hall-magnetoresistance and spin-pumping voltages, thereby revealing more
information about the spin excitations. We also compute the decay of the pumped
spin current through the antiferromagnetic layer as a function of frequency and
the thickness of the antiferromagnetic layer.

###Tunneling spin valves based on Fe$_3$GeTe$_2$/hBN/Fe$_3$GeTe$_2$ van der Waals heterostructures|Zhe Wang,Deepak Sapkota,Takashi Taniguchi,Kenji Watanabe,David Mandrus,Alberto F. Morpurgo###

Tunneling spin valves based on Fe$_3$GeTe$_2$/hBN/Fe$_3$GeTe$_2$ van der Waals heterostructures. Thin van der Waals (vdW) layered magnetic materials disclose the possibility
to realize vdW heterostructures with new functionalities. Here we report on the
realization and investigation of tunneling spin valves based on van der Waals
heterostructures consisting of an atomically thin hBN layer acting as tunnel
barrier and two exfoliated Fe3GeTe2 crystals acting as ferromagnetic
electrodes. Low-temperature anomalous Hall effect measurements show that thin
Fe3GeTe2 crystals are metallic ferromagnets with an easy axis perpendicular to
the layers, and a very sharp magnetization switching at magnetic field values
that depend slightly on their geometry. In Fe3GeTe2/hBN/Fe3GeTe2
heterostructures, we observe a textbook behavior of the tunneling resistance,
which is minimum (maximum) when the magnetization in the two electrodes is
parallel (antiparallel) to each other. The magnetoresistance is 160% at low
temperature, from which we determine the spin polarization of Fe3GeTe2 to be
0.66, corresponding to 83% and 17% of majority and minority carriers,
respectively. The measurements also show that, with increasing temperature, the
evolution of the spin polarization extracted from the tunneling
magnetoresistance is proportional to the temperature dependence of the
magnetization extracted from the analysis of the anomalous Hall conductivity.
This suggests that the magnetic properties of the surface are representative of
those of the bulk, as it may be expected for vdW materials.

###Field-free Magnetization Switching by Utilizing the Spin Hall Effect and Interlayer Exchange Coupling of Iridium|Yang Liu,Bing Zhou,Jian-Gang Zhu###

Field-free Magnetization Switching by Utilizing the Spin Hall Effect and Interlayer Exchange Coupling of Iridium. Magnetization switching by spin-orbit torque (SOT) via spin Hall effect
represents as a competitive alternative to that by spin-transfer torque (STT)
used for magnetoresistive random access memory (MRAM), as it does not require
high-density current to go through the tunnel junction. For perpendicular MRAM,
however, SOT driven switching of the free layer requires an external in-plane
field, which poses limitation for viability in practical applications. Here we
demonstrate field-free magnetization switching of a perpendicular magnet by
utilizing an Iridium (Ir) layer. The Ir layer not only provides SOTs via spin
Hall effect, but also induce interlayer exchange coupling with an in-plane
magnetic layer that eliminates the need for the external field. Such dual
functions of the Ir layer allows future build-up of magnetoresistive stacks for
memory and logic applications. Experimental observations show that the SOT
driven field-free magnetization reversal is characterized as domain nucleation
and expansion. Micromagnetic modeling is carried out to provide in-depth
understanding of the perpendicular magnetization reversal process in the
presence of an in-plane exchange coupling field.

###Magnetic and magnetoresistive behavior of the ferromagnetic heavy fermion YbNi$_2$|O. Olicón,R. Escamilla,A. Conde-Gallardo,F. Morales###

Magnetic and magnetoresistive behavior of the ferromagnetic heavy fermion YbNi$_2$. We present a study on the magnetic susceptibility $\chi(T)$ and electrical
resistance, as a function of temperature and magnetic field $R(T,H)$, of the
ferromagnetic heavy fermion YbNi$_2$. The X-ray diffraction analysis shows that
the synthesized polycrystalline samples crystallizes in the cubic Laves phase
structure C15, with a spatial group $Fd\overline{3}m$. The magnetic
measurements indicate a ferromagnetic behavior with transition temperature at 9
K. The electrical resistance is metallic-like at high temperatures and no
signature of Kondo effect was observed. In the ferromagnetic state, the
electrical resistance can be justified by electron-magnon scattering
considering the existence of an energy gap in the magnonic spectrum. The energy
gap was determined for various applied magnetic fields. Magnetoresistance as a
function of applied magnetic field, subtracted from the $R(T,H)$ curves at
several temperatures, is negative from 2 K until about 40 K for all applied
magnetic fields. The negative magnetoresistance originates from the suppression
of magnetic disorder by the magnetic field.

###Hole-pocket-driven superconductivity and its universal features in the electron-doped cuprates|Yangmu Li,W. Tabis,Y. Tang,G. Yu,J. Jaroszynski,N. Barišić,M. Greven###

Hole-pocket-driven superconductivity and its universal features in the electron-doped cuprates. After three decades of enormous scientific inquiry, the emergence of
superconductivity in the cuprates remains an unsolved puzzle. One major
challenge has been to arrive at a satisfactory understanding of the unusual
metallic normal state from which the superconducting state emerges upon
cooling. A second challenge has been to achieve a unified understanding of
hole- and electron-doped compounds. Here we report detailed magnetoresistivity
measurements for the archetypal electron-doped cuprate
Nd$_{2-x}$Ce$_x$CuO$_{4+{\delta}}$ that, in combination with prior data,
provide crucial links between the normal and superconducting states and between
the electron- and hole-doped parts of the phase diagram. The characteristics of
the normal state (magnetoresistivity, quantum oscillations, and Hall
coefficient) and those of the superconducting state (superfluid density and
upper critical field) consistently indicate two-band (electron and hole)
features and clearly point to hole-pocket-driven superconductivity in these
nominally electron-doped materials. We show that the approximate Uemura scaling
between the superconducting transition temperature and the superfluid density
found for hole-doped cuprates also holds for the small hole component of the
superfluid density in the electron-doped cuprates.

###Evidence for exchange Dirac gap in magneto-transport of topological insulator-magnetic insulator heterostructures|S. R. Yang,Y. T. Fanchiang,C. C. Chen,C. C. Tseng,Y. C. Liu,M. X. Guo,M. Hong,S. F. Lee,J. Kwo###

Evidence for exchange Dirac gap in magneto-transport of topological insulator-magnetic insulator heterostructures. Transport signatures of exchange gap opening because of magnetic proximity
effect (MPE) are reported for bilayer structures of Bi2Se3 thin films on
yttrium iron garnet (YIG) and thulium iron garnet (TmIG) of perpendicular
magnetic anisotropy (PMA). Pronounced negative magnetoresistance (MR) was
detected, and attributed to an emergent weak localization (WL) effect
superimposing on a weak antilocalization (WAL). Thickness-dependent study shows
that the WL originates from the time-reversal-symmetry breaking of topological
surface states by interfacial exchange coupling. The weight of WL declined when
the interfacial magnetization was aligned toward the in-plane direction, which
is understood as the effect of tuning the exchange gap size by varying the
perpendicular magnetization component. Importantly, magnetotransport study
revealed anomalous Hall effect (AHE) of square loops and anisotropic
magnetoresistance (AMR) characteristic, typifying a ferromagnetic conductor in
Bi2Se3/TmIG, and the presence of an interfacial ferromagnetism driven by MPE.
Coexistence of MPE-induced ferromagnetism and the finite exchange gap provides
an opportunity of realizing zero magnetic-field dissipation-less transport in
topological insulator/ferromagnetic insulator heterostructures.

###Shubnikov-de Haas and de Haas-van Alphen oscillations in topological semimetal CaAl4|Sheng Xu,Jian-Feng Zhang,Yi-Yan Wang,Lin-Lin Sun,Huan Wang,Yuan Su,Xiao-Yan Wang,Kai Liu,Tian-Long Xia###

Shubnikov-de Haas and de Haas-van Alphen oscillations in topological semimetal CaAl4. We report the magneto-transport properties of CaAl$_4$ single crystals with
$C2/m$ structure at low temperature. CaAl$_4$ exhibits large unsaturated
magnetoresistance $\sim$3000$\%$ at 2.5 K and 14 T. The nonlinear Hall
resistivity is observed, which indicates the multi-band feature. The
first-principles calculations show the electron-hole compensation and the
complex Fermi surface in CaAl$_4$, to which the two-band model with
over-simplified carrier mobility can't completely apply. Evident quantum
oscillations have been observed with B//c and B//ab configurations, from which
the nontrivial Berry phase is extracted by the multi-band Lifshitz-Kosevich
formula fitting. An electron-type quasi-2D Fermi surface is found by the
angle-dependent Shubnikov-de Haas oscillations, de Haas-van Alphen oscillations
and the first-principles calculations. The calculations also elucidate that
CaAl$_4$ owns a Dirac nodal line type band structure around the $\Gamma$ point
in the $Z$-$\Gamma$-$L$ plane, which is protected by the mirror symmetry as
well as the space inversion and time reversal symmetries. Once the spin-orbit
coupling is included, the crossed nodal line opens a negligible gap (less than
3 meV). The open-orbit topology is also found in the electron-type Fermi
surfaces, which is believed to help enhance the magnetoresistance observed.

###Maltese Cross anisotropy in Ho0.8Lu0.2B12 antiferromagnetic metal with dynamic charge stripes|A. L. Khoroshilov,V. N. Krasnorussky,K. M. Krasikov,A. V. Bogach,V. V. Glushkov,S. V. Demishev,N. A. Samarin,V. V. Voronov,N. Yu. Shitsevalova,V. B. Filipov,S. Gabáni,K. Flachbart,K. Siemensmeyer,S. Yu. Gavrilkin,N. E. Sluchanko###

Maltese Cross anisotropy in Ho0.8Lu0.2B12 antiferromagnetic metal with dynamic charge stripes. The model strongly correlated electron system Ho0.8Lu0.2B12 which
demonstrates a cooperative Jahn-Teller instability of the boron sub-lattice in
combination with rattling modes of Ho(Lu) ions, dynamic charge stripes and
unusual antiferromagnetic (AF) ground state has been studied in detail at low
temperatures by magnetoresistance, magnetization and heat capacity
measurements. Based on received results it turns out that the angular H-fi-T
magnetic phase diagrams of this non-equilibrium AF metal can be reconstructed
in the form of a Maltese cross. The dramatic AF ground state symmetry lowering
of this dodecaboride with fcc crystal structure can be attributed to the
redistribution of conduction electrons which leave the RKKY oscillations of the
electron spin density to participate in the dynamic charge stripes providing
with extraordinary changes in the indirect exchange interaction between
magnetic moments of Ho3+ ions and resulting in the emergence of a number of
various magnetic phases. It is also shown that the two main contributions to
magnetoresistance in the complex AF phase, the (i) positive linear on magnetic
field and the (ii) negative quadratic component can be separated and analyzed
quantitatively, correspondingly, in terms of charge carrier scattering on spin
density wave (5d) component of the magnetic structure and on local 4f-5d spin
fluctuations of holmium sites.

###The Hall effect in ballistic flow of two-dimensional interacting particles|P. S. Alekseev,M. A. Semina###

The Hall effect in ballistic flow of two-dimensional interacting particles. In high-quality solid-state systems at low temperatures, the hydrodynamic or
the ballistic regimes of heat and charge transport are realized in the electron
and the phonon systems. In these regimes, the thermal and the electric
conductance of the sample can reach abnormally large magnitudes. In this paper,
we study the Hall effect in a system of interacting two-dimensional charged
particles in a ballistic regime. We demonstrated that the Hall electric field
is caused by a change in the densities of particles due to the effect of
external fields on their free motions between the sample edges. In
one-component (electron or hole) systems the Hall coefficient turns out to one
half compared with the one in conventional disordered Ohmic samples. This
result is consistent with the recent experiment on measuring of the Hall
resistance in ultra-high-mobility GaAs quantum wells. In two-component
electron-hole systems the Hall electric field depends linearly on the
difference between the concentrations of electrons and holes near the charge
neutrality point (the equilibrium electron and hole densities coincide) and
saturates to the Hall field of a one-component system far from the charge
neutrality point. We also studied the corrections to magnetoresistance and the
Hall electric field due to inter-particle scattering being a precursor of
forming a viscous flow. For the samples shorter than the inter-particle
scattering length, the obtained corrections govern the dependencies of
magnetoresistance and the Hall field on temperature.

###Atomically Thin CrCl3: An in-Plane Layered Antiferromagnetic Insulator|Xinghan Cai,Tiancheng Song,Nathan P. Wilson,Genevieve Clark,Minhao He,Xiaoou Zhang,Takashi Taniguchi,Kenji Watanabe,Wang Yao,Di Xiao,Michael A. McGuire,David H. Cobden,Xiaodong Xu###

Atomically Thin CrCl3: An in-Plane Layered Antiferromagnetic Insulator. The recent discovery of magnetism in atomically thin layers of van der Waals
(vdW) crystals has created new opportunities for exploring magnetic phenomena
in the two-dimensional (2D) limit. In most 2D magnets studied to date the
c-axis is an easy axis, so that at zero applied field the polarization of each
layer is perpendicular to the plane. Here, we demonstrate that atomically thin
CrCl3 is a layered antiferromagnetic insulator with an easy-plane normal to the
c-axis, that is the polarization is in the plane of each layer and has no
preferred direction within it. Ligand field photoluminescence at 870 nm is
observed down to the monolayer limit, demonstrating its insulating properties.
We investigate the in-plane magnetic order using tunneling magnetoresistance in
graphene/CrCl3/graphene tunnel junctions, establishing that the interlayer
coupling is antiferromagnetic down to the bilayer. From the temperature
dependence of the magnetoresistance we obtain an effective magnetic phase
diagram for the bilayer. Our result shows that CrCl3 should be useful for
studying the physics of 2D phase transitions and for making new kinds of vdW
spintronic devices.

###YBa2Cu3O7/LaXMnO3 (X: Ca, Sr) based Superconductor/Ferromagnet/Superconductor junctions with memory functionality|R. de Andres Prada,T. Golod,O. M. Kapran,E. A. Borodianskyi,Ch. Bernhard,V. M. Krasnov###

YBa2Cu3O7/LaXMnO3 (X: Ca, Sr) based Superconductor/Ferromagnet/Superconductor junctions with memory functionality. Complex oxides exhibit a variety of unusual physical properties, which can be
used for designing novel electronic devices. Here we fabricate and study
experimentally nano-scale Superconductor/ Ferromagnet/Superconductor junctions
with the high-Tc cuprate superconductor YBa2Cu3O7 and the colossal
magnetoresistive (CMR) manganite ferromagnets LaXMnO3 (X: Ca or Sr). We
demonstrate that in a broad temperature range the magnetization of a manganite
nanoparticle, forming the junction interface, switches abruptly in a
mono-domain manner. The CMR phenomenon translates the magnetization loop into a
hysteretic magnetoresistance loop. The latter facilitates a memory
functionality of such a junction with just a single CMR ferromagnetic layer.
The orientation of the magnetization (stored information) can be read out by
simply measuring the junction resistance in an applied magnetic field. The CMR
facilitates a large read-out signal in a small applied field. We argue that
such a simple single layer CMR junction can operate as a memory cell both in
the superconducting state at cryogenic temperatures and in the normal state up
to room temperature.

###Pressure-tuning of the electrical-transport properties in the Weyl semimetal TaP|M. Besser,R. D. dos Reis,F. -R. Fan,M. O. Ajeesh,Y. Sun,M. Schmidt,C. Felser,M. Nicklas###

Pressure-tuning of the electrical-transport properties in the Weyl semimetal TaP. We investigated the pressure evolution of the electrical transport in the
almost compensated Weyl semimetal TaP. In addition, we obtained information on
the modifications of the Fermi-surface topology with pressure from the analysis
of pronounced Shubnikov-de Haas (SdH) quantum oscillations present in the
Hall-effect and magnetoresistance data. The simultaneous analysis of the Hall
and longitudinal conductivity data in a two-band model revealed an only weak
decrease in the electron- and hole charge-carrier densities up to 1.2 GPa,
while the mobilities are essentially pressure independent along the a-direction
of the tetragonal crystal structure. Only weak changes in the SdH frequencies
for B||a and B||c point at a robust Fermi-surface topology. In contrast to the
stability of the Fermi-surface topology and of the density of charge carriers,
our results evidence a strong pressure variation of the magnitude of transverse
magnetoresistance for B||a contrary to the results for B||c. We can relate the
former to an increase in the charge-carrier mobilities along the
crystallographic c-direction.

###Highly anisotropic interlayer magnetoresistance in ZrSiS nodal-line Dirac semimetal|M. Novak,S. N. Zhang,F. Orbanic,N. Biliskov,G. Eguchi,S. Paschen,A. Kimura,X. X. Wang,T. Osada,K. Uchida,M. Sato,Q. S. Wu,O. V. Yazyev,I. Kokanovic###

Highly anisotropic interlayer magnetoresistance in ZrSiS nodal-line Dirac semimetal. We instigate the angle-dependent magnetoresistance (AMR) of the layered
nodal-line Dirac semimetal ZrSiS for the in-plane and out-of-plane current
directions. This material has recently revealed an intriguing butterfly-shaped
in-plane AMR that is not well understood. Our measurements of the polar
out-of-plane AMR show a surprisingly different response with a pronounced
cusp-like feature. The maximum of the cusp-like anisotropy is reached when the
magnetic field is oriented in the $a$-$b$ plane. Moreover, the AMR for the
azimuthal out-of-plane current direction exhibits a very strong four-fold
$a$-$b$ plane anisotropy. Combining the Fermi surfaces calculated from first
principles with the Boltzmann's semiclassical transport theory we reproduce and
explain all the prominent features of the unusual behavior of the in-plane and
out-of-plane AMR. We are also able to clarify the origin of the strong
non-saturating transverse magnetoresistance as an effect of imperfect
charge-carrier compensation and open orbits. Finally, by combining our
theoretical model and experimental data we estimate the average relaxation time
of $2.6\times10^{-14}$~s and the mean free path of $15$~nm at 1.8~K in our
samples of ZrSiS.

###Antisymmetric magnetoresistance in van der Waals Fe3GeTe2/graphite/Fe3GeTe2 tri-layer heterostructures|Sultan Albarakati,Cheng Tan,Zhong-Jia Chen,James G. Partridge,Guolin Zheng,Lawrence Farrar,Edwin L. H. Mayes,Matthew R. Field,Changgu Lee,Yihao Wang,Yiming Xiong,Mingliang Tian,Feixiang Xiang,Alex R. Hamilton,Oleg A. Tretiakov,Dimitrie Culcer,Yu-Jun Zhao,Lan Wang###

Antisymmetric magnetoresistance in van der Waals Fe3GeTe2/graphite/Fe3GeTe2 tri-layer heterostructures. Van der Waals (vdW) ferromagnetic materials are rapidly establishing
themselves as effective building blocks for next generation spintronic devices.
When layered with non-magnetic vdW materials, such as graphene and/or
topological insulators, vdW heterostructures can be assembled (with no
requirement for lattice matching) to provide otherwise unattainable device
structures and functionalities. We report a hitherto rarely seen antisymmetric
magnetoresistance (MR) effect in van der Waals heterostructured
Fe3GeTe2/graphite/Fe3GeTe2 devices. Unlike conventional giant magnetoresistance
(GMR) which is characterized by two resistance states, the MR in these vdW
heterostructures features distinct high, intermediate and low resistance
states. This unique characteristic is suggestive of underlying physical
mechanisms that differ from those observed before. After theoretical
calculations, the three resistance behavior was attributed to a spin momentum
locking induced spin polarized current at the graphite/FGT interface. Our work
reveals that ferromagnetic heterostructures assembled from vdW materials can
exhibit substantially different properties to those exhibited by similar
heterostructures grown in vacuum. Hence, it highlights the potential for new
physics and new spintronic applications to be discovered using vdW
heterostructures.

###Possible Topological Phase Transition in Fe-Vacancy-Ordered $β$-Fe$_{4+δ}$Se$_{5}$ Nanowires|Keng-Yu Yeh,Tung-Sheng Lo,Chung-Chieh Chang,Phillip Wu,Kuei-Shu Chang-Liao,Ming-Jye Wang,Maw-Kuen Wu###

Possible Topological Phase Transition in Fe-Vacancy-Ordered $β$-Fe$_{4+δ}$Se$_{5}$ Nanowires. We studied the electrical transport on $\beta$-Fe$_{4+\delta}$Se$_{5}$
single-crystal nanowires, exhibiting $\sqrt{5}\times\sqrt{5}$ Fe-vacancy order
and mixed valence of Fe. We observed a first-order metal-insulator transition
of the transition temperature at $\sim$28~K at zero magnetic field. The
dielectric relaxation reveals that the transition is related to an energy gap
expansion of $\sim$12~meV, involving the charge-orbital ordering. At nearly
28~K, colossal positive magnetoresistance emerges, resulting from the
magnetic-field dependent shift of the transition temperature. Through the
transition, the magnetotransport behavior transits from two-dimension-like to
one-dimension-like conduction. The transition temperature demonstrates
anisotropy with the $c$-axis as the preferred orientation in magnetic fields,
suggesting the spin-orbital coupling. Our findings demonstrate the novel
magnetoresistive transition intimating a topological transition in the
Fe-vacancy-ordered $\beta$-Fe$_{4+\delta}$Se$_{5}$ nanowires. The results
provide valuable information to better understand the orbital nature and the
emergence of superconductivity in FeSe-based materials.

###Observation of a mesoscopic magnetic modulation in chiral Mn1/3NbS2|Sunil K. Karna,F. N. Womack,R. Chapai,D. P. Young,M. Marshall,Weiwei Xie,D. Graf,Yan Wu,Huibo Cao,L. DeBeer-Schmitt,P. W. Adams,R. Jin,J. F. DiTusa###

Observation of a mesoscopic magnetic modulation in chiral Mn1/3NbS2. We have investigated the structural, magnetic, thermodynamic, and charge
transport properties of Mn1/3NbS2 single crystals through x-ray and neutron
diffraction, magnetization, specific heat, magnetoresistance, and Hall effect
measurements. Mn1/3NbS2 displays a magnetic transition at TC ~ 45 K with highly
anisotropic behavior expected for a hexagonal structured material. Below TC,
neutron diffraction reveals increased scattering near the structural Bragg
peaks having a wider Q-dependence along the c-axis than the nuclear Bragg
peaks. This indicates helimagnetism with a long pitch length of ~250 nm (or a
wavevector q~0.0025 {\AA}-1) along the c-axis. This q is substantially smaller
than that found for the helimagnetic state in isostructural Cr1/3NbS2 (0.015
{\AA}-1). Specific heat capacity measurements confirm a second-order magnetic
phase transition with a substantial magnetic contribution that persists to low
temperature. The large low-temperature specific heat capacity is consistent
with a large density of low-lying magnetic excitations that are likely
associated with topologically interesting magnetic modes. Changes to the
magnetoresistance, the magnetization, and the magnetic neutron diffraction,
which become more apparent below 20 K, imply a modification in the character of
the magnetic ordering corresponding to the magnetic contribution to the
specific heat capacity. These observations signify a more complex magnetic
structure both at zero and finite fields for Mn1/3NbS2 than for the
well-investigated Cr1/3NbS2.

###Direct evidence for charge compensation induced large magnetoresistance in thin WTe2|Yaojia Wang,Lizheng Wang,Xiaowei Liu,Heng Wu,Pengfei Wang,Dayu Yan,Bin Cheng,Youguo Shi,Kenji Watanabe,Takashi Taniguchi,Shi-Jun Liang,Feng Miao###

Direct evidence for charge compensation induced large magnetoresistance in thin WTe2. Since the discovery of extremely large non-saturating magnetoresistance (MR)
in WTe2, much effort has been devoted to understanding the underlying
mechanism, which is still under debate. Here, we explicitly identify the
dominant physical origin of the large non-saturating MR through in-situ tuning
of the magneto-transport properties in thin WTe2 film. With an electrostatic
doping approach, we observed a non-monotonic gate dependence of the MR. The MR
reaches a maximum (10600%) in thin WTe2 film at certain gate voltage where
electron and hole concentrations are balanced, indicating that the charge
compensation is the dominant mechanism of the observed large MR. Besides, we
show that the temperature dependent magnetoresistance exhibits similar tendency
with the carrier mobility when the charge compensation is retained, revealing
that distinct scattering mechanisms may be at play for the temperature
dependence of magneto-transport properties. Our work would be helpful for
understanding mechanism of the large MR in other nonmagnetic materials and
offers an avenue for achieving large MR in the non-magnetic materials with
electron-hole pockets.

###Anomalous conductance scaling in strained Weyl semimetals|Jan Behrends,Roni Ilan,Jens H. Bardarson###

Anomalous conductance scaling in strained Weyl semimetals. Magnetotransport provides key experimental signatures in Weyl semimetals. The
longitudinal magnetoresistance is linked to the chiral anomaly and the
transversal magnetoresistance to the dominant charge relaxation mechanism.
Axial magnetic fields that act with opposite sign on opposite chiralities
facilitate new transport experiments that probe the low-energy Weyl nodes. As
recently realized, these axial fields can be achieved by straining samples or
adding inhomogeneities to them. Here, we identify a robust signature of axial
magnetic fields: an anomalous scaling of the conductance in the diffusive
ultraquantum regime. In particular, we demonstrate that the longitudinal
conductivity in the ultraquantum regime of a disordered Weyl semimetal
subjected to an axial magnetic field increases with both the field strength and
sample width due to a spatial separation of charge carriers. We contrast axial
magnetic with real magnetic fields to clearly distinguish the different
behavior of the conductance. Our results rely on numerical tight-binding
simulations and are supported by analytical arguments. We argue that the
spatial separation of charge carriers can be used for directed currents in
microstructured electronic devices.

###Symmetry breaking and skyrmionic transport in twisted bilayer graphene|Shubhayu Chatterjee,Nick Bultinck,Michael P. Zaletel###

Symmetry breaking and skyrmionic transport in twisted bilayer graphene. Motivated by recent low-temperature magnetoresistance measurements in twisted
bilayer graphene aligned with hexagonal Boron Nitride substrate, we perform a
systematic study of possible symmetry breaking orders in this device at a
filling of two electrons per Moir\'e unit cell. We find that the surprising
non-monotonic dependence of the resistance on an out-of-plane magnetic field is
difficult to reconcile with particle-hole charge carriers from the low-energy
bands in symmetry broken phases. We invoke the non-zero Chern numbers of the
twisted bilayer graphene flat bands to argue that skyrmion textures provide an
alternative for the dominant charge carriers. Via an effective field-theory for
the spin degrees of freedom, we show that the effect of spin Zeeman splitting
on the skyrmion excitations provides a possible explanation for the
non-monotonic magnetoresistance. We suggest several experimental tests,
including the functional dependence of the activation gap on the magnetic
field, for our proposed correlated insulating states at different integer
fillings. We also discuss possible exotic phases and quantum phase transitions
that can arise via skyrmion-pairing on doping such an insulator.

###Surface state transport in double-gated and magnetized topological insulators with hexagonal warping effects|Masomeh Arabikhah,Alireza Saffarzadeh###

Surface state transport in double-gated and magnetized topological insulators with hexagonal warping effects. We explore the scattering of Dirac electrons in a double-gated topological
insulator in the presence of magnetic proximity effects and warped surface
states. It is found that a magnetic field can shift the Dirac cone in momentum
space and deform the constant-energy contour, or opens up a band gap at the
Dirac point, depending on the magnetization orientation. The double gate
voltage induces quantum wells and/or quantum barriers on the surface of
topological insulators, generating surface resonant tunnelling states. It is
found that the hexagonal warping effect can increase the electronic transport
at high energies when the constant-energy contour exhibits a snowflake shape.
The energy-dependent conductances in the parallel and antiparallel magnetic
configurations exhibit out-of-phase oscillations due to the quantum
interference of propagating waves in the region between the two magnetized
segments. Although the conductance spectrum of the double-well structure is
higher than that of the double-barrier structure, the magnetoresistance ratio
versus the separation distance between the two magnetized barriers exhibits
pronounced oscillations due to the resonant tunnelling states. We show that the
surface state transport can be controlled by the exchange field and gate
voltage without breaking time reversal symmetry, suggesting that the double
gated and magnetized topological insulators can be utilized to achieve a large
magnetoresistance ratio with a tunable sign.

###Novel universality class for the ferromagnetic transition in the low carrier concentration systems UTeS and USeS exhibiting large negative magnetoresistance|Naoyuki Tateiwa,Yoshinori Haga,Hironori Sakai,Etsuji Yamamoto###

Novel universality class for the ferromagnetic transition in the low carrier concentration systems UTeS and USeS exhibiting large negative magnetoresistance. We report the novel critical behavior of magnetization in low carrier
concentration systems UTeS and USeS that exhibit the large negative
magnetoresistance around the ferromagnetic transition temperatures T_C ~ 85 and
23 K, respectively. UTeS and USeS crystallize in the same orthorhombic
TiNiSi-type crystal structure as those of uranium ferromagnetic superconductors
URhGe and UCoGe. We determine the critical exponents, beta for the spontaneous
magnetization M_s, gamma for the magnetic susceptibility chi, and delta for the
magnetization isotherm at T_C with several methods. The ferromagnetic states in
UTeS and USeS have strong uniaxial magnetic anisotropy. However, the critical
exponents in the two compounds are different from those in the
three-dimensional Ising model with short-range magnetic exchange interactions.
Similar sets of the critical exponents have been reported for the uranium
ferromagnetic superconductors UGe_2 and URhGe, and uranium intermetallic
ferromagnets URhSi, UIr and U(Co_0.98Os_0.02)Al. The universality class of the
ferromagnetic transitions in UTeS and USeS may belong to the same one for the
uranium compounds. The novel critical phenomenon associated with the
ferromagnetic transition is observed not only in the uranium intermetallic
ferromagnets with the itinerant 5f electrons but also in the low carrier
concentration systems UTeS and USeS with the localized 5f electrons. The large
negative magnetoresistance in UTeS and USeS, and the superconductivity in UGe_2
and URhGe share the similarity of their closeness to the ferromagnetism
characterized by the novel critical exponents.

###Giant magnetoresistance amplifier for spin-orbit torque nano-oscillators|Jen-Ru Chen,Andrew Smith,Eric A. Montoya,Jia G. Lu,Ilya N. Krivorotov###

Giant magnetoresistance amplifier for spin-orbit torque nano-oscillators. Spin-orbit torque nano-oscillators based on bilayers of ferromagnetic (FM)
and nonmagnetic (NM) metals are ultra-compact current-controlled microwave
signal sources. They serve as a convenient testbed for studies of spin-orbit
torque physics and are attractive for practical applications such as microwave
assisted magnetic recording, neuromorphic computing, and chip-to-chip wireless
communications. However, a major drawback of these devices is low output
microwave power arising from the relatively small anisotropic magnetoresistance
(AMR) of the FM layer. Here we experimentally show that the output power of a
spin-orbit torque nano-oscillator can be enhanced by nearly three orders of
magnitude without compromising its structural simplicity. Addition of a FM
reference layer to the oscillator allows us to employ current-in-plane giant
magnetoresistance (CIP GMR) to boost the output power of the device. This
enhancement of the output power is a result of both large magnitude of GMR
compared to that of AMR and different angular dependences of GMR and AMR. Our
results pave the way for practical applications of spin-orbit torque
nano-oscillators.

###Weak antilocalization in a noncentrosymmetric CaAgBi single crystal|Souvik Sasmal,Rajib Mondal,Ruta Kulkarni,Bahadur Singh,A. Thamizhavel###

Weak antilocalization in a noncentrosymmetric CaAgBi single crystal. We report on the single crystal growth and transport properties of a
topological semimetal CaAgBi which crystallises in the hexagonal $ABC-$type
structure with the non-centrosymmetric space group $\mathit{P6_3mc}$ (No. 186).
The transverse magnetoresistance measurements with current in the basal plane
of the hexagonal crystal structure reveal a value of about 30 % for I //
[10-10] direction and about 50 % for I // [1-210] direction at 10 K in an
applied magnetic field of 14 T. The magnetoresistance shows a cusp-like
behavior in the low magnetic-field region, suggesting the presence of weak
antilocalization effect for temperatures less than 100 K. The Hall measurements
reveal that predominant charge carriers are $p$ type exhibiting a linear
behavior for fields up to 14 T and can be explained based on the single band
model. The magnetoconductance of CaAgBi is analysed based on the modified
Hikami-Larkin-Nagaoka (HLN) model. Our first-principles calculations within a
density-functional theory framework reveal that CaAgBi supports a topological
Dirac semimetal state with Dirac points located on the rotational axis slightly
above the Fermi level and are protected by $C_{6v}$ point-group symmetry. The
Fermi surface consists of both the electron and hole pockets. However, the size
of hole pockets is much larger than electron pockets suggesting the dominant
$p$ type carriers in accord with our experimental results.

###Role of quantum confinement and interlayer coupling in CrI$_3$-graphene magnetic tunnel junctions|Jonathan J. Heath,Marcio Costa,Marco Buongiorno-Nardelli,Marcelo A. Kuroda###

Role of quantum confinement and interlayer coupling in CrI$_3$-graphene magnetic tunnel junctions. Recent demonstrations of magnetic ordering and spin transport in
two-dimensional heterostructures have opened research venues in these material
systems. In order to control and enhance the related physical phenomena,
quantitative descriptions linking experimental observations to atomic details
must be produced. Here we combine first principles and quantum ballistic
transport calculations to shed important insights from an atomistic viewpoint
on the underlying mechanisms governing spin transport in graphene/CrI$_3$
junctions. Descriptions of the electronic structure reveal that tunneling is
the dominant transport mechanism in these heterostructures and help
differentiate intermediate metamagnetic states present in the switching
process. We find that quantum confinement and layer-layer interactions are key
to describing transport in these two-dimensional systems. Ballistic transport
calculations further support these findings and yield magnetoresistance values
in remarkable agreement with experiments. The short width of these barriers
limits analysis solely based on the bulk complex band structure often employed
in the description of magnetic tunnel junctions. Our work devises mechanisms to
attain larger tunneling magnetoresistances, proving valuable to the advancement
of spin valves in layered heterostructures.

###Resistive contribution in electrical switching experiments with antiferromagnets|Tristan Matalla-Wagner,Jan-Michael Schmalhorst,Günter Reiss,Nobumichi Tamura,Markus Meinert###

Resistive contribution in electrical switching experiments with antiferromagnets. Recent research demonstrated the electrical switching of antiferromagnets via
intrinsic spin-orbit torque or the spin Hall effect of an adjacent heavy metal
layer. The electrical readout is typically realized by measuring the transverse
anisotropic magnetoresistance at planar cross- or star-shaped devices with four
or eight arms, respectively. Depending on the material, the current density
necessary to switch the magnetic state can be large, often close to the
destruction threshold of the device. We demonstrate that the resulting
electrical stress changes the film resistivity locally and thereby breaks the
fourfold rotational symmetry of the conductor. This symmetry breaking due to
film inhomogeneity produces signals, that resemble the anisotropic
magnetoresistance and is experimentally seen as a "saw-tooth"-shaped transverse
resistivity. This artifact can persist over many repeats of the switching
experiment and is not easily separable from the magnetic contribution. We
discuss the origin of the artifact, elucidate the role of the film
crystallinity, and propose approaches how to separate the resistive
contribution from the magnetic contribution.

###Magnetoresistance from time-reversal symmetry breaking in topological materials|J. C. de Boer,D. P. Leusink,A. Brinkman###

Magnetoresistance from time-reversal symmetry breaking in topological materials. Magnetotransport measurements are a popular way of characterizing the
electronic structure of topological materials and often the resulting datasets
cannot be described by the well-known Drude model due to large, non-parabolic
contributions. In this work, we focus on the effects of magnetic fields on
topological materials through a Zeeman term included in the model Hamiltonian.
To this end, we re-evaluate the simplifications made in the derivations of the
Drude model and pinpoint the scattering time and Fermi velocity as Zeeman-term
dependent factors in the conductivity tensor. The driving mechanisms here are
the aligment of spins along the magnetic field direction, which allows for
backscattering, and a significant change to the Fermi velocity by the opening
of a hybridization gap. After considering 2D and 3D Dirac states, as well as 2D
Rashba surface states and the quasi-2D bulk states of 3D topological
insulators, we find that the 2D Dirac states on the surfaces of 3D topological
insulators produce magnetoresistance, that is significant enough to be
noticable in experiments. As this magnetoresistance effect is strongly
dependent on the spin-orbit energy, it can be used as a telltale sign of a
Fermi energy located close to the Dirac point.

###Noncollinear Spintronics and Electric-Field Control: A Review|Peixin Qin,Han Yan,Xiaoning Wang,Zexin Feng,Huixin Guo,Xiaorong Zhou,Haojiang Wu,Xin Zhang,Zhaoguogang Leng,Hongyu Chen,Zhiqi Liu###

Noncollinear Spintronics and Electric-Field Control: A Review. Our world is composed of various materials with different structures, where
spin structures have been playing a pivotal role in spintronic devices of the
contemporary information technology. Apart from conventional collinear spin
materials such as collinear ferromagnets and collinear antiferromagnetically
coupled materials, noncollinear spintronic materials have emerged as hot spots
of research attention owing to exotic physical phenomena. In this Review, we
firstly introduce two types noncollinear spin structures, i.e., the chiral spin
structure that yields real-space Berry phases and the coplanar noncollinear
spin structure that could generate momentum-space Berry phases, and then move
to relevant novel physical phenomena including topological Hall effect,
anomalous Hall effect, multiferroic, Weyl fermions, spin-polarized current, and
spin Hall effect without spin-orbit coupling in these noncollinear spin
systems. Afterwards, we summarize and elaborate the electric-field control of
the noncollinear spin structure and related physical effects, which could
enable ultralow power spintronic devices in future. In the final outlook part,
we emphasize the importance and possible routes for experimentally detecting
the intriguing theoretically predicted spin-polarized current, verifying the
spin Hall effect in the absence of spin-orbit coupling and exploring the
anisotropic magnetoresistance and domain-wall-related magnetoresistance effects
for noncollinear antiferromagnetic materials.

###Magnetic and transport properties in pyrochlore iridates (Y$_{1-x}$Pr$_x$)$_2$Ir$_2$O$_7$: The role of $f$-$d$ exchange interaction and $d$-$p$ orbital hybridization|Harish Kumar,K. C. Kharkwal,Kranti Kumar,K. Asokan,A. Banerjee,A. K. Pramanik###

Magnetic and transport properties in pyrochlore iridates (Y$_{1-x}$Pr$_x$)$_2$Ir$_2$O$_7$: The role of $f$-$d$ exchange interaction and $d$-$p$ orbital hybridization. The $f$-$d$ magnetic exchange interaction is considered to be a key
ingredient for many exotic topological phases in pyrochlore iridates. Here, we
have investigated the evolution of structural, magnetic and electronic
properties in doped pyrochlore iridate, (Y$_{1-x}$Pr$_x$)$_2$Ir$_2$O$_7$. Apart
from geometrical frustration, pyrochlore iridates are well known for its active
spin-orbit coupling effect. The substitution of Pr$^{3+}$ (4$f^2$) for the
nonmagnetic Y$^{3+}$ (4$d^0$) acts as a magnetic doping, which provides an
ideal platform to study $f$-$d$ exchange interaction without altering the
Ir-sublattice. With Pr substitution, system retains its original cubic
structural symmetry but the local structural parameters show an evolution with
the doping concentration $x$. The robust magnetic-insulating state in
Y$_2$Ir$_2$O$_7$ is drastically weakened, while Pr$_2$Ir$_2$O$_7$ ($x$ = 1.0)
shows a paramagnetic-metallic behavior. A metal-insulator transition is
observed for $x$ = 0.8 sample. This evolution of magnetic and electronic
properties are believed to be induced by an exchange interaction between
localized Pr-4$f$ and itinerant Ir-5$d$ electrons as well as by an increased
hybridization between Ir-$t_{2g}$ and (basal) O-$p$ orbitals as observed in XAS
study. The resistivity in insulating materials follows a power-law behavior
with a decreasing exponent with $x$. A negative magnetoresistance is observed
for present series of samples at low temperature and where the
magnetoresistance shows a quadratic field dependence at higher fields.

###Broadband Magnetoresistance in Ferromagnetic and Paramagnetic Samples of La0.7Ca0.3-xSrxMnO3|U. Chaudhuri,A. Chanda,R. Mahendiran###

Broadband Magnetoresistance in Ferromagnetic and Paramagnetic Samples of La0.7Ca0.3-xSrxMnO3. We have studied the room-temperature magnetoimpedance of paramagnetic (x =
0.06) and ferromagnetic (x = 0.1) samples in La0.7Ca0.3-xSrxMnO3 series using a
radio-frequency impedance analyzer and also microwave power absorption using a
network analyzer. In both measurements, samples were enclosed tightly inside a
copper stripcoil and impedance or reflection coefficient of this copper
stripcoil was measured as a function of the applied magnetic field for
different frequencies of current (f = 0.1 to 2.5 GHz). The direction of the
applied magnetic field was perpendicular to the alternating magnetic field
produced by the coil. In the ferromagnetic sample (x = 0.1), magnetoresistance
shows a peak around zero field for lower frequencies but a peak appears at H
away from the origin at higher frequencies. The position of the peak shifts
towards higher fields with increasing frequency. A similar trend is also found
for the paramagnetic sample (x = 0.06) but the peak occurs at a higher field
compared to the ferromagnetic sample for the same frequency. Microwave power
absorption also shows features similar to magnetoresistance. Line shape
analysis of the data was performed by fitting the data to a Lorentzian
function. It is concluded that the observed features are imprints of
ferromagnetic resonance in x = 0.1 and paramagnetic resonance in x = 0.06
samples.

###Linear and quadratic magnetoresistance in the semimetal SiP2|Yuxing Zhou,Zhefeng Lou,ShengNan Zhang,Huancheng Chen,Qin Chen,Binjie Xu,Jianhua Du,Jinhu Yang,Hangdong Wang,QuanSheng Wu,Oleg V Yazyev,Minghu Fang###

Linear and quadratic magnetoresistance in the semimetal SiP2. Multiple mechanisms for extremely large magnetoresistance (XMR) found in many
topologically nontrivial/trivial semimetals have been theoretically proposed,
but experimentally it is unclear which mechanism is responsible in a particular
sample. In this article, by the combination of band structure calculations,
numerical simulations of magnetoresistance (MR), Hall resistivity and de
Haas-van Alphen (dHvA) oscillation measurements, we studied the MR anisotropy
of SiP$_{2}$ which is verified to be a topologically trivial, incomplete
compensation semimetal. It was found that as magnetic field, $H$, is applied
along the $a$ axis, the MR exhibits an unsaturated nearly linear $H$
dependence, which was argued to arise from incomplete carriers compensation.
For the $H$ $\parallel$ [101] orientation, an unsaturated nearly quadratic $H$
dependence of MR up to 5.88 $\times$ 10$^{4}$$\%$ (at 1.8 K, 31.2 T) and
field-induced up-turn behavior in resistivity were observed, which was
suggested due to the existence of hole open orbits extending along the $k_{x}$
direction. Good agreement of the experimental results with the simulations
based on the calculated Fermi surface (FS) indicates that the topology of FS
plays an important role in its MR.

###Thermopower and Unconventional Nernst in the Predicted Type-II Weyl Semi-metal WTe$_2$|K. Gaurav Rana,Fasil K. Dejene,Neeraj Kumar,Catherine R. Rajamathi,Kornelia Sklarek,Claudia Felser,Stuart S. P. Parkin###

Thermopower and Unconventional Nernst in the Predicted Type-II Weyl Semi-metal WTe$_2$. WTe$_2$ is one of a series of recently discovered high mobility semimetals,
some of whose properties are characteristic of topological Dirac or Weyl
metals. One of its most interesting properties is the unsaturated giant
magnetoresistance that it exhibits at low temperatures. An important question
is the degree to which this property can be ascribed to a conventional
semi-metallic model in which a highly compensated, high mobility metal exhibits
large magnetoresistance. Here we show that the longitudinal thermopower
(Seebeck effect) of semi-metallic WTe$_2$ exfoliated flakes exhibits periodic
sign changes about zero with increasing magnetic field that indicates distinct
electron and hole Landau levels and nearly fully compensated electron and hole
carrier densities. However, inconsistent with a conventional semi-metallic
picture, we find a rapid enhancement of the Nernst effect at low temperatures
that is nonlinear in magnetic field, which is consistent with Weyl points in
proximity to the Fermi energy. Hence, we demonstrate the role played by the
Weyl character of WTe$_2$ in its transport properties.

###Local spin transfer torque and magnetoresistance in domain walls with variable width|Hamidreza Kazemi,Sebastian Eggert,Nicholas Sedlmayr###

Local spin transfer torque and magnetoresistance in domain walls with variable width. Use of a spin polarized current for the manipulation of magnetic domain walls
in ferromagnetic nanowires has been the subject of intensive research for many
years. Recently, due to technological advancements, creating nano-contacts with
special characteristics is becoming more and more prevalent. We now present a
full quantum investigation of the magnetoresistance and the spin transfer
torque in a domain wall, which is embedded in a nano-contact of Ni$_{80}$Fe$_
{20}$, where the size of the domain wall becomes a relevant tunable parameter.
The dependence on the domain wall width as well as the spatial dependence of
the torque along the domain wall can be analyzed in complete detail. The
magnetoresistance drops with increasing domain wall width as expected, but also
shows characteristic modulations and points of resonant spin-flip transmission.
The spin transfer torque has both significant in-plane and out-of-plane
contributions even without considering relaxation. A closer inspection
identifies contributions from the misalignment of the spin density for short
domain walls as well as an effective gauge field for longer domain walls, both
of which oscillate along the domain wall.

###Magnetic-field-induced nontrivial electronic state in the Kondo-lattice semimetal CeSb|Y. Fang,F. Tang,Y. R. Ruan,J. M. Zhang,H. Zhang,H. Gu,W. Y. Zhao,Z. D. Han,W. Tian,B. Qian,X. F. Jiang,X. M. Zhang,X. Ke###

Magnetic-field-induced nontrivial electronic state in the Kondo-lattice semimetal CeSb. Synergic effect of electronic correlation and spin-orbit coupling is an
emerging topic in topological materials. Central to this rapidly developing
area are the prototypes of strongly correlated heavy-fermion systems. Recently,
some Ce-based compounds are proposed to host intriguing topological nature,
among which the electronic properties of CeSb are still under debate. In this
paper, we report a comprehensive study combining magnetic and electronic
transport measurements, and electronic band structure calculations of this
compound to identify its topological nature. Quantum oscillations are clearly
observed in both magnetization and magnetoresistance at high fields, from which
one pocket with a nontrivial Berry phase is recognized. Angular-dependent
magnetoresistance shows that this pocket is elongated in nature and corresponds
to the electron pocket as observed in LaBi. Nontrivial electronic structure of
CeSb is further confirmed by first-principle calculations, which arises from
spin splitting in the fully polarized ferromagnetic state. These features
indicate that magnetic-field can induce nontrivial topological electronic
states in this prototypical Kondo semimetal.

###Effects of the Zhang-Li Torque on Spin Torque nano Oscillators|Jan Albert,Ferran Macià,Joan Manel Hernàndez###

Effects of the Zhang-Li Torque on Spin Torque nano Oscillators. Spin-torque nano-oscillators (STNO) are microwave auto-oscillators based on
magnetic resonances having a nonlinear response with the oscillating amplitude,
which provides them with a large frequency tunability including the possibility
of mutual synchronization. The magnetization dynamics in STNO are induced by
spin transfer torque (STT) from spin currents and can be detected by changes in
electrical resistance due to giant magnetoresistance or tunneling
magnetoresistance. The STT effect is usually treated as a damping-like term
that reduces magnetic dissipation and promotes excitation of magnetic modes.
However, an additional term, known as Zhang-Li term has an effect on
magnetization gradients such as domain walls, and could have an effect on
localized magnetic modes in STNO. Here we study the effect of Zhang-Li torques
in magnetic excitations produced in STNO with a nanocontact geometry. Using
micromagnetic simulations we find that Zhang-Li torque modify threshold
currents of magnetic modes and their effective sizes. Additionally we show that
effects can be controlled by changing the ratio between nanocontact size and
layer thickness.

###Weak antilocalization in partially relaxed 200-nm HgTe films|M. L. Savchenko,D. A. Kozlov,Z. D. Kvon,N. N. Mikhailov,S. A. Dvoretsky###

Weak antilocalization in partially relaxed 200-nm HgTe films. The anomalous magnetoresistance caused by the weak antilocalization (WAL)
effects in 200-nm HgTe films is experimentally studied. The film is a high
quality 3D topological insulator with much stronger spatial separation of
surface states than in previously studied thinner HgTe structures. However, in
contrast to that films, the system under study is characterized by a reduced
partial strain resulting in an almost zero bulk energy gap. It has been shown
that at all positions of the Fermi level the system exhibits a WAL conductivity
correction superimposed on classical parabolic magnetoresistance. Since high
mobility of carriers, the analysis of the obtained results was performed using
a ballistic WAL theory. The maximum of the WAL conductivity correction
amplitude was found at a Fermi level position near the bulk energy gap
indicating to full decoupling of the surface carriers in these conditions. The
WAL amplitude monotonously decreases when the density of either bulk electrons
or holes increases that results from the increasing coupling between surface
and bulk carriers.

###Contrasting physical properties of the trilayer nickelates Nd$_4$Ni$_3$O$_{10}$ and Nd$_4$Ni$_3$O$_8$|Qing Li,Chengping He,Xiyu Zhu,Jin Si,Xinwei Fan,Hai-Hu Wen###

Contrasting physical properties of the trilayer nickelates Nd$_4$Ni$_3$O$_{10}$ and Nd$_4$Ni$_3$O$_8$. We report the crystal structures and physical properties of trilayer
nickelates Nd$_4$Ni$_3$O$_{10}$ and Nd$_4$Ni$_3$O$_8$. Measurements of
magnetization and electrical resistivity display contrasting behaviors in the
two compounds. Nd$_4$Ni$_3$O$_{10}$ shows a paramagnetic metallic behavior with
a metal to metal phase transition($T^{\ast}$) at about 162 K, as revealed by
both magnetic susceptibility and resistivity. Further magnetoresistance and
Hall coefficient results show a negative magnetoresistance at low temperatures
and the carrier type of Nd$_4$Ni$_3$O$_{10}$ is dominated by hole-type charge
carriers. The significant enhancement of Hall coefficient and resistivity below
$T^{\ast}$ suggest that effective charge carrier density decreases when cooling
through the transition temperature. In contrast, Nd$_4$Ni$_3$O$_8$ shows an
insulating behavior despite small value of resistivity at room temperature. The
compound shows paramagnetic behavior, with the similar magnetic moments as in
Nd$_4$Ni$_3$O$_{10}$ derived from the Curie-Weiss fitting. This may suggest
that the magnetic moments in both systems are contributed by the Nd ions. By
applying pressures up to about 49 GPa, the insulating behavior is still present
and becomes even stronger. Our results suggest that the different Ni
configurations ($Ni^{1+/2+}$ or $Ni^{2+/3+}$) and competition between localized
and itinerant electrons may account for the contrasting behaviors in trilayer
nickelates Nd$_4$Ni$_3$O$_{10}$ and Nd$_4$Ni$_3$O$_8$.

###Two-fold symmetry of in-plane magnetoresistance anisotropy in the superconducting states of BiCh2-based LaO0.9F0.1BiSSe single crystal|Kazuhisa Hoshi,Motoi Kimata,Yosuke Goto,Akira Miura,Chikao Moriyoshi,Yoshihiro Kuroiwa,Masanori Nagao,Yoshikazu Mizuguchi###

Two-fold symmetry of in-plane magnetoresistance anisotropy in the superconducting states of BiCh2-based LaO0.9F0.1BiSSe single crystal. Recently, two-fold symmetric in-plane anisotropy of the superconducting
properties have been observed in a single crystal of BiCh2-based (Ch: S, Se)
layered superconductor LaO0.5F0.5BiSSe having a tetragonal
(four-fold-symmetric) in-plane structure; the phenomena are very similar to
those observed in nematic superconductors. To explore the origin of the
two-fold symmetric anisotropy in the BiCh2-based system, we have investigated
the electron-doping dependence on the anisotropy by examining the in-plane
anisotropy of the magnetoresistance in the superconducting states for a single
crystal of LaO0.9F0.1BiSSe under high magnetic fields up to 15 T. We observed a
two-fold symmetry of in-plane anisotropy of magnetoresistance for
LaO0.9F0.1BiSSe. The results obtained for LaO0.9F0.1BiSSe are quite similar to
those observed for LaO0.5F0.5BiSSe, which has a higher electron doping
concentration than LaO0.9F0.1BiSSe. Our present finding suggests that the
emergence of the in-plane symmetry breaking in the superconducting state is
robust to the carrier concentration in the series of LaO1-xFxBiSSe.

###Large magnetoresistance and non-zero Berry phase in the nodal-line semimetal MoO2|Qin Chen,Zhefeng Lou,ShengNan Zhang,Binjie Xu,Yuxing Zhou,Huancheng Chen,Shuijin Chen,Jianhua Du,Hangdong Wang,Jinhu Yang,QuanSheng Wu,Oleg V. Yazyev,Minghu Fang###

Large magnetoresistance and non-zero Berry phase in the nodal-line semimetal MoO2. We performed calculations of the electronic band structure and the Fermi
surface as well as measured the longitudinal resistivity rhoxx(T,H), Hall
resistivity rhoxy(T,H) and quantum oscillations of the magnetization as a
function of temperature at various magnetic fields for MoO2 with monoclinic
crystal structure. The band structure calculations show that MoO2 is a
nodal-line semimetal when spin-orbit coupling is ignored. It was found that a
large magnetoresistance reaching 5.03x10^4% at 2 K and 9 T, its nearly
quadratic field dependence and a field-induced up-turn behavior of rhoxx(T),
the characteristics common for many topologically non-trivial as well as
trivial semimetals, emerge also in MoO2. The observed properties are attributed
to a perfect charge-carrier compensation, evidenced by both calculations
relying on the Fermi surface topology and the Hall resistivity measurements.
Both the observation of negative magnetoresistance for magnetic field along the
current direction and the non-zero Berry phase in de Haas-van Alphen
measurements indicate that pairs of Weyl points appear in MoO2, which may be
due to the crystal symmetry breaking. These results highlight MoO2 as a new
platform materials for studying the topological properties of oxides.

###Magnetotransport properties of the topological nodal-line semimetal CaCdSn|Antu Laha,Sougata Mardanya,Bahadur Singh,Hsin Lin,Arun Bansil,Amit Agarwal,Z. Hossain###

Magnetotransport properties of the topological nodal-line semimetal CaCdSn. Topological nodal-line semimetals support protected band crossings which form
nodal lines or nodal loops between the valence and conduction bands and exhibit
novel transport phenomena. Here we address the topological state of the
nodal-line semimetal candidate material, CaCdSn, and report magnetotransport
properties of its single crystals grown by the self-flux method. Our
first-principles calculations show that the electronic structure of CaCdSn
harbors a single nodal loop around the $\Gamma$ point in the absence of
spin-orbit coupling (SOC) effects. The nodal crossings in CaCdSn are found to
lie above the Fermi level and yield a Fermi surface that consists of both
electron and hole pockets. CaCdSn exhibits high mobility ($\mu \approx
3.44\times 10^4$ cm$^2$V$^{-1}$s$^{-1}$) and displays a field-induced
metal-semiconductor like crossover with a plateau in resistivity at low
temperature. We observe an extremely large and quasilinear non-saturating
transverse as well as longitudinal magnetoresistance (MR) at low temperatures
($\approx 7.44\times 10^3 \%$ and $\approx 1.71\times 10^3\%$, respectively, at
4K). We also briefly discuss possible reasons behind such a large quasilinear
magnetoresistance and its connection with the nontrivial band structure of
CaCdSn.

###Hall effect and symmetry breaking in non-magnetic metal with dynamic charge stripes|N. Sluchanko,A. Azarevich,A. Bogach,S. Demishev,K. Krasikov,V. Voronov,V. Filipov,N. Shitsevalova,V. Glushkov###

Hall effect and symmetry breaking in non-magnetic metal with dynamic charge stripes. A comprehensive study of magnetoresistance and Hall effect has been performed
for the set of the single crystals of non-magnetic metal LuB12 with the
Jahn-Teller instability of the boron cage and dynamic charge stripes forming
along <110> direction. Anomalous positive contribution to Hall effect for
particular direction of magnetic field H//[001] is found in the single crystals
of LuB12 of the highest quality. This contribution arising at T~ 150 K is shown
to increase drastically when approaching the disordered ground state below 60
K. The Hall effect anomaly is shown to appear in combination with the peak of
magnetoresistance. The various scenarios allowing for the topology of Fermi
surface, anisotropy of relaxation time for charge carriers and the filamentary
structure of fluctuating charge stripes are proposed to explain the features of
magnetotransport in this metal with inhomogeneous distribution of electron
density. The origin of SdH oscillations, which are observed in this
non-equilibrium metal with electron phase separation and strong charge carrier
scattering, is discussed.

###Review of experiments on the chiral anomaly in Dirac-Weyl semimetals|N. P. Ong,Sihang Liang###

Review of experiments on the chiral anomaly in Dirac-Weyl semimetals. We provide a review of recent experimental results on the chiral anomaly in
Dirac/Weyl semimetals. After a brief introduction, we trace the steps leading
to the prediction of materials that feature protected 3D bulk Dirac nodes. The
chiral anomaly is presented in terms of charge pumping between the chiral
Landau levels of Weyl fermions in parallel electric and magnetic fields. The
related chiral magnetic effect and chiral zero sound are described. Current
jetting effects, which present major complications in experiments on the
longitudinal magnetoresistance, are carefully analyzed. We describe a recent
test that is capable of distinguishing these semiclassical artifacts from
intrinsic quantum effects. Turning to experiments, we review critically the
longitudinal magnetoresistance experiments in the Dirac/Weyl semimetals Na3Bi,
GdPtBi, ZrTe5 and TaAs. Alternate approaches to the chiral anomaly, including
experiments on non-local transport, thermopower, thermal conductivity and
optical pump-probe response are reviewed. In the Supplement, we provide a brief
discussion of the chiral anomaly in the broader context of high energy physics
and relativistic quantum field theory, as well the anomaly's starring role at
the nexus of quantum physics and differential geometry.

###Domain Wall-Magnetic Tunnel Junction Spin Orbit Torque Devices and Circuits for In-Memory Computing|Mahshid Alamdar,Thomas Leonard,Can Cui,Bishweshwor P. Rimal,Lin Xue,Otitoaleke G. Akinola,T. Patrick Xiao,Joseph S. Friedman,Christopher H. Bennett,Matthew J. Marinella,Jean Anne C. Incorvia###

Domain Wall-Magnetic Tunnel Junction Spin Orbit Torque Devices and Circuits for In-Memory Computing. There are pressing problems with traditional computing, especially for
accomplishing data-intensive and real-time tasks, that motivate the development
of in-memory computing devices to both store information and perform
computation. Magnetic tunnel junction (MTJ) memory elements can be used for
computation by manipulating a domain wall (DW), a transition region between
magnetic domains. But, these devices have suffered from challenges: spin
transfer torque (STT) switching of a DW requires high current, and the multiple
etch steps needed to create an MTJ pillar on top of a DW track has led to
reduced tunnel magnetoresistance (TMR). These issues have limited experimental
study of devices and circuits. Here, we study prototypes of three-terminal
domain wall-magnetic tunnel junction (DW-MTJ) in-memory computing devices that
can address data processing bottlenecks and resolve these challenges by using
perpendicular magnetic anisotropy (PMA), spin-orbit torque (SOT) switching, and
an optimized lithography process to produce average device tunnel
magnetoresistance TMR = 164%, resistance-area product RA = 31
{\Omega}-{\mu}m^2, close to the RA of the unpatterned film, and lower switching
current density compared to using spin transfer torque. A two-device circuit
shows bit propagation between devices. Device initialization variation in
switching voltage is shown to be curtailed to 7% by controlling the DW initial
position, which we show corresponds to 96% accuracy in a DW-MTJ full adder
simulation. These results make strides in using MTJs and DWs for in-memory and
neuromorphic computing applications.

###Accessing topological surface states and negative MR in sculpted nanowires of Bi2Te3 at ultra-low temperature|Reena Yadav,Biplab Bhattacharyya,Animesh Pandey,Mandeep Kaur,R. P. Aloysius,Anurag Gupta,Sudhir Husale###

Accessing topological surface states and negative MR in sculpted nanowires of Bi2Te3 at ultra-low temperature. Milling of 2D flakes is a simple method to fabricate nanomaterial of any
desired shape and size. Inherently milling process can introduce the impurity
or disorder which might show exotic quantum transport phenomenon when studied
at the low temperature. Here we report temperature dependent weak
antilocalization (WAL) effects in the sculpted nanowires of topological
insulator in the presence of perpendicular magnetic field. The quadratic and
linear magnetoconductivity (MC) curves at low temperature indicate the bulk
contribution in the transport. A cusp feature in magnetoconductivity curves
(positive magnetoresistance) at ultra low temperature and at magnetic field,
less than 1T represent the WAL indicating the transport through surface states.
The MC curves are discussed by using the 2D Hikami Larkin Nagaoka theory. The
crossover interplay nature of positive and negative magnetoresistance observed
in the MR curve at ultra low temperature. Our results indicate that transport
through topological surface states (TSS) in sculpted nanowires of Bi2Te3 can be
achieved at mK range and linear MR observed at 2 K could be the coexistence of
electron transport through TSS and contribution from the bulk band.

###Anisotropic proximity-induced superconductivity and edge supercurrent in Kagome metal, K1-xV3Sb5|Yaojia Wang,Shuoying Yang,Pranava K. Sivakumar,Brenden R. Ortiz,Samuel M. L. Teicher,Heng Wu,Abhay K. Srivastava,Chirag Garg,Defa Liu,Stuart S. P. Parkin,Eric S. Toberer,Tyrel McQueen,Stephen D. Wilson,Mazhar N. Ali###

Anisotropic proximity-induced superconductivity and edge supercurrent in Kagome metal, K1-xV3Sb5. Materials with transition metals in triangular lattices are of great interest
for their potential combination of strong correlation, exotic magnetism and
electronic topology. Kagome nets are of particular importance since the
discovery of geometrically frustrated magnetism and topological band structures
in crystals like Herbertsmithite and Fe3Sn2, respectively. KV3Sb5 was
discovered to be a layered topological metal with a Kagome net of vanadium.
Here, we fabricated Josephson Junctions (JJ) of K1-xV3Sb5 and induced
superconductivity over long junction lengths. Through magnetoresistance and
current vs. phase measurements, we observed magnetic field sweeping direction
dependent magnetoresistance, and an anisotropic interference pattern with a
Fraunhofer pattern for in-plane magnetic field, but a suppression of critical
current for out-of-plane magnetic field. These results indicate an anisotropic
internal magnetic field in K1-xV3Sb5 which influences the superconducting
coupling in the junction, possibly giving rise to spin-triplet
superconductivity. In addition, the observation of long-lived fast oscillations
shows evidence of spatially localized conducting channels arising from edge
states. These observations pave the way for studying unconventional
superconductivity and Josephson device based on Kagome metals with electron
correlation and topology.

###Magnetic Field Effects on the Transport Properties of High-Tc Cuprates|E. C. Marino,R. Arouca###

Magnetic Field Effects on the Transport Properties of High-Tc Cuprates. Starting from a recently proposed comprehensive theory for the high-Tc
superconductivity in cuprates, we derive a general analytic expression for the
planar resistivity, in the presence of an applied external magnetic field
$\textbf{H}$ and explore its consequences in the different phases of these
materials. As an initial probe of our result, we show it compares very well
with experimental data for the resistivity of LSCO at different values of the
applied field. We also apply our result to Bi2201 and show that the
magnetoresistivity in the strange metal phase of this material, exhibits the
$H^2$ to $H$ crossover, as we move from the weak to the strong field regime.
Yet, despite of that, the magnetoresistivity does not present a quadrature
scaling. Remarkably, the resistivity H-field derivative does scale as a
function of $\frac{H}{T}$, in complete agreement with recent magneto-transport
measurements made in the strange metal phase of cuprates \cite{Hussey2020}. We,
finally, address the issue of the $T$-power-law dependence of the resistivity
of overdoped cuprates and compare our results with experimental data for
Tl2201. We show that this provides a simple method to determine whether the
quantum critical point associated to the pseudogap temperature $T^*(x)$ belongs
to the SC dome or not.

###Colossal Magnetoresistance without Mixed Valence in a Layered Phosphide Crystal|Zhi-Cheng Wang,Jared D. Rogers,Xiaohan Yao,Renee Nichols,Kemal Atay,Bochao Xu,Jacob Franklin,Ilya Sochnikov,Philip J. Ryan,Daniel Haskel,Fazel Tafti###

Colossal Magnetoresistance without Mixed Valence in a Layered Phosphide Crystal. Materials with strong magnetoresistive responses are the backbone of
spintronic technology, magnetic sensors, and hard drives. Among them, manganese
oxides with a mixed valence and a cubic perovskite structure stand out due to
their colossal magnetoresistance (CMR). A double exchange interaction underlies
the CMR in manganates, whereby charge transport is enhanced when the spins on
neighboring Mn3+ and Mn4+ ions are parallel. Prior efforts to find different
materials or mechanisms for CMR resulted in a much smaller effect. Here we show
an enormous CMR at low temperatures in EuCd2P2 without manganese, oxygen, mixed
valence, or cubic perovskite structure. EuCd2P2 has a layered trigonal lattice
and exhibits antiferromagnetic ordering at 11 K. The magnitude of CMR (104
percent) in as-grown crystals of EuCd2P2 rivals the magnitude in optimized thin
films of manganates. Our magnetization, transport, and synchrotron X-ray data
suggest that strong magnetic fluctuations are responsible for this phenomenon.
The realization of CMR at low temperatures without heterovalency leads to a new
regime for materials and technologies related to antiferromagnetic spintronics.

###Low temperature ferromagnetism in perovskite SrIrO$_3$ films|Rachna Chaurasia,K. Asokan,Kranti Kumar,A. K. Pramanik###

Low temperature ferromagnetism in perovskite SrIrO$_3$ films. The 5$d$ based SrIrO$_3$ represents prototype example of nonmagnetic
correlated metal which mainly originates from a combined effect of spin-orbit
coupling, lattice dimensionality and crystal structure. Therefore, tuning of
these parameters results in diverse physical properties in this material. Here,
we study the structural, magnetic and electrical transport behavior in
epitaxial SrIrO$_3$ film ($\sim$ 40 nm) grown on SrTiO$_3$ substrate. Opposed
to bulk material, the SrIrO$_3$ film exhibits a ferromagnetic ordering at low
temperature below $\sim$ 20 K. The electrical transport data indicate an
insulating behavior where the nature of charge transport follows Mott's
variable-range-hopping model. A positive magnetoresistance is recorded at 2 K
which has correlation with magnetic moment. We further observe a nonlinear Hall
effect at low temperature ($<$ 20 K) which arises due to an anomalous component
of Hall effect. An anisotropic behavior of both magnetoresistance and Hall
effect has been evidenced at low temperature which coupled with anomalous Hall
effect indicate the development of ferromagnetic ordering. We believe that an
enhanced (local) structural distortion caused by lattice strain at low
temperatures induces ferromagnetic ordering, thus showing structural
instability plays vital role to tune the physical properties in SrIrO$_3$.

###Anisotropic transport and de Haas$-$van Alphen oscillations in quasi-one-dimensional TaPtTe$_5$|Wen-He Jiao,Shaozhu Xiao,Bin Li,Chunqiang Xu,Xiao-Meng Xie,Hang-Qiang Qiu,Xiaofeng Xu,Yi Liu,Shi-Jie Song,Wei Zhou,Hui-Fei Zhai,X. Ke,Shaolong He,Guang-Han Cao###

Anisotropic transport and de Haas$-$van Alphen oscillations in quasi-one-dimensional TaPtTe$_5$. Because of the unique physical properties and potential applications, the
exploration of quantum materials with diverse symmetry-protected topological
states has attracted considerable interest in the condensed-matter community in
recent years. Most of the topologically nontirvial materials identified thus
far have two-dimensional or three-dimensional structural characteristics, while
the quasi-one-dimensional (quasi-1D) analogs are rare. Here we report on
anisotropic magnetoresistance, Hall effect, and quantum de Haas$-$van Alphen
(dHvA) oscillations in TaPtTe$_5$ single crystals, which possess a layered
crystal structure with quasi-1D PtTe$_2$ chains. TaPtTe$_5$ manifests an
anisotropic magnetoresistance and a nonlinear Hall effect at low temperatures.
The analysis of the dHvA oscillations reveals two major oscillation frequencies
(63.5 T and 95.2 T). The corresponding light effective masses and the nonzero
Berry phases suggest the nontrivial band topology in TaPtTe$_5$, which is
further corroborated by the first-principles calculations. Our results suggest
that TaPtTe$_5$, in analogy with its sister compounds TaPdTe$_5$ and
TaNiTe$_5$, is another quasi-1D material hosting topological Dirac fermions.

###Large voltage-tunable spin valve based on a double quantum dot|Patrycja Tulewicz,Kacper Wrzesniewski,Szabolcs Csonka,Ireneusz Weymann###

Large voltage-tunable spin valve based on a double quantum dot. We study the spin-dependent transport properties of a spin valve based on a
double quantum dot. Each quantum dot is assumed to be strongly coupled to its
own ferromagnetic lead, while the coupling between the dots is relatively weak.
The current flowing through the system is determined within the perturbation
theory in the hopping between the dots, whereas the spectrum of a quantum
dot-ferromagnetic lead subsystem is determined by means of the numerical
renormalization group method. The spin-dependent charge fluctuations between
ferromagnets and quantum dots generate an effective exchange field, which
splits the double dot levels. Such field can be controlled, separately for each
quantum dot, by the gate voltages or by changing the magnetic configuration of
external leads. We demonstrate that the considered double quantum dot spin
valve setup exhibits enhanced magnetoresistive properties, including both
normal and inverse tunnel magnetoresistance. We also show that this system
allows for the generation of highly spin-polarized currents, which can be
controlled by purely electrical means. The considered double quantum dot with
ferromagnetic contacts can thus serve as an efficient voltage-tunable spin
valve characterized by high output parameters.

###Extremely large magnetoresistance in the "ordinary" metal ReO3|Qin Chen,Zhefeng Lou,ShengNan Zhang,Yuxing Zhou,Binjie Xu,Huancheng Chen,Shuijin Chen,Jianhua Du,Hangdong Wang,Jinhu Yang,QuanSheng Wu,Oleg V. Yazyev,Minghu Fang###

Extremely large magnetoresistance in the "ordinary" metal ReO3. The extremely large magnetoresistance (XMR) observed in many topologically
nontrivial and trivial semimetals has attracted much attention in relation to
its underlying physical mechanism. In this paper, by combining the band
structure and Fermi surface (FS) calculations with the Hall resistivity and de
Haas-Van Alphen (dHvA) oscillation measurements, we studied the anisotropy of
magnetoresistance (MR) of ReO$_3$ with a simple cubic structure, an "ordinary"
nonmagnetic metal considered previously. We found that ReO$_3$ exhibits almost
all the characteristics of XMR semimetals: the nearly quadratic field
dependence of MR, a field-induced upturn in resistivity followed by a plateau
at low temperatures, high mobilities of charge carriers. It was found that for
magnetic field \emph{H} applied along the \emph{c} axis, the MR exhibits an
unsaturated \emph{H}$^{1.75}$ dependence, which was argued to arise from the
complete carrier compensation supported by the Hall resistivity measurements.
For \emph{H} applied along the direction of 15$^\circ$ relative to the \emph{c}
axis, an unsaturated \emph{H}$^{1.90}$ dependence of MR up to
9.43~$\times$~$10^3$$\%$ at 10~K and 9~T was observed, which was explained by
the existence of electron open orbits extending along the $k_{x}$ direction.
Two mechanisms responsible for XMR observed usually in the semimetals occur
also in the simple metal ReO$_3$ due to its peculiar FS (two closed electron
pockets and one open electron pocket), once again indicating that the details
of FS topology are a key factor for the observed XMR in materials.

###Bipolar conduction and giant positive magnetoresistance in doped metallic titanium oxide heterostructures|Ke Huang,Tao Wang,Mengjia Jin,Liang Wu,Junyao Floria Wang,Shengyao Li,Dong-chen Qi,Shuying Cheng,Yangyang Li,Jingsheng Chen,Xiaozhong He,Changjian Li,Stephen J. Pennycook,X. Renshaw Wang###

Bipolar conduction and giant positive magnetoresistance in doped metallic titanium oxide heterostructures. Empowering conventional materials with unexpected magnetoelectric properties
is appealing to the multi-functionalization of existing devices and the
exploration of future electronics. Recently, owing to its unique effect in
modulating a matter's properties, ultra-small dopants, e.g. H, D, and Li,
attract enormous attention in creating emergent functionalities, such as
superconductivity, and metal-insulator transition. Here, we report an
observation of bipolar conduction accompanied by a giant positive
magnetoresistance in D-doped metallic Ti oxide (TiOxDy) films. To overcome the
challenges in intercalating the D into a crystalline oxide, a series of TiOxDy
were formed by sequentially doping Ti with D and surface/interface oxidation.
Intriguingly, while the electron mobility of the TiOxDy increases by an order
of magnitude larger after doping, the emergent holes also exhibit high
mobility. Moreover, the bipolar conduction induces a giant magnetoresistance up
to 900% at 6 T, which is ~6 times higher than its conventional phase. Our study
paves a way to empower conventional materials in existing electronics and
induce novel electronic phases.

###Various magnetism of the compressed antiferromagnetic topological insulator EuSn2As2|Hualei Sun,Cuiqun Chen,Yusheng Hou,Yu Gong,Mengwu Huo,Lisi Li,Jia Yu,Wanping Cai,Naitian Liu,Ruqian Wu,Dao-Xin Yao,Meng Wang###

Various magnetism of the compressed antiferromagnetic topological insulator EuSn2As2. We report a comprehensive high-pressure study on the antiferromagnetic
topological insulator EuSn2As2 up to 21.1 GPa through measurements of
synchrotron x-ray diffraction, electrical resistance, magnetic resistance, and
Hall transports combined with first-principles calculations. No evident trace
of a structural phase transition is detected. The Neel temperatures determined
from resistance are increased from 24 to 77 K under pressure, which is resulted
from the enhanced magnetic exchange couplings between Eu2+ ions yielded by our
first-principles calculations. The negative magnetoresistance of EuSn2As2
persists to higher temperatures accordantly. However, the enhancement of the
observed N\'eel temperatures deviates from the calculations obviously above
10.0 GPa. In addition, the magnitude of the magnetoresistance, the Hall
coefficients, and the charge carrier densities show abrupt changes between 6.9
to 10.0 GPa. The abrupt changes probably originate from a pressure induced
valence change of Eu ions from a divalent state to a divalent and trivalent
mixed state. Our results provide insights into variation of the magnetism of
EuSn2As2 and similar antiferromagnetic topological insulators under pressure.

###Magnetic coupling in Y$_3$Fe$_5$O$_{12}$/Gd$_3$Fe$_5$O$_{12}$ heterostructures|Sven Becker,Zengyao Ren,Felix Fuhrmann,Andrew Ross,Sally Lord,Shilei Ding,Rui Wu,Jinbo Yang,Jun Miao,Mathias Kläui,Gerhard Jakob###

Magnetic coupling in Y$_3$Fe$_5$O$_{12}$/Gd$_3$Fe$_5$O$_{12}$ heterostructures. Ferrimagnetic Y$_3$Fe$_5$O$_{12}$ (YIG) is the prototypical material for
studying magnonic properties due to its exceptionally low damping. By
substituting the yttrium with other rare earth elements that have a net
magnetic moment, we can introduce an additional spin degree of freedom. Here,
we study the magnetic coupling in epitaxial
Y$_3$Fe$_5$O$_{12}$/Gd$_3$Fe$_5$O$_{12}$ (YIG/GIG) heterostructures grown by
pulsed laser deposition. From bulk sensitive magnetometry and surface sensitive
spin Seebeck effect (SSE) and spin Hall magnetoresistance (SMR) measurements,
we determine the alignment of the heterostructure magnetization through
temperature and external magnetic field. The ferromagnetic coupling between the
Fe sublattices of YIG and GIG dominates the overall behavior of the
heterostructures. Due to the temperature dependent gadolinium moment, a
magnetic compensation point of the total bilayer system can be identified. This
compensation point shifts to lower temperatures with increasing thickness of
YIG due the parallel alignment of the iron moments. We show that we can control
the magnetic properties of the heterostructures by tuning the thickness of the
individual layers, opening up a large playground for magnonic devices based on
coupled magnetic insulators. These devices could potentially control the magnon
transport analogously to electron transport in giant magnetoresistive devices.

###Angular dependence of Hall effect and magnetoresistance in SrRuO$_3$-SrIrO$_3$ heterostructures|Sven Esser,Jiongyao Wu,Sebastian Esser,Robert Gruhl,Anton Jesche,Vladimir Roddatis,Vasily Moshnyaga,Rossitza Pentcheva,Philipp Gegenwart###

Angular dependence of Hall effect and magnetoresistance in SrRuO$_3$-SrIrO$_3$ heterostructures. Perovskite SrRuO$_3$ is a prototypical itinerant ferromagnet which allows
interface engineering of its electronic and magnetic properties. We report
synthesis and investigation of atomically flat artificial multilayers of
SrRuO$_3$ with the spin-orbit semimetal SrIrO$_3$ in combination with
band-structure calculations with a Hubbard $U$ term and topological analysis.
They reveal an electronic reconstruction and emergence of flat Ru-4d$_{xz}$
bands near the interface, ferromagnetic interlayer coupling and negative
Berry-curvature contribution to the anomalous Hall effect. We analyze the Hall
effect and magnetoresistance measurements as a function of the field angle from
out of plane towards in-plane orientation (either parallel or perpendicular to
the current direction) by a two-channel model. The magnetic easy direction is
tilted by about $20^\circ$ from the sample normal for low magnetic fields,
rotating towards the out-of-plane direction by increasing fields. Fully
strained epitaxial growth enables a strong anisotropy of magnetoresistance. An
additional Hall effect contribution, not accounted for by the two-channel model
is compatible with stable skyrmions only up to a critical angle of roughly
$45^\circ$ from the sample normal. Within about $20^\circ$ from the thin film
plane an additional peak-like contribution to the Hall effect suggests the
formation of a non-trivial spin structure.

###Optical read-out of the Néel vector in metallic antiferromagnet Mn$_{2}$Au|Vladimir Grigorev,Mariia Filianina,Stanislav Yu. Bodnar,Sergei Sobolev,Nilabha Bhattacharjee,Satya Bommanaboyena,Yaryna Lytvynenko,Yurii Skourski,Dirk Fuchs,Mathias Kläui,Martin Jourdan,Jure Demsar###

Optical read-out of the Néel vector in metallic antiferromagnet Mn$_{2}$Au. Metallic antiferromagnets with broken inversion symmetry on the two
sublattices, strong spin-orbit coupling and high N\'{e}el temperatures offer
new opportunities for applications in spintronics. Especially Mn$_{2}$Au, with
high N\'{e}el temperature and conductivity, is particularly interesting for
real-world applications. Here, manipulation of the orientation of the staggered
magnetization,\textit{\ i.e.} the N\'{e}el vector, by current pulses has been
recently demonstrated, with the read-out limited to studies of anisotropic
magnetoresistance or X-ray magnetic linear dichroism. Here, we report on the
in-plane reflectivity anisotropy of Mn$_{2}$Au (001) films, which were N\'{e}el
vector aligned in pulsed magnetic fields. In the near-infrared, the anisotropy
is $\approx$ 0.6\%, with higher reflectivity for the light polarized along the
N\'{e}el vector. The observed magnetic linear dichroism is about four times
larger than the anisotropic magnetoresistance. This suggests the dichroism in
Mn$_{2}$Au is a result of the strong spin-orbit interactions giving rise to
anisotropy of interband optical transitions, in-line with recent studies of
electronic band-structure. The considerable magnetic linear dichroism in the
near-infrared could be used for ultrafast optical read-out of the N\'{e}el
vector in Mn$_{2}$Au.

###Ultimate In-plane Magnetoresistance Ratio of Graphene by Controlling the Gapped Dirac Cone through Pseudospin|Yusuf Wicaksono,Halimah Harfah,Gagus Ketut Sunnardianto,Muhammad Aziz Majidi,Koichi Kusakabe###

Ultimate In-plane Magnetoresistance Ratio of Graphene by Controlling the Gapped Dirac Cone through Pseudospin. $\require{mediawiki-texvc}$ A theoretical study is presented on the in-plane
conductance of graphene that is partially sandwiched by Ni(111) slabs with a
finite size and atom-scale width of $\approx12.08 \AA$. In the sandwiched part,
the gapped Dirac cone of graphene can be controlled via pseudospin by changing
the magnetic alignment of the Ni(111) slabs. When the magnetic moments of the
upper and lower Ni(111) slabs have antiparallel and parallel configurations,
the bandgap at the Dirac cone is open and closed, respectively. The
transmission probability calculation for the in-plane conductance of the system
indicated that the antiparallel configuration would result in nearly zero
conductance of $E-E_F=0.2$ eV. In the parallel configuration, the transmission
probability calculation indicated that the system would have a profile similar
to that of pristine graphene. A comparison of the transmission probabilities of
the antiparallel and parallel configurations indicated that a high
magnetoresistance of $1450\%$ could be achieved. An ultimate magnetoresistance
can be expected if the Ni(111) slab widths are increased to the nanometer
scale.

###Highly Tunable Magnetic and Magnetotransport Properties of Exchange Coupled Ferromagnet/Antiferromagnet-based Heterostructures|Sri Sai Phani Kanth Arekapudi,Daniel Bülz,Fabian Ganss,Fabian Samad,Chen Luo,Dietrich R. T. Zahn,Kilian Lenz,Georgeta Salvan,Manfred Albrecht,Olav Hellwig###

Highly Tunable Magnetic and Magnetotransport Properties of Exchange Coupled Ferromagnet/Antiferromagnet-based Heterostructures. Antiferromagnets (AFMs) with zero net magnetization are proposed as active
elements in future spintronic devices. Depending on the critical thickness of
the AFM thin films and the measurement temperature, bimetallic Mn-based alloys
and transition metal oxide-based AFMs can host various coexisting ordered,
disordered, and frustrated AFM phases. Such coexisting phases in the exchange
coupled ferromagnetic (FM)/AFM-based heterostructures can result in unusual
magnetic and magnetotransport phenomena. Here, we integrate chemically
disordered AFM IrMn3 thin films with coexisting AFM phases into complex
exchange coupled MgO(001)/Ni3Fe/IrMn3/Ni3Fe/CoO heterostructures and study the
structural, magnetic, and magnetotransport properties in various magnetic field
cooling states. In particular, we unveil the impact of rotating the relative
orientation of the disordered and reversible AFM moments with respect to the
irreversible AFM moments on the magnetic and magnetoresistance properties of
the exchange coupled heterostructures. We further found that the persistence of
AFM grains with thermally disordered and reversible AFM order is crucial for
achieving highly tunable magnetic properties and multi-level magnetoresistance
states. We anticipate that the introduced approach and the heterostructure
architecture can be utilized in future spintronic devices to manipulate the
thermally disordered and reversible AFM order at the nanoscale.

###Boosting room temperature tunnel magnetoresistance in hybrid magnetic tunnel junctions under electric bias|César González-Ruano,Coriolan Tiusan,Michel Hehn,Farkhad G. Aliev###

Boosting room temperature tunnel magnetoresistance in hybrid magnetic tunnel junctions under electric bias. Spin-resolved electron symmetry filtering is a key mechanism behind giant
tunneling magnetoresistance (TMR) in Fe/MgO/Fe and similar magnetic tunnel
junctions (MTJs), providing room temperature functionality in modern spin
electronics. However, the core process of the electron symmetry filtering
breaks down under applied bias, dramatically reducing the TMR above 0.5 V. This
strongly hampers the application range of MTJs. To circumvent the problem,
resonant tunneling between ferromagnetic electrodes through quantum well states
in thin layers has been used so far. This mechanism, however, is mainly
effective at low temperatures. Here, a fundamentally different approach is
demonstrated, providing a strong TMR boost under applied bias in
V/MgO/Fe/MgO/Fe/Co hybrids. This pathway uses spin orbit coupling (SOC)
controlled interfacial states in vanadium, which contrary to the V(001) bulk
states are allowed to tunnel to Fe(001) at low biases. The experimentally
observed strong increase of TMR with bias is modelled using two nonlinear
resistances in series, with the low bias conductance of the first (V/MgO/Fe)
element being boosted by the SOC-controlled interfacial states, while the
conductance of the second (Fe/MgO/Fe) junctions controlled by the relative
alignment of the two ferromagnetic layers. These results pave a way to
unexplored and fundamentally different spintronic device schemes, with
tunneling magnetoresistance uplifted under applied electric bias.

###The Jeff=1/2 antiferromagnet Sr2IrO4: A golden avenue toward new physics and functions|Chengliang Lu,Jun-Ming Liu###

The Jeff=1/2 antiferromagnet Sr2IrO4: A golden avenue toward new physics and functions. Iridates have been providing a fertile ground for studying emergent phases of
matter that arise from delicate interplay of various fundamental interactions
with approximate energy scale. Among these highly focused quantum materials,
perovskite Sr2IrO4 belonging to the Ruddlesden-Popper series stands out and has
been intensively addressed in the last decade, since it hosts a novel Jeff =
1/2 state which is a profound manifestation of strong spin-orbit coupling.
Moreover, the Jeff = 1/2 state represents a rare example of iridates that has
been better understood both theoretically and experimentally. In this progress
report, we take Sr2IrO4 as an example to overview the recent advances of the
Jeff = 1/2 state in two aspects: materials fundamentals and functionality
potentials. In the fundamentals part, we first illustrate basic issues for the
layered canted antiferromagnetic order of the Jeff = 1/2 magnetic moments in
Sr2IrO4, and then review the progress of the antiferromagnetic order modulation
through diverse routes. Subsequently, for the functionality potentials,
fascinating properties such as atomic-scale giant magnetoresistance,
anisotropic magnetoresistance, and nonvolatile memory, will be addressed. This
report will be concluded with our prospected remarks and outlooks.

###Colossal Anomalous Hall Conductivity and Topological Hall Effect in Ferromagnetic Kagome Metal Nd$_3$Al|Durgesh Singh,Jadupati Nag,Sankararao Yadam,V. Ganesan,Aftab Alam,K. G. Suresh###

Colossal Anomalous Hall Conductivity and Topological Hall Effect in Ferromagnetic Kagome Metal Nd$_3$Al. Historically, the genesis of anomalous Hall effect (AHE) in magnetic
materials has always been a fascinating yet controversial topic in the solid
state physics community. Recent progress on the understanding of this topic has
revealed an intimate connection between the Berry curvature of occupied
electronic states and the intrinsic AHE. Magnetic Weyl semimetals with broken
time reversal symmetry is a classic example, which is expected to show large
contributions to Berry curvature around the topological nodes and hence to the
AHE. Here, we report a kagome metallic ferromagnet Nd$_3$Al, with a large
unconventional positive magnetoresistance (~ 80 %) and colossal anomalous Hall
conductivity of 1.8x10^5 S/cm (largest ever reported to the best of our
knowledge). We also show that the magnetic state of this compound is quite
different from its analogues in many respects. While the compound is
predominantly an itinerant ferromagnet, its low temperature phase exhibits
topological band structure, enhanced skew scattering as well as topological
spin texture arising in the spin frustrated kagome lattice. Various
experimental findings such as topological Hall effect, non-saturating positive
magnetoresistance etc. give strong indication to this scenario. Ab-initio
calculations broadly confirm the experimental findings by revealing the
presence of flat bands and Weyl points originating from the itinerant Nd
moments. The non-trivial band structure, enhanced skew scattering and the spin
texture in a clean polycrystalline sample are found be responsible for the
colossal Hall conductivity and topological Hall effect.

###Antiferromagnetism and large magnetoresistance in GdBi single crystal|Gourav Dwari,Souvik Sasmal,Bishal Maity,Vikas Saini,Ruta Kulkarni,Arumugam Thamizhavel###

Antiferromagnetism and large magnetoresistance in GdBi single crystal. Single crystal of the binary equi-atomic compound GdBi crystallizing in the
rock salt type cubic crystal structure with the space group $Fm\bar{3}m$ has
been grown by flux method. The electrical and magnetic measurements have been
performed on well oriented single crystals. The antiferromagnetic ordering of
the Gd moments is confirmed at $T_{\rm N} = 27.5$~K. The magnetization
measurement performed at $2$~K along the principal crystallographic direction
[100] did not show any metamagnetic transition and no sign of saturation up to
$7$~T. Zero field electrical resistivity reveals a sharp drop at $27.5$~K
suggesting a reduction in the spin disorder scattering due to the
antiferromagnetic alignment of the Gd moments. The residual resistivity at
$2$~K is 390~n$\Omega$cm suggesting a good quality of the grown crystal. The
magneto resistance attains a value of $1.0~\times~10^{4}\%$ with no sign of
saturation, in a field of $14$~T, at $T = 2$~K. Shubnikov de Hass (SdH)
oscillations have been observed in the high field range of the
magnetoresistance with five different frequencies corresponding to the extremal
areas of the Fermi surface. Analysis of the Hall data revealed a near
compensation of the charge carriers accounting for the extremely large
magnetoresistance.

###Spin current transport in hybrid Pt / multifunctional magnetoelectric Ga0.6Fe1.4O3 bilayers|Suvidyakumar Homkar,Elodie Martin,Benjamin Meunier,Alberto Anadon-Barcelona,Corinne Bouillet,Jon Gorchon,Karine Dumesnil,Christophe Lefèvre,François Roulland,Olivier Copie,Daniele Preziosi,Sébastien Petit-Watelot,Juan-Carlos Rojas-Sánchez,Nathalie Viart###

Spin current transport in hybrid Pt / multifunctional magnetoelectric Ga0.6Fe1.4O3 bilayers. The low power manipulation of magnetization is currently a highly
sought-after objective in spintronics. Non ferromagnetic large spin-orbit
coupling heavy metal (NM) / ferromagnet (FM) heterostructures offer interesting
elements of response to this issue, by granting the manipulation of the FM
magnetization by the NM spin Hall effect (SHE) generated spin current.
Additional functionalities, such as the electric field control of the spin
current generation, can be offered using multifunctional ferromagnets. We have
studied the spin current transfer processes between Pt and the multifunctional
magnetoelectric Ga0.6Fe1.4O3 (GFO). In particular, via angular dependent
magnetotransport measurements, we were able to differentiate between magnetic
proximity effect (MPE)-induced anisotropic magnetoresistance (AMR) and spin
Hall magnetoresistance (SMR). Our analysis shows that SMR is the dominant
phenomenon at all temperatures and is the only one to be considered near room
temperature, with a magnitude comparable to those observed in Pd/YIG or Pt/YIG
heterostructures. These results indicate that magnetoelectric GFO thin films
show promises for achieving an electric-field control of the spin current
generation in NM/FM oxide-based heterostructures.

###Discovery of charge-4e and charge-6e superconductivity in kagome superconductor CsV3Sb5|Jun Ge,Pinyuan Wang,Ying Xing,Qiangwei Yin,Hechang Lei,Ziqiang Wang,Jian Wang###

Discovery of charge-4e and charge-6e superconductivity in kagome superconductor CsV3Sb5. Superconductivity originates from the condensation of charge-2e Cooper pairs.
Fundamentally new superconducting states due to the condensation of charge-4e
and charge-6e multi-electron bound states, in the absence of the charge-2e
condensate, have been theoretically proposed but so far unobserved
experimentally. Here we report the discovery of the charge-4e and charge-6e
superconductivity in nanopatterned ring devices fabricated using the new
transition-metal kagome lattice superconductor CsV3Sb5. We perform systematic
magneto-transport measurements and observe the quantization of the magnetic
flux in units of h/4e and h/6e in the magnetoresistance oscillations.
Specifically, in the zero-resistance state below the temperature T_c^zero,
magnetoresistance oscillations with period h/2e for charge-2e superconductivity
are detected, as expected from the Little-Parks effect. We find that the h/2e
oscillations are suppressed when the temperature is increased above T_c^zero
and novel resistance oscillations with h/4e periodicity are observed,
indicating the emergence of charge-4e superconductivity. Increasing the
temperature further suppresses the h/4e superconductivity and oscillations with
h/6e periodicity emerge as an incipient charge-6e superconductivity. Our
observations provide direct experimental evidence for the existence of
macroscopic phase coherent paired quantum matter beyond the charge-2e
superconductors described by the Bardeen-Cooper-Schrieffer (BCS) theory, and
reveal new insights into the intertwined and vestigial electronic orders
associated with the primary pair density wave state in kagome superconductors.

###Giant magnetoresistance, Fermi surface topology, Shoenberg effect and vanishing quantum oscillations in type-II Dirac semimetal candidates MoSi$_2$ and WSi$_2$|Orest Pavlosiuk,Przemysław Wojciech Swatek,Jian-Ping Wang,Piotr Wiśniewski,Dariusz Kaczorowski###

Giant magnetoresistance, Fermi surface topology, Shoenberg effect and vanishing quantum oscillations in type-II Dirac semimetal candidates MoSi$_2$ and WSi$_2$. We performed comprehensive theoretical and experimental studies of the
electronic structure and the Fermi surface topology of two novel quantum
materials, MoSi$_2$ and WSi$_2$. The theoretical predictions of the electronic
structure in the vicinity of the Fermi level was verified experimentally by
thorough analysis of the observed quantum oscillations in both electrical
resistivity and magnetostriction. We established that the Fermi surface sheets
in MoSi$_2$ and WSi$_2$ consist of 3D dumbbell-shaped hole-like pockets and
rosette-shaped electron-like pockets, with nearly equal volumes. Based on this
finding, both materials were characterized as almost perfectly compensated
semimetals. In conjunction, the magnetoresistance attains giant values of
$10^4$ and $10^5\,\%$ for WSi$_2$ and MoSi$_2$, respectively. In turn, the
anisotropic magnetoresistance achieves $-95$ and $-98\,\%$ at $T=2\,$K and in
$B=14\,$T for WSi$_2$ and MoSi$_2$, respectively. Furthermore, for both
compounds we observed the Shoenberg effect in their Shubnikov-de Haas
oscillations that persisted at as high temperature as $T=25\,$K in MoSi$_2$ and
$T=12\,$K in WSi$_2$. In addition, we found for MoSi$_2$ a rarely observed
spin-zero phenomenon. Remarkably, the electronic structure calculations
revealed type-II Dirac cones located near 480 meV and 710 meV above the Fermi
level in MoSi$_2$ and WSi$_2$, respectively.

###Consecutive topological phase transitions and colossal magnetoresistance in a magnetic topological semimetal|Feng Du,Lin Yang,Zhiyong Nie,Ninghua Wu,Yong Li,Shuaishuai Luo,Ye Chen,Dajun Su,Michael Smidman,Youguo Shi,Chao Cao,Frank Steglich,Yu Song,Huiqiu Yuan###

Consecutive topological phase transitions and colossal magnetoresistance in a magnetic topological semimetal. The combination of magnetic symmetries and electronic band topology provides
a promising route for realizing topologically nontrivial quasiparticles, and
the manipulation of magnetic structures may enable the switching between
topological phases, with the potential for achieving functional physical
properties. Here, we report measurements of the electrical resistivity of
EuCd$_2$As$_2$ under pressure, which show an intriguing insulating dome at
pressures between $p_{\rm c1}\sim1.0$~GPa and $p_{\rm c2}\sim2.0$~GPa, situated
between two regimes with metallic transport. The insulating state can be fully
suppressed by a small magnetic field, leading to a colossal negative
magnetoresistance on the order of $10^5$\%, accessible via a modest field of
$\sim0.2$~T. First-principles calculations reveal that the dramatic evolution
of the resistivity under pressure is due to consecutive transitions of
EuCd$_2$As$_2$ from a magnetic topological insulator to a trivial insulator,
and then to a Weyl semimetal, with the latter resulting from a pressure-induced
change in the magnetic ground state. Similarly, the colossal magnetoresistance
results from a field-induced polarization of the magnetic moments, transforming
EuCd$_2$As$_2$ from a trivial insulator to a Weyl semimetal. These findings
underscore weak magnetic exchange couplings and spin anisotropy as ingredients
for discovering tunable magnetic topological materials with desirable
functionalities.

###Quantum transport evidence of the boundary states and Lifshitz transition in Bi$_4$Br$_4$|Dong-Yun Chen,Dashuai Ma,Junxi Duan,Dong Chen,Haiwen Liu,Junfeng Han,Yugui Yao###

Quantum transport evidence of the boundary states and Lifshitz transition in Bi$_4$Br$_4$. The quasi-one-dimensional van der Waals compound Bi$_4$Br$_4$ was recently
found to be a promising high-order topological insulator with exotic electronic
states. In this paper, we study the electrical transport properties of
Bi$_4$Br$_4$ bulk crystals. Two electron-type samples with different electron
concentrations are investigated. Both samples have saturation resistivity
behavior in low temperature. In the low-concentration sample, two-dimensional
quantum oscillations are clearly observed in the magnetoresistance
measurements, which are attributed to the band-bending-induced surface state on
the (001) facet. In the high-concentration sample, the angular
magnetoresistance exhibits two pairs of symmetrical sharp valleys with an
angular difference close to the angle between the crystal planes (001) and
(100). The additional valley can be explained by the contribution of the
boundary states on the (100) facet. Besides, Hall measurements at low
temperatures reveal an anomalous decrease of electron concentration with
increasing temperature, which can be explained by the temperature-induced
Lifshitz transition. These results shed light on the abundant surface and
boundary state transport signals and the temperature-induced Lifshitz
transition in Bi$_4$Br$_4$.

###Activated hopping transport in nematic conducting aerogel at low temperatures|V. I. Tsebro,E. G. Nikolaev,L. B. Lugansky,M. S. Kutuzov,R. A. Khmel'nitskii,A. A. Tonkikh,A. I. Khar'kovskii###

Activated hopping transport in nematic conducting aerogel at low temperatures. The transport properties of nematic aerogels, which consist of highly
oriented Al$_2$O$_3\cdot$SiO$_2$ nanofibers coated with a graphene shell with a
large number of defects, are studied. The temperature dependences of the
electrical resistivity in the range of 9-40K strictly follow the formula
derived to describe the variable range hopping (VRH) conductivity, in which
exponent $\alpha$ changes from 0.4 to 0.9 when the number of layers in the
graphene shell decreases from 4-6 to 1-2. The dependence of $\alpha$ on the
shell thickness can be explained by a simultaneous change in the dimensionality
of hopping transport and the character of the energy dependence of the density
of localized states near the Fermi level. The fact that $\alpha$ approaches
unity at the minimum graphene shell thickness indicates a gradual transition
from VRH transport to nearest neighbor hopping (NNH) transport. The
magnetoresistance measured at T = 4.2 K is negative, increases significantly
with decreasing graphene shell thickness, and is approximated by a formula for
the case of weak localization with a good accuracy. The phase coherence lengths
are in a reasonable relation with the graphene grain sizes. The conducting
aerogels under study complement the well-known set of materials that exhibit
hopping electron transport at low temperatures, which is characteristic of
media with strong carrier localization, and also a negative magnetoresistance,
which usually manifests itself under weak localization conditions.

###Record-quality GaAs two-dimensional hole systems|Yoon Jang Chung,C. Wang,S. K. Singh,A. Gupta,K. W. Baldwin,K. W. West,R. Winkler,M. Shayegan,L. N. Pfeiffer###

Record-quality GaAs two-dimensional hole systems. The complex band structure, large spin-orbit induced band splitting, and
heavy effective mass of two-dimensional (2D) hole systems hosted in GaAs
quantum wells render them rich platforms to study many-body physics and
ballistic transport phenomena. Here we report ultra-high-quality (001) GaAs 2D
hole systems, fabricated using molecular beam epitaxy and modulation doping,
with mobility values as high as $5.8\times10^6$ cm$^2$/Vs at a hole density of
$p=1.3\times10^{11}$ /cm$^2$, implying a mean-free path of $\simeq27$ $\mu$m.
In the low-temperature magnetoresistance trace of this sample, we observe
high-order fractional quantum Hall states up to the Landau level filling
$\nu=12/25$ near $\nu=1/2$. Furthermore, we see a deep minimum develop at
$\nu=1/5$ in the magnetoresistance of a sample with a much lower hole density
of $p=4.0\times10^{10}$ /cm$^2$ where we measure a mobility of $3.6\times10^6$
cm$^2$/Vs. These improvements in sample quality were achieved by reduction of
residual impurities both in the GaAs channel and the AlGaAs barrier material,
as well as optimization in design of the sample structure.

###Probing the spin dimensionality in single-layer CrSBr van der Waals heterostructures by magneto-transport measurements|Carla Boix-Constant,Samuel Mañas-Valero,Alberto M. Ruiz,Andrey Rybakov,Krzysztof Aleksander Konieczny,Sébastien Pillet,José J. Baldoví,Eugenio Coronado###

Probing the spin dimensionality in single-layer CrSBr van der Waals heterostructures by magneto-transport measurements. Two-dimensional (2D) magnetic materials offer unprecedented opportunities for
fundamental physics and applied research in spintronics and magnonics. Beyond
the pioneering studies on 2D CrI3 and Cr2Ge2Te6, this emerging field has
expanded to 2D antiferromagnets exhibiting different spin anisotropies and
textures. Of particular interest is the layered metamagnet CrSBr, a relatively
air-stable semiconductor formed by antiferromagnetically-coupled ferromagnetic
layers (Tc~150 K) that can be exfoliated down to the single-layer. It presents
a complex magnetic behavior with a dynamic magnetic crossover leading to a
low-temperature hidden order below T*~40 K. Here, we inspect the
magneto-transport properties of CrSBr vertical heterostructures in the 2D
limit. Our results demonstrate the marked low-dimensional character of the
ferromagnetic monolayer, with short-range correlations above Tc and an
Ising-type in-plane anisotropy, being the spins spontaneously aligned along the
easy-axis b below Tc. By applying moderate magnetic fields along a and c axes,
a spin reorientation occurs, leading to a magnetoresistance enhancement below
T*. In multilayers, a spin-valve behavior is observed, with negative
magnetoresistance strongly enhanced along the three directions below T*. These
results show that CrSBr monolayer/bilayer provides an ideal platform for
studying and controlling field-induced phenomena in two-dimensions, offering
new insights regarding 2D magnets and their integration into vertical
spintronic devices.

###Probing the topological surface states in superconducting Sn4Au single crystal: A magneto transport study|M. M. Sharma,Poonam Rani,V. P. S. Awana###

Probing the topological surface states in superconducting Sn4Au single crystal: A magneto transport study. Materials exhibiting bulk superconductivity along with magnetoresistance (MR)
in their normal state have emerged as suitable candidates for topological
superconductivity. In this article, we report a flux free method to synthesize
single crystal of topological superconductor candidate Sn4Au. The phase purity
and single crystalline nature are confirmed through various characterizations
viz. X-Ray diffraction (XRD), field emission scanning electron microscopy
(FESEM), selected Area electron diffraction (SAED), and transmission electron
microscopy (TEM). Chemical states of the constituent element viz. Sn and Au are
analyzed through X-Ray photoelectron spectroscopy (XPS). Superconductivity in
synthesized Sn4Au single crystal is evident form R-T plot and critical field
(Hc) is determined through R-H plot at 2K i.e., just below critical temperature
Tc. A positive magnetoresistance (MR) is observed in R-H measurements at
different temperatures above Tc, viz. at 3K, 5K, 10K and 20K. Further, the
magnetoconductivity (MC) is analyzed by using Hikami-Larkin-Nagaoka (HLN)
formalism, which signifies the presence of weak antilocalization (WAL) effect
in Sn4Au. Angle dependent magneto-transport measurement has been performed to
detect the origin of the observed WAL effect in Sn4Au single crystal.
Normalized MC vs HcosTheta plot shows presence of topological surface states
(TSS) in the studied system. It is evident that Sn4Au is a 2.6K topological
superconductor.

###Geometrical magnetoresistance effect and mobility in graphene field-effect transistors|Isabel Harrysson Rodrigues,Andrey Generalov,Anamul Md Hoque,Miika Soikkeli,Anton Murros,Sanna Arpiainen,Andrei Vorobiev###

Geometrical magnetoresistance effect and mobility in graphene field-effect transistors. Further development of the graphene field-effect transistors (GFETs) for
high-frequency electronics requires accurate evaluation and study of the
mobility of charge carriers in a specific device. Here, we demonstrate that the
mobility in the GFETs can be directly characterized and studied using the
geometrical magnetoresistance (gMR) effect. The method is free from the
limitations of other approaches since it does not require an assumption of the
constant mobility and the knowledge of the gate capacitance. Studies of a few
sets of GFETs in the wide range of transverse magnetic fields indicate that the
gMR effect dominates up to approximately 0.55 T. In higher fields, the physical
magnetoresistance effect starts to contribute. The advantages of the gMR
approach allowed us to interpret the measured dependencies of mobility on the
gate voltage, i.e., carrier concentration, and identify the corresponding
scattering mechanisms. In particular, the range of the fairly constant mobility
is associated with the dominating Coulomb scattering. The decrease in mobility
at higher carrier concentrations is associated with the contribution of the
phonon scattering. Analysis shows that the gMR mobility is typically 2-3 times
higher than that found via the commonly used drain resistance model. The latter
underestimates the mobility since it does not take the interfacial capacitance
into account.

###Large anomalous unidirectional magnetoresistance in a single ferromagnetic layer|Kaihua Lou,Qianwen Zhao,Baiqing Jiang,Chong Bi###

Large anomalous unidirectional magnetoresistance in a single ferromagnetic layer. Unidirectional magnetoresistance (UMR) in a ferromagnetic bilayer due to the
spin Hall effects (SHEs) provides a facile means of probing in-plane
magnetization to avoid complex magnetic tunnel junctions. However, the UMR
signal is very weak and usually requires a lock-in amplifier for detection even
in the bilayer involving Ta or Pt with a large spin Hall angle (SHA). Here we
report a type of UMR, termed as the anomalous UMR (AUMR), in a single CoFeB
layer without any adjacent SHE layers, where the UMR signal is about 10 times
larger than that in Ta/CoFeB structures and can be detected by using
conventional dc multimeters in the absence of lock-in amplifiers. We further
demonstrate that the extracted AUMR by excluding thermal contributions shows
reversal signs for the CoFeB and NiFe single layers with opposite SHAs,
indicating that the AUMR may originate from the self-generated spin
accumulation interacting with magnetization through the giant
magnetoresistance-like mechanism. These results suggest that the AUMR
contributes UMR signals larger than the interfacial spin Hall UMR in the
CoFeB-involved systems, providing a convenient and reliable approach to detect
in-plane magnetization for the two-terminal spintronic devices.

###Ultra-High Carrier Mobilities in Ferroelectric Domain Wall Corbino Cones at Room Temperature|Conor J. McCluskey,Matthew G. Colbear,James P. V. McConville,Shane J. McCartan,Jesi R. Maguire,Michele Conroy,Kalani Moore,Alan Harvey,Felix Trier,Ursel Bangert,Alexei Gruverman,Manuel Bibes,Amit Kumar,Raymond G. P. McQuaid,J. Marty Gregg###

Ultra-High Carrier Mobilities in Ferroelectric Domain Wall Corbino Cones at Room Temperature. Recently, electrically conducting heterointerfaces between dissimilar
band-insulators (such as lanthanum aluminate and strontium titanate) have
attracted considerable research interest. Charge transport has been thoroughly
explored and fundamental aspects of conduction firmly established. Perhaps
surprisingly, similar insights into conceptually much simpler conducting
homointerfaces, such as the domain walls that separate regions of different
orientations of electrical polarisation within the same ferroelectric
band-insulator, are not nearly so well-developed. Addressing this disparity, we
herein report magnetoresistance in approximately conical 180o charged domain
walls, which occur in partially switched ferroelectric thin film single crystal
lithium niobate. This system is ideal for such measurements: firstly, the
conductivity difference between domains and domain walls is extremely and
unusually large (a factor of at least 1013) and hence currents driven through
the thin film, between planar top and bottom electrodes, are overwhelmingly
channelled along the walls; secondly, when electrical contact is made to the
top and bottom of the domain walls and a magnetic field is applied along their
cone axes (perpendicular to the thin film surface), then the test geometry
mirrors that of a Corbino disc, which is a textbook arrangement for geometric
magnetoresistance measurement. Our data imply carriers at the domain walls with
extremely high room temperature Hall mobilities of up to ~ 3,700cm2V-1s-1. This
is an unparalleled value for oxide interfaces (and for bulk oxides too) and is
most comparable to mobilities in other systems typically seen at cryogenic,
rather than at room, temperature.

###Enhancement of Spin-Charge Conversion Efficiency for Co$_{3}$Sn$_{2}$S$_{2}$ across Transition from Paramagnetic to Ferromagnetic Phase|Takeshi Seki,Yong-Chang Lau,Junya Ikeda,Kohei Fujiwara,Akihiro Ozawa,Satoshi Iihama,Kentaro Nomura,Atsushi Tsukazaki###

Enhancement of Spin-Charge Conversion Efficiency for Co$_{3}$Sn$_{2}$S$_{2}$ across Transition from Paramagnetic to Ferromagnetic Phase. Co$_{3}$Sn$_{2}$S$_{2}$ (CSS) is one of the shandite compounds and becomes a
magnetic Weyl semimetal candidate below the ferromagnetic phase transition
temperature ($\textit{T}_\textrm{C}$). In this paper, we investigate the
temperature ($\textit{T}$) dependence of conversion between charge current and
spin current for the CSS thin film by measuring the spin-torque ferromagnetic
resonance (ST-FMR) for the trilayer consisting of CSS / Cu / CoFeB. Above
$\textit{T}_\textrm{C}$ ~ 170 K, the CSS / Cu / CoFeB trilayer exhibits the
clear ST-FMR signal coming from the spin Hall effect in the paramagnetic CSS
and the anisotropic magnetoresistance (AMR) of CoFeB. Below
$\textit{T}_\textrm{C}$, on the other hand, it is found that the ST-FMR signal
involves the dc voltages ($\textit{V}_\textrm{dc}$) not only through the AMR
but also through the giant magnetoresistance (GMR). Thus, the resistance
changes coming from both AMR and GMR should be taken into account to correctly
understand the characteristic field angular dependence of
$\textit{V}_\textrm{dc}$. The spin Hall torque generated from the ferromagnetic
CSS, which possesses the same symmetry as that for spin Hall effect, dominantly
acts on the magnetization of CoFeB. A definite increase in the spin-charge
conversion efficiency ($\xi$) is observed at $\textit{T}$ <
$\textit{T}_\textrm{C}$, indicating that the phase transition to the
ferromagnetic CSS promotes the highly efficient spin-charge conversion. In
addition, our theoretical calculation shows the increase in spin Hall
conductivity with the emergence of magnetic moment at $\textit{T}$ <
$\textit{T}_\textrm{C}$, which is consistent with the experimental observation.

###Magnetoresistive behaviour of ternary Cu-based materials processed by high-pressure torsion|M. Kasalo,S. Wurster,M. Stückler,M. Zawodzki,L. Weissitsch,R. Pippan,A. Bachmaier###

Magnetoresistive behaviour of ternary Cu-based materials processed by high-pressure torsion. Severe plastic deformation using high-pressure torsion of ternary Cu-based
materials (CuFeCo and CuFeNi) was used to fabricate bulk samples with a
nanocrystalline microstructure. The goal was to produce materials featuring the
granular giant magnetoresistance effect, requiring interfaces between ferro-
and nonmagnetic materials. This magnetic effect was found for both ternary
systems; adequate subsequent annealing had a positive influence. The
as-deformed states, as well as microstructural changes upon thermal treatments,
were studied using scanning electron microscopy and X-ray diffraction
measurements. Deducing from electron microscopy, a single-phase structure was
observed for all as-deformed samples, indicating the formation of a
supersaturated solid solution. However, judging from the presence of the
granular giant-magnetoresistive effect, small ferromagnetic particles have to
be present. The highest drop in room temperature resistivity (2.45% at 1790
kA/m) was found in Cu62Fe19Ni19 after annealing for 1 h at 400 {\deg}C.
Combining the results of classical microstructural studies and magnetic
measurements, insights into the evolution of ferromagnetic particles are
accessible.

###Emergent magnetic states and tunable exchange bias at all 3d nitride heterointerfaces|Qiao Jin,Qinghua Zhang,He Bai,Amanda Huon,Timothy Charlton,Shengru Chen,Shan Lin,Haitao Hong,Ting Cui,Can Wang,Haizhong Guo,Lin Gu,Tao Zhu,Michael R. Fitzsimmons,Kui-juan Jin,Shanmin Wang,Er-Jia Guo###

Emergent magnetic states and tunable exchange bias at all 3d nitride heterointerfaces. Interfacial magnetism stimulates the discovery of giant magnetoresistance and
spin-orbital coupling across the heterointerfaces, facilitating the intimate
correlation between spin transport and complex magnetic structures. Over
decades, functional heterointerfaces composed of nitrides are seldomly explored
due to the difficulty in synthesizing high-quality and correct composition
nitride films. Here we report the fabrication of single-crystalline
ferromagnetic Fe3N thin films with precisely controlled thickness. As film
thickness decreasing, the magnetization deteriorates dramatically, and
electronic state transits from metallic to insulating. Strikingly, the
high-temperature ferromagnetism maintains in a Fe3N layer with a thickness down
to 2 u. c. (~ 8 {\AA}). The magnetoresistance exhibits a strong in-plane
anisotropy and meanwhile the anomalous Hall resistance reserves its sign when
Fe3N layer thickness exceeds 5 u. c. Furthermore, we observe a sizable exchange
bias at the interfaces between a ferromagnetic Fe3N and an antiferromagnetic
CrN. The exchange bias field and saturation moment strongly depend on the
controllable bending curvature using cylinder diameter engineering (CDE)
technique, implying the tunable magnetic states under lattice deformation. This
work provides a guideline for exploring functional nitride films and applying
their interfacial phenomena for innovative perspectives towards the practical
applications.

###Magnetic Structure and Spin Fluctuations in Colossal Magnetoresistance Ferrimagnet Mn3Si2Te6|Feng Ye,Masaaki Matsuda,Zachary Morgan,Todd Sherline,Yifei Ni,Hengdi Zhao,G. Cao###

Magnetic Structure and Spin Fluctuations in Colossal Magnetoresistance Ferrimagnet Mn3Si2Te6. The ferrimagnetic insulator Mn3Si2Te6, which features a Curie temperature Tc
at 78 K and a delicate yet consequential magnetic frustration, exhibits
colossal magnetoresistance (CMR) when the magnetic field is applied along the
magnetic hard axis, surprisingly inconsistent with existing precedents [Y. Ni,
H. Zhao, Y. Zhang et al. Phys. Rev. B 103, L161105 (2021)]. This discovery
motivates a thorough single-crystal neutron diffraction study in order to gain
insights into the magnetic structure and its hidden correlation with the new
type of CMR. Here we report a noncollinear magnetic structure below the Tc
where the moments lie predominantly within the basal plane but tilt toward the
c axis by ~10o at ambient conditions. A substantial magnetic diffuse scattering
decays slowly and persists well above the Tc. The evolution of the spin
correlation lengths agrees well with the electrical resistivity, underscoring
the role of spin fluctuation contributing to the magnetoresistivity near the
transition. Application of magnetic field along the c axis, renders a swift
occurrence of CMR but only a slow tilting of the magnetic moments toward the c
axis. The unparalleled changes indicate a non-consequential role of magnetic
polarization.

###Magnetotransport of Sm$_2$Ir$_2$O$_7$ across the pressure-induced quantum-critical phase boundary|M. J. Coak,K. Götze,T. Northam De La Fuente,C. Castelnovo,J. P. Tidey,J. Singleton,A. T. Boothroyd,D. Prabhakaran,P. A. Goddard###

Magnetotransport of Sm$_2$Ir$_2$O$_7$ across the pressure-induced quantum-critical phase boundary. Rare-earth pyrochlore iridates host two interlocking magnetic sublattices of
corner-sharing tetrahedra and can harbour a unique combination of frustrated
moments, exotic excitations and highly correlated electrons. We have measured
the transport and magnetotransport properties of single-crystal
Sm$_2$Ir$_2$O$_7$ up to and beyond the pressure-induced quantum critical point
(QCP) for all-in-all-out (AIAO) Ir order at $p_{{\rm c}}$ = 63 kbar previously
identified by resonant X-ray scattering. Contrary to prior predictions, we do
not find a crossover from insulating to metallic behavior at low temperatures
above $p_{{\rm c}}$. Instead, the metal-insulator transition temperature, which
tracks the decrease in the AIAO ordering temperature for pressures up to 30
kbar, begins to increase under further application of pressure, pointing to the
presence of an as-yet unidentified localization mechanism. The magnetotransport
does track the suppression of Ir magnetism, however, with a strong hysteresis
observed only within the AIAO phase boundary, similar to that found for
Ho$_2$Ir$_2$O$_7$ and attributed to plastic deformation of Ir domains. Around
$p_{{\rm c}}$ we find the emergence of a new type of electronic behavior,
characterized by a negative magnetoresistance with small hysteresis at the
lowest temperatures, and hysteresis-free positive magnetoresistance above 5 K.
A Weyl semimetal phase is predicted to occur in the vicinity of the QCP. The
temperature dependence of our low-temperature transport data, however, are
found to be best described by a model consistent with a Weyl semimetal across
the entire pressure range.

###Linear colossal magnetoresistance driven by magnetic textures in LaTiO3 thin films on SrTiO3|Teresa Tschirner,Berengar Leikert,Felix Kern,Daniel Wolf,Axel Lubk,Martin Kamp,Kirill Miller,Fabian Hartmann,Sven Höfling,Bernd Büchner,Joseph Dufouleur,Marc Gabay,Michael Sing,Ralph Claessen,Louis Veyrat###

Linear colossal magnetoresistance driven by magnetic textures in LaTiO3 thin films on SrTiO3. Linear magnetoresistance (LMR) is of particular interest for memory,
electronics, and sensing applications, especially when it does not saturate
over a wide range of magnetic fields. One of its principal origins is local
mobility or density inhomogeneities, often structural, which in the
Parish-Littlewood theory leads to an unsaturating LMR proportional to mobility.
Structural disorder, however, also tends to limit the mobility and hence the
overall LMR amplitude. An alternative route to achieve large LMR is via
non-structural inhomogeneities which do not affect the zero field mobility,
like magnetic domains. Here, linear positive magnetoresistance caused by
magnetic texture is reported in \ch{LaTiO3}/\ch{SrTiO3} heterostructures. The
LMR amplitude reaches up to 6500\% at 9T. This colossal value is understood by
the unusual combination of a very high thin film mobility, up to 40 000
cm$^2$/V.s, and a very large coverage of low-mobility regions. These regions
correlate with a striped magnetic structure, compatible with a spiral magnetic
texture in the \ch{LaTiO3} film, revealed by low temperature Lorentz
transmission electron microscopy. These results provide a novel route for the
engineering of large-LMR devices.

###Extremely Large Magnetoresistance and Anisotropic Transport in Multipolar Kondo System PrTi$_{2}$Al$_{20}$|Takachika Isomae,Akito Sakai,Mingxuan Fu,Takanori Taniguchi,Masashi Takigawa,Satoru Nakatsuji###

Extremely Large Magnetoresistance and Anisotropic Transport in Multipolar Kondo System PrTi$_{2}$Al$_{20}$. Multipolar Kondo systems offer unprecedented opportunities for designing
astonishing quantum phases and functionalities beyond spin-only descriptions. A
model material platform of this kind is the cubic heavy-fermion system
Pr$Tr_{2}$Al$_{20}$ ($Tr=$ Ti, V), which hosts a nonmagnetic
crystal-electric-field (CEF) ground state and substantial Kondo entanglement of
the local quadrupolar and octopolar moments with the conduction electron sea.
Here, we explore magnetoresistance (MR) and Hall effect of PrTi$_{2}$Al$_{20}$
that develops ferroquadrupolar (FQ) order below $T_{Q} \sim 2$ K and compare
its behavior with that of the non-4$f$ analog, LaTi$_{2}$Al$_{20}$. In the FQ
ordered phase, PrTi$_{2}$Al$_{20}$ displays extremely large magnetoresistance
(XMR) of $\sim 10^{3}\%$. The unsaturated, quasi-linear field ($B$) dependence
of the XMR violates the conventional Kohler's scaling and defies description
based on carrier compensation alone. By comparing the MR and the Hall effect
observed in PrTi$_{2}$Al$_{20}$ and LaTi$_{2}$Al$_{20}$, we conclude that the
open-orbit topology on the electron-type Fermi surface (FS) sheet is key for
the observed XMR. The low-temperature MR and the Hall resistivity in
PrTi$_{2}$Al$_{20}$ display pronounced anisotropy in the [111] and [001]
magnetic fields, which is absent in LaTi$_{2}$Al$_{20}$, suggesting that the
transport anisotropy ties in with the anisotropic magnetic-field response of
the quadrupolar order parameter.

###Quantum phase transition in two-dimensional NbN superconducting thin films|Tian-Yu Jing,Zi-Yan Han,Zhi-Hao He,Ming-Xin Shao,Peng Li,Zhi-Qing Li###

Quantum phase transition in two-dimensional NbN superconducting thin films. We systematically investigated the low-temperature transport properties of a
series of NbN epitaxial films with thickness $t$ ranging from $\sim$2.0 to
$\sim$4.0 nm. The films undergo a superconductor-insulator transition (SIT)
with decreasing film thickness, and the critical sheet resistance for the SIT
is close to the quantum resistance of Cooper pairs $h/4e^2$ (6.45 k$\Omega$).
Besides the Berezinski-Koterlitz-Thouless transition, a magnetic-field-driven
SIT is observed in those two-dimensional (2D) superconducting films (2.6 nm
$\lesssim t \lesssim 4.0$ nm). Interestingly, it is found that the
low-temperature magnetoresistance isotherms do not cross at a single fixed
point but at a well-distinguished region for these superconducting films. The
dynamical critical exponent obtained by analyzing these magnetoresistance
isotherms is divergent as the quantum critical point is being approached. The
behavior of the dynamical critical exponent, originating from quenched disorder
at ultralow temperatures, provides direct evidence for the occurrence of
quantum Griffiths singularity in the quantum phase transition process of the
films. The field-driven anomalous metal (quantum metal) state does not appear
in these films. Our results suggest that the quantum Griffiths singularity not
only occurs in the highly crystalline 2D superconductors with
superconductor-metal transition but also in those with SIT.

###Synthesis of infinite-layer nickelates and influence of the capping-layer on magnetotransport|Guillaume Krieger,Aravind Raji,Laurent Schlur,Gilles Versini,Corinne Bouillet,Marc Lenertz,Jérôme Robert,Alexandre Gloter,Nathalie Viart,Daniele Preziosi###

Synthesis of infinite-layer nickelates and influence of the capping-layer on magnetotransport. The recent discovery of a zero-resistance state in nickel-based compounds has
generated a re-excitement about the long-standing problem in condensed matter
of high-critical-temperature superconductivity, in light of the analogies
between infinite-layer nickelates and cuprates. However, despite some formal
valence and crystal symmetry analogies, the electronic properties of
infinite-layer nickelates are remarkably original accounting, among other
properties, of a unique Nd5d-Ni3d hybridization. This designates infinite-layer
nickelates as a new class of oxide superconductors which should be considered
on their own. Here we report about Nd1-xSrxNiO2 (x = 0, 0.05 and 0.2) thin
films synthesized with and without a SrTiO3 capping-layer, showing very smooth
and step-terraced surface morphologies. Angle-dependent anisotropic
magnetoresistance measurements performed with a magnetic field rotating
in-plane or out-of-plane with respect to the sample surface, rendered important
information about the magnetic properties of undoped SrTiO3-capped and uncapped
samples. The results point at a key role of the capping-layer in controlling
the magnitude and the anisotropy of the anisotropic magnetoresistance
properties. We discuss this control in terms of a combined effect between the
Nd-Ni hybridization and an intra-atomic exchange coupling between the Nd-4f and
Nd-5d states, the latter essentially contributing to the (magneto)transport.
Further studies foresee the influence of the capping layer on infinite-layer
nickelates with no magnetic rare-earth.

###Strain-programmable van der Waals magnetic tunnel junctions|John Cenker,Dmitry Ovchinnikov,Harvey Yang,Daniel G. Chica,Catherine Zhu,Jiaqi Cai,Geoffrey Diederich,Zhaoyu Liu,Xiaoyang Zhu,Xavier Roy,Ting Cao,Matthew W. Daniels,Jiun-Haw Chu,Di Xiao,Xiaodong Xu###

Strain-programmable van der Waals magnetic tunnel junctions. The magnetic tunnel junction (MTJ) is a backbone device for spintronics.
Realizing next generation energy efficient MTJs will require operating
mechanisms beyond the standard means of applying magnetic fields or large
electrical currents. Here, we demonstrate a new concept for programmable MTJ
operation via strain control of the magnetic states of CrSBr, a layered
antiferromagnetic semiconductor used as the tunnel barrier. Switching the CrSBr
from antiferromagnetic to ferromagnetic order generates a giant tunneling
magnetoresistance ratio without external magnetic field at temperatures up to ~
140 K. When the static strain is set near the phase transition, applying small
strain pulses leads to active flipping of layer magnetization with controlled
layer number and thus magnetoresistance states. Further, finely adjusting the
static strain to a critical value turns on stochastic switching between
metastable states, with a strain-tunable sigmoidal response curve akin to the
stochastic binary neuron. Our results highlight the potential of
strain-programmable van der Waals MTJs towards spintronic applications, such as
magnetic memory, random number generation, and probabilistic and neuromorphic
computing.

###Multi-k magnetic structure and large anomalous Hall effect in candidate magnetic Weyl semimetal NdAlGe|C. Dhital,R. L. Dally,R. Ruvalcaba,R. Gonzalez-Hernandez,J. Guerrero-Sanchez,H. B. Cao,Q. Zhang,W. Tian,Y. Wu,M. D. Frontzek,S. K. Karna,A. Meads,B. Wilson,R. Chapai,D. Graf,J. Bacsa,R. Jin,J. F. DiTusa###

Multi-k magnetic structure and large anomalous Hall effect in candidate magnetic Weyl semimetal NdAlGe. The magnetic structure, magnetoresistance, and Hall effect of
non-centrosymmetric magnetic semimetal NdAlGe are investigated revealing an
unusual magnetic state and anomalous transport properties that are associated
with the electronic structure of this non-centrosymmetric compound. The
magnetization and magnetoresistance measurements are both highly anisotropic
and indicate an Ising-like magnetic system. The magnetic structure is complex
in that it involves three magnetic ordering vectors including an incommensurate
spin density wave and commensurate ferrimagnetic state in zero field. We have
discovered a large anomalous Hall conductivity that reaches = 430
{\Omega}-1cm-1 implying that it originates from an intrinsic Berry curvature
effect stemming from Weyl nodes found in the electronic structure. These
electronic structure calculations indicate the presence of nested Fermi surface
pockets with nesting wave vectors similar to the measured magnetic ordering
wavevector and the presence of Weyl nodes in proximity to the Fermi surface. We
associate the incommensurate magnetic structure with the large anomalous Hall
response to be the result of the combination of Fermi surface nesting and the
Berry curvature associated with Weyl nodes.

###Hysteresis and training effect in the electric control of spin current in Pt/Y3Fe5O12 heterostructures|Y. D. Sun,Lei Wang,Lili Lang,Ke Xia,S. M. Zhou###

Hysteresis and training effect in the electric control of spin current in Pt/Y3Fe5O12 heterostructures. We have reported on the hysteresis and training effect of spin current in
Pt/Y3Fe5O12 heterostructures during subsequent cycles of ionic liquid gate
voltage Vg. The inverse spin Hall effect voltage in spin pumping and spin Hall
magnetoresistance exhibit diode-like behaviors in the first half cycle of Vg
andalsoshowhysteresisinthe first cycle of Vg. Both the diode-like behavior and
the hysteresis become weak and even vanish in the second cycle of Vg due to the
training effect. The above experimental results can be well explained by the
screening charge doping model, in which the charge and the local magnetic
moment are asymmetrically distributed in the Pt layer. The applicability of
this model is further confirmed by measurements of anisotropic
magnetoresistance and ferromagnetic resonance. The diode-like behavior is
attributed to interplay between the asymmetrically distributed local magnetic
moment and the spin current relaxation in the Pt layer. The hysteresis and the
training effect arise from the incompletely reversible process between
oxidation and reduction of Pt atoms and the evolution of the surface morphology
at the ionic liquid/Pt interface under electric gating. This work provides new
insights to improve the functional performance of electrically controlled spin
current devices.

###Optimization of Permalloy properties for magnetic field sensors using He$^+$ irradiation|Giovanni Masciocchi,Johannes Wilhelmus van der Jagt,Maria-Andromachi Syskaki,Jürgen Langer,Gerhard Jakob,Jeffrey McCord,Benjamin Borie,Andreas Kehlberger,Dafine Ravelosona,Mathias Kläui###

Optimization of Permalloy properties for magnetic field sensors using He$^+$ irradiation. Permalloy, despite being a widely utilized soft magnetic material, still
calls for optimization in terms of magnetic softness and magnetostriction for
its use in magnetoresistive sensor applications. Conventional annealing methods
are often insufficient to locally achieve the desired properties for a narrow
parameter range. In this study, we report a significant improvement of the
magnetic softness and magnetostriction in a 30 nm Permalloy film after He$^+$
irradiation. Compared to the as-deposited state, the irradiation treatment
reduces the induced anisotropy by a factor ten and the hard axis coercivity by
a factor five. In addition, the effective magnetostriction of the film is
significantly reduced by a factor ten - below $1\times10^{-7}$ - after
irradiation. All the above mentioned effects can be attributed to the isotropic
crystallite growth of the Ni-Fe alloy and to the intermixing at the magnetic
layer interfaces under light ion irradiation. We support our findings with
X-ray diffraction analysis of the textured Ni$_{81}$Fe$_{19}$ alloy.
Importantly, the sizable magnetoresistance is preserved after the irradiation.
Our results show that compared to traditional annealing methods, the use of
He$^+$ irradiation leads to significant improvements in the magnetic softness
and reduces strain cross sensitivity in Permalloy films required for 3D
positioning and compass applications. These improvements, in combination with
the local nature of the irradiation process make our finding valuable for the
optimization of monolithic integrated sensors, where classic annealing methods
cannot be applied due to complex interplay within the components in the device.

###Thermal hysteretic behavior and negative magnetoresistance in an unusual charge-density-wave material EuTe4|Q. Q. Zhang,Y. Shi,K. Y. Zhai,W. X. Zhao,X. Du,J. S. Zhou,X. Gu,R. Z. Xu,Y. D. Li,Y. F. Guo,Z. K. Liu,C. Chen,S. -K. Mo,T. K. Kim,C. Cacho,J. W. Yu,W. Li,Y. L. Chen,Jiun-Haw Chu,L. X. Yang###

Thermal hysteretic behavior and negative magnetoresistance in an unusual charge-density-wave material EuTe4. EuTe4 is a newly-discovered van der Waals material exhibiting a novel
charge-density wave (CDW) with a large thermal hysteresis in the resistivity
and CDW gap. In this work, we systematically study the electronic structure and
transport properties of EuTe4 using high-resolution angle-resolved
photoemission spectroscopy (ARPES), magnetoresistance measurements, and
scanning tunneling microscopy (STM). We observe a CDW gap of about 200 meV at
low temperatures that persists up to 400 K, suggesting that the CDW transition
occurs at a much higher temperature. We observe a large thermal hysteretic
behavior of the ARPES intensity near the Fermi level, consistent with the
resistivity measurement. The hysteresis in the resistivity measurement does not
change under a magnetic field up to 7 T, excluding the thermal magnetic
hysteresis mechanism. Instead, the surface topography measured with STM shows
surface domains with different CDW trimerization directions, which may be
important for the thermal hysteretic behavior of EuTe4. Interestingly, we
observe a large negative magnetoresistance at low temperatures that can be
associated with the canting of magnetically ordered Eu spins. Our work shed
light on the understanding of magnetic, transport, and electronic properties of
EuTe4.

###Tunneling magnetoresistance in Mn$_2$Au-based pure antiferromagnetic tunnel junction|Xingtao Jia,Hui-Min Tang,Shi-Zhuo Wan###

Tunneling magnetoresistance in Mn$_2$Au-based pure antiferromagnetic tunnel junction. Antiferromagnetic (AF) spintronics is merit on ultra-high operator speed and
stability in the presence of magnetic field. To fully use the merit, the device
should be pure rather than hybrid with ferromagnet or ferrimagnet. For the
magnetism in the antiferromagnet is canceled by that of different sublattices,
breaking the symmetry in the material can revive the native magnetism, which
can be detected by the magnetoresistance (MR) effect. Achieving noticeable MR
effect in the pure AF device is diffcult but essential for the AF spintronic
applications. Here, we study the tunnel magnetoresistance(TMR) effect in the
Nb/Mn$_2$Au/CdO/Mn$_2$Au/Nb pure AF magnetic tunnel junctions (AF-MTJs) based
on a first-principle scattering theory. Giant TMRs with order of 1000% are
predicted in some symmetric junctions, which is originated from the interfacial
resonance tunneling effect related with the k dependent complex band structures
of CdO and Mn$_2$Au in companion with the enhanced spin polarization of the
interfacial magnetic atoms. The effect of voltage bias and interfacial disorder
such as Oxygen vacancy, Manganese vacancy, and Manganese-Cadmium exchanges at
Mn2Au/CdO interfaces are studied also. Our studies suggest
Nb/Mn$_2$Au/CdO/Mn$_2$Au/Nb AFMTJs promising material for AF spintronic
application, and rocksalt CdO a potential symmetry filtering material for
spintronic applications.

###Giant spin-valve effect and chiral anomaly in antiferromagnetic topological insulators Mn(Bi1-xSbx)2Te4|Seng Huat Lee,David Graf,Robert Robinson,John Singleton,Johanna C. Palmstrom,Zhiqiang Mao###

Giant spin-valve effect and chiral anomaly in antiferromagnetic topological insulators Mn(Bi1-xSbx)2Te4. We report c-axis transport studies on magnetic topological insulators
Mn(Bi1-xSbx)2Te4. We performed systematic c-axis magnetoresistivity
measurements under high magnetic fields (up to 35 T) on several representative
samples. We find the lightly hole- and lightly electron-doped samples, while
both having the same order of magnitude of carrier density and similar
spin-flop transitions, exhibit sharp contrast in electronic anisotropy and
transport mechanism. The electronic anisotropy is remarkably enhanced for the
lightly hole-doped sample relative to pristine MnBi2Te4 but not for the lightly
electron-doped sample. The lightly electron-doped sample displays a giant
negative longitudinal magnetoresistivity (LMR) induced by the spin-valve effect
at the spin-flop transition field, whereas the lightly hole-doped sample
exhibits remarkable negative LMR consistent with the chiral anomaly behavior of
a Weyl semimetal. Furthermore, we find the large negative LMR of the lightly
hole-doped sample extends to a wide temperature range above the N\'eel
temperature (T_N) where the magnetoconductivity is proportional to B^2. This
fact, together with the short-range intralayer ferromagnetic correlation
revealed in isothermal magnetization measurements, suggests the possible
presence of the Weyl state above T_N. These results demonstrate that in the
c-axis magnetotransport of Mn(Bi1-xSbx)2Te4, the spin scattering is dominant in
the lightly electron-doped sample but overwhelmed by the chiral anomaly effect
in the lightly hole-doped sample due to the presence of the Weyl state. These
findings extend the understanding of the transport properties of
Mn(Bi1-xSbx)2Te4.

###Magnetic and transport anomalies and large magnetocaloric effect in cubic R4PtAl (R = Ho and Er)|Kartik K. Iyer,Sudhindra Rayaprol,Ram Kumar,Shidaling Matteppanavar,Suneel Dodamani,Kalobaran Maiti,Echur V. Sampathkumaran###

Magnetic and transport anomalies and large magnetocaloric effect in cubic R4PtAl (R = Ho and Er). We report the electronic properties of R4PtAl (R = Ho, and Er), which
contains 3 sites for R, by the measurements of magnetization (ac and dc),
heat-capacity, transport, and magnetoresistance (MR). Dc magnetization data
reveal antiferromagnetic order below 19 K and 12 K in Ho and Er compounds,
respectively. Additional features observed at lower temperatures (12 K for
Ho4PtAl and 5 K for Er4PtAl) are akin to cluster spin-glass phase. Resistivity
data exhibit a weak minimum at a temperature marginally higher than their
respective N\'eel temperature (T_N) which is unusual for such rare-earths with
well localized 4f states. Isothermal magnetization and magnetoresistance data
well below T_N exhibit signatures of a subtle field-induced magnetic transition
for a small magnetic field (less than 10 kOe). Notably, the isothermal entropy
change at T_N has the largest peak value within this rare-earth family; for a
field change from zero to 50 kOe, the entropy change is about 14.5 J/kg K
(Ho4PtAl) and 21.5 J/kg K (Er4PtAl) suggesting a role of anisotropy of 4f
orbital in determining this large value. The results provide some clues for the
advancement of the field of magnetocaloric effect. The magnetocaloric property
of Er4PtAl is nonhysteretic meeting a challenge to find materials with
reversible magnetocaloric effect.

###Double-layer Kagome Metals Pt3Tl2 and Pt3In2|Michael A. McGuire,Eleanor M. Clements,Qiang Zhang,Satoshi Okamoto###

Double-layer Kagome Metals Pt3Tl2 and Pt3In2. The connectivity and inherent frustration of the kagome lattice can produce
interesting electronic structures and behaviors in compounds containing this
structural motif. Here we report the properties of Pt3X2 (X = In and Tl) that
adopt a double-layer kagome net structure related to that of the topologically
nontrivial high temperature ferromagnet Fe3Sn2 and the density wave hosting
compound V3Sb2. We examined the structural and physical properties of single
crystal Pt3Tl2 and polycrystalline Pt3In2 using x-ray and neutron diffraction,
magnetic susceptibility, heat capacity, and electrical transport measurements,
along with density functional theory calculations of the electronic structure.
Our calculations show that Fermi levels lie in pseudogaps in the densities of
states with several bands contributing to transport, and this is consistent
with our Hall effect, magnetic susceptibility, and heat capacity measurements.
While electronic dispersions characteristic of simple kagome nets with
nearest-neighbor hopping are not clearly seen, likely due to the extended
nature of the Pt 5d states, we do observe moderately large and non-saturating
magnetoresistance values and quantum oscillations in the magnetoresistance and
magnetization associated with the kagome nets of Pt.

###Electron focusing, mode spectroscopy and mass enhancement in small GaAs/AlGaAs rings|J Liu,K Ismail,KY Lee,JM Hong,S Washburn###

Electron focusing, mode spectroscopy and mass enhancement in small GaAs/AlGaAs rings. A new electron focusing effect has been discovered in small single and
coupled GaAs/AlGaAs rings. The focusing in the single ring is attributed solely
to internal orbits. The focusing effect allows the ring to be used as a small
mass spectrometer. The focusing causes peaks in the magnetoresistance at low
fields, and the peak positions were used to study the dispersion relation of
the one-dimensional magnetoelectric subbands. The electron effective mass
increases with the applied magnetic field by a factor of $50$, at a magnetic
field of $0.5T$. This is the first time this increase has been measured
directly. General agreement obtains between the experiment and the subband
calculations for straight channels.

###``Hot Spots'' in Quasi-One-Dimensional Organic Conductors|Anatoley T. Zheleznyak,Victor M. Yakovenko###

``Hot Spots'' in Quasi-One-Dimensional Organic Conductors. Distribution of the electron scattering rate on the Fermi surface of a
quasi-one-dimensional conductor is calculated for the electron-electron umklapp
interaction. We find that in certain regions on the Fermi surface the
scattering rate is anomalously high. The reason for the existence of these
``hot spots'' is analogous to the appearance of the van Hove singularities in
the density of states. We employ a generalized $\tau$-approximation (where the
scattering integral in the Boltzmann equation is replaced by the scattering
time which depends on the position at the Fermi surface) to study the
dependence of the electric resistance on the amplitude and the orientation of a
magnetic field. We find that the ``hot spots'' do not produce a considerable
magnetoresistance or commensurability effects at the so-called ``magic
angles''.

###Negative hopping magnetoresistance of two-dimensional electron gas in a smooth random potential|M. E. Raikh,L. I. Glazman###

Negative hopping magnetoresistance of two-dimensional electron gas in a smooth random potential. We show that the tunnel coupling between semiclassical states localized in
different minima of a smooth random potential increases when magnetic field is
applied. This increase originates from the difference in gauge factors which
electron wave functions belonging to different electron ``lakes'' acquire in
the presence of the field. We illustrate the increase of coupling by a model
calculation of tunneling through a saddle point separating two adjacent lakes.
In the common case, when the barrier between two lakes is much narrower than
their size, the characteristic magnetic field is determined by the area of the
lakes, and thus may be quite small. The effect of the field on coupling
constants leads to a negative magnetoresistance in low-temperature conduction.

###Fermi Liquid - Non-Fermi Liquid Transition in the Double Exchange Model|Sanjoy K. Sarker###

Fermi Liquid - Non-Fermi Liquid Transition in the Double Exchange Model. Motivated by recent discovery of colossal magnetoresistance in
La$_(1-x)$Ca$x$MnO$_3$ and other manganites, we have studied the double
exchange model. We argue that the forced alignment of conduction-electron spin
with the core spins that causes ferromagnetism also projects out a large part
of the Hilbert space needed for coherent propagation of electrons carrying spin
and charge. As a result, the electron becomes a composite object and its
Green's function exhibits a two-fluid character: a coherent Fermi-liquid
component associated with the ferromagnetically ordered core spins, and a
non-Fermi liquid component associated with the disordered spins. With
increasing temperature, there is continuous transfer of spectral weight from
the Fermi liquid to the non-Fermi liquid component, until the former disappears
above $T_c$. In an applied field spectral weight is transferred from the
non-Fermi liquid to the component. Implications for the manganites are
discussed.

###Unusual beats of the perpendicular-current giant magneto-resistance and thermopower of magnetic trilayers|S. Krompiewski,U. Krey###

Unusual beats of the perpendicular-current giant magneto-resistance and thermopower of magnetic trilayers. Oscillations of the giant magnetoresistance (GMR) and thermo-electric power
(TEP) vs. both the thickness of the non-magnetic spacer and also that of the
ferromagnetic slabs are studied in the current-perpendicular-to-plane (CPP)
geometry of magnetic trilayer systems, in terms of a single-band tight-binding
model without impurities. The spin-dependent conductance has been calculated
from the Kubo formula by means of a recursion Green's function method and the
semi-infinite ideal-lead wires trick. Additionally the TEP is obtained directly
from Mott's formula. In general, the thickness oscillations of the GMR and the
TEP may have just one or two (short and long) oscillations. The long period,
related to spectacular beats, is apparently of non-RKKY type. The TEP
oscillations are strongly enhanced with respect to those of the GMR, have the
same periods, but different phases and a negative bias.

###Calculation of Giant Magnetoresistance in Laterally Confined Multilayers|Kingshuk Majumdar,Jian Chen,Selman Hershfield###

Calculation of Giant Magnetoresistance in Laterally Confined Multilayers. We have studied the Giant Magnetoresistance (GMR) for laterally confined
multilayers, e.g., layers of wires, using the classical Boltzmann equation in
the current-in-plane (CIP) geometry. For spin-independent specularity factors
at the sides of the wires we find that the GMR due to bulk and surface
scattering decreases with lateral confinement. The length scale at which this
occurs is of order the film thickness and the mean free paths. The precise
prefactor depends on the relative importance of surface and bulk scattering
anisotropies. For spin-dependent specularity factors at the sides of the wires
the GMR can increase in some cases with decreasing width. The origin of the
change in the GMR in both cases can be understood in terms of lateral
confinement changing the effective mean free paths within the layers.

###Positive Magneto-Resistance in Quasi-1D Conductors|Ivar Martin,Philip Phillips###

Positive Magneto-Resistance in Quasi-1D Conductors. We present here a simple qualitative model that interpolates between the high
and low temperature properties of quasi-1D conductors. At high temperatures we
argue that transport is governed by inelastic scattering whereas at low
temperatures the conductance decays exponentially with the electron dephasing
length. The crossover between these regimes occurs at the temperature at which
the elastic and inelastic scattering times become equal. This model is shown to
be in quantitative agreement with the organic conductor $TTT_2I_{3-\delta}$.
Within this model, we also show that on the insulating side, the positive
magnetoresistance of the form $(H/T)^2$ observed in $TTT_2I_{3-\delta}$ and
other quasi-1D conductors can be explained by the role spin-flip scattering
plays in the electron dephasing rate.

###Coulomb effects on the quantum transport of a two-dimensional electron system in periodic electric and magnetic fields|Andrei Manolescu,Rolf R. Gerhardts###

Coulomb effects on the quantum transport of a two-dimensional electron system in periodic electric and magnetic fields. The magnetoresistivity tensor of an interacting two-dimensional electron
system with a lateral and unidirectional electric or magnetic modulation, in a
perpendicular quantizing magnetic field, is calculated within the Kubo
formalism. The influence of the spin splitting of the Landau bands and of the
density of states (DOS) on the internal structure of the Shubnikov-de Haas
oscillations is analyzed. The Coulomb electron - electron interaction is
responsible for strong screening and exchange effects and is taken into account
in a screened Hartree-Fock approximation, in which the exchange contribution is
calculated self-consistently with the DOS at the Fermi level. This
approximation describes both the exchange enhancement of the spin splitting and
the formation of compressible edge strips, unlike the simpler Hartree and
Hartree-Fock approximations, which yield either the one or the other.

###The Role of Density of States Fluctuations in the Normal State Properties of High Tc Superconductors|A. A. Varlamov,G. Balestrino,E. Milani,D. V. Livanov###

The Role of Density of States Fluctuations in the Normal State Properties of High Tc Superconductors. HTS show many puzzling anomalies in their normal state properties. Among them
are:
  - the presence of a peak in the c-axis resistance and its growth in external
magnetic field
  - the anomalous negative magnetoresistance observed above Tc
  - the deviation from the Korringa law in the temperature dependence of the
NMR relaxation rate
  - the opening of a large pseudo-gap in the c-axis optical conductivity well
above Tc
  - the gap-like tunneling anomalies observed above Tc
  - the anomalies in the thermoelectric power above Tc
  We show how all these effects can be explained by the enhanced role played in
quasi-2D systems by the fluctuation decrease of the one-electron density of
states (DOS) at the Fermi level, and its competition with other fluctuation
contributions (AL, MT). The full fluctuation theory in HTS is reviewed and its
resuls compared with experimental data.

###QHE, magnetoresistance and disordered transport on 2D mesoscopic plaquettes|A. Aldea,P. Gartner,M. Nita###

QHE, magnetoresistance and disordered transport on 2D mesoscopic plaquettes. The transport properties of a rectangular mesoscopic plaquette in the
presence of a perpendicular magnetic field are studied in a tight-binding model
with randomly distributed traps. The longitudinal and Hall resistances are
calculted in the four-probe Landauer-B\"{u}ttiker formalism which accounts
automatically both for the quantum coherence and the trapping-induced
localization. The localized character of eigenvectors and the specific aspect
of the density of states at a given magnetic flux are correlated with the
behaviour of the mentioned resistances as function of the Fermi energy. The
Hall insulator and quantum Hall regimes are evidentiated. The dependence on
magnetic field of the configurational averages of the longitudinal and Halll
resistance is studied in a purely quantum-mechanical approach. Both negative
and positive magnetoresistances are found.

###Regularization of the Density of States Fluctuation Contribution in Magnetic Field|A. I. Buzdin,A. A. Varlamov###

Regularization of the Density of States Fluctuation Contribution in Magnetic Field. The fit of the experimental data on c-axis magnetoresistance of HTS above the
transition temperature with the theory based on the fluctuation renormalization
of the one-electron density of states (DOS) is exellent in weak magnetic fields
but meets the noticible difficulties in the region of strong fields. This is
due to the formal divergency of the DOS contribution to conductivity and the
dependence of the cut-off parameter on the magnetic field itself. We propose
the scheme of the regularization of the problem. This permits us to obtain the
expression for the magnetic field dependent part of DOS conductivity as a
convergent serie independent on cut-off. We also calculate analitically the
asymptotics for all regions of magnetic fields. The results demonstrate the
robustness of the DOS contribution with respect to the magnetic field effect:
in strong fields it decreases logarithmically only while Aslamazov-Larkin and
anomalous Maki-Thompson contributions diminish as powers of H_{c2}/H.

###Metal-Insulator Transition and Ferromagnetism in the Electron Doped Layered Manganites La2.3-xYxCa0.7Mn2O7 (x=0,0.3,0.5)|P. Raychaudhuri,C. Mitra,A. Paramekanti,R. Pinto,A. K. Nigam,S. K. Dhar###

Metal-Insulator Transition and Ferromagnetism in the Electron Doped Layered Manganites La2.3-xYxCa0.7Mn2O7 (x=0,0.3,0.5). Bulk samples of La2.3-xYxCa0.7Mn2O7, x=0,0.3,0.5, with layered perovskite
structure have been synthesized and investigated with respect to their
electrical, electronic and magnetic properties. It is found that
La1.8Y0.5Ca0.7Mn2O7 has tetragonal structure and is a metallic ferromagnet with
a magnetic transition temperature of 170 K. The compound shows metallic
behavior below 140 K and has a large magnetoresistance (MR)
Delta-rho/rho(0)~94% at 100 K at 34 kOe. For x=0 and 0.3 the structure is
monoclinic with a suppression of metallicity. For x=0 the material is an
ferromagnetic insulator. We observed a large increase in the coefficient of the
linear term in specific heat with decreasing x. As far as we are aware, this is
the first report of an electron doped manganite showing metal-insulator
transition and ferromagnetism.

###Critical Collapse of the Exchange Enhanced Spin Splitting in 2-D Systems|D. R. Leadley,R. J. Nicholas,J. J. Harris,C. T. Foxon###

Critical Collapse of the Exchange Enhanced Spin Splitting in 2-D Systems. The critical filling factor v_c where Shubnikov-de Haas oscillations become
spin split is investigated for a set of GaAs-GaAlAs heterojunctions. Finite
temperature magnetoresistance measurements are used to extract the value of v_c
at zero temperature. The critically point is where the disorder potential has
the same magnitude as the exchange energy, leading to the empirical
relationship v_c = g* n t h / 2 m_0. This is valid for all the samples studied,
where the density n and single particle lifetime t both vary by more than an
order of magnitude and g* the exchange enhanced g-factor has a weak dependence
on density. For each sample the spin gap energy shows a linear increase with
magnetic field. Experiments in tilted magnetic field show the spin gap is the
sum of the bare Zeeman energy and an exchange term. This explains why
measurements of the enhanced g-factor from activation energy studies in
perpendicular field and the coincidence method in tilted fields have previously
disagreed.

###Composite Polarons in Ferromagnetic Narrow-band Metallic Manganese Oxides|Liang-Jian Zou,H. Q. Lin,Qing-Qi Zheng###

Composite Polarons in Ferromagnetic Narrow-band Metallic Manganese Oxides. A new mechanism is proposed to explain the colossal magnetoresistance and
related phenomena. Moving electrons accompanied by Jahn-Teller phonon and
spin-wave clouds may form composite polarons in ferromagnetic narrow-band
manganites. The ground-state and finite-temperature properties of such
composite polarons are studied in the present paper. By using a variational
method, it is shown that the energy of the system at zero temperature decreases
with the formation of composite polaron; the energy spectrum and effective mass
of the composite polaron at finite temperature is found to be strongly
renormalized by the temperature and the magnetic field. It is suggested that
the composite polaron contribute significantly to the transport and the
thermodynamic properties in ferromagnetic narrow-band metallic manganese
oxides.

###Magnetoresistance of YBa2Cu3O7 in the "cold spots" model|Anatoley T. Zheleznyak,Victor M. Yakovenko,H. D. Drew###

Magnetoresistance of YBa2Cu3O7 in the "cold spots" model. We calculate the in-plane magnetoresistance $\Delta\rho_{xx}/\rho_{xx}$ of
YBa$_2$Cu$_3$O$_7$ in a magnetic field applied perpendicular to the $CuO_2$
planes for the ``cold spots'' model. In this model, the electron relaxation
time $\tau_2\propto1/T^2$ at small regions on the Fermi surface near the
Brillouin zone diagonals is much longer than the relaxation time
$\tau_1\propto1/T$ at the rest of the Fermi surface ($T$ is temperature). In
qualitative agreement with the experiment, we find that Kohler's rule is
strongly violated, but the ratio $\Delta\rho_{xx}/\rho_{xx}\tan^2\theta_H$,
where $\tan\theta_H$ is the Hall angle, is approximately
temperature-independent. We find the ratio is about 5.5, which is of the same
order of magnitude as in the experiment.

###Anderson localization due to spin disorder: a driving force of temperature-dependent metal-semiconductor transition in colossal-magnetoresistance materials|Eugene Kogan,Mark Auslender###

Anderson localization due to spin disorder: a driving force of temperature-dependent metal-semiconductor transition in colossal-magnetoresistance materials. We study temperature induced metal-insulator transition in doped
ferromagnetic semiconductors, described by s-d exchange model. The transition
is a result of the mobility edge movement, the disorder being due to magnetic
ions spin density fluctuations. The electrons are described in the tight
binding approximation. Using ideas and methods of Anderson localization theory
we obtain simple formulas, which connect the mobility edge with short-range
order characteristics of the magnetic subsystem -- static spin correlators. We
discuss the application of the theory to several groups of novel
colossal-magnetoresistance materials and include the reproduction of the paper
[E. M. Kogan and M. I. Auslender, phys. stat. sol. (b) vol. 147, 613 (1988)]
published by us 10 years ago.

###Magnetoresistance of metallic perovskite oxide LaNiO$_{3-δ}$|N. Gayathri,A. K. Raychaudhuri,X. Q. Xu,J. L. Peng,R. L. Greene###

Magnetoresistance of metallic perovskite oxide LaNiO$_{3-δ}$. We report a study of the magnetoresistance (MR) of the metallic perovskite
oxide LaNiO$_{3-\delta}$ as a function of the oxygen stoichiometry $\delta$
($\delta \leq$ 0.14), magnetic field (H $\leq 6T$) and temperature (1.5K $\leq
$ T $\leq $ 25K). We find a strong dependence of the nature of MR on the oxygen
stoichiometry. The MR at low temperatures change from positive to negative as
the sample becomes more oxygen deficient (i.e, $\delta$ increases). Some of the
samples which are more resistive, show a resistivity minima at $T_{min}$
$\approx$ 20K. We find that in these samples the MR is positive at T >
$T_{min}$ and negative for T < $T_{min}$. We conclude that in the absence of
strong magnetic interaction, the negative MR in these oxides can arise from
weak localisation effects.

###P-wave Pairing and Colossal Magnetoresistance in Manganese Oxides|Yong-Jihn Kim###

P-wave Pairing and Colossal Magnetoresistance in Manganese Oxides. We point out that the existing experimental data of most manganese oxides
show the {\sl frustrated} p-wave superconducting condensation in the
ferromagnetic phase in the sense that the superconducting coherence is not long
enough to cover the whole system. The superconducting state is similar to the
$A_{1}$ state in superfluid He-3. The sharp drop of resistivity, the steep jump
of specific heat, and the gap opening in tunneling are well understood in terms
of the p-wave pairing. In addition, colossal magnetoresistance (CMR) is
naturally explained by the superconducting fluctuations with increasing
magnetic fields. The finite resistivity may be due to some magnetic
inhomogeneities. This study leads to the possibility of room temperature
superconductivity.

###Negative magnetoresistance in the nearest-neighbour hopping conduction in granular gold film|B. I. Belevtsev,E. Yu. Beliayev,Yu. F. Komnik,E. Yu. Kopeichenko###

Negative magnetoresistance in the nearest-neighbour hopping conduction in granular gold film. The low temperature (0.5-55 K) conduction of semicontinuous gold film vacuum
deposited at T \approx 50 K is studied. The film is near the percolation
threshold (thickness 3.25 nm). Its resistance is extremely sensitive to the
applied voltage U. At low enough U the film behaves as an insulator
(two-dimensional granular metal). In this state the dependences R(T) \propto
\exp (1/T) (for T \leq 20 K) and R(U) \propto \exp (1/U)) (for T \leq 1 K and U
> 0.1 V) are observed. Magnetoresistance (MR) is negative and can be described
by \Delta R(H)/R(0) \propto -H^2/T. This negative MR which manifests itself for
nearest-neighbour hopping is rather uncommon and, up to now, has not been
clarified. The possible mechanisms of such case of negative MR are discussed.

###Magnetoresistance of Granular Ferromagnets - Observation of a Magnetic Proximity Effect?|A. Frydman,R. C. Dynes###

Magnetoresistance of Granular Ferromagnets - Observation of a Magnetic Proximity Effect?. We have observed a superparamagnetic to ferromagnetic transition in films of
isolated Ni grains covered by non-magnetic overlayers. The magnetoresistance
(MR) of the films was measured as a function of the overlayer thickness.
Initially, the granular Ni films exhibited negative MR curves peaked at H=0. As
different materials were deposited onto the grains hysteresis developed in the
MR. This behavior is ascribed to an increase of the typical domain size due to
magnetic coupling between grains. The strength of the inter-grain coupling is
found to correlate with the magnetic susceptibility of the overlayer material.
We discuss possible mechanisms for this coupling and suggest that the data may
reflect the existence of a magnetic proximity effect (analogous to the
well-known effect in superconductivity) in which a ferromagnetic moment is
induced in the metallic non-magnetic medium.

###Long-range coherence and mesoscopic transport in N-S metallic structures|H. Courtois,Ph. Gandit,B. Pannetier,D. Mailly###

Long-range coherence and mesoscopic transport in N-S metallic structures. We review the mesoscopic transport in a diffusive proximity superconductor
made of a normal metal (N) in metallic contact with a superconductor (S). The
Andreev reflection of electrons on the N-S interface is responsible for the
diffusion of electron pairs in N. Superconducting-like properties are induced
in the normal metal. In particular, the conductivity of the N metal is locally
enhanced by the proximity effect. A re-entrance of the metallic conductance
occurs when all the energies involved (e.g. temperature and voltage) are small.
The relevant characteristic energy is the Thouless energy which is $\hbar$
divided by the diffusion time for an electron travelling throughout the sample.
In loop-shaped devices, a 1/T temperature-dependent oscillation of the
magnetoresistance arises with a large amplitude from the long-range coherence
of low-energy pairs.

###An X-Ray Induced Structural Transition in La_0.875Sr_0.125MnO_3|V. Kiryukhin,Y. J. Wang,F. C. Chou,M. A. Kastner,R. J. Birgeneau###

An X-Ray Induced Structural Transition in La_0.875Sr_0.125MnO_3. We report a synchrotron x-ray scattering study of the magnetoresistive
manganite La_0.875Sr_0.125MnO_3. At low temperatures, this material undergoes
an x-ray induced structural transition at which charge ordering of Mn^3+ and
Mn^4+ ions characteristic to the low-temperature state of this compound is
destroyed. The transition is persistent but the charge-ordered state can be
restored by heating above the charge-ordering transition temperature and
subsequently cooling. The charge-ordering diffraction peaks, which are
broadened at all temperatures, broaden more upon x-ray irradiation, indicating
the finite correlation length of the charge-ordered state. Together with the
recent reports on x-ray induced transitions in Pr_(1-x)Ca_xMnO_3, our results
demonstrate that the photoinduced structural change is a common property of the
charge-ordered perovskite manganites.

###Non-Universal Power Law of the "Hall Scattering Rate" in a Single-Layer Cuprate Bi_{2}Sr_{2-x}La_{x}CuO_{6}|Yoichi Ando,T. Murayama###

Non-Universal Power Law of the "Hall Scattering Rate" in a Single-Layer Cuprate Bi_{2}Sr_{2-x}La_{x}CuO_{6}. In-plane resistivity \rho_{ab}, Hall coefficient, and magnetoresistance (MR)
are measured in a series of high-quality Bi_{2}Sr_{2-x}La_{x}CuO_{6} crystals
with various carrier concentrations, from underdope to overdope. Our crystals
show the highest T_c (33 K) and the smallest residual resistivity ever reported
for Bi-2201 at optimum doping. It is found that the temperature dependence of
the Hall angle obeys a power law T^n with n systematically decreasing with
increasing doping, which questions the universality of the Fermi-liquid-like
T^2 dependence of the "Hall scattering rate". In particular, the Hall angle of
the optimally-doped sample changes as T^{1.7}, not as T^2, while \rho_{ab}
shows a good T-linear behavior. The systematics of the MR indicates an
increasing role of spin scattering in underdoped samples.

###Magnetic precursor effects in Gd alloys|R. Mallik,E. V. Sampathkumaran###

Magnetic precursor effects in Gd alloys. The behaviour of electrical resistivity ($\rho$) and magnetoresistance in the
vicinity of respective magnetic ordering temperatures in a number of Gd alloys
is reported. In some compounds, e.g., GdNi_2Sn_2 and GdPt_2Ge_2, there is an
enhancement of $\rho$ prior to long range magnetic order over a wide
temperature range which can be highlighted by the suppression of $\rho$ caused
by the application of a magnetic field. However, such features are absent in
many other Gd compounds, e.g., GdCu_2Ge_2, GdAg_2Si_2, GdAu_2Si_2, GdPd_2Ge_2
and GdCo_2Si_2. Attempts to relate such features to magnetic precursor effects
in heat capacity are made. On the basis of our studies, we suggest that better
understanding of magnetic precursor effects in Gd alloys will be helpful to
throw light on some of the current trends in magnetism. Various other
interesting findings in the magnetically ordered state in some of these alloys
are also brought out.

###Temperature dependence of electric resistance and magnetoresistance of pressed nanocomposites of multilayer nanotubes with the structure of nested cones|V. I. Tsebro,O. E. Omel'yanovskii,E. F. Kukovitskii,N. A. Sainov,N. A. Kiselev,D. N. Zakharov###

Temperature dependence of electric resistance and magnetoresistance of pressed nanocomposites of multilayer nanotubes with the structure of nested cones. Bulk samples of carbon multilayer nanotubes with the structure of nested
cones (fishbone structure) suitable for transport measurements, were prepared
by compressing under high pressure (~25 kbar) a nanotube precursor synthesized
through thermal decomposition of polyethylene catalyzed by nickel. The
structure of the initial nanotube material was studied using high-resolution
transmission electron microscopy. In the low-temperature range (4.2 - 100 K)
the electric resistance of the samples changes according to the law ln \rho ~
(T_0/T)^{1/3}, where T_0 ~ 7 K. The measured magnetoresistance is quadratic in
the magnetic field and linear in the reciprocal temperature. The measurements
have been interpreted in terms of two-dimensional variable-range hopping
conductivity. It is suggested that the space between the inside and outside
walls of nanotubes acts as a two-dimensional conducting medium. Estimates
suggest a high value of the density of electron states at the Fermi level of
about 5 10^{21} eV^{-1} cm^{-3}.

###Negative magnetoresistance in La(0.6)Y(0.1)Ca(0.3)MnO(3): Evidence for charge localization governed by the Curie-Weiss law|S. Sergeenkov,H. Bougrine,M. Ausloos,A. Gilabert###

Negative magnetoresistance in La(0.6)Y(0.1)Ca(0.3)MnO(3): Evidence for charge localization governed by the Curie-Weiss law. Colossal negative magnetoresistance \Delta \rho (T,B) observed in
La(0.6)Y(0.1)Ca(0.3)MnO(3) at B=1T shows a nearly perfect symmetry around
T_0=160K suggesting a universal field-induced transport mechanism in this
material. Attributing this symmetry to strong magnetic fluctuations (triggered
by the Y substitution and further enhanced by magnetic field, both above and
below the field-dependent Curie temperature T_C(B)=T_0), the data are
interpreted in terms of the nonthermal spin hopping and magnetization M
dependent charge carrier localization scenario leading to \Delta \rho (T,B)=
-\rho_s(1-exp(-\gamma M^2)) with M(T,B)=CB/|T-T_C|^n. The separate fits through
all the data points above and below T_C yield C^{+}\simeq C^{-} and n^{+}\simeq
n^{-}\simeq 1. The obtained results corroborate the importance of fluctuation
effects in this material recently found (cond-mat/9812219) to dominate its
magneto-thermopower behavior far beyond T_C.

###Pseudogaps and Extrinsic Losses in Photoemission Experiments on Poorly Conducting Solids|Robert Joynt###

Pseudogaps and Extrinsic Losses in Photoemission Experiments on Poorly Conducting Solids. It is shown that a photoelectron, on being emitted from a conducting solid,
suffers a substantial energy change due to ohmic losses. Almost all of this
energy loss takes place after the electron leaves the solid. These losses may
be important in isotropic materials with relatively low conductivity, such as
certain colossal magnetoresistance manganates, and in very electrically
anisotropic materials such as high-T_c superconductors and 1-D conductors. In
these materials, the electric field of the photoelectron can penetrate the
system. These losses can drastically affect the observed lineshape on the meV
scale which is now observable due to improved resolution. In particular,
extrinsic losses of this type can mimic pseudogap effects and other peculiar
features of photoemission in cubic manganates. This general point is
illustrated with the particular case of La_{0.67}Ca_{0.33}MnO_3.

###Dependence of Magnetic Anisotropy and Magnetoresistance of Ni81Fe19-Films on Annealing|T. Lorenz,A. Kaeufler,Y. Luo,M. Moske,K. Samwer###

Dependence of Magnetic Anisotropy and Magnetoresistance of Ni81Fe19-Films on Annealing. Permalloy (Py:Ni81Fe19) exhibits an anisotropic magnetoresistance (AMR) which
is very often used to read magnetic signals from storage devices. Py-films of
thickness 20nm were prepared by dc-magnetron sputtering in a magnetic field
onto thermally oxidized Si-wafers and annealed ex situ at temperatures up to
1000K in order to investigate the dependence of the magnetic anisotropy and the
AMR on heat treatments. The films exhibit an uniaxial anisotropy after
preparation which changes during annealing above 520K. The AMR along the former
magnetically easy axis as well as the corresponding field sensitivity are
increased by a heat treatment around 700K reaching maxima of about 8% and a
maximum sensitivity of 1.5%/Oe, respectively. We discuss possible sources for
the change in anisotropy, i.e. strain effects, inhomogeneities, and changes of
the local atomic order.

###Crossover between ballistic and diffusive regime of the spin-conductance and CPP-GMR in magnetic multilayered nanostructures|S. Sanvito,C. J. Lambert,J. H. Jefferson###

Crossover between ballistic and diffusive regime of the spin-conductance and CPP-GMR in magnetic multilayered nanostructures. We analyze the interplay between disorder and band structure in current
perpendicular to the planes (CPP) giant magnetoresistance (GMR). We consider
finite magnetic multilayers attached to pure crystalline leads, described by a
tight-binding simple cubic two-band model (s-d). Several models of disorder are
considered, including random on-site potentials, lattice distortions,
impurities, vacancies, and cross-section fluctuations. Magneto-transport
properties are calculated in the zero-temperature zero-bias limit, within the
Landauer-Buttiker formalism. Using a very efficient numerical scattering
technique, we are able to perform simulations, over large length scales, and to
investigate spin-transport in the ballistic, diffusive and localized regimes,
as well as the crossover between them. The competition between disorder-induced
mean free path reduction and disorder-induced spin asymmetry enhancement of the
conductance highlights several different regimes of GMR.

###Evidence for a Purely Double-Exchange Mechanism for the Anisotropic Conductivities in Layered La-Sr-Mn-O Single Crystals Below TC|Q. A. Li,K. E. Gray,J. F. Mitchell,A. Berger,R. Osgood###

Evidence for a Purely Double-Exchange Mechanism for the Anisotropic Conductivities in Layered La-Sr-Mn-O Single Crystals Below TC. Experimental evidence supports the double-exchange (DE) mechanism for both
in-plane and c-axis conductivity in the colossal-magnetoresistive (CMR) layered
manganite La1.4Sr1.6Mn2O7. Below TC, the data determine both the DE and
antiferromagnetic (AF) superexchange between bilayers. These agree with recent
spin-wave data, such that the ratio of intra- to inter-bilayer DE constants is
very close to the spin-independent conductance anisotropy of ~300. The
conductivity is shown to be proportional to the square of the measured
magnetization over a wide range of fields and for temperatures below the
in-plane ferromagnetic ordering temperature, TC. This dependence is shown to be
consistent with DE coupling and earlier zero-field studies of La1.2Sr1.8Mn2O7
near TC, which used neutron scattering for the local magnetization. A mixed AF
and spin-flop state (similar to the intermediate state of type-I
superconductors) is a rigorous prediction of the data and modeling.

###Paramagnetic limiting of the upper critical field of the layered organic superconductor $κ-(BEDT-TTF)_2Cu(SCN)_2$|F. Zuo,J. S. Brooks,Ross H. McKenzie,J. A. Schlueter,Jack M. Williams###

Paramagnetic limiting of the upper critical field of the layered organic superconductor $κ-(BEDT-TTF)_2Cu(SCN)_2$. We report detailed measurements of the interlayer magnetoresistance of the
layered organic superconductor $\kappa -(BEDT-TTF)_2Cu(SCN)_2$ for temperatures
down to 0.5 K and fields up to 30 tesla. The upper critical field is determined
from the resistive transition for a wide range of temperatures and field
directions. For magnetic fields parallel to the layers, the upper critical
field increases approximately linearly with decreasing temperature. The upper
critical field at low temperatures is compared to the Pauli paramagnetic limit,
at which singlet superconductivity should be destroyed by the Zeeman splitting
of the electron spins. The measured value is comparable to a value for the
paramagnetic limit calculated from thermodynamic quantities but exceeds the
limit calculated from BCS theory. The angular dependence of the upper critical
field shows a cusp-like feature for fields close to the layers, consistent with
decoupled layers.

###On the Relation between Interband Scattering and the "Metallic Phase" of Two Dimensional Holes in GaAs/AlGaAs|Yuval Yaish,Oleg Prus,Evgeny Buchstab,Shye Shapira,Gidi Ben Yoseph,Uri Sivan,Ady Stern###

On the Relation between Interband Scattering and the "Metallic Phase" of Two Dimensional Holes in GaAs/AlGaAs. The "metallic" regime of holes in GaAs/AlGaAs heterostructures corresponds to
densities where two splitted heavy hole bands exist at a zero magnetic field.
Using Landau fan diagrams and weak field magnetoresistance curves we extract
the carrier density in each band and the interband scattering rates. The
measured inelastic rates depend Arrheniusly on temperature with an activation
energy similar to that characterizing the longitudinal resistance. The
"metallic" characteristics, namely, the resistance increase with temperature,
is hence traced to the activation of inelastic interband scattering. The data
are used to extract the bands dispersion relations as well as the two
particle-hole excitation continua. It is then argued that acoustic plasmon
mediated Coulomb scattering might be responsible for the Arrhenius dependence
on temperature. The absence of standard Coulomb scattering characterized by a
power law dependence upon temperature is pointed out.

###New approach to analysis of negative magnetoresistance. The statistics of the closed paths|G. M. Minkov,S. A. Negashev,O. E. Rut,A. V. Germanenko,O. I. Khrykin,V. I. Shashkin,V. M. Danil'tsev###

New approach to analysis of negative magnetoresistance. The statistics of the closed paths. It is shown that a new kind of information can be extracted from the Fourier
transform of negative magnetoresistance (MR) in 2D semiconductor structures.
The procedure proposed provides the information on the area distribution
function of the closed paths and on the area dependence of the mean length of
closed paths $\bar{L} (S)$ . Based on this line of attack the method of
analysis of the negative MR is suggested. The method is used for data treatment
of negative MR in 2D structures. In previous version (cond-mat/9902038) we
suppoused that the difference in area dependence of $\bar{L} (S)$ for
structures investigated came from the difference in scattering ansotropy. The
more detailed analysis shows that main reason for such difference is different
relations between momentum and phase relaxation times.

###Weak localisation in AlGaAs/GaAs p-type quantum wells|S. Pedersen,C. B. Sorensen,A. Kristensen,P. E. Lindelof,L. E. Golub,N. S. Averkiev###

Weak localisation in AlGaAs/GaAs p-type quantum wells. We have for the first time experimentally investigated the weak localisation
magnetoresistance in a AlGaAs/GaAs p-type quantum well. The peculiarity of such
systems is that spin-orbit interaction is strong. On the theoretical side it is
not possible to treat the spin-orbit interaction as a perturbation. This is in
contrast to all prior investigations of weak localisation. In this letter we
compare the experimental results with a newly developed diffusion theory, which
explicitly describes the weak localisation regime when the spin-orbit coupling
is strong. The spin relaxation rates calculated from the fitting parameters was
found to agree with theoretical expectations. Furthermore the fitting
parameters indicate an enhanced phase breaking rate compared to theoretical
predictions.

###Current dependence of grain boundary magnetoresistance in La_0.67Ca_0.33MnO_3 films|W. Westerburg,F. Martin,S. Friedrich,M. Maier,G. Jakob###

Current dependence of grain boundary magnetoresistance in La_0.67Ca_0.33MnO_3 films. We prepared epitaxial ferromagnetic manganite films on bicrystal substrates
by pulsed laser ablation. Their low- and high-field magnetoresistance (MR) was
measured as a function of magnetic field, temperature and current. At low
temperatures hysteretic changes in resistivity up to 70% due to switching of
magnetic domains at the coercitive field are observed. The strongly non-ohmic
behavior of the current-voltage leads to a complete suppression of the MR
effect at high bias currents with the identical current dependence at low and
high magnetic fields. We discuss the data in view of tunneling and mesoscale
magnetic transport models and propose an explicit dependence of the spin
polarization on the applied current in the grain boundary region.

###Comment on ``Spin Dependent Hopping and Colossal Negative Magnetoresistance in Epitaxial $Nd_{0.52}Sr_{0.48}MnO_{3}$ Films in Fields up to 50 T''|Sudhakar Yarlagadda###

Comment on ``Spin Dependent Hopping and Colossal Negative Magnetoresistance in Epitaxial $Nd_{0.52}Sr_{0.48}MnO_{3}$ Films in Fields up to 50 T''. Recently Wagner et al. [Phys. Rev. Lett. Vol. 81, P. 3980 (1998)] proposed
that Mott's original model be modified to incorporate a hopping barrier which
depends on the misorientation between the spins of electrons at the initial and
the final states in an elementary process. They further claimed that using the
model they can explain the observed scaling behavior--
negative-magnetoresistivity scaling proportional to the Brillouin function
$\cal{B}$ in the ferromagnetic state and to ${\cal{B}}^2$ in the paramagnetic
state. In this comment we argue that the modification needed for Mott's
original model is different from that proposed by Wagner et al. and further
show that our picture will successfully explain the observed scaling in the two
regimes.

###Two ferromagnetic phases in La1-xSrxMnO3(x ~1/8)|H. Nojiri,K. Kaneko,M. Motokawa,K. Hirota,K. Takahashi,Y. Endoh###

Two ferromagnetic phases in La1-xSrxMnO3(x ~1/8). It was discovered in La1-xSrxMnO3(x~1/8) that a field induced phase
transition occurs from a ferromagnetic metal(FM) phase to a ferromagnetic
insulator (FI) phase. The magnetization shows a sharp jump at the transition
field accompanying with a remarkable increase of magnetoresistance. Striction
measurements clarified that this transition is associated with the structural
change from a Jahn-Teller(JT) distorted orthorhombic phase to a pseudo cubic
phase. These results evidently show that the FI phase with a pseudo cubic
symmetry is more stable in high fields than the FM phase due to the double
exchange interaction. The driving force of this transition is explained by the
enhancement of the ferromagnetic superexchange interaction induced by an
antiferromagnetic type orbital ordering in the pseudo cubic phase, which was
recently found in the anomalous X-ray scattering experiments.

###The effect of an in-plane magnetic field on the interlayer transport of quasiparticles in layered superconductors|L. N. Bulaevskii,M. J. Graf,M. P. Maley###

The effect of an in-plane magnetic field on the interlayer transport of quasiparticles in layered superconductors. We consider the quasiparticle c-axis conductivity in highly anisotropic
layered compounds in the presence of the magnetic field parallel to the layers.
We show that at low temperatures the quasiparticle interlayer conductivity
depends strongly on the orientation of the in-plane magnetic field if the
excitation gap has nodes on the Fermi surface. Thus measurements of the
angle-dependent c-axis (out-of-plane) magnetoresistance, as a function of the
orientation of the magnetic field in the layers, provide information on the
momentum dependence of the superconducting gap (or pseudogap) on the Fermi
surface. Clean and highly anisotropic layered superconductors seem to be the
best candidates for probing the existence and location of the nodes on the
Fermi surface.

###Negative Magnetoresistance of Bi_2Sr_2CuO_x Single Crystals in a Strong Magnetic Fields|S. I. Vedeneev,A. G. M. Jansen,B. A. Volkov,P. Wyder###

Negative Magnetoresistance of Bi_2Sr_2CuO_x Single Crystals in a Strong Magnetic Fields. Magnetoresistance (MR) in the out-of-plane resistivity $\rho_c$ for the
normal state of the one-layer high-quality Bi_2Sr_2CuO_x single crystals under
various dc magnetic fields up to 28 T over the temperature region 6-100 K has
been measured. We observed the anomalously large negative longitudinal MR up to
60%. At low temperatures the normal-state MR in contrast to the MR in mixed
state is independent of the direction of the current relatively to the field
direction suggesting uniquely the spin dominated origin of that. The magnitude
of the MR is activated in magnetic field and temperature. We interpret the
activated form of $\rho_c$ and the negative MR in terms of 2D stacked
alternating metallic and dielectric layers assuming the tunneling between CuO_2
planes. If the main fluctuations inside CuO_2 planes have magnetic origin, the
magnetic field suppresses these fluctuations leading to the uniform spin
orientation. In this case the interlayer current will be enhanced well.

###Magnetoresistance of magnetic multilayers in the CPP mode:evidence for non-local scattering|Didier Bozec,M. A. Howson,B. J. Hickey,Smadar Shatz,Nathan Wiser###

Magnetoresistance of magnetic multilayers in the CPP mode:evidence for non-local scattering. We have carried out measurements of the magnetoresistance MR(H) in the CPP
(Current Perpendicular to the Plane) mode for two types of magnetic multilayers
which have different layer ordering. The series resistor model predicts that
CPP MR(H) is independent of the ordering of the layers. Nevertheless, the
measured MR(H) curves were found to be completely different for the following
two configurations:[Co(1nm)/Cu(20nm)/Co(6nm)/Cu(20nm)]*N and
[Co(1nm)/Cu(20nm)]*N[Co(6nm)/Cu(20nm)]*N showing that the above model is
incorrect. We have carried out a calculation showing that these results can be
explained quantitatively in terms of the non-local character of the electron
scattering, without the need to invoke spin-flip scattering or a short spin
diffusion length.

###Magnetoresistance in Heavily Underdoped YBa_2Cu_3O_{6+x}: Antiferromagnetic Correlations and Normal-State Transport|A. N. Lavrov,Yoichi Ando,Kouji Segawa,J. Takeya###

Magnetoresistance in Heavily Underdoped YBa_2Cu_3O_{6+x}: Antiferromagnetic Correlations and Normal-State Transport. We report on a contrasting behavior of the in-plane and out-of-plane
magnetoresistance (MR) in heavily underdoped antiferromagnetic (AF)
YBa_2Cu_3O_{6+x} (x<0.37). The out-of-plane MR (I//c) is positive over most of
the temperature range and shows a sharp increase, by about two orders of
magnitude, upon cooling through the Neel temperature T_N. A contribution
associated with the AF correlations is found to dominate the out-of-plane MR
behavior for H//c from far above T_N, pointing to the key role of spin
fluctuations in the out-of-plane transport. In contrast, the transverse
in-plane MR (I//a(b);H//c) appears to be small and smooth through T_N, implying
that the development of the AF order has little effect on the in-plane
resistivity.

###Sn delta-doping in GaAs|V. A. Kulbachinskii,V. G. Kytin,R. A. Lunin,A. V. Golikov,V. G. Mokerov,A. S. Bugaev,A. P. Senichkin,R. T. F. van Schaijk,A. de Visser,P. M. Koenraad###

Sn delta-doping in GaAs. We have prepared a number of GaAs structures delta-doped by Sn using the
well-known molecular beam epitaxy growth technique. The samples obtained for a
wide range of Sn doping densities were characterised by magnetotransport
experiments at low temperatures and in high magnetic fields up to 38 T.
Hall-effect and Shubnikov-de Haas measurements show that the electron densities
reached are higher than for other delta-dopants, like Si and Be. The maximum
carrier density determined by the Hall effect equals 8.4x10^13 cm^-2. For all
samples several Shubnikov-de Haas frequencies were observed, indicating the
population of multiple subbands. The depopulation fields of the subbands were
determined by measuring the magnetoresistance with the magnetic field in the
plane of the delta-layer. The experimental results are in good agreement with
selfconsistent bandstructure calculations. These calculation shows that in the
sample with the highest electron density also the conduction band at the L
point is populated.

###The irreversibility line of overdoped Bi_{2+x}Sr_{2-(x+y)}Cu_{1+y}O_{6 +- delta} at ultra-low temperatures and high magnetic fields|A. Morello,A. G. M. Jansen,R. S. Gonnelli,S. I. Vedeneev###

The irreversibility line of overdoped Bi_{2+x}Sr_{2-(x+y)}Cu_{1+y}O_{6 +- delta} at ultra-low temperatures and high magnetic fields. The irreversible magnetization of the layered high-T_{c} superconductor
Bi_{2+x}Sr_{2-(x+y)}Cu_{1+y}O_{6 +- delta} (Bi-2201) has been measured by means
of a capacitive torquemeter up to B=28 T and down to T=60 mK. No magnetization
jumps, peak effects or crossovers between different pinning mechanisms appear
to be present. The deduced irreversibility field B_{irr} can not be described
by the law B_{irr}(T)=B_{irr}(0)(1-T/T_{c})^n based on flux creep, but an
excellent agreement is found with the analytical form of the melting line of
the flux lattice as calculated from the Lindemann criterion. The behavior of
B_{irr}(T) obtained here is very similar to the resistive critical field of a
Bi-2201 thin film, suggesting that magnetoresistive experiments are likely to
be strongly influenced by flux lattice melting.

###Optical spectral weights and the ferromagnetic transition temperature of CMR manganites: relevance of double-exchange to real materials|A. Chattopadhyay,A. J. Millis,S. Das Sarma###

Optical spectral weights and the ferromagnetic transition temperature of CMR manganites: relevance of double-exchange to real materials. We present a thorough and quantitative comparison of double-exchange models
to experimental data on the colossal magnetoresistance manganese perovskites.
Our results settle a controversy by showing that physics beyond double-exchange
is important even in La$_{0.7}$Sr$_{0.3}$MnO$_3$, which has been regarded as a
conventional double-exchange system. We show that the crucial quantity for
comparisons of different calculations to each other and to data is the
conduction band kinetic energy $K$, which is insensitive to the details of the
band structure and can be experimentally determined from optical conductivity
measurements. The seemingly complicated dependence of $T_c$ on the Hund's
coupling $J$ and carrier concentration $n$ is shown to reflect the variation of
$K$ with $J$, $n$ and temperature. We present results for the optical
conductivity which allow interpretation of experiments and show that a feature
previously interpreted in terms of the Hund's coupling was misidentified. We
also correct minor errors in the phase diagram presented in previous work.

###Wavelength dependent negative and positive persistent photoconductivity in Sn delta-doped GaAs structures|V. A. Kulbachinskii,V. G. Kytin,A. V. Golikov,R. A. Lunin,R. T. F. van Schaijk,A. de Visser,A. P. Senichkin,A. S. Bugaev###

Wavelength dependent negative and positive persistent photoconductivity in Sn delta-doped GaAs structures. The photoconductivity of GaAs structures delta-doped by Sn has been
investigated for wavelengths lambda= 650-1200 nm in the temperature interval T=
4.2-300 K. The electron densities and mobilities, before and after
illumination, have been determined by magnetoresistance, Shubnikov-de Haas
effect and Hall effect measurements, in high magnetic fields. For the heavily
doped structures (n_H> 2x10^13 cm^-2) we observe under illumination by light
with wavelengths larger than the band-gap wavelength of the host material
(lambda= 815 nm at T= 4.2 K) first positive (PPPC) and then negative (NPPC)
persistent photoconductivity. The NPPC is attributed to the ionisation of DX
centres and PPPC is explained by the excitation of electrons from Cr impurity
states in the substrate. For lambda< 815 nm in addition the excitation of
electron over the band gap of GaAs contributes to the PPPC. For the lightly
doped structures (n_H<= 2x10^13 cm^-2) the photoconductivity effect is always
positive.

###Magneto-Transport Properties of the Rutheno-Cuprate RuSr_2GdCu_2O_8|J. E. McCrone,J. R. Cooper,J. L. Tallon###

Magneto-Transport Properties of the Rutheno-Cuprate RuSr_2GdCu_2O_8. RuSr_2GdCu_2O_8 (Ru-1212) is a triple perovskite containing both CuO_2 and
RuO_2 layers. It has attracted a great deal of interest recently because it
displays electronic ferromagnetism and superconductivity coexisting on a
microscopic scale, with T_Curie of 135K and T_c up to 50K.
  We report magnetisation and magnetoresistance (MR) data that exhibit effects
due to the interaction between the ferromagnetic ruthenium moments and the
conduction electrons. The MR is negative at temperatures above T_Curie, and is
proportional to the square of the applied field well above this temperature.
Below T_Curie the MR displays a positive peak at fields of around 15 kOe, but
at high fields it becomes negative again, and approximately linear. We analyse
the high temperature data in terms of spin-disorder scattering theory and
extract a value for the exchange interaction between the carriers in the CuO_2
planes and the Ru spins.

###Carrier density change in Colossal Magnetoresistive Pyrochlore Tl2Mn2O7|H. Imai,Y. Shimakawa,Yu. V. Sushko,Y. Kubo###

Carrier density change in Colossal Magnetoresistive Pyrochlore Tl2Mn2O7. Hall resistivity and magneto-thermopower have been measured for colossal
magnetoresistive Tl2Mn2O7 over wide temperature and magnetic-field ranges.
These measurements revealed that a small number of free electron-like carriers
is responsible for the magneto-transport properties. In contrast to perovskite
CMR materials, the anomalous Hall coefficient is negligible even in the
ferromagnetic state due to negligibly small skew scattering. The characteristic
feature in Tl2Mn2O7 is that the carrier density changes with temperature and
the magnetic field. The carrier density increases around TC as the temperature
is lowered or as the magnetic field is increased, which explains the CMR of
this material. The conduction-band-edge shift, which is caused by the strong
s-d interaction between localized Mn moments and s-like conduction electrons,
is a possible mechanism for the carrier density change.

###Temperature-Dependent Pseudogaps in Colossal Magnetoresistive Oxides|T. Saitoh,D. S. Dessau,Y. Moritomo,T. Kimura,Y. Tokura,N. Hamada###

Temperature-Dependent Pseudogaps in Colossal Magnetoresistive Oxides. Direct electronic structure measurements of a variety of the colossal
magnetoresistive oxides show the presence of a pseudogap at the Fermi energy
E_F which drastically suppresses the electron spectral function at E_F. The
pseudogap is a strong function of the layer number of the samples (sample
dimensionality) and is strongly temperature dependent, with the changes
beginning at the ferromagnetic transition temperature T_c. These trends are
consistent with the major transport trends of the CMR oxides, implying a direct
relationship between the pseudogap and transport, including the "colossal"
conductivity changes which occur across T_c. The k-dependence of the
temperature-dependent effects indicate that the pseudogap observed in these
compounds is not due to the extrinsic effects proposed by Joynt.

###Two-dimensional weak localization effects in high temperature superconductor Nd{2-x}Ce{x}CuO{4-d}|G. I. Harus,A. N. Ignatenkov,A. I. Ponomarev,L. D. Sabirzyanova,N. G. Shelushinina,A. A. Ivanov###

Two-dimensional weak localization effects in high temperature superconductor Nd{2-x}Ce{x}CuO{4-d}. A systematic study of the resistivity and Hall effect in single crystal
Nd{2-x}Ce{x}CuO{4-d} films (0.12 < x < 0.20) is presented, with special
emphasis on the low-temperature dependence of the normal state conductance.
Two-dimensional weak localization effects are found both in a normally
conducting underdoped sample (x = 0.12) and in situ superconducting optimally
doped (x = 0.15) or overdoped (x = 0.18) samples in a high magnetic field B >
B{c2}. The phase coherence time and the effective thickness of a CuO{2}
conducting layer {d} (~ 1.5 A) have been estimated by fitting 2D weak
localization theory expressions to the magnetoresistivity data for magnetic
fields perpendicular to the {ab} plane and in plane. Estimates of the parameter
{d} ensure the condition of strong carrier confinement and justify a model
consisting of almost decoupled 2D metallic sheets for the Nd{2-x}Ce{x}CuO{4-d}
single crystal.

###Competition between ferromagnetic and charge-orbital ordered phases in Pr$_{1-x}$Ca$_{x}$MnO$_3$ for $x$=1/4, 3/8, and 1/2|Takashi Hotta,Elbio Dagotto###

Competition between ferromagnetic and charge-orbital ordered phases in Pr$_{1-x}$Ca$_{x}$MnO$_3$ for $x$=1/4, 3/8, and 1/2. Spin, charge, and orbital structures in models for doped manganites are
studied by a combination of analytic mean-field and numerical relaxation
techniques. At realistic values for the electron-phonon and antiferromagnetic
$t_{2g}$ spin couplings, a competition between a ferromagnetic (FM) phase and a
charge-orbital ordered (COO) insulating state is found for $x$=1/4, 3/8, and
1/2, as experimentally observed in Pr$_{1-x}$Ca$_{x}$MnO$_3$ for
$x$=0.3$\sim$0.5. The theoretical predictions for the spin-charge-orbital
ordering pattern are compared with experiments. The FM-COO energy difference is
surprisingly small for the densities studied, result compatible with the
presence of a robust colossal-magnetoresistive effect in
Pr$_{1-x}$Ca$_{x}$MnO$_3$ in a large density interval.

###Epitaxy and magnetotransport of Sr_2FeMoO_6 thin films|W. Westerburg,D. Reisinger,G. Jakob###

Epitaxy and magnetotransport of Sr_2FeMoO_6 thin films. By pulsed-laser deposition epitaxial thin films of Sr_2FeMoO_6 have been pre-
pared on (100) SrTiO_3 substrates. Already for a deposition temperature of 320
C epitaxial growth is achieved. Depending on deposition parameters the films
show metallic or semiconducting behavior. At high (low) deposition temperature
the Fe,Mo sublattice has a rock-salt (random) structure. The metallic samples
have a large negative magnetoresistance which peaks at the Curie temperature.
The magnetic moment was determined to 4 mu_B per formula unit (f.u.), in
agreement with the expected value for an ideal ferrimagnetic arrangement. We
found an ordinary Hall coefficient of -6.01x10^{-10} m^3/As at 300 K,
corresponding to an electronlike charge-carrier density of 1.3 per Fe,Mo-pair.
In the semiconducting films the magnetic moment is reduced to 1 mu_B/f.u. due
to disorder in the Fe,Mo sublattice. In low fields an anomalous holelike
contribution dominates the Hall voltage, which vanishes at low temperatures for
the metallic films only.

###Temperature dependent changes of the Mn 3d and 4p bands near T$_c$ in Colossal Magnetoresistance systems: a XANES study of La$_{1-x}$Ca$_x$MnO$_3$|F. Bridges,C. H. Booth,G. H. Kwei,J. J. Neumeier,G. A. Sawatzky###

Temperature dependent changes of the Mn 3d and 4p bands near T$_c$ in Colossal Magnetoresistance systems: a XANES study of La$_{1-x}$Ca$_x$MnO$_3$. We report high-resolution X-ray Absorption Near Edge Structure (XANES)
measurements at the Mn K-edge as a function of temperature, for
La$_{1-x}$Ca$_x$MnO$_3$ samples, with a focus mainly on the pre-edge region.
Small peaks labeled A$_1$-A$_3$ are observed which corresponds to 1s-3d
dipole-transitions, made weakly allowed via a hybridization of Mn 4p states
with Mn 3d states on {\it neighboring} atoms. Adjusting the parameters in an
LSDA calculation to approximately match the experimental A$_1$-A$_2$ splitting
yields U = 4 eV and J$_H$ = 0.7 eV. For colossal magnetoresistance samples,
A$_1$ decreases with T while A$_2$ increases with T below T$_c$, which shows
that the 3d bands change significant as T moves through T$_c$. There are also
small changes in the shape of the main edge (1s-4p transitions).

###Many-body CPA for the Holstein-DE model|A. C. M. Green###

Many-body CPA for the Holstein-DE model. A many-body coherent potential approximation (CPA) previously developed for
the double exchange (DE) model is extended to include coupling to local quantum
phonons. The Holstein-DE model studied (equal to the Holstein model for zero
Hund coupling) is considered to be a simple model for the colossal
magnetoresistance manganites. We concentrate on effects due to the quantisation
of the phonons, such as the formation of polaron subbands. The electronic
spectrum and resistivity are investigated for a range of temperature and
electron-phonon coupling strengths. Good agreement with experiment is found for
the Curie temperature and resistivity with intermediate electron-phonon
coupling strength, but phonon quantisation is found not to have a significant
effect in this coupling regime.

###Does Giant Magnetoresistance Survive in Presence of Superconducting Contact?|N. Ryzhanova,C. Lacroix,A. Vedyayev,D. Bagrets,B. Dieny###

Does Giant Magnetoresistance Survive in Presence of Superconducting Contact?. The giant magnetoresistance (GMR) of ferromagnetic bilayers with a
superconducting contact (F1/F2/S) is calculated in ballistic and diffusive
regimes. As in spin-valve, it is assumed that the magnetization in the two
ferromagnetic layers F1 and F2 can be changed from parallel to antiparallel. It
is shown that the GMR defined as the change of conductance between the two
magnetic configurations is an oscillatory function of the thickness of F2 layer
and tends to an asymptotic positive value at large thickness. This is due to
the formation of quantum well states in F2 induced by Andreev reflection at the
F2/S interface and reflection at F1/F2 interface in antiparallel configuration.
In the diffusive regime, if only spin-dependent scattering rates in the
magnetic layers are considered (no difference in Fermi wave-vectors between
spin up and down electrons) then the GMR is supressed due to the mixing of spin
up and down electron-hole channels by Andreev reflection.

###Ferromagnetism and Colossal Magnetoresistance from the Coexistence of Comparable Charge and Spin Density Orders|Georgios Varelogiannis###

Ferromagnetism and Colossal Magnetoresistance from the Coexistence of Comparable Charge and Spin Density Orders. We report a complete multicomponent mean-field-theory for the coexistence and
competition of charge ordering (CO), antiferromagnetic (AFM) and ferromagnetic
(FM) spin ordering in the presence of a uniform magnetic field. Doping the AFM
or CO state always generates a ferromagnetic component. Itinerant FM, AFM and
CO, necessarily coexist and compete in a particle-hole asymmetric system.
Melting of large AFM-CO orders by small magnetic fields and the related
phenomenon of Colossal Magnetoresistance (CMR) may arise whenever the CO and
AFM order parameters have similar magnitude and momentum structure. Hole doping
favors FM metallic states and CMR while electron doping favors AFM-CO states in
agreement with the phase diagram of perovskite manganites.

###Thermokinetic approach of the generalized Landau-Lifshitz-Gilbert equation with spin polarized current|J. -E. Wegrowe###

Thermokinetic approach of the generalized Landau-Lifshitz-Gilbert equation with spin polarized current. In order to describe the recently observed effect of current induced
magnetization reversal in magnetic nanostructures, the thermokinetic theory is
applied to a metallic ferromagnet in contact with a reservoir of spin polarized
conduction electrons. The spin flip relaxation of the conduction electrons is
described thermodynamically as a chemical reaction. The diffusion equation of
the chemical potential (or the giant magnetoresistance) and the usual
Landau-Lifshitz-Gilbert (LLG) equation are derived from the entropy variation.
The expression of the conservation laws of the magnetic moments, including spin
dependent scattering processes, leads then to the generalized LLG equation with
spin polarized current. The equation is applied to the measurements obtained on
single magnetic Ni nanowires.

###Symmetry Dependence of Localization in Quasi- 1- dimensional Disordered Wires|Stefan Kettemann###

Symmetry Dependence of Localization in Quasi- 1- dimensional Disordered Wires. The crossover in energy level statistics of a quasi-1-dimensional disordered
wire as a function of its length L is used, in order to derive its averaged
localization length, without magnetic field, in a magnetic field and for
moderate spin orbit scattering strength. An analytical function of the magnetic
field for the local level spacing is obtained, and found to be in excellent
agreement with the magnetic field dependent activation energy, recently
measured in low-mobility quasi-one-dimensional wires\cite{khavin}. This formula
can be used to extract directly and accurately the localization length from
magnetoresistance experiments. In general, the local level spacing is shown to
be proportional to the excitation gap of a virtual particle, moving on a
compact symmetric space.

###Magnetic and structural properties of the double-perovskite Ca_2FeReO_6|W. Westerburg,O. Lang,C. Felser,W. Tremel,M. Waldeck,F. Renz,P. Guetlich,C. Ritter,G. Jakob###

Magnetic and structural properties of the double-perovskite Ca_2FeReO_6. We suceeded in the preparation of polycrystalline Ca_2FeReO_6 which has a
Curie temperature of 540 K, the highest value of all magnetic perovskites
investigated up to now. This material has been characterised by X-ray and
neutron powder diffraction. We found at 548 K a monoclinic unit cell (space
group P2_1/n) with a=5.4366(5) A, b=5.5393(5) A, c=7.7344(5) A, and
beta=90.044(4) deg. For low temperatures a phase separation in two monoclinic
phases with identical cell volume is observed in neutron scattering. The two
phases possess different magnetic structure and coercivity. 57-Fe-Moessbauer
spectroscopy measurements show the presence of four different Fe(3+) positions
indicating two different phases at room temperature, indistinguishable in the
diffraction experiments. The conductivity is thermally activated for all
temperatures and no significant magnetoresistivity is observed.

###A New Class of Magnetoresistance Oscillations: Interaction of a Two-Dimensional Electron Gas with Leaky Interface Phonons|M. A. Zudov,I. V. Ponomarev,A. L. Efros,R. R. Du,J. A. Simmons,J. L. Reno###

A New Class of Magnetoresistance Oscillations: Interaction of a Two-Dimensional Electron Gas with Leaky Interface Phonons. We report on a new class of magnetoresistance oscillations observed in a
high-mobility two-dimensional electron gas (2DEG) in GaAs-Al$_x$Ga$_{1-x}$As
heterostructures. Appearing in a weak magnetic field ($B<$ 0.3 T) and only in a
narrow temperature range (2 K $<T<$ 9 K), these oscillations are periodic in
1/B with a frequency proportional to the electron Fermi wave vector, $k_F$. We
interpret the effect as a magnetophonon resonance of the 2DEG with leaky
interface-acoustic phonon modes carrying a wave vector $q=2k_F$. Calculations
show a few branches of such modes on the GaAs-Al$_x$Ga$_{1-x}$As interface, and
their velocities are in quantitative agreement with the data.

###Direct measurement of polaron binding energy in AMnO$_{3}$ as a function of the A site ionic size by photoinduced IR absorption|T. Mertelj,M. Hrovat,D. Kuščer,D. Mihailovic###

Direct measurement of polaron binding energy in AMnO$_{3}$ as a function of the A site ionic size by photoinduced IR absorption. Photoinduced IR absorption was measured in undoped (LaMn)_{1-\delta}O_{3} and
(NdMn)_{1-\delta}O_{3}. We observe broadening and a ~44% increase of the
midinfrared anti-Jahn-Teller polaron peak energy when La^{3+} is replaced with
smaller Nd^{3+}. The absence of any concurent large frequency shifts of the
observed PI phonon bleaching peaks and the Brillouin-zone-center internal
perovskite phonon modes measured by Raman and infrared spectroscopy indicate
that the polaron peak energy shift is mainly a consequence of an increase of
the electron phonon coupling constant with decreasing ionic radius <r_{A}> on
the perovskite A site. This indicates that the dynamical lattice effects
strongly contribute to the electronic band narrowing with decreasing <r_{A}> in
doped giant magnetoresistance manganites.

###Voltage and temperature dependence of the grain boundary tunneling magnetoresistance in manganites|C. Hoefener,J. B. Philipp,J. Klein,L. Alff,A. Marx,B. Buechner,R. Gross###

Voltage and temperature dependence of the grain boundary tunneling magnetoresistance in manganites. We have performed a systematic analysis of the voltage and temperature
dependence of the tunneling magnetoresistance (TMR) of grain boundaries (GB) in
the manganites. We find a strong decrease of the TMR with increasing voltage
and temperature. The decrease of the TMR with increasing voltage scales with an
increase of the inelastic tunneling current due to multi-step inelastic
tunneling via localized defect states in the tunneling barrier. This behavior
can be described within a three-current model for magnetic tunnel junctions
that extends the two-current Julliere model by adding an inelastic,
spin-independent tunneling contribution. Our analysis gives strong evidence
that the observed drastic decrease of the GB-TMR in manganites is caused by an
imperfect tunneling barrier.

###On the Theory of a New Maximum Observed in dc Transport in Modulated Quantum Hall Systems Near ν=1/2|Nataliya a. Zimbovskaya,Joseph L. Birman###

On the Theory of a New Maximum Observed in dc Transport in Modulated Quantum Hall Systems Near ν=1/2. We propose a theory for the new maximum recently observed by Willett et al
[1] in the longitudinal magnetoresistance of a weakly modulated two-dimensional
electron gas (2DEG) near filling factor \nu =1/2 for the current driven along
the modulation lines. The maximum is superimposed upon a new resonance
structure. This occurs due to the geometric resonance of composite fermion
cyclotron orbits with the period of modulation of the effective magnetic field.
We propose here a semiquantitative theory of the dc magnetotransport in a
modulated 2DEG near one half filling. Our analysis is based on the Boltzmann
transport equation and it enables us to obtain this maximum which was neither
observed nor predicted previously.

###Resistivity and 1/f Noise in Non-Metallic Phase Separated Manganites|A. L. Rakhmanov,K. I. Kugel,Ya. M. Blanter,M. Yu. Kagan###

Resistivity and 1/f Noise in Non-Metallic Phase Separated Manganites. A simple model is proposed to calculate resistivity, magnetoresistance, and
noise spectrum in non-metallic phase-separated manganites containing small
metallic droplets (magnetic polarons). The system is taken to be far from the
percolation transition into a metallic state. It is assumed that the charge
transfer occurs due to electron tunneling from one droplet to another through
the insulating medium. As a result of this tunneling, the droplets acquire or
lose extra electrons forming metastable two-electron and empty states. In the
framework of this model, explicit expressions for dc conductivity and noise
power of the system are derived. It is shown that the noise spectrum has 1/f
form in the low-frequency range.

###Temperature-Dependence of the Resistivity of a Dilute 2D Electron System in High Parallel Magnetic Field|K. M. Mertes,Hairong Zheng,S. A. Vitkalov,M. P. Sarachik,T. M. Klapwijk###

Temperature-Dependence of the Resistivity of a Dilute 2D Electron System in High Parallel Magnetic Field. We report measurements of the resistance of silicon MOSFETs as a function of
temperature in high parallel magnetic fields where the 2D system of electrons
has been shown to be fully spin-polarized. A magnetic field suppresses the
metallic behavior observed in the absence of a magnetic field. In a field of
10.8 T, insulating behavior is found for densities up to n_s approximately 1.35
x 10^{11} cm^{-2} or 1.5 n_c; above this density the resistance is a very weak
function of temperature, varying less than 10% between 0.25 K and 1.90 K. At
low densities the resistance goes to infinity more rapidly as the temperature
is reduced than in zero field and the magnetoresistance diverges as T goes to
0.

###Enhancement of magnetoresistance in manganite multilayers|A. Venimadhav,M. S. Hegde,V. Prasad,S. V. Subramanyam###

Enhancement of magnetoresistance in manganite multilayers. Magnanite multilayers have been fabricated using La0.67Ca0.33MnO3 as the
ferromagnetic layer and Pr0.7Ca0.3MnO3 and Nd0.5Ca0.5MnO3 as the spacer layers.
All the multilayers were grown on LaAlO3 (100) by pulse laser deposition. An
enhanced magnetoresistnace (defined (RH- R0)/R0) of more than 98% is observed
in these multilayers. Also a low field magnetoresistance of 41% at 5000 Oe is
observed in these multilayer films. The enhanced MR is attributed to the
induced double exchange in the spacer layer, which is giving rise to more
number of conducting carriers. This is compared by replacing the spacer layer
with LaMnO3 where Mn exists only in 3+ state and no enhancement is observed in
the La0.67Ca0.33MnO3 / LaMnO3 multilayers as double exchange mechanism can not
be induced by external magnetic fields.

###Reentrant spin glass transition in La$_{0.96-y}$Nd$_{y}$K$_{0.04}$MnO$_3$: origin and effects on the colossal magnetoresistivity|R. Mathieu,P. Svedlindh,P. Nordblad###

Reentrant spin glass transition in La$_{0.96-y}$Nd$_{y}$K$_{0.04}$MnO$_3$: origin and effects on the colossal magnetoresistivity. Magnetic, electric and structural properties of
La$_{0.96-y}$Nd$_y$K$_{0.04}$MnO$_{3+\delta}$ with 0$\leq y \leq$0.4 have been
studied experimentally. A disordered magnetic state is formed as La is
substituted by Nd, reflecting the competition between ferromagnetic (FM) double
exchange and antiferromagnetic superexchange interactions. Key structural
parameters are identified and correlated with changes in magnetic and electric
properties. By application of a large magnetic field, spin disorder scattering
is removed, creating a new magnetoresistance peak at a temperature lower than
the first near-$T_c$ peak. Time dependent zero-field-cooled magnetisation
measurements have been performed for $y$=0.4 around this temperature. A
reentrant spin glass (RSG) transition is evidenced, with low field ageing
properties in both the RSG and FM phases, similar to those observed in
archetypal spin glass materials.

###Cationic ordering control of magnetization in Sr2FeMoO6 double perovskite|Ll. Balcells,J. Navarro,M. Bibes,A. Roig,B. Martinez,J. Fontcuberta###

Cationic ordering control of magnetization in Sr2FeMoO6 double perovskite. The role of the synthesis conditions on the cationic Fe/Mo ordering in
Sr2FeMoO6 double perovskite is addressed. It is shown that this ordering can be
controlled and varied systematically. The Fe/Mo ordering has a profound impact
on the saturation magnetization of the material. Using the appropriate
synthesis protocol a record value of 3.7muB/f.u. has been obtained. Mossbauer
analysis reveals the existence of two distinguishable Fe sites in agreement
with the P4/mmm symmetry and a charge density at the Fe(m+) ions significantly
larger than (+3) suggesting a Fe contribution to the spin-down conduction band.
The implications of these findings for the synthesis of Sr2FeMoO6 having
optimal magnetoresistance response are discussed.

###Superconductivity and Ferromagnetism from Effective Mass Reduction|J. E. Hirsch###

Superconductivity and Ferromagnetism from Effective Mass Reduction. Within a simple model Hamiltonian, both superconductivity and metallic
ferromagnetism can be understood as arising from lowering of kinetic energy as
the ordered state develops, due to a reduction in the carriers effective mass,
or equivalently, a bandwidth expansion. Experimental manifestation of this
physics has been detected in both high Tc superconductors and large
magnetoresistance ferromagnets, as an anomalous transfer of spectral weight in
optical absorption from high to low frequencies as the ordered state develops.
It is proposed that this general principle is common to the essential physics
of superconductivity and ferromagnetism in nature, and hence that these effects
in optical properties, although often smaller in magnitude, should exist in all
superconductors and metallic ferromagnets.

###Carrier-induced ferromagnetism in p-Zn1-xMnxTe|D. Ferrand,J. Cibert,A. Wasiela,C. Bourgognon,S. Tatarenko,G. Fishman,T. Andrearczyk,J. Jaroszynski,S. Kolesnik,T. Dietl,B. Barbara,D. Dufeu###

Carrier-induced ferromagnetism in p-Zn1-xMnxTe. We present a systematic study of the ferromagnetic transition induced by the
holes in nitrogen doped Zn1-xMnxTe epitaxial layers, with particular emphasis
on the values of the Curie-Weiss temperature as a function of the carrier and
spin concentrations. The data are obtained from thorough analyses of the
results of magnetization, magnetoresistance and spin-dependent Hall effect
measurements. The experimental findings compare favorably, without adjustable
parameters, with the prediction of the Rudermann-Kittel-Kasuya-Yosida (RKKY)
model or its continuous-medium limit, that is, the Zener model, provided that
the presence of the competing antiferromagnetic spin-spin superexchange
interaction is taken into account, and the complex structure of the valence
band is properly incorporated into the calculation of the spin susceptibility
of the hole liquid. In general terms, the findings demonstrate how the
interplay between the ferromagnetic RKKY interaction, carrier localization, and
intrinsic antiferromagnetic superexchange affects the ordering temperature and
the saturation value of magnetization in magnetically and electrostatically
disordered systems.

###Electrical transport properties of bulk Ni$_{c}$Fe$_{1-c}$ alloys and related spin-valve systems|C. Blaas,L. Szunyogh,P. Weinberger,C. Sommers,P. M. Levy###

Electrical transport properties of bulk Ni$_{c}$Fe$_{1-c}$ alloys and related spin-valve systems. Within the Kubo-Greenwood formalism we use the fully relativistic,
spin-polarized, screened Korringa-Kohn-Rostoker method together with the
coherent-potential approximation for layered systems to calculate the
resistivity for the permalloy series Ni$_{c}$Fe$_{1-c}$. We are able to
reproduce the variation of the resistivity across the entire series; notably
the discontinuous behavior in the vicinity of the structural phase transition
from bcc to fcc. The absolute values for the resistivity are within a factor of
two of the experimental data. Also the giant magnetoresistance of a series of
permalloy-based spin-valve structures is estimated; we are able to reproduce
the trends and values observed on prototypical spin-valve structures.

###Shubnikov-de Haas effect and Yamaji oscillations in the antiferromagnetically ordered organic superconductor k-(BETS)2FeBr4: A Fermiology study|L. Balicas,J. S. Brooks,K. Storr,D. Graf,S. Uji,H. Shinagawa,E. Ojima,H. Fujiwara,H. Kobayashi,A. Kobayashi,M. Tokumoto###

Shubnikov-de Haas effect and Yamaji oscillations in the antiferromagnetically ordered organic superconductor k-(BETS)2FeBr4: A Fermiology study. Shubnikov-De Haas effect (SdH) effect and angular dependent magnetoresistance
oscillations (AMRO) were observed in the organic superconductor:
$\kappa$-(BETS)$_2$FeBr$_4$. In contrast to its isostructural compound
$\kappa-(BETS)$_2$FeCl$_4$, SdH oscillations, for fields perpendicular to the
conducting planes, reveal three Fermi Surface (FS) closed orbits $\alpha$,
$\beta$, and $\gamma$ whose cross sectional areas are 19.8 %, 99.9 %, and 2.4 %
of the first Brillouin zone, respectively. The conduction electron effective
masses were found to be: $\mu_{\alpha} = (4.7 \pm 0.2)$ m$_e$, $\mu_{\beta} =
(8.0 \pm 1.0)$ m$_e$, and $\mu_{\gamma} = (2.0 \pm 0.2)$ m$_e$. The observation
of a $\gamma$ orbit is not expected from band structure calculations,
$\mu_{\beta}$ is among the heaviest masses ever reported for an organic
conductor. The observed Yamaji-like AMRO indicates a 2-D closed FS, warped
along the $k_z$ direction.

###Transverse and in-plane modification of superconductivity and electronic structure in the quasi-two dimensional organic conductor $κ $--(BEDT-TTF)$_{2}$Cu(SCN)$_{2}$ by uniaxial stress|E. S. Choi,J. S. Brooks,S. Y. Han,L. Balicas,J. S. Qualls###

Transverse and in-plane modification of superconductivity and electronic structure in the quasi-two dimensional organic conductor $κ $--(BEDT-TTF)$_{2}$Cu(SCN)$_{2}$ by uniaxial stress. We have employed uniaxial stress along the principal axes of the quasi-two
dimensional organic superconductor $\kappa $--(BEDT-TTF)$_{2}$Cu(SCN)$_{2}$.
The lattice anisotropy is thereby altered, with corresponding changes in the
intermolecular transfer energies. The effect of uniaxial stress on the
superconducting transition temperature $T_{c}$ and critical field $B_{c2}$ is
found to be anisotropic.There is an indication of an increase in $T_{c}$ and
$B_{c2}$ for in-plane stress, but both parameters decrease rapidly for
transverse (inter-plane) stress. Magnetotransport studies reveal stress-induced
changes in the Fermi surface through the observation of the Shubnikov de Haas
oscillations. The stress dependence of a resistive anomaly in the
magnetoresistance, which is associated with the critical field $B_{c2}$, is
also investigated. We discuss the experimental findings in the context of
recent phenomenological and theoretical treatments of quasi-two dimensional
systems where the anisotropic triangular lattice Hubbard model has been used to
treat two-dimensional superconductors.

###Leaky interface phonons in AlGaAs/GaAs structures|I. V. Ponomarev,A. L. Efros###

Leaky interface phonons in AlGaAs/GaAs structures. A dispersion equation for the interface waves has been derived for the
interface of two cubic crystals in the plane perpendicular to [001]. A
reasonable hypothesis has been made about the total number of the acoustic
modes. Due to this hypothesis the number is 64, but not all of the modes have
physical meaning of the interface waves. The rules have been worked out to
select physical branches among all 64 roots of dispersion equation. The
physical meaning of leaky interface waves is discussed. The calculations have
been made for the interface Al$_{0.3}$Ga$_{0.7}$As/GaAs. In this case all
physical interface modes have been shown to be leaky. The velocities of the
interface waves are calculated as a function of an angle in the plane of
interface. The results support a recent interpretation of a new type
oscillations of magnetoresistance as a resonant scattering of two-dimensional
electron gas by the leaky interface phonons.

###Spin effects in ferromagnetic single-electron transistors|J. Barnas,J. Martinek,G. Michalek,B. R. Bulka,A. Fert###

Spin effects in ferromagnetic single-electron transistors. Electron tunneling in ferromagnetic single-electron transistors is considered
theoretically in the sequential tunneling regime. A new formalism is developed,
which operates in a two-dimensional space of states, instead of one-dimensiona
space used in the spinless case. It is shown that spin fluctuations can be
significantly larger than the charge fluctuations. The influence of discrete
energy spectrum of a small central electrode on tunneling current, charge and
spin accumulation, charge and spin fluctuations, and on tunnel
magnetoresistance is analyzed in details. Two different scales are found in the
bias dependence of the basic transport characteristics; the shorter one
originates from the discrete energy spectrum and the longer one from discrete
charging of the central electrode. The features due to discrete spectrum and
discrete charging disappear at high temperatures.

###Formation of two-dimensional weak localization in conducting Langmuir-Blodgett films|Yasuo Ishizaki,Mitsuru Izumi,Hitoshi Ohnuki,Krystyna Kalita-Lipinska,Tatsuro Imakubo,Keiji Kobayashi###

Formation of two-dimensional weak localization in conducting Langmuir-Blodgett films. We report the magnetotransport properties up to 7 T in the organic highly
conducting Langmuir-Blodgett(LB) films formed by a molecular association of the
electroactive donor molecule bis(ethylendioxy)tetrathiafulvalene (BEDO-TTF) and
stearic acid CH$_3$(CH$_2$)$_{16}$COOH. We show the logarithmic decrease of dc
conductivity and the negative transverse magnetoresistance at low temperature.
They are interpreted in the weak localization of two-dimensional (2D)
electronic system based on the homogeneous conducting layer with the molecular
size thickness of BEDO-TTF. The electronic length with phase memory is given at
the mesoscopic scale, which provides for the first time evidence of the 2D
coherent charge transport in the conducting LB films.

###The origin of high transport spin polarization in La$_{0.7}$Sr$_{0.3} $MnO$_{3}$: direct evidence for minority spin states|B. Nadgorny,I. I. Mazin,M. Osofsky,R. J. Soulen, Jr.,P. Broussard,R. M. Stroud,D. J. Singh,V. G. Harris,A. Arsenov,Ya. Mukovskii###

The origin of high transport spin polarization in La$_{0.7}$Sr$_{0.3} $MnO$_{3}$: direct evidence for minority spin states. Using the point contact Andreev reflection technique, we have carried out a
systematic study of the spin polarization in the colossal magnetoresistive
manganite, La$_{0.7}$Sr$_{0.3}$MnO$_{3}$} (LSMO). Surprisingly, we observed a
significant increase in the current spin polarization with the residual
resistivity. This counterintuitive trend can be understood as a transition from
ballistic to diffusive transport in the contact. Our results strongly suggest
that LSMO does have minority spin states at the Fermi level. However, since its
current spin polarization is much higher than that of the density of states,
this material can mimic the behavior of a true half-metal in transport
experiments. Based on our results we call this material a {\it transport}
half-metal.

###Magnetization reversal triggered by spin injection in magnetic nanowires|J. -E. Wegrowe,D. Kelly,Ph. Guittienne,J-Ph. Ansermet###

Magnetization reversal triggered by spin injection in magnetic nanowires. It is shown that a pulsed current driven through Ni nanowires provokes an
irreversible magnetization reversal at a field distant from the spontaneous
switching field $H_{sw}$ by $\Delta H$ of as much as 40 % of $H_{sw}$. The
state of the magnetization is assessed by magnetoresistive measurements carried
out on single, isolated nanowires. The reversible part of the magnetization
follows that of a uniform rotation. The switching occurs between the two states
accessible otherwise by normal field ramping. $\Delta H$ is studied as a
function of the angle between the applied field and the wire, and also of the
direction of the pulsed current. The results are interpreted in terms of
spin-flip transfer from the spin-polarized current to the magnetization, while
the switching is approximated by a curling reversal mode.

###Magneto-electronic Properties of a Ferrimagnetic Semiconductor: The Hybrid Cupromanganite CaCu3Mn4O12|Ruben Weht,Warren E. Pickett###

Magneto-electronic Properties of a Ferrimagnetic Semiconductor: The Hybrid Cupromanganite CaCu3Mn4O12. The mixed manganite-cuprate CaCu3Mn4O12 is found, using density functional
methods, to be a narrow gap (90 meV calculated) ferrimagnetic semiconductor. Cu
(formally S=1/2) antialigns with Mn (formally S=3/2), and the net spin moment
is 9 \mu_B consistent with the formal spins. Holes have Cu d_{xy}-O p_{\sigma}
(i.e. antibonding dp\sigma) character with spins aligned antiparallel to the
net magnetization; electrons have the opposite spin and have mixed Cu d_{xy} -
Mn e_g character. Thermally excited electrons and holes will each be fully spin
polarized, but in opposite directions. The properties of this material are
strongly tied to the distorted quadruple perovskite structure, which is closely
related to the skutterudite structure. The observed resistivity,
magnetoresistance, and magnetization are discussed in terms of our results.

###Probing interactions in mesoscopic gold wires|F. Pierre,H. Pothier,D. Esteve,M. H. Devoret,A. B. Gougam,N. O. Birge###

Probing interactions in mesoscopic gold wires. We have measured in gold wires the energy exchange rate between
quasiparticles, the phase coherence time of quasiparticles and the resistance
vs. temperature, in order to probe the interaction processes which are relevant
at low temperatures. We find that the energy exchange rate is higher than
expected from the theory of electron-electron interactions, and that it has a
different energy dependence. The dephasing time is constant at temperatures
between 8 K and 0.5 K, and it increases below 0.5 K. The magnetoresistance is
negative at large field scales, and the resistance decreases logarithmically
with increasing temperatures, indicating the presence of magnetic impurities,
probably Fe. Whereas resistivity and phase coherence measurements can be
attributed to magnetic impurities, the question is raised whether these
magnetic impurities could also mediate energy exchanges between quasiparticles.

###Doped magnetic moments in a disordered electron system: insulator-metal transition, spin glass and `cmr'|Sanjeev Kumar,Pinaki Majumdar###

Doped magnetic moments in a disordered electron system: insulator-metal transition, spin glass and `cmr'. Recent experiments on the amorphous magnetic semiconductor Gd_x Si_{1-x},
Phys. Rev. Lett. 77, 4652 (1996), ibid 83, 2266 (1999), ibid 84, 5411 (2000),
ibid 85, 848 (2000), have revealed an insulator-metal transition (i-m-t), as a
function of doping and magnetic field, a spin glass state at low temperature,
and colossal magnetoresistance close to the i-m-t. There are also signatures of
strong electron-electron interaction close to the i-m-t. Motivated by these
results we examine the role of doped magnetic moments in a strongly disordered
electron system. In this paper we study a model of electrons coupled to
structural disorder and (classical) magnetic moments, through an essentially
exact combination of spin Monte Carlo and fermion exact diagonalisation. Our
preliminary results, ignoring electron-electron interactions, highlights the
interplay of structural and magnetic `disorder' which is primarily responsible
for the observed features in magnetism and transport.

###Stress-induced metallic behavior under magnetic field in Pr$_{1-x}$Ca$_{x}$MnO$_{3}$ (x = 0.5 and 0.4) thin films|W. Prellier,Ch. Simon,B. Mercey,M. Hervieu,A. M. Haghiri-Gosnet,D. Saurel,Ph. Lecoeur,B. Raveau###

Stress-induced metallic behavior under magnetic field in Pr$_{1-x}$Ca$_{x}$MnO$_{3}$ (x = 0.5 and 0.4) thin films. We have investigated the role of the stress-induced by the presence of the
substrate in thin films of colossal magnetoresistive manganites on structural,
resistive and magnetic properties. Because of the strong coupling between the
small structural distortions related to the charge-ordering (CO) and the
resistive properties, the presence of the substrate prevents the full
developpement of the charge ordering in Pr$_{0.5}$Ca$_{0.5}$MnO$_{3}$,
especially in the very thin films. For thicker films, the CO state exists, but
is not fully developped. Correlatively, the magnetic field which is necessary
to suppress the CO is decreased drastically from 25 Tesla to about 5 Tesla on
SrTiO$_{3}$ substrates. We have also investigated the influence of the doping
level by studying the case of Pr$_{0.6}$Ca$_{0.4}$MnO$_{3}$.

###Effect of the In-Plane Magnetic Field on Conduction of the Si-inversion Layer: Magnetic Field Driven Disorder|V. M. Pudalov,G. Brunthaler,A. Prinz,G. Bauer###

Effect of the In-Plane Magnetic Field on Conduction of the Si-inversion Layer: Magnetic Field Driven Disorder. We compare the effects of temperature, disorder and parallel magnetic field
on the metallic-like temperature dependence of the resistivity. We found a
similarity between the effects of disorder and parallel field: the parallel
field weakens the metallic-like conduction in high mobility samples and make it
similar to that for low-mobility samples. We found a smooth continuous effect
of the in-plane field on conduction, without any threshold. While conduction
remains non-activated, the parallel magnetic field restores the same
resistivity value as the high temperature does. This matching sets substantial
constraints on the choice of the theoretical models developed to explain the
mechanism of the metallic conduction and parallel field magnetoresistance in 2D
carrier systems. We demonstrate that the data for magneto- and temperature
dependence of the resistivity of Si-MOS samples in parallel field may be well
described by a simple model of the magnetic field dependent disorder.

###Critical Phenomena of Ferromagnetic Transition in Double-Exchange Systems|Yukitoshi Motome,Nobuo Furukawa###

Critical Phenomena of Ferromagnetic Transition in Double-Exchange Systems. Critical phenomena of ferromagnetic transition at finite temperatures are
studied in double-exchange systems. In order to investigate strong interplay
between charge and spin degrees of freedom, Monte Carlo technique is applied to
include fluctuations in a controlled and unbiased manner. By using finite-size
scaling analysis, critical exponents and transition temperature are estimated
for a model with Ising spin symmetry in two dimensions. The obtained exponents
are far distinct from the mean-field values, but consistent with those of spin
models with short-range exchange interactions. The universality class of this
transition belongs to that of short-range interaction with the same spin
symmetry. We also discuss the case for three dimensions. The results are
compared with experimental results in perovskite manganites which show colossal
magnetoresistance.

###Transport and magnetic anisotropy in CMR thin film La_{1-x}Ca_{x}MnO_{3} (x \approx 1/3) induced by a film-substrate interaction|B. I. Belevtsev,V. B. Krasovitsky,D. G. Naugle,K. D. D. Rathnayaka,A. Parasiris,S. R. Surthi,R. K. Pandey,M. A. Rom###

Transport and magnetic anisotropy in CMR thin film La_{1-x}Ca_{x}MnO_{3} (x \approx 1/3) induced by a film-substrate interaction. We present a study of anisotropy of transport and magnetic properties in
La_{1-x}Ca_{x}MnO_{3} (x \approx 1/3) film prepared by pulsed-laser deposition
onto a LaAlO_{3} sunstrate. We found a non-monotonic dependence of
magnetoresistance (MR) on magnetic field H for both H perpendicular and
parallel to the film plane but perpendicular to the current. This rather
complex behavior of MR manifests itself at low temperatures, far below the
Curie temperature. Two main sources of MR anisotropy have been considered in
the explanantion of the results: (1) the existence of preferential directions
of magnetization (due to strains stemming from the lattice film-substrate
mismatch or other reasons); (2) dependence of resistance on the angle between
current and the magnetization, which is inherent in ferromagnets.

###Superconducting properties and Fermi-surface topology of the quasi-two-dimensional organic superconductor $λ$-(BETS)$_{2}$GaCl$_{4}$|Charles Mielke,John Singleton,Moon-Sun Nam,Neil Harrison,C. C. Agosta,B. Fravel,L. K. Montgomery###

Superconducting properties and Fermi-surface topology of the quasi-two-dimensional organic superconductor $λ$-(BETS)$_{2}$GaCl$_{4}$. The Fermi surface topology of the organic superconductor \lbets has been
determined using the Shubnikov-de Haas and magnetic breakdown effects and
angle-dependent magnetoresistance oscillations. The former experiments were
carried out in pulsed fields of up to 60 T, whereas the latter employed
quasistatic fields of up to 30 T. All of these data show that the Fermi-surface
topology of \lbets is very similar to that of the most heavily-studied organic
superconductor, \cuscn, except in one important respect; the interplane
transfer integral in \lbets is a factor $\sim 10$ larger than that in \cuscn .
The increased three-dimensionality of \lbets is manifested in radiofrequency
penetration-depth measurements, which show a clear dimensional crossover in the
behaviour of $H_{c2}(T)$. The radiofrequency measurements have also been used
to extract the Labusch parameter determining the fluxoid interactions as a
function of temperature, and to map the flux-lattice melting curve.

###Magnetoresistance of proximity coupled Au wires|D. A. Dikin,M. J. Black,V. Chandrasekhar###

Magnetoresistance of proximity coupled Au wires. We report measurements of the magnetoresistance (MR) of narrow Au wires
coupled to a superconducting Al contact on one end, and a normal Au contact on
the other. The MR at low magnetic field $B$ is quadratic in $B$, with a
characteristic field scale $B_c$ determined by phase coherent paths which
encompass not only the wire, but also the two contacts. $B_c$ is essentially
temperature independent at low temperatures, indicating that the area of the
phase coherent paths is not determined by the superconducting coherence length
$L_T$ in the normal metal, which is strongly temperature dependent at low
temperatures. We identify the relevant length scale as a combination of the
electron phase coherence length $L_\phi$ in the normal metal and the coherence
length $\xi_S$ in the superconductor.

###Valley Splitting in Si-Inversion Layers at Low Magnetic Fields|V. M. Pudalov,A. Punnoose,G. Brunthaler,A. Prinz,G. Bauer###

Valley Splitting in Si-Inversion Layers at Low Magnetic Fields. We report novel manifestation of the valley splitting for the two valley
electron system in (100) Si-inversion layers at low carrier density. We found
that valley splitting causes almost 100% modulation of the Shubnikov de Haas
oscillations in very low magnetic fields, almost on the bound of the quantum
interference peak of the negative magnetoresistance. From the interference
pattern of oscillations we determined the valley splitting in the B=0 limit
which appears to vary only within a factor of 1.3 over the density range
(3-7)x10^{11}/cm^2. We found also that level broadenings in both electron
valleys differ only by < 3%. The latter result shows that the inter-valley
scattering is not responsible for the strong (six fold) `metallic-like' changes
of the resistivity with temperature.

###Magnetic phase separation in ordered alloys|Jordi Marcos,Eduard Vives,Teresa Castan###

Magnetic phase separation in ordered alloys. We present a lattice model to study the equilibrium phase diagram of ordered
alloys with one magnetic component that exhibits a low temperature phase
separation between paramagnetic and ferromagnetic phases. The model is
constructed from the experimental facts observed in Cu$_{3-x}$AlMn$_{x}$ and it
includes coupling between configurational and magnetic degrees of freedom which
are appropriated for reproducing the low temperature miscibility gap. The
essential ingredient for the occurrence of such a coexistence region is the
development of ferromagnetic order induced by the long-range atomic order of
the magnetic component. A comparative study of both mean-field and Monte Carlo
solutions is presented. Moreover, the model may enable the study of the
structure of the ferromagnetic domains embedded in the non-magnetic matrix.
This is relevant in relation to phenomena such as magnetoresistance and
paramagnetism.

###Theoretical Description of Resistive Behavior near a Quantum Vortex-Glass Transition|Hideharu Ishida,Ryusuke Ikeda###

Theoretical Description of Resistive Behavior near a Quantum Vortex-Glass Transition. Resistive behaviors at nonzero temperatures (T > 0) reflecting a quantum
vortex-glass (VG) transition (the so-called field-tuned
superconductor-insulator transition at T=0) are studied based on a quantum
Ginzburg-Landau (GL) action for a s-wave pairing case containing microscopic
details. The ordinary dissipative dynamics of the pair-field is assumed on the
basis of a consistency between the fluctuation conductance terms excluded from
GL approach and an observed negative magnetoresistance. It is shown that the VG
contribution, G_{vg}(B=B_{vg}, T \to 0),to 2D fluctuation conductance at the VG
transition field B_{vg} depends on the strength of a repulsive-interaction
between electrons and takes a universal value only in the ordinary dirty limit
neglecting the electron-repulsion. Available resistivity data near B_{vg} are
discussed based on our results, and extensions to the cases of a d-wave pairing
and of 3D systems are briefly commented on.

###Spin-density-wave transition of (TMTSF)$_2$PF$_6$ at high magnetic fields|N. Matsunaga,K. Yamashita,H. Kotani,K. Nomura,T. Sasaki,T. Hanajiri,J. Yamada,S. Nakatsuji,H. Anzai###

Spin-density-wave transition of (TMTSF)$_2$PF$_6$ at high magnetic fields. The transverse magnetoresistance of the Bechgaard salt (TMTSF)$_2$PF$_6$ has
been measured for various pressures, with the field up to 24 T parallel to the
lowest conductivity direction c$^{\ast}$. A quadratic behavior is observed in
the magnetic field dependence of the spin-density-wave (SDW) transition
temperature $T_{\rm {SDW}}$. With increasing pressure, $T_{\rm {SDW}}$
decreases and the coefficient of the quadratic term increases. These results
are consistent with the prediction of the mean-field theory based on the
nesting of the quasi one-dimensional Fermi surface. Using a mean field theory,
$T_{\rm {SDW}}$ for the perfect nesting case is estimated as about 16 K. This
means that even at ambient pressure where $T_{\rm {SDW}}$ is 12 K, the SDW
phase of (TMTSF)$_2$PF$_6$ is substantially suppressed by the
two-dimensionality of the system.

###Magnetism and Transport for Two-Dimensional Electrons : Absence of Stoner Ferromagnetism and Positive In-Plane Magnetoresistance in the Metallic Phase|Philippe Jacquod###

Magnetism and Transport for Two-Dimensional Electrons : Absence of Stoner Ferromagnetism and Positive In-Plane Magnetoresistance in the Metallic Phase. We calculate the interaction kernel K for two-dimensional diffusive
electrons. The screening of the Coulomb interaction together with the Fermi
statistics induces a spin selection rule for electron-electron scattering so
that in leading order in the inverse conductance only pairs of electrons with
antiparallel spins do scatter. At low temperature, this results in a larger
coherence length for fully polarized electrons and thus in a positive in-plane
magnetoresistance. An applied in-plane magnetic field also induces a
nonmonotonous behavior of K at finite temperature. Alternatively, the vanishing
of the scattering in the triplet channel strongly reduces ferromagnetism deep
in the metallic regime. These effects weaken as the density of charge carriers
is reduced.

###Hopping conductivity in heavily doped n-type GaAs layers in the quantum Hall effect regime|S. S. Murzin,M. Weiss,A. G. M. Jansen,K. Eberl###

Hopping conductivity in heavily doped n-type GaAs layers in the quantum Hall effect regime. We investigate the magnetoresistance of epitaxially grown, heavily doped
n-type GaAs layers with thickness (40-50 nm) larger than the electronic mean
free path (23 nm). The temperature dependence of the dissipative resistance
R_{xx} in the quantum Hall effect regime can be well described by a hopping law
(R_{xx} \propto exp{-(T_0/T)^p}) with p=0.6. We discuss this result in terms of
variable range hopping in a Coulomb gap together with a dependence of the
electron localization length on the energy in the gap. The value of the
exponent p>0.5 shows that electron-electron interactions have to be taken into
account in order to explain the occurrence of the quantum Hall effect in these
samples, which have a three-dimensional single electron density of states.

###Control of the colossal magnetoresistance by strain effect in Nd$_{0.5}$Ca$_{0.5}$MnO$_{3}$ thin films|E. Rauwel-Buzin,W. Prellier,Ch. Simon,S. Mercone,B. Mercey,B. Raveau,J. Sebek,J. Hejtmanek###

Control of the colossal magnetoresistance by strain effect in Nd$_{0.5}$Ca$_{0.5}$MnO$_{3}$ thin films. Thin films of Nd$_{0.5}$Ca$_{0.5}$MnO$_{3}$ manganites with colossal
magnetoresistance (CMR) properties have been synthesized by the Pulsed Laser
Deposition technique on (100)-SrTiO$_{3}$. The lattice parameters of these
manganites and correlatively their CMR properties can be controlled by the
substrate temperature $T_{S}$. The maximum CMR effect at 75K, calculated as the
ratio $\rho (H=0T)/\rho (H=7T)$ is 10$^4$ for a deposition temperature of
$T_{S}=680$ degC. Structural studies show that the
Nd$_{0.5}$Ca$_{0.5}$MnO$_{3}$ film is single phase, [010]-oriented and has a
pseudocubic symmetry of the perovskite subcell with a=3.77$\AA$ at room
temperature. We suggest that correlation between lattice parameters, CMR and
substrate temperature $T_{S}$ result mainly from substrate-induced strains
which can weaken the charge-ordered state at low temperature.

###Fermi Surface Nesting and Nanoscale Fluctuating Charge/Orbital Ordering in Colossal Magnetoresistive Oxides|Y. -D. Chuang,A. D. Gromko,D. S. Dessau,T. Kimura,Y. Tokura###

Fermi Surface Nesting and Nanoscale Fluctuating Charge/Orbital Ordering in Colossal Magnetoresistive Oxides. We used high resolution angle-resolved photoemission spectroscopy to reveal
the Fermi surface and key transport parameters of the metallic state of the
layered Colossal Magnetoresistive (CMR) oxide La1.2Sr1.8Mn2O7. With these
parameters the calculated in-plane conductivity is nearly one order of
magnitude larger than the measured DC conductivity. This discrepancy can be
accounted for by including the pseudogap which removes at least 90% of the
spectral weight at the Fermi energy. Key to the pseudogap and many other
properties are the parallel straight Fermi surface sections which are highly
susceptible to nesting instabilities. These nesting instabilities produce
nanoscale fluctuating charge/orbital modulations which cooperate with
Jahn-Teller distortions and compete with the electron itinerancy favored by
double exchange.

###Exchange Bias Theory: a Review|Miguel Kiwi###

Exchange Bias Theory: a Review. Research on the exchange bias (EB) phenomenon has witnessed a flurry of
activity during recent years, which stems from its use in magnetic sensors and
as stabilizers in magnetic reading heads. EB was discovered in 1956 but it
attracted only limited attention until these applications, closely related to
giant magnetoresistance, were developed during the last decade. In this review
I first give a short introduction, listing the most salient experimental
results and what is required from an EB theory. Next, I indicate some of the
obstacles in the road towards a satisfactory understanding of the phenomenon.
The main body of the text reviews and critically discusses the activity that
has flourished, mainly during the last five years, in the theoretical front.
Finally, an evaluation of the progress made, and a critical assessment as to
where we stand nowadays along the road to a satisfactory theory, is presented.

###Current and Spin-Torque in Double Tunnel Barrier Ferromagnet - Superconductor - Ferromagnet Systems|Yaroslav Tserkovnyak,Arne Brataas###

Current and Spin-Torque in Double Tunnel Barrier Ferromagnet - Superconductor - Ferromagnet Systems. We calculate the current and the spin-torque in small symmetric double tunnel
barrier ferromagnet - superconductor - ferromagnet (F-S-F) systems.
Spin-accumulation on the superconductor governs the transport properties when
the spin-flip relaxation time is longer than the transport dwell time. In the
elastic transport regime, it is demonstrated that the relative change in the
current (spin-torque) for F-S-F systems equals the relative change in the
current (spin-torque) for F-N-F systems upon changing the relative
magnetization direction of the two ferromagnets. This differs from the results
in the inelastic transport regime where spin-accumulation suppresses the
superconducting gap and dramatically changes the magnetoresistance [S.
Takahashi, H. Imamura, and S. Maekawa, Phys. Rev. Lett. 82, 3911 (1999)]. The
experimental relevance of the elastic and inelastic transport regimes,
respectively, as well as the reasons for the change in the transport properties
are discussed.

###Quantum criticality, particle-hole symmetry, and duality of the plateau-insulator transition in the quantum Hall regime|A. M. M. Pruisken,D. T. N. de Lang,L. A. Ponomarenko,A. de Visser###

Quantum criticality, particle-hole symmetry, and duality of the plateau-insulator transition in the quantum Hall regime. We report new experimental data on the plateau-insulator transition in the
quantum Hall regime, taken from a low mobility InGaAs/InP heterostructure. By
employing the fundamental symmetries of the quantum transport problem we are
able to disentangle the universal quantum critical aspects of the
magnetoresistance data (critical indices and scaling functions) and the sample
dependent aspects due to macroscopic inhomogeneities. Our new results and
methodology indicate that the previously established experimental value for the
critical index (kappa = 0.42) resulted from an admixture of both universal and
sample dependent behavior. A novel, non-Fermi liquid value is found (kappa =
0.57) along with the leading corrections to scaling. The statement of
self-duality under the Chern Simons flux attachment transformation is verified.

###Enhancement of the electronic contribution to the low temperature specific heat of Fe/Cr magnetic multilayer|B. Revaz,M. -C. Cyrille,B. Zink,Ivan K. Schuller,F. Hellman###

Enhancement of the electronic contribution to the low temperature specific heat of Fe/Cr magnetic multilayer. We measured the low temperature specific heat of a sputtered
$(Fe_{23\AA}/Cr_{12\AA})_{33}$ magnetic multilayer, as well as separate
$1000\AA$ thick Fe and Cr films. Magnetoresistance and magnetization
measurements on the multilayer demonstrated antiparallel coupling between the
Fe layers. Using microcalorimeters made in our group, we measured the specific
heat for $4<T<30 K$ and in magnetic fields up to $8 T$ for the multilayer. The
low temperature electronic specific heat coefficient of the multilayer in the
temperature range $4<T<14 K$ is $\gamma_{ML}=8.4 mJ/K^{2}g-at$. This is
significantly larger than that measured for the Fe or Cr films (5.4 and $3.5
mJ/K^{2}mol$ respectively). No magnetic field dependence of $\gamma_{ML}$ was
observed up to $8 T$. These results can be explained by a softening of the
phonon modes observed in the same data and the presence of an Fe-Cr alloy phase
at the interfaces.

###Magnetotransport and the upper critical magnetic field in MgB2|P. Szabo,P. Samuely,A. G. M. Jansen,T. Klein,J. Marcus,D. Fruchart,S. Miraglia###

Magnetotransport and the upper critical magnetic field in MgB2. Magnetotransport measurements are presented on polycrystalline MgB2 samples.
The resistive upper critical magnetic field reveals a temperature dependence
with a positive curvature from Tc = 39.3 K down to about 20 K, then changes to
a slightly negative curvature reaching 25 T at 1.5 K. The 25- Tesla upper
critical field is much higher than what is known so far on polycrystals of MgB2
but it is in agreement with recent data obtained on epitaxial MgB2 films. The
deviation of Bc2(T) from standard BCS might be due to the proposed two-gap
superconductivity in this compound. The observed quadratic normal-state
magnetoresistance with validity of Kohler's rule can be ascribed to classical
trajectory effects in the low-field limit.

###Magnetotransport Properties of Antiferromagnetic YBa_2Cu_3O_6.25 Single Crystals|E. Cimpoiasu,C. C. Almasan,A. P. Paulikas,B. W. Veal###

Magnetotransport Properties of Antiferromagnetic YBa_2Cu_3O_6.25 Single Crystals. In-plane and out-of-plane magnetoresistivities (MR) of antiferromagnetic
YBa_2Cu_3O_6.25 single crystals were measured in magnetic fields H applied
along the (ab) plane. In-plane MR is a superposition of two components: The
first component is strongly in-plane anisotropic, changing sign from negative
when H is parallel to the electrical current I to positive when H is
perpendicular to I. The second component is positive, quadratic in H, and
isotropic in the (ab)-plane. The out-of-plane MR displays a fourfold symmetry
upon in-plane rotation of the magnetic field, with maxima along the easy axes
of antiferromagnetic spin ordering and minima along unfavorable directions of
spin orientation (45 degrees from the Cu-O-Cu bonds).

###Ferromagnetic Domain Walls in finite systems: mean-field critical exponents and applications|B. Uchoa,G. G. Cabrera###

Ferromagnetic Domain Walls in finite systems: mean-field critical exponents and applications. The distribution of magnetic moments in finite ferromagnetic bodies was first
investigated by Landau and Lifshitz in a famous paper [\textit{Phys. Z. Soviet
Union}, \textbf{8}, 153 (1935)], where they obtained the domain structure of a
ferromagnetic crystal at low temperatures, in the regime of saturated
magnetization. In this article, we investigate the general properties of
ferromagnetic domain walls of uniaxial crystals from the view point of the
Landau free energy. We present the basic ideas at an introductory level, for
non-experts. Extending the formalism to the vicinity of the Curie temperature,
where a general qualitative description by the Landau theory of phase
transitions can be applied, we find that domain walls tend to suppress the
layers, leading to a continuous vanishing of the domain structure with
anomalous critical exponents. In the saturated regime, we discuss the role of
domain walls in mesoscopic systems and ferromagnetic nanojunctions, relating
the observed magnetoresistance with promising applications in the recent area
of spintronics.

###Magnetic and transport properties of the new antiferromagnetic Kondo-lattice CeNiBi2|M. H. Jung,A. H. Lacerda,T. Takabatake###

Magnetic and transport properties of the new antiferromagnetic Kondo-lattice CeNiBi2. We report results of the first studies on the magnetic and transport
properties of a new material CeNiBi_2. The magnetic susceptibility exhibits a
sharp peak at T_N = 6K, indicating an antiferromagnetic phase transition. This
antiferromagnetic order below T_N is confirmed by magnetization measurement,
which displays a metamagnetic-like transition at H_m = 5 T. Both
low-temperature susceptibility and high-field magnetization are suggestive of
strong crystalline-electric-field effect in CeNiBi_2. The electrical
resistivity shows the presence of Kondo and crystal-field effects with a sharp
drop below TN due to the antiferromagnetic ordering. This sharp drop below T_N
in the electrical resistivity is suppressed slightly to higher temperatures by
an applied magnetic field to 18 T. With increasing magnetic field, the slope of
magnetoresistance changes from positive to negative, being indicative of the
transition to a ferromagnetic state.

###Observation of large anisotropy in c-axis oriented thin films of MgB$_{2}$ prepared by an in situ pulsed laser deposition process|S. R. Shinde,S. B. Ogale,A. Biswas,R. L. Greene,T. Venkatesan###

Observation of large anisotropy in c-axis oriented thin films of MgB$_{2}$ prepared by an in situ pulsed laser deposition process. A large anisotropy in the upper critical field (H$_{C2}$) is observed for
MgB$_{2}$ films grown in situ by a pulsed laser deposition process involving
growth and annealing of Mg and B multilayers. Measurements of resistivity as a
function of temperature and magnetic field yield the estimated zero temperature
values of H$_{C2}$ in the range 100 to 130 T and about 10 T, for the field in
ab plane and along c axis, respectively, depending on the criterion chosen for
the transition temperature. The corresponding anisotropy parameter is thus in
the range 9 to 13. The estimated coherence length in ab plane is about 50
\r{A}, whereas that in the c direction is much smaller (\approx 5 \r{A}). No
significant magnetoresistance is observed in the normal state.

###First order transition and phase separation in pyrochlores with colossal-magnetoresistance|P. Velasco,J. Mira,F. Guinea,J. Rivas,M. J. Martinez-Lope,J. A. Alonso,J. L. Martinez###

First order transition and phase separation in pyrochlores with colossal-magnetoresistance. Tl$_{2}$Mn$_{2}$O$_{7}$ pyrochlores present colossal magnetoresistance (CMR)
around the long range ferromagnetic ordering temperature (T$_{C}$). The
character of this magnetic phase transition has been determined to be first
order, by purely magnetic methods, in contrast to the second order character
previously reported by Zhao et al. (Phys. Rev. Lett. 83, 219 (1999)). The
highest CMR effect, as in Tl$_{1.8}$Cd$_{0.2}$Mn$_{2}$O$_{7}$, corresponds to a
stronger first order character. This character implies a second type of
magnetic interaction, besides the direct superexchange between the Mn$^{4+}$
ions, as well as a phase coexistence. A model is proposed, with a complete
Hamiltonian (including superexchange and an indirect interaction), which
reproduce the observed phenomenology.

###Extrinsic Magnetotransport Phenomena in Ferromagnetic Oxides|Michael Ziese###

Extrinsic Magnetotransport Phenomena in Ferromagnetic Oxides. This review is focused on extrinsic magnetotransport effects in ferromagnetic
oxides. It consists of two parts; the second part is devoted to an overview of
experimental data and theoretical models for extrinsic magnetotransport
phenomena. Here a critical discussion of domain-wall scattering is given.
Results on surfacial and interfacial magnetism in oxides are presented.
Spin-polarized tunnelling in ferromagnetic junctions is reviewed and
grain-boundary magnetoresistance is interpreted within a model of
spin-polarized tunnelling through natural oxide barriers. The situation in
ferromagnetic oxides is compared with data and models for conventional
ferromagnets. The first part of the review summarizes basic material
properties, especially data on the spin-polarization and evidence for
half-metallicity. Furthermore, intrinsic conduction mechanisms are discussed.
An outlook on the further development of oxide spin-electronics concludes this
review.

###Quantum Effects in the Conductivity of a Quasi 2D Electron Gas|M. Levanda,V. Fleurov###

Quantum Effects in the Conductivity of a Quasi 2D Electron Gas. We consider the role of the third dimension in the conductivity of a quasi 2D
electron gas. If the transverse correlation radius of the scattering potential
is smaller than the width of the channel, i.e. the width of the transverse
electron density distribution, then scattering to higher levels of the
confinement potential becomes important, which causes a broadening of the
current flow profile. The resulting conductivity is larger than that obtained
from a 2D Boltzmann equation. A magnetic field, parallel to the driving
electric field, effectively competes with the confining potential and, in the
limit of a strong magnetic field, it is the field, which largely shapes the
electron and current profile, rather than the potential. As a result the
current flow profile increases and a negative longitudinal magnetoresistivity
of the quasi 2D electron gas may be observed.

###Common features of nanoscale structural correlations in magnetoresistive manganites with ferromagnetic low-temperature state|V. Kiryukhin,T. Y. Koo,A. Borissov,Y. J. Kim,C. S. Nelson,J. P. Hill,D. Gibbs,S-W. Cheong###

Common features of nanoscale structural correlations in magnetoresistive manganites with ferromagnetic low-temperature state. We report x-ray scattering studies of nanoscale structural correlations in
Nd$_{1-x}$Sr$_x$MnO$_3$ and La$_{1-x}$(Ca,Sr)$_x$MnO$_3$, $x$=0.2--0.5. We find
that the correlated regions possess a temperature-independent correlation
length of 2-3 lattice constants which is the same in all samples. The period of
the lattice modulation of the correlated regions is proportional to the Ca/Sr
doping concentration $x$. Remarkably, the lattice modulation periods of these
and several other manganites with a ferromagnetic ground state fall on the same
curve when plotted as a function of $x$. Thus, the structure of the correlated
regions in these materials appears to be determined by a single parameter, $x$.
We argue that these observations provide important clues for understanding the
Colossal Magnetoresistance phenomenon in manganites.

###First order transition from ferromagnetism to antiferromagnetism in Ce(Fe$_{0.96}$Al$_{0.04}$)$_2$: a magnetotransport study|Kanwal Jeet Singh,Sujeet Chaudhary,M. K. Chattopadhyay,M. A. Manekar,S. B. Roy,P. Chaddah###

First order transition from ferromagnetism to antiferromagnetism in Ce(Fe$_{0.96}$Al$_{0.04}$)$_2$: a magnetotransport study. The magnetotransport behaviour is investigated in detail across the first
order magnetic phase transition from ferromagnetic to antiferromagnetic state
in polycrystalline Ce(Fe$_{0.96}$Al$_{0.04}$)$_2$ sample. The study clearly
brings out various generic features associated with a first order transition,
viz., hysteresis, phase coexistence, supercooling and superheating, presence
and limits of the metastable regimes. These results of magnetotransport study
exhibit and support all the interesting thermomagnetic history effects that
were observed in our earlier dc-magnetisation study on the same sample. Most
notable here is the initial (or virgin) resistivity vs. field curve lying
outside the hysteretic "butterfly shaped" magnetoresistivity loops obtained on
cyclying the magnetic field between high enough positive and negative
strengths. These findings, bearing one-to-one similarity with the data obtained
in their magnetic counterpart (i.e., dc-magnetisation), have been ascribed an
origin due to the arresting of this first order transition kinetics at low
temperature and high magnetic field.

###Memory Effects in Electron Transport in Si Inversion Layers in the Dilute Regime: Individuality versus Universality|V. M. Pudalov,M. E. Gershenson,H. Kojima###

Memory Effects in Electron Transport in Si Inversion Layers in the Dilute Regime: Individuality versus Universality. In order to separate the universal and sample-specific effects in the
conductivity of high-mobility Si inversion layers, we studied the electron
transport in the same device after cooling it down to 4K at different fixed
values of the gate voltage V^{cool}. Different V^{cool} did not modify
significantly either the momentum relaxation rate or the strength of
electron-electron interactions. However, the temperature dependences of the
resistance and the magnetoresistance in parallel magnetic fields, measured in
the vicinity of the metal-insulator transition in 2D, carry a strong imprint of
individuality of the quenched disorder determined by V^{cool}. This
demonstrates that the observed transition between ``metallic'' and insulating
regimes involves both, universal effects of electron-electron interaction and
sample-specific effects. Far away from the transition, at lower carrier
densities and lower resistivities < 0.1 h/e^2, the transport and
magnetotransport become nearly universal.

###DC transport properties and microwave absorption in bulk ceramic sample and film of La_{0.5}Sr_{0.5}CoO_{3-δ}: magnetic inhomogeneity effects|B. I. Belevtsev,N. T. Cherpak,I. N. Chukanova,A. I. Gubin,V. B. Krasovitsky,A. A. Lavrinovich###

DC transport properties and microwave absorption in bulk ceramic sample and film of La_{0.5}Sr_{0.5}CoO_{3-δ}: magnetic inhomogeneity effects. The DC transport properties and microwave absorption (at 41 GHz) are measured
in a bulk ceramic sample and a film (220 nm thick) of
La$_{0.5}$Sr$_{0.5}$CoO$_{3-\delta}$. The samples are polycrystalline. The
microwave conductivity, which is related mainly to the intragrain conductivity,
increases by the order of the magnitude at the transition to the ferromagnetic
state. The increase is far greater than that of found in the known DC
measurements in doped cobaltates of the best crystal perfection. The found
microwave effect is attributed to inherent magnetically inhomogeneous state of
the doped cobaltates. Relaying on the results obtained it can be suggested that
rather low magnetoresistance in the doped cobaltates as compared with that of
the manganites is attributable to their more inhomogenenous magnetic state.

###Microwave properties of Nd_0.5Sr_0.5MnO_3: a key role of the (x^2-y^2)-orbital effects|S. Zvyagin,A. Angerhofer,K. V. Kamenev,L. -C. Brunel,G. Balakrishnan,D. McK. Paul###

Microwave properties of Nd_0.5Sr_0.5MnO_3: a key role of the (x^2-y^2)-orbital effects. Transmittance of the colossal magnetoresistive compound Nd_0.5Sr_0.5MnO_3
showing metal-insulator phase transition has been studied by means of the
submm- and mm-wavelength band spectroscopy. An unusually high transparency of
the material provided direct evidence for the significant suppression of the
coherent Drude weight in the ferromagnetic metallic state. Melting of the
A-type antiferromagnetic states has been found to be responsible for a
considerable increase in the microwave transmission, which was observed at the
transition from the insulating to the metallic phase induced by magnetic field
or temperature. This investigation confirmed a dominant role of the
(x^2-y^2)-orbital degree of freedom in the low-energy optical properties of
Nd_0.5Sr_0.5MnO_3 and other doped manganites with planar (x^2-y^2)-orbital
order, as predicted theoretically. The results are discussed in terms of the
orbital-liquid concept.

###Ferromagnetism and electron-phonon coupling in the manganites|D. M. Edwards###

Ferromagnetism and electron-phonon coupling in the manganites. The physics of ferromagnetic doped manganites, such as
\chem{La_{1-x}Ca_xMnO_3} with $x\approx0.2$--0.4, is reviewed. The concept of
double exchange is discussed within the general framework of itinerant electron
magnetism. The new feature in this context is the coupling of electrons to
local phonon modes. Emphasis is placed on the quantum nature of the phonons and
the link with polaron physics. However it is stressed that the manganites fall
in an intermediate coupling regime where standard small-polaron theory does not
apply. The recently-developed many-body coherent potential approximation is
able to deal with this situation and Green's recent application to the Holstein
double-exchange model is described. Issues addressed include the nature of the
basic electronic structure, the metal-insulator transition, a unification of
colossal magnetoresistance, pressure effects and the isotope effect, pseudogaps
in spectroscopy and the effect of electron-phonon coupling on spin waves.

###Non-volatile magnetoresistive memory in phase separated La$_{0.325}$Pr$_{0.300}$Ca$_{0.375}$MnO$_3$|P. Levy,F. Parisi,M. Quintero,L. Granja,J. Curiale,J. Sacanell,G. Leyva,G. Polla,R. S. Freitas,L. Ghivelder###

Non-volatile magnetoresistive memory in phase separated La$_{0.325}$Pr$_{0.300}$Ca$_{0.375}$MnO$_3$. We have measured magnetic and transport response on the polycrystalline
La$_{5/8-y}$Pr$_y$Ca$_{3/8}$MnO$_3$ ($y=0.30$, average grain size 2 microns)
compound. In the temperature range where ferromagnetic metallic and insulating
regions coexist we observed a persistent memory of low magnetic fields ($<$ 1
T) which is determined by the actual amount of the ferromagnetic phase. The
possibility to manipulate this fraction with relatively small external
perturbations is related to the phase separated nature of these manganese oxide
based compounds. The colossal magnetoresistance figures obtained (about 80%)
are determined by the fraction enlargement mechanism. Self-shielding of the
memory to external fields is found under certain described circumstances. We
show that this non-volatile memory has multilevel capability associated with
different applied low magnetic field values.

###Anisotropic Magnetoresistance in Ga$_{1-x}$Mn$_x$As|David V. Baxter,Dmitry Ruzmetov,Julia Scherschligt,Y. Sasaki,X. Liu,J. K. Furdyna,C. H. Mielke###

Anisotropic Magnetoresistance in Ga$_{1-x}$Mn$_x$As. We have measured the magnetoresistance in a series of Ga$_{1-x}$Mn$_x$As
samples with 0.033$\le x \le$ 0.053 for three mutually orthogonal orientations
of the applied magnetic field. The spontaneous resistivity anisotropy (SRA) in
these materials is negative (i.e. the sample resistance is higher when its
magnetization is perpendicular to the measuring current than when the two are
parallel) and has a magnitude on the order of 5% at temperatures near 10K and
below. This stands in contrast to the results for most conventional magnetic
materials where the SRA is considerably smaller in magnitude for those few
cases in which a negative sign is observed. The magnitude of the SRA drops from
its maximum at low temperatures to zero at T$_C$ in a manner that is consistent
with mean field theory. These results should provide a significant test for
emerging theories of transport in this new class of materials.

###Impurity and band effects competition on the appearence of Inverse Giant Magnetoresistence in Cu/Fe multilayers with Cr|J. Milano,A. M. Llois,L. B. Steren###

Impurity and band effects competition on the appearence of Inverse Giant Magnetoresistence in Cu/Fe multilayers with Cr. We have studied the dependence of impurity vs. band effects in the appearance
of inverse giant magnetoresistance (IGMR) in Cu/Fe superlattices whit Cr.
Current in plane (CIP) and current perpendicular to the plane (CPP) geometries
are considered. For the calculation of the conductivities we have used the
linearized Boltzmann equation in the relaxation time approximation. Cr impurity
effects are taken into account through the spin dependent relaxation times and
the band effects through the semiclassical velocities obtained from the LDA
calculated electronic structure.
  The larger the Cr/Fe hybridization strength, the bigger is the tendency
towards
  IGMR. In particular, in CIP geometry roughness at these interfaces increases
the IGMR range.
  The results are compared with experiments and we conclude that the
experimental GMR curves can only be explained if Cr bands are present.

###Ballistic Spin Injection and Detection in Fe/Semiconductor/Fe Junctions|Phivos Mavropoulos,Olaf Wunnicke,Peter H. Dederichs###

Ballistic Spin Injection and Detection in Fe/Semiconductor/Fe Junctions. We present {\it ab initio} calculations of the spin-dependent electronic
transport in Fe/GaAs/Fe and Fe/ZnSe/Fe (001) junctions simulating the situation
of a spin-injection experiment. We follow a ballistic Landauer-B\"uttiker
approach for the calculation of the spin-dependent dc conductance in the
linear-responce regime, in the limit of zero temperature. We show that the bulk
band structure of the leads and of the semiconductor, and even more the
electronic structure of a clean and abrupt interface, are responsible for a
current polarisation and a magnetoresistance ratio of almost the ideal 100%, if
the transport is ballistic. In particular we study the significance of the
transmission resonances caused by the presence of two interfaces.

###Anisotropic transport in unidirectional lateral superlattice around half-filling of the second Landau level|A. Endo,Y. Iye###

Anisotropic transport in unidirectional lateral superlattice around half-filling of the second Landau level. We have observed marked transport anisotropy in short period (a=92 nm)
unidirectional lateral superlattices around filling factors nu=5/2 and 7/2:
magnetoresistance shows a sharp peak for current along the modulation grating
while a dip appears for current across the grating. By altering the ratio a/l
(with l=sqrt{hbar/eB_perp} the magnetic length) via changing the electron
density n_e, it is shown that the nu=5/2 anisotropic features appear in the
range 6.6 alt a/l alt 7.2 varying their intensities, becoming most conspicuous
at a/l simeq 6.7. The peak/dip broadens with temperature roughly preserving its
height/depth up to 250 mK. Tilt experiments reveal that the structures are
slightly enhanced by an in-plane magnetic field B_| perpendicular to the
grating but are almost completely destroyed by B_| parallel to the grating. The
observations suggest the stabilization of a unidirectional charge-density-wave
or stripe phase by weak external periodic modulation at the second Landau
level.

###Epitaxial Growth of La$_{1/3}$Sr$_{2/3}$FeO$_3$ thin films by laser ablation|W. Prellier,B. Mercey###

Epitaxial Growth of La$_{1/3}$Sr$_{2/3}$FeO$_3$ thin films by laser ablation. We report on the synthesis of high quality La$_{1/3}$Sr$_{2/3}$FeO$_3$ (LSFO)
thin films using the pulsed laser deposition technique on both SrTiO$_3$ (STO)
and LaAlO$_3$ (LAO) substrates (100)-oriented. From X-Ray diffraction (XRD)
studies, we find that the films have an out-of-plane lattice parameter around
0.3865nm, almost independent of the substrate (i.e. the nature of the strains).
The transport properties reveal that, while LSFO films deposited on STO exhibit
an anomaly in the resistivity vs temperature at 180K (corresponding to the
charge-ordered transition and associated with a transition from a paramagnetic
to an antiferromagnetic state), the films grown on LAO display a very small
magnetoresistance behavior and present an hysteresis around 270K under the
application of a 4T magnetic field. The changes in transport properties between
both substrates are discussed and compared with the corresponding single
crystals.

###Exchange-driven Magnetic Excitation and Integrated Magnetoelectronics|J. C. Slonczewski###

Exchange-driven Magnetic Excitation and Integrated Magnetoelectronics. Theory and recent experiments concerning exchange-driven magnetic excitation
(EDME) are reviewed. This phenomenon employs the exchange field produced by a
narrowly distributed spin-polarized electron current to excite Larmor
precession in a magnetic film or particle. Predicted threshold currents for
such excitation of both two-dimensional spin-waves and of monodomain reversal
are now experimentally supported at both helium and ambient temperatures. The
present status of this field suggests a high potential for applications of EDME
to the write operation of magnetic recording and, when combined with tunneling
magnetoresistance, to a memory latch using sub-200 nm lithography. This
potential is buoyed by very recent experiments at Cornell University implying
the theoretical availability of almost hundred-fold advantage in excitation
efficiency favoring exchange fields over Maxwell fields.

###Interplay of charge, spin, orbital and lattice correlations in colossal magnetoresistance manganites|Alexander Weisse,Holger Fehske###

Interplay of charge, spin, orbital and lattice correlations in colossal magnetoresistance manganites. We derive a realistic microscopic model for doped colossal magnetoresistance
manganites, which includes the dynamics of charge, spin, orbital and lattice
degrees of freedom on a quantum mechanical level. The model respects the SU(2)
spin symmetry and the full multiplet structure of the manganese ions within the
cubic lattice. Concentrating on the hole doped domain ($0\le x\le 0.5$) we
study the influence of the electron-lattice interaction on spin and orbital
correlations by means of exact diagonalisation techniques. We find that the
lattice can cause a considerable suppression of the coupling between spin and
orbital degrees of freedom and show how changes in the magnetic correlations
are reflected in dynamic phonon correlations. In addition, our calculation
gives detailed insights into orbital correlations and demonstrates the
possibility of complex orbital states.

###Role of the dimerized gap due to anion ordering in spin-density wave phase of (TMTSF)$_2$ClO$_4$ at high magnetic fields|N. Matsunaga,A. Ayari,P. Monceau,A. Ishikawa,K. Nomura,M. Watanabe,J. Yamada,S. Nakatsuji###

Role of the dimerized gap due to anion ordering in spin-density wave phase of (TMTSF)$_2$ClO$_4$ at high magnetic fields. Magnetoresistance measurements have been carried out along the highly
conducting a axis in the FISDW phase of hydrogened and deuterated
(TMTSF)$_2$ClO$_4$ for various cooling rates through the anion ordering
temperature. With increasing the cooling rate, a) the high field phase boundary
$\beta_{\rm {HI}}$, observed at 27 T in hydrogened samples for slowly cooled,
is shifted towards a lower field, b) the last semimetallic SDW phase below
$\beta_{\rm {HI}}$ is suppressed, and c) the FISDW insulating phase above
$\beta_{\rm {HI}}$ is enhanced in both salts. The cooling rate dependence of
the FISDW transition and of $\beta_{\rm {HI}}$ in both salts can be explained
by taking into account the peculiar SDW nesting vector stabilized by the
dimerized gap due to anion ordering.

###Orbital effects in manganites|Jeroen van den Brink,Giniyat Khaliullin,Daniel Khomskii###

Orbital effects in manganites. We review some aspects related to orbital degrees of freedom in manganites.
The Mn$^{3+}$ ions in these compounds have double orbital degeneracy and are
strong Jahn-Teller ions, causing structural distortions and orbital ordering.
We discuss ordering mechanisms and the consequences of orbital order. The
additional degeneracy of low-energy states and the extreme sensitivity of the
chemical bonds to the spatial orientation of the orbitals result in a variety
of competing interactions. This quite often leads to frustration of classical
ordered states and to the enhancement of quantum effects. Quantum fluctuations
and related theoretical models are briefly discussed, including the occurence
of resonating orbital bonds in the metallic phase of the colossal
magnetoresistance manganites.

###The effect of uniaxial pressure on the magnetic anomalies of the heavy-fermion metamagnet CeRu2Si2|S. R. Saha,H. Sugawara,T. Namiki,Y. Aoki,H. Sato###

The effect of uniaxial pressure on the magnetic anomalies of the heavy-fermion metamagnet CeRu2Si2. The effect of uniaxial pressure (P_u) on the magnetic susceptibility (X),
magnetization (M), and magnetoresistance (MR) of the heavy-fermion metamagnet
CeRu2Si2 has been investigated. For the magnetic field along the tetragonal c
axis, it is found that characteristic physical quantities, i.e., the
temperature of the susceptibility maximum (T_max), the pagamagnetic Weiss
temperature (Q_p), 1/X at 2 K, and the magnetic field of the metamagnetic
anomaly (H_M), scale approximately linearly with P_u, indicating that all the
quantities are related to the same energy scale, probably of the Kondo
temperature. The increase (decrease) of the quantities for P_u || c axis (P_u
|| a axis) can be attributed to a decrease (increase) in the nearest Ce-Ru
distance. Consistently in MR and X, we observed a sign that the anisotropic
nature of the hybridization, which is believed to play an important role in the
metamagnetic anomaly, can be controlled by applying the uniaxial pressure.
  PACS numbers: 75.20.Hr, 71.27.+a, 74.62.Fj

###Switching the magnetic configuration of a spin valve by current induced domain wall motion|J. Grollier,D. Lacour,V. Cros,A. Hamzic,A. Vaures,A. Fert,D. Adam,G. Faini###

Switching the magnetic configuration of a spin valve by current induced domain wall motion. We present experimental results on the displacement of a domain wall by
injection of a dc current through the wall. The samples are 1 micron wide long
stripes of a CoO/Co/Cu/NiFe classical spin valve structure.
  The stripes have been patterned by electron beam lithography. A neck has been
defined at 1/3 of the total length of the stripe and is a pinning center for
the domain walls, as shown by the steps of the giant magnetoresistance curves
at intermediate levels (1/3 or 2/3) between the resistances corresponding to
the parallel and antiparallel configurations. We show by electric transport
measurements that, once a wall is trapped, it can be moved by injecting a dc
current higher than a threshold current of the order of magnitude of 10^7
A/cm^2. We discuss the different possible origins of this effect, i.e. local
magnetic field created by the current and/or spin transfer from spin polarized
current.

###Effects of unreacted Mg impurities on the transport properties of MgB2|C. U. Jung,Heon-Jung Kim,Min-Seok Park,Mun-Seog Kim,J. Y. Kim,Zhonglian Du,Sung-Ik Lee,K. H. Kim,J. B. Betts,M. Jaime,A. H. Lacerda,G. S. Boebinger###

Effects of unreacted Mg impurities on the transport properties of MgB2. We synthesized polycrystalline MgB2 from a stoichiometric mixture of Mg and
the 11 B isotope under different conditions. All the samples showed bulk
superconductivity with Tc = 38~39 K. The samples containing the least amount of
unreacted Mg showed the highest Tc and the sharpest transition width
(Delta_Tc). A residual resistivity ratio (RRR) of ~ 5.8, and a
magnetoresistance (MR), at 40 K, of 12% were obtained for these samples.
Moreover, there was no upturn of resistivity in a low temperature region at 10
Tesla. The samples containing appreciable amounts of unreacted Mg showed quite
different behaviors; the values of Delta_Tc, RRR, and MR were much larger. An
upturn appeared in resistivity of the samples below about 50 K at 10 T and is
thought to be due to the unreacted Mg.

###Spin-polarized bipolar transport and its applications|S. Das Sarma,Jaroslav Fabian,Igor Zutic###

Spin-polarized bipolar transport and its applications. In spin-polarized bipolar transport both electrons and holes in doped
semiconductors contribute to spin-charge coupling. The current conversion
between the minority (as referred to carriers and not spin) and majority
carriers leads to novel spintronic schemes if nonequilibrium spin is present.
Most striking phenomena occur in inhomogeneously doped magnetic {\it p-n}
junctions, where the presence of nonequilibrium spin at the depletion layer
leads to the spin-voltaic effect: electric current flows without external bias,
powered only by spin. The spin-voltaic effect manifests itself in giant
magnetoresistance of magnetic {\it p-n} junctions, where the relative change of
the magnitude of electric current upon reversing magnetic field can be more
than 1000%. The paper reviews nonmagnetic and magnetic spin-polarized {\it p-n}
junctions, formulates the essentials of spin-polarized bipolar transport as
carrier recombination and spin relaxation limited drift and diffusion, and
discusses specific device schemes of spin-polarized solar cells and magnetic
diodes.

###Spin-polarized Tunneling in Hybrid Metal-Semiconductor Magnetic Tunnel Junctions|S. H. Chun,S. J. Potashnik,K. C. Ku,P. Schiffer,N. Samarth###

Spin-polarized Tunneling in Hybrid Metal-Semiconductor Magnetic Tunnel Junctions. We demonstrate efficient spin-polarized tunneling between a ferromagnetic
metal and a ferromagnetic semiconductor with highly mismatched conductivities.
This is indicated by a large tunneling magnetoresistance (up to 30%) at low
temperatures in epitaxial magnetic tunnel junctions composed of a ferromagnetic
metal (MnAs) and a ferromagnetic semiconductor (GaMnAs) separated by a
nonmagnetic semiconductor (AlAs). Analysis of the current-voltage
characteristics yields detailed information about the asymmetric tunnel
barrier. The low temperature conductance-voltage characteristics show a zero
bias anomaly and a V^1/2 dependence of the conductance, indicating a
correlation gap in the density of states of GaMnAs. These experiments suggest
that MnAs/AlAs heterostructures offer well characterized tunnel junctions for
high efficiency spin injection into GaAs.

###Low temperature annealing studies of Ga1-xMnxAs|I. Kuryliszyn,T. Wojtowicz,X. Liu,J. K. Furdyna,W. Dobrowolski,J. -M. Broto,M. Goiran,O. Portugall,H. Rakoto,B. Raquet###

Low temperature annealing studies of Ga1-xMnxAs. High- and low-field magneto-transport measurements, as well as SQUID
measurements of magnetization, were carried out on Ga1-xMnxAs epilayers grown
by low temperature molecular beam epitaxy, and subsequently annealed under
various conditions. We observe a large enhancement of ferromagnetism when the
samples are annealed at an optimal temperature, typically about 280 0C. Such
optimal annealing leads to an increase of Curie temperature, accompanied by an
increase of both the conductivity and the saturation magnetization. A decrease
of the coercive field and of magnetoresistivity is also observed for Ga1-xMnxAs
annealed at optimal conditions. We suggest that the experimental results
reported in this paper are related to changes in the domain structure of
Ga1-xMnxAs.

###Magneto- and Electrotransport Properties of Nd0.67Sr0.33Mn1-xFexO3 (x = 0.00, 0.05)|Chang Yoke Ling,C. K. Ong###

Magneto- and Electrotransport Properties of Nd0.67Sr0.33Mn1-xFexO3 (x = 0.00, 0.05). Simultaneous studies on the magnetic and electrotransport properties of
Nd_{0.67} Sr_{0.33} Mn_{1-x} Fe_x O_3 polycrystalline bulk and epitaxial thin
films (x = 0.00 and 0.05) have been carried out. A magnetoresistance (MR) as
high as ~ 33% is observed for Nd_{0.67} Sr_{0.33} MnO_3 bulk at the
metal-insulator transition (MIT) temperature (T_p) of 273 K in a magnetic field
(H) of 10 kOe. Fe substitution at Mn sites reduces the ferromagnetic (FM)
ordering temperature (T_c) and leads to an overall increase in MR. MR as high
as ~ 90% is observed for thin film (x = 0.05) at H = 10 kOe with T_p = 100 K
while the corresponding bulk has a MR of only ~ 43%. Low field MR in epitaxial
thin films also display a pronounced anisotropy effect compared to bulk
materials.

###Transport and magnetic properties in multi-walled carbon nanotube ropes: Evidence for superconductivity above room temperature|Guo-meng Zhao###

Transport and magnetic properties in multi-walled carbon nanotube ropes: Evidence for superconductivity above room temperature. Detailed analyses are made on previously published data for multi-walled
carbon nanotubes. The field dependence of the Hall voltage, the temperature
dependence of the Hall coefficient, and the magnetoresistance effect (Phys.
Rev. Lett. 72, 697 (1994)) can all be consistently explained in terms of the
coexistence of physically separated tubes and Josephson-coupled superconducting
tubes with superconductivity above room temperature. The observed temperature
dependencies of the remnant magnetization, the diamagnetic susceptibility, and
the conductance are consistent with superconductivity above room temperature,
but are inconsistent with ferromagnetic contamination. We also interpret the
paramagnetic signal and unusual field dependence of the magnetization at 300 K
(Phys. Rev. B 49, 15122 (1994)) as arising from the paramagnetic Meissner
effect in a multiply connected superconducting network.

###Resistance of multilayers with long length scale interfacial roughness|Jason Alicea,Selman Hershfield###

Resistance of multilayers with long length scale interfacial roughness. The resistance of multilayers with interface roughness on a length scale
which is large compared to the atomic spacing is computed in several cases via
the Boltzmann equation. This type of roughness is common in magnetic
multilayers. When the electronic mean free paths are small compared to the
layer thicknesses, the current flow is non-uniform, and the resistance
decreases in the Current-Perpendicular-to-Plane (CPP) configuration and
increases in the Current-In-Plane (CIP) configuration. For mean free paths much
longer than the layer thicknesses, the current flow is uniform, and the
resistance increases in both the CPP and CIP configurations due to enhanced
surface scattering. In both the CPP and CIP geometries, the giant
magnetoresistance can be either enhanced or reduced by the presence of long
length scale interface roughness depending on the parameters. Finally, the
changes in the CPP and CIP resistivities due to increasing interface roughness
are estimated using experimentally determined parameters.

###Characterization of one-dimensional quantum channels in InAs/AlSb|C. H. Yang,M. J. Yang,K. A. Cheng,J. C. Culbertson###

Characterization of one-dimensional quantum channels in InAs/AlSb. We report the magnetoresistance characteristics of one-dimensional electrons
confined in a single InAs quantum well sandwiched between AlSb barriers. As a
result of a novel nanofabrication scheme that utilizes a 3nm-shallow wet
chemical etching to define the electrostatic lateral confinement, the system is
found to possess three important properties: specular boundary scattering, a
strong lateral confinement potential, and a conducting channel width that is
approximately the lithography width. Ballistic transport phenomena, including
the quenching of the Hall resistance, the last Hall plateau, and a strong
negative bend resistance, are observed at 4K in cross junctions with sharp
corners. In a ring geometry, we have observed Aharonov-Bohm interference that
exhibits characteristics different from those of the GaAs counterpart due to
the ballistic nature of electron transport and the narrowness of the conducting
channel width.

###Magnetic Field Induced Spin Polarization of AlAs Two-dimensional Electrons|E. P. De Poortere,E. Tutuc,Y. P. Shkolnikov,K. Vakili,M. Shayegan###

Magnetic Field Induced Spin Polarization of AlAs Two-dimensional Electrons. Two-dimensional (2D) electrons in an in-plane magnetic field become fully
spin polarized above a field B_P, which we can determine from the in-plane
magnetoresistance. We perform such measurements in modulation-doped AlAs
electron systems, and find that the field B_P increases approximately linearly
with 2D electron density. These results imply that the product |g*|m*, where g*
is the effective g-factor and m* the effective mass, is a constant essentially
independent of density. While the deduced |g*|m* is enhanced relative to its
band value by a factor of ~ 4, we see no indication of its divergence as 2D
density approaches zero. These observations are at odds with results obtained
in Si-MOSFETs, but qualitatively confirm spin polarization studies of 2D GaAs
carriers.

###Fermiology and superconductivity studies on the non-tetrachalcogenafulvalene structured organic superconductor beta-(BDA-TTP)_2SbF_6|E. S. Choi,E. Jobiling,A. Wade,E. Goetz,J. S. Brooks,J. Yamada,T. Mizutani,T. Kinoshita,M. Tokumoto###

Fermiology and superconductivity studies on the non-tetrachalcogenafulvalene structured organic superconductor beta-(BDA-TTP)_2SbF_6. The quantum oscillatory effect and superconductivity in a
non-tetrachalcogenafulvalene (TCF) structure based organic superconductor
beta-(BDA-TTP)_2SbF_6 are studied. Here the Shubnikov-de Haas effect (SdH) and
angular dependent magnetoresistance oscillations (AMRO) are observed. The
oscillation frequency associated with a cylindrical Fermi surface is found to
be about 4050 tesla, which is also verified by the tunnel diode oscillator
(TDO) measurement. The upper critical field Hc2 measurement in a tilted
magnetic field and the TDO measurement in the mixed state reveal a highly
anisotropic superconducting nature in this material. We compared physical
properties of beta-(BDA-TTP)_2SbF_6 with typical TCF structure based quasi
two-dimensional organic conductors. A notable feature of beta-(BDA-TTP)_2SbF_6
superconductor is a large value of effective cyclotron mass m_c^*=12.4+/1.1
m_e, which is the largest yet found in an organic superconductor. A possible
origin of the enhanced effective mass and its relation to the superconductivity
are briefly discussed.

###Localization Length in Anderson Insulator with Kondo Impurities|S. Kettemann,M. E. Raikh###

Localization Length in Anderson Insulator with Kondo Impurities. The localization length, $\xi$, in a 2--dimensional Anderson insulator
depends on the electron spin scattering rate by magnetic impurities,
$\tau_s^{-1}$. For antiferromagnetic sign of the exchange, %constant, the time
$\tau_s$ is {\em itself a function of $\xi$}, due to the Kondo correlations. We
demonstrate that the unitary regime of localization is impossible when the
concentration of magnetic impurities, $n_{\tiny M}$, is smaller than a critical
value, $n_c$. For $n_{\tiny M}>n_c$, the dependence of $\xi$ on the
dimensionless conductance, $g$, is {\em reentrant}, crossing over to unitary,
and back to orthogonal behavior upon increasing $g$. Sensitivity of Kondo
correlations to a weak {\em parallel} magnetic field results in a giant
parallel magnetoresistance.

###High Field Studies of the Hidden Order Transition in URu$_2$Si$_2$|M. Jaime,K. H. Kim,G. Jorge,S. McCall,J. A Mydosh###

High Field Studies of the Hidden Order Transition in URu$_2$Si$_2$. We studied in detail the low temperature/high magnetic field phases of
URu$_{2}$Si$_{2}$ single crystals with specific heat, magnetocaloric effect,
and magnetoresistance in magnetic fields up to 45 T. Data obtained down to 0.5
K, and extrapolated to T = 0, show a suppression of the hidden order phase at
H$_{o}$(0) = 35.9 $\pm$ 0.35 T and the appearance of a new phase for magnetic
fields in excess of H$_{1}$(0) = 36.1 $\pm$ 0.35 T observed \textit{only} at
temperatures lower than 6 K. In turn, complete suppression of this high field
state is attained at a critical magnetic field H$_{2}$(0) = 39.7 $\pm$ 0.35 T.
No phase transitions are observed above 40 T. We discuss our results in the
context of itinerant vs. localized \textit{f}-electron behavior and consider
the implications for the hidden order phase.

###Nanoscale Phase Separation in Colossal Magnetoresistance Materials: A Lesson for the Cuprates?|Elbio Dagotto,Jan Burgy,Adriana Moreo###

Nanoscale Phase Separation in Colossal Magnetoresistance Materials: A Lesson for the Cuprates?. A recent vast experimental and theoretical effort in manganites has shown
that the colossal magnetoresistance effect can be understood based on the
competition of charge-ordered and ferromagnetic phases. The general aspects of
the theoretical description appear to be valid for any compound with intrinsic
phase competition. In high temperature superconductors, recent experiments have
shown the existence of intrinsic inhomogeneities in many materials, revealing a
phenomenology quite similar to that of manganese oxides. Here, the results for
manganites are briefly reviewed with emphasis on the general aspects. In
addition, theoretical speculations are formulated in the context of Cu-oxides
by mere analogy with manganites. This includes a tentative explanation of the
spin-glass regime as a mixture of antiferromagnetic and superconducting
islands, the rationalization of the pseudogap temperature T* as a Griffiths
temperature where clusters start forming upon cooling, the prediction of
"colossal" effects in cuprates, and the observation that quenched disorder may
be far more relevant in Cu-oxides than previously anticipated.

###Spin-Dependent Transport Through An Interacting Quantum Dot|Ping Zhang,Qi-Kun Xue,Yu-Peng Wang,X. C. Xie###

Spin-Dependent Transport Through An Interacting Quantum Dot. We study the nonequilibrium spin transport through a quantum dot containing
two spin levels coupled to the magnetic electrodes. A formula for the
spin-dependent current is obtained and is applied to discuss the linear
conductance and magnetoresistance in the interacting regime, where the
so-called Kondo effect arises. We show that the Kondo resonance and the
correlation-induced spin splitting of the dot levels may be systematically
controlled by internal magnetization in the electrodes. As a result, when the
electrodes are in parallel magnetic configuration, the linear conductance is
characterized by two spin-resolved peaks. Furthermore, the presence of the
spin-flip process in the dot splits the Kondo resonance into three peaks.

###Spectral Function Analysis on Spin Dynamics in Double-Exchange Systems with Randomness|Yukitoshi Motome,Nobuo Furukawa###

Spectral Function Analysis on Spin Dynamics in Double-Exchange Systems with Randomness. Spin excitation spectrum is studied in the double-exchange model with
randomness. Applying the spin wave approximation and the spectral function
analysis, we examine excitation energy and linewidth using analytical as well
as numerical methods. For small wave number $q \sim 0$, the excitation energy
is cosine-like and the linewidth shows a $q$-linear behavior. This indicates
that the spin excitation becomes incoherent or localized near $q = 0$.
Crossover takes place to marginally-coherent regime where both the excitation
energy and the linewidth are proportional to $q^2$. The incoherence is due to
local fluctuations of the kinetic energy of electrons. Comparison with
experimental results in colossal magnetoresistance manganites suggests that
spatially-correlated or mesoscopic-scale fluctuations are more important in
real compounds than local or atomic-scale ones.

###Suppression of superconductivity due to spin imbalance in Co/Al/Co single electron transistor|Jan Johansson,Mattias Urech,David Haviland,V. Korenivski###

Suppression of superconductivity due to spin imbalance in Co/Al/Co single electron transistor. Transport properties of ferromagnetic/non-magnetic/ferromagnetic single
electron transistors are investigated as a function of external magnetic field,
temperature, bias and gate voltage. By designing the magnetic electrodes to
have different switching fields, a two-mode device is realized having two
stable magnetization states, with the electrodes aligned in parallel and
antiparallel. Magnetoresistance of approximately 100% is measured in
Co/AlO$_{X}$/Al/AlO$_{X}$/Co double tunnel junction spin valves at low bias,
with the Al spacer in the superconducting state. The effect is substantially
reduced at high bias and temperatures above the $T_{C}$ of the Al. The
experimental results are interpreted as due to spin imbalance of charge
carriers resulting in suppression of the superconducting gap of the Al island.

###Do we understand electron correlation effects in Gadolinium based intermetallic compounds?|E. V. Sampathkumaran,R. Mallik###

Do we understand electron correlation effects in Gadolinium based intermetallic compounds?. Recognising the difficulties in systematic understanding of the physical
characteristics of strongly correlated f-electron systems, we considered it
worthwhile to subject the so-called "normal" f-electron systems like those of
Gd to careful investigations. We find that the spin-disorder contribution to
electrical resistivity ($\rho$) in the paramagnetic state, instead of remaining
contant, surprisingly increases with decreasing temperature (T) in the
paramagnetic state in some of the Gd alloys. In some cases, this "excess
resistance" is so large that a distinct minimum in the plot of $\rho$ versus T
can be seen, mimicking the behaviour of Kondo lattices. This excess resistance
can be suppressed by the application of a magnetic field, naturally resulting
in large magnetoresistance. In addition, these alloys are found to exhibit
heavy-fermion-like heat-capacity behavior. These unusual findings imply
hither-to-unexplored electron correlation effects even in Gd-based alloys.

###Field-Induced Quantum Critical Point in CeCoIn5|Johnpierre Paglione,M. A. Tanatar,D. G. Hawthorn,Etienne Boaknin,R. W. Hill,F. Ronning,M. Sutherland,Louis Taillefer,C. Petrovic,P. C. Canfield###

Field-Induced Quantum Critical Point in CeCoIn5. The resistivity of the heavy-fermion superconductor CeCoIn5 was measured as a
function of temperature, down to 25 mK and in magnetic fields of up to 16 T
applied perpendicular to the basal plane. With increasing field, we observe a
suppression of the non-Fermi liquid behavior, rho ~ T, and the development of a
Fermi liquid state, with its characteristic rho = rho_0 + AT^2 dependence. The
field dependence of the T^2 coefficient shows critical behavior with an
exponent of 1.37. This is evidence for a field-induced quantum critical point
(QCP), occuring at a critical field which coincides, within experimental
accuracy, with the superconducting critical field H_c2. We discuss the relation
of this field-tuned QCP to a change in the magnetic state, seen as a change in
magnetoresistance from positive to negative, at a crossover line that has a
common border with the superconducting region below ~ 1 K.

###Dynamical mean field theory for transition temperature and optics of CMR manganites|B. Michaelis,A. J. Millis###

Dynamical mean field theory for transition temperature and optics of CMR manganites. A tight binding parametrization of local spin density functional band theory
is combined with a dynamical mean field treatment of correlations to obtain a
theory of the magnetic transition temperature, optical conductivity and T=0
spinwave stiffness of a minimal model for the pseudocubic metallic $CMR$
manganites such a $La_{1-X}Sr_{x}MnO_{3}$. The results indicate that previous
estimates of $T_{c}$ obtained by one of us (Phys. Rev. \textbf{B61} 10738-49
(2000)) are in error, that in fact the materials are characterized by Hunds
coupling $J\approx 1.5eV$, and that magnetic-order driven changes in the
kinetic energy may not be the cause of the observed 'colossal' magnetoresistive
and multiphase behavior in the manganites, raising questions about our present
understanding of these materials.

###Localization and electron-electron interaction effects in magnetoresistance of p-type Ge/Ge_{1-x}Si_x heterostructures|Yu. G. Arapov,G. I. Harus,V. N. Neverov,A. T. Lonchakov,N. G. Shelushinina,M. V. Yakunin###

Localization and electron-electron interaction effects in magnetoresistance of p-type Ge/Ge_{1-x}Si_x heterostructures. We report on the results of investigation the conductivity and
magnetoresistance (MR) temperature dependencies for the two strained multilayer
p-type Ge/Ge_{1-x}Si_x heterostructures. The usual logarithmic temperature
dependencies for zero magnetic field conductivity due to the weak localization
(WL) and electron- electron interaction (EEI) effects take place in both
samples. For one of the samples the negative MR is observed in a whole range of
magnetic fields up to ~1T at T <=12K, but for the other sample the MR
transforms from the negative to positive at B >= 0.2T and T >=1.3K. We
attribute such a behavior to the interplay of two types of holes due to partial
filling of the second subband. Extrapolation of the observed high-field
parabolic MR to B = 0 allows to separate WL and EEI contributions to the total
quantum corrections to conductivity at B = 0 resulting for both of our
structures in that EEI part is ~2/3 and the WL part is ~1/3.

###Kondo effect in underdoped n-type superconductors|Tsuyoshi Sekitani,Michio Naito,Noboru Miura###

Kondo effect in underdoped n-type superconductors. We present high-field magnetotransport properties of high-quality
single-crystalline thin films of heavily underdoped nonsuperconducting
(La,Ce)2CuO4, (Pr,Ce)2CuO4, and (Nd,Ce)2CuO4. All three materials show
identical behavior. They are metallic at high temperatures and show an
insulating upturn at low temperatures. The insulating upturn has a log T
dependence, but saturates toward the lowest temperatures. Notably, the
insulating upturn tends to be suppressed by applying magnetic fields. This
negative magnetoresistance has a log B dependence, and its anisotropy shows non
simple behavior. We discuss these findings from the viewpoints of Kondo
scattering and also two-dimensional weak localization, and demonstrate Kondo
scattering as a more plausible explanation. The Kondo scatters are identified
as Cu2+ spins in the CuO2 planes.

###Mixed-phase description of colossal magnetoresistive manganites|Alexander Weiße,Jan Loos,Holger Fehske###

Mixed-phase description of colossal magnetoresistive manganites. In view of recent experiments, indicating the spatial coexistence of
conducting and insulating regions in the ferromagnetic metallic phase of doped
manganites, we propose a refined mixed-phase description. The model is based on
the competition of a double-exchange driven metallic component and a polaronic
insulating component, whose volume fractions and carrier concentrations are
determined self-consistently by requiring equal pressure and chemical
potential. The resulting phase diagram as well as the order of the phase
transition are in very good agreement with measured data. In addition,
modelling the resistivity of the mixed, percolative phase by a random resistor
network, we obtain a pronounced negative magnetoresistance in the vicinity of
the Curie temperature $T_C$.

###Magnetotransport in a two-dimensional electron gas in the presence of spin-orbit interaction|X. F. Wang,P. Vasilopoulos###

Magnetotransport in a two-dimensional electron gas in the presence of spin-orbit interaction. We evaluate the transport coefficients of a two-dimensional electron gas
(2DEG) in the presence of a perpendicular magnetic field and of the spin-orbit
interaction (SOI) described only by the Rashba term. The SOI mixes the spin-up
and spin-down states of neighboring Landau levels into two new, unequally
spaced energy branches. The broadened density of states, as a function of the
energy, and the longitudinal resistivity, as a function of the magnetic field,
show beating patterns in agreement with observations. The positions of any two
successive nodes in the beating pattern approximately determine the strength of
the Rashba term.
  A strong SOI results in a splitting of the magnetoresistance peaks and a
doubling of the number of the Hall plateaus. The peak value in derivative of
the Hall resistivity reflects the strength of the SOI.

###Simulations of a classical spin system with competing superexchange and double-exchange interactions|Shan-Ho Tsai,D. P. Landau###

Simulations of a classical spin system with competing superexchange and double-exchange interactions. Monte-Carlo simulations and ground-state calculations have been used to map
out the phase diagram of a system of classical spins, on a simple cubic
lattice, where nearest-neighbor pairs of spins are coupled via competing
antiferromagnetic superexchange and ferromagnetic double-exchange interactions.
For a certain range of parameters, this model is relevant for some magnetic
materials, such as doped manganites, which exhibit the remarkable colossal
magnetoresistance effect. The phase diagram includes two regions in which the
two sublattice magnetizations differ in magnitude. Spin-dynamics simulations
have been used to compute the time- and space-displaced spin-spin correlation
functions, and their Fourier transforms, which yield the dynamic structure
factor $S(q,\omega)$ for this system. Effects of the double-exchange
interaction on the dispersion curves are shown.

###Anomalous Hall Effect and Magnetoresistance of SrFe1-xCoxO3-d|Takahiko Ido,Yukio Yasui,Masatoshi Sato###

Anomalous Hall Effect and Magnetoresistance of SrFe1-xCoxO3-d. Transport and magnetic studies on polycrystalline samples of SrFe1-xCoxO3-d
have been carried out to investigate the relationship between the magnetic
structure and the anomalous Hall resistivity rH. The hysteretic behavior of the
magnetization observed in the measurements with varying temperature T up and
then down after zero field cooling indicates that the system has the reentrant
spin-glass phase, which is supported by the increasing width of the magnetic
reflections observed by neutron diffraction with decreasing T below the Curie
temperature TC. Detailed analyses of the observed Hall resistivity rH indicate
that the anomalous Hall coefficient exhibits unusual behavior in the reentrant
spin-glass phase. The magnetic field (H)- and T-dependence of the
magnetoresistance of the present system can be understood by a spin dependent
tunneling model.

###X-Ray Study of the Density Wave Instability of alpha-(BEDT-TTF)2MHg(SCN)4 with M=K and Rb|P. Foury-Leylekian,S. Ravy,J. -P. Pouget,H. Muller###

X-Ray Study of the Density Wave Instability of alpha-(BEDT-TTF)2MHg(SCN)4 with M=K and Rb. We present an X-ray diffraction study of the quasi-2D conductors
a-(BEDTTTF)2MHg(SCN), with M=K and Rb. They exhibit a phase transition of the
density wave type at TDW=8-10K and 12-13K respectively, evidenced by
magnetoresistivity, specific heat, NMR and Hall constant measurements. The
structural study shows the presence of satellite reflections already at ambient
temperature. The related modulation is incommensurate with multiple harmonics.
For some of the compounds studied, the intensity of the satellite reflections
strongly increases below TDW. According to Fermi surface (FS) calculations, the
wave vector of the structural modulation achieves a quite good nesting of the
global FS. This suggests a coupling of the modulation with the electronic
degrees of freedom leading to a charge density wave ground state.

###Single-Band Model for Diluted Magnetic Semiconductors: Dynamical and Transport Properties and Relevance of Clustered States|G. Alvarez,E. Dagotto###

Single-Band Model for Diluted Magnetic Semiconductors: Dynamical and Transport Properties and Relevance of Clustered States. Dynamical and transport properties of a simple single-band spin-fermion
lattice model for (III,Mn)V diluted magnetic semiconductors (DMS) is here
discussed using Monte Carlo simulations. This effort is a continuation of
previous work (G. Alvarez, Phys. Rev. Lett. 89, 277202 (2002)) where the static
properties of the model were studied. The present results support the view that
the relevant regime of J/t (standard notation) is that of intermediate
coupling, where carriers are only partially trapped near Mn spins, and locally
ordered regions (clusters) are present above the Curie temperature T_C. This
conclusion is based on the calculation of the resistivity vs. temperature, that
shows a soft metal to insulator transition near T_C, as well on the analysis of
the density-of-states and optical conductivity. In addition, in the clustered
regime a large magnetoresistance is observed in simulations. Formal analogies
between DMS and manganites are also discussed.

###Magnetoresistance of atomic-sized contacts: an ab-initio study|Alexei Bagrets,Nikos Papanikolaou,Ingrid Mertig###

Magnetoresistance of atomic-sized contacts: an ab-initio study. The magnetoresistance (MR) effect in metallic atomic-sized contacts is
studied theoretically by means of first-principle electronic structure
calculations. We consider three-atom chains formed from Co, Cu, Si, and Al
atoms suspended between semi-infinite Co leads. We employ the screened
Korringa-Kohn-Rostoker Green's function method for the electronic structure
calculation and evaluate the conductance in the ballistic limit using the
Landauer approach. The conductance through the constrictions reflects the
spin-splitting of the Co bands and causes high MR ratios, up to 50%. The
influence of the structural changes on the conductance is studied by
considering different geometrical arrangements of atoms forming the chains. Our
results show that the conductance through s-like states is robust against
geometrical changes, whereas the transmission is strongly influenced by the
atomic arrangement if p or d states contribute to the current.

###Electronic inhomogeneity at magnetic domain walls in strongly-correlated systems|M. S. Rzchowski,Robert Joynt###

Electronic inhomogeneity at magnetic domain walls in strongly-correlated systems. We show that nano-scale variations of the order parameter in
strongly-correlated systems can induce local spatial regions such as domain
walls that exhibit electronic properties representative of a different, but
nearby, part of the phase diagram. This is done by means of a Landau-Ginzburg
analysis of a metallic ferromagnetic system near an antiferromagnetic phase
boundary. The strong spin gradients at a wall between domains of different spin
orientation drive the formation of a new type of domain wall, where the central
core is an insulating antiferromagnet, and connects two metallic ferromagnetic
domains. We calculate the charge transport properties of this wall, and find
that its resistance is large enough to account for recent experimental results
in colossal magnetoresistance materials. The technological implications of this
finding for switchable magnetic media are discussed.

###Pressure effect on magnetism in CeTe$_{1.82}$|M. H. Jung,A. Alsmadi,H. C. Kim,J. Kamarad,T. Takabatake###

Pressure effect on magnetism in CeTe$_{1.82}$. We report the normal-state transport and magnetic properties of a
pressure-induced superconductor CeTe$_{1.82}$. We found that the applied
pressure is required to increase the Kondo temperature scale ($T^*_{\rm K}
\sim$ 170 K), associated with the two-dimensional motion of the carriers
confined within the Te plane. Both the short-range ferromagnetic ordering
temperature ($T_{\rm SRF} \sim$ 6 K) and the long-range antiferromagnetic
transition temperature ($T_{\rm N} \sim$ 4.3 K) are slightly increased with
pressure. We suggest that the application of pressure enhances a coupling
between the 4$f$ and conduction electrons. We also found that the field effect
on the transport under pressure is analogous to that at ambient pressure, where
a large magnetoresistance is observed in the vicinity of $T_{\rm SRF}$.

###Magnetotransport in two-dimensional electron gas at large filling factors|M. G. Vavilov,I. L. Aleiner###

Magnetotransport in two-dimensional electron gas at large filling factors. We derive the quantum Boltzmann equation for the two-dimensional electron gas
in a magnetic field such that the filling factor $\nu \gg 1$. This equation
describes all of the effects of the external fields on the impurity collision
integral including Shubnikov-de Haas oscillations, smooth part of the
magnetoresistance, and non-linear transport. Furthemore, we obtain quantitative
results for the effect of the external microwave radiation on the linear and
non-linear $dc$ transport in the system. Our findings are relevant for the
description of the oscillating resistivity discovered by Zudov {\em et al.},
zero-resistance state discovered by Mani {\em et al.} and Zudov {\em et al.},
and for the microscopic justification of the model of Andreev {\em et al.}. We
also present semiclassical picture for the qualitative consideration of the
effects of the applied field on the collision integral.

###Tunnel magnetoresistance in double spin filter junctions|Alireza Saffarzadeh###

Tunnel magnetoresistance in double spin filter junctions. We consider a new type of magnetic tunnel junction, which consists of two
ferromagnetic tunnel barriers acting as spin filters (SFs), separated by a
nonmagnetic metal (NM) layer. Using the transfer matrix method and the
free-electron approximation, the dependence of the tunnel magnetoresistance
(TMR) on the thickness of the central NM layer, bias voltage and temperature in
the double SF junction are studied theoretically. It is shown that the TMR and
electron-spin polarization in this structure can reach very large values under
suitable conditions. The highest value of the TMR can reach 99%. By an
appropriate choice of the thickness of the central NM layer, the degree of spin
polarization in this structure will be higher than that of the single SF
junctions. These results may be useful in designing future spin-polarized
tunnelling devices.

###Giant radio-frequency magnetoabsorption effect in the cobaltite ceramic La_{0.5}Sr_{0.5}CoO_3|B. I. Belevtsev,A. Ya. Kirichenko,N. T. Cherpak,G. V. Golubnichaya,I. G. Maximchuk,A. B. Beznosov,V. B. Krasovitsky,P. P. Pal-Val,I. N. Chukanova###

Giant radio-frequency magnetoabsorption effect in the cobaltite ceramic La_{0.5}Sr_{0.5}CoO_3. The DC transport properties of and the radio-frequency (RF) wave absorption
(at 1.33 MHz) in a ceramic sample of La_{0.5}Sr_{0.5}CoO_{3-\delta} are
measured. The Curie temperature, T_{c}, of the sample is about 250 K. A giant
negative magnetoabsorption effect is found. In the vicinity of T_{c}, the
absolute value of the magnetoabsorption is about 38 % in the rather low
magnetic field 2.1 kOe. This differs drastically from the measured DC
magnetoresistance (MR) \delta (H) =[R(0)-R(H)]/R(0) which is a mere 0.26 % near
T_{c}in the same field and increases to about 2.15 % in H=20 kOe. The
phenomenon can be understood taking into account that the magnetoabsorption is
determined by influence of magnetic field on the conductivity and the magnetic
permeability, while the MR is determined solely by the former. The
magnetoabsorption effect can be used to develop RF devices controlled by
magnetic field and temperature.

###Diagnosis and Location of Pinhole Defects in Tunnel Junctions using only Electrical Measurements|Zhongsheng Zhang,David A. Rabson###

Diagnosis and Location of Pinhole Defects in Tunnel Junctions using only Electrical Measurements. In the development of the first generation of sensors and memory chips based
on spin-dependent tunneling through a thin trilayer, it has become clear that
pinhole defects can have a deleterious effect on magnetoresistance. However,
current diagnostic protocols based on Andreev reflection and the temperature
dependence of junction resistance may not be suitable for production quality
control. We show that the current density in a tunnel junction in the
cross-strip geometry becomes very inhomogeneous in the presence of a single
pinhole, yielding a four-terminal resistance that depends on the location of
the pinhole in the junction. Taking advantage of this position dependence, we
propose a simple protocol of four four-terminal measurements. Solving an
inverse problem, we can diagnose the presence of a pinhole and estimate its
position and resistance.

###Parallel magnetic field induced magnetoresistance peculiarities of the double quantum well filled with electrons or holes|M. V. Yakunin,G. A. Alshanskii,Yu. G. Arapov,G. I. Harus,V. N. Neverov,N. G. Shelushinina,O. A. Kuznetsov,B. N. Zvonkov,E. A. Uskova,L. Ponomarenko,A. de Visser###

Parallel magnetic field induced magnetoresistance peculiarities of the double quantum well filled with electrons or holes. In In_xGa_{1-x}As/n-GaAs double quantum wells (DQWs) containing an electron
gas, the magnetoresistance (MR) peculiarities under parallel magnetic fields
caused by the passing of the tunnel gap edges through the Fermi level are
revealed. Peculiarities positioned in high fields (~30 T) can only be explained
if the spin-splitting of the In_xGa_{1-x}As conduction band is considered, that
was neglected in the GaAs/AlGaAs heterostructures, for which solely the effects
of this nature have been observed so far. In Ge/p-Ge_{1-x}Si_x DQWs containing
a hole gas, local MR peculiarities under parallel fields are discovered as
well. But the tunnel gap in these DQWs is too narrow to be responsible for
these observations. We suppose, they are due to a complicated shape of the hole
confinement subbands.

###Spin-dependent shot noise of inelastic transport through molecular quantum dots|Kamil Walczak###

Spin-dependent shot noise of inelastic transport through molecular quantum dots. Here we present a theoretical analysis of the effect of inelastic electron
scattering on spin-dependent transport characteristics (conductance,
current-voltage dependence, magnetoresistance, shot noise spectrum, Fano
factor) for magnetic nanojunction. Such device is composed of molecular quantum
dot (with discrete energy levels)connected to ferromagnetic electrodes (treated
within the wide-band approximation), where molecular vibrations are modeled as
dispersionless phonons. Non-perturbative computational scheme, used in this
work, is based on the Green's function theory within the framework of mapping
technique (GFT-MT) which transforms the many-body electron-phonon interaction
problem into a single-electron multi-channel scattering problem. The
consequence of the localized electron-phonon coupling is polaron formation. It
is shown that polaron shift and additional peaks in the transmission function
completely change the shape of considered transport characteristics.

###Electron Coherence in Mesoscopic Kondo Wires|F. Schopfer,C. Bäuerle,W. Rabaud,L. Saminadayar###

Electron Coherence in Mesoscopic Kondo Wires. We present measurements of the magnetoresistance of long and narrow quasi
one-dimensional gold wires containing magnetic iron impurities. The electron
phase coherence time extracted from the weak antilocalisation shows a
pronounced plateau in a temperature region of 300 mK - 800 mK, associated with
the phase breaking due to the Kondo effect. Below the Kondo temperature, the
phase coherence time increases, as expected in the framework of Kondo physics.
At much lower temperatures, the phase coherence time saturates again, in
contradiction with standard Fermi liquid theory. In the same temperature
regime, the resistivity curve displays a characteristic maximum at zero
magnetic field, associated with the formation of a spin glass state. We argue
that the interactions between the magnetic moments are responsible for the low
temperature saturation of the phase coherence time.

###Hall effect and magnetoresistance in p-type ferromagnetic semiconductors|Tomasz Dietl,Fumihiro Matsukura,Hideo Ohno,Joel Cibert,David Ferrand###

Hall effect and magnetoresistance in p-type ferromagnetic semiconductors. Recent works aiming at understanding magnetotransport phenomena in
ferromagnetic III-V and II-VI semiconductors are described. Theory of the
anomalous Hall effect in p-type magnetic semiconductors is discussed, and the
relative role of side-jump and skew-scattering mechanisms assessed for
(Ga,Mn)As and (Zn,Mn)Te. It is emphasized that magnetotransport studies of
ferromagnetic semiconductors in high magnetic fields make it possible to
separate the contributions of the ordinary and anomalous Hall effects, to
evaluate the role of the spins in carrier scattering and localization as well
as to determine the participation ratio of the ferromagnetic phase near the
metal-insulator transition. A sizable negative magnetoresistance in the regime
of strong magnetic fields is assigned to the weak localization effect.

###Growth and properties of ferromagnetic In(1-x)Mn(x)Sb alloys|T. Wojtowicz,W. L. Lim,X. Liu,G. Cywinski,M. Kutrowski,L. V. Titova,K. Yee,M. Dobrowolska,J. K. Furdyna,K. M. Yu,W. Walukiewicz,G. B. Kim,M. Cheon,X. Chen,S. M. Wang,H. Luo,I. Vurgaftman,J. R. Meyer###

Growth and properties of ferromagnetic In(1-x)Mn(x)Sb alloys. We discuss a new narrow-gap ferromagnetic (FM) semiconductor alloy,
In(1-x)Mn(x)Sb, and its growth by low-temperature molecular-beam epitaxy. The
magnetic properties were investigated by direct magnetization measurements,
electrical transport, magnetic circular dichroism, and the magneto-optical Kerr
effect. These data clearly indicate that In(1-x)Mn(x)Sb possesses all the
attributes of a system with carrier-mediated FM interactions, including
well-defined hysteresis loops, a cusp in the temperature dependence of the
resistivity, strong negative magnetoresistance, and a large anomalous Hall
effect. The Curie temperatures in samples investigated thus far range up to 8.5
K, which are consistent with a mean-field-theory simulation of the
carrier-induced ferromagnetism based on the 8-band effective band-orbital
method.

###Domain-wall profile in the presence of anisotropic exchange interactions: Effective on-site anisotropy|A. O. Garcia Rodriguez,A. Villares Ferrer,A. O. Caldeira###

Domain-wall profile in the presence of anisotropic exchange interactions: Effective on-site anisotropy. Starting from a D-dimensional XXZ ferromagnetic Heisenberg model in an
hypercubic lattice, it is demonstrated that the anisotropy in the exchange
coupling constant leads to a D-dependent effective on-site anisotropy
interaction often ignored for D>1. As a result the effective width of the wall
depends on the dimensionality of the system. It is shown that the effective
one-dimensional Hamiltonian is not the one-dimensional XXZ version as assumed
in previous theoretical work. We derive a new expression for the wall profile
that generalizes the standard Landau-Lifshitz form. Our results are found to be
in very good agreement with earlier numerical work using the Monte Carlo
method. Preceding theories concerning the domain wall contribution to
magnetoresistance have considered the role of D only through the modification
of the density of states in the electronic band structure. This Brief Report
reveals that the wall profile itself contains an additional D dependence for
the case of anisotropic exchange interactions.

###Magnetic-field induced superconductor-metal-insulator transitions in bismuth metal-graphite|Masatsugu Suzuki,Itsuko S. Suzuki,Robert Lee,Jürgen Walter###

Magnetic-field induced superconductor-metal-insulator transitions in bismuth metal-graphite. Bismuth-metal graphite (MG) has a unique layered structure where Bi
nanoparticles are encapsulated between adjacent sheets of nanographites. The
superconductivity below $T_{c}$ (= 2.48 K) is due to Bi nanoparticles. The
Curie-like susceptibility below 30 K is due to conduction electrons localized
near zigzag edges of nanographites. A magnetic-field induced transition from
metallic to semiconductor-like phase is observed in the in-plane resistivity
$\rho_{a}$ around $H_{c}$ ($\approx$ 25 kOe) for both $H$$\perp$$c$ and
$H$$\parallel$$c$ ($c$: c axis). A negative magnetoresistance in $\rho_{a}$ for
$H$$\perp$$c$ (0$<H\leq$3.5 kOe) and a logarithmic divergence in $\rho_{a}$
with decreasing temperature for $H$$\parallel$$c$ ($H$ $>$ 40 kOe) suggest the
occurrence of two-dimensional weak localization effect.

###Evidence for current flow anomalies in the irradiated 2D electron system at small magnetic fields|R. L. Willett,L. N. Pfeiffer,K. W. West###

Evidence for current flow anomalies in the irradiated 2D electron system at small magnetic fields. We report experimental results of low temperature magnetotransport in high
mobility 2D electron systems exposed to radiation up to 20GHz frequency using a
simple dipole configuration. Magnetoresistance oscillations are observed as in
previously reported higher frequency radiation on 2D systems, however minima
here can be seen to extend to negative biases, and zeroes previously reported
are not observed persistently around the full sample perimeters. In addition,
under radiation, voltages are observed from internal to external contacts in
the absence of applied driving currents not due to simple rectification. These
findings are consistent with micro- and macroscopic theoretical pictures of
radiation induced transport and current instabilities due to local negative
resistivities. However, the temperature dependent development of minima is
shown to be severely power dependent, and outside of present theoretical
understanding.

###Evidence for two electronic components in NaxCoO2 (x = 0.7-0.75)|M. Brühwiler,B. Batlogg,S. M. Kazakov,J. Karpinski###

Evidence for two electronic components in NaxCoO2 (x = 0.7-0.75). Thermodynamic and transport measurements on NaxCoO2 (x ~ 0.7-0.75) over a
wide temperature range reveal a strongly enhanced low energy excitation
spectrum. The zero-field specific heat and resistance at low temperature are
proportional to T^n with n<1, in sharp contrast to behavior found in ordinary
Landau Fermi-liquid metals. For temperatures below ~5 K this unusual excitation
seen in the specific heat is partially suppressed in a magnetic field,
following a T/B scaling. The specific heat reduction at low T is partially
compensated by an increase at higher temperature. A quantitative comparison
with the magnetoresistance and the thermopower indicates that the low- energy
electronic state requires a description beyond the single band model.

###Controllable Josephson current through a pseudo-spin-valve structure|C. Bell,G. Burnell,C. W. Leung,E. J. Tarte,D. -J. Kang,M. G. Blamire###

Controllable Josephson current through a pseudo-spin-valve structure. A thin Co/Cu/Permalloy (Ni$_{80}$Fe$_{20}$) pseudo-spin-valve structure is
sandwiched between superconducting Nb contacts. When the current is passed
perpendicular to the plane of the film a Josephson critical current ($I_C$) is
observed at 4.2 K, in addition to a magnetoresistance (MR) of $\sim$ 0.5 % at
high bias. The hysteresis loop of the spin-valve structure can be cycled to
modulate the zero field $I_C$ of the junction in line with the MR measurements.
These modulations of resistance and $I_C$ occur both smoothly and sharply with
the applied field. For each type of behaviour there is a strong correlation
between shape of the MR loops and the $I_C$ modulation.

###Giant Quantum Oscillations of the Longitudinal Magnetoresistance in Quasi two-dimensional Metals|T. Champel,V. P. Mineev###

Giant Quantum Oscillations of the Longitudinal Magnetoresistance in Quasi two-dimensional Metals. We have investigated in frame of the quantum transport theory the magnetic
quantum oscillations of the longitudinal magnetoresistance $\rho_{zz}$ in quasi
two-dimensional metals for a magnetic field perpendicular to the layers.
  Giant Shubnikov-de Haas oscillations are found when the cyclotron energy
$\hbar \omega_{c}$ is much larger than the interlayer transfer integral $t$
(the two-dimensional limit). In large magnetic fields and at low temperatures,
the minima of the magnetoconductivity $\sigma_{zz}=\rho_{zz}^{-1}$ exhibit a
thermally activated behavior in presence of negligibly small chemical potential
oscillations, as observed in the organic layered conductor
$\beta''\mathrm{-(BEDT-TTF)}_{2}\mathrm{SF}_{5}\mathrm{CH}_{2}\mathrm{CF}_{2}\m
athrm{SO}_{3}$.
  The questions concerning the absence of strong chemical potential
oscillations in such compound and the impurity self-energy are discussed.

###Modelling of strain effects in manganite films|C. A. Perroni,V. Cataudella,G. De Filippis,G. Iadonisi,V. Marigliano,F. Ventriglia###

Modelling of strain effects in manganite films. Thickness dependence and strain effects in films of $La_{1-x}A_xMnO_3$
perovskites are analyzed in the colossal magnetoresistance regime. The
calculations are based on a generalization of a variational approach previously
proposed for the study of manganite bulk. It is found that a reduction in the
thickness of the film causes a decrease of critical temperature and
magnetization, and an increase of resistivity at low temperatures. The strain
is introduced through the modifications of in-plane and out-of-plane electron
hopping amplitudes due to substrate-induced distortions of the film unit cell.
The strain effects on the transition temperature and transport properties are
in good agreement with experimental data only if the dependence of the hopping
matrix elements on the $Mn-O-Mn$ bond angle is properly taken into account.
Finally variations of the electron-phonon coupling linked to the presence of
strain turn out important in influencing the balance of coexisting phases in
the film

###The role of the cooperative Jahn-Teller effect in the charge ordered La1-xCaxMnO3 (0.5<=x<=0.87) manganites|R. K. Zheng,G. Li,A. N. Tang,Y. Yang,W. Wang,X. G. Li,Z. D. Wang,H. C. Ku###

The role of the cooperative Jahn-Teller effect in the charge ordered La1-xCaxMnO3 (0.5<=x<=0.87) manganites. Based on the magnetoresistance, magnetization, ultrasound, and
crystallographic data, we studied the role of the cooperative Jahn-Teller
effect in the charge ordered (CO) state for La1-xCaxMnO3. We found that, with
increasing the fraction of Q3 mode of Jahn-Teller distortion and decreasing
that of Q2 mode in the CO state, the magnetic structure evolves from CE-type to
C-type and the orbital ordering changes from 3d(x2-r2)/3d(y2-r2)-type to
3d(x2-z2)-type, with the strength of ferromagnetism and the phase separation
tendency being suppressed. At the same time, the stability of the CO state and
the cooperative Jahn-Teller lattice distortion increase. These effects imply
that the cooperative Jahn-Teller effect with different vibration modes is the
key ingredient in understanding the essential physics of the CO state.

###Paramagnetic anisotropic magnetoresistance in thin films of SrRuO3|Isaschar Genish,Yevgeny Kats,Lior Klein,James W. Reiner,M. R. Beasley###

Paramagnetic anisotropic magnetoresistance in thin films of SrRuO3. SrRuO3 is an itinerant ferromagnet and in its thin film form when grown on
miscut SrTiO3 it has Tc of ~ 150 K and strong uniaxial anisotropy. We measured
both the Hall effect and the magnetoresistance (MR) of the films as a function
of the angle between the applied field and the normal to the films at
temperatures above Tc. We extracted the extraordinary Hall effect that is
proportional to the perpendicular component of the magnetization and thus the
MR for each angle of the applied field could be correlated with the magnitude
and orientation of the induced magnetization. We successfully fit the MR data
with a second order magnetization expansion, which indicates large anisotropic
MR in the paramagnetic state. The extremum values of resistivity are not
obtained for currents parallel or perpendicular to the magnetization, probably
due to the crystal symmetry.

###Correlated vortex pinning in Si-nanoparticle doped MgB2|I. Kusevic,E. Babic,O. Husnjak,S. Soltanian,X. L. Wang,S. X. Dou###

Correlated vortex pinning in Si-nanoparticle doped MgB2. The magnetoresistivity and critical current density of well characterized
Si-nanoparticle doped and undoped Cu-sheathed MgB$_{2}$ tapes have been
measured at temperatures $T\geq 28$ K in magnetic fields $B\leq 0.9$ T. The
irreversibility line $B_{irr}(T)$ for doped tape shows a stepwise variation
with a kink around 0.3 T. Such $B_{irr}(T)$ variation is typical for
high-temperature superconductors with columnar defects (a kink occurs near the
matching field $% B_{\phi}$) and is very different from a smooth $B_{irr}(T)$
variation in undoped MgB$_{2}$ samples. The microstructure studies of
nanoparticle doped MgB$_{2}$ samples show uniformly dispersed nanoprecipitates,
which probably act as a correlated disorder. The observed difference between
the field variations of the critical current density and pinning force density
of the doped and undoped tape supports the above findings.

###Weak antilocalization in quantum wells in tilted magnetic fields|G. M. Minkov,A. V. Germanenko,O. E. Rut,A. A. Sherstobitov,L. E. Golub,B. N. Zvonkov,M. Willander###

Weak antilocalization in quantum wells in tilted magnetic fields. Weak antilocalization is studied in an InGaAs quantum well. Anomalous
magnetoresistance is measured and described theoretically in fields
perpendicular, tilted and parallel to the quantum well plane. Spin and phase
relaxation times are found as functions of temperature and parallel field. It
is demonstrated that spin dephasing is due to the Dresselhaus spin-orbit
interaction. The values of electron spin splittings and spin relaxation times
are found in the wide range of 2D density. Application of in-plane field is
shown to destroy weak antilocalization due to competition of Zeeman and
microroughness effects. Their relative contributions are separated, and the
values of the in-plane electron g-factor and characteristic size of interface
imperfections are found.

###Substrate surface engineering for tailoring properties of functional ceramic thin films|H. -U. Habermeier###

Substrate surface engineering for tailoring properties of functional ceramic thin films. Using oxide substrates for functional ceramic thin film deposition beyond
their usual application as chemical inert, lattice-matched support for the
films represents a novel concept in ceramic thin film research. The substrates
are applied as a functional element in order to controllably modify the atom
arrangement and the growth mode of ceramic prototype materials such as cuprate
superconductors and colossal magnetoresistance manganites. One example is the
use of epitaxial strain to adjust the relative positions of cations and anions
in the film and thus modify their physical properties. The other makes use of
vicinal cut SrTiO3 which enables the fabrication of regular nanoscale step and
terrace structures. In YBa2Cu3O7-x thin films grown on vicinal cut SrTiO3
single crystals a regular array of antiphase boundaries is generated causing an
anisotropic enhancement of flux-line pinning. In the case of La-Ca-Mn-O thin
films grown on vicinal cut substrates it could be demonstrated that magnetic
in-plane anisotropy is achieved.

###Interactions in high-mobility 2D electron and hole systems|E. A. Galaktionov,A. K. Savchenko,S. S. Safonov,Y. Y. Proskuryakov,L. Li,M. Pepper,M. Y. Simmons,D. A. Ritchie,E. H. Linfield,Z. D. Kvon###

Interactions in high-mobility 2D electron and hole systems. Electron-electron interactions mediated by impurities are studied in several
high-mobility two-dimensional (electron and hole) systems where the parameter
$k_BT\tau /\hbar $ changes from 0.1 to 10 ($\tau$ is the momentum relaxation
time). This range corresponds to the \textit{intermediate} and \textit
{ballistic} regimes where only a few impurities are involved in
electron-electron interactions. The interaction correction to the Drude
conductivity is detected in the temperature dependence of the resistance and in
the magnetoresistance in parallel and perpendicular magnetic fields. The
effects are analysed in terms of the recent theories of electron interactions
developed for the ballistic regime. It is shown that the character of the
fluctuation potential (short-range or long-range) is an important factor in the
manifestation of electron-electron interactions in high-mobility 2D systems.

###Competition Between Fractional Quantum Hall Liquid, Bubble and Wigner Crystal Phases in the Third Landau Level|G. Gervais,L. W. Engel,H. L. Stormer,D. C. Tsui,K. W. Baldwin,K. W. West,L. N. Pfeiffer###

Competition Between Fractional Quantum Hall Liquid, Bubble and Wigner Crystal Phases in the Third Landau Level. Magnetotransport measurements were performed in a ultra-high mobility
GaAs/AlGaAs quantum well of density $\sim 3.0 \times 10^{11}$ $cm^{-2}$. The
temperature dependence of the magnetoresistance $R_{xx}$ was studied in detail
in the vicinity of $\nu={9/2}$. In particular, we discovered new minima in
$R_{xx}$ at filling factor $\nu\simeq 4{1/5}$ and $4{4/5}$, but only at
intermediate temperatures $80\lesssim T\lesssim 120$ mK. We interpret these as
evidence for a fractional quantum Hall liquid forming in the N=2 Landau level
and competing with bubble and Wigner crystal phases favored at lower
temperatures. Our data suggest that a magnetically driven insulator-insulator
quantum phase transition occurs between the bubble and Wigner crystal phases at
T=0.

###Giant magnetoresistance of multiwall carbon nanotubes: modeling the tube/ferromagnetic-electrode burying contact|S. Krompiewski,R. Gutierrez,G. Cuniberti###

Giant magnetoresistance of multiwall carbon nanotubes: modeling the tube/ferromagnetic-electrode burying contact. We report on the giant magnetoresistance (GMR) of multiwall carbon nanotubes
with ultra small diameters. In particular, we consider the effect of the
inter-wall interactions and the lead/nanotube coupling. Comparative studies
have been performed to show that in the case when all walls are well coupled to
the electrodes, the so-called inverse GMR can appear. The tendency towards a
negative GMR depends on the inter-wall interaction and on the nanotube le ngth.
If, however, the inner nanotubes are out of contact with one of the electrodes,
the GMR remains positive even for relatively strong inter-wall interactions
regardless of the outer nanotube length. These results shed additional light on
recently reported experimental data, where an inverse GMR was found in some
multiwall carbon nanotube samples.

###Crossover in the Structure Between Bloch and Linear Domain Walls|Pavel Krotkov###

Crossover in the Structure Between Bloch and Linear Domain Walls. Near the Curie temperature of a ferromagnet the form of a domain wall changes
from the Bloch type to (asymptotically) the linear Zhirnov wall. Unlike the
simple 180 degree rotation of the magnetization vector in a Bloch wall, its
absolute value diminishes near the center of the wall. This leads to a decrease
of the total transverse component of the exchange field inside the wall and to
an increase of mistracking of the spins of the electrons traversing the wall.
This mechanism may help explain large magnetoresistance of domain walls in thin
nanowires, as the Curie temperatures of low-dimensional nanostructures are
known to be lower than in bulk ferromagnets while the anisotropy energy stays
virtually unchanged.

###Asymmetric I-V characteristics and magnetoresistance in magnetic point contacts|A. R. Rocha,S. Sanvito###

Asymmetric I-V characteristics and magnetoresistance in magnetic point contacts. We present a theoretical study of the transport properties of magnetic point
contacts under bias. Our calculations are based on the Keldish's
non-equilibrium Green's function formalism combined with a self-consistent
empirical tight-binding Hamiltonian, which describes both strong ferromagnetism
and charging effects. We demonstrate that large magnetoresistance solely due to
electronic effects can be found when a sharp domain wall forms inside a
magnetic atomic-scale point contact. Moreover we show that the symmetry of the
$I$-$V$ characteristic depends on the position of the domain wall in the
constriction. In particular diode-like curves can arise when the domain wall is
placed off-center within the point contact, although the whole structure does
not present any structural asymmetry.

###Giant magnetic-field changes in radio-frequency absorption in La$_{0.67}$Sr$_{0.33}$MnO$_3$ near the Curie temperature|B. I. Belevtsev,A. Ya. Kirichenko,N. T. Cherpak,G. V. Golubnichaya,I. G. Maximchuk,E. Yu. Beliayev,A. S. Panfilov,J. Fink-Finowicki###

Giant magnetic-field changes in radio-frequency absorption in La$_{0.67}$Sr$_{0.33}$MnO$_3$ near the Curie temperature. The DC transport properties of and the radio-frequency (RF) wave absorption
(at 2.525 MHz) in a sample of La$_{0.67}$Sr$_{0.33}$MnO$_{3}$ prepared by
floating-zone method are measured. The Curie temperature, $T_{c}$, of the
sample is about 374 K. Giant temperature and magnetic-field variations in RF
absorption are found in the vicinity of $T_{c}$. Relative change of the RF
absorption in magnetic field (magnetoabsorption) is about 67% in field 2.1 kOe
and about 55% in field 1 kOe. This giant magnetoabsorption effect can be used
to develop RF devices controlled by temperature and low magnetic field. A weak
temperature dependence of magnetoabsorption for the sample studied in the range
from room temperature to about 350 K makes it especially attractive for
practical use. The RF study supplemented with transport, magnetoresistive and
magnetic measurements enables us to discuss the optimal properties of manganite
samples for observation of giant magnetoabsorption in low field.

###Metamagnetic Transition in Na$_{0.85}$CoO$_2$ Single Crystals|J. L. Luo,N. L. Wang,G. T. Liu,D. Wu,X. N. Jing,F. Hu,T. Xiang###

Metamagnetic Transition in Na$_{0.85}$CoO$_2$ Single Crystals. We report the magnetization, specific heat and transport measurements of high
quality Na$_{0.85}$CoO$_2$ single crystals in applied magnetic fields up to
14T. In high temperatures, the system is in a paramagnetic phase. It undergoes
a magnetic phase transition below about 20K. When the field is applied along
the c-axis, the measurement data of magnetization, specific heat and
magnetoresistance reveal a metamagnetic transition from an antiferromagnetic
state to a quasi-ferromagnetic state at about 8T in low temperatures. However,
no transition is observed in the magnetization measurements up to 14T when the
field is applied perpendicular to the c-axis. The low temperature magnetic
phase diagram of Na$_{0.85}$CoO$_2$ is determined.

###Magic angle effects in the interlayer magnetoresistance of quasi-one-dimensional metals due to interchain incoherence|Urban Lundin,Ross H. McKenzie###

Magic angle effects in the interlayer magnetoresistance of quasi-one-dimensional metals due to interchain incoherence. The dependence of the magnetoresistance of quasi-one-dimensional metals on
the direction of the magnetic field show dips when the field is tilted at the
so called magic angles determined by the structural dimensions of the
materials. There is currently no accepted explanation for these magic angle
effects. We present a possible explanation. Our model is based on the
assumption that, the intralayer transport in the second most conducting
direction has a small contribution from incoherent electrons. This incoherence
is modelled by a small uncertainty in momentum perpendicular to the most
conducting (chain) direction. Our model predicts the magic angles seen in
interlayer transport measurements for different orientations of the field. We
compare our results to predictions by other models and to experiment.

###Percolation and Colossal Magnetoresistance in Eu-based Hexaborides|G. A. Wigger,C. Beeli,E. Felder,H. R. Ott,A. D. Bianchi,Z. Fisk###

Percolation and Colossal Magnetoresistance in Eu-based Hexaborides. Upon substituting Ca for Eu in the local-moment ferromagnet EuB$_6$, the
Curie temperature $T_C$ decreases substantially with increasing dilution of the
magnetic sublattice and is completely suppressed for $x$ $\leq$ 0.3. The Ca
substitution leads to significant changes of the electronic properties across
the Eu$_x$Ca$_{1-x}$B$_6$ series. Electron microscopy data for $x$ $\approx$
0.27 indicate a phase separation into Eu- and Ca-rich clusters of 5 to 10 nm
diameter, leading to percolation-type phenomena in the electrical transport
properties. The related critical concentration $x_p$ is approximately 0.3. For
$x$ $\approx$ 0.27, we observe colossal negative magnetoresistance effects at
low temperatures, similar in magnitude as those reported for manganese oxides.

###A Circuit Model for Domain Walls in Ferromagnetic Nanowires: Application to Conductance and Spin Transfer Torques|Peter E. Falloon,Rodolfo A. Jalabert,Dietmar Weinmann,Robert L. Stamps###

A Circuit Model for Domain Walls in Ferromagnetic Nanowires: Application to Conductance and Spin Transfer Torques. We present a circuit model to describe the electron transport through a
domain wall in a ferromagnetic nanowire. The domain wall is treated as a
coherent 4-terminal device with incoming and outgoing channels of spin up and
down and the spin-dependent scattering in the vicinity of the wall is modelled
using classical resistances. We derive the conductance of the circuit in terms
of general conductance parameters for a domain wall. We then calculate these
conductance parameters for the case of ballistic transport through the domain
wall, and obtain a simple formula for the domain wall magnetoresistance which
gives a result consistent with recent experiments. The spin transfer torque
exerted on a domain wall by a spin-polarized current is calculated using the
circuit model and an estimate of the speed of the resulting wall motion is
made.

###Polaronic excitations in CMR manganite films|Ch. Hartinger,F. Mayr,A. Loidl,T. Kopp###

Polaronic excitations in CMR manganite films. In the colossal magnetoresistance manganites polarons have been proposed as
the charge carrier state which localizes across the metal-insulator transition.
The character of the polarons is still under debate. We present an assessment
of measurements which identify polarons in the metallic state of
La{2/3}Sr{1/3}MnO{3} (LSMO) and La{2/3}Ca{1/3}MnO{3} (LCMO) thin films. We
focus on optical spectroscopy in these films which displays a pronounced
resonance in the mid-infrared. The temperature dependent resonance has been
previously assigned to polaron excitations. These polaronic resonances are
qualitatively distinct in LSMO and LCMO and we discuss large and small polaron
scenarios which have been proposed so far. There is evidence for a large
polaron excitation in LSMO and small polarons in LCMO. These scenarios are
examined with respect to further experimental probes, specifically charge
carrier mobility (Hall-effect measurements) and high-temperature
dc-resistivity.

###Carrier-Induced Magnetic Circular Dichloism in the Magnetoresistive Pyrochlore Tl2Mn2O7|H. Okamura,T. Koretsune,S. Kimura,T. Nanba,H. Imai,Y. Shimakawa,Y. Kubo###

Carrier-Induced Magnetic Circular Dichloism in the Magnetoresistive Pyrochlore Tl2Mn2O7. Infrared magnetic circular dichloism (MCD), or equivalently magneto-optical
Kerr effect, has been measured on the Tl2Mn2O7 pyrochlore, which is well known
for exhibiting a large magnetoresistance around the Curie temperature T_C ~ 120
K. A circularly polarized, infrared synchrotron radiation is used as the light
source. A pronounced MCD signal is observed exactly at the plasma edge of the
reflectivity near and below T_c. However, contrary to the conventional behavior
of MCD for ferromagnets, the observed MCD of Tl2Mn2O7 grows with the applied
magnetic field, and not scaled with the internal magnetization. It is shown
that these results can be basically understood in terms of a classical
magnetoplasma resonance. The absence of a magnetization-scaled MCD indicates a
weak spin-orbit coupling of the carriers in Tl2Mn2O7. We discuss the present
results in terms of the microscopic electronic structures of Tl2Mn2O7.

###Feasible Nanometric Magnetoresistance Devices|Oded Hod,Roi Baer,Eran Rabani###

Feasible Nanometric Magnetoresistance Devices. The electrical conductance through a ring is sensitive to the threading
magnetic flux. It contains a component that is periodic with an Aharonov-Bohm
(AB) period equal to the quantum flux. In molecular/atomic loops on the
nanometer scale, encircling very small areas, the AB period involves
unrealistically huge magnetic fields. We show that despite this, moderate
magnetic fields can have a strong impact on the conductance. By controlling the
lifetime of the conduction electron through a pre-selected single state that is
well separated from other states due to the quantum confinement effect, we
demonstrate that magnetic fields comparable to one Tesla can be used to switch
a nanometric AB device. Using atomistic electronic structure calculations, we
show that such effects can be expected for loops composed of monovalent metal
atoms (quantum corals). Our findings suggest that future fabrication of
nanometric magnetoresistance devices is feasible.

###The effects of a magnetic barrier and a nonmagnetic spacer in tunnel structures|Ali A. Shokri,Alireza Saffarzadeh###

The effects of a magnetic barrier and a nonmagnetic spacer in tunnel structures. The spin-polarized transport is investigated in a new type of magnetic tunnel
junction which consists of two ferromagnetic electrodes separated by a magnetic
barrier and a nonmagnetic metallic spacer. Based on the transfer matrix method
and the nearly-free-electron-approximation the dependence of the tunnel
magnetoresistance (TMR) and electron-spin polarization on the nonmagnetic layer
thickness and the applied bias voltage are studied theoretically. The TMR and
spin polarization show an oscillatory behavior as a function of the spacer
thickness and the bias voltage. The oscillations originate from the quantum
well states in the spacer, while the existence of the magnetic barrier gives
rise to a strong spin polarization and high values of the TMR. Our results may
be useful for the development of spin electronic devices based on coherent
transport.

###Thermopower peak in phase transition region of (1-x)La$_{2/3}$Ca$_{1/3}$MnO$_{3}$/xYSZ|Wei Liu,Jun Zhao,Chinping Chen,Shousheng Yan,Zhengcai Xia,Sheng Liu###

Thermopower peak in phase transition region of (1-x)La$_{2/3}$Ca$_{1/3}$MnO$_{3}$/xYSZ. The thermoelectric power (TEP) and the electrical resistivity of the
intergranular magnetoresistance (IGMR) composite,
(1-x)La$_{2/3}$Ca$_{1/3}$MnO$_{3}$/xYSZ (LCMO/YSZ) with x = 0, 0.75%, 1.25%,
4.5%, 13% 15% and 80% of the yttria-stabalized zirconia (YSZ), have been
measured from 300 K down to 77 K. Pronounced TEP peak appears during the phase
transition for the samples of x $>$ 0, while not observed for x = 0. We suggest
that this is due to the magnetic structure variation induced by the lattice
strain which is resulting from the LCMO/YSZ boundary layers. The transition
width in temperature derived from $d\chi/dT$, with $\chi$ being the AC magnetic
susceptibility, supports this interpretation.

###Reorientation in Antiferromagnetic Multilayers: Spin-Flop Transition and Surface Effects|U. K. Roessler,A. N. Bogdanov###

Reorientation in Antiferromagnetic Multilayers: Spin-Flop Transition and Surface Effects. Nanoscale superlattices with uniaxial ferromagnetic layers
antiferromagnetically coupled through non-magnetic spacers are recently used as
components of magnetoresistive and recording devices. In the last years
intensive experimental investigations of these artificial antiferromagnets have
revealed a large variety of surface induced reorientational effects and other
remarkable phenomena unknown in other magnetic materials. In this paper we
review and generalize theoretical results, which enable a consistent
description of the complex magnetization processes in antiferromagnetic
multilayers, and we explain the responsible physical mechanism. The general
structure of phase diagrams for magnetic states in these systems is discussed.
In particular, our results resolve the long standing problem of a ``surface
spin-flop'' in antiferromagnetic layers. This explains the different appearance
of field-driven reorientation transitions in systems like Fe/Cr (001) and (211)
superlattices, and in [CoPt]/Ru multilayers with strong perpendicular
anisotropy.

###Electronic phase separation in the itinerant metamagnetic transition of Sr$_4$Ru$_3$O$_{10}$|Zhiqiang Mao,Meng Zhou,Joe Hooper,Vladimir Golub,Charles J. O'Connor###

Electronic phase separation in the itinerant metamagnetic transition of Sr$_4$Ru$_3$O$_{10}$. Triple-layered ruthenate Sr$_4$Ru$_3$O$_{10}$ shows a first-order itinerant
metamagnetic transition for in-plane magnetic fields. Our experiments revealed
rather surprising behavior in the low-temperature transport properties near
this transition. The in-plane magnetoresistivity $\rho$$_{ab}$(H) exhibits
ultrasharp steps as the magnetic field sweeps down through the transition.
Temperature sweeps of $\rho$$_{ab}$ for fields within the transition regime
show non-metallic behavior in the up-sweep cycle of magnetic field, but show a
significant drop in the down-sweep cycle. These observations indicate that the
transition occurs via a new electronic phase separation process; a lowly
polarized state is mixed with a ferromagnetic state within the transition
regime.

###Magnetoresistance Devices Based on Single Walled Carbon Nanotubes|Oded Hod,Eran Rabani,Roi Baer###

Magnetoresistance Devices Based on Single Walled Carbon Nanotubes. We demonstrate the physical principles for the construction of a nanometer
sized magnetoresistance device based on the Aharonov-Bohm effect. The proposed
device is made of a short single-walled carbon nanotube (SWCNT) placed on a
substrate and coupled to a tip. We consider conductance due to motion of
electrons along the circumference of the tube (as opposed to motion parallel to
its axis). We find that the circumference conductance is sensitive to magnetic
fields threading the SWCNT due to the Aharonov-Bohm effect, and show that by
retracting the tip, so that its coupling to the SWCNT is reduced, very high
sensitivity to the threading magnetic field develops. This is due to the
formation of a narrow resonance through which the tunneling current flows.
Using a bias potential the resonance can be shifted to low magnetic fields,
allowing the control of conductance with magnetic fields of the order of 1
Tesla.

###Large LFMR observed in twinned La2/3Ca1/3MnO3 thin films epitaxially grown on YSZ-buffered SOI substrates|J. Li,P. Wang,J. Y. Xiang,X. H. Zhu,W. Peng,Y. F. Chen,D. N. Zheng,Z. W. Li###

Large LFMR observed in twinned La2/3Ca1/3MnO3 thin films epitaxially grown on YSZ-buffered SOI substrates. La2/3Ca1/3MnO3 thin films have been grown on yttria-stabilized zirconia (YSZ)
buffered silicon-on-insulator (SOI) substrate by the pulsed laser deposition
technique. While full cube-on-cube epitaxy was achieved for the YSZ layer, the
top manganite layer was multi-domain-oriented, with a coexistence of
cube-on-cube and cube-on-diagonal epitaxy. Due to a combined influence from the
magnetocrystalline anisotropy and the magnetoelastic anisotropy, in zero field
the local spin orientation varies across the twin boundaries. As a result, a
quite large low-field magnetoresistance (LFMR) based on spin-dependent
tunnelling was observed. The film shows a resistance change of ~20% in a
magnetic field <1000 Oe at 50 K, which is promising for real applications.

###Hysteresis in the quantum Hall regimes in electron double quantum well structures|W. Pan,J. L. Reno,J. A. Simmons###

Hysteresis in the quantum Hall regimes in electron double quantum well structures. We present in this paper experimental results on the transport hysteresis in
electron double quantum well structures. Exploring the measurement technique of
fixing the magnetic field and sweeping a front gate voltage (Vg), we are able
to study the hysteresis by varying the top layer Landau level fillings while
maintaining a relatively constant filling factor in the bottom layer, allowing
us to tackle the question of the sign of Rxx(up)-Rxx(down), where Rxx(up) is
the magnetoresistance when Vg is swept up and Rxx(down) when Vg swept down.
Furthermore, we observe that hysteresis is generally stronger in the even
integer quantum Hall effect (IQHE) regime than in the odd-IQHE regime. This, we
argue, is due to a larger energy gap for an even-IQHE state, determined by the
Landau level separation, than that for an odd-IQHE state, determined by the
Zeeman splitting.

###Recent Advances in Unconventional Density Waves|Balázs Dóra,Kazumi Maki,Attila Virosztek###

Recent Advances in Unconventional Density Waves. Unconventional density wave (UDW) has been speculated as a possible
electronic ground state in excitonic insulator in 1968. Recent surge of
interest in UDW is partly due to the proposal that the pseudogap phase in high
T_c cuprate superconductors is d-wave density wave (d-DW).
  Here we review our recent works on UDW within the framework of mean field
theory. In particular we have shown that many properties of the low temperature
phase (LTP) in alpha-(BEDT-TTF)_2MHg(SCN)_4 with M=K, Rb and Tl are well
characterized in terms of unconventional charge density wave (UCDW). In this
identification the Landau quantization of the quasiparticle motion in a
magnetic field (the Nersesyan effect) plays the crucial role. Indeed the
angular dependent magnetoresistance and the negative giant Nernst effect are
two hallmarks of UDW.

###Room temperature tunneling magnetoresistance in magnetite based junctions: Influence of tunneling barrier|D. Reisinger,P. Majewski,M. Opel,L. Alff,R. Gross###

Room temperature tunneling magnetoresistance in magnetite based junctions: Influence of tunneling barrier. Magnetite (Fe3O4) based tunnel junctions with turret/mesa structure have been
investigated for different barrier materials (SrTiO3, NdGaO3, MgO, SiO2, and
Al2O(3-x)). Junctions with a Ni counter electrode and an aluminium oxide
barrier showed reproducibly a tunneling magnetoresistance (TMR) effect at room
temperature of up to 5% with almost ideal switching behavior. This number only
partially reflects the intrinsic high spin polarization of Fe3O4. It is
considerably decreased due to an additional series resistance within the
junction. Only SiO2 and Al2O(3-x) barriers provide magnetically decoupled
electrodes as necessary for sharp switching. The observed decrease of the TMR
effect as a function of increasing temperature is due to a decrease in spin
polarization and an increase in spin-scattering in the barrier. Among the oxide
half-metals magnetite has the potential to enhance the performance of TMR based
devices.

###Correlation between tunneling magnetoresistance and magnetization in dipolar coupled nanoparticle arrays|D. Kechrakos,K. N. Trohidou###

Correlation between tunneling magnetoresistance and magnetization in dipolar coupled nanoparticle arrays. The tunneling magnetoresistance (TMR) of a hexagonal array of dipolar coupled
anisotropic magnetic nanoparticles is studied using a resistor network model
and a realistic micromagnetic configuration obtained by Monte Carlo
simulations. Analysis of the field-dependent TMR and the corresponding
magnetization curve shows that dipolar interactions suppress the maximum TMR
effect, increase or decrease the field-sensitivity depending on the direction
of applied field and introduce strong dependence of the TMR on the direction of
the applied magnetic field. For off-plane magnetic fields, maximum values in
the TMR signal are associated with the critical field for irreversible rotation
of the magnetization. This behavior is more pronounced in strongly interacting
systems (magnetically soft), while for weakly interacting systems (magnetically
hard) the maximum of TMR (Hmax) occurs below the coercive field (Hc), in
contrast to the situation for non-interacting nanoparticles or in-plane fields
(Hmax=Hc). The relation of our simulations to recent TMR measurements in
self-assembled Co nanoparticle arrays is discussed.

###Insulator-metal transition and the magnetic phase diagram of La1-xTexMnO3|J. Yang,W. H. Song,Y. Q. Ma,R. L. Zhang,B. C. Zhao,Z. G. Sheng,G. H. Zheng,J. M. Dai,Y. P. Sun###

Insulator-metal transition and the magnetic phase diagram of La1-xTexMnO3. The structural, electrical transport and magnetic properties of perovskite
oxides La1-xTexMnO3 have been investigated and thus the magnetic phase diagram
of La1-xTexMnO3 compounds as a function of temperature and the doping level x
has been obtained. All samples have rhombohedral structure and undergo
paramagnetic-ferromagnetic (PM-FM) transition accompanied with metal-insulator
transition (MIT). Whereas a charge ordering (CO) transition begins to appear at
for the sample with x=0.60. Moreover, the variation of the Curie temperature
and the MIT temperature is quite complex and the results are discussed in terms
of three factors including the average A-site cation radius <rA>, the size
mismatch and the Te content. In addition, there has an evident
magnetoresistance (MR) at low temperatures for all samples.

###Low-Temperature Hall Effect in Substituted Sr2RuO4|N. Kikugawa,A. P. Mackenzie,C. Bergemann,Y. Maeno###

Low-Temperature Hall Effect in Substituted Sr2RuO4. We report the results of a study of the Hall effect and magnetoresistance in
single crystals of Sr2RuO4 in which Sr^(2+) has been substituted by La^(3+)
(Sr(2-y)La(y)RuO(4)) or Ru^(4+) by Ti^(4+) (Sr(2)Ru(1-x)Ti(x)O(4)). For undoped
Sr2RuO4, the purity is so high that the strong-field Hall coefficient can be
measured for fields above 4 T. The conventional weak-field Hall coefficient as
a function of doping shows a sharp jump and sign change at y ~ 0.01 that is
unrelated to either a sharp change in Fermi-surface topography or a magnetic
instability. The implications of these results are discussed.

###Current-induced metallic behavior in Pr$_{0.5}$Ca$_{0.5}$MnO$_3$ thin films: competition between Joule heating and nonlinear conduction mechanism|P. Padhan,W. Prellier,Ch. Simon,R. C. Budhani###

Current-induced metallic behavior in Pr$_{0.5}$Ca$_{0.5}$MnO$_3$ thin films: competition between Joule heating and nonlinear conduction mechanism. Thin films of Pr0.5Ca0.5MnO3 manganites exhibiting charge/orbital-ordered
properties with colossal magnetoresistance have been synthesized by the pulsed
laser deposition technique on both (100)-SrTiO3 and (100)-LaAlO3 substrates.
The effects of current-induced metallic-behavior of the films are investigated
as a function of the temperature and the magnetic field. Calculations based on
a heat transfer model across the substrate, and our resistivity measurements
reveal effects of Joule heating on charge transport over certain ranges of
temperatures and magnetic fields. Our results also indicate that a nonlinear
conduction, which cannot be explained by homogeneous Joule heating of the film,
is observed when the material is less resistive (10-2 W.cm). The origin of this
behavior is explained with a model based on local thermal instabilities
associated with phase-separation mechanism and a change in the long range
charge-ordered state.

###Theory of Zero-Bias Anomaly in Magnetic Tunnel Junctions: Inelastic Tunneling via Impurities|L. Sheng,D. Y. Xing,D. N. Sheng###

Theory of Zero-Bias Anomaly in Magnetic Tunnel Junctions: Inelastic Tunneling via Impurities. Using the closed-time path integral approach, we nonperturbatively study
inelastic tunneling of electrons via magnetic impurities in the barrier
accompanied by phonon emission in a magnetic tunnel junction. The spectrum
density of phonon emission is found to show a power-law infrared singularity
$\sim\omega^{-(1-g)}$ with $g$ the dimensionless electron-phonon coupling. As a
consequence, the tunneling conductance $G(V)$ increases with bias voltage $|
V|$ as $G(V)-G(0)\sim| V|^{2g}$, exhibiting a discontinuity in slope at V=0 for
$g\le 0.5$. This theory can reproduce both cusp-like and non-cusp-like feature
of the zero-bias anomaly of tunneling resistance and magnetoresistance widely
observed in experiments.

###Transition from a fractional quantum Hall liquid to an electron solid at Landau level filling nu = 1/3 in tilted magnetic fields|W. Pan,G. A. Csathy,D. C. Tsui,L. N. Pfeiffer,K. W. West###

Transition from a fractional quantum Hall liquid to an electron solid at Landau level filling nu = 1/3 in tilted magnetic fields. We have observed in a low density two-dimensional hole system (2DHS) of
extremely high quality (with hole density p=1.6x10^{10} cm^{-2} and mobility
\mu=0.8x10^6 cm^2/Vs) that, as the 2DHS is continuously tilted with respect to
the direction of the magnetic field, the \nu=1/3 fractional quantum Hall effect
(FQHE) state is weakened and its magnetoresistivity rises from ~ 0.4
kohm/square in the normal orientation to ~ 180 kohm/square at tilt angle \theta
\~ 80 degrees. We attribute this phenomenon to the transition of the 2DHS from
the FQHE liquid state to the pinned Wigner solid state, and argue that its
origin is the strong coupling of subband Landau levels under the tilted
magnetic fields.

###Microwave strengths to induce magnetoresistance oscillations in high-mobility 2DES in a photon-assisted impurity scattering model|X. L. Lei###

Microwave strengths to induce magnetoresistance oscillations in high-mobility 2DES in a photon-assisted impurity scattering model. It is shown that, although the major feature of the microwave-induced
magnetoresistance oscillations in two-dimensional (2D) electron systems is
insensitive to the behavior of the elastic scattering in the photon-assisted
impurity scattering model [X.L. Lei and S.Y. Liu, Phys. Rev. Lett. 91, 226805
(2003)], the required microwave intensity to induce an effective oscillation
depends strongly on the form of the impurity potential. A microwave electric
field of a few Volts per cm in amplitude is sufficient to induce remarkable
oscillations if the elastic scatterings are due to background charged
impurities, which is an order of magnitude smaller than that needed if the
scatterings are due to remote charged impurities located 60 nm away from 2D
electron gas.

###Investigation into the Itinerant metamagnetism of Sr3Ru2O7 for the Field Parallel to the Ruthenium Oxygen Planes|Robin S. Perry,Takashi Tayama,Kentaro Kitagawa,Toshiro Sakakibara,Kenji Ishida,Yoshiteru Maeno###

Investigation into the Itinerant metamagnetism of Sr3Ru2O7 for the Field Parallel to the Ruthenium Oxygen Planes. We report a detailed investigation into the metamagnetism of Sr3Ru2O7 at low
temperatures for the magnetic field parallel to the ruthenium oxygen planes.
The metamagnetism is studied as a function of temperature, magnetic field and
sample quality using magnetisation, magnetotransport and specific heat as
probes. From hysteretic behaviour in the magnetisation, we confirm earlier work
and observe a finite temperature critical point at (5 T, >0.25 K). In our
highest quality samples two-step metamagnetic transitions are additionally
observed at 5.8 T and at 6.3 T, which coincide with a range of broad maximum in
the magnetoresistance. At low temperatures, these two metamagnetic features
each further split in two. Such behaviour of the multiple transitions are
qualitatively different from the first order transition at 5.1 T.

###How to map a pseudogap?|V. N. Zavaritsky###

How to map a pseudogap?. A pseudogap (PG) is believed to be responsible for the non Fermi-liquid
normal state of cuprate superconductors. In particular, field induced PG
collapse causes negative longitudinal magnetoresistance (MR), for details, see
V.N. Zavaritsky, M. Springford, A.S. Alexandrov, cond-mat/0006089;
cond-mat/0011192. The PG collapses because of spin-splitting of the polaron
band while the orbital effects are irrelevant. Recently these conclusions,
including the Zeeman relation, $k_BT^*=gB_{pg}$, which couples the PG
temperature, $T^*$, and the PG closing field, $B_{pg}$, were reaffirmed by T.
Shibauchi {\it et al.}, Phys. Rev. Lett. {\bf 86}, 5763 (2001). It will
demonstrate that the article by T. Shibauchi {\it et al.} lacks consistency and
its conclusions are based on fallacious propositions and unsupported by the
authors' own experimental results.

###Spin effects in electron tunnelling through a quantum dot coupled to non-collinearly polarized ferromagnetic leads|W. Rudzinski,J. Barnas,R. Swirkowicz,M. Wilczynski###

Spin effects in electron tunnelling through a quantum dot coupled to non-collinearly polarized ferromagnetic leads. Spin-dependent transport through an interacting single-level quantum dot
coupled to ferromagnetic leads with non-collinear magnetizations is analyzed
theoretically. The transport properties and average spin of the dot are
investigated within the nonequilibrium Green function technique based on the
equation of motion in the Hartree-Fock approximation. Numerical results show
that Coulomb correlations on the dot and strong spin polarization of the leads
significantly enhance precession of the average dot spin around the effective
molecular field created by the external electrodes. Moreover, they also show
that spin precession may lead to negative differential conductance in the
voltage range between the two relevant threshold voltages. Nonmonotonous
angular variation of electric current and change in sign of the tunnel
magnetoresistance are also found. It is also shown that the diode-like behavior
in asymmetrical junctions with one electrode being half-metallic is
significantly reduced in noncollinear configurations.

###Magnetic properties of pure and Gd doped EuO probed by NMR|Arnaud Comment,Jean-Philippe Ansermet,Charles P. Slichter,Heesuk Rho,Clark S. Snow,S. Lance Cooper###

Magnetic properties of pure and Gd doped EuO probed by NMR. An Eu NMR study in the ferromagnetic phase of pure and Gd doped EuO was
performed. A complete description of the NMR lineshape of pure EuO allowed for
the influence of doping EuO with Gd impurities to be highlighted. The presence
of a temperature dependent static magnetic inhomogeneity in Gd doped EuO was
demonstrated by studying the temperature dependence of the lineshapes. The
results suggest that the inhomogeneity in 0.6% Gd doped EuO is linked to
colossal magnetoresistance. The measurement of the spin-lattice relaxation
times as a function of temperature led to the determination of the value of the
exchange integral J as a function of Gd doping. It was found that J is
temperature independent and spatially homogeneous for all the samples and that
its value increases abruptly with increasing Gd doping.

###Time-dependent universal conductance fluctuations and coherence in AuPd and Ag|A. Trionfi,S. Lee,D. Natelson###

Time-dependent universal conductance fluctuations and coherence in AuPd and Ag. Quantum transport phenomena allow experimental assessment of the phase
coherence information in metals. We report quantitative comparisons of
coherence lengths inferred from weak localization magnetoresistance
measurements and time-dependent universal conductance fluctuation data. We
describe these two measurements and their analysis. Strong agreement is
observed in both quasi-2D and quasi-1D AuPd samples, a metal known to have high
spin-orbit scattering. However, quantitative {\it disagreement} is seen in
quasi-1D Ag wires below 10 K, a material with intermediate spin-orbit
scattering. We consider explanations of this discrepancy, with particular
emphasis on the theoretical expressions used to analyze the field dependence of
the conductance fluctuations. We also discuss the mechanism of the suppression
of conductance fluctuations at high drive levels, and dephasing mechanisms at
work in these systems.

###Magnetic-field-induced Fermi surface reconstruction in Na$_{0.5}$CoO$_2$|L. Balicas,M. Abdel-Jawad,N. E. Hussey,F. C. Chou,P. A. Lee###

Magnetic-field-induced Fermi surface reconstruction in Na$_{0.5}$CoO$_2$. We have performed electrical transport measurements at low temperatures and
high magnetic fields in Na$_{0.5}$CoO$_2$ single crystals. Shubnikov de Haas
oscillations were observed for two frequencies F_1 150 and F_2 40 T
corresponding respectively to 1 and .25% of the area of the orthorhombic
Brillouin zone. These small Fermi surface (FS) pockets indicate that most of
the original FS vanishes at the charge ordering (CO) transition. Furthermore,
in-plane magnetic fields strongly suppress the CO state. For fields rotating
within the conducting planes we observe angular magnetoresistance oscillations
(AMRO), whose periodicity changes from two- to six-fold at the transition,
suggesting that a reconstructed hexagonal FS emerges at a field of about 40 T.

###Magnetoresistance of p-GaAs/AlGaAs structures in the vicinity of metal-insulator transition: Effect of superconducting leads|N. V. Agrinskaya,V. I. Kozub,A. V. Chernyaev,D. V. Shamshur,A. A. Zuzin###

Magnetoresistance of p-GaAs/AlGaAs structures in the vicinity of metal-insulator transition: Effect of superconducting leads. Experimental and theoretical studies on transport in semiconductor samples
with superconducting electrodes are reported. We focus on the samples close to
metal-insulator transition. In metallic samples, a peak of negative
magnetoresistance at fields lower than critical magnetic field of the leads was
observed. This peak is attributed to restoration of a single-particle tunneling
emerging with suppression of superconductivity. The experimental results allow
us to estimate tunneling transparency of the boundary between superconductor
and metal. In contrast, for the insulating samples no such a peak was observed.
We explain this behavior as related to properties of transport through the
contact between superconductor and hopping conductor. This effect can be used
to discriminate between weak localization and strong localization regimes.

###Spin-dependent resonant tunneling through quantum-well states in magnetic metallic thin films|Zhong-Yi Lu,X. -G. Zhang,Sokrates T. Pantelides###

Spin-dependent resonant tunneling through quantum-well states in magnetic metallic thin films. Quantum-well (QW) states in {\it nonmagnetic} metal layers contained in
magnetic multilayers are known to be important in spin-dependent transport, but
the role of QW states in {\it magnetic} layers remains elusive. Here we
identify the conditions and mechanisms for resonant tunneling through QW states
in magnetic layers and determine candidate structures. We report
first-principles calculations of spin-dependent transport in epitaxial
Fe/MgO/FeO/Fe/Cr and Co/MgO/Fe/Cr tunnel junctions. We demonstrate the
formation of sharp QW states in the Fe layer and show discrete conductance
jumps as the QW states enter the transport window with increasing bias. At
resonance, the current increases by one to two orders of magnitude. The
tunneling magnetoresistance ratio is several times larger than in simple spin
tunnel junctions and is positive (negative) for majority- (minority-) spin
resonances, with a large asymmetry between positive and negative biases. The
results can serve as the basis for novel spintronic devices.

###Nonlinear transport through a finite Hubbard chain connected to the electrodes|Kamil Walczak###

Nonlinear transport through a finite Hubbard chain connected to the electrodes. Coherent electronic transport through a molecular device is studied using
non-equilibrium Green's function (NEGF) formalism. Such device is made of a
short linear wire which is connected to para- and ferromagnetic electrodes.
Molecule itself is described with the help of Huckel (tight-binding) model with
the electron interactions treated within Hubbard approach, while the coupling
to the electrodes is modeled through the use of a broad-band theory. Coulomb
interactions within molecular wire are treated by means of the Hartree-Fock
(HF) approximation. For the case of asymmetric coupling to paramagnetic
electrodes, charging-induced rectification effect in biased molecular devices
is discussed as a consequence of Coulomb repulsion. For the system with
ferromagnetic electrodes, a significant magnetoresistance (MR) is predicted and
its oscillations generated by Coulomb interactions are considered.

###High-frequency transport in $p$-type Si/Si$_{0.87}$Ge$_{0.13}$ heterostructures studied with surface acoustic waves in the quantum Hall regime|I. L. Drichko,A. M. Diakonov,I. Yu. Smirnov,G. O. Andrianov,O. A. Mironov,M. Myronov,D. R. Leadley,T. E. Whall###

High-frequency transport in $p$-type Si/Si$_{0.87}$Ge$_{0.13}$ heterostructures studied with surface acoustic waves in the quantum Hall regime. The interaction of surface acoustic waves (SAW) with $p$-type
Si/Si$_{0.87}$Ge$_{0.13}$ heterostructures has been studied for SAW frequencies
of 30-300 MHz. For temperatures in the range 0.7$<T<$1.6 K and magnetic fields
up to 7 T, the SAW attenuation coefficient $\Gamma$ and velocity change $\Delta
V /V$ were found to oscillate with filling factor. Both the real $\sigma_1$ and
imaginary $\sigma_2$ components of the high-frequency conductivity have been
determined and compared with quasi-dc magnetoresistance measurements at
temperatures down to 33 mK. By analyzing the ratio of $\sigma_1$ to $\sigma_2$,
carrier localization can be followed as a function of temperature and magnetic
field. At $T$=0.7 K, the variations of $\Gamma$, $\Delta V /V$ and $\sigma_1$
with SAW intensity have been studied and can be explained by heating of the two
dimensional hole gas by the SAW electric field. Energy relaxation is found to
be dominated by acoustic phonon deformation potential scattering with weak
screening.

###Effect of oxygen content on the transport properties and magnetoresistance in [Ca$_{2}$CoO$_{3-δ}$]$_{0.62}$[CoO$_{2}$] single crystals|X. G. Luo,X. H. Chen,G. Y. Wang,C. H. Wang,Y. M. Xiong,H. B. Song,H. Li,X. X. Lu###

Effect of oxygen content on the transport properties and magnetoresistance in [Ca$_{2}$CoO$_{3-δ}$]$_{0.62}$[CoO$_{2}$] single crystals. Transport property is investigated in
[Ca$_{2}$CoO$_{3-\delta}$]$_{0.62}$[CoO$_{2}$] single crystals obtained by
varying annealing conditions. The $\rho_{ab}(T)$ exhibits a resistivity
minimum, and the temperature corresponding to this minimum increases with the
loss of oxygen content, indicative of the enhancement of spin density wave
(SDW). Large negative magnetoresistance (MR) was observed in all single
crystals [Ca$_{2}$CoO$_{3-\delta}$]$_{0.62}$[CoO$_{2}$], while a
magnetic-field-driven insulator-to-metal (IM) transition in oxygen annealed
samples. These results suggest a ferromagnetic correlation in system enhanced
by oxygen content. In addition, a low temperature thermal activation
resistivity induced by fields was observed in single crystals annealed in
oxygen atmosphere.

###Quantum interference of electrons in Nb_{5-δ}Te_4 single crystals|A. Stolovits,A. Sherman,R. K. Kremer,Hj. Mattausch,H. Okudera,X-M. Ren,A. Simon,J. R. O'Brien###

Quantum interference of electrons in Nb_{5-δ}Te_4 single crystals. The compound $Nb_{5-\delta}Te_4$ ($\delta=0.23$) with quasi-one-dimensional
crystal structure undergoes a transition to superconductivity at $T_c$=0.6--0.9
K. Its electronic transport properties in the normal state are studied in the
temperature range 1.3--270 K and in magnetic fields up to 11 T. The temperature
variation of the resistivity is weak ($<2%$) in the investigated temperature
range. Nonmonotonic behavior of the resistivity is observed which is
characterized by two local maxima at $T\sim$2 K and $\sim$30 K. The temperature
dependence of the resistivity is interpreted as an interplay of weak
localization, weak antilocalization, and electron-electron interaction effects
in the diffusion and the Cooper channel. The temperature dependence of the
dephasing time $\tau_\phi$ extracted from the magnetoresistance data is
determined by the electron-phonon interaction. The saturation of $\tau_\phi$ in
the low-temperature limit correlates with $T_c$ of the individual crystal and
is ascribed to the scattering on magnetic impurities.

###Hysteresis and Anisotropic Magnetoresistance in Antiferromagnetic $Nd_{2-x}Ce_xCuO_{4}$|X. H. Chen,C. H. Wang,G. Y. Wang,X. G. Luo,J. L. Luo,G. T. Liu,N. L. Wang###

Hysteresis and Anisotropic Magnetoresistance in Antiferromagnetic $Nd_{2-x}Ce_xCuO_{4}$. The out-of-plane resistivity ($\rho_c$) and magnetoresistivity (MR) are
studied in antiferromangetic (AF) $Nd_{2-x}Ce_xCuO_{4}$ single crystals, which
have three types of noncollinear antiferromangetic spin structures. The
apparent signatures are observed in $\rho_c(T)$ measured at the zero-field and
14 T at the spin structure transitions, giving a definite evidence for the
itinerant electrons directly coupled to the localized spins. One of striking
feature is an anisotropy of the MR with a fourfold symmetry upon rotating the
external field (B) within ab plane in the different phases, while twofold
symmetry at spin reorientation transition temperatures. The intriguing thermal
hysteresis in $\rho_c(T,B)$ and magnetic hysteresis in MR are observed at spin
reorientation transition temperatures.

###Anomalous Magnetoresistance in Pb-doped Bi$_2$Sr$_2$Co$_2$O$_y$ Single Crystals|X. G. Luo,X. H. Chen,G. Y. Wang,C. H. Wang,X. Li,W. J. Miao,G. Wu,Y. M. Xiong###

Anomalous Magnetoresistance in Pb-doped Bi$_2$Sr$_2$Co$_2$O$_y$ Single Crystals. Magnetoresistance (MR) of the Bi$_{2-x}$Pb$_x$Sr$_2$Co$_2$O$_y$ ($x$=0, 0.3,
0.4) single crystals is investigated systematically. A nonmonotonic variation
of the isothermal in-plane and out-of-plane MR with the field is observed. The
out-of-plane MR is positive in high temperatures and increases with decreasing
$T$, and exhibits a pronounced hump, and changes the sign from positive to
negative at a centain temperature. These results strongly suggest that the
observed MR consists of two contributions: one \emph{negative} and one
\emph{positive} component. The isothermal MR in high magnetic fields follows a
$H^2$ law. While the negative contribution comes from spin scattering of
carriers by localized-magnetic-moments based on the Khosla-Fischer model.

###Temperature and voltage dependence of magnetic barrier junctions with a nonmagnetic spacer|Ali A. Shokri,Alireza Saffarzadeh###

Temperature and voltage dependence of magnetic barrier junctions with a nonmagnetic spacer. The temperature and voltage dependence of spin transport is theoretically
investigated in a new type of magnetic tunnel junction, which consists of two
ferromagnetic outer electrodes separated by a ferromagnetic barrier and a
nonmagnetic (NM) metallic spacer. The effect of spin fluctuation in magnetic
barrier, which plays an important role at finite temperature, is included by
taking the mean-field approximation. It is found that, the tunnel
magnetoresistance (TMR) and the electron-spin polarization depend strongly on
the temperature and the applied voltage. The TMR and spin polarization at
different temperatures show an oscillatory behavior as a function of the NM
spacer thickness. Also, the amplitude of these oscillations is regularly
reduced when the temperature increases. The maximum TMR value, varies
approximately from 270% in reverse bias (at $T$=0 K) to 25% in forward bias (at
$T\geq T_C$).

###Magnetism and Transport in YbMn2Sb2|R. Nirmala,S. K. Malik,A. V. Morozkin,K. G. Suresh,H. -D. Kim,J. -Y. Kim,B. -G. Park,S. -J. Oh###

Magnetism and Transport in YbMn2Sb2. A new ternary intermetallic compound, namely, YbMn2Sb2, has been synthesized
and its magnetic and electrical transport properties have been studied in the
temperature range of 2 to 300 K. This compound crystallizes in a trigonal,
La2O2S type structure (space group P3bm1, No. 164) and is found to be
ferromagnetically ordered at room temperature. The magnetism is attributed to
the ordering of Mn sublattice. M5 xray absorption spectrum of YbMn2Sb2 obtained
at room temperature suggests that the valency of Yb in this compound is close
to 2. Electrical resistivity of this compound is metal like and a positive
magnetoresistance of 13 percent is observed at 5 K in an applied field of 9T.
Key words Rare earth intermetallics and alloys, Magnetic properties, Xray
absorption spectroscopy, Electrical transport.

###Specific heat and magnetization of a ZrB12 single crystal: characterization of a type II/1 superconductor|Yuxing Wang,Rolf Lortz,Yuriy Paderno,Vladimir Filippov,Satoko Abe,Ulrich Tutsch,Alain Junod###

Specific heat and magnetization of a ZrB12 single crystal: characterization of a type II/1 superconductor. We measured the specific heat, the magnetization, and the magnetoresistance
of a single crystal of ZrB12, which is superconducting below Tc ~ 6 K. The
specific heat in zero field shows a BCS-type superconducting transition. The
normal- to superconducting-state transition changes from first order (with a
latent heat) to second order (without latent heat) with increasing magnetic
field, indicating that the pure compound is a low-kappa, type-II/1
superconductor in the classification of Auer and Ullmaier [J. Auer and H.
Ullmaier, Phys. Rev.B 7, 136 (1973)]. This behavior is confirmed by
magnetization measurements. The H-T phase diagram based on specific-heat and
magnetization data yields Hc2(0) =550 G for the bulk upper critical field,
whereas the critical field defined by vanishing resistance is a surface
critical field Hc3(0) ~ 1000 G.

###The effect of Cu-doping on the magnetic and transport properties of La0.7Sr0.3MnO3|M. S. Kim,J. B. Yang,Q. Cai,X. D. Zhou,W. J. James,W. B. Yelon,P. E. Parris,D. Buddhikot,S. K. Malik###

The effect of Cu-doping on the magnetic and transport properties of La0.7Sr0.3MnO3. The effects of Cu-doping on the structural, magnetic, and transport
properties of La0.7Sr0.3Mn1-xCuxO3 (0 < x < 0.20) have been studied using
neutron diffraction, magnetization and magnetoresistance (MR) measurements. All
samples show the rhombohedral structure with the R3c space-group from 10K to
room temperature (RT). Neutron diffraction data suggest that some of the Cu
ions have a Cu3+ state in these compounds. The substitution of Mn by Cu affects
the Mn-O bond length and Mn-O-Mn bond angle resulting from the minimization of
the distortion of the MnO6 octahedron. Resistivity measurements show that a
metal to insulator transition occurs for the x more than 0.15 samples. The x =
0.15 sample shows the highest MR(_80%), which might result from the
co-existence of Cu3+/Cu2+ and the dilution effect of Cu-doping on the double
exchange interaction.

###Reversing the training effect in exchange biased CoO/Co bilayers|Steven Brems,Dieter Buntinx,Kristiaan Temst,Chris Van Haesendonck,Florin Radu,Hartmut Zabel###

Reversing the training effect in exchange biased CoO/Co bilayers. We performed a detailed study of the training effect in exchange biased
CoO/Co bilayers. High-resolution measurements of the anisotropic
magnetoresistance (AMR) are consistent with nucleation of magnetic domains in
the antiferromagnetic CoO layer during the first magnetization reversal. This
accounts for the enhanced spin rotation observed in the ferromagnetic Co layer
for all subsequent reversals. Surprisingly, the AMR measurements as well as
magnetization measurements reveal that it is possible to partially reinduce the
untrained state by performing a hysteresis measurement with an in plane
external field perpendicular to the cooling field. Indeed, the next hysteresis
loop obtained in a field parallel to the cooling field resembles the initial
asymmetric hysteresis loop, but with a reduced amount of spin rotation
occurring at the first coercive field. This implies that the antiferromagnetic
domains, which are created during the first reversal after cooling, can be
partially erased.

###Dependence of Modulation Amplitude on Electron Density in Unidirectional Lateral Superlattices: The Effect of the Thickness of the Two-dimensional Electron Gas|Akira Endo,Yasuhiro Iye###

Dependence of Modulation Amplitude on Electron Density in Unidirectional Lateral Superlattices: The Effect of the Thickness of the Two-dimensional Electron Gas. The amplitude V_0 of unidirectional periodic potential modulation introduced
by a surface grating into a two-dimensional electron gas (2DEG) formed at
AlGaAs/GaAs heterointerface is measured as a function of electron density n_e
by analyzing commensurability oscillation of the magnetoresistance. The
electron density is varied either by applying a bias to a metallic back gate or
by illumination. The amplitude decreases with increasing density, with the rate
|dV_0/dn_e| roughly an order of magnitude larger for the former method. The
result is interpreted in terms of the rate, dE_1/d(delta E_c), of the change in
the first subband level E_1 in response to the variation of the conduction-band
edge delta E_c above the heterointerface. The rate crucially depends on the
thickness of the 2DEG.

###Giant Tunneling Magnetoresistance, Glassiness, and the Energy Landscape at Nanoscale Cluster Coexistence|Sanjeev Kumar,Chandra Shekhar Mohapatra,Pinaki Majumdar###

Giant Tunneling Magnetoresistance, Glassiness, and the Energy Landscape at Nanoscale Cluster Coexistence. We present microscopic results on the giant tunneling magnetoresistance that
arises from the nanoscale coexistence of ferromagnetic metallic (FMM) and
antiferromagnetic insulating (AFI) clusters in a disordered two dimensional
electron system with competing double exchange and superexchange interactions.
Our Monte Carlo study allows us to map out the different field regimes in
magnetotransport and correlate it with the evolution of spatial structures. At
coexistence, the isotropic O(3) model shows signs of slow relaxation, and has a
high density of low energy metastable states, but no genuine glassiness.
However, in the presence of weak magnetic anisotropy, and below a field
dependent irreversibility temperature $T_{irr}$, the response on field cooling
(FC) differs distinctly from that on zero field cooling (ZFC). We map out the
phase diagram of this `phase coexistence glass', highlight how its response
differs from that of a standard spin glass, and compare our results with data
on the manganites.

###Macrospin Models of Spin Transfer Dynamics|Jiang Xiao,A. Zangwill,M. D. Stiles###

Macrospin Models of Spin Transfer Dynamics. The current-induced magnetization dynamics of a spin valve are studied using
a macrospin (single domain) approximation and numerical solutions of a
generalized Landau-Lifshitz-Gilbert equation. For the purpose of quantitative
comparison with experiment [Kiselev {\it et al.} Nature {\bf 425}, 380 (2003)],
we calculate the resistance and microwave power as a function of current and
external field including the effects of anisotropies, damping, spin-transfer
torque, thermal fluctuations, spin-pumping, and incomplete absorption of
transverse spin current. While many features of experiment appear in the
simulations, there are two significant discrepancies: the current dependence of
the precession frequency and the presence/absence of a microwave quiet magnetic
phase with a distinct magnetoresistance signature. Comparison is made with
micromagnetic simulations designed to model the same experiment.

###LCAO model for 3D Fermi surface of high-T_c cuprate Tl_2Ba_2CuO_{6+delta}|Martin Stoev,Todor Mishonov###

LCAO model for 3D Fermi surface of high-T_c cuprate Tl_2Ba_2CuO_{6+delta}. A simple analytical formula for three-dimensional Fermi surface (3D FS) of
${\rm Tl_{2}Ba_{2}CuO_{6+\delta}}$ is derived in the framework of LCAO
approximation spanned over Cu~4s, Cu~3d$_{x^2-y^2}$, O~2p$_x$ and O~2p$_y$
states. This analytical result can be used for fitting of experimental data for
3D FS such as polar angle magnetoresistance oscillation. The model takes into
account effective copper-copper hopping amplitude \tss between Cu~4s orbitals
from neighbouring \cuo layers. The acceptable correspondence with the
experimental data gives a hint that the \tss amplitude dominates in formation
of coherent 3D FS, and other oxygen-oxygen and copper-oxygen amplitudes are
rather negligible. For absolute determination of the hopping parameters a
simple electronic experiment with a field effect transistor type microstructure
is suggested. The thin superconductor layer is the source-drain channel of the
layered structure where an AC current is applied.

###Competition between ferromagnetism and spin glass: the key for large magnetoresistance in oxygen deficient perovskites SrCo1-xMxO3-d (M = Nb, Ru)|T. Motohashi,V. Caignaert,V. Pralong,M. Hervieu,A. Maignan,B. Raveau###

Competition between ferromagnetism and spin glass: the key for large magnetoresistance in oxygen deficient perovskites SrCo1-xMxO3-d (M = Nb, Ru). The magnetic and magnetotransport properties of the oxygen deficient
perovskites, SrCo1-xMxO3-d with M = Nb and Ru, were investigated. Both Nb- and
Ru-substituted cobaltites are weak ferromagnets, with transition temperatures
Tm of 130-150 K and 130-180 K, respectively, and both exhibit a spin glass
behavior at temperatures below Tf = 80-90 K. It is demonstrated that there
exists a strong competition between ferromagnetism and spin glass state, where
Co4+ induces ferromagnetism, whereas Nb or Ru substitution at the cobalt sites
induces magnetic disorder, and this particular magnetic behavior is the origin
of large negative magnetoresistance of these oxides, reaching up to 30% at 5 K
in 7 T. The differences between Nb- and Ru-substituted cobaltites are discussed
on the basis of the different electronic configuration of niobium and ruthenium
cations.

###Possible Localization Behavior of the Inherent Conducting Polymer (CH$_3$)$_{0.9}$ReO$_3$|E. --W. Scheidt,R. Miller,Ch. Helbig,G. Eickerling,F. Mayr,R. Herrmann,P. Schwab,W. Scherer###

Possible Localization Behavior of the Inherent Conducting Polymer (CH$_3$)$_{0.9}$ReO$_3$. Polymeric methyltrioxorhenium (poly-MTO) represents the first example of an
inherent conducting organometallic oxide. It adopts the structural motives and
transport properties of some classical perovskites in two dimensions. In this
study we present resistivity data down to 30 mK which exhibit a crossover from
a metallic (d$\rho$/d$T >$ 0) to an insulating (d$\rho$/d$T <$ 0) behavior at
about 30 K. Below 30 K an unusual resistivity behavior, similar to that of some
doped cuprate systems, is observed: initially the resistivity increases
approximately as $\rho \sim$ log$(1/T$) before it starts to saturate below 2 K.
Furthermore, a linear positive magnetoresistance is found (up to 7 T).
Temperature dependent magnetization and specific heat measurements in various
magnetic fields indicate that the unusual resistivity behavior may be driven by
spatial localization of the d$^1$ moments at the Re atoms.

###Fermi surface of the filled-skutterudite superconductor LaRu4P12: A clue to the origin of the metal-insulator transition in PrRu4P12|S. R. Saha,H. Sugawara,Y. Aoki,H. Sato,Y. Inada,H. Shishido,R. Settai,Y. Onuki,H. Harima###

Fermi surface of the filled-skutterudite superconductor LaRu4P12: A clue to the origin of the metal-insulator transition in PrRu4P12. We report the de Haas-van Alphen (dHvA) effect and magnetoresistance in the
filled-skutterudite superconductor LaRu4P12, which is a reference material of
PrRu4P12 that exhibits a metal-insulator (M-I) transition at T_MI~60 K. The
observed dHvA branches for the main Fermi surface (FS) are well explained by
the band-structure calculation, using the full potential linearized
augmented-plane-wave method with the local-density approximation, suggesting a
nesting instability with q =(1,0,0) in the main multiply connected FS as
expected also in PrRu4P12. Observed cyclotron effective masses of
(2.6-11.8)m_0, which are roughly twice the calculated masses, indicate the
large mass enhancement even in the La-skutterudites. Comparing the FS between
LaRu4P12 and PrRu4P12, an essential role of c-f hybridization cooperating with
the FS nesting in driving the the M-I transition in PrRu4P12 has been
clarified.

###Transport properties of the heavy fermion superconductor PrOs$_{4}$Sb$_{12}$|H. Sugawara,M. Kobayashi,S. Osaki,S. R. Saha,T. Namiki,Y. Aoki,H. Sato###

Transport properties of the heavy fermion superconductor PrOs$_{4}$Sb$_{12}$. We have measured the electrical resistivity, thermoelectric power, Hall
coefficient, and magnetoresistance (MR) on single crystals of
PrOs$_{4}$Sb$_{12}$, LaOs$_{4}$Sb$_{12}$ and NdOs$_{4}$Sb$_{12}$. All the
transport properties in PrOs$_{4}$Sb$_{12}$ are similar to those in
LaOs$_{4}$Sb$_{12}$ and NdOs$_{4}$Sb$_{12}$ at high temperatures, indicating
the localized character of 4$f$-electrons. The transverse MR both in
LaOs$_{4}$Sb$_{12}$ and PrOs$_{4}$Sb$_{12}$ tends to saturate for wide field
directions, indicating these compounds to be uncompensated metals with no open
orbit. We have determined the phase diagram of the field induced ordered phase
by the MR measurement for all the principle field directions, which indicates
an unambiguous evidence for the $\Gamma_{\rm 1}$ singlet crystalline electric
field ground state.

###Transport properties of moderately disordered UCu$_4$Pd|A. Otop,S. Süllow,M. B. Maple,A. Weber,E. W. Scheidt,T. J. Gortenmulder,J. A. Mydosh###

Transport properties of moderately disordered UCu$_4$Pd. We present a detailed study on the (magneto)transport properties of as-cast
and heat treated material UCu$_4$Pd. We find a pronounced sample dependence of
the resistivity $\rho$ of as-cast samples, and reproduce the annealing
dependence of $\rho$. In our study of the Hall effect we determine a metallic
carrier density for all samples, and a temperature dependence of the Hall
constant which is inconsistent with the Skew scattering prediction. The
magnetoresistive response is very small and characteristic for spin disorder
scattering, suggesting that overall the resistivity is controlled mostly by
nonmagnetic scattering processes. We discuss possible sources for the
temperature and field dependence of the transport properties, in particular
with respect to quantum criticality and electronic localization effects.

###Quantum corrections to the conductivity and Hall coefficient of a two-dimensional electron gas in a dirty AlGaAs/GaAs/AlGaAs quantum well: from the diffusive to the ballistic regime|V. T. Renard,I. V. Gornyi,O. A. Tkachenko,V. A. Tkachenko,Z. D. Kvon,E. B. Olshanetsky,A. I. Toropov,J. -C. Portal###

Quantum corrections to the conductivity and Hall coefficient of a two-dimensional electron gas in a dirty AlGaAs/GaAs/AlGaAs quantum well: from the diffusive to the ballistic regime. We report an experimental study of quantum conductivity corrections in a low
mobility, high density two-dimensional electron gas in a AlGaAs/GaAs/AlGaAs
quantum well in a wide temperature range (1.5K - 110K). This temperature range
covers both the diffusive and the ballistic interaction regimes for our
samples. It has been therefore possible to study the crossover between these
regimes for both the longitudinal conductivity and the Hall effect. We perform
a parameter free comparison of our experimental data for the longitudinal
conductivity at zero magnetic field, the Hall coefficient, and the
magnetoresistivity to the recent theories of interaction-induced corrections to
the transport coefficients. A quantitative agreement between these theories and
our experimental results has been found.

###Anisotropic magnetoresistance and spin polarization of La0.7Sr0.3MnO3 / SrTiO3 superlattices|L. M. Wang###

Anisotropic magnetoresistance and spin polarization of La0.7Sr0.3MnO3 / SrTiO3 superlattices. The crystalline structure, anisotropic magnetoresistance (AMR), and
magnetization of La0.7Sr0.3MnO3/SrTiO3 (LSMO/STO) superlattices grown by an rf
sputtering system are systematically analyzed to study the spin polarization of
manganite at interfaces. A perfectly epitaxial growth with sharp interfaces
between LSMO and STO layers is confirmed by the transmission electron
microscopy (TEM) image and the x-ray diffraction. The presence of positive
low-temperature AMR in LSMO/STO superlattices with thinner LSMO layers or
thicker STO layers implies that two bands of majority and minority character
contribute to the transport properties, leading to a reduced spin polarization.
Furthermore, the magnetization of superlattices follows the T3/2 law at low
temperatures and decays more quickly as the thickness ratio dSTO/dLSMO
increases, corresponding to a reduced exchange coupling. The results clearly
show that the spin polarization is strongly correlated with the influence of
interface-induced strain on the structure.

###Magnetocapacitance effect in perovskite-superlattice based multiferroics|M. P. Singh,W. Prellier,Ch. Simon,B. Raveau###

Magnetocapacitance effect in perovskite-superlattice based multiferroics. We report the structural and magnetoelectrical properties of
La$_{0.7}$Ca$_{0.3}$MnO$_3$/BaTiO$_3$ perovskite superlattices grown on
(001)-oriented SrTiO$_3$ by the pulsed laser deposition technique. Magnetic
hysteresis loops together with temperature dependent magnetic properties
exhibit well-defined coercivity and magnetic transition temperature (T$_C$)
\symbol{126}140 K. $DC$ electrical studies of films show that the
magnetoresistance (MR) is dependent on the BaTiO$_3$ thickness and negative
$MR$ as high as 30% at 100K are observed. The $AC$ electrical studies reveal
that the impedance and capacitance in these films vary with the applied
magnetic field due to the magnetoelectrical coupling in these structures - a
key feature of multiferroics. A negative magnetocapacitance value in the film
as high as 3% per tesla at 1kHz and 100K is demonstrated, opening the route for
designing novel functional materials.

###The O-M-O triatomic molecule: Basic unit of cuprates & manganates|S. Tsintsarska,M. D. Ivanovich,M. Georgiev,Alexander D. Gochev###

The O-M-O triatomic molecule: Basic unit of cuprates & manganates. The O(oxygen)-M(metal)-O(oxygen) molecule is a basic unit of high-temperature
superconducting cuprates and colossal magnetoresistance exhibiting manganates.
This molecule can be regarded either as an element of a linear chain or as an
ingredient of the corresponding cuprate or manganate lattice. The symmetry of
the unit being different in the two approaches, group theory imposes different
limitations on conceivable vibrational modes and atomic otbitals that control
its transport and optical properties. We now calculate the electron hopping
energies along Cu(P0-O(A) bonds, sites for nonlocal electron-vibrational mode
coupling. We find the electric transport along the O(A)-Cu(P)-O(A) molecule
dominated by scattering from bond polarons which is reflected in the two-branch
character of the temperature dependence of its electric resistance.

###Itinerant vibronic polarons: A Merrifield approach I. Low energy range calculations|S. G. Tsintsarska,M. D. Ivanovich,A. Andreev,D. W. Brown,K. Lindenberg,M. Georgiev###

Itinerant vibronic polarons: A Merrifield approach I. Low energy range calculations. We extend Merrifield's Variational Ansatz in the variational band theory of
polarons to cover a frame of two electronic bands mixed by an Einstein phonon.
The Hamiltonian is composed of the local and hopping energy terms, the
vibrational energy, and a band-mixing term linear in the electron-phonon
coupling. The eigenstate is a linear combination of Merrifield states in either
electron band. The variational equations are solved numerically, so as to
obtain the energy vs. momentum relation in ground state. Our variational method
generates either Jahn-Teller polarons if the electronic bands degenerate or
Pseudo-Jahn-Teller polarons if they nearly degenerate, both entities regarded
as likely carriers in metal-oxide manifolds of high-Tc superconducting cuprates
and colossal magnetoresistance exhibiting manganates.

###Magnetoresistance and spin polarization in the insulating regime of a Si two-dimensional electron system|Mitsuaki Ooya,Kiyohiko Toyama,Tohru Okamoto###

Magnetoresistance and spin polarization in the insulating regime of a Si two-dimensional electron system. We have studied the magnetoresistance in a high-mobility Si inversion layer
down to low electron concentrations at which the longitudinal resistivity
$\rho_{xx}$ has an activated temperature dependence. The angle of the magnetic
field was controlled so as to study the orbital effect proportional to the
perpendicular component $B_\perp$ for various total strengths $B_{\rm tot}$. A
dip in $\rho_{xx}$, which corresponds to the Landau level filling factor of
$\nu=4$, survives even for high resistivity of $\rho_{xx} \sim 10^8 \Omega$ at
$T= 150 {\rm mK}$. The linear $B_{\rm tot}$-dependence of the value of
$B_\perp$ at the dip for low $B_{\rm tot}$ indicates that a ferromagnetic
instability does not occur even in the far insulating regime.

###Severe Fermi Surface Reconstruction at a Metamagnetic-Transition in Ca$_{2-x}$Sr$_x$RuO$_4$ (for $0.2 \leq x \leq 0.5$)|L. Balicas,S. Nakatsuji,D. Hall,H. Lee,Z. Fisk,Y. Maeno,D. J. Singh###

Severe Fermi Surface Reconstruction at a Metamagnetic-Transition in Ca$_{2-x}$Sr$_x$RuO$_4$ (for $0.2 \leq x \leq 0.5$). We report an electrical transport study in Ca$_{2-x}$Sr$_{x}$RuO$_4$ single
crystals at high magnetic fields ($B$). For $x =0.2$, the Hall constant
$R_{xy}$ decreases sharply at an anisotropic metamagnetic (MM) transition
reaching its value for Sr$_2$RuO$_4$ at high fields. A sharp decrease in the
$A$ coefficient of the resistivity $T^2$-term and a change in the structure of
the angular magnetoresistance oscillations (AMRO) for $B$ rotating in the
planes, confirms the reconstruction of the Fermi surface (FS). Our observations
and LDA calculations indicate a strong dependence of the FS on the Ca
concentration and suggest the coexistence of itinerant and localized electronic
states in single layered ruthenates.

###Observation of oscillatory magnetoresistance periodic in 1/B and B in Ca3Ru2O7|V. Durairaj,X. N. Lin,Z. X. Zhou,S. Chikara,E. Ehami,A. Douglass,P. Schlottmann,G. Cao###

Observation of oscillatory magnetoresistance periodic in 1/B and B in Ca3Ru2O7. We report magnetoresistance oscillations in high magnetic fields, B, up to 45
T and over a wide range of temperature in the Mott-like system Ca3Ru2O7. For B
rotating within the ac-plane, slow and strong Shubnikov-de Haas (SdH)
oscillations periodic in 1/B are observed for T&#8804;1.5 K in the presence of
metamagnetism. These oscillations are highly angular dependent and intimately
correlated with the spin-polarization of the ferromagnetic state. For B||[110],
oscillations are also observed but periodic in B (rather than 1/B) which
persist up to 15 K. While the SdH oscillations are a manifestation of the
presence of small Fermi surface (FS) pockets in the Mott-like system, the
B-periodic oscillations, an exotic quantum phenomenon, may be a result of
anomalous coupling of the magnetic field to the t2g-orbitals that makes the
extremal cross-section of the FS field-dependent.

###Spin-transfer-induced excitations in bilayer magnetic nanopillars at high fields: The effects of contact layers|Wenyu Chen,Andrew D. Kent,M. J. Rooks,N. Ruiz,Jonathan Z. Sun###

Spin-transfer-induced excitations in bilayer magnetic nanopillars at high fields: The effects of contact layers. Current-induced excitations in bilayer magnetic nanopillars have been studied
with large magnetic fields applied perpendicular to the layers at low
temperature. Junctions investigated all have Cu/Co/Cu/Co/Cu as core layer
stacks. Two types of such junctions are compared, one with the core stack
sandwiched between Pt layers (type A), the other with Pt only on one side of
the stack (type B). Transport measurements show that these two types of
junctions have similar magnetoresistance and slope of critical current with
respect to field, while A samples have higher resistance. The high-field
bipolar excitation, as was previously reported [Oezyilmaz et al., Phys. Rev. B
71, 140403(R) (2005)], is present in B samples only. This illustrates the
importance of contact layers to spin-current-induced phenomena. This also
confirms a recent prediction on such spin-wave excitations in bilayers.

###First- and Second-Order Phase Transitions, Fulde-Ferrel Inhomogeneous State and Quantum Criticality in Ferromagnet/Superconductor Double Tunnel Junctions|Biao Jin,Gang Su,Qing-Rong Zheng###

First- and Second-Order Phase Transitions, Fulde-Ferrel Inhomogeneous State and Quantum Criticality in Ferromagnet/Superconductor Double Tunnel Junctions. First- and second-order phase transitions, Fulde-Ferrel (FF) inhomogeneous
superconducting (SC) state and quantum criticality in
ferromagnet/superconductor/ferromagnet double tunnel junctions are
investigated. For the antiparallel alignment of magnetizations, it is shown
that a first-order phase transition from the homogeneous BCS state to the
inhomogeneous FF state occurs at a certain bias voltage $V^{\ast}$; while the
transitions from the BCS state and the FF state to the normal state at $%
V_{c}$ are of the second-order. A phase diagram for the central superconductor
is presented. In addition, a quantum critical point (QCP), $% V_{QCP}$, is
identified. It is uncovered that near the QCP, the SC gap, the chemical
potential shift induced by the spin accumulation, and the difference of free
energies between the SC and normal states vanish as $% |V-V_{QCP}|^{z\nu}$ with
the quantum critical exponents $z\nu =1/2$, 1 and 2, respectively. The tunnel
conductance and magnetoresistance are also discussed.

###Mott-Hubbard quantum criticality in paramagnetic CMR pyrochlores|L. Craco,C. I. Ventura,A. N. Yaresko,E. Müller-Hartmann###

Mott-Hubbard quantum criticality in paramagnetic CMR pyrochlores. We present a correlated {\it ab initio} description of the paramagnetic phase
of Tl$_2$Mn$_2$O$_7$, employing a combined local density approximation (LDA)
with multiorbital dynamical mean field theory (DMFT) treatment. We show that
the insulating state observed in this colossal magnetoresistance (CMR)
pyrochlore is determined by strong Mn intra- and inter-orbital local
electron-electron interactions. Hybridization effects are reinforced by the
correlation-induced spectral weight transfer. Our result coincides with optical
conductivity measurements, whose low energy features are remarkably accounted
for by our theory. Based on this agreement, we study the disorder-driven
insulator-metal transition of doped compounds, showing the proximity of
Tl$_2$Mn$_2$O$_7$ to quantum phase transitions, in agreement with recent
measurements.

###Anomalous magnetoresistance peak in (110) GaAs two-dimensional holes: Evidence for Landau-level spin-index anticrossings|F. Fischer,R. Winkler,D. Schuh,M. Bichler,M. Grayson###

Anomalous magnetoresistance peak in (110) GaAs two-dimensional holes: Evidence for Landau-level spin-index anticrossings. We measure an anomalous magnetoresistance peak within the lowest Landau level
(nu = 1) minimum of a two-dimensional hole system on (110) GaAs.
Self-consistent calculations of the valence band mixing show that the two
lowest spin-index Landau levels anticross in a perpendicular magnetic field B
consistent with where the experimental peak is measured, Bp. The temperature
dependence of the anomalous peak height is interpreted as an activated behavior
across this anticrossing gap. Calculations of the spin polarization in the
lowest Landau levels predict a rapid switch from about -3/2 to +3/2 spin at the
anticrossing. The peak position Bp is shown to be affected by the confinement
electrostatics, and the utility of a tunable anticrossing position for
spintronics applications is discussed.

###Stress deformations and structural quenching in Sm0.5Ca0.5MnO3 thin films allow a huge decrease of the charge order melting magnetic field|E. Rauwel,W. Prellier,B. Mercey,S. de Brion,G. Chouteau###

Stress deformations and structural quenching in Sm0.5Ca0.5MnO3 thin films allow a huge decrease of the charge order melting magnetic field. Thin films of Sm0.5Ca0.5MnO3 manganites with charge ordering (CO) properties
and colossal magnetoresistance were synthesized by pulsed laser deposition
technique on (100)-SrTiO3 and (100)-LaAlO3 substrates. We first compare the
structural modifications as function of the substrate and film thickness.
Secondly, measuring transport properties in magnetic fields up to 24T, we
establish the temperature-field phase diagram describing the stability of the
CO state and compare it to bulk material. We show that some structural
modification induced by the substrate occurs and that the CO melting magnetic
field is greatly reduced. Moreover, with the temperature decrease, no
modification of the lattice parameters is observed. We then propose an
explanation based on the quenching of the unit cell of the film that adopts the
in-plane lattice parameters of the substrate and thus, prevents the complete
growth of the CO state at low temperature.

###Antiferromagnetically coupled CoFeB/Ru/CoFeB trilayers|N. Wiese,T. Dimopoulos,M. Ruhrig,J. Wecker,H. Bruckl,G. Reiss###

Antiferromagnetically coupled CoFeB/Ru/CoFeB trilayers. This work reports on the magnetic interlayer coupling between two amorphous
CoFeB layers, separated by a thin Ru spacer. We observe an antiferromagnetic
coupling which oscillates as a function of the Ru thickness x, with the second
antiferromagnetic maximum found for x=1.0 to 1.1 nm. We have studied the
switching of a CoFeB/Ru/CoFeB trilayer for a Ru thickness of 1.1 nm and found
that the coercivity depends on the net magnetic moment, i.e. the thickness
difference of the two CoFeB layers. The antiferromagnetic coupling is almost
independent on the annealing temperatures up to 300 degree C while an annealing
at 350 degree C reduces the coupling and increases the coercivity, indicating
the onset of crystallization. Used as a soft electrode in a magnetic tunnel
junction, a high tunneling magnetoresistance of about 50%, a well defined
plateau and a rectangular switching behavior is achieved.

###Spin Transfer Switching and Spin Polarization in Magnetic Tunnel Junctions with Mgo and Alox Barriers|Zhitao Diao,Dmytro Apalkov,Mahendra Pakala,Alex Panchula,Yiming Huai###

Spin Transfer Switching and Spin Polarization in Magnetic Tunnel Junctions with Mgo and Alox Barriers. We present spin transfer switching results for MgO based magnetic tunneling
junctions (MTJs)with large tunneling magnetoresistance (TMR) ratio of up to
150% and low intrinsic switching current density of 2-3 x 10 MA/cm2. The
switching data are compared to those obtained on similar MTJ nanostructures
with AlOx barrier. It is observed that the switching current density for MgO
based MTJs is 3-4 times smaller than that for AlOx based MTJs, and that can be
attributed to higher tunneling spin polarization (TSP) in MgO based MTJs. In
addition, we report a qualitative study of TSP for a set of samples, ranging
from 0.22 for AlOx to 0.46 for MgO based MTJs, and that shows the TSP (at
finite bias) responsible for the current-driven magnetization switching is
suppressed as compared to zero-bias tunneling spin polarization determined from
TMR.

###Modulated optical reflectance measurements on La2/3Sr1/3MnO3 thin films|Laurence Mechin,Stephane Flament,Andy Perry,Darryl P. Almond,Radoslav A. Chakalov###

Modulated optical reflectance measurements on La2/3Sr1/3MnO3 thin films. The modulated optical reflectance (MOR) measurement technique was applied to
colossal magnetoresistive materials, in particular, La2/3Sr1/3MnO3 (LSMO) thin
films. The contactless measurement scheme is prospective for many applications
spanning from materials characterization to new devices like reading heads for
magnetically recorded media. A contrasted room temperature surface scan of a
100 microns wide 400 microns long bridge patterned into LSMO film provided
preliminary information about the film homogeneity. Then the temperature was
varied between 240 and 400 K, i.e. through the ferromagnetic to paramagnetic
transition. A clear relation between the MOR signal measured as function of the
temperature and the relative derivative of the resistivity up to the Curie
temperature was observed. This relationship is fundamental for the MOR
technique and its mechanism was explored in the particular case of LSMO.
Analysis in the framework of the Drude model showed that, within certain
conditions, the measured MOR signal changes are correlated to changes in the
charge carrier concentration.

###Current-driven magnetization switching in CoFeB/MgO/CoFeB magnetic tunnel junctions|Jun Hayakawa,Shoji Ikeda,Young Min Lee,Ryutaro Sasaki,Toshiyasu Meguro,Fumihiro Matsukura,Hiromasa Takahashi,Hideo Ohno###

Current-driven magnetization switching in CoFeB/MgO/CoFeB magnetic tunnel junctions. Current-driven magnetization switching in low-resistance
Co40Fe40B20/MgO/Co40Fe40B20 magnetic tunnel junctions (MTJs) is reported. The
critical-current densities Jc required for current-driven switching in samples
annealed at 270C and 300C are found to be as low as 7.8 x 10^5 A/cm^2 and 8.8 x
10^5 A/cm^2 with accompanying tunnel magnetoresistance (TMR) ratios of 49% and
73 %, respectively. Further annealing of the samples at 350C increases TMR
ratio to 160 %, while accompanying Jc increases to 2.5 x 10^6 A/cm^2. We
attribute the low Jc to the high spin-polarization of tunnel current and small
MsV product of the CoFeB single free layer, where Ms is the saturation
magnetization and V the volume of the free layer.

###Lateral diffusive spin transport in layered structures|H. Dery,L. Cywinski,L. J. Sham###

Lateral diffusive spin transport in layered structures. A one dimensional theory of lateral spin-polarized transport is derived from
the two dimensional flow in the vertical cross section of a stack of
ferromagnetic and paramagnetic layers. This takes into account the influence of
the lead on the lateral current underneath, in contrast to the conventional 1D
modeling by the collinear configuration of lead/channel/lead. Our theory is
convenient and appropriate for the current in plane configuration of an
all-metallic spintronics structure as well as for the planar structure of a
semiconductor with ferromagnetic contacts. For both systems we predict the
optimal contact width for maximal magnetoresistance and propose an electrical
measurement of the spin diffusion length for a wide range of materials.

###Measuring the Localization Length through the superconductor-insulator transition in ultrathin amorphous beryllium films|Wenhao Wu,E. Bielejec###

Measuring the Localization Length through the superconductor-insulator transition in ultrathin amorphous beryllium films. Electron transport and tunneling across the superconductor-insulator (SI)
transition have been measured simultaneously for quench-condensed ultrathin
amorphous beryllium films. The anomalous negative magnetoresistance previously
observed in insulating films disappears when Mn impurities are introduced to
the films, restoring a rather clean Efros-Shklovskii type hopping behavior. The
combination of transport and tunneling data allows us to determine,
independently and up to a constant on the order of unity, the localization
length, \xi_{L}, and the dielectric constant, \kappa, for the films. As the
normal-state sheet resistance of the films at 20 K is reduced with increasing
film thickness, \xi_{L} increases exponentially. The SI transition occurs when
\xi_{L} crosses the Ginzburg-Landau coherence length, \xi_{S}.

###Charge ordering, stripes and phase separation in manganese perovskite oxides: an STM/STS study|Ch. Renner,G. Aeppli,H. M. Ronnow###

Charge ordering, stripes and phase separation in manganese perovskite oxides: an STM/STS study. A microscopic characterisation of the phase transitions associated with
colossal magnetoresistance (CMR) in manganese perovskite oxides is a very
important ingredient in the quest of understanding its underlying mechanism.
Scanning tunneling microscopy (STM) is most suitable to investigate some of
their reported hallmarks, including charge ordering, lattice distortions, and
electronic phase separation. Here we investigate Bi1-XCaXMnO3 (BCMO) with
x=0.76. At this composition, BCMO develops an insulating charge-ordered phase
upon cooling, whose study as a function of temperature will allow identifying
atomic scale characteristics of the metal-insulator phase transition (MIT). We
observe distinct atomic scale phases at temperatures above and below the MIT,
with very different electronic and structural characteristics. Combining STM
micrographs and current-voltage tunneling characteristics, we find that charge
ordering correlates both with the local conduction state (metallic or
insulating) and the local structural order. Furthermore, STM shows coexistence
of these phases as expected for a first order phase transition.

###Effect of ferroelectric layers on the magnetocapacitance properties of superlattices-based oxide multiferroics|M. P. Singh,W. Prellier,L. Mechin,W. Prellier###

Effect of ferroelectric layers on the magnetocapacitance properties of superlattices-based oxide multiferroics. A series of superlattices composed of ferromagnetic
La$_{0.7}$Ca$_{0.3}$MnO$_3$ (LCMO) and ferroelectric/paraelectric
Ba$_{1-x}$Sr$_x$TiO$_3$ (0$\leq $x$\leq $1) were deposited on SrTiO$_3$
substrates using the pulsed laser deposition. Films of epitaxial nature
comprised of spherical mounds having uniform size are obtained.
Magnetotransport properties of the films reveal a ferromagnetic Curie
temperature in the range of 145-158 K and negative magnetoresistance as high as
30%, depending on the type of ferroelectric layers employed for their growth
(\QTR{it}{i.e.} '\QTR{it}{x'} value). Ferroelectricity at temperatures ranging
from 55 K to 105 K is also observed, depending on the barium content. More
importantly, the multiferroic nature of the film is determined by the
appearance of negative magnetocapacitance, which was found to be maximum around
the ferroelectric transition temperature (3% per \QTR{it}{tesla}). These
results are understood based on the role of the ferroelectric/paraelectric
layers and strains in inducing the multiferroism.

###The quantum Hall ferromagnet at high filling factors: A magnetic field induced Stoner transition|B. A. Piot,D. K. Maude,M. Henini,Z. R. Wasilewski,K. J. Friedland,R. Hey,K. H. Ploog,A. I. Toropov,R. Airey,G. Hill###

The quantum Hall ferromagnet at high filling factors: A magnetic field induced Stoner transition. Spin splitting in the integer quantum Hall effect is investigated for a
series of Al$_{x}$Ga$_{1-x}$As/GaAs heterojunctions and quantum wells.
Magnetoresistance measurements are performed at mK temperature to characterize
the electronic density of states and estimate the strength of many body
interactions. A simple model with no free parameters correctly predicts the
magnetic field required to observe spin splitting confirming that the
appearance of spin splitting is a result of a competition between the disorder
induced energy cost of flipping spins and the exchange energy gain associated
with the polarized state. In this model, the single particle Zeeman energy
plays no role, so that the appearance of this quantum Hall ferromagnet in the
highest occupied Landau level can also be thought of as a magnetic field
induced Stoner transition.

###From zero resistance states to absolute negative conductivity in microwave irradiated 2D electron systems|J. Inarrea,G. Platero###

From zero resistance states to absolute negative conductivity in microwave irradiated 2D electron systems. Recent experimental results regarding a 2D electron gas subjected to
microwave radiation reveal that magnetoresistivity, apart from presenting
oscillations and zero resistance states, can evolve to negative values at
minima. In other words, the current can evolve from flowing with no
dissipation, to flow in the opposite direction of the dc bias applied. Here we
present a theoretical model in which the existence of radiation-induced
absolute negative conductivity is analyzed. Our model explains the transition
from zero resistance states to absolute negative conductivity in terms of
multiphoton assisted electron scattering due to charged impurities. It shows as
well, how this transition can be driven by tuning microwave frequency and
intensity. Then it opens the possibility of controlling the electron Larmor
orbits dynamics (magnetoconductivity) in microwave driven nanodevices. The
analysis of zero resistance states is therefore promising because new optical
and transport properties in nanodevices will be expected.

###Field-induced first-order magnetic phase transition in an intermetallic compound, Nd7Rh3: Evidence for kinetic-hindrance, phase co-existence and percolative conduction|Kausik Sengupta,E. V. Sampathkumaran###

Field-induced first-order magnetic phase transition in an intermetallic compound, Nd7Rh3: Evidence for kinetic-hindrance, phase co-existence and percolative conduction. The compound, Nd7Rh3, crystallizing in Th7Fe3-type hexagonal structure, was
previously known to exhibit two magnetic transitions, one at 32 K and the other
at 10 K (in zero magnetic field). Here, we report the existence of a
field-induced first-order antiferromagnetic to ferromagnetic transition at 1.8
K in this compound. On the basis of the measurements of isothermal
magnetization and magnetoresistance, we provide evidence for the occurence of
kinetic-hindrance, proposed in the literature, resulting in phase co-existence
(super-cooled ferromagnetic + antifferomagnetic) and percolative electrical
conduction in this stoichiometric intermetallic compound. A point of emphasis,
as inferred from ac susceptibility data, is that such a co-existing phase is
different from spin-glasses, thereby clarifying a question raised in the field
of phase-separation.

###Prospect for room temperature tunneling anisotropic magnetoresistance effect: density of states anisotropies in CoPt systems|A. B. Shick,F. Maca,J. Masek,T. Jungwirth###

Prospect for room temperature tunneling anisotropic magnetoresistance effect: density of states anisotropies in CoPt systems. Tunneling anisotropic magnetoresistance (TAMR) effect, discovered recently in
(Ga,Mn)As ferromagnetic semiconductors, arises from spin-orbit coupling and
reflects the dependence of the tunneling density of states in a ferromagnetic
layer on orientation of the magnetic moment. Based on ab initio relativistic
calculations of the anisotropy in the density of states we predict sizable TAMR
effects in room-temperature metallic ferromagnets. This opens prospect for new
spintronic devices with a simpler geometry as these do not require
antiferromagnetically coupled contacts on either side of the tunnel junction.
We focus on several model systems ranging from simple hcp-Co to more complex
ferromagnetic structures with enhanced spin-orbit coupling, namely bulk and
thin film L1$_0$-CoPt ordered alloys and a monatomic-Co chain at a Pt surface
step edge. Reliability of the predicted density of states anisotropies is
confirmed by comparing quantitatively our ab initio results for the
magnetocrystalline anisotropies in these systems with experimental data.

###Enhancement of giant magnetoresistance effect in the Ruddlesden-Popper phase Sr3Fe2-xCoxO7-d: Predominant role of oxygen nonstoichiometry and magnetic phase separation|T. Motohashi,B. Raveau,M. Hervieu,A. Maignan,V. Pralong,N. Nguyen,V. Caignaert###

Enhancement of giant magnetoresistance effect in the Ruddlesden-Popper phase Sr3Fe2-xCoxO7-d: Predominant role of oxygen nonstoichiometry and magnetic phase separation. The magnetic and magnetotransport properties of the Sr3Fe2-xCoxO7-d system
(0.2 <= x <= 1.0) were systematically investigated. This oxide system exhibits
a giant magnetoresistance (GMR) effect at low temperatures, reaching up to 80%
in 7 T at 5 K. Ac-susceptibility measurements show that there exists a strong
competition between ferromagnetic (F) and spin glass states, and the balance
between these two magnetic states can be controlled by varying cobalt (x)
and/or oxygen contents (d). Importantly, the MR effect is closely related to
the magnetic property: the development of magnetic disordering leads to
enhancement in the negative MR effect. It is suggested that the compound
segregates into F clusters embedded in a non-F matrix, being a naturally
occurring analog of the artificial granular-GMR materials, as in the doped
perovskite cobaltites, La1-xSrxCoO3 (x < 0.18).

###Borderline magnetism in Sr4Ru3O10: Impact of dilute La and Ca doping on itinerant ferromagnetism and metamagnetism|S. Chikara,V. Durairaj,W. H. Song,Y. P. Sun,X. N. Lin,A. Douglass,G. Cao,P. Schlottmann###

Borderline magnetism in Sr4Ru3O10: Impact of dilute La and Ca doping on itinerant ferromagnetism and metamagnetism. An investigation of La and Ca doped Sr4Ru3O10, featuring a coexistence of
interlayer ferromagnetism and intralayer metamagnetism, is presented. La doping
readily changes magnetism between ferromagnetism and metamagnetism by tuning
the density of states. It also results in different Curie temperatures for the
c-axis and the basal plane, highlighting a rare spin-orbit coupling with the
crystal field states. In contrast, Ca doping enhances the c-axis ferromagnetism
and the magnetic anisotropy. La doping also induces a dimensional crossover in
the interlayer transport whereas Ca doping exhibits a tunneling
magnetoresistance and an extraordinary T3/2-dependence of the resisitivity. The
drastic changes caused by the dilute doping demonstrate a rare borderline
magnetism that is delicately linked to the interplay of the density of states
and spin-orbit coupling.

###Crystal structure and high-field magnetism of La2CuO4|M. Reehuis,C. Ulrich,K. Prokes,A. Gozar,G. Blumberg,Seiki Komiya,Yoichi Ando,P. Pattison,B. Keimer###

Crystal structure and high-field magnetism of La2CuO4. Neutron diffraction was used to determine the crystal structure and magnetic
ordering pattern of a La2CuO4 single crystal, with and without applied magnetic
field. A previously unreported, subtle monoclinic distortion of the crystal
structure away from the orthorhombic space group Bmab was detected. The
distortion is also present in lightly Sr-doped crystals. A refinement of the
crystal structure shows that the deviation from orthorhombic symmetry is
predominantly determined by displacements of the apical oxygen atoms. An
in-plane magnetic field is observed to drive a continuous reorientation of the
copper spins from the orthorhombic b-axis to the c-axis, directly confirming
predictions based on prior magnetoresistance and Raman scattering experiments.
A spin-flop transition induced by a c-axis oriented field previously reported
for non-stoichiometric La2CuO4 is also observed, but the transition field (11.5
T) is significantly larger than that in the previous work.

###Positive and negative magnetocapacitance in magnetic nanoparticle systems|G. Lawes,R. Tackett,O. Masala,B. Adhikary,R. Naik,R. Seshadri###

Positive and negative magnetocapacitance in magnetic nanoparticle systems. The dielectric properties of MnFe$_2$O$_4$ and $\gamma$-Fe$_2$O$_3$ magnetic
nanoparticles embedded in insulating matrices were investigated. The samples
showed frequency dependent dielectric anomalies coincident with the magnetic
blocking temperature and significant magnetocapacitance above this blocking
temperature, as large as 0.4% at H = 10kOe. For both samples the magnetic field
induced change in dielectric constant was proportional to the square of the
sample magnetization. These measurements suggest that the dielectric properties
of magnetic nanoparticles are closely related to the disposition of magnetic
moments in the system. As neither bulk gamma-Fe2O3 nor MnFe2O3 are
magnetoelectric materials, this magnetodielectric coupling is believed to arise
from extrinsic effects which are discussed in light of recent work relating
magnetoresistive and magnetocapacitive behavior.

###Non-collinear Magnetoelectronics|Arne Brataas,Gerrit E. W. Bauer,Paul J. Kelly###

Non-collinear Magnetoelectronics. The electron transport properties of hybrid ferromagnetic|normal metal
structures such as multilayers and spin valves depend on the relative
orientation of the magnetization direction of the ferromagnetic elements.
Whereas the contrast in the resistance for parallel and antiparallel
magnetizations, the so-called Giant Magnetoresistance, is relatively well
understood for quite some time, a coherent picture for non-collinear
magnetoelectronic circuits and devices has evolved only recently. We review
here such a theory for electron charge and spin transport with general
magnetization directions that is based on the semiclassical concept of a vector
spin accumulation. In conjunction with first-principles calculations of
scattering matrices many phenomena, e.g. the current-induced spin-transfer
torque, can be understood and predicted quantitatively for different material
combinations.

###Spin-transfer in bilayer magnetic nanopillars at high fields as a function of free layer thickness|W. Chen,A. D. Kent,M. J. Rooks,N. Ruiz,J. Z. Sun###

Spin-transfer in bilayer magnetic nanopillars at high fields as a function of free layer thickness. Spin transfer in asymmetric Co/Cu/Co bilayer magnetic nanopillars junctions
has been studied at low temperature as a function of free-layer thickness. The
phase diagram for current-induced magnetic excitations has been determined for
magnetic fields up to 7.5 T applied perpendicular to the junction surface and
free-layers thicknesses from 2 to 5 nm. The junction magnetoresistance is
independent of thickness. The critical current for magnetic excitations
decreases linearly with decreasing free-layer thickness, but extrapolates to a
finite critical current in the limit of zero thickness. The limiting current is
in quantitative agreement with that expected due to a spin-pumping contribution
to the magnetization damping. It may also be indicative of a decrease in the
spin-transfer torque efficiency in ultrathin magnetic layers.

###Effect of intrinsic spin relaxation on the spin-dependent cotunneling transport through quantum dots|Ireneusz Weymann,Józef Barnas###

Effect of intrinsic spin relaxation on the spin-dependent cotunneling transport through quantum dots. Spin-polarized transport through quantum dots is analyzed theoretically in
the cotunneling regime. It is shown that the zero-bias anomaly, found recently
in the antiparallel configuration, can also exist in the case when one
electrode is magnetic while the other one is nonmagnetic. Physical mechanism of
the anomaly is also discussed. It is demonstrated that intrinsic spin
relaxation in the dot has a significant influence on the zero-bias maximum in
the differential conductance -- the anomaly becomes enhanced by weak spin-flip
scattering in the dot and then disappears in the limit of fast spin relaxation.
Apart from this, inverse tunnel magnetoresistance has been found in the limit
of fast intrinsic spin relaxation in the dot. The diode-like behavior of
transport characteristics in the cotunneling regime has been found in the case
of quantum dots asymmetrically coupled to the leads. This behavior may be
enhanced by the spin-flip relaxation processes.

###The effects of Mn concentration on spin-polarized transport through ZnSe/ZnMnSe/ZnSe heterostructures|Alireza Saffarzadeh###

The effects of Mn concentration on spin-polarized transport through ZnSe/ZnMnSe/ZnSe heterostructures. We have studied the effects of Mn concentration on the ballistic
spin-polarized transport through diluted magnetic semiconductor
heterostructures with a single paramagnetic layer. Using a fitted function for
zero-field conduction band offset based on the experimental data, we found that
the spin current densities strongly depend on the Mn concentration. The
magnitude as well as the sign of the electron-spin polarization and the tunnel
magnetoresistance can be tuned by varying the Mn concentration, the width of
the paramagnetic layer, and the external magnetic field. By an appropriate
choice of the Mn concentration and the width of the paramagnetic layer, the
degree of spin polarization for the output current can reach 100% and the
device can be used as a spin filter.

###Large magnetoresistance in La2/3Ca1/3MnO3 thin films induced by metal masked ion damage technique|M. J. Zhang,J. Li,Z. H. Peng,D. N. Zheng,A. Z. Jin,C. Z. Gu###

Large magnetoresistance in La2/3Ca1/3MnO3 thin films induced by metal masked ion damage technique. e have developed a simple process to obtain large magnetoresistance (MR) in
perovskite manganite thin films by a combination of focused ion beam (FIB)
milling and 120 keV H$_{2}^{+}$ ion implantation. Metal slits about 70 nm in
width were printed by 30 kV focused Ga ion beam nanolithography on a 4 mm
track, and the materials in these slits are then irradiated by the accelerated
H$_{2}^{+}$ ions. Using this method, in a magnetic field of 5 T we can get a
MR${>}$60% over a 230 K temperature scope, with a maximum value of 95% at
around 70 K. This technique is very promising in terms of its simplicity and
flexibility of fabrication and has potential for high-density integration.

###Dynamical Mean-Field Study of the Ferromagnetic Transition Temperature of a Two-Band Model for Colossal Magnetoresistance Materials|F. Popescu,C. Sen,E. Dagotto###

Dynamical Mean-Field Study of the Ferromagnetic Transition Temperature of a Two-Band Model for Colossal Magnetoresistance Materials. The ferromagnetic (FM) transition temperature (Tc) of a two-band
Double-Exchange (DE) model for colossal magnetoresistance (CMR) materials is
studied using dynamical mean-field theory (DMFT), in wide ranges of coupling
constants, hopping parameters, and carrier densities. The results are shown to
be in excellent agreement with Monte Carlo simulations. When the bands overlap,
the value of Tc is found to be much larger than in the one-band case, for all
values of the chemical potential within the energy overlap interval. A nonzero
interband hopping produces an additional substantial increase of Tc, showing
the importance of these nondiagonal terms, and the concomitant use of multiband
models, to boost up the critical temperatures in DE-based theories.

###High Temperature Mixed State $c-$Axis Dissipation in Low Carrier Density $Y_{0.54}Pr_{0.46}Ba_{2}Cu_{3}O_{7-δ}$|T. Katuwal,V. Sandu,B. J. Taylor,M. B. Maple,C. C. Almasan###

High Temperature Mixed State $c-$Axis Dissipation in Low Carrier Density $Y_{0.54}Pr_{0.46}Ba_{2}Cu_{3}O_{7-δ}$. The nature of the out-of-plane dissipation was investigated in underdoped
$Y_{0.54}Pr_{0.46}Ba_{2}Cu_{3}O_{7-\delta}$ single crystals at temperatures
close to the critical temperature. For this goal, temperature and angle
dependent out-of-plane resistivity measurements were carried out both below and
above the critical temperature. We found that the Ambegaokar-Halperin
relationship [V. Ambegaokar, and B. I. Halperin, Phys. Rev. Lett. \textbf{22},
1364 (1969)] depicts very well the angular magnetoresistivity in the
investigated range of field and temperature. The main finding is that the
in-plane phase fluctuations decouple the layers above the critical temperature
and the charge transport is governed only by the quasiparticles. We also have
calculated the interlayer Josephson critical current density, which was found
to be much smaller than the one predicted by the theory of layered
superconductors. This discrepancy could be a result of the d-wave symmetry of
the order parameter and/or of the non BCS temperature dependence of the c-axis
penetration length.

###Structural and magneto-transport characterization of Co_2Cr_xFe_(1-x)Al Heusler alloy films|A. D. Rata,H. Braak,D. E. Buergler,S. Cramm,C. M. Schneider###

Structural and magneto-transport characterization of Co_2Cr_xFe_(1-x)Al Heusler alloy films. We investigate the structure and magneto-transport properties of thin films
of the Co_2Cr_xFe_(1-x)Al full-Heusler compound, which is predicted to be a
half-metal by first-principles theoretical calculations. Thin films are
deposited by magnetron sputtering at room temperature on various substrates in
order to tune the growth from polycrystalline on thermally oxidized Si
substrates to highly textured and even epitaxial on MgO(001) substrates,
respectively. Our Heusler films are magnetically very soft and ferromagnetic
with Curie temperatures up to 630 K. The total magnetic moment is reduced
compared to the theoretical bulk value, but still comparable to values reported
for films grown at elevated temperature. Polycrystalline Heusler films combined
with MgO barriers are incorporated into magnetic tunnel junctions and yield 37%
magnetoresistance at room temperature.

###Intervalley scattering, long-range disorder, and effective time reversal symmetry breaking in graphene|A. F. Morpurgo,F. Guinea###

Intervalley scattering, long-range disorder, and effective time reversal symmetry breaking in graphene. We discuss the effect of certain types of static disorder, like that induced
by curvature or topological defects, on the quantum correction to the
conductivity in graphene. We find that when the intervalley scattering time is
long or comparable to $\tau_{\phi}$, these defects can induce an effective time
reversal symmetry breaking of the hamiltonian associated to each one of the two
valleys in graphene. The phenomenon suppresses the magnitude of the quantum
correction to the conductivity and may result in the complete absence of a low
field magnetoresistance, as recently found experimentally. Our work shows that
a quantitative description of weak localization in graphene must include the
analysis of new regimes, not present in conventional two dimensional electron
gases.

###Quasi-2D superconductivity and Fermi-liquid behavior in bulk CaC$_6$|E. Jobiliong,H. D. Zhou,J. A. Janik,Y. -J. Jo,L. Balicas,J. S. Brooks,C. R. Wiebe###

Quasi-2D superconductivity and Fermi-liquid behavior in bulk CaC$_6$. The intercalated graphite superconductor CaC6 with Tc ~ 11.5 K has been
synthesized and characterized with magnetoresistance measurements. Above the
transition, the resistivity follows a T^2 dependence up to 50 K, which suggests
Fermi liquid behavior. Above 50 K, the data can be fit to the Bloch-Gruneisen
model providing a Debye temperature of theta = 263 K. By using McMillan
formula, we estimate the electron-phonon coupling constant of lambda = 0.85
which places this material in the intermediate-coupling regime. The upper
critical field is determined parallel and perpendicular to the superconducting
planes, and the dependence of the upper critical field as a function of angle
suggests that this is a quasi-2D superconductivity. All of these measurements
are consistent with BCS-like superconductivity.

###Influence of Domain Wall on Magnetocaloric Effect in GdPt$_{2}$|Tapas Samanta,I. Das###

Influence of Domain Wall on Magnetocaloric Effect in GdPt$_{2}$. The resistivity, magnetoresistance and in-field heat capacity measurements
were performed on GdPt$_{2}$ intermetallic compound. The magnetocaloric
parameters $\Delta T_{ad}$ and $-\Delta S$ were derived from the in-field heat
capacity data. Comparison has been made between the magnetocaloric effect
$-\Delta S$ and difference in resistivity $-\Delta \rho$ $(=\rho(H)-\rho(0))$
as a function of temperature. There is distinct difference in the temperature
dependence of $-\Delta S$ and $-\Delta \rho$ below the ferromagnetic transition
temperature. However after removing the domain wall contribution from $-\Delta
\rho$, the nature of $-\Delta S$ and $-\Delta \rho$ dependence as a function of
temperature are similar. Our observation indicates that the domain wall
contribution in magnetocaloric effect is negligible in spite of the fact that
it has significant contribution in magnetotransport.

###Electronic and Magnetic Properties of Sr and Ca Doped Lanthanum Manganites from First-Principles|M. -H. Tsai,Y. -H. Tang,H. Chou,W. T. Wu###

Electronic and Magnetic Properties of Sr and Ca Doped Lanthanum Manganites from First-Principles. The complicated electronic, magnetic, and colossal magnetoresistant (CMR)
properties of Sr and Ca doped lanthanum manganites can be understood by
spin-polarized first-principles calculations. The electronic properties can be
attributed to a detailed balancing between Sr and Ca induced metal-like O 2p
and majority-spin (majority-spin) Mn eg delocalized states and the
insulator-like minority-spin (minority-spin) Mn t2g band near the Fermi level
(EF). The magnetic properties can be attributed to a detailed balancing between
O mediated antiferromagnetic superexchange and delocalized majority-spin Mn
eg-state mediated ferromagnetic spin-spin couplings. While CMR can be
attributed to the lining up of magnetic domains trigged by the applied magnetic
field, which suppresses the trapping ability of the empty Mn t2g states that
resists the motion of conducting Mn majority-spin eg electrons.

###First principles modeling of tunnel magnetoresistance of Fe/MgO/Fe trilayers|Derek Waldron,Vladimir Timoshevskii,Yibin Hu,Ke Xia,Hong Guo###

First principles modeling of tunnel magnetoresistance of Fe/MgO/Fe trilayers. By carrying out density functional theory analysis within the Keldysh
non-equilibrium Green's functional formalism, we have calculated the nonlinear
and non-equilibrium quantum transport properties of Fe/MgO/Fe trilayer
structures as a function of external bias voltage. For well relaxed atomic
structures of the trilayer, the equilibrium tunnel magnetoresistance ratio
(TMR) is found to be very large and also fairly stable against small variations
in the atomic structure. As a function of external bias voltage, the TMR
reduces monotonically to zero with a voltage scale of about 1V, in agreement
with experimental observations. We present understanding of the nonequilibrium
transport properties by investigating microscopic details of the scattering
states and the Bloch bands of the Fe leads.

###Magnetoresistance of a quantum dot with spin-active interfaces|Audrey Cottet,Mahn-Soo Choi###

Magnetoresistance of a quantum dot with spin-active interfaces. We study the zero-bias magnetoresistance MR of an interacting quantum dot
connected to two ferromagnetic leads and capacitively coupled to a gate voltage
source Vg. We investigate the effects of the spin-activity of the contacts
between the dot and the leads by introducing an effective exchange field in an
Anderson model. This spin-activity makes easier negative MR effects, and can
even lead to a giant MR effect with a sign tunable with Vg. Assuming a twofold
orbital degeneracy, our approach allows to interpret in an interacting picture
the MR(Vg) measured by S. Sahoo et al. [Nature Phys. 2, 99 (2005)] in single
wall carbon nanotubes with ferromagnetic contacts. If this experiment is
repeated on a larger Vg-range, we expect that the MR(Vg) oscillations are not
regular like in the presently available data, due to Coulomb interactions.

###Radiation-induced magnetoresistance oscillations in two-dimensional electron systems under bichromatic irradiation|X. L. Lei###

Radiation-induced magnetoresistance oscillations in two-dimensional electron systems under bichromatic irradiation. We analyze the magnetoresistance $R_{xx}$ oscillations in high-mobility
two-dimensional electron systems induced by the combined driving of two
radiation fields of frequency $\omega_1$ and $\omega_2$, based on the
balance-equation approach to magnetotransport for high-carrier-density systems
in Faraday geometry. It is shown that under bichromatic irradiation of
$\omega_2\sim 1.5 \omega_1$, most of the characterstic peak-valley pairs in the
curve of $R_{xx}$ versus magnetic field in the case of monochromatic
irradiation of either $\omega_1$ or $\omega_2$ disappear, except the one around
$\omega_1/\omega_c\sim 2$ or $\omega_2/\omega_c\sim 3$. $R_{xx}$ oscillations
show up mainly as new peak-valley structures around other positions related to
multiple photon processes of mixing frequencies $\omega_1+\omega_2$,
$\omega_2-\omega_1$, etc. Many minima of these resistance peak-valley pairs can
descend down to negative with enhancing radiation strength, indicating the
possible bichromaticzero-resistance states.

###Large enhancement of the thermopower in Na$_x$CoO$_2$ at high Na doping|Minhyea Lee,Liliana Viciu,Lu Li,Yayu Wang,M. L. Foo,S. Watauchi,R. A. Pascal Jr.,R. J. Cava,N. P. Ong###

Large enhancement of the thermopower in Na$_x$CoO$_2$ at high Na doping. Research on the oxide perovskites has uncovered electronic properties that
are strikingly enhanced compared with those in conventional metals. Examples
are the high critical temperatures of the cuprate superconductors and the
colossal magnetoresistance in the manganites. The conducting layered cobaltate
$\rm Na_xCoO_2$ displays several interesting electronic phases as $x$ is varied
including water-induced superconductivity and an insulating state that is
destroyed by field. Initial measurements showed that, in the as-grown
composition, $\rm Na_xCoO_2$ displays moderately large thermopower $S$ and
conductivity $\sigma$. However, the prospects for thermoelectric cooling
applications faded when the figure of merit $Z$ was found to be small at this
composition (0.6$<x<$0.7). Here we report that, in the poorly-explored
high-doping region $x>$0.75, $S$ undergoes an even steeper enhancement. At the
critical doping $x_p\sim$ 0.85, $Z$ (at 80 K) reaches values $\sim$40 times
larger than in the as-grown crystals. We discuss prospects for low-temperature
thermoelectric applications.

###Effect of Ga doping on magnetotransport properties in collosal magnetoresistive La0.7Ca0.3Mn1-xGaxO3 (0 < x < 0.1)|Marek Pekala,Jan Mucha,Benedicte Vertruyen,Rudi Cloots,Marcel Ausloos###

Effect of Ga doping on magnetotransport properties in collosal magnetoresistive La0.7Ca0.3Mn1-xGaxO3 (0 < x < 0.1). Samples of La0.7Ca0.3Mn1-xGaxO3 with x = 0, 0.025, 0.05 and 0.10 were
prepared by standard solid-state reaction. They were first characterized
chemically, including the microstructure. The magnetic properties and various
transport properties, i.e. the electrical resistivity, magnetoresistivity (for
a field below 8T), thermoelectric power and thermal conductivity measured each
time on the same sample, are reported. The markedly different behavior of the x
= 0.1 sample from those with a smaller Ga content, is discussed. The dilution
of the Mn3+/Mn4+ interactions with Ga doping considerably reduces the
ferromagnetic double exchange interaction within the manganese lattice leading
to a decrease of the Curie temperature. The polaron binding energy varies from
224 to 243 meV with increased Ga doping.

###Angular dependence of domain wall resistivity in artificial magnetic domain structures|A. Aziz,S. J. Bending,H. G. Roberts,S. Crampin,P. J. Heard,C. H. Marrows###

Angular dependence of domain wall resistivity in artificial magnetic domain structures. We exploit the ability to precisely control the magnetic domain structure of
perpendicularly magnetized Pt/Co/Pt trilayers to fabricate artificial domain
wall arrays and study their transport properties. The scaling behaviour of this
model system confirms the intrinsic domain wall origin of the
magnetoresistance, and systematic studies using domains patterned at various
angles to the current flow are excellently described by an angular-dependent
resistivity tensor containing perpendicular and parallel domain wall
resistivities. We find that the latter are fully consistent with Levy-Zhang
theory, which allows us to estimate the ratio of minority to majority spin
carrier resistivities, rho-down/rho-up~5.5, in good agreement with thin film
band structure calculations.

###Transport through two-level quantum dots weakly coupled to ferromagnetic leads|I. Weymann,J. Barnas###

Transport through two-level quantum dots weakly coupled to ferromagnetic leads. Spin-dependent transport through a two-level quantum dot in the sequential
tunneling regime is analyzed theoretically by means of a real-time diagrammatic
technique. It is shown that the current, tunnel magnetoresistance, and shot
noise (Fano factor) strongly depend on the transport regime, providing a
detailed information on the electronic structure of quantum dots and their
coupling to external leads. When the dot is asymmetrically coupled to the
leads, a negative differential conductance may occur in certain bias regions,
which is associated with a super-Poissonian shot noise. In the case of a
quantum dot coupled to one half-metallic and one nonmagnetic lead, one finds
characteristic Pauli spin blockade effects. Transport may be also suppressed
when the dot levels are coupled to the leads with different coupling strengths.
The influence of an external magnetic field on transport properties is also
discussed.

###Phase coherence of conduction electrons below the Kondo temperature|Gassem M. Alzoubi Norman O. Birge###

Phase coherence of conduction electrons below the Kondo temperature. We have measured the phase decoherence rate, $\tau_{\phi}^{-1}$ of conduction
electrons in disordered Ag wires implanted with 2 and 10 parts per million Fe
impurities, by means of the weak localization magnetoresistance. The Kondo
temperature of Fe in Ag, $T_K \approx 4$ K, is in the ideal temperature range
to study the progressive screening of the Fe spins as the temperature $T$ falls
below $T_K$. The contribution to $\tau_{\phi}^{-1}$ from the Fe impurities is
clearly visible over the temperature range 40 mK -- 10 K. Below $T_K$,
$\tau_{\phi}^{-1}$ falls rapidly until $T/T_K \approx 0.1$, in agreement with
recent theoretical calculations. At lower $T$, $\tau_{\phi}^{-1}$ deviates from
theory with a flatter $T$-dependence. We speculate that this latter behavior is
due to incomplete screening of the s=2 Fe impurities by the conduction
electrons.

###Magnetic-field-induced transition in BaVS3|P. Fazekas,N. Barisic,I. Kezsmarki,L. Demko,H. Berger,L. Forro,G. Mihaly###

Magnetic-field-induced transition in BaVS3. The metal-insulator transition (MIT) of BaVS3 is suppressed under pressure
and above the critical pressure of p~2GPa the metallic phase is stabilized. We
present the results of detailed magnetoresistivity measurements carried out at
pressures near the critical value, in magnetic fields up to B=12T. We found
that slightly below the critical pressure the structural tetramerization --
which drives the MIT -- is combined with the onset of magnetic correlations. If
the zero-field transition temperature is suppressed to a sufficiently low value
(T_MI<15K), the system can be driven into the metallic state by application of
magnetic field. The main effect is not the reduction of T_MI with increasing B,
but rather the broadening of the transition due to the applied magnetic field.
We tentatively ascribe this phenomenon to the influence on the magnetic
structure coupled to the bond-order of the tetramers.

###Angle-dependent magnetotransport in cubic and tetragonal ferromagnets: Application to (001)- and (113)A-oriented (Ga,Mn)As|W. Limmer,M. Glunk,J. Daeubler,T. Hummel,W. Schoch,R. Sauer,C. Bihler,H. Huebl,M. S. Brandt,S. T. B. Goennenwein###

Angle-dependent magnetotransport in cubic and tetragonal ferromagnets: Application to (001)- and (113)A-oriented (Ga,Mn)As. General expressions for the longitudinal and transverse resistivities of
single-crystalline cubic and tetragonal ferromagnets are derived from a series
expansion of the resistivity tensor with respect to the magnetization
orientation. They are applied to strained (Ga,Mn)As films, grown on (001)- and
(113)A-oriented GaAs substrates, where the resistivities are theoretically and
experimentally studied for magnetic fields rotated within various planes
parallel and perpendicular to the sample surface. We are able to model the
measured angular dependences of the resistivities within the framework of a
single ferromagnetic domain, calculating the field-dependent orientation of the
magnetization by numerically minimizing the free-enthalpy density.
Angle-dependent magnetotransport measurements are shown to be a powerful tool
for probing both anisotropic magnetoresistance and magnetic anisotropy. The
anisotropy parameters of the (Ga,Mn)As films inferred from the magnetotransport
measurements agree with those obtained by ferromagnetic resonance measurements
within a factor of two.

###Influence of magnetic field on paramagnetic-ferromagnetic transition in La$_{1-x}$Ca$_{x}$MnO$_{3}$ ($x\approx 0.25$) crystal: ultrasonic and transport studies|B. I. Belevtsev,G. A. Zvyagina,K. R. Zhekov,I. G. Kolobov,E. Yu. Beliayev,A. S. Panfilov,N. N. Galtsov,A. I. Prokhvatilov,J. Fink-Finowicki###

Influence of magnetic field on paramagnetic-ferromagnetic transition in La$_{1-x}$Ca$_{x}$MnO$_{3}$ ($x\approx 0.25$) crystal: ultrasonic and transport studies. The ultrasonic properties of La$_{1-x}$Ca$_{x}$MnO$_{3}$ ($x\approx 0.25$)
with the Curie temperature $T_C$ about 200 K are studied. Temperature
dependences of longitudinal and transverse sound velocities were measured in
zero magnetic field and for different constant magnetic fields as well. The
ultrasonic study is supported by magnetic, resistive, magnetoresistive,
structural and other measurements of the sample that facilitate interpretation
of the results obtained. The magnetic field influence on sound properties found
in this study presents some new features of the interplay between the elastic
and magnetic properties of these compounds. It is shown that the
paramagnetic-ferromagnetic transition in the sample studied is first order, but
can become second order under the influence of applied magnetic field.

###Theoretical proposal predicting anomalous magnetoresistance and quadratic Hall effect in the partially ordered state of MnSi|B. Binz,A. Vishwanath###

Theoretical proposal predicting anomalous magnetoresistance and quadratic Hall effect in the partially ordered state of MnSi. In [B. Binz, A. Vishwanath and V. Aji, Phys. Rev. Lett. 96, 207202 (2006)], a
magnetic structure that breaks time reversal symmetry in the absence of net
magnetization was proposed as an explanation for the high pressure "partially
ordered" state of MnSi. Here we make explicit the anomalous magneto-transport
properties of such a state: a magnetoresistivity which is linear and a Hall
conductance which is quadratic in the applied magnetic field. Field cooling
procedures for obtaining single domain samples are discussed. The anomalous
effects are elaborated in the case of three geometries chosen to produce
experimentally unambiguous signals of this unusual magnetic state; e.g., it is
predicted that a field in z-direction induces an anisotropy in the x-y plane.
Another geometry leads to a Hall voltage parallel to the magnetic field.

###Microwave spectroscopy of Q1D and Q2D organic conductors|Stephen Hill,Susumu Takahashi###

Microwave spectroscopy of Q1D and Q2D organic conductors. This chapter reviews recent experimental studies of a novel open-orbit
magnetic resonance phenomenon. The technique involves measurement of
angle-dependent microwave magneto-conductivity and is, thus, closely related to
the cyclotron resonance and angle-dependent magnetoresistance techniques. Data
for three contrasting materials are presented: (TMTSF)2ClO4,
alpha-(BEDT-TTF)2KHg(SCN)4 and kappa-(BEDT-TTF)2I3. These studies reveal
important insights into the Fermiology of these novel materials, as well as
providing access to important electronic parameters such as the in-plane Fermi
velocity and quasiparticle scattering rate. It is argued that all three
compounds exhibit coherent three-dimensional band transport at liquid helium
temperatures, and that their low-energy magnetoelectrodynamic properties appear
to be well explained on the basis of a conventional semiclassical Boltzmann
approach. It is also suggested that this technique could be used to probe
quasiparticles in nodal superconductors.

###Low-frequency noise and tunnelling magnetoresistance in Fe(110)/MgO(111)/Fe(110) epitaxial magnetic tunnel junctions|R. Guerrero,F. G. Aliev,R. Villar,J. Hauch,M. Fraune,G. Guntherodt,K. Rott,H. Bruckl,G. Reiss###

Low-frequency noise and tunnelling magnetoresistance in Fe(110)/MgO(111)/Fe(110) epitaxial magnetic tunnel junctions. We report on tunnelling magnetoresistance (TMR), current-voltage (IV)
characteristics and low frequency noise in epitaxially grown
Fe(110)/MgO(111)/Fe(110) magnetic tunnel junctions (MTJs) with dimensions from
2x2 to 20x20 um2. The evaluated MgO energy barrier (0.50+/-0.08 eV), the
barrier width (13.1+/-0.5 angstrom) as well as the resistance times area
product (7+/-1 Mohmsum2) show relatively small variation, confirming a high
quality epitaxy and uniformity of all MTJs studied. The noise power, though
exhibiting large variation, was observed to be roughly anticorrelated with the
TMR. Surprisingly, for the largest junctions we observed a strong enhancement
of the normalized low-frequency noise in the antiparallel magnetic
configuration. This behaviour could be related to an interplay between the
magnetic state and the local barrier defects structure of the epitaxial MTJs

###Swift-heavy-ion-irradiation-induced enhancement in electrical conductivity of chemical solution deposited La0.7Ba0.3MnO3 thin films|R. N. Parmar,J. H. Markna,D. G. Kuberkar,Ravi Kumar,D. S. Rana,Vivas C. Bagve,S. K. Malik###

Swift-heavy-ion-irradiation-induced enhancement in electrical conductivity of chemical solution deposited La0.7Ba0.3MnO3 thin films. Epitaxial thin films of La0.7Ba0.3MnO3 manganite, deposited using Chemical
Solution Deposition technique, were irradiated by 200 MeV Ag+15 ions with a
maximum ion dose up to 1x10^12 ions/cm2. Temperature- and magnetic
field-dependent resistivity measurements on all the films (before and after
irradiation) reveal a sustained decrease in resistivity with increasing ion
dose. A maximum dose of 1x10^12 ions/cm2 suppresses resistivity by factors of 3
and 10, at 330 K [insulator-metal (I-M) transition] and at 10 K, respectively.
On the other hand, with increasing ion dose, the magnetoresistance (MR)
enhances in the vicinity of I-M transition but decreases at low temperatures.
These results, corroborated by surface morphology of films, suggest that the
origin of such properties lies in the irradiation induced improved
crystallinity and epitaxial orientation, enhanced connectivity between grains,
and conglomeration of grains which result in better conductivity at grain
boundaries.

###Sensitivity of the interlayer magnetoresistance of layered metals to intralayer anisotropies|Malcolm P. Kennett,Ross H. McKenzie###

Sensitivity of the interlayer magnetoresistance of layered metals to intralayer anisotropies. Many of the most interesting and technologically important electronic
materials discovered in the past two decades have two common features: a
layered crystal structure and strong interactions between electrons. Two of the
most fundamental questions about such layered metals concern the origin of
intralayer anisotropies and the coherence of interlayer charge transport. We
show that angle dependent magnetoresistance oscillations (AMRO) are sensitive
to anisotropies around an intralayer Fermi surface. Hence, AMRO can be a probe
of intralayer anisotropies that is complementary to angle-resolved
photoemission spectroscopy (ARPES) and scanning tunneling microscopy (STM).
However, AMRO are not very sensitive to the coherence of the interlayer
transport. We illustrate this with comparisons to recent AMRO experiments on an
overdoped cuprate.

###Hopping Conduction in Disordered Carbon Nanotubes|D. P. Wang,D. E. Feldman,B. R. Perkins,A. J. Yin,G. H. Wang,J. M. Xu,A. Zaslavsky###

Hopping Conduction in Disordered Carbon Nanotubes. We report electrical transport measurements on individual disordered carbon
nanotubes, grown catalytically in a nanoporous anodic aluminum oxide template.
In both as-grown and annealed types of nanotubes, the low-field conductance
shows as exp[-(T_{0}/T)^{1/2}] dependence on temperature T, suggesting that
hopping conduction is the dominant transport mechanism, albeit with different
disorder-related coefficients T_{0}. The field dependence of low-temperature
conductance behaves an exp[-(xi_{0}/xi)^{1/2}] with high electric field xi at
sufficiently low T. Finally, both annealed and unannealed nanotubes exhibit
weak positive magnetoresistance at low T = 1.7 K. Comparison with theory
indicates that our data are best explained by Coulomb-gap variable range
hopping conduction and permits the extraction of disorder-dependent
localization length and dielectric constant.

###Cotunneling through two-level quantum dots weakly coupled to ferromagnetic leads|Ireneusz Weymann###

Cotunneling through two-level quantum dots weakly coupled to ferromagnetic leads. The spin-polarized transport through two-level quantum dots weakly coupled to
ferromagnetic leads is considered theoretically in the Coulomb blockade regime.
It is assumed that the dot is doubly occupied, so that the current flows due to
cotunneling through singlet and triplet states of the dot. It is shown that
transport characteristics strongly depend on the ground state of quantum dot.
If the ground state is a singlet, differential conductance ($G$) displays a
broad minimum at low bias voltage, while tunnel magnetoresistance (TMR) is
given by the Julliere value. If triplet is the ground state of the system,
there is a maximum in differential conductance at zero bias when the leads are
magnetized in antiparallel. The maximum is accompanied by a minimum in TMR. The
different behavior of $G$ and TMR may thus help to determine the ground state
of the dot and the energy difference between the singlet and triplet states.

###Transport in chemically doped graphene in the presence of adsorbed molecules|E. H. Hwang,S. Adam,S. Das Sarma###

Transport in chemically doped graphene in the presence of adsorbed molecules. Motivated by a recent experiment reporting on the possible application of
graphene as sensors, we calculate transport properties of 2D graphene
monolayers in the presence of adsorbed molecules. We find that the adsorbed
molecules, acting as compensators that partially neutralize the random charged
impurity centers in the substrate, enhance the graphene mobility without much
change in the carrier density. We predict that subsequent field-effect
measurements should preserve this higher mobility for both electrons and holes,
but with a voltage induced electron-hole asymmetry that depends on whether the
adsorbed molecule was an electron or hole donor in the compensation process. We
also calculate the low density magnetoresistance and find good quantitative
agreement with experimental results.

###Pressure dependence of the magnetoresistance oscillations spectrum of beta''-(BEDT-TTF)4(NH4)[Fe(C2O4)3].DMF|Alain Audouard,Vladimir N. Laukhin,Jérome Béard,David Vignolles,Marc Nardone,Enric Canadell,Tatyana G. Prokhorova,Eduard Yagubskii###

Pressure dependence of the magnetoresistance oscillations spectrum of beta''-(BEDT-TTF)4(NH4)[Fe(C2O4)3].DMF. The pressure dependence of the interlayer magnetoresistance of the quasi-two
dimensional organic metal beta''-(BEDT-TTF)4(NH4)[Fe(C2O4)3].DMF has been
investigated up to 1 GPa in pulsed magnetic fields up to 55 T. The Shubnikov-de
Haas oscillations spectra can be interpreted on the basis of three compensated
orbits in all the pressure range studied, suggesting that the Fermi surface
topology remains qualitatively the same as the applied pressure varies. In
addition, all the observed frequencies, normalized to their value at ambient
pressure, exhibit the same sizeable pressure dependence. Despite this behavior,
which is at variance with that of numerous charge transfer salts based on the
BEDT-TTF molecule, non-monotonous pressure-induced variations of parameters
such as the scattering rate linked to the various detected orbits are observed.

###Cotunneling through quantum dots coupled to magnetic leads: zero-bias anomaly for non-collinear magnetic configurations|Ireneusz Weymann,Jozef Barnas###

Cotunneling through quantum dots coupled to magnetic leads: zero-bias anomaly for non-collinear magnetic configurations. Cotunneling transport through quantum dots weakly coupled to non-collinearly
magnetized leads is analyzed theoretically by means of the real-time
diagrammatic technique. The electric current, dot occupations, and dot spin are
calculated in the Coulomb blockade regime and for arbitrary magnetic
configuration of the system. It is shown that an effective exchange field
exerted on the dot by ferromagnetic leads can significantly modify the
transport characteristics in non-collinear magnetic configurations, in
particular the zero-bias anomaly found recently for antiparallel configuration.
For asymmetric Anderson model, the exchange field gives rise to precession of
the dot spin, which leads to a nonmonotonic dependence of the differential
conductance and tunnel magnetoresistance on the angle between magnetic moments
of the leads. An enhanced differential conductance and negative TMR are found
for certain non-collinear configurations.

###Anomalous Resistance Ridges Along Filling Factor $ν= 4i$|K. Takashina,M. Brun,T. Ota,D. K. Maude,A. Fujiwara,Y. Ono,Y. Takahashi,Y. Hirayama###

Anomalous Resistance Ridges Along Filling Factor $ν= 4i$. We report anomalous structure in the magnetoresistance of
SiO$_2$/Si(100)/SiO$_2$ quantum wells. When Landau levels of opposite valleys
are driven through coincidence at the Fermi level, the longitudinal resistance
displays elevations at filling factors that are integer multiples of 4
$(\nu=4i)$ accompanied by suppression on either side of $\nu=4i$. This persists
when either magnetic field or valley splitting is swept leading to resistance
ridges running along $\nu=4i$. The range of field over which they are observed
points to the role of spin degeneracy, which is directly confirmed by their
disappearance under in-plane magnetic field. The data suggest a new type of
many-body effect due to the combined degeneracy of valley and spin.

###Epitaxial Co2Cr0.6Fe0.4Al thin films and magnetic tunneling junctions|A. Conca,M. Jourdan,H. Adrian###

Epitaxial Co2Cr0.6Fe0.4Al thin films and magnetic tunneling junctions. Epitaxial thin films of the theoretically predicted half metal
Co2Cr0.6Fe0.4Al were deposited by dc magnetron sputtering on different
substrates and buffer layers. The samples were characterized by x-ray and
electron beam diffraction (RHEED) demonstrating the B2 order of the Heusler
compound with only a small partition of disorder on the Co sites. Magnetic
tunneling junctions with Co2Cr0.6Fe0.4Al electrode, AlOx barrier and Co counter
electrode were prepared. From the Julliere model a spin polarisation of
Co2Cr0.6Fe0.4Al of 54% at T=4K is deduced. The relation between the annealing
temperature of the Heusler electrodes and the magnitude of the tunneling
magnetoresistance effect was investigated and the results are discussed in the
framework of morphology and surface order based of in situ STM and RHEED
investigations.

###Structural, magnetic, and transport properties of Co$_2$FeSi Heusler films|H. Schneider,Ch. Herbort,G. Jakob,H. Adrian,S. Wurmehl,C. Felser###

Structural, magnetic, and transport properties of Co$_2$FeSi Heusler films. We report the deposition of thin Co$_2$FeSi films by RF magnetron sputtering.
Epitaxial (100)-oriented and L2$_1$ ordered growth is observed for films grown
on MgO(100) substrates. (110)-oriented films on Al$_2$O$_3$(110) show several
epitaxial domains in the film plane. Investigation of the magnetic properties
reveals a saturation magnetization of 5.0 $mu_B/f.u.$ at low temperatures. The
temperature dependence of the resistivity $rho_{xx}(T)$ exhibits a crossover
from a T^3.5 law at T<50K to a T^1.65 behaviour at elevated temperatures.
$rho_{xx}(H)$ shows a small anisotropic magnetoresistive effect. A weak
dependence of the normal Hall effect on the external magnetic field indicates
the compensation of electron and hole like contributions at the Fermi surface.

###Sequential tunneling and shot noise in ferromagnet/normal-metal/ferromagnet double tunnel junctions|H. Giang Bach,V. Hung Nguyen,T. Anh Pham###

Sequential tunneling and shot noise in ferromagnet/normal-metal/ferromagnet double tunnel junctions. The tunneling through a ferromagnet/normal metal/ferromagnet double junction
in the Coulomb blockade regime is studied, assuming that the spin relaxation
time of electron in the central metallic island is sufficiently large. Using
the master equation, the current, the tunnel magnetoresistance (TMR), and the
current noise spectrum have been calculated for devices of different
parameters. It was shown that the interplay between spin and charge
correlations strongly depends on the asymmetry of measured device. The charge
correlation makes both the chemical potential shift, which describes the spin
accumulation in the central island, and the TMR oscillated with the same period
as the Coulomb staircase in current-voltage characteristics. This effect is
smeared by the temperature. The spin correlation may cause an enhancement of
noise at finite frequencies, while the zero frequency noise is still always
sub-poissonian. The gate voltage causes an oscillation of not only conductance,
but also TMR and noise.

###Negative magnetoresistance and phase slip process in superconducting nanowires|D. Y. Vodolazov###

Negative magnetoresistance and phase slip process in superconducting nanowires. We argue that the negative magnetoresistance of superconducting nanowires,
which was observed in recent experiments, can be explained by the influence of
the external magnetic field on the critical current of the phase slip process.
We show that the suppression of the order parameter in the bulk superconductors
made by an external magnetic field can lead to an enhancement of both the first
$I_{c1}$ and the second $I_{c2}$ critical currents of the phase slip process in
nanowires. Another mechanism of an enhancement of $I_{c1}$ can come from
decreasing the decay length of the charge imbalance $\lambda_Q$ at weak
magnetic fields because $I_{c1}$ is inversely proportional to $\lambda_Q$. The
enhancement of the first critical current leads to a larger intrinsic
dissipation of the phase slip process. It suppresses the rate of both the
thermo-activated and/or quantum fluctuated phase slips and results in
decreasing the fluctuated resistance.

###Calculations of giant magnetoresistance in Fe/Cr trilayers using layer potentials determined from {\it ab-initio} methods|M. Pereiro,D. Baldomir,S. V. Man'kovsky,K. Warda,J. E. Arias,L. Wojtczak,J. Botana###

Calculations of giant magnetoresistance in Fe/Cr trilayers using layer potentials determined from {\it ab-initio} methods. The ab initio full-potential linearized augmented plane-wave method
explicitly designed for the slab geometry was employed to elucidate the
physical origin of the layer potentials for the trilayers nFe/3Cr/nFe(001),
where n is the number of Fe monolayers. The thickness of the transition-metal
ferromagnet has been ranged from $n=1$ up to n=8 while the spacer thickness was
fixed to 3 monolayers. The calculated potentials were inserted in the
Fuchs-Sondheimer formalism in order to calculate the giant magnetoresistance
(GMR) ratio. The predicted GMR ratio was compared with the experiment and the
oscillatory behavior of the GMR as a function of the ferromagnetic layer
thickness was discussed in the context of the layer potentials. The reported
results confirm that the interface monolayers play a dominant role in the
intrinsic GMR.

###Anisotropic Magnetoresistance components in (Ga,Mn)As|A. W. Rushforth,K. Výborný,C. S. King,K. W. Edmonds,R. P. Campion,C. T. Foxon,J. Wunderlich,A. C. Irvine,P. Vašek,V. Novák,K. Olejník,Jairo Sinova,T. Jungwirth,B. L. Gallagher###

Anisotropic Magnetoresistance components in (Ga,Mn)As. Our experimental and theoretical study of the non-crystalline and crystalline
components of the anisotropic magnetoresistance (AMR) in (Ga,Mn)As is aimed at
exploring the basic physical aspects of this relativistic transport effect. The
non-crystalline AMR reflects anisotropic lifetimes of the holes due to
polarized Mn impurities while the crystalline AMR is associated with valence
band warping. We find that the sign of the non-crystalline AMR is determined by
the form of spin-orbit coupling in the host band and by the relative strengths
of the non-magnetic and magnetic contributions to the impurity potential. We
develop experimental methods directly yielding the non-crystalline and
crystalline AMR components which are then independently analyzed. We report the
observation of an AMR dominated by a large uniaxial crystalline component and
show that AMR can be modified by local strain relaxation. We discuss generic
implications of our experimental and theoretical findings including predictions
for non-crystalline AMR sign reversals in dilute moment systems.

###Extensions to the Kondo lattice model to achieve realistic Curie temperatures and appropriate behavior of the resistivity for manganites|Martin Stier,Wolfgang Nolting###

Extensions to the Kondo lattice model to achieve realistic Curie temperatures and appropriate behavior of the resistivity for manganites. We investigate the influence of the Jahn-Teller distortion and a direct
antiferromagnetic moment coupling as extensions to a two-band Kondo lattice
model for the magnetic and electronic properties of manganites. Those are
calculated self-consistently via an interpolating self-energy model and a
modified RKKY technique using finite Hund coupling and quantum spins. We found
that both effects are essential to achieve realistic Curie temperatures if we
regard intraband Coulomb repulsion. Using reliable model parameters we got
results which are in very good agreement with experimental data in the whole
ferromagnetic doping range. In the calculated phase diagram there are
ferromagnetic metal to paramagnetic insulator transitions, accompanied by a
Colossal Magnetoresistance (CMR) behavior. To improve the comparability of the
measured behavior of the resistivity with the calculated one, we have to switch
on interband Coulomb correlations.

###Magnetic effects at the interface between nonmagnetic oxides|A. Brinkman,M. Huijben,M. van Zalk,J. Huijben,U. Zeitler,J. C. Maan,W. G. van der Wiel,G. Rijnders,D. H. A. Blank,H. Hilgenkamp###

Magnetic effects at the interface between nonmagnetic oxides. The electronic reconstruction at the interface between two insulating oxides
can give rise to a highly-conductive interface. In analogy to this remarkable
interface-induced conductivity we show how, additionally, magnetism can be
induced at the interface between the otherwise nonmagnetic insulating
perovskites SrTiO3 and LaAlO3. A large negative magnetoresistance of the
interface is found, together with a logarithmic temperature dependence of the
sheet resistance. At low temperatures, the sheet resistance reveals magnetic
hysteresis. Magnetic ordering is a key issue in solid-state science and its
underlying mechanisms are still the subject of intense research. In particular,
the interplay between localized magnetic moments and the spin of itinerant
conduction electrons in a solid gives rise to intriguing many-body effects such
as Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions, the Kondo effect, and
carrier-induced ferromagnetism in diluted magnetic semiconductors. The
conducting oxide interface now provides a versatile system to induce and
manipulate magnetic moments in otherwise nonmagnetic materials.

###Frequency combinations in the magnetoresistance oscillations spectrum of a linear chain of coupled orbits with a high scattering rate|David Vignolles,Alain Audouard,Vladimir N. Laukhin,Jérome Béard,Enric Canadell,Nataliya G. Spitsina,Eduard Yagubskii###

Frequency combinations in the magnetoresistance oscillations spectrum of a linear chain of coupled orbits with a high scattering rate. The oscillatory magnetoresistance spectrum of the organic metal
(BEDO)$_5$Ni(CN)$_4\cdot$3C$_2$H$_4$(OH)$_2$ has been studied up to 50 T, in
the temperature range from 1.5 K to 4.2 K. In high magnetic field, its Fermi
surface corresponds to a linear chain of quasi-two-dimensional orbits coupled
by magnetic breakdown (MB). The scattering rate consistently deduced from the
data relevant to the basic $\alpha$ and the MB-induced $\beta$ orbits is very
large which points to a significant reduction of the chemical potential
oscillation. Despite of this feature, the oscillations spectrum exhibits many
frequency combinations. Their effective masses and (or) Dingle temperature are
not in agreement with either the predictions of the quantum interference model
or the semiclassical model of Falicov and Stachowiak.

###The Origin of Tunneling Anisotropic Magnetoresistance in Break Junctions|J. D. Burton,R. F. Sabirianov,J. P. Velev,O. N. Mryasov,E. Y. Tsymbal###

The Origin of Tunneling Anisotropic Magnetoresistance in Break Junctions. First-principles calculations of electron tunneling transport in Ni and Co
break junctions reveal strong dependence of the conductance on the
magnetization direction, an effect known as tunneling anisotropic
magnetoresistance (TAMR). The origin of this phenomenon stems from resonant
states localized in the electrodes near the junction break. The energy and
broadening of these states is strongly affected by the magnetization
orientation due to spin-orbit coupling, causing TAMR to be sensitive to bias
voltage on a scale of a few mV. Our results bear a resemblance to recent
experimental data and suggest that TAMR driven by resonant states is a general
phenomenon typical for magnetic broken contacts and other experimental
geometries where a magnetic tip is used to probe electron transport.

###Electrical transport and percolation in magnetoresistive manganite / insulating oxide composites: case of La0.7Ca0.3MnO3 / Mn3O4|B. Vertruyen,R. Cloots,M. Ausloos,J. -F. Fagnard,Ph. Vanderbemden###

Electrical transport and percolation in magnetoresistive manganite / insulating oxide composites: case of La0.7Ca0.3MnO3 / Mn3O4. We report the results of electrical resistivity measurements carried out on
well-sintered La0.7Ca0.3MnO3 / Mn3O4 composite samples with almost constant
composition of the magnetoresistive manganite phase (La0.7Ca0.3MnO3). A
percolation threshold (fc) occurs when the La0.7Ca0.3MnO3 volume fraction is ~
0.19. The dependence of the electrical resistivity as a function of
La0.7Ca0.3MnO3 volume fraction (fLCMO) can be described by percolation-like
phenomenological equations. Fitting the conducting regime (fLCMO > fc) by the
percolation power law returns a critical exponent t value of 2.0 +/- 0.2 at
room temperature and 2.6 +/-0.2 at 5 K. The increase of t is ascribed to the
influence of the grain boundaries on the electrical conduction process at low
temperature.

###Organic Spintronics|W. J. M. Naber,S. Faez,W. G. van der Wiel###

Organic Spintronics. In this paper we review the recent field of organic spintronics, where
organic materials are applied as a medium to transport and control
spin-polarized signals. The contacts for injecting and detecting spins are
formed by metals, oxides, or inorganic semiconductors. First, the basic
concepts of spintronics and organic electronics are addressed and phenomena
which are in particular relevant for organic spintronics are highlighted.
Experiments using different organic materials, including carbon nanotubes,
organic thin films, self-assembled monolayers and single molecules are then
reviewed. Observed magnetoresistance points toward successful spin injection
and detection, but spurious magnetoresitance effects can easily be confused
with spin accumulation. A few studies report long spin relaxation times and
lengths, which forms a promising basis for further research. We conclude with
discussing outstanding questions and problems.

###Ferromagnetic/superconducting bilayer structure: A model system for spin diffusion length estimation|S. Soltan,J. Albrecht,H. --U. Habermeier###

Ferromagnetic/superconducting bilayer structure: A model system for spin diffusion length estimation. We report detailed studies on ferromagnet--superconductor bilayer structures.
Epitaxial bilayer structures of half metal--colossal magnetoresistive
La$_{\mathrm{2/3}}$Ca$_{\mathrm{1/3}}$MnO$_{\mathrm{3}}$ (HM--CMR) and
high--$T_{\mathrm{c}}$ superconducting
YBa$_{\mathrm{2}}$Cu$_{\mathrm{3}}$O$_{\mathrm{7-\delta}}$(HTSC) are grown on
SrTiO$_3$ (100) single--crystalline substrates using pulsed laser deposition.
Magnetization $M$(T) measurements show the coexistence of ferromagnetism and
superconductivity in these structures at low temperatures. Using the HM--CMR
layer as an electrode for spin polarized electrons, we discuss the role of spin
polarized self injection into the HTSC layer. The experimental results are in
good agreement with a presented theoretical estimation, where the spin
diffusion length $\xi_{\mathrm {FM}}$ is found to be in the range of
$\xi_{\mathrm{FM}} \approx$ 10 nm.

###Macroscopic coherence effects in a mesoscopic system: Weak localization of thin silver films in an undergraduate lab|A. D. Beyer,M. Koesters,K. G. Libbrecht,E. D. Black###

Macroscopic coherence effects in a mesoscopic system: Weak localization of thin silver films in an undergraduate lab. We present an undergraduate lab that investigates weak localization in thin
silver films. The films prepared in our lab have thickness, $a$, between 60-200
\AA, a mesoscopic length scale. At low temperatures, the inelastic dephasing
length for electrons, $L_{\phi}$, exceeds the thickness of the film ($L_{\phi}
\gg a$), and the films are then quasi-2D in nature. In this situation, theory
predicts specific corrections to the Drude conductivity due to coherent
interference between conducting electrons' wavefunctions, a macroscopically
observable effect known as weak localization. This correction can be destroyed
with the application of a magnetic field, and the resulting magnetoresistance
curve provides information about electron transport in the film. This lab is
suitable for Junior or Senior level students in an advanced undergraduate lab
course.

###Spin-polarized transport through weakly coupled double quantum dots in the Coulomb-blockade regime|I. Weymann###

Spin-polarized transport through weakly coupled double quantum dots in the Coulomb-blockade regime. We analyze cotunneling transport through two quantum dots in series weakly
coupled to external ferromagnetic leads. In the Coulomb blockade regime the
electric current flows due to third-order tunneling, while the second-order
single-barrier processes have indirect impact on the current by changing the
occupation probabilities of the double dot system. We predict a zero-bias
maximum in the differential conductance, whose magnitude is conditioned by the
value of the inter-dot Coulomb interaction. This maximum is present in both
magnetic configurations of the system and results from asymmetry in cotunneling
through different virtual states. Furthermore, we show that tunnel
magnetoresistance exhibits a distinctively different behavior depending on
temperature, being rather independent of the value of inter-dot correlation.
Moreover, we find negative TMR in some range of the bias voltage.

###Magnetic Coupling and Long-Range Order in the Spin-Chain Sulphide Ba2cos3|Andrew D. J. Barnes,Thomas Baikie,Vincent Hardy,Marie-Bernadette Lepetit,Antoine Maignan,Nigel A. Young,M. Grazia Francesconi###

Magnetic Coupling and Long-Range Order in the Spin-Chain Sulphide Ba2cos3. In this paper, we report on the magnetic properties of Ba2CoS3, a spin-chain
compound recently found to be the first Co2+ containing one-dimensional
sulphide to show metallic-like conductivity and negative magnetoresistance. We
carried out an in-depth experimental investigation of the local structure of
the cobalt atoms, and ab-initio calculations of the resulting electronic
configuration of Co2+. From theoretical considerations, the intra-chain
coupling was predicted to be antiferromagnetic. Experimentally, several
estimates of this magnetic coupling were derived by analysing the temperature
dependence of the magnetic susceptibility. Magnetic and heat capacity
measurements also provided evidence of a three-dimensional antiferromagnetic
ordering, a feature indicative of a noticeable inter-chain coupling in this
quasi-1D system.

###Andreev reflection and strongly enhanced magnetoresistance oscillations in GaInAs/InP heterostructures with superconducting contacts|I. E. Batov,Th. Schapers,N. M. Chtchelkatchev,H. Hardtdegen,A. V. Ustinov###

Andreev reflection and strongly enhanced magnetoresistance oscillations in GaInAs/InP heterostructures with superconducting contacts. We study the magnetotransport in small hybrid junctions formed by
high-mobility GaInAs/InP heterostructures coupled to superconducting (S) and
normal metal (N) terminals. Highly transmissive superconducting contacts to a
two-dimensional electron gas (2DEG) located in a GaInAs/InP heterostructure are
realized by using a Au/NbN layer system. The magnetoresistance of the S/2DEG/N
structures is studied as a function of dc bias current and temperature. At bias
currents below a critical value, the resistance of the S/2DEG/N structures
develops a strong oscillatory dependence on the magnetic field, with an
amplitude of the oscillations considerably larger than that of the reference
N/2DEG/N structures. The experimental results are qualitatively explained by
taking Andreev reflection in high magnetic fields into account.

###Scanning magnetoresistance microscopy of atom chips|M. Volk,S. Whitlock,B. V. Hall,A. I. Sidorov###

Scanning magnetoresistance microscopy of atom chips. Surface based geometries of microfabricated wires or patterned magnetic films
can be used to magnetically trap and manipulate ultracold neutral atoms or
Bose-Einstein condensates. We investigate the magnetic properties of such atom
chips using a scanning magnetoresistive (MR) microscope with high spatial
resolution and high field sensitivity. We show that MR sensors are ideally
suited to observe small variations of the magnetic field caused by
imperfections in the wires or magnetic materials which ultimately lead to
fragmentation of ultracold atom clouds. Measurements are also provided for the
magnetic field produced by a thin current-carrying wire with small geometric
modulations along the edge. Comparisons of our measurements with a full numeric
calculation of the current flow in the wire and the subsequent magnetic field
show excellent agreement. Our results highlight the use of scanning MR
microscopy as a convenient and powerful technique for precisely characterizing
the magnetic fields produced near the surface of atom chips.

###Transient Charging and Discharging of Spin-polarized Electrons in a Quantum Dot|F. M. Souza,S. A. Leao,R. M. Gester,A. P. Jauho###

Transient Charging and Discharging of Spin-polarized Electrons in a Quantum Dot. We study spin-polarized transient transport in a quantum dot coupled to two
ferromagnetic leads subjected to a rectangular bias voltage pulse.
Time-dependent spin-resolved currents, occupations, spin accumulation, and
tunneling magnetoresistance (TMR) are calculated using both nonequilibrium
Green function and master equation techniques. Both parallel and antiparallel
leads' magnetization alignments are analyzed. Our main findings are: a
dynamical spin accumulation that changes sign in time, a short-lived pulse of
spin polarized current in the emitter lead (but not in the collector lead), and
a dynamical TMR that develops negative values in the transient regime. We also
observe that the intra-dot Coulomb interaction can enhance even further the
negative values of the TMR.

###Magnetotransport properties of strained (Ga0.95, Mn0.05)As epilayers close to the metal-insulator transition: Description using Aronov-Altshuler three-dimensional scaling theory|J. Honolka,S. Masmanidis,H. X. Tang,D. D. Awschalom,M. L. Roukes###

Magnetotransport properties of strained (Ga0.95, Mn0.05)As epilayers close to the metal-insulator transition: Description using Aronov-Altshuler three-dimensional scaling theory. The magnitude of the anisotropic magnetoresistance (AMR) and the longitudinal
resistance in compressively strained (Ga0.95, Mn0.05)As epilayers were measured
for the first time down to temperatures as low as 30 mK. Below temperatures of
3K the conductivity decreases ~ T^1/3 over two orders of magnitude in
temperature. The conductivity can be well described within the framework of a
3D scaling theory of Anderson's transition in the presence of spin scattering
in semiconductors. It is shown that the samples are on the metallic side but
very close to the metal-insulator transition (MIT). At lowest temperatures a
decrease in the AMR effect is observed, which is assigned to changes in the
coupling between the remaining itinerant carriers and the local Mn 5/2-spin
moments.

###Transport properties of microstructured ultrathin films of La0.67Ca0.33MnO3 on SrTiO3|C. Beekman,I. Komissarov,M. Hesselberth,J. Aarts###

Transport properties of microstructured ultrathin films of La0.67Ca0.33MnO3 on SrTiO3. We have investigated the electrical transport properties of 8 nm thick
La0.67Ca0.33MnO3 films, sputter-deposited on SrTiO3 (STO), and etched into 5
micrometer-wide bridges by Ar-ion etching. We find that even slight overetching
of the film leads to conductance of the STO substrate, and asymmetric and
non-linear current-voltage (I-V) characteristics. However, a brief oxygen
plasma etch allows full recovery of the insulating character of the substrate.
The I-V characteristics of the bridges are then fully linear over a large range
of current densities. We find colossal magnetoresistance properties typical for
strained LCMO on STO but no signature of non-linear effects (so-called
electroresistance) connected to electronic inhomogeneites. In the metallic
state below 150 K, the highest current densities lead to heating effects and
non-linear I-V characteristics.

###Effect of Mo doping for the Mn site in the ferromagnetic manganite La0.7Ca0.3MnO3|G. Narsinga Rao,J. W. Chen###

Effect of Mo doping for the Mn site in the ferromagnetic manganite La0.7Ca0.3MnO3. The structure, electronic, and magnetic properties of the Mo-doped perovskite
La0.7Ca0.3Mn1-xMoxO3 (x < 0.1) have been studied. A significant increase in
resistivity and lattice parameters were observed with Mo doping. A marginal
decrease in the Curie temperature Tc and the associated metal-insulator
transition Tp were observed. Magnetization data reveal that long-range
ferromagnetic ordering persists in all samples studied and the saturation
moment decreases linearly as x increases. Enhancement in magnetoresistance at
near Tc in the Mo-doped compounds with an optimum doping value x = 0.05 was
observed. The overall experimental results can be explained by considering the
induced Mn2+ ions with Mo6+ in the Mo-doped systems, with the strong FM
coupling between Mn4+/2+- O - Mn3+.

###Measurement of the Spin-Transfer-Torque Vector in Magnetic Tunnel Junctions|J. C. Sankey,Y. -T. Cui,R. A. Buhrman,D. C. Ralph,J. Z. Sun,J. C. Slonczewski###

Measurement of the Spin-Transfer-Torque Vector in Magnetic Tunnel Junctions. Spin-polarized currents can transfer spin angular momentum to a ferromagnet,
generating a torque that can efficiently reorient its magnetization. Achieving
quantitative measurements of the spin-transfer-torque vector in magnetic tunnel
junctions (MTJs) is important for understanding fundamental mechanisms
affecting spin-dependent tunneling, and for developing magnetic memories and
nanoscale microwave oscillators. Here we present direct measurements of both
the magnitude and direction of the spin torque in Co60Fe20B20/MgO/Co60Fe20B20
MTJs. At low bias V, the differential torque vector d{tau}/dV lies in the plane
defined by the electrode magnetizations, and its magnitude is in excellent
agreement with a prediction for highly-spin-polarized tunneling. With
increasing bias, the in-plane component d{tau}_{parallel}/dV remains large, in
striking contrast to the decreasing magnetoresistance ratio. The differential
torque vector also rotates out of the plane under bias; we measure a
perpendicular component tau_{perp}(V) with bias dependence proportional to V^2
for low V, that becomes as large as 30% of the in-plane torque.

###Anomalous magnetoresistance of EuB$_{5.99}$C$_{0.01}$: Enhancement of magnetoresistance in systems with magnetic polarons|M. Batkova,I. Batko,K. Flachbart,K. Jurek,E. S. Konovalova,J. Kovac,M. Reiffers,V. Sechovsky,N. Shitsevalova,E. Santava,J. Sebek###

Anomalous magnetoresistance of EuB$_{5.99}$C$_{0.01}$: Enhancement of magnetoresistance in systems with magnetic polarons. We present results of measurements of electrical, magnetic and thermal
properties of EuB$_{5.99}$C$_{0.01}$. The observed anomalously large negative
magnetoresistance as above, so below the Curie temperature of ferromagnetic
ordering $T_C$ is attributed to fluctuations in carbon concentration. Below
$T_C$ the carbon richer regions give rise to helimagnetic domains, which are
responsible for an additional scattering term in the resistivity, which can be
suppressed by a magnetic field. Above $T_C$ these regions prevent the process
of percolation of magnetic polarons (MPs), acting as "spacers" between MPs. We
propose that such "spacers", being in fact volumes incompatible with existence
of MPs, may be responsible for the decrease of the percolation temperature and
for the additional (magneto)resistivity increase in systems with MPs.

###Magnetic confinement of the superconducting condensate in superconductor/ferromagnet hybrid composites|W. Gillijns,A. Aladyshkin,A. V. Silhanek,V. V. Moshchalkov###

Magnetic confinement of the superconducting condensate in superconductor/ferromagnet hybrid composites. The influence of an inhomogeneous magnetic field on the magnetoresistance of
thin Al films, used in different superconductor/ferromagnet hybrids, has been
investigated. Two contrasting magnetic textures with out-of-plane magnetization
are explored, namely (i) a plain film in a multidomain state and (ii) an array
of micro-sized dots. The stray fields of the ferromagnetic structures confine
the superconducting condensate and, accordingly, modify the condition for the
nucleation of superconductivity. By switching between different magnetic states
of the ferromagnet, this confinement can be tuned at will, hereby reversibly
changing the dependence of the critical temperature Tc on an external magnetic
field H. In particular, the continuous evolution from a conventional linear
Tc(H) dependence with a single maximum to a reentrant superconducting phase
boundary with multiple Tc peaks has been demonstrated.

###Giant Anisotropy of Magnetoresistance and "Spin Valve" effect in Antiferromagnetic $Nd_{2-x}Ce_xCuO_{4}$|T. Wu,C. H. Wang,G. Wu,D. F. Fang,J. L. Luo,G T. Liu,X. H. Chen###

Giant Anisotropy of Magnetoresistance and "Spin Valve" effect in Antiferromagnetic $Nd_{2-x}Ce_xCuO_{4}$. We have studied anisotropic magnetoresistance (MR) and magnetization with
rotating magnetic field (B) within $CuO_2$ plane in lightly doped AF
$Nd_{2-x}Ce_xCuO_{4}$. \emph{A giant anisotropy} in MR is observed at low
temperature below 5 K. The c-axis resistivity can be tuned about one order of
magnitude just by changing B direction within $CuO_2$ plane and a scaling
behavior between out-of-plane and in-plane MR is found. A "Spin valve" effect
is proposed to understand the giant anisotropy of out-of-plane MR and the
evolution of scaling parameters with the external field. It is found that the
field-induced spin-flop transition of Nd$^{3+}$ layer under high magnetic field
is the key to understand the giant anisotropy. These results suggest that a
novel entanglement between charge and spin dominates the underlying physics.

###Transport properties of chemically synthesized polypyrrole thin films|C. C. Bof Bufon,T. Heinzel###

Transport properties of chemically synthesized polypyrrole thin films. The electronic transport in polypyrrole thin films synthesized chemically
from the vapor phase is studied as a function of temperature as well as of
electric and magnetic fields. We find distinct differences in comparison to the
behavior of both polypyrrole films prepared by electrochemical growth as well
as of the bulk films obtained from conventional chemical synthesis. For small
electric fields F, a transition from Efros-Shklovskii variable range hopping to
Arrhenius activated transport is observed at 30 K. High electric fields induce
short range hopping. The characteristic hopping distance is found to be
proportional to F^(-1/2). The magnetoresistance R(B) is independent of F below
a critical magnetic field, above which F counteracts the magnetic field induced
localization.

###Room temperature spin filtering in epitaxial cobalt-ferrite tunnel barriers|A. V. Ramos,M. -J. Guittet,J. -B. Moussy,R. Mattana,C. Deranlot,F. Petroff,C. Gatel###

Room temperature spin filtering in epitaxial cobalt-ferrite tunnel barriers. We report direct experimental evidence of room temperature spin filtering in
magnetic tunnel junctions (MTJs) containing CoFe2O4 tunnel barriers via
tunneling magnetoresistance (TMR) measurements.
Pt(111)/CoFe2O4(111)/gamma-Al2O3(111)/Co(0001) fully epitaxial MTJs were grown
in order to obtain a high quality system, capable of functioning at room
temperature. Spin polarized transport measurements reveal significant TMR
values of -18% at 2 K and -3% at 290 K. In addition, the TMR ratio follows a
unique bias voltage dependence that has been theoretically predicted to be the
signature of spin filtering in MTJs containing magnetic barriers. CoFe2O4
tunnel barriers therefore provide a model system to investigate spin filtering
in a wide range of temperatures.

###Spin transport in proximity induced ferromagnetic graphene|H. Haugen,Daniel Huertas-Hernando,Arne Brataas###

Spin transport in proximity induced ferromagnetic graphene. Magnetic gates in close proximity to graphene can induce ferromagnetic
correlations. We study the effect of such induced magnetization dependent
Zeeman splittings on the graphene transport properties. We estimate that
induced spin splittings of the order of \Delta ~ 5 meV could be achieved with
the use of magnetic insulator gates, e.g. EuO-gates, deposited on top of
graphene. We demonstrate that such splittings in proximity induced
ferromagnetic graphene could be determined directly from the tunneling
resonances in the linear response conductance, as the top gate creates also a
tunable barrier in the graphene layer. We show how such splittings could also
be determined independently by magnetoresistance measurements in a spin-valve
geometry. Because the spin polarization of the current near the Dirac point
increases with the length of the barrier, long magnetic gates are desirable for
determining \Delta experimentally.

###Photon-assisted spin transport in a two-dimensional electron gas|M. V. Fistul,K. B. Efetov###

Photon-assisted spin transport in a two-dimensional electron gas. We study spin-dependent transport in a two-dimensional electron gas subject
to an external step-like potential $V(x)$ and irradiated by an electromagnetic
field (EF). In the absence of EF the electronic spectrum splits into spin
sub-bands originating from the "Rashba" spin-orbit coupling. We show that the
resonant interaction of propagating electrons with the component EF parallel to
the barrier induces a \textit{% non-equilibrium dynamic gap} $(2\Delta_{R})$
between the spin sub-bands. Existence of this gap results in coherent spin-flip
processes that lead to a spin-polarized current and a large magnetoresistance,
i.e the spin valve effect. These effects may be used for controlling spin
transport in semiconducting nanostructures, e.g. spin transistors,
spin-blockade devices etc., by variation of the intensity S and frequency
$\omega $ of the external radiation.

###Normal State Nernst Effect in Electron-doped Pr2-xCexCuO4: Superconducting Fluctuations and Two-band Transport|Pengcheng Li,R. L. Greene###

Normal State Nernst Effect in Electron-doped Pr2-xCexCuO4: Superconducting Fluctuations and Two-band Transport. We report a systematic study of normal state Nernst effect in the
electron-doped cuprates Pr$_{2-x}$Ce$_x$CuO$_{4-\delta}$ over a wide range of
doping (0.05$\leq x \leq$0.21) and temperature. At low temperatures, we
observed a notable vortex Nernst signal above T$_c$ in the underdoped films,
but no such normal state vortex Nernst signal is found in the overdoped region.
The superconducting fluctuations in the underdoped region are most likely
incoherent phase fluctuations as found in hole-doped cuprates. At high
temperatures, a large normal state Nernst signal is found at dopings from
slightly underdoped to highly overdoped. Combined with normal state
thermoelectric power, Hall effect and magnetoresistance measurements, the large
Nernst effect is compatible with two-band model. For the highly overdoped
films, the large Nernst effect is anomalous and not explainable with a simple
hole-like Fermi surface seen in photoemission experiments.

###Angle dependent magnetoresistance measurements in Tl$_2$Ba$_2$CuO$_{6+δ}$ and the need for anisotropic scattering|J. G. Analytis,M. Abdel-Jawad,L. Balicas,M. M. J. French,N. E. Hussey###

Angle dependent magnetoresistance measurements in Tl$_2$Ba$_2$CuO$_{6+δ}$ and the need for anisotropic scattering. The angle-dependent interlayer magnetoresistance of overdoped
Tl$_2$Ba$_2$CuO$_{6+\delta}$ has been measured in high magnetic fields up to 45
Tesla. A conventional Boltzmann transport analysis with no basal-plane
anisotropy in the cyclotron frequency $\omega_c$ or transport lifetime $\tau$
is shown to be inadequate for explaining the data. We describe in detail how
the analysis can be modified to incorporate in-plane anisotropy in these two
key quantities and extract the degree of anisotropy for each by assuming a
simple four-fold symmetry. While anisotropy in $\omega_c$ and other Fermi
surface parameters may improve the fit, we demonstrate that the most important
anisotropy is that in the transport lifetime, thus confirming its role in the
physics of overdoped superconducting cuprates.

###Magnons in Ferromagnetic Metallic Manganites|Jiandi Zhang,F. Ye,Hao Sha,Pengcheng Dai,J. A. Fernandez-Baca,E. W. Plummer###

Magnons in Ferromagnetic Metallic Manganites. Ferromagnetic (FM) manganites, a group of likely half-metallic oxides, are of
special interest not only because they are a testing ground of the classical
doubleexchange interaction mechanism for the colossal magnetoresistance, but
also because they exhibit an extraordinary arena of emergent phenomena. These
emergent phenomena are related to the complexity associated with strong
interplay between charge, spin, orbital, and lattice. In this review, we focus
on the use of inelastic neutron scattering to study the spin dynamics, mainly
the magnon excitations in this class of FM metallic materials. In particular,
we discussed the unusual magnon softening and damping near the Brillouin zone
boundary in relatively narrow band compounds with strong Jahn-Teller lattice
distortion and charge/orbital correlations. The anomalous behaviors of magnons
in these compounds indicate the likelihood of cooperative excitations involving
spin, lattice, as well as orbital degrees of freedom.

###Transport properties and magnetic field induced localization in the misfit cobaltite [Bi$_2$Ba$_{1.3}$K$_{0.6}$Co$_{0.1}$]$^{RS}$[CoO$_2$]$_{1.97}$ single crystal|X. G. Luo,H. Chen,G. Y. Wang,G. Wu,T. Wu,L. Zhao,X. H. Chen###

Transport properties and magnetic field induced localization in the misfit cobaltite [Bi$_2$Ba$_{1.3}$K$_{0.6}$Co$_{0.1}$]$^{RS}$[CoO$_2$]$_{1.97}$ single crystal. Resistivity under magnetic field, thermopower and Hall coefficient are
systematically studied for
[Bi$_2$Ba$_{1.3}$K$_{0.6}$Co$_{0.1}$]$^{RS}$[CoO$_2$]$_{1.97}$ single crystal.
In-plane resistivity ($\rho_{ab}$(T)) shows metallic behavior down to 2 K with
a $T^2$ dependence below 30 K; while out-of-plane resistivity ($\rho_{c}(T)$)
shows metallic behavior at high temperature and a thermal activation
semiconducting behavior below about 12 K. Striking feature is that magnetic
field induces a ln(1/$T$) diverging behavior in both $\rho_{ab}$ and
$\rho_{c}(T)$ at low temperature. The positive magnetoresistance (MR) could be
well fitted by the formula based on multi-band electronic structure. The
ln(1/$T$) diverging behavior in $\rho_{ab}$ and $\rho_{c}(T)$ could arise from
the magnetic-field-induced 2D weak localization or spin density wave.

###Modulation of bilayer quantum Hall states by tilted-field-induced subband-Landau-level coupling|N. Kumada,K. Iwata,K. Tagashira,Y. Shimoda,K. Muraki,Y. Hirayama,A. Sawada###

Modulation of bilayer quantum Hall states by tilted-field-induced subband-Landau-level coupling. We study effects of tilted magnetic fields on energy levels in a
double-quantum-well (DQW) system, focusing on the coupling of subbands and
Landau levels (LLs). The subband-LL coupling induces anticrossings between LLs,
manifested directly in the magnetoresistance. The anticrossing gap becomes
larger than the spin splitting at the tilting angle $\theta \sim 20^\circ $ and
larger than the cyclotron energy at $\theta \sim 50^\circ $, demonstrating that
the subband-LL coupling exerts a strong influence on quantum Hall states even
in at a relatively small $\theta $ and plays a dominant role for larger $\theta
$. We also find that when the DQW potential is asymmetric, LL coupling occurs
even within a subband. Calculations including higher-order coupling reproduce
the experimental results quantitatively well.

###Modeling a Schottky-barrier carbon nanotube field-effect transistor with ferromagnetic contacts|S. Krompiewski###

Modeling a Schottky-barrier carbon nanotube field-effect transistor with ferromagnetic contacts. In this study, a model of a Schottky-barrier carbon nanotube field- effect
transistor (CNT-FET), with ferromagnetic contacts, has been developed. The
emphasis is put on analysis of current-voltage characteristics as well as shot
(and thermal) noise. The method is based on the tight-binding model and the
non- equilibrium Green's function technique. The calculations show that, at
room temperature, the shot noise of the CNT FET is Poissonian in the
sub-threshold region, whereas in elevated gate and drain/source voltage regions
the Fano factor gets strongly reduced. Moreover, transport properties strongly
depend on relative magnetization orientations in the source and drain contacts.
In particular, one observes quite a large tunnel magnetoresistance, whose
absolute value may exceed 50%.

###Pseudospin Soliton in the $ν=1$ Bilayer Quantum Hall State|A. Fukuda,D. Terasawa,M. Morino,K. Iwata,S. Kozumi,N. Kumada,Y. Hirayama,Z. F. Ezawa,A. Sawada###

Pseudospin Soliton in the $ν=1$ Bilayer Quantum Hall State. We investigate a domain structure of pseudospins, a soliton lattice in the
bilayer quantum Hall state at total Landau level filling factor $\nu =1$, in a
tilted magnetic field, where the pseudospin represents the layer degree of
freedom. An anomalous peak in the magnetoresistance $R_{xx}$ appears at the
transition point between the commensurate and incommensurate phases. The
$R_{xx}$ at the peak is highly anisotropic for the angle between the in-plain
magnetic field $B_\parallel $ and the current, and indicates a formation of the
soliton lattice aligned parallel to $B_\parallel $. Temperature dependence of
the $R_{xx}$ peak reveals that the dissipation is caused by thermal
fluctuations of pseudospin solitons. We construct a phase diagram of the
bilayer $\nu =1$ system as a function of $B_\parallel$ and the total electron
density. We also study effects of density imbalance between the two layers.

###Preparation and magnetoresistance of Ag 2+x Se thin films deposited via Pulsed Laser Deposition|B. Mogwitz,C. Korte,M. von Kreutzbruck,L. Kienle,J. Janek###

Preparation and magnetoresistance of Ag 2+x Se thin films deposited via Pulsed Laser Deposition. The preparation of Ag 2+x Se thin films with thicknesses between 4 nm and
3000 nm by pulsed laser deposition on single crystalline NaCl and MgO
substrates is reported. The films are perfectly dense and show a good lateral
uniformity with a small number of defects. The microstructure of the films
corresponds to a nanoparquet, being composed of two different phases of silver
selenide. One phase is identified as the Naumannite low temperature phase of
silver selenide, the structure of the other phase has not been reported in
detail before and probably represents a metastable phase. Silver-rich films
contain silver precipitates with typical sizes on the nanoscale. Their presence
and their size appears to be responsible for the large and linear
magnetoresistance effect of silver-rich silver selenide.

###Multicritical end-point of the first-order ferromagnetic transition in colossal magnetoresistive manganites|L. Demkó,I. Kézsmárki,G. Mihály,N. Takeshita,Y. Tomioka,Y. Tokura###

Multicritical end-point of the first-order ferromagnetic transition in colossal magnetoresistive manganites. We have studied the bandwidth-temperature-magnetic field phase diagram of
RE(0.55)Sr(0.45)MnO(3) colossal magnetoresistance manganites with ferromagnetic
metallic (FM) ground state. The bandwidth (or equivalently the double exchange
interaction) was controlled both via chemical substitution and hydrostatic
pressure with a focus on the vicinity of the critical pressure p* where the
character of the zero-field FM transition changes from first to second order.
Below p* the first-order FM transition extends up to a critical magnetic field,
H_cr. It is suppressed by pressure and approaches zero on the larger bandwidth
side where the surface of the first-order FM phase boundary is terminated by a
multicritical end-point (p*~32 kbar, T*~188 K, H*=0). The change in the
character of the transition and the decrease of the CMR effect is attributed to
the reduced CO/OO fluctuations.

###Magnetic structure and phase diagram of TmB4|S. Gabani,S. Matas,P. Priputen,K. Flachbart,K. Siemensmeyer,E. Wulf,A. Evdokimova,N. Shitsevalova###

Magnetic structure and phase diagram of TmB4. Magnetic structure of single crystalline TmB4 has been studied by
magnetization, magnetoresistivity and specific heat measurements. A complex
phase diagram with different antiferromagnetic (AF) phases was observed below
TN1 = 11.7 K. Besides the plateau at half-saturated magnetization (1/2 MS),
also plateaus at 1/9, 1/8 and 1/7 of MS were observed as function of applied
magnetic field B//c. From additional neutron scattering experiments on TmB4, we
suppose that those plateaus arise from a stripe structure which appears to be
coherent domain boundaries between AF ordered blocks of 7 or 9 lattice
constants. The received results suggest that the frustration among the Tm3+
magnetic ions, which maps to a geometrically frustrated Shastry-Sutherland
lattice lead to strong competition between AF and ferromagnetic (FM) order.
Thus, stripe structures in intermediate field appear to be the best way to
minimize the magnetostatic energy against other magnetic interactions between
the Tm ions combined with very strong Ising anisotropy.

###Shot noise and tunnel magnetoresistance in multilevel quantum dots: Effects of cotunneling|I. Weymann,J. Barnas###

Shot noise and tunnel magnetoresistance in multilevel quantum dots: Effects of cotunneling. Spin-dependent transport through a multilevel quantum dot weakly coupled to
ferromagnetic leads is analyzed theoretically by means of the real-time
diagrammatic technique. Both the sequential and cotunneling processes are taken
into account, which makes the results on tunnel magnetoresistance (TMR) and
shot noise applicable in the whole range of relevant bias and gate voltages.
Suppression of the TMR due to inelastic cotunneling and super-Poissonian shot
noise have been found in some of the Coulomb blockade regions. Furthermore, in
the Coulomb blockade regime there is an additional contribution to the noise
due to bunching of cotunneling processes involving the spin-majority electrons.
On the other hand, in the sequential tunneling regime TMR oscillates with the
bias voltage, while the current noise is generally sub-Poissonian.

###Crossover from Kondo assisted suppression to co-tunneling enhancement of tunneling magnetoresistance via ferromagnetic nanodots in MgO tunnel barriers|Hyunsoo Yang,See-Hun Yang,Stuart Parkin###

Crossover from Kondo assisted suppression to co-tunneling enhancement of tunneling magnetoresistance via ferromagnetic nanodots in MgO tunnel barriers. Recently, it has been shown that magnetic tunnel junctions with thin MgO
tunnel barriers exhibit extraordinarily high tunneling magnetoresistance (TMR)
values at room temperature1, 2. However, the physics of spin dependent
tunneling through MgO barriers is only beginning to be unravelled. Using planar
magnetic tunnel junctions in which ultra-thin layers of magnetic metals are
deposited in the middle of a MgO tunnel barrier here we demonstrate that the
TMR is strongly modified when these layers are discontinuous and composed of
small pancake shaped nanodots. At low temperatures, in the Coulomb blockade
regime, for layers less than ~1 nm thick, the conductance of the junction is
increased at low bias consistent with Kondo assisted tunneling. In the same
regime we observe a suppression of the TMR. For slightly thicker layers, and
correspondingly larger nanodots, the TMR is enhanced at low bias, consistent
with co-tunneling.

###The Origin and Control of the Sources of AMR in (Ga,Mn)As Devices|A. W. Rushforth,K. Výborný,C. S. King,K. W. Edmonds,R. P. Campion,C. T. Foxon,J. Wunderlich,A. C. Irvine,V. Novák,K. Olejník,A. A. Kovalev,Jairo Sinova,T. Jungwirth,B. L. Gallagher###

The Origin and Control of the Sources of AMR in (Ga,Mn)As Devices. We present details of our experimental and theoretical study of the
components of the anisotropic magnetoresistance (AMR) in (Ga,Mn)As. We develop
experimental methods to yield directly the non-crystalline and crystalline AMR
components which are then independently analyzed. These methods are used to
explore the unusual phenomenology of the AMR in ultra thin (5nm) (Ga,Mn)As
layers and to demonstrate how the components of the AMR can be engineered
through lithography induced local lattice relaxations. We expand on our
previous [Phys. Rev. Lett. \textbf{99}, 147207 (2007)] theoretical analysis and
numerical calculations to present a simplified analytical model for the origin
of the non-crystalline AMR. We find that the sign of the non-crystalline AMR is
determined by the form of spin-orbit coupling in the host band and by the
relative strengths of the non-magnetic and magnetic contributions to the
impurity potential.

###Quantum Oscillations of Tunnel Magnetoresistance Induced by Spin-Wave Excitations in Ferromagnet-Ferromagnet-Ferromagnet Double Barrier Tunnel Junctions|Xi Chen,Qing-Rong Zheng,Gang Su###

Quantum Oscillations of Tunnel Magnetoresistance Induced by Spin-Wave Excitations in Ferromagnet-Ferromagnet-Ferromagnet Double Barrier Tunnel Junctions. The possibility of quantum oscillations of the tunnel conductance and
magnetoresistance induced by spin-wave excitations in a
ferromagnet-ferromagnet-ferromagnet double barrier tunnel junction, when the
magnetizations of the two side ferromagnets are aligned antiparallel to that of
the middle ferromagnet, is investigated in a self-consistent manner by means of
Keldysh nonequilibrium Green function method. It has been found that owing to
the s-d exchange interactions between conduction electrons and the spin density
induced by spin accumulation in the middle ferromagnet, the differential
conductance and the TMR indeed oscillate with the increase of bias voltage,
being consistent with the phenomenon that is observed recently in experiments.
The effects of magnon modes, the energy levels of electrons as well as the
molecular field in the central ferromagnet on the oscillatory transport
property of the system are also discussed.

###Ferromagnet proximity effects and magnetoresistance of bilayer graphene|Y. G. Semenov,K. W. Kim,J. M. Zavada###

Ferromagnet proximity effects and magnetoresistance of bilayer graphene. A drastic modification of electronic band structure is predicted in bilayer
graphene when it is placed between two ferromagnetic insulators. Due to the
exchange interaction with the proximate ferromagnet, the electronic energy
dispersion in the graphene channel strongly depends on the magnetization
orientation of two ferromagnetic layers, $\mathbf{M_{1}}$ and $\mathbf{M_{2}}
$. While the parallel configuration $\mathbf{M_{1}}= \mathbf{M_{2}}$ leads to
simple spin splitting of both conduction and valence bands, an energy gap is
induced as soon as the angle $\theta$ between $\mathbf{M_{1}}$ and $%
\mathbf{M_{2}}$ becomes non-zero with the maximum achieved at $\theta=\pi$
(i.e., antiparallel alignment). Consequently, bilayer graphene may exhibit a
sizable magnetoresistive effect in the current-in-plane configuration. A rough
estimate suggests the resistance changes on the order of tens of percent at
room temperature. This effect is expected to become more pronounced as the
temperatures decreases.

###Magneto-transport and Magneto-dielectric effect in Bi-based Perovskite Manganites|Asish K. Kundu,R. Ranjith,V. Pralong,V. Caignaert,B. Raveau###

Magneto-transport and Magneto-dielectric effect in Bi-based Perovskite Manganites. The effect of cobalt and nickel substitutions for manganese on the physical
properties of the perovskite manganite La1.2Bi0.8Mn2-x(Ni/Co)xO6+d, with x =
0.0-0.8, has been investigated. It is observed that the ferromagnetism is
enhanced, TC being increased from 103 K for the parent compound (x = 0.0) to
178 K for Ni-phase, and to 181 K for the Co-phase (x = 0.8). Moreover, the
systems remain insulating and depict relatively large values of
magnetoresistance effect at low temperatures (up to 67 % at 90K and 70 kOe, for
x = 0.0 phase). These phenomena are interpreted by means of electronic phase
separation, where the ferromagnetic Mn4+/Ni2+ and Mn4+/Co2+ interactions
reinforce the Mn3+/Mn4+ interactions by super-exchange interaction. The
dielectric measurements below the magnetic transition temperatures exhibit weak
magneto-dielectric effect of around 0.25% at 80K, which may be due to
spin-lattice interaction.

###GaMnAs-based hybrid multiferroic memory device|M. Overby,A. Chernyshov,L. P. Rokhinson,X. Liu,J. K. Furdyna###

GaMnAs-based hybrid multiferroic memory device. A rapidly developing field of spintronics is based on the premise that
substituting charge with spin as a carrier of information can lead to new
devices with lower power consumption, non-volatility and high operational
speed. Despite efficient magnetization detection, magnetization manipulation is
primarily performed by current-generated local magnetic fields and is very
inefficient. Here we report a novel non-volatile hybrid multiferroic memory
cell with electrostatic control of magnetization based on strain-coupled GaMnAs
ferromagnetic semiconductor and a piezoelectric material. We use the
crystalline anisotropy of GaMnAs to store information in the orientation of the
magnetization along one of the two easy axes, which is monitored via transverse
anisotropic magnetoresistance. The magnetization orientation is switched by
applying voltage to the piezoelectric material and tuning magnetic anisotropy
of GaMnAs via the resulting stress field.

###Low temperature electron-phonon resonance in dc-current-biased two-dimensional electron systems|X. L. Lei###

Low temperature electron-phonon resonance in dc-current-biased two-dimensional electron systems. Effects of resonant acoustic phonon scattering on magnetoresistivity are
examined in two-dimensional electron systems at low temperatures by using a
balance-equation magnetotransport scheme direct controlled by the current. The
experimentally observed resonances in linear resistivity are shown to result
from the conventional bulk phonon modes in a GaAs-based system, without
invoking leaky interface phonons. Due to quick heating of electrons, phonon
resonances can be dramatically enhanced by a finite bias current. When the
electron drift velocity increases to the speed of sound, additional and
prominent phonon resonance peaks begin to emerge. As a result, remarkable
resistance oscillation and negative differential resistivity can appear in
nonlinear transport in a modest mobility sample at low temperatures, which is
in agreement with recent experiments.

###Large Magnetoresistance in a Manganite Spin-Tunnel-Junction Using LaMnO3 as Insulating Barrier|S. Yunoki,E. Dagotto,S. Costamagna,J. A. Riera###

Large Magnetoresistance in a Manganite Spin-Tunnel-Junction Using LaMnO3 as Insulating Barrier. A spin-tunnel-junction based on manganites, with La$_{1-x}$Sr$_x$MnO$_3$
(LSMO) as ferromagnetic metallic electrodes and the undoped parent compound
LaMnO$_3$ (LMO) as insulating barrier, is here theoretically discussed using
double exchange model Hamiltonians and numerical techniques. For an even number
of LMO layers, the ground state is shown to have anti-parallel LSMO magnetic
moments. This highly resistive, but fragile, state is easily destabilized by
small magnetic fields, which orient the LSMO moments in the direction of the
field. The magnetoresistance associated with this transition is very large,
according to Monte Carlo and Density Matrix Renormalization Group studies. The
influence of temperature, the case of an odd number of LMO layers, and the
differences between LMO and SrTiO$_3$ as barriers are also addressed. General
trends are discussed.

###Giant orbital moments are responsible for the anisotropic magnetoresistance of atomic contacts|Gabriel Autes,Cyrille Barreteau,Marie-Catherine Desjonquères,Daniel Spanjaard,Michel Viret###

Giant orbital moments are responsible for the anisotropic magnetoresistance of atomic contacts. We study here, both experimentally and theoretically, the anisotropy of
magnetoresistance in atomic contacts. Our measurements on iron break junctions
reveal an abrupt and hysteretic switch between two conductance levels when a
large applied field is continuously rotated. We show that this behaviour stems
from the coexistence of two metastable electronic states which result from the
anisotropy of electronic interactions responsible for the enhancement of
orbital magnetization. In both states giant orbital moments appear on the low
coordinated central atom in a realistic contact geometry. However they differ
by their orientation, parallel or perpendicular, with respect to the axis of
the contact. Our explanation is totally at variance with the usual model based
on the band structure of a monatomic linear chain, which we argue cannot be
applied to 3d ferromagnetic metals.

###Advanced resistivity model for arbitrary magnetization orientation applied to a series of compressive- to tensile-strained (Ga,Mn)As layers|W. Limmer,J. Daeubler,L. Dreher,M. Glunk,W. Schoch,S. Schwaiger,R. Sauer###

Advanced resistivity model for arbitrary magnetization orientation applied to a series of compressive- to tensile-strained (Ga,Mn)As layers. The longitudinal and transverse resistivities of differently strained
(Ga,Mn)As layers are theoretically and experimentally studied as a function of
the magnetization orientation. The strain in the series of (Ga,Mn)As layers is
gradually varied from compressive to tensile using (In,Ga)As templates with
different In concentrations. Analytical expressions for the resistivities are
derived from a series expansion of the resistivity tensor with respect to the
direction cosines of the magnetization. In order to quantitatively model the
experimental data, terms up to the fourth order have to be included. The
expressions derived are generally valid for any single-crystalline cubic and
tetragonal ferromagnet and apply to arbitrary surface orientations and current
directions. The model phenomenologically incorporates the longitudinal and
transverse anisotropic magnetoresistance as well as the anomalous Hall effect.
The resistivity parameters obtained from a comparison between experiment and
theory are found to systematically vary with the strain in the layer.

###Lithographically and electrically controlled strain effects on anisotropic magnetoresistance in (Ga,Mn)As|E. De Ranieri,A. W. Rushforth,K. Vyborny,U. Rana,E. Ahmed,R. P. Campion,C. T. Foxon,B. L. Gallagher,A. C. Irvine,J. Wunderlich,T. Jungwirth###

Lithographically and electrically controlled strain effects on anisotropic magnetoresistance in (Ga,Mn)As. It has been demonstrated that magnetocrystalline anisotropies in (Ga,Mn)As
are sensitive to lattice strains as small as 10^-4 and that strain can be
controlled by lattice parameter engineering during growth, through post growth
lithography, and electrically by bonding the (Ga,Mn)As sample to a
piezoelectric transducer. In this work we show that analogous effects are
observed in crystalline components of the anisotropic magnetoresistance (AMR).
Lithographically or electrically induced strain variations can produce
crystalline AMR components which are larger than the crystalline AMR and a
significant fraction of the total AMR of the unprocessed (Ga,Mn)As material. In
these experiments we also observe new higher order terms in the
phenomenological AMR expressions and find that strain variation effects can
play important role in the micromagnetic and magnetotransport characteristics
of (Ga,Mn)As lateral nanoconstrictions.

###Detailed transport investigation of the magnetic anisotropy of (Ga,Mn)As|K. Pappert,C. Gould,M. Sawicki,J. Wenisch,K. Brunner,G. Schmidt,L. W. Molenkamp###

Detailed transport investigation of the magnetic anisotropy of (Ga,Mn)As. This paper discusses transport methods for the investigation of the (Ga,Mn)As
magnetic anisotropy. Typical magnetoresistance behaviour for different
anisotropy types is discussed, focusing on an in depth discussion of the
anisotropy fingerprint technique and extending it to layers with primarily
uniaxial magnetic anisotropy. We find that in all (Ga,Mn)As films studied,
three anisotropy components are always present. The primary biaxial along
([100] and [010]) along with both uniaxial components along the [110] and [010]
crystal directions which are often reported separately. Various fingerprints of
typical (Ga,Mn)As transport samples at 4 K are included to illustrate the
variation of the relative strength of these anisotropy terms. We further
investigate the temperature dependence of the magnetic anisotropy and the
domain wall nucleation energy with the help of the fingerprint method.

###The Fermi surface and f-valence electron count of UPt3|G. J. McMullan,P. M. C. Rourke,M. R. Norman,A. D. Huxley,N. Doiron-Leyraud,J. Flouquet,G. G. Lonzarich,A. McCollam,S. R. Julian###

The Fermi surface and f-valence electron count of UPt3. Combining old and new de Haas-van Alphen (dHvA) and magnetoresistance data,
we arrive at a detailed picture of the Fermi surface of the heavy fermion
superconductor UPt3. Our work was partially motivated by a new proposal that
two 5f valence electrons per formula unit in UPt3 are localized by correlation
effects -- agreement with previous dHvA measurements of the Fermi surface was
invoked in its support. Comprehensive comparison with our new observations
shows that this 'partially localized' model fails to predict the existence of a
major sheet of the Fermi surface, and is therefore less compatible with
experiment than the originally proposed 'fully itinerant' model of the
electronic structure of UPt3. In support of this conclusion, we offer a more
complete analysis of the fully itinerant band structure calculation, where we
find a number of previously unrecognized extremal orbits on the Fermi surface.

###Quantum interference and weak localisation effects in the interlayer magnetoresistance of layered metals|Malcolm P. Kennett,Ross. H. McKenzie###

Quantum interference and weak localisation effects in the interlayer magnetoresistance of layered metals. Studies of angle-dependent magnetoresistance oscillations (AMRO) in the
interlayer conductivity of layered metals have generally considered
semi-classical electron transport. We consider a quantum correction to the
semi-classical conductivity that arises from what can be described as an
interlayer Cooperon. This depends on both the disorder potential within a layer
and the correlations of the disorder potential between layers. We compare our
results with existing experimental data on organic charge transfer salts that
are not explained within the standard semi-classical transport picture. In
particular, our results may be applicable to effects that have been seen when
the applied magnetic field is almost parallel to the conducting layers. We
predict the presence of a peak in the resistivity as the field direction
approaches the plane of the layers. The peak can occur even when there is
weakly incoherent transport between layers.

###Effects of dilution on magnetic and transport properties of La0.7Ca0.3Mn1-xM'xO3|D. N. H. Nam,H. S. Hong,N. V. Khien,N. V. Dai,T. D. Thanh,L. T. C. Tuong,L. V. Hong,N. X. Phuc###

Effects of dilution on magnetic and transport properties of La0.7Ca0.3Mn1-xM'xO3. Magnetic and transport properties of La0.7Ca0.3Mn1-xM'xO3 (M'=Al,Ti) are
studied. The dilution of the Mn lattice results in a weakening of the
ferromagnetism, a deterioration of the metallic conductivity, and a strong
enhancement of the magnetoresistance. Although Tc linearly decreases with x in
the low substitution ranges for both M' series, the scaling behavior Tc(np)
previously observed for La0.7Sr0.3Mn1-xM'xO3 [Phys. Rev. B 73, 184403 (2006)]
is no longer obtained. Extrapolations of the Tc(np) linear curves to Tc=0 give
np values much smaller than 1. These results suggest that, according to a
molecular-field approximation, antiferromagnetic superexchange between Mn ions
is significant in La0.7Ca0.3MnO3, in contrast to what observed in
La0.7Sr0.3MnO3. Additionally, structural data of the Al-substituted samples
suggest that variations of the eg-electron bandwidth W cannot explain the
decrease of Tc in magnetically diluted manganites.

###Single-band tight-binding parameters for Fe-MgO-Fe magnetic heterostructures|Tehseen Z. Raza,Hassan Raza###

Single-band tight-binding parameters for Fe-MgO-Fe magnetic heterostructures. We present a computationally efficient transferable single-band tight-binding
model (SBTB) for spin polarized transport in heterostructures with an effort to
capture the band structure effects. As an example, we apply it to study
transport through Fe-MgO-Fe(100) magnetic tunnel junction devices. We propose a
novel approach to extract suitable tight-binding parameters for a material by
using the energy resolved transmission as the benchmark, which inherently has
the bandstructure effects over the two dimensional transverse Brillouin zone.
The SBTB parameters for each of the four symmetry bands for bcc Fe(100) are
first proposed which are complemented with the transferable tight-binding
parameters for the MgO tunnel barrier for the Delta_1 and Delta_5 bands. The
non-equilibrium Green's function formalism is then used to calculate the
transport. Features like I-V characteristics, voltage dependence and the
barrier width dependence of the tunnel magnetoresistance ratio are captured
quantitatively and the trends match well with the ones observed by ab initio
methods.

###Enhancement of Jc by Hf -Doping in the Superconductor MgB2: A Hyperfine Interaction Study|A. Talapatra,S. K. Das,S. K. Bandyopadhyay,P. Barat,Pintu Sen,R. Rawat,A. Banerjee,T. Butz###

Enhancement of Jc by Hf -Doping in the Superconductor MgB2: A Hyperfine Interaction Study. Measurements of the critical current density (Jc) by magnetization and the
upper critical field (Hc2) by magnetoresistance have been performed for
hafnium-doped MgB2. There has been a remarkable enhancement of Jc as compared
to that by ion irradiation without any appreciable decrease in Tc, which is
beneficial from the point of view of applications. The irreversibility line
extracted from Jc shows an upward shift. In addition, there has been an
increase in the upper critical field which indicates that Hf partially
substitutes for Mg. Hyperfine interaction parameters obtained from time
differential perturbed angular correlation (TDPAC) measurements revealed the
formation of HfB and HfB2 phases along with the substitution of Hf. A possible
explanation is given for the role of these species in the enhancement of Jc in
MgB2 superconductor.

###Anisotropic superconductivity in graphite intercalation compound YbC6|N. F. Kawai,Hiroshi Fukuyama###

Anisotropic superconductivity in graphite intercalation compound YbC6. We report anisotropy of the upper critical field (Bc2) of an intercalated
graphite superconductor YbC6 (Tc = 6.5 K) determined from angular dependent
magnetoresistance measurements. Though the perpendicular coherence length is
much longer than interlayer spacing, measured angular dependences of Bc2 are
well fitted by the Lawrence-Doniach model or the Tinkham model, which are known
to be applicable to quasi two-dimensional materials or thin films, rather than
the effective mass model. This observation is similar to the measurements for
the other intercalated graphite superconductor, CaC6, by Jobiliong et al. [E.
Jobiliong, H.D. Zhou, J.A. Janik, Y.-J. Jo, L. Balicas, J.S. Brooks, C.R.
Wiebe, Phys. Rev. B 76 (2007) 31 052511]. A possible explanation for the
unexpected applicability of these models is that our YbC6 samples are
synthesized as thin flakes in the host graphite.

###Resonant electronic states and I-V curves of Fe/MgO/Fe(100) tunnel junctions|Ivan Rungger,Oleg N. Mryasov,Stefano Sanvito###

Resonant electronic states and I-V curves of Fe/MgO/Fe(100) tunnel junctions. The bias dependence of the tunnel magnetoresistance (TMR) of Fe/MgO/Fe tunnel
junctions is investigated theoretically with a fully self-consistent scheme
that combines the non-equilibrium Green's functions method with density
functional theory. At voltages smaller than 20 mVolt the I-V characteristics
and the TMR are dominated by resonant transport through narrow interface states
in the minority spin-band. In the parallel configuration this contribution is
quenched by a voltage comparable to the energy width of the interface state,
whereas it persists at all voltages in the anti-parallel configuration. At
higher bias the transport is mainly determined by the relative positions of the
$\Delta_1$ band-edges in the two Fe electrodes, which causes a decrease of the
TMR.

###Magnetic phase diagram in Eu$_{1-x}$La$_x$Fe$_2$As$_2$ single crystals|T. Wu,G. Wu,H. Chen,Y. L. Xie,R. H. Liu,X. F. Wang,X. H. Chen###

Magnetic phase diagram in Eu$_{1-x}$La$_x$Fe$_2$As$_2$ single crystals. We have systematically measured resistivity, susceptibility and specific heat
under different magnetic fields (H) in Eu$_{1-x}$La$_x$Fe$_2$As$_2$ single
crystals. It is found that a metamagnetic transition from A-type
antiferromagnetism to ferromagnetism occurs at a critical field for magnetic
sublattice of $Eu^{2+}$. The jump of specific heat is suppressed and shifts to
low temperature with increasing H up to the critical value, then shifts to high
temperature with further increasing H. Such behavior supports the metamagnetic
transition. Detailed H-T phase diagrams for x=0 and 0.15 crystals are given,
and possible magnetic structure is proposed. Magnetoresistance measurements
indicate that there exists a strong coupling between local moment of $Eu^{2+}$
and charge in Fe-As layer. These results are very significant to understand the
underlying physics of FeAs superconductors.

###Magnetic and charge transport properties of the Na-based Os oxide pyrochlore|Y. G. Shi,A. A. Belik,M. Tachibana,M. Tanaka,Y. Katsuya,K. Kobayashi,K. Yamaura,E. Takayama-Muromachi###

Magnetic and charge transport properties of the Na-based Os oxide pyrochlore. Na-based osmium oxide pyrochlore was synthesized for the first time by an
ion-exchange method. KOs2O6 was used as a host compound. Elelectron probe
micro-analysis, synchrotron x-ray diffraction analysis, and thermo-gravimetric
analysis confirmed its structure not as the beta-type but as the defect-type
pyrochlore. The composition was identified as Na1.4Os2O6.H2O. Electrical
resistivity, heat capacity, and magnetization measurements of the
polycrystalline Na1.4Os2O6.H2O clarified absence of superconductivity above 2
K, being in contrast to what were found for the beta-pyrochlore AOs2O6 (A = Cs,
Rb, K). Sommerfeld coefficient of 22 mJ K-2 mol-1 of Na1.4Os2O6.H2O was
smallest among those of AOs2O6. A magnetic anomaly at ~57 K and possible
associated magnetoresistance (+3.7 % at 2 K in 70 kOe) were found.

###Magnetotransport in the CeIrIn${_5}$ system: The influence of antiferromagnetic fluctuations|Sunil Nair,M. Nicklas,J. L. Sarrao,J. D. Thompson,F. Steglich,S. Wirth###

Magnetotransport in the CeIrIn${_5}$ system: The influence of antiferromagnetic fluctuations. We present an overview of magnetotransport measurements on the heavy-fermion
superconductor CeIrIn$_5$. Sensitive measurements of the Hall effect and
magnetoresistance (MR) are used to elucidate the low temperature phase diagram
of this system. The normal-state magnetotransport is highly anomalous, and
experimental signatures of a pseudogap-like precursor state to
superconductivity as well as evidence for two distinct scattering times
governing the Hall effect and the MR are observed. Our observations point out
the influence of antiferromagnetic fluctuations on the magnetotransport in this
class of materials. The implications of these findings, both in the context of
unconventional superconductivity in heavy-fermion systems as well as in
relation to the high temperature superconducting cuprates are discussed.

###Nonlinear theory of fractional microwave-induced magnetoresistance oscillations in a dc-driven two-dimensional electron system|X. L. Lei###

Nonlinear theory of fractional microwave-induced magnetoresistance oscillations in a dc-driven two-dimensional electron system. Microwave-induced nonlinear magnetoresistance in a dc-driven two-dimensional
electron system is examined using a multi-photon-assisted transport scheme
direct controlled by the current. It is shown that near the 2nd subharmonic of
the cyclotron resonance, the frequency of the resistivity oscillation with the
magnetic-field-normalized current-density is double that at the cyclotron
resonance and its harmonics, in excellent agreement with recent experimental
findings by Hatke {\it et al.} [Phys. Rev. Lett. {\bf 101}, 246811 (2008)]. The
current-induced alternative emergence of resonant two-photon and single-photon
processes is responsible for this frequency doubling. Near the third
subharmonic of the cyclotron resonance, the current-induced consecutive
appearance of resonant 0-/3-photon, two-photon, and single-photon processes may
lead to the frequency tripling of the resistivity oscillation.

###Bridging charge-orbital ordering and Fermi surface instabilities in half-doped single-layered manganite La_0.5Sr_1.5MnO_4|D. V. Evtushinsky,D. S. Inosov,G. Urbanik,V. B. Zabolotnyy,R. Schuster,P. Sass,T. Haenke,C. Hess,B. Buechner,R. Follath,P. Reutler,A. Revcolevschi,A. A. Kordyuk,S. V. Borisenko###

Bridging charge-orbital ordering and Fermi surface instabilities in half-doped single-layered manganite La_0.5Sr_1.5MnO_4. Density waves are inherent to the phase diagrams of materials that exhibit
unusual, and sometimes extraordinarily useful properties, such as
superconductivity and colossal magnetoresistance. While the pure charge density
waves (CDW) are well described by an itinerant approach, where electrons are
treated as waves propagating through the crystal, the charge-orbital ordering
(COO) is usually explained by a local approach, where the electrons are treated
as localized on the atomic sites. Here we show that in the half-doped manganite
La0.5Sr1.5MnO4 (LSMO) the electronic susceptibility, calculated from the
angle-resolved photoemission spectra (ARPES), exhibits a prominent
nesting-driven peak at one quarter of the Brillouin zone diagonal, that is
equal to the reciprocal lattice vector of the charge-orbital pattern. Our
results demonstrate that the Fermi surface geometry determines the propensity
of the system to form a COO state which, in turn, implies the applicability of
the itinerant approach also to the COO.

###Localized Spins on Graphene|P. S. Cornaglia,Gonzalo Usaj,C. A. Balseiro###

Localized Spins on Graphene. The problem of a magnetic impurity, atomic or molecular, absorbed on top of a
carbon atom in otherwise clean graphene is studied using the numerical
renormalization group. The spectral, thermodynamic, and scattering properties
of the impurity are described in detail. In the presence of a small magnetic
field, the low energy electronic features of graphene make possible to inject
spin polarized currents through the impurity using a scanning tunneling
microscope (STM). Furthermore, the impurity scattering becomes strongly spin
dependent and for a finite impurity concentration it leads to spin polarized
bulk currents and a large magnetoresistance. In gated graphene the impurity
spin is Kondo screened at low temperatures. However, at temperatures larger
than the Kondo temperature, the anomalous magnetotransport properties are
recovered.

###Hyperactivated resistance in TiN films on the insulating side of the disorder-driven superconductor-insulator transition|T. I. Baturina,A. Yu. Mironov,V. M. Vinokur,M. R. Baklanov,C. Strunk###

Hyperactivated resistance in TiN films on the insulating side of the disorder-driven superconductor-insulator transition. We investigate the insulating phase that forms in a titanium nitride film in
a close vicinity of the disorder-driven superconductor-insulator transition. In
zero magnetic field the temperature dependence of the resistance reveals a
sequence of distinct regimes upon decreasing temperature crossing over from
logarithmic to activated behavior with the variable-range hopping squeezing in
between. In perpendicular magnetic fields below 2 T, the thermally activated
regime retains at intermediate temperatures, whereas at ultralow temperatures,
the resistance increases faster than that of the thermally activated type. This
indicates a change of the mechanism of the conductivity. We find that at higher
magnetic fields the thermally activated behavior disappears and the
magnetoresistive isotherms saturate towards the value close to quantum
resistance h/e^2.

###Systematic characterization of upper critical fields for MgB$_2$ thin films using the two-band superconducting theory|S. Noguchi,A. Kuribayashi,T. Ishida,T. Oba,H. Iriuda,M. Yoshizawa,Y. Harada,S. Miki,H. Shimakage,Z. Wang,K. Satoh,T. Yotsuya###

Systematic characterization of upper critical fields for MgB$_2$ thin films using the two-band superconducting theory. We present experimental results of the upper critical fields $H_{\rm c2}$ of
various MgB$_2$ thin films prepared by the molecular beam epitaxy,
multiple-targets sputtering, and co-evaporation deposition apparatus.
Experimental data of the $H_{\rm c2}(T)$ are successfully analyzed by applying
the Gurevich theory of dirty two-band superconductivity in the case of
$D_{\pi}/D_{\sigma}>1$, where $D_{\pi}$ and $D_{\sigma}$ are the intraband
electron diffusivities for $\pi$ and $\sigma$ bands, respectively. We find that
the parameters obtained from the analysis are strongly correlated to the
superconducting transition temperature $T_{\rm c}$ of the films. We also
discuss the anormalous narrowing of the transition width at intermediate
temperatures confirmed by the magnetoresistance measurements.

###The Observation of Percolation-Induced 2D Metal-Insulator Transition in a Si MOSFET|L. A. Tracy,E. H. Hwang,K. Eng,G. A. Ten Eyck,E. P. Nordberg,K. Childs,M. S. Carroll,M. P. Lilly,S. Das Sarma###

The Observation of Percolation-Induced 2D Metal-Insulator Transition in a Si MOSFET. By analyzing the temperature ($T$) and density ($n$) dependence of the
measured conductivity ($\sigma$) of 2D electrons in the low density
($\sim10^{11}$cm$^{-2}$) and temperature (0.02 - 10 K) regime of high-mobility
(1.0 and 1.5 $\times 10^4$ cm$^2$/Vs) Si MOSFETs, we establish that the
putative 2D metal-insulator transition is a density-inhomogeneity driven
percolation transition where the density-dependent conductivity vanishes as
$\sigma (n) \propto (n - n_p)^p$, with the exponent $p \sim 1.2$ being
consistent with a percolation transition. The `metallic' behavior of $\sigma
(T)$ for $n > n_p$ is shown to be well-described by a semi-classical Boltzmann
theory, and we observe the standard weak localization-induced negative
magnetoresistance behavior, as expected in a normal Fermi liquid, in the
metallic phase.

###Structural relaxation effects on interface and transport properties of Fe/MgO(001) tunnel junctions|Xiaobing Feng,O. Bengone,M. Alouani,S. Lebégue,I. Rungger,S. Sanvito###

Structural relaxation effects on interface and transport properties of Fe/MgO(001) tunnel junctions. The interface structure of Fe/MgO(100) magnetic tunnel junctions predicted by
density functional theory (DFT) depends significantly on the choice of exchange
and correlation functional. Bader analysis reveals that structures obtained by
relaxing the cell with the local spin-density approximation (LSDA) display a
different charge transfer than those relaxed with the generalized gradient
approximation (GGA). As a consequence, the electronic transport is found to be
extremely sensitive to the interface structure. In particular, the conductance
for the LSDA-relaxed geometry is about one order of magnitude smaller than that
of the GGA-relaxed one. The high sensitivity of the electronic current to the
details of the interface might explain the discrepancy between the experimental
and calculated values of magnetoresistance.

###Anomalous Hall voltage rectification and quantized spin-wave excitation induced by the simultaneous dc- and rf-current application in Ni81Fe19 wire|A. Yamaguchi,K. Motoi,A. Hirohata,H. Miyajima###

Anomalous Hall voltage rectification and quantized spin-wave excitation induced by the simultaneous dc- and rf-current application in Ni81Fe19 wire. An anomalous Hall effect and rectification of a Hall voltage are observed by
applying a radio-frequency (rf) current through a single-layered ferromagnetic
wire located on a coplanar waveguide. The components of the magnetization
precession, both in and perpendicular to the plane, can be detected via the
Hall voltage rectification of the rf current by incorporating an additional
direct (dc) current. In this paper, we propose a phenomenological model, which
describes the time-dependent anisotropic magnetoresistance and time-dependent
planer Hall effect. The nonlinearity of the spin dynamics accompanied by
spin-waves as functions of rf and dc currents is also studied, as well as those
of the magnitude and orientation of the external magnetic field.

###Current-perpendicular-to-plane giant magnetoresistance of a spin valve using Co2MnSi Heusler alloy electrodes|K. Kodama,T. Furubayashi,H. Sukegawa,T. M. Nakatani,K. Inomata,K. Hono###

Current-perpendicular-to-plane giant magnetoresistance of a spin valve using Co2MnSi Heusler alloy electrodes. We report the current-perpendicular-to-plane giant magnetoresistance of a
spin valve with Co2MnSi (CMS) Heusler alloy ferromagnetic electrodes. A
multilayer stack of Cr/Ag/Cr/CMS/Cu/CMS/Fe25Co75/Ir28Mn72/Ru was deposited on a
MgO (001) single crystal substrate. The bottom CMS layer was epitaxially grown
on the Cr/Ag/Cr buffer layers and was ordered to the L21 structure after
annealing at 673 K. The upper CMS layer was found to grow epitaxially on the Cu
spacer layer despite the large lattice mismatch between Cu and CMS. The highest
MR ratios of 8.6% and 30.7% for CPP-GMR were recorded at room temperature and 6
K, respectively. The high spin polarization of the epitaxial CMS layers is the
most likely origin of the high MR ratio.

###Temperature Dependence of Interlayer Magnetoresistance in Anisotropic Layered Metals|Braden A. W. Brinkman,Malcolm P. Kennett###

Temperature Dependence of Interlayer Magnetoresistance in Anisotropic Layered Metals. Studies of interlayer transport in layered metals have generally made use of
zero temperature conductivity expressions to analyze angle-dependent
magnetoresistance oscillations (AMRO). However, recent high temperature AMRO
experiments have been performed in a regime where the inclusion of finite
temperature effects may be required for a quantitative description of the
resistivity. We calculate the interlayer conductivity in a layered metal with
anisotropic Fermi surface properties allowing for finite temperature effects.
We find that resistance maxima are modified by thermal effects much more
strongly than resistance minima. We also use our expressions to calculate the
interlayer resistivity appropriate to recent AMRO experiments in an overdoped
cuprate which led to the conclusion that there is an anisotropic, linear in
temperature contribution to the scattering rate and find that this conclusion
is robust.

###Tunnelling magnetoresistance anomalies of a Coulomb blockaded quantum dot|Piotr Stefanski###

Tunnelling magnetoresistance anomalies of a Coulomb blockaded quantum dot. We consider quantum transport and tunneling magnetoresistance (TMR) through
an interacting quantum dot in the Coulomb blockade regime, attached to
ferromagnetic leads. We show that there exist two kinds of anomalies of TMR,
which have different origin. One type, associated with TMR sign change and
appearing at conductance resonances, is of single particle origin. The second
type, inducing a pronounced increase of TMR value far beyond 100%, is caused by
electron correlations. It is manifested in-between Coulomb blockade conductance
peaks. Both types of anomalies are discussed for zero and finite bias and their
robustness to the temperature increase is also demonstrated. The results are
presented in the context of recent experiments on semiconductor quantum dots in
which similar features of TMR have been observed.

###Investigating superconductor-insulator transition in thin films using drag resistance:Theoretical analysis of a proposed experiment|Yue Zou,Gil Refael,Jongsoo Yoon###

Investigating superconductor-insulator transition in thin films using drag resistance:Theoretical analysis of a proposed experiment. The magnetically driven superconductor-insulator transition in amorphous thin
films (e.g., InO, Ta) exhibits several mysterious phenomena, such as a putative
metallic phase and a huge magnetoresistance peak. Unfortunately, several
conflicting categories of theories, particularly quantum-vortex condensation,
and normal region percolation, explain key observations equally well. We
propose a new experimental setup, an amorphous thin-film bilayer, where a drag
resistance measurement would clarify the role quantum vortices play in the
transition, and hence decisively point to the correct picture. We provide a
thorough analysis of the device, which shows that the vortex paradigm gives
rise to a drag with an opposite sign and orders of magnitude larger than the
drag measured if competing paradigms apply.

###Magnetic tunnel junctions with ferroelectric barriers: Prediction of four resistance states from first-principles|Julian P. Velev,Chun-Gang Duan,J. D. Burton,Alexander Smogunov,Manish K. Niranjan,Erio Tosatti,S. S. Jaswal,Evgeny Y. Tsymbal###

Magnetic tunnel junctions with ferroelectric barriers: Prediction of four resistance states from first-principles. Magnetic tunnel junctions (MTJs), composed of two ferromagnetic electrodes
separated by a thin insulating barrier layer, are currently used in spintronic
devices, such as magnetic sensors and magnetic random access memories.
Recently, driven by demonstrations of ferroelectricity at the nanoscale,
thin-film ferroelectric barriers were proposed to extend the functionality of
MTJs. Due to the sensitivity of conductance to the magnetization alignment of
the electrodes (tunnelling magnetoresistance) and the polarization orientation
in the ferroelectric barrier (tunnelling electroresistance), these multiferroic
tunnel junctions (MFTJs) may serve as four-state resistance devices. Based on
first-principles calculations we demonstrate four resistance states in
SrRuO3/BaTiO3/SrRuO3 MFTJs with asymmetric interfaces. We find that the
resistance of such a MFTJ is significantly changed when the electric
polarization of the barrier is reversed and/or when the magnetizations of the
electrodes are switched from parallel to antiparallel. These results reveal the
exciting prospects of MFTJs for application as multifunctional spintronic
devices.

###Re-examination of half-metallic ferromagnetism for doped LaMnO3 in quasiparticle self-consistent $GW$ method|Takao Kotani,Hiori Kino###

Re-examination of half-metallic ferromagnetism for doped LaMnO3 in quasiparticle self-consistent $GW$ method. We apply the quasiparicle self-consistent $GW$ (\qsgw) method to a cubic
virtual-crystal alloy La$_{1-x}$Ba$_x$MnO$_3$ %(LBMO) as a theoretical
representative for colossal magnetoresistive perovskite manganites. The \qsgw\
predicts it as a fully-polarized half-metallic ferromagnet for a wide range of
$x$ and lattice constant. Calculated density of states and dielectric functions
are consistent with experiments. In contrast, the energies of calculated spin
wave are very low in comparison with experiments. This is affected neither by
rhombohedral deformation nor the intrinsic deficiency in the \qsgw method. Thus
we ends up with a conjecture that phonons related to the Jahn-Teller distortion
should hybridize with spin waves more strongly than people thought until now.

###Weak Localization and Transport Gap in Graphene Antidot Lattices|J. Eroms,D. Weiss###

Weak Localization and Transport Gap in Graphene Antidot Lattices. We fabricated and measured antidot lattices in single layer graphene with
lattice periods down to 90 nm. In large-period lattices, a well-defined quantum
Hall effect is observed. Going to smaller antidot spacings the quantum Hall
effect gradually disappears, following a geometric size effect. Lattices with
narrow constrictions between the antidots behave as networks of nanoribbons,
showing a high-resistance state and a transport gap of a few mV around the
Dirac point. We observe pronounced weak localization in the magnetoresistance,
indicating strong intervalley scattering at the antidot edges. The area of
phase-coherent paths is bounded by the unit cell size at low temperatures, so
each unit cell of the lattice acts as a ballistic cavity.

###Spin-Orbit Scattering and Quantum Metallicity in Ultra-Thin Be Films|Y. M. Xiong,A. B. Karki,D. P. Young,P. W. Adams###

Spin-Orbit Scattering and Quantum Metallicity in Ultra-Thin Be Films. We compare and contrast the low temperature magnetotransport properties of
ultra-thin, insulating, Be films with and without spin-orbit scattering (SOS).
Beryllium films have very little intrinsic SOS, but by "dusting" them with
sub-monolayer coverages of Au, one can introduce a well controlled SOS rate.
Pure Be films with sheet resistance R >R_Q exhibit a low-temperature negative
magnetoresistance (MR) that saturates to the quantum resistance R_Q = h/e^2.
This high-field quantum metal phase is believed to represent a new ground state
of the system. In contrast, the corresponding negative MR in Be/Au films is
greatly diminished, suggesting that, in the presence of strong SOS, the quantum
metal phase can only be reached at field scales well beyond those typically
available in a low temperature laboratory.

###Magnetotransport through graphene spin valves|Kai-He Ding,Zhen-Gang Zhu,Jamal Berakdar###

Magnetotransport through graphene spin valves. We present a theoretical study on the spin-dependent transport through a spin
valve consisting of graphene sandwiched between two magnetic leads with an
arbitrary orientation of the lead magnetization. No gate voltage is applied.
Using Keldysh's nonequilibrium Green's function method we show that, in absence
of external magnetic fields, the current-voltage curves are nonlinear. Around
zero bias the differential conductance versus bias voltage possesses a strong
dip. The zero-bias anomaly in the tunnel magnetoresistance (TMR) is affected
strongly by the leads spin polarization. Depending on the value of the bias
voltage TMR exhibits a behavior ranging from an insulating to a metallic-type.
In presence of a static external magnetic field the differential conductance
and TMR as a function of the bias voltage and the strength of the magnetic
field show periodic oscillations due to Landau-level crossings. We also inspect
the effects of the temperature and the polarization degrees on the differential
conductance and TMR.

###Nonvolatile SRAM architecture using MOSFET-based spin-transistors|Yusuke Shuto,Shuu'ichirou Yamamoto,Satoshi Sugahara###

Nonvolatile SRAM architecture using MOSFET-based spin-transistors. The authors proposed and computationally analyzed nonvolatile static random
access memory (NV-SRAM) architecture using metal-oxide-semiconductor
field-effect transistor (MOSFET) type of spin-transistors referred to as
pseudo-spin-MOSFET (PS-MOSFET). PS-MOSFET is a new circuit approach to
reproduce the functions of spin-transistors, based on recently progressed
magnetoresistive random access memory (MRAM) technology. The proposed NV-SRAM
cell can be simply configured by connecting two PS-MOSFETs to the storage nodes
of a standard SRAM cell. The logic information of the storage nodes can be
electrically stored into the magnetic tunnel junctions (MTJs) of the PS-MOSFETs
by current-induced magnetization switching (CIMS), and the stored information
is automatically restored when the inverter loop circuit wakes up. In addition,
the proposed NV-SRAM cell has no influence on the performance of normal SRAM
operations. Low power dissipation and high degree of freedom of MTJ design are
also remarkable features for NV-SRAM using PS-MOSFETs.

###Enhancement of positive magnetoresistance following a magnetic-field-induced ferromagnetic transition in an intermetallic compound, Tb5Si3|S. Narayana Jammalamadaka,Niharika Mohapatra,Sitikantha D Das,E. V. Sampathkumaran###

Enhancement of positive magnetoresistance following a magnetic-field-induced ferromagnetic transition in an intermetallic compound, Tb5Si3. We report the existence of a field-induced ferromagnetic transition in the
magnetically ordered state (<69 K) of an intermetallic compound, Tb5Si3, and
this transition is distinctly first-order at 1.8 K (near 60 kOe), whereas it
appears to become second order near 20 K. The finding we stress is that the
electrical resistivity becomes suddenly large in the high-field state after
this transition and this is observed in the entire temperature range in the
magnetically ordered state. Such an enhancement of 'positive' magnetoresistance
(below 100 kOe) at the metamagnetic transition field is unexpected on the basis
that the application of magnetic field should favor a low-resistive state due
to alignment of spins.

###Critical properties of superconducting Ba1-xKxFe2As2|A. Bharathi,Shilpam Sharma,R. Paulraj,A. T. Satya,Y. Hariharan,C. S. Sundar###

Critical properties of superconducting Ba1-xKxFe2As2. Magnetisation and magnetoresistance measurements have been carried out on
superconducting Ba1-xKxFe2As2 samples with x=0.40 and 0.50. From low field
magnetization data carried out at different temperatures below TC, HC1 has been
extracted. The plot of HC1 versus temperature shows an anomalous increase at
low temperatures. From high field magnetization hysterisis measurements carried
out in fields up to 16 T at 4.2 K and 20 K, the critical current density has
been evaluated using the Bean critical state model. The JC determined from the
high field data is >104A/cm2 at 4.2 K and 5 T. The superconducting transitions
were also measured resistively in increasing applied magnetic fields up to 12
Tesla. From the variation of the TC onset with applied field, dHC2/dT at TC was
obtained to be -7.708 T/K and -5.57 T/K in the samples with x=0.40 and 0.50.

###Unusual Magnetic, Thermal, and Transport Behaviors of Single Crystal EuRh2As2|Yogesh Singh,Y. Lee,B. N. Harmon,D. C. Johnston###

Unusual Magnetic, Thermal, and Transport Behaviors of Single Crystal EuRh2As2. An antiferromagnetic transition is observed in single crystal EuRh2As2 at a
high temperature T_N = 47 K compared to the ferromagnetic Weiss temperature
theta = 12 K. We show that this is, surprisingly, consistent with mean field
theory. A first-order field-induced magnetic transition is observed at T < T_N
with an unusual temperature dependence of the transition field. A dramatic
magnetic field-induced reduction of the electronic specific heat coefficient at
1.8-5.0 K by 38% at 9 T is observed. In addition, a strong positive
magnetoresistance and a large change in the Hall coefficient occur below 25 K.
Band structure calculations indicate that the Fermi energy lies on a steep edge
of a narrow peak in the density of states.

###Correlations between the morphology and the electronic structure at the surface of thin film manganites, investigated with STM|S. Kelly,F. Galli,I. Komissarov,J. Aarts###

Correlations between the morphology and the electronic structure at the surface of thin film manganites, investigated with STM. Thin-film colossal magnetoresistance manganites such as
La$_{0.67}$Ca$_{0.33}$MnO$_{3}$ (LCMO) have now been intensely studied for more
than a decade, but the issue of possible nanoscale electronic phase separation
is not fully solved. Scanning Tunneling Microscopy / Spectroscopy (STS) has
been pivotal in studying phase separation, but is hindered by being surface-
rather than bulk-sensitive. For our sputtered LCMO films the data indicates a
strong correlation between surface morphology and signatures of phase
separation; rough films show phase separation while atomically flat films are
electronically homogeneous but have a more or less inactive surface layer.
Regardless of surface morphology, the film bulk is electronically and
magnetically active. Many of the reported conclusions about electronic
inhomogeneities measured by STS have been confused by this issue. We study both
strained and unstrained films and find no correlation between substrate-induced
strain and either electronic phase separation or dead layers.

###Magnetic-field-induced reentrance of Fermi-liquid behavior and spin-lattice relaxation rates in YbCu_{5-x}Au_x|V. R. Shaginyan,A. Z. Msezane,K. G. Popov,V. A. Stephanovich###

Magnetic-field-induced reentrance of Fermi-liquid behavior and spin-lattice relaxation rates in YbCu_{5-x}Au_x. A strong departure from Landau-Fermi liquid (LFL) behavior have been recently
revealed in observed anomalies in both the magnetic susceptibility $\chi$ and
the muon and $\rm ^{63}Cu$ nuclear spin-lattice relaxation rates $1/T_1$ of
${\rm {YbCu_{5-x}Au_x}}$ ($x=0.6$). We show that the above anomalies along with
magnetic-field-induced reentrance of LFL properties are indeed determined by
the scaling behavior of the quasiparticle effective mass. We obtain the scaling
behavior theoretically utilizing our approach based on fermion condensation
quantum phase transition (FCQPT) notion. Our theoretical analysis of
experimental data on the base of FCQPT approach permits not only to explain
above two experimental facts in a unified manner, but to clarify the physical
reasons for a scaling behavior of the longitudinal magnetoresistance in $\rm
YbRh_2Si_2$.

###Energy scales and magnetoresistance at a quantum critical point|V. R. Shaginyan,M. Ya. Amusia,A. Z. Msezane,K. G. Popov,V. A. Stephanovich###

Energy scales and magnetoresistance at a quantum critical point. The magnetoresistance (MR) of CeCoIn_5 is notably different from that in many
conventional metals. We show that a pronounced crossover from negative to
positive MR at elevated temperatures and fixed magnetic fields is determined by
the scaling behavior of quasiparticle effective mass. At a quantum critical
point (QCP) this dependence generates kinks (crossover points from fast to slow
growth) in thermodynamic characteristics (like specific heat, magnetization
etc) at some temperatures when a strongly correlated electron system transits
from the magnetic field induced Landau Fermi liquid (LFL) regime to the
non-Fermi liquid (NFL) one taking place at rising temperatures. We show that
the above kink-like peculiarity separates two distinct energy scales in QCP
vicinity - low temperature LFL scale and high temperature one related to NFL
regime. Our comprehensive theoretical analysis of experimental data permits to
reveal for the first time new MR and kinks scaling behavior as well as to
identify the physical reasons for above energy scales.

###Spin currents and magnetoresistance of graphene-based magnetic junctions|Alireza Saffarzadeh,Mahdi Ghorbani Asl###

Spin currents and magnetoresistance of graphene-based magnetic junctions. Using the tight-binding approximation and the nonequilibrium Green's function
approach, we investigate the coherent spin-dependent transport in planar
magnetic junctions consisting of two ferromagnetic (FM) electrodes separated by
a graphene flake (GF) with zigzag or armchair interfaces. It is found that the
electron conduction strongly depends on the geometry of contact between the GF
and the FM electrodes. In the case of zigzag interfaces, the junction
demonstrates a spin-valve effect with high magnetoresistance (MR) ratios and
shows negative differential resistance features for a single spin channel at
positive gate voltage. In the case of armchair interfaces, the current-voltage
characteristics behave linearly at low bias voltages and hence, both spin
channels are in on state with low MR ratios.

###Metal-insulator transition in vanadium dioxide nanobeams: probing sub-domain properties of strongly correlated materials|Jiang Wei,Zenghui Wang,Wei Chen,David H. Cobden###

Metal-insulator transition in vanadium dioxide nanobeams: probing sub-domain properties of strongly correlated materials. Many strongly correlated electronic materials, including high-temperature
superconductors, colossal magnetoresistance and metal-insulator-transition
(MIT) materials, are inhomogeneous on a microscopic scale as a result of domain
structure or compositional variations. An important potential advantage of
nanoscale samples is that they exhibit the homogeneous properties, which can
differ greatly from those of the bulk. We demonstrate this principle using
vanadium dioxide, which has domain structure associated with its dramatic MIT
at 68 degrees C. Our studies of single-domain vanadium dioxide nanobeams reveal
new aspects of this famous MIT, including supercooling of the metallic phase by
50 degrees C; an activation energy in the insulating phase consistent with the
optical gap; and a connection between the transition and the equilibrium
carrier density in the insulating phase. Our devices also provide a
nanomechanical method of determining the transition temperature, enable
measurements on individual metal-insulator interphase walls, and allow general
investigations of a phase transition in quasi-one-dimensional geometry.

###Angular dependence of the tunneling anisotropic magnetoresistance|A. Matos-Abiague,M. Gmitra,J. Fabian###

Angular dependence of the tunneling anisotropic magnetoresistance. Based on general symmetry considerations we investigate how the dependence of
the tunneling anisotropic magnetoresistance (TAMR) on the magnetization
direction is determined by the specific form of the spin-orbit coupling field.
By extending a phenomenological model, previously proposed for explaining the
main trends of the TAMR in (001) ferromagnet/semiconductor/normal-metal
magnetic tunnel junctions (MTJs) [J. Moser {\it et al.}, Phys. Rev. Lett. 99,
056601 (2007)], we provide a unified qualitative description of the TAMR in
MTJs with different growth directions. In particular, we predict the forms of
the angular dependence of the TAMR in (001),(110), and (111) MTJs with
structure inversion asymmetry and/or bulk inversion asymmetry. The effects of
in-plane uniaxial strain on the TAMR are also investigated.

###Effect of resistance feedback on spin torque-induced switching of nanomagnets|Samir Garzon,Richard A. Webb,Mark Covington,Shehzaad Kaka,Thomas M. Crawford###

Effect of resistance feedback on spin torque-induced switching of nanomagnets. In large magnetoresistance devices spin torque-induced changes in resistance
can produce GHz current and voltage oscillations which can affect magnetization
reversal. In addition, capacitive shunting in large resistance devices can
further reduce the current, adversely affecting spin torque switching. Here, we
simultaneously solve the Landau-Lifshitz-Gilbert equation with spin torque and
the transmission line telegrapher's equations to study the effects of
resistance feedback and capacitance on magnetization reversal of both spin
valves and magnetic tunnel junctions. While for spin valves parallel (P) to
anti-parallel (AP) switching is adversely affected by the resistance feedback
due to saturation of the spin torque, in low resistance magnetic tunnel
junctions P-AP switching is enhanced. We study the effect of resistance
feedback on the switching time of MTJ's, and show that magnetization switching
is only affected by capacitive shunting in the pF range.

###Role of Oxygen Electrons in the Metal-Insulator Transition in the Magnetoresistive Oxide La$_{2-2x}$Sr$_{1+2x}$Mn$_2$O$_7$ Probed by Compton Scattering|B. Barbiellini,A. Koizumi,P. E. Mijnarends,W. Al-Sawai,Hsin Lin,T. Nagao,K. Hirota,M. Itou,Y. Sakurai,A. Bansil###

Role of Oxygen Electrons in the Metal-Insulator Transition in the Magnetoresistive Oxide La$_{2-2x}$Sr$_{1+2x}$Mn$_2$O$_7$ Probed by Compton Scattering. We have studied the [100]-[110] anisotropy of the Compton profile in the
bilayer manganite. Quantitative agreement is found between theory and
experiment with respect to the anisotropy in the two metallic phases (i.e. the
low temperature ferromagnetic and the colossal magnetoresistant phase under a
magnetic field of 7 T). Robust signatures of the metal-insulator transition are
identified in the momentum density for the paramagnetic phase above the Curie
temperature. We interpret our results as providing direct evidence for the
transition from the metallic-like to the admixed ionic-covalent bonding
accompanying the magnetic transition. The number of electrons involved in this
phase transition is estimated from the area enclosed by the Compton profile
anisotropy differences. Our study demonstrates the sensitivity of the Compton
scattering technique for identifying the number and type of electrons involved
in the metal-insulator transition.

###Low-temperature thermal conductivity of BaFe2As2: Parent compound of iron-arsenide superconductors|N. Kurita,F. Ronning,C. F. Miclea,E. D. Bauer,J. D. Thompson,A. S. Sefat,M. A. McGuire,B. C. Sales,D. Mandrus,R. Movshovich###

Low-temperature thermal conductivity of BaFe2As2: Parent compound of iron-arsenide superconductors. We report low-temperature thermal conductivity down to 40 mK of the
antiferromagnet BaFe$_2$As$_{2}$, which is the parent compound of recently
discovered iron-based superconductors. In the investigated temperature range
below 4 K, the thermal conductivity $\kappa$ is well described by the
expression $\kappa$ = $aT$ + $bT^{2.22}$. We attribute the ``$aT$''-term to an
electronic contribution which is found to satisfy the Wiedemann-Franz law in
the $T$ $\to$ 0 K limit, and the remaining thermal conductivity, $\sim$
$T^{2.22}$, is attributed to phonon conductivity. A small influence on thermal
conductivity by magnetic fields up to 8 T is well accounted by the observed
magnetoresistance. The result is consistent with a fully gapped magnon
spectrum, inferred previously from inelastic neutron scattering measurements.

###Correlation between Organic Magnetoresistance (OMAR) and Ferromagnetic ordering|Sayani Majumdar,Himadri Majumdar,Jan-Olof Lill,Johan Rajander,Reino Laiho,Ronald Osterbacka###

Correlation between Organic Magnetoresistance (OMAR) and Ferromagnetic ordering. We report observation of ferromagnetic (FM) ordering in organic
semiconductors, namely regio-regular poly (3-hexyl thiophene) (RRP3HT) and
1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]-methanofullerene (PCBM), in the
temperature range of 5-300 K in addition to magnetoresistance (OMAR) observed
in the diodes made from the same materials. Particle induced x-ray emission
spectroscopy confirms the presence of dilute magnetic impurities in the
materials mainly as residues from the synthesis process. However, upon blending
these two materials with FM signal, the FM ordering is suppressed by a huge
paramagnetic (PM) signal indicating ground state charge transfer formation in
the blend. Together with the magneto-transport studies, these results indicate
that OMAR response is observed in a device only when the corresponding active
materials are FM. In the diodes with P3HT:PCBM complex, that as a blend shows
PM response, OMAR vanishes almost completely. We propose that ferromagnetism in
the active material can have important correlation with the OMAR response in
the diodes.

###Tracking anisotropic scattering in overdoped Tl$_2$Ba$_2$CuO$_{6+δ}$ above 100 K|M. M. J. French,J. G. Analytis,A. Carrington,L. Balicas,N. E. Hussey###

Tracking anisotropic scattering in overdoped Tl$_2$Ba$_2$CuO$_{6+δ}$ above 100 K. This article describes new polar angle-dependent magnetoresistance (ADMR)
measurements in the overdoped cuprate Tl$_2$Ba$_2$CuO$_{6+\delta}$ over an
expanded range of temperatures and azimuthal angles. These detailed
measurements re-affirm the analysis of earlier data taken over a more
restricted temperature range and at a single azimuthal orientation, in
particular the delineation of the intraplane scattering rate into isotropic and
anisotropic components. These new measurements also reveal additional features
in the temperature and momentum dependence of the scattering rate, including
anisotropy in the $T^2$ component and the preservation of both the $T$-linear
and $T^2$ components up to 100 K. The resultant form of the scattering rate
places firm constraints on the development of any forthcoming theoretical
framework for the normal state charge response of high temperature
superconducting cuprates.

###Evolution from Non-Fermi to Fermi Liquid Transport Properties by Isovalent Doping in BaFe2(As1-xPx)2 Superconductors|S. Kasahara,T. Shibauchi,K. Hashimoto,K. Ikada,S. Tonegawa,R. Okazaki,H. Ikeda,H. Takeya,K. Hirata,T. Terashima,Y. Matsuda###

Evolution from Non-Fermi to Fermi Liquid Transport Properties by Isovalent Doping in BaFe2(As1-xPx)2 Superconductors. The normal-state charge transport is studied systematically in high-quality
single crystals of BaFe$_2$(As$_{1-x}$P$_x$)$_2$ ($0 \leq x \leq 0.71$). By
substituting isovalent P for As, the spin-density-wave (SDW) state is
suppressed and the dome-shaped superconducting phase ($T_c \lesssim 31$ K)
appears. Near the SDW end point ($x\approx0.3$), we observe striking linear
temperature ($T$) dependence of resistivity in a wide $T$-range, and remarkable
low-$T$ enhancement of Hall coefficient magnitude from the carrier number
estimates. We also find that the magnetoresistance apparently violates the
Kohler's rule and is well scaled by the Hall angle $\Theta_H$ as
$\Delta\rho_{xx}/\rho_{xx} \propto \tan^2\Theta_H$. These non-Fermi liquid
transport anomalies cannot be attributed to the simple multiband effects. These
results capture universal features of correlated electron systems in the
presence of strong antiferromagnetic fluctuations.

###Interlayer magnetoresistance in an anisotropic pseudogap state|M. F. Smith,Ross H. McKenzie###

Interlayer magnetoresistance in an anisotropic pseudogap state. The interlayer magnetoresistance of a quasi-two-dimensional layered metal
with a d-wave pseudogap is calculated semiclassically. An expression for the
interlayer resistivity as a function of the strength and direction of the
magnetic field, the magnitude of the pseudogap, temperature, and scattering
rate is obtained. We find that the pseudogap, by introducing low-energy nodal
quasiparticle contours, smooths the dependence on field direction in a manner
characteristic of its anisotropy. We thus propose that interlayer resistance
measurements under a strong field of variable orientation can be used to fully
characterize an anisotropic pseudogap. The general result is applied to the
case of a magnetic field parallel to the conducting layers using a model band
structure appropriate for overdoped T$\ell$2201.

###The observation of a positive magnetoresistance and close correlation among lattice, spin and charge around TC in antipervoskite SnCMn3|B. S. Wang,P. Tong,Y. P. Sun,X. B. Zhu,W. H. Song,Z. R. Yang,J. M. Dai###

The observation of a positive magnetoresistance and close correlation among lattice, spin and charge around TC in antipervoskite SnCMn3. The temperature dependences of magnetization, electrical transport, and
thermal transport properties of antiperovskite compound SnCMn3 have been
investigated systematically. A positive magnetoresistance (~11%) is observed
around the ferrimagnetic-paramagnetic transition (TC ~ 280 K) in the field of
50 kOe, which can be attributed to the field-induced magnetic phase transition.
The abnormalities of resistivity, Seebeck coefficient, normal Hall effect and
thermal conductivity near TC are suggested to be associated with an abrupt
reconstruction of electronic structure. Further, our results indicate an
essential interaction among lattice, spin and charge degrees of freedom around
TC. Such an interaction among various degrees of freedom associated with sudden
phase transition is suggested to be characteristic of Mn-based antiperovskite
compounds.

###Magnetotransport properties of individual InAs nanowires|Sajal Dhara,Hari S. Solanki,Vibhor Singh,Arjun Narayanan,Prajakta Chaudhari,Mahesh Gokhale,Arnab Bhattacharya,Mandar M. Deshmukh###

Magnetotransport properties of individual InAs nanowires. We probe the magnetotransport properties of individual InAs nanowires in a
field effect transistor geometry. In the low magnetic field regime we observe
magnetoresistance that is well described by the weak localization (WL)
description in diffusive conductors. The weak localization correction is
modified to weak anti-localization (WAL) as the gate voltage is increased. We
show that the gate voltage can be used to tune the phase coherence length
($l_\phi$) and spin-orbit length ($l_{so}$) by a factor of $\sim$ 2. In the
high field and low temperature regime we observe the mobility of devices can be
modified significantly as a function of magnetic field. We argue that the role
of skipping orbits and the nature of surface scattering is essential in
understanding high field magnetotransport in nanowires.

###Evidence for Antiferromagnetic Order in La$_{2-x}$Ce$_{x}$CuO$_{4}$ from Angular Magnetoresistance Measurements|K. Jin,X. H. Zhang,P. Bach,R. L. Greene###

Evidence for Antiferromagnetic Order in La$_{2-x}$Ce$_{x}$CuO$_{4}$ from Angular Magnetoresistance Measurements. We investigated the in-plane angular magnetoresistivity (AMR) of $%
T^{^{\prime}}$-phase La$_{2-x}$Ce$_{x}$CuO$_{4}$ (LCCO) thin films ($%
x=0.06-0.15$) fabricated by a pulsed laser deposition technique. The in-plane
AMR with $\mathbf{H}\parallel ab$ shows a twofold symmetry instead of the
fourfold behavior found in other electron-doped cuprates such as Pr$%
_{2-x}$Ce$_{x}$CuO$_{4}$ and Nd$_{2-x}$Ce$_{x}$CuO$_{4}$. The twofold AMR
disappears above a certain temperature, $T_{D}$. The $T_{D}(x)$ is well above
$T_{c}(x)$ for $x=0.06$ ($\sim 110$ K), and decreases with increasing doping,
until it is no longer observed above $T_{c}(x)$ at $x=0.15$. This twofold AMR
below $T_{D}(x)$ is suggested to originate from an antiferromagnetic or spin
density wave order.

###Microscopic mechanism of the non-crystalline anisotropic magnetoresistance in (Ga,Mn)As|Karel Výborný,Jan Kucera,Jairo Sinova,A. W. Rushforth,B. L. Gallagher,T. Jungwirth###

Microscopic mechanism of the non-crystalline anisotropic magnetoresistance in (Ga,Mn)As. Starting with a microscopic model based on the Kohn-Luttinger Hamiltonian and
kinetic p-d exchange combined with Boltzmann formula for conductivity we
identify the scattering from magnetic Mn combined with the strong spin-orbit
interaction of the GaAs valence band as the dominant mechanism of the
anisotropic magnetoresistance (AMR) in (Ga,Mn)As. This fact allows to construct
a simple analytical model of the AMR consisting of two heavy-hole bands whose
charge carriers are scattered on the impurity potential of the Mn atoms. The
model predicts the correct sign of the AMR (resistivity parallel to
magnetization is smaller than perpendicular to magnetization) and identifies
its origin arising from the destructive interference between electric and
magnetic part of the scattering potential of magnetic ionized Mn acceptors when
the carriers move parallel to the magnetization.

###Indication for the coexistence of closed orbit and quantum interferometer with the same cross section in the organic metal (ET)4(H3O)[Fe(C2O4)3].C6H4Cl2: Persistence of SdH oscillations above 30 K|David Vignolles,Alain Audouard,Vladimir N. Laukhin,Enric Canadell,Tatyana G. Prokhorova,Eduard B. Yagubskii###

Indication for the coexistence of closed orbit and quantum interferometer with the same cross section in the organic metal (ET)4(H3O)[Fe(C2O4)3].C6H4Cl2: Persistence of SdH oscillations above 30 K. Shubnikov-de Haas (SdH) and de Haas-van Alphen (dHvA) oscillations spectra of
the quasi-two dimensional charge transfer salt
$\beta$"-(ET)$_4$(H$_3$O)[Fe(C$_2$O$_4$)$_3$]$\cdot$C$_6$H$_4$Cl$_2$ have been
investigated in pulsed magnetic fields up to 54 T. The data reveal three basic
frequencies F$_a$, F$_b$ and F$_{b - a}$, which can be interpreted on the basis
of three compensated closed orbits at low temperature. However a very weak
thermal damping of the Fourier component F$_b$, with the highest amplitude, is
evidenced for SdH spectra above about 6 K. As a result, magnetoresistance
oscillations are observed at temperatures higher than 30 K. This feature, which
is not observed for dHvA oscillations, is in line with quantum interference,
pointing to a Fermi surface reconstruction in this compound.

###Observation of Giant Positive Magnetoresistance in a Cooper Pair Insulator|H. Q. Nguyen,S. M. Hollen,M. D. Stewart Jr.,J. Shainline,Aijun Yin,J. M. Xu,J. M. Valles Jr###

Observation of Giant Positive Magnetoresistance in a Cooper Pair Insulator. Ultrathin amorphous Bi films, patterned with a nano-honeycomb array of holes,
can exhibit an insulating phase with transport dominated by the incoherent
motion of Cooper pairs of electrons between localized states. Here we show that
the magnetoresistance of this Cooper pair insulator phase is positive and grows
exponentially with decreasing temperature, for temperatures well below the pair
formation temperature. It peaks at a field estimated to be sufficient to break
the pairs and then decreases monotonically into a regime in which the film
resistance assumes the temperature dependence appropriate for weakly localized
single electron transport. We discuss how these results support proposals that
the large MR peaks in other unpatterned, ultrathin film systems disclose a
Cooper Pair Insulator phase and provide new insight into the Cooper pair
localization.

###Fingerprint of dynamical charge/spin correlations in the tunneling spectra of colossal magnetoresistive manganites|S. Seiro,Y. Fasano,I. Maggio-Aprile,E. Koller,R. Lortz,Ø. Fischer###

Fingerprint of dynamical charge/spin correlations in the tunneling spectra of colossal magnetoresistive manganites. We present temperature-dependent scanning tunneling spectroscopy measurements
on $La_{1-x}Ca_{x}MO_{3}$ ($x\sim0.33$) films with different degrees of biaxial
strain. A depletion in normalized conductance around the Fermi level is
observed both above and below the insulator-to-metal transition temperature
$T_{MI}$, for weakly as well as highly-strained films. This pseudogap-like
depletion globally narrows on cooling. The zero-bias conductance decreases on
cooling in the insulating phase, reaches a minimum close to $T_{MI}$ and
increases on cooling in the metallic phase, following the trend of macroscopic
conductivity. These results support a recently proposed scenario in which
dynamical short-range antiferromagnetic/charge order correlations play a
preeminent role in the transport properties of colossal magnetoresistive
manganites [R. Yu \textit{et al}., Phys. Rev. B \textbf{77}, 214434 (2008)].

###Synthetic antiferromagnet with Heusler alloy Co2FeAl ferromagnetic layers|X. G. Xu,D. L. Zhang,X. Q. Li,J. Bao,Y. Jiang###

Synthetic antiferromagnet with Heusler alloy Co2FeAl ferromagnetic layers. Heusler alloy Co2FeAl was employed as ferromagnetic layers in
Co2FeAl/Ru/Co2FeAl synthetic antiferromagnet structures. The experimental
results show that the structure with a Ru thickness of 0.45 nm takes on
strongly antiferromagnetic coupling, which maintains up to 150 oC annealing for
1 hour. The structure has a very low saturation magnetization Ms of 425 emu/cc,
a low switching field Hsw of 4.3 Oe and a high saturation field Hs of 5257 Oe
at room temperature, which are favorable for application in ultrahigh density
magnetic read heads or other magnetic memory devices. XRD study testifies that
the as-deposited Co2FeAl film is in B2 phase. Therefore Heusler alloys can be
used to fabricate SyAF and it is possible to make "all-Heusler" spin-valves or
magnetic tunneling junctions with better magnetic switching properties and high
magnetoresistance.

###Theoretical studies of spin-dependent electronic transport in ferromagnetically contacted graphene flakes|S. Krompiewski###

Theoretical studies of spin-dependent electronic transport in ferromagnetically contacted graphene flakes. Based on a tight-binding model and a recursive Green's function technique,
spin-depentent ballistic transport through tinny graphene sheets (flakes) is
studied. The main interest is focussed on: electrical conductivity, giant
magnetoresistance (GMR) and shot noise. It is shown that when graphene flakes
are sandwiched between two ferromagnetic electrodes, the resulting GMR
coefficient may be quite significant. This statement holds true both for zigzag
and armchair chiralities, as well as for different aspect (width/length)
ratios. Remarkably, in absolute values the GMR of the armchair-edge graphene
flakes is systematically greater than that corresponding to the zigzag-edge
graphene flakes. This finding is attributed to the different degree of
conduction channel mixing for the two chiralities in question. It is also shown
that for big aspect ratio flakes, 3-dimensional end-contacted leads, very much
like invasive contacts, result in non-universal behavior of both conductivity
and Fano factor.

###Aharonov-Bohm interference in topological insulator nanoribbons|Hailin Peng,Keji Lai,Desheng Kong,Stefan Meister,Yulin Chen,Xiao-Liang Qi,Shou-Cheng Zhang,Zhi-Xun Shen,Yi Cui###

Aharonov-Bohm interference in topological insulator nanoribbons. Topological insulators represent novel phases of quantum matter with an
insulating bulk gap and gapless edges or surface states. The two-dimensional
topological insulator phase was predicted in HgTe quantum wells and confirmed
by transport measurements. Recently, Bi2Se3 and related materials have been
proposed as three-dimensional topological insulators with a single Dirac cone
on the surface and verified by angle-resolved photoemission spectroscopy
experiments. Here, we show unambiguous transport evidence of topological
surface states through periodic quantum interference effects in layered
single-crystalline Bi2Se3 nanoribbons. Pronounced Aharonov-Bohm oscillations in
the magnetoresistance clearly demonstrate the coverage of two-dimensional
electrons on the entire surface, as expected from the topological nature of the
surface states. The dominance of the primary h/e oscillation and its
temperature dependence demonstrate the robustness of these electronic states.
Our results suggest that topological insulator nanoribbons afford novel
promising materials for future spintronic devices at room temperature.

###Effect of electron-electron scattering on magnetointersubband resistance oscillations of two-dimensional electrons in GaAs quantum wells|A. V. Goran,A. A. Bykov,A. I. Toropov,S. A. Vitkalov###

Effect of electron-electron scattering on magnetointersubband resistance oscillations of two-dimensional electrons in GaAs quantum wells. The low-temperature($4.2<T<12.5$ K) magnetotransport ($B<2$ T) of
two-dimensional electrons occupying two subbands (with energy $E_1$ and $E_2$)
is investigated in GaAs single quantum well with AlAs/GaAs superlattice
barriers. Two series of Shubnikov-de Haas oscillations are found to be
accompanied by magnetointersubband (MIS) oscillations, periodic in the inverse
magnetic field. The period of the MIS oscillations obeys condition
$\Delta_{12}=(E_2-E_1)=k \cdot \hbar \omega_c$, where $\Delta_{12}$ is the
subband energy separation, $\omega_c$ is the cyclotron frequency, and $k$ is
the positive integer. At $T$=4.2 K the oscillations manifest themselves up to
$k$=100. Strong temperature suppression of the magnetointersubband oscillations
is observed. We show that the suppression is a result of electron-electron
scattering. Our results are in good agreement with recent experiments,
indicating that the sensitivity to electron-electron interaction is the
fundamental property of magnetoresistance oscillations, originating from the
second-order Dingle factor.

###Exchange bias effect and intragranular magnetoresistance in Nd$_{0.84}Sr_{0.16}CoO_3|M. Patra,S. Majumdar,S. Giri###

Exchange bias effect and intragranular magnetoresistance in Nd$_{0.84}Sr_{0.16}CoO_3. Electrical transport properties as a function of magnetic field and time have
been investigated in polycrystalline, Nd_{0.84}Sr_{0.16}CoO_3. A strong
exchange bias (EB) effect is observed associated with the fairly large
intragranular magnetoresistance (MR). The EB effect observed in the MR curve is
compared with the EB effect manifested in magnetic hysteresis loop. Training
effect, described as the decrease of EB effect when the sample is successively
field-cycled at a particular temperature, has been observed in the shift of the
MR curve. Training effect could be analysed by the successful models. The EB
effect, MR and a considerable time dependence in MR are attributed to the
intrinsic nanostructure giving rise to the varieties of magnetic interfaces in
the grain interior.

###Magnetic properties of PrPd$_{2}$Si$_{2}$ and PrPt$_{2}$Si$_{2}$|V. K. Anand,Z. Hossain,C. Geibel###

Magnetic properties of PrPd$_{2}$Si$_{2}$ and PrPt$_{2}$Si$_{2}$. We have investigated the two rare-earth intermetallic compounds
PrPd$_{2}$Si$_{2}$ and PrPt$_{2}$Si$_{2}$ by means of magnetization, electrical
resistivity and heat capacity measurements. While PrPd$_{2}$Si$_{2}$ exhibits
an antiferromagnetic ordering at 3 K, no magnetic ordering is observed in
PrPt$_{2}$Si$_{2}$ down to 2 K. The different magnetic behaviors of these two
compounnds are due to different crystalline electric field (CEF) level schemes.
The specific heat data suggest a quasi-quartet ground state in PrPd$_2$Si$_2$
in contrast to a nonmagnetic singlet ground state in PrPt$_2$Si$_2$. This
difference is attributed to the loss of a mirror plane upon changing the
crystal structure from the ThCr$_2$Si$_2$ type (PrPd$_2$Si$_2$) to the
CaBe$_2$Ge$_2$ type (PrPt$_2$Si$_2$). Further on, a large magnetoresistance is
also observed in the magnetically ordered state of PrPd$_2$Si$_2$.

###Momentum-Resolved Bragg Spectroscopy in Optical Lattices|P. T. Ernst,S. Götze,J. S. Krauser,K. Pyka,D. -S. Lühmann,D. Pfannkuche,K. Sengstock###

Momentum-Resolved Bragg Spectroscopy in Optical Lattices. Strongly correlated many-body systems show various exciting phenomena in
condensed matter physics such as high-temperature superconductivity and
colossal magnetoresistance. Recently, strongly correlated phases could also be
studied in ultracold quantum gases possessing analogies to solid-state physics,
but moreover exhibiting new systems such as Fermi-Bose mixtures and magnetic
quantum phases with high spin values. Particularly interesting systems here are
quantum gases in optical lattices with fully tunable lattice and atomic
interaction parameters. While in this context several concepts and ideas have
already been studied theoretically and experimentally, there is still great
demand for new detection techniques to explore these complex phases in detail.
  Here we report on measurements of a fully momentum-resolved excitation
spectrum of a quantum gas in an optical lattice by means of Bragg spectroscopy.
The bandstructure is measured with high resolution at several lattice depths.
Interaction effects are identified and systematically studied varying density
and excitation fraction.

###$A$-site substitution effect on physical properties of Sr$_3$Fe$_{2-x}$Co$_x$O$_{7-δ}$|J. Tozawa,M. Akaki,D. Akahoshi,H. Kuwahara,K. Itatani###

$A$-site substitution effect on physical properties of Sr$_3$Fe$_{2-x}$Co$_x$O$_{7-δ}$. We have investigated the $Ln^{3+}$-substitution ($Ln$ = lanthanoid) effect of
a quasi two-dimensional ferromagnet Sr$_3$Fe$_{2-x}$Co$_x$O$_{7-\delta}$ ($x$$
= $0.5). %$Ln^{3+}$-substitution creates antiferromagnetic insulating clusters
around $Ln^{3+}$. With increasing $Ln^{3+}$-concentration, the ferromagnetism
is gradually suppressed and the resistivity is increasing, which are ascribed
to an increase in antiferromagnetic (AFM) clusters created by
$Ln^{3+}$-substitution. In
Sr$_{2.7}$Gd$_{0.3}$Fe$_{1.5}$Co$_{0.5}$O$_{7-\delta}$, the magnetoresistance
(MR) is enhanced by about 20 % compared with that of
Sr$_3$Fe$_{1.5}$Co$_{0.5}$O$_{7-\delta}$. Coexistence of ferromagnetic (FM) and
AFM phases is essential for the enhancement of the MR\@. Applied magnetic
fields align the FM clusters in the same direction, resulting in a reduction in
the resistivity. A metamagnetic transition observed in the $Ln^{3+}$-doped
samples also contributes to the enhancement of the MR.

###$R$-site Randomness Effect in Double-Perovskite $R$BaMn$_{2}$O$_{6}$|Y. Miyauchi,S. Fukushima,J. Tozawa,M. Akaki,H. Kuwahara,D. Akahoshi###

$R$-site Randomness Effect in Double-Perovskite $R$BaMn$_{2}$O$_{6}$. We have investigated the $R$-site randomness effect of $R$/Ba-ordered
$R$BaMn$_{2}$O$_{6}$ ($R$ = rare earth) by using Y$_{1-y}$La$_y$BaMn$_2$O$_6$
(0 (\leq) $y$ (\leq) 1) in which $R$ (Y,La) and Ba are regularly arranged while
Y and La randomly occupy the $R$-site. YBaMn$_2$O$_6$ ($y$ = 0) undergoes
charge/orbital ordering (CO) transition at $T_{\rm CO}$ = 500 K while
LaBaMn$_{2}$O$_{6}$ ($y$ = 1) shows ferromagnetic metallic (FM) behavior below
350 K\@. In 0 (\leq) $y$ (\leq) 0.6, $T_{\rm CO}$ decreases with an increase in
$y$. In 0.6 (\leq) $y$ (\leq) 0.8, $R$-site randomness causes strong phase
separation tendencies among the FM, antiferromagnetic (AFM), and CO insulating
(COI) states. The large magnetoresistance is observed in the phase separated
region.

###Electric Pulse Induced Resistive Switching, Electronic Phase Separation, and Possible Superconductivity in a Mott insulator|C. Vaju,L. Cario,B. Corraze,E. Janod,V. Dubost,T. Cren,D. Roditchev,D. Braithwaite,O. Chauvet###

Electric Pulse Induced Resistive Switching, Electronic Phase Separation, and Possible Superconductivity in a Mott insulator. Metal-insulator transitions (MIT) belong to a class of fascinating physical
phenomena, which includes superconductivity, and colossal magnetoresistance
(CMR), that are associated with drastic modifications of electrical resistance.
In transition metal compounds, MIT are often related to the presence of strong
electronic correlations that drive the system into a Mott insulator state. In
these systems the MIT is usually tuned by electron doping or by applying an
external pressure. However, it was noted recently that a Mott insulator should
also be sensitive to other external perturbations such as an electric field. We
report here the first experimental evidence of a non-volatile
electric-pulse-induced insulator-to-metal transition and possible
superconductivity in the Mott insulator GaTa4Se8. Our Scanning Tunneling
Microscopy experiments show that this unconventional response of the system to
short electric pulses arises from a nanometer scale Electronic Phase Separation
(EPS) generated in the bulk material.

###Large Positive Magnetoresistance of the Lightly Doped La_{2}CuO_{4} Mott Insulator|I. Raicevic,Dragana Popovic,C. Panagopoulos,T. Sasagawa###

Large Positive Magnetoresistance of the Lightly Doped La_{2}CuO_{4} Mott Insulator. The in-plane and out-of-plane magnetoresistance (MR) of single crystals of
La_2CuO_4, lightly doped (x=0.03) with either Sr (La_{2-x}Sr_xCuO_4) or Li
(La_2Cu_{1-x}Li_xO_4), have been measured in the fields applied parallel and
perpendicular to the CuO_2 planes. Both La_{1.97}Sr_{0.03}CuO_4 and
La_2Cu_{0.97}Li_{0.03}O_4 exhibit the emergence of a positive MR at
temperatures (T) well below the spin glass (SG) transition temperature T_{sg},
where charge dynamics is also glassy. This positive MR grows as T->0 and shows
hysteresis and memory. In this regime, the in-plane resistance R_{ab}(T,B) is
described by a scaling function, suggesting that short-range Coulomb repulsion
between two holes in the same disorder-localized state plays a key role at low
T. The results highlight similarities between this magnetic material and a
broad class of well-studied, nonmagnetic disordered insulators.

###Ballistic quantum spin Hall state and enhanced edge backscattering in strong magnetic fields|G. Tkachov,E. M. Hankiewicz###

Ballistic quantum spin Hall state and enhanced edge backscattering in strong magnetic fields. The quantum spin Hall (QSH) state, observed in a zero magnetic field in HgTe
quantum wells, respects the time-reversal symmetry and is distinct from quantum
Hall (QH) states. We show that the QSH state persists in strong quantizing
fields and is identified by counter-propagating (helical) edge channels with
nonlinear dispersion inside the band gap. If the Fermi level is shifted into
the Landau-quantized conduction or valence band, we find a transition between
the QSH and QH regimes. Near the transition the longitudinal conductance of the
helical channels is strongly suppressed due to the combined effect of the
spectrum nonlinearity and enhanced backscattering. It shows a power-law decay
1/B^2N with magnetic field B, determined by the number of backscatterers on the
edge, N. This suggests a rather simple and practical way to probe the quality
of recently realized quasiballistic QSH devices using magnetoresistance
measurements.

###Non-monotonic Fermi surface evolution and its correlation with stripe ordering in bilayer manganites|Z. Sun,Q. Wang,J. F. Douglas,Y. -D. Chuang,A. V. Fedorov,E. Rotenberg,H. Lin,S. Sahrakorpi,B. Barbiellini,R. S. Markiewicz,A. Bansil,H. Zheng,J. F. Mitchell,D. S. Dessau###

Non-monotonic Fermi surface evolution and its correlation with stripe ordering in bilayer manganites. In correlated electron systems such as cuprate superconductors and colossal
magnetoresistive (CMR) oxides there is often a tendency for a nanoscale
self-organization of electrons that can give rise to exotic properties and to
extreme non-linear responses. The driving mechanisms for this self-organization
are highly debated, especially in the CMR oxides in which two types of
self-organized stripes of charge and orbital order coexist with each other. By
utilizing angle-resolved photoemission spectroscopy measurements over a wide
doping range, we show that one type of stripe is exclusively linked to long
flat portions of nested Fermi surface, while the other type prefers to be
commensurate with the real space lattice but also may be driven away from this
by the Fermi surface. Complementarily, the Fermi surface also appears to be
driven away from its non-interacting value at certain doping levels, giving
rise to a host of unusual electronic properties.

###Interplay among spin, orbital effects and localization in a GaAs two-dimensional electron gas in a strong in-plane magnetic field|B. A. Piot,D. K. Maude,U. Gennser,A. Cavanna,D. Mailly###

Interplay among spin, orbital effects and localization in a GaAs two-dimensional electron gas in a strong in-plane magnetic field. The magnetoresistance of a low carrier density, disordered GaAs based
two-dimensional (2D) electron gas has been measured in parallel magnetic fields
up to 32 T. The feature in the resistance associated with the complete spin
polarization of the carriers shifts down by more than 20 T as the electron
density is reduced, consistent with recent theories taking into account the
enhancement of the electron-electron interactions at low densities.
Nevertheless, the magnetic field for complete polarization, Bp, remains 2-3
times smaller than predicted for a disorder free system. We show, in particular
by studying the temperature dependance of Bp to probe the effective size of the
Fermi sea, that localization plays an important role in determining the spin
polarization of a 2D electron gas.

###Quantifying spin Hall angles from spin pumping: Experiments and Theory|O. Mosendz,J. E. Pearson,F. Y. Fradin,G. E. W. Bauer,S. D. Bader,A. Hoffmann###

Quantifying spin Hall angles from spin pumping: Experiments and Theory. Spin Hall effects intermix spin and charge currents even in nonmagnetic
materials and, therefore, ultimately may allow the use of spin transport
without the need for ferromagnets. We show how spin Hall effects can be
quantified by integrating permalloy/normal metal (N) bilayers into a coplanar
waveguide. A dc spin current in N can be generated by spin pumping in a
controllable way by ferromagnetic resonance. The transverse dc voltage detected
along the permalloy/N has contributions from both the anisotropic
magnetoresistance (AMR) and the spin Hall effect, which can be distinguished by
their symmetries. We developed a theory that accounts for both. In this way, we
determine the spin Hall angle quantitatively for Pt, Au and Mo. This approach
can readily be adapted to any conducting material with even very small spin
Hall angles.

###Multiple Localized States and Magnetic Orderings in Partially Open Zigzag Carbon Nanotube Superlattices: An Ab Initio Study|Bing Huang,Zuanyi Li,Young-Woo Son,Gunn Kim,Wenhui Duan,Jisoon Ihm###

Multiple Localized States and Magnetic Orderings in Partially Open Zigzag Carbon Nanotube Superlattices: An Ab Initio Study. Using first-principles calculations, we examine the electronic and magnetic
properties of partially open zigzag carbon nanotube (CNT) superlattices. It is
found that depending on their opening degree, these superlattices can exhibit
multiple localized states around the Fermi energy. More importantly, some
electronic states confined in some parts of the structure even have special
magnetic orderings. We demonstrate that, as a proof of principle, some
partially open zigzag CNT superlattices are by themselves giant (100%)
magnetoresistive devices. Furthermore, the localized(and spin-polarized) states
as well as the band gaps of the superlattices could be further modulated by
external electric fields perpendicular to the tube axis, and a bias voltage
along the tube axis may be used to control the conductance of two spin states.
We believe that these results will open the way to the production of novel
nanoscale electronic and spintronic devices.

###Strain, magnetic anisotropy, and anisotropic magnetoresistance in (Ga,Mn)As on high-index substrates: application to (113)A-oriented layers|L. Dreher,D. Donhauser,J. Daeubler,M. Glunk,C. Rapp,W. Schoch,R. Sauer,W. Limmer###

Strain, magnetic anisotropy, and anisotropic magnetoresistance in (Ga,Mn)As on high-index substrates: application to (113)A-oriented layers. Based on a detailed theoretical examination of the lattice distortion in
high-index epilayers in terms of continuum mechanics, expressions are deduced
that allow the calculation and experimental determination of the strain tensor
for (hhl)-oriented (Ga,Mn)As layers. Analytical expressions are derived for the
strain-dependent free-energy density and for the resistivity tensor for
monoclinic and orthorhombic crystal symmetry, phenomenologically describing the
magnetic anisotropy (MA) and anisotropic magnetoresistance (AMR) by appropriate
anisotropy and resistivity parameters, respectively. Applying the results to
(113)A orientation with monoclinic crystal symmetry, the expressions are used
to determine the strain tensor and the shear angle of a series of
(113)A-oriented (Ga,Mn)As layers by high-resolution x-ray diffraction and to
probe the MA and AMR at 4.2 K by means of angle-dependent magnetotransport.
Whereas the transverse resistivity parameters are nearly unaffected by the
magnetic field, the parameters describing the longitudinal resistivity are
strongly field dependent.

###Energy scales and the non-Fermi liquid behavior in YbRh2Si2|V. R. Shaginyan,M. Ya. Amusia,K. G. Popov,S. A. Artamonov###

Energy scales and the non-Fermi liquid behavior in YbRh2Si2. Multiple energy scales are detected in measurements of the thermodynamic and
transport properties in heavy fermion metals. We demonstrate that the
experimental data on the energy scales can be well described by the scaling
behavior of the effective mass at the fermion condensation quantum phase
transition, and show that the dependence of the effective mass on temperature
and applied magnetic fields gives rise to the non-Fermi liquid behavior. Our
analysis is placed in the context of recent salient experimental results. Our
calculations of the non-Fermi liquid behavior, of the scales and thermodynamic
and transport properties are in good agreement with the heat capacity,
magnetization, longitudinal magnetoresistance and magnetic entropy obtained in
remarkable measurements on the heavy fermion metal YbRh2Si2.

###Magnetic field effect on Fe-induced short-range magnetic correlation and electrical conductivity in Bi$_{1.75}$Pb$_{0.35}$Sr$_{1.90}$Cu$_{0.91}$Fe$_{0.09}$O$_{6+y}$|S. Wakimoto,H. Hiraka,K. Kudo,D. Okamoto,T. Nishizaki,K. Kakurai,Tao Hong,A. Zheludev,J. M. Tranquada,N. Kobayashi,K. Yamada###

Magnetic field effect on Fe-induced short-range magnetic correlation and electrical conductivity in Bi$_{1.75}$Pb$_{0.35}$Sr$_{1.90}$Cu$_{0.91}$Fe$_{0.09}$O$_{6+y}$. We report electrical resistivity measurements and neutron diffraction studies
under magnetic fields of
Bi$_{1.75}$Pb$_{0.35}$Sr$_{1.90}$Cu$_{0.91}$Fe$_{0.09}$O$_{6+y}$, in which hole
carriers are overdoped. This compound shows short-range incommensurate magnetic
correlation with incommensurability $\delta=0.21$, whereas a Fe-free compound
shows no magnetic correlation. Resistivity shows an up turn at low temperature
in the form of $ln(1/T)$ and shows no superconductivity. We observe reduction
of resistivity by applying magnetic fields (i.e., a negative magnetoresistive
effect) at temperatures below the onset of short-range magnetic correlation.
Application of magnetic fields also suppresses the Fe induced incommensurate
magnetic correlation. We compare and contrast these observations with two
different models: 1) stripe order, and 2) dilute magnetic moments in a metallic
alloy, with associated Kondo behavior. The latter picture appears to be more
relevant to the present results.

###Magnetic and Electrical Properties of Ordered 112-type Perovskite LnBaCoMnO5+δ(Ln = Nd, Eu)|Asish K. Kundu,V. Pralong,B. Raveau,V. Caignaert###

Magnetic and Electrical Properties of Ordered 112-type Perovskite LnBaCoMnO5+δ(Ln = Nd, Eu). Investigation of the oxygen-deficient 112-type ordered oxides of the type
LnBaCoMnO5+\delta (Ln = Nd, Eu) evidences certain unusual magnetic behavior at
low temperatures, compared to the LnBaCo2O5+\delta cobaltites. One observes
that the substitution of manganese for cobalt suppresses the ferromagnetic
state and induces strong antiferromagnetic interactions. Importantly,
NdBaCoMnO5.9 depicts a clear paramagnetic to antiferromagnetic type transition
around 220 K, whereas for EuBaCoMnO5.7 one observes an unusual magnetic
behavior below 177 K which consists of ferromagnetic regions embedded in an
antiferromagnetic matrix. The existence of two sorts of crystallographic sites
for Co/Mn and their mixed valence states favor the ferromagnetic interaction
whereas antiferromagnetism originates from the Co3+-O-Co3+ and Mn4+-O-Mn4+
interactions. Unlike the parent compounds, the present Mn-substituted phases do
not exhibit prominent magnetoresistance effects in the temperature range
75-400K.

###Beating in electronic transport through quantum dot based devices|Piotr Trocha###

Beating in electronic transport through quantum dot based devices. Electronic transport through a two-level system driven by external electric
field and coupled to (magnetic or non-magnetic) electron reservoirs is
considered theoretically. The basic transport characteristics such as current
and tunnel magnetoresistance (TMR) are calculated in the weak coupling
approximation by the use of rate equation connected with Green function
formalism and slave-boson approach. The time dependent phenomenon is considered
in the gradient expansion approximation. The results show that coherent beats
pattern can be observed both in current and TMR. The proposed system consisting
of two quantum dots attached to external leads, in which the dots' levels can
be tuned independently, can be realized experimentally to test this well known
physical phenomenon. Finally, we also indicate possible practical applications
of such device.

###The Realization of Artificial Kondo Lattices in Nanostructured Arrays|D. K. Singh,M. T. Tuominen###

The Realization of Artificial Kondo Lattices in Nanostructured Arrays. The interplay of magnetic energies in a Kondo lattice is the underlying
physics of a heavy fermion system. Creating an artificial Kondo lattice system
by localizing the moments in an ordered metallic array provides a prototype
system to tune and study the energetic interplay while avoiding the
complications introduced by random alloying of the material. In this article,
we create a Kondo lattice system by fabricating a hexagonally ordered
nanostructured array using niobium as the host metal and cobalt as the magnetic
constituent. Electrical transport measurements and magnetoresistivity
measurements of these artificial lattices show that the competing exchange
coupling properties can be easily tuned by controlling the impurity percentage.
These artificial Kondo lattice systems enable the exploration of an artificial
superconductor which should lead to a deep understanding of the role of
magnetism in unconventional superconductors.

###Orbital Order and Spontaneous Orthorhombicity in Iron Pnictides|C. -C. Chen,J. Maciejko,A. P. Sorini,B. Moritz,R. R. P. Singh,T. P. Devereaux###

Orbital Order and Spontaneous Orthorhombicity in Iron Pnictides. A growing list of experiments show orthorhombic electronic anisotropy in the
iron pnictides, in some cases at temperatures well above the spin density wave
transition. These experiments include neutron scattering, resistivity and
magnetoresistance measurements, and a variety of spectroscopies. We explore the
idea that these anisotropies stem from a common underlying cause: orbital order
manifest in an unequal occupation of $d_{xz}$ and $d_{yz}$ orbitals, arising
from the coupled spin-orbital degrees of freedom. We emphasize the distinction
between the total orbital occupation (the integrated density of states), where
the order parameter may be small, and the orbital polarization near the Fermi
level which can be more pronounced. We also discuss light-polarization studies
of angle-resolved photoemission, and demonstrate how x-ray absorption linear
dichroism may be used as a method to detect an orbital order parameter.

###Van der Waals epitaxy of Bi2Se3 on Si(111) vicinal surface: An approach to prepare high-quality thin films of topological insulator|H. D. Li,Z. Y. Wang,X. Kan,X. Guo,H. T. He,Z. Wang,J. N. Wang,T. L. Wong,N. Wang,M. H. Xie###

Van der Waals epitaxy of Bi2Se3 on Si(111) vicinal surface: An approach to prepare high-quality thin films of topological insulator. Epitaxial growth of topological insulator Bi2Se3 thin films on nominally flat
and vicinal Si(111) substrates is studied. In order to achieve planner growth
front and better quality epifilms, a two-step growth method is adopted for the
van der Waal epitaxy of Bi2Se3 to proceed. By employing vicinal Si(111)
substrate surfaces, the in-pane growth rate anisotropy of Bi2Se3 is explored to
achieve single crystalline Bi2Se3 epifilms, in which threading defects and
twins are effectively suppressed. Optimization of the growth parameters has
resulted in vicinal Bi2Se3 films showing a carrier mobility of ~ 2000 cm2V-1s-1
and the background doping of ~ 3 x 1018 cm-3 of the as-grown layers. Such
samples not only show relatively high magnetoresistance but also a linear
dependence on magnetic field.

###Spin and Charge Transport on the Surface of a Topological Insulator|A. A. Burkov,D. G. Hawthorn###

Spin and Charge Transport on the Surface of a Topological Insulator. We derive diffusion equations, which describe spin-charge coupled transport
on the helical metal surface of a three-dimensional topological insulator. The
main feature of these equations is a large magnitude of the spin-charge
coupling, which leads to interesting and observable effects. In particular, we
predict a new magnetoresistance effect, which manifests in a nonohmic
correction to a voltage drop between a ferromagnetic spin-polarized electrode
and a nonmagnetic electrode, placed on top of the helical metal. This
correction is proportional to the cross-product of the spin polarization of the
ferromagnetic electrode and the charge current between the two electrodes. We
also demonstrate tunability of this effect by applying a gate voltage, which
makes it possible to operate the proposed device as a transistor.

###Metal-terminated Graphene Nanoribbons|Yan Wang,Chao Cao,Hai-Ping Cheng###

Metal-terminated Graphene Nanoribbons. We have investigated structure, electronic, and magnetic properties of
metal-terminated zigzag graphene nanoribbons (M-ZGNRs) by first-principles
calculations. Two families of metal terminations are studied: (1) 3d-transition
metals (TMs) Fe, Co, and Ni and (2) noble metals (NMs) Cu, Ag, and Au. All
systems have spin-polarized edge states with antiferromagnetic (AFM) ordering
between two edges, except Co-ZGNRs and Ni-ZGNRs which exhibit negligibly small
energy differences between AFM and ferromagnetic states with the given ribbon
width. In the AFM state the TM terminations transform semiconducting ZGNRs into
metallic ones while the band gap remains in ZGNR with NM terminations.
Ferromagnetic states of M-ZGNRs with TM terminations show a high degree of spin
polarization at the Fermi energy. We predict a large magnetoresistance in
Fe-ZGNR junctions with a low, uniform magnetic switching field.

###Existence of Fine Structure inside Spin Gap in CeRu2Al10|Hiroshi Tanida,Daiki Tanaka,Masafumi Sera,Chikako Moriyoshi,Yoshihiro Kuroiwa,Tomoaki Takesaka,Takashi Nishioka,Harukazu Kato,Masahiro Matsumura###

Existence of Fine Structure inside Spin Gap in CeRu2Al10. We investigate the magnetic field effect on the spin gap state in CeRu2Al10
by measuring the magnetization and electrical resistivity. We found that the
magnetization curve for the magnetic field H//c shows a metamagnetic-like
anomaly at H*~4 T below T_0=27 K, but no anomaly for H//a and H//b. A shoulder
of the electrical resistivity at Ts~5 K for I//c is suppressed by applying a
longitudinal magnetic field above 5 T. Many anomalies are also found in the
magnetoresistance for Hkc below ~5 K. The obtained magnetic phase diagram
consists of at least two or three phases below T_0. These results strongly
indicate the existence of a fine structure at a low energy side in a spin gap
state with the excitation energy of 8 meV recently observed in the inelastic
neutron scattering experiments.

###The dynamics of magnetic vortex states in a single permalloy nanoparticle|Dmitry Ruzmetov,Venkat Chandrasekhar###

The dynamics of magnetic vortex states in a single permalloy nanoparticle. We demonstrate a novel method allowing the study of the magnetic state
dynamics of a single nanoparticle by means of electron transport measurements.
Elliptical 550 nm x 240 nm permalloy nanoparticles are wired with non-magnetic
leads for magnetotransport measurements in the presence of a radio-frequency
(RF) field. Their resistance exhibits sharp jumps due to the anisotropic
magnetoresistance even at room temperature. An RF field induces DC voltage
across the nanoparticle which can be partially depleted at a certain RF
frequency when a magnetic vortex core resonance is present. An application of
an additional DC magnetic field eliminates the vortex and reinstates the
unperturbed DC voltage level. The vortex core resonance frequencies are found
and the smallest resonance widths are estimated to be less than 6 MHz.

###Microwave imaging of mesoscopic percolating network in a manganite thin film|Keji Lai,Masao Nakamura,Worasom Kundhikanjana,Masashi Kawasaki,Yoshinori Tokura,Michael A. Kelly,Zhi-Xun Shen###

Microwave imaging of mesoscopic percolating network in a manganite thin film. Many unusual behaviors in complex oxides are deeply associated with the
spontaneous emergence of microscopic phase separation. Depending on the
underlying mechanism, the competing phases can form ordered or random patterns
at vastly different length scales. Using a microwave impedance microscope, we
observed an orientation-ordered percolating network in strained Nd0.5Sr0.5MnO3
thin films with a large period of 100 nm. The filamentary metallic domains
align preferentially along certain crystal axes of the substrate, suggesting
the anisotropic elastic strain as the key interaction in this system. The local
impedance maps provide microscopic electrical information of the hysteretic
behavior in strained thin film manganites, suggesting close connection between
the glassy order and the colossal magnetoresistance effects at low
temperatures.

###Interlayer Exchange Coupling Beyond the Proximity Force Approximation|Ching-Hao Chang,Tzay-Ming Hong###

Interlayer Exchange Coupling Beyond the Proximity Force Approximation. Ion bombardment has been shown to be capable of enhancing the interlayer
exchange coupling in a trilayer system that exhibits giant magnetoresistance.
We demonstrate that this phenomenon can be derived from the phase coherence
among scattered paths within the two rough interfaces when their topographies
are correlated. In the case of mild corrugations, our method reproduces the
predictions by the proximity force approximation which does not consider the
interference. When the characteristic Fourier conjugate of the tomography
becomes large and comparable to the Fermi momentum, interesting new features
arise and can only be captured by our more general approach. Among our
findings, the scenario of an enhanced interlayer exchange coupling due to the
interface roughness is explained, along with how it depends on the sample
parameters. An additional channel for the resonant transmission is identified
due to extra scattering paths from the roughness.

###Spin-Boson Theory for Magnetotransport in Organic Semiconducting Materials|Yao Yao,Wei Si,Xiaoyuan Hou,Chang-Qin Wu###

Spin-Boson Theory for Magnetotransport in Organic Semiconducting Materials. We present a spin-boson theory for magnetotransport in organic semiconducting
materials, on the basis of a coupling between charge carriers' spin and a local
bosonic environment, which is shown to be an irreducible ingredient in
understanding of the anomalous organic magnetoresistance (OMR). Among those
composing this environment triplet-excitons play a basic role. The incoherent
hopping rate between molecules is calculated to give out the fundamental
behavior of OMR. The underlying mechanism is revealed from the calculation of
entanglement, represented by the von Neumann entropy, between the carrier's
spin and bosons. We also obtain the dependence of OMR on the bias voltage, the
spin-boson coupling, and the boson frequency. The results obtained from the
theory are in good agreement with experiments.

###Transition from a ferromagnetic insulating to a ferromagnetic metallic state in nanoparticles of Nd0.8Sr0.2MnO3 : Study of the electronic - and magneto - transport properties|S. Kundu,T. K. Nath###

Transition from a ferromagnetic insulating to a ferromagnetic metallic state in nanoparticles of Nd0.8Sr0.2MnO3 : Study of the electronic - and magneto - transport properties. A detailed investigation of the electronic - and magneto - transport
properties of Nd0.8Sr0.2MnO3 with the variation of grain size (down to 42 nm)
is presented here. Interestingly, we observe that the ferromagnetic insulating
state is suppressed and a metallic state is stabilized as the grain size of the
sample is reduced. As a result, metal insulator transition is observed in this
low doped manganite which is insulating in nature in its bulk form.
Destabilization of polaronic order in the ferromagnetic insulating state due to
enhanced surface disorder on grain size reduction has been attributed to this
effect. A phenomenological model has been proposed to represent the concept of
destabilization of polaron formation in the surface region of the nano grains.
Resistivity and magnetoresistance data have been carefully analyzed employing
different suitable models. Electrical third harmonic resistance has been
measured to directly probe the electrical nonlinearity in the samples.

###Proposed measurements of the interlayer magnetoresistance of underdoped cuprate superconductors can distinguish closed pockets from open arcs in the Fermi surface|M. F. Smith,Ross H. McKenzie###

Proposed measurements of the interlayer magnetoresistance of underdoped cuprate superconductors can distinguish closed pockets from open arcs in the Fermi surface. An outstanding question concerning the underdoped cuprate concerns the true
nature of their Fermi surface which appears as a set of disconnected arcs.
Theoretical models have proposed two distinct possibilities: (1) each arc is
the observable part of a partially-hidden closed pocket, and (2) each arc is
open, truncated at its apparent ends. We show that measurements of the
variation of the interlayer resistance with the direction of a magnetic field
parallel to the layers can qualitatively distinguish closed pockets from open
arcs. This is possible because the field can be oriented such that all
electrons on arcs encounter a large Lorentz force and resulting
magnetoresistance whereas some electrons on pockets escape the effect by moving
parallel to the field.

###Modulation of the ferromagnetic insulating phase in Pr0.8Ca0.2MnO3 by Co substitution|T. Harada,I. Ohkubo,M. Lippmaa,Y. Matsumoto,M. Sumiya,H. Koinuma,M. Oshima###

Modulation of the ferromagnetic insulating phase in Pr0.8Ca0.2MnO3 by Co substitution. Ferromagnetic insulator Pr0.8Ca0.2Mn1-yCoyO3 (0 <= y <= 0.7) thin films were
epitaxially grown on (LaAlO3)0.3-(SrAl0.5Ta0.5O3)0.7 (100) substrates by pulsed
laser deposition. To probe the ferromagnetic insulator state of hole-doped
manganites, the Co content dependences of the structural, magnetic, and
transport properties were studied. Variation of lattice constant by the
substitution of Co ions is well reproduced considering that divalent and
trivalent Co ions substitute for Mn ions at the perovskite B-sites. For 0 <= y
<= 0.3, the Curie temperature, saturation magnetization, and magnetoresistance
increase with increasing Co content, retaining the insulating properties.
Detailed analyses of transport and magnetic properties indicate the
contribution of both double exchange and superexchange interactions to the
appearance of the ferromagnetic insulating phase.

###Weak Localization and Dimensional Crossover in Carbon Nanotube Systems|M. Salvato,M. Lucci,I. Ottaviani,M. Cirillo,S. Orlanducci,F. Toschi,M. L. Terranova###

Weak Localization and Dimensional Crossover in Carbon Nanotube Systems. We investigate the effects of magnetic and electric fields on electron
wavefunction interactions in single walled carbon nanotube bundles. The
magnetoresistance measurements performed at 4.2K and the dependence of the data
upon the electric field, obtained by varying the bias current through the
samples, reveal good agreement with weak localization theory. Recording
current-voltage characteristics at different temperatures we find an ohmic
non-ohmic transition which disappears above 85K. Conductance vs temperature
measurements are also well explained in the framework of weak localization
theory by the predicted temperature dependence of the electric
field-conditioned characteristic length. This length results equal to the
average bundles diameter just at T{\backcong}85K, indicating that the observed
conductance transition is due to a 2D-3D crossover.

###Discontinuous Hall coefficient at the quantum critical point in YbRh2Si2|Sven Friedemann,Niels Oeschler,Steffen Wirth,Cornelius Krellner,Christoph Geibel,Frank Steglich,Silke Paschen,Stefan Kirchner,Qimiao Si###

Discontinuous Hall coefficient at the quantum critical point in YbRh2Si2. YbRh2Si2 is a model system for quantum criticality. Particularly, Hall effect
measurements helped identify the unconventional nature of its quantum critical
point. Here, we present a high-resolution study of the Hall effect and
magnetoresistivity on samples of different quality. We find a robust crossover
on top of a sample dependent linear background contribution. Our detailed
analysis provides a complete characterization of the crossover in terms of its
position, width, and height. Importantly, we find in the extrapolation to zero
temperature a discontinuity of the Hall coefficient occurring at the quantum
critical point for all samples. Particularly, the height of the jump in the
Hall coefficient remains finite in the limit of zero temperature. Hence, our
data solidify the conclusion of a collapsing Fermi surface. Finally, we
contrast our results to the smooth Hall-effect evolution seen in Chromium, the
prototype system for a spin-density-wave quantum critical point.

###Spin-wave interference patterns created by spin-torque nano-oscillators for memory and computation|F. Macià,A. D. Kent,F. C. Hoppensteadt###

Spin-wave interference patterns created by spin-torque nano-oscillators for memory and computation. Magnetization dynamics in nanomagnets has attracted broad interest since it
was predicted that a dc-current flowing through a thin magnetic layer can
create spin-wave excitations. These excitations are due to spin-momentum
transfer, a transfer of spin angular momentum between conduction electrons and
the background magnetization, that enables new types of information processing.
Here we show how arrays of spin-torque nano-oscillators (STNO) can create
propagating spin-wave interference patterns of use for memory and computation.
Memristic transponders distributed on the thin film respond to threshold tunnel
magnetoresistance (TMR) values thereby detecting the spin-waves and creating
new excitation patterns. We show how groups of transponders create resonant
(reverberating) spin-wave interference patterns that may be used for
polychronous wave computation of arithmetic and boolean functions and
information storage.

###Detection and quantification of inverse spin Hall effect from spin pumping in permalloy/normal metal bilayers|O. Mosendz,V. Vlaminck,J. E. Pearson,F. Y. Fradin,G. E. W. Bauer,S. D. Bader,A. Hoffmann###

Detection and quantification of inverse spin Hall effect from spin pumping in permalloy/normal metal bilayers. Spin pumping is a mechanism that generates spin currents from ferromagnetic
resonance (FMR) over macroscopic interfacial areas, thereby enabling sensitive
detection of the inverse spin Hall effect that transforms spin into charge
currents in non-magnetic conductors. Here we study the spin-pumping-induced
voltages due to the inverse spin Hall effect in permalloy/normal metal bilayers
integrated into coplanar waveguides for different normal metals and as a
function of angle of the applied magnetic field direction, as well as microwave
frequency and power. We find good agreement between experimental data and a
theoretical model that includes contributions from anisotropic
magnetoresistance (AMR) and inverse spin Hall effect (ISHE). The analysis
provides consistent results over a wide range of experimental conditions as
long as the precise magnetization trajectory is taken into account. The spin
Hall angles for Pt, Pd, Au and Mo were determined with high precision to be
$0.013\pm0.002$, $0.0064\pm0.001$, $0.0035\pm0.0003$ and $-0.0005\pm0.0001$,
respectively.

###Huge enhancement of the magnetoresistance in nanoparticle arrays|V. Estevez,E. Bascones###

Huge enhancement of the magnetoresistance in nanoparticle arrays. We show that the interplay between charging effects and the non-equilibrium
spin accumulation has a dramatic effect in the current through an array of
nanostructures attached to ferromagnetic electrodes. Large oscillations in the
current as a function of bias voltage show up for parallel orientation of the
electrodes' magnetizations. These oscillations originate in the inhomogeneity
of the spin potentials through the array and correlate with oscillations in the
spin accumulation. For antiparallel orientation the spin potential is
homogeneous and the oscillations do not show up.This sensitivity results in a
huge enhancement of the tunneling magnetoresistance as compared to the
single-island case, and open new routes for improving the spintronic response
of nanodevices.

###Magneto-transport in impurity-doped few-layer graphene spin valve|Kai-He Ding,Zhen-Gang Zhu,Zhen-Hua Zhang,Jamal Berakdar###

Magneto-transport in impurity-doped few-layer graphene spin valve. Using Keldysh nonequilibrium Green's function method we study the
spin-dependent transport through impurity-doped few layer graphene sandwiched
between two magnetic leads with an arbitrary mutual orientations of the
magnetizations. We find for parallel electrodes magnetizations that the
differential conductance possesses two resonant peaks as the applied bias
increases. These peaks are traced back to a buildup of a magnetic moment on the
impurity due to the electrodes spin polarization. For a large mutual angle of
the electrodes magnetization directions, the two resonant peaks approach each
others and merge into a single peak for antiparallel orientation of the
electrodes magnetizations. We point out that the tunneling magnetoresistance
(TMR) may change sign for relatively small changes in the values of the
polarization parameters. Furthermore, we inspect the behaviour of the
differential conductance and TMR upon varying the temperature.

###Impact of bicritical fluctuation on magnetocaloric phenomena in perovskite manganites|H. Sakai,Y. Taguchi,Y. Tokura###

Impact of bicritical fluctuation on magnetocaloric phenomena in perovskite manganites. Variation of magnetocaloric (MC) effects has been systematically investigated
for colossal magnetoresistive (CMR) manganites R0.6Sr0.4MnO3 (R=La-Gd). As the
one-electron bandwidth is reduced, the temperature profile of MC effect, i.e.,
field-induced entropy change, exhibits a steeper drop below the ferromagnetic
transition temperature due to its first-order nature promoted by a competing
charge-orbital ordering instability. For these small-bandwidth systems adjacent
to the metal-insulator phase boundary, a rectangular-shaped profile for the
entropy change emerges with an anomalously wide temperature range and a
considerable magnitude. Model calculations have indicated that the fluctuation
enhanced in the phase-competing region has a strong impact on such MC features,
which can be extensively controlled by the chemical composition.

###Vortex ratchet reversal at fractional matching fields in kagomé-like array with symmetric pinning centers|D. Perez de Lara,A. Alija,E. M. Gonzalez,M. Velez,J. I. Martin,J. L. Vicent###

Vortex ratchet reversal at fractional matching fields in kagomé-like array with symmetric pinning centers. Arrays of Ni nanodots embedded in Nb superconducting films have been
fabricated by sputtering and electron beam lithography techniques. The arrays
are periodic triangular lattices of circular Ni dots arranged in a
kagom\'e-like pattern with broken reflection symmetry. Relevant behaviors are
found in the vortex lattice dynamics : i) At values lower than the first
integer matching field, several fractional matching fields are present when the
vortex lattice moves parallel or perpendicular to the reflection symmetry axis
of the array showing a clear anisotropic character in the magnetoresistance
curves, ii) injecting an ac current perpendicular to the reflection symmetry
axis of the array yields an unidirectional motion of the vortex lattice
(ratchet effect) as a result of the interaction between the whole vortex
lattice and the asymmetric lattice of dots, iii) increasing the input current
amplitudes the ratchet effect changes polarity independently of matching field
values. These experimental results can be explained taking into account the
vortex lattice density.

###Observation of a cyclotron harmonic spike in microwave-induced resistances in ultraclean GaAs/AlGaAs quantum wells|Yanhua Dai,R. R. Du,L. N. Pfeiffer,K. W. West###

Observation of a cyclotron harmonic spike in microwave-induced resistances in ultraclean GaAs/AlGaAs quantum wells. We report the observation of a colossal, narrow resistance peak that arises
in ultraclean (mobility 3X10^7cm^2/Vs) GaAs/AlGaAs quantum wells (QWs) under
millimeterwave irradiation and a weak magnetic field. Such a spike is
superposed on the 2nd harmonic microwave-induced resistance oscillations (MIRO)
but having an amplitude > 300% of the MIRO, and a typical FWHM ~50 mK,
comparable with the Landau level width. Systematic studies show a correlation
between the spike and a pronounced negative magnetoresistance in these QWs,
suggesting a mechanism based on the interplay of strong scatterers and smooth
disorder. Alternatively, the spike may be interpreted as a manifestation of
quantum interference between the quadrupole resonance and the higher-order
cyclotron transition in well-separated Landau levels.

###Electronic structure of fully epitaxial Co2TiSn thin films|Markus Meinert,Jan-Michael Schmalhorst,Hendrik Wulfmeier,Günter Reiss,Elke Arenholz,Tanja Graf,Claudia Felser###

Electronic structure of fully epitaxial Co2TiSn thin films. In this article we report on the properties of thin films of the full Heusler
compound Co2TiSn prepared by DC magnetron co-sputtering. Fully epitaxial,
stoichiometric films were obtained by deposition on MgO (001) substrates at
substrate temperatures above 600{\deg}C. The films are well ordered in the L21
structure, and the Curie temperature exceeds slightly the bulk value. They show
a significant, isotropic magnetoresistance and the resistivity becomes strongly
anomalous in the paramagnetic state. The films are weakly ferrimagnetic, with
nearly 1 \mu_B on the Co atoms, and a small antiparallel Ti moment, in
agreement with theoretical expectations. From comparison of x-ray absorption
spectra on the Co L3/L2 edges, including circular and linear magnetic
dichroism, with ab initio calculations of the x-ray absorption and circular
dichroism spectra we infer that the electronic structure of Co2TiSn has
essentially non-localized character. Spectral features that have not been
explained in detail before, are explained here in terms of the final state band
structure.

###Thermally activated intersubband scattering and oscillating magnetoresistance in quantum wells|S. Wiedmann,G. M. Gusev,O. E. Raichev,A. K. Bakarov,J. C. Portal###

Thermally activated intersubband scattering and oscillating magnetoresistance in quantum wells. Experimental studies of magnetoresistance in high-mobility wide quantum wells
reveal oscillations which appear with an increase in temperature to 10 K and
whose period is close to that of Shubnikov-de Haas oscillations. The observed
phenomenon is identified as magnetointersubband oscillations caused by the
scattering of electrons between two occupied subbands and the third subband
which becomes occupied as a result of thermal activation. These small-period
oscillations are less sensitive to thermal suppression than the largeperiod
magnetointersubband oscillations caused by the scattering between the first and
the second subbands. Theoretical study, based on consideration of electron
scattering near the edge of the third subband, gives a reasonable explanation
of our experimental findings.

###Nanopattern-stimulated superconductor-insulator transition in thin TiN films|T. I. Baturina,V. M. Vinokur,A. Yu. Mironov,N. M. Chtchelkatchev,D. A. Nasimov,A. V. Latyshev###

Nanopattern-stimulated superconductor-insulator transition in thin TiN films. We present the results of the comparative study of the influence of disorder
on transport properties in continuous and nanoperforated TiN films. We show
that nanopatterning turns a thin TiN film into an array of superconducting weak
links and stimulates both, the disorder- and magnetic field-driven
superconductor-to-insulator transitions, pushing them to lower degree of
disorder. We find that nanopatterning enhances the role of the two-dimensional
Coulomb interaction in the system transforming the originally insulating film
into a more pronounced insulator. We observe magnetoresistance oscillations
reflecting collective behaviour of the multiconnected nanopatterned
superconducting film in the wide range of temperatures and uncover the physical
mechanism of these oscillations as phase slips in superconducting weak link
network.

###Orbital Order, Metal Insulator Transition, and Magnetoresistance-Effect in the two-orbital Hubbard model|Robert Peters,Norio Kawakami,Thomas Pruschke###

Orbital Order, Metal Insulator Transition, and Magnetoresistance-Effect in the two-orbital Hubbard model. We study the effects of temperature and magnetic field on a two-orbital
Hubbard model within dynamical mean field theory. We focus on the quarter
filled system, which is a special point in the phase diagram due to orbital
degeneracy. At this particular filling the model exhibits two different
long-range order mechanisms, namely orbital order and ferromagnetism. Both can
cooperate but do not rely on each other's presence, creating a rich phase
diagram. Particularly, in the vicinity of the phase transition to an orbitally
ordered ferromagnetic state, we observe a strong magnetoresistance effect.
Besides the low temperature phase transitions, we also observe a crossover
between a paramagnetic insulating and a paramagnetic metallic state for
increasing Hund's coupling at high temperatures.

###Anomalous galvanomagnetism, cyclotron resonance and microwave spectroscopy of topological insulators|G. Tkachov,E. M. Hankiewicz###

Anomalous galvanomagnetism, cyclotron resonance and microwave spectroscopy of topological insulators. The surface quantum Hall state, magneto-electric phenomena and their
connection to axion electrodynamics have been studied intensively for
topological insulators. One of the obstacles for observing such effects comes
from nonzero conductivity of the bulk. To overcome this obstacle we propose to
use an external magnetic field to suppress the conductivity of the bulk
carriers. The magnetic field dependence of galvanomagnetic and electromagnetic
responses of the whole system shows anomalies due to broken time-reversal
symmetry of the surface quantum Hall state, which can be used for its
detection. In particular, we find linear bulk dc magnetoresistivity and a
quadratic field dependence of the Hall angle, shifted rf cyclotron resonance,
nonanalytic microwave transmission coefficient and saturation of the Faraday
rotation angle with increasing magnetic field or wave frequency.

###Overtaking while approaching equilibrium|P. Chaddah,S. Dash,Kranti Kumar,A. Banerjee###

Overtaking while approaching equilibrium. A system initially far from equilibrium is expected to take more time to
reach equilibrium than a system that was initially closer to equilibrium. The
old puzzling observation (also called Mpemba effect) that when a sample of hot
water and another sample of cold water are put in a freezer to equilibrate, the
hot water sometimes overtakes as they cool, has been highlighted recently. In
the extensively studied colossal magnetoresistance manganites, cooling in a
magnetic field (H) often results in an inhomogeneous mixture of transformed
equilibrium phase and a kinetically arrested non-equilibrium phase which
relaxes slowly towards equilibrium at fixed H and temperature (T). Here we show
that the magnetization decay rate at the same H and T is larger for the state
that was initially farther from equilibrium, and it continues to relax faster
even after these have become equal. Our result should help propose an
explanation, for Mpemba effect, that does not attribute it to any artifact.

###Spin Transfer Torque and Tunneling Magnetoresistance Dependences on the Finite Bias Voltages and Insulator Barrier Energy|Chun-Yeol You,Jae-Ho Han,Hyun-Woo Lee###

Spin Transfer Torque and Tunneling Magnetoresistance Dependences on the Finite Bias Voltages and Insulator Barrier Energy. We investigate the dependence of perpendicular and parallel spin transfer
torque (STT) and tunneling magnetoresistance (TMR) on the insulator barrier
energy in the magnetic tunnel junction (MTJ). We employed single orbit tight
binding model combined with the Keldysh non-equilibrium Green's function method
in order to calculate the perpendicular and parallel STT, and TMR in MTJ with
the finite bias voltages. The dependences of STT and TMR on the insulator
barrier energy are calculated for the semi-infinite half metallic ferromagnetic
electrodes. We find that perfect linear relation between the parallel STT and
the tunneling current for the wide range of the insulator barrier energy.
Furthermore, the TMR also depends on the insulator barrier energy, which
contradicts to the Julliere's simple model.

###Abrupt recovery of Fermi-liquid transport by the c-axis collapse in CaFe2(As1-xPx)2 single crystals|S. Kasahara,T. Shibauchi,Y. Nakai,K. Hashimoto,H. Ikeda,T. Terashima,Y. Matsuda###

Abrupt recovery of Fermi-liquid transport by the c-axis collapse in CaFe2(As1-xPx)2 single crystals. Single crystals of CaFe$_2$(As$_{1-x}$P$_x$)$_2$ are found to exhibit the
tetragonal (T) to collapsed-tetragonal (cT) transition at $T_{\rm cT}
\lesssim100$\,K for $x>0.05$. The c-axis shrinks by $\sim9$% below $T_{\rm
cT}$, which substantially diminishes the interband nesting between the hole and
electron bands. In sharp contrast to the superconducting T phase of
$A$Fe$_2$(As$_{1-x}$P$_x$)$_2$ ($A=$ Ba, Sr), where the anomalous non-Fermi
liquid transport properties are observed, the resistivity, Hall coefficient,
and magnetoresistance data in the Ca-based system all indicate that the
standard Fermi liquid behaviors are recovered abruptly below $T_{\rm cT}$, and
the superconductivity disappears completely. The intimate link between the
superconductivity and the non-Fermi liquid transport enlightens the essential
role of interband-associated fluctuation effects in Fe-pnictides.

###Transport Spin Polarization of High-Curie Temperature MnBi Films|P. Kharel,P. Thapa,P. Lukashev,R. F. Sabirianov,E. Y. Tsymbal,D. J. Sellmyer,B. Nadgorny###

Transport Spin Polarization of High-Curie Temperature MnBi Films. We report on the study of the structural, magnetic and transport properties
of highly textured MnBi films with the Curie temperature of 628K. In addition
to detailed measurements of resistivity and magnetization, we measure transport
spin polarization of MnBi by Andreev reflection spectroscopy and perform fully
relativistic band structure calculations of MnBi. A spin polarization from
51\pm1 to 63\pm1% is observed, consistent with the calculations and with an
observation of a large magnetoresistance in MnBi contacts. The band structure
calculations indicate that, in spite of almost identical densities of states at
the Fermi energy, the large disparity in the Fermi velocities leads to high
transport spin polarization of MnBi. The correlation between the values of
magnetization and spin polarization is discussed.

###Electron and hole Dirac cone states in-pairs in Ba(FeAs)$_2$ confirmed by magnetoresistance|Khuong K. Huynh,Yoichi Tanabe,Katsumi Tanigaki###

Electron and hole Dirac cone states in-pairs in Ba(FeAs)$_2$ confirmed by magnetoresistance. The quantum transport of Dirac cone states in the iron pnictide Ba(FeAs)$_2$
with a d-\,multiband system is studied by using single crystal samples. The
transverse magnetoresistance develops linearly against magnetic field at low
temperatures. The transport phenomena are interpreted in terms of the 0$^{th}$
Landau level by applying the theory predicted by Abrikosov. The results of the
semiclassical analyses of a two carrier system under low magnetic field limit
show that both electron and hole reside as the high mobility states, being
indicative to the fact that both electron- and hole Dirac cone states should be
taken into account in pairs for having the real interpretation of low
temperature electronic states in iron pnictides, being in contrast to the
previous reports.

###Low frequency noise characteristics of sub-micron magnetic tunnel junctions|B. Zhong,Y. Chen,S. Garzon,T. M. Crawford,R. A. Webb###

Low frequency noise characteristics of sub-micron magnetic tunnel junctions. We report that low frequency (up to 200 kHz) noise spectra of magnetic tunnel
junctions with areas ~10^{-10}cm^2$ at 10 Kelvin deviate significantly from the
typical 1/f behavior found in large area junctions at room temperature. In most
cases, a Lorentzian-like shape with characteristic time between 0.1 and 10 ms
is observed, which indicates only a small number of fluctuators contribute to
the measured noise. By investigating the dependence of noise on both the
magnitude and orientation of an applied magnetic field, we find that
magnetization fluctuations in both free and reference layers are the main
sources of noise in these devices. At small fields, where the noise from the
free layer is dominant, a linear relation between the measured noise and
angular magnetoresistance susceptibility can be established.

###Holographic quantum criticality and strange metal transport|Bom Soo Kim,Elias Kiritsis,Christos Panagopoulos###

Holographic quantum criticality and strange metal transport. A holographic model of a quantum critical theory at a finite but low
temperature, and finite density is studied. The model exhibits non-relativistic
z=2 Schr\"odinger symmetry and is realized by the Anti-de-Sitter-Schwarzschild
black hole in light-cone coordinates. Our approach addresses the electrical
conductivities in the presence or absence of an applied magnetic field and
contains a control parameter that can be associated to quantum tuning via
charge carrier doping or an external field in correlated electron systems. The
Ohmic resistivity, the inverse Hall angle, the Hall coefficient and the
magnetoresistance are shown to be in good agreement with experimental results
of strange metals at very low temperature. The holographic model also predicts
new scaling relations in the presence of a magnetic field.

###Robustness of the magnetoresistance of nanoparticle arrays|V. Estevez,E. Bascones###

Robustness of the magnetoresistance of nanoparticle arrays. Recent work has found that the interplay between spin accumulation and
Coulomb blockade in nanoparticle arrays results in peaky I-V and tunneling
magnetoresistance (TMR) curves and in huge values of the TMR. We analyze how
these effects are influenced by a polarization asymmetry of the electrodes, the
dimensionality of the array, the temperature, resistance or charge disorder and
long-range interactions. We show that the magnitude and voltage dependence of
the TMR does not change with the dimensionality of the array or the presence of
junction resistance disorder. A different polarization in the electrodes
modifies the peak shape in the I-V and TMR curves but not their order of
magnitude. Increasing the temperature or length of the interaction reduces to
some extent the size of the peaks, being the reduction due to long-range
interactions smaller in longer arrays. Charge disorder should be avoided to
observe large TMR values.

###A Study of Spin-Flipping in Sputtered IrMn using Py-based Exchange-Biased Spin-Valves|R. Acharyya,H. Y. T. Nguyen,W. P. Pratt Jr.,J. Bass###

A Study of Spin-Flipping in Sputtered IrMn using Py-based Exchange-Biased Spin-Valves. To study spin flipping within the antiferromagnet IrMn, we extended prior
Current-Perpendicular-to-Plane (CPP) Giant Magnetoresistance (GMR) studies of
Py-based exchange-biased-spin-valves containing IrMn inserts to thicker IrMn
layers-5 nm less than or equal to t(IrMn) less than or equal to 30 nm.
Unexpectedly, A{\Delta}R = A[R(AP) - R(P)]--the difference in specific
resistance between the anti-parallel (AP) and parallel (P) magnetic states of
the two Py layers-did not decrease with increasing t(IrMn), for t(IrMn) greater
than 5 nm, but rather became constant to within our measuring uncertainty. This
constant looks to be due mostly to a new, small MR in thin Py layers. The
constant complicates isolating the spin-diffusion length, lsf(IrMn), in bulk
IrMn, but lsf(IrMn) is probably short, less than or equal to 1 nm. Similar
results were found with FeMn.

###Conduction Electron Scattering and Spin-Flipping at Sputtered Co/Ni Interfaces|H. Y. T. Nguyen,R. Acharyya,E. Huey,B. Richard,R. Loloee,W. P. Pratt Jr.,J. Bass,Shuai Wang,Ke Xia###

Conduction Electron Scattering and Spin-Flipping at Sputtered Co/Ni Interfaces. Current-perpendicular-to-plane magnetoresistance (CPP-MR) measurements let us
quantify conduction electron scattering and spin-flipping at a sputtered
ferromagnetic/ferromagnetic (F1/F2 = Co/Ni) interface, with important
consequences for CPP-MR and spin-torque experiments with perpendicular
anisotropy. We use ferromagnetically coupled ([Ni/Co]xn)Ni multilayers, and
Py-based, symmetric double exchange-biased spin-valves (DEBSVs) containing
inserts of ferromagnetically coupled ([Co/Ni]xn)Co or ([Ni/Co]xn)Ni
multilayers, to derive Co/Ni interface specific resistances AR(Co/Ni)(Up) =
0.03 (+0.02)(-0.03) f-ohm-m^2 and AR(Co/Ni)(down) = 1.00 +/- 0.07 f-ohm-m^2,
and interface spin-flipping parameter delta(Co/Ni) = 0.35 +/- 0.05. The
specific resistances are consistent with our no-free-parameter calculations for
an interface thickness between 2 and 4 monolayers (ML) that is compatible with
expectations.

###Probing photo-induced melting of antiferromagnetic order in La0.5Sr1.5MnO4 by ultrafast resonant soft X-ray diffraction|H. Ehrke,R. I. Tobey,S. Wall,S. A. Cavill,M. Först,V. Khanna,Th. Garl,N. Stojanovic,D. Prabhakaran,A. T. Boothroyd,M. Gensch,A. Mirone,P. Reutler,A. Revcolevschi,S. S. Dhesi,A. Cavalleri###

Probing photo-induced melting of antiferromagnetic order in La0.5Sr1.5MnO4 by ultrafast resonant soft X-ray diffraction. Photo-excitation in complex oxides1 transfers charge across semicovalent
bonds, drastically perturbing spin and orbital orders2. Light may then be used
in compounds like magnetoresistive manganites to control magnetism on nanometre
lengthscales and ultrafast timescales. Here, we show how ultrafast resonant
soft x-ray diffraction can separately probe the photo-induced dynamics of spin
and orbital orders in La0.5Sr1.5MnO4. Ultrafast melting of CE antiferromagnetic
spin order is evidenced by the disappearance of a (1/4,1/4,1/2) diffraction
peak. On the other hand the (1/4,1/4,0) peak, reflecting orbital order, is only
partially reduced. Cluster calculations aid our interpretation by considering
different magnetically ordered states accessible after photo-excitation.
Nonthermal coupling between light and magnetism emerges as a primary aspect of
photo-induced phase transitions in manganites.

###Superconductivity and Magnetic Properties of high-quality single crystals of $A_{x}$Fe$_2$Se$_2$ ($A$ = K and Cs)|J. J. Ying,X. F. Wang,X. G. Luo,A. F. Wang,M. Zhang,Y. J. Yan,Z. J. Xiang,R. H. Liu,P. Cheng,G. J. Ye,X. H. Chen###

Superconductivity and Magnetic Properties of high-quality single crystals of $A_{x}$Fe$_2$Se$_2$ ($A$ = K and Cs). We successfully grew the high-quality single crystals of $A_{x}$Fe$_2$Se$_2$
($A$ = K and Cs) by self-flux method. Sharp superconducting transition was
observed for both types of crystals. The crystals show the onset
superconducting transition temperatures ($T_{\rm c}$) of 31 K and 30 K for K-
and Cs-compounds, respectively, with nearly 100% shielding fraction. The
crystals show quite high resistivity in the normal state of more than 160
m$\Omega$ cm and 1300 m$\Omega$ cm maximum resistivity for
$K_{0.86}Fe_2Se_{1.82}$ and $Cs_{0.86}Fe_{1.66}Se_{2}$ single crystals,
respectively. Much larger upper critical field $H_{\rm c2}$ is inferred from
low-temperature iso-magnetic-field magnetoresistance in these crystals than in
FeSe. The anisotropy $H^{ab}_{\rm c2}$(0)/$H^{c}_{\rm c2}$(0) is around 3 for
both of the two materials. Anisotropic peculiar magnetic behavior in normal
state has been found for $Cs_{0.86}Fe_{1.66}Se_{2}$

###Enhanced electrical resistance at the field-induced magnetic transitions in some stoichiometric and nonstoichiometric Tb-based ternary germanides|K. Mukherjee,Kartik K Iyer,E. V. Sampathkumaran###

Enhanced electrical resistance at the field-induced magnetic transitions in some stoichiometric and nonstoichiometric Tb-based ternary germanides. We present the magnetic and transport behavior of some Tb compounds, viz.,
TbIrGe2, TbFe(0.4)Ge2, and TbCo(0.4)Ge2. The stoichoometric germanide TbIrGe2
exhibits at least two distinct magnetic transitions in a close temperature
interval around 10 K. The non-stoichiometric compounds, TbFe(0.4)Ge2 and
TbCo(0.4)Ge2, undergo magnetic ordering around 17 and 19 K respectively. The
magnetic state of these compouds appears to be antiferromagnetic-like.
Qualitatively, there is a correlation between the field response of the
magnetization (M), the magnetoresistance (MR) and the entropy change curve in
all these compouds. That is, these Tb compounds exhibit a "positive" MR and
entropy change beyond a magnetic field where M also shows a field-induced
transition. On the basis of this correlaion, we conclude that magnetic
disorder/fluctuations beyond a critical field - "a phenomenon called inverse
metamagnetism" - rather than metamagnetism,is induced in these compounds.

###Magnetic Field Tuned Quantum Phase Transition in the Insulating Regime of Ultrathin Amorphous Bi Films|Yen-Hsiang Lin,A. M. Goldman###

Magnetic Field Tuned Quantum Phase Transition in the Insulating Regime of Ultrathin Amorphous Bi Films. A surprisingly strong variation of resistance with perpendicular magnetic
field, and a peak in the resistance vs. field, R(B) has been found in
insulating films of a sequence of homogeneous, quench-condensed films of
amorphous Bi undergoing a thickness-tuned superconductor-insulator transition.
Isotherms of magnetoresistance, rather than resistance, vs. field were found to
cross at a well-defined magnetic field higher than the field corresponding to
the peak in R(B). For all values of B, R(T) was found to obey an Arrhenius
form. At the crossover magnetic field the prefactor became equal to the quantum
resistance of electron pairs, h/4e^2, and the activation energy returned to its
zero field value. These observations suggest that the crossover is the
signature of a quantum phase transition between two distinct insulating ground
states, tuned by magnetic field.

###Large Magnetoresistance and Spin-Polarized Heavy-Mass Electron State in a Doped Valence Bond Solid (Ti1-xVx)2O3|M. Uchida,Y. Onose,Y. Tokura###

Large Magnetoresistance and Spin-Polarized Heavy-Mass Electron State in a Doped Valence Bond Solid (Ti1-xVx)2O3. A heavy-mass electron state is realized in a doped valence bond solid
(Ti1-xVx)2O3. In this system, itinerant holes mediate the mainly ferromagnetic
RKKY interaction between the localized magnetic moments and become readily
spin-polarized under a magnetic field, while showing large negative
magnetoresistance. In spite of the ferromagnetic interaction among the
carriers, their effective mass is found to be 1 or 2 orders of magnitude larger
than that of usual doped semiconductors. Such strong mass renormalization is
ascribable to the polaron formation on the Ti-dimer, where the spin-singlet
state is originally formed. Doping dependence of the electronic specific-heat
coefficient implies that the dimeric lattice fluctuation or softening is
responsible for the enhanced electron-phonon interaction.

###The role of magnetic anisotropy in spin filter junctions|R. V. Chopdekar,B. B. Nelson-Cheeseman,M. Liberati,E. Arenholz,Y. Suzuki###

The role of magnetic anisotropy in spin filter junctions. We have fabricated oxide based spin filter junctions in which we demonstrate
that magnetic anisotropy can be used to tune the transport behavior of spin
filter junctions. Until recently, spin filters have been largely comprised of
polycrystalline materials where the spin filter barrier layer and one of the
electrodes are ferromagnetic. These spin filter junctions have relied on the
weak magnetic coupling between one ferromagnetic electrode and a barrier layer
or the insertion of a nonmagnetic insulating layer in between the spin filter
barrier and electrode. We have demonstrated spin filtering behavior in
La0.7Sr0.3MnO3/chromite/Fe3O4 junctions without nonmagnetic spacer layers where
the interface anisotropy plays a significant role in determining transport
behavior. Detailed studies of chemical and magnetic structure at the interfaces
indicate that abrupt changes in magnetic anisotropy across the
non-isostructural interface is the cause of the significant suppression of
junction magnetoresistance in junctions with MnCr2O4 barrier layers.

###Anisotropic magnetotransport of superconducting and normal state in an electron-doped Nd_{1.85}Ce_{0.15}CuO_{4-δ} single crystal|Yue Wang,Hong Gao###

Anisotropic magnetotransport of superconducting and normal state in an electron-doped Nd_{1.85}Ce_{0.15}CuO_{4-δ} single crystal. The anisotropic properties of an optimally doped
Nd_{1.85}Ce_{0.15}CuO_{4-\delta} single crystal have been studied both below
and above the critical temperature Tc via the resistivity measurement in
magnetic field H up to 12 T. By scaling the conductivity fluctuation around the
superconducting transition, the upper critical field H_{c2}(T) has been
determined for field parallel to the c-axis or to the basal ab-plane. The
anisotropy factor \gamma={H_c2||ab}/{H_c2||c} is estimated to be about 8. In
the normal state (50=<T=<180 K), the magnetoresistance (MR) basically follows
an H^2 dependence and for H||c it is almost 10 times larger than that for
H||ab. Comparing with hole-doped cuprates it suggests that the optimally doped
Nd_{1.85}Ce_{0.15}CuO_{4-\delta} cuprate superconductor has a moderate
anisotropy.

###Surface state band mobility and thermopower in semiconducting bismuth nanowires|T. E. Huber,A. Adeyeye,A. Nikolaeva,L. Konopko,R. C. Johnson,M. J. Graf###

Surface state band mobility and thermopower in semiconducting bismuth nanowires. Many thermoelectrics like Bi exhibit Rashba spin-orbit surface bands for
which topological insulator behavior consisting of ultrahigh mobilities and
enhanced thermopower has been predicted. Bi nanowires realize surface-only
electronic transport since they become bulk insulators when they undergo the
bulk semimetal-semiconductor transition as a result of quantum confinement for
diameters close to 50 nm. We studied 20-, 30-, 50- and 200-nm trigonal Bi
wires. Shubnikov-de Haas magnetoresistance oscillations caused by surface
electrons and bulklike holes enable the determination of their densities and
mobilities. Surface electrons have high mobilities exceeding 2(m^2)/(Vsec) and
contribute strongly to the thermopower, dominating for temperatures T< 100 K.
The surface thermopower is - 1.2 T microvolt/(K^2), a value that is consistent
with theory, raising the prospect of developing nanoscale thermoelectrics based
on surface bands.

###Magnetodielectric study in SiO2-coated Fe3O4 nanoparticle compacts|C. -C. Chang,L. Zhao,M. -K. Wu###

Magnetodielectric study in SiO2-coated Fe3O4 nanoparticle compacts. The dielectric properties of Fe$_{3}$O$_{4}$ magnetic nanoparticles with an
insulating coating layer of SiO$_{2}$ were investigated. At high temperatures,
the changes of the dielectric constant and loss induced by the magnetic field
are opposite in sign and strongly frequency-dependent, which originates from
extrinsic magnetodielectric coupling-the Maxwell-Wagner effect combined with
magnetoresistance. And the interface defects leads to the obvious hysteresis
phenomena observed in the measurements. On the other hand, the strong coupling
of dielectric and magnetic properties at low temperatures contradicts the
Maxwell-Wagner model, suggesting the intrinsic magnetodielectric coupling. Our
observations are consistent with the recent polarization switching
measurements, which confirm the low-temperature multiferroic state existing in
highly-lossy Fe$_{3}$O$_{4}$. And the core/shell nanostructure may provide a
new route to achieve applicable magnetoelectric materials with low loss.

###Bilayer manganites: polarons in the midst of a metallic breakdown|F. Massee,S. de Jong. Y. Huang,W. K. Siu,I. Santoso,A. Mans,A. T. Boothroyd,D. Prabhakaran,R. Follath,A. Varykhalov,L. Patthey,M. Shi,J. B. Goedkoop,M. S. Golden###

Bilayer manganites: polarons in the midst of a metallic breakdown. The exact nature of the low temperature electronic phase of the manganite
materials family, and hence the origin of their colossal magnetoresistant (CMR)
effect, is still under heavy debate. By combining new photoemission and
tunneling data, we show that in La{2-2x}Sr{1+2x}Mn2O7 the polaronic degrees of
freedom win out across the CMR region of the phase diagram. This means that the
generic ground state is that of a system in which strong electron-lattice
interactions result in vanishing coherent quasi-particle spectral weight at the
Fermi level for all locations in k-space. The incoherence of the charge
carriers offers a unifying explanation for the anomalous charge-carrier
dynamics seen in transport, optics and electron spectroscopic data. The
stacking number N is the key factor for true metallic behavior, as an
intergrowth-driven breakdown of the polaronic domination to give a metal
possessing a traditional Fermi surface is seen in the bilayer system.

###Coexistence of superconductivity and ferromagnetism in two dimensions|D. A. Dikin,M. Mehta,C. W. Bark,C. M. Folkman,C. B. Eom,V. Chandrasekhar###

Coexistence of superconductivity and ferromagnetism in two dimensions. Ferromagnetism is usually considered to be incompatible with conventional
superconductivity, as it destroys the singlet correlations responsible for the
pairing interaction. Superconductivity and ferromagnetism are known to coexist
in only a few bulk rare-earth materials. Here we report evidence for their
coexistence in a two-dimensional system: the interface between two bulk
insulators, LaAlO$_3$ (LAO) and SrTiO$_3$ (STO), a system that has been studied
intensively recently. Magnetoresistance, Hall and electric-field dependence
measurements suggest that there are two distinct bands of charge carriers that
contribute to the interface conductivity. The sensitivity of properties of the
interface to an electric field make this a fascinating system for the study of
the interplay between superconductivity and magnetism.

###On the origin of non-monotonic doping dependence of the in-plane resistivity anisotropy in Ba(Fe$_{1-x}T_x$)$_2$As$_2$, $T$ = Co, Ni and Cu|Hsueh-Hui Kuo,Jiun-Haw Chu,Scott C. Riggs,Leo Yu,Peter L. McMahon,Kristiaan De Greve,Yoshihisa Yamamoto,James G. Analytis,Ian R. Fisher###

On the origin of non-monotonic doping dependence of the in-plane resistivity anisotropy in Ba(Fe$_{1-x}T_x$)$_2$As$_2$, $T$ = Co, Ni and Cu. The in-plane resistivity anisotropy has been measured for detwinned single
crystals of Ba(Fe$_{1-x}$Ni$_x$)$_2$As$_2$ and Ba(Fe$_{1-x}$Cu$_x$)$_2$As$_2$.
The data reveal a non-monotonic doping dependence, similar to previous
observations for Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$. Magnetotransport measurements
of the parent compound reveal a non-linear Hall coefficient and a strong linear
term in the transverse magnetoresistance. Both effects are rapidly suppressed
with chemical substitution over a similar compositional range as the onset of
the large in-plane resistivity anisotropy. It is suggested that the relatively
small in-plane anisotropy of the parent compound in the spin density wave state
is due to the presence of an isotropic, high mobility pocket of reconstructed
Fermi surface. Progressive suppression of the contribution to the conductivity
arising from this isotropic pocket with chemical substitution eventually
reveals the underlying in-plane anisotropy associated with the remaining FS
pockets.

###Giant Positive Magnetoresistance in Co@CoO Nanoparticle Arrays|Hui Xing,Wenjie Kong,Chaehyun Kim,Sheng Peng,Shouheng Sun,Zhu-An Xu,Hao Zeng###

Giant Positive Magnetoresistance in Co@CoO Nanoparticle Arrays. We report the magnetotransport properties of self-assembled Co@CoO
nanoparticle arrays at temperatures below 100 K. Resistance shows thermally
activated behavior that can be fitted by the general expression of R
exp{(T/T0)^v}. Efros-Shklovskii variable range hopping (v=1/2) and simple
activation (hard gap, v=1) dominate the high and low temperature region,
respectively, with a strongly temperature-dependent transition regime in
between. A giant positive magnetoresistance of >1,400% is observed at 10K,
which decreases with increasing temperature. The positive MR and most of its
features can be explained by the Zeeman splitting of the localized states that
suppresses the spin dependent hopping paths in the presence of on-site Coulomb
repulsion.

###Spin-filtering and Disorder Induced Giant Magnetoresistance in Carbon Nanotubes: Ab Initio Calculations|J. M. de Almeida,A. R. Rocha,A. J. R. da Silva,A. Fazzio###

Spin-filtering and Disorder Induced Giant Magnetoresistance in Carbon Nanotubes: Ab Initio Calculations. Nitrogen-doped carbon nanotubes can provide reactive sites on the
porphyrin-like defects. It's well known that many porphyrins have transition
metal atoms, and we have explored transition metal atoms bonded to those
porphyrin-like defects in N-doped carbon nanotubes. The electronic structure
and transport are analyzed by means of a combination of density functional
theory and recursive Green's functions methods. The results determined the Heme
B-like defect (an iron atom bonded to four nitrogens) as the most stable and
with a higher polarization current for a single defect. With randomly
positioned Heme B-defects in a few hundred nanometers long nanotubes the
polarization reaches near 100% meaning an effective spin filter. A disorder
induced magnetoresistance effect is also observed in those long nanotubes,
values as high as 20000% are calculated with non-magnectic eletrodes.

###Neutron scattering study of magnetic phase separation in nanocrystalline La$_{5/8}$Ca$_{3/8}$MnO$_3$|Chetan Dhital,Clarina de la Cruz,C. Opeil,A. Treat,K. F. Wang,J. -M. Liu,Z. F. Ren,Stephen D. Wilson###

Neutron scattering study of magnetic phase separation in nanocrystalline La$_{5/8}$Ca$_{3/8}$MnO$_3$. We demonstrate that magnetic phase separation and competing spin order in the
colossal magnetoresistive (CMR) manganites can be directly explored via tuning
strain in bulk samples of nanocrystalline La$_{1-x}$Ca$_x$MnO$_3$. Our results
show that strain can be reversibly frozen into the lattice in order to
stabilize coexisting antiferromagnetic domains within the nominally
ferromagnetic metallic state of La$_{5/8}$Ca$_{3/8}$MnO$_3$. The measurement of
tunable phase separation via magnetic neutron powder diffraction presents a
direct route of exploring the correlated spin properties of phase separated
charge/magnetic order in highly strained CMR materials and opens a potential
avenue for realizing intergrain spin tunnel junction networks with enhanced CMR
behavior in a chemically homogeneous material.

###The Kondo effect in magnetic impurities and ferromagnetic contacts|Hyunsoo Yang,See-Hun Yang,Grzegorz Ilnicki,Jan Martinek,Stuart S. P. Parkin###

The Kondo effect in magnetic impurities and ferromagnetic contacts. Planar macroscopic magnetic tunnel junctions exhibit well defined zero bias
anomalies when a thin layer of ferromagnetic CoFe(B) nanodots is inserted
within a MgO based tunnel barrier. The conductance curves exhibit a single and
a double peak, respectively, for anti-parallel and parallel alignment of the
magnetizations of the electrodes which sandwich the tunnel barrier. This leads
to a suppression of the tunneling magnetoresistance near zero bias. We show
that the double peak structure indicates that the zero-bias anomaly is
spin-split due to a magnetic exchange interaction between the magnetic nanodots
and the ferromagnetic electrodes. Using a model based on an Anderson quantum
dot coupled to ferromagnetic leads, we show that these results imply the
coexistence of a Kondo effect and ferromagnetism.

###Enhanced photon-assisted spin transport in a quantum dot attached to ferromagnetic leads|Fabricio M. Souza,Thiago L. Carrara,E. Vernek###

Enhanced photon-assisted spin transport in a quantum dot attached to ferromagnetic leads. We investigate real-time dynamics of spin-polarized current in a quantum dot
coupled to ferromagnetic leads in both parallel and antiparallel alignments.
While an external bias voltage is taken constant in time, a gate terminal,
capacitively coupled to the quantum dot, introduces a periodic modulation of
the dot level. Using non equilibrium Green's function technique we find that
spin polarized electrons can tunnel through the system via additional
photon-assisted transmission channels. Owing to a Zeeman splitting of the dot
level, it is possible to select a particular spin component to be
photon-transfered from the left to the right terminal, with spin dependent
current peaks arising at different gate frequencies. The ferromagnetic
electrodes enhance or suppress the spin transport depending upon the leads
magnetization alignment. The tunnel magnetoresistance also attains negative
values due to a photon-assisted inversion of the spin-valve effect.

###Effect of Fe substitution on the magnetic, transport, thermal and magnetocaloric properties in Ni50Mn38-xFexSb12 Heusler alloys|Roshnee Sahoo,Ajaya K. Nayak,K. G. Suresh,A. K. Nigam###

Effect of Fe substitution on the magnetic, transport, thermal and magnetocaloric properties in Ni50Mn38-xFexSb12 Heusler alloys. The structural, magnetic, transport, thermal and magnetothermal properties of
quaternary Heusler alloys Ni50Mn38-xFexSb12 have been studied. Powder x-ray
diffraction and temperature dependence of magnetization studies reveal that
with addition of Fe in Mn site, the martensitic transition shifts to lower
temperatures. It is also found that the martensitic transition becomes broader
for the higher Fe concentrations. The metamagnetic transition in M(H) isotherms
becomes very prominent in x=2 and vanishes for x=3 and 4. A maximum positive
magnetic entropy change of 14.2 J/kg K is observed for x=2 at 288 K for 50 kOe.
Resistivity shows an abrupt decrease across the martensitic transition in all
the alloys, except x=6, which does not have the martensitic transition. Maximum
negative magnetoresistance of 21% has been obtained for x=2 at 50 kOe. The same
alloy also shows an exchange bias field of 288 Oe.

###A Feedback Spin-Valve Memristive System|Weiran Cai,Torsten Schmidt,Udo Jörges,Frank Ellinger###

A Feedback Spin-Valve Memristive System. We propose theoretically a generalized memristive system based on controlled
spin polarizations in the giant magnetoresistive material using a feedback loop
with the classical Hall Effect. The dynamics can exhibit a memristive pinched
hysteretic loop that possesses the self-crossing knot not located at the
origin. Additionally, one can also observe a single-looped orbit in the device.
We also provide a sufficient condition for the stability based on an estimation
of the Floquet exponent. The analysis shows that the non-origin-crossing
dynamics is generally permitted in a class of passive memory systems that are
not subject to Ohm's Law. We further develop the prevailing homogeneous
definition to a broadened concept of generalized heterogeneous memristive
systems, permitting no self-crossing knot at the origin, and ultimately to the
compound memory electronic systems.

###Fourfold Symmetry of Anisotropic Magnetoresistance in Epitaxial Fe3O4 Thin Films|C. R. Hu,J. Zhu,G. Chen,J. X. Li,Y. Z. Wu###

Fourfold Symmetry of Anisotropic Magnetoresistance in Epitaxial Fe3O4 Thin Films. We studied the angular dependence of anisotropic magnetoresistance (AMR) and
Planar Hall effect (PHE) at various temperatures in high quality epitaxial
Fe3O4 films grown on MgO(001) substrates. The PHE contains only a twofold
angular dependence, but the AMR below 200K is constituted with both twofold and
fourfold symmetric terms. A quantitative fitting based on a phenomenological
model indicates the nonmonotonics temperature dependence of the twofold
component of AMR can be ascribed to the competition between the term and the
term. A unidirectional component was observed in the angular dependent AMR. The
fourfold symmetric AMR also existed for the magnetic field rotating in the
plane perpendicular to the current. Our results indicate the AMR and PHE in
single crystalline films have different origins, and also prove that the origin
of the four-fold symmetry of AMR is related to the lattice symmetry rather than
the spin scattering near the antiphase boundaries.

###Current induced anisotropic magnetoresistance in topological insulator films|Jian Wang,Handong Li,Cui-Zu Chang,Ke He,Joon Sue Lee,Xu-Cun Ma,Nitin Samarth,Qi-Kun Xue,Maohai Xie,M. H. W. Chan###

Current induced anisotropic magnetoresistance in topological insulator films. Topological insulators are insulating in the bulk but possess spin-momentum
locked metallic surface states protected by time-reversal symmetry. The
existence of these surface states has been confirmed by angle-resolved
photoemission spectroscopy (ARPES) and scanning tunneling microscopy (STM).
Detecting these surface states by transport measurement, which might at first
appear to be the most direct avenue, was shown to be much more challenging than
expected. Here, we report a detailed electronic transport study in high quality
Bi2Se3 topological insulator thin films. Measurements under in-plane magnetic
field, along and perpendicular to the bias current show opposite
magnetoresistance. We argue that this contrasting behavior is related to the
locking of the spin and current direction providing evidence for helical spin
structure of the topological surface states.

###Electrical measurement of antiferromagnetic moments in exchange-coupled IrMn/NiFe stacks|X. Marti,B. G. Park,J. Wunderlich,H. Reichlova,Y. Kurosaki,M. Yamada,H. Yamamoto,A. Nishide,J. Hayakawa,H. Takahashi,T. Jungwirth###

Electrical measurement of antiferromagnetic moments in exchange-coupled IrMn/NiFe stacks. We employ the recently discovered antiferromagnetic tunneling anisotropic
magnetoresistance to study the behavior of antiferromagnetically ordered
moments in IrMn exchange coupled to NiFe. Experiments performed by common
laboratory tools for magnetization and electrical transport measurements allow
us to directly link the broadening of the NiFe hysteresis loop and its shift
(exchange bias) to the rotation and pinning of antiferromagnetic moments in
IrMn. At higher temperatures, the broadened loops show zero shift which
correlates with the observation of fully rotating antiferromagnetic moments
inside the IrMn film. The onset of exchange bias at lower temperatures is
linked to a partial rotation between distinct metastable states and pinning of
the IrMn antiferromagnetic moments in these states. The observation complements
common pictures of exchange bias and reveals the presence of an electrically
measurable memory effect in an antiferromagnet.

###Magneto-optical imaging of voltage-controlled magnetization reorientation|A. Brandlmaier,M. Brasse,S. Geprägs,M. Weiler,R. Gross,S. T. B. Goennenwein###

Magneto-optical imaging of voltage-controlled magnetization reorientation. We study the validity and limitations of a macrospin model to describe the
voltage-controlled manipulation of ferromagnetic magnetization in nickel thin
film/piezoelectric actuator hybrid structures. To this end, we correlate
simultaneously measured spatially resolved magneto-optical Kerr effect imaging
and integral magnetotransport measurements at room temperature. Our results
show that a macrospin approach is adequate to model the magnetoresistance as a
function of the voltage applied to the hybrid, except for a narrow region
around the coercive field - where the magnetization reorientation evolves via
domain effects. Thus, on length scales much larger than the typical magnetic
domain size, the voltage control of magnetization is well reproduced by a
simple Stoner-Wohlfarth type macrospin model.

###Microwave-induced resistance oscillations and zero-resistance states in 2D electron systems with two occupied subbands|Jesus Inarrea,Gloria Platero###

Microwave-induced resistance oscillations and zero-resistance states in 2D electron systems with two occupied subbands. We report on theoretical studies of recently discovered microwave-induced
resistance oscillations and zero resistance states in Hall bars with two
occupied subbands. In the same results, resistance presents a peculiar shape
which appears to have a built-in interference effect not observed before. We
apply the microwave-driven electron orbit model, which implies a
radiation-driven oscillation of the two-dimensional electron system. Thus, we
calculate different intra and inter-subband electron scattering rates and times
that are revealing as different microwave-driven oscillations frequencies for
the two electronic subbands. Through scattering, these subband-dependent
oscillation motions interfere giving rise to a striking resistance profile. We
also study the dependence of irradiated magnetoresistance with power and
temperature. Calculated results are in good agreement with experiments.

###Field-Tuned Superconductor-Insulator Transition in BaPb1-xBixO3|P. Giraldo-Gallo,H. Lee,Y. Zhang,M. J. Kramer,M. R. Beasley,T. H. Geballe,I. R. Fisher###

Field-Tuned Superconductor-Insulator Transition in BaPb1-xBixO3. BaPb$_{1-x}$Bi$_x$O$_3$ is found to exhibit a field-tuned superconductor to
insulator transition for Bi compositions 0.24 $\leq x \leq$ 0.29. The
magnetoresistance of optimally doped samples manifests a
temperature-independent crossing point and scaling of the form
$\rho(T,H)=\rho_c F(|H-H_{c}|T^{-1/z\nu})$, where $H_c$ is the field determined
by the temperature-independent crossing point, and $z\nu$ = 0.69 $\pm$ 0.03.
High resolution transmission electron microscopy measurements reveal a complex
intergrown nanostructure comprising tetragonal and orthorhombic polymorphs.
Data are analyzed in terms of both a classical effective medium theory and a
field-tuned quantum phase transition, neither of which provides a completely
satisfactory explanation for this remarkable phenomenology.

###Reversible room-temperature ferromagnetism in Nb-doped SrTiO3 single crystals|Z. Q. Liu,W. M. Lu,S. L. Lim,X. P. Qiu,N. N. Bao,M. Motapothula,J. B. Yi,M. Yang,S. Dhar,T. Venkatesan,Ariando###

Reversible room-temperature ferromagnetism in Nb-doped SrTiO3 single crystals. The search for oxide-based room-temperature ferromagnetism has been one of
the holy grails in condensed matter physics. Room-temperature ferromagnetism
observed in Nb-doped SrTiO3 single crystals is reported in this Rapid
Communication. The ferromagnetism can be eliminated by air annealing (making
the samples predominantly diamagnetic) and can be recovered by subsequent
vacuum annealing. The temperature dependence of magnetic moment resembles the
temperature dependence of carrier density, indicating that the magnetism is
closely related to the free carriers. Our results suggest that the
ferromagnetism is induced by oxygen vacancies. In addition, hysteretic
magnetoresistance was observed for magnetic field parallel to current,
indicating that the magnetic moments are in the plane of the samples. The x-ray
photoemission spectroscopy, the static time-of-flight and the dynamic secondary
ion mass spectroscopy and proton induced x-ray emission measurements were
performed to examine magnetic impurities, showing that the observed
ferromagnetism is unlikely due to any magnetic contaminant.

###Giant resistance change across the phase transition in spin crossover molecules|N. Baadji,S. Sanvito###

Giant resistance change across the phase transition in spin crossover molecules. The electronic origin of a large resistance change in nanoscale junctions
incorporating spin crossover molecules is demonstrated theoretically by using a
combination of density functional theory and the non-equilibrium Green's
functions method for quantum transport. At the spin crossover phase transition
there is a drastic change in the electronic gap between the frontier molecular
orbitals. As a consequence, when the molecule is incorporated in a two terminal
device, the current increases by up to four orders of magnitude in response to
the spin change. This is equivalent to a magnetoresistance effect in excess of
3,000 %. Since the typical phase transition critical temperature for spin
crossover compounds can be extended to well above room temperature, spin
crossover molecules appear as the ideal candidate for implementing spin devices
at the molecular level.

###Huge First-Order Metamagnetic Transition in the Paramagnetic Heavy-Fermion System CeTiGe|Micha Deppe,Stefan Lausberg,Franziska Weickert,Manuel Brando,Yurii Skourski,Nubia Caroca-Canales,Chistoph Geibel,Frank Steglich###

Huge First-Order Metamagnetic Transition in the Paramagnetic Heavy-Fermion System CeTiGe. We report on the observation of large, step-like anomalies in the
magnetization ($\Delta M = 0.74$\,$\mu_{\rm B}$/Ce), in the magnetostriction
($\Delta l/l_{0} = 2.0 \cdot 10^{-3}$), and in the magnetoresistance in
polycrystals of the paramagnetic heavy-fermion system CeTiGe at a critical
magnetic field $\mu_0 H_c \approx $ 12.5\,T at low temperatures. The size of
these anomalies is much larger than those reported for the prototypical
heavy-fermion metamagnet CeRu$_2$Si$_2$. Furthermore, hysteresis between
increasing and decreasing field data indicate a real thermodynamic, first-order
type of phase transition, in contrast to the crossover reported for
CeRu$_2$Si$_2$. Analysis of the resistivity data shows a pronounced decrease of
the electronic quasiparticle mass across $H_c$. These results establish CeTiGe
as a new metamagnetic Kondo-lattice system, with an exceptionally large,
metamagnetic transition of first-order type at a moderate field.

###Magnetoresistance and negative differential resistance in Ni/Graphene/Ni vertical heterostructures driven by finite bias voltage: A first-principles study|Kamal K. Saha,Anders Blom,Kristian S. Thygesen,Branislav K. Nikolic###

Magnetoresistance and negative differential resistance in Ni/Graphene/Ni vertical heterostructures driven by finite bias voltage: A first-principles study. Using the nonequilibrium Green function formalism combined with density
functional theory, we study finite-bias quantum transport in Ni/Gr_n/Ni
vertical heterostructures where $n$ graphene layers are sandwiched between two
semi-infinite Ni(111) electrodes. We find that recently predicted "pessimistic"
magnetoresistance of 100% for $n \ge 5$ junctions at zero bias voltage $V_b
\rightarrow 0$, persists up to $V_b \simeq 0.4$ V, which makes such devices
promising for spin-torque-based device applications. In addition, for parallel
orientations of the Ni magnetizations, the $n=5$ junction exhibits a pronounced
negative differential resistance as the bias voltage is increased from $V_b=0$
V to $V_b \simeq 0.5$ V. We confirm that both of these nonequilibrium effects
hold for different types of bonding of Gr on the Ni(111) surface while
maintaining Bernal stacking between individual Gr layers.

###Observation of Huge Magnetoresistance and Multiferroic-like Behavior of Co Nanoparticles in a C60 matrix|Yutaka Sakai,Eiiti Tamura,Shuhei Toyokawa,Eiji Shikoh,Vlado K. Lazarov,Atsufumi Hirohata,Teruya Shinjo,Yoshishige Suzuki,Masashi Shiraishi###

Observation of Huge Magnetoresistance and Multiferroic-like Behavior of Co Nanoparticles in a C60 matrix. Tunneling magnetoresistance (TMR) via oxides or molecules includes fruitful
physics, such as spin filtering and hybridized interface states, in addition to
various practical applications using large TMR ratio at room temperature. Then,
a larger TMR effect with a new fundamental physics is awaited because further
progress on spintronics can be realized. Here we report a discovery of a
gigantic TMR ratio of 1,400,000% in a C60-Co nanocomposite spin device. The
observed effect is induced by a combination of a Coulomb blockade effect and a
novel magnetic switching effect. Theoretical investigation reveals that an
electric field and a magnetic field control the magnetization and the
electronic charging state, respectively, of the Co nanoparticles as in physics
of multiferroicity.

###Coexistance of giant tunneling electroresistance and magnetoresistance in an all-oxide magnetic tunnel junction|Nuala Mai Caffrey,Thomas Archer,Ivan Rungger,Stefano Sanvito###

Coexistance of giant tunneling electroresistance and magnetoresistance in an all-oxide magnetic tunnel junction. We demonstrate with first-principles electron transport calculations that
large tunneling magnetoresistance (TMR) and tunneling electroresistance (TER)
effects can coexist in an all-oxide device. The TMR originates from the
symmetry-driven spin filtering provided by the insulating BaTiO3 barrier to the
electrons injected from SrRuO3. In contrast the TER is possible only when a
thin SrTiO3 layer is intercalated at one of the SrRuO3/BaTiO3 interfaces. As
the complex band-structure of SrTiO3 has the same symmetry than that of BaTiO3,
the inclusion of such an intercalated layer does not negatively alter the TMR
and in fact increases it. Crucially, the magnitude of the TER also scales with
the thickness of the SrTiO3 layer. The SrTiO3 thickness becomes then a single
control parameter for both the TMR and the TER effect. This protocol offers a
practical way to the fabrication of four-state memory cells.

###Quantum-fluctuation effects in transport properties of superconductors above the paramagnetic limit|M. Khodas,A. Levchenko,G. Catelani###

Quantum-fluctuation effects in transport properties of superconductors above the paramagnetic limit. We study the transport in ultrathin disordered film near the quantum critical
point induced by the Zeeman field. We calculate corrections to the normal state
conductivity due to quantum pairing fluctuations. The fluctuation-induced
transport is mediated by virtual rather than real quasi-particles. We find that
at zero temperature, where the corrections come from purely quantum
fluctuations, the Aslamazov-Larkin paraconductivity term, the Maki-Thompson
interference contribution and the density of states effects are all of the same
order. The total correction leads to the negative magnetoresistance. This
result is in qualitative agreement with the recent transport observations in
the parallel magnetic field of the homogeneously disordered amorphous films and
superconducting two-dimensional electron gas realized at the oxide interfaces.

###Analogy of RKKY oscillations to the heat exchange in cold atoms|Ching-Hao Chang,Tzay-Ming Hong###

Analogy of RKKY oscillations to the heat exchange in cold atoms. An oscillatory term is found in both the energy expectation and dynamics of a
wave-packet in a time-varying harmonic trap and infinite potential well. They
are proved to oscillate in coherence with the time lapse within each period
depending on both the cutoff in transition energies and the specific route via
which the potential is being varied. This oscillatory term is general to
arbitrary potential forms since it derives from the interference between
crossed transition trajectories. Close analogy is made to the
Ruderman-Kittel-Kasuya-Yosida interaction for giant-magnetoresistance
trilayers, where many-body quantum interference among scattering states renders
the oscillation as a function of spacer width. This connection reveals the
generality of quantum friction due to parasitic oscillations.

###Crystalline anisotropic magnetoresistance with two-fold and eight-fold symmetry in (In,Fe)As ferromagnetic semiconductor|Pham Nam Hai,Daisuke Sasaki,Le Duc Anh,Masaaki Tanaka###

Crystalline anisotropic magnetoresistance with two-fold and eight-fold symmetry in (In,Fe)As ferromagnetic semiconductor. We have investigated the anisotropic magnetoresistance (AMR) of (In,Fe)As
ferromagnetic semiconductor (FMS) layers grown on semi-insulating GaAs
substrates. In a 10 nm-thick (In,Fe)As layer which is insulating at low
temperature, we observed crystalline AMR with two-fold and eight-fold
symmetries. In a metallic 100 nm-thick (In,Fe)As layer with higher electron
concentration, only two-fold symmetric crystalline AMR was observed. Our
results demonstrate the macroscopic ferromagnetism in (In,Fe)As with magnetic
anisotropy that depends on the electron concentration. Non-crystalline AMR is
also observed in the 100 nm-thick layer, but its magnitude is as small as
10^-5, suggesting that there is no s-d scattering near the Fermi level of
(In,Fe)As. We propose the origin of the eight-fold symmetric crystalline
anisotropy in (In,Fe)As.

###Phase Stability, Structures and Properties of the (Bi2)m(Bi2Te3)n Natural Superlattices|J. -W. G. Bos,F. Faucheux,R. A. Downie,A. Marcinkova###

Phase Stability, Structures and Properties of the (Bi2)m(Bi2Te3)n Natural Superlattices. The phase stability of the (Bi2)m(Bi2Te3)n natural superlattices has been
investigated through the low temperature solid state synthesis of a number of
new binary BixTe1-x compositions. Powder X-ray diffraction revealed that an
infinitely adaptive series forms for 0.44 < x < 0.70, while an unusual 2-phase
region with continuously changing compositions is observed for 0.41 < x < 0.43.
For x > 0.70, mixtures of elemental Bi and an almost constant composition
(Bi2)m(Bi2Te3)n phase are observed. Rietveld analysis of synchrotron X-ray
powder diffraction data collected on Bi2Te (m = 2, n = 1) revealed substantial
interchange of Bi and Te between the Bi2 and Bi2Te3 blocks, demonstrating that
the block compositions are variable. All investigated phase pure compositions
are degenerate semiconductors with low residual resistivity ratios and moderate
positive magnetoresistances (R/R0 = 1.05 in 9 T). The maximum Seebeck
coefficient is +80 muV K-1 for x = 0.63, leading to an estimated thermoelectric
figure of merit, zT = 0.2 at 250 K.

###Electron transport in a ferromagnetic/normal/ferromagnetic tunnel junction based on the surface of a topological insulator|Jian-Hui Yuan,Yan Zhang,Jian-Jun Zhang,Ze Cheng###

Electron transport in a ferromagnetic/normal/ferromagnetic tunnel junction based on the surface of a topological insulator. We theoretically study the electron transport properties in a
ferromagnetic/normal/ferromagnetic tunnel junction, which is deposited on the
top of a topological surface. The conductance at the parallel (\textbf{P})
configuration can be much bigger than that at the antiparallel (\textbf{AP})
configuration. Compared \textbf{P} with \textbf{AP} configuration, there exists
a shift of phase which can be tuned by gate voltage. We find that the exchange
field weakly affects the conductance of carriers for \textbf{P} configuration
but can dramatically suppress the conductance of carriers for \textbf{AP}
configuration. This controllable electron transport implies anomalous
magnetoresistance in this topological spin valve, which may contribute to the
development of spintronics . In addition, we find that there is a
Fabry-Perot-like electron interference.

###Carrier-controlled ferromagnetism in SrTiO3|Pouya Moetakef,James R. Williams,Daniel G. Ouellette,Adam Kajdos,David Goldhaber-Gordon,S. James Allen,Susanne Stemmer###

Carrier-controlled ferromagnetism in SrTiO3. Magnetotransport and superconducting properties are investigated for
uniformly La-doped SrTiO3 films and GdTiO3/SrTiO3 heterostructures,
respectively. GdTiO3/SrTiO3 interfaces exhibit a high-density two-dimensional
electron gas on the SrTiO3-side of the interface, while for the SrTiO3 films
carriers are provided by the dopant atoms. Both types of samples exhibit
ferromagnetism at low temperatures, as evidenced by a hysteresis in the
magnetoresistance. For the uniformly doped SrTiO3 films, the Curie temperature
is found to increase with doping and to coexist with superconductivity for
carrier concentrations on the high-density side of the superconducting dome.
The Curie temperature of the GdTiO3/SrTiO3 heterostructures scales with the
thickness of the SrTiO3 quantum well. The results are used to construct a
stability diagram for the ferromagnetic and superconducting phases of SrTiO3.

###Magnetoresistivity in a Tilted Magnetic Field in p-Si/SiGe/Si Heterostructures with an Anisotropic g-Factor: Part II|I. L. Drichko,I. Yu. Smirnov,A. V. Suslov,O. A. Mironov,D. R. Leadley###

Magnetoresistivity in a Tilted Magnetic Field in p-Si/SiGe/Si Heterostructures with an Anisotropic g-Factor: Part II. The magnetoresistance components $\rho_{xx}$ and $\rho_{xy}$ were measured in
two p-Si/SiGe/Si quantum wells that have an anisotropic g-factor in a tilted
magnetic field as a function of temperature, field and tilt angle. Activation
energy measurements demonstrate the existence of a ferromagnetic-paramagnetic
(F-P) transition for a sample with a hole density of
$p$=2$\times10^{11}$\,cm$^{-2}$. This transition is due to crossing of the
0$\uparrow$ and 1$\downarrow$ Landau levels. However, in another sample, with
$p$=7.2$\times10^{10}$\,cm$^{-2}$, the 0$\uparrow$ and 1$\downarrow$ Landau
levels coincide for angles $\Theta$=0-70$^{\text{o}}$. Only for $\Theta$ >
70$^{\text{o}}$ do the levels start to diverge which, in turn, results in the
energy gap opening.

###Metamagnetic transition in Ca$_{1-x}$Sr$_x$Co$_2$As$_2$($x$ = 0 and 0.1) single crystals|J. J. Ying,Y. J. Yan,A. F. Wang,Z. J. Xiang,P. Cheng,G. J. Ye,X. H. Chen###

Metamagnetic transition in Ca$_{1-x}$Sr$_x$Co$_2$As$_2$($x$ = 0 and 0.1) single crystals. We report the magnetism and transport measurements of CaCo$_2$As$_2$ and
Ca$_{0.9}$Sr$_{0.1}$Co$_2$As$_2$ single crystals. Antiferromagnetic transition
was observed at about 70 K and 90 K for CaCo$_2$As$_2$ and
Ca$_{0.9}$Sr$_{0.1}$Co$_2$As$_2$, respectively. Magnetism and magnetoresistance
measurements reveal metamagnetic transition from an antiferromagnetic state to
a ferromagnetic state with the critical field of 3.5 T and 1.5 T respectively
along c-axis for these two materials at low temperature. For the field along
ab-plane, spins can also be fully polarized above the field of 4.5 T for
Ca$_{0.9}$Sr$_{0.1}$Co$_2$As$_2$. While for CaCo$_2$As$_2$, spins can not be
fully polarized up to 7 T. We proposed the cobalt moments of these two
materials should be ordered ferromagnetically within the ab-plane but
antiferromagnetically along the c-axis(A-type AFM).

###Magnetic-field induced resistivity minimum with in-plane linear magnetoresistance of the Fermi liquid in SrTiO3-x single crystals|Z. Q. Liu,W. M. Lü,X. Wang,Z. Huang,A. Annadi,S. W. Zeng,T. Venkatesan,Ariando###

Magnetic-field induced resistivity minimum with in-plane linear magnetoresistance of the Fermi liquid in SrTiO3-x single crystals. We report novel magnetotransport properties of the low temperature Fermi
liquid in SrTiO3-x single crystals. The classical limit dominates the
magnetotransport properties for a magnetic field perpendicular to the sample
surface and consequently a magnetic-field induced resistivity minimum emerges.
While for the field applied in plane and normal to the current, the linear
magnetoresistance (MR) starting from small fields (< 0.5 T) appears. The large
anisotropy in the transverse MRs reveals the strong surface interlayer
scattering due to the large gradient of oxygen vacancy concentration from the
surface to the interior of SrTiO3-x single crystals. Moreover, the linear MR in
our case was likely due to the inhomogeneity of oxygen vacancies and oxygen
vacancy clusters, which could provide experimental evidences for the unusual
quantum linear MR proposed by Abrikosov [A. A. Abrikosov, Phys. Rev. B 58, 2788
(1998)].

###Gap like structure in a nonsuperconducting layered oxycarbonate Bi$_{2+x}$Sr$_{4-x}$Cu$_2$CO$_3$O$_{8+δ}$ single crystal|S. I. Vedeneev,B. A. Piot,D. K. Maude###

Gap like structure in a nonsuperconducting layered oxycarbonate Bi$_{2+x}$Sr$_{4-x}$Cu$_2$CO$_3$O$_{8+δ}$ single crystal. The magnetic field and temperature dependence of the in-plane tunneling
conductance $dI/dV(V)$ in high-quality nonsuperconducting (down to 10 mK)
layered oxycarbonate Bi$_{2+x}$Sr$_{4-x}$Cu$_2$CO$_3$O$_{8+\delta}$ single
crystals has been investigated using break junctions. Combining measurements of
the in-plane magnetoresistivity $\rho_{ab}(T,H)$ and the magnetotunneling, we
present evidence for the existence of a small "pseudogap" in a
nonsuperconducting cuprate, without local incoherent pairs or any correlation
phenomena associated with superconductivity. We are unable to distinguish if
such a "pseudogap" is totally unrelated to superconductivity or if its
existence is a necessary condition for the subsequent occurrence of
superconductivity with increasing carrier density in the sample.

###How branching can change the conductance of ballistic semiconductor devices|D. Maryenko,J. J. Metzger,F. Ospald,V. Umansky,R. Fleischmann,T. Geisel,K. von Klitzing,J. H. Smet###

How branching can change the conductance of ballistic semiconductor devices. We demonstrate that branching of the electron flow in semiconductor
nanostructures can strongly affect macroscopic transport quantities and can
significantly change their dependence on external parameters compared to the
ideal ballistic case even when the system size is much smaller than the mean
free path. In a corner-shaped ballistic device based on a GaAs/AlGaAs
two-dimensional electron gas we observe a splitting of the commensurability
peaks in the magnetoresistance curve. We show that a model which includes a
random disorder potential of the two-dimensional electron gas can account for
the random splitting of the peaks that result from the collimation of the
electron beam. The shape of the splitting depends on the particular realization
of the disorder potential. At the same time magnetic focusing peaks are largely
unaffected by the disorder potential.

###Structural transitions and transport-half-metallic ferromagnetism in LaMnO3 at elevated pressure|J. He,M. -X. Chen,X. -Q Chen,C. Franchini###

Structural transitions and transport-half-metallic ferromagnetism in LaMnO3 at elevated pressure. By means of hybrid density functional theory we investigate the evolution of
the structural, electronic and magnetic properties of the colossal
magnetoresistance (CMR) parent compound LaMnO$_3$ under pressure. We predict a
transition from a low pressure antiferromagnetic (AFM) insulator to a high
pressure ferromagnetic (FM) transport half-metal (tHM), characterized by a
large spin polarization (~ 80-90 %). The FM-tHM transition is associated with a
progressive quenching of the cooperative Jahn-Teller (JT) distortions which
transform the $Pnma$ orthorhombic phase into a perfect cubic one (through a
mixed phase in which JT-distorted and regular MnO6 octahedra coexist), and with
a high-spin (S=2, m_Mn=3.7 mu_B) to low-spin (S=1, m_Mn=1.7 mu_B) magnetic
moment collapse. These results interpret the progression of the experimentally
observed non-Mott metalization process and open up the possibility of realizing
CMR behaviors in a stoichiometric manganite.

###Reply to Comment on "High-field studies of superconducting fluctuations in high-Tc cuprates: Evidence for a small gap distinct from the large pseudogap" by M.V. Ramallo et al|F. Rullier-Albenque,H. Alloul,G. Rikken###

Reply to Comment on "High-field studies of superconducting fluctuations in high-Tc cuprates: Evidence for a small gap distinct from the large pseudogap" by M.V. Ramallo et al. The experimental investigations done in our paper Phys.Rev.B84,014522(2011)
allowed us to establish that the superconducting fluctuations (SCF) always die
out sharply with increasing T. But contrary to the claim done in the comment of
Ramallo et al., this sharp cutoff of SCF measured in YBa2Cu3O{6+x} depends on
hole doping and/or disorder. So our data cannot be used to claim for a
universality of the extended gaussian Ginzburg Landau theory proposed by the
authors of the comment. Furthermore, to explain quantitatively our data near
optimal doping using this model they need to consider that fluctuations in the
two CuO2 planes of a bilayer are totally decoupled, which is not physically
well justified. On the contrary a consistent interpretation of all our data
(paraconductivity, Nernst effect and magnetoresistance) has been done by
considering that the coupling between the two layers of the unit cell is
dominant at least up to 1.1Tc.

###Hall effect characterization of electronic transition behind the metamagnetic transition in FeRh|M. A. de Vries,M. L. Loving,A. P. Mihai,L. H. Lewis,D. Heiman,C. H. Marrows###

Hall effect characterization of electronic transition behind the metamagnetic transition in FeRh. The antiferromagnetic ground state and the metamagnetic transition to the
ferromagnetic state of CsCl-ordered FeRh epilayers have been characterized
using Hall and magnetoresistance measure- ments. On cooling into the ground
state, the metamagnetic transition is found to coincide with a suppression in
carrier density of at least an order of magnitude below the typical metallic
level shown by the ferromagnetic state. The data reveal that this sub-metallic
density of electron-like majority carriers in the antiferromagnetic phase are
attributable to intrinsic doping from Fe/Rh substitution defects, with
approximately two electrons per pair of atoms swapped. Based on these
observations it is suggested that an orbital selective Mott transition,
selective to the Fe 3d electrons drives the metamagnetic transition.

###Tunnelling anisotropic magnetoresistance of Fe/GaAs/Ag(001) junctions from first principles: Effect of hybridized interface resonances|Rudolf Sykora,Ilja Turek###

Tunnelling anisotropic magnetoresistance of Fe/GaAs/Ag(001) junctions from first principles: Effect of hybridized interface resonances. Results of first-principles calculations of the Fe/GaAs/Ag(001) epitaxial
tunnel junctions reveal that hybridization of interface resonances formed at
both interfaces can enhance the tunnelling anisotropic magnetoresistance (TAMR)
of the systems. This mechanism is manifested by a non-monotonic dependence of
the TAMR effect on the thickness of the tunnel barrier, with a maximum for
intermediate thicknesses. A detailed scan of k-resolved transmissions over the
two-dimensional Brillouin zone proves an interplay between a few
hybridization-induced hot spots and a contribution to the tunnelling from the
vicinity of the Gamma-bar point. This interpretation is supported by calculated
properties of a simple tight-binding model of the junction which reproduce
qualitatively most of the features of the first-principles theory.

###Coulomb gap triptychs, $\sqrt{2}$ effective charge, and hopping transport in periodic arrays of superconductor grains|Tianran Chen,Brian Skinner,B. I. Shklovskii###

Coulomb gap triptychs, $\sqrt{2}$ effective charge, and hopping transport in periodic arrays of superconductor grains. In granular superconductors, individual grains can contain bound Cooper pairs
while the system as a whole is strongly insulating. In such cases the
conductivity is determined by electron hopping between localized states in
individual grains. Here we examine a model of hopping conductivity in such an
insulating granular superconductor, where disorder is assumed to be provided by
random charges embedded in the insulating gaps between grains. We use computer
simulations to calculate the single-electron and electron pair density of
states at different values of the superconducting gap $\Delta$, and we identify
"triptych" symmetries and scaling relations between them. At a particular
critical value of $\Delta$, one can define an effective charge $\sqrt{2}e$ that
characterizes the density of states and the hopping transport. We discuss the
implications of our results for magnetoresistance and tunneling experiments.

###Multiorbital effects on the transport and the superconducting fluctuations in LiFeAs|F. Rullier-Albenque,D. Colson,A. Forget,H. Alloul###

Multiorbital effects on the transport and the superconducting fluctuations in LiFeAs. The resistivity, Hall effect and transverse magnetoresistance (MR) have been
measured in low residual resistivity single crystals of LiFeAs. A comparison
with angle resolved photoemission spectroscopy and quantum oscillation data
implies that four carrier bands unevenly contribute to the transport. However
the scattering rates of the carriers all display the T^2 behavior expected for
a Fermi liquid. Near Tc low field deviations of the MR with respect to a H^2
variation permit us to extract the superconducting fluctuation contribution to
the conductivity. Though below Tc the anisotropy of superconductivity is rather
small, the superconducting fluctuations display a quasi ideal two-dimensional
behavior which persists up to 1.4 Tc. These results call for a refined
theoretical understanding of the multiband behavior of superconductivity in
this pnictide.

###Oscillatory tunneling magnetoresistance in magnetic tunnel junctions with inserted nonmagnetic layer|Changsik Choi,Byung Chan Lee###

Oscillatory tunneling magnetoresistance in magnetic tunnel junctions with inserted nonmagnetic layer. Oscillatory tunneling magnetoresistance (TMR) as a function of spacer
thickness is investigated theoretically for a magnetic tunnel junction with a
nonmagnetic layer inserted between the tunnel barrier and the ferromagnetic
layer. TMR is characterized in an analytical form, that is expressed with the
transmission and reflection amplitudes of single interfaces at the Fermi level,
and by the extremal wavevectors. Electronic structures with multiple bands are
taken into account in the derivation characterizing the TMR, and the proposed
analytical expression can be directly applied to real junctions. Based on our
model, the features of TMR dependence on spacer thickness are discussed,
including selection rules for the oscillation period. Numerical calculations
are performed using an envelope-function theory for several cases, and we show
that our model is in good agreement with the exact result.

###Large Magnetoresistance Oscillations in Mesoscopic Superconductors Due to Current-Excited Moving Vortices|G. R. Berdiyorov,M. V. Milošević,M. L. Latimer,Z. L. Xiao,W. K. Kwok,F. M. Peeters###

Large Magnetoresistance Oscillations in Mesoscopic Superconductors Due to Current-Excited Moving Vortices. We show in the case of a superconducting Nb ladder that a mesoscopic
superconductor typically exhibits magnetoresistance oscillations whose
amplitude and temperature dependence are different from those stemming from the
Little-Parks effect. We demonstrate that these large resistance oscillations
(as well as the monotonic background on which they are superimposed) are due to
{\it current-excited moving vortices}, where the applied current in competition
with the oscillating Meissner currents imposes/removes the barriers for vortex
motion in increasing magnetic field. Due to the ever present current in
transport measurements, this effect should be considered in parallel with the
Little-Parks effect in low-$T_c$ samples, as well as with recently proposed
thermal activation of dissipative vortex-antivortex pairs in high-$T_c$
samples.

###A variable temperature study of the crystal and magnetic structures of the giant magnetoresistant materials LnMnAsO (Ln = La, Nd)|N. Emery,E. J. Wildman,J. M. S. Skakle,R. I. Smith,A. N. Fitch,A. C. Mclaughlin###

A variable temperature study of the crystal and magnetic structures of the giant magnetoresistant materials LnMnAsO (Ln = La, Nd). A variable temperature neutron and synchrotron diffraction study have been
performed on the giant magnetoresistant oxypnictides LnMnAsO (Ln = La, Nd). The
low temperature magnetic structures have been studied and results show a spin
reorientation of the Mn2+ spins below TN (Nd) for NdMnAsO. The Mn2+ spins
rotate from alignment along c to alignment into the basal plane and the Mn2+
and Nd3+ moments refine to 3.54(4) \mu B and 1.93(4) \mu B respectively at 2 K.
In contrast there is no change in magnetic structure with temperature for
LaMnAsO. There is no evidence of a structural transition down to 2 K, however
discontinuities in the cell volume, Ln-O and Mn-As bond lengths are detected at
\sim 150 K for both materials. This temperature coincides with the electronic
transition previously reported and suggests a coupling between electronic and
lattice degrees of freedom.

###A MuSR study of the magnetoresistive ruthenocuprates RuSr2Nd1.8-xY0.2CexCu2O_{10-δ} (x = 0.95 and 0.80)|A. C. Mclaughlin,J. P. Attfield,J. Van Duijn,A. D. Hillier###

A MuSR study of the magnetoresistive ruthenocuprates RuSr2Nd1.8-xY0.2CexCu2O_{10-δ} (x = 0.95 and 0.80). Zero field muon spin relaxation (ZF-{\mu}SR) has been used to study the
magnetic properties of the underdoped giant magnetoresistive ruthenocuprates
(GMR) RuSr2Nd1.8-xY0.2CexCu2O10-d (x = 0.95, 0.80). The results show a gradual
loss of initial asymmetry A0 at the ruthenium spin transition temperature, TRu.
At the same time the electronic relaxation rate, lambda shows a gradual
increase with decreasing temperature below TRu. These results have been
interpreted as evidence for Cu spin cluster formation below TRu. These
magnetically ordered clusters grow as the temperature is decreased thus causing
the initial asymmetry to decrease slowly. GMR is observed over a wide
temperature range in the materials studied and the magnitude increases as the
temperature is reduced from TRu to 4 K which suggests a relation between Cu
spin cluster size and -MR.

###Negative differential magneto-resistance in ferromagnetic wires with domain walls|Nicholas Sedlmayr,Jamal Berakdar###

Negative differential magneto-resistance in ferromagnetic wires with domain walls. A domain wall in a ferromagnetic one-dimensional nanowire experiences current
induced motion due to its coupling with the conduction electrons. When the
current is not sufficient to drive the domain wall through the wire, or it is
confined to a perpendicular layer, it nonetheless experiences oscillatory
motion. In turn, this oscillatory motion of the domain wall can couple
resonantly with the electrons in the system affecting the transport properties
further. We investigate the effect of the coupling between these domain wall
modes and the current electrons on the transport properties of the system and
show that such a system demonstrates negative differential magnetoresistance
due to the resonant coupling with the low-lying modes of the domain wall
motion.

###Bipolar-Driven Large Magnetoresistance in Silicon|Michael P. Delmo,Eiji Shikoh,Teruya Shinjo,Masashi Shiraishi###

Bipolar-Driven Large Magnetoresistance in Silicon. Large linear magnetoresistance (MR) in electron-injected p-type silicon at
very low magnetic field is observed experimentally at room temperature. The
large linear MR is induced in electron-dominated space-charge transport regime,
where the magnetic field modulation of electron-to-hole density ratio controls
the MR, as indicated by the magnetic field dependence of Hall coefficient in
the silicon device. Contrary to the space-charge-induced MR effect in unipolar
silicon device, where the large linear MR is inhomogeneity-induced, our results
provide a different insight into the mechanism of large linear MR in
non-magnetic semiconductors that is not based on the inhomogeneity model. This
approach enables homogeneous semiconductors to exhibit large linear MR at low
magnetic fields that until now has only been appearing in semiconductors with
strong inhomogeneities.

###Suppression of backward scattering of Dirac fermions in iron pnictides Ba(Fe$_{1-x}$Ru$_x$As)$_2$|Y. Tanabe,K. K. Huynh,T. Urata,S. Heguri,G. Mu,J. T. Xu,R. Nouchi,K. Tanigaki###

Suppression of backward scattering of Dirac fermions in iron pnictides Ba(Fe$_{1-x}$Ru$_x$As)$_2$. We report electronic transport of Dirac cones when Fe is replaced by Ru,
which has an isoelectronic electron configuration to Fe, using single crystals
of Ba(Fe$_{1-x}$Ru$_x$As)$_2$. The electronic transport of parabolic bands is
shown to be suppressed by scattering due to the crystal lattice distortion and
the impurity effect of Ru, while that of the Dirac cone is not significantly
reduced due to the intrinsic character of Dirac cones. It is clearly shown from
magnetoresistance and Hall coefficient measurements that the inverse of average
mobility, proportional to cyclotron effective mass, develops as the square root
of the carrier number (n) of the Dirac cones. This is the unique character of
the Dirac cone linear dispersion relationship. Scattering of Ru on the Dirac
cones is discussed in terms of the estimated mean free path using experimental
parameters.

###Mixed-Valence-Driven Heavy-Fermion Behavior and Superconductivity in KNi$_2$Se$_2$|James R. Neilson,Anna Llobet,Andreas V. Stier,Liang Wu,Jiajia Wen,Jing Tao,Yimei Zhu,Zlatko B. Tesanovic,N. P. Armitage,Tyrel M. McQueen###

Mixed-Valence-Driven Heavy-Fermion Behavior and Superconductivity in KNi$_2$Se$_2$. Based on specific heat and magnetoresistance measurements, we report that a
"heavy" electronic state exists below $T \approx$ 20 K in KNi$_2$Se$_2$, with
an increased carrier mobility and enhanced effective electronic band mass, $m$*
= 6$m_b$ to 18$m_b$. This "heavy" state evolves into superconductivity at $T_c$
= 0.80(1) K. These properties resemble that of a many-body heavy-fermion state,
which derives from the hybridization between localized magnetic states and
conduction electrons. Yet, no evidence for localized magnetism or magnetic
order is found in KNi$_2$Se$_2$ from magnetization measurements or neutron
diffraction. Instead, neutron pair-distribution-function analysis reveals the
presence of local charge-density-wave distortions that disappear on cooling, an
effect opposite to what is typically observed, suggesting that the
low-temperature electronic state of KNi$_2$Se$_2$ arises from cooperative
Coulomb interactions and proximity to, but avoidance of, charge order.

###Edge state transport through disordered graphene nanoribbons in the quantum Hall regime|Fabian Duerr,Jeroen B. Oostinga,Charles Gould,Laurens W. Molenkamp###

Edge state transport through disordered graphene nanoribbons in the quantum Hall regime. The presence of strong disorder in graphene nanoribbons yields low-mobility
diffusive transport at high charge densities, whereas a transport gap occurs at
low densities. Here, we investigate the longitudinal and transverse
magnetoresistance of a narrow (60 nm) nanoribbon in a six-terminal Hall bar
geometry. At B= 11 T, quantum Hall plateaux appear at $\sigma_{xy}=\pm2e^2/h$,
$\pm6e^2/h$ and $\pm10e^2/h$, for which the Landau level spacing is larger than
the Landau level broadening. Interestingly, the transport gap does not
disappear in the quantum Hall regime, when the zero-energy Landau level is
present at the charge neutrality point, implying that it cannot originate from
a lateral confinement gap. At high charge densities, the longitudinal and Hall
resistance exhibit reproducible fluctuations, which are most pronounced at the
transition regions between Hall plateaux. Bias-dependent measurements strongly
indicate that these fluctuations can be attributed to phase coherent scattering
in the disordered ribbon.

###Self-sustaining dynamical nuclear polarization oscillations in quantum dots|M. S. Rudner,L. S. Levitov###

Self-sustaining dynamical nuclear polarization oscillations in quantum dots. Early experiments on spin-blockaded double quantum dots revealed surprising
robust, large-amplitude current oscillations in the presence of a static (dc)
source-drain bias [see e.g. K. Ono, S. Tarucha, Phys. Rev. Lett. 92, 256803
(2004)]. Experimental evidence strongly indicates that dynamical nuclear
polarization plays a central role, but the mechanism has remained a mystery.
Here we introduce a minimal albeit realistic model of coupled electron and
nuclear spin dynamics which supports robust self-sustained oscillations. Our
mechanism relies on a nuclear-spin analog of the tunneling magnetoresistance
phenomenon (spin-dependent tunneling rates in the presence of an inhomogeneous
Overhauser field) and nuclear spin diffusion, which governs dynamics of the
spatial profile of nuclear polarization. The extremely long oscillation periods
(up to hundreds of seconds) observed in experiments as well as the differences
in phenomenology between vertical and lateral quantum dot structures are
naturally explained in the proposed framework.

###Quantum oscillations from a two-dimensional electron gas at a Mott/band insulator interface|Pouya Moetakef,Daniel G. Ouellette,James R. Williams,S. James Allen,Leon Balents,David Goldhaber-Gordon,Susanne Stemmer###

Quantum oscillations from a two-dimensional electron gas at a Mott/band insulator interface. We report on the magnetotransport properties of a prototype Mott
insulator/band insulator perovskite heterojunction in magnetic fields up to 31
T and at temperatures between 360 mK and 10 K. Shubnikov-de Haas oscillations
in the magnetoresistance are observed. The oscillations are two-dimensional in
nature and are interpreted as arising from either a single, spin-split subband
or two subbands. In either case, the electron system that gives rise to the
oscillations represents only a fraction of the electrons in the space charge
layer at the interface. The temperature dependence of the oscillations are used
to extract an effective mass of ~ 1 me for the subband(s). The results are
discussed in the context of the t2g-states that form the bottom of the
conduction band of SrTiO3.

###Realization of spin gapless semiconductors: the Heusler compound Mn2CoAl|Siham Ouardi,Gerhard H. Fecher,Jürgen Kübler,Claudia Felser###

Realization of spin gapless semiconductors: the Heusler compound Mn2CoAl. Recent studies have reported an interesting class of semiconductor materials
that bridge the gap between semiconductors and halfmetallic ferromagnets. These
materials, called spin gapless semiconductors, exhibit a bandgap in one of the
spin channels and a zero bandgap in the other and thus allow for tunable spin
transport. Here, a theoretical and experimental study of the spin gapless
Heusler compound Mn2CoAl is presented. It turns out that Mn2CoAl is a very
peculiar ferrimagnetic semiconductor with a magnetic moment of 2 {\mu}B and a
high Curie temperature of 720 K. Below 300 K, the compound exhibits nearly
temperature-independent conductivity, very low, temperature-independent carrier
concentration, and a vanishing Seebeck coefficient. The magnetoresistance
changes sign with temperature. In high fields, it is positive and
non-saturating at low temperatures, but negative and saturating at high
temperatures. The anomalous Hall effect is comparatively low, which is
explained by the close antisymmetry of the Berry curvature for kz of opposite
sign.

###The distinct in-plane resistivity anisotropy in the nematic states of detwinned NaFeAs and FeTe single crystals: evidences for Hund's rule metal|Juan Jiang,C. He,Y. Zhang,M. Xu,Q. Q. Ge,Z. R. Ye,F. Chen,B. P. Xie,D. L. Feng###

The distinct in-plane resistivity anisotropy in the nematic states of detwinned NaFeAs and FeTe single crystals: evidences for Hund's rule metal. The in-plane resistivity anisotropy has been studied with the Montgomery
method on two detwinned parent compounds of the iron-based superconductors,
NaFeAs and FeTe. For NaFeAs, the resistivity in the antiferromagnetic (AFM)
direction is smaller than that in the ferromagnetic (FM) direction, similar to
that observed in BaFe2As2 before. While for FeTe, the resistivity in the AFM
direction is larger than that in the FM direction. We show that these two
opposite resistivity anisotropy behaviors could be attributed to the strong
Hund's rule coupling effects: while the iron pnictides are in the itinerant
regime, where the Hund's rule coupling causes strong reconstruction and
nematicity of the electronic structure; the FeTe is in the localized regime,
where Hund's rule coupling makes hopping along the FM direction easier than
along the AFMdirection, similar to the colossal magnetoresistance observed in
some manganites.

###Magnetotransport in graphene on silicon side of SiC|P. Vasek,L. Smrcka,P. Svoboda,V. Jurka,M. Orlita,D. K. Maude,W. Strupinski,R. Stepniewski,R. Yakimova###

Magnetotransport in graphene on silicon side of SiC. We have studied the transport properties of graphene grown on silicon side of
SiC. Samples under study have been prepared by two different growth methods in
two different laboratories. Magnetoresistance and Hall resistance have been
measured at temperatures between 4 and 100 K in resistive magnet in magnetic
fields up to 22 T. In spite of differences in sample preparation, the field
dependence of resistances measured on both sets of samples exhibits two periods
of magneto-oscillations indicating two different parallel conducting channels
with different concentrations of carriers. The semi-quantitative agreement with
the model calculation allows for conclusion that channels are formed by
high-density and low-density Dirac carriers. The coexistence of two different
groups of carriers on the silicon side of SiC was not reported before.

###Negative spin polarization of Mn2VGa probed by tunnel magnetoresistance|Christoph Klewe,Markus Meinert,Jan Schmalhorst,Günter Reiss###

Negative spin polarization of Mn2VGa probed by tunnel magnetoresistance. The ferrimagnetic Heusler compound Mn2VGa is predicted to have a pseudogap in
the majority spin channel, which should lead to a negative tunnel
magnetoresistance. We synthesized epitaxial Mn2VGa thin films on MgO(001)
substrates by dc and rf magnetron co-sputtering, resulting in nearly
stoichiometric films. XRD analysis revealed a mostly B2-ordered structure for
the films deposited at substrate temperatures of 350{\deg}C, 450{\deg}C, and
550{\deg}C. Magnetic tunnel junctions with MgO barrier and CoFe
counter-electrodes were fabricated. After post-annealing at up to
T_a=425{\deg}C negative TMR was obtained around zero bias, providing evidence
for the inverted spin-polarization. Band structures of both electrodes were
computed within the coherent potential approximation and used to calculate the
TMR(V) characteristics, which are in good agreement with our experimental
findings.

###Magnetoresistance of an Anderson insulator of bosons|Anirban Gangopadhyay,Victor Galitski,Markus Mueller###

Magnetoresistance of an Anderson insulator of bosons. We study the magnetoresistance of two-dimensional bosonic Anderson
insulators. We describe the change in spatial decay of localized excitations in
response to a magnetic field, which is given by an interference sum over
alternative tunnelling trajectories. The excitations become more localized with
increasing field (in sharp contrast to generic fermionic excitations which get
weakly delocalized): the localization length \xi(B) is found to change as
\xi^{-1}(B)-\xi^{-1}(0)\sim B^{4/5}. The quantum interference problem maps onto
the classical statistical mechanics of directed polymers in random media
(DPRM). We explain the observed scaling using a simplified droplet model which
incorporates the non-trivial DPRM exponents. Our results have implications for
a variety of experiments on magnetic-field-tuned superconductor-to-insulator
transitions observed in disordered films, granular superconductors, and
Josephson junction arrays, as well as for cold atoms in artificial gauge
fields.

###High magnetoresistance in graphene nanoribbon heterojunction|S. Bala Kumar,M. B. A. Jalil,S. G. Tan###

High magnetoresistance in graphene nanoribbon heterojunction. We show a large magnetoresistance(MR) effect in a graphene heterostructure
consisting of an metallic(M) and semiconductor(SC)-type
armchair-graphene-nanoribbon(aGNR). In the heterostructure, the transmission
across the first subband of the SC-aGNR and M-aGNR is forbidden under zero
magnetic-field, due to the orthogonality of the wavefunctions. A finite
magnetic-field introduces the quantum hall-like effect, which distorts the
wavefunctions. Thus, a finite transmission occurs across the heterojunction,
giving rise to a large MR effect. We study the dependence of this MR on
temperature and electron energy. Finally, we design a
magnetic-field-effect-transistor which yields a MR of close to 100%(85%) at
low(room) temperature.

###Interface characterization of Co2MnGe/Rh2CuSn Heusler multilayers|Ronny Knut,Peter Svedlindh,Klas Gunnarsson,Oleg Mryasov,Peter Warnicke,Dario Arena,Matts Björck,D. D. Sarma,Anindita Sahoo,Sumanta Mukherjee,Sari Granroth,Mihaela Gorgoi,Olof Karis###

Interface characterization of Co2MnGe/Rh2CuSn Heusler multilayers. All-Heusler multilayer structures have been investigated by means of high
kinetic x-ray photoelectron spectroscopy and x-ray magnetic circular dichroism,
aiming to address the amount of disorder and interface diffusion induced by
annealing of the multilayer structure. The studied multilayers consist of
ferromagnetic Co$_2$MnGe and non-magnetic Rh$_2$CuSn layers with varying
thicknesses. We find that diffusion begins already at comparably low
temperatures between 200 $^{\circ}$C and 250 $^{\circ}$C, where Mn appears to
be most prone to diffusion. We also find evidence for a 4 {\AA} thick
magnetically dead layer that, together with the identified interlayer
diffusion, are likely reasons for the small magnetoresistance found for
current-perpendicular-to-plane giant magneto-resistance devices based on this
all-Heusler system.

###Dipolar coupling between nanopillar spin valves and magnetic quantum cellular automata arrays|Madalina Colci,Mark B. Johnson###

Dipolar coupling between nanopillar spin valves and magnetic quantum cellular automata arrays. We experimentally demonstrate magnetostatic coupling between a nanopillar
pseudo spin valve structure and a linear array of dipole coupled Permalloy
nanomagnets. Using magnetic force microscopy, we study the interaction between
the spin valve and the first element of the array, and present evidence that
the nanomagnet couples with the hard layer of the spin valve for two spin
valves with distinctly different composition. Our study includes a statistical
analysis of antiferromagnetic order within the linear array, and provides
insight into the range of behavior that these arrays can display. These results
bear directly on the design of magnetic quantum cellular automata (MQCA) logic
devices, showing that multilayer devices can couple to simple nanomagnets.
Redesigning the hard layer of the magnetoresistive devices would make them
operational as an electronic input that will allow integration of MQCA networks
in complex electronic circuitry.

###Magnetocapacitance without magnetism|Meera M. Parish###

Magnetocapacitance without magnetism. A substantial magnetodielectric effect is often an indication of coupled
magnetic and elastic order, such as is found in the multiferroics. However, it
has recently been shown that magnetism is not necessary to produce either a
magnetoresistance or a magnetocapacitance when the material is inhomogeneous
[M. M. Parish and P. B. Littlewood, Phys. Rev. Lett. 101, 166602 (2008)]. Here,
we will investigate the characteristic magnetic-field-dependent dielectric
response of such an inhomogeneous system using exact calculations and numerical
simulations of conductor-dielectric composites. In particular, we will show
that even simple conductor-dielectric layers exhibit a magnetocapacitance, and
thus random bulk inhomogeneities are not a requirement for this effect. Indeed,
this work essentially provides a natural generalisation of the Maxwell-Wagner
effect to finite magnetic field. We will also discuss how this phenomenon has
already been observed experimentally in some materials.

###Two-dimensional semimetal in a wide HgTe quantum well: magnetotransport and energy spectrum|G. M. Minkov,A. V. Germanenko,O. E. Rut,A. A. Sherstobitov,S. A. Dvoretski,N. N. Mikhailov###

Two-dimensional semimetal in a wide HgTe quantum well: magnetotransport and energy spectrum. The results of experimental study of the magnetoresistivity, the Hall and
Shubnikov-de Haas effects for the heterostructure with HgTe quantum well of
20.2 nm width are reported. The measurements were performed on the gated
samples over the wide range of electron and hole densities including vicinity
of a charge neutrality point. Analyzing the data we conclude that the energy
spectrum is drastically different from that calculated in framework of
$kP$-model. So, the hole effective mass is equal to approximately $0.2 m_0$ and
practically independent of the quasimomentum ($k$) up to $k^2\gtrsim 0.7\times
10^{12}$ cm$^{-2}$, while the theory predicts negative (electron-like)
effective mass up to $k^2=6\times 10^{12}$ cm$^{-2}$. The experimental
effective mass near k=0, where the hole energy spectrum is electron-like, is
close to $-0.005 m_0$, whereas the theoretical value is about $-0.1 m_0$.

###Negative magnetoresistance and anomalous Hall effect in GeMnTe-SnMnTe spin-glass-like system|L. Kilanski,R. Szymczak,W. Dobrowolski,A. Podgórni,A. Avdonin,V. E. Slynko,E. I. Slynko###

Negative magnetoresistance and anomalous Hall effect in GeMnTe-SnMnTe spin-glass-like system. Magnetotransport properties of spin-glass-like Ge/1-x-y/Sn/x/Mn/y/Te mixed
crystals with chemical composition changing in the range of 0.083 < x < 0.142
and 0.012 < y < 0.119 are presented. The observed negative magnetoresistance we
attribute to two mechanisms i.e. weak localization occurring at low fields and
spin disorder scattering giving contribution mainly at higher magnetic fields.
A pronounced hysteretic anomalous Hall effect (AHE) was observed. The estimated
AHE coefficient shows a small temperature dependence and is dependent on
Mn-content, with changes in the range of 10E-7 < R_S < 10E-6 m^3/C. The scaling
law analysis has proven that the AHE in this system is due to the extrinsic
mechanisms, mainly due to the skew scattering accompanied with the side jump
processes.

###Flat Bands and Enigma of Metamagnetic Quantum Critical Regime in Sr3Ru2O7|V. R. Shaginyan,A. Z. Msezane,K. G. Popov,J. W. Clark,M. V. Zverev,V. A. Khodel###

Flat Bands and Enigma of Metamagnetic Quantum Critical Regime in Sr3Ru2O7. Understanding the nature of field-tuned metamagnetic quantum criticality in
the ruthenate Sr3Ru2O7 has presented a significant challenge within condensed
matter physics. It is known from experiments that the entropy within the
ordered phase forms a peak, and is unexpectedly higher than that outside, while
the magnetoresistivity experiences steep jumps near the ordered phase. We find
a challenging connection between Sr3Ru2O7 and heavy-fermion metals expressing
universal physics that transcends microscopic details. Our construction of the
T-B phase diagram of Sr3Ru2O7 permits us to explain main features of the
experimental one, and unambiguously implies an interpretation of its
extraordinary low-temperature thermodynamic in terms of fermion condensation
quantum phase transition leading to the formation of a flat band at the
restricted range of magnetic fields B. We show that it is the flat band that
generates both the entropy peak and the resistivity jumps at the QCPs.

###Emergence of superconductivity from the dynamically heterogeneous insulating state in La_{2-x}Sr_{x}CuO_{4}|Xiaoyan Shi,G. Logvenov,A. T. Bollinger,I. Božović,C. Panagopoulos,Dragana Popović###

Emergence of superconductivity from the dynamically heterogeneous insulating state in La_{2-x}Sr_{x}CuO_{4}. A central issue for copper oxides is the nature of the insulating ground
state at low carrier densities and the emergence of high-temperature
superconductivity from that state with doping. Even though this
superconductor-insulator transition (SIT) is a zero-temperature transition,
measurements are not usually carried out at low temperatures. Here we use
magnetoresistance to probe both the insulating state at very low temperatures
and the presence of superconducting fluctuations in La_{2-x}Sr_{x}CuO_{4}(LSCO)
films, for doping levels that range from the insulator to the superconductor
(x=0.03-0.08). We observe that the charge glass behavior, characteristic of the
insulating state, is suppressed with doping, but it coexists with
superconducting fluctuations that emerge already on the insulating side of the
SIT. The unexpected quenching of the superconducting fluctuations by the
competing charge order at low temperatures provides a new perspective on the
mechanism for the SIT.

###Gate voltage controlled electronic transport through a ferromagnet/normal/ferromagnet junction on the surface of a topological insulator|K. H. Zhang,Z. C. Wang,Q. R. Zheng,G. Su###

Gate voltage controlled electronic transport through a ferromagnet/normal/ferromagnet junction on the surface of a topological insulator. We investigate the electronic transport properties of a
ferromagnet/normal/ferromagnet junction on the surface of a topological
insulator with a gate voltage exerted on the normal segment. It is found that
the conductance oscillates with the width of normal segment and gate voltage,
and the maximum of conductance gradually decreases while the minimum of
conductance approaches zero as the width increases. The conductance can be
controlled by tuning the gate voltage like a spin field-effect transistor. It
is found that the magnetoresistance ratio can be very large, and can also be
negative owing to the anomalous transport. In addition, when there exists a
magnetization component in the surface plane, it is shown that only the
component parallel to the junction interface has an influence on the
conductance.

###Quantum transport modeling of Fe/MgO/Fe magnetic tunnel junction with FeO$_{0.5}$ buffer layer: the effects of correlations|Vladimir Timoshevskii,Yibin Hu,É. Marcotte,Hong Guo###

Quantum transport modeling of Fe/MgO/Fe magnetic tunnel junction with FeO$_{0.5}$ buffer layer: the effects of correlations. We report \textit{ab initio} simulations of quantum transport properties of
Fe/MgO/Fe trilayer structures with FeO$_{0.5}$ buffer iron oxide layer, where
on-site Coulomb interaction is explicitly taken into account by local density
approximation + Hubbard \textit{U} approach. We show that on-site Coulomb
repulsion in the iron-oxygen layer can cause a dramatic drop of the tunnel
magnetoresistance of the system. We present an understanding of microscopic
details of this phenomenon, connecting it to localization of the Fermi
electrons of particular symmetry, which takes place in the buffer Fe-O layer,
when on-site Coulomb repulsion is introduced. We further study the possible
influence of the symmetry reduction in the buffer Fe-O layer on the transport
properties of the Fe/MgO/Fe interface.

###Anisotropic magnetization, resistivity and heat capacity of single crystalline R3Ni2-xSn7 (R = La, Ce, Pr and Nd)|Xiao Lin,Sergey L. Bud'ko,Srinivasa Thimmaiah,Paul C. Canfield###

Anisotropic magnetization, resistivity and heat capacity of single crystalline R3Ni2-xSn7 (R = La, Ce, Pr and Nd). We present a detailed study of R3Ni2-xSn7 (R = La, Ce, Pr and Nd) single
crystals by measurements of crystal structure, stoichiometry, temperature
dependent magnetic susceptibility, magnetization, electrical resistivity,
magnetoresistance, and specific heat. This series forms with partial Ni
occupancy with x varying from ~ 0.1 for R = La to ~0.7 for R = Nd. The
electrical resistivity of this series follows metallic behavior at high
temperatures. Determination of clear anisotropies as well as antiferromagnetic
ordering temperatures for R3Ni2-xSn7 (R = Ce, Pr and Nd) have been made. For
Pr3Ni1.56Sn7 and Nd3Ni1.34Sn7, multiple magnetic transitions take place upon
cooling. Metamagnetic transitions in this family (R = Ce, Pr and Nd) were
detected for applied magnetic fields below 70 kOe. An H-T phase diagram of
Ce3Ni1.69Sn7 was assembled to shed light on its low field properties and to
rule out possible quantum critical effects.

###Graphene single electron transistor as a spin sensor for magnetic adsorbates|J. W. González,F. Delgado,J. Fernández-Rossier###

Graphene single electron transistor as a spin sensor for magnetic adsorbates. We study single electron transport through a graphene quantum dot with
magnetic adsorbates. We focus on the relation between the spin order of the
adsorbates and the linear conductance of the device. The electronic structure
of the graphene dot with magnetic adsorbates is modeled through numerical
diagonalization of a tight-binding model with an exchange potential. We
consider several mechanisms by which the adsorbate magnetic state can influence
transport in a single electron transistor: by tuning the addition energy, by
changing the tunneling rate and, in the case of spin polarized electrodes,
through magnetoresistive effects. Whereas the first mechanism is always
present, the others require that the electrode has either an energy or spin
dependent density of states. We find that graphene dots are optimal systems to
detect the spin state of a few magnetic centers.

###FLUXCAP: A flux-coupled ac/dc magnetizing device|Daniel B. Gopman,Huanlong Liu,Andrew D. Kent###

FLUXCAP: A flux-coupled ac/dc magnetizing device. We report on an instrument for applying ac and dc magnetic fields by
capturing the flux from a rotating permanent magnet and projecting it between
two adjustable pole pieces. This can be an alternative to standard
electromagnets for experiments with small samples or in probe stations in which
an applied magnetic field is needed locally, with advantages that include a
compact form-factor, very low power requirements and dissipation as well as
fast field sweep rates. This flux capture instrument (FLUXCAP) can produce
fields from -400 to +400 mT, with field resolution less than 1 mT. It generates
static magnetic fields as well as ramped fields, with ramping rates as high as
10 T/s. We demonstrate the use of this apparatus for studying the
magnetotransport properties of spin-valve nanopillars, a nanoscale device that
exhibits giant magnetoresistance.

###Low temperature transport properties of multigraphene structures on 6H-SiC obtained by thermal graphitization: evidences of a presence of nearly perfect graphene layer|A. A. Lebedev,N. V. Agrinskaya,V. A. Beresovets,V. I. Kozub,S. P. Lebedev,A. A. Sitnikova###

Low temperature transport properties of multigraphene structures on 6H-SiC obtained by thermal graphitization: evidences of a presence of nearly perfect graphene layer. Transport properties of multigraphene layers on 6H-SiC substrates fabricated
by thermal graphitization of SiC were studied. The principal result is that
these structures were shown to contain a nearly perfect graphene layer situated
between the SiC substrate and multgraphene layer. It was found that the curves
of magnetoresistance and Shubnikov- de Haas oscillations shown the features,
typical for single-layered graphene. The low temperature resistance
demonstrated an increase with temperature increase, which also corresponds to a
behavior typical for single-layered graphene (antilocalization). However at
higher temperatures the resistance decreased with an increase of temperature,
which corresponds to a weak localization. We believe that the observed behavior
can be explained by a parallel combination of contributions to the conductivity
of single-layered graphene and of multigraphene, the latter allowing to escape
damages of the graphene by atmosphere effect.

###Effects of Transverse Magnetic Anisotropy on Current-Induced Spin Switching|Maciej Misiorny,Józef Barnaś###

Effects of Transverse Magnetic Anisotropy on Current-Induced Spin Switching. Spin-polarized transport through bistable magnetic adatoms or single-molecule
magnets (SMMs), which exhibit both uniaxial and transverse magnetic anisotropy,
is considered theoretically. The main focus is on the impact of transverse
anisotropy on transport characteristics and the adatom's/SMM's spin. In
particular, we analyze the role of quantum tunneling of magnetization (QTM) in
the mechanism of the current-induced spin switching, and show that the QTM
phenomenon becomes revealed as resonant peaks in the average values of the
molecule's spin and in the charge current. These features appear at some
resonant fields and are observable when at least one of the electrodes is
ferromagnetic. We also show that the conductance generally depends on the
relative orientation of the average adatom's/SMM's spin and electrode's
magnetic moment. This spin-valve like magnetoresistance effect can be used to
control spin switching of the adatom's/SMM's spin.

###Observation of large positive magnetoresistance and its sign reversal in GdRhGe|Sachin Gupta,K. G. Suresh,A. K. Nigam###

Observation of large positive magnetoresistance and its sign reversal in GdRhGe. Magnetic properties, heat capacity and magnetoresistance (MR) of
polycrystalline GdRhGe are investigated. It shows two antiferromagnetic
transitions, one at T1=31.8 K and the other at T2=24 K, and field induced
metamagnetic transition over a wide temperature range. The ac susceptibility
data reveal that the transition at 24 K is not simple antiferromagnetic.
Dominant contributions to the heat capacity and the resistivity have been
identified. MR is found to show sign reversal just below T1 and attains a large
positive value of 48% at 2 K for 50 kOe. Like MR, the isothermal magnetic
entropy change also undergoes a sign reversal as the temperature is varied,
indicating a change of the magnetic structure and the moment amplitude in
determining these properties.

###Frustration-induced nanometre-scale inhomogeneity in a triangular antiferromagnet|Andrej Zorko,Othon Adamopoulos,Matej Komelj,Denis Arćon,Alexandros Lappas###

Frustration-induced nanometre-scale inhomogeneity in a triangular antiferromagnet. Phase inhomogeneity of otherwise chemically homogenous electronic systems is
an essential ingredient leading to fascinating functional properties, such as
high-$T_c$ superconductivity in cuprates, colossal magnetoresistance in
manganites, and giant electrostriction in relaxors. In these materials distinct
phases compete and can coexist due to intertwined ordered parameters. Charge
degrees of freedom play a fundamental role, although phase-separated ground
states have been envisioned theoretically also for pure spin systems with
geometrical frustration that serves as a source of phase competition. Here we
report a paradigmatic magnetostructurally inhomogenous ground state of the
geometrically frustrated $\alpha$-NaMnO$_2$ that stems from the system's
aspiration to remove magnetic degeneracy and is possible only due to the
existence of near-degenerate crystal structures. Synchrotron X-ray diffraction,
nuclear magnetic resonance and muon spin relaxation show that the spin
configuration of a monoclinic phase is disrupted by magnetically short-range
ordered nanoscale triclinic regions, thus revealing a novel complex state of
matter.

###Electronic and Magnetic Reconstructions in Manganite Superlattices|Kalpataru Pradhan,Arno P. Kampf###

Electronic and Magnetic Reconstructions in Manganite Superlattices. We investigate the electronic reconstruction at the interface between
ferromagnetic metallic (FM) and antiferromagnetic insulating (AFI) manganites
in superlattices using a two-orbital double-exchange model including
superexchange interactions, Jahn-Teller lattice distortions, and long range
Coulomb interactions. The magnetic and the transport properties critically
depend on the thickness of the AFI layers. We focus on superlattices where the
constituent parent manganites have the same electron density n = 0.6. The
induced ferromagnetic moment in the AFI layers decreases monotonically with
increasing layer width, and the electron-density profile and the magnetic
structure in the center of the AFI layer gradually return to the bulk limit.
The width of the AFI layers and the charge-transfer profile at the interfaces
control the magnitude of the magnetoresistance and the metal-insulator
transition of the FM/AFI superlattices.

###Resistance of High-Temperature Cuprate Superconductors|Jamil Tahir-Kheli###

Resistance of High-Temperature Cuprate Superconductors. Cuprate superconductors have many different atoms per unit cell. A large
fraction of cells (5-25%) must be modified ("doped") before the material
superconducts. Thus it is not surprising that there is little consensus on the
superconducting mechanism, despite almost 200,000 papers. Most astonishing is
that for the simplest electrical property, the resistance, "despite sustained
theoretical efforts over the past two decades, its origin and its relation to
the superconducting mechanism remain a profound, unsolved mystery." Currently,
model parameters used to fit normal state properties are experiment specific
and vary arbitrarily from one doping to the other. Here, we provide a
quantitative explanation for the temperature and doping dependence of the
resistivity, Hall effect, and magnetoresistance in one self-consistent model by
showing that cuprates are intrinsically inhomogeneous with a percolating
metallic region and insulating regions. Using simple counting of dopant-induced
plaquettes, we show that the superconducting pairing and resistivity are due to
phonons.

###Exchange magnetic field torques in YIG/Pt bilayers observed by the spin-Hall magnetoresistance|N. Vlietstra,J. Shan,V. Castel,J. Ben Youssef,G. E. W. Bauer,B. J. van Wees###

Exchange magnetic field torques in YIG/Pt bilayers observed by the spin-Hall magnetoresistance. The effective field torque of an yttrium-iron-garnet film on the spin
accumulation in an attached Pt film is measured by the spin-Hall
magnetoresistance (SMR). As a result, the magnetization direction of a
ferromagnetic insulating layer can be measured electrically. Experimental
transverse and longitudinal resistances are well described by the theoretical
model of SMR in terms of the direct and inverse spin-Hall effect, for different
Pt thicknesses [3, 4, 8 and 35nm]. Adopting a spin-Hall angle of Pt
$\theta_{SH}=0.08$, we obtain the spin diffusion length of Pt
($\lambda=1.1\pm0.3$nm) as well as the real
($G_r=(7\pm3)\times10^{14}\Omega^{-1}$m$^{-2}$) and imaginary part
($G_i=(5\pm3)\times10^{13}\Omega^{-1}$m$^{-2}$) of the spin-mixing conductance
and their ratio ($G_r/G_i=16\pm4$).

###Iron impurities in gold and silver: Comparison of transport measurements to numerical renormalization group calculations exploiting non-Abelian symmetries|M. Hanl,A. Weichselbaum,T. A. Costi,F. Mallet,L. Saminadayar,C. Bäuerle,J. von Delft###

Iron impurities in gold and silver: Comparison of transport measurements to numerical renormalization group calculations exploiting non-Abelian symmetries. We consider iron impurities in the noble metals gold and silver and compare
experimental data for the resistivity and decoherence rate to numerical
renormalization group results. By exploiting non-Abelian symmetries we show
improved numerical data for both quantities as compared to previous
calculations [Costi et al., Phys. Rev. Lett. 102, 056802 (2009)], using the
discarded weight as criterion to reliably judge the quality of convergence of
the numerical data. In addition we also carry out finite-temperature
calculations for the magnetoresistivity of fully screened Kondo models with S =
1/2, 1 and 3/2, and compare the results with available measurements for iron in
silver, finding excellent agreement between theory and experiment for the
spin-3/2 three-channel Kondo model. This lends additional support to the
conclusion of Costi et al. that the latter model provides a good effective
description of the Kondo physics of iron impurities in gold and silver.

###Electron-electron interaction correction and magnetoresistance in tilted fields in Si-based 2D systems|A. Yu. Kuntsevich,L. A. Morgun,V. M. Pudalov###

Electron-electron interaction correction and magnetoresistance in tilted fields in Si-based 2D systems. We study diffusive electron-electron interaction correction to conductivity
by analyzing simultaneously $\rho_{xx}$ and $\rho_{xy}$ for disordered 2D
electron systems in Si in tilted magnetic field. Tilting the field is shown to
be a straightforward tool to disentangle spin and orbital effects. In
particular, by changing the tilt angle we prove experimentally that in the
field range $g\mu_BB>k_BT$ the correction depends on modulus of magnetic field
rather than on its direction, which is expected for a system with isotropic
$g$-factor. In the high-field limit the correction behaves as $\ln (B)$, as
expected theoretically (Lee, Ramakrishnan, Phys. Rev. B{\bf 26}, 4009 (1982)).
Our data prove that the diffusive electron-electron interaction correction to
conductivity is not solely responsible for the huge and temperature dependent
magnetoresistance in parallel field, typically observed in Si-MOSFETs.

###Comparative study of magnetic and magnetotransport properties of Sm0.55Sr0.45MnO3 thin films grown on different substrates|Manoj K. Srivastava,Sandeep Singh,P. K. Siwach,Amarjeet Kaur,V. P. S. Awana,K. K. Maurya,H. K. Singh###

Comparative study of magnetic and magnetotransport properties of Sm0.55Sr0.45MnO3 thin films grown on different substrates. Highly oriented polycrystalline SSMO thin films deposited on single crystal
substrates by ultrasonic nebulized spray pyrolysis have been studied. The film
on LAO is under compressive strain while LSAT and STO are under tensile strain.
The presence of a metamagnetic state akin to cluster glass formed due to
coexisting FM and antiferromagnetic/charge order (AFM/CO) clusters. All the
films show colossal magnetoresistance but its temperature and magnetic field
dependence are drastically different. In the lower temperature region the
magnetic field dependent isothermal resistivity also shows signature of
metamagnetic transitions. The observed results have been explained in terms of
the variation of the relative fractions of the coexisting FM and AFM/CO phases
as a function of the substrate induced strain and oxygen vacancy induced
quenched disorder.

###Magnetization reversal in sub-100nm magnetic tunnel junctions with ultrathin MgO barrier biased along hard axis|J. P. Cascales,D. Herranz,J. L. Sambricio,U. Ebels,J. A. Katine,F. G. Aliev###

Magnetization reversal in sub-100nm magnetic tunnel junctions with ultrathin MgO barrier biased along hard axis. We report on room temperature magnetoresistance and low frequency noise in
sub-100nm elliptic CoFeB/MgO/CoFeB magnetic tunnel junctions with ultrathin
(0.9nm) barriers. For magnetic fields applied along the hard axis, we observe
current induced magnetization switching between the antiparallel and parallel
alignments at DC current densities as low as 4*106A/cm2. We attribute the low
value of the critical current to the influence of localized reductions in the
tunnel barrier, which affects the current distribution. The analysis of random
telegraph noise, which appears in the field interval near a magnetization
switch, provides an estimate to the dimension of the pseudo pinholes that
trigger the magnetization switching via local spin torque. Micromagnetic
simulations qualitatively and quantitatively reproduce the main experimental
observations.

###Effect of substrate temperature on the spin transport property in C60-based spin valve devices|Feng Li###

Effect of substrate temperature on the spin transport property in C60-based spin valve devices. We report the effect of the substrate temperature on the magnetoresistance
(MR) of the C60-based spin valve (SV) devices with the sandwich configuration
of La0.67Sr0.33MnO3 (LSMO)/C60/cobalt (Co). The C60 interlayer deposited at
different substrate temperatures resulted in four types of devices. We observed
all types of devices showed a monotonic increase in MR ratio with the substrate
temperature. And more interesting, an especially large MR (28.5%) were obtained
in the device fabricated at higher substrate temperature, while for the other
types of devices, the MR magnitudes were just about a few percent. Based on the
I-V measurements, as well as SEM and AFM characteristics, we have obtained that
the higher substrate temperature can cause many pits and hollows in the organic
film, and these pits will increase the tunneling probability of spin-polarized
carriers from one ferromagnetic electrode to the other.

###One-dimensional weak antilocalization and band Berry phases in HgTe wires|M. Mühlbauer,A. Budewitz,B. Büttner,G. Tkachov,E. M. Hankiewicz,C. Brüne,H. Buhmann,L. W. Molenkamp###

One-dimensional weak antilocalization and band Berry phases in HgTe wires. We study the weak antilocalization (WAL) effect in the magnetoresistance of
narrow HgTe wires fabricated in quantum wells (QWs) with normal and inverted
band ordering. Measurements at different gate voltages indicate that the WAL is
only weakly affected by Rashba spin-orbit splitting and persists when the
Rashba splitting is about zero. The WAL signal in wires with normal band
ordering is an order of magnitude smaller than for inverted ones. These
observations are attributed to a Dirac-like topology of the energy bands in
HgTe QWs. From the magnetic-field and temperature dependencies we extract the
dephasing lengths and band Berry phases. The weaker WAL for samples with a
normal band structure can be explained by a non-universal Berry phase which
always exceeds \pi, the characteristic value for gapless Dirac fermions.

###Interfacial Magnetism in Manganite Superlattices|Kalpataru Pradhan,Arno P. Kampf###

Interfacial Magnetism in Manganite Superlattices. We use a two-orbital double-exchange model including Jahn-Teller lattice
distortions, superexchange interactions, and long-range Coulomb (LRC)
interactions to investigate the origin of magnetically disordered interfaces
between ferromagnetic metallic (FM) and antiferromagnetic insulating (AFI)
manganites in FM/AFI superlattices. The induced magnetic moment in the AFI
layer varies non-monotonically with increasing AFI layer width as seen in the
experiment. We provide a framework for understanding this non-monotonic
behavior which has a one-to-one correspondence with the magnetization of the FM
interface. The obtained insights provide a basis for improving the tunneling
magnetoresistance in FM/AFI manganite superlattices by avoiding a magnetic dead
layer (MDL) in the FM manganite.

###Electron-electron scatttering in Sn-doped indium oxide thick films|Yu-Jie Zhang,Zhi-Qing Li,Juhn-Jong Lin###

Electron-electron scatttering in Sn-doped indium oxide thick films. We have measured the low-field magnetoresistances (MRs) of a series of
Sn-doped indium oxide thick films in the temperature $T$ range 4--35 K. The
electron dephasing rate $1/\tau_{\varphi}$ as a function of $T$ for each film
was extracted by comparing the MR data with the three-dimensional (3D)
weak-localization theoretical predictions. We found that the extracted
$1/\tau_{\varphi}$ varies linearly with $T^{3/2}$. Furthermore, at a given $T$,
$1/\tau_{\varphi}$ varies linearly with $k_F^{-5/2}l^{-3/2}$, where $k_{F}$ is
the Fermi wavenumber, and $l$ is the electron elastic mean free path. These
features are well explained in terms of the small-energy-transfer
electron-electron scattering time in 3D disordered conductors. This electron
dephasing mechanism dominates over the electron-phonon ($e$-ph) scattering
process because the carrier concentrations in our films are $\sim$ 3 orders of
magnitude lower than those in typical metals, which resulted in a greatly
suppressed $e$-ph relaxation rate.

###Electron-electron interaction effects on transport through mesoscopic superconducting hybrid junctions|Arijit Saha###

Electron-electron interaction effects on transport through mesoscopic superconducting hybrid junctions. Effects due to the proximity of a superconductor has motivated a lot of
research work in the last several decades both from theoretical and
experimental point of view. In this review we are going to describe the physics
of systems containing normal metal-superconductor interface. Mainly we discuss
transport properties through such hybrid structures. In particular, we describe
the effects of electron electron interaction on transport through such
superconducting junction of multiple one-dimensional quantum wires. The latter
can be described in terms of a non-Fermi liquid theory called Luttinger liquid.
In this review, from the application point of view, we also demonstrate the
possible scenarios for production of pure spin current and large tunnelling
magnetoresistance in such hybrid junctions and analyze the influence of
electron-electron interaction on the stability of the production of pure spin
current.

###Thin films MnGe grown on Si(111)|Josefin Engelke,Dirk Menzel,Vadim Dyadkin###

Thin films MnGe grown on Si(111). MnGe has been grown as a thin film on Si(111) substrates by molecular beam
epitaxy. A 10 \AA\ layer of MnSi was used as seedlayer in order to establish
the B20 crystal structure. Films of a thickness between 45 and 135 \AA\ have
been prepared and structually characterized by RHEED, AFM and XRD. These
techniques give evidence that MnGe forms in the cubic B20 crystal structure as
islands exhibiting a very smooth surface. The islands become larger with
increasing film thickness. A magnetic characterization reveals that the
ordering temperature of MnGe thin films is enhanced compared to bulk material.
The properties of the helical magnetic structure obtained from magnetization
and magnetoresistivity measurements are compared with films of the related
compound MnSi. The much larger Dzyaloshinskii-Moriya interaction in MnGe
results in a higher rigidness of the spin helix.

###N-VSi-related center in non-irradiated 6H SiC nanostructure|Nikolay Bagraev,Eduard Danilovskii,Dmitrii Gets,Ekaterina Kalabukhova,Leonid Klyachkin,Anna Malyarenko,Dariya Savchenko,Bella Shanina###

N-VSi-related center in non-irradiated 6H SiC nanostructure. We present the first findings of the vacancy-related centers identified by
the electron spin resonance (ESR) and electrically-detected (ED) ESR method in
the non-irradiated 6H-SiC nanostructure. This planar 6H-SiC nanostructure
represents the ultra-narrow p-type quantum well confined by the
{\delta}-barriers heavily doped with boron on the surface of the n-type 6H-SiC
(0001) wafer. The EDESR method by measuring the only magnetoresistance of the
6H SiC nanostructure under the high frequency generation from the
{\delta}-barriers appears to allow the identification of the silicon vacancy
centers as well as the triplet center with spin state S=1. The same triplet
center that is characterized by the larger value of the zero-field splitting
constant D and anisotropic g-factor is revealed by the ESR (X-band) method. The
hyperfine (hf) lines in the ESR and EDESR spectra originating from the hf
interaction with the 14N nucleus allow us to attribute this triplet center to
the N-VSi defect.

###Demonstration of surface transport in a hybrid Bi2Se3/Bi2Te3 heterostructure|Yanfei Zhao,Cui-Zu Chang,Ying Jiang,Ashley DaSilva,Yi Sun,Huichao Wang,Ying Xing,Yong Wang,Ke He,Xucun Ma,Qi-Kun Xue,Jian Wang###

Demonstration of surface transport in a hybrid Bi2Se3/Bi2Te3 heterostructure. In spite of much work on topological insulators (TIs), systematic experiments
for TI/TI heterostructures remain absent. We grow a high quality
heterostructure containing single quintuple layer (QL) of Bi2Se3 on 19 QLs of
Bi2Te3 and compare its transport properties with 20 QLs Bi2Se3 and 20 QLs
Bi2Te3. All three films are grown on insulating sapphire (0001) substrates by
molecular beam epitaxy (MBE). In situ angle-resolved photoemission spectroscopy
(ARPES) provides direct evidence that the surface state of 1 QL Bi2Se3 / 19 QLs
Bi2Te3 heterostructure is similar to the surface state of the 20 QLs Bi2Se3 and
different with that of the 20 QLs Bi2Te3. In ex situ transport measurements,
the observed linear magnetoresistance (MR) and weak antilocalization (WAL) of
the hybrid heterostructure are similar to that of the pure Bi2Se3 film and not
the Bi2Te3 film. This suggests that the single Bi2Se3 QL layer on top of 19 QLs
Bi2Te3 dominates its transport properties.

###The detection of Kondo effect in the resistivity of graphene: artifacts and strategies|Johannes Jobst,Ferdinand Kisslinger,Heiko B. Weber###

The detection of Kondo effect in the resistivity of graphene: artifacts and strategies. We discuss the difficulties to discover Kondo effect in the resistivity of
graphene. Similarly to the Kondo effect, electron-electron interaction effects
and weak localization appear as logarithmic corrections to the resistance. In
order to disentangle these contributions, a refined analysis of the
magnetoconductance and the magnetoresistance is introduced. We present
numerical simulations which display the discrimination of both effects.
Further, we present experimental data of magnetotransport. When magnetic
molecules are added to graphene, a logarithmic correction to the conductance
occurs, which apparently suggests Kondo physics. Our thorough evaluation
scheme, however, reveals that this interpretation is not conclusive: the data
can equally be explained by electron-electron interaction corrections in an
inhomogeneous sample. Our evaluation scheme paves the way for a more refined
search for the Kondo effect in graphene.

###Effect of "dipolar-biasing" on the tunability of tunneling magnetoresistance in transition metal oxide systems|P. Anil Kumar,D. D. Sarma###

Effect of "dipolar-biasing" on the tunability of tunneling magnetoresistance in transition metal oxide systems. We observe an unusual tunneling magnetoresistance (TMR) phenomenon in a
composite of La$_{2/3}$Sr$_{1/3}$MnO$_{3}$ with CoFe$_{2}$O$_{4}$ where the TMR
versus applied magnetic field loop suggests a "negative coercive field".
Tracing its origin back to a "dipolar-biasing" of La$_{2/3}$Sr$_{1/3}$MnO$_{3}$
by CoFe$_{2}$O$_{4}$, we show that the TMR of even a single composite can be
tuned continuously so that the resistance peak or the highest sensitivity of
the TMR can be positioned anywhere on the magnetic field axis with a suitable
magnetic history of the sample. This phenomenon of an unprecedented tunability
of the TMR should be present in general in all such composites.

###Interface Effects on Tunneling Magnetoresistance in Organic Spintronics with Flexible Amine-Au Links|Narjes Gorjizadeh,Su Ying Quek###

Interface Effects on Tunneling Magnetoresistance in Organic Spintronics with Flexible Amine-Au Links. Organic spintronics is a promising emerging field, but the sign of the
tunneling magnetoresistance (TMR) is highly sensitive to interface effects, a
crucial hindrance to applications. A key breakthrough in molecular electronics
was the discovery of amine-Au link groups that give reproducible conductance.
Using first principles calculations, we predict that amine-Au links give
improved reproducibility in organic spintronics junctions with Au-covered Fe
leads. The Au layers allow only states with sp character to tunnel into the
molecule, and the flexibility of amine-Au links results in a narrow range of
TMR for fixed number of Au layers. Even as the Au thickness changes, TMR
remains positive as long as the number of Au layers is the same on both sides
of the junction. Since the number of Au layers on Fe surfaces or Fe
nanoparticles can now be experimentally controlled, amine-Au links provide a
route towards robust TMR in organic spintronics.

###Large low-temperature magnetoresistance in SrFe2As2 single crystals|S. V. Chong,G. V. M. Williams,J. Kennedy,F. Fang,J. L. Tallon,K. Kadowaki###

Large low-temperature magnetoresistance in SrFe2As2 single crystals. We present the first report on a large low-temperature magnetoresistance (MR)
of more than 1600% in a SrFe2As2 single crystal and 1300% in a low-energy Ca
ion-implanted SrFe2As2 single crystal that occurs before the emergence of
crystallographic strain-induced bulk superconductivity arising from a sample
aging effect. In accordance to band structure calculations from literature,
which consitently show more than 2 bands are involved in the transport, we have
modeled this large MR at high fields using a 3-carrier scenario rather than
solely on quantum linear MR model generally used to explain the MR in
iron-pnictides. At and below 20 K the large MR may be due to 3-carrier
transport in an inhomogeneous state where there are superconducting and
metallic regions.

###Unusual magneto-transport of YBa2Cu3O7-d films due to the interplay of anisotropy, random disorder and nanoscale periodic pinning|J. Trastoy,V. Rouco,C. Ulysse,R. Bernard,A. Palau,T. Puig,G. Faini,J. Lesueur,J. Briatico,J. E. Villegas###

Unusual magneto-transport of YBa2Cu3O7-d films due to the interplay of anisotropy, random disorder and nanoscale periodic pinning. We study the general problem of a manifold of interacting elastic lines whose
spatial correlations are strongly affected by the competition between random
and ordered pinning. This is done through magneto-transport experiments with
YBa2Cu3O7-d thin films that contain a periodic vortex pinning array created via
masked ion irradiation, in addition to the native random pinning. The strong
field-matching effects we observe suggest the prevalence of periodic pinning,
and indicate that at the matching field each vortex line is bound to an
artificial pinning site. However, the vortex-glass transition dimensionality,
quasi-2D instead of the usual 3D, evidences reduced vortex-glass correlations
along the vortex line. This is also supported by an unusual angular dependence
of the magneto-resistance, which greatly differs from that of Bose-glass
systems. A quantitative analysis of the angular magnetoresistance allows us to
link this behaviour to the enhancement of the system anisotropy, a collateral
effect of the ion irradiation.

###Tunneling Magneto-Thermopower in Magnetic Tunnel Junctions|Carlos López-Monís,Alex Matos-Abiague,Jaroslav Fabian###

Tunneling Magneto-Thermopower in Magnetic Tunnel Junctions. Thermally induced spin-dependent transport across magnetic tunnel junctions
is theoretically investigated. We analyze the thermal analog of Slonczewski's
model (as well as its limiting case---Julliere's model) of tunneling
magnetoresistance and obtain analytical expressions for the junction
thermopower and the tunneling magneto-thermopower (TMT). The analytical model
is tested numerically for the special case of an Al$_2$O$_3$-based MTJ, for
which we analyze the dependence of the thermopower and TMT on the relative
magnetization orientations, as well as on the barrier height and thickness. We
show that at a certain barrier height TMT vanishes, separating the region of
positive and negative TMT. As its electrical prototype, this thermal spin
transport model should serve as a phenomenological benchmark for analyzing
experimental and first-principles calculations of thermopower in magnetic
tunnel junctions. The analytical expressions can be used as a first estimate of
the magneto-thermopower of the junctions using {\it ab initio} band structure
data of the junction ferromagnets.

###Experimental evidence for direct insulator-quantum Hall transition in multi-layer graphene|Chiashain Chuang,Li-Hung Lin,Nobuyuki Aoki,Takahiro Ouchi,Akram M. Mahjoub,Tak-Pong Woo,J. P. Bird,Yuichi Ochiai,Shun-Tsung Lo,Chi-Te Liang###

Experimental evidence for direct insulator-quantum Hall transition in multi-layer graphene. We have performed magnetotransport measurements on a multi-layer graphene
flake. At the crossing magnetic field Bc, an approximately
temperature-independent point in the measured longitudinal resistivity, which
is ascribed to the direct insulator-quantum Hall (I-QH) transition, is
observed. By analyzing the amplitudes of the magnetoresistivity oscillations,
we are able to measure the quantum mobility of our device. It is found that at
the direct I-QH transition, the product of the quantum mobility and is about
0.37 which is considerably smaller than 1. In contrast, at Bc, the longitudinal
resistivity is close to the Hall resistivity, i.e., the product of the
classical mobility and the crossing field is about 1. Therefore our results
suggest that different mobilities need to be introduced for the direct I-QH
transition observed in multi-layered graphene. Combined with existing
experimental results obtained in various material systems, our data obtained on
graphene suggest that the direct I-QH transition is a universal effect in 2D.

###Chiral skyrmions in cubic helimagnet films: the role of uniaxial anisotropy|M. N. Wilson,A. B. Butenko,A. N. Bogdanov,T. L. Monchesky###

Chiral skyrmions in cubic helimagnet films: the role of uniaxial anisotropy. This paper reports on magnetometry and magnetoresistance measurements of MnSi
epilayers performed in out-of-plane magnetic fields. We present a theoretical
analysis of the chiral modulations that arise in confined cubic helimagnets
where the uniaxial anisotropy axis and magnetic field are both out-of-plane. In
contrast to in-plane field measurements (Wilson et al., Phys. Rev. B 86, 144420
(2012)), the hard-axis uniaxial anisotropy in MnSi/Si(111) increases the energy
of (111)-oriented skyrmions and in-plane helicoids relative to the cone phase,
and makes the cone phase the only stable magnetic texture below the saturation
field. While induced uniaxial anisotropy is important in stabilizing skyrmion
lattices and helicoids in other confined cubic helimagnets, the particular
anisotropy in MnSi/Si(111) entirely suppresses these states in an out-of-plane
magnetic field. However, it is predicted that isolated skyrmions with enlarged
sizes exist in MnSi/Si(111) epilayers in a broad range of out-of-plane magnetic
fields.

###Magnetoresistance of granular Pt-C nanostructures close to the metal-insulator-transition|Fabrizio Porrati,Roland Sachser,Michael Huth###

Magnetoresistance of granular Pt-C nanostructures close to the metal-insulator-transition. We investigate the electrical and magneto-transport properties of Pt-C
granular metals prepared by focused-electron-beam induced deposition. In
particular, we consider samples close to the metal-insulator-transition
obtained from as-grown deposits by means of a low- energy electron irradiation
treatment. The temperature dependence of the conductivity shows a lnT behavior
with a transition to square root of T at low temperature, as expected for
systems in the strong-coupling tunneling regime. The magnetoresistance is
positive and is described within the wave-function shrinkage model, normally
used for disordered system in the weak-coupling regime. In order to fit the
experimental data spin-dependent tunneling has to be taken into account. In the
discussion we attribute the origin of the spin-dependency to confinement
effects of Pt nano-grains embedded in the carbon matrix.

###Magnetic domain and magnetic resistance phase transition in strongly correlated electronic material of perovskites junction|Ren R,Weiren Wang,Xuan Li,Zhongxia Zhao###

Magnetic domain and magnetic resistance phase transition in strongly correlated electronic material of perovskites junction. The junction magnetoresistivity and domain phase transition were studied
between ZnO and La0.4Gd0.1Sr0.5CoO3 thin films grown on LaAlO3 (100) substrates
epitaxially by pulse laser deposit. The ferromagnetic transformation into
phase-separated (two phase) state was displayed below Tc~127 and has observed
that the lattice change discontinuously in the doped cobalt perovskites
La0.4Gd0.1Sr0.5CoO3. The Ginzburg-Landau phase field is introduced to deduce
antiferroelectric domain structure in LGSCO thin film. On the basis of the
domain structures, the phase boundary of thin film is strongly dependent on the
combination of electric-mechanical coupling. The phase transformation into
phase separated state occurs below Tc~127-128K, and have displayed that the
lattice constants change discontinuously at the transformation. The positive MR
of ZnO/LGSCO heterojunction exhibited the MIT behavior at 0.2 T is 4.86%, at
0.5 T is 6.05% for approximately 140K.

###Generalized multi-terminal decoherent transport: Recursive algorithms and applications to SASER and giant magnetoresistance|Carlos J. Cattena,Lucas J. Fernández-Alcázar,Raúl A. Bustos-Marún,Daijiro Nozaki,Horacio M. Pastawski###

Generalized multi-terminal decoherent transport: Recursive algorithms and applications to SASER and giant magnetoresistance. Decoherent transport in mesoscopic and nanoscopic systems can be formulated
in terms of the D'Amato-Pastawski (DP) model. This generalizes the
Landauer-B\"{u}ttiker picture by considering a distribution of local decoherent
processes. However, its generalization for multi-terminal setups is lacking. We
first review the original two-terminal DP model for decoherent transport. Then,
we extend it to a matrix formulation capable of dealing with multi-terminal
problems. We also introduce recursive algorithms to evaluate the Green's
functions for general banded Hamiltonians as well as local density of states,
effective conductances and voltage profiles. We finally illustrate the method
by analyzing two problems of current relevance. 1) Assessing the role of
decoherence in a model for phonon lasers (SASER). 2) Obtaining the classical
limit of Giant Magnetoresistance from a spin-dependent Hamiltonian. The
presented methods should pave the way for computationally demanding
calculations of transport through nanodevices, bridging the gap between fully
coherent quantum schemes and semiclassical ones.

###Magneto-thermoelectric figure of merit of Co/Cu multilayers|X. K. Hu,P. Krzysteczko,N. Liebing,S. Serrano-Guisan,K. Rott,G. Reiss,J. Kimling,T. Böhnert,K. Nielsch,H. W. Schumacher###

Magneto-thermoelectric figure of merit of Co/Cu multilayers. The switching of the magnetization configurations of giant magnetoresistance
multilayer stacks not only changes the electric and thermal conductivities, but
also the thermopower. We study the magnetotransport and the
magneto-thermoelectric properties of Co/Cu multilayer devices in a lateral
thermal gradient. We derive values of the Seebeck coefficient, the
thermoelectric figure of merit, and the thermoelectric power factor. The
Seebeck coefficient reaches values up to -18 microvolt/K at room temperature
and shows a magnetic field dependence up to 28.6 % upon spin reversal. In
combination with thermal conductivity data of the same Co/Cu stack, we find a
spin dependence of the thermoelectric figure of merit of up to 65 %.
Furthermore, a spin dependence of the power factor of up to 110 % is derived.

###Fabrication, properties, and applications of flexible magnetic films|Yiwei Liu,Qingfeng Zhan,Run-Wei Li###

Fabrication, properties, and applications of flexible magnetic films. Flexible magnetic devices, i.e., magnetic devices fabricated on flexible
substrates, are very attractive in application of detecting magnetic field in
arbitrary surface, non-contact actuators, and microwave devices due to the
stretchable, biocompatible, light-weight, portable, and low cost properties.
Flexible magnetic films are essential for the realization of various
functionalities of flexible magnetic devices. To give a comprehensive
understanding for flexible magnetic films and related devices, we have reviewed
recent advances in the studies of flexible magnetic films including fabrication
methods, magnetic and transport properties of flexible magnetic films, and
their applications in magnetic sensors, actuators, and microwave devices. Three
typical methods were introduced to prepare the flexible magnetic films.
Stretching or bending the flexible magnetic films offers a good way to apply
mechanical strain on magnetic films, so that magnetic anisotropy, exchanged
bias, coercivity, and magnetoresistance can be effectively manipulated.
Finally, a series of examples were shown to demonstrate the great potential of
flexible magnetic films for future applications.

###Cu(Ir$_{1-x}$Cr$_x$)$_2$S$_4$: a model system for studying nanoscale phase coexistence at the metal-insulator transition|E. S. Bozin,K. R. Knox,P. Juhas,Y. S. Hor,J. F. Mitchell,S. J. L. Billinge###

Cu(Ir$_{1-x}$Cr$_x$)$_2$S$_4$: a model system for studying nanoscale phase coexistence at the metal-insulator transition. Increasingly, nanoscale phase coexistence and hidden broken symmetry states
are being found in the vicinity of metal-insulator transitions (MIT), for
example, in high temperature superconductors, heavy fermion and colossal
magnetoresistive materials, but their importance and possible role in the MIT
and related emergent behaviors is not understood. Despite their ubiquity, they
are hard to study because they produce weak diffuse signals in most
measurements. Here we propose Cu(Ir$_{1-x}$Cr$_x$)$_2$S$_4$ as a model system,
where robust local structural signals lead to key new insights. We demonstrate
a hitherto unobserved coexistence of a Ir$^{4+}$ charge-localized dimer phase
and Cr-ferromagnetism. The resulting phase diagram that takes into account the
short range dimer order, is highly reminiscent of a generic MIT phase diagram
similar to the cuprates. We suggest that the presence of quenched strain from
dopant ions acts as an arbiter deciding between the competing ground states.

###Magnetoresistance of composites based on graphitic disks and cones|Jozef Černák,Geir Helgesen,Fredrik Sydow Hage,Jozef Kováč###

Magnetoresistance of composites based on graphitic disks and cones. We have studied the magnetotransport of conical and disk-shaped nanocarbon
particles in magnetic fields $\left|B\right|\leq9\:\mathrm{T}$ at temperatures
$2\leq T\leq300\:\mathrm{K}$ to characterize electron scattering in a three
dimensional disordered material of multilayered quasi 2D and 3D carbon
nanoparticles. The microstructure of the particles was modified by
graphitization at temperatures $1600^{\circ}\mathrm{C}$ and
$2700^{\circ}\mathrm{C}$. We find clear correlations between the microstructure
as seen in transmission electron microscopy and the magnetotransport properties
of the particles. The magnetoresistance measurements showed a metallic nature
of samples and positive magnetoconductance which is a signature of weak
localization in disordered systems. We find that the magnetoconductance at low
temperatures resembles quantum transport in single-layer graphene despite the
fact that the samples are macroscopic and three dimensional, consisting of
stacked and layered particles, which are randomly oriented in the bulk sample.
This graphene-like behaviour is attributed to the very weak interlayer coupling
between the graphene layers.

###Partial preservation of chiral symmetry and colossal magnetoresistance in adatom doped graphene|Gonzalo Usaj,Pablo S. Cornaglia,C. A. Balseiro###

Partial preservation of chiral symmetry and colossal magnetoresistance in adatom doped graphene. We analyze the electronic properties of adatom doped graphene in the low
impurity concentration regime. We focus on the Anderson localized regime and
calculate the localization length ($\xi$) as a function of the electron doping
and an external magnetic field. The impurity states hybridize with carbon's
$p_z$ states and form a partially filled band close to the Dirac point. Near
the impurity band center, the chiral symmetry of the system's effective
Hamiltonian is partially preserved which leads to a large enhancement of $\xi$.
The sensitivity of transport properties, namely Mott's variable range hopping
scale $T_0$, to an external magnetic field perpendicular to the graphene sheet
leads to a colossal magnetoresistance effect, as observed in recent
experiments.

###Fabrication and characterisation of nanospintronic devices|J. Samm,J. Gramich,A. Baumgartner,M. Weiss,C. Schoenenberger###

Fabrication and characterisation of nanospintronic devices. We report an improved fabrication scheme for carbon based nanospintronic
devices and demonstrate the necessity for a careful data analysis to
investigate the fundamental physical mechanisms leading to magnetoresistance.
The processing with a low-density polymer and an optimised recipe allows us to
improve the electrical, magnetic and structural quality of ferromagnetic
Permalloy contacts on lateral carbon nanotube (CNT) quantum dot spin valve
devices, with comparable results for thermal and sputter deposition of the
material. We show that spintronic nanostructures require an extended data
analysis, since the magnetisation can affect all characteristic parameters of
the conductance features and lead to seemingly anomalous spin transport. In
addition, we report measurements on CNT quantum dot spin valves that seem not
to be compatible with the orthodox theories for spin transport in such
structures.

###Low-energy electronic properties of clean CaRuO$_3$: elusive Landau quasiparticles|M. Schneider,D. Geiger,S. Esser,U. S. Pracht,C. Stingl,Y. Tokiwa,V. Moshnyaga,I. Sheikin,J. Mravlje,M. Scheffler,P. Gegenwart###

Low-energy electronic properties of clean CaRuO$_3$: elusive Landau quasiparticles. We have prepared high-quality epitaxial thin films of CaRuO$_3$ with residual
resistivity ratios up to 55. Shubnikov-de Haas oscillations in the
magnetoresistance and a $T^2$ temperature dependence in the electrical
resistivity only below 1.5 K, whose coefficient is substantially suppressed in
large magnetic fields, establish CaRuO$_3$ as a Fermi liquid (FL) with
anomalously low coherence scale. Non-Fermi liquid (NFL) $T^{3/2}$ dependence is
found between 2 and 25 K. The high sample quality allows access to the
intrinsic electronic properties via THz spectroscopy. For frequencies below 0.6
THz, the conductivity is Drude-like and can be modeled by FL concepts, while
for higher frequencies non-Drude behavior, inconsistent with FL predictions, is
found. This establishes CaRuO$_3$ as a prime example of optical NFL behavior in
the THz range.

###Spin-orbit coupling and weak antilocalization in thermoelectric material $β$-K$_{2}$Bi$_{8}$Se$_{13}$|J. Hu,J. Y. Liu,Z. Q. Mao###

Spin-orbit coupling and weak antilocalization in thermoelectric material $β$-K$_{2}$Bi$_{8}$Se$_{13}$. We have studied the effect of spin-orbital coupling (SOC) on electronic
transport properties of the thermoelectric material
$\beta$-K$_{2}$Bi$_{8}$Se$_{13}$ via magnetoresistance (MR) measurements. We
found that the strong SOC in this material results in weak antilocalization
(WAL) effect, which can be well described by the three-dimensional weak
localization model. The phase coherence length extracted from theoretical
fitting exhibits a power-law temperature dependence with an exponent around
2.1, indicating that the electron phase dephasing is governed by electron -
transverse phonon interactions. Like in topological insulators, the WAL effect
in $\beta$-K$_{2}$Bi$_{8}$Se$_{13}$ can be quenched by magnetic impurities (Mn)
but is robust against non-magnetic impurities (Te). Although our
magnetotransport studies do not provide any evidences for topological surface
states, our analyses suggest that SOC plays an important role in determining
thermoelectric properties of $\beta$-K$_{2}$Bi$_{8}$Se$_{13}$.

###Ambipolar Transport and Magneto-resistance Crossover in a Mott Insulator, Sr$_{2}$IrO$_{4}$|J. Ravichandran,C. R. Serrao,D. K. Efetov,D. Yi,Y. S. Oh,S. -W. Cheong,R. Ramesh,P. Kim###

Ambipolar Transport and Magneto-resistance Crossover in a Mott Insulator, Sr$_{2}$IrO$_{4}$. Electric field effect (EFE) controlled magnetoelectric transport in thin
films of undoped and La-doped Sr$_{2}$IrO$_{4}$ (SIO) were investigated under
the action of ionic liquid gating. Despite large carrier density modulation,
the temperature dependent resistance measurements exhibit insulating behavior
in chemically and EFE doped samples with the band filling up to 10\%. The
ambipolar transport across the Mott gap is demonstrated by EFE tuning of the
activation energy. Further, we observe a crossover from a negative
magnetoresistance (MR) at high temperatures to positive MR at low temperatures.
The crossover temperature was around $\sim$80-90 K, irrespective of the
filling. This temperature and magnetic field dependent crossover is
qualitatively associated with a change in the conduction mechanism from Mott to
Coulomb gap mediated variable range hopping (VRH). This explains the origin of
robust insulating ground state of SIO in electrical transport studies and
highlights the importance of disorder and Coulombic interaction on electrical
properties of SIO.

###Enhanced spin-orbit interaction and Kondo scattering in $δ$-doped LaTiO$_3$/SrTiO$_3$ interfaces|Shubhankar Das,A. Rastogi,Lijun Wu,Jin-Cheng Zheng,Z. Hossain,Yimei Zhu,R. C. Budhani###

Enhanced spin-orbit interaction and Kondo scattering in $δ$-doped LaTiO$_3$/SrTiO$_3$ interfaces. We present a study of delta ($\delta$) doping at LaTiO$_3$/SrTiO$_3$
(LTO/STO) interface with iso-structural antiferromagnetic perovskite LaCrO$_3$
(LCO) that dramatically alters the properties of the two dimensional electron
gas (2-DEG) at the interface. The effects include a reduction in sheet-carrier
density, prominence of the low temperature resistivity minimum, enhancement of
weak antilocalization below 10 K and observation of a strong anisotropic
magnetoresistance (MR). The positive and negative MR for out-of-plane and
in-plane field respectively and the field and temperature dependencies of MR
suggest Kondo scattering by localized Ti$^{3+}$ moments renormalized by
spin-orbit interaction at T $<$ 10 K, with the increased $\delta$-layer
thickness. Electron energy loss spectroscopy and density functional
calculations provide convincing evidence for blocking of electron transfer from
LTO to STO by the $\delta$-layer.

###Weak localization in low-symmetry quantum wells|F. V. Porubaev,L. E. Golub###

Weak localization in low-symmetry quantum wells. Theory of weak localization is developed for electrons in semiconductor
quantum wells grown along [110] and [111] crystallographic axes. Anomalous
conductivity correction caused by weak localization is calculated for
symmetrically doped quantum wells. The theory is valid for both ballistic and
diffusion regimes of weak localization in the whole range of classically weak
magnetic fields. We demonstrate that in the presence of bulk inversion
asymmetry the magnetoresistance is negative: The linear in the electron
momentum spin-orbit interaction has no effect on the conductivity while the
cubic in momentum coupling suppresses weak localization without a change of the
correction sign. Random positions of impurities in the doping layers in
symmetrically doped quantum wells produce electric fields which result in
position-dependent Rashba coupling. This random spin-orbit interaction leads to
spin relaxation which changes the sign of the anomalous magnetoconductivity.
The obtained expressions allow determination of electron spin relaxation times
in (110) and (111) quantum wells from transport measurements.

###Induced Ferromagnetism at BiFeO3/YBa2Cu3O7 Interfaces|Jian-Xin Zhu,Xiao-Dong Wen,J. T. Haraldsen,Mi He,C. Panagopoulos,Elbert E. M. Chia###

Induced Ferromagnetism at BiFeO3/YBa2Cu3O7 Interfaces. Transition metal oxides (TMOs) exhibit many emergent phenomena ranging from
high-temperature superconductivity and giant magnetoresistance to magnetism and
ferroelectricity. In addition, when TMOs are interfaced with each other, new
functionalities can arise, which are absent in individual components. Here, we
report results from first-principles calculations on the magnetism at the
BiFeO3/YBa2Cu3O7 interfaces. By comparing the total energy for various magnetic
spin configurations inside BiFeO3, we are able to show that a metallic
ferromagnetism is induced near the interface. We further develop an interface
exchange-coupling model and place the extracted exchange coupling interaction
strengths, from the first-principles calculations, into a resultant generic
phase diagram. Our conclusion of interfacial ferromagnetism is confirmed by the
presence of a hysteresis loop in field-dependent magnetization data. The
emergence of interfacial ferromagnetism should have implications to electronic
and transport properties.

###Multistate nonvolatile straintronics controlled by a lateral electric field|V. Iurchuk,B. Doudin,B. Kundys###

Multistate nonvolatile straintronics controlled by a lateral electric field. We present a multifunctional and multistate permanent memory device based on
lateral electric field control of a strained surface. Sub-coercive electrical
writing of a remnant strain of a PZT substrate imprints stable and rewritable
resistance changes on a CoFe overlayer. A proof-of-principle device, with the
simplest resistance strain gage design, is shown as a memory cell exhibiting
17-memory states of high reproducibility and reliability for nonvolatile
operations. Magnetoresistance of the film also depends on the cell state, and
indicates a rewritable change of magnetic properties persisting in the remnant
strain of the substrate. This makes it possible to combine strain, magnetic and
resistive functionalities in a single memory element, and suggests that
sub-coercive stress studies are of interest for straintronics applications.

###Tunnel Magnetoresistance scan of a pristine three-dimensional topological insulator|Sthitadhi Roy,Abhiram Soori,Sourin Das###

Tunnel Magnetoresistance scan of a pristine three-dimensional topological insulator. Though the Fermi surface of surface states of a 3D topological insulator (TI)
has zero magnetization, an arbitrary segment of the full Fermi surface has a
unique magnetic moment consistent with the type of spin-momentum locking in
hand. We propose a three-terminal set up, which directly couples to the
magnetization of a chosen segment of a Fermi surface hence leading to a finite
tunnel magnetoresistance (TMR) response of the nonmagnetic TI surface states,
when coupled to spin polarized STM probe. This multiterminal TMR not only
provides a unique signature of spin-momentum locking for a pristine TI but also
provides a direct measure of momentum resolved out of plane polarization of
hexagonally warped Fermi surfaces relevant for $Bi_2Te_3$, which could be as
comprehensive as spin-resolved ARPES. Implication of this unconventional TMR is
also discussed in the broader context of 2D spin-orbit (SO) materials.

###Transport and pinning properties of Ag-doped FeSe0.94|E. Nazarova,N. Balchev,K. Nenkov,K. Buchkov,D. Kovacheva,A. Zahariev,G. Fuchs###

Transport and pinning properties of Ag-doped FeSe0.94. We investigated the superconducting transition and the pinning properties of
undoped and Ag-doped FeSe0.94 at magnetic fields up to 14 T. It was established
that due to Ag addition the hexagonal phase formation in melted FeSe0.94
samples is suppressed and the grain connectivity is strongly improved. The
obtained superconducting zero-field transition becomes sharp (with a transition
width below 1 K), Tc and the upper critical field were found to increase,
whereas the normal state resistivity significantly reduces becoming comparable
with those of FeSe single crystals. In addition, a considerable
magnetoresistance was observed due to Ag doping. The resistive transition of
undoped and Ag-doped FeSe0.94 is dominated by thermally activated flux flow.
From the activation energy U vs H dependence, a crossover from single-vortex
pinning to a collective creep pinning behavior was found with increasing the
magnetic field.

###Resonant Charge Relaxation as a Likely Source of the Enhanced Thermopower in FeSi|Peijie Sun,Beipei Wei,Dirk Menzel,Frank Steglich###

Resonant Charge Relaxation as a Likely Source of the Enhanced Thermopower in FeSi. The enhanced thermopower of the correlated semiconductor FeSi is found to be
robust against the sign of the relevant charge carriers. At $T$\,$\approx$\,70
K, the position of both the high-temperature shoulder of the thermopower peak
and the nonmagnetic-enhanced paramagnetic crossover, the Nernst coefficient
$\nu$ assumes a large maximum and the Hall mobility $\mu _H$ diminishes to
below 1 cm$^2$/Vs. These cause the dimension-less ratio $\nu$/$\mu_H$ $-$ a
measure of the energy dispersion of the charge scattering time $\tau(\epsilon)$
$-$ to exceed that of classical metals and semiconductors by two orders of
magnitude. Concomitantly, the resistivity exhibits a hump and the
magnetoresistance changes its sign. Our observations hint at a resonant
scattering of the charge carriers at the magnetic crossover, imposing strong
constraints on the microscopic interpretation of the robust thermopower
enhancement in FeSi.

###Magneto-transport properties of oriented Mn2CoAl films sputtered on thermally oxidized Si substrates|G. Z. Xu,Y. Du,X. M. Zhang,H. G. Zhang,E. K. Liu,W. H. Wang,G. H. Wu###

Magneto-transport properties of oriented Mn2CoAl films sputtered on thermally oxidized Si substrates. Spin gapless semiconductors are interesting novel class of materials by
embracing both magnetism and semiconducting. Its potential application in
future spintronics requires realization in thin film form. In this letter, we
report a successful growth of spin gapless Mn2CoAl films on thermally oxidized
Si substrates by magnetron sputtering deposition. The films deposited at 673K
are well oriented to (001) direction and display a uniform-crystalline surface.
Magnetotransport measurements on the oriented films reveal a
semiconducting-like resistivity, small anomalous Hall conductivity and linear
magnetoresistance (MR) representative of the transport signatures of spin
gapless semiconductors. The magnetic properties of the films have also been
investigated and compared to that of bulk Mn2CoAl, with small discrepancy
induced by the composition deviation.

###Strongly anisotropic ballistic magnetoresistance in compact three-dimensional semiconducting nanoarchitectures|Ching-Hao Chang,Jeroen van den Brink,Carmine Ortix###

Strongly anisotropic ballistic magnetoresistance in compact three-dimensional semiconducting nanoarchitectures. We establish theoretically that in nonmagnetic semiconducting bilayer or
multilayer thin film systems rolled up into compact quasi-one-dimensional
nanoarchitectures, the ballistic magnetoresistance is very anisotropic:
conductances depend strongly on the direction of an externally applied magnetic
field. This phenomenon originates from the curved open geometry of rolled-up
nanotubes, which leads to a tunability of the number of quasi-one-dimensional
magnetic subbands crossing the Fermi energy. The experimental significance of
this phenomenon is illustrated by a sizable anisotropy that scales with the
inverse of the winding number, and persists up to a critical temperature that
can be strongly enhanced by increasing the strength of the external magnetic
field or the characteristic radius of curvature, and can reach room
temperature.

###Large linear magnetoresistance in the Dirac semimetal TlBiSSe|Mario Novak,Satoshi Sasaki,Kouji Segawa,Yoichi Ando###

Large linear magnetoresistance in the Dirac semimetal TlBiSSe. The mixed-chalcogenide compound TlBiSSe realizes a three-dimensional (3D)
Dirac semimetal state. In clean, low-carrier-density single crystals of this
material, we found Shubnikov-de Haas oscillations to signify its 3D Dirac
nature. Moreover, we observed very large linear magnetoresistance (MR)
approaching 10,000% in 14 T at 1.8 K, which diminishes rapidly above 30 K. Our
analysis of the magnetotransport data points to the possibility that the linear
MR is fundamentally governed by the Hall field; although such a situation has
been predicted for highly-inhomogeneous systems, inhomogeneity does not seem to
play an important role in TlBiSSe. Hence, the mechanism of large linear MR is
an intriguing open question in a clean 3D Dirac system.

###Weak antilocalization in (111) thin films of a topological crystalline insulator SnTe|Ryota Akiyama,Kazuki Fujisawa,Ryutaro Sakurai,Shinji Kuroda###

Weak antilocalization in (111) thin films of a topological crystalline insulator SnTe. We grew single-crystal thin films of a topological crystalline insulator
(TCI) SnTe with a smooth surface at the atomic scale by molecular beam epitaxy
(MBE). In the magnetoresistance (MR) measurement, we observed both positive and
negative components near zero magnetic field at lowest temperatures of 2 - 3 K,
while we observed only a negative MR at elevated temperatures of 6 - 10 K. The
positive MR is attributed to the weak antilocalization (WAL) in the transport
through the topological surface state (SS), demonstrating $\pi$ berry phase
which is essential to the topological SS, while the negative MR to the weak
localization (WL) in the transport through the bulk state (two-dimensional bulk
subbbands). The absolute value of the prefactor $ \alpha $ deduced from the
fitting of the observed positive MR to the Hikami-Larkin-Nagaoka equation was
much smaller than expected from the number of transport channel of the SS,
suggesting the coupling of the SS to the bulk state.

###Critical behavior at the dynamic Mott transition|Nicola Poccia,Tatyana I. Baturina,Francesco Coneri,Cor G. Molenaar,X. Renshaw Wang,Ginestra Bianconi,Alexander Brinkman,Hans Hilgenkamp,Alexander A. Golubov,Valerii M. Vinokur###

Critical behavior at the dynamic Mott transition. We investigate magnetoresistance of a square array of superconducting islands
placed on a normal metal, which offers a unique tunable laboratory for
realizing and exploring quantum many-body systems and their dynamics. A vortex
Mott insulator where magnetic field-induced vortices are frozen in the dimples
of the egg crate potential by their strong repulsion interaction is discovered.
We find an insulator-to-metal transition driven by the applied electric current
and determine critical exponents that exhibit striking similarity with the
common thermodynamic liquid-gas transition. A simple and straightforward
quantum mechanical picture is proposed that describes both tunneling dynamics
in the deep insulating state and the observed scaling behavior in the vicinity
of the critical point. Our findings offer a comprehensive description of
dynamic Mott critical behavior and establish a deep connection between
equilibrium and nonequilibrium phase transitions.

###Superconducting properties in tantalum decorated three-dimensional graphene and carbon structures|Cayetano S. F. Cobaleda,Xiaoyin Xiao,D. Bruce Burckel,Ronen Polsky,Duanni Huang,Enrique Diez,W. Pan###

Superconducting properties in tantalum decorated three-dimensional graphene and carbon structures. We present here the results on superconducting properties in tantalum thin
films (100nm thick) deposited on three-dimensional graphene (3DG) and carbon
structures. A superconducting transition is observed in both composite thin
films with a superconducting transition temperature of 1.2K and 1.0K,
respectively. We have further measured the magnetoresistance at various
temperatures and differential resistance dV/dI at different magnetic fields in
these two composite thin films. In both samples, a much large critical magnetic
field (~ 2 Tesla) is observed and this critical magnetic field shows linear
temperature dependence. Finally, an anomalously large cooling effect was
observed in the differential resistance measurements in our 3DG-tantalum device
when the sample turns superconducting. Our results may have important
implications in flexible superconducting electronic device applications.

###Electrical detection of ferromagnetic resonance in ferromagnet/n-GaAs heterostructures by tunneling anisotropic magnetoresistance|Changjiang Liu,Yakov Boyko,Chad Geppert,Kevin Christie,Gordon Stecklein,Sahil Patel,Chris Palmstrøm,Paul Crowell###

Electrical detection of ferromagnetic resonance in ferromagnet/n-GaAs heterostructures by tunneling anisotropic magnetoresistance. We observe a dc voltage peak at ferromagnetic resonance (FMR) in samples
consisting of a single ferromagnetic (FM) layer grown epitaxially on the
$\mathit{n-}$GaAs (001) surface. The FMR peak is detected as an interfacial
voltage with a symmetric line shape and is present in samples based on various
FM/$n$-GaAs hetrostructures, including Co$_{2}$MnSi/$n$-GaAs,
Co$_{2}$FeSi/$n$-GaAs and Fe/$n$-GaAs. We show that the interface bias voltage
dependence of the FMR signal is identical to that of the tunneling anisotropic
magnetoresistance (TAMR) over most of the bias range. Furthermore, we show how
the precessing magnetization yields a dc FMR signal through the TAMR effect and
how the TAMR phenomenon can be used to predict the angular dependence of the
FMR signal. This TAMR-induced FMR peak can be observed under conditions where
no spin accumulation is present and no spin-polarized current flows in the
semiconductor.

###Spin transport with traps: dramatic narrowing of the Hanle curve|R. C. Roundy,M. E. Raikh###

Spin transport with traps: dramatic narrowing of the Hanle curve. We study theoretically the spin transport in a device in which the active
layer is an organic film with numerous deep in-gap levels serving as traps. A
carrier, diffusing between magnetized injector and detector, spends a
considerable portion of time on the traps. This new feature of transport does
not affect the giant magnetoresistance, which is sensitive only to the mutual
orientation of magnetizations of the injector and detector. By contrast, the
presence of traps strongly affects the sensitivity of the spin transport to
external magnetic field perpendicular to the magnetizations of the electrodes
(the Hanle effect). Namely, the Hanle curve narrows dramatically. The origin of
such a narrowing is that the spin precession takes place during the entire time
of the carrier motion between the electrodes, while the spin relaxation takes
place only during diffusive motion between the subsequent traps. If the
resulting width of the Hanle curve is smaller than the measurement resolution,
observation of the Hanle peak becomes impossible.

###Theoretical Details of Tunnel Magnetoresistance via inelastic hopping at regime $gμB\ll k_B T \ll eV$|Yang Song###

Theoretical Details of Tunnel Magnetoresistance via inelastic hopping at regime $gμB\ll k_B T \ll eV$. Detailed theoretical derivation is given for the tunnel magnetoresistance via
phonon-assisted hopping through an impurity chain under small magnetic field
and a large bias window. This derivation provides a rigorous basis for the
physical picture of Pauli blockade switch proposed in our previous paper
(arXiv:1404.0633). This picture captures the competition of external magnetic
field and internal spin interactions in the tunnel barrier, and relies
critically on the strong on-site Coulomb correlation at the impurities. The
master equations are obtained by deriving the equations of motion for the Green
functions at the impurity sites in a slave-boson representation, and utilizing
the so-called Langreth theorem to finally express the spin-dependent density
matrix in terms of the equilibrium distributions of the contact electrons and
of the phonon reservoir.

###Strain-enhanced tunneling magnetoresistance in MgO magnetic tunnel junctions|Li Ming Loong,Xuepeng Qiu,Zhi Peng Neo,Praveen Deorani,Yang Wu,Charanjit S. Bhatia,Mark Saeys,Hyunsoo Yang###

Strain-enhanced tunneling magnetoresistance in MgO magnetic tunnel junctions. While the effects of lattice mismatch-induced strain, mechanical strain, as
well as the intrinsic strain of thin films are sometimes detrimental, resulting
in mechanical deformation and failure, strain can also be usefully harnessed
for applications such as data storage, transistors, solar cells, and strain
gauges, among other things. Here, we demonstrate that quantum transport across
magnetic tunnel junctions (MTJs) can be significantly affected by the
introduction of controllable mechanical strain, achieving an enhancement factor
of ~2 in the experimental tunneling magnetoresistance (TMR) ratio. We further
correlate this strain-enhanced TMR with coherent spin tunneling through the MgO
barrier. Moreover, the strain-enhanced TMR is analyzed using non-equilibrium
Green's function (NEGF) quantum transport calculations. Our results help
elucidate the TMR mechanism at the atomic level and can provide a new way to
enhance, as well as tune, the quantum properties in nanoscale materials and
devices.

###Simultaneous detection of the spin-Hall magnetoresistance and the spin-Seebeck effect in Platinum and Tantalum on Yttrium Iron Garnet|N. Vlietstra,M. Isasa,J. Shan,J. Ben Youssef,F. Casanova,B. J. van Wees###

Simultaneous detection of the spin-Hall magnetoresistance and the spin-Seebeck effect in Platinum and Tantalum on Yttrium Iron Garnet. The spin-Seebeck effect (SSE) in platinum (Pt) and tantalum (Ta) on yttrium
iron garnet (YIG) has been investigated by both externally heating the sample
(using an on-chip Pt heater on top of the device) as well as by current-induced
heating. For SSE measurements, external heating is the most common method to
obtain clear signals. Here we show that also by current-induced heating it is
possible to directly observe the SSE, separate from the also present spin-Hall
magnetoresistance (SMR) signal, by using a lock-in detection technique. Using
this measurement technique, the presence of additional 2nd order signals at low
applied magnetic fields and high heating currents is revealed. These signals
are caused by current-induced magnetic fields (Oersted fields) generated by the
used AC-current, resulting in dynamic SMR signals.

###Polaron-mediated spin correlations in metallic and insulating La$_{1-x}A_{x}$MnO$_{3}$ ($A$=Ca, Sr, or Ba)|Joel S. Helton,Daniel M. Pajerowski,Yiming Qiu,Yang Zhao,Dmitry A. Shulyatev,Yakov M. Mukovskii,Georgii L. Bychkov,Sergei N. Barilo,Jeffrey W. Lynn###

Polaron-mediated spin correlations in metallic and insulating La$_{1-x}A_{x}$MnO$_{3}$ ($A$=Ca, Sr, or Ba). Neutron spectroscopy measurements reveal short-range spin correlations near
and above the ferromagnetic-paramagnetic phase transition in manganite
materials of the form La$_{1-x}A_{x}$MnO$_{3}$, including samples with an
insulating ground state as well as colossal magnetoresistive samples with a
metallic ground state. Quasielastic magnetic scattering is revealed that forms
clear ridges running along the [100]-type directions in momentum space. A
simple model consisting of a conduction electron hopping between spin polarized
Mn ions that becomes self-trapped after a few hops captures the essential
physics of this magnetic component of the scattering. We associate this
scattering component with the magnetic part of diffuse polarons, as we observe
a temperature dependence similar to that of the diffuse structural scattering
arising from individual polarons.

###Pressure-dependent magnetization and magnetoresistivity studies on the tetragonal FeS (mackinawite): revealing its intrinsic metallic character|S. J. Denholme,H. Okazaki,S. Demura,K. Deguchi,M. Fujioka,T. Yamaguchi,H. Takeya,M. ElMassalami,H. Fujiwara,T. Wakita,T. Yokoya,Y. Takano###

Pressure-dependent magnetization and magnetoresistivity studies on the tetragonal FeS (mackinawite): revealing its intrinsic metallic character. The transport and magnetic properties of the tetragonal Fe$_{1+\delta}$S were
investigated using magnetoresistivity and magnetization within 2$\leq T\leq
$300 K, $H\leq$70 kOe and $P\leq$ 3.0 GPa. In addition, room-temperature X-ray
diffraction and photoelectron spectroscopy were also applied. In contrast to
previously reported nonmetallic character, Fe$_{1+\delta}$S is intrinsically
metallic but due to a presence of a weak localization such metallic character
is not exhibited below room temperature. An applied pressure reduces strongly
this additional resistive contribution and as such enhances the temperature
range of the metallic character which, for $\sim$3 GPa, is evident down to 75
K. The absence of superconductivity as well as the mechanism behind the weak
localization will be discussed.

###Comment on "Multiorbital Effects on the Transport and the Superconducting Fluctuations in LiFeAs"|A. Ramos-Álvarez,J. Mosqueira,F. Vidal###

Comment on "Multiorbital Effects on the Transport and the Superconducting Fluctuations in LiFeAs". In the commented work (PRL 109, 187005 (2012)), Rullier-Albenque et al.
present measurements of transverse magnetoresistivity above the transition
temperature Tc in clean LiFeAs. By analyzing their data, these authors conclude
that the conductivity induced by fluctuations follows a two-dimensional (2D)
behavior even close to Tc, in spite that for LiFeAs the transverse coherence
length ($\xi_c$(0)=1.6 nm) is larger than the Fe-layers spacing (s=0.636 nm),
which would rather suggest a three-dimensional (3D) behavior. This striking
proposal would have deep implications in the theoretical understanding of the
multiband structure of iron pnictides, but it also contrasts with the 3D
behavior observed near Tc in the same compound and in other iron pnictides with
even smaller $\xi_c$(0)/s ratios. Here we show that the proposal of Rullier et
al. could be just an artifact associated to an inadequate subtraction of the
normal-state contribution.

###Anomalous magnetic ground state in LaAlO3/SrTiO3 interface probed by transport through nanowires|A. Ron,E. Maniv,D. Graf,J. -H. Park,Y. Dagan###

Anomalous magnetic ground state in LaAlO3/SrTiO3 interface probed by transport through nanowires. Resistance as a function of temperature down to 20mK and magnetic fields up
to 18T for various carrier concentrations is measured for nanowires made from
the SrTiO3/LaAlO3 interface using a hard mask shadow deposition technique. The
narrow width of the wires (of the order of 50nm) allows us to separate out the
magnetic effects from the dominant superconducting ones at low magnetic fields.
At this regime hysteresis loops are observed along with the superconducting
transition. From our data analysis we find that the magnetic order probed by
the giant magnetoresistance (GMR) effect vanishes at TCurie = 954 mK. This
order is not a simple ferromagnetic state but consists of domains with opposite
magnetization having a preferred in-plane orientation.

###Calculation of energy-barrier lowering by incoherent switching in STT-MRAM|Kamaram Munira,P. B. Visscher###

Calculation of energy-barrier lowering by incoherent switching in STT-MRAM. To make a useful STT-MRAM (spin-transfer torque magnetoresistive
random-access memory) device, it is necessary to be able to calculate switching
rates, which determine the error rates of the device. In a single-macrospin
model, one can use a Fokker-Planck equation to obtain a low-current thermally
activated rate $\propto \exp(-E_{eff}/k_B T)$. Here the effective energy
barrier $E_{eff}$ scales with the single-macrospin energy barrier $KV$, where
$K$ is the effective anisotropy energy density and $V$ the volume. A
long-standing paradox in this field is that the actual energy barrier appears
to be much smaller than this. It has been suggested that incoherent motions may
lower the barrier, but this has proved difficult to quantify. In the present
paper, we show that the coherent precession has a magnetostatic instability,
which allows quantitative estimation of the energy barrier and may resolve the
paradox.

###Investigation of intrinsic magnetodielectric effect in La2CoMnO6: Role of magnetic disorder|J. Krishna Murthya,K. Devi Chandrasekhar S. Murugavel,A. Venimadhav###

Investigation of intrinsic magnetodielectric effect in La2CoMnO6: Role of magnetic disorder. We present a large magnetodielectric (MD) effect of 65 % at 100 kHz with 5 T
field in B-site ordered La2CoMnO6 (LCMO) polycrystalline sample. Frequency and
temperature dependent impedance and dielectric studies under magnetic field
divulge both intrinsic and extrinsic origins for the observed MD effect. The
temperature dependent Raman spectroscopy measurement has shown spin-lattice
coupling that supports the intrinsic origin of the observed large MD response
in LCMO. Extrinsic contributions to MD response mainly originate from disorder
and interface effects; here, we signify this by hole carrier (Sr) doping at the
A-site of the ordered LCMO sample. The comparison study has disclosed that with
the disorder, the intrinsic polarization due to asymmetric hopping decreases
significantly, and the disorder induced transport dominates in both MD and
magnetoresistance behaviour with close resemblance.

###Unscaling Superconducting Parameters with $T_c$ for Bi-2212 and Bi-2223: A Magnetotransport Study in the Superconductive Fluctuation Regime|Shintaro Adachi,Tomohiro Usui,Hironobu Kudo,Haruki Kushibiki,Kosuke Murata,Takao Watanabe,Kazutaka Kudo,Terukazu Nishizaki,Norio Kobayashi,Shojiro Kimura,Masaki Fujita,Kazuyoshi Yamada,Takashi Noji,Yoji Koike,Takenori Fujii###

Unscaling Superconducting Parameters with $T_c$ for Bi-2212 and Bi-2223: A Magnetotransport Study in the Superconductive Fluctuation Regime. To investigate the origin of the enhanced $T_c$ ($\approx$ 110 K) of the
trilayer cuprate superconductor Bi$_{2}$Sr$_{2}$Ca$_{2}$Cu$_{3}$O$_{10+\delta}$
(Bi-2223), we have performed systematic magnetoresistance (MR) measurements on
this superconductor, as well as on the bilayer superconductor,
Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ (Bi-2212). The in-plane coherence
length, $\xi_{ab}$, and the specific-heat jump, ${\Delta}C$, have been
estimated using the theory of renormalized superconductive fluctuations, and
the doping dependence of these parameters has been qualitatively explained
using the Fermi arc approach. A detailed comparison of the superconducting
parameters with $T_c$ for these compounds suggests that an additional
superconducting condensation energy exists, due to an increase in the number of
stacking CuO$_{2}$ planes in a unit cell.

###Effects of a tilted magnetic field in a Dirac double layer|Sergey S. Pershoguba,D. S. L. Abergel,Victor M. Yakovenko,A. V. Balatsky###

Effects of a tilted magnetic field in a Dirac double layer. We calculate the energy spectrum of a Dirac double layer, where each layer
has the Dirac electronic dispersion, in the presence of a tilted magnetic field
and small interlayer tunneling. We show that the energy splitting between the
Landau levels has an oscillatory dependence on the in-plane magnetic field and
vanishes at a series of special tilt angles of the magnetic field. Using a
semiclassical analysis, we show that these special tilt angles are determined
by the Berry phase of the Dirac Hamiltonian. The interlayer tunneling
conductance also exhibits an oscillatory dependence on the magnetic field tilt
angle, known as the angular magnetoresistance oscillations (AMRO). Our results
are applicable to graphene double layers and thin films of topological
insulators.

###Upper bound for the s-d exchange integral in n-(Ga,Mn)N:Si from magnetotransport studies|R. Adhikari,W. Stefanowicz,B. Faina,M. Sawicki,T. Dietl,A. Bonanni###

Upper bound for the s-d exchange integral in n-(Ga,Mn)N:Si from magnetotransport studies. A series of recent magnetooptical studies pointed to contradicting values of
the s-d exchange energy N0{\alpha} in Mn-doped GaAs and GaN as well as in
Fe-doped GaN. Here, a strong sensitivity of weak-localization phenomena to
symmetry breaking perturbations (such as spin-splitting and spin-disorder
scattering) is exploited to evaluate the magnitude of N0{\alpha} for n-type
wurtzite (Ga,Mn)N:Si films grown by metalorganic vapor phase epitaxy.
Millikelvin magnetoresistance studies and their quantitative interpretation
point to N0{\alpha} < 40 meV, a value at least 5 times smaller than the one
found with similar measurements on, e.g., $n$-(Zn,Mn)O. It is shown that this
striking difference in the values of the s-d coupling between $n$-type III-V
and II-VI dilute magnetic semiconductors can be explained by a theory that
takes into account the acceptor character of Mn in III-V compounds.

###Transport Theory of Metallic B20 Helimagnets|Jian Kang,Jiadong Zang###

Transport Theory of Metallic B20 Helimagnets. B20 compounds are a class of cubic helimagnets harboring nontrivial spin
textures such as spin helices and skyrmions. It has been well understood that
the Dzyaloshinskii-Moriya (DM) interaction is the origin of these textures, and
the physics behind the DM interaction is the spin-orbital coupling (SOC).
However the SOC shows its effect not only on the spins, but also on the
electrons. In this paper, we will discuss effects of the SOC on the electron
and spin transports in B20 compounds. An effective Hamiltonian is presented
from symmetry analysis, and the spin-orbital coupling therein shows anomalous
behaviors in anisotropic magnetoresistance (AMR) and helical resistance. New
effects such as inverse spin-galvanic effect is proposed, and the origin of the
DM interaction is discussed.

###Transport Signatures of Fermi Surface Topology Change in BiTeI|Linda Ye,Joseph G. Checkelsky,Fumitaka Kagawa,Yoshinori Tokura###

Transport Signatures of Fermi Surface Topology Change in BiTeI. We report a quantum magnetotransport signature of a change in Fermi surface
topology in the Rashba semiconductor BiTeI with systematic tuning of the Fermi
level $E_F$. Beyond the quantum limit, we observe a marked increase/decrease in
electrical resistivity when $E_F$ is above/below the Dirac node that we show
originates from the Fermi surface topology. This effect represents a
measurement of the electron distribution on the low-index ($n=0,-1$) Landau
levels and is uniquely enabled by the finite bulk $k_z$ dispersion along the
$c$-axis and strong Rashba spin-orbit coupling strength of the system. The
Dirac node is independently identified by Shubnikov-de Haas oscillations as a
vanishing Fermi surface cross section at $k_z=0$. Additionally we find that the
violation of Kohler's rule allows a distinct insight into the temperature
evolution of the observed quantum magnetoresistance effects.

###Geometric tuning of charge and spin correlations in manganite superlattices|K. Rogdakis,Z. Viskadourakis,A. P. Petrovic,E. Choi,J. Lee,C. Panagopoulos###

Geometric tuning of charge and spin correlations in manganite superlattices. We report a modulation of the in-plane magnetotransport in artificial
manganite superlattice (SL) [(NdMnO3)n /(SrMnO3)n /(LaMnO3)n]m by varying the
layer thickness n while keeping the total thickness of the structure constant.
Charge transport in these heterostructures is confined to the interfaces and
occurs via variable range hopping (VRH). Upon increasing n, the interfacial
separation rises, leading to a suppression of the electrostatic screening
between carriers of neighboring interfaces and the opening of a Coulomb gap at
the Fermi level (EF). The high-field magnetoresistance (MR) is universally
negative due to progressive spin alignment. However at a critical thickness of
n=5 unit cells (u.c.), an exchange field coupling between ferromagnetically
ordered interfaces results in positive MR at low magnetic field (H). Our
results demonstrate the ability to geometrically tune the electrical transport
between regimes dominated by either charge or spin correlations.

###Anomalous Hall effect in YIG$|$Pt bilayers|Sibylle Meyer,Richard Schlitz,Stephan Geprägs,Matthias Opel,Hans Huebl,Rudolf Gross,Sebastian T. B. Goennenwein###

Anomalous Hall effect in YIG$|$Pt bilayers. We measure the ordinary and the anomalous Hall effect in a set of yttrium
iron garnet$|$platinum (YIG$|$Pt) bilayers via magnetization orientation
dependent magnetoresistance experiments. Our data show that the presence of the
ferrimagnetic insulator YIG leads to an anomalous Hall like signature in Pt,
sensitive to both Pt thickness and temperature. Interpretation of the
experimental findings in terms of the spin Hall anomalous Hall effect indicates
that the imaginary part of the spin mixing interface conductance
$G_{\mathrm{i}}$ plays a crucial role in YIG$|$Pt bilayers. In particular, our
data suggest a sign change in $G_{\mathrm{i}}$ between $10\,\mathrm{K}$ and
$300\,\mathrm{K}$. Additionally, we report a higher order Hall effect, which
appears in thin Pt films on YIG at low temperatures.

###Multiband superconductivity in Ta$_4$Pd$_3$Te$_{16}$ with anisotropic gap structure|Wen-He Jiao,Yi Liu,Yu-Ke Li,Xiao-Feng Xu,Jin-Ke Bao,Chun-Mu Feng,Shi-Yan Li,Zhu-An Xu,Guang-Han Cao###

Multiband superconductivity in Ta$_4$Pd$_3$Te$_{16}$ with anisotropic gap structure. We carried out the measurements of magnetoresistance, magnetic susceptibility
and specific heat on crystals of the low-dimensional transition metal telluride
Ta$_4$Pd$_3$Te$_{16}$. Our results indicate that Ta$_4$Pd$_3$Te$_{16}$ is an
anisotropic type-II superconductor with the extracted Ginzburg-Landau parameter
$\kappa_{\text{GL}}=$ 84. The upper critical field $H_{c2}$($T$) shows a linear
dependence at low temperature and the anisotropy of $H_{c2}$($T$) is strongly
$T$-dependent, both of which indicate a multiband scenario. A detailed analysis
reveals that the electronic specific heat $C_{\text{el}}$($T$) can be
consistently described by a two-gap ($s$+$d$ waves) model from the base
temperature $T/T_c\sim$ 0.12 up to $T_c$. Our data suggests multiband
superconductivity in Ta$_4$Pd$_3$Te$_{16}$ with anisotropic gap structure.

###Transport and magnetotransport in 3D Weyl Semimetals|Navneeth Ramakrishnan,Mirco Milletari,Shaffique Adam###

Transport and magnetotransport in 3D Weyl Semimetals. We theoretically investigate the transport and magnetotransport properties of
three-dimensional Weyl semimetals. Using the RPA-Boltzmann transport scattering
theory for electrons scattering off randomly distributed charged impurities,
together with an effective medium theory to average over the resulting
spatially inhomogeneous carrier density, we smoothly connect our results for
the minimum conductivity near the Weyl point with known results for the
conductivity at high carrier density. In the presence of a non-quantizing
magnetic field, we predict that for both high and low carrier densities, Weyl
semimetals show a transition from quadratic magnetoresistance (MR) at low
magnetic fields to linear MR at high magnetic fields, and that the magnitude of
the MR > 10 for realistic parameters. Our results are in quantitative agreement
with recent unexpected experimental observations on the mixed-chalcogenide
compound TlBiSSe.

###Localization of charge carriers in monolayer graphene gradually disordered by ion irradiation|E. Zion,A. Haran,A. V. Butenko,L. Wolfson,Yu. Kaganovskii,T. Havdala,A. Sharoni,D. Naveh,V. Richter,M. Kaveh,E. Kogan,I. Shlimak###

Localization of charge carriers in monolayer graphene gradually disordered by ion irradiation. Gradual localization of charge carriers was studied in a series of micro-size
samples of monolayer graphene fabricated on the common large scale film and
irradiated by different doses of C$^+$ ions with energy 35 keV. Measurements of
the temperature dependence of conductivity and magnetoresistance in fields up
to 4 T showed that at low disorder, the samples are in the regime of weak
localization and antilocalization. Further increase of disorder leads to strong
localization regime, when conductivity is described by the
variable-range-hopping (VRH) mechanism. A crossover from the Mott regime to the
Efros-Shklovskii regime of VRH is observed with decreasing temperature.
Theoretical analysis of conductivity in both regimes showed a remarkably good
agreement with experimental data.

###Raman fingerprint of semi-metal WTe2 from bulk to monolayer|Yucheng Jiang,Ju Gao,Lin Wang###

Raman fingerprint of semi-metal WTe2 from bulk to monolayer. Tungsten ditelluride (WTe2), a layered transition-metal dichalcogenide (TMD),
has recently demonstrated an extremely large magnetoresistance effect, which is
unique among TMDs. This fascinating feature seems to be correlated with its
special electronic structure. Here, we report the observation of 6 Raman peaks
corresponding to the A_2^4, A_1^9, A_1^8, A_1^6, A_1^5 and A_1^2 phonons, from
the 33 Raman-active modes predicted for WTe2. This provides direct evidence to
distinguish the space group of WTe2 from that of other TMDs. Moreover, the
Raman evolution of WTe2 from bulk to monolayer is clearly revealed. It is
interesting to find that the A_2^4 mode, centered at ~109.8 cm-1, is forbidden
in a monolayer, which may be attributable to the transition of the point group
from C2v (bulk) to C2h (monolayer). Our work characterizes all observed Raman
peaks in the bulk and few-layer samples and provides a route to study the
physical properties of two-dimensional WTe2.

###Superpoissonian shot noise in organic magnetic tunnel junctions|Juan Pedro Cascales,Jhen-Yong Hong,Isidoro Martinez,Minn-Tsong Lin,Tomasz Szczepanski,Vitalii K. Dugaev,Jozef Barnas,Farkad G. Aliev###

Superpoissonian shot noise in organic magnetic tunnel junctions. Organic molecules have recently revolutionized ways to create new spintronic
devices. Despite intense studies, the statistics of tunneling electrons through
organic barriers remains unclear. Here we investigate conductance and shot
noise in magnetic tunnel junctions with PTCDA barriers a few nm thick. For
junctions in the electron tunneling regime, with magnetoresistance ratios
between 10 and 40\%, we observe superpoissonian shot noise. The Fano factor
exceeds in 1.5-2 times the maximum values reported for magnetic tunnel
junctions with inorganic barriers, indicating spin dependent bunching in
tunneling. We explain our main findings in terms of a model which includes
tunneling through a two level (or multilevel) system, originated from
interfacial bonds of the PTCDA molecules. Our results suggest that interfaces
play an important role in the control of shot noise when electrons tunnel
through organic barriers.

###Naive model from 1970th applied to CMR manganites: it seems to work|A. Vl. Andrianov###

Naive model from 1970th applied to CMR manganites: it seems to work. Existing experimental data for various colossal magnetoresistance manganites
have been examined employing an ovesimplified model that roots in 1970th. This
model considers a classical semiconductor where conducting bands are affected
by the strong Weiss exchange field that arises from the magnetic order in the
substance. The field--caused shifts of the conducting bands results in the
change in the number of thermally activated carriers, and this change is
presumed to be responsible for the resistivity dependences on temperature and
magnetic field and for the CMR itself. Employing this model we calculate this
hypothetical Weiss field from the experimental data for various CMR manganites
employing minimal set of the adjustable parameters, namely two. The obtained
Weiss field behaves with temperature and external field similarly to the local
magnetization, its supposed source, hence supporting the model.

###Transition from semiconducting to metallic-like conducting and weak antilocalization effect in single crystals of LuPtSb|Zhipeng Hou,Yue Wang,Guizhou Xu,Xiaoming Zhang,Enke Liu,Wenquan Wang,Zhongyuan Liu,Xuekui Xi,Wenhong Wang,Guangheng Wu###

Transition from semiconducting to metallic-like conducting and weak antilocalization effect in single crystals of LuPtSb. High quality half-Heusler single crystals of LuPtSb have been synthesized by
a Pb flux method. The temperature dependent resistivity and Hall effects
indicate that the LuPtSb crystal is a p-type gapless semiconductor showing a
transition from semiconducting to metallic conducting at 150 K. Moreover, a
weakly temperature-dependent positive magnetoresistance (MR) as large as 109 %
and high carrier mobility up to 2950 cm2/Vs are experimentally observed at
temperatures below 150 K. The low-field MR data shows evidence for weak
antilocalization (WAL) effect at temperatures even up to 150 K. Analysis of the
temperature and angle dependent magnetoconductance manifests that the WAL
effect originates from the bulk contribution owing to the strong spin-orbital
coupling.

###Pressure-driven dome-shaped superconductivity and electronic structural evolution in tungsten ditelluride|Xing-Chen Pan,Xuliang Chen,Huimei Liu,Yanqing Feng,Zhongxia Wei,Yonghui Zhou,Zhenhua Chi,Li Pi,Fei Yen,Fengqi Song,Xiangang Wan,Zhaorong Yang,Baigeng Wang,Guanghou Wang,Yuheng Zhang###

Pressure-driven dome-shaped superconductivity and electronic structural evolution in tungsten ditelluride. Tungsten ditelluride has attracted intense research interest due to the
recent discovery of its large unsaturated magnetoresistance up to 60 Tesla.
Motivated by the presence of a small, sensitive Fermi surface of 5d electronic
orbitals, we boost the electronic properties by applying a high pressure, and
introduce superconductivity successfully. Superconductivity sharply appears at
a pressure of 2.5 GPa, rapidly reaching a maximum critical temperature (Tc) of
7 K at around 16.8 GPa, followed by a monotonic decrease in Tc with increasing
pressure, thereby exhibiting the typical dome-shaped superconducting phase.
From theoretical calculations, we interpret the low-pressure region of the
superconducting dome to an enrichment of the density of states at the Fermi
level and attribute the high-pressure decrease in Tc to possible structural
instability. Thus, Tungsten ditelluride may provide a new platform for our
understanding of superconductivity phenomena in transition metal
dichalcogenides.

###Resonant magneto-tunneling between normal and ferromagnetic electrodes in relation to the three-terminal spin transport|Z. Yue,M. E. Raikh###

Resonant magneto-tunneling between normal and ferromagnetic electrodes in relation to the three-terminal spin transport. The recently suggested mechanism [Y. Song and H. Dery, Phys. Rev. Lett. 113,
047205 (2014)] of the three-terminal spin transport is based on the resonant
tunneling of electrons between ferromagnetic and normal electrodes via an
impurity. The sensitivity of current to a weak external magnetic field stems
from a spin blockade, which, in turn, is enabled by strong on-site repulsion.
We demonstrate that this sensitivity exists even in the absence of repulsion
when a single-particle description applies. Within this description, we
calculate exactly the resonant-tunneling current between the electrodes. The
mechanism of magnetoresistance, completely different from the spin blocking,
has its origin in the interference of virtual tunneling amplitudes. Spin
imbalance in ferromagnetic electrode is responsible for this interference and
the resulting coupling of the Zeeman levels. This coupling also affects the
current in the correlated regime.

###Large linear magnetoresistance and weak anti-localization in Y(Lu)PtBi topological insulators|Chandra Shekhar,Erik Kampert,Tobias Foerster,Binghai Yan,Ajaya K. Nayak,Michael Nicklas,Claudia Felser###

Large linear magnetoresistance and weak anti-localization in Y(Lu)PtBi topological insulators. Topological insulators are new kind of Dirac materials that possess bulk
insulating and surface conducting behavior. They are basically known for their
unique electronic properties at the surface. Here we present the
magneto-transport properties of our high quality single crystalline Y(Lu)PtBi
Heusler topological insulators, which belong to a group of noncentrosymmetric
superconductor with Tc = 0:8 K. Both the compounds show semi-metallic behavior
with low charge carrier of 6 x1018 cm^-3 for YPtBi and 8 x1019 cm^-3 for LuPtBi
at 2 K. Magneto-conductivity measurements in the tilted field indicate that the
charge carriers transport through quantum interference. This provide a direct
evidence of weak anti-localization below 50 K, giving a strong signature of
surface transport. Most importantly, these compounds show very high unsaturated
linear magnetoresistance of approximately 2000% at 10 K in a magnetic field of
60 T.

###Possible magnetic-polaron-switched positive and negative magnetoresistance in the GdSi single crystal|Hai-Feng Li,Yinguo Xiao,Berthold Schmitz,Jörg Persson,Wolfgang Schmidt,Paul Meuffels,Georg Roth,Thomas Brückel###

Possible magnetic-polaron-switched positive and negative magnetoresistance in the GdSi single crystal. Magnetoresistance (MR) has attracted tremendous attention for possible
technological applications. Understanding the role of magnetism in manipulating
MR may in turn steer the searching for new applicable MR materials. Here we
show that antiferromagnetic (AFM) GdSi metal displays an anisotropic positive
MR value (PMRV), up to $\sim$ 415%, accompanied by a large negative thermal
volume expansion (NTVE). Around $T_\text{N}$ the PMRV translates to negative,
down to $\sim$ -10.5%. Their theory-breaking magnetic-field dependencies [PMRV:
dominantly linear; negative MR value (NMRV): quadratic] and the unusual NTVE
indicate that PMRV is induced by the formation of magnetic polarons in 5$d$
bands, whereas NMRV is possibly due to abated electron-spin scattering
resulting from magnetic-field-aligned local 4$f$ spins. Our results may open up
a new avenue of searching for giant MR materials by suppressing the AFM
transition temperature, opposite the case in manganites, and provide a
promising approach to novel magnetic and electric devices.

###Persistent semi-metal-like nature of epitaxial perovskite CaIrO3 thin films|Abhijit Biswas,Yoon Hee Jeong###

Persistent semi-metal-like nature of epitaxial perovskite CaIrO3 thin films. Strong spin-orbit coupled 5d transition metal based ABO3 oxides, especially
iridates, allow tuning parameters in the phase diagram and may demonstrate
important functionalities, for example, by means of strain effects and
symmetry-breaking, because of the interplay between the Coulomb interactions
and strong spin-orbit coupling. Here, we have epitaxially stabilized high
quality thin films of perovskite (Pv) CaIrO3. Film on the best lattice-matched
substrate shows semi-metal-like characteristics. Intriguingly, imposing tensile
or compressive strain on the film by altering the underlying lattice-mismatched
substrates still maintains semi-metallicity with minute modification of the
effective correlation as tensile (compressive) strain results in tiny increases
(decreases) of the electronic bandwidth. In addition, magnetoresistance remains
positive with a quadratic field dependence. This persistent semi-metal-like
nature of Pv-CaIrO3 thin films with minute changes in the effective correlation
by strain may provide new wisdom into strong spin-orbit coupled 5d based oxide
physics.

###Tuning the scattering mechanism in three-dimensional Dirac semimetal Cd$_{3}$As$_{2}$|A. Pariari,N. Khan,R. Singha,B. Satpati,P. Mandal###

Tuning the scattering mechanism in three-dimensional Dirac semimetal Cd$_{3}$As$_{2}$. To probe the charge scattering mechanism in Cd$_{3}$As$_{2}$ single crystal,
we have analyzed the temperature and magnetic field dependence of the Seebeck
coefficient ($S$). The large saturation value of $S$ at high field clearly
demonstrates the linear energy dispersion of three-dimensional Dirac fermion. A
wide tunability of the charge scattering mechanism has been realized by varying
the strength of the magnetic field and carrier density via In doping. With the
increase in magnetic field, the scattering time crosses over from being nearly
energy independent to a regime of linear dependence. On the other hand, the
scattering time enters into the inverse energy-dependent regime and the Fermi
surface strongly modifies with 2\% In doping at Cd site. With further increase
in In content from 2 to 4\%, we did not observe any Shubnikov-de Haas
oscillation up to 9 T field, but the magnetoresistance is found to be quite
large as in the case of undoped sample.

###Dichotomy between the hole and electrons behavior in the multiband FeSe probed by ultra high magnetic fields|M. D. Watson,T. Yamashita,S. Kasahara,W. Knafo,M. Nardone,J. Beard,F. Hardy,A. McCollam,A. Narayanan,S. F. Blake,T. Wolf,A. A. Haghighirad,C. Meingast,A. J. Schofield,H. von Lohneysen,Y. Matsuda,A. I. Coldea,T. Shibauchi###

Dichotomy between the hole and electrons behavior in the multiband FeSe probed by ultra high magnetic fields. Magnetoresistivity \r{ho}xx and Hall resistivity \r{ho}xy in ultra high
magnetic fields up to 88T are measured down to 0.15K to clarify the multiband
electronic structure in high-quality single crystals of superconducting FeSe.
At low temperatures and high fields we observe quantum oscillations in both
resistivity and Hall effect, confirming the multiband Fermi surface with small
volumes. We propose a novel and independent approach to identify the sign of
corresponding cyclotron orbit in a compensated metal from magnetotransport
measurements. The observed significant differences in the relative amplitudes
of the quantum oscillations between the \r{ho}xx and \r{ho}xy components,
together with the positive sign of the high-field \r{ho}xy , reveal that the
largest pocket should correspond to the hole band. The low-field
magnetotransport data in the normal state suggest that, in addition to one hole
and one almost compensated electron bands, the orthorhombic phase of FeSe
exhibits an additional tiny electron pocket with a high mobility.

###Robust local and non-local transport in the Topological Kondo Insulator SmB$_{6}$ in the presence of high magnetic field|Sangram Biswas,Ramya Nagarajan,Suman Sarkar,Kazi Rafsanjani Amin,M. Ciomaga Hatnean,S. Tewari,G. Balakrishnan,Aveek Bid###

Robust local and non-local transport in the Topological Kondo Insulator SmB$_{6}$ in the presence of high magnetic field. SmB$_6$ has been predicted to be a Kondo Topological Insulator with
topologically protected conducting surface states. We have studied
quantitatively the electrical transport through surface states in high quality
single crystals of SmB$_6$. We observe a large non-local surface signal at
temperatures lower than the bulk Kondo gap scale. Measurements and finite
element simulations allow us to distinguish unambiguously between the
contributions from different transport channels. In contrast to general
expectations, the electrical transport properties of the surface channels was
found to be insensitive to high magnetic fields. Local and non-local
magnetoresistance measurements allowed us to identify definite signatures of
helical spin states and strong inter-band scattering at the surface.

###High Electron Mobility and Large Magnetoresistance in the Half-Heusler Semimetal LuPtBi|Zhipeng Hou,Wenhong Wang,Guizhou Xu,Xiaoming Zhang,Zhiyang Wei,Shipeng Shen,Enke Liu,Yuan Yao,Yisheng Chai,Young Sun,Xuekui Xi,Wenquan Wang,Zhongyuan Liu,Guangheng Wu,Xi-xiang Zhang###

High Electron Mobility and Large Magnetoresistance in the Half-Heusler Semimetal LuPtBi. Materials with high carrier mobility showing large magnetoresistance (MR)
have recently received much attention because of potential applications in
future high-performance magneto-electric devices. Here, we report on the
discovery of an electron-hole-compensated half-Heusler semimetal LuPtBi that
exhibits an extremely high electron mobility of up to 79000 cm2/Vs with a
non-saturating positive MR as large as 3200% at 2 K. Remarkably, the mobility
at 300 K is found to exceed 10500 cm2/Vs, which is among the highest values
reported in three-dimensional bulk materials thus far. The clean Shubnikov-de
Haas quantum oscillation observed at low temperatures and the first-principles
calculations together indicate that the high electron mobility is due to a
rather small effective carrier mass caused by the distinctive band structure of
the crystal. Our finding provide a new approach for finding large,
high-mobility MR materials by designing an appropriate Fermi surface topology
starting from simple electron-hole-compensated semimetals.

###Aging effect in Magnetotransport Property of Oxygen adsorbed BaFe2As2|Nilotpal Ghosh,Santhosh Raj###

Aging effect in Magnetotransport Property of Oxygen adsorbed BaFe2As2. Presence of Oxygen (O2) has been found by Energy Dispersive X-ray Analysis
(EDAX) on the surfaces of flux grown BaFe2As2 single crystals which were kept
in air ambience for several months. Transport studies show that the O2 adsorbed
crystals are more resistive and do not display any sharp slope change near 140
K which is the well known Spin Density Wave (SDW) transition temperature (TSDW)
accompanying structural transition for as grown BaFe2As2. An anomalous slope
change in resistivity is observed around 18 K at 0 and 5T. Magnetoresistance
(MR) is noticed to increase as a function of applied field (H) quite
differently than that for as grown crystals below TSDW which may be attributed
to aging effec

###Characterization of spin relaxation anisotropy in Co using spin pumping|Yi Li,Wei Cao,William E. Bailey###

Characterization of spin relaxation anisotropy in Co using spin pumping. Ferromagnets are believed to exhibit strongly anisotropic spin relaxation,
with relaxation lengths for spin longitudinal to magnetization significantly
longer than those for spin transverse to magnetization. Here we characterize
the anisotropy of spin relaxation in Co using the spin pumping contribution to
Gilbert damping in noncollinearly magnetized Py$_{1-x}$Cu$_{x}$/Cu/Co trilayer
structures. The static magnetization angle between Py$_{1-x}$Cu$_{x}$ and Co,
adjusted under field bias perpendicular to film planes, controls the
projections of longitudinal and transverse spin current pumped from
Py$_{1-x}$Cu$_{x}$ into Co. We find nearly isotropic absorption of pure spin
current in Co using this technique; fits to a diffusive transport model yield
the longitudinal spin relaxation length $< 2$ nm in Co. The longitudinal spin
relaxation lengths found are an order of magnitude smaller than those
determined by current-perpendicular-to-planes giant magnetoresistance
measurements, but comparable with transverse spin relaxation lengths in Co
determined by spin pumping.

###Spin-valve Effect in NiFe/MoS2/NiFe Junctions|Weiyi Wang,Awadhesh Narayan,Lei Tang,Kapildeb Dolui,Yanwen Liu,Xiang Yuan,Yibo Jin,Yizheng Wu,Ivan Rungger,Stefano Sanvito,Faxian Xiu###

Spin-valve Effect in NiFe/MoS2/NiFe Junctions. Two-dimensional (2D) layered transition metal dichalcogenides (TMDs) have
been recently proposed as appealing candidate materials for spintronic
applications owing to their distinctive atomic crystal structure and exotic
physical properties arising from the large bonding anisotropy. Here we
introduce the first MoS2-based spin-valves that employ monolayer MoS2 as the
nonmagnetic spacer. In contrast with what expected from the semiconducting
band-structure of MoS2, the vertically sandwiched-MoS2 layers exhibit metallic
behavior. This originates from their strong hybridization with the Ni and Fe
atoms of the Permalloy (Py) electrode. The spin-valve effect is observed up to
240 K, with the highest magnetoresistance (MR) up to 0.73% at low temperatures.
The experimental work is accompanied by the first principle electron transport
calculations, which reveal an MR of ~ 9% for an ideal Py/MoS2/Py junction. Our
results clearly identify TMDs as a promising spacer compound in magnetic tunnel
junctions and may open a new avenue for the TMDs-based spintronic applications.

###Pseudospin-valve effect on transport in junctions of three-dimensional topological insulator surfaces|Sthitadhi Roy,Krishanu Roychowdhury,Sourin Das###

Pseudospin-valve effect on transport in junctions of three-dimensional topological insulator surfaces. We show that the surface states of pristine 3D topological insulators (TIs)
are analogs of ferromagnetic half metals due to complete polarization of an
emergent momentum independent pseudospin (SU(2)) degree of freedom on the
surface. To put this claim on firm footing, we present results for TI surfaces
perpendicular to the crystal growth axis, which clearly show that the tunneling
conductance between two such TI surfaces of the same TI material is dominated
by this half metallic behavior leading to physics reminiscent of a spin-valve.
Further using the generalized tunnel magnetoresistance derived in this work we
also study the tunneling current between arbitrary TI surfaces. We also perform
a comprehensive study of the effect of all possible surface potentials allowed
by time reversal symmetry on this spin-valve effect and show that it is robust
against most of such potentials.

###Surface Transport in the ν=0 Quantum Hall Ferromagnetic State in the Organic Dirac Fermion System|Toshihito Osada###

Surface Transport in the ν=0 Quantum Hall Ferromagnetic State in the Organic Dirac Fermion System. We discuss the surface magnetotransport in the quantum Hall (QH)
ferromagnetic state expected in the organic Dirac fermion system
\alpha-(BEDT-TTF)_2I_3. The QH ferromagnetic state is one of the possible \nu=0
QH states in the two-dimensional Dirac fermion system resulting from the
degeneracy breaking of the n=0 Landau level. It is characterized by the helical
edge state. We have studied the interlayer surface transport via helical edge
state in the multilayer QH ferromagnet, in which the bulk region is insulating.
We have clarified that the surface conductivity is much less than e^2/h and
decreases as the magnetic field is tilted to the normal direction of the side
surface. These features explain the observed interlayer magnetoresistance in
\alpha-(BEDT-TTF)_2I_3.

###Density-of-states fluctuation-induced negative out-of-plane magnetoresistance in overdoped Bi-2212|Tomohiro Usui,Shintaro Adachi,Takao Watanabe,Terukazu Nishizaki###

Density-of-states fluctuation-induced negative out-of-plane magnetoresistance in overdoped Bi-2212. We analyzed the in-plane and out-of-plane magnetoresistance (MR) for
overdoped Bi$_{1.6}$Pb$_{0.4}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ (Bi-2212) single
crystals using superconductive fluctuation theory, which considers the
density-of-states (DOS) contribution in layered superconductors with the
conventional s-wave pairing state. The out-of-plane results are well reproduced
by the theory, implying that the large, negative out-of-plane MR as well as the
sharp increase in the zero-field out-of-plane resistivity $\rho_{c}$ near the
superconducting transition temperature $T_c$ originate from the superconductive
DOS fluctuation effect. On the other hand, the in-plane results are better
reproduced without the DOS contribution (i.e., using only the Aslamazov-Larkin
(AL) contribution), which may be explained in terms of the d-wave
superconductivity of the layered superconductors.

###Proximity effect between a topological insulator and a magnetic insulator with large perpendicular anisotropy|Wenmin Yang,Shuo Yang,Qinghua Zhang,Yang Xu,Shipeng Shen,Jian Liao,Jing Teng,Cewen Nan,Lin Gu,Young Sun,Kehui Wu,Yongqing Li###

Proximity effect between a topological insulator and a magnetic insulator with large perpendicular anisotropy. We report that thin films of a prototype topological insulator,
Bi$_{2}$Se$_{3}$, can be epitaxially grown onto the (0001) surface of
BaFe$_{12}$O$_{19}$(BaM), a magnetic insulator with high Curie temperature and
large perpendicular anisotropy. In the Bi$_2$Se$_3$ thin films grown on
non-magnetic substrates, classic weak antilocalization (WAL) is manifested as
cusp-shaped positive magnetoresistance (MR) in perpendicular magnetic fields
and parabola-shaped positive MR in parallel fields, whereas in
Bi$_{2}$Se$_{3}$/BaM heterostructures the low field MR is parabola-shaped,
which is positive in perpendicular fields and negative in parallel fields. The
magnetic field and temperature dependence of the MR is explained as a
consequence of the suppression of WAL due to strong magnetic interactions at
the Bi$_{2}$Se$_{3}$/BaM interface.

###Observation of Shubnikov de Haas and Aharanov-Bohm oscillations in silicon nanowires|Tahir Aslan,Davie Mtsuko,Christopher Coleman,Siphephile Ncube,Somnath Bhattacharyya###

Observation of Shubnikov de Haas and Aharanov-Bohm oscillations in silicon nanowires. We record fine oscillations of 20 to 60 mT superimposed on larger
oscillations having periodicity ~ 2 T at temperatures up to 100 K and fields up
to 10 T from silicon nanowires. Having confirmed that these features appear
from the edge states associated with skipping orbits at nanowire edges and
confined pure orbits in the interior of the nanowires we derive electron
effective mass of 0.001 me to 0.006 me, carrier lifetime in the range 3 to 19
fs and carrier density that varies from 2x10^11 cm^-2 to 9x10^12 cm^-2.
However, at low temperature the observed oscillation amplitude invariant of the
field is attributed to not only a strong size confinement and the pinning of
orbits by impurities but also Aharanov Bohm (AB) oscillations due to
edge-states that propagate quasi-ballistically through the nanowire. The
overall oscillation on a linear positive magnetoresistance background can be
attributed to temperature-dependent crossover of Shubnikov de Haas oscillations
(SdHO) and AB oscillations in silicon nanowires.

###New memory devices based on the proton transfer process|Malgorzata Wierzbowska###

New memory devices based on the proton transfer process. Memory devices operating due to the fast proton transfer (PT) process are
proposed by means of the first-principles calculations. Writing an information
is performed using the electrostatic potential of the scanning tunneling
microscopy (STM). Reading an information is based on the effect of the local
magnetization induced at the zigzag graphene nanoribbon (Z-GNR) edge -
saturated with oxygen or the hydroxy group - and can be realized with the use
of the giant magnetoresistance (GMR), magnetic tunnel junction (MTJ) or
spin-transfer torque (STT) devices. The energetic barriers for the hop-forward
and -backward processes can be tuned by the distance and potential of the STM
tip. Thus, enabling to tailor the non-volatile logic states. The proposed
system enables very dense packing of the logic cells and could be used in the
random access and flash memory devices.

###Giant negative magnetoresistance induced by the chiral anomaly in individual Cd3As2 nanowires|Cai-Zhen Li,Li-Xian Wang,Haiwen Liu,Jian Wang,Zhi-Min Liao,Da-Peng Yu###

Giant negative magnetoresistance induced by the chiral anomaly in individual Cd3As2 nanowires. Cd3As2 is a newly booming Dirac semimetal with linear dispersion along all
three momentum directions and can be viewed as 3D analog of graphene. As
breaking of either time reversal symmetry or spatial inversion symmetry, the
Dirac semimetal is believed to transform into Weyl semimetal with exotic chiral
anomaly effect, while the experimental evidence of the chiral anomaly is still
missing in Cd3As2. Here we report the magneto-transport properties of
individual Cd3As2 nanowires. Large negative magnetoresistance (MR) with
magnitude of -63% at 60 K and -11% at 300 K are observed when the magnetic
field is parallel with the electric field direction, giving the evidence of the
chiral magnetic effect in Cd3As2 nanowires. In addition, the critical magnetic
field BC, where there is an extremum of the negative MR, increases with
increasing temperature. As the first observation of chiral anomaly induced
negative MR in Cd3As2 nanowires, it may offer valuable insights for low
dimensional physics in Dirac semimetals.

###Magnetic state dependent transient lateral photovoltaic effect in patterned ferromagnetic metal-oxide-semiconductor films|Isidoro Martinez,Juan Pedro Cascales,Antonio Lara,Pablo Andres,Farkhad G. Aliev###

Magnetic state dependent transient lateral photovoltaic effect in patterned ferromagnetic metal-oxide-semiconductor films. We investigate the influence of an external magnetic field on the magnitude
and dephasing of the transient lateral photovoltaic effect (T-LPE) in
lithographically patterned Co lines of widths of a few microns grown over
naturally passivated p-type Si(100). The T-LPE peak-to-peak magnitude and
dephasing, measured by lock-in or through the characteristic time of laser OFF
exponential relaxation, exhibit a notable influence of the magnetization
direction of the ferromagnetic overlayer. We show experimentally and by
numerical simulations that the T-LPE magnitude is determined by the Co
anisotropic magnetoresistance. On the other hand, the magnetic field dependence
of the dephasing could be described by the influence of the Lorentz force
acting perpendiculary to both the Co magnetization and the photocarrier drift
directions. Our findings could stimulate the development of fast position
sensitive detectors with magnetically tuned magnitude and phase responses.

###Dephasing time in graphene due to interaction with flexural phonons|Konstantin S. Tikhonov,Wei L. Z. Zhao,Alexander M. Finkel'stein###

Dephasing time in graphene due to interaction with flexural phonons. We investigate decoherence of an electron in graphene caused by
electron-flexural phonon interaction. We find out that flexural phonons can
produce dephasing rate comparable to the electron-electron one. The problem
appears to be quite special because there is a large interval of temperature
where the dephasing induced by phonons can not be obtain using the golden rule.
We evaluate this rate for a wide range of density ($n$) and temperature ($T$)
and determine several asymptotic regions with temperature dependence crossing
over from $\tau_{\phi }^{-1}\sim T^{2}$ to $\tau_{\phi}^{-1}\sim T$ when
temperature increases. We also find $\tau_{\phi}^{-1}$ to be a non-monotonous
function of $n$. These distinctive features of the new contribution can provide
an effective way to identify flexural phonons in graphene through the
electronic transport by measuring the weak localization corrections in
magnetoresistance.

###Spin-dependent transport in a multiferroic tunnel junction: Theory for Co/PbTiO$_{3}$/Co|Vladislav S. Borisov,Sergey Ostanin,Steven Achilles,Jürgen Henk,Ingrid Mertig###

Spin-dependent transport in a multiferroic tunnel junction: Theory for Co/PbTiO$_{3}$/Co. Spin-dependent electronic transport through multiferroic Co/PbTiO$_{3}$/Co
tunnel junctions is studied theoretically. Conductances calculated within the
Landauer-B\"uttiker formalism yield both a large tunnel magnetoresistance (TMR)
and a large tunnel electroresistance (TER). On top of this, we establish a
four-conductance state. The conductances depend crucially on the details of the
electronic structure at the interfaces. In particular, the spin polarization of
the tunneling electronic states is affected by the hybridization of orbitals
and the associated charge transfer at both interfaces. Digital doping of the
PbTiO$_{3}$ barrier with Zr impurities at the TiO$_{2}$/Co$_{2}$ interface
significantly enhances the TMR\@. In addition, it removes the metalization of
the barrier.

###Growth and Characterization of Millimeter-sized Single Crystals of CaFeAsF|Yonghui Ma,Hui Zhang,Bo Gao,Kangkang Hu,Qiucheng Ji,Gang Mu,Fuqiang Huang,Xiaoming Xie###

Growth and Characterization of Millimeter-sized Single Crystals of CaFeAsF. High-quality and sizable single crystals are crucial for studying the
intrinsic properties of unconventional superconductors, which are lacking in
the 1111 phase of the Fe-based superconductors. Here we report the successful
growth of CaFeAsF single crystals with the sizes of 1-2 mm using the self-flux
method. Owning to the availability of the high-quality single crystals, the
structure and transport properties were investigated with a high reliability.
The structure was refined by using the single-crystal x-ray diffraction data,
which confirms the reports earlier on the basis of powder data. A clear anomaly
associated with the structural transition was observed at 121 K from the
resistivity, magnetoresistance, and magnetic susceptibility measurements.
Another kink-feature at 110 K, most likely an indication of the
antiferromagnetic transition, was also detected in the resistivity data. Our
results supply a basis to propel the physical investigations on the 1111 phase
of the Fe-based superconductors.

###Direct Method for Calculating Temperature-Dependent Transport Properties|Yi Liu,Zhe Yuan,R. J. H. Wesselink,Anton A. Starikov,Mark van Schilfgaarde,Paul J. Kelly###

Direct Method for Calculating Temperature-Dependent Transport Properties. We show how temperature-induced disorder can be combined in a direct way with
first-principles scattering theory to study diffusive transport in real
materials. Excellent (good) agreement with experiment is found for the
resistivity of Cu, Pd, Pt (and Fe) when lattice (and spin) disorder are
calculated from first principles. For Fe, the agreement with experiment is
limited by how well the magnetization (of itinerant ferromagnets) can be
calculated as a function of temperature. By introducing a simple Debye-like
model of spin disorder parameterized to reproduce the experimental
magnetization, the temperature dependence of the average resistivity, the
anisotropic magnetoresistance and the spin polarization of a Ni$_{80}$Fe$_{20}$
alloy are calculated and found to be in good agreement with existing data.
Extension of the method to complex, inhomogeneous materials as well as to the
calculation of other finite-temperature physical properties within the
adiabatic approximation is straightforward.

###Tunable electronic anisotropy in single-crystal A2Cr3As3 (A = K, Rb) quasi-one-dimensional superconductors|X. F. Wang,C. Roncaioli,C. Eckberg,H. Kim,J. Yong,Y. Nakajima,S. R. Saha,P. Y. Zavalij,J. Paglione###

Tunable electronic anisotropy in single-crystal A2Cr3As3 (A = K, Rb) quasi-one-dimensional superconductors. Single crystals of A2Cr3As3 (A = K, Rb) were successfully grown using a
self-flux method and studied via structural, transport and thermodynamic
measurement techniques. The superconducting state properties between the two
species are similar, with critical temperatures of 6.1 K and 4.8 K in K2Cr3As3
and Rb2Cr3As3, respectively. However, the emergence of a strong normal state
electronic anisotropy in Rb2Cr3As3 suggests a unique electronic tuning
parameter is coupled to the inter-chain spacing in the A2Cr3As3 structure,
which increases with alkali metal ionic size while the one-dimensional
[(Cr3As3)^{2-}]_{\infty} chain structure itself remains essentially unchanged.
Together with dramatic enhancements in both conductivity and magnetoresistance
(MR), the appearance of a strong anisotropy in the MR of Rb2Cr3As3 is
consistent with the proposed quasi-one-dimensional character of band structure
and its evolution with alkali metal species in this new family of
superconductors.

###Driving and detecting ferromagnetic resonance in insulators with the spin Hall effect|Joseph Sklenar,Wei Zhang,Matthias B. Jungfleisch,Wanjun Jiang,Houchen Chang,John E. Pearson,Mingzhong Wu,John B. Ketterson,Axel Hoffmann###

Driving and detecting ferromagnetic resonance in insulators with the spin Hall effect. We demonstrate the generation and detection of spin-torque ferromagnetic
resonance in Pt/YIG bilayers. A unique attribute of this system is that the
spin Hall effect lies at the heart of both the generation and detection
processes and no charge current is passing through the insulating magnetic
layer. When the YIG undergoes resonance, a dc voltage is detected
longitudinally along the Pt that can be described by two components. One is the
mixing of the spin Hall magnetoresistance with the microwave current. The other
results from spin pumping into the Pt being converted to a dc current through
the inverse spin Hall effect. The voltage is measured with applied magnetic
field directions that range in-plane to nearly perpendicular. We find that for
magnetic fields that are mostly out-of-plane, an imaginary component of the
spin mixing conductance is required to model our data.

###Anisotropic magnetotransport of electron gases at SrTiO3 (111) and (110) surfaces with high mobility|Ludi Miao,Renzhong Du,Yuewei Yin,Qi Li###

Anisotropic magnetotransport of electron gases at SrTiO3 (111) and (110) surfaces with high mobility. Electron gases at the surfaces of (001), (110), and (111) oriented SrTiO3
(STO) have been created using Ar+-irradiation with fully metallic behavior and
low-temperature-mobility as large as 5500 cm2V-1s-1, 1300 cm2V-1s-1 and 8600
cm2V-1s-1 for (001)-, (110)-, and (111)-surfaces, respectively. The in-plane
anisotropic magnetoresistance (AMR) have been studied for the samples with the
current along different crystal axis directions to subtract the Lorentz Force
effect. The AMR shows features which coincide with the fixed orientations to
the crystalline axes, with 4-fold, 2-fold and nearly-6-fold symmetries for
(001)-, (110) and (111)-surfaces, respectively, independent of the current
directions. These features are possibly caused by the polarization of spin
orbit texture of the 2D Fermi surfaces. In addition, a 6-fold to 2-fold
symmetry breaking for (111)-surfaces is observed. Our results demonstrate the
effect of symmetry of two-dimensional electronic structure on the transport
behaviors for the electron gases at STO surfaces.

###Large increase of the anisotropy factor in the overdoped region of Ba(Fe$_{1-x}$Ni$_x$)$_2$As$_2$ as probed by fluctuation spectroscopy|A Ramos-Álvarez,J Mosqueira,F Vidal,Xingye Lu,Huiqian Luo###

Large increase of the anisotropy factor in the overdoped region of Ba(Fe$_{1-x}$Ni$_x$)$_2$As$_2$ as probed by fluctuation spectroscopy. We study the diamagnetism induced by thermal fluctuations above the
superconducting transition of the iron pnictide Ba(Fe$_{1-x}$Ni$_x$)$_2$As$_2$
with different doping levels. The measurements are performed with magnetic
fields up to 7 T applied in the two main crystal directions. These data provide
double information: first, they confirm at a quantitative level the
applicability to these materials of a 3D-anisotropic Ginzburg-Landau approach
valid in the finite field regime. Then, they allow to determine the
doping-level dependence of the in-plane coherence length and of the
superconducting anisotropy factor, $\gamma$. Our results provide a stringent
confirmation of the large increase of $\gamma$ with the doping level, as
recently proposed from magnetoresistivity measurements. The implications of the
applicability of the model used to a multiband superconductor are discussed.

###Temperature induced Lifshitz transition in WTe2|Yun Wu,Na Hyun Jo,Masayuki Ochi,Lunan Huang,Daixiang Mou,Sergey L. Bud'ko,P. C. Canfield,Nandini Trivedi,Ryotaro Arita,Adam Kaminski###

Temperature induced Lifshitz transition in WTe2. We use ultra-high resolution, tunable, VUV laser-based, angle-resolved
photoemission spectroscopy (ARPES) and temperature and field dependent
resistivity and thermoelectric power (TEP) measurements to study the electronic
properties of WTe2, a compound that manifests exceptionally large, temperature
dependent magnetoresistance. The temperature dependence of the TEP shows a
change of slope at T=175 K and the Kohler rule breaks down above 70-140 K
range. The Fermi surface consists of two electron pockets and two pairs of hole
pockets along the X-Gamma-X direction. Upon increase of temperature from 40K,
the hole pockets gradually sink below the chemical potential. Like BaFe2As2,
WTe2 has clear and substantial changes in its Fermi surface driven by modest
changes in temperature. In WTe2, this leads to a rare example of temperature
induced Lifshitz transition, associated with the complete disappearance of the
hole pockets. These dramatic changes of the electronic structure naturally
explain unusual features of the transport data.

###Giant Magneto-Seebeck Effect in Spin Valves|X. M. Zhang,C. H. Wan,Z. H. Yuan,H. Wu,Q. T. Zhang,X. Zhang,B. S. Tao,C. Fang,X. F. Han###

Giant Magneto-Seebeck Effect in Spin Valves. Giant magneto-Seebeck (GMS) effect was observed in Co/Cu/Co and NiFe/Cu/Co
spin valves. Their Seebeck coefficients in parallel state was larger than that
in antiparallel state, and GMS ratio defined as (SAP-SP)/SP could reach -9% in
our case. The GMS originated not only from trivial giant magnetoresistance but
also from spin current generated due to spin polarized thermoelectric
conductivity in ferromagnetic materials and subsequent modulation of the spin
current by spin configurations in spin valves. Simple Mott two-channel model
reproduced a -11% GMS for the Co/Cu/Co spin valves, qualitatively consistent
with our observations. The GMS effect could be applied simultaneously sensing
temperature gradient and magnetic field and also be possibly applied to
determine spin polarization of thermoelectric conductivity and Seebeck
coefficient in ferromagnetic thin films.

###Multi-channel exchange-scattering spin polarimetry|Fuhao Ji,Tan Shi,Mao Ye,Weishi Wan,Zhen Liu,Jiajia Wang,Tao Xu,Shan Qiao###

Multi-channel exchange-scattering spin polarimetry. Electron spin takes critical role in almost all novel phenomena discovered in
modern condensed matter physics (High-temperature superconductivity, Kondo
effect, Giant Magnetoresistance, topological insulator, quantum anomalous Hall
effect, etc.). However, the measurements for electron spin is of poor quality
which blocks the development of material sciences because of the low efficiency
of spin polarimeter. Here we show an imaging type exchange-scattering spin
polarimeter with 5 orders more efficiency compared with a classical Mott
polarimeter. As a demonstration, the fine spin structure of electronic states
in bismuth (111) is investigated, showing the strong Rashba type spin splitting
behavior in both bulk and surface states. This improvement pave the way to
study novel spin related phenomena with unprecedented accuracy.

###Correlation of Crystal Quality and Extreme Magnetoresistance of WTe$_2$|Mazhar N. Ali,Leslie Schoop,Jun Xiong,Steven Flynn,Quinn Gibson,Max Hirschberger,N. P. Ong,R. J. Cava###

Correlation of Crystal Quality and Extreme Magnetoresistance of WTe$_2$. High quality single crystals of WTe$_2$ were grown using a Te flux followed
by a cleaning step involving self-vapor transport. The method is reproducible
and yields consistently higher quality single crystals than are typically
obtained via halide assisted vapor transport methods. Magnetoresistance
(MR)values at 9 Tesla and 2 Kelvin as high as 1.75 million \%, nearly an order
of magnitude higher than previously reported for this material, were obtained
on crystals with residual resistivity ratio (RRR) of approximately 1250. The MR
follows a near B$^2$ law (B = 1.95(1)) and, assuming a semiclassical model, the
average carrier mobility for the highest quality crystal was found to be
~167,000 cm$^2$/Vs at 2 K. A correlation of RRR, MR ratio and average carrier
mobility ($\mu_{avg}$) is found with the cooling rate during the flux growth.

###Separating read and write units in multiferroic devices|Kuntal Roy###

Separating read and write units in multiferroic devices. Strain-mediated multiferroic composites, i.e., piezoelectric-magnetostrictive
heterostructures, hold profound promise for energy-efficient computing in
beyond Moore's law era. While reading a bit of information stored in the
magnetostrictive nanomagnets using a magnetic tunnel junction (MTJ), a material
selection issue crops up since magnetostrictive materials in general cannot be
utilized as the free layer of the MTJ. This is an important issue since we need
to achieve a high magnetoresistance for technological applications. We show
here that magnetically coupling the magnetostrictive nanomagnet and the free
layer e.g., utilizing the magnetic dipole coupling between them can circumvent
this issue. By solving stochastic Landau-Lifshitz-Gilbert equation of
magnetization dynamics in the presence of room-temperature thermal
fluctuations, we show that such design can eventually lead to a superior
energy-delay product.

###Magnetization and magneto-transport studies on Fe$_2$VAl$_{1-x}$Si$_x$|E. P. Amaladass,A. T. Satya,Shilpam Sharma,K. Vinod,V. Srinivas,C. S. Sundar,A. Bharathi###

Magnetization and magneto-transport studies on Fe$_2$VAl$_{1-x}$Si$_x$. We report on magnetoresistance, Hall and magnetization measurements of
Fe2VAl1-xSix Heusler compounds for x= 0.005, 0.015, 0.02. There is a systematic
change in the temperature coefficient of resistance (TCR) from negative to
positive as the Si composition is increased. The Hall co-efficient shows that
the carriers are electron like and the carrier density increases with Si
concentration. Resistance measurements under magnetic field indicate a
decreasing behavior under the application of magnetic field at low temperature
region (T< 60 K), suggesting the suppression of scattering by magnetic field.
Temperature and field dependent magnetization measurements did not show any
significant change apart from the fact that the presence of super paramagnetic
(SPM) cluster and its ordering at low temperatures. Arrott plot analysis of
magnetization versus field also indicates the magnetic ordering with applied
field below 60 K.

###Ferromagnetic resonance and magnetoresistive measurements evidencing magnetic vortex crystal in nickel thin film with patterned antidot array|I. R. B. Ribeiro,J. F. Felix,L. C. Figueiredo,P. C. de Morais,S. O. Ferreira,W. A. Moura-Melo,A. R. Pereira,A. Quindeau,C. I. L. de Araujo###

Ferromagnetic resonance and magnetoresistive measurements evidencing magnetic vortex crystal in nickel thin film with patterned antidot array. Ferromagnetic vortices deliver robust out-of-plane magnetization at extremely
small scales. Their handling and creation therefore has high potential to
become a necessary ingredient for future data storage technologies in order to
keep up with the pace of growing information density demands. In this study we
show that by using one step nanolithography method, we are able to create
ferromagnetic vortex lattices in thin nickel films. The necessary control of
the magnetic stray field at the domain edges was achieved by actively modifying
the ferromagnetic thin film anisotropic properties at nanometer scale. We
present experimental evidence using ferromagnetic resonance and
magnetoresistance measurements supporting simulations based on the theoretical
prediction of the proclaimed vortex structures.

###Transport signatures of surface potentials on three-dimensional topological insulators|Sthitadhi Roy,Sourin Das###

Transport signatures of surface potentials on three-dimensional topological insulators. The spin-momentum locked nature of the robust surface states of three
dimensional topological insulators (3D TI) make them promising candidates for
spintronics applications. Surface potentials which respect time reversal
symmetry can exist at the surface between a 3D TI and the trivial vacuum. These
potentials can distort the spin texture of the surface states while retaining
their gapless nature. In this work, the effect of all such surface potentials
on the spin textures is studied. Since, a tunnel magnetoresistance signal
carries the information of the spin texture, it is proposed that spin-polarized
tunneling of electrons to a 3D TI surface can be used to uniquely identify the
surface potentials and quantitatively characterize them.

###Effective 2D thickness for the Berezinskii-Kosterlitz-Thouless-like transition in a highly underdoped La$_{2-x}$Sr$_x$CuO$_4$|P. G. Baity,Xiaoyan Shi,Zhenzhong Shi,L. Benfatto,Dragana Popović###

Effective 2D thickness for the Berezinskii-Kosterlitz-Thouless-like transition in a highly underdoped La$_{2-x}$Sr$_x$CuO$_4$. The nature of the superconducting transition in highly underdoped thick films
of La$_{2-x}$Sr$_x$CuO$_4$ ($x=0.07$ and 0.08) has been investigated using the
in-plane transport measurements. The contribution of superconducting
fluctuations to the conductivity in zero magnetic field, or paraconductivity,
was determined from the magnetoresistance measured in fields applied
perpendicular to the CuO$_2$ planes. Both the temperature dependence of the
paraconductivity above the transition and the nonlinear current-voltage ($I-V$)
characteristics measured across it, exhibit the main signatures of the
Berezinskii-Kosterlitz-Thouless (BKT) transition. The quantitative comparison
of the superfluid stiffness, extracted from the $I-V$ data, with the
renormalization-group results for the BKT theory, reveals a large value of the
vortex-core energy. This finding is confirmed by the analysis of the
paraconductivity obtained using different methods. The results strongly suggest
that the characteristic energy scale controlling the BKT behavior in this
layered system corresponds to the superfluid stiffness of a few layers.

###Observation of Ising spin-nematic order and its close relationship to the superconductivity in FeSe single crystals|Yuan Dongna,Yuan Jie,Huang Yulong,Ni Shunli,Feng Zhongpei,Zhou Huaxue,Mao Yiyuan,Jin Kui,Zhang Guangming,Dong Xiaoli,Zhou Fang,Zhao Zhongxian###

Observation of Ising spin-nematic order and its close relationship to the superconductivity in FeSe single crystals. Superconducting FeSe single crystals of (001) orientation are synthesized via
a hydrothermal ion-release route. An Ising spin-nematic order is identified by
our systematic measurements of in-plane angular-dependent magnetoresistance
(AMR) and static magnetization. The turn-on temperature of anisotropic AMR
signifies the Ising spin-nematic ordering temperature Tsn, below which a
two-fold rotational symmetry is observed in the iron plane. A downward
curvature appears below Tsn in the temperature dependence of static
magnetization for the weak in-plane magnetic field as reported previously.
Remarkably, we find a universal linear relationship between Tc and Tsn among
various superconducting samples, indicating that the spin nematicity and the
superconductivity in FeSe have a common microscopic origin.

###Thin film growth of a topological crystal insulator SnTe on the CdTe (111) surface by molecular beam epitaxy|Ryo Ishikawa,Tomonari Yamaguchi,Yusuke Ohtaki,Ryota Akiyama,Shinji Kuroda###

Thin film growth of a topological crystal insulator SnTe on the CdTe (111) surface by molecular beam epitaxy. We report molecular beam epitaxial growth of a SnTe (111) layer on a CdTe
template, fabricated by depositing it on a GaAs (111)A substrate, instead of
BaF$_2$ which has been conventionally used as a substrate. By optimizing
temperatures for the growth of both SnTe and CdTe layers, we could obtain SnTe
layers of the single phase grown only in the (111) orientation and of much
improved surface morphology from the viewpoint of the extension and the
flatness of flat regions, compared to the layers grown on BaF$_2$. In this
optimal growth condition, we have also achieved a low hole density of the order
of 10$^{17}$cm$^{-3}$ at 4K, the lowest value ever reported for SnTe thin films
without additional doping. In the magnetoresistance measurement on this
optimized SnTe layer, we observe characteristic negative magneto-conductance
which is attributed to the weak antilocalization effect of the two-dimensional
transport in the topological surface state.

###Chiral Magnetic Effect due to Inhomogeneous Magnetic Fields in Noncentrosymmetric Weyl Semimetals|Yohei Ibe,Hiroaki Sumiyoshi###

Chiral Magnetic Effect due to Inhomogeneous Magnetic Fields in Noncentrosymmetric Weyl Semimetals. The chiral magnetic effect is a phenomenon where an electromagnetic current
is generated along a magnetic field. Recently, in nonequilibrium systems,
negative longitudinal magnetoresistance has been observed experimentally in
Dirac/Weyl semimetals, which provides evidence for the chiral magnetic effect
as a nonequilibrium current. On the other hand, the emergence of the chiral
magnetic effect as an equilibrium current is still controversial. We propose a
possible realization of the chiral magnetic effect as an equilibrium current
using inhomogeneous magnetic fields. By employing tight-binding calculations
and linear response theory, we demonstrate that a finite current density is
generated by inhomogeneous magnetic fields, while the spatial integration of
the current is equal to zero, which is consistent with the so-called "no-go
theorem" of the chiral magnetic effect in real lattice systems. Moreover, we
propose an experimental setup to detect the effect in Weyl semimetal materials.

###Magnetic Domain Wall Engineering in a Nanoscale Permalloy Junction|Junlin Wang,Xichao Zhang,Xianyang Lu,Jason Zhang,Hua Ling,Jing Wu,Yan Zhou,Yongbing Xu###

Magnetic Domain Wall Engineering in a Nanoscale Permalloy Junction. Nanoscale magnetic junction provides a useful approach to act as the building
block for magnetoresistive random access memories (MRAM), where one of the key
issues is to control the magnetic domain configuration. Here, we study the
domain structure and the magnetic switching in the Permalloy (Fe20Ni80)
nanoscale magnetic junctions with different thicknesses by using micromagnetic
simulations. It is found that both the 90-degree and 45-degree domain walls can
be formed between the junctions and the wire arms depending on the thickness of
the device. The magnetic switching fields show distinct thickness dependencies
with a broad peak varying from 7 nm to 22 nm depending on the junction sizes,
and the large magnetic switching fields favor the stability of the MRAM
operation.

###Multiple Dirac cones at the surface of the topological metal LaBi|Jayita Nayak,Shu-Chun Wu,Nitesh Kumar,Chandra Shekhar,Sanjay Singh,Jörg Fink,Emile E. D. Rienks,Gerhard H. Fecher,Stuart S. P. Parkin,Binghai Yan,Claudia Felser###

Multiple Dirac cones at the surface of the topological metal LaBi. The rare-earth monopnictide LaBi exhibits exotic magneto-transport properties
including an extremely large and anisotropic magnetoresistance. Experimental
evidence for topological surface states is still missing although band
inversions have been postulated to induce a topological phase in LaBi. By
employing angle-resolved photoemission spectroscopy (ARPES) in conjunction with
$ab~initio$ calculations, we have revealed the existence of surface states of
LaBi through the observation of three Dirac cones: two coexist at the corners
and one appears at the center of the Brillouin zone. The odd number of surface
Dirac cones is a direct consequence of the odd number of band inversions in the
bulk band structure, thereby proving that LaBi is a topological, compensated
semi-metal, which is equivalent to a time-reversal invariant topological
insulator. Our findings provide insight into the topological surface states of
LaBi's semi-metallicity and related magneto-transport properties.

###Hall-effect within the colossal magnetoresistive semi-metallic state of MoTe2|Qiong Zhou,D. Rhodes,Q. R. Zhang,S. Tang,R. Schönemann,L. Balicas###

Hall-effect within the colossal magnetoresistive semi-metallic state of MoTe2. Here, we report a systematic study on the Hall-effect of the semi-metallic
state of bulk MoTe$_2$, which was recently claimed to be a candidate for a
novel type of Weyl semi-metallic state. The temperature ($T$) dependence of the
carrier densities and of their mobilities, as estimated from a numerical
analysis based on the isotropic two-carrier model, indicates that its
exceedingly large and non-saturating magnetoresistance may be attributed to a
near perfect compensation between the densities of electrons and holes at low
temperatures. A sudden increase in hole density, with a concomitant rapid
increase in the electron mobility below $T \sim 40$ K, leads to comparable
densities of electrons and holes at low temperatures suggesting a possible
electronic phase-transition around this temperature.

###Lorentz-violating type-II Dirac fermions in transition metal dichalcogenide PtTe$_2$|Mingzhe Yan,Huaqing Huang,Kenan Zhang,Eryin Wang,Wei Yao,Ke Deng,Guoliang Wan,Hongyun Zhang,Masashi Arita,Haitao Yang,Zhe Sun,Hong Yao,Yang Wu,Shoushan Fan,Wenhui Duan,Shuyun Zhou###

Lorentz-violating type-II Dirac fermions in transition metal dichalcogenide PtTe$_2$. Topological semimetals have recently attracted extensive research interests
as host materials to condensed matter physics counterparts of Dirac and Weyl
fermions originally proposed in high energy physics. These fermions with linear
dispersions near the Dirac or Weyl points obey Lorentz invariance, and the
chiral anomaly leads to novel quantum phenomena such as negative
magnetoresistance. The Lorentz invariance is, however, not necessarily
respected in condensed matter physics, and thus Lorentz-violating type-II Dirac
fermions with strongly tilted cones can be realized in topological semimetals.
Here, we report the first experimental evidence of type-II Dirac fermions in
bulk stoichiometric PtTe$_2$ single crystal. Angle-resolved photoemission
spectroscopy (ARPES) measurements and first-principles calculations reveal a
pair of strongly tilted Dirac cones along the $\Gamma$-A direction under the
symmetry protection, confirming PtTe$_2$ as a type-II Dirac semimetal. The
realization of type-II Dirac fermions opens a new door for exotic physical
properties distinguished from type-I Dirac fermions in condensed matter
materials.

###Presence of Exotic Electronic Surface States in LaBi and LaSb|X. H. Niu,D. F. Xu,Y. H. Bai,Q. Song,X. P. Shen,B. P. Xie,Z. Sun,Y. B. Huang,D. C. Peets,D. L. Feng###

Presence of Exotic Electronic Surface States in LaBi and LaSb. Extremely high magnetoresistance (XMR) in the lanthanum monopnictides La$X$
($X$ = Sb, Bi) has recently attracted interest in these compounds as candidate
topological materials. However, their perfect electron-hole compensation
provides an alternative explanation, so the possible role of topological
surface states requires verification through direct observation. Our
angle-resolved photoemission spectroscopy (ARPES) data reveal multiple
Dirac-like surface states near the Fermi level in both materials. Intriguingly,
we have observed circular dichroism in both surface and near-surface bulk
bands. Thus the spin-orbit coupling-induced orbital and spin angular momentum
textures may provide a mechanism to forbid backscattering in zero field,
suggesting that surface and near-surface bulk bands may contribute strongly to
XMR in La$X$. The extremely simple rock salt structure of these materials and
the ease with which high-quality crystals can be prepared suggests that they
may be an ideal platform for further investigation of topological matter.

###Rashba interaction and local magnetic moments in a graphene-Boron Nitride heterostructure by intercalation with Au|E. C. T. O'Farrell,J. Y. Tan,Y. Yeo,G. K. W. Koon,K. Watanabe,T. Taniguchi,B. Özyilmaz###

Rashba interaction and local magnetic moments in a graphene-Boron Nitride heterostructure by intercalation with Au. We intercalate a van der Waals heterostructure of graphene and hexagonal
Boron Nitride with Au, by encapsulation, and show that Au at the interface is
two dimensional. A charge transfer upon current annealing indicates
redistribution of Au and induces splitting of the graphene bandstructure. The
effect of in plane magnetic field confirms that splitting is due to
spin-splitting and that spin polarization is in the plane, characteristic of a
Rashba interaction with magnitude approximately 25 meV. Consistent with the
presence of intrinsic interfacial electric field we show that the splitting can
be enhanced by an applied displacement field in dual gated samples. Giant
negative magnetoresistance, up to 75%, and a field induced anomalous Hall
effect at magnetic fields < 1 T are observed. These demonstrate that hybridized
Au has a magnetic moment and suggests the proximity to formation of a
collective magnetic phase. These effects persist close to room temperature.

###Broken rotational symmetry on the Fermi surface of a high-T$_\mathrm{c}$ superconductor|B. J. Ramshaw,N. Harrison,S. E. Sebastian,S. Ghannadzadeh,K. A. Modic,D. A. Bonn,W. N. Hardy,Ruixing Liang,P. A. Goddard###

Broken rotational symmetry on the Fermi surface of a high-T$_\mathrm{c}$ superconductor. Broken fourfold rotational (C$_4$) symmetry is observed in the experimental
properties of several classes of unconventional superconductors. It has been
proposed that this symmetry breaking is important for superconducting pairing
in these materials, but in the high superconducting transition temperature
(high-T$_{\mathrm{c}}$) cuprates this broken symmetry has never been observed
on the Fermi surface. We have measured a pronounced anisotropy in the angle
dependence of the interlayer magnetoresistance of the underdoped
high-T$_{\mathrm{c}}$) superconductor YBa$_2$Cu$_3$O$_{6.58}$, directly
revealing broken C$_4$ symmetry on the Fermi surface. Moreover, we demonstrate
that this Fermi surface has C$_2$ symmetry of the type produced by a uniaxial
or anisotropic density-wave phase. This establishes the central role of C$_4$
symmetry breaking in the Fermi surface reconstruction of
YBa$_2$Cu$_3$O$_{6+\delta}$, and suggests a striking degree of universality
among unconventional superconductors.

###Tunneling magnetoresistance in trilayer structures composed of group-IV ferromagnetic semiconductor Ge1-xFex, MgO, and Fe|Yuki K. Wakabayashi,Kohei Okamoto,Yoshisuke Ban,Shoichi Sato,Masaaki Tanaka,Shinobu Ohya###

Tunneling magnetoresistance in trilayer structures composed of group-IV ferromagnetic semiconductor Ge1-xFex, MgO, and Fe. Group-IV-based ferromagnetic semiconductor Ge1-xFex (GeFe) is one of the most
promising materials for efficient spin injectors and detectors for Si and Ge.
Recent first principles calculations (Sakamoto et al., Ref. 9) suggested that
the Fermi level is located in two overlapping largely spin-polarized bands
formed in the bandgap of GeFe; spin-down d(e) band and spin-up p-d(t2) band.
Thus, it is important to clarify how these bands contribute to spin injection
and detection. In this study, we show the first successful observation of the
tunneling magnetoresistance (TMR) in magnetic tunnel junctions (MTJs)
containing a group-IV ferromagnetic semiconductor, that is, in MTJs composed of
epitaxially grown Fe/MgO/Ge0.935Fe0.065. We find that the p-d(t2) band in GeFe
is mainly responsible for the tunneling transport. Although the obtained TMR
ratio is small (0.3%), the TMR ratio is expected to be enhanced by suppressing
leak current through amorphous-like crystal domains observed in MgO.

###Weak de-localization in graphene on a ferromagnetic insulating film|Luca Pietrobon,Lorenzo Fallarino,Andreas Berger,Andrey Chuvilin,Fèlix Casanova,Luis E. Hueso###

Weak de-localization in graphene on a ferromagnetic insulating film. Graphene has been predicted to develop a magnetic moment by proximity effect
when placed on a ferromagnetic film, a promise that could open exciting
possibilities in the fields of spintronics and magnetic data recording. In this
work, we study in detail the interplay between the magnetoresistance of
graphene and the magnetization of an underlying ferromagnetic insulating film.
A clear correlation between both magnitudes is observed but we find, through a
careful modelling of the magnetization and the weak localization measurements,
that such correspondence can be explained by the effects of the magnetic stray
fields arising from the ferromagnetic insulator. Our results emphasize the
complexity arising at the interface between magnetic and two-dimensional
materials.

###Upper Critical Field and Kondo Effects in Fe(Te0.9Se0.1) Thin Films by Pulsed Field Measurements|M. B. Salamon,N. Cornell,M. Jaime,F. F. Balakirev,A. Zakhidov,J. Huang,H. Wang###

Upper Critical Field and Kondo Effects in Fe(Te0.9Se0.1) Thin Films by Pulsed Field Measurements. The transition temperatures of epitaxial films of Fe(Te0:9Se0:1) are
remarkably insensitive to applied magnetic field, leading to predictions of
upper critical fields Bc2(T = 0) in excess of 100 T. Using pulsed magnetic
fields, we find Bc2(0) to be on the order of 45 T, similar to values in bulk
material and still in excess of the paramagnetic limit. The same films show
strong magnetoresistance in fields above Bc2(T), consistent with the observed
Kondo minimum seen above Tc. Fits to the temperature dependence in the context
of the WHH model, using the experimental value of the Maki parameter, require
an effective spin-orbit relaxation parameter of order unity. We suggest that
Kondo localization plays a similar role to spin-orbit pair breaking in making
WHH fits to the data.

###Magnetic avalanches in granular ferromagnets: Thermal activated collective behavior|Gia-Wei Chern###

Magnetic avalanches in granular ferromagnets: Thermal activated collective behavior. We present a numerical study on the thermal activated avalanche dynamics in
granular materials composed of ferromagnetic clusters embedded in a
non-magnetic matrix. A microscopic dynamical simulation based on the
reaction-diffusion process is developed to modeling the magnetization process
of such systems. The large-scale simulations presented here explicitly
demonstrate inter-granular collective behavior induced by thermal activation of
spin tunneling. In particular, we observe an intriguing criticality controlled
by the rate of energy dissipation. We show that thermal activated avalanches
can be understood in the framework of continuum percolation and the emergent
dissipation induced criticality is in the universality class of
three-dimensional percolation transition. Implications of these results to the
phase-separated states of colossal magnetoresistance materials and other
artificial granular magnetic systems are also~discussed.

###Oscillating magnetoresistance due to fragile spin structure in metallic GdPd$_3$|Abhishek Pandey,Chandan Mazumdar,R. Ranganathan,D. C. Johnston###

Oscillating magnetoresistance due to fragile spin structure in metallic GdPd$_3$. Studies on the phenomenon of magnetoresistance (MR) have produced intriguing
and application-oriented outcomes for decades--colossal MR, giant MR and
recently discovered extremely large MR of millions of percents in semimetals
can be taken as examples. We report here the investigation of oscillating MR in
a cubic intermetallic compound GdPd$_3$, which is the only compound that
exhibits MR oscillations between positive and negative values. Our study shows
that a very strong correlation between magnetic, electrical and
magnetotransport properties is present in this compound. The magnetic structure
in GdPd$_3$ is highly fragile since applied magnetic fields of moderate
strength significantly alter the spin arrangement within the system--a behavior
that manifests itself in the oscillating MR. Intriguing magnetotransport
characteristics of GdPd$_3$ are appealing for field-sensitive device
applications, especially if the MR oscillation could materialize at higher
temperature by manipulating the magnetic interaction through perturbations
caused by chemical substitutions.

###Effect of Mg-Al insertion on magnetotransport properties in epitaxial Fe/sputter-deposited $MgAl_{2}O_{4}$/Fe(001) magnetic tunnel junctions|Mohamed Belmoubarik,Hiroaki Sukegawa,Tadakatsu Ohkubo,Seiji Mitani,Kazuhiro Hono###

Effect of Mg-Al insertion on magnetotransport properties in epitaxial Fe/sputter-deposited $MgAl_{2}O_{4}$/Fe(001) magnetic tunnel junctions. We investigated the effect of a Mg-Al layer insertion at the bottom interface
of epitaxial Fe/$MgAl_{2}O_{4}$/Fe(001) magnetic tunnel junctions (MTJs) on
their spin-dependent transport properties. The tunnel magnetoresistance (TMR)
ratio and differential conductance spectra for the parallel magnetic
configuration exhibited clear dependence on the inserted Mg-Al thickness. A
slight Mg-Al insertion (thickness < 0.1 nm) was effective for obtaining a large
TMR ratio above 200% at room temperature and observing a distinct local minimum
structure in conductance spectra. In contrast, thicker Mg-Al (> 0.2 nm) induced
a reduction of TMR ratios and featureless conductance spectra, indicating a
degradation of the bottom-Fe/$MgAl_{2}O_{4}$ interface. Therefore, a minimal
Mg-Al insertion was found to be effective to maximize the TMR ratio for a
sputtered $MgAl_{2}O_{4}$-based MTJ.

###Superconductivity Induced by High Pressure in Weyl Semimetal TaP|Yufeng Li,Yonghui Zhou,Zhaopeng Guo,Xuliang Chen,Pengchao Lu,Xuefei Wang,Chao An,Ying Zhou,Jie Xing,Guan Du,Xiyu Zhu,Huan Yang,Jian Sun,Zhaorong Yang,Yuheng Zhang,Hai-Hu Wen###

Superconductivity Induced by High Pressure in Weyl Semimetal TaP. Weyl semimetal defines a material with three dimensional Dirac cones which
appear in pair due to the breaking of spatial inversion or time reversal
symmetry. Superconductivity is the state of quantum condensation of paired
electrons. Turning a Weyl semimetal into superconducting state is very
important in having some unprecedented discoveries. In this work, by doing
resistive measurements on a recently recognized Weyl semimetal TaP under
pressure up to about 100 GPa, we observe superconductivity at about 70 GPa. The
superconductivity retains when the pressure is released. The systematic
evolutions of resistivity and magnetoresistance with pressure are well
interpreted by the relative shift between the chemical potential and paired
Weyl points. Calculations based on the density functional theory also
illustrate the structure transition at about 70GPa, the phase at higher
pressure may host superconductivity. Our discovery of superconductivity in TaP
by pressure will stimulate further study on superconductivity in Weyl
semimetals.

###MgGa2O4 spinel barrier for magnetic tunnel junctions: coherent tunneling and low barrier height|Hiroaki Sukegawa,Yushi Kato,Mohamed Belmoubarik,P. -H. Cheng,Tadaomi Daibou,Naoharu Shimomura,Yuuzo Kamiguchi,Junichi Ito,Hiroaki Yoda,Tadakatsu Ohkubo,Seiji Mitani,Kazuhiro Hono###

MgGa2O4 spinel barrier for magnetic tunnel junctions: coherent tunneling and low barrier height. Epitaxial Fe/magnesium gallium spinel oxide (MgGa2O4)/Fe(001) magnetic tunnel
junctions (MTJs) were fabricated by magnetron sputtering. Tunnel
magnetoresistance (TMR) ratio up to 121% at room temperature (196% at 4 K) was
observed, suggesting a TMR enhancement by the coherent tunneling effect in the
MgGa2O4 barrier. The MgGa2O4 layer had a spinel structure and it showed good
lattice matching with the Fe layers owing to slight tetragonal lattice
distortion of MgGa2O4. Barrier thickness dependence of the tunneling resistance
and current-voltage characteristics revealed that the barrier height of the
MgGa2O4 barrier is much lower than that in an MgAl2O4 barrier. This study
demonstrates the potential of Ga-based spinel oxides for MTJ barriers having a
large TMR ratio at a low resistance area product.

###Positive Quantum Magnetoresistance in Tilted Magnetic Field|William Mayer,Areg Ghazaryan,Pouyan Ghaemi,Sergey Vitkalov,A. A. Bykov###

Positive Quantum Magnetoresistance in Tilted Magnetic Field. Transport properties of highly mobile 2D electrons are studied in symmetric
GaAs quantum wells placed in titled magnetic fields. Quantum positive
magnetoresistance (QPMR) is observed in magnetic fields perpendicular to the 2D
layer. Application of in-plane magnetic field produces a dramatic decrease of
the QPMR. This decrease correlates strongly with the reduction of the amplitude
of Shubnikov de Haas resistance oscillations due to modification of the
electron spectrum via enhanced Zeeman splitting. Surprisingly no quantization
of the spectrum is detected when the Zeeman energy exceeds the half of the
cyclotron energy suggesting an abrupt transformation of the electron dynamics.
Observed angular evolution of QPMR implies strong mixing between spin subbands.
Theoretical estimations indicate that in the presence of spin-orbital
interaction the elastic impurity scattering provides significant contribution
to the spin mixing in GaAs quantum wells at high filling factors.

###Magnetic-proximity-induced magnetoresistance on topological insulators|Takahiro Chiba,Saburo Takahashi,Gerrit E. W. Bauer###

Magnetic-proximity-induced magnetoresistance on topological insulators. We theoretically study the magnetoresistance (MR) of two-dimensional massless
Dirac electrons as found on the surface of three-dimensional topological
insulators (3D TIs) that is capped by a ferromagnetic insulator (FI). We
calculate charge and spin transport by Kubo and Boltzmann theories, taking into
account the ladder-vertex correction and the in-scattering due to normal and
magnetic disorder. The induced exchange splitting is found to generate an
electric conductivity that depends on the magnetization orientation, but its
form is very different from both the anisotropic and spin Hall MR. The in-plane
MR vanishes identically for non-magnetic disorder, while out-of-plane
magnetizations cause a large MR ratio. On the other hand, we do find an
in-plane MR and planar Hall effect in the presence of magnetic disorder aligned
with the FI magnetization. Our results may help understand recent transport
measurements on TI|FI systems.

###Evidence of topological insulator state in the semimetal LaBi|R. Lou,B. -B. Fu,Q. N. Xu,P. -J. Guo,L. -Y. Kong,L. -K. Zeng,J. -Z. Ma,P. Richard,C. Fang,Y. -B. Huang,S. -S. Sun,Q. Wang,L. Wang,Y. -G. Shi,H. C. Lei,K. Liu,H. M. Weng,T. Qian,H. Ding,S. -C. Wang###

Evidence of topological insulator state in the semimetal LaBi. By employing angle-resolved photoemission spectroscopy combined with
first-principles calculations, we performed a systematic investigation on the
electronic structure of LaBi, which exhibits extremely large magnetoresistance
(XMR), and is theoretically predicted to possess band anticrossing with
nontrivial topological properties. Here, the observations of the Fermi-surface
topology and band dispersions are similar to previous studies on LaSb [Phys.
Rev. Lett. 117, 127204 (2016)], a topologically trivial XMR semimetal, except
the existence of a band inversion along the $\Gamma$-$X$ direction, with one
massless and one gapped Dirac-like surface state at the $X$ and $\Gamma$
points, respectively. The odd number of massless Dirac cones suggests that LaBi
is analogous to the time-reversal $Z_2$ nontrivial topological insulator. These
findings open up a new series for exploring novel topological states and
investigating their evolution from the perspective of topological phase
transition within the family of rare-earth monopnictides.

###Anomalous Hall Effect in ZrTe5|Tian Liang,Jingjing Lin,Quinn Gibson,Minhao Liu,Wudi Wang,Hongyu Xiong,Jonathan A. Sobota,Makoto Hashimoto,Patrick S. Kirchmann,Zhi-Xun Shen,R. J. Cava,N. P. Ong###

Anomalous Hall Effect in ZrTe5. ZrTe$_5$ has been of recent interest as a potential Dirac/Weyl semimetal
material. Here, we report the results of experiments performed via in-situ 3D
double-axis rotation to extract the full $4\pi$ solid angular dependence of the
transport properties. A clear anomalous Hall effect (AHE) was detected for
every sample, with no magnetic ordering observed in the system to the
experimental sensitivity of torque magnetometry. Interestingly, the AHE takes
large values when the magnetic field is rotated in-plane, with the values
vanishing above $\sim 60$ K where the negative longitudinal magnetoresistance
(LMR) also disappears. This suggests a close relation in their origins, which
we attribute to Berry curvature generated by the Weyl nodes.

###Observation of quantum oscillations in FIB fabricated nanowires of topological insulator (Bi2Se3)|Biplab Bhattacharyya,Alka Sharma,V P S Awana,A. K. Srivastava,T. D. Senguttuvan,Sudhir Husale###

Observation of quantum oscillations in FIB fabricated nanowires of topological insulator (Bi2Se3). Since last few years, research based on topological insulators (TI) is in
great interests due to intrinsic exotic fundamental properties and future
potential applications such as quantum computers or spintronics. The
fabrication of TI nanodevices and study on their transport properties mostly
focused on high quality crystalline nanowires or nanoribbons. Here we report
robust approach of Bi2Se3 nanowire formation from deposited flakes using ion
beam milling method. The fabricated Bi2Se3 nanowire devices have been employed
to investigate the robustness of topological surface state (TSS) to gallium ion
doping and any deformation in the material due to fabrication tools. We report
the quantum oscillations in magnetoresistance curves under the parallel
magnetic field. The resistance versus magnetic field curves have been studied
and compared with Aharonov-Bohm (AB) interference effects which further
demonstrate the transport through TSS. The fabrication route and observed
electronic transport properties indicate clear quantum oscillations and can be
exploited further in studying the exotic electronic properties associated with
TI based nanodevices.

###Giant microwave-induced $B$-periodic magnetoresistance oscillations in a two-dimensional electron gas with a bridged-gate tunnel point contact|A. D. Levin,S. A. Mikhailov,G. M. Gusev,Z. D. Kvon,E. E. Rodyakina,A. V. Latyshev###

Giant microwave-induced $B$-periodic magnetoresistance oscillations in a two-dimensional electron gas with a bridged-gate tunnel point contact. We have studied the magnetoresistance of the quantum point contact fabricated
on the high mobility two-dimensional electron gas (2DEG) exposed to microwave
irradiation. The resistance reveals giant $B$-periodic oscillations with the
relative amplitude $\Delta R/R$ of up to $700$\% resulting from the propagation
and interference of the edge magnetoplasmons (EMPs) in the sample. This giant
photoconductance is attributed to the considerably large local electron density
modulation in the vicinity of the point contact. We have also analyzed the
oscillation periods $\Delta B$ of the resistance oscillations and, comparing
the data with the EMP theory, extracted the EMP interference length $L$. We
have found that the length $L$ substantially exceeds the distance between the
contact leads but rather corresponds to the distance between metallic contact
pads measured along the edge of the 2DEG. This resolves existing controversy in
the literature and should help to properly design highly sensitive microwave
and terahertz spectrometers based on the discussed effect.

###Gyrotropic elastic response of skyrmion crystals to current-induced tensions|Hector Ochoa,Se Kwon Kim,Oleg Tchernyshyov,Yaroslav Tserkovnyak###

Gyrotropic elastic response of skyrmion crystals to current-induced tensions. We theoretically study the dynamics of skyrmion crystals in
electrically-insulating chiral magnets subjected to current-induced spin
torques by adjacent metallic layers. We develop an elasticity theory that
accounts for the gyrotropic force engendered by the non-trivial topology of the
spin texture, tensions at the boundaries due to the exchange of linear and spin
angular momentum with the metallic reservoirs, and dissipation in the bulk of
the film. A steady translation of the skyrmion crystal is triggered by the
current-induced tensions and subsequently sustained by dissipative forces,
generating an electromotive force on itinerant spins in the metals. This
phenomenon should be revealed as a negative drag in an open two-terminal
geometry, or equivalently, as a positive magnetoresistance when the terminals
are connected in parallel. We propose non-local transport measurements with
these salient features as a tool to characterize the phase diagram of
insulating chiral magnets.

###Three-Dimensional Electronic Structure of type-II Weyl Semimetal WTe$_2$|Domenico Di Sante,Pranab Kumar Das,C. Bigi,Z. Ergönenc,N. Gürtler,J. A. Krieger,T. Schmitt,M. N. Ali,G. Rossi,R. Thomale,C. Franchini,S. Picozzi,J. Fujii,V. N. Strocov,G. Sangiovanni,I. Vobornik,R. J. Cava,G. Panaccione###

Three-Dimensional Electronic Structure of type-II Weyl Semimetal WTe$_2$. By combining bulk sensitive soft-X-ray angular-resolved photoemission
spectroscopy and accurate first-principles calculations we explored the bulk
electronic properties of WTe$_2$, a candidate type-II Weyl semimetal featuring
a large non-saturating magnetoresistance. Despite the layered geometry
suggesting a two-dimensional electronic structure, we find a three-dimensional
electronic dispersion. We report an evident band dispersion in the reciprocal
direction perpendicular to the layers, implying that electrons can also travel
coherently when crossing from one layer to the other. The measured Fermi
surface is characterized by two well-separated electron and hole pockets at
either side of the $\Gamma$ point, differently from previous more surface
sensitive ARPES experiments that additionally found a significant quasiparticle
weight at the zone center. Moreover, we observe a significant sensitivity of
the bulk electronic structure of WTe$_2$ around the Fermi level to electronic
correlations and renormalizations due to self-energy effects, previously
neglected in first-principles descriptions.

###Fabrication and electrical transport properties of embedded graphite microwires in a diamond matrix|J. Barzola-Quiquia,T. Lühmann,R. Wunderlich,M. Stiller,M. Zoraghi,J. Meijer,P. Esquinazi,J. Böttner,I. Estrela-Lopis###

Fabrication and electrical transport properties of embedded graphite microwires in a diamond matrix. Micrometer width and nanometer thick wires with different shapes were
produced $\approx 3~\upmu$m below the surface of a diamond crystal using a
microbeam of He$^+$ ions with 1.8~MeV energy. Initial samples are amorphous and
after annealing at $T\approx 1475$~K, the wires crystallized into a
graphite-like structures, according to confocal Raman spectroscopy
measurements. The electrical resistivity at room temperature is only one order
of magnitude larger than the in-plane resistivity of highly oriented pyrolytic
bulk graphite and shows a small resistivity ratio($\rho(2{\rm K})/\rho(315{\rm
K}) \approx 1.275$). A small negative magnetoresistance below $T=200$~K was
measured and can be well understood taking spin-dependent scattering processes
into account. The used method provides the means to design and produce
millimeter to micrometer sized conducting circuits with arbitrary shape
embedded in a diamond matrix.

###Evidence of robust 2D transport and Efros-Shklovskii variable range hopping in disordered topological insulator (Bi2Se3) nanowires|Biplab Bhattacharyya,Alka Sharma,Bhavesh Sinha,Kunjal Shah,Suhas Jejurikar,T. D. Senguttuvan,Sudhir Husale###

Evidence of robust 2D transport and Efros-Shklovskii variable range hopping in disordered topological insulator (Bi2Se3) nanowires. We report the experimental observation of variable range hopping conduction
in focused-ion-beam (FIB) fabricated ultra-narrow nanowires of topological
insulator (Bi2Se3). The value of the exponent in the hopping equation was
extracted as ~ 1/2 for different widths of nanowires, which is the proof of the
presence of Efros-Shklovskii hopping transport mechanism in a strongly
disordered system. High localization lengths (0.5nm, 20nm) were calculated for
the devices. A careful analysis of the temperature dependent fluctuations
present in the magnetoresistance curves, using the standard Universal
Conductance Fluctuation theory, indicates the presence of 2D topological
surface states. Also, the surface state contribution to the conductance was
found very close to one conductance quantum. We believe that our experimental
findings shed light on the understanding of quantum transport in disordered
topological insulator based nanostructures.

###Transport Coefficients of Dirac Ferromagnet: Effects of Vertex Corrections|Junji Fujimoto###

Transport Coefficients of Dirac Ferromagnet: Effects of Vertex Corrections. As a strongly spin-orbit coupled metallic model with ferromagnetism, we have
considered an extended Stoner model to the relativistic regime, named Dirac
ferromagnet in three dimensions.
  In the previous paper~[Phys. Rev. B 90, 214418 (2014)], we studied the
transport properties giving rise to the anisotropic magnetoresistance~(AMR) and
the anomalous Hall effect~(AHE) with the impurity potential being taken into
account only as the self-energy.
  The effects of the vertex corrections~(VCs) to AMR and AHE are reported in
this paper.
  AMR is found not to change quantitatively when the VCs is considered,
although the transport lifetime is different from the one-electron lifetime and
the charge current includes additional contributions from the correlation with
spin currents.
  The side-jump and the skew-scattering contributions to AHE are also
calculated.
  The skew-scattering contribution is dominant in the clean case as can be seen
in the spin Hall effect in the non-magnetic Dirac electron system.

###Emergence of Gapped Bulk and Metallic Side Walls in the Zeroth Landau level in Dirac and Weyl semimetals|Ching-Kit Chan,Patrick A. Lee###

Emergence of Gapped Bulk and Metallic Side Walls in the Zeroth Landau level in Dirac and Weyl semimetals. Recent transport experiments have revealed the activation of longitudinal
magnetoresistance of Weyl semimetals in the quantum limit, suggesting the
breakdown of chiral anomaly in a strong magnetic field. Here we provide a
general mechanism for gapping the zeroth chiral Landau levels applicable for
both Dirac and Weyl semimetals. Our result shows that the zeroth Landau levels
anticross when the magnetic axis is perpendicular to the Dirac/Weyl node
separation and when the inverse magnetic length $l_B^{-1}$ is comparable to the
node separation scale $\Delta k$. The induced bulk gap increases rapidly beyond
a threshold field in Weyl semimetals, but has no threshold and is non-monotonic
in Dirac systems due to the crossover between $l_B^{-1}>\Delta k$ and
$l_B^{-1}<\Delta k$ regions. We also find that the Dirac and possibly Weyl
systems host counterpropagating edge states between the zeroth Landau levels,
leading to a state with metallic side walls and zero Hall conductance.

###Superconducting MoSi nanowires|J. S. Lehtinen,A. Kemppinen,E. Mykkänen,M. Prunnila,A. J. Manninen###

Superconducting MoSi nanowires. We have fabricated disordered superconducting nanowires of molybdenium
silicide. A molybdenium nanowire is first deposited on top of silicon, and the
alloy is formed by rapid thermal annealing. The method allows tuning of the
crystal growth to optimise, e.g., the resistivity of the alloy for potential
applications in quantum phase slip devices and superconducting nanowire
single-photon detectors. The wires have effective diameters from 42 to 79 nm,
enabling the observation of crossover from conventional superconductivity to
regimes affected by thermal and quantum fluctuations. In the smallest diameter
wire and at temperatures well below the superconducting critical temperature,
we observe residual resistance and negative magnetoresistance, which can be
considered as fingerprints of quantum phase slips.

###Spin torque control of antiferromagnetic moments in NiO|Takahiro Moriyama,Kent Oda,Teruo Ono###

Spin torque control of antiferromagnetic moments in NiO. For a long time, there have been no efficient ways of controlling
antiferromagnets. Quite a strong magnetic field was required to manipulate the
magnetic moments because of a high molecular field and a small magnetic
susceptibility. It was also difficult to detect the orientation of the magnetic
moments since the net magnetic moment is effectively zero. For these reasons,
research on antiferromagnets has not been progressed as drastically as that on
ferromagnets which are the main materials in modern spintronic devices. Here we
show that the magnetic moments in NiO, a typical natural antiferromagnet, can
indeed be controlled by the spin torque with a relatively small electric
current density (~5 x 10^7 A/cm^2) and their orientation is detected by the
transverse resistance resulting from the spin Hall magnetoresistance . The
demonstrated techniques of controlling and detecting antiferromagnets would
outstandingly promote the methodologies in the recently emerged
"antiferromagnetic spintronics". Furthermore, our results essentially lead to a
spin torque antiferromagnetic memory.

###Low-Frequency Microwave Induced Quantum Oscillations in A Two-Dimensional Electron System|Jian Mi,Huiying Liu,Junren Shi,L. N. Pfeiffer,K. W. West,K. W. Baldwin,Chi Zhang###

Low-Frequency Microwave Induced Quantum Oscillations in A Two-Dimensional Electron System. We study the magnetoresistance of an ultrahigh mobility GaAs/AlGaAs
two-dimensional electron sample in a weak magnetic field under low-frequency (f
< 20 GHz) microwave (MW) irradiation. We observe that with decreasing MW
frequency, microwave induced resistance oscillations (MIRO) damp and
multi-photon processes become dominant. At very low MW frequency (f < 4 GHz),
MIRO disappears gradually and a new SdH-like oscillation develops. The analysis
indicates that the new oscillation may originate from alternating Hall-field
induced resistance oscillations (ac-HIRO), or can be viewed as a multi-photon
process of MIRO in low MW frequency limit. Our findings bridge the
non-equilibrium states of MIRO and HIRO, which can be brought into a frame of
quantum tunneling junction model.

###Antiferromagnetic anisotropy determination by spin Hall magnetoresistance|Hua Wang,Dazhi Hou,Zhiyong Qiu,Takashi Kikkawa,Eiji Saitoh,Xiaofeng Jin###

Antiferromagnetic anisotropy determination by spin Hall magnetoresistance. An electric method for measuring magnetic anisotropy in antiferromagnetic
insulators (AFIs) is proposed. When a metallic film with strong spin-orbit
interactions, e.g., platinum (Pt), is deposited on an AFI, its resistance
should be affected by the direction of the AFI N eel vector due to the spin
Hall magnetoresistance (SMR). Accordingly, the direction of the AFI N eel
vector, which is affected by both the external magnetic field and the magnetic
anisotropy, is reflected in resistance of Pt. The magnetic field angle
dependence of the resistance of Pt on AFI is calculated by consider- ing the
SMR, which indicates that the antiferromagnetic anisotropy can be obtained
experimentally by monitoring the Pt resistance in strong magnetic fields.
Calculations are performed for realistic systems such as Pt/Cr2O3, Pt/NiO, and
Pt/CoO.

###Temperature dependence of interlayer coupling in perpendicular magnetic tunnel junctions with GdOx barriers|T. Newhouse-Illige,Y. H. Xu,Y. H. Liu,S. Huang,H. Kato,C. Bi,M. Xu,B. J. LeRoy,W. G. Wang###

Temperature dependence of interlayer coupling in perpendicular magnetic tunnel junctions with GdOx barriers. Perpendicular magnetic tunnel junctions with GdOX tunneling barriers have
shown a unique voltage controllable interlayer magnetic coupling effect. Here
we investigate the quality of the GdOX barrier and the coupling mechanism in
these junctions by examining the temperature dependence of the tunneling
magnetoresistance and the interlayer coupling from room temperature down to 11
K. The barrier is shown to be of good quality with the spin independent
conductance only contributing a small portion, 14%, to the total room
temperature conductance, similar to AlOX and MgO barriers. The interlayer
coupling, however, shows an anomalously strong temperature dependence including
sign changes below 80 K. This non-trivial temperature dependence is not
described by previous models of interlayer coupling and may be due to the large
induced magnetic moment of the Gd ions in the barrier.

###Newton's second law in spin-orbit torque|Cong Son Ho,Seng Ghee Tan,Shun-Qing Shen,Mansoor B. A. Jalil###

Newton's second law in spin-orbit torque. Spin-orbit torque (SOT) refers to the excitation of magnetization dynamics
via spin-orbit coupling under the application of a charged current. In this
work, we introduce a simple and intuitive description of the SOT in terms of
spin force. In Rashba spin-orbit coupling system, the damping-like SOT can be
expressed as ${\mathbf T}^\mathrm{so}={\mathbf R}_c\times {\mathbf F}^{{\mathrm
{so}}}$, in analogy to the classical torque-force relation, where $R_c$ is the
effective radius characterizing the Rashba splitting in the momentum space. As
a consequence, the magnetic energy is transferred to the conduction electrons,
which dissipates through Joule heating at a rate of $({\mathbf j}_e\cdot
{\mathbf F}^{\mathrm {so}})$, with $j_e$ being the applied current. Finally, we
propose an experimental verification of our findings via measurement of the
anisotropic magnetoresistance effect.

###Characterizing spin transport: detection of spin accumulation via magnetic stray field|Matthias Pernpeintner,Akashdeep Kamra,Sebastian T. B. Goennenwein,Hans Huebl###

Characterizing spin transport: detection of spin accumulation via magnetic stray field. Spin transport in electric conductors is largely determined by two material
parameters - spin diffusion length and spin Hall angle. In metals, these are
typically determined indirectly by probing magnetoresistance in magnet/metal
heterostructures, assuming knowledge of the interfacial properties. We suggest
profiling the charge current induced spin Hall spin accumulation in metals, via
detection of the magnetic stray field generated by the associated static
magnetization, as a direct means of determining spin transport parameters. We
evaluate the spatial profile of the stray field as well as the Oersted field
generated by the charge current. We thus demonstrate that such a charge current
induced spin accumulation is well within the detection limit of contemporary
technology. Measuring the stray fields may enable direct access to spin-related
properties of metals paving the way for a better and consistent understanding
of spin transport therein.

###Superconductor-insulator transition in fcc-GeSb2Te4 at elevated pressures|Bar Hen,Samar Layek,Moshe Goldstein,Victor Shelukhin,Mark Shulman,Michael Karpovski,Eran Greenberg,Eran Sterer,Yoram Dagan,Gregory Kh. Rozenberg,Alexander Palevski###

Superconductor-insulator transition in fcc-GeSb2Te4 at elevated pressures. We show that polycrystalline GeSb2Te4 in the fcc phase (f-GST), which is an
insulator at low temperature at ambient pressure, becomes a superconductor at
elevated pressures. Our study of the superconductor to insulator transition
versus pressure at low temperatures reveals a second order quantum phase
transition with linear scaling (critical exponent close to unity) of the
transition temperature with the pressure above the critical zero-temperature
pressure. In addition, we demonstrate that at higher pressures the f-GST goes
through a structural phase transition via amorphization to bcc GST (b-GST),
which also become superconducting. We also find that the pressure regime where
an inhomogeneous mixture of amorphous and b-GST exists, there is an anomalous
peak in magnetoresistance, and suggest an explanation for this anomaly.

###Contactless and absolute linear displacement detection based upon 3D printed magnets combined with passive radio-frequency identification|Roman Windl,Claas Abert,Florian Bruckner,Christian Huber,Christoph Vogler,Herbert Weitensfelder,Dieter Suess###

Contactless and absolute linear displacement detection based upon 3D printed magnets combined with passive radio-frequency identification. Within this work a passive and wireless magnetic sensor, to monitor linear
displacements is proposed. We exploit recent advances in 3D printing and
fabricate a polymer bonded magnet with a spatially linear magnetic field
component corresponding to the length of the magnet. Regulating the magnetic
compound fraction during printing allows specific shaping of the magnetic field
distribution. A giant magnetoresistance magnetic field sensor is combined with
a radio-frequency identification tag in order to passively monitor the exerted
magnetic field of the printed magnet. Due to the tailored magnetic field, a
displacement of the magnet with respect to the sensor can be detected within
the sub-mm regime. The sensor design provides good flexibility by controlling
the 3D printing process according to application needs. Absolute displacement
detection using low cost components and providing passive operation, long term
stability and longevity renders the proposed sensor system ideal for structural
health monitoring applications.

###Magnetization reversal in Kagome artificial spin ice studied by first-order reversal curves|L. Sun,C. Zhou,J. H. Liang,T. Xing,N. Lei,P. Murray,Kai Liu,C. Won,Y. Z. Wu###

Magnetization reversal in Kagome artificial spin ice studied by first-order reversal curves. Magnetization reversal of interconnected Kagome artificial spin ice was
studied by the first-order reversal curve (FORC) technique based on the
magneto-optical Kerr effect and magnetoresistance measurements. The
magnetization reversal exhibits a distinct six-fold symmetry with the external
field orientation. When the field is parallel to one of the nano-bar branches,
the domain nucleation/propagation and annihilation processes sensitively depend
on the field cycling history and the maximum field applied. When the field is
nearly perpendicular to one of the branches, the FORC measurement reveals the
magnetic interaction between the Dirac strings and orthogonal branches during
the magnetization reversal process. Our results demonstrate that the FORC
approach provides a comprehensive framework for understanding the magnetic
interaction in the magnetization reversal processes of spin-frustrated systems.

###Zero-Field Quantum Critical Point in Ce$_{0.91}$Yb$_{0.09}$CoIn$_5$|Y. P. Singh,R. B. Adhikari,D. J. Haney,B. D. White,M. B. Maple,M. Dzero,Carmen C. Almasan###

Zero-Field Quantum Critical Point in Ce$_{0.91}$Yb$_{0.09}$CoIn$_5$. We present results of specific heat, electrical resistance, and
magnetoresistivity measurements on single crystals of the heavy-fermion
superconducting alloy Ce$_{0.91}$Yb$_{0.09}$CoIn$_5$. Non-Fermi liquid to Fermi
liquid crossovers are clearly observed in the temperature dependence of the
Sommerfeld coefficient $\gamma$ and resistivity data. Furthermore, we show that
the Yb-doped sample with $x=0.09$ exhibits universality due to an underlying
quantum phase transition without an applied magnetic field by utilizing the
scaling analysis of $\gamma$. Fitting of the heat capacity and resistivity data
based on existing theoretical models indicates that the zero-field quantum
critical point is of antiferromagnetic origin. Finally, we found that at zero
magnetic field the system undergoes a third-order phase transition at the
temperature $T_{c3}\approx 7$ K.

###A conductive topological insulator with colossal spin Hall effect for ultra-low power spin-orbit-torque switching|Nguyen Huynh Duy Khang,Yugo Ueda,Pham Nam Hai###

A conductive topological insulator with colossal spin Hall effect for ultra-low power spin-orbit-torque switching. Spin-orbit-torque (SOT) switching using the spin Hall effect (SHE) in heavy
metals and topological insulators (TIs) has great potential for ultra-low power
magnetoresistive random-access memory (MRAM). To be competitive with
conventional spin-transfer-torque (STT) switching, a pure spin current source
with large spin Hall angle (${\theta}_{SH}$ > 1) and high electrical
conductivity (${\sigma} > 10^5 {\Omega}^{-1}m^{-1}$) is required. Here, we
demonstrate such a pure spin current source: BiSb thin films with
${\sigma}{\sim}2.5*10^5 {\Omega}^{-1}m^{-1}$, ${\theta}_{SH}{\sim}52$, and spin
Hall conductivity ${\sigma}_{SH}{\sim}1.3*10^7 {\hbar}/2e{\Omega}^{-1}m^{-1}$
at room temperature. We show that BiSb thin films can generate a colossal
spin-orbit field of 2770 Oe/(MA/cm$^2$) and a critical switching current
density as low as 1.5 MA/cm$^2$ in Bi$_{0.9}$Sb$_{0.1}$ / MnGa bi-layers. BiSb
is the best candidate for the first industrial application of topological
insulators.

###Exfoliation and van der Waals heterostructure assembly of intercalated ferromagnet Cr1/3TaS2|Yuji Yamasaki,Rai Moriya,Miho Arai,Satoru Masubuchi,Sunseng Pyon,Tsuyoshi Tamegai,Keiji Ueno,Tomoki Machida###

Exfoliation and van der Waals heterostructure assembly of intercalated ferromagnet Cr1/3TaS2. Ferromagnetic van der Waals (vdW) materials are in demand for spintronic
devices with all-two-dimensional-materials heterostructures. Here, we
demonstrate mechanical exfoliation of magnetic-atom-intercalated transition
metal dichalcogenide Cr1/3TaS2 from its bulk crystal; previously such
intercalated materials were thought difficult to exfoliate. Magnetotransport in
exfoliated tens-of-nanometres-thick flakes revealed ferromagnetic ordering
below its Curie temperature TC ~ 110 K as well as strong in-plane magnetic
anisotropy; these are identical to its bulk properties. Further, van der Waals
heterostructure assembly of Cr1/3TaS2 with another intercalated ferromagnet
Fe1/4TaS2 is demonstrated using a dry-transfer method. The fabricated
heterojunction composed of Cr1/3TaS2 and Fe1/4TaS2 with a native Ta2O5 oxide
tunnel barrier in between exhibits tunnel magnetoresistance (TMR), revealing
possible spin injection and detection with these exfoliatable ferromagnetic
materials through the vdW junction.

###Band dependence of charge density wave in quasi-one-dimensional Ta2NiSe7 probed by orbital magnetoresistance|Jiaming He,Yiran Zhang,Libin Wen,Yusen Yang,Jinyu Liu,Yueshen Wu,Hailong Lian,Hui Xing,Shun Wang,Zhiqiang Mao,Ying Liu###

Band dependence of charge density wave in quasi-one-dimensional Ta2NiSe7 probed by orbital magnetoresistance. Ta2NiSe7 is a quasi-one-dimensional (quasi-1D) transition-metal chalcogenide
with Ta and Ni chain structure. An incommensurate charge-density wave (CDW) in
this quasi-1D structure was well studied previously using tunnelling spectrum,
X-ray and electron diffraction, whereas its transport property and the relation
to the underlying electronic states remain to be explored. Here we report our
results of magnetoresistance (MR) on Ta2NiSe7. A breakdown of the Kohler's rule
is found upon entering the CDW state. Concomitantly, a clear change of
curvature in the field dependence of MR is observed. We show that the curvature
change is well described by two-band orbital MR, with the hole density being
strongly suppressed in the CDW state, indicating that the $p$ orbitals from Se
atoms dominate the change in transport through the CDW transition.

###Negative spin Hall magnetoresistance in antiferromagnetic Cr2O3/Ta bilayer at low temperature region|Y. Ji,J. Miao,Y. M. Zhu,K. K. Meng,X. G. Xu,J. K. Chen,Y. Wu,Y. Jiang###

Negative spin Hall magnetoresistance in antiferromagnetic Cr2O3/Ta bilayer at low temperature region. We investigate the observation of negative spin Hall magnetoresistance (SMR)
in antiferromagnetic Cr2O3/Ta bilayers at low temperature. The sign of the SMR
signals is changed from positive to negative monotonously from 300 K to 50 K.
The change of the signs for SMR is related with the competitions between the
surface ferromagnetism and bulky antiferromagnetic of Cr2O3. The surface
magnetizations of Cr2O3 (0001) is considered to be dominated at higher
temperature, while the bulky antiferromagnetics gets to be robust with
decreasing of temperature. The slopes of the abnormal Hall curves coincide with
the signs of SMR, confirming variational interface magnetism of Cr2O3 at
different temperature. From the observed SMR ratio under 3 T, the spin mixing
conductance at Cr2O3/Ta interface is estimated to be 1.12*10^14 (ohm^-1*m^-2),
which is comparable to that of YIG/Pt structures and our early results of
Cr2O3/W. (Appl. Phys. Lett. 110, 262401 (2017))

###Bulk contribution to magnetotransport properties of low defect-density Bi$_2$Te$_3$ topological insulator thin films|Prosper Ngabonziza,Yi Wang,Alexander Brinkman###

Bulk contribution to magnetotransport properties of low defect-density Bi$_2$Te$_3$ topological insulator thin films. An important challenge in the field of topological materials is to carefully
disentangle the electronic transport contribution of the topological surface
states from that of the bulk. For Bi$_2$Te$_3$ topological insulator samples,
bulk single crystals and thin films exposed to air during fabrication processes
are known to be bulk conducting, with the chemical potential in the bulk
conduction band. For Bi$_2$Te$_3$ thin films grown by molecular beam epitaxy,
we combine structural characterization (transmission electron microscopy),
chemical surface analysis as function of time (x-ray photoelectron
spectroscopy) and magnetotransport analysis to understand the low defect
density and record high bulk electron mobility once charge is doped into the
bulk by surface degradation. Carrier densities and electronic mobilities
extracted from the Hall effect and the quantum oscillations are consistent and
reveal a large bulk carrier mobility. Because of the cylindrical shape of the
bulk Fermi surface, the angle dependence of the bulk magnetoresistance
oscillations is two-dimensional in nature.

###Probing magnetism in 2D van der Waals crystalline insulators via electron tunneling|Dahlia R. Klein,David MacNeill,Jose L. Lado,David Soriano,Efrén Navarro-Moratalla,Kenji Watanabe,Takashi Taniguchi,Soham Manni,Paul Canfield,Joaquín Fernández-Rossier,Pablo Jarillo-Herrero###

Probing magnetism in 2D van der Waals crystalline insulators via electron tunneling. Magnetic insulators are a key resource for next-generation spintronic and
topological devices. The family of layered metal halides promises ultrathin
insulating multiferroics, spin liquids, and ferromagnets, but new
characterization methods are required to unlock their potential. Here, we
report tunneling through the layered magnetic insulator CrI3 as a function of
temperature and applied magnetic field. We electrically detect the magnetic
ground state and inter-layer coupling and observe a field-induced metamagnetic
transition. The metamagnetic transition results in magnetoresistances of 95%,
300%, and 550% for bilayer, trilayer, and tetralayer CrI3 barriers,
respectively. We further measure inelastic tunneling spectra for our junctions,
unveiling a rich spectrum of collective magnetic excitations (magnons) in CrI3.
Our results establish vertical tunneling as a versatile probe of magnetism in
atomically thin insulators.

###Quantum anomalies in nodal line semimetals|A. A. Burkov###

Quantum anomalies in nodal line semimetals. Topological semimetals is a new class of condensed matter systems with
nontrivial electronic structure topology. Their unusual observable properties
may often be understood in terms of quantum anomalies. In particular, Weyl and
Dirac semimetals, which have point band touching nodes, are characterized by
the chiral anomaly, which leads to the Fermi arc surface states, anomalous Hall
effect, negative longitudinal magnetoresistance and planar Hall effect. In this
paper we explore analogous phenomena in nodal line semimetals. We demonstrate
that such semimetals realize a three dimensional analog of the parity anomaly,
which is a known property of two dimensional Dirac semimetals arising, for
example, on the surface of a three dimensional topological insulator. We relate
one of the characteristic properties of nodal line semimetals, namely the
drumhead surface states, to this anomaly, and derive the field theory, which
encodes the corresponding anomalous response.

###Structure, magnetic and transport properties of epitaxial thin films of equiatomic CoFeMnGe quaternary Heusler alloy|Varun K. Kushwaha,Jyoti Rani,C. V. Tomy,Ashwin Tulapurkar###

Structure, magnetic and transport properties of epitaxial thin films of equiatomic CoFeMnGe quaternary Heusler alloy. Future spintronics requires the realization of thin film of half-metallic
ferromagnets having high Curie temperature and 100\% spin polarization at the
Fermi level for potential spintronics applications. In this paper, we report
the epitaxial thin films growth of half-metallic CoFeMnGe Heusler alloy on MgO
(001) substrate using pulsed laser deposition system, along with the study of
structural, magnetic and transport properties. The magnetic property
measurements of the thin film suggest a soft ferromagnetic state at room
temperature with an in-plane magnetic anisotropy and a Curie temperature well
above the room temperature. Anisotropic magnetoresistance (AMR) ratio and
temperature dependent electrical resistivity measurements of the thin film
indicate the compound to be half-metallic in nature and therefore suitable for
the fabrications of spintronics devices.

###Dark states in spin-polarized transport through triple quantum dot molecules|Kacper Wrześniewski,Ireneusz Weymann###

Dark states in spin-polarized transport through triple quantum dot molecules. We study the spin-polarized transport through a triple quantum dot molecule
weakly coupled to ferromagnetic leads. The analysis is performed by means of
the real-time diagrammatic technique including up to the second order of
perturbation expansion with respect to the tunnel coupling. The emphasis is put
on the impact of dark states on spin-resolved transport characteristics. It is
shown that the interplay of coherent population trapping and cotunneling
processes results in a highly nontrivial behavior of the tunnel
magnetoresistance, which can take negative values. Moreover, a super-Poissonian
shot noise is found in transport regimes where the current is blocked by the
formation of dark states, which can be additionally enhanced by spin-dependence
of tunneling processes, depending on magnetic configuration of the device. The
mechanisms leading to those effects are thoroughly discussed.

###Colossal magnetoresistance in a Mott insulator via magnetic field-driven insulator-metal transition|M. Zhu,J. Peng,T. Zou,K. Prokes,S. D. Mahanti,T. Hong,Z. Q. Mao,G. Q. Liu,X. Ke###

Colossal magnetoresistance in a Mott insulator via magnetic field-driven insulator-metal transition. We present a new type of colossal magnetoresistance (CMR) arising from an
anomalous collapse of the Mott insulating state via a modest magnetic field in
a bilayer ruthenate, Ti-doped Ca$_3$Ru$_2$O$_7$. Such an insulator-metal
transition is accompanied by changes in both lattice and magnetic structures.
Our findings have important implications because a magnetic field usually
stabilizes the insulating ground state in a Mott-Hubbard system, thus calling
for a deeper theoretical study to reexamine the magnetic field tuning of Mott
systems with magnetic and electronic instabilities and spin-lattice-charge
coupling. This study further provides a model approach to search for CMR
systems other than manganites, such as Mott insulators in the vicinity of the
boundary between competing phases.

###Kondo behavior and metamagnetic phase transition in a heavy fermion compound CeBi2|W. Zhou,C. Q. Xu,B. Li,R. Sankar,F. M. Zhang,B. Qian,C. Cao,J. H. Dai,Jianming Lu,Xiaofeng Xu###

Kondo behavior and metamagnetic phase transition in a heavy fermion compound CeBi2. Heavy fermions represent an archetypal example of strongly correlated
electron systems which, due to entanglement among different interactions, often
exhibit exotic and fascinating physics involving Kondo screening, magnetism and
unconventional superconductivity. Here we report a comprehensive study on the
transport and thermodynamic properties of a cerium-based heavy fermion compound
CeBi$_2$ which undergoes an anti-ferromagnetic transition at $T_N$ $\sim$ 3.3
K. Its high temperature paramagnetic state is characterized by an enhanced heat
capacity with Sommerfeld coefficient $\gamma$ over 200 mJ/molK$^2$. The
magnetization in the magnetically ordered state features a metamagnetic
transition. Remarkably, a large negative magnetoresistance associated with the
magnetism was observed in a wide temperature and field-angle range.
Collectively, CeBi$_2$ may serve as an intriguing system to study the interplay
between $f$ electrons and the itinerant Fermi sea.

###Magnetic-field enhanced high-thermoelectric performance in topological Dirac semimetal Cd$_3$As$_2$ crystal|H. H. Wang,X. G. Luo,W. W. Chen,N. Z. Wang,B. Lei,F. B. Meng,C. Shang,L. K. Ma,T. Wu,X. Dai,Z. F. Wang,X. H. Chen###

Magnetic-field enhanced high-thermoelectric performance in topological Dirac semimetal Cd$_3$As$_2$ crystal. Thermoelectric materials can be used to convert heat to electric power
through the Seebeck effect. We study magneto-thermoelectric figure of merit
(ZT) in three-dimensional Dirac semimetal Cd$_3$As$_2$ crystal. It is found
that enhancement of power factor and reduction of thermal conductivity can be
realized at the same time through magnetic field although magnetoresistivity is
greatly increased. ZT can be highly enhanced from 0.17 to 1.1 by more than six
times around 350 K under a perpendicular magnetic field of 7 Tesla. The huge
enhancement of ZT by magnetic field arises from the linear Dirac band with
large Fermi velocity and the large electric thermal conductivity in
Cd$_3$As$_2$. Our work paves a new way to greatly enhance the thermoelectric
performance in the quantum topological materials.

###Evolution of ferromagnetism in two-dimensional electron gas of LaTiO3/SrTiO3|Fangdi Wen,Yanwei Cao,Xiaoran Liu,Banabir Pal,Srimanta Middey,Mikhail Kareev,Jak Chakhalian###

Evolution of ferromagnetism in two-dimensional electron gas of LaTiO3/SrTiO3. Understanding, creating, and manipulating spin polarization of
two-dimensional electron gases at complex oxide interfaces presents an
experimental challenge. For example, despite almost a decade long research
effort, the microscopic origin of ferromagnetism in LaAlO3/SrTiO3
heterojunction is still an open question. Here, by using a prototypical
two-dimensional electron gas (2DEG) which emerges at the interface between band
insulator SrTiO3 and antiferromagnetic Mott insulator LaTiO3 , the experiment
reveals the evidence for magnetic phase separation in hole-doped Ti d1 t2g
system resulting in spin-polarized 2DEG. The details of electronic and magnetic
properties of the 2DEG were investigated by temperature-dependent d.c.
transport, angle-dependent X-ray photoemission spectroscopy, and
temperature-dependent magnetoresistance. The observation of clear hysteresis in
magnetotransport at low magnetic fields implies spin-polarization from magnetic
islands in the hole rich LaTiO3 near the interface. These findings emphasize
the role of magnetic instabilities in doped Mott insulators thus providing
another path for designing all-oxide structures relevant to spintronics
applications.

###Two-Stage Proximity-Induced Gap-Opening in Topological Insulator - Insulating Ferromagnet (Bi$_x$Sb$_{1-x}$)$_2$Te$_3$ - EuS Bilayers|Qi I. Yang,Aharon Kapitulnik###

Two-Stage Proximity-Induced Gap-Opening in Topological Insulator - Insulating Ferromagnet (Bi$_x$Sb$_{1-x}$)$_2$Te$_3$ - EuS Bilayers. To further investigate the interplay between ferromagnetism and topological
insulators, thin films of the low-carrier topological insulator
(Bi$_x$Sb$_{1-x}$)$_2$Te$_3$ were deposited on the insulating ferromagnet EuS
(100) in situ. AC susceptibility indicates magnetic anomalies between
$T\approx30~\mathrm{K}$ and $T\approx60~\mathrm{K}$, well above the Curie
temperature $T_C \approx 15~\mathrm{K}$ of EuS. When the Fermi level is close
to the Dirac point and the surface state dominates the electric conduction,
sharp increases in resistance with decreasing temperatures were observed
concurrently with the magnetic anomalies. Positive-negative magnetoresistance
crossovers were observed at the Curie temperature, which seem only to appear
when the sheet resistance exceeds the Mott-Ioffe-Regel limit $h/e^2$. A
two-stage gap-opening process due to magnetic proximity is proposed.

###Antidamping torque-induced switching in biaxial antiferromagnetic insulators|X. Z. Chen,R. Zarzuela,J. Zhang,C. Song,X. F. Zhou,G. Y. Shi,F. Li,H. A. Zhou,W. J. Jiang,F. Pan,Y. Tserkovnyak###

Antidamping torque-induced switching in biaxial antiferromagnetic insulators. We investigate the current-induced switching of the Neel order in NiO(001)/Pt
heterostructures,which is manifested electrically via the spin Hall
magnetoresistance. Significant reversible changes in the longitudinal and
transverse resistances are found at room temperature for a current threshold
lying in the range of 10^7 A/cm^2. The order-parameter switching is ascribed to
the antiferromagnetic dynamics triggered by the (current-induced) antidamping
torque, which orients the Neel order towards the direction of the writing
current. This is in stark contrast to the case of antiferromagnets such as
Mn2Au and CuMnAs, where field-like torques induced by the Edelstein effect
drive the Neel switching, therefore resulting in an orthogonal alignment
between the Neel order and the writing current. Our findings can be readily
generalized to other biaxial antiferromagnets, providing broad opportunities
for all-electrical writing and readout in antiferromagnetic spintronics.

###Pressure induced superconductivity bordering a charge-density-wave state in NbTe4 with strong spinorbit coupling|Xiaojun Yang,Yonghui Zhou,Mengmeng Wang,Hua Bai,Xuliang Chen,Chao An,Ying Zhou,Qian Chen,Yupeng Li,Zhen Wang,Jian Chen,Chao Cao,Yuke Li,Yi Zhou,Zhaorong Yang,Zhu-An Xu###

Pressure induced superconductivity bordering a charge-density-wave state in NbTe4 with strong spinorbit coupling. Transition-metal chalcogenides host various phases of matter, such as
charge-density wave (CDW), superconductors, and topological insulators or
semimetals. Superconductivity and its competition with CDW in low-dimensional
compounds have attracted much interest and stimulated considerable research.
Here we report pressure induced superconductivity in a strong spin-orbit (SO)
coupled quasi-one-dimensional (1D) transition-metal chalcogenide NbTe$_4$,
which is a CDW material under ambient pressure. With increasing pressure, the
CDW transition temperature is gradually suppressed, and superconducting
transition, which is fingerprinted by a steep resistivity drop, emerges at
pressures above 12.4 GPa. Under pressure $p$ = 69 GPa, zero resistance is
detected with a transition temperature $T_c$ = 2.2 K and an upper critical
field $H_{c2}$= 2 T. We also find large magnetoresistance (MR) up to 102\% at
low temperatures, which is a distinct feature differentiating NbTe$_4$ from
other conventional CDW materials.

###Origin and evolution of surface spin current in topological insulators|André Dankert,Priyamvada Bhaskar,Dmitrii Khokhriakov,Isabel H. Rodrigues,Bogdan Karpiak,M. Venkata Kamalakar,Sophie Charpentier,Ion Garate,Saroj P. Dash###

Origin and evolution of surface spin current in topological insulators. The Dirac surface states of topological insulators offer a unique possibility
for creating spin polarized charge currents due to the spin-momentum locking.
Here we demonstrate that the control over the bulk and surface contribution is
crucial to maximize the charge-to-spin conversion efficiency. We observe an
enhancement of the spin signal due to surface-dominated spin polarization while
freezing out the bulk conductivity in semiconducting Bi1.5Sb0.5Te1.7Se1.3 below
100K. Detailed measurements up to room temperature exhibit a strong reduction
of the magnetoresistance signal between 2 and 100K, which we attribute to the
thermal excitation of bulk carriers and to the electron-phonon coupling in the
surface states. The presence and dominance of this effect up to room
temperature is promising for spintronic science and technology.

###Origin of planar Hall effect in type-II Weyl semimetal MoTe2|D. D. Liang,Y. J. Wang,W. L. Zhen,J. Yang,S. R. Weng,X. Yan,Y. Y. Han,W. Tong,L. Pi,W. K. Zhu,C. J. Zhang###

Origin of planar Hall effect in type-II Weyl semimetal MoTe2. Besides the negative longitudinal magnetoresistance (MR), planar Hall effect
(PHE) is a newly emerging experimental tool to test the chiral anomaly or
nontrivial Berry curvature in Weyl semimetals (WSMs). However, the origins of
PHE in various systems are not fully distinguished and understood. Here we
perform a systematic study on the PHE and anisotropic MR (AMR) of Td-MoTe2, a
type-II WSM. Although the PHE and AMR curves can be well fitted by the
theoretical formulas, we demonstrate that the anisotropic resistivity arises
from the orbital MR (OMR), instead of the negative MR as expected in the chiral
anomaly effect. In contrast, the absence of negative MR indicates that the
large OMR dominates over the chiral anomaly effect. This explains why it is
difficult to measure negative MR in type-II WSMs. We argue that the measured
PHE can be related with the chiral anomaly only when the negative MR is
simultaneously observed.

###Quantitative evaluation of Dirac physics in PbTe|Kazuto Akiba,Atsushi Miyake,Hideaki Sakai,Keisuke Katayama,Hiroshi Murakawa,Noriaki Hanasaki,Sadao Takaoka,Yoshiki Nakanishi,Masahito Yoshizawa,Masashi Tokunaga###

Quantitative evaluation of Dirac physics in PbTe. The magnetic field dependence of electronic transport, magnetic, and elastic
properties in single crystals of PbTe were investigated in high magnetic fields
up to 55 T. The magnetoresistance, magnetization, ultrasonic attenuation, and
sound velocity showed clear quantum oscillations with pronounced
Zeeman-splitting, which causes a large second harmonic in the frequency
spectra. The ratio of the Zeeman to the cyclotron energy, which is regarded as
an index of `Diracness' [H. Hayasaka and Y. Fuseya, J. Phys.: Condens. Matter
\textbf{28,} 31LT01 (2016).], was determined to be 0.52 and 0.57 in samples
with different carrier densities. We also pointed out that the effect of
Zeeman-splitting seriously affects the Landau-level fan diagram analysis, which
is widely used to extract the nontrivial Berry's phase from the quantum
oscillations.

###Chemical stability and superconductivity in Ag-sheathed CaKFe4As4 superconducting tapes|Zhe Cheng,Chiheng Dong,He Huang,Shifa Liu,Yanchang Zhu,Dongliang Wang,Vitalii Vlasko-Vlasov,Ulrich Welp,Wai-Kwong Kwok,Yanwei Ma###

Chemical stability and superconductivity in Ag-sheathed CaKFe4As4 superconducting tapes. Ag-sheathed CaKFe4As4 superconducting tapes have been fabricated via the
ex-situ powder-in-tube method. Thermal and X-ray diffraction analyses suggest
that the CaKFe4As4 phase is unstable at high temperatures. It decomposes into
the CaAgAs phase which reacts strongly with the silver sheath. We therefore
sintered the tape at 500C and obtain a transport critical current density
Jc(4.2 K, 0 T)~ 2.7x10^4 A/cm2. The pinning potential derived from
magnetoresistance measurements is one order of magnitude lower than that of the
(Ba/Sr)1-xKxFe2As2 tapes. Combining with the scanning electron microscopy and
magneto-optical imaging results, we suggest that bad connectivity between
superconducting grains caused by the low sintering temperature is the main
factor responsible for the low Jc. However, this system is still a promising
candidate for superconducting wires and tapes if we further optimize the
post-annealing process to achieve better grain connectivity.

###Origin of the unconventional magnetoresistance in Sr2FeMoO6|Sugata Ray,Srimanta Middey,Somnath Jana,A. Banerjee,P. Sanyal,Rajeev Rawat,Luca Gregoratti,D. D. Sarma###

Origin of the unconventional magnetoresistance in Sr2FeMoO6. The unusual magnetoresistance (MR) behavior in Sr2FeMoO6, recently termed as
spin-valve type MR (SVMR), presents several anomalies that are little
understood so far. The difficulty in probing the origin of this phenomenon,
arising from the magnetic property of only a small volume fraction of the
ferromagnetic bulk, is circumvented in the present study by the use of ac
susceptibility measurements that are sensitive to the slope rather than the
magnitude of the magnetization. The present study unravels a spin-glass (SG)
like surface layer around each soft ferromagnetic (FM) grain of Sr2FeMoO6. It
is also observed that there is a very strong exchange coupling between the two,
generating `exchange bias' effect, which consequently creates the `valve',
responsible for the unusual MR effects.

###Phase diagram of a strongly disordered s-wave superconductor, NbN, close to the metal-insulator transition|Madhavi Chand,Garima Saraswat,Anand Kamlapure,Mintu Mondal,Sanjeev Kumar,John Jesudasan,Vivas Bagwe,Lara Benfatto,Vikram Tripathi,Pratap Raychaudhuri###

Phase diagram of a strongly disordered s-wave superconductor, NbN, close to the metal-insulator transition. We present a phase diagram as a function of disorder in three-dimensional NbN
thin films, as the system enters the critical disorder for the destruction of
the superconducting state. The superconducting state is investigated using a
combination of magnetotransport and tunneling spectroscopy measurements. Our
studies reveal 3 different disorder regimes. At low disorder the (k_{F}l~10-4),
the system follows the mean field Bardeen-Cooper-Schrieffer behavior where the
superconducting energy gap vanishes at the temperature where electrical
resistance appears. For stronger disorder (k_{F}l<4) a "pseudogap" state
emerges where a gap in the electronic spectrum persists up to temperatures much
higher than Tc, suggesting that Cooper pairs continue to exist in the system
even after the zero resistance state is destroyed. Finally, very strongly
disordered samples (k_{F}l<1) exhibit a pronounced magnetoresistance peak at
low temperatures, suggesting that localized Cooper pairs continue to survive in
the system even after the global superconducting ground state is completely
destroyed.

###Transport and spectroscopic properties of superconductor - ferromagnet - superconductor junctions of $La_{1.9}Sr_{0.1}CuO_4$ - $La_{0.67}Ca_{0.33}MnO_3$ - $La_{1.9}Sr_{0.1}CuO_4$|Gad Koren,Tal Kirzhner###

Transport and spectroscopic properties of superconductor - ferromagnet - superconductor junctions of $La_{1.9}Sr_{0.1}CuO_4$ - $La_{0.67}Ca_{0.33}MnO_3$ - $La_{1.9}Sr_{0.1}CuO_4$. Transport and Conductance spectra measurements of ramp-type junctions made of
cuprate superconducting $La_{1.9}Sr_{0.1}CuO_4$ electrodes and a manganite
ferromagnetic $La_{0.67}Ca_{0.33}MnO_3$ barrier are reported. At low
temperatures below $T_c$, the conductance spectra show Andreev-like broad peaks
superposed on a tunneling-like background, and sometimes also sub-gap Andreev
resonances. The energy gap values $\Delta$ found from fits of the data ranged
mostly between 7-10 mV. As usual, the gap features were suppressed under
magnetic fields but revealed the tunneling-like conductance background. After
field cycling to 5 or 6 T and back to 0 T, the conductance spectra were always
higher than under zero field cooling, reflecting the negative magnetoresistance
of the manganite barrier. A signature of superparamagnetism was found in the
conductance spectra of junctions with a 12 nm thick LCMO barrier. Observed
critical currents with barrier thickness of 12 nm or more, were shown to be an
artifact due to incomplete milling of one of the superconducting electrodes.

###Magnetic and magnetoresistive properties of cubic Laves phase HoAl$_2$ single crystal|M. Patra,S. Majumdar,S. Giri,Y. Xiao,T. Chatterji###

Magnetic and magnetoresistive properties of cubic Laves phase HoAl$_2$ single crystal. We report the magnetization ($M$) and magnetoresistance (MR) results of
HoAl$_2$ single crystals oriented along $<100>$ and $<110>$ directions.
Although HoAl$_2$ has cubic Laves phase structure, a large anisotropy is
observed in $M$ and MR results below Curie temperature ($T_C$) at 31.5 K. A
satisfactory correlation between magnetic entropy change ($\Delta S_M$) and MR
could be established along $<110>$ direction and in $<100>$ direction except
for the temperature ($T$) region, around which spin reorientation takes place.
Large inverse magnetocaloric effect is observed at low-$T$ which is associated
with the spin reorientation process in $<100>$ direction. A theoretical model
based on Landau theory of phase transition can describe $T$-variation of
-$\Delta S_M$ for $T > T_C$.

###Magnetotransport properties of iron microwires fabricated by focused electron beam induced autocatalytic growth|F. Porrati,R. Sachser,M. -M. Walz,F. Vollnhals,H. -P. Steinrück,H. Marbach,M. Huth###

Magnetotransport properties of iron microwires fabricated by focused electron beam induced autocatalytic growth. We have prepared iron microwires in a combination of focused electron beam
induced deposition (FEBID) and autocatalytic growth from the iron
pentacarbonyl, Fe(CO)5, precursor gas under UHV conditions. The electrical
transport properties of the microwires were investigated and it was found that
the temperature dependence of the longitudinal resistivity (rhoxx) shows a
typical metallic behaviour with a room temperature value of about 88
micro{\Omega} cm. In order to investigate the magnetotransport properties we
have measured the isothermal Hall-resistivities in the range between 4.2 K and
260 K. From these measurements positive values for the ordinary and the
anomalous Hall coefficients were derived. The relation between anomalous Hall
resistivity (rhoAN) and longitudinal resistivity is quadratic, rhoAN rho^2 xx,
revealing an intrinsic origin of the anomalous Hall effect. Finally, at low
temperature in the transversal geometry a negative magnetoresistance of about
0.2 % was measured.

###Spin-wave excitations in the ferromagnetic-metallic and in the charge, orbital and spin ordered states in Nd$_{1-x}$Sr$_{x}$MnO$_{3}$ with x$\approx$0.5|H. Ulbrich,F. Krüger,A. A. Nugroho,D. Lamago,Y. Sidis,M. Braden###

Spin-wave excitations in the ferromagnetic-metallic and in the charge, orbital and spin ordered states in Nd$_{1-x}$Sr$_{x}$MnO$_{3}$ with x$\approx$0.5. Inelastic neutron scattering experiments have been performed on single
crystals of Nd$_{1-x}$Sr$_{x}$MnO$_{3}$ with x$\approx$0.5. Colossal
magnetoresistance (CMR) in the manganites arises from the interplay between a
ferromagnetic metallic and antiferromagnetic charge and orbital ordered
insulating state. Therefore, it appears important to compare these phases
concerning their underlying magnetic interaction parameters. Our investigations
of the spin-wave disperion in the AFM ordered state of
Nd$_{0.5}$Sr$_{0.5}$MnO$_{3}$ exhibits a strongly anisotropic stiffness. The
sign of the anisotropy is characteristic for the site-centered model for charge
and orbital ordering in half-doped manganites. Within this model, linear
spin-wave theory yields a perfect description of the experimental dispersion.
Furthermore, magnetic excitations in the ferromagnetic metallic state of
Nd$_{1-x}$Sr$_{x}$MnO$_{3}$ with x=0.49 and x=0.50 exhibit nearly the same
magnon dispersion which can be described with a Heisenberg model including
nearest-neighbor interactions.

###Molecular Beam Epitaxial Growth of Bi2Te3 and Sb2Te3 Topological Insulators on GaAs (111) Substrates: A Potential Route to Fabricate Topological Insulator p-n Junction|Zhaoquan Zeng,Timothy A. Morgan,Dongsheng Fan,Chen Li,Yusuke Hirono,Xian Hu,Yanfei Zhao,Joon Sue Lee,Zhiming M. Wang,Jian Wang,Shuiqing Yu,Michael E. Hawkridge,Mourad Benamara,Gregory J. Salamo###

Molecular Beam Epitaxial Growth of Bi2Te3 and Sb2Te3 Topological Insulators on GaAs (111) Substrates: A Potential Route to Fabricate Topological Insulator p-n Junction. High quality Bi2Te3 and Sb2Te3 topological insulators films were epitaxially
grown on GaAs (111) substrate using solid source molecular beam epitaxy. Their
growth and behavior on both vicinal and non-vicinal GaAs (111) substrates were
investigated by reflection high-energy electron diffraction, atomic force
microscopy, x-ray diffraction, and high resolution transmission electron
microscopy. It is found that non-vicinal GaAs (111) substrate is better than a
vicinal substrate to provide high quality Bi2Te3 and Sb2Te3 films. Hall and
magnetoresistance measurements indicate that p type Sb2Te3 and n type Bi2Te3
topological insulator films can be directly grown on a GaAs (111) substrate,
which may pave a way to fabricate topological insulator p-n junction on the
same substrate, compatible with the fabrication process of present
semiconductor optoelectronic devices.

###Quantum Hall Effect in Hydrogenated Graphene|J. Guillemette,S. S. Sabri,B. Wu,K. Bennaceur,P. E. Gaskell,M. Savard,P. L. Lévesque,F. Mahvash,A. Guermoune,M. Siaj,R. Martel,T. Szkopek,G. Gervais###

Quantum Hall Effect in Hydrogenated Graphene. The quantum Hall effect is observed in a two-dimensional electron gas formed
in millimeter-scale hydrogenated graphene, with a mobility less than 10
$\mathrm{cm^{2}/V\cdot s}$ and corresponding Ioffe-Regel disorder parameter
$(k_{F}\lambda)^{-1}\gg1$. In zero magnetic field and low temperatures, the
hydrogenated graphene is insulating with a two-point resistance of order of
$250 h/e^2$. Application of a strong magnetic field generates a negative
colossal magnetoresistance, with the two-point resistance saturating within
0.5% of $h/2e^{2}$ at 45T. Our observations are consistent with the opening of
an impurity-induced gap in the density of states of graphene. The interplay
between electron localization by defect scattering and magnetic confinement in
two-dimensional atomic crystals is discussed.

###Hall effect measurements on epitaxial SmNiO3 thin films and implications for antiferromagnetism|Sieu D. Ha,R. Jaramillo,D. M. Silevitch,Frank Schoofs,Kian Kerman,John D. Baniecki,Shriram Ramanathan###

Hall effect measurements on epitaxial SmNiO3 thin films and implications for antiferromagnetism. The rare-earth nickelates (RNiO3) exhibit interesting phenomena such as
unusual antiferromagnetic order at wavevector q = (1/2, 0, 1/2) and a tunable
insulator-metal transition that are subjects of active research. Here we
present temperature-dependent transport measurements of the resistivity,
magnetoresistance, Seebeck coefficient, and Hall coefficient (RH) of epitaxial
SmNiO3 thin films with varying oxygen stoichiometry. We find that from room
temperature through the high temperature insulator-metal transition, the Hall
coefficient is hole-like and the Seebeck coefficient is electron-like. At low
temperature the N\'eel transition induces a crossover in the sign of RH to
electron-like, similar to the effects of spin density wave formation in
metallic systems but here arising in an insulating phase ~200 K below the
insulator-metal transition. We propose that antiferromagnetism can be
stabilized by bandstructure even in insulating phases of correlated oxides,
such as RNiO3, that fall between the limits of strong and weak electron
correlation.

###Spin-Hall Magnetoresistance in Platinum on Yttrium Iron Garnet: Dependence on platinum thickness and in-plane/out-of-plane magnetization|N. Vlietstra,J. Shan,V. Castel,J. Ben Youssef,B. J. van Wees###

Spin-Hall Magnetoresistance in Platinum on Yttrium Iron Garnet: Dependence on platinum thickness and in-plane/out-of-plane magnetization. The occurrence of Spin-Hall Magnetoresistance (SMR) in platinum (Pt) on top
of yttrium iron garnet (YIG) has been investigated, for both in-plane and
out-of-plane applied magnetic fields and for different Pt thicknesses [3, 4, 8
and 35nm]. Our experiments show that the SMR signal directly depends on the
in-plane and out-of-plane magnetization directions of the YIG. This confirms
the theoretical description, where the SMR occurs due to the interplay of
spin-orbit interaction in the Pt and spin-mixing at the YIG/Pt interface.
Additionally, the sensitivity of the SMR and spin pumping signals on the YIG/Pt
interface conditions is shown by comparing two different deposition techniques
(e-beam evaporation and dc sputtering).

###Self-induced inverse spin Hall effect in permalloy at room temperature|Ayaka Tsukahara,Yuichiro Ando,Yuta Kitamura,Hiroyuki Emito,Eiji Shikoh,Michael P. Delmo,Teruya Shinjo,Masashi Shiraishi###

Self-induced inverse spin Hall effect in permalloy at room temperature. Inverse spin Hall effect (ISHE) allows the conversion of pure spin current
into charge current in nonmagnetic materials (NM) due to spin-orbit interaction
(SOI). In ferromagnetic materials (FM), SOI is known to contribute to anomalous
Hall effect (AHE), anisotropic magnetoresistance (AMR), and other
spin-dependent transport phenomena. However, SOI in FM has been ignored in ISHE
studies in spintronic devices, and the possibility of "self-induced ISHE" in FM
has never been explored until now. In this paper, we demonstrate the
experimental verification of ISHE in FM. We found that the spin-pumping-induced
spin current in permalloy (Py) film generates a transverse electromotive force
(EMF) in the film itself, which results from the coupling of spin current and
SOI in Py. The control experiments ruled out spin rectification effect and
anomalous Nernst effect as the origin of the EMF.

###Giant Magnetoresistance Effect in the Metal-Insulator Transition of Pyrochlore Oxide Nd2Ir2O7|Kazuyuki Matsuhira,Masashi Tokunaga,Makoto Wakeshima,Yukio Hinatsu,Seishi Takagi###

Giant Magnetoresistance Effect in the Metal-Insulator Transition of Pyrochlore Oxide Nd2Ir2O7. We investigated the magnetoresistance (MR) effect of the pyrochlore oxide
Nd2Ir2O7, which shows a metal-insulator transition at T_MI =33 K. A small
positive MR effect was observed in the metallic state above T_MI, while a large
negative MR effect was observed in the insulating state below T_MI . MR effects
exceeding 3000% were found at 1 K at a field of 9 T. As a result, we confirmed
the crossover from the insulating state to a state with a small or partial band
gap in a field up to 56 T. Furthermore, from the MR effect in Eu2Ir2O7 (T_MI =
120 K) and Gd$_2$Ir$_2$O$_7$ (T_MI = 127 K), we revealed that the large
negative MR effect of the pyrochlore iridate Ln2Ir2O7 depends on the magnetism
of the lanthanide Ln^{3+} ion. The d-f interaction plays a significant role in
the large negative MR effect in the insulating state.

###Low field anisotropic colossal magnetoresistance in $Sm_{0.53} Sr_{0.47} Mn O_3$ thin films|Manoj K. Srivastava,M. P. Singh,Amarjeet Kaur,F. S. Razavi,H. K. Singh###

Low field anisotropic colossal magnetoresistance in $Sm_{0.53} Sr_{0.47} Mn O_3$ thin films. SSMO5347 thin films (thicknesses ~200 nm) were deposited by on-axis dc
magnetron sputtering on the single crystal LSAT (001) substrates. These films
are oriented along the out of plane c-direction. The ferromagnetic and
insulator-metal transition occurs at 96 K and 91 K, respectively. The
magnetization easy axis is observed to lie in the plane of the film while the
magnetic hard axis is found to be along the normal to this. The
magnetotransport of the SSMO films, which was measured as a function of angle
(theta) between the magnetic field (H) and plane of the film, shows colossal
anisotropy. Magnetoresistance (MR) decreases drastically as theta increases
from 0 degree (H//easy axis) to 90 degree (H//hard axis). The out-of-plane
anisotropic MR (AMR) is as high as 88 % at H=3.6 kOe and 78 K. The colossal
anisotropy has been explained in terms of the magnetic anisotropies at play and
the magnetic domain motion in applied magnetic field.

###Data Storage: Review of Heusler Compounds|Zhaoqiang Bai,Lei Shen,Guchang Han,Yuan ping Feng###

Data Storage: Review of Heusler Compounds. In the recent decade, the family of Heusler compounds has attracted
tremendous scientific and technological interest in the field of spintronics.
This is essentially due to their exceptional magnetic properties, which qualify
them as promising functional materials in various data-storage devices, such as
giant-magnetoresistance spin valves, magnetic tunnel junctions, and
spin-transfer torque devices. In this article, we provide a comprehensive
review on the applications of the Heusler family in magnetic data storage. In
addition to their important roles in the performance improvement of these
devices, we also try to point out the challenges as well as possible solutions,
of the current Heusler-based devices. We hope that this review would spark
further investigation efforts into efficient incorporation of this eminent
family of materials into data storage applications by fully arousing their
intrinsic potential.

###All-Heusler giant-magnetoresistance junctions with matched energy bands and Fermi surfaces|Zhaoqiang Bai,Yongqing Cai,Lei Shen,Guchang Han,Yuanping Feng###

All-Heusler giant-magnetoresistance junctions with matched energy bands and Fermi surfaces. We present an all-Heusler architecture which could be used as a rational
design scheme for achieving high spin-filtering efficiency in the
current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices. A
Co2MnSi/Ni2NiSi/Co2MnSi trilayer stack is chosen as the prototype of such an
architecture, of which the electronic structure and magnetotransport properties
are systematically investigated by first principles approaches. Almost
perfectly matched energy bands and Fermi surfaces between the all-Heusler
electrode-spacer pair are found, indicating large interfacial spin-asymmetry,
high spin-injection efficiency, and consequently high GMR ratio. Transport
calculations further confirms the superiority of the all-Heusler architecture
over the conventional Heusler/transition-metal(TM) structure by comparing their
transmission coefficients and interfacial resistances of parallel conduction
electrons, as well as the macroscopic current-voltage (I-V) characteristics. We
suggest future theoretical and experimental efforts in developing novel
all-Heusler GMR junctions for the read heads of the next generation
high-density hard disk drives (HDDs).

###Super-magnetoresistance effect in triplet spin valves|F. Romeo,R. Citro###

Super-magnetoresistance effect in triplet spin valves. We study a triplet spin valve obtained by intercalating a triplet
superconductor spacer between two ferromagnetic regions with non-collinear
magnetizations. We demonstrate that the magnetoresitance of the triplet spin
valve depends on the relative orientations of the d-vector, characterizing the
superconducting state, and the magnetization directions of the ferromagnetic
layers. For devices characterized by a long superconductor, the Cooper pairs
spintronics regime is reached allowing to observe the properties of a polarized
current sustained by Cooper pairs only. In this regime a
super-magnetoresistance effect emerges, and the chiral symmetry of the order
parameter of the superconducting spacer is easily recognized. Our findings open
new perspectives in designing devices based on the cooperative nature of
ferromagnetic and triplet correlations in a spintronic framework.

###Longitudinal magnetoresistance in Co-doped BaFe2As2 and LiFeAs single crystals: Interplay between spin fluctuations and charge transport in iron-pnictides|F. Rullier-Albenque,D. Colson,A. Forget###

Longitudinal magnetoresistance in Co-doped BaFe2As2 and LiFeAs single crystals: Interplay between spin fluctuations and charge transport in iron-pnictides. The longitudinal in-plane magnetoresistance (LMR) has been measured in
different Ba(Fe_(1-x)Co_x)2As2 single crystals and in LiFeAs. For all these
compounds, we find a negative LMR in the paramagnetic phase whose magnitude
increases as H^2. We show that this negative LMR can be readily explained in
terms of suppression of the spin fluctuations by the magnetic field. In the
Co-doped samples, the absolute value of the LMR coefficient is found to
decrease with doping content in the paramagnetic phase. The analysis of its T
dependence in an itinerant nearly antiferromagnetic Fermi liquid model
evidences that the LMR displays a qualitative change of T variation with
increasing Co content. The latter occurs at optimal doping for which the
antiferromagnetic ground state is suppressed. The same type of analysis for the
negative LMR measured in LiFeAs suggests that this compound is on the verge of
magnetism.

###Fluctuation conductivity of disordered superconductors in magnetic fields|Brian Tarasinski,Georg Schwiete###

Fluctuation conductivity of disordered superconductors in magnetic fields. We calculate fluctuation corrections to the longitudinal conductivity of
disordered superconductors subject to an external magnetic field. We derive
analytic expressions that are valid in the entire metallic part of the
temperature-magnetic field phase diagram as long as the effect of the magnetic
field on the spin degrees of freedom of the electrons may be neglected. Our
calculations are based on a kinetic equation approach. For the special case of
superconducting films and wires in parallel magnetic fields we perform a
detailed comparison with results that were previously obtained with
diagrammatic perturbation theory in the imaginary time formalism. As an
application, we study the fluctuation conductivity of films in tilted magnetic
fields with a special focus on the low-temperature regime. We present a
detailed discussion of the phenomenon of the non-monotonous magnetoresistance
and find that it displays a pronounced dependence on the tilting angle.

###Thermal Stability and Electrical Control of Magnetization of Heusler/Oxide Interface and Non-collinear Spin Transport of Its Junction|Zhaoqiang Bai,Lei Shen,Yongqing Cai,Qingyun Wu,Minggang Zeng,Guchang Han,Yuan Ping Feng###

Thermal Stability and Electrical Control of Magnetization of Heusler/Oxide Interface and Non-collinear Spin Transport of Its Junction. Towards next-generation spintronics devices, such as computer memories and
logic chips, it is necessary to satisfy high thermal stability, low-power
consumption and high spin-polarization simultaneously. Here, from
first-principles, we investigate thermal stability (both structure and
magnetization) and the electric field control of magnetic anisotropy on Co2FeAl
(CFA)/MgO. A phase diagram of structural thermal stability of the CFA/MgO
interface is illustrated. An interfacial perpendicular-anisotropy, coming from
the Fe-O orbital hybridization, provides high magnetic thermal stability and a
low stray field. We find an electric-field-induced giant modification of such
perpendicular-anisotropy via a great magnetoelectric effect (the anisotropy
energy coefficient beta~10-7 erg/V cm). Our spin electronic-structure and
non-collinear transport calculations indicate high spin-polarized interfacial
states and good magnetoresistance properties of CFA/MgO/CFA perpendicular
magnetic tunnel junctions.

###Anomalous transport in half-metallic ferromagnetic CrO2|M. S. Anwar,J. Aarts###

Anomalous transport in half-metallic ferromagnetic CrO2. We have investigated transport properties of CrO2 thin films deposited on
TiO2 and sapphire substrates. The films are good metals down to low
temperatures. The residual resistivity is of the order of 6 micro-ohhmcm for
films deposited on TiO2 and two times higher for films on sapphire substrates.
The sign of the magnetoresistance (MR) changes from negative to positive at a
temperature around 100 K. This fact, as well as a rapid change in the ordinary
and anomalous Hall coefficients suggest a change in the electronic state. At
lower temperatures the MR is a linear function of the applied field. This
linear dependence might be explained as intergrain tunneling MR. This
interpretation is also suggested by the angular MR. The planar Hall effect
measurements reveal that the CrO2 thin films are not in a single magnetic
domain state even for films deposited on an isostructural TiO2 substrate.

###Two phase transitions induced by a magnetic field in graphite|Benoît Fauqué,David LeBoeuf,Baptiste Vignolle,Marc Nardone,Cyril Proust,Kamran Behnia###

Two phase transitions induced by a magnetic field in graphite. Different instabilities have been speculated for a three-dimensional electron
gas confined to its lowest Landau level. The phase transition induced in
graphite by a strong magnetic field, and believed to be a Charge Density Wave
(CDW), is the only experimentally established case of such instabilities.
Studying the magnetoresistance in graphite for the first time up to 80 T, we
find that the magnetic field induces two successive phase transitions,
consisting of two distinct ordered states each restricted to a finite field
window. In both states, an energy gap opens up in the out-of-plane conductivity
and coexists with an unexpected in-plane metallicity for a fully gap bulk
system. Such peculiar metallicity may arise as a consequence of edge-state
transport expected to develop in presence of a bulk gap.

###Mott Variable Range Hopping and Weak Antilocalization Effect in Heteroepitaxial Na2IrO3 Thin Films|Marcus Jenderka,José Barzola-Quiquia,Zhipeng Zhang,Heiko Frenzel,Marius Grundmann,Michael Lorenz###

Mott Variable Range Hopping and Weak Antilocalization Effect in Heteroepitaxial Na2IrO3 Thin Films. Iridate thin films are a prerequisite for any application utilizing their
cooperative effects resulting from the interplay of stron spin-orbit coupling
and electronic correlations. Here, heteroepitaxial Na2IrO3 thin films with
excellent (001) out-of-plane crystalline orientation and well defined in-plane
epitaxial relationship are presented on various oxide substrates. Resistivity
is dominated by a three-dimensional variable range hopping mechanism in a large
temperature range between 300 K and 40 K. Optical experiments show the onset of
a small optical gap of about 200 meV and a splitting of the Ir 5d-t2g manifold.
Positive magnetoresistance below 3 T and 25 K shows signatures of a weak
antilocalization effect. This effect can be associated with surface states in a
topological insulator and hence supports proposals for a topological insulator
phase present in Na2IrO3.

###Large room-temperature magnetoresistance in lateral organic spin valves fabricated by in-situ shadow evaporation|M. Grünewald,J. Kleinlein,F. Syrowatka,F. Würthner,L. W. Molenkamp,G. Schmidt###

Large room-temperature magnetoresistance in lateral organic spin valves fabricated by in-situ shadow evaporation. We report the successful fabrication of lateral organic spin valves with a
channel length in the sub $100\,nm$ regime. The fabication process is based on
in-situ shadow evaporation under UHV conditions and therefore yields clean and
oxygen-free interfaces between the ferromagnetic metallic electrodes and the
organic semiconductor. The spin valve devices consist of Nickel and Cobalt-iron
electrodes and the high mobility \emph{n}-type organic semiconductor
$N,N'$-bis(heptafluorobutyl)-$3,4:9,10$-perylene diimide. Our studies comprise
fundamental investigations of the process' and materials' suitability for the
fabrication of lateral spin valve devices as well as magnetotransport
measurements at room temperature. The best devices exhibit a magnetoresistance
of up to $50\,%$, the largest value for room temperature reported so far.

###Crossover of magnetoresistance in the zerogap half-metallic Heusler alloy Fe2CoSi|Y. Du,G. Z. Xu,X. M. Zhang,Z. Y. Liu,S. Y. Yu,E. K. Liu,W. H. Wang,G. H. Wu###

Crossover of magnetoresistance in the zerogap half-metallic Heusler alloy Fe2CoSi. This work reports on the band structure and magneto-transport investigations
of the inverse Heusler compound Fe2CoSi. The first-principles calculations
reveal that Fe2CoSi has a very peculiar band structure with a conducting
property in the majority spin channel and a nearly zero bandgap in the minority
spin channel. The synthesized Fe2CoSi sample shows a high-ordered inverse
Heusler structure with a magnetic moment of 4.88 {\mu}B at 5 K and a high Curie
temperature of 1038 K. With increasing temperature, a crossover from positive
to negative magnetoresistance (MR) is observed. Complemented with the Hall
effect measurements, we suggest the intriguing crossover of MR can be ascribed
to the dominant spin carriers changing from the gapless minority spin channel
to the majority spin channel at Fermi level.

###Intrinsic spin-relaxation induced negative tunnel magnetoresistance in a single-molecule magnet|Haiqing Xie,Qiang Wang,Hai-Bin Xue,HuJun Jiao,J. -Q. Liang###

Intrinsic spin-relaxation induced negative tunnel magnetoresistance in a single-molecule magnet. We investigate theoretically the effects of intrinsic spin-relaxation on the
spin-dependent transport through a single-molecule magnet (SMM), which is
weakly coupled to ferromagnetic leads. The tunnel magnetoresistance (TMR) is
obtained by means of the rate-equation approach including not only the
sequential but also the cotunneling processes. It is shown that the TMR is
strongly suppressed by the fast spin-relaxation in the sequential region and
can vary from a large positive to slight negative value in the cotunneling
region. Moreover, with an external magnetic field along the easy-axis of SMM, a
large negative TMR is found when the relaxation strength increases. Finally, in
the high bias voltage limit the TMR for the negative bias is slightly larger
than its characteristic value of the sequential region, however it can become
negative for the positive bias caused by the fast spin-relaxation.

###Impurity-assisted tunneling magnetoresistance under weak magnetic field|Oihana Txoperena,Yang Song,Lan Qing,Marco Gobbi,Luis E. Hueso,Hanan Dery,Fèlix Casanova###

Impurity-assisted tunneling magnetoresistance under weak magnetic field. Injection of spins into semiconductors is essential for the integration of
the spin functionality into conventional electronics. Insulating layers are
often inserted between ferromagnetic metals and semiconductors for obtaining an
efficient spin injection, and it is therefore crucial to distinguish between
signatures of electrical spin injection and impurity-driven effects in the
tunnel barrier. Here we demonstrate an impurity-assisted tunneling
magnetoresistance effect in nonmagnetic-insulator-nonmagnetic and
ferromagnetic-insulator-nonmagnetic tunnel barriers. In both cases, the effect
reflects on/off switching of the tunneling current through impurity channels by
the external magnetic field. The reported effect, which is universal for any
impurity-assisted tunneling process, finally clarifies the controversy of a
widely used technique that employs the same ferromagnetic electrode to inject
and detect spin accumulation.

###Ferromagnetism and impurity band in a new magnetic semiconductor: InMnP|M. Khalid,E. Weschke,W. Skorupa,M. Helm,S. Zhou###

Ferromagnetism and impurity band in a new magnetic semiconductor: InMnP. We have synthesized ferromagnetic InMnP, a member of III-Mn-V ferromagnetic
semiconductor family, by Mn ion implantation and pulsed laser annealing. Clear
ferromagnetic hysteresis loops and a perpendicular magnetic anisotropy are
observed up to a Curie temperature of 42 K. Large values of negative
magnetoresistance and magnetic circular dichroism as well as anomalous Hall
effect are further evidences of a ferromagnetic order in InMnP. An effort is
made to understand the transport mechanism in InMnP using the theoretical
models. We find that the valence band of InP does not merge with the impurity
band of the heavily doped ferromagnetic InMnP. Our results suggest that
impurity band conduction is a characteristic of Mn-doped III-V semiconductors
which have deep Mn-acceptor levels.

###Impurity induced enhancement of perpendicular magnetic anisotropy in Fe/MgO tunnel junctions|A. Hallal,B. Dieny,M. Chshiev###

Impurity induced enhancement of perpendicular magnetic anisotropy in Fe/MgO tunnel junctions. Using first-principles calculations, we investigated the impact of chromium
(Cr) and vanadium (V) impurities on the magnetic anisotropy and spin
polarization in Fe/MgO magnetic tunnel junctions. It is demonstrated using
layer resolved anisotropy calculation technique, that while the impurity near
the interface has a drastic effect in decreasing the perpendicular magnetic
anisotropy (PMA), its position within the bulk allows maintaining high surface
PMA. Moreover, the effective magnetic anisotropy has a strong tendency to go
from in-plane to out-of-plane character as a function of Cr and V concentration
favoring out-of-plane magnetization direction for ~1.5 nm thick Fe layers at
impurity concentrations above 20 %. At the same time, spin polarization is not
affected and even enhanced in most situations favoring an increase of tunnel
magnetoresistance (TMR) values.

###Ultrahigh mobility and giant magnetoresistance in the Dirac semimetal Cd$_3$As$_2$|Tian Liang,Quinn Gibson,Mazhar N. Ali,Minhao Liu,R. J. Cava,N. P. Ong###

Ultrahigh mobility and giant magnetoresistance in the Dirac semimetal Cd$_3$As$_2$. Dirac semimetals and Weyl semimetals are 3D analogs of graphene in which
crystalline symmetry protects the nodes against gap formation [1-3]. Na$_3$Bi
and Cd$_3$As$_2$ were predicted to be Dirac semimetals [4,5], and recently
confirmed to be so by photoemission [6-8]. Several novel transport properties
in a magnetic field $\bf H$ have been proposed for Dirac semimetals [2,9-11].
Here we report an interesting property in Cd$_3$As$_2$ that was unpredicted,
namely a remarkable protection mechanism that strongly suppresses
back-scattering in zero $\bf H$. In single crystals, the protection results in
a very high mobility that exceeds $>10^7$ cm$^2$/Vs below 4 K. Suppression of
backscattering results in a transport lifetime 10$^4\times$ longer than the
quantum lifetime. The lifting of this protection by $\bf H$ leads to an unusual
giant $\bf H$-linear magnetoresistance that violates Kohler's rule. We discuss
how this may relate to changes to the Fermi surface induced by $\bf H$.

###RKKY interaction between extended magnetic defect lines in graphene|Paul D. Gorman,John M. Duffy,Stephen R. Power,Mauro S. Ferreira###

RKKY interaction between extended magnetic defect lines in graphene. Of fundamental interest in the field of spintronics is the mechanism of
indirect exchange coupling between magnetic impurities embedded in metallic
hosts. A range of physical features, such as magnetotransport and overall
magnetic moment formation, are predicated upon this magnetic coupling, often
referred to as the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction. Recent
theoretical studies on the RKKY in graphene have been motivated by possible
spintronic applications of magnetically doped graphene systems. In this work a
combination of analytic and numerical techniques are used to examine the
effects of defect dimensionality on such an interaction. We show, in a
mathematically transparent manner, that moving from single magnetic impurities
to extended lines of impurities effectively reduces the dimensionality of the
system and increases the range of the interaction. This has important
consequences for the spintronic application of magnetically-doped and we
illustrate this with a simple magnetoresistance device.

###Magnetic-Field Induced Semimetal in Topological Crystalline Insulator Thin Films|Motohiko Ezawa###

Magnetic-Field Induced Semimetal in Topological Crystalline Insulator Thin Films. We investigate electromagnetic properties of a topological crystalline
insulator (TCI) thin film under external electromagnetic fields. The TCI thin
film is a topological insulator indexed by the mirror-Chern number. It is
demonstrated that the gap closes together with the emergence of a pair of
gapless cones carrying opposite chirarities by applying in-plane magnetic
field. A pair of gapless points have opposite vortex numbers. This is a
reminiscence of a pair of Weyl cones in 3D Weyl semimetal. We thus present an a
magnetic-field induced semimetal-semiconductor transition in 2D material. This
is a giant-magnetoresistance, where resistivity is controlled by magnetic
field. Perpendicular electric field is found to shift the gapless points and
also renormalize the Fermi velocity in the direction of the in-plane magnetic
field.

###Magnetic properties of epitaxial Fe$_3$O$_4$ films with various crystal orientations and TMR effect in room temperature|Taro Nagahama,Yuya Matsuda,Kazuya Tate,Shungo Hiratani,Yusuke Watanabe,Takashi Yanase,Toshihiro Shimada###

Magnetic properties of epitaxial Fe$_3$O$_4$ films with various crystal orientations and TMR effect in room temperature. Fe$_3$O$_4$ is a ferrimagnetic spinel ferrite that exhibits electric
conductivity at room temperature (RT). Although the material has been predicted
to be a half metal according to ab-initio calculations, magnetic tunnel
junctions (MTJs) with Fe$_3$O$_4$ electrodes have demonstrated a small tunnel
magnetoresistance effect. Not even the sign of the TMR ratio has been
experimentally established. Here, we report on the magnetic properties of
epitaxial Fe$_3$O$_4$ films with various crystal orientations. The films
exhibited apparent crystal orientation dependence on hysteresis curves. In
particular, Fe$_3$O$_4$(110) films exhibited in-plane uniaxial magnetic
anisotropy. With respect to the squareness of hysteresis, Fe$_3$O$_4$ (111)
demonstrated the largest squareness. Furthermore, we fabricated MTJs with
Fe$_3$O$_4$(110) electrodes, and obtained an TMR effect of -12\% at RT. The
negative TMR ratio corresponded to the negative spin polarization of
Fe$_3$O$_4$ predicted from band calculations.

###Magnetotransport in ferromagnetic Mn5Ge3, Mn5Ge3C0.8, and Mn5Si3C0.8 thin films|Christoph Sürgers,Gerda Fischer,Patrick Winkel,Hilbert v. Löhneysen###

Magnetotransport in ferromagnetic Mn5Ge3, Mn5Ge3C0.8, and Mn5Si3C0.8 thin films. The electrical resistivity, anisotropic magnetoresistance (AMR), and
anomalous Hall effect of ferromagnetic Mn5Ge3, Mn5Ge3C0.8, and Mn5Si3C0.8 thin
films has been investigated. The data show a behavior characteristic for a
ferromagnetic metal, with a linear increase of the anomalous Hall coefficient
with Curie temperature. While for ferromagnetic Mn5Si3C0.8 the normal Hall
coefficient R0 and the AMR ratio are independent of temperature, these
parameters strongly increase with temperature for the germanide films. This
difference is attributed to the different hybridization of electronic states in
the materials due different lattice parameters and different atomic
configurations (Ge vs. Si metalloid). The concomitant sign change of R0 and the
AMR ratio with temperature observed for the germanide films is discussed in a
two-current model indicating an electron-like minority-spin transport at low
temperatures.

###Magnetic Field Effect in One-Dimensional Charge Ordering Systems|Yuichi Otsuka,Hitoshi Seo,Yukitoshi Motome###

Magnetic Field Effect in One-Dimensional Charge Ordering Systems. We study effects of an external magnetic field on charge ordering in the
one-dimensional extended Hubbard model at quarter filling by means of the
quantum Monte Carlo method. We find that the Zeeman coupling enhances the
charge order correlation, which is prominent when the system is located in the
critical regime near the charge ordering transition at zero magnetic field.
This behavior is interpreted in terms of the crossover to the fully
spin-polarized limit where the model is exactly solvable. Furthermore, by
incorporating the interchain Coulomb repulsion, we show that the
charge-ordering transition temperature is raised by the magnetic field. We also
discuss the relevance of our results to magnetoresistance effects observed in
molecular conductors.

###Exchange bias in phase-segregated Nd2/3Ca1/3MnO3 as a function of temperature and cooling magnetic fields|Elena Fertman,Sergiy Dolya,Vladimir Desnenko,Liudmia A. Pozhar,Marcela Kajnakova,Alexander Feher###

Exchange bias in phase-segregated Nd2/3Ca1/3MnO3 as a function of temperature and cooling magnetic fields. Exchange bias (EB) phenomena have been observed in Nd2/3Ca1/3MnO3 colossal
magnetoresistance perovskite below the Curie temperature $T_{C}$ = 70 K and
attributed to an antiferromagnetic (AFM) - ferromagnetic (FM) spontaneous phase
segregated state of this compound. Field cooled magnetic hysteresis loops
exhibit shifts toward negative direction of the magnetic field axis. The values
of exchange field $H_{EB}$ and coercivity $H_{C}$ are found to be strongly
dependent of temperature and strength of the cooling magnetic field $H_{cool}$.
These effects are attributed to evolution of the FM phase content and a size of
FM clusters. A contribution to the total magnetization of the system due to the
FM phase has been evaluated. The exchange bias effect decreases with increasing
temperature up to $T_{C}$ and vanishes above this temperature with
disappearance of FM phase. Relaxation of a non-equilibrium magnetic state of
the compound manifests itself through a training effect also observed while
studying EB in Nd2/3Ca1/3MnO3.

###Engineering Schottky Barrier in Black Phosphorus field effect devices for spintronic applications|M. Venkata Kamalakar,B. N Madhushankar,André Dankert,Saroj P. Dash###

Engineering Schottky Barrier in Black Phosphorus field effect devices for spintronic applications. Black phosphorous (BP) is is recently unveiled as a promising two-dimensional
direct bandgap semiconducting material. Here, we report the ambipolar field
effect transistor behavior of multilayers of BP with ferromagnetic tunnel
contacts. We observe a reduced of Schottky barrier < 50 meV by using
TiO${_2}$/Co contacts, which could be further tuned by gate voltages. Eminently
a good transistor performance is achieved in BP devices, with drain current
modulation on the order of four to six orders of magnitude. The charge carrier
mobility is found to be $\sim$ 155 and 0.18 cm${^2}$ V${^{-1}}$ s${^{-1}}$ for
holes and electrons respectively at room temperature. Furthermore,
magnetoresistance calculations reveal that the resistances of the BP device
with applied gate voltages are in the appropriate range for injection and
detection of spin polarized holes. Our results demonstrate the prospect of
engineering BP nanolayered devices for efficient nanoelectronic and spintronic
applications.

###Anomalous Hall Effect in Ge(1-x-y)Pb(x)Mn(y)Te Composite System|A. Podgórni,L. Kilanski,W. Dobrowolski,M. Górska,V. Domukhovski,B. Brodowska,A. Reszka,B. J. Kowalski,V. E. Slynko,E. I. Slynko###

Anomalous Hall Effect in Ge(1-x-y)Pb(x)Mn(y)Te Composite System. The purpose of this study was to investigate the magnetotransport properties
of the Ge(0.743)Pb(0.183)Mn(0.074)Te mixed crystal. The results of
magnetization measurements indicated that the compound is a spin-glass-like
diluted magnetic semiconductor with critical temperature TSG = 97.5 K.
Nanoclusters in the sample are observed. Both, matrix and clusters are
magnetically active. Resistivity as a function of temperature has a minimum at
30 K. Below the minimum a variable-range hopping is observed, while above the
minimum a metallic-like behavior occurs. The crystal has high hole
concentration, p = 6.6E20 cm-3, temperature-independent. Magnetoresistance
amplitude changes from -0.78 to 1.18% with increase of temperature. In the
magnetotransport measurements we observed the anomalous Hall effect (AHE) with
hysteresis loops. Calculated AHE coefficient, RS = 2.0E6 m3/C, is temperature
independent. The analysis indicates the extrinsic skew scattering mechanism to
be the main physical mechanism responsible for AHE in
Ge(0.743)Pb(0.183)Mn(0.074)Te alloy.

###Enhanced Tunnel Spin Injection into Graphene using Chemical Vapor Deposited Hexagonal Boron Nitride|M. Venkata Kamalakar,André Dankert,Johan Bergsten,Tommy Ive,Saroj P. Dash###

Enhanced Tunnel Spin Injection into Graphene using Chemical Vapor Deposited Hexagonal Boron Nitride. The van der Waals heterostructures of two-dimensional (2D) atomic crystals
constitute a new paradigm in nanoscience. Hybrid devices of graphene with
insulating 2D hexagonal boron nitride (h-BN) have emerged as promising
nanoelectronic architectures through demonstrations of ultrahigh electron
motilities and charge-based tunnel transistors. Here, we expand the functional
horizon of such 2D materials demonstrating the quantum tunneling of
spin-polarized electrons through atomic planes of CVD grown h-BN. We report
excellent tunneling behavior of h-BN layers together with tunnel spin injection
and transport in graphene using ferromagnet/h-BN contacts. Employing h-BN
tunnel contacts, we observe enhancements in both spin signal amplitude and
lifetime by an order of magnitude. We demonstrate spin transport and precession
over micrometer-scale distances with spin lifetime up to 0.46 nanosecond. Our
results and complementary magnetoresistance calculations illustrate that CVD
h-BN tunnel barrier provides a reliable, reproducible and alternative approach
to address the conductivity mismatch problem for spin injection into graphene.

###Tuning the metal-insulator transition in manganite films through surface exchange coupling with magnetic nanodots|T. Z. Ward,Z. Gai,X. Y. Xu,H. W. Guo,L. F. Yin,J. Shen###

Tuning the metal-insulator transition in manganite films through surface exchange coupling with magnetic nanodots. In strongly correlated electronic systems, such as manganites, the global
transport behavior depends sensitively on the spin ordering, whose alteration
often requires a large external magnetic field. Here we show that the spin
ordering in manganites can be easily controlled by exchange field across the
interface between a ferromagnet and a manganite. By depositing isolated
ferromagnetic nanodots on a manganite thin film, we find that it is possible to
overcome dimensionality and strain effects to raise the metal-insulator
transition (MIT) temperature by over 200 K and increase the magnetoresistance
by 5000%. The MIT temperature can also be tuned by controlling the density of
the magnetic nanodots which indicates that the formation process of electronic
phase separation can be controlled by the presence of magnetic nanodots.

###Origin of giant magnetoresistance across the martensitic transformation for Ni44Cu2Mn43In11 alloy: Formation of phase fraction|Mayukh K. Ray,Bibekananda Maji,M. Modak,K. Bagani,S. Banerjee###

Origin of giant magnetoresistance across the martensitic transformation for Ni44Cu2Mn43In11 alloy: Formation of phase fraction. We have studied the phase volume fraction related magnetoresistance (MR)
across the first order martensite transformation (MT) of Ni44Cu2Mn43In11 alloy.
Within the metastability of MT, an isothermal application of magnetic field
converts the martensite into austenite. The field induced austenite phase
fraction (fIA) at any temperature depends on the availability and instability
of martensite phase fraction (fM ) at that temperature. This fIA is found to
contribute most significantly to the observed giant MR while the contribution
from pure martensite and austenite phase fraction is negligible. It is found
that the net MR follows a non linear proportional relation with the fIA and the
ascending and descending branch of fIA follows different power law giving rise
to hysteresis in MR. Here we present a detail explanation of the observed
behaviours of MR based on the existing phase fraction.

###Interface-driven spin-torque ferromagnetic resonance by Rashba coupling at the interface between non-magnetic materials|M. B. Jungfleisch,W. Zhang,J. Sklenar,W. Jiang,J. E. Pearson,J. B. Ketterson,A. Hoffmann###

Interface-driven spin-torque ferromagnetic resonance by Rashba coupling at the interface between non-magnetic materials. The Rashba-Edelstein effect stems from the interaction between the electron's
spin and its momentum induced by spin-orbit interaction at an interface or a
surface. It was shown that the inverse Rashba-Edelstein effect can be used to
convert a spin- into a charge current. Here, we demonstrate that a Bi/Ag Rashba
interface can even drive an adjacent ferromagnet to resonance. We employ a
spin-torque ferromagnetic resonance excitation/detection scheme which was
developed originally for a bulk spin-orbital effect, the spin Hall effect. In
our experiment, the direct Rashba-Edelstein effect generates an oscillating
spin current from an alternating charge current driving the magnetization
precession in a neighboring permalloy (Py, Ni80Fe20) layer. Electrical
detection of the magnetization dynamics is achieved by a rectification
mechanism of the time dependent multilayer resistance arising from the
anisotropic magnetoresistance.

###Anomalous Lattice Dynamics of Mono-, Bi-, and Tri-layer WTe2|Younghee Kim,Young In Jhon,June Park,Jae Hun Kim,Seok Lee,Young Min Jhon###

Anomalous Lattice Dynamics of Mono-, Bi-, and Tri-layer WTe2. Tungsten ditelluride (WTe2) is a layered material that exhibits excellent
magnetoresistance and thermoelectric behaviors, which are deeply related with
its distorted orthorhombic phase that may critically affect the lattice
dynamics. Here, for the first time, we present comprehensive characterization
of the Raman spectroscopic behavior of WTe2 from bulk to monolayer using
experimental and computational methods. We discover that mono and bi-layer WTe2
can be easily identified by Raman spectroscopy since double or single Raman
modes that are observed in higher-layer WTe2 are substantially suppressed in
the monolayer and bilayer WTe2, respectively. In addition, different from
hexagonal metal dichalcogenides, the frequency of in-plane mode of WTe2 remains
almost constant as the layer number decreases, while the other Raman modes
consistently blueshift. First-principles calculation validates the experiments
and reveals that the negligible shift of the mode is attributed to the lattice
vibration along the tungsten chains that make WTe2 structurally
one-dimensional.

###Emergence of non-Fermi liquid behaviors in 5d perovskite SrIrO3 thin films: interplay between correlation, disorder, and spin-orbit coupling|Abhijit Biswas,Ki-Seok Kim,Yoon H. Jeong###

Emergence of non-Fermi liquid behaviors in 5d perovskite SrIrO3 thin films: interplay between correlation, disorder, and spin-orbit coupling. We investigate the effects of compressive strain on the electrical
resistivity of 5d iridium based perovskite SrIrO3 by depositing epitaxial films
of thickness 35 nm on various substrates such as GdScO3 (110), DyScO3 (110),
and SrTiO3 (001). Surprisingly, we find anomalous transport behaviors in the
tempeature dependent resistivity, where the temperature exponent evolves
continuously from 4/5 to 1 and to 3/2 with an increase of compressive strain.
Furthermore, magnetoresistance always remains positive irrespective of
resistivity upturns at low temperatures. These observations imply that the
delicate interplay between correlation and disorder in the presence of strong
spin-orbit coupling is responsible for the emergence of the non-Fermi liquid
behaviors in 5d perovskite SrIrO3 thin films. We offer a theoretical framework
for the interpretation of the experimental results.

###Emergence of an incipient ordering mode in FeSe|Sahana Rößler,Cevriye Koz,Lin Jiao,Ulrich K. Rößler,Frank Steglich,Ulrich Schwarz,Steffen Wirth###

Emergence of an incipient ordering mode in FeSe. The structurally simplest Fe-based superconductor FeSe with a critical
temperature $T_{c}\approx$ 8.5 K displays a breaking of the four-fold
rotational symmetry at a temperature $T_{s}\approx 87$ K. We investigated the
electronic properties of FeSe using scanning tunneling microscopy/spectroscopy
(STM/S), magnetization, and electrical transport measurements. The results
indicated two new energy scales (i) $T^{*} \approx$ 75 K denoted by an onset of
electron-hole asymmetry in STS, enhanced spin fluctuations, and increased
positive magnetoresistance; (ii) $T^{**} \approx$ 22 - 30 K, marked by opening
up of a partial gap of about 8 meV in STS and a recovery of Kohler's rule. Our
results reveal onset of an incipient ordering mode at $T^{*}$ and its
nucleation below $T^{**}$. The ordering mode observed here, both in spin as
well as charge channels, suggests a coupling between the spins with charge,
orbital or pocket degrees of freedom.

###Nonequilibrium low temperature phase in pyrochlore iridate Y$_2$Ir$_2$O$_7$: Possibility of glass-like dynamics|Harish Kumar,A. K. Pramanik###

Nonequilibrium low temperature phase in pyrochlore iridate Y$_2$Ir$_2$O$_7$: Possibility of glass-like dynamics. Geometrical frustration and spin-orbit coupling effect together play vital
role to influence properties in pyrochlore based iridium oxides. Here we have
investigated detailed structural, magnetic, thermodynamic and transport
properties of pyrochlore iridate Y$_2$Ir$_2$O$_7$. Magnetization data show
onset of magnetic irreversibility around temperature $T_{irr}$ $\sim$ 160 K,
however, no sign of long-range type ferromagnetic ordering is observed below
$T_{irr}$. Specific heat data show no visible anomaly across $T_{irr}$, and the
analysis of data indicate sizable density of states across Fermi level.
Temperature dependent x-ray diffraction measurements show no change in
structural symmetry down to low temperature. The material, on the other hand,
shows significant relaxation and aging behavior similar to glassy dynamics. The
electronic charge transport in this highly insulating system is found to follow
power law dependence with temperature. The material shows negative
magnetoresistance which is explained with quantum interference effect.

###Correlation between the spin Hall angle and the structural phases of early 5d transition metals|Jun Liu,Tadakatsu Ohkubo,Seiji Mitani,Kazuhiro Hono,Masamitsu Hayashi###

Correlation between the spin Hall angle and the structural phases of early 5d transition metals. We have studied the relationship between the structure and the spin Hall
angle of the early 5d transition metals in X/CoFeB/MgO (X=Hf, Ta, W, Re)
heterostructures. Spin Hall magnetoresistance (SMR) is used to characterize the
spin Hall angle of the heavy metals. Transmission electron microscopy images
show that all underlayers are amorphous-like when their thicknesses are small,
however, crystalline phases emerge as the thickness is increased for certain
elements. We find that the heavy metal layer thickness dependence of the SMR
reflects these changes in structure. The spin Hall angle largest
|\theta$_{SH}$| of Hf, Ta, W and Re (~0.11, 0.10, 0.23 and 0.07, respectively)
is found when the dominant phase is amorphous-like. We find that the
amorphous-like phase not only possesses large resistivity but also exhibits
sizeable spin Hall conductivity, which both contribute to the emergence of the
large spin Hall angle.

###Quantum oscillations and the Fermi-surface topology of the Weyl semimetal NbP|J. Klotz,Shu-Chun Wu,Chandra Shekhar,Yan Sun,Marcus Schmidt,Michael Nicklas,Michael Baenitz,M. Uhlarz,J. Wosnitza,Claudia Felser,Binghai Yan###

Quantum oscillations and the Fermi-surface topology of the Weyl semimetal NbP. The Weyl semimetal NbP was found to exhibit topological Fermi arcs and exotic
magneto-transport properties. Here, we report on magnetic quantum-oscillation
measurements on NbP and construct the 3D Fermi surface with the help of
band-structure calculations. We reveal a pair of spin-orbit-split electron
pockets at the Fermi energy and a similar pair of hole pockets, all of which
are strongly anisotropic. The Fermi surface well explains the linear
magnetoresistance observed in high magnetic fields by the quantum-limit
scenario. The Weyl points that are located in the $k_z \approx \pi/c$ plane are
found to exist 5 meV above the Fermi energy. Therefore, we predict that the
chiral anomaly effect can be realized in NbP by electron doping to drive the
Fermi energy to the Weyl points.

###Spin transport in molybdenum disulfide multilayer channel|S. H. Liang,Y. Lu,B. S. Tao,S. Mc-Murtry,G. Wang,X. Marie,P. Renucci,H. Jaffrès,F. Montaigne,D. Lacour,J. -M. George,S. Petit-Watelot,M. Hehn,A. Djeffal,S. Mangin###

Spin transport in molybdenum disulfide multilayer channel. Molybdenum disulfide has recently emerged as a promising two-dimensional
semiconducting material for nano-electronic, opto-electronic and spintronic
applications. However, demonstrating spin-transport through a semiconducting
MoS2 channel is challenging. Here we demonstrate the electrical spin injection
and detection in a multilayer MoS2 semiconducting channel. A magnetoresistance
(MR) around 1% has been observed at low temperature through a 450nm long, 6
monolayer thick channel with a Co/MgO spin injector and detector. From a
systematic study of the bias voltage, temperature and back-gate voltage
dependence of MR, it is found that the hopping via localized states in the
contact depletion region plays a key role for the observation of the
two-terminal MR. Moreover, the electron spin-relaxation is found to be greatly
suppressed in the multilayer MoS2 channel for in-plan spin injection. The
underestimated long spin diffusion length (~235nm) and large spin lifetime
(~46ns) open a new avenue for spintronic applications using multilayer
transition metal dichalcogenides.

###Antiferromagnetism and superconductivity in the half-Heusler semimetal HoPdBi|Orest Pavlosiuk,Dariusz Kaczorowski,Xavier Fabreges,Arsen Gukasov,Piotr Wiśniewski###

Antiferromagnetism and superconductivity in the half-Heusler semimetal HoPdBi. We observed the coexistence of superconductivity and antiferromagnetic order
in the single-crystalline ternary pnictide HoPdBi, a plausible topological
semimetal. The compound orders antiferromagnetically at $T_N =$1.9 K and
exhibits superconductivity below $T_c =$0.7 K, which was confirmed by magnetic,
electrical transport and specific heat measurements. The specific heat shows
anomalies corresponding to antiferromagnetic ordering transition and
crystalline field effect, but not to superconducting transition. Single-crystal
neutron diffraction indicates that the antiferromagnetic structure is
characterized by the (1/2, 1/2, 1/2) propagation vector. Temperature variation
of the electrical resistivity reveals two parallel conducting channels of
semiconducting and metallic character. In weak magnetic fields, the
magnetoresistance exhibits weak antilocalization effect, while in strong fields
and temperatures below 50 K it is large and negative. At temperatures below 7 K
Shubnikov-de Haas oscillations with two frequencies appear in the resistivity.
These oscillations have non-trivial Berry phase, which is a distinguished
feature of Dirac fermions.

###Evidence of radiation-driven Landau states in 2D electron systems: magnetoresistance oscillations phase shift|Jesus Inarrea###

Evidence of radiation-driven Landau states in 2D electron systems: magnetoresistance oscillations phase shift. We provide the ultimate explanation of one of the core features of
microwave-induced magnetoresistance oscillations in high mobility two
dimensional electron systems: the 1/4-cycle phase shift of minima. We start
with the radiation-driven electron orbits model with the novel concept of
scattering flight-time between Landau states. We calculate the extrema and
nodes positions obtaining an exact coincidence with the experimental ones. The
main finding is that the physical origin of the phase shift is a delay of
$\frac{\pi}{2}$ of the radiation-driven Landau guiding center with respect to
radiation, demonstrating the oscillating nature of the irradiated Landau
states.
  We analyze the dependence of this minima on radiation frequency and power and
its possible shift with the quality of the sample

###Topological Critical Point and Resistivity Anomaly in HfTe5|L. X. Zhao,X. C. Huang,Y. J. Long,D. Chen,H. Liang,Z. H. Yang,M. Q. Xue,Z. A. Ren,H. M. Weng,Z. Fang,X. Dai,G. F. Chen###

Topological Critical Point and Resistivity Anomaly in HfTe5. There is a long-standing confusion concerning the physical origin of the
anomalous resistivity peak in transition metal pentatelluride HfTe5. Several
mechanisms, like the formation of charge density wave or polaron, have been
proposed, but so far no conclusive evidence has been presented. In this work,
we investigate the unusual temperature dependence of magneto-transport
properties in HfTe5. We find that a three dimensional topological Dirac
semimetal state emerges only at around Tp (at which the resistivity shows a
pronounced peak), as manifested by a large negative magnetoresistance. This
accidental Dirac semimetal state mediates the topological quantum phase
transition between the two distinct weak and strong topological insulator
phases in HfTe5. Our work not only provides the first evidence of a
temperature-induced critical topological phase transition in HfTe5, but also
gives a reasonable explanation on the long-lasting question.

###Strong charge density wave fluctuation and sliding state in PdTeI with quasi-1D PdTe chains|Hechang Lei,Kai Liu,Jun-ichi Yamaura,Sachiko Maki,Youichi Murakami,Zhong-Yi Lu,Hideo Hosono###

Strong charge density wave fluctuation and sliding state in PdTeI with quasi-1D PdTe chains. In quasi-one-dimensional (quasi-1D) system, the charge density wave (CDW)
transition temperature TCDW is usually lower than the mean-field-theory
predicted TMF and a CDW fluctuation region exists between them. Here, we
investigate the physical properties of PdTeI single crystal containing quasi-1D
PdTe chains. Surprisingly, we find that the carrier concentration decreases
gradually before the long-range CDW ordering state occurring at T1 ~ 110 K,
reflecting the existence of strong CDW fluctuation with possible pseudogap
state at T >> T1 because of dynamic charge separation of Pd ions (Pd3+ -> Pd2+
+ Pd4+). Moreover, the sliding CDW state appears below T2 ~ 6 K. Combined such
low T2 with the feature of multiple quasi-1D bands, PdTeI exhibits exotic
crossover behavior from negative to huge positive magnetoresistance under
magnetic field and field-induced localization. Thus, PdTeI provides a novel
platform for studying the CDW fluctuation and the interplay between magnetic
field and CDW state.

###Multiple first order transitions and associated room temperature magneto-functionality in Ni2.048Mn1.312In0.64|S. Pramanick,P. Dutta,S. Chatterjee,S. Giri,S. Majumdar###

Multiple first order transitions and associated room temperature magneto-functionality in Ni2.048Mn1.312In0.64. Present work reports on the observation of multiple magnetic transitions in a
Ni-excess ferromagnetic shape memory alloy with nominal composition
Ni$_{2.048}$Mn$_{1.312}$In$_{0.64}$. The magnetization data reveal two distinct
thermal hystereses associated with two different phase transitions at different
temperature regions. The high temperature magnetic hysteresis is due to the
martensitic phase transition whereas the low temperature hysteresis occurs
around the magnetic anomaly signifying the transition from a paramagnetic-like
state to the ferromagetic ground state within the martensite. Clear thermal
hysteresis along with the sign of the curvatures of Arrott plot curves confirm
the {\it first order nature of both the transitions}. In addition, the studied
alloy is found to be functionally rich with the observation of large
magnetoresistance (-45\% and -4\% at 80 kOe) and magnetocaloric effect (+16.7
J.kg$^{-1}$.K$^{-1}$ and -2.25 J.kg$^{-1}$.K$^{-1}$ at 50 kOe) around these two
hysteresis regions (300 K and 195 K respectively).

###Vector spectroscopy for spin pumping|J. Lustikova,Y. Shiomi,E. Saitoh###

Vector spectroscopy for spin pumping. We propose a method to separate the inverse spin Hall effect (ISHE) from
galvanomagnetic effects in spin pumping experiments on metallic bilayer systems
by measuring the dc electromotive force in two orthogonal directions.
Calculations of dc voltages in longitudinal and Hall directions induced in
Ni81Fe19 and Ni81Fe19/Pt films at ferromagnetic resonance in a microwave cavity
predict that contributions from ISHE and from the galvanomagnetic effects, i.e.
the anisotropic magnetoresistance and the anomalous Hall effect, exhibit
distinct signal symmetry as well as angular dependence when changing the
direction of the external field with respect to the film plane. According to
measurements on Ni81Fe19/Pt, only that dc voltage component which includes ISHE
is more than five times larger than purely galvanomagnetic components. This is
corroborated by results on La0.67Sr0.33MnO3/Pt samples, demonstrating
universality of this method.

###Large magnetoresistance in LaBi: origin of field-induced resistivity upturn and plateau in compensated semimetals|Shanshan Sun,Qi Wang,Peng-Jie Guo,Kai Liu,Hechang Lei###

Large magnetoresistance in LaBi: origin of field-induced resistivity upturn and plateau in compensated semimetals. The discovery of non-magnetic extreme magnetoresistance (XMR) materials has
induced great interests because the XMR phenomenon challenges our understanding
of how a magnetic field can alter electron transport in semimetals. Among XMR
materials, the LaSb shows XMR and field-induced exotic behaviors but it seems
to lack the essentials for these properties. Here, we study the
magnetotransport properties and electronic structure of LaBi, isostructural to
LaSb. LaBi exhibits large MR as in LaSb, which can be ascribed to the nearly
compensated electron and hole with rather high mobilities. More importantly,
our analysis suggests that the XMR as well as field-induced resistivity upturn
and plateau observed in LaSb and LaBi can be well explained by the two-band
model with the compensation situation. We present the critical conditions
leading to these field-induced properties. It will contribute to understanding
the XMR phenomenon and explore novel XMR materials.

###Weak antilocalization in Cd3As2 thin films|Bo Zhao,Peihong Cheng,Haiyang Pan,Shuai Zhang,Baigeng Wang,Guanghou Wang,Faxian Xiu,Fengqi Song###

Weak antilocalization in Cd3As2 thin films. Recently, it has been theoretically predicted that Cd3As2 is a three
dimensional Dirac material, a new topological phase discovered after
topological insulators, which exhibits a linear energy dispersion in the bulk
with massless Dirac fermions. Here, we report on the low-temperature
magnetoresistance measurements on a ~50nm-thick Cd3As2 film. The weak
antilocalization under perpendicular magnetic field is discussed based on the
two-dimensional Hikami-Larkin-Nagaoka (HLN) theory. The electron-electron
interaction is addressed as the source of the dephasing based on the
temperature-dependent scaling behavior. The weak antilocalization can be also
observed while the magnetic field is parallel to the electric field due to the
strong interaction between the different conductance channels in this
quasi-two-dimensional film.

###Large Magnetoresistance in Compensated Semimetals TaAs$_2$ and NbAs$_2$|Zhujun Yuan,Hong Lu,Yongjie Liu,Junfeng Wang,Shuang Jia###

Large Magnetoresistance in Compensated Semimetals TaAs$_2$ and NbAs$_2$. We report large magnetoresistance (MR) at low temperatures in
single-crystalline nonmagnetic compounds TaAs$_2$ and NbAs$_2$. Both compounds
exhibit parabolic-field-dependent MR larger than $5\times10^3$ in a magnetic
field of 9 Tesla at 2 K. The MR starts to deviate from parabolic dependence
above 10 T and intends to be saturated in 45 T for TaAs$_2$ at 4.2 K. The Hall
resistance measurements and band structural calculations reveal their
compensated semimetal characteristics. The large MR at low temperatures is
ascribed to a resonance effect of the balanced electrons and holes with large
mobilities. We also discuss the relation of the MR and samples' quality for
TaAs$_2$ and other semimetals. We found that the magnitudes of MR are strongly
dependent on the samples' quality for different compounds.

###Path dependent resistivity study across field induced paramagnetic to ferromagnetic transition in Se doped CoS$_2$|Saroj Kumar Mishra,R Rawat###

Path dependent resistivity study across field induced paramagnetic to ferromagnetic transition in Se doped CoS$_2$. A systematic study of thermomagnetic irreversibility CoS$_{1.76}$Se$_{0.24}$
has been carried out. Our study shows that the resistivity at low temperature
can be tuned by cooling in different magnetic fields and the critical field
required for paramagnetic (PM) to ferromagnetic (FM) transition varies
non-monotonically with temperature. The field induced PM to FM transition
results in giant positive magnetoresistance (MR) of about 160\% at 5 K.
Measurements under CHUF (cooling and heating in unequal magnetic field)
protocol show reentrant transition on warming under higher magnetic field (than
that applied during cooling). It indicates that the glass like behaviour in
this system can be explained in the framework of the kinetic arrest of first
order transition. Among the growing list of diverse system showing glass like
arrested magnetic states, the present system is the first example where,
kinetic arrest is observed for a disordered (here PM) to ordered (here FM)
first order transition.

###Magnetic radial vortex stabilization and efficient manipulation driven by the Dzyaloshinskii Moriya Interaction and the spin-transfer torque|G. Siracusano,R. Tomasello A. Giordano,V. Puliafito,B. Azzerboni,O. Ozatay,M. Carpentieri,G. Finocchio###

Magnetic radial vortex stabilization and efficient manipulation driven by the Dzyaloshinskii Moriya Interaction and the spin-transfer torque. Solitons are very promising for the design of next generation of ultralow
power devices for storage and computation. The key ingredient to achieve this
goal is the fundamental understanding of their stabilization and manipulation.
Here, we show how the interfacial Dzyaloshinskii Moriya Interaction (i DMI) is
able to lift the energy degeneracy of a magnetic vortex state by stabilizing a
topological soliton with radial chirality, hereafter called radial vortex. It
has a non-integer skyrmion number S (0.5<|S|<1) due to both the vortex core
polarity and the magnetization tilting induced by the i DMI boundary
conditions. Micromagnetic simulations predict that a magnetoresistive memory
based on the radial vortex state in both free and polarizer layers can be
efficiently switched by a threshold current density smaller than 106 A/cm2. The
switching processes occur via the nucleation of topologically connected
vortices and vortex antivortex pairs, followed by spin wave emissions due to
vortex antivortex annihilations.

###Magnetotransport in single layer graphene in a large parallel magnetic field|F. Chiappini,S. Wiedmann,M. Titov,A. K. Geim,R. V. Gorbachev,E. Khestanova,A. Mishchenko,K. S. Novoselov,J. C. Maan,U. Zeitler###

Magnetotransport in single layer graphene in a large parallel magnetic field. Graphene on hexagonal boron-nitride (h-BN) is an atomically flat conducting
system that is ideally suited for probing the effect of Zeeman splitting on
electron transport. We demonstrate by magneto-transport measurements that a
parallel magnetic field up to 30 Tesla does not affect the transport properties
of graphene on h-BN even at charge neutrality where such an effect is expected
to be maximal. The only magnetoresistance detected at low carrier
concentrations is shown to be associated with a small perpendicular component
of the field which cannot be fully eliminated in the experiment. Despite the
high mobility of charge carries at low temperatures, we argue that the effects
of Zeeman splitting are fully masked by electrostatic potential fluctuations at
charge neutrality.

###Weak Localization in Few-Layer Black Phosphorus|Yuchen Du,Adam T. Neal,Hong Zhou,Peide D. Ye###

Weak Localization in Few-Layer Black Phosphorus. We have conducted a comprehensive investigation into the magneto-transport
properties of few-layer black phosphorus in terms of phase coherence length,
phase coherence time, and mobility via weak localization measurement and
Hall-effect measurement. We present magnetoresistance data showing the weak
localization effect in bare p-type few-layer black phosphorus and reveal its
strong dependence on temperature and carrier concentration. The measured weak
localization agrees well with the Hikami-Larkin-Nagaoka model and the extracted
phase coherence length of 104 nm at 350 mK, decreasing as ~T^-0.51+-0.05 with
increased temperature. Weak localization measurement allows us to qualitatively
probe the temperature-dependent phase coherence time {\tau}, which is in
agreement with the theory of carrier interaction in the diffusive regime. We
also observe the universal conductance fluctuation phenomenon in few-layer
black phosphorus within moderate magnetic field and low temperature regime.

###Perfect charge compensation in extremely large magnetoresistance materials LaSb and LaBi revealed by the first-principles calculations|Peng-Jie Guo,Huan-Cheng Yang,Kai Liu,Zhong-Yi Lu###

Perfect charge compensation in extremely large magnetoresistance materials LaSb and LaBi revealed by the first-principles calculations. By the first-principles electronic structure calculations, we have
systematically studied the electronic structures of recently discovered
extremely large magnetoresistance (XMR) materials LaSb and LaBi. We find that
both LaSb and LaBi are semimetals with the electron and hole carriers in
perfect balance. The calculated carrier densities in the order of $10^{20}$
cm$^{-3}$ are in good agreement with the experimental values, implying long
mean free time of carriers and thus high carrier mobilities. With a
semiclassical two-band model, the perfect charge compensation and high carrier
mobilities naturally explain (i) the XMR observed in LaSb and LaBi; (ii) the
non-saturating quadratic dependence of XMR on external magnetic field; and
(iii) the resistivity plateau in the turn-on temperature behavior at very low
temperatures. The explanation of these features without resorting to the
topological effect indicates that they should be the common characteristics of
all perfectly electron-hole compensated semimetals.

###Giant Voltage Manipulation of MgO-based Magnetic Tunnel Junctions via Localized Anisotropic Strain: a Potential Pathway to Ultra-Energy-Efficient Memory Technology|Zhengyang Zhao,Mahdi Jamali,Noel D'Souza,Delin Zhang,Supriyo Bandyopadhyay,Jayasimha Atulasimha,Jian-Ping Wang###

Giant Voltage Manipulation of MgO-based Magnetic Tunnel Junctions via Localized Anisotropic Strain: a Potential Pathway to Ultra-Energy-Efficient Memory Technology. Strain-mediated voltage control of magnetization in
piezoelectric/ferromagnetic systems is a promising mechanism to implement
energy-efficient spintronic memory devices. Here, we demonstrate giant voltage
manipulation of MgO magnetic tunnel junctions (MTJ) on a
Pb(Mg1/3Nb2/3)0.7Ti0.3O3 (PMN-PT) piezoelectric substrate with (001)
orientation. It is found that the magnetic easy axis, switching field, and the
tunnel magnetoresistance (TMR) of the MTJ can be efficiently controlled by
strain from the underlying piezoelectric layer upon the application of a gate
voltage. Repeatable voltage controlled MTJ toggling between high/low-resistance
states is demonstrated. More importantly, instead of relying on the intrinsic
anisotropy of the piezoelectric substrate to generate the required strain, we
utilize anisotropic strain produced using local gating scheme, which is
scalable and amenable to practical memory applications. Additionally, the
adoption of crystalline MgO-based MTJ on piezoelectric layer lends itself to
high TMR in the strain-mediated MRAM devices.

###Pressure-driven Superconductivity in Transition-metal Pentatelluride HfTe5|Yanpeng Qi,Wujun Shi,Pavel G. Naumov,Nitesh Kumar,Walter Schnelle,Oleg Barkalov,Chandra Shekhar,Horst Borrmann,Claudia Felser,Binghai Yan,Sergey A. Medvedev###

Pressure-driven Superconductivity in Transition-metal Pentatelluride HfTe5. Layered transition-metal tellurides have attracted considerable attention
because of their rich physics; for example, tungsten ditelluride WTe2 exhibits
extremely large magnetoresistance; the tritelluride ZrTe3 shows a charge
density wave transition at low temperature; and the pentatelluride ZrTe5
displays an enigmatic resistivity anomaly and large thermoelectric power.
Recently some transition-metal tellurides are predicted to be quantum spin Hall
insulators (e.g. ZrTe5 and HfTe5) or Weyl semimetals (e.g. WTe2 and MoTe2) and
were subjected to intensive investigations. Here, we report on the discovery of
superconductivity in hafnium pentatelluride HfTe5 under high pressure. We
observe two structural phase transitions and metallization with
superconductivity developing at around 5 GPa. A maximal critical temperature of
4.8 K is attained at a pressure of 20 GPa, and superconductivity persists up to
the maximum pressure in our study (42 GPa). Theoretical calculations indicate
that the superconductivity develops mainly in the Te atom layers at medium
pressure and in the Te atom chains at high pressure.

###Transport anomalies and quantum criticality in electron-doped cuprate superconductors|Xu Zhang,Heshan Yu,Ge He,Wei Hu,Jie Yuan,Beiyi Zhu,Kui Jin###

Transport anomalies and quantum criticality in electron-doped cuprate superconductors. Superconductivity research is like running a marathon. Three decades after
the discovery of high-Tc cuprates, there have been mass data generated from
transport measurements, which bring fruitful information. In this review, we
give a brief summary of the intriguing phenomena reported in electron-doped
cuprates from the aspect of electrical transport as well as the complementary
thermal transport. We attempt to sort out common features of the electron-doped
family, e.g. the strange metal, negative magnetoresistance, multiple sign
reversals of Hall in mixed state, abnormal Nernst signal, complex quantum
criticality. Most of them have been challenging the existing theories,
nevertheless, a unified diagram certainly helps to approach the nature of
electron-doped cuprates.

###Magnetoresistance of the heavy-fermion metal CeCoIn5|V. R. Shaginyan,K. G. Popov###

Magnetoresistance of the heavy-fermion metal CeCoIn5. The magnetoresistance (MR) of CeCoIn5 is notably different from that expected
for orbital MR due to the Lorentz force and described by Kohler's rule which
holds in many conventional metals. We show that a pronounced crossover from
negative to positive MR of CeCoIn5 that occurs at elevated temperatures is
determined by the dependence of the effective mass M*(B,T) on both magnetic
field B and temperature T. Thus, the crossover is regulated by the universal
behavior of M*(B,T) observed in heavy-fermion metals. This behavior is
exhibited by M*(B,T) when a strongly correlated electron system transits from
the Landau Fermi liquid behavior induced by the application of magnetic field
to the non-Fermi liquid behavior taking place at rising temperatures. Our
calculations of MR are in good agreement with facts and reveal new scaling
behavior of MR.

###Pseudogap behavior of phase-separated Sm$_{1-x}$Ca$_x$MnO$_3$ : A comparative photoemission study with double exchange|P. Pal,M. K. Dalai,R. Kundu,B. R. Sekhar,C. Martin###

Pseudogap behavior of phase-separated Sm$_{1-x}$Ca$_x$MnO$_3$ : A comparative photoemission study with double exchange. Using valence band photoemission we have demonstrated the presence of a
pseudogap in the near Fermi level electronic spectrum of some of the mixed
phase compositions of Sm$_{1-x}$Ca$_x$MnO$_3$ system. The pseudogap was found
to grow in size over a large region of the phase diagram of this system,
finally leading to a metal-insulator transition. We have made a study comparing
the near Fermi level behaviors of this system to those of a canonical double
exchange system, namely, La$_{1-x}$Sr$_x$MnO$_3$. This study intends to
highlight one of the important differences between the phase separated and
double exchange colossal magnetoresistance systems in the nature of their
energy gaps across the metal-insulator transitions. These differences could be
ascribed to the distortions in the MnO$_6$ octahedra of their structures that
regulate the localization of charge carriers. We have discussed our results
from the point of view of models based on the idea of phase separation.

###Thickness dependent magnetic anisotropy of ultrathin LCMO epitaxial thin films|Norbert M. Nemes,Mar Garcia-Hernandez,Zsolt Szatmari,Titusz Feher,Ferenc Simon,Cristina Visani,Vanessa Pena,Christian Miller,Javier Garcia-Barriocanal,Flavio Bruno,Zouhair Sefrioui,Carlos Leon,Jacobo Santamaria###

Thickness dependent magnetic anisotropy of ultrathin LCMO epitaxial thin films. The magnetic properties of La0.7Ca0.3MnO3 (LCMO) manganite thin films were
studied with magnetometry and ferromagnetic resonance as a function of film
thickness. They maintain the colossal magnetoresistance behavior with a
pronounced metal-insulator transition around 150-200 K, except for the very
thinnest films studied (3 nm). Nevertheless, LCMO films as thin as 3 nm remain
ferromagnetic, without a decrease in saturation magnetization, indicating an
absence of dead-layers, although below approx. 6 nm the films remain insulating
at low temperature. Magnetization hysteresis loops reveal that the magnetic
easy axes lie in the plane of the film for thicknesses in the range of 4-15 nm.
Ferromagnetic resonance studies confirm that the easy axes are in-plane, and
find a biaxial symmetry in-plane with two, perpendicular easy axes. The
directions of the easy axes with respect to the crystallographic directions of
the cubic SrTiO3 substrate differ by 45 degrees in 4 nm and 15 nm thick LCMO
films.

###The role of electron-hole recombination in organic magnetoresistance|Sayani Majumdar,Himadri S Majumdar,Harri Aarnio,Dirk Vanderzande,Reino Laiho,Ronald Osterbacka###

The role of electron-hole recombination in organic magnetoresistance. Magneto-electrical measurements were performed on diodes and bulk
heterojunction solar cells (BHSCs) to clarify the role of formation of
coulombically bound electron-hole (e-h) pairs on the magnetoresistance (MR)
response in organic thin film devices. BHSCs are suitable model systems because
they effectively quench excitons but the probability of forming e-h pairs in
them can be tuned over orders of magnitude by the choice of material and
solvent in the blend. We have systematically varied the e-h recombination
coefficients, which are directly proportional to the probability for the charge
carriers to meet in space, and found that a reduced probability of electrons
and holes meeting in space lead to disappearance of the MR. Our results clearly
show that MR is a direct consequence of e-h pair formation. We also found that
the MR line shape follows a power law-dependence of B0.5 at higher fields.

###Gate control of the tunneling magnetoresistance in double-barrier junctions|J. Peralta-Ramos,A. M. Llois###

Gate control of the tunneling magnetoresistance in double-barrier junctions. We calculate the conductances and the tunneling magnetoresistance (TMR) of
double magnetic tunnel junctions, taking as a model example junctions composed
of Fe/ZnSe/Fe/ZnSe/Fe (001). The calculations are done as a function of the
gate voltage applied to the in-between Fe layer slab. We find that the
application of a gate voltage to the in-between Fe slab strongly affects the
junctions' TMR due to the tuning or untuning of conductance resonances mediated
by quantum well states. The gate voltage allows a significant enhancement of
the TMR, in a more controllable way than by changing the thickness of the
in-between Fe slab. This effect may be useful in the design of future
spintronic devices based on the TMR effect, requiring large and controllable
TMR values.

###Substitutional disorder and charge localization in manganites|Eduardo V. Castro,J. M. B. Lopes dos Santos###

Substitutional disorder and charge localization in manganites. In the manganites $RE_{1-x}AE_{x}$MnO$_{3}$ ($RE$ and $AE$ being rare-earth
and alkaline-earth elements, respectively) the random distribution of $RE^{3+}$
and $AE^{2+}$ induces random, but correlated, shifts of site energies of charge
carriers in the Mn sites. We consider a realistic model of this diagonal
disorder, in addition to the double-exchange hopping disorder, and investigate
the metal-insulator transition as a function of temperature, across the
paramagnetic-ferromagnetic line, and as a function of doping $x$. Contrary to
previous results, we find that values of parameters, estimated from the
electronic structure of the manganites, are not incompatible with the
possibility of a disorder induced metal to insulator transition accompanying
the ferromagnetic to paramagnetic transition at intermediate doping
($x\sim0.2-0.4$). These findings indicate clearly that substitutional disorder
has to be considered as an important effect when addressing the colossal
magnetoresistance properties of manganites.

###Towards printed magnetic sensors based on organic diodes|Sayani Majumdar,Himadri S. Majumdar,Daniel Tobjork,Ronald Osterbacka###

Towards printed magnetic sensors based on organic diodes. We report the study of magnetotransport properties of regio-regular poly
(3-hexyl thiophene) based organic diodes. The devices were fabricated using two
different techniques of spin coating and inkjet printing. Positive
magnetoresistance (MR) effect was observed at room temperature in all the
devices. The highest MR magnitude reached up to 16% for some spin-coated
devices and up to 10% in inkjet printed devices. The MR magnitude and line
shapes were found to depend strongly on the measuring current. We observed
deviation from the theoretically predicted Lorentzian or non-Lorentzian line
shape of the MR traces, which is discussed in detail in the article. Although,
the printed devices exhibit MR response as high as for the spin coated ones,
they still need to be optimized in terms of performance and yield for large
scale applications as magnetic sensors.

###Extremely Large and Anisotropic Upper Critical Field and the Ferromagnetic Instability in UCoGe|Dai Aoki,Tatsuma D. Matsuda,Valentin Taufour,Elena Hassinger,Georg Knebel,Jacques Flouquet###

Extremely Large and Anisotropic Upper Critical Field and the Ferromagnetic Instability in UCoGe. Magnetoresistivity measurements with fine tuning of the field direction on
high quality single crystals of the ferromagnetic superconductor UCoGe show
anomalous anisotropy of the upper critical field H_c2. H_c2 for H // b-axis
(H_c2^b) in the orthorhombic crystal structure is strongly enhanced with
decreasing temperature with an S-shape and reaches nearly 20 T at 0 K. The
temperature dependence of H_c2^a shows upward curvature with a low temperature
value exceeding 30 T, while H_c2^c at 0 K is very small (~ 0.6 T). Contrary to
conventional ferromagnets, the decrease of the Curie temperature with
increasing field for H // b-axis marked by an enhancement of the effective mass
of the conduction electrons appears to be the origin of the S-shaped H_c2^b
curve. These results indicate that the field-induced ferromagnetic instability
or magnetic quantum criticality reinforces superconductivity.

###MgO barrier-perpendicular magnetic tunnel junctions with CoFe/Pd multilayers and ferromagnetic insertion layers|K. Mizunuma,S. Ikeda,J. H. Park,H. Yamamoto,H. Gan,K. Miura,H. Hasegawa,J. Hayakawa,F. Matsukura,H. Ohno###

MgO barrier-perpendicular magnetic tunnel junctions with CoFe/Pd multilayers and ferromagnetic insertion layers. The authors studied an effect of ferromagnetic (Co20Fe60B20 or Fe) layer
insertion on tunnel magnetoresistance (TMR) properties of MgO-barrier magnetic
tunnel junctions (MTJs) with CoFe/Pd multilayer electrodes. TMR ratio in MTJs
with CoFeB/MgO/Fe stack reached 67% at an-nealing temperature (Ta) of 200
degree C and then decreased rapidly at Ta over 250 degree C. The degradation of
the TMR ratio may be related to crystallization of CoFe(B) into fcc(111) or
bcc(011) texture result-ing from diffusion of B into Pd layers. MTJs which were
in-situ annealed at 350oC just after depo-siting bottom CoFe/Pd multilayer
showed TMR ratio of 78% by post annealing at Ta =200 degree C.

###Interfacial Effects of Al-Termination on Spin Transport in Magnetic Tunnel Junctions|T. Tzen Ong,A. M. Black-Schaffer,W. Shen,B. A. Jones###

Interfacial Effects of Al-Termination on Spin Transport in Magnetic Tunnel Junctions. Experiments have shown that the tunneling current in a Co/Al$_2$O$_3$
magnetic tunneling junction (MTJ) is positively spin polarized, opposite to
what is intuitively expected from standard tunneling theory which gives the
spin polarization as exclusively dependent on the density of states (DOS) at
$E_F$ of the Co layers. Here we report theoretical results that give a positive
tunneling spin polarization and tunneling magnetoresistance (TMR) that is in
good agreement with experiments. From density functional theory (DFT)
calculations, an Al-rich interface MTJ with atomic-level disorder is shown to
have a positively polarized DOS near the interface. We also provide an atomic
model calculation which gives insights into the source of the positive
polarization. A layer and spin dependent effective mass model, using values
extracted from the DFT results, is then used to calculate the tunneling
current, which shows positive spin polarization. Finally, we calculate the TMR
from the tunneling spin polarization which shows good agreement with
experiments.

###Contrasting Pair-Breaking Effects by Doping Mn and Zn in Ba0.5K0.5Fe2As2|Peng Cheng,Bing Shen,Jiangping Hu,Hai-Hu Wen###

Contrasting Pair-Breaking Effects by Doping Mn and Zn in Ba0.5K0.5Fe2As2. Resistivity, Hall effect, magnetoresistance and DC magnetization were
measured in Mn and Zn doped Ba$_{0.5}$K$_{0.5}$Fe$_{2}$As$_{2}$ samples. It is
found that the Mn-doping can depress the superconducting transition temperature
drastically with a rate of $\Delta T_c$/Mn-1% = -4.2 K, while that by Zn-doping
is negligible. Detailed analysis reveals that the Mn-doping enhances the
residual resistivity ($\rho_0$) significantly, and induces strong local
magnetic moments ($\sim$ 2.58 $\mu_B$) which play as pair breakers. While the
impurity scattering measured by $\rho_0$ in the Zn-doped samples is much
weaker, accompanied by a negligible pair breaking effect. A possible
explanation is that the impurity scattering by the Zn impurities are mainly
small angle scattering (or small momentum transfer), therefore it cannot break
the pairing induced by the interpocket scattering and thus affect the
superconducting transition temperature weakly.

###Hydrogenated Graphene Nanoribbons for Spintronics|D. Soriano,F. Muñoz-Rojas,J. Fernández-Rossier,J. J. Palacios###

Hydrogenated Graphene Nanoribbons for Spintronics. We show how hydrogenation of graphene nanoribbons at small concentrations can
open new venues towards carbon-based spintronics applications regardless of any
especific edge termination or passivation of the nanoribbons. Density
functional theory calculations show that an adsorbed H atom induces a spin
density on the surrounding $\pi$ orbitals whose symmetry and degree of
localization depends on the distance to the edges of the nanoribbon. As
expected for graphene-based systems, these induced magnetic moments interact
ferromagnetically or antiferromagnetically depending on the relative adsorption
graphene sublattice, but the magnitude of the interactions are found to
strongly vary with the position of the H atoms relative to the edges. We also
calculate, with the help of the Hubbard model, the transport properties of
hydrogenated armchair semiconducting graphene nanoribbons in the diluted regime
and show how the exchange coupling between H atoms can be exploited in the
design of novel magnetoresistive devices.

###A theory for magnetic-field effects of nonmagnetic organic semiconducting materials|X. R. Wang,S. J. Xie###

A theory for magnetic-field effects of nonmagnetic organic semiconducting materials. A universal mechanism for strong magnetic-field effects of nonmagnetic
organic semiconductors is presented. A weak magnetic field (less than hundreds
mT) can substantially change the charge carrier hopping coefficient between two
neighboring organic molecules when the magnetic length is not too much longer
than the molecule-molecule separation and localization length of electronic
states involved. Under the illumination of lights or under a high electric
field, the change of hopping coefficients leads also to the change of polaron
density so that photocurrent, photoluminescence, electroluminescence,
magnetoresistance and electrical-injection current become sensitive to a weak
magnetic field. The present theory can not only explain all observed features,
but also provide a solid theoretical basis for the widely used empirical
fitting formulas.

###Competing magnetic anisotropies in atomic-scale junctions|Alexander Thiess,Yuriy Mokrousov,Stefan Heinze###

Competing magnetic anisotropies in atomic-scale junctions. Using first-principles calculations, we study the magnetism of 5d
transition-metal atomic junctions including structural relaxations and
spin-orbit coupling. Upon stretching monatomic chains of W, Ir, and Pt
suspended between two leads, we find the development of strong magnetism and
large values of the magnetocrystalline anisotropy energy (MAE) of up to 30 meV
per chain atom. We predict that switches of the easy magnetization axis of the
nanocontacts upon elongation should be observable by ballistic anisotropic
magnetoresistance measurements. Due to the different local symmetry, the
contributions to the MAE of the central chain atoms and chain atoms in the
vicinity of the leads can have opposite signs which reduces the total MAE. We
demonstrate that this effect occurs independent of the chain length or geometry
of the electrodes.

###An anomalous butterfly-shaped magnetoresistance loop in an alloy, Tb4LuSi3|K. Mukherjee,Sitikantha D Das,Niharika Mohapatra,Kartik K Iyer,E. V. Sampathkumaran###

An anomalous butterfly-shaped magnetoresistance loop in an alloy, Tb4LuSi3. Magnetic-field (H) induced first-order magnetic transition and the assiciated
electronic phase-separation phenomena are active topics of research in
magnetism. Magnetoresistance (MR) is a key property to probe these phenomena
and, in literature, a butterfly-shaped MR loop has been noted while cycling the
field, with the envelope curve lying below the virgin curve in MR versus H
plots of such materials. Here, we report an opposite behavior of MR loop for an
alloy, Tb4LuSi3, at low temperatures (<<20 K) in the magnetically ordered
state. Such an anomalous curve reveals unexpected domination of higher
resistive high-field phase in electronic conduction, unlike in other materials
where conducion is naturally by low-resistive high-field phase that follows
first-order transition. The observed features reveal an unusual electronic
phase separation, namely involving high-resistive high-field phase and
low-resistive virgin phase.

###Angular-dependent oscillations of the magnetoresistance in Bi_2Se_3 due to the three-dimensional bulk Fermi surface|Kazuma Eto,Zhi Ren,A. A. Taskin,Kouji Segawa,Yoichi Ando###

Angular-dependent oscillations of the magnetoresistance in Bi_2Se_3 due to the three-dimensional bulk Fermi surface. We observed pronounced angular-dependent magnetoresistance (MR) oscillations
in a high-quality Bi2Se3 single crystal with the carrier density of 5x10^18
cm^-3, which is a topological insulator with residual bulk carriers. We show
that the observed angular-dependent oscillations can be well simulated by using
the parameters obtained from the Shubnikov-de Haas oscillations, which
clarifies that the oscillations are solely due to the bulk Fermi surface. By
completely elucidating the bulk oscillations, this result paves the way for
distinguishing the two-dimensional surface state in angular-dependent MR
studies in Bi2Se3 with much lower carrier density. Besides, the present result
provides a compelling demonstration of how the Landau quantization of an
anisotropic three-dimensional Fermi surface can give rise to pronounced
angular-dependent MR oscillations.

###Nonequilibrium phenomena in high Landau levels|I. A. Dmitriev,A. D. Mirlin,D. G. Polyakov,M. A. Zudov###

Nonequilibrium phenomena in high Landau levels. Developments in the physics of 2D electron systems during the last decade
have revealed a new class of nonequilibrium phenomena in the presence of a
moderately strong magnetic field. The hallmark of these phenomena is
magnetoresistance oscillations generated by the external forces that drive the
electron system out of equilibrium. The rich set of dramatic phenomena of this
kind, discovered in high mobility semiconductor nanostructures, includes, in
particular, microwave radiation-induced resistance oscillations and
zero-resistance states, as well as Hall field-induced resistance oscillations
and associated zero-differential resistance states. We review the experimental
manifestations of these phenomena and the unified theoretical framework for
describing them in terms of a quantum kinetic equation. The survey contains
also a thorough discussion of the magnetotransport properties of 2D electrons
in the linear response regime, as well as an outlook on future directions,
including related nonequilibrium phenomena in other 2D electron systems.

###Ab initio theory of galvanomagnetic phenomena in ferromagnetic metals and disordered alloys|Ilja Turek,Josef Kudrnovsky,Vaclav Drchal###

Ab initio theory of galvanomagnetic phenomena in ferromagnetic metals and disordered alloys. We present an ab initio theory of transport quantities of metallic
ferromagnets developed in the framework of the fully relativistic tight-binding
linear muffin-tin orbital method. The approach is based on the Kubo-Streda
formula for the conductivity tensor, on the coherent potential approximation
for random alloys, and on the concept of interatomic electron transport. The
developed formalism is applied to pure 3d transition metals (Fe, Co, Ni) and to
random Ni-based ferromagnetic alloys (Ni-Fe, Ni-Co, Ni-Mn). High values of the
anisotropic magnetoresistance (AMR), found for Ni-rich alloys, are explained by
a negligible disorder in the majority spin channel while a change of the sign
of the anomalous Hall effect (AHE) on alloying is interpreted as a band-filling
effect without a direct relation to the high AMR. The influence of disorder on
the AHE in concentrated alloys is investigated as well.

###A first-order magnetic phase transition near 15 K with novel magnetic-field-induced effects in Er5Si3|Niharika Mohapatra,K. Mukherjee,Kartik K. Iyer,E. V. Sampathkumaran###

A first-order magnetic phase transition near 15 K with novel magnetic-field-induced effects in Er5Si3. We present magnetic characterization of a binary rare-earth intermetallic
compound Er5Si3, crystallizing in Mn5Si3-type hexagonal structure, through
magnetization, heat-capacity, electrical resistivity, and magnetoresistance
measurements. Our investigations confirm that the compound exhibits two
magnetic transitions with decreasing temperature, first one at 35 K and the
second one at 15 K. The present results reveal that the second magnetic
transition is a disorder-broadened first-order transition, as shown by thermal
hysteresis in the measured data. Another important finding is that, below 15 K,
there is a magnetic-field-induced transition with a hysteretic effect with the
electrical resistance getting unusually enhanced at this transition and the
magnetorsistance (MR) is found to exhibit intriguing magnetic-field dependence
indicating novel magnetic phase-co-existence phenomenon. It thus appears that
this compound is characterized by interesting magnetic anomalies in the
temperature-magnetic-field phase diagram.

###Edge superconducting state in Nb thin film with rectangular arrays of antidots|W. J. Zhang,S. K. He,H. F. Liu,G. M. Xue,H. Xiao,B. H. Li,Z. C. Wen,X. F. Han,S. P. Zhao,C. Z. Gu,X. G. Qiu,Victor V. Moshchalkov###

Edge superconducting state in Nb thin film with rectangular arrays of antidots. Superconducting Nb thin films with rectangular arrays of submicron antidots
have been systemically investigated by transport measurements. In low fields,
the magnetoresistance curves demonstrate well-defined dips at integral and
rational numbers of flux quanta per unit cell, which corresponds to a
superconducting wire network-like regime. When the magnetic field is higher
than a saturation field, interstitial vortices interrupt the collective
oscillation in low fields and form vortex sublattice, where a larger magnetic
field interval is observed. In higher fields, a crossover behavior from the
interstitial sublattice state to a single-loop-like state is observed,
characterized by oscillations with a period of $\Phi_0/\pi r_{eff}^2$,
originating from the existence of edge superconducting states with a size
$r_{eff}$ around the antidots.

###Investigation on organic magnetoconductance based on polaron-bipolaron transition|W. Qin,S. Yin,K. Gao,S. J. Xie###

Investigation on organic magnetoconductance based on polaron-bipolaron transition. We explore the magnetoresistance (MC) effect in an organic semiconductor
device based on the magnetic field related bipolaron formation. By establishing
a group of dynamic equations, we present the transition among spin-parallel,
spin-antiparallel polaron pairs and bipolarons. The transition rates are
adjusted by the external magnetic field as well as the hyperfine interaction of
the hydrogen nuclei. The hyperfine interaction is addressed and treated in the
frame work of quantum mechanics. By supposing the different mobility of
polarons from that of bipolarons, we obtain the MC in an organic semiconductor
device. The theoretical calculation is well consistent to the experimental
data. It is predicated that a maximum MC appears at a suitable branching ratio
of bipolarons. Our investigation reveals the important role of hyperfine
interaction in organic magnetic effect.

###Effect of the attachment of ferromagnetic contacts on the conductivity and giant magnetoresistance of graphene nanoribbons|S. Krompiewski###

Effect of the attachment of ferromagnetic contacts on the conductivity and giant magnetoresistance of graphene nanoribbons. Carbon-based nanostructures and graphene, in particular, evoke a lot of
interest as new promising materials for nanoelectronics and spintronics. One of
the most important issue in this context is the impact of external electrodes
on electronic properties of graphene nanoribbons (GNR). The present theoretical
method is based on the tight-binding model and a modified recursive procedure
for Green's functions. The results show that within the ballistic transport
regime, the so called end-contacted geometry (of minimal GNR/electrode
interface area), is usually more advantageous for practical applications than
its side-contacted counterpart (with a larger coverage area), as far as the
electrical conductivity is concerned. As regards the giant magnetoresistance
coefficient, however, the situation is exactly opposite, since spin- splitting
effects are more pronounced in the lower conductive side-contacted setups.

###Heat transport in magnetic fields by quantum spin liquid in the organic insulators EtMe3Sb[Pd(dmit)2]2 and κ-(BEDT-TTF)2Cu2(CN)3|V. R. Shaginyan,A. Z. Msezane,K. G. Popov,G. S. Japaridze,V. A. Khodel###

Heat transport in magnetic fields by quantum spin liquid in the organic insulators EtMe3Sb[Pd(dmit)2]2 and κ-(BEDT-TTF)2Cu2(CN)3. Measurements of the low-temperature thermal conductivity collected on
insulators with geometrical frustration produce important experimental facts
shedding light on the nature of quantum spin liquid composed of spinons. We
employ a model of strongly correlated quantum spin liquid located near the
fermion condensation phase transition to analyze the exciting measurements of
the low-temperature thermal conductivity in magnetic fields collected on the
organic insulators EtMe3Sb[Pd(dmit)_2]2 and \kappa-(BEDT-TTF)2Cu2(CN)3. Our
analysis of the conductivity allows us to reveal a strong dependence of the
effective mass of spinons on magnetic fields, to detect a scaling behavior of
the conductivity, and to relate it to both the spin-lattice relaxation rate and
the magnetoresistivity. Our calculations and observations are in a good
agreement with experimental data.

###Crossover of Magnetoresistance from Fourfold to Twofold Symmetry in SmB6 Single Crystal, a topological Kondo insulator|Zengji Yue,Xiaolin Wang,Duanliang Wang,Jiyang Wang,Dimi Culcer,Shixue Dou###

Crossover of Magnetoresistance from Fourfold to Twofold Symmetry in SmB6 Single Crystal, a topological Kondo insulator. Topological Kondo insulators have been attracting great attention from the
condensed-matter physics community due to their fascinating topological and
strongly correlated properties. Here, we report angle-dependent c-axis
magnetoresistance (MR) oscillations in a Kondo insulator, SmB6 single crystal,
in a magnetic field of up to 13 T rotated in the ab-plane. Four-fold symmetric
MR oscillations are first observed above 8 K, which result from the four-fold
(C4) degeneracy of the bulk Fermi surface of SmB6. With decreasing temperature
down to 2.3 K, the C4 symmetry of the MR oscillations gradually weakens and C2
symmetry appears. This demonstrates a crossover from three-dimensional bulk
states to two-dimensional surface states and implies the possible emergence of
topological nematic states. Our experimental observations shed new light on the
metallic surface states and nematic states in the Kondo insulator SmB6.

###Angular dependence of magnetoresistance in strongly anisotropic quasi-two-dimensional metals for various Landau-level shapes|Taras I. Mogilyuk,Pavel D. Grigoriev###

Angular dependence of magnetoresistance in strongly anisotropic quasi-two-dimensional metals for various Landau-level shapes. We present the quantum-mechanical calculations of the angular dependence of
interlayer conductivity $\sigma _{zz}(\theta )$ in a tilted magnetic field in
quasi-2D layered metals. Our calculation shows that the LL shape is important
for this angular dependence. In particular, the amplitude of angular
magnetoresistance oscillations (AMRO) is much stronger for the Gaussian LL
shape than for the Lorentzian. The ratio $\sigma_{zz}(\theta =0)/
\sigma_{zz}(\theta ->\pm 90^{\circ})$ is also several times larger for the
Gaussian LL shape. AMRO and Zeeman energy splitting lead to a spin current. For
typical organic metals and for a medium magnetic field 10T this spin current is
only a few percent of the charge current, but its value may almost reach the
charge current for special tilt angles of magnetic field. The spin current has
strong angular oscillations, which are phase-shifted as compared to the usual
AMRO.

###Spin-transfer torque switching below 20 kA/cm$^2$ in perpendicular magnetic tunnel junctions|Johannes Christian Leutenantsmeyer,Marvin Walter,Steffen Wittrock,Patrick Peretzki,Henning Schuhmann,Michael Seibt,Markus Münzenberg###

Spin-transfer torque switching below 20 kA/cm$^2$ in perpendicular magnetic tunnel junctions. We demonstrate the reduction of critical spin-transfer torque (STT) switching
currents in Co-Fe-B/MgO based magnetic tunnel junctions (MTJ) with
perpendicular magnetization anisotropy (PMA). The junctions yield tunnel
magnetoresistance (TMR) ratios of up to 64% at 4 monolayer (ML) tunnel barrier
thickness. In this paper, the reduction of the critical switching current
density is studied. By optimizing the applied bias field during DC-STT
measurements, ultra low critical switching current densities of less than 20
kA/cm$^2$, even down to 9 kA/cm$^2$, are found. With the reduced switching
currents, our samples are ideal candidates for further experimental studies
such as the theoretical predicted thermally driven spin-transfer torque effect.

###Magnetic field tuned superconductor-to-insulator transition at the LaAlO$_3$ /SrTiO$_3$ interface|M. M. Mehta,D. A. Dikin,C. W. Bark,S. Ryu,C. M. Folkman,C. B. Eom,V. Chandrasekhar###

Magnetic field tuned superconductor-to-insulator transition at the LaAlO$_3$ /SrTiO$_3$ interface. We present a study of the magnetic field tuned superconductor-to-insulator
transition (SIT) in the electron gas that forms at the LaAlO$_3$/SrTiO$_3$
interface. We find that the magnetic field induces a transition into a weakly
insulating state, as is observed for the electrostatically tuned SIT at this
interface. Finite size scaling of the magnetoresistance yields the critical
exponent product $z\nu \simeq$ 7/3, indicating that the transition is governed
by quantum percolation effects. While such critical exponents have been
reported previously for high resistance films, they have not been reported for
a low resistance system like ours, with a maximum sheet resistance of $\approx$
1.5 k$\Omega$, much less than the quantum of resistance $R_Q \equiv h/4e^2 =
6.45$ k$\Omega$.

###Large lattice distortions associated with the magnetic transition in La0.7Sr0.3MnO3|F. Weber,D. Argyriou,O. Prokhnenko,D. Reznik###

Large lattice distortions associated with the magnetic transition in La0.7Sr0.3MnO3. Colossal magnetoresistance (CMR) is associated with the phase transition from
a metallic ferromagnetic to insulating paramagnetic phase, which can be
controlled by an applied magnetic field. The insulating phase occurs due to
trapping of the charge carriers by polaronic lattice distortions, which raise
the resistivity. Theories based on local physics predict that the magnitude of
the resistivity jump at Tc is determined by how much, on average, the amplitude
of these distortions increases at the phase transition. Using neutron
scattering, we measured the average distortion amplitude in La0.7Sr0.3MnO3.
Surprisingly, its increase from below to above Tc is just as large as in other
manganites, which have a much larger resistivity jump. This result suggests
that the strength of CMR is determined not by the size of distortions, but by
their cooperative nature specific to each compound. Existing theories need to
be extended to include correlations between different unit cells to explain and
predict the strength of CMR.

###Tuning Magnetotransport in PdPt/Y3Fe5O12: Effects of magnetic proximity and spin orbital coupling|X. Zhou,L. Ma,Z. Shi,S. M. Zhou###

Tuning Magnetotransport in PdPt/Y3Fe5O12: Effects of magnetic proximity and spin orbital coupling. Anisotropic magnetoresistance (AMR) ratio and anomalous Hall conductivity
(AHC) in PdPt/Y$_3$Fe$_5$O$_{12}$ (YIG) system are tuned significantly by spin
orbital coupling strength $\xi$ through varying the Pt concentration. For both
Pt/YIG and Pd/YIG, the maximal AMR ratio is located at temperatures for the
maximal susceptibility of paramagnetic Pt and Pd metals. The AHC and ordinary
Hall effect both change the sign with temperature for Pt-rich system and vice
versa for Pd-rich system. The present results ambiguously evidence the spin
polarization of Pt and Pd atoms in contact with YIG layers. The global
curvature near the Fermi surface is suggested to change with the Pt
concentration and temperature.

###Superconducting proximity effect and zero-bias anomaly in transport through quantum dots weakly attached to ferromagnetic leads|I. Weymann,P. Trocha###

Superconducting proximity effect and zero-bias anomaly in transport through quantum dots weakly attached to ferromagnetic leads. The Andreev transport through a quantum dot coupled to two external
ferromagnetic leads and one superconducting lead is studied theoretically by
means of the real-time diagrammatic technique in the sequential and cotunneling
regimes. We show that the tunnel magnetoresistance (TMR) of the Andreev current
displays a nontrivial dependence on the bias voltage and the level detuning,
and can be described by analytical formulas in the zero temperature limit. The
cotunneling processes lead to a strong modification of the TMR, which is most
visible in the Coulomb blockade regime. We find a zero-bias anomaly of the
Andreev differential conductance in the parallel configuration, which is
associated with a nonequilibrium spin accumulation in the dot triggered by
Andreev processes.

###Low anisotropy of the upper critical field in a strongly anisotropic layered cuprate: Evidence for paramagnetically limited superconductivity|S. O. Katterwe,Th. Jacobs,A. Maljuk,V. M. Krasnov###

Low anisotropy of the upper critical field in a strongly anisotropic layered cuprate: Evidence for paramagnetically limited superconductivity. We study angular-dependent magnetoresistance in a low $T_c$ layered cuprate
Bi$_{2.15}$Sr$_{1.9}$CuO$_{6+\delta}$. The low $T_c$ ~ 4 K allows complete
suppression of superconductivity by modest magnetic fields and facilitate
accurate analysis of the upper critical field $H_{c2}$. We observe an universal
exponential decay of fluctuation conductivity in a broad range of temperatures
above $T_c$ and propose a new method for extraction of $H_{c2}(T)$ from the
scaling analysis of the fluctuation conductivity at $T>T_c$. Our main result is
observation of a surprisingly low $H_{c2}$ anisotropy ~ 2, which is much
smaller than the effective mass anisotropy of the material ~ 300. We show that
the anisotropy is decreasing with increasing field and saturates at a small
value when the field reaches the paramagnetic limit. We argue that the dramatic
discrepancy of high field and low field anisotropies is a clear evidence for
paramagnetically limited superconductivity.

###Colossal negative magnetoresistance in a 2D electron gas|Q. Shi,P. D. Martin,Q. A. Ebner,M. A. Zudov,L. N. Pfeiffer,K. W. West###

Colossal negative magnetoresistance in a 2D electron gas. We report on a colossal negative magnetoresistance (MR) in GaAs/AlGaAs
quantum well which, at low temperatures, is manifested by a drop of the
resistivity by more than an order of magnitude at a magnetic field $B \approx
1$ kG. In contrast to MR effects discussed earlier, the MR reported here is not
parabolic, even at small $B$, and persists to much higher in-plane magnetic
fields and temperatures. Remarkably, the temperature dependence of the
resistivity at $B \approx 1$ kG is linear over the entire temperature range
studied (from 1 to 30 K) and appears to coincide with the high-temperature
limit of the zero-field resistivity, hinting on the important role of acoustic
phonons.

###Controllable generation of a spin-triplet supercurrent in a Josephson spin-valve|Adrian Iovan,Taras Golod,Vladimir M. Krasnov###

Controllable generation of a spin-triplet supercurrent in a Josephson spin-valve. It has been predicted theoretically that an unconventional odd-frequency
spin-triplet component of superconducting order parameter can be induced in
multilayered ferromagnetic structures with non-collinear magnetization. In this
work we study experimentally nano-scale devices, in which a ferromagnetic spin
valve is embedded into a Josephson junction. We demonstrate two ways of in-situ
analysis of such Josephson spin valves: via magnetoresistance measurements and
via in-situ magnetometry based on flux quantization in the junction. We observe
that supercurrent through the device depends on the relative orientation of
magnetization of the two ferromagnetic layers and is enhanced in the
non-collinear state of the spin valve. This provides a direct prove of
controllable generation of the spin-triplet superconducting component in a
ferromagnet.

###Spin Hall phenomenology of magnetic dynamics|Yaroslav Tserkovnyak,Scott A. Bender###

Spin Hall phenomenology of magnetic dynamics. We study the role of spin-orbit interactions in the coupled magnetoelectric
dynamics of a ferromagnetic film coated with an electrical conductor. While the
main thrust of this work is phenomenological, several popular simple models are
considered microscopically in some detail, including Rashba and Dirac
two-dimensional electron gases coupled to a magnetic insulator, as well as a
diffusive spin Hall system. We focus on the long-wavelength magnetic dynamics
that experiences current-induced torques and produces fictitious electromotive
forces. Our phenomenology provides a suitable framework for analyzing
experiments on current-induced magnetic dynamics and reciprocal charge pumping,
including the effects of magnetoresistance and Gilbert-damping anisotropies,
without a need to resort to any microscopic considerations or modeling.
Finally, some remarks are made regarding the interplay of spin-orbit
interactions and magnetic textures.

###Large Magnetoresistance over an Extended Temperature Regime in Monophosphides of Tantalum and Niobium|Chenglong Zhang,Cheng Guo,Hong Lu,Xiao Zhang,Zhujun Yuan,Ziquan Lin,Junfeng Wang,Shuang Jia###

Large Magnetoresistance over an Extended Temperature Regime in Monophosphides of Tantalum and Niobium. We report extremely large magnetoresistance (MR) in an extended temperature
regime from 1.5 K to 300 K in non-magnetic binary compounds TaP and NbP. TaP
exhibits linear MR around $1.8\times 10^4$ at 2 K in a magnetic field of 9
Tesla, which further follows its linearity up to $1.4\times 10^5$ in a magnetic
field of 56 Tesla at 1.5 K. At room temperature the MR for TaP and NbP follows
a power law of the exponent about $1.5$ with the values larger than $300\%$ in
a magnetic field of 9 Tesla. Such large MR in a wide temperature regime is not
likely only due to a resonance of the electron-hole balance, but indicates a
complicated mechanism underneath.

###Spin-Hall magnetoresistance and spin Seebeck effect in spin-spiral and paramagnetic phases of multiferroic CoCr2O4 films|Aisha Aqeel,Nynke Vlietstra,Jeroen A. Heuver,Gerrit E. W. Bauer,Beatriz Noheda,Bart J. van Wees,Thomas T. M. Palstra###

Spin-Hall magnetoresistance and spin Seebeck effect in spin-spiral and paramagnetic phases of multiferroic CoCr2O4 films. We report on the spin-Hall magnetoresistance (SMR) and spin Seebeck effect
(SSE) in multiferroic CoCr2O4 (CCO) spinel thin films with Pt contacts. We
observe a large enhancement of both signals below the spin-spiral (Ts = 28 K)
and the spin lock-in transitions (T_{lock_in} = 14 K). The SMR and SSE response
in the spin lock-in phase are one order of magnitude larger than those observed
at the ferrimagnetic transition temperature (Tc = 94 K), which indicates that
the interaction between spins at the Pt|CCO interface is more efficient in the
non-collinear magnetic state below Ts and T_{lock-in}. At T > Tc, magnetic
field-induced SMR and SSE signals are observed, which can be explained by a
high interface susceptibility. Our results show that the spin transport at the
Pt|CCO interface is sensitive to the magnetic phases but cannot be explained
solely by the bulk magnetization.

###Macroscopic evidence of skyrmion lattice inhomogeneity and magnetic vortex states in the A-phase of MnSi|S. V. Demishev,I. I. Lobanova,N. E. Sluchanko,V. V. Glushkov###

Macroscopic evidence of skyrmion lattice inhomogeneity and magnetic vortex states in the A-phase of MnSi. The magnetic inhomogeneity of the A-phase in MnSi chiral magnet is identified
for the first time from the precise measurements of transverse
magnetoresistance (MR) anisotropy. The area inside the A-phase (A-phase core)
corresponds to isotropic MR having no confinement to the MnSi crystal lattice.
Per contra, the MR becomes anisotropic both on the border of the A-phase and in
other magnetic phases, the strongest magnetic scattering being observed when
external magnetic field applied along [001] or [00-1] directions. We argue here
that the established MR features prove the presence of two different types of
the skyrmion lattices inside the A-phase, and the dense skyrmion state of the
A-phase core is built from individual skyrmions similar to Abrikosov-type
magnetic vortexes.

###Density of states and magnetotransport in Weyl semimetals with long-range disorder|D. A. Pesin,E. G. Mishchenko,A. Levchenko###

Density of states and magnetotransport in Weyl semimetals with long-range disorder. We study the density of states and magnetotransport properties of disordered
Weyl semimetals, focusing on the case of a strong long-range disorder. To
calculate the disorder-averaged density of states close to nodal points, we
treat exactly the long-range random potential fluctuations produced by charged
impurities, while the short-range component of disorder potential is included
systematically and controllably with the help of a diagram technique. We find
that for energies close to the degeneracy point, long-range potential
fluctuations lead to a finite density of states. In the context of transport,
we discuss that a self-consistent theory of screening in magnetic field may
conceivably lead to non-monotonic low-field magnetoresistance.

###Theory of spin Hall magnetoresistance (SMR) and related phenomena|Yan-Ting Chen,Saburo Takahashi,Hiroyasu Nakayama,Matthias Althammer,Sebastian T. B. Goennenwein,Eiji Saitoh,Gerrit E. W. Bauer###

Theory of spin Hall magnetoresistance (SMR) and related phenomena. We review the recently discovered spin Hall magnetoresistance (SMR) and
related effects from a theoretical point of view. The SMR is observed in
bilayers of a magnetic insulator and a metal, in which spin currents
aregenerated in the normal metal due to the spin Hall effect. The associated
angular momentum transfer to the ferromagnetic layer and thereby the electrical
resistance is modulated by the angle between the applied current and the
magnetization direction. The SMR provides a convenient tool to non-invasively
measure the magnetization direction and spin-transfer torque to an insulator.
We introduce the minimal theoretical instruments to calculate the SMR, i.e.
spin diffusion theory and quantum mechanical boundary conditions. This leads to
a small set of parameters that can be fitted to experiments. We discuss the
limitations of the theory as well as alternative mechanisms such as the
ferromagnetic proximity effect and Rashba spin-orbit torques, and point out new
developments related to the SMR.

###Perpendicular Reading of Single Confined Magnetic Skyrmions|Dax M. Crum,Mohammed Bouhassoune,Juba Bouaziz,Benedikt Schweflinghaus,Stefan Blügel,Samir Lounis###

Perpendicular Reading of Single Confined Magnetic Skyrmions. Thin-film sub-5 nm magnetic skyrmions constitute an ultimate scaling
alternative for future digital data storage. Skyrmions are robust non-collinear
spin-textures that can be moved and manipulated by small electrical currents.
We show here an innovative technique to detect isolated nanoskyrmions with a
current-perpendicular-to-plane geometry, which has immediate implications for
device concepts. We explore the physics behind such a mechanism by studying the
atomistic electronic structure of the magnetic quasiparticles. We investigate
how the isolated skyrmion local-density-of-states which tunnels into the
vacuum, when compared to the ferromagnetic background, is modified by the
site-dependent spin-mixing of electronic states with different relative canting
angles. Local transport properties are sensitive to this effect, as we report
an atomistic conductance anisotropy of over 20% for magnetic skyrmions in
Pd/Fe/Ir(111) thin-films. In single skyrmions, engineering this spin-mixing
magnetoresistance possibly could be incorporated in future magnetic storage
technologies.

###Superconducting Spintronics|Jacob Linder,Jason W. A. Robinson###

Superconducting Spintronics. Traditional studies that combine spintronics and superconductivity have
mainly focused on the injection of spin-polarized quasiparticles into
superconducting materials. However, a complete synergy between superconducting
and magnetic orders turns out to be possible through the creation of
spin-triplet Cooper pairs, which are generated at carefully engineered
superconductor interfaces with ferromagnetic materials. Currently, there is
intense activity focused on identifying materials combinations that merge
superconductivity and spintronics to enhance device functionality and
performance. The results look promising: it has been shown, for example, that
superconducting order can greatly enhance central effects in spintronics such
as spin injection and magnetoresistance. Here, we review the experimental and
theoretical advances in this field and provide an outlook for upcoming
challenges in superconducting spintronics.

###Improvement of the superconducting properties of polycrystalline FeSe by silver addition|E. Nazarova,N. Balchev,K. Nenkov,K. Buchkov,D. Kovacheva,A. Zahariev,G. Fuchs###

Improvement of the superconducting properties of polycrystalline FeSe by silver addition. We investigated the influence of different Ag additions (up to 10 wt %) on
the superconducting properties of FeSe0.94. The structural investigations (XRD
and SEM) indicated that Ag is present in three different forms. Ag at grain
boundaries supports the excellent intergrain connections and reduces
superconducting transition width to values smaller than 1K at B=0 and smaller
than 2.74 K at B=14 T. Ag insertion in the crystal lattice unit cell provides
additional carriers and changes the electron hole imbalance in FeSe0.94. This
results in an increase in the magnetoresistive effect (MR) and critical
temperature (Tc). Reacted Ag forms a small amount (~1%) of Ag2Se impurity
phase, which may increase the pinning energy in comparison with that of the
undoped sample. The enhanced upper critical field (Bc2) is also a result of the
increased impurity scattering. Thus, unlike cuprates Ag addition enhances the
Tc, Bc2, pinning energy and MR making the properties of polycrystalline
FeSe0.94 similar to those of single crystals.

###Spin-dependent transport properties of a GaMnAs-based vertical spin metal-oxide- semiconductor field-effect transistor structure|Toshiki Kanaki,Hirokatsu Asahara,Shinobu Ohya,Masaaki Tanaka###

Spin-dependent transport properties of a GaMnAs-based vertical spin metal-oxide- semiconductor field-effect transistor structure. We fabricate a vertical spin metal-oxide-semiconductor field-effect
transistor (spin-MOSFET) structure, which is composed of an epitaxial
single-crystal heterostructure with a ferromagnetic-semiconductor GaMnAs
source/drain, and investigate its spin-dependent transport properties. We
modulate the drain-source current IDS by ~+ or -0.5 % with a gate-source
voltage of + or -10.8 V and also modulate IDS by up to 60 % with changing the
magnetization configuration of the GaMnAs source/drain at 3.5 K. The
magnetoresistance ratio is more than two orders of magnitude higher than that
obtained in the previous studies on spin MOSFETs. Our result shows that a
vertical structure is one of the hopeful candidates for spin MOSFET when the
device size is reduced to a sub-micron or nanometer scale.

###Tilted Dirac Fermions|Lukas Muechler,Aris Alexandradinata,Titus Neupert,Roberto Car###

Tilted Dirac Fermions. We introduce the notion of a band-inverted, topological semimetal in
two-dimensional nonsymmorphic crystals. This notion is materialized in the
monolayers of MTe$_2$ (M $=$ W, Mo) if spin-orbit coupling is neglected. We
characterize the Dirac band touching topologically by the Wilson loop of the
non-Abelian Berry gauge field. An additional feature of the Dirac cone in
monolayer MTe$_2$ is that it tilts over in a Lifshitz transition to produce
electron and hole pockets, a type-II Dirac cone. These pockets, together with
the pseudospin structure of the Dirac electrons, suggest a unified, topological
explanation for the recently-reported, non-saturating magnetoresistance in
WTe$_2$, as well as its circular dichroism in photoemission. We complement our
analysis and first-principle bandstructure calculations with an
$\textit{ab-initio}$-derived-derived tight-binding model for the WTe$_2$
monolayer.

###Terahertz-induced resistance oscillations in high mobility two-dimensional electron systems|Jesus Inarrea###

Terahertz-induced resistance oscillations in high mobility two-dimensional electron systems. We report on a theoretical work on magnetotransport under terahertz radiation
with high mobility two-dimensional electron systems. We focus on the
interaction between the obtained radiation-induced magnetoresistance
oscillations (RIRO) and the Shubnikov-de Haas (SdHO) oscillations. We study two
effects experimentally obtained with this radiation. First, the observed
disappearance of the SdHO oscillations simultaneously with the vanishing
resistance at the zero resistance states region. And secondly the strong
modulation of the SdHO oscillations at sufficient terahertz radiation power. We
conclude that both effects share the same physical origin, the interference
between the average advanced distance by the scattered electron between
irradiated Landau states, (RIRO), and the available initial density of states
at a certain magnetic field, (SdHO). Thus, from a physical standpoint, what the
terahertz experiments and theoretical simulations reveal is, on the one hand,
the oscillating nature of the Landau states subjected to radiation and, on the
other hand, how they behave in the presence of scattering.

###Magneto-transport measurements on Nd$_{1.83}$Ce$_{0.17}$CuO$_{4\pmδ}$ thin films|Anita Guarino,Antonio Leo,Francesco Avitabile,Nadia Martucciello,Adolfo Avella,Gaia Grimaldi,Alfonso Romano,Paola Romano,Angela Nigro###

Magneto-transport measurements on Nd$_{1.83}$Ce$_{0.17}$CuO$_{4\pmδ}$ thin films. Nd$_{2-x}$Ce$_x$CuO$_{4\pm\delta}$ (NCCO) epitaxial thin films have been
deposited on (100) SrTiO$_3$ substrates by DC sputtering technique in different
atmosphere. The as-grown samples show different dependence of the in-plane
resistivity at low temperature, when they are grown in pure argon atmosphere or
in oxygen. Moreover, an unusual behaviour is also found when transport takes
place in the presence of an external magnetic field. It is commonly accepted
that the higher anisotropic properties of NCCO crystalline cell with respect to
the hole doped YBCO and LSCO and the electric conduction mainly confined in the
CuO$_2$ plane, strongly support the two-dimensional (2D) character of the
current transport in this system. Results on the temperature dependence of the
resistance, as well as on the magnetoresistance and the Hall coefficient,
obtained on epitaxial NCCO thin films in the over-doped region ($x\ge0.15$) of
the phase diagram are presented and discussed.

###Pressure tuning the Fermi-surface topology of the Weyl semimetal NbP|R. D. dos Reis,S. C. Wu,Y. Sun,M. O. Ajeesh,C. Shekhar,M. Schmidt,C. Felser,B. Yan,M. Nicklas###

Pressure tuning the Fermi-surface topology of the Weyl semimetal NbP. We report on the pressure evolution of the Fermi surface topology of the Weyl
semimetal NbP, probed by Shubnikov-de Haas oscillations in the
magnetoresistance combined with ab-initio calculations of the band-structure.
Although we observe a drastic effect on the amplitudes of the quantum
oscillations, the frequencies only exhibit a weak pressure dependence up to 2.8
GPa. The pressure-induce variations in the oscillation frequencies are
consistent with our band-structure calculations. Furthermore, we can relate the
changes in the amplitudes to small modifications in the shape of the Fermi
surface. Our findings evidenced the stability of the electronic band structure
of NbP and demonstrate the power of combining quantum-oscillation studies and
band-structure calculations to investigate pressure effects on the
Fermi-surface topology in Weyl semimetals.

###Magnetoresistance and Shubnikov-de Hass oscillation in YSb|Qiao-He Yu,Yi-Yan Wang,Rui Lou,Peng-Jie Guo,Sheng Xu,Kai Liu,Shancai Wang,Tian-Long Xia###

Magnetoresistance and Shubnikov-de Hass oscillation in YSb. YSb crystals are grown and the transport properties under magnetic field are
measured. The resistivity exhibits metallic behavior under zero magnetic field
and the low temperature resistivity shows a clear upturn once a moderate
magnetic field is applied. The upturn is greatly enhanced by increasing
magnetic field, finally resulting in a metal-to-insulator-like transition. With
temperature further decreased, a resistivity plateau emerges after the
insulator-like regime. At low temperature (2.5 K) and high field (14 T), the
transverse magnetoresistance (MR) is quite large (3.47 $\times 10^4\%$ ). In
addition, Shubnikov-de Haas (SdH) oscillation has also been observed in YSb.
Periodic behavior of the oscillation amplitude reveals the related information
about Fermi surface and two major oscillation frequencies can be obtained from
the FFT spectra of the oscillations. The trivial Berry phase extracted from SdH
oscillation, band structure revealed by angle-resolved photoemission
spectroscopy (ARPES) and first-principles calculations demonstrate that YSb is
a topologically trivial material.

###Detection of HIV-1 antigen based on magnetic tunnel junction sensor and magnetic nanoparticles|L. Li,K. Y. Mak,Y. Zhou,W. W. Wang,P. W. T. Pong###

Detection of HIV-1 antigen based on magnetic tunnel junction sensor and magnetic nanoparticles. In recent years, it is evidenced that the individuals newly infected HIV are
transmitting the virus prior to knowing their HIV status. Identifying
individuals that are early in infection with HIV antibody negative (window
period) remains problematic. In the newly infected individuals, HIV antigen p24
is usually present in their serum or plasma 7-10 days before the HIV antibody.
After antibody production initiates, the p24 antigen is bound into immune
complexes. That means the detectable p24 antigens in serum/plasma are
short-lived, and their amount is in the pg/ml range. Thus, a rapid quantitative
bio-detection system with high-sensitivity is required to achieve early disease
diagnosis. Magnetoresistive (MR) biosensor with ultra-high sensitivity
possesses great potential in this area. In this study, a p24 detection assay
using MgO-based magnetic tunnel junction (MTJ) sensor and 20-nm magnetic
nanoparticles is reported.

###Compensated semimetal LaSb with unsaturated magnetoresistance|L. -K. Zeng,R. Lou,D. -S. Wu,Q. N. Xu,P. -J. Guo,L. -Y. Kong,Y. -G. Zhong,J. -Z. Ma,B. -B. Fu,P. Richard,P. Wang,G. T. Liu,L. Lu,Y. -B. Huang,C. Fang,S. -S. Sun,Q. Wang,L. Wang,Y. -G. Shi,H. M. Weng,H. -C. Lei,K. Liu,S. -C. Wang,T. Qian,J. -L. Luo,H. Ding###

Compensated semimetal LaSb with unsaturated magnetoresistance. By combining angle-resolved photoemission spectroscopy and quantum
oscillation measurements, we performed a comprehensive investigation on the
electronic structure of LaSb, which exhibits near-quadratic extremely large
magnetoresistance (XMR) without any sign of saturation at magnetic fields as
high as 40 T. We clearly resolve one spherical and one intersecting-ellipsoidal
hole Fermi surfaces (FSs) at the Brillouin zone (BZ) center $\Gamma$ and one
ellipsoidal electron FS at the BZ boundary $X$. The hole and electron carriers
calculated from the enclosed FS volumes are perfectly compensated, and the
carrier compensation is unaffected by temperature. We further reveal that LaSb
is topologically trivial but share many similarities with the Weyl semimetal
TaAs family in the bulk electronic structure. Based on these results, we have
examined the mechanisms that have been proposed so far to explain the
near-quadratic XMR in semimetals.

###Platinum/Yttrium Iron Garnet Inverted Structures for Spin Current Transport|Mohammed Aldosary,Junxue Li,Chi Tang,Yadong Xu,Jian-Guo Zheng,Krassimir N. Bozhilov,Jing Shi###

Platinum/Yttrium Iron Garnet Inverted Structures for Spin Current Transport. 30-80 nm thick yttrium iron garnet (YIG) films are grown by pulsed laser
deposition on a 5 nm thick sputtered Pt atop gadolinium gallium garnet
substrate (GGG) (110). Upon post-growth rapid thermal annealing, single crystal
YIG(110) emerges as if it were epitaxially grown on GGG(110) despite the
presence of the intermediate Pt film. The YIG surface shows atomic steps with
the root-mean-square roughness of 0.12 nm on flat terraces. Both Pt/YIG and
GGG/Pt interfaces are atomically sharp. The resulting YIG(110) films show clear
in-plane uniaxial magnetic anisotropy with a well-defined easy axis along <001>
and a peak-to-peak ferromagnetic resonance linewidth of 7.5 Oe at 9.32 GHz,
similar to YIG epitaxilly grown on GGG. Both spin Hall magnetoresistance and
longitudinal spin Seebeck effects in the inverted bilayers indicate excellent
Pt/YIG interface quality.

###Crystal Structure Manipulation of the Exchange Bias in an Antiferromagnetic Film|Wei Yuan,Tang Su,Qi Song,Wenyu Xing,Yangyang Chen,Tianyu Wang,Zhangyuan Zhang,Xiumei Ma,Peng Gao,Jing Shi,Wei Han###

Crystal Structure Manipulation of the Exchange Bias in an Antiferromagnetic Film. Exchange bias is one of the most extensively studied phenomena in magnetism,
since it exerts a unidirectional anisotropy to a ferromagnet (FM) when coupled
to an antiferromagnet (AFM) and the control of the exchange bias is therefore
very important for technological applications, such as magnetic random access
memory and giant magnetoresistance sensors. In this letter, we report the
crystal structure manipulation of the exchange bias in epitaxial hcp Cr2O3
films. By epitaxially growing twined (10-10) oriented Cr2O3 thin films, of
which the c axis and spins of the Cr atoms lie in the film plane, we
demonstrate that the exchange bias between Cr2O3 and an adjacent permalloy
layer is tuned to in-plane from out-of-plane that has been observed in (0001)
oriented Cr2O3 films. This is owing to the collinear exchange coupling between
the spins of the Cr atoms and the adjacent FM layer. Such a highly anisotropic
exchange bias phenomenon is not possible in polycrystalline films.

###Modelling the angle-dependent magnetoresistance oscillations of Fermi surfaces with hexagonal symmetry|Joseph C. A. Prentice,Amalia I. Coldea###

Modelling the angle-dependent magnetoresistance oscillations of Fermi surfaces with hexagonal symmetry. By solving the Boltzmann transport equation we investigate theoretically the
general form of oscillations in the resistivity caused by varying the direction
of an applied magnetic field for the case of quasi-two dimensional systems on
hexagonal lattices. The presence of the angular magnetoresistance oscillations
can be used to map out the topology of the Fermi surface and we study how this
effect varies as a function of the degree of interplane warping as well as a
function of the degree of isotropic scattering. We find that the angular
dependent effect due to in-plane rotation follows the symmetry imposed by the
lattice whereas for inter-plane rotation the degree of warping dictates the
dominant features observed in simulations. Our calculations make predictions
for specific angle-dependent magnetotransport signatures in magnetic fields
expected for quasi-two dimensional hexagonal compounds similar to PdCoO2 and
PtCoO2.

###Competing effects at Pt/YIG interfaces: spin Hall magnetoresistance, magnon excitations and magnetic frustration|Saül Vélez,Amilcar Bedoya-Pinto,Wenjing Yan,Luis E. Hueso,Fèlix Casanova###

Competing effects at Pt/YIG interfaces: spin Hall magnetoresistance, magnon excitations and magnetic frustration. We study the spin Hall magnetoresistance (SMR) and the magnon spin transport
(MST) in Pt/Y3Fe5O12(YIG)-based devices with intentionally modified interfaces.
Our measurements show that the surface treatment of the YIG film results in a
slight enhancement of the spin-mixing conductance and an extraordinary increase
in the efficiency of the spin-to-magnon excitations at room temperature. The
surface of the YIG film develops a surface magnetic frustration at low
temperatures, causing a sign change of the SMR and a dramatic suppression of
the MST. Our results evidence that SMR and MST could be used to explore
magnetic properties of surfaces, including those with complex magnetic
textures, and stress the critical importance of the non-magnetic/ferromagnetic
interface properties in the performance of the resulting spintronic devices.

###Origin of the large positive magnetoresistance in Ge1-xMnx granular thin films|Yuki K. Wakabayashi,Ryota Akiyama,Yukiharu Takeda,Masafumi Horio,Goro Shibata,Shoya Sakamoto,Yoshisuke Ban,Yuji Saitoh,Hiroshi Yamagami,Atsushi Fujimori,Masaaki Tanaka,Shinobu Ohya###

Origin of the large positive magnetoresistance in Ge1-xMnx granular thin films. GeMn granular thin films are a unique and promising material for spintronics
applications due to large positive magnetoresistance (MR). Previous studies on
GeMn have suggested that the large MR is related to nanospinodal decomposition
of GeMn into Mn-rich ferromagnetic nanoparticles and Mn-poor paramagnetic
matrix. However, its microscopic origin of the MR has not been clarified yet.
Here, using X-ray magnetic circular dichroism (XMCD), which is extremely
sensitive to the local magnetic state of each atom, we investigate the magnetic
properties of the nanoparticles and the matrix in GeMn separately. We find that
the MR ratio is proportional to the product of the magnetizations originating
from the nanoparticles and the matrix. This result indicates that
spin-polarized holes in the nanoparticles penetrate into the matrix and that
these holes undergo spin-disorder magnetic scattering by the paramagnetic Mn
atoms in the matrix, which induces the large MR.

###Bilayer splitting versus Fermi-surface warping as an origin of slow oscillations of in-plane magnetoresistance in rare-earth tritellurides|Pavel D. Grigoriev,Alexander A. Sinchenko,Pascal Lejay,Abdellali Hadj-Azzem,Joel Balay,Olivier Leynaud,Vladimir N. Zverev,Pierre Monceau###

Bilayer splitting versus Fermi-surface warping as an origin of slow oscillations of in-plane magnetoresistance in rare-earth tritellurides. Slow oscillations (SlO) of the in-plane magnetoresistance with a frequency
less than 4 T are observed in the rare-earth tritellurides and proposed as an
effective tool to explore the electronic structure in various strongly
anisotropic quasi-two-dimensional compounds. Contrary to the usual
Shubnikov-de-Haas oscillations, SlO originate not from small Fermi-surface
pockets, but from the entanglement of close frequencies due to a finite
interlayer transfer integral, either between the two Te planes forming a
bilayer or between two adjacent bilayers. From the observed angular dependence
of the frequency and the phase of SlO we argue that they originate from the
bilayer splitting rather than from the Fermi-surface warping. The SlO frequency
gives the value of the interlayer transfer integral $\approx 1$ meV for
TbTe$_3$ and GdTe$_3$.

###Mobility induced unsaturated high linear magnetoresistance in transition-metal monopnictides Weyl semimetals|Chandra Shekhar,Vicky Süss,Marcus Schmidt###

Mobility induced unsaturated high linear magnetoresistance in transition-metal monopnictides Weyl semimetals. Discovery of Weyl fermions in semimetallic tansition-metal monopnictides is a
major breakthrough in condensed matter physics. A Weyl semimetal is
characterized by the existence of robust Weyl points and unclosed topological
surface states in the form of Fermi arc. All the four compounds of the Weyl
semimetal transition monopnictide family i.e. NbP, TaP, NbAs and TaAs exhibit
extremely high mobility and unsaturated high magnetoresistance (MR). For
example, MR values are 8.5x10^5% at 1.85 K for NbP and 1.5x10^5% at 3 K in 9 T
for TaAs. NbP also achieves very low value of residual resistivity 0.63
micro-ohm cm at 2 K due to suppression of scattering resulting in ultra-high
mobility 5x10^6 cm^2/Vs, Interestingly, we find that the mobility of these
compounds play an important role for such a large MR.

###Z_2 and Chiral Anomalies in Topological Dirac Semimetals|Anton A. Burkov,Yong Baek Kim###

Z_2 and Chiral Anomalies in Topological Dirac Semimetals. We demonstrate that topological Dirac semimetals, which possess two Dirac
nodes, separated in momentum space along a rotation axis and protected by
rotational symmetry, exhibit an additional quantum anomaly, distinct from the
chiral anomaly. This anomaly, which we call the $ \mathbb Z_2$ anomaly, is a
consequence of the fact that the Dirac nodes in topological Dirac semimetals
carry a $\mathbb Z_2$ topological charge. The $\mathbb Z_2$ anomaly refers to
nonconservation of this charge in the presence of external fields due to
quantum effects and has observable consequences due to its interplay with the
chiral anomaly. We discuss possible implications of this for the interpretation
of magnetotransport experiments on topological Dirac semimetals. We also
provide a possible explanation for the magnetic field dependent angular
narrowing of the negative longitudinal magnetoresistance, observed in a recent
experiment on Na$_3$Bi.

###Important role of magnetization precession angle measurement in inverse spin Hall effect induced by spin pumping|Surbhi Gupta,Rohit Medwal,Daichi Kodama,Kouta Kondou,YoshiChika Otani,Yasuhiro Fukuma###

Important role of magnetization precession angle measurement in inverse spin Hall effect induced by spin pumping. Here, we investigate spin Hall angle of Pt in Ni80Fe20/Pt bilayer system by
using a broadband spin pumping and inverse spin Hall effect measurement. An
out-of-plane excitation geometry with application of external magnetic field
perpendicular to the charge current direction is utilized in order to suppress
unwanted galvanomagnetic effects. Magnetization precession angle on
ferromagnetic resonance for wide excitation frequency range (4-14 GHz) is
estimated from the rectification voltage of anisotropic magnetoresistance (AMR)
and a conventional method of using microwave power in a coplanar waveguide. A
marked difference in the precession angle profiles for the different methods is
observed, resulting in the large variation in estimated values of spin current
density at Ni80Fe20/Pt interface. The frequency dependence of the spin current
density estimated using AMR effect is found to be similar to that of the
inverse spin Hall voltage. We obtain the frequency-invariant spin Hall angle of
0.067.

###Quantum oscillations in metallic Sb2Te2Se topological insulator|K. Shrestha,V. Marinova,D. Graf,B. Lorenz,C. W. Chu###

Quantum oscillations in metallic Sb2Te2Se topological insulator. We have studied the magnetotransport properties of the metallic, p-type
Sb2Te2Se which is a topological insulator. Magnetoresistance shows Shubnikov de
Haas oscillations in fields above B=15 T. The maxima/minima positions of
oscillations measured at different tilt angles with respect to the B direction
align with the normal component of field Bcosine, implying the existence of a
2D Fermi surface in Sb2Te2Se. The value of the Berry phase determined from a
Landau level fan diagram is very close to 0.5, further suggesting that the
oscillations result from topological surface states. From Lifshitz-Kosevich
analyses, the position of the Fermi level is found to be EF =250 meV, above the
Dirac point. This value of EF is almost 3 times as large as that in our
previous study on the Bi2Se2:1Te0:9 topological insulator; however, it still
touches the tip of the bulk valence band. This explains the metallic behavior
and hole-like bulk charge carriers in the Sb2Te2Se compound.

###Nonlocal magnon spin transport in NiFe$_2$O$_4$ thin films|J. Shan,P. Bougiatioti,L. Liang,G. Reiss,T. Kuschel,B. J. van Wees###

Nonlocal magnon spin transport in NiFe$_2$O$_4$ thin films. We report magnon spin transport in nickel ferrite (NiFe$_2$O$_4$, NFO)/
platinum (Pt) bilayer systems at room temperature. A nonlocal geometry is
employed, where the magnons are excited by the spin Hall effect or by the Joule
heating induced spin Seebeck effect at the Pt injector, and detected at a
certain distance away by the inverse spin Hall effect at the Pt detector. The
dependence of the nonlocal magnon spin signals as a function of the magnetic
field is closely related to the NFO magnetization behavior. In contrast, we
observe that the magnetoresistance measured locally at the Pt injector does not
show a clear relation with the average NFO magnetization. We estimate the
magnon spin relaxation length to be 3.1 $\pm$ 0.2 $\mu$m in the investigated
NFO samples.

###Saturation of resistivity and Kohler's rule in Ni-doped La$_{1.85}$Sr$_{0.15}$CuO$_{4}$ cuprate|A. Malinowski,V. L. Bezusyy,P. Nowicki###

Saturation of resistivity and Kohler's rule in Ni-doped La$_{1.85}$Sr$_{0.15}$CuO$_{4}$ cuprate. We present the results of electrical transport measurements of
La$_{1.85}$Sr$_{0.15}$Cu$_{1-y}$Ni$_{y}$O$_{4}$ thin single-crystal films at
magnetic fields up to 9 T. Adding Ni impurity with strong Coulomb scattering
potential to slightly underdoped cuprate makes the signs of resistivity
saturation at $\rho_{sat}$ visible in the measurement temperature window up to
350 K. Employing the parallel-resistor formalism reveals that $\rho_{sat}$ is
consistent with classical Ioffe-Regel-Mott limit and changes with carrier
concentration $n$ as $\rho_{sat}\propto 1/\sqrt{n}$. Thermopower measurements
show that Ni tends to localize mobile carriers, decreasing their effective
concentration as $n\!\cong0.15\!-\!y$. The classical unmodified Kohler's rule
is fulfilled for magnetoresistance in the nonsuperconducting part of the phase
diagram when applied to the ideal branch in the parallel-resistor model.

###Understanding magnetotransport signatures in networks of connected permalloy nanowires|Brian Le,Jungsik Park,Joseph Sklenar,Gia-Wei Chern,Cristiano Nisoli,Justin Watts,Michael Manno,David Rench,Nitin Samarth,Chris Leighton,Peter Schiffer###

Understanding magnetotransport signatures in networks of connected permalloy nanowires. The change in electrical resistance associated with the application of an
external magnetic field is known as the magnetoresistance (MR). The measured MR
is quite complex in the class of connected networks of single-domain
ferromagnetic nanowires, known as "artificial spin ice", due to the
geometrically-induced collective behavior of the nanowire moments. We have
conducted a thorough experimental study of the MR of a connected honeycomb
artificial spin ice, and we present a simulation methodology for understanding
the detailed behavior of this complex correlated magnetic system. Our results
demonstrate that the behavior, even at low magnetic fields, can be
well-described only by including significant contributions from the vertices at
which the legs meet, opening the door to new geometrically-induced MR
phenomena.

###Understanding stability diagram of perpendicular magnetic tunnel junctions|Witold Skowroński,Maiej Czapkiewicz,Sławomir Ziętek,Jakub Chęciński,Marek Frankowski,Piotr Rzeszut,Jerzy Wrona###

Understanding stability diagram of perpendicular magnetic tunnel junctions. Perpendicular magnetic tunnel junctions (MTJ) with a bottom pinned reference
layer and a composite free layer (FL) are investigated. Different thicknesses
of the FL were tested to obtain an optimal balance between tunneling
magnetoresistance (TMR) ratio and perpendicular magnetic anisotropy. After
annealing at 400 $^\circ$C, the TMR ratio for 1.5 nm thick CoFeB sublayer
reached 180 % at room temperature and 280 % at 20 K with an MgO tunnel barrier
thickness corresponding to the resistance area product RA = 10
Ohm$\mathrm{\mu}$m$^2$. The voltage vs. magnetic field stability diagrams
measured in pillar-shaped MTJs with 130 nm diameter indicate the competition
between spin transfer torque (STT), voltage controlled magnetic anisotropy
(VCMA) and temperature effects in the switching process. An extended stability
phase diagram model that takes into account all three parameters and the
effective damping measured independently using broadband ferromagnetic
resonance technique enabled the determination of both STT and VCMA coefficients
that are responsible for the FL magnetization switching.

###Novel Majorana mode and magnetoresistance in ferromagnetic superconducting topological insulator|Hadi Goudarzi,Maryam Khezerlou,Samin Asgarifar###

Novel Majorana mode and magnetoresistance in ferromagnetic superconducting topological insulator. Among the potential applications of topological insulators, we investigate
theoretically the effect of coexistence of proximity-induced ferromagnetism and
superconductivity on the surface states of 3-dimensional topological insulator,
where the superconducting electron-hole excitations can be significantly
affected by the magnetization of ferromagnetic order. We find that, Majorana
mode energy, as a verified feature of TI F/S structure, along the interface
sensitively depends on the magnitude of magnetization $m_{zfs}$ in FS region,
while its slope in perpendicular incidence presents steep and no change. Since
the superconducting gap is renormalized by a factor $\eta(m_{zfs})$, hence
Andreev reflection is more or less suppressed, and, in particular, resulting
subgap tunneling conductance is more sensitive to the magnitude of
magnetizations in FS and F regions. Furthermore, an interesting scenario
happens at the antiparallel configuration of magnetizations $m_{zf}$ and
$m_{zfs}$ resulting in magnetoresistance in N/F/FS junction, which can be
controlled and decreased by tuning the magnetization magnitude in FS region.

###Negative differential resistance and magnetoresistance in zigzag borophene nanoribbons|Jiayi Liu,Changpeng Chen,Lu Han,Ziqing Zhu,Jinping Wu###

Negative differential resistance and magnetoresistance in zigzag borophene nanoribbons. We investigate the transport properties of pristine zigzag-edged borophene
nanoribbons (ZBNRs) of different widths, using the fist-principles
calculations. We choose ZBNRs with widths of 5 and 6 as odd and even widths.
The differences of the quantum transport properties are found, where even-N
BNRs and odd-N BNRs have different current-voltage relationships. Moreover, the
negative differential resistance (NDR) can be observed within certain bias
range in 5-ZBNR, while 6-ZBNR behaves as metal whose current rises with the
increase of the voltage. The spin filter effect of 36% can be revealed when the
two electrodes have opposite magnetization direction. Furthermore, the
magnetoresistance effect appears to be in even-N ZBNRs, and the maximum value
can reach 70%.

###Impact of the skyrmion spin texture on magnetoresistance|André Kubetzka,Christian Hanneken,Roland Wiesendanger,Kirsten von Bergmann###

Impact of the skyrmion spin texture on magnetoresistance. We investigate the impact of the local spin texture on the differential
conductance by scanning tunneling microscopy. In the focus is the previously
found non-collinear magnetoresistance, which originates from spin mixing
effects upon electron hopping between adjacent sites with canted magnetic
moments. In the present work it is studied with lateral resolution both for the
zero magnetic field spin spiral state as well as for individual magnetic
skyrmions at different magnetic field values. We analyze in detail the response
of the differential conductance and find different dependencies of peak energy
and peak intensity on the local properties of the non-collinear spin texture.
We find that in the center of a skyrmion the peak energy and intensity scale
roughly linear with the angle between nearest neighbor moments. Elsewhere in
the skyrmion, where the non-collinearity is not isotropic and the magnetization
quantization axis varies, the behavior of the peak energy is more complex.

###Magnetic Field-Free Giant Magnetoresistance in a Proximity- and Gate-Induced Graphene Spin Valve|Yu Song###

Magnetic Field-Free Giant Magnetoresistance in a Proximity- and Gate-Induced Graphene Spin Valve. Due to its two dimensional nature, ferromagnetism and charge doping can be
induced by proximity and electric field effects in graphene. Taking advantage
of these features, we propose an electrically engineered spin valve by
combining two magnetic insulators (using EuO, EuS, or YIG) and three coating
gates. Two top gates are used to cancel the heavy electron doping's in these
magnets and one back gate is used to utilize the normal or half-metallic
ferromagnetisms. We demonstrate that, when the second top gate is tuned to
utilize the insulating or spin insulating states, huge giant magnetoresistance
(GMR) at high temperature (several times of $10^5\%$ at 68K and 100K) can be
achieved for EuO and YIG. These results imply a distinguished GMR that is
magnetism tunable, vertical configured (ferromagnetism versus insulating), and
magnetic field-free. Our work may offer a viable path to a tantalizing magnetic
field-free spintronics.

###Negative Magnetoresistance without Chiral Anomaly in Topological Insulators|Xin Dai,Z. Z. Du,Hai-Zhou Lu###

Negative Magnetoresistance without Chiral Anomaly in Topological Insulators. An intriguing phenomenon in topological semimetals and topological insulators
is the negative magnetoresistance (MR) observed when a magnetic field is
applied along the current direction. A prevailing understanding to the negative
MR in topological semimetals is the chiral anomaly, which, however, is not well
defined in topological insulators. We calculate the MR of a three-dimensional
topological insulator, by using the semiclassical equations of motion, in which
the Berry curvature explicitly induces an anomalous velocity and orbital
moment. Our theoretical results are in quantitative agreement with the
experiments. The negative MR is not sensitive to temperature and increases as
the Fermi energy approaches the band edge. The orbital moment and g factors
also play important roles in the negative MR. Our results give a reasonable
explanation to the negative MR in 3D topological insulators and will be helpful
in understanding the anomalous quantum transport in topological states of
matter.

###Aharonov-Bohm effect in monolayer black phosphorus (phosphorene) nanorings|Rui Zhang,Zhenhua Wu,Xiaojing Li,Kai Chang###

Aharonov-Bohm effect in monolayer black phosphorus (phosphorene) nanorings. This work presents theoretical demonstration of Aharonov-Bohm (AB) effect in
monolayer phosphorene nanorings (PNR). Atomistic quantum transport simulations
of PNR are employed to investigate the impact of multiple modulation sources on
the sample conductance. In presence of a perpendicular magnetic field, we find
that the conductance of both armchair and zigzag PNR oscillate periodically in
a low-energy window as a manifestation of the AB effect. Our numerical results
have revealed a giant magnetoresistance (MR) in zigzag PNR (with a maximum
magnitude approaching two thousand percent). It is attributed to the AB effect
induced destructive interference phase in a wide energy range below the bottom
of the second subband. We also demonstrate that PNR conductance is highly
anisotropic, offering an additional way to modulate MR. The giant MR in PNR is
maintained at room temperature in the presence of thermal broadening effect.

###Raman study of electron-phonon coupling in thin films of LiTi$_2$O$_4$ spinel oxide superconductor|D. Chen,Y. -L. Jia,T. -T. Zhang,Z. Fang,K. Jin,P. Richard,H. Ding###

Raman study of electron-phonon coupling in thin films of LiTi$_2$O$_4$ spinel oxide superconductor. We performed a Raman scattering study of thin films of LiTi$_2$O$_4$ spinel
oxide superconductor. We detected four out of five Raman active modes, with
frequencies in good accordance with our first-principles calculations. Three
T$_{2g}$ modes show a Fano lineshape from 5 K to 295 K, which suggests an
electron-phonon coupling in LiTi$_2$O$_4$. Interestingly, the electron-phonon
coupling shows an anomaly across the negative to positive magnetoresistance
transition at 50 K, which may be due to the unset of other competing orders.
The strength of the electron-phonon interaction estimated from the Allen's
formula and the observed lineshape parameters suggests that the three T$_{2g}$
modes contribute little to superconductivity.

###Pressure-induced melting of magnetic order and emergence of new quantum state in alpha-RuCl3|Zhe Wang,Jing Guo,F. F. Tafti,Anthony Hegg,Sudeshna Sen,Vladimir A Sidorov,Le Wang,Shu Cai,Wei Yi,Yazhou Zhou,Honghong Wang,Shan Zhang,Ke Yang,Aiguo Li,Xiaodong Li,Yanchun Li,Jing Liu,Youguo Shi,Wei Ku,Qi Wu,Robert J Cava,Liling Sun###

Pressure-induced melting of magnetic order and emergence of new quantum state in alpha-RuCl3. Here we report the observation of pressure-induced melting of
antiferromagnetic (AFM) order and emergence of a new quantum state in the
honeycomb-lattice halide alpha-RuCl3, a candidate compound in the proximity of
quantum spin liquid state. Our high-pressure heat capacity measurements
demonstrate that the AFM order smoothly melts away at a critical pressure (Pc)
of 0.7 GPa. Intriguingly, the AFM transition temperature displays an increase
upon applying pressure below the Pc, in stark contrast to usual phase diagrams,
for example in pressurized parent compounds of unconventional superconductors.
Furthermore, in the high-pressure phase an unusual steady of magnetoresistance
is observed. These observations suggest that the high-pressure phase is in an
exotic gapped quantum state which is robust against pressure up to ~140 GPa.

###Charge transfer driven emergent phenomena in oxide heterostructures|Hanghui Chen,Andrew J. Millis###

Charge transfer driven emergent phenomena in oxide heterostructures. Complex oxides exhibit many intriguing phenomena, including metal-insulator
transition, ferroelectricity/multiferroicity, colossal magnetoresistance and
high transition temperature superconductivity. Advances in epitaxial thin film
growth techniques enable us to combine different complex oxides with atomic
precision and form an oxide heterostructure. Recent theoretical and
experimental work has shown that charge transfer across oxide interfaces
generally occurs and leads to a great diversity of emergent interfacial
properties which are not exhibited by bulk constituents. In this report, we
review mechanisms and physical consequence of charge transfer across interfaces
in oxide heterostructures. Both theoretical proposals and experimental
measurements of various oxide heterostructures are discussed and compared. We
also review the theoretical methods that are used to calculate charge transfer
across oxide interfaces and discuss the success and challenges in theory.
Finally, we present a summary and perspectives for future research.

###Interaction between magnetic moments and itinerant carriers in d0 ferromagnetic SiC|Yu Liu,Ye Yuan,Fang Liu,Roman Boettger,Wolfgang Anwand,Yutian Wang,Anna Semisalova,Alexey N. Ponomaryov,Xia Lu,Alpha T. N'Diaye,Elke Arenholz,Viton Heera,Wolfgang Skorupa,Manfred Helm,Shengqiang Zhou###

Interaction between magnetic moments and itinerant carriers in d0 ferromagnetic SiC. Elucidating the interaction between magnetic moments and itinerant carriers
is an important step to spintronic applications. Here, we investigate magnetic
and transport properties in d0 ferromagnetic SiC single crystals prepared by
postimplantation pulsed laser annealing. Magnetic moments are contributed by
the p states of carbon atoms, but their magnetic circular dichroism is
different from that in semi-insulating SiC samples. The anomalous Hall effect
and negative magnetoresistance indicate the influence of d0 spin order on free
carriers. The ferromagnetism is relatively weak in N-implanted SiC compared
with that in Al-implanted SiC after annealing. The results suggest that d0
magnetic moments and itinerant carriers can interact with each other, which
will facilitate the development of SiC spintronic devices with d0
ferromagnetism.

###High-temperature intrinsic ferromagnetism in the (In,Fe)Sb semiconductor|A. V. Kudrin,Yu. A. Danilov,V. P. Lesnikov,O. V. Vikhrova,D. A. Pavlov,Yu. V. Usov,I. N. Antonov,R. N. Krukov,N. A. Sobolev###

High-temperature intrinsic ferromagnetism in the (In,Fe)Sb semiconductor. The (In,Fe)Sb layers with the Fe content up to 13 at. % have been grown on
(001) GaAs substrates using the pulsed laser deposition. The TEM investigations
show that the (In,Fe)Sb layers are epitaxial and free of the inclusions of a
second phase. The observation of the hysteretic magnetoresistance curves at
temperatures up to 300 K reveals that the Curie point is above room
temperature. The resonant character of magnetic circular dichroism confirms the
intrinsic ferromagnetism in the (In,Fe)Sb layers. We suggest that the
ferromagnetism of the (In,Fe)Sb matrix is not carrier-mediated and apparently
is determined by the mechanism of superexchange interaction between Fe atoms
(This work was presented at the XXI Symposium Nanophysics and Nanoelectronics,
Nizhny Novgorod, March, 13-16, 2017 (book of proceedings v.1, p. 195),
http://nanosymp.ru/UserFiles/Symp/2017_v1.pdf).

###Electrostatic tuning of magnetism at the conducting (111) (La$_{0.3}$Sr$_{0.7}$)(Al$_{0.65}$Ta$_{0.35}$)/SrTiO$_3$ interface|V. V. Bal,Z. Huang,K. Han,Ariando,T. Venkatesan,V. Chandrasekhar###

Electrostatic tuning of magnetism at the conducting (111) (La$_{0.3}$Sr$_{0.7}$)(Al$_{0.65}$Ta$_{0.35}$)/SrTiO$_3$ interface. We present measurements of the low temperature electrical transport
properties of the two dimensional carrier gas that forms at the interface of
$(111)$ (La$_{0.3}$Sr$_{0.7}$)(Al$_{0.65}$Ta$_{0.35}$)/SrTiO$_3$ (LSAT/STO) as
a function of applied back gate voltage, $V_g$. As is found in (111)
LaAlO$_3$/SrTiO$_3$ interfaces, the low-field Hall coefficient is
electron-like, but shows a sharp reduction in magnitude below $V_g \sim$ 20 V,
indicating the presence of hole-like carriers in the system. This same value of
$V_g$ correlates approximately with the gate voltage below which the
magnetoresistance evolves from nonhysteretic to hysteretic behavior at
millikelvin temperatures, signaling the onset of magnetic order in the system.
We believe our results can provide insight into the mechanism of magnetism in
SrTiO$_3$ based systems.

###Topological Phase Transition Under Pressure in the Topological Nodal Line Superconductor PbTaSe$_2$|C. Q. Xu,R. Sankar,W. Zhou,Bin Li,Z. D. Han,B. Qian,J. H. Dai,Hengbo Cui,A. F. Bangura,F. C. Chou,Xiaofeng Xu###

Topological Phase Transition Under Pressure in the Topological Nodal Line Superconductor PbTaSe$_2$. A first-order-like resistivity hysteresis is induced by a subtle structural
transition under hydrostatic pressure in the topological nodal-line
superconductor PbTaSe$_2$. This structure transition is quickly suppressed to
zero at pressure $\sim$0.25 GPa. As a result, superconductivity shows a marked
suppression, accompanied with fundamental changes in the magnetoresistance and
Hall resistivity, suggesting a Lifshitz transition around $\sim$0.25 GPa. The
first principles calculations show that the spin-orbit interactions partially
gap out the Dirac nodal line around $K$ point in the Brillouin zone upon
applying a small pressure, whilst the Dirac states around $H$ point are
completely destroyed. The calculations further reveal a second structural phase
transition under a pressure as high as $\sim$30 GPa, through which a transition
from a topologically nontrivial phase to a trivial phase is uncovered, with a
superconducting dome emerging under this high-pressure phase.

###Hydrodynamic flows of non-Fermi liquids: magnetotransport and bilayer drag|Aavishkar A. Patel,Richard A. Davison,Alex Levchenko###

Hydrodynamic flows of non-Fermi liquids: magnetotransport and bilayer drag. We consider a hydrodynamic description of transport for generic two
dimensional electron systems that lack Galilean invariance and do not fall into
the category of Fermi liquids. We study magnetoresistance and show that it is
governed only by the electronic viscosity provided that the wavelength of the
underlying disorder potential is large compared to the microscopic
equilibration length. We also derive the Coulomb drag transresistance for
double-layer non-Fermi liquid systems in the hydrodynamic regime. As an
example, we consider frictional drag between two quantum Hall states with
half-filled lowest Landau levels, each described by a Fermi surface of
composite fermions coupled to a $U(1)$ gauge field. We contrast our results to
prior calculations of drag of Chern-Simons composite particles and place our
findings in the context of available experimental data.

###Hidden peculiar magnetic anisotropy at the interface in a ferromagnetic perovskite-oxide heterostructure|Le Duc Anh,Noboru Okamoto,Munetoshi Seki,Hitoshi Tabata,Masaaki Tanaka,Shinobu Ohya###

Hidden peculiar magnetic anisotropy at the interface in a ferromagnetic perovskite-oxide heterostructure. Understanding and controlling the interfacial magnetic properties of
ferromagnetic thin films are crucial for spintronic device applications.
However, using conventional magnetometry, it is difficult to detect them
separately from the bulk properties. Here, by utilizing tunneling anisotropic
magnetoresistance in a single-barrier heterostructure composed of
La0.6Sr0.4MnO3 (LSMO)/ LaAlO3 (LAO)/ Nb-doped SrTiO3 (001), we reveal the
presence of a peculiar strong two-fold magnetic anisotropy (MA) along the
[110]c direction at the LSMO/LAO interface, which is not observed in bulk LSMO.
This MA shows unknown behavior that the easy magnetization axis rotates by
90{\deg} at an energy of 0.2 eV below the Fermi level in LSMO. We attribute
this phenomenon to the transition between the eg and t2g bands at the LSMO
interface. Our finding and approach to understanding the energy dependence of
the MA demonstrate a new possibility of efficient control of the interfacial
magnetic properties by controlling the band structures of oxide
heterostructures.

###The effects of oxygen in spinel oxide Li1+xTi2-xO4-delta thin films|Yanli Jia,Ge He,Wei Hu,Hua Yang,Zhenzhong Yang,Heshan Yu,Qinghua Zhang,Jinan Shi,Zefeng Lin,Jie Yuan,Beiyi Zhu,Lin Gu,Hong Li,Kui Jin###

The effects of oxygen in spinel oxide Li1+xTi2-xO4-delta thin films. The evolution from superconducting LiTi2O4-delta to insulating Li4Ti5O12 thin
films has been studied by precisely adjusting the oxygen pressure during the
sample fabrication process. In the superconducting LiTi2O4-delta films, with
the increase of oxygen pressure, the oxygen vacancies are filled, and the
c-axis lattice constant decreases gradually. With the increase of the oxygen
pressure to a certain critical value, the c-axis lattice constant becomes
stable, which implies that the Li4Ti5O12 phase comes into being. The process of
oxygen filling is manifested by the angular bright-field images of the scanning
transmission electron microscopy techniques. The temperature of
magnetoresistance changed from positive and negative shows a non-monotonous
behavior with the increase of oxygen pressure. The theoretical explanation of
the oxygen effects on the structure and superconductivity of LiTi2O4-delta has
also been discussed in this work.

###Fermi Surface reconstruction and anomalous low temperature resistivity in electron-doped La2-xCexCuO4|Tarapada Sarkar,P. R. Mandal,J. S. Higgins,Yi Zhao,Heshan Yu,Kui Jin,Richard L. Greene###

Fermi Surface reconstruction and anomalous low temperature resistivity in electron-doped La2-xCexCuO4. We report ab-plane Hall Effect and magnetoresistivity measurements on
La2-xCexCuO4 thin films as a function of doping for magnetic fields up to 14T
and temperatures down to 1.8K. A dramatic change in the low temperature (1.8 K)
normal state Hall coefficient is found near a doping Ce=0.14. This, along with
a nonlinear Hall resistance as a function of magnetic field, suggests that the
Fermi surface reconstructs at a critical doping of Ce= 0.14. A competing
antiferromagnetic phase is the likely cause of this Fermi surface
reconstruction. Low temperature linear-in-T resistivity is found at Ce=0.14,
but anomalously, also at higher doping. We compare our data with similar
behavior found in hole-doped cuprates at a doping where the pseudogap ends

###Semitransparent anisotropic and spin Hall magnetoresistance sensor enabled by spin-orbit toque biasing|Yumeng Yang,Yanjun Xu,Hang Xie,Baoxi Xu,Yihong Wu###

Semitransparent anisotropic and spin Hall magnetoresistance sensor enabled by spin-orbit toque biasing. We demonstrate an ultrathin and semitransparent anisotropic and spin Hall
magnetoresistance sensor based on NiFe/Pt heterostructure. The use of
spin-orbit torque effective field for transverse biasing allows to reduce the
total thickness of the sensors down to 3 - 4 nm and thereby leading to the
semitransparency. Despite the extremely simple design, the spin-orbit torque
effective field biased NiFe/Pt sensor exhibits level of linearity and
sensitivity comparable to those of sensors using more complex linearization
schemes. In a proof-of-concept design using a full Wheatstone bridge comprising
of four sensing elements, we obtained a sensitivity up to 202.9 m{\Omega}/Oe,
linearity error below 5%, and a detection limit down to 20 nT. The
transmittance of the sensor is over 50% in the visible range.

###Emerging Magnetic Order In Copper Induced By Proximity To Cobalt: A Detailed Soft X-Ray Spectroscopy Study|Zhao Chen,Hendrik Ohldag,Tyler Chase,Sohrab Sani,Roopali Kukreja,Stefano Bonetti,Andrew D. Kent,Eric E. Fullerton,Hermann A. Dürr,Joachim Stöhr###

Emerging Magnetic Order In Copper Induced By Proximity To Cobalt: A Detailed Soft X-Ray Spectroscopy Study. We present an x-ray magnetic dichroism (XMCD) and soft x-ray absorption
spectroscopy (XAS) study to address the nature of emerging magnetic order in
metallic Copper as Cobalt is added to the matrix. For this purpose line shape
and energy position of XAS and XMCD spectra will be analyzed for a series of
Co/Cu alloys as well as a multilayer reference. We observe an increased
hybridization between Cu and Co sites as well as increased localization of the
Cu d-electrons and an induced magnetic moment in Cu. The emergence of long
range magnetic order in non-magnetic materials that are in proximity to a
ferromagnet is significant for a comprehensive interpretation of transport
phenomena at ferromagnetic/non-magnetic interfaces, like e.g. the giant
magnetoresistance effect. The presented results will further enable us to
interpret Cu XMCD and XAS spectra acquired from unknown Co/Cu samples to
identify the environment of Cu atoms exhibiting proximity induced magnetism.

###Backreacted DBI Magnetotransport with Momentum Dissipation|Sera Cremonini,Anthony Hoover,Li Li###

Backreacted DBI Magnetotransport with Momentum Dissipation. We examine magnetotransport in a holographic Dirac-Born-Infeld model, taking
into account the effects of backreaction on the geometry. The theory we
consider includes axionic scalars, introduced to break translational symmetry
and generate momentum dissipation. The generic structure of the DC conductivity
matrix for these theories is extremely rich, and is significantly more complex
than that obtained in the probe approximation. We find new classes of black
brane solutions, including geometries that exhibit Lifshitz scaling and
hyperscaling violation, and examine their implications on the transport
properties of the system. Depending on the choice of theory parameters, these
backgrounds can lead to metallic or insulating behavior. Negative
magnetoresistance is observed in a family of dynoic solutions. Some of the new
backreacted geometries also support magnetic-field-induced metal-insulator
transitions.

###Polarity-tunable magnetic tunnel junctions based on ferromagnetism at oxide heterointerfaces|Thach D. N. Ngo,Jung-Won Chang,Kyujoon Lee,Seungju Han,Joon Sung Lee,Young Heon Kim,Myung-Hwa Jung,Yong-Joo Doh,Mahn-Soo Choi,Jonghyun Song,Jinhee Kim###

Polarity-tunable magnetic tunnel junctions based on ferromagnetism at oxide heterointerfaces. Complex oxide systems have attracted considerable attention because of their
fascinating properties, including the magnetic ordering at the conducting
interface between two band insulators, such as LaAlO3 (LAO) and SrTiO3 (STO).
However, the manipulation of the spin degree of freedom at the LAO/STO
heterointerface has remained elusive. Here, we have fabricated hybrid magnetic
tunnel junctions consisting of Co and LAO/STO ferromagnets with the insertion
of a Ti layer in between, which clearly exhibit magnetic switching and the
tunnelling magnetoresistance (TMR) effect below 10 K. The magnitude and the of
the TMR are strongly dependent on the direction of the rotational magnetic
field parallel to the LAO/STO plane, which is attributed to a strong
Rashba-type spin orbit coupling in the LAO/STO heterostructure. Our study
provides a further support for the existence of the macroscopic ferromagnetism
at LAO/STO heterointerfaces and opens a novel route to realize interfacial
spintronics devices.

###Scattering, weak localization and Shubnikov-de Haas oscillation in high carrier density AlInN/GaN heterostructures|Leizhi Wang,Ming Yin,Asif Khan,Sakib Muhtadi,Fatima Asif,Eun Sang Choi,Timir Datta###

Scattering, weak localization and Shubnikov-de Haas oscillation in high carrier density AlInN/GaN heterostructures. We provide the first observation of weak localization in high carrier density
two-dimensional electron gas in AlInN/GaN heterostructures; at low temperatures
and low fields the conductivity increases with increasing magnetic field. Weak
localization is further confirmed by the lnT dependence of the zero-field
conductivity and angle dependence of magnetoresistance. The inelastic
scattering rate is linearly proportional to temperature, demonstrating that
electron-electron scattering is the principal phase breaking mechanism.
Shubnikov-de Haas (SdH) oscillations at high magnetic fields are also observed.
From the temperature dependent amplitude of SdH oscillation and Dingle plot,
the effective mass of electron is extracted to be 0.2327me; in addition the
quantum lifetime is smaller than transport time from Hall measurement,
indicating small angle scattering such as from remote ionized impurities is
dominant. Above 20 K, the scattering changes from acoustic phonon to optical
phonon scattering, resulting in a rapid decrease in carrier mobility with
increasing temperature.

###Coexistence of bulk and surface states probed by Shubnikov-de Haas oscillations in Bi$_2$Se$_3$ with high charge-carrier density|E. K. de Vries,S. Pezzini,M. J. Meijer,N. Koirala,M. Salehi,J. Moon,S. Oh,S. Wiedmann,T. Banerjee###

Coexistence of bulk and surface states probed by Shubnikov-de Haas oscillations in Bi$_2$Se$_3$ with high charge-carrier density. Topological insulators are ideally represented as having an insulating bulk
with topologically protected, spin-textured surface states. However, it is
increasingly becoming clear that these surface transport channels can be
accompanied by a finite conducting bulk, as well as additional topologically
trivial surface states. To investigate these parallel conduction transport
channels, we studied Shubnikov-de Haas oscillations in Bi$_2$Se$_3$ thin films,
in high magnetic fields up to 30 T so as to access channels with a lower
mobility. We identify a clear Zeeman-split bulk contribution to the
oscillations from a comparison between the charge-carrier densities extracted
from the magnetoresistance and the oscillations. Furthermore, our analyses
indicate the presence of a two-dimensional state and signatures of additional
states the origin of which cannot be conclusively determined. Our findings
underpin the necessity of theoretical studies on the origin of and the
interplay between these parallel conduction channels for a careful analysis of
the material's performance.

###High-temperature quantum oscillations of the Hall resistance in bulk Bi$_2$Se$_3$|Marco Busch,Olivio Chiatti,Sergio Pezzini,Steffen Wiedmann,Jaime Sánchez-Barriga,Oliver Rader,Lada V. Yashina,Saskia F. Fischer###

High-temperature quantum oscillations of the Hall resistance in bulk Bi$_2$Se$_3$. Helically spin-polarized Dirac fermions (HSDF) in protected topological
surface states (TSS) are of high interest as a new state of quantum matter. In
three-dimensional (3D) materials with TSS, electronic bulk states often mask
the transport properties of HSDF. Recently, the high-field Hall resistance and
low-field magnetoresistance indicate that the TSS may coexist with a layered
two-dimensional electronic system (2DES). Here, we demonstrate quantum
oscillations of the Hall resistance at temperatures up to 50 K in bulk
Bi$_2$Se$_3$ with a high electron density $n$ of about $2\!\cdot\!10^{19}$
cm$^{-3}$. From the angular and temperature dependence of the Hall resistance
and the Shubnikov-de Haas oscillations we identify 3D and 2D contributions to
transport. Angular resolved photoemission spectroscopy proves the existence of
TSS. We present a model for Bi$_2$Se$_3$ and suggest that the coexistence of
TSS and 2D layered transport stabilizes the quantum oscillations of the Hall
resistance.

###Broken mirror symmetry tuned topological transport in PbTe/SnTe heterostructures|Feng Wei,Chieh-Wen Liu,Da Li,Chun-Yang Wang,Hong-Rui Zhang,Ji-rong Sun,Xuan P. A. Gao,Song Ma,Zhidong Zhang###

Broken mirror symmetry tuned topological transport in PbTe/SnTe heterostructures. The tunability of topological surface states and controllable opening of the
Dirac gap are of great importance to the application of topological materials.
In topological crystalline insulators (TCIs), crystal symmetry and topology of
electronic bands intertwine to create topological surface states and thus the
Dirac gap can be modulated by symmetry breaking structural changes of lattice.
By transport measurement on heterostructures composed of p-type topological
crystalline insulator SnTe and n-type conventional semiconductor PbTe, here we
show a giant linear magnetoresistance (up to 2150% under 14 T at 2 K) induced
by the Dirac Fermions at the PbTe/SnTe interface. In contrast, PbTe/SnTe
samples grown at elevated temperature exhibit a cubic-to-rhombohedral
structural phase transition of SnTe lattice below 100 K and weak
antilocalization effect. Such distinctive magneto-resistance behavior is
attributed to the broken mirror symmetry and gapping of topological surface
states. Our work provides a promising application for future
magneto-electronics and spintronics based on TCI heterostructures.

###Vacuum-dressed cavity magnetotransport of a 2D electron gas|Nicola Bartolo,Cristiano Ciuti###

Vacuum-dressed cavity magnetotransport of a 2D electron gas. We present a theory predicting how the linear magnetotransport of a
two-dimensional electron gas is modified by a passive electromagnetic cavity
resonator where no real photons are injected nor created. For a cavity photon
mode with in-plane linear polarization, the dc bulk magnetoresistivity of the
2D electron gas is anisotropic. In the regime of high filling factors of the
Landau levels, the envelope of the Shubnikov-de Haas oscillations is profoundly
modified and the resistivity can be increased or reduced depending on the
system parameters. In the limit of low magnetic fields, the resistivity along
the cavity-mode polarization direction is enhanced in the ultrastrong
light-matter coupling regime. Our work shows the crucial role of virtual
polariton excitations in controlling the dc charge transport properties of
cavity-embedded systems.

###Spin direction controlled electronic band structure in two dimensional ferromagnetic CrI3|Peiheng Jiang,Lei Li,Zhaoliang Liao,Y. X. Zhao,Zhicheng Zhong###

Spin direction controlled electronic band structure in two dimensional ferromagnetic CrI3. Manipulating physical properties using the spin degree of freedom constitutes
a major part of modern condensed matter physics and is very important for
spintronics devices. Using the newly discovered two dimensional van der Waals
ferromagnetic CrI3 as a prototypic material, we theoretically demonstrated a
giant magneto band-structure (GMB) effect whereby a change of magnetization
direction significantly modifies the electronic band structure. Our density
functional theory calculations and model analysis reveal that rotating the
magnetic moment of CrI3 from out-of-plane to in-plane causes a
direct-to-indirect bandgap transition, inducing a magnetic field controlled
photoluminescence. Moreover, our results show a significant change of Fermi
surface with different magnetization directions, giving rise to giant
anisotropic magnetoresistance. Additionally, the spin reorientation is found to
modify the topological states. Given that a variety of properties are
determined by band structures, our predicted GMB effect in CrI3 opens a new
paradigm for spintronics applications.

###L10 Fe-Pd Synthetic Antiferromagnet through an fcc Ru Spacer Utilized for Perpendicular Magnetic Tunnel Junctions|De-Lin Zhang,Congli Sun,Yang Lv,Karl B. Schliep,Zhengyang Zhao,Jun-Yang Chen,Paul M. Voyles,Jian-Ping Wang###

L10 Fe-Pd Synthetic Antiferromagnet through an fcc Ru Spacer Utilized for Perpendicular Magnetic Tunnel Junctions. Magnetic materials that possess large bulk perpendicular magnetic anisotropy
(PMA) are essential for the development of magnetic tunnel junctions (MTJs)
used in future spintronic memory and logic devices. The addition of an
antiferromagnetic layer to these MTJs was recently predicted to facilitate
ultra-fast magnetization switching. Here, we report a demonstration of a bulk
perpendicular synthetic antiferromagnetic (P-SAFM) structure comprised of a
(001) textured FePd/Ru/FePd trilayer with a face-centered-cubic (fcc) phase Ru
spacer. The L10 FePd P-SAFM structure shows a large bulk PMA (~10.2 Merg/cc)
and strong antiferromagnetic coupling (~2.60 erg/cm2). Full perpendicular
magnetic tunnel junctions (P-MTJs) with a L10 FePd P-SAFM layer are then
fabricated. Tunneling magnetoresistance ratios of up to ~25% (~60%) are
observed at room temperature (5K) after post-annealing at 350 C. Exhibiting
high thermal stabilities and large Ku, the bulk P-MTJs with an L10 FePd P-SAFM
layer could pave a way for next-generation ultrahigh-density and
ultra-low-energy spintronic applications.

###Anomalous Nernst effect and field-induced Lifshitz transition in Weyl semimetals TaP and TaAs|Federico Caglieris,Christoph Wuttke,Steffen Sykora,Vicky Süss,Chandra Shekhar,Claudia Felser,Bernd Büchner,Christian Hess###

Anomalous Nernst effect and field-induced Lifshitz transition in Weyl semimetals TaP and TaAs. The discovery of Weyl fermions in transition metal monoarsenides/phosphides
without inversion symmetry represents an exceptional breakthrough in modern
condensed matter physics. However, exploring the inherent nature of these
quasiparticles is experimentally elusive because most of the experimental
probes rely on analysing Fermi arc topology or controversial signatures such as
the appearance of the chiral anomaly and the giant magnetoresistance. Here we
show that the prototypical type-I Weyl semimetals TaP and TaAs possess a giant
anomalous Nernst signal with a characteristic saturation plateau beyond a
critical field which can be understood as a direct consequence of the finite
Berry curvature originating from the Weyl points. Our results thus promote the
Nernst coefficient as an ideal bulk probe for detecting and exploring the
fingerprints of emergent Weyl physics.

###Beating pattern in radiation-induced oscillatory magnetoresistance in 2DES: coupling of plasmon-like and acoustic phonon modes|Jesus Inarrea###

Beating pattern in radiation-induced oscillatory magnetoresistance in 2DES: coupling of plasmon-like and acoustic phonon modes. We present a microscopic theory on the observation of a beating pattern in
the radiation-induced magnetoresistance oscillations at very low magnetic
field. We con- sider that such a beating pattern develops as a result of the
coupling between two oscillatory components: the first is a system of electron
Landau states being harmon- ically driven by radiation. The second is a lattice
oscillation, i.e., an acoustic phonon mode. We analyze the dependence of the
beating pattern on temperature, radiation frequency and power. We conclude that
the beating pattern is an evidence of the radiation-driven nature of the
irradiated Landau states that makes them behave as a collective plasma
oscillation at the radiation frequency. Thus, the frequency of such plasmons
could be tuned from microwave to terahertz in the same nanodevice with an
apparent technological application.

###Extreme magnetoresistance and Shubnikov-de Haas oscillations in ferromagnetic DySb|D. D. Liang,Y. J. Wang,C. Y. Xi,W. L. Zhen,J. Yang,L. Pi,W. K. Zhu,C. J. Zhang###

Extreme magnetoresistance and Shubnikov-de Haas oscillations in ferromagnetic DySb. The electronic structures of a representative rare earth monopnictide (i.e.,
DySb) under high magnetic field (i.e., in the ferromagnetic state) are studied
from both experimental and theoretical aspects. A non-saturated extremely large
positive magnetoresistance (XMR) is observed (as large as 3.7*10^4% at 1.8 K
and 38.7 T), along with the Shubnikov-de Haas oscillations that are well
reproduced by our first principles calculations. Three possible origins of XMR
are examined. Although a band inversion is found theoretically, suggesting that
DySb might be topologically nontrivial, it is deeply underneath the Fermi
level, which rules out a topological nature of the XMR. The total densities of
electron-like and hole-like carriers are not fully compensated, showing that
compensation is unlikely to account for the XMR. The XMR is eventually
understood in terms of high mobility that is associated with the steep linear
bands. This discovery is important to the intensive studies on the XMR of rare
earth monopnictides.

###Magnetotransport and lateral confinement in an InSe van der Waals Heterostructure|Yongjin Lee,Riccardo Pisoni,Hiske Overweg,Marius Eich,Peter Rickhaus,Amalia Patanè,Zakhar R. Kudrynskyi,Zakhar. D. Kovalyuk,Roman Gorbachev,Kenji Watanabe,Takashi Taniguchi,Thomas Ihn,Klaus Ensslin###

Magnetotransport and lateral confinement in an InSe van der Waals Heterostructure. In the last six years, Indium selenide (InSe) has appeared as a new van der
Waals heterostructure platform which has been extensively studied due to its
unique electronic and optical properties. Such as transition metal
dichalcogenides (TMDCs), the considerable bandgap and high electron mobility
can provide a potential optoelectronic application. Here we present
low-temperature transport measurements on a few-layer InSe van der Waals
heterostructure with graphene-gated contacts. For high magnetic fields, we
observe magnetoresistance minima at even filling factors related to two-fold
spin degeneracy. By electrostatic gating with negatively biased split gates, a
one-dimensional channel is realized. Close to pinch-off, transport through the
constriction is dominated by localized states with charging energies ranging
from 2 to 5 meV. This work opens new possibility to explore the low-dimensional
physics including quantum point contact and quantum dot.

###Interplay of Magnetism and Transport in HoBi|H. -Y. Yang,J. Gaudet,A. A. Aczel,D. E. Graf,P. Blaha,B. D. Gaulin,Fazel Tafti###

Interplay of Magnetism and Transport in HoBi. We report the observation of an extreme magnetoresistance (XMR) in HoBi with
a large magnetic moment from Ho f-electrons. Neutron scattering is used to
determine the magnetic wave vectors across several metamagnetic (MM)
transitions on the phase diagram of HoBi. Unlike other magnetic rare-earth
monopnictides, the field dependence of resistivity in HoBi is non-monotonic and
reveals clear signatures of every metamagnetic transition in the
low-temperature and low-field regime, at T < 2 K and H < 2.3 T. The XMR appears
at H > 2.3 T after all the metamagnetic transitions are complete and the system
is spin-polarized by the external magnetic field. The existence of an onset
field for XMR and the intimate connection between magnetism and transport in
HoBi are unprecedented among the magnetic rare-earth monopnictides. Therefore,
HoBi provides a unique opportunity to understand the electrical transport in
magnetic XMR semimetals.

###Unusual magnetotransport in holmium monoantimonide|Yi-Yan Wang,Lin-Lin Sun,Sheng Xu,Yuan Su,Tian-Long Xia###

Unusual magnetotransport in holmium monoantimonide. We report the magnetotransport properties of HoSb, a semimetal with
antiferromagnetic ground state. HoSb shows extremely large magnetoresistance
(XMR) and Shubnikov-de Haas (SdH) oscillation at low temperature and high
magnetic field. Different from previous reports in other rare earth
monopnictides, kinks in $\rho(B)$ and $\rho_{xy}(B)$ curves and the field
dependent resistivity plateau are observed in HoSb, which result from the
magnetic phase transitions. The fast Fourier transform analysis of the SdH
oscillation reveals the split of Fermi surfaces induced by the nonsymmetric
spin-orbit interaction. The Berry phase extracted from SdH oscillation
indicates the possible nontrivial electronic structure of HoSb in the presence
of magnetic field. The Hall measurements suggest that the XMR originates from
the electron-hole compensation and high mobility.

###Antiferromagnetic MnNi tips for spin-polarized scanning probe microscopy|P. R. Forrester,T. Bilgeri,F. Patthey,H. Brune,F. D. Natterer###

Antiferromagnetic MnNi tips for spin-polarized scanning probe microscopy. Spin-polarized scanning tunneling microscopy (SP-STM) measures tunnel
magnetoresistance (TMR) with atomic resolution. While various methods for
achieving SP probes have been developed, each is limited with respect to
fabrication, performance, and allowed operating conditions. In this study, we
present the fabrication and use of SP-STM tips made from commercially available
antiferromagnetic $\rm{Mn_{88}Ni_{12}}$ foil. The tips are intrinsically SP,
which is attractive for exploring magnetic phenomena in the zero field limit.
The tip material is relatively ductile and straightforward to etch. We
benchmark the conventional STM and spectroscopic performance of our tips and
demonstrate their spin sensitivity by measuring the two-state switching of
holmium single atom magnets on MgO/Ag(100).

###Taming the magnetoresistance anomaly in graphite|B. C. Camargo,W. Escoffier###

Taming the magnetoresistance anomaly in graphite. At low temperatures, graphite presents a magnetoresistance anomaly which
manifests as a transition to a high-resistance state (HRS) above a certain
critical magnetic field $\text{B}_\text{c}$. Such HRS is currently attributed
to a c-axis charge-density-wave taking place only when the lowest Landau level
is populated. By controlling the charge carrier concentration of a gated sample
through its charge neutrality level (CNL), we were able to experimentally
modulate the HRS in graphite for the first time. We demonstrate that the HRS is
triggered both when electrons and holes are the majority carriers but is
attenuated near the CNL. Taking screening into account, our results indicate
that the HRS possess a strong in-plane component and can occur below the
quantum limit, being at odds with the current understanding of the phenomenon.
We also report the effect of sample thickness on the HRS.

###Nontrivial topology of bulk HgSe from the study of cyclotron effective mass, electron mobility and phase shift of Shubnikov-de Haas oscillations|S. B. Bobin,A. T. Lonchakov,V. V. Deryushkin,V. N. Neverov###

Nontrivial topology of bulk HgSe from the study of cyclotron effective mass, electron mobility and phase shift of Shubnikov-de Haas oscillations. In this paper, the authors report the results of an experimental study of
effective mass, electron mobility and phase shift of Shubnikov de Haas
oscillations of transverse magnetoresistance in an extended electron
concentration region from 8.8*10^15 cm^-3 to 4.3*10^18 cm^-3 in single crystals
of mercury selenide. The revealed features confirm the existence of a Weyl
semimetal phase in HgSe at low electron density, which has been indicated by
previous magnetotransport studies. However, the most significant result is the
discovery of an abrupt change of Berry phase of Pi at electron concentration
2*10^18 cm^-3, which we explain in terms of a manifestation of topological
Lifshitz transition in HgSe that occurs by tuning Fermi energy via doping.

###Discrete Scale Invariance in Topological Semimetals|Haiwen Liu,Hua Jiang,Ziqiang Wang,Robert Joynt,X. C. Xie###

Discrete Scale Invariance in Topological Semimetals. The discovery of Weyl and Dirac semimetals has produced a number of dramatic
physical effects, including the chiral anomaly and topological Fermi arc
surface states. We point out that a very different but no less dramatic
physical effect is also to be found in these materials: discrete scale
invariance. This invariance leads to bound state spectra for Coulomb impurities
that repeat when the binding energy is changed by a fixed factor, reminiscent
of fractal behavior. We show that this effect follows from the peculiar
dispersion relation in Weyl and Dirac semimetals. It is observed when such a
material is placed in very strong magnetic field B: there are oscillations in
the magnetoresistivity somewhat similar to Shubnikov-de Haas oscillations but
with a periodicity in ln B rather than 1/B. These oscillations should be
present in other thermodynamic and transport properties. The oscillations have
now been seen in three topological semimetals: ZrTe$_{5}$, TaAs, and Bi.

###Effects of Elastic Dephasing on Scaling of ultra-small Magnetic Tunnel Junctions|Debasis Das,Ashwin Tulapurkar,Bhaskaran Muralidharan###

Effects of Elastic Dephasing on Scaling of ultra-small Magnetic Tunnel Junctions. The study of the effects of scaling on magnetic tunnel junction (MTJ) devices
has become an important topic in the field of spin-based memory devices. Here,
we investigate the effect of elastic dephasing on trilayer and pentalayer MTJ
considered at small transverse cross-sectional areas using the non-equilibrium
Green's function spin transport formalism. We consider the structures with and
without dephasing effects and clearly point out as to how the tunnel
magnetoresistance effect gets affected by dephasing. We attribute the trends
noted by analyzing the transmission spectra and hence the currents across the
devices. Although dephasing affects the TMR values for both devices, we note
that the obtained TMR values are still in a reasonable range that may not
hinder their usability for practical applications.

###Double carrier transport in electron doped region in black phosphorus FET|Kohei Hirose,Toshihito Osada,Kazuhito Uchida,Toshihiro Taen,Kenji Watanabe,Takashi Taniguchi,Yuichi Akahama###

Double carrier transport in electron doped region in black phosphorus FET. The double carrier transport has been observed in thin film black phosphorus
(BP) field effect transistor (FET) devices in highly electron doped region. BP
thin films with typical thickness of 15 nm were encapsulated by hexagonal boron
nitride (h-BN) thin films to avoid degradation by air exposure. Their Hall
mobility has reached 5300 cm2/Vs and 5400 cm2/Vs at 4.2 K in the hole and
electron doped regions, respectively. The gate voltage dependence of
conductivity exhibits an anomalous shoulder structure in electron doped region.
In addition, at gate voltages above the shoulder, the magnetoresistance changes
to positive, and there appears an additional slow Shubnikov-de Haas
oscillation. These results strongly suggest the appearance of the second
carriers, which originate from the second subband with localized band edge.

###Magnetotransport in Sr3PbO antiperovskite with three-dimensional massive Dirac electrons|S. Suetsugu,K. Hayama,A. W. Rost,J. Nuss,C. Mühle,J. Kim,K. Kitagawa,H. Takagi###

Magnetotransport in Sr3PbO antiperovskite with three-dimensional massive Dirac electrons. Novel topological phenomena are anticipated for three-dimensional (3D) Dirac
electrons. The magnetotransport properties of cubic ${\rm Sr_{3}PbO}$
antiperovskite, theoretically proposed to be a 3D massive Dirac electron
system, are studied. The measurements of Shubnikov-de Haas oscillations and
Hall resistivity indicate the presence of a low density ($\sim 1 \times
10^{18}$ ${\rm cm^{-3}}$) of holes with an extremely small cyclotron mass of
0.01-0.06$m_{e}$. The magnetoresistance $\Delta\rho_{xx}(B)$ is linear in
magnetic field $B$ with the magnitude independent of temperature. These results
are fully consistent with the presence of 3D massive Dirac electrons in ${\rm
Sr_{3}PbO}$. The chemical flexibility of the antiperovskites and our findings
in the family member, ${\rm Sr_{3}PbO}$, point to their potential as a model
system in which to explore exotic topological phases.

###Non-topological Origin of the Planar Hall Effect in Type-II Dirac Semimetal NiTe2|Qianqian Liu,Bo Chen,Boyuan Wei,Shuai Zhang,Minhao Zhang,Faji Xie,Muhammad Naveed,Fucong Fei,Baigen Wang,Fengqi Song###

Non-topological Origin of the Planar Hall Effect in Type-II Dirac Semimetal NiTe2. Dirac and Weyl semimetals are new discovered topological nontrivial materials
with the linear band dispersions around the Dirac/Weyl points. When applying
non-orthogonal electric current and magnetic field, an exotic phenomenon called
chiral anomaly arises and negative longitudinal resistance can be detected.
Recently, a new phenomenon named planer Hall effect (PHE) is considered to be
another indication of chiral anomaly which has been observed in many
topological semimetals. However, it still remains a question that is the PHE
only attributed to chiral anomaly? Here we demonstrate the PHE in a
new-discovered type-II Dirac semimetal NiTe2 by low temperature transport.
However, after detailed analysis, we conclude that the PHE results from the
trivial orbital magnetoresistance. This work reveals that PHE is not a
sufficient condition of chiral anomaly and one need to take special care of
other non-topological contribution in such studies.

###Tunable magnetic textures in spin valves: From spintronics to Majorana bound states|Tong Zhou,Narayan Mohanta,Jong E. Han,Alex Matos-Abiague,Igor Zutic###

Tunable magnetic textures in spin valves: From spintronics to Majorana bound states. Spin-valve structures in which a change of magnetic configuration is
responsible for magnetoresistance have enabled impressive advances in
spintronics, focusing on magnetically storing and sensing information. However,
this mature technology also offers versatile control of the underlying fringing
fields and entirely different applications by realizing
topologically-nontrivial states. Together with proximity-induced
superconductivity in a two-dimensional electron gas, these fringing fields
realized in commercially-available spin valves could control Majorana bound
states (MBS). Detailed support for the existence and control of MBS is obtained
by combining accurate micromagnetic simulation of fringing fields used as an
input in Bogoliubov de Gennes equation to calculate low-energy spectrum,
wavefunction localization, and local charge neutrality. A generalized condition
for quantum phase transition in these structures provides valuable guidance for
the MBS evolution and implementing reconfigurable effective topological wires.

###Non-local signatures of the chiral magnetic effect in Dirac semimetal Bi$_{0.97}$Sb$_{0.03}$|Jorrit C. de Boer,Daan H. Wielens,Joris A. Voerman,Bob de Ronde,Yingkai Huang,Mark S. Golden,Chuan Li,Alexander Brinkman###

Non-local signatures of the chiral magnetic effect in Dirac semimetal Bi$_{0.97}$Sb$_{0.03}$. The field of topological materials science has recently been focussing on
three-dimensional Dirac semimetals, which exhibit robust Dirac phases in the
bulk. However, the absence of characteristic surface states in accidental Dirac
semimetals (DSM) makes it difficult to experimentally verify claims about the
topological nature using commonly used surface-sensitive techniques. The chiral
magnetic effect (CME), which originates from the Weyl nodes, causes an
$\textbf{E}\cdot\textbf{B}$-dependent chiral charge polarization, which
manifests itself as negative magnetoresistance. We exploit the extended
lifetime of the chirally polarized charge and study the CME through both local
and non-local measurements in Hall bar structures fabricated from single
crystalline flakes of the DSM Bi$_{0.97}$Sb$_{0.03}$. From the non-local
measurement results we find a chiral charge relaxation time which is over one
order of magnitude larger than the Drude transport lifetime, underlining the
topological nature of Bi$_{0.97}$Sb$_{0.03}$.

###Quantitative Study on Current-Induced Effect in an Antiferromagnet Insulator/Pt Bilayer Film|Pengxiang Zhang,Joseph Finley,Taqiyyah Safi,Luqiao Liu###

Quantitative Study on Current-Induced Effect in an Antiferromagnet Insulator/Pt Bilayer Film. Quantitative investigation on the current-induced torque in antiferromagnets
represents a great challenge, due to the lack of an independent method for
controlling N\'eel vectors. Here by utilizing an antiferromagnetic insulator
with Dzyaloshinskii-Moriya interaction, {\alpha}-Fe2O3, we show that the N\'eel
vector can be controlled with a moderate external field, which is further
utilized to calibrate the current-induced magnetic dynamics. We find that the
current-induced magnetoresistance change in antiferromagnets can be complicated
by resistive switching that does not have a magnetic origin. By excluding
non-magnetic switching and comparing the current-induced dynamics with the
field-induced one, we determine the nature and magnitude of current-induced
effects in Pt/{\alpha}-Fe2O3 bilayer films.

###Dissipative-regime measurements as a tool for confirming and characterizing near-room-temperature superconductivity|Charles L. Dean,Milind N. Kunchur###

Dissipative-regime measurements as a tool for confirming and characterizing near-room-temperature superconductivity. The search for new superconducting materials approaching room temperature
benefits from having a variety of testing methodologies to confirm and
characterize the presence of superconductivity. Often the first signatures of
new superconducting species occur incompletely and in very small volume
fractions. These trace amounts may be too weak to produce an observable
Meissner effect and the resistance may not go completely to zero if the
percolation threshold is not met. Under these conditions, secondary
behavior--such as transitions or cross overs in the temperature dependence of
magnetoresistance, magnetic irreversibility, or thermopower--are often used as
indications for the presence of superconductivity. Our group has developed a
rather unique set of fast-timescale and dissipative transport measurements that
can provide another tool set for confirming and characterizing suspected
superconductivity. Here we provide some background for these methods and
elucidate their collaborative value in the search for new superconducting
materials. Keywords: pairbreaking, pair-breaking, vortex, vortices, theory,
tutorial, RTS, room-temperature superconductivity, superconductor, detection,
characterization

###Planar topological Hall effect in a uniaxial van der Waals ferromagnet Fe3GeTe2|Yurong You,Yuanyuan Gong,Hang Li,Zefang Li,Mengmei Zhu,Jiaxuan Tang,Enke Liu,Yuan Yao,Guizhou Xu,Feng Xu,Wenhong Wang###

Planar topological Hall effect in a uniaxial van der Waals ferromagnet Fe3GeTe2. In this work, we reported the observation of a novel planar topological Hall
effect (PTHE) in single crystal of Fe3GeTe2, a paradigmatic two-dimensional
ferromagnet with strong uniaxial anisotropy. The Hall effect and
magnetoresistance varied periodically when the external magnetic field rotated
in the ac (or bc) plane, while the PTHE emerged and maintained robust with
field swept across the hard-magnetized ab plane. The PTHE covers the whole
temperature region below Tc (~150 K) and a comparatively large value is
observed at 100 K. Emergence of an internal gauge field was proposed to explain
the origin of this large PTHE, which is either generated by the possible
topological domain structure of uniaxial Fe3GeTe2 or the non-coplanar spin
structure formed during the in-plane magnetization. Our results promisingly
provide an alternative detection method to the in-plane skyrmion formation and
may bring brand-new prospective to magneto-transport studies in condensed
matter physics.

###Magnetic and electronic structure of Dirac semimetal candidate EuMnSb$_2$|J. -R. Soh,P. Manuel,N. M. B. Schröter,C. J. Yi,D. Prabhakaran,F. Orlandi,Y. G. Shi,A. T. Boothroyd###

Magnetic and electronic structure of Dirac semimetal candidate EuMnSb$_2$. We report an experimental study of the magnetic order and electronic
structure and transport of the layered pnictide EuMnSb$_2$, performed using
neutron diffraction, angle-resolved photoemission spectroscopy (ARPES), and
magnetotransport measurements. We find that the Eu and Mn sublattices display
antiferromagnetic (AFM) order below $T_\mathrm{N}^\mathrm{Eu} = 21(1)$ K and
$T_\mathrm{N}^\mathrm{Mn} = 350(2)$ K respectively. The former can be described
by an A-type AFM structure with the Eu spins aligned along the $c$ axis (an
in-plane direction), whereas the latter has a C-type AFM structure with Mn
moments along the $a$--axis (perpendicular to the layers). The ARPES spectra
reveal Dirac-like linearly dispersing bands near the Fermi energy. Furthermore,
our magnetotransport measurements show strongly anisotropic magnetoresistance,
and indicate that the Eu sublattice is intimately coupled to conduction
electron states near the Dirac point.

###Electron transport in high-entropy alloys: Al$_{x}$CrFeCoNi as a case study|J. Kudrnovský,V. Drchal,F. Máca,I. Turek,S. Khmelevskyi###

Electron transport in high-entropy alloys: Al$_{x}$CrFeCoNi as a case study. The high-entropy alloys Al$_{x}$CrFeCoNi exist over a broad range of Al
concentrations ($0 < x < 2$). With increasing Al content their structure is
changed from the fcc to bcc phase. We investigate the effect of such structural
changes on transport properties including the residual resistivity and the
anomalous Hall resistivity. We have performed a detailed comparison of the
first-principles simulations with available experimental data. We show that the
calculated residual resistivities for all studied alloy compositions are in a
fair agreement with available experimental data as concerns both the
resistivity values and concentration trends. We emphasize that a good agreement
with experiment was obtained also for the anomalous Hall resistivity. We have
completed study by estimation of the anisotropic magnetoresistance,
spin-disorder resistivity, and Gilbert damping. The obtained results prove that
the main scattering mechanism is due to the intrinsic chemical disorder whereas
the effect of spin polarization on the residual resistivity is appreciably
weaker.

###Irradiation-induced metal-insulator transition in monolayer graphene|I. Shlimak,E. Zion,A. Butenko,Yu. Kaganovskii,V. Richter,A. Sharoni,E. Kogan,M. Kaveh###

Irradiation-induced metal-insulator transition in monolayer graphene. A brief review of experiments directed to study a gradual localization of
charge carriers and metal-insulator transition in samples of disordered
monolayer graphene is presented. Disorder was induced by irradiation with
different doses of heavy and light ions. Degree of disorder was controlled by
measurements of the Raman scattering spectra. The temperature dependences of
conductivity and magnetoresistance (MR) showed that at low disorder,
conductivity is governed by the weak localization and antilocalization regime.
Further increase of disorder leads to strong localization of charge carriers,
when the conductivity is described by the variable-range-hopping (VRH)
mechanism. It was observed that MR in the VRH regime is negative in
perpendicular fields and is positive in parallel magnetic fields which allowed
to reveal different mechanisms of hopping MR. Theoretical analysis is in a good
agreement with experimental data.

###Moiré Engineering of Electronic Phenomena in Correlated Oxides|Xinzhong Chen,Xiaodong Fan,Lin Li,Nan Zhang,Zhijing Niu,Tengfei Guo,Suheng Xu,Han Xu,Dongli Wang,Huayang Zhang,A. S. McLeod,Zhenlin Luo,Qingyou Lu,Andrew J. Millis,D. N. Basov,Mengkun Liu,Changgan Zeng###

Moiré Engineering of Electronic Phenomena in Correlated Oxides. Moir\'e engineering has recently emerged as a capable approach to control
quantum phenomena in condensed matter systems. In van der Waals
heterostructures, moir\'e patterns can be formed by lattice misorientation
between adjacent atomic layers, creating long range electronic order. To date,
moir\'e engineering has been executed solely in stacked van der Waals
multilayers. Herein, we describe our discovery of electronic moir\'e patterns
in films of a prototypical magnetoresistive oxide La0.67Sr0.33MnO3 (LSMO)
epitaxially grown on LaAlO3 (LAO) substrates. Using scanning probe
nano-imaging, we observe microscopic moir\'e profiles attributed to the
coexistence and interaction of two distinct incommensurate patterns of strain
modulation within these films. The net effect is that both electronic
conductivity and ferromagnetism of LSMO are modulated by periodic moir\'e
textures extending over mesoscopic scales. Our work provides an entirely new
route with potential to achieve spatially patterned electronic textures on
demand in strained epitaxial materials.

###Magneto-ionic control of spin polarization in magnetic tunnel junctions|Yingfen Wei,Sylvia Matzen,Cynthia P. Quinteros,Thomas Maroutian,Guillaume Agnus,Philippe Lecoeur,Beatriz Noheda###

Magneto-ionic control of spin polarization in magnetic tunnel junctions. Magnetic tunnel junctions (MTJs) with Hf0.5Zr0.5O2 barriers are reported to
show both tunneling magnetoresistance effect (TMR) and tunneling
electroresistance effect (TER), displaying four resistance states by magnetic
and electric field switching. Here we show that, under electric field cycling
of large enough magnitude, the TER can reach values as large as 10^6%.
Moreover, concomitant with this TER enhancement, the devices develop electrical
control of spin polarization, with sign reversal of the TMR effect. Currently,
this intermediate state exists for a limited number of cycles and understanding
the origin of these phenomena is key to improve its stability. The experiments
presented here point to the magneto-ionic effect as the origin of the large TER
and strong magneto-electric coupling, showing that ferroelectric polarization
switching of the tunnel barrier is not the main contribution.

###Electronics without bridging components|V. M. García-Suárez###

Electronics without bridging components. We propose a new paradigm of electronic devices based only on two electrodes
separated by a gap, i.e. without any functional element bridging them. We use a
tight-binding model to show that, depending on the type of material of the
electrodes and its structure, several electronic functionalities can be
achieved: ohmic behaviour, rectification, negative differential resistance,
spin-filtering and magnetoresistance. In particular, we show that it is
possible to deliver a given functionality by changing the coupling between the
surface and bulk states and between the surface states across the gap, which
dramatically changes the current-voltage characteristics. These results prove
that it is possible to have functional electronic and spintronic elements on
the nanoscale without having physical components bridging the electrodes.

###Large spin Hall magnetoresistance in antiferromagnetic α-Fe2O3/Pt heterostructures|Johanna Fischer,Matthias Althammer,Nynke Vlietstra,Hans Huebl,Sebastian T. B. Goennenwein,Rudolf Gross,Stephan Geprägs,Matthias Opel###

Large spin Hall magnetoresistance in antiferromagnetic α-Fe2O3/Pt heterostructures. We investigate the spin Hall magnetoresistance (SMR) at room temperature in
thin film heterostructures of antiferromagnetic, insulating, (0001)-oriented
alpha-Fe2O3 (hematite) and Pt. We measure their longitudinal and transverse
resistivities while rotating an applied magnetic field of up to 17T in three
orthogonal planes. For out-of-plane magnetotransport measurements, we find
indications for a multidomain antiferromagnetic configuration whenever the
field is aligned along the film normal. For in-plane field rotations, we
clearly observe a sinusoidal resistivity oscillation characteristic for the SMR
due to a coherent rotation of the Neel vector. The maximum SMR amplitude of
0.25% is, surprisingly, twice as high as for prototypical ferrimagnetic
Y3Fe5O12/Pt heterostructures. The SMR effect saturates at much smaller magnetic
fields than in comparable antiferromagnets, making the alpha-Fe2O3/Pt system
particularly interesting for room-temperature antiferromagnetic spintronic
applications.

###Field-angle dependence of sound velocity in the Weyl semimetal TaAs|F. Laliberté,F. Bélanger,N. L. Nair,J. G. Analytis,M. -E. Boulanger,M. Dion,L. Taillefer,J. A. Quilliam###

Field-angle dependence of sound velocity in the Weyl semimetal TaAs. The elastic modulus $c_{44}$ of a single crystal of the Weyl semimetal TaAs
was investigated by measuring relative changes in the sound velocity under
application of a magnetic field up to 10 T. Using an ultrasonic pulsed-echo
technique, we studied the shear response of the crystal when the angle between
the sound wave propagation and the magnetic field is changed. We observe a
broken tetragonal symmetry at fields above 6 T, an anisotropy that is likely
related to a longitudinal negative magnetoresistance and therefore might
provide evidence of the chiral anomaly, one of the main topological signatures
of this class of materials. We also observe quantum oscillations in the sound
velocity whose frequencies vary with magnetic field orientation. A fan diagram
of Landau level indices reveals topological and trivial Berry phases, depending
on the field orientation, indicating a sensitivity to different Fermi surface
pockets that do or do not enclose Weyl nodes respectively.

###Magneto-transport and Shubnikov-de Haas oscillations in the layered ternary telluride Ta3SiTe6 topological semimetal|Muhammad Naveed,Fucong Fei,Haijun Bu,Xiangyan Bo,Syed Adil Shah,Bo Chen,Yong Zhang,Qianqian Liu,Boyuan Wei,Shuai Zhang,Chuanying Xi,Xiangang Wan,Fengqi Song###

Magneto-transport and Shubnikov-de Haas oscillations in the layered ternary telluride Ta3SiTe6 topological semimetal. Topological semimetals characterize a novel class of quantum materials
hosting Dirac/Weyl fermions. The important features of topological fermions can
be exhibited by quantum oscillations. Here we report the magnetoresistance and
Shubnikov-de Haas (SdH) quantum oscillation of longitudinal resistance in the
single crystal of topological semimetal Ta3SiTe6 with the magnetic field up to
38 T. Periodic amplitude of the oscillations reveals related information about
the Fermi surface. The fast Fourier transformation spectra represent a single
oscillatory frequency. The analysis of the oscillations shows the Fermi pocket
with a cross-section area of 0.13 angstrom power minus 2. Combining
magneto-transport measurements and the first-principles calculation, we find
that these oscillations come from the hole pocket. Hall resistivity and the SdH
oscillations recommend that Ta3SiTe6 is a hole dominated system.

###Charge Density Modulation and Defect Ordering in Na$_x$MnBi$_y$ magnetic semimetal|Aaron Wegner,Despina Louca,Keith Taddei,Joerg Neuefeind###

Charge Density Modulation and Defect Ordering in Na$_x$MnBi$_y$ magnetic semimetal. The I-Mn-V antiferromagnet, NaMnBi, develops a very large positive
magnetoresistance (MR) up to 10,000% at 2 K and 9 T in crystals showing a
semiconductor-to-metal transition (SMT). In the absence of an SMT, a modest
(20%) MR is achieved. Here, we show that upon cooling below the magnetic
transition, a spatial modulation appears giving rise to new Bragg peaks due to
charge and defect ordering in a checkerboard pattern, with two kinds of
modulation vectors, $q_1$=($\frac23$, 0, 1) and $q_2$=($\frac23, \frac13,
\frac12$). This constitutes a superlattice transition ($T_s$) that lowers the
symmetry from the high temperature centrosymmetric P4/nmm to the
non-centrosymmetric P$\overline4$m2. In crystals with a large MR, a close to
room temperature $T_s$ is observed with $q_1$ appearing first, followed by
$q_2$. In crystals with low MR however, $T_s$ is much lower and only $q_1$ is
observed. The charge modulation and spin fluctuations may both contribute to
the enhancement of MR.

###Spin-accumulation induced magnetic texture in a metal-insulator bilayer|Dion M. F. Hartmann,Andreas Rückriegel,Rembert A. Duine###

Spin-accumulation induced magnetic texture in a metal-insulator bilayer. We consider the influence of a spin accumulation in a normal metal on the
magnetic statics and dynamics in an adjacent magnetic insulator. In particular,
we focus on arbitary angles between the spin accumulation and the easy-axis of
the magnetic insulator. Based on Landau-Lifshitz-Gilbert phenomenology
supplemented with magnetoelectronic circuit theory, we find that the magnetic
texture twists into a stable configuration that turns out to be described by a
virtual, or image, domain wall configuration, i.e., a domain wall outside the
ferromagnet. We show that even when the spin accumulation is perpendicular to
the anisotropy axis, the magnetic texture develops a component parallel to the
spin accumulation for sufficiently large spin bias. The emergence of this
parallel component gives rise to threshold behavior in the spin Hall
magnetoresistance and nonlocal magnon transport. This threshold can be used to
design novel spintronic and magnonic devices that can be operated without
external magnetic fields.

###Ultrafast Dynamical Lifshitz Transition|Samuel Beaulieu,Shuo Dong,Nicolas Tancogne-Dejean,Maciej Dendzik,Tommaso Pincelli,Julian Maklar,R. Patrick Xian,Michael A. Sentef,Martin Wolf,Angel Rubio,Laurenz Rettig,Ralph Ernstorfer###

Ultrafast Dynamical Lifshitz Transition. Fermi surface is at the heart of our understanding of metals and strongly
correlated many-body systems. An abrupt change in the Fermi surface topology,
also called Lifshitz transition, can lead to the emergence of fascinating
phenomena like colossal magnetoresistance and superconductivity. While Lifshitz
transitions have been demonstrated for a broad range of materials by
equilibrium tuning of macroscopic parameters such as strain, doping, pressure
and temperature, a non-equilibrium dynamical route toward ultrafast
modification of the Fermi surface topology has not been experimentally
demonstrated. Combining time-resolved multidimensional photoemission
spectroscopy with state-of-the-art TDDFT+$U$ simulations, we introduce a novel
scheme for driving an ultrafast Lifshitz transition in the correlated type-II
Weyl semimetal T$\mathrm{_{d}}$-MoTe$_{2}$. We demonstrate that this
non-equilibrium topological electronic transition finds its microscopic origin
in the dynamical modification of the effective electronic correlations. These
results shed light on a novel ultrafast scheme for controlling the Fermi
surface topology in correlated quantum materials.

###Anisotropic three-dimensional weak localization in ultrananocrystalline diamond films with nitrogen inclusions|L. H. Willems van Beveren,D. L. Creedon,N. Eikenberg,K. Ganesan,B. C. Johnson,G. Chimowa,D. Churochkin,S. Bhattacharyya,S. Prawer###

Anisotropic three-dimensional weak localization in ultrananocrystalline diamond films with nitrogen inclusions. We present a study of the structural and electronic properties of
ultra-nanocrystalline diamond films that were modified by adding nitrogen to
the gas mixture during chemical vapour deposition growth. Hall bar devices were
fabricated from the resulting films to investigate their electrical conduction
as a function of both temperature and magnetic field. Through low-temperature
magnetoresistance measurements, we present strong evidence that the dominant
conduction mechanism in these films can be explained by a combination of 3D
weak localization (3DWL) and thermally activated hopping at higher
temperatures. An anisotropic 3DWL model is then applied to extract the
phase-coherence time as function of temperature, which shows evidence of a
power law dependence in good agreement with theory.

###Origin of magnetovolume effect in a cobaltite|Ping Miao,Zhijian Tan,Sanghyun Lee,Yoshihisa Ishikawa,Shuki Torii,Masao Yonemura,Akihiro Koda,Kazuki Komatsu,Shinichi Machida,Asami Sano-Furukawa,Takanori Hattori,Xiaohuan Lin,Kuo Li,Takashi Mochiku,Ryosuke Kikuchi,Chizuru Kawashima,Hiroki Takahashi,Qingzhen Huang,Shinichi Itoh,Ryosuke Kadono,Yingxia Wang,Feng Pan,Kunihiko Yamauchi,Takashi Kamiyama###

Origin of magnetovolume effect in a cobaltite. The layered perovskite PrBaCo2O5.5+x demonstrates a strong negative thermal
expansion (NTE) which holds potential for being fabricated into composites with
zero thermal expansion. The NTE was found to be intimately associated with the
spontaneous magnetic ordering, known as magnetovolume effect (MVE). Here we
report with compelling evidences that the continuous-like MVE in PrBaCo2O5.5+x
is intrinsically of discontinuous character, originating from an
magnetoelectric transition from an antiferromagnetic insulating large-volume
(AFILV) phase to a ferromagnetic metallic small-volume (FMSV) phase.
Furthermore, the magnetoelectric effect (ME) shows high sensitivity to multiple
external stimuli such as temperature, carrier doping, hydrostatic pressure,
magnetic field etc. In contrast to the well-known ME such as colossal
magnetoresistance and multiferroic effect which involve symmetry breaking of
crystal structure, the ME in the cobaltite is purely isostructural. Our
discovery provides a new pathway to realizing the ME as well as the NTE, which
may find applications in new techniques.

###Multiple Superconducting Phases and Unusual Enhancement of the Upper Critical Field in UTe2|Dai Aoki,Fuminori Honda,Georg Knebel,Daniel Braithwaite,Ai Nakamura,DeXin Li,Yoshiya Homma,Yusei Shimizu,Yoshiki J. Sato,Jean-Pascal Brison,Jacques Flouquet###

Multiple Superconducting Phases and Unusual Enhancement of the Upper Critical Field in UTe2. We performed AC calorimetry and magnetoresistance measurements under pressure
for H || a-axis (easy-magnetization axis) in the novel heavy-fermion
superconductor UTe2. Thanks to the thermodynamic information, multiple
superconducting phases have been revealed under pressure and magnetic field.
The (H,T) phase diagram of superconductivity under pressure displays an abrupt
increase of the upper critical field (Hc2) at low temperature and in the high
field region, and a strong convex curvature of Hc2 at high temperature. This
behavior of Hc2 and the multiple superconducting phases require a state for the
superconducting order parameter more complex than a spin-triplet equal spin
pairing. Above the superconducting critical pressure, Pc, we find strong
indications that the possible magnetic order is closer to antiferromagnetism
than to ferromagnetism.

###Monitoring of the formation of strontium molybdate intergrain tunneling barriers in strontium ferromolybdate|G. Suchaneck,N. Kalanda,E. Artsiukh,M. Yarmolich,N. A. Sobolev###

Monitoring of the formation of strontium molybdate intergrain tunneling barriers in strontium ferromolybdate. This work is a contribution to the understanding of the electrical
resistivity in strontium ferromolybdate (SFMO) ceramics. It demonstrates that
an appropriate thermal treatment leads to the formation of dielectric SrMoO4
shells at the surface of SFMO nanograins. In samples without SrMoO4 shells, the
sign of the temperature coefficient of resistance changes with increasing
temperature from negative at very low temperature to positive at higher
temperatures. Samples exhibiting a negative temperature coefficient contain
SrMoO4 shells and demonstrate a behavior of the resistivity that can be
described in terms of the fluctuation-induced tunneling model, and near room
temperature the conductivity mechanism converts to a variable-range hopping
one. The results of this work serve as a starting point for the understanding
of the low-field magnetoresistance which is very promising for spintronic
device application.

###Nodal and nematic superconducting phases in NbSe2 monolayers from competing superconducting channels|Chang-woo Cho,Jian Lyu,Liheng An,Tianyi Han,Kwan To Lo,Cheuk Yin Ng,Jiaqi Hu,Yuxiang Gao,Gaomin Li,Mingyuan Huang,Ning Wang,Jörg Schmalian,Rolf Lortz###

Nodal and nematic superconducting phases in NbSe2 monolayers from competing superconducting channels. Transition metal dichalcogenides like 2H-NbSe2 in their two-dimensional (2D)
form exhibit Ising superconductivity with the quasiparticle spins are firmly
pinned in the direction perpendicular to the basal plane. This enables them to
withstand exceptionally high magnetic fields beyond the Pauli limit for
superconductivity. Using field-angle-resolved magnetoresistance experiments for
fields rotated in the basal plane we investigate the field-angle dependence of
the upper critical field (Hc2), which directly reflects the symmetry of the
superconducting order parameter. We observe a six-fold nodal symmetry
superposed on a two-fold symmetry. This agrees with theoretical predictions of
a nodal topological superconducting phase near Hc2, together with a nematic
superconducting state. We demonstrate that in NbSe2 such unconventional
superconducting states can arise from the presence of several competing
superconducting channels.

###Quantum oscillations and electronic structure in the large-Chern number topological chiral semimetal PtGa|Sheng Xu,Liqin Zhou,Xiao-Yan Wang,Huan Wang,Jun-Fa lin,Xiang-Yu Zeng,Peng Cheng,Hongming Weng,Tian-Long Xia###

Quantum oscillations and electronic structure in the large-Chern number topological chiral semimetal PtGa. We report the magnetoresistance(MR), de Haas-van Alphen (dHvA) oscillations
and the electronic structures of single crystal PtGa. The large unsaturated MR
is observed with the magnetic field B//[111]. Evident dHvA oscillations with
B//[001] configuration have been observed, from which twelve fundamental
frequencies are extracted and the spin-orbit coupling effect (SOC) induced band
splitting is revealed. The light cyclotron effective masses are extracted from
the fitting by the thermal damping term of the Lifshitz-Kosevich (LK) formula.
Combining with the calculated frequencies from the first-principles
calculations, the dHvA frequencies F$_1$/F$_3$ and F$_{11}$/F$_{12}$ are
confirmed to originate from the electron pockets at $\Gamma$ and R,
respectively. The first-principles calculations also reveal the existence of
spin-3/2 RSW fermion and time-reversal (TR) doubling of the spin-1 excitation
at $\Gamma$ and R with large Chern number $\pm4$ when SOC is included.

###A way to measure electron spin-flipping at F/N interfaces and application to Co/Cu|B. Dassonneville,R. Acharyya,H. Y. T. Nguyen,R. Loloee,W. P. Pratt Jr.,J. Bass###

A way to measure electron spin-flipping at F/N interfaces and application to Co/Cu. We describe a technique, using the current-perpendicular-to-plane (CPP)
geometry, to measure the parameter delta(F/N), characterizing flipping of
electron spins at a ferromagnetic/non-magnetic (F/N) metallic interface. The
technique involves measuring the CPP magnetoresistance of a sample containing a
ferromagnetically coupled [F/N]x n multilayer embedded within the 20 nm thick
central Cu layer of a symmetric Py-based, double exchange-biased spin-valve. To
focus on delta(F/N), the F- and N-layers are made thin compared to their
spin-diffusion lengths. We test the technique using F/N = Co/Cu. Analysing with
no adjustable parameters, gives inconsistency with delta(Co/Cu) = 0, but
consistency with our prior value of delta(Co/Cu) = 0.25 (+/- 0.1). Taking
delta(Co/Cu) as adjustable gives delta(Co/Cu) = 0.33 (+0.03/-0.08).

###Magnetoresistance and localization in bosonic insulators|Markus Mueller###

Magnetoresistance and localization in bosonic insulators. We study the strong localization of hard core bosons. Using a locator
expansion we find that in the insulator, unlike for typical fermion problems,
nearly all low-energy scattering paths come with positive amplitudes and hence
interfere constructively. As a consequence, the localization length of bosonic
excitations shrinks when the constructive interference is suppressed by a
magnetic field, entailing an exponentially large positive magnetoresistance,
opposite to and significantly stronger than the analogous effect in fermions.
Within the forward scattering approximation, we find that the lowest energy
excitations are the most delocalized. A similar analysis applied to random
field Ising models suggests that the ordering transition is due to a
delocalization initiated at zero energy rather than due to the closure of a
mobility gap in the paramagnet.

###Evolution of transport properties of BaFe2-xRuxAs2 in a wide range of isovalent Ru substitution|M. J. Eom,S. W. Na,C. Hoch,R. K. Kremer,J. S. Kim###

Evolution of transport properties of BaFe2-xRuxAs2 in a wide range of isovalent Ru substitution. The effects of isovalent Ru substitution at the Fe sites of BaFe2-xRuxAs2 are
investigated by measuring resistivity and Hall coefficient on high-quality
single crystals in a wide range of doping (0 < x < 1.4). Ru substitution
weakens the antiferromagnetic (AFM) order, inducing superconductivity for
relatively high doping level of 0.4 < x < 0.9. Near the AFM phase boundary, the
transport properties show non-Fermi-liquid-like behaviors with a
linear-temperature dependence of resistivity and a strong temperature
dependence of Hall coefficient with a sign change. Upon higher doping, however,
both of them recover conventional Fermi-liquid behaviors. Strong doping
dependence of Hall coefficient together with a small magnetoresistance suggest
that the anomalous transport properties can be explained in terms of
anisotropic charge carrier scattering due to interband AFM fluctuations rather
than a conventional multi-band scenario.

###Details of Sample Dependence and Transport Properties of URu2Si2|Tatsuma D. Matsuda,Elena Hassinger,Dai Aoki,Valentin Taufour,Georg Knebel,Naoyuki Tateiwa,Etsuji Yamamoto,Yoshinori Haga,Yoshichika Onuki,Zachary Fisk,Jacques Flouquet###

Details of Sample Dependence and Transport Properties of URu2Si2. Resistivity and specific heat measurements were performed in the low carrier
unconventional superconductor URu2Si2 on various samples with very different
qualities. The superconducting transition temperature (TSC) and the hidden
order transition temperature (THO) of these crystals were evaluated as a
function of the residual resistivity ratio (RRR). In high quality single
crystals the resistivity does not seem to follow a T2 dependence above TSC,
indicating that the Fermi liquid regime is restricted to low temperatures.
However, an analysis of the isothermal longitudinal magnetoresistivity points
out that the T2 dependence may be "spoiled" by residual inhomogeneous
superconducting contribution. We discuss a possible scenario concerning the
distribution of TSC related with the fact that the hidden order phase is very
sensitive to the pressure inhomogeneity.

###Giant thermoelectric effect in Al2O3 magnetic tunnel junctions|Weiwei Lin,Michel Hehn,Laurent Chaput,Béatrice Negulescu,Stéphane Andrieu,François Montaigne,Stéphane Mangin###

Giant thermoelectric effect in Al2O3 magnetic tunnel junctions. Thermoelectric effects in magnetic nanostructures and the so-called spin
caloritronics are attracting much interest. Indeed it provides a new way to
control and manipulate spin currents which are key elements of spin-based
electronics. Here we report on giant magnetothermoelectric effect in Al2O3
magnetic tunnel junctions. The thermovoltage in this geometry can reach 1 mV.
Moreover a magneto-thermovoltage effect could be measured with ratio similar to
the tunnel magnetoresistance ratio. The Seebeck coefficient can then be tuned
by changing the relative magnetization orientation of the two magnetic layers
in the tunnel junction. Therefore our experiments extend the range of
spintronic devices application to thermoelectricity and provide a crucial piece
of information for understanding the physics of thermal spin transport.

###Neutron Reflectometer with Polarization Option at the Budapest Neutron Centre|L. Bottyán,D. G. Merkel,B. Nagy,J. Major###

Neutron Reflectometer with Polarization Option at the Budapest Neutron Centre. The ever increasing need for product advancement and miniaturization keeps
thin film assemblies, membranes, magnetic and non-magnetic multilayer and
patterned heterostructures in the limelight of material science and
technological development. A number of thin film and surface characterization
methods have emerged recently to meet the new challenges. The increased
interest in magnetic thin film analytical instruments - mainly triggered by the
discovery of the giant magnetoresistance and related phenomena1 - resulted in a
boom of PNR studies as well as of the construction of a number of new neutron
reflectometers with polarization option at neutron sources all over the world.
Here we report on the design, construction and operation parameters and first
example uses of the "Grazing Incidence Neutron Apparatus" (GINA) a recently
installed neutron reflectometer at the Budapest Neutron Centre (BNC), Hungary.

###Determination of spin-dependent Seebeck coefficients of CoFeB/MgO/CoFeB magnetic tunnel junction nanopillars|N. Liebing,S. Serrano-Guisan,K. Rott,G. Reiss,J. Langer,B. Ocker,H. W. Schumacher###

Determination of spin-dependent Seebeck coefficients of CoFeB/MgO/CoFeB magnetic tunnel junction nanopillars. We investigate the spin-dependent Seebeck coefficient and the tunneling
magneto thermopower of CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJ) in the
presence of thermal gradients across the MTJ. Thermal gradients are generated
by an electric heater on top of the nanopillars. The thermo power voltage
across the MTJ is found to scale linearly with the heating power and reveals
similar field dependence as the tunnel magnetoresistance. The amplitude of the
thermal gradient is derived from calibration measurements in combination with
finite element simulations of the heat flux. Based on this, large
spin-dependent Seebeck coefficients of the order of (240 \pm 110) \muV/K are
derived. From additional measurements on MTJs after dielectric breakdown, a
tunneling magneto thermopower up to 90% can be derived for 1.5 nm MgO based MTJ
nanopillars.

###Microwave-induced off-resonance giant magnetoresistance in ultraclean two-dimensional electron systems|Jesus Iñarrea,Gloria Platero###

Microwave-induced off-resonance giant magnetoresistance in ultraclean two-dimensional electron systems. We report on theoretical studies of a recently discovered strong
microwave-induced magnetoresistance peak obtained in ultra-clean
two-dimensional electron systems at low temperatures. The most striking feature
of such a peak is that it shows up on the second harmonic of the cyclotron
resonance and with an amplitude that can reach an order of magnitude larger
than the microwave-induced resistance oscillations. We apply the
microwave-driven electron orbits model in the ultra-clean scenario.
Accordingly, we calculate the elastic scattering rate (charged impurity) which
will define the unexpected resonance peak position. We also obtain the
inelastic scattering rate (phonon damping), that will be responsible of the
large peak amplitude. Calculated results are in good agreement with
experiments. These results would be of special interest in nanophotonics; they
could lead to the design of novel ultrasensitive microwave detectors.

###Electronic transport in ferromagnetic barriers on the surface of a topological insulator with $δ$ doping|Jian-Hui Yuan,Yan Zhang,Daizheng Huang,Qinhu Zhong,Xin Zhang###

Electronic transport in ferromagnetic barriers on the surface of a topological insulator with $δ$ doping. We investigate electron transporting through a two-dimensional
ferromagnetic/normal/ferromagnetic tunnel junction on the surface of a
three-dimensional topological insulator with taking into $\delta$ doping
account. It is found that the conductance oscillates with the Fermi energy, the
position and the aptitude of the $\delta$ doping. Also the conductance depends
sensitively on the direction of the magnetization of the two ferromagnets,
which originate from the control of the spin flow due to spin-momentum locked.
It is found that the conductance is the maximum at the parallel configuration
while it is minimum at the antiparallel configuration and vice versa, which may
stem from the half wave loss due to the electron wave entering through the
antiparallel configuration. These characters are very helpful for making new
types of magnetoresistance devices due to the practical applications.

###Large Linear Magnetoresistance and Shubnikov-de Hass Oscillations in Single Crystals of YPdBi Heusler Topological Insulators|Wenhong Wang,Yin Du,Guizhou Xu,Xiaoming Zhang,Enke Liu,Zhongyuan Liu,Youguo Shi,Jinglan Chen,Guangheng Wu,Xixiang Zhang###

Large Linear Magnetoresistance and Shubnikov-de Hass Oscillations in Single Crystals of YPdBi Heusler Topological Insulators. We report the observation of a large linear magnetoresistance (MR) and
Shubnikov-de Hass (SdH) quantum oscillations in single crystals of YPdBi
Heusler topological insulators. Owning to the successfully obtained the
high-quality YPdBi single crystals, large non-saturating linear MR of as high
as 350% at 5K and over 120% at 300 K under a moderate magnetic field of 7 T is
observed. In addition to the large, field-linear MR, the samples exhibit
pronounced SdH quantum oscillations at low temperature. Analysis of the SdH
data manifests that the high-mobility bulk electron carriers dominate the
magnetotransport and are responsible for the observed large linear MR in YPdBi
crystals. These findings imply that the Heusler-based topological insulators
have superiorities for investigating the novel quantum transport properties and
developing the potential applications.

###Effect of annealing on the magnetic, magnetocaloric and magnetoresistance properties of Ni-Co-Mn-Sb melt spun ribbons|Roshnee Sahoo,D. M. Raj Kumar,D. Arvindha Babu,K. G. Suresh,A. K. Nigam,M. Manivel Raja###

Effect of annealing on the magnetic, magnetocaloric and magnetoresistance properties of Ni-Co-Mn-Sb melt spun ribbons. The structural, magnetic, magnetocaloric and magnetotransport properties of
Ni46Co4Mn38Sb12 melt spun ribbons have been systematically investigated. The
partially ordered B2 phase of the as-spun ribbon transforms to fully ordered
L21 phase upon annealing, which signifies a considerable change of the atomic
ordering in the system. The presence of atomic disorder in the as-spun ribbon
gives rise to a higher martensitic transition temperature and a lower
magnetization as compared to the bulk sample. However, annealing the ribbons
helps in regaining the bulk properties to a large extent. Significant changes
in magnetocaloric effect, exchange bias and magnetoresistance have been
observed between the as-spun and the annealed ribbons, indicating the role of
atomic ordering on the functional as well as fundamental properties in the
Heusler system. Importantly, the study shows that one can reduce the hysteresis
loss by preparing melt spun alloys and subjecting them to appropriate annealing
conditions, which enable them to become practical magnetic refrigerants.

###Thermoelectric effects in silicene nanoribbons|K. Zberecki,M. Wierzbicki,J. Barnaś,R. Swirkowicz###

Thermoelectric effects in silicene nanoribbons. Transport and thermoelectric coefficients (including also spin thermopower)
of silicene nanoribbons with zigzag edges are investigated by {\it ab-initio}
numerical methods. Local spin density of such nanoribbons reveals edge
magnetism. Like in graphene, one finds antiferromagnetic and ferromagnetic
ordering, with spin polarization at one edge antiparallel or parallel to that
at the other edge, respectively. Thermoelectric properties, especially the
Seebeck coefficient, significantly depend on the electronic band structure and
are enhanced when the Fermi level is in the energy gap. However, these
thermoelectric properties are significantly reduced when the phonon
contribution to the heat conductance is included. This phonon contribution has
been calculated numerically by two different methods. Transition from
antiferromagnetic to ferromagnetic states leads to a large magnetoresistance as
well as to a considerable magnetothermopower. Thermoelectric parameters in the
antiparallel configuration, when spin polarization in the left part of the
nanoribbon is opposite to that in the right part, are also analyzed.

###Weak Antilocalization and Linear Magnetoresistance in The Surface State of SmB6|S. Thomas,D. J. Kim,S. B. Chung,T. Grant,Z. Fisk,Jing Xia###

Weak Antilocalization and Linear Magnetoresistance in The Surface State of SmB6. Strongly correlated Kondo insulator SmB6 is known for its peculiar low
temperature residual conduction, which has recently been demonstrated to arise
from a robust metallic surface state, as predicted by the theory of topological
Kondo insulator (TKI). Photoemission, quantum oscillation and magnetic doping
experiments have provided evidence for the Dirac-like dispersion and
topological protection. Questions arise as whether signatures of spin-momentum
locking and electron interaction could be resolved in transport measurements.
Here we report metallic conduction of surface state down to mK temperatures
with saturation behaviors suggestive of Kondo effect. We observe in the surface
state the weak-antilocalization (WAL) effect that is in agreement with a
spin-momentum locked metallic surface. At larger perpendicular magnetic fields,
the surface state exhibits an unusual linear magnetoresistance similar to those
found in Bi-based topological insulators and in graphene. (Correspondence to:
xia.jing@uci.edu)

###Non linear magnetotransport theory and Hall induced resistance oscillations in graphene|Ricardo Gutierrez-Jauregui,Manuel Torres###

Non linear magnetotransport theory and Hall induced resistance oscillations in graphene. The quantum oscillations of nonlinear magnetoresistance in graphene that
occurs in response to a dc current bias are investigated. We present a
theoretical model for the nonlinear magnetotransport of graphene carriers. The
model is based on the exact solution of the effective Dirac equation in crossed
electric and magnetic fields, while the effects of randomly distributed
impurities are perturbatively added. To compute the nonlinear current we
develop a covariant formulation of the migration center theory. The analysis of
the differential resistivity in the large magnetic field region, shows that the
extrema of the Shubnikov de Hass oscillations invert when the dc currents
exceeds a threshold value. This results are in good agreement with the
experimental observations. At small magnetic field, the existence of Hall
induced resistance oscillations are predicted for ultra clean graphene samples.
These oscillations originate from Landau-Zener transitions between Landau
levels, that are tilted by the strong electric Hall field.

###Interplay between Aharonov-Bohm interference and parity selective tunneling in zigzag graphene nanoribbon rings|Viet-Hung Nguyen,Yann-Michel Niquet,Philippe Dollfus###

Interplay between Aharonov-Bohm interference and parity selective tunneling in zigzag graphene nanoribbon rings. We report a numerical study on Aharonov-Bohm (AB) effect and parity selective
tunneling in pn junctions based on zigzag graphene nanoribbon rings. We find
that when applying a magnetic field to the ring, the AB interference can
reverse the parity symmetry of incoming waves and hence can strongly modulate
the parity selective transmission through the system. Therefore, the
transmission between two states of different parity exhibits the AB
oscillations with a \pi-phase shift, compared to the case of states of same
parity. On this basis, it is shown that interesting effects such as giant (both
positive and negative) magnetoresistance and strong negative differential
conductance can be achieved in this structure. Our study thus presents a new
property of the AB interference, which could be helpful to further understand
the transport properties of graphene mesoscopic-systems.

###Dirac vs. Weyl in topological insulators: Adler-Bell-Jackiw anomaly in transport phenomena|Heon-Jung Kim,Ki-Seok Kim,J. F. Wang,M. Sasaki,N. Satoh,A. Ohnishi,M. Kitaura,M. Yang,L. Li###

Dirac vs. Weyl in topological insulators: Adler-Bell-Jackiw anomaly in transport phenomena. Dirac metals (gapless semi-conductors) are believed to turn into Weyl metals
when perturbations, which break either time reversal symmetry or inversion
symmetry, are employed. However, no experimental evidence has been reported for
the existence of Weyl fermions in three dimensions. Applying magnetic fields
near the topological phase transition from a topological insulator to a band
insulator in Bi1-xSbx, we observe not only the weak anti-localization
phenomenon in magnetoconductivity near zero magnetic fields (B < 0.4 T) but
also its upturn above 0.4 T only for E // B. This incompatible coexistence
between weak anti-localization and negative magnetoresistivity is attributed to
the Adler-Bell-Jackiw anomaly (topological E B term) in the presence of weak
anti-localization corrections.

###Linear magnetoconductivity in multiband spin-density-wave metals with nonideal nesting|A. E. Koshelev###

Linear magnetoconductivity in multiband spin-density-wave metals with nonideal nesting. In several parent iron-pnictide compounds the resistivity has an extended
range of linear magnetic field dependence. We argue that there is a simple and
natural explanation of this behavior. Spin density wave transition leads to
Fermi-surface reconstruction corresponding to strong modification of the
electronic spectrum near the nesting points. It is difficult for quasiparticles
to pass through these points during their orbital motion in magnetic field,
because they must turn sharply. As the area of the Fermi surface affected by
the nesting points increases proportionally to magnetic field, this mechanism
leads to the linear magnetoresistance. The crossover between the quadratic and
linear regimes takes place at the field scale set by the SDW gap and scattering
rate.

###Aging the Cu-doped Bi2Te3 crystals for the topological transport and its atomic tunneling-clustering dynamics|Taishi Chen,Qian Chen,Koen Schouteden,Wenkai Huang,Xuefeng Wang,Zhe Li,Feng Miao,Xinran Wang,Zhaoguo Li,Bo Zhao,Shaochun Li,Fengqi Song,Jinlan Wang,Chris van Haesendonck,Baigeng Wang,Guanghou Wang###

Aging the Cu-doped Bi2Te3 crystals for the topological transport and its atomic tunneling-clustering dynamics. We report on the observation of the two-dimensional weak antilocalization in
(Cu0.1Bi0.9)2Te3.06 crystals relying on measurements of the magnetoresistance
in a tilted field. The dephasing analysis and scanning tunneling spectroscopy
corroborate the transport of the topological surface states (SS). The SSs
contribute 3.3% conductance in 30{\mu}m-thick material and become dominant in
the 100nm-thick flakes. Such optimized topological SS transport is achieved by
an intense aging process, when the bulk conductance is suppressed by four
orders of magnitude in the long period. Scanning tunneling microscopy reveals
that Cu atoms are initially inside the quintuple layers and migrate to the
layer gaps to form Cu clusters during the aging. In combination with
first-principles calculations, an atomic tunneling-clustering procedure across
a diffusion barrier of 0.57eV is proposed.

###Spin-Transfer-Torque Driven Magneto-Logic OR, AND and NOT Gates|C. Sanid,S. Murugesh###

Spin-Transfer-Torque Driven Magneto-Logic OR, AND and NOT Gates. We show that current induced magneto-logic gates like AND, OR and NOT can be
designed with the simple architecture involving a single nano spin-valve
pillar, as an extension of our recent work on spin-torque-driven magneto-logic
universal gates, NAND and NOR. Here the logical operation is induced by
spin-polarized currents which also form the logical inputs. The operation is
facilitated by the simultaneous presence of a constant controlling magnetic
field, in the absence of which the same element operates as a magnetoresistive
memory element. We construct the relevant phase space diagrams for the free
layer magnetization dynamics in the monodomain approximation and show the
rationale and functioning of the proposed gates. The flipping time for the
logical states of these non-universal gates is estimated to be within nano
seconds, just like their universal counter parts.

###Spin torque building blocks|Nicolas Locatelli,Vincent Cros,Julie Grollier###

Spin torque building blocks. The discovery of the spin torque effect has made magnetic nanodevices
realistic candidates for active elements of memory devices and applications.
Magnetoresistive effects allow the read-out of increasingly small magnetic
bits, and the spin torque provides an efficient tool to manipulate - precisely,
rapidly and at low energy cost - the magnetic state, which is in turn the
central information medium of spintronic devices. By keeping the same magnetic
stack, but by tuning a device's shape and bias conditions, the spin torque can
be engineered to build a variety of advanced magnetic nanodevices. Here we show
that by assembling these nanodevices as building blocks with different
functionalities, novel types of computing architectures can be envisisaged. We
focus in particular on recent concepts such as magnonics and spintronic neural
networks.

###Edge proximity-induced magnetoresistance and spin polarization in ferromagnetic gated bilayer graphene nanoribbon|Vahid Derakhshan,Hosein Cheraghchi###

Edge proximity-induced magnetoresistance and spin polarization in ferromagnetic gated bilayer graphene nanoribbon. Coherent spin-dependent transport through a junction containing of
Normal/Ferromagnetic/Normal bilayer graphene nanoribbon with zigzag edges is
investigated by using Landauer formalism. In a more realistic set-up, the
exchange field is induced by two ferromagnetic insulator strips deposited on
the ribbon edges while a perpendicular electric field is applied by the top
gated electrodes. Our results show that, for antiparallel configuration, a band
gap is opened giving rise a semiconducting behavior, while for parallel
configuration, the band structure has no band gap. As a result, a giant
magnetoresistance is achievable by changing the alignment of induced
magnetization. Application of a perpendicular electric field on the parallel
configuration, results in a spin field-effect transistor where a fully spin
polarization occurs around the Dirac point. To be comparable our results with
the one for monolayer graphene, we demonstrate that the reflection symmetry and
so the parity conservation fails in bilayer graphene nanoribbons with the
zigzag edges.

###Magnetic-Field-Modulated Resonant Tunneling in Ferromagnetic-Insulator-Nonmagnetic junctions|Yang Song,Hanan Dery###

Magnetic-Field-Modulated Resonant Tunneling in Ferromagnetic-Insulator-Nonmagnetic junctions. We present a theory for resonance-tunneling magnetoresistance (MR) in
Ferromagnetic-Insulator-Nonmagnetic junctions. The theory sheds light on many
of the recent electrical spin injection experiments, suggesting that this MR
effect rather than spin accumulation in the nonmagnetic channel corresponds to
the electrically detected signal. We quantify the dependence of the tunnel
current on the magnetic field by quantum rate equations derived from the
Anderson impurity model, with important addition of impurity spin interactions.
Considering the on-site Coulomb correlation, the MR effect is caused by
competition between the field, spin interactions and coupling to the magnetic
lead. By extending the theory, we present a basis for operation of novel
nm-size memories.

###Exchange bias effect in martensitic epitaxial Ni-Mn-Sn thin films applied to pin CoFeB/MgO/CoFeB magnetic tunnel junctions|Niclas Teichert,Alexander Boehnke,Anna Behler,Bruno Weise,Anja Waske,Andreas Hütten###

Exchange bias effect in martensitic epitaxial Ni-Mn-Sn thin films applied to pin CoFeB/MgO/CoFeB magnetic tunnel junctions. The exchange bias effect is commonly used to shift the coercive field of a
ferromagnet. This technique is crucial for the use of magnetic tunnel junctions
as logic or memory devices. Therefore, an independent switching of the two
ferromagnetic electrodes is necessary to guarantee a reliable readout. Here, we
demonstrate that the intrinsic exchange bias effect of Ni-Mn-Sn can be used to
apply a unidirectional anisotropy to magnetic tunnel junctions. For this, we
use epitaxial Ni-Mn-Sn films as pinning layers for microfabricated
CoFeB/MgO/CoFeB magnetic tunnel junctions. We compare the exchange bias field
($H_{\text{EB}}$) measured after field cooling in $-10$\,kOe external field by
magnetization measurements with $H_{\text{EB}}$ obtained from tunnel
magnetoresistance measurements. Consistent for both methods we find an exchange
bias of about $H_{\text{EB}}=130$\,Oe at 10\,K, which decreases with increasing
temperature and vanishes above 70\,K.

###Topological, non topological and instanton droplets driven by spin-transfer torque in materials with perpendicular magnetic anisotropy and Dzyaloshinskii-Moriya Interaction|Mario Carpentieri,Riccardo Tomasello,Roberto Zivieri,Giovanni Finocchio###

Topological, non topological and instanton droplets driven by spin-transfer torque in materials with perpendicular magnetic anisotropy and Dzyaloshinskii-Moriya Interaction. The interfacial Dzyaloshinskii-Moriya Interaction can modify the topology of
droplets excited by a localized spin-polarized current. Here, we show that, in
addition to the stationary droplet excitations with skyrmion number either one
(topological) or zero (non-topological), there exists, for a fixed current, an
excited mode with a non-stationary time behavior. We call this mode "instanton
droplet", which is characterized by time domain transitions of the skyrmion
number. These transitions are coupled to an emission of incoherent spin-waves
that can be observed in the frequency domain as a source of noise. Our results
are interesting from a fundamental point of view to study spin-wave emissions
due to a topological transition in current-driven systems, and could open the
route for experiments based on magnetoresistance effect for the design of a
further generation of nanoscale microwave oscillators.

###Growth-induced electron mobility enhancement at the LaAlO$_3$/SrTiO$_3$ interface|A. Fête,C. Cancellieri,D. Li,D. Stornaiuolo,A. D. Caviglia,S. Gariglio,J. -M. Triscone###

Growth-induced electron mobility enhancement at the LaAlO$_3$/SrTiO$_3$ interface. We have studied the electronic properties of the 2D electron liquid present
at the LaAlO$_3$/SrTiO$_3$ interface in series of samples prepared at different
growth temperatures. We observe that interfaces fabricated at 650{\deg}C
exhibit the highest low temperature mobility ($\approx 10000 \textrm{
cm}^2/\textrm{Vs}$) and the lowest sheet carrier density ($\approx 5\times
10^{12} \textrm{ cm}^{-2}$). These samples show metallic behavior and
Shubnikov-de Haas oscillations in their magnetoresistance. Samples grown at
higher temperatures (800-900{\deg}C) display carrier densities in the range of
$\approx 2-5 \times 10^{13} \textrm{ cm}^{-2}$ and mobilities of $\approx 1000
\textrm{ cm}^2/\textrm{Vs}$ at 4K. Reducing their carrier density by field
effect to $8\times 10^{12} \textrm{ cm}^{-2}$ lowers their mobilites to
$\approx 50 \textrm{ cm}^2/\textrm{Vs}$ bringing the conductance to the
weak-localization regime.

###Magnetotransport of single crystalline NbAs|N. J. Ghimire,Yongkang Luo,M. Neupane,D. J. Williams,E. D. Bauer,F. Ronning###

Magnetotransport of single crystalline NbAs. We report transport measurement in zero and applied magnetic field on a
single crystal of NbAs. Transverse and longitudinal magnetoresistance in the
plane of this tetragonal structure does not saturate up to 9 T. In the
transverse configuration ($H \parallel c$, $I \perp c$) it is 230,000 \% at 2
K. The Hall coefficient changes sign from hole-like at room temperature to
electron-like below $\sim$ 150 K. The electron carrier density and mobility
calculated at 2 K based on a single band approximation are 1.8 x 10$^{19}$
cm$^{-3}$ and 3.5 x 10$^{5}$ cm$^2$/Vs, respectively. These values are similar
to reported values for TaAs and NbP, and further emphasize that this class of
noncentrosymmetric, transition-metal monopnictides is a promising family to
explore the properties of Weyl semimetals and the consequences of their novel
electronic structure.

###Spin Hall magnetoresistance in metallic bilayers|Junyeon Kim,Peng Sheng,Saburo Takahashi,Seiji Mitani,Masamitsu Hayashi###

Spin Hall magnetoresistance in metallic bilayers. Spin Hall magnetoresistance (SMR) is studied in metallic bilayers that
consist of heavy metal (HM) layer and a ferromagnetic metal (FM) layer. We find
nearly a ten-fold increase of SMR in W/CoFeB compared to previously studied
HM/ferromagnetic insulator (FI) systems. The SMR increases with decreasing
temperature despite the negligible change in the W layer resistivity with
temperature. A model is developed to account for the absorption of the
longitudinal spin current to the FM layer, one of the key characteristics of a
metallic ferromagnet. We find that the model not only quantitatively describes
the HM layer thickness dependence of SMR, allowing accurate estimation of the
spin Hall angle and the spin diffusion length of the HM layer, but also can
account for the temperature dependence of SMR by assuming a temperature
dependent spin polarization of the FM layer. These results illustrate the
unique role a metallic ferromagnetic layer plays in defining spin transmission
across the HM/FM interface.

###Discovery of Dirac Node Arcs in PtSn4|Yun Wu,Lin-Lin Wang,Eundeok Mun,D. D. Johnson,Daixiang Mou,Lunan Huang,Yongbin Lee,S. L. Budko,P. C. Canfield,Adam Kaminski###

Discovery of Dirac Node Arcs in PtSn4. In topological quantum materials the conduction and valence bands are
connected at points (Dirac/Weyl semimetals) or along lines (Line Node
semimetals) in the momentum space. Numbers of studies demonstrated that several
materials are indeed Dirac/Weyl semimetals. However, there is still no
experimental confirmation of materials with line nodes, in which the Dirac
nodes form closed loops in the momentum space. Here we report the discovery of
a novel topological structure - Dirac node arcs - in the ultrahigh
magnetoresistive material PtSn4 using laser-based angle-resolved photoemission
spectroscopy (ARPES) data and density functional theory (DFT) calculations.
Unlike the closed loops of line nodes, the Dirac node arc structure resembles
the Dirac dispersion in graphene that is extended along one dimension in
momentum space and confined by band gaps on either end. We propose that this
reported Dirac node arc structure is a novel topological state that provides a
novel platform for studying the exotic properties of Dirac Fermions.

###Observation of Quantum Griffiths Singularity and Ferromagnetism at Superconducting LaAlO3/SrTiO3(110) Interface|Shengchun Shen,Ying Xing,Pengjie Wang,Haiwen Liu,Hai-Long Fu,Yangwei Zhang,Lin He,X. C. Xie,Xi Lin,Jiacai Nie,Jian Wang###

Observation of Quantum Griffiths Singularity and Ferromagnetism at Superconducting LaAlO3/SrTiO3(110) Interface. Diverse phenomena emerge at the interface between band insulators LaAlO3 and
SrTiO3, such as superconductivity and ferromagnetism, showing an opportunity
for potential applications as well as bringing fundamental research interests.
Particularly, the two-dimensional electron gas formed at LaAlO3/SrTiO3
interface offers an appealing platform for quantum phase transition from a
superconductor to a weakly localized metal. Here we report the
superconductor-metal transition in superconducting two-dimensional electron gas
formed at LaAlO3/SrTiO3(110) interface driven by a perpendicular magnetic
field. Interestingly, when approaching the quantum critical point, the dynamic
critical exponent is not a constant but a diverging value, which is a direct
evidence of quantum Griffiths singularity raised from quenched disorder at
ultralow temperatures. Furthermore, the hysteretic property of
magnetoresistance was firstly observed at LaAlO3/SrTiO3(110) interfaces, which
suggests potential coexistence of superconductivity and ferromagnetism.

###Local charge variation enhanced spin canting of BiFeO3/La0.7Sr0.3MnO3 heterostructure|Yuan-Yen Tai,Jian-Xin Zhu###

Local charge variation enhanced spin canting of BiFeO3/La0.7Sr0.3MnO3 heterostructure. Transition-metal oxides (TMOs) exhibit many emergent phenomena ranging from
high-temperature super- conductivity and giant magnetoresistance to magnetism
and ferroelectricity. When TMOs are interfaced with each other, new
multi-functionalities can arise, which are absent in individual components. In
this work, we have systematically studied, within a unified double-exchange
model, the interfacial magnetic response in layered BiFeO3 (BFO) and
La0.7Sr0.3MnO3 (LSMO) heterostructures. The ferromagnetic/antiferromagnetic
canting is shown to be enhanced on the interface of BFO by the influence of
local charge variation. More interestingly, it is found that the spin canting
in BFO can be further enhanced with deeper penetration depth to the bulk when a
local oxygen vacancy is placed around the interface.

###Flexible MgO barrier magnetic tunnel junctions|Li Ming Loong,Wonho Lee,Xuepeng Qiu,Ping Yang,Hiroyo Kawai,Mark Saeys,Jong-Hyun Ahn,Hyunsoo Yang###

Flexible MgO barrier magnetic tunnel junctions. Flexible electronic devices require the integration of multiple crucial
components on soft substrates to achieve their functions. In particular, memory
devices are the fundamental component for data storage and processing in
flexible electronics. Here, we present flexible MgO barrier magnetic tunnel
junction (MTJ) devices fabricated using a transfer printing process, which
exhibit reliable and stable operation under substantial deformation of the
device substrates. In addition, the flexible MTJ devices yield significantly
enhanced tunneling magnetoresistance (TMR) of ~300 % and improved abruptness of
switching, as residual strain in the MTJ structure induced by the fabrication
process is released during the transfer process. This approach could be useful
for a wide range of flexible electronic systems that require high performance
memory components.

###Spin Hall Effect Induced Spin Transfer Through an Insulator|Wei Chen,Manfred Sigrist,Dirk Manske###

Spin Hall Effect Induced Spin Transfer Through an Insulator. When charge current passes through a normal metal that exhibits spin Hall
effect, spin accumulates at the edge of the sample in the transverse direction.
We predict that this spin accumulation, or spin voltage, enables quantum
tunneling of spin through an insulator or vacuum to reach a ferromagnet without
transferring charge. In a normal metal/insulator/ferromagnetic insulator
trilayer (such as Pt/oxide/YIG), the quantum tunneling explains the
spin-transfer torque and spin pumping that exponentially decay with the
thickness of the insulator. In a normal metal/insulator/ferromagnetic metal
trilayer (such as Pt/oxide/Co), the spin transfer in general does not decay
monotonically with the thickness of the insulator. Combining with the spin Hall
magnetoresistance, this tunneling mechanism points to the possibility of a new
type of tunneling spectroscopy that can probe the magnon density of states of a
ferromagnetic insulator in an all-electrical and noninvasive manner.

###Theory of spin loss at metallic interfaces|K. D. Belashchenko,Alexey A. Kovalev,M. van Schilfgaarde###

Theory of spin loss at metallic interfaces. Interfacial spin-flip scattering plays an important role in magnetoelectronic
devices. Spin loss at metallic interfaces is usually quantified by matching the
magnetoresistance data for multilayers to the Valet-Fert model, while treating
each interface as a fictitious bulk layer whose thickness is $\delta$ times the
spin-diffusion length. By employing the properly generalized circuit theory and
the scattering matrix approaches, we derive the relation of the parameter
$\delta$ to the spin-flip transmission and reflection probabilities at an
individual interface. It is found that $\delta$ is proportional to the square
root of the probability of spin-flip scattering. We calculate the spin-flip
transmission probability for flat and rough Cu/Pd interfaces using the
Landauer-B\"uttiker method based on the first-principles electronic structure
and find $\delta$ in reasonable agreement with experiment.

###Magnetic field-dependent inhomogeneities and their effect on the magnetoresponse of 2D superconductors|Sarath Sankar,Vikram Tripathi###

Magnetic field-dependent inhomogeneities and their effect on the magnetoresponse of 2D superconductors. We show that inhomogeneities in the spatial distribution of Cooper pairs and
in the phase of the local superconducting order parameter in the vicinity of a
superconductor-normal state transition (SNT) in two dimensions can be highly
sensitive to a perpendicular magnetic field. We focus on the role of orbital
effects in the field-dependence of local superfluid stiffness and
superconducting phase disorder in homogeneously-disordered two-dimensional
superconductor thin films. The relative importance of these orbital effects is
analyzed in different physical regimes dominated by Coulomb blockade, thermal
phase fluctuations and Aharanov-Bohm phase disorder respectively. Following
this approach, we obtain explicit expressions for the field dependence of
magnetoresistance and superfluid stiffness near the SNT, and attempt an
understanding of some recent experimental findings.

###Anomalous tunnel magnetoresistance and spin transfer torque in magnetic tunnel junctions with embedded nanoparticles|Arthur Useinov,Lin-Xiu Ye,Niazbeck Useinov,Te-Ho Wu,Chih-Huang Lai###

Anomalous tunnel magnetoresistance and spin transfer torque in magnetic tunnel junctions with embedded nanoparticles. The tunnel magnetoresistance (TMR) in the magnetic tunnel junction (MTJ) with
embedded nanoparticles (NPs) was calculated in range of the quantum-ballistic
model. The simulation was performed for electron tunneling through the
insulating layer with embedded magnetic and nonmagnetic NPs within the approach
of the double barrier subsystem connected in parallel to the single barrier
one. This model can be applied for both MTJs with in-plane magnetization and
perpendicular one. We also calculated the in-plane component of the spin
transfer torque (STT) versus the applied voltage in MTJs with magnetic NPs and
determined that its value can be much larger than in single barrier system
(SBS) for the same tunneling thickness. The reported simulation reproduces
experimental data of the TMR suppression and peak-like TMR anomalies at low
voltages available in literature.

###Tunnel magnetoresistance and temperature related effects in magnetic tunnel junctions with embedded nanoparticles|Arthur Useinov,Chih-Huang Lai###

Tunnel magnetoresistance and temperature related effects in magnetic tunnel junctions with embedded nanoparticles. Temperature dependence of the tunnel magnetoresistance (TMR) was calculated
in range of the quantum-ballistic model in the magnetic tunnel junctions (MTJs)
with embedded nanoparticles (NPs). The electron tunnel transport through NP was
simulated in range of double barrier approach, which was integrated into the
model of the magnetic point-like contact. The resonant TMR conditions and
temperature impact were explored in detail. Moreover, the possible reasons of
the temperature induced resonant conditions were discussed in the range of the
lead-tunneling cell-lead model near Kondo temperature. We also found that
redistribution of the voltage drop becomes crucial in this model. Furthermore,
the direct tunneling plays the dominant role and cannot be omitted in the
quantum systems with the total tunneling thickness up to 5-6 nm. Hence, Coulomb
blockade model cannot explain Kondo-induced TMR anomalies in nanometer-sized
tunnel junctions.

###Revealing the nature of magnetic phases in the semi-Heusler alloy Cu0.85Ni0.15MnSb|Madhumita Halder,K. G. Suresh,M. D. Mukadam,S. M. Yusuf###

Revealing the nature of magnetic phases in the semi-Heusler alloy Cu0.85Ni0.15MnSb. We report the magnetic, magnetocaloric, and magnetotransport properties of
the semi-Heusler alloy Cu0.85Ni0.15MnSb, which exhibits coexistence of
antiferromagnetic (AFM) and ferromagnetic (FM) phases. A broad magnetic phase
transition is evident from the temperature variations of magnetization, heat
capacity, and isothermal magnetic entropy change. This is due to the presence
of both AFM and FM phases at low temperatures. The variation of electrical
resistivity with temperature shows three distinct regions of magnetic phases.
The magnetoresistance (MR) results also show the presence of AFM and FM phases
at temperatures below 45 K, and a FM phase at temperature above 45K. Though
there is no signature of a spin-glass state at low temperatures, various
results point towards the presence of short-range magnetic correlations at low
temperatures.

###Strong pinning of vortices by antiferromagnetic domain boundaries in CeCo(In$_{1-x}$Cd$_x$)$_5$|Dong-Jin Jang,Luis Pedrero,L. D. Pham,Z. Fisk,Manuel Brando###

Strong pinning of vortices by antiferromagnetic domain boundaries in CeCo(In$_{1-x}$Cd$_x$)$_5$. We have studied the isothermal magnetization $M(H)$ of
CeCo(In$_{1-x}$Cd$_x$)$_5$ with $x$ = 0.0075 and 0.01 down to 50 mK. Pronounced
field-history dependent phenomena occur in the coexistence regime of the
superconducting and antiferromagnetic phases. At low-fields, a phenomenological
model of magnetic-flux entry well explains $M(H)$ implying the dominance of
bulk pinning effect. However, unless crystallographic quenched disorder is
hysteretic, the asymmetric peak effect (ASPE) which appears at higher fields
cannot be explained by the pinning of vortices due to material defects. Also
the temperature dependence of the ASPE deviates from the conventional scenario
for the peak effect. Comparison of our thermodynamic phase diagrams with those
from previous neutron scattering and magnetoresistance experiments indicates
that the pinning of vortices takes place at the field-history dependent
antiferromagnetic domain boundaries.

###Topological Phase Transition and Chiral-Anomaly Driven Negative Magneto-Resistance in Bulk Black Phosphorus|Chun-Hong Li,Yu-Jia Long,Ling-Xiao Zhao,Lei Shan,Zhi-An Ren,Jian-Zhou Zhao,Hong-Ming Weng,Xi Dai,Zhong Fang,Gen-Fu Chen,Cong Ren###

Topological Phase Transition and Chiral-Anomaly Driven Negative Magneto-Resistance in Bulk Black Phosphorus. We report the anisotropic magneto-transport measurement on a non-compound
band semiconductor black phosphorus (BP) with magnetic field B up to 16 Tesla
applied in both perpendicular and parallel to electric current I under
hydrostatic pressures. The BP undergoes a topological Lifshitz transition from
band semiconductor to a zero-gap Dirac semimetal state, characterized by a weak
localization-weak antilocaliation transition at low magnetic fields and the
emergence of a nontrivial Berry Phase of detected by SdH magneto-oscillations
in magnetoresistance curves. In the transition region, we observe a
pressure-dependent negative MR only in the B//I configuration. This negative
longitudinal MR is attributed to the Adler-Bell-Jackiw anomaly (topological
E$\cdot$B term) in the presence of weak antilocalization corrections.

###Spintronics Detection of Interfacial Magnetic Switching in a Paramagnetic Tris(8-hydroxyquinoline)iron(III) Thin Film|Dali Sun,Christopher M. Kareis,Kipp J. van Schooten,Wei Jiang,Gene Siegel,Marzieh Kavand,Royce A. Davidson,William W. Shum,Chuang Zhang,Ashutosh Tiwari,Christoph Boehme,Feng Liu,Peter W. Stephens,Joel S. Miller,Z. Valy Vardeny###

Spintronics Detection of Interfacial Magnetic Switching in a Paramagnetic Tris(8-hydroxyquinoline)iron(III) Thin Film. Organic semiconductors find increasing importance in spin transport devices
due to the modulation and control of their properties through chemical
synthetic versatility. The organic materials are used as interlayers between
two ferromagnet (FM) electrodes in organic spin valves (OSV), as well as for
magnetic spin manipulation of metal-organic complexes at the molecular level.
In the latter, specifically, the substrate-induced magnetic switching in a
paramagnetic molecule has been evoked extensively, but studied by delicate
surface spectroscopies. Here we present evidence of the substantial magnetic
switching in a nanosized thin film of the paramagnetic molecule,
tris(8-hydroxyquinoline)iron(III) (Feq3) deposited on a FM substrate, using the
magnetoresistance response of electrical spin-injection in an OSV structure,
and the inverse-spin-Hall effect induced by state-of-art pulsed microwave
spin-pumping. We show that interfacial spin control at the molecular level may
lead to a macroscopic organic spin transport device, thus, bridging the gap
between organic spintronics and molecular spintronics.

###Change-over of carrier type and magneto-transport property in Cu doped Bi2Te3 Topological Insulators|Abhishek Singh,Rahul Singh,A. Lakhani,T. Patel,G. S. Okram,V. Ganeshan,A. K. Ghosh,Sandip Chatterjee###

Change-over of carrier type and magneto-transport property in Cu doped Bi2Te3 Topological Insulators. Structural, resistivity, thermoelectric power and magneto-transport
properties of Cu doped Bi2Te3 topological insulators have been investigated.
The occurrence of the tuning of charge carriers from n type to p type by Cu
doping at Te sites of Bi2Te3 is observed both from Hall effect and
thermoelectric power measurements. Carrier mobility decreases with the doping
of Cu which provides evidence of the movement of Fermi level from bulk
conduction band to the bulk valence band. Thermoelectric power also
increaseswith doping of Cu.Moreover linear magnetoresistance (LMR) has been
observed at high magnetic field in pure Bi2Te3 which is associated to the
gapless topological surface states protected by time reversal symmetry (TRS),
whereas doping of Cu breaks TRS and an opening of band gap occurs which
quenches the LMR.

###The mechanism of spin-orbit coupling in a 2D oxide interface|Patrick Seiler,Jone Zabaleta,Robin Wanke,Jochen Mannhart,Thilo Kopp,Daniel Braak###

The mechanism of spin-orbit coupling in a 2D oxide interface. The presence of spin-orbit coupling drives the anomalous magnetotransport at
oxide interfaces and forms the basis for numerous intriguing properties of
these 2D electron systems, such as topologically protected phases or
anti-localization. For many of those systems, the identification of the
underlying coupling mechanism is obfuscated by multi-band effects. We therefore
analyze the transport of LaAlO$_3$/SrTiO$_3$ interfaces under high pressures, a
technique to single out the multi-band contributions. We argue that the
observed magnetoresistance is due to quantum interference and not related to
Coulomb interaction. Therefore, this system is an excellent candidate to
generate a metal-insulator transition of the long-sought symplectic 2D
universality class. It is shown that the spin-orbit coupling can be linked
unambiguously to the band structure with a cubic (Dresselhaus-like) rather than
a linear (Rashba-like) spin-orbit band splitting.

###Spin correlations and colossal magnetoresistance in HgCr$_2$Se$_4$|Chaojing Lin,Changjiang Yi,Youguo Shi,Lei Zhang,Guangming Zhang,Jens Mueller,Yongqing Li###

Spin correlations and colossal magnetoresistance in HgCr$_2$Se$_4$. This study aims to unravel the mechanism of colossal magnetoresistance (CMR)
observed in n-type HgCr$_2$Se$_4$, in which low-density conduction electrons
are exchange-coupled to a three-dimensional Heisenberg ferromagnet with a Curie
temperature $T_C\approx$ 105 K. Near room temperature the electron transport
exhibits an ordinary semiconducting behavior. As temperature drops below
$T^*\simeq2.1T_C$, the magnetic susceptibility deviates from the Curie-Weiss
law, and concomitantly the transport enters an intermediate regime exhibiting a
pronounced CMR effect before a transition to metallic conduction occurs at
$T<T_C$. Our results suggest an important role of spin correlations not only
near the critical point, but also for a wide range of temperatures
($T_C<T<T^*$) in the paramagnetic phase. In this intermediate temperature
regime the transport undergoes a percolation type of transition from isolated
magnetic polarons to a continuous network when temperature is lowered or
magnetic field becomes stronger.

###Effect of temperature on spin-transfer torque induced magnetic solitons|Sergi Lendínez,Jinting Hang,Saül Vélez,Joan Manel Hernàndez,Dirk Backes,Andrew D. Kent,Ferran Macià###

Effect of temperature on spin-transfer torque induced magnetic solitons. Spin-transfer torques in a nanocontact to an extended magnetic film can
create spin waves that condense to form dissipative droplet solitons. Here we
report an experimental study of the temperature dependence of the current and
applied field thresholds for droplet soliton formation, as well as the
nanocontact's electrical characteristics associated with droplet dynamics.
Nucleation of droplet solitons requires higher current densities at higher
temperatures, in contrast to typical spin-transfer torque induced switching
between static magnetic states. Magnetoresistance and electrical noise
measurements show that soliton instabilities become more pronounced with
increasing temperature. These results are of fundamental interest in
understanding the influence of thermal noise on droplet solitons, and in
controlling their dynamics.

###Chiral magnetoresistance in the Weyl semimetal NbP|Anna Corinna Niemann,Johannes Gooth,Shu-Chun Wu,Svenja Bäßler,Philip Sergelius,Ruben Hühne,Bernd Rellinghaus,Chandra Shekhar,Vicky Süß,Marcus Schmidt,Claudia Felser,Binghai Yan,Kornelius Nielsch###

Chiral magnetoresistance in the Weyl semimetal NbP. NbP is a recently realized Weyl semimetal (WSM), hosting Weyl points through
which conduction and valence bands cross linearly in the bulk and exotic Fermi
arcs appear. However, the most intriguing transport phenomenon of a WSM, the
chiral anomaly-induced negative magnetoresistance (NMR) in parallel electric
and magnetic fields, has yet to be observed in NbP. In intrinsic NbP the Weyl
points lie far from the Fermi energy, making chiral magneto-transport elusive.
Here, we use Ga-doping to relocate the Fermi energy in NbP sufficiently close
to the Weyl points, for which the different Fermi surfaces are verified by
resultant quantum oscillations. Consequently, we observe a NMR for parallel
electric and magnetic fields, which is considered as a signature of the chiral
anomaly in condensed-matter physics. The NMR survives up to room temperature,
making NbP a versatile material platform for the development of Weyltronic
applications.

###Current-induced giant diamagnetism in the Mott insulator Ca2RuO4|Chanchal Sow,Shingo Yonezawa,Sota Kitamura,Takashi Oka,Kazuhiko Kuroki,Fumihiko Nakamura,Yoshiteru Maeno###

Current-induced giant diamagnetism in the Mott insulator Ca2RuO4. Mott insulators have surprised us many times by hosting new and diverse
quantum phenomena when the frozen electrons are perturbed by various stimuli.
Superconductivity, metal-insulator transition, and colossal magnetoresistance
induced by element substitution, pressure, and magnetic field are prominent
examples. Here we report a novel phenomenon, namely giant diamagnetism, in the
Mott insulator Ca2RuO4 induced by electric current. With application of 1 A/cm2
current, the strongest diamagnetism among all nonsuperconducting materials is
induced as the system is tuned to a semimetallic state. The origin lies in the
emergence of indirect Dirac cones in the many-body spectrum and associated
monopole-like anomaly in the momentum dependent susceptibility. This
record-breaking and switchable diamagnetism is a new class of non-equilibrium
quantum phenomena on the verge of Mott insulating states.

###Evidence for topological proximity effect in graphene coupled to topological insulator|Liang Zhang,Ben-Chuan Lin,Yan-Fei Wu,Jun Xu,Dapeng Yu,Zhi-Min Liao###

Evidence for topological proximity effect in graphene coupled to topological insulator. The emergence of topological order in graphene is in great demand for the
realization of quantum spin Hall states. Recently, it is theoretically proposed
that the spin textures of surface states in topological insulator can be
directly transferred to graphene by means of proximity effect. Here we report
the observations of the topological proximity effect in the
graphene-topological insulator Bi2Se3 heterojunctions via magnetotransport
measurements. The coupling between the p_z orbitals of graphene and the p
orbitals of surface states on the Bi2Se3 bottom surface can be enhanced by
applying perpendicular negative magnetic field, resulting in a giant negative
magnetoresistance at the Dirac point up to about -91%. An obvious resistivity
dip in the transfer curve at the Dirac point is also observed in the hybrid
devices, which is consistent with the theoretical predictions of the distorted
Dirac bands with unique spin textures inherited from Bi2Se3 surface states.

###Signature of enhanced spin-orbit interaction in the magnetoresistance of LaTiO$_3$/SrTiO$_3$ interfaces on $δ$-doping|Shubhankar Das,Z. Hossain,R. C. Budhani###

Signature of enhanced spin-orbit interaction in the magnetoresistance of LaTiO$_3$/SrTiO$_3$ interfaces on $δ$-doping. We present a study of modulation of spin-orbit interaction (SOI) at the
interface of LaTiO$_3$/SrTiO$_3$ by $\delta$-doping with an iso-structural
ferromagnetic perovskite LaCoO$_3$. The sheet carrier density at the interface
decreases exponentially with $\delta$-doping thickness. We have explored that
the spin-orbit scattering time ($\tau_{so}$) can be decreased by nearly 3
orders of magnitude, whereas the inelastic scattering time ($\tau_{i}$) remains
almost constant with $\delta$-doping thickness. We have also observed that the
$\tau_{i}$ varies almost inversely proportional to temperature and $\tau_{so}$
remains insensitive to temperature, which suggest that the spin relaxation in
these interfaces follows D'yakonov-Perel mechanism. The observed in-plane
anisotropic magnetoresistance is attributed to the mixing of the spin up and
spin down states of d-band at Fermi level due to SOI.

###Observation of semi-localized dispersive states in the strongly correlated electron-doped ferromagnet Eu$_{1-x}$Gd$_{x}$O|Daniel E. Shai,Mark H. Fischer,Alex J. Melville,Eric J. Monkman,John W. Harter,Dawei Shen,Darrell G. Schlom,Michael J. Lawler,Eun-Ah Kim,Kyle M. Shen###

Observation of semi-localized dispersive states in the strongly correlated electron-doped ferromagnet Eu$_{1-x}$Gd$_{x}$O. Chemical substitution plays a key role in controlling the electronic and
magnetic properties of complex materials. For instance, in EuO, carrier doping
can induce a spin-polarized metallic state, colossal magnetoresistance, and
significantly enhance the Curie temperature. Here, we employ a combination of
molecular-beam epitaxy, angle-resolved photoemission spectroscopy, and an
effective model calculation to investigate and understand how semi-localized
states evolve in lightly electron doped Eu$_{1-x}$Gd$_{x}$O above the
ferromagnetic Curie temperature. Our studies reveal a characteristic length
scale for the spatial extent of the donor wavefunctions which remains constant
as a function of doping, consistent with recent tunneling studies of doped EuO.
Our work sheds light on the nature of the semiconductor-to-metal transition in
Eu$_{1-x}$Gd$_{x}$O and should be generally applicable for doped complex
oxides.

###Tunable sign change of spin Hall magnetoresistance in Pt/NiO/YIG structures|Dazhi Hou,Zhiyong Qiu,Joseph Barker,Koji Sato,Kei Yamamoto,Saul Velez,Juan M. Gomez-Perez,Luis E. Hueso,Felix Casanova,Eiji Saitoh###

Tunable sign change of spin Hall magnetoresistance in Pt/NiO/YIG structures. Spin Hall magnetoresistance (SMR) has been investigated in Pt/NiO/YIG
structures in a wide range of temperature and NiO thickness. The SMR shows a
negative sign below a temperature which increases with the NiO thickness. This
is contrary to a conventional SMR theory picture applied to Pt/YIG bilayer
which always predicts a positive SMR. The negative SMR is found to persist even
when NiO blocks the spin transmission between Pt and YIG, indicating it is
governed by the spin current response of NiO layer. We explain the negative SMR
by the NiO 'spin-flop' coupled with YIG, which can be overridden at higher
temperatures by positive SMR contribution from YIG. This highlights the role of
magnetic structure in antiferromagnets for transport of pure spin current in
multilayers.

###A pressure-induced topological phase with large Berry curvature in Pb$_{1-x}$Sn$_x$Te|Tian Liang,Satya Kushwaha,Jinwoong Kim,Quinn Gibson,Jingjing Lin,Nicholas Kioussis,R. J. Cava,N. P. Ong###

A pressure-induced topological phase with large Berry curvature in Pb$_{1-x}$Sn$_x$Te. The picture of how a gap closes in a semiconductor has been radically
transformed by topological concepts. Instead of the gap closing and immediately
re-opening, topological arguments predict that, in the absence of inversion
symmetry, a metallic phase protected by Weyl nodes persists over a finite
interval of the tuning parameter (e.g. pressure $P$) . The gap re-appears when
the Weyl nodes mutually annihilate. We report evidence that Pb$_{1-x}$Sn$_x$Te
exhibits this topological metallic phase. Using pressure to tune the gap, we
have tracked the nucleation of a Fermi surface droplet that rapidly grows in
volume with $P$. In the metallic state we observe a large Berry curvature which
dominates the Hall effect. Moreover, a giant negative magnetoresistance is
observed in the insulating side of phase boundaries, in accord with \emph{ab
initio} calculations. The results confirm the existence of a topological
metallic phase over a finite pressure interval.

###Reduction of the low-temperature bulk gap in samarium hexaboride under high magnetic fields|S. Wolgast,Y. S. Eo,K. Sun,Ç. Kurdak,F. F. Balakirev,M. Jaime,D. -J. Kim,Z. Fisk###

Reduction of the low-temperature bulk gap in samarium hexaboride under high magnetic fields. SmB$_6$ exhibits a small (15-20 meV) bandgap at low temperatures due to
hybridized $d$ and $f$ electrons, a tiny (3 meV) transport activation energy
$(E_{A})$ above 4 K, and surface states accessible to transport below 2 K. We
study its magnetoresistance in 60-T pulsed fields between 1.5 K and 4 K. The
response of the nearly $T$-independent surface states (which show no
Shubnikov-de Haas oscillations) is distinct from that of the activated bulk.
$E_{A}$ shrinks by 50% under fields up to 60 T. Data up to 93 T suggest that
this trend continues beyond 100 T, in contrast with previous explanations. It
rules out emerging theories to explain observed exotic magnetic quantum
oscillations.

###Electric control of Dirac quasiparticles by spin-orbit torque in an antiferromagnet|Libor Šmejkal,Jakub Železný,Jairo Sinova,Tomáš Jungwirth###

Electric control of Dirac quasiparticles by spin-orbit torque in an antiferromagnet. Spin-orbitronics and Dirac quasiparticles are two fields of condensed matter
physics initiated independently about a decade ago. Here we predict that Dirac
quasiparticles can be controlled by the spin-orbit torque reorientation of the
N\'{e}el vector in an antiferromagnet. Using CuMnAs as an example, we formulate
symmetry criteria allowing for the co-existence of Dirac quasiparticles and
N\'{e}el spin-orbit torques. We identify the non-symmorphic crystal symmetry
protection of Dirac band crossings whose on and off switching is mediated by
the N\'{e}el vector reorientation. We predict that this concept, verified by
minimal model and density functional calculations in the CuMnAs semimetal
antiferromagnet, can lead to a topological metal-insulator transition driven by
the N\'{e}el vector and to the corresponding topological anisotropic
magnetoresistance.

###Anomalous transport model with axial magnetic fields|Karl Landsteiner,Yan Liu###

Anomalous transport model with axial magnetic fields. The transport properties of massless fermions in $3+1$ spacetime dimension
have been in the focus of recent theoretical and experimental research. New
transport properties appear as consequences of chiral anomalies. The most
prominent is the generation of a current in a magnetic field, the so-called
chiral magnetic effect leading to an enhancement of the electric conductivity
(negative magnetoresistivity). We study the analogous effect for axial magnetic
fields that couple with opposite signs to fermions of different chirality. We
emphasize local charge conservation and study the induced
magneto-conductivities proportional to an electric field and a gradient in
temperature. We find that the magnetoconductivity is enhanced whereas the
magneto-thermoelectric conductivity is diminished. As a side result we
interpret an anomalous contribution to the entropy current as a generalized
thermal Hall effect.

###Magnetic field induced strong valley polarization in the three dimensional topological semimetal LaBi|Nitesh Kumar,Chandra Shekhar,J. Klotz,J. Wosnitza,Claudia Felser###

Magnetic field induced strong valley polarization in the three dimensional topological semimetal LaBi. LaBi is a three-dimensional rocksalt-type material with a surprisingly
quasi-two-dimensional electronic structure. It exhibits excellent electronic
properties such as the existence of nontrivial Dirac cones, extremely large
magnetoresistance, and high charge-carrier mobility. The cigar-shaped electron
valleys make the charge transport highly anisotropic when the magnetic field is
varied from one crystallographic axis to another. We show that the electrons
can be polarized effectively in these electron valleys under a rotating
magnetic field. We achieved a polarization of 60% at 2 K despite the
coexistence of three-dimensional hole pockets. The valley polarization in LaBi
is compared to the sister compound LaSb where it is found to be smaller. The
performance of LaBi is comparable to the highly efficient bismuth.

###Raman scattering study of large magnetoresistance semimetals TaAs$_2$ and NbAs$_2$|Feng Jin,Xiaoli Ma,Pengjie Guo,Changjiang Yi,Le Wang,Yiyan Wang,Qiaohe Yu,Jieming Sheng,Anmin Zhang,Jianting Ji,Yong Tian,Kai Liu,Youguo Shi,Tianlong Xia,Qingming Zhang###

Raman scattering study of large magnetoresistance semimetals TaAs$_2$ and NbAs$_2$. We have performed polarized and temperature-dependent Raman scattering
measurements on extremely large magnetoresitance compounds TaAs$_2$ and
NbAs$_2$. In both crystals, all the Raman active modes, including six A$_g$
modes and three B$_g$ modes, are clearly observed and well assigned with the
combination of symmetry analysis and first-principles calculations. The
well-resolved periodic intensity modulations of the observed modes with
rotating crystal orientations, verify the symmetry of each assigned mode and
are fitted to experimentally determine the elements of Raman tensor matrixes.
The broadening of two A$_g$ modes seen in both compounds allows us to estimate
electron-phonon coupling constant, which suggests a relatively small
electron-phonon coupling in the semimetals TaAs$_2$ and NbAs$_2$. The present
study provides the fundamental lattice dynamics information on TaAs$_2$ and
NbAs$_2$ and may shed light on the understanding of their extraordinary large
magnetoresistance.

###Thickness dependent electronic structure in WTe$_2$ thin films|Fei-Xiang Xiang,Ashwin Srinivasan,Oleh Klochan,Shi-Xue Dou,Alex R. Hamilton,Xiao-Lin Wang###

Thickness dependent electronic structure in WTe$_2$ thin films. We study the electronic structure of WTe$_2$ thin film fakes with different
thickness down to 11 nm. Angle-dependent quantum oscillations reveal a
crossover from a three-dimensional (3D) to a two-dimensional (2D) electronic
system when the sample thickness is reduced below 26 nm. The quantum
oscillations further show that the Fermi pockets get smaller as the samples are
made thinner, indicating that the overlap between conduction and valence bands
is getting smaller and implying the spatial confinement could lift the overlap
in even thinner samples. In addition, the quadratic magnetoresistance (MR) also
shows a crossover from 3D to 2D behavior as the samples are made thinner, while
gating is shown to affect both the quadratic MR and the quantum oscillations of
a thin sample by tuning its carrier density.

###Magnetotransport properties of the triply degenerate node topological semimetal tungsten carbide|J. B. He,D. Chen,W. L. Zhu,S. Zhang,L. X. Zhao,Z. A. Ren,G. F. Chen###

Magnetotransport properties of the triply degenerate node topological semimetal tungsten carbide. We report the magnetoresistance (MR), Hall effect, and de Haas-van Alphen
(dHvA) effect studies of the single crystals of tungsten carbide, WC, which is
predicted to be a new type of topological semimetal with triply degenerate
nodes. With the magnetic field rotated in the plane perpendicular to the
current, WC shows field induced metal to insulator like transition and large
nonsaturating quadratic MR at low temperature. As the magnetic field parallel
to the current, a pronounced negative longitudinal MR only can be observed when
the current flows along the certain direction. Hall effect indicates WC is a
perfect compensated semimetal, which may be related to the large nonsaturating
quadratic MR. The analysis of dHvA oscillations reveals that WC is a multiband
system with small cross-sectional areas of Fermi surface and light cyclotron
effective masses. Our results indicate that WC is an ideal platform to study
the recently proposed New Fermions with triply degenerate crossing points.

###Extremely high conductivity observed in the triple point topological metal MoP|Nitesh Kumar,Yan Sun,Michael Nicklas,Sarah J. Watzman,Olga Young,Inge Leermakers,Jacob Hornung,Johannes Klotz,Johannes Gooth,Kaustuv Manna,Vicky Süß,Satya N. Guin,Tobias Förster,Marcus Schmidt,Lukas Muechler,Binghai Yan,Peter Werner,Walter Schnelle,Uli Zeitler,Jochen Wosnitza,Stuart S. P. Parkin,Claudia Felser,Chandra Shekhar###

Extremely high conductivity observed in the triple point topological metal MoP. Weyl and Dirac fermions have created much attention in condensed matter
physics and materials science. Recently, several additional distinct types of
fermions have been predicted. Here, we report ultra-high electrical
conductivity in MoP at low temperature, which has recently been established as
a triple point Fermion material. Here we show that the electrical resistivity
is 6 n-ohm cm at 2 K with a large mean free path of 11 microns. de Haas-van
Alphen oscillations reveal spin splitting of the Fermi surfaces. In contrast to
noble metals with similar conductivity and number of carriers, the
magnetoresistance in MoP does not saturate up to 9 T at 2 K. Interestingly, the
momentum relaxing time of the electrons is found to be more than 15 times
larger than the quantum coherence time. This difference between the scattering
scales shows that momentum conserving scattering dominates in MoP at low
temperatures.

###Dynamical amplification of magnetoresistances and Hall currents up to the THz regime|Filipe S. M. Guimarães,Manuel dos Santos Dias,Juba Bouaziz,Antonio T. Costa,Roberto B. Muniz,Samir Lounis###

Dynamical amplification of magnetoresistances and Hall currents up to the THz regime. Spin-orbit-related effects offer a highly promising route for reading and
writing information in magnetic units of future devices. These phenomena rely
not only on the static magnetization orientation but also on its dynamics to
achieve fast switchings that can reach the THz range. In this work, we consider
Co/Pt and Fe/W bilayers to show that accounting for the phase difference
between different processes is crucial to the correct description of the
dynamical currents. By tuning each system towards its ferromagnetic resonance,
we reveal that dynamical spin Hall angles can non-trivially change sign and be
boosted by over 500%, reaching giant values. We demonstrate that charge and
spin pumping mechanisms can greatly magnify or dwindle the currents flowing
through the system, influencing all kinds of magnetoresistive and Hall effects,
thus impacting also dc and second harmonic experimental measurements.

###Theory of anomalous magnetotransport from mass anisotropy|Liujun Zou,Samuel Lederer,T. Senthil###

Theory of anomalous magnetotransport from mass anisotropy. In underdoped YBa$_2$Cu$_3$O$_{6+x}$, there is evidence of a small Fermi
surface pocket subject to substantial mass enhancement in the doping regime $
0.12<p<0.16$. This mass enhancement may vary substantially over the Fermi
surface, due to "hot spot" or other relevant physics. We therefore examine the
magnetotransport of an electron-like Fermi pocket with large effective mass
anisotropy. Within the relaxation time approximation, we show that even for a
pocket with a fixed shape, the magnitude and sign of the Hall effect may change
as the mass anisotropy changes (except at very large, likely inaccessible
magnetic fields). We discuss implications for recent Hall measurements in near
optimally doped cuprates in high fields. In addition we identify a novel
intermediate asymptotic regime of magnetic field, characterized by B-linear
magnetoresistance. Similar phenomena should occur in a variety of other
experimental systems with anisotropic mass enhancement

###Room temperature magneto-optic effect in silicon light-emitting diodes|F. Chiodi,S. L. Bayliss,L. Barast,D. Débarre,H. Bouchiat,R. H. Friend,A. D. Chepelianskii###

Room temperature magneto-optic effect in silicon light-emitting diodes. In weakly spin-orbit coupled materials, the spin-selective nature of
recombination can give rise to large magnetic-field effects, for example on
electro-luminescence from molecular semiconductors. While silicon has weak
spin-orbit coupling, observing spin-dependent recombination through
magneto-electroluminescence is challenging due to the inefficiency of emission
due to silicon's indirect band-gap, and to the difficulty in separating
spin-dependent phenomena from classical magneto-resistance effects. Here we
overcome these challenges to measure magneto-electroluminescence in silicon
light-emitting diodes fabricated via gas immersion laser doping. These devices
allow us to achieve efficient emission while retaining a well-defined geometry
thus suppressing classical magnetoresistance effects to a few percent. We find
that electroluminescence can be enhanced by up to 300\% near room temperature
in a seven Tesla magnetic field showing that the control of the spin degree of
freedom can have a strong impact on the efficiency of silicon LEDs.

###Nematic superconducting state in iron pnictide superconductors|Jun Li,Paulo J. Pereira,Jie Yuan,Yang-Yang Lv,Mei-Ping Jiang,Dachuan Lu,Zi-Quan Lin,Yong-Jie Liu,Jun-Feng Wang,Liang Li,Xiaoxing Ke,Gustaaf Van Tendeloo,Meng-Yue Li,Hai-Luke Feng,Takeshi Hatano,Hua-Bing Wang,Pei-Heng Wu,Kazunari Yamaura,Eiji Takayama-Muromachi,Johan Vanacken,Liviu F. Chibotaru,Victor V. Moshchalkov###

Nematic superconducting state in iron pnictide superconductors. Nematic order often breaks the tetragonal symmetry of iron-based
superconductors. It arises from regular structural transition or electronic
instability in the normal phase. Here, we report the observation of a nematic
superconducting state, by measuring the angular dependence of the in-plane and
out-of-plane magnetoresistivity of Ba0.5K0.5Fe2As2 single crystals. We find
large twofold oscillations in the vicinity of the superconducting transition,
when the direction of applied magnetic field is rotated within the basal plane.
To avoid the influences from sample geometry or current flow direction, the
sample was designed as Corbino-shape for in-plane and mesa-shape for
out-of-plane measurements. Theoretical analysis shows that the nematic
superconductivity arises from the weak mixture of the quasi-degenerate s-wave
and d-wave components of the superconducting condensate, most probably induced
by a weak anisotropy of stresses inherent to single crystals.

###Magnetic and Electronic Properties of Spin-Orbit Coupled Dirac Electrons on a $(001)$ Thin Film of Double Perovskite Sr$_2$FeMoO$_6$|Masahiko G. Yamada,George Jackeli###

Magnetic and Electronic Properties of Spin-Orbit Coupled Dirac Electrons on a $(001)$ Thin Film of Double Perovskite Sr$_2$FeMoO$_6$. We present an interacting model for the electronic and magnetic behavior of a
strained $(001)$ atomic layer of Sr$_2$FeMoO$_6,$ which shows room-temperature
ferrimagnetism and magnetoresistance with potential spintronics application in
the bulk. We find that the strong spin-orbit coupling in the molybdenum 4$d$
shell gives rise to a robust ferrimagnetic state with an emergent
spin-polarized electronic structure consisting of flat bands and four massive
or massless Dirac dispersions. Based on the spin-wave theory, we demonstrate
that the magnetic order remains intact for a wide range of doping, leading to
the possibility of exploring flat band physics, such as Wigner crystallization
in electron-doped Sr$_{2-x}$La$_{x}$FeMoO$_6.$

###Experimental observation of node-line-like surface states in LaBi|Baojie Feng,Jin Cao,Meng Yang,Ya Feng,Shilong Wu,Botao Fu,Masashi Arita,Koji Miyamoto,Shaolong He,Kenya Shimada,Youguo Shi,Taichi Okuda,Yugui Yao###

Experimental observation of node-line-like surface states in LaBi. In a Dirac nodal line semimetal, the bulk conduction and valence bands touch
at extended lines in the Brillouin zone. To date, most of the theoretically
predicted and experimentally discovered nodal lines derive from the bulk bands
of two- and three-dimensional materials. Here, based on combined angle-resolved
photoemission spectroscopy measurements and first-principles calculations, we
report the discovery of node-line-like surface states on the (001) surface of
LaBi. These bands derive from the topological surface states of LaBi and bridge
the band gap opened by spin-orbit coupling and band inversion. Our
first-principles calculations reveal that these "nodal lines" have a tiny gap,
which is beyond typical experimental resolution. These results may provide
important information to understand the extraordinary physical properties of
LaBi, such as the extremely large magnetoresistance and resistivity plateau.

###A Novel Effect of Electron Spin Resonance on Electrical Resistivity|Navinder Singh,Luxmi Rani###

A Novel Effect of Electron Spin Resonance on Electrical Resistivity. We extend the well known phenomenon of magnetoresistance (extra resistivity
of materials in transverse magnetic field) to a new and unexplored regime where
in addition to a transverse magnetic field, a transverse AC field of resonant
frequency is also applied. In a magnetic field, electron spin levels are Zeeman
split. In a resonant AC field, we uncover a new channel of momentum relaxation
in which electrons in upper Zeeman level can deexcite to lower Zeeman level by
generating spin fluctuation excitation in the lattice (similar to what happens
in Electron Spin Resonance (ESR) spectroscopy). An additional resistivity due
to this novel mechanism is predicted in which momentum randomization of Zeeman
split electrons happen via bosonic excitations (spin fluctuations). An order of
magnitude of this additional resistivity is calculated. The whole work is based
upon an extension of Einstein's derivation of equilibrium Planckian formula to
near equilibrium systems.

###Shape anisotropy revisited in single-digit nanometer magnetic tunnel junctions|K. Watanabe,B. Jinnai,S. Fukami,H. Sato,H. Ohno###

Shape anisotropy revisited in single-digit nanometer magnetic tunnel junctions. Nanoscale magnetic tunnel junction plays a pivotal role in magnetoresistive
random access memories. Successful implementation depends on a simultaneous
achievement of low switching current for the magnetization switching by
spin-transfer torque and high thermal stability, along with a continuous
reduction of junction size. Perpendicular-easy-axis CoFeB/MgO stacks possessing
interfacial anisotropy have paved the way down to 20-nm scale, below which a
new approach needs to be explored. Here we show magnetic tunnel junctions that
satisfy the requirements at ultrafine scale by revisiting shape anisotropy,
which is a classical part of magnetic anisotropy but has not been fully
utilized in the current perpendicular systems. Magnetization switching solely
driven by current is achieved for junctions smaller than 10 nm where sufficient
thermal stability is provided by shape anisotropy without adopting new material
systems. This work is expected to push forward the development of magnetic
tunnel junctions towards single-digit-nm-scale nano-magnetics/spintronics.

###High throughput screening for spin-gapless semiconductors in quaternary Heusler compounds|Qiang Gao,Ingo Opahle,Hongbin Zhang###

High throughput screening for spin-gapless semiconductors in quaternary Heusler compounds. Based on high throughput density functional theory calculations, we performed
systematic screening for spin-gapless semiconductors (SGSs) in quaternary
Heusler alloys XX 0 YZ (X, X 0 , and Y are transition metal elements without
Tc, and Z is one of B, Al, Ga, In, Si, Ge, Sn, Pb, P, As, Sb, and Bi).
Following the empirical rule, we focused on compounds with 21, 26, or 28
valence electrons, resulting in 12, 000 possible chemical compositions. After
systematically evaluating the thermodynamic, mechanical, and dynamical
stabilities, we successfully identified 70 stable SGSs, confirmed by explicit
electronic structure calculations with proper magnetic ground states. It is
demonstrated that all four types of SGSs can be realized, defined based on the
spin characters of the bands around the Fermi energy, and the type-II SGSs show
promising transport properties for spintronic applications. The effect of
spin-orbit coupling is investigated, resulting in large anisotropic
magnetoresistance and anomalous Nernst effects.

###The magnetic origin of the metal-insulator transition in V2O3: Mott meets Slater|J. Trastoy,A. Camjayi,J. del Valle,Y. Kalcheim,J. -P. Crocombette,J. E. Villegas,M. Rozenberg,D. Ravelosona,Ivan K. Schuller###

The magnetic origin of the metal-insulator transition in V2O3: Mott meets Slater. Despite decades of experimental and theoretical efforts, the origin of
metal-insulator transitions (MIT) in strongly-correlated materials is one of
the main longstanding problems in condensed matter physics. An archetypal
example is V2O3, where electronic, structural and magnetic phase transitions
occur simultaneously. This remarkable concomitance makes the understanding of
the origin of the MIT a challenge due to the many degrees of freedom at play.
In this work, we demonstrate that magnetism plays the key dominant role. By
acting on the magnetic degree of freedom, we reveal an anomalous behaviour of
the magnetoresistance of V2O3, which provides strong evidence that the origin
of the MIT in V2O3 is the opening of an antiferromagnetic gap in the presence
of strong electronic correlations.

###Significant change in the electronic behavior associated with structural distortions in the single crystalline SrAg4As2|Bing Shen,Eve Emmanouilidou,Xiaoyu Deng,Alix McCollam,Jie Xing,Gabriel Kotliar,Amalia I. Coldea,Ni Ni###

Significant change in the electronic behavior associated with structural distortions in the single crystalline SrAg4As2. We report a combined study of transport and thermodynamic measurements on the
layered pnictide material SrAg4As2. Upon cooling, a drop in electrical and Hall
resistivity, a jump in heat capacity and an increase in susceptibility and
magnetoresistance (MR) are observed around 110 K. These observations suggest
that non-magnetic phase transitions emerge at around 110 K, that are likely
associated with structural distortions. In sharp contrast with the
first-principles calculations based on the crystal structure at room
temperature, quantum oscillations reveal small Fermi pockets with light
effective masses, suggesting a significant change in the Fermi surface topology
caused by the low temperature structural distortion. No superconductivity
emerges in SrAg$_4$As$_2$ down to 2 K and under pressures up to 2.13 GPa;
instead, the low temperature structural distortion increases linearly with
temperature at a rate of ~13 K/GPa above 0.89 GPa.

###Magnetic and structural properties of Co$_2$MnSi based Heusler compound|S. J. Ahmed,C. Boyer,M. Niewczas###

Magnetic and structural properties of Co$_2$MnSi based Heusler compound. The influence of antisite disorder occupancies on the magnetic properties of
the half-metallic Co$_2$MnSi compound was studied by experimental techniques
and first-principles calculations. The neutron diffraction studies show almost
identical amount of Mn and Co disorders of 6.5\% and 7.6\%, which was found to
be in good agreement with density functional theory (DFT) calculations of the
stable Co$_2$MnSi system with the corresponding disorders. DFT studies reveal
that antiferromagnetic interactions introduced by Mn disorder lead to a
reduction of the net magnetic moment. The results are discussed in conjunction
with neutron diffraction and magnetization measurements. Transport property
measurement under magnetic field up to 9 Tesla revealed a positive
magnetoresistance for bulk Co$_2$MnSi that persists up to room temperature. A
Curie temperature of $\sim$1014 K was determined for the compound by high
temperature electrical resistivity and dilatometry measurements.

###Electronic transport properties of Co cluster-decorated graphene|Chaoyi Cai,Jian-Hao Chen###

Electronic transport properties of Co cluster-decorated graphene. Interactions of magnetic elements with graphene may lead to various
electronic states that have potential applications. We report an in-situ
experiment in which the quantum transport properties of graphene are measured
with increasing cobalt coverage in continuous ultra-high vacuum environment.
The results show that e-beam deposited cobalt forms clusters on the surface of
graphene, even at low sample temperatures. Scattering of charge carriers by the
absorbed cobalt clusters results in the disappearance of the Shubnikov-de Haas
(SdH) oscillations and the appearance of negative magnetoresistance (MR) which
shows no sign of saturation up to an applied magnetic field of 9 T. We propose
that these observations could originate from quantum interference driven by
cobalt disorder and can be explained by the weak localization theory.

###Kondo Correlation Induced Low-Field Magnetoresistance Anomalies in InSb Nanowire Josephson Quantum Dot Devices|C. L. Yu,M. T. Deng,P. Caroff,S. G. Ghalamestani,K. A. Dick,H. Q. Xu###

Kondo Correlation Induced Low-Field Magnetoresistance Anomalies in InSb Nanowire Josephson Quantum Dot Devices. We report the observation of sharp suppression of superconductivity-induced
zero-bias conductance peaks at low magnetic fields in InSb nanowire Josephson
quantum dot devices. With multiple gates, the quantum dot devices can be tuned
to the Kondo-superconductivity interplaying regime, in which Kondo-enhanced
superconductivity manifests as a zero-bias conductance peak. In weak magnetic
fields, the zero-bias conductance peak is found to exhibit an unusual negative
magnetoresistance when the Kondo temperature is comparable to the
superconductor gap. The observation could not be explained by magnetic field
induced '0-$\pi$' phase transition, topological phase transition, or other
known mechanisms, but may arise from correlation induced interference when
Cooper pairs cotunnel through the quantum dots.

###Chiral solitons in monoaxial chiral magnets in tilted magnetic field|Yusuke Masaki,Ryuya Aoki,Yoshihiko Togawa,Yusuke Kato###

Chiral solitons in monoaxial chiral magnets in tilted magnetic field. We show that the stability (existence/absence) and interaction
(repulsion/attraction) of chiral solitons in monoaxial chiral magnets can be
varied by tilting the direction of magnetic field. We, thereby, elucidate that
the condensation of attractive chiral solitons causes the discontinuous phase
transition predicted by a mean field calculation. Furthermore we theoretically
demonstrate that the metastable field-polarized-state destabilizes through the
surface instability, which is equivalent to the vanishing surface barrier for
penetration of the solitons. We experimentally measure the magnetoresistance
(MR) of micrometer-sized samples in the tilted fields in demagnetization-free
configuration. We corroborate the scenario that hysteresis in MR is a sign for
existence of the solitons, through agreement between our theory and
experiments.

###Evidence for a strain tuned topological phase transition in ZrTe5|Joshua Mutch,Wei-Chih Chen,Preston Went,Tiema Qian,Ilham Zaky Wilson,Anton Andreev,Cheng-Chien Chen,Jiun-Haw Chu###

Evidence for a strain tuned topological phase transition in ZrTe5. A phase transition between topologically distinct insulating phases involves
closing and reopening of the bandgap. Close to this topological phase
transition, the bulk energy spectrum is characterized by a massive Dirac
dispersion, where the mass plays the role of bandgap. Here we report the
observation of a non-monotonic strain dependence of resistivity and negative
longitudinal magnetoresistance in ZrTe5, which is known to host massive Dirac
Fermions in the bulk. This non-monotonic strain dependence is consistent with
the closing and reopening of the bandgap at the Brillouin-zone center,
indicative of a topological phase transition. This observation suggests that
the topological state of ZrTe5 is highly sensitive to uniaxial stress. Our
study presents a promising platform for continuous in-situ control of
nontrivial topological properties of materials.

###Magneto-transport phenomena in p-doped diamond from first principles|Francesco Macheda,Nicola Bonini###

Magneto-transport phenomena in p-doped diamond from first principles. We present a first-principles study of the magnetotransport phenomena in
p-doped diamond via the exact solution of the linearized Boltzmann transport
equation, in which the materials' parameters, including electron-phonon and
phonon-phonon interactions, are obtained from density functional theory. This
approach gives results in very good agreement with experimental data for Hall
and drift mobilities, low- and high-field magnetoresistance and Seebeck
coefficient, including the phonon-drag effect, in a range of temperatures and
carrier concentrations. In particular, our results provide a detailed
characterisation of the exceptionally high values for mobility and Seebeck
coefficient, and predict a large magnetic field driven enhancement of the
Seebeck coefficient, of up to 30% in a magnetic field of 40 kOe already at room
temperature.

###Imaging of current induced Néel vector switching in antiferromagnetic Mn$_2$Au|S. Yu. Bodnar,M. Filianina,S. P. Bommanaboyena,T. Forrest,F. Maccherozzi,A. A. Sapozhnik,Y. Skourski,M. Kläui,M. Jourdan###

Imaging of current induced Néel vector switching in antiferromagnetic Mn$_2$Au. The effects of current induced N\'eel spin-orbit torques on the
antiferromagnetic domain structure of epitaxial Mn$_2$Au thin films were
investigated by X-ray magnetic linear dichroism - photoemission electron
microscopy (XMLD-PEEM). We observed current induced switching of AFM domains
essentially corresponding to morphological features of the samples. Reversible
as well as irreversible N\'eel vector reorientation was obtained in different
parts of the samples and the switching of up to 30 % of all domains in the
field of view of 10 $\mu$m is demonstrated. Our direct microscopical
observations are compared to and fully consistent with anisotropic
magnetoresistance effects previously attributed to current induced N\'eel
vector switching in Mn$_2$Au.

###Magnon transport in quasi-two-dimensional van der Waals antiferromagnets|Wenyu Xing,Luyi Qiu,Xirui Wang,Yunyan Yao,Yang Ma,Ranran Cai,Shuang Jia,X. C. Xie,Wei Han###

Magnon transport in quasi-two-dimensional van der Waals antiferromagnets. The recent emergence of 2D van der Waals magnets down to atomic layer
thickness provides an exciting platform for exploring quantum magnetism and
spintronics applications. The van der Waals nature stabilizes the long-range
ferromagnetic order as a result of magnetic anisotropy. Furthermore, giant
tunneling magnetoresistance and electrical control of magnetism have been
reported. However, the potential of 2D van der Waals magnets for magnonics,
magnon-based spintronics, has not been explored yet. Here, we report the
experimental observation of long-distance magnon transport in
quasi-twodimensional van der Waals antiferromagnet MnPS3, which demonstrates
the 2D magnets as promising material candidates for magnonics. As the 2D MnPS3
thickness decreases, a shorter magnon diffusion length is observed, which could
be attributed to the surface-impurity-induced magnon scattering. Our results
could pave the way for exploring quantum magnonics phenomena and designing
future magnonics devices based on 2D van der Waals magnets.

###Magnetic tunnel junctions based on ferroelectric Hf0.5Zr0.5O2 tunnel barriers|Yingfen Wei,Sylvia Matzen,Guillaume Agnus,Mart Salverda,Pavan Nukala,Thomas Maroutian,Qihong Chen,Jianting Ye,Philippe Lecoeur,Beatriz Noheda###

Magnetic tunnel junctions based on ferroelectric Hf0.5Zr0.5O2 tunnel barriers. A ferroelectric tunnel barrier in between two ferromagnetic electrodes
(multiferroic tunnel junction, MFTJ), is one of the most promising concepts for
future microelectronic devices. In parallel, Hafnia based ferroelectrics are
showing great potential for device miniaturization down to the nanoscale. Here
we utilize ferroelectric Hf0.5Zr0.5O2 (HZO) with thickness of only 2 nm,
epitaxially grown on La0.7Sr0.3MnO3 (LSMO) ferromagnetic electrodes, as a large
band-gap insulating barrier integrated in MFTJs with cobalt top electrodes. As
previously reported for other MFTJs with similar electrodes, the tunneling
magnetoresistance (TMR) can be tuned and its sign can even be reversed by the
bias voltage across the junction. We demonstrate four non-volatile resistance
states generated by magnetic and electric field switching with high
reproducibility in this system.

###Ferromagnetic order beyond the superconducting dome in a cuprate superconductor|Tarapada Sarkar,D. S. Wei,J. Zhang,N. R. Poniatowski,P. R. Mandal,A. Kapitulnik,Richard L. Greene###

Ferromagnetic order beyond the superconducting dome in a cuprate superconductor. The cuprate high-temperature superconductors (HTSC) have been the subject of
intense study for more than 30 years with no consensus yet on the underlying
mechanism of the superconductivity. Conventional wisdom dictates that the
mysterious and extraordinary properties of the cuprates arise from doping a
strongly correlated antiferromagnetic (AFM) insulator (1,2). The highly
overdoped cuprates$-$those beyond the dome of superconductivity (SC)--are
considered to be conventional Fermi liquid metals (3). Here, we report the
emergence of itinerant ferromagnetic order (FM) below 4K for doping beyond the
SC dome in electron-doped La$_{2-x} $Ce$_x$CuO$_4$ (LCCO). The existence of
this FM order is evidenced by negative, anisotopic and hysteretic
magnetoresistance, hysteretic magnetization, and the polar Kerr effect, all of
which are standard signatures of itinerant FM in metals (4,5). This surprising
new result suggests that the overdoped cuprates are also influenced by electron
correlations and the physics is much richer than that of a conventional Fermi
liquid metal.

###Current-induced fragmentation of antiferromagnetic domains|M. S. Wörnle,P. Welter,Z. Kašpar,K. Olejník,V. Novák,R. P. Campion,P. Wadley,T. Jungwirth,C. L. Degen,P. Gambardella###

Current-induced fragmentation of antiferromagnetic domains. Electrical and optical pulsing allow for manipulating the order parameter and
magnetoresistance of antiferromagnets, opening novel prospects for digital and
analog data storage in spintronic devices. Recent experiments in CuMnAs have
demonstrated giant resistive switching signals in single-layer
antiferromagnetic films together with analog switching and relaxation
characteristics relevant for neuromorphic computing. Here we report
simultaneous electrical pulsing and scanning NV magnetometry of
antiferromagnetic domains in CuMnAs performed using a pump-probe scheme. We
observe a nano-scale fragmentation of the antiferromagnetic domains, which is
controlled by the current amplitude and independent on the current direction.
The fragmented antiferromagnetic state conserves a memory of the pristine
domain pattern, towards which it relaxes. Domain fragmentation coexists with
permanent switching due to the reorientation of the antiferromagnetic moments.
Our simultaneous imaging and resistance measurements show a correlation between
the antiferromagnetic domain fragmentation and the largest resistive switching
signals in CuMnAs.

###Observation of the dominant spin-triplet supercurrent in Josephson spin valves with strong Ni ferromagnets|O. M. Kapran,A. Iovan,T. Golod,V. M. Krasnov###

Observation of the dominant spin-triplet supercurrent in Josephson spin valves with strong Ni ferromagnets. We study experimentally nanoscale Josephson junctions and Josephson
spin-valves containing strong Ni ferromagnets. We observe that in contrast to
junctions, spin valves with the same geometry exhibit anomalous Ic(H) patterns
with two peaks separated by a dip. We develop several techniques for in-situ
characterization of micromagnetic states in our nano-devices, including
magnetoresistance, absolute Josephson fluxometry and
First-Order-Reversal-Curves analysis. They reveal a clear correlation of the
dip in supercurrent with the antiparallel state of a spin-valve and the peaks
with two noncollinear magnetic states, thus providing evidence for generation
of spin-triplet superconductivity. A quantitative analysis brings us to a
conclusion that the triplet current in out Ni-based spin-valves is
approximately three times larger than the conventional singlet supercurrent.

###Detecting chirality in two-terminal electronic devices|Xu Yang,Caspar H. van der Wal,Bart J. van Wees###

Detecting chirality in two-terminal electronic devices. Central to spintronics is the interconversion between electronic charge and
spin currents, and this can arise from the chirality-induced spin selectivity
(CISS) effect. CISS is often studied as magnetoresistance (MR) in two-terminal
(2T) electronic devices containing a chiral (molecular) component and a
ferromagnet. However, fundamental understanding of when and how this MR can
occur is lacking. Here, we uncover an elementary mechanism that generates such
a MR for nonlinear response. It requires energy-dependent transport and energy
relaxation within the device. The sign of the MR depends on chirality, charge
carrier type, and bias direction. Additionally, we reveal how CISS can be
detected in the linear response regime in magnet-free 2T devices, either by
forming a chirality-based spin-valve using two or more chiral components, or by
Hanle spin precession in devices with a single chiral component. Our results
provide operation principles and design guidelines for chirality-based
spintronic devices and technologies.

###Change of electronic properties on transition from high-entropy to Ni-rich (TiZrNbCu)(1-x)Ni(x) alloys|Marko Kuveždić,Emil Tafra,Mario Basletić,Ramir Ristić,Petar Pervan,Vesna Mikšić Trontl,Ignacio A Figueroa,Emil Babić###

Change of electronic properties on transition from high-entropy to Ni-rich (TiZrNbCu)(1-x)Ni(x) alloys. We present results of comprehensive study of electronic properties of
(TiZrNbCu)(1-x)Ni(x) metallic glasses performed in broad composition range x
encompassing both, high entropy (HE) range, and conventional Ni-base alloy
concentration range, x >= 0.35. The electronic structure studied by
photoemission spectroscopy and low temperature specific heat (LTSH) reveal a
split-band structure of density of states inside valence band with d-electrons
of Ti, Zr, Nb and also Ni present at Fermi level N(E_F), whereas LTSH and
magnetoresistivity results show that variation of N(E_F) with x changes in
Ni-base regime. The variation of superconducting transition temperatures with x
closely follows that of N(E_F). The electrical resistivities of all alloys are
high and decrease with increasing temperature over most of explored temperature
range, and their temperature dependence seems dominated by weak localization
effects over a broad temperature range (10-300 K). The preliminary study of
Hall effect shows positive Hall coefficient that decreases rapidly in Ni-base
alloys.

###Resistance fluctuations and Aharonov-Bohm-type oscillations in antidot arrays in the quantum Hall regime|Masanori Kato,Akira Endo,Shingo Katsumoto,Yasuhiro Iye###

Resistance fluctuations and Aharonov-Bohm-type oscillations in antidot arrays in the quantum Hall regime. Resistance fluctuation phenomenon in antidot lattices in the quantum Hall
regime are studied. Magnetoresistance of finite antidot array systems in the
quantum Hall plateau transition regime exhibits two types of oscillatory
effect. One is the aperiodic resistance fluctuations (RFs) and the other is the
Aharonov-Bohm (AB)-type oscillations. Their dependences on the magnetic field
and the gate voltage are quite distinct. While the aperiodic RFs are attributed
to the complex evolution of the conducting network of compressible channels,
the AB-type oscillations are interpreted in terms of edge states formed around
individual antidots. The self-consistent screening effect is important for the
both phenomenon, whereas, the single electron charging effect plays a minor
role in the present case.

###Synthesis, crystal structure, microstructure, transport and magnetic properties of SmFeAsO and SmFeAs(O0.93F0.07)|A. Martinelli,M. Ferretti,P. Manfrinetti,A. Palenzona,M. Tropeano,M. R. Cimberle,C. Ferdeghini,R. Valle,M. Putti,A. S. Siri###

Synthesis, crystal structure, microstructure, transport and magnetic properties of SmFeAsO and SmFeAs(O0.93F0.07). SmFeAsO and the isostructural superconducting SmFeAs(O0.93F0.07) samples were
prepared. Characterization by means of Rietveld refinement of X-ray powder
diffraction data, scanning electron microscope observation, transmission
electron microscope analysis, resistivity and magnetization measurements were
carried out. Sintering treatment strongly improves the grain connectivity, but,
on the other hand, induces a competition between the thermodynamic stability of
the oxy-pnictide and Sm2O3, hence worsening the purity of the sample. In the
pristine sample both magnetization and resistivity measurements clearly
indicate that two different sources of magnetism are present: the former
related to Fe ordering at 140 K and the latter due to the Sm ions that orders
antiferromagnetically at low temperature. The feature at 140 K disappears in
the F-substituted sample and, at low temperatures a superconducting transition
appears. The magnetoresistivity curves of the F-substituted sample probably
indicates very high critical field values.

###Effect of pressure on steplike magnetostriction of single crystalline (La$_{0.4}$Pr$_{0.6}$)$_{1.2}$Sr$_{1.8}$Mn$_{2}$O$_{7}$ bilayered manganite|Y. Yamato,M. Matsukawa,T. Kumagai,R. Suryanarayanan,S. Nimori,M. Apostu,A. Revcolevschi,K. Koyama,N. Kobayashi###

Effect of pressure on steplike magnetostriction of single crystalline (La$_{0.4}$Pr$_{0.6}$)$_{1.2}$Sr$_{1.8}$Mn$_{2}$O$_{7}$ bilayered manganite. e report the effect of pressure on the steplike magnetostriction of single
crystalline bilayered manganite (LaPr)1.2Sr1.8Mn2O8, for our understandings of
the ultrasharp nature of the field-induced first-order transition from a
paramagnetic insulator to a ferromagnetic metal phase. The application of
pressure suppresses a steplike transformation and causes a broad change in the
magnetostriction. The injection of an electric current to the crystal also
weakens the steplike variation in both the magnetostriction and
magnetoresistance. The stabilization of ferromagnetic interaction or the
delocalization of charge carriers is promoted with the applied pressure or
applied current, resulting in the suppressed steplike behavior. Our findings
suggest that the step phenomenon is closely related to the existence of
localized carriers such as the short-range charge-orbital ordered clusters.

###Effective Mass Ratio & positive colossal magnetoresistance of a Nano-wire|Piyush Dua###

Effective Mass Ratio & positive colossal magnetoresistance of a Nano-wire. In the present work, a relation has been established between degree of
polarization and effective mass ratio (EMR) and magnetoresistance (MR) of
one-dimensional non-degenerate system (which can represent a nano-wire or a
linear chain of atoms and molecules in one dimension) by using a non-degenerate
Hubbard model, which includes diagonal and off-diagonal matrix elements of
Coulomb interaction. EMR is one of the most important property, which provides
information that how much itinerant the system is? Within the mean field
approximation, it is found that, due to the presence of off-diagonal elements,
the band narrowing effect dominates over the band splitting effect. The EMR
varies with degree of polarization. EMR for majority (up spin) carriers
decreases as magnetization increases below ferromagnetic transition
temperature. MR decreases as system is cooled below the ferromagnetic
transition temperature. A comparison of our results with existing experimental
observations is made.

###Log-T divergence and Insulator-to-Metal Crossover in the normal state resistivity of fluorine doped SmFeAsO1-xFx|S. C. Riggs,J. B. Kemper,Y. Jo,Z. Stegen,L. Balicas,G. S. Boebinger,F. F. Balakirev,Albert Migliori,H. Chen,R. H. Liu,X. H. Chen###

Log-T divergence and Insulator-to-Metal Crossover in the normal state resistivity of fluorine doped SmFeAsO1-xFx. We report the resistivity of a series of fluorine-doped SmFeAsO1-xFx
polycrystalline superconductors in magnetic fields up to 60T. For underdoped
samples (x < 0.15), the low temperature resistive state is characterized by
pronounced magneto-resistance and a resistive upturn at low temperatures. The
"insulating behavior" is characterized by a log-T divergence observed over a
decade in temperature. In contrast, the normal state for samples with doping x
> 0.15 display metallic behavior with little magnetoresistance, where intense
magnetic fields broaden the superconducting transition rather than suppress Tc.
The location of the insulator-to metal crossover coincides with the reported
suppression of the structural phase transition (SPT)in the phase diagram for
SmFeAsO1-xFx series.

###Multiband Transport in Bilayer Graphene at High Carrier Densities|Dmitri K. Efetov,Patrick Maher,Simas Glinskis,Philip Kim###

Multiband Transport in Bilayer Graphene at High Carrier Densities. We report a multiband transport study of bilayer graphene at high carrier
densities. Employing a poly(ethylene)oxide-CsClO$_4$ solid polymer electrolyte
gate we demonstrate the filling of the high energy subbands in bilayer graphene
samples at carrier densities $|n|\geq2.4\times 10^{13}$ cm$^{-2}$. We observe a
sudden increase of resistance and the onset of a second family of Shubnikov de
Haas (SdH) oscillations as these high energy subbands are populated. From
simultaneous Hall and magnetoresistance measurements together with SdH
oscillations in the multiband conduction regime, we deduce the carrier
densities and mobilities for the higher energy bands separately and find the
mobilities to be at least a factor of two higher than those in the low energy
bands.

###Lattice-Driven Magnetoresistivity and Metal-Insulator Transition in Single-Layered Iridates|M. Ge,T. F. Qi,O. B. Korneta,D. E. De Long,P. Schlottmann,W. P. Crummett,G. Cao###

Lattice-Driven Magnetoresistivity and Metal-Insulator Transition in Single-Layered Iridates. Sr2IrO4 exhibits a novel insulating state driven by spin-orbit interactions.
We report two novel phenomena, namely a large magnetoresistivity in Sr2IrO4
that is extremely sensitive to the orientation of magnetic field but exhibits
no apparent correlation with the magnetization, and a robust metallic state
that is induced by dilute electron (La3+) or hole (K+) doping for Sr2+ ions in
Sr2IrO4. Our structural, transport and magnetic data reveal that a strong
spin-orbit interaction alters the balance between the competing energies so
profoundly that (1) the spin degree of freedom alone is no longer a dominant
force; (2) underlying transport properties delicately hinge on the Ir-O-Ir bond
angle via a strong magnetoelastic coupling; and (3) a highly insulating state
in Sr2IrO4 is proximate to a metallic state, and the transition is governed by
lattice distortions. This work suggests that a novel class of lattice-driven
electronic materials can be developed for applications.

###Observation of the superconducting proximity effect and possible evidence for Pearl vortices in a candidate topological insulator|Duming Zhang,Jian Wang,Ashley M. DaSilva,Joon Sue Lee,Humberto R. Gutierrez,Moses H. W. Chan,Jainendra Jain,Nitin Samarth###

Observation of the superconducting proximity effect and possible evidence for Pearl vortices in a candidate topological insulator. We report the observation of the superconducting proximity effect in
nanoribbons of a candidate topological insulator (Bi2Se3) which is interfaced
with superconducting (tungsten) contacts. We observe a supercurrent and
multiple Andreev reflections for channel lengths that are much longer than the
inelastic and diffusive thermal lengths deduced from normal state transport.
This suggests that the proximity effect couples preferentially to a ballistic
surface transport channel, even in the presence of a coexisting diffusive bulk
channel. When a magnetic field is applied perpendicular to the plane of the
nanoribbon, we observe magnetoresistance oscillations that are periodic in
magnetic field. Quantitative comparison with a model of vortex blockade relates
the occurrence of these oscillations to the formation of Pearl vortices in the
region of proximity induced superconductivity.

###Magnetic and transport properties of rare-earth-based half-Heusler phases RPdBi: prospective systems for topological quantum phenomena|K. Gofryk,D. Kaczorowski,T. Plackowski,A. Leithe-Jasper,Yu. Grin###

Magnetic and transport properties of rare-earth-based half-Heusler phases RPdBi: prospective systems for topological quantum phenomena. RPdBi (R = Er, Ho, Gd, Dy, Y, Nd) compounds were studied by means of x-ray
diffraction, magnetic susceptibility, electrical resistivity,
magnetoresistivity, thermoelectric power and Hall effect measurements,
performed in the temperature range 1.5-300 K and in magnetic fields up to 12 T.
These ternaries, except diamagnetic YPdBi, exhibit localized magnetism of
$R^{3+}$ ions, and order antiferromagnetically at low temperatures ($T_{N}$ =
2-13 K). The transport measurements revealed behavior characteristic of
semimetals or narrow-band semiconductors. Both, electrons and holes contribute
to the conductivity with dominant role of p-type carriers. The Hall effect of
ErPdBi is strongly temperature and magnetic field dependent, reflecting complex
character of the underlying electronic structures with multiple electron and
hole bands. RPdBi, and especially DyPdBi, exhibit very good thermoelectric
properties with a power factor coefficient $PF$ ranging from 6 to 20
$\mu$Wcm$^{-1}$K$^{-2}$.

###Enhancement of the retrapping current of superconducting microbridges of finite length|D. Y. Vodolazov,F. M. Peeters###

Enhancement of the retrapping current of superconducting microbridges of finite length. We theoretically find that the resistance of a superconducting
microbridge/nanowire {\it decreases} while the retrapping current $I_r$ for the
transition to the superconducting state {\it increases} when one suppresses the
magnitude of the order parameter $|\Delta|$ in the attached superconducting
leads. This effect is a consequence of the increased energy interval for
diffusion of the 'hot' nonequilibrium quasiparticles (induced by the
oscillations of $|\Delta|$ in the center of the microbridge) to the leads. The
effect is absent in short microbridges (with length less than the coherence
length) and it is relatively weak in long microbridges (with length larger than
the inelastic relaxation length of the nonequilibrium distribution function). A
nonmonotonous dependence of $I_r$ on the length of the microbridge is
predicted. Our results are important for the explanation of the enhancement of
the critical current and the appearance of negative magnetoresistance observed
in many recent experiments on superconducting microbridges/nanowires.

###Magnetotransport properties of BaRuO$_3$: Observation of two scattering rates|Y. A. Ying,Y. Liu,T. He,R. J. Cava###

Magnetotransport properties of BaRuO$_3$: Observation of two scattering rates. We report results of low-temperature magnetotransport and Hall measurements
on single crystals of four-layered hexagonal (4H) and nine-layered rhombohedral
(9R) BaRuO$_3$ that provide insight into the structure-property relationships
of BaRuO$_3$ polymorphs. We found that 4H BaRuO$_3$ possesses Fermi-liquid
behavior down to the lowest temperature ($T$) of our measurements, 1.8 K. On
the other hand, 9R BaRuO$_3$ was found to show a crossover in the temperature
dependence of resistivity around 150 K, and the existence of two separate
scattering rates at low temperatures. The magnetoresistance in the 9R BaRuO$_3$
was found to be negative while that in the 4H BaRuO$_3$ is positive. We propose
that local moments may be present in 9R but not in 4H BaRuO$_3$, which leads to
distinctly different behavior in the two forms.

###Quantum Hall Effect, Screening and Layer-Polarized Insulating States in Twisted Bilayer Graphene|Javier D. Sanchez-Yamagishi,Thiti Taychatanapat,Kenji Watanabe,Takashi Taniguchi,Amir Yacoby,Pablo Jarillo-Herrero###

Quantum Hall Effect, Screening and Layer-Polarized Insulating States in Twisted Bilayer Graphene. We investigate electronic transport in dual-gated twisted bilayer graphene.
Despite the sub-nanometer proximity between the layers, we identify independent
contributions to the magnetoresistance from the graphene Landau level spectrum
of each layer. We demonstrate that the filling factor of each layer can be
independently controlled via the dual gates, which we use to induce Landau
level crossings between the layers. By analyzing the gate dependence of the
Landau level crossings, we characterize the finite inter-layer screening and
extract the capacitance between the atomically-spaced layers. At zero filling
factor, we observe magnetic and displacement field dependent insulating states,
which indicate the presence of counter-propagating edge states with inter-layer
coupling.

###Manifestation of electron-electron interaction in the magnetoresistance of graphene|Johannes Jobst,Daniel Waldmann,Igor V. Gornyi,Alexander D. Mirlin,Heiko B. Weber###

Manifestation of electron-electron interaction in the magnetoresistance of graphene. We investigate the magnetotransport in large area graphene Hall bars
epitaxially grown on silicon carbide. In the intermediate field regime between
weak localization and Landau quantization the observed temperature-dependent
parabolic magnetoresistivity (MR) is a manifestation of the electron-electron
interaction (EEI). We can consistently describe the data with a model for
diffusive (magneto)transport that also includes magnetic-field dependent
effects originating from ballistic time scales. We find an excellent agreement
between the experimentally observed temperature dependence of MR and the theory
of EEI in the diffusive regime. We can further assign a temperature-driven
crossover to the reduction of the multiplet modes contributing to EEI from 7 to
3 due to intervalley scattering. In addition, we find a temperature independent
ballistic contribution to the MR in classically strong magnetic fields.

###Tunnel magnetoresistance in magnetic tunnel junctions with embedded nanoparticles|Arthur Useinov,Niazbeck Useinov,Lin-Xiu Ye,Te-Ho Wu,Chih-Huang Lai###

Tunnel magnetoresistance in magnetic tunnel junctions with embedded nanoparticles. In this paper, we attempt the theoretical modeling of the magnetic tunnel
junctions with embedded magnetic and nonmagnetic nanoparticles (NPs). A few
abnormal tunnel magnetoresistance (TMR) effects, observed in related
experiments, can be easily simulated within our model: we found, that the
suppressed TMR magnitudes and the TMR sign-reversing effect at small voltages
are related to the electron momentum states of the NP located inside the
insulating layer. All these TMR behaviors can be explained within the tunneling
model, where NP is simulated as a quantum well (QW). The coherent (direct)
double barrier tunneling is dominating over the single barrier one. The origin
of the TMR suppression is the quantized angle transparency for spin polarized
electrons being in one of the lowest QW states. The phenomenon was classified
as the quantized conductance regime due to restricted geometry.

###High Sensitivity Biosensor using Injection Locked Spin Torque Nano-Oscillators|Tathagata Srimani,Bibhas Manna,Anand Kumar Mukhopadhyay,Kaushik Roy,Mrigank Sharad###

High Sensitivity Biosensor using Injection Locked Spin Torque Nano-Oscillators. With ever increasing research on magnetic nano systems it is shown to have
great potential in the areas of magnetic storage, biosensing, magnetoresistive
insulation etc. In the field of biosensing specifically Spin Valve sensors
coupled with Magnetic Nanolabels is showing great promise due to noise immunity
and energy efficiency [1]. In this paper we present the application of
injection locked based Spin Torque Nano Oscillator (STNO) suitable for high
resolution energy efficient labeled DNA Detection. The proposed STNO microarray
consists of 20 such devices oscillating at different frequencies making it
possible to multiplex all the signals using capacitive coupling. Frequency
Division Multiplexing can be aided with Time division multiplexing to increase
the device integration and decrease the readout time while maintaining the same
efficiency in presence of constant input referred noise.

###Spintronics of Organometal Trihalide Perovskites|Dali Sun,Chuang Zhang,Marzieh Kavand,Kipp J. van Schooten,Hans Malissa,Matthew Groesbeck,Ryan McLaughlin,Christoph Boehme,Z. Valy Vardeny###

Spintronics of Organometal Trihalide Perovskites. The family of organometal trihalide perovskite (OTP), CH3NH3PbX3 (where X is
halogen) has recently revolutionized the photovoltaics field and shows promise
in a variety of optoelectronic applications. The characteristic spin properties
of charge and neutral excitations in OTPs are influenced by the large
spin-orbit coupling of the Pb atoms, which may lead to spin-based device
applications. Here we report the first studies of pure spin-current and
spin-aligned carrier injection in OTP spintronics devices using spin-pumping
and spin-injection, respectively. We measure a relatively large
inverse-spin-Hall effect using pulsed microwave excitation in OTP devices at
resonance with a ferromagnetic substrate, from which we derive room temperature
spin diffusion length, lambda_sd~9nm; and low-temperature giant
magnetoresistance in OTP-based spin-valves from which we estimate
lambda_sd~85nm.

###Upper critical field and quantum oscillations in tetragonal superconducting FeS|Taichi Terashima,Naoki Kikugawa,Hai Lin,Xiyu Zhu,Hai-Hu Wen,Takuya Nomoto,Katsuhiro Suzuki,Hiroaki Ikeda,Shinya Uji###

Upper critical field and quantum oscillations in tetragonal superconducting FeS. The magnetoresistance and magnetic torque of FeS are measured in magnetic
fields $B$ of up to 18 T down to a temperature of 0.03 K. The superconducting
transition temperature is found to be $T_c$ = 4.1 K, and the anisotropy ratio
of the upper critical field $B_{c2}$ at $T_c$ is estimated from the initial
slopes to be $\Gamma(T_c)$ = 6.9. $B_{c2}(0)$ is estimated to be 2.2 and 0.36 T
for $B \parallel ab$ and $c$, respectively. Quantum oscillations are observed
in both the resistance and torque. Two frequencies $F$ = 0.15 and 0.20 kT are
resolved and assigned to a quasi-two-dimensional Fermi surface cylinder. The
carrier density and Sommerfeld coefficient associated with this cylinder are
estimated to be 5.8 $\times$ 10$^{-3}$ carriers/Fe and 0.48 mJ/(K$^2$mol),
respectively. Other Fermi surface pockets still remain to be found.
Band-structure calculations are performed and compared to the experimental
results.

###Shubnikov-de Haas oscillations and electronic correlations in the layered organic metal $κ$-(BETS)$_2$Mn[N(CN)$_2$]$_3$|M. V. Kartsovnik,V. N. Zverev,W. Biberacher,S. V. Simonov,I. Sheikin,N. D. Kushch,E. B. Yagubskii###

Shubnikov-de Haas oscillations and electronic correlations in the layered organic metal $κ$-(BETS)$_2$Mn[N(CN)$_2$]$_3$. We present magnetoresistance studies of the quasi-two-dimensional organic
conductor $\kappa$-(BETS)$_2$Mn[N(CN)$_2$]$_3$, where BETS stands for
bis\-(ethylene\-dithio)\-tetra\-selena\-fulvalene. Under a moderate pressure of
1.4\,kbar, required for stabilizing the metallic ground state, Shubnikov - de
Haas oscillations, associated with a classical and a magnetic-breakdown
cyclotron orbits on the cylindrical Fermi surface, have been found at fields
above 10\,T. The effective cyclotron masses evaluated from the temperature
dependence of the oscillation amplitudes reveal strong renormalization due to
many-body interactions. The analysis of the relative strength of the
oscillations corresponding to the different orbits and its dependence on
magnetic field suggests an enhanced role of electron-electron interactions on
flat parts of the Fermi surface.

###Determination of the thickness and orientation of few-layer tungsten ditelluride using polarized Raman spectroscopy|Minjung Kim,Songhee Han,Jung Hwa Kim,Jae-Ung Lee,Zonghoon Lee,Hyeonsik Cheong###

Determination of the thickness and orientation of few-layer tungsten ditelluride using polarized Raman spectroscopy. Orthorhombic tungsten ditelluride (WTe2), with a distorted 1T structure,
exhibits a large magnetoresistance that depends on the orientation, and its
electrical characteristics changes rom semimetallic to insulating as the
thickness decreases. Through polarized Raman spectroscopy in combination with
transmission electron diffraction, we establish a reliable method to determine
the thickness and crystallographic orientation of few-layer WTe2. The Raman
spectrum shows a pronounced dependence on the polarization of the excitation
laser. We found that the separation between two Raman peaks at ~90 cm-1 and at
80-86 cm-1, depending on thickness, is a reliable fingerprint for determination
of the thickness. For determination of the crystallographic orientation, the
polarization dependence of the A1 modes, measured with the 632.8-nm excitation,
turns out to be the most reliable. We also discovered that the polarization
behaviors of some of the Raman peaks depend on the excitation wavelength as
well as thickness, indicating a close interplay between the band structure and
anisotropic Raman scattering cross section.

###Electric transport in three-dimensional Skyrmion/monopole crystal|Xiao-Xiao Zhang,Andrey S. Mishchenko,Giulio De Filippis,Naoto Nagaosa###

Electric transport in three-dimensional Skyrmion/monopole crystal. We study theoretically the transport properties of a three-dimensional spin
texture made from three orthogonal helices, which is essentially a lattice of
monopole-antimonopole pairs connected by Skyrmion strings. This spin structure
is proposed for MnGe based on the neutron scattering experiment as well as the
Lorentz transmission electron microscopy observation. Equipped with a
sophisticated spectral analysis method, we adopt finite temperature Green's
function technique to calculate the longitudinal dc electric transport in such
system. We consider conduction electrons interacting with spin waves of the
topologically nontrivial spin texture, wherein fluctuations of monopolar
emergent magnetic field enter. We study in detail the behavior of electric
resistivity under the influence of temperature, external magnetic field and a
characteristic monopole motion, especially a novel magnetoresistivity effect
describing the latest experimental observations in MnGe, wherein a topological
phase transition signifying strong correlation is identified.

###Emptying Dirac valleys in bismuth using high magnetic fields|Zengwei Zhu,Jinhua Wang,Huakun Zuo,Benoît Fauqué,Ross D. McDonald,Yuki Fuseya,Kamran Behnia###

Emptying Dirac valleys in bismuth using high magnetic fields. The Fermi surface of elemental bismuth consists of three small rotationally
equivalent electron pockets, offering a valley degree of freedom to charge
carriers. A relatively small magnetic field can confine electrons to their
lowest Landau level. This is the quantum limit attained in other dilute metals
upon application of sufficiently strong magnetic field. Here, we report on the
observation of another threshold magnetic field never encountered before in any
other solid. Above this field, $B_{\rm{empty}}$, one or two valleys become
totally empty. Drying up a Fermi sea by magnetic field in the Brillouin zone
leads to a manyfold enhancement in electric conductance. We trace the origin of
the large drop in magnetoresistance across $B_{\rm{empty}}$ to transfer of
carriers between valleys with highly anisotropic mobilities. The
non-interacting picture of electrons with field-dependent mobility explains
most results. Coulomb interaction may play a role in shaping the fine details.

###Raman scattering in transition metal dichalcogenides MTe2 (M = Mo, W)|Xiaoli Ma,Pengjie Guo,Changjing Yi,Qiaohe Yu,Anmin Zhang,Jianting Ji,Yong Tian,Feng Jin,YiyYan Wang,Kai Liu,Tianlong Xia,Youguo Shi,Qingming Zhang###

Raman scattering in transition metal dichalcogenides MTe2 (M = Mo, W). We performed comparable polarized Raman scattering studies of MoTe2 and WTe2.
By rotating crystals to tune the angle between the principal axis of the
crystals and the polarization of the incident/scattered light, we obtained the
angle dependence of the intensities for all the observed modes, which is
perfectly consistent with careful symmetry analysis. Combining these results
with first-principles calculations, we clearly identified the observed phonon
modes in the different phases of both crystals. Fifteen Raman-active phonon
modes (10Ag+5Bg) in the high-symmetry phase 1T'-MoTe2 (300 K) were well
assigned, and all the symmetry-allowed Raman modes (11A1+6A2) in the
low-symmetry phase Td-MoTe2 (10 K) and 12 Raman phonons (8A1+4A2) in Td-WTe2
were observed and identified. The present work provides basic information about
the lattice dynamics in transition-metal dichalcogenides and may shed some
light on the understanding of the extremely large magnetoresistance (MR) in
this class of materials.

###In-plane anisotropic magnetoresistance in antiferromagnetic Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$, (Ba$_{1-x}$K$_x$)Fe$_2$As$_2$ and Ba(Fe$_{1-x}$Ru$_x$)$_2$As$_2$|Gerald Derondeau,Ján Minár,Sebastian Wimmer,Hubert Ebert###

In-plane anisotropic magnetoresistance in antiferromagnetic Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$, (Ba$_{1-x}$K$_x$)Fe$_2$As$_2$ and Ba(Fe$_{1-x}$Ru$_x$)$_2$As$_2$. Using the Kubo-Greenwood formalism the resistivity anisotropy for electron
doped Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$, hole doped (Ba$_{1-x}$K$_x$)Fe$_2$As$_2$
and isovalently doped Ba(Fe$_{1-x}$Ru$_x$)$_2$As$_2$ in their antiferromagnetic
state has been calculated in order to clarify the origin of this important
phenomenon. The results show good agreement with experiment for all cases
without considering impurity states extending over several unit cells or
temperature induced spin fluctuations. From this it is concluded that the
resistivity anisotropy at low temperatures is primarily caused by an in-plane
anisotropic magnetoresistance. Accounting for the band dispersion with respect
to $k_z$ is however mandatory to explain the results, showing the importance of
the three-dimensional character of the electronic structure for the iron
pnictides. Furthermore, it is shown that the counterintuitive sign of the
resistivity anisotropy is no fundamental property but just a peculiarity of the
anisotropic band structure.

###Bias induced up to 100% spin-injection and detection polarizations in ferromagnet/bilayer-hBN/graphene/hBN heterostructures|Mallikarjuna Gurram,Siddhartha Omar,Bart J. van Wees###

Bias induced up to 100% spin-injection and detection polarizations in ferromagnet/bilayer-hBN/graphene/hBN heterostructures. We study spin transport in a fully hBN encapsulated monolayer-graphene van
der Waals (vdW) heterostructure, at room temperature. A top-layer of
bilayer-hBN is used as a tunnel barrier for spin-injection and detection in
graphene with ferromagnetic cobalt electrodes. We report surprisingly large and
bias induced (differential) spin-injection (detection) polarizations up to 50%
(135%) at a positive voltage bias of +0.6 V, as well as sign inverted
polarizations up to -70% (-60%) at a reverse bias of -0.4 V. This demonstrates
the potential of bilayer-hBN tunnel barriers for practical graphene spintronics
applications. With such enhanced spin-injection and detection polarizations, we
report a record two-terminal (inverted) spin-valve signals up to 800 $\Omega$
with a magnetoresistance ratio of 2.7%, and we achieve spin accumulations up to
4.1 meV. We propose how these numbers can be increased further, for future
technologically relevant graphene based spintronic devices.

###Monte Carlo study of magnetoresistance in a chiral soliton lattice|Shun Okumura,Yasuyuki Kato,Yukitoshi Motome###

Monte Carlo study of magnetoresistance in a chiral soliton lattice. Monoaxial chiral magnets can form a peculiar noncollinear spin structure
called the chiral soliton lattice in an applied magnetic field perpendicular to
the helical axis. We study magnetic properties and electrical transport in the
chiral soliton lattice by a Monte Carlo simulation for a one-dimensional Kondo
lattice model including the Dzyaloshinskii-Moriya interaction between classical
localized spins. We show that the model exhibits a helical spin structure at a
zero magnetic field, which turns into the chiral soliton lattice, and finally,
to a forced ferromagnetic state with increasing the external magnetic field. In
the chiral soliton lattice state, we find negative magnetoresistance
proportional to the number of solitons at low temperature, which corroborates
the spin scattering of electrons by chiral solitons. We also discuss the
temperature and magnetic field dependence of the spin structure factor and
electrical resistivity, in comparison with experiments for CrNb$_{3}$S$_{6}$.

###Negative longitudinal magnetoresistance from anomalous N=0 Landau level in topological materials|B. A. Assaf,T. Phuphachong,E. Kampert,V. V. Volobuev,P. S. Mandal,J. Sánchez-Barriga,O. Rader,G. Bauer,G. Springholz,L. A. de Vaulchier,Y. Guldner###

Negative longitudinal magnetoresistance from anomalous N=0 Landau level in topological materials. Negative longitudinal magnetoresistance (NLMR) is shown to occur in
topological materials in the extreme quantum limit, when a magnetic field is
applied parallel to the excitation current. We perform pulsed and DC field
measurements on Pb1-xSnxSe epilayers where the topological state can be
chemically tuned. The NLMR is observed in the topological state, but is
suppressed and becomes positive when the system becomes trivial. In a
topological material, the lowest N=0 conduction Landau level disperses down in
energy as a function of increasing magnetic field, while the N=0 valence Landau
level disperses upwards. This anomalous behavior is shown to be responsible for
the observed NLMR. Our work provides an explanation of the outstanding question
of NLMR in topological insulators and establishes this effect as a possible
hallmark of bulk conduction in topological matter.

###Thermopower and thermal conductivity in the Weyl semimetal NbP|U. Stockert,R. D. dos Reis,M. O. Ajeesh,S. J. Watzman,M. Schmidt,C. Shekhar,J. P. Heremans,C. Felser,M. Baenitz,M. Nicklas###

Thermopower and thermal conductivity in the Weyl semimetal NbP. The Weyl semimetal NbP exhibits an extremely large magnetoresistance (MR) and
an ultra-high mobility. The large MR originates from a combination of the
nearly perfect compensation between electron- and hole-type charge carriers and
the high mobility, which is relevant to the topological band structure. In this
work we report on temperature- and field-dependent thermopower and thermal
conductivity experiments on NbP. Additionally, we carried out complementary
heat capacity, magnetization, and electrical resistivity measurements. We found
a giant adiabatic magnetothermopower with a maximum of 800 $\mu$V/K at 50 K in
a field of 9 T. Such large effects have been observed rarely in bulk materials.
We suggest that the origin of this effect might be related to the high
charge-carrier mobility. We further observe pronounced quantum oscillations in
both thermal conductivity and thermopower. The obtained frequencies compare
well with our heat capacity and magnetization data.

###Theoretical prediction of a giant anisotropic magnetoresistance in carbon nanoscrolls|Ching Hao Chang,Carmine Ortix###

Theoretical prediction of a giant anisotropic magnetoresistance in carbon nanoscrolls. Snake orbits are trajectories of charge carriers curving back and forth which
form at an interface where either the magnetic field direction or the charge
carrier type are inverted. In ballistic samples their presence is manifested in
the appearance of magnetoconductance oscillations at small magnetic fields.
Here we show that signatures of snake orbits can also be found in the opposite
diffusive transport regime. We illustrate this by studying the classical
magnetotransport properties of carbon tubular structures subject to relatively
weak transversal magnetic fields where snake trajectories appear in close
proximity to the zero radial field projections. In carbon nanoscrolls the
formation of snake orbits leads to a strongly directional dependent positive
magnetoresistance with an anisotropy up to 80%.

###Metal-Insulator Transition in Ga doped ZnO via Controlled Thickness|Joynarayan Mukherjee,B. R. K. Nanda,M. S. Ramachandra Rao###

Metal-Insulator Transition in Ga doped ZnO via Controlled Thickness. We report thickness dependent metal insulator transition in Ga doped ZnO
(Ga:ZnO) thin films grown by pulsed laser deposition technique. From the
electrical transport measurements, we find that while the thinnest film
exhibits a resistivity of 0.05 $\Omega$-cm, lying in the insulating regime, the
thickest has resistivity of $6.6\times10^{-4}\Omega$-cm which shows metallic
type of conduction. Our analysis reveals that the Mott's variable range hopping
(VRH) model governs the insulating behavior in the thinner Ga:ZnO whereas the
2D weak localization phenomena is appropriate to explain the electron transport
in the thicker Ga:ZnO. Magnetoresistance study further confirms the presence of
strong localization in 6 nm film while weak localization is observed in 20 nm
and above thicker films. From the density functional calculations, it is found
that due to surface reconstruction and Ga doping, strong crystalline disorder
sets in very thin films to introduce localized states and thereby, restricts
the donor electron mobility.

###Mesoscopic quantum effects in a bad metal, hydrogen-doped vanadium dioxide|Will J. Hardy,Heng Ji,Hanjong Paik,Darrell G. Schlom,Douglas Natelson###

Mesoscopic quantum effects in a bad metal, hydrogen-doped vanadium dioxide. The standard treatment of quantum corrections to semiclassical electronic
conduction assumes that charge carriers propagate many wavelengths between
scattering events, and succeeds in explaining multiple phenomena (weak
localization magnetoresistance (WLMR), universal conductance fluctuations,
Aharonov-Bohm oscillations) observed in polycrystalline metals and doped
semiconductors in various dimensionalities. We report apparent WLMR and
conductance fluctuations in H$_{x}$VO$_{2}$, a poor metal (in violation of the
Mott-Ioffe-Regel limit) stabilized by the suppression of the VO$_{2}$
metal-insulator transition through atomic hydrogen doping. Epitaxial thin
films, single-crystal nanobeams, and nanosheets show similar phenomenology,
though the details of the apparent WLMR seem to depend on the combined effects
of the strain environment and presumed doping level. Self-consistent
quantitative analysis of the WLMR is challenging given this and the high
resistivity of the material, since the quantitative expressions for WLMR are
derived assuming good metallicity. These observations raise the issue of how to
assess and analyze mesoscopic quantum effects in poor metals.

###Theoretical study on magnetic tunneling junctions with semiconductor barriers CuInSe$_2$ and CuGaSe$_2$ including a detailed analysis of band-resolved transmittances|Keisuke Masuda,Yoshio Miura###

Theoretical study on magnetic tunneling junctions with semiconductor barriers CuInSe$_2$ and CuGaSe$_2$ including a detailed analysis of band-resolved transmittances. We study spin-dependent transport properties in magnetic tunneling junctions
(MTJs) with semiconductor barriers, Fe/CuInSe$_2$/Fe(001) and
Fe/CuGaSe$_2$/Fe(001). By analyzing their transmittances at zero bias voltage
on the basis of the first-principles calculations, we find that spin-dependent
coherent tunneling transport of $\Delta_1$ wave functions yields a relatively
high magnetoresistance (MR) ratio in both the MTJs. We carry out a detailed
analysis of the band-resolved transmittances in both the MTJs and find an
absence of the selective transmission of $\Delta_1$ wave functions in some
energy regions a few eV away from the Fermi level due to small band gaps in
CuInSe$_2$ and CuGaSe$_2$.

###Non-s wave superconductivity in boron-doped nanodiamond films with 0-π Josephson junction array|Somnath Bhattacharyya,Christopher Coleman,Davie Mtsuko,Dmitri Churochkin###

Non-s wave superconductivity in boron-doped nanodiamond films with 0-π Josephson junction array. Superconducting transport properties of granular materials are greatly
influenced by the microstructure. We show that in heavily boron-doped diamond
films (HBDDF) films some sharp transport features can be manipulated by
applying a magnetic field and controlled finite bias current. We demonstrate
the conductivity cross-over from dirty metal to the superconducting state
through an insulating peak arising at a very low current or magnetic field
region and particularly pronounced negative magnetoresistance with periodic
oscillatory features. The current-voltage characteristics show features of the
Berezinskii-Kosterlitz-Thouless (BKT) phase transitions which verifies the
two-dimensional structure in HBDDF observed recently. A zero bias conductance
peak can be attributed to the Andreev bound state formed at the grain
boundaries of diamond nanocrystals. The set of observations can be
qualitatively explained consistently through the concept of a superconducting
transition with a non-s wave order parameter in the diamond heterostructures.

###Magnetic field influenced electron-impurity scattering and magnetotransport|Jingjing Feng,Cong Xiao,Yang Gao,Qian Niu###

Magnetic field influenced electron-impurity scattering and magnetotransport. We formulate a quasiclassical theory ($\omega_c\tau \lesssim 1$ with
$\omega_c$ as the cyclotron frequency and $\tau$ as the relaxation time) to
study the influence of magnetic field on electron-impurity scattering process
in the two-dimensional electron gas. We introduce a general recipe based on an
abstraction of the detailed impurity scattering process to define the
scattering parameter such as the incoming and outgoing momentum and coordinate
jump. In this picture, we can conveniently describe the skew scattering and
coordinate jump, which will eventually modify the Boltzmann equation. We find
an anomalous Hall resistivity different from the conventional Boltzmann-Drude
result and a negative magnetoresistivity parabolic in magnetic field. The
origin of these results has been analyzed. The relevance between our theory and
recent simulation and experimental works is also discussed. Our theory
dominates in dilute impurity system where the correlation effect is negligible.

###Evaluation of bulk-interface contributions to Edelstein magnetoresistance at metal/oxide interfaces|Junyeon Kim,Yan-Ting Chen,Shutaro Karube,Saburo Takahashi,Kouta Kondou,Gen Tatara,YoshiChika Otani###

Evaluation of bulk-interface contributions to Edelstein magnetoresistance at metal/oxide interfaces. We report a systematic study on Edelstein magnetoresistance (Edelstein MR) in
Co25Fe75/Cu/Bi2O3 heterostructures with a strong spin-orbit interaction at the
Cu/Bi2O3 interface. We succeed in observing a significant dependence of the
Edelstein MR on both Cu layer thickness and temperature, and also develop a
general analytical model considering distinct bulk and interface contributions
on spin relaxation. Our analysis, based on the above model, quantitatively
illustrates a unique property of the spin transport near the Rashba interface,
revealing a prominent role of the spin relaxation process by determining the
ratios of the spin relaxation inside and outside the interface. We further find
the characteristic spin transport is unaffected by temperature. Our results
provide an essential tool for exploring the transport in a system with
spin-momentum-locked two-dimensional states.

###Relativistic correction to the magnetoresistance of the Dirac electron system|Mitsuaki Owada,Yuki Fuseya###

Relativistic correction to the magnetoresistance of the Dirac electron system. The magnetoresistance (MR) for relativistic electrons, i.e., the Dirac
electrons in solids, is investigated on the basis of the Boltzmann's theory.
The new formula of MR so obtaiend includes a relativistic correction, which has
not appeared in the conventional Boltzmann's theories. Our formula is
quantitatively consistent with that obtained by the Kubo theory except for the
quantum oscillations. While a field dependence of MR is unclear in the formula
by Kubo theory, a clear field dependence is obtained in our formula, which is
useful for the analysis of experimental results. The effects of the
relativistic correction on the MR for the one-band and two-band model are
discussed. By taking into account the field dependence of carrier density in
semimetals, the linear field dependence of MR is explained by our formula based
on the Boltzmann's theory

###Extremely Large Magnetoresistance and Electronic Structure of TmSb|Yi-Yan Wang,Hongyun Zhang,Xiao-Qin Lu,Lin-Lin Sun,Sheng Xu,Zhong-Yi Lu,Kai Liu,Shuyun Zhou,Tian-Long Xia###

Extremely Large Magnetoresistance and Electronic Structure of TmSb. We report the magneto-transport properties and the electronic structure of
TmSb. TmSb exhibits extremely large transverse magnetoresistance and
Shubnikov-de Haas (SdH) oscillation at low temperature and high magnetic field.
Interestingly, the split of Fermi surfaces induced by the nonsymmetric
spin-orbit interaction has been observed from SdH oscillation. The analysis of
the angle-dependent SdH oscillation illustrates the contribution of each Fermi
surface to the conductivity. The electronic structure revealed by
angle-resolved photoemission spectroscopy (ARPES) and first-principles
calculations demonstrates a gap at $X$ point and the absence of band inversion.
Combined with the trivial Berry phase extracted from SdH oscillation and the
nearly equal concentrations of electron and hole from Hall measurements, it is
suggested that TmSb is a topologically trivial semimetal and the observed XMR
originates from the electron-hole compensation and high mobility.

###Probe of Spin Dynamics in Superconducting NbN Thin Films via Spin Pumping|Yunyan Yao,Qi Song,Yota Takamura,Juan Pedro Cascales,Wei Yuan,Yang Ma,Yu Yun,X. C. Xie,Jagadeesh S. Moodera,Wei Han###

Probe of Spin Dynamics in Superconducting NbN Thin Films via Spin Pumping. The emerging field of superconductor (SC) spintronics has attracted intensive
attentions recently. Many fantastic spin dependent properties in SC have been
discovered, including the observation of large magnetoresistance, long spin
lifetimes and the giant spin Hall effect in SC, as well as spin supercurrent in
Josephson junctions, etc. Regarding the spin dynamic in SC films, few studies
has been reported yet. Here, we report the investigation of the spin dynamics
in an s-wave superconducting NbN film via spin pumping from an adjacent
insulating ferromagnet GdN layer. A profound coherence peak of the Gilbert
damping is observed slightly below the superconducting critical temperature of
the NbN layer, which is consistent with recent theoretical studies. Our results
further indicate that spin pumping could be a powerful tool for investigating
the spin dynamics in 2D crystalline superconductors.

###Topological Dirac semimetal phase in the iron-based superconductor Fe(Te,Se)|Peng Zhang,Zhijun Wang,Yukiaki Ishida,Yoshimitsu Kohama,Xianxin Wu,Koichiro Yaji,Yue Sun,Cedric Bareille,Kenta Kuroda,Takeshi Kondo,Kozo Okazaki,Koichi Kindo,Kazuki Sumida,Shilong Wu,Koji Miyamoto,Taichi Okuda,Hong Ding,G. D. Gu,Tsuyoshi Tamegai,Ronny Thomale,Takuto Kawakami,Masatoshi Sato,Shik Shin###

Topological Dirac semimetal phase in the iron-based superconductor Fe(Te,Se). Topological Dirac semimetals (TDSs) exhibit bulk Dirac cones protected by
time reversal and crystal symmetry, as well as surface states originating from
non-trivial topology. While there is a manifold possible onset of
superconducting order in such systems, few observations of intrinsic
superconductivity have so far been reported for TDSs. We observe evidence for a
TDS phase in FeTe$_{1-x}$Se$_x$ ($x$ = 0.45), one of the high transition
temperature ($T_c$) iron-based superconductors. In angle-resolved photoelectron
spectroscopy (ARPES) and transport experiments, we find spin-polarized states
overlapping with the bulk states on the (001) surface, and linear
magnetoresistance (MR) starting from 6 T. Combined, this strongly suggests the
existence of a TDS phase, which is confirmed by theoretical calculations. In
total, the topological electronic states in Fe(Te,Se) provide a promising high
$T_c$ platform to realize multiple topological superconducting phases.

###Effect of charge ordering on the electrical properties and magnetoresistance of manganites|Mahrous R. Ahmed###

Effect of charge ordering on the electrical properties and magnetoresistance of manganites. The Monte Carlo Ferromagnetic Ising model was used to study the electrical
properties of manganese oxides due to the charge ordering phase occurring at
doping, x = 0.5. The half-doped manganites have an insulator antiferromagnetic
ground state. We calculated the internal energy, specific heat, resistivity and
the magneto-resistance, MR, with parallel and anti-parallel applied magnetic
fields. Our simulation reveals that the resistivity decreases exponentially and
the electric current increases with increasing temperature according the free
charge increase, to transport from an insulator to conductor phase. The
magnetoresistance has negative small values with parallel magnetic field but
has positive high values with unti-parallel magnetic field. The obtained
semiconductor-metal transition behavior candidates the half-doped manganites to
be very good semiconductors diode junctions.

###Anisotropic electronic transport and Rashba effect of the two-dimensional electron system in (110) SrTiO$_3$-based heterostructures|K. Wolff,R. Eder,R. Schäfer,R. Schneider,D. Fuchs###

Anisotropic electronic transport and Rashba effect of the two-dimensional electron system in (110) SrTiO$_3$-based heterostructures. The two-dimensional electron system in (110)Al$_2$O$_{3-\delta}$/SrTiO$_3$
heterostructures displays anisotropic electronic transport. Largest and lowest
conductivity and electron mobility $\mu$ are observed along the $[001]$ and
$[1\bar{1}0]$ direction, respectively. The anisotropy of the sheet resistance
and $\mu$ likewise leads to a distinct anisotropic normal magnetotransport (MR)
for T < 30K. However, at temperatures T<5K and magnetic field B<2T MR is
dominated by weak antilocalization.Despite the rather strong anisotropy of the
Fermi surfaces, the in-plane anisotropic magnetoresistance (AMR) displays
two-fold non-crystalline anisotropy. However, the AMR-amplitude is found to be
anisotropic with respect to the current direction, leading to a 60% larger AMR
amplitude for current I along the $[001]$ direction compared to I parallel to
$[1\bar{1}0]$. Tight binding calulations evidence an anisotropic Rashba-induced
band splitting with dominant linear k-dependence. In combination with
semiclassical Boltzmann theory the non-crystalline AMR is well described,
despite the anisotropic Fermi surface.

###Electrical detection of a skyrmion in a magnetic tunneling junction|Keita Hamamoto,Naoto Nagaosa###

Electrical detection of a skyrmion in a magnetic tunneling junction. We theoretically investigated a method to detect a single skyrmion in a
magnetic tunneling junction (MTJ) geometry. Using the tunneling Hamiltonian
approach, we calculated the tunneling magnetoresistance (TMR) ratio of the
skyrmion-ferromagnet bilayer system. We show the TMR ratio is determined sorely
by the spin profile of the skyrmion and geometrical factor of the device, if
only the system is reasonably clean such that the spectral broadening is
smaller than the exchange coupling between the local and the itinerant magnetic
moment. The TMR ratio in that case can amount to $30\%$ or higher when the
diameter of the skyrmion is as large as the size of the device. Since this
criterion is easily achievable in real systems, MTJ geometry can be a good
candidate of the electrical detection of a single skyrmion i.e., the reading
process of the information in the future skyrmionics memory devices.

###Synthetic antiferromagnetic coupling between ultra-thin insulating garnets|Juan M. Gomez-Perez,Saül Vélez,Lauren McKenzie-Sell,Mario Amado,Javier Herrero-Martín,Josu López-López,S. Blanco-Canosa,Luis E. Hueso,Andrey Chuvilin,Jason W. A. Robinson,Fèlix Casanova###

Synthetic antiferromagnetic coupling between ultra-thin insulating garnets. The use of magnetic insulators is attracting a lot of interest due to a rich
variety of spin-dependent phenomena with potential applications to spintronic
devices. Here we report ultra-thin yttrium iron garnet (YIG) / gadolinium iron
garnet (GdIG) insulating bilayers on gadolinium iron garnet (GGG). From spin
Hall magnetoresistance (SMR) and X-ray magnetic circular dichroism
measurements, we show that the YIG and GdIG magnetically couple antiparallel
even in moderate in-plane magnetic fields. The results demonstrate an
all-insulating equivalent of a synthetic antiferromagnet in a garnet-based thin
film heterostructure and could open new venues for insulators in magnetic
devices. As an example, we demonstrate a memory element with orthogonal
magnetization switching that can be read by SMR.

###Doping-induced magnetism in the semiconducting B20 compound RuGe|Mojammel A. Khan,D. P. Young,P. W. Adams,D. Browne,D. M. Gautreau,W. Adam Phelan,Huibo Cao,J. F. DiTusa###

Doping-induced magnetism in the semiconducting B20 compound RuGe. RuGe, a diamagnetic small-band gap semiconductor, and CoGe, a nonmagnetic
semimetal, are both isostructural to the Kondo insulator FeSi and the skyrmion
lattice host MnSi. Here, we have explored the magnetic and transport properties
of Co-doped RuGe: Ru$_{1-x}$Co$_x$Ge. For small values of $x$, a magnetic
ground state emerges with $T_{c}\approx$ 5 $-$ 9 K, which is accompanied by a
moderate decrease in electrical resistivity and a Seebeck coefficient that
indicates electron-like charge carriers. The magnetization, magnetoresistance,
and the specific heat capacity all resemble that of Fe$_{1-x}$Co$_x$Si for
similar Co substitution levels, suggesting that Ru$_{1-x}$Co$_x$Ge hosts
equally as interesting magnetic and charge carrier transport properties.

###Large Thermal Hall Effect in $α$-RuCl$_3$: Evidence for Heat Transport by Kitaev-Heisenberg Paramagnons|Richard Hentrich,Maria Roslova,Anna Isaeva,Thomas Doert,Wolfram Brenig,Bernd Büchner,Christian Hess###

Large Thermal Hall Effect in $α$-RuCl$_3$: Evidence for Heat Transport by Kitaev-Heisenberg Paramagnons. The honeycomb Kitaev model in a magnetic field is a source of a topological
quantum spin liquid with Majorana fermions and gauge flux excitations as
fractional quasiparticles. We present experimental results for the thermal Hall
effect of the material $\alpha$-RuCl$_{3}$ which recently emerged as a prime
candidate for realizing such physics. At temperatures above long-range magnetic
ordering $T\gtrsim T_N\approx8$ K, we observe with an applied magnetic field
$B$ perpendicular to the honeycomb layers a sizeable positive transversal heat
conductivity $\kappa_{xy}$ which increases linearly with $B$. Upon raising the
temperature, $\kappa_{xy}(T)$ increases strongly, exhibits a broad maximum at
around 30 K, and eventually becomes negligible at $T\gtrsim 125$ K. Remarkably,
the longitudinal heat conductivity $\kappa_{xx}(T)$ exhibits a sizeable
positive thermal magnetoresistance effect. Thus, our findings provide clear-cut
evidence for longitudinal and transverse magnetic heat transport and underpin
the unconventional nature of the quasiparticles in the paramagnetic phase of
$\alpha$-RuCl$_{3}$.

###High density carriers at a strongly coupled graphene-topological insulator interface|Ayelet Zalic,Tom Dvir,Hadar Steinberg###

High density carriers at a strongly coupled graphene-topological insulator interface. We report on a strongly coupled bilayer graphene (BLG) - \bise\ device with a
junction resistance of less than 1.5 k$\Omega\mu$m$^2$. This device exhibits
unique behavior at the interface, which cannot be attributed to either material
in absence of the other. We observe quantum oscillations in the
magnetoresistance of the junction, indicating the presence of well-resolved
Landau levels due to hole carriers of unknown origin with a very large Fermi
surface. These carriers, found only at the interface, could conceivably arise
due to significant hole doping of the bilayer graphene with charge transfer on
the order of 2$\times$10$^{13}$ cm$^{-2}$, or due to twist angle dependent
mini-band transport.

###Magnetotransport properties in the magnetic phase of BaFe$_{2-x}$T$_x$As$_2$ (T = Co,Ni): A magnetic excitations approach|J. P. Peña,M. M. Piva,P. F. S. Rosa,P. G. Pagliuso,C. Adriano,T. Grant,Z. Fisk,E. Baggio-Saitovitch,P. Pureur###

Magnetotransport properties in the magnetic phase of BaFe$_{2-x}$T$_x$As$_2$ (T = Co,Ni): A magnetic excitations approach. Because of their complex Fermi surfaces, the identification of the physical
phenomena contributing to electronic scattering in the Fe-based superconductors
is a difficult task. Here, we report on the electrical resistivity,
magnetoresistance, and Hall effect in two series of BaFe$_{2-x}$T$_x$As$_2$ (T
= Co, Ni) crystals with different values of $x$. The T contents were chosen so
that the majority of the investigated samples present an intermediate
magnetically ordered state and a superconducting ground state. We interpret the
obtained results in terms of scattering of charge carriers by magnetic
excitations instead of describing them as resulting uniquely from effects
related to multiple-band conduction. Our samples are single crystals from the
structural point of view and their overall magnetotransport properties are
dominated by a single magnetic state.

###Magnetic and electronic structure of the layered rare-earth pnictide EuCd$_2$Sb$_2$|J. -R. Soh,C. Donnerer,K. M. Hughes,E. Schierle,E. Weschke,D. Prabhakaran,A. T. Boothroyd###

Magnetic and electronic structure of the layered rare-earth pnictide EuCd$_2$Sb$_2$. Resonant elastic X-ray scattering (REXS) at the Eu $M_5$ edge reveals an
antiferromagnetic structure in layered EuCd$_2$Sb$_2$ at temperatures below
$T_\textrm{N}$ = 7.4 K with a magnetic propagation vector of $(0,0,1/2)$ and
spins in the basal plane. Magneto-transport and REXS measurements with an
in-plane magnetic field show that features in the magnetoresistance are
correlated with changes in the magnetic structure induced by the field. Ab
initio electronic structure calculations predict that the observed spin
structure gives rise to a gapped Dirac point close to the Fermi level with a
gap of $\Delta E \sim$0.01 eV. The results of this study indicate that the Eu
spins are coupled to conduction electron states near the Dirac point.

###Complex magnetism and non-Fermi liquid state in the vicinity of the quantum critical point in the CeCo$_{1-x}$Fe$_x$Ge$_3$ series|P. Skokowski,K. Synoradzki,T. Toliński###

Complex magnetism and non-Fermi liquid state in the vicinity of the quantum critical point in the CeCo$_{1-x}$Fe$_x$Ge$_3$ series. We report extensive studies on the CeCo$_{1-x}$Fe$_{x}$Ge$_3$ alloys, which
show quantum critical point (QCP) due to damping the antiferromagnetic order in
CeCoGe$_3$ down to 0 K by doping with the paramagnetic CeFeGe$_3$ compound. The
presence of QCP is confirmed by detecting the non-Fermi liquid behavior (NFL)
using a wide range of the experimental methods: magnetic susceptibility,
specific heat, electrical resistivity, magnetoresistance, and thermoelectric
power. In the case of the thermoelectric power we find a clear enhancement of
the Seebeck coefficient for $x$ around 0.6, i.e. in the neighborhood of QCP.
Finally, the different complementary studies enabled construction of the
complex magnetic phase diagram for the CeCo$_{1-x}$Fe$_{x}$Ge$_3$ system,
including the energy scale imposed by the crystal electric field splitting of
the Ce ground state.

###Superconductivity in half-Heusler compound TbPdBi|H. Xiao,T. Hu,W. Liu,Y. L. Zhu,P. G. Li,G. Mu,J. Su,K. Li,Z. Q. Mao###

Superconductivity in half-Heusler compound TbPdBi. We have studied the half-Heusler compound TbPdBi through resistivity,
magnetization, Hall effect and heat capacity measurements. A semimetal behavior
is observed in its normal state transport properties, which is characterized by
a large negative magnetoresistance below 100 K. Notably, we find the
coexistence of superconductivity and antiferromagnetism in this compound. The
superconducting transition appears at 1.7 K, while the antiferromagnetic phase
transition takes place at 5.5 K. The upper critical field $H_{c2}$ shows an
unusual linear temperature dependence, implying unconventional
superconductivity. Moreover, when the superconductivity is suppressed by
magnetic field, its resistivity shows plateau behavior, a signature often seen
in topological insulators/semimetals. These findings establish TbPdBi as a
platform for study of the interplay between superconductivity, magnetism and
non-trivial band topology.

###Influence of Interfaces on the Transport Properties of Graphite revealed by Nanometer Thickness Reduction|Mahsa Zoraghi,José Barzola-Quiquia,Markus Stiller,Pablo D. Esquinazi,Irina Estrela-Lopis###

Influence of Interfaces on the Transport Properties of Graphite revealed by Nanometer Thickness Reduction. We investigated the influence of thickness reduction on the transport
properties of graphite microflakes. Using oxygen plasma etching we decreased
the thickness of highly oriented pyrolytic graphite (HOPG) microflakes from
$\sim 100$~nm to $\sim 20$~nm systematically. Keeping current and voltage
electrodes intact, the electrical resistance $R(T)$, the magnetoresistance (MR)
and Raman spectra were measured in every individual sample and after each
etching step of a few nm. The results show that $R(T)$ and MR can increase or
decrease with the sample thickness in a non-systematic way. The results
indicate that HOPG samples are inhomogeneous materials, in agreement with
scanning transmission electron microscopy images and X-ray diffraction data.
Our results further indicate that the quantum oscillations in the MR are not an
intrinsic property of the ideal graphite structure but their origin is related
to internal conducting interfaces.

###Large unidirectional spin Hall and Rashba-Edelstein magnetoresistance in topological insulator/magnetic insulator heterostructures|Yang Lv,James Kally,Tao Liu,Protyush Sahu,Mingzhong Wu,Nitin Samarth,Jian-Ping Wang###

Large unidirectional spin Hall and Rashba-Edelstein magnetoresistance in topological insulator/magnetic insulator heterostructures. Thanks to its unique symmetry, the unidirectional spin Hall and
Rashba-Edelstein magnetoresistance (USRMR) is of great fundamental and
practical interest, particularly in the context of reading magnetization states
in two-terminal spin-orbit torque switching memory and logic devices. Recent
studies show that topological insulators could improve USRMR amplitude.
However, the topological insulator device configurations studied so far in this
context, namely ferromagnetic metal/topological insulator bilayers and
magnetically doped topological insulators, suffer from current shunting by the
metallic layer and low Curie temperature, respectively. Here, we report large
USRMR in a new material category - magnetic insulator/topological insulator
bi-layered heterostructures. Such structures exhibit USRMR that is about an
order of magnitude larger than the highest values reported so far in all-metal
Ta/Co bilayers. We also demonstrate current-induced magnetization switching
aided by an Oersted field, and electrical read out by the USRMR, as a prototype
memory device.

###Circuit-Level Evaluation of the Generation of Truly Random Bits with Superparamagnetic Tunnel Junctions|Damir Vodenicarevic,Nicolas Locatelli,Alice Mizrahi,Tifenn Hirtzlin,Joseph S. Friedman,Julie Grollier,Damien Querlioz###

Circuit-Level Evaluation of the Generation of Truly Random Bits with Superparamagnetic Tunnel Junctions. Many emerging alternative models of computation require massive numbers of
random bits, but their generation at low energy is currently a challenge. The
superparamagnetic tunnel junction, a spintronic device based on the same
technology as spin torque magnetoresistive random access memory has recently
been proposed as a solution, as this device naturally switches between two easy
to measure resistance states, due only to thermal noise. Reading the state of
the junction naturally provides random bits, without the need of write
operations. In this work, we evaluate a circuit solution for reading the state
of superparamagnetic tunnel junction. We see that the circuit may induce a
small read disturb effect for scaled superparamagnetic tunnel junctions, but
this effect is naturally corrected in the whitening process needed to ensure
the quality of the generated random bits. These results suggest that
superparamagnetic tunnel junctions could generate truly random bits at 20
fJ/bit, including overheads, orders of magnitudes below CMOS-based solutions.

###Electrical control of the Zeeman spin splitting in two-dimensional hole systems|Elizabeth Marcellina,Ashwin Srinivasan,Dmitry Miserev,Andrew Croxall,David Ritchie,Ian Farrer,Oleg Sushkov,Dimitrie Culcer,Alex Hamilton###

Electrical control of the Zeeman spin splitting in two-dimensional hole systems. Semiconductor holes with strong spin-orbit coupling allow all-electrical spin
control, with broad applications ranging from spintronics to quantum
computation. Using a two-dimensional hole system in a GaAs quantum well, we
demonstrate a new mechanism of electrically controlling the Zeeman splitting,
which is achieved through altering the hole wave vector $k$. We find a
threefold enhancement of the in-plane $g-$factor $g_{\parallel}(k)$. We
introduce a new method for quantifying the Zeeman splitting from
magnetoresistance measurements, since the conventional tilted field approach
fails for two-dimensional systems with strong spin-orbit coupling. Finally, we
show that the Rashba spin-orbit interaction suppresses the in-plane Zeeman
interaction at low magnetic fields. The ability to control the Zeeman splitting
with electric fields opens up new possibilities for future quantum spin-based
devices, manipulating non-Abelian geometric phases, and realising Majorana
systems in $p-$type superconductor systems.

###Quantum transport in a compensated semimetal W2As3 with nontrivial Z2 indices|Yupeng Li,Chenchao Xu,Mingsong Shen,Jinhua Wang,Xiaohui Yang,Xiaojun Yang,Zengwei Zhu,Chao Cao,Zhu-An Xu###

Quantum transport in a compensated semimetal W2As3 with nontrivial Z2 indices. We report a topological semimetal W2As3 with a space group C2/m. Based on the
first-principles calculations, band crossings are partially gapped when
spin-orbit coupling is included. The Z2 indices at the electron filling are
[1;111], characterizing a strong topological insulator and topological surface
states. From the magnetotransport measurements, nearly quadratic field
dependence of magnetoresistance (MR) (B || [200]) at 3 K indicates an
electron-hole compensated compound whose longitudinal MR reaches 115 at 3 K and
15 T. In addition, multiband features are detected from the high-magnetic-field
Shubnikov-de Haas (SdH) oscillation, Hall resistivity, and band calculations. A
nontrivial pi Berry's phase is obtained, suggesting the topological feature of
this material. A two- band model can fit well the conductivity and Hall
coefficient. Our experiments manifest that the transport properties of W2As3
are in good agreement with the theoretical calculations.

###Log-periodic quantum magneto-oscillations and discrete scale invariance in topological material HfTe5|Huichao Wang,Yanzhao Liu,Yongjie Liu,Chuanying Xi,Junfeng Wang,Jun Liu,Yong Wang,Liang Li,Shu Ping Lau,Mingliang Tian,Jiaqiang Yan,David Mandrus,Ji-Yan Dai,Haiwen Liu,X. C. Xie,Jian Wang###

Log-periodic quantum magneto-oscillations and discrete scale invariance in topological material HfTe5. Discrete scale invariance (DSI) is a phenomenon featuring intriguing
log-periodicity which can be rarely observed in quantum systems. Here we report
the log-periodic quantum oscillations in the magnetoresistance (MR) and the
Hall traces of HfTe5 crystals, which reveals the appearance of DSI. The
oscillations show the same logB-periodicity in the behavior of MR and Hall,
indicating an overall effect of the DSI on the transport properties. Moreover,
the DSI feature in the Hall resistance signals its close relation to the
carriers. Combined with theoretical simulations, we further clarify the origin
of the log-periodic oscillations and the DSI in the topological materials. Our
work evidences the universality of the DSI in the Dirac materials and paves way
for the full understanding of the novel phenomenon.

###Large nonvolatile control of magnetic anisotropy in CoPt by a ferroelectric ZnO-based tunneling barrier|Muftah Al-Mahdawi,Mohamed Belmoubarik,Masao Obata,Daiki Yoshikawa,Hideyuki Sato,Tomohiro Nozaki,Tatsuki Oda,Masashi Sahashi###

Large nonvolatile control of magnetic anisotropy in CoPt by a ferroelectric ZnO-based tunneling barrier. The electric control of magnetic anisotropy has important applications for
nonvolatile memory and information processing. By first-principles
calculations, we show a large nonvolatile control of magnetic anisotropy in
ferromagnetic/ferroelectric CoPt/ZnO interface. Using the switched electric
polarization of ZnO, the density-of-states and magnetic anisotropy at the CoPt
surface show a large change. Due to a strong Co/Pt orbitals hybridization and a
large spin-orbit coupling, a large control of magnetic anisotropy was found. We
experimentally measured the change of effective anisotropy by tunneling
resistance measurements in CoPt/Mg-doped ZnO/Co junctions. Additionally, we
corroborate the origin of the control of magnetic anisotropy by observations on
tunneling anisotropic magnetoresistance.

###Spin Seebeck imaging of spin-torque switching in antiferromagnetic Pt/NiO heterostructures|Isaiah Gray,Takahiro Moriyama,Nikhil Sivadas,Gregory M. Stiehl,John T. Heron,Ryan Need,Brian J. Kirby,David H. Low,Katja C. Nowack,Darrell G. Schlom,Daniel C. Ralph,Teruo Ono,Gregory D. Fuchs###

Spin Seebeck imaging of spin-torque switching in antiferromagnetic Pt/NiO heterostructures. As electrical control of N\'eel order opens the door to reliable
antiferromagnetic spintronic devices, understanding the microscopic mechanisms
of antiferromagnetic switching is crucial. Spatially-resolved studies are
necessary to distinguish multiple nonuniform switching mechanisms; however,
progress has been hindered by the lack of tabletop techniques to image the
N\'eel order. We demonstrate spin Seebeck microscopy as a sensitive, table-top
method for imaging antiferromagnetic order in thin films, and apply this
technique to study spin-torque switching in NiO/Pt and Pt/NiO/Pt
heterostructures. We establish the interfacial antiferromagnetic spin Seebeck
effect in NiO as a probe of surface N\'eel order, resolving antiferromagnetic
spin domains within crystalline twin domains. By imaging before and after
applying current-induced spin torque, we resolve spin domain rotation and
domain wall motion, acting simultaneously. We correlate the changes in spin
Seebeck images with electrical measurements of the average N\'eel orientation
through the spin Hall magnetoresistance, confirming that we image
antiferromagnetic order.

###Transport signatures of surface states in a Weyl semimetal: evidence of field driven Fermi arc interferometry|Nityan L. Nair,Marie-Eve Boulanger,Francis Laliberté,Sinead Griffin,Sanyum Channa,Anaëlle Legros,Sahim Benhabib,Cyril Proust,Jeffrey Neaton,Louis Taillefer,James G. Analytis###

Transport signatures of surface states in a Weyl semimetal: evidence of field driven Fermi arc interferometry. A signature property of Weyl semimetals is the existence of topologically
protected surface states - arcs in momentum space that connect Weyl points in
the bulk. However, the presence of bulks states makes detection of surface
contributions to the transport challenging. Here we present a magnetoresistance
study of high-quality samples of the prototypical Weyl semimetal, TaAs. By
measuring the Shubnikov de Haas effect, we reveal the presence of a
two-dimensional cyclotron orbit. This orbit is quantitatively consistent with
the interference of coherent quasiparticles traversing two distinct Fermi arcs
on the [001] crystallographic surface. The observation of this effect suggests
that high magnetic fields can be used to study not only the transport
properties of Fermi arcs, but also the interference of their quantum mechanical
wavefunctions.

###Negative longitudinal magnetoresistance in GaAs quantum wells|Jing Xu,Meng K. Ma,Maksim Sultanov,Zhi-Li Xiao,Yong-Lei Wang,Dafei Jin,Yang-Yang Lyu,Wei Zhang,Loren N. Pfeiffer,Ken W. West,Kirk W. Baldwin,Mansour Shayegan,Wai-Kwong Kwok###

Negative longitudinal magnetoresistance in GaAs quantum wells. Negative longitudinal magnetoresistances (NLMRs) have been recently observed
in a variety of topological materials and often considered to be associated
with Weyl fermions that have a defined chirality. Here we report NLMRs in
non-Weyl GaAs quantum wells. In the absence of a magnetic field the quantum
wells show a transition from semiconducting-like to metallic behaviour with
decreasing temperature. We observed pronounced NLMRs up to 9 Tesla at
temperatures above the transition and weak NLMRs in low magnetic fields at
temperatures close to the transition and below 5 K. The observed NLMRs show
various types of magnetic field behaviour resembling those reported in
topological materials. We attribute them to microscopic disorder and use a
phenomenological three-resistor model to account for their various features.
Our results showcase a new contribution of microscopic disorder in the
occurrence of novel phenomena. They may stimulate further work on tuning
electronic properties via disorder/defect nano-engineering.

###Anisotropy of Dirac cones and van Hove singularity in an organic Dirac fermion system|Ayaka Mori,Mitsuyuki Sato,Takeshi Yajima,Takako Konoike,Kazuhito Uchida,Toshihito Osada###

Anisotropy of Dirac cones and van Hove singularity in an organic Dirac fermion system. We propose an experimental method to examine the in-plane anisotropy of
electronic structure in layered conductors. In the method, we measure the
interlayer magnetoresistance as a function of in-plane magnetic field
orientation. We applied it to an organic Dirac fermion system a-(BEDT-TTF)2I3
to experimentally determine the orientation of the anisotropic Dirac cones. It
is concluded that the long axis of the elliptic constant-energy contours of the
Dirac cone is tilted by approximately -30 deg from the crystalline a-axis to
b-axis under hydrostatic pressures. Additionally, we observed a signature of
van Hove singularity (which is a saddle point of the band dispersion) at 30-40
K above or below the Dirac point. The ridgeline of the saddle point is
estimated as almost parallel to the crystalline b-axis.

###Anisotropic and controllable Gilbert-Bloch dissipation in spin valves|Akashdeep Kamra,Dmytro M. Polishchuk,Vladislav Korenivski,Arne Brataas###

Anisotropic and controllable Gilbert-Bloch dissipation in spin valves. Spin valves form a key building block in a wide range of spintronic concepts
and devices from magnetoresistive read heads to spin-transfer-torque
oscillators. We elucidate the dependence of the magnetic damping in the free
layer on the angle its equilibrium magnetization makes with that in the fixed
layer. The spin pumping-mediated damping is anisotropic and tensorial, with
Gilbert- and Bloch-like terms. Our investigation reveals a mechanism for tuning
the free layer damping in-situ from negligible to a large value via the
orientation of fixed layer magnetization, especially when the magnets are
electrically insulating. Furthermore, we expect the Bloch contribution that
emerges from the longitudinal spin accumulation in the non-magnetic spacer to
play an important role in a wide range of other phenomena in spin valves.

###Extremely large magnetoresistance induced by hidden three-dimensional Dirac bands in nonmagnetic semimetal InBi|K. Okawa,M. Kanou,H. Namiki,T. Sasagawa###

Extremely large magnetoresistance induced by hidden three-dimensional Dirac bands in nonmagnetic semimetal InBi. Extremely large positive magnetoresistance (XMR) was found in a nonmagnetic
semimetal InBi. Using several single crystals with different residual
resistivity ratios (RRRs), we revealed that the XMR strongly depended on the
RRR (sample quality). Assuming that there were no changes in effective mass m*
and carrier concentrations in these single crystals, this dependence was
explained by a semiclassical two-carrier model. First-principle calculations
including the spin-orbit interactions (SOI) unveiled that InBi had a
compensated carrier balance and SOI-induced "hidden" three-dimensional (3D)
Dirac bands at the M and R points. Because the small m* and the large carrier
mobilities will be realized, these hidden 3D Dirac bands should play an
important role for the XMR in InBi. We suggest that this feature can be
employed as a novel strategy for the creation of XMR semimetals.

###Quasiperiodic functions on the plane and electron transport phenomena|Roberto De Leo,Andrei Ya. Maltsev###

Quasiperiodic functions on the plane and electron transport phenomena. While quasiperiodic functions in one variable appeared in applications since
Eighteen hundreds, for example in connection with the trajectories of
mechanical systems with 2n degress of freedom having n commuting first
integrals, the first applications of multivariable quasiperiodic functions were
found only in Seventies, in connection with solitonic solutions of the KdV
equation. Later, several other physical applications were found, especially in
connection with Solid State Physics, in particular with the electron transport
phenomena. In this article we reformulate, specifically in terms of the
topology of level sets of quasiperiodic functions on the plane, some
fundamental theoretical results found in Eighties and Nineties, then we review
the physical models of electron transport and their connections with
quasiperiodic functions and finally we present some old and new numerical
results on the level sets of some specific family of quasiperiodic functions,
some of which related to the magnetoresistance in normal metals.

###Encoding Microreactors with Droplet Chains in Microfluidics|Wenya Song,Gungun Lin,Jin Ge,Jurgen Fassbender,Denys Makarov###

Encoding Microreactors with Droplet Chains in Microfluidics. Droplet-based high throughput biomolecular screening and combinatorial
synthesis entail a viable indexing strategy to be developed for the
identification of each micro-reactor. Here, we propose a novel indexing scheme
based on the generation of droplet sequences on demand to form unique encoding
droplet chains in fluidic networks. These codes are represented by multiunit
and multilevel droplets packages, with each code unit possessing several
distinct signal levels, potentially allowing large encoding capacity. For proof
of concept, we use magnetic nanoparticles as the encoding material and a giant
magnetoresistance (GMR) sensor-based active sorting system supplemented with an
optical detector to generate and decode the sequence of one exemplar sample
droplet reactor and a 4-unit quaternary magnetic code. The indexing capacity
offered by 4-unit multilevel codes with this indexing strategy is estimated to
exceed 104, which holds great promise for large-scale droplet-based screening
and synthesis.

###Hopping Transport in SrTiO3/Nd1-xTiO3/SrTiO3 Heterostructures|Laxman Raju Thoutam,Jin Yue,Peng Xu,Bharat Jalan###

Hopping Transport in SrTiO3/Nd1-xTiO3/SrTiO3 Heterostructures. Electronic transport near the insulator-metal transition is investigated in
the molecular beam epitaxy-grown SrTiO3/Nd1-xTiO3/SrTiO3 heterostructures using
temperature dependent magnetotransport measurements. It was found that
Nd-vacancies introduce localized electronic states resulting in the variable
range hopping transport at low temperatures. At a fixed Nd-vacancies
concentration, a crossover from Mott to Efros-Shklovskii (ES) variable range
hopping transport was observed with decreasing temperature. With increasing
disorder, a sign reversal of magnetoresistance from positive to negative was
observed revealing interplay between intra-state interaction and the energy
dependence of the localization length as a function of disorder. These findings
highlight the important role of stoichiometry when exploring intrinsic effect
using heterostructure and interfaces in addition to offering broad opportunity
to tailor low temperature transport using non-stoichiometry defects.

###Anomalous scalings of the cuprate strange metals from nonlinear electrodynamics|Sera Cremonini,Anthony Hoover,Li Li,Steven Waskie###

Anomalous scalings of the cuprate strange metals from nonlinear electrodynamics. We examine transport in a holographic model which describes, through a
nonlinear gauge field sector, generic nonlinear interactions between the charge
carriers. Scaling exponents are introduced by using geometries which are
nonrelativistic and hyperscaling-violating in the infrared. In the dilute
charge limit in which the gauge field sector does not backreact on the
geometry, a particularly simple nonlinear theory reproduces the anomalous
temperature dependence of the resistivity and Hall angle of the cuprate strange
metals, $R \sim T$ and $\cot\Theta_H \sim T^2$ while also allowing for a linear
entropy $S \sim T$, and predicts that the magnetoresistance for small values of
the magnetic field $h$ should scale as $\sim h^2 T^{-4}$. Our study lends
evidence to the idea that the strange metal behavior of the cuprates relies
crucially on the linear temperature dependence of the entropy.

###Thermal tuning of the carrier density in Dirac semimetal Cd3As2 nanoplates|Min Wu,Guolin Zheng,Zheng Chen,Yequn Liu,Wenshuai Gao,Hongwei Zhang,Yuyan Han,Lan Wang,Jianhui Zhou,Wei Ning,Mingliang Tian###

Thermal tuning of the carrier density in Dirac semimetal Cd3As2 nanoplates. The tunable carrier density plays a key role in the investigation of novel
transport properties in three-dimensional topological semimetals. Here we
demonstrate that the carrier density as well as the mobility of Dirac semimetal
Cd3As2 nanoplates can be effectively tuned by the in-situ thermal treatment at
350 K for one hour, both showing a non-monotonic evolution with the thermal
cycling treatments. The upward shift of Fermi level relative to the Dirac nodes
blurs the surface Fermi-arc states, accompanying with an anomalous phase shift
of oscillations of bulk states due to the change of topology of electrons.
Meanwhile, the peaks of oscillations of bulk longitudinal magnetoresistivity
shift at high fields due to their coupling to the oscillations of the surface
Fermi-arc states. Our work provides a thermal control knob for manipulations of
the quantum states through the carrier density in Dirac semimetal Cd3As2 at
high temperature.

###Controlling magnetoresistance by oxygen impurities in Mq3-based molecular spin valves|Alberto Riminucci,Zhi-Gang Yu,Mirko Prezioso,Raimondo Cecchini,Ilaria Bergenti,Patrizio Graziosi,Valentin Alek Dediu###

Controlling magnetoresistance by oxygen impurities in Mq3-based molecular spin valves. The understanding of magnetoresistance (MR) in organic spin valves (OSVs)
based on molecular semiconductors is still incomplete after its demonstration
more than a decade ago. While carrier concentration may play an essential role
in spin transport in these devices, direct experimental evidence of its
importance is lacking. We probed the role of charge carrier concentration by
studying the interplay between MR and multilevel resistive switching in OSVs.
The present work demonstrates that all salient features of these devices,
particularly the intimate correlation between MR and resistance, can be
accounted for by the impurity band model, based on oxygen migration. Finally,
we highlight the critical importance of carrier concentration in determining
spin transport and MR in OSVs and the role of interface-mediated oxygen
migration in controlling the OSVs response.

###Isolated zero field sub-10 nm skyrmions in ultrathin Co films|Sebastian Meyer,Marco Perini,Stephan von Malottki,André Kubetzka,Roland Wiesendanger,Kirsten von Bergmann,Stefan Heinze###

Isolated zero field sub-10 nm skyrmions in ultrathin Co films. Due to their exceptional topological and dynamical properties magnetic
skyrmions - localized stable spin structures on the nanometre scale - show
great promise for future spintronic applications. To become technologically
competitive, isolated skyrmions with diameters below 10 nm that are stable at
zero magnetic field and room temperature are desired. Despite finding skyrmions
in a wide spectrum of materials, the quest for a material with these envisioned
properties is still ongoing. Here we report zero field isolated skyrmions with
diameters smaller than 5 nm coexisting with 1 nm thin domain walls in Rh/Co
atomic bilayers on the Ir(111) surface. These spin structures are characterized
by spin-polarized scanning tunnelling microscopy and can also be detected using
non-spin-polarized tips due to a large non-collinear magnetoresistance. We
demonstrate that sub-10 nm skyrmions are stabilised in these ferromagnetic Co
films at zero field due to strong frustration of exchange interaction, together
with Dzyaloshinskii-Moriya interaction and a large magnetocrystalline
anisotropy.

###Orientation of hole quantum Hall nematic phases in an out-of-plane electric field|A. F. Croxall,F. Sfigakis,J. Waldie,I. Farrer,D. A. Ritchie###

Orientation of hole quantum Hall nematic phases in an out-of-plane electric field. We present observations of an anisotropic resistance state at Landau level
filling factor $\nu=5/2$ in a two-dimensional hole system (2DHS), which occurs
for certain values of hole density $p$ and average out-of-plane electric field
$E_\perp$. The 2DHS is induced by electric field effect in an undoped
GaAs/AlGaAs quantum well, where front and back gates allow independent tuning
of $p$ and $E_\perp$, and hence the symmetry of the confining potential. For
$p\approx2\times10^{11}$~cm$^{-2}$ and $E_\perp \approx -2 \times10^{5}$~V/m,
the magnetoresistance along $\langle01\bar1\rangle$ greatly exceeds that along
$\langle011\rangle$, suggesting the formation of a quantum Hall nematic or
`stripe' phase. Reversing the sign of $E_\perp$ rotates the stripes by
$90^{\circ}$. We suggest this behavior may arise from the mixing of the hole
Landau levels and a combination of the Rashba and Dresselhaus spin-orbit
coupling effects.

###Topological Hall effect in bulk ferromagnet Cr$_2$Te$_3$ embedded with black-phosphorus-like bismuth nanosheets|Liang Zhou,Junshu Chen,Xiaobin Chen,Bin Xi,Yang Qiu,Junwei Zhang,Linjing Wang,Runnan Zhang,Bicong Ye,Pingbo Chen,Xixiang Zhang,Guoping Guo,Dapeng Yu,Jia-Wei Mei,Fei Ye,Gan Wang,Hongtao He###

Topological Hall effect in bulk ferromagnet Cr$_2$Te$_3$ embedded with black-phosphorus-like bismuth nanosheets. We implement the molecular beam epitaxy method to embed the
black-phosphorus-like bismuth nanosheets into the bulk ferromagnet
Cr$_2$Te$_3$. As a typical surfactant, bismuth lowers the surface tensions and
mediates the layer-by-layer growth of Cr$_2$Te$_3$. Meanwhile, the bismuth
atoms precipitate into black-phosphorus-like nanosheets with the lateral size
of several tens of nanometers. In Cr$_2$Te$_3$ embedded with Bi-nanosheets, we
observe simultaneously a large topological Hall effect together with the
magnetic susceptibility plateau and magnetoresistivity anomaly. As a control
experiment, none of these signals is observed in the pristine Cr$_2$Te$_3$
samples. Therefore, the Bi-nanosheets serve as seeds of topological Hall effect
induced by non-coplanar magnetic textures planted into Cr$_2$Te$_3$. Our
experiments demonstrate a new method to generates a large topological Hall
effect by planting strong spin-orbit couplings into the traditional
ferromagnet, which may have potential applications in spintronics.

###Effect of synthesis conditions on the electrical resistivity of TiSe$_2$|Jaime M. Moya,C. -L. Huang,Jesse Choe,Gelu Costin,Matthew S. Foster,E. Morosan###

Effect of synthesis conditions on the electrical resistivity of TiSe$_2$. Dilute impurities and growth conditions can drastically affect the transport
properties of TiSe$_2$, especially below the charge density wave transition. In
this paper, we discuss the effects of cooling rate, annealing time and
annealing temperature on the transport properties of TiSe$_2$: slow cooling of
polycrystalline TiSe$_2$ post-synthesis drastically increases the low
temperature resistivity, which is in contrast to the metallic behavior of
single-crystalline TiSe$_2$ due to charge doping from the residual iodine
transport agent. A logarithmic increase of resistivity upon cooling and
negative magnetoresistance with a sharp cusp around zero field are observed for
the first time for the polycrystalline TiSe$_2$ samples, pointing to
weak-localization effects due to low dimensionality. Annealing at low
temperatures has a similar, but less drastic effect. Furthermore, rapid
quenching of the polycrystalline samples from high temperatures freezes in
disorder, leading to a decrease in the low temperature resistivity.

###Tuning Rashba spin-orbit coupling at LaAlO3/SrTiO3 interfaces by band filling|Chunhai Yin,Patrick Seiler,Lucas M. K. Tang,Inge Leermakers,Nikita Lebedev,Uli Zeitler,Jan Aarts###

Tuning Rashba spin-orbit coupling at LaAlO3/SrTiO3 interfaces by band filling. The electric-field tunable Rashba spin-orbit coupling at the LaAlO3/SrTiO3
interface shows potential applications in spintronic devices. However,
different gate dependence of the coupling strength has been reported in
experiments. On the theoretical side, it has been predicted that the largest
Rashba effect appears at the crossing point of the $d_{xy}$ and $d_{xz,yz}$
bands. In this work, we study the tuneability of the Rashba effect in
LaAlO3/SrTiO3 by means of back-gating. The Lifshitz transition was crossed
multiple times by tuning the gate voltage so that the Fermi energy is tuned to
approach or depart from the band crossing. By analyzing the weak
antilocalization behavior in the magnetoresistance, we find that the maximum
spin-orbit coupling effect occurs when the Fermi energy is near the Lifshitz
point. Moreover, we find strong evidence for a single spin winding at the Fermi
surface.

###Electronic Transport and quantum oscillation of Topological Semimetals|Jin Hu,Su-Yang Xu,Ni Ni,Zhiqiang Mao###

Electronic Transport and quantum oscillation of Topological Semimetals. Three-dimensional (3D) topological semimetals represent a new class of
topological matters. The study of this family of materials has been at the
frontiers of condensed matter physics, and many breakthroughs have been made.
Several topological semimetal phases, including Dirac semimetals (DSMs), Weyl
semimetals (WSMs), nodal-line semimetals (NLSMs), and triple-point semimetals,
have been theoretically predicted and experimentally demonstrated. The
low-energy excitation around the Dirac/Weyl nodal points, nodal line, or triply
degenerated nodal point can be viewed as emergent relativistic fermions.
Experimental studies have shown that relativistic fermions can result in a rich
variety of exotic transport properties, e.g., extremely large
magnetoresistance, the chiral anomaly, and the intrinsic anomalous Hall effect.
In this review, we first briefly introduce band structural characteristics of
each topological semimetal phase, then review the current studies on quantum
oscillations and exotic transport properties of various topological semimetals,
and finally provide a perspective of this area.

###Large tunneling magnetoresistance in VSe2/MoS2 magnetic tunnel junction|Jiaqi Zhou,Junfeng Qiao,Chun-Gang Duan,Arnaud Bournel,Kang L. Wang,Weisheng Zhao###

Large tunneling magnetoresistance in VSe2/MoS2 magnetic tunnel junction. Two-dimensional (2D) van der Waals (vdW) materials provide the possibility of
realizing heterostructures with coveted properties. Here, we report a
theoretical investigation of the vdW magnetic tunnel junction (MTJ) based on
VSe2/MoS2 heterojunction, where the VSe2 monolayer acts as the ferromagnet with
the room-temperature ferromagnetism. We propose the concept of spin-orbit
torque (SOT) vdW MTJ with reliable reading and efficient writing operations.
The non-equilibrium study reveals a large tunneling magnetoresistance (TMR) of
846 % at 300 Kelvin, identifying significantly its parallel and anti-parallel
states. Thanks to the strong spin Hall conductivity of MoS2, SOT is promising
for the magnetization switching of VSe2 free layer. Quantum-well states come
into being and resonances appear in MTJ, suggesting that the voltage control
can adjust transport properties effectively. The SOT vdW MTJ based on VSe2/MoS2
provides desirable performance and experimental feasibility, offering new
opportunities for 2D spintronics.

###Magnetotransport in Al6Re|Erjian Cheng,Darren C. Peets,Chuanying Xi,Yeyu Huang,Li Pi,Shiyan Li###

Magnetotransport in Al6Re. Since very few Type-I superconductors are known and most are elemental
superconductors, there are very few experimental platforms where the
interaction between Type-I superconductivity and topologically nontrivial band
structure can be probed. The rhenium aluminide Al$_6$Re has recently been
identified as a Type-I superconductor with a transition of 0.74\,K and a
critical field of $\sim$50\,Oe. Here, we report its magnetotransport behavior
including de Haas-van Alphen (dHvA) and Shubnikov-de Haas (SdH) oscillations.
Angular dependence of the magnetoresistance reveals a highly anisotropic Fermi
surface with dominant hole character. From the strong oscillatory component
$\Delta R_{xx}$ in high magnetic fields up to 33\,T, the Landau index
infinite-field intercept in the case of a single oscillation frequency, and the
phase factor $\varphi$ where multiple frequencies coexist, are both $\sim$1/4.
This intermediate value is suggestive of possible nontrivial band topology but
does not allow strong conclusions.

###Current-induced switching of YIG/Pt bilayers with in-plane magnetization due to Oersted fields|Johannes Mendil,Morgan Trassin,Quingquing Bu,Manfred Fiebig,Pietro Gambardella###

Current-induced switching of YIG/Pt bilayers with in-plane magnetization due to Oersted fields. We report on the switching of the in-plane magnetization of thin yttrium iron
garnet (YIG)/Pt bilayers induced by an electrical current. The switching is
either field-induced and assisted by a dc current, or current-induced and
assisted by a static magnetic field. The reversal of the magnetization occurs
at a current density as low as $10^5$~A/cm$^{2}$ and magnetic fields of $\sim
40$~$\mu$T, two orders of magnitude smaller than in ferromagnetic metals,
consistently with the weak uniaxial anisotropy of the YIG layers. We use the
transverse component of the spin Hall magnetoresistance to sense the magnetic
orientation of YIG while sweeping the current. Our measurements and simulations
reveal that the current-induced effective field responsible for switching is
due to the Oersted field generated by the current flowing in the Pt layer
rather than by spin-orbit torques, and that the switching efficiency is
influenced by pinning of the magnetic domains.

###Strong magnetophonon oscillations in extra-large graphene|P. Kumaravadivel,M. T. Greenaway,D. Perello,A. Berdyugin,J. Birkbeck,J. Wengraf,S. Liu,J. H. Edgar,A. K. Geim,L. Eaves,R. Krishna Kumar###

Strong magnetophonon oscillations in extra-large graphene. Van der Waals materials and their heterostructures offer a versatile platform
for studying a variety of quantum transport phenomena due to their unique
crystalline properties and the exceptional ability in tuning their electronic
spectrum. However, most experiments are limited to devices that have lateral
dimensions of only a few micrometres. Here, we perform magnetotransport
measurements on graphene/hexagonal boron-nitride Hall bars and show that wider
devices reveal additional quantum effects. In devices wider than ten
micrometres we observe distinct magnetoresistance oscillations that are caused
by resonant scattering of Landau-quantised Dirac electrons by acoustic phonons
in graphene. The study allows us to accurately determine graphene's low energy
phonon dispersion curves and shows that transverse acoustic modes cause most of
phonon scattering. Our work highlights the crucial importance of device width
when probing quantum effects and also demonstrates a precise, spectroscopic
method for studying electron-phonon interactions in van der Waals
heterostructures.

###Theoretical Study on Four-fold Symmetric Anisotropic Magnetoresistance Effect in Cubic Single-crystal Ferromagnetic Model|Yuta Yahagi,Daisuke Miura,Akimasa Sakuma###

Theoretical Study on Four-fold Symmetric Anisotropic Magnetoresistance Effect in Cubic Single-crystal Ferromagnetic Model. In this study, we present a theoretical interpretation of the experimental
results that the anisotropic magnetoresistance (AMR) effect has a four-fold
symmetric component, $c_4$, in cubic ferromagnetic metals. The theoretical
model that we employ is based on the Anderson impurity model that includes a
four-fold symmetric crystalline electric field, and we assume that the
impurities have 3d electron orbitals and spin--orbit interaction (SOI). We
describe the DC conductivity on the basis of the Kubo formula, and we
investigate $c_4$ by analyzing the magnetization direction dependence of the
resultant AMR ratio. Analytical and numerical calculations are performed; the
analytical calculation reveals that $c_4$ arises from the fourth-order
contribution of the SOI, and the numerical calculation provides the parameter
dependencies of $c_{4}$ in our model. From the calculation results, we observe
that the splitting of impurity 3d levels due to SOI is responsible for the
existence of $c_{4}$ in cubic ferromagnetic metals.

###Charge density wave and large non-saturating magnetoresistance in YNiC$_2$ and LuNiC$_2$|Kamil K. Kolincio,Marta Roman,Tomasz Klimczuk###

Charge density wave and large non-saturating magnetoresistance in YNiC$_2$ and LuNiC$_2$. We report a study of physical properties of two quasi-low dimensional metals
YNiC$_2$ and LuNiC$_2$ including the investigation of transport,
magnetotransport, galvanomagnetic and specific heat properties. In YNiC$_2$ we
reveal two subsequent transitions associated with the formation of weakly
coupled charge density wave at $T_{CDW}$ = 318 K, and its locking in with the
lattice at $T_1$ = 275 K. These characteristic temperatures follow the
previously proposed linear scaling with the unit cell volume, demonstrating its
validity extended beyond the lanthanide-based $R$NiC$_2$. We also find that, in
the absence of magnetic ordering able to interrupt the development of charge
density wave, the Fermi surface nesting leads to opening of small pockets,
containing high mobility carriers. This effect gives rise to substantial
enhancement of magnetoresistance, reaching 470 % for YNiC$_2$ and 50 % for
LuNiC$_2$ at $T$ = 1.9 K and $B$ = 9 T.

###Magnetophonon spectroscopy of Dirac Fermion scattering by transverse and longitudinal acoustic phonons in graphene|M. T. Greenaway,R. Krishna Kumar,P. Kumaravadivel,A. K. Geim,L. Eaves###

Magnetophonon spectroscopy of Dirac Fermion scattering by transverse and longitudinal acoustic phonons in graphene. Recently observed magnetophonon resonances in the magnetoresistance of
graphene are investigated using the Kubo formalism. This analysis provides a
quantitative fit to the experimental data over a wide range of carrier
densities. It demonstrates the predominance of carrier scattering by low energy
transverse acoustic (TA) mode phonons: the magnetophonon resonance amplitude is
significantly stronger for the TA modes than for the longitudinal acoustic (LA)
modes. We demonstrate that the LA and TA phonon speeds and the electron-phonon
coupling strengths determined from the magnetophonon resonance measurements
also provide an excellent fit to the measured dependence of the resistivity at
zero magnetic field over a temperature range of 4-150 K. A semiclassical
description of magnetophonon resonance in graphene is shown to provide a simple
physical explanation for the dependence of the magneto-oscillation period on
carrier density. The correspondence between the quantum calculation and the
semiclassical model is discussed.

###Field-reentrant superconductivity close to a metamagnetic transition in the heavy-fermion superconductor UTe$_2$|Georg Knebel,William Knafo,Alexandre Pourret,Qun Niu,Michal Vališka,Daniel Braithwaite,Gérard Lapertot,Marc Nardone,Abdelaziz Zitouni,Sanu Mishra,Ilya Sheikin,Gabriel Seyfahrt,Jean-Pascal Brison,Dai Aoki,Jacques Flouquet###

Field-reentrant superconductivity close to a metamagnetic transition in the heavy-fermion superconductor UTe$_2$. We present a study of the upper critical field of the newly discovered heavy
fermion superconductor UTe$_2$ by magnetoresistivity measurements in pulsed
magnetic fields up to 60~T and static magnetic fields up to 35~T. We show that
superconductivity survives up to the metamagnetic transition at $H_{\rm m}
\approx 35$~T at low temperature. Above $H_{\rm m}$ superconductivity is
suppressed. At higher temperature superconductivity is enhanced under magnetic
field leading to reentrance of superconductivity or an almost temperature
independent increase of $H_{\rm c2}$. By studying the angular dependence of the
upper critical field close to the $b$ axis (hard magnetization axis) we show
that the maximum of the reentrant superconductivity temperature is depinned
from the metamagnetic field. A key ingredient for the field-reinforcement of
superconductivity on approaching $H_{\rm m}$ appears to be an immediate
interplay with magnetic fluctuations and a possible Fermi-surface
reconstruction.

###Unraveling the Effect of Electron-Electron Interaction on Electronic Transport in High-Mobility Stannate Films|Jin Yue,Laxman R. Thoutam,Abhinav Prakash,Tianqi Wang,Bharat Jalan###

Unraveling the Effect of Electron-Electron Interaction on Electronic Transport in High-Mobility Stannate Films. Contrary to the common belief that electron-electron interaction (EEI) should
be negligible in s-orbital-based conductors, we demonstrated that the EEI
effect could play a significant role on electronic transport leading to the
misinterpretation of the Hall data. We show that the EEI effect is primarily
responsible for an increase in the Hall coefficient in the La-doped SrSnO3
films below 50 K accompanied by an increase in the sheet resistance. The
quantitative analysis of the magnetoresistance (MR) data yielded a large phase
coherence length of electrons exceeding 450 nm at 1.8 K and revealed the
electron-electron interaction being accountable for breaking of electron phase
coherency in La-doped SrSnO3 films. These results while providing critical
insights into the fundamental transport behavior in doped stannates also
indicate the potential applications of stannates in quantum coherent electronic
devices owing to their large phase coherence length.

###Interface ferromagnetism and anomalous Hall effect of CdO/ferromagnetic insulator heterostructures|Yang Ma,Yu Yun,Yuehui Li,Wenyu Xing,Yunyan Yao,Ranran Cai,Yangyang Chen,Yuan Ji,Peng Gao,Xin-Cheng Xie,Wei Han###

Interface ferromagnetism and anomalous Hall effect of CdO/ferromagnetic insulator heterostructures. The experimental observation of quantum anomalous Hall effect (QAHE) in
magnetic topological insulators has stimulated enormous interest in
condensed-matter physics and materials science. For the purpose of realizing
high-temperature QAHE, several material candidates have been proposed, among
which the interface states in the CdO/ferromagnetic insulator heterostructures
are particularly interesting and favorable for technological applications.
Here, we report the experimental observation of the interfacial ferromagnetism
and anomalous Hall effect in the Fe3O4/CdO/Fe3O4 heterostructures grown via
oxide molecular-beam epitaxy. Systematical variation of the CdO thickness
reveals the interface ferromagnetism as the major cause for the observed planar
magnetoresistance and anomalous Hall effect. Our results might pave the way to
engineer oxide interface states for the exploration of QAHE towards exotic
quantum-physical phenomena and potential applications.

###Magnetoresistive RAM for error resilient XNOR-Nets|Michail Tzoufras,Marcin Gajek,Andrew Walker###

Magnetoresistive RAM for error resilient XNOR-Nets. We trained three Binarized Convolutional Neural Network architectures
(LeNet-4, Network-In-Network, AlexNet) on a variety of datasets (MNIST,
CIFAR-10, CIFAR-100, extended SVHN, ImageNet) using error-prone activations and
tested them without errors to study the resilience of the training process.
With the exception of the AlexNet when trained on the ImageNet dataset, we
found that Bit Error Rates of a few percent during training do not degrade the
test accuracy. Furthermore, by training the AlexNet on progressively smaller
subsets of ImageNet classes, we observed increasing tolerance to activation
errors. The ability to operate with high BERs is critical for reducing power
consumption in existing hardware and for facilitating emerging memory
technologies. We discuss how operating at moderate BER can enable
Magnetoresistive RAM with higher endurance, speed and density.

###Spin-Orbit Torque in a Single Ferromagnetic Layer with Large Spin-Orbit Coupling|Ziyan Luo,Qi Zhang,Yanjun Xu,Yumeng Yang,Xinhai Zhang,Yihong Wu###

Spin-Orbit Torque in a Single Ferromagnetic Layer with Large Spin-Orbit Coupling. Spin-orbit torque in heavy metal/ferromagnet heterostructures with broken
spatial inversion symmetry provides an efficient mechanism for manipulating
magnetization using a charge current. Here, we report the presence of a spin
torque in a single ferromagnetic layer in both asymmetric MgO/Fe0.8Mn0.2 and
symmetric MgO/Fe0.8Mn0.2/MgO structures, which manifests itself in the form of
an effective field transverse to the charge current. The current to effective
field conversion efficiency, which is characterized using both the nonlinear
magnetoresistance and second-order planar Hall effect methods, is comparable to
the efficiency in typical heavy metal/ferromagnet bilayers. We argue that the
torque is caused by spin rotation in the vicinity of the surface via impurity
scattering in the presence of a strong spin-orbit coupling. Instead of
cancelling off with each other, the torques from the top and bottom surfaces
simply add up, leading to a fairly large net torque, which is readily observed
experimentally.

###Intrinsic resistance peaks in AB-stacked multilayer graphene with odd number of layers|Tomoaki Nakasuga,Taiki Hirahara,Kota Horii,Ryoya Ebisuoka,Shingo Tajima,Kenji Watanabe,Takashi Taniguchi,Ryuta Yagi###

Intrinsic resistance peaks in AB-stacked multilayer graphene with odd number of layers. The intrinsic resistance peak (ridge) structures were recently found to
appear in the carrier density dependence plot of the resistance of the
AB-stacked multilayer graphene with even numbers of layers.The ridges are due
to topological changes in the Fermi surface. Here, these structures were
studied in AB-stacked multilayer graphene with odd numbers of layers (5 and 7
layers) by performing experiments using encapsulated high-quality graphene
samples equipped with top and bottom gate electrodes.The intrinsic resistance
peaks that appeared on maps plotted with respect to the carrier density and
perpendicular electric field showed particular patterns depending on graphene's
crystallographic structure, and were qualitatively different from those of
graphene with even numbers of layers. Numerical calculations of the dispersion
relation and semi-classical resistivity using information based on the Landau
level structure determined by the magnetoresistance oscillations, revealed that
the difference stemmed from the even-odd layer number effect on the electronic
band structure.

###Tunneling Anisotropic Magnetoresistance in Ferroelectric Tunnel Junctions|A. Alexandrov,M. Ye. Zhuravlev,Evgeny Y. Tsymbal###

Tunneling Anisotropic Magnetoresistance in Ferroelectric Tunnel Junctions. Using a simple quantum-mechanical model, we explore a tunneling anisotropic
magnetoresistance (TAMR) effect in ferroelectric tunnel junctions (FTJs) with a
ferromagnetic electrode and a ferroelectric barrier layer, which spontaneous
polarization gives rise to the Rashba and Dresselhaus spin-orbit coupling
(SOC). For realistic parameters of the model, we predict sizable TAMR
measurable experimentally. For asymmetric FTJs, which electrodes have different
work functions, the built-in electric field affects the SOC parameters and
leads to TAMR dependent on ferroelectric polarization direction. The SOC change
with polarization switching affects tunneling conductance, revealing a new
mechanism of tunneling electroresistance (TER). These results demonstrate new
functionalities of FTJs which can be explored experimentally and used in
electronic devices.

###Magnetoresistance in Metallic Ferroelectrics|Jiesu Wang,Hongbao Yao,Kuijuan Jin,Er-Jia Guo,Qinghua Zhang,Chao Ma,Lin Gu,Pazhanivelu Venkatachalam,Jiali Zhao,Jiaou Wang,Hassen Riahi,Haizhong Guo,Chen Ge,Can Wang,Guozhen Yang###

Magnetoresistance in Metallic Ferroelectrics. Polar metals with ferroelectric-like displacements in metals have been
achieved recently, half century later than Anderson and Blount's prediction.
However, the genuine ferroelectricity with electrical dipolar switching has not
yet been attained experimentally in the conducting materials, especially the
ones possessing magnetic responses. Here we report the coexistence of
ferroelectricity and magnetoresistance (MR) in the metallic PbNb0.12Ti0.88O3
(PNTO) thin films. We found that the conducting and magnetic responses of PNTO
films are highly asymmetric. Negative MR up to 50% is observed under an
in-plane magnetic field; the MR switches to positive with the magnetic field
applied parallel to the surface normal. Such unique behavior is attributed to
the moving electron caused effective magnetic field which couples with the
spins of electrons, which form a dynamic multiferroic state in the metallic
PNTO. These findings break a path to multiferroic metal and offer a great
potential to the multi-functional devices.

###Charging effects and anomalous resistive features of superconducting boron doped diamond films|Christopher Coleman,Somnath Bhattacharyya###

Charging effects and anomalous resistive features of superconducting boron doped diamond films. Anomalous resistive peaks below the superconducting transition temperature in
heavily boron doped nanocrystalline diamond films could have potential
application in switching devices, however the exact origin is still under
study. We establish a temperature dependence of this resistive phase similar to
what has been reported for in Josephson junction arrays and other granular
superconductors where the charge duel of the Berezinskii-Kosterlitz-Thouless
(BKT) transition has been observed. Non-linear magnetoresistance with a
temperature dependent peak feature below the critical field are also presented.
Pronounced temperature dependent hysteresis in the current voltage sweeps at
temperatures below the determined BKT critical point are related to pinning of
charge defects. It is shown that these collective features allude to a
Charge-BKT transition between charge and anti-charge analogues.

###Giant anisotropic magnetoresistance and nonvolatile memory in canted antiferromagnet Sr2IrO4|Haowen Wang,Chengliang Lu,Jun Chen,Yong Liu,S. L. Yuan,Sang-Wook Cheong,Shuai Dong,Jun-Ming Liu###

Giant anisotropic magnetoresistance and nonvolatile memory in canted antiferromagnet Sr2IrO4. Antiferromagnets have been generating intense interest in the spintronics
community, owing to their intrinsic appealing properties like zero stray field
and ultrafast spin dynamics. While the control of antiferromagnetic (AFM)
orders has been realized by various means, applicably appreciated
functionalities on the readout side of AFM-based devices are urgently desired.
Here, we report the remarkably enhanced anisotropic magnetoresistance (AMR) as
giant as ~ 160% in a simple resistor structure made of AFM Sr2IrO4 without
auxiliary reference layer. The underlying mechanism for the giant AMR is an
indispensable combination of atomic scale giant-MR-like effect and
magnetocrystalline anisotropy energy, which was not accessed earlier.
Furthermore, we demonstrate the bistable nonvolatile memory states that can be
switched in-situ without the inconvenient heat-assisted procedure, and robustly
preserved even at zero magnetic field, due to the modified interlayer coupling
by 1% Ga-doping in Sr2IrO4. These findings represent a straightforward step
toward the AFM spintronic devices.

###Quantum oscillation of thermal conductivity and violation of Weidemann-Franz law in TaAs$_2$ and NbAs$_2$|X. Rao,X. Zhao,X. -Y. Wang,H. L. Che,L. G. Chu,G. Hussain,T. -L. Xia,X. F. Sun###

Quantum oscillation of thermal conductivity and violation of Weidemann-Franz law in TaAs$_2$ and NbAs$_2$. We report a study of thermal conductivity and resistivity at ultra-low
temperatures and in high magnetic fields for semi-metal materials TaAs$_2$ and
NbAs$_2$ by using single crystal samples. The thermal conductivity is strongly
suppressed in magnetic fields, having good correspondence with the large
positive magnetoresistance, which indicates a dominant electronic contribution
to thermal conductivity. In addition, not only the resistivity but also the
thermal conductivity display clear quantum oscillations behavior at subKelvin
temperatures and in magnetic fields up to 14 T. The most striking phenomenon is
that the thermal conductivity show a $T^4$ behavior at very low temperatures,
while the resistivity show a $T$-independent behavior. This indicates a strong
violation of the Weidemann-Franz law and points to a non-Feimi liquid state of
these materials.

###Proximity magnetoresistance in graphene induced by magnetic insulators|D. A. Solis,A. Hallal,X. Waintal,M. Chshiev###

Proximity magnetoresistance in graphene induced by magnetic insulators. We demonstrate the existence of Giant proximity magnetoresistance (PMR)
effect in a graphene spin valve where spin polarization is induced by a nearby
magnetic insulator. PMR calculations were performed for yttrium iron garnet
(YIG), cobalt ferrite (CFO), and two europium chalcogenides EuO and EuS. We
find a significant PMR (up to 100%) values defined as a relative change of
graphene conductance with respect to parallel and antiparallel alignment of two
proximity induced magnetic regions within graphene. Namely, for high Curie
temperature (Tc) CFO and YIG insulators which are particularly important for
applications, we obtain 22% and 77% at room temperature, respectively. For low
Tc chalcogenides, EuO and EuS, the PMR is 100% in both cases. Furthermore, the
PMR is robust with respect to system dimensions and edge type termination. Our
findings show that it is possible to induce spin polarized currents in graphene
with no direct injection through magnetic materials.

###Robust magnetoresistance in TaAs2 under pressure up to about 37 GPa|Hongyuan Wang,Cuiying Pei,Hao Su,Zhenhai Yu,Mingtao Li,Wei Xia,Xiaolei Liu,Qifeng Liang,Jinggeng Zhao,Chunyin Zhou,Na Yu,Xia Wang,Zhiqiang Zou,Lin Wang,Yanpeng Qi,Yanfeng Guo###

Robust magnetoresistance in TaAs2 under pressure up to about 37 GPa. The extremely large magnetoresistance (XMR) in nonmagnetic semimetals has
inspired growing interest owing to both intriguing physics and potential
applications. We report results of synchrotron X-ray diffraction (SXRD) and
electrical transport measurements on TaAs2 under pressure up to ~ 37 GPa, which
revealed an anisotropic compression of the unit cell, formation of unusual
As-As bonds above 9.5 GPa, and enhancement of metallicity. Interestingly, the
MR of TaAs2 under pressure changed gently, which at 1.7 GPa is 96.6% and at
36.6 GPa is still 36.7%. The almost robust MR under pressure could be related
to the nearly stable electronic structure unveiled by the ab initio
calculations. The discovery would expand the potential use of XMR even under
high pressure.

###Evidence for Weyl fermions in the elemental semiconductor tellurium|Nan Zhang,Gan Zhao,Lin Li,Pengdong Wang,Lin Xie,Hui Li,Zhiyong Lin,Jiaqing He,Zhe Sun,Zhengfei Wang,Zhenyu Zhang,Changgan Zeng###

Evidence for Weyl fermions in the elemental semiconductor tellurium. The recent discovery of Weyl fermions in solids enables exploitation of
relativistic physics and development of a spectrum of intriguing physical
phenomena. They are constituted of pairs of Weyl points with two-fold band
degeneracy, which in principle can be hosted in any materials without inversion
or time-reversal symmetry. However, previous studies of Weyl fermions have been
limited exclusively to semimetals. Here, by combining magneto-transport
measurements, angle-resolved photoemission spectroscopy, and band structure
calculations, Weyl fermions are identified in an elemental semiconductor
tellurium. This is mainly achieved by direct observation of the representative
transport signatures of the chiral anomaly, including the negative longitudinal
magnetoresistance and the planar Hall effect. Semiconductor materials are well
suited for band engineering, and therefore provide an ideal platform for
manipulating the fundamental Weyl fermionic behaviors. Furthermore,
introduction of Weyl physics into semiconductors to develop "Weyl
semiconductors" also creates a new degree of freedom for the future design of
semiconductor electronic and optoelectronic devices.

###Interplay between disorder driven Non-Fermi-liquid behavior and magnetism in Ce0.24La0.76Ge compound|Karan Singh,K. Mukherjee###

Interplay between disorder driven Non-Fermi-liquid behavior and magnetism in Ce0.24La0.76Ge compound. In this work, we investigate the magnetic, heat capacity and electrical
transport properties of Ce0.6La0.4Ge and Ce0.24La0.76Ge compounds. Our results
show that two antiferromagnetic transitions (~ at 4.7 and 2.7 K) exhibited by
Ce0.6La0.4Ge are suppressed below 1.8 K for Ce0.24La0.76Ge. Interestingly, for
Ce0.24La0.76Ge, susceptibility, heat capacity and electrical resistivity vary
with temperature as: T0.75, T0.5 and T1.6 respectively. The observation of such
anomalous temperature variation suggests to the Non-Fermi-liquid (NFL) behavior
due to the presence of disordered 4f spins due to Ce-site dilution. Under the
application of magnetic field, it is noted that a crossover from the NFL to a
magnetic state occurs around 2 Tesla, where, short-range correlations among the
spins is prevalent due to the dominance of coupling between the magnetic
moments via conduction electrons. Magnetoresistance scaling indicates that
behavior of disorder driven NFL state is described by the dynamical mean field
theory of the spin glass quantum critical point.

###Large Spin Anomalous Hall Effect in L1$\rm_{0}$-FePt: Symmetry and Magnetization Switching|Takeshi Seki,Satoshi Iihama,Tomohiro Taniguchi,Koki Takanashi###

Large Spin Anomalous Hall Effect in L1$\rm_{0}$-FePt: Symmetry and Magnetization Switching. We quantitatively evaluate a spin anomalous Hall effect (SAHE), generating
spin angular momentum flow (spin current, $J_{\rm s}$), in an L1$\rm_{0}$-FePt
ferromagnet by exploiting giant magnetoresistance devices with L1$\rm_{0}$-FePt
/ Cu / Ni$\rm_{81}$Fe$\rm_{19}$ . From the ferromagnetic resonance linewidth
modulated by the charge current ($J_{\rm c}$) injection, the spin anomalous
Hall angle ($ \alpha_{\rm SAH} $) is obtained to be 0.25 $ \pm $ 0.03. The
evaluation of $ \alpha_{\rm SAH} $ at different configurations between $J_{\rm
c}$ and magnetization enables us to discuss the symmetry of SAHE and gives the
unambiguous evidence that SAHE is the source of $J_{\rm s}$. Thanks to the
large $ \alpha_{\rm SAH} $, we demonstrate the SAHE-induced magnetization
switching.

###Combination of informational storage and logical processing based on an all-oxide asymmetric multiferroic tunnel junction|Q. Liu,J. Miao,Z. D. Xu,P. F. Liu,Q. H. Zhang,L. Gu,K. K. Meng,X. G. Xu,J. K. Chen,Y. Wu,Y. Jiang###

Combination of informational storage and logical processing based on an all-oxide asymmetric multiferroic tunnel junction. Multiferroic tunnel junctions (MFTJs) have already been proved to be
promising candidates for application in spintronics devices. The coupling
between tunnel magnetoresistance (TMR) and tunnel electroresistance (TER) in
MFTJs can provide four distinct resistive states in a single memory cell. Here
we show that in an all-oxide asymmetric MFTJ of La0.7Sr0.3MnO3 /PbZr0.2Ti0.8O3
/La0.7Te0.3MnO3 (LSMO/PZT/LTMO) with p-type and n-type electrodes, the
intrinsic rectification is observed and can be modified by the ferroelectric
polarization of PZT. Owing to the combined TMR, TER and diode effects, two
different groups of four resistive states under opposite reading biases are
performed. With two parallel asymmetric junctions and the appropriate series
resistance, the coexistence of logic units and quaternary memory cells can be
realized in the same array devices. The asymmetric MFTJ structure enables more
possibilities for designing next generation of multi-states memory and logical
devices with higher storage density, lower energy consumption and significantly
increased integration level.

###Low offset frequency $1/f$ flicker noise in spin torque vortex oscillators|Steffen Wittrock,Sumito Tsunegi,Kay Yakushiji,Akio Fukushima,Hitoshi Kubota,Paolo Bortolotti,Ursula Ebels,Shinji Yuasa,Gilles Cibiel,Serge Galliou,Enrico Rubiola,Vincent Cros###

Low offset frequency $1/f$ flicker noise in spin torque vortex oscillators. Low frequency noise close to the carrier remains little explored in spin
torque nano oscillators. However, it is crucial to investigate as it limits the
oscillator's frequency stability. This work addresses the low offset frequency
flicker noise of a TMR-based spin-torque vortex oscillator in the regime of
large amplitude steady oscillations. We first phenomenologically expand the
nonlinear auto-oscillator theory aiming to reveal the properties of this noise.
We then present a thorough experimental study of the oscillator's $1/f$ flicker
noise and discuss the results based on the theoretical predictions. Hereby, we
connect the oscillator's nonlinear dynamics with the concept of flicker noise
and furthermore refer to the influence of a standard $1/f$ noise description
based on the Hooge formula, taking into account the non-constant magnetic
oscillation volume, which contributes to the magnetoresistance.

###Electrical and magnetic properties of thin films of the spin-filter material CrVTiAl|Gregory M. Stephen,Christopher Lane,Gianina Buda,David Graf,Stanislaw Kaprzyk,Bernardo Barbiellini,Arun Bansil,Don Heiman###

Electrical and magnetic properties of thin films of the spin-filter material CrVTiAl. The spin-filter material CrVTiAl is a promising candidate for producing
highly spin-polarized currents at room temperature in a nonmagnetic
architecture. Thin films of compensated-ferrimagnetic CrVTiAl have been grown
and their electrical and magnetic properties have been studied. The resistivity
shows two-channel semiconducting behavior with one disordered gapless channel
and a gapped channel with activation energy $\Delta E$=~0.1~-~0.2~eV.
Magnetoresistance measurements to B~=~35~T provide values for the mobilities of
the gapless channel, leading to an order of magnitude difference in the carrier
effective masses, which are in reasonable accord with our
density-functional-theory based results. The density of states and electronic
band structure is computed for permutations of the four sublattices arranged
differently along the (111) body diagonal, yielding metallic (Cr-V-Al-Ti),
spin-gapless (Cr-V-Ti-Al) and spin-filtering (Cr-Ti-V-Al) phases. Robustness of
the spin-gapless phase to substitutional disorder is also considered.

###Planar Hall Effect and Anisotropic Magnetoresistance in a polar-polar interface of LaVO$_3$-KTaO$_3$ with strong spin-orbit coupling|Neha Wadehra,Ruchi Tomar,R. K Gopal,Yogesh Singh,Sushanta Dattagupta,S. Chakraverty###

Planar Hall Effect and Anisotropic Magnetoresistance in a polar-polar interface of LaVO$_3$-KTaO$_3$ with strong spin-orbit coupling. Among the perovskite oxide family, KTaO$_3$ (KTO) has recently attracted
considerable interest as a possible system for the realization of the Rashba
effect. In this work, we improvise a novel conducting interface by juxtaposing
KTO with another insulator, namely LaVO$_3$ (LVO) and report planar Hall effect
(PHE) and anisotropic magnetoresistance (AMR) measurements. This interface
exhibits a signature of strong spin-orbit coupling. Our experimental
observation of two fold AMR at low magnetic fields can be intuitively
understood using a phenomenological theory for a Rashba spin-split system. At
high fields ($\sim$8 T), we see a two fold to four fold transition in the AMR
that could not be explained using only Rashba spin-split energy spectra. We
speculate that it might be generated through an intricate process arising from
the interplay between strong spin-orbit coupling, broken inversion symmetery,
relativistic conduction electron and possible uncompensated localized vanadium
spins.

###Theory of bi-linear magnetoresistance within the minimal model for surface states in topological insulators|A. Dyrdał,J. Barnaś,A. Fert###

Theory of bi-linear magnetoresistance within the minimal model for surface states in topological insulators. A new mechanism of bi-linear magnetoresistance (BMR) is studied theoretically
within the minimal model describing surface electronic states in topological
insulators (TIs). The BMR appears as a consequence of the second-order response
to electric field, and depends linearly on both electric field (current) and
magnetic field. The mechanism is based on the interplay of current-induced spin
polarization and scattering processes due to peculiar spin-orbit defects. The
proposed mechanism is compared to that based on a Fermi surface warping, and is
shown to be dominant at lower Fermi energies. We provide a consistent
theoretical approach based on the Green function formalism and show that the
magnetic field dependent relaxation processes in the presence of
non-equilibrium current-induced spin polarization give rise to the BMR.

###Nonvolatile Multilevel States in Multiferroic Tunnel Junctions|Mei Fang,Sangjian Zhang,Wenchao Zhang,Lu Jiang,Eric Vetter,Ho Nyung Lee,Xiaoshan Xu,Dali Sun,Jian Shen###

Nonvolatile Multilevel States in Multiferroic Tunnel Junctions. Manipulation of tunneling spin-polarized electrons via a ferroelectric
interlayer sandwiched between two ferromagnetic electrodes, dubbed Multiferroic
Tunnel Junctions (MFTJs), can be achieved not only by the magnetic alignments
of two ferromagnets but also by the electric polarization of the ferroelectric
interlayer, providing great opportunities for next-generation multi-state
memory devices. Here we show that a La0.67Sr0.33MnO3
(LSMO)/PbZr0.2Ti0.8O3(PZT)/Co structured MFTJ device can exhibit multilevel
resistance states in the presence of gradually reversed ferroelectric domains
via tunneling electro-resistance and tunneling magnetoresistance, respectively.
The nonvolatile ferroelectric control in the MFTJ can be attributed to separate
contributions arising from two independent ferroelectric channels in the PZT
interlayer with opposite polarization. Our study shows the dominant role of
"mixed" ferroelectric states on achieving accumulative electrical modulation of
multilevel resistance states in MFTJs, paving the way for multifunctional
device applications.

###Longitudinal and transverse magnetoresistance of SrTiO$_3$ with a single closed Fermi surface|Yudai Awashima,Yuki Fuseya###

Longitudinal and transverse magnetoresistance of SrTiO$_3$ with a single closed Fermi surface. The magnetoresistance (MR) of SrTiO$_3$ is theoretically investigated based
on the Boltzmann equation by considering its detailed band structure. The
formula for MR proposed by Mackey and Sybert is extended to be applicable to a
system with an arbitrarily shaped Fermi surface. It is shown that the angular
dependence of the diagonal component of the mass tensor causes transverse MR,
whereas that of the off-diagonal component causes longitudinal MR with only a
single closed Fermi surface, which overturns the textbook understanding of MR.
The calculated MR (300% at 10 T) quantitatively agrees with the experimental
results for SrTiO$_3$ including the behavior of the linear MR. The negative
Gaussian curvature of the Fermi surface of SrTiO$_3$ and its resulting negative
longitudinal and transverse MR are also discussed.

###Magnetic field driven quantum criticality in antiferromagnetic CePtIn4|Debarchan Das,Daniel Gnida,Piotr Wiśniewski,Dariusz Kaczorowski###

Magnetic field driven quantum criticality in antiferromagnetic CePtIn4. Physics of quantum critical point is one of the most perplexing topics in
current condensed-matter physics. Its conclusive understanding is forestalled
by the scarcity of experimental systems displaying novel aspects of quantum
criticality. We present a comprehensive experimental evidence of a magnetic
field tuned tricritical point separating paramagnetic, antiferromagnetic and
metamagnetic phases in novel compound CePtIn$_4$. Analyzing field variations of
its magnetic susceptibility, magnetoresistance and specific heat at very low
temperatures, we trace modifications of antiferromagnetic structure of the
compound. Upon applying magnetic field of increasing strength, the system
undergoes metamagnetic transitions which persist down to the lowest temperature
investigated, exhibiting first-order-like boundaries separating magnetic
phases. This yields a unique phase diagram where the second-order phase
transition line terminates at a tricritical point followed by two first-order
lines reaching quantum critical end points as $T\to$~0. Our findings
demonstrate that CePtIn$_4$ provides innovative perspective for studies of
quantum criticality.

###Pulsed laser deposition of highly c-axis oriented thin films of BSTS topological insulator|Atul Pandey,Sourabh Singh,Bishnupada Ghosh,Subhadip Manna,Rk Gopal,Chiranjib Mitra###

Pulsed laser deposition of highly c-axis oriented thin films of BSTS topological insulator. We report the growth of highly c-axis oriented topological insulator (TI)
BiSbTe1.5Se1.5 (BSTS) thin films by pulsed laser deposition (PLD) technique.
The various growth parameters such as substrate temperature, Argon pressure in
the deposition chamber and target to substrate distance are tuned to obtain the
optimized conditions essential for stoichiometric and bulk insulating TI thin
films. These films are highly c-axis oriented and exhibit all the four Raman
modes characteristic to the R-3m space group. The quality of the deposited thin
films is investigated using X-ray diffraction for crystallinity, Raman
spectroscopy for lattice dynamics, morphological studies using scanning
electron microscope and compositional analysis using Energy dispersive X-ray
spectroscopy. Resistance vs temperature measurements confirm bulk insulating
nature of the prepared thin films and magnetoresistance data exhibits the
phenomena of weak antilocalization with a large phase coherence length.

###Spin Hall magnetoresistance sensor using Au$_x$Pt$_{1-x}$ as the spin-orbit torque biasing layer|Yanjun Xu,Yumeng Yang,Hang Xie,Yihong Wu###

Spin Hall magnetoresistance sensor using Au$_x$Pt$_{1-x}$ as the spin-orbit torque biasing layer. We report on investigation of spin Hall magnetoresistance sensor based on
NiFe/AuxPt1-x bilayers. Compared to NiFe/Pt, the NiFe/AuxPt1-x sensor exhibits
a much lower power consumption (reduced by about 57%), due to 80% enhancement
of spin-orbit torque efficiency of AuxPt1-x at an optimum composition of x =
0.19 as compared to pure Pt. The enhanced spin-orbit torque efficiency allows
to increase the thickness of NiFe from 1.8 nm to 2.5 nm without significantly
increasing the power consumption. We show that, by increasing the NiFe
thickness, we were able to improve the working field range (0.86 Oe), operation
temperature range (150 degree C) and detectivity (0.71 nT/sqrt(Hz) at 1 Hz) of
the sensor, which is important for practical applications.

###In-plane antiferromagnetic moments in axion topological insulator candidate EuIn$_2$As$_2$|Yang Zhang,Ke Deng,Xiao Zhang,Meng Wang,Yuan Wang,Cai Liu,Jia-Wei Mei,Shiv Kumar,Eike F. Schwier,Kenya Shimada,Chaoyu Chen,Bing Shen###

In-plane antiferromagnetic moments in axion topological insulator candidate EuIn$_2$As$_2$. Topological insulator with antiferromagnetic order can serve as an ideal
platform for the realization of axion electrodynamics. In this paper, we report
a systematic study of the axion topological insulator candidate EuIn$_2$As$_2$.
A linear energy dispersion across the Fermi level confirms the existence of the
proposed hole-type Fermi pocket. Spin-flop transitions occur with magnetic
fields applied within the $ab$-plane while are absent for fields parallel to
the $c$-axis. Anisotropic magnetic phase diagrams are observed and the
orientation of the ground magnetic moment is found to be within the $ab$-plane.
The magnetoresistivity for EuIn$_2$As$_2$ behaves non-monotonic as a function
of field strength. It exhibits angular dependent evolving due to field-driven
and temperature-driven magnetic states. These results indicate that the
magnetic states of EuIn$_2$As$_2$ strongly affect the transport properties as
well as the topological nature.

###Pressure-induced superconductivity in topological type II Dirac semimetal NiTe2|Tao Li,Ke Wang,Chunqiang Xu,Qiang Hou,Hao Wu,Jun-Yi Ge,Shixun Cao,Jincang Zhang,Wei Ren,Xiaofeng Xu,Nai-Chang Yeh,Bin Chen,Zhenjie Feng###

Pressure-induced superconductivity in topological type II Dirac semimetal NiTe2. Very recently, NiTe2 has been reported to be a type II Dirac semimetal with
Dirac nodes near the Fermi surface. Furthermore, it is unveiled that NiTe2
presents the Hall Effect, which is ascribed to orbital magnetoresistance. The
physical properties behavior of NiTe2 under high pressure attracts us. In this
paper, we investigate the electrical properties of polycrystalline NiTe2 by
application of pressure ranging from 3.4GPa to 54.45Gpa. Superconductivity
emerges at critical pressure 12GPa with a transition temperature of 3.7K, and
Tc reaches its maximum, 6.4 K, at the pressure of 52.8GPa. Comparing with the
superconductivity in MoP, we purposed the possibility of topological
superconductivity in NiTe2. Two superconductivity transitions are observed with
pressure increasing in single crystal.

###Observation of topological surface state in a superconducting material|Gyanendra Dhakal,M. Mofazzel Hosen,Ayana Ghosh,Christopher Lane,Karolina Gornicka,Michal J. Winiarski,Klauss Dimitri,Firoza Kabir,Christopher Sims,Sabin Regmi,William Neff,Luis Persaud,Yangyang Liu,Dariusz Kaczorowski,Jian-Xin Zhu,Tomasz Klimczuk,Madhab Neupane###

Observation of topological surface state in a superconducting material. The discovery of topological insulator phase has ignited massive research
interests in novel quantum materials. Topological insulators with
superconductivity further invigorate the importance of materials providing the
platform to study the interplay between these two unique states. However, the
candidates of such materials are rare. Here, we report a systematic
angle-resolved photoemission spectroscopy (ARPES) study of a superconducting
material CaBi2 [Tc = 2 K], corroborated by the first principles calculations.
Our study reveals the presence of Dirac cones with a topological protection in
this system. Systematic topological analysis based on symmetry indicator shows
the presence of weak topological indices in this material. Furthermore, our
transport measurements show the presence of large magnetoresistance in this
compound. Our results indicate that CaBi2 could potentially provide a material
platform to study the interplay between superconductivity and topology.

###Mechanism of Universal Conductance Fluctuations|V. V. Brazhkin,I. M. Suslov###

Mechanism of Universal Conductance Fluctuations. Universal conductance fluctuations are usually observed in the form of
aperiodic oscillations in the magnetoresistance of thin wires as a function of
the magnetic field B. If such oscillations are completely random at scales
exceeding \xi_B, their Fourier analysis should reveal a white noise spectrum at
frequencies below \xi_B^{-1}. Comparison with the results for 1D systems
suggests another scenario: according to it, such oscillations are due to the
superposition of incommensurate harmonics and their spectrum should contain
discrete frequencies. An accurate Fourier analysis of the classical experiment
by Washburn and Webb reveals a purely discrete spectrum in agreement with the
latter scenario. However, this spectrum is close in shape to the discrete white
noise spectrum whose properties are similar to a continuous one.

###Dirac Fermions and Possible Weak Antilocalization in LaCuSb$_{2}$|J. R. Chamorro,A. Topp,Y. Fang,M. J. Winiarski,C. R. Ast,M. Krivenkov,A. Varykhalov,B. J. Ramshaw,L. Schoop,T. M. McQueen###

Dirac Fermions and Possible Weak Antilocalization in LaCuSb$_{2}$. Layered heavy-metal square-lattice compounds have recently emerged as
potential Dirac fermion materials due to bonding within those sublattices. We
report quantum transport and spectroscopic data on the layered Sb
square-lattice material LaCuSb$_{2}$. Linearly dispersing band crossings,
necessary to generate Dirac fermions, are experimentally observed in the
electronic band structure observed using angle-resolved photoemission
spectroscopy (ARPES), along with a quasi-two-dimensional Fermi surface. Weak
antilocalization that arises from two-dimensional transport is observed in the
magnetoresistance, as well as regions of linear dependence, both of which are
indicative of topologically non-trivial effects. Measurements of the
Shubnikov-de Haas (SdH) quantum oscillations show low effective mass electrons
on the order of 0.065$m_{e}$, further confirming the presence of Dirac fermions
in this material.

###Phase sensitive detection of extent of corrosion in steel reinforcing bars using eddy currents|Indrani Mukherjee,Jinit Patil,Sauvik Banerjee,Siddharth Tallur###

Phase sensitive detection of extent of corrosion in steel reinforcing bars using eddy currents. Corrosion of steel bars in reinforced cement concrete (RCC) structures leads
to premature deterioration and increase in life cycle maintenance costs.
Non-destructive testing (NDT) of incipient corrosion has been an impending task
in this domain. We present a low cost sensing platform based on eddy current
detection using anisotropic magnetoresistive (AMR) sensor to measure the extent
of corrosion in steel reinforcing bars (rebars). The scheme employs
phase-sensitive detection, wherein the phase shift in the sensor output
(proportional to surface conductivity of the rebar) relative to the reference
stimulus is measured by a lock-in amplifier and used to distinguish corroded
and non-corroded rebars. The proof-of-concept sensor demonstration is able to
resolve varying extents of rebar corrosion and can find potential applications
as an NDT tool in a variety of industries.

###Large and Robust Charge-to-Spin Conversion in Sputtered Conductive WTex with Disorder|Xiang Li,Peng Li,Vincent D. -H. Hou,Mahendra DC,Chih-Hung Nien,Fen Xue,Di Yi,Chong Bi,Chien-Min Lee,Shy-Jay Lin,Wilman Tsai,Yuri Suzuki,Shan X. Wang###

Large and Robust Charge-to-Spin Conversion in Sputtered Conductive WTex with Disorder. Topological materials with large spin-orbit coupling and immunity to
disorder-induced symmetry breaking show great promise for efficiently
converting charge to spin. Here, we report that long-range disordered sputtered
WTex thin films exhibit local chemical and structural order as those of Weyl
semimetal WTe2 and conduction behavior that is consistent with semi-metallic
Weyl fermion. We find large charge-to-spin conversion properties and electrical
conductivity in thermally annealed sputtered WTex films that are comparable
with those in crystalline WTe2 flakes. Besides, the strength of unidirectional
spin Hall magnetoresistance in annealed WTex/Mo/CoFeB heterostructure is 5 to
20 times larger than typical SOT layer/ferromagnet heterostructures reported at
room temperature. We further demonstrate room temperature damping-like
SOT-driven magnetization switching of in-plane magnetized CoFeB. These large
charge-to-spin conversion properties that are robust in the presence of
long-range disorder and thermal annealing pave the way for industrial
application of a new class of sputtered semimetals.

###Creating and manipulating interfacial spin with giant magnetic response in 4$f$ antiferromagnets|Ruyi Zhang,Yujuan Pei,Yang Song,Jiachang Bi,Jingkai Yang,Junxi Duan,Yanwei Cao###

Creating and manipulating interfacial spin with giant magnetic response in 4$f$ antiferromagnets. Creating and manipulating spin polarization in low-dimensional electron
systems (such as two-dimensional electron gases) is fundamentally essential for
spintronic applications, which is yet a challenge to date. In this work, we
establish the metamagnetic phase diagram of 4$f$ antiferromagnetic TbScO$_3$
and reveal its giant magnetic response to sub-tesla magnetic field, which has
not been reported thus far. Utilizing this giant magnetic response, we
demonstrate that the spin polarization of two-dimensional electron gas in
SrTiO$_3$/LaTiO$_3$/TbScO$_3$ heterostructure can be manipulated successfully
in aid of interfacial 3\textit{d}-4\textit{f} exchange interaction. Remarkably,
the hysteretic magnetoresistances of two-dimensional electron gas at the
SrTiO$_3$/LaTiO$_3$ interface are entirely determined by the metamagnetic phase
transitions of the underlying TbScO$_3$ substrate. Our results pave a novel
route to engineer the spin polarization of low-dimensional electron systems in
4$f$ antiferromagnet-based heterostructures.

###Coexistence of the Kondo effect and spin glass physics in Fe-doped NbS$_2$|H. Nobukane,Y. Tabata,T. Kurosawa,D. Sakabe,S. Tanda###

Coexistence of the Kondo effect and spin glass physics in Fe-doped NbS$_2$. We report the coexistence of the Kondo effect and spin glass behavior in
Fe-doped NbS$_2$ single crystals. The Fe$_x$NbS$_2$ shows the resistance
minimum and negative magnetoresistance due to the Kondo effect, and exhibits no
superconducting behavior at low temperatures. The resistance curve follows a
numerical renormalization-group theory using the Kondo temperature $T_K
=12.3$~K for $x=0.01$ as evidence of Kondo effect. Scanning tunneling
microscope/spectroscopy (STM/STS) revealed the presence of Fe atoms near sulfur
atoms and asymmetric spectra. The magnetic susceptibility exhibits a feature of
spin glass. The static critical exponents determined by the universal scaling
of the nonlinear part of the susceptibility suggest a three-dimensional
Heisenberg spin glass. The doped-Fe atoms in the intra- and inter-layers
revealed by the X-ray result can realize the coexistence of the Kondo effect
and spin glass.

###Giant magnetoresistance in antiferromagnetic Mn$_2$Au-based tunnel junction|Xing-Tao Jia,Xiao-Lin Cai,Yu Jia###

Giant magnetoresistance in antiferromagnetic Mn$_2$Au-based tunnel junction. Recent studies on the electrical switching of tetragonal antiferromagnet
(AFM) via N{\'e}el spin-orbit torque have paved the way for the economic use of
antiferromagnetic materials. The most difficult obstacle that presently limits
the application of antiferromagnetic materials in spintronics, especially in
memory storage applications, could be the small and fragile magnetoresistance
(MR) in the AFM-based nanostructure. In this study, we investigated the spin
transports in Mn$_2$Au-based tunnel junctions based onthe first-principle
scattering theory. Giant MRs more than $1000\%$ are predicted in some
Fe/MgO/Ag/Mn$_2$Au/Ta junctions that are about the same order as that in an
MgO-based ferromagnetic tunnel junction with same barrier thickness. The
interplay of the spin filtering effect, the quantum well resonant states, and
the interfacial resonant states could be responsible for the unusual giant and
robust MRs observed in these Mn$_2$Au-based junctions.

###Extraordinary magnetoresistance in encapsulated monolayer graphene devices|Bowen Zhou,Kenji Watanabe,Takashi Taniguchi,Erik A. Henriksen###

Extraordinary magnetoresistance in encapsulated monolayer graphene devices. We report a proof-of-concept study of extraordinary magnetoresistance (EMR)
in devices of monolayer graphene encapsulated in hexagonal boron nitride,
having metallic edge contacts and a central metal shunt. Extremely large EMR
values, $MR=(R(B) - R_0) / R_0\sim 10^5$, are achieved in part because $R_0$
approaches or crosses zero as a function of the gate voltage, exceeding that
achieved in high mobility bulk semiconductor devices. We highlight the
sensitivity, $dR/dB$, which in two-terminal measurements is the highest yet
reported for EMR devices, and in particular exceeds prior results in
graphene-based devices by a factor of 20. An asymmetry in the zero-field
transport is traced to the presence of $pn$-junctions at the graphene-metal
shunt interface.

###Anomalous phase shift of Shubnikov - de Haas oscillations in HgTe quantum well with inverted energy spectrum|Neverov V. N.,Klepikova A. S.,Bogolubskii A. S.,Gudina S. V.,Turutkin K. V.,Shelushinina N. G. 1,Yakunin M. V.,N. N. Mikhailov,S. A. Dvoretsky###

Anomalous phase shift of Shubnikov - de Haas oscillations in HgTe quantum well with inverted energy spectrum. The results of the longitudinal and Hall magnetoresistivity measurements in
the Shubnikov - de Haas oscillation regime for the HgCdTe/HgTe/HgCdTe
heterostructures with a wide (20.3 nm) HgTe quantum well are presented. An
anomalous phase shift of magneto-oscillations is detected: in the region of
spin-unsplit peaks the longitudinal resistivity maxima are located at even
filling factor numbers in contradiction with a conventional situation in 2D
systems. It is shown that the observed features are associated with the
inverted nature of the spectrum in the investigated quantum well with the
electron-type conduction along the size-quantized subband H1 of HgTe band
{\Gamma}8, for which the spin splitting is comparable to (and even greater
than) the orbital one. The results obtained are compared with the phase shift
effects of both magneto-oscillations and the plateau of the quantum Hall effect
in monolayer graphene.

###Signatures of dephasing by mirror-symmetry breaking in weak-antilocalization magnetoresistance across the topological transition in Pb$_{1-x}$Sn$_{x}$Se|Alexander Kazakov,Wojciech Brzezicki,Timo Hyart,Bartłomiej Turowski,Jakub Polaczyński,Zbigniew Adamus,Marta Aleszkiewicz,Tomasz Wojciechowski,Jaroslaw Z. Domagala,Ondrej Caha,Andrei Varykhalov,Gunther Springholz,Tomasz Wojtowicz,Valentine V. Volobuev,Tomasz Dietl###

Signatures of dephasing by mirror-symmetry breaking in weak-antilocalization magnetoresistance across the topological transition in Pb$_{1-x}$Sn$_{x}$Se. Many conductors, including recently studied Dirac materials, show saturation
of coherence length on decreasing temperature. This surprising phenomenon is
assigned to external noise, residual magnetic impurities or two-level systems
specific to non-crystalline solids. Here, by considering the SnTe-class of
compounds as an example, we show theoretically that breaking of mirror symmetry
deteriorates Berry's phase quantization, leading to additional dephasing in
weak-antilocalization magnetoresistance (WAL-MR). Our experimental studies of
WAL-MR corroborate these theoretical expectations in (111) Pb$_{1-x}$Sn$_x$Se
thin film with Sn contents $x$ corresponding to both topological crystalline
insulator and topologically trivial phases. In particular, we find the
shortening of the phase coherence length in samples with intentionally broken
mirror symmetry. Our results indicate that the classification of quantum
transport phenomena into universality classes should encompass, in addition to
time-reversal and spin-rotation invariances, spatial symmetries in specific
systems.

###Evidence for a magnetic-field induced ideal type-II Weyl state in antiferromagnetic topological insulator Mn(Bi1-xSbx)2Te4|Seng Huat Lee,David Graf,Yanglin Zhu,Hemian Yi,Samuel Ciocys,Eun Sang Choi,Rabindra Basnet,Arash Fereidouni,Aaron Wegner,Yi-Fan Zhao,Lujin Min,Katrina Verlinde,Jingyang He,Ronald Redwing,V. Gopalan,Hugh O. H. Churchill,Alessandra Lanzara,Nitin Samarth,Cui-Zu Chang,Jin Hu,Z. Q. Mao###

Evidence for a magnetic-field induced ideal type-II Weyl state in antiferromagnetic topological insulator Mn(Bi1-xSbx)2Te4. The discovery of Weyl semimetals (WSMs) has fueled tremendous interest in
condensed matter physics. WSMs require breaking of either inversion symmetry
(IS) or time-reversal symmetry (TRS); they can be categorized into type-I and
type-II WSMs, characterized by un-tilted and strongly tilted Weyl cones
respectively. Type-I WSMs with breaking of IS or TRS and type-II WSMs with IS
breaking have been realized experimentally, but TRS-breaking type-II WSM still
remains elusive. In this article, we report an ideal TRS-breaking type-II WSM
with only one pair of Weyl nodes observed in the antiferromagnetic topological
insulator Mn(Bi1-xSbx)2Te4 under magnetic fields. This state is manifested by a
large intrinsic anomalous Hall effect, a non-trivial $\mathrm{{\pi}}$ Berry
phase of the cyclotron orbit and a large positive magnetoresistance in the
ferromagnetic phase at an optimal sample composition. Our results establish a
promising platform for exploring the physics underlying the long-sought, ideal
TRS breaking type-II WSM.

###Tuning magnetic confinement of spin-triplet superconductivity|Wen-Chen Lin,Daniel J. Campbell,Sheng Ran,I-Lin Liu,Hyunsoo Kim,Andriy H. Nevidomskyy,David Graf,Nicholas P. Butch,Johnpierre Paglione###

Tuning magnetic confinement of spin-triplet superconductivity. Electrical magnetoresistance and tunnel diode oscillator measurements were
performed under external magnetic fields up to 41 T applied along the
crystallographic b-axis (hard axis) of UTe$_2$ as a function of temperature and
applied pressures up to 18.8 kbar. In this work, we track the field-induced
first-order transition between superconducting and magnetic field-polarized
phases as a function of applied pressure, showing a suppression of the
transition with increasing pressure until the demise of superconductivity near
16 kbar and the appearance of a pressure-induced ferromagnetic-like ground
state that is distinct from the field-polarized phase and stable at zero field.
Together with evidence for the evolution of a second superconducting phase and
its upper critical field with pressure, we examine the confinement of
superconductivity by two orthogonal magnetic phases and the implications for
understanding the boundaries of triplet superconductivity.

###Modulation of field-like spin orbit torque in heavy metal / ferromagnet heterostructure|Zilu Wang,Houyi Cheng,Kewen Shi,Yang Liu,Junfeng Qiao,Daoqian Zhu,Wenlong Cai,Xueying Zhang,Sylvain Eimer,Dapeng Zhu,Jie Zhang,Albert Fert,Weisheng Zhao###

Modulation of field-like spin orbit torque in heavy metal / ferromagnet heterostructure. Recent studies rediscovered the crucial role of field-like spin orbit torque
(SOT) in nanosecond-timescale SOT dynamics. However, there is not yet an
effective way to control its relative amplitude. Here, we experimentally
modulate the field-like SOT in W/CoFeB/MgO trilayers through tuning the
interfacial spin accumulation. By performing spin Hall magnetoresistance
measurement, we find that the CoFeB with enhanced spin dephasing, either
generated from larger layer thickness or from proper annealing, can distinctly
boost the spin absorption and enhance the interfacial spin mixing conductance
G_r. While the damping-like torque efficiency increases with G_r, the
field-like torque efficiency turns out to decrease with it. The results suggest
that the interfacial spin accumulation, which largely contributes to a
field-like torque, is reduced by higher interfacial spin transparency. Our work
shows a new path to further improve the performance of SOT-based magnetic
devices.

###Fermi surface transformation at the pseudogap critical point of a cuprate superconductor|Yawen Fang,Gael Grissonnanche,Anaelle Legros,Simon Verret,Francis Laliberte,Clement Collignon,Amirreza Ataei,Maxime Dion,Jianshi Zhou,David Graf,M. J. Lawler,Paul Goddard,Louis Taillefer,B. J. Ramshaw###

Fermi surface transformation at the pseudogap critical point of a cuprate superconductor. The nature of the pseudogap phase remains a major barrier to our
understanding of cuprate high-temperature superconductivity. Whether or not
this metallic phase is defined by any of the reported broken symmetries, the
topology of its Fermi surface remains a fundamental open question. Here we use
angle-dependent magnetoresistance (ADMR) to measure the Fermi surface of the
cuprate Nd-LSCO. Above the critical doping $p^*$ -- outside of the pseudogap
phase -- we fit the ADMR data and extract a Fermi surface geometry that is in
quantitative agreement with angle-resolved photoemission. Below $p^*$ -- within
the pseudogap phase -- the ADMR is qualitatively different, revealing a clear
transformation of the Fermi surface. Changes in the quasiparticle lifetime
across $p^*$ are ruled out as the cause of this transformation. Instead we find
that our data are most consistent with a reconstruction of the Fermi surface by
a $Q=(\pi, \pi)$ wavevector.

###Low frequency non-resonant rectification in spin-diodes|R. Tomasello,B. Fang,P. Artemchuk,M. Carpentieri,L. Fasano,A. Giordano,O. V. Prokopenko,Z. M. Zeng,G. Finocchio7###

Low frequency non-resonant rectification in spin-diodes. Spin-diodes are usually resonant in nature (GHz frequency) and tuneable by
magnetic field and bias current with performances, in terms of sensitivity and
minimum detectable power, overcoming the semiconductor counterpart, i.e.
Schottky diodes. Recently, spin diodes characterized by a low frequency
detection (MHz frequency) have been proposed. Here, we show a strategy to
design low frequency detectors based on magnetic tunnel junctions having the
interfacial perpendicular anisotropy of the same order of the demagnetizing
field out-of-plane component. Micromagnetic calculations show that to reach
this detection regime a threshold input power has to be overcome and the phase
shift between the oscillation magnetoresistive signal and the input
radiofrequency current plays the key role in determining the value of the
rectification voltage.

###Dynamical time-reversal and inversion symmetry breaking, dimensional crossover, and chiral anomaly in $α$-(BEDT-TTF)$_2$I$_3$|Takao Morinari###

Dynamical time-reversal and inversion symmetry breaking, dimensional crossover, and chiral anomaly in $α$-(BEDT-TTF)$_2$I$_3$. In most Dirac semimetals, time-reversal and inversion symmetries are believed
to play a crucial role in their stability. We demonstrate that these symmetries
are broken in Dirac fermions in the organic conductor
$\alpha$-(BEDT-TTF)$_2$I$_3$ due to the strong electronic correlation. The
system is a three-dimensional type-II Dirac semimetal in the coherent
inter-layer tunneling regime. A chiral anomaly is predicted to be observed in
the magnetoresistance when the magnetic field is tuned to the inter-layer
tunneling direction. Our result suggests that $\alpha$-(BEDT-TTF)$_2$I$_3$ is a
useful platform to explore the interplay between the chiral anomaly and the
strong correlation and/or dimensionality.

###Anomalous Magnetoresistance in Centrosymmetric Skyrmion-Lattice Magnet Gd2PdSi3|Han Zhang,Qing Huang,Lin Hao,Junyi Yang,Kyle Noordhoek,Shashi Pandey,Haidong Zhou,Jian Liu###

Anomalous Magnetoresistance in Centrosymmetric Skyrmion-Lattice Magnet Gd2PdSi3. We performed a systematic study of the temperature- and field-dependence of
magnetization and resistivity of Gd2PdSi3, which is a centrosymmetric skyrmion
crystal. While the magnetization behavior is consistent with the reported phase
diagram based on susceptibility, we show that a phase diagram can also be
constructed based on the anomalous magnetoresistance with one-to-one
correspondence among all the features. In addition, the crossover boundary into
the field-induced ferromagnetic state is also identified. Our results suggest
that the ferromagnetic spin fluctuations above the N\'eel temperature play a
key role in the high sensitivity of the resistivity anomalies to magnetic
field, pointing to the rich interplay of different magnetic correlations at
zero and finite wave vectors underlying the skyrmion lattice in this frustrated
itinerant magnet.

###All-electrical detection of skyrmion lattice state and chiral surface twists|A. Aqeel,M. Azhar,N. Vlietstra,A. Pozzi,J. Sahliger,H. Huebl,T. T. M. Palstra,C. H. Back,M. Mostovoy###

All-electrical detection of skyrmion lattice state and chiral surface twists. We study the high-temperature phase diagram of the chiral magnetic insulator
Cu$_2$OSeO$_3$ by measuring the spin-Hall magnetoresistance (SMR) in a thin Pt
electrode. We find distinct changes in the phase and amplitude of the SMR
signal at critical lines separating different magnetic phases of bulk
Cu$_2$OSeO$_3$. The skyrmion lattice state appears as a strong dip in the SMR
phase. A strong enhancement of the SMR amplitude is observed in the conical
spiral state, which we explain by an additional symmetry-allowed contribution
to the SMR present in non-collinear magnets. We demonstrate that the SMR can be
used as an all-electrical probe of chiral surface twists and skyrmions in
magnetic insulators.

###Spin-Lasers: Spintronics Beyond Magnetoresistance|Igor Žutić,Gaofeng Xu,Markus Lindemann,Paulo E. Faria Junior,Jeongsu Lee,Velimir Labinac,Kristian Stojšić,Guilherme M. Sipahi,Martin R. Hofmann,Nils C. Gerhardt###

Spin-Lasers: Spintronics Beyond Magnetoresistance. Introducing spin-polarized carriers in semiconductor lasers reveals an
alternative path to realize room-temperature spintronic applications, beyond
the usual magnetoresistive effects. Through carrier recombination, the angular
momentum of the spin-polarized carriers is transferred to photons, thus leading
to the circularly polarized emitted light. The intuition for the operation of
such spin-lasers can be obtained from simple bucket and harmonic oscillator
models, elucidating their steady-state and dynamic response, respectively.
These lasers extend the functionalities of spintronic devices and exceed the
performance of conventional (spin-unpolarized) lasers, including an order of
magnitude faster modulation frequency. Surprisingly, this ultrafast operation
relies on a short carrier spin relaxation time and a large anisotropy of the
refractive index, both viewed as detrimental in spintronics and conventional
lasers. Spin-lasers provide a platform to test novel concepts in spin devices
and offer progress connected to the advances in more traditional areas of
spintronics.

###Electrically-Tunable Stochasticity for Spin-based Neuromorphic Circuits: Self-Adjusting to Variation|Hossein Pourmeidani,Punyashloka Debashis,Zhihong Chen,Ronald F. DeMara,Ramtin Zand###

Electrically-Tunable Stochasticity for Spin-based Neuromorphic Circuits: Self-Adjusting to Variation. Energy-efficient methods are addressed for leveraging low energy barrier
nanomagnetic devices within neuromorphic architectures. Using a
Magnetoresistive Random Access Memory (MRAM) probabilistic device (p-bit) as
the basis of neuronal structures in Deep Belief Networks (DBNs), the impact of
reducing the Magnetic Tunnel Junction's (MTJ's) energy barrier is assessed and
optimized for the resulting stochasticity present in the learning system. This
can mitigate the process variation sensitivity of stochastic DBNs which
encounter a sharp drop-off when energy barriers exceed near-zero kT. As
evaluated for the MNIST dataset for energy barriers at near-zero kT to 2.0 kT
in increments of 0.5 kT, it is shown that the stability factor changes by 5
orders of magnitude. The self-compensating circuit developed herein provides a
compact, and low complexity approach to mitigating process variation impacts
towards practical implementation and fabrication.

###Study of single crystalline SrAgSb and SrAuSb semimetals|P. Devi,Lin-Lin Wang,Caiden Abel,Sergey L. Bud'ko,Paul C. Canfield###

Study of single crystalline SrAgSb and SrAuSb semimetals. Given renewed interest in the electronic properties of semimetallic compounds
with varying degrees of spin orbit coupling we have grown single crystals of
SrAgSb and SrAuSb, measured their temperature and field dependent electrical
resistivity and magnetization and performed density functional theory (DFT)
band structure calculations. Magnetization measurements are consistent with a
diamagnetic host with a small amount of local moment bearing impurities.
Although the residual resistivity ratio (RRR) for all samples studied was
relatively low, ranging between 2.4 and 3.4, the compounds had non-saturating
magnetoresistance (MR), reaching values of $\sim$ 17% and $\sim$ 70% at 4 K and
9 T for SrAgSb and SrAuSb respectively. Band structure calculations, using the
experimentally determined Wyckoff positions for the Sr, Ag/Au, and Sb atoms,
show that whereas SrAgSb is a topologically trivial, but compensated,
semimetal; SrAuSb is a topologically non-trivial, Dirac semimetal.

###Eddy Current Testing of Metal Cracks Using Spin Hall Magnetoresistance Sensor and Machine Learning|Yanjun Xu,Yumeng Yang,Yihong Wu###

Eddy Current Testing of Metal Cracks Using Spin Hall Magnetoresistance Sensor and Machine Learning. Recently we have developed a spin Hall magnetoresistance (SMR) sensor which
operates under AC bias and sense currents. Here we demonstrate both
theoretically and experimentally that the SMR sensor is uniquely suited for
eddy current testing applications because both the coil and sensor utilize AC
current as the excitation source. The use of SMR sensor effectively eliminates
the necessity of any demodulation or lock-in technique for detecting the eddy
current, which greatly simplifies the detection system. Furthermore, we show
that the combination of principal component analysis and decision tree model is
effective in classifying the metal cracks. The relatively clean signals
obtained by the SMR sensor greatly facilitates the subsequent signal analysis
and ensures high accuracy in the classification of different types of crack
features.

###Simultaneous observation of anti-damping and inverse spin Hall effect in La$_{0.67}$Sr$_{0.33}$MnO$_{3}$/Pt bilayer system|Pushpendra Gupta,Braj Bhusan Singh,Koustuv Roy,Anirban Sarkar,Markus Waschk,Thomas Brueckel,Subhankar Bedanta###

Simultaneous observation of anti-damping and inverse spin Hall effect in La$_{0.67}$Sr$_{0.33}$MnO$_{3}$/Pt bilayer system. Manganites have shown potential in spintronics because they exhibit high spin
polarization. Here, by ferromagnetic resonance we have studied the damping
properties of La$_{0.67}$Sr$_{0.33}$MnO$_{3}$/Pt bilayers which are prepared by
oxide molecular beam epitaxy. The damping coefficient ($\alpha$) of
La$_{0.67}$Sr$_{0.33}$MnO$_{3}$ (LSMO) single layer is found to be 0.0104.
However the LSMO/Pt bilayers exhibit decrease in $\alpha$ with increase in Pt
thickness. This decrease in the value of $\alpha$ is probably due to high
anti-damping like torque. Further, we have investigated the angle dependent
inverse spin Hall effect (ISHE) to quantify the spin pumping voltage from other
spin rectification effects such as anomalous Hall effect and anisotropic
magnetoresistance. We have observed high spin pumping voltage ($\sim$~20 $ \mu
V$). The results indicate that both anti-damping and spin pumping phenomena are
occuring simultaneously.

###Ferromagnetism and giant magnetoresistance in zinc-blende FeAs monolayers embedded in semiconductor structures|Le Duc Anh,Taiki Hayakawa,Yuji Nakagawa,Hikari Shinya,Tetsuya Fukushima,Masaki Kobayashi,Hiroshi Katayama-Yoshida,Yoshihiro Iwasa,Masaaki Tanaka###

Ferromagnetism and giant magnetoresistance in zinc-blende FeAs monolayers embedded in semiconductor structures. Material structures containing tetrahedral FeAs bonds, depending on their
density and geometrical distribution, can host several competing quantum ground
states ranging from superconductivity to ferromagnetism. Here we examine
structures of quasi two-dimensional (2D) layers of tetrahedral Fe-As bonds
embedded with a regular interval in a semiconductor InAs matrix, which
resembles the crystal structure of Fe-based superconductors. Contrary to the
case of Fe-based pnictides, these FeAs/InAs superlattices (SLs) exhibit
ferromagnetism, whose Curie temperature (Tc) increases rapidly with decreasing
the InAs interval thickness t_InAs (Tc ~ t_InAs^-3), and an extremely large
magnetoresistance up to 500% that is tunable by a gate voltage. Our first
principles calculations reveal the important role of disordered positions of Fe
atoms in the establishment of ferromagnetism in these quasi-2D FeAs-based SLs.
These unique features mark the FeAs/InAs SLs as promising structures for
spintronic applications.

###Current-in-plane spin-valve magnetoresistance in ferromagnetic semiconductor (Ga,Fe)Sb heterostructures with high Curie temperature|Kengo Takase,Le Duc Anh,Kosuke Takiguchi,Masaaki Tanaka###

Current-in-plane spin-valve magnetoresistance in ferromagnetic semiconductor (Ga,Fe)Sb heterostructures with high Curie temperature. We demonstrate spin-valve magnetoresistance with a current-in-plane (CIP)
configuration in (Ga,Fe)Sb / InAs (thickness $t_\mathrm{InAs}$ nm) / (Ga,Fe)Sb
trilayer heterostructures, where (Ga,Fe)Sb is a ferromagnetic semiconductor
(FMS) with high Curie temperature ($T_\mathrm{C}$). An MR curve with an open
minor loop is clearly observed at 3.7 K in a sample with $t_\mathrm{InAs}$ = 3
nm, which originates from the parallel - antiparallel magnetization switching
of the (Ga,Fe)Sb layers and spin-dependent scattering at the (Ga,Fe)Sb / InAs
interfaces. The MR ratio increases (from 0.03 to 1.6%) with decreasing
$t_\mathrm{InAs}$ (from 9 to 3 nm) due to the enhancement of the interface
scattering. This is the first demonstration of the spin-valve effect in
Fe-doped FMS heterostructures, paving the way for device applications of these
high- $T_\mathrm{C}$ FMSs.

###Microscopic Theory of the Spin Hall Magnetoresistance|Takeo Kato,Yuichi Ohnuma,Mamoru Matsuo###

Microscopic Theory of the Spin Hall Magnetoresistance. We consider a microscopic theory for the spin Hall magnetoresistance (SMR).
We generally formulate a spin conductance at an interface between a normal
metal and a magnetic insulator in terms of spin susceptibilities. We reveal
that SMR is composed of static and dynamic parts. The static part, which is
almost independent of the temperature, originates from spin flip caused by an
interfacial exchange coupling. However, the dynamic part, which is induced by
the creation or annihilation of magnons, has an opposite sign from the static
part. By the spin-wave approximation, we predict that the latter results in a
nontrivial sign change of the SMR signal at a finite temperature. In addition,
we derive the Onsager relation between spin conductance and thermal
spin-current noise.

###SOT-MRAM based Sigmoidal Neuron for Neuromorphic Architectures|Brendan Reidy,Ramtin Zand###

SOT-MRAM based Sigmoidal Neuron for Neuromorphic Architectures. In this paper, the intrinsic physical characteristics of spin-orbit torque
(SOT) magnetoresistive random-access memory (MRAM) devices are leveraged to
realize sigmoidal neurons in neuromorphic architectures. Performance
comparisons with the previous power- and area-efficient sigmoidal neuron
circuits exhibit 74x and 12x reduction in power-area-product values for the
proposed SOT-MRAM based neuron. To verify the functionally of the proposed
neuron within larger scale designs, we have implemented a circuit realization
of a 784x16x10 SOT-MRAM based multiplayer perceptron (MLP) for MNIST pattern
recognition application using SPICE circuit simulation tool. The results
obtained exhibit that the proposed SOT-MRAM based MLP can achieve accuracies
comparable to an ideal binarized MLP architecture implemented on GPU, while
realizing orders of magnitude increase in processing speed.

###Temperature evolution of magnetic phases near the thickness-dependent metal-insulator transition in La$_{1-x}$Sr$_x$MnO$_3$ thin films observed by XMCD|Goro Shibata,Kohei Yoshimatsu,Enju Sakai,Keisuke Ishigami,Shoya Sakamoto,Yosuke Nonaka,Fan-Hsiu Chang,Hong-Ji Lin,Di-Jing Huang,Chien-Te Chen,Hiroshi Kumigashira,Atsushi Fujimori###

Temperature evolution of magnetic phases near the thickness-dependent metal-insulator transition in La$_{1-x}$Sr$_x$MnO$_3$ thin films observed by XMCD. Perovskite-type manganites, which are well-known for their intriguing
physical properties such as colossal magnetoresistance (CMR) and half
metalicity, have been considered as candidate materials for spintronics.
However, their ferromagnetic (FM) properties are often suppressed in thin films
when the thickness is reduced down to several monolayers (MLs). In order to
investigate how the magnetic phases evolve near the paramagnetic (PM)-to-FM
phase transition boundary, we have performed temperature-dependent x-ray
magnetic circular dichroism (XMCD) experiments on a La$_{1-x}$Sr$_{x}$MnO$_3$
(LSMO, $x=0.4$) thin film, whose thickness (8 ML) is close to the boundary
between the FM-metallic and the PM-insulating phases. By utilizing the
element-selectiveness of XMCD, we have quantitatively estimated the fractions
of the PM and superparamagnetic (SPM) phases as well as the FM one as a
function of temperature. The results can be reasonably described based on a
microscopic phase-separation model.

###Machine learning dynamics of phase separation in correlated electron magnets|Puhan Zhang,Preetha Saha,Gia-Wei Chern###

Machine learning dynamics of phase separation in correlated electron magnets. We demonstrate machine-learning enabled large-scale dynamical simulations of
electronic phase separation in double-exchange system. This model, also known
as the ferromagnetic Kondo lattice model, is believed to be relevant for the
colossal magnetoresistance phenomenon. Real-space simulations of such
inhomogeneous states with exchange forces computed from the electron
Hamiltonian can be prohibitively expensive for large systems. Here we show that
linear-scaling exchange field computation can be achieved using neural networks
trained by datasets from exact calculation on small lattices. Our
Landau-Lifshitz dynamics simulations based on machine-learning potentials
nicely reproduce not only the nonequilibrium relaxation process, but also
correlation functions that agree quantitatively with exact simulations. Our
work paves the way for large-scale dynamical simulations of correlated electron
systems using machine-learning models.

###Spin transport in a lateral spin valve with a suspended Cu channel|Kenjiro Matsuki,Ryo Ohshima,Livio Leiva,Yuichiro Ando,Teruya Shinjo,Toshiyuki Tsuchiya,Masashi Shiraishi###

Spin transport in a lateral spin valve with a suspended Cu channel. We study spin transport through a suspended Cu channel by an electrical
non-local 4-terminal measurement for future spin mechanics applications. A
magnetoresistance due to spin transport through the suspended Cu channel is
observed, and its magnitude is comparable to that of a conventional fixed Cu
lateral spin valve. The spin diffusion length in the suspended Cu channel is
estimated to be 340 nm at room temperature from the spin signal dependence on
the distance between the ferromagnetic injector and detector electrodes. This
value is found to be slightly shorter than in a fixed Cu. The decrease in the
spin diffusion length in the suspended Cu channel is attributed to an increase
in spin scattering originating from naturally oxidized Cu at the bottom of the
Cu channel.

###Quantum oscillations with magnetic hysteresis observed in CeTe$_{3}$ thin films|Mori Watanabe,Sanghyun Lee,Takuya Asano,Takashi Ibe,Masashi Tokuda,Hiroki Taniguchi,Daichi Ueta,Yoshinori Okada,Kensuke Kobayashi,Yasuhiro Niimi###

Quantum oscillations with magnetic hysteresis observed in CeTe$_{3}$ thin films. We have performed magnetotransport measurements in CeTe$_{3}$ thin films down
to $0.2~{\rm K}$. It is known that CeTe$_{3}$ has two magnetic transitions at
$T_{\rm N1} \approx 3~{\rm K}$ and $T_{\rm N2} \approx 1~{\rm K}$. A clear
Shubnikov-de-Haas (SdH) oscillation was observed at $4~{\rm K}$, demonstrating
the strong two-dimensional nature in this material. Below $T_{\rm N2}$, the SdH
oscillation has two frequencies, indicating that the Fermi surface could be
slightly modulated due to the second magnetic transition. We also observed a
magnetic hysteresis in the SdH oscillation below $T_{\rm N1}$. Especially,
there is a unique spike in the magnetoresistance at $B \approx 0.6~{\rm T}$
only when the magnetic field is swept from a high enough field (more than
$2~{\rm T}$) to zero field.

###Extraction of Isotropic Electron-Nuclear Hyperfine Coupling Constants of Paramagnetic Point Defects from Near-Zero Field Magnetoresistance Spectra via Least Squares Fitting to Models Developed from the Stochastic Quantum Liouville Equation|Elias B. Frantz,Nicholas J. Harmon Stephen R. McMillan,Stephen J. Moxim,Michael E. Flatte,Patrick M. Lenahan###

Extraction of Isotropic Electron-Nuclear Hyperfine Coupling Constants of Paramagnetic Point Defects from Near-Zero Field Magnetoresistance Spectra via Least Squares Fitting to Models Developed from the Stochastic Quantum Liouville Equation. We report on a method by which we can systematically extract spectroscopic
information such as isotropic electron-nuclear hyperfine coupling constants
from near-zero field magnetoresistance spectra. The method utilizes a least
squares fitting of models developed from the stochastic quantum Liouville
equation. We applied our fitting algorithm to two distinct material systems:
Si/SiO2 MOSFETs, and a-Si:H MIS capacitors. Our fitted results and hyperfine
parameters are in reasonable agreement with existing knowledge of the defects
present in the systems. Our work indicates that the NZFMR response and fitting
of the NZFMR spectrum via models developed from the stochastic quantum
Liouville equation could be a relatively simple yet powerful addition to the
family of spin-based techniques used to explore the chemical and structural
nature of point defects in semiconductor devices and insulators.

###Quantification of interfacial spin-charge conversion in metal/insulator hybrid structures by generalized boundary conditions|Cristina Sanz-Fernández,Van Tuong Pham,Edurne Sagasta,Luis E. Hueso,Ilya V. Tokatly,Fèlix Casanova,F. Sebastián Bergeret###

Quantification of interfacial spin-charge conversion in metal/insulator hybrid structures by generalized boundary conditions. We present and verify experimentally a universal theoretical framework for
the description of spin-charge interconversion in non-magnetic metal/insulator
structures with interfacial spin-orbit coupling (ISOC). Our formulation is
based on drift-diffusion equations supplemented with generalized boundary
conditions. The latter encode the effects of ISOC and relate the electronic
transport in such systems to spin loss and spin-charge interconversion at the
interface, which are parameterized, respectively, by $G_{\parallel/\perp}$ and
$\sigma_{\rm{sc/cs}}$. We demonstrate that the conversion efficiency depends
solely on these interfacial parameters. We apply our formalism to two typical
spintronic devices that exploit ISOC: a lateral spin valve and a multilayer
Hall bar, for which we calculate the non-local resistance and the spin Hall
magnetoresistance, respectively. Finally, we perform measurements on these two
devices with a BiO$_x$/Cu interface and verify that transport properties
related to the ISOC are quantified by the same set of interfacial parameters.

###From Weak Antilocalization to Kondo Scattering in a Magnetic Complex Oxide Interface|Xinxin Cai,Jin Yue,Peng Xu,Bharat Jalan,Vlad S. Pribiag###

From Weak Antilocalization to Kondo Scattering in a Magnetic Complex Oxide Interface. Quantum corrections to electrical resistance can serve as sensitive probes of
the magnetic landscape of a material. For example, interference between
time-reversed electron paths gives rise to weak localization effects, which can
provide information about the coupling between spins and orbital motion, while
the Kondo effect is sensitive to the presence of spin impurities. Here we use
low-temperature magnetotransport measurements to reveal a transition from weak
antilocalization (WAL) to Kondo scattering in the quasi-two-dimensional
electron gas formed at the interface between SrTiO$_3$ and the Mott insulator
NdTiO$_3$. This transition occurs as the thickness of the NdTiO$_3$ layer is
increased. Analysis of the Kondo scattering and WAL points to the presence of
atomic-scale magnetic impurities coexisting with extended magnetic regions that
affect transport via a strong magnetic exchange interaction. This leads to
distinct magnetoresistance behaviors that can serve as a sensitive probe of
magnetic properties in two dimensions.

###Tensor monopoles and negative magnetoresistance effect in optical lattices|Hai-Tao Ding,Yan-Qing Zhu,Zhi Li,Lubing Shao###

Tensor monopoles and negative magnetoresistance effect in optical lattices. We propose that a kind of four-dimensional (4D) Hamiltonians, which host
tensor monopoles related to quantum metric tensor in even dimensions, can be
simulated by ultracold atoms in the optical lattices. The topological
properties and bulk-boundary correspondence of tensor monopoles are
investigated in detail. By fixing the momentum along one of the dimensions, it
can be reduced to an effective three-dimensional model manifesting with a
nontrivial chiral insulator phase. Using the semiclassical Boltzmann equation,
we calculate the longitudinal resistance against the magnetic field $B$ and
find the negative relative magnetoresistance effect of approximately $ -B^{2} $
dependence when a hyperplane cuts through the tensor monopoles in the parameter
space. We also propose an experimental scheme to realize this 4D Hamiltonian by
introducing an external cyclical parameter in a 3D optical lattice. Moreover,
we show that the quantum metric tensor and Berry curvature can be detected by
applying an external drive in the optical lattices.

###Ultrahigh efficient spin-orbit torque magnetization switching in all-sputtered topological insulator - ferromagnet multilayers|Tuo Fan,Nguyen Huynh Duy Khang,Soichiro Nakano,Pham Nam Hai###

Ultrahigh efficient spin-orbit torque magnetization switching in all-sputtered topological insulator - ferromagnet multilayers. Spin-orbit torque (SOT) magnetization switching of ferromagnets with large
perpendicular magnetic anisotropy has a great potential for the next-generation
non-volatile magnetoresistive random-access memory (MRAM). It requires a
high-performance pure spin current source with a large spin Hall angle and high
electrical conductivity, which can be fabricated by a mass production
technique. In this work, we demonstrate ultrahigh efficient and robust SOT
magnetization switching in all-sputtered BiSb topological insulator -
perpendicularly magnetized Co/Pt multilayers. Despite fabricated by the
industry-friendly magnetron sputtering instead of the laboratory molecular beam
epitaxy, the topological insulator layer, BiSb, shows a large spin Hall angle
of $\theta$$_{SH}$ = 12.3 and high electrical conductivity of $\sigma$ =
1.5x$10^5$ $\Omega^{-1}$m$^{-1}$. Our results demonstrate the mass production
capability of BiSb topological insulator for implementation of ultralow power
SOT-MRAM and other SOT-based spintronic devices.

###Viscosity of two-dimensional electrons|P. S. Alekseev,A. P. Dmitriev###

Viscosity of two-dimensional electrons. The hydrodynamic regime of electron transport has been recently realized in
conductors with ultra-low densities of defects. Although relaxation processes
in two-dimensional (2D) fluids have been studied in many theoretical works, the
viscosity of the realistic Fermi gas of 2D electrons having the quadratic
energy spectrum and interacting by Coulomb's law has not been reliably
determined either in theory or in experiment up to now. Here we construct a
theory of viscosity and thermal conductivity in such system. We compare the
calculated viscosity of the 2D electron Fermi gas and the previously known
viscosity of a 2D Fermi liquid with available experimental data extracted from
the hydrodynamic negative magnetoresistance of the best-quality GaAs quantum
wells. Based on this comparison, we argue that measurements of the temperature
dependence of the viscosity can allow to trace the transition between an
electron Fermi liquid and a Fermi gas.

###Investigation of in-plane anisotropy of c-axis magnetoresistance for BiCh2-based layered superconductor NdO0.7F0.3BiS2|Kazuhisa Hoshi,Kenta Sudo,Yosuke Goto,Motoi Kimata,Yoshikazu Mizuguchi###

Investigation of in-plane anisotropy of c-axis magnetoresistance for BiCh2-based layered superconductor NdO0.7F0.3BiS2. We have investigated the in-plane anisotropy of the c-axis magnetoresistance
(MR) in both superconducting and normal states of single crystals of
NdO0.7F0.3BiS2 under in-plane magnetic fields. In the superconducting states of
NdO0.7F0.3BiS2, four-fold-symmetric in-plane anisotropy of the c-axis MR was
observed below the superconducting transition temperature. Since the crystal
structure of NdO0.7F0.3BiS2 is tetragonal, the rotational symmetry in the
superconducting state is preserved in the present compound. This result is
clearly different from the previous report observed in LaO0.5F0.5BiSSe single
crystals, where the in-plane MR in the superconducting state shows two-fold
symmetry. On the other hand, in the normal states of NdO0.7F0.3BiS2, two-fold
symmetric MR with a small amplitude was observed. The possible origin of the
two-fold-symmetric behavior was discussed with the presence of local structural
disorder in the conducting plane of BiCh2-based compounds.

###Fe3Se4: A Possible Ferrimagnetic Half-Metal?|Girish C. Tewari,Divya Srivastava,Reijo Pohjonen,Otto Mustonen,Antti J. Karttunen,Johan Lindén,Maarit Karppinen###

Fe3Se4: A Possible Ferrimagnetic Half-Metal?. Half-metallic ferromagnets show 100% spin-polarization at the Fermi level and
are ideal candidates for spintronic applications. Despite the extensive
research in the field, very few materials have been discovered so far. Here we
present results of electronic band structure calculations based on density
functional theory and extensive physical-property measurements for Fe3Se4
revealing signatures of half-metallicity. The spin-polarized electronic band
structure calculations predict half-metallic ferrimagnetism for Fe3Se4. The
electrical resistivity follows exponentially suppressed electron-magnon
scattering mechanism in the low-temperature regime and show a magnetoresistance
effect that changes the sign from negative to positive with decreasing
temperature around 100 K. Other intriguing observations include the anomalous
behavior of Hall resistance below 100 K and an anomalous Hall coefficient that
roughly follows the \r{ho}2 behavior.

###Terahertz spectroscopy evidence of possible 40 K superconductivity in rhenium-doped strontium ruthenates|Yurii Aleshchenko,Boris Gorshunov,Elena Zhukova,Andrey Muratov,Alexander Dudka,Rajendra Dulal,Serafim Teknowijoyo,Sara Chahid,Vahan Nikoghosyan,Armen Gulian###

Terahertz spectroscopy evidence of possible 40 K superconductivity in rhenium-doped strontium ruthenates. Strontium ruthenates have many similarities with copper oxide superconductors
and are of particular interest for the investigation of the mechanisms and
conditions which lead to high-temperature superconductivity. We report here on
multiple experimental indications of superconductivity with onset at 40 K in
strontium ruthenate doped by rhenium and selenium with chlorine used as the
flux. The main experimental evidence arises from terahertz spectroscopy of this
material followed by AC and DC magnetization, as well as measurements of its
heat capacity and magnetoresistance. Structural and morphological studies
revealed the heterophase nature of this polycrystalline material as well as the
changes of lattice parameters relative to the original phases. Experimental
data show a higher critical temperature on the surface compared to that of the
bulk of the sample.

###Colossal magnetoresistance in a nonsymmorphic antiferromagnetic insulator|P. F. S. Rosa,Yuanfeng Xu,S. K. Kushwaha,J. C. Souza,M. C. Rahn,L. S. I. Veiga,A. Bombardi,S. M. Thomas,M. Janoschek,E. D. Bauer,M. K. Chan,Zhijun Wang,J. D. Thompson,P. G. Pagliuso,N. Harrison,B. A. Bernevig,F. Ronning###

Colossal magnetoresistance in a nonsymmorphic antiferromagnetic insulator. Here we investigate antiferromagnetic Eu$_{5}$In$_{2}$Sb$_{6}$, a
nonsymmorphic Zintl phase. Our electrical transport data show that
Eu$_{5}$In$_{2}$Sb$_{6}$ is remarkably insulating and exhibits an exceptionally
large negative magnetoresistance, which is consistent with the presence of
magnetic polarons. From {\it ab initio} calculations, the paramagnetic state of
Eu$_{5}$In$_{2}$Sb$_{6}$ is a topologically nontrivial semimetal within the
generalized gradient approximation (GGA), whereas an insulating state with
trivial topological indices is obtained using a modified Becke-Johnson
potential. Notably, GGA+U calculations suggest that the antiferromagnetic phase
of Eu$_{5}$In$_{2}$Sb$_{6}$ may host an axion insulating state. Our results
provide important feedback for theories of topological classification and
highlight the potential of realizing clean magnetic narrow-gap semiconductors
in Zintl materials.

###Field-induced Metal-Insulator Transition in $β$-EuP$_3$|Guangqiang Wang,Guoqing Chang,Huibin Zhou,Wenlong Ma,Hsin Lin,M. Zahid Hasan,Su-Yang Xu,Shuang Jia###

Field-induced Metal-Insulator Transition in $β$-EuP$_3$. Metal-insulator transition (MIT) is one of the most conspicuous phenomena in
correlated electron systems. However such transition has rarely been induced by
an external magnetic field as the field scale is normally too small compared
with the charge gap. In this paper we present the observation of a
magnetic-field-driven MIT in a magnetic semiconductor $\beta $-EuP$_3$.
Concomitantly, we found a colossal magnetoresistance (CMR) in an extreme way:
the resistance drops billionfold at 2 kelvins in a magnetic field less than 3
teslas. We ascribe this striking MIT as a field-driven transition from an
antiferromagnetic and paramagnetic insulator to a spin-polarized topological
semimetal, in which the spin configuration of $\mathrm{Eu^{2+}}$ cations and
spin-orbital coupling (SOC) play a crucial role. As a phosphorene-bearing
compound whose electrical properties can be controlled by the application of
field, $\beta $-EuP$_3$ may serve as a tantalizing material in the basic
research and even future electronics.

###Evidence for dominant phonon-electron scattering in Weyl semimetal WP$_{2}$|Gavin B. Osterhoudt,Vincent M. Plisson,Yaxian Wang,Christina A. C. Garcia,Johannes Gooth,Claudia Felser,Prineha Narang,Kenneth S. Burch###

Evidence for dominant phonon-electron scattering in Weyl semimetal WP$_{2}$. Topological semimetals have revealed a wide array of novel transport
phenomena, including electron hydrodynamics, quantum field theoretic anomalies,
and extreme magnetoresistances and mobilities. However, the scattering
mechanisms central to these behaviors remain largely unexplored. Here we reveal
signatures of significant phonon-electron scattering in the type-II Weyl
semimetal WP$_{2}$ via temperature-dependent Raman spectroscopy. Over a large
temperature range, we find that the decay rates of the lowest energy $A_{1}$
modes are dominated by phonon-electron rather than phonon-phonon scattering. In
conjunction with first-principles calculations, a combined analysis of the
momentum, energy, and symmetry-allowed decay paths indicates this results from
intraband scattering of the electrons. The excellent agreement with theory
further suggests that such results could be true for the acoustic modes. We
thus provide evidence for the importance of phonons in the transport properties
of topological semimetals and identify specific properties that may contribute
to such behavior in other materials.

###Strange Metallic Transport in the Antiferromagnetic Regime of Electron Doped Cuprates|Tarapada Sarkar,Nicholas R Poniatowski,Joshua S. Higgins,P. R. Mandal,Mun K Chan,Richard L Greene###

Strange Metallic Transport in the Antiferromagnetic Regime of Electron Doped Cuprates. We report magnetoresistance and Hall Effect results for electron-doped films
of the high-temperature superconductor La$_{2-x}$Ce$_x$CuO$_4$ (LCCO) for
temperatures from 0.7 to 45 K and magnetic fields up to 65 T. For x = 0.12 and
0.13, just below the Fermi surface reconstruction (FSR), the normal state
in-plane resistivity exhibits a well-known upturn at low temperature. Our new
results show that this resistivity upturn is eliminated at high magnetic field
and the resistivity becomes linear-in-temperature from $\sim$ 40 K down to 0.7
K. The magnitude of the linear coefficient scales with Tc and doping, as found
previously [1,2] for dopings above the FSR. In addition, the normal state Hall
coefficient has an unconventional field dependence for temperatures below 50K.
This anomalous transport data presents a new challenge to theory and suggests
that the strange metal normal state is also present in the antiferromagnetic
regime.

###Inhomogeneous superconductivity and quasilinear magnetoresistance at amorphous LaTiO3/SrTiO3 interfaces|N. Lebedev,M. Stehno,A. Rana,N. Gauquelin,J. Verbeeck,A. Brinkman,J. Aarts###

Inhomogeneous superconductivity and quasilinear magnetoresistance at amorphous LaTiO3/SrTiO3 interfaces. We have studied the transport properties of LaTiO3/SrTiO3 (LTO/STO)
heterostructures. In spite of 2D growth observed in reflection high energy
electron diffraction, Transmission Electron Microscopy images revealed that the
samples tend to amorphize. Still, we observe that the structures are
conducting, and some of them exhibit high conductance and/or superconductivity.
We established that conductivity arises mainly on the STO side of the
interface, and shows all the signs of the 2-dimensional electron gas usually
observed at interfaces between SrTiO3 and LaTiO3 or LaAlO3, including the
presence of two electron bands and tunability with a gate voltage. Analysis of
magnetoresistance (MR) and superconductivity indicates presence of a spatial
fluctuations of the electronic properties in our samples. That can explain the
observed quasilinear out-of-plane MR, as well as various features of the
in-plane MR and the observed superconductivity.

###Electronic and magnetic properties of stoichiometric CeAuBi$_{2}$|M. M. Piva,R. Tartaglia,G. S. Freitas,J. C. Souza,D. S. Christovam,S. M. Thomas,J. B. Leão,W. Ratcliff,J. W. Lynn,C. Lane,J. -X. Zhu,J. D. Thompson,P. F. S. Rosa,C. Adriano,E. Granado,P. G. Pagliuso###

Electronic and magnetic properties of stoichiometric CeAuBi$_{2}$. We report the electronic and magnetic properties of stoichiometric
CeAuBi$_{2}$ single crystals. At ambient pressure, CeAuBi$_{2}$ orders
antiferromagnetically below a N\'{e}el temperature ($T_{N}$) of 19 K. Neutron
diffraction experiments revealed an antiferromagnetic propagation vector
$\hat{\tau} = [0, 0, 1/2]$, which doubles the paramagnetic unit cell along the
$c$-axis. At low temperatures several metamagnetic transitions are induced by
the application of fields parallel to the $c$-axis, suggesting that the
magnetic structure of CeAuBi$_{2}$ changes as a function of field. At low
temperatures, a linear positive magnetoresistance may indicate the presence of
band crossings near the Fermi level. Finally, the application of external
pressure favors the antiferromagnetic state, indicating that the 4$f$ electrons
become more localized.

###Vortical Reflection and Spiraling Fermi Arcs with Weyl Metamaterials|Hua Cheng,Wenlong Gao,Yangang Bi,Wenwei Liu,Zhancheng Li,Qinghua Guo,Yang Yang,Oubo You,Jing Feng,Hongbo Sun,Jianguo Tian,Shuqi Chen,Shuang Zhang###

Vortical Reflection and Spiraling Fermi Arcs with Weyl Metamaterials. Scatterings and transport in Weyl semimetals have caught growing attention in
condensed matter physics, with observables including chiral zero modes and the
associated magnetoresistance and chiral magnetic effects. Measurement of
electrical conductance is usually performed in these studies, which, however,
cannot resolve the momentum of electrons, preventing direct observation of the
phase singularities in scattering matrix associated with Weyl point. Here we
experimentally demonstrate a helical phase distribution in the angle (momentum)
resolved scattering matrix of electromagnetic waves in a photonic Weyl
metamaterial. It further leads to spiraling Fermi arcs in an air gap sandwiched
between a Weyl metamaterial and a metal plate. Benefiting from the
alignment-free feature of angular vortical reflection, our findings establish a
new platform in manipulating optical angular momenta with photonic Weyl
systems.

###Non-Fermi liquid transport in the vicinity of nematic quantum critical point of FeSe$_{1-x}$S$_x$ superconductor|W. K. Huang,S. Hosoi,M. Čulo,S. Kasahara,Y. Sato,K. Matsuura,Y. Mizukami,M. Berben,N. E. Hussey,H. Kontani,T. Shibauchi,Y. Matsuda###

Non-Fermi liquid transport in the vicinity of nematic quantum critical point of FeSe$_{1-x}$S$_x$ superconductor. Non-Fermi liquids are strange metals whose physical properties deviate
qualitatively from those of conventional metals due to strong quantum
fluctuations. In this paper, we report transport measurements on the
FeSe$_{1-x}$S$_x$ superconductor, which has a quantum critical point of a
nematic order without accompanying antiferromagnetism. We find that in addition
to a linear-in-temperature resistivity $\rho_{xx}\propto T$, which is close to
the Planckian limit, the Hall angle varies as $\cot \theta_{\rm H} \propto T^2$
and the low-field magnetoresistance is well scaled as
$\Delta\rho_{xx}/\rho_{xx}\propto \tan^2 \theta_{\rm H}$ in the vicinity of the
nematic quantum critical point. This set of anomalous charge transport
properties shows striking resemblance with those reported in cuprate,
iron-pnictide and heavy fermion superconductors, demonstrating that the
critical fluctuations of a nematic order with ${\bf q} \approx 0$ can also lead
to a breakdown of the Fermi liquid description.

###Observation of gapped state in rare-earth monopnictide HoSb|M. Mofazzel Hosen,Gyanendra Dhakal,Baokai Wang,Narayan Poudel,Bahadur Singh,Klauss Dimitri,Firoza Kabir,Christopher Sims,Sabin Regmi,William Neff,Anan Bari Sarkar,Amit Agarwal,Daniel Murray,Franziska Weickert,Krzysztof Gofryk,Orest Pavlosiuk,Piotr Wisniewski,Dariusz Kaczorowski,Arun Bansil,Madhab Neupane###

Observation of gapped state in rare-earth monopnictide HoSb. The rare-earth monopnictide family is attracting an intense current interest
driven by its unusual extreme magnetoresistance (XMR) property and the
potential presence of topologically non-trivial surface states. The
experimental observation of non-trivial surface states in this family of
materials are not ubiquitous. Here, using high-resolution angle-resolved
photoemission spectroscopy (ARPES), magnetotransport, and parallel
first-principles modeling, we examine the nature of electronic states in HoSb.
Although we find the presence of bulk band gaps at the G and X-symmetry points
of the Brillouin zone (BZ), we do not find these gaps to exhibit band inversion
so that HoSb does not host a Dirac semimetal state. Our magnetotransport
measurements indicate that HoSb can be characterized as a correlated
nearly-complete electron-hole-compensated semimetal. Our analysis reveals that
the nearly perfect electron-hole compensation could drive the appearance of
non-saturating XMR effect in HoSb.

###Near-Zero-Field Spin-Dependent Recombination Current and Electrically Detected Magnetic Resonance from the Si/SiO$_2$ interface|Nicholas J. Harmon,James P. Ashton,Patrick M. Lenahan,Michael E. Flatté###

Near-Zero-Field Spin-Dependent Recombination Current and Electrically Detected Magnetic Resonance from the Si/SiO$_2$ interface. Dielectric interfaces critical for metal-oxide-semiconductor (MOS) electronic
devices, such as the Si/SiO$_2$ MOS field effect transistor (MOSFET), possess
trap states that can be visualized with electrically-detected spin resonance
techniques, however the interpretation of such measurements has been hampered
by the lack of a general theory of the phenomena. This article presents such a
theory for two electrical spin-resonance techniques, electrically detected
magnetic resonance (EDMR) and the recently observed near-zero field
magnetoresistance (NZFMR), by generalizing Shockley Read Hall trap-assisted
recombination current calculations via stochastic Liouville equations. Spin
mixing at this dielectric interface occurs via the hyperfine interaction, which
we show can be treated either quantum mechanically or semiclassically, yielding
distinctive differences in the current across the interface. By analyzing the
bias dependence of NZFMR and EDMR, we find that the recombination in a
Si/SiO$_2$ MOSFET is well understood within a semiclassical approach.

###Butterfly-shaped magnetoresistance in triangular-lattice antiferromagnet Ag$_2$CrO$_2$|Hiroki Taniguchi,Mori Watanabe,Masashi Tokuda,Shota Suzuki,Eria Imada,Takashi Ibe,Tomonori Arakawa,Hiroyuki Yoshida,Hiroaki Ishizuka,Kensuke Kobayashi,Yasuhiro Niimi###

Butterfly-shaped magnetoresistance in triangular-lattice antiferromagnet Ag$_2$CrO$_2$. Spintronic devices using antiferromagnets (AFMs) are promising candidates for
future applications. Recently, many interesting physical properties have been
reported with AFM-based devices. Here we report a butterfly-shaped
magnetoresistance (MR) in a micrometer-sized triangular-lattice antiferromagnet
Ag$_2$CrO$_2$. The material consists of two-dimensional triangular-lattice
CrO$_2$ layers with antiferromagnetically coupled $S$ = 3/2 spins and Ag$_2$
layers with high electrical conductivity. The butterfly-shaped MR appears only
when the magnetic field is applied perpendicularly to the CrO$_2$ plane with
the maximum MR ratio ($\approx$ 15%) at the magnetic ordering temperature.
These features are distinct from those observed in conventional magnetic
materials. We propose a theoretical model where fluctuations of partially
disordered spins with the Ising anisotropy play an essential role in the
butterfly-shaped MR in Ag$_2$CrO$_2$.

###Room-temperature giant magnetotranstance effect in single-phase multiferroics|Yan-Fen Chang,Young Sun###

Room-temperature giant magnetotranstance effect in single-phase multiferroics. Single-phase multiferroic materials are usually considered useless because of
the weak magnetoelectric effects, low operating temperature, and small electric
polarization induced by magnetic orders. As a result, current studies on
applications of the magnetoelectric effects are mainly focusing on multiferroic
heterostructures and composites. Here we report a room-temperature giant effect
in response to external magnetic fields in single-phase multiferroics. A low
magnetic field of 1000 Oe applied on the spin-driven multiferroic hexaferrites
BaSrCo2Fe11AlO22 and Ba0.9Sr1.1Co2Fe11AlO22 is able to cause a huge change in
the linear magnetoelectric coefficient by several orders, leading to a giant
magnetotranstance (GMT) effect at room temperature. The GMT effect is
comparable to the well-known giant magnetoresistance (GMR) effect in magnetic
multilayers, and thus opens up a door toward practical applications for
single-phase multiferroics.

###Fast, cheap, and scalable magnetic tracker with an array of magnetoresistors|Valerio Biancalana,Roberto Cecchi,Piero Chessa,Giuseppe Bevilacqua,Yordanka Dancheva,Antonio Vigilante###

Fast, cheap, and scalable magnetic tracker with an array of magnetoresistors. We present the hardware of a cheap multi-sensor magnetometric setup where a
relatively large set of magnetic field components is measured in several
positions by calibrated magnetoresistive detectors. The setup is developed with
the scope of mapping the (inhomogeneous) field generated by a known magnetic
source, which is measured as superimposed to the (homogeneous) geomagnetic
field. The final goal is to use the data produced by this hardware to
reconstruct position and orientation of the magnetic source with respect to the
sensor frame, simultaneously with the orientation of the frame with respect to
the environmental field. Possible applications of the setup are shortly
discussed, together with a synthetic description of the data elaboration and
analysis.

###Extraordinary Phase Coherence Length in Epitaxial Halide Perovskites|K. Nasyedkin,I. King,L. Zhang,P. Chen,L. Wang,R. J. Staples,R. R. Lunt,J. Pollanen###

Extraordinary Phase Coherence Length in Epitaxial Halide Perovskites. Inorganic halide perovskites have emerged as a promising platform in a wide
range of applications from solar energy harvesting to computing, and light
emission. The recent advent of epitaxial thin film growth of halide perovskites
has made it possible to investigate low-dimensional quantum electronic devices
based on this class of materials. This study leverages advances in vapor-phase
epitaxy of halide perovskites to perform low-temperature magnetotransport
measurements on single-domain cesium tin iodide (CsSnI$_3$) epitaxial thin
films. The low-field magnetoresistance carries signatures of coherent quantum
interference effects and spin-orbit coupling. These weak anti-localization
measurements reveal a micron-scale low-temperature phase coherence length for
charge carriers in this system. The results indicate that epitaxial halide
perovskite heterostructures are a promising platform for investigating long
coherent quantum electronic effects and potential applications in spintronics
and spin-orbitronics.

###Electronic correlation, magnetic structure and magnetotransport in few-layer CrI3|Soumyajit Sarkar,Peter Kratzer###

Electronic correlation, magnetic structure and magnetotransport in few-layer CrI3. Using density functional theory combined with a Hubbard model (DFT+U ), the
electronic band structure of CrI3 multilayers, both free-standing and enclosed
between graphene contacts, is calculated. We show that the DFT+U approach,
together with the 'around mean field' correction scheme, is able to describe
the vertical magnetotransport in line with the experimental measurements of
magnetoresistance in multi-layered CrI3 enclosed between graphene contacts.
Moreover, by interpolating between different double-counting correction
schemes, namely the 'around mean field' correction and the fully localized
limit, we show their importance for describing both the band structure and the
ground-state total energy consistently. Our description of the magnetic
exchange interaction is compatible with the experimentally observed
antiferromagnetic ground state in the bilayer CrI3 and the transition to a
ferromagnetic arrangement in a small external magnetic field. Thus, using
spin-polarized DFT+U with an 'around mean field' correction, a consistent
overall picture is achieved.

###Universal scaling behaviour near vortex-solid/glass to vortex-fluid transition in type-II superconductors in two- and three-dimensions|Hemanta Kumar Kundu,John Jesudasan,Pratap Raychaudhuri,Subroto Mukerjee,Aveek Bid###

Universal scaling behaviour near vortex-solid/glass to vortex-fluid transition in type-II superconductors in two- and three-dimensions. In this article, we present evidence for the existence of vortex-solid/glass
(VG) to vortex-fluid (VF) transition in a type-II superconductor (SC), NbN. We
probed the VG to VF transition in both 2D and 3D films of NbN through studies
of magnetoresistance and current-voltage characteristics. The dynamical
exponents corresponding to this phase transition were extracted independently
from the two sets of measurements. The $H$-$T$ phase diagram for the 2D and 3D
SC are found to be significantly different near the critical point. In the case
of 3D SC, the exponent values obtained from the two independent measurements
show excellent match. On the other hand, for the 2D SC, the exponents obtained
from the two experiments were significantly different. We attribute this to the
fact that the characteristic length scale diverges near the critical point in a
2D SC in a distinctly different way from its 3D counterpart form scaling
behaviour.

###Surface-induced linear magnetoresistance in antiferromagnetic topological insulator MnBi2Te4|X. Lei,L. Zhou,Z. Y. Hao,X. Z. Ma,C. Ma,Y. Q. Wang,P. B. Chen,B. C. Ye,L. Wang,F. Ye,J. N. Wang,J. W. Mei,H. T. He###

Surface-induced linear magnetoresistance in antiferromagnetic topological insulator MnBi2Te4. Through a thorough magneto-transport study of antiferromagnetic topological
insulator MnBi2Te4 (MBT) thick films, a positive linear magnetoresistance (LMR)
with a two-dimensional (2D) character is found in high perpendicular magnetic
fields and temperatures up to at least 260 K. The nonlinear Hall effect further
reveals the existence of high-mobility surface states in addition to the bulk
states in MBT. We ascribe the 2D LMR to the high-mobility surface states of
MBT, thus unveiling a transport signature of surface states in thick MBT films.
A suppression of LMR near the Neel temperature of MBT is also noticed, which
might suggest the gap opening of surface states due to the
paramagnetic-antiferromagnetic phase transition of MBT. Besides these, the
failure of the disorder and quantum LMR model in explaining the observed LMR
indicates new physics must be invoked to understand this phenomenon.

###Magneto-transport properties of tellurium under extreme conditions|Kazuto Akiba,Kaya Kobayashi,Tatsuo C. Kobayashi,Ryo Koezuka,Atsushi Miyake,Jun Gouchi,Yoshiya Uwatoko,Masashi Tokunaga###

Magneto-transport properties of tellurium under extreme conditions. This study investigates the transport properties of a chiral elemental
semiconductor tellurium (Te) under magnetic fields and pressure. Application of
hydrostatic pressure reduces the resistivity of Te, while its temperature
dependence remains semiconducting up to 4 GPa, contrary to recent theoretical
and experimental studies. Application of higher pressure causes structural as
well as semiconductor--metal transitions. The resulting metallic phase above 4
GPa exhibits superconductivity at 2 K along with a noticeable linear
magnetoresistance effect. On the other hand, at ambient pressure, we identified
metallic surface states on the as-cleaved (10$\bar{1}$0) surfaces of Te. The
nature of these metallic surface states has been systematically studied by
analyzing quantum oscillations observed in high magnetic fields. We clarify
that a well-defined metallic surface state exists not only on chemically etched
samples that were previously reported, but also on as-cleaved ones.

###Diabolical touching point in the magnetic energy levels of topological nodal-line metals|Chong Wang,Zhongyi Zhang,Chen Fang,A. Alexandradinata###

Diabolical touching point in the magnetic energy levels of topological nodal-line metals. For three-dimensional metals, Landau levels disperse as a function of the
magnetic field and the momentum wavenumber parallel to the field. In this
two-dimensional parameter space, it is shown that two conically-dispersing
Landau levels can touch at a diabolical point -- a Landau-Dirac point. The
conditions giving rise to Landau-Dirac points are shown to be magnetic
breakdown (field-induced quantum tunneling) and certain crystallographic
spacetime symmetry. Both conditions are realizable in topological nodal-line
metals, as we exemplify with CaP$_3$. A Landau-Dirac point reveals itself in
anomalous batman-like peaks in the magnetoresistance, as well as in the onset
of optical absorption linearly evolving to zero frequency as a function of the
field magnitude/orientation.

###Weak antilocalization beyond the fully diffusive regime in Pb1-xSnxSe topological quantum wells|Jiashu Wang,X. Liu,C. Bunker,L. Riney,B. Qing,S. K. Bac,M. Zhukovskyi,T. Orlova,S. Rouvimov,M. Dobrowolska,J. K. Furdyna,B. A. Assaf###

Weak antilocalization beyond the fully diffusive regime in Pb1-xSnxSe topological quantum wells. We report the measurements and analysis of weak antilocalization (WAL) in
Pb1-xSnxSe topological quantum wells in a new regime where the elastic
scattering length is larger than the magnetic length. We achieve this regime
through the development of high-quality epitaxy and doping of topological
crystalline insulator (TCI) quantum wells. We obtain elastic scattering lengths
that exceeds 100nm and become comparable to the magnetic length. In this
transport regime, the Hikami-Larkin-Nagaoka model is no longer valid. We employ
the model of Wittmann and Schmid to extract the coherence time from the
magnetoresistance. We find that despite our improved transport characteristics,
the coherence time may be limited by scattering channels that are not strongly
carrier dependent, such as electron-phonon or defect scattering.

###Transport characterization of magnetic states in Superconductor/Ferromagnet Nb/Co multilayers|Olena M. Kapran,Roman Morari,Taras Golod,Evgenii A. Borodianskyi,Vladimir Boian,Andrei Prepelita,Nikolay Klenov,Anatoli Sidorenko,Vladimir M. Krasnov###

Transport characterization of magnetic states in Superconductor/Ferromagnet Nb/Co multilayers. Employment of the non-trivial proximity effect in Superconductor/Ferromagnet
(S/F) heterostructures for creation of novel superconducting devices requires
an accurate control of magnetic states in complex thin-film multilayers
composing such devices. In this work we study experimentally in-plane transport
properties of micro-structured Nb/Co multilayers. We apply various experimental
techniques for characterization of multilayers, including the anisotropic
magnetoresistance, the Hall effect and the first-order-reversal-curves
analysis. We demonstrate that a combination of those techniques can provide a
detailed knowledge of the magnetic state of the multilayer. In particular, we
identify the range of existence of the coherently rotating, monodomain
scissor-like state. It is anticipated, that in this noncollinear magnetic state
the unconventional odd-frequency spin-triplet order parameter should appear.
The non-hystertic nature of this state allows reversible tuning of the magnetic
orientation. Thus, we identify the range of parameters and the procedure for
controllable operation of devices based on such S/F heterostructures.

###Competing spin modulations in a magnetically frustrated semimetal EuCuSb|Hidefumi Takahashi,Kai Aono,Yusuke Nambu,Ryoji Kiyanagi,Takuya Nomoto,Masato Sakano,Kyoko Ishizaka,Ryotaro Arita,Shintaro Ishiwata###

Competing spin modulations in a magnetically frustrated semimetal EuCuSb. The competing magnetic ground states of the itinerant magnet EuCuSb, which
has a hexagonal layered structure, were studied via magnetization, resistivity,
and neutron diffraction measurements on single-crystal samples. EuCuSb has a
three-dimensional semimetallic band structure as confirmed by band calculation
and angle-resolved photoelectron spectroscopy, consistent with the nearly
isotropic metallic conductivity in the paramagnetic state. However, below the
antiferromagnetic transition temperature of TN1 (8.5 K), the resistivity,
especially along the hexagonal axis, increases significantly. This implies the
emergence of anisotropic magnetic ordering coupled to the conducting electrons.
Neutron diffraction measurements show that the Eu spins, which order
ferromagnetically within each layer, are collinearly modulated
(up-up-down-down) along the hexagonal axis below TN1, followed by the partial
emergence of helical spin modulation below TN2 (6 K). Based on the observation
of anomalous magnetoresistance with hysteretic behavior, we discuss the
competing nature of the ground state inherent in a frustrated Heisenberg-like
spin system with a centrosymmetric structure.

###Electrical detection of the spin reorientation transition in antiferromagnetic TmFeO$_3$ thin films by spin Hall magnetoresistance|Sven Becker,Andrew Ross,Romain Lebrun,Lorenzo Baldrati,Shilei Ding,Felix Schreiber,Francesco Maccherozzi,Dirk Backes,Mathias Kläui,Gerhard Jakob###

Electrical detection of the spin reorientation transition in antiferromagnetic TmFeO$_3$ thin films by spin Hall magnetoresistance. TmFeO$_3$ (TFO) is a canted antiferromagnet that undergoes a spin
reorientation transition (SRT) with temperature between 82 K and 94 K in single
crystals. In this temperature region, the N\'eel vector continuously rotates
from the crystallographic $c$-axis (below 82 K) to the $a$-axis (above 94 K).
The SRT allows for a temperature control of distinct antiferromagnetic states
without the need for a magnetic field, making it apt for applications working
at THz frequencies. For device applications, thin films of TFO are required as
well as an electrical technique for reading out the magnetic state. Here we
demonstrate that orthorhombic TFO thin films can be grown by pulsed laser
deposition and the detection of the SRT in TFO thin films can be accessed by
making use of the all electrical spin Hall magnetoresistance (SMR), in good
agreement for the temperature range where the SRT occurs. Our results
demonstrate that one can electrically detect the SRT in insulators.

###Chirality induced Giant Unidirectional Magnetoresistance in Twisted Bilayer Graphene|Yizhou Liu,Tobias Holder,Binghai Yan###

Chirality induced Giant Unidirectional Magnetoresistance in Twisted Bilayer Graphene. Twisted bilayer graphene (TBG) exhibits fascinating correlation-driven
phenomena like the superconductivity and Mott insulating state, with flat bands
and a chiral lattice structure. We find by quantum transport calculations that
the chirality leads to a giant unidirectional magnetoresistance (UMR) in TBG,
where the unidirectionality refers to the resistance change under the reversal
of the direction of the current or magnetic field. We point out that flat bands
significantly enhance this effect. The UMR increases quickly upon reducing the
twist angle and reaches about 20\% for an angle of 1.5$^\circ$ in a 10 T
in-plane magnetic field. We propose the band structure topology (asymmetry),
which leads to a direction-sensitive mean free path, as a useful way to
anticipate the UMR effect. The UMR provides a probe for chirality and band
flatness in the twisted bilayers.

###Demonstration of nanosecond operation in stochastic magnetic tunnel junctions|Christopher Safranski,Jan Kaiser,Philip Trouilloud,Pouya Hashemi,Guohan Hu,Jonathan Z Sun###

Demonstration of nanosecond operation in stochastic magnetic tunnel junctions. Magnetic tunnel junctions operating in the superparamagnetic regime are
promising devices in the field of probabilistic computing, which is suitable
for applications like high-dimensional optimization or sampling problems.
Further, random number generation is of interest in the field of cryptography.
For such applications, a device's uncorrelated fluctuation time-scale can
determine the effective system speed. It has been theoretically proposed that a
magnetic tunnel junction designed to have only easy-plane anisotropy provides
fluctuation rates determined by its easy-plane anisotropy field, and can
perform on nanosecond or faster time-scale as measured by its
magnetoresistance's autocorrelation in time. Here we provide experimental
evidence of nanosecond scale fluctuations in a circular shaped easy-plane
magnetic tunnel junction, consistent with finite-temperature coupled macrospin
simulation results and prior theoretical expectations. We further assess the
degree of stochasticity of such signal.

###Intensity equations for birefringent spin lasers|Gaofeng Xu,David Cao,Velimir Labinac,Igor Žutić###

Intensity equations for birefringent spin lasers. Semiconductor spin lasers are distinguished from their conventional
counterparts by the presence of spin-polarized carriers. The transfer of
angular momentum of the spin-polarized carriers to photons provides important
opportunities for the operation of lasers. With the injection of spin-polarized
carriers, which lead to the circularly polarized light, the polarization of the
emitted light can be changed an order of magnitude faster than its intensity.
This ultrafast operation of spin lasers relies on a large birefringence,
usually viewed as detrimental in spin and conventional lasers. We introduce a
transparent description of spin lasers using intensity equations, which
elucidate the influence of birefringence on the intensity and polarization
modulation of lasers. While intensity modulation is independent of
birefringence, for polarization modulation an increase in birefringence
directly increases the resonant frequency. Our results for dynamical operation
of lasers provide a guide for their spin-dependent response and spintronic
applications beyond magnetoresistance.

###Thermodynamically Induced Transport Anomaly in Dilute Metals ZrTe$_5$ and HfTe$_5$|Chenjie Wang###

Thermodynamically Induced Transport Anomaly in Dilute Metals ZrTe$_5$ and HfTe$_5$. A 40-year-old puzzle in transition metal pentatellurides ZrTe$_5$ and
HfTe$_5$ is the anomalous peak in the temperature dependence of the
longitudinal resistivity, which is accompanied by sign reverses of the Hall and
Seebeck coefficients. We give a plausible explanation for these phenomena
without assuming any phase transition or strong interaction effect. We show
that due to intrinsic thermodynamics and diluteness of the conducting electrons
in these materials, the chemical potential displays a strong dependence on the
temperature and magnetic field. With that, we compute resistivity, Hall and
Seebeck coefficients in zero field, and magnetoresistivity and Hall resistivity
in finite magnetic fields, in all of which we reproduce the main features that
are observed in experiments.

###Large angle precession of magnetization maintained by a microwave voltage|Hiroshi Imamura,Rie Matsumoto###

Large angle precession of magnetization maintained by a microwave voltage. Effects of a microwave voltage on magnetization precession are analyzed based
on a macrospin model. The microwave voltage induces the oscillating anisotropy
field through the voltage controlled magnetic anisotropy (VCMA) effect, and
then stimulates the magnetization. The large angle precession is maintained if
the magnetization synchronizes with the microwave voltage. The effective
equations of motion of the magnetization with an oscillating anisotropy field
are derived, and the mechanism of the synchronization is clarified by analyzing
the derived equations of motion. The conditions of the angular frequency
detuning and the amplitude of the oscillating anisotropy field for
synchronization are obtained. The results are useful for development of the
VCMA-based energy-efficient spintronics devices using magnetization precession
such as a VCMA-based magnetoresistive random access memory and a nano-scale
microwave magnetic field generator.

###Electrical conduction of Ti/TiOx/Ti structures at low temperatures and high magnetic fields|Marianna Batkovaa,Ivan Batko###

Electrical conduction of Ti/TiOx/Ti structures at low temperatures and high magnetic fields. We present results of electrical conduction studies of Ti/TiOx/Ti planar
structures prepared by tip-induced local anodic oxidation (LAO) of titanium
thin films. The prepared structures have shown almost linear I-V curves at
temperatures between 300 K and 30 K, and only slight deviation from linear
behaviour at lower temperatures. Electrical conductance of the structures can
be adequately explained by a two-channel model where variable range hopping
channels and metallic ones coexist in parallel, while a crossover from Mott to
Efros-Shklovskii variable-range-hopping conductivity has been observed at
decreasing temperature. The magnetoresistance of the studied structures is very
small even in magnetic fields up to 9 T. The reported electrical properties of
the structures indicate their promising applications as very low heat capacity
temperature sensors for cryogenic region and high magnetic fields.

###Picosecond Switching of Optomagnetic Tunnel Junctions|Luding Wang,Houyi Cheng,Pingzhi Li,Yang Liu,Youri L. W. van Hees,Reinoud Lavrijsen,Xiaoyang Lin,Kaihua Cao,Bert Koopmans,Weisheng Zhao###

Picosecond Switching of Optomagnetic Tunnel Junctions. Perpendicular magnetic tunnel junctions are one of the building blocks for
spintronic memories, which allow fast nonvolatile data access, offering
substantial potentials to revolutionize the mainstream computing architecture.
However, conventional switching mechanisms of such devices are fundamentally
hindered by spin polarized currents4, either spin transfer torque or spin orbit
torque with spin precession time limitation and excessive power dissipation.
These physical constraints significantly stimulate the advancement of modern
spintronics. Here, we report an optomagnetic tunnel junction using a
spintronic-photonic combination. This composite device incorporates an
all-optically switchable Co/Gd bilayer coupled to a CoFeB/MgO-based
perpendicular magnetic tunnel junction by the Ruderman-Kittel-Kasuya-Yosida
interaction. A picosecond all-optical operation of the optomagnetic tunnel
junction is explicitly confirmed by time-resolved measurements. Moreover, the
device shows a considerable tunnel magnetoresistance and thermal stability.
This proof-of-concept device represents an essential step towards ultrafast
spintronic memories with THz data access, as well as ultralow power
consumption.

###Topological Mott transition in a Weyl-Hubbard model with dynamical mean-field theory|Bernhard Irsigler,Tobias Grass,Jun-Hui Zheng,Mathieu Barbier,Walter Hofstetter###

Topological Mott transition in a Weyl-Hubbard model with dynamical mean-field theory. Weyl semimetals are three-dimensional, topologically protected, gapless
phases which show exotic phenomena such as Fermi arc surface states or negative
magnetoresistance. It is an open question whether interparticle interactions
can turn the topological semimetal into a topologically nontrivial Mott
insulating phase. We investigate an experimentally motivated model for Weyl
physics of cold atoms in optical lattices, with the main focus on interaction
effects and topological properties by means of dynamical mean-field theory
(DMFT). We characterize topological phases by numerically evaluating the Chern
number via the Ishsikawa-Matsuyama formula for interacting phases. Within our
studies, we find that the Chern numbers become trivial when interactions lead
to insulating behavior. For a deeper understanding of the
Weyl-semimetal-to-Mott-insulator topological phase transition, we evaluate the
topological properties of quasiparticle bands as well as so-called blind bands.
Our study is complementary to recent studies of Weyl semimetals with DMFT.

###Dichotomy Between Orbital and Magnetic Nematic Instabilities in BaFe2S3|Suguru Hosoi,Takuya Aoyama,Kousuke Ishida,Yuta Mizukami,Kazuki Hashizume,Satoshi Imaizumi,Yoshinori Imai,Kenya Ohgushi,Yusuke Nambu,Motoi Kimata,Shojiro Kimura,Takasada Shibauchi###

Dichotomy Between Orbital and Magnetic Nematic Instabilities in BaFe2S3. Nematic orders emerge nearly universally in iron-based superconductors, but
elucidating their origins is challenging because of intimate couplings between
orbital and magnetic fluctuations. The iron-based ladder material BaFe2S3,
which superconducts under pressure, exhibits antiferromagnetic order below TN ~
117K and a weak resistivity anomaly at T* ~ 180K, whose nature remains elusive.
Here we report angle-resolved magnetoresistance (MR) and elastoresistance (ER)
measurements in BaFe2S3, which reveal distinct changes at T*. We find that MR
anisotropy and ER nematic response are both suppressed near T*, implying that
an orbital order promoting isotropic electronic states is stabilized at T*.
Such an isotropic state below T* competes with the antiferromagnetic order,
which is evidenced by the nonmonotonic temperature dependence of nematic
fluctuations. In contrast to the cooperative nematic orders in spin and orbital
channels in iron pnictides, the present competing orders can provide a new
platform to identify the separate roles of orbital and magnetic fluctuations.

###Anomalous Magnetoresistance by Breaking Ice Rule in Bi2Ir2O7/Dy2Ti2O7 Heterostructure|H. Zhang,C. K. Xing,K. Noordhoek,Z. Liu,T. H. Zhao,L. Horák,Q. Huang,L. Hao,J. Yang,S. Pandey,E. Dagotto,Z. Jiang,J. H. Chu,Y. Xin,E. S. Choi,H. D. Zhou,J. Liu###

Anomalous Magnetoresistance by Breaking Ice Rule in Bi2Ir2O7/Dy2Ti2O7 Heterostructure. While geometrically frustrated quantum magnets are known for a variety of
exotic spin states that are of great interests of understanding emergent
phenomena as well as enabling revolutionary quantum technologies, most of them
are necessarily good insulators which are difficult to be integrated with
modern electrical circuit that relies on moving charge carriers. The grand
challenge of converting fluctuations and excitations of frustrated moments into
electronic responses is finding ways to introduce charge carriers that interact
with the localized spins without destroying the spin states. Here, we show
that, by designing a Bi2Ir2O7/Dy2Ti2O7 heterostructure, the breaking of the
spin ice rule in insulating Dy2Ti2O7 can lead to a charge response in the
Bi2Ir2O7 conducting layer that can be detected as anomalous magnetoresistance.
These results demonstrate a novel and feasible interfacial approach for
electronically probing exotic spin states in insulating magnets, laying out a
blueprint for the metallization of frustrated quantum magnets.

###Unconventional Hall effect and its variation with Co-doping in van der Waals Fe3GeTe2|Rajeswari Roy Chowdhury,Samik DuttaGupta,Chandan Patra,Oleg A. Tretiakov,Sudarshan Sharma,Shunsuke Fukami,Hideo Ohno,Ravi Prakash Singh###

Unconventional Hall effect and its variation with Co-doping in van der Waals Fe3GeTe2. Two-dimensional (2D) van der Waals (vdW) magnetic materials have attracted a
lot of attention owing to the stabilization of long-range magnetic order down
to atomic dimensions, and the prospect of novel spintronic devices with unique
functionalities. The clarification of the magnetoresistive properties and its
correlation to the underlying magnetic configurations is essential for 2D
vdW-based spintronic devices. Here, the effect of Co-doping on the magnetic and
magnetotransport properties of Fe3GeTe2 have been investigated.
Magnetotransport measurements reveal an unusual Hall effect behavior whose
strength was considerably modified by Co-doping and attributed to arise from
the underlying complicated spin textures. The present results provide a clue to
tailoring of the underlying interactions necessary for the realization of a
variety of unconventional spin textures for 2D vdW FM-based spintronics.

###Direct evidence of electron-hole compensation for XMR in topologically trivial YBi|Shaozhu Xiao,Yinxiang Li,Yong Li,Xiufu Yang,Shiju Zhang,Wei Liu,Xianxin Wu,Bin Li,Masashi Arita,Kenya Shimada,Youguo Shi,Shaolong He###

Direct evidence of electron-hole compensation for XMR in topologically trivial YBi. The prediction of topological states in rare earth monopnictide compounds has
attracted renewed interest. Extreme magnetoresistance (XMR) has also been
observed in several nonmagnetic rare earth monopnictide compounds. The origin
of XMR in these compounds could be attributed to several mechanisms, such as
topologically nontrivial electronic structures and electron-hole carrier
balance. YBi is a typical rare earth monopnictide exhibiting XMR, and expected
to have a nontrivial electronic structure. In this work, we performed a direct
investigation of the electronic structure of YBi by combining angle resolved
photoemission spectroscopy and theoretical calculations. Our results show that
YBi is topologically trivial without the expected band inversion, and they rule
out the topological effect as the cause of XMR in YBi. Furthermore, we directly
observed perfect electron-hole compensation in the electronic structure of YBi,
which could be the primary mechanism accounting for the XMR.

###A Single-Cycle MLP Classifier Using Analog MRAM-based Neurons and Synapses|Ramtin Zand###

A Single-Cycle MLP Classifier Using Analog MRAM-based Neurons and Synapses. In this paper, spin-orbit torque (SOT) magnetoresistive random-access memory
(MRAM) devices are leveraged to realize sigmoidal neurons and binarized
synapses for a single-cycle analog in-memory computing (IMC) architecture.
First, an analog SOT-MRAM-based neuron bitcell is proposed which achieves a 12x
reduction in power-area-product compared to the previous most power- and
area-efficient analog sigmoidal neuron design. Next, proposed neuron and
synapse bit cells are used within memory subarrays to form an analog IMC-based
multilayer perceptron (MLP) architecture for the MNIST pattern recognition
application. The architecture-level results exhibit that our analog IMC
architecture achieves at least two and four orders of magnitude performance
improvement compared to a mixed-signal analog/digital IMC architecture and a
digital GPU implementation, respectively while realizing a comparable
classification accuracy.

###Importance of Electronic Correlation in the Intermetallic Half-Heusler Compounds|Minjie Lu,Hao Chen,Glenn Agnolet###

Importance of Electronic Correlation in the Intermetallic Half-Heusler Compounds. Low temperature scanning tunneling spectroscopy of HfNiSn shows a V^m(m < 1)
zero bias anomaly around the Fermi level. This local density of states with a
fractional power law shape is well known to be a consequence of electronic
correlations. For comparison, we have also measured the tunneling conductances
of other half-Heusler compounds with 18 valence electrons. ZrNiPb shows a
metal-like local density of states, whereas ZrCoSb and NbFeSb show a linear and
V^2 anomaly. One interpretation of these anomalies is that a correlation gap is
opening in these compounds. By analyzing the magnetoresistance of HfNiSn, we
demonstrate that at low temperatures, electron-electron scattering dominates.
The T^m(m < 1) temperature dependence of the conductivity confirms that the
electronic correlations are a bulk rather than a surface property.

###Experimental and theoretical study of the correlated compound YbCdSn: Evidence for large magnetoresistance and mass enhancement|Antu Laha,P. Rambabu,V. Kanchana,L. Petit,Z. Szotek,Z. Hossain###

Experimental and theoretical study of the correlated compound YbCdSn: Evidence for large magnetoresistance and mass enhancement. The unusual features of topological semimetals arise from its nontrivial band
structure. The impact of strong electron correlations on the topological states
remains largely unexplored in real materials. Here, we report the
magnetotransport properties of YbCdSn single crystals. We found two fundamental
experimental evidences of electron correlations through magnetic susceptibility
and specific heat. The electron correlations in this compound lead to an
intermediate valence state and enhance the effective mass of the charge
carriers. This correlated state exhibits large nonsaturating magnetoresistance,
low carrier density, magnetic field induced metal-semiconductor-like crossover
and a plateau in resistivity at low temperatures. This compound also shows a
cusp-like magnetoconductivity at low magnetic field which indicates the
presence of weak antilocalization effect. Our band structure calculations of
Yb$^{2+}$ state predict YbCdSn to be a topological nodal-line semimetal.

###Spin-torque Dynamics for Noise Reduction in Vortex-based Sensors|Mafalda Jotta Garcia,Julien Moulin,Steffen Wittrock,Sumito Tsunegi,Kay Yakushiji,Akio Fukushima,Hitoshi Kubota,Shinji Yuasa,Ursula Ebels,Myriam Pannetier-Lecoeur,Claude Fermon,Romain Lebrun,Paolo Bortolotti,Aurélie Solignac,Vincent Cros###

Spin-torque Dynamics for Noise Reduction in Vortex-based Sensors. Performance of magnetoresistive sensors is today mainly limited by their 1/f
low-frequency noise. Here, we study this noise component in vortex-based TMR
sensors. We compare the noise level in different magnetization configurations
of the device, i.e vortex state or uniform parallel or antiparallel states. We
find that the vortex state is at least an order of magnitude noisier than the
uniform states. Nevertheless, by activating the spin-transfer induced dynamics
of the vortex configuration, we observe a reduction of the 1/f noise, close to
the values measured in the AP state, as the vortex core has a lower probability
of pinning into defect sites. Additionally, by driving the dynamics of the
vortex core by a non-resonant rf field or current we demonstrate that the 1/f
noise can be further decreased. The ability to reduce the 1/f low-frequency
noise in vortex-based devices by leveraging their spin-transfer dynamics thus
enhances their applicability in the magnetic sensors' landscape.

###Magnetic order of Dy$^{3+}$ and Fe$^{3+}$ moments in antiferromagnetic DyFeO$_{3}$ probed by spin Hall magnetoresistance and spin Seebeck effect|G. R. Hoogeboom,T. Kuschel,G. E. W. Bauer,M. V. Mostovoy,A. V. Kimel,B. J. van Wees###

Magnetic order of Dy$^{3+}$ and Fe$^{3+}$ moments in antiferromagnetic DyFeO$_{3}$ probed by spin Hall magnetoresistance and spin Seebeck effect. We report on spin Hall magnetoresistance (SMR) and spin Seebeck effect (SSE)
in single crystal of the rare-earth antiferromagnet DyFeO$_{3}$ with a thin Pt
film contact. The angular shape and symmetry of the SMR at elevated
temperatures reflect the antiferromagnetic order of the Fe$^{3+}$ moments as
governed by the Zeeman energy, the magnetocrystalline anisotropy and the
Dzyaloshinskii-Moriya interaction. We interpret the observed linear dependence
of the signal on the magnetic field strength as evidence for field-induced
order of the Dy$^{3+}$ moments up to room temperature. At and below the Morin
temperature of 50$\,$K, the SMR monitors the spin-reorientation phase
transition of Fe$^{3+}$ spins. Below 23$\,$K, additional features emerge that
persist below 4$\,$K, the ordering temperature of the Dy$^{3+}$ magnetic
sublattice. We conclude that the combination of SMR and SSE is a simple and
efficient tool to study spin reorientation phase transitions and sublattice
magnetizations.

###Incommensurate magnetism mediated by Weyl fermions in NdAlSi|Jonathan Gaudet,Hung-Yu Yang,Santu Baidya,Baozhu Lu,Guangyong Xu,Yang Zhao,Jose A. Rodriguez,Christina M. Hoffmann,David E. Graf,Darius H. Torchinsky,Predrag Nikolić,David Vanderbilt,Fazel Tafti,Collin L. Broholm###

Incommensurate magnetism mediated by Weyl fermions in NdAlSi. Emergent relativistic quasiparticles in Weyl semimetals are the source of
exotic electronic properties such as surface Fermi arcs, the anomalous Hall
effect, and negative magnetoresistance, all observed in real materials. Whereas
these phenomena highlight the effect of Weyl fermions on the electronic
transport properties, less is known about what collective phenomena they may
support. Here, we report a new Weyl semimetal, NdAlSi that offers an example.
Using neutron diffraction, we report a long-wavelength magnetic order in NdAlSi
whose periodicity is linked to the nesting vector between two topologically
non-trivial Fermi pockets, which we characterize using density functional
theory and quantum oscillation measurements. Our work provides a rare example
of Weyl fermions driving collective magnetism.

###Signature of multilayer graphene strain-controlled domain walls in quantum Hall effect|Paul Anderson,Yifan Huang,Yuanjun Fan,Sara Qubbaj,Sinisa Coh,Qin Zhou,Claudia Ojeda-Aristizabal###

Signature of multilayer graphene strain-controlled domain walls in quantum Hall effect. Domain walls, topological defects that define the frontier between regions of
different stacking in multilayer graphene, have proved to host exciting
physics. The ability of tuning these topological defects in-situ in an
electronic transport experiment brings a wealth of possibilities in terms of
fundamental understanding of domain walls as well as for electronic
applications. Here, we demonstrate through a MEMS (micro-electromechanical
system) actuator and magnetoresistance measurements the effect of domain walls
in multilayer graphene quantum Hall effect. Reversible and controlled uniaxial
strain triggers these topological defects, manifested as new quantum Hall
effect plateaus as well as a discrete and reversible modulation of the current
across the device. Our findings are supported by theoretical calculations and
constitute the first indication of the in-situ tuning of topological defects in
multilayer graphene probed through electronic transport, opening the way to the
use of reversible topological defects in electronic applications.

###Spin-circuit representation of spin-torque ferromagnetic resonance|Kuntal Roy###

Spin-circuit representation of spin-torque ferromagnetic resonance. Spin-torque ferromagnetic resonance (ST-FMR) particularly using magnetic
insulators and heavy metals possessing a giant spin Hall effect (SHE) has
gotten a lot of attention for the development of spintronic devices. To devise
complex functional devices, it is necessary to construct the equivalent
spin-circuit representations of different phenomena. Such representation is
useful to translate physical equations into circuit elements, benchmarking
experiments, and then proposing creative and efficient designs. We utilize the
superposition principle in circuit theory to separate the spin Hall
magnetoresistance and spin pumping contributions in the ST-FMR experiments. We
show that the proposed spin-circuit representation reproduces the standard
results in literature. We further consider multilayers like a spin-valve
structure with an SHE layer sandwiched by two magnetic layers and show how the
corresponding spin-circuit representation can be constructed by simply writing
a vector netlist and solved using circuit theory.

###Anisotropic magneto-thermal transport in Co$_2$MnGa thin films|Philipp Ritzinger,Helena Reichlova,Dominik Kriegner,Anastasios Markou,Richard Schlitz,Michaela Lammel,Gyu Hyeon Park,Andy Thomas,Pavel Streda,Claudia Felser,Sebastian T. B. Goennenwein,Karel Vyborny###

Anisotropic magneto-thermal transport in Co$_2$MnGa thin films. Ferromagnetic Co$_2$MnGa has recently attracted significant attention due to
effects related to non-trivial topology of its band structure, however a
systematic study of canonical magneto-galvanic transport effects is missing.
Focusing on high quality thin films, here we systematically measure anisotropic
magnetoresistance (AMR) and its thermoelectric counterpart (AMTP). We model the
AMR data by free energy minimisation within the Stoner-Wohlfarth formalism and
conclude that both crystalline and non-crystalline components of this
magneto-transport phenomenon are present in Co$_2$MnGa. Unlike the AMR which is
small in relative terms, the AMTP is large due to a change of sign of the
Seebeck coefficient as a function of temperature. This fact is discussed in the
context of the Mott rule and further analysis of AMTP components is presented.

###Pressure effect on the topologically nontrivial electronic state and transport of lutecium monobismuthide|H. Gu1,F. Tang,Y. -R. Ruan,J. -M. Zhang,R. -J. Tang,W. Zhao,R. Zhao,L. Zhang,Z. -D. Han,B. Qian,X. -F. Jiang,Y. Fang###

Pressure effect on the topologically nontrivial electronic state and transport of lutecium monobismuthide. Rare-earth monopnictides are predicted to be nontrivial semimetal candidates
and show pressure-induced superconductivity. Here, we grow LuBi single crystal
and study the magnetization, transport behaviors and electronic band structures
to reveal its topological semimetal feature and superconductivity under
pressure. At 0 GPa, the quantum oscillations indicate that there are several
topologically nontrivial carrier pockets around the Fermi level, among which
the hole ones are isotropic in shape, while the electron ones are anisotropic
and responsible for the angular magnetoresistance. Upon compression, the
superconductivity emerges in the titled compound, showing a similar pressure
dependence as that observed in LaBi. Our calculation suggests that the
electronic band structures are robust at low- and high-pressure respectively
and thus the topological features are always preserved. Besides, the nearly
pressure-independent density of state in LuBi indicates that the conventional
electron-phonon coupling appears to play a minor role in the superconductivity.

###New paradigm for a disordered superconductor in a magnetic field|Anushree Datta,Anurag Banerjee,Nandini Trivedi,Amit Ghosal###

New paradigm for a disordered superconductor in a magnetic field. We show that while orbital magnetic field and disorder, acting individually
weaken superconductivity, acting together they produce an intriguing evolution
of a two-dimensional type-II s-wave superconductor. For weak disorder, the
critical field H_c at which the superfluid density collapses is coincident with
the field at which the superconducting energy gap gets suppressed. However,
with increasing disorder these two fields diverge from each other creating a
pseudogap region. The nature of vortices also transform from Abrikosov vortices
with a metallic core for weak disorder to Josephson vortices with gapped and
insulating cores for higher disorder. Our results naturally explain two
outstanding puzzles: (1) the gigantic magnetoresistance peak observed as a
function of magnetic field in thin disordered superconducting films; and (2)
the disappearance of the celebrated zero-bias Caroli-de Gennes-Matricon peak in
disordered superconductors.

###Magnetism and electrical transport in Y-doped layered iridate Sr$_2$IrO$_4$|Imtiaz Noor Bhatti,A. K. Pramanik###

Magnetism and electrical transport in Y-doped layered iridate Sr$_2$IrO$_4$. Here, we report an investigation of structural, magnetic and electronic
properties in Y-doped layered iridate (Sr$_{1-x}$Y$_x$)$_2$IrO$_4$ ($x$ $\leq$
0.1). The parent Sr$_2$IrO$_4$ is a well-studied spin-orbit coupling (SOC)
induced insulator with an antiferromagnetic ground state. The Y-doping here
equivalently acts for electron doping without altering the vital parameters
such as, SOC and electron correlation. Experimental results show a minute
change in structural parameters and an equivalent charge conversion from
Ir$^{4+}$ to Ir$^{3+}$. Unlike similarly other electron-doped system, the low
temperature magnetic and electronic state in present series is minimally
influenced. The charge conduction mechanism follows 2-dimensional hopping model
in whole series. Magnetoresistance (MR) data show an interesting sign change
with both temperature and magnetic field. The positive MR both at low
temperature follows weak antilocalization behavior where the sign change in MR
is believed to be caused by an interplay between SOC and magnetic moment.

###Magnetotransport in overdoped La$_{2-x}$Sr$_x$CuO$_4$: a Fermi liquid approach|Rui-Ying Mao,Da Wang,Congjun Wu,Qiang-Hua Wang###

Magnetotransport in overdoped La$_{2-x}$Sr$_x$CuO$_4$: a Fermi liquid approach. Recently, several experiments on La$_{2-x}$Sr$_x$CuO$_4$ (LSCO) challenged
the Fermi liquid picture for overdoped cuprates, and stimulated intensive
debates [1]. In this work, we study the magnetotransport phenomena in such
systems based on the Fermi liquid assumption. The Hall coefficient $R_H$ and
magnetoresistivity $\rho_{xx}$ are investigated near the van Hove singularity
$x_{\tiny\text{VHS}}\approx0.2$ across which the Fermi surface topology changes
from hole- to electron-like. Our main findings are: (1) $R_H$ depends on the
magnetic field $B$ and drops from positive to negative values with increasing
$B$ in the doping regime $x_{\tiny\text{VHS}}<x\lesssim0.3$; (2) $\rho_{xx}$
grows up as $B^2$ at small $B$ and saturates at large $B$, while in the
transition regime a "nearly linear" behavior shows up. Our results can be
further tested by future magnetotransport experiments in the overdoped LSCO.

###Non-Ohmic negative longitudinal magnetoresistance in two-dimensional electron gas|Yang-Yang Lyu,Xian-Jing Zhou,Zhi-Li Xiao,Roxanna Fotovat,Jing Xu,Gobind Basnet,Yong-Lei Wang,Dafei Jin,Ralu Divan,Hua-Bing Wang,Wai-Kwong Kwok###

Non-Ohmic negative longitudinal magnetoresistance in two-dimensional electron gas. Negative longitudinal magnetoresistance (NLMR) has been reported in a variety
of materials and has attracted extensive attention as an electrotransport
hallmark of topological Weyl semimetals. However, its origin is still under
debate. Here, we demonstrate that the NLMR in a two dimensional electron gas
can be influenced by the measurement current. While the NLMR persists up to 130
K, its magnitude and magnetic field response become dependent on the applied
current below 60 K. The tunable NLMR at low and high currents can be best
attributed to quantum interference and disorder scattering effects,
respectively. This work uncovers non-Ohmic NLMR in a non-Weyl material and
highlights potential effects of the measurement current in elucidating
electrotransport phenomena. We also demonstrate that NLMRs can be a valuable
phenomenon in revealing the origins of other properties, such as negative MRs
in perpendicular magnetic fields.

###Resistive transition of hydrogen-rich superconductors|Evgeny F. Talantsev,Karoline Stolze###

Resistive transition of hydrogen-rich superconductors. Critical temperature, $T_c$, and the transition width, $\Delta$$T_c$, are two
primary parameters of the superconducting transition. The latter parameter
reflects the superconducting state disturbance originating from the
thermodynamic fluctuations, atomic disorder, applied magnetic field, the
presence of secondary crystalline phases, applied pressure, etc. Recently,
Hirsch and Marsiglio (2020 arXiv:2012.12796) performed an analysis of the
transition width in several near-room-temperature superconductors (NRTS) and
reported that the reduced transition width, $\Delta$$T_c$$/$$T_c$, in these
materials does not follow a conventional trend of transition width broadening
on applied magnetic field observed in low- and high-$T_c$ superconductors. Here
we present thorough mathematical analysis of the magnetoresistive data,
$\it{R(T,B)}$, for the high-entropy alloy $(ScZrNb)_{0.65}$$[RhPd]_{0.35}$ and
hydrogen-rich superconductors of Im-3m-$H_{3}S$, C2/m-$LaH_{10}$ and
P63/mmc-$CeH_9$. We found that the reduced transition width,
$\Delta$$T_c$$/$$T_c$, in these materials does follow a conventional broadening
trend on applied magnetic field.

###Viscous magnetotransport and Gurzhi effect in bilayer electron system|G. M. Gusev,A. S. Jaroshevich,A. D. Levin,Z. D. Kvon,A. K. Bakarov###

Viscous magnetotransport and Gurzhi effect in bilayer electron system. We observe a large negative magnetoresistance and a decrease of resistivity
with increasing temperature, known as the Gurzhi effect, in a bilayer electron
(BL) system formed by a wide GaAs quantum well. A hydrodynamic model for the
single fluid transport parameters in narrow channels is employed and
successfully describes our experimental findings.
  We find that the electron-electron scattering in the bilayer is more
intensive in comparison with a single-band well (SW).
  The hydrodynamic assumption implies a strong dependence on boundary
conditions, which can be characterized by slip length, describing the behavior
of a liquid near the edge. Our results reveal that slip length in a BL is
shorter than in a SW, and that the BL system goes deeper into the hydrodynamic
regime. This is in agreement with the model proposed where the slip length is
of the order of the electron-electron mean free path.

###Superconducting contacts to a monolayer semiconductor|M. Ramezani,I. Correa Sampaio,K. Watanabe,T. Taniguchi,C. Schönenberger,A. Baumgartner###

Superconducting contacts to a monolayer semiconductor. We demonstrate superconducting vertical interconnect access (VIA) contacts to
a monolayer of molybdenum disulfide (MoS$_2$), a layered semiconductor with
highly relevant electronic and optical properties. As a contact material we use
MoRe, a superconductor with a high critical magnetic field and high critical
temperature. The electron transport is mostly dominated by a single
superconductor/normal conductor junction with a clear superconductor gap. In
addition, we find MoS$_2$ regions that are strongly coupled to the
superconductor, resulting in resonant Andreev tunneling and junction dependent
gap characteristics, suggesting a superconducting proximity effect.
Magnetoresistance measurements show that the bandstructure and the high
intrinsic carrier mobility remain intact in the bulk of the MoS$_2$. This type
of VIA contact is applicable to a large variety of layered materials and
superconducting contacts, opening up a path to monolayer semiconductors as a
platform for superconducting hybrid devices.

###Modeling of Magneto-Conductivity of Bismuth Selenide -- A Topological Insulator|Yogesh Kumar,Rabia Sultana,Prince Sharma,V. P. S. Awana###

Modeling of Magneto-Conductivity of Bismuth Selenide -- A Topological Insulator. We report the magneto-conductivity analysis of Bi2Se3 single crystal at
different temperatures in a magnetic field range of 14Tesla. The single
crystals are grown by the self-flux method and characterized through X-ray
diffraction, Scanning Electron Microscopy, and Raman Spectroscopy. The single
crystals show magnetoresistance (MR) of around 380 percent at a magnetic field
of 14T and a temperature of 5K. The Hikami Larkin Nagaoka (HLN) equation has
been used to fit the magneto-conductivity (MC) data. However, the HLN fitted
curve deviates at higher magnetic fields above 1 Tesla, suggesting that the
role of surface driven conductivity suppresses with an increasing magnetic
field. This article proposes a speculative model comprising of surface-driven
HLN and added quantum diffusive and bulk carriers driven classical terms. The
model successfully explains the MC of the Bi2Se3 single crystal at various
temperatures (5 to 200K) and applied magnetic fields (up to 14Tesla).

###High magnetic field induced crossover from the Kondo to Fermi liquid behavior in 1$T$-VTe$_{2}$ single crystals|Xiaxin Ding,Jie Xing,Gang Li,Luis Balicas,Krzysztof Gofryk,Hai-Hu Wen###

High magnetic field induced crossover from the Kondo to Fermi liquid behavior in 1$T$-VTe$_{2}$ single crystals. The magnetic and magnetotransport properties of metallic 1$T$-VTe$_{2}$
single crystals were investigated at temperatures from 1.3 to 300 K and in
magnetic fields up to 35 T. Upon applying a high magnetic field, it is found
that the electrical resistivity displays a crossover from the logarithmic
divergence of the single-impurity Kondo effect to the Fermi liquid behavior at
low temperatures. The Brillouin scale of the negative magnetoresistivity above
the Kondo temperature $T_{\rm{K}}$ = 12 K indicates that the Kondo features
originate from intercalated V ions, with $S$ = 1/2. Both magnetic
susceptibility and Hall effect show an anomaly around $T_{\rm{K}}$. By using
the modified Hamann expression we successfully describe the
temperature-dependent resistivity under various magnetic fields, which shows
the characteristic peak below $T_{\rm{K}}$ due to the splitting of the Kondo
resonance.

###Electric Quantum Oscillation in Weyl Semimetals|Kyusung Hwang,Woo-Ram Lee,Kwon Park###

Electric Quantum Oscillation in Weyl Semimetals. Electronic transport in Weyl semimetals is quite extraordinary due to the
topological property of the chiral anomaly generating the charge pumping
between two distant Weyl nodes with opposite chiralities under parallel
electric and magnetic fields. Here, we develop a full nonequilibrium quantum
transport theory of the chiral anomaly, based on the fact that the chiral
charge pumping is essentially nothing but the Bloch oscillation. Specifically,
by using the Keldysh nonequilibrium Green function method, it is shown that
there is a rich structure in the chiral anomaly transport, including the
negative magnetoresistance, the non-Ohmic behavior, the Esaki-Tsu peak, and
finally the resonant oscillation of the DC electric current as a function of
electric field, called the electric quantum oscillation. We argue that, going
beyond the usual behavior of linear response, the non-Ohmic behavior observed
in BiSb alloys can be regarded as a precursor to the occurrence of electric
quantum oscillation, which is both topologically and energetically protected in
Weyl semimetals.

###Observation of an Unusual Colossal Anisotropic Magnetoresistance Effect in an Antiferromagnetic Semiconductor|Huali Yang,Qing Liu,Zhaoliang Liao,Liang Si,Peiheng Jiang,Xiaolei Liu,Yanfeng Guo,Junjie Yin,Meng Wang,Zhigao Sheng,Yuxin Zhao,Zhiming Wang,Zhicheng Zhong,Run-Wei Li###

Observation of an Unusual Colossal Anisotropic Magnetoresistance Effect in an Antiferromagnetic Semiconductor. Searching for novel antiferromagnetic materials with large magnetotransport
response is highly demanded for constructing future spintronic devices with
high stability, fast switching speed, and high density. Here we report a
colossal anisotropic magnetoresistance effect in an antiferromagnetic binary
compound with layered structure rare-earth dichalcogenide EuTe2. The AMR
reaches 40000%, which is 4 orders of magnitude larger than that in conventional
antiferromagnetic alloys. Combined magnetization, resistivity, and theoretical
analysis reveal that the colossal AMR effect is attributed to a novel mechanism
of vector-field tunable band structure, rather than the conventional spin-orbit
coupling mechanism. Moreover, it is revealed that the strong hybridization
between orbitals of Eu-layer with localized spin and Te-layer with itinerant
carriers is extremely important for the large AMR effect. Our results suggest a
new direction towards exploring AFM materials with prominent magnetotransport
properties, which creates an unprecedented opportunity for AFM spintronics
applications.

###Self-induced spin-orbit torques in metallic ferromagnets|Hector Ochoa,Ricardo Zarzuela,Yaroslav Tserkovnyak###

Self-induced spin-orbit torques in metallic ferromagnets. We present a phenomenological theory of spin-orbit torques in a metallic
ferromagnet with spin-relaxing boundaries. The model is rooted in the coupled
diffusion of charge and spin in the bulk of the ferromagnet, where we account
for the anomalous Hall effects as well as the anisotropic magnetoresistance in
the corresponding constitutive relations for both charge and spin sectors. The
diffusion equations are supplemented with suitable boundary conditions
reflecting the spin-sink capacity of the environment. In inversion-asymmetric
heterostructures, the uncompensated spin accumulation exerts a dissipative
torque on the order parameter, giving rise to a current-dependent linewidth in
the ferromagnetic resonance with a characteristic angular dependence. We
compare our model to recent spin-torque ferromagnetic resonance measurements,
illustrating how rich self-induced spin-torque phenomenology can arise even in
simple magnetic structures.

###Signatures of a Quantum Griffiths Phase close to an Electronic Nematic Quantum Phase Transition|Pascal Reiss,David Graf,Amir A. Haghighirad,Thomas Vojta,Amalia I. Coldea###

Signatures of a Quantum Griffiths Phase close to an Electronic Nematic Quantum Phase Transition. In the vicinity of a quantum critical point, quenched disorder can lead to a
quantum Griffiths phase, accompanied by an exotic power-law scaling with a
continuously varying dynamical exponent that diverges in the zero-temperature
limit. Here, we investigate a nematic quantum critical point in the iron-based
superconductor FeSe$_{0.89}$S$_{0.11}$ using applied hydrostatic pressure. We
report an unusual crossing of the magnetoresistivity isotherms in the
non-superconducting normal state which features a continuously varying
dynamical exponent over a large temperature range. We interpret our results in
terms of a quantum Griffiths phase caused by nematic islands that result from
the local distribution of Se and S atoms. At low temperatures, the Griffiths
phase is masked by the emergence of a Fermi liquid phase due to a strong
nematoelastic coupling and a Lifshitz transition that changes the topology of
the Fermi surface.

###Spin-orbit torque characterization in a nutshell|Minh-Hai Nguyen,Chi-Feng Pai###

Spin-orbit torque characterization in a nutshell. Spin current and spin torque generation through the spin-orbit interactions
in solids, of bulk or interfacial origin, is at the heart of spintronics
research. The realization of spin-orbit torque (SOT) driven magnetic dynamics
and switching in diverse magnetic heterostructures also pave the way for
developing SOT magnetoresistive random access memory and other novel SOT memory
and logic devices. Of scientific and technological importance are accurate and
efficient SOT quantification techniques, which have been abundantly developed
in the last decade. In this article, we summarize popular techniques to
experimentally quantify SOTs in magnetic heterostructures at micro- and
nano-scale. For each technique, we give an overview of its principle,
variations, strengths, shortcomings, error sources, and any cautions in usage.
Finally, we discuss the remaining challenges in understanding and quantifying
the SOTs in heterostructures.

###Current-induced magnetization dynamics in single and double layer magnetic nanopillars grown by molecular beam epitaxy|N. Müsgens,E. Maynicke,M. Weidenbach,C. J. P. Smits,M. Bückins,J. Mayer,B. Beschoten,G. Güntherodt###

Current-induced magnetization dynamics in single and double layer magnetic nanopillars grown by molecular beam epitaxy. Molecular beam epitaxy is used to fabricate magnetic single and double layer
junctions which are deposited in prefabricated nanostencil masks. For all Co |
Cu | Co double layer junctions we observe a stable intermediate resistance
state which can be reached by current starting from the parallel configuration
of the respective ferromagnetic layers. The generation of spin waves is
investigated at room temperature in the frequency domain by spectrum analysis,
demonstrating both in-plane and out-of-plane precessions of the magnetization
of the free magnetic layer. Current-induced magnetization dynamics in magnetic
single layer junctions of Cu | Co | Cu has been investigated in magnetic fields
which are applied perpendicular to the magnetic layer. We find a hysteretic
switching in the current sweeps with resistance changes significantly larger
than the anisotropic magnetoresistance effect.

###Effective strain manipulation of the antiferromagnetic state of polycrystalline NiO|A. Barra,A. Ross,O. Gomonay,L. Baldrati,A. Chavez,R. Lebrun,J. D. Schneider,P. Shirazi,Q. Wang,J. Sinova,G. P. Carman,M. Kläui###

Effective strain manipulation of the antiferromagnetic state of polycrystalline NiO. As a candidate material for applications such as magnetic memory,
polycrystalline antiferromagnets offer the same robustness to external magnetic
fields, THz spin dynamics, and lack of stray field as their single crystalline
counterparts, but without the limitation of epitaxial growth and lattice
matched substrates. Here, we first report the detection of the average Neel
vector orientiation in polycrystalline NiO via spin Hall magnetoresistance
(SMR). Secondly, by applying strain through a piezo-electric substrate, we
reduce the critical magnetic field required to reach a saturation of the SMR
signal, indicating a change of the anisotropy. Our results are consistent with
polycrystalline NiO exhibiting a positive sign of the in-plane
magnetostriction. This method of anisotropy-tuning offers an energy efficient,
on-chip alternative to manipulate a polycrystalline antiferromagnets magnetic
state.

###Theory of spin-Hall magnetoresistance in the AC (terahertz) regime|David A. Reiss,Tobias Kampfrath,Piet W. Brouwer###

Theory of spin-Hall magnetoresistance in the AC (terahertz) regime. In bilayers consisting of a normal metal (N) with spin-orbit coupling and a
ferromagnet (F), the combination of the spin-Hall effect, the spin-transfer
torque, and the inverse spin-Hall effect gives a small correction to the
in-plane conductivity of N, which is referred to as spin-Hall magnetoresistance
(SMR). We here present a theory of the SMR and the associated off-diagonal
conductivity corrections for frequencies up to the terahertz regime. We show
that the SMR signal has pronounced singularities at the spin-wave frequencies
of F, which identifies it as a potential tool for all-electric spectroscopy of
magnon modes. A systematic change of the magnitude of the SMR at lower
frequencies is associated with the onset of a longitudinal magnonic
contribution to spin transport across the F-N interface.

###Spin transfer torque and anisotropic conductance in spin orbit coupled graphene|Morteza Salehi,Razieh Beiranvand,Mohammad Alidoust###

Spin transfer torque and anisotropic conductance in spin orbit coupled graphene. We theoretically study spin-transfer torque (STT) in a graphene system with
spin-orbit coupling (SOC). We consider a graphene-based junction where the
spin-orbit coupled region is sandwiched between two ferromagnetic (F) segments.
The magnetization in each ferromagnetic segment can possess arbitrary
orientations. Our results show that the presence of SOC results in
anisotropically modified STT, magnetoresistance, and charge conductance as a
function of relative magnetization misalignment in the F regions. We have found
that within the Klein regime, where particles hit the interfaces
perpendicularly, the spin-polarized Dirac fermions transmit perfectly through
the boundaries of an F-F junction (i.e., with zero reflection), regardless of
the relative magnetization misalignment and exert zero STT. In the presence of
SOC, however, due to band structure modification, a nonzero STT reappears. Our
findings can be exploited for experimentally examining proximity-induced SOC
into a graphene system

###Magnetoresistance driven by the magnetic Berezinskii-Kosterlitz-Thouless transition|B. Flebus###

Magnetoresistance driven by the magnetic Berezinskii-Kosterlitz-Thouless transition. While the Berezinskii-Kosterlitz-Thouless transition (BKT) has been under
intense scrutiny for decades, unambiguous experimental signatures in magnetic
systems remain elusive. Here, we investigate the interplay between electronic
and magnetic degrees of freedom near the BKT transition. Focusing on a metal
with easy-plane ferromagnetic order, we establish a framework that accounts
both for the coupling between the charge current and the flow of topological
magnetic defects and for electron scattering on their inhomogeneous spin
texture. We show that electron scattering is responsible for a
temperature-dependent magnetoresistance effect scaling as the density of the
topological defects, which is expected to increase dramatically above the BKT
transition temperature. Our findings call for further experimental
investigations.

###Localization of the Helical Edge States in the Absense of External Magnetic Field|A. V. Bubis,N. N. Mikhailov,S. A. Dvoretsky,A. G. Nasibulin,E. S. Tikhonov###

Localization of the Helical Edge States in the Absense of External Magnetic Field. Theoretically, the helical edge states of two-dimensional topological
insulators are protected from coherent backscattering due to nonmagnetic
disorder provided electron interactions are not too strong. Experimentally, the
edges typically do not demonstrate the systematic and robust quantization, at
the same time little is known about the sub-Kelvin temperature behavior. Here,
we report the surprising localization of the edge states in an 8 nm HgTe
quantum well in zero magnetic field at millikelvin temperatures. Additionally,
the magnetoresistance data at 0.5 K for the edges few micrometers long suggests
the field-dependent localization length $l_B\propto B^{-\alpha}$, with $\alpha$
ranging approximately from $1.6$ to $2.8$ at fields $B\lesssim0.1\,\text{T}$
and $\alpha\approx1.1$ at higher fields up to $0.5\,\text{T}$. In the frame of
disordered interacting edge, these values of $\alpha$ correspond to the
Luttinger liquid parameters $K\approx 0.9-1.1$ and $K\approx 0.6$,
respectively. We discuss possible scenarios which could result in the zero
magnetic field localization.

###Arrested phase separation in double-exchange models: machine-learning enabled large-scale simulation|Puhan Zhang,Gia-Wei Chern###

Arrested phase separation in double-exchange models: machine-learning enabled large-scale simulation. We present large-scale dynamical simulations of electronic phase separation
in the single-band double-exchange model based on deep-learning neural-network
potentials trained from small-size exact diagonalization solutions. We uncover
an intriguing correlation-induced freezing behavior as doped holes are
segregated from half-filled insulating background during equilibration. While
the aggregation of holes is stabilized by the formation of ferromagnetic
clusters through Hund's coupling between charge carriers and local magnetic
moments, this stabilization also creates confining potentials for holes when
antiferromagnetic spin-spin correlation is well developed in the background.
The dramatically reduced mobility of the self-trapped holes prematurely
disrupts further growth of the ferromagnetic clusters, leading to an arrested
phase separation. Implications of our findings for phase separation dynamics in
materials that exhibit colossal magnetoresistance effect are discussed.

###Spatio-temporal dynamics of voltage-induced resistance transition in the double-exchange model|Gia-Wei Chern###

Spatio-temporal dynamics of voltage-induced resistance transition in the double-exchange model. We present multi-scale dynamical simulations of voltage-induced
insulator-to-metal transition in the double exchange model, a canonical example
of itinerant magnet and correlated electron systems. By combining
nonequilibrium Green's function method with large-scale Landau-Lifshitz-Gilbert
dynamics, we show that the transition from an antiferromagnetic insulator to
the low-resistance state is initiated by the nucleation of a thin ferromagnetic
conducting layer at the anode. The metal-insulator interface separating the two
phases is then driven toward the opposite electrode by the voltage stress,
giving rise to a growing metallic region. We further show that the initial
transformation kinetics is well described by the Kolmogorov-Avrami-Ishibashi
model with an effective spatial-dimension that depends on the applied voltage.
Implications of our findings for the resistive switching in colossal
magnetoresistant materials are also discussed.

###Transport properties around the metal-insulator transition for SrVO3 ultrathin films fabricated by electrochemical etching|Hikaru Okuma,Yumiko Katayama,Keisuke Otomo,Kazunori Ueno###

Transport properties around the metal-insulator transition for SrVO3 ultrathin films fabricated by electrochemical etching. By using electrochemical etching, we fabricated conductive ultrathin SrVO3
(SVO) films that exhibited metallic behavior down to 3 monolayers (ML). From an
observed systematic change in transport properties with decreasing film
thickness, it was found that the disorder in the films remained nearly
unchanged during etching, and only the thickness was reduced. This is in
contrast to the insulating behavior found for as-deposited SVO ultrathin films.
For the etched films, the electron mobility at 200 K decreased with decreasing
film thickness below 10 ML, originating from an increased scattering rate and
electron effective mass near the metal-insulator transition. A slight upturn in
the resistivity and a positive magnetoresistance at low temperatures were
typically observed for the etched films down to 3 ML, which was explained by
weak anti-localization of electrons in a weakly disordered metal.

###A Compact Model for Scalable MTJ Simulation|Fernando García-Redondo,Pranay Prabhat,Mudit Bhargava,Cyrille Dray###

A Compact Model for Scalable MTJ Simulation. This paper presents a physics-based modeling framework for the analysis and
transient simulation of circuits containing Spin-Transfer Torque (STT) Magnetic
Tunnel Junction (MTJ) devices. The framework provides the tools to analyze the
stochastic behavior of MTJs and to generate Verilog-A compact models for their
simulation in large VLSI designs, addressing the need for an industry-ready
model accounting for real-world reliability and scalability requirements.
Device dynamics are described by the Landau-Lifshitz-Gilbert-Slonczewsky
(s-LLGS ) stochastic magnetization considering Voltage-Controlled Magnetic
Anisotropy (VCMA) and the non-negligible statistical effects caused by thermal
noise. Model behavior is validated against the OOMMF magnetic simulator and its
performance is characterized on a 1-Mb 28 nm Magnetoresistive-RAM (MRAM) memory
product.

###Spin pumping and inverse spin Hall effect in CoFeB/C$_{60}$ bilayers|Purbasha Sharangi,Braj Bhusan Singh,Sagarika Nayak,Subhankar Bedanta###

Spin pumping and inverse spin Hall effect in CoFeB/C$_{60}$ bilayers. Pure spin current based research is mostly focused on ferromagnet (FM)/heavy
metal (HM) system. Because of the high spin orbit coupling (SOC) these HMs
exhibit short spin diffusion length and therefore possess challenges for device
application. Low SOC (elements of light weight) and large spin diffusion length
make the organic semiconductors (OSCs) suitable for future spintronic
applications. From theoretical model it is explained that, due to $\pi$ -
$\sigma$ hybridization the curvature of the C$_{60}$ molecules may increase the
SOC strength. Here, we have investigated spin pumping and inverse spin hall
effect (ISHE) in CoFeB/C$_{60}$ bilayer system using coplanar wave guide based
ferromagnetic resonance (CPW-FMR) set-up. We have performed angle dependent
ISHE measurement to disentangle the spin rectification effects for example
anisotropic magnetoresistance, anomalous Hall effect etc. Further, effective
spin mixing conductance (g$_{eff}^{\uparrow\downarrow}$) and spin Hall angle
($\theta_{SH}$) for C$_{60}$ have been reported here. The evaluated value for
$\theta_{SH}$ is 0.055.

###Probing the Topological Surface States through Magnetoresistance and Ultrafast Charge Carrier Dynamics in (Bi/Sb)2Te3|Prince Sharma,Yogesh Kumar,V. P. S. Awana,Mahesh Kumar###

Probing the Topological Surface States through Magnetoresistance and Ultrafast Charge Carrier Dynamics in (Bi/Sb)2Te3. Topological insulators with their topological protected surface states are
highly promising quantum materials. In this article the micro-flakes of
single-crystalline topological insulators Bi2Te3 and Sb2Te3 are explored
through physical parameter measurement at low temperatures and thereby the
charge carrier dynamics are investigated at 5K to study the various optical
transitions related to these surface states. The magnetoresistance is
experimentally investigated at temperatures of 5K and 100K for a field range of
1Tesla. The occurrence of the weak anti-localization effect predicts the
presence of topologically protected surface states in the systems. Further, the
ultrafast femtosecond transient reflectance spectroscopy is performed at
different temperatures, varying from a room temperature (300K) to a low
temperature of 5K, to find the TSS related transitions at low temperatures.

###Signature of topological non-trivial band structure in Ta$_{3}$SiTe$_{6}$|Shubhankar Roy,Ratnadwip Singha,Arup Ghosh,Prabhat Mandal###

Signature of topological non-trivial band structure in Ta$_{3}$SiTe$_{6}$. The study of topology protected electronic properties is a fascinating topic
in present day condensed matter physics research. New topological materials are
frequently being proposed and explored through various experimental techniques.
Ta$_{3}$SiTe$_{6}$ is a newly predicted topological semimetal with fourfold
degenerate nodal-line crossing in absence of spin-orbit coupling (SOC) and an
hourglass Dirac loop, when SOC is included. Recent angle-resolved photoemission
spectroscopy study in this material, has also confirmed Dirac like dispersions
and two nodal-lines near the Fermi energy, protected by nonsymmorphic glide
mirror symmetry. In this work, we present the detailed magnetotransport
properties of single crystalline Ta$_{3}$SiTe$_{6}$. A nonsaturating
magnetoresistance has been observed. Hall measurements reveal hole type charge
carriers with high carrier density and a moderate value of carrier mobility.
Furthermore, we report a robust planar Hall effect, which persists up to high
temperatures. These results validate the nontrivial nature of the electronic
band structure.

###Identifying intrinsic and extrinsic mechanisms of anisotropic magnetoresistance with terahertz probes|Ji-Ho Park,Hye-Won Ko,Jeong-Mok Kim,Jungmin Park,Seung-Young Park,Younghun Jo,Byong-Guk Park,Se Kwon Kim,Kyung-Jin Lee,Kab-Jin Kim###

Identifying intrinsic and extrinsic mechanisms of anisotropic magnetoresistance with terahertz probes. Identifying the intrinsic and extrinsic origins of magneto-transport in
spin-orbit coupled systems has long been a central theme in condensed matter
physics. However, it has been elusive owing to the lack of an appropriate
experimental tool. In this work, using terahertz time-domain spectroscopy, we
unambiguously disentangle the intrinsic and extrinsic contributions to the
anisotropic magnetoresistance (AMR) of a permalloy film. We find that the
scattering-independent intrinsic contribution to AMR is sizable and is as large
as the scattering-dependent extrinsic contribution to AMR. Moreover, the
portion of intrinsic contribution to total AMR increases with increasing
temperature due to the reduction of extrinsic contribution. Further
investigation reveals that the reduction of extrinsic contribution is caused by
the phonon/magnon-induced negative AMR. Our result will stimulate further
researches on other spin-orbit-interaction-induced phenomena for which
identifying the intrinsic and extrinsic contributions is important.

###Electrically Controllable van der Waals Antiferromagnetic Spin Valve|Xue-Chao Zhai,Ziming,Xu,Qirui Cui,Yingmei Zhu,Hongxin Yang,Yaroslav M. Blanter###

Electrically Controllable van der Waals Antiferromagnetic Spin Valve. We propose a spin valve that is based on van der Waals antiferromagnetism and
fully electrically controlled. The device is composed of two antiferromagnetic
terminals that allow for vertical bias control and a linked central scattering
potential region. The magnetoresistance varies significantly when the bias
orientations in two terminals are switched from parallel to antiparallel
because this switch induces a mismatch of the bands for the same spin
projection in different parts of the system. It is shown from density
functional calculations that bilayer graphene encapsulated by two atomic layers
of Cr$_2$Ge$_2$Te$_6$ provides a material platform to realize the
antiferromagnetism, which is robust against the required vertical electric
fields.

###Shubnikov-de Haas Oscillations and Nontrivial Topological State in a New Weyl Semimetal Candidate SmAlSi|Longmeng Xu,Haoyu Niu,Yuming Bai,Haipeng Zhu,Songliu Yuan,Xiong He,Yang Yang,Zhengcai Xia,Lingxiao Zhao,Zhaoming Tian###

Shubnikov-de Haas Oscillations and Nontrivial Topological State in a New Weyl Semimetal Candidate SmAlSi. We perform the quantum magnetotransport measurements and first-principles
calculations on high quality single crystals of SmAlSi, a new topological Weyl
semimetal candidate. At low temperatures, SmAlSi exhibits large non-saturated
magnetoresistance (MR)~5200% (at 2 K, 48 T) and prominent Shubnikov-de Haas
(SdH) oscillations, where MRs follow the power-law field dependence with
exponent 1.52 at low fields ({\mu}0H < 15 T) and linear behavior 1 under high
fields ({\mu}0H > 18 T). The analysis of angle dependent SdH oscillations
reveal two fundamental frequencies originated from the Fermi surface (FS)
pockets with non-trivial {\pi} Berry phases, small cyclotron mass and
electron-hole compensation with high mobility at 2 K. In combination with the
calculated nontrivial electronic band structure, SmAlSi is proposed to be a
paradigm for understanding the Weyl fermions in the topological materials.

###Narrow-gap semiconducting behavior in antiferromagnetic Eu$_{11}$InSb$_9$|S. S. Fender,S. M. Thomas,F. Ronning,E. D. Bauer,J. D. Thompson,P. F. S. Rosa###

Narrow-gap semiconducting behavior in antiferromagnetic Eu$_{11}$InSb$_9$. Here we investigate the thermodynamic and electronic properties of
Eu$_{11}$InSb$_9$ single crystals. Electrical transport data show that
Eu$_{11}$InSb$_9$ has a semiconducting ground state with a relatively narrow
band gap of $320$~meV. Magnetic susceptibility data reveal antiferromagnetic
order at low temperatures, whereas ferromagnetic interactions dominate at high
temperature. Specific heat, magnetic susceptibility, and electrical resistivity
measurements reveal three phase transitions at $T_{N1}=9.3$~K, $T_{N2} =8.3$~K,
and $T_{N3} =4.3$~K. Unlike Eu$_{5}$In$_{2}$Sb$_6$, a related
europium-containing Zintl compound, no colossal magnetoresistance (CMR) is
observed in Eu$_{11}$InSb$_9$. We attribute the absence of CMR to the smaller
carrier density and the larger distance between Eu ions and In-Sb polyhedra in
Eu$_{11}$InSb$_9$. Our results indicate that Eu$_{11}$InSb$_9$ has potential
applications as a thermoelectric material through doping or as a
long-wavelength detector due to its narrow gap.

###Emergence of Ferromagnetism Through the Metal-Insulator Transition in Undoped Indium Tin Oxide Films|Samuel Mumford,Tiffany Paul,Aharon Kapitulnik###

Emergence of Ferromagnetism Through the Metal-Insulator Transition in Undoped Indium Tin Oxide Films. We present a detailed study of the emergence of bulk ferromagnetism in low
carrier density samples of undoped indium tin oxide (ITO). We used annealing to
increase the density of oxygen vacancies and change sample morphology without
introducing impurities through the metal insulator transition (MIT). We
utilized a novel and highly sensitive "Corbino-disk torque magnetometry"
technique to simultaneously measure the thermodynamic and transport effects of
magnetism on the same sample after successive annealing. With increased sample
granularity, carrier density increased, the sample became more metallic, and
ferromagnetism appeared as resistance approached the MIT. Ferromagnetism was
observed through the detection of magnetization hysteresis, anomalous Hall
effect (AHE), and hysteretic magnetoresistance. A sign change of the AHE as the
MIT is approached may elucidate the interplay between the impurity band and the
conduction band in the weakly insulating side of the MIT.

###Large Magnetoresistance and Nontrivial Berry Phase in Nb3Sb Crystals with A15 Structure|Qin Chen,Yuxing Zhou,Binjie Xu,Zhefeng Lou,Huancheng Chen,Shuijin Chen,Chunxiang Wu,Jianhua Du,Hangdong Wang,Jinhu Yang,Minghu Fang###

Large Magnetoresistance and Nontrivial Berry Phase in Nb3Sb Crystals with A15 Structure. Compounds with the A15 structure have attracted extensive attention due to
their superconductivity and nontrivial topological band structure. We have
successfully grown Nb$_3$Sb single crystals with a A15 structure and
systematically measured the longitudinal resistivity, Hall resistivity and
quantum oscillations in magnetization. Similar to other topological
trivial/nontrivial semimetals, Nb$_3$Sb, exhibits large magnetoresistance (MR)
at low temperatures (717$\%$, 2 K and 9 T), unsaturating quadratic field
dependence of MR and up-turn behavior in $\rho_{xx}$(\emph{T}) curves under
magnetic field, which is considered to result from a perfect hole-electron
compensation, as evidenced by the Hall resistivity measurements. The nonzero
Berry phase obtained from the de-Hass van Alphen (dHvA) oscillations
demonstrates that Nb$_3$Sb is topologically nontrivial. These results indicate
that Nb$_{3}$Sb superconductor is also a semimetal with large MR and nontrivial
Berry phase, indicating that Nb$_{3}$Sb may be another platform to search for
Majorana zero-energy mode.

###Terahertz charge and spin transport in metallic ferromagnets: the role of crystalline and magnetic order|Kumar Neeraj,Apoorva Sharma,Maria Almeida,Patrick Matthes,Fabian Samad,Georgeta Salvan,Olav Hellwig,Stefano Bonetti###

Terahertz charge and spin transport in metallic ferromagnets: the role of crystalline and magnetic order. We study the charge and spin dependent scattering in a set of CoFeB thin
films whose crystalline order is systematically enhanced and controlled by
annealing at increasingly higher temperatures. Terahertz conductivity
measurements reveal that charge transport closely follows the development of
the crystalline phase, with increasing structural order leading to higher
conductivity. The terahertz-induced ultrafast demagnetization, driven by
spin-flip scattering mediated by the spin-orbit interaction, is measurable in
the pristine amorphous sample and much reduced in the sample with highest
crystalline order. Surprisingly, the largest demagnetization is observed at
intermediate annealing temperatures, where the enhancement in spin-flip
probability is not associated with an increased charge scattering. We are able
to correlate the demagnetization amplitude with the magnitude of the in-plane
magnetic anisotropy, which we characterize independently, suggesting a
magnetoresistance-like description of the phenomenon.

###Field-induced multiple metal-insulator crossovers of correlated Dirac electrons of perovskite CaIrO$_3$|R. Yamada,J. Fujioka,M. Kawamura,S. Sakai,M. Hirayama,R. Arita,T. Okawa,D. Hashizume,T. Sato,F. Kagawa,R. Kurihara,M. Tokunaga,Y. Tokura###

Field-induced multiple metal-insulator crossovers of correlated Dirac electrons of perovskite CaIrO$_3$. The interplay between electron correlation and topology of relativistic
electrons may lead to a new stage of the research on quantum materials and
emergent functions. The emergence of various collective electronic
orderings/liquids, which are tunable by external stimuli, is a remarkable
feature of correlated electron systems, but has rarely been realized in the
topological semimetals with high-mobility relativistic electrons. Here, we
report that the correlated Dirac electrons with the Mott criticality in
perovskite CaIrO$_3$ show unconventional field-induced successive
metal-insulator-metal crossovers in the quantum limit accompanying a giant
magnetoresistance (MR) with MR ratio of 3,500 % (18 T and 1.4 K). The analysis
shows that the insulating state originates from the collective electronic
ordering such as charge/spin density wave promoted by electron correlation,
whereas it turns into the quasi-one-dimensional metal at higher fields due to
the field-induced reduction of chemical potential, highlighting the highly
field-sensitive character of correlated Dirac electrons.

###Crucial role of interfacial $s$-$d$ exchange interaction in the temperature dependence of tunnel magnetoresistance|Keisuke Masuda,Terumasa Tadano,Yoshio Miura###

Crucial role of interfacial $s$-$d$ exchange interaction in the temperature dependence of tunnel magnetoresistance. The tunnel magnetoresistance (TMR) is one of the most important spintronic
phenomena but its reduction at finite temperature is a severe drawback for
applications. Here, we reveal a crucial determinant of the drawback, that is,
the $s$-$d$ exchange interaction between conduction $s$ and localized $d$
electrons at interfacial ferromagnetic layers. By calculating the temperature
dependence of the TMR ratio in Fe/MgO/Fe(001), we show that the obtained TMR
ratio significantly decreases with increasing temperature owing to the
spin-flip scattering in the $\Delta_1$ state induced by the $s$-$d$ exchange
interaction. The material dependence of the coupling constant $J_{sd}$ is also
discussed on the basis of a nonempirical method.

###On dielectric screening in twisted double bilayer graphene|Fumiya Mukai,Kota Horii,Nazuna Hata,Ryoya Ebisuoka,Kenji Watanabe,Takashi Taniguchi,Ryuta Yagi###

On dielectric screening in twisted double bilayer graphene. We have studied the dielectric screening of electric field which is induced
by a gate voltage in twisted double bilayer graphene by using a sample with a
mismatch angle of about 5 degrees. In low temperature magnetotransport
measurements, quantum oscillations of magnetoresistance originating from two
bands with different carrier density were observed. The behavior of the carrier
densities with respect to the total carrier density were distinct from that of
the AB-stacked tetralayer graphene. The carrier density ratio was theoretically
analyzed in terms of the model that the induced charge decays exponentially
with distance with a screening length {\lambda}. The estimated {\lambda} was
slightly larger than that of AB-stacked graphene, which would possibly reflect
the difference in the inter-plane distribution of probability of the wave
function.

###Giant Piezospintronic Effect in a Noncollinear Antiferromagnetic Metal|Huixin Guo,Zexin Feng,Han Yan,Jiuzhao Liu,Jia Zhang,Xiaorong Zhou,Peixin Qin,Jialin Cai,Zhongming Zeng,Xin Zhang,Xiaoning Wang,Hongyu Chen,Haojiang Wu,Chengbao Jiang,Zhiqi Liu###

Giant Piezospintronic Effect in a Noncollinear Antiferromagnetic Metal. One of the main bottleneck issues for room-temperature antiferromagnetic
spintronic devices is the small signal read-out owing to the limited
anisotropic magnetoresistance in antiferromagnets. However, this could be
overcome by either utilizing the Berry-curvature-induced anomalous Hall
resistance in noncollinear antiferromagnets or establishing tunnel junction
devices based on effective manipulation of antiferromagnetic spins. In this
work, we demonstrate the giant piezoelectric strain control of the spin
structure and the anomalous Hall resistance in a noncollinear antiferromagnetic
metal - D019 hexagonal Mn3Ga. Furthermore, we built tunnel junction devices
with a diameter of 200 nm to amplify the maximum tunneling resistance ratio to
more than 10% at room-temperature, which thus implies significant potential of
noncollinear antiferromagnets for large signal-output and high-density
antiferromagnetic spintronic device applications.

###Electric-Field-Controlled Antiferromagnetic Spintronic Devices|Han Yan,Zexin Feng,Peixin Qin,Xiaorong Zhou,Huixin Guo,Xiaoning Wang,Hongyu Chen,Xin Zhang,Haojiang Wu,Chengbao Jiang,Zhiqi Liu###

Electric-Field-Controlled Antiferromagnetic Spintronic Devices. In recent years, the field of antiferromagnetic spintronics has been
substantially advanced. Electric-field control is a promising approach to
achieving ultra-low power spintronic devices via suppressing Joule heating. In
this article, cutting-edge research, including electric-field modulation of
antiferromagnetic spintronic devices using strain, ionic liquids, dielectric
materials, and electrochemical ionic migration, are comprehensively reviewed.
Various emergent topics such as the Neel spin-orbit torque, chiral spintronics,
topological antiferromagnetic spintronics, anisotropic magnetoresistance,
memory devices, two-dimensional magnetism, and magneto-ionic modulation with
respect to antiferromagnets are examined. In conclusion, we envision the
possibility of realizing high-quality room-temperature antiferromagnetic tunnel
junctions, antiferromagnetic spin logic devices, and artificial
antiferromagnetic neurons. It is expected that this work provides an
appropriate and forward-looking perspective that will promote the rapid
development of this field.

###Three-dimensional chiral Veselago lensing|Serguei Tchoumakov,Jérôme Cayssol,Adolfo G. Grushin###

Three-dimensional chiral Veselago lensing. The effect by which light focuses upon entering a medium with a negative
refractive index, known as Veselago lensing, may enable optical imaging below
the diffraction limit. Similarly, focusing electrons across a $pn$-junction
could realize a technologically promising electronic Veselago lens. However,
its scope remains limited by the lack of three-dimensional platforms and its
insensitivity to computational degrees of freedom, like spin or chirality. Here
we propose a single-material three-dimensional electronic Veselago lens that
selectively focuses electrons of a given chirality. Using the chiral anomaly of
topological semimetals it is possible to create a sharp $pn$-junction for a
single chirality, a chiral Veselago lens, and tune it with a magnetic field to
an ideal lensing condition. We estimate that chiral Veselago lensing is
observable in non-local transport and spectroscopy experiments. In particular
we show that the chiral Veselago lens leads to giant non-local
magnetoresistance.

###Anomalous Hall effect in ferrimagnetic metal RMn6Sn6 (R = Tb, Dy, Ho) with clean Mn kagome lattice|Lingling Gao,Shiwei Shen,Qi Wang,Wujun Shi,Yi Zhao,Changhua Li,Weizheng Cao,Cuiying Pei,Jun-Yi Ge,Gang Li,Jun Li,Yulin Chen,Shichao Yan,Yanpeng Qi###

Anomalous Hall effect in ferrimagnetic metal RMn6Sn6 (R = Tb, Dy, Ho) with clean Mn kagome lattice. Kagome lattice, made of corner-sharing triangles, provides an excellent
platform for hosting exotic topological quantum states. Here we systematically
studied the magnetic and transport properties of RMn6Sn6 (R = Tb, Dy, Ho) with
clean Mn kagome lattice. All the compounds have a collinear ferrimagnetic
structure with different easy axis at low temperature. The low-temperature
magnetoresistance (MR) is positive and has no tendency to saturate below 7 T,
while the MR gradually declines and becomes negative with the increasing
temperature. A large intrinsic anomalous Hall conductivity about 250
{\Omega}-1cm-1, 40 {\Omega}-1cm-1, 95 {\Omega}-1cm-1 is observed for TbMn6Sn6,
DyMn6Sn6, HoMn6Sn6, respectively. Our results imply that RMn6Sn6 system is an
excellent platform to discover other intimately related topological or quantum
phenomena and also tune the electronic and magnetic properties in future
studies.

###Unusual Magnetic Properties in Layered Magnetic Topological Insulator EuSn2As2|Huijie Li,Wenshuai Gao,Zheng Chen,Weiwei Chu,Yong Nie,Shuaiqi Ma,Yuyan Han,Min Wu,Tian Li,Qun Niu,Wei Ning,Xiangde Zhu,Mingliang Tian###

Unusual Magnetic Properties in Layered Magnetic Topological Insulator EuSn2As2. EuSn2As2 with layered rhombohedral crystal structure is proposed to be a
candidate of intrinsic antiferromagnetic (AFM) topological insulator. Here, we
have investigated systematic magnetoresistance (MR) and magnetization
measurements on the high quality EuSn2As2 single crystal with the magnetic
field both parallel and perpendicular to (00l) plane. Both the kink of magnetic
susceptibility and longitudinal resistivity reveal that EuSn2An2 undergoes an
AFM transition at TN = 21 K. At T = 2 K, the magnetization exhibits two
successive plateaus of ~ 5.6 {\mu}B/Eu and ~ 6.6 {\mu}B/Eu at the corresponding
critical magnetic fields. Combined with the negative longitudinal MR and
abnormal Hall resistance, we demonstrate that EuSn2An2 undergoes complicated
magnetic transitions from an AFM state to a canted ferromagnetic (FM) state at
Hc and then to a polarized FM state at Hs as the magnetic field increase.

###Anisotropic MagnetoMemristance|Francesco Caravelli,Ezio Iacocca,Gia-Wei Chern,Cristiano Nisoli,Clodoaldo I. L. de Araujo###

Anisotropic MagnetoMemristance. In the last decade, nanoscale resistive devices with memory have been the
subject of intense study because of their possible use in brain-inspired
computing. However, operational endurance is one of the limiting factors in the
adoption of such technology. For this reason, we discuss the emergence of
current-induced memristance in magnetic materials, known for their durability.
We show analytically and numerically that a single ferromagnetic layer can
possess GHz memristance, due to a combination of two factors: a current-induced
transfer of angular momentum (Zhang-Li torque) and the anisotropic
magnetoresistance (AMR). We term the resulting effect the anisotropic
magneto-memristance (AMM). We connect the AMM to the topology of the
magnetization state, within a simple model of a 1-dimensional annulus-shaped
magnetic layer, confirming the analytical results with micromagnetic
simulations for permalloy. Our results open a new path towards the realization
of single-layer magnetic memristive devices operating at GHz frequencies.

###Roller-Coaster in a Flatland: Magnetoresistivity in Eu-intercalated Graphite|A. L. Chernyshev,O. A. Starykh###

Roller-Coaster in a Flatland: Magnetoresistivity in Eu-intercalated Graphite. Novel phenomena in magnetically-intercalated graphite has been a subject of
much research, pioneered and promoted by M.~S. and G.~Dresselhaus and many
others in the 1980s. Among the most enigmatic findings of that era was a
dramatic, roller-coaster-like behavior of the magnetoresistivity in EuC$_6$
compound, in which magnetic Eu$^{2+}$ ions form a triangular lattice that is
commensurate to graphite honeycomb planes. In this study, we provide a
long-awaited {\it microscopic} explanation of this behavior, demonstrating that
the resistivity of EuC$_6$ is dominated by spin excitations in Eu-planes and
their highly nontrivial evolution with the magnetic field. Together with our
theoretical analysis, the present study showcases the power of the synthetic 2D
materials as a source of potentially significant insights into the nature of
exotic spin excitations.

###Transport anomalies in the layered compound BaPt4Se6|Sheng Li,Yichen Zhang,Hanlin Wu,Huifei Zhai,Wenhao Liu,Daniel Peirano Petit,Ji Seop Oh,Jonathan Denlinger,Gregory T. McCandless,Julia Y. Chan,Robert J. Birgeneau,Gang Li,Ming Yi,Bing Lv###

Transport anomalies in the layered compound BaPt4Se6. We report a layered ternary selenide BaPt4Se6 featuring sesqui-selenide
Pt2Se3 layers sandwiched by Ba atoms. The Pt2Se3 layers in this compound can be
derived from the Dirac-semimetal PtSe2 phase with Se vacancies that form a
honeycomb structure. This structure results in a Pt (VI) and Pt (II)
mixed-valence compound with both PtSe6 octahedra and PtSe4 square net
coordination configurations. Temperature dependent electrical transport
measurements suggest two distinct anomalies: a resistivity crossover, mimic to
the metal-insulator (M-I) transition at ~150K, and a resistivity plateau at
temperatures below 10K. The resistivity crossover is not associated with any
structural, magnetic or charge order modulated phase transitions.
Magnetoresistivity, Hall and heat capacity measurements concurrently suggest an
existing hidden state below 5K in this system. Angle-resolved photoemission
spectroscopy measurements reveal a metallic state and no dramatic
reconstruction of the electronic structure up to 200K.

###Magneto-Seebeck effect and ambipolar Nernst effect in CsV$_3$Sb$_5$ superconductor|Yuhan Gan,Wei Xia,Long Zhang,Kunya Yang,Xinrun Mi,Aifeng Wang,Yisheng Chai,Yanfeng Guo,Xiaoyuan Zhou,Mingquan He###

Magneto-Seebeck effect and ambipolar Nernst effect in CsV$_3$Sb$_5$ superconductor. We present a study of Seebeck and Nernst effect in combination with
magnetoresistance and Hall measurements of the Kagome superconductor
CsV$_3$Sb$_5$. Sizable magneto-Seebeck signal appears once the charge density
wave (CDW) order sets in below $T_{CDW}$=94 K. The Nernst signal peaks at a
lower temperature $T^*$=35 K, crossing which the Hall coefficient switches
sign, which we attribute to the ambipolar transport of compensated bands due to
the multi-band nature of CsV$_3$Sb$_5$. Sublinear Nernst signal as a function
of magnetic field, together with large anomalous Nernst effect (ANE) also
emerge inside the CDW phase, despite the absence of long-range magnetic order.
These findings suggest that, the transport properties are dominated by small
pockets with multi-band profile, and that the unusual band topology also plays
an import role in the CDW state of CsV$_3$Sb$_5$.

###Electron transport in folded bilayer-bilayer graphene/hexagonal boron nitride superlattices under high magnetic fields|Takuya Iwasaki,Motoi Kimata,Yoshifumi Morita,Shu Nakaharai,Yutaka Wakayama,Eiichiro Watanabe,Daiju Tsuya,Kenji Watanabe,Takashi Taniguchi,Satoshi Moriyama###

Electron transport in folded bilayer-bilayer graphene/hexagonal boron nitride superlattices under high magnetic fields. Employing graphene as a template, we fabricate moir\'e superlattices by
stacking bilayer or folded bilayer-bilayer graphene (BLG or fBBLG) and
hexagonal boron nitride (hBN), i.e., hBN/BLG/hBN or hBN/fBBLG/hBN stacks, with
a small twist angle between the graphene and one of the two hBN layers. Because
of the modulation due to the hBN, higher-generation Dirac points can emerge
with a narrow bandwidth and van Hove singularities. In the moir\'e superlattice
devices, we can therefore access the higher-generation Dirac points by in-situ
gate tuning. This study is based on our previous paper (Appl. Phys. Express 13,
035003 (2020)). Here we show more extended data by applying high magnetic
fields up to ~24 T. We also comment on the temperature dependence of the
resistivity and magnetoresistance with reference to the 'plain' BLG data for a
comparative study.

###Threshold behavior in spin lasers: Spontaneous emission and nonlinear gain|Gaofeng Xu,Krish Patel,Igor Žutić###

Threshold behavior in spin lasers: Spontaneous emission and nonlinear gain. A hallmark of spin-lasers, injected with spin-polarized carriers, is their
threshold behavior with the onset of stimulated emission. Unlike the single
threshold in conventional lasers with unpolarized carriers, two thresholds are
expected in spin lasers. With the progress in scaled-down lasers and the use of
novel two-dimensional materials it is unclear if the common description of spin
lasers assuming a negligible spontaneous emission and linear optical gain
remains relevant or even how to identify the lasing thresholds. Our
rate-equation description addresses these questions by considering a large
spontaneous emission and a nonlinear optical gain. We provide a transparent
approach and analytical results to explore the resulting threshold behavior,
its deviation from the prior studies, as well as guide future spin-lasers as a
versatile platform for spintronics beyond magnetoresistance.

###Ballistic magnetotransport in graphene|Ke Wang,T. A. Sedrakyan###

Ballistic magnetotransport in graphene. We report that a perpendicular magnetic field introduces an anomalous
interaction correction, $\delta \sigma$, to the static conductivity of doped
graphene in the ballistic regime. The correction implies that the
magnetoresistance, $\delta \rho_{xx}$ scales inversely with temperature $\delta
\rho_{xx}(T) \propto 1/T$ in a parametrically large interval. When the disorder
is scalar-like, the $\propto 1/T$ behavior is the leading contribution in the
crossover between diffusive regime exhibiting weak localization and quantum
magnetooscillations. The behavior originates from the field-induced breaking of
the chiral symmetry of Dirac electrons around a single valley. The result is
specific for generic two-dimensional Dirac materials which deviate from the
half-filling. We conclude by proposing magnetotransport experiments, which have
the capacity to detect the nature of impurities and defects in high-mobility
Dirac monolayers such as recently fabricated ballistic graphene samples.

###Higher-order Oscillatory Planar Hall Effect in Topological Kagome Metal|Leyi Li,Enkui Yi,Bin Wang,Guoqiang Yu,Bing Shen,Zhongbo Yan,Meng Wang###

Higher-order Oscillatory Planar Hall Effect in Topological Kagome Metal. Exploration of exotic transport behavior for quantum materials is of great
interest and importance for revealing exotic orders to bring new physics. In
this Letter, we report the observation of exotic prominent planar Hall effect
(PHE) and planar anisotropic magnetoresistivity (PAMR) in strange kagome metal
KV$_3$Sb$_5$. The PHE and PAMR, which are driven by an in-plane magnetic field
and display sharp difference from other Hall effects driven by an out-of-plane
magnetic field or magnetization, exhibit exotic higher-order oscillations in
sharp contrast to those following empirical rule only allowing twofold
symmetrical oscillations. These higher-order oscillations exhibit strong field
and temperature dependence and vanish around charge density wave (CDW)
transition. The unique transport properties suggest a significant interplay of
the lattice, magnetic and electronic structure in KV$_3$Sb$_5$. This interplay
can couple the hidden anisotropy and transport electrons leading to the novel
PHE and PAMR in contrast to other materials.

###Bulk Rashba spin splitting and Dirac surface state in $p$-type (Bi$_{0.9}$Sb$_{0.1})_2$Se$_3$ single crystal|P. K. Ghose,S. Bandyopadhyay,T. K. Dalui,J. -C. Tseng,J. K. Dey,R. Tomar,S. Chakraverty,S. Majumdar,I. Dasgupta,S. Giri###

Bulk Rashba spin splitting and Dirac surface state in $p$-type (Bi$_{0.9}$Sb$_{0.1})_2$Se$_3$ single crystal. We report bulk Rashba spin splitting (RSS) and associated Dirac surface state
in (Bi$_{0.9}$Sb$_{0.1})_2$Se$_3$, exhibiting dominant $p$-type conductivity.
We argue from the synchrotron diffraction studies that origin of the bulk RSS
is due to a structural transition to a non-centrosymmetric $R3m$ phase below
$\sim$ 30 K. The Shubnikov-de Haas Van (SdH) oscillations observed in the
magnetoresistance curves at low temperature and the Landau level fan diagram,
as obtained from these oscillations, confirm the presence of nontrivial Dirac
surface state. The magnetization data at low temperature exhibit substantial
orbital magnetization consistent with the bulk RSS. The existance of both the
bulk RSS and Dirac surface states are confirmed by first principles density
functional theory calculations. Coexistence of orbital magnetism, bulk RSS, and
Dirac surface state is unique for $p$-type (Bi$_{0.9}$Sb$_{0.1})_2$Se$_3$,
making it an ideal candidate for spintronic applications.

###Graphene's non-equilibrium fermions reveal Doppler-shifted magnetophonon resonances accompanied by Mach supersonic and Landau velocity effects|M. T. Greenaway,P. Kumaravadivel,J. Wengraf,L. A. Ponomarenko,A. I. Berdyugin. J. Li,J. H. Edgar,R. Krishna Kumar,A. K. Geim,L. Eaves###

Graphene's non-equilibrium fermions reveal Doppler-shifted magnetophonon resonances accompanied by Mach supersonic and Landau velocity effects. Oscillatory magnetoresistance measurements on graphene have revealed a wealth
of novel physics. These phenomena are typically studied at low currents. At
high currents, electrons are driven far from equilibrium with the atomic
lattice vibrations so that their kinetic energy can exceed the thermal energy
of the phonons. Here, we report three non-equilibrium phenomena in monolayer
graphene at high currents: (i) a "Doppler-like" shift and splitting of the
frequencies of the transverse acoustic (TA) phonons emitted when the electrons
undergo inter-Landau level (LL) transitions; (ii) an intra-LL Mach effect with
the emission of TA phonons when the electrons approach supersonic speed, and
(iii) the onset of elastic inter-LL transitions at a critical carrier drift
velocity, analogous to the superfluid Landau velocity. All three quantum
phenomena can be unified in a single resonance equation. They offer avenues for
research on out-of-equilibrium phenomena in other two-dimensional fermion
systems.

###A Heavy-Fermion Zn-deficient CaBe2Ge2-Type Phase with Rare Ce-based Ferromagnetism and Large Magnetoresistance|Robin Lefèvre,Fabian O von Rohr###

A Heavy-Fermion Zn-deficient CaBe2Ge2-Type Phase with Rare Ce-based Ferromagnetism and Large Magnetoresistance. We report on the hitherto unknown compound CeZn2-dGe2 (d approx 0.41). We
find this compound to crystallize in a defect version of the well-known
CaBe2Ge2 structure type. The phase forms in a Zn/In flux and with Zn-deficiency
on one of its crystallographic sites. We find the compound to display uncommon
localized Ce-based (4f1) ferromagnetism with a Tc = 6.6 K, a large positive
magnetoresistance reaching an MR of approximately 32 % below $T$ = 10 K, and
strongly correlated electrons, as evidenced by a Kadowaki-Woods ratio A/gamma^2
close to known heavy fermion compounds. The here discovered material is
therefore a promising model platform for the investigation of these entangled
interacting and potentially competing electronic states paired with complex
crystal chemistry.

###Evidence for unconventional superconductivity in a spinel oxide|Huanyi Xue,Lijie Wang,Zhongjie Wang,Guanqun Zhang,Wei Peng,Shiwei Wu,Chunlei Gao,Zhenghua An,Yan Chen,Wei Li###

Evidence for unconventional superconductivity in a spinel oxide. The charge frustration with the mixed-valence state inherent to
LiTi$_2$O$_4$, which is found to be a unique spinel oxide superconductor, is
the impetus for paying special attention to reveal the existence of intriguing
superconducting properties. Here, we report a pronounced fourfold rotational
symmetry of the superconductivity in high-quality single-crystalline
LiTi$_2$O$_4$ (001) thin films. Both the magnetoresistivity and upper critical
field under an applied magnetic field manifest striking fourfold oscillations
deep inside the superconducting state, whereas the anisotropy vanishes in the
normal state, demonstrating that it is an intrinsic property of the
superconducting phase. We attribute this behavior to the unconventional
$d$-wave superconducting Cooper pairs with the irreducible representation of
$E_g$ protected by $O_h$ point group in LiTi$_2$O$_4$. Our findings demonstrate
the unconventional character of the pairing interaction in a three-dimensional
spinel oxide superconductor and shed new light on the pairing mechanism of
unconventional superconductivity.

###Spatially-resolved electronic structure of stripe domains in IrTe$_2$ through electronic structure microscopy|Changhua Bao,Hongyun Zhang,Qian Li,Shaohua Zhou,Haoxiong Zhang,Ke Deng,Kenan Zhang,Laipeng Luo,Wei Yao,Chaoyu Chen,José Avila,Maria C. Asensio,Yang Wu,Shuyun Zhou###

Spatially-resolved electronic structure of stripe domains in IrTe$_2$ through electronic structure microscopy. Phase separation in the nanometer- to micrometer-scale is characteristic for
correlated materials, for example, high temperature superconductors, colossal
magnetoresistance manganites, Mott insulators, etc. Resolving the electronic
structure with spatially-resolved information is critical for revealing the
fundamental physics of such inhomogeneous systems yet this is challenging
experimentally. Here by using nanometer- and micrometer-spot angle-resolved
photoemission spectroscopies (NanoARPES and MicroARPES), we reveal the
spatially-resolved electronic structure in the stripe phase of IrTe$_2$. Each
separated domain shows two-fold symmetric electronic structure with the mirror
axis aligned along 3 equivalent directions, and 6$\times$1 replicas are clearly
identified. Moreover, such electronic structure inhomogeneity disappears across
the stripe phase transition, suggesting that electronic phase with broken
symmetry induced by the 6$\times$1 modulation is directly related to the stripe
phase transition of IrTe$_2$. Our work demonstrates the capability of NanoARPES
and MicroARPES in elucidating the fundamental physics of phase-separated
materials.

###Influence of Device Geometry on Transport Properties of Topological Insulator Microflakes|Fan Gao,Yongqing Li###

Influence of Device Geometry on Transport Properties of Topological Insulator Microflakes. In the transport studies of topological insulators, microflakes exfoliated
from bulk single crystals are often used because of the convenience in sample
preparation and the accessibility to high carrier mobilities. Here, based on
finite element analysis, we show that for the non-Hall-bar shaped topological
insulator samples, the measured four-point resistances can be substantially
modified by the sample geometry, bulk and surface resistivities, and magnetic
field. Geometry correction factors must be introduced for accurately converting
the four-point resistances to the longitudinal resistivity and Hall
resistivity. The magnetic field dependence of inhomogeneous current density
distribution can lead to pronounced positive magnetoresistance and nonlinear
Hall effect that would not exist in the samples of ideal Hall bar geometry.

###Nature of the 1/f Noise in Graphene, Direct Evidence for the Mobility Fluctuations Mechanism|Adil Rehman,Juan Antonio Delgado Notario,Juan Salvador Sanchez,Yahya Moubarak Meziani,Grzegorz Cywiński,Wojciech Knap,Alexander A. Balandin,Michael Levinshtein,Sergey Rumyantsev###

Nature of the 1/f Noise in Graphene, Direct Evidence for the Mobility Fluctuations Mechanism. The nature of the low-frequency current fluctuations, i.e. carrier number vs.
mobility, defines the strategies for noise reduction in electronic devices.
While the 1/f noise in metals has been attributed to the electron mobility
fluctuations, the direct evidence is lacking (f is the frequency). Here we
measured noise in h-BN encapsulated graphene transistor under the condition of
geometrical magnetoresistance to directly assess the mechanism of low-frequency
electronic current fluctuations. It was found that the relative noise spectral
density of the graphene resistance fluctuations depends non-monotonically on
the magnetic field (B) with a minimum at approximately uB=1 (u is the electron
mobility). This observation proves unambiguously that the mobility fluctuations
are the dominant mechanism of the electronic noise in high-quality graphene.
Our results are important for all proposed applications of graphene in
electronics and add to the fundamental understanding of the 1/f noise origin in
any electronic device.

###Quantum oscillations in Noncentrosymmetric Weyl semimetals RAlSi (R = Sm and Ce)|Weizheng Cao,Qi Wang,Cuiying Pei,Lingling Gao,Yi Zhao,Changhua Li,Na Yu,Jinghui Wang,Yulin Chen,Jun Li,Yanpeng Qi###

Quantum oscillations in Noncentrosymmetric Weyl semimetals RAlSi (R = Sm and Ce). Weyl semimetal (WSM) as a new type of quantum state of matter hosting low
energy relativistic quasiparticles, has attracted significant attention for
both scientific community and potential quantum device applications. Here, we
report a comprehensive investigation of the structural, magnetic and transport
properties of noncentrosymmetric RAlSi (R = Sm, Ce), which have been predicted
to be new magnetic WSM candidates. Both samples exhibit non-saturated
magnetoresistance (MR), with ~ 900% for SmAlSi and 80% for CeAlSi at 1.8 K, 9
T. The carrier densities of SmAlSi and CeAlSi display remarkable change around
magnetic transition temperatures, signifying that the electronic states are
sensitive to magnetic ordering of rare earth elements. At low temperatures,
SmAlSi reveals prominent Shubnikov-de Haas (SdH) oscillations associated with
the nontrivial Berry phase. High pressure experiments demonstrate that the
magnetic order is robust and survival under high pressure. Our results would
yield valuable insights of WSM physics and potentials in application to the
next-generation spintronic devices in RAX family.

###Magnetotransport in ferromagnetic Fe$_2$Ge semimetallic thin films|Andrew W. Forbes,Niraj Bhattarai,Christopher Gassen,Raghad S. H. Saqat,Ian L. Pegg,John Philip###

Magnetotransport in ferromagnetic Fe$_2$Ge semimetallic thin films. Thin films of the ferromagnet Fe$_2$Ge were grown via molecular beam epitaxy,
and their electrical and magneto-transport properties measured for the first
time. X-ray diffraction and vibrating sample magnetometry measurements
confirmed the crystalline ferromagnetic Fe$_2$Ge phase. The observed high
temperature maximum in the longitudinal resistivity, as well as the observed
suppression of electron-magnon scattering at low temperatures, point to the
presence of strong spin polarization in this material. Measurements of the Hall
resistivity, $\rho_{xy}$, show contributions from both the ordinary Hall effect
and anomalous Hall effect, $\rho_{xy}^{AH}$, from which we determined the
charge carrier concentration and mobility. Measurements also show a small
negative magnetoresistance in both the longitudinal and transverse geometries.
Fe$_2$Ge holds promise as a useful spintronic material, especially for its
semiconductor compatibility.

###Magnetic Proximity-Induced Superconducting Diode Effect and Infinite Magnetoresistance in van der Waals Heterostructure|Jeacheol Shin,Suhan Son,Jonginn Yun,Giung Park,Kaixuan Zhang,Young Jae Shin,Je-Geun Park,Dohun Kim###

Magnetic Proximity-Induced Superconducting Diode Effect and Infinite Magnetoresistance in van der Waals Heterostructure. We report unidirectional charge transport in a $\mathrm{NbSe_2}$
noncentrosymmetric superconductor, which is exchange-coupled with a
$\mathrm{CrPS_4}$ van der Waals layered antiferromagnetic insulator. The
$\mathrm{NbSe_2/CrPS_4}$ bilayer device exhibits bias-dependent superconducting
critical-current variations of up to $16\%$, with the magnetochiral anisotropy
reaching $\sim 10^5\mathrm{\ T^{-1}A^{-1}}$. Furthermore, the
$\mathrm{CrPS_4/NbSe_2/CrPS_4}$ spin-valve structure exhibits the
superconducting diode effect with critical-current variations of up to $40\%$.
We also utilize the magnetic proximity effect to induce switching in the
superconducting state of the spin-valve structure. It exhibits an infinite
magnetoresistance ratio depending on the field sweep direction and
magnetization configuration. Our result demonstrates a novel route for
enhancing the nonreciprocal response in the weak external field regime
($<50\mathrm{\ mT}$) by exploiting the magnetic proximity effect.

###Unidirectional spin Hall magnetoresistance and spin-orbit torques in HM$_1$/Co/HM$_2$ trilayer systems|Anastasiia Moskaltsova,Denis Dyck,Jan-Michael Schmalhorst,Günter Reiss,Timo Kuschel###

Unidirectional spin Hall magnetoresistance and spin-orbit torques in HM$_1$/Co/HM$_2$ trilayer systems. We present a detailed analysis of harmonic longitudinal and Hall voltage
measurements for in-plane magnetized Pt/Co/Ta and Ta/Co/Pt trilayers in
reference to Pt/Co and Ta/Co bilayers. Enhancement of spin-orbit torques (SOTs)
and unidirectional spin Hall magnetoresistance (USMR) is achieved by
introducing the second heavy metal (HM) with the opposite sign of the spin Hall
angle. The extracted SOT efficiencies are larger for the trilayers as compared
to the bilayers, confirming the enhanced values reported for the trilayers with
perpendicularly magnetized Co. The maximum effective spin Hall angle found for
the Pt/Co/Ta trilayer reaches $\theta_{SH}$ = 20%. The USMR of the trilayer
yields up to 27% higher effect as for the respective bilayers with the largest
effective USMR amplitude of -0.32 $\times$ 10$^{-5}$ for the Pt/Co/Ta trilayer
at a charge current density of 10$^{7}$ A/cm$^2$.

###Chiral Coupling between Magnetic Layers with Orthogonal Magnetization|Can Onur Avci,Charles-Henri Lambert,Giacomo Sala,Pietro Gambardella###

Chiral Coupling between Magnetic Layers with Orthogonal Magnetization. We report on the occurrence of strong interlayer Dzyaloshinskii-Moriya
interaction (DMI) between an in-plane magnetized Co layer and a perpendicularly
magnetized TbFe layer through a Pt spacer. The DMI causes a chiral coupling
that favors one-handed orthogonal magnetic configurations of Co and TbFe, which
we reveal through Hall effect and magnetoresistance measurements. The DMI
coupling mediated by Pt causes effective magnetic fields on either layer of up
to 10-15 mT, which decrease monotonously with increasing Pt thickness. Ru, Ta,
and Ti spacers mediate a significantly smaller coupling compared to Pt,
highlighting the essential role of Pt in inducing the interlayer DMI. These
results are relevant to understand and maximize the interlayer coupling induced
by the DMI as well as to design spintronic devices with chiral spin textures.

###Room temperature two terminal tunnel magnetoresistance in lateral graphene transistor|C. I. L. de Araujo,H. A. Teixeira,O. O. Toro,C. Liao,J. Borme,L. C. Benetti,D. Schafer,I. S. Brandt,R. Ferreira,P. Alpuim,P. P. Freitas,A. A. Pasa###

Room temperature two terminal tunnel magnetoresistance in lateral graphene transistor. We investigate the behavior of both pure spin and spin-polarized currents
measured with four probe non-local and two probe local configurations up to
room temperature and under external gate voltage in a lateral graphene
transistor, produced using a standard large-scale microfabrication process. The
high spin diffusion length of pristine graphene in the channel, measured both
directly and by the Hanle effect, and the tuning of relation between electrode
resistance area present in the device architecture, allowed us to observe local
tunnel magnetoresistance at room temperature, a new finding for this type of
device. Results also indicate that while pure spin currents are less sensitive
to temperature variations, spin-polarized current switching by external voltage
is more efficient, due to a combination of the Rashba effect and change in
carrier mobility by Fermi level shift

###High-Pressure Synthesis of a Massive and Non-Symmorphic Dirac Semimetal Candidate MoP$_4$|Alex Hiro Mayo,Jon Alexander Richards,Hidefumi Takahashi,Shintaro Ishiwata###

High-Pressure Synthesis of a Massive and Non-Symmorphic Dirac Semimetal Candidate MoP$_4$. Single crystal and polycrystalline samples of MoP$_4$ with a
black-phosphorus-derived structure have been successfully synthesized by a
high-pressure technique. The polycrystalline samples show a large positive
magnetoresistance and a small negative Seebeck coefficient at low temperatures,
reflecting a semi-metallic nature with high-mobility electrons. Consistent with
the transport properties, the band structure calculation reveals a
semi-metallic state with the presence of two types of Dirac nodes slightly
below the Fermi level. The Dirac node along the $\Gamma$-X direction normal to
the phosphorus layers is gapped out in the presence of spin-orbit coupling
(SOC), whereas the band crossing at the Z-point is immune to SOC because of the
non-symmorphic symmetry. This work demonstrates a great potential of
phosphorus-based layered Zintl compounds for topological semimetal candidates
allowing chemical band engineering.

###Observation of coexisting weak localization and superconducting fluctuations in strained Sn1-xInxTe thin films|Jiashu Wang,William Powers,Zhan Zhang,Michael Smith,Bradlee J. McIntosh,Seul-Ki Bac,Logan Riney,Maksym Zhukovskyi,Tatyana Orlova,Leonid P. Rokhinson,Yi-Ting Hsu,Xinyu Liu,Badih A. Assaf###

Observation of coexisting weak localization and superconducting fluctuations in strained Sn1-xInxTe thin films. Topological superconductors have attracted tremendous excitement as they are
predicted to host Majorana zero modes that can be utilized for topological
quantum computing. Candidate topological superconductor Sn1-xInxTe thin films
(0<x<0.3) grown by molecular beam epitaxy and strained in the (111) plane are
shown to host three coexisting quantum effects: localization, antilocalization
and superconducting fluctuations above the critical temperature Tc. An analysis
of the normal state magnetoresistance reveals these effects. Weak localization
is consistently observed in superconducting samples, indicating that
superconductivity originates dominantly from trivial valence band states that
may be strongly spin-orbit split. A large enhancement of the conductivity is
observed above Tc, indicating that quantum coherent quasiparticle effects
coexist with superconducting fluctuations. Our results motivate a
re-examination of the debated pairing symmetry of this material when subjected
to quantum confinement and lattice strain.

###Enhanced Tunnel magnetoresistance in Fe/Mg4Al-Ox/Fe(001) Magnetic Tunnel Junctions|Thomas Scheike,Zhenchao Wen,Hiroaki Sukegawa,Seiji Mitani###

Enhanced Tunnel magnetoresistance in Fe/Mg4Al-Ox/Fe(001) Magnetic Tunnel Junctions. Spinel MgAl2O4 and family oxides are emerging barrier materials useful for
magnetic tunnel junctions (MTJs). We report large tunnel magnetoresistance
(TMR) ratios up to 429% at room temperature (RT) and 1,034% at 10 K in a
Fe/MgAl2O4/Fe(001)-based MTJ prepared using electron-beam evaporation of
Mg4Al-Ox. Resistance oscillations with a MTJ barrier thickness of 0.3-nm were
significantly enhanced compared to those of a Fe/MgO/Fe(001) MTJ, resulting in
a large TMR oscillation peak-to-valley difference of 125% at RT. The
differential conductance spectra were symmetric with bias polarity, and the
spectrum in the parallel magnetization state at low temperature demonstrate
significant peaks within broad local minima at |0.2-0.6| V, indicating improved
barrier interfaces by the Mg4Al-Ox barrier. This study demonstrates that TMR
ratios in Fe(001)-MTJs can still be improved.

###Gate-tuneable and chirality-dependent charge-to-spin conversion in Tellurium nanowires|Francesco Calavalle,Manuel Suárez-Rodríguez,Beatriz Martín-García,Annika Johansson,Diogo C. Vaz,Haozhe Yang,Igor V. Maznichenko,Sergey Ostanin Aurelio Mateo-Alonso,Andrey Chuvilin,Ingrid Mertig,Marco Gobbi,Fèlix Casanova,Luis E. Hueso###

Gate-tuneable and chirality-dependent charge-to-spin conversion in Tellurium nanowires. Chiral materials are the ideal playground for exploring the relation between
symmetry, relativistic effects, and electronic transport. For instance, chiral
organic molecules have been intensively studied to electrically generate
spin-polarized currents in the last decade, but their poor electronic
conductivity limits their potential for applications. Conversely, chiral
inorganic materials such as Tellurium are excellent electrical transport
materials, but have not been explored to enable the electrical control of spin
polarization in devices. Here, we demonstrate the all-electrical generation,
manipulation, and detection of spin polarization in chiral single-crystalline
Tellurium nanowires. By recording a large (up to 7%) and chirality-dependent
unidirectional magnetoresistance, we show that the orientation of the
electrically generated spin polarization is determined by the nanowire
handedness and uniquely follows the current direction, while its magnitude can
be manipulated by an electrostatic gate. Our results pave the way for the
development of magnet-free chirality-based spintronic devices.

###Endless Dirac nodal lines in kagome-metal Ni3In2S2|Tiantian Zhang,T. Yilmaz,E. Vescovo,H. X. Li,R. G. Moore,H. N. Lee,H. Miao,S. Murakami,M. A. McGuire###

Endless Dirac nodal lines in kagome-metal Ni3In2S2. Topological semimetals are a frontier of quantum materials. In multi-band
electronic systems, topological band-crossings can form closed curves, known as
nodal lines. In the presence of spin-orbit coupling and/or symmetry-breaking
operations, topological nodal lines can break into Dirac/Weyl nodes and give
rise to novel transport properties, such as the chiral anomaly and giant
anomalous Hall effect. Recently the time-reversal symmetry-breaking induced
Weyl fermions are observed in a kagome-metal Co3Sn2S2, triggering interests in
nodal-line excitations in multiband kagome systems. Here, using
first-principles calculations and symmetry based indicator theories, we find
six endless nodal lines along the stacking direction of kagome layers and two
nodal rings in the kagome plane in nonmagnetic Ni3 In2 S2 . The linear
dipsersive electronic structure, confirmed by angle-resolved photoemission
spectroscopy, induces large magnetoresistance up to 2000% at 9 T. Our results
establish a diverse topological landscape of multi-band kagome metals.

###Microscopic probe of magnetic polarons in antiferromagnetic Eu$_{5}$In$_{2}$Sb$_{6}$|J. C. Souza,S. M. Thomas,E. D. Bauer,J. D. Thompson,F. Ronning,P. G. Pagliuso,P. F. S. Rosa###

Microscopic probe of magnetic polarons in antiferromagnetic Eu$_{5}$In$_{2}$Sb$_{6}$. Colossal magnetoresistance (CMR) emerges from intertwined spin and charge
degrees of freedom in the form of ferromagnetic clusters also known as trapped
magnetic polarons. As a result, CMR is rarely observed in antiferromagnetic
materials. Here we use electron spin resonance (ESR) to reveal microscopic
evidence for the formation of magnetic polarons in antiferromagnetic
Eu$_{5}$In$_{2}$Sb$_{6}$. First, we observe a reduction of the Eu$^{2+}$ ESR
linewidth as a function of the applied magnetic field consistent with
ferromagnetic clusters that are antiferromagnetically coupled. Additionally,
the Eu$^{2+}$ lineshape changes markedly below T' ~ 200 K, a temperature scale
that coincides with the onset of CMR. The combination of these two effects
provide strong evidence that magnetic polarons grow in size below T' and start
influencing the macroscopic properties of the system.

###NdAlSi: a magnetic Weyl semimetal candidate with rich magnetic phases and atypical transport properties|Jin-Feng Wang,Qing-Xin Dong,Zhao-Peng Guo,Meng Lv,Yi-Fei Huang,Jun-Sen Xiang,Zhi-An Ren,Zhi-Jun Wang,Pei-Jie Sun,Gang Li,Gen-Fu Chen###

NdAlSi: a magnetic Weyl semimetal candidate with rich magnetic phases and atypical transport properties. Magnetic Weyl semimetals (MWSM) have attracted significant attention due to
their intriguing physical properties and potential applications in
spin-electronic devices. Here we report the characterization of NdAlSi
including transport, magnetization, and heat capacity on single crystals, as
well as band structure calculation. It is a newly proposed MWSM candidate which
breaks both time-reversal and spacial inversion symmetries. A
temperature-magnetic field phase diagram is experimentally established.
Remarkably, on the angular magnetoresistance (AMR), a two-fold symmetric sharp
peak instead of a smooth variation is observed in the field-induced
ferrimagnetic phase. We argue that the tunability of both the topological and
magnetic properties in NdAlSi is crucial for realizing such a behavior. Our
results indicate that 4f-electron-based MWSM can provide a unique platform to
explore new and intriguing quantum phenomena arising from the interaction
between magnetism and topology.

###Memristive effects in nanopatterned permalloy Kagomé array|Wesley B. J. Fonseca,Flavio Garcia,Francesco Caravelli,Clodoaldo I. L de Araujo###

Memristive effects in nanopatterned permalloy Kagomé array. We study memristive effects in Kagom\'{e} nanopatterned permalloy. We observe
that at low frequencies a thermistor effect is present, a phenomenon arising
due to the lithography and absent in similar experiments for thin films.
However, we also show via an independent anisotropic magnetoresistive study
that a small hysteresis accounting for 1% of the effect is not attributable to
a thermistive effect. Such effect is also confirmed by a careful subtraction
scheme between nearby thermal hysteresis. In the millihertz regime, an
effective model is provided to describe the experimental results for the
thermistor, showing that there should be a crossover from the millihertz to the
gigahertz, from a thermistor to an memresistive effect for nanopatterned
permalloy.

###Anomalous Nernst effect in La0.5Ca0.5Coo3|A. Ghosh,M. Manikandan,R. Mahendiran###

Anomalous Nernst effect in La0.5Ca0.5Coo3. We report the occurrence of the anomalous Nernst effect (ANE) in
polycrystalline perovskite La0.5Ca0.5CoO3. The sample is ferromagnetic below TC
= 147 K and resistivity shows non-metallic behavior above and below the TC with
only a small negative magnetoresistance (~2%) around TC. Field dependence of
magnetization at 10 K shows large hysteresis with a coercive field of 6 kOe but
a small magnetization ~ 0.64 Bohr magneton/Co even in a field of 50 kOe, which
indicates the presence of magnetically heterogeneous ground state consisting of
ferromagnetic and non-ferromagnetic phases. The field dependence of the Nernst
thermopower (Sxy) at low temperatures shows complete saturation but the
magnetization does not. This indicates that the ANE in La0.5Ca0.5CoO3 depends
only on the transport properties of the ferromagnetic phase, while it is not
affected by the non-ferromagnetic phase. Due to the higher value of remnant
Sxy, the magnetized polycrystalline sample exhibits ANE in absence of an
external magnetic field.

###Observation of magnetization surface textures of the van der Waals antiferromagnet FePS3 by spin Hall magnetoresistance|F. Feringa,G. E. W. Bauer,B. J. van Wees###

Observation of magnetization surface textures of the van der Waals antiferromagnet FePS3 by spin Hall magnetoresistance. Van der Waals materials are a new platform to study two-dimensional systems,
including magnetic order. Since the number of spins is relatively small,
measuring the magnetization is challenging. Here we report spin Hall
magnetoresistance (SMR) up to room temperature caused by the magnetic surface
texture of exfoliated flakes of magnetic van der Waals materials. For the
antiferromagnet FePS3 the SMR amounts to 0.1 % for an applied magnetic field of
7 T at 5 K which implies a substantial canting of the magnetic moments relative
to the colinear antiferromagnetic order. The canting is substantial even for a
magnetic field along the N\'eel vector, which illustrates the unique power of
the SMR to detect magnetic surface textures in van der Waals magnets.

###1T-FeS$_2$$:$ a new type of two-dimensional metallic ferromagnet|Govindan Kutty Rajendran Nair,Xiaoyu Ji,Dong Guo,Chao Zhu,Xiaodong Xu,Xinyi Zheng,Xue Yang,Jian Cui,Peiling Li,Xiaowei Wang,Wu Yao,Jiadong Zhou,Teddy Salim,Jian Yi,Fengcai Ma,Changli Yang,Hua Ke,Fanming Qu,Jie Shen,Xiunian Jing,Zheng Liu,Xingji Li,Guangtong Liu,Li Lu###

1T-FeS$_2$$:$ a new type of two-dimensional metallic ferromagnet. Discovery of intrinsic two-dimensional (2D) magnetic materials is crucial for
understanding the fundamentals of 2D magnetism and realizing next-generation
magnetoelectronic and magneto-optical devices. Although significant efforts
have been devoted to identifying 2D magnetism by exfoliating bulk magnetic
layered materials, seldom studies are performed to synthesize ultra-thin
magnetic materials directly for non-layered magnetic materials. Here, we report
the successful synthesis of a new type of theoretically proposed 2D metallic
ferromagnet 1T FeS2, through the molten-salt-assisted chemical vapor deposition
(CVD) method. The long-range 2D ferromagnetic order is confirmed by the
observation of a large anomalous Hall effect (AHE) and a hysteretic
magnetoresistance. The experimentally detected out-of-plane ferromagnetic
ordering is theoretically suported with Stoner criterion. Our findings open up
new possibilities to search novel 2D ferromagnets in non-layered compounds and
render opportunities for realizing realistic ultra-thin spintronic devices.

###Giant topological and planar Hall effect in Cr$_{1/3}$NbS$_{2}$|D. A. Mayoh,J. Bouaziz,A. E. Hall,J. B. Staunton,M. R. Lees,G. Balakrishnan###

Giant topological and planar Hall effect in Cr$_{1/3}$NbS$_{2}$. Cr$_{1/3}$NbS$_{2}$ is a transition metal dichalcogenide that has been of
significant interest due to its ability to host a magnetic chiral soliton
lattice. Conventional and planar Hall measurements provide valuable insight
into the detection of exotic spin structures in chiral magnets. We show that
the presence of a giant planar Hall effect can be attributed to a tilted
soliton lattice in Cr$_{1/3}$NbS$_{2}$. Our detailed angular dependent study
shows the planar Hall effect and anisotropic magnetoresistance are
intrinsically linked in complex non-coplanar magnets. From the conventional
Hall signal we show the presence of a giant unconventional, likely topological
Hall component, that is the fingerprint of non-coplanar spin textures.

###Unusual electrical and magnetic properties in layered EuZn2As2|Joanna Blawat,Madalynn Marshall,John Singleton,Erxi Feng,Huibo Cao,Weiwei Xie,Rongying Jin###

Unusual electrical and magnetic properties in layered EuZn2As2. Eu-based compounds often exhibit unusual magnetism, which is critical for
nontrivial topological properties seen in materials such as EuCd2As2. We
investigate the structure and physical properties of EuZn2As2 through
measurements of the electrical resistivity, Hall effect, magnetization, and
neutron diffraction. Our data show that EuZn2As2 orders antiferromagnetically
with an A-type spin configuration below TN = 19 K. Surprisingly, there is
strong evidence for dominant ferromagnetic fluctuations above TN, as reflected
by positive Curie-Weiss temperature and extremely large negative
magnetoresistance (MR) between TN and Tfl {\guillemotright} 200 K. Furthermore,
the angle dependence of the MRab indicates field-induced spin reorientation
from the ab-plane to a direction approximately 45{\deg} from the ab plane.
Compared to EuCd2As2, the doubled TN and Tfl make EuZn2As2 a better platform
for exploring topological properties in both magnetic fluctuation (TN < T <
Tfl) and ordered (T < TN) regimes.

###Do cities have a unique magnetic pulse?|Vincent Dumont,Trevor A. Bowen,Roger Roglans,Gregory Dobler,Mohit S. Sharma,Andy Karpf,Stuart D. Bale,Arne Wickenbrock,Elena Zhivun,Tom Kornack,Jonathan S. Wurtele,Dmitry Budker###

Do cities have a unique magnetic pulse?. We present a comparative analysis of urban magnetic fields between two
American cities: Berkeley (California) and Brooklyn Borough of New York City
(New York). Our analysis uses data taken over a four-week period during which
magnetic field data were continuously recorded using a fluxgate magnetometer of
70 pT/$\sqrt{\mathrm{Hz}}$ sensitivity. We identified significant differences
in the magnetic signatures. In particular, we noticed that Berkeley reaches a
near-zero magnetic field activity at night whereas magnetic activity in
Brooklyn continues during nighttime. We also present auxiliary measurements
acquired using magnetoresistive vector magnetometers (VMR), with sensitivity of
300 pT/$\sqrt{\mathrm{Hz}}$, and demonstrate how cross-correlation, and
frequency-domain analysis, combined with data filtering can be used to extract
urban magnetometry signals and study local anthropogenic activities. Finally,
we discuss the potential of using magnetometer networks to characterize the
global magnetic field of cities and give directions for future development.

###Quantum sensing on magnetic field inspired by Avian compass|Wei-Yin Chiang,Yuan-Chung Cheng,Min-Hsiu Hsieh###

Quantum sensing on magnetic field inspired by Avian compass. Magnetic measurement can be performed by various sensors, such as SQUID and
Giant Magnetoresistance. This device can achieve high accuracy while losing
efficiency and convenience. The model of biological magnetic sensing in avian
proposes a radical pair response to the external field on the FLY results in
regulating animal behaviour. Inspired by the radical pair system found in
biological system, the effect of intra-radical coupling and the initial
condition is studied in this simplified radical pair model as the quantum
advantage results from entanglement and superposition are investigated in
metrology. To identify the sensing benefit from the cooperation between the
radical pairs, the inter-radical coupling is considered. We find the
intra-radical coupling determines the sensing regime while the coupled radical
pair system enables a new sensing scheme that provides a more general and
flexible way for magnetic sensing in a broader range through a easier
manipulation to the system.

###Emergence of insulating ferrimagnetism and perpendicular magnetic anisotropy in 3d-5d perovskite oxide composite films for insulator spintronic|Zeliang Ren,Bin Lao,Xuan Zheng,Lei Liao,Zengxing Lu,Sheng Li,Yongjie Yang,Bingshan Cao,Lijie Wen,Kenan Zhao,Lifen Wang,Xuedong Bai,Xianfeng Hao,Zhaoliang Liao,Zhiming Wang,Run-Wei Li###

Emergence of insulating ferrimagnetism and perpendicular magnetic anisotropy in 3d-5d perovskite oxide composite films for insulator spintronic. Magnetic insulators with strong perpendicular magnetic anisotropy (PMA) play
a key role in exploring pure spin current phenomena and developing
ultralow-dissipation spintronic devices, thereby it is highly desirable to
develop new material platforms. Here we report epitaxial growth of
La2/3Sr1/3MnO3 (LSMO)-SrIrO3 (SIO) composite oxide films (LSMIO) with different
crystalline orientations fabricated by sequential two-target ablation process
using pulsed laser deposition. The LSMIO films exhibit high crystalline quality
with homogeneous mixture of LSMO and SIO at atomic level. Ferrimagnetic and
insulating transport characteristics are observed, with the
temperature-dependent electric resistivity well fitted by Mott
variable-range-hopping model. Moreover, the LSMIO films show strong PMA.
Through further constructing all perovskite oxide heterostructures of the
ferrimagnetic insulator LSMIO and a strong spin-orbital coupled SIO layer,
pronounced spin Hall magnetoresistance (SMR) and spin Hall-like anomalous Hall
effect (SH-AHE) were observed. These results illustrate the potential
application of the ferrimagnetic insulator LSMIO in developing all-oxide
ultralow-dissipation spintronic devices.

###Weak localization on moiré superlattice in twisted double bilayer graphene|Masaki Kashiwagi,Toshihiro Taen,Kazuhito Uchida,Kenji Watanabe,Takashi Taniguchi,Toshihito Osada###

Weak localization on moiré superlattice in twisted double bilayer graphene. Moir\'e superlattice created by twist stacking has multiple physical
properties. These physical properties depend on the twist angle, hence
investigation of the twist angle dependency is important for the deep
understanding of physical phenomena in moir\'e superlattice. In this work,
negative magnetoresistance owing to weak localization (WL) was investigated in
twisted double bilayer graphene (TDBG) as a function of the twist angle. The
ratio of the intervalley scattering time to the intravalley scattering time,
estimated using the WL formula for bilayer graphene, tended to decrease as the
twist angle increased. This feature is qualitatively explained by the
enhancement of intervalley scattering due to the reduction of the intervalley
distance in the moir\'e Brillouin zone (BZ) of the TDBG. This indicates that WL
in the TDBG occurs for the moir\'e superlattice with the reconstructed BZ.

###Complex electronic structure evolution of NdSb across the magnetic transition|Anup Pradhan Sakhya,Baokai Wang,Firoza Kabir,Cheng-Yi Huang,M. Mofazzel Hosen,Bahadur Singh,Sabin Regmi,Gyanendra Dhakal,Klauss Dimitri,Milo Sprague,Robert Smith,Eric D. Bauer,Filip Ronning,Arun Bansil,Madhab Neupane###

Complex electronic structure evolution of NdSb across the magnetic transition. The rare-earth monopnictide (REM) family, which hosts magnetic ground states
with extreme magnetoresistance, has established itself as a fruitful playground
for the discovery of interesting topological phases. Here, by using
high-resolution angle-resolved photoemission spectroscopy complemented by
first-principles density functional-theory based modeling, we examine the
evolution of the electronic structure of the candidate REM Dirac semimetal NdSb
across the magnetic transition. A complex angel-wing-like band structure near
the zone center and three arc-like features at the zone corner have been
observed. This dramatic reconstruction of the itinerant bands around the zone
center is shown to be driven by the magnetic transition: Specifically,, the Nd
5d electron band backfolds at the Gamma point and hybridizes with the Sb 5p
hole bands in the antiferromagnetic phase. Our study indicates that
antiferromagnetism plays an intricate role in the electronic structure of the
REM family.

###Magnetic field-Temperature Phase Diagram of CeCoSi Constructed by Specific Heat, Magnetoresistivity, and Magnetization Measurements for a Single Crystal|Hiroyuki Hidaka,Shun Yanagiya,Eikai Hayasaka,Yuma Kaneko,Tatsuya Yanagisawa,Hiroshi Tanida,Hiroshi Amitsuka###

Magnetic field-Temperature Phase Diagram of CeCoSi Constructed by Specific Heat, Magnetoresistivity, and Magnetization Measurements for a Single Crystal. A Ce-based metallic compound CeCoSi with a tetragonal structure exhibits
successive phase transitions: the one whose order parameter is unidentified at
T_0 = 12 K and the antiferromagnetic one at T_N = 9.4 K. We performed specific
heat, magnetoresistivity (MR), and magnetization measurements for a single
crystal CeCoSi at low temperatures in magnetic fields B of up to 14 T and
constructed detailed magnetic field--temperature phase diagrams for both B ||
[100] and [001]. The longitudinal MR measured for B || [100] shows a sign
change from negative to positive across T_0 = 13 K updated in the present
sample, indicating a clear change in an electronic state. In addition, the
constructed magnetic phase diagrams for both the field directions have a
B-induced region in each ordered state. The presence of the newly found regions
would be attributed to a change in the symmetry of the order parameter or
domain alignment by applying B.

###Large anomalous Hall effect and anisotropic magnetoresistance in intrinsic nanoscale spin-valve-type structure of an antiferromagnet|Dong Gun Oh,Jong Hyuk Kim,Mi Kyung Kim,Ki Won Jeong Hyun Jun Shin,Jae Min Hong,Jin Seok Kim,Kyungsun Moon,Nara Lee,Young Jai Choi###

Large anomalous Hall effect and anisotropic magnetoresistance in intrinsic nanoscale spin-valve-type structure of an antiferromagnet. A spin valve is a prototype of spin-based electronic devices found on
ferromagnets, in which an antiferromagnet plays a supporting role. Recent
findings in antiferromagnetic spintronics show that an antiferromagnetic order
in single-phase materials solely governs dynamic transport, and
antiferromagnets are considered promising candidates for spintronic technology.
In this work, we demonstrated antiferromagnet-based spintronic functionality on
an itinerant Ising antiferromagnet of Ca0.9Sr0.1Co2As2 by integrating nanoscale
spin-valve-type structure and investigating anisotropic magnetic properties
driven by spin-flips. Multiple stacks of 1 nm thick spin-valve-like unit are
intrinsically embedded in the antiferromagnetic spin structure. In the presence
of a rotating magnetic field, a new type of the spin-valve-like operation was
observed for large anomalous Hall conductivity and anisotropic
magnetoresistance, whose effects are maximized above the spin-flip transition.
In addition, a joint experimental and theoretical study provides an efficient
tool to read out various spin states, which scheme can be useful for
implementing extensive spintronic applications.

###Sign-tunable anisotropic magnetoresistance and electrically detectable dual magnetic phases in a helical antiferromagnet|Jong Hyuk Kim,Hyun Jun Shin,Mi Kyung Kim,Jae Min Hong,Ki Won Jeong,Jin Seok Kim,Kyungsun Moon,Nara Lee,Young Jai Choi###

Sign-tunable anisotropic magnetoresistance and electrically detectable dual magnetic phases in a helical antiferromagnet. The helimagnetic order describes a non-collinear spin texture of
antiferromagnets, arising from competing exchange interactions. Although
collinear antiferromagnets are elemental building blocks of antiferromagnetic
(AFM) spintronics, the potential of implementing spintronic functionality in
non-collinear antiferromagnets has not been clarified thus far. Here, we
propose an AFM helimagnet of EuCo2As2 as a novel single-phase spintronic
material that exhibits a remarkable sign reversal of anisotropic
magnetoresistance (AMR). The contrast in the AMR arises from two electrically
distinctive magnetic phases with spin reorientation driven by magnetic field
lying on the easy-plane, which switches the sign of the AMR from positive to
negative. Further, various AFM memory states associated with the evolution of
the spin structure under magnetic fields were identified theoretically, based
on an easy-plane anisotropic spin model. These results reveal that
non-collinear antiferromagnets hold potential for developing spintronic
devices.

###Nonlinear magnetoconductivity in Weyl and multi-Weyl semimetal in quantizing magnetic field|Sunit Das,Kamal Das,Amit Agarwal###

Nonlinear magnetoconductivity in Weyl and multi-Weyl semimetal in quantizing magnetic field. Magnetotransport and magneto-optics experiments offer a very powerful probe
for studying the physical properties of materials. Here, we investigate the
second-order nonlinear magnetoconductivity of tilted type-I Weyl and multi-Weyl
semimetal. In contrast to the presence of chiral anomaly in the linear response
regime, we show that Weyl semimetal do not host chiral charge pumping in the
nonlinear transport regime. We predict that an inversion symmetry broken and
tilted Weyl semimetal can support finite longitudinal nonlinear
magnetoconductivity, which is otherwise absent in untilted Weyl semimetal. The
nonlinear magnetoconductivity vanishes in the ultra-quantum limit, oscillates
in the intermediate magnetic field regime and saturates in the semiclassical
limit. The nonlinear magnetoconductivity depends intricately on the tilt
orientation, and it can be used to determine the tilt orientation in Weyl and
multi-Weyl semimetals, via nonlinear magnetoresistivity or second harmonic
generation experiments.

###Quantum oscillations and weak anisotropic resistivity in the chiral Fermion semimetal PdGa|Xiang-Yu Zeng,Zheng-Yi Dai,Sheng Xu,Ning-Ning Zhao,Huan Wang,Xiao-Yan Wang,Jun-Fa Lin,Jing Gong,Xiao-Ping Ma,Kun Han,Yi-Ting Wang,Peng Cheng,Kai Liu,Tian-Long Xia###

Quantum oscillations and weak anisotropic resistivity in the chiral Fermion semimetal PdGa. We perform a detailed analysis of the magnetotransport and de Haas-van Alphen
(dHvA) oscillations in crystal PdGa which is predicted to be a typical chiral
Fermion semimetal from CoSi family holding a large Chern number. The
unsaturated quadratic magnetoresistance (MR) and nonlinear Hall resistivity
indicate that PdGa is a multi-band system without electron-hole compensation.
Angle-dependent resistivity in PdGa shows weak anisotropy with twofold or
threefold symmetry when the magnetic field rotates within the (1$\bar{1}$0) or
(111) plane perpendicular to the current. Nine or three frequencies are
extracted after the fast Fourier-transform analysis (FFT) of the dHvA
oscillations with B//[001] or B//[011], respectively, which is confirmed to be
consistent with the Fermi surfaces (FSs) obtained from first-principles
calculations with spin-orbit coupling (SOC) considered.

###Anisotropic three-dimensional quantum Hall effect and magnetotransport in mesoscopic Weyl semimetals|Xiao-Xiao Zhang,Naoto Nagaosa###

Anisotropic three-dimensional quantum Hall effect and magnetotransport in mesoscopic Weyl semimetals. Weyl semimetals are emerging to become a new class of quantum-material
platform for various novel phenomena. Especially, the Weyl orbit made from
surface Fermi arcs and bulk relativistic states is expected to play a key role
in magnetotransport, leading even to a three-dimensional quantum Hall effect
(QHE). It is experimentally and theoretically important although yet unclear
whether it bears essentially the same phenomenon as the conventional
two-dimensional QHE. We discover an unconventional fully three-dimensional
anisotropy in the quantum transport under magnetic field. Strong suppression
and even disappearance of QHE occur when Hall-bar current is rotated away from
being transverse to parallel with respect to the Weyl point alignment, which is
attributed to a peculiar absence of conventional bulk-boundary correspondence.
Besides, transport along the magnetic field can exhibit a remarkable reversal
from negative to positive magnetoresistance. These results establish the
uniqueness of this QHE system as a novel three-dimensional quantum matter.

###MRAM-based Analog Sigmoid Function for In-memory Computing|Md Hasibul Amin,Mohammed Elbtity,Mohammadreza Mohammadi,Ramtin Zand###

MRAM-based Analog Sigmoid Function for In-memory Computing. We propose an analog implementation of the transcendental activation function
leveraging two spin-orbit torque magnetoresistive random-access memory
(SOT-MRAM) devices and a CMOS inverter. The proposed analog neuron circuit
consumes 1.8-27x less power, and occupies 2.5-4931x smaller area, compared to
the state-of-the-art analog and digital implementations. Moreover, the
developed neuron can be readily integrated with memristive crossbars without
requiring any intermediate signal conversion units. The architecture-level
analyses show that a fully-analog in-memory computing (IMC) circuit that use
our SOT-MRAM neuron along with an SOT-MRAM based crossbar can achieve more than
1.1x, 12x, and 13.3x reduction in power, latency, and energy, respectively,
compared to a mixed-signal implementation with analog memristive crossbars and
digital neurons. Finally, through cross-layer analyses, we provide a guide on
how varying the device-level parameters in our neuron can affect the accuracy
of multilayer perceptron (MLP) for MNIST classification.

###NAND-SPIN-Based Processing-in-MRAM Architecture for Convolutional Neural Network Acceleration|Yinglin Zhao,Jianlei Yang,Bing Li,Xingzhou Cheng,Xucheng Ye,Xueyan Wang,Xiaotao Jia,Zhaohao Wang,Youguang Zhang,Weisheng Zhao###

NAND-SPIN-Based Processing-in-MRAM Architecture for Convolutional Neural Network Acceleration. The performance and efficiency of running large-scale datasets on traditional
computing systems exhibit critical bottlenecks due to the existing "power wall"
and "memory wall" problems. To resolve those problems, processing-in-memory
(PIM) architectures are developed to bring computation logic in or near memory
to alleviate the bandwidth limitations during data transmission. NAND-like
spintronics memory (NAND-SPIN) is one kind of promising magnetoresistive
random-access memory (MRAM) with low write energy and high integration density,
and it can be employed to perform efficient in-memory computation operations.
In this work, we propose a NAND-SPIN-based PIM architecture for efficient
convolutional neural network (CNN) acceleration. A straightforward data mapping
scheme is exploited to improve the parallelism while reducing data movements.
Benefiting from the excellent characteristics of NAND-SPIN and in-memory
processing architecture, experimental results show that the proposed approach
can achieve $\sim$2.6$\times$ speedup and $\sim$1.4$\times$ improvement in
energy efficiency over state-of-the-art PIM solutions.

###Finite field transport response of a dilute magnetic topological insulator based Josephson junction|Pankaj Mandal,Nicolai Taufertshöfer,Lukas Lunczer,Martin P. Stehno,Charles Gould,Laurens W. Molenkamp###

Finite field transport response of a dilute magnetic topological insulator based Josephson junction. Hybrid samples combining superconductors with magnetic topological insulators
are a promising platform for exploring exotic new transport physics. We examine
a Josephson junction of such a system, based on the dilute magnetic topological
insulator (Hg,Mn)Te and the type II superconductor MoRe. In the zero and very
low field limit, to the best of our knowledge, the device shows, for the first
time, induced supercurrent through a magnetically doped semiconductor, in this
case a topological insulator. At higher fields, a rich and hysteretic
magnetoresistance is revealed. Careful analysis shows that the explanation of
this behaviour can be found in magnetic flux focusing stemming from the
Meissner effect in the superconductor, without invoking any role of proximity
induced superconductivity. The phenomena is important, as it will ubiquitously
co-exist with any exotic new physics that may be present in this class of
devices.

###In situ transport characterization of magnetic states in Nb/Co superconductor/ferromagnet heterostructures|Olena M. Kapran,Roman Morari,Taras Golod,Evgenii A. Borodianskyi,Vladimir Boian,Andrei Prepelita,Nikolay Klenov,Anatoli S. Sidorenko,Vladimir M. Krasnov###

In situ transport characterization of magnetic states in Nb/Co superconductor/ferromagnet heterostructures. Employment of the non-trivial proximity effect in superconductor/ferromagnet
(S/F) heterostructures for the creation of novel superconducting devices
requires accurate control of magnetic states in complex thin-film multilayers.
In this work, we study experimentally in-plane transport properties of
microstructured Nb/Co multilayers. We apply various transport characterization
techniques, including magnetoresistance, Hall effect, and the
first-order-reversal-curves (FORC) analysis. We demonstrate how FORC can be
used for detailed in situ characterization of magnetic states. It reveals that
upon reduction of the external field, the magnetization in ferromagnetic layers
first rotates in a coherent scissor-like manner, then switches abruptly into
the antiparallel state and after that splits into the polydomain state, which
gradually turns into the opposite parallel state.

###Spin Manipulation by Giant Valley-Zeeman Spin-Orbit Field in Atom-Thick WSe2|Xinhe Wang,Wei Yang,Wang Yang,Yuan Cao,Xiaoyang Lin,Guodong Wei,Haichang Lu,Peizhe Tang,Weisheng Zhao###

Spin Manipulation by Giant Valley-Zeeman Spin-Orbit Field in Atom-Thick WSe2. The phenomenon originating from spin-orbit coupling (SOC) provides
energy-efficient strategies for spin manipulation and device applications. The
broken inversion symmetry interface and resulting electric field induce a
Rashba-type spin-orbit field (SOF), which has been demonstrated to generate
spin-orbit torque for data storage applications. In this study, we found that
spin flipping can be achieved by the valley-Zeeman SOF in monolayer WSe2 at
room temperature, which manifests as a negative magnetoresistance in the
vertical spin valve. Quantum transmission calculations based on an effective
model near the K valley of WSe2 confirm the precessional spin transport of
carriers under the giant SOF, which is estimated to be 650 T. In particular,
the valley-Zeeman SOF-induced spin dynamics was demonstrated to be tunable with
the layer number and stacking phase of WSe2 as well as the gate voltage, which
provides a novel strategy for spin manipulation and can benefit the development
of ultralow-power spintronic devices.

###Chiral anomaly in noncentrosymmetric systems induced by spin-orbit coupling|Suik Cheon,Gil Young Cho,Ki-Seok Kim,Hyun-Woo Lee###

Chiral anomaly in noncentrosymmetric systems induced by spin-orbit coupling. The chiral anomaly may be realized in condensed matter systems with pairs of
Weyl points. Here we show that the chiral anomaly can be realized in diverse
noncentrosymmetric systems even without Weyl point pairs when spin-orbit
coupling induces nonzero Berry curvature flux through Fermi surfaces. This
motivates the condensed matter chiral anomaly to be interpreted as a Fermi
surface property rather than a Weyl point property. The
spin-orbit-coupling-induced anomaly reproduces the well-known charge transport
properties of the chiral anomaly such as the negative longitudinal
magnetoresistance and the planar Hall effect in Weyl semimetals. Since it is of
spin-orbit coupling origin, it also affects the spin transport and gives rise
to anomaly-induced longitudinal spin currents and the magnetic spin Hall
effect, which are absent in conventional Weyl semimetals.

###Hydrodynamic charge transport in GaAs/AlGaAs ultrahigh-mobility two-dimensional electron gas|Xinghao Wang,Peizhe Jia,Rui-Rui Du,L. N. Pfeiffer,K. W. Baldwin,K. W. West###

Hydrodynamic charge transport in GaAs/AlGaAs ultrahigh-mobility two-dimensional electron gas. Viscous fluid in an ultrahigh-mobility two-dimensional electron gas (2DEG) in
GaAs/AlGaAs quantum wells is systematically studied through measurements of
negative magnetoresistance (NMR) and photoresistance under microwave radiation,
and the data are analyzed according to recent theoretical work by e.g.,
Alekseev, Physical Review Letters 117,166601 (2016). Size-dependent and
temperature dependent NMR are found to conform to the theoretical predictions.
In particular, transport of 2DEG with relatively weak Coulomb interaction
(interparticle interaction parameter r_s<1) manifests a crossover between
viscous liquid and viscous gas. The size dependence of microwave induced
resistance oscillations and that of the '2nd harmonic' peak indicate that 2DEG
in a moderate magnetic field should be regarded as viscous fluid as well. Our
results suggest that the hydrodynamic effects must be considered in order to
understand semiclassical electronic transport in a clean 2DEG.

###Fourfold anisotropic magnetoresistance of L1$_0$ FePt due to relaxation time anisotropy|Y. Dai,Y. W. Zhao,L. Ma,M. Tang,X. P. Qiu,Y. Liu,Z. Yuan,S. M. Zhou###

Fourfold anisotropic magnetoresistance of L1$_0$ FePt due to relaxation time anisotropy. Experimental measurements show that the angular dependence of the anisotropic
magnetoresistance (AMR) in L1$_0$ ordered FePt epitaxial films on the current
orientation and magnetization direction is a superposition of the corresponding
dependences of twofold and fourfold symmetries. The twofold AMR exhibits a
strong dependence on the current orientation, whereas the fourfold term only
depends on the magnetization direction in the crystal and is independent of the
current orientation. First-principles calculations reveal that the fourfold AMR
arises from the relaxation time anisotropy due to the variation of the density
of states near the Fermi energy under rotation of the magnetization. This
relaxation time anisotropy is a universal property in ferromagnetic metals and
determines other anisotropic physical properties that are observable in
experiment.

###Rare-Earth Control of the Superconducting Upper Critical Field in Infinite-Layer Nickelates|Bai Yang Wang,Tiffany C. Wang,Yu-Te Hsu,Motoki Osada,Kyuho Lee,Chunjing Jia,Caitlin Duffy,Danfeng Li,Jennifer Fowlie,Malcolm R. Beasley,Thomas P. Devereaux,Ian R. Fisher,Nigel E. Hussey,Harold Y. Hwang###

Rare-Earth Control of the Superconducting Upper Critical Field in Infinite-Layer Nickelates. The consequences of varying the rare-earth element in the superconducting
infinite-layer nickelates have been much debated. Here we show striking
differences in the magnitude and anisotropy of the superconducting upper
critical field across the La-, Pr-, and Nd-nickelates. These 5 distinctions
originate from the 4f electron characteristics of the rare-earth ions in the
lattice: they are absent for La3+, nonmagnetic for the Pr3+ singlet ground
state, and magnetic for the Nd3+ Kramer's doublet. The unique polar and
azimuthal angle-dependent magnetoresistance found in the Nd-nickelates can be
understood to arise from the magnetic contribution of the Nd3+ 4f moments. In
the absence of rare-earth effects, we find that the nickelates broadly violate
the Pauli limit. Such robust and tunable superconductivity suggests potential
in future high-field applications.

###Spin-Orbit Proximity Effect in Bi/Co Multilayer: The Role of Interface Scattering|Arthur Casa Nova Nonnig,Alexandre da Cas Viegas,Fabiano Mesquita da Rosa,Paulo Pureur,Milton Andre Tumelero###

Spin-Orbit Proximity Effect in Bi/Co Multilayer: The Role of Interface Scattering. The Spin-Orbit Proximity Effect is the raise of Spin-Orbit Coupling at a
layer near to the interface with a strong spin-orbit material. It has been seen
in several system such as graphene and ferromagnetic layers. The control of the
Spin-Orbit Coupling can be a pathway to discover novel and exotic phases in
superconductor and semimetallic systems. Here, we study the magnetoelectrical
transport, i.e., magnetoresistance and anomalous Hall effect, in Cobalt/Bismuth
multilayers looking for traces of spin-orbit proximity effect and evaluate the
origin of such effect. Our results point for an increase of Spontaneous
Magnetic Anisotropy of Resistivity and Anomalous Hall Resistivity at very low
thicknesses of Cobalt. The analysis of the Anomalous Hall Resisitivity indicate
that the Bismuth layers change the scattering mechanism of Hall effect to the
extrinsic skew-scattering type, indicating that the spin-orbit proximity effect
could be related to the elastic scattering of cobalt free carriers by bismuth
sites at the interface.

###Unidirectional Spin Hall Magnetoresistance in Antiferromagnetic Heterostructures|Yang Cheng,Junyu Tang,Justin J. Michel,Su Kong Chong,Fengyuan Yang,Ran Cheng,Kang L. Wang###

Unidirectional Spin Hall Magnetoresistance in Antiferromagnetic Heterostructures. Unidirectional spin Hall magnetoresistance (USMR) has been widely reported in
the heavy metal / ferromagnet (HM/FM) bilayer systems. We observe the USMR in
the Pt/{\alpha}-Fe2O3 bilayers where the {\alpha}-Fe2O3 is an antiferromagnetic
(AFM) insulator. Systematic field and temperature dependent measurements
confirm the magnonic origin of the USMR. The appearance of AFM-USMR is driven
by the imbalance of creation and annihilation of AFM magnons by spin orbit
torque due to thermal random field. However, unlike its ferromagnetic
counterpart, theoretical modeling reveals that the USMR in Pt/{\alpha}-Fe2O3 is
determined by the antiferromagtic magnon number, and with a non-monotonic field
dependence. Our findings extend the generality of the USMR which pave the ways
for the highly sensitive detection of AF spin state.

###Colossal negative magnetoresistance in the complex charge density wave regime of an antiferromagnetic Dirac semimetal|Ratnadwip Singha,Kirstine J. Dalgaard,Dmitry Marchenko,Maxim Krivenkov,Emile D. L. Rienks,Milena Jovanovic,Samuel M. L. Teicher,Jiayi Hu,Tyger H. Salters,Jingjing Lin,Andrei Varykhalov,N. Phuan Ong,Leslie M. Schoop###

Colossal negative magnetoresistance in the complex charge density wave regime of an antiferromagnetic Dirac semimetal. Colossal magnetoresistance (MR) is a well-known phenomenon, notably observed
in hole-doped ferromagnetic manganites. It remains a major research topic due
to its potential in technological applications. Though topological semimetals
also show large MR, its origin and nature are completely different. Here, we
show that in the highly electron doped region, the Dirac semimetal CeSbTe
demonstrates similar properties as the manganites. CeSb$_{0.11}$Te$_{1.90}$
hosts multiple charge density wave (CDW) modulation-vectors and has a complex
magnetic phase diagram. We confirm that this compound is an antiferromagnetic
Dirac semimetal. Despite having a metallic Fermi surface, the electronic
transport properties are semiconductor-like and deviate from known theoretical
models. An external magnetic field induces a semiconductor-metal-like
transition, which results in a colossal negative MR. Moreover, signatures of
the coupling between the CDW and a spin modulation are observed in resistivity.
This spin modulation also produces a giant anomalous Hall response.

###Quantum Transport and Magnetism of Dirac Electrons in Solids|Hiroki Isobe,Naoto Nagaosa###

Quantum Transport and Magnetism of Dirac Electrons in Solids. The relativistic Dirac equation covers the fundamentals of electronic
phenomena in solids and as such it effectively describes the electronic states
of the topological insulators like Bi$_2$Se$_3$ and Bi$_2$Te$_3$. Topological
insulators feature gapless surface states and, moreover, magnetic doping and
resultant ferromagnetic ordering break time-reversal symmetry to realize
quantum anomalous Hall and Chern insulators. Here we focus on the bulk and
investigate the mutual coupling of electronic and magnetic properties of Dirac
electrons. Without carrier doping, spiral magnetic orders cause a ferroelectric
polarization through the spin-orbit coupling. In a doped metallic state, the
anisotropic magnetoresistance arises without uniform magnetization. We find
that electric current induces uniform magnetization and conversely an
oscillating magnetic order induces electric current. Our model provides a
coherent and unified description of all those phenomena. The mutual control of
electric and magnetic properties demonstrates implementations of
antiferromagnetic spintronics. We also discuss the stoichiometric magnetic
topological insulator MnBi$_2$Te$_4$.

###Electronic structure and physical properties of EuAuAs single crystal|S. Malick,J. Singh,A. Laha,V. Kanchana,Z. Hossain,D. Kaczorowski###

Electronic structure and physical properties of EuAuAs single crystal. High-quality single crystals of EuAuAs were studied by means of powder x-ray
diffraction, magnetization, magnetic susceptibility, heat capacity, electrical
resistivity and magnetoresistance measurements. The compound crystallizes with
a hexagonal structure of the ZrSiBe type (space group $P6_3/mmc$). It orders
antiferromagnetically below 6 K due to the magnetic moments of divalent Eu
ions. The electrical resistivity exhibits metallic behavior down to 40 K,
followed by a sharp increase at low temperatures. The magnetotransport
isotherms show a distinct metamagnetic-like transition in concert with the
magnetization data. The antiferromagnetic ground state in \mbox{EuAuAs} was
corroborated in the \textit{ab initio} electronic band structure calculations.
Most remarkably, the calculations revealed the presence of nodal line without
spin-orbit coupling and Dirac point with inclusion of spin-orbit coupling. The
\textit{Z}$_2$ invariants under the effective time reversal and inversion
symmetries make this system nontrivial topological material. Our findings,
combined with experimental analysis, makes EuAuAs a plausible candidate for an
antiferromagnetic topological nodal-line semimetal.

###Multiple topological nodal structure in LaSb2 with large linear magnetoresistance|Y. X. Qiao,Z. C. Tao,F. Y. Wang,Huaiqiang Wang,Z. C. Jiang,Z. T. Liu,Soohyun Cho,F. Y. Zhang,Q. K. Meng,W. Xia,Y. C. Yang,Z. Huang,J. S. Liu,Z. H. Liu,Z. W. Zhu,S. Qiao,Y. F. Guo,Haijun Zhang,Dawei Shen###

Multiple topological nodal structure in LaSb2 with large linear magnetoresistance. Unconventional fermions in the immensely studied topological semimetals are
the source for rich exotic topological properties. Here, using symmetry
analysis and first-principles calculations, we propose the coexistence of
multiple topological nodal structure in LaSb2, including topological nodal
surfaces, nodal lines and in particular eightfold degenerate nodal points,
which have been scarcely observed in a single material. Further, utilizing high
resolution angle-resolved photoemission spectroscopy in combination with
Shubnikov-de Haas quantum oscillations measurements, we confirm the existence
of nodal surfaces and eightfold degenerate nodal points in LaSb2, and extract
the {\pi} Berry phase proving the non-trivial electronic band structure
topology therein. The intriguing multiple topological nodal structure might
play a crucial role in giving rise to the large linear magnetoresistance. Our
work renews the insights into the exotic topological phenomena in LaSb2 and its
analogous.

###Transport evidence for the surface state and spin-phonon interaction in FeTe$_{0.5}$Se$_{0.5}$|Mu-Yun Li,Jia-Wei Hu,Ge Huang,Wei-Jian Li,Ya-Kang Peng,Guangyong Xu,Genda Gu,Xiao-Jia Chen###

Transport evidence for the surface state and spin-phonon interaction in FeTe$_{0.5}$Se$_{0.5}$. The iron chalcogenides have been proved to be intrinsic topological
superconductors to implement quantum computation because of their unique
electronic structures. The topologically nontrivial surface states of
FeTe$_{0.5}$Se$_{0.5}$ have been predicted by several calculations and then
confirmed by high-resolution photoemission and scanning tunneling experiments.
However, so far, the shreds of the electrical transport evidence for
topological surface states are still in absence. By carrying out electrical
transport experiments, we observe a topological transition with a nonlinear
Hall conductivity and simultaneous linear magnetoresistance near the
superconducting transition temperature. Furthermore, we observe a sign reversal
of the Hall coefficient accompanied by a concurrently softening of the
${A}_{1g}$ phonon mode at about 40 K, indicating a nematic transition. The
synchronized phonon softening with nematicity manifests an enhanced fluctuation
state through spin-phonon interaction. Our results solidly corroborate the
topological surface states of FeTe$_{0.5}$Se$_{0.5}$ and provide an
understanding of the mechanism of the superconductivity in iron chalcogenides.

###Observation of strange metal in hole-doped valley-spin insulator|Tuan Dung Nguyen,Baithi Mallesh,Seon Je Kim,Houcine Bouzid,Byeongwook Cho,Xuan Phu Le,Tien Dat Ngo,Won Jong Yoo,Young-Min Kim,Dinh Loc Duong,Young Hee Lee###

Observation of strange metal in hole-doped valley-spin insulator. Temperature-linear resistance at low temperatures in strange metals is an
exotic characteristic of strong correlation systems, as observed in high-TC
superconducting cuprates, heavy fermions, Fe-based superconductors, ruthenates,
and twisted bilayer graphene. Here, we introduce a hole-doped valley-spin
insulator, V-doped WSe2, with hole pockets in the valence band. The strange
metal characteristic was observed in VxW1-xSe2 at a critical carrier
concentration of 9.5 x 10^20 cm-3 from 150 K to 1.8 K. The unsaturated
magnetoresistance is almost linearly proportional to the magnetic field. Using
the ansatz R(H,T) - R(0,0) ~ [(alpha.k.T)^2+(gamma.mu.B)^2]^1/2, the
gamma/alpha ratio is estimated approximately to 4, distinct from that for the
quasiparticles of LSCO, BaFe2(As1-xPx)2 (gamma/alpha=1) and bosons of YBCO
(gamma/alpha=2). Our observation opens up the possible routes that induce
strong correlation and superconductivity in two-dimensional materials with
strong spin-orbit coupling.

###Weak antilocalization and ferromagnetism in magnetic Weyl semimetal Co3Sn2S2|Kapil Kuma,M. M. Sharma,V. P. S. Awana###

Weak antilocalization and ferromagnetism in magnetic Weyl semimetal Co3Sn2S2. Here we report successful synthesis of single crystalline magnetic Weyl
semimetal Co3Sn2S2. The synthesized crystal is characterized through various
tools viz. X-ray diffraction, field emission electron microscopy and X-ray
photoelectron spectroscopy. A clear ferromagnetic transition is observed in
magnetization and heat capacity at around 175K, which is further verified
through electrical transport measurements. Hysteresis is observed in R-T
measurements in cooling and warming cycle, showing the presence of first order
phase transition and charge ordering in the synthesized sample. The synthesized
Co3Sn2S2 exhibits high magnetoresistance of around 230% at 2K. The transport
phenomenon in synthesized Co3Sn2S2 appears to have contributions from
topological surface states at low temperature below say 70 K, and above that
the same is found to be strongly dependent on its bulk magnetic state.
Magnetoconductivity data at low fields of up to plus minus 1T (Tesla) is fitted
with Hikami Larkin Nagaoka model, which shows the presence of weak
antilocalization effect in synthesized Co3Sn2S2 crystal at low temperatures
below 30K.

###Large Bilinear Magnetoresistance from Rashba Spin-Splitting on the Surface of a Topological Insulator|Yang Wang,Binbin Liu,Yue-Xin Huang,Sivakumar V. Mambakkam,Yong Wang,Shengyuan A. Yang,Xian-Lei Sheng,Stephanie A. Law,John Q. Xiao###

Large Bilinear Magnetoresistance from Rashba Spin-Splitting on the Surface of a Topological Insulator. In addition to the topologically protected linear dispersion, a
band-bending-confined two-dimensional electron gas with tunable Rashba
spin-splitting (RSS) was found to coexist with the topological surface states
on the surface of topological insulators (TIs). Here, we report the observation
of large bilinear magnetoresistance (BMR) in Bi2Se3 films decorated with
transition metal atoms. The magnitude of the BMR sensitively depends on the
type and amount of atoms deposited, with a maximum achieved value close to
those of strong Rashba semiconductors. Our first-principles calculations
reproduce the quantum well states and reveal sizable RSS in all Bi2Se3
heterostructures with broken inversion symmetry. Our results show that
charge-spin interconversion through RSS states in TIs can be fine-tuned through
surface atom deposition and easily detected via BMR for potential spintronic
applications.

###Onset Temperatures for Superconducting Fluctuations in Te-annealed FeTe$_{1-x}$Se$_x$ Single Crystals: Evidence for the BCS-BEC Crossover|Yu Uezono,Takumi Otsuka,Shotaro Hagisawa,Haruka Taniguchi,Michiaki Matsukawa,Takenori Fujii,Takao Watanabe###

Onset Temperatures for Superconducting Fluctuations in Te-annealed FeTe$_{1-x}$Se$_x$ Single Crystals: Evidence for the BCS-BEC Crossover. Recently, the superconductors' community has witnessed an unsettled debate
regarding whether iron-based superconductors, in particular FeSe and
FeSe$_{1-x}$S$_x$, are in the Bardeen-Cooper-Shrieffer (BCS) - Bose-Einstein
condensation (BEC) crossover regime. Nonetheless, one particular system,
FeTe$_{1-x}$Se$_x$, has been less investigated in this regard owing to the
screening of its intrinsic superconducting properties by the inevitable iron
excess. Herein, the onset temperatures for superconducting fluctuations
($T_{scf}$) are investigated by measuring the magnetoresistance (MR) of
Te-annealed, high-quality FeTe$_{1-x}$Se$_x$ ($x$ = 0.1, 0.2, 0.3, and 0.4)
single crystals. The results reveal very high $T_{scf}$ values for these
crystals. Particularly for $x$ = 0.4, $T_{scf}$ reaches approximately 40 K,
which is 2.7 times larger than $T_c$. This indicates that the superconductivity
of the FeTe$_{1-x}$Se$_x$ system is well within the BCS-BEC crossover regime.

###Unidirectional orbital magnetoresistance in light metal/ferromagnet bilayers|Shilei Ding,Paul Noël,Gunasheel Kauwtilyaa Krishnaswamy,Pietro Gambardella###

Unidirectional orbital magnetoresistance in light metal/ferromagnet bilayers. We report the observation of a unidirectional magnetoresistance (UMR) that
originates from the nonequilibrium orbital momentum induced by an electric
current in a naturally oxidized Cu/Co bilayer. The orbital-UMR scales with the
torque efficiency due to the orbital Rashba-Edelstein effect upon changing the
Co thickness and temperature, reflecting their common origin. We attribute the
UMR to orbital-dependent electron scattering and orbital-to-spin conversion in
the ferromagnetic layer. In contrast to the spin-current induced UMR, the
magnon contribution to the orbital-UMR is absent in thin Co layers, which we
ascribe to the lack of coupling between low energy magnons and orbital current.
The magnon contribution to the UMR emerges in Co layers thicker than about 5
nm, which is comparable to the orbital-to-spin conversion length. Our results
provide insight into orbital-to-spin momentum transfer processes relevant for
the optimization of spintronic devices based on light metals and orbital
transport.

###A non-inductive magnetic eye-tracker: from dipole tracking to gaze retrieval|Valerio Biancalana,Piero Chessa###

A non-inductive magnetic eye-tracker: from dipole tracking to gaze retrieval. We analyze the information that can be retrieved from the tracking parameters
produced by an innovative wearable eye tracker. The latter is based on a
permanent-magnet marked corneal lens and by an array of magnetoresistive
detectors that measure the magnetostatic field in several positions in the eye
proximity. We demonstrate that, despite missing information due to the axial
symmetry of the measured field, physiological constraints or measurement
conditions make possible to infer complete eye-pose data. Angular precision and
accuracy achieved with the current prototypical device are also assessed and
briefly discussed. The results show that the instrumentation considered is
suitable as a new, moderately invasive medical diagnostics for the
characterization of ocular movements and associated disorders.

###Tunneling magnetoresistance and spin-valley polarization of aperiodic magnetic silicene superlattices|P. Villasana-Mercado,J. G. Rojas-Briseño,S. Molina-Valdovinos,I. Rodríguez-Vargas###

Tunneling magnetoresistance and spin-valley polarization of aperiodic magnetic silicene superlattices. Magnetic silicene superlattices (MSSLs) are versatile structures with
spin-valley polarization and tunneling magnetoresistance (TMR) capabilities.
However, the oscillating transport properties related to the superlattice
periodicity impede stable spin-valley polarization states reachable by
reversing the magnetization direction. Here, we show that aperiodicity can be
used to improve the spin-valley polarization and TMR by reducing the
characteristic conductance oscillations of periodic MSSLs (P-MSSLs). Using the
Landauer-B\"uttiker formalism and the transfer matrix method, we investigate
the spin-valley polarization and the TMR of Fibonacci (F-) and Thue-Morse (TM-)
MSSLs as typical aperiodic superlattices. Our findings indicate that aperiodic
superlattices with higher disorder provide better spin-valley polarization and
TMR values. In particular, TM-MSSLs reduce considerably the conductance
oscillations giving rise to two well-defined spin-valley polarization states
and a better TMR than F- and P-MSSLs. F-MSSLs also improve the spin-valley
polarization and TMR, however they depend strongly on the parity of the
superlattice generation.

###Perspectives on Antiferromagnetic Spintronics|Kang Wang,Vineetha Bheemarasetty,Junhang Duan,Shiyu Zhou,Gang Xiao###

Perspectives on Antiferromagnetic Spintronics. Although the development of spintronic devices has advanced significantly
over the past decade with the use of ferromagnetic materials, the extensive
implementation of such devices has been limited by the notable drawbacks of
these materials. Antiferromagnets claim to resolve many of these shortcomings
leading to faster, smaller, more energy-efficient, and more robust electronics.
Antiferromagnets exhibit many desirable properties including zero net
magnetization, imperviousness to external magnetic fields, intrinsic
high-frequency dynamics with a characteristic precession frequency on the order
of terahertz (THz), and the ability to serve as passive exchange-bias materials
in multiple magnetoresistance (MR)- based devices. In this Perspective article,
we will discuss the fundamental physics of magnetic structures in
antiferromagnets and their interactions with external stimuli such as spin
current, voltage, and magnons. A discussion on the challenges lying ahead is
also provided along with an outlook of future research directions of these
systems.

###High-field and high-temperature magnetoresistance reveals the superconducting behaviour of the stacking faults in multilayer graphene|Christian E. Precker,José Barzola-Quiquia,Mun K. Chan,Marcelo Jaime,Pablo D. Esquinazi###

High-field and high-temperature magnetoresistance reveals the superconducting behaviour of the stacking faults in multilayer graphene. In spite of 40 years of experimental studies and several theoretical
proposals, an overall interpretation of the complex behavior of the
magnetoresistance (MR) of multilayer graphene, i.e. graphite, at high fields
($B \lesssim 70~$T) and in a broad temperature range is still lacking. Part of
the complexity is due to the contribution of stacking faults (SFs), which most
of thick enough multilayer graphene samples have. We propose a procedure that
allows us to extract the SF contribution to the MR we have measured at 0.48~K
$\leq T \leq$ 250~K and 0~T$\leq B \lesssim$ 65~T. We found that the MR
behavior of part of the SFs is similar to that of granular superconductors with
a superconducting critical temperature $T_c \sim $ 350~K, in agreement with
recent publications. The measurements were done on a multilayer graphene TEM
lamella, contacting the edges of the two-dimensional SFs.

###Local density of states as a probe for tunneling magnetoresistance effect: application to ferrimagnetic tunnel junctions|Katsuhiro Tanaka,Takuya Nomoto,Ryotaro Arita###

Local density of states as a probe for tunneling magnetoresistance effect: application to ferrimagnetic tunnel junctions. We investigate the tunneling magnetoresistance (TMR) effect using the lattice
models which describe the magnetic tunnel junctions (MTJ). First, taking a
conventional ferromagnetic MTJ as an example, we show that the product of the
local density of states (LDOS) at the center of the barrier traces the TMR
effect qualitatively. The LDOS inside the barrier has the information on the
electrodes and the electron tunneling through the barrier, which enables us to
easily evaluate the tunneling conductance more precisely than the conventional
Julliere's picture. We then apply this method to the MTJs with collinear
ferrimagnets and antiferromagnets. We find that the TMR effect in the
ferrimagnetic and antiferromagnetic MTJs changes depending on the interfacial
magnetic structures originating from the sublattice structure, which can also
be captured by the LDOS. Our findings will reduce the computational cost for
the qualitative evaluation of the TMR effect, and be useful for a broader
search for the materials which work as the TMR devices showing high
performance.

###Comprehensive Demonstration of Spin-Hall Hanle Effects in Epitaxial Pt Thin Films|Jing Li,Andrew H. Comstock,Dali Sun,Xiaoshan Xu###

Comprehensive Demonstration of Spin-Hall Hanle Effects in Epitaxial Pt Thin Films. We demonstrate a nonlinear Hall effect due to the boundary spin accumulation
in Pt films grown on Al2O3 substrates. This Hall effect and the previously
demonstrated Hanle magnetoresistance provide a complete picture of the
spin-precession control of the spin and charge transport at the boundary of a
spin-orbit coupled material, which we refer to as spin-Hall Hanle effects
(SHHE). We also show that the SHHE can be employed to measure the spin
diffusion length, the spin-Hall angle, and the spin relaxation time of heavy
metal without the need of magnetic interface or the input from other
measurements. The comprehensive demonstration of SHHE in such a simple system
suggests they may be ubiquitous and needs to be considered for unravelling the
spin and charge transport in more complex thin film structures of spin-orbit
coupled materials.

###Magnetotransport Properties and Fermi Surface Topology of Nodal line Semimetal InBi|Sambhab Dan,Kuldeep Kargeti,R. C. Sahoo,Shovan Dan,Debarati Pal,Sunil Verma,Sujay Chakravarty,S. K. Panda,S Patil###

Magnetotransport Properties and Fermi Surface Topology of Nodal line Semimetal InBi. In the present study, we have discussed the up-turn behavior in the
resistivity pattern of the topological nodal line semimetal InBi. We argued
that such nature could be generalized with a mathematical model, that can be
applied to any compounds exhibiting similar behavior. The extremely high
magnetoresistance (XMR) has also been explained by the carrier compensation in
the compound, estimated from the Hall conductivity. Moreover, from the study of
Subhnikov-de Haas (SdH) oscillation and density functional theory (DFT), we
obtained the complete three-dimensional (3D) Fermi surface topology of the
compound InBi. A detailed understanding of carriers' behavior has been
discussed using those studies. We have also unfurled the topology of each
electron and hole pocket and its possible modulation with electron and hole
doping.

###Evidence of a compensated semimetal with electronic correlations at the CNP of twisted double bilayer graphene|Ayan Ghosh,Souvik Chakraborty,Unmesh Ghorai,Arup Kumar Paul,K. Watanabe,T. Taniguchi,Rajdeep Sensarma,Anindya Das###

Evidence of a compensated semimetal with electronic correlations at the CNP of twisted double bilayer graphene. Recently, magic-angle twisted bilayer graphene (MATBLG) has shown the
emergence of various interaction-driven novel quantum phases at the
commensurate fillings of the moir'e superlattice, while the charge neutrality
point (CNP) remains mostly a vanilla insulator. Here, we show an emerging phase
of nearly compensated semimetallicity at the CNP of twisted double bilayer
graphene (TDBLG), a close cousin of MATBLG, with signatures of electronic
correlation. Using electrical and thermal transport, we find almost two orders
of magnitude enhancement of the thermopower in magnetic fields much smaller
than the extreme quantum limit, accompanied by a large magnetoresistance($\sim
2500\%$) at CNP. This provides indisputable experimental evidence that TDBLG
near CNP is a compensated semimetal. Moreover, at low temperatures, we observe
an unusual sublinear temperature dependence of resistance. A recent theory
predicts the formation of an excitonic metal near CNP, where small electron and
hole pockets coexist. We understand the sublinear temperature dependence in
terms of critical fluctuations in this theory.

###3D Interconnected Magnetic Nanowire Networks as Potential Integrated Multistate Memristors|Dhritiman Bhattacharya,Zhijie Chen,Christopher J. Jensen,Chen Liu,Edward C. Burks,Dustin A. Gilbert,Xixiang Zhang,Gen Yin,Kai Liu###

3D Interconnected Magnetic Nanowire Networks as Potential Integrated Multistate Memristors. Interconnected magnetic nanowire (NW) networks offer a promising platform for
3-dimensional (3D) information storage and integrated neuromorphic computing.
Here we report discrete propagation of magnetic states in interconnected Co
nanowire networks driven by magnetic field and current, manifested in distinct
magnetoresistance (MR) features. In these networks, when only a few
interconnected NWs were measured, multiple MR kinks and local minima were
observed, including a significant minimum at a positive field during the
descending field sweep. Micromagnetic simulations showed that this unusual
feature was due to domain wall (DW) pinning at the NW intersections, which was
confirmed by off-axis electron holography imaging. In a complex network with
many intersections, sequential switching of nanowire sections separated by
interconnects was observed, along with stochastic characteristics. The
pinning/depinning of the DWs can be further controlled by the driving current
density. These results illustrate the promise of such interconnected networks
as integrated multistate memristors.

###A topological transition-induced giant transverse thermoelectric effect in polycrystalline Dirac semimetal Mg3Bi2|Tao Feng,Panshuo Wang,Zhijia Han,Liang Zhou,Zhiran Wang,Wenqing Zhang,Qihang Liu,Weishu Liu###

A topological transition-induced giant transverse thermoelectric effect in polycrystalline Dirac semimetal Mg3Bi2. To achieve thermoelectric energy conversion, a large transverse
thermoelectric effect in topological materials is crucial. However, the general
relationship between topological electronic structures and transverse
thermoelectric effect remains unclear, restricting the rational design of novel
transverse thermoelectric materials. Herein, we demonstrate a topological
transition-induced giant transverse thermoelectric effect in polycrystalline
Mn-doped Mg3+{\delta}Bi2 material, which has a competitively large transverse
thermopower (617 uV/K), power factor (20393 uWm-1K-2), magnetoresistance
(16600%), and electronic mobility (35280cm2V-1S-1). The high performance is
triggered by the modulation of chemical pressure and disorder effects in the
presence of Mn doping, which induces the transition from a topological
insulator to a Dirac semimetal. The high-performance polycrystalline Mn-doped
Mg3+{\delta} Bi2 described in this work robustly boosts transverse
thermoelectric effect through topological phase transition, paving a new avenue
for the material design of transverse thermoelectricity.

###Tuning the Band Topology of GdSb by Epitaxial Strain|Hadass S. Inbar,Dai Q. Ho,Shouvik Chatterjee,Aaron N. Engel,Shoaib Khalid,Connor P. Dempsey,Mihir Pendharkar,Yu Hao Chang,Shinichi Nishihaya,Alexei V. Fedorov,Donghui Lu,Makoto Hashimoto,Dan Read,Anderson Janotti,Christopher J. Palmstrøm###

Tuning the Band Topology of GdSb by Epitaxial Strain. Rare-earth monopnictide (RE-V) semimetal crystals subjected to hydrostatic
pressure have shown interesting trends in magnetoresistance, magnetic ordering,
and superconductivity, with theory predicting pressure-induced band inversion.
Yet, thus far, there have been no direct experimental reports of interchanged
band order in RE-Vs due to strain. This work studies the evolution of band
topology in biaxially strained GdSb (001) epitaxial films using angle-resolved
photoemission spectroscopy (ARPES) and density functional theory (DFT). We find
that biaxial strain continuously tunes the electronic structure from
topologically trivial to nontrivial, reducing the gap between the hole and the
electron bands dispersing along the [001] direction. The conduction and valence
band shifts seen in DFT and ARPES measurements are explained by a tight-binding
model that accounts for the orbital symmetry of each band. Finally, we discuss
the effect of biaxial strain on carrier compensation and magnetic ordering
temperature.

###Electronic Origin of Half-metal to Semiconductor Transition and Colossal Magnetoresistance in Spinel HgCr2Se4|Aiji Liang,Zhilin Li,Shihao Zhang,Shucui Sun,Shuai Liu,Cheng Chen,Haifeng Yang,Shengtao Cui,Sung-Kwan Mo,Shuai Yang,Yongqing Li,Meixiao Wang,Lexian Yang,Jianpeng Liu,Zhongkai Liu,Yulin Chen###

Electronic Origin of Half-metal to Semiconductor Transition and Colossal Magnetoresistance in Spinel HgCr2Se4. Half-metals are ferromagnets hosting spin-polarized conducting carriers and
crucial for spintronics applications. The chromium spinel HgCr2Se4 represents a
unique type of half-metal, which features a half-metal to semiconductor
transition (HMST) and exhibits colossal magnetoresistance (CMR) across the
ferromagnetic-paramagnetic (FM-PM) transition. Using angle-resolved
photoemission spectroscopy (ARPES), we find that the Fermi surface of n-type
HgCr2Se4 (n-HgCr2Se4) consists of a single electron pocket which moves above
the Fermi level (EF) upon the FM-PM transition, leading to the HMST. Such a
Lifshitz transition manifests a giant band splitting which originates from the
exchange interaction unveiled with a specific chemical nonstoichiometry. The
exchange band splitting and the chemical nonstoichiometry are two key
ingredients to the HMST and CMR, consistent with our ab-initio calculation. Our
findings provide spectroscopic evidences of the electronic origin of the
anomalous properties of HgCr2Se4, which address the unique phase transition in
half-metals.

###Strain driven antiferromagnetic exchange interaction in SrMnO$_3$ probed by phase shifted Spin Hall magnetoresistance|J. J. L. van Rijn,D. Wang,B. Sanyal,T. Banerjee###

Strain driven antiferromagnetic exchange interaction in SrMnO$_3$ probed by phase shifted Spin Hall magnetoresistance. Multiferroics have found renewed interest in topological magnetism and for
logic-in-memory applications. Among them, SrMnO$_{3}$, possessing strong
magnetoelectric coupling is gaining attention for the design of coexisting
magnetic and polar orders upon straining. Here we demonstrate antiferromagnetic
exchange interactions in strained SMO thin films extracted from a new feature
in the phase response of Spin Hall magnetoresistance, which has not been
explored in earlier works, such as in magnetic insulators. We explain our
findings with a model that incorporates magnetic anisotropy along [110]
direction, corroborates with DFT studies and is consistent with the direction
of ferroelectric polarization in SrMnO$_{3}$. The fundamental insights obtained
from our studies establishes the potential of this material in
magnetoelectrically coupled devices for different logic and memory
applications.

###Resonant weak-value enhancement for solid-state quantum metrology|Mahadevan Subramanian,Amal Mathew,Bhaskaran Muralidharan###

Resonant weak-value enhancement for solid-state quantum metrology. Quantum metrology that employs weak-values can potentially effectuate
parameter estimation with an ultra-high sensitivity and has been typically
explored across quantum optics setups. Recognizing the importance of sensitive
parameter estimation in the solid-state, we propose a spintronic device
platform to realize this. The setup estimates a very weak localized Zeeman
splitting by exploiting a resonant tunneling enhanced magnetoresistance
readout. We establish that this paradigm offers nearly optimal performance with
a quantum Fisher information enhancement of about $10^4$ times that of single
high-transmissivity barriers. The obtained signal also offers a high
sensitivity in the presence of dephasing effects typically encountered in the
solid state. These results put forth definitive possibilities in harnessing the
inherent sensitivity of resonant tunneling for solid-state quantum metrology
with potential applications, especially, in the sensitive detection of small
induced Zeeman effects in quantum material heterostructures.

###Unification of Nonlinear Anomalous Hall Effect and Nonreciprocal Magnetoresistance in Metals by the Quantum Geometry|Daniel Kaplan,Tobias Holder,Binghai Yan###

Unification of Nonlinear Anomalous Hall Effect and Nonreciprocal Magnetoresistance in Metals by the Quantum Geometry. The quantum geometry has significant consequences in determining transport
and optical properties in quantum materials. Here, we derive a quantum kinetic
equation unifying the nonlinear anomalous Hall effect (NLAHE) and nonreciprocal
magnetoresistance (NMR) from the quantum geometry. In the dc limit, both
transverse and longitudinal nonlinear conductivities include a term due to the
normalized quantum metric dipole. The quantum metric contribution is intrinsic
and does not scale with the quasiparticle lifetime. We demonstrate the
coexistence of large a NLAHE and NMR driven by the quantum metric dipole in
films of the doped antiferromagentic topological insulator MnBi$_2$Te$_4$. Our
work indicates that both longitudinal and transverse nonlinear transports
provide a sensitive probe of the quantum geometry in solids.

###Optical Switching in Tb/Co-Multilayer Based Nanoscale Magnetic Tunnel Junctions|Sucheta Mondal,Debanjan Polley,Akshay Pattabi,Jyotirmoy Chatterjee,David Salomoni,Luis Aviles-Felix,Aurélien Olivier,Miguel Rubio-Roy,Bernard Diény,Liliana Daniela Buda Prejbeanu,Ricardo Sousa,Ioan Lucian Prejbeanu,Jeffrey Bokor###

Optical Switching in Tb/Co-Multilayer Based Nanoscale Magnetic Tunnel Junctions. Magnetic tunnel junctions (MTJs) are elementary units of magnetic memory
devices. For high-speed and low-power data storage and processing applications,
fast reversal by an ultrashort laser pulse is extremely important. We
demonstrate optical switching of Tb/Comultilayer-based nanoscale MTJs by
combining optical writing and electrical read-out methods. A 90 fs-long laser
pulse switches the magnetization of the storage layer (SL). The change in
magnetoresistance between the SL and a reference layer (RL) is probed
electrically across the tunnel barrier. Single-shot switching is demonstrated
by varying the cell diameter from 300 nm to 20 nm. The anisotropy,
magnetostatic coupling, and switching probability exhibit cell-size dependence.
By suitable association of laser fluence and magnetic field, successive
commutation between high-resistance and low-resistance states is achieved. The
switching dynamics in a continuous film is probed with the magneto-optical Kerr
effect technique. Our experimental findings provide strong support for the
growing interest in ultrafast spintronic devices.

###Spin Hall Induced Magnetization Dynamics in Multiferroic Tunnel Junction|Jakub Pawlak,Witold Skowroński,Piotr Kuświk,Félix Casanova,Marek Przybylski###

Spin Hall Induced Magnetization Dynamics in Multiferroic Tunnel Junction. The combination of spin-orbit coupling driven effects and multiferroic
tunneling properties was explored experimentally in thin Pt/Co/BTO/LSMO
multilayers. The presence of a Pt heavy metal allows for the spin
current-induced magnetization precession of Co upon radio-frequency charge
current injection. The utilization of a BTO ferroelectric tunnel barrier
separating the Co and LSMO ferromagnetic electrodes gives rise to both
tunneling-magnetoresistance and electroresistance. Using the spin-orbit torque
ferromagnetic resonance, the maganetization dynamics of the Co/Pt bilayers was
studied at room temperature. Unexpectedly the magnetization dynamics study in
the same geometry performed at low temperature reveals the existence of both Co
and LSMO resonance peaks indicating efficient spin current generation both
using the spin Hall effect in Pt and spin pumping in LSMO that tunnel via the
BTO barrier.

###Anisotropic magnetic and magnetotransport properties in morphologically distinct Nd0.6Sr0.4MnO3 thin films|R S Mrinaleni,E P Amaladass,A. T. Sathyanarayana,S Amirthapandian,Jegadeesan P,Pooja Gupta,T Geetha Kumary,S. K. Rai,Awadhesh Mani###

Anisotropic magnetic and magnetotransport properties in morphologically distinct Nd0.6Sr0.4MnO3 thin films. We investigate the magnetic and magnetotransport properties of nanostructured
Nd0.6Sr0.4MnO3 (NSMO) thin films grown on (100) oriented SrTiO3 (STO)
substrates. The thin films fabricated using the pulsed laser deposition
technique have been found to possess two distinct surface morphologies:
granular and nano rod type. Magnetization measurements have revealed that the
films with rod-type morphology exhibit improved in-plane magnetic anisotropy.
Magnetotransport studies have revealed that the granular thin films display a
characteristic butterfly-shaped low-field magneto-resistive (LFMR) behavior.
Furthermore, we investigate the anisotropic magneto-resistive (AMR) phenomenon
in the samples and we find that morphology greatly affects AMR. Thin films with
rod-type morphology show an enhanced AMR %. Such morphology dependent
tunability in magnetoresistance properties over a wide temperature range is
potentially interesting for developing oxide-based sensors and devices.

###Magnetic properties of hematite revealed by an ab initio parameterized spin model|Tobias Dannegger,András Deák,Levente Rózsa,E. Galindez-Ruales,Shubhankar Das,Eunchong Baek,Mathias Kläui,László Szunyogh,Ulrich Nowak###

Magnetic properties of hematite revealed by an ab initio parameterized spin model. Hematite is a canted antiferromagnetic insulator, promising for applications
in spintronics. Here, we present ab initio calculations of the tensorial
exchange interactions of hematite and use them to understand its magnetic
properties by parameterizing a semiclassical Heisenberg spin model. Using
atomistic spin dynamics simulations, we calculate the equilibrium properties
and phase transitions of hematite, most notably the Morin transition. The
computed isotropic and Dzyaloshinskii--Moriya interactions result in a N\'eel
temperature and weak ferromagnetic canting angle that are in good agreement
with experimental measurements. Our simulations show how dipole-dipole
interactions act in a delicate balance with first and higher-order on-site
anisotropies to determine the material's magnetic phase. Comparison with
spin-Hall magnetoresistance measurements on a hematite single-crystal reveals
deviations of the critical behavior at low temperatures. Based on a mean-field
model, we argue that these differences result from the quantum nature of the
fluctuations that drive the phase transitions.

###Observation of Weak Kondo Effect and Angle Dependent Magnetoresistance in Layered Antiferromagnetic V$_5$S$_8$ Single Crystal|Indrani Kar,Sayan Routh,Soumya Ghorai,Shubham Purwar,S. Thirupathaiah###

Observation of Weak Kondo Effect and Angle Dependent Magnetoresistance in Layered Antiferromagnetic V$_5$S$_8$ Single Crystal. The compound V$_5$S$_8$ can also be represented by V$_{1.25}$S$_2$, a
transition metal dichalcogenide (TMDC) with excess V. Very few TMDCs show
magnetism and/or Kondo effect. Among them, the sister compounds VSe$_2$ and
VTe$_2$ are recently proved to show ferromagnetism in addition to the
low-temperature resistivity upturn due to Kondo effect. In this study, we show
Kondo effect in V$_5$S$_8$ originated from the antiferromagnetic exchange
interactions among the intercalated V atoms below the N$\acute{e}$el ($T_N$)
temperature of 27 K. We find isotropic magnetic properties above $T_N$, while a
strong magnetic anisotropy is noticed below $T_N$. In addition, below $T_N$ we
find an out-of-plane ($H\parallel c$) spin-flop transition triggered at a
critical field of 3.5 T that is absent from the in-plane ($H\perp c$).
Angle-dependent magnetoresistance is found to be highly anisotropic in the
antiferromagnetic state.

###Electrical characterization of the azimuthal anisotropy of $(\mathrm{Ni}_x\mathrm{Co}_{1-x})\mathrm{B}$-based ferromagnetic nanotubes|Dhananjay Tiwari,Martin Christoph Scheuerlein,Mahdi Jaber,Eric Gautier,Laurent Vila,Jean-Philippe Attané,Michael Schöbitz,Aurélien Masseboeuf,Tim Hellmann,Jan P. Hofmann,Wolfgang Ensinger,Olivier Fruchart###

Electrical characterization of the azimuthal anisotropy of $(\mathrm{Ni}_x\mathrm{Co}_{1-x})\mathrm{B}$-based ferromagnetic nanotubes. We report on the structural, electric and magnetic properties of
$(\mathrm{Ni}_x\mathrm{Co}_{1-x})\mathrm{B}$ ferromagnetic nanotubes,
displaying azimuthal magnetization. The tubes are fabricated using electroless
plating in polycarbonate porous templates, with lengths several tens of
micrometers, diameters from 100nm to 500nm and wall thicknesses from 10nm to
80nm. The resistivity is $\sim 1.5\times10^{-6}\mathrm{\Omega/m}$, and the
anisotropic magnetoresistance~(AMR) of 0.2-0.3%, one order of magnitude
larger~(resp. smaller) than in the bulk material, which we attribute to the
resistance at grain boundaries. We determined the azimuthal anisotropy field
from M(H) AMR loops of single tubes contacted electrically. Its magnitude is
around 10mT, and tends to increase with the tube wall thickness, as well as the
Co content. However, surprisingly it does not dependent much on the diameter
nor on the curvature.

###Magnetoresistance signature of two-dimensional electronic states in Co$_3$Sn$_2$S$_2$|Jiaji Zhao,Bingyan Jiang,Shen Zhang,Lujunyu Wang,Enke Liu,Zhilin Li,Xiaosong Wu###

Magnetoresistance signature of two-dimensional electronic states in Co$_3$Sn$_2$S$_2$. Two-dimensional (2D) Dirac bands and flat bands are characteristics of a
kagome lattice. However, experimental studies on their electrical transport are
few, because three-dimensional (3D) bulk bands of kagome materials, consisting
of stacked 2D kagome layers, dominate the transport. We report a
magnetoresistance (MR) study of a kagome material, Co$_3$Sn$_2$S$_2$. Based on
analysis of the temperature, magnetic field, and field angle dependence of the
resistivity, we obtain a complete anatomy of MR. Besides a magnon MR, a
chirality-dependent MR, and a chiral-anomaly-induced MR, the most intriguing
feature is an orbital MR that scales only with the out-of-plane field, which
strongly indicates its 2D nature. We attribute it to the Dirac band of the
kagome lattice.

###Anomalous Nernst effect in a ferrimagnetic nodal-line semiconductor Mn$_3$Si$_2$Te$_6$|Chen Ran,Xinrun Mi,Junying Shen,Honghui Wang,Kunya Yang,Yan Liu,Guiwen Wang,Guoyu Wang,Youguo Shi,Aifeng Wang,Yisheng Chai,Xiaolong Yang,Mingquan He,Xin Tong,Xiaoyuan Zhou###

Anomalous Nernst effect in a ferrimagnetic nodal-line semiconductor Mn$_3$Si$_2$Te$_6$. In the ferrimagnetic nodal-line semiconductor Mn$_3$Si$_2$Te$_6$, colossal
magnetoresistance (CMR) arises below $T_\mathrm{c}=78$ K due to the interplay
of magnetism and topological nodal-line fermiology. The Berry curvature
associated with the topological nodal-line is expected to produce an anomalous
Nernst effect. Here, we present sizable anomalous Nernst signal in
Mn$_3$Si$_2$Te$_6$ below $T_\mathrm{c}$. In the low-magnetic-field region where
CMR is most apparent, the scaling ratio between the Nernst signal and
magnetization is significantly enhanced compared to that in conventional
magnetic materials. The enhanced Nernst effect and CMR likely share the same
mechanisms, which are closely linked to the nodal-line topology.

###Ferromagnetism and Metal-Insulator transition in F-doped LaMnO3|Ekta Yadav,Pramod Ghising,K. P. Rajeev,Z. Hossain###

Ferromagnetism and Metal-Insulator transition in F-doped LaMnO3. We present our studies on polycrystalline samples of fluorine doped LaMnO3
(LaMnO3-yFy). LaMnO2.5F0.5 exhibits remarkable magnetic and electrical
properties. It shows ferromagnetic and metallic behavior with a high Curie
temperature of ~ 239 K and a high magnetoresistance of -64. This drastic change
in magnetic properties in comparison to pure LaMnO3 is ascribed to the presence
of mixed-valence Mn ions driven by the F-doping at the O-sites, which enables
double exchange (DE) in LMOF. Furthermore, the resistivity data exhibits two
resistivity peaks at 239 K and 213 K, respectively. Our results point towards
the possibility of multiple double exchange hopping paths of two distinct
resistances existing simultaneously in the sample below 213 K.

###Magnetic order in nanoscale gyroid networks|Ami S. Koshikawa,Justin Llandro,Masayuki Ohzeki,Shunsuke Fukami,Hideo Ohno,Naëmi Leo###

Magnetic order in nanoscale gyroid networks. Three-dimensional magnetic metamaterials feature interesting phenomena that
arise from a delicate interplay of material properties, local anisotropy,
curvature, and connectivity. A particularly interesting magnetic lattice that
combines these aspects is that of nanoscale gyroids, with a
highly-interconnected chiral network with local three-connectivity reminiscent
of three-dimensional artificial spin ices. Here, we use finite-element
micromagnetic simulations to elucidate the anisotropic behaviour of nanoscale
nickel gyroid networks at applied fields and at remanence. We simplify the
description of the micromagnetic spin states with a macrospin model to explain
the anistropic global response, to quantify the extent of ice-like
correlations, and to discuss qualitative features of the anisotropic
magnetoresistance in the three-dimensional network. Our results demonstrate the
large variability of the magnetic order in extended gyroid networks, which
might enable future spintronic functionalities, including neuromorphic
computing and non-reciprocal transport.

###Large and tunable magnetoresistance in van der Waals Ferromagnet/Semiconductor junctions|Wenkai Zhu,Yingmei Zhu,Tong Zhou,Xianpeng Zhang,Hailong Lin,Qirui Cui,Faguang Yan,Ziao Wang,Yongcheng Deng,Hongxin Yang,Lixia Zhao,Igor Žutić,Kirill D. Belashchenko,Kaiyou Wang###

Large and tunable magnetoresistance in van der Waals Ferromagnet/Semiconductor junctions. Magnetic tunnel junctions (MTJs) with conventional bulk ferromagnets
separated by a nonmagnetic insulating layer are key building blocks in
spintronics for magnetic sensors and memory. A radically different approach of
using atomically-thin van der Waals (vdW) materials in MTJs is expected to
boost their figure of merit, the tunneling magnetoresistance (TMR), while
relaxing the lattice-matching requirements from the epitaxial growth and
supporting high-quality integration of dissimilar materials with
atomically-sharp interfaces. We report TMR up to 192% at 10 K in all-vdW
Fe3GeTe2/GaSe/Fe3GeTe2 MTJs. Remarkably, instead of the usual insulating
spacer, this large TMR is realized with a vdW semiconductor GaSe. Integration
of two-dimensional ferromagnets in semiconductor-based vdW junctions offers
gate-tunability, bias dependence, magnetic proximity effects, and
spin-dependent optical-selection rules. We demonstrate that not just the
magnitude, but also the TMR sign is tuned by the applied bias or the
semiconductor thickness, enabling modulation of highly spin-polarized carriers
in vdW semiconductors.

###Mechanism of electrical switching of ultra-thin CoO/Pt bilayers|Christin Schmitt,Adithya Rajan,Grischa Beneke,Aditya Kumar,Tobias Sparmann,Hendrik Meer,Beatrice Bednarz,Rafael Ramos,Miguel Angel Nino,Michael Foerster,Eiji Saitoh,Mathias Kläui###

Mechanism of electrical switching of ultra-thin CoO/Pt bilayers. We study current-induced switching of the N\'eel vector in CoO/Pt bilayers to
understand the underlaying antiferromagnetic switching mechanism. Surprisingly,
we find that for ultra-thin CoO/Pt bilayers electrical pulses along the same
path can lead to an increase or decrease of the spin Hall magnetoresistance
signal, depending on the current density of the pulse. By comparing the results
of these electrical measurements to XMLD-PEEM imaging of the antiferromagnetic
domain structure before and after the application of current pulses, we reveal
the reorientation of the N\'eel vector in ultra-thin CoO(4 nm). This allows us
to determine that even opposite resistance changes can result from a
thermomagnetoelastic switching mechanism. Importantly, our spatially resolved
imaging shows that regions where the current pulses are applied and regions
further away exhibit different switched spin structures, which can be explained
by a spin-orbit torque based switching mechanism that can dominate in very thin
films.

###Two-fold symmetric superconductivity in the kagome superconductor RbV3Sb5|Shuo Wang,Ze-Nan Wu,Jing-Zhi Fang,Zhongming Wei,Zhiwei Wang,Wen Huang,Yugui Yao,Jia-Jie Yang,Ben-Chuan Lin,Dapeng Yu###

Two-fold symmetric superconductivity in the kagome superconductor RbV3Sb5. The recent discovered kagome superconductors provide a good platform for
studying intertwined orders and novel states such as topology, superconductor,
charge density wave, et al. The interplay of these orders may spontaneously
break the rotational symmetry, and induce exotic phenomena such as nematicity,
or even nematic superconductor. Here we report a two-fold rotational symmetric
superconductivity of thin-film RbV3Sb5 in response to a direction-dependent
in-plane magnetic fields, in contrast to the six-fold structural symmetry of
the crystal lattice. The two-fold symmetry was evidenced by the
magnetoresistance transport experiments, critical magnetic field measurements
and the anisotropic superconducting gap. With different configuration, we
further observed the six-fold symmetry superimposed on the two-fold symmetry
near the boundary between normal states and superconducting states. Our results
present the correlation-driven symmetry breaking and highlight the promising
platform to study the intertwined orders such as unconventional
superconductivity in this correlated kagome family.

###Observation of Colossal Terahertz Magnetoresistance and Magnetocapacitance in a Perovskite Manganite|Fuyang Tay,Swati Chaudhary,Jiaming He,Nicolas Marquez Peraca,Andrey Baydin,Gregory A. Fiete,Jianshi Zhou,Junichiro Kono###

Observation of Colossal Terahertz Magnetoresistance and Magnetocapacitance in a Perovskite Manganite. We have studied the terahertz response of a bulk single crystal of
La$_{0.875}$Sr$_{0.125}$MnO$_3$ at around its Curie temperature, observing
large changes in the real and imaginary parts of the optical conductivity as a
function of magnetic field. The terahertz resistance and capacitance extracted
from the optical conductivity rapidly increased with increasing magnetic field
and did not show any sign of saturation up to 6 T, reaching 60% and 15%,
respectively, at 180 K. The observed terahertz colossal magnetoresistance and
magnetocapacitance effects can be qualitatively explained by using a
two-component model that assumes the coexistence of two phases with vastly
different conductivities. These results demonstrate the potential use of
perovskite manganites for developing efficient terahertz devices based on
magnetic modulations of the amplitude and phase of terahertz waves.

###Effect of atomic anti-site disorder on the AMR in FeCo alloys|Mingsong Zhang,Bin Peng,Wanli Zhang,Wenxu Zhang###

Effect of atomic anti-site disorder on the AMR in FeCo alloys. In order to understand the anti-site disorder effect on the anisotropic
magnetoresistance (AMR) effect in alloys, $\rm{Fe}_{50}Co_{50}$ alloys were
studied in this work using the fully relativistic spin-polarized screened (KKR)
method. The anti-site effect was modeled by interchanging Fe and Co atoms and
treated by the coherent potential approximation (CPA). We find that the
anti-site disorder broadens the spectral function and decreases the
conductivity. Our work emphasizes that the absolute variations of resistivity
under magnetic moment rotation are less affected by atomic disorders. The
annealing procedure improves the AMR by reduction of the total resistivity. At
the same time, we also find that the fourth-order term in the angular dependent
resistivity becomes weaker when the disorder increases, resulting from
increased scattering of the states around the band-crossing.

###Real-space investigation of polarons in hematite Fe2O3|Jesus Redondo,Michele Reticcioli,Vit Gabriel,Dominik Wrana,Florian Ellinger,Michele Riva,Giada Franceschi,Erik Rheinfrank,Igor Sokolovic,Zdenek Jakub,Florian Kraushofer,Aji Alexander,Laerte L. Patera,Jascha Repp,Michael Schmid,Ulrike Diebold,Gareth S. Parkinson,Cesare Franchini,Pavel Kocan,Martin Setvin###

Real-space investigation of polarons in hematite Fe2O3. In polarizable materials, electronic charge carriers interact with the
surrounding ions, leading to quasiparticle behaviour. The resulting polarons
play a central role in many materials properties including electrical
transport, optical properties, surface reactivity and magnetoresistance, and
polaron properties are typically investigated indirectly through such
macroscopic characteristics. Here, noncontact atomic force microscopy (nc-AFM)
is used to directly image polarons in Fe2O3 at the single quasiparticle limit.
A combination of Kelvin probe force microscopy (KPFM) and kinetic Monte Carlo
(KMC) simulations shows that Ti doping dramatically enhances the mobility of
electron polarons, and density functional theory (DFT) calculations indicate
that a metallic transition state is responsible for the enhancement. In
contrast, hole polarons are significantly less mobile and their hopping is
hampered further by the introduction of trapping centres.

###Effect of the resonant ac-drive on the spin-dependent recombination of polaron pairs: Relation to organic magnetoresistance|M. E. Raikh###

Effect of the resonant ac-drive on the spin-dependent recombination of polaron pairs: Relation to organic magnetoresistance. The origin of magnetoresistance is bipolar organic materials is the influence
of magnetic field on the dynamics of recombination within localized
electron-hole pairs. Recombination from the $S$ spin-state of the pair in
preceded by the beatings between the states $S$ and $T_0$. Period of the
beating is set by the the random hyperfine field. For the case when
recombination time from $S$ is shorter than the period, we demonstrate that a
{\em weak} resonant ac drive, which couples $T_0$ to $T_+$ and $T_{-}$ affects
dramatically the recombination dynamics and, thus, the current A distinctive
characteristics of the effect is that the current versus the drive amplitude
exhibits a {\em maximum}.

###Electrical transport properties driven by unique bonding configuration in gamma-GeSe|Jeongsu Jang,Joonho Kim,Dongchul Sung,Jong Hyuk Kim,Joong-Eon Jung,Sol Lee,Jinsub Park,Chaewoon Lee,Heesun Bae,Seongil Im,Kibog Park,Young Jai Choi,Suklyun Hong,Kwanpyo Kim###

Electrical transport properties driven by unique bonding configuration in gamma-GeSe. Group-IV monochalcogenides have recently shown great potential for their
thermoelectric, ferroelectric, and other intriguing properties. The electrical
properties of group-IV monochalcogenides exhibit a strong dependence on the
chalcogen type. For example, GeTe exhibits high doping concentration, whereas
S/Se-based chalcogenides are semiconductors with sizable bandgaps. Here, we
investigate the electrical and thermoelectric properties of gamma-GeSe, a
recently identified polymorph of GeSe. gamma-GeSe exhibits high electrical
conductivity (~106 S/m) and a relatively low Seebeck coefficient (9.4 uV/K at
room temperature) owing to its high p-doping level (5x1021 cm-3), which is in
stark contrast to other known GeSe polymorphs. Elemental analysis and
first-principles calculations confirm that the abundant formation of Ge
vacancies leads to the high p-doping concentration. The magnetoresistance
measurements also reveal weak-antilocalization because of spin-orbit coupling
in the crystal. Our results demonstrate that gamma-GeSe is a unique polymorph
in which the modified local bonding configuration leads to substantially
different physical properties.

###Efficient characteristics of exchange coupling and spin-flop transition in Py/Gd bilayer using anisotropic magnetoresistance|Kaiyuan Zhou,Xiang Zhan,Zishuang Li,Haotian Li,Chunjie Yan,Lina Chen,Ronghua Liu###

Efficient characteristics of exchange coupling and spin-flop transition in Py/Gd bilayer using anisotropic magnetoresistance. The interlayer antiferromagnetic coupling rare-earth/transition-metal bilayer
ferrimagnet systems have attracted much attention because they present
variously unusual temperature-and field-dependent nontrivial magnetic states
and dynamics. These properties and the implementation of their applications in
spintronics highly depend on the significant temperature dependence of the
magnetic exchange stiffness constant A. Here, we quantitatively determine the
temperature dependence of magnetic exchange stiffness A_{Py-Gd} and A_{Gd} in
the artificially layered ferrimagnet consisting of a Py/Gd bilayer, using a
measurement of anisotropic magnetoresistance (AMR) of the bilayer thin film at
different temperatures and magnetic fields. The obtained temperature dependence
of A_{Py-Gd} and A_{Gd} exhibit a scaling power law with the magnetization of
Gd. The critical field of spin-flop transition and its temperature dependence
can also be directly obtained by this method. Additionally, the experimental
results are well reproduced by micromagnetic simulations with the obtained
parameters A_{Py-Gd} and A_{Gd}, which further confirms the reliability of this
easily accessible technique.

###Magnetic behavior of cubic Dy4RhAl with respect to isostructural Dy4PtAl, revealing a novel 4f d-band interaction|K. K. Iyer,S. Matteppanavar,S. Dodamani,K. Maiti,E. V. Sampathkumaran###

Magnetic behavior of cubic Dy4RhAl with respect to isostructural Dy4PtAl, revealing a novel 4f d-band interaction. We have investigated for the first time the magnetic behaviour of an
intermetallic compound, Dy4RhAl, crystallizing in Gd4RhIn type cubic structure
containing 3 sites for rare-earth (R), by several bulk measurements down to 1.8
K. This work is motivated by the fact that the isostructural Dy compound in the
R4PtAl family surprisingly orders ferromagnetically unlike other members of
this series, which order antiferromagnetically. The results reveal that the
title compound undergoes antiferromagnetic order at about 18 K, similar to
other heavy R members of R4RhAl family, unlike its Pt counterpart, indicating a
subtle difference in the role of conduction electrons to decide magnetism of
these compounds. Besides, spin-glass features coexisting with antiferromagnetic
order could be observed, which could mean cluster antiferromagnetism. The
electrical resistivity and magnetoresistance behaviours in the magnetically
ordered state are typical of magnetic materials exhibiting antiferromagnetic
gap. Features attributable to spin-reorientation as a function of temperature
and magnetic field can be seen in the magnetization data.

###Ultrafast electron-phonon scattering in antiferromagnetic Dirac-semimetals|Marius Weber,Kai Leckron,Libor Šmejkal,Jairo sinova,Baerbel Rethfeld,Hans Christian Schneider###

Ultrafast electron-phonon scattering in antiferromagnetic Dirac-semimetals. Recent novel topological antiferromagnetic systems have shown a strong
magnetoresistance effects driven by Dirac fermion characteristics whose
topology can be dynamically controlled by the N\'eel vector orientation. These
new antiferromagnets are characterized by anisotropic band structures combined
with complex relativistic spin structures in momentum space. While these
systems have been studied in transport experiments, very little is known about
their spin-dependent electronic dynamics on ultrafast timescales and
far-from-equilibrium behavior. This paper investigates spin-dependent
electronic dynamics due to electron-phonon scattering in a model electronic
band structure that corresponds to a Dirac semimetal antiferromagnet. Following
a spin-independent instantaneous excitation, we obtain a change of the
antiferromagnetic spin polarization due to the scattering dynamics for the
site-resolved spin expectation values. This allows us to identify fingerprints
of the anisotropic band structure in the carrier dynamics on ultrashort
timescales which should be observable in present experimental set-ups.

###Josephson coupling driven magnetoresistance in superconducting NiBi3 nanowires|Laxmipriya Nanda,Bidyadhar Das,Subhashree Sahoo,Pratap K Sahoo,Kartik Senapati###

Josephson coupling driven magnetoresistance in superconducting NiBi3 nanowires. We present results of magnetoresistance (MR) measurements in granular NiBi3
nanowires in the resistive state below the superconducting transition
temperature. MR of 100 nm wide nanowires fabricated by focused Ion beam
lithography from granular films of NiBi3 with and without magnetic Ni impurity
were compared. The nanowire containing high concentration of Ni impurity showed
oscillations in MR and also exhibited a negative MR in certain temperature and
field range. None of these effects were observed in the nanowire with no Ni
impurities. Therefore, we argue that this effect is a result of the random
Josephson couplings realized across superconducting NiBi3 grains via magnetic
inter grain regions. Such random couplings can cause local fluctuations in the
density and sign of supercurrent, which can lead to negative MR and
oscillations in MR, as proposed by Kivelson & Spivak [Kivelson et al. Phy. Rev.
B. 45, 10490 (1992)].

###A Trivial Geometrical Phase of an Electron Wavefunction in a Direct Band Gap Semiconductor CdGeAs$_{2}$|Vikas Saini,Souvik Sasmal,Vikash Sharma,Suman Nandi,Gourav Dwari,Bishal Maity,Ruta Kulkarni,Arumugam Thamizhavel###

A Trivial Geometrical Phase of an Electron Wavefunction in a Direct Band Gap Semiconductor CdGeAs$_{2}$. Chalcopyrite compounds are extensively explored for their exotic topological
phases and associated phenomena in a variety of experiments. Here, we discuss
the electrical transport properties of a direct energy gap semiconductor
CdGeAs$_{2}$. The observed transverse magnetoresistance (MR) is found to be
around 136% at a temperature of 1.8 K and a magnetic field of 14 T, following
the semiclassical exponent MR $\sim$ $B^{2.18}$. The MR analysis exhibits a
violation of the Kohler rule, suggesting the involvement of multiple carriers
in the system. Below 15 K, with decreasing magnetic field, the MR increases,
leading to the well known quantum interference phenomenon weak localization
(WL). The analysis of the magnetoconductivity data based on the
Hikami-Larkin-Nagaoka (HLN) model unveils three dimensional nature of the WL
and the weak spin-orbit coupling in CdGeAs$_{2}$. The phase coherence length
follows the $L_{\phi}$ $\sim$ $T^{-0.66}$ power law, which exhibits the 3D
nature of the observed WL feature.

###Lectures on spintronics and magnonincs|M. Mazanov,V. A. Shklovskij###

Lectures on spintronics and magnonincs. In this series of lectures, we discuss the basic theoretical concepts of
magnonics and spintronics. We first briefly recall the relevant topics from
quantum mechanics, electrodynamics of continuous media, and basic theory of
magnetism. We then discuss the classical theory of magnetic dynamics:
ferromagnetic and antiferromagnetic resonance, dynamic susceptibilities, and
spin waves. We open the main discussion with phenomena of spin and exchange
spin currents, spin torques, the spin Hall effect, and the spin Hall and Hanle
magnetoresistance. Special emphasis is given to the effects of spin transfer
torque and spin pumping, where we follow the celebrated derivation utilizing
Landauer quantum multi-channel scattering matrix approach. Finally, we outline
the most important features distinguishing antiferromagnetic dynamics from
ferromagnetic one, which make antiferromagnets particularly promising material
candidates for spintronics and magnonics.

###Magnetoresistive RAM with n-doped AlGaAs/GaAs writing/reading channels|Sushmita Saha,Deepak Sain,Alestin Mawrie###

Magnetoresistive RAM with n-doped AlGaAs/GaAs writing/reading channels. We show that the tunable gate voltage in n-doped AlGaAs/GaAs QW (quantum
well) is a key in designing an efficient and ultrafast MRAM (magnetoresistive
random access memory). The Rashba spin-orbit coupling in such QWs can be tuned
appropriately by the gate voltage to create an intense spin-Hall field which in
turns interacts with the ferromagnetic layer of the MRAM through the mechanism
of spin orbit torque. The strong spin-Hall field leads to an infinitesimally
small switching time of the MRAM. Our proposed MRAM is thus a better
alternative to the conventional ferromagnetic/spin-Hall effect bi-layers MRAM
for the reason that the switching time can be varied with ease, which is
unfeasible in the later. Concisely, not only that this work signals a
possibility to design an ultra-fast MRAM, but it also suggests a model to
fabricate a tunable switching time MRAM.

###Aging effects in critical behavior of Heisenberg anisotropic ultrathin films|Marina M. Boldyreva,Pavel V. Prudnikov,Vladimir V. Prudnikov,Marina V. Mamonova,Vadim O. Borzilov,Natalia I. Piskunova###

Aging effects in critical behavior of Heisenberg anisotropic ultrathin films. The nonequilibrium behavior of Co/Cu/Co and Pt/Co/Cu/Co/Pt multilayer
structures was studied by the Monte Carlo method for various types of magnetic
anisotropy. An analysis of the results of calculations of the two-time
autocorrelation function was carried out, and the evolution of structures from
various initial states was considered. An analysis of the results shows aging
with a slowdown in the correlation characteristics with an increase in the
waiting time. The dependence of the aging characteristics of the studied
structures on the film thickness is considered. There is a difference in
behavior from bulk systems, aging in multilayer structures occurs in a wide
temperature range at $T \leq T_c$ and not only at the ordering temperature
$T_c$. Investigation of transport properties makes it possible to reveal
nontrivial aging in the two-time dependence of magnetoresistance, as well as
the influence of anisotropy and initial states on its values.

###Unconventional anomalous Hall effect in epitaxially stabilized orthorhombic Ru$^{3+}$ perovskite thin films|L. -F. Zhang,T. C. Fujita,Y. Masutake,M. Kawamura,T. Arima,H. Kumigashira,M. Tokunaga,M. Kawasaki###

Unconventional anomalous Hall effect in epitaxially stabilized orthorhombic Ru$^{3+}$ perovskite thin films. Complex oxides are mesmerizing material systems to realize multiple physical
properties and functionalities by integrating different elements in a single
compound. However, owing to the chemical instability, not all the combinations
of elements can be materialized despite the intriguing potential expected from
their magnetic and electronic properties. In this study, we demonstrate an
epitaxial stabilization of orthorhombic Ru$^{3+}$ perovskite oxides: LaRuO$_3$
and NdRuO$_3$, and their magnetotransport properties that reflect the
difference between non-magnetic La$^{3+}$ and magnetic Nd$^{3+}$. Above all, an
unconventional anomalous Hall effect accompanied by an inflection point in
magnetoresistance is observed around 1.3 T below 1 K for NdRuO$_3$, which is
ascribed to topological Hall effect possibly due to a non-coplanar spin texture
on Nd$^{3+}$ sublattice. These studies not only serve a new testbed for the
interplay between spin-orbit coupling and Coulomb interaction but also open a
new avenue to explore topological emergent phenomena in well-studied perovskite
oxides.

###Piezostrain -- a local handle to control gyrotropic dynamics in magnetic vortices|Vadym Iurchuk,Serhii Sorokin,Jürgen Lindner,Jürgen Fassbender,Attila Kákay###

Piezostrain -- a local handle to control gyrotropic dynamics in magnetic vortices. We present a study of the piezostrain-tunable gyrotropic dynamics in
Co$_{40}$Fe$_{40}$B$_{20}$ vortex microstructures fabricated on a 0.7PMN-0.3PT
single crystalline substrate. Using field-modulated spin rectification
measurements, we demonstrate large frequency tunability (up to 45 %) in
individual microdisks accessed locally with low surface voltages, and
magnetoresistive readout. With increased voltage applied to the PMN-PT, we
observe a gradual decrease of the vortex core gyrotropic frequency associated
with the strain-induced magnetoelastic energy contribution. The frequency
tunability strongly depends on the disk size, with increased frequency
downshift for the disks with larger diameter. Micromagnetic simulations suggest
that the observed size effects originate from the joint action of the
strain-induced magnetoelastic and demagnetizing energies in large magnetic
disks. These results enable a selective energy-efficient tuning of the vortex
gyrotropic frequency in individual vortex-based oscillators with all-electrical
operation.

###Spontaneous spin selectivity and linear magnetoelectric effect in chiral molecules|Kouta Kondou,Shinji Miwa,Daigo Miyajima###

Spontaneous spin selectivity and linear magnetoelectric effect in chiral molecules. Chirality-induced spin selectivity (CISS) has been extensively studied over
the past two decades. While current-induced spin polarization in chiral
molecules is widely recognized as the fundamental principle of the CISS, only a
few studies have been reported on bias-current-free CISS, where there is no
bias electric current in chiral molecules. In this paper, we discuss the
microscopic origin of bias-free CISS using chiral molecule/ferromagnet bilayer
systems. Recent studies on the chirality-induced exchange bias and
current-in-plane magnetoresistance (CIP-MR) effects indicate that chiral
molecules possess thermally driven broken-time-reversal symmetry at the
interface, which induces bias-current-free CISS, i.e. a spontaneous effective
magnetic field in the system. We also discuss the possibility of the linear
magnetoelectric effect of chiral molecules at the interface and its potential
impact on the observed CISS phenomena.

###Perpendicular in-plane negative magnetoresistance in ZrTe5|Ning Ma,Xiao-Bin Qiang,Zhijian Xie,Yu Zhang,Shili Yan,Shimin Cao,Peipei Wang,Liyuan Zhang,G. D. Gu,Qiang Li,X. C. Xie,Hai-Zhou Lu,Xinjian Wei,Jian-Hao Chen###

Perpendicular in-plane negative magnetoresistance in ZrTe5. The unique band structure in topological materials frequently results in
unusual magneto-transport phenomena, one of which is in-plane longitudinal
negative magnetoresistance (NMR) with the magnetic field aligned parallel to
the electrical current direction. This NMR is widely considered as a hallmark
of chiral anomaly in topological materials. Here we report the observation of
in-plane NMR in the topological material ZrTe5 when the in-plane magnetic field
is both parallel and perpendicular to the current direction, revealing an
unusual case of quantum transport beyond the chiral anomaly. We find that a
general theoretical model, which considers the combined effect of Berry
curvature and orbital moment, can quantitatively explain this in-plane NMR. Our
results provide new insights into the understanding of in-plane NMR in
topological materials.

###Spin Hall magnetoresistance in Pt/Y$_{3}$Fe$_{5}$O$_{12}$ bilayers grown on Si and Gd$_{3}$Ga$_{5}$O$_{12}$ substrates|Kenta Fukushima,Kohei Ueda,Naoki Moriuchi,Takanori Kida,Masayuki Hagiwara,Jobu Matsuno###

Spin Hall magnetoresistance in Pt/Y$_{3}$Fe$_{5}$O$_{12}$ bilayers grown on Si and Gd$_{3}$Ga$_{5}$O$_{12}$ substrates. We study spin Hall magnetoresistance (SMR) in Pt/ferrimagnetic insulator
Y$_{3}$Fe$_{5}$O$_{12}$ (YIG) bilayers by focusing on crystallinity,
magnetization, and interface roughness by controlling post-annealing
temperatures. The SMR in the Pt/YIG grown on Si substrate is comparable to that
grown on widely used Gd$_{3}$Ga$_{5}$O$_{12}$ substrate, indicating that the
large SMR can be achieved irrespective to the crystallinity. We deduced the
spin mixing conductance from the Pt thickness dependence of the SMR to find the
high interface quality of the optimized Pt/YIG grown on Si in terms of spin
current. We also clarified that the SMR correlates well with the magnetization,
the interface roughness, and carrier density. These findings highlight that
optimizing YIG properties is a key to control of magnetization by spin current,
leading to the development of low power consumption spintronic device based on
the magnetic insulator.

###Extraordinary Tunneling Magnetoresistance in Antiferromagnetic Tunnel Junctions with Antiperovskite Electrodes|Gautam Gurung,Ding-Fu Shao,Evgeny Y. Tsymbal###

Extraordinary Tunneling Magnetoresistance in Antiferromagnetic Tunnel Junctions with Antiperovskite Electrodes. Recent theoretical predictions and experimental demonstrations of a large
tunneling magnetoresistance (TMR) effect in antiferromagnetic (AFM) tunnel
junctions (AFMTJs) offer a new paradigm for information technologies where the
AFM N\`eel vector serves as a state variable. A large TMR is beneficial for the
applications. Here, we predict the emergence of an extraordinary TMR (ETMR)
effect in AFMTJs utilizing noncollinear AFM antiperovskite XNMn$_{3}$ (X = Ga,
Sn,...) electrodes and a perovskite oxide ATiO$_{3}$ (A = Sr, Ba,...) barrier
layer. The ETMR effect stems from the perfectly spin-polarized electronic
states in the AFM antiperovskites that can efficiently tunnel through the
low-decay-rate evanescent states of the perovskite oxide while preserving their
spin state. Using an GaNMn$_{3}$/SrTiO$_{3}$/GaNMn$_{3}$ (001) AFMTJ as a
representative example, we demonstrate a giant TMR ratio exceeding $10^{4}$%
and originating from the ETMR effect. These results are promising for the
efficient detection and control of the N\`eel vector in AFM spintronics.

###Insight into the structural and magnetotransport properties of epitaxial heterostructures $α$-Fe$_2$O$_3$-Pt(111): Role of the reversed layer sequence|A. Kozioł-Rachwał,N. Kwiatek,W. Skowroński,K. Grochot,J. Kanak,E. Madej,K. Freindl,J. Korecki,N. Spiridis###

Insight into the structural and magnetotransport properties of epitaxial heterostructures $α$-Fe$_2$O$_3$-Pt(111): Role of the reversed layer sequence. We report on the chemical structure and spin Hall magnetoresistance (SMR) in
epitaxial $\alpha$-Fe$_2$O$_3$(hematite)(0001)/Pt(111) bilayers with hematite
thicknesses of 6 nm and 15 nm grown by molecular beam epitaxy on a MgO(111)
substrate. Unlike previous studies that involved Pt overlayers on hematite, the
present hematite films were grown on a stable Pt buffer layer and displayed
structural changes as a function of thickness. These structural differences
(the presence of a ferrimagnetic phase in the thinner film) significantly
affected the magnetotransport properties of the bilayers. We observed a sign
change of the SMR from positive to negative when the thickness of hematite
increased from 6 nm to 15 nm. For $\alpha$-Fe$_2$O$_3$(15 nm)/Pt, we
demonstrated room-temperature switching of the N\'eel order with rectangular,
nondecaying switching characteristics. Such structures open the way to
extending magnetotransport studies to more complex systems with double
asymmetric metal/hematite/Pt interfaces.

###Coexistence or Separation of the Superconducting, Antiferromagnetic, and Paramagnetic Phases in Quasi One-Dimensional (TMTSF)2PF6 ?|A. V. Kornilov,V. M. Pudalov,Y. Kitaoka,K. Ishida,G. -q. Zheng,T. Mito,J. S. Qualls###

Coexistence or Separation of the Superconducting, Antiferromagnetic, and Paramagnetic Phases in Quasi One-Dimensional (TMTSF)2PF6 ?. We report on experimental studies of the character of phase transitions in
the quasi-1D organic compound (TMTSF)2PF6 in the close vicinity of the borders
between the paramagnetic metal PM, antiferromagnetic insulator AF, and
superconducting SC states. In order to drive the system through the phase
border P_0(T_0), the sample was maintained at fixed temperature T and pressure
P, whereas the critical pressure P_0 was tuned by applying the magnetic field
B. In this approach, the magnetic field was used (i) for tuning (P-P_0), and
(ii) for identifying the phase composition (due to qualitatively different
magnetoresistance behavior in different phases). Experimentally, we measured
R(B) and its temperature dependence R(B,T) in the pressure range (0 - 1)GPa.
Our studies focus on the features of the magnetoresistance at the phase
transition between the PM and AF phases, in the close vicinity to the
superconducting transition at T~1K. We found pronounced history effects arising
when the AF/PM phase border is crossed by sweeping the magnetic field: the
resistance depends on a trajectory which the system arrives at a given point of
the P-B-T phase space. In the transition from the PM to AF phase, the features
of the PM phase extends well into the AF phase. At the opposite transition from
the AF to PM phase, the features of the AF phase are observed in the PM phase.
These results evidence for a macroscopically inhomogeneous state, which
contains macroscopic inclusions of the minority phase. When the system is
driven away from the transition, the homogeneous state is restored; upon a
return motion to the phase boundary, no signatures of the minority phase are
observed up to the very phase boundary.

###Transport and magnetic properties of GdBaCo_{2}O_{5+x} single crystals: A cobalt oxide with square-lattice CoO_2 planes over a wide range of electron and hole doping|A. A. Taskin,A. N. Lavrov,Yoichi Ando###

Transport and magnetic properties of GdBaCo_{2}O_{5+x} single crystals: A cobalt oxide with square-lattice CoO_2 planes over a wide range of electron and hole doping. Single crystals of the layered perovskite GdBaCo_{2}O_{5+x} (GBCO) have been
grown by the floating-zone method, and their transport, magnetic, and
structural properties have been studied in detail over a wide range of oxygen
contents. The obtained data are used to establish a rich phase diagram centered
at the "parent'' compound GdBaCo_{2}O_{5.5} -- an insulator with Co ions in the
3+ state. An attractive feature of GBCO is that it allows a precise and
continuous doping of CoO_{2} planes with either electrons or holes, spanning a
wide range from the charge-ordered insulator at 50% electron doping (x=0) to
the undoped band insulator (x=0.5), and further towards the heavily hole-doped
metallic state. This continuous doping is clearly manifested in the behavior of
thermoelectric power which exhibits a spectacular divergence with approaching
x=0.5, where it reaches large absolute values and abruptly changes its sign. At
low temperatures, the homogeneous distribution of doped carriers in GBCO
becomes unstable, and both the magnetic and transport properties point to an
intriguing nanoscopic phase separation. We also find that throughout the
composition range the magnetic behavior in GBCO is governed by a delicate
balance between ferromagnetic (FM) and antiferromagnetic (AF) interactions,
which can be easily affected by temperature, doping, or magnetic field,
bringing about FM-AF transitions and a giant magnetoresistance (MR) phenomenon.
An exceptionally strong uniaxial anisotropy of the Co spins, which dramatically
simplifies the possible spin arrangements, together with the possibility of
continuous ambipolar doping turn GBCO into a model system for studying the
competing magnetic interactions, nanoscopic phase separation and accompanying
magnetoresistance phenomena.

###c-axis magnetotransport in CeCoIn$_{5}$|A. Malinowski,M. F. Hundley,C. Capan,F. Ronning,R. Movshovich,N. O. Moreno,J. L. Sarrao,J. D. Thompson###

c-axis magnetotransport in CeCoIn$_{5}$. We present the results of out-of-plane electrical transport measurements on
the heavy fermion superconductor CeCoIn$_{5}$ at temperatures from 40 mK to 400
K and in magnetic field up to 9 T. For $T <$ 10 K transport measurements show
that the zero-field resistivity $\rho_{c}$ changes linearly with temperature
and extrapolates nearly to zero at 0 K, indicative of non-Fermi-liquid (nFL)
behavior associated with a quantum critical point (QCP). The longitudinal
magnetoresistance (LMR) of CeCoIn$_{5}$ for fields applied parallel to the
c-axis is negative and scales as $B/(T+T^{*})$ between 50 and 100 K, revealing
the presence of a single-impurity Kondo energy scale $T^{*} \sim 2$ K.
Beginning at 16 K a small positive LMR feature is evident for fields less than
3 tesla that grows in magnitude with decreasing temperature. For higher fields
the LMR is negative and increases in magnitude with decreasing temperature.
This sizable negative magnetoresistance scales as $B{^2}/T$ from 2.6 K to
roughly 8 K, and it arises from an extrapolated residual resistivity that
becomes negative and grows quadratically with field in the nFL temperature
regime. Applying a magnetic field along the c-axis with B $>$ B$_{c2}$ restores
Fermi-liquid behavior in $\rho_{c}(T)$ at $T$ less than 130 mK. Analysis of the
$T{^2}$ resistivity coefficient's field-dependence suggests that the QCP in
CeCoIn$_{5}$ is located \emph{below} the upper critical field, inside the
superconducting phase. These data indicate that while high-$T$ c-axis transport
of CeCoIn$_{5}$ exhibits features typical for a heavy fermion system, low-$T$
transport is governed both by spin fluctuations associated with the QCP and
Kondo interactions that are influenced by the underlying complex electronic
structure intrinsic to the anisotropic CeCoIn$_{5}$ crystal structure.

###Magnetization depinning transition, anisotropic magnetoresistance and inplane anisotropy in two polytypes of La$_{2 / 3}$Sr$_{1 / 3}$MnO$_{3}$ epitaxial films|Soumen Mandal,R. C. Budhani###

Magnetization depinning transition, anisotropic magnetoresistance and inplane anisotropy in two polytypes of La$_{2 / 3}$Sr$_{1 / 3}$MnO$_{3}$ epitaxial films. The isothermal magnetoresistance [R($\theta$)] of [001] and [110] epitaxial
films of La$_{2 / 3}$Sr$_{1 / 3}$MnO$_{3}$ measured as a function of the angle
$\theta$ between current ($\vec{I}$) and magnetic field ($\vec{H}$), both in
the plane of the film, is measured at several temperatures between 10 and 300K.
The magnetic easy axis of these polytypes is intimately related to the
orientation of Mn - O - Mn bonds with respect to the crystallographic axis on
the plane of the substrate and energy equivalence of some of these axes. The
magnetization vector ($\vec{M}$) of the [001] and [110] type films is pinned
along the [110] and [001] directions respectively at low fields. A
magnetization orientation phase transition (MRPT) which manifests itself as a
discontinuity and hysteresis in $R(\psi)$ where $\psi$ is the angle between
$\vec{H}$ and the easy axis for the $\vec{H}$ below a critical value
$\vec{H}^*$ has been established. The boundary of the pinned and depinned phase
on the H-T plane has been established. The highly robust pinning of
magnetization seen in [110] films is related to their uniquely defined easy
axis. The isothermal resistance R$_\bot$ and R$_\|$ for $\vec{I} \bot \vec{H}$
and $\vec{I} \| \vec{H}$, respectively for both polytypes follows the
inequality R$_\bot >$ R$_\|$ for all ranges of fields ($0 \leq H \leq 3500Oe$)
and temperatures (10K - 300K). A full fledged analysis of the rotational
magnetoresistance is carried out in the framework of D\"oring theory for MR in
single crystal samples. Strong deviations from the predicted angular dependence
are seen in the irreversible regime of magnetization.

###Long Range Coulomb Interactions and Nanoscale Electronic Inhomogeneities in Correlated Oxides|Vijay B. Shenoy,Tribikram Gupta,H. R. Krishnamurthy,T. V. Ramakrishnan###

Long Range Coulomb Interactions and Nanoscale Electronic Inhomogeneities in Correlated Oxides. Electronic, magnetic or structural inhomogeneities ranging in size from
nanoscopic to mesoscopic scales seem endemic, and are possibly generic, to
colossal magnetoresistance manganites and other transition metal oxides. We
show here that an extension, to include long range Coulomb interactions, of a
quantum two-fluid $\ell-b$ model proposed recently for manganites [Phys. Rev.
Lett., {\bf 92}, 157203 (2004)] leads to an excellent description of such
inhomogeneities. In the $\ell-b$ model two very different kinds of electronic
states, one localized and polaronic ($\ell$), and the other extended or broad
band ($b$) co-exist. For model parameters appropriate to manganites, and even
within a simple dynamical mean-filed theory (DMFT) framework, it describes many
of the unusual phenomena seen in manganites, including colossal
magnetoresistance (CMR), qualitatively and quantitatively. However, in the
absence of long ranged Coulomb interaction, a system described by such a model
would actually phase separate, into macroscopic regions of $l$ and $b$
electrons respectively. As we show in this paper, in the presence of Coulomb
interactions, the {\em macroscopic} phase separation gets suppressed, and
instead nanometer scale regions of polarons interspersed with band electron
puddles appear, constituting a new kind of quantum Coulomb glass. Our work
points to an interplay of strong correlations, long range Coulomb interaction
and dopant ion disorder as the origin of nanoscale inhomogeneities, rather than
disorder frustrated phase competition as is generally believed. Based on this,
we argue that the observed micrometer(meso)-scale inhomogeneities owe their
existence to extrinsic causes, eg. strain due to cracks and defects. We suggest
possible experiments to validate our speculation.

###{Rearrangement of the antiferromagnetic ordering at high magnetic fields in SmFeAsO and SmFeAsO$_{0.9}$F$_{0.1}$ single crystals|S. Weyeneth,P. J. W. Moll,R. Puzniak,K. Ninios,F. F. Balakirev,R. D. McDonald,H. B. Chan,N. D. Zhigadlo,S. Katrych,Z. Bukowski,J. Karpinski,H. Keller,B. Batlogg,L. Balicas###

{Rearrangement of the antiferromagnetic ordering at high magnetic fields in SmFeAsO and SmFeAsO$_{0.9}$F$_{0.1}$ single crystals. The low-temperature antiferromagnetic state of the Sm-ions in both
nonsuperconducting SmFeAsO and superconducting SmFeAsO$_{0.9}$F$_{0.1}$ single
crystals was studied by magnetic torque, magnetization, and magnetoresistance
measurements in magnetic fields up to 60~T and temperatures down to 0.6~K. We
uncover in both compounds a distinct rearrangement of the antiferromagnetically
ordered Sm-moments near $35-40$~T. This is seen in both, static and pulsed
magnetic fields, as a sharp change in the sign of the magnetic torque, which is
sensitive to the magnetic anisotropy and hence to the magnetic moment in the
$ab$-plane, ({\it i.e.} the FeAs-layers), and as a jump in the magnetization
for magnetic fields perpendicular to the conducting planes. This rearrangement
of magnetic ordering in $35-40$~T is essentially temperature independent and
points towards a canted or a partially polarized magnetic state in high
magnetic fields. However, the observed value for the saturation moment above
this rearrangement, suggests that the complete suppression of the
antiferromagnetism related to the Sm-moments would require fields in excess of
60~T. Such a large field value is particularly remarkable when compared to the
relatively small N\'{e}el temperature $T_{\rm N}\simeq5$~K, suggesting very
anisotropic magnetic exchange couplings. At the transition, magnetoresistivity
measurements show a crossover from positive to negative field-dependence,
indicating that the charge carriers in the FeAs planes are sensitive to the
magnetic configuration of the rare-earth elements. This is indicates a finite
magnetic/electronic coupling between the SmO and the FeAs layers which are
likely to mediate the exchange interactions leading to the long range
antiferromagnetic order of the Sm ions.

###Transport properties of the metallic state of overdoped cuprate superconductors from an anisotropic marginal Fermi liquid model|Jure Kokalj,Nigel E. Hussey,Ross H. McKenzie###

Transport properties of the metallic state of overdoped cuprate superconductors from an anisotropic marginal Fermi liquid model. We consider the implications of a phenomenological model self-energy for the
charge transport properties of the metallic phase of the overdoped cuprate
superconductors. The self-energy is the sum of two terms with characteristic
dependencies on temperature, frequency, location on the Fermi surface, and
doping. The first term is isotropic over the Fermi surface, independent of
doping, and has the frequency and temperature dependence characteristic of a
Fermi liquid. The second term is anisotropic over the Fermi surface (vanishing
at the same points as the superconducting energy gap), strongly varies with
doping (scaling roughly with $T_c$, the superconducting transition
temperature), and has the frequency and temperature dependence characteristic
of a marginal Fermi liquid. Previously it has been shown this self-energy can
describe a range of experimental data including angle-dependent
magnetoresistance (ADMR) and quasi-particle renormalisations determined from
specific heat, quantum oscillations, and angle-resolved photo-emission
spectroscopy (ARPES). Without introducing new parameters and neglecting vertex
corrections we show that this model self-energy can give a quantitative
description of the temperature and doping dependence of a range of reported
transport properties of Tl2201 samples. These include the intra-layer
resistivity, the frequency dependent optical conductivity, the intra-layer
magnetoresistance, and the Hall coefficient. The temperature dependence of the
latter two are particularly sensitive to the anisotropy of the scattering rate
and to the shape of the Fermi surface. In contrast, the temperature dependence
of the Hall angle is dominated by the Fermi liquid contribution to the
self-energy that determines the scattering rate in the nodal regions of the
Fermi surface.

###One-dimensional ballistic transport with FLAPW Wannier functions|Björn Hardrat,Nengping Wang,Frank Freimuth,Yuriy Mokrousov,Stefan Heinze###

One-dimensional ballistic transport with FLAPW Wannier functions. We present an implementation of the ballistic Landauer-B\"uttiker transport
scheme in one-dimensional systems based on density functional theory (DFT)
calculations within the full-potential linearized augmented plane-wave (FLAPW)
method. In order to calculate the conductance within the Green's function
method we map the electronic structure from the extended states of the FLAPW
calculation to Wannier functions which constitute a minimal localized basis
set. Our approach benefits from the high accuracy of the underlying FLAPW
calculations allowing us to address the complex interplay of structure,
magnetism, and spin-orbit coupling and is ideally suited to study
spin-dependent electronic transport in one-dimensional magnetic nanostructures.
To illustrate our approach we study ballistic electron transport in
non-magnetic Pt monowires with a single stretched bond including spin-orbit
coupling, and in ferromagnetic Co monowires with different collinear magnetic
alignment of the electrodes with the purpose of analysing the magnetoresistance
when going from tunneling to the contact regime. We further investigate
spin-orbit scattering due to an impurity atom. We consider two configurations:
a Co atom in a Pt monowire and vice versa. In both cases, the spin-orbit
induced band mixing leads to a change of the conductance upon switching the
magnetization direction from along the chain axis to perpendicular to it. The
main contribution stems from ballistic spin-scattering for the magnetic Co
impurity in the non-magnetic Pt monowire and for the Pt scatterer in the
magnetic Co monowire from the band formed from states with $d_{xy}$ and
$d_{x^2-y^2}$ orbital symmetry. We quantify this effect by calculating the
ballistic anisotropic magnetoresistance which displays values up to as much as
7% for ballistic spin-scattering and gigantic values of around 100% for the Pt
impurity in the Co wire.

###Resistive and magnetoresistive properties of CrO2 pressed powders with different types of inter-granular dielectric layers|N. V. Dalakova,B. I. Belevtsev,E. Yu. Beliayev,O. M. Bludov,V. A. Pashchenko,M. G. Osmolovsky,O. M. Osmolovskaya###

Resistive and magnetoresistive properties of CrO2 pressed powders with different types of inter-granular dielectric layers. Resistive, magnetoresistive and magnetic properties of four kinds of pressed
CrO2 powders, synthesized by hydrothermal method of chromic anhydride have been
investigated. The particles in powders constituted of rounded particles
(diameter 120 nm) or needle-shaped crystals with an average diameter of 22.9 nm
and average length of 302 nm. All of the particles had a surface dielectric
shell of varying thickness and different types (such as oxyhydroxide -CrOOH or
chromium oxide Cr2O3). For all the samples at low temperatures we found
non-metallic temperature dependence of resistivity and giant negative
magnetoresistance (MR). The maximum value of MR at low temperatures (T \approx
5 K) is \approx 37% in relatively small fields (0.5 T). At higher temperatures
there was a rapid decrease of MR (up to \approx 1% / T at T \approx 200 K). The
main objective of this work was studying the influence of properties and
thickness of the intergranular dielectric layers, as well as CrO2 particle
shape, on the magnitude of the tunneling resistance and MR of the pressed
powder. The new results obtained in this study include: (1) detection at low
temperatures in powders with needle-like particles a new type of MR hysteresis,
and nonmonotonic MR behaviour with increasing magnetic field (absolute value of
the MR at first grows rather rapidly with the field, and then begins
diminishing markedly, forming a maximum), and (2) detection of non-monotonic
temperature dependence, where - a field in which the resistance in a magnetic
field has a maximum, as well as finding discrepancies in values of and
coercivity fields, (3) detection of the anisotropy of MR, depending on the
relative orientation of the transport current and the magnetic field, (4) a new
method of synthesis, to regulate the thickness of dielectric coating.

###Conductance fingerprints of non-collinear magnetic states in single atom contacts: a first-principles Wannier functions study|Björn Hardrat,Frank Freimuth,Stefan Heinze,Yuriy Mokrousov###

Conductance fingerprints of non-collinear magnetic states in single atom contacts: a first-principles Wannier functions study. We present a first-principles computational scheme for investigating the
ballistic transport properties of one-dimensional nanostructures with
non-collinear magnetic order. The electronic structure is obtained within
density functional theory as implemented in the full-potential linearized
augmented plane-wave (FLAPW) method and mapped to a tight-binding like
transport Hamiltonian via non-collinear Wannier functions. The conductance is
then computed based on the Landauer formula using the Green's function method.
As a first application we study the conductance between two ferromagnetic Co
monowires terminated by single Mn apex atoms as a function of Mn-Mn separation.
We vary the Mn-Mn separation from the contact (about 2.5 to 5 {\AA}) to the far
tunneling regime (5 to 10 {\AA}). The magnetization direction of the Co
electrodes is chosen either in parallel or antiparallel alignment and we allow
for different spin configurations of the two Mn spins. In the tunneling and
into the contact regime the conductance is dominated by $s$-$d_{z^2}$-states.
In the close contact regime (below 3.5 {\AA}) there is an additional
contribution for a parallel magnetization alignment from the $d_{xz}$- and
$d_{yz}$-states which give rise to an increase of the magnetoresistance as it
is absent for antiparallel magnetization. If we allow the Mn spins to relax a
non-collinear spin state is formed close to contact. We demonstrate that the
transition from a collinear to such a non-collinear spin structure as the two
Mn atoms approach leaves a characteristic fingerprint in the distance-dependent
conductance and magnetoresistance of the junction. We explain the effect of the
non-collinear spin state on the conductance based on the spin-dependent
hybridization between the $d_{xz,yz}$-states of the Mn spins and their coupling
to the Co electrodes.

###Magnetic anisotropy in strained manganite films and bicrystal junctions|G. A. Ovsyannikov,V. V. Demidov,A. M. Petrzhik,I. V. Borisenko,A. V. Shadrin,R. Gunnarsson###

Magnetic anisotropy in strained manganite films and bicrystal junctions. Transport and magnetic properties of LSMO manganite thin films and bicrystal
junctions were investigated. Manganite films were epitaxially grown on STO,
LAO, NGO and LSAT substrates and their magnetic anisotropy were determined by
two techniques of magnetic resonance spectroscopy. Compare with cubic
substrates a small (about 0.3 persentage), the anisotropy of the orthorhombic
NGO substrate leads to a uniaxial anisotropy of the magnetic properties of the
films in the plane of the substrate. Samples with different tilt of
crystallographic basal planes of manganite as well as bicrystal junctions with
rotation of the crystallographic axes (RB - junction) and with tilting of basal
planes (TB - junction) were investigated. It was found that on vicinal NGO
substrates the value of magnetic anisotropy could be varied by changing the
substrate inclination angle from 0 to 25 degrees. Measurement of magnetic
anisotropy of manganite bicrystal junction demonstrated the presence of two
ferromagnetically ordered spin subsystems for both types of bicrystal
boundaries RB and TB. The magnitude of the magnetoresistance for TB - junctions
increased with decreasing temperature and with the misorientation angle even
misorientation of easy axes in the parts of junction does not change. Analysis
of the voltage dependencies of bicrystal junction conductivity show that the
low value of the magnetoresistance for the LSMO bicrystal junctions can be
caused by two scattering mechanisms with the spin- flip of spin - polarized
carriers due to the strong electron - electron interactions in a disordered
layer at the bicrystal boundary at low temperatures and the spin-flip by anti
ferromagnetic magnons at high temperatures.

###Review on magnetic and related properties of RTX compounds|Sachin Gupta,K. G. Suresh###

Review on magnetic and related properties of RTX compounds. RTX (R=rare earths, T= 3d/4d/5d, transition metals such as Sc, Ti, Mn, Fe,
Co, Ni, Cu, Ru, Rh, Pd, Ag, Os, Ir, Pt, Au, and X=p-block elements such as Al,
Ga, In, Si, Ge, Sn, As, Sb, Bi) series is a huge family of intermetallics
compounds. These compounds crystallize in different crystal structures
depending on the constituents. Though these compounds have been known for a
long time, they came to limelight recently in view of the large magnetocaloric
effect (MCE) and magnetoresistance (MR) shown by many of them. Most of these
compounds crystallize in hexagonal and tetragonal crystal structures. Some of
them show crystal structure modification with annealing temperature; while a
few of them show iso-structural transition in the paramagnetic regime. Their
magnetic ordering temperatures vary from very low temperatures to temperatures
well above room temperature (~510 K). Depending on the crystal structure, they
show a variety of magnetic and electrical properties. These compounds have been
characterized by means of a variety of techniques/measurements such as x-ray
diffraction, neutron diffraction, magnetic properties, heat capacity,
magnetocaloric properties, electrical resistivity, magnetoresistance,
thermoelectric power, thermal expansion, Hall effect, optical properties, XPS,
M\"ossbauer spectroscopy, ESR, {\mu}SR, NMR, NQR etc. Some amount of work on
theoretical calculations on electronic structure, crystal field interaction and
exchange interactions has also been reported. The interesting aspect of this
series is that they show a variety of physical properties such as Kondo effect,
heavy fermion behavior, spin glass state, intermediate valence,
superconductivity, multiple magnetic transitions, metamagnetism, large MCE,
large positive as well as negative MR, spin orbital compensation, magnetic
polaronic behavior, pseudo gap effect etc.

###Magnetotransport Measurements of the Surface States of Samarium Hexaboride using Corbino Structures|Steven Wolgast,Yun Suk Eo,Teoman Ozturk,Gang Li,Ziji Xiang,Colin Tinsman,Tomoya Asaba,Ben Lawson,Fan Yu,J. W. Allen,Kai Sun,Lu Li,Cagliyan Kurdak,Dae-Jeong Kim,Zachary Fisk###

Magnetotransport Measurements of the Surface States of Samarium Hexaboride using Corbino Structures. The recent conjecture of a topologically-protected surface state in SmB$_6$
and the verification of robust surface conduction below 4 K have prompted a
large effort to understand the surface states. Conventional Hall transport
measurements allow current to flow on all surfaces of a topological insulator,
so such measurements are influenced by contributions from multiple surfaces of
varying transport character. Instead, we study magnetotransport of SmB$_6$
using a Corbino geometry, which can directly measure the conductivity of a
single, independent surface. Both (011) and (001) crystal surfaces show a
strong negative magnetoresistance at all magnetic field angles measured. The
(011) surface has a carrier mobility of $122\text{
cm}^2/\text{V}\cdot\text{sec}$ with a carrier density of $2.5\times10^{13}
\text{ cm}^{-2}$, which are significantly smaller than indicated by Hall
transport studies. This mobility value can explain a failure so far to observe
Shubnikov-de Haas oscillations. Analysis of the angle-dependence of
conductivity on the (011) surface suggests a combination of a field-dependent
enhancement of the carrier density and a suppression of Kondo scattering from
native oxide layer magnetic moments as the likely origin of the negative
magnetoresistance. Our results also reveal a hysteretic behavior whose
magnitude depends on the magnetic field sweep rate and temperature. Although
this feature becomes smaller when the field sweep is slower, does not disappear
or saturate during our slowest sweep-rate measurements, which is much slower
than a typical magnetotransport trace. These observations cannot be explained
by quantum interference corrections such as weak anti-localization, but are
more likely due to an extrinsic magnetic effect such as the magnetocaloric
effect or glassy ordering.

###Ambipolar High Mobility Hexagonal Transistors on Hydrogen-Terminated Silicon (111) Surfaces|Binhui Hu,Mohamad M. Yazdanpanah,Joyce E. Coppock,B. E. Kane###

Ambipolar High Mobility Hexagonal Transistors on Hydrogen-Terminated Silicon (111) Surfaces. We have fabricated ambipolar transistors on chemically prepared
hydrogen-terminated Si(111) surfaces, in which a two-dimensional electron
system (2DES) or a two-dimensional hole system (2DHS) can be populated in the
same conduction channel by changing the gate voltage of a global gate applied
through a vacuum gap. Depending on the gate bias, ion implanted n$^+$ and p$^+$
regions function either as Ohmic contacts or as in-plane gates, which laterally
confine the carriers induced by the global gate. On one device, electron and
hole densities of up to $7.8\times10^{11}$ cm$^{-2}$ and $7.6\times10^{11}$
cm$^{-2}$ respectively are obtained. The peak electron mobility is
$1.76\times10^5$ cm$^{2}$/Vs, and the peak hole mobility is $9.1\times10^3$
cm$^{2}$/Vs at 300 mK; the ratio of about 20 is mainly due to the very
different valley degeneracies (6:1) of electrons and holes on the Si(111)
surface. On another device, the peak electron mobility of $2.2\times10^5$
cm$^{2}$/Vs is reached at 300 mK. These devices are hexagonal in order to
investigate the underlying symmetry of the 2DESs, which have a sixfold valley
degeneracy at zero magnetic field. Three magnetoresistance measurements with
threefold rotational symmetry are used to determine the symmetry of the 2DESs
at different magnetic field. At filling factor $1 < \nu < 2$, the observed
anisotropy can be explained by a single valley pair occupancy of composite
fermions (CFs). Qualitatively the CFs preserve the valley anisotropy, in
addition to the twofold valley degeneracy. At magnetic field up to 35 T, the
2/3 fractional quantum Hall state is observed with a well developed hall
plateau; at $\nu<2/3$, the three magnetoresistances show a large anisotropy
(50:1). We also show that device degradation is not a serious issue for our
measurements, if the device is kept in vacuum or a nitrogen gas environment and
its time in air is minimized.

###Insight into the magnetism of a distorted Kagome lattice, Dy3Ru4Al12, based on polycrystalline studies|Venkatesh Chandragiri,Kartik K Iyer,E. V. Sampathkumaran###

Insight into the magnetism of a distorted Kagome lattice, Dy3Ru4Al12, based on polycrystalline studies. The layered compound with distorted Kagome nets, Dy3Ru4Al12, was previously
reported to undergo antiferromagnetic ordering below (TN=) 7 K, based on
investigations on single crystals. Here, we report the results of our
investigation of ac and dc magnetic susceptibility (\c{hi}), isothermal remnant
magnetization (MIRM), heat-capacity, magnetocaloric effect and
magnetoresistance measurements on polycrystals. The present results reveal that
there is an additional magnetic anomaly around 20 K, as though the N\'eel order
is preceded by the formation of ferromagnetic clusters. We attribute this
feature to geometric frustration of magnetism. In view of the existence of this
phase, the interpretation of the linear-term in the heat-capacity in terms of
spin-fluctuations from the Ru 4d band needs to be revisited. Additionally, in
the vicinity of TN, AC \c{hi} shows a prominent frequency dependence and, below
TN, MIRM exhibits a slow decay with time. This raises a question whether the
antiferromagnetic structure in this compound is characterized by
spin-glass-like dynamics. In contrast to what was reported earlier, there is a
change in the sign of the magnetoresistance (MR) at the metamagnetic
transition. A butter-fly-shaped (isothermal) MR loop (interestingly spanning
over all the four quadrants) is observed at 2 K with distinct evidence for the
magnetic phase co-existence phenomenon in zero field after travelling through
metamagnetic transition field. The results on polycrystals thus provide
additional information about the magnetism of this compound, revealing that the
magnetism of this compound is more complex than what is believed, due to
geometric frustration intrinsic to Kagome net.

###Fermi Surface Reconstruction in the Electron-doped Cuprate Pr(2-x)CexCuO4|Yoram Dagan,Richard L. Greene###

Fermi Surface Reconstruction in the Electron-doped Cuprate Pr(2-x)CexCuO4. We report extensive resistivity, Hall, and magnetoresistance measurements on
thin films of the electron-doped cuprate \PCCO~(PCCO), as a function of doping,
temperature and magnetic field. The doping dependence of the resistivity and
Hall number at low temperatures are characteristic of a system near a quantum
phase transition or a Fermi Surface Reconstruction (FSR) point. The spin
magnetoresistance drops to zero near the critical point. The data presented in
this paper were compiled during the 2004-2007 period but were never published
in this comprehensive form. Because of the recent interest in very similar
results now being found in the normal state of hole-doped cuprates, we believe
the results of our older, mostly unpublished, work will be of interest to the
present community of cuprate researchers. In particular, Fig.11 shows the large
change in Hall number at the FSR point in \PCCO, similar to that found recently
in YBCO and LSCO (See ref[1] and [2]). Also, Fig.6 illustrates how the
resistivity upturn is affected by the FSR. The cause of the resistivity upturn
has been attributed to the loss of carriers at doping below the FSR in the
hole-doped cuprates (see Ref. 3), however, this scenario does not explain the
data for PCCO. The upturn in n-doped cuprates is more-likely due to a
combination of carrier decrease and a change in the scattering rate below the
FSR (see also Ref. 4). The change in spin scattering below the FSR is
illustrated by Fig.18 in this paper. Chen et al. [5] have developed a model
based on spin scattering that is able to explain qualitatively the resistivity
upturn in all the cuprates.

###Magnetoresistance and valley degree of freedom in bulk bismuth|Zengwei Zhu,Benoît Fauqué,Kamran Behnia,Yuki Fuseya###

Magnetoresistance and valley degree of freedom in bulk bismuth. In this paper, we first review fundamental aspects of magnetoresistance in
multi-valley systems based on the semiclassical theory. Then we will review
experimental evidence and theoretical understanding of magnetoresistance in an
archetypal multi-valley system, where the electric conductivity is set by the
sum of the contributions of different valleys. Bulk bismuth has three valleys
with an extremely anisotropic effective mass. As a consequence, the
magnetoconductivity in each valley is extremely sensitive to the orientation of
the magnetic field. Therefore, a rotating magnetic field plays the role of a
valley valve tuning the contribution of each valley to the total conductivity.
In addition to this simple semi-classical effect, other phenomena arise in the
high-field limit as a consequence of an intricate Landau spectrum. In the
vicinity of the quantum limit, the orientation of magnetic field significantly
affects the distribution of carriers in each valley, namely, the valley
polarization is induced by the magnetic field. Moreover, experiment has found
that well beyond the quantum limit, one or two valleys become totally empty.
This is the only case in condensed-matter physics where a Fermi sea is
completely dried up by a magnetic field without a metal-insulator transition.
There have been two long-standing problems on bismuth near the quantum limit:
the large anisotropic Zeeman splitting of holes, and the extra peaks in quantum
oscillations, which cannot be assigned to any known Landau levels. These
problems are solved by taking into account the interband effect due to the
spin-orbit couplings for the former, and the contributions from the twinned
crystal for the latter. Up to here, the whole spectrum can be interpreted
within the one-particle theory. Finally, we will discuss transport and
thermodynamic signatures of breaking of the valley symmetry in this system.

###Experimental tests of the chiral anomaly magnetoresistance in the Dirac-Weyl semimetals Na$_3$Bi and GdPtBi|Sihang Liang,Jingjing Lin,Satya Kushwaha,Jie Xing,Ni Ni,R. J. Cava,N. P. Ong###

Experimental tests of the chiral anomaly magnetoresistance in the Dirac-Weyl semimetals Na$_3$Bi and GdPtBi. In the Dirac/Weyl semimetal, the chiral anomaly appears as an "axial" current
arising from charge-pumping between the lowest (chiral) Landau levels of the
Weyl nodes, when an electric field is applied parallel to a magnetic field $\bf
B$. Evidence for the chiral anomaly was obtained from the longitudinal
magnetoresistance (LMR) in Na$_3$Bi and GdPtBi. However, current jetting
effects (focussing of the current density $\bf J$) have raised general concerns
about LMR experiments. Here we implement a litmus test that allows the
intrinsic LMR in Na$_3$Bi and GdPtBi to be sharply distinguished from pure
current jetting effects (in pure Bi). Current jetting enhances $J$ along the
mid-ridge (spine) of the sample while decreasing it at the edge. We measure the
distortion by comparing the local voltage drop at the spine (expressed as the
resistance $R_{spine}$) with that at the edge ($R_{edge}$). In Bi, $R_{spine}$
sharply increases with $B$ but $R_{edge}$ decreases (jetting effects are
dominant). However, in Na$_3$Bi and GdPtBi, both $R_{spine}$ and $R_{edge}$
decrease (jetting effects are subdominant). A numerical simulation allows the
jetting distortions to be removed entirely. We find that the intrinsic
longitudinal resistivity $\rho_{xx}(B)$ in Na$_3$Bi decreases by a factor of
10.9 between $B$ = 0 and 10 T. A second litmus test is obtained from the
parametric plot of the planar angular magnetoresistance. These results
strenghthen considerably the evidence for the intrinsic nature of the
chiral-anomaly induced LMR. We briefly discuss how the squeeze test may be
extended to test ZrTe$_5$.

###Field-induced resistivity plateau and unsaturated negative magnetoresistance in topological semimetal TaSb2|Yuke Li,Lin Li,Jialu Wang,Tingting Wang,Xiaofeng Xu,Chuanying Xi,Chao Cao,Jianhui Dai###

Field-induced resistivity plateau and unsaturated negative magnetoresistance in topological semimetal TaSb2. Several prominent transport properties have been identified as key signatures
of topologicalmaterials. One is the resistivity plateau at low temperatures as
observed in several topological insulators (TIs), another is the negative
magnetoresistance (MR) when the applied magnetic field is parallel to the
current direction as observed in several topological semimetals (TSMs)
including Dirac semimetals (DSMs) and Weyl semimetals (WSMs). Usually, these
two exotic phenomena emerge in distinct materials with or without time reversal
symmetry (TRS), respectively. Here we report the discovery of a new member in
TSMs, TaSb2, which clearly exhibits both of these phenomena in a single
material. This compound crystallizes in a base-centered monoclinic,
centrosymmetric structure, and is metallic with a low carrier density in the
zero field. While applying magnetic field it exhibits insulating behavior
before appearance of a resistivity plateau below Tc =13 K. In the plateau
regime, the ultrahigh carrier mobility and extreme magnetoresistance (XMR) for
the field perpendicular to the current are observed as in DSMs and WSMs, in
addition to a quantum oscillation behavior with non-trivial Berry phases. In
contrast to the most known DSMs and WSMs, the negative MR in TaSb2 does not
saturate up to 9 T, which, together with the almost linear Hall resistivity,
manifests itself an electron-hole non-compensated TMS. These findings indicate
that the resistivity plateau could be a generic feature of topology-protected
metallic states even in the absence of TRS and compatible with the negative MR
depending on the field direction. Our experiment extends a materials basis
represented by TaSb2 as a new platform for future theoretical investigations
and device applications of topological materials.

###Thermoballistic spin-polarized electron transport in paramagnetic semiconductors|R. Lipperheide,U. Wille###

Thermoballistic spin-polarized electron transport in paramagnetic semiconductors. Spin-polarized electron transport in diluted magnetic semiconductors (DMS) in
the paramagnetic phase is described within the thermoballistic transport model.
In this (semiclassical) model, the ballistic and diffusive transport mechanisms
are unified in terms of a thermoballistic current in which electrons move
ballistically across intervals enclosed between arbitrarily distributed points
of local thermal equilibrium. The contribution of each interval to the current
is governed by the momentum relaxation length. Spin relaxation is assumed to
take place during the ballistic electron motion. In paramagnetic DMS exposed to
an external magnetic field, the conduction band is spin-split due to the giant
Zeeman effect. In order to deal with this situation, we extend our previous
formulation of thermoballistic spin-polarized transport so as to take into
account an arbitrary (position-dependent) spin splitting of the conduction
band. The current and density spin polarizations as well as the
magnetoresistance are each obtained as the sum of an equilibrium term
determined by the spin-relaxed chemical potential, and an off-equilibrium
contribution expressed in terms of a spin transport function that is related to
the splitting of the spin-resolved chemical potentials. The procedures for the
calculation of the spin-relaxed chemical potential and of the spin transport
function are outlined. As an illustrative example, we apply the thermoballistic
description to spin-polarized transport in DMS/NMS/DMS heterostructures formed
of a nonmagnetic semiconducting sample (NMS) sandwiched between two DMS layers.
We evaluate the current spin polarization and the magnetoresistance for this
case and, in the limit of small momentum relaxation length, find our results to
agree with those of the standard drift-diffusion approch to electron transport.

###Coupling of electronic and magnetic properties in Fe1+y(Te1-xSex)|J. Hu,T. J. Liu,B. Qian,Z. Q. Mao###

Coupling of electronic and magnetic properties in Fe1+y(Te1-xSex). We have studied the coupling of electronic and magnetic properties in
Fe1+y(Te1-xSex) via systematic specific heat, magnetoresistivity, and Hall
coefficient measurements on two groups of samples with y = 0.02 and 0.1. In the
y = 0.02 series, we find that the 0.09 < x < 0.3 composition region, where
superconductivity is suppressed, has large Sommerfeld coefficient Gamma (~55-65
mJ/mol K^2), positive Hall coefficient R_H and negative magnetoresistance MR at
low temperature, in sharp contrast with the x=0.4-0.5 region where Gamma drops
to ~ 26 mJ/mol K^2 and R_H / MR becomes negative/positive at low temperature.
Dramatic changes of Gamma, as well as sign reversal in low-temperature RH and
MR, are also observed across the x~0.1 boundary where the long-range
antiferromagnetic order is suppressed. However, for the system with rich
interstitial excess Fe (y = 0.1), where bulk superconductivity is suppressed
even for x=0.4-0.5, the variations of Gamma, R_H and MR with x are distinct
from those seen in y = 0.02 system: Gamma is ~40 mJ/mol K^2 for 0.1 < x < 0.3,
and drops to ~ 34 mJ/mol K^2 for x = 0.4-0.5; R_H and MR does not show any sign
reversal as x is increased above 0.3. We will show that all these results can
be understood in light of the evolution of the incoherent magnetic scattering
by (pi,0) magnetic fluctuations with Se concentration. In addition, with the
suppression of magnetic scattering by magnetic field, we observed the
surprising effect of a remarkable increase in the superconducting volume
fraction under moderate magnetic fields for x=0.3-0.4 samples in the y = 0.02
system.

###Giant Rashba effect at the topological surface of PrGe revealing antiferromagnetic spintronics|Soma Banik,Pranab Kumar Das,Azzedine Bendounan,Ivana Vobornik,A. Arya,Nathan Beaulieu,Jun Fujii,A. Thamizhavel,P. U. Sastry,A. K. Sinha,D. M. Phase,S. K. Deb###

Giant Rashba effect at the topological surface of PrGe revealing antiferromagnetic spintronics. Rashba spin-orbit splitting in the magnetic materials opens up a new
perspective in the field of spintronics. Here, we report a giant Rashba-type
spin-orbit effect on PrGe [010] surface in the paramagnetic phase with Rashba
coefficient {\alpha}_R=5 eV{\AA}. Significant changes in the electronic band
structure has been observed across the phase transitions from paramagnetic to
antiferromagnetic (44 K) and from antiferromagnetic to the ferromagnetic ground
state (41.5 K). We find that Pr 4f states in PrGe is strongly hybridized with
the Pr 5d and Ge 4s-4p states near the Fermi level. The behavior of Rashba
effect is found to be different in the k_x and the k_y directions showing
electron-like and the hole-like bands, respectively. The possible origin of
Rashba effect in the paramagnetic phase is related to the anti-parallel spin
polarization present in this system. First-principles density functional
calculations of Pr terminated surface with the anti-parallel spins shows a fair
agreement with the experimental results. We find that the anti-parallel spins
are strongly coupled to the lattice such that the PrGe system behaves like weak
ferromagnetic system. Analysis of the energy dispersion curves at different
magnetic phases showed that there is a competition between the
Dzyaloshinsky-Moriya interaction and the exchange interaction which gives rise
to the magnetic ordering in PrGe. Supporting evidences of the presence of
Dzyaloshinsky-Moriya interaction are observed as anisotropic magnetoresistance
with respect to field direction and first-order type hysteresis in the X-ray
diffraction measurements. A giant negative magnetoresistance of 43% in the
antiferromagnetic phase and tunable Rashba parameter with temperature across
the magnetic transitions makes this material a suitable candidate for
technological application in the antiferromagnetic spintronic devices.

###Strong spin-orbit coupling and magnetism in (111) (La$_{0.3}$Sr$_{0.7}$)(Al$_{0.65}$Ta$_{0.35})$/SrTiO$_3$|V. V. Bal,Z. Huang,K. Han,Ariando,T. Venkatesan,V. Chandrasekhar###

Strong spin-orbit coupling and magnetism in (111) (La$_{0.3}$Sr$_{0.7}$)(Al$_{0.65}$Ta$_{0.35})$/SrTiO$_3$. Strong correlations, multiple lattice degrees of freedom, and the ease of
doping make complex oxides a source of great research interest. Complex oxide
heterointerfaces break inversion symmetry and can host a two dimensional
carrier gas, which can display a variety of coexisting and competing phenomena.
In the case of heterointerfaces based on SrTiO$_3$, many of these phenomena can
be effectively tuned by using an electric gate, due to the large dielectric
constant of SrTiO$_3$. Most studies so far have focused on (001) oriented
heterostructures; however, (111) oriented heterostructures have recently gained
attention due to the possibility of finding exotic physics in these systems due
their hexagonal surface crystal symmetry. In this work, we use
magnetoresistance to study the evolution of spin-orbit interaction and
magnetism in a new system, (111) oriented
(La$_{0.3}$Sr$_{0.7}$)(Al$_{0.65}$Ta$_{0.35}$)/SrTiO$_3$. At more positive
values of the gate voltage, which correspond to high carrier densities, we find
that transport is multiband, and dominated by high mobility carriers with a
tendency towards weak localization. At more negative gate voltages, the carrier
density is reduced, the high mobility bands are depopulated, and weak
antilocalization effects begin to dominate, indicating that spin-orbit
interaction becomes stronger. At millikelvin temperatures, and gate voltages
corresponding to the strong spin-orbit regime, we observe hysteresis in
magnetoresistance, indicative of ferromagnetism in the system. Our results
suggest that in the (111)
(La$_{0.3}$Sr$_{0.7}$)(Al$_{0.65}$Ta$_{0.35}$)/SrTiO$_3$ system, low mobility
carriers which experience strong spin-orbit interactions participate in
creating magnetic order in the system.

###Structure and Giant Magnetoresistance of Electrodeposited Co/Cu Multilayers Prepared by Two-Pulse (G/P) and Three-Pulse (G/P/G) Plating|N. Rajasekaran,L. Pogány,Á. Révész,B. G. Tóth,S. Mohan,L. Péter,I. Bakonyi###

Structure and Giant Magnetoresistance of Electrodeposited Co/Cu Multilayers Prepared by Two-Pulse (G/P) and Three-Pulse (G/P/G) Plating. The giant magnetoresistance (GMR) was investigated for electrodeposited Co/Cu
multilayers. In order to better understand the formation of individual layers
and their influence on GMR, multilayers produced by two different deposition
strategies were compared. One series of Co(2 nm)/Cu(tCu) multilayers with tCu
ranging from 0.5 nm to 6 nm was produced with the conventional two-pulse
plating by using a galvanostatic/potentiostatic (G/P) pulse combination for the
magnetic/non-magnetic layer deposition, respectively, whereby the Cu layer
deposition was carried out at the electrochemically optimized potential.
Another Co(2 nm)/Cu(tCu) multilayer series with the same tCu range was prepared
with the help of a G/P/G pulse combination. In this latter case, first a
bilayer of Co(2 nm)/Cu(6 nm) was deposited in each cycle as in the G/P mode
after which a third G pulse was applied with a small anodic current to dissolve
part of the 6 nm thick Cu layer in order to ensure the targeted tCu value. The
comparison of the two series revealed that the G/P/G pulse combination yields
multilayers for which GMR can be obtained even at such low nominal Cu layer
thicknesses where G/P multilayers already exhibit bulk-like anisotropic
magnetoresistance only. Surface roughness measurements by atomic force
microscopy revealed that the two kinds of pulse combination yield different
surface roughness values which correlate with the structural quality of the
multilayers as indicated by the absence or presence of multilayer satellite
reflections in the X-ray diffraction patterns. The results of multilayer
chemical analysis revealed that mainly an increased Cu content of the magnetic
layer is responsible for the onset of SPM regions in the form of Co
segregations in the G/P/G multilayers with small Cu layer thicknesses.

###Electronic properties of type-II Weyl semimetal WTe$_2$. A review perspective|P. K. Das,D. Di Sante,F. Cilento,C. Bigi,D. Kopic,D. Soranzio,A. Sterzi,J. A. Krieger,I. Vobornik,J. Fujii,T. Okuda,V. N. Strocov,M. B. H. Breese,F. Parmigiani,G. Rossi,S. Picozzi,R. Thomale,G. Sangiovanni,R. J. Cava,G. Panaccione###

Electronic properties of type-II Weyl semimetal WTe$_2$. A review perspective. Currently, there is a flurry of research interest on materials with an
unconventional electronic structure, and we have already seen significant
progress in their understanding and engineering towards real-life applications.
The interest erupted with the discovery of graphene and topological insulators
in the previous decade. The electrons in graphene simulate massless Dirac
Fermions with a linearly dispersing Dirac cone in their band structure, while
in topological insulators, the electronic bands wind non-trivially in momentum
space giving rise to gapless surface states and bulk bandgap. Weyl semimetals
in condensed matter systems are the latest addition to this growing family of
topological materials. Weyl Fermions are known in the context of high energy
physics since almost the beginning of quantum mechanics. They apparently
violate charge conservation rules, displaying the "chiral anomaly", with such
remarkable properties recently theoretically predicted and experimentally
verified to exist as low energy quasiparticle states in certain condensed
matter systems. Not only are these new materials extremely important for our
fundamental understanding of quantum phenomena, but also they exhibit
completely different transport phenomena. For example, massless Fermions are
susceptible to scattering from non-magnetic impurities. Dirac semimetals
exhibit non-saturating extremely large magnetoresistance as a consequence of
their robust electronic bands being protected by time reversal symmetry. These
open up whole new possibilities for materials engineering and applications
including quantum computing. In this review, we recapitulate some of the
outstanding properties of WTe$_2$, namely, its non-saturating titanic
magnetoresistance due to perfect electron and hole carrier balance up to a very
high magnetic field observed for the very first time. (Continued. Please see
the main article).

###Anisotropic Magnetoresistance in Multiband Systems: 2DEGs and Polar Metals at Oxide Interfaces|Nazim Boudjada,Ilia Khait,Arun Paramekanti###

Anisotropic Magnetoresistance in Multiband Systems: 2DEGs and Polar Metals at Oxide Interfaces. Low density two-dimensional electron gases (2DEGs) with spin-orbit coupling
are highly sensitive to an in-plane magnetic field, which impacts their Fermi
surfaces and transport properties. Such 2DEGs, formed at transition metal oxide
surfaces or interfaces, can also undergo surface phase transitions leading to
polar metals which exhibit electronic nematicity. Motivated by experiments on
such systems, we theoretically study magnetotransport in $t_{2g}$ orbital
systems, using Hamiltonians which include atomic spin-orbit coupling (SOC) and
broken inversion symmetry, for both square symmetry (001) and hexagonal
symmetry (111) 2DEGs. Using a numerical solution to the full multiband
matrix-Boltzmann equation, together with insights gleaned from the impurity
scattering overlap matrix, we explore the anisotropic magnetoresistance (AMR)
in the presence of impurities which favor small momentum scattering. We find
that transport in the (001) 2DEG is dominated by a single pair of bands, weakly
coupled by impurity scattering, one of which has a larger Fermi velocity while
the other provides an efficient current-relaxation mechanism. This leads to
strong angle-dependent current damping and a large AMR with many angular
harmonics. In contrast, AMR in the (111) 2DEG typically features a single
$\cos(2\vartheta)$ harmonic, with the angle-averaged magnetoresistance being
highly tunable by a symmetry-allowed trigonal distortion. We also explore how
the (111) 2DEG Fermi sufaces are impacted by electronic nematicity via a
surface phase transition into a 2D polar metal for which we discuss a Landau
theory, and show that this leads to distinct symmetry components and higher
angular harmonics in the AMR. Our results are in qualitative agreement with
experiments from various groups for 2DEGs at the SrTiO$_3$ surface or the
LaAlO$_3$-SrTiO$_3$ interface.

###Single-parameter scaling in the magnetoresistance of optimally doped La$_{2-x}$Sr$_{x}$CuO$_4$|Christian Boyd,Philip W. Phillips###

Single-parameter scaling in the magnetoresistance of optimally doped La$_{2-x}$Sr$_{x}$CuO$_4$. We show that the recent magnetoresistance data on thin-film
La$_{2-x}$Sr$_{x}$CuO$_4$ (LSCO) in strong magnetic fields ($B$) obeys a
single-parameter scaling of the form MR$(B,T)=f(\mu_H(T)B)$, where
$\mu_H^{-1}(T)\sim T^{\alpha}$ ($1\le\alpha\le2$), from $T=180$K until
$T\sim20$K, at which point the single-parameter scaling breaks down. The
functional form of the MR is distinct from the simple quadratic-to-linear
quadrature combination of temperature and magnetic field found in the optimally
doped iron superconductor BaFe${}_2$(As${}_{1-x}$P${}_x$)${}_2$. Further,
low-temperature departure of the MR in LSCO from its high-temperature scaling
law leads us to conclude that the MR curve collapse is not the result of
quantum critical scaling. We examine the classical effective medium theory
(EMT) previously used to obtain the quadrature resistivity dependence on field
and temperature for metals with a $T$-linear zero-field resistivity. It appears
that this scaling form results only for a binary, random distribution of
metallic components. More generally, we find a low-temperature, high-field
region where the resistivity is simultaneously $T$ and $B$ linear when multiple
metallic components are present. Our findings indicate that if mesoscopic
disorder is relevant to the magnetoresistance in strange metal materials, the
binary-distribution model which seems to be relevant to the iron pnictides is
distinct from the more broad-continuous distributions relevant to the cuprates.
Using the latter, we examine the applicability of classical effective medium
theory to the MR in LSCO and compare calculated MR curves with the experimental
data.

###Magnetotransport as diagnostic of spin reorientation: kagome ferromagnet as a case study|Neeraj Kumar,Y. Soh,Yihao Wang,Y. Xiong###

Magnetotransport as diagnostic of spin reorientation: kagome ferromagnet as a case study. While in most ferro or antiferromagnetic materials there is a unique
crystallographic direction, including crystallographically equivalent
directions, in which the moments like to point due to spin-orbit coupling, in
some, the direction of the spin reorients as a function of a certain physical
parameter such as temperature, pressure etc. Fe3Sn2 is a kagome ferromagnet
with an onset of ferromagnetism below 650 K, and undergoes a spin reorientation
near 150 K. While it is known that the moments in Fe3Sn2 point perpendicular to
the kagome plane at high temperatures and parallel to the kagome plane at low
temperatures, how the distribution of the magnetic domains in the two different
spin orientations evolve throughout the spin reorientation is not well known.
Furthermore, while there have been various reports on the magnetotransport
properties in the Hall configuration, the angular dependence of
magnetoresistance has not been studied so far. In this paper, we have examined
the spin reorientation by using anisotropic magnetoresistivity in detail,
exploiting the dependence of the resistivity on the direction between
magnetization and applied current. We are able to determine the distribution of
the magnetic domains as a function of temperature between 360 K to 2 K and the
reorientation transition to peak at 120 K. We discover that both out of plane
and in plane phases coexist at temperatures around the spin reorientation,
indicative of a first order transition. Although the volume of the magnetic
domains in the different phases sharply changes at the spin reorientation
transition, the electronic structure for a specific magnetization is not
influenced by the spin reorientation. In contrast, we observe an electronic
transition around 40 K, hitherto unreported, and reflected in both the
zero-field resistivity and anisotropic resistivity.

###High-temperature intrinsic ferromagnetism in heavily Fe-doped GaAs layers|A. V. Kudrin,V. P. Lesnikov,Yu. A. Danilov,M. V. Dorokhin,O. V. Vikhrova,P. B. Demina,D. A. Pavlov,Yu. V. Usov,V. E. Milin,Yu. M. Kuznetsov,R. N. Kriukov,A. A. Konakov,N. Yu. Tabachkova###

High-temperature intrinsic ferromagnetism in heavily Fe-doped GaAs layers. The layers of a high-temperature novel GaAs:Fe diluted magnetic semiconductor
(DMS) with an average Fe content up to 20 at. % were grown on (001) i-GaAs
substrates using a pulsed laser deposition in a vacuum. The transmission
electron microscopy (TEM) and energy-dispersive X-ray spectroscopy
investigations revealed that the conductive layers obtained at 180 and 200 C
are epitaxial, do not contain any second-phase inclusions, but contain the
Fe-enriched columnar regions of overlapped microtwins. The TEM investigations
of the non-conductive layer obtained at 250 C revealed the embedded coherent
Fe-rich clusters of GaAs:Fe DMS. The X-ray photoelectron spectroscopy
investigations showed that Fe atoms form chemical bonds with Ga and As atoms
with almost equal probability and thus the comparable number of Fe atoms
substitute on Ga and As sites. The n-type conductivity of the obtained
conductive GaAs:Fe layers is apparently associated with electron transport in a
Fe acceptor impurity band within the GaAs band gap. A hysteretic negative
magnetoresistance was observed in the conductive layers up to room temperature.
Magnetoresistance measurements point to the out-of-plane magnetic anisotropy of
the conductive GaAs:Fe layers related to the presence of the columnar regions.
The studies of the magnetic circular dichroism confirm that the layers obtained
at 180, 200 and 250 C are intrinsic ferromagnetic semiconductors and the Curie
point can reach up to at least room temperature in case of the conductive layer
obtained at 200 C. It was suggested that in heavily Fe-doped GaAs layers the
ferromagnetism is related to the Zener double exchange between Fe atoms with
different valence states via an intermediate As and Ga atom.

###Orbital effect and weak localization physics in the longitudinal magnetoresistance of the Weyl semimetals NbP, NbAs, TaP and TaAs|M. Naumann,F. Arnold,M. D. Bachmann,K. A. Modic,P. J. W. Moll,V. Süß,M. Schmidt,E. Hassinger###

Orbital effect and weak localization physics in the longitudinal magnetoresistance of the Weyl semimetals NbP, NbAs, TaP and TaAs. Weyl semimetals such as the TaAs family (TaAs, TaP, NbAs, NbP) host
quasiparticle excitations resembling the long sought after Weyl fermions at
special band-crossing points in the band structure denoted as Weyl nodes. They
are predicted to exhibit a negative longitudinal magnetoresistance (LMR) due to
the chiral anomaly if the Fermi energy is sufficiently close to the Weyl
points. However, current jetting effects, i.e. current inhomogeneities caused
by a strong, field-induced conductivity anisotropy in semimetals, have a
similar experimental signature and therefore have hindered a determination of
the intrinsic LMR in the TaAs family so far. This work investigates the
longitudinal magnetoresistance of all four members of this family along the
crystallographic $a$ and $c$ direction. Our samples are of similar quality as
those previously studied in the literature and have a similar chemical
potential as indicated by matching quantum oscillation (QO) frequencies. Care
was taken to ensure homogeneous currents in all measurements. As opposed to
previous studies where this was not done, we find a positive LMR that saturates
in fields above 4 T in TaP, NbP and NbAs for $B||c$. Using Fermi-surface
geometries from band structure calculations that had been confirmed by
experiment, we show that this is the behaviour expected from a classical purely
orbital effect, independent on the distance of the Weyl node to the Fermi
energy. The TaAs family of compounds is the first to show such a simple LMR
without apparent influences of scattering anisotropy. In configurations where
the orbital effect is small, i.e. for $B||a$ in NbAs and NbP, we find a
non-monotonous LMR including regions of negative LMR. We discuss a weak
antilocalisation scenario as an alternative interpretation than the chiral
anomaly for these results, since it can fully account for the overall field
dependence.

###Magnetism-induced topological transition in EuAs3|Erjian Cheng,Wei Xia,Xianbiao Shi,Chengwei Wang,Chuanying Xi,Shaowen Xu,Darren C. Peets,Linshu Wang,Hao Su,Li Pi,Wei Ren,Xia Wang,Na Yu,Yulin Chen,Weiwei Zhao,Zhongkai Liu,Yanfeng Guo,Shiyan Li###

Magnetism-induced topological transition in EuAs3. The nature of the interaction between magnetism and topology in magnetic
topological semimetals remains mysterious, but may be expected to lead to a
variety of novel physics. We present $ab$ $initio$ band calculations,
electrical transport and angle-resolved photoemission spectroscopy (ARPES)
measurements on the magnetic semimetal EuAs$_3$, demonstrating a
magnetism-induced topological transition from a topological nodal-line
semimetal in the paramagnetic or the spin-polarized state to a topological
massive Dirac metal in the antiferromagnetic (AFM) ground state at low
temperature, featuring a pair of massive Dirac points, inverted bands and
topological surface states on the (010) surface. Shubnikov-de Haas (SdH)
oscillations in the AFM state identify nonzero Berry phase and a negative
longitudinal magnetoresistance ($n$-LMR) induced by the chiral anomaly,
confirming the topological nature predicted by band calculations. When magnetic
moments are fully polarized by an external magnetic field, an unsaturated and
extremely large magnetoresistance (XMR) of $\sim$ 2$\times10^5$ % at 1.8 K and
28.3 T is observed, likely arising from topological protection. Consistent with
band calculations for the spin-polarized state, four new bands in quantum
oscillations different from those in the AFM state are discerned, of which two
are topologically protected. Nodal-line structures at the $Y$ point in the
Brillouin zone (BZ) are proposed in both the spin-polarized and paramagnetic
states, and the latter is proven by ARPES. Moreover, a temperature-induced
Lifshitz transition accompanied by the emergence of a new band below 3 K is
revealed. These results indicate that magnetic EuAs$_3$ provides a rich
platform to explore exotic physics arising from the interaction of magnetism
with topology.

###Spin-canting effects in GMR sensors with wide dynamic field range|Clemens Muehlenhoff,Christoph Vogler,Wolfgang Raberg,Dieter Suess,Manfred Albrecht###

Spin-canting effects in GMR sensors with wide dynamic field range. Magnetoresistive (xMR) sensors find extensive application in science and
industry, replacing Hall sensors in various low field environments. While there
have been some efforts in increasing the dynamic field range of xMR sensors,
Hall sensors remain to dominate high field applications due to their wide
linear range. Using a perpendicular magnetized reference system and an in-plane
free layer allows us to overcome this disadvantage of xMR sensors, and,
furthermore, investigate spin-canting effects in interlayer exchange coupled
perpendicular synthetic antiferromagnets (p-SAF). We created p-SAFs with
exchange coupling fields of up to 10 kOe, based on magnetic Co/Pt multilayer
systems. The p-SAFs are either designed as "single" p-SAFs, where two Co/Pt
multilayers are interlayer exchange coupled via a 4 {\AA} thick Ru spacer, or
as "double" p-SAFs, where an additional Co layer is interlayer exchange coupled
to the top multilayer. These p-SAFs are used for giant magnetoresistance (GMR)
sensors with wide dynamic field range. By using a p-SAF as the reference system
and employing an in-plane magnetic layer as the GMR's free layer, the linear
range can be effectively increased limited only by the p-SAF's switching
fields. Additionally, the magnetic anisotropy of the in-plane free layer is
fully controlled, which allows saturation fields by design. Different
configurations were investigated, ranging from free layer magnetic saturation
at lower to far higher fields than the p-SAF's switching fields. We can show
through micromagnetic simulations that certain GMR transfer curves are
dominated by spin-canting effects in the interlayer exchange coupled reference
system. Finally, our simulation results lay out the correlation of the p-SAF's
design parameters and its magnetization reversal behavior.

###Giant oscillatory tunnel magnetoresistance in CoFe/MgO/CoFe(001) junctions|Thomas Scheike,Zhenchao Wen,Hiroaki Sukegawa,Seiji Mitani###

Giant oscillatory tunnel magnetoresistance in CoFe/MgO/CoFe(001) junctions. The tunnel magnetoresistance (TMR) effect observed in magnetic tunnel
junctions (MTJs) is commonly used in many spintronic applications because the
effect can easily convert from local magnetic states to electric signals in a
wide range of device resistances. In this study, we demonstrated TMR ratios of
up to 631% at room temperature (RT), which is two or more times larger than
those used currently for magnetoresistive random access memory (MRAM) devices,
using CoFe/MgO/CoFe(001) epitaxial MTJs. The TMR ratio increased up to 1143% at
10 K, which corresponds to an effective tunneling spin polarization of 0.923.
The observed large TMR ratios resulted from the fine-tuning of atomic-scale
structures of the MTJs, such as crystallographic orientations and MgO interface
oxidation, in which the well-known Delta1 coherent tunneling mechanism for the
giant TMR effect is expected to be pronounced. However, behavior that is not
covered by the standard coherent tunneling theory was unexpectedly manifested;
i.e., (i) TMR saturation at a thick MgO barrier region and (ii) enhanced TMR
oscillation with a 0.32 nm period in MgO thickness. Particularly, the TMR
oscillatory behavior dominates the transport in a wide range of MgO
thicknesses; the peak-to-valley difference of the TMR oscillation exceeded 140%
at RT, attributable to the appearance of large oscillatory components in
resistance area product (RA). Further, we found that the oscillatory behaviors
of the TMR ratio and RA survive, even under a +-1 V bias voltage application,
indicating the robustness of the oscillation. Our demonstration of the giant
RT-TMR ratio will be an essential step for establishing spintronic
architectures, such as large-capacity MRAMs and spintronic artificial neural
networks. More essentially, the present observations can trigger us to revisit
the true TMR mechanism in crystalline MTJs.

###Colossal transverse magnetoresistance due to nematic superconducting phase fluctuations in a copper oxide|Jonatan Wårdh,Mats Granath,Jie Wu,A. T. Bollinger,Xi He,Ivan Božović###

Colossal transverse magnetoresistance due to nematic superconducting phase fluctuations in a copper oxide. Electronic anisotropy (or `nematicity') has been detected in all main
families of cuprate superconductors by a range of experimental techniques --
electronic Raman scattering, THz dichroism, thermal conductivity, torque
magnetometry, second-harmonic generation -- and was directly visualized by
scanning tunneling microscope (STM) spectroscopy. Using angle-resolved
transverse resistance (ARTR) measurements, a very sensitive and background-free
technique that can detect 0.5$\%$ anisotropy in transport, we have observed it
also in La$_{2-x}$Sr$_{x}$CuO$_{4}$ (LSCO) for $0.02 \leq x \leq 0.25$.
Arguably the key enigma in LSCO is the rotation of the nematic director with
temperature; this has not been seen before in any material. Here, we address
this puzzle by measuring the angle-resolved transverse magnetoresistance
(ARTMR) in LSCO. We report a discovery of colossal transverse magnetoresistance
(CTMR) -- an order-of-magnitude drop in the transverse resistivity in the
magnetic field of $6\,$T, while none is seen in the longitudinal resistivity.
We show that the apparent rotation of the nematic director is caused by
superconducting phase fluctuations, which are much more anisotropic than the
normal-electron fluid, and their respective directors are not parallel. This
qualitative conclusion is robust and follows straight from the raw experimental
data. We quantify this by modelling the measured (magneto-)conductivity by a
sum of two conducting channels that correspond to distinct anisotropic Drude
and Cooper-pair effective mass tensors. Strikingly, the anisotropy of
Cooper-pair stiffness is significantly larger than that of the normal
electrons, and it grows dramatically on the underdoped side, where the
fluctuations become effectively quasi-one dimensional.

###High-field magnetoresistance of microcrystalline and nanocrystalline Ni metal at 3 K and 300 K|I. Bakonyi,F. D. Czeschka,L. F. Kiss,V. A. Isnaini,A. T. Krupp,K. Palotás,S. Zsurzsa,L. Péter###

High-field magnetoresistance of microcrystalline and nanocrystalline Ni metal at 3 K and 300 K. The magnetoresistance (MR) and the magnetization isotherms were studied up to
high magnetic fields at T = 3 K and 300 K for a microcrystalline ($\mu$c) Ni
foil corresponding to bulk Ni and for a nanocrystalline (nc) Ni foil. At T = 3
K, for the $\mu$c-Ni sample with a residual resistivity ratio (RRR) of 331, the
field dependence of the resistivity was similar to what was reported previously
for high-purity ferromagnets whereas the MR(H) behavior for the nc-Ni sample
with RRR = 9 resembled that what was observed at low temperatures for Ni-based
alloys with low impurity concentration. In the magnetically saturated state,
the resistivity increased with magnetic field for both samples at T = 3 K and
the field dependence was dominated by the ordinary MR due to the Lorentz force
acting on the electron trajectories. However, the MR(H) curves were found to be
saturating for $\mu$c-Ni and non-saturating for nc-Ni, the difference arising
from their very different electron mean free paths. At T = 300 K, the MR(H)
curves of both Ni samples were very similar to those known for bulk Ni. After
magnetic saturation, the resistivity decreased nearly linearly with magnetic
field which behavior is due to the suppression of thermally-induced magnetic
disorder with increasing magnetic field. The MR(H) data were analyzed at both
temperatures with the help of Kohler plots from which the resistivity
anisotropy splitting ($\Delta\rho_{AMR}$) and the anisotropic magnetoresistance
(AMR) ratio were derived. It was demonstrated that at T = 300 K,
$\rho(H\rightarrow 0)=\rho(B\rightarrow 0)$ due to the negligible contribution
of the ordinary MR. The data for the two Ni samples at 3 K and 300 K were found
to indicate an approximately linear scaling of $\Delta\rho_{AMR}$ with the
zero-field resistivity. This implies that the AMR ratio does not vary
significantly with temperature in either microstructural state of Ni.

###Epitaxial growth, magnetoresistance, and electronic band structure of GdSb magnetic semimetal films|Hadass S. Inbar,Dai Q. Ho,Shouvik Chatterjee,Mihir Pendharkar,Aaron N. Engel,Jason T. Dong,Shoaib Khalid,Yu Hao Chang,Taozhi Guo,Alexei V. Fedorov,Donghui Lu,Makoto Hashimoto,Dan Read,Anderson Janotti,Christopher J. Palmstrøm###

Epitaxial growth, magnetoresistance, and electronic band structure of GdSb magnetic semimetal films. Motivated by observations of extreme magnetoresistance (XMR) in bulk crystals
of rare-earth monopnictide (RE-V) compounds and emerging applications in novel
spintronic and plasmonic devices based on thin-film semimetals, we have
investigated the electronic band structure and transport behavior of epitaxial
GdSb thin films grown on III-V semiconductor surfaces. The Gd3+ ion in GdSb has
a high spin S=7/2 and no orbital angular momentum, serving as a model system
for studying the effects of antiferromagnetic order and strong exchange
coupling on the resulting Fermi surface and magnetotransport properties of
RE-Vs. We present a surface and structural characterization study mapping the
optimal synthesis window of thin epitaxial GdSb films grown on III-V
lattice-matched buffer layers via molecular beam epitaxy. To determine the
factors limiting XMR in RE-V thin films and provide a benchmark for band
structure predictions of topological phases of RE-Vs, the electronic band
structure of GdSb thin films is studied, comparing carrier densities extracted
from magnetotransport, angle-resolved photoemission spectroscopy (ARPES), and
density functional theory (DFT) calculations. ARPES shows hole-carrier rich
topologically-trivial semi-metallic band structure close to complete
electron-hole compensation, with quantum confinement effects in the thin films
observed through the presence of quantum well states. DFT predicted Fermi
wavevectors are in excellent agreement with values obtained from quantum
oscillations observed in magnetic field-dependent resistivity measurements. An
electron-rich Hall coefficient is measured despite the higher hole carrier
density, attributed to the higher electron Hall mobility. The carrier
mobilities are limited by surface and interface scattering, resulting in lower
magnetoresistance than that measured for bulk crystals.

###Surprisingly large anomalous Hall effect and giant negative magnetoresistance in half-topological semimetals|Yanglin Zhu,Cheng-Yi Huang,Yu Wang,David Graf,Hsin Lin,Seng Huat Lee,John Singleton,Lujin Min,Johanna C. Palmstrom,Arun Bansil,Bahadur Singh,Zhiqiang Mao###

Surprisingly large anomalous Hall effect and giant negative magnetoresistance in half-topological semimetals. Large intrinsic anomalous Hall effect (AHE) due to the Berry curvature in
magnetic topological semimetals is attracting enormous interest due to its
fundamental importance and technological relevance. Mechanisms resulting in
large intrinsic AHE include diverging Berry curvature in Weyl semimetals,
anticrossing nodal rings or points of non-trivial bands, and noncollinear spin
structures. Here we show that a half-topological semimetal (HTS) state near a
topological critical point can provide a new mechanism for driving an
exceptionally large AHE. We reveal this through a systematic experimental and
theoretical study of the antiferromagnetic (AFM) half-Heusler compound TbPdBi.
We not only observed an unusual AHE with a surprisingly large anomalous Hall
angle {\Theta}H (tan {\Theta}H ~ 2, the largest among the antiferromagnets) in
its field-driven ferromagnetic (FM) phase, but also found a distinct Hall
resistivity peak in the canted AFM phase within a low field range, where its
isothermal magnetization is nearly linearly dependent on the field. Moreover,
we observed a nearly isotropic, giant negative magnetoresistance with a
magnitude of ~98%. Our in-depth theoretical modelling demonstrates that these
exotic transport properties originate from the HTS state. A minimal Berry
curvature cancellation between the trivial spin-up and nontrivial spin-down
bands results not only in an extremely large AHE, but it also enhances the spin
polarization of the spin-down bands substantially and thus leads to a giant
negative magnetoresistance. Our study advances the understanding of the
interplay between band topology and magnetism and offers new clues for
materials design for spintronics and other applications.

###CoRuVSi: A potential candidate for spin semimetal with promising spintronic and thermoelectric properties|Jadupati Nag,R. Venkatesh,Ajay Jha,Plamen Stamenov,P. D. Babu,Aftab Alam,K. G. Suresh###

CoRuVSi: A potential candidate for spin semimetal with promising spintronic and thermoelectric properties. Based on our experimental and theoretical studies, we report the
identification of the quaternary Heusler alloy, CoRuVSi as a new member of the
recently discovered spin semimetals class. Spin polarised semimetals possess a
unique band structure in which one of the spin bands shows semimetallic nature,
while the other shows semiconducting/insulating nature. Our findings show that
CoRuVSi possesses interesting spintronic and thermoelectric properties.
Magnetization data reveal a weak ferri-/antiferro magnetic ordering at low
temperatures, with only a very small moment $\sim$ 0.13 $\mu_B$/f.u.,
attributed to the disorder. Transport results provide strong evidence of
semimetallicity dominated by two-band conduction, while magnetoresistance data
show a non-saturating, linear, positive, magnetoresistance. Spin polarization
measurements using point-contact Andreev reflection spectra reveal a reasonably
high spin polarization of $\sim$ 50\%, which matches fairly well with the
simulated result. Furthermore, CoRuVSi shows a high thermopower value of $0.7$
$m Watt/ m-K^{2}$ at room temperature with the dominant contribution from the
semimetallic bands, rendering it as a promising thermoelectric material as
well. Our ab-initio simulation not only confirms a unique semimetallic feature,
but also reveals that the band structure hosts a linear band crossing at $\sim$
-0.4 eV below the Fermi level incorporated by a band-inversion. In addition,
the observed topological non-trivial features of the band structure is
corroborated with the simulated Berry curvature, intrinsic anomalous Hall
conductivity and the Fermi surface. The coexistence of many interesting
properties relevant for spintronic, topological and thermoelectric applications
in a single material is extremely rare and hence this study could promote a
similar strategy to identify other potential materials belonging to same class.

###Probing electron-electron interaction along with superconducting fluctuations in disordered TiN thin films|Sachin Yadav,Vinay Kaushik,M. P. Saravanan,Sangeeta Sahoo###

Probing electron-electron interaction along with superconducting fluctuations in disordered TiN thin films. Here, we demonstrate an interplay between superconducting fluctuations and
electron-electron interaction (EEI) by low temperature magnetotransport
measurements for a set of 2D disordered TiN thin films. While cooling down the
sample, a characteristic temperature T* is obtained from the R(T) at which
superconducting fluctuations start to appear. The upturn in R(T) above T*
corresponds to weak localization (WL) and/or EEI. By the temperature and field
dependences of the observed resistance, we show that the upturn in R(T)
originates mainly from EEI with a negligible contribution from WL. Further, we
have used the modified Larkins electron-electron attraction strength
beta(T/Tc), containing a field induced pair breaking parameter, in the
Maki-Thompson (MT) superconducting fluctuation term. Here, the temperature
dependence of the beta(T/Tc) obtained from the magnetoresistance analysis shows
a diverging behavior close to Tc and it remains almost constant at higher
temperature within the limit of ln(T/Tc) < 1. Interestingly, the variation of
beta(T/Tc) on the reduced temperature (T/Tc) offers a common trend which has
been closely followed by all the concerned samples presented in this study.
Finally, the temperature dependence of inverse phase scattering time , as
obtained from the magnetoresistance analysis, clearly shows two different
regimes; the first one close to Tc follows the Ginzburg-Landau relaxation rate
, whereas, the second one at high temperature varies almost linearly with
temperature indicating the dominance of inelastic electron-electron scattering
for the dephasing mechanism. These two regimes are followed in a generic way by
all the samples in spite of being grown under different growth conditions.

###Normal state property of the t-J model|Yu-Liang Liu###

Normal state property of the t-J model. Using the spin-hole coherent state representation and taking a long range
antiferromagnetic N\`{e}el order as a background of the localized spin degree
part, we have studied the normal state behavior of the t-J model, and shown
that a strongly short-range antiferromagnetic correlation of the localized spin
degree part is responsible for the anomalous non-Korringa-like relaxation
behavior of the planar copper spin, the Korringa-like behavior of the planar
oxygen spin may derive from the charge degree part describing a Zhang-Rice
spin-singlet; The charge degree part feels a strongly staggered magnetic field
induced by this short-range antiferromagnetic correlation as a doping hole
hopping, this staggered magnetic field enforces the charge degrees to have
different responses to external magnetic and electric fields and to show two
relaxation rate behaviors corresponding to the planar resistivity and Hall
angle, respectively. We have found that the temperature dependence of
magnetoresistance is $T^{-n}$, $n\simeq 3$, near the optimal doping, $n\simeq
4$, in the underdoping region, violating Kohler's rule, the transport
relaxation rate is of the order of $2k_{B}T$, all that are consistent with the
normal state of the cuprate superconductors.

###Correlated-electron theory of strongly anisotropic metamagnets|K. Held,M. Ulmke,N. Bl"umer,D. Vollhardt###

Correlated-electron theory of strongly anisotropic metamagnets. The microscopic origin of metamagnetism and metamagnetic transitions in
strongly anisotropic antiferromagnets is investigated within a quantum
mechanical theory of correlated electrons. To this end the Hubbard model with
staggered magnetization m_st along an easy axis e in a magnetic field H || e is
studied both analytically and numerically within the dynamical mean field
theory (DMFT). At intermediate couplings the self-consistent DMFT equations,
which become exact in the limit of large coordination number, are solved by
finite temperature Quantum Monte Carlo techniques. The temperature and magnetic
field dependence of the homogeneous and staggered magnetization are calculated
and the magnetic phase diagram is constructed. At half filling the metamagnetic
transitions are found to change from first order at low temperatures to second
order near the N'eel temperature, implying the existence of a multicritical
point. Doping with holes or electrons has a strong effect: the system becomes
metallic, the electronic compressibility increases and the critical
temperatures and fields decrease. These results are related to known properties
of insulating metamagnets such as FeBr_2, metallic metamagnets such as UPdGe,
and the giant and colossal magnetoresistance found in a number of magnetic bulk
systems.

###Intermediate Valence Model for the Colossal Magnetoresistance in Tl_{2}Mn_{2}O_{7}|C. I. Ventura,B. Alascio###

Intermediate Valence Model for the Colossal Magnetoresistance in Tl_{2}Mn_{2}O_{7}. The colossal magnetoresistance exhibited by Tl_{2}Mn_{2}O_{7} is an
interesting phenomenon, as it is very similar to that found in perovskite
manganese oxides although the compound differs both in its crystalline
structure and electronic properties from the manganites. At the same time,
other pyrochlore compounds, though sharing the same structure with
Tl_{2}Mn_{2}O_{7}, do not exhibit the strong coupling between magnetism and
transport properties found in this material. Mostly due to the absence of
evidence for significant doping into the Mn-O sublattice, and the tendency of
Tl to form conduction bands, the traditional double exchange mechanism
mentioned in connection with manganites does not seem suitable to explain the
experimental results in this case. We propose a model for Tl_{2}Mn_{2}O_{7}
consisting of a lattice of intermediate valence ions fluctuating between two
magnetic configurations, representing Mn-3d orbitals, hybridized with a
conduction band, which we associate with Tl. This model had been proposed
originally for the analysis of intermediate valence Tm compounds. With a
simplified treatment of the model we obtain the electronic structure and
transport properties of Tl_{2}Mn_{2}O_{7}, with good qualitative agreement to
experiments. The presence of a hybridization gap in the density of states seems
important to understand the reported Hall data.

###Spin Tunneling in Conducting Oxides|Alexander Bratkovsky###

Spin Tunneling in Conducting Oxides. Direct tunneling in ferromagnetic junctions is compared with
impurity-assisted, surface state assisted, and inelastic contributions to a
tunneling magnetoresistance (TMR). Theoretically calculated direct tunneling in
iron group systems leads to about a 30% change in resistance, which is close to
experimentally observed values. It is shown that the larger observed values of
the TMR might be a result of tunneling involving surface polarized states. We
find that tunneling via resonant defect states in the barrier radically
decreases the TMR (down to 4% with Fe-based electrodes), and a resonant tunnel
diode structure would give a TMR of about 8%. With regards to inelastic
tunneling, magnons and phonons exhibit opposite effects: one-magnon emission
generally results in spin mixing and, consequently, reduces the TMR, whereas
phonons are shown to enhance the TMR. The inclusion of both magnons and phonons
reasonably explains an unusual bias dependence of the TMR.
  The model presented here is applied qualitatively to half-metallics with 100%
spin polarization, where one-magnon processes are suppressed and the change in
resistance in the absence of spin-mixing on impurities may be arbitrarily
large. Even in the case of imperfect magnetic configurations, the resistance
change can be a few 1000 percent. Examples of half-metallic systems are
CrO$_2$/TiO$_2$ and CrO$_2$/RuO$_2$, and an account of their peculiar band
structures is presented. The implications and relation of these systems to CMR
materials which are nearly half-metallic, are discussed.

###Coherent Resonant Tunneling Through an Artificial Molecule|C. A. Stafford,R. Kotlyar,S. Das Sarma###

Coherent Resonant Tunneling Through an Artificial Molecule. Coherent resonant tunneling through an artificial molecule of quantum dots in
an inhomogeneous magnetic field is investigated using an extended Hubbard
model. Both the multiterminal conductance of an array of quantum dots and the
persistent current of a quantum dot molecule embedded in an Aharanov-Bohm ring
are calculated. The conductance and persistent current are calculated
analytically for the case of a double quantum dot and numerically for larger
arrays using a multi-terminal Breit-Wigner type formula, which allows for the
explicit inclusion of inelastic processes. Cotunneling corrections to the
persistent current are also investigated, and it is shown that the sign of the
persistent current on resonance may be used to determine the spin quantum
numbers of the ground state and low-lying excited states of an artificial
molecule. An inhomogeneous magnetic field is found to strongly suppress
transport due to pinning of the spin-density-wave ground state of the system,
and giant magnetoresistance is predicted to result from the ferromagnetic
transition induced by a uniform external magnetic field.

###The Density of States of hole-doped Manganites: A Scanning Tunneling Microscopy/Spectroscopy study|Amlan Biswas,Suja Elizabeth,A. K. Raychaudhuri,H. L. Bhat###

The Density of States of hole-doped Manganites: A Scanning Tunneling Microscopy/Spectroscopy study. Variable temperature scanning tunneling microscopy/spectroscopy studies on
single crystals and epitaxial thin films of hole-doped manganites, which show
colossal magnetoresistance, have been done. We have investigated the variation
of the density of states, at and near the Fermi energy ($E_f$), as a function
of temperature. Simple calculations have been carried out, to find out the
effect of temperature on the tunneling spectra and extract the variation of
density of states with temperature, from the observed data. We also report
here, atomic resolution images, on the single crystals and larger range images
showing the growth patterns on thin films. Our investigation shows
unambiguously that there is a rapid variation in density of states for
temperatures near the Curie temperature ($T_c$). While for temperatures below
$T_c$, a finite DOS is observed at $E_f$, for temperatures near $T_c$ a hard
gap opens up in the density of states near $E_f$. For temperatures much higher
than $T_c$, this gap most likely gives way to a soft gap. The observed hard gap
for temperatures near $T_c$, is somewhat higher than the transport gap for all
the materials. For different materials, we find that the magnitude of the hard
gap decreases as the $T_c$ of the material increases and eventually, for
materials with a $T_c$ close to 400 K, the value of the gap approaches zero.

###Non-linear effects in hopping conduction of single-crystal La_{2}CuO_{4 + δ}|B. I. Belevtsev,N. V. Dalakova,A. S. Panfilov###

Non-linear effects in hopping conduction of single-crystal La_{2}CuO_{4 + δ}. The unusual non-linear effects in hopping conduction of single-crystal
La_{2}CuO_{4 + \delta} with excess oxygen has been observed. The resistance is
measured as a function of applied voltage U (10^{-3} V - 25 V) in the
temperature range 5 K < T < 300 K. At relatively high voltage (U > 0.1 V) the
conduction of sample investigated corresponds well to Mott's variable-range
hopping (VRH). An unusual conduction behavior is found, however, in low voltage
range (approximately below 0.1 V), where the influence of electric field and
(or) electron heating effect on VRH ought to be neglected. Here we have
observed strong increase in resistance at increasing U at T < 20 K, whereas at
T > 20 K the resistance decreases with increasing U. The magnetoresistance of
the sample below 20 K has been positive at low voltage and negative at high
voltage. The observed non-Ohmic behavior is attributable to inhomogeneity of
the sample, and namely, to the enrichment of sample surface with oxygen during
the course of the heat treatment of the sample in helium and air atmosphere
before measurements. At low enough temperature (below 20 K) the surface layer
with increased oxygen concentration is presumed to consist of disconnected
superconducting regions (with T_{c} about 20 K) in poor-conducting matrix. The
results obtained demonstrate that transport properties of cuprate oxides may be
determined in essential degree by structural or stoichimetric inhomogeneities.
This should be taken into account at evaluation of "quality" of
high-temperature superconductors on the basis of transport properties
measurements.

###Hall Effect of La2/3(Ca,Pb)1/3MnO3 Single Crystals near the Critical Temperature|S. H. Chun,M. B. Salamon,P. D. Han###

Hall Effect of La2/3(Ca,Pb)1/3MnO3 Single Crystals near the Critical Temperature. The Hall resistivity rho_{xy} of a La_{2/3}(Ca,Pb)_{1/3}MnO_3 single crystal
has been measured as a function of temperature and field. The overall behavior
is similar to that observed previously in thin-films. At 5 K, rho_{xy} is
positive and linear in field, indicating that the anomalous contribution $R_S$
is negligible. However, the effective carrier density in a free electron model
is n_{eff}=2.4 holes/Mn, even larger than the 0.85-1.9 holes/Mn reported for
thin-films and far larger than the 0.33 holes/Mn expected from the doping
level. As temperature increases, a strong, negative contribution to rho_{xy}
appears, that we ascribe to R_S. Using detailed magnetization data, we separate
the ordinary (\propto B) and anomalous (\propto M) contributions. Below T_C,
R_S \propto rho_{xx}, indicating that magnetic skew scattering is the dominant
mechanism in the metallic ferromagnetic regime. At and above the
resistivity-peak temperature, we find that rho_{xy}/rho_{xx}M is a constant,
independent of temperature and field. This implies that the anomalous Hall
coefficient is proportional to the magnetoresistance. A different explanation
based on two fluid model is also presented.

###Transport and magnetic anomalies due to A-site ionic size mismatch in La$_{0.5}$Ca$_{0.5-x}$Ba_{x}MnO$_3$|R. Mallik,E. S. Reddy,P. L. Paulose,Subham Mazumdar,E. V. Sampathkumaran###

Transport and magnetic anomalies due to A-site ionic size mismatch in La$_{0.5}$Ca$_{0.5-x}$Ba_{x}MnO$_3$. We present results of electrical resistivity, magnetoresistance and ac and dc
magnetic susceptibility on polycrystalline samples of the type
La(0.5)Ca(0.5-x)Ba(x)MnO(3) synthesized under identical heat treatment
conditions. The substitution of larger Ba ions for Ca results in a non-
monotonic variation of the curie temperature as the system evolves from a
charge ordered insulating state for x=0 to a ferromagnetic metallic state for
x=0.5. An intermediate compositino, x=0.1, interestingly exhibits
ferromagnetic. insulating behaviour with thermal hysteresis in ac chi around
the curie tem- perature (120K). The x=0.2 and 0.3 compounds exhibit
semiconducting like behavior as the temperature is lowered below 300K, with a
broad peak in rho around 80-100K: These compositions exhibit a weak increase in
rho as the temperature lowered below 30K, indicative of electron localization
effects. These compositions also undergo ferromagnetic transitions below about
200 and 235K respectively, though these are non-hysteretic; above all, for
these compositions, MR is large and conveniently measurable over the entire
tempera- ture range of measurement below Tc. This experimental finding may be
of interest from the application point of view. We infer that the A-site
ionic-size mismatch plays a crucial role in the deciding these properties.

###Theory of Colossal Magnetoresistance in Doped Manganites|A. S. Alexandrov,A. M. Bratkovsky###

Theory of Colossal Magnetoresistance in Doped Manganites. The exchange interaction of polaronic carriers with localized spins leads to
a ferromagnetic/paramagnetic transition in doped charge-transfer insulators
with strong electron-phonon coupling. The relative strength of the exchange and
electron-phonon interactions determines whether the transition is first or
second order. A giant drop in the number of current carriers during the
transition, which is a consequence of local bound pair (bipolaron) formation in
the paramagnetic phase, is extremely sensitive to an external magnetic field.
Below the critical temperature of the transition, $T_c$, the binding of the
polarons into immobile pairs competes with the ferromagnetic exchange between
polarons and the localized spins on Mn ions, which tends to align the polaron
moments and, therefore, breaks up those pairs. The number of carriers abruptly
increases below $T_c$ leading to a sudden drop in resistivity. We show that the
carrier density collapse describes the colossal magnetoresistance of doped
manganites close to the transition.
  Below $T_c$, transport occurs by polaronic tunneling, whereas at high
temperatures the transport is by hopping processes. The transition is
accompanied by a spike in the specific heat, as experimentally observed. The
gap feature in tunneling spectroscopy is related to the bipolaron binding
energy, which depends on the ion mass. This dependence explains the giant
isotope effect of the magnetization and resistivity upon substitution of
$^{16}$O by $^{18}$O. It is shown also that the localization of polaronic
carriers by disorder {\em cannot} explain the observed huge sensitivity of the
transport properties to the magnetic field in doped manganites.

###Huge oxygen isotope effect on local lattice fluctuations in La(2-x)Sr(x)CuO(4) superconductor|A. Lanzara,N. L. Saini,A. Bianconi,Guo-meng Zhao,K. Conder,H. Keller,K. A. Muller###

Huge oxygen isotope effect on local lattice fluctuations in La(2-x)Sr(x)CuO(4) superconductor. Recently a growing number of experiments have provided indications of the key
role of polarons (composite particles formed by a charge strongly coupled with
a local lattice deformation) in doped perovskites, hosting colossal
magnetoresistance (CMR) and high Tc superconductivity. While the role of
polarons is generally recognized in manganites due to the large amplitude of
the local lattice deformation, the scientific debate remains open on the
cuprates where the lattice deformation is smaller and the anomalous normal
metallic phase becomes complex due to the coexistence of polarons with
itinerant carriers. Moreover the segregation of polarons and itinerant charges
in different spatial domains forming lattice-charge stripes as well as the slow
dynamic 1D spin fluctuations have been observed. The debate on the driving
force for the stripe formation remains object of discussion since it could be
purely due to electronic interactions and/or due to strong electron-lattice
(polaronic) interactions. In order to explore the important role of the latter
in stripe charge segregation, we have studied isotope effects on the dynamical
lattice fluctuations and polaron ordering temperature. Here we report a
compelling evidence for a huge isotope effect on local lattice fluctuations of
La(2-x)Sr(x)CuO(4) high Tc superconductor by x-ray absorption spectroscopy, a
fast (~10^(-15) sec) and local probe (~5 A). Upon replacing $^{16}$O with
$^{18}$O, the characteristic temperature T^{*} for polaron ordering in
La(1.94)Sr(0.06)CuO(4) increases from about 110 K to 170 K.

###Hall-effect in LuNi_2B_2C and YNi_2B_2C borocarbides: a comparative study|V. N. Narozhnyi,J. Freudenberger,V. N. Kochetkov,K. A. Nenkov,G. Fuchs,A. Handstein,K. -H. Müller###

Hall-effect in LuNi_2B_2C and YNi_2B_2C borocarbides: a comparative study. The Hall effect in LuNi_2B_2C and YNi_2B_2C borocarbides has been
investigated in normal and superconducting mixed states. The Hall resistivity
rho_{xy} for both compounds is negative in the normal as well as in the mixed
state and has no sign reversal below T_c typical for high-T_c superconductors.
In the mixed state the behavior of both systems is quite similar. The scaling
relation rho_{xy}\sim\rho_{xx}^\beta (\rho_{xx} is the longitudinal
resistivity) was found with \beta=2.0 and 2.1 for annealed Lu- and Y-based
compounds, respectively. The scaling exponent \beta decreases with increasing
degree of disorder and can be varied by annealing. This is attributed to a
variation of the strength of flux pinning. In the normal state weakly
temperature dependent Hall coefficients were observed for both compounds. A
distinct nonlinearity in the \rho_{xy} dependence on field H was found for
LuNi_2B_2C in the normal state below 40K, accompanied by a large
magnetoresistance (MR) reaching +90% for H=160kOe at T=20K. At the same time
for YNi_2B_2C only linear \rho_{xy}(H) dependences were observed in the normal
state with an approximately three times lower MR value. This difference in the
normal state behavior of the very similar Lu- and Y-based borocarbides seems to
be connected with the difference in the topology of the Fermi surface of these
compounds.

###Properties of the ferrimagnetic double-perovskite A_{2}FeReO_{6} (A=Ba and Ca)|W. Prellier,V. Smolyaninova,Amlan Biswas,C. Galley,R. L. Greene,K. Ramesha,J. Gopalakrishnan###

Properties of the ferrimagnetic double-perovskite A_{2}FeReO_{6} (A=Ba and Ca). Ceramics of A_{2}FeReO_{6} double-perovskite have been prepared and studied
for A=Ba and Ca. Ba_{2}FeReO_{6} has a cubic structure (Fm3m) with $a\approx
$8.0854(1) \AA whereas Ca_{2}FeReO_{6} has a distorted monoclinic symmetry with
$a\approx 5.396(1) \AA, b\approx 5.522(1) \AA, c\approx 7.688(2) \AA$ and
$\beta =90.4^{\circ} (P21/n)$. The barium compound is metallic from 5 K to 385
K, i.e. no metal-insulator transition has been seen up to 385 K, and the
calcium compound is semiconducting from 5 K to 385 K. Magnetization
measurements show a ferrimagnetic behavior for both materials, with T_{c}=315 K
for Ba_{2}FeReO_{6} and above 385 K for Ca_{2}FeReO_{6}. A specific heat
measurement on the barium compound gave an electron density of states at the
Fermi level, N(E_{F}) equal to 6.1$\times 10^{24} eV^{-1}mole^{-1}$. At 5 K, we
observed a negative magnetoresistance of 10 % in a magnetic field of 5 T, but
only for Ba_{2}FeReO_{6}. Electrical, thermal and magnetic properties are
discussed and compared to the analogous compounds Sr_{2}Fe(Mo,Re)O_{6}.

###Transport and Magnetic properties of laser ablated La0.7Ce0.3MnO3 films on LaAlO3: Effect of oxygen pressure, sample thickness and co-doping with Ca|P. Raychaudhuri,S. Mukherjee,A. K. Nigam,J. John,U. D. Vaisnav,R. Pinto###

Transport and Magnetic properties of laser ablated La0.7Ce0.3MnO3 films on LaAlO3: Effect of oxygen pressure, sample thickness and co-doping with Ca. La0.7Ce0.3MnO3 is a relatively new addition in the family of colossal
magnetoresistive manganites where the cerium ion is believed to be in the Ce4+
state. In this paper we report an extensive study the magnetotransport
properties of laser ablated La0.7Ce0.3MnO3 films on LaAlO3 with variation in
ambient oxygen pressure during growth and film thickness. We observe that the
transport and magnetic properties of the film depend on the interplay between
oxygen pressure, surface morphology, film thickness and epitaxial strain. The
films were characterized by x-ray diffraction on a 4-circle x-ray goniometer.
We observe an increase in the metal-insulator transition temperature with
decreasing oxygen pressure. This is in direct contrast with the oxygen pressure
dependence of La0.7Ca-0.3MnO-3 films suggesting the electron doped nature of
the La0.7Ce0.3MnO3 system. With decreasing film thickness we observe an
increase in the metal-insulator transition temperature. This is associated with
a compression of the unit cell in the a-b plane due to epitaxial strain. When
the system is co-doped with 50% Ca at the Ce site the system
(La0.7Ca0.15Ce0.15MnO3) is driven into a insulating state suggesting that the
electrons generated by Ce4+ is compensated by the holes generated by Ca2+
valence thus making the average valence at the rare-earth site 3+ as in the
parent material LaMnO3.

###Interference and Interaction in Multiwall Carbon Nanotubes|C. Schonenberger,A. Bachtold,C. Strunk,J. -P. Salvetat,L. Forro###

Interference and Interaction in Multiwall Carbon Nanotubes. We report equilibrium electric resistance R and tunneling spectroscopy dI/dV
measurements obtained on single multiwall nanotubes contacted by four metallic
Au fingers from above. At low temperature quantum interference phenomena
dominate the magnetoresistance. The phase-coherence and elastic-scattering
lengths are deduced. Because the latter is of order of the circumference of the
nanotubes, transport is quasi-ballistic. This result is supported by a dI/dV
spectrum which is in good agreement with the density-of-states (DOS) due to the
one-dimensional subbands expected for a perfect single-wall tube. As a function
of temperature T the resistance increases on decreasing T and saturates at
approx. 1-10 K for all measured nanotubes. R(T) cannot be related to the
energy-dependent DOS of graphene but is mainly caused by interaction and
interference effects. On a relatively small voltage scale of order 10 meV, a
pseudogap is observed in dI/dV which agrees with Luttinger-Liquid theories for
nanotubes. Because we have used quantum diffusion based on Fermi-Liquid as well
as Luttinger-Liquid theory in trying to understand our results, a large
fraction of this paper is devoted to a careful discussion of all our results.

###Influence of the cooperative Jahn-Teller effect on the transport- and magnetic properties of La_{7/8}Sr_{1/8}MnO_3 single crystals|P. Wagner,I. Gordon,S. Mangin,V. V. Moshchalkov,Y. Bruynseraede,L. Pinsard,A. Revcolevschi###

Influence of the cooperative Jahn-Teller effect on the transport- and magnetic properties of La_{7/8}Sr_{1/8}MnO_3 single crystals. The low-doped magnetic perovskite La_{7/8}Sr_{1/8}MnO_3 undergoes within the
paramagnetic-semiconducting phase a first-order structural transition due to
antiferrodistorsive ordering of Jahn-Teller deformed MnO_6 octahedra. This
allows to study not only the influence of the spin configuration on the
magneto-transport properties (CMR effect) but also the role of orbital order
and disorder. The orbital ordering transition (at 269 K in zero magnetic field)
causes a doubling of the resistivity (regardless of the CMR effect in applied
magnetic fields) and a drop of the paramagnetic susceptibility. The latter
might be interpreted in terms of a shrinking of spin polarons. External
magnetic fields shift the ordering transition to lower temperatures according
to the field-induced decrease of the carrier localization. The magnetic field -
temperature phase boundary line was investigated by means of magnetoresistance
(up to 12 T) and pulsed-fields magnetization measurements up to 50 T. The
pronounced magnetization anomalies, associated with the phase transition,
vanish for fields exceeding 20 T. This behaviour has been attributed to a
field-induced crossover from antiferrodistorsive order to a
nondistorsive/ferromagnetic orbital configuration.

###Silence of magnetic layers to magnetoresistive process and electronic separation at low temperatures in (La, Sm)Mn$_2$Ge$_2$|E. V. Sampathkumaran,R. Mallik,P. L. Paulose,Subham Majumdar###

Silence of magnetic layers to magnetoresistive process and electronic separation at low temperatures in (La, Sm)Mn$_2$Ge$_2$. A closer look at the temperature (T) dependence of magnetoresistance (MR) of
two polycrystalline magnetic compounds, LaMn$_2$Ge$_2$ and SmMn$_2$Ge$_2$,
previously reported by us, is made. A common feature for both these compounds
is that the low temperature MR is positive (say, below, 30 K) in spite of the
fact that both are ferromagnetic at such low temperatures; in addition, MR as a
function of magnetic field (H) does not track magnetization (M) in the sense
that M saturates at low fields, while MR varies linearly with H. These
observations suggest that the magnetic layers interestingly do not dominate low
temperature magnetotransport process. Interestingly enough, as the T is
increased, say around 100 K, these magnetic layers dominate MR process as
evidenced by the tracking of M and MR in SmMn$_2$Ge$_2$. These results tempts
us to propose that there is an unusual "electronic separation" for MR process
as the T is lowered in this class of compounds.

###Resonant Spin-Dependent Tunneling in Spin-Valve Junctions in the Presence of Paramagnetic Impurities|A. Vedyayev,D. Bagrets,A. Bagrets,B. Dieny###

Resonant Spin-Dependent Tunneling in Spin-Valve Junctions in the Presence of Paramagnetic Impurities. The tunnel magnetoresistance (TMR) of F/O/F magnetic junctions, (F's are
ferromagnetic layers and O is an oxide spacer) in the presence of magnetic
impurities within the barrier, is investigated. We assume that magnetic
couplings exist both between the spin of impurity and the bulk magnetization of
the neighboring magnetic electrode, and between the spin of impurity and the
spin of tunneling electron. Consequently, the resonance levels of the system
formed by a tunneling electron and a paramagnetic impurity with spin S=1, are a
sextet. As a result the resonant tunneling depends on the direction of the
tunneling electron spin. At low temperatures and zero bias voltage the TMR of
the considered system may be larger than TMR of the same structure without
paramagnetic impurities. It is calculated that an increase in temperature leads
to a decrease in the TMR amplitude due to excitation of spin-flip processes
resulting in mixing of spin up and down channels. It is also shown that
asymmetry in the location of the impurities within the barrier can lead to
asymmetry in $I(V)$ characteristics of impurity assisted current and two
mechanisms responsible for the origin of this effect are established. The first
one is due to the excitation of spin-flip processes at low voltages and the
second one arises from the shift of resonant levels inside the insulator layer
under high applied voltages.

###Magnetoresistance From Quantum Interference Effects in Ferromagnets|N. Manyala,Y Siids,J. F. DiTusa,G. Aeppli,D. P. Young,Z. Fisk###

Magnetoresistance From Quantum Interference Effects in Ferromagnets. The desire to maximize the sensitivity of read/write heads and thus the
information density of magnetic storage devices has produced an intense
interest in the magnetoresistance (MR) of magnetic materials. Recent
discoveries include "colossal" MR of the manganites1-4 and the enhanced MR of
low carrier density ferromagnets4-6. In the low carrier density systems
investigated to date as well as the manganites, a key feature is that the
electrical conduction is due to a different set of electrons than the localized
electrons responsible for the magnetism. Here we propose a mechanism for
ferromagnetic MR originating from quantum interference effects, rather than
simple scattering. The new mechanism obtains in disordered low carrier density
magnets where the magnetism as well as the electrical conduction are due to the
same electrons. Here the MR is positive and only weakly temperature dependent
below the Curie point. This is very different from the MR seen when conduction
electrons and local moments can be treated separately, in which case the MR is
negative and strongly peaked at the Curie point.

###Electrical spin injection and detection in a semiconductor. Is it feasible?|A. T. Filip,B. H. Hoving,F. J. Jedema,B. J. van Wees###

Electrical spin injection and detection in a semiconductor. Is it feasible?. The electrical injection of spin polarized electrons in a semiconductor can
be achieved in principle by driving a current from a ferromagnetic metal, where
current is known to be significantly spin polarized, into the semiconductor via
ohmic conduction. For detection a second ferromagnet can be used as drain. We
studied submicron lateral spin valve junctions, based on high mobility
InAs/AlSb two-dimensional electron gas (2DEG), with Ni, Co and Permalloy as
ferromagnetic electrodes. In the standard geometry it is very difficult to
separate true spin injection from other effects, including local Hall effect,
anomalous magnetoresistance (AMR) contribution from the ferromagnetic
electrodes and weak localization/anti-localization corrections, which can
closely mimic the signal expected from spin valve effect. The reduction in
size, and the use of a multiterminal non-local geometry allowed us to reduce
the unwanted effects to a minimum. Despite all our efforts, we have not been
able to observe spin injection. However, we find that this 'negative' result in
these systems is actually consistent with theoretical predictions for spin
transport in diffusive systems.

###Muon Spin Relaxation Study of (La, Ca)MnO3|R. H. Heffner,J. E. Sonier,D. E. MacLaughlin,G. J. Nieuwenhuys,G. M. Luke,Y. J. Uemura,S-W. Cheong,G. Balakrishnan###

Muon Spin Relaxation Study of (La, Ca)MnO3. We report predominantly zero field muon spin relaxation measurements in a
series of Ca-doped LaMnO_3 compounds which includes the colossal
magnetoresistive manganites. Our principal result is a systematic study of the
spin-lattice relaxation rates 1/T_1 and magnetic order parameters in the series
La_{1-x}Ca_xMnO_3, x = 0.0, 0.06, 0.18, 0.33, 0.67 and 1.0. In LaMnO_3 and
CaMnO_3 we find very narrow critical regions near the Neel temperatures T_N and
temperature independent 1/T_1 values above T_N. From the 1/T_1 in LaMnO_3 we
derive an exchange integral J = 0.83 meV which is consistent with the mean
field expression for T_N. All of the doped manganites except CaMnO_3 display
anomalously slow, spatially inhomogeneous spin-lattice relaxation below their
ordering temperatures. In the ferromagnetic (FM) insulating
La_{0.82}Ca_{0.18}MnO_3 and ferromagnetic conducting La_{0.67}Ca_{0.33}MnO_3
systems we show that there exists a bi-modal distribution of \muSR rates
\lambda_f and \lambda_s associated with relatively 'fast' and 'slow' Mn
fluctuation rates, respectively. A physical picture is hypothesized for these
FM phases in which the fast Mn rates are due to overdamped spin waves
characteristic of a disordered FM, and the slower Mn relaxation rates derive
from distinct, relatively insulating regions in the sample. Finally, likely
muon sites are identified, and evidence for muon diffusion in these materials
is discussed.

###Magnetoresistance in High-Tc Superconductors: The Role of Vertex Corrections|Hiroshi Kontani###

Magnetoresistance in High-Tc Superconductors: The Role of Vertex Corrections. In high-Tc cuprates, the orbital magnetoresistance in plane (MR,
$\Delta\rho/\rho$) is anomalously enhanced at lower tempemeratures compared
with conventional Fermi liquids, and thus Kohler's rule is strongly violated.
Moreover, it should be noted that an intimate relation between the MR and the
Hall coefficient ($R_H$), $\Delta\rho/\rho \propto (R_H/\rho)^2$, holds well
experimentally, and is called the "modified Kohler's rule". In this letter, we
study this long-standing problem in terms of the nearly antiferromagnetic (AF)
Fermi liquid. We analyze the exact expression for the MR by including the
vertex corrections (VC's) to keep the conservation laws, and find the
approximate "scaling relation" $\Delta\rho/\rho \propto \xi_{AF}^4 /\rho^2$
($\xi_{AF}$ being the AF correlation length.) in the presence of AF
fluctuations. The factor $\xi_{AF}^4$, which comes from the VC's for the
current, gives the additional temperature dependence. By taking account of the
relation $R_H \propto \xi_{AF}^2$ [Kontani et al., PRB 59 (1999) 14723.], we
can naturally explain the modified Kohler's rule. In conclusion, based on the
Fermi liquid theory, the famous {\it seemingly} non-Fermi liquid behaviors of
the Hall coefficient and the MR in high-Tc cuprates are naturally understood on
an equal footing.

###General Formula for the Magnetoresistance on the Basis of the Fermi Liquid Theory|Hiroshi Kontani###

General Formula for the Magnetoresistance on the Basis of the Fermi Liquid Theory. The general expression for the magnetoresistance (MR) due to the Lorentz
force is derived by using the Fermi liquid transport theory based on the Kubo
formula. The obtained gauge-invariant expression is exact for any strength of
the interaction, as for the most singular term with respect to 1/\gamma^\ast
(\gammak^\ast being the quasiparticle damping rate). By virtue of the
exactness, the conserving laws are satisfied rigorously in the present
expression, which is indispensable for avoiding unphysical solutions. Based on
the derived expression, we can calculate the MR within the framework of the
Baym-Kadanoff type conserving approximation, by including all the vertex
corrections required by the Ward identity. The present expression is
significant especially for strongly correlated systems because the current
vertex corrections will be much important. On the other hand, if we drop all
the vertex corrections in the formula, we get the MR of the relaxation time
approximation (RTA), which is commonly used because of the simplicity. However,
the RTA is dangerous because it may give unphysical results owing to the lack
of conserving laws. In conclusion, the present work enables us to study the MR
with satisfying the conserving laws which is highly demanded in strongly
correlated electrons, such as high-Tc superconductors, organic metals, and
heavy Fermion systems. In Appendix D, we reply to the comment by O. Narikiyo
[cond-mat/0006028]. (Note that Appendix D exists only in the e-preprint
version.)

###Relativistic corrections in magnetic systems|A. Crépieux,P. Bruno###

Relativistic corrections in magnetic systems. We present a weak-relativistic limit comparison between the Kohn-Sham-Dirac
equation and its approximate form containing the exchange coupling, which is
used in almost all relativistic codes of density-functional theory. For these
two descriptions, an exact expression of the Dirac Green's function in terms of
the non-relativistic Green's function is first derived and then used to
calculate the effective Hamiltonian, i.e., Pauli Hamiltonian, and effective
velocity operator in the weak-relativistic limit. We point out that, besides
neglecting orbital magnetism effects, the approximate Kohn-Sham-Dirac equation
also gives relativistic corrections which differ from those of the exact
Kohn-Sham-Dirac equation. These differences have quite serious consequences: in
particular, the magnetocrystalline anisotropy of an uniaxial ferromagnet and
the anisotropic magnetoresistance of a cubic ferromagnet are found from the
approximate Kohn-Sham-Dirac equation to be of order $1/c^2$, whereas the
correct results obtained from the exact Kohn-Sham-Dirac equation are of order
$1/c^4$ . We give a qualitative estimate of the order of magnitude of these
spurious terms.

###Colossal Magnetoresistant Materials: The Key Role of Phase Separation|Elbio Dagotto,Takashi Hotta,Adriana Moreo###

Colossal Magnetoresistant Materials: The Key Role of Phase Separation. The study of the manganese oxides, widely known as manganites, that exhibit
the ``Colossal'' Magnetoresistance (CMR) effect is among the main areas of
research within the area of Strongly Correlated Electrons. After considerable
theoretical effort in recent years, mainly guided by computational and
mean-field studies of realistic models, considerable progress has been achieved
in understanding the curious properties of these compounds. These recent
studies suggest that the ground states of manganite models tend to be
intrinsically inhomogeneous due to the presence of strong tendencies toward
phase separation, typically involving ferromagnetic metallic and
antiferromagnetic charge and orbital ordered insulating domains. Calculations
of the resistivity versus temperature using mixed states lead to a good
agreement with experiments. The mixed-phase tendencies have two origins: (i)
electronic phase separation between phases with different densities that lead
to nanometer scale coexisting clusters, and (ii) disorder-induced phase
separation with percolative characteristics between equal-density phases,
driven by disorder near first-order metal-insulator transitions. The coexisting
clusters in the latter can be as large as a micrometer in size. It is argued
that a large variety of experiments reviewed in detail here contain results
compatible with the theoretical predictions. It is concluded that manganites
reveal such a wide variety of interesting physical phenomena that their
detailed study is quite important for progress in the field of Correlated
Electrons.

###Electrical Transport Properties of Single Crystal Sr3Ru2O7: The Possible Existence of an Antiferromagnetic Instability at Low Temperatures|Y. Liu,R. Jin,Z. Q. Mao,K. D. Nelson,M. K. Haas,R. J. Cava###

Electrical Transport Properties of Single Crystal Sr3Ru2O7: The Possible Existence of an Antiferromagnetic Instability at Low Temperatures. We report the results of Hall coefficient R_H and magnetoresistance (MR)
measurements on single crystalline samples of Sr3Ru2O7 grown by the floating
zone method. R_H was found to be positive over the entire temperature range
studied (0.3 - 300K). Its temperature (T) dependence follows closely that of
the magnetic susceptibility, including a maximum at a characteristic
temperature T=17 K. We show that R_H can be decomposed into normal and
anomalous parts as in the case of skew scattering in heavy-fermion compounds
and ferromagnetic metals. This, together with the observation that the
longitudinal MR is greater than the transverse MR at the same magnetic field
and temperature, suggests that magnetic fluctuations dominate the electrical
transport properties in Sr3Ru2O7. We found a crossover in the sign of the MR at
T*, from positive to negative as the temperature increased, for both the
transverse and the longitudinal configurations. In addition, a non-monotonic
behavior in the field dependence of the MR was found at low temperatures. These
observations suggest that the magnetic correlations in Sr3Ru2O7 at ambient
pressure undergo a qualitative change as the temperature is lowered. Above T*,
they are dominated by ferromagnetic instability. However, below T*, the system
crosses over to a different behavior, controlled possibly by a canted
antiferromagnetic instability.

###Novel Phases in the Field Induced Spin Density Wave State in (TMTSF)_2PF_6|A. V. Kornilov,V. M. Pudalov,Y. Kitaoka,K. Ishida,T. Mito,J. S. Brooks,J. S. Qualls,J. A. A. J. Perenboom,N. Tateiwa,T. C. Kobayashi###

Novel Phases in the Field Induced Spin Density Wave State in (TMTSF)_2PF_6. Magnetoresistance measurements on the quasi one-dimensional organic conductor
(TMTSF)_2PF_6 performed in magnetic fields B up to 16T, temperatures T down to
0.12K and under pressures P up to 14kbar have revealed new phases on its P-B-T
phase diagram. We found a new boundary which subdivides the field induced spin
density wave (FISDW) phase diagram into two regions. We showed that a
low-temperature region of the FISDW diagram is characterized by a hysteresis
behavior typical for the first order transitions, as observed in a number of
studies. In contrast to the common believe, in high temperature region of the
FISDW phase diagram, the hysteresis and, hence, the first order transitions
were found to disappear. Nevertheless, sharp changes in the resistivity slope
are observed both in the low and high temperature domains indicating that the
cascade of transitions between different subphases exists over all range of the
FISDW state. We also found that the temperature dependence of the resistance
(at a constant B) changes sign at about the same boundary. We compare these
results with recent theoretical models.

###Metal-insulator transition in 2D: a role of the upper Habbard band|V. I. Kozub,and N. V. Agrinskaya###

Metal-insulator transition in 2D: a role of the upper Habbard band. To explain the main features of the metal-insulator transition (MIT) in 2D we
suggest a simple model taking into account strongly localized states in the
band tail of 2D conductivity band with a specific emphasize of a role of
doubly-occupied states (upper Hubbard band). The metallic behavior of
resistance is explained as result of activation of localized electrons to
conductance band leading to a suppression of non-linear screening of the
disorder potential. The magnetoresistance (MR) in the critical region is
related to depopulation of double occupied localized states also leading to
partial suppression of the nonlinear screening. The most informative data are
related to nearly activated temperature dependence of MR in strongly insulating
limit (which can be in particular reached from the metallic state in high
enough fields). According to our model this behavior originates due to a
lowering of a position of chemical potential in the upper Hubbard band due to
Zeeman splitting. We compare the theoretical predictions to the existing
experimental data and demonstrate that the model explains such features of the
2D MIT as scaling behavior in the critical region, saturation of MR and H/T
scaling of MR in the insulating limit. The quantitative analysis of MR in
strongly insulating limit based on the model suggested leads to the values of
g-factors being in good agreement with known values for localized states in
corresponding materials.

###Towards an understanding of CMR pyrochlore Tl2Mn2O7|C. I. Ventura,M. A. Gusmao,.###

Towards an understanding of CMR pyrochlore Tl2Mn2O7. Tl2Mn2O7 exhibits important differences with other colossal magnetoresistance
(CMR) compounds, like the Mn-perovskites, in its crystal structure and
electronic properties, indicating the possibility of different mechanisms for
CMR being present. The larger experimental background now existent, has
received diverse interpretations. We aim to contribute to the understanding of
the properties of Tl2Mn2O7 through the study of a generic model for the
compound, including Hund and superexchange couplings as well as hybridization
effects. It includes two kinds of electronic orbitals, as widely believed to be
present: one, directly related to magnetism, involving localized Mn magnetic
moments, and a narrow band strongly Hund-coupled to them. Also, more extended
electronic orbitals, related to the carriers in Tl2Mn2O7, appear and hybridize
with the narrow band. The possibility of a superexchange coupling between the
localized spins is also allowed for. This generic model allows exploration of
many of the proposals put forward by other researchers for Tl2Mn2O7. As a first
approach to the problem, we study the phase diagram and electronic structure
employing simplifications, for sets of parameters including previous
suggestions for the compound. Furthermore, we are able to exhibit similarities
with results obtained in 1997 using an intermediate valence model for Tl2Mn2O7,
in particular, for the electronic structure in the ferromagnetic phase.

###On the Role of Exchange Interaction in Magnetic Ordering and Conductivity of Manganites|M. V. Krasinkova###

On the Role of Exchange Interaction in Magnetic Ordering and Conductivity of Manganites. A model of chemical bonding between ions in manganites involving covalent
one-electron $\sigma$ bonding is suggested. The covalent one-electron $\sigma$
bonding gives rise to a strongly correlated state of electrons resulting from
the exchange interaction between electrons when they are simultaneously at
cation and anion orbitals. The manifestation of the correlatred state is the
spin and spatial ordering of the electrons resulting in the formation of a
spin- ordered electron lattice. The conductivity of manganites in this model is
the consequence of displacement of the electron lattice (or its part) from one
localization site to another and depends on the type of spin ordering of the
electrons in the electron lattice and the localization energy determined by the
energy of the one-electron $\sigma$ bond. The model also assumes a strong
polarization of an anion by cations, which facilitates the 3s2p hybridization
of the anion and transition of one of the pairs of 2p electrons from the
singlet state into the triplet state. This transition leads to formation of the
spin-polarized electron lattice (electron spins are parallel) and ferromagnetic
ordering of manganese ions. In the model, the effect of colossal
magnetoresistance is explained by a change of the conductivity mechanism on
application of an external magnetic field, i.e., transition from the
conductivity mechnism typical of an ionic crystal to the conductivity provided
by the spin-polarized electron lattice.

###Large Thermopower in Metallic Oxides: Misfit Cobaltites and Mangano-Ruthenates|Sylvie Hebert,Christine Martin,Antoine Maignan,Raymond Fresard,Jiri Hejtmanek,Bernard Raveau###

Large Thermopower in Metallic Oxides: Misfit Cobaltites and Mangano-Ruthenates. Two different kinds of metal transition oxides have been studied for their
large thermopower values. The first one corresponds to the Tl-based misfit
cobaltite which is a hole-doped metal. We demonstrate that the partial
Bi-substitution for Tl in this phase induces an increase of the room
temperature (RT) thermopower (TEP) value. Same result is obtained with the new
Pb_{1/3}SrCoO_{3+delta} misfit corresponding to the Tl complete replacement by
lead. Simultaneously, the T dependence of their resistivity exhibits a
re-entrance below 70-90K where a large negative magnetoresistance is observed.
Magnetic measurements reveal a strong interplay between spins and charges for
this class of materials. Electron-doped (n-type) perovskite manganites are a
second class of potential candidates for applications. In particular, the
Ru^{4+/5+} substitution for Mn in the CaMnO_3 semi-conductor induces a drastic
drop of the resistivity values. Metals with large RT TEP values and not too
large thermal conductivities are generated. A comparison with best known
materials, Bi_2Te_3 and NaCo_2O_4 is made.

###Multi-patch model for transport properties of cuprate superconductors|A. Perali,M. Sindel,G. Kotliar###

Multi-patch model for transport properties of cuprate superconductors. A number of normal state transport properties of cuprate superconductors are
analyzed in detail using the Boltzmann equation. The momentum dependence of the
electronic structure and the strong momentum anisotropy of the electronic
scattering are included in a phenomenological way via a multi-patch model. The
Brillouin zone and the Fermi surface are divided in regions where scattering
between the electrons is strong and the Fermi velocity is low (hot patches) and
in regions where the scattering is weak and the Fermi velocity is large (cold
patches). We present several motivations for this phenomenology starting from
various microscopic approaches. A solution of the Boltzmann equation in the
case of N patches is obtained and an expression for the distribution function
away from equilibrium is given. Within this framework, and limiting our
analysis to the two patches case, the temperature dependence of resistivity,
thermoelectric power, Hall angle, magnetoresistance and thermal Hall
conductivity are studied in a systematic way analyzing the role of the patch
geometry and the temperature dependence of the scattering rates. In the case of
Bi-based cuprates, using ARPES data for the electronic structure, and assuming
an inter-patch scattering between hot and cold states with a linear temperature
dependence, a reasonable agreement with the available experiments is obtained.

###Spin-dependent electrical transport in ion-beam sputter deposited Fe-Cr multilayers|A. K. Majumdar,A. F. Hebard,Avinash Singh,D. Temple###

Spin-dependent electrical transport in ion-beam sputter deposited Fe-Cr multilayers. The temperature dependence of the electrical resistivity and
magnetoresistance of Xe-ion beam sputtered Fe-Cr multilayers has been
investigated. The electrical resistivity between 5 and 300 K in the fully
ferromagnetic state, obtained by applying a field beyond the saturation field
(H_sat) necessary for the antiferromagnetic(AF)-ferromagnetic(FM) field-induced
transition, shows evidence of spin-disorder resistivity as in crystalline Fe
and an s-d scattering contribution (as in 3d metals and alloys). The sublattice
magnetization m(T) in these multilayers has been calculated in terms of the
planar and interlayer exchange energies. The additional spin-dependent
scattering \Delta \rho (T) = \rho(T,H=0)_AF - \rho(T,H=H_sat)_FM in the AF
state over a wide range of temperature is found to be proportional to the
sublattice magnetization, both \Delta \rho(T) and m(T) reducing along with the
antiferromagnetic fraction. At intermediate fields, the spin-dependent part of
the electrical resistivity (\rho_s (T)) fits well to the power law \rho_s (T) =
b - cT^\alpha where c is a constant and b and \alpha are functions of H. At low
fields \alpha \approx 2 and the intercept b decreases with H much the same way
as the decrease of \Delta \rho (T) with T. A phase diagram (T vs. H_sat) is
obtained for the field- induced AF to FM transition. Comparisons are made
between the present investigation and similar studies using dc magnetron
sputtered and molecular beam epitaxy (MBE) grown Fe-Cr multilayers.

###Atomic-scale images of charge ordering in a mixed-valence manganite|Ch. Renner,G. Aeppli,B-G. Kim,Yeong-Ah Soh,S. -W. Cheong###

Atomic-scale images of charge ordering in a mixed-valence manganite. Transition-metal perovskite oxides exhibit a wide range of extraordinary but
imperfectly understood phenomena. Charge, spin, orbital, and lattice degrees of
freedom all undergo order-disorder transitions in regimes not far from where
the best-known of these phenomena, namely high-temperature superconductivity of
the copper oxides, and the 'colossal' magnetoresistance of the manganese
oxides, occur. Mostly diffraction techniques, sensitive either to the spin or
the ionic core, have been used to measure the order. Unfortunately, because
they are only weakly sensitive to valence electrons and yield superposition of
signals from distinct mesoscopic phases, they cannot directly image mesoscopic
phase coexistence and charge ordering, two key features of the manganites. Here
we describe the first experiment to image charge ordering and phase separation
in real space with atomic-scale resolution in a transition metal oxide. Our
scanning tunneling microscopy (STM) data show that charge order is correlated
with structural order, as well as with whether the material is locally metallic
or insulating, thus giving an atomic-scale basis for descriptions of the
manganites as mixtures of electronically and structurally distinct phases.

###Nernst coefficient and Magnetoresistance in High-Tc Superconductors|Hiroshi Kontani###

Nernst coefficient and Magnetoresistance in High-Tc Superconductors. In hole-doped high-Tc cuprates, the Nernst coefficient (\nu) as well as the
magnetoresistance (\Delta\rho/\rho) increase drastically below the pseudo-gap
temperature, T^*. This unexpected result attracts much attention in that it
reflects the fundamental feature of the electronic state in the pseudo-gap
region, which has been a central issue on high-Tc cuprates. In this letter, we
study these transport phenomena in terms of the fluctuation-exchange
(FLEX)+T-matrix approximation. In this present theory, the d-wave
superconducting (SC) fluctuations, which are mediated by antiferromagnetic (AF)
correlations, become dominant below T^*. We focus on the role of the vertex
corrections both for the charge current and the heat one, which are
indispensable to keep the conservation laws. As a result, the mysterious
behaviors of \nu and \Delta\rho/\rho, which are the key phenomena in the
pseudo-gap region, are naturally explained as the reflection of the enhancement
of the SC fluctuation, without assuming thermally excited vortices. The present
result suggests that the pseudo-gap region in high-Tc cuprates is well
described in terms of the Fermi liquid with AF and SC fluctuations.

###Hole-doping dependence of percolative phase separation in Pr_(0.5-delta)Ca_(0.2+delta)Sr_(0.3)MnO_(3) around half doping|Dario G. Niebieskikwiat,Rodolfo D. Sanchez,Liliana Morales,Boris Maiorov###

Hole-doping dependence of percolative phase separation in Pr_(0.5-delta)Ca_(0.2+delta)Sr_(0.3)MnO_(3) around half doping. We address the problem of the percolative phase separation in polycrystalline
samples of Pr$_{0.5-\delta}$Ca$_{0.2+\delta}$Sr$_{0.3}$MnO$_3$ for $-0.04\leq
\delta \leq 0.04$ (hole doping $n$ between 0.46 and 0.54). We perform
measurements of X-ray diffraction, dc magnetization, ESR, and electrical
resistivity. These samples show at $T_C$ a paramagnetic (PM) to ferromagnetic
(FM) transition, however, we found that for $n>0.50$ there is a coexistence of
both of these phases below $T_C$. On lowering $T$ below the charge-ordering
(CO) temperature $T_{CO}$ all the samples exhibit a coexistence between the FM
metallic and CO (antiferromagnetic) phases. In the whole $T$ range the FM phase
fraction ($X$) decreases with increasing $n$. Furthermore, we show that only
for $n\leq 0.50$ the metallic fraction is above the critical percolation
threshold $X_C\simeq 15.5%$. As a consequence, these samples show very
different magnetoresistance properties. In addition, for $n\leq 0.50$ we
observe a percolative metal-insulator transition at $T_{MI}$, and for
$T_{MI}<T<T_{CO}$ the insulating-like behavior generated by the enlargement of
$X$ with increasing $T$ is well described by the percolation law $\rho
^{-1}=\sigma \sim (X-X_C)^t$, where $t$ is a critical exponent. On the basis of
the values obtained for this exponent we discuss different possible percolation
mechanisms, and suggest that a more deep understanding of geometric and
dimensionality effects is needed in phase separated manganites. We present a
complete $T$ vs $n$ phase diagram showing the magnetic and electric properties
of the studied compound around half doping.

###Theory of spin-polarized bipolar transport in magnetic p-n junctions|Jaroslav Fabian,Igor Zutic,S. Das Sarma###

Theory of spin-polarized bipolar transport in magnetic p-n junctions. The interplay between spin and charge transport in electrically and
magnetically inhomogeneous semiconductor systems is investigated theoretically.
In particular, the theory of spin-polarized bipolar transport in magnetic p-n
junctions is formulated, generalizing the classic Shockley model. The theory
assumes that in the depletion layer the nonequilibrium chemical potentials of
spin up and spin down carriers are constant and carrier recombination and spin
relaxation are inhibited. Under the general conditions of an applied bias and
externally injected (source) spin, the model formulates analytically carrier
and spin transport in magnetic p-n junctions at low bias. The evaluation of the
carrier and spin densities at the depletion layer establishes the necessary
boundary conditions for solving the diffusive transport equations in the bulk
regions separately, thus greatly simplifying the problem. The carrier and spin
density and current profiles in the bulk regions are calculated and the I-V
characteristics of the junction are obtained. It is demonstrated that spin
injection through the depletion layer of a magnetic p-n junction is not
possible unless nonequilibrium spin accumulates in the bulk regions--either by
external spin injection or by the application of a large bias. Implications of
the theory for majority spin injection across the depletion layer, minority
spin pumping and spin amplification, giant magnetoresistance, spin-voltaic
effect, biasing electrode spin injection, and magnetic drift in the bulk
regions are discussed in details, and illustrated using the example of a GaAs
based magnetic p-n junction.

###Spin diffusion and injection in semiconductor structures: Electric field effects|Z. G. Yu,M. E. Flatte###

Spin diffusion and injection in semiconductor structures: Electric field effects. In semiconductor spintronic devices, the semiconductor is usually lightly
doped and nondegenerate, and moderate electric fields can dominate the carrier
motion. We recently derived a drift-diffusion equation for spin polarization in
the semiconductors by consistently taking into account electric-field effects
and nondegenerate electron statistics and identified a high-field diffusive
regime which has no analogue in metals. Here spin injection from a ferromagnet
(FM) into a nonmagnetic semiconductor (NS) is extensively studied by applying
this spin drift-diffusion equation to several typical injection structures such
as FM/NS, FM/NS/FM, and FM/NS/NS structures. We find that in the high-field
regime spin injection from a ferromagnet into a semiconductor is enhanced by
several orders of magnitude. For injection structures with interfacial
barriers, the electric field further enhances spin injection considerably. In
FM/NS/FM structures high electric fields destroy the symmetry between the two
magnets at low fields, where both magnets are equally important for spin
injection, and spin injection becomes locally determined by the magnet from
which carriers flow into the semiconductor. The field-induced spin injection
enhancement should also be insensitive to the presence of a highly doped
nonmagnetic semiconductor (NS$^+$) at the FM interface, thus FM/NS$^+$/NS
structures should also manifest efficient spin injection at high fields.
Furthermore, high fields substantially reduce the magnetoresistance observable
in a recent experiment on spin injection from magnetic semiconductors.

###Thermal Expansion and Magnetostriction Studies of a Kondo Lattice Compound: Ceagsb2|D. T. Adroja,P. C. Riedi,J. G. M. Armitage,D. Fort###

Thermal Expansion and Magnetostriction Studies of a Kondo Lattice Compound: Ceagsb2. We have investigated a single crystal of CeAgSb2 using low field
ac-susceptibility, thermal expansion and magnetostriction measurements in the
temperature range 1.5K to 90K. The ac-susceptibility exhibits a sharp peak at
9.7K for both B//c and B perp c due to the magnetic ordering of the Ce moment.
The thermal expansion coefficient alpha, exhibits highly anisotropic behaviour
between 3K and 80K : alpha is positive for dL/L perp c, but negative for dL/L
// c. Furthermore, alpha (for dL/L) perp c (i.e. in ab-plane) exhibits a sharp
peak at TN followed by a broad maximum at 20K, while a sharp negative peak at
TN followed by a minimum at 20K has been observed for (dL/L //) the c
direction. The observed maximum and minimum in alpha(T) at 20K have been
attributed to the crystalline field effect on the J=5/2 state of the Ce3+ ion.
The magnetostriction also exhibits anisotropic behaviour with a large
magnetostriction along the c-axis. The ab-plane magnetostriction exhibits a
peak at B=3.3T at 3K, which is consistent with the observed peak in the
magnetoresistance measurements.

###Resistivity, Hall effect and Shubnikov-de Haas oscillations in CeNiSn|T. Terashima,C. Terakura,S. Uji,H. Aoki,Y. Echizen,T. Takabatake###

Resistivity, Hall effect and Shubnikov-de Haas oscillations in CeNiSn. The resistivity and Hall effect in CeNiSn are measured at temperatures down
to 35 mK and in magnetic fields up to 20 T with the current applied along the
{\it b} axis. The resistivity at zero field exhibits quadratic temperature
dependence below $\sim$0.16 K with a huge coefficient of the $T^2$ term (54
$\mu$$\Omega$cm/K$^2$). The resistivity as a function of field shows an
anomalous maximum and dip, the positions of which vary with field directions.
Shubnikov-de Haas (SdH) oscillations with a frequency {\it F} of $\sim$100 T
are observed for a wide range of field directions in the {\it ac} and {\it bc}
planes, and the quasiparticle mass is determined to be $\sim$10-20 {\it m}$_e$.
The carrier density is estimated to be $\sim10^{-3}$ electron/Ce. In a narrow
range of field directions in the {\it ac} plane, where the
magnetoresistance-dip anomaly manifests itself clearer than in other field
directions, a higher-frequency ($F=300\sim400\text{T}$) SdH oscillation is
found at high fields above the anomaly. This observation is discussed in terms
of possible field-induced changes in the electronic structure.

###On magnetoconductivity of metallic manganite phases and heterostructures|M. Dzero,L. P. Gor'kov,V. Z. Kresin###

On magnetoconductivity of metallic manganite phases and heterostructures. We use the double exchange (DE) model via degenerate orbitals and
tight-binding approximation to study the magnetoconductivity of a canted
A-phase of pseudo-cubic manganites. It is argued that the model is applicable
in a broad concentration range for manganites with the tolerance factor, t,
close to one. As for the substitutional disorder, scattering on random
Jahn-Teller distortions of MnO6 octahedra is chosen. We emphasize an intimate
correlation between the carrier concentration and resistivity value of metallic
manganites. Magnetoresistance as a function of magnetization is calculated for
a canted A-phase for both in-plane and out-of-plane current directions. A
contact between two manganite phases is considered and structure of the
transition region near the contact is discussed. Numerical calculations show
charge re-distribution near the contact and a large screening length of the
order of five inter-atomic distances. We employed our results to interpret data
obtained in recent experiments on La0.4Sr0.6MnO3/La0.55Sr0.45MnO3
superlattices. We also briefly discuss the relative importance of the
cooperative Jahn-Teller distortions, double exchange mechanism and
super-exchange interactions for the formation of the A-phase at increasing Sr
concentrations x>0.45 in LSMO to suggest that the Jahn-Teller contraction of
octahedra, c/a<1, plays a prevailing role.

###Ground state properties of ferromagnetic metal/conjugated polymer interfaces|S. J. Xie,K. H. Ahn,D. L. Smith,A. R. Bishop,A. Saxena###

Ground state properties of ferromagnetic metal/conjugated polymer interfaces. We theoretically investigate the ground state properties of ferromagnetic
metal/conjugated polymer interfaces. The work is partially motivated by recent
experiments in which injection of spin polarized electrons from ferromagnetic
contacts into thin films of conjugated polymers was reported. We use a
one-dimensional nondegenerate Su-Schrieffer-Heeger (SSH) Hamiltonian to
describe the conjugated polymer and one-dimensional tight-binding models to
describe the ferromagnetic metal. We consider both a model for a conventional
ferromagnetic metal, in which there are no explicit structural degrees of
freedom, and a model for a half-metallic ferromagnetic colossal
magnetoresistance (CMR) oxide which has explicit structural degrees of freedom.
The Fermi energy of the magnetic metallic contact is adjusted to control the
degree of electron transfer into the polymer. We investigate electron charge
and spin transfer from the ferromagnetic metal to the organic polymer, and
structural relaxation near the interface. Bipolarons are the lowest energy
charge state in the bulk polymer for the nondegenerate SSH model Hamiltonian.
As a result electrons (or holes) transferred into the bulk of the polymer form
spinless bipolarons. However, there can be spin density in the polymer
localized near the interface.

###Glass component induced hysteresis/memory effect in magnetoresistance of ferromagnetic Pr0.9Sr0.1CoO2.99|V. P. S. Awana,J. Nakamura,M. Karppinen,H. Yamauchi,S. K. Malik###

Glass component induced hysteresis/memory effect in magnetoresistance of ferromagnetic Pr0.9Sr0.1CoO2.99. Pr0.9Sr0.1CoO2.99 sample exhibits magnetoresistivity (MR) of up to 40 % at 5
K with a strong hysteresis/memory effect. Magnetisation measurements on
Pr0.9Sr0.1CoO2.99 in an applied field of 100 Oe show that, as temperature
decreases, the zero-field-cooled (ZFC) and field-cooled (FC) magnetisation
curves branch clearly at 50 K, and a cusp appears in the ZFC branch at Tcusp 20
K. Magnetisation measurements in various fields between 100 and 10,000 Oe show
that both the ZFC-FC branching temperature and, Tcusp, decrease with increasing
field. The magnetization-field isotherms at 5 and 10 K show hysteresis loops
typical of ferromagnets. No appreciable MR is seen in this compound at 50 K,
i.e. at a temperature close to ZFC-FC branching temperature. At 20 K, negative
MR of above 16% is observed without any hysteresis effect. We believe that the
appearance of a ferromagnetic component at 5 K and 10 K (i.e. at temperatures
below Tcusp) within the spin glass state of Co spins is responsible for both
large MR and the prominent hysteresis/memory effect in MR.

###Effect of Impurities and Effective Masses on Spin-Dependent Electrical Transport in Ferromagnet-Normal Metal-Ferromagnet Hybrid Junctions|Zhen-Gang Zhu,Gang Su,Biao Jin,Qing-Rong Zheng###

Effect of Impurities and Effective Masses on Spin-Dependent Electrical Transport in Ferromagnet-Normal Metal-Ferromagnet Hybrid Junctions. The effect of nonmagnetic impurities and the effective masses on the
spin-dependent transport in a ferromagnet-normal metal-ferromagnet junction is
investigated on the basis of a two-band model. Our results show that impurities
and the effective masses of electrons in two ferromagnetic electrodes have
remarkable effects on the behaviors of the conductance, namely, both affect the
oscillating amplitudes, periods, as well as the positions of the resonant peaks
of the conductance considerably. The impurity tends to suppress the amplitudes
of the conductance, and makes the spin-valve effect less obvious, but under
certain conditions the phenomenon of the so-called impurity-induced resonant
tunneling is clearly observed. The impurity and the effective mass both can
lead to nonmonotonous oscillation of the junction magnetoresistance (JMR) with
the incident energy and the thickness of the normal metal. It is also observed
that a smaller difference of the effective masses of electrons in two
ferromagnetic electrodes would give rise to a larger amplitude of the JMR.

###Theory of Manganites|Takashi Hotta,Elbio Dagotto###

Theory of Manganites. In this review, the present status of theories for manganites is discussed.
The complex phase diagrams of these materials, with a variety of
spin-charge-orbital ordering tendencies, is addressed using mean-field and
Monte Carlo simulation techniques. The stability of the charge-ordered states,
such as the CE-state at half-doping, appears to originate, in part, in the
topology of the zigzag chains present in those states. In addition, it is
argued that phase separation tendencies are notorious in realistic models for
Mn-oxides. They produce nanoscale clusters of competing phases, either through
an electronic separation tendency or through the influence of disorder on
first-order transitions. These inhomogeneities lead to a ``colossal''
magnetoresistance (CMR) effect, compatible with experiments. This brief review
is based on a more extensive work recently presented [E. Dagotto, T. Hotta, and
A. Moreo, Phys. Rep. {\bf 344}, 1 (2001)]. There, a comprehensive analysis of
the experimental literature can be found. In real manganites, the tendencies
toward inhomogeneous states are notorious in CMR regimes, in excellent
agreement with the theoretical description outlined here.

###Magnetoresistance of Highly Correlated Electron Liquid|V. R. Shaginyan###

Magnetoresistance of Highly Correlated Electron Liquid. The behavior in magnetic fields of a highly correlated electron liquid
approaching the fermion condensation quantum phase transition from the
disordered phase is considered. We show that at sufficiently high temperatures
$T\geq T^*(x)$ the effective mass starts to depend on $T$, $M^*\propto
T^{-1/2}$. This $T^{-1/2}$ dependence of the effective mass at elevated
temperatures leads to the non-Fermi liquid behavior of the resistivity,
$\rho(T)\propto T$ and at higher temperatures $\rho(T)\propto T^{3/2}$. The
application of a magnetic field $B$ restores the common $T^2$ behavior of the
resistivity. The effective mass depends on the magnetic field, $M^*(B)\propto
B^{-2/3}$, being approximately independent of the temperature at $T\leq
T^*(B)\propto B^{4/3}$. At $T\geq T^*(B)$, the $T^{-1/2}$ dependence of the
effective mass is re-established. We demonstrate that this $B-T$ phase diagram
has a strong impact on the magnetoresistance (MR) of the highly correlated
electron liquid. The MR as a function of the temperature exhibits a transition
from the negative values of MR at $T\to 0$ to the positive values at $T\propto
B^{4/3}$. Thus, at $T\geq T^*(B)$, MR as a function of the temperature
possesses a node at $T\propto B^{4/3}$.

###Dephasing of Electrons in Mesoscopic Metal Wires|F. Pierre,A. B. Gougam,A. Anthore,H. Pothier,D. Esteve,Norman O. Birge###

Dephasing of Electrons in Mesoscopic Metal Wires. We have extracted the phase coherence time $\tau_{\phi}$ of electronic
quasiparticles from the low field magnetoresistance of weakly disordered wires
made of silver, copper and gold. In samples fabricated using our purest silver
and gold sources, $\tau_{\phi}$ increases as $T^{-2/3}$ when the temperature
$T$ is reduced, as predicted by the theory of electron-electron interactions in
diffusive wires. In contrast, samples made of a silver source material of
lesser purity or of copper exhibit an apparent saturation of $\tau_{\phi}$
starting between 0.1 and 1 K down to our base temperature of 40 mK. By
implanting manganese impurities in silver wires, we show that even a minute
concentration of magnetic impurities having a small Kondo temperature can lead
to a quasi saturation of $\tau_{\phi}$ over a broad temperature range, while
the resistance increase expected from the Kondo effect remains hidden by a
large background. We also measured the conductance of Aharonov-Bohm rings
fabricated using a very pure copper source and found that the amplitude of the
$h/e$ conductance oscillations increases strongly with magnetic field. This set
of experiments suggests that the frequently observed ``saturation'' of
$\tau_{\phi}$ in weakly disordered metallic thin films can be attributed to
spin-flip scattering from extremely dilute magnetic impurities, at a level
undetectable by other means.

###Kondo-type transport through an interacting quantum dot coupled to ferromagnetic leads|Bing Dong,H. L. Cui,S. Y. Liu,X. L. Lei###

Kondo-type transport through an interacting quantum dot coupled to ferromagnetic leads. We investigate the equilibrium and out-of-equilibrium Kondo effects in a
single-level interacting quantum dot connected to two ferromagnetic leads.
Within the non-crossing approximation, we calculate the total density of states
(DOS), the linear conductance, and the nonlinear differential conductance for
both the parallel and the anti-parallel alignments of the spin polarization
orientation in the leads, followed by a brief discussion regarding the validity
of this approach. Numerical calculations show that for the anti-parallel
alignment, a single Kondo peak always appears in the equilibrium DOS, resulting
in the conventional temperature behavior in the linear conductance and the
zero-bias maximum in the differential conductance. The strength of the DOS peak
is gradually suppressed with increasing polarization, due to the fact that
formation of the Kondo-correlated state is more difficult in the presence of
higher polarization. On the contrary, for the parallel configuration the Kondo
peak in the DOS descends precipitately and splits into two peaks to form a very
steep valley between them. This splitting contributes to the appearance of a
"hump" in the temperature-dependent linear conductance and a nonzero-bias
maximum in the differential conductance. Moreover, application of a bias
voltage can split each Kondo peak into two in the nonequilibrium DOS for both
configurations. Finally we point out that the tunnel magnetoresistance could be
an effective tool to demonstrate the different Kondo effects in different spin
configurations found here.

###Disorder Effect on Spin Excitation in Double Exchange Systems|Yukitoshi Motome,Nobuo Furukawa###

Disorder Effect on Spin Excitation in Double Exchange Systems. Spin excitation spectrum is studied in the double exchange model in the
presence of disorder. Spin wave approximation is applied in the lowest order of
1/S expansion. The disorder causes anomalies in the spin excitation spectrum
such as broadening, branching, anticrossing with gap opening. The origin of the
anomalies is the Friedel oscillation, in which the perfectly polarized
electrons form the charge density wave to screen the disorder effect. Near the
zone center $q = 0$, the linewidth has a $q$ linear component while the
excitation energy scales to $q^2$, which indicates that the magnon excitation
is incoherent. As $q$ increases, there appears a crossover from this incoherent
behavior to the marginally coherent one in which both the linewidth and the
excitation energy are proportional to $q^2$. The results are compared with
experimental results in colossal magnetoresistance manganese oxides.
Quantitative comparison of the linewidth suggests that spatially-correlated or
mesoscopic-scale disorder is more relevant in real compounds than local or
atomic-scale disorder. Comparison with other theoretical proposals is also
discussed. Experimental tests are proposed for the relevance of disorder.

###Magnetic anisotropy and magnetoresistance of sputtered [(FeTaN)/(TaN)](n) multilayers|H. B. Nie,S. Y. Xu,J. Li,C. K. Ong,J. P. Wang###

Magnetic anisotropy and magnetoresistance of sputtered [(FeTaN)/(TaN)](n) multilayers. We studied the in-plane magnetic anisotropy of rf (radio frequency) sputtered
[(FeTaN)/(TaN)](n) multilayers synthesized on Si substrates. In the multilayers
where n=5, the FeTaN thickness is fixed at 30 nm and the thickness of TaN,
t(TaN), is varied from 0 to 6.0 nm, we observed a clear trend that, with
increasing t(TaN), the values of coercivity, grain size, and amplitude of
maximum magnetoresistance (MR) of the samples all decrease first and then
increase after reaching a minimum when t(TaN) is around 2.0-4.0 nm. This trend
is also associated with an evolution of in-plane magnetic anisotropy, where the
multilayers change from uniaxial anisotropy to biaxial at t(TaN) around 4.0 nm
and above. We attribute the phenomena to the interlayer coupling effect of
FeTaN films as a function of the coupling layer (TaN) thickness, rather than to
the thickness dependence observed in single-layered FeTaN films, where the
direction of easy axis switches 90degrees when the film is thicker than 300 nm.
The in-plane anisotropy of the [(FeTaN)/(TaN)](n) multilayers also shows signs
of oscillation when the number of coupling layers varies. The MR effects
observed are mainly due to anisotropy MR (AMR), while the grain size and
exchange coupling may also contribute to the change of maximum MR ratios in the
multilayers with changing t(TaN).

###First-order transition in the itinerant ferromagnet CoS$_{1.9}$Se$_{0.1}$|T. J. Sato,J. W. Lynn,Y. S. Hor,S. -W. Cheong###

First-order transition in the itinerant ferromagnet CoS$_{1.9}$Se$_{0.1}$. Undoped CoS$_2$ is an isotropic itinerant ferromagnet with a continuous or
nearly continuous phase transition at $T_{\rm C} = 122$ K. In the doped
CoS$_{1.9}$Se$_{0.1}$ system, the Curie temperature is lowered to $T_{\rm C} =
90$ K, and the transition becomes clearly first order in nature. In particular
we find a discontinuous evolution of the spin dynamics as well as strong time
relaxation in the ferromagnetic Bragg intensity and small angle neutron
scattering in vicinity of the ferromagnetic transition. In the ordered state
the long-wavelength spin excitations were found to be conventional
ferromagnetic spin-waves with negligible spin-wave gap ($ < 0.04$ meV),
indicating that this system is also an excellent isotropic (soft) ferromagnet.
In a wide temperature range up to $0.9T_{\rm C}$, the spin-wave stiffness
$D(T)$ follows the prediction of the two-magnon interaction theory, $D(T) =
D(0)(1 - AT^{5/2})$, with $D(0) = 131.7 \pm 2.8$ meV-\AA$^{2}$. The stiffness,
however, does not collapse as $T \to T_{\rm C}$ from below. Instead a
quasielastic central peak abruptly develops in the excitation spectrum, quite
similar to results found in the colossal magnetoresistance oxides such as
(La-Ca)MnO$_3$.

###Quantum rate equations for electron transport through an interacting system in the sequential tunneling regime|Bing Dong,H. L. Cui,X. L. Lei###

Quantum rate equations for electron transport through an interacting system in the sequential tunneling regime. We present a set of modified quantum rate equations, with the help of the
nonequilibrium Green's function and slave-particle techniques along with the
correct quantization, for description of the quantum transport through an
interacting mesoscopic region connected with two leads, in the sequential
tunneling regime. The assumption that only leading order of $|V|^2$ ($V$ is the
tunneling coupling between the interacting central region and the leads) has
been taken into account in deriving these equations implies that the quantum
rate equations are only valid in the case of weak coupling between the central
region and the leads. For demonstrations, we consider two special cases in the
central region, a single interacting quantum dot (SQD) with weak spin-flip
scattering and a weakly coupled double quantum dots (CQD), as examples. In the
limit of zero temperature and large bias voltage, the resulting equations are
identical to the previous results derived from the many-body Schr\"odinger
equation. The numerical simulations reveal: 1) the dependence of the spin-flip
scattering on the temperature and bias voltage in the SQD; and 2) the possible
negative differential conductance and negative tunnel magnetoresistance in the
CQD, depending on the hopping between the two quantum dots.

###Theory of Manganites Exhibiting Colossal Magnetoresistance|T. V. Ramakrishnan,H. R. Krishnamurthy,S. R. Hassan,G. Venketeswara Pai###

Theory of Manganites Exhibiting Colossal Magnetoresistance. The electronic properties of many transition metal oxide systems require new
ideas concerning the behaviour of electrons in solids for their explanation. A
recent example, subsequent to that of cuprate superconductors, is of rare earth
manganites doped with alkaline earths, namely $Re_{1-x}A_x MnO_3$, which
exhibit colossal magnetoresistance, metal insulator transition and many other
poorly understood phenomena. Here we show that the strong Jahn Teller coupling
between the twofold degenerate ($d_{x^2 -y^2}$ and $d_{3z^2 -r^2}$) $e_g$
orbitals of $Mn$ and lattice modes of vibration (of the oxygen octahedra
surrounding the $Mn$ ions) dynamically reorganizes the former into a set of
states (which we label $\ell$) which are localized with large local lattice
distortion and exponentially small intersite overlap, and another set (labelled
$b$) which form a broad band. This hitherto unsuspected but microscopically
inevitable $coexistence$ of radically different $\ell$ and $b$ states, and
their relative energies and occupation as influenced by doping $x$, temperature
$T$, local Coulomb repulsion $U$ etc., underlies the unique effects seen in
manganites. We present results from strong correlation calculations using the
dynamical mean-field theory which accord with a variety of observations in the
orbital liquid regime (say, for $0.2\stackrel{<}\sim x \stackrel{<}\sim
0.5$).We outline extensions to include intersite $\ell$ coherence and spatial
correlations/long range order.

###Ultrafast collective dynamics of short-range charge/orbital ordering fluctuations in colossal magnetoresistive oxides|Y. H. Ren,Y. F. Hu,Qi Li,C. S. Hong,N. H. Hur,G. L\U{fc}pke###

Ultrafast collective dynamics of short-range charge/orbital ordering fluctuations in colossal magnetoresistive oxides. The "colossal magnetoresistive" (CMR) manganites are highly correlated
systems with a strong coupling between spin, charge, orbital, and lattice
degrees of freedom, which leads to complex phase diagrams and to the
coexistence of various forms of ordering. For example, nanoscale charge/orbital
ordering (CO) fluctuations appear to cooperate with Jahn-Teller (JT)
distortions of the MnO$_{6} octahedra in CMR manganites and compete with the
electron itinerancy favored by double exchange. However, access to the ordered
dynamical state has been challenging, mostly due to intrinsic experimental
difficulties in measuring fast short-range correlations. Here, we report on a
strongly damped low-energy collective mode originating from fast short-range CO
fluctuations in La}$_{0.67}Ca$_{0.33}Mn{O}$_{3}(LCMO) single crystal and thin
films. We elucidate the collective mode in terms of its dispersion relation and
dependence on average A-site ion radius, r$_{A}, and hole-doping concentration.
Our results show for the first time that dynamical short-range CO correlations
in CMR manganites can be detected with high momentum resolution by coherent
ultrafast optical techniques.

###Universal Behavior of Heavy-Fermion Metals Near a Quantum Critical Point|V. R. Shaginyan###

Universal Behavior of Heavy-Fermion Metals Near a Quantum Critical Point. The behavior of the electronic system of heavy fermion metals is considered.
We show that there exist at least two main types of the behavior when the
system is nearby a quantum critical point which can be identified as the
fermion condensation quantum phase transition (FCQPT). We show that the first
type is represented by the behavior of a highly correlated Fermi-liquid, while
the second type is depicted by the behavior of a strongly correlated
Fermi-liquid. If the system approaches FCQPT from the disordered phase, it can
be viewed as a highly correlated Fermi-liquid which at low temperatures
exhibits the behavior of Landau Fermi liquid (LFL). At higher temperatures $T$,
it demonstrates the non-Fermi liquid (NFL) behavior which can be converted into
the LFL behavior by the application of magnetic fields $B$. If the system has
undergone FCQPT, it can be considered as a strongly correlated Fermi-liquid
which demonstrates the NFL behavior even at low temperatures. It can be turned
into LFL by applying magnetic fields $B$. We show that the effective mass $M^*$
diverges at the very point that the N\'eel temperature goes to zero. The $B-T$
phase diagrams of both liquids are studied. We demonstrate that these $B-T$
phase diagrams have a strong impact on the main properties of heavy-fermion
metals such as the magnetoresistance, resistivity, specific heat,
magnetization, volume thermal expansion, etc.

###High magnetic field induced charge density wave states in a quasi-one dimensional organic conductor|D. Graf,E. S. Choi,J. S. Brooks,Rui T. Henriques,M. Almeida,M. Matos###

High magnetic field induced charge density wave states in a quasi-one dimensional organic conductor. We have measured the high field magnetoresistence and magnetization of
quasi-one- dimensional (Q1D) organic conductor (Per)2Pt(mnt)2 (where Per =
perylene and mnt = maleonitriledithiolate), which has a charge density wave
(CDW) ground state at zero magnetic field below 8 K. We find that the CDW
ground state is suppressed with moderate magnetic fields of order 20 T, as
expected from a mean field theory treatment of Pauli effects[W. Dieterich and
P. Fulde, Z. Physik 265, 239 - 243 (1973)]. At higher magnetic fields, a new,
density wave state with sub-phases is observed in the range 20 to 50 T, which
is reminiscent of the cascade of field induced, quantized, spin density wave
phases (FISDW) observed in the Bechgaard salts. The new density wave state,
which we tenatively identify as a field induced charge density wave state
(FICDW), is re-entrant to a low resistance state at even higher fields, of
order 50 T and above. Unlike the FISDW ground state, the FICDW state is only
weakly orbital, and appears for all directions of magnetic field. Our findings
are substantiated by electrical resistivity, magnetization, thermoelectric, and
Hall measurements. We discuss our results in light of theoretical work
involving magnetic field dependent Q1D CDW ground states in high magnetic
fields [D. Zanchi, A. Bjelis, and G. Montambaux, Phys. Rev. B 53, (1996)1240;
A. Lebed, JETP Lett. 78,138(2003)].

###New Electronic Phase Transitions in α-(BEDT-TTF)2KHg(SCN)4|M. V. Kartsovnik,D. Andres,W. Biberacher,P. D. Grigoriev,E. A. Schuberth,H. Mueller###

New Electronic Phase Transitions in α-(BEDT-TTF)2KHg(SCN)4. \alpha-(BEDT-TTF)2KHg(SCN)4 is considered to be in the charge-density-wave
(CDW) state below 8 K. We present new magnetoresistance data suggesting that
the material undergoes a series of field-induced CDW (FICDW) transitions at
pressures slightly exceeding the critical pressure Pc at which the zero-field
CDW state is destroyed. Further, we argue that a novel kind of FICDW
transitions, entirely determined by a superposition of the strong Pauli and
quantizing orbital effects of magnetic field on the CDW wavevector, arises when
the field is strongly tilted towards the conducting layers. These new
transitions can take place even in the case of a relatively well nested Fermi
surface. Finally we report on the superconducting (SC) state and its
coexistence with the CDW in the title compound under quasi-hydrostatic
pressure. Below Pc the material is most likely a heterogeneous SC/CDW mixture,
with the SC phase persisting down to ambient pressure. The SC onset temperature
appears to drastically increase upon entering the SC/CDW coexistence region.

###Magnetic and transport anomalies in the compounds, RCuAs2 (R= Pr, Nd, Sm, Gd, Tb, Dy, Ho, and Er)|Kausik Sengupta,S. Rayaprol,E. V. Sampathkumaran,Th. Doert,J. P. F. Jemetio###

Magnetic and transport anomalies in the compounds, RCuAs2 (R= Pr, Nd, Sm, Gd, Tb, Dy, Ho, and Er). The results of dc magnetization, heat capacity, electrical resistivity (rho)
and magnetoresistance measurements are reported in detail for the compounds,
RCuAs2 for R= Pr, Nd, Sm, Gd, Tb, Dy, Ho, and Er, crystallizing in HfCuSi2-type
tetragonal structure, with the aim of bringing out anomalies among 'normal'
(that is, other than Ce and Yb) rare-earths. The results establish that all
these compounds order antiferromagnetically at low temperatures with deviations
from de Gennes scaling. Isothermal magnetization (M) data below respective Neel
temperatures (TN) reveal the existence of field-induced metamagnetic-like
transitions for most of the compounds (except R= Sm and Gd), whereas in Sm and
Gd compounds M varies essentially linearly with magnetic field. With respect to
the rho behavior, there appears to be a subtle difference in the temperature
dependence beyond 50 K between Sm on the one hand and the rest on the other. In
addition, the unexpected rho(T) minimum reported recently for R = Sm, Gd, Tb
and Dy in the paramagnetic state (around 20 to 30 K) is essentially absent for
R = Ho and Er. The results overall reveal that the normal rare-earths in this
series present an interesting situation in magnetism, warranting a new
theoretical approach to describe the transport behavior in the paramagnetic
state particularly in the vicinity of TN.

###Insulator to Metal Transition Induced by Disorder in a Model for Manganites|C. Sen,G. Alvarez,E. Dagotto###

Insulator to Metal Transition Induced by Disorder in a Model for Manganites. The physics of manganites appears to be dominated by phase competition among
ferromagnetic metallic and charge-ordered antiferromagnetic insulating states.
Previous investigations (Burgy {\it et al.}, Phys. Rev. Lett. {\bf 87}, 277202
(2001)) have shown that quenched disorder is important to smear the first-order
transition between those competing states, and induce nanoscale inhomogeneities
that produce the colossal magnetoresistance effect. Recent studies (Motome {\it
et al.} Phys. Rev. Lett. {\bf 91}, 167204 (2003)) have provided further
evidence that disorder is important in the manganite context, unveiling an
unexpected insulator-to-metal transition triggered by disorder in a one-orbital
model with cooperative phonons. In this paper, a qualitative explanation for
this effect is presented. It is argued that the transition occurs for disorder
in the form of local random energies. Acting over an insulating states made out
of a checkerboard arrangement of charge, with ``effective'' site energies
positive and negative, this form of disorder can produce lattice sites with an
effective energy near zero, favorable for the transport of charge. This
explanation is based on Monte Carlo simulations and the study of simplified toy
models, measuring the density-of-states, cluster conductances using the
Landauer formalism, and other observables. The applicability of these ideas to
real manganites is discussed.

###Observation of ferromagnetism above 900 K in Cr-GaN and Cr-AlN|H. X. Liu,Stephen Y. Wu,R. K. Singh,Lin Gu,David J. Smith,N. R. Dilley,L. Montes,M. B. Simmonds,N. Newman###

Observation of ferromagnetism above 900 K in Cr-GaN and Cr-AlN. We report the observation of ferromagnetism at over 900K in Cr-GaN and Cr-AlN
thin films. The saturation magnetization moments in our best films of Cr-GaN
and Cr-AlN at low temperatures are 0.42 and 0.6 u_B/Cr atom, respectively,
indicating that 14% and 20%, of the Cr atoms, respectively, are magnetically
active. While Cr-AlN is highly resistive, Cr-GaN exhibits thermally activated
conduction that follows the exponential law expected for variable range hopping
between localized states. Hall measurements on a Cr-GaN sample indicate a
mobility of 0.06 cm^2/V.s, which falls in the range characteristic of hopping
conduction, and a free carrier density (1.4E20/cm^3), which is similar in
magnitude to the measured magnetically-active Cr concentration (4.9E19/cm^3). A
large negative magnetoresistance is attributed to scattering from loose spins
associated with non-ferromagnetic impurities. The results indicate that
ferromagnetism in Cr-GaN and Cr-AlN can be attributed to the double exchange
mechanism as a result of hopping between near-midgap substitutional Cr impurity
bands.

###Inverse flux quantum periodicity of magnetoresistance oscillations in two-dimensional short-period surface superlattices|X. F. Wang,P. Vasilopoulos,F. M. Peeters###

Inverse flux quantum periodicity of magnetoresistance oscillations in two-dimensional short-period surface superlattices. Transport properties of the two-dimensional electron gas (2DEG) are
considered in the presence of a perpendicular magnetic field $B$ and of a {\it
weak} two-dimensional (2D) periodic potential modulation in the 2DEG plane. The
symmetry of the latter is rectangular or hexagonal. The well-known solution of
the corresponding tight-binding equation shows that each Landau level splits
into several subbands when a rational number of flux quanta $h/e$ pierces the
unit cell and that the corresponding gaps are exponentially small. Assuming the
latter are closed due to disorder gives analytical wave functions and
simplifies considerably the evaluation of the magnetoresistivity tensor
$\rho_{\mu\nu}$. The relative phase of the oscillations in $\rho_{xx}$ and
$\rho_{yy}$ depends on the modulation periods involved. For a 2D modulation
with a {\bf short} period $\leq 100$ nm, in addition to the Weiss oscillations
the collisional contribution to the conductivity and consequently the tensor
$\rho_{\mu\nu}$ show {\it prominent peaks when one flux quantum $h/e$ passes
through an integral number of unit cells} in good agreement with recent
experiments. For periods $300- 400$ nm long used in early experiments, these
peaks occur at fields 10-25 times smaller than those of the Weiss oscillations
and are not resolved.

###The transport, ultrasound, and structural properties for the charge ordered Pr1-xCaxMnO3 (0.5<=x<=0.875) manganites|R. K. Zheng,G. Li,Y. Yang,A. N. Tang,W. Wang,T. Qian,X. G. Li###

The transport, ultrasound, and structural properties for the charge ordered Pr1-xCaxMnO3 (0.5<=x<=0.875) manganites. The effects of the cooperative Jahn-Teller effect on the crystal structure
and the stability of the charge ordered (CO) state were studied by measurements
of powder X-ray diffraction, resistivity, and ultrasound for Pr1-xCaxMnO3
(0.5<=x<=0.875). Powder X-ray diffraction revealed a change of the crystal
structure from tetragonally compressed to tetragonally elongated orthorhombic
between x=0.75 and x=0.8 in the CO state, resulting from the crossover of the
cooperative Jahn-Teller vibration mode from Q2 to Q3. The relative stiffening
of the ultrasound (DeltaV/V) reflecting the magnitude of the cooperative
Jahn-Teller lattice distortion in the CO state increases with increasing x from
0.5 to 0.625, reaching the largest and being almost x-independence for
0.625<x<0.8, and drops steeply with further increase of x. Coincident with the
variation of the DeltaV/V with x, the stability of the CO state reflected by
the magnetoresistance effect increases with increasing x from 0.5 to 0.625,
reaching the most stable for 0.625<x<0.825, and becomes unstable with further
increase of x. These features demonstrate that the cooperative Jahn-Teller
lattice distortion is one of the key ingredients in understanding the essential
physics of the CO state in manganites.

###Possible Competition between superconductivity and magnetism in RuSr2Gd1.5Ce0.5Cu2O10-d (Ru-1222) Rutheno-cuprate compounds|V. P. S. Awana,M. A. Ansari,Anurag Gupta,R. B. Saxena,H. Kishan,Devendra Buddhikot,S. K. Malik###

Possible Competition between superconductivity and magnetism in RuSr2Gd1.5Ce0.5Cu2O10-d (Ru-1222) Rutheno-cuprate compounds. The RuSr2Gd1.5Ce0.5Cu2O10-d (Ru-1222) compounds, with varying oxygen content,
crystallize in a tetragonal crystal structure (space group I4/mmm).
  Resistance (R) versus temperature (T) measurements show that the air-annealed
samples exhibit superconductivity with superconducting transition temperature
(Tc) onset at around 32 K and R=0 at 3.5 K. On the other hand, the N2-annealed
sample is semiconducting down to 2 K. Magneto-transport measurements on
air-annealed sample in applied magnetic fields of 3 and 6 Tesla show a decrease
in both Tc onset and TR=0. Magnetoresistance of up to 20% is observed in
N2-annealed sample at 2 K and 3 T applied field. The DC magnetization data (M
vs. T) reveal magnetic transitions (Tmag.) at 100 K and 106 K, respectively,
for both air- and N2-annealed samples. Ferromagnetic components in the
magnetization are observed for both samples at 5K and 20 K. The superconducting
transition temperature (Tc) seems to compete with the magnetic transition
temperature (Tmag.). Our results suggest that the magnetic ordering temperature
(Tmag.) of Ru moments in RuO6 octahedra may have direct influence/connection
with the appearance of superconductivity in Cu-O2 planes of Ru-1222 compounds.
Key words: Ruthenocuprates, Superconductivity and Magnetism, Magneto transport
and Magneto resistance. PACS: 74.25. Ha, 74.72. Jt, 75.25. +z, 75.30. Cr.

###Non-collinear magnetic structures: a possible cause for current induced switching|P. Weinberger,A. Vernes,B. L. Gyorffy,L. Szunyogh###

Non-collinear magnetic structures: a possible cause for current induced switching. Current induced switching in Co/Cu/Co trilayers is described in terms of
ab-initio determined magnetic twisting energies and corresponding sheet
resistances. In viewing the twisting energy as an energy flux the
characteristic time thereof is evaluated by means of the
Landau-Lifshitz-Gilbert equation using ab-initio parameters. The obtained
switching times are in very good agreement with available experimental data. In
terms of the calculated currents, scalar quantities since a classical Ohm's law
is applied, critical currents needed to switch magnetic configurations from
parallel to antiparallel and vice versa can unambiguously be defined. It is
found that the magnetoresistance viewed as a function of the current is
essentially determined by the twisting energy as a function of the relative
angle between the orientations of the magnetization in the magnetic slabs,
which in turn can also explain in particular cases the fact that after having
switched off the current the system remains in the switched magnetic
configuration. For all ab-initio type calculations the fully relativistic
Screened Korringa-Kohn-Rostoker method and the corresponding Kubo-Greenwood
equation in the context of density functional theory are applied.

###Orbital and spin correlations in Ca$_{2-x}$Sr$_x$RuO$_4$: A mean field study|Manfred Sigrist,Matthias Troyer###

Orbital and spin correlations in Ca$_{2-x}$Sr$_x$RuO$_4$: A mean field study. The alloy Ca$_{2-x}$Sr$_x$RuO$_4$ exhibits a complex phase diagram with
peculiar magnetic metallic phases. In this paper some aspects of this alloy are
discussed based on a mean field theory for an effective Kugel-Khomskii model of
localized orbital and spin degrees of freedom. This model results from an
orbital selective Mott transition which in the three-band system localized two
orbitals while leaving the third one itinerant. Special attention is given to
the region around a structure quantum phase transition at $ x \approx 0.5 $
where the crystal lattice changes from tetragonal to orthorhombic symmetry
while leaving the system metallic. This transition yields, a change from
ferromagnetic to antiferromagnetic spin correlations. The complete mean field
phase diagram for this transition is given including orbital and spin order.
The anisotropy of spin susceptibility, a consequence of spin-orbit coupling and
orbital correlation, is a tell-tale sign of one of these phases. In the
predominantly antiferromagnetic phase we describe a metamagnetic transition in
a magnetic field and show that coupling of the itinerant band to the localized
degrees of freedom yields an anomalous longitudinal magnetoresistance
transition. Both phenomena are connected with the evolution of the
ferromagnetic and antiferromagnetic domains in the external magnetic field and
agree qualitatively with the experimental findings.

###Enhancement of TC and reentrant spin-glass transition in La0.86Ca0.14Mn1-yCryO3 (y = 0, 0.1 and 0.2)|R. Suryanarayanan,T. Sudyoadsuk,T. Winotai###

Enhancement of TC and reentrant spin-glass transition in La0.86Ca0.14Mn1-yCryO3 (y = 0, 0.1 and 0.2). We report on the structural, frequency dependent ac susceptibility, dc
magnetization and magnetoresistance (MR) measurements on polycrystalline
samples of La0.86Ca0.14Mn1-yCryO3(y = 0, 0.1 and 0.2) prepared by sol-gel
technique. For y = 0, a paramagnetic to ferromagnetic transition was observed
at TC = 185 K. For y = 0.1, the value of TC = 200 K, an increase of 15 K and
for y = 0.2, the TC = 195 K, an increase of 10 K. The imaginary part of the ac
susceptibility of all the three samples shows a secondary transition at Tf <
TC. For y = 0, there is no definite law to account for the frequency dependence
of Tf and is attributed to a transition arising out of a canted structure.
However, in the case of y = 0.1 and 0.2, the frequency dependence indicate the
presence of a reentrant spin glass transition at Tf. Though all the three
samples show a semi-conducting behavior between 300 and 5 K, a negative MR was
observed corresponding to TC and Tf. The value of MR decreased for the Cr
substituted samples.

###Application of Kondo-lattice theory to Mott-Hubbard metal-insulator crossover in disordered cuprate-oxide superconductors|Fusayoshi J. Ohkawa###

Application of Kondo-lattice theory to Mott-Hubbard metal-insulator crossover in disordered cuprate-oxide superconductors. A theory of Kondo lattices is applied to the crossover between local-moment
magnetism and itinerant-electron magnetism in the t-J model on a quasi-two
dimensional lattice. The Kondo temperature T_K is defined as a characteristic
temperature or energy scale of local quantum spin fluctuations. Magnetism with
T_N >> T_K, where T_N is the N\eel temperature, is characterized as
local-moment one, while magnetism with T_N << T_K is characterized as
itinerant-electron one. The Kondo temperature, which also gives a measure of
the strength of the quenching of magnetic moments, is renormalized by the Fock
term of the superexchange interaction. Because the renormalization depends on
life-time widths \gamma of quasiparticles in such a way that T_K is higher for
smaller \gamma, T_N can be controlled by disorder. The asymmetry of T_N between
electron-doped and hole-doped cuprates must mainly arise from that of disorder;
an almost symmetric behavior of T_N must be restored if we can prepare
hole-doped and electron-doped cuprates with similar degree of disorder to each
other. Because effective disorder is enhanced by magnetic fields in Kondo
lattices, antiferromagnetic ordering must be induced by magnetic fields in
cuprates that exhibit large magnetoresistance.

###Time-Dependent Spintronic Transport and Current-Induced Spin Transfer Torque in Magnetic Tunnel Junctions|Zhen-Gang Zhu,Gang Su,Qing-Rong Zheng,Biao Jin###

Time-Dependent Spintronic Transport and Current-Induced Spin Transfer Torque in Magnetic Tunnel Junctions. The responses of the electrical current and the current-induced spin transfer
torque (CISTT) to an ac bias in addition to a dc bias in a magnetic tunnel
junction are investigated by means of the time-dependent nonquilibrium Green
function technique. The time-averaged current (time-averaged CISTT) is
formulated in the form of a summation of dc current (dc CISTT) multiplied by
products of Bessel functions with the energy levels shifted by $m\hbar \omega
_{0}$. The tunneling current can be viewed as to happen between the photonic
sidebands of the two ferromagnets. The electrons can pass through the barrier
easily under high frequencies but difficultly under low frequencies. The tunnel
magnetoresistance almost does not vary with an ac field. It is found that the
spin transfer torque, still being proportional to the electrical current under
an ac bias, can be changed by varying frequency. Low frequencies could yield a
rapid decrease of the spin transfer torque, while a large ac signal leads to
both decrease of the electrical current and the spin torque. If only an ac bias
is present, the spin transfer torque is sharply enhanced at the particular
amplitude and frequency of the ac bias. A nearly linear relation between such
an amplitude and frequency is observed.

###Investigation of the Spin Density Wave in NaxCoO2|J. Wooldridge,D. McK Paul,G. Balakrishnan,M. R. Lees###

Investigation of the Spin Density Wave in NaxCoO2. Magnetic susceptibility, transport and heat capacity measurements of single
crystal NaxCoO2 (x=0.71) are reported. A transition to a spin density wave
(SDW) state at Tmag = 22 K is observable in all measurements, except chi(ac)
data in which a cusp is observed at 4 K and attributed to a low temperature
glassy phase. M(H) loops are hysteretic below 15 K. Both the SDW transition and
low temperature hysteresis are only visible along the c-axis. The system also
exhibits a substantial (~40%) positive magnetoresistance below this
temperature. Calculations of the electronic heat capacity gamma above and below
Tmag and the size of the jump in C indicate that the onset of the SDW brings
about the opening of gap and the removal of part of the Fermi surface. Reduced
in-plane electron-electron scattering counteracts the loss of carriers below
the transition and as a result we see a net reduction in resistivity below
Tmag. Sodium ordering transitions at higher temperatures are observable as
peaks in the heat capacity with a corresponding increase in resistivity.

###A Theoretical Study on Spin-Dependent Transport of "Ferromagnet/Carbon Nanotube Encapsulating Magnetic Atoms/Ferromagnet" Junctions with 4-Valued Conductances|Satoshi Kokado,Kikuo Harigaya###

A Theoretical Study on Spin-Dependent Transport of "Ferromagnet/Carbon Nanotube Encapsulating Magnetic Atoms/Ferromagnet" Junctions with 4-Valued Conductances. As a novel function of ferromagnet (FM)/spacer/FM junctions, we theoretically
investigate multiple-valued (or multi-level) cell property, which is in
principle realized by sensing conductances of four states recorded with
magnetization configurations of two FMs; (up,up), (up,down), (down,up),
(down,down). In order to sense all the states, 4-valued conductances
corresponding to the respective states are necessary. We previously proposed
that 4-valued conductances are obtained in FM1/spin-polarized spacer (SPS)/FM2
junctions, where FM1 and FM2 have different spin polarizations, and the spacer
depends on spin [J. Phys.: Condens. Matter 15, 8797 (2003)]. In this paper, an
ideal SPS is considered as a single-wall armchair carbon nanotube encapsulating
magnetic atoms, where the nanotube shows on-resonance or off-resonance at the
Fermi level according to its length. The magnitude of the obtained 4-valued
conductances has an opposite order between the on-resonant nanotube and the
off-resonant one, and this property can be understood by considering electronic
states of the nanotube. Also, the magnetoresistance ratio between (up,up) and
(down,down) can be larger than the conventional one between parallel and
anti-parallel configurations.

###Rounding of a first-order magnetic phase transition in Ga doped La0.67Ca0.33MnO3|S. Roessler,U. K. Roessler,K. Nenkov,D. Eckert,S. M. Yusuf,K. Dorr,K. -H. Muller###

Rounding of a first-order magnetic phase transition in Ga doped La0.67Ca0.33MnO3. The effect of disorder on the critical properties of the ferromagnetic phase
transition in colossal magnetoresistive manganite La0.67Ca0.33MnO3 has been
studied by substituting Ga for Mn. It is found that, upon 10% Ga substitution,
the peak in the specific heat at the Curie point T_C changes drastically and
appears as a small anomaly. Static magnetization data analyzed in the
asymptotic critical region using modified Arrott plots and the Kouvel-Fisher
method give values for the critical exponents beta=0.387(6), gamma=1.362(2),
and delta=4.60(3). The results show that the first-order transition in
La0.67Ca0.33MnO3 becomes continuous by Ga substitution. The critical properties
of the rounded transition in La0.67Ca0.33Mn0.9Ga0.1O3 suggest that the magnetic
subsystem in this mixed-valent perovskite is close to that of a conventional
isotropic ferromagnet belonging to the Heisenberg universality class with
short-range interactions. It is concluded that the first-order magnetic
transition in pure La0.67Ca0.33MnO3 is induced by fluctuations from a competing
mode, which couples to the magnetic subsystem.

###Coexisting charge modulation and ferromagnetism produces long period phases in manganites: new example of electronic soft matter|G. C. Milward,M. J. Calderon,P. B. Littlewood###

Coexisting charge modulation and ferromagnetism produces long period phases in manganites: new example of electronic soft matter. The phenomenon of colossal magnetoresistance in manganites is generally
agreed to be a result of competition between crystal phases with different
electronic, magnetic, and structural order; a competition which can be strong
enough to cause phase separation between metallic ferromagnet and insulating
charge modulated states. Nevertheless, closer inspection of phase diagrams in
many manganites reveals complex phases where the two order parameters of
magnetism and charge modulation unexpectedly coexist. Here we show that such
experiments can be naturally explained within a phenomenological
Ginzburg-Landau theory. In contrast to models where phase separation originates
from disorder or as a strain induced kinetic phenomenon, we argue that magnetic
and charge modulation coexist in new thermodynamic phases. This leads to a rich
diagram of equilibrium phases, qualitatively similar to those seen in
experiment. The success of this model argues for a fundamental reinterpretation
of the nature of charge modulation in these materials from a localised to a
more extended "charge density wave" picture. The same symmetry considerations
that favour textured coexistance of charge and magnetic order may apply to many
electronic systems with competing phases. The resulting "Electronically soft"
phases of matter with incommensurate, inhomogeneous and mixed order may be
general phenomena in correlated systems.

###Low temperature synthesis, magnetic and magnetotransport properties of (La1-xLux)0.67Ca0.33MnO3 (0 < x < 0.12) system|D. Das,M. R. Raj,D. Bahadur,C. M. Srivastava,A. K. Nigam,S. K. Malik###

Low temperature synthesis, magnetic and magnetotransport properties of (La1-xLux)0.67Ca0.33MnO3 (0 < x < 0.12) system. We have been able to synthesize Lu+3 substituted La0.67Ca0.33MnO3 (LCMO) by
an auto-combustion method. Synthesis of this compound is not successful by
conventional ceramic or other chemical methods. Magnetic and electrical
transport properties of the Lu substituted LCMO [(La1-xLux)0.67Ca0.33MnO3 (0 <
x < 0.12)] system have been investigated and compared with those of the Y+3,
Pr+3, Dy+3 and Tb+3 substituted LCMO systems. All the compounds show a
ferromagnetic metal to paramagnetic insulator transition at TC. The tolerance
factor reduces from 0.917 for x = 0 to 0.909 for x = 0.12 and for this range
all are ferromagnetic metals indicating the dominance of the coupling between
spins due to double exchange over the antiferromagnetic superexchange
interaction. The transition temperatures and magnetization decrease as the Lu
concentration increases. This is satisfactorily accounted for on the basis of
transition from ferromagnetic at x = 0 to canted spin order for x > 0. All the
samples show higher magnitude of MR compared to that in pure LCMO at 80 kOe
field in the temperature range of 5 to 320K. A fairly high value of low field
magnetoresistance (LFMR) of about 30% is obtained in all the samples at a field
less than 5 kOe.

###Irreversible spin-transfer and magnetization reversal under spin-injection|J. -E. Wegrowe,H. -J. Drouhin###

Irreversible spin-transfer and magnetization reversal under spin-injection. In the context of spin electronics, the two spin-channel model assumes that
the spin carriers are composed of two distinct populations: the conduction
electrons of spin up, and the conduction electrons of spin down. In order to
distinguish the paramagnetic and ferromagnetic contributions in spin injection,
we describe the current injection with four channels : the two spin populations
of the conduction bands ($s$ or paramagnetic) and the two spin populations of
the more correlated electrons ($d$ or ferromagnetic). The redistribution of the
conduction electrons at the interface is described by relaxation mechanisms
between the channels. Providing that the $d$ majority-spin band is frozen,
$s-d$ relaxation essentially concerns the minority-spin channels. Accordingly,
even in the abscence of spin-flip scattering (i.e. without standard
spin-accumulation or giant magnetoresistance), the $s-d$ relaxation leads to a
$d$ spin accumulation effect. The coupled diffusion equations for the two
relaxation processes ($s-d$ and spin-flip) are derived. The link with the
ferromagnetic order parameter $\vec{M}$ is performed by assuming that only the
$d$ channel contributes to the Landau-Lifshitz-Gilbert equation. The effect of
magnetization reversal induced by spin injection is explained by these
relaxations under the assumption that the spins of the conduction electrons act
as environmental degrees of freedom on the magnetization.

###Spin reorientation and in-plane magnetoresistance of lightly doped La_{2-x}Sr_{x}CuO_{4} in magnetic fields up to 55 T|S. Ono,Seiki Komiya,A. N. Lavrov,Yoichi Ando,F. F. Balakirev,J. B. Betts,G. S. Boebinger###

Spin reorientation and in-plane magnetoresistance of lightly doped La_{2-x}Sr_{x}CuO_{4} in magnetic fields up to 55 T. The magnetoresistance (MR) in the in-plane resistivity is measured in
magnetic fields up to 55 T in lightly doped La_{2-x}Sr_{x}CuO_{4} in the N\'eel
state (x = 0.01) and in the spin-glass state (x = 0.03) using high-quality
untwinned single crystals. In both cases, a large negative MR is observed to
appear when the magnetic order is established. For x = 0.01, it is found that
the MR is indicative of a one-step transition into a high-field
weak-ferromagnetic state at around 20 T when the magnetic field is applied from
the spin easy axis (b axis), which means that there is no spin-flop transition
in the N\'eel state of this material; this is contrary to a previous report,
but is natural in light of the peculiar in-plane magnetic susceptibility
anisotropy recently found in this system. In the spin-glass state, we observe
that the large (up to \sim20%) negative MR saturates at around 40 T, and this
MR is found to be essentially isotropic when the magnetic field is rotated
within the ab plane. Our data show that the large negative MR is inherent to
LSCO in a magnetically ordered state, in which the weak-ferromagnetic (WF)
moment becomes well-defined; we discuss that the observed MR is essentially due
to the reorientation of the WF moments towards the magnetic field direction
both in the N\'eel state and in the spin-glass state.

###Realization of an N-shaped IVC of nanoscale metallic junctions using the antiferromagnetic transition|Yu. G. Naidyuk,K. Gloos,I. K. Yanson###

Realization of an N-shaped IVC of nanoscale metallic junctions using the antiferromagnetic transition. We have observed at low temperatures (<8K) hysteretic I(V) characteristics
for sub-mkm (~200nm) metallic break-junctions based on the heavy-fermion
compound UPd2Al3. Degrading the quality of the contacts by in situ increasing
the local residual resistivity or temperature rise reduces the hysteresis. We
demonstrate that those hysteretic I(V) curves can be reproduced theoretically
by assuming the constriction to be in the thermal regime. Our calculations show
that such anomalous I(V) curves are due to the sharp increase of \rho(T) of
UPd2Al3 near the Neel temperature T_N ~ 14K. From this point of view each metal
with similar \rho(T) should produce similar hysteretic I(V) curves. As example
we show calculations for the rare-earth manganite La{0.75}Sr{0.25}MnO3, a
system with colossal magnetoresistance. In this way we demonstrate that
nano-sized point contacts can be non-linear devices with N-shaped I(V)
characteristics, i. e. with negative differential resistance, that could serve
like Esaki tunnel diodes or Gunn diodes as amplifiers, generators, and
switching units. Their characteristic response time is estimated to be less
than 1ns for the investigated contacts.

###Large magnetoresistance anomalies in Dy7Rh3|Kausik Sengupta,S. Rayaprol,E. V. Sampathkumaran###

Large magnetoresistance anomalies in Dy7Rh3. The compound Dy7Rh3 ordering antiferromagnetically below (TN=) 59 K has been
known to exhibit a temperature (T) dependent electrical resistivity (rho)
behavior in the paramagnetic state unusual for intermetallic compounds in the
sense that there is a broad peak in rho(T) in the paramagnetic state (around
130 K) as though there is a semi-conductor to metal transition. In addition,
there is an upturn below T_N due to magnetic super-zone gap effects. Here we
report the influence of external magnetic field (H) on the rho(T) behavior of
this compound below 300 K. The rise of rho(T) found below TN could be
suppressed at very high fields (>> 60 kOe), thus resulting in a very large
magnetoresistance (MR) in the magnetically ordered state. The most notable
finding is that the magnitude of MR is large for moderate applications of H
(say 80 kOe) in a temperature range far above T_N as well, which is untypical
of intermetallic compounds. Thus, this compound is characterized by large MR
anomalies in the entire T range of investigation.

###Spin-Charge Coupling in lightly doped Nd$_{2-x}$Ce$_{x}$CuO$_4$|Shiliang Li,Stephen D. Wilson,David Mandrus,Bairu Zhao,Y. Onose,Y. Tokura,Pengcheng Dai###

Spin-Charge Coupling in lightly doped Nd$_{2-x}$Ce$_{x}$CuO$_4$. We use neutron scattering to study the influence of a magnetic field on spin
structures of Nd$_2$CuO$_4$. On cooling from room temperature, Nd$_2$CuO$_4$
goes through a series of antiferromagnetic (AF) phase transitions with
different noncollinear spin structures. While a c-axis aligned magnetic field
does not alter the basic zero-field noncollinear spin structures, a field
parallel to the CuO$_2$ plane can transform the noncollinear structure to a
collinear one ("spin-flop" transition), induce magnetic disorder along the
c-axis, and cause hysteresis in the AF phase transitions. By comparing these
results directly to the magnetoresistance (MR) measurements of
Nd$_{1.975}$Ce$_{0.025}$CuO$_4$, which has essentially the same AF structures
as Nd$_2$CuO$_4$, we find that a magnetic-field-induced spin-flop transition,
AF phase hysteresis, and spin c-axis disorder all affect the transport
properties of the material. Our results thus provide direct evidence for the
existence of a strong spin-charge coupling in electron-doped copper oxides.

###Metal-to-insulator crossover and pseudogap in single-layer compound Bi$_{2+x}$Sr$_{2-x}$Cu$_{1+y}$O$_{6+δ}$ single crystals in high magnetic fields|S. I. Vedeneev,D. K. Maude###

Metal-to-insulator crossover and pseudogap in single-layer compound Bi$_{2+x}$Sr$_{2-x}$Cu$_{1+y}$O$_{6+δ}$ single crystals in high magnetic fields. The in-plane $\rho_{ab}(H)$ and the out-of-plane $\rho_c(H)$
magneto-transport in magnetic fields up to 28 T has been investigated in a
series of high quality, single crystal, hole-doped La-free Bi2201 cuprates for
a wide doping range and over a wide range of temperatures down to 40 mK. With
decreasing hole concentration going from the overdoped (p=0.2) to the
underdoped (p=0.12) regimes, a crossover from a metallic to and insulating
behavior of $\rho_{ab}(T)$ is observed in the low temperature normal state,
resulting in a disorder induced metal insulator transition. In the zero
temperature limit, the normal state ratio $\rho_c(H)/\rho_{ab}(H)$ of the
heavily underdoped samples in pure Bi2201 shows an anisotropic 3D behavior, in
striking contrast with that observed in La-doped Bi2201 and LSCO systems. Our
data strongly support that that the negative out-of-plane magnetoresistance is
largely governed by interlayer conduction of quasiparticles in the
superconducting state, accompanied by a small contribution of normal state
transport associated with the field dependent pseudogap. Both in the optimal
and overdoped regimes, the semiconducting behavior of $\rho_c(H)$ persists even
for magnetic fields above the pseudogap closing field $H_{pg}$. The method
suggested by Shibauchi \textit{et al.} (Phys. Rev. Lett. \textbf{86}, 5763,
(2001)) for evaluating $H_{pg}$ is unsuccessful for both under- and overdoped
Bi2201 samples. Our findings suggest that the normal state pseudogap is not
always a precursor of superconductivity.

###Origin of Colossal Dielectric Response of Pr(0.6)Ca(0.4)MnO(3)|N. Biskup,A. de Andres,J. L. Martinez,C. Perca###

Origin of Colossal Dielectric Response of Pr(0.6)Ca(0.4)MnO(3). We report the detailed study of dielectric response of Pr(0.6)Ca(0.4)MnO(3)
(PCMO), member of manganite family showing colossal magnetoresistance.
Measurements have been performed on four polycrystalline samples and four
single crystals, allowing us to compare and extract the essence of dielectric
response in the material. High frequency dielectric function is found to be 30,
as expected for the perovskite material. Dielectric relaxation is found in
frequency window of 20Hz-1MHz at temperatures of 50-200K that yields to
colossal low-frequency dielectric function, i.e. static dielectric constant.
Static dielectric constant is always colossal, but varies considerably in
different samples from 1000 until 100000. The measured data can be simulated
very well by blocking (surface barrier) capacitance in series with sample
resistance. This indicates that the large dielectric constant in PCMO arises
from the Schottky barriers at electrical contacts. Measurements in magnetic
field and with d.c. bias support this interpretation. Weak anomaly at the
charge ordering temperature can also be attributed to interplay of sample and
contact resistance. We comment our results in the framework of related studies
by other groups.

###Transport properties in CeOs$_{4}$Sb$_{12}$: Possibility of the ground state being semiconducting|H. Sugawara,S. Osaki,M. Kobayashi,T. Namiki,S. R. Saha,Y. Aoki,H. Sato###

Transport properties in CeOs$_{4}$Sb$_{12}$: Possibility of the ground state being semiconducting. We have measured both magnetoresistance and Hall effect in CeOs$_4$Sb$_{12}$
to clarify the large resistivity state ascribed to the Kondo insulating one and
the origin of the phase transition near 0.9 K reported in the specific heat
measurement. We found unusual temperature ($T$) dependence both in the
electrical resistivity $\rho\sim T^{-1/2}$ and the Hall coefficient $R_{\rm
H}\sim T^{\rm -1}$ over the wide temperature range of about two order of
magnitude below $\sim30$ K, which can be explained as a combined effect of the
temperature dependences of carrier density and carrier scattering by spin
fluctuation. An anomaly related with the phase transition has been clearly
observed in the transport properties, from which the $H-T$ phase diagram is
determined up to 14 T. Taking into account the small entropy change, the phase
transition is most probably the spin density wave one. Both the electrical
resistivity and Hall resistivity at 0.3 K is largely suppressed about an order
of magnitude by magnetic fields above $\sim3$ T, suggesting a drastic change of
electronic structure and a suppression of spin fluctuations under magnetic
fields.

###Large magnetoresistance at room-temperature in small molecular weight organic semiconductor sandwich devices|Ö. Mermer,G. Veeraraghavan,T. L. Francis,M. Wohlgenannt###

Large magnetoresistance at room-temperature in small molecular weight organic semiconductor sandwich devices. We present an extensive study of a large, room temperature negative
magnetoresistance (MR) effect in tris-(8-hydroxyquinoline) aluminum sandwich
devices in weak magnetic fields. The effect is similar to that previously
discovered in polymer devices. We characterize this effect and discuss its
dependence on field direction, voltage, temperature, film thickness, and
electrode materials. The MR effect reaches almost 10% at fields of
approximately 10 mT at room temperature. The effect shows only a weak
temperature dependence and is independent of the sign and direction of the
magnetic field. Measuring the devices' current-voltage characteristics, we find
that the current depends on the voltage through a power-law. We find that the
magnetic field changes the prefactor of the power-law, whereas the exponent
remains unaffected. We also studied the effect of the magnetic field on the
electroluminescence (MEL) of the devices and analyze the relationship between
MR and MEL. We find that the largest part of MEL is simply a consequence of a
change in device current caused by the MR effect.

###Orbital polarons versus itinerant e_g electrons in doped manganites|M. Daghofer,A. M. Oles,W. von der Linden###

Orbital polarons versus itinerant e_g electrons in doped manganites. We study an effective one-dimensional (1D) orbital t-J model derived for
strongly correlated e_g electrons in doped manganites. The ferromagnetic spin
order at half filling is supported by orbital superexchange prop. to J which
stabilizes orbital order with alternating x^2-y^2 and 3z^2-r^2 orbitals. In a
doped system it competes with the kinetic energy prop. to t. When a single hole
is doped to a half-filled chain, its motion is hindered and a localized orbital
polaron is formed. An increasing doping generates either separated polarons or
phase separation into hole-rich and hole-poor regions, and eventually polarizes
the orbitals and gives a it metallic phase with occupied 3z^2-r^2 orbitals.
This crossover, investigated by exact diagonalization at zero temperature, is
demonstrated both by the behavior of correlation functions and by spectral
properties, showing that the orbital chain with Ising superexchange is more
classical and thus radically different from the 1D spin t-J model. At finite
temperature we derive and investigate an effective 1D orbital model using a
combination of exact diagonalization with classical Monte-Carlo for spin
correlations. A competition between the antiferromagnetic and ferromagnetic
spin order was established at half filling, and localized polarons were found
for antiferromagnetic interactions at low hole doping. Finally, we clarify that
the Jahn-Teller alternating potential stabilizes the orbital order with
staggered orbitals, inducing the ferromagnetic spin order and enhancing the
localized features in the excitation spectra. Implications of these findings
for colossal magnetoresistance manganites are discussed.

###Current induced magnetization switching in exchange biased spin-valves for CPP-GMR heads|A. Deac,K. J. Lee,Y. Liu,O. Redon,M. Li,P. Wang,J. P. Nozieres,B. Dieny###

Current induced magnetization switching in exchange biased spin-valves for CPP-GMR heads. In contrast to earlier studies performed on simple Co/Cu/Co sandwiches, we
have investigated spin transfer effects in complex spin-valve pillars with a
diameter of 130nm developed for current-perpendicular to the plane (CPP)
magneto-resistive heads. The structure of the samples included an exchange
biased synthetic pinned layer and a free layer both laminated by insertion of
several ultrathin Cu layers. Despite the small thickness of the polarizing
layer, our results show that the free layer can be switched between the
parallel (P) and the antiparallel (AP) states by applying current densities of
the order of 10^7 A/cm^2. A strong asymmetry is observed between the two
critical currents IcAP-P and IcP-AP, as predicted by the model of Slonczewski
model. Thanks to the use of exchange biased structures, the stability phase
diagrams could be obtained in the four quadrants of the (H, I) plan. The
critical lines derived from the magnetoresistance curves measured with
different sense currents, and from the resistance versus current curves
measured for different applied fields, match each other very well. The main
features of the phase diagrams can be reproduced by investigating the stability
of the solutions of the Landau Lifshitz Gilbert equation including spin torque
term within a macrospin model. A spin-transfer saturation effect was observed
in the positive currents range. We attribute it to a de-depolarization effect
which appears as a consequence of the asymmetric heating of the pillars, whose
top and the bottom leads are made of different materials.

###Angular-dependent Magnetoresistance Oscillations in Na$_{0.48}$CoO$_{2}$ Single Crystal|F. Hu,G. T. Liu,J. L. Luo,D. Wu,N. L. Wang,T. Xiang###

Angular-dependent Magnetoresistance Oscillations in Na$_{0.48}$CoO$_{2}$ Single Crystal. We report measurements of the c-axis angular-dependent magnetoresistance
(AMR) for a Na$_{0.48}$CoO$_{2}$ single crystal, with a magnetic field of 10 T
rotating within Co-O planes. Below the metal-insulator transition temperature
induced by the charge ordering, the oscillation of the AMR is dominated by a
two-fold rotational symmetry. The amplitudes of the oscillation corresponding
to the four- and six-fold rotational symmetries are distinctive in low
temperatures, but they merge into the background simultaneously at about 25 K.
The six-fold oscillation originates naturally from the lattice symmetry. The
observation of the four-fold rotational symmetry is consistent with the picture
proposed by Choy, et al., that the Co lattice in the charge ordered state will
split into two orthorhombic sublattice with one occupied by Co$^{3+}$ ions and
the other by Co$^{4+}$ ions. We have also measured the c-axis AMR for
Na$_{0.35}$CoO$_{2}$ and Na$_{0.85}$CoO$_{2}$ single crystals, and found no
evidence for the existence of two- and four-fold symmetries.

###A new method for direct rf power absorption studies in CMR materials and high T_c superconductors|S. Sarangi,S. V. Bhat###

A new method for direct rf power absorption studies in CMR materials and high T_c superconductors. The design, fabrication and performance of an apparatus for the measurement
of direct rf power absorption in colossal magnetoresistive (CMR) and
superconducting samples are described. The system consists of a self-resonant
LC tank circuit of an oscillator driven by a NOT logic gate. The samples under
investigation are placed in the core of the coil forming the inductance L and
the absorbed power is determined from the measured change in the current
supplied to the oscillator circuit. A customized low temperature insert is used
to integrate the experiment with a commercial Oxford Instruments cryostat and
temperature controller. The oscillator working in the rf range between 1 MHz to
25 MHz is built around an IC 74LS04. The temperature can be varied from 4.2 to
400 K and the magnetic field from 0 to 1.4 T. The apparatus is capable of
measuring direct power absorption in CMR and superconducting samples of volume
as small as 1/1000 cm^3 with a signal to noise ratio of 10:1. Further increase
in the sensitivity can be obtained by summing the results of repeated
measurements obtained at a given temperature. The system performance is
evaluated by measuring the absorbed power in La_0.7 Sr_0.3 MnO_3 (LSMO) CMR
manganite samples and superconducting Y Ba_2 Cu_3 O_7 (YBCO) samples at
different rf frequencies. All operations during the measurements are automated
using a computer with a menu-driven software system, user input being required
only for the initiation of the measurement sequence.

###Impurity scattering and quantum confinement in giant magnetoresistance systems|Peter Zahn,Jörg Binder,Ingrid Mertig###

Impurity scattering and quantum confinement in giant magnetoresistance systems. Ab initio calculations for the giant magnetoresistance (GMR) in Co/Cu, Fe/Cr,
and Fe/Au multilayers are presented. The electronic structure of the
multilayers and the scattering potentials of point defects therein are
calculated self-consistently. Residual resistivities are obtained by solving
the quasi-classical Boltzmann equation including the electronic structure of
the layered system, the anisotropic scattering cross sections derived by a
Green's function method and the vertex corrections. Furthermore, the influence
of scattering centers at the interfaces and within the metallic layers is
incorporated by averaging the scattering cross sections of different impurities
at various sites. An excellent agreement of experimental and theoretical
results concerning the general trend of GMR in Co/Cu systems depending on the
type and the position of impurities is obtained. Due to the quantum confinement
in magnetic multilayers GMR can be tailored as a function of the impurity
position. In Co/Cu and Fe/Au systems impurities in the magnetic layer lead to
high GMR values, whereas in Fe/Cr systems defects at the interfaces are most
efficient to increase GMR.

###Transport and Localisation in the Presence of Strong Structural and Spin Disorder|Sanjeev Kumar,Pinaki Majumdar###

Transport and Localisation in the Presence of Strong Structural and Spin Disorder. We study a tight binding model including both on site disorder and coupling
of the electrons to randomly oriented magnetic moments. The transport
properties are calculated via the Kubo-Greenwood scheme, using the exact
eigenstates of the disordered system and large system size extrapolation of the
low frequency optical conductivity. We first benchmark our method in the model
with only structural disorder and then use it to map out the transport regimes
and metal- insulator transitions in problems involving (i) scattering from
random magnetic moments, and (ii) the combined effect of structural disorder
and magnetic scattering. We completely map out the dependence of the d.c
conductivity on electron density (n) the structural disorder (\Delta) and the
magnetic coupling (J'), and locate the insulator-metal phase boundary in the
space of n-\Delta-J'. These results serve as a reference for understanding
transport in systems ranging from magnetic semiconductors to double exchange
`colossal magnetoresistance' systems. A brief version of this study appears in
our earlier paper Europhys. Lett. vol 65, 75 (2004).

###Relaxation of thermo-remanent magnetization in Fe-Cr GMR multilayers|R. S. Patel,A. K. Majumdar,A. K. Nigam###

Relaxation of thermo-remanent magnetization in Fe-Cr GMR multilayers. The time decay of the thermo-remanent magnetization (TRM) in Fe-Cr giant
magnetoresistive (GMR) multilayers has been investigated. The magnetization in
these multilayers relaxes as a function of time after being cooled in a small
magnetic field of 100 Oe to a low temperature and then the magnetic field is
switched off. Low-field ($<$ 500 Oe) magnetization studies of these samples
have shown hysteresis. This spin-glass-like behavior may originate from
structural imperfections at the interfaces and in the bulk. We find that the
magnetization relaxation is logarithmic. Here the magnetic viscosity is found
to increase first with increasing temperature, then it reaches a maximum around
T$_g$, and then it decreases with increasing temperature. This behavior is
different from that of conventional spin glasses where the logarithmic creep
rate is observed to increase with temperature. Power law also gives good fits
and it is better than the logarithmic fit at higher temperatures. The dynamical
effects of these multilayers are related to the relaxation of thermally blocked
superparamagnetic grains and magnetic domains in the film layers.

###Magnetoresistance Anisotropy of Polycrystalline Cobalt Films: Geometrical-Size- and Domain-Effects|Woosik Gil,Detlef Goerlitz,Michael Horisberger,Juergen Koetzler###

Magnetoresistance Anisotropy of Polycrystalline Cobalt Films: Geometrical-Size- and Domain-Effects. The magnetoresistance (MR) of 10 nm to 200 nm thin polycrystalline Co-films,
deposited on glass and insulating Si(100), is studied in fields up to 120 kOe,
aligned along the three principal directions with respect to the current:
longitudinal, transverse (in-plane), and polar (out-of-plane). At technical
saturation, the anisotropic MR (AMR) in polar fields turns out to be up to
twice as large as in transverse fields, which resembles the yet unexplained
geometrical size-effect (GSE), previously reported for Ni- and Permalloy films.
Upon increasing temperature, the polar and transverse AMR's are reduced by
phonon-mediated sd-scattering, but their ratio, i.e. the GSE remains unchanged.
Basing on Potters's theory [Phys.Rev.B 10, 4626(1974)], we associate the GSE
with an anisotropic effect of the spin-orbit interaction on the sd-scattering
of the minority spins due to a film texture. Below magnetic saturation, the
magnitudes and signs of all three MR's depend significantly on the domain
structures depicted by magnetic force microscopy. Based on hysteresis loops and
taking into account the GSE within an effective medium approach, the three MR's
are explained by the different magnetization processes in the domain states.
These reveal the importance of in-plane uniaxial anisotropy and out-of-plane
texture for the thinnest and thickest films, respectively.

###Anisotropic Magnetoresistance and Magnetic Anisotropy in High-quality (Ga,Mn)As Films|K. Y. Wang,K. W. Edmonds,R. P. Campion,L. X. Zhao,C. T. Foxon,B. L. Gallagher###

Anisotropic Magnetoresistance and Magnetic Anisotropy in High-quality (Ga,Mn)As Films. We have performed a systematic investigation of magnetotransport of a series
of as-grown and annealed Ga1-xMnxAs samples with 0.011 <= x <= 0.09. We find
that the anisotropic magnetoresistance (AMR) generally decreases with
increasing magnetic anisotropy, with increasing Mn concentration and on low
temperature annealing. We show that the uniaxial magnetic anisotropy can be
clearly observed from AMR for the samples with x >= 0.02. This becomes the
dominant anisotropy at elevated temperatures, and is shown to rotate by 90o on
annealing. We find that the in-plane longitudinal resistivity depends not only
on the relative angle between magnetization and current direction, but also on
the relative angle between magnetization and the main crystalline axes. The
latter term becomes much smaller after low temperature annealing. The planar
Hall effect is in good agreement with the measured AMR indicating the sample is
approximately in a single domain state throughout most of the magnetisation
reversal, with a two-step magnetisation jump ascribed to domain wall nucleation
and propagation.

###Domain Wall Magnetoresistance of Co Nanowires|R. F. Sabirianov,A. K. Solanki,J. D. Burton,S. S. Jaswal,E. Y. Tsymbal###

Domain Wall Magnetoresistance of Co Nanowires. Using density functional theory implemented within a tight-binding linear
muffin-tin orbital method we perform calculations of electronic, magnetic and
transport properties of ferromagnetic free-standing fcc Co wires with diameters
up to 1.5 nm. We show that finite-size effects play an important role in these
nanowires resulting in oscillatory behavior of electronic charge and the
magnetization as a function of the wire thickness, and a non-monotonic behavior
of spin-dependent quantized conductance. We calculate the magnetoresistance
(MR) of a domain wall (DW) modeled by a spin-spiral region of finite width
sandwiched between two semi-infinite Co wire leads. We find that the DW MR
decreases very rapidly, on the scale of a few interatomic layers, with the
increasing DW width. The largest MR value of about 250% is predicted for an
abrupt DW in the monatomic wire. We show that, for some energy values, the
density of states and the conductance may be non-zero only in one spin channel,
making the MR for the abrupt DW infinitely large. We also demonstrate that for
the abrupt DW a large MR may occur due to the hybridization between two spin
subbands across the DW interface. We do not find, however, such a behavior at
the Fermi energy for the Co wires considered.

###Strong-coupling theory of high-temperature superconductivity and colossal magnetoresistance|A. S. Alexandrov###

Strong-coupling theory of high-temperature superconductivity and colossal magnetoresistance. We argue that the extension of the BCS theory to the strong-coupling regime
describes the high-temperature superconductivity of cuprates and the colossal
magnetoresistance (CMR) of ferromagnetic oxides if the phonon dressing of
carriers and strong attractive correlations are taken into account. The
long-range Froehlich electron-phonon interaction has been identified as the
most essential in cuprates providing "superlight" lattice polarons and
bipolarons. Here some kinetic, magnetic, and more recent thermomagnetic normal
state measurements are interpreted in the framework of the strong-coupling
theory, including the Nernst effect and normal state diamagnetism. Remarkably,
a similar strong-coupling approach offers a simple explanation of CMR in
ferromagnetic oxides. The pairing of oxygen holes into heavy bipolarons in the
paramagnetic phase and their magnetic pair-breaking in the ferromagnetic phase
account for the first-order ferromagnetic phase transition, CMR, isotope
effects, and pseudogaps in doped manganites. Here we propose an explanation of
the phase coexistence and describe the shape of resistivity of manganites near
the transition in the framework of the strong-coupling approach.

###Magnetic and transport properties of Mo substituted La0.67Ba0.33Mn1-xMoxO3 perovskite system|Darshan C. Kundaliya,Reeta Vij,R. G. Kulkarni,B. Varughese,A. K. Nigam,S. K. Malik###

Magnetic and transport properties of Mo substituted La0.67Ba0.33Mn1-xMoxO3 perovskite system. The effect of doping Mo for Mn on the magnetic and transport properties of
the colossal magnetoresistance material, La0.67Ba0.33MnO3, has been studied.
Compounds of the series La0.67Ba0.33Mn1-xMoxO3 (x=0.0 to 0.1) have been
prepared and found to crystallize in the orthorhombic structure (space group
Pbnm). Energy Dispersive X-ray Analysis (EDAX) measurements confirm the
stoichiometry of all the samples. Magnetotransport and magnetization
measurements reveal that the metal-insulator transition temperature (Tp)
decreases from 330K for x=0 to 255K for x=0.1. The change in Tp on Mo
substitution is relatively much smaller than the corresponding change observed
on substitution by other transition elements, such as Ti, Fe, Co, Ni, etc.
Further, the ferromagnetic transition temperature (TC) is nearly unchanged by
Mo substitution. This is in striking contrast to the large decrease in TC
observed with substitution of above-mentioned 3d elements. These unusual
magnetic and transport properties of La0.67Ba0.33Mn1-xMoxO3 may be either due
to the formation of magnetic pair between Mn and Mo or due to strong
Mo(4d)-O(2p) overlap, which in turn, may affect the Mn-Mn interaction via the
oxygen atoms

###Gossamer Superconductivity, New Paradigm?|H. Won,S. Haas,K. Maki,D. Parker,B. Dora,A. Virosztek###

Gossamer Superconductivity, New Paradigm?. We shall review our recent works on d-wave density wave (dDW) and gossamer
superconductivity (i.e. d-wave superconductivity in the presence of dDW) in
high-T$_{c}$ cuprates and CeCoIn$_{5}$. a) We show that both the giant Nernst
effect and the angle dependent magnetoresistance (ADMR) in the pseudogap phases
of the cuprates and CeCoIn$_{5}$ are manifestations of dDW. b) The phase
diagram of high-T$_{c}$ cuprates is understood in terms of mean field theory,
which includes two order parameters $\Delta_{1}$ and $\Delta_{2}$, where one
order parameter is from dDW and the other from d-wave superconductivity. c) In
the optimally to the overdoped region we find the spatially periodic dDW, an
analogue of the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, becomes more
stable. d) In the underdoped region where $\Delta_{2}/\Delta_{1} \ll 1$ the
Uemera relation is obtained within the present model. We speculate that the
gossamer superconductivity is at the heart of high-T$_{c}$ cuprate
superconductors, the heavy-fermion superconductor CeCoIn$_{5}$ and the organic
superconductors $\kappa$- (ET)$_{2}$Cu(NCS)$_{2}$ and (TMTSF)$_2$PF$_{6}$.

###Spinel ferrites: old materials bring new opportunities for spintronics|Ulrike Lueders,Agnes Barthelemy,Manuel Bibes,Karim Bouzehouane,Stephane Fusil,Eric Jacquet,Jean-Pierre Contour,Jean-Francois Bobo,Josep Fontcuberta,Albert Fert###

Spinel ferrites: old materials bring new opportunities for spintronics. Over the past few years, intensive studies of ultrathin epitaxial films of
perovskite oxides have often revealed exciting properties like giant
magnetoresistive tunnelling and electric field effects. Spinel oxides appear as
even more versatile due to their more complex structure and the resulting many
degrees of freedom. Here we show that the epitaxial growth of nanometric
NiFe2O4 films onto perovskite substrates allows the stabilization of novel
ferrite phases with properties dramatically differing from bulk ones. Indeed,
NiFe2O4 films few nanometres thick have a saturation magnetization at least
twice that of the bulk compound and their resistivity can be tuned by orders of
magnitude, depending on the growth conditions. By integrating such thin NiFe2O4
layers into spin-dependent tunnelling heterostructures, we demonstrate that
this versatile material can be useful for spintronics, either as a conductive
electrode in magnetic tunnel junctions or as a spin-filtering insulating
barrier in the little explored type of tunnel junction called spin-filter. Our
findings are thus opening the way for the realisation of monolithic spintronics
architectures integrating several layers of a single material, where the layers
are functionalised in a controlled manner.

###Complexity in Strongly Correlated Electronic Systems|Elbio Dagotto###

Complexity in Strongly Correlated Electronic Systems. A wide variety of experimental results and theoretical investigations in
recent years have convincingly demonstrated that several transition metal
oxides and other materials, have dominant states that are not spatially
homogeneous. This occurs in cases in which several physical interactions --
spin, charge, lattice, and/or orbital -- are simultaneously active. This
phenomenon causes interesting effects, such as colossal magnetoresistance, and
it also appears crucial to understand the high temperature superconductors. The
spontaneous emergence of electronic nanometer-scale structures in transition
metal oxides, and the existence of many competing states, are properties often
associated with complex matter where nonlinearities dominate, such as soft
materials and biological systems. This electronic complexity could have
potential consequences for applications of correlated electronic materials,
because not only charge (semiconducting electronic), or charge and spin
(spintronics) are of relevance, but in addition the lattice and orbital degrees
of freedom are active, leading to giant responses to small perturbations.
Moreover, several metallic and insulating phases compete, increasing the
potential for novel behavior.

###Nodal quasiparticle in pseudogapped colossal magnetoresistive manganites|N. Mannella,W. Yang,X. J. Zhou,H. Zheng,J. F. Mitchell,J. Zaanen,T. P. Devereaux,N. Nagaosa,Z. Hussain,Z. -X. Shen###

Nodal quasiparticle in pseudogapped colossal magnetoresistive manganites. A characteristic feature of the copper oxide high-temperature superconductors
is the dichotomy between the electronic excitations along the nodal (diagonal)
and antinodal (parallel to the Cu-O bonds) directions in momentum space,
generally assumed to be linked to the "d-wave" symmetry of the superconducting
state. Angle-resolved photoemission measurements in the superconducting state
have revealed a quasiparticle spectrum with a d-wave gap structure that
exhibits a maximum along the antinodal direction and vanishes along the nodal
direction. Subsequent measurements have shown that, at low doping levels, this
gap structure persists even in the high-temperature metallic state, although
the nodal points of the superconducting state spread out in finite "Fermi
arcs". This is the so-called pseudogap phase, and it has been assumed that it
is closely linked to the superconducting state, either by assigning it to
fluctuating superconductivity or by invoking orders which are natural
competitors of d-wave superconductors. Here we report experimental evidence
that a very similar pseudogap state with a nodal-antinodal dichotomous
character exists in a system that is markedly different from a superconductor:
the ferromagnetic metallic groundstate of the colossal magnetoresistive bilayer
manganite La1.2Sr1.8Mn2O7. Our findings therefore cast doubt on the assumption
that the pseudogap state in the copper oxides and the nodal-antinodal dichotomy
are hallmarks of the superconductivity state.

###Enhanced tunneling magnetoresistance in Fe|ZnSe double junctions|Jeronimo Peralta Ramos,Ana Maria Llois###

Enhanced tunneling magnetoresistance in Fe|ZnSe double junctions. We calculate the tunneling magnetoresistance (TMR) of Fe|ZnSe|Fe|ZnSe|Fe
(001) double magnetic tunnel junctions as a function of the in-between Fe
layer's thickness, and compare these results with those of Fe|ZnSe|Fe simple
junctions. The electronic band structures are modeled by a parametrized
tight-binding Hamiltonian fitted to ab initio calculations, and the conductance
is calculated within the Landauer formalism expressed in terms of Green's
functions. We find that the conductances for each spin channel and the TMR
strongly depend on the in-between Fe layer's thickness, and that in some cases
they are enhanced with respect to simple junctions, in qualitative agreement
with recent experimental studies performed on similar systems. By using a 2D
double junction as a simplified system, we show that the conductance
enhancement can be explained in terms of the junctions energy spectrum. These
results are relevant for spintronics because they demonstrate that the TMR in
double junctions can be tuned and enhanced by varying the in-between metallic
layer's thickness.

###Interface effects in spin-dependent tunneling|E. Y. Tsymbal,K. D. Belashchenko,J. P. Velev,S. S. Jaswal,M. van Schilfgaarde,I. I. Oleynik,D. A. Stewart###

Interface effects in spin-dependent tunneling. In the past few years the phenomenon of spin dependent tunneling (SDT) in
magnetic tunnel junctions (MTJs) has aroused enormous interest and has
developed into a vigorous field of research. The large tunneling
magnetoresistance (TMR) observed in MTJs garnered much attention due to
possible application in random access memories and magnetic field sensors. This
led to a number of fundamental questions regarding the phenomenon of SDT. One
such question is the role of interfaces in MTJs and their effect on the spin
polarization of the tunneling current and TMR. In this paper we consider
different models which suggest that the spin polarization is primarily
determined by the electronic and atomic structure of the ferromagnet/insulator
interfaces rather than by their bulk properties. First, we consider a simple
tight-binding model which demonstrates that the existence of interface states
and their contribution to the tunneling current depend on the degree of
hybridization between the orbitals on metal and insulator atoms. The decisive
role of the interfaces is further supported by studies of spin-dependent
tunneling within realistic first-principles models of Co/vacuum/Al,
Co/Al2O3/Co, Fe/MgO/Fe, and Co/SrTiO3/Co MTJs. We find that variations in the
atomic potentials and bonding strength near the interfaces have a profound
effect resulting in the formation of interface resonant states, which
dramatically affect the spin polarization and TMR. The strong sensitivity of
the tunneling spin polarization and TMR to the interface atomic and electronic
structure dramatically expands the possibilities for engineering optimal MTJ
properties for device applications.

###Lower critical field and intragrain critical current density in the ruthenate-cuprate RuSr$_{2}$Gd$_{1.5}$Ce$_{0.5}$Cu$_{2}$O$_{10}$|M. G. das Virgens,S. García,L. Ghivelder###

Lower critical field and intragrain critical current density in the ruthenate-cuprate RuSr$_{2}$Gd$_{1.5}$Ce$_{0.5}$Cu$_{2}$O$_{10}$. The lower critical field of the grains, $H_{c1}$, and the intragrain critical
current density, $J_{c}$, were determined for the superconducting
ruthenate-cuprate RuSr$_{2}$Gd$_{1.5}$Ce$_{0.5}$Cu$_{2}$O$_{10-\delta}$
[Ru-1222(Gd)] through a systematic study of the hysteresis in magnetoresistance
loops. A reliable method, based on the effects of the magnetization of the
grains on the net local field at the intergranular junctions is provided,
circumventing the problem of the strong masking of the superconducting
diamagnetic signal by the ferromagnetic background. The temperature dependency
of $H_{c1}$ and $J_{c}$ both exhibit a smooth increase on cooling without
saturation down to $T/T_{SC}$ $\cong $ 0.2. The obtained $H_{c1}$ values vary
between 150 and 1500 Oe in the 0.2 $\leq $ $% T/T_{SC}$ $\leq $ 0.4 interval,
for samples annealed in an oxygen flow; oxygenation under high pressure (50
atm) leads to a further increase. These values are much larger than the
previously reported rough assessments (25-50 Oe), using conventional
magnetization measurements. High $J_{c}$ values of $% \sim $ 10$^{7}$
A/cm$^{2}$, comparable to the high-T$_{c}$ cuprates, were obtained. The
$H_{c1}(T)$ and $J_{c}(T)$ dependencies are explained in the context of a
magnetic phase separation scenario.

###Magnetoresistance Effects in SrFeO(3-x): Dependence on Phase Composition and Relation to Magnetic and Charge Order|P. Adler,A. Lebon,V. Damljanovic,C. Ulrich,C. Bernhard,A. V. Boris,A. Maljuk,C. T. Lin,B. Keimer###

Magnetoresistance Effects in SrFeO(3-x): Dependence on Phase Composition and Relation to Magnetic and Charge Order. Single crystals of iron(IV) rich oxides SrFeO(3-x) with controlled oxygen
content have been studied by Moessbauer spectroscopy, magnetometry,
magnetotransport measurements, Raman spectroscopy, and infrared ellipsometry in
order to relate the large magnetoresistance (MR) effects in this system to
phase composition, magnetic and charge order. It is shown that three different
types of MR effects occur. In cubic SrFeO3 (x = 0) a large negative MR of 25%
at 9 T is associated with a hitherto unknown 60 K magnetic transition and a
subsequent drop in resistivity. The 60 K transition appears in addition to the
onset of helical ordering at ~130 K. In crystals with vacancy-ordered
tetragonal SrFeO(3-x) as majority phase (x ~0.15) a coincident
charge/antiferromagnetic ordering transition near 70 K gives rise to a negative
giant MR effect of 90% at 9 T. A positive MR effect is observed in tetragonal
and orthorhombic materials with increased oxygen deficiency (x = 0.19, 0.23)
which are insulating at low temperatures. Phase mixtures can result in a
complex superposition of these different MR phenomena. The MR effects in
SrFeO(3-x) differ from those in manganites as no ferromagnetic states are
involved.

###Three--body Correlation Effects on the Spin Dynamics of Double--Exchange Ferromagnets|M. D. Kapetanakis,A. Manousaki,I. E. Perakis###

Three--body Correlation Effects on the Spin Dynamics of Double--Exchange Ferromagnets. We present a variational calculation of the spin wave excitation spectrum of
double--exchange ferromagnets in different dimensions. Our theory recovers the
Random Phase approximation and 1/S expansion results as limiting cases and can
be used to study the intermediate exchange coupling and electron concentration
regime relevant to the manganites. In particular, we treat exactly the long
range three--body correlations between a Fermi sea electron--hole pair and a
magnon excitation and show that they strongly affect the spin dynamics in the
parameter range relevant to experiments in the manganites. The manifestations
of these correlations are many-fold. We demonstrate that they significantly
change the ferromagnetic phase boundary. In addition to a decrease in the
magnon stiffness, we obtain an instability of the ferromagnetic state against
spin wave excitations close to the Brillouin zone boundary.Within a range of
intermediate concentrations, we find a strong softening of the spin wave
dispersion as compared to the Heisenberg ferromagnet with the same stiffness,
which changes into hardening for other concentrations. We discuss the relevance
of these results to experiments in colossal magnetoresistance ferromagnets.

###Interface bonding of a ferromagnetic/semiconductor junction : a photoemission study of Fe/ZnSe(001)|M. Eddrief,M. Marangolo,V. H. Etgens,S. Ustaze,F. Sirotti,M. Mulazzi,G. Panaccione,D. H. Mosca,B. Lepine,P. Schieffer###

Interface bonding of a ferromagnetic/semiconductor junction : a photoemission study of Fe/ZnSe(001). We have probed the interface of a ferromagnetic/semiconductor (FM/SC)
heterojunction by a combined high resolution photoemission spectroscopy and
x-ray photoelectron diffraction study. Fe/ZnSe(001) is considered as an example
of a very low reactivity interface system and it expected to constitute large
Tunnel Magnetoresistance devices. We focus on the interface atomic environment,
on the microscopic processes of the interface formation and on the iron
valence-band. We show that the Fe contact with ZnSe induces a chemical
conversion of the ZnSe outermost atomic layers. The main driving force that
induces this rearrangement is the requirement for a stable Fe-Se bonding at the
interface and a Se monolayer that floats at the Fe growth front. The released
Zn atoms are incorporated in substitution in the Fe lattice position. This
formation process is independent of the ZnSe surface termination (Zn or Se).
The Fe valence-band evolution indicates that the d-states at the Fermi level
show up even at submonolayer Fe coverage but that the Fe bulk character is only
recovered above 10 monolayers. Indeed, the Fe &#61508;1-band states,
theoretically predicted to dominate the tunneling conductance of Fe/ZnSe/Fe
junctions, are strongly modified at the FM/SC interface.

###Coulomb blockade anisotropic magnetoresistance: Singleelectronics meets spintronics|J. Wunderlich,T. Jungwirth,B. Kaestner,A. C. Irvine,K. Wang,N. Stone,U. Rana,A. D. Giddings,A. B. Shick,C. T. Foxon,R. P. Campion,D. A. Williams,B. L Gallagher###

Coulomb blockade anisotropic magnetoresistance: Singleelectronics meets spintronics. Single-electronics and spintronics are among the most intensively
investigated potential complements or alternatives to CMOS electronics.
Single-electronics, which is based on the discrete charge of the electron, is
the ultimate in miniaturization and electro-sensitivity. Spintronics, which is
based on manipulating electron spins,delivers high magneto-sensitivity and
non-volatile memory effects. So far, major developments in the two fields have
followed independent paths with only a few experimental studies of hybrid
single-electronic/spintronic devices. Intriguing new effects have been
discovered in such devices but these have not, until now, offered the
possibility of useful new functionalities. Here we demonstrate a device which
shows a new physical effect, Coulomb blockade anisotropic magnetoresistance,
and which offers a route to non-volatile, low-field, and highly electro- and
magneto-sensitive operation. Since this new phenomenon reflects the
magnetization orientation dependence of the classical single-electron charging
energy it does not impose constraints on the operational temperature associated
with more subtle quantum effects, such as resonant or spin-coherent tunneling.

###Nanoscopic processes of Current Induced Switching in thin tunnel junctions|J. Ventura,J. P. Araujo,J. B. Sousa,Y. Liu,Z. Zhang,P. P. Freitas###

Nanoscopic processes of Current Induced Switching in thin tunnel junctions. In magnetic nanostructures one usually uses a magnetic field to commute
between two resistance (R) states. A less common but technologically more
interesting alternative to achieve R-switching is to use an electrical current,
preferably of low intensity. Such Current Induced Switching (CIS) was recently
observed in thin magnetic tunnel junctions, and attributed to electromigration
of atoms into/out of the insulator. Here we study the Current Induced
Switching, electrical resistance, and magnetoresistance of thin
MnIr/CoFe/AlO$_x$/CoFe tunnel junctions. The CIS effect at room temperature
amounts to 6.9% R-change between the high and low states and is attributed to
nanostructural rearrangements of metallic ions in the electrode/barrier
interfaces. After switching to the low R-state some electro-migrated ions
return to their initial sites through two different energy channels. A low
(high) energy barrier of $\sim$0.13 eV ($\sim$0.85 eV) was estimated. Ionic
electromigration then occurs through two microscopic processes associated with
different types of ions sites/defects. Measurements under an external magnetic
field showed an additional intermediate R-state due to the simultaneous
conjugation of the MR (magnetic) and CIS (structural) effects.

###Electron Transport through Disordered Domain Walls: Coherent and Incoherent Regimes|Peter E. Falloon,Rodolfo A. Jalabert,Dietmar Weinmann,Robert L. Stamps###

Electron Transport through Disordered Domain Walls: Coherent and Incoherent Regimes. We study electron transport through a domain wall in a ferromagnetic nanowire
subject to spin-dependent scattering. A scattering matrix formalism is
developed to address both coherent and incoherent transport properties. The
coherent case corresponds to elastic scattering by static defects, which is
dominant at low temperatures, while the incoherent case provides a
phenomenological description of the inelastic scattering present in real
physical systems at room temperature. It is found that disorder scattering
increases the amount of spin-mixing of transmitted electrons, reducing the
adiabaticity. This leads, in the incoherent case, to a reduction of conductance
through the domain wall as compared to a uniformly magnetized region which is
similar to the giant magnetoresistance effect. In the coherent case, a
reduction of weak localization, together with a suppression of spin-reversing
scattering amplitudes, leads to an enhancement of conductance due to the domain
wall in the regime of strong disorder. The total effect of a domain wall on the
conductance of a nanowire is studied by incorporating the disordered regions on
either side of the wall. It is found that spin-dependent scattering in these
regions increases the domain wall magnetoconductance as compared to the effect
found by considering only the scattering inside the wall. This increase is most
dramatic in the narrow wall limit, but remains significant for wide walls.

###Unconventional Density Waves in Organic Conductors and in Superconductors|Kazumi Maki,Balázs Dóra,Attila Virosztek###

Unconventional Density Waves in Organic Conductors and in Superconductors. Unconventional density waves (UDW) are one of the ground states in metallic
crystalline solids and have been speculated already in 1968. However, more
focused studies on UDW started only recently, perhaps after the identification
of the low temperature phase in alpha-(BEDT-TTF)_2KHg(SCN)_4 as unconventional
charge density wave (UCDW) in 2002. More recently, the metallic phase of
Bechgaard salts (TMTSF)_2X with X=PF_6 and ReO_4 under both pressure and
magnetic field appears to be unconventional spin density wave (USDW). The
pseudogap regime of high T_c superconductors LSCO, YBCO, Bi2212 and the one in
CeCoIn_5 belong to d-wave density waves (d-DW).
  In these identifications, the angular dependent magnetoresistance and the
giant Nernst effect have played the crucial role. These are the simplest
manifestations of the Landau quantization of quasiparticle energy in UDW in the
presence of magnetic field (the Nersesyan effect). Also we speculate that UDW
will be most likely found in alpha$-(BEDT-TTF)_2I_3, alpha-(BEDT-TTF)_2I_2Br,
kappa-(BEDT-TTF)_2Cu(NCS)_2, kappa-(BEDT-TTF)_2Cu(CN)_2Br,
lambda-(BEDT)_2GaCl_4 and in many other organic compounds.

###Ballistic transport in ferromagnet-superconductor-ferromagnet trilayers with arbitrary orientation of magnetizations|Milos Bozovic,Zoran Radovic###

Ballistic transport in ferromagnet-superconductor-ferromagnet trilayers with arbitrary orientation of magnetizations. Transport phenomena in clean ferromagnet-superconductor-ferromagnet (FSF)
trilayers are studied theoretically for a general case of arbitrary orientation
of in-plane magnetizations and interface transparencies. Generalized
expressions for scattering probabilities are derived and the differential
conductance is computed using solutions of the Bogoliubov-de Gennes equation.
We focus on size and coherence effects that characterize ballistic transport,
in particular on the subgap transmission and geometrical oscillations of the
conductance. We find a monotonic dependence of conductance spectra and
magnetoresistance on the angle of misorientation of magnetizations as their
alignment is changed from parallel to antiparallel. Spin-triplet pair
correlations in FSF heterostructures induced by non-collinearity of
magnetizations are investigated by solving the Gor'kov equations in the clean
limit. Unlike diffusive FSF junctions, where the triplet correlations have a
long-range monotonic decay, we show that in clean ferromagnet-superconductor
hybrids both singlet and triplet pair correlations induced in the F layers are
oscillating and power-law decaying with the distance from the S-F interfaces.

###The Anderson-Mott transition induced by hole-doping in Nd1-xTiO3|A. S. Sefat,J. E. Greedan,G. M. Luke,M. Niewczas,J. D. Garrett,H. Dabkowska,A. Dabkowski###

The Anderson-Mott transition induced by hole-doping in Nd1-xTiO3. The insulator/metal transition induced by hole-doping due to neodymium
vacancies of the Mott- Hubbard antiferromagnetic insulator, Nd1-xTiO3, is
studied over the composition range 0.010(6) < x < 0.243(10). Insulating p-types
conduction is found for x < 0.071(10). Anderson localization in the presence of
a Mott-Hubbard gap, is the dominant localization mechanism for the range of
0.074(10) < x < 0.089(1) samples. For x < 0.089(1), n-type conduction is
observed and the activation energy extrapolates to zero by x < 0.1. The
0.095(8) < x < 0.203(10) samples are Fermi-liquid metals and the effects of
strong electronic correlations are evident near the metal-to-insulator
boundaries in features such as large Fermi liquid T2 coefficients. For 0.074(9)
< x < 0.112(4), a weak negative magnetoresistance is found below ~ 15 K and it
is attributed to the interaction of conduction electrons with Nd3+ magnetic
moments. Combining information from our companion study of the magnetic
properties of Nd1-xTiO3 solid solution, a phase diagram is proposed. The main
conclusions are that long range antiferromagnetic order disappears before the
onset of metallic behavior and that the Anderson-Mott transition occurs over a
finite range of doping levels. Our results differ from conclusions drawn from a
similar study on the hole doped Nd1-xCaxTiO3 system which found the
co-existence of antiferromagnetic order and metallic behavior and that the Mott
transition occurs at a discrete doping level.

###Dielectric breakdown in underoxidized magnetic tunnel junctions: Dependence on oxidation time and area|J. Ventura,R. Ferreira,J. B. Sousa,P. P. Freitas###

Dielectric breakdown in underoxidized magnetic tunnel junctions: Dependence on oxidation time and area. Magnetic tunnel junctions (MTJs) with partially oxidized 9 \AA
AlO$_x$-barriers were recently shown to have the necessary characteristics to
be used as magnetoresistive sensors in high-density storage devices. Here we
study dielectric breakdown in such underoxidized magnetic tunnel junctions,
focusing on its dependence on tunnel junction area and oxidation time. A clear
relation between breakdown mechanism and junction area is observed for the MTJs
with the highest studied oxidation time: samples with large areas fail usually
due to extrinsic causes (characterized by a smooth resistance decrease at
dielectric breakdown). Small area junctions fail mainly through an intrinsic
mechanism (sharp resistance decrease at breakdown). However, this dependence
changes for lower oxidation times, with extrinsic breakdown becoming dominant.
In fact, in the extremely underoxidized magnetic tunnel junctions, failure is
exclusively related with extrinsic causes, independently of MTJ-area. These
results are related with the presence of defects in the barrier (weak spots
that lead to intrinsic breakdown) and of metallic unoxidized Al
nanoconstrictions (leading to extrinsic breakdown).

###The origin of the spin glass transition in a model geometrically frustrated magnet|W. Bisson,A. S. Wills###

The origin of the spin glass transition in a model geometrically frustrated magnet. Highly frustrated systems have macroscopically degenerate ground states that
lead to novel properties. In magnetism its consequences underpin exotic and
technologically important effects, such as, high temperature superconductivity,
colossal magnetoresistence, and the anomalous Hall effect. One of the enduring
mysteries of frustrated magnetism is why certain experimental systems have a
spin glass transition and its exact nature, given that it is not determined by
the strength of the dominant magnetic interactions. There have been some
suggestions that real systems possess disorder of the magnetic sites or bonds
that are responsible. We show that the spin glass transition in the model
kagome antiferromagnet hydronium jarosite arises from a spin anisotropy. This
weaker energy scale is much smaller than that of the magnetic exchange, yet it
is responsible for the energy barriers that are necessary to stabilise a glassy
magnetic phase at finite temperature. The resultant glassy phase is quite
unlike those found in conventional disordered spin glasses as it is based on
complex collective rearrangements of spins called "spin folds". This simplifies
hugely theoretical treatment of both the complex dynamics characteristic of a
spin glass and the microscopic nature of the spin glass transition itself.

###Angular magnetoresistance oscillations in quasi-one-dimensional organic conductors in the presence of a crystal superstructure|Anand Banerjee,Victor M. Yakovenko###

Angular magnetoresistance oscillations in quasi-one-dimensional organic conductors in the presence of a crystal superstructure. We study the effect of crystal superstructures, produced by orientational
ordering of the ReO4 and ClO4 anions in the quasi-one-dimensional organic
conductors (TMTSF)2ReO4 and (TMTSF)2ClO4, on the angular magnetoresistance
oscillations (AMRO) observed in these materials. Folding of the Brillouin zone
due to anion ordering generates effective tunneling amplitudes between distant
chains. These amplitudes cause multiple peaks in interlayer conductivity for
the magnetic field orientations along the rational crystallographic directions
(the Lebed magic angles). Different wave vectors of the anion ordering in
(TMTSF)2ReO4 and (TMTSF)2ClO4 result in the odd and even Lebed angles, as
observed experimentally. When a strong magnetic field is applied parallel to
the layers and perpendicular to the chains and exceeds a certain threshold, the
interlayer tunneling between different branches of the folded electron spectrum
becomes possible, and interlayer conductivity should increase sharply. This
effect can be utilized to probe the anion ordering gaps in (TMTSF)2ClO4 and
(TMTSF)2ReO4. An application of this effect to kappa-(ET)2Cu(NCS)2 is also
briefly discussed.

###Systematic study of disorder induced by neutron irradiation in MgB2 thin films|V. Ferrando,I. Pallecchi,C. Tarantini,D. Marre,M. Putti,F. Gatti,H. U. Aebersold,E. Lehmann,E. Haanappel,I. Sheikin,X. X. Xi,P. Orgiani,C. Ferdeghini###

Systematic study of disorder induced by neutron irradiation in MgB2 thin films. The effects of neutron irradiation on normal state and superconducting
properties of epitaxial magnesium diboride thin films are studied up to
fluences of 1020 cm-2. All the properties of the films change systematically
upon irradiation. Critical temperature is suppressed and, at the highest
fluence, no superconducting transition is observed down to 1.8 K. Residual
resistivity progressively increases from 1 to 190 microohmcm; c axis expands
and then saturates at the highest damage level. We discuss the mechanism of
damage through the comparison with other damage procedures. The normal state
magnetoresistivity of selected samples measured up to high fields (28 and 45T)
allows to determine unambiguously the scattering rates in each band; the
crossover between the clean and dirty limit in each sample can be monitored.
This set of samples, with controlled amount of disorder, is suitable to study
the puzzling problem of critical field in magnesium diboride thin films. The
measured critical field values are extremely high (of the order of 50T in the
parallel direction at low fluences) and turns out to be rather independent on
the experimental resistivity, at least at low fluences. A simple model to
explain this phenomenology is presented.

###Tl2Ba2CuO6+d Brings Spectroscopic Probes Deep Into the Overdoped Regime of the High-Tc Cuprates|D. C. Peets,J. D. F. Mottershead,B. Wu,I. S. Elfimov,R. Liang,W. N. Hardy,D. A. Bonn,M. Raudsepp,N. J. C. Ingle,A Damascelli###

Tl2Ba2CuO6+d Brings Spectroscopic Probes Deep Into the Overdoped Regime of the High-Tc Cuprates. Single-particle spectroscopic probes, such as scanning tunneling and
angle-resolved photoemission spectroscopy (ARPES), have provided us with
crucial insights into the complex electronic structure of the high-Tc cuprates,
in particular for the under and optimally doped regimes where high-quality
crystals suitable for surface-sensitive experiments are available. Conversely,
the elementary excitations on the heavily overdoped side of the phase diagram
remain largely unexplored. Important breakthroughs could come from the study of
Tl2Ba2CuO6+d (Tl2201), a structurally simple system whose doping level can be
tuned from optimal to extreme overdoping by varying the oxygen content. We have
grown single crystals of Tl2201, which were then carefully annealed under
controlled oxygen partial pressures. Their high quality and homogeneity are
demonstrated by narrow rocking curves and superconducting transition widths.
These crystals have enabled the first successful ARPES study of both normal and
superconducting-state electronic structure in Tl2201, allowing a direct
comparison with the Fermi surface from magnetoresistance and the gap from
thermal conductivity experiments. This establishes Tl2201 as the first high-Tc
cuprate for which a surface-sensitive single-particle spectroscopy and a
comparable bulk transport technique have arrived at quantitative agreement on a
major feature such as the normal state Fermi surface. The surprising momentum
dependence of the ARPES lineshape is also discussed.

###Collective Josephson vortex dynamics in a finite number of intrinsic Josephson junctions|Myung-Ho Bae,Jae-Hyun Choi,Hu-Jong Lee###

Collective Josephson vortex dynamics in a finite number of intrinsic Josephson junctions. We report the experimental confirmation of the collective transverse plasma
modes excited by the Josephson vortex lattice in stacks of intrinsic Josephson
junctions in Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+x}$ single crystals. The
excitation was confirmed by analyzing the temperature ($T$) and magnetic field
($H$) dependencies of the multiple sub-branches in the Josephson-vortex-flow
region of the current-voltage characteristics of the system. In the near-static
Josephson vortex state for a low tunneling bias current, pronounced
magnetoresistance oscillations were observed, which represented a
triangular-lattice vortex configuration along the c axis. In the dynamic vortex
state in a sufficiently high magnetic field and for a high bias current,
splitting of a single Josephson vortex-flow branch into multiple sub-branches
was observed. Detailed examination of the sub-branches for varying $H$ field
reveals that sub-branches represent the different modes of the Josephson-vortex
lattice along the c axis, with varied configuration from a triangular to a
rectangular lattices. These multiple sub-branches merge to a single curve at a
characteristic temperature, above which no dynamical structural transitions of
the Josephson vortex lattice is expected.

###Infrared and THz studies of polar phonons and improper magnetodielectric effect in multiferroic BFO3 ceramics|S. Kamba,D. Nuzhnyy,M. Savinov,J. Sebek,J. Petzelt,J. Prokleska,R. Haumont,J. Kreisel###

Infrared and THz studies of polar phonons and improper magnetodielectric effect in multiferroic BFO3 ceramics. BFO3 ceramics were investigated by means of infrared reflectivity and time
domain THz transmission spectroscopy at temperatures 20 - 950 K, and the
magnetodielectric effect was studied at 10 - 300 K, with the magnetic field up
to 9 T. Below 175 K, the sum of polar phonon contributions into the
permittivity corresponds to the value of measured permittivity below 1 MHz. At
higher temperatures, a giant low-frequency permittivity was observed, obviously
due to the enhanced conductivity and possible Maxwell-Wagner contribution.
Above 200 K the observed magnetodielectric effect is caused essentially through
the combination of magnetoresistance and the Maxwell-Wagner effect, as recently
predicted by Catalan (Appl. Phys. Lett. 88, 102902 (2006)). Since the
magnetodielectric effect does not occur due to a coupling of polarization and
magnetization as expected in magnetoferroelectrics, we call it improper
magnetodielectric effect. Below 175 K the magnetodielectric effect is by
several orders of magnitude lower due to the decreased conductivity. Several
phonons exhibit gradual softening with increasing temperature, which explains
the previously observed high-frequency permittivity increase on heating. The
observed non-complete phonon softening seems to be the consequence of the
first-order nature of the ferroelectric transition.

###Coexisting tuneable fractions of glassy and equilibrium long-range-order phases in manganites|A. Banerjee,A. K. Pramanik,Kranti Kumar,P. Chaddah###

Coexisting tuneable fractions of glassy and equilibrium long-range-order phases in manganites. Antiferromagnetic-insulating(AF-I) and the ferromagnetic-metallic(FM-M)
phases coexist in various half-doped manganites over a range of temperature and
magnetic field, and this is often believed to be an essential ingredient to
their colossal magnetoresistence. We present magnetization and resistivity
measurements on Pr(0.5)Ca(0.5)Mn(0.975)Al(0.025)O(3) and Pr(0.5)Sr(0.5)MnO(3)
showing that the fraction of the two coexisting phases at low-temperature in
any specified measuring field H, can be continuously controlled by following
designed protocols traversing field-temperature space; for both materials the
FM-M fraction rises under similar cooling paths. Constant-field temperature
variations however show that the former sample undergoes a 1st order transition
from AF-I to FM-M with decreasing T, while the latter undergoes the reverse
transition. We suggest that the observed path-dependent phase-separated states
result from the low-T equilibrium phase coexisting with supercooled glass-like
high temperature phase, where the low-T equilibrium phases are actually
homogeneous FM-M and AF-I phases respectively for the two materials.

###Anisotropic magnetic properties of CeAg$_2$Ge$_2$ single crystal|A. Thamizhavel,R. Kulkarni,S. K. Dhar###

Anisotropic magnetic properties of CeAg$_2$Ge$_2$ single crystal. In order to investigate the anisotropic magnetic properties of
CeAg$_2$Ge$_2$, we have successfully grown the single crystals, for the first
time, by high temperature solution growth (flux) method. We have performed a
detailed study of the grown single crystals by measuring their electrical
resistivity, magnetic susceptibility, magnetization, specific heat and
magnetoresistance. A clear anisotropy and an antiferromagnetic transition at
$T_{\rm N}$ = 4.6 K have been observed in the magnetic properties. The magnetic
entropy reaches $R$ ln 4 at 20 K indicating that the ground state and the first
excited state are very closely spaced (a quasi-quartet state). From the
specific heat measurements and crystalline electric field (CEF) analysis of the
magnetic susceptibility, we have found the level splitting energies as 5 K and
130 K. The magnetization measurements reveal that the a-axis is the easy axis
of magnetization and the saturation moment is $\mu_{\rm s}$ = 1.6 $\mu_{\rm
B}$/Ce, corroborating the previous neutron diffraction measurements on a
polycrystalline sample.

###Colossal electroresistance in ferromagnetic insulating state of single crystal Nd$_0.7$Pb$_0.3$MnO$_3$|Himanshu Jain,A. K. Raychaudhuri,Nilotpal Ghosh,H. L. Bhat###

Colossal electroresistance in ferromagnetic insulating state of single crystal Nd$_0.7$Pb$_0.3$MnO$_3$. Colossal electroresistance (CER) has been observed in the ferromagnetic
insulating (FMI) state of a manganite. Notably, the CER in the FMI state occurs
in the absence of magnetoresistance (MR). Measurements of electroresistance
(ER) and current induced resistivity switching have been performed in the
ferromagnetic insulating state of a single crystal manganite of composition
Nd$_0.7$Pb$_0.3$MnO$_3$ (NPMO30). The sample has a paramagnetic to
ferromagnetic (Curie) transition temperature, Tc = 150 K and the ferromagnetic
insulating state is realized for temperatures, T <~ 130 K. The colossal
electroresistance, arising from a strongly nonlinear dependence of resistivity
($\rho$) on current density (j), attains a large value ($\approx 100%$) in the
ferromagnetic insulating state. The severity of this nonlinear behavior of
resistivity at high current densities is progressively enhanced with decreasing
temperature, resulting ultimately, in a regime of negative differential
resistivity (NDR, d$\rho$/dj < 0) for temperatures <~ 25 K. Concomitant with
the build-up of the ER however, is a collapse of the MR to a small value (<
20%) even in magnetic field, H = 7 T. This demonstrates that the mechanisms
that give rise to ER and MR are effectively decoupled in the ferromagnetic
insulating phase of manganites. We establish that, the behavior of
ferromagnetic insulating phase is distinct from the ferromagnetic metallic
(FMM) phase as well as the charge ordered insulating (COI) phase, which are the
two commonly realized ground state phases of manganites.

###Negative Spin Valve effects in manganite/organic based devices|A. Riminucci,I. Bergenti,L. E. Hueso,M. Murgia,C. Taliani,Y. Zhan,F. Casoli,M. P. de Jong,V. Dediu###

Negative Spin Valve effects in manganite/organic based devices. We report detailed investigations of hybrid organic-inorganic vertical spin
valves. Spin polarized injection in tris(8-hydroxyquinoline) aluminum (Alq3)
organic semiconductor (OS) was performed using La0.7Sr0.3MnO3 manganite as the
bottom electrode and Co as the top electrode. While manganite was directly
connected to the organic semiconductor layer, a thin tunnel barrier was placed
between the OS and the Co electrode. A clear negative spin valve effect - low
resistance for antiparallel electrodes configuration - was observed below 210 K
in various devices using two different tunnel barriers: LiF and Al2O3. The
magnetoresistance effect was found to be strongly asymmetric with respect to
the bias voltage. Photoelectron Spectroscopy (PES) investigation of the
interface between manganite and Alq3 revealed a strong interface dipole, which
leads to a better matching of the metal Fermi level with Alq3 LUMO (1.1 eV)
rather than with HOMO level (1.7 eV). This unequivocally indicates that the
current in these devices is dominated by the electron channel, and not by holes
as previously suggested. The knowledge of the energy diagram at the bottom
interface allowed us to work out a semi- quantitative model explaining both
negative spin valve effect and strong voltage asymmetry. This model involves a
sharp energy selection of the moving charges by the very narrow LUMO level of
the organic material leading to peculiar resonant effects.

###Microstructure, magneto-transport and magnetic properties of Gd-doped magnetron-sputtered amorphous carbon|L. Zeng,E. Helgren,F. Hellman,R. Islam,D. J. Smith,J. W. Ager III###

Microstructure, magneto-transport and magnetic properties of Gd-doped magnetron-sputtered amorphous carbon. The magnetic rare earth element gadolinium (Gd) was doped into thin films of
amorphous carbon (hydrogenated \textit{a}-C:H, or hydrogen-free \textit{a}-C)
using magnetron co-sputtering. The Gd acted as a magnetic as well as an
electrical dopant, resulting in an enormous negative magnetoresistance below a
temperature ($T'$). Hydrogen was introduced to control the amorphous carbon
bonding structure. High-resolution electron microscopy, ion-beam analysis and
Raman spectroscopy were used to characterize the influence of Gd doping on the
\textit{a-}Gd$_x$C$_{1-x}$(:H$_y$) film morphology, composition, density and
bonding. The films were largely amorphous and homogeneous up to $x$=22.0 at.%.
As the Gd doping increased, the $sp^{2}$-bonded carbon atoms evolved from
carbon chains to 6-member graphitic rings. Incorporation of H opened up the
graphitic rings and stabilized a $sp^{2}$-rich carbon-chain random network. The
transport properties not only depended on Gd doping, but were also very
sensitive to the $sp^{2}$ ordering. Magnetic properties, such as the spin-glass
freezing temperature and susceptibility, scaled with the Gd concentration.

###Subgap tunneling via quantum-interference effect: insulators and charge density waves|S. Duhot,R. Mélin###

Subgap tunneling via quantum-interference effect: insulators and charge density waves. A quantum interference effect is discussed for subgap tunneling over a
distance comparable to the coherence length, which is a consequence of
``advanced-advanced'' and ``retarded-retarded'' transmission modes [Altland and
Zirnbauer, Phys. Rev. B 55, 1142 (1997)]. Effects typical of disorder are
obtained from the interplay between multichannel averaging and higher order
processes in the tunnel amplitudes. Quantum interference effects similar to
those occurring in normal tunnel junctions explain magnetoresistance
oscillations of a CDW pierced by nanoholes [Latyshev et al., Phys. Rev. Lett.
78, 919 (1997)], having periodicity h/2e as a function of the flux enclosed in
the nanohole. Subgap tunneling is coupled to the sliding motion by charge
accumulation in the interrupted chains. The effect is within the same trend as
random matrix theory for normal metal-CDW hybrids [Visscher et al., Phys. Rev.
B 62, 6873 (2000)]. We suggest that the experiment by Latyshev et al. probes
weak localization-like properties of evanescent quasiparticles, not an
interference effect related to the quantum mechanical ground state.

###Colossal magnetocapacitance and scale-invariant dielectric response in phase-separated manganites|Ryan P. Rairigh,Guneeta Singh-Bhalla,Sefaatin Tongay,Tara Dhakal,Amlan Biswas,Arthur F. Hebard###

Colossal magnetocapacitance and scale-invariant dielectric response in phase-separated manganites. Thin films of strongly-correlated electron materials (SCEM) are often grown
epitaxially on planar substrates and typically have anisotropic properties that
are usually not captured by edge-mounted four-terminal electrical measurements,
which are primarily sensitive to in-plane conduction paths. Accordingly, the
correlated interactions in the out-of-plane (perpendicular) direction cannot be
measured but only inferred. We address this shortcoming and show here an
experimental technique in which the SCEM under study, in our case a 600
Angstrom-thick (La1-yPry)0.67Ca0.33MnO3 (LPCMO) film, serves as the base
electrode in a metal-insulator-metal (MIM) trilayer capacitor structure. This
unconventional arrangement allows for simultaneous determination of colossal
magnetoresistance (CMR) associated with dc transport parallel to the film
substrate and colossal magnetocapacitance (CMC) associated with ac transport in
the perpendicular direction. We distinguish two distinct strain-related
direction-dependent insulator-metal (IM) transitions and use Cole-Cole plots to
establish a heretofore unobserved collapse of the dielectric response onto a
universal scale-invariant power-law dependence over a large range of frequency,
temperature and magnetic field.

###Microwave photoconductivity of a 2D electron gas: Mechanisms and their interplay at high radiation power|I. A. Dmitriev,A. D. Mirlin,D. G. Polyakov###

Microwave photoconductivity of a 2D electron gas: Mechanisms and their interplay at high radiation power. We develop a systematic theory of microwave-induced oscillations in the
magnetoresistivity of a two-dimensional electron gas, focusing on the regime of
strongly overlapping Landau levels. At linear order in microwave power, two
novel mechanisms of the oscillations (``quadrupole'' and ``photovoltaic'') are
identified, in addition to those studied before (``displacement'' and
``inelastic''). The quadrupole and photovoltaic mechanisms are shown to be the
only ones that give rise to oscillations in the nondiagonal part of the
photoconductivity tensor. In the diagonal part, the inelastic contribution
dominates at moderate microwave power, while at elevated power the other
mechanisms become relevant. We demonstrate the crucial role of feedback
effects, which lead to a strong interplay of the four mechanisms in the
nonlinear photoresponse and yield, in particular, a nonmonotonic power
dependence of the photoconductivity, narrowing of the magnetoresonances, and a
nontrivial structure of the Hall photoresponse. At ultrahigh power, all effects
related to the Landau quantization decay due to a combination of the feedback
and multiphoton effects, restoring the classical Drude conductivity.

###Magnetic field induced spin-flop transition in Na$_x$CoO$_2$ (0.5$<$x$<$0.55)|T. Wu,D. F. Fang,G. Y. Wang,L. Zhao,G. Wu,X. G. Luo,C. H. Wang,X. H. Chen###

Magnetic field induced spin-flop transition in Na$_x$CoO$_2$ (0.5$<$x$<$0.55). The isothermal magnetoresistance (MR) with magnetic field (H) parallel to and
perpendicular to ab plane is systematically studied on the single crystal
Na$_{0.52}$CoO$_2$ with charge ordering at $\sim 50$ K and an in-plane
ferromagnetism below 25 K. The isothermal MR behavior with H $\parallel$ ab
plane and H $\perp$ ab plane is quite different. When H $\parallel$ ab plane,
the MR is always negative and the in-plane ferromagnetic behavior is enhanced.
While the MR with H $\perp$ ab plane changes from negative to positive with
decreasing temperature or increasing H, and the in-plane ferromagnetic behavior
is suppressed. A striking feature is that the MR with H $\perp$ ab plane shows
a hysteresis behavior below 25 K, which is absent for the case of H $\parallel$
ab plane. These results provide strong evidence for a spin-flop transition of
small moments of Co$^{3.5-\delta}$ sites induced by H $\perp$ ab plane, leading
to a metamagnetic transition for small moments of Co$^{3.5-\delta}$ sites.
These complex magnetism suggests an unconventional superconductivity in
Na$_x$CoO$_2$ system because the Na$_x$CoO$_2$ around x=0.5 is considered to be
the parent compound of superconductivity.

###Non-saturating magnetoresistance of inhomogeneous conductors: comparison of experiment and simulation|Jingshi Hu,Meera M. Parish,T. F. Rosenbaum###

Non-saturating magnetoresistance of inhomogeneous conductors: comparison of experiment and simulation. The silver chalcogenides provide a striking example of the benefits of
imperfection. Nanothreads of excess silver cause distortions in the current
flow that yield a linear and non-saturating transverse magnetoresistance (MR).
Associated with the large and positive MR is a negative longitudinal MR. The
longitudinal MR only occurs in the three-dimensional limit and thereby permits
the determination of a characteristic length scale set by the spatial
inhomogeneity. We find that this fundamental inhomogeneity length can be as
large as ten microns. Systematic measurements of the diagonal and off-diagonal
components of the resistivity tensor in various sample geometries show clear
evidence of the distorted current paths posited in theoretical simulations. We
use a random resistor network model to fit the linear MR, and expand it from
two to three dimensions to depict current distortions in the third (thickness)
dimension. When compared directly to experiments on Ag$_{2\pm\delta}$Se and
Ag$_{2\pm\delta}$Te, in magnetic fields up to 55 T, the model identifies
conductivity fluctuations due to macroscopic inhomogeneities as the underlying
physical mechanism. It also accounts reasonably quantitatively for the various
components of the resistivity tensor observed in the experiments.

###Magnetization oscillations induced by a spin-polarized current in a point-contact geometry: mode hopping and non-linear damping effects|Dmitri V. Berkov,Natalia L. Gorn###

Magnetization oscillations induced by a spin-polarized current in a point-contact geometry: mode hopping and non-linear damping effects. In this paper we study magnetization excitations induced in a thin extended
film by a spin-polarized dc-current injected through a point contact in the
current-perpendicular-to-plane (CPP) geometry. Using full-scale micromagnetic
simulations, we demonstrate that in addition to the oscillations of the
propagating wave type, there exist also two localized oscillation modes. The
first localized mode has a relatively homogeneous magnetization structure of
its kernel and corresponds to the so called 'bullet' predicted analytically by
Slavin and Tiberkevich (Phys. Rev. Lett., 95 (2005) 237201). Magnetization
pattern of the second localized mode kernel is highly inhomogeneous, leading to
a much smaller power of magnetoresistance oscillations caused by this mode. We
have also studied the influence of a non-linear damping for this system and
have found the following main qualitative effects: (i) the appearance of
frequency jumps within the existence region of the propagating wave mode and
(ii) the narrowing of the current region where the 'bullet' mode exists, until
this mode completely disappears for a sufficiently strong non-linear damping.

###Nonequilibrium spin-dependent phenomena in mesoscopic superconductor-normal metal tunnel structures|F. Giazotto,F. Taddei,P. D'Amico,Rosario Fazio,F. Beltram###

Nonequilibrium spin-dependent phenomena in mesoscopic superconductor-normal metal tunnel structures. We analyze the broad range of spin-dependent nonequilibrium transport
properties of hybrid systems composed of a normal region tunnel coupled to two
superconductors with exchange fields induced by the proximity to thin
ferromagnetic layers and highlight its functionalities. By calculating the
quasiparticle distribution functions in the normal region we find that they are
spin-dependent and strongly sensitive to the relative angle between exchange
fields in the two superconductors. The impact of inelastic collisions on their
properties is addressed. As a result, the electric current flowing through the
system is found to be strongly dependent on the relative angle between exchange
fields, giving rise to a huge value of magnetoresistance. Moreover, the current
presents a complete spin-polarization in a wide range of bias voltages, even in
the quasiequilibrium case. In the nonequilibrium limit we parametrize the
distributions with an ``effective`` temperature, which turns out to be strongly
spin-dependent, though quite sensitive to inelastic collisions. By tunnel
coupling the normal region to an additional superconducting electrode we show
that it is possible to implement a spin-polarized current source of both spin
species, depending on the bias voltages applied.

###Bipolar spintronics: From spin injection to spin-controlled logic|Igor Zutic,Jaroslav Fabian,Steven C. Erwin###

Bipolar spintronics: From spin injection to spin-controlled logic. An impressive success of spintronic applications has been typically realized
in metal-based structures which utilize magnetoresistive effects for
substantial improvements in the performance of computer hard drives and
magnetic random access memories. Correspondingly, the theoretical understanding
of spin-polarized transport is usually limited to a metallic regime in a linear
response, which, while providing a good description for data storage and
magnetic memory devices, is not sufficient for signal processing and digital
logic. In contrast, much less is known about possible applications of
semiconductor-based spintronics and spin-polarized transport in related
structures which could utilize strong intrinsic nonlinearities in
current-voltage characteristics to implement spin-based logic. Here we discuss
the challenges for realizing a particular class of structures in semiconductor
spintronics: our proposal for bipolar spintronic devices in which carriers of
both polarities (electrons and holes) contribute to spin-charge coupling. We
formulate the theoretical framework for bipolar spin-polarized transport, and
describe several novel effects in two- and three-terminal structures which
arise from the interplay between nonequilibrium spin and equilibrium
magnetization.

###Spin-Dependent Ringing and Beats in a Quantum Dot System|Fabricio M. Souza###

Spin-Dependent Ringing and Beats in a Quantum Dot System. We report spin-dependent quantum coherent oscillations (ringing) and beats of
the total and spin currents flowing through a quantum dot with Zeeman split
levels. The spin dependent transport is calculated via nonequilibrium Green
function in the transient after a bias voltage is turned on at t=0. The dot is
coupled to two electrodes that can be ferromagnetic or nonmagnetic. In the
ferromagnetic case both parallel and antiparallel alignments are considered.
The coherent oscillation and beat frequencies are controlled via the Zeeman
energy E_Z. In particular, for E_Z=0 no beats are observed and the spin current
is zero for nonmagnetic leads. In the ferromagnetic case a finite spin current
is found for E_Z=0. The effects of temperature are also analyzed. We observe
that with increasing temperature the ringing response and the beats tend to
disappear. Additionally, the spin current goes to zero for nonmagnetic leads,
remaining finite in the ferromagnetic case. The tunnel magnetoresistance (TMR)
also reveals quantum coherent oscillations and beats, and it attains negative
values for small enough temperatures and short times.

###KCrF_3: Electronic Structure, Magnetic and Orbital Ordering from First Principles|Gianluca Giovannetti,Serena Margadonna,Jeroen van den Brink###

KCrF_3: Electronic Structure, Magnetic and Orbital Ordering from First Principles. The electronic, magnetic and orbital structures of KCrF_3 are determined in
all its recently identified crystallographic phases (cubic, tetragonal, and
monoclinic) with a set of {\it ab initio} LSDA and LSDA+U calculations. The
high-temperature undistorted cubic phase is metallic within the LSDA, but at
the LSDA+U level it is a Mott insulator with a gap of 1.72 eV. The tetragonal
and monoclinic phases of KCrF_3 exhibit cooperative Jahn-Teller distortions
concomitant with staggered 3x^2-r^2/3y^2-r^2 orbital order. We find that the
energy gain due to the Jahn-Teller distortion is 82/104 meV per chromium ion in
the tetragonal/monoclinic phase, respectively. These phases show A-type
magnetic ordering and have a bandgap of 2.48 eV. In this Mott insulating state
KCrF_3 has a substantial conduction bandwidth of 2.1 eV, leading to the
possibility for the kinetic energy of charge carriers in electron- or
hole-doped derivatives of KCrF_3 to overcome the polaron localization at low
temperatures, in analogy with the situation encountered in the colossal
magnetoresistive manganites.

###A model for the study of the Shubnikov-de Haas and the integer quantum Hall effects in a two dimensional electronic system|M. A. Hidalgo R. Cangas###

A model for the study of the Shubnikov-de Haas and the integer quantum Hall effects in a two dimensional electronic system. Up to know all the experimental results concerning the integer and fractional
quantum Hall effect are related to semiconductor heterostructures (and more
recently with graphene). The common characteristic of all these systems is the
presence of a reservoir of electrons, which, in fact, in the initial stage is
the source of the electrons, providing the two-dimensional electron gas (2DES).
Then, any physical realization of a 2DES is necessarily embedded in a 3D
structure, which establishes the Fermi level. Hence, the 2DES appears to be an
open system. In this paper we present an analytical approach to the integer
quantum Hall effect (IQHE) and the Shubnikov-de Haas (SdH) phenomena in the
2DES, basing us in fundamental principles and showing the secondary role of the
localized electron states in both phenomena. In fact, we show that the IQHE is
a consequence of the fluctuations of electrons in the 2DES. Once we obtain the
density of states of the 2DES under the application of a magnetic field we
calculate both magnetoconductivities (diagonal and Hall) deducing them from the
Boltzman semiclassical equation. The model proposed reproduces both phenomena,
the width of the Hall plateaus (with the precision reached in the experimental
measurements, of the order of 10-8-10-9) and the corresponding minima of the
diagonal magnetoresistivity, and also the dependence with temperature of the
IQHE and SdH.

###The anomalous Hall Effect and magnetoresistance in the layered ferromagnet Fe_{1/4}TaS_2: the inelastic regime|J. G. Checkelsky,Minhyea Lee,E. Morosan,R. J. Cava,N. P. Ong###

The anomalous Hall Effect and magnetoresistance in the layered ferromagnet Fe_{1/4}TaS_2: the inelastic regime. The large magnetic anisotropy in the layered ferromagnet Fe_{1/4}TaS_2 leads
to very sharp reversals of the magnetization $\bf M$ at the coercive field. We
have exploited this feature to measure the anomalous Hall effect (AHE),
focussing on the AHE conductivity $\sigma^A_{xy}$ in the inelastic regime. At
low temperature T (5-50 K), $\sigma^A_{xy}$ is T-independent, consistent with
the Berry-phase/Karplus-Luttinger theory. Above 50 K, we extract an inelastic
AHE conductivity $\sigma^{in}_{xy}$ that scales as the square of $\Delta\rho$
(the T dependent part of the resistivity $\rho$). The term $\sigma^{in}_{xy}$
clarifies the T dependence and sign-reversal of the AHE coefficient R_s(T). We
discuss the possible ubiquity of $\sigma^{in}_{xy}$ in ferromagnets, and ideas
for interpreting its scaling with $(\Delta\rho)^2$. Measurements of the
magnetoresistance (MR) reveal a rich pattern of behavior vs. T and field
tilt-angle. We show that the 2 mechanisms, the anisotropic MR effect and
field-suppression of magnons, account for the intricate MR behavior, including
the bow-tie features caused by the sharp reversals in $\bf M$.

###Relationship between macroscopic physical properties and local distortions of low doping La{1-x}Ca{x}MnO3: an EXAFS study|Y. Jiang,F. Bridges,L. Downward,J. J. Neumeier###

Relationship between macroscopic physical properties and local distortions of low doping La{1-x}Ca{x}MnO3: an EXAFS study. A temperature-dependent EXAFS investigation of La{1-x}Ca{x}MnO3 is presented
for the concentration range that spans the ferromagnetic-insulator (FMI) to
ferromagnetic-metal (FMM) transition region, x = 0.16-0.22. The samples are
insulating for x = 0.16-0.2 and show a metal/insulator transition for x = 0.22.
All samples are ferromagnetic although the saturation magnetization for the 16%
Ca sample is only ~ 70% of the expected value at 0.4T. We find that the FMI
samples have similar correlations between changes in the local Mn-O distortions
and the magnetization as observed previously for the colossal magnetoresistance
(CMR) samples (0.2 < x < 0.5) - except that the FMI samples never become fully
magnetized. The data show that there are at least two distinct types of
distortions. The initial distortions removed as the insulating sample becomes
magnetized are small and provides direct evidence that roughly 50% of the Mn
sites have a small distortion/site and are magnetized first. The large
remaining Mn-O distortions at low T are attributed to a small fraction of
Jahn-Teller-distorted Mn sites that are either antiferromagnetically ordered or
unmagnetized. Thus the insulating samples are very similar to the behavior of
the CMR samples up to the point at which the M/I transition occurs for the CMR
materials. The lack of metallic conductivity for x <= 0.2, when 50% or more of
the sample is magnetic, implies that there must be preferred magnetized Mn
sites and that such sites do not percolate at these concentrations.

###Local atomic arrangement and martensitic transformation in Ni$_{50}$Mn$_{35}$In$_{15}$: An EXAFS Study|P. A. Bhobe,K. R. Priolkar,P. R. Sarode###

Local atomic arrangement and martensitic transformation in Ni$_{50}$Mn$_{35}$In$_{15}$: An EXAFS Study. Heusler alloys that undergo martensitic transformation in ferromagnetic state
are of increasing scientific and technological interest. These alloys show
large magnetic field induced strains upon martensitic phase change thus making
it a potential candidate for magneto-mechanical actuation. The crystal
structure of martensite is an important factor that affects both the magnetic
anisotropy and mechanical properties of such materials. Moreover, the local
chemical arrangement of constituent atoms is vital in determining the overall
physical properties. Ni$_{50}$Mn$_{35}$In$_{15}$ is one such ferromagnetic
shape memory alloy that displays exotic properties like large magnetoresistance
at moderate field values. In this work, we present the extended x-ray
absorption fine-structure measurements (EXAFS) on the bulk
Ni$_{50}$Mn$_{35}$In$_{15}$ which reveal the local structural change that
occurs upon phase transformation. The change in the bond lengths between
different atomic species helps in understanding the type of hybridization which
is an important factor in driving such Ni-Mn based systems towards martensitic
transformation.

###Non-gapped Fermi surfaces, quasiparticles and the anomalous temperature dependence of the near-$E_F$ electronic states in the CMR oxide La$_{2-2x}$Sr$_{1+2x}$Mn$_2$O$_7$ with $x=0.36$|S. de Jong,Y. Huang,I. Santoso,F. Massee,R. Follath,O. Schwarzkopf,L. Patthey,M. Shi,M. S. Golden###

Non-gapped Fermi surfaces, quasiparticles and the anomalous temperature dependence of the near-$E_F$ electronic states in the CMR oxide La$_{2-2x}$Sr$_{1+2x}$Mn$_2$O$_7$ with $x=0.36$. After years of research into colossal magnetoresistant (CMR) manganites using
bulk techniques, there has been a recent upsurge in experiments directly
probing the electronic states at or near the surface of the bilayer CMR
materials La$_{2-2x}$Sr$_{1+2x}$Mn$_2$O$_7$ using angle-resolved photoemission
or scanning probe microscopy. Here we report new, temperature dependent, angle
resolved photoemission data from single crystals with a doping level of
$x=0.36$. The first important result is that there is no sign of a pseudogap in
the charge channel of this material for temperatures below the Curie
temperature $T_C$. The second important result concerns the temperature
dependence of the electronic states. The temperature dependent changes in the
Fermi surface spectra both at the zone face and zone diagonal regions in
$k$-space indicate that the coherent quasiparticle weight disappears for
temperatures significantly above $T_C$, and that the $k$-dependence of the
T-induced changes in the spectra invalidate an interpretation of these data in
terms of the superposition of a `universal' metallic spectrum and an insulating
spectrum whose relative weight changes with temperature. In this sense, our
data are not compatible with a phase separation scenario.

###Optical phase diagram of perovskite-type colossal magnetoresistance manganites with near-half doping|I. Kezsmarki,Y. Tomioka,S. Miyasaka,L. Demko,Y. Okimoto,Y. Tokura###

Optical phase diagram of perovskite-type colossal magnetoresistance manganites with near-half doping. We present a systematic optical study for a bandwidth-controlled series of
nearly half doped colossal magnetoresistive manganites
RE$_{0.55}$AE$_{0.45}$MnO$_3$ (RE and AE being rare earth and alkaline earth
ions, respectively) under the presence of quenched disorder over a broad
temperature region $T=10-800$ K. The ground state of the compounds ranges from
the charge and orbital ordered insulator through the spin glass to the
ferromagnetic metal. The enhanced phase fluctuations, namely the short-range
charge and orbital correlations dominate the paramagnetic region of the phase
diagram above all the ground-state phases. This paramagnetic region is
characterized by a full-gap to pseudo-gap crossover towards elevated
temperatures where a broad low-energy electronic structure appears in the
conductivity spectra over a large variation of the bandwidth. This pseudo-gap
state with local correlations is robust against thermal fluctuations at least
up to T=800 K. For small bandwidth the onset of the long-range charge order is
accompanied by an instantaneous increase of the gap. The emergence of the
ferromagnetic state is manifested in the optical spectra as a first-order
insulator to metal transition for compounds with moderate bandwidth while it
becomes a second-order transition on the larger bandwidth side. Unusually large
scattering rate of the metallic carriers is observed in the ferromagnetic state
which is attributed to orbital correlation with probably rod-like
($3z^2-r^2$-like) character.

###Interplay of structure and spin-orbit strength in magnetism of metal-benzene sandwiches: from single molecules to infinite wires|Y. Mokrousov,N. Atodiresei,G. Bihlmayer,S. Heinze,S. Blügel###

Interplay of structure and spin-orbit strength in magnetism of metal-benzene sandwiches: from single molecules to infinite wires. Based on first-principles density functional theory calculations we explore
electronic and magnetic properties of experimentally producible sandwiches and
infinite wires made of repeating benzene molecules and transition-metal atoms
of V, Nb, and Ta. We describe the bonding mechanism in the molecules and in
particular concentrate on the origin of magnetism in these structures. We find
that all the considered systems have sizable magnetic moments and ferromagnetic
spin-ordering, with the single exception of the V3-Bz4 molecule. By including
the spin-orbit coupling into our calculations we determine the easy and hard
axes of the magnetic moment, the strength of the uniaxial magnetic anisotropy
energy (MAE), relevant for the thermal stability of magnetic orientation, and
the change of the electronic structure with respect to the direction of the
magnetic moment, important for spin-transport properties. While for the V-based
compounds the values of the MAE are only of the order of 0.05-0.5 meV per metal
atom, increasing the spin-orbit strength by substituting V with heavier Nb and
Ta allows to achieve an increase in anisotropy values by one to two orders of
magnitude. The rigid stability of magnetism in these compounds together with
the strong ferromagnetic ordering makes them attractive candidates for
spin-polarized transport applications. For a Nb-benzene infinite wire the
occurrence of ballistic anisotropic magnetoresistance is demonstrated.

###Searching for hexagonal analogues of the half-metallic half-Heusler XYZ compounds|Frederick Casper,Claudia Felser,Ram Seshadri,C. Peter Sebastian,Rainer Poettgen###

Searching for hexagonal analogues of the half-metallic half-Heusler XYZ compounds. The XYZ half-Heusler crystal structure can conveniently be described as a
tetrahedral zinc blende YZ structure which is stuffed by a slightly ionic X
species. This description is well suited to understand the electronic structure
of semiconducting 8-electron compounds such as LiAlSi (formulated
Li$^+$[AlSi]$^-$) or semiconducting 18-electron compounds such as TiCoSb
(formulated Ti$^{4+}$[CoSb]$^{4-}$). The basis for this is that [AlSi]$^-$
(with the same electron count as Si$_2$) and [CoSb]$^{4-}$ (the same electron
count as GaSb), are both structurally and electronically, zinc-blende
semiconductors. The electronic structure of half-metallic ferromagnets in this
structure type can then be described as semiconductors with stuffing magnetic
ions which have a local moment: For example, 22 electron MnNiSb can be written
Mn$^{3+}$[NiSb]$^{3-}$. The tendency in the 18 electron compound for a
semiconducting gap -- believed to arise from strong covalency -- is carried
over in MnNiSb to a tendency for a gap in one spin direction. Here we similarly
propose the systematic examination of 18-electron hexagonal compounds for
semiconducting gaps; these would be the "stuffed wurtzite" analogues of the
"stuffed zinc blende" half-Heusler compounds. These semiconductors could then
serve as the basis for possibly new families of half-metallic compounds,
attained through appropriate replacement of non-magnetic ions by magnetic ones.
These semiconductors and semimetals with tunable charge carrier concentrations
could also be interesting in the context of magnetoresistive and thermoelectric
materials.

###Anomalous Transport Phenomena in Fermi Liquids with Strong Magnetic Fluctuations|Hiroshi Kontani###

Anomalous Transport Phenomena in Fermi Liquids with Strong Magnetic Fluctuations. In many strongly correlated electron systems, remarkable violation of the
relaxation time approximation (RTA) is observed. The most famous example would
be high-Tc superconductors (HTSCs), and similar anomalous transport phenomena
have been observed in metals near their antiferromagnetic (AF) quantum critical
point (QCP). Here, we develop a transport theory involving resistivity and Hall
coefficient on the basis of the microscopic Fermi liquid theory, by considering
the current vertex correction (CVC). In nearly AF Fermi liquids, the CVC
accounts for the significant enhancements in the Hall coefficient,
magnetoresistance, thermoelectric power, and Nernst coefficient in nearly AF
metals. According to the numerical study, aspects of anomalous transport
phenomena in HTSC are explained in a unified way by considering the CVC,
without introducing any fitting parameters; this strongly supports the idea
that HTSCs are Fermi liquids with strong AF fluctuations. In addition, the
striking \omega-dependence of the AC Hall coefficient and the remarkable
effects of impurities on the transport coefficients in HTSCs appear to fit
naturally into the present theory. The present theory also explains very
similar anomalous transport phenomena occurring in CeCoIn5 and CeRhIn5, which
is a heavy-fermion system near the AF QCP, and in the organic superconductor
\kappa-(BEDT-TTF).

###Quantum effects in atomically perfect specular spin valve structures|J. M. Teixeira,J. Ventura,Yu. G. Pogorelov,J. B. Sousa###

Quantum effects in atomically perfect specular spin valve structures. A simple tight-binding theoretical model is proposed for spin dependent,
current-in-plane transport in highly coherent spin valve structures under
specularity conditions. Using quantum-mechanically coherent and spatially
quantized Fermi states in the considered multilayered system, a system of
partial Boltzmann kinetic equations is built for relevant subbands to yield the
expressions for conductance in parallel or antiparallel spin valve states and
thus for the magneto-conductance. It is shown that specularity favors the
magnetoresistance to reach its theoretical maximum for this structure close to
100%. This result is practically independent of the model parameters, in
particular it does not even need that lifetimes of majority and minority
carriers be different (as necessary for the quasiclassical regimes). The main
MR effect in the considered limit is due to the transformation of coherent
quantum states, induced by the relative rotation of magnetization in the FM
layers. Numerical calculation based on the specific Boltzmann equation with an
account of spin-dependent specular reflection at the interfaces is also
performed for a typical choice of material parameters.

###Transport in the metallic regime of Mn doped III-V Semiconductors|Louis-Francois Arsenault,B. Movaghar,P. Desjardins,A. Yelon###

Transport in the metallic regime of Mn doped III-V Semiconductors. The standard model of Mn doping in GaAs is subjected to a coherent potential
approximation (CPA) treatment. Transport coefficients are evaluated within the
linear response Kubo formalism. Both normal (NHE) and anomalous contributions
(AHE) to the Hall effect are examined. We use a simple model density of states
to describe the undoped valence band. The CPA bandstructure evolves into a spin
split band caused by the $p-d$ exchange scattering with Mn dopants. This gives
rise to a strong magnetoresistance, which decreases sharply with temperature.
The temperature ($T$) dependence of the resistance is due to spin disorder
scattering (increasing with $T$), CPA bandstructure renormalization and charged
impurity scattering (decreasing with $T$). The calculated transport
coefficients are discussed in relation to experiment, with a view of assessing
the overall trends and deciding whether the model describes the right physics.
This does indeed appear to be case, bearing in mind that the hopping limit
needs to be treated separately, as it cannot be described within the band CPA.

###Bandstructure meets many-body theory: The LDA+DMFT method|K. Held,O. K. Andersen,M. Feldbacher,A. Yamasaki,Y. -F. Yang###

Bandstructure meets many-body theory: The LDA+DMFT method. Ab initio calculation of the electronic properties of materials is a major
challenge for solid state theory. Whereas the experience of forty years has
proven density functional theory (DFT) in a suitable, e.g. local approximation
(LDA) to give a satisfactory description in case electronic correlations are
weak, materials with strongly correlated, say d- or f-electrons remain a
challenge. Such materials often exhibit colossal responses to small changes of
external parameters such as pressure, temperature, and magnetic field, and are
therefore most interesting for technical applications.
  Encouraged by the success of dynamical mean field theory (DMFT) in dealing
with model Hamiltonians for strongly correlated electron systems, physicists
from the bandstructure and many-body communities have joined forces and have
developed a combined LDA+DMFT method for treating materials with strongly
correlated electrons ab initio. As a function of increasing Coulomb
correlations, this new approach yields a weakly correlated metal, a strongly
correlated metal, or a Mott insulator.
  In this paper, we introduce the LDA+DMFT by means of an example, LaMnO_3 .
Results for this material, including the colossal magnetoresistance of doped
manganites are presented. We also discuss advantages and disadvantages of the
LDA+DMFT approach.

###Magnetoresistance behavior of a ferromagnetic shape memory alloy: Ni_1.75Mn_1.25Ga|S. Banik,R. Rawat,P. K. Mukhopadhyay,B. L. Ahuja,Aparna Chakrabarti,P. L. Paulose,S. Singh,A. K. Singh,D. Pandey,S. R. Barman###

Magnetoresistance behavior of a ferromagnetic shape memory alloy: Ni_1.75Mn_1.25Ga. A negative-positive-negative switching behavior of magnetoresistance (MR)
with temperature is observed in a ferromagnetic shape memory alloy
Ni_1.75Mn_1.25Ga. In the austenitic phase between 300 and 120 K, MR is negative
due to s-d scattering. Curiously, below 120K MR is positive, while at still
lower temperatures in the martensitic phase, MR is negative again. The positive
MR cannot be explained by Lorentz contribution and is related to a magnetic
transition. Evidence for this is obtained from ab initio density functional
theory, a decrease in magnetization and resistivity upturn at 120 K. Theory
shows that a ferrimagnetic state with anti-ferromagnetic alignment between the
local magnetic moments of the Mn atoms is the energetically favoured ground
state. In the martensitic phase, there are two competing factors that govern
the MR behavior: a dominant negative trend up to the saturation field due to
the decrease of electron scattering at twin and domain boundaries; and a weaker
positive trend due to the ferrimagnetic nature of the magnetic state. MR
exhibits a hysteresis between heating and cooling that is related to the first
order nature of the martensitic phase transition.

###Enhanced annealing, high Curie temperature and low-voltage gating in (Ga,Mn)As: A surface oxide control study|K. Olejnik,M. H. S. Owen,V. Novak,J. Masek,A. C. Irvine,J. Wunderlich,T. Jungwirth###

Enhanced annealing, high Curie temperature and low-voltage gating in (Ga,Mn)As: A surface oxide control study. (Ga,Mn)As and related diluted magnetic semiconductors play a major role in
spintronics research because of their potential to combine ferromagnetism and
semiconducting properties in one physical system. Ferromagnetism requires
~1-10% of substitutional Mn_Ga. Unintentional defects formed during growth at
these high dopings significantly suppress the Curie temperature. We present
experiments in which by etching the (Ga,Mn)As surface oxide we achieve a
dramatic reduction of annealing times necessary to optimize the ferromagnetic
film after growth, and report Curie temperature of 180 K at approximately 8% of
Mn_Ga. Our study elucidates the mechanism controlling the removal of the most
detrimental, interstitial Mn defect. The limits and utility of electrical
gating of the highly-doped (Ga,Mn)As semiconductor are not yet established; so
far electric-field effects have been demonstrated on magnetization with tens of
Volts applied on a top-gate, field effect transistor structure. In the second
part of the paper we present a back-gate, n-GaAs/AlAs/GaMnAs transistor
operating at a few Volts. Inspired by the etching study of (Ga,Mn)As films we
apply the oxide-etching/re-oxidation procedure to reduce the thickness (arial
density of carriers) of the (Ga,Mn)As and observe a large enhancement of the
gating efficiency. We report gatable spintronic characteristics on a series of
anisotropic magnetoresistance measurements.

###Small angle neutron scattering study of the step-like magnetic transformation in Pr0.70Ca0.30MnO3|D. Saurel,Ch. Simon,A. Brulet,A. Heinemann,C. Martin###

Small angle neutron scattering study of the step-like magnetic transformation in Pr0.70Ca0.30MnO3. Small angle neutron scattering (SANS) magnetic and electrical transport
measurements were performed to study a single crystal of Pr0.7Ca0.3MnO3, a
colossal magnetoresistive (CMR) material. While the magnetic field induced
transformation of this phase separated compound consisting of an
antiferromagnetic insulating phase (AFI) and a ferromagnetic insulating phase
(FI), is continuous at high temperature (above 5K), at lower temperature a step
like transformation is observed (around 5T at 2K). Macroscopic magnetization
measurements and SANS indicate that this transformation occurs by the formation
of mesoscopic ferromagnetic metallic (FM) domains in the AFI phase, and,
eventually, in the FI phase. Although above 5K this transformation is
continuous, below 5K a magnetization step marks the abrupt transition from a
large scale FI/AFI phase separation to a large scale phase separation between
AFI, FI and FM phases. Our results suggest that relaxation of elastic strains
inherent to the coexistence of these different phases plays a crucial role in
the mechanism of these transformations. The occurrence of magnetization steps
could result from an intrinsic behavior of the AFI phase at low temperature.

###Study of Short-distance Spin and Charge Correlations and Local Density-of-States in the CMR regime of the One-Orbital Model for Manganites|Rong Yu,Shuai Dong,Cengiz Sen,Gonzalo Alvarez,Elbio Dagotto###

Study of Short-distance Spin and Charge Correlations and Local Density-of-States in the CMR regime of the One-Orbital Model for Manganites. The metal-insulator transition, and the associated magnetic transition, in
the colossal magnetoresistance (CMR) regime of the one-orbital model for
manganites is here studied using Monte Carlo (MC) techniques. Both cooperative
oxygen lattice distortions and a finite superexchange coupling among the
$t_{\rm 2g}$ spins are included in our investigations. Charge and spin
correlations are studied. In the CMR regime, a strong competition between the
ferromagnetic metallic and antiferromagnetic charge-ordered insulating states
is observed. This competition is shown to be important to understand the
resistivity peak that appears near the critical temperature. Moreover, it is
argued that the system is dynamically inhomogeneous, with short-range charge
and spin correlations that slowly evolve with MC time, producing the glassy
characteristics of the CMR state. The local density-of-states (LDOS) is also
investigated, and a pseudogap (PG) is found to exist in the CMR temperature
range. The width of the PG in the LDOS is calculated and directly compared with
recent scanning-tunneling-spectroscopy (STS) experimental results. The
agreement between our calculation and the experiment suggests that the
depletion of the conductance at low bias observed experimentally is a
reflection on the existence of a PG in the LDOS spectra, as opposed to a hard
gap. The apparent homogeneity observed via STS techniques could be caused by
the slow time characteristics of this probe. Faster experimental methods should
unveil a rather inhomogeneous state in the CMR regime, as already observed in
neutron scattering experiments.

###Piezo-control of magnetic anisotropy in GaMnAs: Reversible manipulation of magnetization orientation and irreversible magnetization switching|C. Bihler,M. Althammer,A. Brandlmaier,S. Gepraegs,M. Weiler,M. Opel,W. Schoch,W. Limmer,R. Gross,M. S. Brandt,S. T. B. Goennenwein###

Piezo-control of magnetic anisotropy in GaMnAs: Reversible manipulation of magnetization orientation and irreversible magnetization switching. We have investigated the magnetic properties of a piezoelectric
actuator/ferromagnetic semiconductor hybrid structure. Using a GaMnAs epilayer
as the ferromagnetic semiconductor and applying the piezo-stress along its
[110] direction, we quantify the magnetic anisotropy as a function of the
voltage V_p applied to the piezoelectric actuator using anisotropic
magnetoresistance techniques. We find that the easy axis of the strain-induced
uniaxial magnetic anisotropy contribution can be inverted from the [110] to the
[1-10] direction via the application of appropriate voltages V_p. At T=5K the
magnetoelastic term is a minor contribution to the magnetic anisotropy.
Nevertheless, we show that the switching fields of rho(H) loops are shifted as
a function of V_p at this temperature. At 50K - where the magnetoelastic term
dominates the magnetic anisotropy - we are able to tune the magnetization
orientation by about 70 degree solely by means of the electrical voltage V_p
applied. Furthermore, we derive the magnetostrictive constant lambda_111 as a
function of temperature and find values consistent with earlier results. We
argue that the piezo-voltage control of magnetization orientation is directly
transferable to other ferromagnetic/piezoelectric hybrid structures, paving the
way to innovative multifunctional device concepts. As an example, we
demonstrate piezo-voltage induced irreversible magnetization switching at
T=40K, which constitutes the basic principle of a nonvolatile memory element.

###Electrical transport and ferromagnetism in Ga1-xMnxAs synthesized by ion implantation and pulsed-laser melting|M. A. Scarpulla,R. Farshchi,P. R. Stone,R. V. Chopdekar,K. M. Yu,Y. Suzuki,O. D. Dubon###

Electrical transport and ferromagnetism in Ga1-xMnxAs synthesized by ion implantation and pulsed-laser melting. We present a detailed investigation of the magnetic and magnetotransport
properties of thin films of ferromagnetic Ga1-xMnxAs synthesized using ion
implantation and pulsed-laser melting (II-PLM). The field and
temperature-dependent magnetization, magnetic anisotropy, temperature-dependent
resistivity, magnetoresistance, and Hall effect of II-PLM Ga1-xMnxAs films have
all of the characteristic signatures of the strong p-d interaction of holes and
Mn ions observed in the dilute hole-mediated ferromagnetic phase. The
ferromagnetic and electrical transport properties of II-PLM films correspond to
the peak substitutional Mn concentration meaning that the non-uniform Mn depth
distribution is unimportant in determining the film properties. Good
quantitative agreement is found with films grown by low temperature molecular
beam epitaxy (LT-MBE) and having the similar substitutional Mn_Ga composition.
Additionally, we demonstrate that II-PLM Ga1-xMnxAs films are free from
interstitial Mn_I because of the high temperature processing. At high Mn
implantation doses the kinetics of solute redistribution during solidification
alone determine the maximum resulting Mn_Ga concentration. Uniaxial anisotropy
between in-plane [-110]and [110] directions is present in II-PLM Ga1-xMnxAs
giving evidence for this being an intrinsic property of the carrier-mediated
ferromagnetic phase.

###Anisotropic scattering in angular-dependent magnetoresistance oscillations of quasi-2D and quasi-1D metals: beyond the relaxation-time approximation|M. F. Smith,Ross McKenzie###

Anisotropic scattering in angular-dependent magnetoresistance oscillations of quasi-2D and quasi-1D metals: beyond the relaxation-time approximation. The electrical resistivity for a current moving perpendicular to layers
(chains) in quasi-2D (quasi-1D) metals under an applied magnetic field of
varying orientation is studied using Boltzmann transport theory. We consider
the simplest non-trivial quasi-2D and quasi-1D Fermi surfaces but allow for an
arbitrary elastic collision integral (i.e., a scattering probability with
arbitrary dependence on momentum-transfer) and obtain an expression for the
resistivity which generalizes that previously found using a single
relaxation-time approximation. The dependence of the resistivity on the angle
between the magnetic field and current changes depending on the
momentum-dependence of the scattering probability. So, whereas zero-field
intra-layer transport is sensitive only to the momentum-averaged scattering
probability (the transport relaxation rate) the resistivity perpendicular to
layers measured in a tilted magnetic field provides detailed information about
the momentum-dependence of interlayer scattering. These results help clarify
the meaning of the relaxation rate determined from fits of angular-dependent
magnetoresistance oscillations (AMRO) experimental data to theoretical
expressions. Furthermore, we suggest how AMRO might be used to probe the
dominant scattering mechanism.

###Modeling of Spin Metal-Oxide-Semiconductor Field-Effect-Transistor: A Non-Equilibrium Green's Function Approach with Spin Relaxation|Tony Low,Mark S. Lundstrom,Dmitri E. Nikonov###

Modeling of Spin Metal-Oxide-Semiconductor Field-Effect-Transistor: A Non-Equilibrium Green's Function Approach with Spin Relaxation. A spin metal-oxide-semiconductor field-effect-transistor (spin MOSFET), which
combines a Schottky-barrier MOSFET with ferromagnetic source and drain
contacts, is a promising device for spintronic logic. Previous simulation
studies predict that this device should display a very high magnetoresistance
(MR) ratio (between the cases of parallel and anti-parallel magnetizations) for
the case of half-metal ferromagnets (HMF). We use the non-equilibrium Green's
function (NEGF) formalism to describe tunneling and carrier transport in this
device and to incorporate spin relaxation at the HMF-semiconductor interfaces.
Spin relaxation at interfaces results in non-ideal spin injection. Minority
spin currents arise and dominate the leakage current for anti-parallel
magnetizations. This reduces the MR ratio and sets a practical limit for spin
MOSFET performance. We found that MR saturates at a lower value for smaller
source-to-drain bias. In addition, spin relaxation at the detector side is
found to be more detrimental to MR than that at the injector side, for drain
bias less than the energy difference of the minority spin edge and the Fermi
level.

###Large Magnetoresistance of a Dilute $p$-Si/SiGe/Si Quantum Well in a Parallel Magnetic Field|I. L. Drichko,I. Yu. Smirnov,A. V. Suslov,O. A. Mironov,D. R. Leadley###

Large Magnetoresistance of a Dilute $p$-Si/SiGe/Si Quantum Well in a Parallel Magnetic Field. We report the results of an experimental study of the magnetoresistance
$\rho_{xx}$ in two samples of $p$-Si/SiGe/Si with low carrier concentrations
$p$=8.2$\times10^{10}$ cm$^{-2}$ and $p$=2$\times10^{11}$ cm$^{-2}$. The
research was performed in the temperature range of 0.3-2 K in the magnetic
fields of up to 18 T, parallel to the two-dimensional (2D) channel plane at two
orientations of the in-plane magnetic field $B_{\parallel}$ against the current
$I$: $B_{\parallel} \perp I$ and $B_{\parallel} \parallel I$. In the sample
with the lowest density in the magnetic field range of 0-7.2 T the temperature
dependence of $\rho_{xx}$ demonstrates the metallic characteristics ($d
\rho_{xx}/dT>$0). However, at $B_{\parallel}$ =7.2 T the derivative $d
\rho_{xx}/dT$ reverses the sign. Moreover, the resistance depends on the
current orientation with respect to the in-plane magnetic field. At
$B_{\parallel} \cong$ 13 T there is a transition from the dependence
$\ln(\Delta\rho_{xx} / \rho_{0})\propto B_{\parallel}^2$ to the dependence
$\ln(\Delta\rho_{xx} / \rho_{0})\propto B_{\parallel}$. The observed effects
can be explained by the influence of the in-plane magnetic field on the orbital
motion of the charge carriers in the quasi-2D system.

###Localization and the Anomalous Hall Effect in a "Dirty" Metallic Ferromagnet|P. Mitra,N. Kumar,N. Samarth###

Localization and the Anomalous Hall Effect in a "Dirty" Metallic Ferromagnet. We report magnetoresistance measurements over an extensive temperature range
(0.1 K $\leq T \leq$ 100 K) in a disordered ferromagnetic semiconductor (\gma).
The study focuses on a series of metallic \gma~ epilayers that lie in the
vicinity of the metal-insulator transition ($k_F l_e\sim 1$). At low
temperatures ($T < 4$ K), we first confirm the results of earlier studies that
the longitudinal conductivity shows a $T^{1/3}$ dependence, consistent with
quantum corrections from carrier localization in a ``dirty'' metal. In
addition, we find that the anomalous Hall conductivity exhibits universal
behavior in this temperature range, with no pronounced quantum corrections. We
argue that observed scaling relationship between the low temperature
longitudinal and transverse resistivity, taken in conjunction with the absence
of quantum corrections to the anomalous Hall conductivity, is consistent with
the side-jump mechanism for the anomalous Hall effect. In contrast, at high
temperatures ($T \gtrsim 4$ K), neither the longitudinal nor the anomalous Hall
conductivity exhibit universal behavior, indicating the dominance of inelastic
scattering contributions down to liquid helium temperatures.

###Correlation between microstructure and magnetotransport in organic semiconductor spin valve structures|Yaohua Liu,Shannon M. Watson,Taegweon Lee,Justin M. Gorham,Howard E. Katz,Julie A. Borchers,Howard D. Fairbrother,Daniel H. Reich###

Correlation between microstructure and magnetotransport in organic semiconductor spin valve structures. We have studied magnetotransport in organic-inorganic hybrid multilayer
junctions. In these devices, the organic semiconductor (OSC) Alq$_3$
(tris(8-hydroxyquinoline) aluminum) formed a spacer layer between ferromagnetic
(FM) Co and Fe layers. The thickness of the Alq$_3$ layer was in the range of
50-150 nm. Positive magnetoresistance (MR) was observed at 4.2 K in a current
perpendicular to plane geometry, and these effects persisted up to room
temperature. The devices' microstructure was studied by X-ray reflectometry,
Auger electron spectroscopy and polarized neutron reflectometry (PNR). The
films show well-defined layers with modest average chemical roughness (3-5 nm)
at the interface between the Alq$_3$ and the surrounding FM layers.
Reflectometry shows that larger MR effects are associated with smaller
FM/Alq$_3$ interface width (both chemical and magnetic) and a magnetically dead
layer at the Alq$_3$/Fe interface. The PNR data also show that the Co layer,
which was deposited on top of the Alq$_3$, adopts a multi-domain magnetic
structure at low field and a perfect anti-parallel state is not obtained. The
origins of the observed MR are discussed and attributed to spin coherent
transport. A lower bound for the spin diffusion length in Alq$_3$ was estimated
as $43 \pm 5$ nm at 80 K. However, the subtle correlations between
microstructure and magnetotransport indicate the importance of interfacial
effects in these systems.

###Synthesis, structural and transport properties of the hole-doped Superconductor Pr_{1-x}Sr_xFeAsO|Gang Mu,Bin Zeng,Xiyu Zhu,Fei Han,Peng Cheng,Bing Shen,Hai-Hu Wen###

Synthesis, structural and transport properties of the hole-doped Superconductor Pr_{1-x}Sr_xFeAsO. Superconductivity was achieved in PrFeAsO by partially substituting Pr^{3+}
with Sr^{2+}. The electrical transport properties and structure of this new
superconductor Pr_{1-x}Sr_xFeAsO at different doping levels (x = 0.05$\sim$
0.25) were investigated systematically. It was found that the lattice constants
(a-axis and c-axis) increase monotonously with Sr or hole concentration. The
superconducting transition temperature at about 16.3 K (95% $\rho_n$) was
observed around the doping level of 0.20$\sim$ 0.25. A detailed investigation
was carried out in the sample with doping level of x = 0.25. The domination of
hole-like charge carriers in this material was confirmed by Hall effect
measurements. The magnetoresistance (MR) behavior can be well described by a
simple two-band model. The upper critical field of the sample with T_c = 16.3 K
(x = 0.25) was estimated to be beyond 45 Tesla. Our results suggest that the
hole-doped samples may have higher upper critical fields comparing to the
electron-doped ones, due to the higher quasi-particle density of states at the
Fermi level.

###Synthesizing and characterization of hole doped nickel based superconductor (La$_{1-x}$Sr$_{x}$)NiAsO|Lei Fang,Huan Yang,Peng Cheng,Xiyu Zhu,Gang Mu,Hai-Hu Wen###

Synthesizing and characterization of hole doped nickel based superconductor (La$_{1-x}$Sr$_{x}$)NiAsO. We report the synthesizing and characterization of the hole doped Ni-based
superconductor ($La_{1-x}Sr_{x})NiAsO$. By substituting La with Sr, the
superconducting transition temperature $T_c$ is increased from 2.4 K of the
parent phase $LaNiAsO$ to 3.7 K at the doping levels x= 0.1 - 0.2. The curve
$T_c$ versus hole concentration shows a symmetric behavior as the electron
doped samples $LaNiAs(O_{1-x}F_{x})$. The normal state resistivity in Ni-based
samples shows a good metallic behavior and reveals the absence of spin density
wave induced anomaly which appears in the Fe-based system at about 150 K. Hall
effect measurements indicate that the electron conduction in the parent phase
$LaNiAsO$ is dominated by electron-like charge carriers, while with more Sr
doping, a hole-like band will emerge and finally prevail over the conduction,
such a phenomenon reflects that the Fermi surface of $LaNiAsO$ comprises of
electron pockets and hole pockets, thus the sign of charge carriers could be
changed once the contribution of hole pockets overwhelms that of electron
pockets. Magnetoresistance measurements and the violation of Kohler rule
provide further proof that multiband effect dominate the normal state transport
of ($La_{1-x}Sr_{x})NiAsO$.

###Electrical rectification effect in single domain magnetic microstrips: a micromagnetics-based analysis|Andre Thiaville,Yoshinobu Nakatani###

Electrical rectification effect in single domain magnetic microstrips: a micromagnetics-based analysis. Upon passing an a.c. electrical current along magnetic micro- or nanostrips,
the measurement of a d.c. voltage that depends sensitively on current frequency
and applied field has been recently reported by A. Yamaguchi and coworkers. It
was attributed to the excitation of spin waves by the spin transfer torque,
leading to a time-varying anisotropic magnetoresistance and, by mixing of a.c.
current and resistance, to a d.c. voltage. We have performed a quantitative
analysis by micromagnetics, including the spin transfer torque terms considered
usually, of this situation. The signals found from the spin transfer torque
effect are several orders of magnitude below the experimental values, even if a
static inhomogeneity of magnetization (the so-called ripple) is taken into
account. On the other hand, the presence of a small non-zero average Oersted
field is shown to be consistent with the full set of experimental results, both
qualitatively and quantitatively. We examine, quantitatively, several sources
for this average field and point to the contacts to the sample as a likely
origin.

###Non-equilibrium magnetism in dual spin valves|A. Aziz,O. P. Wessely,M. Ali,D. M. Edwards,C. H. Marrows,B. J. Hickey,M. G. Blamire###

Non-equilibrium magnetism in dual spin valves. The field of spin electronics (spintronics) was initiated by the discovery of
giant magnetoresistance (GMR) for which Fert[1] and Grunberg[2] were awarded
the 2007 Nobel Prize for Physics. GMR arises from differential scattering of
the majority and minority spin electrons by a ferromagnet (FM) so that the
resistance when the FM layers separated by non-magnetic (NM) spacers are
aligned by an applied field is different to when they are antiparallel. In 1996
Slonczewski[3] and Berger[4] predicted that a large spin-polarised current
could transfer spin-angular momentum and so exert a spin transfer torque (STT)
sufficient to switch thin FM layers between stable magnetisation states[5] and,
for even higher current densities, drive continuous precession which emits
microwaves[6]. Thus, while GMR is a purely passive phenomenon which ultimately
depends on the intrinsic band structure of the FM, STT adds an active element
to spintronics by which the direction of the magnetisation may be manipulated.
Here we show that highly non-equilibrium spin injection can modify the
scattering asymmetry and, by extension, the intrinsic magnetism of a FM. This
phenomenon is completely different to STT and provides a third ingredient which
should further expand the range of opportunities for the application of
spintronics.

###Upper critical fields and thermally-activated transport of Nd(O_0.7F_0.3)FeAs single crystal|J. Jaroszynski,F. Hunte,L. Balicas,Youn-jung Jo,I. Raicevic,A. Gurevich,D. C. Larbalestier,F. F. Balakirev,L. Fang,P. Cheng,Y. Jia,H. H. Wen###

Upper critical fields and thermally-activated transport of Nd(O_0.7F_0.3)FeAs single crystal. We present measurements of the resistivity and the upper critical field H_c2
of Nd(O_0.7F_0.3)FeAs single crystals in strong DC and pulsed magnetic fields
up to 45 T and 60 T, respectively. We found that the field scale of H_c2 is
comparable to ~100 T of high T_c cuprates. H_c2(T) parallel to the c-axis
exhibits a pronounced upward curvature similar to what was extracted from
earlier measurements on polycrystalline samples. Thus this behavior is indeed
an intrinsic feature of oxypnictides, rather than manifestation of vortex
lattice melting or granularity. The orientational dependence of H_c2 shows
deviations from the one-band Ginzburg-Landau scaling. The mass anisotropy
decreases as T decreases, from 9.2 at 44K to 5 at 34K. Spin dependent
magnetoresistance and nonlinearities in the Hall coefficient suggest
contribution to the conductivity from electron-electron interactions modified
by disorder reminiscent that of diluted magnetic semiconductors. The Ohmic
resistivity measured below T_c but above the irreversibility field exhibits a
clear Arrhenius thermally activated behavior over 4-5 decades. The activation
energy has very different field dependencies for H||ab and H\perp ab. We
discuss to what extent different pairing scenarios can manifest themselves in
the observed behavior of H_{c2}, using the two-band model of superconductivity.
The results indicate the importance of paramagnetic effects on H_c2(T),which
may significantly reduce H_c2(0) as compared toH_c2(0)~200-300 T based on
extrapolations of H_c2(T) near T_c down to low temperatures.

###SrFeAsF as a parent compound for iron pnictide superconductors|Fei Han,Xiyu Zhu,Gang Mu,Peng Cheng,Hai-Hu Wen###

SrFeAsF as a parent compound for iron pnictide superconductors. We have successfully synthesized the fluo-arsenide SrFeAsF, a new parent
phase with the ZrCuAsSi structure. The temperature dependence of resistivity
and dc magnetization both reveal an anomaly at about T_{an} = 173 K, which may
correspond to the structural and/or Spin-Density-Wave (SDW) transition. Strong
Hall effect and magnetoresistance were observed below T_{an}. Interestingly,
the Hall coefficient R_H is positive below T_{an}, which is opposite to the
cases in the two parent phases of FeAs-based systems known so far, i.e.,
LnFeAsO (Ln = rare earth elements) and (Ba, Sr)Fe_2As_2 where the Hall
coefficient R_H is negative. This strongly suggests that the gapping to the
Fermi surfaces induced by the SDW order is more complex than we believed before
that it removes the density of states on some Fermi pockets and leaves one of
the electron pockets less-gapped or un-gapped. Our data clearly show that it is
possible for the parent phase to have electron-like or hole-like charge
carriers.

###Phase separation of electrons strongly coupled with phonons in cuprates and manganites|A. S. Alexandrov###

Phase separation of electrons strongly coupled with phonons in cuprates and manganites. Recent advanced Monte Carlo simulations have not found superconductivity and
phase separation in the Hubbard model with on-site repulsive electron-electron
correlations. We argue that microscopic phase separations in cuprate
superconductors and colossal magnetoresistance (CMR) manganites originate from
a strong electron-phonon interaction (EPI) combined with unavoidable disorder.
Attractive electron correlations, caused by an almost unretarded EPI, are
sufficient to overcome the direct inter-site Coulomb repulsion in these
charge-transfer Mott-Hubbard insulators, so that low energy physics is that of
small polarons and small bipolarons (real-space electron (hole) pairs dressed
by phonons). They form clusters localised by disorder below the mobility edge,
but propagate as the Bloch states above the mobility edge. I identify the
Froehlich finite-range EPI with optical phonons as the most essential for
pairing and phase separation in superconducting layered cuprates. The pairing
of oxygen holes into heavy bipolarons in the paramagnetic phase
(current-carrier density collapse (CCDC)) explains also CMR of doped manganites
due to magnetic break-up of bipolarons in the ferromagnetic phase. Here I
briefly present an explanation of high and low-resistance phase coexistence
near the ferromagnetic transition as a mixture of polaronic ferromagnetic and
bipolaronic paramagnetic domains due to unavoidable disorder in doped
manganites.

###Magnetoresistance in paramagnetic heavy fermion metals|D. Parihari,N. S. Vidhyadhiraja###

Magnetoresistance in paramagnetic heavy fermion metals. A theoretical study of magnetic field (h) effects on single-particle spectra
and transport quantities of heavy fermion metals in the paramagnetic phase is
carried out. We have employed a non-perturbative local moment approach (LMA) to
the asymmetric periodic Anderson model within the dynamical mean field
framework. The lattice coherence scale $\om_L$, which is proportional within
the LMA to the spin-flip energy scale, and has been shown in earlier studies to
be the energy scale at which crossover to single impurity physics
occurs,increases monotonically with increasing magnetic field. The many body
Kondo resonance in the density of states at the Fermi level splits into two
with the splitting being proportional to the field itself. For h$\geq$ 0, we
demonstrate adiabatic continuity from the strongly interacting case to a
corresponding non-interacting limit, thus establishing Fermi liquid behaviour
for heavy fermion metals in the presence of magnetic field. In the Kondo
lattice regime, the theoretically computed magnetoresistance is found to be
negative in the entire temperature range. We argue that such a result could be
understood at $T\gtrsim \om_L$ by field-induced suppression of spin-flip
scattering and at $T\lesssim \om_L$ through lattice coherence. The coherence
peak in the heavy fermion resistivity diminishes and moves to higher
temperatures with increasing field. Direct comparison of the theoretical
results to the field dependent resistivity measurements in CeB$_6$ yields good
agreement.

###Transport and magnetotransport properties of cold-pressed CrO$_2$ powder, prepared by hydrothermal synthesis|B. I. Belevtsev,N. V. Dalakova,M. G. Osmolowsky,E. Yu. Beliayev,A. A. Selutin###

Transport and magnetotransport properties of cold-pressed CrO$_2$ powder, prepared by hydrothermal synthesis. Submicron powder of CrO$_2$ was prepared by hydrothermal synthesis method
from chromium trioxide. Particles obtained were of rounded form with mean
diameter about 120 nm. The powder (stabilized with thin surface layer of
\beta-CrOOH) has been characterized by structural, X-ray and magnetic
measurements. The powder (with Curie temperature about 385 K) was cold-pressed
and its transport and magnetotransport properties have been measured in the
temperature range 4--450 K in magnetic field up to 1.6 T. The samples studied
is characterized by non-metallic temperature behavior of resistance and large
negative magnetoresistance (MR) in low temperature range. At T=5 K the MR
magnitude has been -17% at H=0.3 T and -20% at H=1.4 T. Its magnitude decreased
fast with increase in temperature reducing to 0.3% and less for T>200 K. It is
shown that this MR behavior is inherent for a system of magnetic grains with
spin-dependent intergrain tunnelling. Some peculiarities of MR behavior in
low-temperature range (below 40 K) can be associated with percolating character
of tunnelling conductivity of this granular system under conditions of
availability of only few conducting current paths through the sample.

###Metal-insulator transition and electroresistance in lanthanum/calcium manganites La_<1-x>Ca_<x>MnO_<3> (x = 0-0.5) from voltage-current-temperature surfaces|J C Knott,D C Pond,R A Lewis###

Metal-insulator transition and electroresistance in lanthanum/calcium manganites La_<1-x>Ca_<x>MnO_<3> (x = 0-0.5) from voltage-current-temperature surfaces. Of the perovskites, ABX_<3>, a subset of special interest is the family in
which the A site is occupied by a lanthanide ion, the B site by a rare earth
and X is oxygen, as such materials often exhibit a large change in electrical
resistance in a magnetic field, a phenomenon known as "colossal"
magnetoresistance (MR). Two additional phenomena in this family have also drawn
attention: the metal-insulator transition (MIT) and electroresistance (ER). The
MIT is revealed by measuring resistance as a function of temperature, and
observing a change in the sign of the gradient. ER - the dependence of the
resistance on applied current - is revealed by measuring resistance as a
function of applied current. Up until now, the phenomena of MIT and ER have
been treated separately. Here we report simultaneous observation of the MIT and
ER in the lanthanum/calcium manganites. We accomplish this by measuring
voltage-current curves over a wide temperature range (10-300 K) allowing us to
build up an experimental voltage surface over current-temperature axes. These
data directly lead to resistance surfaces. This approach provides additional
insight into the phenomena of electrical transport in the lanthanum/calcium
manganites, in particular the close connection of the maximum ER to the
occurrence of the MIT in those cases of a paramagnetic insulator (PMI) to
ferromagnetic metal (FMM) transition.

###Nanoscale Electronic Inhomogeneity in In2Se3 Nanoribbons Revealed by Microwave Impedance Microscopy|Keji Lai,Hailin Peng,Worasom Kundhikanjana,David T. Schoen,Chong Xie,Stefan Meister,Yi Cui,Michael A. Kelly,Zhi-Xun Shen###

Nanoscale Electronic Inhomogeneity in In2Se3 Nanoribbons Revealed by Microwave Impedance Microscopy. Driven by interactions due to the charge, spin, orbital, and lattice degrees
of freedom, nanoscale inhomogeneity has emerged as a new theme for materials
with novel properties near multiphase boundaries. As vividly demonstrated in
complex metal oxides and chalcogenides, these microscopic phases are of great
scientific and technological importance for research in high-temperature
superconductors, colossal magnetoresistance effect, phase-change memories, and
domain switching operations. Direct imaging on dielectric properties of these
local phases, however, presents a big challenge for existing scanning probe
techniques. Here, we report the observation of electronic inhomogeneity in
indium selenide (In2Se3) nanoribbons by near-field scanning microwave impedance
microscopy. Multiple phases with local resistivity spanning six orders of
magnitude are identified as the coexistence of superlattice, simple hexagonal
lattice and amorphous structures with 100nm inhomogeneous length scale,
consistent with high-resolution transmission electron microscope studies. The
atomic-force-microscope-compatible microwave probe is able to perform
quantitative sub-surface electronic study in a noninvasive manner. Finally, the
phase change memory function in In2Se3 nanoribbon devices can be locally
recorded with big signal of opposite signs.

###Thermal and Transport Behavior of Single Crystalline R2CoGa8 (R = Gd, Tb, Dy, Ho, Er, Tm, Lu and Y) Compounds|Devang A. Joshi,A. K. Nigam,S. K. Dhar,A. Thamizhavel###

Thermal and Transport Behavior of Single Crystalline R2CoGa8 (R = Gd, Tb, Dy, Ho, Er, Tm, Lu and Y) Compounds. The anisotropy in electrical transport and thermal behavior of single
crystalline R$_{2}$CoGa$_{8}$ series of compounds is presented. These compounds
crystallize in a tetragonal structure with space gropup P4/mmm. The nonmagnetic
counterparts of the series namely Y$_{2}$CoGa$_{8}$ and Lu$_{2}$CoGa$_{8}$show
a behavior consistent with the low density of states at the fermi level. In
Y$_{2}$CoGa$_{8}$, a possibility of charge density wave transition is observed
at $\approx$ 30 K. Gd$_{2}$CoGa$_{8}$ and Er$_{2}$CoGa$_{8}$ show a presence of
short range correlation above the magnetic ordering temperature of the
compound. In case of Gd$_{2}$CoGa$_{8}$, the magnetoresistance exhibits a
significant anisotropy for current parallel to {[}100{]} and {[}001{]}
directions. Compounds with other magnetic rare earths (R = Tb, Dy, Ho and Tm)
show the normal expected magnetic behavior whereas Dy$_{2}$CoGa$_{8}$ exhibits
the possibility of charge density wave (CDW) transition at approximately same
temperature as that of Y$_{2}$CoGa$_{8}$. The thermal property of these
compounds is analysed on the basis of crystalline electric field (CEF)
calculations.

###High field magneto-transport in high mobility gated InSb/InAlSb quantum well heterostructures|A. M. Gilbertson,W. R. Branford,M. Fearn,L. Buckle,P. D. Buckle,T. Ashley,L. F. Cohen###

High field magneto-transport in high mobility gated InSb/InAlSb quantum well heterostructures. We present high field magneto-transport data from a range of 30nm wide
InSb/InAlSb quantum wells. The low temperature carrier mobility of the samples
studied ranged from 18.4 to 39.5 m2V-1s-1 with carrier densities between
1.5x1015 and 3.28x1015 m-2. Room temperature mobilities are reported in excess
of 6 m2V-1s-1. It is found that the Landau level broadening decreases with
carrier density and beating patterns are observed in the magnetoresistance with
non-zero node amplitudes in samples with the narrowest broadening despite the
presence of a large g-factor. The beating is attributed to Rashba splitting
phenomenon and Rashba coupling parameters are extracted from the difference in
spin populations for a range of samples and gate biases. The influence of
Landau level broadening and spin-dependent scattering rates on the observation
of beating in the Shubnikov-de Haas oscillations is investigated by simulations
of the magnetoconductance. Data with non-zero beat node amplitudes are
accompanied by asymmetric peaks in the Fourier transform, which are
successfully reproduced by introducing a spin-dependent broadening in the
simulations. It is found that the low-energy (majority) spin up state suffers
more scattering than the high-energy (minority) spin down state and that the
absence of beating patterns in the majority of (lower density) samples can be
attributed to the same effect when the magnitude of the level broadening is
large.

###Anisotropic magnetoresistance of spin-orbit coupled carriers scattered from polarized magnetic impurities|Maxim Trushin,Karel Vyborny,Peter Moraczewski,Alexey A. Kovalev,John Schliemann,Tomas Jungwirth###

Anisotropic magnetoresistance of spin-orbit coupled carriers scattered from polarized magnetic impurities. Anisotropic magnetoresistance (AMR) is a relativistic magnetotransport
phenomenon arising from combined effects of spin-orbit coupling and broken
symmetry of a ferromagnetically ordered state of the system. In this work we
focus on one realization of the AMR in which spin-orbit coupling enters via
specific spin-textures on the carrier Fermi surfaces and ferromagnetism via
elastic scattering of carriers from polarized magnetic impurities. We report
detailed heuristic examination, using model spin-orbit coupled systems, of the
emergence of positive AMR (maximum resistivity for magnetization along
current), negative AMR (minimum resistivity for magnetization along current),
and of the crystalline AMR (resistivity depends on the absolute orientation of
the magnetization and current vectors with respect to the crystal axes)
components. We emphasize potential qualitative differences between pure
magnetic and combined electro-magnetic impurity potentials, between short-range
and long-range impurities, and between spin-1/2 and higher spin-state carriers.
Conclusions based on our heuristic analysis are supported by exact solutions to
the integral form of the Boltzmann transport equation in archetypical
two-dimensional electron systems with Rashba and Dresselhaus spin-orbit
interactions and in the three-dimensional spherical Kohn-Littinger model. We
include comments on the relation of our microscopic calculations to standard
phenomenology of the full angular dependence of the AMR, and on the relevance
of our study to realistic, two-dimensional conduction-band carrier systems and
to anisotropic transport in the valence band of diluted magnetic
semiconductors.

###Strong electron-electron correlation and weak localization in CeO_{0.9}F_{0.1}Fe_{1-x}Co_xAs|S. J. Singh,J. Prakash,S. Patnaik,A. K. Ganguli###

Strong electron-electron correlation and weak localization in CeO_{0.9}F_{0.1}Fe_{1-x}Co_xAs. Electron-doping of the semimetal (CeOFeAs) by either fluorine (max Tc ~ 43
K)or cobalt (max Tc ~ 11 K) leads to superconductivity. Here we show the effect
of transition metal (Co) substitution at the iron site on the superconducting
properties of CeO0.9F0.1FeAs (Tc ~38 K)to understand the interplay of charge
carriers in both the rare earth-oxygen and Fe-As layers. Simultaneous doping of
equivalent number of charge carriers in both layers leads to a Tc of 9.8 K
which is lower than the Tc obtained when either the conducting layer (CeAs) or
charge reservoir layer (CeO) is individually doped. This suggests a clear
interplay between the two layers to control the superconductivity. The
resistivity shows a T2 dependence (T >>Tc) which indicates strong
electron-electron correlation. Hall coefficient and thermoelectric power
indicate increased carrier concentration with cobalt doping in CeO0.9F0.1FeAs.
The rf penetration depth both for CeO0.9F0.1Fe0.95Co0.05As and CeO0.9F0.1FeAs
show an exponential temperature dependence with a gap value of ~ 1.6 and 1.9
meV. A resistance minimum is observed in the normal state near Tc which also
shows negative magnetoresistance and provides evidence for the onset of weak
localization.

###Magnetism in Nb(1-y)Fe(2+y) - composition and magnetic field dependence|D. Moroni-Klementowicz,M. Brando,C. Albrecht,W. J. Duncan,F. M. Grosche,D. Gruener,G. Kreiner###

Magnetism in Nb(1-y)Fe(2+y) - composition and magnetic field dependence. We present a systematic study of transport and thermodynamic properties of
the Laves phase system Nb$_{1-y}$Fe$_{2+y}$. Our measurements confirm that
Fe-rich samples, as well as those rich in Nb (for $\mid y\mid\geq 0.02$), show
bulk ferromagnetism at low temperature. For stoichiometric NbFe$_2$, on the
other hand, magnetization, magnetic susceptibility and magnetoresistance
results point towards spin-density wave (SDW) order, possibly helical, with a
small ordering wavevector $Q \sim 0.05$ \AA$^{-1}$. Our results suggest that on
approaching the stoichiometric composition from the iron-rich side,
ferromagnetism changes into long-wavelength SDW order. In this scenario, $Q$
changes continuously from 0 to small, finite values at a Lifshitz point in the
phase diagram, which is located near $y=+0.02$. Further reducing the Fe content
suppresses the SDW transition temperature, which extrapolates to zero at
$y\approx -0.015$. Around this Fe content magnetic fluctuations dominate the
temperature dependence of the resistivity and of the heat capacity which
deviate from their conventional Fermi liquid forms, inferring the presence of a
quantum critical point. Because the critical point is located between the SDW
phase associated with stoichiometric NbFe$_2$ and the ferromagnetic order which
reemerges for very Nb-rich NbFe$_2$, the observed temperature dependences could
be attributed both to proximity to SDW order or to ferromagnetism.

###Information Processing with Pure Spin Currents in Silicon: Spin Injection, Extraction, Manipulation and Detection|Olaf M. J. van "t Erve,Chaffra Awo-Affouda,Aubrey T. Hanbicki,Connie H. Li,Phillip E. Thompson,Berend T. Jonker###

Information Processing with Pure Spin Currents in Silicon: Spin Injection, Extraction, Manipulation and Detection. We demonstrate that information can be transmitted and processed with pure
spin currents in silicon. Fe/Al2O3 tunnel barrier contacts are used to produce
significant electron spin polarization in the silicon, generating a spin
current which flows outside of the charge current path. The spin orientation of
this pure spin current is controlled in one of three ways: (a) by switching the
magnetization of the Fe contact, (b) by changing the polarity of the bias on
the Fe/Al2O3 (injector) contact, which enables the generation of either
majority or minority spin populations in the Si, providing a way to
electrically manipulate the injected spin orientation without changing the
magnetization of the contact itself, and (c) by inducing spin precession
through application of a small perpendicular magnetic field. Spin polarization
by electrical extraction is as effective as that achieved by the more common
electrical spin injection. The output characteristics of a planar silicon three
terminal device are very similar to those of non-volatile giant
magnetoresistance metal spin-valve structures

###Annular Spin-Transfer Memory Element|Andrew D. Kent,Daniel L. Stein###

Annular Spin-Transfer Memory Element. An annular magnetic memory that uses a spin-polarized current to switch the
magnetization direction or helicity of a magnetic region is proposed. The
device has magnetic materials in the shape of a ring (1 to 5 nm in thickness,
20 to 250 nm in mean radius and 8 to 100 nm in width), comprising a reference
magnetic layer with a fixed magnetic helicity and a free magnetic layer with a
changeable magnetic helicity. These are separated by a thin non-magnetic layer.
Information is written using a current flowing perpendicular to the layers,
inducing a spin-transfer torque that alters the magnetic state of the free
layer. The resistance, which depends on the magnetic state of the device, is
used to read out the stored information. This device offers several important
advantages compared to conventional spin-transfer magnetic random access memory
(MRAM) devices. First, the ring geometry offers stable magnetization states,
which are, nonetheless, easily altered with short current pulses. Second, the
ring geometry naturally solves a major challenge of spin-transfer devices:
writing requires relatively high currents and a low impedance circuit, whereas
readout demands a larger impedance and magnetoresistance. The annular device
accommodates these conflicting requirements by performing reading and writing
operations at separate read and write contacts placed at different locations on
the ring.

###Ferromagnetic transition metal implanted ZnO: a diluted magnetic semiconductor?|Shengqiang Zhou,K. Potzger,Qingyu Xu,G. Talut,M. Lorenz,W. Skorupa,M. Helm,J. Fassbender,M. Grundmann,H. Schmidt###

Ferromagnetic transition metal implanted ZnO: a diluted magnetic semiconductor?. Recently theoretical works predict that some semiconductors (e.g. ZnO) doped
with magnetic ions are diluted magnetic semiconductors (DMS). In DMS magnetic
ions substitute cation sites of the host semiconductor and are coupled by free
carriers resulting in ferromagnetism. One of the main obstacles in creating DMS
materials is the formation of secondary phases because of the solid-solubility
limit of magnetic ions in semiconductor host. In our study transition metal
ions were implanted into ZnO single crystals with the peak concentrations of
0.5-10 at.%. We established a correlation between structural and magnetic
properties. By synchrotron radiation X-ray diffraction (XRD) secondary phases
(Fe, Ni, Co and ferrite nanocrystals) were observed and have been identified as
the source for ferromagnetism. Due to their different crystallographic
orientation with respect to the host crystal these nanocrystals in some cases
are very difficult to be detected by a simple Bragg-Brentano scan. This results
in the pitfall of using XRD to exclude secondary phase formation in DMS
materials. For comparison, the solubility of Co diluted in ZnO films ranges
between 10 and 40 at.% using different growth conditions pulsed laser
deposition. Such diluted, Co-doped ZnO films show paramagnetic behaviour.
However, only the magnetoresistance of Co-doped ZnO films reveals possible s-d
exchange interaction as compared to Co-implanted ZnO single crystals.

###Exchange bias effect involved with tunneling magnetoresistance in polycrystalline La_{0.88}Sr_{0.12}CoO_3|M. Patra,S. Majumdar,S. Giri###

Exchange bias effect involved with tunneling magnetoresistance in polycrystalline La_{0.88}Sr_{0.12}CoO_3. We report the exchange bias (EB) effect along with tunneling
magnetoresistance (MR) in polycrystalline La_{0.88}Sr_{0.12}CoO_3. Analogous to
the shift in the magnetic hysteresis loop along the field (H)-axis a shift is
clearly observed in the MR-H curve when the sample is cooled in a static
magnetic field. Training effect (TE) is a significant manifestation of EB
effect which describes the decrease of EB effect when sample is successively
field-cycled at a particular temperature. We observe TE in the shift of the
MR-H curve which could be interpreted by the spin configurational relaxation
model. A strong field-cooled (FC) effect in the temperature as well as time
dependence of resistivity is observed below spin freezing temperature. The
unusual MR results measured in FC mode are interpreted in terms of
intragranular interface effect between short range ferromagnetic clusters and
spin-glass matrix giving rise to the EB effect. EB effect in MR has been
observed in bilayer or multilayer films which has not yet seen in a
polycrystalline compound. EB effect involved with tunneling MR and
semiconducting transport property attributed to the intragranular intrinsic
nanostructure is promising for the spintronic applications.

###The pseudogap behavior in the stoichiometric FeSe superconductor (Tc~9.4 K)|Yoo Jang Song,Jong Beom Hong,Byeong Hun Min,Kyu Jun Lee,Myung Hwa Jung,Jong-Soo Rhyee,Yong Seung Kwon###

The pseudogap behavior in the stoichiometric FeSe superconductor (Tc~9.4 K). This paper reports the synthesis and superconducting behaviors of the
tetragonal iron-chalcogenide superconductor FeSe. The electrical resistivity
and magnetic moment measurements confirmed its superconductivity with a
$T_c^{zero}$ and $T_c^{mag}$ at 9.4 K under ambient pressure. EPMA indicated
the sample to have a stoichiometric Fe:Se ratio of 1:1 ($\pm$0.02). The Seebeck
coefficient which was 12.3 $\mu$V/K at room temperature, changed to a negative
value near 200 K, indicating it to be a two carriers material. Above $T_c$, the
$\rho(T)$ curve revealed an 'S' shape. Hence $d\rho(T)/dT$, and
$d^2\rho(T)/dT^2$ showed pseudogap-like behavior at $T^*$=110 K according to
the resistivity curvature mapping (RCM) method for high $T_c$ cuprates.
Moreover, the magnetoresistance $\rho_H(T)/\rho_{H=0}$ under a magnetic field
and the Seebeck coefficient $S(T)$ revealed revealed pseudogap-like behavior
near $T^*$. Interestingly, at the same temperature, 30 K, the sign of $S(T)$
and all signs of $d^2\rho(T)/dT^2$ changed from negative to positive above
$T_c$.

###Electronic transport through a graphene-based ferromagnetic/normal/ferromagnetic junction|Jiang-chai Chen,Shu-guang Cheng,Shun-Qing Shen,Qing-feng Sun###

Electronic transport through a graphene-based ferromagnetic/normal/ferromagnetic junction. Electronic transport in a graphene-based ferromagnetic/normal/ferromagnetic
junction is investigated by means of Landauer-B\"{u}ttiker formulism and the
nonequilibrium Green's function technique. For the zigzag edge case, the
results show that the conductance is always larger than $e^{2}/h$ for the
parallel configuration of lead magnetizations, but for the antiparallel
configuration the conductance becomes zero because of the band-selective rule.
So a magnetoresistance (MR) plateau emerges with the value 100% when the Fermi
energy is located around the Dirac point. Besides, choosing narrower graphene
ribbons can obtain the wider 100% MR plateaus and the length change of the
central graphene region does not affect the 100% MR plateaus. Although the
disorder will reduce the MR plateau, the plateau value can be still kept about
50% even in a large disorder strength case. In addition, when the
magnetizations of the left and right leads have a relative angle, the
conductance changes as a cosine function of the angle. What is more, for the
armchair edge case, the MR is usually small. So, it is more favorable to
fabricate the graphene-based spin valve device by using the zigzag edge
graphene ribbon.

###Necessary and sufficient condition for longitudinal magnetoresistance|H. K. Pal,D. L. Maslov###

Necessary and sufficient condition for longitudinal magnetoresistance. Since the Lorentz force is perpendicular to the magnetic field, it should not
affect the motion of a charge along the field. This argument seems to imply
absence of longitudinal magnetoresistance (LMR) which is, however, observed in
many materials and reproduced by standard semiclassical transport theory
applied to particular metals. We derive a necessary and sufficient condition on
the shape of the Fermi surface for non-zero LMR. Although an anisotropic
spectrum is a pre-requisite for LMR, not all types of anisotropy can give rise
to the effect: a spectrum should not be separable in any sense. More precisely,
the combination $k_{\rho}v_{\phi}/v_{\rho}$, where $k_\rho$ is the radial
component of the momentum in a cylindrical system with the z-axis along the
magnetic field and $v_{\rho} (v_{\phi}$) is the radial (tangential) component
of the velocity, should depend on the momentum along the field. For some
lattice types, this condition is satisfied already at the level of
nearest-neighbor hopping; for others, the required non-separabality occurs only
if next-to-nearest-neighbor hopping is taken into account.

###Superconductor-insulator quantum phase transition|V. F. Gantmakher,V. T. Dolgopolov###

Superconductor-insulator quantum phase transition. The current understanding of the superconductor-insulator transition is
discussed level by level in a cyclic spiral-like manner. At the first level,
physical phenomena and processes are discussed which, while of no formal
relevance to the topic of transitions, are important for their implementation
and observation; these include superconductivity in low electron density
materials, transport and magnetoresistance in superconducting island films and
in highly resistive granular materials with superconducting grains, and the
Berezinskii-Kosterlitz-Thouless transition. The second level discusses and
summarizes results from various microscopic approaches to the problem, whether
based on the Bardeen-Cooper-Schrieffer theory (the disorder-induced reduction
in the superconducting transition temperature; the key role of Coulomb blockade
in high-resistance granular superconductors; superconducting fluctuations in a
strong magnetic field) or on the theory of the Bose-Einstein condensation. A
special discussion is given to phenomenological scaling theories. Experimental
investigations, primarily transport measurements, make the contents of the
third level and are for convenience classified by the type of material used
(ultrathin films, variable composition materials, high-temperature
superconductors, superconductor-poor metal transitions). As a separate topic,
data on nonlinear phenomena near the superconductor-insulator transition are
presented. At the final, summarizing, level the basic aspects of the problem
are enumerated again to identify where further research is needed and how this
research can be carried out. Some relatively new results, potentially of key
importance in resolving the remaining problems, are also discussed.

###Theoretical Analysis of Drag Resistance in Amorphous Thin Films Exhibiting Superconductor-Insulator-Transition|Yue Zou,Gil Refael,Jongsoo Yoon###

Theoretical Analysis of Drag Resistance in Amorphous Thin Films Exhibiting Superconductor-Insulator-Transition. The magnetical field tuned superconductor-insulator transition in amorphous
thin films, e.g., Ta and InO, exhibits a range of yet unexplained curious
phenomena, such as a putative low-resistance metallic phase intervening the
superconducting and the insulating phase, and a huge peak in the
magnetoresistance at large magnetic field. Qualitatively, the phenomena can be
explained equally well within several significantly different pictures,
particularly the condensation of quantum vortex liquid, and the percolation of
superconducting islands embedded in normal region. Recently, we proposed and
analyzed a new measurement that should be able to decisively point to the
correct picture: a drag resistance measurement in an amorphous thin-film
bilayer setup. Neglecting interlayer tunneling, we found that the drag
resistance within the vortex paradigm has opposite sign and is orders of
magnitude larger than that in competing paradigms. For example, two identical
films as in Sambandamurthy et al. 2004 with 25 nm layer separation at 0.07 K
would produce a drag resistance $\sim10^{-4}\Omega$ according the vortex
theory, but only $\sim10^{-12}\Omega$ for the percolation theory. We provide
details of our theoretical analysis of the drag resistance within both
paradigms, and report some new results as well.

###AC-driven Vortices and the Hall Effect in a Superconductor with a Tilted Washboard Pinning Potential|Valerij A. Shklovskij,Oleksandr V. Dobrovolskiy###

AC-driven Vortices and the Hall Effect in a Superconductor with a Tilted Washboard Pinning Potential. The Langevin equation for a two-dimensional (2D) nonlinear guided vortex
motion in a tilted cosine pinning potential in the presence of an ac is exactly
solved in terms of a matrix continued fraction at arbitrary value of the Hall
effect. The influence of an ac of arbitrary amplitude and frequency on the dc
and ac magnetoresistivity tensors is analyzed. The ac density and frequency
dependence of the overall shape and the number and position of the Shapiro-like
steps on the anisotropic current-voltage characteristics are considered. The
influence of a subcritical or overcritical dc on the time-dependent stationary
ac longitudinal and transverse resistive vortex responses (on the frequency of
an ac drive W) in terms of the nonlinear impedance tensor Z and the nonlinear
ac response at W-harmonics are studied. Analytical formulas for 2D
temperature-dependent linear impedance tensor Zl in the presence of a dc which
depend on the angle a between the current-density vector and the guiding
direction of the washboard planar pinning potential are derived and analyzed.
Influence of a-anisotropy and the Hall effect on the nonlinear power absorption
by vortices is discussed.

###Large capacitance enhancement and negative compressibility of two-dimensional electronic systems at LaAlO$_3$/SrTiO$_3$ interfaces|Lu Li,C. Richter,S. Paetel,T. Kopp,J. Mannhart,R. C. Ashoori###

Large capacitance enhancement and negative compressibility of two-dimensional electronic systems at LaAlO$_3$/SrTiO$_3$ interfaces. Novel electronic systems forming at oxide interfaces comprise a class of new
materials with a wide array of potential applications. A high mobility electron
system forms at the LaAlO$_3$/SrTiO$_3$ interface and, strikingly, both
superconducts and displays indications of hysteretic magnetoresistance. An
essential step for device applications is establishing the ability to vary the
electronic conductivity of the electron system by means of a gate. We have
fabricated metallic top gates above a conductive interface to vary the electron
density at the interface. By monitoring capacitance and electric field
penetration, we are able to tune the charge carrier density and establish that
we can completely deplete the metallic interface with small voltages. Moreover,
at low carrier densities, the capacitance is significantly enhanced beyond the
geometric capacitance for the structure. In the same low density region, the
metallic interface overscreens an external electric field. We attribute these
observations to a negative compressibility of the electronic system at the
interface. Similar phenomena have been observed previously in semiconducting
two-dimensional electronic systems. The observed compressibility result is
consistent with the interface containing a system of mobile electrons in two
dimensions.

###Optical conductivity and superconductivity in LaSb$_2$|J. F. DiTusa,V. Guritanu,S. Guo,D. P. Young,P. W. Adams,R. G. Goodrich,J. Y. Chan,D. van der Marel###

Optical conductivity and superconductivity in LaSb$_2$. We have measured the resistivity, optical conductivity, and magnetic
susceptibility of LaSb$_2$ to search for clues as to the cause of the
extraordinarily large linear magnetoresistance and to explore the properties of
the superconducting state. We find no evidence in the optical conductivity for
the formation of a charge density wave state above 20 K despite the highly
layered crystal structure. In addition, only small changes to the optical
reflectivity with magnetic field are observed indicating that the MR is due to
scattering rate, not charge density, variations with field. Although a
superconducting ground state was previously reported below a critical
temperature of 0.4 K, we observe, at ambient pressure, a fragile
superconducting transition with an onset at 2.5 K. In crystalline samples, we
find a high degree of variability with a minority of samples displaying a full
Meissner fraction below 0.2 K and fluctuations apparent up to 2.5 K. The
application of pressure stabilizes the superconducting transition and reduces
the anisotropy of the superconducting phase.

###Tuning Low Temperature Physical Properties of CeNiGe$_{3}$ by Magnetic Field|E. D. Mun,S. L. Bud'ko,A. Kreyssig,P. C. Canfield###

Tuning Low Temperature Physical Properties of CeNiGe$_{3}$ by Magnetic Field. We have studied the thermal, magnetic, and electrical properties of the
ternary intermetallic system CeNiGe$_{3}$ by means of specific heat,
magnetization, and resistivity measurements. The specific heat data, together
with the anisotropic magnetic susceptibility, was analyzed on the basis of the
point charge model of crystalline electric field. The $J$\,=\,5/2 multiplet of
the Ce$^{3+}$ is split by the crystalline electric field (CEF) into three
Kramers doublets, where the second and third doublet are separated from the
first (ground state) doublet by $\Delta_{1}$ $\sim$ 100\,K and $\Delta_{2}$
$\sim$ 170\,K, respectively. In zero field CeNiGe$_{3}$ exhibits an
antiferromangeic order below $T_{N}$ = 5.0\,K. For
\textbf{H}\,$\parallel$\,\textbf{a} two metamagnetic transitions are clearly
evidenced between 2\,$\sim$\,4\,K from the magnetization isotherm and extended
down to 0.4\,K from the magnetoresistance measurements. For
\textbf{H}\,$\parallel$\,\textbf{a}, $T_{N}$ shifts to lower temperature as
magnetic field increases, and ultimately disappears at $H_{c}$ $\sim$
32.5\,kOe. For $H\,>\,H_{c}$, the electrical resistivity shows the quadratic
temperature dependence ($\Delta\rho = A T^{2}$). For $H \gg H_{c}$, an
unconventional $T^{n}$-dependence of $\Delta\rho$ with $n > 2$ emerges, the
exponent $n$ becomes larger as magnetic field increases. Although the
antiferromagnetic phase transition temperature in CeNiGe$_{3}$ can be
continuously suppressed to zero, it provides an example of field tuning that
does not match current simple models of Quantum criticality.

###Unveiling a two-dimensional electron gas with universal subbands at the surface of SrTiO3|A. F. Santander-Syro,O. Copie,T. Kondo,F. Fortuna,S. Pailhes,R. Weht,X. G. Qiu,F. Bertran,A. Nicolaou,A. Taleb-Ibrahimi,P. Le Fevre,G. Herranz,M. Bibes,Y. Apertet,P. Lecoeur,M. J. Rozenberg,A. Barthelemy###

Unveiling a two-dimensional electron gas with universal subbands at the surface of SrTiO3. Similar to silicon that is the basis of conventional electronics, strontium
titanate (SrTiO3) is the bedrock of the emerging field of oxide electronics.
SrTiO3 is the preferred template to create exotic two-dimensional (2D) phases
of electron matter at oxide interfaces, exhibiting metal-insulator transitions,
superconductivity, or large negative magnetoresistance. However, the physical
nature of the electronic structure underlying these 2D electron gases (2DEGs)
remains elusive, although its determination is crucial to understand their
remarkable properties. Here we show, using angle-resolved photoemission
spectroscopy (ARPES), that there is a highly metallic universal 2DEG at the
vacuum-cleaved surface of SrTiO3, independent of bulk carrier densities over
more than seven decades, including the undoped insulating material. This 2DEG
is confined within a region of ~5 unit cells with a sheet carrier density of
~0.35 electrons per a^2 (a is the cubic lattice parameter). We unveil a
remarkable electronic structure consisting on multiple subbands of heavy and
light electrons. The similarity of this 2DEG with those reported in
SrTiO3-based heterostructures and field-effect transistors suggests that
different forms of electron confinement at the surface of SrTiO3 lead to
essentially the same 2DEG. Our discovery provides a model system for the study
of the electronic structure of 2DEGs in SrTiO3-based devices, and a novel route
to generate 2DEGs at surfaces of transition-metal oxides.

###Spintronics of metal ferromagnetic structures: New approaches in the theory and experiments|S. G. Chigarev,E. M. Epshtein,Yu. V. Gulyaev,P. E. Zilberman###

Spintronics of metal ferromagnetic structures: New approaches in the theory and experiments. Two channels of the sd exchange interaction are considered in magnetic
junctions. The first channel describes the interaction of transversal spins
with the lattice magnetization. The second one describes the interaction of
longitudinal spins with magnetization. We show the longitudinal channel leads
to a number of significant effects: 1) drastic lowering of the current
instability threshold down to three (or even more) orders of magnitude; 2)
creation of large enough distortion of equilibrium due to current driven spin
injection leading to inversion of energy spin subband populations and
laser-like instability in THz frequency range at room temperature. External
magnetic field may tend to lower additionally the instability threshold due to
the proximity effect of purely magnetic reorientation phase transition. This
effect demonstrates the new properties: the giant magnetoresistance (GMR)
becomes strongly current dependent and the exchange switching becomes of very
low threshold. We derived some matching condition that should be satisfied to
achieve high spin injection level. Some characteristic quantities were appeared
in the condition. We investigated also the junctions having variable lateral
dimensions of the layers, for example, a ferromagnetic rod contacting with a
very thin ferromagnetic film. Large enhancement of the current density may
appear near the contact region leading to the spin injection luminescence.

###Noise-induced effects in magnetization reversal and chirality control of circular array of single-domained nanomagnets|A. L. Pankratov,S. N. Vdovichev,I. M. Nefedov,I. R. Karetnikova###

Noise-induced effects in magnetization reversal and chirality control of circular array of single-domained nanomagnets. The effect of noise on the process of high-speed remagnetization of vortex
state of a pentagonal array of five circular magnetic nanoparticles is studied
by means of computer simulation of Landau-Lifshits model. The mean switching
time and its standard deviation of the reversal between the counterclockwise
and clockwise vorticities have been computed. It has been demonstrated that
with the reversal by the pulse with sinusoidal shape, the optimal pulse
duration exists, which minimizes both the mean switching time (MST) and the
standard deviation (SD). Besides, both MST and SD significantly depend on the
angle between the reversal magnetic field and pentagon edge, and the optimal
angle roughly equals 10 degrees. Also, it is demonstrated that the optimization
of the angle, duration and the amplitude of the driving field leads to
significant decrease of both MST and SD. In particular, for the considered
parameters, the MST can be decreased from 60 ns to 2-3 ns. Such a chain of
magnetic nanoparticles can effectively be used as an element of
magnetoresistive memory, and at the temperature 300K the stable operation of
the element is observed up to rather small size of nanoparticles with the
raduis of 20 nm.

###Anderson Localization Triggered by Spin Disorder---with an Application to Eu_x Ca_1-x B_6|Daniel Egli,Jürg Fröhlich,Hans-Rudolf Ott###

Anderson Localization Triggered by Spin Disorder---with an Application to Eu_x Ca_1-x B_6. The phenomenon of Anderson localization is studied for a class of
one-particle Schr\"odinger operators with random Zeeman interactions. These
operators arise as follows: Static spins are placed randomly on the sites of a
simple cubic lattice according to a site percolation process with density x and
coupled to one another ferromagnetically. Scattering of an electron in a
conduction band at these spins is described by a random Zeeman interaction term
that originates from indirect exchange. It is shown rigorously that, for
positive values of x below the percolation threshold, the spectrum of the
one-electron Schr\"odinger operator near the band edges is dense pure-point,
and the corresponding eigenfunctions are exponentially localized.
  Localization near the band edges persists in a weak external magnetic field,
H, but disappears gradually, as H is increased. Our results lead us to predict
the phenomenon of colossal (negative) magnetoresistance and the existence of a
Mott transition, as H and/or x are increased.
  Our analysis is motivated directly by experimental results concerning the
magnetic alloy Eu_x Ca_1-x B_6.

###Cooper pair insulator in amorphous films induced by nanometer-scale thickness variations|S. M. Hollen,H. Q. Nguyen,E. Rudisaile,M. D. Stewart Jr.,J. Shainline,J. M. Xu,J. M. Valles Jr###

Cooper pair insulator in amorphous films induced by nanometer-scale thickness variations. Unusual transport properties of superconducting (SC) materials, such as the
under doped cuprates, low dimensional superconductors in strong magnetic
fields, and insulating films near the Insulator Superconductor Transition
(IST), have been attributed to the formation of inhomogeneous phases.
Difficulty correlating the behaviors with observations of the inhomogeneities
make these connections uncertain. Of primary interest here are proposals that
insulating films near the IST, which show an activated resistance and giant
positive magnetoresistance, contain islands of Cooper Pairs (CPs). Here we
present evidence that these types of inhomogeneities are essential to such an
insulating phase in amorphous Bi (a-Bi) films deposited on substrates patterned
with nanometer-sized holes. The patterning induces film thickness variations,
and corresponding coupling constant variations, that transform the composition
of the insulator from localized electrons to CPs. Analyses near the
thickness-tuned ISTs of films on nine different substrates show that weak links
between SC islands dominate the transport. In particular, the ISTs all occur
when the link resistance approaches the resistance quantum for pairs. These
observations lead to a detailed picture of CPs localized by spatial variations
of the superconducting coupling constant.

###Incoherent Effect of Fe and Ni Substitutions in the Ferromagnetic-Insulator La0.6Bi0.4MnO3+d|Asish K. Kundu,Md. Motin Seikh,Akhilesh Srivastava,S. Mahajan,R. Chatterjee,V. Pralong,B. Raveau###

Incoherent Effect of Fe and Ni Substitutions in the Ferromagnetic-Insulator La0.6Bi0.4MnO3+d. A comparative study of the effect of Fe and Ni doping on the bismuth based
perovskite La0.6Bi0.4MnO3.1, a projected spintronics magnetic semiconductor has
been carried out. The doped systems show an expressive change in magnetic
ordering temperature. However, the shifts in ferromagnetic transition (TC) of
these doped phases are in opposite direction with respect to the parent phase
TC of 115 K. The Ni-doped phase shows an increase in TC ~200 K, whereas the
Fe-doped phase exhibits a downward shift to TC~95 K. Moreover, the Fe-doped is
hard-type whereas the Ni-doped compound is soft-type ferromagnet. It is
observed that the materials are semiconducting in the ferromagnetic phase with
activation energies of 77 & 82 meV for Fe & Ni-doped phases respectively. In
the presence of external magnetic field of 7 Tesla, they exhibit minor changes
in the resistivity behaviours and the maximum isothermal magnetoresistance is
around -20 % at 125 K for the Ni-phase. The results are explained on the basis
of electronic phase separation and competing ferromagnetic and
antiferromagnetic interactions between the various mixed valence cations.

###The Influence of Magnetic Anisotropy on the Kondo Effect and Spin-Polarized Transport through Magnetic Molecules, Adatoms and Quantum Dots|Maciej Misiorny,Ireneusz Weymann,Jozef Barnas###

The Influence of Magnetic Anisotropy on the Kondo Effect and Spin-Polarized Transport through Magnetic Molecules, Adatoms and Quantum Dots. Transport properties in the Kondo regime of a nanosystem displaying uniaxial
magnetic anisotropy (such as a magnetic molecule, magnetic adatom or quantum
dot coupled to a localized magnetic moment) are analyzed theoretically. In
particular, the influence of spin-polarized transport through a local orbital
of the system and exchange coupling of conduction electrons to the system's
magnetic core on the Kondo effect is discussed. The numerical renormalization
group method is applied to calculate the spectral functions and linear
conductance in the case of the parallel and antiparallel configurations of the
electrodes' magnetic moments. It is shown that both the magnetic anisotropy as
well as the exchange coupling between electrons tunneling through the
conducting orbital and magnetic core play an important role in formation of the
Kondo resonance, leading generally to its suppression. Specific transport
properties of such a system appear also as a nontrivial behavior of tunnel
magnetoresistance. It is also shown that the Kondo effect can be restored by an
external magnetic field in both the parallel and antiparallel magnetic
configurations.

###Effect of hydrogen plasma treatment and oxygen deficiency on conducting properties of In$_2$O$_3$:Sn thin films|V. G. Kytin,V. A. Kulbachinskii,O. V. Reukova,Y. M. Galperin,T. H. Johansen,S. Diplas,A. G. Ulyashin###

Effect of hydrogen plasma treatment and oxygen deficiency on conducting properties of In$_2$O$_3$:Sn thin films. Electrical conductivity, Hall effect and magnetoresistance of In$_2$O$_3$:Sn
thin films deposited on a glass substrates at different temperatures and oxygen
pressures, as well as the films treated in a hydrogen plasma, have been
investigated in the temperature range 1.5-300 K. The observed temperature
dependences of resistivity were typical for metallic transport of electrons
except temperature dependence of resistivity of the In$_2$O$_3$:Sn film
deposited in the oxygen deficient atmosphere. The electron concentration and
mobility for the film deposited at 230$^\circ$C was larger than that for the
film deposited nominally at room temperature. Short (5 minutes) treatment of
the films in hydrogen plasma leads to the enhancement of electrical
conductivity while longer (30 minute) treatment has the opposite effect. The
electrical measurements were accompanied by AFM and SEM studies of structural
properties, as well as by XPS analysis. Basic on structural and electrical
measurements we conclude the reduction process initiated by the hydrogen plasma
provides essential modification of the ITO films surface. At the same time,
electrical properties of the remaining (located beneath the surface layer)
parts of the ITO films remain mostly unchangeable. XPS analysis shows that
grown in situ oxygen deficient ITO films have enhanced DOS between the Fermi
level and the valence band edge. The extra localized states behave as acceptors
leading to a compensation of $n$-type ITO. That can explain lower $n$-type
conductivity in this material crossing over to a Mott-type hopping.

###Seebeck Effect in Magnetic Tunnel Junctions|Marvin Walter,Jakob Walowski,Vladyslav Zbarsky,Markus Münzenberg,Markus Schäfers,Daniel Ebke,Günter Reiss,Andy Thomas,Patrick Peretzki,Michael Seibt,Jagadeesh S. Moodera,Michael Czerner,Michael Bachmann,Christian Heiliger###

Seebeck Effect in Magnetic Tunnel Junctions. Creating temperature gradients in magnetic nanostructures has resulted in a
new research direction, i.e., the combination of magneto- and thermoelectric
effects. Here, we demonstrate the observation of one important effect of this
class: the magneto-Seebeck effect. It is observed when a magnetic configuration
changes the charge based Seebeck coefficient. In particular, the Seebeck
coefficient changes during the transition from a parallel to an antiparallel
magnetic configuration in a tunnel junction. In that respect, it is the analog
to the tunneling magnetoresistance. The Seebeck coefficients in parallel and
antiparallel configuration are in the order of the voltages known from the
charge-Seebeck effect. The size and sign of the effect can be controlled by the
composition of the electrodes' atomic layers adjacent to the barrier and the
temperature. Experimentally, we realized 8.8 % magneto-Seebeck effect, which
results from a voltage change of about -8.7 {\mu}V/K from the antiparallel to
the parallel direction close to the predicted value of -12.1 {\mu}V/K.

###Sondheimer Oscillation as a Fingerprint of Surface Dirac Fermions|Heon-Jung Kim,Ki-Seok Kim,Mun Dae Kim,S. -J. Lee,J. -W. Han,A. Ohnishi,M. Kitaura,M. Sasaki,A. Kondo,K. Kindo###

Sondheimer Oscillation as a Fingerprint of Surface Dirac Fermions. Topological states of matter challenge the paradigm of symmetry breaking,
characterized by gapless boundary modes and protected by the topological
property of the ground state. Recently, angle-resolved photoemission
spectroscopy (ARPES) has revealed that semiconductors of Bi$_{2}$Se$_{3}$ and
Bi$_{2}$Te$_{3}$ belong to such a class of materials. Here, we present
undisputable evidence for the existence of gapless surface Dirac fermions from
transport in Bi$_{2}$Te$_{3}$. We observe Sondheimer oscillation in
magnetoresistance (MR). This oscillation originates from the quantization of
motion due to the confinement of electrons within the surface layer. Based on
Sondheimer's transport theory, we determine the thickness of the surface state
from the oscillation data. In addition, we uncover the topological nature of
the surface state, fitting consistently both the non-oscillatory part of MR and
the Hall resistance.
  The side-jump contribution turns out to dominate around 1 T in Hall
resistance while the Berry-curvature effect dominates in 3 T $\sim$ 4 T.

###Crossover between different regimes of inhomogeneous superconductivity in planar superconductor-ferromagnet hybrids|A. Yu. Aladyshkin,J. Fritzsche,R. Werner,R. B. G. Kramer,S. Guenon,R. Kleiner,D. Koelle,V. V. Moshchalkov###

Crossover between different regimes of inhomogeneous superconductivity in planar superconductor-ferromagnet hybrids. We studied experimentally the effect of a stripe-like domain structure in a
ferromagnetic BaFe_{12}O_{19} substrate on the magnetoresistance of a
superconducting Pb microbridge. The system was designed in such a way that the
bridge is oriented perpendicular to the domain walls. It is demonstrated that
depending on the ratio between the amplitude of the nonuniform magnetic field
B_0, induced by the ferromagnet, and the upper critical field H_{c2} of the
superconducting material, the regions of the reverse-domain superconductivity
in the H-T plane can be isolated or can overlap (H is the external magnetic
field, T is temperature). The latter case corresponds to the condition
B_0/H_{c2}<1 and results in the formation of superconductivity above the
magnetic domains of both polarities. We discovered the regime of edge-assisted
reverse-domain superconductivity, corresponding to localized superconductivity
near the edges of the bridge above the compensated magnetic domains. Direct
verification of the formation of inhomogeneous superconducting states and
external-field-controlled switching between normal state and inhomogeneous
superconductivity were obtained by low-temperature scanning laser microscopy.

###Correlated conformation and charge transport in multiwall carbon nanotube - conducting polymer nanocomposites|Paramita Kar Choudhury,S. Ramaprabhu,K. P. Ramesh,Reghu Menon###

Correlated conformation and charge transport in multiwall carbon nanotube - conducting polymer nanocomposites. The strikingly different charge transport behaviors in nanocomposites of
multiwall carbon nanotubes (MWNTs) and conducting polymer polyethylene
dioxythiophene - polystyrene sulfonic acid (PEDOT-PSS) at low temperatures are
explained by probing their conformational properties using small angle X-ray
scattering (SAXS). The SAXS studies indicate assembly of elongated PEDOT-PSS
globules on the walls of nanotubes, coating them partially thereby limiting the
interaction between the nanotubes in the polymer matrix. This results in a
charge transport governed mainly by small polarons in the conducting polymer
despite the presence of metallic MWNTs. At T > 4 K, hopping of the charge
carriers following 1D-VRH is evident which also gives rise to a positive
magnetoresistance (MR) with an enhanced localization length (~ 5 nm) due to the
presence of MWNTs. However, at T < 4 K, the observation of an unconventional
positive temperature coefficient of resistivity (TCR) is attributed to small
polaron tunnelling. The exceptionally large negative MR observed in this
temperature regime is conjectured to be due to the presence of quasi-1D MWNTs
that can aid in lowering the tunnelling barrier across the nanotube - polymer
boundary resulting in large delocalization.

###Conductance anisotropy and linear magnetoresistance in La2-xSrxCuO4 thin films|M. van Zalk,A. Brinkman,H. Hilgenkamp###

Conductance anisotropy and linear magnetoresistance in La2-xSrxCuO4 thin films. We have performed a detailed study of conductance anisotropy and
magnetoresistance (MR) of La2-xSrxCuO4 (LSCO) thin films (0.10 < x < 0.25).
These two observables are promising for the detection of stripes. Subtle
features of the conductance anisotropy are revealed by measuring the transverse
resistance Rxy in zero magnetic field. It is demonstrated that the sign of Rxy
depends on the orientation of the LSCO Hall bar with respect to the terrace
structure of the substrate. Unit-cell-high substrate step edges must therefore
be a dominant nucleation source for antiphase boundaries during film growth. We
show that the measurement of Rxy is sensitive enough to detect the
cubic-tetragonal phase transition of the SrTiO3(100) (STO) substrate at 105 K.
The MR of LSCO thin films shows for 0.10 < x < 0.25 a non-monotonic temperature
dependence, resulting from the onset of a linear term in the MR above 90 K. We
show that the linear MR scales with the absolute Hall resistivity, with the
constant of proportionality independent of temperature. Such scaling suggests
that the linear MR originates from current distortions induced by structural or
electronic inhomogeneities. The possible role of stripes for both the MR and
the conductance anisotropy is discussed throughout the paper.

###Direct imaging of the coexistence of ferromagnetism and superconductivity at the LaAlO3/SrTiO3 interface|J. A. Bert,B. Kalisky,C. Bell,M. Kim,Y. Hikita,H. Y. Hwang,K. A. Moler###

Direct imaging of the coexistence of ferromagnetism and superconductivity at the LaAlO3/SrTiO3 interface. LaAlO3 and SrTiO3 are insulating, nonmagnetic oxides, yet the interface
between them exhibits a two-dimensional electron system with high electron
mobility,1 superconductivity at low temperatures,2-6 and electric-field-tuned
metal-insulator and superconductorinsulator phase transitions.3,6-8 Bulk
magnetization and magnetoresistance measurements also suggest some form of
magnetism depending on preparation conditions5,9-11 and suggest a tendency
towards nanoscale electronic phase separation.10 Here we use local imaging of
the magnetization and magnetic susceptibility to directly observe a landscape
of ferromagnetism, paramagnetism, and superconductivity. We find submicron
patches of ferromagnetism in a uniform background of paramagnetism, with a
nonuniform, weak diamagnetic superconducting susceptibility at low temperature.
These results demonstrate the existence of nanoscale phase separation as
suggested by theoretical predictions based on nearly degenerate interface
sub-bands associated with the Ti orbitals.12,13 The magnitude and temperature
dependence of the paramagnetic response suggests that the vast majority of the
electrons at the interface are localized, and do not contribute to transport
measurements.3,6,7 In addition to the implications for magnetism, the existence
of a 2D superconductor at an interface with highly broken inversion symmetry
and a ferromagnetic landscape in the background suggests the potential for
exotic superconducting phenomena.

###First order antiferro-ferromagnetic transition in Fe49(Rh0.93Pd0.07)51 under simultaneous application of magnetic field and external pressure|Pallavi Kushwaha,Pallab Bag,R Rawat,P Chaddah###

First order antiferro-ferromagnetic transition in Fe49(Rh0.93Pd0.07)51 under simultaneous application of magnetic field and external pressure. The magnetic field-pressure-temperature (H-P-T) phase diagram for first order
antiferromagnetic (AFM) to ferromagnetic (FM) transition in
Fe49(Rh0.93Pd0.07)51 has been constructed using resistivity measurements under
simultaneous application of magnetic field (up to 8 Tesla) and pressure (up to
20 kbar). Temperature dependence of resistivity ({\rho}-T) shows that with
increasing pressure, the width of the transition and the extent of hysteresis
decreases whereas with the application of magnetic field it increases.
Consistent with existing literature the first order transition temperature (TN)
increases with the application of external pressure (~ 7.3 K/ kbar) and
decreases with magnetic field (~ - 12.8 K/Tesla). Exploiting these opposing
trends, resistivity under simultaneous application of magnetic field and
pressure is used to distinguish the relative effect of temperature, magnetic
field and pressure on disorder broadened first order transition. For this a set
of H and P values are chosen for which TN (H1, P1) = TN (H2, P2). Measurements
for such combinations of H and P show that the temperature dependence of
resistivity is similar i.e. the broadening (in temperature) of transition as
well as extent of hysteresis remains independent of H and P. The transition
width decreases exponentially with increasing temperature. Isothermal
magnetoresistance measurement under various constant pressure show that even
though the critical field required for AFM-FM transition depends on applied
pressure, the hysteresis as well as transition width (in magnetic field) both
remains independent of pressure, consistent with our conclusions drawn from
{\rho}-T measurements.

###Observation of Quantum Interference in Molecular Charge Transport|Constant M. Guedon,Hennie Valkenier,Troels Markussen,Kristian S. Thygesen,Jan C. Hummelen,Sense Jan van der Molen###

Observation of Quantum Interference in Molecular Charge Transport. As the dimensions of a conductor approach the nano-scale, quantum effects
will begin to dominate its behavior. This entails the exciting possibility of
controlling the conductance of a device by direct manipulation of the electron
wave function. Such control has been most clearly demonstrated in mesoscopic
semiconductor structures at low temperatures. Indeed, the Aharanov-Bohm effect,
conductance quantization and universal conductance fluctuations are direct
manifestations of the electron wave nature. However, an extension of this
concept to more practical emperatures has not been achieved so far. As
molecules are nano-scale objects with typical energy level spacings (~eV) much
larger than the thermal energy at 300 K (~25 meV), they are natural candidates
to enable such a break-through. Fascinating phenomena including giant
magnetoresistance, Kondo effects and conductance switching, have previously
been demonstrated at the molecular level. Here, we report direct evidence for
destructive quantum interference in charge transport through two-terminal
molecular junctions at room temperature. Furthermore, we show that the degree
of interference can be controlled by simple chemical modifications of the
molecule. Not only does this provide the experimental demonstration of a new
phenomenon in quantum charge transport, it also opens the road for a new type
of molecular devices based on chemical or electrostatic control of quantum
interference.

###Spintronic oxides grown by laser-MBE|Matthias Opel###

Spintronic oxides grown by laser-MBE. The recent study of oxides led to the discovery of several new fascinating
physical phenomena. High-temperature superconductivity, colossal
magnetoresistance, dilute magnetic doping, or multiferroicity were discovered
and investigated in transition-metal oxides, representing a prototype class of
strongly correlated electronic systems. This development was accompanied by an
enormous progress regarding thin film fabrication. Within the past two decades,
epitaxial thin films with crystalline quality approaching semiconductor
standards became available using laser molecular beam epitaxy. This evolution
is reviewed, particularly with emphasis on transition-metal oxide thin films,
their versatile physical properties, and their impact on the field of
spintronics. First, the physics of ferromagnetic half-metallic oxides, such as
the doped manganites, the double perovskites and magnetite is presented
together with possible applications based on magnetic tunnel junctions. Second,
the wide bandgap semiconductor zinc oxide is discussed particularly with regard
to the controversy of dilute magnetic doping with transition-metal ions and the
possibility of realizing p-type conductivity. Third, the field of oxide
multiferroics is presented with the recent developments in single-phase
multiferroic thin film perovskites as well as in composite multiferroic
hybrids.

###Influence of spin polarization on resistivity of a two-dimensional electron gas in Si MOSFET at metallic densities|I. Shlimak,A. Butenko,D. I. Golosov,K. -J. Friedland,S. V. Kravchenko###

Influence of spin polarization on resistivity of a two-dimensional electron gas in Si MOSFET at metallic densities. Positive magnetoresistance (PMR) of a silicon MOSFET in parallel magnetic
fields B has been measured at high electron densities n >> n_c where n_c is the
critical density of the metal-insulator transition (MIT). It turns out that the
normalized PMR curves, R(B)/R(0), merge together when the field is scaled
according to B/B_c(n) where B_c is the field in which electrons become fully
spin polarized. The values of B_c have been calculated from the simple equality
between the Zeeman splitting energy and the Fermi energy taking into account
the experimentally measured dependence of the spin susceptibility on the
electron density. This extends the range of validity of the scaling all the way
to a deeply metallic regime far away from MIT. The subsequent analysis of PMR
for low n >~ n_c demonstrated that the merging of the initial parts of curves
can bee achieved only with taking into account the temperature dependence of
B_c. It is also shown that the shape of the PMR curves at strong magnetic
fields is affected by a crossover from a purely two-dimensional (2D) electron
transport to a regime where out-of-plane carrier motion becomes important
(quasi-three-dimensional regime).

###Anisotropic conductance at improper ferroelectric domain walls|Dennis Meier,Jan Seidel,Andres Cano,Kris Delaney,Yu Kumagai,Maxim Mostovoy,Nicola A. Spaldin,Ramamoorthy Ramesh,Manfred Fiebig###

Anisotropic conductance at improper ferroelectric domain walls. Transition metal oxides hold great potential for the development of new
device paradigms because of the field-tunable functionalities driven by their
strong electronic correlations, combined with their earth abundance and
environmental friendliness. Recently, the interfaces between transition-metal
oxides have revealed striking phenomena such as insulator-metal transitions,
magnetism, magnetoresistance, and superconductivity. Such oxide interfaces are
usually produced by sophisticated layer-by-layer growth techniques, which can
yield high quality, epitaxial interfaces with almost monolayer control of
atomic positions. The resulting interfaces, however, are fixed in space by the
arrangement of the atoms. Here we demonstrate a route to overcoming this
geometric limitation. We show that the electrical conductance at the
interfacial ferroelectric domain walls in hexagonal ErMnO3 is a continuous
function of the domain wall orientation, with a range of an order of magnitude.
We explain the observed behaviour using first-principles density functional and
phenomenological theories, and relate it to the unexpected stability of
head-to-head and tail-to-tail domain walls in ErMnO3 and related hexagonal
manganites. Since the domain wall orientation in ferroelectrics is tunable
using modest external electric fields, our finding opens a degree of freedom
that is not accessible to spatially fixed interfaces.

###Universal conductance fluctuations in indium tin oxide nanowires|Ping-Yu Yang,L. Y. Wang,Yao-Wen Hsu,Juhn-Jong Lin###

Universal conductance fluctuations in indium tin oxide nanowires. Magnetic field dependent universal conductance fluctuations (UCF's) are
observed in weakly disordered indium tin oxide nanowires from 0.26 K up to
$\sim 25$ K. The fluctuation magnitudes increase with decreasing temperature,
reaching a fraction of $e^2/h$ at $T \lesssim 1$ K. The shape of the UCF
patterns is found to be very sensitive to thermal cycling of the sample to room
temperatures, which induces irreversible impurity reconfigurations. On the
other hand, the UCF magnitudes are insensitive to thermal cycling. Our measured
temperature dependence of the root-mean-square UCF magnitudes are compared with
the existing theory [C. W. J. Beenakker and H. van Houten, Phys. Rev. B
\textbf{37}, 6544 (1988)]. A notable discrepancy is found, which seems to imply
that the experimental UCF's are not cut off by the thermal diffusion length
$L_T$, as would be expected by the theoretical prediction when $L_T <
L_\varphi$, where $L_\varphi$ is the electron dephasing length. The approximate
electron dephasing length is inferred from the UCF magnitudes and compared with
that extracted from the weak-localization magnetoresistance studies. A
reasonable semiquantitative agreement is observed.

###Audio Cards for High-Resolution and Economical Electronic Transport Studies|Daniel B. Gopman,Daniel Bedau,Andrew D. Kent###

Audio Cards for High-Resolution and Economical Electronic Transport Studies. We report on a technique for determining electronic transport properties
using commercially available audio cards. Using a typical 24-bit audio card
simultaneously as a sine wave generator and a narrow bandwidth ac voltmeter, we
show the spectral purity of the analog-to-digital and digital-to-analog
conversion stages, including an effective number of bits greater than 16 and
dynamic range better than 110 dB. We present two circuits for transport studies
using audio cards: a basic circuit using the analog input to sense the voltage
generated across a device due to the signal generated simultaneously by the
analog output; and a digitally-compensated bridge to compensate for nonlinear
behavior of low impedance devices. The basic circuit also functions as a high
performance digital lock-in amplifier. We demonstrate the application of an
audio card for studying the transport properties of spin-valve nanopillars, a
two-terminal device that exhibits Giant Magnetoresistance (GMR) and whose
nominal impedance can be switched between two levels by applied magnetic fields
and by currents applied by the audio card.

###Extraordinary magnetoresistance in graphite: experimental evidence for the time-reversal symmetry breaking|Y. Kopelevich,R. R. da Silva,A. S. Alexandrov###

Extraordinary magnetoresistance in graphite: experimental evidence for the time-reversal symmetry breaking. The ordinary magnetoresistance (MR) of doped semiconductors is positive and
quadratic in a low magnetic field, B, as it should be in the framework of the
Boltzmann kinetic theory or in the conventional hopping regime. We observe an
unusual highly-anisotropic in-plane MR in graphite, which is neither quadratic
nor always positive. In a certain current direction MR is negative and linear
in B in fields below a few tens of mT with a crossover to a positive MR at
higher fields, while in a perpendicular current direction we observe a giant
super-linear and positive MR. These extraordinary MRs are respectively
explained by a hopping magneto-conductance via non-zero angular momentum
orbitals, and by the magneto-conductance of inhomogeneous media. The linear
orbital NMR is a unique signature of the broken time-reversal symmetry (TRS) in
graphite. While some local paramagnetic centers could be responsible for the
broken TRS, the observed large diamagnetism suggests a more intriguing
mechanism of this breaking, involving superconducting clusters with
unconventional (chiral) order parameters and spontaneously generated
normal-state current loops in graphite.

###Size-dependent electronic-transport mechanism and sign reversal of magnetoresistance in Nd0.5Sr0.5CoO3|S. Kundu,T. K. Nath###

Size-dependent electronic-transport mechanism and sign reversal of magnetoresistance in Nd0.5Sr0.5CoO3. A detailed investigation of electronic-transport properties of Nd0.5Sr0.5CoO3
has been carried out as a function of grain size ranging from micrometer order
down to an average size of 28 nm. Interestingly, we observe a size induced
metal-insulator transition in the lowest grain size sample while the bulk-like
sample is metallic in the whole measured temperature regime. An analysis of the
temperature dependent resistivity in the metallic regime reveals that the
electron-electron interaction is the dominating mechanism while other processes
like electron-magnon and electron-phonon scatterings are also likely to be
present. The fascinating observation of enhanced low temperature upturn and
minimum in resistivity on reduction of grain size is found due to
electron-electron interaction (quantum interference effect). This effect is
attributed to enhanced disorder on reduction of grain size. Interestingly, we
observed a cross over from positive to negative magnetoresistance in the low
temperature regime as the grain size is reduced. This observed sign reversal is
attributed to enhanced phase separation on decreasing the grain size of the
cobaltite.

###Molecular Magnetocapacitance|Yu-Ning Wu,Xiao-Guang Zhang,Hai-Ping Cheng###

Molecular Magnetocapacitance. Capacitance of a nanoscale system is usually thought of having two
contributions, a classical electrostatic contribution and a quantum
contribution dependent on the density of states and/or molecular orbitals close
to the Fermi energy. In this letter we demonstrate that in molecular
nano-magnets and other magnetic nanoscale systems, the quantum part of the
capacitance becomes spin-dependent, and is tunable by an external magnetic
field. This molecular magnetocapacitance can be realized using single molecule
nano-magnets and/or other nano-structures that have antiferromagnetic ground
states. As a proof of principle, first-principles calculation of the
nano-magnet [Mn3O(sao)3(O2CMe)(H2O)(py)3] shows that the charging energy of the
high-spin state is 260 meV lower than that of the low-spin state, yielding a 6%
difference in capacitance. A magnetic field of ~40T can switch the spin state,
thus changing the molecular capacitance. A smaller switching field may be
achieved using nanostructures whose physical properties such as magnetic moment
are size-dependent. Molecular magnetocapacitance may lead to revolutionary
device designs, e.g., by exploiting the Coulomb blockade magnetoresistance
whereby a small change in capacitance can lead to a huge change in resistance.

###Effects of carrier mobility and morphology in organic semiconductor spin valves|Yaohua Liu,Taegweon Lee,Howard E. Katz,Daniel H. Reich###

Effects of carrier mobility and morphology in organic semiconductor spin valves. We studied spin transport in four organic semiconductors (OSCs) with
different electronic properties, with Fe and Co as the top and bottom
ferromagnetic (FM) contacts, respectively. Magnetoresistance (MR) effects were
observed up to room temperature in junctions based on an electron-carrying OSC,
tris(8-hyroxyquinoline) aluminum (Alq$_3$) and a hole-carrying OSC, copper
phthalocyanine (CuPc). The MR shows similar temperature dependence for these
two OSCs, which suggests that the FM leads rather than the OSCs play a dominant
role on the spin-transport degradation with increasing temperature. We also
investigated junctions based on two high lateral mobility electron-carrying
OSCs, 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) and N,
N'-bis(4-trifluoromethylbenzyl)-1,4,5,8-naphthalenetetracarboxylic diimide
(CF$_3$-NTCDI). However, these junctions showed much weaker spin transport
effects. Morphological studies suggest that these high mobility OSC films have
much rougher surfaces than either Alq$_3$ or CuPc, therefore the degradation of
spin transport may originate from enhanced scattering due to the rougher FM/OSC
interfaces. Our study shows that FM/OSC interfaces play an important role for
spin transport in organic devices and need further exploration.

###Properties of Binary Transition-Metal Arsenides (TAs)|B. Saparov,J. E. Mitchell,A. S. Sefat###

Properties of Binary Transition-Metal Arsenides (TAs). We present thermodynamic and transport properties of transition-metal (T)
arsenides, TAs with T = Sc to Ni (3d), Zr, Nb, Ru (4d), Hf and Ta (5d).
Characterization of these binaries is made with powder X-ray diffraction,
temperature and field-dependent magnetization and resistivity,
temperature-dependent heat capacity, Seebeck coefficient, and thermal
conductivity. All binaries show metallic behavior except TaAs and RuAs. TaAs,
NbAs, ScAs and ZrAs are diamagnetic, while CoAs, VAs, TiAs, NiAs and RuAs show
approximately Pauli paramagnetic behavior. FeAs and CrAs undergo
antiferromagnetic order below TN = 71 K and TN \approx 260 K, respectively.
MnAs is a ferromagnet below TC = 317 K and undergoes
hexagonal-orthorhombic-hexagonal transitions at TS = 317 K and 384 K,
respectively. For TAs, Seebeck coefficients vary between + 40 uV/K and - 40
uV/K in the 2 K to 300 K range, whereas thermal conductivity values stay below
18 W/(m K). The Sommerfeld-coefficient {\gamma} are less than 10 mJ/(K2mol). At
room temperature with application of 8 Tesla magnetic field, large positive
magnetoresistance is found for TaAs (~25%), MnAs (~90%) and for NbAs (~75%).

###Laser-assisted spin-polarized transport in graphene tunnel junctions|Kai-He Ding,Zhen-Gang Zhu,Jamal Berakdar###

Laser-assisted spin-polarized transport in graphene tunnel junctions. Keldysh nonequilibrium Green's function method is utilized to study
theoretically the spin polarized transport through a graphene spin valve
irradiated by a monochromatic laser field. It is found that the bias dependence
of the differential conductance exhibits successive peaks corresponding to the
resonant tunneling through the photon-assisted sidebands. The multi photon
processes originate from the combined effects of the radiation field and the
graphene tunneling properties, and are shown to be substantially suppressed in
a graphene spin valve which results in a decrease of the differential
conductance for a high bias voltage. We also discussed the appearance of a
dynamical gap around zero bias due to the radiation field. The gap width can be
tuned by changing the radiation electric field strength and the frequency. This
leads to a shift of the resonant peaks in the differential conductance. We also
demonstrate numerically the dependencies of the radiation and spin valve
effects on the parameters of the external fields and those of the electrodes.
We find that the combined effects of the radiation field, the graphene, and the
spin valve properties bring about an oscillatory behavior in the tunnel
magnetoresistance (TMR), and this oscillatory amplitude can be changed by
scanning the radiation field strength and/or the frequency.

###Hysteresis and stepwise structure in MR curves of granular superconducting ruthenocuprates RuSr$_2$(Gd$_{1.5}$Ce$_{0.5})$Cu$_2$O$_{10-δ}$}|B. I. Belevtsev,E. Yu. Beliayev,D. G. Naugle,K. D. D. Rathnayaka###

Hysteresis and stepwise structure in MR curves of granular superconducting ruthenocuprates RuSr$_2$(Gd$_{1.5}$Ce$_{0.5})$Cu$_2$O$_{10-δ}$}. Granular superconductivity effects in a polycrystalline sample of
ruthenocuprate RuSr$_2$(Gd$_{1.5}$Ce$_{0.5})$Cu$_2$O$_{10-\delta}$ are studied.
The main attention has been devoted to manifestation of these effects in
current and magnetic-field dependences of resistive transition to
superconducting state. It is found that current dependences of differential
resistance taken at different temperatures intersect strictly at two definite
values of current demonstrating crossing point effect. This phenomenon has been
explained taking into account inhomogeneous state of intergrain medium which
can be considered as a two-component system. The particular attention has been
given to magnetoresistance (MR) hysteresis in mixed state of this inhomogeneous
system and to influence of applied current and temperature on this phenomenon.
Two types of hysteresis (clockwise and anticlockwise) have been found with
transition from clockwise to anticlockwise hysteresis with increasing
temperature. Stepwise structure in MR hysteretic curves has been observed in
low-field range. Possible reasons of the change in hysteresis behavior with
increasing temperature and appearance of the stepwise structure in MR curves
are discussed taking into consideration inhomogeneous state of the granular
superconductor studied.

###Anisotropic magnetothermoelectric power of ferromagnetic thin films|M. S. Anwar,B. Lacoste,J. Aarts###

Anisotropic magnetothermoelectric power of ferromagnetic thin films. We compare the behavior of the magnetothermoelectric power (MTEP)in metallic
ferromagnetic thin films of Ni80Fe20 (Permalloy; Py), Co and CrO2 at
temperatures in the range of 100 K to 400 K. In 25 nm thick Py films and 50 nm
thick Co films both the anisotropic magnetoresistance (AMR) and MTEP show a
relative change in resistance and thermoelectric power (TEP) of the order of
0.2% when the magnetic field is reversed, and in both cases there is no
significant change in AMR or MTEP any more after the saturation field has been
reached. Surprisingly, both Py and Co films have opposite MTEP behavior
although both have the same sign for AMR and TEP. The data on 100 nm films of
fully spin-polarized CrO2, grown both on TiO2 and on sapphire, show a different
picture. The MTEP behavior at low fields shows peaks similar to the AMR in
these films, with variations up to 1%. With increasing field both the MR and
the MTEP variations keeps growing, with MTEP showing relative changes of 1.5%
with the thermal gradient along the b-axis and even 20% with the gradient along
the c-axis, with an intermediate value of 3% for the film on sapphire. It
appears that the low-field effects are due to magnetic domain switching, while
the high-field effects are intrinsic to the electronic structure of CrO2.

###Magnetic anomalies in single crystalline Tb5Si3|Kartik K. Iyer,K. Mukherjee,P. L. Paulose,E. V. Sampathkumaran,Y. Xu,W. Löser###

Magnetic anomalies in single crystalline Tb5Si3. The polycrystalline form of the compound, Tb5Si3, crystallizing in
Mn5Si3-type hexagonal structure, which was earlier believe to order
antiferromagnetically below 69 K, has been recently reported by us to exhibit
interesting magnetoresistance (MR) anomalies. In order to understand the
magnetic anomalies of this compound better, we synthesized single crystals of
this compound and subjected them to intense magnetization and MR studies. The
results reveal that the magnetic behavior is strongly anisotropic as the easy
axis is along a basal plane. There appear to be multiple magnetic features in
the close vicinity of 70 K. In addition, there are multiple steps in isothermal
magnetization (which could not be resolved in the data for polycrystalline
data) for magnetic-field (H) along a basal plane. The sign of MR is positive in
the magnetically ordered state, and, interestingly, the magnitude dramatically
increases at the initial step for H parallel to basal plane, but decreases at
subsequent steps as though the origin of these steps are different. However,
for the perpendicular orientation (H || [0 0 0 1]), there is no evidence for
any step either in M(H) or in MR(H). These results establish this compound is
an interesting magnetic material.

###Interplay between ferromagnetism, surface states, and quantum corrections in a magnetically doped topological insulator|Duming Zhang,Anthony Richardella,David W. Rench,Su-Yang Xu,Abhinav Kandala,Thomas C. Flanagan,Haim Beidenkopf,Andrew L. Yeats,Bob B. Buckley,Paul V. Klimov,David D. Awschalom,Ali Yazdani,Peter Schiffer,M. Zahid Hasan,Nitin Samarth###

Interplay between ferromagnetism, surface states, and quantum corrections in a magnetically doped topological insulator. The breaking of time-reversal symmetry by ferromagnetism is predicted to
yield profound changes to the electronic surface states of a topological
insulator. Here, we report on a concerted set of structural, magnetic,
electrical and spectroscopic measurements of \MBS thin films wherein
photoemission and x-ray magnetic circular dichroism studies have recently shown
surface ferromagnetism in the temperature range 15 K $\leq T \leq 100$ K,
accompanied by a suppressed density of surface states at the Dirac point.
Secondary ion mass spectroscopy and scanning tunneling microscopy reveal an
inhomogeneous distribution of Mn atoms, with a tendency to segregate towards
the sample surface. Magnetometry and anisotropic magnetoresistance measurements
are insensitive to the high temperature ferromagnetism seen in surface studies,
revealing instead a low temperature ferromagnetic phase at $T \lesssim 5$ K.
The absence of both a magneto-optical Kerr effect and anomalous Hall effect
suggests that this low temperature ferromagnetism is unlikely to be a
homogeneous bulk phase but likely originates in nanoscale near-surface regions
of the bulk where magnetic atoms segregate during sample growth. Although the
samples are not ideal, with both bulk and surface contributions to electron
transport, we measure a magnetoconductance whose behavior is qualitatively
consistent with predictions that the opening of a gap in the Dirac spectrum
drives quantum corrections to the conductance in topological insulators from
the symplectic to the orthogonal class.

###Influence of the substrate and precursor on the magnetic and magneto-transport properties in magnetite films|Enio Lima Jr,Giancarlo E. S. Brito,Christian Cavelius,Vladimir Sivakov,Hao Shen,Sanjay Mathur,Gerardo F. Goya###

Influence of the substrate and precursor on the magnetic and magneto-transport properties in magnetite films. We have investigated the magnetic and transport properties of nanoscaled
Fe3O4 films obtained from Chemical Vapor Deposition (CVD) technique using
[FeIIFe2III(OBut)8] and [Fe2III(OBut)6] precursors. Samples were deposited on
different substrates (i.e., MgO (001), MgAl2O4 (001) and Al2O3 (0001)) with
thicknesses varying from 50 to 350 nm. Atomic Force Microscopy analysis
indicated a granular nature of the samples, irrespective of the synthesis
conditions (precursor and deposition temperature, Tpre) and substrate. Despite
the similar morphology of the films, magnetic and transport properties were
found to depend on the precursor used for deposition. Using [FeIIFe2III(OBut)8]
as precursor resulted in lower resistivity, higher MS and a sharper
magnetization decrease at the Verwey transition (TV). The temperature
dependence of resistivity was found to depend on the precursor and Tpre. We
found that the transport is dominated by the density of antiferromagnetic
antiphase boundaries (AF-APB's) when [FeIIFe2III(OBut)8] precursor and Tpre =
363 K are used. On the other hand, grain boundary-scattering seems to be the
main mechanism when [Fe2III(OBut)6] is used. The Magnetoresistance (MR(H))
displayed an approximate linear behavior in the high field regime (H > 796
kA/m), with a maximum value at room-temperature of \sim2-3% for H = 1592 kA/m,
irrespective from the transport mechanism.

###Experimental observation of the optical spin-orbit torque|N. Tesarova,P. Nemec,E. Rozkotova,J. Zemen,F. Trojanek,K. Olejnik,V. Novak,P. Maly,T. Jungwirth###

Experimental observation of the optical spin-orbit torque. Spin polarized carriers electrically injected into a magnet from an external
polarizer can exert a spin transfer torque (STT) on the magnetization. The phe-
nomenon belongs to the area of spintronics research focusing on manipulating
magnetic moments by electric fields and is the basis of the emerging
technologies for scalable magnetoresistive random access memories. In our
previous work we have reported experimental observation of the optical
counterpart of STT in which a circularly polarized pump laser pulse acts as the
external polarizer, allowing to study and utilize the phenomenon on several
orders of magnitude shorter timescales than in the electric current induced
STT. Recently it has been theoretically proposed and experimentally
demonstrated that in the absence of an external polarizer, carriers in a magnet
under applied electric field can develop a non-equilibrium spin polarization
due to the relativistic spin-orbit coupling, resulting in a current induced
spin-orbit torque (SOT) acting on the magnetization. In this paper we report
the observation of the optical counterpart of SOT. At picosecond time-scales,
we detect excitations of magnetization of a ferromagnetic semiconductor
(Ga,Mn)As which are independent of the polarization of the pump laser pulses
and are induced by non-equilibrium spin-orbit coupled photo-holes.

###Ultrafast transient generation of spin-densitywave order in the normal state of BaFe2As2 driven by coherent lattice vibrations|K. W. Kim,A. Pashkin,H. Schäfer,M. Beyer,M. Porer,T. Wolf,C. Bernhard,J. Demsar,R. Huber,A. Leitenstorfer###

Ultrafast transient generation of spin-densitywave order in the normal state of BaFe2As2 driven by coherent lattice vibrations. The interplay among charge, spin and lattice degrees of freedom in solids
gives rise to intriguing macroscopic quantum phenomena such as colossal
magnetoresistance, multiferroicity and high-temperature superconductivity.
Strong coupling or competition between various orders in these systems presents
the key to manipulate their functional properties by means of external
perturbations such as electric and magnetic fields or pressure. Ultrashort and
intense optical pulses have emerged as an interesting tool to investigate
elementary dynamics and control material properties by melting an existing
order. Here, we employ few-cycle multi-terahertz pulses to resonantly probe the
evolution of the spin-density-wave (SDW) gap of the pnictide compound BaFe2As2
following excitation with a femtosecond optical pulse. When starting in the
low-temperature ground state, optical excitation results in a melting of the
SDW order, followed by ultrafast recovery. In contrast, the SDW gap is induced
when we excite the normal state above the transition temperature. Very
surprisingly, the transient ordering quasi-adiabatically follows a coherent
lattice oscillation at a frequency as high as 5.5 THz. Our results attest to a
pronounced spin-phonon coupling in pnictides that supports rapid development of
a macroscopic order on small vibrational displacement even without breaking the
symmetry of the crystal.

###Magnetic, magnetocaloric and magnetotransport properties of RSn_{1+x}Ge_{1-x} compounds (R=Gd, Tb, Er; x=0.1)|Sachin B. Gupta,K. G. Suresh,A. K. Nigam###

Magnetic, magnetocaloric and magnetotransport properties of RSn_{1+x}Ge_{1-x} compounds (R=Gd, Tb, Er; x=0.1). We have studied the magnetic, magnetocaloric and magnetotransport properties
of RSn1+xGe1-x(R=Gd, Tb, Er; x=0.1) series by means of magnetization, heat
capacity and resistivity measurements. It has been found that all the compounds
crystallize in the orthorhombic crystal structure described by the
centrosymmetric space group Cmcm (No. 63). The magnetic susceptibility and heat
capacity data suggest that all the compounds are antiferromagnetic. Large
negative values of {\theta}p in case of GdSn1.1Ge0.9 and TbSn1.1Ge0.9 indicate
that strong antiferromagnetic interactions are involved, which is also
reflected in the magnetization isotherms. On the other hand ErSn1.1Ge0.9 shows
weak antiferromagnetic interaction. The heat capacity data have been analyzed
by fitting the temperature dependence and the values of {\theta}D and {\gamma}
have been estimated. Among these three compounds, ErSn1.1Ge0.9 shows
considerable magnetic entropy change of 9.5 J/kg K and an adiabatic temperature
change of 3.2 K for a field of 50 kOe. The resistivity data in different
temperature regimes have been analyzed and the dominant contributions have been
identified. All the compounds show small but positive magnetoresistance.

###Observation of a Phase Transition at 55 K in Single-Crystal CaCu1.7As2|V. K. Anand,D. C. Johnston###

Observation of a Phase Transition at 55 K in Single-Crystal CaCu1.7As2. We present the structural, magnetic, thermal and ab-plane electronic
transport properties of single crystals of CaCu1.7As2 grown by the self-flux
technique that were investigated by powder x-ray diffraction, magnetic
susceptibility chi, isothermal magnetization M, specific heat Cp, and
electrical resistivity rho measurements as a function of temperature T and
magnetic field H. X-ray diffraction analysis of crushed crystals at room
temperature confirm the collapsed tetragonal ThCr2Si2-type structure with \sim
15% vacancies on the Cu sites as previously reported, corresponding to the
composition CaCu1.7As2. The chi(T) data are diamagnetic, anisotropic and nearly
independent of T. The chi is larger in the ab-plane than along the c-axis, as
also observed previously for SrCu2As2 and for pure and doped BaFe2As2. The
Cp(T) and rho(T) data indicate metallic sp-band character. In contrast to the
chi(T) and Cp(T) data that do not show any evidence for phase transitions below
300 K, the rho(T) data exhibit a sharp increase in slope on cooling below a
temperature Tt = 54-56 K, depending on the crystal. The \rho(T) data show no
hysteresis on warming and cooling through Tt and the transition appears to be
second order. The phase transition may arise from spatial ordering of the
vacancies on the Cu sublattice. The Tt is found to be independent of H for H
\leq 8 T. A positive magnetoresistance is observed below Tt that increases with
decreasing T and attains a value in H = 8.0 T of 8.7% at T = 1.8 K.

###A Gate-tunable Polarized Phase of Two-Dimensional Electrons at the LaAlO3/SrTiO3 Interface|Arjun Joshua,J. Ruhman,S. Pecker,E. Altman,S. Ilani###

A Gate-tunable Polarized Phase of Two-Dimensional Electrons at the LaAlO3/SrTiO3 Interface. Controlling the coupling between localized spins and itinerant electrons can
lead to exotic magnetic states. A novel system featuring local magnetic moments
and extended 2D electrons is the interface between LaAlO3 and SrTiO3. The
magnetism of the interface, however, was observed to be insensitive to the
presence of these electrons and is believed to arise solely from extrinsic
sources like oxygen vacancies and strain. Here we show the existence of
unconventional electronic phases in the LaAlO3/SrTiO3 system pointing to an
underlying tunable coupling between itinerant electrons and localized moments.
Using anisotropic magnetoresistance and anomalous Hall effect measurements in a
unique in-plane configuration, we identify two distinct phases in the space of
carrier density and magnetic field. At high densities and fields, the
electronic system is strongly polarized and shows a response, which is highly
anisotropic along the crystalline directions. Surprisingly, below a
density-dependent critical field, the polarization and anisotropy vanish
whereas the resistivity sharply rises. The unprecedented vanishing of the easy
axes below a critical field is in sharp contrast with other coupled magnetic
systems and indicates strong coupling with the moments that depends on the
symmetry of the itinerant electrons. The observed interplay between the two
phases indicates the nature of magnetism at the LaAlO3/SrTiO3 interface as both
having an intrinsic origin and being tunable.

###Gate tunable quantum transport in double layer graphene|K. Kechedzhi,E. H. Hwang,S. Das Sarma###

Gate tunable quantum transport in double layer graphene. We analyze the effect of screening provided by the additional graphene layer
in double layer graphene heterostructures (DLGs) on transport characteristics
of DLG devices in the metallic regime. The effect of gate-tunable charge
density in the additional layer is two-fold: it provides screening of the
long-range potential of charged defects in the system, and screens out Coulomb
interactions between charge carriers. We find that the efficiency of defect
charge screening is strongly dependent on the concentration and location of
defects within the DLG. In particular, only a moderate suppression of
electron-hole puddles around the Dirac point induced by the high concentration
of remote impurities in the silicon oxide substrate could be achieved. A
stronger effect is found on the elastic relaxation rate due to charged defects
resulting in mobility strongly dependent on the electron denisty in the
additional layer of DLG. We find that the quantum interference correction to
the resistivity of graphene is also strongly affected by screening in DLG. In
particular, the dephasing rate is strongly suppressed by the additional
screening that supresses the amplitude of electron-electron interaction and
reduces the diffusion time that electrons spend in proximity of each other. The
latter effect combined with screening of elastic relaxation rates results in a
peculiar gate tunable weak-localization magnetoresistance and quantum
correction to resistivity. We propose suitable experiments to test our theory
and discuss the possible relevance of our results to exisiting data.

###Microwave Spectroscopy Evidence of Superconducting Pairing in the Magnetic-Field-Induced Metallic State of InO$_x$ Films at Zero Temperature|Wei Liu,LiDong Pan,Jiajia Wen,Minsoo Kim,G. Sambandamurthy,N. P. Armitage###

Microwave Spectroscopy Evidence of Superconducting Pairing in the Magnetic-Field-Induced Metallic State of InO$_x$ Films at Zero Temperature. We investigate the field tuned quantum phase transition in a 2D low-disorder
amorphous InO$_x$ film in the frequency range of 0.05 to 16 GHz employing
microwave spectroscopy. In the zero temperature limit, the AC data are
consistent with a scenario where this transition is from a superconductor to a
metal instead of a direct transition to an insulator. The intervening metallic
phase is unusual with a small but finite resistance that is much smaller than
the normal state sheet resistance at the lowest measured temperatures.
Moreover, it exhibits a superconducting response on short length and time
scales while global superconductivity is destroyed. We present evidence that
the true quantum critical point of this 2D superconductor metal transition is
located at a field $B_{sm}$ far below the conventionally defined critical field
$B_{cross}$ where different isotherms of magnetoresistance cross each other.
The superfluid stiffness in the low frequency limit and the superconducting
fluctuation frequency from opposite sides of the transition both vanish at B
$\approx B_{sm}$. The lack of evidence for finite-frequency superfluid
stiffness surviving $B_{cross}$ signifies that $B_{cross}$ is a crossover above
which superconducting fluctuations make a vanishing contribution to DC and AC
measurements.

###Multiscale modeling in micromagnetics: existence of solutions and numerical integration|Florian Bruckner,Michael Feischl,Thomas Führer,Petra Goldenits,Marcus Page,Dirk Praetorius,Michele Ruggeri,Dieter Suess###

Multiscale modeling in micromagnetics: existence of solutions and numerical integration. Various applications ranging from spintronic devices, giant magnetoresistance
sensors, and magnetic storage devices, include magnetic parts on very different
length scales. Since the consideration of the Landau-Lifshitz-Gilbert equation
(LLG) constrains the maximum element size to the exchange length within the
media, it is numerically not attractive to simulate macroscopic parts with this
approach. On the other hand, the magnetostatic Maxwell equations do not
constrain the element size, but cannot describe the short-range exchange
interaction accurately. A combination of both methods allows to describe
magnetic domains within the micromagnetic regime by use of LLG and also
considers the macroscopic parts by a non-linear material law using the Maxwell
equations. In our work, we prove that under certain assumptions on the
non-linear material law, this multiscale version of LLG admits weak solutions.
Our proof is constructive in the sense that we provide a linear-implicit
numerical integrator for the multiscale model such that the numerically
computable finite element solutions admit weak $H^1$-convergence (at least for
a subsequence) towards a weak solution.

###Anomalous magnetoresistance and magnetocaloric properties of NdRu2Ge2|Bibekananda Maji,K. G. Suresh,A. K. Nigam###

Anomalous magnetoresistance and magnetocaloric properties of NdRu2Ge2. It is found that the polycrystalline NdRu2Ge2 undergoes two successive
magnetic transitions at Tt=10 K and TN=19 K. Evidence of metamagnetic
transition is detected in the magnetization isotherm data in the
antiferromagnetic regime. Temperature dependence of magnetoresistance (MR) show
that the relative magnitudes of MR at TN and Tt change considerably as the
field is increased from 10 kOe to 30 kOe. Moreover, the MR is found to be
positive below 9 K for 30 kOe field although the material is ferromagnetic at
these temperatures. The highest value of negative MR near TN is about 42% in a
field of 30 kOe, while the positive MR is about 35 % at 3 K in a field of 50
kOe. Like MR, the magnetocaloric effect at TN and Tt also shows anomalous
behavior. The relative magnitudes of MCE at these temperatures are found to
change with increase in field. It appears that the high field (>10 kOe)
magnetic state below TN is complex, giving rise to some antiferromagnetic-like
fluctuations, affecting the MR and MCE behavior.

###Fermionic and bosonic ac conductivities at strong disorder|S. V. Syzranov,O. M. Yevtushenko,K. B. Efetov###

Fermionic and bosonic ac conductivities at strong disorder. We study the ac conduction in a system of fermions or bosons strongly
localised in a disordered array of sites with short-range interactions at
frequencies larger than the intersite tunnelling but smaller than the
characteristic fluctuation of the on-site energy. While the main contribution
$\sigma_0(\omega)$ to the conductivity comes from local dipole-type excitations
on close pairs of sites, coherent processes on three or more sites lead to an
interference correction $\sigma_1(\omega)$, which depends on the statistics of
the charge carriers and can be suppressed by magnetic field. For bosons the
correction is always positive, while for fermions it can be positive or
negative depending on whether the conduction is dominated by effective
single-particle or single-hole processes. We calculate the conductivity
explicitly assuming a constant density of states of single-site excitations.
Independently of the statistics, $\sigma_0(\omega)=const$. For bosons
$\sigma_1(\omega)\propto \log(C/\omega)$. For fermions
$\sigma_1(\omega)\propto\log[\max(A,\omega)/\omega]-\log[\max(B,\omega)/\omega]$,
where the first and the second term are respectively the particle and hole
contributions, $A$ and $B$ being the particle and hole energy cutoffs. The ac
magnetoresistance has the same sign as $\sigma_1(\omega)$.

###Valley-dependent 2D transport in Si-MOSFETs|E. H. Hwang,S. Das Sarma###

Valley-dependent 2D transport in Si-MOSFETs. Motivated by interesting recent experimental results, we consider
theoretically charged-impurity scattering-limited 2D electronic transport in
(100), (110), and (111)-Si inversion layers at low temperatures and carrier
densities, where screening effects are important. We show conclusively that,
given the same bare Coulomb disorder, the 2D mobility for a given system
increases monotonically with increasing valley degeneracy. We also show that
the temperature and the parallel magnetic field dependence of the 2D
conductivity is strongly enhanced by increasing valley degeneracy. We
analytically consider the low temperature limit of 2D transport, particularly
its theoretical dependence on valley degeneracy, comparing with our full
numerical results and with the available experimental results. We make
qualitative and quantitative predictions for the parallel magnetic field
induced 2D magnetoresistance in recently fabricated high-mobility 6-valley
Si(111)-on-vacuum inversion layers. We also provide a theory for 2D transport
in ultrahigh mobility Si(111) structures recently fabricated in the laboratory,
discussing the possibility of observing the fractional quantum Hall effect in
such Si(111) structures.

###Organic magnetoresistance near saturation: mesoscopic effects in small devices|R. C. Roundy,Z. V. Vardeny,M. E. Raikh###

Organic magnetoresistance near saturation: mesoscopic effects in small devices. In organic light emitting diodes with small area the current may be dominated
by a finite number, N of sites in which the electron-hole recombination occurs.
As a result, averaging over the hyperfine magnetic fields, b_h, that are
generated in these sites by the environment nuclei is incomplete. This creates
a random (mesoscopic) current component, {\Delta}I(B), at field B having
relative magnitude ~ N^(-1/2). To quantify the statistical properties of
{\Delta}I(B) we calculate the correlator K(B, {\Delta}B)= <{\delta}I(B -
{\Delta}B/2){\delta}I(B + {\Delta}B/2)> for parallel and perpendicular
orientations of {\Delta}B. We demonstrate that mesoscopic fluctuations develop
at fields B>>b_h, where the average magnetoresistance is near saturation. These
fluctuations originate from the slow beating between S and T_0 states of the
recombining e-h spin pair-partners. We identify the most relevant processes
responsible for the current fluctuations as due to anomalously slow beatings
that develop in sparse e-h polaron pairs at sites for which the b_h projections
on the external field direction almost coincide.

###Strong magnetoresistance of disordered graphene|P. S. Alekseev,A. P. Dmitriev,I. V. Gornyi,V. Yu. Kachorovskii###

Strong magnetoresistance of disordered graphene. We study theoretically magnetoresistance (MR) of graphene with different
types of disorder. For short-range disorder, the key parameter determining
magnetotransport properties---a product of the cyclotron frequency and
scattering time---depends in graphene not only on magnetic field $H$ but also
on the electron energy $\varepsilon$. As a result, a strong, square-root in
$H$, MR arises already within the Drude-Boltzmann approach. The MR is
particularly pronounced near the Dirac point. Furthermore, for the same reason,
"quantum" (separated Landau levels) and "classical" (overlapping Landau levels)
regimes may coexist in the same sample at fixed $H.$ We calculate the
conductivity tensor within the self-consistent Born approximation for the case
of relatively high temperature, when Shubnikov-de Haas oscillations are
suppressed by thermal averaging. We predict a square-root MR both at very low
and at very high $H:$ $[\varrho_{xx}(H)-\varrho_{xx}(0)]/\varrho_{xx}(0)\approx
C \sqrt{H},$ where $C$ is a temperature-dependent factor, different in the low-
and strong-field limits and containing both "quantum" and "classical"
contributions. We also find a nonmonotonic dependence of the Hall coefficient
both on magnetic field and on the electron concentration. In the case of
screened charged impurities, we predict a strong temperature-independent MR
near the Dirac point. Further, we discuss the competition between disorder- and
collision-dominated mechanisms of the MR. In particular, we find that the
square-root MR is always established for graphene with charged impurities in a
generic gated setup at low temperature.

###Electronic phase separation due to magnetic polaron formation in the semimetallic ferromagnet EuB$_6$ - A weakly-nonlinear-transport study|A. Amyan,P. Das,J. Müller,Z. Fisk###

Electronic phase separation due to magnetic polaron formation in the semimetallic ferromagnet EuB$_6$ - A weakly-nonlinear-transport study. We report measurements of weakly nonlinear electronic transport, as measured
by third-harmonic voltage generation $V_{3\omega}$, in the low-carrier density
semimetallic ferromagnet EuB$_6$, which exhibits an unusual magnetic ordering
with two consecutive transitions at $T_{c_1} = 15.6$\,K and $T_{c_2} =
12.5$\,K. Upon cooling in zero magnetic field through the ferromagnetic
transition, the dramatic drop in the linear resistivity at the upper transition
$T_{c_1}$ coincides with the onset of nonlinearity, and upon further cooling is
followed by a pronounced peak in $V_{3 \omega}$ at the lower transition
$T_{c_2}$. Likewise, in the paramagnetic regime, a drop of the material's
magnetoresistance $R(H)$ precedes a magnetic-field-induced peak in nonlinear
transport. A striking observation is a linear temperature dependence of
$V_{3\omega}^{\rm peak}(H)$. We suggest a picture where at the upper transition
$T_{c_1}$ the coalescing MP form a conducting path giving rise to a strong
decrease in the resistance. The MP formation sets in at around $T^\ast \sim
35$\,K below which these entities are isolated and strongly fluctuating, while
growing in number. The MP then start to form links at $T_{c_1}$, where
percolative electronic transport is observed. The MP merge and start forming a
continuum at the threshold $T_{c_2}$. In the paramagnetic temperature regime
$T_{c_1} < T < T^\ast$, MP percolation is induced by a magnetic field, and the
threshold accompanied by charge carrier delocalization occurs at a single
critical magnetization.

###Integration of the Ferromagnetic Insulator EuO onto Graphene|Adrian G. Swartz,Patrick M. Odenthal,Yufeng Hao,Rodney S. Ruoff,Roland K. Kawakami###

Integration of the Ferromagnetic Insulator EuO onto Graphene. We have demonstrated the deposition of EuO films on graphene by reactive
molecular beam epitaxy in a special adsorption-controlled and oxygen-limited
regime, which is a critical advance toward the realization of the exchange
proximity interaction (EPI). It has been predicted that when the ferromagnetic
insulator (FMI) EuO is brought into contact with graphene, an overlap of
electronic wavefunctions at the FMI/graphene interface can induce a large spin
splitting inside the graphene. Experimental realization of this effect could
lead to new routes for spin manipulation, which is a necessary requirement for
a functional spin transistor. Furthermore, EPI could lead to novel spintronic
behavior such as controllable magnetoresistance, gate tunable exchange bias,
and quantized anomalous Hall effect. However, experimentally, EuO has not yet
been integrated onto graphene. Here we report the successful growth of high
quality crystalline EuO on highly-oriented pyrolytic graphite (HOPG) and
single-layer graphene. The epitaxial EuO layers have (001) orientation and do
not induce an observable D peak (defect) in the Raman spectra. Magneto-optic
measurements indicate ferromagnetism with Curie temperature of 69 K, which is
the value for bulk EuO. Transport measurements on exfoliated graphene before
and after EuO deposition indicate only a slight decrease in mobility.

###Spin Pumping and Inverse Spin Hall Effect in Germanium|J. -C. Rojas-Sánchez,M. Cubukcu,A. Jain,C. Vergnaud,C. Portemont,C. Ducruet,A. Barski,A. Marty,L. Vila,J. -P. Attané,E. Augendre,G. Desfonds,S. Gambarelli,H. Jaffrès,J. -M. George,M. Jamet###

Spin Pumping and Inverse Spin Hall Effect in Germanium. We have measured the inverse spin Hall effect (ISHE) in \textit{n}-Ge at room
temperature. The spin current in germanium was generated by spin pumping from a
CoFeB/MgO magnetic tunnel junction in order to prevent the impedance mismatch
issue. A clear electromotive force was measured in Ge at the ferromagnetic
resonance of CoFeB. The same study was then carried out on several test
samples, in particular we have investigated the influence of the MgO tunnel
barrier and sample annealing on the ISHE signal. First, the reference CoFeB/MgO
bilayer grown on SiO$_{2}$ exhibits a clear electromotive force due to
anisotropic magnetoresistance and anomalous Hall effect which is dominated by
an asymmetric contribution with respect to the resonance field. We also found
that the MgO tunnel barrier is essential to observe ISHE in Ge and that sample
annealing systematically lead to an increase of the signal. We propose a
theoretical model based on the presence of localized states at the interface
between the MgO tunnel barrier and Ge to account for these observations.
Finally, all of our results are fully consistent with the observation of ISHE
in heavily doped $n$-Ge and we could estimate the spin Hall angle at room
temperature to be $\approx$0.001.

###Current Perpendicular-to-Plane (CPP) Magnetoresistance (MR)|Jack Bass###

Current Perpendicular-to-Plane (CPP) Magnetoresistance (MR). Measurements of Giant Magnetoresistance (GMR) in ferromagnetic/non-magnetic
(F/N) multilayers with Current flow Perpendicular to the layer Planes
(CPP-geometry) can give better access to the fundamental physics underlying GMR
than measurements with the more usual Current flow In the layer Planes (CIP
geometry). Because the same measuring current passes through all of the layers,
the CPP-MR can often be described by simpler equations that allow separation of
effects of scattering within the bulk of the F- and N-metals and at F/N, N1/N2,
and F/S (S = superconductor) interfaces. We first describe the parameters that
are used to characterize the CPP-MR, the different techniques used to measure
these parameters, and the different types of multilayers used to control the
two orientations of the magnetizations of adjacent F-layers, anti-parallel (AP)
and parallel (P), that permit isolation of the parameters. We then detail what
has been learned about the parameters of bulk F-metals, of bulk N-metals, and
of F/N, N1/N2, and F/S interfaces. Especially important are the parameters of
interfaces and the spin-diffusion lengths in F-metals and F-alloys, about which
almost nothing was known in advance. Lastly, we describe work toward CPP-MR
devices and studies of magnetothermoelectric effects, before summarizing what
has been learned and listing some items not yet understood.

###Low-Dilution Limit of Zn_{1-x}Mn_{x}GeAs_{2}: electrical and magnetic properties|L. Kilanski,K. Szałowski,R. Szymczak,M. Górska,E. Dynowska,P. Aleshkevych,A. Podgórni,A. Avdonin,W. Dobrowolski,I. V. Fedorchenko,S. F. Marenkin###

Low-Dilution Limit of Zn_{1-x}Mn_{x}GeAs_{2}: electrical and magnetic properties. We present the studies of electrical transport and magnetic interactions in
Zn_{1-x}Mn_{x}GeAs_{2} crystals with low Mn content 0 \leq x \leq 0.043. We
show that the ionic-acceptor defects are mainly responsible for the strong
p-type conductivity of our samples. We found that the negative
magnetoresistance (MR) with maximum values of about -50% is related to the weak
localization phenomena. The magnetic properties of Zn1-xMnxGeAs2 samples show
that the random Mn-distribution in the cation sites of the host lattice occurs
only for the sample with the lowest Mn-content, x=0.003. The samples with
higher Mn-content show a high level of magnetic frustration. Nonzero
Curie-Weiss temperature observed in all our samples indicates that weak
ferromagnetic (for x=0.003) or antiferromagnetic (for x>0.005) interactions
with |{\Theta}|<3 K are present in this system. The RKKY model, used to
estimate the Mn-hole exchange integral Jpd for the diluted
Zn/0.997/Mn/0.003/GeAs/2/ sample, makes possible to estimate the value of Jpd
=(0.75+/-0.09) eV.

###Tunnel magnetoresistance in organic spin valves in the regime of multi-step tunneling|R. C. Roundy,M. E. Raikh###

Tunnel magnetoresistance in organic spin valves in the regime of multi-step tunneling. A model of a spin valve in which electron transport between the magnetized
electrodes is due to multistep tunneling is analyzed. Motivated by recent
experiments on organic spin valves, we assume that spin memory loss in the
course of transport is due to random hyperfine fields acting on electron while
it waits for the next tunneling step. Amazingly, we identify the three-step
configurations of sites, for which the tunnel magnetoresistance (TMR) is
negative, suggesting that the resistance for antiparallel magnetizations of the
electrodes is smaller than for parallel magnetizations. We analyze the phase
volume of these configurations with respect to magnitudes and relative
orientations of the on-site hyperfine fields. The effect of sign reversal of
TMR is exclusively due to interference of the spin-flip amplitudes on each
site, it does not emerge within commonly accepted probabilistic description of
spin transport. Another feature specific to multistep inelastic tunneling is
bouncing of electron between nearest neighbors while awaiting a "hard" hop. We
demonstrate that this bouncing, being absolutely insignificant for conduction
of current, can strongly affect the spin memory loss. This effect is also of
interference origin.

###Origin of the energy gap in the narrow-gap semiconductor FeSb2 revealed by high-pressure magnetotransport measurements|H. Takahashi,R. Okazaki,I. Terasaki,Y. Yasui###

Origin of the energy gap in the narrow-gap semiconductor FeSb2 revealed by high-pressure magnetotransport measurements. To elucidate an origin of the two energy gaps in the narrow-gap semiconductor
FeSb2, we have investigated the effects of hydrostatic pressure on the
resistivity, Hall resistance and magnetoresistance at low temperatures. The
larger energy gap evaluated from the temperature dependence of resistivity
above 100 K is enhanced from 30 to 40 meV with pressure from 0 to 1.8 GPa, as
generally observed in conventional semiconductors. In the low-temperature range
where a large Seebeck coefficient was observed, we evaluate the smaller energy
gap from the magnetotransport tensor using a two-carrier model and find that
the smaller gap exhibits a weak pressure dependence in contrast to that of the
larger gap. To explain the pressure variations of the energy gaps, we propose a
simple model that the smaller gap is a gap from the impurity level to the
conduction band and the larger one is a gap between the valence and conduction
bands, suggesting that the observed large Seebeck coefficient is not relevant
to electron correlation effects.

###Spin-Flipping in Pt and at Co/Pt Interfaces|Hoang Yen Thi Nguyen,Jack Bass,William P. Pratt Jr###

Spin-Flipping in Pt and at Co/Pt Interfaces. There has been recent controversy about the magnitude of spin-flipping in the
heavy metal Pt, characterized by the spin-diffusion length, lsf(Pt) We propose
a resolution of this controversy, and also present evidence for the importance
of a phenomenon neglected in prior studies of transport across sputtered
Ferromagnetic/Pt (F/Pt) interfaces, spin-flipping at the interface. The latter
is characterized by an interface spin-flipping parameter, delta(Co/Pt) that
specifies the probability P = [1 - exp(-delta)] of a conduction electron
flipping its spin direction as it traverses a Co/Pt interface. From studies of
the Current-Perpendicular-to-Plane (CPP) Resistances and Magnetoresistances of
sputtered ferromagnetically coupled Co/Pt multilayers by themselves, and
embedded within Py-based Double Exchange-biased Spin-Valves, we derive values
at 4.2K of delta(Co/Pt) = 0.9 (+0.5/-0.2), the interface specific resistance,
AR*(Co/Pt) = 0.74 +/- 0.15 fohm-m(2). and the interface spin-scattering
asymmetry, gamma(Co/Pt) = 0.58 +/- 0.12. This value of delta(Co/Pt) is much
larger than ones previously found for interfaces involving Co but not Pt. To
derive delta requires knowledge of the spin-diffusion length, lsf(Pt), for our
sputtered Pt. We derive lsf(Pt) from separate measurements. Combining our
results with those from others, we find that lsf(Pt) for Pt is approximately
proportional to the inverse resistivity, 1/rho(Pt).

###Cluster glass magnetism in the phase-separated Nd2/3Ca1/3MnO3 perovskite|Elena Fertman,Sergiy Dolya,Vladimir Desnenko,Anatoly Beznosov,Marcela Kajnakova,Alexander Feher###

Cluster glass magnetism in the phase-separated Nd2/3Ca1/3MnO3 perovskite. A detailed study of the low-temperature magnetic state and the relaxation in
the phase-separated colossal magnetoresistance Nd2/3Ca1/3MnO3 perovskite has
been carried out. Clear experimental evidence of the cluster-glass magnetic
behavior of this compound has been revealed. Well defined maxima in the
in-phase linear ac susceptibility $\chi ^{/}(T)$ were observed, indicative of
the magnetic glass transition at $T_{g}$ = 60 K. Strongly divergent
zero-field-cooled and field-cooled static magnetizations and frequency
dependent ac susceptibility are evident of the glassy-like magnetic state of
the compound at low temperatures. The frequency dependence of the cusp
temperature Tmax of the $\chi ^{/}(T)$ susceptibility was found to follow the
critical slowing down mechanism. The Cole-Cole analysis of the dynamic
susceptibility at low temperature has shown extremely broad distribution of
relaxation times, indicating that spins are frozen at "macroscopic" time scale.
Slow relaxation in the zero-field-cooled magnetization has been experimentally
revealed. The obtained results do not agree with a canonical spin-glass state
and indicate a cluster glass magnetic state of the compound below $T_{g}$,
associated with its antiferromagnetic-ferromagnetic nano-phase segregated
state. It was found that the relaxation mechanisms below the cluster glass
freezing temperature $T_{g}$ and above it are strongly different. Magnetic
field up to about $\mu_{0}$H = 0.4 T suppresses the glassy magnetic state of
the compound.

###Chiral anomaly, dimensional reduction, and magnetoresistivity of Weyl and Dirac semimetals|E. V. Gorbar,V. A. Miransky,I. A. Shovkovy###

Chiral anomaly, dimensional reduction, and magnetoresistivity of Weyl and Dirac semimetals. By making use of the Kubo formula, we calculate the conductivity of Dirac and
Weyl semimetals in a magnetic field. We find that the longitudinal (along the
direction of the magnetic field) magnetoresistivity is negative at sufficiently
large magnetic fields for {\it both} Dirac and Weyl semimetals. The physical
reason of this phenomenon is intimately connected with the dimensional spatial
reduction $3 \to 1$ in the dynamics of the lowest Landau level. The
off-diagonal component of the transverse (with respect to the direction of the
magnetic field) conductivity in Weyl semimetals contains an anomalous
contribution directly proportional to the momentum space separation between the
Weyl nodes. This contribution comes exclusively from the lowest Landau level
and, as expected, is independent of the temperature, chemical potential, and
magnetic field. The other part of the off-diagonal conductivity is the same as
in Dirac semimetals and is connected with a nonzero density of charge carriers.
The signatures for experimental distinguishing Weyl semimetals from Dirac ones
through the measurements of conductivity are discussed.

###Hyperfine Interactions in MnAs studied by Perturbed Angular Correlations of $γ$-Rays using the probe $^{77}$Br$\rightarrow^{77}$Se and first principles calculations for MnAs and other Mn pnictides|J. N. Gonçalves,V. S. Amaral,J. G. Correia,A. M. L. Lopes###

Hyperfine Interactions in MnAs studied by Perturbed Angular Correlations of $γ$-Rays using the probe $^{77}$Br$\rightarrow^{77}$Se and first principles calculations for MnAs and other Mn pnictides. The MnAs compound shows a first-order transition at T$_C\approx42$ C, and a
second-order transition at T$_t\approx120$ C. The first-order transition, with
structural (hexagonal-orthorhombic), magnetic (FM-PM) and electrical
conductivity changes, is associated to magnetocaloric, magnetoelastic, and
magnetoresistance effects. We report a study in a large temperature range from
$-196$ up to $140$ C, using the $\gamma-\gamma$ perturbed angular correlations
method with the radioactive probe $^{77}$Br$\rightarrow^{77}$Se, produced at
the ISOLDE-CERN facility. The electric field gradients and magnetic hyperfine
fields are determined across the first- and second-order phase transitions
encompassing the pure and mixed phase regimes in cooling and heating cycles.
The temperature irreversibility of the 1st order phase transition is seen
locally, at the nanoscopic scale sensitivity of the hyperfine field, by its
hysteresis, detailing and complementing information obtained with macroscopic
measurements (magnetization and X-ray powder diffraction). To interpret the
results, hyperfine parameters were obtained with first-principles
spin-polarized density functional calculations using the generalized gradient
approximation with the full potential (L)APW+lo method (\textsc{Wien2k} code)
by considering the Se probe at both Mn and As sites. A clear assignment of the
probe location at the As site is made and complemented with the calculated
densities of states and local magnetic moments. We model electronic and
magnetic properties of the chemically similar MnSb and MnBi compounds,
complementing previous calculations.

###Unravelling the effect of SrTiO3 antiferrodistortive phase transition on the magnetic properties of La0.7Sr0.3MnO3 thin films|D. A. Mota,Y. Romaguera Barcelay,A. M. R. Senos,C. M. Fernandes,P. B. Tavares,I. T. Gomes,P. Sá,L. Fernandes,B. G. Almeida,F. Figueiras,P. Mirzadeh Vaghefi,V. S. Amaral,A. Almeida,J. Pérez de la Cruz,J. Agostinho Moreira###

Unravelling the effect of SrTiO3 antiferrodistortive phase transition on the magnetic properties of La0.7Sr0.3MnO3 thin films. Epitaxial La0.7Sr0.3MnO3 (LSMO) thin films, with different thickness ranging
from 20 nm up to 330 nm, were deposited on (100)-oriented strontium titanate
(STO) substrates by pulsed laser deposition, and their structure and morphology
characterized at room temperature. Magnetic and electric transport properties
of the as-processed thin films reveal an abnormal behavior in the temperature
dependent magnetization M(T) below the antiferrodistortive STO phase transition
(TSTO) and also an anomaly in the magnetoresistance and electrical resistivity
close to the same temperature. Up to 100 nm LSMO thin films, an in-excess
magnetization and pronounced changes in the coercivity are evidenced, achieved
through the interface-mediated magnetoelastic coupling with antiferrodistortive
domain wall movement occurring below TSTO. Contrarily, for thicker LSMO thin
films, above 100 nm, an in-defect magnetization is observed. This reversed
behavior can be understood within the emergence in the upper layer of the film,
observed by high resolution transmission electron microscopy, of a branched
structure needed to relax elastic energy stored in the film which leads to
randomly oriented magnetic domain reconstructions. For enough high-applied
magnetic fields, as thermodynamic equilibrium is reached, a fully suppression
of the anomalous magnetization occurs, wherein the temperature dependence of
the magnetization starts to follow the expected Brillouin behavior.

###Ferromagnetism and Spin-dependent Transport in n-type Mn-Bi2Te3 Thin Films|Joon Sue Lee,Anthony Richardella,David W. Rench,Robert D. Fraleigh,Thomas C. Flanagan,Julie A. Borchers,Jing Tao,Nitin Samarth###

Ferromagnetism and Spin-dependent Transport in n-type Mn-Bi2Te3 Thin Films. We describe a detailed study of the structural, magnetic, and
magneto-transport properties of single-crystal, n-type, Mn-doped Bi2Te3 thin
films grown by molecular beam epitaxy. With increasing Mn concentration, the
crystal structure changes from the tetradymite structure of the Bi2Te3 parent
crystal at low Mn concentrations towards a BiTe phase in the (Bi2Te3)m(Bi2)n
homologous series. Magnetization measurements reveal the onset of
ferromagnetism with a Curie temperature in the range 13.8 K - 17 K in films
with 2 % - 10 % Mn concentration. Magnetization hysteresis loops reveal that
the magnetic easy axis is along the c-axis of the crystal (perpendicular to the
plane). Polarized neutron reflectivity measurements of a 68 nm-thick sample
show that the magnetization is uniform through the film. The presence of
ferromagnetism is also manifest in a strong anomalous Hall effect and a
hysteretic magnetoresistance arising from domain wall scattering. Ordinary Hall
effect measurements show that the carrier density is n-type, increases with Mn
doping, and is high enough (> 2.8 x 10^{13} cm^{-2}) to place the chemical
potential in the conduction band. Thus, the observed ferromagnetism is likely
associated with both bulk and surface states. Surprisingly, the Curie
temperature does not show any clear dependence on the carrier density but does
increase with Mn concentration. Our results suggest that the ferromagnetism
probed in these Mn-doped Bi2Te3 films is not mediated by carriers in the
conduction band or in an impurity band.

###Strong and nonmonotonic temperature dependence of Hall coefficient in superconducting K$_x$Fe$_{2-y}$Se$_2$ single crystals|Xiaxin Ding,Yiming Pan,Huan Yang,Hai-Hu Wen###

Strong and nonmonotonic temperature dependence of Hall coefficient in superconducting K$_x$Fe$_{2-y}$Se$_2$ single crystals. In-plane resistivity, magnetoresistance and Hall effect measurements have
been conducted on quenched K$_x$Fe$_{2-y}$Se$_2$ single crystals in order to
analysis the normal-state transport properties. It is found that the Kohler's
rule is well obeyed below about 80 K, but clearly violated above 80 K.
Measurements of the Hall coefficient reveal a strong but non-monotonic
temperature dependence with a maximum at about 80 K, in contrast to any other
FeAs-based superconductors. With the two-band model analysis on the Hall
coefficient, we conclude that a gap may open below 65 K. The data above 65 K
are interpreted as a temperature induced crossover from a metallic state at a
low temperature to an orbital-selective Mott phase at a high temperature. This
is consistent with the recent data of angle resolved photoemission
spectroscopy. These results call for a refined theoretical understanding,
especially when the hole pockets are absent or become trivial in
K$_x$Fe$_{2-y}$Se$_2$ superconductors.

###Optical evidence of quantum rotor orbital excitations in orthorhombic manganites|N. N. Kovaleva,K. I. Kugel,Z. Potucek,N. S. Goryachev,O. E. Kusmartseva,Z. Bryknar,V. A. Trepakov,E. I. Demikhov,A. Dejneka,F. V. Kusmartsev,A. M. Stoneham###

Optical evidence of quantum rotor orbital excitations in orthorhombic manganites. In magnetic compounds with Jahn-Teller (JT) ions (such as Mn3+ or Cu2+), the
ordering of the electron or hole orbitals is associated with cooperative
lattice distortions. There the role of JT effect, although widely recognised,
is still elusive in the ground state properties. We suggest that, in these
materials, there exist elementary excitations whose energy spectrum is
described in terms of the total angular momentum eigenstates and is quantised
as in quantum rotors found in JT centers. We observed features originating from
these excitations in the optical spectra of a model compound LaMnO3 using
ellipsometry technique. They appear clearly as narrow sidebands accompanying
the electron transition between the JT split orbitals on neighbouring Mn3+
ions, strongly influenced by anisotropic spin correlations. We present these
results together with new experimental data on photoluminescence and its
kinetics found in LaMnO3, which lend additional support to the ellipsometry
implying the existence of the quantum rotor orbital excitations. We note that
the discovered elementary excitations of quantum rotors may play an important
role in many unusual properties observed in these materials upon doping, such
as high-temperature superconductivity and colossal magnetoresistance.

###Comparison between thermal and current driven spin-transfer torque in nanopillar metallic spin valves|J. Flipse,F. K. Dejene,B. J. van Wees###

Comparison between thermal and current driven spin-transfer torque in nanopillar metallic spin valves. We investigate the relation between thermal spin-transfer torque (TSTT) and
the spin-dependent Seebeck effect (SDSE), which produces a spin current when a
temperature gradient is applied across a metallic ferromagnet, in nanopillar
metallic spin valves. Comparing its angular dependence (aSDSE) with the angle
dependent magnetoresistance (aMR) measurements on the same device, we are able
to verify that a small spin heat accumulation builds up in our devices. From
the SDSE measurement and the observed current driven STT switching current of
0.8 mA in our spin valve devices, it was estimated that a temperature
difference of 230 K is needed to produce an equal amount of TSTT. Experiments
specifically focused on investigating TSTT show a response that is dominated by
overall heating of the magnetic layer. Comparing it to the current driven STT
experiments we estimate that only ~10% of the response is due to TSTT. This
leads us to conclude that switching dominated by TSTT requires a direct
coupling to a perfect heat sink to minimize the effect of overall heating.
Nevertheless the combined effect of heating, STT and TSTT could prove useful
for inducing magnetization switching when further investigated and optimized.

###Magnetic, thermodynamic, and electrical transport properties of the noncentrosymmetric B20 germanides MnGe and CoGe|J. F. DiTusa,S. B. Zhang,K. Yamaura,Y. Xiong,J. C. Prestigiacomo,B. W. Fulfer,P. W. Adams,M. I. Brickson,D. A. Browne,C. Capan,Z. Fisk,Julia Y. Chan###

Magnetic, thermodynamic, and electrical transport properties of the noncentrosymmetric B20 germanides MnGe and CoGe. We present magnetization, specific heat, resistivity, and Hall effect
measurements on the cubic B20 phase of MnGe and CoGe and compare to
measurements of isostructural FeGe and electronic structure calculations. In
MnGe, we observe a transition to a magnetic state at $T_c=275$ K as identified
by a sharp peak in the ac magnetic susceptibility, as well as second phase
transition at lower temperature that becomes apparent only at finite magnetic
field. We discover two phase transitions in the specific heat at temperatures
much below the Curie temperature one of which we associate with changes to the
magnetic structure. A magnetic field reduces the temperature of this transition
which corresponds closely to the sharp peak observed in the ac susceptibility
at fields above 5 kOe. The second of these transitions is not affected by the
application of field and has no signature in the magnetic properties or our
crystal structure parameters. Transport measurements indicate that MnGe is
metal with a negative magnetoresistance similar to that seen in isostructural
FeGe and MnSi. Hall effect measurements reveal a carrier concentration of about
0.5 carriers per formula unit also similar to that found in FeGe and MnSi. CoGe
is shown to be a low carrier density metal with a very small, nearly
temperature independent diamagnetic susceptibility.

###Tunneling magnetoresistance devices based on topological insulators: Ferromagnet/insulator/topological-insulator junctions employing Bi$_{2}$Se$_{3}$|Matthias Götte,Tomi Paananen,Günter Reiss,Thomas Dahm###

Tunneling magnetoresistance devices based on topological insulators: Ferromagnet/insulator/topological-insulator junctions employing Bi$_{2}$Se$_{3}$. We theoretically investigate tunneling magnetoresistance (TMR) devices, which
are probing the spin-momentum coupled nature of surface states of the
three-dimensional topological insulator Bi$_{2}$Se$_{3}$. Theoretical
calculations are performed based on a realistic tight-binding model for
Bi$_{2}$Se$_{3}$. We study both three dimensional devices, which exploit the
surface states of Bi$_{2}$Se$_{3}$, as well as two-dimensional devices, which
exploit the edge states of thin Bi$_{2}$Se$_{3}$ strips. We demonstrate that
the material properties of Bi$_{2}$Se$_{3}$ allow a TMR ratio at room
temperature of the order of 1000%. Analytical formulas are derived that allow a
quick estimate of the achievable TMR ratio in these devices. The devices can be
used to measure the spin polarization of the topological surface states as an
alternative to spin-ARPES. Unlike TMR devices based on magnetic tunnel
junctions the present devices avoid the use of a second ferromagnetic electrode
whose magnetization needs to be pinned.

###Thermoelectric and galvanomagnetic properties of bismuth chalcogenide nanostructured hetero-epitaxial films|L. N. Lukyanova,Yu. A. Boikov,V A Danilov,O A Usov,M P Volkov,V. A. Kutasov###

Thermoelectric and galvanomagnetic properties of bismuth chalcogenide nanostructured hetero-epitaxial films. Hot wall technique was used to grow block single crystal films of Bi_2Te_3
and solid solutions of Bi_(0.5)Sb_(1.5)Te_3 on mica (muscovite) substrates.
X-ray diffraction studies demonstrated that the crystalline c-axis in the films
was normal to the substrate plane. Seebeck coefficient, electrical conductivity
and magnetoresistivity tensor components were measured at various orientations
of magnetic and electric fields in the temperature interval 77-300 K and
magnetic field up to 14 T. Scattering mechanism of charge carriers in the films
were studied using temperature dependences of the degeneracy parameter and the
Seebeck coefficient in terms of a many-valley model of energy spectrum.
Obtained results have shown that the effective scattering parameter is
considerably differed from the value specific for an acoustic scattering of
charge carriers in the weakly degenerate films due to an additional scattering
of charge carriers on interface and interctystallite boundaries. These features
of charge carrier scattering are supposed to affect electronic transport in the
films and enhance figure of merit.

###High pressure effect on superconductivity of YB6|S. Gabáni,I. Takáčová,G. Pristáš,E. Gažo,K. Flachbart,T. Mori,D. Braithwaite,M. Míšek,K. V. Kamenev,M. Hanfland,P. Samuely###

High pressure effect on superconductivity of YB6. Pressure effect on superconducting properties of two YB6 samples (Tc = 5.9
and 7.5 K) were investigated by measurements of electrical resistivity,
magnetic susceptibility, and X-ray diffraction in the pressure range up to 320
kbar. Magnetoresistivity measurements down to 60 mK and up to 47 kbar have
shown a negative pressure effect on Tc as well as on the third critical field
Hc3 with the slopes dlnTc/dp = -0.59%/kbar and dlnHc3/dp = -1.1%/kbar,
respectively. The magnetic susceptibility measurements evidenced that the slope
of dlnTc/dp gradually decreases with pressure reaching 3 times smaller value at
112 kbar. The lattice parameter measurements revealed the volume reduction of
14% at 320 kbar. The pressure-volume dependence is described by the Rose-Vinet
equation of state. The obtained relative volume dependence dlnTc/dlnV analyzed
by the McMillan formula for Tc indicates that the reduction of the
superconducting transition temperature is mainly due to hardening of the
Einstein-like phonon mode responsible for the superconducting coupling. This is
confirmed by the analysis of the resistivity measurements in the normal state
up to T = 300 K performed at pressures up to 28 kbar.

###Direct epitaxial integration of the ferromagnetic semiconductor EuO with silicon for spintronic applications|Dmitry V. Averyanov,Peter E. Teterin,Yuri G. Sadofyev,Andrey M. Tokmachev,Alexey E. Primenko,Igor A. Likhachev,Vyacheslav G. Storchak###

Direct epitaxial integration of the ferromagnetic semiconductor EuO with silicon for spintronic applications. Materials in which charge and spin degrees of freedom interact strongly offer
applications known as spintronics. Following a remarkable success of metallic
spintronics based on the giant-magnetoresistive effect, tremendous efforts have
been invested into the less developed semiconductor spintronics, in particular,
with the aim to produce three-terminal spintronic devices, e.g. spin
transistors. One of the most important prerequisites for such a technology is
an effective injection of spin-polarized carriers from a ferromagnetic
semiconductor into a nonmagnetic semiconductor, preferably one of those
currently used for industrial applications such as Si - a workhorse of modern
electronics. Ferromagnetic semiconductor EuO is long believed to be the best
candidate for integration of magnetic semiconductor with Si. Although EuO
proved to offer optimal conditions for effective spin injection into silicon
and in spite of considerable efforts, the direct epitaxial stabilization of
stoichiometric EuO thin films on Si without any buffer layer has not been
demonstrated to date. Here we report a new technique for control of EuO/Si
interface on submonolayer level which may have general implications for the
growth of functional oxides on Si. Using this technique we solve a
long-standing problem of direct epitaxial growth on silicon of thin EuO films
which exhibit structural and magnetic properties of EuO bulk material. This
result opens up new possibilities in developing all-semiconductor spintronic
devices.

###Fermi Surface Instabilities in Ferromagnetic Superconductor URhGe|Dai Aoki,Georg Knebel,Jacques Flouquet###

Fermi Surface Instabilities in Ferromagnetic Superconductor URhGe. The field-reentrant (field-reinforced) superconductivity on ferromagnetic
superconductors is one of the most interesting topics in unconventional
superconductivity. The enhancement of effective mass and the induced
ferromagnetic fluctuations play key roles for reentrant superconductivity.
However, the associated change of the Fermi surface, which is often observed at
(pseudo-) metamagnetic transition, can also be a key ingredient. In order to
study the Fermi surface instability, we performed Hall effect measurements in
the ferromagnetic superconductor URhGe. The Hall effect of URhGe is well
explained by two contributions, namely by the normal Hall effect and by the
large anomalous Hall effect due to skew scattering. The large change in the
Hall coefficient is observed at low fields between the paramagnetic and
ferromagnetic states for H // c-axis (easy-magnetization axis) in the
orthorhombic structure, indicating that the Fermi surface is reconstructed in
the ferromagnetic state below the Curie temperature (T_Curie=9.5K). At low
temperatures (T << T_Curie), when the field is applied along the b-axis, the
reentrant superconductivity was observed in both the Hall resistivity and the
magnetoresistance below 0.4K. Above 0.4K, a large jump with the first-order
nature was detected in the Hall resistivity at a spin-reorientation field H_R ~
12.5T, demonstrating that the marked change of the Fermi surface occurs between
the ferromagnetic state and the polarized state above H_R. The results can be
understood by the Lifshitz-type transition, induced by the magnetic field or by
the change of the effective magnetic field.

###Tunnel magnetoresistance and spin-transfer-torque switching in polycrystalline Co2FeAl full-Heusler alloy magnetic tunnel junctions on Si/SiO2 amorphous substrates|Zhenchao Wen,Hiroaki Sukegawa,Shinya Kasai,Koichiro Inomata,Seiji Mitani###

Tunnel magnetoresistance and spin-transfer-torque switching in polycrystalline Co2FeAl full-Heusler alloy magnetic tunnel junctions on Si/SiO2 amorphous substrates. We studied polycrystalline B2-type Co2FeAl (CFA) full-Heusler alloy based
magnetic tunnel junctions (MTJs) fabricated on a Si/SiO2 amorphous substrate.
Polycrystalline CFA films with a (001) orientation, a high B2 ordering, and a
flat surface were achieved using a MgO buffer layer. A tunnel magnetoresistance
(TMR) ratio up to 175% was obtained for an MTJ with a CFA/MgO/CoFe structure on
a 7.5-nm-thick MgO buffer. Spin-transfer torque induced magnetization switching
was achieved in the MTJs with a 2-nm-thick polycrystalline CFA film as a
switching layer. Using a thermal activation model, the intrinsic critical
current density (Jc0) was determined to be 8.2 x 10^6 A/cm^2, which is lower
than 2.9 x 10^7 A/cm^2, the value for epitaxial CFA-MTJs [Appl. Phys. Lett.
100, 182403 (2012)]. We found that the Gilbert damping constant evaluated using
ferromagnetic resonance measurements for the polycrystalline CFA film was
~0.015 and was almost independent of the CFA thickness (2~18 nm). The low Jc0
for the polycrystalline MTJ was mainly attributed to the low damping of the CFA
layer compared with the value in the epitaxial one (~0.04).

###Anomalous magnetoresistance in the spinel superconductor LiTi2O4|Kui Jin,Ge He,Xiaohang Zhang,Shingo Maruyama,Shintaro Yasui,Richard Suchoski,Jongmoon Shin,Yeping Jiang,Heshan Yu,Lei Shan,Richard L. Greene,Ichiro Takeuchi###

Anomalous magnetoresistance in the spinel superconductor LiTi2O4. Transition-metal oxides offer an opportunity to explore unconventional
superconductors, where the superconductivity (SC) is often interrelated with
novel phenomena such as spin/charge order, fluctuations, and Fermi surface
instability (1-3). LiTi2O4 (LTO) is a unique compound in that it is the only
known spinel oxide superconductor. In addition to electron-phonon coupling,
electron-electron and spin fluctuation contributions have been suggested as
playing important roles in the microscopic mechanism for its superconductivity
(4-8). However, the lack of high quality single crystals has thus far prevented
systematic investigation of their transport properties (9). Here, we report a
careful study of transport and tunneling spectroscopy in epitaxial LTO thin
films. In the superconducting state, the energy gap was found to decrease as a
quadratic function of magnetic field. In the normal state, an unusual
magnetoresistance (MR) was observed where it changes from anisotropic positive
to isotropic negative as the temperature is increased. A constant charge
carrier concentration without any abrupt change in lattice parameters as a
function of temperature suggests that the isotropic MR stems from the
suppression of spin scattering/fluctuations, while the anisotropic term
originates from an orbital contribution. These observations point to an
important role strong correlations play in this unique superconductor.

###Conductivity and magnetoresistance of La$_{0.7}$Ce$_{0.3}$MnO$_3$ thin films under photoexcitation|Andreas Thiessen,Elke Beyreuther,Robert Werner,Reinhold Kleiner,Dieter Koelle,Lukas M. Eng###

Conductivity and magnetoresistance of La$_{0.7}$Ce$_{0.3}$MnO$_3$ thin films under photoexcitation. La$_{0.7}$Ce$_{0.3}$MnO$_3$ thin films of different thicknesses, degrees of
CeO$_2$-phase segregation and oxygen deficiency, grown on SrTiO$_3$ single
crystal substrates, were comparatively investigated with respect to both their
spectral and temperature-dependent photoconductivity (PC) and their
magnetoresistance (MR) behaviour under photoexcitation. While as-grown films
were insensitive to optical excitation, oxygen reduction appeared to be an
effective way to decrease the film resistance, but the film thickness was found
to play a minor role. However, from the evaluation of the spectral behaviour of
the PC and the comparison of the MR of the LCeMO/substrate-samples with a bare
substrate under illumination we find that the photoconductivity data reflects
not only contributions from (i) photogenerated charge carriers in the film and
(ii) carriers injected from the photoconductive substrate (as concluded from
earlier works), but also (iii) a decisive parallel photoconduction in the
SrTiO$_3$ substrate. Furthermore -- also by analyzing the MR characteristics --
the unexpected occurence of a strong electroresistive effect in the sample with
the highest degree of CeO$_2$ segregation and oxygen deficiency could be
attributed to the electroresistance of the SrTiO$_3$ substrate as well. The
results suggest a critical reconsideration and possibly a reinterpretation of
several previous photoconductivity and electroresistance investigations of
manganite thin films on SrTiO$_3$.

###Point contact investigations of film and interface magnetoresistance of La$_{0.7}$Sr$_{0.3}$MnO$_3$ heterostructures on Nb:SrTiO$_{3}$|Asmund Monsen,Jos E. Boschker,Per Nordblad,Roland Mathieu,Thomas Tybell,Erik Wahlström###

Point contact investigations of film and interface magnetoresistance of La$_{0.7}$Sr$_{0.3}$MnO$_3$ heterostructures on Nb:SrTiO$_{3}$. STM based magnetotransport measurements of epitaxial
La$_{0.7}$Sr$_{0.3}$MnO$_3$ 32 nm thick films with and without an internal
LaMnO$_3$ layer (0-8 nm thick) grown on Nb doped SrTiO$_3$ are presented. The
measurements reveal two types of low field magnetoresistance (LFMR) with a
magnitude of $\sim 0.1-1.5\%$. One LFMR contribution is identified as a
conventional grain boundary/domain wall scattering through the symmetric I-V
characteristics, high dependence on tip placements and insensitivity to
introduction of LaMnO$_3$ layers. The other contribution originates from the
reverse biased Nb doped SrTiO$_3$ interface and the interface layer of
La$_{0.7}$Sr$_{0.3}$MnO$_3$. Both LFMR contributions display a field dependence
indicative of a higher coercivity ($\sim$200 Oe) than the bulk film. LaMnO$_3$
layers are found to reduce the rectifying properties of the junctions, and sub
micron lateral patterning by electron beam lithography enhances the diodic
properties, in accordance with a proposed transport model based on the locality
of the injected current.

###Accessing Different Spin-Disordered States using First Order Reversal Curves|Randy K. Dumas,Peter K. Greene,Dustin A. Gilbert,Li Ye,Chaolin Zha,Johan Åkerman,Kai Liu###

Accessing Different Spin-Disordered States using First Order Reversal Curves. Combined first order reversal curve (FORC) analyses of the magnetization
(M-FORC) and magnetoresistance (MR-FORC) have been employed to provide a
comprehensive study of the M-MR correlation in two canonical systems: a
NiFe/Cu/FePt pseudo spin-valve (PSV) and a [Co/Cu]8 multilayer. In the PSV, due
to the large difference in switching fields and minimal interactions between
the NiFe and FePt layers, the M and MR show a simple one-to-one relationship
during reversal. In the [Co/Cu]8 multilayer, the correlation between the
magnetization reversal and MR evolution is more complex. This is primarily due
to the similar switching fields of, and interactions between, the constituent
Co layers. The FORC protocol accesses states with much higher spin disorders
and larger MR than those found along the conventional major loop field-cycle.
Unlike the M-FORC measurements, which only probe changes in the macroscopic
magnetization, the MR-FORCs are more sensitive to the microscopic domain
configurations, as those are most important in determining the resultant MR
effect size. This approach is generally applicable to spintronic systems to
realize the maximum spin-disorder and the largest MR.

###Controlling and distinguishing electronic transport of topological and trivial surface states in a topological insulator|Helin Cao,Chang Liu,Jifa Tian,Yang Xu,Ireneusz Miotkowski,M. Zahid Hasan,Yong P. Chen###

Controlling and distinguishing electronic transport of topological and trivial surface states in a topological insulator. Topological insulators (TI), with characteristic Dirac-fermion topological
surface states (TSS), have emerged as a new class of electronic materials with
rich potentials for both novel physics and device applications. However, a
major challenge with realistic TI materials is to access, distinguish and
manipulate the electronic transport of TSS often obscured by other possible
parallel conduction channels that include the bulk as well as a two-dimensional
electron gas (2DEG) formed near the surface due to bending of the bulk bands.
Such a (Schrodinger-fermion) 2DEG represents topologically-trivial surface
states, whose coexistence with the TSS has been revealed by angle resolved
photoemission spectroscopy. Here we show that simple manipulations of surface
conditions can be used to access and control both types of surface states and
their coexistence in bulk-insulating Bi2Te2Se, whose surface conduction is
prominently manifested in temperature dependent resistance and nonlocal
transport. The trivial 2DEG and TSS can both exhibit clear Shubnikov-de Haas
oscillations in magnetoresistance, with different Berry phases ~0 and ~pi that
distinguish their different topological characters. We also report a deviation
from the typical weak antilocalization behavior, possibly due to high mobility
TSS. Our study enables distinguishing, controlling and harnessing electronic
transport of TI surface carriers with different topological natures.

###Electrically tuned magnetic order and magnetoresistance in a topological insulator|Zuocheng Zhang,Xiao Feng,Minghua Guo,Kang Li,Jinsong Zhang,Yunbo Ou,Yang Feng,Lili Wang,Xi Chen,Ke He,Xucun Ma,Qikun Xue,Yayu Wang###

Electrically tuned magnetic order and magnetoresistance in a topological insulator. The Dirac-like surface states of the topological insulators (TIs) are
protected by time reversal symmetry (TRS) and exhibit a host of novel
properties. Introducing magnetism into TI, which breaks the TRS, is expected to
create exotic topological magnetoelectric effects. A particularly intriguing
phenomenon in this case is the magnetic field dependence of electrical
resistance, or magnetoresistance (MR). The intricate interplay between
topological protection and broken-TRS may lead to highly unconventional MR
behaviour that can find unique applications in magnetic sensing and data
storage. However, so far the MR of TI with spontaneously broken TRS is still
poorly understood, mainly due to the lack of well-controlled experiments. In
this work, we investigate the magneto transport properties of a ferromagnetic
TI thin film fabricated into a field effect transistor device. We observe an
unusually complex evolution of MR when the Fermi level (EF) is tuned across the
Dirac point (DP) by gate voltage. In particular, MR tends to be positive when
EF lies close to the DP but becomes negative at higher energies. This trend is
opposite to that expected from the Berry phase picture for localization, but is
intimately correlated with the gate-tuned magnetic order. We show that the
underlying physics is the competition between the topology-induced weak
antilocalization and magnetism-induced negative MR. The simultaneous electrical
control of magnetic order and magneto transport facilitates future TI-based
spintronic devices.

###Decoding Spatial Complexity in Strongly Correlated Electronic Systems|E. W. Carlson,S. Liu,B. Phillabaum,K. A. Dahmen###

Decoding Spatial Complexity in Strongly Correlated Electronic Systems. Inside the metals, semiconductors, and magnets of our everyday experience,
electrons are uniformly distributed throughout the material. By contrast,
electrons often form clumpy patterns inside of strongly correlated electronic
systems (SCES) such as colossal magnetoresistance materials and high
temperature superconductors. In copper-oxide based high temperature
superconductors, scanning tunneling microscopy (STM) has detected an electron
nematic on the surface of the material, in which the electrons form nanoscale
structures which break the rotational symmetry of the host crystal. These
structures may hold the key to unlocking the mystery of high temperature
superconductivity in these materials, but only if the nematic also exists
throughout the entire bulk of the material. Using newly developed methods for
decoding these surface structures, we find that the nematic indeed persists
throughout the bulk of the material. We furthermore find that the intricate
pattern formation is set by a delicate balance among disorder, interactions,
and material anisotropy, leading to a fractal nature of the cluster pattern.
The methods we have developed can be extended to many other surface probes and
materials, enabling surface probes to determine whether surface structures are
confined only to the surface, or whether they extend throughout the material.

###Excitonic and Nematic Instabilities on the Surface of Topological Kondo Insulators|Bitan Roy,Johannes Hofmann,Valentin Stanev,Jay D. Sau,Victor Galitski###

Excitonic and Nematic Instabilities on the Surface of Topological Kondo Insulators. We study the effects of strong electron-electron interactions on the surface
of cubic topological Kondo insulators (such as samarium hexaboride, SmB$_6$).
Cubic topological Kondo insulators generally support three copies of massless
Dirac nodes on the surface, but only two of them are energetically degenerate
and exhibit an energy offset relative to the third one. With a tunable chemical
potential, when the surface states host electron and hole pockets of comparable
size, strong interactions may drive this system into rotational symmetry
breaking nematic and translational symmetric breaking excitonic spin- or
charge-density-wave phases, depending on the relative chirality of the Dirac
cones. Taking a realistic surface band structure into account we analyze the
associated Ginzburg-Landau theory and compute the mean field phase diagram for
interacting surface states. Beyond mean field theory, this system can be
described by a two-component isotropic Ashkin-Teller model at finite
temperature, and we outline the phase diagram of this model. Our theory
provides a possible explanation of recent measurements which detect a two-fold
symmetric magnetoresistance and an upturn in surface resistivity with tunable
gate voltage in SmB$_6$. Our discussion can also be germane to other cubic
topological insulators, such as ytterbium hexaboride (YbB$_6$), plutonium
hexaboride (PuB$_6$).

###Kinetic arrest, and ubiquity of interrupted 1st order magnetic transitions|P. Chaddah###

Kinetic arrest, and ubiquity of interrupted 1st order magnetic transitions. Phase transitions are caused by varying temperature, or pressure, or magnetic
field. The observation of 1st order magneto-structural transitions has created
application possibilities based on magnetoresistance, magnetocaloric effect,
magnetic shape memory effect, and magneto-dielectric effect. Magnetic field
induced transitions, and phase coexistence of competing magnetic phases down to
the lowest temperature, gained prominence over a decade ago with theoretical
models suggesting that the ground state is not homogeneous. Researchers at
Indore pushed an alternative view that this phase coexistence could be due to
glasslike kinetic arrest of a disorder-broadened first-order magnetic
transition between two states with long-range magnetic order, resulting in
phase coexistence down to the lowest temperatures. The CHUF (cooling and
heating in unequal field) protocol created at Indore allows the observation of
devitrification, followed by melting. I show examples of measurements
establishing kinetic arrest in various materials, emphasizing that glasslike
arrest of 1st order magnetic transitions may be as ubiquitous as glass
formation following the arrest of 1st order structural transitions.

###Temperature evolution of magnetic and transport behavior in 5\textit{d} Mott insulator Sr$_2$IrO$_4$: Significance of magneto-structural coupling|Imtiaz Noor Bhatti,R. Rawat,A. Banerjee,A. K. Pramanik###

Temperature evolution of magnetic and transport behavior in 5\textit{d} Mott insulator Sr$_2$IrO$_4$: Significance of magneto-structural coupling. We have investigated the temperature evolution of magnetism and its
interrelation with structural parameters in perovskite-based layered compound
Sr$_2$IrO$_4$, which is believed to be a $J_{eff}$ = 1/2 Mott insulator. The
structural distortion plays an important role in this material which induces a
weak ferromagnetism in otherwise antiferromagnetically ordered magnetic state
with transition temperature around 240 K. Interestingly, at low temperature
below around 100 K, a change in magnetic moment has been observed. Temperature
dependent x-ray diffraction measurements show sudden changes in structural
parameters around 100 K are responsible for this. Resistivity measurements show
insulating behavior throughout the temperature range across the magnetic phase
transition. The electronic transport can be described with Mott's
two-dimensional variable range hopping (VRH) mechanism, however, three
different temperature ranges are found for VRH, which is a result of varying
localization length with temperature. A negative magnetoresistance (MR) has
been observed at all temperatures in contrast to positive behavior generally
observed in strongly spin-orbit coupled materials. The quadratic field
dependence of MR implies a relevance of a quantum interference effect.

###Determination of the Fermi Contour and Spin-polarization of $ν=3/2$ Composite Fermions via Ballistic Commensurability Measurements|D. Kamburov,M. A. Mueed,I. Jo,Yang Liu,M. Shayegan,L. N. Pfeiffer,K. W. West,K. W. Baldwin,J. J. D. Lee###

Determination of the Fermi Contour and Spin-polarization of $ν=3/2$ Composite Fermions via Ballistic Commensurability Measurements. We report ballistic transport commensurability minima in the
magnetoresistance of $\nu =3/2$ composite fermions (CFs). The CFs are formed in
high-quality two-dimensional electron systems confined to wide GaAs quantum
wells and subjected to an in-plane, unidirectional periodic potential
modulation. We observe a slight asymmetry of the CF commensurability positions
with respect to $\nu=3/2$, which we explain quantitatively by comparing three
CF density models and concluding that the $\nu=3/2$ CFs are likely formed by
the minority carriers in the upper energy spin state of the lowest Landau
level. Our data also allow us to probe the shape and size of the CF Fermi
contour. At a fixed electron density of $\simeq 1.8 \times 10^{11}$ cm$^{-2}$,
as the quantum well width increases from 30 to 60 nm, the CFs show increasing
spin-polarization. We attribute this to the enhancement of the Zeeman energy
relative to the Coulomb energy in wider wells where the latter is softened
because of the larger electron layer thickness. The application of an
additional parallel magnetic field ($B_{||}$) leads to a significant distortion
of the CF Fermi contour as $B_{||}$ couples to the CFs' out-of-plane orbital
motion. The distortion is much more severe compared to the $\nu=1/2$ CF case at
comparable $B_{||}$. Moreover, the applied $B_{||}$ further spin-polarizes the
$\nu=3/2$ CFs as deduced from the positions of the commensurability minima.

###Experimental and theoretical investigations on magnetic and related properties of ErRuSi|Sachin Gupta,A. Das,K. G. Suresh,A. Hoser,Yu. V. Knyazev,Yu. I. Kuz'min,A. V. Lukoyanov###

Experimental and theoretical investigations on magnetic and related properties of ErRuSi. We report experimental and theoretical studies of magnetic and related
properties of ErRuSi compound. Various experimental techniques such as neutron
diffraction, magnetization, magneto-thermal, magneto-transport, optical have
been used to study the compound. Neutron diffraction shows ferromagnetic
ordering at low temperatures with moments aligned in ab plane. Neutron
diffraction and magnetization data show reduction in magnetic moment, which may
be due to crystalline electric field effects at low temperatures. The compound
shows good magnetocaloric properties with a low field adiabatic temperature
change of 4.7 K, which is larger than that of many proposed materials for
magnetic refrigeration at low temperatures. Magnetoresistance shows large
negative value at 8 K, which changes its sign and increases in magnitude, with
decrease in temperature and/or increase in field. The positive MR at low
temperatures attributed to the Lorentz force effect. The electronic structure
calculations accounting for electronic correlations of the 4f electrons of Er
reproduces the ferromagnetic ordering and effective magnetic moment. Interband
transitions between the Ru and Er d states and Er f states in one spin
projection are found to form the main features of the measured optical
conductivity in this compound.

###Anisotropic Fermi Surface and Quantum Limit Transport in High Mobility 3D Dirac Semimetal Cd3As2|Yanfei Zhao,Haiwen Liu,Chenglong Zhang,Huichao Wang,Junfeng Wang,Ziquan Lin,Ying Xing,Hong Lu,Jun Liu,Yong Wang,Shuang Jia,X. C. Xie,Jian Wang###

Anisotropic Fermi Surface and Quantum Limit Transport in High Mobility 3D Dirac Semimetal Cd3As2. The three-dimensional (3D) topological Dirac semimetal is a new topological
phase of matter, viewed as the 3D analogy of graphene with a linear dispersion
in the 3D momentum space. Here, we report the angular dependent
magnetotransport in Cd3As2 single crystal and clearly show how the Fermi
surface evolves when tilting the magnetic field. Remarkably, when the magnetic
field lies in [112] and [44-1] axis, only single oscillation period features
present, however, the system shows double period oscillations when the field is
applied along [1-10] direction. Moreover, tilting the magnetic field at certain
direction also gives double period oscillations. We attribute the anomalous
oscillation behavior to the sophisticated geometry of Fermi surface and
illustrate a complete 3D Fermi surfaces with two nested anisotropic ellipsoids
around the Dirac point. Additionally, a sub-millimeter mean free path at 6 K is
observed in Cd3As2 crystal, indicating a large ballistic transport region in
this material. Tracking the magnetoresistance oscillations to 60 T, we reach
the quantum limit (n = 1 Landau Level) at about 43 T. These results improve the
knowledge of the Dirac semimetal material Cd3As2, and also pave the way for
proposing new electronic applications based on 3D Dirac materials.

###Two-stage magnetic-field-tuned superconductor-insulator transition in underdoped La$_{2-x}$Sr$_{x}$CuO$_{4}$|Xiaoyan Shi,Ping V. Lin,T. Sasagawa,V. Dobrosavljević,Dragana Popović###

Two-stage magnetic-field-tuned superconductor-insulator transition in underdoped La$_{2-x}$Sr$_{x}$CuO$_{4}$. In the underdoped pseudogap regime of cuprate superconductors, the normal
state is commonly probed by applying a magnetic field ($H$). However, the
nature of the $H$-induced resistive state has been the subject of a long-term
debate, and clear evidence for a zero-temperature ($T=0$) $H$-tuned
superconductor-insulator transition (SIT) has proved elusive. Here we report
magnetoresistance measurements in underdoped La$_{2-x}$Sr$_{x}$CuO$_{4}$,
providing striking evidence for quantum critical behavior of the resistivity --
the signature of a $H$-driven SIT. The transition is not direct: it is
accompanied by the emergence of an intermediate state, which is a
superconductor only at $T=0$. Our finding of a two-stage $H$-driven SIT goes
beyond the conventional scenario in which a single quantum critical point
separates the superconductor and the insulator in the presence of a
perpendicular $H$. Similar two-stage $H$-driven SIT, in which both disorder and
quantum phase fluctuations play an important role, may also be expected in
other copper-oxide high-temperature superconductors.

###Gate-tunable quantum oscillations in ambipolar Cd3As2 thin films|Yanwen Liu,Cheng Zhang,Xiang Yuan,Tang Lei,Chao Wang,Domenico Di Sante,Awadhesh Narayan,Liang He,Silvia Picozzi,Stefano Sanvito,Renchao Che,Faxian Xiu###

Gate-tunable quantum oscillations in ambipolar Cd3As2 thin films. Electrostatic doping in materials can lead to various exciting electronic
properties, such as metal-insulator transition and superconductivity, by
altering the Fermi level position or introducing exotic phases. Cd3As2, a
three-dimensional (3D) analog of graphene with extraordinary carrier mobility,
was predicted to be a 3D Dirac semimetal, a feature confirmed by recent
experiments. However, most research so far has been focused on metallic bulk
materials that are known to possess ultra-high mobility and giant
magnetoresistance but limited carrier transport tunability. Here, we report on
the first observation of a gate-induced transition from band conduction to
hopping conduction in single-crystalline Cd3As2 thin films via electrostatic
doping by solid electrolyte gating. The extreme charge doping enables the
unexpected observation of p-type conductivity in a 50 nm-thick Cd3As2 thin film
grown by molecular beam epitaxy. More importantly, the gate-tunable
Shubnikov-de Haas (SdH) oscillations and the temperature-dependent resistance
reveal a unique band structure and bandgap opening when the dimensionality of
Cd3As2 is reduced. This is also confirmed by our first-principles calculations.
The present results offer new insights towards nanoelectronic and
optoelectronic applications of Dirac semimetals in general, and provide new
routes in the search for the intriguing quantum spin Hall effect in
low-dimension Dirac semimetals, an effect that is theoretically predicted but
not yet experimentally realized.

###Magnetoresistance near a quantum critical point|I. M. Hayes,Nicholas P. Breznay,Toni Helm,Philip Moll,Mark Wartenbe,Ross D. McDonald,Arkady Shekhter,James G. Analytis###

Magnetoresistance near a quantum critical point. In metals near a quantum critical point, the electrical resistance is thought
to be determined by the lifetime of the carriers of current, rather than the
scattering from defects. The observation of $T$-linear resistivity suggests
that the lifetime only depends on temperature, implying the vanishing of an
intrinsic energy scale and the presence of a quantum critical point. Our data
suggest that this concept extends to the magnetic field dependence of the
resistivity in the unconventional superconductor
BaFe$_2$(As$_{1-x}$P$_{x}$)$_2$ near its quantum critical point. We find that
the lifetime depends on magnetic field in the same way as it depends on
temperature, scaled by the ratio of two fundamental constants $\mu_B/k_B$.
These measurements imply that high magnetic fields probe the same quantum
dynamics that give rise to the $T$-linear resistivity, revealing a novel kind
of magnetoresistance that does not depend on details of the Fermi surface, but
rather on the balance of thermal and magnetic energy scales. This opens new
opportunities for the investigation of transport near a quantum critical point
by using magnetic fields to couple selectively to charge, spin and spatial
anisotropies.

###Observation of the chiral magnetic effect in ZrTe5|Qiang Li,Dmitri E. Kharzeev,Cheng Zhang,Yuan Huang,I. Pletikosic,A. V. Fedorov,R. D. Zhong,J. A. Schneeloch,G. D. Gu,T. Valla###

Observation of the chiral magnetic effect in ZrTe5. The chiral magnetic effect is the generation of electric current induced by
chirality imbalance in the presence of magnetic field. It is a macroscopic
manifestation of the quantum anomaly in relativistic field theory of chiral
fermions (massless spin $1/2$ particles with a definite projection of spin on
momentum) -- a dramatic phenomenon arising from a collective motion of
particles and antiparticles in the Dirac sea. The recent discovery of Dirac
semimetals with chiral quasi-particles opens a fascinating possibility to study
this phenomenon in condensed matter experiments. Here we report on the first
observation of chiral magnetic effect through the measurement of
magneto-transport in zirconium pentatelluride, ZrTe_5. Our angle-resolved
photoemission spectroscopy experiments show that this material's electronic
structure is consistent with a 3D Dirac semimetal. We observe a large negative
magnetoresistance when magnetic field is parallel with the current. The
measured quadratic field dependence of the magnetoconductance is a clear
indication of the chiral magnetic effect. The observed phenomenon stems from
the effective transmutation of Dirac semimetal into a Weyl semimetal induced by
the parallel electric and magnetic fields that represent a topologically
nontrivial gauge field background.

###Angle dependence of the orbital magnetoresistance in bismuth|Aurelie Collaudin,Benoit Fauque,Yuki Fuseya,Woun Kang,Kamran Behnia###

Angle dependence of the orbital magnetoresistance in bismuth. We present an extensive study of angle-dependent transverse magnetoresistance
in bismuth, with a magnetic field perpendicular to the applied electric current
and rotating in three distinct crystallographic planes. The observed angular
oscillations are confronted with the expectations of semi-classic transport
theory for a multi-valley system with anisotropic mobility and the agreement
allows us to quantify the components of the mobility tensor for both electrons
and holes. A quadratic temperature dependence is resolved. As Hartman argued
long ago, this indicates that inelastic resistivity in bismuth is dominated by
carrier-carrier scattering. At low temperature and high magnetic field, the
threefold symmetry of the lattice is suddenly lost. Specifically, a $2\pi/3$
rotation of magnetic field around the trigonal axis modifies the amplitude of
the magneto-resistance below a field-dependent temperature. By following the
evolution of this anomaly as a function of temperature and magnetic field, we
mapped the boundary in the (field, temperature) plane separating two electronic
states. In the less-symmetric state, confined to low temperature and high
magnetic field, the three Dirac valleys cease to be rotationally invariant. We
discuss the possible origins of this spontaneous valley polarization, including
a valley-nematic scenario.

###State of Co and Mn in half-metallic ferromagnet Co$_2$MnSi explored by magnetic circular dichroism in hard X-ray photoelectron emission and soft X-ray absorption spectroscopies|Gerhard H. Fecher,Daniel Ebke,Siham Ouardi,Stefano Agrestini,Chang-Yang Kuo,Nils Hollmann,Zhiwei Hu,Andrei Gloskovskii,Flora Yakhou,Nicholas B. Brookes,Claudia Felser###

State of Co and Mn in half-metallic ferromagnet Co$_2$MnSi explored by magnetic circular dichroism in hard X-ray photoelectron emission and soft X-ray absorption spectroscopies. The half-metallic Heusler compound Co$_2$MnSi is a very attractive material
for spintronic devices because it exhibits very high tunnelling
magnetoresistance ratios. This work reports on a spectroscopic investigation of
thin Co$_2$MnSi films as they are used as electrodes in magnetic tunnel
junctions. The investigated films exhibit a remanent in-plane magnetisation
with a magnetic moment of about 5~$\mu_B$ when saturated, as expected. The low
coercive field of only 4~mT indicates soft magnetic behaviour. Magnetic
dichroism in emission and absorption was measured at the Co and Mn $2p$ core
levels. The photoelectron spectra were excited by circularly polarised hard
X-rays with an energy of of 6~keV and taken from the remanently magnetised
film. The soft X-ray absorption spectra were taken in an induction field of
4~T. Both methods yielded large dichroism effects. An analysis reveals the
localised character of the electrons and magnetic moments attributed to the Mn
atoms, whereas the electrons related to the Co atoms contribute an itinerant
part to the total magnetic moment.

###Tantalum Monoarsenide: an Exotic Compensated Semimetal|Chenglong Zhang,Zhujun Yuan,Suyang Xu,Ziquan Lin,Bingbing Tong,M. Zahid Hasan,Junfeng Wang,Chi Zhang,Shuang Jia###

Tantalum Monoarsenide: an Exotic Compensated Semimetal. Compared with the semiconductors such as silicon and gallium arsenide which
have been used widely for decades, semimetals have not received much attention
in the field of condensed matter physics until very recently. The realization
of electronic topological properties has motivated interest of investigations
on Dirac semimetals and Weyl semimetals, which are predicted to show
unprecedented features beyond the classical electronic theories of metals. In
this letter for the first time we report the electric transport properties of a
robust Weyl semimetal candidate proposed by recent theoretical calculations,
TaAs. Our study shows that this bulk material manifests ultrahigh carrier
mobility ($\mathrm{5\times10^5 cm^2/V\cdot{s}}$) accompanied by an extremely
large, unsaturated linear magnetoresistance ($\mathrm{MR}$), which reaches 5400
at 10 Kelvins in a magnetic field of 9 Teslas and 2.47$\times$10$^4$ at 1.5
Kelvins in a magnetic field of 56 Teslas. We also observed strong Shubnikov-de
Haas (SdH) oscillations associated with an extremely low quantum limit ($\sim$8
Teslas). Further studies on TaAs, especially in the ultraquantum limit regime,
will help to extend the realization of the topological properties of these
exotic electrons.

###Enhanced conduction band density of states in intermetallic EuTSi$_3$ (T=Rh, Ir)|A. Maurya,P. Bonville,A. Thamizhavel,S. K. Dhar###

Enhanced conduction band density of states in intermetallic EuTSi$_3$ (T=Rh, Ir). We report on the physical properties of single crystalline EuRhSi$_3$ and
polycrystalline EuIrSi$_3$, inferred from magnetisation, electrical transport,
heat capacity and $^{151}$Eu M\"ossbauer spectroscopy. These previously known
compounds crystallise in the tetragonal BaNiSn$_3$-type structure. The single
crystal magnetisation in EuRhSi$_3$ has a strongly anisotropic behaviour at 2 K
with a spin-flop field of 13 T, and we present a model of these magnetic
properties which allows the exchange constants to be determined. In both
compounds, specific heat shows the presence of a cascade of two close
transitions near 50 K, and the $^{151}$Eu M\"ossbauer spectra demonstrate that
the intermediate phase has an incommensurate amplitude modulated structure. We
find anomalously large values, with respect to other members of the series, for
the RKKY N\'eel temperature, for the spin-flop field (13 T), for the spin-wave
gap ($\simeq$ 20-25 K) inferred from both resistivity and specific heat data,
for the spin-disorder resistivity in EuRhSi$_3$ ($\simeq 35$ $\mu$Ohm.cm) and
for the saturated hyperfine field (52 T). We show that all these quantities
depend on the electronic density of states at the Fermi level, implying that
the latter must be strongly enhanced in these two materials. EuIrSi$_3$
exhibits a giant magnetoresistance ratio, with values exceeding 600 % at 2 K in
a field of 14 T.

###Distinct itinerant spin-density waves and local-moment antiferromagnetism in an intermetallic ErPd$_2$Si$_2$ single crystal|Hai-Feng Li,Chongde Cao,Andrew Wildes,Wolfgang Schmidt,Karin Schmalzl,Binyang Hou,Louis-Pierre Regnault,Cong Zhang,Paul Meuffels,Wolfgang Löser,Georg Roth###

Distinct itinerant spin-density waves and local-moment antiferromagnetism in an intermetallic ErPd$_2$Si$_2$ single crystal. Identifying the nature of magnetism, itinerant or localized, remains a major
challenge in condensed-matter science. Purely localized moments appear only in
magnetic insulators, whereas itinerant moments more or less co-exist with
localized moments in metallic compounds such as the doped-cuprate or the
iron-based superconductors, hampering a thorough understanding of the role of
magnetism in phenomena like superconductivity or magnetoresistance. Here we
distinguish two antiferromagnetic modulations with respective propagation wave
vectors of $Q_{\pm}$ = ($H \pm 0.557(1)$, 0, $L \pm 0.150(1)$) and $Q_\text{C}$
= ($H \pm 0.564(1)$, 0, $L$), where $\left(H, L\right)$ are allowed Miller
indices, in an ErPd$_2$Si$_2$ single crystal by neutron scattering and
establish their respective temperature- and field-dependent phase diagrams. The
modulations can co-exist but also compete depending on temperature or applied
field strength. They couple differently with the underlying lattice albeit with
associated moments in a common direction. The $Q_{\pm}$ modulation may be
attributed to localized 4\emph{f} moments while the $Q_\text{C}$ correlates
well with itinerant conduction bands, supported by our transport studies.
Hence, ErPd$_2$Si$_2$ represents a new model compound that displays
clearly-separated itinerant and localized moments, substantiating early
theoretical predictions and providing a unique platform allowing the study of
itinerant electron behavior in a localized antiferromagnetic matrix.

###Topological Insulator Thin Films Starting from the Amorphous Phase - Bi$_2$Se$_3$ as Example|J. Barzola-Quiquia,T. Lehmann,M. Stiller,D. Spemann,P. Esquinazi,P. Häussler###

Topological Insulator Thin Films Starting from the Amorphous Phase - Bi$_2$Se$_3$ as Example. We present a new method to obtain topological insulator Bi$_2$Se$_3$ thin
films with a centimeter large lateral length. To produce amorphous Bi$_2$Se$_3$
thin films we have used a sequential flash-evaporation method at room
temperature. Transmission electron microscopy has been used to verify that the
prepared samples are in a pure amorphous state. During annealing the samples
transform into the rhombohedral Bi$_2$Se$_3$ crystalline strcuture which was
confirmed using X-ray diffraction and Raman spectroscopy. Resistance
measurements of the amorphous films show the expected Mott variable range
hopping conduction process with a high specific resistance compared to the one
obtained in the crystalline phase (metallic behavior). We have measured the
magnetoresistance (MR) and the Hall effect (HE) at different temperatures
between 2 K and 275 K. At temperatures $T \lesssim 50$ K and fields $B \lesssim
1$ T we observe weak anti-localization in the MR; the Hall measurements confirm
the n-type character of the samples. All experimental results of our films are
in quantitative agreement with results from samples prepared using more
sophisticated methods.

###Magnetic coherent tunnel junctions with periodic grating barrier|Henan Fang,Mingwen Xiao,Wenbin Rui,Jun Du,Zhikuo Tao###

Magnetic coherent tunnel junctions with periodic grating barrier. A new spintronic theory has been developed for the magnetic tunnel junction
(MTJ) with single-crystal barrier. The barrier will be treated as a diffraction
grating with intralayer periodicity, the diffracted waves of tunneling
electrons thus contain strong coherence, both in charge and especially in spin.
The theory can answer the two basic problems present in MgO-based MTJs: (1) Why
does the tunneling magnetoresistance (TMR) oscillate with the barrier
thickness? (2) Why is the TMR still far away from infinity when the two
electrodes are both half-metallic? Other principal features of TMR can also be
explained and reproduced by the present work. It also provides possible ways to
modulate the oscillation of TMR, and to enhance TMR so that it can tend to
infinity. Within the theory, the barrier, as a periodic diffraction grating,
can get rid of the confinement in width, it can vary from nanoscale to
microscale. Based on those results, a future-generation MTJ is proposed where
the three pieces can be fabricated separately and then assembled together, it
is especially appropriate for the layered materials, e.g., MoS2 and graphite,
and most feasible for industries.

###Ultraquantum magnetoresistance in single-crystalline $β$-Ag$_2$Se|Chenglong Zhang,Haiwen Li,Tay-Rong Chang,Su-Yang Xu,Wei Hua,Hua Jiang,Zhujun Yuan,Junliang Sun,Horng-Tay Jeng,M. Zahid Hasan,X. C. Xie,Shuang Jia###

Ultraquantum magnetoresistance in single-crystalline $β$-Ag$_2$Se. In the history of condensed matter physics, reinvestigation of a well-studied
material with enhanced quality sometimes led to important scientific
discoveries. A well-known example is the discovery of fractional quantum Hall
effect in high quality GaAs/AlGaAs heterojunctions. Here we report the first
single crystal growth and magnetoresistance (MR) measurements of the silver
chalcogenide $\beta $-Ag$_2$Se (Naumannite), a compound has been known for the
unusual, linear-field-dependent MR in its polycrystalline form for over a
decade. With the quantum limit (QL) as low as 3 Tesla, a moderate field
produced by a superconductor magnet available in many laboratories can easily
drive the electrons in Ag$_2$Se to an unprecedented state. We observed
significant negative longitudinal MR beyond the QL, which was understood as a
`charge-pumping' effect between the novel fermions with opposite chiralities.
Characterization of the single-crystalline Ag$_2$Se and the fabrication of
electric devices working above the QL, will represent a new direction for the
study of these exotic electrons.

###Magnetic properties of 2D nickel nanostrips: structure dependent magnetic anomaly|Vikas Kashid,Vaishali Shah,H. G. Salunke,Yuriy Mokrousov,Stefan Blügel###

Magnetic properties of 2D nickel nanostrips: structure dependent magnetic anomaly. We have investigated different geometries of two dimensional (2D) infinite
length Ni nanowires of increasing width using spin density functional theory
calculations. Our simulations demonstrate that the parallelogram motif is the
most stable and structures that incorporate the parallelogram motif are more
stable as compared to rectangular structures. The wires are conducting and the
conductance channels increase with increasing width. The wires have a
non-linear behavior in the ballistic anistropic magnetoresistance ratios with
respect to the magnetization directions. All 2D nanowires as well as Ni (111)
and Ni (100) monolayer investigated are ferromagnetic under the Stoner
criterion and exhibit enhanced magnetic moments as compared to bulk Ni and the
respective Ni monolayers. The Stoner parameter is seen to depend on the
structure and the dimension of the Nws. The easy axis for all nickel nanowires
under investigation is observed to be along the wire axis. The double
rectangular nanowire exhibits a magnetic anomaly with a smaller magnetic moment
when compared to Ni (100) monolayer and is the only structure with an easy axis
perpendicular to the wire axis.

###Experimental observation of Weyl points|Ling Lu,Zhiyu Wang,Dexin Ye,Lixin Ran,Liang Fu,John D. Joannopoulos,Marin Soljačić###

Experimental observation of Weyl points. In 1929, Hermann Weyl derived the massless solutions from the Dirac equation
- the relativistic wave equation for electrons. Neutrinos were thought, for
decades, to be Weyl fermions until the discovery of the neutrino mass.
Moreover, it has been suggested that low energy excitations in condensed matter
can be the solutions to the Weyl Hamiltonian. Recently, photons have also been
proposed to emerge as Weyl particles inside photonic crystals. In all cases,
two linear dispersion bands in the three-dimensional (3D) momentum space
intersect at a single degenerate point - the Weyl point. Remarkably, these Weyl
points are monopoles of Berry flux with topological charges defined by the
Chern numbers. These topological invariants enable materials containing Weyl
points to exhibit a wide variety of novel phenomena including surface Fermi
arcs, chiral anomaly, negative magnetoresistance, nonlocal transport, quantum
anomalous Hall effect, unconventional superconductivity[15] and others [16,
17]. Nevertheless, Weyl points are yet to be experimentally observed in nature.
In this work, we report on precisely such an observation in an
inversion-breaking 3D double-gyroid photonic crystal without breaking
time-reversal symmetry.

###A combined experimental and theoretical study of the electronic and vibrational properties of bulk and few-layer Td-WTe2|Manoj K. Jana,Anjali Singh,Dattatray J. Late,Catherine Rajamathi,Kanishka Biswas,Claudia Felser,Umesh V. Waghmare,C. N. R. Rao###

A combined experimental and theoretical study of the electronic and vibrational properties of bulk and few-layer Td-WTe2. The recent discovery of non-saturating giant positive magnetoresistance in
Td-WTe2 has aroused great interest in this material. We have studied the
structural, electronic and vibrational properties of bulk and few-layer Td-WTe2
experimentally and theoretically. Spin-orbit coupling is found to govern the
semi-metallic character of Td-WTe2. Its structural link with the metallic 1T
form provides an understanding of its structural stability. We observe a metal
to insulator transition and a change in the sign of the Seebeck coefficient
around 373 K. Lattice vibrations in Td-WTe2 have been analyzed by first
principle calculations. Out of the 33 possible zone-center Raman active modes,
five distinct Raman bands are observed around 112, 118, 134, 165 and 212 cm-1
in bulk Td-WTe2. Based on symmetry analysis and the calculated Raman tensors,
we assign the intense bands at 165 cm-1 and 212 cm-1 to the A_1^' and A_1^"
modes respectively. We have examined the effect of temperature and the number
of layers on the Raman spectrum. Most of the bands of Td-WTe2 stiffen, and the
ratio of the integrated intensities of the A_1^" to A_1^' bands decreases in
the few-layer sample, while all the bands soften in both bulk and few-layer
samples with increasing temperature.

###Redefinition of spin Hall magnetoresistance|Yan-Qing Zhang,Hua-Rui Fu,Niu-Yi Sun,Wen-Ru Che,Ding Ding,Juan Qin,Cai-Yin You,Zhen-Gang Zhu,Rong Shan###

Redefinition of spin Hall magnetoresistance. Using a multi-conduction-channel model, we redefined the micromechanism of
spin Hall magnetoresistance (SMR). Four conduction channels are created by spin
accumulation of nonpolarized electron flow at top, bottom, left and right
interfaces of the film sample, which corresponds to different resistance states
of polarized electron flow with various spin directions relative to the applied
magnetic field ($\mathbf{H}$), and brings about the SMR effect finally. The
magnetic insulator layer, such as yttrium iron garnet (YIG), is not a requisite
for the observation of SMR. Instead, the SMR effect is perfectly realized, with
an order of magnitude increase, in the sample with a discontinuous layer of
isolated-Co$_2$FeAl (0.3 nm) grains covered by 2.5-nm-thick Pt layer on MgO
substrate. The model intuitively gives the typical relationship of SMR effect,
i.e. $\rho_{\parallel}\approx\rho_{\bot}>\rho_{T}$, where $\rho_{\bot}$,
$\rho_{\parallel}$ and $\rho_{T}$ are longitudinal reisitivities with applied
magnetic field ($\mathbf{H}$) direction perpendicular to the current direction
out of plane (as Z direction), parallel with and perpendicular to it in plane
(as X and Y direction), respectively. Our research reveals that the scattering
between polarized and nonpolarized conduction electrons is the origin of SMR,
and the intrinsic SMR is not constant when $\mathbf{H}$ direction rotates in XZ
plane, which is distinct from that in the reported SMR mechanism.

###Electrically Tunable Band Gap in Antiferromagnetic Mott Insulator Sr2IrO4|Cheng Wang,Heidi Seinige,Gang Cao,Jian-Shi Zhou,John B. Goodenough,Maxim Tsoi###

Electrically Tunable Band Gap in Antiferromagnetic Mott Insulator Sr2IrO4. The electronic band gap in conventional semiconductor materials, such as
silicon, is fixed by the material's crystal structure and chemical composition.
The gap defines the material's transport and optical properties and is of great
importance for performance of semiconductor devices like diodes, transistors
and lasers. The ability to tune its value would allow enhanced functionality
and flexibility of future electronic and optical devices. Recently, an
electrically tunable band gap was realized in a 2D material - electronically
gated bilayer graphene [1-3]. Here we demonstrate the realization of an
electrically tunable band gap in a 3D antiferromagnetic Mott insulator Sr2IrO4.
Using nano-scale contacts between a sharpened Cu tip and a single crystal of
Sr2IrO4, we apply a variable external electric field up to a few MV/m and
demonstrate a continuous reduction in the band gap of Sr2IrO4 by as much as
16%. We further demonstrate the feasibility of reversible resistive switching
and electrically tunable anisotropic magnetoresistance,which provide evidence
of correlations between electronic transport, magnetic order, and orbital
states in this 5d oxide. Our findings suggest a promising path towards band gap
engineering in 5d transition-metal oxides that could potentially lead to
appealing technical solutions for next-generation electronic devices.

###Electrical Probing of Field-Driven Cascading Quantized Transitions of Skyrmion Cluster States in MnSi Nanowires|Haifeng Du,Dong Liang,Chiming Jin,Lingyao Kong,Matthew J. Stolt,Wei Ning,Jiyong Yang,Ying Xing,Jian Wang,Renchao Che,Jiadong Zang,Song Jin,Yuheng Zhang,Mingliang Tian###

Electrical Probing of Field-Driven Cascading Quantized Transitions of Skyrmion Cluster States in MnSi Nanowires. Magnetic skyrmions are topologically stable whirlpool-like spin textures that
offer great promise as information carriers for future ultra-dense memory and
logic devices1-4. To enable such applications, particular attention has been
focused on the skyrmions properties in highly confined geometry such as one
dimensional nanowires5-8. Hitherto it is still experimentally unclear what
happens when the width of the nanowire is comparable to that of a single
skyrmion. Here we report the experimental demonstration of such scheme, where
magnetic field-driven skyrmion cluster (SC) states with small numbers of
skyrmions were demonstrated to exist on the cross-sections of ultra-narrow
single-crystal MnSi nanowires (NWs) with diameters, comparable to the skyrmion
lattice constant (18 nm). In contrast to the skyrmion lattice in bulk MnSi
samples, the skyrmion clusters lead to anomalous magnetoresistance (MR)
behavior measured under magnetic field parallel to the NW long axis, where
quantized jumps in MR are observed and directly associated with the change of
the skyrmion number in the cluster, which is supported by Monte Carlo
simulations. These jumps show the key difference between the clustering and
crystalline states of skyrmions, and lay a solid foundation to realize
skyrmion-based memory devices that the number of skyrmions can be counted via
conventional electrical measurements.

###Colossal magnetoresistance in topological Kondo insulator|Igor O. Slieptsov,Igor N. Karnaukhov###

Colossal magnetoresistance in topological Kondo insulator. Abnormal electronic properties of complex systems require new ideas
concerning explanation of their behavior and possibility of realization. In
this acticle we show that a colossal magnetoresistance is realized in the state
of the topological Kondo insulator, that is similar to the Kondo insulator
state in the Kondo lattice. The mechanism of the phenomenon is the following:
in the spin gapless phase an external magnetic field induces the gap in the
spectrum of spin excitations, the gap in the spectrum of fermions is opened due
to a hybridization between spin and fermion subsystems at half filling, as the
result the magnetic field leads to metal-insulator (or bad metal - insulator)
phase transition. A model of the topological Kondo lattice defined on a
honeycomb lattice is studied for the case when spinless fermion bands are half
filled. It is shown that the hybridization between local moments and itinerant
fermions should be understood as the hybridization between corresponding
Majorana fermions of the spin and charge sectors. The system is a topological
insulator, single fermion and spin excitations at low energies are massive. We
will show that a spin gap induces a gap in the charge channel, it leads to an
appearance of a topological insulator state with chiral gapless edge modes and
the Chern number one or two depending on the exchange integrals' values. The
relevance of this to the traditional Kondo insulator state is discussed.

###Magnetic coupling at ferromagnetic rare earth / transition-metal interfaces: A comprehensive study|T. D. C. Higgs,S. Bonetti,H. Ohldag,N. Banerjee,X. L. Wang,A. Rosenberg,Z. Cai,J. H. Zhao,K. A. Moler,J. W. A. Robinson###

Magnetic coupling at ferromagnetic rare earth / transition-metal interfaces: A comprehensive study. Thin film magnetic heterostructures with competing interfacial coupling and
Zeeman energy pro- vide a fertile ground to study phase transition between
different equilibrium states as a function of external magnetic field and
temperature. A rare-earth (RE) / transition metal (TM) ferro- magnetic
multilayer is a classic example where the magnetic state is determined by a
competition between the Zeeman energy and antiferromagnetic interfacial
exchange coupling energy. Techno- logically, such structures offer the
possibility to engineer the macroscopic magnetic response by tuning the
microscopic interactions between the layers. We have performed an exhaustive
study of a nickel/gadolinium system by using the element-specific measurement
technique x-ray magnetic circular dichroism, and determined the full magnetic
state diagrams as a function of temperature and magnetic layer thickness. We
explain our result based on a modified Stoner-Wohlfarth formal- ism and provide
evidence of a thickness-dependent phase transition to a magnetic fan state
which is critical in understanding magnetoresistance effects in RE/TM systems.
The results provide im- portant insight for spintronics and superconducting
spintronics where engineering tunable magnetic inhomogeneity is key for certain
applications.

###Robust linear magnetoresistance in WTe2|Xing-Chen Pan,Yiming Pan,Juan Jiang,Huakun Zuo,Huimei Liu,Xuliang Chen,Zhongxia Wei,Shuai Zhang,Zhihe Wang,Xiangang Wan,Zhaorong Yang,Donglai Feng,Zhengcai Xia,Liang Li,Fengqi Song,Baigeng Wang,Yuheng Zhang,Guanghou Wang###

Robust linear magnetoresistance in WTe2. Unsaturated magnetoresistance (MR) has been reported in WTe2, and remains
irrepressible up to very high field. Intense optimization of the crystalline
quality causes a squarely-increasing MR, as interpreted by perfect compensation
of opposite carriers. Herein we report our observation of linear MR (LMR) in
WTe2 crystals, the onset of which is first identified by constructing the
mobility spectra of the MR at low fields. The LMR further intensifies and
predominates at fields higher than 20 Tesla while the parabolic MR gradually
decays. The LMR remains unsaturated up to a high field of 60 Tesla and
persists, even at a high pressure of 6.2 GPa. Assisted by density functional
theory calculations and detailed mobility spectra, we find the LMR to be robust
against the applications of high field, broken carrier balance, and mobility
suppression. Angle-resolved photoemission spectroscopy reveals a unique
quasilinear energy dispersion near the Fermi level. Our results suggest that
the robust LMR is the low bound of the unsaturated MR in WTe2.

###Helicity protected ultrahigh mobility Weyl fermions in NbP|Zhen Wang,Yi Zheng,Zhixuan Shen,Yi Zhou,Xiaojun Yang,Yupeng Li,Chunmu Feng,Zhu-An Xu###

Helicity protected ultrahigh mobility Weyl fermions in NbP. Non-centrosymmetric transition metal monopnictides, including TaAs, TaP,
NbAs, and NbP, are emergent topological Weyl semimetals (WSMs) hosting exotic
relativistic Weyl fermions. In this letter, we elucidate the physical origin of
the unprecedented charge carrier mobility of NbP, which can reach
$1\times10^{7}$ cm $^{2}$V$^{-1}$s$^{-1}$ at 1.5 K. Angle- and
temperature-dependent quantum oscillations, supported by density function
theory calculations, reveal that NbP has the coexistence of p- and n-type WSM
pockets in the $k_{z}$=1.16$\pi$/c plane (W1-WSM) and in the $k_{z}$=0 plane
near the high symmetry points $\Sigma$ (W2-WSM), respectively. Uniquely, each
W2-WSM pocket forms a large dumbbell-shaped Fermi surface (FS) enclosing two
neighboring Weyl nodes with the opposite chirality. The magneto-transport in
NbP is dominated by these highly anisotropic W2-WSM pockets, in which Weyl
fermions are well protected from defect backscattering by real spin
conservation associated to the chiral nodes. However, with a minimal doping of
$\sim$1\% Cr, the mobility of NbP is degraded by more than two order of
magnitude, due to the invalid of helicity protection to magnetic impurities.
Helicity protected Weyl fermion transport is also manifested in chiral anomaly
induced negative magnetoresistance, controlled by the W1-WSM states. In the
quantum regime below 10 K, the intervalley scattering time by impurities
becomes a large constant, producing the sharp and nearly identical conductivity
enhancement at low magnetic field.

###Origin of interfacial perpendicular magnetic anisotropy in MgO/CoFe/metallic capping layer structures|Shouzhong Peng,Mengxing Wang,Hongxin Yang,Lang Zeng,Jiang Nan,Jiaqi Zhou,Youguang Zhang,Ali Hallal,Mairbek Chshiev,Kang L. Wang,Qianfan Zhang,Weisheng Zhao###

Origin of interfacial perpendicular magnetic anisotropy in MgO/CoFe/metallic capping layer structures. Spin-transfer-torque magnetic random access memory (STT-MRAM) attracts
extensive attentions due to its non-volatility, high density and low power
consumption. The core device in STT-MRAM is CoFeB/MgO-based magnetic tunnel
junction (MTJ), which possesses a high tunnel magnetoresistance ratio as well
as a large value of perpendicular magnetic anisotropy (PMA). It has been
experimentally proven that a capping layer coating on CoFeB layer is essential
to obtain a strong PMA. However, the physical mechanism of such effect remains
unclear. In this paper, we investigate the origin of the PMA in
MgO/CoFe/metallic capping layer structures by using a first-principles
computation scheme. The trend of PMA variation with different capping materials
agrees well with experimental results. We find that interfacial PMA in the
three-layer structures comes from both the MgO/CoFe and CoFe/capping layer
interfaces, which can be analyzed separately. Furthermore, the PMAs in the
CoFe/capping layer interfaces are analyzed through resolving the magnetic
anisotropy energy by layer and orbital. The variation of PMA with different
capping materials is attributed to the different hybridizations of both d and p
orbitals via spin-orbital coupling. This work can significantly benefit the
research and development of nanoscale STT-MRAM.

###Chemical doping and high pressure studies of layered beta-PdBi2 single crystals|Kui Zhao,Bing Lv,Yu-Yi Xue,Xi-Yu Zhu,Liangzi Deng,Zheng Wu,C. W. Chu###

Chemical doping and high pressure studies of layered beta-PdBi2 single crystals. We have systematically grown large single crystals of layered compound
beta-PdBi2, both the hole-doped PdBi2-xPbx and the electron-doped NaxPdBi2, and
studied their magnetic and transport properties. Hall-effect measurement on
PdBi2, PdBi1.8Pb0.2, and Na0.057PdBi2 shows that the charge transport is
dominated by electrons in all of the samples. The electron concentration is
substantially reduced upon Pb-doping in PdBi2-xPbx and increased upon
Na-intercalation in NaxPdBi2, indicating the effective hole-doping by Pb and
electron-doping by Na. We observed a monotonic decrease of superconducting
transition temperature (Tc) from 5.4K in undoped PdBi2 to less than 2K for x >
0.35 in hole-doped PdBi2-xPbx. Meanwhile, a rapid decrease of Tc with the Na
intercalation is also observed in the electron-doped NaxPdBi2, which is in
disagreement with the theoretical expectation. In addition, both the
magnetoresistance and Hall resistance further reveal evidence for a possible
spin density wave (SDW)-like transition below 50K in the Na-intercalated PdBi2
sample. The complete phase diagram is thus established from hole-doping to
electron-doping. Meanwhile, high pressure study of the undoped PdBi2 shows that
the Tc is linearly suppressed under pressure with a dTc/dP coefficient of
-0.28K/GPa.

###Spin-flip scattering of critical quasiparticles and the phase diagram of YbRh2Si2|Peter Woelfle,Elihu Abrahams###

Spin-flip scattering of critical quasiparticles and the phase diagram of YbRh2Si2. Several observed transport and thermodynamic properties of the heavy-fermion
compound YbRh2Si2 in the quantum critical regime are unusual and suggest that
the fermionic quasiparticles are critical, characterized by a scale-dependent
diverging effective mass. A theory based on the concept of critical
quasiparticles (CQP) scattering off antiferromagnetic spin fluctuations in a
strong-coupling regime has been shown to successfully explain the unusual
existing data and to predict a number of so far unobserved properties. In this
paper, we point out a new feature of a magnetic field-tuned quantum critical
point of a heavy-fermion metal: anomalies in the transport and thermodynamic
properties caused by the freezing out of spin-flip scattering of critical
quasiparticles and the scattering off collective spin excitations. We show that
a step-like behavior as a function of magnetic field of e.g. the Hall
coefficient and magnetoresistivity results, which accounts quantitatively for
the observed behavior of these quantities. That behavior has been described as
a crossover line T*(H) in the T - H phase diagram of YbRh2Si2. Whereas some
authors have interpreted this observation as signaling the breakdown of Kondo
screening and an associated abrupt change of the Fermi surface, our results
suggest that the T* line may be quantitatively understood within the picture of
robust critical quasiparticles.

###Magnetoresistance and gating effects in ultrathin NbN-$\rm Bi_2Se_3$ bilayers|Gad Koren###

Magnetoresistance and gating effects in ultrathin NbN-$\rm Bi_2Se_3$ bilayers. Ultrathin $\rm Bi_2Se_3$-NbN bilayers comprise a simple proximity system of a
topological insulator and an s-wave superconductor for studying gating effects
on topological superconductors. Here we report on 3 nm thick NbN layers of
weakly connected superconducting islands, overlayed with 10 nm thick $\rm
Bi_2Se_3$ film which facilitates enhanced proximity coupling between them.
Resistance versus temperature of the most resistive bilayers shows insulating
behavior but with signs of superconductivity. We measured the magnetoresistance
(MR) of these bilayers versus temperature with and without a magnetic field H
normal to the wafer (MR=[R(H)-R(0)]/\{[R(H)+R(0)]/2\}), and under three
electric gate-fields of 0 and $\pm2$ MV/cm. The MR results showed a complex set
of gate sensitive peaks which extended up to about 30 K. The results are
discussed in terms of vortex physics, and the origin of the different MR peaks
is identified and attributed to flux-flow MR in the isolated NbN islands and
the different proximity regions in the $\rm Bi_2Se_3$ cap-layer. The dominant
MR peak was found to be consistent with enhanced proximity induced
superconductivity in the topological edge currents regions. The high
temperature MR data suggest a possible pseudogap phase or a highly extended
fluctuation regime.

###Dirac Cone Protected by Non-Symmorphic Symmetry and 3D Dirac Line Node in ZrSiS|Leslie M. Schoop,Mazhar N. Ali,Carola Straßer,Viola Duppel,Stuart S. P. Parkin,Bettina V. Lotsch,Christian R. Ast###

Dirac Cone Protected by Non-Symmorphic Symmetry and 3D Dirac Line Node in ZrSiS. Materials harboring exotic quasiparticles, such as Dirac and Weyl
fermions\cite{xu2015discovery,borisenko2015time,weng2015weyl,xu2015observation},
have garnered much attention from the physics and material science communities.
These fermions are massless and, in some materials, have shown exceptional
physical properties such as ultrahigh mobility and extremely large
magnetoresistances
\cite{liang2015ultrahigh,ali2014large,du2015unsaturated,shekhar2015large}.
Recently, new materials have been predicted to exist which exhibit line nodes
of Dirac cones
\cite{PhysRevLett.115.036806,xie2015new,burkov2011topological,rhim2015landau}.
Here, we show with angle resolved photoemission studies supported by \textit{ab
initio} calculations that the highly stable, non-toxic and earth-abundant
material, ZrSiS, has an electronic band structure that hosts several Dirac
cones which form a Fermi surface with a diamond-shaped line of Dirac nodes. We
also experimentally show, for the first time, that the square Si lattice in
ZrSiS is an excellent template for realizing the new types of 2D Dirac cones
recently predicted by Young and Kane \cite{young2015dirac} and image an
unforseen surface state that arises close to the 2D Dirac cone. Finally, we
find that the energy range of the linearly dispersed bands is as high as 2\,eV
above and below the Fermi level; much larger than of any known Dirac material
so far. This makes ZrSiS a very promising candidate to study the exotic
behavior of Dirac electrons, or Weyl fermions if a magnetic field is applied,
as well as the properties of lines of Dirac nodes

###Investigation of ferromagnetic domain behavior and phase transition at nanoscale in bilayer manganites|C. Phatak,A. K. Petford-Long,H. Zheng,J. F. Mitchell,S. Rosenkranz,M. R. Norman###

Investigation of ferromagnetic domain behavior and phase transition at nanoscale in bilayer manganites. Understanding the underlying mechanism and phenomenology of colossal
magnetoresistance in manganites has largely focused on atomic and nanoscale
physics such as double exchange, phase separation, and charge order. Here we
consider a more macroscopic view of manganite materials physics, reporting on
the ferromagnetic domain behavior in a bilayer manganite sample with a nominal
composition of La$_{2-2x}$Sr$_{1+2x}$Mn$_2$O$_7$ with $x=0.38$, studied using
in-situ Lorentz transmission electron microscopy. The role of
magnetocrystalline anisotropy on the structure of domain walls was elucidated.
On cooling, magnetic domain contrast was seen to appear first at the Curie
temperature within the $a-b$ plane. With further reduction in temperature, the
change in area fraction of magnetic domains was used to estimate the critical
exponent describing the ferromagntic phase transition. The ferromagnetic phase
transition was accompanied by a distinctive nanoscale granular contrast close
to the Curie temperature, which we infer to be related to the presence of
ferromagnetic nanoclusters in a paramagnetic matrix, which has not yet been
reported in bilayer manganites.

###Linear magnetoconductivity in an intrinsic topological Weyl semimetal|Song-Bo Zhang,Hai-Zhou Lu,Shun-Qing Shen###

Linear magnetoconductivity in an intrinsic topological Weyl semimetal. Searching for the signature of the violation of chiral charge conservation in
solids has inspired a growing passion on the magneto-transport in topological
semimetals. One of the open questions is how the conductivity depends on
magnetic fields in a semimetal phase when the Fermi energy crosses the Weyl
nodes. Here, we study both the longitudinal and transverse magnetoconductivity
of a topological Weyl semimetal near the Weyl nodes with the help of a two-node
model that includes all the topological semimetal properties. In the semimetal
phase, the Fermi energy crosses only the 0th Landau bands in magnetic fields.
For a finite potential range of impurities, it is found that both the
longitudinal and transverse magnetoconductivity are positive and linear at the
Weyl nodes, leading to an anisotropic and negative magnetoresistivity. The
longitudinal magnetoconductivity depends on the potential range of impurities.
The longitudinal conductivity remains finite at zero field, even though the
density of states vanishes at the Weyl nodes. This work establishes a relation
between the linear magnetoconductivity and the intrinsic topological Weyl
semimetal phase.

###Electronic and magnetic transitions in perovskite SrRu1-xIrxO3 thin films|Abhijit Biswas,Yong Woo Lee,Yoon Hee Jeong###

Electronic and magnetic transitions in perovskite SrRu1-xIrxO3 thin films. We have investigated the electronic and magnetic properties of perovskite
SrRu1-xIrxO3 thin films grown by pulsed laser deposition on atomically-flat
(001) SrTiO3 substrates. SrRuO3 has the properties of a ferromagnetic metal
with Curie temperature 150 K. Substituting Ir for Ru in SrRuO3, films showed
fully-metallic behavior and ferromagnetic ordering, although resistivity
increased and the ferromagnetic TC decreased. Films with x = 0.25 underwent the
metal-to-insulator transition at 75 K, and spin-glass-like ordering at 45 K
with the elimination of ferromagnetic long-range ordering caused by the
electron localization at the substitution sites. In ferromagnetic films,
resistivity increased near-linearly with T, but in paramagnetic film (x = 0.25)
resistivity increased as T3/2. Moreover, observed spin-glass-like (TSG)
ordering with the negative magnetoresistance in film with x = 0.25; validates
the hypothesis that (Anderson) localization favors glassy ordering at amply
disorder limit. These observations provide a promising approach for future
applications and of fundamental interest in 4d and 5d mixed perovskites.

###Metal insulator transition and magnetotransport anomalies in perovskite SrIr0.5Ru0.5O3 thin films|Abhijit Biswas,Yong Woo Lee,Sang Woo Kim,Yoon Hee Jeong###

Metal insulator transition and magnetotransport anomalies in perovskite SrIr0.5Ru0.5O3 thin films. We investigated the nature of transport and magnetic properties in
SrIr0.5Ru0.5O3, (SIRO) which has characteristics intermediate between a
correlated non-Fermi liquid state and an itinerant Fermi liquid state, by
growing perovskite thin films on various substrates (SrTiO3 (001),
(LaAlO3)0.3(Sr2TaAlO6)0.7 (001) and LaAlO3 (001)). We observed systematic
variation of underlying substrate dependent metal-to-insulator transition
temperatures at 80 K on SrTiO3, 90 K on (LaAlO3)0.3(Sr2TaAlO6)0.7 and 100 K on
LaAlO3) in resistivity. Resistivity in the metallic region follows a T3/2 power
law; whereas insulating nature at low T is due to the localization effect.
Magnetoresistance (MR) measurement of SIRO on SrTiO3 (001) shows negative MR
upto 25 K and positive MR above 25 K, with negative MR proportional to B1/2 and
positive MR proportional to B2; consistent with the localized-to-normal
transport crossover dynamics. Furthermore, observed spin glass like behavior of
SIRO on SrTiO3 (001) in the localized regime, validates the hypothesis that
(Anderson) localization favors glassy ordering. These remarkable features
provide a promising approach for future applications and of fundamental
interest in oxide thin films.

###Merging Dirac electrons and correlation effect in the heterostructured Bi2Te3/Fe1+dTe|Guan Du,Zengyi Du,Xiong Yang,Enyu Wang,Delong Fang,Huan Yang,Hai-Hu Wen###

Merging Dirac electrons and correlation effect in the heterostructured Bi2Te3/Fe1+dTe. The topological insulator and strong electronic correlation effect are two
important subjects in the frontier studies of modern condensed matter physics.
A topological insulator exhibits a unique pair of surface conduction bands with
the Dirac dispersion albeit the bulk insulating behaviour. These surface states
are protected by the topological order, and thus the spin and momentum of these
surface electrons are locked together demonstrating the feature of time
reversal invariance. On the other hand, the electronic correlation effect
becomes the very base of many novel electronic states, such as high temperature
superconductivity, giant magnetoresistance etc. Here we report the discovery of
merging the two important components: Dirac electrons and the correlation
effect in heterostructured Bi2Te3/Fe1+dTe. By measuring the scanning tunneling
spectroscopy on Bi2Te3 thin films (a typical topological insulator) thicker
than 6 quintuple layers on top of the Fe1+dTe single crystal (a parent phase of
the iron based superconductors FeSe1-xTex), we observed the quantum oscillation
of Landau levels of the Dirac electrons and the gapped feature at the Fermi
energy due to the correlation effect of Fe1+dTe. Our observation challenges the
ordinary understandings and must demonstrate some unexplored territory
concerning the combination of topological insulator and strong correlation
effect.

###Two-Carrier Transport Induced Hall Anomaly and Large Tunable Magnetoresistance in Dirac Semimetal Cd3As2 Nanoplates|Cai-Zhen Li,Jin-Guang Li,Li-Xian Wang,Liang Zhang,Jing-Min Zhang,Dapeng Yu,Zhi-Min Liao###

Two-Carrier Transport Induced Hall Anomaly and Large Tunable Magnetoresistance in Dirac Semimetal Cd3As2 Nanoplates. Cd3As2 is a model material of Dirac semimetal with a linear dispersion
relation along all three directions in the momentum space. The unique band
structure of Cd3As2 makes it with both Dirac and topological properties. It can
be driven into a Weyl semimetal by the symmetry breaking or a topological
insulator by enhancing the spin-orbit coupling. Here we report the temperature
and gate voltage dependent magnetotransport properties of Cd3As2 nanoplates
with Fermi level near the Dirac point. The Hall anomaly demonstrates the
two-carrier transport accompanied by a transition from n-type to p-type
conduction with decreasing temperature. The carrier-type transition is
explained by considering the temperature dependent spin-orbit coupling. The
magnetoresistance exhibits a large non-saturating value up to 2000% at high
temperatures, which is ascribed to the electron-hole compensation in the
system. Our results are valuable for understanding the experimental
observations related to the two-carrier transport in Dirac/Weyl semimetals,
such as Na3Bi, ZrTe5, TaAs, NbAs, and HfTe5.

###Ferromagnetism in orthorhombic RAgAl3 (R = Ce and Pr) compounds|S. Nallamuthu,Andrea Dzubinska,Marian Reiffers,Jesus Rodriguez Fernandez,R. Nagalakshmi###

Ferromagnetism in orthorhombic RAgAl3 (R = Ce and Pr) compounds. We present a detailed study on magnetic, thermodynamic and transport
properties of polycrystalline RAgAl3(R = Ce and Pr) compounds. Both compounds
crystallize in orthorhombic structure, which is distorted from the tetragonal
BaAl4 structure with the space group Cmcm. Heat capacity measurement indicates
the bulk magnetic ordering of the compounds. CeAgAl3 and PrAgAl3 order
ferromagnetically at TC = 3.8 K and 5.8 K, respectively as it was confirmed
from magnetic measurements. CeAgAl3 exhibits heavy Fermion behaviour. The
Schottky behaviour in heat capacity data was observed in both compounds. The
crystalline electric field (CEF) analysis of the magnetic parts of heat
capacity of CeAgAl3 and PrAgAl3 yielded to a CEF level scheme with three
doublets and nine singlets and with an overall splitting of 51 K and 180 K,
respectively. Fit yielded a magnetic doublet state for CeAgAl3, whereas for
PrAgAl3 a pseudo-doublet ground-state with an energy difference of 15 K has
been obtained. The resistivity measurements display a low temperature drop at
the magnetic ordering temperature of the compounds. Negative magnetoresistance
(MR) due to the ferromagnetic ordering has been observed for both Ce and Pr
compounds.

###Large influence of capping layers on tunnel magnetoresistance in magnetic tunnel junctions|Jiaqi Zhou,Weisheng Zhao,Yin Wang,Shouzhong Peng,Junfeng Qiao,Li Su,Lang Zeng,Na Lei,Lei Liu,Youguang Zhang,Arnaud Bournel###

Large influence of capping layers on tunnel magnetoresistance in magnetic tunnel junctions. It has been reported in experiments that capping layers which enhance the
perpendicular magnetic anisotropy (PMA) of magnetic tunnel junctions (MTJs)
induce great impact on the tunnel magnetoresistance (TMR). To explore the
essential influence caused by capping layers, we carry out ab initio
calculations on TMR in the X(001)|CoFe(001)|MgO(001)|CoFe(001)|X(001) MTJ,
where X represents the capping layer material which can be tungsten, tantalum
or hafnium. We report TMR in different MTJs and demonstrate that tungsten is an
ideal candidate for a giant TMR ratio. The transmission spectrum in Brillouin
zone is presented. It can be seen that in the parallel condition of MTJ, sharp
transmission peaks appear in the minority-spin channel. This phenomenon is
attributed to the resonant tunnel transmission effect and we explained it by
the layer-resolved density of states (DOS). In order to explore transport
properties in MTJs, the density of scattering states (DOSS) was studied from
the point of band symmetry. It has been found that CoFe|tungsten interface
blocks scattering states transmission in the anti-parallel condition. This work
reports TMR and transport properties in MTJs with different capping layers, and
proves that tungsten is a proper capping layer material, which would benefit
the design and optimization of MTJs.

###Large transverse Hall-like signal in topological Dirac semimetal Cd3As2|Shih-Ting Guo,R. Sankar,Yung-Yu Chien,Tay-Rong Chang,Horng-Tay Jeng,Guang-Yu Guo,F. C. Chou,Wei-Li Lee###

Large transverse Hall-like signal in topological Dirac semimetal Cd3As2. Cadmium arsenide ($\rm Cd_3As_2$) is known for its inverted band structure
and ultra-high electron mobility. It has been theoretically predicted and also
confirmed by ARPES experiments to exhibit a 3D Dirac semimetal phase containing
degenerate Weyl nodes. From magneto-transport measurements in high quality
single crystals of $\rm Cd_3As_2$, a small effective mass $m^* \approx$ 0.05
$m_e$ is determined from the Shubnikov-de Haas (SdH) oscillations. In certain
field orientations, we find a splitting of the SdH oscillation frequency in the
FFT spectrum suggesting a possible lifting of the double degeneracy in accord
with the helical spin texture at outer and inner Fermi surfaces with opposite
chirality predicted by our \textit{ab initio} calculations. Strikingly, a large
antisymmetric magnetoresistance with respect to the applied magnetic fields is
uncovered over a wide temperature range in needle crystal of $\rm Cd_3As_2$
with its long axis along [112] crystal direction. It reveals a possible
contribution of intrinsic anomalous velocity term in the transport equation
resulting from a unique 3D Rashba-like spin splitted bands that can be obtained
from band calculations with the inclusion of Cd antisite defects.

###Probing chiral superconductivity in Sr$_{2}$RuO$_{4}$ underneath the surface by point contact measurements|He Wang,Jiawei Luo,Weijian Lou,Jian Wei,J. E. Ortmann,Z. Q. Mao,Y. Liu###

Probing chiral superconductivity in Sr$_{2}$RuO$_{4}$ underneath the surface by point contact measurements. Sr$_{2}$RuO$_{4}$ (SRO) is the prime candidate for chiral $p$-wave
superconductor with critical temperature $T_{c}(SRO)\sim$1.5 K. Chiral domains
with opposite chiralities $p_{x}\pm ip_{y}$ were proposed, but yet to be
confirmed. We measure the field dependence of the point contact (PC) resistance
between a tungsten tip and the SRO-Ru eutectic crystal, where micrometer-sized
Ru inclusions are embedded in SRO with atomic sharp interface. Ruthenium is an
$s$-wave superconductor with $T_{c}(Ru)\sim$0.5 K, flux pinned near the Ru
inclusions can suppress its superconductivity as reflected from the PC
resistance and spectra. This flux pinning effect is originated from SRO
\textit{underneath} the surface and is very strong. To fully remove it, one has
to thermal cycle the sample above $T_{c}(SRO)$. This resembles the thermal
demagnetization for a ferromagnet, where ferromagnetic domains are randomized
above its Curie temperature. Another way is by applying alternating fields with
decreasing amplitude, resembling field demagnetization for the ferromagnet. The
observed hysteresis in magnetoresistance can be explained by domain dynamics,
providing support for the existence of chiral domains. The origin of strong
pinning \textit{underneath} the surface is also discussed.

###Signatures of an annular Fermi sea|Insun Jo,Yang Liu,L. N. Pfeiffer,K. W. West,K. W. Baldwin,M. Shayegan,R. Winkler###

Signatures of an annular Fermi sea. We report Shubnikov-de Haas oscillations measurements revealing experimental
signatures of an annular Fermi sea that develops near the energy band edge of
the excited subband of two-dimensional holes confined in a wide GaAs quantum
well. As we increase the hole density, when the Fermi level reaches the excited
subband edge, the low-field magnetoresistance traces show a sudden emergence of
new oscillations at an unexpectedly large frequency whose value does
$\textit{not}$ correspond to the (negligible) density of holes in the excited
subband. There is also a sharp and significant increase in zero-field
resistance near this onset of subband occupation. Guided by numerical energy
dispersion calculations, we associate these observations with the unusual shape
of the excited subband dispersion which results in a "ring of extrema" at
finite wavevectors and an annular Fermi sea. Such a dispersion and Fermi sea
have long been expected from energy band calculations in systems with strong
spin-orbit interaction but their experimental signatures have been elusive.

###Chiral anomaly from strain-induced gauge fields in Dirac and Weyl semimetals|D. I. Pikulin,Anffany Chen,M. Franz###

Chiral anomaly from strain-induced gauge fields in Dirac and Weyl semimetals. Dirac and Weyl semimetals form an ideal platform for testing ideas developed
in high energy physics to describe massless relativistic particles. One such
quintessentially field-theoretic idea of chiral anomaly already resulted in the
prediction and subsequent observation of the pronounced negative
magnetoresistance in these novel materials for parallel electric and magnetic
fields. Here we predict that the chiral anomaly occurs - and has experimentally
observable consequences - when real electromagnetic fields E and B are replaced
by strain-induced pseudo-electromagnetic fields e and b. For example, a uniform
pseudomagnetic field b is generated when a Weyl semimetal nanowire is put under
torsion. In accord with the chiral anomaly equation we predict a negative
contribution to the wire resistance proportional to the square of the torsion
strength. Remarkably, left and right moving chiral modes are then spatially
segregated to the bulk and surface of the wire forming a "topological coaxial
cable". This produces hydrodynamic flow with potentially very long relaxation
time. Another effect we predict is the ultrasonic attenuation and
electromagnetic emission due to a time periodic mechanical deformation causing
pseudoelectric field e. These novel manifestations of the chiral anomaly are
most striking in the semimetals with a single pair of Weyl nodes but also occur
in Dirac semimetals such as Cd3As2 and Na3Bi and Weyl semimetals with unbroken
time reversal symmetry.

###Reading and Writing Single-Atom Magnets|Fabian D. Natterer,Kai Yang,William Paul,Philip Willke,Taeyoung Choi,Thomas Greber,Andreas J. Heinrich,Christopher P. Lutz###

Reading and Writing Single-Atom Magnets. The highest-density magnetic storage media will code data in single-atom
bits. To date, the smallest individually addressable bistable magnetic bits on
surfaces consist of 5-12 atoms. Long magnetic relaxation times were
demonstrated in molecular magnets containing one lanthanide atom, and recently
in ensembles of single holmium (Ho) atoms supported on magnesium oxide (MgO).
Those experiments indicated the possibility for data storage at the fundamental
limit, but it remained unclear how to access the individual magnetic centers.
Here we demonstrate the reading and writing of individual Ho atoms on MgO, and
show that they independently retain their magnetic information over many hours.
We read the Ho states by tunnel magnetoresistance and write with current pulses
using a scanning tunneling microscope. The magnetic origin of the long-lived
states is confirmed by single-atom electron paramagnetic resonance (EPR) on a
nearby Fe sensor atom, which shows that Ho has a large out-of-plane moment of
$(10.1 \pm 0.1)$ $\mu_{\rm B}$ on this surface. In order to demonstrate
independent reading and writing, we built an atomic scale structure with two Ho
bits to which we write the four possible states and which we read out remotely
by EPR. The high magnetic stability combined with electrical reading and
writing shows that single-atom magnetic memory is possible.

###Picosecond all-optical switching of magnetic tunnel junctions|Jun-Yang Chen,Li He,Jian-Ping Wang,Mo Li###

Picosecond all-optical switching of magnetic tunnel junctions. Control of magnetism without using magnetic fields enables large-scale
integration of spintronic devices for memory, computation and communication in
the beyond-CMOS era. Mechanisms including spin torque transfer, spin Hall
effect, and electric field or strain assisted switching have been implemented
to switch magnetization in various spintronic devices. Their operation speed,
however, is fundamentally limited by the spin precession time to be longer than
10-100 picoseconds. Overcoming such a speed constraint is critical for the
prospective development of spintronics. Here we report the demonstration of
picosecond all-optical switching of a magnetic tunnel junction (MTJ)- the
building block of spintronic logic and memory -only using single telecom-band,
infrared laser pulses. This first optically switchable MTJ uses ferrimagnetic
GdFeCo as the free layer, and its switching is directly readout by measuring
its tunneling magnetoresistance with a DR/R ratio of 0.6%. An instrument
limited switching repetition rate at MHz has been demonstrated, but the
fundamental limit should be higher than tens of GHz. This result represents an
important step toward integrated opto-spintronic devices that combines
spintronics and photonics technologies to enable ultrafast conversion between
fundamental information carriers of electron spins and photons.

###Crystal field states of Kondo lattice heavy fermions CeRuSn3 and CeRhSn3|V. K. Anand,D. T. Adroja,D. Britz,A. M. Strydom,J. W. Taylor,W. Kockelmann###

Crystal field states of Kondo lattice heavy fermions CeRuSn3 and CeRhSn3. Inelastic neutron scattering experiments have been carried out to determine
the crystal field states of the Kondo lattice heavy fermions CeRuSn3 and
CeRhSn3. Both the compounds crystallize in LaRuSn3-type cubic structure (space
group Pm-3n) in which the Ce atoms occupy two distinct crystallographic sites
with cubic (m-3) and tetragonal (-4m.2) point symmetries. The INS data of
CeRuSn3 reveal the presence of a broad excitation centered around 6-8 meV which
is accounted by a model based on crystal electric field (CEF) excitations. On
the other hand, the INS data of isostructural CeRhSn3 reveal three CEF
excitations around 7.0, 12.2 and 37.2 meV. The neutron intensity sum rule
indicates that the Ce ions at both cubic and tetragonal Ce sites are in Ce3+
state in both CeRuSn3 and CeRhSn3. The CEF level schemes for both the compounds
are deduced. We estimate the Kondo temperature T_K = 3.1(2) K for CeRuSn3 from
neutron quasielastic linewidth in excellent agreement with that determined from
the scaling of magnetoresistance which gives T_K = 3.2(1) K. For CeRhSn3 the
neutron quasielastic linewidth gives T_K = 4.6 K. For both CeRuSn3 and CeRhSn3,
the ground state of Ce3+ turns out to be a quartet for the cubic site and a
doublet for the tetragonal site.

###Mesoscopic superconductivity and high spin polarization coexisting at metallic point contacts on the Weyl semimetal TaAs|Leena Aggarwal,Sirshendu Gayen,Shekhar Das,Ritesh Kumar,Vicky Süß,Chandra Shekhar,Claudia Felser,Goutam Sheet###

Mesoscopic superconductivity and high spin polarization coexisting at metallic point contacts on the Weyl semimetal TaAs. A Weyl semimetal is a topologically non-trivial phase of matter that hosts
mass-less Weyl fermions, the particles that remained elusive for more than 80
years since their theoretical discovery. The Weyl semimetals exhibit unique
transport and magneto-transport properties and remarkably high surface spin
polarization. Here we show that a unique mesoscopic superconducting phase with
a critical temperature up to 7 K can be realized by forming metallic point
contacts with silver (Ag) on single crystals of TaAs, while neither Ag nor TaAs
are superconductors. The Andreev reflection spectra obtained from such point
contacts are fitted well within a modified Blonder-Tinkham-Klapwijk (BTK) model
with a superconducting energy gap up to 1.2 meV. The analysis within this model
also reveals high transport spin polarization up to 60\% indicating a spin
polarized supercurrent flowing through the point contacts on TaAs. Such point
contacts also show a large anisotropic magnetoresistance (AMR) originating from
the spin polarized current. Therefore, apart from the discovery of a novel
mesoscopic superconducting phase and it's coexistence with a large spin
polarization, our results also show that the point contacts on Weyl semimetals
are potentially important for applications in spintronics.

###Electrical detection of spiral spin structures in Pt|Cu_2OSeO_3 heterostructures|A. Aqeel,N. Vlietstra,A. Roy,M. Mostovoy,B. J. van Wees,T. T. M. Palstra###

Electrical detection of spiral spin structures in Pt|Cu_2OSeO_3 heterostructures. The interaction between the itinerant spins in metals and localized spins in
magnetic insulators thus far has only been explored in collinear spin systems,
such as garnets. Here, we report the spin-Hall magnetoresistance (SMR)
sensitive to the surface magnetization of the spin-spiral material, Cu_2OSeO_3.
We experimentally demonstrate that the angular dependence of the SMR changes
drastically at the transition between the helical spiral and the conical spiral
phases. Furthermore, the sign and magnitude of the SMR in the conical spiral
state are controlled by the cone angle. We show that this complex behaviour can
be qualitatively explained within the SMR theory initially developed for
collinear magnets. In addition, we studied the spin Seebeck effect (SSE), which
is sensitive to the bulk magnetization. It originates from the conversion of
thermally excited low-energy spin waves in the magnet, known as magnons, into
the spin current in the adjacent metal contact (Pt). The SSE displays
unconventional behavior where not only the magnitude but also the phase of the
SSE vary with the applied magnetic field.

###Highly mobile carriers in orthorhombic phases of iron-based superconductors FeSe${}_{1-x}$S${}_{x}$|Y. A. Ovchenkov,D. A. Chareev,V. A. Kulbachinskii,V. G. Kytin,D. E. Presnov,O. S. Volkova,A. N. Vasiliev###

Highly mobile carriers in orthorhombic phases of iron-based superconductors FeSe${}_{1-x}$S${}_{x}$. The field and temperature dependencies of the longitudinal and Hall
resistivity have been measured for FeSe${}_{1-x}$S${}_{x}$ (x=0.04, 0.09 and
0.19) single crystals. The sample FeSe${}_{0.81}$S${}_{0.19}$ does not show a
transition to an orthorhombic phase and exhibits at low temperatures the
transport properties quite different from those of orthorhombic samples. The
behavior of FeSe${}_{0.81}$S${}_{0.19}$ is well described by the simple two
band model with comparable values of hole and electron mobility. In particular,
at low temperatures the transverse resistance shows a linear field dependence,
the magnetoresistance follow a quadratic field dependence and obeys to Kohler's
rule. In contrast, Kohler's rule is strongly violated for samples having an
orthorhombic low temperature structure. However, the transport properties of
the orthorhombic samples can be satisfactory described by the three band model
with the pair of almost equivalent to the tetragonal sample hole and electron
bands, supplemented with the highly mobile electron band which has two order
smaller carrier number. Therefore, the peculiarity of the low temperature
transport properties of the orthorhombic Fe(SeS) samples, as probably of many
other orthorhombic iron superconductors, is due to the presence of a small
number of highly mobile carriers which originate from the local regions of the
Fermi surface, presumably, nearby the Van Hove singularity points.

###FIB synthesis of Bi2Se3 1D nanowires demonstrating the co-existence of Shubnikov-de Haas oscillations and linear magnetoresistance|Biplab Bhattacharyya,Alka Sharma,V P S Awana,T. D. Senguttuvan,Sudhir Husale###

FIB synthesis of Bi2Se3 1D nanowires demonstrating the co-existence of Shubnikov-de Haas oscillations and linear magnetoresistance. Since the discovery of topological insulators (TI), there are considerable
interests in demonstrating metallic surface states, their shielded robust
nature to the backscattering and study their properties at nanoscale dimensions
by fabricating nanodevices. Here we address an important scientific issue
related to TI whether one can clearly demonstrate the robustness of topological
surface states (TSS) to the presence of disorder that does not break any
fundamental symmetry. The simple straightforward method of FIB milling was used
to synthesize nanowires of Bi2Se3 which we believe an interesting route to test
robustness of TSS and obtained results are new compared to many of the earlier
papers on quantum transport in TI demonstrating robustness of metallic SS to
gallium doping. In presence of perpendicular magnetic field, we have observed
the co-existence of Shubnikov de Haas oscillations and linear magnetoresistance
which was systematically investigated at different channel lengths indicating
the Dirac dispersive surface states. The transport properties and estimated
physical parameters shown here demonstrate the robustness of SS to the
fabrication tools triggering flexibility to explore new exotic quantum
phenomena at nanodevice level.

###Two-carrier analyses of the transport properties of black phosphorus under pressure|Kazuto Akiba,Atsushi Miyake,Yuichi Akahama,Kazuyuki Matsubayashi,Yoshiya Uwatoko,Masashi Tokunaga###

Two-carrier analyses of the transport properties of black phosphorus under pressure. We report on the electronic transport properties of black phosphorus and
analyze them using a two-carrier model in a wide range of pressure up to 2.5
GPa. In semiconducting state at 0.29 GPa, the remarkable non-linear behavior in
the Hall resistance is reasonably reproduced by assuming the coexistence of two
kinds of hole with different densities and mobilities. On the other hand,
two-carrier analyses of the magnetotransport properties above 1.01 GPa suggest
the coexistence of high mobility electron and hole carriers that have almost
the same densities, i.e., nearly compensated semimetallic nature of black
phosphorus. In the semimetallic state, analyses of both the two-carrier model
and quantum oscillations indicate a systematic increase in the carrier
densities as pressure increases. An observed sign inversion of Hall resistivity
at low magnetic fields suggests the existence of high mobility electrons
(\sim105 cm2 V-1 s-1) that is roughly ten times larger than that of holes, in
the semimetallic black phosphorus. We conclude that the extremely large
positive magnetoresistance that has been observed in semimetallic state cannot
be reproduced by a conventional two-carrier model.

###Linear magnetoresistance in a quasi-free two dimensional electron gas in an ultra-high mobility GaAs quantum well|T. Khouri,U. Zeitler,C. Reichl,W. Wegscheider,N. E. Hussey,S. Wiedmann,J. C. Maan###

Linear magnetoresistance in a quasi-free two dimensional electron gas in an ultra-high mobility GaAs quantum well. We report a magnetotransport study of an ultra-high mobility
($\bar{\mu}\approx 25\times 10^6$\,cm$^2$\,V$^{-1}$\,s$^{-1}$) $n$-type GaAs
quantum well up to 33 T. A strong linear magnetoresistance (LMR) of the order
of 10$^5$ % is observed in a wide temperature range between 0.3 K and 60 K. The
simplicity of our material system with a single sub-band occupation and free
electron dispersion rules out most complicated mechanisms that could give rise
to the observed LMR. At low temperature, quantum oscillations are superimposed
onto the LMR. Both, the featureless LMR at high $T$ and the quantum
oscillations at low $T$ follow the empirical resistance rule which states that
the longitudinal conductance is directly related to the derivative of the
transversal (Hall) conductance multiplied by the magnetic field and a constant
factor $\alpha$ that remains unchanged over the entire temperature range. Only
at low temperatures, small deviations from this resistance rule are observed
beyond $\nu=1$ that likely originate from a different transport mechanism for
the composite fermions.

###High-Tc superconductivity in FeSe at high pressure: Dominant hole carriers and enhanced spin fluctuations|J. P. Sun,G. Z. Ye,P. Shahi,J. -Q. Yan,K. Matsuura,H. Kontani,G. M. Zhang,Q. Zhou,B. C. Sales,T. Shibauchi,Y. Uwatoko,D. J. Singh,J. -G. Cheng###

High-Tc superconductivity in FeSe at high pressure: Dominant hole carriers and enhanced spin fluctuations. The importance of electron-hole interband interactions is widely acknowledged
for iron-pnictide superconductors with high transition temperatures (Tc).
However, high-Tc superconductivity without hole carriers has been suggested in
FeSe single-layer films and intercalated iron-selenides, raising a fundamental
question whether iron pnictides and chalcogenides have different pairing
mechanisms. Here, we study the properties of electronic structure in the
high-Tc phase induced by pressure in bulk FeSe from magneto-transport
measurements and first-principles calculations. With increasing pressure, the
low-Tc superconducting phase transforms into high-Tc phase, where we find the
normal-state Hall resistivity changes sign from negative to positive,
demonstrating dominant hole carriers in striking contrast to other FeSe-derived
high-Tc systems. Moreover, the Hall coefficient is remarkably enlarged and the
magnetoresistance exhibits anomalous scaling behaviors, evidencing strongly
enhanced interband spin fluctuations in the high-Tc phase. These results in
FeSe highlight similarities with high-Tc phases of iron pnictides, constituting
a step toward a unified understanding of iron-based superconductivity.

###Orbital-driven Mottness collapse in 1T-TaS2-xSex transition metal dichalcogenide|Shuang Qiao,Xintong Li,Naizhou Wang,Wei Ruan,Cun Ye,Peng Cai,Zhenqi Hao,Hong Yao,Xianhui Chen,Jian Wu,Yayu Wang,Zheng Liu###

Orbital-driven Mottness collapse in 1T-TaS2-xSex transition metal dichalcogenide. The vicinity of a Mott insulating phase has constantly been a fertile ground
for finding exotic quantum states, most notably the high Tc cuprates and
colossal magnetoresistance manganites. The layered transition metal
dichalcogenide 1T-TaS2 represents another intriguing example, in which the Mott
insulator phase is intimately entangled with a series of complex
charge-density-wave (CDW) orders. More interestingly, it has been recently
found that 1T-TaS2 undergoes a Mott-insulator-to-superconductor transition
induced by high pressure, charge doping, or isovalent substitution. The nature
of the Mott insulator phase and transition mechanism to the conducting state is
still under heated debate. Here, by combining scanning tunneling microscopy
(STM) measurements and first-principles calculations, we investigate the atomic
scale electronic structure of 1T-TaS2 Mott insulator and its evolution to the
metallic state upon isovalent substitution of S with Se. We identify two
distinct types of orbital textures - one localized and the other extended - and
demonstrates that the interplay between them is the key factor that determines
the electronic structure. Especially, we show that the continuous evolution of
the charge gap visualized by STM is due to the immersion of the
localized-orbital-induced Hubbard bands into the extended-orbital-spanned Fermi
sea, featuring a unique evolution from a Mott gap to a charge-transfer gap.
This new mechanism of orbital-driven Mottness collapse revealed here suggests
an interesting route for creating novel electronic state and designing future
electronic devices.

###Intra-wire coupling in segmented Ni/Cu nanowires deposited by electrodeposition|Philip Sergelius,Ji Lee,Olivier Fruchart,Mohamed Salem,Sebastian Allende,Robert Escobar,Johannes Gooth,Robert Zierold,Jean-Christophe Toussaint,Sebastian Schneider,Darius Pohl,Bernd Rellinghaus,Sylvain Martin,Javier Garcia,Heiko Reith,Anne Spende,Maria Toimil-Molares,Dora Altbir,Russel Cowburn,Detlef Görlitz,Kornelius Nielsch###

Intra-wire coupling in segmented Ni/Cu nanowires deposited by electrodeposition. Segmented magnetic nanowires are a promising route for the development of
three dimensional data storage techniques. Such devices require a control of
the coercive field and the coupling mechanisms between individual magnetic
elements. In our study, we investigate electrodeposited nanomagnets within host
templates using vibrating sample magnetometry and observe a strong dependence
between nanowire length and coercive field (25 nm to 5 $\mu$m) and diameter (25
nm to 45 nm). A transition from a magnetization reversal through coherent
rotation to domain wall propagation is observed at an aspect ratio of
approximately 2. Our results are further reinforced via micromagnetic
simulations and angle dependent hysteresis loops. The found behavior is
exploited to create nanowires consisting of a fixed and a free segment in a
spin-valve like structure. The wires are released from the membrane and
electrically contacted, displaying a giant magnetoresistance effect that is
attributed to individual switching of the coupled nanomagnets. We develop a
simple analytical model to describe the observed switching phenomena and to
predict stable and unstable regimes in coupled nanomagnets of certain
geometries.

###Tensile Strained Gray Tin: a New Dirac Semimetal for Observing Negative Magnetoresistance with Shubnikov-de-Haas Oscillation|Huaqing Huang,Feng Liu###

Tensile Strained Gray Tin: a New Dirac Semimetal for Observing Negative Magnetoresistance with Shubnikov-de-Haas Oscillation. The extremely stringent requirement on material quality has hindered the
investigation and potential applications of exotic chiral magnetic effect in
Dirac semimetals. Here, we propose that gray tin is a perfect candidate for
observing the chiral anomaly effect and Shubnikov-de-Haas (SdH) oscillation at
relatively low magnetic field. Based on effective $k.p$ analysis and
first-principles calculations, we discover that gray tin becomes a Dirac
semimetal under tensile uniaxial strain, in contrast to a topological insulator
under compressive uniaxial strain as known before. In this newly found Dirac
semimetal state, two Dirac points which are tunable by tensile [001] strains,
lie in the $k_z$ axis and Fermi arcs appear in the (100) surface. Duo the low
carrier concentration and high mobility of gray tin, a large chiral anomaly
induced negative magnetoresistance and a strong SdH oscillation are anticipated
in this half of strain spectrum. Comparing to other Dirac semimetals, the
proposed Dirac semimetal state in the nontoxic elemental gray tin can be more
easily manipulated and accurately controlled. We envision that gray tin
provides a perfect platform for strain engineering of chiral magnetic effects
by sweeping through the strain spectrum from positive to negative and vice
versa.

###Large phase relaxation length in the topological surface states of epitaxial Bi2-xSnxTe3 thin films|Seong Won Cho,Kwang-Chon Kim,Seong Keun Kim,Byung-ki Cheong,Jin-Sang Kim,Suyoun Lee###

Large phase relaxation length in the topological surface states of epitaxial Bi2-xSnxTe3 thin films. A topological insulator (TI), a new quantum state featured with the
topologically-protected surface state (TSS) originating from its peculiar
topology in band structure, has attracted much interest due to academic and
practical importance. Nonetheless, a large contribution of the bulk conduction,
induced by unintended doping by defects, has hindered the characterization of
the unique surface state and the utilization of it into a device. To resolve
this problem, we have investigated the transport properties of epitaxial
Bi2-xSnxTe3 thin films with varying x. With the bulk conduction being strongly
suppressed, the TSS is separately characterized, resulting in a large phase
relaxation length of ~250 nm at 1.8 K, a record-high value in TIs. In addition,
the magnetoresistance ratio (MR) has shown a non-monotonic temperature
dependence with a maximum value at an elevated temperature depending on x.
These results are associated with the compensation of carriers and, we believe,
provide an important step for the application of topological insulators for
developing novel functional devices based on the topological surface states.

###Negative Magnetoresistance in Weyl semimetals NbAs and NbP: Intrinsic Chiral Anomaly and Extrinsic Effects|Yupeng Li,Zhen Wang,Pengshan Li,Xiaojun Yang,Zhixuan Shen,Feng Sheng,Xiaodong Li,Yunhao Lu,Yi Zheng,Zhu-An Xu###

Negative Magnetoresistance in Weyl semimetals NbAs and NbP: Intrinsic Chiral Anomaly and Extrinsic Effects. Chiral anomaly induced negative magnetoresistance (NMR) has been widely used
as a critical transport evidence on the existence of Weyl fermions in
topological semimetals. In this mini review, we discuss the general observation
of the NMR phenomena in non-centrosymmetric NbP and NbAs. We show that NMR can
be contributed by intrinsic chiral anomaly of Weyl fermions and/or extrinsic
effects, such as superimposition of Hall signals, field-dependent inhomogeneous
current flow in the bulk, i.e. current jetting, and weak localization (WL) of
coexistent trivial carriers. Such WL controlled NMR is heavily dependent on
sample quality, and is characterized by pronounced crossover from positive to
negative MR growth at elevated temperatures, as a result of the competition
between the phase coherence time and the spin-orbital scattering constant of
the bulk trivial pockets. Thus, the correlation of NMR and chiral anomaly needs
to be scrutinized, without the support of other complimentary techniques. Due
to the lifting of spin degeneracy, the spin orientations of Weyl fermions are
either parallel or antiparallel to the momentum, a unique physical property
known as helicity. The conservation of helicity provides strong protection for
the transport of Weyl fermions, which can only be effectively scattered by
magnetic impurities. Chemical doping of magnetic and non-magnetic impurities
are thus more convincing in probing the existence of Weyl fermions than the NMR
method.

###Magnetotransport studies of Superconducting Pr$_4$Fe$_2$As$_2$Te$_{1-x}$O$_4$|A. Pisoni,P. Szirmai,S. Katrych,B. Náfrádi,R. Gaál,J. Karpinski,L. Forró###

Magnetotransport studies of Superconducting Pr$_4$Fe$_2$As$_2$Te$_{1-x}$O$_4$. We report a detailed study of the electrical transport properties of single
crystals of Pr$_4$Fe$_2$As$_2$Te$_{1-x}$O$_4$, a recently discovered iron-based
superconductor. Resistivity, Hall effect and magnetoresistance are measured in
a broad temperature range revealing the role of electrons as dominant charge
carriers. The significant temperature dependence of the Hall coefficient and
the violation of Kohler's law indicate multiband effects in this compound. The
upper critical field and the magnetic anisotropy are investigated in fields up
to 16 T, applied parallel and perpendicular to the crystallographic c-axis.
Hydrostatic pressure up to 2 GPa linearly increases the critical temperature
and the resistivity residual ratio. A simple two-band model is used to describe
the transport and magnetic properties of Pr$_4$Fe$_2$As$_2$Te$_{1-x}$O$_4$. The
model can successfully explain the strongly temperature dependent negative Hall
coefficient and the high magnetic anisotropy assuming that the mobility of
electrons is higher than that of holes.

###Pure spin current transport in gallium doped zinc oxide|Matthias Althammer,Joynarayan Mukherjee,Stephan Geprägs,Sebastian T. B. Goennenwein,Matthias Opel,M. S. Ramachandra Rao,Rudolf Gross###

Pure spin current transport in gallium doped zinc oxide. We study the flow of a pure spin current through zinc oxide by measuring the
spin Hall magnetoresistance (SMR) in thin film trilayer samples consisting of
bismuth-substituted yttrium iron garnet (Bi:YIG), gallium-doped zinc oxide
(Ga:ZnO), and platinum. We investigate the dependence of the SMR magnitude on
the thickness of the Ga:ZnO interlayer and compare to a Bi:YIG/Pt bilayer. We
find that the SMR magnitude is reduced by almost one order of magnitude upon
inserting a Ga:ZnO interlayer, and continuously decreases with increasing
interlayer thickness. Nevertheless, the SMR stays finite even for a
$12\;\mathrm{nm}$ thick Ga:ZnO interlayer. These results show that a pure spin
current indeed can propagate through a several nm-thick degenerately doped zinc
oxide layer. We also observe differences in both the temperature and the field
dependence of the SMR when comparing tri- and bilayers. Finally, we compare our
data to predictions of a model based on spin diffusion. This shows that
interface resistances play a crucial role for the SMR magnitude in these
trilayer structures.

###Resonant spin transfer torque nano-oscillators|Abhishek Sharma,Ashwin A Tulapurkar,Bhaskaran Muralidharan###

Resonant spin transfer torque nano-oscillators. Spin transfer torque nano-oscillators are potential candidates for replacing
the traditional inductor based voltage controlled oscillators in modern
communication devices. Typical oscillator designs are based on trilayer
magnetic tunnel junctions which are disadvantaged by low power outputs and poor
conversion efficiencies. In this letter, we theoretically propose to use
resonant spin filtering in pentalayer magnetic tunnel junctions as a possible
route to alleviate these issues and present device designs geared toward a high
microwave output power and an efficient conversion of the d.c. input power. We
attribute these robust qualities to the resulting non-trivial spin current
profiles and the ultra high tunnel magnetoresistance, both arising from
resonant spin filtering. The device designs are based on the nonequilibrium
Green's function spin transport formalism self-consistently coupled with the
stochastic Landau-Lifshitz-Gilbert-Slonczewski's equation and the Poisson's
equation. We demonstrate that the proposed structures facilitate oscillator
designs featuring a large enhancement in microwave power of around $775\%$ and
an efficiency enhancement of over $1300\%$ in comparison with typical trilayer
designs. We also rationalize the optimum operating regions via an analysis of
the dynamic and static device resistances. This work sets stage for pentalyer
spin transfer torque nano-oscillator device designs that extenuate most of the
issues faced by the typical trilayer designs.

###Heterogeneous Memristive Devices Enabled by Magnetic Tunnel Junction Nanopillars Surrounded by Resistive Silicon Switches|Yu Zhang,Xiaoyang Lin,Jean-Paul Adam,Guillaume Agnus,Wenlong Cai,Jean-Rene Coudevylle,Nathalie Isac,Jianlei Yang,Huaiwen Yang,Wang Kang,Kaihua Cao,Hushan Cui,Deming Zhang,Youguang Zhang,Chao Zhao,Weisheng Zhao,Dafine Ravelosona###

Heterogeneous Memristive Devices Enabled by Magnetic Tunnel Junction Nanopillars Surrounded by Resistive Silicon Switches. Emerging non-volatile memories (NVMs) have currently attracted great interest
for their potential applications in advanced low-power information storage and
processing technologies. Conventional NVMs, such as magnetic random access
memory (MRAM) and resistive random access memory (RRAM) suffer from limitations
of low tunnel magnetoresistance (TMR), low access speed or finite endurance.
NVMs with synergetic advantages are still highly desired for future computer
architectures. Here, we report a heterogeneous memristive device composed of a
magnetic tunnel junction (MTJ) nanopillar surrounded by resistive silicon
switches, named resistively enhanced MTJ (Re-MTJ), that may be utilized for
novel memristive memories, enabling new functionalities that are inaccessible
for conventional NVMs. The Re-MTJ device features a high ON/OFF ratio of >1000%
and multilevel resistance behaviour by combining magnetic switching together
with resistive switching mechanisms. The magnetic switching originates from the
MTJ, while the resistive switching is induced by a point-switching filament
process that is related to the mobile oxygen ions. Microscopic evidence of
silicon aggregated as nanocrystals along the edges of the nanopillars verifies
the synergetic mechanism of the heterogeneous memristive device. This device
may provide new possibilities for advanced memristive memory and computing
architectures, e.g., in-memory computing and neuromorphics.

###Gate tunable spin-orbit coupling and weak antilocalization effect in an epitaxial La$_{2/3}$Sr$_{1/3}$MnO$_3$ thin film|Shao-Pin Chiu,Michihiko Yamanouchi,Tatsuro Oyamada,Hiromichi Ohta,Juhn-Jong Lin###

Gate tunable spin-orbit coupling and weak antilocalization effect in an epitaxial La$_{2/3}$Sr$_{1/3}$MnO$_3$ thin film. Epitaxial La$_{2/3}$Sr$_{1/3}$MnO$_3$ (LSMO) films have been grown on
SrTiO$_3$ (001) substrates via pulsed laser deposition. In a 22-nm thick LSMO
film with a low residual resistivity of $\rho_0$ = 59 $\mu \Omega$ cm, we found
a zero-field dip in the magnetoresistance (MR) below 10 K, manifesting the weak
antilocalization (WAL) effect due to strong spin-orbit coupling (SOC). We have
analyzed the MR data by including the D'yakonov-Perel' spin-relaxation
mechanism in the WAL theory. We explain that the delocalized spin-down electron
subband states play a crucial role for facilitating marked SOC in clean LSMO.
Moreover, we find that the SOC strength and gate voltage tunability is similar
to that in the 2DEG at LaAlO$_3$/SrTiO$_3$ interface, indicating the presence
of an internal electric field near the LSMO/SrTiO$_3$ interface. In a control
measurement on a 5-nm thick high resistivity ($\rho_0$ = 280 $\mu \Omega$ cm)
LSMO film, we observe only a small zero-field peak in MR from weak localization
effect, indicating negligible SOC.

###High Surface Conductivity of Fermi Arc Electrons in Weyl semimetals|Giacomo Resta,Shu-Ting Pi,Xiangang Wan,Sergey Y. Savrasov###

High Surface Conductivity of Fermi Arc Electrons in Weyl semimetals. Weyl semimetals (WSMs), a new type of topological condensed matter, are
currently attracting great interest due to their unusual electronic states and
intriguing transport properties such as chiral anomaly induced negative
magnetoresistance, a semi--quantized anomalous Hall effect and the debated
chiral magnetic effect. These systems are close cousins of topological
insulators (TIs) which are known for their disorder tolerant surface states.
Similarly, WSMs exhibit unique topologically protected Fermi arcs surface
states. Here we analyze electron--phonon scattering, a primary source of
resistivity in metals at finite temperatures, as a function of the shape of the
Fermi arc where we find that the impact on surface transport is significantly
dependent on the arc curvature and disappears in the limit of a straight arc.
Next, we discuss the effect of strong surface disorder on the resistivity by
numerically simulating a tight binding model with the presence of quenched
surface vacancies using the Coherent Potential Approximation (CPA) and
Kubo--Greenwood formalism. We find that the limit of a straight arc geometry is
remarkably disorder tolerant, producing surface conductivity that is a factor
of 50 larger of a comparable set up with surface states of TI. Finally, a
simulation of the effects of surface vacancies on TaAs is presented,
illustrating the disorder tolerance of the topological surface states in a
recently discovered WSM material.

###Experimental evidence of giant chiral magnetic effect in type-II Weyl semimetal WP$_{2+δ}$ crystals|Yang-Yang Lv,Xiao Li,Bin Pang,Y. B. Chen,Shu-Hua Yao,Jian Zhou,Yan-Feng Chen###

Experimental evidence of giant chiral magnetic effect in type-II Weyl semimetal WP$_{2+δ}$ crystals. Chiral magnetic effect is a quantum phenomenon that is breaking of chiral
symmetry of relativistic Weyl fermions by quantum fluctuation under paralleled
electric field E and magnetic field B. Intuitively, Weyl fermions with
different chirality, under stimulus of paralleled E and B, will have different
chemical potential that gives rise to an extra current, whose role likes a
chiral battery in solids. However, up to now, the experimental evidence for
chiral magnetic effect is the negative longitudinal magnetoresistance rather
than a chiral electric source. Here, totally different from previous reports,
we observed the giant chiral magnetic effect evidenced by: 'negative'
resistivity and corresponding voltage-current curves lying the second-fourth
quadrant in type-II Weyl semimetal WP$_{2+\delta}$ under following conditions:
the misaligned angle between E and B is smaller than 20$^\circ$, temperature
<30 K and externally applied E<50 mA. Phenomenologically, based on macroscopic
Chern-Simon-Maxwell equation, the giant chiral magnetic effect observed in
WP$_{2+\delta}$ is attributed to two-order higher coherent time of chiral
Weyl-fermion quantum state over Drude transport relaxation-time. This work
demonstrates the giant chiral-magnetic/chiral-battery effect in Weyl
semimetals.

###Quantum Oscillations and Coherent Interlayer Transport in a New Topological Dirac Semimetal Candidate: YbMnSb$_2$|Yi-Yan Wang,Sheng Xu,Lin-Lin Sun,Tian-Long Xia###

Quantum Oscillations and Coherent Interlayer Transport in a New Topological Dirac Semimetal Candidate: YbMnSb$_2$. Dirac semimetals (DSMs), which host Dirac fermions and represent new state of
quantum matter, have been studied intensively in condensed matter physics. The
exploration of new materials with topological states is im- portant in both
physics and materials science. In this article, we report the synthesis and the
transport properties of high quality single crystals of YbMnSb$_2$. YbMnSb$_2$
is a new compound with metallic behavior. Quantum oscillations, including
Shubnikov-de Haas (SdH) oscillation and de Haas-van Alphen (dHvA) type
oscillation, have been observed at low temperature and high magnetic field.
Small effective masses and nontrivial Berry phase are extracted from the
analyses of quantum oscillations, which provide the transport evidence for the
possible existence of Dirac fermions in YbMnSb$_2$. The measurements of
angular-dependent interlayer magnetoresistance (MR) indicate the interlayer
transport is coherent. The Fermi surface (FS) of YbMnSb$_2$ possesses quasi-two
dimensional (2D) characteristic as determined by the angular dependence of SdH
oscillation frequency. These findings suggest that YbMnSb$_2$ is a new
candidate of topological Dirac semimetal.

###Probing the Fermi surface and magnetotransport properties in MoAs$_{2}$|Ratnadwip Singha,Arnab Pariari,Prabhat Mandal,Gaurav Kumar Gupta,Tanmoy Das###

Probing the Fermi surface and magnetotransport properties in MoAs$_{2}$. Transition metal dipnictides (TMDs) have recently been identified as possible
candidates to host topology protected electronic band structure. These
materials belong to an isostructural family and show several exotic transport
properties. Especially, the large values of magnetoresistance (MR) and carrier
mobility have drawn significant attention from the perspective of technological
applications. In this report, we have investigated the magnetotransport and
Fermi surface properties of single crystalline MoAs$_{2}$, another member of
this group of compounds. Field induced resistivity plateau and a large MR have
been observed, which are comparable to several topological systems.
Interestingly, in contrast to other isostructural materials, the carrier
density in MoAs$_{2}$ is quite high and shows single-band dominated transport.
The Fermi pockets, which have been identified from the quantum oscillation, are
largest among the members of this group and have significant anisotropy with
crystallographic direction. Our first-principles calculations reveal a
substantial difference between the band structures of MoAs$_{2}$ and other
TMDs. The calculated Fermi surface consists of one electron pocket and another
'open-orbit' hole pocket, which has not been observed in TMDs so far.

###Commensurate Stripes and Phase Coherence in Manganites Revealed with Cryogenic Scanning Transmission Electron Microscopy|Ismail El Baggari,Benjamin H. Savitzky,Alemayehu S. Admasu,Jaewook Kim,Sang-Wook Cheong,Robert Hovden,Lena F. Kourkoutis###

Commensurate Stripes and Phase Coherence in Manganites Revealed with Cryogenic Scanning Transmission Electron Microscopy. Incommensurate charge order in hole-doped oxides is intertwined with exotic
phenomena such as colossal magnetoresistance, high-temperature
superconductivity, and electronic nematicity. Here, we map at atomic resolution
the nature of incommensurate order in a manganite using scanning transmission
electron microscopy at room temperature and cryogenic temperature ($\sim$ 93K).
In diffraction, the ordering wavevector changes upon cooling, a behavior
typically associated with incommensurate order. However, using real space
measurements, we discover that the underlying ordered state is
lattice-commensurate at both temperatures. The cations undergo picometer-scale
($\sim $6-11 pm) transverse displacements, which suggests that charge-lattice
coupling is strong and hence favors lattice-locked modulations. We further
unearth phase inhomogeneity in the periodic lattice displacements at room
temperature, and emergent phase coherence at 93K. Such local phase variations
not only govern the long range correlations of the charge-ordered state, but
also results in apparent shifts in the ordering wavevector. These
atomically-resolved observations underscore the importance of lattice coupling
and provide a microscopic explanation for putative "incommensurate" order in
hole-doped oxides.

###Calculation of the magnetotransport for a spin-density-wave quantum critical theory in the presence of weak disorder|Hermann Freire###

Calculation of the magnetotransport for a spin-density-wave quantum critical theory in the presence of weak disorder. We compute the Hall angle and the magnetoresistance of the spin-fermion
model, which is a successful phenomenological theory to describe the physics of
the cuprates and iron-based superconductors within a wide range of doping
regimes. We investigate both the role of the spin-fermion interaction that
couples the large-momentum antiferromagnetic fluctuations to the so-called
"hot-spots" at the Fermi surface and also of an effective higher-order
composite operator in the theory. The latter operator provides a scattering
mechanism such that the momentum transfer for the fermions close to the Fermi
surface can be small. We also include weak disorder that couples to both the
bosonic order-parameter field and the fermionic degrees of freedom. Since the
quasiparticle excitations were shown in recent works to be destroyed at the
"hot-spots" in the low-energy limit of the model, we employ the Mori-Zwanzig
memory-matrix approach that permits the evaluation of all transport
coefficients without assuming well-defined Landau quasiparticles in the system.
We then apply this transport theory to discuss universal metallic-state
properties as a function of temperature and magnetic field of the cuprates from
the perspective of their fermiology, which turn out to be in qualitative
agreement with key experiments in those materials.

###Observation of Magnetic Radial Vortex Nucleation in a Multilayer Stack with Tunable Anisotropy|Vedat Karakas,Aisha Gokce,Ali Taha Habiboglu,Sevdenur Arpaci,Kaan Ozbozduman,Ibrahim Cinar,Cenk Yanik,Riccardo Tomasello,Silvia Tacchi,Giulio Siracusano,Mario Carpentieri,Giovanni Finocchio,Thomas Hauet,Ozhan Ozatay###

Observation of Magnetic Radial Vortex Nucleation in a Multilayer Stack with Tunable Anisotropy. Recently discovered exotic magnetic configurations, namely magnetic solitons
appearing in the presence of bulk or interfacial Dzyaloshinskii-Moriya
Interaction (i-DMI), have excited scientists to explore their potential
applications in emerging spintronic technologies such as race-track magnetic
memory, spin logic, radio frequency nano-oscillators and sensors. Such studies
are motivated by their foreseeable advantages over conventional micro-magnetic
structures due to their small size, topological stability and easy spin-torque
driven manipulation with much lower threshold current densities giving way to
improved storage capacity, and faster operation with efficient use of energy.
In this work, we show that in the presence of i-DMI in Pt/CoFeB/Ti multilayers
by tuning the magnetic anisotropy (both in-plane and perpendicular-to-plane)
via interface engineering and postproduction treatments, we can stabilize a
variety of magnetic configurations such as N\'eel skyrmions, horseshoes and
most importantly for the first time, the recently predicted isolated radial
vortices at room temperature and under zero bias field. Especially, the radial
vortex state with its absolute convergence to or divergence from a single point
can potentially offer exciting new applications such as particle
trapping/detrapping in addition to magnetoresistive memories with efficient
switching, where the radial vortex state can act as a source of spin-polarized
current with radial polarization.

###Asymmetric $d$-wave superconducting topological insulator in proximity with a magnetic order|M. Khezerlou,H. Goudarzi###

Asymmetric $d$-wave superconducting topological insulator in proximity with a magnetic order. In the framework of the Dirac-Bogoliubov-de Gennes formalism, we investigate
the transport properties in the surface of a 3-dimensional topological
insulator-based hybrid structure, where the ferromagnetic and superconducting
orders are simultaneously induced to the surface states via the proximity
effect. The superconductor gap is taken to be spin-singlet $d$-wave symmetry.
The asymmetric role of this gap respect to the electron-hole exchange, in one
hand, affects the topological insulator superconducting binding excitations
and, on the other hand, gives rise to forming distinct Majorana bound states at
the ferromagnet/superconductor interface. We propose a topological insulator
N/F/FS junction and proceed to clarify the role of $d$-wave asymmetry pairing
in the resulting subgap and overgap tunneling conductance. The perpendicular
component of magnetizations in F and FS regions can be at the parallel and
antiparallel configurations leading to capture the experimentally important
magnetoresistance (MR) of junction. It is found that the zero-bias conductance
is strongly sensitive to the magnitude of magnetization in FS region $m_{zfs}$
and orbital rotated angle $\alpha$ of superconductor gap. The negative MR only
occurs in zero orbital rotated angle. This result can pave the way to
distinguish the unconventional superconducting state in the relating
topological insulator hybrid structures.

###The sign phase transition in the problem of interfering directed paths|C. L. Baldwin,C. R. Laumann,B. Spivak###

The sign phase transition in the problem of interfering directed paths. We investigate the statistical properties of interfering directed paths in
disordered media. At long distance, the average sign of the sum over paths may
tend to zero (sign-disordered) or remain finite (sign-ordered) depending on
dimensionality and the concentration of negative scattering sites $x$. We show
that in two dimensions the sign-ordered phase is unstable even for arbitrarily
small $x$ by identifying rare destabilizing events. In three dimensions, we
present strong evidence that there is a sign phase transition at a finite $x_c
> 0$. These results have consequences for several different physical systems.
In 2D insulators at low temperature, the variable range hopping
magnetoresistance is always negative, while in 3D, it changes sign at the point
of the sign phase transition. We also show that in the sign-disordered regime a
small magnetic field may enhance superconductivity in a random system of D-wave
superconducting grains embedded into a metallic matrix. Finally, the existence
of the sign phase transition in 3D implies new features in the spin glass phase
diagram at high temperature.

###Reentrant Metallic Behavior in the Weyl Semimetal NbP|J. Xu,D. E. Bugaris,Z. L. Xiao,Y. L. Wang,D. Y. Chung,M. G. Kanatzidis,W. K. Kwok###

Reentrant Metallic Behavior in the Weyl Semimetal NbP. We report the occurrence of reentrant metallic behavior in the Weyl semimetal
NbP. When the applied magnetic field $H$ is above a critical value $H_c$, a
reentrance appears as a peak in the temperature dependent resistivity
$\rho_{xx}(T)$ at $T$ = $T_p$, similar to that observed in graphite where it
was attributed to local superconductivity. The $T_p(H)$ relationship follows a
power-law dependence $T_p\sim(H-H_c)^{1/v}$ where $v$ can be derived from the
temperature dependence of the zero-field resistivity $\rho_0(T) \sim T^v$. From
concurrent measurements of the transverse $\rho_{xx}(T)$ and Hall
$\rho_{xy}(T)$ magnetoresistivities, we reveal a clear correlation between the
rapidly increasing $\rho_{xy}(T)$ and the occurrence of a peak in the
$\rho_{xx}(T)$ curve. Quantitative analysis indicates that the reentrant
metallic behavior arises from the competition of the magneto conductivity
$\sigma_{xx}(T)$ with an additional component
$\Delta\sigma_{xx}(T)=\kappa_H\sigma_{xx}(T)$ where
$\kappa_H=[\rho_{xy}(T)/\rho_{xx}(T)]^2$ is the Hall factor. We find that the
Hall factor ($\kappa_H \approx 0.4$) at peak temperature $T_p$ is nearly
field-independent, leading to the observed $T_p(H)$ relationship. Furthermore,
the reentrant metallic behavior in $\rho_{xx}(T)$ also is reflected in the
behavior of $\rho_{xx}(H)$ that ranges from non-saturating at $T>70$ K to
saturation at liquid helium temperatures. The latter can be explained with the
magnetic field dependence of the Hall factor $\kappa_H(H)$. Our studies
demonstrate that a semiclassical theory can account for the 'anomalies' in the
magnetotransport phenomena of NbP without invoking an exotic mechanism.

###Magnetic and magnetotransport properties of Bi$_2$Se$_3$ thin films doped by Eu|B. A. Aronzon,L. N. Oveshnikov,V. A. Prudkoglyad,Yu. G. Selivanov,E. G. Chizhevskii,K. I. Kugel,I. A. Karateev,A. L. Vasiliev,E. Lahderanta###

Magnetic and magnetotransport properties of Bi$_2$Se$_3$ thin films doped by Eu. Structural, magnetic and magnetotransport properties of
(Bi$_{1-x}$Eu$_x$)$_2$Se$_3$ thin films have been studied experimentally as a
function of Eu content. The films were synthesized by MBE. It is demonstrated
that Eu distribution is not uniform, it enter quint-layers forming inside them
plain (pancake-like) areas containing Eu atoms, which sizes and concentration
increase with the growth of Eu content. Positive magnetoresistance related to
the weak antilocalization was observed up to 15K. The antilocalization was not
followed by weak localization as theory predicts for nontrivial topological
states. Surprisingly, the features of antilocalization were seen even at Eu
content $x$ $=$ 0.21. With the increase of Eu content the transition to
ferromagnetic state occurs at $x$ about 0.1 and with the Curie temperature
$\approx$ 8K, that rises up to 64K for $x$ $=$ 0.21. At temperatures above 1-2
K, the dephasing length is proportional to $T^{-1/2}$ indicating the dominant
contribution of inelastic $e-e$ scattering into electron phase breaking.
However, at low temperatures the dephasing length saturates, that could be due
to the scattering on magnetic ions.

###The SU(4) Kondo effect in double quantum dots with ferromagnetic leads|Ireneusz Weymann,Razvan Chirla,Piotr Trocha,Catalin Pascu Moca###

The SU(4) Kondo effect in double quantum dots with ferromagnetic leads. We investigate the spin-resolved transport properties, such as the linear
conductance and the tunnel magnetoresistance, of a double quantum dot device
attached to ferromagnetic leads and look for signatures of SU(4) symmetry in
the Kondo regime. We show that the transport behavior greatly depends on the
magnetic configuration of the device, and the spin-SU(2) as well as the orbital
and spin-SU(4) Kondo effects become generally suppressed when the magnetic
configuration of the leads varies from the antiparallel to the parallel one.
Furthermore, a finite spin polarization of the leads lifts the spin degeneracy
and drives the system from the SU(4) to an orbital-SU(2) Kondo state. We
analyze in detail the crossover and show that the Kondo temperature between the
two fixed points has a non-monotonic dependence on the degree of spin
polarization of the leads. In terms of methods used, we characterize transport
by using a combination of analytical and numerical renormalization group
approaches.

###Spin driven emergent antiferromagnetism and metal insulator transition in nanoscale p-Si|Paul C Lou,Sandeep Kumar###

Spin driven emergent antiferromagnetism and metal insulator transition in nanoscale p-Si. The entanglement of the charge, spin and orbital degrees of freedom can give
rise to emergent behavior especially in thin films, surfaces and interfaces.
Often, materials that exhibit those properties require large spin orbit
coupling. We hypothesize that the emergent behavior can also occur due to spin,
electron and phonon interactions in widely studied simple materials such as Si.
That is, large intrinsic spin-orbit coupling is not an essential requirement
for emergent behavior. The central hypothesis is that when one of the specimen
dimensions is of the same order (or smaller) as the spin diffusion length, then
non-equilibrium spin accumulation due to spin injection or spin-Hall effect
(SHE) will lead to emergent phase transformations in the non-ferromagnetic
semiconductors. In this experimental work, we report spin mediated emergent
antiferromagnetism and metal insulator transition in a Pd (1 nm)/Ni81Fe19 (25
nm)/MgO (1 nm)/p-Si (~400 nm) thin film specimen. The spin-Hall effect in p-Si,
observed through Rashba spin-orbit coupling mediated spin-Hall
magnetoresistance behavior, is proposed to cause the spin accumulation and
resulting emergent behavior. The phase transition is discovered from the
diverging behavior in longitudinal third harmonic voltage, which is related to
the thermal conductivity and heat capacity.

###Spin-Hall effect and emergent antiferromagnetic phase transition in n-Si|Paul C Lou,Sandeep Kumar###

Spin-Hall effect and emergent antiferromagnetic phase transition in n-Si. Spin current experiences minimal dephasing and scattering in Si due to small
spin-orbit coupling and spin-lattice interactions is the primary source of spin
relaxation. We hypothesize that if the specimen dimension is of the same order
as the spin diffusion length then spin polarization will lead to
non-equilibrium spin accumulation and emergent phase transition. In n-Si, spin
diffusion length has been reported up to 6 {\mu}m. The spin accumulation in Si
will modify the thermal transport behavior of Si, which can be detected with
thermal characterization. In this study, we report observation of spin-Hall
effect and emergent antiferromagnetic phase transition behavior using
magneto-electro-thermal transport characterization. The freestanding Pd (1 nm)/
Ni80Fe20 (75 nm)/ MgO (1 nm)/ n-Si (2 micron) thin film specimen exhibits a
magnetic field dependent thermal transport and spin-Hall magnetoresistance
behavior attributed to Rashba effect. An emergent phase transition is
discovered using self-heating 3omega method, which shows a diverging behavior
at 270 K as a function of temperature similar to a second order phase
transition. We propose that spin-Hall effect leads to the spin accumulation and
resulting emergent antiferromagnetic phase transition. We propose that the
length scale for Rashba effect can be equal to the spin diffusion length and
two-dimensional electron gas is not essential for it. The emergent
antiferromagnetic phase transition is attributed to the site inversion
asymmetry in diamond cubic Si lattice.

###Discovery of highly spin-polarized conducting surface states in the strong spin-orbit coupling semiconductor Sb$_2$Se$_3$|Shekhar Das,Suman Kamboj,Anshu Sirohi,Aastha Vasdev,Sirshendu Gayen,Prasenjit Guptasarma,Goutam Sheet###

Discovery of highly spin-polarized conducting surface states in the strong spin-orbit coupling semiconductor Sb$_2$Se$_3$. Majority of the A$_2$B$_3$ type chalcogenide systems with strong spin-orbit
coupling, like Bi$_2$Se$_3$, Bi$_2$Te$_3$ and Sb$_2$Te$_3$ etc., are
topological insulators. One important exception is Sb$_2$Se$_3$, where a
topological non-trivial phase was argued to be possible under ambient
conditions, but such a phase could be detected to exist only under pressure. In
this Letter, we show that like Bi$_2$Se$_3$, Sb$_2$Se$_3$, displays generation
of highly spin-polarized current under mesoscopic superconducting point
contacts as measured by point contact Andreev reflection spectroscopy. In
addition, we observe a large negative and anisotropic magnetoresistance in
Sb$_2$Se$_3$, when the field is rotated in the basal plane. However, unlike in
Bi$_2$Se$_3$, in case of Sb$_2$Se$_3$ a prominent quasiparticle interference
(QPI) pattern around the defects could be obtained in STM conductance imaging.
Thus, our experiments indicate that Sb$_2$Se$_3$ is a regular band insulator
under ambient conditions, but due to it's high spin-orbit coupling, non-trivial
spin-texture exists on the surface and the system could be on the verge of a
topological insulator phase.

###Large current modulation and tunneling magnetoresistance change by a side-gate electric field in a GaMnAs-based vertical spin metal-oxide-semiconductor field-effect transistor|Toshiki Kanaki,Hiroki Yamasaki,Tomohiro Koyama,Daichi Chiba,Shinobu Ohya,Masaaki Tanaka###

Large current modulation and tunneling magnetoresistance change by a side-gate electric field in a GaMnAs-based vertical spin metal-oxide-semiconductor field-effect transistor. A vertical spin metal-oxide-semiconductor field-effect transistor (spin
MOSFET) is a promising low-power device for the post scaling era. Here, using a
ferromagnetic-semiconductor GaMnAs-based vertical spin MOSFET with a GaAs
channel layer, we demonstrate a large drain-source current IDS modulation by a
gate-source voltage VGS with a modulation ratio up to 130%, which is the
largest value that has ever been reported for vertical spin field-effect
transistors thus far. We find that the electric field effect on indirect
tunneling via defect states in the GaAs channel layer is responsible for the
large IDS modulation. This device shows a tunneling magnetoresistance (TMR)
ratio up to ~7%, which is larger than that of the planar-type spin MOSFETs,
indicating that IDS can be controlled by the magnetization configuration.
Furthermore, we find that the TMR ratio can be modulated by VGS. This result
mainly originates from the electric field modulation of the magnetic anisotropy
of the GaMnAs ferromagnetic electrodes as well as the potential modulation of
the nonmagnetic semiconductor GaAs channel layer. Our findings provide
important progress towards high-performance vertical spin MOSFETs.

###Cyclotron Orbits of Composite Fermions in the Fractional Quantum Hall Regime|Insun Jo,Hao Deng,Yang Liu,L. N. Pfeiffer,K. W. West,K. W. Baldwin,M. Shayegan###

Cyclotron Orbits of Composite Fermions in the Fractional Quantum Hall Regime. We study a bilayer GaAs hole system that hosts two distinct many-body phases
at low temperatures and high perpendicular magnetic fields. The higher-density
(top) layer develops a Fermi sea of composite fermions (CFs) in its half-filled
lowest Landau level, while the lower-density (bottom) layer forms a Wigner
crystal (WC) as its filling becomes very small. Owing to the inter-layer
interaction, the CFs in the top-layer feel the periodic Coulomb potential of
the WC in the bottom-layer. We measure the magnetoresistance of the top-layer
while changing the bottom-layer density. As the WC layer density increases, the
resistance peaks separating the adjacent fractional quantum Hall states in the
top-layer change nonmonotonically and attain maximum values when the cyclotron
orbit of the CFs encloses one WC lattice point. These features disappear at T =
275 mK when the WC melts. The observation of such geometric resonance features
is unprecedented and surprising as it implies that the CFs retain a
well-defined cyclotron orbit and Fermi wave vector even deep in the fractional
quantum Hall regime, far from half-filling.

###High temperature linear magnetoresistance and scaling behavior in the Ba(Fe${_{1-x}}$Co${_{x}}$)$_{2}$As$_{2}$ series|Rohit Kumar,Surjeet Singh,Sunil Nair###

High temperature linear magnetoresistance and scaling behavior in the Ba(Fe${_{1-x}}$Co${_{x}}$)$_{2}$As$_{2}$ series. We present magnetotransport studies of the parent, an underdoped and an
optimally doped composition of the Ba(Fe${_{1-x}}$Co${_{x}}$)${_{2}}$As${_{2}}$
series. We observe that both the Kohler's and modified Kohler's scaling is
typically violated in both the magnetically ordered and paramagnetic regimes. A
notable exception is the magnetically ordered state of the underdoped
composition where the modified Kohler's scaling is observed, indicating its
relative similarity to the cuprates and some heavy fermion systems. This
composition also exhibits a feature in the Hall angle, which could signify the
opening of a pseudogap before the onset of long range magnetic order.
Interestingly, the transverse magnetoresistance is seen to exhibit a linear
field dependence in the paramagnetic regimes of all these compositions. We also
demonstrate that the $B/T$ scaling proposed recently in the context of quantum
critical systems is seen to be valid in all these systems. The implications of
our observations are discussed in the context of magnetotransport of metals
with incipient magnetic fluctuations.

###Interplay between superconductivity and magnetism in one-unit-cell LaAlO3 capped with SrTiO3|Yongsu Kwak,Woojoo Han,Thach D. N. Ngo,Dorj Odkhuu,Jihwan Kim,Young Heon Kim,Noejung Park,Sonny H. Rhim,Myung-Hwa Jung,Junho Suh,Seung-Bo Shim,Mahn-Soo Choi,Yong-Joo Doh,Joon Sung Lee,Jonghyun Song,Jinhee Kim###

Interplay between superconductivity and magnetism in one-unit-cell LaAlO3 capped with SrTiO3. To form a conducting layer at the interface between the oxide insulators
LaAlO3 and SrTiO3, the LaAlO3 layer on the SrTiO3 substrate must be at least
four unit-cells-thick. The LaAlO3 SrTiO3 heterointerface thus formed exhibits
various intriguing phenomena such as ferromagnetism and superconductivity. It
has been widely studied for being a low-dimensional ferromagnetic oxide
superconducting system with a strong gate-tunable spin-orbit interaction.
However, its lack of stability and environmental susceptiveness have been an
obstacle to its further experimental investigations and applications. Here, we
demonstrate that capping the bilayer with SrTiO3 relieves this thickness limit,
while enhancing the stability and controllability of the interface. In
addition, the SrTiO3-capped LaAlO3 exhibits unconventional superconductivity;
the critical current dramatically increases under a parallel magnetic field,
and shows a reversed hysteresis contrary to the conventional hysteresis of
magnetoresistance. Its superconducting energy gap of $\Delta \sim 1.31k_BT_c$
also deviates from conventional BCS-type superconductivity. The oxide trilayer
could be a robust platform for studying the extraordinary interplay of
superconductivity and ferromagnetism at the interface electron system between
LaAlO3 and SrTiO3.

###Microstructural control of the transport properties of $β$-FeSe films grown by sputtering|M. V. Ale Crivillero,M. L. Amigó,N. Haberkorn,G. Nieva,J. Guimpel###

Microstructural control of the transport properties of $β$-FeSe films grown by sputtering. We have investigated the correlation between structural and transport
properties in sputtered $\beta$-FeSe films grown onto SrTiO$_3$ (100). The
growth parameters, such as substrate temperature and thickness, have been
varied in order to explore different regimes. In the limit of textured thick
films, we found promising features like an enhanced $T_{\rm c}\sim12\,$K, a
relatively high $H_{\rm c2}$ and a low anisotropy. By performing
magnetoresistance and Hall coefficient measurements, we investigate the
influence of the disorder associated with the textured morphology on some
features attributed to subtle details of the multi-band electronic structure of
$\beta$-FeSe. Regarding the superconductor-insulator transition (SIT) induced
by reducing the thickness, we found a non-trivial evolution of the structural
properties and morphology associated with a strained initial growth and the
coalescence of grains. Finally, we discuss the origin of the insulating
behavior in high-quality stressed epitaxial thin films. We found that a lattice
distortion, described by the Poisson's coefficient associated with the lattice
parameters \textit{a} and \textit{c}, may play a key role.

###Structural distortion behind the nematic superconductivity in Sr$_x$Bi$_2$Se$_3$|A. Yu. Kuntsevich,M. A. Bryzgalov,V. A. Prudkoglyad,V. P. Martovitskii,Yu. G. Selivanov,E. G. Chizhevskii###

Structural distortion behind the nematic superconductivity in Sr$_x$Bi$_2$Se$_3$. An archetypical layered topological insulator Bi$_2$Se$_3$ becomes
superconductive upon doping with Sr, Nb or Cu. Superconducting properties of
these materials in the presence of in-plane magnetic field demonstrate
spontaneous symmetry breaking: 180$^\circ$-rotation symmetry of
superconductivity versus 120$^\circ$-rotation symmetry of the crystal. Such
behavior brilliantly confirms nematic topological superconductivity. To what
extent this nematicity is due to superconducting pairing in these materials,
rather than due to crystal structure distortions? This question remained
unanswered, because so far no visible deviations from the 3-fold crystal
symmetry were resolved in these materials. To address this question we grow
high quality single crystals of Sr$_x$Bi$_2$Se$_3$, perform detailed X-ray
diffraction and magnetotransport studies and reveal that the observed
superconducting nematicity direction correlates with the direction of small
structural distortions in these samples( $\sim 0.02$\% elongation in one
crystallographic direction). Additional anisotropy comes from orientation of
the crystallite axes. 2-fold symmetry of magnetoresistance observed in the most
uniform crystals well above critical temperature demonstrates that these
structural distortions are nevertheless strong enough. Our data in combination
with strong sample-to-sample variation of the superconductive anisotropy
parameter are indicative for significance of the structural factor in the
apparent nematic superconductivity in Sr$_x$Bi$_2$Se$_3$.

###Magneto-transport properties of proposed triply degenerate topological semimetal Pd$_{3}$Bi$_{2}$S$_{2}$|Shubhankar Roy,Arnab Pariari,Ratnadwip Singha,Biswarup Satpati,Prabhat Mandal###

Magneto-transport properties of proposed triply degenerate topological semimetal Pd$_{3}$Bi$_{2}$S$_{2}$. We report transport properties of single-crystalline Pd$_{3}$Bi$_{2}$S$_{2}$,
which has been predicted to host an unconventional electronic phase of matter
beyond three-dimensional Dirac and Weyl semimetals. Similar to several
topological systems, the resistivity shows field induced
metal-semiconductor-like crossover at low temperature. Large, anisotropic and
non-saturating magnetoresistance (MR) has been observed in transverse
experimental configuration. At 2 K and 9 T, the MR value reaches as high as
$\sim$1.1$\times$10$^{3}$ \%. Hall resistivity reveals the presence of two
types of charge carriers and has been analyzed using two-band model. In spite
of the large density ($>$ 10$^{21}$ cm$^{-3}$), the mobility of charge carriers
is found to be quite high ($\sim$ 0.75$\times$10$^{4}$ cm$^{2}$ V$^{-1}$
s$^{-1}$ for hole and $\sim$ 0.3$\times$10$^{4}$ cm$^{2}$ V$^{-1}$ s$^{-1}$ for
electron). The observed magneto-electrical properties indicate that
Pd$_{3}$Bi$_{2}$S$_{2}$ may be a new member of the topological semimetal
family, which can have a significant impact in technological applications.

###Electrical-current-induced magnetic hysteresis in self-assembled vertically aligned La_{2/3}Sr_{1/3}MnO_3:ZnO-nanopillar composites|W. Pan,P. Lu,J. F. Ihlefeld,S. R. Lee,E. S. Choi,Y. Jiang,Q. X. Jia###

Electrical-current-induced magnetic hysteresis in self-assembled vertically aligned La_{2/3}Sr_{1/3}MnO_3:ZnO-nanopillar composites. Magnetoresistive random-access memory (MRAM) is poised to become a
next-generation information storage device. Yet, many materials challenges
remain unsolved before it can become a widely used memory storage solution.
Among them, an urgent need is to identify a material system that is suitable
for downscaling and is compatible with low-power logic applications.
Self-assembled, vertically-aligned La_{2/3}Sr_{1/3}MnO_3:ZnO nanocomposites, in
which La_{2/3}Sr_{1/3}MnO_3 (LSMO) matrix and ZnO nanopillars form an
intertwined structure with coincident-site-matched growth occurring between the
LSMO and ZnO vertical interfaces, may offer new MRAM applications by combining
their superior electric, magnetic (B), and optical properties. In this paper,
we show the results of electrical current induced magnetic hysteresis in
magneto-resistance measurements in these nano-pillar composites. We observe
that when the current level is low, for example, 1 uA, the magneto-resistance
displays a linear, negative, non-hysteretic B field dependence. Surprisingly,
when a large current is used, I > 10 uA, a hysteretic behavior is observed when
the B field is swept in the up and down directions. This hysteresis weakens as
the sample temperature is increased. A possible spin-valve mechanism related to
this electrical current induced magnetic hysteresis is proposed and discussed.

###Strain-mediated spin-orbit torque switching for magnetic memory|Qianchang Wang,John Domann,Guoqiang Yu,Anthony Barra,Kang L. Wang,Gregory P. Carman###

Strain-mediated spin-orbit torque switching for magnetic memory. Spin-orbit torque (SOT) represents an energy efficient method to control
magnetization in magnetic memory devices. However, deterministically switching
perpendicular memory bits usually requires the application of an additional
bias field for breaking lateral symmetry. Here we present a new approach of
field-free deterministic perpendicular switching using a strain-mediated SOT
switching method. The strain-induced magnetoelastic anisotropy breaks the
lateral symmetry, and the resulting symmetry-breaking is controllable. A finite
element model and a macrospin model are used to numerically simulate the
strain-mediated SOT switching mechanism. The results show that a relatively
small voltage (${\pm}0.5$ V) along with a modest current ($3.5 \times 10^{7}
A/cm^{2}$) can produce a 180{\deg} perpendicular magnetization reversal. The
switching direction (up or down) is dictated by the voltage polarity (positive
or negative) applied to the piezoelectric layer in the magnetoelastic/heavy
metal/piezoelectric heterostructure. The switching speed can be as fast as 10
GHz. More importantly, this control mechanism can be potentially implemented in
a magnetic random-access memory system with small footprint, high endurance and
high tunnel magnetoresistance (TMR) readout ratio.

###Griffiths phase and symmetry breaking in the hidden-order phase of URu2Si2|Yi Liu,Wen Zhang,Xiaoying Wang,Donghua Xie,Xinchun Lai###

Griffiths phase and symmetry breaking in the hidden-order phase of URu2Si2. The heavy-fermion compound URu2Si2 exhibits a hidden-order phase below the
temperature, ~ 17.5 K. In spite of intense research for past three decades, no
consensus on the order parameter exists and the nature has posed a
long-standing mystery. Here we report the discovery of a Griffiths phase within
the hidden-order phase, characterized by residual short-range correlations on
the collapse of long-range orders due to the dilution effects. In the Griffiths
phase scenario, strong evidence are provided for those cluster-like spins, such
as the unique power-law behavior of magnetic susceptibility and specific heat
as well as the frequency dispersion of AC susceptibility. In this way, the
existence of an order parameter is excluded, and the hidden order has a
significant kinship with the long-range large-moment antiferromagnetism which
is accessible by tuning the hydrostatic pressure or the chemical pressure
(i.e., isoelectronic Fe doping). Moreover, an unidirectional anisotropy of
resistivity measurements in rotating magnetic fields is observed in the
hidden-order phase. The anisotropic magnetoresistance and the associated broken
symmetries directly reflect the freezing behavior of at least part of magnetic
clusters. Thus, the demonstrations of the Griffiths phase as an alternative
proposal for the hidden-order phase of URu2Si2 are very promising, challenging
the understanding of exotic electronic states in correlated matter and quantum
materials.

###Tunneling magnetoresistance enhancement by symmetrization in spin-orbit torque magnetic tunnel junction|Jiaqi Zhou,Weisheng Zhao,Kaihua Cao,Shouzhong Peng,Zilu Wang,Arnaud Bournel###

Tunneling magnetoresistance enhancement by symmetrization in spin-orbit torque magnetic tunnel junction. Heavy metals with strong spin-orbit coupling (SOC) have been employed to
generate spin current to control the magnetization dynamics by spin-orbit
torque (SOT). Magnetic tunnel junction based on SOT (SOT-MTJ) is a promising
application with efficient writing operation. Unfortunately, SOT-MTJ faces the
low tunneling magnetoresistance (TMR) problem. In this work, we present an ab
initio calculation on the TMR in SOT-MTJ. It is demonstrated that TMR would be
enhanced by SOT-MTJ symmetry structure. The symmetrization induces interfacial
resonant states (IRSs). When IRSs match identical resonances at the opposite
barrier interface, resonant tunneling occurs in SOT-MTJ, which significantly
contributes to the conductance in parallel configuration and improves TMR. We
demonstrate the occurrence of resonant tunneling by transmission spectra,
density of scattering states and differential density of states. We also point
out that the thickness of heavy metal has limited influence on TMR. This work
would benefit the TMR optimization in SOT-MTJ, as well as the SOT spintronics
device.

###Electron and hole contributions to normal-state transport in the superconducting system Sn$_{1-x}$In$_x$Te|Cheng Zhang,Xu-Gang He,Hang Chi,Ruidan Zhong,Wei Ku,Genda Gu,J. M. Tranquada,Qiang Li###

Electron and hole contributions to normal-state transport in the superconducting system Sn$_{1-x}$In$_x$Te. Indium-doped SnTe has been of interest because the system can exhibit both
topological surface states and bulk superconductivity. While the enhancement of
the superconducting transition temperature is established, the character of the
electronic states induced by indium doping remains poorly understood. We report
a study of magneto-transport in a series of Sn$_{1-x}$In$_x$Te single crystals
with $0.1\le x \le 0.45$. From measurements of the Hall effect, we find that
the dominant carrier type changes from hole-like to electron-like at
$x\sim0.25$; one would expect electron-like carriers if the In ions have a
valence of $+3$. For single crystals with $x = 0.45$, corresponding to the
highest superconducting transition temperature, pronounced Shubnikov-de Haas
oscillations are observed in the normal state. In measurements of
magnetoresistance, we find evidence for weak anti-localization (WAL). We
attribute both the quantum oscillations and the WAL to bulk Dirac-like hole
pockets, previously observed in photoemission studies, which coexist with the
dominant electron-like carriers.

###Hall coefficient and magnetoresistance in boson+fermion dimer models for the pseudogap phase of high Tc superconductors|Garry Goldstein###

Hall coefficient and magnetoresistance in boson+fermion dimer models for the pseudogap phase of high Tc superconductors. We show that the Hall coefficient of the boson+fermion dimer model for the
pseudogap phase of high temperature superconductivity introduced in Punk et al.
changes sign from negative at low temperatures to positive at high temperatures
at a characteristic temperature scaling proportional to the the cyclotron
frequency of the fermionic dimers (divided by k), (here k~0.7 fits the
experimental data well). We show that this is an effect of the changing of the
sign of the coupling between the fermionic dimer and the magnetic field from
negative coupling -e at low temperatures to positive coupling +e at high
temperature, with the Hall coefficient being proportional to R_H~e_B*e_E*e_J
(the product of the magnetic charge, electric charge and current charge all of
which we carefully define). We relate the Hall conductivity to the coefficient
in Kohler's like rule for magnetoconductivity and calculate some corrections
which are relevant near the intermediate temperature range ~50K (typical values
for the cyclotron frequency of the dimers). Furthermore we make a sharp
prediction that the magnetoresistance effect vanishes to order B^2 at the
temperature and magnetic field where the Hall coefficient vanishes.

###Magnetometric Mapping of Superconducting RF Cavities|B. Schmitz,J. Köszegi,K. Alomari,O. Kugeler,J. Knobloch###

Magnetometric Mapping of Superconducting RF Cavities. A scalable mapping system for superconducting RF cavities is presented.
Currently, it combines local temperature measurement with 3D magnetic field
mapping along the outer surface of the resonator. This allows for the
observation of dynamic effects that have an impact on the superconducting
properties of a cavity, such as the normal to superconducting phase transition
or a quench. The system was developed for a single cell 1.3 GHz TESLA-type
cavity, but can be easily adopted to arbitrary other cavity types. A data
acquisition rate of 500 Hz for all channels simultaneously (i.e.2ms)
acquisition time for a complete map) and a magnetic field resolution of
currently up to 14 mA/m/mu0 = 17 nT has been implemented. While temperature
mapping is a well known technique in SRF research, the integration of magnetic
field mapping opens the possibility of detailed studies of trapped magnetic
flux and its impact on the surface resistance. It is shown that magnetic field
sensors based on the anisotropic magnetoresistance (AMR) effect can be used in
the cryogenic environment with improved sensitivity compared to room
temperature. Furthermore, examples of first successful combined temperature and
magnetic-field maps are presented.

###Extremely large magnetoresistance in topologically trivial semimetal $α$-WP$_2$|Jianhua Du,Zhefeng Lou,ShengNan Zhang,Yuxing Zhou,Binjie Xu,Qin Chen,Yanqing Tang,Shuijin Chen,Huancheng Chen,Qinqing Zhu,Hangdong Wang,Jinhu Yang,quanSheng Wu,Oleg V. Yazyev,Minghu Fang###

Extremely large magnetoresistance in topologically trivial semimetal $α$-WP$_2$. Extremely large magnetoresistance (XMR) was recently discovered in many
non-magnetic materials, while its underlying mechanism remains poorly
understood due to the complex electronic structure of these materials. Here, we
report an investigation of the $\alpha$-phase WP$_2$, a topologically trivial
semimetal with monoclinic crystal structure (C2/m), which contrasts to the
recently discovered robust type-II Weyl semimetal phase in $\beta$-WP$_2$. We
found that $\alpha$-WP$_2$ exhibits almost all the characteristics of XMR
materials: the near-quadratic field dependence of MR, a field-induced up-turn
in resistivity following by a plateau at low temperature, which can be
understood by the compensation effect, and high mobility of carriers confirmed
by our Hall effect measurements. It was also found that the normalized MRs
under different magnetic fields has the same temperature dependence in
$\alpha$-WP$_2$, the Kohler scaling law can describe the MR data in a wide
temperature range, and there is no obvious change in the anisotropic parameter
$\gamma$ value with temperature. The resistance polar diagram has a peanut
shape when field is rotated in $\textit{ac}$ plane, which can be understood by
the anisotropy of Fermi surface. These results indicate that both
field-induced-gap and temperature-induced Lifshitz transition are not the
origin of up-turn in resistivity in the $\alpha$-WP$_2$ semimetal. Our findings
establish $\alpha$-WP$_2$ as a new reference material for exploring the XMR
phenomena.

###Tuning spin one channel to exotic orbital two-channel Kondo effect in ferrimagnetic composites of LaNiO3 and CoFe2O4|Ananya Patra,Krishna Prasad Maity,Ramesh B Kamble,V Prasad###

Tuning spin one channel to exotic orbital two-channel Kondo effect in ferrimagnetic composites of LaNiO3 and CoFe2O4. We report the tuning from spin one channel (1CK) to orbital two-channel Kondo
(2CK) effect by varying CoFe2O4 (CFO) content in the composites with LaNiO3
(LNO) along with the presence of ferrimagnetism. Although there is no signature
of resistivity upturn in case of pure LNO, all the composites exhibit a
distinct upturn in the temperature range 30-80 K. For composite with lower
percentage of CFO (10 %), the electron spin plays the key role in the emergence
of resistivity upturn which is affected by external magnetic field. On the
other hand, when the CFO content is increased (15%), the upturn shows strong
robustness against high magnetic field (14 T) and a crossover in temperature
variation from lnT to T^1/2 at the Kondo temperature, indicating the appearance
of orbital 2CK effect. The orbital 2CK effect is originated due to the
scattering of conduction electrons from the structural two-level systems which
is created at the interfaces between the two phases (LNO and CFO) of different
crystal structures as well as inside the crystal planes. A negative
magnetoresistance (MR) is observed at low temperature (< 30 K) for composites
containing both lower (10 %) and higher percentage (15 %) of CFO. We have
analyzed the negative MR using Khosla and Fisher semi-empirical model based on
spin dependent scattering of conduction electrons from localized spins.

###Emergent Magnetism at the 3$d$-5$d$ Interface: SrMnO$_3/$SrIrO$_3$|Sayantika Bhowal,Sashi Satpathy###

Emergent Magnetism at the 3$d$-5$d$ Interface: SrMnO$_3/$SrIrO$_3$. Recent experiments have found new magnetic behaviors, which are different
from the parent bulk materials, at the interfaces between 3$d$ and 5$d$ oxides
such as SrMnO$_3$ (SMO) and SrIrO$_3$ (SIO). The system is of considerable
interest due to the strong spin-orbit coupling in the 5$d$ materials on one
hand and the double exchange physics in SMO on the other, which belongs to the
class of the colossal magnetoresistive (CMR) manganites. In order to gain
insight into the physics of the system, we have performed density-functional
studies on a selected interface structure, viz., the (SMO)$_1$(SIO)$_1$
superlattice, which has been experimentally grown and studied. Our
density-functional results show that the interfacial magnetism is controlled by
a net charge transfer at the interface from the SIO to the SMO side, turning
both of them into ferromagnetic metal from the original antiferromagnetic
insulating state in the bulk. The transferred electrons to the SMO side make it
ferromagnetic through the Anderson-Hasegawa double exchange interaction, while
the SIO part becomes ferromagnetic due to the doping of the half-filled
Mott-Hubbard insulator as suggested by the Nagaoka Theorem. Our results are
discussed in the context of the experiments for the same structure.

###Current Controlled Magnetization Switching in Cylindrical Nanowires for High-Density 3D Memory Applications|Hanan Mohammed,Hector Corte-León,Yurii P. Ivanov,Sergei Lopatin,Julian A. Moreno,Andrey Chuvilin,Akshaykumar Salimath,Aurelien Manchon,Olga Kazakova,Jurgen Kosel###

Current Controlled Magnetization Switching in Cylindrical Nanowires for High-Density 3D Memory Applications. A next-generation memory device utilizing a three-dimensional nanowire system
requires the reliable control of domain wall motion. In this letter, domain
walls are studied in cylindrical nanowires consisting of alternating segments
of cobalt and nickel. The material interfaces acting as domain wall pinning
sites, are utilized in combination with current pulses, to control the position
of the domain wall, which is monitored using magnetoresistance measurements.
Magnetic force microscopy results further confirm the occurrence of current
assisted domain wall depinning. Data bits are therefore shifted along the
nanowire by sequentially pinning and depinning a domain wall between successive
interfaces, a requirement necessary for race-track type memory devices. We
demonstrate that the direction, amplitude and duration of the applied current
pulses determine the propagation of the domain wall across pinning sites. These
results demonstrate a multi-bit cylindrical nanowire device, utilizing current
assisted data manipulation. The prospect of sequential pinning and depinning in
these nanowires allows the bit density to increase by several Tbs, depending on
the number of segments within these nanowires.

###Asymmetric Coulomb Oscillation and Giant Anisotropic Magnetoresistance in Doped Graphene Nanojunctions|Subramani Amutha,Arijit Sen###

Asymmetric Coulomb Oscillation and Giant Anisotropic Magnetoresistance in Doped Graphene Nanojunctions. We report here the charge transport behavior in graphene nanojunctions in
which graphene nanodots, with relatively long relaxation time, are interfaced
with ferromagnetic electrodes. Subsequently we explore the effect of
substitutional doping of transition metal atoms in zigzag graphene nanodots
(z-GNDs) on the charge transport under non-collinear magnetization. Only
substitutional doping of transition metal atoms in z-GNDs at certain sites
demonstrates the spin filtering effect with a large tunnelling
magnetoresistance as high as 700%, making it actually suitable for spintronic
applications. From the electrical field simulation around the junction area
within the electrostatic physics model, we find that the value of electric
field strength increases especially with doped graphene nanodots, as the gap
between the gate electrode and tip axis is reduced from 3 nm to 1 nm. Our
detailed analysis further suggests the onset of asymmetric Coulomb oscillations
with varying amplitudes in graphene nanodots, on being doped with magnetic
ions. Such kind of tunability in the electronic conductance can potentially be
exploited in designing spintronic logic gates at nanoscale.

###Structural distortion and incommensurate noncollinear magnetism in EuAg4As2|Bing Shen,Chaowei Hu,Huibo Cao,Xin Gui,Eve Emmanouilidou,Weiwei Xie,Ni Ni###

Structural distortion and incommensurate noncollinear magnetism in EuAg4As2. Layered pnictide materials have provided a fruitful platform to study various
emergent phenomena, including superconductivity, magnetism, charge density
waves, etc. Here we report the observation of structural distortion and
noncollinear magnetism in layered pnictide EuAg$_4$As$_2$ via transport,
magnetization, single crystal X-ray and neutron diffraction data.
EuAg$_4$As$_2$ single crystal shows a structural distortion at 120 K, where two
sets of superlattice peaks with the propagation vectors of $q_1=\pm$(0, 0.25,
0.5) and $q_2=\pm$(0.25, 0, 1) emerge. Between 9 K to 15 K, the hexagonal
Eu$^{2+}$ sub-lattice enters an unpinned state, with magnetic Bragg reflections
pictured as circular-sectors. Below 9 K, it orders in an incommensurate
noncollinear antiferromagnetic state with a well-defined propagation wavevector
of (0, 0.1, 0.12), where the magnetic structure is helical along the $c$ axis
and cycloidal along the $b$ axis with a moment of 6.4 $\mu_B$/Eu$^{2+}$.
Furthermore, rich magnetic phases under magnetic fields, large
magnetoresistance, and strong coupling between charge carriers and magnetism in
EuAg$_4$As$_2$ are revealed.

###Ionic Tuning of Cobaltites at the Nanoscale|Dustin A. Gilbert,Alexander J. Grutter,Peyton D. Murray,Rajesh V. Chopdekar,Alexander M. Kane,Aleksey L. Ionin,Michael S. Lee,Steven R. Spurgeon,Brian J. Kirby,Brian B. Maranville,Alpha T. N'Diaye,Apurva Mehta,Elke Arenholz,Kai Liu,Yayoi Takamura,Julie A. Borchers###

Ionic Tuning of Cobaltites at the Nanoscale. Control of materials through custom design of ionic distributions represents
a powerful new approach to develop future technologies ranging from spintronic
logic and memory devices to energy storage. Perovskites have shown particular
promise for ionic devices due to their high ion mobility and sensitivity to
chemical stoichiometry. In this work, we demonstrate a solid-state approach to
control of ionic distributions in (La,Sr)CoO$_{3}$ thin films. Depositing a Gd
capping layer on the perovskite film, oxygen is controllably extracted from the
structure, up-to 0.5 O/u.c. throughout the entire 36 nm thickness. Commensurate
with the oxygen extraction, the Co valence state and saturation magnetization
show a smooth continuous variation. In contrast, magnetoresistance measurements
show no-change in the magnetic anisotropy and a rapid increase in the
resistivity over the same range of oxygen stoichiometry. These results suggest
significant phase separation, with metallic ferromagnetic regions and
oxygen-deficient, insulating, non-ferromagnetic regions, forming percolated
networks. Indeed, X-ray diffraction identifies oxygen-vacancy ordering,
including transformation to a brownmillerite crystal structure. The unexpected
transformation to the brownmillerite phase at ambient temperature is further
confirmed by high-resolution scanning transmission electron microscopy which
shows significant structural - and correspondingly chemical - phase separation.
This work demonstrates room-temperature ionic control of magnetism, electrical
resistivity, and crystalline structure in a 36 nm thick film, presenting new
opportunities for ionic devices that leverage multiple material
functionalities.

###Low-energy band structure and even-odd layer number effect in AB-stacked multilayer graphene|Ryuta Yagi,Taiki Hirahara,Ryoya Ebisuoka,Tomoaki Nakasuga,Shingo Tajima,Kenji Watanabe,Takashi Taniguchi###

Low-energy band structure and even-odd layer number effect in AB-stacked multilayer graphene. How atoms acquire three-dimensional bulk character is one of the fundamental
questions in materials science. Before addressing this question, how atomic
layers become a bulk crystal might give a hint to the answer. While atomically
thin films have been studied in a limited range of materials, a recent
discovery showing how to mechanically exfoliate bulk crystals has opened up the
field to study the atomic layers of various materials. Here, we show systematic
variation in the band structure of high mobility graphene with one to seven
layers by measuring the quantum oscillation of magnetoresistance. The Landau
fan diagram showed distinct structures that reflected differences in the band
structure, as if they were finger prints of multilayer graphene. In particular,
an even-odd layer number effect was clearly observed, with the number of bands
increasing by one for every two layers and a Dirac cone observed only for an
odd number of layers. The electronic structure is significantly influenced by
the potential energy arising from carrier screening associated with a gate
electric field.

###SDW transition of Fe1 zigzag chains and metamagnetic transition of Fe2 in TaFe$_{1+y}$Te$_3$|R. H. Liu,M. Zhang,P. Cheng,Y. J. Yan,Z. J. Xiang,J. J. Ying,X. F. Wang,A. F. Wang,G. J. Ye,X. G. Luo,X. H. Chen###

SDW transition of Fe1 zigzag chains and metamagnetic transition of Fe2 in TaFe$_{1+y}$Te$_3$. We systematically study the AFM order of Fe1 zigzag chains and spin-flop of
excess Fe2 under high magnetic field H through the susceptibility,
magnetoresistance (MR), Hall effect and specific heat measurements in
high-quality single crystal TaFe$_{1+y}$Te$_3$. These properties suggest that
the high temperature AFM transition of the TaFeTe$_3$ layers should be a
SDW-type AFM order. Below T$_N$, Fe1 antiferromangetic zigzag chains will
induce a inner magnetic field \textbf{H$_{int}$} to interstitial Fe2 and lead
Fe2 also forms an AFM alignment, in which the magnetic coupling strength
between Fe1 and Fe2 is enhanced by decreasing temperature. On the other hand,
the external magnetic field \textbf{H$_{ext}$} inclines to tune interstitial
Fe2 to form FM alignment along \textbf{H$_{ext}$}. When \textbf{H$_{ext}$}
arrives at the "coercive" field H$_C$, which is able to break the coupling
between Fe1 and Fe2, these interstitial Fe2 atoms take a spin-flop from AFM to
FM alignment. The local moment of Fe2 is about 4 $\mu_{\textrm{B}}$/Fe. From
low field ($<$H$_C$) AFM to high field ($>$H$_C$) FM for Fe2, it also induces
sharp drop on resistivity and an anomalous Hall effect. The possible magnetic
structure of TaFe$_{1+y}$Te$_3$ is proposed from the susceptibility and MR. The
properties related to the spin-flop of Fe2 supply a good opportunity to study
the coupling between Fe1 and Fe2 in these TaFe$_{1+y}$Te$_3$ or Fe$_{1+y}$Te
with interstitial Fe2 compounds.

###Weak antilocalization in topological insulator Bi$_{2}$Te$_{3}$ microflakes|Shao-Pin Chiu,Juhn-Jong Lin###

Weak antilocalization in topological insulator Bi$_{2}$Te$_{3}$ microflakes. We have studied the carrier transport in two topological insulator (TI)
Bi$_{2}$Te$_{3}$ microflakes between 0.3 and 10 K and under applied backgate
voltages ($V_{\rm BG}$). Logarithmic temperature dependent resistance
corrections due to the two-dimensional electron-electron interaction effect in
the presence of weak disorder were observed. The extracted Coulomb screening
parameter is negative, which is in accord with the situation of strong
spin-orbit scattering as is inherited in the TI materials. In particular,
positive magnetoresistances (MRs) in the two-dimensional weak-antilocalization
(WAL) effect were measured in low magnetic fields, which can be satisfactorily
described by a multichannel-conduction model. Both at low temperatures of $T <
1$ K and under high positive $V_{\rm BG}$, signatures of the presence of two
coherent conduction channels were observed, as indicated by an increase by a
factor of $\approx$ 2 in the prefactor which characterizes the WAL MR
magnitude. Our results are discussed in terms of the (likely) existence of the
Dirac fermion surface states, in addition to the bulk states, in the
three-dimensional TI Bi$_2$Te$_3$ material.

###Spin heat accumulation and spin-dependent temperatures in nanopillar spin valves|F. K. Dejene,J. Flipse,G. E. W. Bauer,B. J. van Wees###

Spin heat accumulation and spin-dependent temperatures in nanopillar spin valves. Since the discovery of the giant magnetoresistance (GMR) effect the use of
the intrinsic angular momentum of the electrons has opened up new spin based
device concepts. The two channel model of spin-up and spin-down electrons with
spin-dependent conductivities very well describes spin and charge transport in
such devices. In studies of the interaction between heat and spin transport, or
spin caloritronics, until recently it was assumed that both spin species are
always at the same temperature. Here we report the observation of different
temperatures for the spin up (T_\uparrow) and spin down (T_\downarrow)
electrons in a nanopillar spin valve subject to a heat current. The weak
relaxation, especially at room temperature, of the spin heat accumulation (T_s
= T_\uparrow-T_\downarrow) is essential for its detection in our devices. Using
3D finite element modeling spin heat accumulation (SHA) values of 120 mK and
350 mK are extracted at room temperature and 77 K, respectively, which is of
the order of 10% of the total temperature bias over the pillar. This technique
uniquely allows the study of inelastic spin scattering at low energies and
elevated temperatures, which is not possible by spectroscopic methods.

###Slow dynamics of spin pairs in random hyperfine field: Role of inequivalence of electrons and holes in organic magnetoresistance|R. C. Roundy,M. E. Raikh###

Slow dynamics of spin pairs in random hyperfine field: Role of inequivalence of electrons and holes in organic magnetoresistance. In an external magnetic field B, the spins of the electron and hole will
precess in effective fields b_e + B and b_h + B, where b_e and b_h are random
hyperfine fields acting on the electron and hole, respectively. For sparse
"soft" pairs the magnitudes of these effective fields coincide. The dynamics of
precession for these pairs acquires a slow component, which leads to a slowing
down of recombination. We study the effect of soft pairs on organic
magnetoresistance, where slow recombination translates into blocking of the
passage of current. It appears that when b_e and b_h have identical gaussian
distributions the contribution of soft pairs to the current does not depend on
B. Amazingly, small inequivalence in the rms values of b_e and b_h gives rise
to a magnetic field response, and it becomes progressively stronger as the
inequivalence increases. We find the expression for this response by performing
the averaging over b_e, b_h analytically. Another source of magnetic field
response in the regime when current is dominated by soft pairs is inequivalence
of the g-factors of the pair partners. Our analytical calculation indicates
that for this mechanism the response has an opposite sign.

###High spin polarization of the anomalous Hall current in Co-based Heusler compounds|Jen-Chuan Tung,Guang-Yu Guo###

High spin polarization of the anomalous Hall current in Co-based Heusler compounds. Based on first principles density functional calculations of the intrinsic
anomalous and spin Hall conductivities, we predict that the charge Hall current
in Co-based full Heusler compounds Co$_2$XZ (X = Cr and Mn; Z = Al, Si, Ga, Ge,
In and Sn) except Co$_2$CrGa would be almost fully spin-polarized even although
Co$_2$MnAl, Co$_2$MnGa, Co$_2$MnIn and Co$_2$MnSn do not have a half-metallic
band structure. Furthermore, the ratio of the associated spin current to the
charge Hall current is slightly larger than 1.0. This suggests that these
Co-based Heusler compounds, especially Co$_2$MnAl, Co$_2$MnGa and Co$_2$MnIn
which are found to have large anomalous and spin Hall conductivities, might be
called anomalous Hall half-metals and could have valuable applications in
spintronics such as spin valves as well as magnetoresistive and spin-torque
driven nanodevices. These interesting findings are discussed in terms of the
calculated electronic band structures, magnetic moments and also anomalous and
spin Hall conductivities as a function of the Fermi level.

###Transition Temperature and Upper Critical Field in SmFeAsO1-xFx Synthesized at Low Heating Temperatures|S. J. Singh,J. Shimoyama,A. Yamamoto,H. Ogino,K. Kishio###

Transition Temperature and Upper Critical Field in SmFeAsO1-xFx Synthesized at Low Heating Temperatures. Low-temperature synthesis is a promising and potentially effective method for
improving superconducting properties. We report on the fabrication of
polycrystalline samples of SmFeAsO1-xFx with nominal x content varying in a
wide range of x = 0-0.35 synthesized at 900 deg C. This synthesis temperature
is around 300 deg C lower than the conventional synthesis temperature. The
variation in the lattice parameters and transition temperature (Tc) of various
F-doped samples indicates that reduction of the unit cell volume (V) seems to
be the main reason for the rise of Tc up to 57.8 K. Magnetoresistance
measurements showed that the upper critical field slope (dHc2/dT) increased
with increasing F concentration up to x = 0.2, where it reached a maximum value
of -8 T/K corresponding to a coherence length of 10 angstrom. At still higher F
doping levels, dHc2/dT and the low field Jc decreased; above 0.5 T, however, Jc
had almost the same value. Compared with previous reports, the present
synthesis route with low synthesis temperatures and commonly available FeF2 as
the source of F is more effective at introducing F into the SmFeAsO system and
thereby resulting in improved superconducting properties for the system. In
addition, this new sample preparation method also reduces unnecessary problems
such as the evaporation of F and reaction between the crucible and
superconductor during the solid-state reaction.

###Anisotropic magnetoresistance in antiferromagnetic semiconductor Sr2IrO4 epitaxial heterostructure|X. Marti,I. Fina,Di Yi,Jian Liu,Jiun-Haw Chu,C. Rayan-Serrao,S. Suresha,J. Železný,T. Jungwirth,J. Fontcuberta,R. Ramesh###

Anisotropic magnetoresistance in antiferromagnetic semiconductor Sr2IrO4 epitaxial heterostructure. Lord Kelvin with his discovery of the anisotropic magnetoresistance (AMR)
phenomenon in Ni and Fe was 70 years ahead of the formulation of relativistic
quantum mechanics the effect stems from, and almost one and a half century
ahead of spintronics whose first commercial applications relied on the AMR.
Despite the long history and importance in magnetic sensing and memory
technologies, the microscopic understanding of the AMR has struggled to go far
beyond the basic notion of a relativistic magnetotransport phenomenon arising
from combined effects on diffusing carriers of spin-orbit coupling and broken
symmetry of a metallic ferromagnet. Our work demonstrates that even this
seemingly generic notion of the AMR phenomenon needs revisiting as we observe
the ohmic AMR effect in a nano-scale film of an antiferromagnetic (AFM)
semiconductor Sr2IrO4 (SIO). Our work opens the recently proposed path for
integrating semiconducting and spintronic technologies in AFMs. SIO is a
particularly favorable material for exploring this path since its
semiconducting nature is entangled with the AFM order and strong spin-orbit
coupling. For the observation of the low-field Ohmic AMR in SIO we prepared an
epitaxial heterostructure comprising a nano-scale SIO film on top of an
epilayer of a FM metal La2/3Sr1/3MnO3 (LSMO). This allows the magnetic field
control of the orientation of AFM spins in SIO via the exchange spring effect
at the FM-AFM interface.

###Quantum corrections to conductivity in Si doped ZnO thin films|Amit K. Das,R. S. Ajimsha###

Quantum corrections to conductivity in Si doped ZnO thin films. Si doped ZnO thin films with Si concentrations ranging from 0.4 to 10 % have
been grown by sequential pulsed laser deposition on sapphire substrates. The
resistivity of the films first decreased from ~ 6.6x10-3 to 4.7x10-4 ohm-cm as
the Si concentration was increased from ~ 0.4 to 2% and then it increased with
further increase in Si concentration. The electron concentrations in the films
were in the range from 3x1019 to 4x1020 cm-3 showing their degenerate nature.
However, temperature dependent resistivity measurements in the range from 300
to 4.2 K revealed negative temperature coefficient of resistivity (TCR) for the
0.4, 6 and 10% Si doped ZnO films in the entire measurement temperature range.
The 0.6, 0.9 and 2% Si doped films showed a transition from negative to
positive TCR with increasing temperature. The negative magnetoresistance found
in the films at low temperatures and 0.5 T magnetic field pointed to weak
localization as the dominant contributor towards negative TCR. A quantitative
fit of the temperature dependent resistivity data for all the films could be
obtained by considering the quantum correction to conductivity arising due to
disorder induced weak localization effect.

###A high-mobility two-dimensional electron gas at the heteroepitaxial spinel/perovskite complex oxide interface of γ-Al2O3/SrTiO3|Y. Z. Chen,N. Bovet,F. Trier,D. V. Christensen,F. M. Qu,N. H. Andersen,T. Kasama,W. Zhang,R. Giraud,J. Dufouleur,T. S. Jespersen,J. R. Sun,A. Smith,J. Nygård,L. Lu,B. Büchner,B. G. Shen,S. Linderoth,N. Pryds###

A high-mobility two-dimensional electron gas at the heteroepitaxial spinel/perovskite complex oxide interface of γ-Al2O3/SrTiO3. The discovery of two-dimensional electron gases (2DEGs) at the
heterointerface between two insulating perovskite-type oxides, such as LaAlO3
and SrTiO3, provides opportunities for a new generation of all-oxide electronic
and photonic devices. However, significant improvement of the interfacial
electron mobility beyond the current value of approximately 1,000 cm2V-1s-1 (at
low temperatures), remains a key challenge for fundamental as well as applied
research of complex oxides. Here, we present a new type of 2DEG created at the
heterointerface between SrTiO3 and a spinel {\gamma}-Al2O3 epitaxial film with
excellent quality and compatible oxygen ions sublattices. This
spinel/perovskite oxide heterointerface exhibits electron mobilities more than
one order of magnitude higher than those of perovskite/perovskite oxide
interfaces, and demonstrates unambiguous two-dimensional conduction character
as revealed by the observation of quantum magnetoresistance oscillations.
Furthermore, we find that the spinel/perovskite 2DEG results from
interface-stabilized oxygen vacancies and is confined within a layer of 0.9 nm
in proximity to the heterointerface. Our findings pave the way for studies of
mesoscopic physics with complex oxides and design of high-mobility all-oxide
electronic devices.

###Lattice strain accompanying the colossal magnetoresistance effect in EuB$_6$|Rudra Sekhar Manna,Pintu Das,Mariano de Souza,Michael Lang,Jens Müller,Stephan von Molnár,Zachary Fisk###

Lattice strain accompanying the colossal magnetoresistance effect in EuB$_6$. The coupling of magnetic and electronic degrees of freedom to the crystal
lattice in the ferromagnetic semimetal EuB$_6$, which exhibits a complex
ferromagnetic order and a colossal magnetoresistance (CMR) effect, %, very
likely involving magnetic polarons, is studied by high-resolution thermal
expansion and magnetostriction experiments. EuB$_6$ may be viewed as a model
system, where pure magnetism-tuned transport and the response of the crystal
lattice can be studied in a comparatively simple environment,i.e., not
influenced by strong crystal-electric field effects and Jahn-Teller
distortions. We find a very large lattice response, quantified by (i) the
magnetic Gr\"uneisen parameter, (ii) the spontaneous strain when entering the
ferromagnetic region and (iii) the magnetostriction in the paramagnetic
temperature regime. Our analysis reveals that a significant part of the lattice
effects originates in the magnetically-driven delocalization of charge
carriers, consistent with the scenario of percolating magnetic polarons. A
strong effect of the formation and dynamics of local magnetic clusters on the
lattice parameters is suggested to be a general feature of CMR materials.

###Quantum transport evidence for a three-dimensional Dirac semimetal phase in Cd3As2|L. P. He,X. C. Hong,J. K. Dong,J. Pan,Z. Zhang,J. Zhang,S. Y. Li###

Quantum transport evidence for a three-dimensional Dirac semimetal phase in Cd3As2. The material termed three-dimensional (3D) Dirac semimetal has attracted
great interests recently, since it is an electronic analogue to two-dimensional
graphene. Starting from this novel phase, various topologically distinct phases
may be obtained, such as topological insulator, Weyl semimetal, quantum spin
Hall insulator, and topological superconductor. Soon after the theoretical
predictions, the angle-resolve photoemission spectroscopy and scanning
tunnelling microscopy experiments gave evidences for 3D Dirac points in Na3Bi
and Cd3As2. Here we report quantum transport properties of Cd3As2 single
crystal in magnetic field. A sizable linear quantum magnetoresistance is
observed at high temperature. With decreasing temperature, the Shubnikov-de
Haas oscillations appear in both longitudinal resistance Rxx and transverse
Hall resistance Rxy. From the strong oscillatory component \Delta Rxx, the
linear dependence of Landau index n on 1/B gives an n-axis intercept 0.58. Our
quantum transport result clearly reveals a nontrivial \pi\ Berry's phase, thus
provides strong bulk evidence for a 3D Dirac semimetal phase in Cd3As2. This
may open new perspectives for its use in electronic devices.

###Doping Dependencies of Onset Temperatures for the Pseudogap and Superconductive Fluctuation in Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+δ}$, Studied from both In-Plane and Out-of-Plane Magnetoresistance Measurements|Tomohiro Usui,Daiki Fujiwara,Shintaro Adachi,Hironobu Kudo,Kosuke Murata,Haruki Kushibiki,Takao Watanabe,Kazutaka Kudo,Terukazu Nishizaki,Norio Kobayashi,Shojiro Kimura,Kazuyoshi Yamada,Tomoyuki Naito,Takashi Noji,Yoji Koike###

Doping Dependencies of Onset Temperatures for the Pseudogap and Superconductive Fluctuation in Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+δ}$, Studied from both In-Plane and Out-of-Plane Magnetoresistance Measurements. To investigate the relationship between the pseudogap and superconductivity,
we measured both the in-plane ($\rho_{ab}$) and out-of-plane ($\rho_c$)
resistivity for oxygen-controlled Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$
single crystals subject to magnetic fields (parallel to the $c$ axis) of up to
17.5 T. The onset temperature for the superconductive fluctuation, $T_{scf}$,
is determined by the large positive in-plane magnetoresistance (MR) and
negative out-of-plane MR observed near $T_c$, whereas the pseudogap opening
temperature $T^*$ is determined by the semiconductive upturn of the zero-field
$\rho_c$. $T_{scf}$ was found to scale roughly as $T_c$, with a decreasing
temperature interval between them upon doping. On the other hand, $T^*$ starts
out much higher than $T_{scf}$ but decreases monotonically upon doping;
finally, at a heavily overdoped state, it is not observed above $T_{scf}$.
These results imply that the pseudogap is not a simple precursor of
superconductivity, but that further study is needed to determine whether or not
$T^*$ exists below $T_{scf}$ in the heavily overdoped state.

###Transport Properties of Dirac Ferromagnet|Junji Fujimoto,Hiroshi Kohno###

Transport Properties of Dirac Ferromagnet. We propose a model ferromagnet based on the Dirac Hamiltonian in three
spatial dimensions, and study its transport properties which include
anisotropic magnetoresistance (AMR) and anomalous Hall (AH) effect. This
relativistic extension allows two kinds of ferromagnetic order parameters,
denoted by $\bm{M}$ and $\bm{S}$, which are distinguished by the relative sign
between the positive- and negative-energy states (at zero momentum) and become
degenerate in the non-relativistic limit. Because of the relativistic coupling
between the spin and the orbital motion, both $\bm{M}$ and $\bm{S}$ induce
anisotropic deformations of the energy dispersion (and the Fermi surfaces) but
in mutually opposite ways. The AMR is determined primarily by the anisotropy of
the Fermi surface (group velocity), and secondarily by the anisotropy of the
damping; the latter becomes important for ${\bm M}=\pm{\bm S}$, where the Fermi
surfaces are isotropic. Even when the chemical potential lies in the gap, the
AH conductivity is found to take a finite non-quantized value, $\sigma_{ij} =
-(\alpha /3\pi^2 \hbar) \epsilon_{ijk} S_k $, where $\alpha$ is the (effective)
fine structure constant. This offers an example of Hall insulator in three
spatial dimensions.

###A study of the magnetotransport properties of the graphene (I. Monolayer)|M. A. Hidalgo###

A study of the magnetotransport properties of the graphene (I. Monolayer). We present a single electron approach to analyse the magnetotransport
properties of the monolayer graphene as a function of both, the gate voltage
and the magnetic field; and, also, their evolution with temperature. The model
proposed means the extension of our previous one developed for studying the
quantum Hall and Shubnikov-de Haas effects of a two-dimensional electron system
in a semiconductor quantum well. Now, the study in this framework of both
phenomena in graphene involves including the presence of two bands and two
degeneracy valleys, (points K and K' in the reciprocal space). Based in a
single electron approximation, we show it is capable to reproduce the entire
characteristics observed in the experiments for the Hall and diagonal
magnetoconductivities (and the corresponding magnetoresistivities), as a
function of the gate voltage and the magnetic field. In the model the observed
Hall plateaux series in the monolayer graphene, determined by the expression
2(2n+1), arises in a natural way as a consequence of the particular
quantization of the energy spectrum of graphene. Therefore, on the other hand
the proposed approach integrates the quantum Hall effects observed in graphene
and quantum wells semiconductors

###Evidence of topological two-dimensional metallic surface states in thin bismuth nanoribbons|Wei Ning,Fengyu Kong,Chuanying Xi,David Graf,Haifeng Du,Yuyan Han,Jiyong Yang,Kun Yang,Mingliang Tian,Yuheng Zhang###

Evidence of topological two-dimensional metallic surface states in thin bismuth nanoribbons. Understanding of the exotic quantum phenomena in bulk bismuth beyond its
ultraquantum limit still remains controversial and gives rise to a renewed
interest. The focus of the issues is whether these quantum properties have a
conventional bulk nature or just the surface effect due to the significant
spin-orbital interaction and in relation to the Bi-based topological
insulators. Here, we present angular-dependent magnetoresistance (AMR)
measurements on single-crystal bismuth nanoribbons of different thickness with
magnetic fields up to 31 T. In thin nanoribbons with thickness of ~40 nm, a
two-fold rational symmetry of the low field AMR spectra and two sets of
1/2-shifted (i.e. {\gamma}=1/2) Shubnikov-de Haas (SdH) quantum oscillations
with exact two- dimensional (2D) character were obtained. However, when the
thickness of the ribbon increases, a 3D bulk-like SdH oscillations with
{\gamma}=0 and a four-fold rotational symmetry of the AMR spectra appear. These
results unambiguously provided the first transport evidence of the topological
2D metallic surface states in thinner nanoribbons with an insulating bulk. Our
observations provide a promising pathway to understand the quantum phenomena in
Bi arising from the surface states.

###Multiband Effect and Possible Dirac Fermions in Fe$_{1+y}$Te$_{0.6}$Se$_{0.4}$|Yue Sun,Toshihiro Taen,Tatsuhiro Yamada,Sunseng Pyon,Terukazu Nishizaki,Zhixiang Shi###

Multiband Effect and Possible Dirac Fermions in Fe$_{1+y}$Te$_{0.6}$Se$_{0.4}$. We investigated the transport properties of Fe$_{1+y}$Te$_{0.6}$Se$_{0.4}$
single crystals with different amounts of excess Fe prepared by O$_2$
annealing. The O$_2$ annealing remarkably improves transport properties. In
particular, a strongly nonlinear Hall resistivity was observed only in the
fully-annealed crystal, and the magnetoresistance (MR) is drastically enhanced
after annealing, reaching a value larger than 17% at 16 K and 14 T. The obvious
change of transport properties after the annealing indicates that the band
structure of Fe$_{1+y}$Te$_{0.6}$Se$_{0.4}$ is affected by the excess Fe. The
nonlinear Hall resistivity and violation of (modified) Kohler's scaling of the
large MR prove the multiband effects in the Fe$_{1+y}$Te$_{0.6}$Se$_{0.4}$
single crystal. The MR for the fully-annealed crystal develops linearly against
magnetic field from intermediate field (e. g. 2 T at 16 K) to the measurement
limit of 14 T. This phenomenon is interpreted by the existence of Dirac cone
state, in which all the Dirac fermions occupy only the lowest Landau level in
the quantum limit.

###Long-ranged magnetic proximity effects in noble metal-doped cobalt probed with spin- dependent tunnelling|Mihai S. Gabureac,Donald A. Mac Laren,Hervé Courtois,Christopher M. Marrows###

Long-ranged magnetic proximity effects in noble metal-doped cobalt probed with spin- dependent tunnelling. We inserted non-magnetic layers of Au and Cu into sputtered AlOx-based
magnetic tunnel junctions and Meservey-Tedrow junctions in order to study their
effect on tunnelling magnetoresistance (TMR) and spin polarization (TSP). When
either Au or Cu are inserted into a Co/AlOx interface, we find that TMR and TSP
remain finite and measurable for thicknesses up to several nanometres.
High-resolution transmission electron microscopy shows that the Cu and Au
interface layers are fully continuous when their thickness exceeds ~3 nm,
implying that spin-polarized carriers penetrate the interface noble metal to
dis- tances exceeding this value. A power law model based on exchange
scattering is found to fit the data better than a phenomenological exponential
decay. The discrepancy between these length scales and the much shorter ones
reported from x-ray magnetic circular dichroism studies of magnetic
proximitization is ascribed to the fact that our tunnelling transport
measurements selectively probe s-like electrons close to the Fermi level. When
a 0.1 nm thick Cu or Au layer is inserted within the Co, we find that the
suppression of TMR and TSP is restored on a length scale of <=1 nm, indicating
that this is a sufficient quantity of Co to form a fully spin-polarized band
structure at the interface with the tunnel barrier.

###Odd-parity magnetoresistance in pyrochlore iridate thin films with broken time-reversal symmetry|T. C. Fujita,Y. Kozuka,M. Uchida,A. Tsukazaki,T. Arima,M. Kawasaki###

Odd-parity magnetoresistance in pyrochlore iridate thin films with broken time-reversal symmetry. A new class of materials termed topological insulators have been intensively
investigated due to their unique Dirac surface state carrying dissipationless
edge spin currents. Recently, it has been theoretically proposed that the three
dimensional analogue of this type of band structure, the Weyl Semimetal phase,
is materialized in pyrochlore oxides with strong spin-orbit coupling,
accompanied by all-in-all-out spin ordering. Here, we report on the fabrication
and magnetotransport of Eu2Ir2O7 single crystalline thin films. We reveal that
one of the two degenerate all-in-all-out domain structures, which are connected
by time-reversal operation, can be selectively formed by the polarity of the
cooling magnetic field. Once formed, the domain is robust against an oppositely
polarised magnetic field, as evidenced by an unusual odd field dependent term
in the magnetoresistance and an anomalous term in the Hall resistance. Our
findings pave the way for exploring the predicted novel quantum transport
phenomenon at the surfaces/interfaces or magnetic domain walls of pyrochlore
iridates.

###Magnetic and magnetocaloric properties of La$_{0.6}$Ca$_{0.4}$MnO$_{3}$ tunable by particle size and dimensionality|Vivian M. Andrade,Richard J. Caraballo Vivas,Sandra S. Pedro,Julio César G. Tedesco,André L. Rossi,Adelino A. Coelho,Daniel L. Rocco,Mario S. Reis###

Magnetic and magnetocaloric properties of La$_{0.6}$Ca$_{0.4}$MnO$_{3}$ tunable by particle size and dimensionality. Manganites have been attracted considerable attention due to some intriguing
magnetic properties, such as magnetoresistance, spin glass behavior and
superparamagnetism. In recent years, some studies point to the effect of
particle size and dimensionality of these compounds in their magnetic features.
Particularly, LaCaMnO material research is well explored concerning the bulk
material. To overcome the lack of the information we successfully produced
advanced nanostructures of La$_{0.6}$Ca$_{0.4}$MnO$_{3}$ manganites, namely
nanotubes and nanoparticles by using a sol-gel modified method, to determine
the size particle effect on the magnetism. The manganites crystal structure,
magnetic and magnetocaloric properties were studied in a broad temperature
range. Transmission electron microscopy revealed nanoparticles with sizes from
45 up to 223 nm, depending on the calcination temperature. It was found that
the magnetic and magnetocaloric properties can be optimized by tuning the
particle size; for instance, the magnetic transition broadening by decreasing
the particle size. We report the relative cooling power (RCP) of these samples;
it was found that the best RCP was observed for the 223 nm particle (508 J/Kg).
Finally, this work contributes to the research on the magnetic properties and
magnetocaloric potentials in nanostructured systems with distinct morphologies.

###Superconductivity in Weyl Semimetal Candidate MoTe2|Yanpeng Qi,Pavel G. Naumov,Mazhar N. Ali,Catherine R. Rajamathi,Oleg Barkalov,Michael Hanfland,Shu-Chun Wu,Chandra Shekhar,Yan Sun,Vicky Süß,Marcus Schmidt,Eckhard Pippel,Peter Werner,Reinald Hillebrand,Tobias Förster,Erik Kampertt,Walter Schnelle,Stuart Parkin,R. J. Cava,Claudia Felser,Binghai Yan,Sergiy A. Medvedev###

Superconductivity in Weyl Semimetal Candidate MoTe2. In recent years, layered transition-metal dichalcogenides (TMDs) have
attracted considerable attention because of their rich physics; for example,
these materials exhibit superconductivity, charge density waves, and the valley
Hall effect. As a result, TMDs have promising potential applications in
electronics, catalysis, and spintronics. Despite the fact that the majority of
related research focuses on semiconducting TMDs (e.g., MoS2), the
characteristics of WTe2 are provoking strong interest in semimetallic TMDs with
extremely large magnetoresistance, pressure-driven superconductivity, and the
predicted Weyl semimetal (WSM) state. In this work, we investigate the sister
compound of WTe2, MoTe2, which is also predicted to be a WSM and a quantum spin
Hall insulator in bulk and monolayer form, respectively. We find that MoTe2
exhibits superconductivity with a resistive transition temperature Tc of 0.1 K.
The application of a small pressure (such as 0.4 GPa) is shown to dramatically
enhance the Tc, with a maximum value of 8.2 K being obtained at 11.7 GPa (a
more than 80-fold increase in Tc). This yields a dome-shaped superconducting
phase diagram. Further explorations into the nature of the superconductivity in
this system may provide insights into the interplay between strong correlations
and topological physics.

###Multiple-stable anisotropic magnetoresistance memory in antiferromagnetic MnTe|D. Kriegner,K. Vyborny,K. Olejnik,H. Reichlova,V. Novak,X. Marti,J. Gazquez,V. Saidl,P. Nemec,V. V. Volobuev,G. Springholz,V. Holy,T. Jungwirth###

Multiple-stable anisotropic magnetoresistance memory in antiferromagnetic MnTe. A common perception assumes that magnetic memories require ferromagnetic
materials with a non-zero net magnetic moment. However, it has been recently
proposed that compensated antiferromagnets with a zero net moment may represent
a viable alternative to ferromagnets. So far, experimental research has focused
on bistable memories in antiferromagnetic metals. In the present work we
demonstrate a multiple-stable memory device in epitaxial manganese telluride
(MnTe) which is an antiferromagnetic counterpart of common II-VI
semiconductors. Favorable micromagnetic characteristics of MnTe allow us to
demonstrate a smoothly varying antiferromagnetic anisotropic magnetoresistance
(AMR) with a harmonic angular dependence on the applied magnetic field,
analogous to ferromagnets. The continuously varying AMR provides means for the
electrical read-out of multiple-stable antiferromagnetic memory states which we
set by heat-assisted magneto-recording and by changing the angle of the writing
field. We explore the dependence of the magnitude of the zero-field read-out
signal on the strength of the writing field and demonstrate the robustness of
the antiferromagnetic memory states against strong magnetic field
perturbations. We ascribe the multiple-stability in our antiferromagnetic
memory to different distributions of domains with the N\'eel vector aligned
along one of the three $c$-plane magnetic easy axes in the hexagonal MnTe film.
The domain redistribution is controlled during the heat-assisted recording by
the strength and angle of the writing field and freezes when sufficiently below
the N\'eel temperature.

###A strong-topological-metal material with multiple Dirac cones|Huiwen Ji,I Pletikosić,Q. D. Gibson,Girija Sahasrabudhe,T. Valla,R. J. Cava###

A strong-topological-metal material with multiple Dirac cones. We report a new, cleavable, strong-topological-metal, Zr2Te2P, which has the
same tetradymite-type crystal structure as the topological insulator Bi2Te2Se.
Instead of being a semiconductor, however, Zr2Te2P is metallic with a pseudogap
between 0.2 and 0.7 eV above the fermi energy (EF). Inside this pseudogap, two
Dirac dispersions are predicted: one is a surface-originated Dirac cone
protected by time-reversal symmetry (TRS), while the other is a bulk-originated
and slightly gapped Dirac cone with a largely linear dispersion over a 2 eV
energy range. A third surface TRS-protected Dirac cone is predicted, and
observed using ARPES, making Zr2Te2P the first system to realize TRS-protected
Dirac cones at M points. The high anisotropy of this Dirac cone is similar to
the one in the hypothetical Dirac semimetal BiO2. We propose that if EF can be
tuned into the pseudogap where the Dirac dispersions exist, it may be possible
to observe ultrahigh carrier mobility and large magnetoresistance in this
material.

###Origin of the superconductivity of WTe2 under pressure|Pengchao Lu,Joon-Seok Kim,Jing Yang,Hao Gao,Juefei Wu,Dexi Shao,Bin Li,Dawei Zhou,Jian Sun,Deji Akinwande,Jung-Fu Lin,Dingyu Xing###

Origin of the superconductivity of WTe2 under pressure. Tungsten ditelluride (WTe2) has attracted significant attention due to its
interesting electronic properties, such as the unsaturated magnetoresistance
and superconductivity. Recently, it has been proposed to be a new type of Weyl
semimetal, which is distinguished from other transition metal dichalcogenides
(TMDs) from a topological prospective. Here, we study the structure of WTe2
under pressure with a crystal structure prediction and ab initio calculations
combined with high pressure synchrotron X-ray diffraction and Raman
spectroscopy measurements. We find that the ambient orthorhombic structure (Td)
transforms into a monoclinic structure (1T') at around 4-5 GPa. As the
transition pressure is very close to the critical point in recent high-pressure
electrical transport measurements, the emergence of superconductivity in WTe2
under pressure is attributed to the Td-1T' structure phase transition, which
associates with a sliding mechanism of the TMD layers and results in a shorter
Te-Te interlayer distance compared to the intralayer ones. These results
highlight the critical role of the interlayer stacking and chalcogen
interactions on the electronic and superconducting properties of multilayered
TMDs under hydrostatic strain environments.

###Current and field stimulated motion of domain wall in narrow permalloy stripe|L. S. Uspenskaya,S. V. Egorov###

Current and field stimulated motion of domain wall in narrow permalloy stripe. Of the new types of cryoelectronic devices under development, including phase
shifters, giant magnetoresistance switches, diodes, transistors, and memory
cells, some are based on hybrid superconductor-normal metal or
superconductor-ferromagnet films. Control of these devices is realized by means
of pulses of voltage, light, or magnetic field. Spin-polarized current may be
used to switch low-temperature devices, as in spin-electronic devices. In the
superconducting layer, the current is dissipation less, which would bring large
reduction of energy consumption. We demonstrate that mag-netic domain walls in
bilayer niobium-permalloy stripes are shifted by electrical current along the
stripe even at low tem-perature, with the niobium in the superconducting state.
The wall motion in response to current pulses is quite different from that
induced by a magnetic field pulses only. The effect could be used to create a
new type of sequentially switched serial devices because of very high value of
the wall velocity, which excides by many orders of magnitude the velocity of
the wall moved with magnetic field pulses.

###Kondo effect in CeX$_{c}$ (X$_{c}$=S, Se, Te) studied by electrical resistivity under high pressure|Y. Hayashi,S. Takai,T. Matsumura,H. Tanida,M. Sera,K. Matsubayashi,Y. Uwatoko,A. Ochiai###

Kondo effect in CeX$_{c}$ (X$_{c}$=S, Se, Te) studied by electrical resistivity under high pressure. We have measured the electrical resistivity of cerium monochalcogenices, CeS,
CeSe, and CeTe, under high pressures up to 8 GPa. Pressure dependences of the
antiferromagnetic ordering temperature $T_{N}$, crystal field splitting, and
the $\ln T$ anomaly of the Kondo effect have been studied to cover the whole
region from the magnetic ordering regime at low pressure to the Fermi liquid
regime at high pressure. $T_{N}$ initially increases with increasing pressure,
and starts to decrease at high pressure as expected from the Doniach's diagram.
Simultaneously, the $\ln T$ behavior in the resistivity is enhanced, indicating
the enhancement of the Kondo effect by pressure. It is also characteristic in
CeX$_{c}$ that the crystal field splitting rapidly decreases at a common rate
of $-12.2$ K/GPa. This leads to the increase in the degeneracy of the $f$ state
and further enhancement of the Kondo effect. It is shown that the pressure
dependent degeneracy of the $f$ state is a key factor to understand the
pressure dependence of $T_{N}$, Kondo effect, magnetoresistance, and the peak
structure in the temperature dependence of resistivity.

###All-in-all-out magnetic domain size in pyrochlore iridate thin films as probed by local magnetotransport|T. C. Fujita,M. Uchida,Y. Kozuka,S. Ogawa,A. Tsukazaki,T. Arima,M. Kawasaki###

All-in-all-out magnetic domain size in pyrochlore iridate thin films as probed by local magnetotransport. Pyrochlore iridates have attracted growing attention because of a theoretical
prediction of a possible topological semimetal phase originating from
all-in-all-out spin ordering. Related to the topological band structure, recent
findings of the magnetic domain wall conduction have stimulated investigations
of magnetic domain distribution in this system. Here, we investigate the size
of magnetic domains in Eu$_2$Ir$_2$O$_7$ single crystalline thin films by
magnetoresistance (MR) using microscale Hall bars. Two distinct magnetic
domains of the all-in-all-out spin structure are known to exhibit linear MR but
with opposite signs, which enables us to estimate the ratio of the two domains
in the patterned channel. The linear MR for 80 ${\times}$ 60 ${\mu}$m$^2$
channel is nearly zero after zero-field cooling, suggesting random distribution
of domains smaller than the channel size. In contrast, the wide distribution of
the value of the linear MR is detected in 2 ${\times}$ 2 ${\mu}$m$^2$ channel,
reflecting the detectable domain size depending on each cooling-cycle. Compared
to simulation results, we estimate the average size of a single all-in-all-out
magnetic domain as 1-2 ${\mu}$m.

###Resistivity plateau and extremely large magnetoresistance in NbAs2 and TaAs2|Yi-Yan Wang,Qiao-He Yu,Tian-Long Xia###

Resistivity plateau and extremely large magnetoresistance in NbAs2 and TaAs2. In topological insulators (TIs), metallic surface conductance saturates the
insulating bulk resistance with de- creasing temperature, resulting in
resistivity plateau at low temperatures as a transport signature originating
from metallic surface modes protected by time reversal symmetry (TRS). Such
characteristic has been found in several materials including Bi2Te2Se, SmB6
etc. Recently, similar behavior has been observed in metallic com- pound LaSb,
accompanying an extremely large magetoresistance (XMR). Shubnikov-de Hass (SdH)
oscillation at low temperatures further confirms the metallic behavior of
plateau region under magnetic fields. LaSb[1] has been proposed by the authors
as a possible topological semimetal (TSM), while negative magnetoresistance is
absent at this moment. Here, high quality single crystals of NbAs2/TaAs2 with
inversion symmetry have been grown and the resistivity under magnetic field is
systematically investigated. Both of them exhibit metallic behavior under zero
magnetic field, and a metal-to-insulator transition occurs when a nonzero
magnetic field is applied, resulting in XMR (1.0*105% for NbAs2 and 7.3*105%
for TaAs2 at 2.5 K & 14 T). With tempera- ture decreased, a resistivity plateau
emerges after the insulator-like regime and SdH oscillation has also been
observed in NbAs2 and TaAs2.

###Robust tunability of magnetorestance in Half-Heusler RPtBi (R = Gd, Dy, Tm, and Lu) compounds|Eundeok Mun,Sergey L. Bud'ko,Paul C. Canfield###

Robust tunability of magnetorestance in Half-Heusler RPtBi (R = Gd, Dy, Tm, and Lu) compounds. We present the magnetic field dependencies of transport properties for
$R$PtBi ($R$ = Gd, Dy, Tm, and Lu) half-Heusler compounds. Temperature and
field dependent resistivity measurements of high quality $R$PtBi single
crystals reveal an unusually large, non-saturating magnetoresistance (MR) up to
300 K under a moderate magnetic field of $H$ = 140 kOe. At 300 K, the large MR
effect decreases as the rare-earth is traversed from Gd to Lu and the magnetic
field dependence of MR shows a deviation from the conventional $H^{2}$
behavior. The Hall coefficient ($R_{H}$) for $R$ = Gd indicates a sign change
around 120 K, whereas $R_{H}$ curves for $R$ = Dy, Tm, and Lu remain positive
for all measured temperatures. At 300 K, the Hall resistivity reveals a
deviation from the linear field dependence for all compounds. Thermoelectric
power measurements on this family show strong temperature and magnetic field
dependencies which are consistent with resistivity measurements. A highly
enhanced thermoelectric power under applied magnetic field is observed as high
as $\sim$100 $\mu$V/K at 140 kOe. Analysis of the transport data in this series
reveals that the rare-earth-based Half-Husler compounds provide opportunities
to tune MR effect through lanthanide contraction and to elucidate the mechanism
of non-trivial MR.

###The role of band-index-dependent transport relaxation times in anomalous Hall effect|Cong Xiao,Dingping Li,Zhongshui Ma###

The role of band-index-dependent transport relaxation times in anomalous Hall effect. We revisit model calculations of the anomalous Hall effect (AHE) and show
that, in isotropic Rashba-coupled two-dimensional electron gas (2DEG) with
pointlike potential impurities, the full solution of the semiclassical
Boltzmann equation (SBE) may differ from the widely-used $1/\tau^{||}$ &
$1/\tau^{\perp}$ solution [Phys. Rev. B 68, 165311 (2003)]. Our approach to AHE
is analogous to the SBE-based analysis of the anisotropic magnetoresistance
leading to an integral equation for the distribution function [Phys. Rev. B 79,
045427 (2009)] but in the present case, we reduce the description to
band-index-dependent transport relaxation times. When both Rashba bands are
partially occupied, these are determined by solving a system of linear
equations. Detailed calculations show that, for intrinsic and hybrid skew
scatterings the difference between $1/\tau^{||}$ & $1/\tau^{\perp}$ and the
full solution of SBE is notable for large Fermi energies. For coordinate-shift
effects, the side-jump velocity acquired in the inter-band elastic scattering
process is shown to be more important for larger Rashba coupling and may even
exceed the intra-band one for the outer Rashba band. The coordinate-shift
contribution to AHE in the considered case notably differs from that in the
limit of smooth disorder potential analyzed before.

###Large nonsaturating magnetoresistance and signature of non-degenerate Dirac nodes in ZrSiS|R. Singha,A. Pariari,B. Satpati,P. Mandal###

Large nonsaturating magnetoresistance and signature of non-degenerate Dirac nodes in ZrSiS. While the discovery of Dirac and Weyl type excitations in electronic systems
is a major breakthrough in recent condensed matter physics, finding appropriate
materials for fundamental physics and technological applications, is an
experimental challenge. In all the reported materials, linear dispersion
survives only up to a few hundred meV from the Dirac or Weyl nodes. On the
other hand, real materials are subject to uncontrolled doping during
preparation and thermal effect near room temperature can hinder the rich
physics. In ZrSiS, ARPES measurements have shown an unusually robust linear
dispersion (up to $\sim$2 eV) with multiple non-degenerate Dirac nodes. In this
context, we present the magnetotransport study on ZrSiS crystal, which
represents a large family of materials (\textit{WHM} with \textit{W} = Zr, Hf;
\textit{H} = Si, Ge, Sn; \textit{M} = O, S, Se, Te) with identical band
topology. Along with extremely large and non-saturating magnetoresistance (MR),
$\sim$ 1.4 $\times$ 10$^{5}$ \% at 2 K and 9 T, it shows strong anisotropy
depending on the direction of the magnetic field. Quantum oscillation and Hall
effect measurements have revealed large hole and small electron Fermi pockets.
Non-trivial $\pi$ Berry phase confirms the Dirac fermionic nature for both
types of charge carriers. The long-sought relativistic phenomenon of massless
Dirac fermions, known as Adler-Bell-Jackiw chiral anomaly, has also been
observed.

###Pressure dependence of upper critical fields in FeSe single crystals|Ji-Hoon Kang,Soon-Gil Jung,Sangyun Lee,Eunsung Park,Jiunn-Yuan Lin,Dmitriy A Chareev,Alexander N Vasiliev,Tuson Park###

Pressure dependence of upper critical fields in FeSe single crystals. We investigate the pressure dependence of the upper critical fields
({\mu}$_0$$H$$_{c2}$) for FeSe single crystals with pressure up to 2.57 GPa.
The superconducting (SC) properties show a disparate behavior across a critical
pressure where the pressure-induced antiferromagnetic phase coexists with
superconductivity. The magnetoresistance for $H//ab$ and $H//c$ is very
different: for $H//c$, magnetic field induces and enhances a hump in the
resistivity close to the $T_c$ for pressures higher than 1.2 GPa, while it is
absent for $H//ab$. Since the measured {\mu}$_0$$H$$_{c2}$ for FeSe samples is
smaller than the orbital limited upper critical field ($H$$^{orb}$$_{c2}$)
estimated by the Werthamer Helfand and Hohenberg (WHH) model, the Maki
parameter ({\alpha}) related to Pauli spin-paramagnetic effects is additionally
considered to describe the temperature dependence of {\mu}$_0$$H$$_{c2}$($T$).
Interestingly, the {\alpha} value is hardly affected by pressure for $H//ab$,
while it strongly increases with pressure for $H//c$. The pressure evolution of
the {\mu}$_0$$H$$_{c2}$(0)s for the FeSe single crystals is found to be almost
similar to that of $T_c$($P$), suggesting that the pressure-induced magnetic
order adversely affects the upper critical fields as well as the SC transition
temperature.

###Antiferromagnetic Coupling between Surface and Bulk Magnetization and Anomalous Magnetic Transport in Electro-deposited Co Film|Surendra Singh,C. L. Prajapat,D. Bhattacharya,S. K. Ghosh,M. R. Gonal,S. Basu###

Antiferromagnetic Coupling between Surface and Bulk Magnetization and Anomalous Magnetic Transport in Electro-deposited Co Film. We report an interesting magnetic behavior of a Co film (thickness ~ 350
{\AA}) grown on Si/Ti/Cu buffer layer by electro-deposition (ED) technique.
Using depth sensitive X-ray reflectivity and polarized neutron reflectivity
(PNR) we observed two layer structures for the Co film grown by ED with a
surface layer (thickness ~ 100 {\AA}) of reduced density (~ 68% of bulk)
compared to rest of the Co film (thickness ~ 250 {\AA}). The two layer
structure is consistent with the histogram profile obtained from atomic force
microscope (AFM) of the film. Interestingly, using PNR, we found that the
magnetization in the surface Co layer is inversely (antiferomagnetically)
coupled (negative magnetization for surface Co layer) with the rest of the Co
layer for the ED grown film. While we compare PNR result for a Co film of
similar layered structure grown by sputtering, the film showed a uniform
magnetization as expected. We also show that the depth dependent unusual
magnetic behavior of ED grown Co film may be responsible for anomalous
anisotropic magnetoresistance observed in low field in this film as compared to
the Co film grown by sputtering. Combining X-ray scattering, AFM,
superconducting quantum interface device magnetometry (SQUID), PNR and
magneto-transport measurements we attempted to correlate and compare the
structural, magnetic and morphological properties with magneto-transport of Co
films grown by ED and sputtering. The study indicates that the interesting
surface magnetic property and magneto-transport property of the ED film is
caused by its unique surface morphology.

###The chiral anomaly and thermopower of Weyl fermions in the half-Heusler GdPtBi|Max Hirschberger,Satya Kushwaha,Zhijun Wang,Quinn Gibson,Carina A. Belvin,B. A. Bernevig,R. J. Cava,N. P. Ong###

The chiral anomaly and thermopower of Weyl fermions in the half-Heusler GdPtBi. The Dirac and Weyl semimetals are unusual materials in which the nodes of the
bulk states are protected against gap formation by crystalline symmetry. The
chiral anomaly~\cite{Adler,Bell}, predicted to occur in both systems, was
recently observed as a negative longitudinal magnetoresistance (LMR) in
Na$_3$Bi and in TaAs. An important issue is whether Weyl physics appears in a
broader class of materials. We report evidence for the chiral anomaly in the
half-Heusler GdPtBi. In zero field, GdPtBi is a zero-gap semiconductor with
quadratic bands. In a magnetic field, the Zeeman energy leads to Weyl nodes. We
have observed a large negative LMR with the field-steering properties specific
to the chiral anomaly. The chiral anomaly also induces strong suppression of
the thermopower. We report a detailed study of the thermoelectric response
function $\alpha_{xx}$ of Weyl fermions. The scheme of creating Weyl nodes from
quadratic bands suggests that the chiral anomaly may be observable in a broad
class of semimetals.

###Interference Evidence for Rashba-Type Spin-Split on Semimetallic WTe2 Surface|Qing Li,Jiaqiang Yan,Biao Yang,Yunyi Zang,Junjie Zhang,Ke He,Menghao Wu,Yanfei Zhao,David Mandrus,Jian Wang,Qikun Xue,Lifeng Chi,David J. Singh,Minghu Pan###

Interference Evidence for Rashba-Type Spin-Split on Semimetallic WTe2 Surface. Semimetallic tungsten ditelluride (WTe2) displays an extremely large
non-saturating magnetoresistance (XMR), which is the subject of intense
interest. This phenomenon is thought to arise from the combination of perfect
n-p charge compensation with low carrier densities in WTe2 and presumably
details of its band structure. Recently, "spin texture" induced by strong
spin-orbital coupling (SOC) has been observed in WTe2 by angle-resolved
photoemission spectroscopy (ARPES). This provides a mechanism for protecting
backscattering for the states involved and thus was proposed to play an
important role in the XMR of WTe2. Here, based on our density functional
calculations for bulk WTe2, we found a strong Rashba spin-orbit effect in the
calculated band structure due to its non-centrosymmetric structure. This splits
bands and two-fold spin degeneracy of bands is lifted. A prominent Umklapp
interference pattern (a spectroscopic feature with involving reciprocal lattice
vectors) can be observed by scanning tunneling microscopic (STM) measurements
on WTe2 surface at 4.2 K. This differs distinctly from the surface atomic
structure demonstrated at 77 K. The energy dependence of Umklapp interference
shows a strong correspondence with densities of states integrated from ARPES
measurement, manifesting a fact that the bands are spin-split on the opposites
side of Gamma point. Spectroscopic survey reveals the ratio of electron/hole
asymmetry changes alternately with lateral locations along b axis, providing a
microscopic picture for double-carrier transport of semimetallic WTe2. The
calculated band structure and Fermi surface is further supported by our ARPES
results and Shubnikov-de Haas (SdH) oscillations measurements.

###Enhanced tunneling magnetoresistance in Fe$\mid$ZnSe double junctions|J. Peralta-Ramos,A. M. Llois###

Enhanced tunneling magnetoresistance in Fe$\mid$ZnSe double junctions. We calculate the tunneling magnetoresistance (TMR) of
Fe$\mid$ZnSe$\mid$Fe$\mid$ZnSe$\mid$Fe (001) double magnetic tunnel junctions
as a function of the in-between Fe layer's thickness, and compare these results
with those of Fe$\mid$ZnSe$\mid$Fe simple junctions. The electronic band
structures are modeled by a parametrized tight-binding Hamiltonian fitted to
{\it ab initio} calculations, and the conductance is calculated within the
Landauer formalism expressed in terms of Green's functions. We find that the
conductances for each spin channel and the TMR strongly depend on the
in-between Fe layer's thickness, and that in some cases they are enhanced with
respect to simple junctions, in qualitative agreement with recent experimental
studies performed on similar systems. By using a 2D double junction as a
simplified system, we show that the conductance enhancement can be explained in
terms of the junctions energy spectrum. These results are relevant for
spintronics because they demonstrate that the TMR in double junctions can be
tuned and enhanced by varying the in-between metallic layer's thickness.

###Modelling Electron Spin Accumulation in a Metallic Nanoparticle|Y. G. Wei,C. E. Malec,D. Davidović###

Modelling Electron Spin Accumulation in a Metallic Nanoparticle. A model describing spin-polarized current via discrete energy levels of a
metallic nanoparticle, which has strongly asymmetric tunnel contacts to two
ferromagnetic leads, is presented.
  In absence of spin-relaxation, the model leads to a spin-accumulation in the
nanoparticle, a difference ($\Delta\mu$) between the chemical potentials of
spin-up and spin-down electrons, proportional to the current and the Julliere's
tunnel magnetoresistance. Taking into account an energy dependent
spin-relaxation rate $\Omega (\omega)$, $\Delta\mu$ as a function of bias
voltage ($V$) exhibits a crossover from linear to a much weaker dependence,
when $|e|\Omega (\Delta\mu)$ equals the spin-polarized current through the
nanoparticle. Assuming that the spin-relaxation takes place via electron-phonon
emission and Elliot-Yafet mechanism, the model leads to a crossover from linear
to $V^{1/5}$ dependence. The crossover explains recent measurements of the
saturation of the spin-polarized current with $V$ in Aluminum nanoparticles,
and leads to the spin-relaxation rate of $\approx 1.6 MHz$ in an Aluminum
nanoparticle of diameter $6nm$, for a transition with an energy difference of
one level spacing.

###Transport and infrared properties of SmFeAs(O1-xFx): from SDW to superconducting ordering|M. Tropeano,C. Fanciulli,C. Ferdeghini,D. Marre',A. S. Siri,M. Putti,A. Martinelli,M. Ferretti,A. Palenzona,M. R. Cimberle,C. Mirri,S. Lupi,R. Sopracase,P. Calvani,A. Perucchi###

Transport and infrared properties of SmFeAs(O1-xFx): from SDW to superconducting ordering. We report measurements of resistivity, magnetoresistivity, Hall effect,
Seebeck coefficient, infrared reflectivity of undoped SmFeAsO and lightly doped
SmFeAs(O0.93F0.07) oxypnictides. All the properties measured on SmFeAsO are
characterized by clear signatures of the magnetic instability. A
self-consistent picture emerges in which below the magnetic transition carrier
condensation occurs due to the opening of spin density wave (SDW) gap. This is
accompanied by the mobility increase of not gapped carriers due to the
suppression of electron-electron scattering. SmFeAs(O0.93F0.07) exhibits an
increase of the metallic character on cooling consistent with electron doping,
even though at room temperature values of all the properties nearly overlaps
with those of SmFeAsO. However, with temperature decrease all anomalies related
to the SDW instability are missed and the superconducting transition occurs.
This suggests that doping breaks abruptly the symmetries of the Fermi surface
inhibiting the SDW formation in favor of the superconducting transition, with
no substantial changes in the density of states or in the effective mass.

###139La NMR evidence for phase solitons in the ground state of overdoped manganites|D. Koumoulis,N. Panopoulos,A. Reyes,M. Fardis,M. Pissas,A. Douvalis,T. Bakas,D. Argyriou,G. Papavassiliou###

139La NMR evidence for phase solitons in the ground state of overdoped manganites. Hole doped transition metal oxides are famous due to their extraordinary
charge transport properties, such as high temperature superconductivity
(cuprates) and colossal magnetoresistance (manganites). Astonishing, the mother
system of these compounds is a Mott insulator, whereas important role in the
establishment of the metallic or superconducting state is played by the way
that holes are self-organized with doping. Experiments have shown that by
adding holes the insulating phase breaks into antiferromagnetic (AFM) regions,
which are separated by hole rich clumps (stripes) with a rapid change of the
phase of the background spins and orbitals. However, recent experiments in
overdoped manganites of the La(1-x)Ca(x)MnO(3) (LCMO) family have shown that
instead of charge stripes, charge in these systems is organized in a uniform
charge density wave (CDW). Besides, recent theoretical works predicted that the
ground state is inhomogeneously modulated by orbital and charge solitons, i.e.
narrow regions carrying charge (+/-)e/2, where the orbital arrangement varies
very rapidly. So far, this has been only a theoretical prediction. Here, by
using 139La Nuclear Magnetic Resonance (NMR) we provide direct evidence that
the ground state of overdoped LCMO is indeed solitonic. By lowering temperature
the narrow NMR spectra observed in the AFM phase are shown to wipe out, while
for T<30K a very broad spectrum reappears, characteristic of an incommensurate
(IC) charge and spin modulation. Remarkably, by further decreasing temperature,
a relatively narrow feature emerges from the broad IC NMR signal, manifesting
the formation of a solitonic modulation as T->0.

###Signature of checkerboard fluctuations in the phonon spectra of a possible polaronic metal La1.2Sr1.8Mn2O7|F. Weber,N. Aliouane,H. Zheng,J. F. Mitchell,D. N. Argyriou,D. Reznik###

Signature of checkerboard fluctuations in the phonon spectra of a possible polaronic metal La1.2Sr1.8Mn2O7. Charge carriers in low-doped semiconductors may distort the atomic lattice
and trap themselves forming so-called small polarons. High carrier
concentrations can lead to short range ordered polarons (large polarons) and
even to long range charge and orbital order. Both systems should be insulating
with a large electrical resistivity, which decreases with increasing
temperature. However, photoemission measurements recently found a polaronic
pseudogap, in a metallic phase of La2-2xSr1+2xMn2O7. This layered manganite is
famous for colossal magnetoresistance (CMR) associated with a phase transition
from this low-temperature metallic phase to a high temperature insulating
phase. Broad charge order peaks due to large polarons observed by neutron and
x-ray scattering in the insulating phase disappear when La2-2xSr1+2xMn2O7
becomes metallic. We report results of inelastic neutron scattering
measurements showing that polarons remain inside the metallic phase as
fluctuations that strongly broaden and soften certain phonons near the wave
vectors where the charge order peaks appeared in the insulating phase. Our
findings imply that polaronic signatures in metals may generally come from a
competing insulating charge-ordered phase. It is highly relevant to cuprate
superconductors with both a pseudogap, and a similar phonon effect associated
with a competing stripe order.

###Structure and giant magnetoresistance of granular Co-Cu nanolayers prepared by cross-beam PLD|A. Jesche,A. Gorbunoff,A. Mensch,H. Stöcker,A. A. Levin,D. C. Meyer###

Structure and giant magnetoresistance of granular Co-Cu nanolayers prepared by cross-beam PLD. A series of Co_xCu_{100-x} (x = 0, 40...75, 100) layers with thicknesses
in-between 13 nm and 55 nm were prepared on silicon substrates using cross-beam
pulsed laser deposition. Wide-angle X-ray diffraction (WAXRD), transmission
electron microscopy (TEM) and electrical transport measurements revealed a
structure consisting of decomposed cobalt and copper grains with grain sizes of
about 10 nm. The influence of cobalt content and layer thickness on the grain
size is discussed. Electron diffraction (ED) indicates the presence of an
intermetallic Co-Cu phase of Cu3Au structure-type. Thermal treatment at
temperatures between 525 K and 750 K results in the progressive decomposition
of Co and Cu, with an increase of the grain sizes up to about 100 nm. This is
tunable by controlling the temperature and duration of the anneal, and is
directly observable in WAXRD patterns and TEM images. A careful analysis of
grain size and the coherence length of the radiation used allows for an
accurate interpretation of the X-ray diffraction patterns, by taking into
account coherent and non-coherent scattering. The alloy films show a giant
magnetoresistance of 1...2.3 % with the maximum obtained after annealing at
around 725 K.

###Absence of nonlocal resistance in microstructures of PbTe quantum wells|K. A. Kolwas,G. Grabecki,S. Trushkin,J. Wróbel,M. Aleszkiewicz,Ł. Cywiński,T. Dietl,G. Springholz,G. Bauer###

Absence of nonlocal resistance in microstructures of PbTe quantum wells. We report on experiments allowing to set an upper limit on the magnitude of
the spin Hall effect and the conductance by edge channels in quantum wells of
PbTe embedded between PbEuTe barriers. We reexamine previous data obtained for
epitaxial microstructures of n-type PbSe and PbTe, in which pronounced nonlocal
effects and reproducible magnetoresistance oscillations were found. Here we
show that these effects are brought about by a quasi-periodic network of
threading dislocations adjacent to the BaF$_2$ substrate, which give rise to a
p-type interfacial layer and an associated parasitic parallel conductance. We
then present results of transport measurements on microstructures of modulation
doped PbTe/(Pb,Eu)Te:Bi heterostructures for which the influence of parasitic
parallel conductance is minimized, and for which quantum Hall transport had
been observed, on similar samples, previously. These structures are of H-shaped
geometry and they are patterned of 12 nm thick strained PbTe quantum wells
embedded between Pb$_{0.92}$Eu$_{0.08}$Te barriers. The structures have
different lateral sizes corresponding to both diffusive and ballistic electron
transport in non-equivalent L valleys. For these structures no nonlocal
resistance is detected confirming that PbTe is a trivial insulator. The
magnitude of spin Hall angle gamma is estimated to be smaller than 0.02 for
PbTe/PbEuTe microstructures in the diffusive regime.

###Anisotropic Magnetoresistance Effects in Fe, Co, Ni, Fe_4N, and Half-Metallic Ferromagnet: A Systematic Analysis|Satoshi Kokado,Masakiyo Tsunoda,Kikuo Harigaya,Akimasa Sakuma###

Anisotropic Magnetoresistance Effects in Fe, Co, Ni, Fe_4N, and Half-Metallic Ferromagnet: A Systematic Analysis. We theoretically analyze the anisotropic magnetoresistance (AMR) effects of
bcc Fe (+), fcc Co (+), fcc Ni (+), Fe$_4$N (-), and a half-metallic
ferromagnet (-). The sign in each ( ) represents the sign of the AMR ratio
observed experimentally. We here use the two-current model for a system
consisting of a spin-polarized conduction state and localized d states with
spin--orbit interaction. From the model, we first derive a general expression
of the AMR ratio. The expression consists of a resistivity of the conduction
state of the $\sigma$ spin ($\sigma=\uparrow$ or $\downarrow$), $\rho_{s
\sigma}$, and resistivities due to s--d scattering processes from the
conduction state to the localized d states. On the basis of this expression, we
next find a relation between the sign of the AMR ratio and the s--d scattering
process. In addition, we obtain expressions of the AMR ratios appropriate to
the respective materials. Using the expressions, we evaluate their AMR ratios,
where the expressions take into account the values of $\rho_{s
\downarrow}/\rho_{s \uparrow}$ of the respective materials. The evaluated AMR
ratios correspond well to the experimental results.

###Evolution of a metastable phase with a magnetic phase coexistence phenomenon and its unusual sensitivity to magnetic field cycling in the alloys Tb5-xLuxSi3 (x <= 0.7)|K. Mukherjee,Kartik K. Iyer,E. V. Sampathkumaran###

Evolution of a metastable phase with a magnetic phase coexistence phenomenon and its unusual sensitivity to magnetic field cycling in the alloys Tb5-xLuxSi3 (x <= 0.7). Recently, we reported an anomalous enhancement of the positive
magnetoresistance beyond a critical magnetic field in Tb5Si3 in the
magnetically ordered state, attributable to 'inverse metamagnetism'. This
results in unusual magnetic hysteresis loops for the pressurized specimens,
which are relevant to the topic of 'electronic phase separation'. In this
paper, we report the influence of small substitutions of Lu for Tb, to show the
evolution of these magnetic anomalies. We find that, at low temperatures, the
high-field high-resistivity phase could be partially stabilized on returning
the magnetic field to zero in many of these Lu substituted alloys, as measured
through the electrical resistivity ({\rho}). Also, the relative fractions of
this phase and the virgin phase appear to be controlled by a small tuning of
the composition and temperature. Interestingly, at 1.8 K a sudden 'switch-over'
of the value of {\rho} for this mixed phase to that for the virgin phase for
some compositions is observed at low fields after a few field cycles,
indicating metastability of this mixed phase.

###Reduction of spin polarization by incoherent tunneling in Co2FeAl/MgO/CoFe magnetic tunnel junctions with thick MgO barriers|M. S. Gabor,C. Tiusan,T. Petrisor Jr,T. Petrisor,M. Hehn,Y. Lu,E. Snoeck###

Reduction of spin polarization by incoherent tunneling in Co2FeAl/MgO/CoFe magnetic tunnel junctions with thick MgO barriers. We report on spin polarization reduction by incoherent tunneling in realistic
single crystal Co2FeAl/MgO/Co50Fe50 magnetic tunnel junctions (MTJ) compared to
reference Fe/MgO/Fe. A large density of misfit dislocations in the Heusler
based MTJs has been insured by a thick MgO barrier and its 3.8% lattice
mismatch with the Co2FeAl electrode. Our analysis implicates a correlated
structural-transport approach. The crystallographic coherence, in the real
space, is investigated using High Resolution Transmission Electron Microscopy
phase analysis. The electronic transport experiments in variable temperature,
fitted with a theoretical extended-Glazman-Matveev model, address different
levels of the tunneling mechanisms from direct to multi-center hopping. We
demonstrate a double negative impact of dislocations, as extended defects, on
the tunneling polarization. Firstly, the breaking of the crystal symmetry
destroys the longitudinal and lateral coherence of the propagating Bloch
functions. This affects the symmetry filtering efficiency of the Delta_1 states
across the (100) MgO barriers and reduces the associated effective tunneling
polarization. Secondly, dislocations provide localized states within the MgO
gap. This determines temperature activated spin-conserving inelastic tunneling
through chains of defects which are responsible for the one order of magnitude
drop of the tunnel magnetoresistance from low to room temperature.

###A first-principles study of tunneling magnetoresistance in Fe/MgAl2O4/Fe(001) magnetic tunnel junctions|Yoshio Miura,Shingo Muramoto,Kazutaka Abe,Masafumi Shirai###

A first-principles study of tunneling magnetoresistance in Fe/MgAl2O4/Fe(001) magnetic tunnel junctions. We investigated the spin-dependent transport properties of Fe/MgAl2O4/Fe(001)
magnetic tunneling junctions (MTJs) on the basis of first-principles
calculations of the electronic structures and the ballistic conductance. The
calculated tunneling magnetoresistance (TMR) ratio of a Fe/MgAl2O4/Fe(001) MTJ
was about 160%, which was much smaller than that of a Fe/MgO/Fe(001) MTJ
(1600%) for the same barrier thickness. However, there was an evanescent state
with delta 1 symmetry in the energy gap around the Fermi level of normal spinel
MgAl2O4, indicating the possibility of a large TMR in Fe/MgAl2O4/Fe(001) MTJs.
The small TMR ratio of the Fe/MgAl2O4/Fe(001) MTJ was due to new conductive
channels in the minority spin states resulting from a band-folding effect in
the two-dimensional (2-D) Brillouin zone of the in-plane wave vector (k//) of
the Fe electrode. Since the in-plane cell size of MgAl2O4 is twice that of the
primitive in-plane cell size of bcc Fe, the bands in the boundary edges are
folded, and minority-spin states coupled with the delta 1 evanescent state in
the MgAl2O4 barrier appear at k//=0, which reduces the TMR ratio of the MTJs
significantly.

###Giant off-resonance resistance spike related phenomena in irradiated ultraclean two-dimensional electron systems|Jesus Inarrea###

Giant off-resonance resistance spike related phenomena in irradiated ultraclean two-dimensional electron systems. We report on theoretical studies of a recently discovered strong
radiation-induced magnetoresistance spike obtained in ultraclean
two-dimensional electron systems at low temperatures. The most striking feature
of this spike is that it shows up on the second harmonic of the cyclotron
resonance and with an amplitude that can reach an order of magnitude larger
than the radiation-induced resistance oscillations. We apply the
radiation-driven electron orbits model in the ultraclean scenario. Accordingly,
we calculate the elastic scattering rate (charged impurity) which will define
the unexpected resonance spike position. We also obtain the inelastic
scattering rate (phonon damping), that will be responsible of the large spike
amplitude. We present a microscopical model to explain the dependence of the
Landau level width on the magnetic field for ultraclean samples. We find that
this dependence explains the experimental shift of the resistance oscillations
with respect to the magnetic field found in this kind of samples. We study also
recent results on the influence of an in-plane magnetic field on the spike. We
are able to reconcile the obtained different experimental response of both
spike and resistance oscillations versus an increasing in-plane field. The same
model on the variation of the LL width, allows us to explain such surprising
results based in the increasing disorder in the sample caused by the in-planed
magnetic field. Calculated results are in good agreement with experiments.
These results would be of special interest in nanophotonics; they could lead to
the design of novel ultrasensitive microwave detectors.

###Multifunctional L10-Mn1.5Ga films with ultrahigh coercivity, giant perpendicular magnetocrystalline anisotropy and large magnetic energy product|Lijun Zhu,Shuaihua Nie,Kangkang Meng,Dong Pan,Jianhua Zhao,Houzhi Zheng###

Multifunctional L10-Mn1.5Ga films with ultrahigh coercivity, giant perpendicular magnetocrystalline anisotropy and large magnetic energy product. We present the fascinating magnetic properties in homogenous noble-metal-free
and rare-earth-free L10-Mn1.5Ga epitaxial films on GaAs (001), including
ultrahigh perpendicular coercivity remarkably tunable from 8.1 to 42.8 kOe,
giant perpendicular magnetocrystalline anisotropy with a maximum of 22.9
Merg/cc, easily controllable magnetization from 27.3 to 270.5 emu/cc, excellent
squareness exceeding 0.94 and large magnetic energy product up to 2.6 MGOe.
These magnificent room-temperature magnetic characteristics make our
L10-Mn1.5Ga films multifunctional as outstanding and cost-effective alternative
for not only perpendicular magnetic recording bits with areal density over 30
Tb inch-2 and thermal stability over 60 years, but variety of novel devices
with high magnetic-noise immunity and thermal stability like spin-torque MRAMs
and oscillators pillars below 5 nm in dimension, and giant magnetoresistance
sensors able to measure high fileds up to 42 kOe . Moreover, this kind of
materials can also be expected as permanent magnets for replacing the expensive
rare-earth magnets widely used today.

###Nature of the magnetic ground state in the mixed valence compound CeRuSn: a single-crystal study|Fikacek jan,Prokleska Jan,Prchal Jiri,Custers Jeroen,Sechovsky Vladimir###

Nature of the magnetic ground state in the mixed valence compound CeRuSn: a single-crystal study. We report on detailed low temperature measurements of the magnetization, the
specific heat and the electrical resistivity on high quality CeRuSn single
crystals. The compound orders antiferromagnetically at $T_{\rm N} = 2.8$ K with
the Ce$^{3+}$ ions locked within the $a-c$ plane of the monoclinic structure.
Magnetization shows that below $T_{\rm N}$ CeRuSn undergoes a metamagnetic
transition when applying a magnetic field of 1.5 and 0.8 T along the $a$ and
$c$--axis, respectively. This transition manifests in a tremendous negative
jump of $\sim 25$% in the magnetoresistance. The value of the saturated
magnetization along the easy magnetization direction ($c$--axis) and the
magnetic entropy above $T_{\rm N}$ derived from specific heat data correspond
to the scenario where only one third of the Ce ions in the compound being
trivalent and carrying a stable Ce$^{3+}$ magnetic moment, whereas the other
two thirds of the Ce ions are in a nonmagnetic tetravalent and/or mixed valence
state. This is consistent with the low temperature CeRuSn crystal structure
i.\,e.\,, a superstructure consisting of three unit cells of the CeCoAl-type
piled up along the $c$--axis, and in which the Ce$^{3+}$ ions are characterized
by large distances from the Ru ligands while the Ce-Ru distances of the other
Ce ions are much shorter causing a strong 4{\it f}-ligand hybridization and
hence leading to tetravalent and/or mixed valence Ce ions.

###Bias dependence of tunneling magnetoresistance in magnetic tunnel junctions with asymmetric barriers|Alan Kalitsov,Pierre-Jean Zermatten,Frédéric Bonell,Gilles Gaudin,Stéphane Andrieu,Coriolan Tiusan,Mairbek Chshiev,Julian P. Velev###

Bias dependence of tunneling magnetoresistance in magnetic tunnel junctions with asymmetric barriers. The transport properties of magnetic tunnel junctions (MTJs) are very
sensitive to interface modifications. In this work we investigate both
experimentally and theoretically the effect of asymmetric barrier modifications
on the bias dependence of tunneling magnetoresistance (TMR) in single crystal
Fe/MgO-based MTJs with (i) one crystalline and one rough interface and (ii)
with a monolayer of O deposited at the crystalline interface. In both cases we
observe an asymmetric bias dependence of TMR and a reversal of its sign at
large bias. We propose a general model to explain the bias dependence in these
and similar systems reported earlier. The model predicts the existence of two
distinct TMR regimes: (i) tunneling regime when the interface is modified with
layers of a different insulator and (ii) resonant regime when thin metallic
layers are inserted at the interface. We demonstrate that in the tunneling
regime negative TMR is due to the high voltage which overcomes the exchange
splitting in the electrodes, while the asymmetric bias dependence of TMR is due
to the interface transmission probabilities. In the resonant regime inversion
of TMR could happen at zero voltage depending on the alignment of the resonance
levels with the Fermi surfaces of the electrodes. Moreover, the model predicts
a regime in which TMR has different sign at positive and negative bias
suggesting possibilities of combining memory with logic functions.

###Observation of a topological 3D Dirac semimetal phase in high-mobility Cd3As2|Madhab Neupane,SuYang Xu,R. Sankar,N. Alidoust,G. Bian,Chang Liu,I. Belopolski,T. -R. Chang,H. -T. Jeng,H. Lin,A. Bansil,Fangcheng Chou,M. Zahid Hasan###

Observation of a topological 3D Dirac semimetal phase in high-mobility Cd3As2. Experimental identification of three-dimensional (3D) Dirac semimetals in
solid state systems is critical for realizing exotic topological phenomena and
quantum transport such as the Weyl phases, high temperature linear quantum
magnetoresistance and topological magnetic phases. Using high resolution
angle-resolved photoemission spectroscopy, we performed systematic electronic
structure studies on well-known compound Cd3As2. For the first time, we observe
a highly linear bulk Dirac cone located at the Brillouin zone center projected
onto the (001) surface which is consistent with a 3D Dirac semimetal phase in
Cd3As2. Remarkably, an unusually high Dirac Fermion velocity up to 10.2
\textrm{\AA}{\cdot}$eV (1.5 \times 10^{6} ms^-1) is seen in samples where the
mobility far exceeds 40,000 cm^2/V.s suggesting that Cd3As2 can be a promising
candidate as a hypercone analog of graphene in many device-applications which
can also incorporate topological quantum phenomena in a large gap setting. Our
experimental identification of this novel topological 3D Dirac semimetal phase,
distinct from a 3D topological insulator phase discovered previously, paves the
way for exploring higher dimensional relativistic physics in bulk transport and
for realizing novel Fermionic matter such as a Fermi arc nodal metal.

###Topological insulator based spin valve devices: evidence for spin polarized transport of spin-momentum-locked topological surface states|Jifa Tian,Isaac Childres,Helin Cao,Shen Tian,Ireneusz Miotkowski,Yong P. Chen###

Topological insulator based spin valve devices: evidence for spin polarized transport of spin-momentum-locked topological surface states. Spin-momentum helical locking is one of the most important properties of the
nontrivial topological surface states (TSS) in 3D topological insulators (TI).
It underlies the iconic topological protection (suppressing elastic
backscattering) of TSS and is foundational to many exotic physics (eg.,
majorana fermions) and device applications (eg., spintronics) predicted for
TIs. Based on this spin-momentum locking, a current flowing on the surface of a
TI would be spin-polarized in a characteristic in-plane direction perpendicular
to the current, and the spin-polarization would reverse when the current
direction reverses. Observing such a spin-helical current in transport
measurements is a major goal in TI research and applications. We report
spin-dependent transport measurements in spin valve devices fabricated from
exfoliated thin flakes of Bi2Se3 (a prototype 3D TI) with ferromagnetic (FM) Ni
contacts. Applying an in-plane magnetic (B) field to polarize the Ni contacts
along their easy axis, we observe an asymmetry in the hysteretic
magnetoresistance (MR) between opposite B field directions. The polarity of the
asymmetry in MR can be reversed by reversing the direction of the DC current.
The observed asymmetric MR can be understood as a spin-valve effect between the
current-induced spin polarization on the TI surface (due to
spin-momentum-locking of TSS) and the spin-polarized ferromagnetic contacts.
Our results provide a direct transport evidence for the spin helical current in
TSS.

###Local noncentrosymmetricity and possible spin-momentum locking in Sr$_3$Ru$_2$O$_7$|Chenyi Shen,Hui Xing,Xinxin Cai,David Fobes,Mingliang Tian,Zhi-Qiang Mao,Zhuan Xu,Ying Liu###

Local noncentrosymmetricity and possible spin-momentum locking in Sr$_3$Ru$_2$O$_7$. Strong spin-orbital coupling (SOC) was found previously to lead to dramatic
effects in quantum materials, such as those found in topological insulators. It
was shown theoretically that local noncentrosymmetricity resulting from the
rotation of RuO$_6$ octahedral in Sr$_3$Ru$_2$O$_7$ will also give rise to an
effective SOC\cite{SocSr327,MicroscopicnematicSr327}. In the presence of a
magnetic field applied along a specific in-plane direction, the Fermi surface
was predicted to undergo a reconstruction. Here we report results of our
in-plane magnetoresistivity and magnetothermopower measurements on single
crystals of Sr$_3$Ru$_2$O$_7$ with an electrical or a thermal current applied
along specific crystalline directions and a magnetic field rotating in the $ab$
plane (Fig. 1a), showing a minimal value for field directions predicted by the
local noncentrosymmetricity theory. Furthermore, the thermopower, and
therefore, the electron entropy, were found to be suppressed as the field was
applied perpendicular to the thermal current, which suggests that the spin and
the momentum in Sr$_3$Ru$_2$O$_7$ are locked over substantial parts of the
Fermi surface, likely originating from local noncentrosymmetricity as well.

###Discovery of a Weyl Semimetal in non-Centrosymmetric Compound TaAs|Lexian Yang,Zhongkai Liu,Yan Sun,Han Peng,Haifeng Yang,Teng Zhang,Bo Zhou,Yi Zhang,Yanfeng Guo,Marein Rahn,Dharmalingam Prabhakaran,Zahid Hussain,Sung-Kwan Mo,Claudia Felser,Binghai Yan,Yulin Chen###

Discovery of a Weyl Semimetal in non-Centrosymmetric Compound TaAs. Three-dimensional (3D) topological Weyl semimetals (TWSs) represent a novel
state of quantum matter with unusual electronic structures that resemble both a
"3D graphene" and a topological insulator by possessing pairs of Weyl points
(through which the electronic bands disperse linearly along all three momentum
directions) connected by topological surface states, forming the unique
"Fermi-arc" type Fermi-surface (FS). Each Weyl point is chiral and contains
half of the degrees of freedom of a Dirac point, and can be viewed as a
magnetic monopole in the momentum space. Here, by performing angle-resolved
photoemission spectroscopy on non-centrosymmetric compound TaAs, we observed
its complete band structures including the unique "Fermi-arc" FS and linear
bulk band dispersion across the Weyl points, in excellent agreement with the
theoretical calculations. This discovery not only confirms TaAs as the first 3D
TWS, but also provides an ideal platform for realizing exotic physical
phenomena (e.g. negative magnetoresistance, chiral magnetic effects and quantum
anomalous Hall effect) which may also lead to novel future applications.

###Hopping magnetoresistance in ion irradiated monolayer graphene|I. Shlimak,E. Zion,A. V. Butenko,L. Wolfson,V. Richter,Yu. Kaganovskii,A. Sharoni,A. Haran,D. Naveh,E. Kogan,M. Kaveh###

Hopping magnetoresistance in ion irradiated monolayer graphene. Magnetoresistance (MR) of ion irradiated monolayer graphene samples with
variable-range hopping (VRH) mechanism of conductivity was measured at
temperatures down to $T = 1.8$ K in magnetic fields up to $B = 8$ T. It was
observed that in perpendicular magnetic fields, hopping resistivity $R$
decreases, which corresponds to negative MR (NMR), while parallel magnetic
field results in positive MR (PMR) at low temperatures. NMR is explained on the
basis of the "orbital" model in which perpendicular magnetic field suppresses
the destructive interference of many paths through the intermediate sites in
the total probability of the long-distance tunneling in the VRH regime. At low
fields, a quadratic dependence ($|\Delta R/R|\sim B^2$) of NMR is observed,
while at $B > B^*$, the quadratic dependence is replaced by the linear one. It
was found that all NMR curves for different samples and different temperatures
could be merged into common dependence when plotted as a function of $B/B^*$.
It is shown that $B^*\sim T^{1/2}$ in agreement with predictions of the
"orbital" model. The obtained values of $B^*$ allowed also to estimate the
localization radius $\xi$ of charge carriers for samples with different degree
of disorder. PMR in parallel magnetic fields is explained by suppression of
hopping transitions via double occupied states due to alignment of electron
spins.

###Unsaturated both large positive and negative magnetoresistance in Weyl Semimetal TaP|Jianhua Du,Hangdong Wang,Qianhui Mao,Rajwali Khan,Binjie Xu,Yuxing Zhou,Yannan Zhang,Jinhu Yang,Bin Chen,Chunmu Feng,Minghu Fang###

Unsaturated both large positive and negative magnetoresistance in Weyl Semimetal TaP. After growing successfully TaP single crystal, we measured its longitudinal
resistivity (rhoxx) and Hall resistivity (rhoyx) at magnetic fields up to 9T in
the temperature range of 2-300K. It was found that at 2K its magnetoresistivity
(MR) reaches to 328000 percent, at 300K to 176 percent at 8T, and both do not
appear saturation. We confirmed that TaP is indeed a low carrier concentration,
hole-electron compensated semimetal, with a high mobility of hole muh=371000
cm2V-1s-1, and found that a magnetic-field-induced metal-insulator transition
occurs at room temperature. Remarkably, as a magnetic field (H) is applied in
parallel to the electric field (E), the negative MR due to chiral anomaly is
observed, and reaches to -3000 percent at 9T without any signature of
saturation, too, which distinguishes with other Weyl semimetals (WSMs). The
analysis on the Shubnikov-de Haas (SdH) oscillations superimposing on the MR
reveals that a nontrivial Berry phase with strong offset of 0.3958 realizes in
TaP, which is the characteristic feature of the charge carriers enclosing a
Weyl nodes. These results indicate that TaP is a promising candidate not only
for revealing fundamental physics of the WSM state but also for some novel
applications.

###Twofold and Fourfold Symmetric Anisotropic Magnetoresistance Effect in A Model with Crystal Field|Satoshi Kokado,Masakiyo Tsunoda###

Twofold and Fourfold Symmetric Anisotropic Magnetoresistance Effect in A Model with Crystal Field. We theoretically study the twofold and fourfold symmetric anisotropic
magnetoresistance (AMR) effects of ferromagnets. We here use the two-current
model for a system consisting of a conduction state and localized d states. The
localized d states are obtained from a Hamiltonian with a spin--orbit
interaction, an exchange field, and a crystal field. From the model, we first
derive general expressions for the coefficient of the twofold symmetric term
($C_2$) and that of the fourfold symmetric term ($C_4$) in the AMR ratio. In
the case of a strong ferromagnet, the dominant term in $C_2$ is proportional to
the difference in the partial densities of states (PDOSs) at the Fermi energy
($E_{\rm F}$) between the $d\varepsilon$ and $d\gamma$ states, and that in
$C_4$ is proportional to the difference in the PDOSs at $E_{\rm F}$ among the
$d\varepsilon$ states. Using the dominant terms, we next analyze the
experimental results for Fe$_4$N, in which $|C_2|$ and $|C_4|$ increase with
decreasing temperature. The experimental results can be reproduced by assuming
that the tetragonal distortion increases with decreasing temperature.

###Fermi liquid behavior of the in-plane resistivity in the pseudogap state of YBa_2Cu_4O_8|Cyril Proust,B. Vignolle,J. Levallois,S. Adachi,N. E. Hussey###

Fermi liquid behavior of the in-plane resistivity in the pseudogap state of YBa_2Cu_4O_8. Our knowledge of the ground state of underdoped hole-doped cuprates has
evolved considerably over the last few years. There is now compelling evidence
that inside the pseudogap phase, charge order breaks translational symmetry
leading to a reconstructed Fermi surface made of small pockets. Quantum
oscillations, [Doiron-Leyraud N, et al. (2007) Nature 447:564-568], optical
conductivity [Mirzaei SI, et al. (2013) Proc Natl Acad Sci USA 110:5774-5778]
and the validity of Wiedemann-Franz law [Grissonnache G, et al. (2016) Phys.
Rev. B 93:064513] point to a Fermi liquid regime at low temperature in the
underdoped regime. However, the observation of a quadratic temperature
dependence in the electrical resistivity at low temperatures, the hallmark of a
Fermi liquid regime, is still missing. Here, we report magnetoresistance
measurements in the magnetic-field-induced normal state of underdoped
YBa_2Cu_4O_8 which are consistent with a T^2 resistivity extending down to 1.5
K. The magnitude of the T^2 coefficient, however, is much smaller than expected
for a single pocket of the mass and size observed in quantum oscillations,
implying that the reconstructed Fermi surface must consist of at least one
additional pocket.

###Modulating spin relaxation in nanowires with infrared light at room temperature|Md. Iftekhar Hossain,Saumil Bandyopadhyay,Jayasimha Atulasimha,Supriyo Bandyopadhyay###

Modulating spin relaxation in nanowires with infrared light at room temperature. Spintronic devices usually rely on long spin relaxation times and/or lengths
for optimum performance. Therefore, the ability to modulate these quantities
with an external agent offers unique possibilities. The dominant spin
relaxation mechanism in most technologically important semiconductors is the
D'yakonov-Perel' (DP) mechanism which vanishes if the spin carriers (electrons)
are confined to a single conduction subband in a quantum wire grown in certain
crystallographic directions, or polycrystalline quantum wires. Here, we report
modulating the DP spin relaxation rate (and hence the spin relaxation length)
in self assembled 50-nm diameter InSb nanowires with infrared light at room
temperature. In the dark, almost all the electrons in the nanowires are in the
lowest conduction subband at room temperature, resulting in near-complete
absence of DP relaxation. This allows observation of spin-sensitive effects in
the magnetoresistance. Under infrared illumination, electrons are photoexcited
to higher subbands and the DP spin relaxation mechanism is revived, leading to
a three-fold decrease in the spin relaxation length. Consequently, the spin
sensitive effects are no longer observable under illumination. This phenomenon
may have applications in spintronic room-temperature infrared photodetection.

###Anomalous metallic state in quasi-two-dimensional BaNiS$_{2}$|David Santos-Cottin,Andrea Gauzzi,Marine Verseils,Benoit Baptiste,Gwendal Feve,Vincent Freulon,Bernard Placais,Michele Casula,Yannick Klein###

Anomalous metallic state in quasi-two-dimensional BaNiS$_{2}$. We report on a systematic study of the thermodynamic, electronic and charge
transport properties of high-quality single crystals of BaNiS$_2$, the metallic
end-member of the quasi-twodimensional BaCo$_{1-x}$Ni$_x$S$_2$ system
characterized by a metal-insulator transition at $x_{cr}=0.22$. Our analysis of
magnetoresistivity and specific heat data consistently suggests a picture of
compensated semimetal with two hole- and one electron-bands, where
electron-phonon scattering dominates charge transport and the minority holes
exhibit, below $\sim$100 K, a very large mobility, $\mu_h\sim$ 15000
cm$^2$V$^{-1}$s$^{-1}$, which is explained by a Dirac-like band. Evidence of
unconventional metallic properties is given by an intriguing crossover of the
resistivity from a Bloch-Gr\"uneisen regime to a linear$-T$ regime occurring at
2 K and by a strong linear term in the paramagnetic susceptibility above 100 K.
We discuss the possibility that these anomalies reflect a departure from
conventional Fermi-liquid properties in presence of short-range AF fluctuations
and of a large Hund coupling.

###Engineering the interlayer exchange coupling in magnetic trilayers|Ching-Hao Chang,Kun-Peng Dou,Ying-Chin Chen,Tzay-Ming Hong,Chao-Cheng Kaun###

Engineering the interlayer exchange coupling in magnetic trilayers. When the thickness of metal film approaches the nanoscale, itinerant carriers
resonate between its boundaries and form quantum well states (QWSs), which are
crucial to account for the film electrical, transport and magnetic properties.
Besides the classic origin of particle-in-a-box, the QWSs are also susceptible
to the crystal structures that affect the quantum resonance. Here we
investigate the QWSs and the magnetic interlayer exchange coupling (IEC) in the
Fe/Ag/Fe (001) trilayer from first-principles calculations. We find that the
carriers at the Brillouin-zone center (belly) and edge (neck) separately form
electron- and hole-like QWSs that give rise to an oscillatory feature for the
IEC as a function of the Ag-layer thickness with long and short periods. Since
the QWS formation sensitively depends on boundary conditions, one can switch
between these two IEC periods by changing the Fe-layer thickness. These
features, which also occur in the magnetic trilayers with other noble-metal
spacers, open a new degree of freedom to engineer the IEC in magnetoresistance
devices.

###Consequences of breaking time reversal symmetry in LaSb: a resistivity plateau and extreme magnetoresistance|F. F. Tafti,Q. D. Gibson,S. K. Kushwaha,N. Haldolaarachchige,R. J. Cava###

Consequences of breaking time reversal symmetry in LaSb: a resistivity plateau and extreme magnetoresistance. Time reversal symmetry (TRS) protects the metallic surface modes of
topological insulators (TIs). The transport signature of robust metallic
surface modes of TIs is a plateau that arrests the exponential divergence of
the insulating bulk with decreasing temperature. This universal behavior is
observed in all TI candidates ranging from Bi2Te2Se to SmB6. Recently, several
topological semimetals (TSMs) have been found that exhibit extreme
magnetoresistance (XMR) and TI universal resistivity behavior revealed only
when breaking TRS, a regime where TIs theoretically cease to exist. Among these
new materials, TaAs and NbP are nominated for Weyl semimetal due to their lack
of inversion symmetry, Cd3As2 is nominated for Dirac semimetal due to its
linear band crossing at the Fermi level, and WTe2 is nominated for resonant
compensated semimetal due to its perfect electron-hole symmetry. Here we
introduce LaSb, a simple rock-salt structure material without broken inversion
symmetry, without perfect linear band crossing, and without perfect
electron-hole symmetry. Yet LaSb portrays all the exotic field induced
behaviors of the aforementioned semimetals in an archetypal fashion. It shows
(a) the universal TI resistivity with a plateau at 15 K, revealed by a magnetic
field, (b) ultrahigh mobility of carriers in the plateau region, (c) quantum
oscillations with a non-trivial Berry phase, and (d) XMR of about one million
percent at 9 tesla rivaled only by WTe2 and NbP. Due to its dramatic
simplicity, LaSb is the ideal model system to formulate a theoretical
understanding of the exotic consequences of breaking TRS in TSMs.

###Origin of the turn-on temperature behavior in WTe$_2$|Y. L. Wang,L. R. Thoutam,Z. L. Xiao,J. Hu,S. Das,Z. Q. Mao,J. Wei,R. Divan,A. Luican-Mayer,G. W. Crabtree,W. K. Kwok###

Origin of the turn-on temperature behavior in WTe$_2$. A hallmark of materials with extremely large magnetoresistance (XMR) is the
transformative 'turn-on' temperature behavior: when the applied magnetic field
$H$ is above certain value, the resistivity versus temperature $\rho(T)$ curve
shows a minimum at a field dependent temperature $T^*$, which has been
interpreted as a magnetic-field-driven metal-insulator transition or attributed
to an electronic structure change. Here, we demonstrate that $\rho(T)$ curves
with turn-on behavior in the newly discovered XMR material WTe$_2$ can be
scaled as MR $\sim(H/\rho_0)^m$ with $m\approx 2$ and $\rho_0$ being the
resistivity at zero-field. We obtained experimentally and also derived from the
observed scaling the magnetic field dependence of the turn-on temperature $T^*
\sim (H-H_c)^\nu$ with $\nu \approx 1/2$, which was earlier used as evidence
for a predicted metal-insulator transition. The scaling also leads to a simple
quantitative expression for the resistivity $\rho^* \approx 2 \rho_0$ at the
onset of the XMR behavior, which fits the data remarkably well. These results
exclude the possible existence of a magnetic-field-driven metal-insulator
transition or significant contribution of an electronic structure change to the
low-temperature XMR in WTe$_2$. This work resolves the origin of the turn-on
behavior observed in several XMR materials and also provides a general route
for a quantitative understanding of the temperature dependence of MR in both
XMR and non-XMR materials.

###A close look at antiferromagnetism in multidimensional phase diagram of electron-doped copper oxide|Heshan Yu,Ge He,Ziquan Lin,Jie Yuan,Beiyi Zhu,Yi-feng Yang,Tao Xiang,Feo. V. Kusmartsev,Liang Li,Junfeng Wang,Kui Jin###

A close look at antiferromagnetism in multidimensional phase diagram of electron-doped copper oxide. Emergency of superconductivity at the instabilities of antiferromagnetism
(AFM), spin/charge density waves has been widely recognized in unconventional
superconductors. In copper-oxide superconductors, spin fluctuations play a
predominant role in electron pairing with electron dopants yet composite orders
veil the nature of superconductivity for hole-doped family. However, in
electron-doped ones the ending point of AFM is still in controversy for
different probes or its sensitivity to oxygen content. Here, by carefully
tuning the oxygen content, a systematic study of Hall signal and
magnetoresistivity up to 58 Tesla on optimally doped La2-xCexCuO4+-{\delta} (x
= 0.10) thin films identifies two characteristic temperatures at 62.5+-7.5 K
and 25+-5 K. The former is quite robust whereas the latter becomes flexible
with increasing magnetic field, thereby linked to two- and three-dimensional
AFM, evident from the multidimensional phase diagram as a function of oxygen as
well as Ce dopants. Consequently, the observation of extended AFM phase in
contrast to {\mu}SR probe corroborates an elevated critical doping in field,
providing an unambiguous picture to understand the interactions between AFM and
superconductivity.

###Creating stable Floquet-Weyl semimetals by laser-driving of 3D Dirac materials|Hannes Hübener,Michael A. Sentef,Umberto de Giovannini,Alexander F. Kemper,Angel Rubio###

Creating stable Floquet-Weyl semimetals by laser-driving of 3D Dirac materials. Tuning and stabilising topological states, such as Weyl semimetals, Dirac
semimetals, or topological insulators, is emerging as one of the major topics
in materials science. Periodic driving of many-body systems offers a platform
to design Floquet states of matter with tunable electronic properties on
ultrafast time scales. Here we show by first principles calculations how
femtosecond laser pulses with circularly polarised light can be used to switch
between Weyl semimetal, Dirac semimetal, and topological insulator states in a
prototypical 3D Dirac material, Na$_3$Bi. Our findings are general and apply to
any 3D Dirac semimetal. We discuss the concept of time-dependent bands and
steering of Floquet-Weyl points (Floquet-WPs), and demonstrate how light can
enhance topological protection against lattice perturbations. Our work has
potential practical implications for the ultrafast switching of materials
properties, like optical band gaps or anomalous magnetoresistance. Moreover, we
introduce Floquet time-dependent density functional theory (Floquet-TDDFT) as a
general and robust first principles method for predictive Floquet engineering
of topological states of matter.

###Remarkable magnetostructural coupling around the magnetic transition in CeCo$_{0.85}$Fe$_{0.15}$Si|V. F. Correa,D. Betancourth,J. G. Sereni,N. Caroca-Canales,C. Geibel###

Remarkable magnetostructural coupling around the magnetic transition in CeCo$_{0.85}$Fe$_{0.15}$Si. We report a detailed study of the magnetic properties of
CeCo$_{0.85}$Fe$_{0.15}$Si under high magnetic fields (up to 16 Tesla)
measuring different physical properties such as specific heat, magnetization,
electrical resistivity, thermal expansion and magnetostriction.
CeCo$_{0.85}$Fe$_{0.15}$Si becomes antiferromagnetic at $T_N \approx$ 6.7 K.
However, a broad tail (onset at $T_X \approx$ 13 K) in the specific heat
precedes that second order transition. This tail is also observed in the
temperature derivative of the resistivity. However, it is particularly
noticeable in the thermal expansion coefficient where it takes the form of a
large bump centered at $T_X$. A high magnetic field practically washes out that
tail in the resistivity. But surprisingly, the bump in the thermal expansion
becomes a well pronounced peak fully split from the magnetic transition at
$T_N$. Concurrently, the magnetoresistance also switches from negative to
positive just below $T_X$. The magnetostriction is considerable and
irreversible at low temperature ($\frac {\Delta L}{L} \left(16 T\right) \sim$
4$\times$10$^{-4}$ at 2 K) when the magnetic interactions dominate. A broad
jump in the field dependence of the magnetostriction observed at low $T$ may be
the signature of a weak ongoing metamagnetic transition. Taking altogether, the
results indicate the importance of the lattice effects in the development of
the magnetic order in these alloys.

###Magnetotransport of single crystalline YSb|N. J. Ghimire,A. S. Botana,D. Phelan,H. Zheng,J. F. Mitchell###

Magnetotransport of single crystalline YSb. We report magnetic field dependent transport measurements on a single crystal
of cubic YSb together with first principles calculations of its electronic
structure. The transverse magnetoresistance does not saturate up to 9 T and
attains a value of 75,000 % at 1.8 K. The Hall coefficient is electron-like at
high temperature, changes sign to hole-like between 110 and 50 K, and again
becomes electron-like below 50 K. First principles calculations show that YSb
is a compensated semimetal with a qualitatively similar electronic structure to
that of isostructural LaSb and LaBi, but with larger Fermi surface volume. The
measured electron carrier density and Hall mobility calculated at 1.8 K, based
on a single band approximation, are 6.5$\times10^{20}/$cm$^{3}$ and
6.2$\times10^{4}$cm$^{2}$/Vs, respectively. These values are comparable with
those reported for LaBi and LaSb. Like LaBi and LaSb, YSb undergoes a magnetic
field-induced metal-insulator-like transition below a characteristic
temperature T$_{m}$, with resistivity saturation below 13 K. Thickness
dependent electrical resistance measurements show a deviation of the resistance
behavior from that expected for a normal metal; however, they do not
unambiguously establish surface conduction as the mechanism for the resistivity
plateau.

###Non-thermal separation of electronic and structural orders in a persisting charge density wave|M. Porer,U. Leierseder,J. -M. Ménard,H. Dachraoui,L. Mouchliadis,I. E. Perakis,U. Heinzmann,J. Demsar,K. Rossnagel,R. Huber###

Non-thermal separation of electronic and structural orders in a persisting charge density wave. The simultaneous ordering of different degrees of freedom in complex
materials undergoing spontaneous symmetry-breaking transitions often involves
intricate couplings that have remained elusive in phenomena as wide ranging as
stripe formation, unconventional superconductivity or colossal
magnetoresistance. Ultrafast optical, x-ray and electron pulses can elucidate
the microscopic interplay between these orders by probing the electronic and
lattice dynamics separately, but a simultaneous direct observation of multiple
orders on the femtosecond scale has been challenging. Here we show that
ultrabroadband terahertz pulses can simultaneously trace the ultrafast
evolution of coexisting lattice and electronic orders. For the example of a
charge-density-wave (CDW) in 1T-TiSe2, we demonstrate that two components of
the CDW order parameter - excitonic correlations and a periodic lattice
distortion (PLD) - respond very differently to 12-fs optical excitation. Even
when the excitonic order of the CDW is quenched, the PLD can persist in a
coherently excited state. This observation proves that excitonic correlations
are not the sole driving force of the CDW transition in 1T-TiSe2, and
exemplifies the sort of profound insight that disentangling strongly coupled
components of order parameters in the time domain may provide for the
understanding of a broad class of phase transitions.

###Resonance-based Detection of Magnetic Nanoparticles and Microbeads Using Nanopatterned Ferromagnets|Manu Sushruth,Junjia Ding,Jeremy Duczynski,Robert C. Woodward,Ryan Begley,Hans Fangohr,Rebecca O. Fuller,Adekunle O. Adeyeye,Mikhail Kostylev,Peter J. Metaxas###

Resonance-based Detection of Magnetic Nanoparticles and Microbeads Using Nanopatterned Ferromagnets. Biosensing with ferromagnet-based magnetoresistive devices has been dominated
by electrical detection of particle-induced changes to the devices' static
magnetic configuration. There are however potential advantages to be gained
from using field dependent, high frequency magnetization dynamics for magnetic
particle detection. Here we demonstrate the use of nano-confined ferromagnetic
resonances in periodically patterned magnetic films for the detection of
adsorbed magnetic particles with diameters ranging from 6 nm to 4 $\mu$m. The
nanopatterned films contain arrays of holes which can act as preferential
adsorption sites for small particles. Hole-localized particles act in unison to
shift the resonant frequencies of the various modes of the patterned layer with
shift polarities determined by the localization of each mode within the
nanopattern's repeating unit cell. The same polarity shifts are observed for a
large range of coverages, even when hole-localized particles are covered by
quasi-continuous particle sheets. For large particles however, preferential
adsorption no longer occurs, leading to resonance shifts with polarities which
are independent of the mode localization. Analogous shifts are seen in
continuous layers where, for small particles, the shift of the layer's
fundamental mode is typically about 10 times less than in patterned systems and
induced by relatively weak fields emanating beyond the particle in the
direction of the static applied field. This highlights the importance of having
confined modes consistently positioned with respect to nearby particles.

###Weak localization effect in topological insulator micro flakes grown on insulating ferrimagnet BaFe12O19|Guolin Zheng,Ning Wang,Jiyong Yang,Weike Wang,Haifeng Du,Wei Ning,Zhaorong Yang,Hai-Zhou Lu,Yuheng Zhang,Mingliang Tian###

Weak localization effect in topological insulator micro flakes grown on insulating ferrimagnet BaFe12O19. Many exotic physics anticipated in topological insulators require a gap to be
opened for their topologica surface states by breaking time reversal symmetry.
The gap opening has been achieved by doping magnetic impurities, which however
inevitably create extra carriers and disorder that undermine the electronic
transport. In contrast, the proximity to a ferromagnetic/ferrimagnetic
insulator may improve the device quality, thus promises a better way to open
the gap while minimizing the side-effects. Here, we grow thin single-crystal
Sb1.9Bi0.1Te3 micro flakes on insulating ferrimagnet BaFe12O19 by using the van
der Waals epitaxy technique. The micro flakes show a negative magnetoresistance
in weak perpendicular fields below 50 K, which can be quenched by increasing
temperature. The signature implies the weak localization effect as its origin,
which is absent in intrinsic topological insulators, unless a surface state gap
is opened. The surface state gap is estimated to be 10 meV by using the theory
of the gap-induced weak localization effect. These results indicate that the
magnetic proximity effect may open the gap for the topological surface attached
to BaM insulating ferrimagnet. This heterostructure may pave the way for the
realization of new physical effects as well as the potential applications of
spintronics devices.

###Anomalous conductivity, Hall factor, magnetoresistance, and thermopower of accumulation layer in $\text{SrTiO}_3$|Han Fu,K. V. Reich,B. I. Shklovskii###

Anomalous conductivity, Hall factor, magnetoresistance, and thermopower of accumulation layer in $\text{SrTiO}_3$. We study the low temperature conductivity of the electron accumulation layer
induced by the very strong electric field at the surface of $\text{SrTiO}_3$
sample. Due to the strongly nonlinear lattice dielectric response, the
three-dimensional density of electrons $n(x)$ in such a layer decays with the
distance from the surface $x$ very slowly as $n(x) \propto 1/x^{12/7}$. We show
that when the mobility is limited by the surface scattering the contribution of
such a tail to the conductivity diverges at large $x$ because of growing time
electrons need to reach the surface. We explore truncation of this divergence
by the finite sample width, by the bulk scattering rate, or by the crossover to
the bulk linear dielectric response with the dielectric constant $\kappa$. As a
result we arrive at the anomalously large mobility, which depends not only on
the rate of the surface scattering, but also on the physics of truncation.
Similar anomalous behavior is found for the Hall factor, the magnetoresistance,
and the thermopower.

###Anisotropic magnetoresistance and upper critical fields up to 63 T in CaKFe$_4$As$_4$ single crystals|Tai Kong,Fedor F. Balakirev,William R. Meier,Sergey L. Bud'ko,Alex Gurevich,Paul C. Canfield###

Anisotropic magnetoresistance and upper critical fields up to 63 T in CaKFe$_4$As$_4$ single crystals. We report the temperature dependencies of the upper critical fields
$H_{c\text{2}}^{\text{c}}(T)$ parallel to the c-axis and
$H_{c\text{2}}^{\text{ab}}(T)$ parallel to the ab-plane of single crystalline
CaKFe$_4$As$_4$ inferred from the measurements of the temperature-dependent
resistance in static magnetic fields up to 14 T and magnetoresistance in pulsed
fields up to 63 T. We show that the observed decrease of the anisotropy
parameter $\gamma(T)=H_{c\text{2}}^{\text{ab}}/H_{c\text{2}}^{\text{c}}$ from
$\simeq 2.5$ at $T_c$ to $\simeq 1.5$ at 25 K can be explained by interplay of
paramagnetic pairbreaking and orbital effects in a multiband theory of
$H_{c2}$. The slopes of $dH_{c\text{2}}^{\text{c}}/dT\simeq-4.4$ T/K and
$dH_{c\text{2}}^{\text{ab}}/dT \simeq-10.9$ T/K at $T_c$ yield an electron mass
anisotropy of $m_{ab}/m_c\simeq 1/6$ and short coherence lengths $\xi_c\simeq
5.8\,\text{\AA}$ and $\xi_{ab}\simeq 14.3\,\text{\AA}$. The behavior of
$H_{c\text{2}}(T)$ turns out to be similar to that of the optimal doped
(Ba,K)Fe$_2$As$_2$, with $H_{c\text{2}}^{\text{ab}}(0)$ extrapolating to
$\simeq 92$ T, well above the BCS paramagnetic limit.

###Spin-Orbit Interaction and Kondo Scattering at the PrAlO$_3$/SrTiO$_3$ Interface: Effects of Oxygen Content|Shirin Mozaffari,Samaresh Guchhait,John T. Markert###

Spin-Orbit Interaction and Kondo Scattering at the PrAlO$_3$/SrTiO$_3$ Interface: Effects of Oxygen Content. We report the effect of oxygen pressure during growth ($P_{O_{2}}$) on the
electronic and magnetic properties of PrAlO$_3$ films grown on $\rm
TiO_{2}$-terminated SrTiO$_3$ substrates. Resistivity measurements show an
increase in the sheet resistance as $P_{O_{2}}$ is increased. The temperature
dependence of the sheet resistance at low temperatures is consistent with Kondo
theory for $P_{O_{2}} \ge 10^{-5}$ torr. Hall effect data exhibit a complex
temperature dependence that suggests a compensated carrier density. We observe
behavior consistent with two different types of carriers at interfaces grown at
$P_{O_{2}} \ge 10^{-4}$ torr. For these interfaces, we measured a moderate
positive magnetoresistance (MR) due to a strong spin-orbit (SO) interaction at
low magnetic fields that evolves into a larger negative MR at high fields.
Positive high MR values are associated with samples where a fraction of
carriers are derived from oxygen vacancies. Analysis of the MR data permitted
the extraction of the SO interaction critical field ( e.g. $ H_{SO}=$1.25 T for
$P_{O_{2}}=10^{-5}$ torr). The weak anti-localization effect due to a strong SO
interaction becomes smaller for higher $P_{O_{2}}$ grown samples, where MR
values are dominated by the Kondo effect, particularly at high magnetic fields.

###Conetronics in 2D Metal-Organic Frameworks: Double Dirac Cones, Magnetic Half Dirac Cones and Quantum Anomalous Hall Effect|Menghao Wu,Zhijun Wang,Junwei Liu,Huahua Fu,Lei Sun,Xin Liu,Minghu Pan,Hongming Weng,Mircea Dinca,Liang Fu,Ju Li###

Conetronics in 2D Metal-Organic Frameworks: Double Dirac Cones, Magnetic Half Dirac Cones and Quantum Anomalous Hall Effect. Based on recently synthesized Ni3C12S12 class 2D metal-organic frameworks, we
predict electronic properties of M3C12S12 and M3C12O12, where M is Zn, Cd, Hg,
Be, or Mg with no M orbital contributions to bands near Fermi level. For
M3C12S12, their band structures exhibit double Dirac cones with different Fermi
velocities that are n and p type, respectively, which are switchable by
few-percent strain. The crossing of two cones are symmetry-protected to be
non-hybridizing, leading to two independent channels in 2D node-line semimetals
at the same k-point akin to spin-channels in spintronics, rendering conetronics
device possible. The node line rings right at their crossing, which are both
electron and hole pockets at the Fermi level, can give rise to
magnetoresistance that will not saturate when the magnetic field is infinitely
large, due to perfect n-p compensation. For M3C12O12, together with conjugated
metal-tricatecholate polymers M3(HHTP)2, the spin-polarized slow Dirac cone
center is pinned precisely at the Fermi level, making the systems conducting in
only one spin or cone channel. Quantum anomalous Hall effect can arise in MOFs
with non-negligible spin-orbit coupling like Cu3C12O12. Compounds of M3C12S12
and M3C12O12 with different M, can be used to build spintronic and
cone-selecting heterostructure devices, tunable by strain or electrostatic
gating.

###Discrimination between spin-dependent charge transport and spin dependent recombination in π-conjugated polymers by correlated current and electroluminescence-detected magnetic resonance|Marzieh Kavand,Douglas Baird,Kipp van Schooten,Hans Malissa,John M. Lupton,Christoph Boehme###

Discrimination between spin-dependent charge transport and spin dependent recombination in π-conjugated polymers by correlated current and electroluminescence-detected magnetic resonance. Spin-dependent processes play a crucial role in organic electronic devices.
Spin coherence can give rise to spin mixing due to a number of processes such
as hyperfine coupling, and leads to a range of magnetic field effects. However,
it is not straightforward to differentiate between pure single-carrier
spin-dependent transport processes which control the current and therefore the
electroluminescence, and spin-dependent electron-hole recombination which
determines the electroluminescence yield and in turn modulates the current. We
therefore investigate the correlation between the dynamics of spin-dependent
electric current and spin-dependent electroluminescence in two derivatives of
the conjugated polymer poly(phenylene-vinylene) using simultaneously measured
pulsed electrically detected (pEDMR) and optically detected (pODMR) magnetic
resonance spectroscopy. This experimental approach requires careful analysis of
the transient response functions under optical and electrical detection. At
room temperature and under bipolar charge-carrier injection conditions, a
correlation of the pEDMR and the pODMR signals is observed, consistent with the
hypothesis that the recombination currents involve spin-dependent electronic
transitions. This observation is inconsistent with the hypothesis that these
signals are caused by spin-dependent charge carrier transport. These results
therefore provide no evidence that supports earlier claims that spindependent
transport plays a role for room temperature magnetoresistance effects. At low
temperatures, however, the correlation between pEDMR and pODMR is weakened,
demonstrating that more than one spin-dependent process influences the
optoelectronic materials properties.

###Spin Transport at Interfaces with Spin-Orbit Coupling: Formalism|V. P. Amin,M. D. Stiles###

Spin Transport at Interfaces with Spin-Orbit Coupling: Formalism. We generalize magnetoelectronic circuit theory to account for spin transfer
to and from the atomic lattice via interfacial spin-orbit coupling. This
enables a proper treatment of spin transport at interfaces between a
ferromagnet and a heavy-metal non-magnet. This generalized approach describes
spin transport in terms of drops in spin and charge accumulations across the
interface (as in the standard approach), but additionally includes the
responses from in-plane electric fields and offsets in spin accumulations. A
key finding is that in-plane electric fields give rise to spin accumulations
and spin currents that can be polarized in any direction, generalizing the
Rashba-Edelstein and spin Hall effects. The spin accumulations exert torques on
the magnetization at the interface when they are misaligned from the
magnetization. The additional out-of-plane spin currents exert torques via the
spin-transfer mechanism on the ferromagnetic layer. To account for these
phenomena we also describe spin torques within the generalized circuit theory.
The additional effects included in this generalized circuit theory suggest
modifications in the interpretations of experiments involving spin orbit
torques, spin pumping, spin memory loss, the Rashba-Edelstein effect, and the
spin Hall magnetoresistance.

###Anisotropic electron-phonon coupling in the spinel oxide superconductor|Ge He,Yanli Jia,Xingyuan Hou,Zhongxu Wei,Haidong Xie,Zhenzhong Yang,Jinan Shi,Jie Yuan,Lei Shan,Beiyi Zhu,Hong Li,Lin Gu,Kai Liu,Tao Xiang,Kui Jin###

Anisotropic electron-phonon coupling in the spinel oxide superconductor. Among hundreds of spinel oxides, LiTi2O4 (LTO) is the only one that exhibits
superconductivity (Tc ~13 K). Although the general electron-phonon coupling is
still the main mechanism for electron pairing in LTO, unconventional behaviors
such as the anomalous magnetoresistance, anisotropic orbital/spin
susceptibilities, etc. reveal that both the spin and the orbital interactions
should also be considered for understanding the superconductivity. Here, we
investigate tunneling spectra of [111]-, [110]- and [001]-oriented high quality
LTO thin films. Several bosonic modes in tunneling spectra are observed in the
[111]- and [110]-oriented films but not in [001]-oriented ones, and these modes
still exist at T = 2Tc and beyond the upper critical field, which are confirmed
as stemming from electron-phonon interaction by DFT calculations. These modes
only appear in special surface orientations, indicating that the
electron-phonon coupling in LTO system is highly anisotropic and may be
enhanced by orbital-related state. The anisotropic electron-phonon coupling
should be taken seriously in understanding the nature of LTO superconductivity.

###Finite bias dependent evolution of superconductor-insulator transition and Zero Bias Conductance in boron doped nanodiamond films|Davie Mtsuko,Christopher Coleman,Somnath Bhattacharyya###

Finite bias dependent evolution of superconductor-insulator transition and Zero Bias Conductance in boron doped nanodiamond films. We report on transport features in heavily boron doped nanocrystalline
diamond (BNCD) films which are not seen in conventional (s-wave) granular
superconductors. Observations include an anomalous resistance peak near to the
superconducting transition temperature as well as a strong zero bias
conductance peak in the current-voltage spectra. The effect of finite bias
current on the evolution of the resistance peak is systematically investigated
in this system. The shape of the resistance-temperature curves near the
critical temperature is seen to be strongly influenced by both magnetic field
and bias current. As the bias current is lowered the resistance peak becomes
more pronounced whereas when the magnetic field is varied the peak shifts
towards lower temperatures, the resistance upturn shows a quadratic temperature
dependence as expected for a Kondo transition. We find that a number of
transport features such as resistance peak height, zero bias conduction peak
height and width as well as magnetoresistance peaks scale according to a power
law dependence. We interpret these features as a result of a charge-Kondo
effect where hole dopants act as degenerate Kondo impurities by opening
additional pseudo-spin scattering channels.

###Spin Filtering through Single-Wall Carbon Nanotubes Functionalized with Single-Stranded DNA|Kazi M. Alam,Sandipan Pramanik###

Spin Filtering through Single-Wall Carbon Nanotubes Functionalized with Single-Stranded DNA. High spin polarization materials or spin filters are key components in
spintronics, a niche subfield of electronics where carrier spins play a
functional role. Carrier transmission through these materials is "spin
selective" i.e. these materials are able to discriminate between "up" and
"down" spins. Common spin filters include transition metal ferromagnets and
their alloys, with typical spin selectivity (or, polarization) ~50% or less.
Here we consider carrier transport in an archetypical one-dimensional molecular
hybrid in which a single wall carbon nanotube (SWCNT) is wrapped around by
single stranded deoxyribonucleic acid (ssDNA). By magnetoresistance
measurements we show that this system can act as a spin filter with maximum
spin polarization approaching ~74% at low temperatures, significantly larger
than transition metals under comparable conditions. Inversion asymmetric
helicoidal potential of the charged ssDNA backbone induces a Rashba spin-orbit
interaction in the SWCNT channel and polarizes carrier spins. Our results are
consistent with recent theoretical work that predicted spin dependent
conductance in ssDNA-SWCNT hybrid. Ability to generate highly spin polarized
carriers using molecular functionalization can lead to magnet-less and
contact-less spintronic devices in the future. This can eliminate the
conductivity mismatch problem and open new directions for research in organic
spintronics.

###Thermoelectric power factor enhancement by spin-polarized currents - a nanowire case study|Anna Corinna Niemann,Tim Böhnert,Ann-Kathrin Michel,Svenja Bäßler,Bernd Gotsmann,Katalin Neuróhr,Bence Tóth,László Péter,Imre Bakonyi,Victor Vega,Victor M. Prida,Johannes Gooth,Kornelius Nielsch###

Thermoelectric power factor enhancement by spin-polarized currents - a nanowire case study. Thermoelectric (TE) measurements have been performed on the workhorses of
today's data storage devices, exhibiting either the giant or the anisotropic
magnetoresistance effect (GMR and AMR). The temperature-dependent (50-300 K)
and magnetic field-dependent (up to 1 T) TE power factor (PF) has been
determined for several Co-Ni alloy nanowires with varying Co:Ni ratios as well
as for Co-Ni/Cu multilayered nanowires with various Cu layer thicknesses, which
were all synthesized via a template-assisted electrodeposition process. A
systematic investigation of the resistivity, as well as the Seebeck
coefficient, is performed for Co-Ni alloy nanowires and Co-Ni/Cu multilayered
nanowires. At room temperature, measured values of TE PFs up to 3.6 mWK-2m-1
for AMR samples and 2.0 mWK-2m-1 for GMR nanowires are obtained. Furthermore,
the TE PF is found to increase by up to 13.1 % for AMR Co-Ni alloy nanowires
and by up to 52 % for GMR Co-Ni/Cu samples in an external applied magnetic
field. The magnetic nanowires exhibit TE PFs that are of the same order of
magnitude as TE PFs of Bi-Sb-Se-Te based thermoelectric materials and,
additionally, give the opportunity to adjust the TE power output to changing
loads and hotspots through external magnetic fields.

###A quantitative description of Nernst effect in high-temperature superconductors|Rong Li,Zhen-Su She###

A quantitative description of Nernst effect in high-temperature superconductors. A quantitative vortex-fluid model for flux-flow resistivity $\rho$ and Nernst
signal $e_N$ in high-temperature superconductors (HTSC) is proposed. Two kinds
of vortices, magnetic and thermal, are considered, and the damping viscosity
$\eta$ is modeled by extending the Bardeen-Stephen model to include the
contributions of flux pinning at low temperature and in weak magnetic fields,
and vortex-vortex collisions in strong magnetic fields. Remarkably accurate
descriptions for both Nernst signal of six samples and flux flow resistivity
are achieved over a wide range of temperature $T$ and magnetic field $B$. A
discrepancy of three orders of magnitude between data and Anderson's model of
Nernst signal is pointed out and revised using experimental values of $\eta$
from magnetoresistance. Furthermore, a two-step procedure is developed to
reliably extract, from the Nernst signal, a set of physical parameters
characterizing the vortex dynamics, which yields predictions of local
superfluid density $n_s$, the Kosterlitz coefficient $b$ of thermal vortices,
and upper critical field and temperature. Application of the model and
systematic measurement of relevant physical quantities from Nernst signal in
other HTSC samples are discussed.

###Superconductivity and Dirac Fermions in 112-phase Pnictides|S. J. Ray,L. Alff###

Superconductivity and Dirac Fermions in 112-phase Pnictides. This article reviews the status of current research on the 112-phase of
pnictides. The 112-phase has gained augmented attention due to the recent
discovery of high-temperature superconductivity in $\cl$ with a maximum
critical temperature $\tc\sim$ 47\,K upon Sb substitution. The structural,
magnetic, and electronic properties of $\cl$ bear some similarities with other
superconducting pnictide phases, however, the different valence states of the
pnictogen and the presence of a metallic spacer layer are unique features of
the 112-system. Low-temperature superconductivity which coexists with
antiferromagnetic order was observed in transition metal (Ni, Pd) deficient
112-compounds like $\cn$, $\lpb$, $\lps$, $\lns$. Besides superconductivity,
the presence of naturally occurring anisotropic Dirac Fermionic states were
observed in the layered 112-compounds $\smb$, $\cmb$, $\lab$ which are of
significant interest for future nanoelectronics as an alternative to graphene.
In these compounds, the linear energy dispersion resulted in a high
magnetoresistance that stayed unsaturated even at the highest applied magnetic
fields. Here, we describe various 112-type materials systems combining
experimental results and theoretical predictions to stimulate further research
on this less well-known member of the pnictide family.

###Carrier driven coupling in ferromagnetic oxide heterostructures|Ching-Hao Chang,Sujit Das,Sanjeev Kumar,R. Ganesh###

Carrier driven coupling in ferromagnetic oxide heterostructures. Transition metal oxides are well known for their complex magnetic and
electrical properties. When brought together in heterostructure geometries,
they show particular promise for spintronics and colossal magnetoresistance
applications. In this letter, we propose a new mechanism for the coupling
between layers of itinerant ferromagnetic materials in heterostructures. The
coupling is mediated by charge carriers that strive to maximally delocalize
through the heterostructure to gain kinetic energy. In doing so, they force a
ferromagnetic or antiferromagnetic coupling between the constituent layers. To
illustrate this, we focus on heterostructures composed of SrRuO$_3$ and
La$_{1-x}$A$_{x}$MnO$_3$ (A=Ca/Sr). Our mechanism is consistent with
antiferromagnetic alignment that is known to occur in multilayers of
SrRuO$_3$-La$_{1-x}$A$_{x}$MnO$_3$. To support our assertion, we present a
minimal Kondo-lattice model which reproduces the known magnetization properties
of such multilayers. In addition, we discuss a quantum well model for
heterostructures and argue that the spin-dependent density of states determines
the nature of the coupling. As a smoking gun signature, we propose that
bilayers with the same constituents will oscillate between ferromagnetic and
antiferromagnetic coupling upon tuning the relative thicknesses of the layers.

###Dynamic coupling of ferromagnets via spin Hall magnetoresistance|Tomohiro Taniguchi###

Dynamic coupling of ferromagnets via spin Hall magnetoresistance. The synchronized magnetization dynamics in ferromagnets on a nonmagnetic
heavy metal caused by the spin Hall effect is investigated theoretically. The
direct and inverse spin Hall effects near the ferromagnetic/nonmagnetic
interface generate longitudinal and transverse electric currents. The
phenomenon is known as the spin Hall magnetoresistance effect, whose magnitude
depends on the magnetization direction in the ferromagnet due to the spin
transfer effect. When another ferromagnet is placed onto the same nonmagnet,
these currents are again converted to the spin current by the spin Hall effect
and excite the spin torque to this additional ferromagnet, resulting in the
excitation of the coupled motions of the magnetizations. The in-phase or
antiphase synchronization of the magnetization oscillations, depending on the
value of the Gilbert damping constant and the field-like torque strength, is
found in the transverse geometry by solving the Landau-Lifshitz-Gilbert
equation numerically. On the other hand, in addition to these synchronizations,
the synchronization having a phase difference of a quarter of a period is also
found in the longitudinal geometry. The analytical theory clarifying the
relation among the current, frequency, and phase difference is also developed,
where it is shown that the phase differences observed in the numerical
simulations correspond to that giving the fixed points of the energy supplied
by the coupling torque.

###Three-dimensionality of the bulk electronic structure in WTe2|Yun Wu,Na Hyun Jo,Daixiang Mou,Lunan Huang,S. L. Bud'ko,P. C. Canfield,Adam Kaminski###

Three-dimensionality of the bulk electronic structure in WTe2. We use temperature- and field-dependent resistivity measurements
[Shubnikov--de Haas (SdH) quantum oscillations] and ultrahigh resolution,
tunable, vacuum ultraviolet (VUV) laser-based angle-resolved photoemission
spectroscopy (ARPES) to study the three-dimensionality (3D) of the bulk
electronic structure in WTe2, a type-II Weyl semimetal. The bulk Fermi surface
(FS) consists of two pairs of electron pockets and two pairs of hole pockets
along the X-Gamma-X direction as detected by using an incident photon energy of
6.7 eV, which is consistent with the previously reported data. However, if
using an incident photon energy of 6.36 eV, another pair of tiny electron
pockets is detected on both sides of the Gamma point, which is in agreement
with the small quantum oscillation frequency peak observed in the
magnetoresistance. Therefore, the bulk, 3D FS consists of three pairs of
electron pockets and two pairs of hole pockets in total. With the ability of
fine tuning the incident photon energy, we demonstrate the strong
three-dimensionality of the bulk electronic structure in WTe2. The combination
of resistivity and ARPES measurements reveal the complete, and consistent,
picture of the bulk electronic structure of this material.

###Spin mediated magneto-electro-thermal transport behavior in Ni80Fe20/MgO/p-Si thin films|P. C. Lou,W. P. Beyermann,S. Kumar###

Spin mediated magneto-electro-thermal transport behavior in Ni80Fe20/MgO/p-Si thin films. In Si, spin-phonon interaction is the primary spin relaxation mechanism. At
low temperatures, the absence of spin-phonon relaxation will lead to enhanced
spin accumulation. Spin accumulation may change the electro-thermal transport
within the material, and thus may serve as an investigative tool for
characterizing spin-mediated behavior. Here we present the first experimental
proof of spin accumulation induced electro-thermal transport behavior in a Pd
(1 nm)/Ni80Fe20 (25 nm)/MgO (1 nm)/p-Si (2 um) specimen. The spin accumulation
originates from the spin-Hall effect. The spin accumulation changes the
phononic thermal transport in p-Si causing the observed magneto-electro-thermal
transport behavior. We also observe the inverted switching behavior in
magnetoresistance measurement at low temperatures in contrast to magnetic
characterization, which is attributed to the canted spin states in p-Si due to
spin accumulation. The spin accumulation is elucidated by current dependent
anomalous Hall resistance measurement, which shows a decrease as the electric
current is increased. This result may open a new paradigm in the field of
spin-mediated transport behavior in semiconductor and semiconductor
spintronics.

###Unconventional slowing down of electronic recovery in photoexcited charge-ordered La$_{1/3}$Sr$_{2/3}$FeO$_3$|Yi Zhu,Jason Hoffman,Clare E. Rowland,Hyowon Park,Donald A. Walko,John W. Freeland,Philip J. Ryan,Richard D. Schaller,Anand Bhattacharya,Haidan Wen###

Unconventional slowing down of electronic recovery in photoexcited charge-ordered La$_{1/3}$Sr$_{2/3}$FeO$_3$. Ordered electronic phases are intimately related to emerging phenomena such
as high Tc superconductivity and colossal magnetoresistance. The coupling of
electronic charge with other degrees of freedom such as lattice and spin are of
central interest in correlated systems. Their correlations have been
intensively studied from femtosecond to picosecond time scales, while the
dynamics of ordered electronic phases beyond nanoseconds are usually assumed to
follow a trivia thermally driven recovery. Here, we report an unusual slowing
down of the recovery of an electronic phase across a first-order phase
transition, far beyond thermal relaxation time. Following optical excitation,
the recovery time of both transient optical reflectivity and x-ray diffraction
intensity from a charge-ordered superstructure in a La$_{1/3}$Sr$_{2/3}$FeO$_3$
thin film increases by orders of magnitude longer than the independently
measured lattice cooling time when the sample temperature approaches the phase
transition temperature. The combined experimental and theoretical
investigations show that the slowing down of electronic recovery corresponds to
the pseudo-critical dynamics that originates from magnetic interactions close
to a weakly first-order phase transition. This extraordinary long electronic
recovery time exemplifies an interplay of ordered electronic phases with
magnetism beyond thermal processes in correlated systems.

###MoTe2 : An uncompensated semimetal with extremely large magnetoresistance|S. Thirupathaiah,Rajveer Jha,Banabir Pal,J. S. Matias,P. Kumar Das,P. K. Sivakumar,I. Vobornik,N. C. Plumb,M. Shi,R. A. Ribeiro,D. D. Sarma###

MoTe2 : An uncompensated semimetal with extremely large magnetoresistance. Transition-metal dichalcogenides (WTe$_2$ and MoTe$_2$) have drawn much
attention, recently, because of the nonsaturating extremely large
magnetoresistance (XMR) observed in these compounds in addition to the
predictions of likely type-II Weyl semimetals. Contrary to the topological
insulators or Dirac semimetals where XMR is linearly dependent on the field, in
WTe$_2$ and MoTe$_2$ the XMR is nonlinearly dependent on the field, suggesting
an entirely different mechanism. Electron-hole compensation has been proposed
as a mechanism of this nonsaturating XMR in WTe$_2$, while it is yet to be
clear in the case of MoTe$_2$ which has an identical crystal structure of
WTe$_2$ at low temperatures. In this paper, we report low-energy electronic
structure and Fermi surface topology of MoTe$_2$ using angle-resolved
photoemission spectrometry (ARPES) technique and first-principle calculations,
and compare them with that of WTe$_2$ to understand the mechanism of XMR. Our
measurements demonstrate that MoTe$_2$ is an uncompensated semimetal, contrary
to WTe$_2$ in which compensated electron-hole pockets have been identified,
ruling out the applicability of charge compensation theory for the
nonsaturating XMR in MoTe$_2$. In this context, we also discuss the
applicability of the existing other conjectures on the XMR of these compounds.

###Time-of-flight elastic and inelastic neutron scattering studies on the localized $4d$ electron layered perovskite La$_5$Mo$_4$O$_{16}$|K. Iida,R. Kajimoto,Y. Mizuno,K. Kamazawa,Y. Inamura,A. Hoshikawa,Y. Yoshida,T. Matsukawa,T. Ishigaki,Y. Kawamura,S. Ibuka,T. Yokoo,S. Itoh,T. Katsufuji###

Time-of-flight elastic and inelastic neutron scattering studies on the localized $4d$ electron layered perovskite La$_5$Mo$_4$O$_{16}$. The magnetic structure and spin-wave excitations in the quasi-square-lattice
layered perovskite compound La$_5$Mo$_4$O$_{16}$ were studied by a combination
of neutron diffraction and inelastic neutron scattering techniques using
polycrystalline sample. Neutron powder diffraction refinement revealed that the
magnetic structure is ferrimagnetic in the $ab$ plane with antiferromagnetic
stacking along the $c$ axis where the magnetic propagation vector is
$\mathbf{k}=\left(0,0,\frac{1}{2}\right)$. The ordered magnetic moments are
estimated to be $0.54(2)\mu_\text{B}$ for Mo$^{5+}$ ($4d^1$) ions and
$1.07(3)\mu_\text{B}$ for Mo$^{4+}$ ($4d^2$) ions at 4 K, which are about half
of the expected values. The inelastic neutron scattering results display strong
easy-axis magnetic anisotropy along the $c$ axis due to the spin-orbit
interaction in Mo ions evidenced by the spin gap at the magnetic zone center.
The model Hamiltonian consisting of in-plane anisotropic exchange interactions,
the interlayer exchange interaction, and easy-axis single-ion anisotropy can
explain our inelastic neutron scattering data well. Strong Ising-like
anisotropy and weak interlayer coupling compared with the intralayer exchange
interaction can explain both the high-temperature magnetoresistance and
long-time magnetization decay recently observed in La$_5$Mo$_4$O$_{16}$.

###Magnetic behavior of new compounds, Gd3RuSn6 and Tb3RuSn6|Sanjay K Upadhyay,Kartik K Iyer,E. V. Sampathkumaran###

Magnetic behavior of new compounds, Gd3RuSn6 and Tb3RuSn6. We report temperature (T) dependence of dc magnetization, electrical
resistivity (rho(T)), and heat-capacity of rare-earth (R) compounds, Gd3RuSn6
and Tb3RuSn6, which are found to crystallize in the Yb3CoSn6-type orthorhombic
structure (space group: Cmcm). The results establish that there is an onset of
antiferromagnetic order near (T_N) 19 and 25 K respectively. In addition, we
find that there is another magnetic transition for both the cases around 14 and
17 K respectively. In the case of the Gd compound, the spin-scattering
contribution to rho is found to increase below 75 K as the material is cooled
towards T_N, thereby resulting in a minimum in the plot of rho(T) unexpected
for Gd based systems. Isothermal magnetization at 1.8 K reveals an upward
curvature around 50 kOe. Isothermal magnetoresistance plots show interesting
anomalies in the magnetically ordered state. There are sign reversals in the
plot of isothermal entropy change versus T in the magnetically ordered state,
indicating subtle changes in the spin reorientation with T. The results reveal
that these compounds exhibit interesting magnetic properties.

###Deficiency of the Bulk Spin Hall Effect Model for Spin-Orbit Torques in Magnetic Insulator/Heavy Metal Heterostructures|Junxue Li,Guoqiang Yu,Chi Tang,Yizhou Liu,Zhong Shi,Yawen Liu,Aryan Navabi,Mohammed Aldosary,Qiming Shao,Kang L. Wang,Roger Lake,Jing Shi###

Deficiency of the Bulk Spin Hall Effect Model for Spin-Orbit Torques in Magnetic Insulator/Heavy Metal Heterostructures. Electrical currents in a magnetic insulator/heavy metal heterostructure can
induce two simultaneous effects, namely, spin Hall magnetoresistance (SMR) on
the heavy metal side and spin-orbit torques (SOTs) on the magnetic insulator
side. Within the framework of the pure spin current model based on the bulk
spin Hall effect (SHE), the ratio of the spin Hall-induced anomalous Hall
effect (SH-AHE) to SMR should be equal to the ratio of the field-like torque
(FLT) to damping-like torque (DLT). We perform a quantitative study of SMR,
SH-AHE, and SOTs in a series of thulium iron garnet/platinum or Tm3Fe5O12/Pt
heterostructures with different Tm3Fe5O12 thicknesses, where Tm3Fe5O12 is a
ferrimagnetic insulator with perpendicular magnetic anisotropy. We find the
ratio between measured effective fields of FLT and DLT is at least 2 times
larger than the ratio of the SH-AHE to SMR. In addition, the bulk SHE model
grossly underestimates the spin torque efficiency of FLT. Our results reveal
deficiencies of the bulk SHE model and also address the importance of
interfacial effects such as the Rashba and magnetic proximity effects in
magnetic insulator/heavy metal heterostructures.

###Nontrivial Berry phase in magnetic BaMnSb2 semimetal|Silu Huang,Jisun Kim,W. A. Shelton,E. W. Plummer,Rongying Jin###

Nontrivial Berry phase in magnetic BaMnSb2 semimetal. The subject of topological materials has attracted immense attention in
condensed-matter physics, because they host new quantum states of matter
containing Dirac, Majorana, or Weyl fermions. Although Majorana fermions can
only exist on the surface of topological superconductors, Dirac and Weyl
fermions can be realized in both 2D and 3D materials. The latter are semimetals
with Dirac/Weyl cones either not tilted (type I) or tilted (type II). Although
both Dirac and Weyl fermions have massless nature with the nontrivial Berry
phase, the formation of Weyl fermions in 3D semimetals require either
time-reversal or inversion symmetry breaking to lift degeneracy at Dirac
points. Here, we demonstrate experimentally that canted antiferromagnetic
BaMnSb2 is a 3D Weyl semimetal with a 2D electronic structure. The Shubnikov-de
Hass oscillations of the magnetoresistance give nearly zero effective mass with
high mobility and the nontrivial Berry phase. The ordered magnetic arrangement
(ferromagnetic ordering in the ab plane and antiferromagnetic ordering along
the c axis below 286 K) breaks the time-reversal symmetry, thus offering us an
ideal platform to study magnetic Weyl fermions in a centrosymmetric material.

###Temperature independent band structure of WTe2 as observed from ARPES|S. Thirupathaiah,Rajveer Jha,Banabir Pal,J. S. Matias,P. Kumar Das,I. Vobornik,R. A. Ribeiro,D. D. Sarma###

Temperature independent band structure of WTe2 as observed from ARPES. Extremely large magnetoresistance (XMR), observed in transition metal
dichalcogendies, WTe$_2$, has attracted recently a great deal of research
interests as it shows no sign of saturation up to the magnetic field as high as
60 T, in addition to the presence of type-II Weyl fermions. Currently, there
has been a lot of discussion on the role of band structure changes on the
temperature dependent XMR in this compound. In this contribution, we study the
band structure of WTe$_2$ using angle-resolved photoemission spectroscopy
(ARPES) and first-principle calculations to demonstrate that the temperature
dependent band structure has no substantial effect on the temperature dependent
XMR as our measurements do not show band structure changes on increasing the
sample temperature between 20 and 130 K. We further observe an electronlike
surface state, dispersing in such a way that it connects the top of bulk
holelike band to the bottom of bulk electronlike band. Interestingly, similar
to bulk states, the surface state is also mostly intact with the sample
temperature. Our results provide invaluable information in shaping the
mechanism of temperature dependent XMR in WTe$_2$.

###Spin-orbit coupling and transport of strongly correlated two-dimensional systems|Jian Huang,L. N. Pfeiffer,K. W. West###

Spin-orbit coupling and transport of strongly correlated two-dimensional systems. Measuring the magnetoresistance (MR) of ultraclean {\it GaAs} two-dimensional
holes in a large $r_s$ range of 20-50, two striking behaviors in relation to
the spin-orbit coupling (SOC) emerge in response to strong electron-electron
interaction. First, in exact correspondence to the zero-field
metal-to-insulator transition (MIT), the sign of the MR switches from being
positive in the metallic regime to being negative in the insulating regime when
the carrier density crosses the critical density $p_c$ of MIT ($r_s\sim 39$).
Second, as the SOC-driven correction $\Delta\rho$ to the MR decreases with
reducing carrier density (or the in-plane wave vector), it exhibits an upturn
in the close proximity just above $p_c$ where $r_s$ is beyond 30, indicating a
substantially enhanced SOC effect. This peculiar behavior echoes with a trend
of delocalization long suspected for the SOC-interaction interplay. Meanwhile,
for $p<p_c$ or $r_s>40$, in contrast to the common belief that a magnet field
enhances Wigner crystallization, the negative MR is likely linked to enhanced
interaction.

###Anisotropic Fermi surface probed by the de Haas-van Alphen oscillation in proposed Dirac Semimetal TaSb$_{2}$|Arnab Pariari,Ratnadwip Singha,Shubhankar Roy,Biswarup Satpati,Prabhat Mandal###

Anisotropic Fermi surface probed by the de Haas-van Alphen oscillation in proposed Dirac Semimetal TaSb$_{2}$. TaSb$_{2}$ has been predicted theoretically and proposed through
magnetotransport experiment to be a topological semimetal. In earlier reports,
the Shubnikov-de Haas oscillation has been analyzed to probe the Fermi surface,
with magnetic field along a particular crystallographic axis only. By employing
a sample rotator, we reveal highly anisotropic transverse magnetoresistance by
rotating the magnetic field along different crystallographic directions. To
probe the anisotropy in the Fermi surface, we have performed magnetization
measurements and detected strong de Haas-van Alphen (dHvA) oscillations for the
magnetic field applied along \textbf{b} and \textbf{c} axes as well as
perpendicular to \textbf{bc} plane of the crystals. Three Fermi pockets have
been identified by analyzing the dHvA oscillations. Hall measurement reveals
electron as the only charge carrier, i.e., all the three Fermi pockets are
electron type. With the application of magnetic field along different crystal
directions, the cross sectional areas of the Fermi pockets have been found
significantly different. Other physical parameters, such as the effective mass
of the charge carrier and Fermi velocity have also been calculated using the
Lifshitz-Kosevich formula.

###Negative spin Hall magnetoresistance of Pt on the bulk easy-plane antiferromagnet NiO|Geert R. Hoogeboom,Aisha Aqeel,Timo Kuschel,Thomas T. M. Palstra,Bart J. van Wees###

Negative spin Hall magnetoresistance of Pt on the bulk easy-plane antiferromagnet NiO. We report on spin Hall magnetoresistance (SMR) measurements of Pt Hall bars
on the antiferromagnetic NiO(111) single crystal. An SMR with a sign opposite
of conventional SMR is observed over a wide range of temperatures as well as
magnetic fields stronger than 0.25T. The negative sign of the SMR can be
explained by the alignment of magnetic moments being almost perpendicular to
the external magnetic field within the easy plane (111) of the antiferromagnet.
This correlation of magnetic moment alignment and external magnetic field
direction is realized just by the easy-plane nature of the material without the
need of any exchange coupling to an additional ferromagnet. The SMR signal
strength decreases with increasing temperature, primarily due to the decrease
in N\'eel order by including fluctuations. An increasing magnetic field
increases the SMR signal strength as there are less domains and the magnetic
moments are more strongly manipulated at high magnetic fields. The SMR is
saturated at an applied magnetic field of $6$~T resulting in a spin-mixing
conductance of $\sim10^{18}~ \Omega^{-1}$m$^{-2}$, which is comparable to that
of Pt on insulating ferrimagnets such as yttrium iron garnet. An argon plasma
treatment doubles the spin-mixing conductance.

###The extremely large magnetoresistance in the Candidate Type-II Weyl semimetal MoTe2|F. C. Chen,H. Y. Lv,X. Luo,W. J. Lu,Q. L. Pei,G. T. Lin,Y. Y. Han,X. B. Zhu,W. H. Song,Y. P. Sun###

The extremely large magnetoresistance in the Candidate Type-II Weyl semimetal MoTe2. We performed the angle dependent magnetoresistance (MR), Hall effect
measurements, the temperature dependent magneto-thermoelectric power (TEP) S(T)
measurements, and the first-principles calculations to study the electronic
properties of orthorhombic phase MoTe2 (Td-MoTe2), which was proposed to be
electronically two-dimensional (2D). There are some interesting findings about
Td-MoTe2: (1) A scaling approach
{\epsilon}{\theta}=(sin2{\theta}+{\gamma}-2cos2{\theta})1/2 is applied, where
{\theta} is the magnetic field angle with respect to the c axis of the crystal
and {\gamma} is the mass anisotropy. Unexpectedly, the electronically 3D
character with {\gamma} as low as 1.9 is observed in Td-MoTe2; (2) The possible
Lifshitz transition and the following electronic structure change can be
verified around T~150 K and T~60 K, which is supported by the evidence of the
slop changing of the temperature dependence of TEP, the carrier density
extracted from Hall resistivity and the onset temperature of {\gamma} obtained
from the MR measurements. The extremely large MR effect in Td-MoTe2 could
originate from the combination of the electron-hole compensation and a
particular orbital texture on the electron pocket, which is supported by the
calculations of electronic structure. Our results may provide a general scaling
relation for the anisotropic MR and help to recognize the origins of the MR
effect in other systems, such as the Weyl semimetals and the Dirac ones.

###Spin Hall effect from hybridized 3$d$-4$p$ orbitals|Yong-Chang Lau,Hwachol Lee,Kohji Nakamura,Masamitsu Hayashi###

Spin Hall effect from hybridized 3$d$-4$p$ orbitals. Electrical manipulation of magnetization by spin-orbit torque (SOT) has shown
promise for realizing reliable magnetic memories and oscillators. To date, the
generation of transverse spin current and SOT, whether it is of spin Hall
effect (SHE), Rashba-Edelstein effect or spin-momentum locking origin, relies
primarily on materials or heterostructures containing 5$d$ or 6$p$ heavy
elements with strong spin-orbit coupling. Here we show that a paramagnetic CoGa
compound possesses large enough spin Hall angle to allow robust SOT switching
of perpendicularly-magnetized ferrimagnetic MnGa films in CoGa/MnGa/Oxide
heterostructures. The spin Hall efficiency estimated via spin Hall
magnetoresistance and harmonic Hall measurements is +0.05$\pm$0.01, which is
surprisingly large for a system that does not contain any heavy metal element.
First-principles calculations corroborate our experimental observations and
suggest that the hybridized Co 3$d$ - Ga 4$p$ orbitals along R-X in the
Brillouin zone is responsible for the intrinsic SHE. Our results suggest that
efficient spin current generation can be realized in intermetallic by alloying
a transition metal with a $p$-orbital element and by Fermi level tuning.

###Ferroic collinear multilayer magnon spin valve|Joel Cramer,Felix Fuhrmann,Ulrike Ritzmann,Vanessa Gall,Tomohiko Niizeki,Rafael Ramos,Zhiyong Qiu,Dazhi Hou,Takashi Kikkawa,Jairo Sinova,Ulrich Nowak,Eiji Saitoh,Mathias Kläui###

Ferroic collinear multilayer magnon spin valve. Information transport and processing by pure magnonic spin currents in
insulators is a promising alternative to conventional charge-current driven
spintronic devices. The absence of Joule heating as well as the reduced spin
wave damping in insulating ferromagnets has been suggested to enable the
implementation of efficient logic devices. After the proof of concept for a
logic majority gate based on the superposition of spin waves has been
successfully demonstrated, further components are required to perform complex
logic operations. A key component is a switch that corresponds to a
conventional magnetoresistive spin valve. Here, we report on magnetization
orientation dependent spin signal detection in collinear magnetic multilayers
with spin transport by magnonic spin currents. We find in Y3Fe5O12|CoO|Co
tri-layers that the detected spin signal depends on the relative alignment of
Y3Fe5O12 and Co. This demonstrates a spin valve behavior with an effect
amplitude of 120% in our systems. We demonstrate the reliability of the effect
and investigate the origin by both temperature and power dependent
measurements, showing that spin rectification effects and a magnetic layer
alignment dependent spin transport effect result in the measured signal.

###Boundary-Driven Twist States in Systems with Broken Spatial Inversion Symmetry|Kjetil M. D. Hals,Karin Everschor-Sitte###

Boundary-Driven Twist States in Systems with Broken Spatial Inversion Symmetry. A full description of a magnetic sample includes a correct treatment of the
boundary conditions (BCs). This is in particular important in thin film
systems, where even bulk properties might be modified by the properties of the
boundary of the sample. We study generic ferromagnets with broken spatial
inversion symmetry and derive the general micromagnetic BCs of a system with
Dzyaloshinskii-Moriya interaction (DMI). We demonstrate that the BCs require
the full tensorial structure of the third-rank DMI tensor and not just the
antisymmetric part, which is usually taken into account. Specifically, we study
systems with $C_{\infty v}$ symmetry and explore the consequences of the DMI.
Interestingly, we find that the DMI already in the simplest case of a
ferromagnetic thin-film leads to a purely boundary-driven magnetic twist state
at the edges of the sample. The twist state represents a new type of
DMI-induced spin structure, which is completely independent of the internal DMI
field. We estimate the size of the texture-induced magnetoresistance effect
being in the range of that of domain walls.

###Magnetotransport properties of MoP$_2$|Aifeng Wang,D. Graf,Yu Liu,C. Petrovic###

Magnetotransport properties of MoP$_2$. We report magnetotransport and de Haas-van Alphen (dHvA) effect studies on
MoP$_2$ single crystals, predicted to be type-2 Weyl semimetal with four pairs
of robust Weyl points located below the Fermi level and long Fermi arcs. The
temperature dependence of resistivity shows a peak before saturation, which
does not move with magnetic field. Large nonsaturating magnetoresistance (MR)
was observed, and the field dependence of MR exhibits a crossover from
semicalssical weak-field $B^2$ dependence to the high-field linear-field
dependence, indicating the presence of Dirac linear energy dispersion. In
addition, systematic violation of Kohler's rule was observed, consistent with
multiband electronic transport. Strong spin-orbit coupling (SOC) splitting has
an effect on dHvA measurements whereas the angular-dependent dHvA orbit
frequencies agree well with the calculated Fermi surface. The cyclotron
effective mass $\sim$ 1.6$m_e$ indicates the bands might be trivial, possibly
since the Weyl points are located below the Fermi level. Interestingly,
quasi-two dimensional(2D) band structure is observed even though the crystal
structure of MoP$_2$ is not layered.

###Defects controlled hole doping and multi-valley transport in SnSe single crystals|Zhen Wang,Congcong Fan,Zhixuan Shen,Chenqiang Hua,Yifeng Hu,Feng Sheng,Yunhao Lu,Hanyan Fang,Zhizhan Qiu,Jiong Lu,Zhu-An Xu,D. W. Shen,Yi Zheng###

Defects controlled hole doping and multi-valley transport in SnSe single crystals. SnSe is a promising thermoelectric material with record-breaking figure of
merit, \textit{i.e., ZT}. As a semiconductor, optimal electrical dosage is the
key challenge to maximize \textit{ZT} in SnSe. However, to date a comprehensive
understanding of the electronic structure and most critically, the self-hole
doping mechanism in SnSe is still absent. Here, we report the highly
anisotropic electronic structure of SnSe investigated by both angle-resolved
photoemission spectroscopy and quantum transport, in which a unique
"\textit{pudding-mold}" shaped valence band with quasi-linear energy dispersion
is revealed. We prove that the electrical doping in SnSe is extrinsically
controlled by the formation of SnSe$_{2}$ micro-domains induced by local phase
segregation. Using different growth methods and conditions, we have achieved
wide tuning of hole doping in SnSe, ranging from intrinsic semiconducting
behaviour to typical metal with carrier density of $1.23\times 10^{18}$
cm$^{-3}$ at room temperature. The resulting multi-valley transport in $p$-SnSe
is characterized by non-saturating weak localization along the armchair axis,
due to strong intervalley scattering enhanced by in-plane ferroelectric dipole
field of the puckering lattice. Strikingly, quantum oscillations of
magnetoresistance reveal three-dimensional electronic structure with unusual
interlayer coupling strength in $p$-SnSe, which is correlated to the
interweaving of SnSe individual layers by unique point dislocation defects. Our
results suggest that defect engineering may provide versatile routes in
improving the thermoelectric performance of the SnSe family.

###Enhanced electron correlations in the new binary stannide PdSn4: a homologue of the Dirac nodal arc semimetal PtSn4|C. Q. Xu,W. Zhou,R. Sankar,X. Z. Xing,Z. X. Shi,Z. D. Han,B. Qian,J. H. Wang,Zengwei Zhu,J. L. Zhang,A. F. Bangura,N. E. Hussey,Xiaofeng Xu###

Enhanced electron correlations in the new binary stannide PdSn4: a homologue of the Dirac nodal arc semimetal PtSn4. The advent of nodal-line semi-metals, i.e. systems in which the conduction
and valence bands cross each other along a closed trajectory (line or loop)
inside the Brillouin zone, has opened up a new arena for the exploration of
topological condensed matter in which, due to a vanishing density of states
near the Fermi level, electron correlation effects may also play an important
role. In spite of this conceptual richness however, material realization of
nodal-line (loop) fermions is rare, with PbTaSe2, ZrSiS and PtSn4 the only
promising known candidates. Here we report the synthesis and physical
properties of a new compound PdSn4 that is isostructural with PtSn4 yet
possesses quasiparticles with significantly enhanced effective masses. In
addition, PdSn4 displays an unusual polar angular magnetoresistance which at a
certain field orientation, varies linearly with field up to 55 Tesla. Our study
suggests that, in association with its homologue PtSn4 whose low-lying
excitations were recently claimed to possess Dirac node arcs, PdSn4 may be a
promising candidate in the search for novel topological states with enhanced
correlation effects.

###Bending and Breaking of Stripes in a Charge-Ordered Manganite|Benjamin H. Savitzky,Ismail El Baggari,Alemayehu S. Admasu,Jaewook Kim,Sang-Wook Cheong,Robert Hovden,Lena F. Kourkoutis###

Bending and Breaking of Stripes in a Charge-Ordered Manganite. In complex electronic materials, coupling between electrons and the atomic
lattice gives rise to remarkable phenomena, including colossal
magnetoresistance and metal-insulator transitions. Charge-ordered phases are a
prototypical manifestation of charge-lattice coupling, in which the atomic
lattice undergoes periodic lattice displacements (PLDs). Here we directly map
the picometer scale PLDs at individual atomic columns in the room temperature
charge-ordered manganite Bi$_{0.35}$Sr$_{0.18}$Ca$_{0.47}$MnO$_3$ using
aberration corrected scanning transmission electron microscopy (STEM). We
measure transverse, displacive lattice modulations of the cations, distinct
from existing manganite charge-order models. We reveal locally unidirectional
striped PLD domains as small as $\sim$5 nm, despite apparent bidirectionality
over larger length scales. Further, we observe a direct link between disorder
in one lattice modulation, in the form of dislocations and shear deformations,
and nascent order in the perpendicular modulation. By examining the defects and
symmetries of PLDs near the charge-ordering phase transition, we directly
visualize the local competition underpinning spatial heterogeneity in a complex
oxide.

###Anomalous Hall effect in two-dimensional non-collinear antiferromagnetic semiconductor Cr0.68Se|J. Yan,X. Luo,F. C. Chen,Q. L. Pei,G. T. Lin,Y. Y. Han,L. Hu,P. Tong,W. H. Song,X. B. Zhu,Y. P. Sun###

Anomalous Hall effect in two-dimensional non-collinear antiferromagnetic semiconductor Cr0.68Se. Cr0.68Se single crystals with two-dimensional (2D) character have been grown,
and the detailed magnetization M(T), electrical transport properties (including
longitudinal resistivity and Hall resistivity and thermal transport ones
(including heat capacity Cp(T) and thermoelectric power (TEP) S(T)) have been
measured. There are some interesting phenomena: (i) Cr0.68Se presents a
non-collinear antiferromagnetic (AFM) semiconducting behavior with the Neel
temperature TN = 42 K and the activated energy Eg=3.9 meV; (ii) It exhibits the
anomalous Hall effect (AHE) below TN and large negative magnetoresistance (MR)
about 83.7% (2 K, 8.5 T). The AHE coefficient RS is 0.385 cm-3/C at T=2 K and
the AHE conductivity {\sigma}H is about 1 ohm-1cm-1 at T=40 K, respectively;
(iii) The scaling behavior between the anomalous Hall resistivity and the
longitudinal resistivity is linear and further analysis implies that the origin
of the AHE in Cr0.68Se is dominated by the skew-scattering mechanism. Our
results may be helpful for exploring the potential application of these kind of
2D AFM semiconductors.

###The origin of the turn-on phenomenon in Td-MoTe2|Q. L. Pei,W. J. Meng,X. Luo,H. Y. Lv,F. C. Chen,W. J. Lu,Y. Y. Han,P. Tong,W. H. Song,Y. B. Hou,Q. Y. Lu,Y. P. Sun###

The origin of the turn-on phenomenon in Td-MoTe2. We did the resistivity and scanning tunneling microscope/spectroscopy
(STM/STS) experiments at different temperatures and magnetic fields to
investigate the origin of the turn-on (t-o) phenomenon of Td-MoTe2. There are
two interesting observations. Firstly, magnetoresistance (MR) follows the
Kohler rule scaling: MR - (H/p0)m with m - 1.92 and the t-o temperature T under
different magnetic fields can also be scaled by T - (H-Hc)u with u = 1/2.
Secondly, a combination of compensated electron-hole pockets and a possible
electronic structure phase transition induced by the temperature have been
validated in Td-MoTe2 by the STM/STS experiments. Compared with the STS of
Td-MoTe2 single crystal under H = 0, the STS hardly changes even when the
applied field is up to 7 T. The origins of the t-o phenomenon in Td-MoTe2 are
discussed. Meanwhile, we analyzed the universality and applicability of the t-o
phenomenon in the extreme MR materials with almost balanced hole and electron
densities as well as with other systems where the density of hole or electron
is in dominant position.

###Anomalous Nernst effect in type-II Weyl semimetals|Subhodip Saha,Sumanta Tewari###

Anomalous Nernst effect in type-II Weyl semimetals. Topological Weyl semimetals (WSM), a new state of quantum matter with gapless
nodal bulk spectrum and open Fermi arc surface states, have recently sparked
enormous interest in condensed matter physics. Based on the symmetry and
fermiology, it has been proposed that WSMs can be broadly classified into two
types, type-I and type-II Weyl semimetals. While the undoped, conventional,
type-I WSMs have point like Fermi surface and vanishing density of states (DOS)
at the Fermi energy, the type-II Weyl semimetals break Lorentz symmetry
explicitly and have tilted conical spectra with electron and hole pockets
producing finite DOS at the Fermi level. The tilted conical spectrum and finite
DOS at Fermi level in type-II WSMs have recently been shown to produce
interesting effects such as a chiral anomaly induced longitudinal
magnetoresistance that is strongly anisotropic in direction and a novel
anomalous Hall effect. In this work, we consider the anomalous Nernst effect in
type-II WSMs in the absence of an external magnetic field using the framework
of semi-classical Boltzmann theory. Based on both a linearized model of
time-reversal breaking WSM with a higher energy cut-off and a more realistic
lattice model, we show that the anomalous Nernst response in these systems is
strongly anisotropic in space, and can serve as a reliable signature of type-II
Weyl semimetals in a host of magnetic systems with spontaneously broken time
reversal symmetry.

###Observation of Open-Orbit Fermi Surface Topology in Extremely Large Magnetoresistance Semimetal MoAs$_2$|R. Lou,Y. F. Xu,L. -X. Zhao,Z. -Q. Han,P. -J. Guo,M. Li,J. -C. Wang,B. -B. Fu,Z. -H. Liu,Y. -B. Huang,P. Richard,T. Qian,K. Liu,G. -F. Chen,H. M. Weng,H. Ding,S. -C. Wang###

Observation of Open-Orbit Fermi Surface Topology in Extremely Large Magnetoresistance Semimetal MoAs$_2$. While recent advances in band theory and sample growth have expanded the
series of extremely large magnetoresistance (XMR) semimetals in transition
metal dipnictides $TmPn_2$ ($Tm$ = Ta, Nb; $Pn$ = P, As, Sb), the experimental
study on their electronic structure and the origin of XMR is still absent.
Here, using angle-resolved photoemission spectroscopy combined with
first-principles calculations and magnetotransport measurements, we performed a
comprehensive investigation on MoAs$_2$, which is isostructural to the $TmPn_2$
family and also exhibits quadratic XMR. We resolve a clear band structure well
agreeing with the predictions. Intriguingly, the unambiguously observed Fermi
surfaces (FSs) are dominated by an open-orbit topology extending along both the
[100] and [001] directions in the three-dimensional Brillouin zone. We further
reveal the trivial topological nature of MoAs$_2$ by bulk parity analysis.
Based on these results, we examine the proposed XMR mechanisms in other
semimetals, and conclusively ascribe the origin of quadratic XMR in MoAs$_2$ to
the carriers motion on the FSs with dominant open-orbit topology, innovating in
the understanding of quadratic XMR in semimetals.

###Stabilizing isolated skyrmions at low magnetic fields exploiting vanishing magnetic anisotropy|Marie Hervé,Bertrand Dupé,Rafael Lopes,Marie Böttcher,Maximiliano D. Martins,Timofey Balashov,Lukas Gerhard,Jairo Sinova,Wulf Wulfhekel###

Stabilizing isolated skyrmions at low magnetic fields exploiting vanishing magnetic anisotropy. Skyrmions are topologically protected non-collinear magnetic structures.
Their stability and dynamics, arising from their topological character, have
made them ideal information carriers e.g. in racetrack memories. The success of
such a memory critically depends on the ability to stabilize and manipulate
skyrmions at low magnetic fields. The driving force for skyrmion formation is
the non-collinear Dzyaloshinskii-Moriya exchange interaction (DMI) originating
from spin-orbit coupling (SOC). It competes with both the nearest neighbour
Heisenberg exchange interaction and the magnetic anisotropy, which favour
collinear states. While skyrmion lattices might evolve at vanishing magnetic
fields, the formation of isolated skyrmions in ultra-thin films so far required
the application of an external field which can be as high as several T. Here,
we show that isolated skyrmions in a monolayer (ML) of Co epitaxially grown on
a Ru(0001) substrate can be stabilized at magnetic fields as low as 100 mT.
Even though SOC is weak in the 4d element Ru, a homochiral spin spiral ground
state and isolated skyrmions could be detected and laterally resolved using a
combination of tunneling and anisotropic tunneling magnetoresistance effect in
spin-sensitive scanning tunneling microscopy (STM). Density functional theory
(DFT) calculations confirm these chiral magnetic textures, even though the
stabilizing DMI interaction is weak. We find that the key factor is the absence
of magnetocristalline anisotropy in this system which enables non-collinear
states to evolve in spite of weak SOC, opening up a wide choice of materials
beyond 5d elements.

###Spin-orbit torques from interfacial spin-orbit coupling for various interfaces|Kyoung-Whan Kim,Kyung-Jin Lee,Jairo Sinova,Hyun-Woo Lee,M. D. Stiles###

Spin-orbit torques from interfacial spin-orbit coupling for various interfaces. We use a perturbative approach to study the effects of interfacial spin-orbit
coupling in magnetic multilayers by treating the two-dimensional Rashba model
in a fully three-dimensional description of electron transport near an
interface. This formalism provides a compact analytic expression for
current-induced spin-orbit torques in terms of unperturbed scattering
coefficients, allowing computation of spin-orbit torques for various contexts,
by simply substituting scattering coefficients into the formulas. It applies to
calculations of spin-orbit torques for magnetic bilayers with bulk magnetism,
those with interface magnetism, a normal metal/ferromagnetic insulator
junction, and a topological insulator/ferromagnet junction. It predicts a
dampinglike component of spin-orbit torque that is distinct from any intrinsic
contribution or those that arise from particular spin relaxation mechanisms. We
discuss the effects of proximity-induced magnetism and insertion of an
additional layer and provide formulas for in-plane current, which is induced by
a perpendicular bias, anisotropic magnetoresistance, and spin memory loss in
the same formalism.

###Surface superconductivity in the Weyl semimetal MoTe2 detected by point contact spectroscopy|Yu. G. Naidyuk,O. E. Kvitnitskaya,D. L. Bashlakov,S. Aswartham,I. V. Morozov,I. O. Chernyavskii,G. Fuchs,S. -L. Drechsler,R. Hühne,K. Nielsch,B. Büchner,D. V. Efremov###

Surface superconductivity in the Weyl semimetal MoTe2 detected by point contact spectroscopy. MoTe2 is a Weyl semimetal, which exhibits unique non-saturating
magnetoresistance and strongly reinforced superconductivity under pressure.
Here, we demonstrate that a novel mesoscopic superconductivity at ambient
pressure arises on the surface of MoTe2 with a critical temperature up to 5 K
significantly exceeding the bulk Tc=0.1K. We measured the derivatives of I-V
curves for metallic hetero-contacts of MoTe2 with Ag or Cu, homo-contacts of
MoTe2 as well as "soft" point contacts (PCs). Large number of these
hetero-contacts exhibit a dV/dI dependence, which is characteristic for Andreev
reflection. It allows to determine the superconducting gap \Delta. The average
gap values are 2\Delta=1.30+/-0.15 meV with a 2\Delta/kBTc ratio of 3.7+/-0.4,
which slightly exceeds the standard BCS value of 3.52. Furthermore, the
temperature dependence of the gap follows a BCS-like behavior, which points to
a nodeless superconducting order parameter with some strong-coupling
renormalization. Remarkably, the observation of a "gapless-like" single minimum
in the dV/dI of "soft" PCs may indicate a topological superconducting state of
the MoTe2 surface as these contacts probe mainly the interface and avoid
additional pressure effect. Therefore, MoTe2 might be a suitable material to
study new forms of topological superconductivity.

###Pressure-induced spin reorientation transition in layered ferromagnetic insulator Cr2Ge2Te6|Zhisheng Lin,Mark Lohmann,Zulfikhar A. Ali,Chi Tang,Junxue Li,Wenyu Xing,Jiangnan Zhong,Shuang Jia,Wei Han,Sinisa Coh,Ward Beyermann,Jing Shi###

Pressure-induced spin reorientation transition in layered ferromagnetic insulator Cr2Ge2Te6. Anisotropic magnetoresistance (AMR) of Cr2Ge2Te6 (CGT), a layered
ferromagnetic insulator, is investigated under an applied hydrostatic pressure
up to 2 GPa. The easy axis direction of the magnetization is inferred from the
AMR saturation feature in the presence and absence of the applied pressure. At
zero applied pressure, the easy axis is along the c-direction or perpendicular
to the layer. Upon application of a hydrostatic pressure>1 GPa, the uniaxial
anisotropy switches to easy-plane anisotropy which drives the equilibrium
magnetization from the c-axis to the ab-plane at zero magnetic field, which
amounts to a giant magnetic anisotropy energy change (>100%). As the
temperature is increased across the Curie temperature, the characteristic AMR
effect gradually decreases and disappears. Our first-principles calculations
confirm the giant magnetic anisotropy energy change with moderate pressure and
assign its origin to the increased off-site spin-orbit interaction of Te atoms
due to a shorter Cr-Te distance. Such a pressure-induced spin reorientation
transition is very rare in three-dimensional ferromagnets, but it may be common
to other layered ferromagnets with similar crystal structures to CGT, and
therefore offers a unique way to control magnetic anisotropy.

###Spincaloric properties of epitaxial Co$_2$MnSi/MgO/Co$_2$MnSi magnetic tunnel junctions|Benjamin Geisler,Peter Kratzer###

Spincaloric properties of epitaxial Co$_2$MnSi/MgO/Co$_2$MnSi magnetic tunnel junctions. The electronic transport and spincaloric properties of epitaxial magnetic
tunnel junctions with half-metallic Co$_2$MnSi Heusler electrodes, MgO
tunneling barriers, and different interface terminations are investigated by
using first-principles calculations. A new approach to spincaloric properties
is presented that circumvents the linear response approximation inherent in the
Seebeck coefficient and compared to the method of Sivan and Imry. This approach
supports two different temperatures in the two electrodes and provides the
exact current and/or voltage response of the system. Moreover, it accounts for
temperature-dependent chemical potentials in the electrodes and finite-bias
effects. We find that especially the former are important for obtaining
qualitatively correct results, even if the variations of the chemical
potentials are small. It is shown how the spincaloric properties can be
tailored by the choice of the growth conditions. We find a large effective and
spin-dependent Seebeck coefficient of $-65$ $\mu$V/K at room temperature for
the purely Co-terminated interface. We suggest to use such interfaces in
thermally operated magnetoresistive random access memory modules, which exploit
the magneto-Seebeck effect, to maximize the thermally induced readout voltage.

###Impact of thermal fluctuations on transport in antiferromagnetic semimetals|Youngseok Kim,Moon Jip Park,David G. Cahill,Matthew J. Gilbert###

Impact of thermal fluctuations on transport in antiferromagnetic semimetals. Recent demonstrations on manipulating antiferromagnetic (AF) order have
triggered a growing interest in antiferromagnetic metal (AFM), and potential
high-density spintronic applications demand further improvements in the
anisotropic magnetoresistance (AMR). The antiferromagnetic semimetals (AFS) are
newly discovered materials that possess massless Dirac fermions that are
protected by the crystalline symmetries. In this material, a reorientation of
the AF order may break the underlying symmetries and induce a finite energy
gap. As such, the possible phase transition from the semimetallic to insulating
phase gives us a choice for a wide range of resistance ensuring a large AMR. To
further understand the robustness of the phase transition, we study thermal
fluctuations of the AF order in AFS at a finite temperature. For macroscopic
samples, we find that the thermal fluctuations effectively decrease the
magnitude of the AF order by renormalizing the effective Hamiltonian. Our
finding suggests that the insulating phase exhibits a gap narrowing at elevated
temperatures, which leads to a substantial decrease in AMR. We also examine
spatially correlated thermal fluctuations for microscopic samples by solving
the microscopic Landau-Lifshitz-Gilbert equation finding a qualitative
difference of the gap narrowing in the insulating phase. For both cases, the
semimetallic phase shows a minimal change in its transmission spectrum
illustrating the robustness of the symmetry protected states in AFS. Our
finding may serve as a guideline for estimating and maximizing AMR of the AFS
samples at elevated temperatures.

###Spin-Hall magnetoresistance in a low-dimensional magnetic insulator|Saül Vélez,Vitaly N. Golovach,Juan M. Gomez-Perez,Cong Tinh Bui,F. Rivadulla,Luis E. Hueso,F. Sebastian Bergeret,Fèlix Casanova###

Spin-Hall magnetoresistance in a low-dimensional magnetic insulator. We observe an unusual behavior of the spin Hall magnetoresistance (SMR)
measured in a Pt ultra-thin film deposited on a ferromagnetic insulator, which
is a tensile-strained LaCoO3 (LCO) thin film with the Curie temperature Tc=85K.
The SMR displays a strong magnetic-field dependence below Tc, with the SMR
amplitude continuing to increase (linearly) with increasing the field far
beyond the saturation value of the ferromagnet. The SMR amplitude decreases
gradually with raising the temperature across Tc and remains measurable even
above Tc. Moreover, no hysteresis is observed in the field dependence of the
SMR. These results indicate that a novel low-dimensional magnetic system forms
on the surface of LCO and that the Pt/LCO interface decouples magnetically from
the rest of the LCO thin film. To explain the experiment, we revisit the
derivation of the SMR corrections and relate the spin-mixing conductances to
the microscopic quantities describing the magnetism at the interface. Our
results can be used as a technique to probe quantum magnetism on the surface of
a magnetic insulator.

###Magnetotransport of a 2DEG with anisotropic Rashba interaction at the LaAlO$_3$/SrTiO$_3$ interface|Azadeh Faridi,Reza Asgari,Abdollah Langari###

Magnetotransport of a 2DEG with anisotropic Rashba interaction at the LaAlO$_3$/SrTiO$_3$ interface. We investigate the magnetotransport properties of a two-dimensional electron
gas with anisotropic k-cubic Rashba interaction at the
$\rm{LaAlO_3}$/$\rm{SrTiO_3}$ interface. The Landau levels and density of
states of the system as well as the magnetotransport coefficients are
evaluated. A somehow anomalous beating pattern in low magnetic field regime is
found both in the density profile and magnetoresistivity. We discuss the impact
of electron density, Landau level broadening and Rashba spin-orbit constant on
the appearance of the beatings in low magnetic fields and find that at low
electron concentrations and not very strong spin-orbit interactions the
beatings smooth out. On the other hand, as the magnetic field increases, the
Zeeman term becomes the dominant splitting mechanism leading to the spin-split
peaks in SdH oscillations. We also show that the observation of the beatings in
low magnetic fields needs a system with rather higher carrier concentration so
that the beatings persist up to sufficiently large fields where the
oscillations are not smoothed out by Landau level broadening. The quantum Hall
plateaus are evaluated and we show the Chern number with both even and odd
values is replaced by the odd numbers when two subband energies are close with
spin degenerate energy levels. Along with the numerical evaluation of the
magnetotransport properties, a perturbative calculation is also performed which
can be used in the case of low densities and not very large filling factors.

###Interplay between interlayer exchange and stacking in CrI$_3$ bilayers|D. Soriano,C. Cardoso,J. Fernández-Rossier###

Interplay between interlayer exchange and stacking in CrI$_3$ bilayers. We address the interplay between stacking and interlayer exchange for
ferromagnetically ordered CrI$_3$, both for bilayers and bulk. Whereas bulk
CrI$_3$ is ferromagnetic, both magneto-optical and transport experiments show
that interlayer exchange for CrI$_3$ bilayers is antiferromagnetic. Bulk
CrI$_3$ is known to assume two crystal structures, rhombohedral and monoclinic,
that differ mostly in the stacking between monolayers. Below 210-220 Kelvin,
bulk CrI$_3$ orders in a rhombohedral phase. Our density functional theory
calculations show a very strong dependence of interlayer exchange and stacking.
Specifically, the ground states of both bulk and free-standing CrI$_3$ bilayers
are ferromagnetic for the rhombohedral phase. In contrast, the energy
difference between both configurations is more than one order of magnitude
smaller for the monoclinic phase, and eventually becomes antiferromagnetic when
either positive strain or on-site Hubbard interactions ($U \geq 3$) are
considered. We also explore the interplay between interlayer hybrydization and
stacking, using a Wannier basis, and between interlayer hybrydization and
relative magnetic alignment for CrI$_3$ bilayers, that helps to account for the
very large tunnel magnetoresistance obvserved in recent experiments.

###Spin transistor built on 2D van der Waals heterostructures|Shengwei Jiang,Lizhong Li,Zefang Wang,Jie Shan,Kin Fai Mak###

Spin transistor built on 2D van der Waals heterostructures. Spin transistors (whose on-off operation is achieved by
electric-field-controlled spin orientation 1), if realized, can revolutionize
modern electronics through the implementation of a faster and a more
energy-efficient performance as well as non-volatile data storage 2, 3. The
original proposal by Datta and Das 1 that relies on electric-field-controlled
spin precession in a semiconductor channel faces significant challenges
including inefficient spin injection, spin relaxation and spread of the spin
precession angle 4, 5. Recent demonstration of electric-field switching of
magnetic order 6-8 and spin filtering 9-12 in two-dimensional magnetic
insulator CrI3 has inspired a new operational principle for spin transistors.
Here we demonstrate spin field-effect transistors based on dual-gated
graphene/CrI3 tunnel junctions. These devices show an ambipolar transistor
behavior and tunnel magnetoresistance widely tunable by gating when the CrI3
magnetic tunnel barrier undergoes an antiferromagnetic-ferromagnetic spin-flip
transition. Under a constant magnetic bias in the vicinity of the spin-flip
transition, the gate voltage can repeatedly alter the device between a high and
a low conductance state with a large hysteresis. This new spin transistor
concept based on the electric-field-controlled spin-flip transition in the
magnetic tunnel barrier is immune to interface imperfections and allows spin
injection, control and detection in a single device.

###Voltage Control of a van der Waals Spin-Filter Magnetic Tunnel Junction|Tiancheng Song,Matisse Wei-Yuan Tu,Caitlin Carnahan,Xinghan Cai,Takashi Taniguchi,Kenji Watanabe,Michael A. McGuire,David H. Cobden,Di Xiao,Wang Yao,Xiaodong Xu###

Voltage Control of a van der Waals Spin-Filter Magnetic Tunnel Junction. Atomically thin chromium triiodide (CrI3) has recently been identified as a
layered antiferromagnetic insulator, in which adjacent ferromagnetic monolayers
are antiferromagnetically coupled. This unusual magnetic structure naturally
comprises a series of anti-aligned spin filters which can be utilized to make
spin-filter magnetic tunnel junctions with very large tunneling
magnetoresistance (TMR). Here we report voltage control of TMR formed by
four-layer CrI3 sandwiched by monolayer graphene contacts in a dual-gated
structure. By varying the gate voltages at fixed magnetic field, the device can
be switched reversibly between bistable magnetic states with the same net
magnetization but drastically different resistance (by a factor of ten or
more). In addition, without switching the state, the TMR can be continuously
modulated between 17,000% and 57,000%, due to the combination of spin-dependent
tunnel barrier with changing carrier distributions in the graphene contacts.
Our work demonstrates new kinds of magnetically moderated transistor action and
opens up possibilities for voltage-controlled van der Waals spintronic devices.

###Nematicity of correlated systems driven by anisotropic chemical phase separation|Ye Yuan,René Hübner,Magdalena Birowska,Chi Xu,Mao Wang,Slawomir Prucnal,Rafal Jakiela,Kay Potzger,Roman Böttger,Stefan Facsko,Jacek A. Majewski,Manfred Helm,Maciej Sawicki,Shengqiang Zhou,Tomasz Dietl###

Nematicity of correlated systems driven by anisotropic chemical phase separation. The origin of nematicity, i.e., in-plane rotational symmetry breaking, and in
particular the relative role played by spontaneous unidirectional ordering of
spin, orbital, or charge degrees of freedom, is a challenging issue of
magnetism, unconventional superconductivity, and quantum Hall effect systems,
discussed in the context of doped semiconductor systems, such as
Ga$_{1-x}$Mn$_x$As, Cu$_x$Bi$_2$Se$_3$, and Ga(Al)As/Al$_x$Ga$_{1-x}$As quantum
wells, respectively. Here, guided by our experimental and theoretical results
for In$_{1-x}$Fe$_x$As, we demonstrate that spinodal phase separation at the
growth surface (that has a lower symmetry than the bulk) can lead to a quenched
nematic order of alloy components, which then governs low temperature magnetic
and magnetotransport properties, in particular the magnetoresistance anisotropy
whose theory for the $C_{2v}$ symmetry group is advanced here. These findings,
together with earlier data for Ga$_{1-x}$Mn$_x$As, show under which conditions
anisotropic chemical phase separation accounts for the magnitude of transition
temperature to a collective phase or merely breaks its rotational symmetry. We
address the question to what extent the directional distribution of impurities
or alloy components setting in during the growth may account for the observed
nematicity in other classes of correlated systems.

###Galvanomagnetic properties of the putative type-II Dirac semimetal PtTe$_2$|Orest Pavlosiuk,Dariusz Kaczorowski###

Galvanomagnetic properties of the putative type-II Dirac semimetal PtTe$_2$. Platinum ditelluride has recently been characterized, based on angle-resolved
photoemission spectroscopy data and electronic band structure calculations, as
a possible representative of type-II Dirac semimetals. Here, we report on the
magnetotransport behavior (electrical resistivity, Hall effect) in this
compound, investigated on high-quality single-crystalline specimens. The
magnetoresistance (MR) of PtTe$_2$ is large (over $3000\%$ at $T=1.8$ K in
$B=9$ T) and unsaturated in strong fields in the entire temperature range
studied. The MR isotherms obey a Kohler's type scaling with the exponent $m$ =
1.69, different from the case of ideal electron-hole compensation. In applied
magnetic fields, the resistivity shows a low-temperature plateau,
characteristic of topological semimetals. In strong fields, well-resolved
Shubnikov - de Haas (SdH) oscillations with two principle frequencies were
found, and their analysis yielded charge mobilities of the order of
$10^3\,\rm{cm^2V^{-1}s^{-1}}$ and rather small effective masses of charge
carriers, $0.11m_e$ and $0.21m_e$. However, the extracted Berry phases point to
trivial character of the electronic bands involved in the SdH oscillations. The
Hall effect data corroborated a multi-band character of the electrical
conductivity in PtTe$_2$, with moderate charge compensation.

###Sign-alternating photoconductivity and magnetoresistance oscillations induced by terahertz radiation in HgTe quantum wells|M. Otteneder,I. A. Dmitriev,S. Candussio,M. L. Savchenko,D. A. Kozlov,V. V. Bel'kov,Z. D. Kvon,N. N. Mikhailov,S. A. Dvoretsky,S. D. Ganichev###

Sign-alternating photoconductivity and magnetoresistance oscillations induced by terahertz radiation in HgTe quantum wells. We report on the observation of terahertz radiation induced photoconductivity
and of terahertz analog of the microwave-induced resistance oscillations (MIRO)
in HgTe-based quantum well (QW) structures of different width. The MIRO-like
effect has been detected in QWs of 20 nm thickness with inverted band structure
and a rather low mobility of about 3 $\times$ 10$^5$ cm$^2$/V s. In a number of
other structures with QW widths ranging from 5 to 20 nm and lower mobility we
observed an unconventional non-oscillatory photoconductivity signal which
changes its sign upon magnetic field increase. This effect was observed in
structures characterized by both normal and inverted band ordering, as well as
in QWs with critical thickness and linear dispersion. In samples having Hall
bar and Corbino geometries an increase of the magnetic field resulted in a
single and double change of the sign of the photoresponse, respectively. We
show that within the bolometric mechanism of the photoresponse these unusual
features imply a non-monotonic behavior of the transport scattering rate, which
should decrease (increase) with temperature for magnetic fields below (above)
the certain value. This behavior is found to be consistent with the results of
dark transport measurements of magnetoresistivity at different sample
temperatures. Our experiments demonstrate that photoconductivity is a very
sensitive probe of the temperature variations of the transport characteristics,
even those that are hardly detectable using standard transport measurements.

###Giant negative magnetoresistance and kinetic arrest of first-order ferrimagnetic-antiferomagnetic transition in Ge doped Mn$_2$Sb|Vikram Singh,R Rawat,Pallavi Kushwaha###

Giant negative magnetoresistance and kinetic arrest of first-order ferrimagnetic-antiferomagnetic transition in Ge doped Mn$_2$Sb. Effect of Ge substitution on first order ferrimagnetic (FRI) -
antiferromagnetic (AFM) transition in Mn$_2$Sb has been studied. It shows that
transition temperature (T$_t$) can be tuned between 119~K - 271~K by
substituting 2.5-10\% Ge at Sb site in Mn$_2$Sb. The variation of density of
state at Fermi level N(E$_f$) with Ge substitution shows that dN(E)/dE is
positive at E$_f$ in the AFM state. With the application of magnetic field
T$_t$ shifts to low temperature, which results in a giant negative
magnetoresistance (MR) reaching a value of 70\% for 2.5\% substitution. Our
results show that FRI to AFM transformation during cooling stops around 35 K,
even though it remains incomplete. It along with non-monotonic variation of
lower critical field, open loop in isothermal MR and increasing difference in
zero field cooled warming (ZFCW) and field cooled warming (FCW) resistivity
with increasing magnetic field shows that FRI to AFM transition is kinetically
arrested in the case of 2.5\% Ge substitution.

###Anisotropies and magnetic phase transitions in insulating antiferromagnets determined by a Spin-Hall magnetoresistance probe|Romain Lebrun,Andrew Ross,Olena Gomonay,Scott Bender,Lorenzo Baldrati,Florian Kronast,Alireza Qaiumzadeh,Jairo Sinova,Arne Brataas,Rembert Duine,Mathias Kläui###

Anisotropies and magnetic phase transitions in insulating antiferromagnets determined by a Spin-Hall magnetoresistance probe. We demonstrate that we can determine the antiferromagnetic anisotropies and
the bulk Dzyaloshinskii-Moriya fields of the insulating iron oxide hematite,
{\alpha}-Fe2O3, using a surface sensitive spin-Hall magnetoresistance (SMR)
technique. We develop an analytical model that in combination with SMR
measurements, allow for the identification of the material parameters of this
prototypical antiferromagnet over a wide range of temperatures and magnetic
field values. Using devices with different orientations, we demonstrate that
the SMR response strongly depends on the direction of the charge current with
respect to the magneto-crystalline anisotropies axis. We show that we can
extract the anisotropies over a wide temperature range including across the
Morin phase transition. We observe that the electrical response is dominated by
the orientation of the antiferromagnetic N\'eel order parameter, rather than by
the emergent weak magnetic moment. Our results highlight that the surface
sensitivity of the SMR allows accessing the magnetic anisotropies of
antiferromagnetic crystals and in particular thin films where other methods to
determine anisotropies such as bulk-sensitive magnetic susceptibility
measurements do not provide sufficient sensitivity.

###Field-induced phases in a heavy-fermion U(Ru$_{0.92}$Rh$_{0.08}$)$_{2}$Si$_{2}$ single crystal|K. Prokes,T. Förster,Y. -K. Huang,J. A. Mydosh###

Field-induced phases in a heavy-fermion U(Ru$_{0.92}$Rh$_{0.08}$)$_{2}$Si$_{2}$ single crystal. We report the high-field induced magnetic phases and phase diagram of a high
quality \urxrs~single crystal prepared using a modified Czochralski method. Our
study, that combines high-field magnetization and electrical resistivity
measurements, shows for fields applied along the $c$-axis direction three
field-induced magnetic phase transitions at $\mu_{0} H_{c1}$ = 21.60 T,
$\mu_{0} H_{c2}$ = 37.90 T and $\mu_{0} H_{c3}$ = 38.25 T, respectively. In
agreement with a microscopic up-up-down arrangement of the U magnetic moments
the phase above $H_{c1}$ has a magnetization of about one third of the
saturated value. In contrast the phase between $H_{c2}$ and $H_{c3}$ has a
magnetization that is a factor of two lower than above the $H_{c3}$, where a
polarized Fermi-liquid state with a saturated moment $M_{s}$ $\approx$ 2.1
$\mu_{B}$/U is realized. Most of the respective transitions are reflected in
the electrical resistivity as sudden drastic changes. Most notably, the phase
between $H_{c1}$ and $H_{c2}$ exhibits substantially larger values. As the
temperature increases, transitions smear out and disappear above $\approx$ 15
K. However, a substantial magnetoresistance is observed even at temperatures as
high as 80 K. Due to a strong uniaxial magnetocrystalline anisotropy a very
small field effect is observed for fields apllied perpendicular to the $c$-axis
direction.

###A Piezoelectric, Strain-Controlled Antiferromagnetic Memory Insensitive to Magnetic Fields|Han Yan,Zexin Feng,Shunli Shang,Xiaoning Wang,Zexiang Hu,Jinhua Wang,Zengwei Zhu,Hui Wang,Zuhuang Chen,Hui Hua,Wenkuo Lu,Jingmin Wang,Peixin Qin,Huixin Guo,Xiaorong Zhou,Zhaoguogang Leng,Zikui Liu,Chengbao Jiang,Michael Coey,Zhiqi Liu###

A Piezoelectric, Strain-Controlled Antiferromagnetic Memory Insensitive to Magnetic Fields. Spintronic devices based on antiferromagnetic (AFM) materials hold the
promise of fast switching speeds and robustness against magnetic fields.
Different device concepts have been predicted and experimentally demonstrated,
such as low-temperature AFM tunnel junctions that operate as spin-valves, or
room-temperature AFM memory, for which either thermal heating in combination
with magnetic fields, or N\'eel spin-orbit torque is used for the information
writing process. On the other hand, piezoelectric materials were employed to
control magnetism by electric fields in multiferroic heterostructures, which
suppresses Joule heating caused by switching currents and may enable low
energy-consuming electronic devices. Here, we combine the two material classes
to explore changes of the resistance of the high-N\'eel-temperature
antiferromagnet MnPt induced by piezoelectric strain. We find two non-volatile
resistance states at room temperature and zero electric field, which are stable
in magnetic fields up to 60 T. Furthermore, the strain-induced resistance
switching process is insensitive to magnetic fields. Integration in a tunnel
junction can further amplify the electroresistance. The tunneling anisotropic
magnetoresistance reaches ~11.2% at room temperature. Overall, we demonstrate a
piezoelectric, strain-controlled AFM memory which is fully operational in
strong magnetic fields and has potential for low-energy and high-density memory
applications.

###Inducing out-of-plane precession of magnetization for microwave assisted magnetic recording using an oscillating polarizer in spin torque oscillator|W. Zhou,H. Sepehri-Amin,T. Taniguchi,S. Tamaru,Y. Sakuraba,S. Kasai,H. Kubota,K. Hono###

Inducing out-of-plane precession of magnetization for microwave assisted magnetic recording using an oscillating polarizer in spin torque oscillator. We investigated the dynamics of a novel design of spin torque oscillator
(STO) for microwave assisted magnetic recording. Using Ni$_{80}$Fe$_{20}$
(NiFe) as the polarizer and Fe$_{67}$Co$_{33}$ (FeCo) as the field generating
layer, we experimentally observed the magnetization reversal of NiFe, followed
by multiple signals in the power spectra as the bias voltage increased. The
signals reflected the out-of-plane precession (OPP) mode oscillation of both
FeCo and NiFe, as well as the magnetoresistance effect of the STO device, which
had the frequency equal to the difference between the oscillation frequency of
NiFe and FeCo. Such dynamics were reproduced by micromagnetic simulation. In
addition to the merit of realizing the OPP mode oscillation with a simple and
thin structure suitable for a narrow gap recording head, the experimental
results using this design suggested that a large cone angle of $\sim$
70$^{\circ}$ for the OPP mode oscillation of FeCo was achieved, which was
estimated based on the macrospin model.

###Unoccupied surface and interface states in Pd thin films deposited on Fe/Ir(111) surface|Mohammed Bouhassoune,Imara L. Fernandes,Stefan Blügel,Samir Lounis###

Unoccupied surface and interface states in Pd thin films deposited on Fe/Ir(111) surface. We present a systematic first-principles study of the electronic surface
states and resonances occuring in thin films of Pd of various thicknesses
deposited on a single ferromagnetic monolayer of Fe on top of Ir(111)
substrate. This system is of interest since one Pd layer deposited on
Fe/Ir(111) hosts small magnetic skyrmions. The latter are topological magnetic
objects with swirling spin-textures with possible implications in the context
of spintronic devices since they have the potential to be used as magnetic bits
for information technology. The stabilization, detection and manipulation of
such non-collinear magnetic entities require a quantitative investigation and a
fundamental understanding of their electronic structure. Here we investigate
the nature of the unoccupied electronic states in Pd/Fe/Ir(111), which are
essential in the large spin-mixing magnetoresistance (XMR) signature captured
using non spin-polarized scanning tunnelling microscopy [Crum et al., Nat.
Commun. {\bf 6} 8541 (2015); Hanneken et al., Nat. Nanotech. {\bf 10}, 1039
(2015)]. To provide a complete analysis, we investigate bare Fe/Ir(111) and
Pd$_{n=2,7}$/Fe/Ir(111) surfaces. Our results demonstrate the emergence of
surface and interface states after deposition of Pd monolayers, which are
strongly impacted by the large spin-orbit coupling of Ir surface.

###Fluctuations and magnetoresistance oscillations near the half-filled Landau level|Amartya Mitra,Michael Mulligan###

Fluctuations and magnetoresistance oscillations near the half-filled Landau level. We study theoretically the magnetoresistance oscillations near a half-filled
lowest Landau level ($\nu = 1/2$) that result from the presence of a periodic
one-dimensional electrostatic potential. We use the Dirac composite fermion
theory of Son [Phys. Rev. X 5 031027 (2015)], where the $\nu=1/2$ state is
described by a $(2+1)$-dimensional theory of quantum electrodynamics. We extend
previous work that studied these oscillations in the mean-field limit by
considering the effects of gauge field fluctuations within a large flavor
approximation. A self-consistent analysis of the resulting Schwinger--Dyson
equations suggests that fluctuations dynamically generate a Chern-Simons term
for the gauge field and a magnetic field-dependent mass for the Dirac composite
fermions away from $\nu=1/2$. We show how this mass results in a shift of the
locations of the oscillation minima that improves the comparison with
experiment [Kamburov et. al., Phys. Rev. Lett. 113, 196801 (2014)]. The
temperature-dependent amplitude of these oscillations may enable an alternative
way to measure this mass. This amplitude may also help distinguish the Dirac
and Halperin, Lee, and Read composite fermion theories of the half-filled
Landau level.

###Tunneling anisotropic magnetoresistance of Pb and Bi adatoms and dimers on Mn/W(110): A first-principles study|Soumyajyoti Haldar,Mara Gutzeit,Stefan Heinze###

Tunneling anisotropic magnetoresistance of Pb and Bi adatoms and dimers on Mn/W(110): A first-principles study. We show that Pb and Bi adatoms and dimers have a large tunneling anisotropic
magnetoresistance (TAMR) of up to 60% when adsorbed on a magnetic
transition-metal surface due to strong spin-orbit coupling and the
hybridization of 6p orbitals with 3d states of the magnetic layer. Using
density functional theory, we have explored the TAMR effect of Pb and Bi
adatoms and dimers adsorbed on a Mn monolayer on W(110). This surface exhibits
a noncollinear cycloidal spin spiral ground state with an angle of 173$^\circ$
between neighboring spins which allows to rotate the spin quantization axis of
an adatom or dimer quasi-continuously and is ideally suited to explore the
angular dependence of TAMR using scanning tunneling microscopy (STM). We find
that the induced magnetic moments of Pb and Bi adatoms and dimers are small,
however, the spin-polarization of the local density of states (LDOS) is still
very large. The TAMR obtained from the anisotropy of the vacuum LDOS is up to
50-60 % for adatoms. For dimers the TAMR depends sensitively on the dimer
orientation with respect to the crystallographic directions of the surface due
to the formation of bonds between the adatoms with the Mn surface atoms and the
symmetry of the spin-orbit coupling induced mixing. Dimers oriented along the
spin spiral direction of the Mn monolayer display the largest TAMR of 60 %
which is due to hybrid 6p-3d states of the dimers and the Mn layer

###Electronic Transport Evidence for Topological Nodal-Line Semimetals of ZrGeSe single crystals|Lei Guo,Ting-Wei Chen,Chen Chen,Lei Chen,Yang Zhang,Guan-Yin Gao,Jie Yang,Xiao-Guang Li,Wei-Yao Zhao,Shuai Dong,Ren-Kui Zheng###

Electronic Transport Evidence for Topological Nodal-Line Semimetals of ZrGeSe single crystals. Although the band topology of ZrGeSe has been studied via magnetic torque
technique, the electronic transport behaviors related to the relativistic
Fermions in ZrGeSe are still unknown. Here, we first report systematic
electronic transport properties of high-quality ZrGeSe single crystals under
magnetic fields up to 14 T. Resistivity plateaus of temperature dependent
resistivity curves both in the presence and absence of magnetic fields as well
as large, non-saturating magnetoresistance in low-temperature region were
observed. By analyzing the temperature- and angular-dependent Shubnikov-de Haas
oscillations and fitting it via the Lifshitz-Kosevich (LK) formula with the
Berry phase being taken into account, we proved that Dirac fermions dominate
the electronic transport behaviors of ZrGeSe and the presence of non-trivial
Berry phase. First principles calculations demonstrate that ZrGeSe possesses
Dirac bands and normal bands near Fermi surface, resulting in the observed
magnetotransport phenomena. These results demonstrate that ZrGeSe is a
topological nodal-line semimetal, which provides a fundamentally important
platform to study the quantum physics of topological semimetals.

###Strain-driven nematicity of the odd-parity superconductivity in Sr$_x$Bi$_2$Se$_3$|A. Yu. Kuntsevich,M. A. Bryzgalov,V. P. Martovitskii,R. S. Akzyanov,Yu. G. Selivanov,A. L. Rakhmanov###

Strain-driven nematicity of the odd-parity superconductivity in Sr$_x$Bi$_2$Se$_3$. We present a novel experimental evidence for the odd-parity nematic
superconductivity in high-quality single crystals of doped topological
insulator Sr$_x$Bi$_2$Se$_3$. The X-ray diffraction shows that the grown single
crystals are either weakly stretched or compressed uniaxially in the basal
plane along one of the crystal axis. We show that in the superconducting state,
the upper critical magnetic field $H_{c2}$ has a two-fold rotational symmetry
and depends on the sign of the strain: in the stretched samples, the maximum of
$H_{c2}$ is achieved when the in-plane magnetic field is transverse to the
strain axis, while in the compressed samples this maximum is observed when the
field is along the strain direction. This result is naturally explained within
a framework of the odd-parity nematic superconductivity coupled to the strain.
Magnetoresistance in the normal state is independent of the current direction
and also has a two-fold rotational symmetry that demonstrates the nematicity of
the electronic system in the normal state.

###Interlayer quantum transport in Dirac semimetal BaGa$_2$|Sheng Xu,Changhua Bao,Yi-Yan Wang,Peng-Jie Guo,Qiao-He Yu,Lin-Lin Sun,Yuan Su,Kai Liu,Zhong-Yi Lu,Shuyun Zhou,Tian-Long Xia###

Interlayer quantum transport in Dirac semimetal BaGa$_2$. Quantum limit is quite easy to achieve once the band crossing exists exactly
at the Fermi level ($E_F$) in topological semimetals. In multilayered Dirac
fermion system, the density of Dirac fermions on the zeroth Landau levels (LLs)
increases in proportion to the magnetic field, resulting in intriguing angle-
and field-dependent interlayer tunneling conductivity near the quantum limit.
BaGa$_2$ is an example of multilayered Dirac semimetal with anisotropic Dirac
cone close to $E_F$, providing a good platform to study its interlayer
transport properties. In this paper, we report the negative interlayer
magnetoresistance (NIMR, I//c and B//c) induced by the tunneling of Dirac
fermions on the zeroth LLs of neighbouring Ga layers in BaGa$_2$. When the
field deviates from the c-axis, the interlayer resistivity $\rho_{zz}(\theta)$
increases and finally results in a peak with the field perpendicular to the
c-axis. These unusual interlayer transport properties (NIMR and resistivity
peak with B$\perp$c) are observed together for the first time in Dirac
semimetal under ambient pressure and are well explained by the model of
tunneling between Dirac fermions in the quantum limit.

###Unveiling Quadrupolar Kondo Effect in the Heavy Fermion Superconductor PrV$_2$Al$_{20}$|Mingxuan Fu,Akito Sakai,Naoki Sogabe,Masaki Tsujimoto,Yosuke Matsumoto,Satoru Nakatsuji###

Unveiling Quadrupolar Kondo Effect in the Heavy Fermion Superconductor PrV$_2$Al$_{20}$. Heavy fermion metals hosting multipolar local moments set a new stage for
exploring exotic spin-orbital entangled quantum phases. In such systems, the
quadrupolar Kondo effect serves as the key ingredient in the orbital-driven
non-Fermi liquid (NFL) behavior and quantum critical phenomena. The cubic heavy
fermion superconductor Pr$Tr_2$Al$_{20}$ ($Tr$: Ti, V) is a prime candidate for
realizing the quadrupolar Kondo lattice. Here, we present a systematic study of
the NFL phenomena in PrV$_2$Al$_{20}$ based on magnetoresistance (MR), magnetic
susceptibility and specific heat measurements. Upon entering the NFL regime, we
observe a universal scaling behavior expected for the quadrupolar Kondo lattice
in PrV$_2$Al$_{20}$, which indicates a prominent role of the quadrupolar Kondo
effect in driving the NFL behavior. Deviations from this scaling relation occur
below $\sim 8$ K, accompanied by a sign change in the MR and a power-law
divergence in the specific heat. This anomalous low-temperature state points to
the presence of other mechanisms which are not included in the theory, such as
heavy fermion coherence or multipolar quantum critical fluctuations.

###A Synthetic Skyrmion Platform with Robust Tunability|Yong Li,Qiyuan Feng,Sihua Li,Ke Huang,Weiliang Gan,Haibiao Zhou,Xiangjun Jin,Xiao Renshaw Wang,Fusheng Ma,Qingyou Lu,Wen Siang Lew###

A Synthetic Skyrmion Platform with Robust Tunability. Magnetic skyrmions are topologically non-trivial spin structure, and their
existence in ferromagnetically coupled multilayers has been reported with
disordered arrangement. In these multilayers, the heavy metal spacing layers
provide an interfacial Dzyaloshinskii-Moriya interaction (DMI) for stabilizing
skyrmions at the expense of interlayer exchanging coupling (IEC). To meet the
functional requirement of ordered/designable arrangement, in this work, we
proposed and experimentally demonstrated a scenario of skyrmion nucleation
using nanostructured synthetic antiferromagnetic (SAF) multilayers. Instead of
relying on DMI, the antiferromagnetic IEC in the SAF multilayers fulfills the
role of nucleation and stabilization of skyrmions. The IEC induced skyrmions
were identified directly imaged with MFM and confirmed by magnetometry and
magnetoresistance measurements as well as micromagnetic simulation.
Furthermore, the robustness of the proposed skyrmion nucleation scenario was
examined against temperature (from 4.5 to 300 K), device size (from 400 to 1200
nm), and different lattice designs. Hence, our results provide a synthetic
skyrmion platform meeting the functional needs in magnonic and spintronic
applications.

###Superconducting phase transitions in disordered NbTiN films|M. V. Burdastyh,S. V. Postolova,T. Proslier,S. S. Ustavshikov,A. V. Antonov,V. M. Vinokur,A. Yu. Mironov###

Superconducting phase transitions in disordered NbTiN films. The suppression of superconductivity in disordered systems is a fundamental
problem of condensed matter physics. Here we investigate the superconducting
niobium-titanium-nitride (Nb_{1-x}Ti_{x}N) thin films grown by atomic layer
deposition (ALD) where disorder is controlled by the slight tuning of the ALD
process parameters. We observe the smooth crossover from the disorder-driven
superconductor-normal metal transition (often reffered to as fermionic
mechanism) to the case where bosonic mechanism dominates and increasing
disorder leads to formation of metal with Cooper pairing. We show that, in
moderately disordered films, the transition to zero-resistance state occurs in
a full agreement with the conventional theories of superconducting fluctuations
and Berezinskii-Kosterlitz-Thouless transition. However, the critically
disordered films violate this accord showing low-temperature features possibly
indicating the Bose metal phase. We show that it is the interrelation between
film's sheet resistance in the maximum, R_{max}, of the resistive curve R(T)
and R_q = h/4e^2 that distinguishes between these two behaviors. We reveal the
characteristic features in magnetoresistance of the critically disordered films
with R_{max} > R_q

###Room temperature 2D ferromagnetism in few-layered 1$T$-CrTe$_{2}$|Xingdan Sun,Wanying Li,Xiao Wang,Qi Sui,Tongyao Zhang,Zhi Wang,Long Liu,Da Li,Shun Feng,Siyu Zhong,Hanwen Wang,Vincent Bouchiat,Manuel Nunez Regueiro,Nicolas Rougemaille,Johann Coraux,Zhenhua Wang,Baojuan Dong,Xing Wu,Teng Yang,Guoqiang Yu,Bingwu Wang,Zheng Vitto Han,Xiufeng Han,Zhidong Zhang###

Room temperature 2D ferromagnetism in few-layered 1$T$-CrTe$_{2}$. Spin-related electronics using two dimensional (2D) van der Waals (vdW)
materials as a platform are believed to hold great promise for revolutionizing
the next generation spintronics. Although many emerging new phenomena have been
unravelled in 2D electronic systems with spin long-range orderings, the
scarcely reported room temperature magnetic vdW material has thus far hindered
the related applications. Here, we show that intrinsic ferromagnetically
aligned spin polarization can hold up to 316 K in a metallic phase of
1$T$-CrTe$_{2}$ in the few-layer limit. This room temperature 2D long range
spin interaction may be beneficial from an itinerant enhancement. Spin
transport measurements indicate an in-plane room temperature negative
anisotropic magnetoresistance (AMR) in few-layered CrTe$_{2}$, but a sign
change in the AMR at lower temperature, with -0.6$\%$ at 300 K and +5$\%$ at 10
K, respectively. This behavior may originate from the specific spin polarized
band structure of CrTe$_{2}$. Our findings provide insights into magnetism in
few-layered CrTe$_{2}$, suggesting potential for future room temperature
spintronic applications of such 2D vdW magnets.

###Immunity of nanoscale magnetic tunnel junctions to ionizing radiation|Eric Arturo Montoya,Jen-Ru Chen,Randy Ngelale,Han Kyu Lee,Hsin-Wei Tseng,Lei Wan,En Yang,Patrick Braganca,Ozdal Boyraz,Nader Bagherzadeh,Mikael Nilsson,Ilya N. Krivorotov###

Immunity of nanoscale magnetic tunnel junctions to ionizing radiation. Spin transfer torque magnetic random access memory (STT-MRAM) is a promising
candidate for next generation memory as it is non-volatile, fast, and has
unlimited endurance. Another important aspect of STT-MRAM is that its core
component, the nanoscale magnetic tunneling junction (MTJ), is thought to be
radiation hard, making it attractive for space and nuclear technology
applications. However, studies of the effects of high doses of ionizing
radiation on STT-MRAM writing process are lacking. Here we report measurements
of the impact of high doses of gamma and neutron radiation on nanoscale MTJs
with perpendicular magnetic anistropy used in STT-MRAM. We characterize the
tunneling magnetoresistance, the magnetic field switching, and the
current-induced switching before and after irradiation. Our results demonstrate
that all these key properties of nanoscale MTJs relevant to STT-MRAM
applications are robust against ionizing radiation. Additionally, we perform
experiments on thermally driven stochastic switching in the gamma ray
environment. These results indicate that nanoscale MTJs are promising building
blocks for radiation-hard non-von Neumann computing.

###Perdeuteration of poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene] (d-MEHPPV): control of microscopic charge-carrier spin-spin coupling and of magnetic-field effects in optoelectronic devices|Dani M. Stoltzfus,Gajadhar Joshi,Henna Popli,Shirin Jamali,Marzieh Kavand,Sebastian Milster,Tobias Grünbaum,Sebastian Bange,Adnan Nahlawi,Mandefro Y. Teferi,Sabastian I. Atwood,Anna E. Leung,Tamim A. Darwish,Hans Malissa,Paul L. Burn,John M. Lupton,Christoph Boehme###

Perdeuteration of poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene] (d-MEHPPV): control of microscopic charge-carrier spin-spin coupling and of magnetic-field effects in optoelectronic devices. Control of the effective local hyperfine fields in a conjugated polymer,
poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene] (MEHPPV), by
isotopic engineering is reported. These fields, evident as a
frequency-independent line broadening mechanism in electrically detected
magnetic resonance spectroscopy (EDMR), originate from the unresolved hyperfine
coupling between the electronic spin of charge carrier pairs and the nuclear
spins of surrounding hydrogen isotopes. The room temperature study of effects
caused by complete deuteration of this polymer through magnetoresistance,
magnetoelectroluminescence, coherent pulsed and multi-frequency EDMR, as well
as inverse spin-Hall effect measurements, confirm the weak hyperfine broadening
of charge carrier magnetic resonance lines. As a consequence, we can resolve
coherent charge-carrier spin-beating, allowing for direct measurements of the
magnitude of electronic spin-spin interactions. In addition, the weak hyperfine
coupling allows us to resolve substantial spin-orbit coupling effects in EDMR
spectra, even at low magnetic field strengths. These results illustrate the
dramatic influence of hyperfine fields on the spin physics of organic
light-emitting diode (OLED) materials at room temperature, and point to routes
to reaching exotic ultra-strong resonant-drive regimes needed for the study of
light-matter interactions.

###First-principles theory of proximity spin-orbit torque on a two-dimensional magnet: Current-driven antiferromagnet-to-ferromagnet reversible transition in bilayer CrI$_3$|Kapildeb Dolui,Marko D. Petrovic,Klaus Zollner,Petr Plechac,Jaroslav Fabian,Branislav K. Nikolic###

First-principles theory of proximity spin-orbit torque on a two-dimensional magnet: Current-driven antiferromagnet-to-ferromagnet reversible transition in bilayer CrI$_3$. The recently discovered two-dimensional (2D) magnetic insulator CrI$_3$ is an
intriguing case for basic research and spintronic applications since it is a
ferromagnet in the bulk, but an antiferromagnet in bilayer form, with its
magnetic ordering amenable to external manipulations. Using first-principles
quantum transport approach, we predict that injecting unpolarized charge
current parallel to the interface of bilayer-CrI$_3$/monolayer-TaSe$_2$ van der
Waals heterostructure will induce spin-orbit torque (SOT) and thereby driven
dynamics of magnetization on the first monolayer of CrI$_3$ in direct contact
with TaSe$_2$. By combining calculated complex angular dependence of SOT with
the Landau-Lifshitz-Gilbert equation for classical dynamics of magnetization,
we demonstrate that current pulses can switch the direction of magnetization on
the first monolayer to become parallel to that of the second monolayer, thereby
converting CrI$_3$ from antiferromagnet to ferromagnet while not requiring any
external magnetic field. We explain the mechanism of this reversible
current-driven nonequilibrium phase transition by showing that first monolayer
of CrI$_3$ carries current due to evanescent wavefunctions injected by metallic
transition metal dichalcogenide TaSe$_2$, while concurrently acquiring strong
spin-orbit coupling (SOC) via such proximity effect, whereas the second
monolayer of CrI$_3$ remains insulating. The transition can be detected by
passing vertical read current through the vdW heterostructure, encapsulated by
bilayer of hexagonal boron nitride and sandwiched between graphite electrodes,
where we find tunneling magnetoresistance of $\simeq 240$%.

###Resonance peak shift in the photo-current of ultrahigh-mobility two-dimensional electron systems|Jesus Inarrea###

Resonance peak shift in the photo-current of ultrahigh-mobility two-dimensional electron systems. We report on a theoretical study on the rise of strong peaks at the harmonics
of the cyclotron resonance in the irradiated magnetoresistance in ultraclean
two-dimensional electron systems. The motivation is the experimental
observation of a totally unexpected strong resistance peak showing up at the
second harmonic. We extend the radiation-driven electron orbit model
(previously developed to study photocurrent oscillations and zero resistance
states) to a ultraclean scenario that implies longer scattering time and longer
mean free path. Thus, when the mean free path is equivalent, in terms of
energy, to twice the cyclotron energy ($2\hbar w_{c}$), the electron behaves as
under an effective magnetic field twice the one really applied. Then, at high
radiation power and/or low temperature, a resistance spike can be observed {\it
at the second harmonic}. For even cleaner samples the energy distance could
increase to three or four times the cyclotron energy giving rise to resistance
peaks at higher harmonics (third, fourth, etc.), i.e., a resonance peak shift
to lower magnetic fields as the quality of the sample increases. Thus, by
selecting the sample mobility one automatically would select the radiation
resonance response without altering the radiation frequency.

###Anisotropy of the Upper Critical Field in the Heavy-Fermion Superconductor UTe2 under Pressure|Georg Knebel,Motoi Kimata,Michal Vališka,Fuminori Honda,Dexin Li,Daniel Braithwaite,Gérard Lapertot,William Knafo,Alexandre Pourret,Yoshiki J. Sato,Yusei Shimizu,Takumi Kihara,Jean-Pascal Brison,Jacques Flouquet,Dai Aoki###

Anisotropy of the Upper Critical Field in the Heavy-Fermion Superconductor UTe2 under Pressure. We studied the anisotropy of the superconducting upper critical field $H_{\rm
c2}$ in the heavy-fermion superconductor UTe$_2$ under hydrostatic pressure by
magnetoresistivity measurements. In agreement with previous experiments we
confirm that superconductivity disappears near a critical pressure $p_{\rm c}
\approx 1.5$~GPa, and a magnetically ordered state appears. The unusual $H_{\rm
c2}(T)$ at low temperatures for $H \parallel a$ suggests that the multiple
superconducting phases which appear under pressure have quite different $H_{\rm
c2}$. For a field applied along the hard magnetization $b$ axis $H_{\rm c2}
(0)$ is glued to the metamagnetic transition $H_{\rm m}$ which is suppressed
near $p_{\rm c}$. The suppression of $H_{\rm m}$ with pressure follows the
decrease of temperature $T_{\chi}^{\rm max}$, at the maximum in the
susceptibility along $b$. The strong reinforcement of $H_{\rm c2}$ at ambient
pressure for $H \parallel b$ above 16~T is rapidly suppressed under pressure
due to the increase of $T_{\rm sc}$ and the decrease of $H_{\rm m}$. The change
in the hierarchy of the anisotropy of $H_{\rm c2}(0)$ on approaching $p_{\rm
c}$ points out that the $c$ axis becomes the hard magnetization axis.

###Evidence of tunable magnetic coupling in hydrogenated graphene|Shimin Cao,Chuanwu Cao,Shibing Tian,Jian-Hao Chen###

Evidence of tunable magnetic coupling in hydrogenated graphene. A lot of efforts have been devoted to understanding the origin and effects of
magnetic moments induced in graphene with carbon atom vacancy, or light adatoms
like hydrogen or fluorine. At the meantime, the large negative
magnetoresistance (MR) widely observed in these systems is not well understood,
nor had it been associated with the presence of magnetic moments. In this
paper, we study the systematic evolution of the large negative MR of in-situ
hydrogenated graphene in ultra-high vacuum (UHV) environment. We find for most
combination of electron density ($n_e$) and hydrogen density ($n_H$), MR at
different temperature can be scaled to $\alpha=(\mu_BB)/[k_B(T-T^*)]$, where
$T^*$ is the Curie-Weiss temperature. The sign of $T^*$ indicates the existence
of tunable ferromagnetic-like ($T^* >0$) and anti-ferromagnetic-like ($T^* <0$)
coupling in hydrogenated graphene. However, the lack of hysteresis of MR or
anomalous Hall effect below $|T^*|$ points to the fact that long-range magnetic
order did not emerge, which we attribute to the competition of different
magnetic orders and disordered arrangement of magnetic moments on graphene. We
also find that localized impurity states introduced by H adatoms could modify
the capacitance of hydrogenated graphene. This work provides a new way to
extract information from large negative MR behavior and can be a key to help
understanding interactions of magnetic moments in graphene.

###Giant gate-controlled odd-parity magnetoresistance in one-dimensional channels with a magnetic proximity effect|Kosuke Takiguchi,Le Duc Anh,Takahiro Chiba,Ryota Fukuzawa,Takuji Takahashi,Masaaki Tanaka###

Giant gate-controlled odd-parity magnetoresistance in one-dimensional channels with a magnetic proximity effect. According to Onsager's principle, electrical resistance $R$ of general
conductors behaves as an even function of external magnetic field $B$. Only in
special circumstances, which involve time reversal symmetry (TRS) broken by
ferromagnetism, the odd component of $R$ against $B$ is observed. This unusual
phenomenon, called odd-parity magnetoresistance (OMR), was hitherto subtle (<
2%) and hard to control by external means. Here, we report a giant OMR as large
as 27% in edge transport channels of an InAs quantum well, which is magnetized
by a proximity effect from an underlying ferromagnetic semiconductor (Ga,Fe)Sb
layer. Combining experimental results and theoretical analysis using the
linearized Boltzmann's equation, we found that simultaneous breaking of both
the TRS by the magnetic proximity effect (MPE) and spatial inversion symmetry
(SIS) in the one-dimensional (1D) InAs edge channels is the origin of this
giant OMR. We also demonstrated the ability to turn on and off the OMR using
electrical gating of either TRS or SIS in the edge channels. These findings
provide a deep insight into the 1D semiconducting system with a strong magnetic
coupling.

###Electron spin relaxations of phosphorus donors in bulk silicon under large electric field|Daniel K. Park,Sejun Park,Hyejung Jee,Soonchil Lee###

Electron spin relaxations of phosphorus donors in bulk silicon under large electric field. Modulation of donor electron wavefunction via electric fields is vital to
quantum computing architectures based on donor spins in silicon. For practical
and scalable applications, the donor-based qubits must retain sufficiently long
coherence times in any realistic experimental conditions. Here, we present
pulsed electron spin resonance studies on the longitudinal $(T_1)$ and
transverse $(T_2)$ relaxation times of phosphorus donors in bulk silicon with
various electric field strengths up to near avalanche breakdown in high
magnetic fields of about 1.2 T and low temperatures of about 8 K. We find that
the $T_1$ relaxation time is significantly reduced under large electric fields
due to electric current, and $T_2$ is affected as the $T_1$ process can
dominate decoherence. Furthermore, we show that the magnetoresistance effect in
silicon can be exploited as a means to combat the reduction in the coherence
times. While qubit coherence times must be much longer than quantum gate times,
electrically accelerated $T_1$ can be found useful when qubit state
initialization relies on thermal equilibration.

###Generalized magnetoelectronic circuit theory and spin relaxation at interfaces in magnetic multilayers|G. G. Baez Flores,Alexey A. Kovalev,M. van Schilfgaarde,K. D. Belashchenko###

Generalized magnetoelectronic circuit theory and spin relaxation at interfaces in magnetic multilayers. Spin transport at metallic interfaces is an essential ingredient of various
spintronic device concepts, such as giant magnetoresistance, spin-transfer
torque, and spin pumping. Spin-orbit coupling plays an important role in many
such devices. In particular, spin current is partially absorbed at the
interface due to spin-orbit coupling. We develop a general magnetoelectronic
circuit theory and generalize the concept of the spin mixing conductance,
accounting for various mechanisms responsible for spin-flip scattering. For the
special case when exchange interactions dominate, we give a simple expression
for the spin mixing conductance in terms of the contributions responsible for
spin relaxation (i.e., spin memory loss), spin torque, and spin precession. The
spin-memory loss parameter $\delta$ is related to spin-flip transmission and
reflection probabilities. There is no straightforward relation between spin
torque and spin memory loss. We calculate the spin-flip scattering rates for
N|N, F|N, F|F interfaces using the Landauer-B\"uttiker method within the linear
muffin-tin orbital method and determine the values of $\delta$ using circuit
theory.

###Pressure induced topological quantum phase transition in Weyl semimetal T_d-MoTe_2|Z. Guguchia,A. M. dos Santos,F. O. von Rohr,J. J. Molaison,S. Banerjee,D. Rhodes,J. -X. Yin,R. Khasanov,J. Hone,Y. J. Uemura,M. -Z. Hasan,H. Luetkens,E. S. Bozin,A. Amato###

Pressure induced topological quantum phase transition in Weyl semimetal T_d-MoTe_2. We report the pressure (p_max = 1.5 GPa) evolution of the crystal structure
of the Weyl semimetal T_d-MoTe_2 by means of neutron diffraction experiments.
We find that the fundamental non-centrosymmetric structure T_d is fully
suppressed and transforms into a centrosymmertic 1T' structure at a critical
pressure of p_cr = 1.2 GPa. This is strong evidence for a pressure induced
quantum phase transition (QPT) between topological to a trivial electronic
state. Although the topological QPT has strong effect on magnetoresistance, it
is interesting that the superconducting critical temperature T_c, the
superfluid density, and the SC gap all change smoothly and continuously across
p_cr and no sudden effects are seen concomitantly with the suppression of the
T_d structure. This implies that the T_c, and thus the SC pairing strength, is
unaffected by the topological QPT. However, the QPT requires the change in the
SC gap symmetry from non-trivial s+- to a trivial s++ state, which we discuss
in this work. Our systematic characterizations of the structure and
superconducting properties associated with the topological QPT provide deep
insight into the pressure induced phase diagram in this topological quantum
material.

###Influence of ion implantation on the magnetic and transport properties of manganite films|M. Sirena,A. Zimmers,N. Haberkorn,E. Kaul,L. B. Steren,J. Lesueur,T. Wolf,Y. Le Gall,J. -J. Grob,G. Faini###

Influence of ion implantation on the magnetic and transport properties of manganite films. We have used oxygen ions irradiation to generate controlled structural
disorder in thin manganite films. Conductive atomic force microscopy CAFM),
transport and magnetic measurements were performed to analyze the influence of
the implantation process in the physical properties of the films. CAFM images
show regions with different conductivity values, probably due to the random
distribution of point defect or inhomogeneous changes of the local Mn3+/4+
ratio to reduce lattice strains of the irradiated areas. The transport and
magnetic properties of these systems are interpreted in this context.
Metal-insulator transition can be described in the frame of a percolative
model. Disorder increases the distance between conducting regions, lowering the
observed TMI. Point defect disorder increases localization of the carriers due
to increased disorder and locally enhanced strain field. Remarkably, even with
the inhomogeneous nature of the samples, no sign of low field magnetoresistance
was found. Point defect disorder decreases the system magnetization but doesn t
seem to change the magnetic transition temperature. As a consequence, an
important decoupling between the magnetic and the metal-insulator transition is
found for ion irradiated films as opposed to the classical double exchange
model scenario.

###Influence of pressure on the magnetic behavior and the anomalous magnetoresistance in Tb5Si3|Niharika Mohapatra,Sitikantha D Das,K. Mukherjee,Kartik K Iyer,E. V. Sampathkumaran###

Influence of pressure on the magnetic behavior and the anomalous magnetoresistance in Tb5Si3. The compound, Tb5Si3, crystallizing in Mn5Si3-type hexagonal structure, was
recently reported by us to exhibit a sudden and huge enhancement in electrical
resistivity (rho) at a critical magnetic field (H_cr) in the magnetically
ordered state (<70 K) tracking isothermal magnetization (M) behavior. We have
investigated the influence of external pressure (<15 kbar) and negative
chemical pressure induced by Ge substitution for Si on M and rho as a function
of temperature (5-300 K) and magnetic field (<120 kOe), with the primary aim of
understanding the field-induced anomalies. Focussing on isothermal M and
magnetoresistance (MR) at two temperatures, 5 and 20K, we find that this rho
anomaly persists under external as well as negative chemical pressures, however
with a large change in the H_cr. The pressure-derivative of H_cr is negative
and this trend and the MR behavior at the H_cr are comparable to that observed
in some Laves phase itinerant magnetic systems. On the basis of this
observation, we speculate that the magnetic fluctuations induced at this
critical field could be responsible for the MR anomal.ies

###Resonant soft x-ray scattering from La(1-x)Sr(x)MnO(3) quantum wire arrays|X. M. Chen,E. M. Spanton,S. Wang,J. C. T. Lee,S. Smadici,X. Zhai,T. Naibert,J. N. Eckstein,A. Bhattacharya,T. Santos,R. Budakian,P. Abbamonte###

Resonant soft x-ray scattering from La(1-x)Sr(x)MnO(3) quantum wire arrays. We describe a strategy for using resonant soft x-ray scattering (RSXS) to
study the electronic structure of transition metal oxide quantum wires. Using
electron beam lithography and ion milling, we have produced periodic, patterned
arrays of colossal magnetoresistance (CMR) phase La(1-x)Sr(x)MnO(3) consisting
of ~ 5000 wires, each of which is 80 nm in width. The scattered intensity
exhibits a series of peaks that can be interpreted as Bragg reflections from
the periodic structure or, equivalently, diffraction orders from the
grating-like structure. RSXS measurements at the Mn L(2,3) edge, which has a
large magnetic cross section, show clear evidence for a magnetic superstructure
with a commensurate period of five wires, which we interpret as commensurately
modulated antiferromagnetism. This superstructure, which is accompanied by
non-trivial reorganization of the magnetization within each wire, likely
results from classical dipole interactions among the wires. We introduce a
simple, exactly soluble, analytic model of the scattering that captures,
semi-quantitatively, the primary features in the RSXS data; this model will act
as a foundation for forthcoming, detailed studies of the magnetic structure in
these systems.

###Time-dependent magneto-transport in a driven graphene spin valve|Kai-He Ding,Zhen-Gang Zhu,Jamal Berakdar###

Time-dependent magneto-transport in a driven graphene spin valve. Based on the time-dependent nonequilibrium Green's function method we
investigate theoretically the time and spin-dependent transport through a
graphene layer upon the application of a static bias voltage to the electrodes
and a time-alternating gate voltage to graphene. The electrodes are magnetic
with arbitrary mutual orientations of their magnetizations. We find features in
the current that are governed by an interplay of the strength of the
alternating field and the Dirac point in graphene: The influence of a weak
alternating field on the zero bias conductance is strongly suppressed by the
zero density of state at the Dirac point. In contrast, for a strong amplitude
of the alternating field the current is dominated by several resonant peaks, in
particular a marked peak appears at zero bias. This subtle competition results
in a transition of the tunnel magnetoresistance from a broad peak to a sharp
dip at a zero bias voltage applied to the electrodes. The dip amplitude can be
manipulated by tuning the ac field frequency.

###Local and Global Superconductivity in Bismuth|Luis A. Baring,Robson R. da Silva,Yakov Kopelevich###

Local and Global Superconductivity in Bismuth. We performed magnetization M(H,T) and magnetoresistance R(T,H) measurements
on powdered (grain size ~ 149 micrometers) as well as highly oriented
rhombohedral (A7) bismuth (Bi) samples consisting of single crystalline blocks
of size ~ 1x1 mm2 in the plane perpendicular to the trigonal c-axis. The
obtained results revealed the occurrence of (1) local superconductivity in
powdered samples with Tc(0) = 8.75 \pm 0.05 K, and (2) global superconductivity
at Tc(0) = 7.3 \pm 0.1 K in polycrystalline Bi triggered by low-resistance
Ohmic contacts with silver (Ag) normal metal. The results provide evidence that
the superconductivity in Bi is localized in a tiny volume fraction, probably at
intergrain or Ag/Bi interfaces. On the other hand, the occurrence of global
superconductivity observed for polycrystalline Bi can be accounted for by
enhancement of the superconducting order parameter phase stiffness induced by
the normal metal contacts, the scenario proposed in the context of "pseudogap
regime" in cuprates [E. Berg et al., PRB 78, 094509 (2008)].

###Vortex glass line and vortex liquid resistivity in doped BaFe2As2 single crystals|S. R. Ghorbani,X. L. Wang,M. Shabazi,S. X. Dou,K. Y. Choi,C. T. Lin###

Vortex glass line and vortex liquid resistivity in doped BaFe2As2 single crystals. The vortex liquid-to-glass transition has been studied in Ba0.72K0.28Fe2As2,
Ba0.9Co0.1Fe2As2, and Ba(Fe0.45Ni0.05)2As2 single crystal with superconducting
transition temperature, Tc = 31.7, 17.3, and 18 K, respectively, by
magnetoresistance measurements. For temperatures below Tc, the resistivity
curves were measured in magnetic fields within the range of 0 \leq B \leq 13 T,
and the pinning potential was scaled according to a modified model for vortex
liquid resistivity. Good scaling of the resistivity {\rho}(B, T) and the
effective pinning energy U0(B,T) was obtained with the critical exponents s and
B0. The vortex state is three-dimensional at temperatures lower than a
characteristic temperature T*. The vortex phase diagram was determined based on
the evolution of the vortex-glass transition temperature Tg with magnetic field
and the upper critical field, Hc2. We found that non-magnetic K doping results
in a high glass line close to the Hc2, while magnetic Ni and Co doping cause a
low glass line which is far away from the Hc2. Our results suggest that
non-magnetic induced disorder is more favourable for enhancement of pinning
strength compared to magnetic induced disorder. Our results show that the
pinning potential is responsible for the difference in the glass states.

###Magnetic scattering and electron pair breaking by rare-earth-ion substitution in BaFe2As2 epitaxial films|Takayoshi Katase,Hidenori Hiramatsu,Toshio Kamiya,Hideo Hosono###

Magnetic scattering and electron pair breaking by rare-earth-ion substitution in BaFe2As2 epitaxial films. The effect of electron doping by trivalent charge state rare-earth ion (RE =
La, Ce, Pr, and Nd) substitutions on the superconductivity in BaFe2As2 was
examined using epitaxial films. Each of the RE substitutions suppressed the
resistivity anomaly associated with the magnetic/structural phase transitions,
leading to the resistivity drops and superconductivity transitions. Bulk
superconductivity was observed at the maximum onset critical temperature
(Tconset) of 22.4 K for La-doping and 13.4 K for Ce-doping, while only broad
resistivity drops were observed at 6.2 K for Pr-doping and 5.8 K for Nd-doping
but neither zero resistivity nor distinct Meissner effect were observed at
least down to 2 K. The decrease in Tconset with increasing the number of RE 4f
electrons cannot be explained in terms of the crystalline qualities or
crystallographic structure parameters of the BaFe2As2 films. It was clarified,
based on resistivity-temperature analyses, that magnetic scattering became
increasingly significant in the above order of the RE dopants. The negative
magnetoresistance was enhanced by the Ce- and Pr-doping, implying that the
decrease in Tc originates from magnetic pair breaking by interaction of the
localized 4f orbitals in the RE dopants with the itinerant Fe 3d orbitals.

###First-principles study of Co concentration and interfacial resonance states in Fe$_{1-x}$Co$_x$ magnetic tunnel junctions|Jonathan Trinastic,Yan Wang,Hai-Ping Cheng###

First-principles study of Co concentration and interfacial resonance states in Fe$_{1-x}$Co$_x$ magnetic tunnel junctions. The optimal Co concentration in Fe$_{1-x}$Co$_{x}$/MgO magnetic tunnel
junctions (MTJs) that maximizes tunneling magnetoresistance (TMR) is still
under investigation. We perform a first-principles transport study on MTJs
using disordered electrodes modeled using the virtual crystal approximation
(VCA) and ordered alloys with various MgO barrier thicknesses. We find that
10-20$%$ Co concentration maximizes TMR using VCA to represent disorder in the
electrodes. This TMR peak arises due to a minority d-type interfacial resonance
state (IRS) that becomes filled with small Co doping, leading to a decrease in
antiparallel conductance. Calculations with ordered Fe$_{1-x}$Co$_{x}$
electrodes confirm the filling of this minority d-type IRS for small Co
concentrations. In addition, we construct a 10x10 supercell without VCA to
explicitly represent disorder at the Fe$_{1-x}$Co$_x$/MgO interface, which
demonstrates a quenching of the minority-d IRS and significant reduction in
available states at the Fermi level that agrees with VCA calculations. These
results explain recent experimental findings and provide implications for the
impact of IRS on conductance and TMR in Fe$_{1-x}$Co$_x$/MgO tunnel junctions.

###Vortex-induced negative magnetoresistance and peak effect in narrow superconducting films|D. Y. Vodolazov###

Vortex-induced negative magnetoresistance and peak effect in narrow superconducting films. In framework of Ginzburg-Landau model it is shown that narrow superconducting
film with width w ~ 3-8 \xi(T) (\xi(T) is a temperature dependent coherence
length) exhibits unusual transport properties. In the absence of bulk pinning
its critical current Ic nonmonotonically depends on perpendicular magnetic
field H and has one minima (dip) and one maxima (peak) at some magnetic fields.
At currents I << Ic(H) the finite magnetoresistance R(H) of such a samples due
to thermo-activated vortex hopping via edge barriers also shows both local
maxima(peak) and minima(dip) nearly at the same magnetic fields. In narrower
films such an effect is absent due to absence of the vortices and in wider
films the effect is weaker due to increased vortex-vortex interaction. Finite
length of the film produces additional periodic variation in both Ic(H) and
R(H) because of discrete change in the number of the vortices, which is
superimposed on the above mentioned nonmonotonic dependence. The obtained
results are directly related to many experiments on narrow superconducting
films/bridges where such a nonmonotonic dependencies Ic(H) and R(H) were
observed.

###Quantitative magnetic imaging at the nanometer scale by ballistic electron magnetic microscopy|Marie Hervé,Sylvain Tricot,Sophie Guézo,Gabriel Delhaye,Bruno Lépine,Philippe Schieffer,Pascal Turban###

Quantitative magnetic imaging at the nanometer scale by ballistic electron magnetic microscopy. We demonstrate quantitative ballistic electron magnetic microscopy (BEMM)
imaging of simple model Fe(001) nanostructures. We use in situ nanostencil
shadow mask resistless patterning combined with molecular beam epitaxy
deposition to prepare under ultra-high vacuum conditions nanostructured
epitaxial Fe/Au/Fe/GaAs(001) spin-valves. In this epitaxial system, the
magnetization of the bottom Fe/GaAs(001) electrode is parallel to the [110]
direction, defining accurately the analysis direction for the BEMM experiments.
The large hot-electron magnetoresistance of the Fe/Au/Fe/GaAs(001) epitaxial
spin-valve allows us to image various stable magnetic configurations on the
as-grown Fe(001) microstructures with a high sensitivity, even for small
misalignments of both magnetic electrodes. The angular dependence of the
hot-electron magnetocurrent is used to convert magnetization maps calculated by
micromagnetic simulations into simulated BEMM images. The calculated BEMM
images and magnetization rotation profiles show quantitative agreement with
experiments and allow us to investigate the magnetic phase diagram of these
model Fe(001) microstructures. Finally, magnetic domain reversals are observed
under high current density pulses. This opens the way for further BEMM
investigations of current-induced magnetization dynamics.

###Resistance asymmetry of a two-dimensional electron gas caused by an effective spin injection|D. I. Golosov,I. Shlimak,A. Butenko,K. -J. Friedland,S. V. Kravchenko###

Resistance asymmetry of a two-dimensional electron gas caused by an effective spin injection. We have performed conductivity measurements on a Si-MOSFET sample with a slot
in the upper gate, allowing for different electron densities n_1 and n_2 across
the slot. Dynamic longitudinal resistance was measured by a standard lock-in
technique, while maintaining a large DC current through the source-drain
channel. We find that in a parallel magnetic field, the resistance of the
sample, R(I_DC), is asymmetric with respect to the direction of the DC current.
The asymmetry becomes stronger with an increase of either the magnetic field or
the difference between n_1 and n_2. These observations are interpreted in terms
of the effective spin injection: the degree of spin polarisation is different
in the two parts of the sample, implying different magnitudes of spin current
away from the slot. The carriers thus leave the excess spin (of the appropriate
sign) in the region around the slot, leading to spin accumulation (or
depletion) and to the spin drift-diffusion phenomena. Due to the positive
magnetoresistance of the two-dimensional electron gas, this change in a local
magnetisation affects the resistivity near the slot and the measured net
resistance, giving rise to an asymmetric contribution. We further observe that
the value of R(I_DC) saturates at large I_DC; we suggest that this is due to
electron tunnelling from the two-dimensional n-type layer into the p-type
silicon (or into another "spin reservoir") at the slot.

###Strain-induced effects on the magnetic and electronic properties of epitaxial Fe$_{1-x}$Co$_{x}$Si thin films|P. Sinha,N. A. Porter,C. H. Marrows###

Strain-induced effects on the magnetic and electronic properties of epitaxial Fe$_{1-x}$Co$_{x}$Si thin films. We have investigated the Co-doping dependence of the structural, transport,
and magnetic properties of \epsilon-FeCoSi epilayers grown by molecular beam
epitaxy on silicon (111) substrates. Low energy electron diffraction, atomic
force microscopy, X-ray diffraction, and high resolution transmission electron
microscopy studies have confirmed the growth of phase-pure, defect-free
\epsilon-FeCoSi epitaxial films with a surface roughness of ~1 nm. These
epilayers are strained due to lattice mismatch with the substrate, deforming
the cubic B20 lattice so that it becomes rhombohedral. The temperature
dependence of the resistivity changes as the Co concentration is increased,
being semiconducting-like for low $x$ and metallic-like for x \gtrsim 0.3. The
films exhibit the positive linear magnetoresistance that is characteristic of
\epsilon-FeCoSi below their magnetic ordering temperatures $T_\mathrm{ord}$, as
well as the huge anomalous Hall effect of order several \mu\Omega cm. The
ordering temperatures are higher than those observed in bulk, up to 77 K for x
= 0.4. The saturation magnetic moment of the films varies as a function of Co
doping, with a contribution of ~1 \mu_{B}/ Co atom for x \lesssim 0.25. When
taken in combination with the carrier density derived from the ordinary Hall
effect, this signifies a highly spin-polarised electron gas in the low x,
semiconducting regime.

###Signature of strong spin-orbital coupling in the large non-saturating magnetoresistance material WTe2|J. Jiang,F. Tang,X. C. Pan,H. M. Liu,X. H. Niu,Y. X. Wang,D. F. Xu,H. F. Yang,B. P. Xie,F. Q. Song,X. G. Wan,D. L. Feng###

Signature of strong spin-orbital coupling in the large non-saturating magnetoresistance material WTe2. We report the detailed electronic structure of WTe$_2$ by high resolution
angle-resolved photoemission spectroscopy. Unlike the simple one electron plus
one hole pocket type of Fermi surface topology reported before, we resolved a
rather complicated Fermi surface of WTe$_2$. Specifically, there are totally
nine Fermi pockets, including one hole pocket at the Brillouin zone center
$\Gamma$, and two hole pockets and two electron pockets on each side of
$\Gamma$ along the $\Gamma$-$X$ direction. Remarkably, we have observed
circular dichroism in our photoemission spectra, which suggests that the
orbital angular momentum exhibits a rich texture at various sections of the
Fermi surface. As reported previously for topological insulators and Rashiba
systems, such a circular dichroism is a signature for spin-orbital coupling
(SOC). This is further confirmed by our density functional theory calculations,
where the spin texture is qualitatively reproduced as the conjugate consequence
of SOC. Since the backscattering processes are directly involved with the
resistivity, our data suggest that the SOC and the related spin and orbital
angular momentum textures may be considered in the understanding of the
anomalous magnetoresistance of WTe$_2$.

###Molecular Beam Epitaxy Growth of Superconducting LiFeAs Film on SrTiO3(001) Substrate|Kai Chang,Peng Deng,Teng Zhang,Hai-Cheng Lin,Kun Zhao,Shuai-Hua Ji,Lili Wang,Ke He,Xu-Cun Ma,Xi Chen,Qi-Kun Xue###

Molecular Beam Epitaxy Growth of Superconducting LiFeAs Film on SrTiO3(001) Substrate. The stoichiometric "111" iron-based superconductor, LiFeAs, has attacted
great research interest in recent years. For the first time, we have
successfully grown LiFeAs thin film by molecular beam epitaxy (MBE) on
SrTiO3(001) substrate, and studied the interfacial growth behavior by
reflection high energy electron diffraction (RHEED) and low-temperature
scanning tunneling microscope (LT-STM). The effects of substrate temperature
and Li/Fe flux ratio were investigated. Uniform LiFeAs film as thin as 3
quintuple-layer (QL) is formed. Superconducting gap appears in LiFeAs films
thicker than 4 QL at 4.7 K. When the film is thicker than 13 QL, the
superconducting gap determined by the distance between coherence peaks is about
7 meV, close to the value of bulk material. The ex situ transport measurement
of thick LiFeAs film shows a sharp superconducting transition around 16 K. The
upper critical field, Hc2(0)=13.0 T, is estimated from the temperature
dependent magnetoresistance. The precise thickness and quality control of
LiFeAs film paves the road of growing similar ultrathin iron arsenide films.

###Giant Anisotropic Magnetoresistance in a Quantum Anomalous Hall Insulator|A. Kandala,A. Richardella,S. Kempinger,C-X. Liu,N. Samarth###

Giant Anisotropic Magnetoresistance in a Quantum Anomalous Hall Insulator. When a three-dimensional (3D) ferromagnetic topological insulator thin film
is magnetized out-of-plane, conduction ideally occurs through dissipationless,
one-dimensional (1D) chiral states that are characterized by a quantized,
zero-field Hall conductance. The recent realization of this phenomenon - the
quantum anomalous Hall effect - provides a conceptually new platform for
studies of edge-state transport, distinct from the more extensively studied
integer and fractional quantum Hall effects that arise from Landau level
formation. An important question arises in this context: how do these 1D edge
states evolve as the magnetization is changed from out-of-plane to in-plane? We
examine this question by studying the field-tilt driven crossover from
predominantly edge state transport to diffusive transport in Cr-doped
(Bi,Sb)2Te3 thin films, as the system transitions from a quantum anomalous Hall
insulator to a gapless, ferromagnetic topological insulator. The crossover
manifests itself in a giant, electrically tunable anisotropic magnetoresistance
that we explain using the Landauer-Buttiker formalism. Our methodology provides
a powerful means of quantifying edge state contributions to transport in
temperature and chemical potential regimes far from perfect quantization.

###High-field magnetoconductivity of topological semimetals with short-range potential|Hai-Zhou Lu,Song-Bo Zhang,Shun-Qing Shen###

High-field magnetoconductivity of topological semimetals with short-range potential. Weyl semimetals are three-dimensional topological states of matter, in a
sense that they host paired monopoles and antimonopoles of Berry curvature in
momentum space, leading to the chiral anomaly. The chiral anomaly has long been
believed to give a positive magnetoconductivity or negative magnetoresistivity
in strong and parallel fields. However, several recent experiments on both Weyl
and Dirac topological semimetals show a negative magnetoconductivity in high
fields. Here, we study the magnetoconductivity of Weyl and Dirac semimetals in
the presence of short-range scattering potentials. In a strong magnetic field
applied along the direction that connects two Weyl nodes, we find that the
conductivity along the field direction is determined by the Fermi velocity,
instead of by the Landau degeneracy. We identify three scenarios in which the
high-field magnetoconductivity is negative. Our findings show that the
high-field positive magnetoconductivity may not be a compelling signature of
the chiral anomaly and will be helpful for interpreting the inconsistency in
the recent experiments and earlier theories.

###Resistivity and magnetoresistance of FeSe single crystals under Helium-gas pressure|S. Knöner,D. Zielke,S. Köhler,B. Wolf,Th. Wolf,L. Wang,A. Böhmer,C. Meingast,M. Lang###

Resistivity and magnetoresistance of FeSe single crystals under Helium-gas pressure. We present temperature-dependent in-plane resistivity measurements on FeSe
single crystals under He-gas pressure up to 800 MPa and magnetic fields $B
\leq$ 10 T. A sharp phase transition anomaly is revealed at the
tetragonal-to-orthorhombic transition at $T_s$ slightly below 90 K. $T_s$
becomes reduced with increasing pressure in a linear fashion at a rate
d$T_{s}$/d$P$ $\simeq$ -31 K/GPa. This is accompanied by a $P$-linear increase
of the superconducting transition temperature at $T_c \sim$ 8.6 K with
d$T_{c}$/d$P$ $\simeq$ +5.8 K/GPa. Pressure studies of the normal-state
resistivity highlight two distinctly different regimes: for $T > T_s$, i.e., in
the tetragonal phase, the in-plane resistivity changes strongly with pressure.
This contrasts with the state deep in the orthorhombic phase at $T \ll T_s$,
preceding the superconducting transition. Here a $T$-linear resistivity is
observed the slope of which does not change with pressure. Resistivity studies
in varying magnetic fields both at ambient and finite pressure reveal clear
changes of the magnetoresistance, $\Delta \rho \propto B^{2}$, upon cooling
through $T_s$. Our data are consistent with a reconstruction of the Fermi
surface accompanying the structural transition.

###Signature of the chiral anomaly in a Dirac semimetal: a current plume steered by a magnetic field|Jun Xiong,Satya K. Kushwaha,Tian Liang,Jason W. Krizan,Wudi Wang,R. J. Cava,N. P. Ong###

Signature of the chiral anomaly in a Dirac semimetal: a current plume steered by a magnetic field. In this talk, we describe recent experimental progress in detecting the
chiral anomaly in the Dirac semimetal Na$_3$Bi in the presence of a magnetic
field. The chiral anomaly, which plays a fundamental role in chiral gauge
theories, was predicted to be observable in crystals by Nielsen and Ninomiya in
1983 [1]. Theoretical progress in identifying and investigating Dirac and Weyl
semimetals has revived strong interest in this issue [2-6]. In the Dirac
semimetal, the breaking of time-reversal symmetry by a magnetic field $\bf B$
splits each Dirac node into two chiral Weyl nodes. If an electric field $\bf E$
is applied parallel to $\bf B$, charge is predicted to flow between the Weyl
nodes. We report the observation in the Dirac semimetal Na$_3$Bi of a novel,
negative and highly anisotropic magnetoresistance (MR). We show that the
enhanced conductivity has the form of a narrowly defined plume that can be
steered by the applied field. The novel MR is acutely sensitive to deviations
of $\bf B$ from $\bf E$, a feature incompatible with conventional transport.
The locking of the current plume to the field appears to be a defining
signature of the chiral anomaly.

###Electron carriers with possible Dirac-cone-like dispersion in FeSe$_{1-x}$S$_x$ ($x$ = 0 and 0.14) single crystals triggered by structural transition|Yue Sun,Sunseng Pyon,Tsuyoshi Tamegai###

Electron carriers with possible Dirac-cone-like dispersion in FeSe$_{1-x}$S$_x$ ($x$ = 0 and 0.14) single crystals triggered by structural transition. We report detailed study of the transport properties of FeSe$_{1-x}$S$_x$
($x$ = 0 and 0.14) single crystals grown by vapor transport method. 14\% S
doping is found significantly suppress the structural transition from $T_s$
$\sim$ 86 K in FeSe to $\sim$ 49 K, although the superconducting transition
temperature, $T_c$, is only slightly affected. A pronounced linear
magnetoresistance (MR) is observed in both FeSe and FeSe$_{0.86}$S$_{0.14}$
single crystals, which is found to be triggered by the structural transition.
The linear MR and related discussion indicate the possible existence of
Dirac-cone-like state, which may come from the band shift induced by
ferro-orbital order. The mobility of the Dirac-cone-like band is found to
decrease after S doping. Besides, the invalid Kohler's scaling of MR is found
for temperature below $T_s$ in both crystals, however the re-establishment of
the Kohler's scaling at temperatures below 30 K is observed in FeSe, but not in
FeSe$_{0.86}$S$_{0.14}$. All these observations above support that the orbital
ordering causes the band reconstruction in FeSe, and also that the orbital
ordering in FeSe is suppressed by the chemical pressure from S doping.

###Quantum Critical Behavior in a Concentrated Ternary Solid Solution|Brian C. Sales,Ke Jin,Hongbin Bei,G. Malcolm Stocks,German D. Samolyuk,Andrew F. May,Michael A. McGuire###

Quantum Critical Behavior in a Concentrated Ternary Solid Solution. Quantum critical behavior has been associated with some of the most exotic
emergent states of matter including high-temperature superconductivity. Much of
the research into quantum critical point (QCP) physics has been hampered by the
lack of model systems simple enough to be analyzed by theory. Here, we show
that the concentrated solid solution fcc alloys, including the so-called
high-entropy alloys, are ideal model systems to study the effects of chemical
disorder on emergent properties near a quantum critical region. The face
centered cubic (fcc) alloy NiCoCrx with x near 1 is found to be close to the Cr
concentration where the ferromagnetic transition temperature, Tc, goes to 0.
Near this composition these alloys exhibit a resistivity linear in temperature
to 2 K, a linear magnetoresistance, an excess -TlnT contribution to the low
temperature heat capacity and excess low temperature entropy. All of the low
temperature electrical, magnetic and thermodynamic properties of the alloys
with compositions near x near 1 are not typical of a Fermi liquid and suggest
strong magnetic fluctuations associated with a quantum critical region. The
limit of extreme chemical disorder in these simple fcc materials thus provides
a novel and unique platform to study quantum critical behavior in a highly
tunable system.

###Double-phase transition and giant positive magnetoresistance in the quasi-skutterudite Gd$_3$Ir$_4$Sn$_{13}$|Harikrishnan S. Nair,Sarit K. Ghosh,Ramesh Kumar,André M. Strydom###

Double-phase transition and giant positive magnetoresistance in the quasi-skutterudite Gd$_3$Ir$_4$Sn$_{13}$. The magnetic, thermodynamic and electrical/thermal transport properties of
the caged-structure quasi-skutterudite Gd$_3$Ir$_4$Sn$_{13}$ are
re-investigated. The magnetization $M(T)$, specific heat $C_p(T)$ and the
resistivity $\rho(T)$ reveal a double-phase transition -- at $T_{N1}\sim$ 10~K
and at $T_{N2}\sim$ 8.8~K -- which was not observed in the previous report on
this compound. The antiferromagnetic transition is also visible in the thermal
transport data, thereby suggesting a close connection between the electronic
and lattice degrees of freedom in this Sn-based quasi-skutterudite. The
temperature dependence of $\rho(T)$ is analyzed in terms of a power-law for
resistivity pertinent to Fermi liquid picture. Giant, positive
magnetoresistance (MR) $\approx$ 80$\%$ is observed in Gd$_3$Ir$_4$Sn$_{13}$ at
2~K with the application of 9~T. The giant MR and the double magnetic
transition can be attributed to the quasi-cages and layered antiferromagnetic
structure of Gd$_3$Ir$_4$Sn$_{13}$ vulnerable to structural distortions and/or
dipolar or spin-reorientation effects. The giant value of MR observed in this
class of 3:4:13 type alloys, especially in a Gd-compound, is the highlight of
this work.

###Single- and Few-Layer WTe2 and Their Suspended Nanostructures: Raman Signatures and Nanomechanical Resonances|Jaesung Lee,Fan Ye,Zenghui Wang,Rui Yang,Jin Hu,Zhiqiang Mao,Jiang Wei,Philip X. -L. Feng###

Single- and Few-Layer WTe2 and Their Suspended Nanostructures: Raman Signatures and Nanomechanical Resonances. Single crystal tungsten ditelluride (WTe2) has recently been discovered to
exhibit non-saturating extreme magnetoresistance in bulk; it has also emerged
as a new layered material from which atomic layer crystals can be extracted.
While atomically thin WTe2 is attractive for its unique properties, little
study has been conducted on single- and few-layer WTe2. Here we report the
isolation of single- and few-layer WTe2, as well as fabrication and
characterization of the first WTe2 suspended nanostructures. We have observed
new Raman signatures of few-layer WTe2 that have been theoretically predicted
but not yet reported to date, in both on-substrate and suspended WTe2 flakes.
We have further probed the nanomechanical properties of suspended WTe2
structures by measuring their flexural resonances, and obtain a Young's modulus
of E_Y~80GPa for the suspended WTe2 flakes. This study paves the way for future
investigations and utilization of the multiple new Raman fingerprints of
single- and few-layer WTe2, and for exploring mechanical control of WTe2 atomic
layers.

###Low-temperature quantum transport in CVD-grown single crystal graphene|Shaohua Xiang,Vaidotas Miseikis,Luca Planat,Stefano Guiducci,Stefano Roddaro,Camilla Coletti,Fabio Beltram,Stefan Heun###

Low-temperature quantum transport in CVD-grown single crystal graphene. Chemical vapor deposition (CVD) has been proposed for large-scale graphene
synthesis for practical applications. However, the inferior electronic
properties of CVD graphene are one of the key problems to be solved. In this
study, we present a detailed study on the electronic properties of high-quality
single crystal monolayer graphene. The graphene is grown by CVD on copper using
a cold-wall reactor and then transferred to Si/SiO2. Our low-temperature
magneto-transport data demonstrate that the characteristics of the measured
single-crystal CVD graphene samples are superior to those of polycrystalline
graphene and have a quality which is comparable to that of exfoliated graphene
on Si/SiO2. The Dirac point in our best samples is located at back-gate
voltages of less than 10V, and their mobility can reach 11000 cm2/Vs. More than
12 flat and discernible half-integer quantum Hall plateaus have been observed
in high magnetic field on both the electron and hole side of the Dirac point.
At low magnetic field, the magnetoresistance shows a clear weak localization
peak. Using the theory of McCann et al., we find that the inelastic scattering
length is larger than 1 {\mu}m in these samples even at the charge neutrality
point.

###Current-induced asymmetric magnetoresistance due to energy transfer via quantum spin-flip process|K. J. Kim,T. Moriyama,T. Koyama,D. Chiba,S. W. Lee,S. J. Lee,K. J. Lee,H. W. Lee,T. Ono###

Current-induced asymmetric magnetoresistance due to energy transfer via quantum spin-flip process. Current-induced magnetization excitation is a core phenomenon for
next-generation magnetic nanodevices, and has been attributed to the
spin-transfer torque (STT) that originates from the transfer of the spin
angular momentum between a conduction electron and a local magnetic moment
through the exchange coupling. However, the same coupling can transfer not only
spin but also energy, though the latter transfer mechanism has been largely
ignored. Here we report on experimental evidence concerning the energy transfer
in ferromagnet/heavy metal bilayers. The magnetoresistance (MR) is found to
depend significantly on the current direction down to low in-plane currents,
for which STT cannot play any significant role. Instead we find that the
observed MR is consistent with the energy transfer mechanism through the
quantum spin-flip process, which predicts short wavelength,
current-direction-dependent magnon excitations in the THz frequency range. Our
results unveil another aspect of current-induced magnetic excitation, and open
a channel for the dc-current-induced generation of THz magnons.

###Influence of Cu deposition potential on the giant magnetoresistance and surface roughness of electrodeposited Ni-Co/Cu multilayers|B. G. Tóth,L. Péter,J. Dégi,Á. Révész,D. Oszetzky,G. Molnár,I. Bakonyi###

Influence of Cu deposition potential on the giant magnetoresistance and surface roughness of electrodeposited Ni-Co/Cu multilayers. It has been shown previously for electrodeposited Co/Cu multilayers that the
single-bath electrodeposition process can be optimized from an electrochemical
point of view in order to avoid unwanted Co dissolution and incorporation of Co
in the non-magnetic layer during the Cu deposition pulse. In the present work,
electrodeposition of Ni-Co/Cu multilayers has been studied to clarify if the
same optimization method is appropriate when two magnetic elements are present
and if this potential results in the largest giant magnetoresistance (GMR) for
the particular alloy system studied. For this purpose, several Ni-Co/Cu
multilayers were prepared by varying the deposition potential of the Cu layer.
The composition analysis of the deposits showed that the Ni:Co ratio exhibits a
minimum as a function of the Cu deposition potential, which can be explained by
considering both the dissolution of Co and the mass transport of the reactants.
Both the saturation GMR value and the intensity of the satellite peaks in the
X-ray diffractograms were highly correlated with the resulting surface
roughness of the deposits which was strongly varying with the Cu deposition
potential. Higher GMR values, lower saturation fields and more perfect
multilayer structure were observed for sufficiently positive Cu deposition
potentials only which enabled a partial Co dissolution resulting in a reduced
surface roughness. The results draw attention to the complexity of the
optimization procedure of the deposition of multilayers with several alloying
components.

###Observation of spontaneous spin-splitting in the band structure of an n-type zinc-blende ferromagnetic semiconductor|Le Duc Anh,Pham Nam Hai,Masaaki Tanaka###

Observation of spontaneous spin-splitting in the band structure of an n-type zinc-blende ferromagnetic semiconductor. Large spin splitting in the conduction band (CB) and valence band (VB) of
ferromagnetic semiconductors (FMSs), predicted by the influential mean-field
Zener model[1,2] and assumed in many spintronic device proposals[3-8], has
never been observed in the mainstream p-type Mn-doped FMSs[9-15]. Here using
tunnelling spectroscopy in Esaki-diode structures, we report the observation of
such a large spontaneous spin-splitting energy ({\Delta}E = 31.7 - 50 meV) in
the CB bottom of n-type FMS (In,Fe)As, which is surprising considering the very
weak s-d exchange interaction reported in several zinc-blende (ZB) type
semiconductors[16,17]. The mean-field Zener model also fails to explain
consistently the ferromagnetism and the spin splitting energy {\Delta}E of
(In,Fe)As, because we found that the Curie temperature (TC) values calculated
using the observed {\Delta}E are much lower than the experimental TC by a
factor of 400. These results urge the need for a more sophisticated theory of
FMSs. Furthermore, bias-dependent tunnelling anisotropic magnetoresistance
(TAMR) reveals the magnetic anisotropy of each component of the (In,Fe)As band
structure [CB, VB, and impurity band (IB)]. The results suggest that the energy
range of IB overlaps with the CB bottom or VB top, which may be important to
understand the strong s-d exchange interaction in (In,Fe)As[18,19].

###Temperature-Dependent Band Structure of SrTiO$_3$ Interfaces|Amany Raslan,Patrick Lafleur,W. A. Atkinson###

Temperature-Dependent Band Structure of SrTiO$_3$ Interfaces. We build a theoretical model for the electronic properties of the
two-dimensional (2D) electron gas that forms at the interface between
insulating SrTiO$_3$ and a number of polar cap layers, including LaTiO$_3$,
LaAlO$_3$, and GdTiO$_3$. The model treats conduction electrons within a
tight-binding approximation, and the dielectric polarization via a
Landau-Devonshire free energy that incorporates strontium titanate's strongly
nonlinear, nonlocal, and temperature-dependent dielectric response. The
self-consistent band structure comprises a mix of quantum 2D states that are
tightly bound to the interface, and quasi-three-dimensional (3D) states that
extend hundreds of unit cells into the SrTiO$_3$ substrate. We find that there
is a substantial shift of electrons away from the interface into the 3D tails
as temperature is lowered from 300 K to 10 K. This shift is least important at
high electron densities ($\sim 10^{14}$ cm$^{-2}$), but becomes substantial at
low densities; for example, the total electron density within 4~nm of the
interface changes by a factor of two for 2D electron densities $\sim 10^{13}$
cm$^{-2}$. We speculate that the quasi-3D tails form the low-density
high-mobility component of the interfacial electron gas that is widely inferred
from magnetoresistance measurements.

###First-principles study on magnetic tunneling junctions with semiconducting CuInSe${}_{2}$ and CuGaSe${}_{2}$ barriers|Keisuke Masuda,Yoshio Miura###

First-principles study on magnetic tunneling junctions with semiconducting CuInSe${}_{2}$ and CuGaSe${}_{2}$ barriers. We theoretically investigate two different magnetic tunneling junctions
(MTJs) with semiconductor barriers, CuInSe${}_{2}$ (CIS) and CuGaSe${}_{2}$
(CGS), which are the terminal compounds of recently reported mixed
semiconductor barrier, CuIn${}_{1-x}$Ga$_{\it x}$Se${}_{2}$. To discuss the
transport properties of these systems, we analyze complex band structures,
magnetoresistance (MR) ratios, and resistance-area products ($RA$) by using
first-principles based calculations in combination with the Landauer formula.
It is found that the $\Delta_{1}$ wave functions have dominant contributions to
the spin-dependent tunneling transport in both CIS- and CGS-based MTJs. We also
find that the CGS-based MTJ has a much larger MR ratio and slightly higher $RA$
than those of the CIS-based MTJ, which indicates that a larger MR ratio is
expected for a higher Ga concentration $x$ in the
CuIn${}_{1-x}$Ga${}_{x}$Se${}_{2}$-based MTJs. We further study the
relationship between the band gaps in the barriers and MR ratios by changing
the Coulomb repulsions in the Cu 3$d$ states of the CIS and CGS. It is shown
that the barrier with a larger band gap yields a larger MR ratio. The
comparison of MR ratios and $RA$ between the CIS-, CGS-, and MgO-based MTJs are
also given.

###Magnetotransport properties and evidence of topological insulating state in LaSbTe|Ratnadwip Singha,Arnab Pariari,Biswarup Satpati,Prabhat Mandal###

Magnetotransport properties and evidence of topological insulating state in LaSbTe. In this report, we present the magnetotransport and magnetization properties
of LaSbTe single crystals. Magnetic field-induced turn-on behavior and
low-temperature resistivity plateau have been observed. By adopting both
metal-semiconductor crossover and Kohler scaling analysis, we have discussed
the possible origin of the temperature and magnetic field dependence of
resistivity. At 5 K and 9 T, a large, non-saturating transverse
magnetoresistance (MR) $\sim$ 5$\times$10$^{3}$ \% has been obtained. The MR
shows considerable anisotropy, when the magnetic field is applied along
different crystallographic directions. The non-linear field dependence of the
Hall resistivity confirms the presence of two types of charge carriers. From
the semiclassical two-band fitting of Hall conductivity and longitudinal
conductivity, very high carrier mobilities and almost equal electron and hole
densities have been deduced, which result in large MR. The Fermi surface
properties have been analyzed from de Haas-van Alphen oscillation. From the
magnetization measurement, the signature of non-trivial surface state has been
detected, which confirms that LaSbTe is a topological insulator, consistent
with the earlier first-principles calculations.

###Spin-polarized quantum transport properties through flexible phosphorene|Mingyan Chen,Zhizhou Yu,Yiqun Xie,Yin Wang###

Spin-polarized quantum transport properties through flexible phosphorene. We report a first-principles study on the tunnel magnetoresistance (TMR) and
spin-injection efficiency (SIE) through phosphorene with nickel electrodes
under the mechanical tension and bending on the phosphorene region. Both the
TMR and SIE are largely improved under these mechanical deformations. For the
uniaxial tension ($\varepsilon_y$) varying from 0 to 15\% applied along the
armchair transport ({\it y}-)direction of the phosphorene, the TMR ratio is
enhanced with a maximum of 107\% at the $\varepsilon_y=10\%$, while the SIE
increases monotonously from 8\% up to 43\% with the increasing of the strain.
Under the out-of-plane bending, the TMR overall increases from 7\% to 50\%
within the bending ratio of 0-3.9\%, and meanwhile the SIE is largely improved
to around 70\%, as compared to that (30\%) of the flat phosphorene. Such
behaviors of the TMR and SIE are mainly affected by the transmission of spin-up
electrons in the parallel configuration, which is highly depended on the
applied mechanical tension and bending. Our results indicate that the
phosphorene based tunnel junctions have promising applications in flexible
electronics.

###Notes on Anomaly Induced Transport|Karl Landsteiner###

Notes on Anomaly Induced Transport. Chiral anomalies give rise to dissipationless transport phenomena such as the
chiral magnetic and vortical effects. In these notes I review the theory from a
quantum field theoretic, hydrodynamic and holographic perspective. A physical
interpretation of the otherwise somewhat obscure concepts of consistent and
covariant anomalies will be given. Vanishing of the CME in strict equilibrium
will be connected to the boundary conditions in momentum space imposed by the
regularization. The role of the gravitational anomaly will be explained. That
it contributes to transport in an unexpectedly low order in the derivative
expansion can be easiest understood via holography. Anomalous transport is
supposed to play also a key role in understanding the electronics of advanced
materials, the Dirac- and Weyl (semi)metals. Anomaly related phenomena such as
negative magnetoresistivity, anomalous Hall effect, thermal anomalous Hall
effect and Fermi arcs can be understood via anomalous transport. Finally I
briefly review a holographic model of Weyl semimetal which allows to infer a
new phenomenon related to the gravitational anomaly: the presence of odd
viscosity.

###A conducting nano-filament (CNF) network as a precursor to the origin of superconductivity in electron-doped copper oxides|Heshan Yu,Ge He,Ziquan Lin,Anna Kusmartseva,Jie Yua,Beiyi Zhu,Yi-feng Yang,Tao Xiang,Liang Li,Junfeng Wang,F. V. Kusmartsev,Kui Jin###

A conducting nano-filament (CNF) network as a precursor to the origin of superconductivity in electron-doped copper oxides. Emergency of superconductivity at the instabilities of antiferromagnetism has
been widely recognized in unconventional superconductors. In copper-oxide
superconductors, spin fluctuations play a predominant role in electron pairing
with electron dopants yet composite orders veil the nature of superconductivity
for hole-doped family. However, in electron-doped copper oxide superconductors
(cuprates) the AFM critical end point is still in controversy for different
probes, demonstrating high sensitivity to oxygen content. Here, by carefully
tuning the oxygen content, a systematic study of the Hall signal and
magnetoresistivity up to 58 Tesla on LCCO thin films identifies two
characteristic temperatures. The former is quite robust, whereas the latter
becomes flexible with increasing magnetic field, thereby linking respectively
to two- and three-dimensional AFM, evident from the multidimensional phase
diagram as a function of oxygen and Ce dopants. A rigorous theoretical analysis
of the presented data suggest the existence of conductive nano-filamentary
structures that effectively corroborate all previously reported field studies.
The new findings provide a uniquely consistent alternative picture in
understanding the interactions between AFM and superconductivity in
electron-doped cuprates and offer a consolidating interpretation to the
pioneering scaling law in cuprates recently established by Bozovic et al.
(Nature, 2016)

###Thickness-Dependent and Magnetic-Field-Driven Suppression of Antiferromagnetic Order in Thin V$_{5}$S$_{8}$ Single Crystals|Will J. Hardy,Jiangtan Yuan,Hua Guo,Panpan Zhou,Jun Lou,Douglas Natelson###

Thickness-Dependent and Magnetic-Field-Driven Suppression of Antiferromagnetic Order in Thin V$_{5}$S$_{8}$ Single Crystals. With materials approaching the 2d limit yielding many exciting systems with
intriguing physical properties and promising technological functionalities,
understanding and engineering magnetic order in nanoscale, layered materials is
generating keen interest. One such material is V$_{5}$S$_{8}$, a metal with an
antiferromagnetic ground state below the N\'eel temperature $T_{N} \sim$ 32 K
and a prominent spin-flop signature in the magnetoresistance (MR) when $H||c
\sim$ 4.2 T. Here we study nanoscale-thickness single crystals of
V$_{5}$S$_{8}$, focusing on temperatures close to $T_{N}$ and the evolution of
material properties in response to systematic reduction in crystal thickness.
Transport measurements just below $T_{N}$ reveal magnetic hysteresis that we
ascribe to a metamagnetic transition, the first-order magnetic field-driven
breakdown of the ordered state. The reduction of crystal thickness to $\sim$ 10
nm coincides with systematic changes in the magnetic response: $T_{N}$ falls,
implying that antiferromagnetism is suppressed; and while the spin-flop
signature remains, the hysteresis disappears, implying that the metamagnetic
transition becomes second order as the thickness approaches the 2d limit. This
work demonstrates that single crystals of magnetic materials with nanometer
thicknesses are promising systems for future studies of magnetism in reduced
dimensionality and quantum phase transitions.

###Electric control of antiferromagnets|I. Fina,X. Marti###

Electric control of antiferromagnets. In the past five years, most of the paradigmatic concepts employed in
spintronics have been replicated substituting ferromagnets by antiferromagnets
in critical parts of the devices. The numerous research efforts directed to
manipulate and probe the magnetic moments in antiferromagnets have been
gradually established a new and independent field known as antiferromagnetic
spintronics. In this paper, we focus on the electrical control and detection of
antiferromagnetic moments at a constant temperature. We address separately the
experimental results concerning insulating and metallic thin films as they
correspond to voltage and electrical current controlled devices, respectively.
First, we present results on the voltage control of antiferromagnetic order in
insulating thin films. The experiments show that voltage pulses can switch the
chirality of a modulated antiferromagnetic structure. Second, we describe the
recent advances in metallic antiferromagnetic systems. We present results
obtained with the first USB-operated portable device able to perform the
non-volatile electrical current-induced switching of an antiferromagnet
combined with magnetoresistive readout at room temperature. We discuss on
potential applications that can be realized using antiferromagnetic memory
cells.

###Magnetoresistance and robust resistivity plateau in MoAs2|Jialu Wang,Lin Li,Wei You,Tingting Wang,Chao Cao,Jianhui Dai,Yuke Li###

Magnetoresistance and robust resistivity plateau in MoAs2. We have grown the MoAs$_2$ single crystal which crystallizes in a monoclinic
structure with C2/m space group. Transport measurements show that MoAs$_2$
displays a metallic behavior at zero field and undergoes a
metal-to-semiconductor crossover at low temperatures when the applied magnetic
field is over 5 T. A robust resistivity plateau appears below 18 K and persists
for the field up to 9 T. A large positive magnetoresistance (MR), reaching
about 2600\% at 2 K and 9 T, is observed when the field is perpendicular to the
current.The MR becomes negative below 40 K when the field is rotated to be
parallel to the current. The Hall resistivity shows the non-linear
field-dependence below 70 K. The analysis using two-band model indicates a
compensated electron-hole carrier density at low temperatures. A combination of
the breakdown of Kohler's rule, the abnormal drop and the cross point in Hall
data implies that a possible Lifshitz transition has occurred between 30 K and
60 K, likely driving the compensated electron-hole density, the large MR as
well as the metal-semiconductor transition in MoAs$_2$. Our results indicate
that the family of centrosymmetric transition-metal dipnictides has rich
transport behavior which can in general exhibit variable metallic and
topological features.

###Interplay of orbital effects and nanoscale strain in topological crystalline insulators|Daniel Walkup,Badih Assaf,Kane L Scipioni,R. Sankar,Fangcheng Chou,Guoqing Chang,Hsin Lin,Ilija Zeljkovic,Vidya Madhavan###

Interplay of orbital effects and nanoscale strain in topological crystalline insulators. Orbital degrees of freedom can have pronounced effects on the fundamental
properties of electrons in solids. In addition to influencing bandwidths, gaps,
correlation strength and dispersion, orbital effects have also been implicated
in generating novel electronic and structural phases, such as Jahn-Teller
effect and colossal magnetoresistance. In this work, we show for the first time
how the orbital nature of bands can result in non-trivial effects of strain on
the band structure. We use scanning tunneling microscopy and quasiparticle
interference imaging to study the effects of strain on the electronic structure
of a heteroepitaxial thin film of a topological crystalline insulator, SnTe. We
find a surprising effect where strain applied in one direction affects the band
structure in the perpendicular direction. Our theoretical calculations indicate
that this effect directly arises from the orbital nature of the conduction and
valance bands. Our results imply that a microscopic model capturing strain
effects on the band structure must include a consideration of the orbital
nature of the bands.

###Magneto-transport properties of the "hydrogen atom" nodal-line semimetal candidates CaTX (T=Ag, Cd, X=As, Ge)|Eve Emmanouilidou,Bing Shen,Xiaoyu Deng,Tay-Rong Chang,Aoshuang Shi,Gabriel Kotliar,Su-Yang Xu,Ni Ni###

Magneto-transport properties of the "hydrogen atom" nodal-line semimetal candidates CaTX (T=Ag, Cd, X=As, Ge). Topological semimetals are characterized by protected crossings between
conduction and valence bands. These materials have recently attracted
significant interest because of the deep connections to high-energy physics,
the novel topological surface states, and the unusual transport phenomena.
While Dirac and Weyl semimetals have been extensively studied, the nodal-line
semimetal remains largely unexplored due to the lack of an ideal material
platform. In this paper, we report the magneto-transport properties of two
nodal-line semimetal candidates CaAgAs and CaCdGe. First, our single
crystalline CaAgAs supports the first "hydrogen atom" nodal-line semimetal,
where only the topological nodal-line is present at the Fermi level. Second,
our CaCdGe sample provides an ideal platform to perform comparative studies
because it features the same topological nodal line but has a more complicated
Fermiology with irrelevant Fermi pockets. As a result, the magnetoresistance of
our CaCdGe sample is more than 100 times larger than that of CaAgAs. Through
our systematic magneto-transport and first-principles band structure
calculations, we show that our CaTX compounds can be used to study, isolate,
and control the novel topological nodal-line physics in real materials.

###Semimetallic and charge-ordered $α$-(BEDT-TTF)$_2$I$_3$: on the role of disorder in dc transport and dielectric properties|Tomislav Ivek,Matija Čulo,Marko Kuveždić,Eduard Tutiš,Mario Basletić,Branimir Mihaljević,Emil Tafra,Silvia Tomić,Anja Löhle,Martin Dressel,Dieter Schweitzer,Bojana Korin-Hamzić###

Semimetallic and charge-ordered $α$-(BEDT-TTF)$_2$I$_3$: on the role of disorder in dc transport and dielectric properties. $\alpha$-(BEDT-TTF)$_2$I$_3$ is a prominent example of charge ordering among
organic conductors. In this work we explore the details of transport within the
charge-ordered as well as semimetallic phase at ambient pressure. In the
high-temperature semimetallic phase, the mobilities and concentrations of both
electrons and holes conspire in such a way to create an almost
temperature-independent conductivity as well as a low Hall effect. We explain
these phenomena as a consequence of a predominantly inter-pocket scattering
which equalizes mobilities of the two types of charge carriers. At low
temperatures, within the insulating charge-ordered phase two channels of
conduction can be discerned: a temperature-dependent activation which follows
the mean-field behavior, and a nearest-neighbor hopping contribution. Together
with negative magnetoresistance, the latter relies on the presence of disorder.
The charge-ordered phase also features a prominent dielectric peak which bears
a similarity to relaxor ferroelectrics. Its dispersion is determined by
free-electron screening and pushed by disorder well below the transition
temperature. The source of this disorder can be found in the anion layers which
randomly perturb BEDT-TTF molecules through hydrogen bonds.

###Effects of proton irradiation on flux-pinning properties of underdoped Ba(Fe$_{0.96}$Co$_{0.04}$)$_2$As$_2$ pnictide superconductor|S. Salem-Sugui Jr.,D. Moseley,S. J. Stuard,A. D. Alvarenga,A. S. Sefat,L. F. Cohen,L. Ghivelder###

Effects of proton irradiation on flux-pinning properties of underdoped Ba(Fe$_{0.96}$Co$_{0.04}$)$_2$As$_2$ pnictide superconductor. We study the effect of proton irradiation on
Ba(Fe$_{0.96}$Co$_{0.04}$)$_2$As$_2$ superconducting single crystals from
combined magnetisation and magnetoresistivity measurements. The study allows
the extraction of the values of the apparent pinning energy $U_0$ of the
samples prior to and after irradiation, as well as comparison of the values of
$U_0$ obtained from the flux-flow reversible region with those from the
flux-creep irreversible region. Irradiation reduces $T_c$ modestly, but
significantly reduces $U_0$ in both regimes: the critical current density $J_c$
is modified, most strikingly by the disappearance of the second magnetisation
peak after irradiation. Analysis of the functional form of the pinning force
and of the temperature dependence of $J_c$ for zero field, indicates that
proton irradiation in this case has not changed the pinning regime, but has
introduced a high density of shallow point-like defects. By consideration of a
model that takes into account the effect of disorder on the irreversibility
line, the data suggests that irradiation produced a considerable reduction in
the average effective disorder overall, consistent with the changes observed in
$U_0$ and $J_c$.

###Unconventional Large Linear Magnetoresistance in Cu$_{2-x}$Te|Ali A. Sirusi,Alexander Page,Lucia Steinke,Meigan C. Aronson,Ctirad Uher,Joseph H. Ross Jr###

Unconventional Large Linear Magnetoresistance in Cu$_{2-x}$Te. We report a large linear magnetoresistance in Cu$_{2-x}$Te, reaching
$\Delta\rho/\rho(0)$ = 250\% at 2 K in a 9 T field. This is observed for
samples with $x$ in the range 0.13 to 0.22, and the results are comparable to
the effects observed in Ag$_2 X$ materials, although in this case the results
appear for a much wider range of bulk carrier density. Examining the magnitude
vs. crossover field from low-field quadratic to high-field linear behavior, we
show that models based on classical transport behavior best explain the
observed results. The effects are traced to misdirected currents due to
topologically inverted behavior in this system, such that stable surface states
provide the high mobility transport channels. The resistivity also crosses over
to a $T^2$ dependence in the temperature range where the large linear MR
appears, an indicator of electron-electron interaction effects within the
surface states. Thus this is an example of a system in which these interactions
dominate the low-temperature behavior of the surface states.

###Gigantic negative magnetoresistance in a disordered topological insulator|Oliver Breunig,Zhiwei Wang,A. A. Taskin,Jonathan Lux,Achim Rosch,Yoichi Ando###

Gigantic negative magnetoresistance in a disordered topological insulator. With the recent discovery of Weyl semimetals, the phenomenon of negative
magnetoresistance (MR) is attracting renewed interest. While small negative MR
can occur due to the suppression of spin scattering or weak localization, large
negative MR is rare in materials, and when it happens, it is usually related to
magnetism. The large negative MR in Weyl semimetals is peculiar in that it is
unrelated to magnetism and comes from chiral anomaly. Here we report that there
is a new mechanism for large negative MR which is not related to magnetism but
is related to disorder. In the newly-synthesized bulk-insulating topological
insulator TlBi$_{0.15}$Sb$_{0.85}$Te$_2$, we observed gigantic negative MR
reaching 98% in 14 T at 10 K, which is unprecedented in a nonmagnetic system.
Supported by numerical simulations, we argue that this phenomenon is likely due
to the Zeeman effect on a barely percolating current path formed in the
disordered bulk. Since disorder can also lead to non-saturating linear MR in
Ag$_{2+\delta}$Se, the present finding suggests that disorder engineering in
narrow-gap systems is useful for realizing gigantic MR in both positive and
negative directions.

###Nearly isotropic superconductivity in layered Weyl semimetal WTe$_2$ at 98.5 kbar|Yuk Tai Chan,P. L. Alireza,K. Y. Yip,Q. Niu,K. T. Lai,Swee K. Goh###

Nearly isotropic superconductivity in layered Weyl semimetal WTe$_2$ at 98.5 kbar. Layered transition metal dichalcogenide WTe$_2$ has recently attracted
significant attention due to the discovery of an extremely large
magnetoresistance, a predicted type-II Weyl semimetallic state, and the
pressure-induced superconducting state. By a careful measurement of the
superconducting upper critical fields as a function of the magnetic field angle
at a pressure as high as 98.5 kbar, we provide the first detailed examination
of the dimensionality of the superconducting condensate in WTe$_2$. Despite the
layered crystal structure, the upper critical field exhibits a negligible field
anisotropy. The angular dependence of the upper critical field can be
satisfactorily described by the anisotropic mass model from 2.2 K
($T/T_c\sim0.67$) to 0.03 K ($T/T_c\sim0.01$), with a practically identical
anisotropy factor $\gamma\sim1.7$. The temperature dependence of the upper
critical field, determined for both $H\perp ab$ and $H\parallel ab$, can be
understood by a conventional orbital depairing mechanism. Comparison of the
upper critical fields along the two orthogonal field directions results in the
same value of $\gamma\sim1.7$, leading to a temperature independent anisotropy
factor from near $T_c$ to $<0.01T_c$. Our findings thus identify WTe$_2$ as a
nearly isotropic superconductor, with an anisotropy factor among one of the
lowest known in superconducting transition metal dichalcogenides.

###Theory of magnetotransport in artificial kagome spin ice|Gia-Wei Chern###

Theory of magnetotransport in artificial kagome spin ice. Magnetic nanoarray with special geometries exhibits nontrivial collective
behaviors similar to those observed in the spin ice materials. Here we present
a novel circuit model to describe the complex magnetotransport phenomena in
artificial kagome spin ice. In this picture, the system can be viewed as a
resistor network driven by voltage sources that are located at vertices of the
honeycomb array. The differential voltages across different terminals of these
sources are related to the ice-rules that govern the local magnetization
ordering. The circuit model relates the transverse Hall voltage of kagome ice
to the underlying spin correlations. Treating the magnetic nanoarray as
metamaterials, we present a mesoscopic constitutive equation relating the Hall
resistance to magnetization components of the system. We further show that the
Hall signal is significantly enhanced when the kagome ice undergoes a
magnetic-charge ordering transition. Our analysis can be readily generalized to
other lattice geometry, providing a quantitative method for the design of
magnetoresistance devices based on artificial spin ices.

###Nematic topological superconducting phase in Nb-doped Bi2Se3|Junying Shen,Wen-Yu He,Noah Fan Qi Yuan,Zengle Huang,Chang-woo Cho,Seng Huat Lee,Yew San Hor,Kam Tuen Law,Rolf Lortz###

Nematic topological superconducting phase in Nb-doped Bi2Se3. A nematic topological superconductor has an order parameter symmetry, which
spontaneously breaks the crystalline symmetry in its superconducting state.
This state can be observed, for example, by thermodynamic or upper critical
field experiments in which a magnetic field is rotated with respect to the
crystalline axes. The corresponding physical quantity then directly reflects
the symmetry of the order parameter. We present a study on the superconducting
upper critical field of the Nb-doped topological insulator NbxBi2Se3 for
various magnetic field orientations parallel and perpendicular to the basal
plane of the Bi2Se3 layers. The data were obtained by two complementary
experimental techniques, magnetoresistance and DC magnetization, on three
different single crystalline samples of the same batch. Both methods and all
samples show with perfect agreement that the in-plane upper critical fields
clearly demonstrate a two-fold symmetry that breaks the three-fold crystal
symmetry. The two-fold symmetry is also found in the absolute value of the
magnetization of the initial zero-field-cooled branch of the hysteresis loop
and in the value of the thermodynamic contribution above the irreversibility
field, but also in the irreversible properties such as the value of the
characteristic irreversibility field and in the width of the hysteresis loop.
This provides strong experimental evidence that Nb-doped Bi2Se3 is a nematic
topological superconductor similar to the Cu- and Sr-doped Bi2Se3.

###Valleytronics in merging Dirac cones: All-electric-controlled valley filter, valve and universal reversible logic gate|Yee Sin Ang,Shengyuan A. Yang,C. Zhang,Zhongshui Ma,L. K. Ang###

Valleytronics in merging Dirac cones: All-electric-controlled valley filter, valve and universal reversible logic gate. Despite much anticipation of valleytronics as a candidate to replace the
ageing CMOS-based information processing, its progress is severely hindered by
the lack of practical ways to manipulate valley polarization all-electrically
in an electrostatic setting. Here we propose a class of all-electric-controlled
valley filter, valve and logic gate based on the valley-contrasting transport
in a merging Dirac cones system. The central mechanism of these devices lies on
the pseudospin-assisted quantum tunneling which effectively quenches the
transport of one valley when its pseudospin configuration mismatches that of a
gate-controlled scattering region. The valley polarization can be abruptly
switched into different states and remains stable over semi-infinite
gate-voltage windows. Colossal tunneling valley-pseudo-magnetoresistance ratio
of over 10,000\% can be achieved in a valley-valve setup. We further propose a
valleytronic-based logic gate capable of covering all 16 types of two-input
Boolean logics. Remarkably, the valley degree of freedom can be harnessed to
resurrect logical-reversibility in two-input universal Boolean gate. The (2+1)
polarization states -- two distinct valleys plus a null polarization --
re-establish one-to-one input-to-output mapping, a crucial requirement for
logical-reversibility, and significantly reduce the complexity of reversible
circuits due to the built-in nature of valley degree of freedom. Our results
suggest that the synergy of valleytronics and digital logics may provide new
paradigms for valleytronic-based information processing and reversible
computing.

###Nanoclustering phase competition induces the resistivity hump in colossal magnetoresistive manganites|Kalpataru Pradhan,Seiji Yunoki###

Nanoclustering phase competition induces the resistivity hump in colossal magnetoresistive manganites. Using a two-band double-exchange model with Jahn-Teller lattice distortions
and super-exchange interactions, supplemented by quenched disorder, at electron
density $n=0.65$, we explicitly demonstrate the coexistence of the $n$ =
1/2-type ($\pi, \pi$) charge-ordered and the ferromagnetic nanoclusters above
the ferromagnetic transition temperature $T_{\rm c}$ in colossal
magnetoresistive (CMR) manganites. The resistivity increases due to the
enhancement of the volume fraction of the charge-ordered and the ferromagnetic
nanoclusters with decreasing the temperature down to $T_{\rm c}$. The
ferromagnetic nanoclusters start to grow and merge, and the volume fraction of
the charge-ordered nanoclusters decreases below $T_{\rm c}$, leading to the
sharp drop in the resistivity. By applying a small external magnetic field $h$,
we show that the resistivity above $T_{\rm c}$ increases, as compared with the
case when $h=0$, a fact which further confirms the coexistence of the
charge-ordered and the ferromagnetic nanoclusters. In addition, we show that
the volume fraction of the charge-ordered nanoclusters decreases with
increasing the bandwidth and consequently the resistivity hump diminishes for
large bandwidth manganites, in good qualitative agreement with experiments. The
obtained insights from our calculations provide a complete pathway to
understand the phase competition in CMR manganites.

###Periodic chiral magnetic domains in single-crystal nickel nanowires|Jimmy J. Kan,Marko V. Lubarda,Keith T. Chan,Vojtech Uhlir,Andreas Scholl,Vitaliy Lomakin,Eric E. Fullerton###

Periodic chiral magnetic domains in single-crystal nickel nanowires. We report on experimental and computational investigations of the domain
structure of ~0.2 x 0.2 x 8 {\mu}m single-crystal Ni nanowires (NWs). The Ni
NWs were grown by a thermal chemical vapor deposition technique that results in
highly-oriented single-crystal structures on amorphous SiOx coated Si
substrates. Magnetoresistance measurements of the Ni NWs suggest the average
magnetization points largely off the NW long axis at zero field. X-ray
photoemission electron microscopy images show a well-defined periodic
magnetization pattern along the surface of the nanowires with a period of
{\lambda} = 250 nm. Finite element micromagnetic simulations reveal that an
oscillatory magnetization configuration with a period closely matching
experimental observation ({\lambda} = 240 nm) is obtainable at remanence. This
magnetization configuration involves a periodic array of alternating chirality
vortex domains distributed along the length of the NW. Vortex formation is
attributable to the cubic anisotropy of the single crystal Ni NW system and its
reduced structural dimensions. The periodic alternating chirality vortex state
is a topologically protected metastable state, analogous to an array of
360{\deg} domain walls in a thin strip. Simulations show that other remanent
states are also possible, depending on the field history. Effects of material
properties and strain on the vortex pattern are investigated. It is shown that
at reduced cubic anisotropy vortices are no longer stable, while negative
uniaxial anisotropy and magnetoelastic effects in the presence of compressive
biaxial strain contribute to vortex formation.

###Non-Abelian Charge Transport in Three-Flavor Gauge Semimetal Model with Braiding Majoranas|Halina V. Grushevskaya,George Krylov###

Non-Abelian Charge Transport in Three-Flavor Gauge Semimetal Model with Braiding Majoranas. Known Majorana fermions models are considered as promising ones for the
purposes of quantum computing robust to decoherence. One of the most expecting
but unachieved goals is an effective control for braiding of Majoranas. Another
one is to describe ${\mathbb{Z}}_2$ topological semimetals, APRES spectra of
which testify on eight-fold degenerate chiral fermions with $SU(2)$ holonomy of
wave functions, whereas the last can not be reproduced within existing models.
Quasi-relativistic theory of non-abelian quantum charge transport in
topological semimetals is developed for a model with a number of flavors equal
three. Majorana-like quasi-particle excitations in the model are described with
accounting of dynamic mass term arising due to relativistic exchange
interactions. Such exotic features of $\mathbb{Z}_2$ semimetals as splitting
zero-conductance peaks, longitudinal magnetoresistance, minimal direct current
conductivity, negative differential conductivity have been calculated in
perfect agreement with experimental data. We propose a new scheme of braiding
for three flavor Majorana-like fermions with new non-trivial braiding operator.
We demonstrate that in this model, the presence of chiral Majorana-like bound
states is controlled as emergence of three pairs of resonance-antiresonance in
frequency dependence of dielectric permeability.

###Giant anomalous Hall effect in a ferromagnetic Kagome-lattice semimetal|Enke Liu,Yan Sun,Nitesh Kumar,Lukas Meuchler,Aili Sun,Lin Jiao,Shuo-Ying Yang,Defa Liu,Aiji Liang,Qiunan Xu,Johannes Kroder,Vicky Seuss,Horst Borrmann,Chandra Shekhar,Zhaosheng Wang,Chuanying Xi,Wenhong Wang,Walter Schnelle,Steffen Wirth,Yulin Chen,Sebastian T. B. Goennenwein,Claudia Felser###

Giant anomalous Hall effect in a ferromagnetic Kagome-lattice semimetal. Magnetic Weyl semimetals with broken time-reversal symmetry are expected to
generate strong intrinsic anomalous Hall effects, due to their large Berry
curvature. Here, we report a magnetic Weyl semimetal candidate Co3Sn2S2 with a
quasi-two-dimensional crystal structure consisting of stacked Kagome lattices.
This lattice provides an excellent platform for hosting exotic quantum
topological states. We observe a negative magnetoresistance that is consistent
with the chiral anomaly expected from the presence of Weyl fermions close to
the Fermi level. The anomalous Hall conductivity is robust against both
increased temperature and charge conductivity, which corroborates the intrinsic
Berry-curvature mechanism in momentum space. Owing to the low carrier density
in this material and the significantly enhanced Berry curvature from its band
structure, the anomalous Hall conductivity and the anomalous Hall angle
simultaneously reach 1130 S cm-1 and 20%, respectively, an order of magnitude
larger than typical magnetic systems. Combining the Kagome-lattice structure
and the long-range out-of-plane ferromagnetic order of Co3Sn2S2, we expect that
this material is an excellent candidate for observation of the quantum
anomalous Hall state in the two-dimensional limit.

###Influence of disorder on the signature of pseudogap and multigap superconducting behavior in FeSe|Sahana Rößler,Chien-Lung Huang,Lin Jiao,Cevriye Koz,Ulrich Schwarz,Steffen Wirth###

Influence of disorder on the signature of pseudogap and multigap superconducting behavior in FeSe. We investigated several FeSe single crystals grown by two different methods
by utilizing experimental techniques namely, resistivity, magnetoresistance,
specific heat, scanning tunneling microscopy, and spectroscopy. The residual
resistivity ratio (RRR) shows systematic differences between samples grown by
chemical vapor transport and flux vapor transport, indicating variance in the
amount of scattering centers. Although the superconducting transition
temperature $T_c$ is not directly related to RRR, our study evidences subtle
differences in the features of an incipient ordering mode related to a
depletion of density of states at the Fermi level. For instance, the onset
temperature of anisotropic spin-fluctuations at $T^* \approx 75$ K, and the
temperature of the opening-up of a partial gap in the density of states at
$T^{**} \approx 30$ K are not discernible in the samples with lower RRR.
Further, we show that the functional dependence of the electronic specific heat
below 2 K, which allows to determine the nodal features as well as the small
superconducting gap, differs significantly in crystals grown by these two
different methods. Our investigation suggests that some of the controversies
about the driving mechanism for the superconducting gap or its structure and
symmetry is related to minute differences in the crystals arising due to the
growth techniques used and the total amount of scattering centers present in
the sample.

###Effect of multiband transport on charge carrier density fluctuations at the LaAlO$_3$/SrTiO$_3$ interface|Gopi Nath Daptary,Pramod Kumar,Anjana Dogra,Aveek Bid###

Effect of multiband transport on charge carrier density fluctuations at the LaAlO$_3$/SrTiO$_3$ interface. Multiband transport in superconductors is interesting both from an academic
as well as an application point of view. It has been postulated that interband
scattering can significantly affect the carrier dynamics in these materials. In
this article we present a detailed study of the electrical transport properties
of the high-mobility two-dimensional electron gas residing at the interface of
LaAlO$_3$/SrTiO$_3$, a prototypical multi-band superconductor. We show, through
careful measurements of the gate dependence of the magnetoresistance and
resistance fluctuations at ultra-low temperatures, that transport in the
superconducting regime of this system has contributions from two bands which
host carriers of very different characters. We identify a gate-voltage tunable
Lifshitz transition in the system and show that the resistance fluctuations
have strikingly different features on either side of it. At low carrier
densities, resistance noise is dominated by number-density fluctuations arising
from trapping-detrapping of charge carriers from defects in the underlying
SrTiO$_3$ substrate, characteristic of a single-band semiconductor. Above the
Lifshitz transition, the noise presumably originates from inter-band
scattering. Our work highlights the importance of inter-band scattering
processes in determining the transport properties of low-dimensional systems
and projects resistance fluctuation spectroscopy as a viable technique for
probing the charge carrier dynamics across a Lifshitz transition.

###On the possibility of magnetic Weyl fermions in non-symmorphic compound PtFeSb|M. G. Vergniory,L. Elcoro,F. Orlandi,B. Balke,Y. -H. Chan,J. Nuss,A. P. Schnyder,L. M. Schoop###

On the possibility of magnetic Weyl fermions in non-symmorphic compound PtFeSb. Weyl fermions are expected to exhibit exotic physical properties such as the
chiral anomaly, large negative magnetoresistance or Fermi arcs. Recently a new
platform to realize these fermions has been introduced based on the appearance
of a three-fold band crossing at high symmetry points of certain space groups.
These band crossings are composed of two linearly dispersed bands that are
topologically protected by a Chern number, and a at band with no topological
charge. In this paper we present a new way of inducing two kinds of Weyl
fermions, based on two- and three-fold band crossings, in the non-symmorphic
magnetic material PtFeSb. By means of density functional theory calculations
and group theory analysis we show that magnetic order can split a six-fold
degeneracy enforced by non-symmoprhic symmetry to create three-fold or two-fold
degenerate Weyl nodes. We also report on the synthesis of a related phase
potentially containing two-fold degenerate magnetic Weyl points and extend our
group theory analysis to that phase. This is the first study showing that
magnetic ordering has the potential to generate new threefold degenerate Weyl
nodes, advancing the understanding of magnetic interactions in topological
materials.

###Graphite in 90 T: Evidence for Strong-coupling Excitonic Pairing|Zengwei Zhu,Pan Nie,Benoît Fauqué,Ross D. McDonald,Neil Harrison,Kamran Behnia###

Graphite in 90 T: Evidence for Strong-coupling Excitonic Pairing. Strong magnetic field induces at least two phase transitions in graphite
beyond the quantum limit where many-body effects are expected. We report on a
study using a state-of-the-art non-destructive magnet allowing to attain 90.5 T
at 1.4 K, which reveals a new field-induced phase and evidence that the
insulating state destroyed at 75 T is an excitonic condensate of electron-hole
pairs. By monitoring the angle dependence of in-plane and out-of-plane
magnetoresistance, we distinguish between the role of cyclotron and Zeeman
energies in driving various phase transitions. We find that, with the notable
exception of the transition field separating the two insulating states, the
threshold magnetic field for all other transitions display an exact cosine
angular dependence. Remarkably, the threshold field for the destruction of the
second insulator (phase B) is temperature-independent with no detectable
Landau-level crossing nearby. We conclude that the field-induced insulator
starts as a weak-coupling spin-density-wave, but ends as a strong-coupling
excitonic insulator of spin-polarized electron-hole pairs.

###Unconventional Planar Hall Effect in Exchange-Coupled Topological Insulator-Ferromagnetic Insulator Heterostructures|David Rakhmilevich,Fei Wang,Weiwei Zhao,Moses H. W. Chan,Jagadeesh S. Moodera,Chaoxing Liu,Cui-Zu Chang###

Unconventional Planar Hall Effect in Exchange-Coupled Topological Insulator-Ferromagnetic Insulator Heterostructures. The Dirac electrons occupying the surface states (SSs) of topological
insulators (TIs) have been predicted to exhibit many exciting magneto-transport
phenomena. Here we report on the first experimental observation of an
unconventional planar Hall effect (PHE) and an electrically gate-tunable
hysteretic planar magnetoresistance (PMR) in EuS/TI heterostructures, in which
EuS is a ferromagnetic insulator (FMI) with an in-plane magnetization. In such
exchange-coupled FMI/TI heterostructures, we find a significant (suppressed)
PHE when the in-plane magnetic field is parallel (perpendicular) to the
electric current. This behavior differs from previous observations of the PHE
in ferromagnets and semiconductors. Furthermore, as the thickness of the 3D TI
films is reduced into the 2D limit, in which the Dirac SSs develop a
hybridization gap, we find a suppression of the PHE around the charge neutral
point indicating the vital role of Dirac SSs in this phenomenon. To explain our
findings, we outline a symmetry argument that excludes linear-Hall mechanisms
and suggest two possible non-linear Hall mechanisms that can account for all
the essential qualitative features in our observations.

###Spin-dependent scattering and magnetic proximity effect in Ni-doped Co/Cu multilayers as a probe of atomic magnetism|Yu O Tykhonenko-Polishchuk,D M Polishchuk,T I Polek,D D Yaremkevych,A F Kravets,A I Tovstolytkin,A N Timoshevskii,V Korenivski###

Spin-dependent scattering and magnetic proximity effect in Ni-doped Co/Cu multilayers as a probe of atomic magnetism. We investigate the spin transport and ferromagnetic resonance properties of
giant magnetoresistive (GMR) Co/Cu-Ni multilayers with variable levels of Ni
doping in the Cu spacer. We present an experimental evidence for a
magnetic-to-diamagnetic transition in the atomic magnetic moment of Ni in the
Cu matrix for concentrations below 15 at. % Ni. As its concentration is
increased, Ni atoms turn into spin scattering centers, which is manifested
experimentally as a step-like change in the GMR of the multilayers. This
behavior is observed in multilayers with gradient-doped Cu spacers, where only
the inner region was doped with Ni. In the uniformly doped spacers the GMR
decreases monotonously with increasing Ni content, indicating that Ni atoms are
magnetic and act as spin relaxation centers in the entire dopant-concentration
range studied. We explain the difference in the observed GMR behavior as due to
a strong magnetic proximity effect in the uniform spacers, which is efficiently
suppressed in the gradient spacers. The observed magnetic phase transition is
fully supported by our detailed ab-initio calculations, taking into
consideration structural relaxation in the system as well as potential Ni
clustering. Controlling the loss or gain of the atomic magnetism for a specific
dopant can be a tool in probing and controlling spin relaxation in materials
and devices for spin-valve and spin-torque based applications.

###Surface Termination Dependent Quasiparticle Scattering Interference and Magneto-transport Study on ZrSiS|Chih-Chuan Su,Chi-Sheng Li,Tzu-Cheng Wang,Syu-You Guan,Raman Sankar,Fangcheng Chou,Chia-Seng Chang,Wei-Li Lee,Guang-Yu Guo,Tien-Ming Chuang###

Surface Termination Dependent Quasiparticle Scattering Interference and Magneto-transport Study on ZrSiS. Dirac nodal line semimetals represent a new state of quantum matters in which
the electronic bands touch to form a closed loop with linear dispersion. Here,
we report a combined study on ZrSiS by density functional theory calculation,
scanning tunneling microscope (STM) and magneto-transport measurements. Our STM
measurements reveal the spectroscopic signatures of a diamond-shaped Dirac bulk
band and a surface band on two types of cleaved surfaces as well as a spin
polarized surface band at ${\bar{\Gamma}}$ at E~0.6eV on S-surface, consistent
with our band calculation. Furthermore, we find the surface termination does
not affect the surface spectral weight from the Dirac bulk bands but greatly
affect the surface bands due to the change in the surface orbital composition.
From our magneto-transport measurements, the primary Shubnikov de-Haas
frequency is identified to stem from the hole-type quasi-two-dimensional Fermi
surface between {\Gamma} and X. The extracted non-orbital magnetoresistance
(MR) contribution D($\theta$, H) yields a nearly H-linear dependence, which is
attributed to the intrinsic MR in ZrSiS. Our results demonstrate the unique
Dirac line nodes phase and the dominating role of Zr-d orbital on the
electronic structure in ZrSiS and the related compounds.

###Non-monotonic pressure dependence of high-field nematicity and magnetism in CeRhIn$_5$|Toni Helm,Audrey D. Grockowiak,Fedor F. Balakirev,John Singleton,Jonathan B. Betts,Kent R. Shirer,Markus König,Tobias Förster,Eric D. Bauer,Filip Ronning,Stanley W. Tozer,Philip J. W. Moll###

Non-monotonic pressure dependence of high-field nematicity and magnetism in CeRhIn$_5$. CeRhIn$_5$ provides a textbook example of quantum criticality in a heavy
fermion system: Pressure suppresses local-moment antiferromagnetic (AFM) order
and induces superconductivity in a dome around the associated quantum critical
point (QCP) near $p_{c} \approx 23\,$kbar. Strong magnetic fields also suppress
the AFM order at a field-induced QCP at $B_{\rm c}\approx 50\,$T. In its
vicinity, a nematic phase at $B^*\approx 28\,$T characterized by a large
in-plane resistivity anisotropy emerges. Here, we directly investigate the
interrelation between these phenomena via magnetoresistivity measurements under
high pressure. As pressure increases, the nematic transition shifts to higher
fields, until it vanishes just below $p_{\rm c}$. While pressure suppresses
magnetic order in zero field as $p_{\rm c}$ is approached, we find magnetism to
strengthen under strong magnetic fields due to suppression of the Kondo effect.
We reveal a strongly non-mean-field-like phase diagram, much richer than the
common local-moment description of CeRhIn$_5$ would suggest.

###Nanomechanical characterization of quantum interference in a topological insulator nanowire|Minjin Kim,Jihwan Kim,Yasen Hou,Dong Yu,Yong-Joo Doh,Bongsoo Kim,Kun Woo Kim,Junho Suh###

Nanomechanical characterization of quantum interference in a topological insulator nanowire. The discovery of two-dimensional gapless Dirac fermions in graphene and
topological insulators (TI) has sparked extensive ongoing research toward
applications of their unique electronic properties. The gapless surface states
in three-dimensional insulators indicate a distinct topological phase of matter
with a non-trivial Z2 invariant that can be verified by angle-resolved
photoemission spectroscopy or magnetoresistance quantum oscillation. In TI
nanowires, the gapless surface states exhibit Aharonov-Bohm (AB) oscillations
in conductance, with this quantum interference effect accompanying a change in
the number of transverse one-dimensional modes in transport. Thus, while the
density of states (DOS) of such nanowires is expected to show such AB
oscillation, this effect has yet to be observed. Here, we adopt nanomechanical
measurements that reveal AB oscillations in the DOS of a topological insulator.
The TI nanowire under study is an electromechanical resonator embedded in an
electrical circuit, and quantum capacitance effects from DOS oscillation
modulate the circuit capacitance thereby altering the spring constant to
generate mechanical resonant frequency shifts. Detection of the quantum
capacitance effects from surface-state DOS is facilitated by the small
effective capacitances and high quality factors of nanomechanical resonators,
and as such the present technique could be extended to study diverse quantum
materials at nanoscale.

###Low Barrier Magnet Design for Efficient Hardware Binary Stochastic Neurons|Orchi Hassan,Rafatul Faria,Kerem Y. Camsari,Jonathan Z. Sun,Supriyo Datta###

Low Barrier Magnet Design for Efficient Hardware Binary Stochastic Neurons. Binary stochastic neurons (BSN's) form an integral part of many machine
learning algorithms, motivating the development of hardware accelerators for
this complex function. It has been recognized that hardware BSN's can be
implemented using low barrier magnets (LBM's) by minimally modifying
present-day magnetoresistive random access memory (MRAM) devices. A crucial
parameter that determines the response of these LBM based BSN designs is the
\emph{correlation time} of magnetization, $\tau_c$. In this letter, we show
that for magnets with low energy barriers ($\Delta \approx k_BT$ and below),
circular disk magnets with in-plane magnetic anisotropy (IMA) lead to $\tau_c$
values that are two orders of magnitude smaller compared to $\tau_c$ for
magnets having perpendicular magnetic anisotropy (PMA) and provide analytical
descriptions. We show that this striking difference in $\tau_c$ is due to a
precession-like fluctuation mechanism that is enabled by the large
demagnetization field in IMA magnets. We provide a detailed energy-delay
performance evaluation of previously proposed BSN designs based on
Spin-Orbit-Torque (SOT) MRAM and Spin-Transfer-Torque (STT) MRAM employing low
barrier circular IMA magnets by SPICE simulations. The designs exhibit sub-ns
response times leading to energy requirements of $\sim$a few fJ to evaluate the
BSN function, orders of magnitude lower than digital CMOS implementations with
a much larger footprint. While modern MRAM technology is based on PMA magnets,
results in this paper suggest that low barrier circular IMA magnets may be more
suitable for this application.

###$h/e$ Oscillations in Interlayer Transport of Delafossites|Carsten Putzke,Maja D. Bachmann,Philippa McGuinness,Elina Zhakina,Veronika Sunko,Marcin Konczykowski,Takashi Oka,Roderich Moessner,Ady Stern,Markus König,Seunghyun Khim,Andrew P. Mackenzie,Philip J. W. Moll###

$h/e$ Oscillations in Interlayer Transport of Delafossites. Transport of electrons in a bulk metal is usually well captured by their
particle-like aspects, while their wave-like nature is commonly harder to
observe. Microstructures can be are fully designed to reveal the quantum phase,
for example mesoscopic metal rings resembling interferometers. Here we report a
new type of phase coherent oscillation of the out-of-plane magnetoresistance in
the layered delafossites PdCoO$_2$ and PtCoO$_2$. The oscillation period is
equivalent to that determined by the magnetic flux quantum, $h/e$, threading an
area defined by the atomic interlayer separation and the sample width. The
phase of the electron wave function in these crystals appears remarkably robust
over macroscopic length scales exceeding 10$\mu$m and persisting up to elevated
temperatures of $T$>50K. We show that, while the experimental signal cannot be
explained in a standard Aharonov-Bohm analysis, it arises due to periodic
field-modulation of the out-of-plane hopping. These results demonstrate
extraordinary single-particle quantum coherence lengths in the delafossites,
and identify a new form of quantum interference in solids.

###Spin-charge conversion in NiMnSb Heusler alloy films|Zhenchao Wen,Zhiyong Qiu,Sebastian Tolle,Cosimo Gorini,Takeshi Seki,Dazhi Hou,Takahide Kubota,Ulrich Eckern,Eiji Saitoh,Koki Takanashi###

Spin-charge conversion in NiMnSb Heusler alloy films. Half-metallic Heusler alloys are attracting considerable attention because of
their unique half-metallic band structures which exhibit high spin polarization
and yield huge magnetoresistance ratios. Besides serving as ferromagnetic
electrodes, Heusler alloys also have the potential to host spin-charge
conversion which has been recently demonstrated in other ferromagnetic metals.
Here, we report on the spin-charge conversion effect in the prototypical
Heusler alloy NiMnSb. Spin currents were injected from Y3Fe5O12 into NiMnSb
films by spin pumping, and then the spin currents were converted to charge
currents via spin-orbit interactions. Interestingly, an unusual charge signal
was observed with a sign change at low temperature, which can be manipulated by
film thickness and ordering structure. It is found that the spin-charge
conversion has two contributions. First, the interfacial contribution causes a
negative voltage signal, which is almost constant versus temperature. The
second contribution is temperature dependent because it is dominated by
minority states due to thermally excited magnons in the bulk part of the film.
This work provides a pathway for the manipulation of spin-charge conversion in
ferromagnetic metals by interface-bulk engineering for spintronic devices.

###Terahertz frequency spectrum analysis with a nanoscale antiferromagnetic tunnel junction|P. Yu. Artemchuk,O. R. Sulymenko,S. Louis,J. Li,R. Khymyn,E. Bankowski,T. Meitzler,V. S. Tyberkevych,A. N. Slavin,O. V. Prokopenko###

Terahertz frequency spectrum analysis with a nanoscale antiferromagnetic tunnel junction. A method to perform spectrum analysis on low power signals between 0.1 and 10
THz is proposed. It utilizes a nanoscale antiferromagnetic tunnel junction
(ATJ) that produces an oscillating tunneling anisotropic magnetoresistance,
whose frequency is dependent on the magnitude of an evanescent spin current. It
is first shown that the ATJ oscillation frequency can be tuned linearly with
time. Then, it is shown that the ATJ output is highly dependent on matching
conditions that are highly dependent on the dimensions of the dielectric
tunneling barrier. Spectrum analysis can be performed by using an appropriately
designed ATJ, whose frequency is driven to increase linearly with time, a low
pass filter, and a matched filter. This method of THz spectrum analysis, if
realized in experiment, will allow miniaturized electronics to rapidly analyze
low power signals with a simple algorithm. It is also found by simulation and
analytical theory that for an ATJ with a 0.09 $\mu$m$^2$ footprint, spectrum
analysis can be performed over a 0.25 THz bandwidth in just 25 ns on signals
that are at the Johnson-Nyquist thermal noise floor.

###A Double Quantum Dot Spin Valve|Arunav Bordoloi,Valentina Zannier,Lucia Sorba,Christian Schönenberger,Andreas Baumgartner###

A Double Quantum Dot Spin Valve. A most fundamental and longstanding goal in spintronics is to electrically
tune highly efficient spin injectors and detectors, preferably compatible with
nanoscale electronics. Here, we demonstrate all these points using
semiconductor quantum dots (QDs), individually spin-polarized by ferromagnetic
split-gates (FSGs). As a proof of principle, we fabricated a double QD spin
valve consisting of two weakly coupled semiconducting QDs in an InAs nanowire
(NW), each with independent FSGs that can be magnetized in parallel or
anti-parallel. In tunneling magnetoresistance (TMR) experiments at zero
external magnetic field, we find a strongly reduced spin valve conductance for
the two anti-parallel configurations, with a single QD polarization of $\sim
27\%$. The TMR can be significantly improved by a small external field and
optimized gate voltages, which results in a continuously electrically tunable
TMR between $+80\%$ and $-90\%$. A simple model quantitatively reproduces all
our findings, suggesting a gate tunable QD polarization of $\pm 80\%$. Such
versatile spin-polarized QDs are suitable for various applications, for example
in spin projection and correlation experiments in a large variety of
nanoelectronics experiments.

###Exploration of The Duality Between Generalized Geometry and Extraordinary Magnetoresistance|Sathwik Bharadwaj,L. R. Ram-Mohan,Leo Rodriguez,Shanshan Rodriguez###

Exploration of The Duality Between Generalized Geometry and Extraordinary Magnetoresistance. We outline the duality between the extraordinary magnetoresistance (EMR),
observed in semiconductor-metal hybrids, and non-symmetric gravity coupled to a
diffusive $U(1)$ gauge field. The corresponding gravity theory may be
interpreted as the generalized complex geometry of the semi-direct product of
the symmetric metric and the antisymmetric Kalb-Ramond field:
($g_{\mu\nu}+\beta_{\mu\nu}$). We construct the four dimensional covariant
field theory and compute the resulting equations of motion. The equations
encode the most general form of EMR within a well defined variational
principle, for specific lower dimensional embedded geometric scenarios. Our
formalism also reveals the emergence of additional diffusive pseudo currents
for a completely dynamic field theory of EMR. The proposed equations of motion
now include terms that induce geometrical deformations in the device geometry
in order to optimize the EMR. This bottom-up dual description between EMR and
generalized geometry/gravity lends itself to a deeper insight into the EMR
effect with the promise of potentially new physical phenomena and properties.

###Magnetization and magneto-transport measurements on CeBi single crystals|Brinda Kuthanazhi,Na Hyun Jo,Li Xiang,Sergey L. Bud'ko,Paul C. Canfield###

Magnetization and magneto-transport measurements on CeBi single crystals. We report the synthesis of CeBi single crystals out of Bi self flux and a
systematic study of the magnetic and transport properties with varying
temperature and applied magnetic fields. From these $R(T,H)$ and $M(T,H)$ data
we could assemble the field-temperature ($H-T$) phase diagram for CeBi and
visualize the three dimensional $M-T-H$ surface. In the phase diagram, we
identify regions with well defined magnetization values, and identify a new
phase region. The magnetoresistance (MR) in the low temperature regime shows,
above $6~$T a power-law, non-saturated behavior with large MR ($\sim
3\times10^5 \%$ at $2~$K and $13.95~$T), along with Shubnikov-de Haas
oscillations. With increasing temperatures, MR decreases, and then becomes
negative for $T\gtrsim 10~$K. This crossover in MR seems to be unrelated to any
specific magnetic or metamagnetic transitions, but rather is associated with
changing from a low-temperature normal metal regime with little or no
scattering from the Ce$^{3+}$ moments and an anomalously large MR, to an
increased scattering from local Ce moments and a negative MR as temperature
increases.

###Flux pinning mechanism in NdFeAsO0.82F0.18 superconductor: Thermally activated flux flow and charge carrier mean free path fluctuation pinning|X. L. Wang,S. R. Ghorbani,S. X. Dou,Xiao-Li Shen,Wei Yi,Zheng-Cai Li,Zhi-An Ren###

Flux pinning mechanism in NdFeAsO0.82F0.18 superconductor: Thermally activated flux flow and charge carrier mean free path fluctuation pinning. The flux pinning mechanism of NdO0.82F0.18FeAs superconductor made under high
pressure, with a critical temperature, Tc, of 51 K, has been investigated in
detail in this work. The field dependence of the magnetization and the
temperature dependence of the magnetoresistivity were measured in fields up to
13 T. The field dependence of the critical current density, Jc(B), was analyzed
within the collective pinning model. A crossover field, Bsb, from the single
vortex to the small vortex bundle pinning regime was observed. The temperature
dependence of Bsb(T) is in good agreement with the delta-l pinning mechanism,
i.e., pinning associated with fluctuations in the charge-carrier mean free
path, l. Analysis of resistive transition broadening revealed that thermally
activated flux flow is found to be responsible for the resistivity contribution
in the vicinity of Tc. The activation energy U0/kB is 2000 K in low fields and
scales as B (-1/3) over a wide field range. Our results indicate that the
NdO0.82F0.18FeAs has stronger intrinsic pinning than Bi-2212 and also stronger
than MgB2 for H > 8 T.

###Transport and anisotropy in single-crystalline SrFe$_2$As$_2$ and $A_{0.6}$K$_{0.4}$Fe$_2$As$_2$ ($A$ = Sr, Ba) superconductors|G. F. Chen,Z. Li,J. Dong,G. Li,W. Z. Hu,X. D. Zhang,X. H. Song,P. Zheng,N. L. Wang,J. L. Luo###

Transport and anisotropy in single-crystalline SrFe$_2$As$_2$ and $A_{0.6}$K$_{0.4}$Fe$_2$As$_2$ ($A$ = Sr, Ba) superconductors. We have successfully grown high quality single crystals of SrFe$_2$As$_2$ and
A$_{0.6}$K$_{0.4}$Fe$_2$As$_2$(A=Sr, Ba) using flux method. The resistivity,
specific heat and Hall coefficient have been measured. For parent compound
SrFe$_2$As$_2$, an anisotropic resistivity with $\rho_c$ / $\rho_{ab}$ as large
as 130 is obtained at low temperatures. A sharp drop in both in-plane and
out-plane resistivity due to the SDW instability is observed below 200 K. The
angular dependence of in-plane magnetoresistance shows 2-fold symmetry with
field rotating within ab plane below SDW transition temperature. This is
consistent with a stripe-type spin ordering in SDW state. In K doped
A$_{0.6}$K$_{0.4}$Fe$_2$As$_2$(A=Sr. Ba), the SDW instability is suppressed and
the superconductivity appears with T$_c$ above 35 K. The rather low anisotropy
in upper critical field between H$\parallel$ab and H$\parallel$c indicates
inter-plane coupling play an important role in hole doped Fe-based
superconductors.

###Spin-flip scattering in time-dependent transport through a quantum dot: Enhanced spin-current and inverse tunneling magnetoresistance|Enrico Perfetto,Gianluca Stefanucci,Michele Cini###

Spin-flip scattering in time-dependent transport through a quantum dot: Enhanced spin-current and inverse tunneling magnetoresistance. We study the effects of spin-flip scatterings on the time-dependent transport
properties through a magnetic quantum dot attached to normal and ferromagnetic
leads. The transient spin-dynamics as well as the steady-state tunneling
magnetoresistance (TMR) of the system are investigated. The absence of a
definite spin quantization axis requires the time-propagation of two-component
spinors. We present numerical results in which the electrodes are treated both
as one-dimensional tight-binding wires and in the wide-band limit
approximation. In the latter case we derive a transparent analytic formula for
the spin-resolved current, and transient oscillations damped over different
time-scales are identified. We also find a novel regime for the TMR inversion.
For any given strength of the spin-flip coupling the TMR becomes negative
provided the ferromagnetic polarization is larger than some critical value.
Finally we show how the full knowledge of the transient response allows for
enhancing the spin-current by properly tuning the period of a pulsed bias.

###Effects of different geometries on the conductance, shot noise and tunnel magnetoresistance of double quantum dots|I. Weymann###

Effects of different geometries on the conductance, shot noise and tunnel magnetoresistance of double quantum dots. The spin-polarized transport through a coherent strongly coupled double
quantum dot (DQD) system is analyzed theoretically in the sequential and
cotunneling regimes. Using the real-time diagrammatic technique, we analyze the
current, differential conductance, shot noise and tunnel magnetoresistance
(TMR) as a function of both the bias and gate voltages for double quantum dots
coupled in series, in parallel as well as for T-shaped systems. For DQDs
coupled in series, we find a strong dependence of the TMR on the number of
electrons occupying the double dot, and super-Poissonian shot noise in the
Coulomb blockade regime. In addition, for asymmetric DQDs, we analyze transport
in the Pauli spin blockade regime and explain the existence of the leakage
current in terms of cotunneling and spin-flip cotunneling-assisted sequential
tunneling. For DQDs coupled in parallel, we show that the transport
characteristics in the weak coupling regime are qualitatively similar to those
of DQDs coupled in series. On the other hand, in the case of T-shaped quantum
dots we predict a large super-Poissonian shot noise and TMR enhanced above the
Julliere value due to increased occupation of the decoupled quantum dot. We
also discuss the possibility of determining the geometry of the double dot from
transport characteristics. Furthermore, where possible, we compare our results
with existing experimental data on nonmagnetic systems and find qualitative
agreement.

###Electric-field control of magnetic ordering in the tetragonal BiFeO3|Hang-Chen Ding,Chun-Gang Duan###

Electric-field control of magnetic ordering in the tetragonal BiFeO3. We propose a way to use electric-field to control the magnetic ordering of
the tetragonal BiFeO3. Based on systematic first-principles studies of the
epitaxial strain effect on the ferroelectric and magnetic properties of the
tetragonal BiFeO3, we find that there exists a transition from C-type to G-type
antiferromagnetic (AFM) phase at in-plane constant a ~ 3.905 {\AA} when the
ferroelectric polarization is along [001] direction. Such magnetic phase
transition can be explained by the competition between the Heisenberg exchange
constant J1c and J2c under the influence of biaxial strain. Interestingly, when
the in-plane lattice constant enlarges, the preferred ferroelectric
polarization tends to be canted and eventually lies in the plane (along [110]
direction). It is found that the orientation change of ferroelectric
polarization, which can be realized by applying external electric-field, has
significant impact on the Heisenberg exchange parameters and therefore the
magnetic orderings of tetragonal BiFeO3. For example, at a ~ 3.79 {\AA}, an
electric field along [111] direction with magnitude of 2 MV/cm could change the
magnetic ordering from C-AFM to G-AFM. As the magnetic ordering affects many
physical properties of the magnetic material, e.g. magnetoresistance, we expect
such strategy would provide a new avenue to the application of multiferroic
materials.

###Double-percolation and magnetoresistance effects in ferromagnet-superconductor nanoparticle composites|Xiangdong Liu,Raghava P. Panguluri,Daniel P. Shoemaker,Zhi-Feng Huang,Boris Nadgorny###

Double-percolation and magnetoresistance effects in ferromagnet-superconductor nanoparticle composites. We investigate transport and magnetotransport properties of binary networks
composed of superconducting (MgB2) and ferromagnetic (CrO2 or LSMO)
nanoparticles. While for the LSMO/MgB2 system a single percolation threshold is
observed, for CrO2/MgB2 binary composites an anomalously high resistance state
with two distinct percolation thresholds corresponding to conductor-insulator
and superconductor-insulator transitions is found. The existence of this double
percolation effect becomes possible when the interface conductance between the
two different constituents is suppressed and the condition for the two
thresholds PI + PII > 1 is satisfied. For MgB2 an unusually large value of the
threshold is observed, which can be explained by the significant geometric
disparity between nanoparticles of the two constituents, resulting in a large
excluded volume for MgB2 nanoparticles. The scaling behavior near both
thresholds is determined, with the two critical exponents identified: \mu
\approx 2.16 \pm 0.15 for the insulating-conducting transition on the CrO2 side
and s = 1.37\pm 0.05 for the insulating - superconducting transition on the
MgB2 side. We also measure the magnetoresistance for the entire series of
CrO2/MgB2 samples, with a maximum of approximately 45% observed near the
percolation threshold at liquid He temperatures.

###Spin-dependent transport for armchair-edge graphene nanoribbons between ferromagnetic leads|Benhu Zhou,Xiongwen Chen,Benliang Zhou,Kai-He Ding,Guanghui Zhou###

Spin-dependent transport for armchair-edge graphene nanoribbons between ferromagnetic leads. We theoretically investigate the spin-dependent transport for the system of
an armchair-edge graphene nanoribbon (AGNR) between two ferromagnetic (FM)
leads with arbitrary polarization directions at low temperatures, where a
magnetic insulator is deposited on the AGNR to induce an exchange splitting
between spin-up and -down carriers. By using the standard nonequilibrium
Green's function (NGF) technique, it is demonstrated that, the spin-resolved
transport property for the system depends sensitively on both the width of AGNR
and the polarization strength of FM leads. The tunneling magnetoresistance
(TMR) around zero bias voltage possesses a pronounced plateau structure for
system with semiconducting 7-AGNR or metallic 8-AGNR in the absence of exchange
splitting, but this plateau structure for 8-AGNR system is remarkably broader
than that for 7-AGNR one. Interestingly, the increase of exchange splitting
$\Delta$ suppresses the amplitude of the structure for 7-AGNR system. However,
the TMR is enhanced much for 8-AGNR system under the bias amplitude comparable
to splitting strength. Further, the current-induced spin transfer torque (STT)
for 7-AGNR system is systematically larger than that for 8-AGNR one. The
findings here suggest the design of GNR-based spintronic devices by using a
metallic AGNR, but it is more favorable to fabricate a current-controlled
magnetic memory element by using a semiconducting AGNR.

###Mott-insulator to metal transition in filling-controlled SmMnAsO_{1-x}|Y. Shiomi,S. Ishiwata,Y. Taguchi,Y. Tokura###

Mott-insulator to metal transition in filling-controlled SmMnAsO_{1-x}. Transport and magnetic properties have been systematically investigated for
SmMnAsO_{1-x} with controlled electron-doping. As the electron band-filling is
increased with the increase of oxygen deficiency (x), the resistivity
monotonically decreases and the transition from Mott-insulator to metal occurs
between x=0.17 and 0.2. Seebeck coefficient at room temperature abruptly
changes around the critical doping level from a large value (\sim -300 \mu V/K)
to a small one (\sim -50 \mu V/K) both with negative sign. In the metallic
compounds with x=0.2 and x=0.3, Mn spins order antiferromagnetically around 30
K, and the Hall coefficient with the negative sign shows a reduction in
magnitude upon the magnetic transition, indicating the change in the multiple
Fermi surfaces. Gigantic positive magnetoresistance effect is observed in a
wide range of temperature, reaching up to 60 % at 2 K for the x=0.3 compound.
The effect is attributed to the field-induced change of the complex Fermi
surfaces in this multi-orbital correlated electron system.

###Hysteretic magnetoresistance and thermal bistability in a magnetic two-dimensional hole system|Ursula Wurstbauer,Cezary Śliwa,Dieter Weiss,Tomasz Dietl,Werner Wegscheider###

Hysteretic magnetoresistance and thermal bistability in a magnetic two-dimensional hole system. Colossal negative magnetoresistance and the associated field-induced
insulator-to-metal transition, the most characteristic features of magnetic
semiconductors, are observed in n-type rare earth oxides and chalcogenides,
p-type manganites, n-type and p-type diluted magnetic semiconductors (DMS) as
well as in quantum wells of n-type DMS. Here, we report on magnetostransport
studies of Mn modulation-doped InAs quantum wells, which reveal a magnetic
field driven and bias voltage dependent insulator-to-metal transition with
abrupt and hysteretic changes of resistance over several orders of magnitude.
These phenomena coexist with the quantised Hall effect in high magnetic fields.
We show that the exchange coupling between a hole and the parent Mn acceptor
produces a magnetic anisotropy barrier that shifts the spin relaxation time of
the bound hole to a 100 s range in compressively strained quantum wells. This
bistability of the individual Mn acceptors explains the hysteretic behaviour
while opening prospects for information storing and processing. At high bias
voltage another bistability, caused by the overheating of electrons10, gives
rise to abrupt resistance jumps.

###Manifestations of multiple-carrier charge transport in the magnetostructurally ordered phase of undoped BaFe$_2$As$_2$|S. Ishida,T. Liang,M. Nakajima,K. Kihou,C. H. Lee,A. Iyo,H. Eisaki,T. Kakeshita,T. Kida,M. Hagiwara,Y. Tomioka,T. Ito,S. Uchida###

Manifestations of multiple-carrier charge transport in the magnetostructurally ordered phase of undoped BaFe$_2$As$_2$. We investigated the transport properties of BaFe$_2$As$_2$ single crystals
before and after annealing with BaAs powder. The annealing remarkably improves
transport properties, in particular the magnitude of residual resistivity which
decreases by a factor of more than 10. From the resistivity measurement on
detwinned crystals we found that the anisotropy of the in-plane resistivity is
remarkably diminished after annealing, indicative of dominant contributions to
the charge transport from the carriers with isotropic and high mobility below
magnetostructural transition temperature $T_{\rm s}$ and the absence of nematic
state above $T_{\rm s}$. We found that the Hall resistivity shows strong
non-linearity against magnetic field and the magnetoresistance becomes very
large at low temperatures. These results give evidence for the manifestation of
multiple carriers with distinct characters in the ordered phase below $T_{\rm
s}$. By analyzing the magnetic field dependences, we found that at least three
carriers equally contribute to the charge transport in the ordered phase, which
is in good agreement with the results of recent quantum oscillation
measurements.

###Magnetoresistance of 2D and 3D Electron Gas in LaAlO3/SrTiO3 Heterostructures: Influence of Magnetic Ordering, Interface Scattering and Dimensionality|X. Wang,W. M Lü,A. Annadi,Z. Q. Liu,S. Dhar,T. Venkatesan,Ariando###

Magnetoresistance of 2D and 3D Electron Gas in LaAlO3/SrTiO3 Heterostructures: Influence of Magnetic Ordering, Interface Scattering and Dimensionality. Magnetoresistance (MR) anisotropy in LaAlO3/SrTiO3 (LAO/STO) interfaces is
compared between samples prepared in high oxygen partial pressure (PO2) of 10-4
mbar exhibiting quasi-two-dimensional (quasi-2D) electron gas and low PO2 of
10-6 mbar exhibiting 3D conductivity. While MR of an order of magnitude larger
was observed in low PO2 samples compared to those of high PO2 samples, large MR
anisotropies were observed in both cases. The MR with the out-of-plane field is
always larger compared to the MR with in-plane field suggesting lower
dissipation of electrons from interface versus defect scattering. The quasi-2D
interfaces show a negative MR at low temperatures while the 3D interfaces show
positive MR for all temperatures. Furthermore, the angle relationship of MR
anisotropy for these two different cases and temperature dependence of in-plane
MR are also presented. Our study demonstrates that MR can be used to
distinguish the dimensionality of the charge transport and various (defect,
magnetic center, and interface boundary) scattering processes in this system.

###Strength of the symmetry spin filtering effect in magnetic tunnel junctions|Sergey V. Faleev,Stuart S. P. Parkin,Oleg N. Mryasov###

Strength of the symmetry spin filtering effect in magnetic tunnel junctions. Strength of the the symmetry spin filtering effect (as defined by the
asymptotic behavior of the tunneling magnetoresistance (TMR) at large barrier
thicknesses induced by this effect) is studied for the Fe/MgO/Fe magnetic
tunnel junctions (MTJ). Based on the analysis of the band structure of bulk Fe
and complex band structure of MgO we predict \emph{native} for the symmetry
spin filtering effect linear increase of the TMR in Fe/MgO/Fe MTJ with
increasing number of MgO layers, $N$. \emph{Ab initio} calculations of
transmission functions performed for the Fe/MgO/Fe MTJ confirm our theoretical
predictions for the strength of the symmetry spin filtering effect in broad
range of energies and $N$. Our calculations also show that the
\emph{combination} of the symmetry spin filtering effect and small surface
transmission function in minority spin channel at the Fe/MgO interface is
responsible for large $TMR>10,000\%$ predicted for Fe/MgO/Fe MTJ for $N
\geqslant 8$. Proposed analysis of the strength of the symmetry filtering
effect derived from the band structure of bulk electrode material could serve
as a tool for quick material discovery search of suitable electrodes in context
of emerging technologies that require high TMR.

###Superconducting Bi2Te: pressure-induced universality in the (Bi2)m(Bi2Te3)n series|Ryan L. Stillwell,Zsolt Jenei,Samuel T. Weir,Yogesh K. Vohra,Jason R. Jeffries###

Superconducting Bi2Te: pressure-induced universality in the (Bi2)m(Bi2Te3)n series. Using high-pressure magnetotransport techniques we have discovered
superconductivity in Bi2Te, a member of the infinitely adaptive (Bi2)m(Bi2Te3)n
series, whose end members, Bi and Bi2Te3, can be tuned to display topological
surface states or superconductivity. Bi2Te has a maximum Tc= 8.6 K at P= 14.5
GPa and goes through multiple high pressure phase transitions, ultimately
collapsing into a bcc structure that suggests a universal behavior across the
series. High-pressure magnetoresistance and Hall measurements suggest a
semi-metal to metal transition near 5.4 GPa, which accompanies the hexagonal to
intermediate phase transition seen via x-ray diffraction measurements. In
addition, the linearity of Hc2(T) exceeds the Werthamer-Helfand-Hohenberg
limit, even in the extreme spin-orbit scattering limit, yet is consistent with
other strong spin-orbit materials. Considering these results in combination
with similar reports on strong spin-orbit scattering materials seen in the
literature, we suggest the need for a new theory that can address the
unconventional nature of their superconducting states.

###Environmental Instability and Degradation of Single- and Few-Layer WTe2 Nanosheets in Ambient Conditions|Fan Ye,Jaesung Lee,Jin Hu,Zhiqiang Mao,Jiang Wei,Philip X. -L. Feng###

Environmental Instability and Degradation of Single- and Few-Layer WTe2 Nanosheets in Ambient Conditions. Since the discovery of large, non-saturating magnetoresistance in bulk WTe2
which allows microexfoliation, single- and few-layer WTe2 crystals have
attracted increasing interests. However, as it mentioned in existing studies,
WTe2 flakes appear to degrade in ambient conditions. Here we report
experimental observations of saturating degradation in few-layer WTe2 through
Raman spectroscopy characterization and careful monitoring of the degradation
of single-, bi- and tri-layer (1L, 2L & 3L) WTe2 over long time. Raman peak
intensity decreases during WTe2 degradation and 1L flakes degrade faster than
2L and 3L flakes. The relatively faster degradation in 1L WTe2 could be
attributed to low energy barrier of oxygen reaction with WTe2. We further
investigate the degradation mechanisms of WTe2 using XPS and AES and find that
oxidation of Te and W atoms is the main reason of WTe2 degradation. In
addition, we observe oxidation occurs only in the depth of 0.5nm near the
surface, and the oxidized WTe2 surface could help prevent inner layers from
further degradation.

###Non-Fermi liquid behavior of electrical resistivity close to the nematic critical point in Fe$_{1-x}$Co$_x$Se and FeSe$_{1-y}$S$_y$|Takahiro Urata,Yoichi Tanabe,Khuong Kim Huynh,Hidetoshi Oguro,Kazuo Watanabe,Katsumi Tanigaki###

Non-Fermi liquid behavior of electrical resistivity close to the nematic critical point in Fe$_{1-x}$Co$_x$Se and FeSe$_{1-y}$S$_y$. Temperature dependence of resistivity of single crystals of
Fe$_{1-x}$Co$_x$Se and FeSe$_{1-y}$S$_y$ is studied in detail under zero and
high magnetic field (magnetoresistance), the latter of which enables to monitor
the temperature ($T$) evolution of resistivity below the onset of
superconducting transition temperature ($T_{\rm c}$). In FeSe$_{1-y}$S$_y$,
$T$-linear dependence of resistivity is prominent in $y$ = 0.160 below 40 K,
whereas it changes to a Fermi-liquid(FL)-like $T^2$ one below 10 K in $y$ =
0.212. These suggest that the quantum critical point (QCP) originating from the
electronic nematicity resides around $y$ = 0.160 and the fluctuation in QCP
gives rise anomalous $T$-linear dependence in resistivity in a wide $T$ range.
In Fe$_{1-x}$Co$_x$Se, resistivity gradually changes from linear- to quadratic-
$T$-dependent one at low temperatures in the range between $x$ = 0.036 and
0.075. These could be interpreted by scenarios of both the nematic QCP and the
crossover in the ground states between the orthorhombic nematic phase and the
tetragonal phase. The anomalies found as $T$-linear resistivity are discussed
in terms of orbital and spin fluctuation arising from the nematic QCP.

###Superconductor to Mott insulator transition in YBa$_2$Cu$_3$O$_7$/LaCaMnO$_3$ heterostructures|B. A. Gray,S. Middey,G. Conti,A. X. Gray,C. -T. Kuo,A. M. Kaiser,S. Ueda,K. Kobayashi,D. Meyers,M. Kareev,I. C. Tung,Jian Liu,C. S. Fadley,J. Chakhalian,J. W. Freeland###

Superconductor to Mott insulator transition in YBa$_2$Cu$_3$O$_7$/LaCaMnO$_3$ heterostructures. The superconductor-to-insulator transition (SIT) induced by means such as
external magnetic fields, disorder or spatial confinement is a vivid
illustration of a quantum phase transition dramatically affecting the
superconducting order parameter. In pursuit of a new realization of the SIT by
interfacial charge transfer, we developed extremely thin superlattices composed
of high $T_c$ superconductor YBa$_2$Cu$_3$O$_7$ (YBCO) and colossal
magnetoresistance ferromagnet La$_{0.67}$Ca$_{0.33}$MnO$_3$ (LCMO). By using
linearly polarized resonant X-ray absorption spectroscopy and magnetic circular
dichroism, combined with hard X-ray photoelectron spectroscopy, we derived a
complete picture of the interfacial carrier doping in cuprate and manganite
atomic layers, leading to the transition from superconducting to an unusual
Mott insulating state emerging with the increase of LCMO layer thickness. In
addition, contrary to the common perception that only transition metal ions may
response to the charge transfer process, we found that charge is also actively
compensated by rare-earth and alkaline-earth metal ions of the interface. Such
deterministic control of $T_c$ by pure electronic doping without any hindering
effects of chemical substitution is another promising route to disentangle the
role of disorder on the pseudo-gap and charge density wave phases of underdoped
cuprates.

###Effect of aging-induced disorder on the quantum transport properties of atomically thin WTe$_{2}$|W. L. Liu,M. L. Chen,X. X. Li,S. Dubey,T. Xiong,Z. M. Dai,J. Yin,W. L. Guo,J. L. Ma,Y. N. Chen,J. Tan,D. Li,Z. H. Wang,W. Li,V. Bouchiat,D. M. Sun,Z. Han,Z. D. Zhang###

Effect of aging-induced disorder on the quantum transport properties of atomically thin WTe$_{2}$. Atomically thin layers of transition-metal dicalcogenides (TMDCs) are often
known to be metastable in the ambient atmosphere. Understanding the mechanism
of degradation is essential for their future applications in nanoelectronics,
and thus has attracted intensive interest recently. Here, we demonstrate a
systematic study of atomically thin WTe$_{2}$ in its low temperature quantum
electronic transport properties. Strikingly, while the temperature dependence
of few layered WTe$_{2}$ showed clear metallic tendency in the fresh state,
degraded devices first exhibited a re-entrant insulating behavior, and finally
entered a fully insulating state. Correspondingly, a crossover from parabolic
to linear magnetoresistance, and finally to weak anti-localization was seen.
Real-time Raman scattering measurement, together with transmission electron
microscopy studies done before and after air degradation of atomically thin
WTe$_{2}$ further confirmed that the material gradually form amorphous islands.
It thus leads to localized electronic states and explains the low temperature
Coulomb gap observed in transport measurements. Our study reveals for the first
time the correlation between the unusual magnetotransport and disorder in
few-layered WTe$_{2}$, which is indispensable in providing guidance on its
future devices application.

###Gate-Tunable Negative Longitudinal Magnetoresistance in the Predicted Type-II Weyl Semimetal WTe2|Yaojia Wang,Erfu Liu,Huimei Liu,Yiming Pan,Longqiang Zhang,Junwen Zeng,Yajun Fu,Miao Wang,Kang Xu,Zhong Huang,Zhenlin Wang,Haizhou Lu,Dingyu Xing,Baigeng Wang,Xiangang Wan,Feng Miao###

Gate-Tunable Negative Longitudinal Magnetoresistance in the Predicted Type-II Weyl Semimetal WTe2. The progress in exploiting new electronic materials and devices has been a
major driving force in solid-state physics. As a new state of matter, a Weyl
semimetal (WSM), particularly a type-II WSM, hosts Weyl fermions as emergent
quasiparticles and may harbor novel electrical transport properties because of
the exotic Fermi surface. Nevertheless, such a type-II WSM material has not
been experimentally observed in nature. In this work, by performing systematic
magneto-transport studies on thin films of a predicted material candidate WTe2,
we observe notable angle-sensitive (between the electric and magnetic fields)
negative longitudinal magnetoresistance (MR), which can likely be attributed to
the chiral anomaly in WSM. This phenomenon also exhibits strong planar
orientation dependence with the absence of negative longitudinal MR along the
tungsten chains (a axis), which is consistent with the distinctive feature of a
type-II WSM. By applying a gate voltage, we demonstrate that the Fermi energy
can be tuned through the Weyl points via the electric field effect; this is the
first report of controlling the unique transport properties in situ in a WSM
system. Our results have important implications for investigating simulated
quantum field theory in solid-state systems and may open opportunities for
implementing new types of electronic applications, such as field-effect chiral
electronic devices.

###Magnetoresistence engineering and singlet/triplet switching in InAs nanowire quantum dots with ferromagnetic sidegates|G. Fábián,P. Makk,M. H. Madsen,J. Nygård,C. Schönenberger,A. Baumgartner###

Magnetoresistence engineering and singlet/triplet switching in InAs nanowire quantum dots with ferromagnetic sidegates. We present magnetoresistance (MR) experiments on an InAs nanowire quantum dot
device with two ferromagnetic sidegates (FSGs) in a split-gate geometry. The
wire segment can be electrically tuned to a single dot or to a double dot
regime using the FSGs and a backgate. In both regimes we find a strong MR and a
sharp MR switching of up to 25\% at the field at which the magnetizations of
the FSGs are inverted by the external field. The sign and amplitude of the MR
and the MR switching can both be tuned electrically by the FSGs. In a double
dot regime close to pinch-off we find {\it two} sharp transitions in the
conductance, reminiscent of tunneling MR (TMR) between two ferromagnetic
contacts, with one transition near zero and one at the FSG switching fields.
These surprisingly rich characteristics we explain in several simple resonant
tunneling models. For example, the TMR-like MR can be understood as a
stray-field controlled transition between singlet and a triplet double dot
states. Such local magnetic fields are the key elements in various proposals to
engineer novel states of matter and may be used for testing electron spin-based
Bell inequalities.

###Epitaxial thin films of pyrochlore iridate Bi_{2+x}Ir_{2-y}O_{7-delta}: structure, defects and transport properties|Wencao Yang,Yuantao Xie,Wenka Zhu,Kyungwha Park,Aiping Chen,Yaroslav Losovyj,Zhen Li,Haoming Liu,Matthew Starr,Jaime A. Acosta,Chenggang Tao,Nan Li,Quanxi Jia,Jean J. Heremans,Shixiong Zhang###

Epitaxial thin films of pyrochlore iridate Bi_{2+x}Ir_{2-y}O_{7-delta}: structure, defects and transport properties. While pyrochlore iridate thin films are theoretically predicted to possess a
variety of emergent topological properties, experimental verification of these
predictions can be obstructed by the challenge in thin film growth. Here we
report on the pulsed laser deposition and characterization of thin films of a
representative pyrochlore compound Bi2Ir2O7. The films were epitaxially grown
on yttria-stabilized zirconia substrates and have lattice constants that are a
few percent larger than that of the bulk single crystals. The film composition
shows a strong dependence on the oxygen partial pressure.
Density-functional-theory calculations indicate the existence of Bi_Ir antisite
defects, qualitatively consistent with the high Bi: Ir ratio found in the
films. Both Ir and Bi have oxidation states that are lower than their nominal
values, suggesting the existence of oxygen deficiency. The iridate thin films
show a variety of intriguing transport characteristics, including multiple
charge carriers, logarithmic dependence of resistance on temperature,
antilocalization corrections to conductance due to spin-orbit interactions, and
linear positive magnetoresistance.

###Bias voltage effects on tunneling magnetoresistance in Fe/MgAl${}_2$O${}_4$/Fe(001) junctions: Comparative study with Fe/MgO/Fe(001) junctions|Keisuke Masuda,Yoshio Miura###

Bias voltage effects on tunneling magnetoresistance in Fe/MgAl${}_2$O${}_4$/Fe(001) junctions: Comparative study with Fe/MgO/Fe(001) junctions. We investigate bias voltage effects on the spin-dependent transport
properties of Fe/MgAl${}_2$O${}_4$/Fe(001) magnetic tunneling junctions (MTJs)
by comparing them with those of Fe/MgO/Fe(001) MTJs. By means of the
nonequilibrium Green's function method and the density functional theory, we
calculate bias voltage dependences of magnetoresistance (MR) ratios in both the
MTJs. We find that in both the MTJs, the MR ratio decreases as the bias voltage
increases and finally vanishes at a critical bias voltage $V_{\rm c}$. We also
find that the critical bias voltage $V_{\rm c}$ of the MgAl${}_2$O${}_4$-based
MTJ is clearly larger than that of the MgO-based MTJ. Since the in-plane
lattice constant of the Fe/MgAl${}_2$O${}_4$/Fe(001) supercell is twice that of
the Fe/MgO/Fe(001) one, the Fe electrodes in the MgAl${}_2$O${}_4$-based MTJs
have an identical band structure to that obtained by folding the Fe band
structure of the MgO-based MTJs in the Brillouin zone of the in-plane wave
vector. We show that such a difference in the Fe band structure is the origin
of the difference in the critical bias voltage $V_{\rm c}$ between the
MgAl${}_2$O${}_4$- and MgO-based MTJs.

###Large magnetoresistance and Fermi surface study of Sb$_2$Se$_2$Te single crystal|K. Shrestha,V. Marinova,D. Graf,B. Lorenz,C. W. Chu###

Large magnetoresistance and Fermi surface study of Sb$_2$Se$_2$Te single crystal. We have studied the magnetotransport properties of a Sb$_2$Se$_2$Te single
crystal. Magnetoresistance (MR) is maximum when the magnetic field is
perpendicular to the sample surface and reaches to a value of 1100\% at $B$=31
T with no sign of saturation. MR shows Shubnikov de Haas (SdH) oscillations
above $B$=15 T. The frequency spectrum of SdH oscillations consists of three
distinct peaks at $\alpha$=32 T, $\beta$=80 T and $\gamma$=117 T indicating the
presence of three Fermi surface pockets. Among these frequencies, $\beta$ is
the prominent peak in the frequency spectrum of SdH oscillations measured at
different tilt angles of the sample with respect to the magnetic field. From
the angle dependence $\beta$ and Berry phase calculations, we have confirmed
the trivial topology of the $\beta$-pocket. The cyclotron masses of charge
carriers, obtained by using the Lifshitz-Kosevich formula, are found to be
$m^{*}_{\beta}=0.16m_o$ and $m^{*}_{\gamma}=0.63m_o$ for the $\beta$ and
$\gamma$ bands respectively. Large MR of Sb$_2$Se$_2$Te is suitable for
utilization in electronic instruments such as a computer hard disc, high field
magnetic sensors, and memory devices.

###Possible topologically non-trivial superconducting order parameter in type-II Weyl semimetal T_d-MoTe_2|Z. Guguchia,F. v. Rohr,Z. Shermadini,A. T. Lee,S. Banerjee,A. R. Wieteska,C. A. Marianetti,H. Luetkens,Z. Gong,B. A. Frandsen,S. C. Cheung,C. Baines,A. Shengelaya,A. N. Pasupathy,E. Morenzoni,S. J. L. Billinge,A. Amato,R. J. Cava,R. Khasanov,Y. J. Uemura###

Possible topologically non-trivial superconducting order parameter in type-II Weyl semimetal T_d-MoTe_2. MoTe_2, with the orthorhombic T_d phase, is a new type (type-II) of Weyl
semimetal, where the Weyl Fermions emerge at the boundary between electron and
hole pockets. Non-saturating magnetoresistance (MR), and superconductivity were
also observed in T_d-MoTe_2. Understanding the superconductivity in T_d-MoTe_2,
which was proposed to be topologically non-trivial, is of eminent interest.
Here, we report high-pressure (p_max = 1.3 GPa) muon spin rotation experiments
on the temperature-dependent magnetic penetration depth in T_d-MoTe_2. A
substantial increase of the superfluid density n_s/m^* and a linear scaling
with T_c is observed under pressure. Moreover, the superconducting order
parameter in T_d-MoTe_2 is determined to be two gap (s+s)-wave symmetric. We
also excluded time reversal symmetry breaking in the SC state with sensitive
zero-field ${\mu}$SR experiments. Considering the previous report
\cite{Balicas1} on the strong suppression of T_c in T_d-MoTe_2 by disorder, we
suggest that s^{+-} (topological order parameter) state is more likely to be
realized in MoTe_2 than the s^{++} (trivial) state. Should s^{+-} be the SC gap
symmetry, the T_d-MoTe_2 is, to our knowledge, the first known example of a
time reversal invariant topological (Weyl) superconductor.

###Potential Fluctuations at Low Temperatures in Mesoscopic-Scale SmTiO$_{3}$/SrTiO$_{3}$/SmTiO$_{3}$ Quantum Well Structures|Will J. Hardy,Brandon Isaac,Patrick Marshall,Evgeny Mikheev,Panpan Zhou,Susanne Stemmer,Douglas Natelson###

Potential Fluctuations at Low Temperatures in Mesoscopic-Scale SmTiO$_{3}$/SrTiO$_{3}$/SmTiO$_{3}$ Quantum Well Structures. Heterointerfaces of SrTiO$_{3}$ with other transition metal oxides make up an
intriguing family of systems with a bounty of coexisting and competing physical
orders. Some examples, such as LaAlO$_{3}$/SrTiO$_{3}$, support a high carrier
density electron gas at the interface whose electronic properties are
determined by a combination of lattice distortions, spin-orbit coupling,
defects, and various regimes of magnetic and charge ordering. Here, we study
electronic transport in mesoscale devices made with heterostructures of
SrTiO$_{3}$ sandwiched between layers of SmTiO$_{3}$, in which the transport
properties can be tuned from a regime of Fermi-liquid like resistivity ($\rho
\sim T^{2}$) to a non-Fermi liquid ($\rho \sim T^{5/3}$) by controlling the
SrTiO$_{3}$ thickness. In mesoscale devices at low temperatures, we find
unexpected voltage fluctuations that grow in magnitude as $T$ is decreased
below 20 K, are suppressed with increasing contact electrode size, and are
independent of the drive current and contact spacing distance.
Magnetoresistance fluctuations are also observed, which are reminiscent of
universal conductance fluctuations but not entirely consistent with their
conventional properties. Candidate explanations are considered, and a mechanism
is suggested based on mesoscopic temporal fluctuations of the Seebeck
coefficient. An improved understanding of charge transport in these model
systems, especially their quantum coherent properties, may lead to insights
into the nature of transport in strongly correlated materials that deviate from
Fermi liquid theory.

###Enhancement of electron mobility at oxide interfaces induced by WO3 overlayers|Giordano Mattoni,David J. Baek,Nicola Manca,Nils Verhagen,Lena F. Kourkoutis,Alessio Filippetti,Andrea D. Caviglia###

Enhancement of electron mobility at oxide interfaces induced by WO3 overlayers. Interfaces between complex oxides constitute a unique playground for 2D
electron systems (2DES), where superconductivity and magnetism can arise from
combinations of bulk insulators. The 2DES at the LaAlO3/SrTiO3 interface is one
of the most studied in this regard, and its origin is determined by both the
presence of a polar field in LaAlO3 and the insurgence of point defects, such
as oxygen vacancies and intermixed cations. These defects usually reside in the
conduction channel and are responsible for a decreased electronic mobility. In
this work we use an amorphous WO3 overlayer to control the defect formation and
obtain an increased electron mobility and effective mass in WO3/LaAlO3/SrTiO3
heterostructures. The studied system shows a sharp insulator-to-metal
transition as a function of both LaAlO3 and WO3 layer thickness.
Low-temperature magnetotransport reveals a strong magnetoresistance reaching
900% at 10 T and 1.5 K, the presence of multiple conduction channels with
carrier mobility up to 80 000 cm2/Vs and an unusually high effective mass of
5.6 me. The amorphous character of the WO3 overlayer makes this a versatile
approach for defect control at oxide interfaces, which could be applied to
other heterestrostures disregarding the constraints imposed by crystal
symmetry.

###Geometrical dependence of domain wall propagation and nucleation fields in magnetic domain wall sensor devices|B. Borie,A. Kehlberger,J. Wahrhusen,H. Grimm,M. Kläui###

Geometrical dependence of domain wall propagation and nucleation fields in magnetic domain wall sensor devices. We study the key domain wall properties in segmented nanowires loop-based
structures used in domain wall based sensors. The two reasons for device
failure, namely the distribution of domain wall propagation field (depinning)
and the nucleation field are determined with Magneto-Optical Kerr Effect (MOKE)
and Giant Magnetoresistance (GMR) measurements for thousands of elements to
obtain significant statistics. Single layers of Ni$_{81}$Fe$_{19}$, a complete
GMR stack with Co$_{90}$Fe$_{10}$/Ni$_{81}$Fe$_{19}$ as a free layer and a
single layer of Co$_{90}$Fe$_{10}$ are deposited and industrially patterned to
determine the influence of the shape anisotropy, the magnetocrystalline
anisotropy and the fabrication processes. We show that the propagation field is
little influenced by the geometry but significantly by material parameters. The
domain wall nucleation fields can be described by a typical Stoner-Wohlfarth
model related to the measured geometrical parameters of the wires and fitted by
considering the process parameters. The GMR effect is subsequently measured in
a substantial number of devices (3000), in order to accurately gauge the
variation between devices. This reveals a corrected upper limit to the
nucleation fields of the sensors that can be exploited for fast
characterization of working elements.

###Ferromagnetism and spin-dependent transport at a complex oxide interface|Yilikal Ayino,Peng Xu,Juan Tigre-Lazo,Jin Yue,Bharat Jalan,Vlad S. Pribiag###

Ferromagnetism and spin-dependent transport at a complex oxide interface. Complex oxide interfaces are a promising platform for studying a wide array
of correlated electron phenomena in low-dimensions, including magnetism and
superconductivity. The microscopic origin of these phenomena in complex oxide
interfaces remains an open question. Here we investigate for the first time the
magnetic properties of semi-insulating NdTiO$_3$/SrTiO$_3$ (NTO/STO) interfaces
and present the first milli-Kelvin study of NTO/STO. The magnetoresistance (MR)
reveals signatures of local ferromagnetic order and of spin-dependent
thermally-activated transport, which are described quantitatively by a simple
phenomenological model. We discuss possible origins of the interfacial
ferromagnetism. In addition, the MR also shows transient hysteretic features on
a timescale of ~10-100 seconds. We demonstrate that these are consistent with
an extrinsic magneto-thermal origin, which may have been misinterpreted in
previous reports of magnetism in STO-based oxide interfaces. The existence of
these two MR regimes (steady-state and transient) highlights the importance of
time-dependent measurements for distinguishing signatures of ferromagnetism
from other effects that can produce hysteresis at low temperatures.

###Anomalous magnetotransport properties of high-quality single crystals of Weyl semimetal WTe2: Sign change of Hall resistivity|Rajveer Jha,Ryuji Higashinaka,Tatsuma D. Matsuda,Raquel A. Ribeiro,Yuji Aoki###

Anomalous magnetotransport properties of high-quality single crystals of Weyl semimetal WTe2: Sign change of Hall resistivity. We report on a systematic study of Hall effect using high quality single
crystals of type-II Weyl semimetal WTe2 with the applied magnetic field B//c.
The residual resistivity ratio of 1330 and the large magnetoresistance of
1.5\times10^6 % in 9 T at 2 K, being in the highest class in the literature,
attest to their high quality. Based on a simple two-band model, the densities
(n_e and n_h) and mobilities (\mu_e and \mu_h) for electron and hole carriers
have been uniquely determined combining both Hall- and electrical-resistivity
data. The difference between ne and nh is ~1% at 2 K, indicating that the
system is in an almost compensated condition. The negative Hall resistivity
growing rapidly below ~20 K is due to a rapidly increasing \mu_h/\mu_e
approaching one. Below 3 K in a low field region, we found the Hall resistivity
becomes positive, reflecting that \mu_h/\mu_e finally exceeds one in this
region. These anomalous behaviors of the carrier densities and mobilities might
be associated with the existence of a Lifshitz transition and/or the spin
texture on the Fermi surface.

###Temperature- dependence of anomalous Hall conductivity in Rashba-type ferromagnets|Akimasa Sakuma###

Temperature- dependence of anomalous Hall conductivity in Rashba-type ferromagnets. The applicability and usefulness of Rashba model have been extended by recent
observations in the field of spintronics, such as the spin-orbit torque at the
junction interfaces between ferromagnetic (FM) metals and non-magnetic (NM)
metals and the perpendicular anomalous magnetoresistance (AMR) in
heterostructures such as FI/NM or FM/NI (I denotes an insulator). In
particular, the observations of the perpendicular AMR effect stimulate further
interest in the Rashba-type spin-orbit interaction (SOI) at interfaces. Thus,
the Rashba model with exchange splitting (EXS) is considered not only to play
as an effective model for the physical understanding but also to reflect actual
bi-layer systems in current spintronics devices. In the present work, we have
first investigated the temperature dependence of anomalous Hall conductivity
(AHC) of Rashba-type ferromagnets considered effects of spin fluctuations
within the disordered local moment (DLM) scheme. The most distinctive feature
that we observed is that intrinsic AHC increases with increasing temperature.
This can be understood from the aspect of spin chirality, which indicates that
the AHC increases with decreasing EXS when the SOI is much smaller than the
EXS. The extrinsic part of the Fermi surface term also increases with
increasing temperature and has a large contribution, comparable to that of the
intrinsic part. Although, such a behaviour has not yet been observed
experimentally, we suggest that the physical picture found in this work might
lurk in an anomalous Hall effects in Rashbe-type ferromagnets.

###Probing the Chiral Anomaly by Planar Hall Effect in Three-dimensional Dirac Semimetal Cd3As2 Nanoplates|Min Wu,Guolin Zheng,Weiwei Chu,Wenshuai Gao,Hongwei Zhang,Jianwei Lu,Yuyan Han,Jiyong Yang,Haifeng Du,Wei Ning,Yuheng Zhang,Mingliang Tian###

Probing the Chiral Anomaly by Planar Hall Effect in Three-dimensional Dirac Semimetal Cd3As2 Nanoplates. Searching for exotic transport properties in new topological state of matters
is an active topic. One of the most fascinating achievements is the chiral
anomaly in recently discovered Weyl semimetals (WSMs), which is manifested as a
negative longitudinal magnetoresistance (LMR) in the presence of a magnetic
field B parallel to an electric field E. Another predicted key effect closely
related to the chiral anomaly is the planar Hall effect (PHE), which has not
been identified in WSMs so far. Here we carried out the planar Hall
measurements on Cd3As2 nanoplates, and found that, accompanied by the large
negative LMR, a PHE with non-zero transverse voltage can be developed while
tilting the in-plane magnetic field B away from the electric field E. Further
experiments reveal that both the PHE and the negative LMR can be suppressed
synchronously by increasing the temperature, but still visible at room
temperature, indicating the same origin of these two effects. The observation
of PHE in Cd3As2 nanoplates gives another transport evidence for the chiral
anomaly and provides a deep insight into the chiral charge pumping in Weyl
Fermions system.

###Elastic and electronic tuning of magnetoresistance in MoTe$_2$|Junjie Yang,Jonathan Colen,Jun Liu,Manh Cuong Nguyen,Gia-Wei Chern,Despina Louca###

Elastic and electronic tuning of magnetoresistance in MoTe$_2$. Quasi-two dimensional transition metal dichalcogenides (TMD) exhibit dramatic
properties that may transform electronic and photonic devices. We report on how
the anomalously large magnetoresistance (MR) observed under high magnetic field
in MoTe$_2$, a type II Weyl semimetal, can be reversibly controlled under
tensile strain. The MR is enhanced by as much as ~ 30 % at low temperatures and
high magnetic fields, when uniaxial strain is applied along the
$a$-crystallographic direction and reduced by about the same amount when strain
is applied along the $b$-direction. We show that the large in-plane electric
anisotropy is coupled with the structural transition from the 1T' monoclinic to
the Td orthorhombic Weyl phase. A shift of the Td - 1T' phase boundary is
achieved by minimal tensile strain. The sensitivity of the MR to tensile strain
suggests the possibility of a nontrivial spin-orbital texture of the electron
and hole pockets in the vicinity of Weyl points. Our ab initio calculations
indeed show a significant orbital mixing on the Fermi surface, which is
modified by the tensile strains.

###Fermi surface with Dirac fermions in CaFeAsF determined via quantum oscillation measurements|Taichi Terashima,Hishiro T. Hirose,David Graf,Yonghui Ma,Gang Mu,Tao Hu,Katsuhiro Suzuki,Shinya Uji,Hiroaki Ikeda###

Fermi surface with Dirac fermions in CaFeAsF determined via quantum oscillation measurements. Despite the fact that 1111-type iron arsenides hold the record transition
temperature of iron-based superconductors, their electronic structures have not
been studied much because of the lack of high-quality single crystals. In this
study, we completely determine the Fermi surface in the antiferromagnetic state
of CaFeAsF, a 1111 iron-arsenide parent compound, by performing quantum
oscillation measurements and band-structure calculations. The determined Fermi
surface consists of a symmetry-related pair of Dirac electron cylinders and a
normal hole cylinder. From analyses of quantum-oscillation phases, we
demonstrate that the electron cylinders carry a nontrivial Berry phase $\pi$.
The carrier density is of the order of 10$^{-3}$ per Fe. This unusual metallic
state with the extremely small carrier density is a consequence of the
previously discussed topological feature of the band structure which prevents
the antiferromagnetic gap from being a full gap. We also report a nearly
linear-in-$B$ magnetoresistance and an anomalous resistivity increase above
about 30 T for $B \parallel c$, the latter of which is likely related to the
quantum limit of the electron orbit. Intriguingly, the electrical resistivity
exhibits a nonmetallic temperature dependence in the paramagnetic tetragonal
phase ($T >$ 118 K), which may suggest an incoherent state. Our study provides
a detailed knowledge of the Fermi surface in the antiferromagnetic state of
1111 parent compounds and moreover opens up a new possibility to explore
Dirac-fermion physics in those compounds.

###A Brief Review of Ferroelectric Control of Magnetoresistance in Organic Spin Valves|Xiaoshan Xu###

A Brief Review of Ferroelectric Control of Magnetoresistance in Organic Spin Valves. Magnetoelectric coupling has been a trending research topic in both organic
and inorganic materials and hybrids. The concept of controlling magnetism using
an electric field is particularly appealing in energy efficient applications.
In this spirit, ferroelectricity has been introduced to organic spin valves to
manipulate the magneto transport, where the spin transport through the
ferromagnet/organic spacer interfaces (spinterface) are under intensive study.
The ferroelectric materials in the organic spin valves provide a knob to vary
the interfacial energy alignment and the interfacial crystal structures, both
are critical for the spin transport. In this review, we first go over the basic
concepts of spin transport in organic spin valves. Then we introduce the recent
efforts of controlling magnetoresistance of organic spin valves using
ferroelectricity, where the ferroelectric material is either inserted as an
interfacial layer or used as a spacer material. The realization of the
ferroelectric control of magneto transport in organic spin valve, advances our
understanding in the spin transport through the ferromagnet/organic interface
and suggests more functionality of organic spintronic devices.

###Competition between the inter-valley scattering and the intra-valley scattering on magnetoconductivity induced by screened Coulomb disorder in Weyl semimetals|Xuan-Ting Ji,Hai-Zhou Lu,Zhen-Gang Zhu,Gang Su###

Competition between the inter-valley scattering and the intra-valley scattering on magnetoconductivity induced by screened Coulomb disorder in Weyl semimetals. Recent experiments on Weyl semimetals reveal that charged impurities may play
an important role. We use a screened Coulomb disorder to model the charged
impurities, and study the magneto-transport in a two-node Weyl semimetal. It is
found that when the external magnetic field is applied parallel to the electric
field, the calculated longitudinal magnetoconductivity shows positive in the
magnetic field, which is just the negative longitudinal magnetoresistivity
(LMR) observed in experiments. When the two fields are perpendicular to each
other, the transverse magnetoconductivities are measured. It is found that the
longitudinal (transverse) magnetoconductivity is suppressed (enhanced)
sensitively with increasing the screening length. This feature makes it hardly
to observe the negative LMR in Weyl semimetals experimentally owing to a small
screening length. Our findings gain insight into further understanding on
recently actively debated magneto-transport behaviors in Weyl semimetals.
Furthermore we studied the relative weight of the inter-valley scattering and
the intra-valley scattering. It shows that the former is as important as the
latter and even dominates in the case of strong magnetic fields and small
screening length. We emphasize that the discussions on inter-valley scattering
is out of the realm of one-node model which has been studied.

###Spin Filtering with Poly-T Wrapped Single Wall Carbon Nanotubes|K. M. Alam,Sandipan Pramanik###

Spin Filtering with Poly-T Wrapped Single Wall Carbon Nanotubes. Spin filtering is an essential operation in spintronics that allows creation
and detection of spin polarized carriers. Transition metal ferromagnets are
used as spin filters in most cases, though their spin filtering efficiency is
only around ~50%, thereby limiting the efficiency of spintronic devices.
Recently, chiral systems such as DNA have been shown to exhibit efficient spin
filtering, a phenomenon often dubbed as "chirality induced spin selectivity"
(CISS). In this work, we consider single wall carbon nanotubes helically
wrapped with single stranded poly-T DNA. By magnetoresistance measurements we
show that this system exhibits significant spin polarization of ~80%, which
could be attributed to the Rashba spin-orbit interaction induced by the
inversion asymmetric helical potential of the DNA. Observed spin polarization
is larger than that reported before for d(GT)15 strands. Such systems allow
tailoring spin polarization by chemical means and also allow extremely
localized creation and detection of spin polarization without any magnetic
element and could lead to extreme miniaturization and compact integration of
spintronic devices and circuits.

###Temperature effects of the magnetic tunnel junctions with periodic grating barrier|Henan Fang,Mingwen Xiao,Wenbin Rui,Jun Du,Zhikuo Tao###

Temperature effects of the magnetic tunnel junctions with periodic grating barrier. We have developed a tunneling theory to describe the temperature dependence
of tunneling magnetoresistance (TMR) of the magnetic tunnel junctions (MTJs)
with periodic grating barrier. Through the Patterson function approach, the
theory can handle easily the influence of the lattice distortion of the barrier
on the tunneling process of the electrons. The lattice distortion of the
barrier is sensible to the temperature and can be quite easily weakened by the
thermal relaxation of the strain, and thus the tunneling process of the
electrons gets changed highly with the variation of the temperature of the
system. That is just the physical mechanism for the temperature dependence of
the TMR. From it, we find that the decrease of TMR with rising temperature is
mostly carried by a change in the antiparallel resistance ($R_{AP}$), and the
parallel resistance ($R_{P}$) changes so little that it seems roughly constant,
if compared to the $R_{AP}$, and that, for the annealed MTJ, the $R_{AP}$ is
significantly more sensitive to the strain than the $R_{P}$, and for
non-annealed MTJ, both the $R_{P}$ and $R_{AP}$ are not sensitive to the
strain. They are both in agreement with the experiments of the MgO-based MTJs.
Other relevant properties are also discussed.

###Berry phase induced localization to anti-localization transition in two-dimensional Dirac fermion systems|Ting Zhang,Jie Pan,Ping Sheng###

Berry phase induced localization to anti-localization transition in two-dimensional Dirac fermion systems. We study theoretically the electrical transport of two-dimensional (2D)
massive Dirac fermions, which are described by the 2 by 2 massive Dirac
Hamiltonian, and with a gap at the charge neutrality point. Through analytical
diagrammatical calculations of electrical conductivity in the presence of long
range Coulomb scattering centers, we show that attendant with the variation of
the Berry phase from 0 to {\pi} as the Fermi energy moves away from the Dirac
point/band boundary, a continuous Anderson-localization (AL) to
weak-localization (WL), and further to weak anti-localization (WAL) transition
occurs, implying a change in the sign of the magnetoresistance. Such transition
indicates the presence of metal-insulator transition (MIT) in this 2D system,
in contrast to the classical scaling theory. The WL to WAL transition occurs at
a certain critical Berry phase despite the concentration of Coulomb impurities,
while the MIT critical point, which is the distinguishing doping level
separating the AL and WL phases, depends on the competition of conventional
conductivity and the negative maximally crossed diagram (MCD) corrections near
the bottom of conduction band.

###Measurement independent magnetocaloric effect in Mn-rich Mn-Fe-Ni-Sn(Sb/In) Heusler alloys|Arup Ghosh,Rajeev Rawat,Arpan Bhattacharyya,Guruprasad Mandal,A. K. Nigam,Sunil Nair###

Measurement independent magnetocaloric effect in Mn-rich Mn-Fe-Ni-Sn(Sb/In) Heusler alloys. We report a systematic study on the magneto-structural transition in Mn-rich
Fe-doped Mn-Fe-Ni-Sn(Sb/In) Heusler alloys by keeping the total valence
electron concentration (e/a ratio) fixed. The martensitic transition (MT)
temperature is found to shift by following a proportional relationship with the
e/a ratio of the magnetic elements alone. The magnetic entropy change across MT
for a selected sample (Mn49FeNi40Sn9In) has been estimated from three different
measurement methods (isofield magnetization (M) vs temperature (T), isothermal
M vs field (H) and heat capacity (HC) vs T). We observed that though the peak
value of magnetic entropy change changes with the measurement methods, the
broadened shape of the magnetic entropy change vs T curves and the
corresponding cooling power (~140 Jkg-1) remains invariant. The equivalent
adiabatic temperature change ~ -2.6 K has been obtained from indirect
measurements of temperature change. Moreover, an exchange bias field ~ 783 Oe
at 5 K and a magnetoresistance of -30% are also obtained in one of these
materials.

###Helical magnetic structure and the anomalous and topological Hall effects in epitaxial B20 Fe$_{1-y}$Co$_y$Ge films|Charles S. Spencer,Jacob Gayles,Nicholas A. Porter,Satoshi Sugimoto,Zabeada Aslam,Christian J. Kinane,Timothy R. Charlton,Frank Freimuth,Stanislav Chadov,Sean Langridge,Jairo Sinova,Claudia Felser,Stefan Blügel,Yuriy Mokrousov,Christopher H. Marrows###

Helical magnetic structure and the anomalous and topological Hall effects in epitaxial B20 Fe$_{1-y}$Co$_y$Ge films. Epitaxial films of the B20-structure alloy Fe$_{1-y}$Co$_y$Ge were grown by
molecular beam epitaxy on Si (111) substrates. The magnetization varied
smoothly from the bulk-like values of one Bohr magneton per Fe atom for FeGe to
zero for non-magnetic CoGe. The chiral lattice structure leads to a
Dzyaloshinskii-Moriya interaction (DMI), and the films' helical magnetic ground
state was confirmed using polarized neutron reflectometry measurements. The
pitch of the spin helix, measured by this method, varies with Co content $y$
and diverges at $y \sim 0.45$. This indicates a zero-crossing of the DMI, which
we reproduced in calculations using first principle methods. We also measured
the longitudinal and Hall resistivity of our films as a function of magnetic
field, temperature, and Co content $y$. The Hall resistivity is expected to
contain contributions from the ordinary, anomalous, and topological Hall
effects. Both the anomalous and topological Hall resistivities show peaks
around $y \sim 0.5$. Our first principles calculations show a peak in the
topological Hall constant at this value of $y$, related to the strong
spin-polarisation predicted for intermediate values of $y$. Half-metallicity is
predicted for $y = 0.6$, consistent with the experimentally observed linear
magnetoresistance at this composition. Whilst it is possible to reconcile
theory with experiment for the various Hall effects for FeGe, the large
topological Hall resistivities for $y \sim 0.5$ are much larger then expected
when the very small emergent fields associated with the divergence in the DMI
are taken into account.

###Spin transport across antiferromagnets induced by the spin Seebeck effect|Joel Cramer,Ulrike Ritzmann,Bo-Wen Dong,Samridh Jaiswal,Zhiyong Qiu,Eiji Saitoh,Ulrich Nowak,Mathias Kläui###

Spin transport across antiferromagnets induced by the spin Seebeck effect. For prospective spintronics devices based on the propagation of pure spin
currents, antiferromagnets are an interesting class of materials that
potentially entail a number of advantages as compared to ferromagnets. Here, we
present a detailed theoretical study of magnonic spin current transport in
ferromagnetic-antiferromagnetic multilayers by using atomistic spin dynamics
simulations. The relevant length scales of magnonic spin transport in
antiferromagnets are determined. We demonstrate the transfer of angular
momentum from a ferromagnet into an antiferromagnet due to the excitation of
only one magnon branch in the antiferromagnet. As an experimental system, we
ascertain the transport across an antiferromagnet in
YIG$|$Ir$_{20}$Mn$_{80}|$Pt heterostructures. We determine the spin transport
signals for spin currents generated in the YIG by the spin Seebeck effect and
compare to measurements of the spin Hall magnetoresistance in the
heterostructure stack. By means of temperature-dependent and
thickness-dependent measurements, we deduce conclusions on the spin transport
mechanism across IrMn and furthermore correlate it to its
paramagnetic-antiferromagnetic phase transition.

###Observation of Chiral character deep in the topological insulating regime in Bi$_{1-x}$Sb$_x$|Amit,R. K. Gopal,Yogesh Singh###

Observation of Chiral character deep in the topological insulating regime in Bi$_{1-x}$Sb$_x$. Bi$_{1-x}$Sb$_x$ is a topological insulator (TI) for $x \approx 0.03
$--$0.20$. Close to the Topological phase transition at $x = 0.03$, a magnetic
field induced Weyl semi-metal (WSM) state is stabilized due to the splitting of
the Dirac cone into two Weyl cones of opposite chirality. A signature of the
Weyl state is the observation of a Chiral anomaly [negative longitudnal
magnetoresistance (LMR)] and a violation of the Ohm's law (non-linear $I-V$).
We report the unexpected discovery of a Chiral anomaly in the whole range ($x =
0.032, 0.072, 0.16$) of the TI state. This points to a field induced WSM state
in an extended $x$ range and not just near the topological transition at $x =
0.03$. Surprisingly, the strongest Weyl phase is found at $x = 0.16$ with a
non-saturating negative LMR much larger than observed for $x = 0.03$. The
negative LMR vanishes rapidly with increasing angle between $B$ and $I$.
Additionally, non-linear $I$--$V$ is found for $x = 0.16$ indicating a
violation of Ohm's law. This unexpected observation of a strong Weyl state in
the whole TI regime in Bi$_{1-x}$Sb$_x$ points to a gap in our understanding of
the detailed electronic structure evolution in this alloy system.

###Diffuson contribution to anomalous Hall effect in disordered Co2FeSi thin films|Binoy Krishna Hazra,S. N. Kaul,S. Srinath,M. Manivel Raja,R. Rawat,Archana Lakhani###

Diffuson contribution to anomalous Hall effect in disordered Co2FeSi thin films. A wide variation in the disorder strength, as inferred from an order of
magnitude variation in the longitudinal resistivity of Co2FeSi (CFS) Huesler
alloy thin films of fixed (50 nm) thickness, has been achieved by growing these
films on Si(111) substrates at substrate temperatures ranging from room
temperature (RT) to 600 C. An in-depth study of the influence of disorder on
anomalous Hall resistivity,longitudinal resistivity(LR) and magnetoresistance,
enabled by this approach, reveals the following. The side-jump mechanism gives
a dominant contribution to anomalous Hall resistivity (AHR) in the CFS thin
films, regardless of the degree of disorder present. A new and novel
contribution to both LR and AHR characterized by the logarithmic temperature
dependence at temperatures below the minimum, exclusive to the amorphous CFS
films, originates from the scattering of conduction electrons from the
diffusive hydrodynamic modes associated with the longitudinal component of
magnetization, called diffusons. In these amorphous CFS films, the
electron-diffuson, e d, scattering and weak localization (WL) mechanisms
compete with that arising from the inelastic electron magnon, e m, scattering
to produce the minimum in longitudinal resistivity, whereas the minimum in AHR
is caused by the competing contributions from the e d and e m scattering, as WL
does not make any contribution to AHR. In sharp contrast, in crystalline films,
enhanced electron electron Coulomb interaction (EEI), which is basically
responsible for the resistivity minimum, makes no contribution to AHR with the
result that AHR does not exhibit a minimum.

###Collapse of ferromagnetism with Ti doping in Sm$_{0.55}$Sr$_{0.45}$MnO$_3$: A combined experimental and theoretical study|P. Sarkar,N. Khan,K. Pradhan,P. Mandal###

Collapse of ferromagnetism with Ti doping in Sm$_{0.55}$Sr$_{0.45}$MnO$_3$: A combined experimental and theoretical study. We have investigated the effect of Ti doping on the transport properties
coupled with the magnetic ones in
Sm$_{0.55}$Sr$_{0.45}$Mn$_{1-\eta}$Ti$_{\eta}$O$_3$ ($0 \leq \eta \leq 0.04$).
The parent compound, Sm$_{0.55}$Sr$_{0.45}$MnO$_3$, exhibits a first-order
paramagnetic-insulator to ferromagnetic-metal transition just below $T_{\rm c}$
= 128 K. With substitution of Ti at Mn sites ($B$-site), $T_{\rm c}$ decreases
approximately linearly at the rate of 22 K$\%^{-1}$ while the width of thermal
hysteresis in magnetization and resistivity increases almost in an exponential
fashion. The most spectacular effect has been observed for the composition
$\eta$=0.03, where a magnetic field of only 1 T yields a huge
magnetoresistance, $1.2 \times 10^7$ $\%$ at $T_c\approx$ 63 K. With increasing
magnetic field, the transition shifts towards higher temperature, and the
first-order nature of the transition gets weakened and eventually becomes
crossover above a critical field ($H_{cr}$) which increases with Ti doping. For
Ti doping above 0.03, the system remains insulting without any ferromagnetic
ordering down to 2 K. The Monte-Carlo calculations based on a two-band double
exchange model show that the decrease of $T_{\rm c}$ with Ti doping is
associated with the increase of the lattice distortions around the doped Ti
ions.

###Extreme magnetoresistance in the topologically trivial lanthanum monopnictide LaAs|H. -Y. Yang,T. Nummy,H. Li,S. Jaszewski,M. Abramchuk,D. S. Dessau,Fazel Tafti###

Extreme magnetoresistance in the topologically trivial lanthanum monopnictide LaAs. The family of binary Lanthanum monopnictides, LaBi and LaSb, have attracted a
great deal of attention as they display an unusual extreme magnetoresistance
(XMR) that is not well understood. Two classes of explanations have been raised
for this: the presence of non-trivial topology, and the compensation between
electron and hole densities. Here, by synthesizing a new member of the family,
LaAs, and performing transport measurements, Angle Resolved Photoemission
Spectroscopy (ARPES), and Density Functional Theory (DFT) calculations, we show
that (a) LaAs retains all qualitative features characteristic of the XMR effect
but with a siginificant reduction in magnitude compared to LaSb and LaBi, (b)
the absence of a band inversion or a Dirac cone in LaAs indicates that topology
is insignificant to XMR, (c) the equal number of electron and hole carriers
indicates that compensation is necessary for XMR but does not explain its
magnitude, and (d) the ratio of electron and hole mobilities is much different
in LaAs compared to LaSb and LaBi. We argue that the compensation is
responsible for the XMR profile and the mobility mismatch constrains the
magnitude of XMR.

###Electrically induced and detected Néel vector reversal in a collinear antiferromagnet|J. Godinho,H. Reichlova,D. Kriegner,V. Novak,K. Olejnik,Z. Kaspar,Z. Soban,P Wadley,R. P. Campion,R. M. Otxoa,P. E. Roy,J. Zelezny,T. Jungwirth,J. Wunderlich###

Electrically induced and detected Néel vector reversal in a collinear antiferromagnet. Electrical detection of the 180 deg spin reversal, which is the basis of the
operation of ferromagnetic memories, is among the outstanding challenges in the
research of antiferromagnetic spintronics. Analogous effects to the
ferromagnetic giant or tunneling magnetoresistance have not yet been realized
in antiferromagnetic multilayers. Anomalous Hall effect (AHE), which has been
recently employed for spin reversal detection in non-collinear
antiferromagnets, is limited to materials that crystalize in ferromagnetic
symmetry groups. Here we demonstrate electrical detection of the 180 deg N\'eel
vector reversal in CuMnAs which comprises two collinear spin sublattices and
belongs to an antiferromagnetic symmetry group with no net magnetic moment. We
detect the spin reversal by measuring a second-order magnetotransport
coefficient whose presence is allowed in systems with broken space inversion
symmetry. The phenomenology of the non-linear transport effect we observe in
CuMnAs is consistent with a microscopic scenario combining anisotropic
magneto-resistance (AMR) with a transient tilt of the N\'eel vector due to a
current-induced, staggered spin-orbit field. We use the same staggered
spin-orbit field, but of a higher amplitude, for the electrical switching
between reversed antiferromagnetic states which are stable and show no sign of
decay over 25 hour probing times.

###Role of external and internal perturbations on ferromagnetic phase transitions in manganites: Existence of tricritical points|Prabir K Mukherjee,Prosenjit Sarkar,Amit K Chattopadhyay###

Role of external and internal perturbations on ferromagnetic phase transitions in manganites: Existence of tricritical points. A phenomenological mean-field theory is presented to describe the role of
external magnetic field, pressure and chemical substitution on the nature of
ferromagnetic (FM) to paramagnetic (PM) phase transition in manganites. The
application of external field (or pressure) shifts the transition, leading to a
field (or pressure) dependent phase boundary along which a tricritical point is
shown to exist where a first-order FM-PM transition becomes second-order. We
show that the effect of chemical substitution on the FM transition is analogous
to that of external perturbations (magnetic field and pressure); this includes
the existence of a tricritical point at which the order of transition changes.
Our theoretical predictions satisfactorily explain the nature of FM-PM
transition, observed in several systems. The modeling hypothesis has been
critically verified from our experimental data from a wide range of colossal
magnetoresistive manganite single crystals like Sm$_{0.52}$Sr$_{0.48}$MnO$_3$.
The theoretical model prediction of a tricritical point has been validated in
this experiment which provides a major ramification of the strength of the
model proposed.

###Electronic properties across metal-insulator transition in β-pyrochlore-type CsW2O6 epitaxial films|Takuto Soma,Kohei Yoshimatsu,Koji Horiba,Hiroshi Kumigashira,Akira Ohtomo###

Electronic properties across metal-insulator transition in β-pyrochlore-type CsW2O6 epitaxial films. In CsW2O6, which undergoes a metal-insulator transition (MIT) at 213 K, the
emergence of exotic properties associated with rattling motion of Cs is
expected owing to its characteristic \beta-pyrochlore-type structure. However,
a hurdle for crystal growth hampers elucidation of detailed properties and
mechanisms of the MIT. Here we report on the epitaxial growth of
\beta-pyrochlore-type CsW2O6 films and their electronic properties across the
MIT. Using pulsed-laser deposi-tion technique, we grew single-crystalline
CsW2O6 films exhibiting remarkably lower resistivity compared with a
poly-crystalline bulk and sharp MIT around 200 K. Negative magnetoresistance
and positive Hall coefficient were found, which became pronounced below 200 K.
The valence-band and core-levels photoemission spectra indicated the drastic
changes across the MIT. In the valence band photoemission spectrum, the finite
density of states was observed at the Fermi level in the metallic phase. In
contrast, an energy gap appeared in the insulating phase. The split of W 4f
core-level spectrum suggested the charge disproportionation of W5+ and W6+ in
the insulating phase. The change of spectral shape in the Cs 4d core levels
reflected the rattling motion of Cs+ cations. These results strongly suggest
that CsW2O6 is a novel material, in which MIT is driven by the charge
disproportionation associated with the rattling motion.

###Tunable disorder and localization in the rare-earth nickelates|Changan Wang,Ching-Hao Chang,Angus Huang,Pei-Chun Wang,Ping-Chun Wu,Lin Yang,Chi Xu,Parul Pandey,Min Zeng,Roman Böttger,Horng-Tay Jeng,Yu-Jia Zeng,Manfred Helm,Ying-Hao Chu,R. Ganesh,Shengqiang Zhou###

Tunable disorder and localization in the rare-earth nickelates. The rare-earth nickelates are a rich playground for transport properties,
known to host non-Fermi liquid character, resistance saturation and
metal-insulator transitions. We report a study of transport in LaNiO3 in the
presence of tunable disorder induced by irradiation. While pristine LaNiO3
samples are metallic, highly irradiated samples show insulating behaviour at
all temperatures. Using irradiation fluence as a tuning handle, we uncover an
intermediate region hosting a metal-insulator transition. This transition falls
within the Mott-Ioffe-Regel regime wherein the mean free path is comparable to
lattice spacing. In the high temperature metallic regime, we find a transition
from non-Fermi liquid to a Fermi-liquid-like character. On the insulating side
of the metal-insulator transition, we find behaviour that is consistent with
weak localization. This is reflected in magnetoresistance that scales with the
square of the field and in resistivity. In the highly irradiated insulating
samples, we find good agreement with variable range hopping, consistent with
Anderson localization. We find qualitatively similar behaviour in thick PrNiO3
films as well. Our results demonstrate that ion irradiation can be used to
tailor transport, serving as an excellent tool to study the physics of
localization.

###Unconventional critical state in YBa$_{2}$Cu$_{3}$O$_{7-δ}$ thin films with a vortex-pin lattice fabricated by masked He$^+$ ion beam irradiation|Georg Zechner,Kristijan L. Mletschnig,Wolfgang Lang,Meirzhan Dosmailov,Marius A. Bodea,Johannes D. Pedarnig###

Unconventional critical state in YBa$_{2}$Cu$_{3}$O$_{7-δ}$ thin films with a vortex-pin lattice fabricated by masked He$^+$ ion beam irradiation. Thin superconducting YBa$_{2}$Cu$_{3}$O$_{7-\delta}$ films are patterned with
a vortex-pin lattice consisting of columnar defect regions (CDs) with 180 nm
diameter and 300 nm spacing. They are fabricated by irradiation with 75 keV
He$^+$ ions through a stencil mask. Peaks of the critical current reveal the
commensurate trapping of vortices in domains near the edges of the sample. Upon
ramping an external magnetic field, the positions of the critical current peaks
are shifted from their equilibrium values to lower magnetic fields in virgin
and to higher fields in field-saturated down-sweep curves, respectively. Based
on previous theoretical predictions, this irreversibility is interpreted as a
nonuniform, terrace-like critical state, in which individual domains are
occupied by a constant number of vortices per pinning site. The
magnetoresistance, probed at low current densities, is hysteretic and angle
dependent and exhibits minima that correspond to the peaks of the critical
current. The minima's positions scale with the component of the magnetic field
parallel to the axes of the CDs, as long as the tilted vortices can be
accommodated within the CDs. This behavior, different from unirradiated films,
confirms that the CDs dominate the pinning.

###Planar Hall effect in type II Dirac semimetal VAl$_{3}$|Ratnadwip Singha,Shubhankar Roy,Arnab Pariari,Biswarup Satpati,Prabhat Mandal###

Planar Hall effect in type II Dirac semimetal VAl$_{3}$. The study of electronic properties in topological systems is one of the most
fascinating topics in condensed matter physics, which has generated enormous
interests in recent times. New materials are frequently being proposed and
investigated to identify their non-trivial band structure. While sophisticated
techniques such as angle-resolved photoemission spectroscopy have become
popular to map the energy-momentum relation, the transport experiments lack any
direct confirmation of Dirac and Weyl fermions in a system. From band structure
calculations, VAl$_{3}$ has been proposed to be a type II topological Dirac
semimetal. This material represents a large family of isostructural compounds,
all having similar electronic band structure and is an ideal system to explore
the rich physics of Lorentz symmetry violating Dirac fermions. In this work, we
present a detailed analysis on the magnetotransport properties of VAl$_{3}$. A
large, non-saturating magnetoresistance has been observed. Hall resistivity
reveals the presence of two types of charge carriers with high mobility. Our
measurements show a large planar Hall effect in this material, which is robust
and can be easily detectable up to high temperature. This phenomenon originates
from the relativistic chiral anomaly and non-trivial Berry curvature, which
validates the theoretical prediction of the Dirac semimetal phase in VAl$_{3}$.

###Spin-flop phase transition in the orthorhombic antiferromagnetic topological semimetal Cu0.95MnAs|Eve Emmanouilidou,Jinyu Liu,David Graf,Huibo Cao,Ni Ni###

Spin-flop phase transition in the orthorhombic antiferromagnetic topological semimetal Cu0.95MnAs. The orthorhombic antiferromagnetic compound CuMnAs was recently predicted to
be an antiferromagnetic Dirac semimetal if both the Ry gliding and S2z
rotational symmetries are preserved in its magnetic ordered state. In our
previous work on Cu0.95MnAs and Cu0.98Mn0.96As, we showed that in their low
temperature commensurate antiferromagnetic state the b axis is the magnetic
easy axis, which breaks the S2z symmetry. As a result, while the existence of
Dirac fermions is no longer protected, the polarized surface state makes this
material potentially interesting for antiferromagnetic spintronics. In this
paper, we report a detailed study of the anisotropic magnetic properties and
magnetoresistance of Cu0.95MnAs and Cu0.98Mn0.96As. Our study shows that in
Cu0.95MnAs the b axis is the easy axis and the c axis is the hard axis.
Furthermore, it reveals that Cu0.95MnAs features a spin-flop phase transition
at high temperatures and low fields when the field is applied along the easy b
axis, resulting in canted antiferromagnetism. However, no metamagnetic
transition is observed in Cu0.98Mn0.96As, indicating that the magnetic
interactions in this system are very sensitive to Cu vacancies and Cu/Mn site
mixing.

###Two-terminal spin-orbit torque magnetoresistive random access memory|Noriyuki Sato,Fen Xue,Robert M. White,Chong Bi,Shan X. Wang###

Two-terminal spin-orbit torque magnetoresistive random access memory. Spin-transfer torque magnetoresistive random access memory (STT-MRAM) is an
attractive alternative to current random access memory technologies due to its
non-volatility, fast operation and high endurance. STT-MRAM does though have
limitations including the stochastic nature of the STT-switching and a high
critical switching current, which makes it unsuitable for ultrafast operation
at nanosecond and sub-nanosecond regimes. Spin-orbit torque (SOT) switching,
which relies on the torque generated by an in-plane current, has the potential
to overcome these limitations. However, SOT-MRAM cells studied so far use a
three-terminal structure in order to apply the in-plane current, which
increases the size of the cells. Here we report a two-terminal SOT-MRAM cell
based on a CoFeB/MgO magnetic tunnel junction pillar on an ultrathin and narrow
Ta underlayer. In this device, an in-plane and out-of-plane current are
simultaneously generated upon application of a voltage, and we demonstrate that
the switching mechanism is dominated by SOT. We also compare our device to a
STT-MRAM cell built with the same architecture and show that critical write
current in the SOT-MRAM cell is reduced by more than 70%.

###Chaos and relaxation oscillations in spin-torque windmill neurons|Rie Matsumoto,Steven Lequeux,Hiroshi Imamura,Julie Grollier###

Chaos and relaxation oscillations in spin-torque windmill neurons. Spintronic neurons which emit sharp voltage spikes are required for the
realization of hardware neural networks enabling fast data processing with
low-power consumption. In many neuroscience and computer science models,
neurons are abstracted as non-linear oscillators. Magnetic nano-oscillators
called spin-torque nano-oscillators are interesting candidates for imitating
neurons at nanoscale. These oscillators, however, emit sinusoidal waveforms
without spiking while biological neurons are relaxation oscillators that emit
sharp voltage spikes. Here we propose a simple way to imitate neuron spiking in
high-magnetoresistance nanoscale spin valves where both magnetic layers are
free and thin enough to be switched by spin torque. Our numerical-simulation
results show that the windmill motion induced by spin torque in the proposed
spintronic neurons gives rise to spikes whose shape and frequency, set by the
charging and discharging times, can be tuned through the amplitude of injected
dc current. We also found that these devices can exhibit chaotic oscillations.
Chaotic-like neuron dynamics has been observed in the brain, and it is
desirable in some neuromorphic computing applications whereas it should be
avoided in others. We demonstrate that the degree of chaos can be tuned in a
wide range by engineering the magnetic stack and anisotropies and by changing
the dc current. The proposed spintronic neuron is a promising building block
for hardware neuromorphic chips leveraging non-linear dynamics for computing.

###Anisotropic electrical and thermal magnetotransport in the magnetic semimetal GdPtBi|Clemens Schindler,Stanislaw Galeski,Walter Schnelle,Rafał Wawrzyńczak,Wajdi Abdel-Haq,Satya N. Guin,Johannes Kroder,Nitesh Kumar,Chenguang Fu,Horst Borrmann,Chandra Shekhar,Claudia Felser,Tobias Meng,Adolfo G. Grushin,Yang Zhang,Yan Sun,Johannes Gooth###

Anisotropic electrical and thermal magnetotransport in the magnetic semimetal GdPtBi. The half-Heusler rare-earth intermetallic GdPtBi has recently gained
attention due to peculiar magnetotransport phenomena that have been associated
with the possible existence of Weyl fermions, thought to arise from the
crossings of spin-split conduction and valence bands. On the other hand,
similar magnetotransport phenomena observed in other rare-earth intermetallics
have often been attributed to the interaction of itinerant carriers with
localized magnetic moments stemming from the $4f$-shell of the rare-earth
element. In order to address the origin of the magnetotransport phenomena in
GdPtBi, we performed a comprehensive study of the magnetization, electrical and
thermal magnetoresistivity on two single-crystalline GdPtBi samples. In
addition, we performed an analysis of the Fermi surface via Shubnikov-de Haas
oscillations in one of the samples and compared the results to \emph{ab initio}
band structure calculations. Our findings indicate that the electrical and
thermal magnetotransport in GdPtBi cannot be solely explained by Weyl physics
and is strongly influenced by the interaction of both itinerant charge carriers
and phonons with localized magnetic Gd-ions and possibly also paramagnetic
impurities.

###Magnon contribution to unidirectional spin Hall magnetoresistance|W. P. Sterk,D. Peerlings,R. A. Duine###

Magnon contribution to unidirectional spin Hall magnetoresistance. We develop a model for the magnonic contribution to the unidirectional spin
Hall magnetoresistance (USMR) of heavy metal/ferromagnetic insulator bilayer
films. We show that diffusive transport of Holstein-Primakoff magnons leads to
an accumulation of spin near the bilayer interface, giving rise to a
magnoresistance which is not invariant under inversion of the current
direction. Unlike the electronic contribution described by Zhang and Vignale
[Phys. Rev. B 94, 140411 (2016)], which requires an electrically conductive
ferromagnet, the magnonic contribution can occur in ferromagnetic insulators
such as yttrium iron garnet. We show that the magnonic USMR is, to leading
order, cubic in the spin Hall angle of the heavy metal, as opposed to the
linear relation found for the electronic contribution. We estimate that the
maximal magnonic USMR in Pt|YIG bilayers is on the order of $10^{-8}$, but may
reach values of up to $10^{-5}$ if the magnon gap is suppressed, and can thus
become comparable to the electronic contribution in, e.g., Pt|Co. We show that
the magnonic USMR at a finite magnon gap may be enhanced by an order of
magnitude if the magnon diffusion length is decreased to a specific optimal
value that depends on various system parameters.

###Correlation between scale-invariant normal state resistivity and superconductivity in an electron-doped cuprate|Tarapada Sarkar,P. R. Mandal,N. R. Poniatowski,M. K. Chan,Richard L. Greene###

Correlation between scale-invariant normal state resistivity and superconductivity in an electron-doped cuprate. An understanding of the normal state in the high-temperature superconducting
cuprates is crucial to the ultimate understanding of the long-standing problem
of the origin of the superconductivity itself. This so-called strange metal
state is thought to be associated with a quantum critical point (QCP) hidden
beneath the superconductivity(1,2). In electron-doped cuprates in contrast to
hole-doped cuprates it is possible to access the normal state at very low
temperatures and low magnetic fields to study this putative QCP and to probe
the T~0 K state of these materials(3,4). We report measurements of the low
temperature normal state magnetoresistance (MR) of the n-type cuprate system
La2-xCexCuO4 (LCCO) and find that it is characterized by a linear-in-field
behavior, which follows a scaling relation with applied field and temperature,
for doping (x) above the putative QCP (x= 0.14)(5). This unconventional
behavior suggests that magnetic fields probe the same physics that gives rise
to the anomalous low-temperature linear-in-T resistivity(4). The magnitude of
the linear MR decreases as Tc decreases and goes to zero at the end of the
superconducting dome (x ~0.175) above which a conventional quadratic MR is
found. These results show that there is a strong correlation between the
quantum critical excitations of the strange metal state and the high-Tc
superconductivity.

###Magnetic behavior, Griffiths phase and magneto-transport study in 3$d$ based nano-crystalline double perovskite Pr$_2$CoMnO$_6$|Ilyas Noor Bhatti,Rabindra Nath Mahato,Imtiaz Noor Bhatti,M. A. H. Ahsan###

Magnetic behavior, Griffiths phase and magneto-transport study in 3$d$ based nano-crystalline double perovskite Pr$_2$CoMnO$_6$. Double perovskite (DP) oxide material receive extensive research interest due
to exciting physical properties with potential technological application. 3$d$
based DP oxides are promising for exciting physics like magnetodielectric,
ferroelectric, Griffith phase etc., specially Co/Mn DPs are gaining much
research interest. In this paper we present the study of magnetic phase and
transport properties in nano-crystalline Pr$_2$CoMnO$_6$ a 3$d$ based double
perovskite compound. This material shows a paramagnetic (PM) to ferromagnetic
(FM) phase transition below 173 K marked by a rapid increase in magnetic moment
due to spin ordering. We found divergence in inverse magnetic susceptibility
($\chi$$^{-1}$) from Curie weiss behavior around 206 K which indicates the
evolution of Griffiths phase before actual PM-FM transition. We found that the
Griffiths phase suppressed with increasing applied magnetic filed. For the
understanding of charge transport in this material we have measured temperature
dependent electrical resistivity. Pr$_2$CoMnO$_6$ is a strong insulator where
resistivity increase abruptly below magnetic phase transition. To understand
the effect of magnetic field on transport behavior we have also measured the
magnetoresistance (MR) at different temperatures. Sample shows the negative MR
with maximum value $\sim$22 $\%$ under applied magnetic field of 50 kOe at 125
K. MR follows quadratic field dependency above $T_c$ however below $T_c$ the MR
shows deviation from this field dependency at low field.

###Transport in magnetically doped topological insulators: Effects of magnetic clusters|A. N. Zarezad,J. Abouie###

Transport in magnetically doped topological insulators: Effects of magnetic clusters. We study the electron transport in a magnetically doped three dimensional
topological insulator (TI) by taking the effects of impurity-impurity exchange
interactions into account. The interactions between magnetic impurities give
rise to the formation of {\it magnetic clusters} with temperature dependent
mean sizes, randomly distributed on the surface of the TI. Instead of dealing
with single magnetic impurities, we consider surface Dirac electrons to be
scattered off magnetic clusters, and define the scattering potential in terms
of clusters mean sizes. Within the semiclassical Boltzmann approach, employing
a generalized relaxation time approximation, we obtain the surface conductivity
of the TI by solving four sets of recursive relations and demonstrate that, the
system is highly anisotropic and the surface conductivities possess
non-monotonic behaviors, they strongly depends on the direction, the mean size
and the number of magnetic clusters. We demonstrate that the dependence of the
anisotropic magnetoresistance (AMR) to the spin direction of the magnetic
clusters is inconsistent with the angular dependence of the TI doped with
non-interacting magnetic impurities. Our results are consistent with the recent
experiment on the AMR of the Cr-doped $\rm {(Bi, Sb)}_2{\rm Te}_3$ TI.

###Angle-dependent magnetoresistance as a sensitive probe of the charge density wave in quasi-one-dimensional semimetal Ta$_2$NiSe$_7$|Jiaming He,Libin Wen,Yueshen Wu,Jinyu Liu,Guoxiong Tang,Yusen Yang,Hui Xing,Zhiqiang Mao,Hong Sun,Ying Liu###

Angle-dependent magnetoresistance as a sensitive probe of the charge density wave in quasi-one-dimensional semimetal Ta$_2$NiSe$_7$. The behavior of charge density wave (CDW) in an external magnetic field is
dictated by both orbital and Pauli (Zeeman) effects. A quasi-one-dimensional
(Q1D) system features Q1D Fermi surfaces that allow these effects to be
distinguished, which in turn can provide sensitive probe to the underlying
electronic states. Here we studied the field dependence of an incommensurate
CDW in a transition-metal chalcogenide Ta2NiSe7 with a Q1D chain structure. The
angle-dependent magnetoresistance (MR) is found to be very sensitive to the
relative orientation between the magnetic field and the chain direction. With
an applied current fixed along the b axis (the chain direction), the
angle-dependent MR shows a striking change of the symmetry below T_CDW only for
a rotating magnetic field in the ac plane. In contrast, the symmetry axis
remains unchanged for other configurations (H in ab and bc plane). The orbital
effect conforms to the lattice symmetry, while Pauli effect in the form of
{\mu}B B / v_F can be responsible for such symmetry change, provided that the
Fermi velocity v_F is significantly anisotropic and the nesting vector changes
in a magnetic field, which is corroborated by our first-principles
calculations. Our results show that the angle-dependent MR is a sensitive
transport probe of CDW and can be useful for the study of low-dimensional
systems in general.

###Doping induced site-selective Mott insulating phase in LaFeO$_3$|S. Jana,S. K. Panda,D. Phuyal,B. Pal,S. Mukherjee,A. Dutta,P. Anil Kumar,D. Hedlund,J. Schott,P. Thunstrom,Y. Kvashnin,H. Rensmo,M. Venkata Kamalakar,Carlo. U. Segre,P. Svedlindh,K. Gunnarsson,S. Biermann,O. Eriksson,O. Karis,D. D. Sarma###

Doping induced site-selective Mott insulating phase in LaFeO$_3$. Tailoring transport properties of strongly correlated electron systems in a
controlled fashion counts among the dreams of materials scientists. In copper
oxides, varying the carrier concentration is a tool to obtain high-temperature
superconducting phases. In manganites, doping results in exotic physics such as
insulator-metal transitions (IMT), colossal magnetoresistance (CMR), orbital-
or charge-ordered (CO) or charge-disproportionate (CD) states. In most oxides,
antiferromagnetic order and charge-disproportionation are asssociated with
insulating behavior. Here we report the realization of a unique physical state
that can be induced by Mo doping in LaFeO$_3$: the resulting metallic state is
a site-selective Mott insulator where itinerant electrons evolving in
low-energy Mo states coexist with localized carriers on the Fe sites. In
addition, a local breathing-type lattice distortion induces charge
disproportionation on the latter, without destroying the antiferromagnetic
order. A state, combining antiferromangetism, metallicity and CD phenomena is
rather rare in oxides and may be of utmost significance for future
antiferromagnetic memory devices.

###Observation of superconductivity in pressurized Weyl semimetal candidate TaIrTe4|Shu Cai,Eve Emmanouilidou,Jing Guo,Xiaodong Li,Yanchuan Li,Ke Yang,Aiguo Li,Qi Wu,Ni Ni,Liling Sun###

Observation of superconductivity in pressurized Weyl semimetal candidate TaIrTe4. Here we report the observation of superconductivity in pressurized type-II
Weyl semimetal (WSM) candidate TaIrTe4 by means of complementary high-pressure
transport and synchrotron X-ray diffraction measurements. We find that TaIrTe4
shows superconductivity with transition temperature (TC) of 0.57 K at the
pressure of ~23.8 GPa. Then, the TC value increases with pressure and reaches
~2.1 K at 65.7 GPa. In situ high-pressure Hall coefficient (RH) measurements at
low temperatures demonstrate that the positive RH increases with pressure until
the critical pressure of the superconducting transition is reached, but starts
to decrease upon further increasing pressure. Above the critical pressure, the
positive magnetoresistance effect disappears simultaneously. Our high pressure
X-ray diffraction measurements reveal that, at around the critical pressure the
lattice of the TaIrTe4 sample is distorted by the application of pressure and
its volume is reduced by ~19.2%, the value of which is predicted to result in
the change of the electronic structure significantly. We propose that the
pressure-induced distortion in TaIrTe4 is responsible for the change of
topology of Fermi surface and such a change favors the emergence of
superconductivity. Our results clearly demonstrate the correlation among the
lattice distortion, topological physics and superconductivity in the WSM.

###Anatomy of electrical signals and dc-voltage lineshape in spin torque ferromagnetic resonance|Yin Zhang,Q. Liu,B. F. Miao,H. F. Ding,X. R. Wang###

Anatomy of electrical signals and dc-voltage lineshape in spin torque ferromagnetic resonance. The electrical detection of spin torque ferromagnetic resonance (st-FMR) is
becoming a popular method for measuring the spin-Hall angle of heavy metals
(HM). However, various sensible analysis on the same material with either the
same or different experimental setups yielded different spin-Hall angles with
large discrepancy, indicating some missing ingredients in our current
understanding of st-FMR. Here we carry out a careful analysis of electrical
signals of the st-FMR in a HM/ferromagnet (HM/FM) bilayer with an arbitrary
magnetic anisotropy. The FM magnetization is driven by two radio-frequency (rf)
forces: the rf Oersted field generated by an applied rf electric current and
the so called rf spin-orbit torque from the spin current flowing
perpendicularly from the HM to the FM due to the spin-Hall effect. By using the
universal form of the dynamic susceptibility matrix of magnetic materials at
the st-FMR, the electrical signals originated from the anisotropic
magnetoresistance, anomalous Hall effect and inverse spin-Hall effect are
analysed and dc-voltage lineshape near the st-FMR are obtained.
Angle-dependence of dc-voltage is given for two setups. A way of experimentally
extracting the spin-Hall angle of a HM is proposed.

###Tunable induced magnetic moment and in-plane conductance of graphene in Ni/graphene/Ni nano-spin-valve-like structure: a first principles study|Yusuf Wicaksono,Shingo Teranishi,Kazutaka Nishiguchi,Koichi Kusakabe###

Tunable induced magnetic moment and in-plane conductance of graphene in Ni/graphene/Ni nano-spin-valve-like structure: a first principles study. This study theoretically investigated the magnetic properties and electronic
structure of a graphene-based nano-spin-valve-like structure. Magnetic nickel
layers on both sides of the graphene were considered. A spin-polarized
generalized-gradient approximation determined the electronic states. In an
energetically stable stacking arrangement of graphene and two nickel layers,
the anti-parallel spin configuration of the underlayer and overlayer magnetic
moments had the lowest energy, which is in agreement with previous experimental
studies. The spin density mapping and obtained band-structure results show that
when the upper and lower Ni(111) slabs have an anti-parallel (parallel)
magnetic-moment configuration, the carbon atoms of sublattices A and B will
have an antiferromagnetic (ferromagnetic) spin configuration. A band gap at the
Dirac cone was open when the alignment had an anti-parallel configuration and
closed when the alignment had a parallel configuration. Therefore, the in-plane
conductance of the graphene layer depends on the magnetic alignment of the two
nickel slabs when the Fermi level is adjusted at the Dirac point. Both the
magnetic properties and electronic structures of the Ni/graphene/Ni
nanostructure cause the system to be a new prospective spintronic device
showing controllable in-plane magnetoresistance.

###Antiferromagnet-based spintronic functionality by controlling isospin domains in a layered perovskite iridate|Nara Lee,Eunjung Ko,Hwan Young Choi,Yun Jeong Hong,Muhammad Nauman,Woun Kang,Hyoung Joon Choi,Young Jai Choi,Younjung Jo###

Antiferromagnet-based spintronic functionality by controlling isospin domains in a layered perovskite iridate. The novel electronic state of the canted antiferromagnetic (AFM) insulator,
strontium iridate (Sr2IrO4) has been well described by the spin-orbit-entangled
isospin Jeff = 1/2, but the role of isospin in transport phenomena remains
poorly understood. In this study, antiferromagnet-based spintronic
functionality is demonstrated by combining unique characteristics of the
isospin state in Sr2IrO4. Based on magnetic and transport measurements, large
and highly anisotropic magnetoresistance (AMR) is obtained by manipulating the
antiferromagnetic isospin domains. First-principles calculations suggest that
electrons whose isospin directions are strongly coupled to in-plane net
magnetic moment encounter the isospin mismatch when moving across
antiferromagnetic domain boundaries, which generates a high resistance state.
By rotating a magnetic field that aligns in-plane net moments and removes
domain boundaries, the macroscopically-ordered isospins govern dynamic
transport through the system, which leads to the extremely angle-sensitive AMR.
As with this work that establishes a link between isospins and magnetotransport
in strongly spin-orbit-coupled AFM Sr2IrO4, the peculiar AMR effect provides a
beneficial foundation for fundamental and applied research on AFM spintronics.

###Current direction anisotropy of the spin Hall magnetoresistance in nickel ferrite thin films with bulk-like magnetic properties|Matthias Althammer,Amit Vikam Singh,Tobias Wimmer,Zbigniew Galazka,Hans Huebl,Matthias Opel,Rudolf Gross,Arunava Gupta###

Current direction anisotropy of the spin Hall magnetoresistance in nickel ferrite thin films with bulk-like magnetic properties. We utilize spin Hall magnetoresistance (SMR) measurements to experimentally
investigate the pure spin current transport and magnetic properties of nickel
ferrite (NiFe2O4,NFO)/normal metal (NM) thin film heterostructures. We use
(001)-oriented NFO thin films grown on lattice-matched magnesium gallate
substrates by pulsed laser deposition, which significantly improves the
magnetic and structural properties of the ferrimagnetic insulator. The NM in
our experiments is either Pt or Ta. A comparison of the obtained SMR magnitude
for charge currents applied in the [100]- and [110]-direction of NFO yields a
change of 50% for Pt at room temperature. We also investigated the temperature
dependence of this current direction anisotropy and find that it is
qualitatively different for the conductivity and the SMR magnitude. From our
results we conclude that the observed current direction anisotropy may
originate from an anisotropy of the spin mixing conductance or of the spin Hall
effect in these Pt and Ta layers, and/or additional spin-galvanic contributions
from the NFO/NM interface.

###Magneto-Transport in a Chiral Fluid from Kinetic Theory|Navid Abbasi,Farid Taghinavaz,Omid Tavakol###

Magneto-Transport in a Chiral Fluid from Kinetic Theory. We argue that in order to study the magneto-transport in a relativistic Weyl
fluid, it is needed to take into account the associated quantum corrections,
namely the side-jump effect, at least to second order. To this end, we impose
Lorentz invariance to a system of free Weyl fermions in the presence of the
magnetic field and find the second order correction to the energy dispersion.
By developing a scheme to compute the integrals in the phase space, we show
that the mentioned correction has non-trivial effects on the thermodynamics of
the system. Specifically, we predict the form of the negative magnetoresistance
in the system from the enthalpy density in equilibrium. Then in analogy with
Weyl semimetal, in the framework of the chiral kinetic theory and under the
relaxation time approximation, we explicitly compute the
magneto-conductivities, at low temperature limit ($T\ll \mu$). We show that the
conductivities obey the set of Ward identities which follow from the generating
functional including the Chern-Simons part.

###Itinerant antiferromagnetic BaMn$_2$Pn$_2$'s showing both negative and positive magnetoresistances|Kim-Khuong Huynh,Takuma Ogasawara,Keita Kitahara,Yoichi Tanabe,Stephane Yu Matsushita,Time Tahara,Takanori Kida,Masayuki Hagiwara,Denis Arčon,Katsumi Tanigaki###

Itinerant antiferromagnetic BaMn$_2$Pn$_2$'s showing both negative and positive magnetoresistances. We report the discovery of a novel giant magnetoresistance (GMR) phenomenon
in a family of BaMn$_{2}$Pn$_{2}$ antiferromagnets (Pn stands for P, As, Sb,
and Bi) with a parity-time symmetry. The resistivities of these materials are
reduced by $60$ times in magnetic fields ($\vec{H}$'s), thus yielding the GMR
of about $-98\%$. The GMR changes systematically along with the Pn elements,
hinting that its origin is the spin orbit coupling (SOC) and/or $d$-$p$ orbital
hybridization. A positive MR component emerging on top of the negative GMR at
low temperatures suggests an orbital-sensitive magnetotransport as $\vec{H}$
suppresses the conduction of the electron-like carriers in the $d$-like band
but enhances those of hole-like ones in the $d$-$p$ hybridized band. The
anisotropy of the GMR reveals that the electrical conductivity is extremely
sensitive to the minute changes in the direction of the antiferromagnetic
moments induced by the parity-time breaking $\vec{H}$, which seems to be
associated with a magnetoelectric effect in the dynamic regime of conduction
electrons. We attribute the observed GMR to the non-trivial low energy band of
BMPn's, which is governed by the parity-time symmetry and an magnetic
hexadecapole ordering.

###Room-temperature Low-field Colossal Magneto-resistance in Double-perovskite Manganite|S. Yamada,N. Abe,H. Sagayama,K. Ogawa,T. Yamagami,T. Arima###

Room-temperature Low-field Colossal Magneto-resistance in Double-perovskite Manganite. The gigantic decrease of resistance by an applied magnetic field, which is
often referred to as colossal magnetoresistance (CMR), has been an attracting
phenomenon in strongly correlated electron systems. The discovery of CMR in
manganese oxide compounds has developed the science of strong coupling among
charge, orbital, and spin degrees of freedom. CMR is also attracting scientists
from the viewpoint of possible applications to sensors, memories, and so on.
However, no application using CMR effect has been achieved so far, partly
because the CMR materials which satisfy all of the required conditions for the
application, namely, high operating temperature, low operating magnetic field,
and sharp resistive change, have not been discovered. Here we report a
resistance change of more than two-orders of magnitude at a magnetic field
lower than 2 T near 300 K in an A-site ordered NdBaMn_2_O_6_ crystal. When
temperature and a magnetic field sweep from insulating (metallic) phase to
metallic (insulating) phase, the insulating (metallic) conduction changes to
the metallic (insulating) conduction within 1 K and 0.5 T, respectively. The
CMR is ascribed to the melting of the charge ordering. The entropy change which
is estimated from the B-T phase diagram is smaller than what is expected for
the charge and orbital ordering. The suppression of the entropy change is
attributable to the loss of the short range ferromagnetic fluctuation of Mn
spin moments, which an important key of the high temperature and low magnetic
field CMR effect.

###Composable Probabilistic Inference Networks Using MRAM-based Stochastic Neurons|Ramtin Zand,Kerem Y. Camsari,Supriyo Datta,Ronald F. DeMara###

Composable Probabilistic Inference Networks Using MRAM-based Stochastic Neurons. Magnetoresistive random access memory (MRAM) technologies with thermally
unstable nanomagnets are leveraged to develop an intrinsic stochastic neuron as
a building block for restricted Boltzmann machines (RBMs) to form deep belief
networks (DBNs). The embedded MRAM-based neuron is modeled using precise
physics equations. The simulation results exhibit the desired sigmoidal
relation between the input voltages and probability of the output state. A
probabilistic inference network simulator (PIN-Sim) is developed to realize a
circuit-level model of an RBM utilizing resistive crossbar arrays along with
differential amplifiers to implement the positive and negative weight values.
The PIN-Sim is composed of five main blocks to train a DBN, evaluate its
accuracy, and measure its power consumption. The MNIST dataset is leveraged to
investigate the energy and accuracy tradeoffs of seven distinct network
topologies in SPICE using the 14nm HP-FinFET technology library with the
nominal voltage of 0.8V, in which an MRAM-based neuron is used as the
activation function. The software and hardware level simulations indicate that
a $784\times200\times10$ topology can achieve less than 5% error rates with
$\sim400 pJ$ energy consumption. The error rates can be reduced to 2.5% by
using a $784\times500\times500\times500\times10$ DBN at the cost of
$\sim10\times$ higher energy consumption and significant area overhead.
Finally, the effects of specific hardware-level parameters on power dissipation
and accuracy tradeoffs are identified via the developed PIN-Sim framework.

###Application of an extended van der Pauw method to anisotropic magnetoresistance measurements of ferromagnetic films|Movaffaq Kateb,Egill Jacobsen,Snorri Ingvarsson###

Application of an extended van der Pauw method to anisotropic magnetoresistance measurements of ferromagnetic films. We demonstrate anisotropic resistivity measurements using the extended van
der Pauw (vdP) method in ferromagnetic Ni80Fe20 (Py) films. We apply it to
measure anisotropic magnetoresistance (AMR) and compare the results of the vdP
method with the more conventional Hall-bar method along the hard and easy axis
of the film and show that the vdP method gives more reliable AMR result. For
instance, the AMR result along the hard and easy axis of the film are in close
agreement. Further, we applied the vdP method to study AMR in a series of Py
films with thicknesses ranging between 10-250 nm. The films were grown by
sputtering deposition at an angle with respect to the substrate normal and with
an in-situ magnetic field, both conditions assisting in the definition of
in-plane uniaxial anisotropy. The microstructure of Py films was characterized
using X-ray reflectivity, diffraction and polar mapping of (111) planes. We
detected no off-normal texture and negligible surface roughness, which
indicates that self-shadowing is not dominating in our growth. Yet the films
have well defined uniaxial anisotropy. Abrupt changes in the average
resistivity vs. film thickness were observed, which cannot be explained by the
models accounting for the thickness and grain size but strongly correlate with
the changes in (111) texture in the films. We compared our results with the
literature and show that independent of growth method, substrate and deposition
temperature, the AMR value presents a saturation behavior with thickness at
about 100 nm.

###Spin scattering and noncollinear spin structure-induced intrinsic anomalous Hall effect in antiferromagnetic topological insulator $\mathrm{MnBi_2Te_4}$|Seng Huat Lee,Yanglin Zhu,Yu Wang,Leixin Miao,Timothy Pillsbury,Susan Kempinger,David Graf,Nasim Alem,Cui-Zu Chang,Nitin Samarth,Zhiqiang Mao###

Spin scattering and noncollinear spin structure-induced intrinsic anomalous Hall effect in antiferromagnetic topological insulator $\mathrm{MnBi_2Te_4}$. $\mathrm{MnBi_2Te_4}$ has recently been established as an intrinsic
antiferromagnetic (AFM) topological insulator and predicted to be an ideal
platform to realize quantum anomalous Hall (QAH) insulator and axion insulator
states. We performed comprehensive studies on the structure, nontrivial surface
state and magnetotransport properties of this material. Our results reveal an
intrinsic anomalous Hall effect arising from a non-collinear spin structure for
the magnetic field parallel to the $c$-axis. We also observed remarkable
negative magnetoresistance under arbitrary field orientation below and above
the Neel temperature (T$_N$), providing clear evidence for strong spin
fluctuation-driven spin scattering in both the AFM and paramagnetic states.
Further, we found that the nontrivial surface state opens a large gap (~85 meV)
even at temperatures far above T$_N$ = 25K. These findings demonstrate that the
bulk band structure of $\mathrm{MnBi_2Te_4}$ is strongly coupled to the
magnetic structure and that a net Berry curvature in momentum space can be
created in a canted AFM state. In addition, our results imply that the gap
opening in the surface states is intrinsic, likely caused by the strong spin
fluctuations near the surface layers.

###Scaling of intrinsic domain wall magneto-resistance with confinement in electromigrated nanocontacts|Robert M. Reeve,André Loescher,Hamidreza Kazemi,Bertrand Dupé,Thomas Winkler,Daniel Schönke,Jun Miao,Kai Litzius,Nicholas Sedlmayr,Imke Schneider,Jairo Sinova,Sebastian Eggert,Mathias Kläui###

Scaling of intrinsic domain wall magneto-resistance with confinement in electromigrated nanocontacts. In this work we study the evolution of intrinsic domain wall
magnetoresistance (DWMR) with domain wall confinement. Clean permalloy notched
half-ring nanocontacts are fabricated using a special ultra-high vacuum
electromigration procedure to tailor the size of the wire in-situ and through
the resulting domain wall confinement we tailor the domain wall width from a
few tens of nm down to a few nm. Through measurements of the dependence of the
resistance with respect to the applied field direction we extract the
contribution of a single domain wall to the MR of the device, as a function of
the domain wall width in the confining potential at the notch. In this size
range, an intrinsic positive MR is found, which dominates over anisotropic MR,
as confirmed by comparison to micromagnetic simulations. Moreover, the MR is
found to scale monotonically with the size of the domain wall, $\delta_{DW}$,
as 1/$\delta_{DW}^b$, with $b=2.31\pm 0.39 $. The experimental result is
supported by quantum-mechanical transport simulations based on ab-initio
density functional theory calculations.

###Observation of planar Hall effect in Type-II Dirac semimetal PtTe$_{2}$|Amit Vashist,R. K. Singh,Neha Wadehra,S. Chakraverty,Yogesh Singh###

Observation of planar Hall effect in Type-II Dirac semimetal PtTe$_{2}$. We report experimental observation of the Planar Hall effect (PHE) in a
type-II Dirac semimetal PtTe$_2$. This unusual Hall effect is not expected in
nonmagnetc materials such as PtTe$_2$, and has been observed previously mostly
in magnetic semiconductors or metals. Remarkably, the PHE in PtTe$_2$ can be
observed up to temperatures near room temperature which indicates the
robustness of the effect. This is in contrast to the chiral anomaly induced
negative longitudnal magnetoresistance (LMR), which can be observed only in the
low temperature regime and is sensitive to extrinsic effects, such as current
jetting and chemical inhomogeneities in crystals of high mobility. Planar Hall
effect on the other hand is a purely intrinsic effect generated by the Berry
curvature in Weyl semimetals. Additionally, the PHE is observed for PtTe$_2$
even though the Dirac node is $\approx 0.8$~eV away from the Fermi level. Thus
our results strongly indicate that PHE can be used as a crucial transport
diagnostic for topological character even for band structures with Dirac nodes
slightly away from the Fermi energy.

###Interfacial Spin-Orbit Coupling: New Platform for Superconducting Spintronics|Isidoro Martínez,Petra Högl,César González-Ruano,Juan Pedro Cascales,Coriolan Tiusan,Yuan Lu,Michel Hehn,Alex Matos-Abiague,Jaroslav Fabian,Igor Žutić,Farkhad G. Aliev###

Interfacial Spin-Orbit Coupling: New Platform for Superconducting Spintronics. Spin-orbit coupling (SOC) is a key interaction in spintronics, allowing an
electrical control of spin or magnetization and, vice versa, a magnetic control
of electrical current. However, recent advances have revealed much broader
implications of SOC that is also central to the design of topological states,
including topological insulators, skyrmions, and Majorana fermions, or to
overcome the exclusion of two-dimensional ferro-magnetism expected from the
Mermin-Wagner theorem. SOC and the resulting emergent interfacial spin-orbit
fields are simply realized in junctions through structural inversion asymmetry,
while the anisotropy in magnetoresistance (MR) allows for their experimental
detection. Surprisingly, we demonstrate that an all-epitaxial
ferromagnet/MgO/metal junction with only a negligible MR anisotropy undergoes a
remarkable transformation below the superconducting transition temperature of
the metal. The superconducting junction has a three orders of magnitude higher
MR anisotropy and supports the formation of spin-triplet superconductivity,
crucial for superconducting spintronics, and topologically-protected quantum
computing. Our findings call for revisiting the role of SOC in other systems
which, even when it seems negligible in the normal state, could have a profound
influence on the superconducting response.

###Optical Signatures of the Chiral Anomaly in Mirror-Symmetric Weyl Semimetals|Aaron Hui,Yi Zhang,Eun-Ah Kim###

Optical Signatures of the Chiral Anomaly in Mirror-Symmetric Weyl Semimetals. The chiral anomaly is a phenomenon characteristic of Weyl fermions, which has
condensed matter realizations in Weyl semimetals. Efforts to observe smoking
gun signatures of the chiral anomaly in Weyl semimetals have mostly focused on
a negative longitudinal magnetoresistance in electronic transport.
Unfortunately, disentangling the chiral anomaly contribution in transport or
optical measurements has proven non-trivial. Recent works have proposed an
alternative approach of probing pseudoscalar phonon dynamics for signatures of
the chiral anomaly in non-mirror-symmetric crystals. Here, we show that such
phonon signatures can be extended to scalar phonon modes and mirror-symmetric
crystals, broadening the pool of candidate materials. We show that the presence
of the background magnetic field can break mirror symmetry strongly enough to
yield observable signatures of the chiral anomaly even in mirror-symmetric
materials. Specifically for mirror-symmetric Weyl semimetals such as TaAs and
NbAs, including the Zeeman interaction at $B \approx 10$T, we predict an IR
reflectivity peak will develop with an $\mathbf{E}_\text{IR}\cdot\mathbf{B}$
dependence.

###Effect of atomic ordering on the magnetic anisotropy of single crystal Ni80Fe20|Movaffaq Kateb,Jon Tomas Gudmundsson,Snorri Ingvarsson###

Effect of atomic ordering on the magnetic anisotropy of single crystal Ni80Fe20. We investigate the effect of atomic ordering on the magnetic anisotropy of
Ni80Fe20 at.% (Py). To this end, Py films were grown epitaxially on MgO (001)
using dc magnetron sputtering (dcMS) and high power impulse magnetron
sputtering (HiPIMS). Aside from twin boundaries observed in the latter case,
both methods present high quality single crystals with cube-on-cube epitaxial
relationship as verified by the polar mapping of important crystal planes.
However, X-ray diffraction results indicate higher order for the dcMS deposited
film towards L12 Ni3Fe superlattice. This difference can be understood by the
very high deposition rate of HiPIMS during each pulse which suppresses adatom
mobility and ordering. We show that the dcMS deposited film presents biaxial
anisotropy while HiPIMS deposition gives well defined uniaxial anisotropy.
Thus, higher order achieved in the dcMS deposition behaves as predicted by
magnetocrystalline anisotropy i.e. easy axis along the [111] direction that
forced in the plane along the [110] direction due to shape anisotropy. The
uniaxial behaviour in HiPIMS deposited film then can be explained by pair
ordering or more recent localized composition non-uniformity theories. Further,
we studied magnetoresistance of the films along the [100] directions using an
extended van der Pauw method. We find that the electrical resistivities of the
dcMS deposited film are lower than in their HiPIMS counterparts verifying the
higher order in the dcMS case.

###Theoretical Study on Anisotropic Magnetoresistance Effects of I//[100], I//[110], and I//[001] for Ferromagnets with A Crystal Field of Tetragonal Symmetry|Satoshi Kokado,Masakiyo Tsunoda###

Theoretical Study on Anisotropic Magnetoresistance Effects of I//[100], I//[110], and I//[001] for Ferromagnets with A Crystal Field of Tetragonal Symmetry. Using the electron scattering theory, we obtain analytic expressions for
anisotropic magnetoresistance (AMR) ratios for ferromagnets with a crystal
field of tetragonal symmetry. Here, a tetragonal distortion exists in the [001]
direction, the magnetization ${\mbox{\boldmath $M$}}$ lies in the (001) plane,
and the current ${\mbox{\boldmath $I$}}$ flows in the [100], [010], or [001]
direction. When the ${\mbox{\boldmath $I$}}$ direction is denoted by $i$, we
obtain the AMR ratio as ${\rm AMR}^i (\phi_i)= C_0^i + C_2^i \cos 2\phi_i +
C_4^i \cos 4 \phi_i \ldots = \sum_{j=0,2,4,\ldots} C_j^i \cos j\phi_i$, with
$i=[100]$, $[110]$, and $[001]$, $\phi_{[100]} = \phi_{[001]}=\phi$, and
$\phi_{[110]}=\phi'$. The quantity $\phi$ ($\phi'$) is the relative angle
between ${\mbox{\boldmath $M$}}$ and the $[100]$ ($[110]$) direction, and
$C_j^i$ is a coefficient composed of a spin--orbit coupling constant, an
exchange field, the crystal field, and resistivities. We elucidate the origin
of $C_j^i \cos j\phi_i$ and the features of $C_j^i$. In addition, we obtain the
relation $C_4^{[100]} = -C_4^{[110]}$, which was experimentally observed for
Ni, under a certain condition. We also qualitatively explain the experimental
results of $C_2^{[100]}$, $C_4^{[100]}$, $C_2^{[110]}$, and $C_4^{[110]}$ at
293 K for Ni.

###Unconventional Superconductivity in Heavy Fermion UTe2|Dai Aoki,Ai Nakamura,Fuminori Honda,DeXin Li,Yoshiya Homma,Yusei Shimizu,Yoshiki J. Sato,Georg Knebel,Jean-Pascal Brison,Alexandre Pourret,Daniel Braithwaite,Gerard Lapertot,Qun Niu,Michal Valiska,Hisatomo Harima,Jacques Flouquet###

Unconventional Superconductivity in Heavy Fermion UTe2. We grew single crystals of the recently discovered heavy fermion
superconductor UTe2, and measured the resistivity, specific heat and
magnetoresistance. Superconductivity (SC) was clearly detected at Tsc=1.65K as
sharp drop of the resistivity in a high quality sample of RRR=35. The specific
heat shows a large jump at Tsc indicating strong coupling. The large Sommerfeld
coefficient, 117mJ K-2mol-1 extrapolated in the normal state and the
temperature dependence of C/T below Tsc are the signature of unconventional SC.
The discrepancy in the entropy balance at Tsc between SC and normal states
points out that hidden features must occur. Surprisingly, a large residual
value of the Sommerfeld coefficient seems quite robust (gamma_0/gamma ~ 0.5).
The large upper critical field Hc2 along the three principal axes favors
spin-triplet SC. For H // b-axis, our experiments do not reproduce the huge
upturn of Hc2 reported previously. This discrepancy may reflect that Hc2 is
very sensitive to the sample quality. A new perspective in UTe2 is the
proximity of a Kondo semiconducting phase predicted by the LDA band structure
calculations.

###Angular dependence of the upper critical field in the high-pressure $1T'$ phase of MoTe$_2$|Y. J. Hu,Yuk Tai Chan,Kwing To Lai,Kin On Ho,Xiaoyu Guo,Hai-Peng Sun,K. Y. Yip,Dickon H. L. Ng,Hai-Zhou Lu,Swee K. Goh###

Angular dependence of the upper critical field in the high-pressure $1T'$ phase of MoTe$_2$. Superconductivity in the type-II Weyl semimetal candidate MoTe$_2$ has
attracted much attention due to the possible realization of topological
superconductivity. Under applied pressure, the superconducting transition
temperature is significantly enhanced, while the structural transition from the
high-temperature 1$T'$ phase to the low-temperature $T_d$ phase is suppressed.
Hence, applying pressure allows us to investigate the dimensionality of
superconductivity in 1$T'$-MoTe$_2$. We have performed a detailed study of the
magnetotransport properties and upper critical field $H_{c2}$ of MoTe$_2$ under
pressure. The magnetoresistance (MR) and Hall coefficient of MoTe$_2$ are found
to be decreasing with increasing pressure. In addition, the Kohler's scalings
for the MR data above $\sim$11 kbar show a change of exponent whereas the data
at lower pressure can be well scaled with a single exponent. These results are
suggestive of a Fermi surface reconstruction when the structure changes from
the $T_d$ to 1$T'$ phase. The $H_{c2}$-temperature phase diagram constructed at
15 kbar, with $H\parallel ab$ and $H\perp ab$, can be satisfactorily described
by the Werthamer-Helfand-Hohenberg model with the Maki parameters $\alpha \sim$
0.77 and 0.45, respectively. The relatively large $\alpha$ may stem from a
small Fermi surface and a large effective mass of semimetallic MoTe$_2$. The
angular dependence of $H_{c2}$ at 15 kbar can be well fitted by the Tinkham
model, suggesting the two-dimensional nature of superconductivity in the
high-pressure 1$T'$ phase.

###Coexistence of orbital and quantum critical magnetoresistance in FeSe$_{1-x}$S$_{x}$|S. Licciardello,N. Maksimovic,J. Ayres,J. Buhot,M. Culo,B. Bryant,S. Kasahara,Y. Matsuda,T. Shibauchi,V. Nagarajan,J. G. Analytis,N. E. Hussey###

Coexistence of orbital and quantum critical magnetoresistance in FeSe$_{1-x}$S$_{x}$. The recent discovery of a non-magnetic nematic quantum critical point (QCP)
in the iron chalcogenide family FeSe$_{1-x}$S$_{x}$ has raised the prospect of
investigating, in isolation, the role of nematicity on the electronic
properties of correlated metals. Here we report a detailed study of the normal
state transverse magnetoresistance (MR) in FeSe$_{1-x}$S$_{x}$ for a series of
S concentrations spanning the nematic QCP. For all temperatures and
\textit{x}-values studied, the MR can be decomposed into two distinct
components: one that varies quadratically in magnetic field strength
$\mu_{0}\textit{H}$ and one that follows precisely the quadrature scaling form
recently reported in metals at or close to a QCP and characterized by a
\textit{H}-linear MR over an extended field range. The two components evolve
systematically with both temperature and S-substitution in a manner that is
determined by their proximity to the nematic QCP. This study thus reveals
unambiguously the coexistence of two independent charge sectors in a quantum
critical system. Moreover, the quantum critical component of the MR is found to
be less sensitive to disorder than the quadratic (orbital) MR, suggesting that
detection of the latter in previous MR studies of metals near a QCP may have
been obscured.

###Tunnel magnetoresistance of a supramolecular spin valve|A. Plominska,I. Weymann###

Tunnel magnetoresistance of a supramolecular spin valve. We theoretically study the transport properties of a supramolecular spin
valve, consisting of a carbon nanotube with two attached magnetic molecules,
weakly coupled to metallic contacts. The emphasis is put on analyzing the
change of the system's transport properties with the application of an external
magnetic field, which aligns the spins of the molecules. It is shown that
magnetoresistive properties of the considered molecular junction, which are
associated with changing the state of the molecules from superparamagnetic to
the ferromagnetic one, strongly depend on the applied bias voltage and the
position of the nanotube's orbital levels, which can be tuned by a gate
voltage. A strong dependence on the transport regime is also found in the case
of the spin polarization of the current flowing through the system. The
mechanisms leading to those effects are explained by invoking appropriate
molecular states responsible for transport. The analysis is done with aid of
the real-time diagrammatic technique up to the second order of expansion with
respect to tunneling processes.

###Magnetic properties and domain structure of ultrathin yttrium iron garnet/Pt bilayers|Johannes Mendil,Morgan Trassin,Qingqing Bu,Jakob Schaab,Manuel Baumgartner,Christoph Murer,Phuong T. Dao,Jaianth Vijayakumar,David Bracher,Corinne Bouillet,Carlos A. F. Vaz,Manfred Fiebig,Pietro Gambardella###

Magnetic properties and domain structure of ultrathin yttrium iron garnet/Pt bilayers. We report on the structure, magnetization, magnetic anisotropy, and domain
morphology of ultrathin yttrium iron garnet (YIG)/Pt films with thickness
ranging from 3 to 90 nm. We find that the saturation magnetization is close to
the bulk value in the thickest films and decreases towards low thickness with a
strong reduction below 10 nm. We characterize the magnetic anisotropy by
measuring the transverse spin Hall magnetoresistance as a function of applied
field. Our results reveal strong easy plane anisotropy fields of the order of
50-100 mT, which add to the demagnetizing field, as well as weaker in-plane
uniaxial anisotropy ranging from 10 to 100 $\mu$T. The in-plane easy axis
direction changes with thickness, but presents also significant fluctuations
among samples with the same thickness grown on the same substrate. X-ray
photoelectron emission microscopy reveals the formation of zigzag magnetic
domains in YIG films thicker than 10 nm, which have dimensions larger than
several 100 $\mu$m and are separated by achiral N\'{e}el-type domain walls.
Smaller domains characterized by interspersed elongated features are found in
YIG films thinner than 10 nm.

###Fast learning synapses with molecular spin valves via selective magnetic potentiation|Alberto Riminucci,Robert Legenstein###

Fast learning synapses with molecular spin valves via selective magnetic potentiation. We studied LSMO/Alq3/AlOx/Co molecular spin valves in view of their use as
synapses in neuromorphic computing. In neuromorphic computing, the learning
ability is embodied in specific changes of the synaptic weight. In this
perspective, the relevant parameter is the conductance of the molecular spin
valve, which plays the role of the synaptic weight. In this work we
demonstrated that the conductance can be changes by the repeated application of
voltage pulses. We studied the parameter space of the pulses in order to
determine the most effective voltage and duration of the pulses. The
conductance could also be modified by aligning the magnetizations of the
ferromagnetic electrodes parallel or anti parallel to each other. This
phenomenon, known as magnetoresistance, affects high conductance devices while
leaving low conductance devices unaffected. We studied how this weight update
rule affected the speed of reward-based learning in an actor-critic framework,
compared to a linear update rule. This nonlinear update performed significantly
better (50 learning trials; Epochs to reach a performance goal of 0.975 was
896+/-301 in the nonlinear case and 1076+/-484 in the nonlinear case; Welch
t-test: p<0.05). The linear update resulted in more learning trails with very
long convergence times, which was largely absent in the nonlinear update.

###Magnetic competition induced colossal magnetoresistance in n-type HgCr2Se4 under high pressures|J. P. Sun,Y. Y. Jiao,C. J. Yi,S. E. Dissanayake,M. Matsuda,Y. Uwatoko,Y. G. Shi,Y. Q. Li,Z. Fang,J. -G. Cheng###

Magnetic competition induced colossal magnetoresistance in n-type HgCr2Se4 under high pressures. The n-type HgCr2Se4 exhibits a sharp semiconductor-to-metal transition (SMT)
in resistivity accompanying the ferromagnetic order at TC = 106 K. Here, we
investigate the effects of pressure and magnetic field on the concomitant SMT
and ferromagnetic order by measuring resistivity, dc and ac magnetic
susceptibility, as well as single-crystal neutron diffraction under various
pressures up to 8 GPa and magnetic fields up to 8 T. Our results demonstrate
that the ferromagnetic metallic ground state of n-type HgCr2Se4 is destabilized
and gradually replaced by an antiferromagnetic, most likely a spiral magnetic,
and insulating ground state upon the application of high pressure. On the other
hand, the application of external magnetic fields can restore the ferromagnetic
metallic state again at high pressures, resulting in a colossal
magnetoresistance (CMR) as high as ~ 3 * 10^11 % under 5 T and 2 K at 4 GPa.
The present study demonstrates that n-type HgCr2Se4 is located at a peculiar
critical point where the balance of competion between ferromagnetic and
antiferromagnetic interactions can be easily tipped by the external stimuli,
providing a new platform for achieving CMR in a single-valent system.

###Fermi surface topology and large magnetoresistance in the topological semimetal candidate PrBi|Amit Vashist,R. K. Gopal,Divya Srivastava,M. Karppinen,Yogesh Singh###

Fermi surface topology and large magnetoresistance in the topological semimetal candidate PrBi. We report a detailed magnetotransport study on single crystals of PrBi. The
presence of $f$-electrons in this material raises the prospect of realizing a
strongly correlated version of topological semimetals. PrBi shows a magnetic
field induced metal insulator transition below $T \sim 20$ K and a very large
magnetoresistance ($\approx 4.4 \times 10^4~$) at low temperatures ($T= 2$ K).
We have also probed the Fermi surface topology by de Haas van Alphen (dHvA) and
Shubnikov de Haas (SdH) quantum oscillation measurements complimented with
density functional theory (DFT) calculations of the band structure and the
Fermi surface. Angle dependence of the SdH oscillations have been carried out
to probe the possible signature of surface Dirac fermions. We find three
frequencies corresponding to one electron ($\alpha$) and two hole ($\beta$ and
$\gamma$) pockets in experiments, consistent with DFT calculations. The angular
dependence of these frequencies is not consistent with a two dimensional Fermi
surface suggesting that the transport is dominated by bulk bands. Although the
transport properties of this material originate from the bulk bands, the high
mobility and small effective mass are comparable to other compounds in this
series proposed as topologically nontrivial.

###Possibility of a new order parameter driven by multipolar moment and Fermi surface evolution in CeGe|Karan Singh,K. Mukherjee###

Possibility of a new order parameter driven by multipolar moment and Fermi surface evolution in CeGe. Polycrystalline CeGe is investigated by means of DC and AC susceptibility,
non-linear DC susceptibility, electrical transport and heat capacity
measurements in the low temperature regime. This compound shows two peaks at
low magnetic field approximately around 10.7 and 7.3 K due to antiferromagnetic
ordering and subsequent spin rearrangement respectively. Investigation of
non-linear DC susceptibility reveals a presence of higher order magnetization
which results in the development of a new order parameter around 10.7 K. This
leads to a lowering of symmetry of the magnetic state. The order parameter
increases with decreasing temperature and stabilizes around 7.3 K.
Consequently, the symmetry of the magnetic state is preserved below this
transition. Heat capacity and resistivity results indicate the presence of a
gap opening around 10.7 K on portion of Fermi surface, due to evolution of the
Fermi surface. Magnetoresistance behavior and violation of Kohlers rule suggest
that the evolution of Fermi surface changes the symmetry of magnetic state. The
observation of new order parameter (which is of second order) is also confirmed
from the Landau free energy theory.

###Anomalous high-magnetic field electronic state of the nematic superconductors FeSe$_{1-x}$S$_x$|M. Bristow,P. Reiss,A. A. Haghighirad,Z. Zajicek,S. J. Singh,T. Wolf,D. Graf,W. Knafo,A. McCollam,A. I. Coldea###

Anomalous high-magnetic field electronic state of the nematic superconductors FeSe$_{1-x}$S$_x$. Understanding superconductivity requires detailed knowledge of the normal
electronic state from which it emerges. A nematic electronic state that breaks
the rotational symmetry of the lattice can potentially promote unique
scattering relevant for superconductivity. Here, we investigate the normal
transport of superconducting FeSe$_{1-x}$S$_x$ across a nematic phase
transition using high magnetic fields up to 69 T to establish the temperature
and field-dependencies. We find that the nematic state is an anomalous
non-Fermi liquid, dominated by a linear resistivity at low temperatures that
can transform into a Fermi liquid, depending on the composition $x$ and the
impurity level. Near the nematic end point, we find an extended temperature
regime with $T^{1.5}$ resistivity. The transverse magnetoresistance inside the
nematic phase has as a $H^{1.55}$ dependence over a large magnetic field range
and it displays an unusual peak at low temperatures inside the nematic phase.
Our study reveals anomalous transport inside the nematic phase, driven by the
subtle interplay between the changes in the electronic structure of a
multi-band system and the unusual scattering processes affected by large
magnetic fields and disorder

###Tuning insulator-semimetal transitions in 3D topological insulator thin films by inter-surface hybridization and in-plane magnetic fields|Yang Xu,Guodong Jiang,Ireneusz Miotkowski,Rudro R. Biswas,Yong P. Chen###

Tuning insulator-semimetal transitions in 3D topological insulator thin films by inter-surface hybridization and in-plane magnetic fields. A pair of Dirac points (analogous to a vortex-antivortex pair) associated
with opposite topological numbers (with $\pm\pi$ Berry phases) can be merged
together through parameter tuning and annihilated to gap the Dirac spectrum,
offering a canonical example of a topological phase transition. Here, we report
transport studies on thin films of BiSbTeSe$_2$ (BSTS), which is a 3D TI that
hosts spin-helical gapless (semi-metallic) Dirac fermion surface states (SS)
for sufficiently thick samples, with an observed resistivity close to $h/4e^2$
at the charge neutral point. When the sample thickness is reduced to $\sim$10
nm thick, the Dirac cones from the top and bottom surfaces can hybridize
(analogous to a "merging" in the real space) and become gapped to give a
trivial insulator. Furthermore, we observe that an in-plane magnetic field can
drive the system again towards a metallic behavior, with a prominent negative
magnetoresistance (MR, up to $\sim$$-$95\%) and a temperature-insensitive
resistivity close to $h/2e^2$ at the charge neutral point. The observation is
interpreted in terms of a predicted effect of an in-plane magnetic field to
reduce the hybridization gap (which, if small enough, may be smeared by
disorder and a metallic behavior). A sufficiently strong magnetic field is
predicted to restore and split again the Dirac points in the momentum space,
inducing a distinct 2D topological semimetal (TSM) phase with 2 single-fold
Dirac cones of opposite spin-momentum windings.

###Spin-dependent transport in van der Waals magnetic tunnel junctions with Fe3GeTe2 electrodes|Xinlu Li,Evgeny Y. Tsymbal,Jing-Tao Lü,Jia Zhang,Long You,Yurong Su###

Spin-dependent transport in van der Waals magnetic tunnel junctions with Fe3GeTe2 electrodes. Van der Waals (vdW) heterostructures, stacking different two-dimensional
materials, have opened up unprecedented opportunities to explore new physics
and device concepts. Especially interesting are recently discovered
two-dimensional magnetic vdW materials, providing new paradigms for spintronic
applications. Here, using density functional theory (DFT) calculations, we
investigate the spin-dependent electronic transport across vdW magnetic tunnel
junctions (MTJs) composed of Fe3GeTe2 ferromagnetic electrodes and a graphene
or hexagonal boron nitride (h-BN) spacer layer. For both types of junctions, we
find that the junction resistance changes by thousands of percent when the
magnetization of the electrodes is switched from parallel to antiparallel. Such
a giant tunneling magnetoresistance (TMR) effect is driven by dissimilar
electronic structure of the two spin-conducting channels in Fe3GeTe2, resulting
in a mismatch between the incoming and outgoing Bloch states in the electrodes
and thus suppressed transmission for an antiparallel-aligned MTJ. The vdW
bounding between electrodes and a spacer layer makes this result virtually
independent of the type of the spacer layer, making the predicted giant TMR
effect robust with respect to strain, lattice mismatch, interface distance and
other parameters which may vary in the experiment. We hope that our results
will further stimulate experimental studies of vdW MTJs and pave the way for
their applications in spintronics.

###Tuning the metal-insulator transition in epitaxial SrVO3 films by uniaxial strain|Changan Wang,Hongbin Zhang,Kumar Deepak,5Chao Chen,Arnaud Fouchet,Juanmei Duan,Donovan Hilliard,Ulrich Kentsch,Deyang Chen,Min Zeng,Xingsen Gao,Yu-Jia Zeng,Manfred Helm,Wilfrid Prellier,Shengqiang Zhou###

Tuning the metal-insulator transition in epitaxial SrVO3 films by uniaxial strain. Understanding of the metal-insulator transition (MIT) in correlated
transition-metal oxides is a fascinating topic in condensed matter physics and
a precise control of such transitions plays a key role in developing novel
electronic devices. Here we report an effective tuning of the MIT in epitaxial
SrVO3 (SVO) films by expanding the out-of-plane lattice constant without
changing in-plane lattice parameters, through helium ion irradiation. Upon
increase of the ion fluence, we observe a MIT with a crossover from metallic to
insulating state in SVO films. A combination of transport and magnetoresistance
measurements in SVO at low temperatures reveals that the observed MIT is mainly
ascribed to electron-electron interactions rather than disorder-induced
localization. Moreover, these results are well supported by the combination of
density functional theory and dynamical mean field theory (DFT+DMFT)
calculations, further confirming the decrease of the bandwidth and the enhanced
electron-electron interactions resulting from the expansion of out-of-plane
lattice constant. These findings provide new insights into the understanding of
MIT in correlated oxides and perspectives for the design of unexpected
functional devices based on strongly correlated electrons.

###Fermions and bosons in nonsymmorphic PdSb2 with sixfold degeneracy|Ramakanta Chapai,Yating Jia,W. A. Shelton,Roshan Nepal,Mohammad Saghayezhian,J. F. DiTusa,E. W. Plummer,Changqing Jin,Rongying Jin###

Fermions and bosons in nonsymmorphic PdSb2 with sixfold degeneracy. PdSb2 is a candidate for hosting 6-fold-degenerate exotic fermions (beyond
Dirac and Weyl fermions).The nontrivial band crossing protected by the
nonsymmorphic symmetry plays a crucial role in physical properties. We have
grown high-quality single crystals of PdSb2 and characterized their physical
properties under several stimuli (temperature, magnetic field, and pressure).
While it is a diamagnetic Fermi-liquid metal under ambient pressure, PdSb2
exhibits a large magnetoresistance with continuous increase up to 14 T, which
follows the Kohler's scaling law at all temperatures. This implies one-band
electrical transport, although multiple bands are predicted by first principles
calculations. By applying magnetic field along the [111] direction, de Haas-van
Alphen oscillations are observed with frequency of 102 T. The effective mass is
nearly zero (0.045m0) with the Berry phase close to {\pi}, confirming that the
band close to the R point has a nontrivial character. Under quasihydrostatic
pressure (p), evidence for superconductivity is observed in the resistivity
below the critical temperature Tc. The dome-shaped Tc versus p is obtained with
maximum Tc~2.9 K. We argue that the formation of Cooper pairs (bosons) is the
consequence of the redistribution of the 6-fold-degenerate fermions under
pressure.

###Antisymmetric magnetoresistance and helical magnetic structure in compensated Gd/Co multilayer|Surendra Singh,M. A. Basha,C. L. Prajapat,Harsh Bhatt,Yogesh Kumar,M. Gupta,C. J. Kinane,J. Cooper,M. R. Gonal,S. Langridge,S. Basu###

Antisymmetric magnetoresistance and helical magnetic structure in compensated Gd/Co multilayer. Using spin dependent specular and off-specular polarized neutron reflectivity
(PNR), we report the observation of a twisted helical magnetic structure with
planar 2{\pi} domain wall (DW) and highly correlated magnetic domains in a
Gd/Co multilayer. Specular PNR with polarization analysis reveals the formation
of planar 2{\pi}DWs below a compensation temperature (TComp), resulting to
positive exchange bias in this system. Off-specular PNR with spin polarization
showed development of magnetic inhomogenities (increase in magnetic roughness)
for central part (thickness ~ 25-30 {\AA}) of each Gd layer, where
magnetization is aligned perpendicular (in-plane) to an applied field. These
magnetic roughness are vertically correlated and results into Bragg sheet in
spin flip channel of Off-specular PNR data, which is contributing towards an
antisymmetric magnetoresistance at TComp in the system. The growth and
tunability of highly correlated magnetic inhomogeneities (roughness) and domain
structure around TComp in combination of twisted helical magnetic structure
with planar 2{\pi}DWs will be key for application in all-spin-based technology.

###On the Angular Dependence of InP High Electron Mobility Transistors for Cryogenic Low Noise Amplifiers in a Magnetic Field|Isabel Harrysson Rodrigues,David Niepce,Arsalan Pourkabirian,Giuseppe Moschetti,Joel Schleeh,Thilo Bauch,Jan Grahn###

On the Angular Dependence of InP High Electron Mobility Transistors for Cryogenic Low Noise Amplifiers in a Magnetic Field. The InGaAs-InAlAs-InP high electron mobility transistor (InP HEMT) is the
preferred active device used in a cryogenic low noise amplifier (LNA) for
sensitive detection of microwave signals. We observed that an InP HEMT
0.3-14GHz LNA at 2K, where the in-going transistors were oriented perpendicular
to a magnetic field, heavily degraded in gain and average noise temperature
already up to 1.5T. Dc measurements for InP HEMTs at 2K revealed a strong
reduction in the transistor output current as a function of static magnetic
field up to 14T. In contrast, the current reduction was insignificant when the
InP HEMT was oriented parallel to the magnetic field. Given the transistor
layout with large gate width/gate length ratio, the results suggest a strong
geometrical magnetoresistance effect occurring in the InP HEMT. This was
confirmed in the angular dependence of the transistor output current with
respect to the magnetic field. Key device parameters such as transconductance
and on-resistance were significantly affected at small angles and magnetic
fields. The strong angular dependence of the InP HEMT output current in a
magnetic field has important implications for the alignment of cryogenic LNAs
in microwave detection experiments involving magnetic fields.

###Strong magnetoelectric coupling in mixed ferrimagnetic-multiferroic phases of a double perovskite|M. K. Kim,J. Y. Moon,S. H. Oh,D. G. Oh,Y. J. Choi,N. Lee###

Strong magnetoelectric coupling in mixed ferrimagnetic-multiferroic phases of a double perovskite. Exploring new magnetic materials is essential for finding advantageous
functional properties such as magnetoresistance, magnetocaloric effect,
spintronic functionality, and multiferroicity. Versatile classes of double
perovskite compounds have been recently investigated because of intriguing
physical properties arising from the proper combination of several magnetic
ions. In this study, it is observed that the dominant ferrimagnetic phase is
coexisted with a minor multiferroic phase in single-crystalline
double-perovskite Er2CoMnO6. The majority portion of the ferrimagnetic order is
activated by the long-range order of Er3+ moments below TEr = 10 K in addition
to the ferromagnetic order of Co2+ and Mn4+ moments arising at TC = 67 K,
characterized by compensated magnetization at TComp = 3.15 K. The inverted
magnetic hysteresis loop observed below TComp can be described by an extended
Stoner-Wohlfarth model. The additional multiferroic phase is identified by the
ferroelectric polarization of 0.9 uC/m2 at 2 K. The coexisting ferrimagnetic
and multiferroic phases appear to be strongly correlated in that metamagnetic
and ferroelectric transitions occur simultaneously. The results based on
intricate magnetic correlations and phases in Er2CoMnO6 enrich fundamental and
applied research on magnetic materials through the scope of distinct magnetic
characteristics in double perovskites.

###Effective spin-mixing conductance of topological-insulator/ferromagnet and heavy-metal/ferromagnet spin-orbit-coupled interfaces: A first-principles Floquet-nonequilibrium-Green-function approach|Kapildeb Dolui,Utkarsh Bajpai,Branislav K. Nikolic###

Effective spin-mixing conductance of topological-insulator/ferromagnet and heavy-metal/ferromagnet spin-orbit-coupled interfaces: A first-principles Floquet-nonequilibrium-Green-function approach. The spin mixing conductance (SMC) is a key quantity determining efficiency of
spin transport across interfaces. Thus, knowledge of its precise value is
required for accurate measurement of parameters quantifying numerous effects in
spintronics, such as spin-orbit torque, spin Hall magnetoresistance, spin Hall
effect and spin pumping. However, the standard expression for SMC, provided by
the scattering theory in terms of the reflection probability amplitudes, is
inapplicable when strong spin-orbit coupling (SOC) is present directly at the
interface. This is the precisely the case of topological-insulator/ferromagnet
and heavy-metal/ferromagnet interfaces of great contemporary interest. We
introduce an approach where first-principles Hamiltonian of these interfaces,
obtained from noncollinear density functional theory (ncDFT) calculations, is
combined with charge conserving Floquet-nonequilibrium-Green-function formalism
to compute {\em directly} the pumped spin current $I^{S_z}$ into semi-infinite
left lead of two-terminal heterostructures Cu/X/Co/Cu or Y/Co/Cu---where
X=Bi$_2$Se$_3$ and Y=Pt or W---due to microwave-driven steadily precessing
magnetization of the Co layer. This allows us extract an effective SMC as a
prefactor in $I^{S_z}$ vs. precession cone angle $\theta$ dependence, as long
as it remains the same, $I^{S_z} \propto \sin^2 \theta$, as in the case where
SOC is absent. By comparing calculations where SOC in switched off vs. switched
on in ncDFT calculations, we find that SOC consistently reduces the pumped spin
current and, therefore, the effective SMC.

###Nonsaturating magnetoresistance and nontrivial band topology of type-II Weyl semimetal NbIrTe4|W. Zhou,B. Li,C. Q. Xu,M. R. van Delft,Y. G. Chen,X. C. Fan,B. Qian,N. E. Hussey,Xiaofeng Xu###

Nonsaturating magnetoresistance and nontrivial band topology of type-II Weyl semimetal NbIrTe4. Weyl semimetals, characterized by nodal points in the bulk and Fermi arc
states on the surface, have recently attracted extensive attention due to the
potential application on low energy consumption electronic materials. In this
report, the thermodynamic and transport properties of a theoretically predicted
Weyl semimetal NbIrTe4 is measured in high magnetic fields up to 35 T and low
temperatures down to 0.4 K. Remarkably, NbIrTe4 exhibits a nonsaturating
transverse magnetoresistance which follows a power-law dependence in B.
Low-field Hall measurements reveal that hole-like carriers dominate the
transport for T $>$ 80 K, while the significant enhancement of electron
mobilities with lowering T results in a non-negligible contribution from
electron-like carriers which is responsible for the observed non-linear Hall
resistivity at low T. The Shubnikov-de Haas oscillations of the Hall
resistivity under high B give the light effective masses of charge carriers and
the nontrivial Berry phase associated with Weyl fermions. Further
first-principles calculations confirm the existence of 16 Weyl points located
at kz = 0, $\pm$0.02 and $\pm$0.2 planes in the Brillouin zone.

###Magnetic-Field-Induced Phenomena in the Paramagnetic Superconductor UTe$_{2}$|William Knafo,Michal Vališka,Daniel Braithwaite,Gérard Lapertot,Georg Knebel,Alexandre Pourret,Jean-Pascal Brison,Jacques Flouquet,Dai Aoki###

Magnetic-Field-Induced Phenomena in the Paramagnetic Superconductor UTe$_{2}$. We present magnetoresistivity measurements on the heavy-fermion
superconductor UTe$_{2}$ in pulsed magnetic fields $\mu_0H$ up to 68~T and
temperatures $T$ from 1.4 to 80~K. Magnetic fields applied along the three
crystallographic directions $\mathbf{a}$ (easy magnetic axis), $\mathbf{b}$,
and $\mathbf{c}$ (hard magnetic axes), are found to induce different phenomena
- depending on the field direction - beyond the low-field suppression of the
superconducting state. For $\mathbf{H}\parallel\mathbf{a}$, a broad anomaly in
the resistivity is observed at $\mu_0H^*\simeq10$~T and $T = 1.4$~K. For
$\mathbf{H}\parallel\mathbf{c}$, no magnetic transition nor crossover are
observed. For $\mathbf{H}\parallel\mathbf{b}$, a sharp first-order-like step in
the resistivity indicates a metamagnetic transition at the field $\mu_0H_m
\simeq 35$~T. When the temperature is raised signature of first-order
metamagnetism is observed up to a critical endpoint at $T_{CEP}\simeq7$~K. At
higher temperatures a crossover persists up to 28~K, i.e., below the
temperature $T_\chi^{max} = 35$~K where the magnetic susceptibility is maximal.
A sharp maximum in the Fermi-liquid quadratic coefficient $A$ of the
low-temperature resistivity is found at $H_m$. It indicates an enhanced
effective mass associated with critical magnetic fluctuations, possibly coupled
with a Fermi surface instability. Similarly to the URhGe case, we show that
UTe$_{2}$ is a candidate for field-induced reentrant superconductivity in the
proximity of $H_m$.

###Magnetic tunnel junctions with a B2-ordered CoFeCrAl equiatomic Heusler alloy|Tomoki Tsuchiya,Tufan Roy,Kelvin Elphick,Jun Okabayashi,Lakhan Bainsla,Tomohiro Ichinose,Kazuya Suzuki,Masahito Tsujikawa,Masafumi Shirai,Atsufumi Hirohata,Shigemi Mizukami###

Magnetic tunnel junctions with a B2-ordered CoFeCrAl equiatomic Heusler alloy. The equiatomic quaternary Heusler alloy CoFeCrAl is a candidate material for
spin-gapless semiconductors (SGSs). However, to date, there have been no
experimental attempts at fabricating a junction device. This paper reports a
fully epitaxial (001)-oriented MgO barrier magnetic tunnel junction (MTJ) with
CoFeCrAl electrodes grown on a Cr buffer. X-ray and electron diffraction
measurements show that the (001) CoFeCrAl electrode films with atomically flat
surfaces have a $B2$-ordered phase. The saturation magnetization is 380
emu/cm$^3$, almost the same as the value given by the Slater--Pauling--like
rule, and the maximum tunnel magnetoresistance ratios at 300 K and 10 K are 87%
and 165%, respectively. Cross-sectional electron diffraction analysis shows
that the MTJs have MgO interfaces with fewer dislocations. The temperature- and
bias-voltage-dependence of the transport measurements indicates magnon-induced
inelastic electron tunneling overlapping with the coherent electron tunneling.
X-ray magnetic circular dichroism (XMCD) measurements show a ferromagnetic
arrangement of the Co and Fe magnetic moments of $B2$-ordered CoFeCrAl, in
contrast to the ferrimagnetic arrangement predicted for the $Y$-ordered state
possessing SGS characteristics. Ab-initio calculations taking account of the
Cr-Fe swap disorder qualitatively explain the XMCD results. Finally, the effect
of the Cr-Fe swap disorder on the ability for electronic states to allow
coherent electron tunneling is discussed.

###Quantum oscillations and nontrivial topological state in a compensated semimetal TaP2|Hongyuan Wang,Hao Su,Jiuyang Zhang,Wei Xia,Yishi Lin,Xiaolei Liu,Xiaofei Hou,Zhenhai Yu,Na Yu,Xia Wang,Zhiqiang Zou,Yihua Wang,Qifeng Liang,Yuhua Zhen,Yanfeng Guo###

Quantum oscillations and nontrivial topological state in a compensated semimetal TaP2. We report systematic magneto-transport measurements and ab initio
calculations on single-crystalline TaP2, a new member of the transition-metal
dipnictides. We observed unsaturated magnetoresistance (MR) reaching ~ 700% at
a magnetic field (B) of 9 T at 2 K along with striking Shubnikov-de Hass (SdH)
oscillations. Our analysis on the SdH oscillations reveals nonzero Berry phase,
indicating nontrivial band topology. The analysis also uncovers three
fundamental magnetic oscillation frequencies of 72 T, 237 T, and 356 T,
consistent with the theoretical calculations which reveal one hole pocket and
two electron pockets at the L point and one electron pocket at the Z point of
the Brillouin zone. We also found negative longitudinal MR (n-MR) within a
narrow window of the angles between B and the electric current (I). The n-MR
could be fitted with the Adler-Bell-Jackiw chiral anomaly equation but the
origin remains yet ambiguous. The ab inito calculations suggest TaP2 as a weak
topological insulator with the Z2 indices of (0; 111), which exhibits
topological surface states on the (001) surface.

###Stochastic Computing for Hardware Implementation of Binarized Neural Networks|Tifenn Hirtzlin,Bogdan Penkovsky,Marc Bocquet,Jacques-Olivier Klein,Jean-Michel Portal,Damien Querlioz###

Stochastic Computing for Hardware Implementation of Binarized Neural Networks. Binarized Neural Networks, a recently discovered class of neural networks
with minimal memory requirements and no reliance on multiplication, are a
fantastic opportunity for the realization of compact and energy efficient
inference hardware. However, such neural networks are generally not entirely
binarized: their first layer remains with fixed point input. In this work, we
propose a stochastic computing version of Binarized Neural Networks, where the
input is also binarized. Simulations on the example of the Fashion-MNIST and
CIFAR-10 datasets show that such networks can approach the performance of
conventional Binarized Neural Networks. We evidence that the training procedure
should be adapted for use with stochastic computing. Finally, the ASIC
implementation of our scheme is investigated, in a system that closely
associates logic and memory, implemented by Spin Torque Magnetoresistive Random
Access Memory. This analysis shows that the stochastic computing approach can
allow considerable savings with regards to conventional Binarized Neural
networks in terms of area (62% area reduction on the Fashion-MNIST task). It
can also allow important savings in terms of energy consumption, if we accept
reasonable reduction of accuracy: for example a factor 2.1 can be saved, with
the cost of 1.4% in Fashion-MNIST test accuracy. These results highlight the
high potential of Binarized Neural Networks for hardware implementation, and
that adapting them to hardware constrains can provide important benefits.

###Signatures of Helical Edge Transport in Millimetre-Scale Thin Films of Na3Bi|Chang Liu,Dimitrie Culcer,Mark T. Edmonds,Michael S. Fuhrer###

Signatures of Helical Edge Transport in Millimetre-Scale Thin Films of Na3Bi. A two-dimensional topological insulator (2DTI) has an insulating bulk and
helical spin-polarised edge modes robust to backscattering by non-magnetic
disorder. While ballistic transport has been demonstrated in 2DTIs over short
distances, larger samples show significant backscattering and a nearly
temperature-independent resistance whose origin is unclear. 2DTI edges have
shown a spin polarisation, however the degree of helicity is difficult to
quantify from spin measurements. Here, we study 2DTI few-layer Na3Bi on
insulating Al2O3. A non-local conductance measurement geometry enables
sensitive detection of the edge conductance in the topological regime, with an
edge mean free path ~100 nm. Magnetic field suppresses spin-flip scattering in
the helical edges, resulting in a giant negative magnetoresistance (GNMR), up
to 80% at 0.9 T. Comparison to theory indicates >98% of scattering is helical
spin scattering significantly exceeding the maximum (67%) expected for a
non-helical metal. GNMR, coupled with non-local measurements demonstrating edge
conduction, thus provides an unambiguous experimental signature of helical
edges that we expect to be generically useful in understanding 2DTIs.

###Tuning spin filtering by anchoring groups in benzene derivative molecular junctions|Dongzhe Li,Yannick J. Dappe,Alexander Smogunov###

Tuning spin filtering by anchoring groups in benzene derivative molecular junctions. One of the important issues of molecular spintronics is the control and
manipulation of charge transport and, in particular, its spin polarization
through single-molecule junctions. Using $ab$ $initio$ calculations, we explore
spin-polarized electron transport across single benzene derivatives attached
with six different anchoring groups (S, CH$_3$S, COOH, CNH$_2$NH, NC and
NO$_2$) to Ni(111) electrodes. We find that molecule-electrode coupling,
conductance and spin polarization (SP) of electric current can be modified
significantly by anchoring groups. In particular, a high spin polarization (SP
$>$ 80%) and a giant magnetoresistance (MR $>$ 140%) can be achieved for NO$_2$
terminations and, more interestingly, SP can be further enhanced (up to 90%) by
a small voltage. The S and CH$_3$S systems, on the contrary, exhibit rather low
SP while intermediate values are found for COOH and CNH$_2$NH groups. The
results are analyzed in detail and explained by orbital symmetry arguments,
hybridization and spatial localization of frontier molecular orbitals. We hope
that our comparative and systematic studies will provide valuable quantitative
information for future experimental measurements on that kind of systems and
will be useful for designing high-performance spintronics devices.

###Tunneling Magnetoresistance and Spin-Dependent Diode Performance in Fully Epitaxial Magnetic Tunnel Junctions with Rock-salt Type ZnO/MgO|Hidekazu Saito,Sai Krishna Narayananellore,Norihiro Matsuo,Naoki Doko,Shintaro Kon,Yukiko Yasukawa,Hiroshi Imamura,Shinji Yuasa###

Tunneling Magnetoresistance and Spin-Dependent Diode Performance in Fully Epitaxial Magnetic Tunnel Junctions with Rock-salt Type ZnO/MgO. We fabricate fully epitaxial Fe/ZnO/MgO/Fe magnetic tunnel junctions (MTJs)
with a bilayer tunnel barrier, in which ZnO has a metastable rock-salt crystal
structure. We observe a high magnetoresistance ratio up to 96% at room
temperature (RT) and find that these MTJs have asymmetric current-voltage
characteristics, and their rectifying performances are largely dependent on the
magnetization alignments of the Fe electrodes. Diode responsibilities at a
zero-bias voltage ($\beta_{0}$), which is an important performance index for
harvesting applications, are observed up to 1.3 A/W at RT in the antiparallel
alignment of the magnetizations while maintaining rather low resistance-area
(RA) products (a few tens of k${\Omega\mu}$m$^2$). Even with the same top and
bottom electrodes (Fe), the obtained $\beta_{0}$ values are comparable to those
of reported high-performance tunnel diodes consisting of amorphous bilayer
tunnel barriers with polycrystalline dissimilar electrodes. This strongly
suggests that the epitaxial ZnO/MgO bilayer tunnel barrier is effective for
enhancing the $\beta_{0}$ without significant increase in the RA. In addition,
we demonstrate that a zero-bias anomaly in thetunnel conductance, which
originates from the magnon excitations at the Fe/barrier interfaces, plays a
crucial role in observed spin-dependent diode performance. The results indicate
that a fully epitaxial MTJ with a bilayer tunnel barrier is a promising
candidate to establish a high-performance high-frequency rectifying system.

###Nonlinear planar Hall effect|Pan He,Steven S. -L. Zhang,Dapeng Zhu,Shuyuan Shi,Olle G. Heinonen,Giovanni Vignale,Hyunsoo Yang###

Nonlinear planar Hall effect. An intriguing property of three-dimensional (3D) topological insulator (TI)
is the existence of surface states with spin-momentum locking, which offers a
new frontier of exploration in spintronics. Here, we report the observation of
a new type of Hall effect in a 3D TI Bi2Se3 film. The Hall resistance scales
linearly with both the applied electric and magnetic fields and exhibits a
{\pi}/2 angle offset with respect to its longitudinal counterpart, in contrast
to the usual angle offset of {\pi}/4 between the linear planar Hall effect and
the anisotropic magnetoresistance. This novel nonlinear planar Hall effect
originates from the conversion of a nonlinear transverse spin current to a
charge current due to the concerted actions of spin-momentum locking and time
reversal symmetry breaking, which also exists in a wide class of
non-centrosymmetric materials with a large span of magnitude. It provides a new
way to characterize and utilize the nonlinear spin-to-charge conversion in a
variety of topological quantum materials.

###Crossover from two-dimensional to three-dimensional superconducting states in bismuth-based cuprate superconductor|Jing Guo,Yazhou Zhou,Cheng Huang,Shu Cai,Yutao Sheng,Genda Gu,Chongli Yang,Gongchang Lin,Ke Yang,Aiguo Li,Qi Wu,Tao Xiang,Liling Sun###

Crossover from two-dimensional to three-dimensional superconducting states in bismuth-based cuprate superconductor. To decipher the mechanism of high temperature superconductivity, it is
important to know how the superconducting pairing emerges from the unusual
normal states of cuprate superconductors, including pseudogap, anomalous Fermi
liquid and strange metal (SM). A long-standing issue under debate is how the
superconducting pairing is formed and condensed in the SM phase because the
superconducting transition temperature is the highest in this phase. Here, we
report the first experimental observation of a pressure-induced crossover from
two- to three-dimensional superconducting states in the optimally-doped
Bi2Sr2CaCu2O8+delta bulk superconductor at a pressure above 2.8 GPa, through
state-of-the-art in-situ high-pressure measurements of resistance,
magnetoresistance and magnetic susceptibility. By analyzing the temperature
dependence of resistance, we find that the two-dimensional (2D) superconducting
transition exhibits a Berezinski-Kosterlitz-Thouless-like behavior. The
emergence of this 2D superconducting transition provides direct and strong
evidence that the SM state is predominantly 2D-like. This is important to a
thorough understanding of the phase diagram of cuprate superconductors.

###Crystal Growth and basic transport and magnetic properties of MnBi2Te4|Poonam Rani,Ankush Saxena,Rabia Sultana,Vipin Nagpal,S. S. Islam,S. Patnaik,V. P. S. Awana###

Crystal Growth and basic transport and magnetic properties of MnBi2Te4. We report successful growth of magnetic topological insulator (MTI) MnBi2Te4.
The heating schedule basically deals with growth of the crystal from melt at
900C and very slow cooling (1C/hr) to around 600C with 24 hours hold time,
followed by cooling to room temperature. Our detailed, PXRD Reitveld analysis
showed that the resultant crystal is dominated mainly by MnBi2Te4 and minor
phases of Bi2Te3 and MnTe. The transport measurements showed a step like
behavior at around 150K followed by cusp like structure in resistivity at
around 25K (TP) due reported anti-ferromagnetic ordering of Mn. Both the
resistivity transitions are seen clearly in dR/dT measurements at 150K and 20K
respectively. The 25K transition of the compound is also seen in magnetic
susceptibility. Low temperature (5K) magnetoresistance (MR) in applied field of
up to 6 Tesla exhibited negative ve MR below 3 Tesla and +ve for higher fields.
Also, seen are steps in MR below one Tesla. The studied MnBi2Te4 MTI crystal
could be a possible candidate for Quantum Anomalous Hall (QAH) effect.

###Observation of charge density wave transition in TaSe3 mesowires|J. Yang,Y. Q. Wang,R. R. Zhang,L. Ma,W. Liu,Z. Qu,L. Zhang,S. L. Zhang,W. Tong,L. Pi,W. K. Zhu,C. J. Zhang###

Observation of charge density wave transition in TaSe3 mesowires. The quasi-one-dimensional (quasi-1D) TaSe3 attracts considerable attention
for its intriguing superconductivity and possible interplay with nontrivial
topology and charge density wave (CDW) state. However, unlike the isostructural
analogues, CDW has not been observed for TaSe3 despite its quasi-1D character
that is supposed to promote Peierls instabilities and CDW. Here we synthesize
TaSe3 mesowires (MWs) using a one-step approach. For the MW of ~300 nm thick, a
distinct CDW transition occurs at 65 K in the resistivity measurement, which
has not been reported before and is further evidenced by the Raman
characterization and susceptibility measurement. For comparison, we have also
prepared bulk single crystal TaSe3. Although no anomaly appears in the
resistivity and magnetoresistance measurements, the carrier type detected by
Hall effect varies from n-type to p-type below 50 K, suggesting a
reconstruction of Fermi surface that could be associated with CDW. The
enhancement of CDW in the MWs is attributed to the reduced dimensionality.
TaSe3 is demonstrated to be a promising platform to study the correlation and
competition of CDW and superconductivity in the quasi-1D systems.

###Itinerancy-dependent non-collinear spin textures in SrFeO3, CaFeO3, and CaFeO3/SrFeO3 heterostructures probed via resonant x-ray scattering|Paul C. Rogge,Robert J. Green,Ronny Sutarto,Steven J. May###

Itinerancy-dependent non-collinear spin textures in SrFeO3, CaFeO3, and CaFeO3/SrFeO3 heterostructures probed via resonant x-ray scattering. Non-collinear, multi-q spin textures can give rise to exotic, topologically
protected spin structures such as skyrmions, but the reason for their formation
over simple single-q structures is not well understood. While lattice
frustration and the Dzyaloshinskii-Moriya interaction are known to produce
non-collinear spin textures, the role of electron itinerancy in multi-q
formation is much less studied. Here we investigated the non-collinear, helical
spin structures in epitaxial films of the perovskite oxides SrFeO3 and CaFeO3
using magnetotransport and resonant soft x-ray magnetic diffraction. Metallic
SrFeO3 exhibits features in its magnetoresistance that are consistent with its
recently proposed multi-q structure. Additionally, the magnetic Bragg peak of
SrFeO3 measured at the Fe L edge resonance energy asymmetrically broadens with
decreasing temperature in its multi-q state. In contrast, insulating CaFeO3 has
a symmetric scattering peak with an intensity 10x weaker than SrFeO3. Enhanced
magnetic scattering at O K edge prepeak energies demonstrates the role of a
negative charge transfer energy and the resulting oxygen ligand holes in the
magnetic ordering of these ferrates. By measuring magnetic diffraction of
CaFeO3/SrFeO3 superlattices with thick CaFeO3 layers, we find that the CaFeO3
helical ordering is coherent across 1 unit cell-thick SrFeO3 layers but not 6
unit cell-thick layers. We conclude that insulating CaFeO3 supports only a
simple single-q helical structure in contrast to metallic SrFeO3 that hosts
multi-q structures. Our results provide important insight into the role of
electron itinerancy in the formation of multi-q spin structures.

###Extremely large magnetoresistance and compensated Fermi surfaces in the antiferromagnetic semimetal YbAs|W. Xie,Y. Wu,F. Du,A. Wang,H. Su,Y. Chen,Z. Y. Nie,S. -K. Mo,M. Smidman,C. Cao,Y. Liu,T. Takabatake,H. Q. Yuan###

Extremely large magnetoresistance and compensated Fermi surfaces in the antiferromagnetic semimetal YbAs. A number of rare-earth monopnictides have topologically non-trivial band
structures together with magnetism and strong electronic correlations. In order
to examine whether the antiferromagnetic (AFM) semimetal YbAs ($T\rm_N$ = 0.5
K) exhibits such a scenario, we have grown high-quality single crystals using a
flux method, and characterized the magnetic properties and electronic structure
using specific heat, magnetotransport and angle-resolved photoemission
spectroscopy (ARPES) measurements, together with density functional theory
(DFT) calculations. Both ARPES and DFT calculations find no evidence for band
inversions in YbAs, indicating a topologically trivial electronic structure.
From low-temperature magnetotransport measurements, we map the
field-temperature phase diagram, where we find the presence of a field
stabilized phase distinct from the AFM phase at low temperatures. An extremely
large magnetoresistance (XMR) for both YbAs and the nonmagnetic counterpart
LuAs, is also observed, which can consistently be accounted for by the presence
of electron-hole compensation. Moreover, an angle-dependent study of the
Shubnikov-de Haas effect oscillations reveals very similar Fermi surfaces
between YbAs and LuAs, with light effective masses down to at least 0.5 K,
indicating that the Yb-$4f$ electrons are well localized, and do not contribute
to the Fermi surface. However, the influence of the localized Yb-$4f$ electrons
on the magnetotransport of YbAs can be discerned from the distinct temperature
dependence of the XMR compared to that of LuAs, which we attribute to the
influence of short-ranged spin correlations that appear well above $T\rm_N$.

###Complex magnetic phase diagram of metamagnetic MnPtSi|Monika B. Gamża,Walter Schnelle,Helge Rosner,Sarah V. Ackerbauer,Yuri Grin,Andreas Leithe-Jasper###

Complex magnetic phase diagram of metamagnetic MnPtSi. The magnetic, thermal and transport properties as well as electronic band
structure of MnPtSi are reported. MnPtSi is a metal that undergoes a
ferromagnetic transition at $T_{\mathrm{C}}=340$(1) K and a spin-reorientation
transition at $T_{\mathrm{N}}=326$(1) K to an antiferromagnetic phase.
First-principles electronic structure calculations indicate a not-fully
polarized spin state of Mn in a $d^5$ electron configuration with $J=S=3$/2, in
agreement with the saturation magnetization of 3~$\mu_{\mathrm{B}}$ in the
ordered state and the observed paramagnetic effective moment. A sizeable
anomalous Hall effect in the antiferromagnetic phase alongside the
computational study suggests that the antiferromagnetic structure is
non-collinear. Based on thermodynamic and resistivity data we construct a
magnetic phase diagram. Magnetization curves $M$($H$) at low temperatures
reveal a metamagnetic transition of spin-flop type. The spin-flopped phase
terminates at a critical point with $T_{\mathrm{cr}}\approx 300$ K and
$H_{\mathrm{cr}}\approx 10$ kOe, near which a peak of the magnetocaloric
entropy change is observed. Using Arrott plot analysis and magnetoresistivity
data we argue that the metamagnetic transition is of a first-order type,
whereas the strong field dependence of $T_{\mathrm{N}}$ and the linear
relationship of the $T_{\mathrm{N}}$ with $M^2$ hint at its magnetoelastic
nature.

###Crossover from charge density wave stabilized antiferromagnetism to superconductivity in Nd$_{1-x}$La$_x$NiC$_2$ compounds|Marta Roman,Leszek Litzbarski,Tomasz Klimczuk,Kamil K. Kolincio###

Crossover from charge density wave stabilized antiferromagnetism to superconductivity in Nd$_{1-x}$La$_x$NiC$_2$ compounds. The path from the charge density wave antiferromagnet NdNiC$_2$ to a
noncentrosymmetric superconductor LaNiC$_2$ has been studied by gradual
replacement of Nd by La ions. The evolution of physical properties has been
explored by structural, magnetic, transport, magnetoresistance and specific
heat measurements. With the substitution of La for Nd, the Peierls temperature
is gradually suppressed, which falls within the BCS mean-field relation for
chemical pressure with a critical concentration of $x_c$ = 0.38. As long as
charge density wave is maintained, the antiferromagnetic ground state remains
robust against doping and despite of a N\'eel temperature reduction shows a
rapid and sharp magnetic transition. Once the CDW is completely suppressed,
intermediate compounds of the Nd$_{1-x}$La$_x$NiC$_2$ series reveal symptoms of
a gradual softening of the features associated with AFM transition and increase
of the spin disorder. Immediately after the antiferromagnetic transition is
depressed to zero temperature, the further incorporation of La ions results in
the emergence of superconductivity. This crossover in the
Nd$_{1-x}$La$_x$NiC$_2$ is discussed in the terms of the possible quantum
critical point.

###Temperature-induced band shift in ferromagnetic Weyl semimetal Co3Sn2S2|Run Yang,Tan Zhang,Liqin Zhou,Yaomin Dai,Zhiyu Liao,Hongming Weng,Xianggang Qiu###

Temperature-induced band shift in ferromagnetic Weyl semimetal Co3Sn2S2. The discovery of nonmagnetic Weyl semimetals (WSMs) in TaAs compounds has
triggered lots of efforts in finding its magnetic counterpart. While the direct
observation of the Weyl nodes and Fermi arcs in a magnetic candidate through
angle-resolved photoemission spectroscopy is hindered by the complex magnetic
domains. The transport features of magnetic WSMs, including negative
magnetoresistivity and anomalous Hall conductivity, are not conclusive since
these are sensitive to extrinsic factors like defects and disorders in lattice
or magnetic ordering. Here, we systematically study the temperature-dependent
optical spectra of ferromagnetic Co$_3$Sn$_2$S$_2$ experimentally and simulated
by first-principles calculations. The many-body correlation effect due to Co
$3d$ electrons leads to the renormalization of bands by a factor about 1.33,
which is moderate and the description within density functional theory is
suitable. As the temperature drops down, the magnetic phase transition happens
and the magnetization drives the band shift through exchange splitting. The
optical spectra can well detect these changes, including the transitions
sensitive and insensitive to the magnetization, and those from the bands around
the Weyl nodes. The results strongly support that Co$_3$Sn$_2$S$_2$ is a
magnetic WSM and the Weyl nodes can be tuned by magnetization with temperature
change.

###Implementing Binarized Neural Networks with Magnetoresistive RAM without Error Correction|Tifenn Hirtzlin,Bogdan Penkovsky,Jacques-Olivier Klein,Nicolas Locatelli,Adrien F. Vincent,Marc Bocquet,Jean-Michel Portal,Damien Querlioz###

Implementing Binarized Neural Networks with Magnetoresistive RAM without Error Correction. One of the most exciting applications of Spin Torque Magnetoresistive Random
Access Memory (ST-MRAM) is the in-memory implementation of deep neural
networks, which could allow improving the energy efficiency of Artificial
Intelligence by orders of magnitude with regards to its implementation on
computers and graphics cards. In particular, ST-MRAM could be ideal for
implementing Binarized Neural Networks (BNNs), a type of deep neural networks
discovered in 2016, which can achieve state-of-the-art performance with a
highly reduced memory footprint with regards to conventional artificial
intelligence approaches. The challenge of ST-MRAM, however, is that it is prone
to write errors and usually requires the use of error correction. In this work,
we show that these bit errors can be tolerated by BNNs to an outstanding level,
based on examples of image recognition tasks (MNIST, CIFAR-10 and ImageNet):
bit error rates of ST-MRAM up to 0.1% have little impact on recognition
accuracy. The requirements for ST-MRAM are therefore considerably relaxed for
BNNs with regards to traditional applications. By consequence, we show that for
BNNs, ST-MRAMs can be programmed with weak (low-energy) programming conditions,
without error correcting codes. We show that this result can allow the use of
low energy and low area ST-MRAM cells, and show that the energy savings at the
system level can reach a factor two.

###Band-pass Magnetic Tunnel Junction based Magnetoresistive Random Access Memory|Abhishek Sharma,Ashwin Tulapurkar,Bhaskaran Muralidharan###

Band-pass Magnetic Tunnel Junction based Magnetoresistive Random Access Memory. We propose spin transfer torque--magnetoresistive random access memory
(STT-MRAM) based on magneto-resistance and spin transfer torque physics of
band-pass spin filtering. Utilizing the electronic analogs of optical phenomena
such as anti-reflection coating and resonance for spintronic devices, we
present the design of an STT-MRAM device with improved features when compared
with a traditional trilayer device. The device consists of a superlattice
heterostructure terminated with the anti-reflective regions sandwiched between
the fixed and free ferromagnetic layers. Employing the Green's function spin
transport formalism coupled self-consistently with the stochastic
Landau-Lifshitz-Gilbert-Slonczewski equation, we present the design of an
STT-MRAM based on the band-pass filtering having an ultra-high TMR (3.5*10e4)
and large spin current. We demonstrate that the STT-MRAM design having
band-pass spin filtering are nearly 1100% more energy efficient than
traditional trilayer magnetic tunnel junction (MTJ) based STT-MRAM. We also
present detailed probabilistic switching and energy analysis for a trilayer MTJ
and band-pass filtering based STT-MRAM. Our predictions serve as a template to
consider the heterostructures for next-generation spintronic device
applications.

###Low-temperature monoclinic layer stacking in atomically thin CrI$_3$ crystals|Nicolas Ubrig,Zhe Wang,Jérémie Teyssier,Takashi Taniguchi,Kenji Watanabe,Enrico Giannini,Alberto F. Morpurgo,Marco Gibertini###

Low-temperature monoclinic layer stacking in atomically thin CrI$_3$ crystals. Chromium triiodide, CrI$_3$, is emerging as a promising magnetic
two-dimensional semiconductor where spins are ferromagnetically aligned within
a single layer. Potential applications in spintronics arise from an
antiferromagnetic ordering between adjacent layers that gives rise to spin
filtering and a large magnetoresistance in tunnelling devices. This key feature
appears only in thin multilayers and it is not inherited from bulk crystals,
where instead neighbouring layers share the same ferromagnetic spin
orientation. This discrepancy between bulk and thin samples is unexpected, as
magnetic ordering between layers arises from exchange interactions that are
local in nature and should not depend strongly on thickness. Here we solve this
controversy and show through polarization resolved Raman spectroscopy that thin
multilayers do not undergo a structural phase transition typical of bulk
crystals. As a consequence, a different stacking pattern is present in thin and
bulk samples at the temperatures at which magnetism sets in and, according to
previous first-principles simulations, this results in a different interlayer
magnetic ordering. Our experimental findings provide evidence for the strong
interplay between stacking order and magnetism in CrI$_3$, opening interesting
perspectives to design the magnetic state of van der Waals multilayers.

###Large surface conductance and two-dimensional superconductivity in microstructured crystalline topological insulators|Yangmu Li,Jie Wu,Fernando Camino,G. D. Gu,Ivan Božović,John M. Tranquada###

Large surface conductance and two-dimensional superconductivity in microstructured crystalline topological insulators. Controllable geometric manipulation via micromachining techniques provides a
promising tool for enhancing useful topological electrical responses relevant
to future applications such as quantum information science. Here we present
microdevices fabricated with focused ion beam from indium-doped topological
insulator Pb1-xSnxTe. With device thickness on the order of 1 {\mu}m and an
extremely large bulk resistivity, we achieve an unprecedented enhancement of
the surface contribution to about 30% of the total conductance near room
temperature. The surface contribution increases as the temperature is reduced,
becoming dominant below approximately 180 K, compared to 30 K in mm-thickness
crystals. In addition to the enhanced surface contribution to normal-state
transport, we observe the emergence of a two-dimensional superconductivity
below 6 K. Measurements of magnetoresistivity at high magnetic fields reveal a
weak antilocalization behavior in the normal-state magnetoconductance at low
temperature and a variation in the power-law dependence of resistivity on
temperature with field. These results demonstrate that interesting electrical
response relevant to practical applications can be achieved by suitable
engineering of single crystals.

###Colossal magnetoresistance in the insulating ferromagnetic double perovskites Tl$_2$NiMnO$_6$: A neutron diffraction study|Lei Ding,Dmitry D. Khalyavin,Pascal Manuel,Joseph Blake,Fabio Orlandi,Wei Yi,Alexei A. Belik###

Colossal magnetoresistance in the insulating ferromagnetic double perovskites Tl$_2$NiMnO$_6$: A neutron diffraction study. In the family of double perovskites, colossal magnetoresistance (CMR) has
been so far observed only in half-metallic ferrimagnets such as the known case
Sr$_2$FeMoO$_6$ where it has been assigned to the tunneling MR at grain
boundaries due to the half-metallic nature. Here we report a new
material-Tl$_2$NiMnO$_6$, a relatively ordered double perovskite stablized by
the high pressure and high temperature synthesis-showing CMR in the vicinity of
its Curie temperature. We explain the origin of such effect with neutron
diffraction experiment and electronic structure calculations that reveal the
material is a ferromagnetic insulator. Hence the ordered Tl$_2$NiMnO$_6$ (~70%
of Ni$^{2+}$/Mn$^{4+}$ cation ordering) represents the first realization of a
ferromagnetic insulating double perovskite, showing CMR. The study of the
relationship between structure and magnetic properties allows us to clarify the
nature of spin glass behaviour in the disordered Tl$_2$NiMnO$_6$ (~31% of
cation ordering), which is related to the clustering of antisite defects and
associated with the short-range spin correlations. Our results highlight the
key role of the cation ordering in establishing the long range magnetic ground
state and lay out new avenues to exploit advanced magnetic materials in double
perovskites.

###A Low Temperature Functioning CoFeB/MgO Based Perpendicular Magnetic Tunnel Junction for Cryogenic Nonvolatile Random Access Memory|Lili Lang,Yujie Jiang,Fei Lu,Cailu Wang,Yizhang Chen,Andrew D. Kent,Li Ye###

A Low Temperature Functioning CoFeB/MgO Based Perpendicular Magnetic Tunnel Junction for Cryogenic Nonvolatile Random Access Memory. We investigated the low temperature performance of CoFeB/MgO based
perpendicular magnetic tunnel junctions (pMTJs) by characterizing their
quasi-static switching voltage, high speed pulse write error rate and endurance
down to 9 K. pMTJ devices exhibited high magnetoresistance (>120%) and reliable
(error rate<10-4) bi-directional switching with 2 to 200 ns voltage pulses. The
endurance of the devices at 9 K surpassed that at 300 K by three orders of
magnitude under the same write conditions, functioning for more than 10^12
cycles with 10 ns write pulses. The critical switching voltage at 9 K was
observed to increase by 33% to 93%, depending on pulse duration, compared to
that at 350 K. Ferromagnetic resonance and magnetization measurements on
blanket pMTJ film stacks suggest that the increased switching voltage is
associated with an increase in effective magnetic anisotropy and magnetization
of free layer with decreasing temperature. Our work demonstrates that CoFeB/MgO
based pMTJs have great potential to enable cryogenic MRAM and that their low
temperature magnetization and effective magnetic anisotropy can be further
optimized to lower operating power and improve endurance.

###Site dilution and charge disorder effect on physical properties in SrRu$_{1-x}$Ga$_x$O$_3$|Renu Gupta,Imtiaz Noor Bhatti,A K Pramanik###

Site dilution and charge disorder effect on physical properties in SrRu$_{1-x}$Ga$_x$O$_3$. Here, we report an evolution of structural, magnetic and transport behavior
in doped SrRu$_{1-x}$Ga$_x$O$_3$ ($x$ $\le$ 0.2). The nonmagnetic dopant
Ga$^{3+}$ (3$d^{10}$) not only acts for magnetic site dilution in SrRuO$_3$ but
also it modifies the Ru charge state and electronic density. Our studies show
that Ga$^{3+}$ substitution does not affect the original
orthorhombic-\textit{Pbnm} structure of SrRuO$_3$ which is due to its matching
ionic radii with Ru$^{4+}$. However, Ga$^{3+}$ has a substantial effect on the
magnetic behavior of SrRuO$_3$ where it decreases both magnetic moment as well
as magnetic transition temperature $T_c$. Further, this dilution induces
Griffiths phase behavior across $T_c$ and cluster-glass behavior at low
temperature with higher concentration of doping. The magnetic critical exponent
$\beta$ increases with $x$ due to this site dilution effect. The Ga$^{3+}$
induces an insulating state in SrRuO$_3$ with $x$ $>$ 0.05. The charge
transport in paramagnetic as well as in insulating state of samples can be well
described with Mott's modified variable-range-hopping model. The metallic
charge transport just below $T_c$ in SrRuO$_3$ obeys Fermi liquid behavior
which, however breaks down at low temperature. We further find a correlation
between field dependent magnetoresistance and magnetization through power-law
behavior over the series.

###Energy-efficient ultrafast SOT-MRAMs based on low-resistivity spin Hall metal Au0.25Pt0.75|Lijun Zhu,Lujun Zhu,Shengjie Shi,D. C. Ralph,R. A. Buhrman###

Energy-efficient ultrafast SOT-MRAMs based on low-resistivity spin Hall metal Au0.25Pt0.75. Many key electronic technologies (e.g., large-scale computing, machine
learning, and superconducting electronics) require new memories that are fast,
reliable, energy-efficient, and of low-impedance at the same time, which has
remained a challenge. Non-volatile magnetoresistive random access memories
(MRAMs) driven by spin-orbit torques (SOTs) have promise to be faster and more
energy-efficient than conventional semiconductor and spin-transfer-torque
magnetic memories. This work reports that the spin Hall effect of
low-resistivity Au0.25Pt0.75 thin films enables ultrafast antidamping-torque
switching of SOT-MRAM devices for current pulse widths as short as 200 ps. If
combined with industrial-quality lithography and already-demonstrated
interfacial engineering, our results show that an optimized MRAM cell based on
Au0.25Pt0.75 can have energy-efficient, ultrafast, and reliable switching, e.g.
a write energy of < 1 fJ (< 50 fJ) for write error rate of 50% (<1e-5) for 1 ns
pulses. The antidamping torque switching of the Au0.25Pt0.75 devices is 10
times faster than expected from a rigid macrospin model, most likely because of
the fast micromagnetics due to the enhanced non-uniformity within the free
layer. These results demonstrate the feasibility of Au0.25Pt0.75-based
SOT-MRAMs as a candidate for ultrafast, reliable, energy-efficient,
low-impedance, and unlimited-endurance memory.

###Multi-frequency Shubnikov-de Haas oscillations in topological semimetal Pt$_2$HgSe$_3$|Diego Mauro,Hugo Henck,Marco Gibertini,Michele Filippone,Enrico Giannini,Ignacio Gutierrez-Lezama,Alberto F. Morpurgo###

Multi-frequency Shubnikov-de Haas oscillations in topological semimetal Pt$_2$HgSe$_3$. Monolayer jacutingaite (Pt$_2$HgSe$_3$) has been recently identified as a
candidate quantum spin Hall system with a 0.5 eV band gap, but no transport
measurements have been performed so far on this material, neither in monolayer
nor in the bulk. By using a dedicated high-pressure technique, we grow crystals
enabling the exfoliation of 50-100 nm thick layers and the realization of
devices for controlled transport experiments. Magnetoresistance measurements
indicate that jacutingaite is a semimetal, exhibiting Shubnikov-de Haas (SdH)
resistance oscillations with a multi-frequency spectrum. We adapt the
Lifshitz-Kosevich formula to analyze quantitatively the SdH resistance
oscillations in the presence of multiple frequencies, and find that the
experimental observations are overall reproduced well by band structure
ab-initio calculations for bulk jacutingaite. Together with the relatively high
electron mobility extracted from the experiments ($\approx 2000$ cm$^2$/Vs,
comparable to what is observed in WTe$_2$ crystals of the same thickness), our
results indicate that monolayer jacutingaite should provide an excellent
platform to investigate transport in 2D quantum spin Hall systems.

###Observation of spin-momentum locked surface states in amorphous Bi$_{2}$Se$_{3}$|Paul Corbae,Samuel Ciocys,Daniel Varjas,Ellis Kennedy,Steven Zeltmann,Manel Molina-Ruiz,Sinead Griffin,Chris Jozwiak,Zhanghui Chen,Lin-Wang Wang,Andrew M. Minor,Mary Scott,Adolfo G. Grushin,Alessandra Lanzara,Frances Hellman###

Observation of spin-momentum locked surface states in amorphous Bi$_{2}$Se$_{3}$. Crystalline symmetries have played a central role in the identification of
topological materials. The use of symmetry indicators and band representations
have enabled a classification scheme for crystalline topological materials,
leading to large scale topological materials discovery. In this work we address
whether amorphous topological materials, which lie beyond this classification
due to the lack of long-range structural order, exist in the solid state. We
study amorphous Bi$_2$Se$_3$ thin films, which show a metallic behavior and an
increased bulk resistance. The observed low field magnetoresistance due to weak
antilocalization demonstrates a significant number of two dimensional surface
conduction channels. Our angle-resolved photoemission spectroscopy data is
consistent with a dispersive two-dimensional surface state that crosses the
bulk gap. Spin resolved photoemission spectroscopy shows this state has an
anti-symmetric spin texture resembling that of the surface state of crystalline
Bi$_2$Se$_3$. These experimental results are consistent with theoretical
photoemission spectra obtained with an amorphous tight-binding model that
utilizes a realistic amorphous structure. This discovery of amorphous materials
with topological properties uncovers an overlooked subset of topological matter
outside the current classification scheme, enabling a new route to discover
materials that can enhance the development of scalable topological devices.

###Spin memory of the topological material under strong disorder|Inna Korzhovska,Haiming Deng,Lukas Zhao,Zhiyi Chen,Marcin Konczykowski,Shihua Zhao,Simone Raoux,Lia Krusin-Elbaum###

Spin memory of the topological material under strong disorder. Robustness to disorder - the defining property of any topological state - has
been mostly tested in low-disorder translationally-invariant materials systems
where the protecting underlying symmetry, such as time reversal, is preserved.
The ultimate disorder limits to topological protection are still unknown,
however, a number of theories predict that even in the amorphous state a
quantized conductance might yet reemerge. Here we report a directly detected
robust spin response in structurally disordered thin films of the topological
material Sb2Te3 free of extrinsic magnetic dopants, which we controllably tune
from a strong (amorphous) to a weak crystalline) disorder state. The magnetic
signal onsets at a surprisingly high temperature (~ 200 K) and eventually
ceases within the crystalline state. We demonstrate that in a strongly
disordered state disorder-induced spin correlations dominate the transport of
charge - they engender a spin memory phenomenon, generated by the
nonequilibrium charge currents controlled by localized spins. The negative
magnetoresistance (MR) in the extensive spin-memory phase space is isotropic.
Within the crystalline state, it transitions into a positive MR corresponding
to the weak antilocalization (WAL) quantum interference effect, with a 2D
scaling characteristic of the topological state. Our findings demonstrate that
these nonequilibrium currents set a disorder threshold to the topological
state; they lay out a path to tunable spin-dependent charge transport and point
to new possibilities of spin control by disorder engineering of topological
materials

###Role of spin mixing conductance in determining thermal spin pumping near the ferromagnetic phase transition in EuO_{1-x} and La2NiMnO6|Kingshuk Mallick,Aditya A. Wagh,Adrian Ionescu,Crispin H. W. Barnes,P. S. Anil Kumar###

Role of spin mixing conductance in determining thermal spin pumping near the ferromagnetic phase transition in EuO_{1-x} and La2NiMnO6. We present a comprehensive study of the temperature (T) dependence of the
longitudinal spin Seebeck effect (LSSE) in Pt/EuO_{1-x} and Pt/La2NiMnO6 (LNMO)
hybrid structures across their Curie temperatures (Tc). Both systems host
ferromagnetic interaction below Tc, hence present optimal conditions for
testing magnon spin current based theories against ferrimagnetic YIG. Notably,
we observe an anomalous Nernst effect (ANE) generated voltage in bare
EuO_{1-x}, however, we find LSSE predominates the thermal signals in the
bilayers with Pt. The T-dependence of the LSSE in small T-range near Tc could
be fitted to a power law of the form (Tc-T)^P. The derived critical exponent,
P, was verified for different methods of LSSE representation and sample
crystallinity. The results are explained based on the magnon-driven thermal
spin pumping mechanism that relate the T-dependence of LSSE to the spin mixing
conductance (Gmix) at the heavy metal/ferromagnet (HM/FM) interface, which in
turn is known to vary in accordance with the square of the spontaneous
magnetization (Ms). Additionally, the T-dependence of the real part of Gmix
derived from spin Hall magnetoresistance measurements at different temperatures
for the Pt/LNMO structure, further establish the interdependence.

###Magnetic field effects in the near-field radiative heat transfer between planar structures|Edwin Moncada-Villa,Juan Carlos Cuevas###

Magnetic field effects in the near-field radiative heat transfer between planar structures. One of the main challenges in the field of thermal radiation is to actively
control the near-field radiative heat transfer (NFRHT) between closely spaced
bodies. In this context, the use of an external magnetic field has emerged as a
very attractive possibility and a plethora of physical phenomena have been put
forward in the last few years. Here, we predict some additional
magnetic-field-induced phenomena that can take place in the context of NFRHT
between planar layered structures containing magneto-optical (MO) materials
(mainly doped semiconductors like InSb). In particular, we predict the
possibility of increasing the NFRHT upon applying an external magnetic field in
an asymmetric structure consisting of two infinite plates made of InSb and Au.
We also study the impact of a magnetic field in the NFRHT between structures
containing MO thin films and show that the effect is more drastic than in their
bulk counterparts. Finally, we systematically investigate the anisotropic
thermal magnetoresistance, i.e., the dependence of the radiative heat
conductance on the orientation of an external magnetic field, in the case of
two infinite plates made of InSb and show that one can strongly modulate the
NFRHT by simply changing the orientation of the magnetic field. All the
phenomena predicted in this work can be experimentally tested with existent
technology and provide a new insight into the topic of active control of NFRHT.

###Magnetic field-induced type-II Weylsemimetallic state in geometrically frustrated Shastry-Sutherland lattice GdB4|Wonhyuk Shon,Dong-Choon Ryu,Kyoo Kim,B. I. Min,Bongjae Kim,Boyoun Kang,B. K. Cho,Heon-Jung Kim,Jong-Soo Rhyee###

Magnetic field-induced type-II Weylsemimetallic state in geometrically frustrated Shastry-Sutherland lattice GdB4. Weyl semimetal is a topologically non-trivial phase of matter with pairs of
Weyl nodes in the k-space, which act as monopole and anti-monopole pairs of
Berry curvature. Two hallmarks of the Weyl metallic state are the topological
surface state called the Fermi arc and the chiral anomaly. It is known that the
chiral anomaly yields anomalous magneto-transport phenomena. In this study, we
report the emergence of the type-II Weyl semimetallic state in the
geometrically frustrated non-collinear antiferromagnetic Shastry-Sutherland
lattice (SSL) GdB4 crystal. When we apply magnetic fields perpendicular to the
noncollinear moments in SSL plane, Weyl nodes are created above and below the
Fermi energy along the M-A line (tau-band) because the spin tilting breaks the
time-reversal symmetry and lifts band degeneracy while preserving C4z or C2z
symmetry. The unique electronic structure of GdB4 under magnetic fields applied
perpendicular to the SSL gives rise to a non-trivial Berry phase, detected in
de Haas-van Alphen experiments and chiral-anomaly-induced negative
magnetoresistance. The emergence of the magnetic field-induced Weyl state in
SSL presents a new guiding principle to develop novel types of Weyl semimetals
in frustrated spin systems.

###Magnetotransport properties of the layered CaAl2Si2 semimetal hosting multiple nontrivial topological states|Hao Su,Xianbiao Shi,Wei Xia,Hongyuan Wang,Xuesong Hanli,Zhenhai Yu,Xia Wang,Zhiqiang Zou,Na Yu,Weiwei Zhao,Gang Xu,Yanfeng Guo###

Magnetotransport properties of the layered CaAl2Si2 semimetal hosting multiple nontrivial topological states. Combination of different nontrivial topological states in a single material
is capable of realizing multiple functionalities and exotic physics, but such
materials are still very sparse. We report herein the results of
magnetotransport measurements and ab initio calculations on single crystalline
CaAl2Si2 semimetal. The transport properties could be well understood in
connection with the two-band model, agreeing well with the theoretical
calculations indicating four main sheets of Fermi surface consisting of three
hole pockets centered at the {\Gamma} point and one electron pocket centered at
the M point in the Brillouin zone. The single fundamental frequency imposed in
the quantum oscillations of magnetoresistance corresponds to the electron Fermi
pocket. Without spin-orbit coupling (SOC), the ab initio calculations suggest
CaAl2Si2 as a system hosting a topological nodal-line setting around the
{\Gamma} point in the Brillouin zone close to the Fermi level. Once including
the SOC, the fragile nodal-line will be gapped and a pair of Dirac points
emerge along the high symmetric {\Gamma}-A direction, which is about 1.22 eV
below the Fermi level. The SOC can also induce a topological insulator state
along the {\Gamma}-A direction with a gap of about 3 meV. The results
demonstrate CaAl2Si2 as an excellent platform for the study of novel
topological physics with multiple topological states.

###Iridium Enabled Field-free Spin-orbit Torque Switching of Perpendicular Magnetic Tunnel Junction Device|Yang Liu,Bing Zhou,Zhengkun Dai,Enbo Zhang,Jian-Gang Zhu###

Iridium Enabled Field-free Spin-orbit Torque Switching of Perpendicular Magnetic Tunnel Junction Device. Writing magnetic bits by spin-orbit torques (SOTs) arising from spin Hall
effect creates new possibilities for ultrafast and low-power magnetoresistive
random access memory (MRAM). For perpendicular MRAM, an extra in-plane field is
required to break the symmetry for the deterministic SOT writing of the
perpendicular storage layer. Although schemes have been demonstrated in
external-field-free SOT switching of a perpendicular layer, practically
integrating them with perpendicular MTJs still appears to be challenging. Here,
we present experimental demonstration of spin-orbit torques (SOTs) switching a
perpendicular magnetic tunnel junction (MTJ) device without applying an
external magnetic field. An Ir layer is used to serve dual-purpose of both
injecting the pure spin current via spin Hall effect and mediating an in-plane
exchange field to the perpendicular free layer of the MTJ. Robust field-free
SOT switching with pulsed write path current is demonstrated for various MTJ
sizes ranging from 50 nm to 500 nm. The effect of MTJ size and pulse width on
the critical switching current is studied. Combined micromagnetic simulations
are carried out to provide in-depth analysis of the switching dynamics as well
as the thermal effect on the switching.

###Cation spin and superexchange interaction in oxide materials below and above spin crossover under high pressure|Vladimir A. Gavrichkov,Semyon I. Polukeev,Sergey G. Ovchinnikov###

Cation spin and superexchange interaction in oxide materials below and above spin crossover under high pressure. We derived simple rules for the sign of superexchange interaction based on
the multielectron calculations of the superexchange interaction in the
transition metal oxides that are valid both below and above spin crossover
under high pressure. The superexchange interaction between two cations in d$^n$
configurations is given by a sum of individual contributions related to the
electron-hole virtual excitations to the different states of the d$^{n + 1}$
and d$^{n - 1}$ configurations. Using these rules, we have analyzed the sign of
the superexchange interaction of a number of oxides with magnetic cations in
electron configurations from d$^2$ till d$^8$: the iron, cobalt, chromium,
nickel, copper and manganese oxides with increasing pressure. The most
interesting result concerns the magnetic state of cobalt and nickel oxides CoO,
Ni$_2$O$_3$ and also La$_2$CoO$_4$, LaNiO$_3$ isostructural to well-known
high-T$_C$ and colossal magnetoresistance materials. These oxides have a spin
$\frac{1}{2}$ at the high pressure. Change of the interaction from
antiferromagnetic below spin crossover to ferromagnetic above spin crossover is
predicted for oxide materials with cations in d$^5$(FeBO$_3$) and d$^7$(CoO)
configurations, while for materials with the other d$^n$ configurations spin
crossover under high pressure does not change the sign of the superexchange
interaction.

###Magnetotransport of SrIrO3 films on (110) DyScO3|A. K. Jaiswal,A. G. Zaitsev,R. Singh,R. Schneider,D. Fuchs###

Magnetotransport of SrIrO3 films on (110) DyScO3. Epitaxial perovskite (110) oriented SrIrO3 (SIO) thin films were grown by
pulsed laser deposition on (110) oriented DyScO3 (DSO) substrates with various
film thickness t (2 nm < t < 50 nm). All the films were produced with
stoichiometric composition, orthorhombic phase, and with high crystallinity.
The nearly perfect in-plane lattice matching of DSO with respect to SIO and
same symmetry result in a full epitaxial inplane alignment, i.e., the c-axis of
DSO and SIO are parallel to each other with only slightly enlarged d110
out-of-plane lattice spacing (+0.38%) due to the small in-plane compressive
strain caused by the DSO substrate. Measurements of the magnetoresistance MR
were carried out for current flow along the [001] and [1-10] direction of SIO
and magnetic field perpendicular to the film plane. MR appears to be distinctly
different for both directions. The anisotropy MR001/MR1-10 > 1 increases with
decreasing T and is especially pronounced for the thinnest films, which
likewise display a hysteretic field dependence below T* ~ 3 K. The coercive
field Hc amounts to 2-5 T. Both, T* and Hc are very similar to the magnetic
ordering temperature and coercivity of DSO which strongly suggests
substrate-induced mechanism as a reason for the anisotropic magnetotransport in
the SIO films.

###Valley polarization and valleyresistance in monolayer transition metal dichalcogenides superlattice|Hui-Ying Mu,Yi-Tong Yao,Jie-Ru Li,Guo-Cai Liu,Chao He,Ying-Jie Sun,Guang Yang,Xing-Tao An,Yong-Zhe Zhang,Jian-Jun Liu###

Valley polarization and valleyresistance in monolayer transition metal dichalcogenides superlattice. Manipulating the valley degree of freedom to encode information for potential
valleytronic devices has ignited a new direction in solid-state physics. A
significant, fundamental challenge in the field of valleytronics is how to
generate and regulate valley-polarized currents by practical ways. Here, we
discover a new mechanism of producing valley polarization in a monolayer
transition metal dichalcogenides superlattice, in which valley-resolved gaps
are formed at the supercell Brillouin zone boundaries and centers due to the
intervalley scattering. When the energy of the incident electron is in the
gaps, the available states are valley polarized, thus providing a
valley-polarized current from the superlattice. We show that the direction and
strength of the valley polarization may further be tuned by varying the
potential applied the superlattice. The transmission can have a net valley
polarization of 55% for a 4-period heterojunction. Moreover, such two valley
filters in series may function as an electrostatically controlled giant
valleyresistance device, representing a zero magnetic field counterpart to the
familiar giant magnetoresistance device.

###Machine learning analysis of tunnel magnetoresistance of magnetic tunnel junctions with disordered MgAl2O4|Shenghong Ju,Yoshio Miura,Kaoru Yamamoto,Keisuke Masuda,Ken-ichi Uchida,Junichiro Shiomi###

Machine learning analysis of tunnel magnetoresistance of magnetic tunnel junctions with disordered MgAl2O4. Through Bayesian optimization and the least absolute shrinkage and selection
operator (LASSO) technique combined with first-principles calculations, we
investigated the tunnel magnetoresistance (TMR) effect of
Fe/disordered-MgAl2O4(MAO)/Fe(001) magnetic tunnel junctions (MTJs) to
determine structures of disordered-MAO that give large TMR ratios. The optimal
structure with the largest TMR ratio was obtained by Bayesian optimization with
1728 structural candidates, where the convergence was reached within 300
structure calculations. Characterization of the obtained structures suggested
that the in-plane distance between two Al atoms plays an important role in
determining the TMR ratio. Since the Al-Al distance of disordered MAO
significantly affects the imaginary part of complex band structures, the
majority-spin conductance of the {\Delta}1 state in Fe/disordered-MAO/Fe MTJs
increases with increasing in-plane Al-Al distance, leading to larger TMR
ratios. Furthermore, we found that the TMR ratio tended to be large when the
ratio of the number of Al, Mg, and vacancies in the [001] plane was 2:1:1,
indicating that the control of Al atomic positions is essential to enhancing
the TMR ratio in MTJs with disordered MAO. The present work reveals the
effectiveness and advantage of material informatics combined with
first-principles transport calculations in designing high-performance
spintronic devices based on MTJs.

###Nonsaturating magnetoresistance, anomalous Hall effect, and magnetic quantum oscillations in ferromagnetic semimetal PrAlSi|Meng Lyu,Junsen Xiang,Zhenyu Mi,Hengcan Zhao,Zhen Wang,Enke Liu,Genfu Chen,Zhian Ren,Gang Li,Peijie Sun###

Nonsaturating magnetoresistance, anomalous Hall effect, and magnetic quantum oscillations in ferromagnetic semimetal PrAlSi. We report a comprehensive investigation of the structural, magnetic,
transport and thermodynamic properties of a single crystal PrAlSi, in
comparison to its nonmagnetic analogue LaAlSi. PrAlSi exhibits a ferromagnetic
transition at $T_C$ = 17.8 K which, however, is followed by two weak phase
transitions at lower temperatures. Based on the combined dc and ac magnetic
susceptibility measurements, we propose the two reentrant magnetic phases below
$T_C$ to be spin glasses or ferromagnetic cluster glasses. When the magnetic
glassy states are suppressed by small field, several remarkable features
appear. These include a linear, nonsaturating magnetoresistance as a function
of field that is reminiscent of a topological or charge-compensated semimetal,
and a large anomalous Hall conductivity amounting to $\sim$2000 $\Omega
^{-1}$cm$^{-1}$. Specific-heat measurements indicate a non-Kramers doublet
ground state and a relatively low crystal electric field splitting of the
Pr$^{3+}$ multiplets of less than 100 K. Shubnikov-de Hass oscillations are
absent in LaAlSi, whereas they are clearly observed below about 25 K in PrAlSi,
with an unusual temperature dependence of the dominating oscillation frequency
$F$. It increases from $F$ = 18 T at 25 K to $F$ = 33 T at 2 K, hinting at an
emerging Fermi pocket upon cooling into the ordered phase. These results
suggest that PrAlSi is a new system where a small Fermi pocket of likely
relativistic fermions is strongly coupled to magnetism. Whether hybridization
between $f$ and conduction band is also involved remains an intriguing open
problem.

###Tailoring magnetic order via atomically stacking 3d/5d electrons|Ke Huang,Liang Wu,Maoyu Wang,Nyayabanta Swain,M. Motapothula,Yongzheng Luo,Kun Han,Mingfeng Chen,Chen Ye,Allen Jian Yang,Huan Xu,Dong-chen Qi,Alpha T. N'Diaye,Christos Panagopoulos,Daniel Primetzhofer,Lei Shen,Pinaki Sengupta,Jing Ma,Zhenxing Feng,Ce-Wen Nan,X. Renshaw Wang###

Tailoring magnetic order via atomically stacking 3d/5d electrons. The ability to tune magnetic orders, such as magnetic anisotropy and
topological spin texture, is desired in order to achieve high-performance
spintronic devices. A recent strategy has been to employ interfacial
engineering techniques, such as the introduction of spin-correlated interfacial
coupling, to tailor magnetic orders and achieve novel magnetic properties. We
chose a unique polar-nonpolar LaMnO3/SrIrO3 superlattice because Mn (3d)/Ir
(5d) oxides exhibit rich magnetic behaviors and strong spin-orbit coupling
through the entanglement of their 3d and 5d electrons. Through magnetization
and magnetotransport measurements, we found that the magnetic order is
interface-dominated as the superlattice period is decreased. We were able to
then effectively modify the magnetization, tilt of the ferromagnetic easy axis,
and symmetry transition of the anisotropic magnetoresistance of the
LaMnO3/SrIrO3 superlattice by introducing additional Mn (3d) and Ir (5d)
interfaces. Further investigations using in-depth first-principles calculations
and numerical simulations revealed that these magnetic behaviors could be
understood by the 3d/5d electron correlation and Rashba spin-orbit coupling.
The results reported here demonstrate a new route to synchronously engineer
magnetic properties through the atomic stacking of different electrons,
contributing to future applications.

###Magnetism at iridate/manganite interface: influence of strong spin-orbit interaction|G. A. Ovsyannikov,T. A Shaikhulov,V. V. Demidov,K. L. Stankevich,Yu. Khaydukov,N. V. Andreev###

Magnetism at iridate/manganite interface: influence of strong spin-orbit interaction. The complex investigation of dc transport and magnetic properties of the
epitaxial manganite/iridate heterostructure was carried out by mean of X-ray
(XRD), dc resistance measurements, ferromagnetic resonance (FMR) and polarized
neutron reflectivity (PNR). Epitaxial growth of the heterostructure proceeded
according to the cube-to-cube mechanism with the small lattice turn. The dc
measurement indicates the presence of a conduction channel at the
iridate/manganite interface due to the charge leakage from iridate that makes
it hole doped, while the manganite side becomes electron doped. This is
confirmed by the first principles calculations based on density functional
theory [Sayantika Bhowal, and Sashi Satpathy AIP Conference Proceedings 2005,
020007 (2018)] that show the charge transfer at the interface from the
half-filled spin-orbit entangled Jeff = 1/2 state of the iridate to the empty e
states of manganite. The neutron scattering data show the turn of magnetization
vector of the heterostructure (mainly manganite) on 26 degree closer to the
external field with reducing temperature down to 10K. Additional ferromagnetic
state appearing at T<100K indicate on emergence of ferromagnetism in the thin
(10 nm) paramagnetic SIO film close to the interface. We have measured the dc
voltage aroused on the SIO film caused by spin pumping and the anisotropic
magnetoresistance in the heterostructure.

###Electronic and magnetic properties of 3$d$ transition-metal adatoms on Mn/W(110)|Mara Gutzeit,Soumyajyoti Haldar,Stefan Heinze###

Electronic and magnetic properties of 3$d$ transition-metal adatoms on Mn/W(110). Using density functional theory, we investigate the electronic and magnetic
properties of $3d$ transition-metal adatoms adsorbed on a monolayer of Mn on
W(110). Mn/W(110) has a noncollinear cycloidal spin-spiral ground state with an
angle of 173$^\circ$ between magnetic moments of adjacent Mn rows. It allows to
rotate the spin orientation of an adsorbed magnetic adatom quasi-continuously.
Therefore, this surface is ideally suited for manipulating the spin direction
of individual atoms and exploring their magnetic properties using scanning
tunneling microscopy (STM). The adsorbed V and Cr transition-metal adatoms
couple antiferromagnetically to the nearest neighbor Mn atom of Mn monolayer
while Mn, Fe, Co, and Ni couple ferromagnetically. The magnetic moments of the
$3d$ adatoms are large and show a Hund's rule type of trend with a peak in the
middle of the series. We find large spin splitting of the $3d$ transition-metal
adatoms, large spin polarization of the local vacuum density of states up to
73\% at the Fermi energy, and significant tunneling anisotropic
magnetoresistance enhancement up to 27\%. We conclude that such large values
stem from the strong hybridization between the adatoms and the Mn atoms of the
monolayer. Furthermore, identification of spin orientations of the adatom using
spin-polarized STM is only possible for Co and V adatoms.

###Tailoring Magnetic Anisotropy in Cr$_2$Ge$_2$Te$_6$ by Electrostatic Gating|Ivan. A. Verzhbitskiy,Hidekazu Kurebayashi,Haixia Cheng,Jun Zhou,Safe Khan,Yuan Ping Feng,Goki Eda###

Tailoring Magnetic Anisotropy in Cr$_2$Ge$_2$Te$_6$ by Electrostatic Gating. Electrical control of magnetism of a ferromagnetic semiconductor offers
exciting prospects for future spintronic devices for processing and storing
information. Here, we report observation of electrically modulated magnetic
phase transition and magnetic anisotropy in thin crystal of Cr$_2$Ge$_2$Te$_6$
(CGT), a layered ferromagnetic semiconductor. We show that heavily
electron-doped ($\sim$ $10^{14}$ cm$^{-2}$) CGT in an electric double-layer
transistor device is found to exhibit hysteresis in magnetoresistance (MR), a
clear signature of ferromagnetism, at temperatures up to above 200 K, which is
significantly higher than the known Curie temperature of 61 K for an undoped
material. Additionally, angle-dependent MR measurements reveal that the
magnetic easy axis of this new ground state lies within the layer plane in
stark contrast to the case of undoped CGT, whose easy axis points in the
out-of-plane direction. We propose that significant doping promotes
double-exchange mechanism mediated by free carriers, prevailing over the
superexchange mechanism in the insulating state. Our findings highlight that
electrostatic gating of this class of materials allows not only charge flow
switching but also magnetic phase switching, evidencing their potential for
spintronics applications.

###Topological effects of three-dimensional porous graphene on Dirac quasiparticles|Takuya Okamoto,Yoshikazu Ito,Naoka Nagamura,Keishi Akada,Takeshi Fujita,Yukio Kawano###

Topological effects of three-dimensional porous graphene on Dirac quasiparticles. This paper reports on the topological effects of three-dimensional (3D)
porous graphene with tunable pore sizes and a preserved 2D graphene system of
Dirac quasiparticles on its electrical properties. This 3D architecture is
characterized by the intrinsic curvature of smoothly interconcnected graphene
sheets without edges, the structures and properties of which can be controlled
with its pore sizes. The impact of pore size on the electrical transport
properties was investigated through magnetoresistance measurements. We observed
that 3D graphene with small pores exhibits transitioning to weak localization
with decreasing temperature. The comparison with the theory based on the
quantum correction clarified that an increase in the intrinsic curvature
significantly induces the intervalley scattering event, which breaks the
chirality. This increase in the intervalley scattering rate originates from the
unique topological effects of 3D graphene, i.e., the topological defects
required to form the high curvature and the resulting chirality mixing. We also
discuss the scattering processes due to microscopic chemical bonding states as
found by high spatial-resolved X-ray photoemission spectral imaging, to support
the validity of our finding.

###Resistivity minimum in diluted metallic magnets|Zhentao Wang,Cristian D. Batista###

Resistivity minimum in diluted metallic magnets. Resistivity minima are commonly seen in itinerant magnets and they are often
attributed to the Kondo effect. However, recent experiments are revealing an
increasing number of materials showing resistivity minima in the absence of
indications of Kondo singlet formation. In a previous work [Z. Wang, K. Barros,
G.-W. Chern, D. L. Maslov, and C. D. Batista, Phys. Rev. Lett. 117, 206601
(2016)], we demonstrated that the Ruderman-Kittel-Kasuya-Yosida (RKKY)
interaction can produce a classical spin liquid state at finite temperature,
whose resistivity increases with decreasing temperature. The classical spin
liquid exists over a relatively large temperature window because of the
frustrated nature of the RKKY interaction produced by a 2D electron gas. In
this work, we investigate the robustness of the RKKY-induced resistivity upturn
against site dilution, which provides an alternative, and more robust, way of
stabilizing the classical spin liquid state down to T=0. By using series
expansions and stochastic Landau-Lifshitz dynamics simulation, we show that
site dilution competes with thermal fluctuations and further stabilizes the
resistivity upturn, which is accompanied by a negative magnetoresistivity due
to suppression of the electron-spin scattering.

###Giant electron-phonon coupling of the breathing plane oxygen phonons in the dynamic stripe phase of La$_{1.67}$Sr$_{0.33}$NiO$_4$|A. M. Merritt,A. D. Christianson,A. Banerjee,G. D. Gu,A. S. Mishchenko,D. Reznik###

Giant electron-phonon coupling of the breathing plane oxygen phonons in the dynamic stripe phase of La$_{1.67}$Sr$_{0.33}$NiO$_4$. Doped antiferromagnets host a vast array of physical properties and learning
how to control them is one of the biggest challenges of condensed matter
physics. La$_{1.7}$Sr$_{0.3}$NiO$_4$ (LSNO) is a classic example of such a
material. At low temperatures holes introduced via substitution of La by Sr
segregate into lines to form boundaries between magnetically ordered domains in
the form of stripes. The stripes become dynamic at high temperatures, but LSNO
remains insulating presumably because an interplay between magnetic
correlations and electron-phonon coupling localizes charge carriers. Magnetic
degrees of freedom have been extensively investigated in this system, but
phonons are almost completely unexplored. We searched for electron-phonon
anomalies in LSNO by inelastic neutron scattering. Giant renormalization of
plane Ni-O bond-stretching modes that modulate the volume around Ni appears on
entering the dynamic charge stripe phase. Other phonons are a lot less
sensitive to stripe melting. Dramatic overdamping of the breathing modes
indicates that dynamic stripe phase may host small polarons. We argue that this
feature sets electron-phonon coupling in nickelates apart from that in cuprates
where breathing phonons are not overdamped and point out remarkable
similarities with the colossal magnetoresistance (CMR) manganites.

###Ion-Irradiation-Induced Cobalt/Cobalt Oxide Heterostructures: Printing 3D Interfaces|Oğuz Yıldırım,Donovan Hilliard,Sri Sai Phani Kanth Arekapudi,Ciarán Fowley,Hamza Cansever,Leopold Koch,Lakshmi Ramasubramanian,Shengqiang Zhou,Roman Böttger,Jürgen Lindner,Jürgen Faßbender,Olav Hellwig,Alina M. Deac###

Ion-Irradiation-Induced Cobalt/Cobalt Oxide Heterostructures: Printing 3D Interfaces. Interfaces separating ferromagnetic (FM) layers from non-ferromagnetic layers
offer unique properties due to spin-orbit coupling and symmetry breaking,
yielding effects such as exchange bias, perpendicular magnetic anisotropy,
spin-pumping, spin-transfer torques, conversion between charge and spin
currents and vice-versa. These interfacial phenomena play crucial roles for
magnetic data storage and transfer applications, which require forming FM
nano-structures embedded in non-ferromagnetic matrices. Here, we investigate
the possiblity of creating such nano-structures by ion-irradiation. We study
the effect of lateral confinement on the ion-irradiation-induced reduction of
non-magnetic metal oxides (e.g., antiferro- or paramagnetic) to form
ferromagnetic metals. Our findings are later exploited to form 3-dimensional
magnetic interfaces between Co, CoO and Pt by spatially-selective irradiation
of CoO/Pt multilayers. We demonstrate that the mechanical displacement of the O
atoms plays a crucial role during the reduction from insulating,
non-ferromagnetic cobalt oxides to metallic cobalt. Metallic cobalt yields both
perpendicular magnetic anisotropy in the generated Co/Pt nano-structures, and,
at low temperatures, exchange bias at vertical interfaces between Co and CoO.
If pushed to the limit of ion-irradiation technology, this approach could, in
principle, enable the creation of densely-packed, atomic scale ferromagnetic
point-contact spin-torque oscillator (STO) networks, or conductive channels for
current-confined-path based current perpendicular-to-plane giant
magnetoresistance read-heads.

###Giant anisotropic magnetoresistance through a tilted molecular $π$-orbital|Dongzhe Li,Fabian Pauly,Alexander Smogunov###

Giant anisotropic magnetoresistance through a tilted molecular $π$-orbital. Anisotropic magnetoresistance (AMR), originating from spin-orbit coupling
(SOC), is the sensitivity of the electrical resistance in magnetic systems to
the direction of spin magnetization. Although this phenomenon has been
experimentally reported for several nanoscale junctions, a clear understanding
of the physical mechanism behind it is still elusive. Here we discuss a novel
concept based on orbital symmetry considerations to attain a significant AMR of
up to 95\% for a broad class of $\pi$-type molecular spin-valves. It is
illustrated at the benzene-dithiolate molecule connected between two monoatomic
nickel electrodes. We find that SOC opens, via spin-flip events at the
ferromagnet-molecule interface, a new conduction channel, which is fully
blocked by symmetry without SOC. Importantly, the interplay between main and
new transport channels turns out to depend strongly on the magnetization
direction in the nickel electrodes due to the tilting of molecular orbital.
Moreover, due to multi-band quantum interference, appearing at the band edge of
nickel electrodes, a transmission drop is observed just above the Fermi energy.
Altogether, these effects lead to a significant AMR around the Fermi level,
which even changes a sign. Our theoretical understanding, corroborated in terms
of \textit{ab initio} calculations and simplified analytical models, reveals
the general principles for an efficient realization of AMR in molecule-based
spintronic devices.

###Spin-orbit magnetic state readout in scaled ferromagnetic/heavy metal nanostructures|Van Tuong Pham,Inge Groen,Sasikanth Manipatruni,Won Young Choi,Dmitri E. Nikonov,Edurne Sagasta,Chia-Ching Lin,Tanay Gosavi,Alain Marty,Luis E. Hueso,Ian Young,Fèlix Casanova###

Spin-orbit magnetic state readout in scaled ferromagnetic/heavy metal nanostructures. Efficient detection of the magnetic state at nanoscale dimensions is an
important step to utilize spin logic devices for computing. Magnetoresistance
effects have been hitherto used in magnetic state detection, but they suffer
from energetically unfavorable scaling and do not generate an electromotive
force that can be used to drive a circuit element for logic device
applications. Here, we experimentally show that a favorable miniaturization law
is possible via the use of spin-Hall detection of the in-plane magnetic state
of a magnet. This scaling law allows us to obtain a giant signal by spin Hall
effect in CoFe/Pt nanostructures and quantify an effective spin-to-charge
conversion rate for the CoFe/Pt system. The spin-to-charge conversion can be
described as a current source with an internal resistance, i.e., it generates
an electromotive force that can be used to drive computing circuits. We predict
that the spin-orbit detection of magnetic states can reach high efficiency at
reduced dimensions, paving the way for scalable spin-orbit logic devices and
memories.

###Angle-dependent magnetoresistance and its implications for Lifshitz transition in W2As3|Jialu Wang,Haiyang Yang,Linchao Ding,Wei You,Chuanying Xi,Jie Cheng,Zhixiang Shi,Chao Cao,Yongkang Luo,Zengwei Zhu,Jianhui Dai,Mingliang Tian,Yuke Li###

Angle-dependent magnetoresistance and its implications for Lifshitz transition in W2As3. Lifshitz transition represents a sudden reconstruction of Fermi surface
structure, giving rise to anomalies in electronic properties of materials. Such
a transition does not necessarily rely on symmetry-breaking and thus is
topological. It holds a key to understand the origin of many exotic quantum
phenomena, for example the mechanism of extremely large magnetoresistance (MR)
in topological Dirac/Weyl semimetals. Here, we report studies of the
angle-dependent MR (ADMR) and the thermoelectric effect in W2As3 single
crystal. The compound shows a large unsaturated MR (of about 70000% at 4.2 K
and 53 T). The most striking finding is that the ADMR significantly deforms
from the horizontal dumbbell-like shape above 40 K to the vertical lotus-like
pattern below 30 K. The window of 30-40 K also corresponds substantial changes
in Hall effect, thermopower and Nernst coefficient, implying an abrupt change
of Fermi surface topology. Such a temperature-induced Lifshitz transition
results in a compensation of electron-hole transport and the large MR as well.
We thus suggest that the similar method can be applicable in detecting a
Fermi-surface change of a variety of quantum states when a direct Fermi-surface
measurement is not possible.

###Physical properties and thermal stability of Fe5GeTe2 single crystals|Andrew F. May,Craig A. Bridges,Michael A. McGuire###

Physical properties and thermal stability of Fe5GeTe2 single crystals. The magnetic and transport properties of Fe-deficient Fe5GeTe2 single
crystals (Fe5-xGeTe2 with x~0.3) were studied and the impact of thermal
processing was explored. Quenching crystals from the growth temperature has
been previously shown to produce a metastable state that undergoes a strongly
hysteretic first-order transition upon cooling below ~100K. The first-order
transition impacts the magnetic properties, yielding an enhancement in the
Curie temperature T_C from 270 to 310K. In the present work, T_HT ~550K has
been identified as the temperature above which metastable crystals are obtained
via quenching. Diffraction experiments reveal a structural change at this
temperature, and significant stacking disorder occurs when samples are slowly
cooled through this temperature range. The transport properties are
demonstrated to be similar regardless of the crystal's thermal history. The
scattering of charge carriers appears to be dominated by moments fluctuating on
the Fe(1) sublattice, which remain dynamic down to 100-120K. Maxima in the
magnetoresistance and anomalous Hall resistance are observed near 120K. The
Hall and Seebeck coefficients are also impacted by magnetic ordering on the
Fe(1) sublattice. The data suggest that both electrons and holes contribute to
conduction above 120K, but that electrons dominate at lower temperature when
all of the Fe sublattices are magnetically ordered. This study demonstrates a
strong coupling of the magnetism and transport properties in Fe5-xGeTe2 and
complements the previous results that demonstrated strong magnetoelastic
coupling as the Fe(1) moments order. The published version of this manuscript
is DOI:10.1103/PhysRevMaterials.3.104401 (2019)

###Interlayer exchange coupling through Ir-doped Cu spin Hall material|Hiroto Masuda,Takeshi Seki,Yong-Chang Lau,Takahide Kubota,Koki Takanashi###

Interlayer exchange coupling through Ir-doped Cu spin Hall material. Metallic superlattices where the magnetization vectors in the adjacent
ferromagnetic layers are antiferromagnetically coupled by the interlayer
exchange coupling through nonmagnetic spacer layers are systems available for
the systematic study on antiferromagnetic (AF) spintronics. As a candidate of
nonmagnetic spacer layer material exhibiting remarkable spin Hall effect, which
is essential to achieve spin-orbit torque switching, we selected the Ir-doped
Cu in this study. The AF-coupling for the Co / Cu$_{95}$Ir$_{5}$ / Co was
investigated, and was compared with those for the Co / Cu / Co and Co / Ir /
Co. The maximum magnitude of AF-coupling strength was obtained to be 0.39
mJ/m$^{2}$ at the Cu$_{95}$Ir$_{5}$ thickness of about 0.75 nm. Furthermore, we
found a large spin Hall angle of Cu$_{95}$Ir$_{5}$ in Co / Cu$_{95}$Ir$_{5}$
bilayers by carrying out spin Hall magnetoresistance and harmonic Hall voltage
measurements, which are estimated to be 3 ~ 4 %. Our experimental results
clearly indicate that Cu$_{95}$Ir$_{5}$ is a nonmagnetic spacer layer allowing
us to achieve moderately strong AF-coupling and to generate appreciable
spin-orbit torque via the spin Hall effect.

###Tunable and Enhanced Rashba Spin-Orbit Coupling in Iridate-Manganite Heterostructures|T. S. Suraj,Ganesh Ji Omar,Hariom Jani,Muhammad Mangattuchali Juvaid,Sonu Hooda,Anindita Chaudhuri,Andrivo Rusydi,Kanikrishnan Sethupathi,Thirumalai Venkatesan,Ariando Ariando,Mamidanna Sri Ramachandra Rao###

Tunable and Enhanced Rashba Spin-Orbit Coupling in Iridate-Manganite Heterostructures. Tailoring spin-orbit interactions and Coulomb repulsion are the key features
to observe exotic physical phenomena such as magnetic anisotropy and
topological spin texture at oxide interfaces. Our study proposes a novel
platform for engineering the magnetism and spin-orbit coupling at LaMnO3/SrIrO3
(3d-5d oxide) interfaces by tuning the LaMnO3 growth conditions which controls
the lattice displacement and spin-correlated interfacial coupling through
charge transfer. We report on a tunable and enhanced interface-induced Rashba
spin-orbit coupling and Elliot-Yafet spin relaxation mechanism in LaMnO3/SrIrO3
bilayer with change in the underlying magnetic order of LaMnO3. We also
observed enhanced spin-orbit coupling strength in LaMnO3/SrIrO3 compared to
previously reported SrIrO3 layers. The X-Ray spectroscopy measurement reveals
the quantitative valence of Mn and their impact on charge transfer. Further, we
performed angle-dependent magnetoresistance measurements, which show signatures
of magnetic proximity effect in SrIrO3 while reflecting the magnetic order of
LaMnO3. Our work thus demonstrates a new route to engineer the interface
induced Rashba spin-orbit coupling and magnetic proximity effect in 3d-5d oxide
interfaces which makes SrIrO3 an ideal candidate for spintronics applications.

###Quantum transport evidence of Weyl fermions in an epitaxial ferromagnetic oxide|Kosuke Takiguchi,Yuki K. Wakabayashi,Hiroshi Irie,Yoshiharu Krockenberger,Takuma Otsuka,Hiroshi Sawada,Sergey A. Nikolaev,Hena Das,Masaaki Tanaka,Yoshitaka Taniyasu,Hideki Yamamoto###

Quantum transport evidence of Weyl fermions in an epitaxial ferromagnetic oxide. Magnetic Weyl fermions, which occur in magnets, have novel transport
phenomena related to pairs of Weyl nodes, and they are, of both, scientific and
technological interest, with the potential for use in high-performance
electronics, spintronics and quantum computing. Although magnetic Weyl fermions
have been predicted to exist in various oxides, evidence for their existence in
oxide materials remains elusive. SrRuO3, a 4d ferromagnetic metal often used as
an epitaxial conducting layer in oxide heterostructures, provides a promising
opportunity to seek for the existence of magnetic Weyl fermions. Advanced oxide
thin film preparation techniques, driven by machine learning technologies, may
allow access to such topological matter. Here we show direct quantum transport
evidence of magnetic Weyl fermions in an epitaxial ferromagnetic oxide SrRuO3:
unsaturated linear positive magnetoresistance (MR), chiral-anomaly-induced
negative MR, Pi Berry phase accumulated along cyclotron orbits, light cyclotron
masses and high quantum mobility of about 10000 cm2/Vs. We employed
machine-learning-assisted molecular beam epitaxy (MBE) to synthesize SrRuO3
films whose quality is sufficiently high to probe their intrinsic quantum
transport properties. We also clarified the disorder dependence of the
transport of the magnetic Weyl fermions, and provided a brand-new diagram for
the Weyl transport, which gives a clear guideline for accessing the
topologically nontrivial transport phenomena. Our results establish SrRuO3 as a
magnetic Weyl semimetal and topological oxide electronics as a new research
field.

###Spin Hall magnetoresistance in antiferromagnetic insulators|Stephan Geprägs,Matthias Opel,Johanna Fischer,Olena Gomonay,Philipp Schwenke,Matthias Althammer,Hans Huebl,Rudolf Gross###

Spin Hall magnetoresistance in antiferromagnetic insulators. Antiferromagnetic materials promise improved performance for spintronic
applications, as they are robust against external magnetic field perturbations
and allow for faster magnetization dynamics compared to ferromagnets. The
direct observation of the antiferromagnetic state, however, is challenging due
to the absence of a macroscopic magnetization. Here, we show that the spin Hall
magnetoresistance (SMR) is a versatile tool to probe the antiferromagnetic spin
structure via simple electrical transport experiments by investigating the
easy-plane antiferromagnetic insulators $\alpha$-Fe2O3 (hematite) and NiO in
bilayer heterostructures with a Pt heavy metal top electrode. While rotating an
external magnetic field in three orthogonal planes, we record the longitudinal
and the transverse resistivities of Pt and observe characteristic resistivity
modulations consistent with the SMR effect. We analyze both their amplitude and
phase and compare the data to the results from a prototypical collinear
ferrimagnetic Y3Fe5O12/Pt bilayer. The observed magnetic field dependence is
explained in a comprehensive model, based on two magnetic sublattices and
taking into account magnetic field-induced modifications of the domain
structure. Our results show that the SMR allows us to understand the spin
configuration and to investigate magnetoelastic effects in antiferromagnetic
multi-domain materials. Furthermore, in $\alpha$-Fe2O3/Pt bilayers, we find an
unexpectedly large SMR amplitude of $2.5 \times 10^{-3}$, twice as high as for
prototype Y3Fe5O12/Pt bilayers, making the system particularly interesting for
room-temperature antiferromagnetic spintronic applications.

###Magnetic and transport anomalies in R2RhSi3 (R= Gd, Tb, and Dy), resembling those of an exotic magnetic skyrmion Gd2PdSi3|Ram Kumar,Kartik K Iyer,P. L. Paulose,E. V. Sampathkumaran###

Magnetic and transport anomalies in R2RhSi3 (R= Gd, Tb, and Dy), resembling those of an exotic magnetic skyrmion Gd2PdSi3. We have carried out magnetization, heat capacity, electrical and
magnetoresistance measurements (2-300 K) for the polycrystalline form of
intermetallic compounds, R2RhSi3 (R= Gd, Tb, and Dy), forming in a AlB2 derived
hexagonal structure with a triangular R network. This work was primarily
motivated by a revival of interest on Gd2PdSi3 after about two decades in the
field of Toplogical Hall Effect due to magnetic skyrmions. We report here that
these compounds are characterized by double antiferromagnetic transitions (T_N=
13.5 and 12 K for Gd, 13.5 and 6.5 K for Tb; 6.5 and 2.5 for Dy), but
antiferromagnerism seems to be complex. The most notable observations common to
all these compounds are: (i) There are many features in the data mimicking
those seen for Gd2PdSi3, including the two field-induced changes in isothermal
magnetization as though there are two metamagnetic transitions well below T_N.
In view of such a resemblance of the properties, we speculate that these
Rh-based materials offer a good playground to study toplogical Hall effect in a
centrosymmetric structure, with its origin lying in triangular lattice of
magnetic R ions; (ii) There is an increasing contribution of electronic
scattering with decreasing temperature towards T_N in all cases, similar to
Gd2PdSi3, thereby serving as examples for a theoretical prediction for a
classical spin-liquid phase in metallic systems due to geometrical frustration.

###Ion beam modification of magnetic tunnel junctions|B. M. S. Teixeira,A. A. Timopheev,N. Caçoilo,L. Cuchet,J. Mondaud,J. R. Childress,S. Magalhães,E. Alves,N. A. Sobolev###

Ion beam modification of magnetic tunnel junctions. The impact of 400 keV $Ar^+$ ion irradiation on the magnetic and electrical
properties of in-plane magnetized magnetic tunnel junction (MTJ) stacks was
investigated by ferromagnetic resonance, vibrating sample magnetometry and
current-in-plane tunneling techniques. The irradiation-induced changes of the
magnetic anisotropy, coupling energies and tunnel magnetoresistance (TMR)
exhibited a correlated dependence on the ion fluence, which allowed us to
distinguish between two irradiation regimes. In the low-fluence regime, ${\Phi}
< 10^{14} cm^{-2}$, the parameters required for having a functioning MTJ were
preserved: the anisotropy of the FeCoB free layer (FL) was weakly modulated
following a small decrease in the saturation magnetization $M_S$; the TMR
decreased continuously; the interlayer exchange coupling (IEC) and the exchange
bias (EB) decreased slightly. In the high-fluence regime, ${\Phi} > 10^{14}
cm^{-2}$, the MTJ was rendered inoperative: the modulation of the FL anisotropy
was strong, caused by a strong decrease in $M_S$, ascribed to a high degree of
interface intermixing between the FL and the Ta capping; the EB and IEC were
also lost, likely due to intermixing of the layers composing the synthetic
antiferromagnet; and the TMR vanished due to the irradiation-induced
deterioration of the MgO barrier and MgO/FeCoB interfaces. We demonstrate that
the layers surrounding the FL play a decisive role in determining the trend of
the magnetic anisotropy evolution resulting from the irradiation, and that an
ion-fluence window exists where such a modulation of magnetic anisotropy can
occur, while not losing the TMR or the magnetic configuration of the MTJ.

###A micromagnetic study of the switching dynamics of the BiFeO$_3$/CoFe heterojunction|Yu-Ching Liao,Dmitri E. Nikonov,Sourav Dutta,Sou-Chi Chang,Chia-Sheng Hsu,Ian A. Young,Azad Naeemi###

A micromagnetic study of the switching dynamics of the BiFeO$_3$/CoFe heterojunction. The switching dynamics of a single-domain BiFeO3/CoFe heterojunction is
modeled and key parameters such as interface exchange coupling coefficient are
extracted from experimental results. The lower limit of the magnetic order
response time of CoFe in the BiFeO3/CoFe heterojunction is theoretically
quantified to be on to the order of 100 ps. Our results indicate that the
switching behavior of CoFe in the BiFeO3/CoFe heterojunction is dominated by
the rotation of the Neel vector in BiFeO3 rather than the unidirectional
exchange bias at the interface. We also quantify the magnitude of the interface
exchange coupling coefficient J_int to be 0.32 pJ/m by comparing our simulation
results with the giant magnetoresistance (GMR) curves and the magnetic
hysteresis loop in the experiments. To the best of our knowledge, this is the
first time that J_int is extracted quantitatively from experiments.
Furthermore, we demonstrate that the switching success rate and the thermal
stability of the BiFeO3/CoFe heterojunction can be improved by reducing the
thickness of CoFe and increasing the length to width aspect ratio of the
BiFeO3/CoFe heterojunction. Our theoretical model provides a comprehensive
framework to study the magnetoelectric properties and the manipulation of the
magnetic order of CoFe in the BiFeO3/CoFe heterojunction.

###Synthesis of WTe2 thin films and highly-crystalline nanobelts from pre-deposited reactants|John B. Mc Manus,Cansu Ilhan,Bastien Balsamo,Clive Downing,Conor P. Cullen,Tanja Stimpfel-Lidner,Graeme Cunningham,Lisanne Peters,Lewys Jones,Daragh Mullarkey,Igor V. Shvets,Georg S. Duesberg,Niall McEvoy###

Synthesis of WTe2 thin films and highly-crystalline nanobelts from pre-deposited reactants. Tungsten ditelluride is a layered transition metal dichalcogenide (TMD) that
has attracted increasing research interest in recent years. WTe2 has
demonstrated large non-saturating magnetoresistance, potential for spintronic
applications and promise as a type-II Weyl semimetal. The majority of works on
WTe2 have relied on mechanically-exfoliated flakes from chemical vapour
transport (CVT) grown crystals for their investigations. While producing
high-quality samples, this method is hindered by several disadvantages
including long synthesis times, high-temperature anneals and an inherent lack
of scalability. In this work, a synthesis method is demonstrated that allows
the production of large-area polycrystalline films of WTe2. This is achieved by
the reaction of pre-deposited films of W and Te at a relatively low temperature
of 550 degC. Sputter X-ray photoelectron spectroscopy reveals the rapid but
self-limiting nature of the oxidation of these WTe2 films in ambient
conditions. The WTe2 films are composed of areas of micrometre sized nanobelts
that can be isolated and offer potential as an alternative to CVT-grown
samples. These nanobelts are highly crystalline with low defect densities
indicated by TEM and show promising initial electrical results.

###Strong interfacial exchange field in a heavy metal/ferromagnetic insulator system determined by spin Hall magnetoresistance|Juan M. Gomez-Perez,Xian-Peng Zhang,Francesco Calavalle,Maxim Ilyn,Carmen González-Orellana,Marco Gobbi,Celia Rogero,Andrey Chuvilin,Vitaly N. Golovach,Luis E. Hueso,F. Sebastian Bergeret,Fèlix Casanova###

Strong interfacial exchange field in a heavy metal/ferromagnetic insulator system determined by spin Hall magnetoresistance. Spin-dependent transport at heavy metal/magnetic insulator interfaces is at
the origin of many phenomena at the forefront of spintronics research. A proper
quantification of the different interfacial spin conductances is crucial for
many applications. Here, we report the first measurement of the spin Hall
magnetoresistance (SMR) of Pt on a purely ferromagnetic insulator (EuS). We
perform SMR measurements in a wide range of temperatures and fit the results by
using a microscopic model. From this fitting procedure we obtain the
temperature dependence of the spin conductances ($G_s$, $G_r$ and $G_i$),
disentangling the contribution of field-like torque ($G_i$), damping-like
torque ($G_r$), and spin-flip scattering ($G_s$). An interfacial exchange field
of the order of 1 meV acting upon the conduction electrons of Pt can be
estimated from $G_i$, which is at least three times larger than $G_r$ below the
Curie temperature. Our work provides an easy method to quantify this
interfacial spin-splitting field, which play a key role in emerging fields such
as superconducting spintronics and caloritronics, and topological quantum
computation.

###Magneto-transport and Berry phase in magnetically doped Bi$_{0.97-x}$Sb$_{0.03}$ single crystals|V. K. Maurya,Manju Mishra Patidar,Anita Dhaka,R. Rawat,V. Ganesan,R. S. Dhaka###

Magneto-transport and Berry phase in magnetically doped Bi$_{0.97-x}$Sb$_{0.03}$ single crystals. We report large magnetoresistance (MR) and Shubnikov-de Haas (SdH)
oscillations in single crystals of magnetically (M= Ni and Fe) doped
M$_x$Bi$_{0.97-x}$Sb$_{0.03}$ ($x=$ 0, 0.02) topological insulators. The
R$\bar{3}$m symmetry and phase have been confirmed by the Rietveld refinement
of x-ray diffraction data. Interestingly, a magnetic field induced phase
transition from semi-metallic to semi-conducting type is found with the energy
gap around 80 meV at 15 Tesla in the $x=$ 0 sample. Moreover, we observe linear
behavior of MR up to 15 Tesla in transverse mode and SdH oscillations in
longitudinal mode where the field direction is with respect to the current and
crystal plane. For the parent sample, we found the coherence length L$_\phi=$
12.7 nm through the fitting of MR data in transverse mode with modified H-L-N
equation. The extracted frequencies of SdH oscillations using the fast Fourier
transform method and Landau level (LL) fan diagram are found to be consistent
for the parent and Ni doped samples. The determined Fermi surface area is found
to be slightly larger in Ni doped as compared to the parent sample possibly due
to change in the Fermi energy. The Kohler's plot indicates a single scattering
mechanism below 100 K. More importantly, the analysis with the help of LL fan
diagram reveals the non-zero Berry phase $\phi_{\rm B}= -$(1$\pm$0.1)$\pi$,
which demonstrates the non-trivial topological states near the Dirac point in
the parent and Ni doped samples.

###Enhanced all-optical switching and domain wall velocity in annealed synthetic-ferrimagnetic multilayers|Luding Wang,Youri L. W. van Hees,Reinoud Lavrijsen,Weisheng Zhao,Bert Koopmans###

Enhanced all-optical switching and domain wall velocity in annealed synthetic-ferrimagnetic multilayers. All optical switching (AOS) of the magnetization in synthetic ferrimagnetic
Pt/Co/Gd stacks has received considerable interest due to its high potential
towards integration with spintronic devices, such as magnetic tunnel junctions
(MTJs), to enable ultrafast memory applications. Post-annealing is an essential
process in the MTJ fabrication to obtain optimized tunnel magnetoresistance
(TMR) ratio. However, with integrating AOS with an MTJ in prospect, the
annealing effects on single-pulse AOS and domain wall (DW) dynamics in the
Pt/Co/Gd stacks haven't been systematically investigated yet. In this study, we
experimentally explore the annealing effect on AOS and field-induced DW motion
in Pt/Co/Gd stacks. The results show that the threshold fluence (F_0) for AOS
is reduced significantly as a function of annealing temperature (T_a) ranging
from 100C to 300C. Specifically, a 28% reduction of F_0 can be observed upon
annealing at 300C, which is a critical T_a for MTJ fabrication. Lastly, we also
demonstrate a significant increase of the DW velocity in the creep regime upon
annealing, which is attributed to annealing-induced Co/Gd interface
intermixing. Our findings show that annealed Pt/Co/Gd system facilitates
ultrafast and energy-efficient AOS, as well as enhanced DW velocity, which is
highly suitable towards opto-spintronic memory applications.

###Superconductivity in Hydrogenated Graphites|Nadina Gheorghiu,Charles R. Ebbing,Timothy J. Haugan###

Superconductivity in Hydrogenated Graphites. We report transport and magnetization measurements on graphitic materials
that have been hydrogenated after being treated with octane. The
temperature-dependent electrical resistivity shows anomalies manifested as
re-entrant insulator-metal transitions. Below 50 K, the magnetoresistance data
shows both antiferromagnetic and ferromagnetic behavior as the magnetic field
is decrease or increased, respectively. The system is possibly an
unconventional magnetic superconductor. The irreversible behavior observed in
the field-cooled vs. the zero-field cooled data for a sufficiently high
magnetic field suggests that the system might enter a superconducting state
below 50 K. Energy gap data is obtained from nonlocal electric differential
conductance measurements. An exciton-based mechanism is likely driving the
system to the superconducting state below 50 K, where the gap is divergent. We
find that the hydrogenated carbon fiber is a multiple gap system with critical
temperatures estimates above room temperature. The temperature dependence of
the superconducting gap follows the flat-band energy relationship, with the
flat band gap parameter linearly increasing with the temperature above 50 K.
Thus, we find that either a magnetic or an electric field can drive this
hydrogenated graphitic system to superconducting state below 50 K. In addition,
AF spin fluctuations creates pseudo-gap states above 50 K.

###Layered Antiferromagnetism Induces Large Negative Magnetoresistance in the van der Waals Semiconductor CrSBr|Evan J. Telford,Avalon H. Dismukes,Kihong Lee,Minghao Cheng,Andrew Wieteska,Amymarie K. Bartholomew,Yu-Sheng Chen,Xiaodong Xu,Abhay N. Pasupathy,Xiaoyang Zhu,Cory R. Dean,Xavier Roy###

Layered Antiferromagnetism Induces Large Negative Magnetoresistance in the van der Waals Semiconductor CrSBr. The recent discovery of magnetism within the family of exfoliatable van der
Waals (vdW) compounds has attracted considerable interest in these materials
for both fundamental research and technological applications. However current
vdW magnets are limited by their extreme sensitivity to air, low ordering
temperatures, and poor charge transport properties. Here we report the magnetic
and electronic properties of CrSBr, an air-stable vdW antiferromagnetic
semiconductor that readily cleaves perpendicular to the stacking axis. Below
its N\'{e}el temperature, $T_N = 132 \pm 1$ K, CrSBr adopts an A-type
antiferromagnetic structure with each individual layer ferromagnetically
ordered internally and the layers coupled antiferromagnetically along the
stacking direction. Scanning tunneling spectroscopy and photoluminescence (PL)
reveal that the electronic gap is $\Delta_E = 1.5 \pm 0.2$ eV with a
corresponding PL peak centered at $1.25 \pm 0.07$ eV. Using magnetotransport
measurements, we demonstrate strong coupling between magnetic order and
transport properties in CrSBr, leading to a large negative magnetoresistance
response that is unique amongst vdW materials. These findings establish CrSBr
as a promising material platform for increasing the applicability of vdW
magnets to the field of spin-based electronics.

###Glassy dielectric anomaly and negative magneto-capacitance effect in electron-doped Ca$_{1-x}$Sr$_x$Mn$_{0.85}$Sb$_{0.15}$O$_3$|Haruka Taniguchi,Hidenori Takahashi,Akihiro Terui,Kensuke Sadamitsu,Yuka Sato,Michihiro Ito,Katsuhiko Nonaka,Satoru Kobayashi,Michiaki Matsukawa,Ramanathan Suryanarayanan,Nae Sasaki,Shunpei Yamaguchi,Takao Watanabe###

Glassy dielectric anomaly and negative magneto-capacitance effect in electron-doped Ca$_{1-x}$Sr$_x$Mn$_{0.85}$Sb$_{0.15}$O$_3$. Manganites exhibit various types of electronic phenomena, and these
electronic characteristics can be controlled by carrier doping. Herein, we
report the dielectric and magnetic properties of electron-doped manganite
Ca$_{1-x}$Sr$_x$Mn$_{0.85}$Sb$_{0.15}$O$_3$ ($x$ = 0, 0.1, 0.2, and 0.3). The
temperature dependence of the real part of the dielectric constant exhibits a
broad and large peak just below the kink temperature of magnetization and a
sharp decrease at lower temperatures, accompanied by an anomaly of the
imaginary part. Furthermore, isovalent Sr substitution enhances the temperature
of the dielectric peak by more than 50 K. Interestingly, the dielectric peak
exhibits a negative magnetic-field effect. For all measured samples, the
low-temperature variation of the dielectric constant can be qualitatively
explained based on the Maxwell-Wagner (MW) model that describes a system
composed of grain boundaries and semiconducting grains. However, the observed
peak and its negative magneto-capacitance effect at high temperatures cannot be
reproduced by a combination of the MW model and magnetoresistance effect. The
dielectric peak strongly indicates polaronic relaxation in the present system.
These results suggest that polarons form clusters with a dipole ordering and
magneto-electric coupling, which might be consistently understood by the
charge-ordering scenario.

###Applying configurational complexity to the 2D Ruddlesden-Popper crystal structure|Wenrui Zhang,Alessandro R. Mazza,Elizabeth Skoropata,Debangshu Mukherjee,Brianna L. Musico,Jie Zhang,Veerle Keppens,Lihua Zhang,Kim Kisslinger,Eli Stavitski,Mathew Brahlek,John W. Freeland,Ping Lu,Thomas Z. Ward###

Applying configurational complexity to the 2D Ruddlesden-Popper crystal structure. The 2D layered Ruddlesden-Popper crystal structure can host a broad range of
functionally important behaviors. Here we establish extraordinary
configurational disorder in a two dimensional layered Ruddlesden-Popper (RP)
structure using entropy stabilization assisted synthesis. A protype A2CuO4 RP
cuprate oxide with five components (La, Pr, Nd, Sm, Eu) on the A-site
sublattice is designed and fabricated into epitaxial single crystal films using
pulsed laser deposition. By comparing (La0.2Pr0.2Nd0.2Sm0.2Eu0.2)2CuO4 crystals
grown under identical conditions but different substrates, it is found that
heteroepitaxial strain plays an important role in crystal phase formation. When
grown on a near lattice matched substrate, the high entropy oxide film features
a T'-type RP structure with uniform A-site cation mixing and square-planar CuO4
units, however, growing under strong compressive strain results in a single
crystal non-RP cubic phase consistent with a CuX2O4 spinel structure. These
observations are made with a range of combined characterizations using X-ray
diffraction, atomic-resolution scanning transmission electron microscopy,
energy-dispersive X-ray spectroscopy, and X-ray absorption spectroscopy
measurements. Designing configurational complexity and moving between 2D
layered RP and 3D cubic crystal structures in this class of cuprate materials
opens many opportunities for new design strategies related to
magnetoresistance, unconventional superconductivity, ferroelectricity,
catalysis, and ion transport.

###Magnetic order and transport in a spin-fermion model on a superlattice|Sabyasachi Tarat,Jian Li,Richard T. Scalettar,Rubem Mondaini###

Magnetic order and transport in a spin-fermion model on a superlattice. We consider a spin-fermion model consisting of free electrons coupled to
classical spins, where the latter are embedded in a quasi one-dimensional
superlattice structure consisting of spin blocks separated by spinless buffers.
Using a spiral ansatz for the spins, we study the effect of the electron
mediated Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction on the $T=0$ ground
state of the system. We find that the RKKY interaction can lead to
ferromagnetic, antiferromagnetic, or intermediate spiral phases for different
system parameters. When the width is much larger than the length of the
individual blocks, the spiral phases are suppressed, and the ground state
oscillates between ferromagnetic and antiferromagnetic order as the size of the
buffer regions is varied. This is accompanied by a corresponding oscillation in
the Drude weight reflecting an increased conductivity in the ferromagnetic
state compared to the antiferromagnetic one. These results are reminiscent of
classic giant magnetoresistance phenomena observed in a similar geometry of
thin, sandwiched magnetic and non-magnetic layers. Our analysis provides a
robust framework for understanding the role of the RKKY interaction on the
ground state order and corresponding transport properties of such systems,
extending beyond the conventional perturbative regime.

###Topological Dirac states in a layered telluride TaPdTe$_5$ with quasi-one-dimensional PdTe$_2$ chains|Wen-He Jiao,Xiao-Meng Xie,Yi Liu,Xiaofeng Xu,Bin Li,Chun-Qiang Xu,Ji-Yong Liu,Wei Zhou,Yu-Ke Li,Hai-Yang Yang,Shan Jiang,Yongkang Luo,Zeng-Wei Zhu,Guang-Han Cao###

Topological Dirac states in a layered telluride TaPdTe$_5$ with quasi-one-dimensional PdTe$_2$ chains. We report the synthesis and systematic studies of a new layered ternary
telluride TaPdTe5 with quasi-one-dimensional PdTe2 chains. This compound
crystalizes in a layered orthorhombic structure with space group Cmcm. Analysis
of its curved field-dependent Hall resistivity, using the two-band model,
indicates the hole-dominated transport with a high mobility ${\mu}_h$ = 2.38
$\times$ 10$^3$ cm$^2$ V$^{-1}$ s$^{-1}$ at low temperatures. The in-plane
magnetoresistance (MR) displays significant anisotropy with field applied along
the crystallographic $b$ axis. The MR with the current applied along the
$c$-axis is also measured in high magnetic fields up to 51.7 T. Remarkably, it
follows a power-law dependence and reaches (9.5 $\times$ 10$^3$)% at 2.1 K
without any signature of saturation. The De Haas-van Alphen oscillations show a
small Fermi-surface pocket with a nontrivial Berry phase. The Shubnikov-de Haas
(SdH) oscillations are detected at low temperatures and under magnetic fields
above 28.5 T. Two effective masses $m^*$ (0.26$m_e$ and 0.41$m_e$) are
extracted from the oscillatory SdH data. Our first-principles calculations
unveil a topological Dirac cone in its surface states, and, in particular, the
topological index indicates that TaPdTe$_5$ is a topologically nontrivial
material.

###Current-induced CrI3 surface spin-flop transition probed by proximity magnetoresistance in Pt|Tang Su,Mark Lohmann,Junxue Li,Yadong Xu,Ben Niu,Mohammed Alghamdi,Haidong Zhou,Yongtao Cui,Ran Cheng,Takashi Taniguchi,Kenji Watanabe,Jing Shi###

Current-induced CrI3 surface spin-flop transition probed by proximity magnetoresistance in Pt. By exploiting proximity coupling, we probe the spin state of the surface
layers of CrI3, a van der Waals magnetic semiconductor, by measuring the
induced magnetoresistance (MR) of Pt in Pt/CrI3 nano-devices. We fabricate the
devices with clean and stable interfaces by placing freshly exfoliated CrI3
flake atop pre-patterned thin Pt strip and encapsulating the Pt/CrI3
heterostructure with hexagonal boron nitride (hBN) in a protected environment.
In devices consisting of a wide range of CrI3 thicknesses (30 to 150 nm), we
observe that an abrupt upward jump in Pt MR emerge at a 2 T magnetic field
applied perpendicularly to the layers when the current density exceeds
2.5x10^10 A/m2, followed by a gradual decrease over a range of 5 T. These
distinct MR features suggest a spin-flop transition which reveals strong
antiferromagnetic interlayer coupling in the surface layers of CrI3. We study
the current dependence by holding the Pt/CrI3 sample at approximately the same
temperature to exclude the joule heating effect, and find that the MR jump
increases with the current density, indicating a spin current origin. This spin
current effect provides a new route to control spin configurations in
insulating antiferromagnets, which is potentially useful for spintronic
applications.

###Current-induced in-plane magnetization switching in biaxial ferrimagnetic insulator|Yongjian Zhou,Chenyang Guo,Caihua Wan,Xianzhe Chen,Xiaofeng Zhou,Ruiqi Zhang,Youdi Gu,Ruyi Chen,Huaqiang Wu,Xiufeng Han,Feng Pan,Cheng Song###

Current-induced in-plane magnetization switching in biaxial ferrimagnetic insulator. Ferrimagnetic insulators (FiMI) have been intensively used in microwave and
magneto-optical devices as well as spin caloritronics, where their
magnetization direction plays a fundamental role on the device performance. The
magnetization is generally switched by applying external magnetic fields. Here
we investigate current-induced spin-orbit torque (SOT) switching of the
magnetization in Y3Fe5O12 (YIG)/Pt bilayers with in-plane magnetic anisotropy,
where the switching is detected by spin Hall magnetoresistance. Reversible
switching is found at room temperature for a threshold current density of 10^7
A cm^-2. The YIG sublattices with antiparallel and unequal magnetic moments are
aligned parallel or antiparallel to the direction of current pulses, which is
consistent to the Neel order switching in antiferromagnetic system. It is
proposed that such a switching behavior may be triggered by the
antidamping-torque acting on the two antiparallel sublattices of FiMI. Our
finding not only broadens the magnetization switching by electrical means and
promotes the understanding of magnetization switching, but also paves the way
for all-electrically modulated microwave devices and spin caloritronics with
low power consumption.

###Interfacial giant tunnel magnetoresistance and bulk-induced large perpendicular magnetic anisotropy in (111)-oriented junctions with fcc ferromagnetic alloys: A first-principles study|Keisuke Masuda,Hiroyoshi Itoh,Yoshiaki Sonobe,Hiroaki Sukegawa,Seiji Mitani,Yoshio Miura###

Interfacial giant tunnel magnetoresistance and bulk-induced large perpendicular magnetic anisotropy in (111)-oriented junctions with fcc ferromagnetic alloys: A first-principles study. We study the tunnel magnetoresistance (TMR) effect and magnetocrystalline
anisotropy in a series of magnetic tunnel junctions (MTJs) with $L1_1$-ordered
fcc ferromagnetic alloys and MgO barrier along the [111] direction. Considering
the (111)-oriented MTJs with different $L1_1$ alloys, we calculate their TMR
ratios and magnetocrystalline anisotropies on the basis of the first-principles
calculations. The analysis shows that the MTJs with Co-based alloys (CoNi,
CoPt, and CoPd) have high TMR ratios over 2000$\%$. These MTJs have
energetically favored Co-O interfaces where interfacial antibonding between Co
$d$ and O $p$ states is formed around the Fermi level. We find that the
resonant tunneling of the antibonding states, called the interface resonant
tunneling, is the origin of the obtained high TMR ratios. Our calculation of
the magnetocrystalline anisotropy shows that many $L1_1$ alloys have large
perpendicular magnetic anisotropy (PMA). In particular, CoPt has the largest
value of anisotropy energy $K_{\rm u} \approx 10\,{\rm MJ/m^3}$. We further
conduct a perturbation analysis of the PMA with respect to the spin-orbit
interaction and reveal that the large PMA in CoPt and CoNi mainly originates
from spin-conserving perturbation processes around the Fermi level.

###Current-induced magnetization switching of exchange-biased NiO heterostructures characterized by spin-orbit torque|Krzysztof Grochot,Łukasz Karwacki,Stanisław Łazarski,Witold Skowroński,Jarosław Kanak,Wiesław Powroźnik,Piotr Kuświk,Mateusz Kowacz,Feliks Stobiecki,Tomasz Stobiecki###

Current-induced magnetization switching of exchange-biased NiO heterostructures characterized by spin-orbit torque. In this work, we study magnetization switching induced by spin-orbit torque
in W(Pt)/Co/NiO heterostructures with variable thickness of heavy-metal layers
W and Pt, perpendicularly magnetized Co layer and an antiferromagnetic NiO
layer. Using current-driven switching, magnetoresistance and anomalous Hall
effect measurements, perpendicular and in-plane exchange bias field were
determined. Several Hall-bar devices possessing in-plane exchange bias from
both systems were selected and analyzed in relation to our analytical switching
model of critical current density as a function of Pt and W thickness,
resulting in estimation of effective spin Hall angle and perpendicular
effective magnetic anisotropy. We demonstrate in both the Pt/Co/NiO and the
W/Co/NiO systems the deterministic Co magnetization switching without external
magnetic field which was replaced by in-plane exchange bias field. Moreover, we
show that due to a higher effective spin Hall angle in W than in Pt-systems the
relative difference between the resistance states in the magnetization current
switching to difference between the resistance states in magnetic field
switching determined by anomalous Hall effect ($\Delta R/\Delta
R_{\text{AHE}}$) is about twice higher in W than Pt, while critical switching
current density in W is one order lower than in Pt-devices. The current
switching stability and training process is discussed in detail.

###Magnetic Immunoassays: A Review of Virus and Pathogen Detection Before and Amidst the Coronavirus Disease-19 (COVID-19)|Kai Wu,Renata Saha,Diqing Su,Venkatramana D. Krishna,Jinming Liu,Maxim C-J Cheeran,Jian-Ping Wang###

Magnetic Immunoassays: A Review of Virus and Pathogen Detection Before and Amidst the Coronavirus Disease-19 (COVID-19). The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which
causes coronavirus disease 2019 (COVID-19), is a threat to the global
healthcare system and economic security. As of July 2020, no specific drugs or
vaccines are yet available for COVID-19, fast and accurate diagnosis for
SARS-CoV-2 is essential in slowing down the spread of COVID-19 and for
efficient implementation of control and containment strategies. Magnetic
immunoassay is a novel and emerging topic representing the frontiers of current
biosensing and magnetics areas. The past decade has seen rapid growth in
applying magnetic tools for biological and biomedical applications. Recent
advances in magnetic materials and nanotechnologies have transformed current
diagnostic methods to nanoscale and pushed the detection limit to early stage
disease diagnosis. Herein, this review covers the literatures of magnetic
immunoassay platforms for virus and pathogen detections, before COVID-19. We
reviewed the popular magnetic immunoassay platforms including magnetoresistance
(MR) sensors, magnetic particle spectroscopy (MPS), and nuclear magnetic
resonance (NMR). Magnetic Point-of-Care (POC) diagnostic kits are also reviewed
aiming at developing plug-and-play diagnostics to manage the SARS-CoV-2
outbreak as well as preventing future epidemics. In addition, other platforms
that use magnetic materials as auxiliary tools for enhanced pathogen and virus
detections are also covered. The goal of this review is to inform the
researchers of diagnostic and surveillance platforms for SARS-CoV-2 and their
performances.

###Colossal Negative Magnetoresistance Effect in A La$_{1.37}$Sr$_{1.63}$Mn$_2$O$_7$ Single Crystal Grown by Laser-Diode-Heated Floating-Zone Technique|Si Wu,Yinghao Zhu,Junchao Xia,Pengfei Zhou,Haiyong Ni,Hai-Feng Li###

Colossal Negative Magnetoresistance Effect in A La$_{1.37}$Sr$_{1.63}$Mn$_2$O$_7$ Single Crystal Grown by Laser-Diode-Heated Floating-Zone Technique. We have grown La$_{1.37}$Sr$_{1.63}$Mn$_2$O$_7$ single crystals with a
laser-diode-heated floating-zone furnace and studied the crystallinity,
structure, and magnetoresistance (MR) effect by in-house X-ray Laue
diffraction, X-ray powder diffraction, and resistance measurements. The
La$_{1.37}$Sr$_{1.63}$Mn$_2$O$_7$ single crystal crystallizes into a tetragonal
structure with space group \emph{I}4{/}\emph{mmm} at room temperature. At 0 T,
the maximum resistance centers around $\sim$166.9 K. Below $\sim$35.8 K, it
displays an insulating character with an increase in resistance upon cooling.
An applied magnetic field of \emph{B}~=~7~T strongly suppresses the resistance
indicative of a negative MR effect. The minimum MR value equals $-$91.23\% at 7
T and 128.7 K. The magnetic-field-dependent resistance shows distinct features
at 1.67, 140, and 322 K, from which we calculated the corresponding MR values.
At 14 T and 140 K, the colossal negative MR value is down to $-$94.04(5)\%. We
schematically fit the MR values with different models for an ideal describing
of the interesting features of the MR value versus \emph{B} curves.

###Crystalline symmetry-protected non-trivial topology in prototype compound BaAl$_4$|Kefeng Wang,Ryo Mori,Zhijun Wang,Limin Wang,Jonathan Han Son Ma,Drew W. Latzke,David E. Graf,Jonathan D. Denlinger,Daniel Campbell,B. Andrei Bernevig,Alessandra Lanzara,Johnpierre Paglione###

Crystalline symmetry-protected non-trivial topology in prototype compound BaAl$_4$. The BaAl$_4$ prototype crystal structure is the most populous of all
structure types, and is the building block for a diverse set of sub-structures
including the famous ThCr$_2$Si$_2$ family that hosts high-temperature
superconductivity and numerous magnetic and strongly correlated electron
systems. The MA$_4$ family of materials (M=Sr, Ba, Eu; A=Al, Ga, In) themselves
present an intriguing set of ground states including charge and spin orders,
but have largely been considered as uninteresting metals. Using electronic
structure calculations, symmetry analysis and topological quantum chemistry
techniques, we predict the exemplary compound BaAl$_4$ to harbor a
three-dimensional Dirac spectrum with non-trivial topology and possible nodal
lines crossing the Brillouin zone, wherein one pair of semi-Dirac points with
linear dispersion along the $k_z$ direction and quadratic dispersion along the
$k_x/k_y$ direction resides on the rotational axis with $C_{4v}$ point group
symmetry. Electrical transport measurements reveal the presence of an extremely
large, unsaturating positive magnetoresistance in BaAl$_4$ despite an
uncompensated band structure, and quantum oscillations and angle-resolved
photoemission spectroscopy measurements confirm the predicted multiband
semimetal structure with pockets of Dirac holes and a Van Hove singularity
(VHS) remarkably consistent with the theoretical prediction. We thus present
BaAl$_4$ as a new topological semimetal, casting its prototype status into a
new role as building block for a vast array of new topological materials.

###Magnetic Multilayer Edges in Bernal-Stacked Hexagonal Boron Nitride|Mehmet Dogan,Marvin L. Cohen###

Magnetic Multilayer Edges in Bernal-Stacked Hexagonal Boron Nitride. Single-layer $\it{h}$-BN is known to have edges with unique magnetism,
however, in the commonly fabricated multilayer
$\text{AA}^{\prime}$-$\it{h}$-BN, edge relaxations occur that create interlayer
bonds and eliminate the unpaired electrons at the edge. Recently, a robust
method of growing the unconventional Bernal-stacked $\it{h}$-BN
(AB-$\it{h}$-BN) has been reported. Here, we use theoretical approaches to
investigate the nitrogen-terminated zigzag edges in AB-$\it{h}$-BN that can be
formed in a controlled fashion using a high-energy electron beam. We find that
these "open" edges remain intact in bilayer and multilayer AB-$\it{h}$-BN,
enabling researchers potentially to investigate these edge states
experimentally. We also investigate the thermodynamics of the spin
configurations at the edge by constructing a lattice model that is based on
parameters extracted from a set of first-principles calculations. We find that
the edge spins in neighboring layers interact very weakly, resulting in a
sequence of independent spin chains in multilayer samples. By solving this
model using Monte Carlo simulations, we can determine nm-scale correlation
lengths at liquid-N$_{2}$ temperatures and lower. At low temperatures, these
edges may be utilized in magnetoresistance and spintronics applications.

###Pressure induced superconductivity in a CeRhSi$_{3}$ single crystal -- the high pressure study|Daniel Staško,Jaroslav Valenta,Marie Kratochvílová,Jiří Prchal,Petr Proschek,Milan Klicpera###

Pressure induced superconductivity in a CeRhSi$_{3}$ single crystal -- the high pressure study. Pressure induced superconductivity in non-centrosymmetric CeRhSi$_{3}$ and
CeIrSi$_{3}$ compounds has attracted significant attention of the scientific
community since its discovery 15 years ago. Up-to-date, all reported
experimental results were obtained employing the hybrid-cylinder piston
pressure cells with a maximum reachable pressure of 3 GPa. Present study
focuses on the superconducting state at higher, so far unreported, pressures
using the Bridgman anvil cell and a CeRhSi$_{3}$ single crystal synthesized by
the Sn-true-flux method. The initial increase of superconducting critical
temperature from 0.4 K at 1.1 GPa to 1.1 K at 2.4 GPa is followed by a gradual
suppression of SC state upon increasing the pressure above 3.0 GPa, forming a
typical dome. The pressure induced superconductivity is expected to be
completely suppressed in the pressure region between 4.5 and 5.0 GPa.
Temperature dependence of electrical resistivity in constant magnetic fields
and high pressures, as well as the magnetoresistance measurements, reveal a
large critical field, exceeding 19 T at 0.6 K and 2.4 GPa, sharply decreasing
receding the superconductivity dome. The previously reported $\it{T-p}$ and
$\it{H-T}$ phase diagrams are completed by our high-pressure data and discussed
in the frame of previous results.

###Giant perpendicular magnetic anisotropy enhancement in MgO-based magnetic tunnel junction by using Co/Fe composite layer|Libor Vojáček,Fatima Ibrahim,Ali Hallal,Bernard Dieny,Mairbek Chshiev###

Giant perpendicular magnetic anisotropy enhancement in MgO-based magnetic tunnel junction by using Co/Fe composite layer. Magnetic tunnel junctions with perpendicular anisotropy form the basis of the
spin-transfer torque magnetic random-access memory (STT-MRAM), which is
non-volatile, fast, dense, and has quasi-infinite write endurance and low power
consumption. Based on density functional theory (DFT) calculations, we propose
an alternative design of magnetic tunnel junctions comprising
Fe(n)Co(m)Fe(n)/MgO storage layers with greatly enhanced perpendicular magnetic
anisotropy (PMA) up to several mJ/m2, leveraging the interfacial perpendicular
anisotropy of Fe/MgO along with a stress-induced bulk PMA discovered within bcc
Co. This giant enhancement dominates the demagnetizing energy when increasing
the film thickness. The tunneling magnetoresistance (TMR) estimated from the
Julliere model is comparable with that of the pure Fe/MgO case. We discuss the
advantages and pitfalls of a real-life fabrication of the structure and propose
the Fe(3ML)Co(4ML)Fe(3ML) as a storage layer for MgO-based STT-MRAM cells. The
large PMA in strained bcc Co is explained in the framework of Bruno's model by
the MgO-imposed strain and consequent changes in the energies of dyz and dz2
minority-spin bands.

###Paramagnetic spin Hall magnetoresistance|Koichi Oyanagi,Juan M. Gomez-Perez,Xian-Peng Zhang,Takashi Kikkawa,Yao Chen,Edurne Sagasta,Andrey Chuvilin,Luis E. Hueso,Vitaly N. Golovach,F. Sebastian Bergeret,Fèlix Casanova,Eiji Saitoh###

Paramagnetic spin Hall magnetoresistance. Spin Hall magnetoresistance (SMR) refers to a resistance change in a metallic
film reflecting the magnetization direction of a magnet attached to the film.
The mechanism of this phenomenon is spin exchange between conduction-electron
spins and magnetization at the interface. SMR has been used to read out
information written in a small magnet and to detect magnetization dynamics, but
it has been limited to magnets; magnetic ordered phases or instability of
magnetic phase transition has been believed to be indispensable. Here, we
report the observation of SMR in a paramagnetic insulator
Gd$_{3}$Ga$_{5}$O$_{12}$ (GGG) without spontaneous magnetization combined with
a Pt film. The paramagnetic SMR can be attributed to spin-transfer torque
acting on localized spins in GGG. We determine the efficiencies of spin torque
and spin-flip scattering at the Pt/GGG interface, and demonstrate these
quantities can be tuned with external magnetic fields. The results clarify the
mechanism of spin-transport at a metal/paramagnetic insulator interface, which
gives new insight into the spintronic manipulation of spin states in
paramagnetic systems.

###Stabilization of a honeycomb lattice of IrO$_6$ octahedra in superlattices with ilmenite-type MnTiO$_3$|Kei Miura,Kohei Fujiwara,Kei Nakayama,Ryo Ishikawa,Naoya Shibata,Atsushi Tsukazaki###

Stabilization of a honeycomb lattice of IrO$_6$ octahedra in superlattices with ilmenite-type MnTiO$_3$. In the quest for quantum spin liquids, thin films are expected to open the
way for the control of intricate magnetic interactions in actual materials by
exploiting epitaxial strain and two-dimensionality. However, materials
compatible with conventional thin-film growth methods have largely remained
undeveloped. As a promising candidate towards the materialization of quantum
spin liquids in thin films, we here present a robust ilmenite-type oxide with a
honeycomb lattice of edge-sharing IrO$_6$ octahedra artificially stabilized by
superlattice formation with an ilmenite-type antiferromagnetic oxide MnTiO$_3$.
The stabilized sub-unit-cell-thick Mn-Ir-O layer is isostructural to MnTiO$_3$,
having the atomic arrangement corresponding to ilmenite-type MnTiO$_3$ not
discovered yet. By spin Hall magnetoresistance measurements, we found that
antiferromagnetic ordering in the ilmenite Mn sublattice is suppressed by
modified magnetic interactions in the MnO$_6$ planes via the IrO$_6$ planes.
These findings lay the foundation for the creation of two-dimensional Kitaev
candidate materials, accelerating the discovery of exotic physics and
applications specific to quantum spin liquids.

###Novel polymorphic phase of BaCu2As2: impact of flux for new phase formation in crystal growth|Hanlin Wu,Sheng Li,Zheng Wu,Xiqu Wang,Gareth A. Ofenstein,Sunah Kwon,Moon J. Kim,Paul C. W. Chu,Bing Lv###

Novel polymorphic phase of BaCu2As2: impact of flux for new phase formation in crystal growth. In this work, we have thoroughly studied the effects of flux composition and
temperature on the crystal growth of the BaCu2As2 compound. While Pb and CuAs
self-flux produce the well-known {\alpha}-phase ThCr2Si2-type structure (Z=2),
a new polymorphic phase of BaCu2As2 (\b{eta} phase) with a much larger c
lattice parameter (Z=10), which could be considered an intergrowth of the
ThCr2Si2- and CaBe2Ge2-type structures, has been discovered via Sn flux growth.
We have characterized this structure through single-crystal X-ray diffraction,
transmission electron microscopy (TEM), and scanning transmission electron
microscopy (STEM) studies. Furthermore, we compare this new polymorphic
intergrowth structure with the {\alpha}-phase BaCu2As2 (ThCr2Si2 type with Z=2)
and the \b{eta}-phase BaCu2Sb2 (intergrowth of ThCr2Si2 and CaBe2Ge2 types with
Z=6), both with the same space group I4/mmm. Electrical transport studies
reveal p-type carriers and magnetoresistivity up to 22% at 5 K and under a
magnetic field of 7 T. Our work suggests a new route for the discovery of new
polymorphic structures through flux and temperature control during material
synthesis.

###Changes of Fermi Surface Topology due to the Rhombohedral Distortion in SnTe|Christopher D. O'Neill,Oliver J. Clark,Harry D. J. Keen,Federico Mazzola,Igor Marković,Dmitry A. Sokolov,Andreas Malekos,Phil D. C. King,Andreas Hermann,Andrew D. Huxley###

Changes of Fermi Surface Topology due to the Rhombohedral Distortion in SnTe. Stoichiometric SnTe is theoretically a small gap semiconductor that undergoes
a ferroelectric distortion on cooling. In reality however, crystals are always
non-stoichiometric and metallic; the ferroelectric transition is therefore more
accurately described as a polar structural transition. Here we study the Fermi
surface using quantum oscillations as a function of pressure. We find the
oscillation spectrum changes at high pressure, due to the suppression of the
polar transition and less than 10 kbar is sufficient to stabilize the
undistorted cubic lattice. This is accompanied by a large decrease in the Hall
and electrical resistivity. Combined with our density functional theory (DFT)
calculations and angle resolved photoemission spectroscopy (ARPES) measurements
this suggests the Fermi surface $L$-pockets have lower mobility than the
tubular Fermi surfaces that connect them. Also captured in our DFT calculations
is a small widening of the band gap and shift in density of states for the
polar phase. Additionally we find the unusual phenomenon of a linear
magnetoresistance that exists irrespective of the distortion that we attribute
to regions of the Fermi surface with high curvature.

###Proximity-induced hidden order transition in a correlated heterostructure Sr$_2$VO$_3$FeAs|Sunghun Kim,Jong Mok Ok,Hanbit Oh,Chang-il Kwon,Y. Zhang,J. D. Denlinger,S. -K. Mo,F. Wolff-Fabris,E. Kampert,Eun-Gook Moon,C. Kim,Jun Sung Kim,Y. K. Kim###

Proximity-induced hidden order transition in a correlated heterostructure Sr$_2$VO$_3$FeAs. Symmetry is one of the most significant concepts in physics, and its
importance has been largely manifested in phase transitions by its spontaneous
breaking. In strongly correlated systems, however, mysterious and enigmatic
phase transitions, inapplicable of the symmetry description, have been
discovered and often dubbed hidden order transitions, as found in, $\it{e.g.}$,
high-$T_C$ cuprates, heavy fermion superconductors, and quantum spin liquid
candidates. Here, we report a new type of hidden order transition in a
correlated heterostructure Sr$_2$VO$_3$FeAs, whose origin is attributed to an
unusually enhanced Kondo-type proximity coupling between localized spins of V
and itinerant electrons of FeAs. Most notably, a fully isotropic gap opening,
identified by angle-resolved photoemission spectroscopy, occurs selectively in
one of the Fermi surfaces below $T_{\rm HO}$ $\sim$ 150 K, associated with a
singular behavior of the specific heat and a strong enhancement on the
anisotropic magnetoresistance. These observations are incompatible with the
prevalent broken-symmetry-driven scenarios of electronic gap opening and
highlight a critical role of proximity coupling. Our findings demonstrate that
correlated heterostructures offer a novel platform for design and engineering
of exotic hidden order phases.

###Demonstration of Dissipative Quasihelical Edge Transport in Quantum Anomalous Hall Insulators|Shu-Wei Wang,Di Xiao,Ziwei Dou,Moda Cao,Yi-Fan Zhao,Nitin Samarth,Cui-Zu Chang,Malcolm R. Connolly,Charles G. Smith###

Demonstration of Dissipative Quasihelical Edge Transport in Quantum Anomalous Hall Insulators. Doping a topological insulator (TI) film with transition metal ions can break
its time-reversal symmetry and lead to the realization of the quantum anomalous
Hall (QAH) effect. Prior studies have shown that the longitudinal resistance of
the QAH samples usually does not vanish when the Hall resistance shows a good
quantization. This has been interpreted as a result of the presence of possible
dissipative conducting channels in magnetic TI samples. By studying the
temperature- and magnetic field-dependence of the magnetoresistance of a
magnetic TI sandwich heterostructure device, we demonstrate that the
predominant dissipation mechanism in thick QAH insulators can switch between
non-chiral edge states and residual bulk states in different magnetic field
regimes. The interactions between bulk states, chiral edge states, and
non-chiral edge states are also investigated. Our study provides a way to
distinguish between the dissipation arising from the residual bulk states and
non-chiral edge states, which is crucial for achieving true dissipationless
transport in QAH insulators and for providing deeper insights into QAH-related
phenomena.

###Electronic properties in itinerant ferromagnet SrRu$_{1-x}$Ti$_x$O$_3$|Renu Gupta,R. Rawat,A. K. Pramanik###

Electronic properties in itinerant ferromagnet SrRu$_{1-x}$Ti$_x$O$_3$. Here, we study the electrical transport and specific heat in 4$d$ based
ferromagnetic material SrRuO$_3$ and its Ti substituted SrRu$_{1-x}$Ti$_x$O$_3$
series ($x$ $\le$ 0.7). The SrRuO$_3$ is a metal and shows itinerant
ferromagnetism with transition temperature $T_c$ $\sim$ 160 K. The nonmagnetic
Ti$^{4+}$ (3$d^0$) substitution would not only weaken the active Ru-O-Ru
channel but is also expected to tune the electronic density and electron
correlation effect. A metal to insulator transition has been observed around
$x$ $\sim$ 0.4. The nature of charge transport in paramagnetic-metallic state
($x$ $\leq$ 0.4) and in insulating state ($x$ $>$ 0.4) follows modified Mott's
variable range hopping model. In ferromagnetic-metallic state, resistivity
shows a $T^2$ dependence below $T_c$ which though modifies to $T^{3/2}$
dependence at low temperature. In Ti substituted samples, temperature range for
$T^{3/2}$ dependence extends to higher temperature. Interestingly, this
$T^{3/2}$ dependence dominates in whole ferromagnetic regime in presence of
magnetic field. This evolution of electronic transport behavior can be
explained within the framework of Fermi liquid theory and electron-magnon
scattering mechanism. The negative magnetoresistance exhibits a hysteresis and
a crossover between negative and positive value with magnetic field which is
connected with magnetic behavior in series. The decreasing electronic
coefficient of specific heat with $x$ supports the increasing insulating
behavior in present series. We calculate a high Kadowaki-Woods ratio ($x$
$\leq$ 0.3) for SrRuO$_3$ which increases with substitution concentration. This
signifies an increasing electronic correlation effect with substitution
concentration.

###Sign reversal of anomalous Hall conductivity and magnetoresistance in cubic non-collinear antiferromagnet Mn$_3$Pt thin films|Joynarayan Mukherjee,T. S. Suraj,Himalaya Basumatary,K. Sethupathi,Karthik V. Raman###

Sign reversal of anomalous Hall conductivity and magnetoresistance in cubic non-collinear antiferromagnet Mn$_3$Pt thin films. The two dimensional kagome spin lattice structure of Mn atoms in the family
of Mn$_3$X non-collinear antiferromagnets are providing substantial excitement
in the exploration of Berry curvature physics and the associated non-trivial
magnetotransport responses. Much of these studies are performed in the
hexagonal systems, mainly Mn$_3$Sn and Mn$_3$Ge, with the kagome planes having
their normal along the [001] direction. In this manuscript, we report our study
in the cubic Mn$_3$Pt thin films with their kagome planes normal to the [111]
crystal axis. Our studies reveal a hole conduction dominant Hall response with
a non-monotonic temperature dependence of anomalous Hall conductivity (AHC),
increasing from 9 $\Omega^{-1}$cm$^{-1}$ at room temperature to 29
$\Omega^{-1}$cm$^{-1}$ at 100 K, followed by a drop and unexpected
sign-reversal at lower temperatures. Similar sign reversal is also observed in
magnetoresistance measurements. We attribute this sign reversal to the
transition from a Berry curvature dominated AHC at high temperature to a weak
canted ferromagnetic AHC response at lower temperature, below 70 K, caused by
the reorientation of Mn moments out of the kagome plane. Our above results in
thin films of Mn$_3$Pt make advances in their integration with room temperature
antiferromagnetic spintronics.

###Bulk Fermi surfaces of the Dirac type-II semimetallic candidate NiTe2|Wenkai Zheng,Rico Schönemann,Shirin Mozaffari,Yu-Che Chiu,Zachary Bryce Goraum,Niraj Aryal,Efstratios Manousakis,Theo M. Siegrist,Kaya Wei,Luis Balicas###

Bulk Fermi surfaces of the Dirac type-II semimetallic candidate NiTe2. Here, we present a study on the Fermi-surface of the Dirac type-II
semi-metallic candidate NiTe$_2$ via the temperature and angular dependence of
the de Haas-van Alphen (dHvA) effect measured in single-crystals grown through
Te flux. In contrast to its isostructural compounds like PtSe$_2$, band
structure calculations predict NiTe$_2$ to display a tilted Dirac node very
close to its Fermi level that is located along the $\Gamma$ to A high symmetry
direction within its first Brillouin zone (FBZ). The angular dependence of the
dHvA frequencies is found to be in agreement with the first-principle
calculations when the electronic bands are slightly shifted with respect to the
Fermi level ($\varepsilon_F$), and therefore provide support for the existence
of a Dirac type-II node in NiTe$_2$. Nevertheless, we observed mild
disagreements between experimental observations and density Functional theory
calculations as, for example, nearly isotropic and light experimental effective
masses. This indicates that the dispersion of the bands is not well captured by
DFT. Despite the coexistence of Dirac-like fermions with topologically trivial
carriers, samples of the highest quality display an anomalous and large, either
linear or sub-linear magnetoresistivity. This suggests that Lorentz invariance
breaking Dirac-like quasiparticles dominate the carrier transport in this
compound.

###Enhancement of YIG$|$Pt spin conductance by local Joule annealing|Ryuhei Kohno,Nicolas Thiery,Kyongmo An,Paul Noël,Laurent Vila,Vladimir V. Naletov,Nathan Beaulieu,Jamal Ben Youssef,Grégoire de Loubens,Olivier Klein###

Enhancement of YIG$|$Pt spin conductance by local Joule annealing. We report that Joule heating can be used to enhance the interfacial spin
conductivity between a metal and an oxide. We observe that local annealing of
the interface at about 550\,K by injecting large current densities
($>10^{12}\text{A/m}^{2}$) into a pristine 7\,nm thick Pt nanostrip evaporated
on top of yttrium iron garnet (YIG), can improve the spin transmission up to a
factor 3: a result of particular interest for interfacing ultra thin garnet
films where strong chemical etching of the surface has to be avoided. The
effect is confirmed by different methods: spin Hall magnetoresistance, spin
pumping and non-local spin transport. We use it to study the influence of the
YIG$|$Pt coupling on the non-linear spin transport properties. We find that the
cross-over current from a linear to a non-linear spin transport regime is
independent of this coupling, suggesting that the behavior of pure spin
currents circulating in the dielectric are mostly governed by the physical
properties of the bare YIG film beside the Pt nanostrip.

###Strange metal from incoherent bosons|Anurag Banerjee,Maxence Grandadam,Hermann Freire,Catherine Pépin###

Strange metal from incoherent bosons. The breakdown of the celebrated Fermi liquid theory in the strange metal
phase is the central enigma of correlated quantum matter. Motivated by recent
experiments reporting short-lived carriers, along with the ubiquitous
observations of modulated excitations in the phase diagram of cuprates, we
propose a model for this phase. We introduce bosons emerging from the remnants
of a pair density wave as additional current carriers in the strange metal
phase. These bosonic excitations are finite momentum Cooper pairs and thus
carry twice the electronic charge, and its net spin can either be zero or one
arising from the two spin-$1/2$ electrons. We show that such a model can
capture the famous linear relationship of resistivity with temperature and
manifests the Drude form of ac-conductivity with a Planckian dissipation rate.
Furthermore, such bosons are incoherent and hence do not contribute to the Hall
conductivity. The bosons emerging from the electron pairs of spin-triplet
symmetry also reproduce the recently observed linear in-field magnetoresistance
[P. Giraldo-Gallo et al., Science 361, 479 (2018); J. Ayres et al., arXiv:
2012.01208 (2020)].

###A continuous metal-insulator transition driven by spin correlations|Yejun Feng,Yishu Wang,D. M. Silevitch,S. E. Cooper,D. Mandrus,Patrick A. Lee,T. F. Rosenbaum###

A continuous metal-insulator transition driven by spin correlations. Metal-insulator transitions involve a mix of charge, spin, and structural
degrees of freedom, and when strongly-correlated, can underlay the emergence of
exotic quantum states. Mott insulators induced by the opening of a Coulomb gap
are an important and well-recognized class of transitions, but insulators
purely driven by spin correlations are much less common, as the reduced energy
scale often invites competition from other degrees of freedom. Here we
demonstrate a clean example of a spin-correlation-driven metal-insulator
transition in the all-in-all-out pyrochlore antiferromagnet Cd2Os2O7, where the
lattice symmetry is fully preserved by the antiferromagnetism. After the
antisymmetric linear magnetoresistance from conductive, ferromagnetic domain
walls is carefully removed experimentally, the Hall coefficient of the bulk
reveals four Fermi surfaces, two of electron type and two of hole type,
sequentially departing the Fermi level with decreasing temperature below the
N\'eel temperature, T_N. Contrary to the common belief of concurrent magnetic
and metal-insulator transitions in Cd2Os2O7, the charge gap of a continuous
metal-insulator transition opens only at T~10K, well below T_N=227K. The
insulating mechanism resolved by the Hall coefficient parallels the Slater
picture, but without a folded Brillouin zone, and contrasts sharply with the
behavior of Mott insulators and spin density waves, where the electronic gap
opens above and at T_N, respectively.

###Large negative magnetoresistance in BaMn$_2$Bi$_2$ antiferromagnet|Takuma Ogasawara,Kim-Khuong Huynh,Time Tahara,Takanori Kida,Masayuki Hagiwara,Denis Arčon,Motoi Kimata,Stephane Yu Matsushita,Kazumasa Nagata,Katsumi Tanigaki###

Large negative magnetoresistance in BaMn$_2$Bi$_2$ antiferromagnet. A very large negative magnetoresistance (LNMR) is observed in the insulating
regime of the antiferromagnet BaMn$_2$Bi$_2$ when a magnetic field is applied
perpendicular to the direction of the sublattice magnetization. High
perpendicular magnetic field eventually suppresses the insulating behavior and
allows BaMn$_2$Bi$_2$ to re-enter a metallic state. This effect is seemingly
unrelated to any field induced magnetic phase transition, as measurements of
magnetic susceptibility and specific heat did not find any anomaly as a
function of magnetic fields at temperatures above $2\,\mathrm{K}$. The LNMR
appears in both current-in-plane and current-out-of-plane settings, and Hall
effects suggest that its origin lies in an extreme sensitivity of conduction
processes of holelike carriers to the infinitesimal field-induced canting of
the sublattice magnetization. The LNMR-induced metallic state may thus be
associated with the breaking of the antiferromagnetic parity-time symmetry by
perpendicular magnetic fields and/or the intricate multi-orbital electronic
structure of BaMn$_2$Bi$_2$.

###Evidence formagnetic phase separation in colossal magnetoresistance compound EuB5.99C0.01|Ivan Batko,Marianna Batkova,Vinh Hung Tran,Uwe Keiderling,Volodimir Filipov###

Evidence formagnetic phase separation in colossal magnetoresistance compound EuB5.99C0.01. EuB5.99C0.01 is a low-carrier density ferromagnet that is believed to be
intrinsically inhomogeneous due to fluctuations of carbon content. In
accordance with our previous studies, electric trasport of EuB5.99C0.01 close
above temperature of the bulk ferromagnetic (FM) ordering is governed by
magnetic polarons. Carbon-rich regions are incompatible with FM phase and
therefore they act as spacers preventing magnetic polarons to link, to form FM
clusters, and eventually to percolate and establish a (homogoneous) bulk FM
state in this compound, what consequently causes additional (magneto)resistance
increase. Below the temperature of the bulk FM ordering, carbon-rich regions
give rise to helimagnetic domains, which are responsible for an additional
scattering term in the electrical resistivity. Unfortunately, there has not
been provided any direct evidence for magnetic phase separation in EuB5.99C0.01
yet. Here reported results of electrical, heat capacity, Hall resistivity and
small-angle neutron scattering studies bring evidence for formation of mixed
magnetic structure, and provide consistent support for the previously proposed
scenario of the magnetoresistance enhancement in EuB5.99C0.01.

###Physical properties and electronic structure of single-crystal KCo$_2$As$_2$|D. J. Campbell,B. Wilfong,M. P. Zic,G. Levy,M. X. Na,T. M. Pedersen,S. Gorovikov,P. Y. Zavalij,S. Zhdanovich,A. Damascelli,E. E. Rodriguez,J. Paglione###

Physical properties and electronic structure of single-crystal KCo$_2$As$_2$. We present a method for producing high quality KCo2As2 crystals, stable in
air and suitable for a variety of measurements. X-ray diffraction, magnetic
susceptibility, electrical transport and heat capacity measurements confirm the
high quality and an absence of long range magnetic order down to at least 2 K.
Residual resistivity values approaching 0.25 $\mu\Omega$~cm are representative
of the high quality and low impurity content, and a Sommerfeld coefficient
$\gamma$ = 7.3 mJ/mol K$^2$ signifies weaker correlations than the Fe-based
counterparts. Together with Hall effect measurements, angle-resolved
photoemission experiments reveal a Fermi surface consisting of electron pockets
at the center and corner of the Brillouin zone, in line with theoretical
predictions and in contrast to the mixed carrier types of other pnictides with
the ThCr2Si2 structure. A large, linear magnetoresistance of 200\% at 14~T,
together with an observed linear and hyperbolic, rather than parabolic, band
dispersions are unusual characteristics of this metallic compound and may
indicate more complex underlying behavior.

###High tunnel magnetoresistance and magnetism in metastable bcc Co$_{1-x}$Mn$_x$-based magnetic tunnel junctions|Kazuma Kunimatsu,Tufan Roy,Jun Okabayashi,Kelvin Elphick,Tomoki Tsuchiya,Tomohiro Ichinose,Masahito Tsujikawa,Atsufumi Hirohata,Masafumi Shirai,Shigemi Mizukami###

High tunnel magnetoresistance and magnetism in metastable bcc Co$_{1-x}$Mn$_x$-based magnetic tunnel junctions. Co-rich Co$_{1-x}$Mn$_x$ alloys have hcp or fcc disordered phases and those
ferromagnetic orderings are significantly deteriorated with increasing Mn
concentration $x$ in bulk. On the other hand, those metastable bcc phases show
properties attractive to spintronics, e.g., high tunnel magnetoresistance (TMR)
ratio of more than 200% (600%) at 300 K (10 K) in magnetic tunnel junctions
(MTJs) with the $x$ = 0.25 bcc alloy electrodes [Kunimatsu et al., Appl. Phys.
Express 13, 083007 (2020)]. Here, we report systematic study of structure and
magnetism for epitaxial thin films as well as the TMR effect in
MgO(001)-barrier MTJs with electrodes comprising those bcc films. The single
phase bcc Co$_{1-x}$Mn$_x$(001) films were pseudomorphically grown on Cr(001)
for 0.14 < $x$ < 0.50 with a sputtering technique. The magnetization was larger
than that of pure Co for $x$ = 0.14-0.25 and deceased with further increasing
$x$. This behavior mainly stemmed from the composition dependence of magnetic
moment of Mn that exceeded 2 $\mu _B$ at the maximum, unveiled by X-ray
magnetic circular dichroism. Correspondingly, within the range of 0.25 < $x$ <
0.37, the TMR ratio decreased from 620% (229%) to 450% (194%) at 10 K (300 K)
as $x$ increased. We discussed the relationship between the magnetism and high
TMR ratio with different $x$ with the aid of the ab-initio band structure
calculations.

###Lattice Softening in Metastable bcc CoxMn100-x(001) Ferromagnetic Layers for a Strain-Less Magnetic Tunnel Junction|Kelvin Elphick,Kenta Yoshida,Tufan Roy,Tomohiro Ichinose,Kazuma Kunimatsu,Tomoki Tsuchiya,Masahito Tsujikawa,Yasuyoshi Nagai,Shigemi Mizukami,Masafumi Shirai,Atsufumi Hirohata###

Lattice Softening in Metastable bcc CoxMn100-x(001) Ferromagnetic Layers for a Strain-Less Magnetic Tunnel Junction. In spintronics, one of the long standing questions is why the MgO-based
magnetic tunnel junction (MTJ) is almost the only option to achieve a large
tunnelling magnetoresistance (TMR) ratio at room temperature (RT) but not as
large as the theoretical prediction. This study focuses on the development of
an almost strain-free MTJ using metastable bcc CoxMn100-x ferromagnetic films.
We have investigated the degree of crystallisation in MTJ consisting of
CoxMn100-x/MgO/CoxMn100-x (x = 66, 75, 83 and 86) in relation to their TMR
ratios. Cross-sectional high resolution transmission electron microscopy
(HRTEM) reveals that almost consistent lattice constants of these layers for 66
< x < 83 with maintaining large TMR ratios of 229% at RT, confirming the soft
nature of the CoxMn100-x layer with some dislocations at the MgO/Co75Mn25
interfaces. For x = 86, on the other hand, the TMR ratio is found to be reduced
to 142% at RT, which is partially attributed to the increased number of the
dislocations at the MgO/Co86Mn14 interfaces and amorphous grains identified in
the MgO barrier. Ab-initio calculations confirm the crystalline deformation
stability across a broad compositional range in CoMn, proving the advantage of
a strain-free interface for much larger TMR ratios.

###Capping layer influence and isotropic in-plane upper critical field of the superconductivity at the FeSe/SrTiO3 interface|Yanan Li,Ziqiao Wang,Run Xiao,Qi Li,Ke Wang,Anthony Richardella,Jian Wang,Nitin Samarth###

Capping layer influence and isotropic in-plane upper critical field of the superconductivity at the FeSe/SrTiO3 interface. Understanding the superconductivity at the interface of FeSe/SrTiO3 is a
problem of great contemporary interest due to the significant increase in
critical temperature (Tc) compared to that of bulk FeSe, as well as the
possibility of an unconventional pairing mechanism and topological
superconductivity. We report a study of the influence of a capping layer on
superconductivity in thin films of FeSe grown on SrTiO3 using molecular beam
epitaxy. We used in vacuo four-probe electrical resistance measurements and ex
situ magneto-transport measurements to examine the effect of three capping
layers that provide distinctly different charge transfer into FeSe: compound
FeTe, non-metallic Te, and metallic Zr. Our results show that FeTe provides an
optimal cap that barely influences the inherent Tc found in pristine
FeSe/SrTiO3, while the transfer of holes from a non-metallic Te cap completely
suppresses superconductivity and leads to insulating behavior. Finally, we used
ex situ magnetoresistance measurements in FeTe-capped FeSe films to extract the
angular dependence of the in-plane upper critical magnetic field. Our
observations reveal an almost isotropic in-plane upper critical field,
providing insight into the symmetry and pairing mechanism of high temperature
superconductivity in FeSe.

###Landau Quantization and Highly Mobile Fermions in an Insulator|Pengjie Wang,Guo Yu,Yanyu Jia,Michael Onyszczak,F. Alexandre Cevallos,Shiming Lei,Sebastian Klemenz,Kenji Watanabe,Takashi Taniguchi,Robert J. Cava,Leslie M. Schoop,Sanfeng Wu###

Landau Quantization and Highly Mobile Fermions in an Insulator. In strongly correlated materials, quasiparticle excitations can carry
fractional quantum numbers. An intriguing possibility is the formation of
fractionalized, charge-neutral fermions, e.g., spinons and fermionic excitons,
that result in neutral Fermi surfaces and Landau quantization in an insulator.
While previous experiments in quantum spin liquids, topological Kondo
insulators, and quantum Hall systems have hinted at charge-neutral Fermi
surfaces, evidence for their existence remains far from conclusive. Here we
report experimental observation of Landau quantization in a two dimensional
(2D) insulator, i.e., monolayer tungsten ditelluride (WTe$_{2}$), a large gap
topological insulator. Using a detection scheme that avoids edge contributions,
we uncover strikingly large quantum oscillations in the monolayer insulator's
magnetoresistance, with an onset field as small as ~ 0.5 tesla. Despite the
huge resistance, the oscillation profile, which exhibits many periods, mimics
the Shubnikov-de Haas oscillations in metals. Remarkably, at ultralow
temperatures the observed oscillations evolve into discrete peaks near 1.6
tesla, above which the Landau quantized regime is fully developed. Such a low
onset field of quantization is comparable to high-mobility conventional
two-dimensional electron gases. Our experiments call for further investigation
of the highly unusual ground state of the WTe$_{2}$ monolayer. This includes
the influence of device components and the possible existence of mobile
fermions and charge-neutral Fermi surfaces inside its insulating gap.

###Broadband terahertz probes of anisotropic magnetoresistance disentangle extrinsic and intrinsic contributions|Lukáš Nadvorník,Martin Borchert,Liane Brandt,Richard Schlitz,Koen A. de Mare,Karel Výborný,Ingrid Mertig,Gerhard Jakob,Matthias Kläui,Sebastian T. B. Goennenwein,Martin Wolf,Georg Woltersdorf,Tobias Kampfrath###

Broadband terahertz probes of anisotropic magnetoresistance disentangle extrinsic and intrinsic contributions. Anisotropic magnetoresistance (AMR) is a ubiquitous and versatile probe of
magnetic order in contemporary spintronics research. Its origins are usually
ascribed to extrinsic effects (i.e. spin-dependent electron scattering),
whereas intrinsic (i.e. scattering-independent) contributions are neglected.
Here, we measure AMR of polycrystalline thin films of the standard ferromagnets
Co, Ni, Ni81Fe19 and Ni50Fe50 over the frequency range from DC to 28 THz. The
large bandwidth covers the regimes of both diffusive and ballistic intraband
electron transport and, thus, allows us to separate extrinsic and intrinsic AMR
components. Analysis of the THz response based on Boltzmann transport theory
reveals that the AMR of the Ni, Ni81Fe19 and Ni50Fe50 samples is of
predominantly extrinsic nature. However, the Co thin film exhibits a sizeable
intrinsic AMR contribution, which is constant up to 28 THz and amounts to more
than 2/3 of the DC AMR contrast of 1%. These features are attributed to the
hexagonal structure of the Co crystallites. They are interesting for
applications in terahertz spintronics and terahertz photonics. Our results show
that broadband terahertz electromagnetic pulses provide new and contact-free
insights into magneto-transport phenomena of standard magnetic thin films on
ultrafast time scales.

###Spin torque gate magnetic field sensor|Hang Xie,Xin Chen,Ziyan Luo,Yihong Wu###

Spin torque gate magnetic field sensor. Spin-orbit torque provides an efficient pathway to manipulate the magnetic
state and magnetization dynamics of magnetic materials, which is crucial for
energy-efficient operation of a variety of spintronic devices such as magnetic
memory, logic, oscillator, and neuromorphic computing. Here, we describe and
experimentally demonstrate a strategy for the realization of a spin torque gate
magnetic field sensor with extremely simple structure by exploiting the
longitudinal field dependence of the spin torque driven magnetization
switching. Unlike most magnetoresistance sensors which require a delicate
magnetic bias to achieve a linear response to the external field, the spin
torque gate sensor can achieve the same without any magnetic bias, which
greatly simplifies the sensor structure. Furthermore, by driving the sensor
using an ac current, the dc offset is automatically suppressed, which
eliminates the need for a bridge or compensation circuit. We verify the concept
using the newly developed WTe2/Ti/CoFeB trilayer and demonstrate that the
sensor can work linearly in the range of 3-10 Oe with negligible dc offset.

###Synthesis of narrow SnTe nanowires using alloy nanoparticles|Pengzi Liu,Hyeuk Jin Han,Julia Wei,David J. Hynek,James L. Hart,Myung Geun Han,Christie J. Trimble,James R. Williams,Yimei Zhu,Judy J. Cha###

Synthesis of narrow SnTe nanowires using alloy nanoparticles. Topological crystalline insulator tin telluride (SnTe) provides a rich
playground to examine interactions of correlated electronic states, such as
ferroelectricity, topological surface states, and superconductivity. Making
SnTe into nanowires further induces novel electronic states due to
one-dimensional (1D) confinement effects. Thus, for transport measurements,
SnTe nanowires must be made narrow in their diameters to ensure the 1D
confinement and phase coherence of the topological surface electrons. This
study reports a facile growth method to produce narrow SnTe nanowires with a
high yield using alloy nanoparticles as growth catalysts. The average diameter
of the SnTe nanowires grown using the alloy nanoparticles is 85 nm, nearly a
factor of three reduction from the previous average diameter of 240 nm using
gold nanoparticles as growth catalysts. Transport measurements reveal the
effect of the nanowire diameter on the residual resistance ratio and
magnetoresistance. Particularly, the ferroelectric transition temperature for
SnTe is observed to change systematically with the nanowire diameter. In situ
cryogenic cooling of narrow SnTe nanowires in a transmission electron
microscope directly reveals the cubic to rhombohedral structural transition,
which is associated with the ferroelectric transition. Thus, these narrow SnTe
nanowires represent a model system to study electronic states arising from the
1D confinement, such as 1D topological superconductivity as well as a potential
multi-band superconductivity.

###The electron-phonon coupling constant, the Fermi temperature and unconventional superconductivity in the carbonaceous sulfur hydride 190 K superconductor|E. F. Talantsev###

The electron-phonon coupling constant, the Fermi temperature and unconventional superconductivity in the carbonaceous sulfur hydride 190 K superconductor. Recently, Snider et al (2020 Nature 586 373) reported on the observation of
superconductivity in highly-compressed carbonaceous sulfur hydride,
$H_x$$(S,C)_y$. The highest critical temperature in $H_x$$(S,C)_y$ by 5 K
exceeds previous record of Tc = 280 K reported by Somayazulu et al (2019 Phys.
Rev. Lett. 122 027001) for highly-compressed $La$$H_{10}$. In this paper we
analyze experimental temperature dependent magnetoresistance data, R(T,B),
reported by Snider et al. The analysis shows that $H_x$$(S,C)_y$ compound
exhibited Tc = 190 K (P = 210 GPa) has the electron-phonon coupling constant
$\lambda$$_{e-ph}$ = 2.0 and the ratio of critical temperature, Tc, to the
Fermi temperature, Tf, in the range of 0.011 < Tc/Tf < 0.018. These deduced
values are very close to ones reported for $H_x$$S$ at P = 155-165 GPa by
Drozdov et al (2015 Nature 525 73). This means that in all considered scenarios
the carbonaceous sulfur hydride 190 K superconductor falls into unconventional
superconductors band in the Uemura plot, where all other highly-compressed
super-hydride/deuterides are located. It should be noted that that our analysis
shows that all raw R(T,B) datasets for $H_x$$(S,C)_y$ samples for which Snider
et al (2020 Nature 586 373) reported Tc > 200 K cannot be characterized as
reliable data sources. Thus, independent experimental confirmation/disprove
high-Tc values in the carbonaceous sulfur hydride is required.

###Large Rashba unidirectional magnetoresistance in the Fe/Ge(111) interface states|T. Guillet,C. Zucchetti,A. Marty,G. Isella,C. Vergnaud,Q. Barbedienne,H. Jaffrès,N. Reyren,J. -M. George,A. Fert,M. Jamet###

Large Rashba unidirectional magnetoresistance in the Fe/Ge(111) interface states. The structure inversion asymmetry at surfaces and interfaces give rise to the
Rashba spin-orbit interaction (SOI), that breaks the spin degeneracy of surface
or interface states. Hence, when an electric current runs through a surface or
interface, this Rashba effect generates an effective magnetic field acting on
the electron spin. This provides an additional tool to manipulate the spin
state in materials such as Si and Ge that, in their bulk form, possess
inversion symmetry (or lack structural inersion asymmetry). The existence of
Rashba states could be demonstrated by photoemission spectroscopy at the
interface between different metals and Ge(111) and by spin-charge conversion
experiments at the Fe/Ge(111) interface even though made of two light elements.
In this work, we identify the fingerprint of the Rashba states at the
Fe/Ge(111) interface by magnetotransport measurements in the form of a large
unidirectional magnetoresistance of up to 0.1 \%. From its temperature
dependence, we find that the Rashba energy splitting is larger than in pure
Ge(111) subsurface states.

###Synthesis and characterization of vertically aligned La0.7Sr0.3MnO3:NiO nanocomposite thin films for spintronic applications|Gyanendra Panchal,Anjali Panchwanee,Manish Kumar,Katharina Fritsch,Ram Janay Choudhary,Deodutta Moreshwar Phase###

Synthesis and characterization of vertically aligned La0.7Sr0.3MnO3:NiO nanocomposite thin films for spintronic applications. The microstructures and interfaces of two-phase vertically aligned
nanocomposite (VAN) thin films play a key role in the design of spintronic
device architectures and their multifunctional properties. Here, we show how
the microstructures in self-assembled VAN thin films of La0.7Sr0.3MnO3:NiO
(LSMO:NiO) can be effectively tuned from nano-granular to nano-columnar, and to
nano-maze by controlling the number of laser shots from the two constituent
phase targets in the pulsed laser deposition (PLD) film growth. The observed
microstructural induced strain is found to significantly enhance the
magnetoresistance in a very broad temperature range between 10-240 K and to
modulate the in-plane exchange bias (EB), with the largest EB value observed in
the maximally strained heterostructures. Most interestingly, a unique
perpendicular exchange bias (PEB) effect is also observed for these
heterostructures with an enhanced PEB field of up to 230 Oe. X-ray magnetic
circular dichroism and training effect measurements demonstrate that the
observed EB is disorder-induced and arises due to the pinning of NiO
uncompensated moments at the disordered interface which is ferromagnetically
coupled with LSMO. Furthermore, systematic changes in the electronic structure
across the vertical interface related to a variation of the Mn3+/Mn4+ content
arise as a consequence of out-of-plane tensile strain.

###Thickness-dependent quantum transport of Weyl fermions in ultra-high-quality SrRuO3 films|Shingo Kaneta-Takada,Yuki K. Wakabayashi,Yoshiharu Krockenberger,Shinobu Ohya,Masaaki Tanaka,Yoshitaka Taniyasu,Hideki Yamamoto###

Thickness-dependent quantum transport of Weyl fermions in ultra-high-quality SrRuO3 films. The recent observation of Weyl fermions in the itinerant 4d ferromagnetic
perovskite SrRuO3 points to this material being a good platform for exploring
novel physics related to a pair of Weyl nodes in epitaxial heterostructures. In
this letter, we report the thickness-dependent magnetotransport properties of
ultra-high-quality epitaxial SrRuO3 films grown under optimized conditions on
SrTiO3 substrates. Signatures of Weyl fermion transport, i.e., unsaturated
linear positive magnetoresistance accompanied by a quantum oscillation having a
{\pi} Berry phase, were observed in films with thicknesses as small as 10 nm.
Residual resistivity increased with decreasing film thickness, indicating
disorder near the interface between SrRuO3 and the SrTiO3 substrate. Since this
disorder affects the magnetic and electrical properties of the films, the Curie
temperature decreases and the coercive field increases with decreasing
thickness. Thickness-dependent magnetotransport measurements revealed that the
threshold residual resistivity ratio (RRR) to observe Weyl fermion transport is
21. These results provide guidelines for realizing quantum transport of Weyl
fermions in SrRuO3 near heterointerfaces.

###Exceeding 400% tunnel magnetoresistance at room temperature in epitaxial Fe/MgO/Fe(001) spin-valve-type magnetic tunnel junctions|Thomas Scheike,Qingyi Xiang,Zhenchao Wen,Hiroaki Sukegawa,Tadakatsu Ohkubo,Kazuhiro Hono,Seiji Mitani###

Exceeding 400% tunnel magnetoresistance at room temperature in epitaxial Fe/MgO/Fe(001) spin-valve-type magnetic tunnel junctions. Giant tunnel magnetoresistance (TMR) ratios of 417% at room temperature (RT)
and 914% at 3 K were demonstrated in epitaxial Fe/MgO/Fe(001) exchanged-biased
spin-valve magnetic tunnel junctions (MTJs) by tuning growth conditions for
each layer, combining sputter deposition for the Fe layers, electron-beam
evaporation of the MgO barrier, and barrier interface tuning. Clear TMR
oscillation as a function of the MgO thickness with a large peak-to-valley
difference of ~80% was observed when the layers were grown on a highly
(001)-oriented Cr buffer layer. Specific features of the observed MTJs are
symmetric differential conductance (dI/dV) spectra for the bias polarity and
plateau-like deep local minima in dI/dV (parallel configuration) at |V| =
0.2~0.5 V. At 3K, fine structures with two dips emerge in the plateau-like
dI/dV, reflecting highly coherent tunneling through the Fe/MgO/Fe. We also
observed a 496% TMR ratio at RT by a 2.24-nm-thick-CoFe insertion at the
bottom-Fe/MgO interface.

###Non-planar geometrical effects on the magnetoelectrical signal in a three-dimensional nanomagnetic circuit|Fanfan Meng,Claire Donnelly,Claas Abert,Luka Skoric,Stuart Holmes,Zhuocong Xiao,Jung-Wei Liao,Peter J. Newton,Crispin H. W. Barnes,Dédalo Sanz-Hernández,Aurelio Hierro-Rodriguez,Dieter Suess,Russell P. Cowburn,Amalio Fernández-Pacheco###

Non-planar geometrical effects on the magnetoelectrical signal in a three-dimensional nanomagnetic circuit. Expanding nanomagnetism and spintronics into three dimensions (3D) offers
great opportunities for both fundamental and technological studies. However,
probing the influence of complex 3D geometries on magnetoelectrical phenomena
poses important experimental and theoretical challenges. In this work, we
investigate the magnetoelectrical signals of a ferromagnetic 3D nanodevice
integrated into a microelectronic circuit using direct-write nanofabrication.
Due to the 3D vectorial nature of both electrical current and magnetisation, a
complex superposition of several magnetoelectrical effects takes place. By
performing electrical measurements under the application of 3D magnetic fields,
in combination with macrospin simulations and finite element modelling, we
disentangle the superimposed effects, finding how a 3D geometry leads to
unusual angular dependences of well-known magnetotransport effects such as the
anomalous Hall effect. Crucially, our analysis also reveals a strong role of
the noncollinear demagnetising fields intrinsic to 3D nanostructures, which
results in an angular dependent magnon magnetoresistance contributing strongly
to the total magnetoelectrical signal. These findings are key to the
understanding of 3D spintronic systems and underpin further fundamental and
device-based studies.

###An insulating doped antiferromagnet with low magnetic symmetry as a room temperature spin conduit|Andrew Ross,Romain Lebrun,Lorenzo Baldrati,Akashdeep Kamra,Olena Gomonay,Shilei Ding,Felix Schreiber,Dirk Backes,Francesco Maccherozzi,Daniel A. Grave,Avner Rothschild,Jairo Sinova,Mathias Kläui###

An insulating doped antiferromagnet with low magnetic symmetry as a room temperature spin conduit. We report room temperature long-distance spin transport of magnons in
antiferromagnetic thin film hematite doped with Zn. The additional dopants
significantly alter the magnetic anisotropies, resulting in a complex
equilibrium spin structure that is capable of efficiently transporting spin
angular momentum at room temperature without the need for a well-defined, pure
easy-axis or easy-plane anisotropy. We find intrinsic magnon spin-diffusion
lengths of up to 1.5 {\mu}m, and magnetic domain governed decay lengths of 175
nm for the low frequency magnons, through electrical transport measurements
demonstrating that the introduction of non-magnetic dopants does not strongly
reduce the transport length scale showing that the magnetic damping of hematite
is not significantly increased. We observe a complex field dependence of the
non-local signal independent of the magnetic state visible in the local
magnetoresistance and direct magnetic imaging of the antiferromagnetic domain
structure. We explain our results in terms of a varying and
applied-field-dependent ellipticity of the magnon modes reaching the detector
electrode allowing us to tune the spin transport.

###Linear-in temperature resistivity from an isotropic Planckian scattering rate|G. Grissonnanche,Y. Fang,A. Legros,S. Verret,F. Laliberté,C. Collignon,J. Zhou,D. Graf,P. Goddard,L. Taillefer,B. J. Ramshaw###

Linear-in temperature resistivity from an isotropic Planckian scattering rate. A variety of "strange metals" exhibit resistivity that decreases linearly
with temperature as $T\rightarrow 0$, in contrast with conventional metals
where resistivity decreases as $T^2$. This $T$-linear resistivity has been
attributed to charge carriers scattering at a rate given by $\hbar/\tau=\alpha
k_{\rm B} T$, where $\alpha$ is a constant of order unity. This simple
relationship between the scattering rate and temperature is observed across a
wide variety of materials, suggesting a fundamental upper limit on
scattering---the "Planckian limit"---but little is known about the underlying
origins of this limit. Here we report a measurement of the angle-dependent
magnetoresistance (ADMR) of Nd-LSCO---a hole-doped cuprate that displays
$T$-linear resistivity down to the lowest measured temperatures. The ADMR
unveils a well-defined Fermi surface that agrees quantitatively with
angle-resolved photoemission spectroscopy (ARPES) measurements and reveals a
$T$-linear scattering rate that saturates the Planckian limit, namely $\alpha =
1.2 \pm 0.4$. Remarkably, we find that this Planckian scattering rate is
isotropic, i.e. it is independent of direction, in contrast with expectations
from "hot-spot" models. Our findings suggest that $T$-linear resistivity in
strange metals emerges from a momentum-independent inelastic scattering rate
that reaches the Planckian limit.

###Single pair of Weyl nodes in the spin-canted structure of EuCd$_2$As$_2$|K. M. Taddei,L. Yin,L. D. Sanjeewa,Y. Li,J. Xing,C. dela Cruz,D. Phelan,A. S. Sefat,D. Parker###

Single pair of Weyl nodes in the spin-canted structure of EuCd$_2$As$_2$. Time reversal symmetry breaking Weyl semimetals are unique among Weyl
materials in allowing the minimal number of Weyl points thus offering the
clearest signatures of the associated physics. Here we present neutron
diffraction, density functional theory and transport measurement results which
indicate that EuCd$_2$As$_2$ , under ambient field, strain and pressure, is
such a material with a single pair of Weyl points. Our work reveals a magnetic
structure (magnetic space group $C2'/m'$) with Eu moments pointing along the
[210] direction in-plane and canted $\sim$ 30$^{\circ}$ out-of-plane. Density
functional theory calculations using this structure show that the observed
canting drastically alters the relevant electronic bands, relative to the
in-plane order, leading to a single set of well defined Weyl points.
Furthermore, we find the canting angle can tune the distance of the Weyl points
above the Fermi level, with the smallest distance at low canting angles.
Finally, transport measurements of the anomalous Hall Effect and longitudinal
magnetoresistance exhibit properties indicative of a chiral anomaly, thus
supporting the neutron scattering and DFT results suggesting EuCd$_2$As$_2$ is
close to the ideal situation of the Weyl "Hydrogen atom".

###Evolution of possible Weyl semimetal states across the hole-doping induced Mott transition in pyrochlore iridates|Kentaro Ueda,Hikaru Fukuda,Ryoma Kaneko,Jun Fujioka,Yoshinori Tokura###

Evolution of possible Weyl semimetal states across the hole-doping induced Mott transition in pyrochlore iridates. We study possible Weyl semimetals of strongly-correlated electrons by
investigating magnetotransport properties in pyrochlore R2Ir2O7 (R=rare-earth
ions), choosing three types of R ions to design the exchange coupling scheme
between R 4f and Ir 5d moments; non-magnetic Eu (4f6), isotropic Gd (4f7), and
anisotropic Tb (4f8). In the doping-induced semimetallic state, distinctive
features of magnetoresistance and Hall effect are observed in R=Gd and Tb
compounds due to the effects of the exchange-enhanced isotropic and anisotropic
Zeeman fields, respectively, exemplifying the double Weyl semimetal and the
2-in 2-out line-node semimetal as predicted by theories. In particular, a Hall
angle of R=Gd compound is strongly enhanced to 1.5 % near above the critical
doping for the Mott transition. Furthermore, an unconventional Hall
contribution is discerned for a lower doping regime of R=Gd compound, which can
be ascribed to the emergence of Weyl points with the field-distorted all-in
all-out order state. These findings indicate that the hole-doping induced Mott
transition as well as the characteristic f-d exchange interaction stabilizes
versatile topological semimetal states in a wide range of material parameter
space.

###Detection of graphene's divergent orbital diamagnetism at the Dirac point|J. Vallejo,N. J. Wu,C. Fermon,M. Pannetier-Lecoeur,T. Wakamura,K. Watanabe,T. Tanigushi,T. Pellegrin,A. Bernard,S. Daddinounou,V. Bouchiat,S. Guéron,M. Ferrier,G. Montambaux,H. Bouchiat###

Detection of graphene's divergent orbital diamagnetism at the Dirac point. The electronic properties of graphene have been intensively investigated over
the last decade, and signatures of the remarkable features of its linear Dirac
spectrum have been displayed using transport and spectroscopy experiments. In
contrast, the orbital magnetism of graphene, which is one of the most
fundamental signature of the characteristic Berry phase of graphene's
electronic wave functions, has not yet been measured in a single flake. In
particular, the striking prediction of a divergent diamagnetic response at zero
doping calls for an experimental test. Using a highly sensitive Giant
Magnetoresistance sensor (GMR) we have measured the gate voltage-dependent
magnetization of a single graphene monolayer encapsulated between boron nitride
crystals. The signal exhibits a diamagnetic peak at the Dirac point whose
magnetic field and temperature dependences agree with theoretical predictions
starting from the work of Mc Clure \cite{McClure1956}. Our measurements open a
new field of investigation of orbital currents in graphene and 2D topological
materials, offering a new means to monitor Berry phase singularities and
explore correlated states generated by combined effects of Coulomb
interactions, strain or moir\'e potentials.

###Sondheimer oscillations as a probe of non-ohmic flow in type-II Weyl semimetal WP$_2$|Maarten R. van Delft,Yaxian Wang,Carsten Putzke,Jacopo Oswald,Georgios Varnavides,Christina A. C. Garcia,Chunyu Guo,Heinz Schmid,Vicky Süss,Horst Borrmann,Jonas Diaz,Yan Sun,Claudia Felser,Bernd Gotsmann,Prineha Narang,Philip J. W. Moll###

Sondheimer oscillations as a probe of non-ohmic flow in type-II Weyl semimetal WP$_2$. As conductors in electronic applications shrink, microscopic conduction
processes lead to strong deviations from Ohm's law. Depending on the length
scales of momentum conserving ($l_{MC}$) and relaxing ($l_{MR}$) electron
scattering, and the device size ($d$), current flows may shift from ohmic to
ballistic to hydrodynamic regimes and more exotic mixtures thereof. So far, an
in situ, in-operando methodology to obtain these parameters self-consistently
within a micro/nanodevice, and thereby identify its conduction regime, is
critically lacking. In this context, we exploit Sondheimer oscillations,
semi-classical magnetoresistance oscillations due to helical electronic motion,
as a method to obtain $l_{MR}$ in micro-devices even when $l_{MR}\gg d$. This
gives information on the bulk $l_{MR}$ complementary to quantum oscillations,
which are sensitive to all scattering processes. We extract $l_{MR}$ from the
Sondheimer amplitude in the topological semi-metal WP$_2$, at elevated
temperatures up to $T\sim 50$~K, in a range most relevant for hydrodynamic
transport phenomena. Our data on micrometer-sized devices are in excellent
agreement with experimental reports of the large bulk $l_{MR}$ and thus confirm
that WP$_2$ can be microfabricated without degradation. Indeed, the measured
scattering rates match well with those of theoretically predicted
electron-phonon scattering, thus supporting the notion of strong momentum
exchange between electrons and phonons in WP$_2$ at these temperatures. These
results conclusively establish Sondheimer oscillations as a quantitative probe
of $l_{MR}$ in micro-devices in studying non-ohmic electron flow.

###Magnetoresistance and Kondo effect in the nodal-line semimetal VAs$_2$|Shuijin Chen,Zhefeng Lou,Yuxing Zhou,Qin Chen,Binjie Xu,Jianhua Du,Jinhu Yang,Haangdong Wang,Minghu Fang###

Magnetoresistance and Kondo effect in the nodal-line semimetal VAs$_2$. We performed calculations of the electronic band structure and the Fermi
surface as well as measured the longitudinal resistivity $\rho_{xx}(T,H)$, Hall
resistivity $\rho_{xy}(T,H)$, and magnetic susceptibility as a function of
temperature and various magnetic fields for VAs$_2$ with a monoclinic crystal
structure. The band structure calculations show that VAs$_2$ is a nodal-line
semimetal when spin-orbit coupling is ignored. The emergence of a minimum at
around 11 K in $\rho_{xx}(T)$ measured at $H$ = 0 demonstrates that an
additional magnetic impurity (V$^{4+}$, $S$ = 1/2) occurs in VAs$_2$ single
crystals, evidenced by both the fitting of $\rho_{xx}(T)$ data and the
susceptibility measurements. It was found that a large positive
magnetoresistance (MR) reaching 649\% at 10 K and 9 T, its nearly quadratic
field dependence, and a field-induced up-turn behavior of $\rho_{xx}(T)$ emerge
also in VAs$_2$, although MR is not so large due to the existence of additional
scattering compared with other topological nontrival/trival semimetals. The
observed properties are attributed to a perfect charge-carrier compensation,
which is evidenced by both calculations relying on the Fermi surface and the
Hall resistivity measurements. These results indicate that the compounds
containing V ($3d^3 4s^2$) element as a platform for studying the influence of
magnetic impurities to the topological properties.

###Identifying the fingerprints of topological states by tuning magnetoresistance in a semimetal: the case of topological half-Heusler Pt1-xAuxLuSb|Shouvik Chatterjee,Felipe Crasto de Lima,John A. Logan,Yuan Fang,Hadass Inbar,Aranya Goswami,Connor Dempsey,Shoaib Khalid,Tobias Brown-Heft,Yu-Hao Chang,Taozhi Guo,Daniel Pennacchio,Nathaniel Wilson,Jason Dong,Shalinee Chikara,Alexey Suslov,Alexei V. Fedorov,Dan Read,Jennifer Cano,Anderson Janotti,Christopher J. Palmstrom###

Identifying the fingerprints of topological states by tuning magnetoresistance in a semimetal: the case of topological half-Heusler Pt1-xAuxLuSb. Topological materials often exhibit remarkably linear, non-saturating
magnetoresistance (LMR), which is both of scientific and technological
importance. However, the role of topologically non-trivial states in the
emergence of such a behaviour has eluded clear demonstration in experiments.
Here, by reducing the coupling between the topological surface states (TSS) and
the bulk carriers we controllably tune the LMR behavior in Pt1-xAuxLuSb into
distinct plateaus in Hall resistance, which we show arise from a quantum Hall
phase. This allowed us to reveal how smearing of the Landau levels, which
otherwise give rise to a quantum Hall phase, results in an LMR behavior due to
strong interaction between the TSS with a positive g-factor and the bulk
carriers. We establish that controlling the coupling strength between the
surface and the bulk carriers in topological materials can bring about dramatic
changes in their magnetotransport behavior. In addition, our work outlines a
strategy to reveal macroscopic physical observables of TSS in compounds with a
semi-metallic bulk band structure, as is the case in multi-functional Heusler
compounds, thereby opening up opportunities for their utilization in hybrid
quantum structures.

###Observation of triplet superconductivity in CoSi$_2$/TiSi$_2$ heterostructures|Shao-Pin Chiu,C. C. Tsuei,Sheng-Shiuan Yeh,Fu-Chun Zhang,Stefan Kirchner,Juhn-Jong Lin###

Observation of triplet superconductivity in CoSi$_2$/TiSi$_2$ heterostructures. Unconventional superconductivity and in particular triplet superconductivity
have been front and center of topological materials and quantum technology
research. Here we report our observation of triplet superconductivity in
nonmagnetic CoSi$_2$/TiSi$_2$ heterostructures on silicon. CoSi$_2$ undergoes a
sharp superconducting transition at a critical temperature $T_c \approx$ 1.5 K,
while TiSi$_2$ is a normal metal. We investigate conductance spectra of both
two-terminal CoSi$_2$/TiSi$_2$ tunnel junctions and three-terminal T-shaped
CoSi$_2$/TiSi$_2$ superconducting proximity structures. We report an
unexpectedly large spin-orbit coupling in CoSi$_2$ heterostructures. Below
$T_c$, we observe (1) a narrow zero-bias conductance peak on top of a broad
hump, accompanied by two symmetric side dips in the tunnel junctions, (2) a
narrow zero-bias conductance peak in T-shaped structures, and (3) hysteresis in
the junction magnetoresistance. These three independent and complementary
observations are indicative of chiral $p$-wave pairing in CoSi$_2$/TiSi$_2$
heterostructures. This chiral triplet superconductivity and the excellent
fabrication compatibility of CoSi$_2$ and TiSi$_2$ with present-day silicon
integrated-circuit technology facilitate full scalability for potential use in
quantum-computing devices.

###Giant anisotropic magnetoresistance with dual-four-fold symmetry in CaMnO3/CaIrO3 heterostructures|Suman Sardar,Megha Vagadia,Tejas Tank Sarmistha Das,Brandon Gunn,Parul Pandey,R. Hübner,Fanny Rodolakis,Gilberto Fabbris,Yongseong Choi,Daniel Haskel,Alex Frano,D. S. Rana###

Giant anisotropic magnetoresistance with dual-four-fold symmetry in CaMnO3/CaIrO3 heterostructures. The realization of four-fold anisotropic magnetoresistance (AMR) in novel
3d-5d heterostructures has boosted major efforts in antiferromagnetic
spintronics. However, despite the potential of incorporating strong spin-orbit
coupling, only small AMR signals have been detected thus far, prompting a
search for new mechanisms to enhance the signal. In this study on CaMnO3/CaIrO3
heterostructures, we report a unique dual-four-fold symmetric 70% AMR; a signal
two orders of magnitude larger than previously observed in similar systems. We
find that one order is enhanced by tuning a large biaxial anisotropy through
octahedral tilts of similar sense in the constituent layers, while the second
order is triggered by a spin-flop transition in a nearly Mott-type phase.
Dynamics between these two phenomena as evidenced by the step-like AMR and a
superimposed biaxial-anisotropy-induced AMR capture a subtle interplay of
pseudospin coupling with the lattice and external magnetic field. Our study
shows that a combination of charge-transfer, interlayer coupling, and a
spin-flop transition can yield a giant AMR relevant for sensing and
antiferromagnetic memory applications.

###Detection of magnetic gap in the topological surface states of MnBi2Te4|Haoran Ji,Yanzhao Liu,He Wang,Jiawei Luo,Jiaheng Li,Hao Li,Yang Wu,Yong Xu,Jian Wang###

Detection of magnetic gap in the topological surface states of MnBi2Te4. Recently, intrinsic antiferromagnetic topological insulator MnBi2Te4 has
drawn intense research interest and leads to plenty of significant progress in
physics and materials science by hosting quantum anomalous Hall effect, axion
insulator state, and other quantum phases. An essential ingredient to realize
these quantum states is the magnetic gap in the topological surface states
induced by the out-of-plane ferromagnetism on the surface of MnBi2Te4. However,
the experimental observations of the surface gap remain controversial. Here, we
report the observation of the surface gap via the point contact tunneling
spectroscopy. In agreement with theoretical calculations, the gap size is
around 50 meV, which vanishes as the sample becomes paramagnetic with
increasing temperature. The magnetoresistance hysteresis is detected through
the point contact junction on the sample surface with an out-of-plane magnetic
field, substantiating the surface ferromagnetism. Furthermore, the non-zero
transport spin polarization coming from the ferromagnetism is determined by the
point contact Andreev reflection spectroscopy. Combining these results, the
magnetism-induced gap in topological surface states of MnBi2Te4 is revealed.

###Giant anisotropic magnetoresistance in Ising superconductor-magnetic insulator tunnel junctions|Kaifei Kang,Shengwei Jiang,Helmuth Berger,Kenji Watanabe,Takashi Taniguchi,László Forró,Jie Shan,Kin Fai Mak###

Giant anisotropic magnetoresistance in Ising superconductor-magnetic insulator tunnel junctions. Superconductivity and magnetism are generally incompatible because of the
opposing requirement on electron spin alignment. When combined, they produce a
multitude of fascinating phenomena, including unconventional superconductivity
and topological superconductivity. The emergence of two-dimensional (2D)layered
superconducting and magnetic materials that can form nanoscale junctions with
atomically sharp interfaces presents an ideal laboratory to explore new
phenomena from coexisting superconductivity and magnetic ordering. Here we
report tunneling spectroscopy under an in-plane magnetic field of
superconductor-ferromagnet-superconductor (S/F/S) tunnel junctions that are
made of 2D Ising superconductor NbSe2 and ferromagnetic insulator CrBr3. We
observe nearly 100% tunneling anisotropic magnetoresistance (AMR), that is,
difference in tunnel resistance upon changing magnetization direction from
out-of-plane to inplane. The giant tunneling AMR is induced by
superconductivity, particularly, a result of interfacial magnetic exchange
coupling and spin-dependent quasiparticle scattering. We also observe an
intriguing magnetic hysteresis effect in superconducting gap energy and
quasiparticle scattering rate with a critical temperature that is 2 K below the
superconducting transition temperature. Our study paves the path for exploring
superconducting spintronic and unconventional superconductivity in van der
Waals heterostructures.

###Magnetic field-tuned quantum criticality in optimally electron-doped cuprate thin films|Xu Zhang,Heshan Yu,Qihong Chen,Runqiu Yang,Ge He,Ziquan Lin,Qian Li,Jie Yuan,Beiyi Zhu,Liang Li,Yi-feng Yang,Tao Xiang,Rong-Gen Cai,Anna Kusmartseva,F. V. Kusmartsev,Jun-Feng Wang,Kui Jin###

Magnetic field-tuned quantum criticality in optimally electron-doped cuprate thin films. Antiferromagnetic (AF) spin fluctuations are commonly believed to play a key
role in electron pairing of cuprate superconductors. In electron-doped
cuprates, it is still in paradox about the interplay among different electronic
states in quantum perturbations, especially between superconducting and
magnetic states. Here, we report a systematic transport study on
cation-optimized La2-xCexCuO4 (x = 0.10) thin films in high magnetic fields. We
find an AF quantum phase transition near 60 T, where the Hall number jumps from
nH =-x to nH = 1-x, resembling the change of nH at the AF boundary (xAF = 0.14)
tuned by Ce doping. In the AF region a spin dependent state manifesting
anomalous positive magnetoresistance is observed, which is closely related to
superconductivity. Once the AF state is suppressed by magnetic field, a
polarized ferromagnetic state is predicted, reminiscent of the recently
reported ferromagnetic state at the quantum endpoint of the superconducting
dome by Ce doping. The magnetic field that drives phase transitions in a
similar but distinct manner to doping thereby provides a unique perspective to
understand the quantum criticality of electron-doped cuprates.

###Structural and transport properties of highly Ru-deficient SrRu0.7O3 thin films prepared by molecular beam epitaxy: comparison with stoichiometric SrRuO3|Yuki K. Wakabayashi,Shingo Kaneta-Takada,Yoshiharu Krockenberger,Kosuke Takiguchi,Shinobu Ohya,Masaaki Tanaka,Yoshitaka Taniyasu,Hideki Yamamoto###

Structural and transport properties of highly Ru-deficient SrRu0.7O3 thin films prepared by molecular beam epitaxy: comparison with stoichiometric SrRuO3. We investigate structural and transport properties of highly Ru-deficient
SrRu0.7O3 thin films prepared by molecular beam epitaxy on (001) SrTiO3
substrates. To distinguish the influence of the two types of disorders in the
films, Ru vacancies within lattices and disorders near the interface, SrRu0.7O3
thin films with various thicknesses (t = 1-60 nm) were prepared. It was found
that the influence of the former dominates the electrical and magnetic
properties when t > 5-10 nm, while that of the latter does when t < 5-10 nm.
Structural characterizations revealed that the crystallinity, in terms of the
Sr and O sublattices, of SrRu0.7O3 thin films, is as high as that of the
ultrahigh-quality SrRuO3 ones. The Curie temperature (TC) analysis elucidated
that SrRu0.7O3 (TC = 140 K) is a material distinct from SrRuO3 (TC = 150 K).
Despite the large Ru deficiency (30%), the SrRu0.7O3 films showed metallic
conduction when t > 5 nm. In high-field magnetoresistance measurements, the
fascinating phenomenon of Weyl fermion transport was not observed for the
SrRu0.7O3 thin films irrespective of thickness, which is in contrast to the
stoichiometric SrRuO3 films. The (magneto)transport properties suggest that a
picture of carrier scattering due to the Ru vacancies is appropriate for
SrRu0.7O3, and also that proper stoichiometry control is a prerequisite to
utilizing the full potential of SrRuO3 as a magnetic Weyl semimetal and
two-dimensional spin-polarized system. Nevertheless, the large tolerance in Ru
composition (30 %) to metallic conduction is advantageous for some practical
applications where SrRu1-xO3 is exploited as an epitaxial conducting layer.

###Oxygen doping and polaron magnetic coupling in Alq$_3$ films|Andrea Droghetti###

Oxygen doping and polaron magnetic coupling in Alq$_3$ films. The understanding of the Physics underlying the performances of organic
spin-valve devices is still incomplete. According to some recent models, spin
transport takes place in an impurity band inside the fundamental gap of organic
semiconductors. This seems to be confirmed by recent experiments performed with
La$_{0.7}$Sr$_{0.3}$MnO$_3$/Alq$_3$/AlO$_x$/Co devices. The reported results
suggest a possible correlation between the magnetoresistance and the variable
oxygen doping in the Alq$_3$ spacer. In this paper we investigate by means of
first-principles calculations the electronic and magnetic properties of O$_2$
molecules and ions in Alq$_3$ films to establish whether oxygen plays any
important role for spin transport in
La$_{0.7}$Sr$_{0.3}$MnO$_3$/Alq$_3$/AlO$_x$/Co devices. The conclusion is that
it does not. In fact, we show that O$_2$ molecules do not form an impurity band
and there is no magnetic interaction between them. In contrast, we suggest that
spin-transport may be enabled by the direct exchange coupling between Alq$_3^-$
ions.

###Room-temperature colossal magnetoresistance in terraced single-layer graphene|J. X. Hu,J. Gou,M. Yang,G. J. Omar,J. Y. Tan,S. W. Zeng,Y. P. Liu,K. Han,Z. S. Lim,Z. Huang,A. T. S. Wee,A. Ariando###

Room-temperature colossal magnetoresistance in terraced single-layer graphene. Disorder-induced magnetoresistance (MR) effect is quadratic at low
perpendicular magnetic fields and linear at high fields. This effect is
technologically appealing, especially in the two-dimensional (2D) materials
such as graphene, since it offers potential applications in magnetic sensors
with nanoscale spatial resolution. However, it is a great challenge to realize
a graphene magnetic sensor based on this effect because of the difficulty in
controlling the spatial distribution of disorder and enhancing the MR
sensitivity in the single-layer regime. Here, we report a room-temperature
colossal MR of up to 5,000% at 9 T in terraced single-layer graphene. By
laminating single-layer graphene on a terraced substrate, such as TiO2
terminated SrTiO3, we demonstrate a universal one order of magnitude
enhancement in the MR compared to conventional single-layer graphene devices.
Strikingly, a colossal MR of >1,000% was also achieved in the terraced graphene
even at a high carrier density of ~1012 cm-2. Systematic studies of the MR of
single-layer graphene on various oxide- and non-oxide-based terraced surfaces
demonstrate that the terraced structure is the dominant factor driving the MR
enhancement. Our results open a new route for tailoring the physical property
of 2D materials by engineering the strain through a terraced substrate.

###Magnon-mediated interlayer coupling in an all-antiferromagnetic junction|Yongjian Zhou,Liyang Liao,Xiaofeng Zhou,Hua Bai,Mingkun Zhao,Caihua Wan,Siqi Yin,Lin Huang,Tingwen Guo,Lei Han,Ruyi Chen,Zhiyuan Zhou,Xiufeng Han,Feng Pan,Cheng Song###

Magnon-mediated interlayer coupling in an all-antiferromagnetic junction. The interlayer coupling mediated by fermions in ferromagnets brings about
parallel and anti-parallel magnetization orientations of two magnetic layers,
resulting in the giant magnetoresistance, which forms the foundation in
spintronics and accelerates the development of information technology. However,
the interlayer coupling mediated by another kind of quasi-particle, boson, is
still lacking. Here we demonstrate such a static interlayer coupling at room
temperature in an antiferromagnetic junction Fe2O3/Cr2O3/Fe2O3, where the two
antiferromagnetic Fe2O3 layers are functional materials and the
antiferromagnetic Cr2O3 layer serves as a spacer. The N\'eel vectors in the top
and bottom Fe2O3 are strongly orthogonally coupled, which is bridged by a
typical bosonic excitation (magnon) in the Cr2O3 spacer. Such an orthogonally
coupling exceeds the category of traditional collinear interlayer coupling via
fermions in ground state, reflecting the fluctuating nature of the magnons, as
supported by our magnon quantum well model. Besides the fundamental
significance on the quasi-particle-mediated interaction, the strong coupling in
an antiferromagnetic magnon junction makes it a realistic candidate for
practical antiferromagnetic spintronics and magnonics with ultrahigh-density
integration.

###A Colossal Electroresistance response, accompanied by metal-insulator transition, in a mixed-valent vanadate|Rafikul Ali Saha,Abhisek Bandyopadhyay,Irene Schiesaro,Carlo Meneghini,Sugata Ray###

A Colossal Electroresistance response, accompanied by metal-insulator transition, in a mixed-valent vanadate. Colossal electroresistance (CER) in manganites, i.e., a large change in
electrical resistance under the influence of either an applied electric field
or an applied electric current, has often been described as complimentary to
the colossal magnetoresistance (CMR) effect. Mixed valent vanadates with active
t2g and empty eg orbitals, unlike manganites, have not naturally been discussed
in this context, as double exchange based CMR is not realizable in them.
However, presence of coupled spin and orbital degrees of freedom,
metal-insulator transition (MIT) accompanied by orbital order-disorder
transition, etc., anyway make the vanadates an exciting group of materials.
Here we probe a Fe-doped hollandite lead vanadate PbFe1.75V4.25O11 (PFVO),
which exhibits a clear MIT as a function of temperature. Most importantly, a
giant fall in the resistivity, indicative of a CER, as well as a systematic
shift in the MIT towards higher temperature are observed as a function of
applied electric current. Detailed structural, magnetic, thermodynamic and
transport studies point towards a complex interplay between orbital
order/disorder effect, MIT and double exchange in this system.

###Recent progress and challenges in magnetic tunnel junctions with 2D materials for spintronic applications|Lishu Zhang,Jun Zhou,Hui Li,Lei Shen,Yuan Ping Feng###

Recent progress and challenges in magnetic tunnel junctions with 2D materials for spintronic applications. As Moore's law is gradually losing its effectiveness, developing alternative
high-speed and low-energy-consuming information technology with post-silicon
advanced materials is urgently needed. The successful application of tunneling
magnetoresistance (TMR) in magnetic tunnel junctions (MTJs) has given rise to a
tremendous economic impact on magnetic informatics, including MRAM,
radio-frequency sensors, microwave generators and neuromorphic computing
networks. The emergence of two-dimensional (2D) materials brings opportunities
for MTJs based on 2D materials which have many attractive characters and
advantages. Especially, the recently discovered intrinsic 2D ferromagnetic
materials with high spin-polarization hold the promise for next-generation
nanoscale MTJs. With the development of advanced 2D materials, many efforts on
MTJs with 2D materials have been made both theoretically and experimentally.
Various 2D materials, such as semi-metallic graphene, insulating h-BN,
semiconducting MoS2, magnetic semiconducting CrI3, magnetic metallic Fe3GeTe2
and some other recently emerged 2D materials are discussed as the electrodes
and/or central scattering materials of MTJs in this review. We discuss the
fundamental and main issues facing MTJs, and review the current progress made
with 2D MTJs, briefly comment on work with some specific 2D materials, and
highlight how they address the current challenges in MTJs, and finally offer an
outlook and perspective of 2D MTJs.

###Monopole density and antiferromagnetic domain control in spin-ice iridates|M. J. Pearce,K. Götze,A. Szabó,T. S. Sikkenk,M. R. Lees,A. T. Boothroyd,D. Prabhakaran,C. Castelnovo,P. A. Goddard###

Monopole density and antiferromagnetic domain control in spin-ice iridates. Frustration in magnetic systems is fertile ground for complex behaviour,
including unconventional ground states with emergent symmetries, topological
properties, and exotic excitations. A canonical example is the emergence of
magnetic-charge-carrying quasiparticles in spin-ice compounds. Despite
extensive work, a reliable experimental indicator of the density of these
magnetic monopoles in spin-ice systems is yet to be found. Here, using
measurements on single crystals of Ho$_{2}$Ir$_{2}$O$_{7}$ in combination with
dipolar Monte Carlo simulations, we show that the magnetoresistance is highly
sensitive to the density of monopoles. Moreover, we find that for the
orientations of magnetic field in which the monopole density is enhanced, a
strong coupling emerges between the magnetic charges on the holmium sublattice
and the antiferromagnetically ordered iridium ions, leading to an ability to
manipulate the antiferromagnetic domains via a uniform external field. Our
results pave the way to a quantitative experimental measure of monopole density
and provide a powerful illustration of the interplay between the various
magnetic and electronic degrees of freedom in the frustrated pyrochlore
iridates. This interdependence holds promise for potential functional
properties arising from the link between magnetic and electric charges, as well
as for the control of antiferromagnetic domain walls, a key goal in the design
of next-generation spintronic devices.

###Stability of multielectron bubbles in high Landau levels|Dohyung Ro,S. A. Myers,N. Deng,J. D. Watson,M. J. Manfra,L. N Pfeiffer,K. W. West,G. A. Csáthy###

Stability of multielectron bubbles in high Landau levels. We study multielectron bubble phases in the $N=2$ and $N=3$ Landau levels in
a high mobility GaAs/AlGaAs sample. We found that the longitudinal
magnetoresistance versus temperature curves in the multielectron bubble region
exhibit sharp peaks, irrespective of the Landau level index. We associate these
peaks with an enhanced scattering caused by thermally fluctuating domains of a
bubble phase and a uniform uncorrelated electron liquid at the onset of the
bubble phases. Within the $N=3$ Landau level, onset temperatures of
three-electron and two-electron bubbles exhibit linear trends with respect to
the filling factor; the onset temperatures of three-electron bubbles are
systematically higher than those of two-electron bubbles. Furthermore, onset
temperatures of the two-electron bubble phases across $N=2$ and $N=3$ Landau
levels are similar, but exhibit an offset. This offset and the dominant nature
of the three-electron bubbles in the $N=3$ Landau level reveals the role of the
short-range part of the electron-electron interaction in the formation of the
bubbles.

###A low-cost flexible instrument made of off-the-shelf components for pulsed eddy current testing: overview and application to pseudo-noise excitation|Hamed Malekmohammadi,Andrea Migali,Stefano Laureti,Marco Ricci###

A low-cost flexible instrument made of off-the-shelf components for pulsed eddy current testing: overview and application to pseudo-noise excitation. A flexible and low-cost device for eddy current non-destructive testing made
of off-the-shelf components is described. The proposed system is compact and
easy to operate, and it consists of a dual H-bridge stepper motor driver, a
coil winded in-house on an additively manufactured support, a tunnel
magnetoresistance sensor, and a data generation/acquisition module. For the
latter, two different commercial devices have been used, and both setups have
been then tested on a benchmark sample to detect small artificial cracks. The
system can flexibly generate the square pulse or square wave with tunable
duration and frequency, as well as pseudo-noise binary waveforms that are here
used in combination with pulse-compression to increase the inspection
sensitivity with respect to standard pulsed eddy current testing. A benchmark
sample was analysed, and all the defects were correctly located, demonstrating
the good detection capability of the sensor. This was achieved by assembling a
very low-cost handy device, which can be further improved in portability and
performances with the use of different off-the-shelf components, and that can
be easily integrated with single-board PC, paving the way for future
developments in this field.

###Unusual high-field metal in a Kondo insulator|Ziji Xiang,Lu Chen,Kuan-Wen Chen,Colin Tinsman,Yuki Sato,Tomoya Asaba,Helen Lu,Yuichi Kasahara,Marcelo Jaime,Fedor Balakirev,Fumitoshi Iga,Yuji Matsuda,John Singleton,Lu Li###

Unusual high-field metal in a Kondo insulator. Within condensed-matter systems, strong electronic interactions often lead to
exotic quantum phases. A recent manifestation of this is the unexpected
observation of magnetic quantum oscillations and metallic thermal transport,
both properties of systems with Fermi surfaces of itinerant quasiparticles, in
the Kondo insulators SmB6 and YbB$_{12}$. To understand these phenomena, it is
informative to study their evolution as the energy gap of the Kondo-Insulator
state is closed by a large magnetic field. We show here that both the
quantum-oscillation frequency and the cyclotron mass display a strong field
dependence in the resulting high-field metallic state in $_{12}$. By tracking
the Fermi-surface area, we conclude that the same quasiparticle band gives rise
to the quantum oscillations in both insulating and metallic states. These data
are understood most simply using a two-fluid picture where unusual
quasiparticles, contributing little or nothing to charge transport, coexist
with conventional fermions. In the metallic state this leads to a heavy-fermion
bad metal with negligible magnetoresistance, relatively high resistivity and a
very large Kadowaki-Woods ratio, underlining the exotic nature of the fermion
ensemble inhabiting $_{12}$.

###Dimensional Control of Octahedral Tilt in SrRuO3 via Infinite-layered Oxides|Shan Lin,Qinghua Zhang,Xiahan Sang,Jiali Zhao,Sheng Cheng,Amanda Huon,Qiao Jin,Shuang Chen,Shengru Chen,Haizhong Guo,Meng He,Chen Ge,Can Wang,Jia-Ou Wang,Michael R. Fitzsimmons,Lin Gu,Tao Zhu,Kui-juan Jin,Er-Jia Guo###

Dimensional Control of Octahedral Tilt in SrRuO3 via Infinite-layered Oxides. Manipulation of octahedral distortion at atomic length scale is an effective
means to tune the physical ground states of functional oxides. Previous work
demonstrates that epitaxial strain and film thickness are variable parameters
to modify the octahedral rotation and tilt. However, selective control of
bonding geometry by structural propagation from adjacent layers is rarely
studied. Here we propose a new route to tune the ferromagnetic response in
SrRuO3 (SRO) ultrathin layers by oxygen coordination of adjacent SrCuO2 (SCO)
layers. The infinite-layered CuO2 in SCO exhibits a structural transformation
from "planar-type" to "chain-type" as reducing film thickness. These two
orientations dramatically modify the polyhedral connectivity at the interface,
thus altering the octahedral distortion of SRO. The local structural variation
changes the spin state of Ru and hybridization strength between Ru 4d and O 2p
orbitals, leading to a significant change in the magnetoresistance and
anomalous Hall resistivity of SRO layers. These findings could launch further
investigations into adaptive control of magnetoelectric properties in quantum
oxide heterostructures using oxygen coordination.

###Understanding the role of exchange and correlations in complex oxides under strain and oxide heterostructures|Hrishit Banerjee###

Understanding the role of exchange and correlations in complex oxides under strain and oxide heterostructures. The study of complex oxides and oxide heterostructures have dominated the
field of experimental and theoretical condensed matter research for the better
part of the last few decades. Powerful experimental techniques like molecular
beam epitaxy and pulsed laser deposition have made fabrication of oxide
heterostructures with atomically sharp interfaces possible, while more and more
sophisticated handling of exchange and correlations within first principles
methods including density functional theory (DFT) supplemented with Hubbard U
corrections and hybrid functionals, and beyond DFT techniques like dynamical
mean field theory (DMFT) have made understanding of such correlated oxides and
oxide interfaces easier. The emergence of the high mobility two dimensional
electron gas with fascinating properties like giant photoconductance, large
negative magnetoresistance, superconductivity, ferromagnetism, and the
mysterious coexistence of the latter two have indeed caught the attention of
condensed matter community at large. Similarly strain tuning of oxides have
generated considerable interest particularly after the recent discovery of
piezoelectric methods of strain generation. Theoretical understanding and
prediction of the possible exotic phases emerging in such complex oxides both
under strain and in heterostructures will eventually lead to better design of
device applications in this new emerging field of oxide electronics, along with
possible discovery of exotic physics in condensed matter systems which may be
of wider significance! In this review we briefly look at theoretical studies of
novel phenomena in oxides under strain and oxide heterostructures, and try to
understand the role of exchange and particularly correlation in giving rise to
such exotic electronic states.

###Thin Film Growth of Heavy Fermion Chiral Magnet YbNi3Al9|Hiroaki Shishido,Akira Okumura,Tatsuya Saimyoji,Shota Nakamura,Shigeo Ohara,Yoshihiko Togawa###

Thin Film Growth of Heavy Fermion Chiral Magnet YbNi3Al9. We grew thin films of a heavy fermion chiral magnet YbNi$_3$Al$_9$ by using
molecular beam epitaxy. They were grown on $c$-plane sapphire substrates under
ultra-high vacuum while maintaining a deposition rate at a stoichiometric ratio
among Yb, Ni, and Al. The resulting thin films contain epitaxial grains with a
$c$ axis parallel to the substrate surface: The YbNi$_3$Al$_9$ $c$ axis is
parallel to the sapphire $b$ or $a$ axis. The temperature dependence of the
resistivity exhibits a typical feature of a dense Kondo system with a broad
shoulder structure at $\sim$40\,K, as well as a kink as a signature of the
chiral helimagnetic ordering at 3.6\,K. These features are consistent with
those previously observed in bulk samples. The shift in the kink associated
with the field-induced phase transition is found in the magnetoresistance
curves under a magnetic field applied in the direction perpendicular to the
$c$-axis. The magnetic phase diagram well reproduces that for the bulk
crystals, implying that the chiral soliton lattice phase arises under magnetic
fields, even in thin films.

###Enhancement of Superconductivity Linked with Linear-in-Temperature/Field Resistivity in Ion-Gated FeSe Films|Xingyu Jiang,Mingyang Qin,Xinjian Wei,Zhongpei Feng,Jiezun Ke,Haipeng Zhu,Fucong Chen,Liping Zhang,Li Xu,Xu Zhang,Ruozhou Zhang,Zhongxu Wei,Peiyu Xiong,Qimei Liang,Chuanying Xi,Zhaosheng Wang,Jie Yuan,Beiyi Zhu,Kun Jiang,Ming Yang,Junfeng Wang,Jiangping Hu,Tao Xiang,Brigitte Leridon,Rong Yu,Qihong Chen,Kui Jin,Zhongxian Zhao###

Enhancement of Superconductivity Linked with Linear-in-Temperature/Field Resistivity in Ion-Gated FeSe Films. Iron selenide (FeSe) - the structurally simplest iron-based superconductor,
has attracted tremendous interest in the past years. While the transition
temperature (Tc) of bulk FeSe is $\sim$ 8 K, it can be significantly enhanced
to 40 - 50 K by various ways of electron doping. However, the underlying
physics for such great enhancement of Tc and so the Cooper pairing mechanism
still remain puzzles. Here, we report a systematic study of the
superconducting- and normal-state properties of FeSe films via ionic liquid
gating. With fine tuning, Tc evolves continuously from below 10 K to above 40
K; in situ two-coil mutual inductance measurements unambiguously confirm the
gating is a uniform bulk effect. Close to Tc, the normal-state resistivity
shows a linear dependence on temperature and the linearity extends to lower
temperatures with the superconductivity suppressed by high magnetic fields. At
high fields, the normal-state magnetoresistance exhibits a linear-in-field
dependence and obeys a simple scaling relation between applied field and
temperature. Consistent behaviors are observed for different-Tc states
throughout the gating process, suggesting the pairing mechanism very likely
remains the same from low- to high-Tc state. Importantly, the coefficient of
the linear-in-temperature resistivity is positively correlated with Tc,
similarly to the observations in cuprates, Bechgaard salts and iron pnictide
superconductors. Our study points to a short-range antiferromagnetic exchange
interaction mediated pairing mechanism in FeSe.

###Boundary conductance in macroscopic bismuth crystals|Woun Kang,Felix Spathelf,Benoît Fauqué,Yuki Fuseya,Kamran Behnia###

Boundary conductance in macroscopic bismuth crystals. The interface between a solid and vacuum can become electronically distinct
from the bulk. This feature, encountered in the case of quantum Hall effect,
has a manifestation in insulators with topologically protected metallic surface
states. Non-trivial Berry curvature of the Bloch waves or periodically driven
perturbation are known to generate it. Here, by studying the angle-dependent
magnetoresistance in prismatic bismuth crystals of different shapes, we detect
a robust surface contribution to electric conductivity when the magnetic field
is aligned parallel to a two-dimensional boundary between the three-dimensional
crystal and vacuum. The effect is absent in antimony, which has an identical
crystal symmetry, a similar Fermi surface structure and equally ballistic
carriers, but an inverted band symmetry and a topological invariant of opposite
sign. Our observation confirms that the boundary interrupting the cyclotron
orbits remains metallic in bismuth, which is in agreement with what was
predicted by Azbel decades ago. However, the absence of the effect in antimony
indicates an intimate link between band symmetry and this boundary conductance.

###Spin-neutral currents for spintronics|Ding-Fu Shao,Shu-Hui Zhang,Ming Li,Chang-Beom Eom,Evgeny Y. Tsymbal###

Spin-neutral currents for spintronics. Electric currents carrying a net spin polarization are widely used in
spintronics, whereas globally spin-neutral currents are expected to play no
role in spin-dependent phenomena. Here we show that, in contrast to this common
expectation, spin-independent conductance in compensated antiferromagnets and
normal metals can be efficiently exploited in spintronics, provided their
magnetic space group symmetry supports a non-spin-degenerate Fermi surface. Due
to their momentum-dependent spin polarization, such antiferromagnets can be
used as active elements in antiferromagnetic tunnel junctions (AFMTJs) and
produce a giant tunneling magnetoresistance (TMR) effect. Using RuO$_{2}$ as a
representative compensated antiferromagnet exhibiting spin-independent
conductance along the [001] direction but a non-spin-degenerate Fermi surface,
we design a RuO$_{2}$/TiO$_{2}$/RuO$_{2}$ (001) AFMTJ, where a globally
spin-neutral charge current is controlled by the relative orientation of the
N\'eel vectors of the two RuO$_{2}$ electrodes, resulting in the TMR effect as
large as ~500%. These results are expanded to normal metals which can be used
as a counter electrode in AFMTJs with a single antiferromagnetic layer or other
elements in spintronic devices. Our work uncovers an unexplored potential of
the materials with no global spin polarization for utilizing them in
spintronics.

###Quantum transport properties of beta-Bi4I4 near and well beyond the extreme quantum limit|Peipei Wang,Fangdong Tang,Peng Wang,Haipeng Zhu,Chang-Woo Cho,Junfeng Wang,Xu Du,Yonghong Shao,Liyuan Zhang###

Quantum transport properties of beta-Bi4I4 near and well beyond the extreme quantum limit. We have investigated the magneto-transport properties of beta-Bi4I4 bulk
crystal, which was recently theoretically proposed and experimentally
demonstrated to be a topological insulator. At low temperature T and magnetic
field B, a series of Shubnikov-De Haas(SdH) oscillations are observed on the
magnetoresistivity (MR). The detailed analysis reveals a light cyclotron mass
of 0.1 me, and the field angle dependence of MR reveals that the SdH
oscillations originate from a convex Fermi surface. In the extreme quantum
limit (EQL) region, there is a metal-insulator transition occurring soon after
the EQL. We perform the scaling analysis, and all the isotherms fall onto a
universal scaling with a fitted critical exponent of 6.5. The enormous value of
critical exponent implies this insulating quantum phase originated from strong
electron-electron interactions in high fields. However, in the far end of EQL,
both the longitudinal and Hall resistivity increase exponentially with B, and
the temperature dependence of the MR reveals an energy gap induced by the high
magnetic field, signifying a magnetic freeze-out effect. Our findings indicate
that bulk beta-Bi4I4 is an excellent candidate for a 3D topological system for
exploring EQL physics and relevant exotic quantum phases.

###Evidence for competition between the superconductor proximity effect and quasiparticle spin-decay in superconducting spin-valves|B. Stoddart-Stones,X. Montiel,M. G. Blamire,J. W. A. Robinson###

Evidence for competition between the superconductor proximity effect and quasiparticle spin-decay in superconducting spin-valves. The difference in the density of states for up- and down-spin electrons in a
ferromagnet (F) results in spin-dependent scattering of electrons at a
ferromagnet / nonmagnetic (F/N) interface. In a F/N/F spin-valve, this causes a
current-independent difference in resistance ($\Delta R$) between antiparallel
(AP) and parallel (P) magnetization states. Giant magnetoresistance (GMR),
$\Delta R = R(AP) - R(P)$, is positive due to increased scattering of majority
and minority spin-electrons in the AP-state. If N is substituted for a
superconductor (S), there exists a competition between GMR and the
superconducting spin-valve effect: in the AP-state the net magnetic exchange
field acting on S is lowered and the superconductivity is reinforced meaning
$R(AP)$ decreases. For current-perpendicular-to-plane (CPP) spin-valves,
existing experimental studies show that GMR dominates ($\Delta R>0$) over the
superconducting spin valve effect ($\Delta R<0$) [J. Y. Gu et al., Phys. Rev. B
66, 140507(R) (2002)]. Here, however, we report a crossover from GMR ($\Delta R
> 0$) to the superconducting spin valve effect ($\Delta R < 0$) in CPP F/S/F
spin-valves as the superconductor thickness decreases below a critical value.

###Magnetic generation and switching of topological quantum phases in a trivial semimetal $α{\mathrm{-EuP}}_3$|Alex Hiro Mayo,Hidefumi Takahashi,Mohammad Saeed Bahramy,Atsuro Nomoto,Hideaki Sakai,Shintaro Ishiwata###

Magnetic generation and switching of topological quantum phases in a trivial semimetal $α{\mathrm{-EuP}}_3$. Topological materials have drawn increasing attention owing to their rich
quantum properties, as highlighted by a large intrinsic anomalous Hall effect
(AHE) in Weyl and nodal-line semimetals. However, the practical applications
for topological electronics have been hampered by the difficulty in the
external control of the band topology. Here we demonstrate a
magnetic-field-induced switching of band topology in $\alpha{\mathrm{-EuP}}_3$,
a magnetic semimetal with a layered crystal structure derived from black
phosphorus. When the magnetic field is applied perpendicular to the single
mirror plane of the monoclinic structure, a giant AHE signal abruptly emerges
at a certain threshold magnetization value, giving rise to a prominently large
anomalous Hall angle of $\left|\Theta_{\mathrm{AHE}}\right| \sim 20^{\circ}$.
When the magnetic field is applied along the inter-layer direction, which
breaks the mirror symmetry, the system shows a pronounced negative longitudinal
magnetoresistance. On the basis of electronic structure calculations and
symmetry considerations, these anomalous magneto-transport properties can be
considered as manifestations of two distinct topological phases: topological
nodal-line and Weyl semimetals, respectively. Notably, the nodal-line structure
is composed of bands with the same spin character and spans a wide energy range
around the Fermi level. These topological phases are stabilized via the
exchange coupling between localized Eu-4$f$ moments and mobile carriers
conducting through the phosphorus layers. Our findings provide a realistic
solution for external manipulation of band topology, enriching the functional
aspects of topological materials.

###Positive magnetoresistance and chiral anomaly in exfoliated type-II Weyl semimetal $T_\mathrm{d}$-WTe$_{2}$|R. Adhikari,S. Adhikari,B. Faina,M. Terschanski,S. Bork,C. Leimhofer,M. Cinchetti,A. Bonanni###

Positive magnetoresistance and chiral anomaly in exfoliated type-II Weyl semimetal $T_\mathrm{d}$-WTe$_{2}$. Layered van der Waals semimetallic $T_\mathrm{d}$-WTe$_{2}$, exhibiting
intriguing properties which include non-saturating extreme positive
magnetoresistance (MR) and tunable chiral anomaly, has emerged as model
topological type-II Weyl semimetal system. Here, $\sim$45 nm thick mechanically
exfoliated flakes of $T_\mathrm{d}$-WTe$_{2}$ are studied $via$ atomic force
microscopy, Raman spectroscopy, low-$T$/high-$\mu_{0}H$ magnetotransport
measurements and optical reflectivity. The contribution of anisotropy of the
Fermi liquid state to the origin of the large positive transverse
$\mathrm{MR}_\perp$ and the signature of chiral anomaly of the type-II Weyl
fermions are reported. The samples are found to be stable in air and no
oxidation or degradation of the electronic properties are observed. A
transverse $\mathrm{MR}_\perp$ $\sim$1200\,\% and an average carrier mobility
of $5000$\, cm$^{2}$V$^{-1}$s$^{-1}$ at $T=5\,\mathrm{K}$ for an applied
perpendicular field $\mu_{0}H_{\perp} = 7\,\mathrm{T}$ are established. The
system follows a Fermi liquid model for $T\leq50\,\mathrm{K}$ and the
anisotropy of the Fermi surface is concluded to be at the origin of the
observed positive MR. The anisotropy of the electronic behaviour is also
confirmed by optical reflectivity measurements. The relative orientation of the
crystal axes and of the applied electric and magnetic fields is proven to give
rise to the observed chiral anomaly in the in-plane magnetotransport.

###Anisotropic superconducting properties of Kagome metal CsV3Sb5|Shunli Ni,Sheng Ma,Yuhang Zhang,Jie Yuan,Haitao Yang,Zouyouwei Lu,Ningning Wang,Jianping Sun,Zhen Zhao,Dong Li,Shaobo Liu,Hua Zhang,Hui Chen,Kui Jin,Jinguang Cheng,Li Yu,Fang Zhou,Xiaoli Dong,Jiangping Hu,Hong-Jun Gao,Zhongxian Zhao###

Anisotropic superconducting properties of Kagome metal CsV3Sb5. We systematically measure the superconducting (SC) and mixed state properties
of high-quality CsV3Sb5 single crystals with Tc ~ 3.5 K. We find that the upper
critical field Hc2(T) exhibits a large anisotropic ratio of Hc2^(ab)/Hc2^(c) ~
9 at zero temperature and fitting its temperature dependence requires a minimum
two-band effective model. Moreover, the ratio of the lower critical field,
Hc1^(ab)/Hc1^(c), is also found to be larger than 1, which indicates that the
in-plane energy dispersion is strongly renormalized near Fermi energy. Both
Hc1(T) and SC diamagnetic signal are found to change little initially below Tc
~ 3.5 K and then to increase abruptly upon cooling to a characteristic
temperature of ~2.8 K. Furthermore, we identify a two-fold anisotropy of
in-plane angular-dependent magnetoresistance in the mixed state. Interestingly,
we find that, below the same characteristic T ~ 2.8 K, the orientation of this
two-fold anisotropy displays a peculiar twist by an angle of 60o characteristic
of the Kagome geometry. Our results suggest an intriguing superconducting state
emerging in the complex environment of Kagome lattice, which, at least, is
partially driven by electron-electron correlation.

###Field-Induced Superconductivity near the Superconducting Critical Pressure in UTe2|Dai Aoki,Motoi Kimata,Yoshiki J. Sato,Georg Knebel,Fuminori Honda,Ai Nakamura,Dexin Li,Yoshiya Homma,Yusei Shimizu,William Knafo,Daniel Braithwaite,Michal Valiska,Alexandre Pourret,Jean-Pascal Brison,Jacques Flouquet###

Field-Induced Superconductivity near the Superconducting Critical Pressure in UTe2. We report the magnetoresistance in the novel spin-triplet superconductor UTe2
under pressure close to the critical pressure Pc, where the superconducting
phase terminates, for field along the three a, b and c-axes in the orthorhombic
structure. The superconducting phase for H // a-axis just below Pc shows a
field-reentrant behavior due to the competition with the emergence of magnetic
order at low fields. The upper critical field Hc2 for H // c-axis shows a
quasi-vertical increase in the H-T phase diagram just below Pc, indicating that
superconductivity is reinforced by the strong fluctuations which persist even
at high fields above 20T. Increasing pressure leads to the disappearance of
superconductivity at zero field with the emergence of magnetic order.
Surprisingly, field-induced superconductivity is observed at high fields, where
a spin-polarized state is realized due to the suppression of the magnetic
ordered phases; the spin-polarized state is favorable for superconductivity,
whereas the magnetic ordered phase at low field seems to be unfavorable. The
huge Hc2 in the spin-polarized state seems to imply a spin-triplet state.
Contrary to the a- and c-axes, no field-reinforcement of superconductivity
occurs for magnetic field along the b-axis. We compare the results with the
field-reentrant superconductivity above the metamagnetic field, Hm for the
field direction tilted by about 30 deg. from b to c-axis at ambient pressure as
well as the field-reentrant (-reinforced) superconductivity in ferromagnetic
superconductors, URhGe and UCoGe.

###Comparison of highly-compressed C2/m-SnH12 superhydride with conventional superconductors|E. F. Talantsev###

Comparison of highly-compressed C2/m-SnH12 superhydride with conventional superconductors. Satterthwaite and Toepke (1970 Phys. Rev. Lett. 25 741) predicted
high-temperature superconductivity in hydrogen-rich metallic alloys, based on
an idea that these compounds should exhibit high Debye frequency of the proton
lattice, which boosts the superconducting transition temperature, Tc. The idea
has got full confirmation more than four decades later when Drozdov et al (2015
Nature 525 73) experimentally discovered near-room-temperature
superconductivity in highly-compressed sulphur superhydride, H3S. To date, more
than a dozen of high-temperature hydrogen-rich superconducting phases in Ba-H,
Pr-H, P-H, Pt-H, Ce-H, Th-H, S-H, Y-H, La-H, and (La,Y)-H systems have been
synthesized and, recently, Hong et al (2021 arXiv:2101.02846) reported on the
discovery of C2/m-SnH12 phase with superconducting transition temperature of Tc
~ 70 K. Here we analyse the magnetoresistance data, R(T,B), of C2/m-SnH12 phase
and report that this superhydride exhibits the ground state superconducting gap
of $\Delta$(0) = 9.2 meV, the ratio of 2$\Delta$(0)/k$_B$Tc = 3.3, and 0.010 <
Tc/Tf < 0.014 (where Tf is the Fermi temperature) and, thus, C2/m-SnH12 falls
into unconventional superconductors band in the Uemura plot.

###Field-induced metal-to-insulator transition and colossal anisotropic magnetoresistance in a nearly Dirac material EuMnSb$_2$|Z. L. Sun,A. F. Wang,H. M. Mu,H. H. Wang,Z. F. Wang,T. Wu,Z. Y. Wang,X. Y. Zhou,X. H. Chen###

Field-induced metal-to-insulator transition and colossal anisotropic magnetoresistance in a nearly Dirac material EuMnSb$_2$. How to realize applicably appreciated functionalities based on the coupling
between charge and spin degrees of freedom is still a challenge in the field of
spintronics. For example, anisotropic magnetoresistance (AMR) effect is
utilized to read out the information stored by various magnetic structures,
which usually originates from atomic spin-orbit coupling (SOC). However, the
application of AMR in antiferromagnet-based spintronics is still hindered by
rather small AMR value. Here, we discover a colossal AMR effect during the
field-induced metal-to-insulator transition (MIT) in a nearly Dirac material
EuMnSb$_2$ with an antiferromagnetic order of Eu$^{2+}$ moments. The colossal
AMR reaches to an unprecedented value of 1.84$\times$10$^6$% at 2 K, which is
four orders of magnitude larger than previously reported values in
antiferromagnets. Based on density functional theory calculations, a Dirac-like
band structure, which is strongly dependent on SOC, is confirmed around Y point
and dominates the overall transport properties in the present sample with
predominant electron-type carriers. Moreover, it is also revealed that the
indirect band gap around Fermi level is dependent on the magnetic structure of
Eu$^{2+}$ moments, which leads to the field-induced MIT and plays a key role on
the colossal AMR effect. Finally, our present work suggests that the similar
antiferromagnetic topological materials as EuMnSb$_2$, in which Dirac-like
fermions is strongly modulated by SOC and antiferromagnetism, would be a
fertile ground to explore applicably appreciated AMR effect.

###Emergence of spin-orbit coupled ferromagnetic surface state derived from Zak phase in a nonmagnetic insulator FeSi|Yusuke Ohtsuka,Naoya Kanazawa,Motoaki Hirayama,Akira Matsui,Takuya Nomoto,Ryotaro Arita,Taro Nakajima,Takayasu Hanashima,Victor Ukleev,Hiroyuki Aoki,Masataka Mogi,Kohei Fujiwara,Atsushi Tsukazaki,Masakazu Ichikawa,Masashi Kawasaki,Yoshinori Tokura###

Emergence of spin-orbit coupled ferromagnetic surface state derived from Zak phase in a nonmagnetic insulator FeSi. A chiral compound FeSi is a nonmagnetic narrow-gap insulator, exhibiting
peculiar charge and spin dynamics beyond a simple band-structure picture. Those
unusual features have been attracting renewed attention from topological
aspects. Although a signature of surface conduction was indicated according to
size-dependent resistivity in bulk crystals, its existence and topological
properties remain elusive. Here we demonstrate an inherent surface
ferromagnetic-metal state of FeSi thin films and its strong spin-orbit-coupling
(SOC) properties through multiple characterizations of the two-dimensional (2D)
conductance, magnetization and spintronic functionality. Terminated
covalent-bonding orbitals constitute the polar surface state with
momentum-dependent spin textures due to Rashba-type spin splitting, as
corroborated by unidirectional magnetoresistance measurements and
first-principles calculations. As a consequence of the spin-momentum locking,
non-equilibrium spin accumulation causes magnetization switching. These surface
properties are closely related to the Zak phase of the bulk band topology. Our
findings propose another route to explore noble-metal-free materials for
SOC-based spin manipulation.

###Striping of orbital-order with charge-disorder in optimally doped manganites|Wei-Tin Chen,Chin-Wei Wang,Ching-Chia Cheng,Yu-Chun Chuang,Arkadiy Simonov,Nicholas C. Bristowe,Mark S. Senn###

Striping of orbital-order with charge-disorder in optimally doped manganites. The phase diagrams of LaMnO$_3$ perovskites have been intensely studied due
to the colossal magnetoresistance (CMR) exhibited by compositions around the
$\frac{3}{8}^{th}$ doping level. However, phase segregation between
ferromagnetic (FM) metallic and antiferromagnetic (AFM) insulating states,
which itself is believed to be responsible for the colossal change in
resistance under applied magnetic field, has prevented an atomistic-level
understanding of the orbital ordered (OO) state at this doping level. Here,
through the detailed crystallographic analysis of the phase diagram of a
prototype system (AMn$_3^{A'}$Mn$_4^B$O$_{12}$), we show that the superposition
of two distinct lattice modes gives rise to a striping of OO Jahn-Teller active
Mn$^{3+}$ and charge disordered (CD) Mn$^{3.5+}$ layers in a 1:3 ratio. This
superposition only gives a cancellation of the Jahn-Teller-like displacements
at the critical doping level. This striping of CD Mn$^{3.5+}$ with Mn$^{3+}$
provides a natural mechanism though which long range OO can melt, giving way to
a conducting state.

###Competing magnetic interactions and magnetoresistance anomalies in cubic intermetallic compounds, Gd4RhAl and Tb4RhAl, and enhanced magnetocaloric effect for the Tb case|Ram Kumar,Kartik K Iyer,P. L. Paulose,E. V. Sampathkumaran###

Competing magnetic interactions and magnetoresistance anomalies in cubic intermetallic compounds, Gd4RhAl and Tb4RhAl, and enhanced magnetocaloric effect for the Tb case. We report complex magnetic, magnetoresistance (MR) and magnetocaloric
properties of Gd4RhAl and Tb4RhAl forming in the Gd4RhIn type cubic structure.
Though the synthesis of the compounds was reported long ago, to our knowledge,
no attempt was made to investigate the properties of these compounds. The
present results of ac and dc magnetization, electrical resistivity and
heat-capacity measurements down to 1.8 K establish that these compounds undergo
antiferromagnetic order initially, followed by complex spin-glass features with
decreasing temperature. These characteristic temperatures are: For Gd case, TN
is about 46K and TG is about 21 K, and for Tb, about 32 and 28 K respectively.
Additionally, there are field induced magnetic effects, interestingly leading
to non-monotonic variations in MR. There is a significant MR over a wide
temperature range above TN, similar to the behavior of magnetocaloric effect
(MCE) as measured by isothermal entropy change (DeltaS). An intriguing finding
we made is that DeltaS at the onset of magnetic order is significantly larger
for the Tb compound than that observed for the Gd analogue near its TN. On the
basis of this observation in a cubic material, we raise a question whether
aspherical nature of the 4f orbital can play a role to enhance MCE under
favorable circumstances, a clue that could be useful to find materials for
magnetocaloric applications.

###Ni$_{80}$Fe$_{20}$ Nanotubes with Optimized Spintronic Functionalities Prepared by Atomic Layer Deposition|Maria Carmen Giordano,Simon Escobar Steinvall,Sho Watanabe,Anna Fontcuberta i Morral,Dirk Grundler###

Ni$_{80}$Fe$_{20}$ Nanotubes with Optimized Spintronic Functionalities Prepared by Atomic Layer Deposition. Permalloy Ni$_{80}$Fe$_{20}$ is one of the key magnetic materials in the
field of magnonics. Its potential would be further unveiled if it could be
deposited in three dimensional (3D) architectures of sizes down to the
nanometer. Atomic Layer Deposition, ALD, is the technique of choice for
covering arbitrary shapes with homogeneous thin films. Early successes with
ferromagnetic materials include nickel and cobalt. Still, challenges in
depositing ferromagnetic alloys reside in the synthesis via decomposing the
consituent elements at the same temperature and homogeneously. We report
plasma-enhanced ALD to prepare permalloy Ni$_{80}$Fe$_{20}$ thin films and
nanotubes using nickelocene and iron(III) tert-butoxide as metal precursors,
water as the oxidant agent and an in-cycle plasma enhanced reduction step with
hydrogen. We have optimized the ALD cycle in terms of Ni:Fe atomic ratio and
functional properties. We obtained a Gilbert damping of 0.013, a resistivity of
28 $\mu\Omega$cm and an anisotropic magnetoresistance effect of 5.6 $\%$ in the
planar thin film geometry. We demonstrate that the process also works for
covering GaAs nanowires, resulting in permalloy nanotubes with high aspect
ratios and diameters of about 150 nm. Individual nanotubes were investigated in
terms of crystal phase, composition and spin-dynamic response by microfocused
Brillouin Light Scattering. Our results enable NiFe-based 3D spintronics and
magnonic devices in curved and complex topology operated in the GHz frequency
regime.

###Observation of current-induced switching in non-collinear antiferromagnetic IrMn$_3$ by differential voltage measurements|Sevdenur Arpaci,Victor Lopez-Dominguez,Jiacheng Shi,Luis Sánchez-Tejerina,Francesca Garesci,Chulin Wang,Xueting Yan,Vinod K. Sangwan,Matthew Grayson,Mark C. Hersam,Giovanni Finocchio,Pedram Khalili Amiri###

Observation of current-induced switching in non-collinear antiferromagnetic IrMn$_3$ by differential voltage measurements. There is accelerating interest in developing memory devices using
antiferromagnetic (AFM) materials, motivated by the possibility for
electrically controlling AFM order via spin-orbit torques, and its read-out via
magnetoresistive effects. Recent studies have shown, however, that high current
densities create non-magnetic contributions to resistive switching signals in
AFM/heavy metal (AFM/HM) bilayers, complicating their interpretation. Here we
introduce an experimental protocol to unambiguously distinguish current-induced
magnetic and nonmagnetic switching signals in AFM/HM structures, and
demonstrate it in IrMn$_3$/Pt devices. A six-terminal double-cross device is
constructed, with an IrMn$_3$ pillar placed on one cross. The differential
voltage is measured between the two crosses with and without IrMn$_3$ after
each switching attempt. For a wide range of current densities, reversible
switching is observed only when write currents pass through the cross with the
IrMn$_3$ pillar, eliminating any possibility of non-magnetic switching
artifacts. Micromagnetic simulations support our findings, indicating a complex
domain-mediated switching process.

###Observation of nearly identical superconducting transition temperatures in pressurized Weyl semimetal MIrTe4 (M=Nb and Ta)|Sijin Long,Shu Cai,Rico Schonemann,Priscila F. S. Rosa,Luis Balicas,Cheng Huang,Jing Guo,Yazhou Zhou,Jinyu Han,Liqin Zhou,Yanchun Li,Xiaodong Li,Qi Wu,Hongming Weng,Tao Xiang,Liling Sun###

Observation of nearly identical superconducting transition temperatures in pressurized Weyl semimetal MIrTe4 (M=Nb and Ta). Here we report the observation of pressure-induced superconductivity in
type-II Weyl semimetal (WSM) candidate NbIrTe4 and the evolution of its Hall
coefficient (RH), magnetoresistance (MR), and lattice with increasing pressure
to ~57 GPa. These results provide a significant opportunity to investigate the
universal high-pressure behavior of ternary WSMs, including the sister compound
TaIrTe4 that has been known through our previous studies. We find that the
pressure-tuned evolution from the WSM to the superconducting (SC) state in
these two compounds exhibit the same trend, i.e., a pressure-induced SC state
emerges from the matrix of the non-superconducting WSM state at ~ 27 GPa, and
then the WSM state and the SC state coexist up to 40 GPa. Above this pressure,
an identical high-pressure behavior, characterized by almost the same value of
RH and MR in its normal state and the same value of Tc in its SC state, appears
in both compounds. Our results not only reveal a universal connection between
the WSM state and SC state, but also demonstrate that NbIrTe4 and TaIrTe4 can
make the same contribution to the normal and SC states that inhabit in the
high-pressure phase, although these two compounds have dramatically different
topological band structure at ambient pressure.

###Extremely large magnetoresistance in the hourglass Dirac loop chain metal β-ReO$_{2}$|Daigorou Hirai,Takahito Anbai,Shinya Uji,Tamio Oguchi,Zenji Hiroi###

Extremely large magnetoresistance in the hourglass Dirac loop chain metal β-ReO$_{2}$. The transport and thermodynamic properties of $\beta$-ReO$_{2}$ crystallizing
in a nonsymmorphic structure were studied using high-quality single crystals.
An extremely large magnetoresistance (XMR) reaching 22,000 $\%$ in a transverse
magnetic field of 10 T at 2 K was observed. However, distinguished from other
topological semimetals with low carrier densities that show XMR,
$\beta$-ReO$_{2}$ has a high electron carrier density of 1 $\times$ $10^{22}$
cm$^{-3}$ as determined by Hall measurements and large Fermi surfaces in the
electronic structure. In addition, a small Fermi surface with a small effective
mass was evidenced by de Haas-van Alphen oscillation measurements. The previous
band structure calculations [S. S. Wang, et al., Nat. Commun. 8, 1844 (2017)]
showed that two kinds of loops made of Dirac points of hourglass-shaped
dispersions exist and are connected to each other by a point to form a string
of alternating loops, called the Dirac loop chain (DLC), which are protected by
the multiple glide symmetries. Our first-principles calculations revealed the
complex Fermi surfaces with the smallest one corresponding to the observed
small Fermi surface, which is just located near the DLC. The XMR of
$\beta$-ReO$_{2}$ is attributed to the small Fermi surface and thus is likely
caused by the DLC.

###Quantum-well tunneling anisotropic magnetoresistance above room temperature|Muftah Al-Mahdawi,Qingyi Xiang,Yoshio Miura,Mohamed Belmoubarik,Keisuke Masuda,Shinya Kasai,Hiroaki Sukegawa,Seiji Mitani###

Quantum-well tunneling anisotropic magnetoresistance above room temperature. Quantum-well (QW) devices have been extensively investigated in semiconductor
structures. More recently, spin-polarized QWs were integrated into magnetic
tunnel junctions (MTJs). In this work, we demonstrate the spin-based control of
the quantized states in iron $3d$-band QWs, as observed in experiments and
theoretical calculations. We find that the magnetization rotation in the Fe QWs
significantly shifts the QW quantization levels, which modulate the
resonant-tunneling current in MTJs, resulting in a tunneling anisotropic
magnetoresistance (TAMR) effect of QWs. This QW-TAMR effect is sizable compared
to other types of TAMR effect, and it is present above the room-temperature. In
a QW MTJ of Cr/Fe/MgAl$_2$O$_4$/top electrode, where the QW is formed by a
mismatch between Cr and Fe in the $d$ band with $\Delta_1$ symmetry, a QW-TAMR
ratio of up to 5.4 % was observed at 5 K, which persisted to 1.2 % even at
380K. The magnetic control of QW transport can open new applications for
spin-coupled optoelectronic devices, ultra-thin sensors, and memories.

###Layered van der Waals topological metals of TaTMTe4 (TM = Ir, Rh, Ru) family|G. Shipunov,B. R. Piening,C. Wuttke,T. A. Romanova,A. V. Sadakov,O. A. Sobolevskiy,E. Yu. Guzovsky,A. S. Usoltsev,V. M. Pudalov,D. Efremov,S. Subakti,D. Wolf,A. Lubk,B. Büchner,S. Aswartham###

Layered van der Waals topological metals of TaTMTe4 (TM = Ir, Rh, Ru) family. Layered van~der~Waals materials of the family TaTMTe$_4$ (TM=Ir, Rh, Ru) are
showing very interesting electronic properties. Here we report the synthesis,
crystal growth and structural characterization of TaIrTe$_4$, TaRhTe$_4$,
TaIr$_{1-x}$Rh$_{x}$Te$_4$ ($x = 0.06$; 0.14; 0.78; 0.92) and
Ta$_{1+x}$Ru$_{1-x}$Te$_4$ single crystals. For Ta$_{1+x}$Ru$_{1-x}$Te$_4$
off-stoichiometry is shown. X-ray powder diffraction confirms that TaRhTe4 is
isostructural to TaIrTe4. We show that all these compounds are metallic with
diamagnetic behavior. Ta$_{1.26(2)}$Ru$_{0.75(2)}$Te$_{4.000(8)}$ exhibits an
upturn in the resistivity at low temperatures which is strongly field
dependent. Below $T \approx 4$K we observed signatures of the superconductivity
in the TaIr$_{1-x}$Rh$_{x}$Te$_4$ compounds for $x = 0.92$. Magnetotransport
measurements on all samples show weak magnetoresistance (MR) field dependence
that is typically quadratic-in-field. However, for TaIr$_{1-x}$Rh$_{x}$Te$_4$
with $x\approx 0.78$, the MR has a linear term dominating in low fields that
indicates the presence of Dirac cones in the vicinity of the Fermi energy. For
TaRhTe$_4$ series the MR is almost isotropic. We have performed electronic
structure calculations for isostructural TaIrTe$_4$ and TaRhTe$_4$ together
with the projected total density of states. The main difference is appearance
of the Rh-band close to the Fermi level.

###Radiation-induced magnetoresistance oscillations with massive Dirac fermions|Jesus Inarrea,Gloria Platero###

Radiation-induced magnetoresistance oscillations with massive Dirac fermions. We report on a theoretical study on the rise of radiation-induced
magnetoresistance oscillations in two-dimensional systems of massive Dirac
fermions. We study the bilayer system of monolayer graphene and hexagonal boron
nitride (h-BN/graphene) and the trilayer system of hexagonal boron nitride
encapsulated graphene (h-BN/graphene/h-BN). We extend the radiation-driven
electron orbit model that was previously devised to study the same oscillations
in two-dimensional systems of Schr\"odinger electrons (GaAs/AlGaAS
heterostructure) to the case of massive Dirac fermions. In the simulations we
obtain clear oscillations for radiation frequencies in the terahertz and
far-infrared bands. %which contrasts with the two-dimensional Schrodinger
electrons case, %that are mainly sensitive to microwave frequencies. We
investigate also the power and temperatures dependence. For the former we
obtain similar results as for Schr\"odinger electrons and predict the rise of
zero resistance states. For the latter we obtain a similar qualitatively
dependence but quantitatively different when increasing temperature. While in
GaAs the oscillations are wiped out in a few degrees, interestingly enough, for
massive Dirac fermions, we obtain observable oscillations for temperatures
above $100$ K and even at room temperature for the higher frequencies used in
the simulations.

###Exotic spintronic properties of transition-metal monolayers on graphyne|Xiaoxiong Ren,Junsheng Huang,Ping Li,Yun Zhang,Zhi-Xin Guo###

Exotic spintronic properties of transition-metal monolayers on graphyne. The recent discovery of two-dimensional (2D) magnetic materials which are
compound of transition metal (TM) with other elements, has opened new avenues
for basic research on low-dimensional magnetism and potential applications in
spintronics. To further explore new 2D magnets of pure TM is thus of an
interesting topic. Based on the first-principles calculations, here we propose
a strategy of obtaining monolayer TM magnets, i.e., depositing TM atoms on
graphyne (Gy) which has proper hexagonal hollow geometry. We find that TM
monolayer with perfect hexagonal geometry can be formed on Gy. The TM monolayer
exhibits a wealth of physical properties in dependence of TM species, such as
ferromagnetic and antiferromagnetic ground states, as well as intriguing
semimetal and half-metal characteristics. We also find that the half-metal
characteristics makes the monolayer TM have great potential applications in the
horizontal magnetic tunnel junction (MTJ) devices, where the tunneling
magnetoresistance can reach as high as 850000%. Our results provide a new
framework for obtaining 2D magnets with outstanding spintronic properties.

###An In-Memory Analog Computing Co-Processor for Energy-Efficient CNN Inference on Mobile Devices|Mohammed Elbtity,Abhishek Singh,Brendan Reidy,Xiaochen Guo,Ramtin Zand###

An In-Memory Analog Computing Co-Processor for Energy-Efficient CNN Inference on Mobile Devices. In this paper, we develop an in-memory analog computing (IMAC) architecture
realizing both synaptic behavior and activation functions within non-volatile
memory arrays. Spin-orbit torque magnetoresistive random-access memory
(SOT-MRAM) devices are leveraged to realize sigmoidal neurons as well as
binarized synapses. First, it is shown the proposed IMAC architecture can be
utilized to realize a multilayer perceptron (MLP) classifier achieving orders
of magnitude performance improvement compared to previous mixed-signal and
digital implementations. Next, a heterogeneous mixed-signal and mixed-precision
CPU-IMAC architecture is proposed for convolutional neural networks (CNNs)
inference on mobile processors, in which IMAC is designed as a co-processor to
realize fully-connected (FC) layers whereas convolution layers are executed in
CPU. Architecture-level analytical models are developed to evaluate the
performance and energy consumption of the CPU-IMAC architecture. Simulation
results exhibit 6.5% and 10% energy savings for CPU-IMAC based realizations of
LeNet and VGG CNN models, for MNIST and CIFAR-10 pattern recognition tasks,
respectively.

###Superconductivity and Quantum Oscillations in Single Crystals of the Compensated Semimetal CaSb$_{2}$|M. Oudah,J. Bannies,D. A. Bonn,M. C. Aronson###

Superconductivity and Quantum Oscillations in Single Crystals of the Compensated Semimetal CaSb$_{2}$. Bulk superconductivity in a topological semimetal is a first step towards
realizing topological superconductors, which can host Majorana fermions
allowing us to achieve quantum computing. Here, we report superconductivity and
compensation of electrons and holes in single crystals of the nodal-line
semimetal CaSb$_2$. We characterize the superconducting state and find that
Cooper pairs have moderate-weak coupling, and the superconducting transition in
specific heat down to 0.22 K deviates from that of a BCS superconductor. The
non-saturating magnetoresistance and electron-hole compensation at low
temperature are consistent with density functional theory (DFT) calculations
showing nodal-line features. Furthermore, we observe de Haas-van Alphen (dHvA)
oscillations consistent with a small Fermi surface in the semimetallic state of
CaSb$_2$. Our DFT calculations show that the two electron bands crossing the
Fermi level are associated with Sb1 zig-zag chains, while the hole band is
associated with Sb2 zig-zag chains. The Sb1 zig-zag chains form a distorted
square net, which may relate the $M$Sb$_2$ family to the well known $M$SbTe
square net semimetals. Realization of superconductivity and a compensated
semimetal state in single crystals of CaSb$_2$ establishes the diantimonide
family as a candidate class of materials for achieving topological
superconductivity.

###Unusual competition of superconductivity and charge-density-wave state in a compressed topological kagome metal|F. H. Yu,D. H. Ma,W. Z. Zhuo,S. Q. Liu,X. K. Wen,B. Lei,J. J. Ying,X. H. Chen###

Unusual competition of superconductivity and charge-density-wave state in a compressed topological kagome metal. Understanding the competition between superconductivity and other ordered
states (such as antiferromagnetic or charge-density-wave (CDW) state) is a
central issue in condensed matter physics. The recently discovered layered
kagome metal AV3Sb5 (A = K, Rb, and Cs) provides us a new playground to study
the interplay of superconductivity and CDW state by involving nontrivial
topology of band structures. Here, we conduct high-pressure electrical
transport and magnetic susceptibility measurements to study CsV3Sb5 with the
highest Tc of 2.7 K in AV3Sb5 family. While the CDW transition is monotonically
suppressed by pressure, superconductivity is enhanced with increasing pressure
up to P1~0.7 GPa, then an unexpected suppression on superconductivity happens
until pressure around 1.1 GPa, after that, Tc is enhanced with increasing
pressure again. The CDW is completely suppressed at a critical pressure P2~2
GPa together with a maximum Tc of about 8 K. In contrast to a common dome-like
behavior, the pressure-dependent Tc shows an unexpected double-peak behavior.
The unusual suppression of Tc at P1 is concomitant with the rapidly damping of
quantum oscillations, sudden enhancement of the residual resistivity and rapid
decrease of magnetoresistance. Our discoveries indicate an unusual competition
between superconductivity and CDW state in pressurized kagome lattice.

###Quasi-uniaxial pressure induced superconductivity in stoichiometric compound UTe$_2$|Chongli Yang,Jing Guo,Yazhou Zhou,Shu Cai,Vladimir A. Sidorov,Cheng Huang,Sijin Long,Youguo Shi,Qiuyun Chen,Shiyong Tan,Yu Gong,Yanchun Li,Xiaodong Li,Qi Wu,Piers Coleman,Tao Xiang,Liling Sun###

Quasi-uniaxial pressure induced superconductivity in stoichiometric compound UTe$_2$. The recent discovery of superconductivity in heavy Fermion compound UTe2, a
candidate topological and triplet-paired superconductor, has aroused widespread
interest. However, to date, there is no consensus on whether the stoichiometric
sample of UTe2 is superconducting or not due to lack of reliable evidence to
distinguish the difference between the nominal and real compositions of
samples. Here, we are the first to clarify that the stoichiometric UT2 is
non-superconducting at ambient pressure and under hydrostatic pressure up to 6
GPa, however we find that it can be compressed into superconductivity by
application of quasi-uniaxial pressure. Measurements of resistivity,
magnetoresistance and susceptibility reveal that the quasi-uniaxial pressure
results in a suppression of the Kondo coherent state seen at ambient pressure,
and then leads to a superconductivity initially emerged on the ab-plane at 1.5
GPa. At 4.8 GPa, the superconductivity is developed in three crystallographic
directions. The superconducting state coexists with an exotic magnetic ordered
state that develops just below the onset temperature of the superconducting
transition. The discovery of the quasi-uniaxial-pressure-induced
superconductivity with exotic magnetic state in the stoichiometric UTe2 not
only provide new understandings on this compound, but also highlight the vital
role of Te deficiency in developing the superconductivity at ambient pressures.

###Theory of unidirectional magnetoresistance and nonlinear Hall effect|Frank Freimuth,Stefan Blügel,Yuriy Mokrousov###

Theory of unidirectional magnetoresistance and nonlinear Hall effect. We study the unidirectional magnetoresistance (UMR) and the nonlinear Hall
effect (NLHE) in the ferromagnetic Rashba model. For this purpose we derive
expressions to describe the response of the electric current quadratic in the
applied electric field. We compare two different formalisms, namely the
standard Keldysh nonequilibrium formalism and the Moyal-Keldysh formalism, to
derive the nonlinear conductivities of UMR and NLHE. We find that both
formalisms lead to identical numerical results when applied to the
ferromagnetic Rashba model. The UMR and the NLHE nonlinear conductivities tend
to be comparable in magnitude according to our calculations. Additionally,
their dependencies on the Rashba parameter and on the quasiparticle broadening
are similar. The nonlinear zero-frequency response considered here is several
orders of magnitude higher than the one at optical frequencies that describes
the photocurrent generation in the ferromagnetic Rashba model. Additionally, we
compare our Keldysh nonequilibrium expression in the independent-particle
approximation to literature expressions of the UMR that have been obtained
within the constant relaxation time approximation of the Boltzmann formalism.
We find that both formalisms converge to the same analytical formula in the
limit of infinite relaxation time. However, remarkably, we find that the
Boltzmann result does not correspond to the intraband term of the Keldysh
expression. Instead, the Boltzmann result corresponds to the sum of the
intraband term and an interband term that can be brought into the form of an
effective intraband term due to the f-sum rule.

###Spin-Torque-driven Terahertz Auto Oscillations in Non-Collinear Coplanar Antiferromagnets|Ankit Shukla,Shaloo Rakheja###

Spin-Torque-driven Terahertz Auto Oscillations in Non-Collinear Coplanar Antiferromagnets. We theoretically and numerically study the terahertz auto oscillations in
thin-film metallic non-collinear coplanar antiferromagnets (AFMs), such as
$\mathrm{Mn_{3}Sn}$ and $\mathrm{Mn_{3}Ir}$, under the effect of anti-damping
spin-torque with spin polarization perpendicular to the plane of the film. To
obtain the order parameter dynamics in these AFMs, we solve three
Landau-Lifshitz-Gilbert equations coupled by exchange interactions assuming
both single- and multi-domain (micromagnetics) dynamical processes. In the
limit of strong exchange interaction, the oscillatory dynamics of the order
parameter in these AFMs, which have opposite chiralities, could be mapped to
that of a linear damped-driven pendulum in the case of $\mathrm{Mn_{3}Sn}$, and
a non-linear damped-driven pendulum in case of $\mathrm{Mn_{3}Ir}$. The
theoretical framework allows us to identify the input current requirements as a
function of the material and geometry parameters for exciting an oscillatory
response. We also obtain a closed-form approximate solution of the oscillation
frequency for large input currents in case of both $\mathrm{Mn_{3}Ir}$ and
$\mathrm{Mn_{3}Sn}$. Our analytical predictions of threshold current and
oscillation frequency agree well with the numerical results and thus can be
used as compact models to design and optimize the auto oscillator. Employing a
circuit model, based on the principle of tunnel anisotropy magnetoresistance,
we present detailed models of the output power and efficiency versus
oscillation frequency of the auto oscillator. Finally, we explore the spiking
dynamics of two unidirectional as well as bidirectional coupled AFM oscillators
using non-linear damped-driven pendulum equations.

###Study of Spin-Orbit Interactions and Interlayer Ferromagnetic Coupling in Co/Pt/Co Trilayers in Wide Range of Heavy Metal Thickness|Piotr Ogrodnik,Krzysztof Grochot,Łukasz Karwacki,Jarosław Kanak,Michał Prokop,Jakub Chęciński,Witold Skowroński,Sławomir Ziętek,Tomasz Stobiecki###

Study of Spin-Orbit Interactions and Interlayer Ferromagnetic Coupling in Co/Pt/Co Trilayers in Wide Range of Heavy Metal Thickness. The spin-orbit torque, a torque induced by a charge current flowing through
the heavy-metal conducting layer with strong spin-orbit interactions, provides
an efficient way to control the magnetization direction in
heavy-metal/ferromagnet nanostructures, required for applications in the
emergent magnetic technologies like random access memories, high-frequency nano
oscillators, or bio-inspired neuromorphic computations. We study the interface
properties, magnetization dynamics, magnetostatic features and spin-orbit
interactions within the multilayer system
Ti(2)/Co(1)/Pt(0-4)/Co(1)/MgO(2)/Ti(2) (thicknesses in nanometers) patterned by
optical lithography on micrometer-sized bars. In the investigated devices, Pt
is used as a source of the spin current and as a non-magnetic spacer with
variable thickness, which enables the magnitude of the interlayer ferromagnetic
exchange coupling to be effectively tuned. We also find the Pt
thickness-dependent changes in magnetic anisotropies, magnetoresistance,
effective Hall angle and, eventually, spin-orbit torque fields at interfaces.
The experimental findings are supported by the relevant interface
structure-related simulations, micromagnetic, macrospin, as well as the spin
drift-diffusion models. Finally, the contribution of the spin-orbital
Edelstein-Rashba interfacial fields is also briefly discussed in the analysis.

###Large anomalous Hall effect in the kagome ferromagnet LiMn$_6$Sn$_6$|Dong Chen,Congcong Le,Chenguang Fu,Haicheng Lin,Walter Schnelle,Yan Sun,Claudia Felser###

Large anomalous Hall effect in the kagome ferromagnet LiMn$_6$Sn$_6$. Kagome magnets are believed to have numerous exotic physical properties due
to the possible interplay between lattice geometry, electron correlation and
band topology. Here, we report the large anomalous Hall effect in the kagome
ferromagnet LiMn$_6$Sn$_6$, which has a Curie temperature of 382 K and easy
plane along with the kagome lattice. At low temperatures, unsaturated positive
magnetoresistance and opposite signs of ordinary Hall coefficient for
$\rho_{xz}$ and $\rho_{yx}$ indicate the coexistence of electrons and holes in
the system. A large intrinsic anomalous Hall conductivity of 380 $\Omega^{-1}$
cm$^{-1}$, or 0.44 $e^2/h$ per Mn layer, is observed in $\sigma_{xy}^A$. This
value is significantly larger than those in other $R$Mn$_6$Sn$_6$ ($R$ = rare
earth elements) kagome compounds. Band structure calculations show several band
crossings, including a spin-polarized Dirac point at the K point, close to the
Fermi energy. The calculated intrinsic Hall conductivity agrees well with the
experimental value, and shows a maximum peak near the Fermi energy. We
attribute the large anomalous Hall effect in LiMn$_6$Sn$_6$ to the band
crossings closely located near the Fermi energy.

###Smart fingertip sensor for food quality control: fruit maturity assessment with a magnetic device|Maria Carvalho,Pedro Ribeiro,Verónica Romão,Susana Cardoso###

Smart fingertip sensor for food quality control: fruit maturity assessment with a magnetic device. Automated technologies for quality inspection of fruits have attracted great
interest in the food industry. The development of nondestructive mechanisms to
assess the quality of individual fruit prior to sale may lead to an increase in
overall product quality, value, and consequently, producer competitiveness.
However, the existing methods have limitations. Herein, a texture sensor based
on highly sensitive hair-like cilia receptors, to allow a quick quality
evaluation of fruit is proposed. The texture sensor consists of up to 100
magnetized nanocomposite cilia attached to a chip with magnetoresistive sensors
in a full Wheatstone bridge architecture. In this paper we demonstrate the use
of ciliary sensors in scanning fruits (blueberries and strawberries) in
different maturation stages. The contact of the cilia with the fruit skin
provided qualitative information about its texture in terms of ripeness stage.
Less mature fruits exhibited, on average, a highest peak voltage of 0.14 mV for
blueberries and 0.12 mV for strawberries, while overripe fruits exhibited 0.58
mV and 0.56 mV, respectively. The results were confirmed by sensorial
assessment of the fruit freshness, and therefore attesting the application
potential of the sensing technology for fruit quality control.

###Ferromagnetic Cr4PtGa17: A Novel Half-Heusler-Type Compound with a Breathing Pyrochlore Lattice|Xin Gui,Erxi Feng,Huibo Cao,Robert J. Cava###

Ferromagnetic Cr4PtGa17: A Novel Half-Heusler-Type Compound with a Breathing Pyrochlore Lattice. We describe the crystal structure and elementary magnetic properties of a
previously unreported ternary intermetallic compound, Cr4PtGa17, which
crystallizes in a rhombohedral unit cell in the noncentrosymmetric space group
R3m. The crystal structure is closely related to those of XYZ half-Heusler
compounds, where X, Y and Z are reported to be single elements only, occupying
three different face-centered cubic sublattices. The new material, Cr4PtGa17,
can be most straightforwardly illustrated by writing the formula as
(PtGa2)(Cr4Ga14)Ga (X=PtGa2, Y = Cr4Ga14, Z = Ga), that is, the X and Y sites
are occupied by clusters instead of single elements. The magnetic Cr occupies a
breathing pyrochlore lattice. Ferromagnetic ordering is found below TC ~61 K,
by both neutron diffraction and magnetometer studies, with a small, saturated
moment of ~0.25 muB/Cr observed at 2 K, making Cr4PtGa17 the first
ferromagnetically ordered material with a breathing pyrochlore lattice. A
magnetoresistance of ~140% was observed at 2 K. DFT calculations suggest that
the material has a nearly-half-metallic electronic structure. The new material,
Cr4PtGa17, the first realization of both a half-Heusler-type structure and a
breathing pyrochlore lattice, might pave a new way to achieve novel types of
half-Heusler compounds.

###Spin Hall effect in a spin-1 chiral semimetal|Ke Tang,Yong-Chang Lau,Kenji Nawa,Zhenchao Wen,Qingyi Xiang,Hiroaki Sukegawa,Takeshi Seki,Yoshio Miura,Koki Takanashi,Seiji Mitani###

Spin Hall effect in a spin-1 chiral semimetal. Spin-1 chiral semimetal is a new state of quantum matter hosting
unconventional chiral fermions that extend beyond the common Dirac and Weyl
fermions. B20-type CoSi is a prototypal material that accommodates such an
exotic quasiparticle. To date, the spin transport properties in the spin-1
chiral semimetals, have not been explored yet. In this work, we fabricated
B20-CoSi thin films on sapphire c-plane substrates by magnetron sputtering and
studied the spin Hall effect (SHE) by combining experiments and
first-principles calculations. The SHE of CoSi using CoSi/CoFeB/MgO
heterostructures was investigated via spin Hall magnetoresistance and harmonic
Hall measurements. First-principles calculations yield an intrinsic spin Hall
conductivity (SHC) at the Fermi level that is consistent with the experiments
and reveal its unique Fermi-energy dependence. Unlike the Dirac and Weyl
fermion-mediated Hall conductivities that exhibit a peak-like structure
centering around the topological node, SHC of B20-CoSi is odd and crosses zero
at the node with two antisymmetric local extrema of opposite sign situated
below and above in energy. Hybridization between Co d-Si p orbitals and
spin-orbit coupling are essential for the SHC, despite the small (~1%) weight
of Si p-orbital near the Fermi level. This work expands the horizon of
topological spintronics and highlights the importance of Fermi-level tuning in
order to fully exploit the topology of spin-1 chiral fermions for spin current
generation.

###Spin-orbit torques and magnetotransport properties of $α$-Sn and $β$-Sn heterostructures|Federico Binda,Can Onur Avci,Santos Francisco Alvarado,Paul Noël,Charles-Henri Lambert,Pietro Gambardella###

Spin-orbit torques and magnetotransport properties of $α$-Sn and $β$-Sn heterostructures. Topological insulators have emerged as an important material class for
efficient spin-charge interconversion. Most topological insulators considered
to date are binary or ternary compounds, with the exception of $\alpha$-Sn.
Here we report a comprehensive characterization of the growth, magnetotransport
properties, and current-induced spin-orbit torques of $\alpha$-Sn and
$\beta$-Sn-based ferromagnetic heterostructures. We show that $\alpha$-Sn grown
with a Bi surfactant on CdTe(001) promotes large spin-orbit torques in a
ferromagnetic FeCo layer at room temperature, comparable to Pt, whereas
$\alpha$-Sn grown without Bi surfactant and the non-topological phase,
$\beta$-Sn, induce lower torques. The dampinglike and fieldlike spin-orbit
torque efficiency in $\alpha$-Sn with Bi are 0.12 and 0.18, respectively.
Further, we show that $\alpha$-Sn grown with and without Bi presents a spin
Hall-like magnetoresistance comparable to that found in heavy metal/ferromagnet
bilayers. Our work demonstrates direct and efficient charge-to-spin conversion
in $\alpha$-Sn ferromagnetic heterostructures, showing that $\alpha$-Sn is a
promising material for current-induced magnetization control in spintronic
devices.

###Anisotropic Upper Critical Field, Seebeck and Nernst Coefficient in Nb0.20Bi2Se3 Topological Superconductor|Shailja Sharma,C. S. Yadav###

Anisotropic Upper Critical Field, Seebeck and Nernst Coefficient in Nb0.20Bi2Se3 Topological Superconductor. We present the magneto-transport and the thermoelectric (Seebeck and Nernst
coefficient) studies of the Nb-doped Bi2Se3 topological superconductor. The
angle-dependent magnetoresistance study highlights the anisotropy in the upper
critical field (Hc2) with the anisotropy parameter Gamma ~1.2. We observed a
gradual decrease in low-temperature Hall resistivity on the application of
magnetic field like any conventional superconductor, instead of the finite Hall
resistivity which was linked to the chiral superconducting phase. The estimated
value of the carrier concentration (~ 10^19 cm-3) for Nb0.2Bi2Se3 is one order
larger than for Bi2Se3. Doping of Nb shows a significant decrease in the
Seebeck coefficient value and the estimated Fermi temperature of the
three-dimensional Fermi surface at the centre of Brillouin zone in the
zero-temperature limit enhances by ~4 times in comparison to pristine Bi2Se3.
We have observed a large value (~2.3 micro V K-1 T-1) of Nernst coefficient for
Bi2Se3 at room temperature which decreases with Nb doping ( ~0.5 micro V K-1
T-1).

###Singular angular magnetoresistance and sharp resonant features in a high-mobility metal with open orbits, ReO3|Nicholas P. Quirk,Loi T. Nguyen,Jiayi Hu,R. J. Cava,N. P. Ong###

Singular angular magnetoresistance and sharp resonant features in a high-mobility metal with open orbits, ReO3. We report high-resolution angular magnetoresistance (AMR) experiments
performed on crystals of ReO$_3$ with high mobility (90,000 cm$^2$/Vs at 2 K)
and extremely low residual resistivity (5-8 n$\Omega$cm). The Fermi surface,
comprised of intersecting cylinders, supports open orbits. The resistivity
$\rho_{xx}$ in a magnetic field $B$ = 9 T displays a singular pattern of
behavior. With $\bf E\parallel \hat{x}$ and $\bf B$ initially
$\parallel\bf\hat{z}$, tilting $\bf B$ in the longitudinal $k_z$-$k_x$ plane
leads to a steep decrease in $\rho_{xx}$ by a factor of 40. However, if $\bf B$
is tilted in the transverse $k_y$-$k_z$ plane, $\rho_{xx}$ increases steeply by
a factor of 8. Using the Shockley tube integral approach, we show that, in
ReO$_3$, the singular behavior results from the rapid conversion of closed to
open orbits, resulting in opposite signs for AMR in orthogonal planes. The
floor values of $\rho_{xx}$ in both AMR scans are identified with specific sets
of open and closed orbits. Also, the "completion angle" $\gamma_c$ detected in
the AMR is shown to be an intrinsic geometric feature that provides a new way
to measure the Fermi radius $k_F$. However, additional sharp resonant features
which appear at very small tilt angles in the longitudinal AMR scans are not
explained by the tube integral approach.

###Topological surface conduction in Kondo insulator YbB$_{12}$|Y. Sato,Z. Xiang,Y. Kasahara,S. Kasahara,Lu Chen,C. Tinsman,F. Iga,J. Singleton,N. L. Nair,N. Maksimovic,J. G. Analytis,Lu Li,Y. Matsuda###

Topological surface conduction in Kondo insulator YbB$_{12}$. Kondo insulators have recently aroused great interest because they are
promising materials that host a topological insulator state caused by the
strong electron interactions. Moreover, recent observations of the quantum
oscillations in the insulating state of Kondo insulators have come as a great
surprise. Here, to investigate the surface electronic state of a prototype
Kondo insulator YbB$_{12}$, we measured transport properties of single crystals
and microstructures. In all samples, the temperature dependence of the
electrical resistivity is insulating at high temperatures and the resistivity
exhibits a plateau at low temperatures. The magnitude of the plateau value
decreases with reducing sample thickness, which is quantitatively consistent
with the surface electronic conduction in the bulk insulating YbB$_{12}$.
Moreover, the magnetoresistance of the microstructures exhibits a
weak-antilocalization effect at low field. These results are consistent with
the presence of topologically protected surface state, suggesting that
YbB$_{12}$ is a candidate material of the topological Kondo insulator. The high
field resistivity measurements up to $\mu_0H$ = 50 T of the microstructures
provide supporting evidence that the quantum oscillations of the resistivity in
YbB$_{12}$ occurs in the insulating bulk.

###Negative thermal expansion and itinerant ferromagnetism in Mn$_{1.4}$Fe$_{3.6}$Si$_{3}$|Vikram Singh,R. Nath###

Negative thermal expansion and itinerant ferromagnetism in Mn$_{1.4}$Fe$_{3.6}$Si$_{3}$. We report the thermal expansion, critical behavior, magnetocaloric effect
(MCE), and magnetoresistance ($MR$) on the polycrystalline
Mn$_{1.4}$Fe$_{3.6}$Si$_{3}$ compound around the ferromagnetic transition. A
large negative volume thermal expansion ($\alpha_{\rm V}\sim -20 \times
10^{-6}$ K$^{-1}$) is observed across the transition temperature with a strong
anisotropic variation of lattice parameters in the $ab$-plane. The anisotropic
magnetoelasticity arises from the competition between magnetic ordering and
structural deformation which could be responsible for the large MCE ($\Delta
S_{\rm m} \simeq -6$ J/Kg-K) across the magnetic transition in this compound.
The large and negative $MR$ ($\sim -3\%$ in 80 kOe) is also observed at the
transition temperature which can be attributed to the suppression of spin
disorder. Further, the Rhodes-Wolfarth ratio (RWR $> 1$) and identical field
dependence of $MR$ and MCE isotherms indicate the itinerant character of the
$3d$ electrons. The critical exponents determined from the analysis of
magnetization and MCE are consistent with the quasi-two-dimensional (2D) Ising
model with long range exchange interactions which decays as $J(r)\sim
r^{-3.41}$. This unconventional quasi-2D Ising character with long-range
interactions can be ascribed to strong $ab$-plane anisotropy and the
delocalized $3d$ electrons in the studied compound.

###Magnetic-Field-Induced Spin Nematicity in FeSe1-xSx and FeSe1-yTey Superconductor Systems|Shaobo Liu,Jie Yuan,Sheng Ma,Zouyouwei Lu,Yuhang Zhang,Mingwei Ma,Hua Zhang,Kui Jin,Li Yu,Fang Zhou,Xiaoli Dong,Zhongxian Zhao###

Magnetic-Field-Induced Spin Nematicity in FeSe1-xSx and FeSe1-yTey Superconductor Systems. The angular-dependent magnetoresistance (AMR) of the ab plane is measured on
the single crystals of FeSe1-xSx (x = 0, 0.07, 0.13 and 1) and FeSe1-yTey (y =
0.06, 0.61 and 1) at various temperatures under fields up to 9 T. A pronounced
twofold-anisotropic carrier-scattering effect is identified by AMR, and
attributed to a magnetic-field-induced spin nematicity that emerges from the
tetragonal normal-state regime below a characteristic temperature Tsn. This
magnetically polarized spin nematicity is found to be ubiquitous in the
isoelectronic FeSe1-xSx and FeSe1-yTey systems, no matter whether the sample
shows an electronic nematic order at Ts < Tsn, or an antiferromagnetic order at
TN < Tsn, or neither order. Importantly, we find that the isoelectronic
substitution with sulfur does not suppress but even enhances the characteristic
Tsn of the induced spin nematicity in FeSe1-xSx samples. This contrasts sharply
with their rapidly suppressed Ts, the transition temperature of the spontaneous
electronic nematicity. Furthermore, we find that the superconductivity is
significantly suppressed with the enhancement of the induced spin nematicity in
both FeSe1-xSx and FeSe1-yTey samples.

###Magnetization-tuned topological quantum phase transition in MnBi2Te4 devices|Jun Ge,Yanzhao Liu,Pinyuan Wang,Zhiming Xu,Jiaheng Li,Hao Li,Zihan Yan,Yang Wu,Yong Xu,Jian Wang###

Magnetization-tuned topological quantum phase transition in MnBi2Te4 devices. Recently, the intrinsic magnetic topological insulator MnBi2Te4 has attracted
enormous research interest due to the great success in realizing exotic
topological quantum states, such as the quantum anomalous Hall effect (QAHE),
axion insulator state, high-Chern-number and high-temperature Chern insulator
states. One key issue in this field is to effectively manipulate these states
and control topological phase transitions. Here, by systematic angle-dependent
transport measurements, we reveal a magnetization-tuned topological quantum
phase transition from Chern insulator to magnetic insulator with gapped Dirac
surface states in MnBi2Te4 devices. Specifically, as the magnetic field is
tilted away from the out-of-plane direction by around 40-60 degrees, the Hall
resistance deviates from the quantization value and a colossal, anisotropic
magnetoresistance is detected. The theoretical analyses based on modified
Landauer-Buttiker formalism show that the field-tilt-driven switching from
ferromagnetic state to canted antiferromagnetic state induces a topological
quantum phase transition from Chern insulator to magnetic insulator with gapped
Dirac surface states in MnBi2Te4 devices. Our work provides an efficient means
for modulating topological quantum states and topological quantum phase
transitions.

###Quantum contribution to magnetotransport in weak magnetic fields and negative longitudinal magnetoresistance|Hridis K. Pal###

Quantum contribution to magnetotransport in weak magnetic fields and negative longitudinal magnetoresistance. Longitudinal magnetoresistance (LMR) refers to the change in resistance due
to a magnetic field when the current and the magnetic field are parallel to
each other. For this to be nonzero in weak magnetic fields, kinetic theory
stipulates that the electronic dispersion must satisfy certain conditions: it
should either be sufficiently anisotropic or have topological features. The
former results in a positive LMR, while the latter results in a negative LMR.
Here, I propose a different mechanism that leads to LMR in any dispersion
without a need to satisfy the above requirements. The mechanism is quantum in
origin but is applicable in the said regime. It arises due to the change in the
density of states with the magnetic field and is not kinetic in origin.
Remarkably, LMR is found to be negative even if the dispersion is
nontopological, provided it is nonparabolic. An analytical expression is
derived for this contribution to LMR. It is found to depend on the orbital
magnetic susceptibility. The analytical findings are confirmed by numerical
calculations.

###Hysteretic Magnetoresistance in a Non-Magnetic SrSnO3 Film via Thermal Coupling to Dynamic Substrate Behavior|Laxman Raju Thoutam,Tristan K. Truttmann,Anil Kumar Rajapitamahuni,Bharat Jalan###

Hysteretic Magnetoresistance in a Non-Magnetic SrSnO3 Film via Thermal Coupling to Dynamic Substrate Behavior. Hysteretic magnetoresistance (MR) is often used as a signature of
ferromagnetism in conducting oxide thin films and heterostructures. Here,
magnetotransport is investigated in a non-magnetic uniformly La-doped SrSnO3
film grown using hybrid molecular beam epitaxy. A 12 nm La:SrSnO3/2 nm
SrSnO3/GdScO3 (110) film with insulating behavior exhibited a robust hysteresis
loop in the MR at T < 5 K accompanied by an anomaly at ~ +/- 3 T at T < 2.5 K.
Furthermore, MR with the field in-plane yielded a value exceeded 100% at 1.8 K.
Using detailed temperature-, angle- and magnetic field-dependent resistance
measurements, we illustrate the origin of hysteresis is not due to magnetism in
the film but rather is associated with the magnetocaloric effect of the GdScO3
substrate. Given GdScO3 and similar substrates are commonly used in complex
oxide research, this work highlights the importance of thermal coupling to
processes in the substrates which must be carefully accounted for in the data
interpretation for thin films and heterostructures utilizing these substrates.

###Large Unidirectional Magnetoresistance in Metallic Heterostructures in the Spin Transfer Torque Regime|Ting-Yu Chang,Chih-Lin Cheng,Chao-Chung Huang,Cheng-Wei Peng,Yu-Hao Huang,Tian-Yue Chen,Yan-Ting Liu,Chi-Feng Pai###

Large Unidirectional Magnetoresistance in Metallic Heterostructures in the Spin Transfer Torque Regime. A large unidirectional magnetoresistance (UMR) ratio of UMR/$R_{xx}\sim$
$0.36\%$ is found in W/CoFeB metallic bilayer heterostructures at room
temperature. Three different regimes in terms of the current dependence of UMR
ratio are identified: A spin-dependent-scattering mechanism regime at small
current densities $J \sim$ $10$$^{9}$A/m$^{2}$ (UMR ratio $\propto$ $J$), a
spin-magnon-interaction mechanism regime at intermediate $J \sim$
$10$$^{10}$A/m$^{2}$ (UMR ratio $\propto$ $J$$^{3}$), and a spin-transfer
torque (STT) regime at $J \sim$ $10$$^{11}$A/m$^{2}$ (UMR ratio independent of
$J$). We verify the direct correlation between this large UMR and the transfer
of spin angular momentum from the W layer to the CoFeB layer by both
field-dependent and current-dependent UMR characterizations. Numerical
simulations further confirm that the large STT-UMR stems from the tilting of
the magnetization affected by the spin Hall effect-induced spin-transfer
torques. An alternative approach to estimate damping-like spin-torque
efficiencies from magnetic heterostructures is also proposed.

###Evolution of magnetic and transport properties in Cu doped pyrochlore iridate Eu2(Ir1-xCux)2O7|Sampad Mondal,M. Modak,B. Maji,Swapan K. Mandal,B. Ghosh,Surajit Saha,M. Sardar,S. Banerjee###

Evolution of magnetic and transport properties in Cu doped pyrochlore iridate Eu2(Ir1-xCux)2O7. We have investigated the effect of Cu substitution in Eu2(Ir1-xCux)2O7 with
the help of magnetic and transport property measurements. XPS measurement
reveals that each Cu2+ converts Ir4+ to double amount of Ir5+ ions. The
metal-insulator transition temperature (T_MI) is obtained around 120 K. In the
insulating phase, at lower temperature below 50 K, the temperature dependent
resistivity follows a power law dependence and the magnitude of the exponent
increases with Cu concentrations. The temperature dependent thermopower is
observed to follow the electrical resistivity down to 50 K, except for a sudden
drop in thermopower at temperature below 50 K. We find negligible Hall voltage
in the metallic regime of the samples but a sudden Hall voltage is developed
below 50 K. We observe bifurcation in zero field cooled and field cooled
(ZFC-FC) magnetization below irreversibility temperature, exchange bias and
negative magnetoresistance at 3 K and the magnitude of all these properties
increases with Cu concentrations. In the insulating region (below 6 K) there
exists a linear specific heat and its coefficient decreases with Cu doping
which indicates the reduction of spinon contribution with Cu doping.

###Quantum oscillations in 2D insulators induced by graphite gates|Jiacheng Zhu,Tingxin Li,Andrea F. Young,Jie Shan,Kin Fai Mak###

Quantum oscillations in 2D insulators induced by graphite gates. We demonstrate a mechanism for magnetoresistance oscillations in insulating
states of two-dimensional (2D) materials arising from the interaction of the 2D
layer and proximal graphite gates. We study a series of devices based on
different two-dimensional systems, including mono- and bilayer Td-WTe2,
angle-aligned MoTe2/WSe2 heterobilayers and Bernal-stacked bilayer graphene,
which all share a similar graphite-gated geometry. We find that the resistivity
of the 2D system generically shows quantum oscillations as a function of
magnetic field corresponding to a high-density Fermi surface when they are
tuned near an insulating state, in contravention of na\"ive band theory.
Simultaneous measurement of the resistivity of the graphite gates show that
these oscillations are precisely correlated with quantum oscillations in the
resistivity of the graphite gates themselves. Further supporting this
connection, the oscillations are quenched when the graphite gate is replaced by
TaSe2, a high-density metal that does not show quantum oscillations. The
observed phenomenon arises from the oscillatory behavior of graphite density of
states, which modulates the device capacitance and, as a consequence, the
carrier density in the sample layer even when a constant electrochemical
potential is maintained between the sample and the gate electrode. Oscillations
are most pronounced near insulating states where the resistivity is strongly
density dependent. Our study suggests a unified mechanism for quantum
oscillations in graphite-gated 2D insulators based on sample-gate coupling.

###Evolution of transport properties in FeSe thin flakes with thickness approaching the two-dimensional limit|C. S. Zhu,B. Lei,Z. L. Sun,J. H. Cui,M. Z. Shi,W. Z. Zhuo,X. G. Luo,X. H. Chen###

Evolution of transport properties in FeSe thin flakes with thickness approaching the two-dimensional limit. Electronic properties of FeSe can be tuned by various routes. Here, we
present a comprehensive study on the evolution of the superconductivity and
nematicity in FeSe with thickness from bulk single crystal down to bilayer
($\sim$ 1.1 nm) through exfoliation. With decreasing flake thickness, both the
structural transition temperature $T_{\rm s}$ and the superconducting
transition temperature $T_{\rm c}^{\rm zero}$ are greatly suppressed. The
magnetic field ($B$) dependence of Hall resistance $R_{xy}$ at 15 K changes
from $B$-nonlinear to $B$-linear behavior up to 9 T, as the thickness ($d$) is
reduced to 13 nm. $T_{\rm c}$ is linearly dependent on the inverse of flake
thickness (1/$d$) when $d\le$ 13 nm, and a clear drop of $T_{\rm c}$ appears
with thickness smaller than 27 nm. The $I$-$V$ characteristic curves in
ultrathin flakes reveal the signature of Berezinskii-Kosterlitz-Thouless (BKT)
transition, indicating the presence of two-dimensional superconductivity.
Anisotropic magnetoresistance measurements further support 2D superconductivity
in few-layer FeSe. Increase of disorder scattering, anisotropic strains and
dimensionality effect with reducing the thickness of FeSe flakes, might be
taken into account for understanding these behaviors. Our study provides
systematic insights into the evolution of the superconducting properties,
structural transition and Hall resistance of a superconductor FeSe with flakes
thickness and provides an effective way to find two-dimensional
superconductivity as well as other 2D novel phenomena.

###Anatomy of Type-X Spin-Orbit Torque Switching|Yan-Ting Liu,Chao-Chung Huang,Kuan-Hao Chen,Yu-Hao Huang,Chia-Chin Tsai,Ting-Yu Chang,Chi-Feng Pai###

Anatomy of Type-X Spin-Orbit Torque Switching. Using type-x spin-orbit torque (SOT) switching scheme, in which the easy axis
(EA) of the ferromagnetic (FM) layer and the charge current flow direction are
collinear, is possible to realize a lower-power-consumption, higher-density,
and better-performance SOT magnetoresistive random access memory (SOT-MRAM) as
compared to the conventional type-y design. Here, we systematically investigate
type-x SOT switching properties by both macrospin and micromagnetic
simulations. The out-of-plane external field and anisotropy field dependence of
the switching current density ($J_{sw}$) is first examined in the ideal type-x
configuration. Next, we study the FM layer canting angle ($\phi_{EA}$)
dependence of $J_{sw}$ through macrospin simulations and experiments, which
show a transformation of switching dynamics from type-x to type-y with
increasing $\phi_{EA}$. By further integrating field-like torque (FLT) into the
simulated system, we find that a positive FLT can assist type-x SOT switching
while a negative one brings about complex dynamics. More crucially, with the
existence of a sizable FLT, type-x switching mode results in a lower critical
switching current than type-y at current pulse width less than ~ 10 ns,
indicating the advantage of employing type-x design for ultrafast switching
using materials systems with FLT. Our work provides a thorough examination of
type-x SOT scheme with various device/materials parameters, which can be
informative for designing next-generation SOT-MRAM.

###Spin-scattering asymmetry at half-metallic ferromagnet/ferromagnet interface|Y. Fujita,Y. Miura,T. Sasaki,T. Nakatani,K. Hono,Y. Sakuraba###

Spin-scattering asymmetry at half-metallic ferromagnet/ferromagnet interface. We study spin-scattering asymmetry at the interface of two ferromagnets (FMs)
based on a half-metallic Co$_{2}$Fe$_{0.4}$Mn$_{0.6}$Si (CFMS)/CoFe interface.
First-principles ballistic transport calculations based on Landauer formula for
(001)-CoFe/CFMS/CoFe indicate strong spin-dependent conductance at the
CFMS/CoFe interface, suggesting a large interface spin-scattering asymmetry
coefficient ($\gamma$). Fully epitaxial current-perpendicular-to-plane giant
magnetoresistance (CPP-GMR) pseudo-spin-valve (PSV) devices involving
CoFe/CFMS/Ag/CFMS/CoFe structures exhibit an enhancement in MR output owing to
the formation of the CFMS/CoFe interface at room temperature (RT). This is well
reproduced qualitatively by a simulation based on a generalized two-current
series-resistor model with considering the presence of $\gamma$ at the
CFMS/CoFe interface, half-metallicity of CFMS, and combinations of terminated
atoms at the interfaces in the CPP-GMR PSV structure. We show direct evidence
for a large $\gamma$ at a half-metallic FM/FM interface and its impact on
CPP-GMR effect even at RT.

###The power of flexible lattice in Ca3Ru2O7: Exquisite control of the electrical transport via anisotropic magnetostriction|Hengdi Zhao,Hao Zheng,Jasminka Terzic,Wenhai Song,Yifei Ni,Yu Zhang,Pedro Schlottmann,Gang Cao###

The power of flexible lattice in Ca3Ru2O7: Exquisite control of the electrical transport via anisotropic magnetostriction. Ca3Ru2O7 is a correlated and spin-orbit-coupled system with an extraordinary
anisotropy. It is both interesting and unique largely because this material
exhibits conflicting phenomena that are often utterly inconsistent with
traditional precedents, particularly, the quantum oscillations in the
nonmetallic state and colossal magnetoresistivity achieved by avoiding a fully
spin-polarized state. This work focuses on the relationship between the lattice
and transport properties along each crystalline axis and reveals that
application of magnetic field, H, along different crystalline axes readily
stretches or shrinks the lattice in a uniaxial manner, resulting in distinct
electronic states. Furthermore, application of modest pressure drastically
amplifies the anisotropic magnetoelastic effect, leading to either an
occurrence of a robust metallic state at H || hard axis or a reentrance of the
nonmetallic state at H || easy axis. Ca3Ru2O7 presents a rare lattice-dependent
magnetotransport mechanism, in which the extraordinary lattice flexibility
enables an exquisite control of the electronic state via magnetically
stretching or shrinking the crystalline axes, and the spin polarization plays
an unconventional role unfavorable for maximizing conductivity. At the heart of
the intriguing physics is the anisotropic magnetostriction that leads to exotic
states.

###Sign reversal of magnetoresistivity in massive nodal-line semimetals due to Lifshitz transition of Fermi surface|Min-Xue Yang,Hao Geng,Wei Luo,Li Sheng,Wei Chen,D. Y. Xing###

Sign reversal of magnetoresistivity in massive nodal-line semimetals due to Lifshitz transition of Fermi surface. Topological nodal-line semimetals offer an interesting research platform to
explore novel phenomena associated with its torus-shaped Fermi surface. Here,
we study magnetotransport in the massive nodal-line semimetal with spin-orbit
coupling and finite Berry curvature distribution which exists in many
candidates. The magnetic field leads to a deformation of the Fermi torus
through its coupling to the orbital magnetic moment, which turns out to be the
main scenario of the magnetoresistivity (MR) induced by the Berry curvature
effect. We show that a small deformation of the Fermi surface yields a positive
MR $\propto B^2$, different from the negative MR by pure Berry curvature effect
in other topological systems. As the magnetic field increases to a critical
value, a topological Lifshitz transition of the Fermi surface can be induced,
and the MR inverts its sign at the same time. The temperature dependence of the
MR is investigated, which shows a totally different behavior before and after
the Lifshitz transition. Our work uncovers a novel scenario of the MR induced
solely by the deformation of the Fermi surface and establishes a relation
between the Fermi surface topology and the sign of the MR.

###Metamagnetic Transitions in Few-Layer CrOCl Controlled by Magnetic Anisotropy Flipping|Minjie Zhang,Qifeng Hu,Chenqiang Hua,Man Cheng,Zhou Liu,Shijie Song,Fanggui Wang,Pimo He,Guang-Han Cao,Zhu-An Xu,Yunhao Lu,Jinbo Yang,Yi Zheng###

Metamagnetic Transitions in Few-Layer CrOCl Controlled by Magnetic Anisotropy Flipping. The pivotal role of magnetic anisotropy in stabilising two-dimensional (2D)
magnetism has been widely accepted, however, direct correlation between
magnetic anisotropy and long-range magnetic ordering in the 2D limit is yet to
be explored. Here, using angle- and temperature-dependent tunnelling
magnetoresistance, we report unprecedented metamagnetic phase transitions in
atomically-thin CrOCl, triggered by magnetic easy-axis flipping instead of the
conventional spin flop mechanism. Few-layer CrOCl tunnelling devices of various
thicknesses consistently show an in-plane antiferromagnetic (AFM) ground state
with the easy axis aligned along the Cr-O-Cr direction (b-axis). Strikingly,
with the presence of a magnetic field perpendicular to the easy-axis (H||c),
magnetization of CrOCl does not follow the prevalent spin rotation and
saturation pattern, but rather exhibits an easy-axis flipping from the in-plane
to out-of-plane directions. Such magnetic anisotropy controlled metamagnetic
phase transitions are manifested by a drastic upturn in tun- nelling current,
which shows anomalous shifts towards higher H when temperature increases. By 2D
mapping of tunnelling currents as a function of both temperature and H, we
determine a unique ferrimagnetic state with a superstructure periodicity of
five unit cells after the field-induced metam- agnetic transitions. The
feasibility to control 2D magnetism by manipulating magnetic anisotropy may
open enormous opportunities in spin-based device applications.

###Superconducting-like and magnetic transitions in oxygen-implanted diamond-like and amorphous carbon films, and in highly oriented pyrolytic graphite|Nadina Gheorghiu,Charles R. Ebbing,John P. Murphy,Benjamin T. Pierce,Timothy J. Haugan###

Superconducting-like and magnetic transitions in oxygen-implanted diamond-like and amorphous carbon films, and in highly oriented pyrolytic graphite. In our previously published work, we have reported colossal
magnetoresistance, Andreev oscillations, ferromagnetism, and granular
superconductivity in oxygen-implanted carbon fibers, graphite foils, and highly
oriented pyrolytic graphite. In this follow-up research, more results on these
oxygen-implanted graphite samples are presented. We show results from transport
measurements on oxygen-implanted diamond-like carbon thin coatings, amorphous
carbon films, and highly oriented pyrolytic graphite. Significantly, a
three-order magnitude drop in the electrical resistance of the oxygen-implanted
diamond-like carbon films is observed at the 50 K temperature that we have
previously reported for the transition to the superconducting state. Below 50
K, the films resistance oscillates between the high and low resistance states,
less when the sample is under a transverse magnetic field. This metastability
between the insulating and superconducting-like states possibly reflects the
evolution of the amplitude for the superconducting order parameter also known
as the longitudinal Higgs mode. Transitions to low resistance state and
metastability are also observed for amorphous carbon films. Finally, the highly
oriented pyrolytic graphite samples resistance have a thermally activated term
that can be understood on the basis of the LAMH model applied to narrow SC
channels in which thermal fluctuations can cause phase slips. We also find that
in oxygen-implanted carbon materials, the electron charge and spin correlations
do not compete and their interplay rather facilitates the emergence of
high-temperature superconductivity, and thus, additional unexpected effects
like Heisenberg spin waves and magneto-structural transitions are observed.

###Spin-charge interconversion in KTaO$_3$ two-dimensional electron gases|Luis M. Vicente-Arche,Julien Bréhin,Sara Varotto,Maxen Cosset-Cheneau,Srijani Mallik,Raphaël Salazar,Paul Noël,Diogo Castro Vaz,Felix Trier,Suvam Bhattacharya,Anke Sander,Patrick Le Fèvre,François Bertran,Guilhem Saiz,Gerbold Ménard,Nicolas Bergeal,Agnès Barthélémy,Hai Li,Chia-Ching Lin,Dmitri E. Nikonov,Ian A. Young,Julien Rault,Laurent Vila,Jean-Philippe Attané,Manuel Bibes###

Spin-charge interconversion in KTaO$_3$ two-dimensional electron gases. Oxide interfaces exhibit a broad range of physical effects stemming from
broken inversion symmetry. In particular, they can display non-reciprocal
phenomena when time reversal symmetry is also broken, e.g., by the application
of a magnetic field. Examples include the direct and inverse Edelstein effects
(DEE, IEE) that allow the interconversion between spin currents and charge
currents. The DEE and IEE have been investigated in interfaces based on the
perovskite SrTiO$_3$ (STO), albeit in separate studies focusing on one or the
other. The demonstration of these effects remains mostly elusive in other oxide
interface systems despite their blossoming in the last decade. Here, we report
the observation of both the DEE and IEE in a new interfacial two-dimensional
electron gas (2DEG) based on the perovskite oxide KTaO$_3$. We generate 2DEGs
by the simple deposition of Al metal onto KTaO$_3$ single crystals,
characterize them by angle-resolved photoemission spectroscopy and
magnetotransport, and demonstrate the DEE through unidirectional
magnetoresistance and the IEE by spin-pumping experiments. We compare the
spin-charge interconversion efficiency with that of STO-based interfaces,
relate it to the 2DEG electronic structure, and give perspectives for the
implementation of KTaO$_3$ 2DEGs into spin-orbitronic devices.

###Quantum critical behavior in magic-angle twisted bilayer graphene|Alexandre Jaoui,Ipsita Das,Giorgio Di Battista,Jaime Díez-Mérida,Xiaobo Lu,Kenji Watanabe,Takashi Taniguchi,Hiroaki Ishizuka,Leonid Levitov,Dmitri K. Efetov###

Quantum critical behavior in magic-angle twisted bilayer graphene. The flat bands of magic-angle twisted bilayer graphene (MATBG) host
strongly-correlated electronic phases such as correlated insulators,
superconductors and a strange-metal state. The latter state, believed to be key
for understanding the electronic properties of MATBG, is obscured by various
phase transitions and thus could not be unequivocally differentiated from a
metal undergoing frequent electron-phonon collisions. Here, we report transport
measurements in superconducting MATBG in which the correlated insulator states
are suppressed by screening. The uninterrupted metallic ground state shows
resistivity that is linear in temperature over three decades and spans a broad
range of doping including those where a correlation-driven Fermi surface
reconstruction occurs. This strange-metal behavior is distinguished by
Planckian scattering rates and a linear magnetoresistivity. In contrast, near
charge neutrality or a fully-filled flat band, as well as for devices twisted
away from the magic angle, we observe the archetypal Fermi liquid behavior. Our
measurements demonstrate the existence of a quantum critical phase whose
fluctuations dominate the metallic ground state throughout a continuum of
doping. Further, we observe a transition to the strange metal upon suppression
of the superconducting order, suggesting a relationship between quantum
fluctuations and superconductivity in MATBG.

###Large linear magnetoresistance and evidence of degeneracy lifting of valence bands in rhombohedral phase of topological crystalline insulator SnTe|Sonali Baral,Mukesh Kumar Dasoundhi,Indu Rajput,Devendra Kumar,Archana Lakhani###

Large linear magnetoresistance and evidence of degeneracy lifting of valence bands in rhombohedral phase of topological crystalline insulator SnTe. We report a comprehensive magneto-transport study on single crystalline
p-type topological crystalline insulator (TCI) SnTe, across the
cubic-to-rhombohedral (R3m) transition which occurs as a function of
temperature. The electrical resistivity of a well-characterized SnTe crystal
shows evidence for the cubic-to-rhombohedral structural transition at T$_s$
$\sim$64,K and a carrier density of $\sim$1.8$\times$10$^{20}$ at 77,K. As a
function of applied magnetic field perpendicular to the (100) plane, SnTe
exhibits a large unsaturated linear magnetoresistance (LMR) reaching a value of
42% at 5K and 8T. LMR is found to have a direct dependence on the mobility and
a detailed analysis shows that it follows the classical Parish-Littlewood model
of conductivity fluctuations arising from macroscopic inhomogeneity of
tellurium interstitial atoms. We also observe SdH oscillations in the
rhombohedral (R3m) phase with a Berry phase of $\pi$ and significantly lower
carrier density $\sim$5.32$\times$10$^{11}$cm$^{-2}$ at 2K, which provides
direct evidence of protected topological surface states in the (R3m) phase. The
Hall conductivity shows a transformation from one band to two-band behavior
across the structural transition, thus providing experimental evidence for the
degeneracy lifting of bulk valence bands below the cubic symmetry breaking
point which is consistent with recent band structure calculations. The overall
results indicate that magneto-transport studies can distinctly probe the
surface and bulk sensitive properties of SnTe, and can also track the
band-splitting of degenerate bands at the Fermi level across the
cubic-to-rhombohedral (R3m) transition.

###IrCrMnZ (Z=Al, Ga, Si, Ge) Heusler alloys as electrode materials for MgO-based magnetic tunneling junctions: A first-principles study|Tufan Roy,Masahito Tsujikawa,Masafumi Shirai###

IrCrMnZ (Z=Al, Ga, Si, Ge) Heusler alloys as electrode materials for MgO-based magnetic tunneling junctions: A first-principles study. We study IrCrMnZ (Z=Al, Ga, Si, Ge) systems using first-principles
calculations from the perspective of their application as the electrode
materials of MgO-based MTJs. These materials have highly spin-polarized
conduction electrons with partially occupied $\Delta_1$ band, which is
important for coherent tunneling in parallel magnetization configuration. The
Curie temperatures of IrCrMnAl and IrCrMnGa are very high (above 1300 K) as
predicted from mean-field-approximation. The stability of ordered phase against
various antisite disorders has been investigated. We discuss here the effect of
"spin-orbit-coupling" on the electronic structure around Fermi level. Further,
we investigate the electronic structure of IrCrMnZ/MgO heterojunction along
(001) direction. IrCrMnAl/MgO and IrCrMnGa/MgO maintain half-metallicity even
at the MgO interface, with no interfacial states at/around Fermi level in the
minority-spin channel. Large majority-spin conductance of IrCrMnAl/MgO/IrCrMnAl
and IrCrMnGa/MgO/IrCrMnGa is reported from the calculation of ballistic
spin-transport property for parallel magnetization configuration. We propose
IrCrMnAl/MgO/IrCrMnAl and IrCrMnGa/MgO/IrCrMnGa as promising MTJs with a weaker
temperature dependence of tunneling magnetoresistance ratio, owing to their
very high Curie temperatures.

###Distinguishing spin pumping from spin rectification in organic semiconductor-based lateral spin pumping device architectures|Piotr Skalski,Olga Zadvorna,Deepak Venkateshvaran,Henning Sirringhaus###

Distinguishing spin pumping from spin rectification in organic semiconductor-based lateral spin pumping device architectures. Over the last two decades organic spintronics has developed into a striving
field with exciting reports of long spin diffusion lengths and spin relaxation
times in organic semiconductors (OSCs). Easily processed and inexpensive, OSCs
are considered a potential alternative to inorganic materials for use in
spintronic applications. Spin currents have been detected in a wide range of
materials, however, there is still uncertainty over the origin of the signals.
Recently, we explored spin transport through an organic semiconductor with
lateral spin injection and detection architectures, where the injected spin
current is detected non-locally via spin-to-charge conversion in an inorganic
detector. In this work we show that the widely-used control experiments like
linear power dependence and inversion of the signal with the magnetic field are
not sufficient evidence of spin transport and can lead to an incorrect
interpretation of the signal. Here, we use in-plane angular dependent
measurements to separate pure spin signal from parasitic effects arising from
spin rectification (SREs). Apart from well established anisotropic
magnetoresistance (AMR) and anomalous Hall effect (AHE), we observed a novel
effect which we call spurious inverse spin Hall effect (ISHE). It strongly
resembles ISHE behaviour, but arises in the ferromagnet rather than the
detector meaning this additional effect has to be considered in future work.

###Electrical switching of antiferromagnetic CoO | Pt across the Néel temperature|M. J. Grzybowski,C. F. Schippers,M. E. Bal,K. Rubi,U. Zeitler,M. Foltyn,B. Koopmans,H. J. M. Swagten###

Electrical switching of antiferromagnetic CoO | Pt across the Néel temperature. One of the most important challenges in antiferromagnetic spintronics is the
read-out of the N\'eel vector state. High current densities up to 10$^8$
Acm$^{-2}$ used in the electrical switching experiments cause notorious
difficulty in distinguishing between magnetic and thermal origins of the
electrical signals. To overcome this problem, we present a temperature
dependence study of the transverse resistance changes in the switching
experiment with CoO|Pt devices. We demonstrate the possibility to extract a
pattern of spin Hall magnetoresistance for current pulses density of $5 \times
10^7$ Acm$^{-2}$ that is present only below the N\'eel temperature and does not
follow a trend expected for thermal effects. This is the compelling evidence
for the magnetic origin of the signal, which is observed using purely
electrical techniques. We confirm these findings by complementary experiments
in an external magnetic field. Such an approach can allow determining the
optimal conditions for switching antiferromagnets and be very valuable when no
imaging techniques can be applied to verify the origin of the electrical
signal.

###Weak Antilocalization Effect up to ~ 120 K in the van der Waals Crystal Fe5-xGeTe2 with Near Room Temperature Ferromagnetism|Zhengxian Li,Kui Huang,Deping Guo,Guodong Ma,Xiaolei Liu,Yueshen Wu,Jian Yuan,Zicheng Tao,Binbin Wang,Xia Wang,Zhiqiang Zou,Na Yu,Geliang Yu,Jiamin Xue,Jun Li,Zhongkai Liu,Wei Ji,Yanfeng Guo###

Weak Antilocalization Effect up to ~ 120 K in the van der Waals Crystal Fe5-xGeTe2 with Near Room Temperature Ferromagnetism. The weak antilocalization (WAL) effect is known as a quantum correction to
the classical conductivity, which never appeared in two-dimensional magnets. In
this work, we reported the observation of a WAL effect in the van der Waals
ferromagnet Fe5-xGeTe2 with a Curie temperature Tc ~ 270 K, which can even
reach as high as ~ 120 K. The WAL effect could be well described by the
Hikami-Larkin-Nagaoka and Maekawa-Fukuyama theories in the presence of strong
spin-orbit coupling (SOC). Moreover, A crossover from a peak to dip behavior
around 60 K in both the magnetoresistance and magnetoconductance was observed,
which could be ascribed to a rare example of temperature driven Lifshitz
transition as indicated by the angle-resolved photoemission spectroscopy
measurements and first principles calculations. The reflective magnetic
circular dichroism measurements indicate a possible spin reorientation that
kills the WAL effect above 120 K. Our findings present a rare example of WAL
effect in two-dimensional ferromagnet and also a magnetotransport fingerprint
of the strong SOC in Fe5-xGeTe2. The results would be instructive for
understanding the interaction Hamiltonian for such high Tc itinerant
ferromagnetism as well as be helpful for the design of next-generation room
temperature spintronic or twistronic devices.

###Coexistence of resistance oscillations and the anomalous metal phase in a lithium intercalated TiSe$_2$ superconductor|Menghan Liao,Heng Wang,Yuying Zhu,Runan Shang,Mohsin Rafique,Lexian Yang,Hao Zhang,Ding Zhang,Qi-Kun Xue###

Coexistence of resistance oscillations and the anomalous metal phase in a lithium intercalated TiSe$_2$ superconductor. Superconductivity and charge density wave (CDW) appear in the phase diagram
of a variety of materials including the high - $T$$_c$ cuprate family and many
transition metal dichalcogenides (TMDs). Their interplay may give rise to
exotic quantum phenomena. Here, we show that superconducting arrays can
spontaneously form in TiSe$_2$ - a TMD with coexisting superconductivity and
CDW - after lithium ion intercalation. We induce a superconducting dome in the
phase diagram of Li$_x$TiSe$_2$ by using the ionic solid-state gating
technique. Around optimal doping, we observe magnetoresistance oscillations,
indicating the emergence of periodically arranged domains. In the same
temperature, magnetic field and carrier density regime where the resistance
oscillations occur, we observe signatures for the anomalous metal - a state
with a resistance plateau across a wide temperature range below the
superconducting transition. Our study not only sheds further insight into the
mechanism for the periodic electronic structure, but also reveals the interplay
between the anomalous metal and superconducting fluctuations.

###Superconductivity in a quintuple-layer square-planar nickelate|Grace A. Pan,Dan Ferenc Segedin,Harrison LaBollita,Qi Song,Emilian M. Nica,Berit H. Goodge,Andrew T. Pierce,Spencer Doyle,Steve Novakov,Denisse Córdova Carrizales,Alpha T. N'Diaye,Padraic Shafer,Hanjong Paik,John T. Heron,Jarad A. Mason,Amir Yacoby,Lena F. Kourkoutis,Onur Erten,Charles M. Brooks,Antia S. Botana,Julia A. Mundy###

Superconductivity in a quintuple-layer square-planar nickelate. Since the discovery of high-temperature superconductivity in the copper oxide
materials, there have been sustained efforts to both understand the origins of
this phase and discover new cuprate-like superconducting materials. One prime
materials platform has been the rare-earth nickelates and indeed
superconductivity was recently discovered in the doped compound
Nd$_{0.8}$Sr$_{0.2}$NiO$_2$. Undoped NdNiO$_2$ belongs to a series of layered
square-planar nickelates with chemical formula Nd$_{n+1}$Ni$_n$O$_{2n+2}$ and
is known as the 'infinite-layer' ($n = \infty$) nickelate. Here, we report the
synthesis of the quintuple-layer ($n = 5$) member of this series,
Nd$_6$Ni$_5$O$_{12}$, in which optimal cuprate-like electron filling
($d^{8.8}$) is achieved without chemical doping. We observe a superconducting
transition beginning at $\sim$13 K. Electronic structure calculations, in
tandem with magnetoresistive and spectroscopic measurements, suggest that
Nd$_6$Ni$_5$O$_{12}$ interpolates between cuprate-like and infinite-layer
nickelate-like behavior. In engineering a distinct superconducting nickelate,
we identify the square-planar nickelates as a new family of superconductors
which can be tuned via both doping and dimensionality.

###Electronic phase separation: recent progress in the old problem|M. Yu. Kagan,K. I. Kugel,A. L. Rakhmanov###

Electronic phase separation: recent progress in the old problem. We consider the nanoscale electronic phase separation in a wide class of
different materials, mostly in strongly correlated electron systems. The phase
separation turns out to be quite ubiquitous manifesting itself in different
situations, where the itineracy of charge carriers competes with their tendency
toward localization. The latter is often related to some specific type of
magnetic ordering, e.g. antiferromagnetic in manganites and low-spin states in
cobaltites. The interplay between the localization-induced lowering of
potential energy and metallicity (which provides the gain in the kinetic
energy) favors an inhomogeneous ground state such as nanoscale ferromagnetic
droplets in an antiferromagnetic insulating background. The present review
article deals with the advances in the subject of electronic phase separation
and formation of different types of nanoscale ferromagnetic (FM) metallic
droplets (FM polarons or ferrons) in antiferromagnetically ordered (AFM),
charge-ordered (CO), or orbitally-ordered (OO) insulating matrices, as well as
the colossal magnetoresistance (CMR) effect and tunneling electron transport in
the nonmetallic phase-separated state of complex magnetic oxides. It also
touches upon the compounds with spin-state transitions, inhomogeneous
phase-separated state in strongly correlated multiband systems, and electron
polaron effect. A special, attention is paid to the systems with the imperfect
Fermi surface nesting such as chromium alloys, iron-based pnictides, and AA
stacked graphene bilayers.

###Nanoscale devices with superconducting electrodes to locally channel current in 3D Weyl semimetals|Biswajit Datta,Jaykumar Vaidya,Subhamoy Ghatak,Raghav Dhingra,Rajib Mondal,John Jesudasan,A. Thamizhavel,Mandar M. Deshmukh###

Nanoscale devices with superconducting electrodes to locally channel current in 3D Weyl semimetals. We report on the fabrication of nano-devices on the \hkl[-1 0 1] surface of a
Weyl semimetal, a macroscopic crystal of TaAs, and low-temperature transport
measurements. We can implement electron beam lithography by peeling off and
transferring the resist for nanofabrication onto the irregular crystal. We
fabricate the device electrodes with superconducting Niobium nitride (NbN) to
control the current flow through the intended active area of the devices. Our
device structure enables the reduction of the current jetting effect, and we
demonstrate the negative magnetoresistance measurement as a function of angle.
The high field magnetotransport show three distinct oscillation frequencies
corresponding to the three bands at the Fermi level. Resistance measured in the
low magnetic field shows the usual weak anti-localization dip near the
zero-field -- a signature of a Weyl material. Our method of fabricating devices
with superconducting electrodes provides a way to probe the electrical
properties of macroscopic single crystals at the nanoscale. As we use
conventional lithographic techniques for patterning, this method can be
extended to a wide gamut of electrode materials and a large class of 3D quantum
materials.

###Stacking-order effect on spin-orbit torque, spin-Hall magnetoresistance, and magnetic anisotropy in Ni$_{81}$Fe$_{19}$-IrO$_2$ bilayers|Kohei Ueda,Naoki Moriuchi,Kenta Fukushima,Takanori Kida,Masayuki Hagiwara,Jobu Matsuno###

Stacking-order effect on spin-orbit torque, spin-Hall magnetoresistance, and magnetic anisotropy in Ni$_{81}$Fe$_{19}$-IrO$_2$ bilayers. The 5d transition-metal oxides have been an intriguing platform to
demonstrate efficient charge to spin current conversion due to a unique
electronic structure dominated by strong spin-orbit coupling. Here, we report
on stacking-order effect of spin-orbit torque (SOT), spin-Hall
magnetoresistance, and magnetic anisotropy in bilayer Ni$_{81}$Fe$_{19}$-5d
iridium oxide, IrO$_2$. While all the IrO$_2$ and Pt control samples exhibit
large dampinglike-SOT generation stemming from the efficient charge to spin
current conversion, the magnitude of the SOT is larger in the IrO$_2$
(Pt)-bottom sample than in the IrO$_2$ (Pt)-top one. The fieldlike-SOT has even
more significant stack order effect, resulting in an opposite sign in the
IrO$_2$ samples in contrast to the same sign in the Pt samples. Furthermore, we
observe that the magnetic anisotropy energy density and the anomalous Hall
effect are increased in the IrO$_2$ (Pt)-bottom sample, suggesting enhanced
interfacial perpendicular magnetic anisotropy. Our findings highlight the
significant influence of the stack order on spin transport and magnetotransport
properties of Ir oxide/ferromagnet systems, providing useful information on
design of SOT devices including 5d transition-metal oxides.

###Proposal of Analog In-Memory Computing with Magnified Tunnel Magnetoresistance Ratio and Universal STT-MRAM Cell|Hao Cai,Yanan Guo,Bo Liu,Mingyang Zhou,Juntong Chen,Xinning Liu,Jun Yang###

Proposal of Analog In-Memory Computing with Magnified Tunnel Magnetoresistance Ratio and Universal STT-MRAM Cell. In-memory computing (IMC) is an effectual solution for energy-efficient
artificial intelligence applications. Analog IMC amortizes the power
consumption of multiple sensing amplifiers with analog-to-digital converter
(ADC), and simultaneously completes the calculation of multi-line data with
high parallelism degree. Based on a universal one-transistor one-magnetic
tunnel junction (MTJ) spin transfer torque magnetic RAM (STT-MRAM) cell, this
paper demonstrates a novel tunneling magnetoresistance (TMR) ratio magnifying
method to realize analog IMC. Previous concerns include low TMR ratio and
analog calculation nonlinearity are addressed using device-circuit interaction.
Peripheral circuits are minimally modified to enable in-memory matrix-vector
multiplication. A current mirror with feedback structure is implemented to
enhance analog computing linearity and calculation accuracy. The proposed
design maximumly supports 1024 2-bit input and 1-bit weight
multiply-and-accumulate (MAC) computations simultaneously. The 2-bit input is
represented by the width of the input (IN) pulses, while the 1-bit weight is
stored in STT-MRAM and the x7500 magnified TMR (m-TMR) ratio is obtained by
latching. The proposal is simulated using 28-nm CMOS process and MTJ compact
model. The integral nonlinearity is reduced by 57.6% compared with the
conventional structure. 9.47-25.4 TOPS/W is realized with 2-bit input, 1-bit
weight and 4-bit output convolution neural network (CNN).

###Topological phonons in an inhomogeneously strained silicon-1: Evidence of long-distance spin transport and unidirectional magnetoresistance of phonons|Anand Katailiha,Ravindra G. Bhardwaj,Paul C. Lou,Ward P. Beyermann,Sandeep Kumar###

Topological phonons in an inhomogeneously strained silicon-1: Evidence of long-distance spin transport and unidirectional magnetoresistance of phonons. Transverse acoustic waves in an inhomogeneous medium are analogues to
electromagnetic waves and will exhibit topological behavior due to the Berry
gauge potential in the momentum space due to inhomogeneity. The inhomogeneous
(or gradient) medium can be created using an applied strain gradient in a
semiconductor thin film (silicon) since the phonon frequency and dispersion
will be a function of the local strain along the strain gradient direction. As
a consequence, topological phonon mediated spin and heat transport can be
engineered in the semiconductor thin films. Here, we present evidence of a
long-distance (100 um) spin transport in the freestanding Si thin film sample
under an applied strain gradient using transverse spin-Nernst effect
measurement. The long-distance spin transport was attributed to the topological
spin-Hall effect of phonons in an inhomogeneous medium. The inhomogeneous
medium was validated using unidirectional magnetoresistance of phonons where
the magnitude of the coefficient of the non-reciprocal response at room
temperature was as large as reported in the BiTeBr at low temperatures. The
topological phonons also manifested the topological Nernst effect. This work
not only enhances the current understanding of inhomogeneous systems but also
lays the foundation of the topological and spin phononics.

###Topological phonons in an inhomogeneously strained silicon-5: Inhomogeneous magnetoelectronic effect in a conductor|Paul C. Lou,Ravindra G. Bhardwaj,Anand Katailiha,Ward Beyermann,Sandeep Kumar###

Topological phonons in an inhomogeneously strained silicon-5: Inhomogeneous magnetoelectronic effect in a conductor. The spatially inhomogeneity in a magnetic crystal give rise to electric
polarization, which is known as inhomogeneous magnetoelectric effect.
Similarly, an inhomogeneous magnetoelectronic effect in a conducting
multiferroic material give rise to spatially inhomogeneous magnetic moment and
spin distribution due to spatially inhomogeneity in the charge carrier
concentration. In this study, we present experimental evidence of inhomogeneous
magnetoelectronic effect in Py/p-Si layered structure. The Py/p-Si layered
structure exhibit electronic multiferroicity due to superposition of
flexoelectronic charge carrier doping and topological phonons. It gives rise to
spatially modulations in the spin density and magnetic moment, which are
discovered using the Hall effect measurement. The charge carrier density as
well as type of the charge carrier are found to be a function of spatial
coordinate as well as direction of magnetic field. The observed modulations can
also be interpreted as incommensurate SDW with wavelength of ~142 um. The
inhomogeneous magnetoelectronic effect also give rise to magnetocaloric effect,
which is uncovered using thermal hysteresis in the magnetoresistance
measurement. This is a first experimental evidence of inhomogeneous
magnetoelectronic effect, which is electronic counterpart of the
magnetoelectric effect.

###Controllable spin filtering and half metallicity in $β_{12}$-borophene nanoribbons|Fahimeh Norouzi,Mohsen Farokhnezhad,Mahdi Esmaeilzadeh,Bartlomiej Szafran###

Controllable spin filtering and half metallicity in $β_{12}$-borophene nanoribbons. The experimental observation of the Dirac fermion states in
$\beta_{12}$-borophene sheets and the discovery of their novel topological
properties properties have made them a promising candidate for spintronic
applications. Here, by combining non-equilibrium Green's function (NEGF) and
tight-binding (TB) approximation, we study the charge and spin transport
properties through a $\beta_{12}$-borophene nanoribbon (BNR) with the different
edge shapes. We show when a BNR exposed to a nonlocal exchange magnetic field,
the spin filtering occurs for both spin-up and spin-down so that the spin
direction of transmitted electrons could be controlled by adjusting the energy
of incoming electrons with the help of an external backgate voltage. It is
found that an armchair BNR (ABNR) in the simultaneous presence of a transverse
electric field and a nonlocal exchange field indicates a half-metallic nature
which is electrically controllable. Moreover, the influence of local exchange
field fields is evaluated by exposing the edges of ABNR to ferromagnetic strips
with parallel and antiparallel configurations. Our findings show that the edge
manipulations in ABNRs lead to the emergence of a giant magnetoresistance and a
perfect spin filter. Finally, we studied the effects of edge vacancies and
Anderson disorder on the spin-dependent conductance of an ABNR and find that
the perfect spin polarization is not destroyed in the presence of Anderson
disorder and various single vacancies. Our results reveal the outstanding spin
transport properties of ABNRs for future spintronic devices.

###Superconductor-insulator transitions in three-dimensional indium-oxide at high pressures|Bar Hen,Victor Shelukhin,Eran Greenberg,Gregory Kh. Rozenberg,Aharon Kapitulnik,Alexander Palevski###

Superconductor-insulator transitions in three-dimensional indium-oxide at high pressures. Experiments investigating magnetic-field-tuned superconductor-insulator
transition (HSIT) mostly focus on two-dimensional material systems where the
transition and its proximate ground-state phases, often exhibit features that
are seemingly at odds with the expected behavior. Here we present a
complementary study of a three-dimensional pressure-packed amorphous
indium-oxide (InOx) powder where granularity controls the HSIT. Above a low
threshold pressure of ~0.2 GPa, vestiges of superconductivity are detected,
although neither a true superconducting transition nor insulating behavior are
observed. Instead, a saturation at very high resistivity at low pressure is
followed by saturation at very low resistivity at higher pressure. We identify
both as different manifestations of anomalous metallic phases dominated by
superconducting fluctuations. By analogy with previous identification of the
low resistance saturation as a "failed superconductor", our data suggests that
the very high resistance saturation is a manifestation of a "failed insulator".
Above a threshold pressure of ~6 GPa, the sample becomes fully packed, and
superconductivity is robust, with TC tunable with pressure. A quantum critical
point at PC~25 GPa marks the complete suppression of superconductivity. For a
finite pressure below PC, a magnetic field is shown to induce a HSIT from a
true zero-resistance superconducting state to a weakly insulating behavior.
Determining the critical field, HC, we show that similar to the 2D behavior,
the insulating-like state maintains a superconducting character, which is
quenched at higher field, above which the magnetoresistance decreases to its
fermionic normal state value.

###Giant magnetoresistance and topological Hall effect in the EuGa4 antiferromagnet|H. Zhang,X. Y. Zhu,Y. Xu,D. J. Gawryluk,W. Xie,S. L. Ju,M. Shi,T. Shiroka,Q. F. Zhan,E. Pomjakushina,T. Shang###

Giant magnetoresistance and topological Hall effect in the EuGa4 antiferromagnet. We report on systematic temperature- and magnetic field-dependent studies of
the EuGa$_4$ binary compound, which crystallizes in a centrosymmetric
tetragonal BaAl$_4$-type structure with space group $I4/mmm$. The electronic
properties of EuGa$_4$ single crystals, with an antiferromagnetic (AFM)
transition at $T_\mathrm{N} \sim 16.4$ K, were characterized via electrical
resistivity and magnetization measurements. A giant nonsaturating
magnetoresistance was observed at low temperatures, reaching $\sim 7 \times
10^4$ % at 2 K in a magnetic field of 9 T. In the AFM state, EuGa$_4$ undergoes
a series of metamagnetic transitions in an applied magnetic field, clearly
manifested in its field-dependent electrical resistivity. Below $T_\mathrm{N}$,
in the $\sim$4-7 T field range, we observe also a clear hump-like anomaly in
the Hall resistivity which is part of the anomalous Hall resistivity. We
attribute such a hump-like feature to the topological Hall effect, usually
occurring in noncentrosymmetric materials known to host topological spin
textures (as e.g., magnetic skyrmions). Therefore, the family of materials with
a tetragonal BaAl$_4$-type structure, to which EuGa$_4$ and EuAl$_4$ belong,
seems to comprise suitable candidates on which one can study the interplay
among correlated-electron phenomena (such as charge-density wave or exotic
magnetism) with topological spin textures and topologically nontrivial bands.

###Magnetic field induced transition from a vortex liquid to Bose metal in ultrathin a-MoGe thin film|Surajit Dutta,John Jesudasan,Pratap Raychaudhuri###

Magnetic field induced transition from a vortex liquid to Bose metal in ultrathin a-MoGe thin film. We identify a magnetic field induced transition from a vortex liquid to Bose
metal in a 2-dimensional amorphous superconductor, a-MoGe, using a combination
of magnetotransport and scanning tunnelling spectroscopy (STS). Below the
superconducting transition, Tc ~ 1.36 K, the magnetoresistance isotherms cross
at a nearly temperature independent magnetic field, H_c^*~ 36 kOe. Above this
field, the temperature coefficient of resistance is weakly negative, but the
resistance remains finite as T --> 0, as expected in a bad metal. From STS
conductance maps at 450 mK we observe a very disordered vortex lattice at very
low fields that melts into a vortex liquid above 3 kOe. Up to H_c^* the
tunnelling spectra display superconducting gap and coherence peak over a broad
background caused by electron-electron interactions, as expected in a vortex
liquid. However, above H_c^* the tunnelling spectra continue to display the gap
but the coherence peak gets completely suppressed, suggesting that Cooper pairs
lose their phase coherence. We conclude that H_c^* demarcates a transition from
a vortex liquid to Bose metal, that eventually transforms to a regular metal at
a higher field H* where the gap vanishes in the electronic spectrum.

###Three-dimensional ferromagnetism and magnetotransport in van der Waals Mn-intercalated tantalum disufide|Yu Liu,Zhixiang Hu,Eli Stavitski,Klaus Attenkofer,C. Petrovic###

Three-dimensional ferromagnetism and magnetotransport in van der Waals Mn-intercalated tantalum disufide. Van der Waals (vdW) ferromagnets are an important class of materials for
spintronics applications. The recent discovery of atomically vdW magnets
CrI$_3$ and Cr$_2$Ge$_2$Te$_6$ has triggered a renaissance in the area of
two-dimensional (2D) magnetism. Herein we systematically studied
2H-Mn$_{0.28}$TaS$_2$ single crystal, a 2D vdW ferromagnet with $T_c$ $\sim$
82.3 K and a large in-plane magnetic anisotropy. Mn $K$-edge x-ray absorption
spectroscopy was measured to provide information on its electronic state and
local atomic environment. The detailed magnetic isotherms measured in the
vicinity of $T_c$ indicates that the spin coupling inside 2H-Mn$_{0.28}$TaS$_2$
is of a three-dimensional (3D) Heisenberg-type coupled with the attractive
long-range interaction between spins that decay as $J(r)\approx r^{-4.85}$.
Both resistivity $\rho(T)$ and thermopower $S(T)$ exhibit anomalies near $T_c$,
confirming that the hole-type transport carriers strongly interact with local
moments. An unusual angle-dependent magnetoresistance is further observed,
suggesting a possible field-induced novel magnetic structure.

###Polaronic transport and thermoelectricity in Mn$_3$Si$_2$Te$_6$ single crystals|Yu Liu,Zhixiang Hu,Milinda Abeykoon,Eli Stavitski,Klaus Attenkofer,Eric D. Bauer,C. Petrovic###

Polaronic transport and thermoelectricity in Mn$_3$Si$_2$Te$_6$ single crystals. We carried out a comprehensive study of the structural, electrical transport,
thermal and thermodynamic properties in ferrimagnetic Mn$_3$Si$_2$Te$_6$ single
crystals. Mn and Te $K$-edge X-ray absorption spectroscopy and synchrotron
powder X-ray diffraction were measured to provide information on the local
atomic environment and the average crystal structure. The dc and ac magnetic
susceptibility measurements indicate a second-order paramagnetic to
ferrimagnetic transition at $T_c$ $\sim$ 74 K, which is further confirmed by
the specific heat measurement. Mn$_3$Si$_2$Te$_6$ exhibits semiconducting
behavior along with a large negative magnetoresistance of -87\% at $T_c$ and
relatively high value of thermopower up to $\sim$ 10 mV/K at 5 K. Besides the
rapidly increasing resistivity $\rho(T)$ and thermopower $S(T)$ below 20 K, the
large discrepancy between activation energy for resistivity $E_\rho$ and
thermopower $E_S$ above 20 K indicates the polaronic transport mechanism.
Furthermore, the thermal conductivity $\kappa(T)$ of Mn$_3$Si$_2$Te$_6$ is
notably rather low, comparable to Cr$_2$Si$_2$Te$_6$, and is strongly
suppressed in magnetic field across $T_c$, indicating the presence of strong
spin-lattice coupling, also similar with Cr$_2$Si$_2$Te$_6$.

###Structures and physical properties of V-based kagome metals CsV$_{6}$Sb$_{6}$ and CsV$_{8}$Sb$_{12}$|Qiangwei Yin,Zhijun Tu,Chunsheng Gong,Shangjie Tian,Hechang Lei###

Structures and physical properties of V-based kagome metals CsV$_{6}$Sb$_{6}$ and CsV$_{8}$Sb$_{12}$. We report two new members of V-based kagome metals CsV$_{6}$Sb$_{6}$ and
CsV$_{8}$Sb$_{12}$. The most striking structural feature of CsV$_{6}$Sb$_{6}$
is the V kagome bilayers. For CsV$_{8}$Sb$_{12}$, there is an intergrowth of
two-dimensional V kagome layers and one-dimensional V chains and the latter
lead to the orthorhombic symmetry of this material. Further measurements
indicate that these two materials exhibit metallic and Pauli paramagnetic
behaviors. More importantly, different from CsV$_{3}$Sb$_{5}$, the charge
density wave state and superconductivity do not emerge in CsV$_{6}$Sb$_{6}$ and
CsV$_{8}$Sb$_{12}$ when temperature is above 2 K. Small magnetoresistance with
saturation behavior and linear field dependence of Hall resistivity at high
field and low temperature suggest that the carriers in both materials should be
uncompensated with much different concentrations. The discovery of these two
new V-based kagome metals sheds light on the exploration of correlated
topological materials based on kagome lattice.

###Persistent large anisotropic magnetoresistance and insulator to metal transition in spin-orbit coupled antiferromagnets Sr2(Ir1-xGax)O4|Haowen Wang,Wei Wang,Ni Hu,Tianci Duan,Songliu Yuan,Shuai Dong,Chengliang Lu,Jun-Ming Liu###

Persistent large anisotropic magnetoresistance and insulator to metal transition in spin-orbit coupled antiferromagnets Sr2(Ir1-xGax)O4. Antiferromagnetic (AFM) spintronics, where magneto-transport is governed by
an antiferromagnet instead of a ferromagnet, opens fascinating new perspectives
for both fundamental research and device technology, owing to their intrinsic
appealing properties like rigidness to magnetic field, absence of stray field,
and ultrafast spin dynamics. One of the urgent challenges, hindering the
realization of the full potential of AFM spintronics, has been the performance
gap between AFM metals and insulators. Here, we demonstrate the insulator-metal
transition and persistently large anisotropic magnetoresistance (AMR) in single
crystals Sr2(Ir1-xGax)O4 (0<x<0.09) which host the same basal-plane AFM lattice
with strong spin-orbit coupling. The non-doped Sr2IrO4 shows the insulating
transport with the AMR as big as ~16.8% at 50 K. The Ga substitution of Ir
allows a gradual reduction of electrical resistivity, and a clear
insulator-to-metal transition is identified in doped samples with x above 0.05,
while the AMR can still have ~1%, sizable in comparison with those in AFM
metals reported so far. Our experiments reveal that all the samples have the
similar fourfold AMR symmetry, which can be well understood in the scenario of
magnetocrystalline anisotropy. It is suggested that the spin-orbit coupled
antiferromagnets Sr2(Ir1-xGax)O4 are promising candidate materials for AFM
spintronics, providing a rare opportunity to integrate the superior spintronic
functionalities of AFM metals and insulators.

###Spontaneous rotational symmetry breaking in KTaO$_3$ heterointerface superconductors|Guanqun Zhang,Lijie Wang,Jinghui Wang,Guoan Li,Guangyi Huang,Guang Yang,Huanyi Xue,Zhongfeng Ning,Yueshen Wu,Jin-Peng Xu,Yanru Song,Zhenghua An,Changlin Zheng,Jie Shen,Jun Li,Yan Chen,Wei Li###

Spontaneous rotational symmetry breaking in KTaO$_3$ heterointerface superconductors. Broken symmetries play a fundamental role in superconductivity and influence
many of its properties in a profound way. Understanding these symmetry breaking
states is essential to elucidate the various exotic quantum behaviors in
non-trivial superconductors. Here, we report an experimental observation of
spontaneous rotational symmetry breaking of superconductivity at the
heterointerface of amorphous (a)-YAlO$_3$/KTaO$_3$(111) with a superconducting
transition temperature of 1.86 K. Both the magnetoresistance and
superconducting critical field in an in-plane field manifest striking twofold
symmetric oscillations deep inside the superconducting state, whereas the
anisotropy vanishes in the normal state, demonstrating that it is an intrinsic
property of the superconducting phase. We attribute this behavior to the
mixed-parity superconducting state, which is an admixture of \emph{s}-wave and
\emph{p}-wave pairing components induced by strong spin-orbit coupling inherent
to inversion symmetry breaking at the heterointerface of a-YAlO$_3$/KTaO$_3$.
Our work suggests an unconventional nature of the underlying pairing
interaction in the KTaO$_3$ heterointerface superconductors, and brings a new
broad of perspective on understanding non-trivial superconducting properties at
the artificial heterointerfaces.

###Tuning the Room Temperature Ferromagnetism in Fe5GeTe2 by Arsenic Substitution|Andrew F. May,Jiaqiang Yan,Raphael Hermann,Mao-Hua Du,Michael A. McGuire###

Tuning the Room Temperature Ferromagnetism in Fe5GeTe2 by Arsenic Substitution. In order to tune the magnetic properties of the cleavable high-Curie
temperature ferromagnet Fe$_{5-x}$GeTe$_2$, the effect of increasing the
electron count through arsenic substitution has been investigated. Small
additions of arsenic (2.5 and 5%) seemingly enhance ferromagnetic order in
polycrystalline samples by quenching fluctuations on one of the three magnetic
sublattices, whereas larger As concentrations decrease the ferromagnetic Curie
temperature ($T_{\rm C}$) and saturation magnetization. This work also
describes the growth and characterization of Fe$_{4.8}$AsTe$_2$ single crystals
that are structurally analogous to Fe$_{5-x}$GeTe$_2$ but with some phase
stability complications. Magnetization measurements reveal dominant
antiferromagnetic behavior in Fe$_{4.8}$AsTe$_2$ with a N\'{e}el temperature of
$T_{\rm N}$ $\approx$42K. A field-induced spin-flop below $T_{\rm N}$ results
in a switch from negative to positive magnetoresistance, with significant
hysteresis causing butterfly-shaped resistance loops. In addition to reporting
the properties of Fe$_{4.8}$AsTe$_2$, this work shows the importance of
manipulating the individual magnetic sublattices in Fe$_{5-x}$GeTe$_2$ and
motivates further efforts to control the magnetic properties in related
materials by fine tuning of the Fermi energy or crystal chemistry.

###HgTe quantum wells for QHE metrology under soft cryomagnetic conditions: permanent magnets and liquid ${^4He}$ temperatures|I. Yahniuk,A. Kazakov,B. Jouault,S. S. Krishtopenko,S. Kret,G. Grabecki,G. Cywiński,N. N. Mikhailov,S. A. Dvoretskii,J. Przybytek,V. I. Gavrilenko,F. Teppe,T. Dietl,W. Knap###

HgTe quantum wells for QHE metrology under soft cryomagnetic conditions: permanent magnets and liquid ${^4He}$ temperatures. HgTe quantum wells with a thickness of ${\sim}$7 nm may have a graphene-like
band structure and have been recently proposed to be potential candidates for
quantum Hall effect (QHE) resistance standards under the condition of operation
in the fields above certain critical field $B_c$, above which the topological
phase (with parasitic edge conduction) disappears. We present experimental
studies of the magnetoresistance of different of HgTe quantum wells as a
function temperature and magnetic field, determining the critical magnetic
field $B_c$. We demonstrate that for QWs of specific width $B_c$ becomes low
enough to grant observation of remarkably wide QHE plateaus at the filling
factor ${v=-1}$ (holes) in relaxed cryomagnetic conditions: while using
commercial 0.82 T Neodymium permanent magnets and temperature of a few Kelvin
provided by ${^4He}$ liquid system only. Band structure calculations allow us
to explain qualitatively observed phenomena due to the interplay between light
holes and heavy holes energy sub-bands (side maxima of the valence band). Our
work clearly shows that the peculiar band structure properties of HgTe QWs with
massless Dirac fermions make them an ideal platform for developing metrological
devices with relaxed cryomagnetic conditions.

###Exchange coupling in synthetic anion-engineered chromia heterostructures|Shan Lin,Zhiwen Wang,Qinghua Zhang,Shengru Chen,Qiao Jin,Hongbao Yao,Shuai Xu,Fanqi Meng,Xinmao Yin,Can Wang,Chen Ge,Haizhong Guo,Chi Sin Tang,Andrew T. S. Wee,Lin Gu,Kui-juan Jin,Hongxin Yang,Er-Jia Guo###

Exchange coupling in synthetic anion-engineered chromia heterostructures. Control of magnetic states by external factors has garnered a mainstream
status in spintronic research for designing low power consumption and
fast-response information storage and processing devices. Previously,
magnetic-cation substitution is the conventional means to induce ferromagnetism
in an intrinsic antiferromagnet. Theoretically, the anion-doping is proposed to
be another effect means to change magnetic ground states. Here we demonstrate
the synthesis of high-quality single-phase chromium oxynitride thin films using
in-situ nitrogen doping. Unlike antiferromagnetic monoanionic chromium oxide
and nitride phases, chromium oxynitride exhibits a robust ferromagnetic and
insulating state, as demonstrated by the combination of multiple magnetization
probes and theoretical calculations. With increasing the nitrogen content, the
crystal structure of chromium oxynitride transits from trigonal (R3c) to
tetragonal (4mm) phase and its saturation magnetization reduces significantly.
Furthermore, we achieve a large and controllable exchange bias field in the
chromia heterostructures by synthetic anion engineering. This work reflects the
anion engineering in functional oxides towards the potential applications in
giant magnetoresistance and tunnelling junctions of modern magnetic sensors and
read heads.

###TaCo$_{2}$Te$_{2}$: An air-stable, magnetic van der Waals material with high mobility|Ratnadwip Singha,Fang Yuan,Guangming Cheng,Tyger H. Salters,Yuzki M. Oey,Graciela V. Villalpando,Milena Jovanovic,Nan Yao,Leslie M. Schoop###

TaCo$_{2}$Te$_{2}$: An air-stable, magnetic van der Waals material with high mobility. Van der Waals (vdW) materials are an indispensable part of functional device
technology due to their versatile physical properties and ease of exfoliating
to the low-dimensional limit. Among all the compounds investigated so far, the
search for magnetic vdW materials has intensified in recent years, fueled by
the realization of magnetism in two dimensions (2D). However, metallic magnetic
vdW systems are still uncommon. In addition, they rarely host high-mobility
charge carriers, which is an essential requirement for high-speed electronic
applications. Another shortcoming of 2D magnets is that they are highly air
sensitive. Using chemical reasoning, we introduce TaCo2Te2 as an air-stable,
high-mobility, magnetic vdW material. It has a layered structure, which
consists of Peierls distorted Co chains and a large vdW gap between the layers.
We find that the bulk crystals can be easily exfoliated and the obtained thin
flakes are robust to ambient conditions after four months of monitoring using
an optical microscope. We also observe signatures of canted antiferromagntic
behavior at low-temperature. TaCo2Te2 shows a metallic character and a large,
non-saturating, anisotropic magnetoresistance. Furthermore, our Hall data and
quantum oscillation measurements reveal the presence of both electron- and
hole-type carriers and their high mobility.

###CoFeVSb: A Promising Candidate for Spin Valve and Thermoelectric Applications|Jadupati Nag,Deepika Rani,Durgesh Singh,R. Venkatesh,Bhawna Sahni,A. K. Yadav,S. N. Jha,D. Bhattacharyya,P. D. Babu,K. G. Suresh,Aftab Alam###

CoFeVSb: A Promising Candidate for Spin Valve and Thermoelectric Applications. We report a combined theoretical and experimental study of a novel quaternary
Heusler system CoFeVSb from the view point of room temperature spintronics and
thermoelectric applications. It crystallizes in cubic structure with small
DO$_3$-type disorder. The presence of disorder is confirmed by room temperature
synchrotron X-ray diffraction(XRD) and extended X-ray absorption fine structure
(EXAFS) measurements. Magnetization data reveal high ordering temperature with
a saturation magnetization of 2.2 $\mu_B$/f.u. Resistivity measurements reflect
half-metallic nature. Double hysteresis loop along with asymmetry in the
magnetoresistance(MR) data reveals room temperature spin-valve feature, which
remains stable even at 300 K. Hall measurements show anomalous behavior with
significant contribution from intrinsic Berry phase. This compound also large
room temperature power factor ($\sim0.62$ mWatt/m/K$^{2}$) and ultra low
lattice thermal conductivity ($\sim0.4$ W/m/K), making it a promising candidate
for thermoelectric application. Ab-initio calculations suggest weak
half-metallic behavior and reduced magnetization (in agreement with experiment)
in presence of DO$_3$ disorder. We have also found an energetically competing
ferromagnetic FM)/antiferromagnetic (AFM) interface structure within an
otherwise FM matrix: one of the prerequisites for spin valve behavior.
Coexistence of so many promising features in a single system is rare, and hence
CoFeVSb gives a fertile platform to explore numerous applications in future.

###Modification of unconventional Hall effect with doping at the non-magnetic site in a 2D van der Waals ferromagnet|Rajeswari Roy Chowdhury,Chandan Patra,Samik DuttaGupta,Sayooj Satheesh,Shovan Dan,Shunsuke Fukami,Ravi Prakash Singh###

Modification of unconventional Hall effect with doping at the non-magnetic site in a 2D van der Waals ferromagnet. Two-dimensional (2D) van der Waals (vdW) magnetic materials have garnered
considerable attention owing to the existence of magnetic order down to atomic
dimensions and flexibility towards interface engineering, offering an
attractive platform to explore novel spintronic phenomena and functionalities.
Understanding of the magnetoresistive properties and their correlation to the
underlying magnetic configurations is essential for 2D vdW-based spintronic or
quantum information devices. Among the promising candidates, vdW ferromagnet
(FM) Fe3GeTe2 shows an unusual magnetotransport behavior, tunable by doping at
the magnetic (Fe) site, and tentatively arising from complicated underlying
spin texture configurations. Here, we explore an alternative route towards
manipulation of magnetotransport properties of a vdW FM without directly
affecting the magnetic site i.e., by doping at the non-magnetic (Ge) site of
Fe3(Ge,As)Te2. Interestingly, doping at the non-magnetic (Ge) site results in
an unconventional Hall effect whose strength was considerably modified by
increasing As concentration, possibly arising from emergent electromagnetic
behavior from underlying complicated spin configurations. The present results
provide a possible route to understand the intricate role played by the
non-magnetic (Ge) atom towards magnetic properties of vdW FMs, and shows a
novel direction towards tailoring of underlying interactions responsible for
the stabilization of non trivial spin textures in 2D magnetic vdW materials.

###Tunneling Magnetoresistance in Noncollinear Antiferromagnetic Tunnel Junctions|Jianting Dong,Xinlu Li,Gautam Gurung,Meng Zhu,Peina Zhang,Fanxing Zheng,Evgeny Y. Tsymbal,Jia Zhang###

Tunneling Magnetoresistance in Noncollinear Antiferromagnetic Tunnel Junctions. Antiferromagnetic (AFM) spintronics has emerged as a subfield of spintronics
driven by the advantages of antiferromagnets producing no stray fields and
exhibiting ultrafast magnetization dynamics. The efficient method to detect an
AFM order parameter, known as the N\'eel vector, by electric means is critical
to realize concepts of AFM spintronics. Here, we demonstrate that non-collinear
AFM metals, such as Mn3Sn, exhibit a momentum dependent spin polarization which
can be exploited in AFM tunnel junctions to detect the N\'eel vector. Using
first-principles calculations based on density functional theory, we predict a
tunneling magnetoresistance (TMR) effect as high as 300% in AFM tunnel
junctions with Mn3Sn electrodes, where the junction resistance depends on the
relative orientation of their N\'eel vectors and exhibits four non-volatile
resistance states. We argue that the spin-split band structure and the related
TMR effect can also be realized in other non-collinear AFM metals like Mn3Ge,
Mn3Ga, Mn3Pt, and Mn3GaN. Our work provides a robust method for detecting the
N\'eel vector in non-collinear antiferromagnets via the TMR effect, which may
be useful for their application in AFM spintronic devices.

###Gate-controlled proximity magnetoresistance in In1-xGaxAs/(Ga,Fe)Sb bilayer heterostructures|Kosuke Takiguchi,Kyosuke Okamura,Le Duc Anh,Masaaki Tanaka###

Gate-controlled proximity magnetoresistance in In1-xGaxAs/(Ga,Fe)Sb bilayer heterostructures. The magnetic proximity effect (MPE), ferromagnetic coupling at the interface
of magnetically dissimilar layers, attracts much attention as a promising
pathway for introducing ferromagnetism into a high-mobility non-magnetic
conducting channel. Recently, our group found giant proximity magnetoresistance
(PMR), which is caused by MPE at an interface between a non-magnetic
semiconductor InAs quantum well (QW) layer and a ferromagnetic semiconductor
(Ga,Fe)Sb layer. The MPE in the non-magnetic semiconductor can be modulated by
applying a gate voltage and controlling the penetration of the electron
wavefunction in the InAs QW into the neighboring insulating ferromagnetic
(Ga,Fe)Sb layer. However, optimal conditions to obtain strong MPE at the
InAs/(Ga,Fe)Sb interface have not been clarified. In this paper, we
systematically investigate the PMR properties of In1-xGaxAs (x = 0%, 5%, 7.5%,
and 10%) / (Ga,Fe)Sb bilayer semiconductor heterostructures under a wide range
of gate voltage. The inclusion of Ga alters the electronic structures of the
InAs thin film, in particular changing the effective mass and the QW potential
of electron carriers. Our experimental results and theoretical analysis of the
PMR in these In1-xGaxAs/(Ga,Fe)Sb heterostructures show that the MPE depends
not only on the degree of penetration of the electron wavefunction into
(Ga,Fe)Sb but also on the electron density. These findings help us to unveil
the microscopic mechanism of MPE in semiconductor-based
non-magnetic/ferromagnetic heterojunctions.

###Stress-tailoring magnetic anisotropy of V$_2$O$_3$/Ni bilayers|Christian T. Wolowiec,Juan Gabriel Ramírez,Min-Han Lee,Nicolas M. Vargas,Ali C. Basaran,Pavel Salev,Ivan K. Schuller###

Stress-tailoring magnetic anisotropy of V$_2$O$_3$/Ni bilayers. We report on a temperature-driven reversible change of the in-plane magnetic
anisotropy of V$_2$O$_3$/Ni bilayers. This is caused by the rhombohedral to
monoclinic structural phase transition of V$_2$O$_3$ at $T_C$ = 160 K. The
in-plane magnetic anisotropy is uniaxial above $T_C$, but as the bilayer is
cooled through the structural phase transition, a secondary magnetic easy axis
emerges. Ferromagnetic resonance measurements show that this change in magnetic
anisotropy is reversible with temperature. We identify two structural
properties of the V$_2$O$_3$/Ni bilayers affecting the in-plane magnetic
anisotropy: (1) a growth-induced uniaxial magnetic anisotropy associated with
step-like terraces in the bilayer microstructure and (2) a low-temperature
strain-induced biaxial anisotropy associated with the V$_2$O$_3$ structural
phase transition. Magnetoresistance measurements corroborate the change in
magnetic anisotropy across the structural transition and suggest that the
negative magnetostriction of Ni leads to the emergence of a strain-induced
easy-axis. This shows that a temperature-dependent structural transition in
V$_2$O$_3$ may be used to tune the magnetic anisotropy in an adjacent
ferromagnetic thin film.

###Tuning Ferroelectrics to Antiferroelectrics in Multiferroic LaxSr1-xFe12O19 Ceramics|Cong-Cong Duan,Guo-Long Tan###

Tuning Ferroelectrics to Antiferroelectrics in Multiferroic LaxSr1-xFe12O19 Ceramics. The combination of antiferroelectricity (AFE) and ferromagnetism (FM) in one
structure would allow the development of new type of multiferroic candidates,
which be applicable not only in magnetoelectric memories but also in novel
energy storage devices. Here we propose a novel type of multiferroic candidate
LaxSr1-xFe12O19, whose room temperature state could betuned from ferroelectrics
(FE) to antiferroelectrics by changing x from 0 to 0.5. The emphasis of this
paper will be focused on the La0.5Sr0.5Fe12O19 system, in which full AFE and FM
coexist. The pure antiferroelectric behavior in La0.5Sr0.5Fe12O19 ceramics is
demonstrated by double polarization-electric field (P-E) hysteresis loops,
which are fully separated by a linear antiferroelectric AFE component with zero
net polarization. The material of La0.2Sr0.7Fe12O19 with the intermediate
composition exhibits a hybrid ferroelectric/antiferroelectric state. The
recoverable energy density of the antiferroelectric La0.5Sr0.5Fe12O19 phase
reaches 14.3 J/cm3. This material demonstrates strong magnetoelectric coupling
and giant magnetoresistance (GMR) effect. A 1.1T magnetic field generates
electronic polarization up to 0.95uC/cm2, reduce the resistance by 117%,
enhances dielectric constants by 540% and right shifts the maximum dielectric
loss peak by 208 kHz. The combined functional responses provide an opportunity
to develop novel multifunctional electric and energy storage devices.

###Spectral analysis of universal conductance fluctuations|I. M. Suslov###

Spectral analysis of universal conductance fluctuations. Universal conductance fluctuations are usually observed in the form of
aperiodic oscillations in the magnetoresistance of thin wires as a function of
the magnetic field B. If such oscillations are completely random at scales
exceeding \xi_B, their Fourier analysis should reveal a white noise spectrum at
frequencies below \xi_B^{-1}. Comparison with the results for 1D systems
suggests another scenario: according to it, such oscillations are due to the
superposition of incommensurate harmonics and their spectrum should contain
discrete frequencies. An accurate Fourier analysis of the classical experiment
by Washburn and Webb reveals a practically discrete spectrum in agreement with
the latter scenario. However, this spectrum is close in shape to the discrete
white noise spectrum whose properties are similar to a continuous one. More
detailed analysis reveals the existence of the continuous component, whose
smallness is explained theoretically. A lot of qualitative results are
obtained, which confirm the presented picture. The distribution of phases,
frequency differences and the growth exponents agree with theoretical
predictions. Discrete frequencies depends weakly on the treatment procedure.
The discovered shift oscillations confirm the analogy with 1D systems.
Microscopical estimates show agreement of the obtained results with geometrical
dimensions of the sample.

###Magneto-Transport and High-Resolution Angle-Resolved Photoelectron Spectroscopy Studies of Palladium Doped Bi$_{2}$Te$_{3}$|Shailja Sharma,Shiv Kumar,Girish C. Tewari,Girish Sharma,Eike F. Schwier,Kenya Shimada,A. Taraphder,C. S. Yadav###

Magneto-Transport and High-Resolution Angle-Resolved Photoelectron Spectroscopy Studies of Palladium Doped Bi$_{2}$Te$_{3}$. We have performed magneto-transport and high-resolution angle-resolved
photoelectron spectroscopy (ARPES) measurements on palladium (Pd) doped
topological insulator Pd$_{x}$Bi$_{2}$Te$_{3}$ (0 $\leq$ x $\leq$ 0.20) single
crystals. We have observed unusually high values of magnetoresistance ($\sim$
1500%) and mobility ($\sim$ 93000 cm$^{2}$V$^{-1}$s$^{-1}$) at low temperatures
for pristine Bi2Te3 that decrease on Pd doping. The Shubnikov-de Haas (SdH)
oscillations have been detected for x = 0.05, 0.10, confirming the presence of
2D topological surface states (TSSs) for these samples. The Hall measurement
shows the crossover from n-type charge carriers in pristine Bi$_{2}$Te$_{3}$ to
p-type charge carriers upon Pd doping. The ARPES measurements show that the
conduction band crosses the Fermi level for pristine Bi$_{2}$Te$_{3}$ , and the
Dirac point of the TSSs and bulk-derived valence bands indicated shift to lower
binding energy upon Pd doping in a rigid-band-like way up to x $\sim$0.10.
Based on the comparison of the parameters obtained from the SdH and ARPES
measurements, the reduction in the kF value in the magneto-transport
measurements likely due to the band bending induced by the Schottky barrier.

###On the origin of Field-Induced Boson Insulating States in a 2D Superconducting Electron Gas with Strong Spin-Orbit Scatterings|Tsofar Maniv,Vladimir Zhuravlev###

On the origin of Field-Induced Boson Insulating States in a 2D Superconducting Electron Gas with Strong Spin-Orbit Scatterings. We search for the deep origin of the field-induced
superconductor-to-insulator transitions observed experimentally in
electron-doped SrTiO$_{3}$/LaAlO$_{3}$ interfaces, which were analyzed
theoretically very recently within the framework of superconducting
fluctuations approach (Phys. Rev. B $\bf{104}$, 054503 (2021)). Employing the
2D electron-gas model with strong spin-orbit scatterings, we have found that in
the zero temperature limit, field-induced unbounded growth of the fluctuation
mass, and consequent divergence of Cooper-pair density in mesoscopic puddles,
drives the system to Boson insulating states at high fields. Application of
this model to the gate-voltage tuned 2D electron system, created in the
SrTiO$_{3}$/LaAlO$_{3}$ (111) interface at low temperatures, shows that, at
sufficiently high fields, the DOS conductivity prevails over the
paraconductivity, resulting in strongly enhanced magnetoresistance in systems
with sufficiently small carriers density. Dynamical quantum tunneling of Cooper
pairs breaking into mobile normal-electrons states, which prevent the
divergence at zero temperature, contain the high-field resistance onset.

###A theory for anisotropic magnetoresistance in materials with two vector order parameters|X. R. Wang###

A theory for anisotropic magnetoresistance in materials with two vector order parameters. Anisotropic magnetoresistance (AMR) and related planar Hall resistance (PHR)
are ubiquitous phenomena of magnetic materials. Although the universal angular
dependences of AMR and PHR in magnetic polycrystalline materials with one order
parameter are well known, no similar universal relation for other class of
magnetic materials are known to date. Here I present a general theory of
galvanomagnetic effects in magnetic materials with two vector order parameters,
such as magnetic single crystals with a dominated crystalline axis or
polycrystalline non-collinear ferrimagnetic materials. It is shown that AMR and
PHR have a universal angular dependence. In general, both longitudinal and
transverse resistivity are non-reciprocal in the absence of inversion symmetry:
Resistivity takes different value when the current is reversed. Different from
simple magnetic polycrystalline materials where AMR and PHR have the same
magnitude, and $\pi/4$ out of phase, the magnitude of AMR and PHR of materials
with two vector order parameters are not the same in general, and the phase
difference is not $\pi/4$. Instead of $\pi$ periodicity of the usual AMR and
PHR, the periodicities of materials with two order parameters are $2\pi$.

###Nonreciprocal Nature and Magnetochiral Charge Polarization in Chiral Molecular Devices|Jiewen Xiao,Binghai Yan###

Nonreciprocal Nature and Magnetochiral Charge Polarization in Chiral Molecular Devices. The chirality--spin interaction is a fascinating topic for physicists and
chemists. For example, chiral molecules like DNA generate giant spin
polarization in nanodevices characterized by large magnetoresistance (MR). This
phenomenon, called chirality-induced spin selectivity (CISS), paves pathways
for unconventional spintronic devices and enantiomer separation. Different from
ordinary transport, CISS MR violates Onsager's reciprocal relation, and its
physical mechanism is elusive and debated. In this work, we propose that the
CISS MR is intimately related to the electric magnetochiral anisotropy (EMCA)
while EMCA respects Onsager's relation. In a molecular device including a
ferromagnetic electrode, the chiral molecule, as a spin polarizer, leads to
EMCA in the second-order response to the electric field. However, EMCA further
generates extra charge accumulation in the device given the insulating nature
of the molecule. Here, reversing either electrode magnetization or molecule
chirality changes the charge accumulation, which we term magnetochiral charge
polarization (MCCP). Then MCCP modifies the tunneling barrier, alters the
tunneling resistance sensitively, and thus, leads to a higher-order MR that
violates Onsager's reciprocity. Our model reveals the deep connection between
EMCA and CISS MR and explains the unusually large MR ratio and nonequilibrium
nature of CISS. We predict that the molecular spin valve device exhibits a
crossover from CISS-MR to EMCA when the chiral molecule turns more metallic
because of losing the accumulated charge. We further anticipate CISS MR may
appear in chiral molecular devices without ferromagnetic electrodes but in an
external magnetic field in case EMCA and charge accumulation co-exist.

###Robust Dirac lines against Ge vacancy and possible spin-orbit Dirac points in nonsymmorphic HfGe0.92Te|L. Chen,L. Q. Zhou,Y. Zhou,C. Liu,Z. N. Guo,S. Y. Gao,W. H. Fan,J. F. Xu,Y. X. Guo,K,Liao,J. O. Wang,H. M. Weng,G. Wang###

Robust Dirac lines against Ge vacancy and possible spin-orbit Dirac points in nonsymmorphic HfGe0.92Te. Looking for new materials with Dirac points has been a fascinating subject of
research. Here we report the growth, crystal structure, and band structure of
HfGe0.92Te single crystals, featuring three different types of Dirac points.
HfGe0.92Te crystalizes in a nonsymmorphic tetragonal space group P4/nmm (No.
129), having square Ge-atom plane with vacancies about 8%. Despite the
vacancies on Ge site, the Dirac nodal line composed of conventional Dirac
points vulnerable to spin-orbit coupling (SOC) is observed using angle-resolved
photoemission spectroscopy, accompanied with the robust Dirac line protected by
the nonsymmorphic symmetry against both SOC and vacancies. Specially,
spin-orbit Dirac points (SDPs) originated from the surface formed under SOC are
hinted to exist according to our experiments and calculations.
Quasi-two-dimensional (quasi-2D) characters are observed and further confirmed
by angular-resolved magnetoresistance. HfGe0.92Te is a good candidate to
explore exotic topological phases or topological properties with three
different types of Dirac points and a promising candidate to realize 2D SDPs.

###3D Fermi surfaces from charge order in layered CsV$_3$Sb$_5$|Xiangwei Huang,Chunyu Guo,Carsten Putzke,Yan Sun,Maia G. Vergniory,Ion Errea,Martin Gutierrez-Amigo,Dong Chen,Claudia Felser,Philip J. W. Moll###

3D Fermi surfaces from charge order in layered CsV$_3$Sb$_5$. The cascade of electronic phases in CsV$_3$Sb$_5$ raises the prospect to
disentangle their mutual interactions in a clean, strongly interacting Kagome
lattice. When the Kagome planes are stacked into a crystal, its electronic
dimensionality encodes how much of the Kagome physics and its topological
aspects survive. The layered structure of CsV$_3$Sb$_5$ reflects in
Brillouin-zone-sized quasi-2D Fermi surfaces and a significant transport
anisotropy. Yet here we demonstrate that CsV$_3$Sb$_5$ is a three-dimensional
metal within the charge-density-wave (CDW) state. Small 3D pockets play a
crucial role in its low-temperature magneto- and quantum transport. Their
emergence at $T_{CDW}\sim 93$ K results in an anomalous sudden increase of the
in-plane magnetoresistance by 4 orders of magnitude. The presence of these 3D
pockets is further confirmed by quantum oscillations under in-plane magnetic
fields - demonstrating their closed nature. These results emphasize the impact
of interlayer coupling on the Kagome physics in 3D materials.

###Non-adiabatic corrections to chiral charge pumping in topological nodal semimetals|Matej Badin###

Non-adiabatic corrections to chiral charge pumping in topological nodal semimetals. Studying many-body versions of Landau-Zener-like problems of non-interacting
electrons in the Slater formalism for several $k \cdot p$ models representing
Weyl and Dirac semimetals, we systematically include non-adiabatic corrections
to a quantum limit of chiral charge pumping in these models. In this paper, we
show that relative homotopy invariant [Sun et al., Phys. Rev. Lett. 121, 106402
(2018)] and Euler class invariant [Bouhon et al., Nat. Phys. 16, 1137 (2020)]
non-trivially manifest in the non-adiabatic corrections to the quantum limit of
chiral charge pumping. These corrections could affect conductivity channels
connected with the presence of chiral anomaly. Moreover, we show that, for
non-symmorphic systems, this contribution is sensitive to the direction of the
applied magnetic field (in respect to the so-called non-symmorphic nodal loop),
suggesting that the conjectured direction-selective chiral anomaly in
non-symmorphic systems [Bzdu\v{s}ek et al., Nature (London) 538, 75 (2016)]
could lead to a strongly anisotropic longitudinal magnetoresistance. The
presented approach can be easily applied to other $k \cdot p$ or tight-binding
models.

###Magnetostriction in microwave synthesized La0.5Ba0.5CoO3|M. Manikandan,A. Ghosh,R. Mahendiran###

Magnetostriction in microwave synthesized La0.5Ba0.5CoO3. A single-phase polycrystalline La0.5Ba0.5CoO3-d sample was synthesized by
microwave irradiation within 20 minutes of processing time and its structural,
magnetic, electrical, and magnetostrictive properties were investigated. While
the temperature dependence of field-cooled magnetization (M) in a field of H =
0.5 kOe indicates the onset of ferromagnetic transition at TC = 177 K,
irreversibility between the zero field-cooled and field cooled M(T) persists
even at H = 3 kOe. M(H) at 10 K does not saturate at the maximum available
field and has a much smaller value (0.87 {\mu}B/Co in a field of 50 kOe) than
1.9 {\mu}B/Co expected for spin-only contribution from intermediate Co3+ and
Co4+ spins. The resistivity shows insulating behavior down to 10 K and only a
small magnetoresistance (~ 2% for H = 70 kOe) occurs around TC. All these
results suggest a magnetically heterogeneous ground state with weakly
interacting ferromagnetic clusters coexisting with a non-ferromagnetic phase.
The length of the sample expands in the direction of the applied magnetic field
(positive magnetostriction) and does not show saturation even at 50 kOe. The
magnetostriction has a maximum value (= 252 ppm) at 10 K and it decreases with
increasing temperature. The smaller value of magnetostriction compared to the
available data on La0.5Sr0.5CoO3 suggests that non-ferromagnetic matrix is most
likely antiferromagnetic and it restrains the field-induced expansion of
ferromagnetic clusters in the microwave synthesized La0.5Ba0.5CoO3-d sample.

###Dynamical Mean-Field Theory for spin-dependent electron transport in spin-valve devices|Andrea Droghetti,Milos M. Radonjić,Liviu Chioncel,Ivan Rungger###

Dynamical Mean-Field Theory for spin-dependent electron transport in spin-valve devices. We present the combination of Density Functional Theory (DFT) and Dynamical
Mean Field Theory (DMFT) for computing the electron transmission through
two-terminals nanoscale devices. The method is then applied to metallic
junctions presenting alternating Cu and Co layers, which exhibit spin-dependent
charge transport and giant magnetoresistance (GMR) effect. The calculations
show that the coherent transmission through the $3d$ states is greatly
suppressed by electron correlations. This is mainly due to the finite lifetime
induced by the electron-electron interaction and is directly related to the
imaginary part of the computed many-body DMFT self-energy. At the Fermi energy,
where in accordance with the Fermi-liquid behavior the imaginary part of the
self-energy vanishes, the suppression of the transmission is entirely due to
the shifts of the energy spectrum induced by electron correlations. Based our
results, we finally suggest that the GMR measured in Cu/Co heterostructures for
electrons with energies about 1 eV above the Fermi energy is a clear
manifestation of dynamical correlation effects.

###Control of sensitivity in vortex-type magnetic tunnel junction magnetometer sensors by the pinned layer geometry|Motoki Endo,Muftah Al-Mahdawi,Mikihiko Oogane,Yasuo Ando###

Control of sensitivity in vortex-type magnetic tunnel junction magnetometer sensors by the pinned layer geometry. The tuning of sensitivity and dynamic range in linear magnetic sensors is
required in various applications. We demonstrate the control and design of the
sensitivity in magnetic tunnel junction (MTJ) sensors with a vortex-type
sensing layer. In this work, we develop sensor MTJs with NiFe sensing layers
having a vortex magnetic configuration. We demonstrate that by varying the
pinned layer size, the sensitivity to magnetic field is tuned linearly. We
obtain a high magnetoresistance ratio of 140 %, and we demonstrate a
controllable sensitivity from 0.85 to 4.43 %/Oe, while keeping the vortex layer
fixed in size. We compare our experimental results with micromagnetic
simulations. We find that the linear displacement of vortex core by an applied
field makes the design of vortex sensors simple. The control of the pinned
layer geometry is an effective method to increase the sensitivity, without
affecting the vortex state of the sensing layer. Furthermore, we propose that
the location of the pinned layer can be used to realize more sensing
functionalities from a single sensor.

###Direct observation of the perpendicular shape anisotropy and thermal stability of p-STT-MRAM nano-pillars|Trevor P. Almeida,Steven Lequeux,Alvaro Palomino,Ricardo C. Sousa,Olivier Fruchart,Ioan Lucian Prejbeanu,Bernard Dieny,Aurélien Masseboeuf,David Cooper###

Direct observation of the perpendicular shape anisotropy and thermal stability of p-STT-MRAM nano-pillars. Perpendicular shape anisotropy (PSA) offers a practical solution to downscale
spin-transfer torque Magnetic Random-Access Memory (STT-MRAM) beyond the sub-20
nm technology node whilst retaining thermal stability of the storage layer
magnetization. However, our understanding of the thermomagnetic behavior of
PSA-STT-MRAM is often indirect, relying on magnetoresistance measurements and
micromagnetic modelling. Here, the magnetism of a FeCoB / NiFe PSA-STT-MRAM
nano-pillar is investigated using off-axis electron holography, providing
spatially resolved magnetic information as a function of temperature, which has
been previously inaccessible. Magnetic induction maps reveal the micromagnetic
configuration of the NiFe storage layer (60 nm high, 20 nm diameter),
confirming the PSA induced by its 3:1 aspect ratio. In-situ heating
demonstrates that the PSA of the FeCoB / NiFe composite storage layer is
maintained up to at least 250 degrees centigrade, and direct quantitative
measurements reveal the very moderate decrease of magnetic induction with
temperature. Hence, this study shows explicitly that PSA provides significant
stability in STT-MRAM applications that require reliable performance over a
range of operating temperatures.

###Field-induced Topological Hall effect in antiferromagnetic axion insulator candidate EuIn$_2$As$_2$|J. Yan,Z. Z. Jiang,R. C. Xiao,W. J. Lu,W. H. Song,X. B. Zhu,X. Luo,Y. P. Sun,M. Yamashita###

Field-induced Topological Hall effect in antiferromagnetic axion insulator candidate EuIn$_2$As$_2$. The magnetic topological materials have attracted significant attention due
to their potential realization of variety of novel quantum phenomena.
EuIn$_2$As$_2$ has recently been theoretically recognized as a long awaited
intrinsic antiferromagnetic bulk axion insulator. However, the experimental
study on transport properties arising from the topological states in this
material is scarce. In this paper, we perform the detailed magnetoresistance
(MR) and Hall measurements to study the magnetotransport properties of this
material. We find that the transport is strongly influenced by the spin
configuration of the Eu moments from the concomitant change in the field
dependence of the MR and that of the magnetization below the N\'eel
temperature. Most importantly, an anomalous Hall effect (AHE) and a large
topological Hall effect (THE) are observed. We suggest that the AHE is
originated from a nonvanishing net Berry curvature due to the helical spin
structure and that the THE is attributed to the formation of a noncoplanar spin
texture with a finite scalar spin chirality induced by the external magnetic
field in EuIn$_2$As$_2$. Our studies provide a platform to understand the
influence of the interplay between the topology of electronic bands and the
field-induced magnetic structure on magnetoelectric transport properties. In
addition, our observations give a hint to realize axion insulator states and
high-order topological insulator states through manipulating the magnetic state
of EuIn$_2$As$_2$.

###Theoretical Study on Anisotropic Magnetoresistance Effects of Arbitrary Directions of Current and Magnetization for Ferromagnets: Application to Transverse Anisotropic Magnetoresistance Effect|Satoshi Kokado,Masakiyo Tsunoda###

Theoretical Study on Anisotropic Magnetoresistance Effects of Arbitrary Directions of Current and Magnetization for Ferromagnets: Application to Transverse Anisotropic Magnetoresistance Effect. We develop a theory of the anisotropic magnetoresistance (AMR) effects of
arbitrary directions of current and magnetization for ferromagnets. Here, we
use the electron scattering theory with the $s$--$s$ and $s$--$d$ scattering
processes, where $s$ is the conduction electron state and $d$ is the localized
d states. The resistivity due to electron scattering is expressed by the
probability density of the d states of the current direction. The d states are
numerically obtained by applying the exact diagonalization method to the
Hamiltonian of the d states with the exchange field, crystal field, and
spin--orbit interaction. Using the theory, we investigate the transverse AMR
(TAMR) effect for strong ferromagnets with a crystal field of cubic or
tetragonal symmetry. The cubic systems exhibit the fourfold symmetric TAMR
effect, whereas the tetragonal systems show the twofold and fourfold symmetric
TAMR effect. On the basis of the above results, we also comment on the
experimental results of the TAMR effect for Fe$_4$N.

###Giant transverse and longitudinal magneto-thermoelectric effect in polycrystalline nodal-line semimetal Mg3Bi2|Tao Feng,Panshuo Wang,Zhijia Han,Liang Zhou,Wenqing Zhang,Qihang Liu,Weishu Liu###

Giant transverse and longitudinal magneto-thermoelectric effect in polycrystalline nodal-line semimetal Mg3Bi2. Topological semimetals provide new opportunities for exploring new
thermoelectric phenomena, because of their exotic and nontrivial electronic
structure topology around the Fermi surface. In this study, we report on the
discovery of giant transverse and longitudinal magneto-thermoelectric (MTE)
effects in Mg3Bi2, which is predicted to be a type-II nodal-line semimetal in
the absence of spin-orbit coupling (SOC). The maximum transverse power factor
is 2182 {\mu}Wm^{-1}K^{-2} at 13.5 K and 6 Tesla. The longitudinal power factor
reaches up to 3043{\mu}Wm^{-1}K^{-2} at 15 K and 13 Tesla, which is 20 times
higher than in a zero-strength magnetic field and is also comparable to
state-of-the-art MTE materials. By compensating Mg loss in the Mg-rich
conditions for turning carrier concentration, the sample obtained in this work
shows a large linear non-saturating magnetoresistance of 940% under a field of
14 Tesla. This is a two-orders-of-magnitude increase with respect to the normal
Mg-deficiency Mg3Bi2 sample. Using density functional calculations, we
attribute the underlying mechanism to the parent nodal-line electronic
structure without SOC and the anisotropic Fermi surface shape with SOC,
highlighting the essential role of high carrier mobility and open electron
orbits in moment space. Our work offers a new avenue toward highly efficient
thermoelectric materials through the design of Fermi surfaces with special
topological electronic structures in novel quantum materials.

###Electron-Electron Interaction and Weak Antilocalization Effect in a Transition Metal Dichalcogenide Superconductor|Chushan Li,Mebrouka Boubeche,Lingyong Zeng,Yi Ji,Qixuan Li,Donghui Guo,Qizhong Zhu,Dingyong Zhong,Huixia Luo,Huichao Wang###

Electron-Electron Interaction and Weak Antilocalization Effect in a Transition Metal Dichalcogenide Superconductor. In disordered transition-metal dichalcogenide (TMD) superconductor, both the
strong spin-orbit coupling (SOC) and disorder show remarkable effects on
superconductivity. However, the features of SOC and disorder were rarely
detected directly. Here we report the quantum transport behaviors arising from
the interplay of SOC and disorder in the TMD superconductor 1T-NbSeTe. Before
entering the superconducting state, the single crystal at low temperature shows
a resistivity upturn, which is T1/2 dependent and insensitive to the applied
magnetic fields. The magnetoresistance (MR) at low temperatures shows a H1/2
dependence at high magnetic fields. The characteristics are in good agreement
with the electron-electron interaction (EEI) in a disordered conductor. In
addition, the upturn changes and MR at low magnetic fields suggest the
contribution of weak antilocalization (WAL) effect arising from the strong SOC
in the material. Moreover, the quantitative analyses of the transport features
in different samples imply anomalous disorder-enhanced superconductivity that
needs to be further understood. The results reveal the disorder enhanced EEI
and the strong SOC induced WAL effect in 1T-NbSeTe, which illustrate the
resistivity minimum in the widely studied doped superconductors. The work also
provides insights into the disorder effect on the superconductivity.

###Spin Hall magnetoresistance effect from a disordered interface|Sara Catalano,Juan M. Gomez-Perez,M. Xochitl Aguilar-Pujol,Andrey Chuvilin,Marco Gobbi,Luis E. Hueso,Fèlix Casanova###

Spin Hall magnetoresistance effect from a disordered interface. The Spin Hall magnetoresistance (SMR) emerged as a reference tool to
investigate the magnetic properties of materials with an all-electrical set-up.
Its sensitivity to the magnetization of thin films and surfaces may turn it
into a valuable technique to characterize Van der Waals magnetic materials,
which support long range magnetic order in atomically thin layers. However,
realistic surfaces can be affected by defects and disorder, which may result in
unexpected artifacts in the SMR, rather than the sole appearance of electrical
noise. Here, we study the SMR response of heterostructures combining a platinum
(Pt) thin film with the Van der Waals antiferromagnet MnPSe3 and observe a
robust SMR-like signal, which turns out to originate from the presence of
strong interfacial disorder in the system. We use transmission electron
microscopy (TEM) to characterize the interface between MnPSe3 and Pt, revealing
the formation of a few-nanometer-thick platinum-chalcogen amorphous layer. The
analysis of the transport and TEM measurements suggests that the signal arises
from a disordered magnetic system formed at the Pt/MnPSe3 interface, washing
out the interaction between the spins of the Pt electrons and the MnPSe3
magnetic lattice. Our results show that damaged interfaces can yield an
important contribution to SMR, questioning a widespread assumption on the role
of disorder in such measurements.

###Cooperative effect of electrons spin polarization in a hybrid nanostructure of a magnetic thin film with adsorbed chiral molecules studied with non-spin-polarized scanning tunneling microscopy|Nguyen T. N. Ha,L. Rasabathina,O. Hellwig,A. Sharma,G. Salvan,S. Yochelis,Y. Paltiel,L. T. Baczewski,C. Tegenkamp###

Cooperative effect of electrons spin polarization in a hybrid nanostructure of a magnetic thin film with adsorbed chiral molecules studied with non-spin-polarized scanning tunneling microscopy. Polyalanine molecules (PA) with an {\alpha}-helix conformation gathered
recently a lot of interest as the propagation of electrons through the chiral
backbone structure comes along with spin polarization of the transmitted
electrons. By means of scanning tunneling microscopy and spectroscopy at
ambient conditions, PA molecules adsorbed on surfaces of epitaxial magnetic
Al2O3/Pt/Au/Co/Au nanostructures with perpendicular anisotropy were studied.
Thereby, a correlation between the PA molecules ordering at the surface with
the electron tunneling across this hybrid system as a function of the substrate
magnetization orientation as well as the coverage density and helicity of the
was observed. The highest spin polarization values, P, were found for
well-ordered self-assembled monolayers and with a defined chemical coupling of
the molecules to the magnetic substrate surface, showing that the current
induced spin selectivity is a cooperative effect. Thereby, P deduced from the
electron transmission along unoccupied molecular orbitals of the helical
molecules is larger as compared to values derived from the occupied molecular
orbitals. Apparently, the larger orbital overlap is resulting in a higher
electron mobility yielding a higher P value. By switching the magnetization
direction of the Co-layer, it was demonstrated that the non-spin-polarized STM
can be used to study chiral molecules with a sub-molecular resolution, to
detect properties of buried magnetic layers and to detect the spin polarization
of the molecules from the change of the magnetoresistance of such hybrid
structures.

###Anisotropy of the magnetic and transport properties in EuZn$_2$As$_2$|Zhi-Cheng Wang,Emily Been,Jonathan Gaudet,Gadeer Matook A. Alqasseri,Kyle Fruhling,Xiaohan Yao,Uwe Stuhr,Qinqing Zhu,Zhi Ren,Yi Cui,Chunjing Jia,Brian Moritz,Sugata Chowdhury,Thomas Devereaux,Fazel Tafti###

Anisotropy of the magnetic and transport properties in EuZn$_2$As$_2$. Several recent studies have shown that the anisotropy in the magnetic
structure of \ECA\ plays a significant role in stabilizing the Weyl nodes. To
investigate the relationship between magnetic anisotropy and Weyl physics, we
present a comparative study between EuZn$_2$As$_2$ and EuCd$_2$As$_2$ that are
isostructural but with different magnetic anisotropy. We performed structural
analysis, electronic transport, and magnetization experiments on
millimeter-sized single crystals of EuZn$_2$As$_2$, and compared the results to
those of EuCd$_2$As$_2$. By combining the first principle calculations and
neutron diffraction experiment, we identify the magnetic ground state of
EuZn$_2$As$_2$ as A-type antiferromagnetic order with a transition temperature
($T_\mathrm{N}$ = 19.6 K) twice that of EuCd$_2$As$_2$. Like EuCd$_2$As$_2$,
the negative magnetoresistance of EuZn$_2$As$_2$ is observed after suppressing
the resistivity peak at $T_\mathrm{N}$ with increasing fields. However, the
anisotropy in both transport and magnetization are much reduced in
EuZn$_2$As$_2$. The difference could be ascribed to the weaker spin-orbit
coupling, more localized $d$-orbitals, and a larger contribution from the Eu
$s$-orbitals in the zinc compound, as suggested by the electronic band
calculations. The same band structure effect could be also responsible for the
observation of a smaller non-linear anomalous Hall effect in EuZn$_2$As$_2$
compared to EuCd$_2$As$_2$.

###Quasi 1D electronic transport in a 2D magnetic semiconductor|Fan Wu,Ignacio Gutiérrez-Lezama,Sara A. Lopéz-Paz,Marco Gibertini,Kenji Watanabe,Takashi Taniguchi,Fabian O. von Rohr,Nicolas Ubrig,Alberto F. Morpurgo###

Quasi 1D electronic transport in a 2D magnetic semiconductor. We investigate electronic transport through exfoliated multilayers of CrSBr,
a 2D semiconductor that is attracting attention because of its magnetic
properties. We find an extremely pronounced anisotropy that manifests itself in
qualitative and quantitative differences of all quantities measured along the
in-plane \textit{a} and \textit{b} crystallographic directions. In particular,
we observe a qualitatively different dependence of the conductivities
$\sigma_a$ and $\sigma_b$ on temperature and gate voltage, accompanied by
orders of magnitude differences in their values ($\sigma_b$/$\sigma_a \approx
3\cdot10^2-10^5$ at low temperature and large negative gate voltage). We also
find a different behavior of the longitudinal magnetoresistance in the two
directions, and the complete absence of the Hall effect in transverse
resistance measurements. These observations appear not to be compatible with a
description in terms of conventional band transport of a 2D doped
semiconductor. The observed phenomenology -- together with unambiguous
signatures of a 1D van Hove singularity that we detect in energy resolved
photocurrent measurements -- indicate that electronic transport through CrSBr
multilayers is better interpreted by considering the system as formed by weakly
and incoherently coupled 1D wires, than by conventional 2D band transport. We
conclude that CrSBr is the first 2D semiconductor to show distinctly quasi 1D
electronic transport properties.

###Magnetism and Interlayer Bonding in Pores of Bernal-Stacked Hexagonal Boron Nitride|Mehmet Dogan,Marvin L. Cohen###

Magnetism and Interlayer Bonding in Pores of Bernal-Stacked Hexagonal Boron Nitride. When single-layer h-BN is subjected to a high-energy electron beam,
triangular pores with nitrogen edges are formed. Because of the broken sp2
bonds, these pores are known to possess magnetic states. We report on the
magnetism and electronic structure of triangular pores as a function of their
size. Moreover, in the Bernal-stacked h-BN (AB-h-BN), multilayer pores with
parallel edges can be created, which is not possible in the commonly fabricated
multilayer AA'-h-BN. Given that these pores can be manufactured in a
well-controlled fashion using an electron beam, it is important to understand
the interactions of pores in neighboring layers. We find that in certain
configurations, the edges of the neighboring pores remain open and retain their
magnetism, and in others, they form interlayer bonds. We present a
comprehensive report on these configurations for small nanopores. We find that
at low temperatures, these pores have near degenerate magnetic configurations,
and may be utilized in magnetoresistance and spintronics applications. In the
process of forming larger multilayer nanopores, interlayer bonds can form,
reducing the magnetization. Yet, unbonded parallel multilayer edges remain
available at all sizes. Understanding these pores is also helpful in a
multitude of applications such as DNA sequencing and quantum emission.

###Tuning the competition between superconductivity and charge order in kagome superconductor Cs(V1-xNbx)3Sb5|Yongkai Li,Qing Li,Xinwei Fan,Jinjin Liu,Qi Feng,Min Liu,Chunlei Wang,Jia-Xin Yin,Junxi Duan,Xiang Li,Zhiwei Wang,Hai-Hu Wen,Yugui Yao###

Tuning the competition between superconductivity and charge order in kagome superconductor Cs(V1-xNbx)3Sb5. The recently discovered coexistence of superconductivity and charge density
wave order in the kagome systems AV3Sb5 (A = K, Rb, Cs) has stimulated enormous
interest. According to theory, a vanadium-based kagome system may host a flat
band, nontrivial linear dispersive Dirac surface states and electronic
correlation. Despite intensive investigations, it remains controversial about
the origin of the charge density wave (CDW) order, how does the
superconductivity relate to the CDW, and whether the anomalous Hall effect
(AHE) arises primarily from the kagome lattice or the CDW order. We report an
extensive investigation on Cs(V1-xNbx)3Sb5 samples with systematic Nb doping.
Our results show that the Nb doping induces apparent suppression of CDW order
and promotes superconductivity; meanwhile, the AHE and magnetoresistance (MR)
will be significantly weakened together with the CDW order. Combining with our
density functional calculations, we interpret these effects by an antiphase
shift of the Fermi energy with respect to the saddle points near M and the
Fermi surface centered around {\Gamma}. It is found that the former depletes
the filled states for the CDW instability and worsens the nesting condition for
CDW order; while the latter lifts the Fermi level upward and enlarges the Fermi
surface surrounding the {\Gamma} point, and thus promotes superconductivity.
Our results uncover a delicate but unusual competition between the CDW order
and superconductivity.

###The drastic effect of the impurity scattering on the electronic and superconducting properties of Cu-doped FeSe|Z. Zajicek,S. J. Singh,H. Jones,P. Reiss,M. Bristow,A. Martin,A. Gower,A. McCollam,A. I. Coldea###

The drastic effect of the impurity scattering on the electronic and superconducting properties of Cu-doped FeSe. Non-magnetic impurities in iron-based superconductors can provide an
important tool to understand the pair symmetry and they can influence
significantly the transport and the superconducting behaviour. Here, we present
a study of the role of strong impurity potential in the Fe plane, induced by Cu
substitution, on the electronic and superconducting properties of single
crystals of FeSe. The addition of Cu quickly suppresses both the nematic and
superconducting states, and increases the residual resistivity due to enhanced
impurity scattering. Using magnetotransport data up to 35 T for a small amount
of Cu impurity, we detect a significant reduction in the mobility of the charge
carriers by a factor of ~3. While the electronic conduction is strongly
disrupted by Cu substitution, we identify additional signatures of anisotropic
scattering which manifest in linear resistivity at low temperatures and
$H^{1.6}$ dependence of magnetoresistance. The suppression of superconductivity
by Cu substitution is consistent with a sign-changing $s_{\pm}$ order
parameter. Additionally, in the presence of compressive strain, the
superconductivity is enhanced, similar to FeSe.

###Nematic single-component superconductivity and loop-current order from pair-density wave instability|Jonatan Wårdh,Mats Granath###

Nematic single-component superconductivity and loop-current order from pair-density wave instability. We investigate the nematic and loop-current type orders that may arise as
vestigial precursor phases in a model with an underlying pair-density wave
(PDW) instability. We discuss how such a vestigial phase gives rise to a highly
anisotropic stiffness for a coexisting single-component superconductor with low
intrinsic stiffness, as is the case for the underdoped cuprate superconductors.
Next, focusing on a regime with a mean-field PDW ground state with loop-current
and nematic $xy$ (B$_{2g}$) order, we find a preemptive transition into a low
and high-temperature vestigial phase with loop-current and nematic order
corresponding to $xy$ (B$_{2g}$) and $x^2-y^2$ (B$_{1g}$) symmetry
respectively. Near the transition between the two phases, a state of soft
nematic order emerges for which we expect that the nematic director is readily
pinned away from the high-symmetry directions in the presence of an external
field. Results are discussed in relation to findings in the cuprates,
especially to the recently inferred highly anisotropic superconducting
fluctuations [W{\aa}rdh {\em et al.}, ``Colossal transverse magnetoresistance
due to nematic superconducting phase fluctuations in a copper oxide'',
arXiv:2203.06769], giving additional evidence for an underlying ubiquitous PDW
instability in these materials.

###TMR transition and highly sensitive pressure sensors based on magnetic tunnel junctions with black phosphorus barrier|Fang Henan,Li Qian,Xiao Mingwen,Liu Yan###

TMR transition and highly sensitive pressure sensors based on magnetic tunnel junctions with black phosphorus barrier. Black phosphorus is a promising material to serve as the barrier of magnetic
tunnel junctions (MTJs) due to the weak van der Waals interlayer interactions.
In particular, the special band features of black phosphorus may bring
intriguing physical characteristics. Here, we study theoretically the effect of
band gap tunability of black phosphorus on the MTJs with black phosphorus
barrier. It is found that, the tunneling magnetoresistance (TMR) may achieve a
transition from finite value to infinity owing to the variation of the band gap
of black phosphorus. Combining with the latest experimental results of the
pressure-induced band gap tunability, we further investigate the pressure
effect of TMR in the MTJs with black phosphorus barrier. The calculations show
that the pressure sensitivity can be quite high under appropriate parameters.
Physically, the high sensitivity originates from the TMR transition phenomenon.
To take advantage of the high pressure sensitivity, we propose and design a
detailed structure of highly sensitive pressure sensors based on MTJs with
black phosphorus barrier, whose working mechanism is basically different from
the convential pressure sensors. The present pressure sensors possess four
advantages and benifits: (1) high sensitivity, (2) well anti-interference, (3)
high spatial resolution, and (4) fast response speed. Our study may advance new
research area for both the MTJs and pressure sensors.

###Correlated states of 2D electrons near the Landau level filling $ν=1/7$|Yoon Jang Chung,D. Graf,L. W. Engel,K. A. Villegas Rosales,P. T. Madathil,K. W. Baldwin,K. W. West,L. N. Pfeiffer,M. Shayegan###

Correlated states of 2D electrons near the Landau level filling $ν=1/7$. The ground state of two-dimensional electron systems (2DESs) at low Landau
level filling factors ($\nu\lesssim1/6$) has long been a topic of interest and
controversy in condensed matter. Following the recent breakthrough in the
quality of ultra-high-mobility GaAs 2DESs, we revisit this problem
experimentally and investigate the impact of reduced disorder. In a GaAs 2DES
sample with density $n=6.1\times10^{10}$ /cm$^2$ and mobility
$\mu=25\times10^6$ cm$^2$/Vs, we find a deep minimum in the longitudinal
magnetoresistance ($R_{xx}$) at $\nu=1/7$ when $T\simeq104$ mK. There is also a
clear sign of a developing minimum in the $R_{xx}$ at $\nu=2/13$. While
insulating phases are still predominant when $\nu\lesssim1/6$, these minima
strongly suggest the existence of fractional quantum Hall states at filling
factors that comply with the Jain sequence $\nu=p/(2mp\pm1)$ even in the very
low Landau level filling limit. The magnetic field dependent activation
energies deduced from the relation $R_{xx}\propto e^{E_A/2kT}$ corroborate this
view, and imply the presence of pinned Wigner solid states when $\nu\neq
p/(2mp\pm1)$. Similar results are seen in another sample with a lower density,
further generalizing our observations.

###Fluctuation Conductivity and Vortex State in Superconductor with Strong Paramagnetic Pair Breaking|Naratip Nunchot,Dai Nakashima,Ryusuke Ikeda###

Fluctuation Conductivity and Vortex State in Superconductor with Strong Paramagnetic Pair Breaking. The fluctuation conductivity of a moderately clean type II superconductor
with strong Pauli paramagnetic pair-breaking (PPB) is studied by focusing on
the quantum regime at low temperatures and in high magnetic fields. First, it
is pointed out that, as the PPB effect becomes stronger, the quantum
superconducting fluctuation is generally enhanced so that the Aslamasov-Larkin
(AL) fluctuation conductivity tends to vanish upon cooling. Further, by
examining other (the DOS and the Maki-Thompson (MT)) terms of the fluctuation
conductivity, the field dependence of the resulting total conductivity is found
to depend significantly on the type of the vortex lattice (or, glass) ordered
state at low temperatures where the strong PPB plays important roles. By
comparing the present theoretical results with the fluctuation-induced negative
magnetoresistance behavior upon entering a PPB-induced novel SC phase of Iron
selenide (FeSe), it is argued that the vortex matter states of the
superconducting order parameter in the second lowest ($n=1$) Landau level are
realized in FeSe in the parallel field configuration in high fields and at low
temperatures

###Electronic structure and open-orbit Fermi surface topology in isostructural semimetals NbAs$_2$ and W$_2$As$_3$ with extremely large magnetoresistance|Rui Lou,Yiyan Wang,Lingxiao Zhao,Chenchao Xu,Man Li,Xiaoyang Chen,Anmin Zhang,Yaobo Huang,Chao Cao,Genfu Chen,Tianlong Xia,Qingming Zhang,Hong Ding,Shancai Wang###

Electronic structure and open-orbit Fermi surface topology in isostructural semimetals NbAs$_2$ and W$_2$As$_3$ with extremely large magnetoresistance. In transition-metal dipnictides $TmPn_2$ ($Tm$ = Ta, Nb; $Pn$ = P, As, Sb),
the origin of extremely large magnetoresistance (XMR) is yet to be studied by
the direct visualization of the experimental band structures. Here, using
angle-resolved photoemission spectroscopy, we map out the three-dimensional
electronic structure of NbAs$_2$. The open-orbit topology contributes to a
non-negligible part of the Fermi surfaces (FSs), like that of the isostructural
compound MoAs$_2$, where the open FS is proposed to likely explain the origin
of XMR. We further demonstrate the observation of open characters in the
overall FSs of W$_2$As$_3$, which is also a XMR semimetal with the same space
group of $C$12/$m$1 as $TmPn_2$ family and MoAs$_2$. Our results suggest that
the open-orbit FS topology may be a shared feature between XMR materials with
the space group of $C$12/$m$1, and thus could possibly play a role in
determining the corresponding XMR effect together with the electron-hole
compensation.

###Probing FeSi, a d-electron topological Kondo insulator candidate, with magnetic field, pressure, and microwaves|Alexander Breindel,Yuhang Deng,Camilla M. Moir,Yuankan Fang,Sheng Ran,Hongbo Lou,Shubin Li,Qiaoshi Zeng,Lei Shu,Christian T. Wolowiec,Ivan K. Schuller,Priscila F. S. Rosa,Zachary Fisk,John Singleton,M. Brian Maple###

Probing FeSi, a d-electron topological Kondo insulator candidate, with magnetic field, pressure, and microwaves. Recently, evidence for a conducting surface state below 19 K was reported for
the correlated d-electron small gap semiconductor FeSi. In the work reported
herein, the conducting surface state and the bulk phase of FeSi were probed via
electrical resistivity measurements as a function of temperature T, magnetic
field B to 60 T and pressure P to 7.6 GPa, and by means of a magnetic field
modulated microwave spectroscopy (MFMMS) technique. The properties of FeSi were
also compared to those of the Kondo insulator SmB6 to address the question of
whether FeSi is a d-electron analogue of an f-electron Kondo insulator and, in
addition, a topological Kondo insulator. The overall behavior of the
magnetoresistance MR of FeSi at temperatures above and below the onset
temperature (T_S) 19 K of the conducting surface state is similar to that of
SmB6. The two energy gaps, inferred from the resistivity data in the
semiconducting regime, increase with pressure up to about 7 GPa, followed by a
drop which coincides with a sharp suppression of T_S. This behavior is similar
to that reported for SmB6, except that the two energy gaps in SmB6 decrease
with pressure before dropping abruptly at T_S. The MFMMS measurements showed a
sharp feature at T_S (19 K) for FeSi, but no such feature was observed at T_S
4.5 K for SmB6. The absence of a feature at T_S for SmB6 may be due to
experimental issues and will be the subject of a future investigation.

###Hall field-induced magneto-oscillations near charge neutrality point in graphene|Mrityunjay Pandey,Kenji Watanabe,Takashi Taniguchi,Srinivasan Raghavan,U. Chandni###

Hall field-induced magneto-oscillations near charge neutrality point in graphene. We explore the non-equilibrium transport regime in graphene using a large dc
current in combination with a perpendicular magnetic field. The strong in-plane
Hall field that is generated in the bulk of the graphene channel results in
Landau levels that are tilted spatially. The energy of cyclotron orbits in the
bulk varies as a function of the spatial position of the guiding center,
enabling us to observe a series of compelling features. While Shubnikov-de Haas
oscillations are predictably suppressed in the presence of the Hall field, a
set of fresh magnetoresistance oscillations emerge near the charge neutrality
point as a function of dc current. Two branches of oscillations with linear
dispersions are evident as we vary carrier density and dc current, the velocity
of which closely resembles the TA and LA phonon modes, suggestive of
phonon-assisted intra-Landau level transitions between adjacent cyclotron
orbits. Our results offer unique possibilities to explore non-equilibrium
phenomena in two-dimensional materials and van der Waals heterostructures.

###Chiral-anomaly-driven magnetotransport in the correlated Weyl magnet Mn$_3$Sn|Shunichiro Kurosawa,Takahiro Tomita,Ikhlas Muhammad,Mingxuan Fu,Akito Sakai,Satoru Nakatsuji###

Chiral-anomaly-driven magnetotransport in the correlated Weyl magnet Mn$_3$Sn. The quest for topological states in strongly correlated materials is
challenging but essential from fundamental research and application
perspectives. The magnetic Weyl semimetal (WSM) state in the chiral
antiferromagnet Mn$_3$Sn emerges with strong electronic correlations, offering
an intriguing arena for exploring the interplay between Weyl fermions and
correlation physics. One prominent characteristic of the WSM state is the
chiral anomaly, yet the potential effects of electronic correlations on the
chiral anomaly remain unexplored. Here, we report a comprehensive study of the
in-plane magnetotransport properties of single-crystal Mn$_{3+x}$Sn$_{1-x}$
with three different Mn doping levels ($x=0.053$, 0.070, and 0.090). The excess
Mn leads to glassy ferromagnetic behavior and the Kondo effect, aside from
shifting the chemical potential relative to the Weyl nodes. Thus, systematic
tuning of the Mn doping level enables us to study the interplay between the
spin-fluctuation scatterings, the correlation effect, and the chiral anomaly.
We identify negative longitudinal magnetoresistance and planar Hall effect
specific to the chiral anomaly for all three doping levels, indicating that the
chiral anomaly persists in the presence of strong correlations.

###Spin sensitive transport in a spin liquid material: revealing a robustness of spin anisotropy|H. Idzuchi,M. Kimata,S. Okamoto,P. Laurell,N. Mohanta,M. Cothrine,S. E. Nagler,D. Mandrus,A. Banerjee,Y. P. Chen###

Spin sensitive transport in a spin liquid material: revealing a robustness of spin anisotropy. Alpha-phase (a-) RuCl_3 has emerged as a prime candidate for a quantum spin
liquid (QSL) that promises exotic quasiparticles relevant for fault-tolerant
quantum computation. Here, we report spin sensitive transport measurements to
probe spin correlation in a-RuCl_3 using a proximal spin Hall metal platinum
(Pt). Both transverse and longitudinal resistivities exhibit oscillations as
function of the angle between an in-plane magnetic field and the current, akin
to previously measured spin Hall magnetoresistance (SMR) in antiferromagnet/Pt
heterostructures. The oscillations are observed from 1.5 T to 18 T, both within
and beyond the magnetic field range where the antiferromagnetic order and QSL
state are reported in a-RuCl_3. The SMR oscillations show that spins in a-RuCl3
are largely locked to an in-plane quantization axis transverse to the magnetic
field, constituting a continuous-symmetry-broken state that does not
necessarily represent a long-range order. This robust anisotropy of spin axis
uncovers critical energy scales connected with reported QSL signatures in
a-RuCl_3. Simulations suggest a predominantly antiferromagnetic correlation to
moderately high magnetic-fields, that may support the SMR oscillations. The
coupling of the spin states within a-RuCl_3 and Pt demonstrated in our
experiment opens a transport route to exploring exotic spin phases and device
functionalities of QSL materials.

###Magnetoquantum Oscillations in the Specific Heat of a Topological Kondo Insulator|P. G. LaBarre,A. Rydh,J. Palmer-Fortune,J. A. Frothingham,S. T. Hannahs,A. P. Ramirez,N. A. Fortune###

Magnetoquantum Oscillations in the Specific Heat of a Topological Kondo Insulator. Surprisingly, magnetoquantum oscillations (MQO) characteristic of a metal
with a Fermi surface have been observed in measurements of the topological
Kondo insulator SmB6. As these MQO have only been observed in measurements of
magnetic torque (dHvA) and not in measurements of magnetoresistance (SdH), a
debate has arisen as to whether the MQO are an extrinsic effect arising from
rare-earth impurities, defects, and/or aluminum inclusions or an intrinsic
effect revealing the existence of charge-neutral excitations. We report here
the first observation of magnetoquantum oscillations in the low-temperature
specific heat of SmB6. The observed frequencies and their angular dependence
for these flux-grown samples are consistent with previous results based on
magnetic torque for SmB6 but the inferred effective masses are significantly
larger than previously reported. Such oscillations can only be observed if the
MQO are of bulk thermodynamic origin; the measured magnetic-field dependent
oscillation amplitude and effective mass allow us to rule out suggestions of an
extrinsic, aluminium inclusion-based origin for the MQO.

###Electronic properties and phase transition in Kagome metal, Yb0.5Co3Ge3|Yaojia Wang,Xiaoping Wang,Gregory T. McCandless,Kulatheepan Thanabalasingam,Heng Wu,Damian Bouwmeester,Herra van der Zant,Mazhar N. Ali,Julia Y. Chan###

Electronic properties and phase transition in Kagome metal, Yb0.5Co3Ge3. The Kagome lattice is an important fundamental structure in condensed matter
physics for investigating the interplay of electron correlation, topology, and
frustrated magnetism. Recent work on Kagome metals in the AV3Sb5 (A = K, Rb,
Cs) family, has shown a multitude of correlation-driven distortions, including
symmetry breaking charge density waves and nematic superconductivity at low
temperatures. Here we study the new Kagome metal Yb0.5Co3Ge3 and find a
temperature-dependent kink in the resistivity that is highly similar to the
AV3Sb5 behavior and is commensurate with an in-plane structural distortion of
the Co Kagome lattice along with a doubling of the c-axis. The space group is
found to lower from P6/mmm to P63/m below the transition temperature, breaking
the in-plane mirror planes and C6 rotation, while gaining a screw axis along
the c-direction. At very low temperatures, anisotropic negative
magnetoresistance is observed, which may be related to anisotropic magnetism.
This raises questions about the types of the distortions in Kagome nets and
their resulting physical properties including superconductivity and magnetism.

###Off-axis electron holography for the direct visualization of perpendicular shape anisotropy in nano-scale 3D magnetic random-access-memory devices|Trevor P. Almeida,Alvaro Palomino,Steven Lequeux,Victor Boureau,Olivier Fruchart,Ioan Lucian Prejbeanu,Bernard Dieny,David Cooper###

Off-axis electron holography for the direct visualization of perpendicular shape anisotropy in nano-scale 3D magnetic random-access-memory devices. Perpendicular shape anisotropy (PSA) and double magnetic tunnel junctions
(DMTJ) offer practical solutions to downscale spin-transfer-torque Magnetic
Random-Access Memory (STT-MRAM) beyond 20 nm technology nodes, whilst retaining
their thermal stability and reducing critical currents applied. However, as
these modern devices become smaller and three-dimensionally (3D) complex, our
understanding of their functional magnetic behavior is often indirect, relying
on magnetoresistance measurements and micromagnetic modelling. In this paper,
we review recent work that was performed on these structures using a range of
advanced electron microscopy techniques, focusing on aspects specific to the 3D
and nanoscale nature of such elements. We present the methodology for the
systematic transfer of individual SST-MRAM nano-pillars from large-scale arrays
to image their magnetic configurations directly using off-axis electron
holography. We show that improved phase sensitivity through stacking of
electron holograms can be used to image subtle variations in DMTJs and the
thermal stability of < 20 nm PSA-STT-MRAM nano-pillars during in-situ heating.
The experimental practicalities, benefits and limits of using electron
holography for analysis of MRAM devices are discussed, unlocking practical
pathways for direct imaging of the functional magnetic performance of these
systems with high spatial resolution and sensitivity.

###Scaling of Berry-curvature monopole dominated large linear positive magnetoresistance|Shen Zhang,Yibo Wang,Qingqi Zeng,Jianlei Shen,Xinqi Zheng,Jinying Yang,Zhaosheng Wang,Chuanying Xi,Binbin Wang,Min Zhou,Rongjin Huang,Hongxiang Wei,Yuan Yao,Shouguo Wang,Stuart S. P. Parkin,Claudia Felser,Enke Liu,Baogen Shen###

Scaling of Berry-curvature monopole dominated large linear positive magnetoresistance. The linear positive magnetoresistance (LPMR) is a widely observed phenomenon
in topological materials, which is promising for potential applications on
topological spintronics. However, its mechanism remains ambiguous yet and the
effect is thus uncontrollable. Here, we report a quantitative scaling model
that correlates the LPMR with the Berry curvature, based on a ferromagnetic
Weyl semimetal CoS2 that bears the largest LPMR of over 500% at 2 Kelvin and 9
Tesla, among known magnetic topological semimetals. In this system, masses of
Weyl nodes existing near the Fermi level, revealed by theoretical calculations,
serve as Berry-curvature monopoles and low-effective-mass carriers. Based on
the Weyl picture, we propose a relation \[\text{MR}=\frac{e}{\hbar }B{{\Omega
}_{\text{F}}}\], with B being the applied magnetic field and \[{{\Omega
}_{\text{F}}}\] the average Berry curvature near the Fermi surface, and further
introduce temperature factor to both MR/B slope (MR per unit field) and
anomalous Hall conductivity, which establishes the connection between the model
and experimental measurements. A clear picture of the linearly slowing down of
carriers, i.e., the LPMR effect, is demonstrated under the cooperation of the
k-space Berry curvature and real-space magnetic field. Our study not only
provides an experimental evidence of Berry curvature induced LPMR for the first
time, but also promotes the common understanding and functional designing of
the large Berry-curvature MR in topological Dirac/Weyl systems for magnetic
sensing or information storage.

###Surface states induced weak anti-localization effect in Bi0.85Sb0.15 topological single crystal|Yogesh Kumar,VPS Awana###

Surface states induced weak anti-localization effect in Bi0.85Sb0.15 topological single crystal. We report, an experimental evidence of surface states (SS) driven
magneto-transport in a Bi0.85Sb0.15 single crystal. Detailed high field (up to
12T) and low temperature (down to 2K) magneto-transport measurements are been
carried out on the studied Bi0.85Sb0.15 single crystal. The phase, composition
and Raman modes are studied through X-ray diffraction, Energy dispersive X-ray,
and Raman spectroscopy. The obtained crystal shows non-saturating
magnetoresistance (4250%) at 2K and 12T, along with the existence of weak-anti
localization (WAL) effect at around zero magnetic field. Further, the
Hikami-Larkin-Nagaoka (HLN) analysis is performed to analyse the WAL effect.
The prefactor and phase coherence length are deduced at various temperatures,
which signified the presence of more than one conduction channel in the studied
Bi0.85Sb0.15 single crystal. The effect of quantum scattering, bulk
contribution from underneath the surface states and defects are been studied by
adding various field dependent quadratic, linear and constant terms to the SS
driven HLN equation. Various possible scattering mechanism are studied by
analysing the temperature dependence of the phase coherence length. Angle
dependent magneto-conductivity of the studied Bi0.85Sb0.15 single crystal
clearly confirmed the surface states dominated transport in present crystal.

###de Haas-van Alphen effect and the first-principles study of the possible topological stannide Cu$_3$Sn|Chengxu Liu,Bin Li,Yongheng Ge,Wen-He Jiao,Chuanying Xi,Yi Liu,Chunqiang Xu,Qi Lu,Yunlong Li,Hang-Qiang Qiu,Qin-Qing Zhu,Zhi Ren,Ziming Zhu,Dong Qian,Xianglin Ke,Xiaofeng Xu###

de Haas-van Alphen effect and the first-principles study of the possible topological stannide Cu$_3$Sn. The quest for quantum materials with diverse symmetry-protected topological
states has been the focus of recent research interest, primarily due to their
fascinating physical properties and the potential technological utility. In
this work, we report on the magnetotransport, de Haas-van Alphen (dHvA)
oscillations, and the first-principles calculations of the stannide Cu$_3$Sn
that is isostructural with the recently reported topological semimetal
Ag$_3$Sn. The magnetoresistance was found to vary quasi-linearly in field.
Clear dHvA oscillations were observed under a field as low as 1 Tesla at 2 K,
with three major oscillation frequencies $F_{\alpha}$=8.74 T,
$F_{\beta}$=150.19 T and $F_{\gamma}$=229.66 T and extremely small effective
masses. The analysis of dHvA quantum oscillations revealed a possible nonzero
Berry phase, suggestive of the nontrivial band topology. The corroborating
evidence for the nontrivial electronic topology also comes from the
first-principles calculations which yield a nonzero $\mathbb{Z}_2$ topological
index. These results collectively suggest that Cu$_3$Sn, in analogy to its
homologue Ag$_3$Sn, may be another intermetallic stannide hosting topological
Dirac fermions.

###Shubnikov-de Haas and de Haas-van Alphen oscillation in Czochralski grown CoSi single crystal|Souvik Sasmal,Gourav Dwari,Bishal Baran Maity,Vikas Saini,Rajib Mondal,A. Thamizhavel###

Shubnikov-de Haas and de Haas-van Alphen oscillation in Czochralski grown CoSi single crystal. Anisotropic transport, Shubnikov-de Haas (SdH), and de Haas-van Alphen (dHvA)
quantum oscillations studies are reported on a high-quality CoSi single crystal
grown by the Czochralski method. Temperature-dependent resistivities indicate
the dominating electron-electron scattering. Magnetoresistance (MR) at 2 K
reaches 610% for I||[111] and B||[01-1], whereas it is 500% for I||[01-1] and
B||[111]. A negative slope in field-dependent Hall resistivity suggests
electrons are the majority carriers. The carrier concentration extracted from
Hall conductivity indicates no electron-hole compensation. In 3D CoSi, the
electron transport lifetime is found to be approximately in the same order as
quantum lifetime, whereas in 2D electron gas the long-range scattering drives
the transport life much larger than the quantum lifetime. From linear and Hall
SdH oscillations the effective masses and Dingle temperatures have been
calculated. The dHvA oscillation reveals three frequencies at 18 ($\gamma$),
558 ($\alpha$) and 663 T ($\beta$)), whereas, SdH oscillation results in only
two frequencies $\alpha$ and $\beta$. The $\gamma$ frequency observed in dHvA
oscillation is a tiny hole pocket at the $\Gamma$ point.

###Magneto-Transport Properties of Kagome Magnet TmMn$_6$Sn$_6$|Bin Wang,Enkui Yi,Leyi Li,Jianwei Qin,Bing-Feng Hu,Bing Shen,Meng Wang###

Magneto-Transport Properties of Kagome Magnet TmMn$_6$Sn$_6$. Kagome magnet usually hosts nontrivial electronic or magnetic states drawing
great interests in condensed matter physics. In this paper, we report a
systematic study on transport properties of kagome magnet TmMn$_6$Sn$_6$. The
prominent topological Hall effect (THE) has been observed in a wide temperature
region spanning over several magnetic phases and exhibits strong temperature
and field dependence. This novel phenomenon due to non-zero spin chirality
indicates possible appearance of nontrival magnetic states accompanying with
strong fluctuations. The planar applied field drives planar Hall effect(PHE)
and anistropic magnetoresisitivity(PAMR) exhibiting sharp disconnections in
angular dependent planar resistivity violating the empirical law. By using an
effective field, we identify a magnetic transition separating the PAMR into two
groups belonging to various magnetic states. We extended the empirical formula
to scale the field and temperature dependent planar magnetoresistivity and
provide the understandings for planar transport behaviors with the crossover
between various magnetic states. Our results shed lights on the novel transport
effects in presence of multiple nontrivial magnetic states for the kagome
lattice with complicated magnetic structures.

###Ground-state structure, orbital ordering and metal-insulator transition in double-perovskite PrBaMn2O6|Sergey V. Streltsov,R. E. Ryltsev,N. M. Chtchelkatchev###

Ground-state structure, orbital ordering and metal-insulator transition in double-perovskite PrBaMn2O6. In recent years, A-site ordered half-doped double-perovskite manganites $\rm
RBaMn_2O_6$ (R=rare earth) have attracted much attention due to their
remarkable physical properties and a prospect of application as
magnetoresistance, multiferroic, and oxygen storage materials. The nature of
the ground state in ${\rm RBaMn_2O_6}$ as well as sequence of phase transitions
taking place at cooling are not yet well understood due to complexity in both
experimental and theoretical studies. Here we address the origin of the
ground-state structure in PrBaMn$_2$O$_6$ as well as its electronic and
magnetic properties. Utilizing GGA+U approach and specially designed strategy
to perform structural optimization, we show that the system has two competing
AFM-A and AFM-CE magnetic structures with very close energies. The AFM-A
structure is a metal, while AFM-CE is an insulator and the transition to the
insulating state is accompanied by the charge Mn$^{3+}$/Mn$^{4+}$, and orbital
$3x^2-r^2$/$3y^2-r^2$ orderings. This orbital ordering results in strong
cooperative Jahn-Teller (JT) distortions, which lower the crystal symmetry. Our
findings give a key to understanding contradictions in available experimental
data on ${\rm PrBaMn_2O_6}$ and opens up the prospects to theoretical
refinements of ground-state structures in other ${\rm RBaMn_2O_6}$ compounds.

###Rashba spin-orbit interaction induced modulation of magnetic anisotropy|Megha Vagadia,Jaya Prakash Sahoo,Ankit Kumar,Suman Sardar,Tejas Tank,D. S. Rana###

Rashba spin-orbit interaction induced modulation of magnetic anisotropy. In past few decades, Rashba spin-orbit coupling (SOC) has been successfully
employed for the emergence of exotic phenomena at the quantum oxide interfaces.
In these systems, the combined effect of charge transfer, broken symmetries and
SOC yields intriguing interfacial magnetism and transport properties. Here, we
provide an insight to control and tune interfacial phenomena in CaMnO3/CaIrO3
based 3d-5d oxide heterostructures by the charge transfer driven Rashba SOC.
Anomalous Hall effect in these canted antiferromagnetic heterostructures
originates from the intrinsic contribution associated with the topology of the
electronic band structure and it is mostly confined to the interface. Rashba
SOC reconstructs the Berry curvature and enhances the anomalous Hall
conductivity by two orders of magnitude. From the anisotropy magnetoresistance
measurements we demonstrate that Rashba SOC is instrumental in tailoring
magnetic anisotropy where magnetization easy-axis rotates from the out-of-plane
direction to the in-plane direction. The ability to tune Rashba SOC and
resulting competing magnetic anisotropy provides a route to manipulate
electronic band structure for the origin of non-trivial spin texture useful for
spin-orbitronics applications.

###Link between Weyl-fermion chirality and spin texture|Kenta Hagiwara,Philipp Rüßmann,Xin Liang Tan,Ying-Jiun Chen,Keiji Ueno,Vitaliy Feyer,Giovanni Zamborlini,Matteo Jugovac,Shigemasa Suga,Stefan Blügel,Claus Michael Schneider,Christian Tusche###

Link between Weyl-fermion chirality and spin texture. Topological semimetals have recently attracted great attention due to
prospective applications governed by their peculiar Fermi surfaces. Weyl
semimetals host chiral fermions that manifest as pairs of non-degenerate
massless Weyl points in their electronic structure, giving rise to novel
macroscopic quantum phenomena such as the chiral anomaly, an unusual
magnetoresistance, and various kinds of Hall effects These properties enable
the engineering of non-local electric transport devices, magnetic sensors and
memories, and spintronics devices. Nevertheless, little is known about the
underlying spin- and orbital-degrees of freedom of the electron wave functions
in Weyl semimetals, that govern the electric transport. Here, we give evidence
that the chirality of the Weyl points in the Type-II Weyl semimetal MoTe$_2$ is
directly linked to the spin texture and orbital angular momentum of the
electron wave functions. By means of state-of-the-art spin- and
momentum-resolved photoemission spectroscopy the spin- and orbital texture in
the Fermi surface is directly resolved. Supported by first-principles
calculations, we examined the relationship between the topological chiral
charge and spin texture, which significantly contributes to the understanding
of the electronic structure in topological quantum materials.

###Perspective on Epitaxial NiCo2O4 Film as an Emergent Spintronic Material: Magnetism and Transport Properties|Xiaoshan Xu,Corbyn Mellinger,Zhi Gang Cheng,Xuegang Chen,Xia Hong###

Perspective on Epitaxial NiCo2O4 Film as an Emergent Spintronic Material: Magnetism and Transport Properties. The ferrimagnetic inverse spinel NiCo2O4 has attracted extensive research
interests for its versatile electrochemical properties, robust magnetic order,
high conductivity, and fast spin dynamics, as well as its highly tunable nature
due to the closely coupled charge, spin, orbital, lattice, and defect effects.
Single-crystalline epitaxial thin films of NiCo2O4 present a model system for
elucidating the intrinsic physical properties and strong tunability, which are
not viable in bulk single crystals. In this perspective, we discuss the recent
advances in epitaxial NiCo2O4 thin films, focusing on understanding its unusual
magnetic and transport properties in light of crystal structure and electronic
structure. The perpendicular magnetic anisotropy in compressively strained
NiCo2O4 films is explained by considering the strong spin-lattice coupling,
particularly on Co ions. The prominent effect of growth conditions reveals the
complex interplay between the crystal structure, cation stoichiometry, valence
state, and site occupancy. NiCo2O4 thin films also exhibit various
magnetotransport anomalies, including linear magnetoresistance and sign change
in anomalous Hall effect, which illustrate the competing effects of band
intrinsic Berry phase and impurity scattering. The fundamental understanding of
these phenomena will facilitate the functional design of NiCo2O4 thin films for
nanoscale spintronic applications.

###Anomalous Transport Properties of Re$_3$Ge$_7$|Anja Rabus,Eundeok Mun###

Anomalous Transport Properties of Re$_3$Ge$_7$. Single crystals of intermetallic Re$_3$Ge$_7$ were grown and characterized by
measuring magnetization, electrical resistivity, Hall coefficient, and specific
heat. Magnetization measurements show the material is weakly diamagnetic. A
phase transition is indicated by a kink in magnetic susceptibility at $T_{c} =
58.5$K and is confirmed by a $\lambda$-like anomaly in specific heat. In
zero-field, the temperature dependence of electrical resistivity $\rho(T)$
follows a typical metallic behavior above $T_c$ and sharply increases below
$T_c$, showing a metal-to-insulator-like transition. When a magnetic field is
applied, strong effects on the transport properties are observed. The
temperature dependence of magnetoresistivity $\Delta\rho$ = $\rho (T, H)$ -
$\rho (T, H=0)$ develops a maximum around 30 K, deviating from ordinary
metallic behavior. Analysis of the Hall coefficient measurements indicates that
the carrier density is 0.04 per formula unit at 300 K and drops by two orders
of magnitude below $T_c$. The effective mass of charge carriers is inferred
from the analysis of the Shubnikov-de Haas quantum oscillations to be close to
the bare electron mass.

###Observation of surface superconductivity in a three-dimensional Dirac material|Qi Liu,Peng-Jie Guo,Xiao-Yu Yue,Zhe-Kai Yi,Qing-Xin Dong,Hui Liang,Dan-Dan Wu,Yan Sun,Qiu-Ju Li,Wen-Liang Zhu,Tian-Long Xia,Xue-Feng Sun,Yi-Yan Wang###

Observation of surface superconductivity in a three-dimensional Dirac material. Superconductivity becomes more interesting when it encounters dimensional
constraint or topology, because it is of importance for exploring exotic
quantum phenomena or developing superconducting electronics. Here we report the
coexistence of naturally formed surface superconducting state and
three-dimensional topological Dirac state in single crystals of BaMg$_2$Bi$_2$.
The electronic structure obtained from the first-principles calculations
demonstrates that BaMg$_2$Bi$_2$ is an ideal Dirac material, in which the Dirac
point is very close to the Fermi level and no other energy band crosses the
Fermi level. Superconductivity up to 4.77 K can be observed under ambient
pressure in the measurements of resistivity. The angle dependent
magnetoresistance reveals the two-dimensional characteristic of
superconductivity, indicating that superconductivity occurs on the surface of
the sample and is absent in the bulk state. Our study not only provides
BaMg$_2$Bi$_2$ as a suitable platform to study the interplay between
superconductivity and topological Dirac state, but also indicates that
MgBi-based materials may be a promising system for exploring new
superconductors.

###Proximity-induced superconducting gap in the intrinsic magnetic topological insulator MnBi2Te4|Wen-Zheng Xu,Chun-Guang Chu,Zhen-Cun Pan,Jing-Jing Chen,An-Qi Wang,Zhen-Bing Tan,Peng-Fei Zhu,Xing-Guo Ye,Da-Peng Yu,Zhi-Min Liao###

Proximity-induced superconducting gap in the intrinsic magnetic topological insulator MnBi2Te4. We report magnetotransport measurements in the NbN/ magnetic topological
insulator MnBi2Te4 (MBT)/ NbN junction at low temperature. At 10 mK, the
nonlinear current-voltage characteristic of the junction shows a tunneling
behavior, indicating the existence of interfacial potential barriers within the
heterostructure. Under an out of plane perpendicular magnetic field, a
transition from negative to positive magnetoresistance (MR) is found when
increasing the bias voltage. A proximity-induced superconducting gap is
estimated to be 0.1meV by a pair of differential resistance dips. Moreover, the
induced gap is enhanced by gradually tuning the Fermi level toward the charge
neutral point by a back gate voltage, which is ascribed to the increased
transport contribution of the topological surface states in MBT. Intriguingly,
the induced gap exhibits an anomalous magnetic field assisted enhancement,
which may originate from the spin orbit coupling and magnetic order of MBT. Our
results reveal the interplay between magnetism and superconductivity in MBT,
paving the way for further studies on topological superconductivity and chiral
Majorana edge modes in quantum anomalous Hall insulator/superconductor hybrid
systems.

###Exchange field enhanced upper critical field of the superconductivity in compressed antiferromagnetic EuTe2|Hualei Sun,Liang Qiu,Yifeng Han,Yunwei Zhang,Weiliang Wang,Chaoxin Huang,Naitian Liu,Mengwu Huo,Lisi Li,Hui Liu,Zengjia Liu,Peng Cheng,Hongxia Zhang,Hongliang Wang,Lijie Hao,Man-Rong Li,Dao-Xin Yao,Yusheng Hou,Pengcheng Dai,Meng Wang###

Exchange field enhanced upper critical field of the superconductivity in compressed antiferromagnetic EuTe2. We report high pressure studies on the C-type antiferromagnetic semiconductor
EuTe2 up to 36.0 GPa. A structural transition from the I4/mcm to C2/m space
group is identified at ~16 GPa. Superconductivity is discovered above ~5 GPa in
both the I4/mcm and C2/m space groups. In the low-pressure phase (< 16 GPa),
the antiferromagnetic transition temperature is enhanced with increasing
pressure due to the enhanced magnetic exchange interactions. Magnetoresistance
measurements indicate an interplay between the local moments of Eu2+ and the
conduction electrons of Te 5p orbits. The upper critical field of the
superconductivity is well above the Pauli limit. Across the structural
transition to the high-pressure phase (> 16 GPa), EuTe2 becomes nonmagnetic and
the superconducting transition temperature evolves smoothly with the upper
critical field below the Pauli limit. Therefore, the high upper critical field
of EuTe2 in the low-pressure phase is due to the exchange field compensation
effect of the Eu magnetic order and the superconductivity in both structures
may arise in the framework of the BCS theory.

###Nodal superconducting exchange coupling|Angelo Di Bernardo,Sachio Komori,Giorgio Livanas,Giorgio Divitini,Paola Gentile,Mario Cuoco,Jason W. A. Robinson###

Nodal superconducting exchange coupling. The superconducting equivalent of giant magnetoresistance, involves placing a
thin-film superconductor between two ferromagnetic layers. A change of
magnetization-alignment in such a superconducting spin-valve from parallel (P)
to antiparallel (AP) creates a positive shift in the superconducting transition
temperature ({\Delta}Tc) due to an interplay of the magnetic exchange energy
and the superconducting condensate. The magnitude of {\Delta}Tc scales
inversely with the superconductor thickness (dS) and is zero when dS exceeds
the superconducting coherence length ({\xi}) as predicted by de Gennes. Here,
we report a superconducting spin-valve effect involving a different underlying
mechanism that goes beyond de Gennes in which magnetization-alignment and
{\Delta}Tc are determined by the nodal quasiparticle-excitation states on the
Fermi surface of the d-wave superconductor YBa2Cu3O7-{\delta} (YBCO) grown
between insulating layers of ferromagnetic Pr0.8Ca0.2MnO3. We observe
{\Delta}Tc values that approach 2 K with {\Delta}Tc oscillating with dS over a
length scale exceeding 100 {\xi} and, for particular values of dS, we find that
the superconducting state reinforces an antiparallel magnetization-alignment.
These results pave the way for all-oxide superconducting memory in which
superconductivity modulates the magnetic state.

###Temperature dependent cloaking of the Quantum Griffiths Singularity in LaScO$_3$/SrTiO$_3$ heterostructures|Simrandeep Kaur,Hemanta Kumar Kundu,Sumit Kumar,Anjana Dogra,Rajesh Narayanan,Thomas Vojta,Aveek Bid###

Temperature dependent cloaking of the Quantum Griffiths Singularity in LaScO$_3$/SrTiO$_3$ heterostructures. We study the superconductor-insulator transition in the quasi-two-dimensional
electron gas (q-2DEG) formed at the interface of LaScO$_3$/SrTiO$_3$
heterostructures. Using various tuning parameters such as the gate voltage and
the magnetic field, we show an intervening anomalous metallic state apart from
the usual superconducting and insulating ground states. Further, by studying
the scaling of the magnetoresistivity data, we find a highly unusual two-stage
divergence of the dynamical critical exponent. The first increase, at higher
temperatures, demonstrates that the system hosts a quantum Griffiths phase
caused by disorder-induced rare puddles of superconductivity embedded in a
non-superconducting matrix. The second, stronger, increase of the dynamical
exponent at lower temperatures indicates that the quantum Griffiths phase is
cut-off or cloaked below a crossover temperature scale. We elucidate possible
mechanisms that account for the cloaking of the Griffiths phase. Finally, we
construct a phase diagram that encapsulates the various phases of the q-2DEG as
a function of the applied magnetic field and temperature. We further discuss
the various cross-overs and phase transitions in the system by utilizing this
phase diagram.

###Thermal spin current generation in the multifunctional ferrimagnet Ga$_{0.6}$Fe$_{1.4}$O$_{3}$|Alberto Anadón,Elodie Martin,Suvidyakumar Homkar,Benjamin Meunier,Maxime Verges,Heloise Damas,Junior Alegre,Christophe Lefevre,Francois Roulland,Carsten Dubs,Morris Lindner,Ludovic Pasquier,Olivier Copie,Karine Dumesnil,Rafael Ramos,Daniele Preziosi,Sébastien Petit-Watelot,Nathalie Viart,Juan-Carlos Rojas-Sánchez###

Thermal spin current generation in the multifunctional ferrimagnet Ga$_{0.6}$Fe$_{1.4}$O$_{3}$. In recent years, multifunctional materials have attracted increasing interest
for magnetic memories and energy harvesting applications. Magnetic insulating
materials are of special interest for this purpose, since they allow the design
of more efficient devices due to the lower Joule heat losses. In this context,
Ga$_{0.6}$Fe$_{1.4}$O$_3$ (GFO) is a good candidate for spintronics
applications, since it can exhibit multiferroicity and presents a spin Hall
magnetoresistance similar to the one observed in a yttrium iron garnet (YIG)/Pt
bilayer. Here, we explore GFO utilizing thermo-spin measurements in an on-chip
approach. By carefully considering the geometry of our thermo-spin devices we
are able to quantify the spin Seebeck effect and the spin current generation in
a GFO/Pt bilayer, obtaining a value comparable to that of YIG/Pt. This further
confirms the promises of an efficient spin current generation with the
possibility of an electric-field manipulation of the magnetic properties of the
system in an insulating ferrimagnetic material.

###Effect of gallium doping on structural and transport properties of the topological insulator Bi2Se3 grown by molecular beam epitaxy|Daniel Brito,Ana Pérez-Rodriguez,Ishwor Khatri,Carlos José Tavares,Mario Amado,Eduardo Castro,Enrique Diez,Sascha Sadewasser,Marcel S Claro###

Effect of gallium doping on structural and transport properties of the topological insulator Bi2Se3 grown by molecular beam epitaxy. Topological insulators possess a non-conductive bulk and present surface
states, henceforth, they are electrically conductive along their boundaries.
Bismuth selenide ($Bi_2Se_3$) is one of the most promising topological
insulators. However, a major drawback is its n-type nature arising from its
natural doping, which makes the transport in the bulk dominant. This effect can
be overcome by shifting the chemical potential into the bandgap, turning the
transport of the surface states to be more pronounced than the bulk
counterpart. In this work, $Bi_2Se_3$ was grown by molecular beam epitaxy and
doped with 0.8, 2, 7, and 14 at. % of Ga, with the aim of shifting the chemical
potential into the bandgap. The structural, morphological, and electronic
properties of the Ga doped $Bi_2Se_3$ are studied. Raman and X-ray diffraction
measurements confirmed the incorporation of the dopants into the crystal
structure. Transport and magnetoresistance measurements in the temperature
range of 1.5 to 300 K show that Ga-doped $Bi_2Se_3$ is n-type with a bulk
charge carrier concentration of $10^{19} cm^{-3}$. Remarkably, magnetotransport
of the weak antilocalization effect (WAL) measurements confirm the existence of
surface states up to a doping percentage of 2 at. % of Ga and coherence length
values between 50-800 nm, which envisages the possibility of topological
superconductivity in this material.

###Unidirectional Magnetoresistance in Antiferromagnet/Heavy-metal bilayers|Soho Shim,M. Mehraeen,Joseph Sklenar,Junseok Oh,Jonathan Gibbons,Hilal Saglam,Axel Hoffmann,Steven S. -L. Zhang,Nadya Mason###

Unidirectional Magnetoresistance in Antiferromagnet/Heavy-metal bilayers. The interplay between electronic transport and antiferromagnetic order has
attracted a surge of interest as recent studies have shown that a moderate
change in the spin orientation of a collinear antiferromagnet may have a
significant effect on the electronic band structure. Among numerous electrical
probes to read out such magnetic order, unidirectional magnetoresistance (UMR),
where the resistance changes under the reversal of the current direction, can
provide rich insights into the transport properties of spin-orbit coupled
systems. However, UMR has never been observed in antiferromagnets before, given
the absence of intrinsic spin-dependent scattering. Here, we report a UMR in
the antiferromagnetic phase of a FeRh$|$Pt bilayer, which undergoes a sign
change and then increases strongly with an increasing external magnetic field,
in contrast to UMRs in ferromagnetic and nonmagnetic systems. We show that
Rashba spin-orbit coupling alone cannot explain the sizable UMR in the
antiferromagnetic bilayer and that field-induced spin canting distorts the
Fermi contours to greatly enhance the UMR by two orders of magnitude. Our
results can motivate the growing field of antiferromagnetic spintronics, and
suggest a route to the development of tunable antiferromagnet-based spintronics
devices.

###Topological magnetic phase transition in Eu-based A-type antiferromagnets|Eliot Heinrich,Thore Posske,Benedetta Flebus###

Topological magnetic phase transition in Eu-based A-type antiferromagnets. Recently, a colossal magnetoresistance (CMR) was observed in EuCd$_2$P$_2$ --
a compound that does not fit the conventional mixed-valence paradigm. Instead,
experimental evidence points at a resistance driven by strong magnetic
fluctuations within the two-dimensional ($2d$) ferromagnetic (FM) planes of the
layered antiferromagnetic (AFM) structure. While the experimental results have
not yet been fully understood, a recent theory relates the CMR to a topological
vortex-antivortex unbinding, i.e., Berezinskii-Kosterlitz-Thouless (BKT), phase
transition. Motivated by these observations, in this work we explore the
magnetic phases hosted by a microscopic classical magnetic model for
EuCd$_2$P$_2$, which easily generalizes to other Eu A-type antiferromagnetic
compounds. Using Monte Carlo techniques to probe the specific heat and the
helicity modulus, we show that our model can exhibit a vortex-antivortex
unbinding phase transition. We find that this phase transition displays the
same sensitivity to in-plane magnetization, interlayer coupling, and easy-plane
anisotropy that is observed experimentally in the CMR signal, providing
qualitative numerical evidence that the effect is related to a magnetic BKT
transition.

###Phase transformation-induced superconducting aluminium-silicon alloy rings|B. C. Johnson,M. Stuiber,D. L. Creedon,A. Berhane,L. H. Willems van Beveren,S. Rubanov,J. H. Cole,V. Mourik,A. R. Hamilton,T. L. Duty,J. C. McCallum###

Phase transformation-induced superconducting aluminium-silicon alloy rings. The development of a materials platform that exhibits both superconducting
and semiconducting properties is an important endeavour for a range of emerging
quantum technologies. We investigate the formation of superconductivity in
nanowires fabricated with silicon-on-insulator (SOI). Aluminium from deposited
contact electrodes is found to interdiffuses with the Si nanowire structures to
form an Al-Si alloy along the entire length of the predefined nanowire device
over micron length scales at temperatures well below that of the Al-Si
eutectic. The resultant transformed nanowire structures are layered in geometry
with a continuous Al-Si alloy wire sitting on the buried oxide of the SOI and a
residual Si cap sitting on top of the wire. The phase transformed material is
conformal with any predefined device patterns and the resultant structures are
exceptionally smooth-walled compared to similar nanowire devices formed by
silicidation processes. The superconducting properties of a mesoscopic AlSi
ring formed on a SOI platform are investigated. Low temperature
magnetoresistance oscillations, quantized in units of the fluxoid, h/2e, are
observed.

###Influence of nonuniform magnetization reorientation on spin-orbit torque measurements|Ryan W. Greening,Xin Fan###

Influence of nonuniform magnetization reorientation on spin-orbit torque measurements. Measurements of spin-orbit torques in a ferromagnetic/nonmagnetic multilayer
are typically based on an assumption that the entire ferromagnetic layer
uniformly responds to the spin-orbit torque. This assumption breaks down when
the thickness of the ferromagnetic layer is comparable to the dynamic exchange
coupling length, which can be as short as a few nanometers in certain
measurement geometries. The nonuniform magnetization reorientation coupled with
nonuniform contribution of each magnetic sublayer to the magnetoresistance or
the Kerr effect may impact the accuracy in the extrapolation of spin-orbit
torque, particularly if a thick ferromagnetic layer is used. In this paper, we
use numerical models to investigate such an impact in three different
techniques: the magneto-optic-Kerr-effect method, the second-harmonic method
and the spin torque ferromagnetic resonance method. We show that the
second-harmonic and magneto-optic-Kerr-effect methods are prone to be
influenced by the nonuniform magnetization reorientation, while the spin torque
ferromagnetic resonance method is much less impacted.

###First-principles insights into all-optical spin switching in the half-metallic Heusler ferrimagnet Mn$_2$RuGa|G. P. Zhang,Y. H. Bai,M. S. Si,Thomas F. George###

First-principles insights into all-optical spin switching in the half-metallic Heusler ferrimagnet Mn$_2$RuGa. All-optical spin switching (AOS) represents a new frontier in magnetic
storage technology -- spin manipulation without a magnetic field, -- but its
underlying working principle is not well understood. Many AOS ferrimagnets such
as GdFeCo are amorphous and renders the high-level first-principles study
unfeasible. The crystalline half-metallic Heusler Mn$_2$RuGa presents an
opportunity. Here we carry out hitherto the comprehensive density functional
investigation into the material properties of Mn$_2$RuGa, and introduce two
concepts - the spin anchor site and the optical active site - as two pillars
for AOS in ferrimagnets. In Mn$_2$RuGa, Mn$(4a)$ serves as the spin anchor
site, whose band structure is below the Fermi level and has a strong spin
moment, while Mn$(4c)$ is the optical active site whose band crosses the Fermi
level. Our magneto-optical Kerr spectrum and band structure calculation jointly
reveal that the delicate competition between the Ru-$4d$ and Ga-$4p$ states is
responsible for the creation of these two sites. These two sites found here not
only present a unified picture for both Mn$_2$RuGa and GdFeCo, but also open
the door for the future applications. Specifically, we propose a
Mn$_2$Ru$_x$Ga-based magnetic tunnel junction where a single laser pulse can
control magnetoresistance.

###Antiferromagnetic Skyrmion based Energy-Efficient Leaky Integrate and Fire Neuron Device|Namita Bindal,Ravish Kumar Raj,Md Mahadi Rajib,Jayasimha Atulasimha,Brajesh Kumar Kaushik###

Antiferromagnetic Skyrmion based Energy-Efficient Leaky Integrate and Fire Neuron Device. The development of energy-efficient neuromorphic hardware using spintronic
devices based on antiferromagnetic (AFM) skyrmion motion on nanotracks has
gained considerable interest. Owing to its properties such as robustness
against external magnetic fields, negligible stray fields, and zero net
topological charge, AFM skyrmions follow straight trajectories that prevent
their annihilation at nanoscale racetrack edges. This makes the AFM skyrmions a
more favorable candidate over the ferromagnetic (FM) skyrmion for future
spintronic applications. This work proposes an AFM skyrmion-based neuron device
exhibiting the leaky-integrate-fire (LIF) functionality by exploiting thermal
gradient or alternatively perpendicular magnetic anisotropy (PMA) gradient in
the nanotrack for leaky behavior by moving the skyrmion in the direction to
minimize the system energy. Furthermore, it is shown that the AFM skyrmion
couples efficiently to the soft ferromagnetic layer of a magnetic tunnel
junction enabling efficient read-out of the skyrmion. The maximum change of
9.2% in tunnel magnetoresistance (TMR) is estimated for detecting the AFM
skyrmion. Moreover, the proposed neuron device has the energy dissipation of
4.32 fJ per LIF operation thus, paving the path for developing energy-efficient
devices in antiferromagnetic spintronics for neuromorphic computing.

###Spin-orbit torque switching of magnetic tunnel junctions for memory application|Viola Krizakova,Manu Perumkunnil,Sebastien Couet,Pietro Gambardella,Kevin Garello###

Spin-orbit torque switching of magnetic tunnel junctions for memory application. Spin-orbit torques (SOT) provide a versatile tool to manipulate the
magnetization of diverse classes of materials and devices using electric
currents, leading to novel spintronic memory and computing approaches. In
parallel to spin transfer torques (STT), which have emerged as a leading
non-volatile memory technologie, SOT broaden the scope of current-induced
magnetic switching to applications that run close to the clock speed of the
central processing unit and unconventional computing architectures. In this
paper, we review the fundamental characteristics of SOT and their use to switch
magnetic tunnel junction (MTJ) devices, the elementary unit of the
magnetoresistive random access memory (MRAM). In the first part, we illustrate
the physical mechanisms that drive the SOT and magnetization reversal in
nanoscale structures. In the second part, we focus on the SOT-MTJ cell. We
discuss the anatomy of the MTJ in terms of materials and stack development,
summarize the figures of merit for SOT switching, review the field-free
operation of perpendicularly magnetized MTJs, and present options to combine
SOT, STT and voltage-gate assisted switching. In the third part, we consider
SOT-MRAMs in the perspective of circuit integration processes, introducing
considerations on scaling and performance, as well as macro-design
architectures. We thus bridge the fundamental description of SOT-driven
magnetization dynamics with an application-oriented perspective, including
device and system-level considerations, goals, and challenges.

###Low-temperature transport properties of intermetallic compound HoAgGe with kagome spin ice state|N. Li,Q. Huang,X. Y. Yue,S. K. Guang,K. Xia,Y. Y. Wang,Q. J. Li,X. Zhao,H. D. Zhou,X. F. Sun###

Low-temperature transport properties of intermetallic compound HoAgGe with kagome spin ice state. We study the magnetic susceptibility, magnetization, resistivity and thermal
conductivity of intermetallic HoAgGe single crystals at low temperatures and in
magnetic fields along the $a$ and $c$ axis, while the electric and heat
currents are along the $c$ axis. The magnetization curves show a series of
metamagnetic transitions and small hysteresis at low field for $B \parallel a$,
and a weak metamagnetic transition for $B \parallel c$, respectively. Both the
magnetic susceptibility and $\rho(T)$ curve show anomalies at the
antiferromagnetic transition ($T\rm_N \sim$ 11.3 K) and spin reorientation
transition ($\sim$ 7 K). In zero field and at very low temperatures, the
electrons are found to be the main heat carriers. For $B \parallel a$, the
$\rho(B)$ curves display large and positive transverse magnetoresistance (MR)
with extraordinary field dependence between $B^2$ and $B$-linear, accompanied
with anomalies at the metamagnetic transitions and low-field hysteresis;
meanwhile, the $\kappa(B)$ mainly decrease with increasing field and display
some anomalies at the metamagnetic transitions. For $B \parallel c$, there is
weak and negative longitudinal MR while the $\kappa(B)$ show rather strong
field dependence, indicating the role of phonon heat transport.

###Cr$_3$X$_4$ (X=Se, Te) monolayers as new platform to realize robust spin filter, spin diode and spin valve|Qihong Wu,Rongkun Liu,Zhanjun Qiu,Dengfeng Li,Jie Li,Xiaotian Wang,Guangqian Ding###

Cr$_3$X$_4$ (X=Se, Te) monolayers as new platform to realize robust spin filter, spin diode and spin valve. Two-dimensional ferromagnetic (FM) half-metals are promising candidates for
advanced spintronic devices with small-size and high-capacity. Motivated by
recent report on controlling synthesis of FM Cr$_3$Te$_4$ nanosheet, herein, to
explore the potential application in spintronics, we designed spintronic
devices based on Cr$_3$X$_4$ (X=Se, Te) monolayers and investigated their spin
transport properties. We found that Cr$_3$Te$_4$ monolayer based device shows
spin filtering and dual spin diode effect when applying bias voltage, while
Cr$_3$S$_4$ monolayer is an excellent platform to realize a spin valve. The
different transport properties are primarily ascribed to the semiconducting
spin channel, which is close to and away from the Fermi level in Cr$_3$Te$_4$
and Cr$_3$Se$_4$ monolayers, respectively. Interestingly, the current in
monolayer Cr$_3$Se$_4$ based device also displays a negative differential
resistance effect (NDRE) and a high magnetoresistance ratio (up to 2*10$^3$).
Moreover, we found thermally induced spin filtering effect and NDRE in
Cr$_3$Se$_4$ junction when applying temperature gradient instead of bias
voltage. These theoretical findings highlight the potential of Cr$_3$X$_4$
(X=Se, Te) monolayers in spintronic applications and put forward realistic
materials to realize nanosale spintronic device.

###Magnetotransport in graphene/Pb0.24Sn0.76Te heterostructures: finding a way to avoid catastrophe|Gregory M. Stephen,Ivan Naumov,Nicholas A. Blumenschein,Yi-Jan Leo Sun,Jennifer E. DeMell,Sharmila Shirodkar,Pratibha Dev,Patrick J. Taylor,Jeremy T. Robinson,Paul M. Campbell,Aubrey T. Hanbicki,Adam L. Friedman###

Magnetotransport in graphene/Pb0.24Sn0.76Te heterostructures: finding a way to avoid catastrophe. While heterostructures are ubiquitous tools enabling new physics and device
functionalities, the palette of available materials has never been richer.
Combinations of two emerging material classes, two-dimensional materials and
topological materials, are particularly promising because of the wide range of
possible permutations that are easily accessible. Individually, both graphene
and Pb0.24Sn0.76Te (PST) are widely investigated for spintronic applications
because graphene's high carrier mobility and PST's topologically protected
surface states are attractive platforms for spin transport. Here, we combine
monolayer graphene with PST and demonstrate a hybrid system with properties
enhanced relative to the constituent parts. Using magnetotransport
measurements, we find carrier mobilities up to 20,000 cm2/Vs and a
magnetoresistance approaching 100 percent, greater than either material prior
to stacking. We also establish that there are two distinct transport channels
and determine a lower bound on the spin relaxation time of 4.5 ps. The results
can be explained using the polar catastrophe model, whereby a high mobility
interface state results from a reconfiguration of charge due to a
polar/non-polar interface interaction. Our results suggest that proximity
induced interface states with hybrid properties can be added to the still
growing list of remarkable behaviors in these novel materials.

###Weak antilocalization effect and triply degenerate state in Cu-doped CaAuAs|Sudip Malick,Arup Ghosh,Chanchal K. Barman,Aftab Alam,Z. Hossain,Prabhat Mandal,J. Nayak###

Weak antilocalization effect and triply degenerate state in Cu-doped CaAuAs. The effect of 50\% Cu doping at the Au site in the topological Dirac
semimetal CaAuAs is investigated through electronic band structure
calculations, electrical resistivity, and magnetotransport measurements.
Electronic structure calculations a suggest broken-symmetry-driven topological
phase transition from the Dirac to triple-point state in CaAuAs via alloy
engineering. The electrical resistivity of both the CaAuAs and
CaAu$_{0.5}$Cu$_{0.5}$As compounds shows metallic behavior. Nonsaturating
quasilinear magnetoresistance (MR) behavior is observed in CaAuAs. On the other
hand, MR of the doped compound shows a pronounced cusplike feature in the
low-field regime. Such behavior of MR in CaAu$_{0.5}$Cu$_{0.5}$As is attributed
to the weak antilocalization (WAL) effect. The WAL effect is analyzed using
different theoretical models, including the semiclassical $\sim\sqrt{B}$ one
which accounts for the three-dimensional WAL and modified Hikami-Larkin-Nagaoka
model. Strong WAL effect is also observed in the longitudinal MR, which is well
described by the generalized Altshuler-Aronov model. Our study suggests that
the WAL effect originates from weak disorder and the spin-orbit coupled bulk
state. Interestingly, we have also observed the signature of chiral anomaly in
longitudinal MR, when both current and field are applied along the $c$ axis.
The Hall resistivity measurements indicate that the charge conduction mechanism
in these compounds is dominated by the holes with a concentration
$\sim$10$^{20}$ cm$^{-3}$ and mobility $\sim 10^2$ cm$^2$ V$^{-1}$ S$^{-1}$.

###Physical Vapor Transport Growth of Antiferromagnetic CrCl$_3$ Flakes Down to Monolayer Thickness|Jia Wang,Zahra Ahmadi,David Lujan,Jeongheon Choe,Takashi Taniguchi,Kenji Watanabe,Xiaoqin Li,Jeffrey E. Shield,Xia Hong###

Physical Vapor Transport Growth of Antiferromagnetic CrCl$_3$ Flakes Down to Monolayer Thickness. The van der Waals magnets CrX$_3$ (X = I, Br, and Cl) exhibit highly tunable
magnetic properties and are promising candidates for developing novel
two-dimensional (2D) magnetic devices such as magnetic tunnel junctions and
spin tunneling transistors. Previous studies of CrCl$_3$ have mainly focused on
mechanically exfoliated samples. Controlled synthesis of high quality
atomically thin flakes is critical for their technological implementation but
has not been achieved to date. Here, we report the growth of large CrCl$_3$
flakes with well-defined facets down to monolayer thickness (~0.6 nm) via the
physical vapor transport technique. Both isolated flakes with well-defined
facets and long stripe samples with the trilayer portion exceeding 60 $\mu$m
have been obtained. High-resolution transmission electron microscopy studies
show that the CrCl$_3$ flakes are single crystalline in the monoclinic
structure, consistent with the Raman results. The room temperature stability of
the CrCl$_3$ flakes decreases with decreasing thickness. The tunneling
magnetoresistance of graphite/CrCl$_3$/graphite tunnel junctions confirms that
few-layer CrCl$_3$ possesses in-plane magnetic anisotropy and N\'eel
temperature of 17 K. Our study paves the path for developing CrCl$_3$-based
scalable 2D spintronic applications.

###All-electric spin device operation using the Weyl semimetal, WTe$_2$, at room temperature|Kosuke Ohnishi,Motomi Aoki,Ryo Ohshima,Ei Shigematsu,Yuichiro Ando,Taishi Takenobu,Masashi Shiraishi###

All-electric spin device operation using the Weyl semimetal, WTe$_2$, at room temperature. Topological quantum materials (TQMs) possess abundant and attractive spin
physics, and a Weyl semimetal is the representative material because of the
generation of spin polarization that is available for spin devices due to
fictitious Weyl monopoles at the edge of the Weyl node. Meanwhile, a Weyl
semimetal allows the other but unexplored spin polarization due to local
symmetry breaking. Here, we report all-electric spin device operation using a
type-II Weyl semimetal, WTe$_2$, at room temperature. The polarization of spins
propagating in the all-electric device is perpendicular to the WTe$_2$ plane,
which is ascribed to local in-plane symmetry breaking in WTe$_2$, yielding the
spin polarization creation of propagating charged carriers, namely, the
spin-polarized state creation from the non-polarized state. Systematic control
experiments unequivocally negate unexpected artifacts, such as the anomalous
Hall effect, the anisotropic magnetoresistance etc. Creation of all-electric
spin devices made of TQMs and their operation at room temperature can pave a
new pathway for novel spin devices made of TQMs resilient to thermal
fluctuation.

###Anomalous electrical transport and magnetic skyrmions in Mn-tuned Co9Zn9Mn2 single crystals|Fangyi Qi,Yalei Huang,Xinyu Yao,Wenlai Lu,Guixin Cao###

Anomalous electrical transport and magnetic skyrmions in Mn-tuned Co9Zn9Mn2 single crystals. \b{eta}-Mn-type CoxZnyMnz (x + y + z = 20) alloys have recently attracted
increasing attention as a new class of chiral magnets with skyrmions at and
above room temperature. However, experimental studies on the transport
properties of this material are scarce. In this work, we report the successful
growth of the \b{eta}-Mn-type Co9.24Zn9.25Mn1.51 and Co9.02Zn9.18Mn1.80 single
crystals and a systematic study on their magnetic and transport properties. The
skyrmion phase was found in a small temperature range just below the Curie
temperature. The isothermal ac susceptibility and dc magnetization as a
function of magnetic field confirm the existence of the skyrmion phase. A
negative linear magnetoresistance over a wide temperature range from 2 K to 380
K is observed and attributed to the suppression of the magnetic ordering
fluctuation under high fields. Both the magnetization and electrical
resistivity are almost isotropic. The quantitative analysis of the Hall
resistance suggests that the anomalous Hall effect of Co9.24Zn9.25Mn1.51 and
Co9.02Zn9.18Mn1.80 single crystals is dominated by the intrinsic mechanism. Our
findings contribute to a deeper understanding of the properties of CoxZnyMnz (x
+ y + z = 20) alloys material and advance their application in spintronic
devices.

###Semimetallic Kondo lattice behavior in YbPdAs with a distorted kagome structure|W. Xie,F. Du,X. Y. Zheng,H. Su,Z. Y. Nie,B. Q. Liu,Y. H. Xia,T. Shang,C. Cao,M. Smidman,T. Takabatake,H. Q. Yuan###

Semimetallic Kondo lattice behavior in YbPdAs with a distorted kagome structure. We have synthesized YbPdAs with the hexagonal ZrNiAl-type structure, in which
the Yb-atoms form a distorted kagome sublattice in the hexagonal basal plane.
Magnetic, transport, and thermodynamic measurements indicate that YbPdAs is a
low-carrier Kondo lattice compound with an antiferromagnetic transition at
$T_\mathrm{N}$ = 6.6 K, which is slightly suppressed in applied magnetic fields
up to 9 T. The magnetic entropy at $T_\mathrm{N}$ recovers only 33\% of
$R\ln{2}$, the full entropy of the ground state doublet of the Yb-ions. The
resistivity displays a $-\ln T$ dependence between 30 and 15 K, followed by a
broad maximum at $T\rm_{coh}$ = 12 K upon cooling. Below $T\rm_{coh}$, the
magnetoresistance changes from negative to positive, suggesting a crossover
from single-ion Kondo scattering processes at intermediate temperatures to
coherent Kondo lattice behaviors at low temperatures. Both the Hall resistivity
measurements and band structure calculations indicate a relatively low carrier
concentration in YbPdAs. Our results suggest that YbPdAs could provide an
opportunity for examining the interplay of Kondo physics and magnetic
frustration in low carrier systems.

###Dominance of Electron-Magnon Scattering in Itinerant Ferromagnet Fe3GeTe2|P. Saha,M. Singh,V. Nagpal,P. Das,S. Patnaik###

Dominance of Electron-Magnon Scattering in Itinerant Ferromagnet Fe3GeTe2. Fe3GeTe2 is a 2-dimensional van der Waals material exhibiting itinerant
ferromagnetism upto 230 K. Here, we study aspects of scattering mechanism in
Fe3Ge2Te2 single crystals via resistivity, magneto-transport and Hall effect
measurements. The quadratic temperature dependence of electrical resistivity
below the Curie temperature hints towards the dominance of electron-magnon
scattering. A non-saturating positive magnetoresistance (MR) is observed at low
temperatures when the magnetic field is applied parallel to the sample plane.
The linear negative MR at high fields for T < TC corroborates to the
suppression in magnon population due to the damping of spin waves. In the high
temperature regime T > TC,MR can be described by the scattering from spin
fluctuations using the model described by Khosla and Fischer. Isothermal Hall
resistivity curves unveil the presence of anomalous Hall resistivity.
Correlation between MR and side jump mechanism further reveals that the
electron-magnon scattering is responsible for the side jump contribution to the
anomalous Hall effect. Our results provide a clear understanding of the role of
electron-magnon scattering on anomalous Hall effect that rules out its origin
to be the topological band structure.

###Interface-Assisted Room-Temperature Magnetoresistance in Cu-Phenalenyl-based Magnetic Tunnel Junctions|Neha Jha,Anand Paryar,Tahereh Sadat Parvini,Christian Denker,Pavan K. Vardhanapu,Gonela Vijaykumar,Arne Ahrens,Michael Seibt,Jagadeesh S. Moodera,Swadhin K. Mandal,Markus Münzenberg###

Interface-Assisted Room-Temperature Magnetoresistance in Cu-Phenalenyl-based Magnetic Tunnel Junctions. Delocalized carbon-based radical species with unpaired spin, such as
phenalenyl (PLY) radical, opened avenues for developing multifunctional organic
spintronic devices. Here we develop a novel technique based on a
three-dimensional shadow mask and the in-situ deposition to fabricate PLY-,
Cu-PLY-, and Zn-PLY-based organic magnetic tunnel junctions (OMTJs) with area
3x8 {\mu}m2 and improved morphology. The nonlinear and weakly
temperature-dependent current-voltage (I-V) characteristics in combination with
the low organic barrier height suggest tunneling as the dominant transport
mechanism in the structurally and dimensionally optimized OMTJs. Cu-PLY-based
OMTJs, show a significant magnetoresistance up to 14 percent at room
temperature due to the formation of hybrid states at the metal-molecule
interfaces called spinterface, which reveals the importance of spin-dependent
interfacial modification in OMTJs design. In particular, Cu-PLY OMTJs shows a
stable voltage-driven resistive switching response that suggests their use as a
new viable and scalable platform for building molecular scale quantum
memristors and processors.

###Band-folding-driven high tunnel magnetoresistance ratios in (111)-oriented junctions with SrTiO$_3$ barriers|Keisuke Masuda,Hiroyoshi Itoh,Yoshiaki Sonobe,Hiroaki Sukegawa,Seiji Mitani,Yoshio Miura###

Band-folding-driven high tunnel magnetoresistance ratios in (111)-oriented junctions with SrTiO$_3$ barriers. We theoretically study the tunnel magnetoresistance (TMR) effect in
(111)-oriented magnetic tunnel junctions (MTJs) with SrTiO$_{3}$ barriers,
Co/SrTiO$_{3}$/Co(111) and Ni/SrTiO$_{3}$/Ni(111). Our analysis combining the
first-principles calculation and the Landauer formula shows that the Co-based
MTJ has a high TMR ratio over 500%, while the Ni-based MTJ has a smaller value
(290%). Since the in-plane lattice periodicity of SrTiO$_{3}$ is about twice
that of the primitive cell of fcc Co (Ni), the original bands of Co (Ni) are
folded in the $k_x$-$k_y$ plane corresponding to the $ab$ plane of the MTJ
supercell. We find that this band folding gives a half-metallic band structure
in the $\Lambda_1$ state of Co (Ni) and the coherent tunneling of such a
half-metallic $\Lambda_1$ state yields a high TMR ratio. We also reveal that
the difference in the TMR ratio between the Co- and Ni-based MTJs can be
understood by different $s$-orbital weights in the $\Lambda_1$ band at the
Fermi level.

###Field effect two-dimensional electron gases in modulation-doped InSb surface quantum wells|E. Annelise Bergeron,F. Sfigakis,Y. Shi,George Nichols,P. C. Klipstein,A. Elbaroudy,Sean M. Walker,Z. R. Wasilewski,J. Baugh###

Field effect two-dimensional electron gases in modulation-doped InSb surface quantum wells. We report on transport characteristics of field effect two-dimensional
electron gases (2DEG) in surface indium antimonide quantum wells. The topmost 5
nm of the 30 nm wide quantum well is doped and shown to promote the formation
of reliable, low resistance Ohmic contacts to surface InSb 2DEGs. High quality
single-subband magnetotransport with clear quantized integer quantum Hall
plateaus are observed to filling factor $\nu=1$ in magnetic fields of up to
$B=18$ T. We show that the electron density is gate-tunable, reproducible, and
stable from pinch-off to 4$\times 10^{11}$ cm$^{-2}$, and peak mobilities
exceed 24,000 cm$^2$/Vs. Large Rashba spin-orbit coefficients up to 110
meV$\cdot$\r{A} are obtained through weak anti-localization measurements. An
effective mass of 0.019$m_e$ is determined from temperature-dependent
magnetoresistance measurements, and a g-factor of 41 at a density of 3.6$\times
10^{11}$ cm$^{-2}$ is obtained from coincidence measurements in tilted magnetic
fields. By comparing two heterostructures with and without a delta-doped layer
beneath the quantum well, we find that the carrier density is stable with time
when doping in the ternary Al$_{0.1}$In$_{0.9}$Sb barrier is not present.
Finally, the effect of modulation doping on structural asymmetry between the
two heterostructures is characterized.

###Unusual magnetotransport in twisted bilayer graphene from strain-induced open Fermi surfaces|Xiaoyu Wang,Joe Finney,Aaron L. Sharpe,Linsey K. Rodenbach,Connie L. Hsueh,Kenji Watanabe,Takashi Taniguchi,M. A. Kastner,Oskar Vafek,David Goldhaber-Gordon###

Unusual magnetotransport in twisted bilayer graphene from strain-induced open Fermi surfaces. Anisotropic hopping in a toy Hofstadter model was recently invoked to explain
a rich and surprising Landau spectrum measured in twisted bilayer graphene away
from the magic angle. Suspecting that such anisotropy could arise from
unintended uniaxial strain, we extend the Bistritzer-MacDonald model to include
uniaxial heterostrain. We find that such strain strongly influences band
structure, shifting the three otherwise-degenerate van Hove points to different
energies. Coupled to a Boltzmann magnetotransport calculation, this reproduces
previously-unexplained non-saturating $B^2$ magnetoresistance over broad ranges
of density near filling $\nu=\pm 2$, and predicts subtler features that had not
been noticed in the experimental data. In contrast to these distinctive
signatures in longitudinal resistivity, the Hall coefficient is barely
influenced by strain, to the extent that it still shows a single sign change on
each side of the charge neutrality point -- surprisingly, this sign change no
longer occurs at a van Hove point. The theory also predicts a marked rotation
of the electrical transport principal axes as a function of filling even for
fixed strain and for rigid bands. More careful examination of
interaction-induced nematic order versus strain effects in twisted bilayer
graphene could thus be in order.

###Control of chiral orbital currents in a colossal magnetoresistance material|Yu Zhang,Yifei Ni,Hengdi Zhao,Sami Hakani,Feng Ye,Lance DeLong,Itamar Kimchi,Gang Cao###

Control of chiral orbital currents in a colossal magnetoresistance material. Colossal magnetoresistance (CMR) is an extraordinary enhancement of the
electric conductivity in the presence of a magnetic field. It is conventionally
associated with a field-induced spin polarization, which drastically reduces
spin scattering and thus electric resistance. However, ferrimagnetic Mn3Si2Te6
is an intriguing exception to this rule: it exhibits a 7-order-of-magnitude
reduction in ab-plane resistivity with a 13-Tesla anisotropy field which occur
only when a magnetic polarization is avoided [1]. Here we report an exotic
quantum state that is driven by ab-plane chiral orbital currents (COC) flowing
along edges of MnTe6 octahedra. The c-axis orbital moments of ab-plane COC
couple to the ferrimagnetic Mn spins to drastically increase the ab-plane
conductivity (CMR) when an external magnetic field is aligned along the
magnetic hard c-axis. Both the COC state and its CMR are extraordinarily
susceptible to small DC currents exceeding a critical threshold, and a hallmark
of this COC state is an exotic time-dependent, bistable switching mimicking a
first-order melting transition. The control of the COC-enabled CMR and bistable
switching offers a fundamentally new paradigm for quantum technologies.

###Proximity-induced diversified magnetic states and electrically-controllable spin polarization in bilayer graphene: Towards layered spintronics|Xuechao Zhai,Yaroslav M. Blanter###

Proximity-induced diversified magnetic states and electrically-controllable spin polarization in bilayer graphene: Towards layered spintronics. Compared to monolayer graphene, electrons in Bernal-stacked bilayer graphene
(BLG) have an additional layer degree of freedom, offering a platform for
developing {\it layered spintronics} with the help of proximity-induced
magnetism. Based on an effective phenomenological model, we systematically
study the effect of this magnetism on the spin-dependent band structure near
the Fermi energy and identify the magnetic phases induced in BLG by proximity
with magnets. We show that spin polarization can develop in BLG due to this
proximity effect. This spin polarization depends strongly on the layer
distribution of magnetism, and can always be controlled by gate voltage which
shifts spin-dependent band edges and modifies the total band gap. We further
show that the band spin polarization can be modified by the proximity-induced
staggered sublattice potential. By taking full advantage of layer-dependent
magnetism in BLG, we propose that spintronic devices such as a spin filter, a
giant magnetoresistence device, and a spin diode can operate under fully
electric control, which is easier than the common magnetic field control.

###High-field Studies on Layered Magnetic and Polar Dirac Metals|Hideaki Sakai###

High-field Studies on Layered Magnetic and Polar Dirac Metals. Recently, the interplay between the Dirac/Weyl fermion and various bulk
properties, such as magnetism, has attracted considerable attention, since
unconventional transport and optical phenomena were discovered. However, the
design principles for such materials have not been established well. Here, we
propose that the layered material $A$Mn$X_2$ ($A$: alkaline and rare-earth
ions, $X$: Sb, Bi) is a promising platform for systematically exploring
strongly correlated Dirac metals, which consists of the alternative stack of
the $X^-$ square net layer hosting a 2D Dirac fermion and the
$A^{2+}$-Mn$^{2+}$-$X^{3-}$ magnetic block layer. In this article, we shall
review recent high-field studies on this series of materials to demonstrate
that various types of Dirac fermions are realized by designing the block layer.
First, we give an overview of the Dirac fermion coupled with the magnetic order
in EuMnBi$_2$ ($A$=Eu). This material exhibits large magnetoresistance by the
field-induced change in the magnetic order of Eu layers, which is associated
with the strong exchange interaction between the Dirac fermion and the local Eu
moment. Second, we review the Dirac fermion coupled with the lattice
polarization in BaMn$X_2$ ($A$=Ba). There, spin-valley coupling manifests
itself owing to the Zeeman-type spin-orbit interaction, which is experimentally
evidenced by the bulk quantum Hall effect observed at high fields.

###In-plane electronic anisotropy revealed by interlayer resistivity measurements on the iron-based superconductor parent compound CaFeAsF|Taichi Terashima,Hishiro T. Hirose,Yoshitaka Matsushita,Shinya Uji,Hiroaki Ikeda,Yuki Fuseya,Teng Wang,Gang Mu###

In-plane electronic anisotropy revealed by interlayer resistivity measurements on the iron-based superconductor parent compound CaFeAsF. Both cuprates and iron-based superconductors demonstrate nematicity, defined
as the spontaneous breaking of rotational symmetry in electron systems. The
nematic state can play a role in the high-transition-temperature
superconductivity of these compounds. However, the microscopic mechanism
responsible for the transport anisotropy in iron-based compounds remains
debatable. Here, we investigate the electronic anisotropy of CaFeAsF by
measuring its interlayer resistivity under magnetic fields with varying field
directions. Counterintuitively, the interlayer resistivity was larger in the
longitudinal configuration ($B \parallel I \parallel c$) than in the transverse
one ($B \perp I \parallel c$). The interlayer resistivity exhibited a so-called
coherence peak under in-plane fields and was highly anisotropic with respect to
the in-plane field direction. At $T$ = 4 K and $B$ = 14 T, the
magnetoresistance $\Delta\rho/\rho_0$ was seven times larger in the $B
\parallel b_o$ than in the $B \parallel a_o$ configuration. Our theoretical
calculations of the conductivity based on the first-principles electronic band
structure qualitatively reproduced the above observations but underestimated
the magnitudes of the observed features. The proposed methodology can be a
powerful tool for probing the nematic electronic state in various materials.

###Spin re-orientation induced anisotropic magnetoresistance switching in LaCo$_{0.5}$Ni$_{0.5}$O$_{3-δ}$ thin films|P. K. Sreejith,T. S. Suraj,Hari Babu Vasili,Suresh Sreya,Pierluigi Gargiani,K. Sethupathi,Oscar Cespedes,V. Sankaranarayanan,M. S. Ramachandra Rao###

Spin re-orientation induced anisotropic magnetoresistance switching in LaCo$_{0.5}$Ni$_{0.5}$O$_{3-δ}$ thin films. Realization of novel functionalities by tuning magnetic interactions in rare
earth perovskite oxide thin films opens up exciting technological prospects.
Strain-induced tuning of magnetic interactions in rare earth cobaltates and
nickelates is of central importance due to their versatility in electronic
transport properties. Here we reported the spin re-orientation induced
switching of anisotropic magnetoresistance (AMR) and its tunability with strain
in epitaxial LaCo$_{0.5}$Ni$_{0.5}$O$_{3-\delta}$ thin films across the
ferromagnetic transition. Moreover, with strain tuning, we could observe a
two-fold to four-fold symmetry crossover in AMR across the magnetic transition
temperature. The magnetization measurements revealed an onset of ferromagnetic
transition around 50 K, and a further reduction in temperature showed a subtle
change in the magnetization dynamics, which reduced the ferromagnetic
long-range ordering and introduced glassiness in the system. X-ray absorption
and X-ray magnetic circular dichroism spectroscopy measurements over Co and Ni
L edges revealed the Co spin state transition below the magnetic transition
temperature leading to the AMR switching and also the presence of Ni$^{2+}$ and
Co$^{4+}$ ions evidencing the charge transfer from Ni to Co ions. Our work
demonstrated the tunability of magnetic interactions mediated electronic
transport in cobaltate-nickelate thin films, which is relevant in understanding
Ni-Co interactions in oxides for their technological applications such as in
AMR sensors.

###Anomalous Hall effect and two-dimensional Fermi surfaces in the charge-density-wave state of kagome metal RbV$_3$Sb$_5$|Lingfei Wang,Wei Zhang,Zheyu Wang,Tsz Fung Poon,Wenyan Wang,Chun Wai Tsang,Jianyu Xie,Xuefeng Zhou,Yusheng Zhao,Shanmin Wang,Kwing To Lai,Swee K. Goh###

Anomalous Hall effect and two-dimensional Fermi surfaces in the charge-density-wave state of kagome metal RbV$_3$Sb$_5$. AV$_3$Sb$_5$ (A=Cs, K, Rb) are recently discovered superconducting systems
($T_{\rm c}\sim0.9-2.5$ K) in which the vanadium atoms adopt the kagome
structure. Intriguingly, these systems enter a charge-density-wave (CDW) phase
($T_{\rm CDW}\sim80-100$ K), and further evidence shows that the time-reversal
symmetry is broken in the CDW phase. Concurrently, the anomalous Hall effect
has been observed in KV$_3$Sb$_5$ and CsV$_3$Sb$_5$ inside the novel CDW phase.
Here, we report a comprehensive study of a high-quality RbV$_3$Sb$_5$ single
crystal with magnetotransport measurements. Our data demonstrate the emergence
of anomalous Hall effect in RbV$_3$Sb$_5$ when the charge-density-wave state
develops. The magnitude of anomalous Hall resistivity at the low temperature
limit is comparable to the reported values in KV$_3$Sb$_5$ and CsV$_3$Sb$_5$.
The magnetoresistance channel further reveals a rich spectrum of quantum
oscillation frequencies, many of which have not been reported before. In
particular, a large quantum oscillation frequency (2235 T), which occupies
$\sim$56% of the Brillouin zone area, has been recorded. For the quantum
oscillation frequencies with sufficient signal-to-noise ratio, we further
perform field-angle dependent measurements and our data indicate
two-dimensional Fermi surfaces in RbV$_3$Sb$_5$. Our results provide
indispensable information for understanding the anomalous Hall effect and band
structure in kagome metals AV$_3$Sb$_5$.

###Rotational symmetry breaking in superconducting nickelate Nd0.8Sr0.2NiO2 films|Haoran Ji,Yanan Li,Yi Liu,Xiang Ding,Zheyuan Xie,Shichao Qi,Liang Qiao,Yi-feng Yang,Guang-Ming Zhang,Jian Wang###

Rotational symmetry breaking in superconducting nickelate Nd0.8Sr0.2NiO2 films. The infinite-layer nickelates, isostructural to the high-Tc superconductor
cuprates, have risen as a promising platform to host unconventional
superconductivity and stimulated growing interests in the condensed matter
community. Despite numerous researches, the superconducting pairing symmetry of
the nickelate superconductors, the fundamental characteristic of a
superconducting state, is still under debate. Moreover, the strong electronic
correlation in the nickelates may give rise to a rich phase diagram, where the
underlying interplay between the superconductivity and other emerging quantum
states with broken symmetry is awaiting exploration. Here, we study the angular
dependence of the transport properties on the infinite-layer nickelate
Nd0.8Sr0.2NiO2 superconducting films with Corbino-disk configuration. The
azimuthal angular dependence of the magnetoresistance (R({\phi})) manifests the
rotational symmetry breaking from isotropy to four-fold (C4) anisotropy with
increasing magnetic field, revealing a symmetry breaking phase transition.
Approaching the low temperature and large magnetic field regime, an additional
two-fold (C2) symmetric component in the R({\phi}) curves and an anomalous
upturn of the temperature-dependent critical field are observed simultaneously,
suggesting the emergence of an exotic electronic phase. Our work uncovers the
evolution of the quantum states with different rotational symmetries and
provides deep insight into the global phase diagram of the nickelate
superconductors.

###Weak antilocalization induced by Se substitution in layered BiCh$_2$-based (Ch = S, Se) superconductors LaO$_{1-x}$F$_x$BiS$_{2-y}$Se$_y$|Kazuhisa Hoshi,Hiroto Arima,Noriyuki Kataoka,Masayuki Ochi,Aichi Yamashita,Anne de Visser,Takayoshi Yokoya,Kazuhiko Kuroki,Yoshikazu Mizuguchi###

Weak antilocalization induced by Se substitution in layered BiCh$_2$-based (Ch = S, Se) superconductors LaO$_{1-x}$F$_x$BiS$_{2-y}$Se$_y$. We report transport properties for layered BiCh2-based (Ch = S, Se)
superconductors LaO1-xFxBiS2-ySey (x = 0.2, 0.5, y = 0-1.05) and the
observation of weak antilocalization (WAL). Electrical resistivity and Hall
coefficients for the Se-poor samples increase with decreasing temperature. The
increase becomes less pronounced with increasing Se concentration indicating a
loss of insulating behavior. Interestingly, the moderately Se-substituted
samples exhibit metallic behavior in the high-temperature region and a weak
increase in the resistivity in the low-temperature regions, which indicates the
existence of carrier localization. The heavily Se-substituted compounds show
metallic behavior in the entire-temperature region. Sign changes of the Hall
coefficients are observed for the x = 0.2 samples, which possibly is related to
a charge-density wave (CDW). Magnetoresistance measurements indicate that WAL
is realized in the heavily Se-substituted systems. The WAL behavior is weakened
by the changes in F and Se concentrations. A crossover state of the WAL and WL
emerges around the moderately F-doped and Se-free LaO0.8F0.2BiS2. The change of
the resistivity behavior by the F and Se substitution clearly correlates to the
difference of the magnetoconductance. Moreover, the localization regions of the
WAL-WL crossover and weak WAL states are possibly associated with the CDW. We
propose that the BiCh2-based system is a good platform for studying
relationship between WAL, superconductivity, and electronic ordering because
those states are tunable by element substitutions with bulk single crystals.

###Electric field tunable multi-state tunnel magnetoresistances in 2D van der Waals magnetic heterojunctions|X. X. Ren,B. Liu,Xian Zhang,Ping Li,Zhi-Xin Guo###

Electric field tunable multi-state tunnel magnetoresistances in 2D van der Waals magnetic heterojunctions. Magnetic tunnel junction (MTJ) based on van der Waals (vdW) magnetic layers
has been found to present excellent tunneling magnetoresistance (TMR) property,
which has great potential applications in field sensing, non-volatile magnetic
random access memories, and spin logics. Although MTJs composed of multilayer
vdW magnetic homojunction have been extensively investigated, the ones composed
of vdW magnetic heterojunction is still to be explored. Here we use
first-principles approaches to reveal that the magnetic heterojunction MTJs
have much more distinguishable TMR values than the homojunction ones. In the
MTJ composed of bilayer CrI3/bilayer Cr2Ge2Te6 heterojunction, we find there
are eight stable magnetic states, leading to six distinguishable electronic
resistances. As a result, five sizable TMRs larger than 300% can be obtained
(the maximum TMR is up to 620,000%). Six distinguishable memories are obtained
which is two times larger than that of a four-layered homojunction MTJ. The
underlying relationships among magnetic state, spin-polarized band structures,
and transmission spectrums are further revealed to explain the multiple TMR
values. We also find that the magnetic states and thus TMRs can be efficiently
modulated by an external electric field. This study opens an avenue to the
design of high-performance MTJ devices based on vdW heterojunctions.

###Room-Temperature Spin-Valve Effect in Fe$_3$GaTe$_2$/MoS$_2$/Fe$_3$GaTe$_2$ 2D van der Waals Heterojunction Devices|Wen Jin,Gaojie Zhang,Hao Wu,Li Yang,Wenfeng Zhang,Haixin Chang###

Room-Temperature Spin-Valve Effect in Fe$_3$GaTe$_2$/MoS$_2$/Fe$_3$GaTe$_2$ 2D van der Waals Heterojunction Devices. Spin-valve effect has been the focus of spintronics over the last decades due
to its potential in many spintronic devices. Two-dimensional (2D) van der Waals
(vdW) materials are highly expected to build the spin-valve heterojunction.
However, the Curie temperatures (TC) of the vdW ferromagnetic 2D crystals are
mostly below room temperature (~30-220 K). It is very challenging to develop
room temperature, ferromagnetic (FM) 2D crystals based spin-valve devices which
are still not available to date. We report the first room temperature, FM 2D
crystal based all-2D vdW Fe3GaTe2/MoS2/Fe3GaTe2 spin valve devices. The
Magnetoresistance (MR) of the all- devices is up to 15.89% at 2.3 K and 11.97%
at 10 K, 4-30 times of MR from the spin valves of
Fe$_3$GaTe$_2$/MoS$_2$/Fe$_3$GaTe$_2$ and conventional NiFe/MoS$_2$/NiFe.
Typical spin valve effect shows strong dependence on MoS2 spacer thickness in
the vdW heterojunction. Importantly, the spin valve effect (0.31%) still
robustly exists at 300 K with low working currents down to 10 nA (0.13
A/cm$^2$). The results provide a general vdW platform to room temperature, 2D
FM crystals based 2D spin valve devices.

###Heavily Damped Precessional Switching with Very Low Write-error Rate in Elliptical-cylinder Magnetic Tunnel Junction|Rie Matsumoto,Shinji Yuasa,Hiroshi Imamura###

Heavily Damped Precessional Switching with Very Low Write-error Rate in Elliptical-cylinder Magnetic Tunnel Junction. Voltage-induced dynamic switching in magnetic tunnel junctions (MTJs) is a
writing technique for voltage-controlled magnetoresistive random access memory
(VCMRAM), which is expected to be an ultimate non-volatile memory with
ultra-low power consumption. In conventional dynamic switching, the width of
sub-nanosecond write voltage pulses must be precisely controlled to achieve a
sufficiently low write-error rate (WER). This very narrow tolerance of pulse
width is the biggest technical difficulty in developing VCMRAM. Heavily damped
precessional switching is a writing scheme for VCMRAM with a substantially high
tolerance of pulse width although the minimum WER has been much higher than
that of conventional dynamic switching with an optimum pulse width. In this
study, we theoretically investigate the effect of MTJ shape and the direction
of the applied magnetic field on the WER of heavily damped precessional
switching. The results show that the WER in elliptical-cylinder MTJ can be
several orders of magnitude smaller than that in usual circular-cylinder MTJ
when the external magnetic field is applied parallel to the minor axis of the
ellipse. The reduction in WER is due to the fact that the demagnetization field
narrows the component of the magnetization distribution perpendicular to the
plane direction immediately before the voltage is applied.

###Magnetotransport induced by anomalous Hall effect|Jiaji Zhao,Bingyan Jiang,Jinying Yang,Lujunyu Wang,Hengjie Shi,Guang Tian,Zhilin Li,Enke Liu,Xiaosong Wu###

Magnetotransport induced by anomalous Hall effect. In a magnetic metal, the Hall resistance is generally taken to be the sum of
the ordinary Hall resistance and the anomalous Hall resistance. Here it is
shown that this empirical relation is no longer valid when either the ordinary
Hall angle or the anomalous Hall angle is not small. Using the proper
conductivity relation, we reveal an unexpected magnetoresistance (MR) induced
by the anomalous Hall effect (AHE). A $B$-linear MR arises and the sign of the
slope depends on the sign of the anomalous Hall angle, giving rise to a
characteristic bowtie shape. The Hall resistance in a single-band system can
exhibit a nonlinearity which is usually considered as a characteristic of a
two-band system. A $B$-symmetric component appears in the Hall. These effects
reflect the fundamental difference between the ordinary Hall effect and the
AHE. Furthermore, we experimentally reproduce the unusual MR and Hall reported
before in Co$_3$Sn$_2$S$_2$ and show that these observations can be well
explained by the proposed mechanism. MR often observed in quantum anomalous
Hall insulators provides further confirmation of the picture. The effect may
also account for the large MR observed in non-magnetic three-dimensional
topological Dirac semimetals.

###Superconductivity and orbital-selective nematic order in a new titanium-based kagome metal CsTi3Bi5|Haitao Yang,Yuhan Ye,Zhen Zhao,Jiali Liu,Xin-Wei Yi,Yuhang Zhang,Jinan Shi,Jing-Yang You,Zihao Huang,Bingjie Wang,Jing Wang,Hui Guo,Xiao Lin,Chengmin Shen,Wu Zhou,Hui Chen,Xiaoli Dong,Gang Su,Ziqiang Wang,Hong-Jun Gao###

Superconductivity and orbital-selective nematic order in a new titanium-based kagome metal CsTi3Bi5. Fabrication of new types of superconductors with novel physical properties
has always been a major thread in the research of superconducting materials. An
example is the enormous interests generated by the cascade of correlated
topological quantum states in the newly discovered vanadium-based kagome
superconductors AV3Sb5 (A=K, Rb, and Cs) with a Z2 topological band structure.
Here we report the successful fabrication of single-crystals of titanium-based
kagome metal CsTi3Bi5 and the observation of superconductivity and electronic
nematicity. The onset of the superconducting transition temperature Tc is
around 4.8 K. In sharp contrast to the charge density wave superconductor
AV3Sb5, we find that the kagome superconductor CsTi3Bi5 preserves translation
symmetry, but breaks rotational symmetry and exhibits an electronic nematicity.
The angular-dependent magnetoresistivity shows a remarkable two-fold rotational
symmetry as the magnetic field rotates in the kagome plane. The scanning
tunneling microscopy and spectroscopic imaging detect rotational-symmetry
breaking C2 quasiparticle interference patterns (QPI) at low energies,
providing further microscopic evidence for electronic nematicity. Combined with
first-principle calculations, we find that the nematic QPI is orbital-selective
and dominated by the Ti dxz and dyz orbitals, possibly originating from the
intriguing orbital bond nematic order. Our findings in the new "135" material
CsTi3Bi5 provide new directions for exploring the multi-orbital correlation
effect and the role of orbital or bond order in the electron liquid crystal
phases evidenced by the symmetry breaking states in kagome superconductors.

###Non-linear Transport Phenomena and Current-induced Hydrodynamics in Ultra-high Mobility Two-dimensional Electron Gas|Zitong Wang,Michael Hilke,Norm Fong,Guy Austing,Sergei Studenikin,Ken West,Loren Pfeiffer###

Non-linear Transport Phenomena and Current-induced Hydrodynamics in Ultra-high Mobility Two-dimensional Electron Gas. We report on non-linear transport phenomena at high filling factor and DC
current-induced electronic hydrodynamics in an ultra-high mobility (mu=20x10^6
cm^2/Vs) two-dimensional electron gas in a narrow (15 micron wide) GaAs/AlGaAs
Hall bar for DC current densities reaching 0.67 A/m. The various phenomena and
the boundaries between the phenomena are captured together in a two-dimensional
differential resistivity map as a function of magnetic field (up to 250 mT) and
DC current. This map, which resembles a phase diagram, demarcate distinct
regions dominated by Shubnikov-de Haas (SdH) oscillations (and phase inversion
of these oscillations) around zero DC current; negative magnetoresistance and a
double-peak feature (both ballistic in origin) around zero field; and Hall
field-induced resistance oscillations (HIROs) radiating out from the origin.
From a detailed analysis of the data near zero field, we show that increasing
the DC current suppresses the electron-electron scattering length that drives a
growing hydrodynamic contribution to both the differential longitudinal and
transverse (Hall) resistivities. Our approach to induce hydrodynamics with DC
current differs from the more usual approach of changing the temperature. We
also find a significant (factor of two to four) difference between the quantum
lifetime extracted from SdH oscillations, and the quantum lifetime extracted
from HIROs. In addition to observing HIRO peaks up to the seventh order, we
observe an unexpected HIRO-like feature close to mid-way between the
first-order and the second-order HIRO maxima at high DC current.

###Detecting Magnetic Ink Barcodes with Handheld Magnetoresistive Sensors|Sofia Abrunhosa,Ian Gibb,Rita Macedo,Emrys Williams,Nathalie Muller,Paulo P. Freitas,Susana Cardoso###

Detecting Magnetic Ink Barcodes with Handheld Magnetoresistive Sensors. Information encoding in barcodes using magnetic-based technology is a unique
strategy to read data buried underneath non-transparent surfaces since a direct
line-of-sight between the code and the reader is not required. This technology
is of particular interest in secure labelling and recyclable packaging
applications. However, current magnetic reading heads, such as those employed
for magnetic ink character recognition, need to be placed in contact with the
magnetic structures, limiting the depths at which the information can be read.
This paper describes a strategy to overcome that limitation by replacing the
traditional inductive heads with tunnel magnetoresistive (TMR) sensors.
Soft-magnetic codes can be printed using conventional LaserJet toners and, by
having their magnetisation set with a permanent magnet included in the device,
the resulting magnetic field can be read using a TMR sensor. We demonstrate
that such a device can read barcodes at depths of at least 1 mm. It can also
resolve individual structures as thin as 200 {\mu}m when used in contact.

###Magnetic and Electrical Properties of high-entropy rare-earth manganites|Ashutosh Kumar,David Bérardan,Diana Dragoe,Eric Riviere,Tomohiro Takayama,Hidenori Takagi,Nita Dragoe###

Magnetic and Electrical Properties of high-entropy rare-earth manganites. Detailed investigations of structural, magnetic and electronic transport
properties of hole-doped high-entropy rare-earth manganites are presented. The
high-entropy samples (LaNdPrSmEu)$_{1-x}$Sr$_x$MnO$_3$
(0$\leq$\textit{x}$\leq$0.5), synthesized using the solid-state technique, show
a change in the crystal structure from \textit{Pbnm} to \textit{R-3c} with
increasing Sr substitution, attributed to the change in the tolerance factor.
Prominent ferromagnetic ordering is observed in the sample with a rhombohedral
structure (\textit{x}$\geq$0.3), originating from the dominant double exchange
mechanism mediated by itinerant electrons. Further, the Curie temperature is
smaller for the high-entropy sample with \textit{x}=0.3, as compared to
La$_{0.7}$Sr$_{0.3}$MnO$_3$, suggesting a strong relation between the Curie
temperature and the Mn-O-Mn bond angle associated with the reduced ionic radii
at the rare-earth site. The electrical resistivity of the high-entropy samples
is larger than those of La$_{1-x}$Sr$_x$MnO$_3$, which can be ascribed to the
reduced bandwidth due to the enhanced structural distortion. A concomitant rise
in magnetoresistance is observed for high-entropy samples with the increase in
Sr concentration. These findings considering the configurational complexity of
different rare-earths advance the understanding of high-entropy rare earth
manganites.

###FeRhCrSi: A new spin semimetal with room temperature spin-valve behavior|Y. Venkateswara,Jadupati Nag,S. Shanmukharao Samatham,Akhilesh Kumar Patel,P. D. Babu,Manoj Raama Varma,Jayita Nayak,K. G. Suresh,Aftab Alam###

FeRhCrSi: A new spin semimetal with room temperature spin-valve behavior. Spin semimetals are a recently discovered new class of spintronic materials,
which exhibit a band gap in one spin channel while a semimetallic feature in
the other and thus allows for tunable spin transport. Here, we present
experimental verification of spin semimetallic behavior in FeRhCrSi, a
quaternary Heusler alloy with saturation moment 2 $\mu_B$ and Curie temperature
$>$ 400 K. It crystallises in the L2$_1$ structure with 50$\%$ antisite
disorder between Fe and Rh. Below 300 K, it shows a weakly temperature
dependent electrical resistivity with negative temperature coefficient,
indicating the normal semimetal or spin semimetal behavior. Anomalous
magnetoresistance data reveals dominant contribution from asymmetric part, a
clear signature of spin-valve nature, which is retained even at room
temperature. \textcolor{black}{The asymmetric part of magneto-resistance shows
an unusual increase with increasing temperature.} Hall measurements confirm the
anomalous nature of conductivity originating from the intrinsic Berry
curvature, with holes being the majority carriers. Ab-initio simulation
confirms a unique long-range ferrimagnetic ordering to be the ground state,
explaining the origin behind the unexpected low saturation moment. The
ferrimagnetic disordered structure confirms the spin semimetallic feature of
FeRhCrSi, as observed experimentally.

###Néel Spin Currents in Antiferromagnets|Ding-Fu Shao,Yuan-Yuan Jiang,Jun Ding,Shu-Hui Zhang,Zi-An Wang,Rui-Chun Xiao,Gautam Gurung,W. J. Lu,Y. P. Sun,Evgeny Y. Tsymbal###

Néel Spin Currents in Antiferromagnets. Ferromagnets are known to support spin-polarized currents that control
various spin-dependent transport phenomena useful for spintronics. On the
contrary, fully compensated antiferromagnets are expected to support only
globally spin-neutral currents. Here, we demonstrate that these globally
spin-neutral currents can represent the N\'eel spin currents, i.e. staggered
spin currents flowing through different magnetic sublattices. The N\'eel spin
currents emerge in antiferromagnets with strong intra-sublattice coupling
(hopping) and drive the spin-dependent transport phenomena such as tunneling
magnetoresistance (TMR) and spin-transfer torque (STT) in antiferromagnetic
tunnel junctions (AFMTJs). Using RuO$_{2}$ and Fe$_{4}$GeTe$_{2}$ as
representative antiferromagnets, we predict that the N\'eel spin currents with
a strong staggered spin-polarization produce a sizable field-like STT capable
of the deterministic switching of the N\'eel vector in the associated AFMTJs.
Our work uncovers the previously unexplored potential of fully compensated
antiferromagnets and paves a new route to realize the efficient writing and
reading of information for antiferromagnetic spintronics.

###Unconventional topological phase transition from semimetal to insulator in SnBi2Te4: Role of anomalous thermal expansion|T. K. Dalui,B. Das,C. K. Barman,P. K. Ghose,A. Sarma,S. K. Mahatha,F. Diekmann,K. Rossnagel,S. Majumdar,A. Alam,S. Giri###

Unconventional topological phase transition from semimetal to insulator in SnBi2Te4: Role of anomalous thermal expansion. We propose SnBi2Te4 to be a novel candidate material exhibiting temperature
(T) mediated transitions between rich topological phases. From a combined
theoretical and experimental studies, we find that SnBi2Te4 goes from a low-T
topological semimetallic phase to a high-T (room temperature) topological
insulating phase via an intermediate topological metallic phase. Single
crystals of SnBi2Te4 are characterized by various experimental probes including
Synchrotron based X-ray diffraction, magnetoresistance, Hall effect, Seebeck
coefficient, magnetization and angle-resolved photoemission spectroscopy
(ARPES). X-ray diffraction data confirms an anomalous thermal expansion of the
unit cell volume below 100 K, which significantly affects the bulk band
structure and hence the transport properties, as confirmed by our density
functional theory calculations. Simulated surface states at 15 K agree fairly
well with our ARPES data and are found to be robust with varying T. This
indirectly supports the experimentally observed paramagnetic singularity in the
entire T-range. The proposed coexistence of rich topological phases is a rare
occurrence, yet paves a fertile ground to tune various topological phases in a
material driven by structural distortion.

###Microstructuring YbRh2Si2 for resistance and noise measurements down to ultra-low temperatures|Alexander Steppke,Sandra Hamann,Markus König,Andrew P. Mackenzie,Kristin Kliemt,Cornelius Krellner,Marvin Kopp,Martin Lonsky,Jens Müller,Lev V. Levitin,John Saunders,Manuel Brando###

Microstructuring YbRh2Si2 for resistance and noise measurements down to ultra-low temperatures. The discovery of superconductivity in the quantum critical Kondo-lattice
system YbRh2Si2 at an extremely low temperature of 2 mK has inspired efforts to
perform high-resolution electrical resistivity measurements down to this
temperature range in highly conductive materials. Here we show that control
over the sample geometry by microstructuring using focused-ion-beam (FIB)
techniques allows to reach ultra-low temperatures and increase signal-to-noise
ratios (SNR) tenfold, without adverse effects to sample quality. In five
experiments we show four-terminal sensing resistance and magnetoresistance
measurements which exhibit sharp phase transitions at the N\'eel temperature,
and Shubnikov-de-Haas (SdH) oscillations between 13 T and 18 T where we
identified a new SdH frequency of 0.39 kT. The increased SNR allowed resistance
fluctuation (noise) spectroscopy that would not be possible for bulk crystals,
and confirmed intrinsic 1/f-type fluctuations. Under controlled strain, two
thin microstructured samples exhibited a large increase of T_N from 67 mK up to
188 mK while still showing clear signatures of the phase transition and SdH
oscillations. SQUID-based thermal noise spectroscopy measurements in a nuclear
demagnetisation refrigerator down to 0.95 mK, show a sharp superconducting
transition at T_c = 1.2 mK. These experiments demonstrate microstructuring as a
powerful tool to investigate the resistance and the noise spectrum of highly
conductive correlated metals over wide temperature ranges.

###Domain Wall-Magnetic Tunnel Junction Analog Content Addressable Memory Using Current and Projected Data|Harrison Jin,Hanqing Zhu,Keren Zhu,Thomas Leonard,Jaesuk Kwon,Mahshid Alamdar,Kwangseok Kim,Jungsik Park,Naoki Hase,David Z. Pan,Jean Anne C. Incorvia###

Domain Wall-Magnetic Tunnel Junction Analog Content Addressable Memory Using Current and Projected Data. With the rise in in-memory computing architectures to reduce the
compute-memory bottleneck, a new bottleneck is present between analog and
digital conversion. Analog content-addressable memories (ACAM) are being
recently studied for in-memory computing to efficiently convert between analog
and digital signals. Magnetic memory elements such as magnetic tunnel junctions
(MTJs) could be useful for ACAM due to their low read/write energy and high
endurance, but MTJs are usually restricted to digital values. The spin orbit
torque-driven domain wall-magnetic tunnel junction (DW-MTJ) has been recently
shown to have multi-bit function. Here, an ACAM circuit is studied that uses
two domain wall-magnetic tunnel junctions (DW-MTJs) as the analog storage
elements. Prototype DW-MTJ data is input into the magnetic ACAM (MACAM) circuit
simulation, showing ternary CAM function. Device-circuit co-design is carried
out, showing that 8-10 weight bits are achievable, and that designing
asymmetrical spacing of the available DW positions in the device leads to
evenly spaced ACAM search bounds. Analyzing available spin orbit torque
materials shows platinum provides the largest MACAM search bound while still
allowing spin orbit torque domain wall motion, and that the circuit is
optimized with minimized MTJ resistance, minimized spin orbit torque material
resistance, and maximized tunnel magnetoresistance. These results show the
feasibility of using DW-MTJs for MACAM and provide design parameters.

###Cryogenic temperature deposition of high-performance CoFeB/MgO/CoFeB magnetic tunnel junctions on 300 mm wafers|Tomohiro Ichinose,Tatsuya Yamamoto,Takayuki Nozaki,Kay Yakushiji,Shingo Tamaru,Makoto Konoto,Shinji Yuasa###

Cryogenic temperature deposition of high-performance CoFeB/MgO/CoFeB magnetic tunnel junctions on 300 mm wafers. We developed a cryogenic temperature deposition process for high-performance
CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJs) on 300 mm thermally oxidized
silicon wafers. The effect of the deposition temperature of the CoFeB layers on
the nanostructure, magnetic and magneto-transport properties of the MTJs were
investigated in detail. When CoFeB was deposited at 100 K, the MTJs exhibited a
perpendicular magnetic anisotropy (PMA) of 214 uJ/m2 and a voltage-controlled
magnetic anisotropy (VCMA) coefficient of -45 fJ/Vm, corresponding to 1.4- and
1.7-fold enhancements in PMA and VCMA, respectively, compared to the case of
room-temperature deposition of CoFeB. The improvement in the MTJ properties was
not simply due to the morphology of the MTJ films. The interface-sensitive
magneto-transport properties indicated that interfacial qualities such as
intermixing and oxidation states at the MgO/CoFeB interfaces were improved by
the cryogenic temperature deposition. Cryogenic-temperature sputtering
deposition is expected to be a standard manufacturing process for
next-generation magnetoresistive random-access memory.

###Spin-orbital order and excitons in magnetoresistive HoBi|J. Gaudet,H. -Y. Yang,E. M. Smith,T. Halloran,J. P. Clancy,J. A. Rodriguez-Rivera,Guangyong Xu,Y. Zhao,W. C. Chen,G. Sala,A. A. Aczel,B. D. Gaulin,F. Tafti,C. Broholm###

Spin-orbital order and excitons in magnetoresistive HoBi. The magnetism of the rock-salt $fcc$ rare-earth monopnictide HoBi, a
candidate topological material with extreme magnetoresistance, is investigated.
From the Ho$^{3+}$ non-Kramers $J$=8 spin-orbital multiplet, the cubic crystal
electric field yields six nearly degenerate low-energy levels. These constitute
an anisotropic magnetic moment with a Jahn-Teller-like coupling to the lattice.
In the cubic phase for $T>T_N~=~5.72(1)~K$, the paramagnetic neutron scattering
is centered at $\mathbf{k}=(\frac{1}{2}\frac{1}{2}\frac{1}{2})$ and was fit to
dominant antiferromagnetic interactions between Ho spins separated by $\{100\}$
and ferromagnetic interactions between spins displaced by
$\{\frac{1}{2}\frac{1}{2}0\}$. For $T<T_N$, a type-II AFM long-range order with
$\mathbf{k}=(\frac{1}{2}\frac{1}{2}\frac{1}{2})$ develops along with a
tetragonal lattice distortion. While neutron diffraction from a multi-domain
sample cannot unambiguously determine the spin orientation within a domain, the
bulk magnetization, structural distortion, and our measurements of the magnetic
excitations all show the easy axis coincides with the tetragonal axis. The
weakly dispersive excitons for $T<T_N$ can be accounted for by a spin
Hamiltonian that includes the crystal electric field and exchange interactions
within the Random Phase Approximation.

###Debye temperature, electron-phonon coupling constant, and moderate nonadiabaticity in highly-compressed I-43d-TaH3 superconductor|E. F. Talantsev###

Debye temperature, electron-phonon coupling constant, and moderate nonadiabaticity in highly-compressed I-43d-TaH3 superconductor. Recently, He et al (arXiv2212.13739 (2022)) reported on the discovery of
high-temperature superconductivity in highly-compressed polyhydride of
tantalum. At pressure ${\it P}=197 GPa$, the polyhydride I-43d-phase of $TaH_3$
exhibits zero-resistance transition temperature $T_{c,zero}=25.6 K$.
Measurements of the low-temperature magnetoresistance showed that this
superconductor has the ground state upper critical field (defined by the zero
resistance criterion) $B_{c2}(0) = 11 Tesla$. Here, we performed detailed
analysis of the reported experimental data by He et al (arXiv2212.13739 (2022))
and deduced several parameters of the I-43d-phase of $TaH_3$: (a) the Debye
temperature, $T_{\theta}=263 K$, (b) the electron-phonon coupling constant,
${\lambda}_{e-ph}=1.53$; (c) the Fermi temperature $T_{F}=1324 K$; (d) the
strength of nonadiabaticity, $T_{\theta}/T_F =0.19$; (e) and the ratio of
$T_{c}/T_{F} =0.0185 $ which implies that I-43d-phase of $TaH_3$ falls in
unconventional superconductors band in the Uemura plot. Deduced parameters
indicate that the I-43d-phase of $TaH_3$ (${\it P}=197 GPa$) can be classified
as typical unconventional high-temperature superconductor.

###Record-high Mobility and Extreme Magnetoresistance on Kagome-lattice in Compensated Semimetal Ni3In2S2|Hongwei Fang,Meng Lyu,Hao Su,Jian Yuan,Yiwei Li,Lixuan Xu,Shuai Liu,Liyang Wei,Xinqi Liu,Haifeng Yang,Qi Yao,Meixiao Wang,Yanfeng Guo,Wujun Shi,Yulin Chen,Enke Liu,Zhongkai Liu###

Record-high Mobility and Extreme Magnetoresistance on Kagome-lattice in Compensated Semimetal Ni3In2S2. The kagome-lattice crystal hosts various intriguing properties including the
frustrated magnetism, charge order, topological state, superconductivity and
correlated phenomena. To achieve high-performance kagome-lattice compounds for
electronic and spintronic applications, careful tuning of the band structure
would be desired. Here, the electronic structures of kagome-lattice crystal
Ni3In2S2 were investigated by transport measurements, angle-resolved
photoemission spectroscopy as well as ab initio calculations. The transport
measurements reveal Ni3In2S2 as a compensated semimetal with record-high
carrier mobility (~8683 cm2 V-1 S-1 and 7356 cm2 V-1 S-1 for holes and
electrons) and extreme magnetoresistance (15518% at 2 K and 13 T) among
kagome-lattice materials. These extraordinary properties are well explained by
its band structure with indirect gap, small electron/hole pockets and large
bandwidth of the 3d electrons of Ni on the kagome lattice. This work
demonstrates that the crystal field and doping serve as the key tuning knobs to
optimize the transport properties in kagome-lattice crystals. Our work provides
material basis and optimization routes for kagome-lattice semimetals as
electronics and spintronics applications.

###Incoherent transport in a model for the strange metal phase: Memory-matrix formalism|Emile Pangburn,Anurag Banerjee,Hermann Freire,Catherine Pépin###

Incoherent transport in a model for the strange metal phase: Memory-matrix formalism. We revisit a phenomenological model of fermions coupled to fluctuating bosons
that emerges from finite-momentum particle-particle pairs for describing the
strange metal phase in the cuprates. The incoherent bosons dominate the
transport properties for the resistivity and optical conductivity in the
non-Fermi liquid phase. Within the Kubo formalism, the resistivity is
approximately linear in temperature with a Drude form for the optical
conductivity, such that the Drude lifetime is inversely proportional to the
temperature. Additionally, when the bosons emerge from electron pairs with
spin-triplet symmetry, the magnetoresistance has a linear magnetic field
dependence. Here, we compute the transport properties of such bosons within the
memory-matrix approach that successfully captures the hydrodynamic regime. This
technique emerges as the appropriate framework for describing the transport
coefficients of the strange metal phase. Our analysis confirms the $T$-linear
resistivity due to the Umklapp scattering that we obtained for this effective
model. Finally, we provide new predictions regarding the variation of the
thermal conductivity with temperature and examine the validity of the
Wiedemann-Franz law.

###Dimensionality control and rotational symmetry breaking superconductivity in square-planar layered nickelates|Lin Er Chow,Km Rubi,King Yau Yip,Mathieu Pierre,Maxime Leroux,Xinyou Liu,Zhaoyang Luo,Shengwei Zeng,Changjian Li,Michel Goiran,Neil Harrison,Walter Escoffier,Swee Kuan Goh,A. Ariando###

Dimensionality control and rotational symmetry breaking superconductivity in square-planar layered nickelates. The interplay between dimensionality and various phases of matter is a
central inquiry in condensed matter physics. New phases are often discovered
through spontaneously broken symmetry. Understanding the dimensionality of
superconductivity in the high-temperature cuprate analogue $-$ layered
nickelates and revealing a new symmetry-breaking state are the keys to
deciphering the underlying pairing mechanism. Here, we demonstrate the
highly-tunable dimensionality and a broken rotational symmetry state in the
superconductivity of square-planar layered nickelates. The superconducting
state, probed by superconducting critical current and magnetoresistance within
superconducting transition under direction-dependent in-plane magnetic fields,
exhibits a $C_2$ rotational symmetry which breaks the $C_4$ rotational symmetry
of the square-planar lattice. Furthermore, by performing detailed examination
of the angular dependent upper critical fields at temperatures down to 0.5 K
with high-magnetic pulsed-fields, we observe a crossover from two-dimensional
to three-dimensional superconducting states which can be manipulated by the
ionic size fluctuations in the rare-earth spacer layer. Such a large degree of
controllability is desired for tailoring strongly two/three-dimensional
superconductors and navigating various pairing landscapes for a better
understanding of the correlation between reduced dimensionality and
unconventional pairing. These results illuminate new directions to unravel the
high-temperature superconducting pairing mechanism.

###Pressure-induced superconductivity in quasi-one-dimensional semimetal $\mathrm{Ta}_2 \mathrm{PdSe}_6$|Haiyang Yang,Yonghui Zhou,Liangyu Li,Zheng Chen,Zhuyi Zhang,Shuyang Wang,Jing Wang,Xuliang Chen,Chao An,Ying Zhou,Min Zhang,Ranran Zhang,Xiangde Zhu,Lili Zhang,Xiaoping Yang,Zhaorong Yang###

Pressure-induced superconductivity in quasi-one-dimensional semimetal $\mathrm{Ta}_2 \mathrm{PdSe}_6$. Here we report the discovery of pressure-induced superconductivity in
quasi-one-dimensional $\mathrm{Ta}_2 \mathrm{PdSe}_6$, through a combination of
electrical transport, synchrotron x-ray diffraction, and theoretical
calculations. Our transport measurements show that the superconductivity
appears at a critical pressure $P_{\mathrm{c}} \sim 18.3$ GPa and is robust
upon further compression up to $62.6$ GPa. The estimated upper critical field
$\mu_0 H_{\mathrm{c} 2}(0)$ in the pressurized $\mathrm{Ta}_2 \mathrm{PdSe}_6$
is much lower than the Pauli limiting field, in contrast to the case in its
isostructural analogs $M_2 \mathrm{Pd}_{\mathrm{x}} X_5$ $(M=\mathrm{Nb}$, Ta;
$X=\mathrm{S}, \mathrm{Se})$. Concomitant with the occurrence of
superconductivity, anomalies in pressuredependent transport properties are
observed, including sign reversal of Hall coefficient, abnormally enhanced
resistance, and dramatically suppressed magnetoresistance. Meanwhile,
room-temperature synchrotron x-ray diffraction experiments reveal the stability
of the pristine monoclinic structure (space group $C 2 / m$ ) upon compression.
Combined with the density functional theory calculations, we argue that a
pressure-induced Lifshitz transition could be the electronic origin of the
emergent superconductivity in $\mathrm{Ta}_2 \mathrm{PdSe}_6$.

###Ferromagnetic Resonance in Two-dimensional van der Waals Magnets: A Probe for Spin Dynamics|Chunli Tang,Laith Alahmed,Muntasir Mahdi,Yuzan Xiong,Jerad Inman,Nathan J. McLaughlin,Christoph Zollitsch,Tae Hee Kim,Chunhui Rita Du,Hidekazu Kurebayashi,Elton J. G. Santos,Wei Zhang,Peng Li,Wencan Jin###

Ferromagnetic Resonance in Two-dimensional van der Waals Magnets: A Probe for Spin Dynamics. The discovery of atomic monolayer magnetic materials has stimulated intense
research activities in the two-dimensional (2D) van der Waals (vdW) materials
community. The field is growing rapidly and there has been a large class of 2D
vdW magnetic compounds with unique properties, which provides an ideal platform
to study magnetism in the atomically thin limit. In parallel, based on
tunneling magnetoresistance and magneto-optical effect in 2D vdW magnets and
their heterostructures, emerging concepts of spintronic and optoelectronic
applications such as spin tunnel field-effect transistors and spin-filtering
devices are explored. While the magnetic ground state has been extensively
investigated, reliable characterization and control of spin dynamics play a
crucial role in designing ultrafast spintronic devices. Ferromagnetic resonance
(FMR) allows direct measurements of magnetic excitations, which provides
insight into the key parameters of magnetic properties such as exchange
interaction, magnetic anisotropy, gyromagnetic ratio, spin-orbit coupling,
damping rate, and domain structure. In this review article, we present an
overview of the essential progress in probing spin dynamics of 2D vdW magnets
using FMR techniques. Given the dynamic nature of this field, we focus mainly
on the broadband FMR, optical FMR, and spin-torque FMR, and their applications
in studying prototypical 2D vdW magnets including CrX3 (X = Cl, Br, I),
Fe5GeTe2, and Cr2Ge2Te6. We conclude with the recent advances in laboratory-
and synchrotron-based FMR techniques and their opportunities to broaden the
horizon of research pathways into atomically thin magnets.

###Ab initio Prediction of Mechanical, Electronic, Magnetic and Transport Properties of Bulk and Heterostructure of a Novel Fe-Cr based Full Heusler Chalcogenide|Joydipto Bhattacharya,Rajeev Dutt,Aparna Chakrabarti###

Ab initio Prediction of Mechanical, Electronic, Magnetic and Transport Properties of Bulk and Heterostructure of a Novel Fe-Cr based Full Heusler Chalcogenide. Using electronic structure calculations based on density functional theory,
we predict and study the structural, mechanical, electronic, magnetic and
transport properties of a new full Heusler chalcogenide, namely, Fe$_2$CrTe,
both in bulk and heterostructure form. The system shows a ferromagnetic and
half-metallic(HM) like behavior, with a very high (about 95%) spin polarization
at the Fermi level, in its cubic phase. Interestingly, under tetragonal
distortion, a clear minimum (with almost the same energy as the cubic phase)
has also been found, at a c/a value of 1.26, which, however, shows a
ferrimagnetic and fully metallic nature. The compound has been found to be
dynamically stable in both the phases against the lattice vibration. The
elastic properties indicate that the compound is mechanically stable in both
the phases, following the stability criteria of the cubic and tetragonal
phases. The elastic parameters unveil the mechanically anisotropic and ductile
nature of the alloy system. Due to the HM-like behavior of the cubic phase and
keeping in mind the practical aspects, we probe the effect of strain as well as
substrate on various physical properties of this alloy. Transmission profile of
the Fe$_2$CrTe/MgO/Fe$_2$CrTe heterojunction has been calculated to probe it as
a magnetic tunneling junction (MTJ) material in both the cubic and tetragonal
phases. Considerably large tunneling magnetoresistance ratio (TMR) of 1000% is
observed for the tetragonal phase, which is found to be one order of magnitude
larger than that of the cubic phase.

###Ferromagnetism of sputtered Fe3GeTe2 ultrathin films in the absence of two-dimensional crystalline order|Qianwen Zhao,ChaoChao Xia,Hanying Zhang,Baiqing Jiang,Tunan Xie,Kaihua Lou,Chong Bi###

Ferromagnetism of sputtered Fe3GeTe2 ultrathin films in the absence of two-dimensional crystalline order. The discovery of ferromagnetism in two-dimensional (2D) monolayers has
stimulated growing research interest in both spintronics and material science.
However, these 2D ferromagnetic layers are mainly prepared through an
incompatible approach for large-scale fabrication and integration, and
moreover, a fundamental question whether the observed ferromagnetism actually
correlates with the 2D crystalline order has not been explored. Here, we choose
a typical 2D ferromagnetic material, Fe3GeTe2, to address these two issues by
investigating its ferromagnetism in an amorphous state. We have fabricated
nanometer-thick amorphous Fe3GeTe2 films approaching the monolayer thickness
limit of crystallized Fe3GeTe2 (0.8 nm) through magnetron sputtering. Compared
to crystallized Fe3GeTe2, we found that the basic ferromagnetic attributes,
such as the Curie temperature that directly reflects magnetic exchange
interactions and local anisotropic energy, do not change significantly in the
amorphous states. This is attributed to that the short-range atomic order, as
confirmed by valence state analysis, is almost the same for both phases. The
persistence of ferromagnetism in the ultrathin amorphous counterpart has also
been confirmed through magnetoresistance measurements, where two unconventional
switching dips arising from electrical transport within domain walls are
clearly observed in the amorphous Fe3GeTe2 single layer. These results indicate
that the long-range ferromagnetic order of crystallized Fe3GeTe2 may not
correlate to the 2D crystalline order and the corresponding ferromagnetic
attributes can be utilized in an amorphous state which suits large-scale
fabrication in a semiconductor technology-compatible manner for spintronics
applications.

###Leveraging symmetry for an accurate spin-orbit torques characterization in ferrimagnetic insulators|Martín Testa-Anta,Charles-Henri Lambert,Can Onur Avci###

Leveraging symmetry for an accurate spin-orbit torques characterization in ferrimagnetic insulators. Spin-orbit torques (SOTs) have emerged as an efficient means to electrically
control the magnetization in ferromagnetic heterostructures. Lately, an
increasing attention has been devoted to SOTs in heavy metal (HM)/magnetic
insulator (MI) bilayers owing to their tunable magnetic properties and
insulating nature. Quantitative characterization of SOTs in HM/MI
heterostructures are, thus, vital for fundamental understanding of charge-spin
interrelations and designing novel devices. However, the accurate determination
of SOTs in MIs have been limited so far due to small electrical signal outputs
and dominant spurious thermoelectric effects caused by Joule heating. Here, we
report a simple methodology based on harmonic Hall voltage detection and
macrospin simulations to accurately quantify the damping-like and field-like
SOTs, and thermoelectric contributions separately in MI-based systems.
Experiments on the archetypical Bi-doped YIG/Pt heterostructure using the
developed method yield precise values for the field-like and damping-like SOTs,
reaching -0.14 and -0.15 mT per 1.7x$10^{ 11}$ A/$m^2$, respectively. We
further reveal that current-induced Joule heating changes the spin transparency
at the interface, reducing the spin Hall magnetoresistance and damping-like
SOT, simultaneously. These results and the devised method can be beneficial for
fundamental understanding of SOTs in MI-based heterostructures and designing
new devices where accurate knowledge of SOTs is necessary.

###Non-Fermi liquid behavior of doped Kondo insulator: The unique properties of CeRhSb$_{1-x}$Te$_x$|A. Ślebarski,Józef Spałek,M. Fijałkowski###

Non-Fermi liquid behavior of doped Kondo insulator: The unique properties of CeRhSb$_{1-x}$Te$_x$. It follows from our analysis of CeRhSb that the formation of Kondo insulator
state due to the presence of the collective spin singlet state is strongly
reduced by its doping with various dopants when their amount exceeds 8--10\%,
regardless of whether they are substituted for Ce, Rh or Sb. A wide variety of
experimental results (electrical resistivity $\rho$, magnetic susceptibility
$\chi$, specific heat $C$, x-ray photoelectron spectroscopy) and theoretical
investigations have convincingly demonstrated the proposed earlier scaling law
$\chi\times\rho=const.$ in the Kondo insulator regime, which is universal for
all known Kondo insulators. We also analyze the properties of the
Griffiths--phase for CeRhSb when Pd substitutes Rh, or Sb is fractionally
replaced by Te and Sn, whereas doping of Ce with La leads to the formation of
magnetic cluster structure as a result of the Kondo hole effect.
Magnetoresistance of CeRhSb and CeRhSb$_{0.98}$Te$_{0.02}$ as a function of the
field $B$ shows a $-B^2$ behavior, which provides evidence for the
topologically nontrivial nature of these compounds, as was previously predicted
theoretically for CeRhSb on the basis on the band structure calculations.

###Covalency, correlations, and inter-layer interactions governing the magnetic and electronic structure of Mn$_3$Si$_2$Te$_6$|Chiara Bigi,Lei Qiao,Chao Liu,Paolo Barone,Monica Ciomaga Hatnean,Gesa-R. Siemann,Barat Achinuq,Daniel Alexander Mayoh,Giovanni Vinai,Vincent Polewczyk,Deepak Dagur,Federico Mazzola,Peter Bencok,Thorsten Hesjedal,Gerrit van der Laan,Wei Ren,Geetha Balakrishnan,Silvia Picozzi,Phil D. C. King###

Covalency, correlations, and inter-layer interactions governing the magnetic and electronic structure of Mn$_3$Si$_2$Te$_6$. Mn$_3$Si$_2$Te$_6$ is a rare example of a layered ferrimagnet. It has
recently been shown to host a colossal angular magnetoresistance as the spin
orientation is rotated from the in- to out-of-plane direction, proposed to be
underpinned by a topological nodal-line degeneracy in its electronic structure.
Nonetheless, the origins of its ferrimagnetic structure remain controversial,
while its experimental electronic structure, and the role of correlations in
shaping this, are little explored to date. Here, we combine x-ray and
photoemission-based spectroscopies with first-principles calculations, to probe
the elemental-selective electronic structure and magnetic order in
Mn$_3$Si$_2$Te$_6$. Through these, we identify a marked Mn-Te hybridisation,
which weakens the electronic correlations and enhances the magnetic anisotropy.
We demonstrate how this strengthens the magnetic frustration in
Mn$_3$Si$_2$Te$_6$, which is key to stabilising its ferrimagnetic order, and
find a crucial role of both exchange interactions extending beyond
nearest-neighbours and anti-symmetric exchange in dictating its ordering
temperature. Together, our results demonstrate a powerful methodology of using
experimental electronic structure probes to constrain the parameter space for
first-principles calculations of magnetic materials, and through this approach,
reveal a pivotal role played by covalency in stabilising the ferrimagnetic
order in Mn$_3$Si$_2$Te$_6$.

###First-principles study of enhancement of perpendicular magnetic anisotropy obtained by inserting an ultrathin LiF layer at an Fe/MgO interface|Yukie Kitaoka,Hiroshi Imamura###

First-principles study of enhancement of perpendicular magnetic anisotropy obtained by inserting an ultrathin LiF layer at an Fe/MgO interface. Perpendicular magnetic anisotropy (PMA) is a key property of magnetoresistive
random access memory (MRAM). To increase areal density of MRAM it is important
to find a way to enhance the PMA. Recently a strong enhancement of the PMA by
inserting an ultrathin LiF layer at an Fe/MgO interface was reported [T. Nozaki
et al., NPG Asia Materials (2022) 14: 5]. To understand the origin of the
observed enhancement of the PMA we perform first-principles calculations of
magetocrystalline anisotropy energy (MAE) of the following four kind of
multilayer structures: Fe/MgO, Fe/LiF/MgO, Fe/FeO/MgO, and Fe/FeF/LiF/MgO. We
find that the MAEs of the Fe/LiF/MgO and the Fe/FeF/LiF/MgO structures are
almost the same as that of the Fe/MgO structure, while the MAE of the
Fe/FeO/MgO structure is less than a half of that of the Fe/MgO structure. The
results show that the major origin of the enhancement of the PMA obtained by
inserting an ultrathin LiF layer at an Fe/MgO interface is the suppression of
the mixing of Fe and O atoms at the interface. We also find that the in-plane
Fe-F coupling gives a positive contribution to the MAE while the in-plane Fe-O
coupling gives a negative contribution. The results are useful for designing of
high-PMA materials.

###Spin-valve nature and giant coercivity of a ferrimagnetic spin semimetal Mn$_2$IrGa|Akhilesh Kumar Patel,Y. Venkateswara,S. Shanmukharao Samatham,Archana Lakhani,Jayita Nayak,K. G. Suresh,Aftab Alam###

Spin-valve nature and giant coercivity of a ferrimagnetic spin semimetal Mn$_2$IrGa. Spin semimetals are amongst the most recently discovered new class of
spintronic materials, which exhibit a band gap in one spin channel and
semimetallic feature in the other, thus facilitating tunable spin transport.
Here, we report Mn$_2$IrGa to be a candidate material for spin semimetal along
with giant coercivity and spin-valve characteristics using a combined
experimental and theoretical study. The alloy crystallizes in an inverse
Heusler structure (without any martensitic transition) with a para- to
ferri-magnetic transition at $T_\mathrm{C} \sim$ 243 K. It shows a giant
coercive field of about 8.5 kOe (at 2 K). The negative temperature coefficient,
relatively low magnitude and weak temperture dependance of electrical
resistivity suggest the semimetallic character of the alloy. This is further
supported by our specific heat measurement. Magnetoresistance (MR) confirms an
irreversible nature (with its magnitude $\sim$1\%) along with a change of sign
across the magnetic transition indicating the potentiality of Mn$_2$IrGa in
magnetic switching applications. In addition, asymmetric nature of MR in the
positive and negative field cycles is indicative of spin-valve characteristics.
Our ab-initio calculations confirm the inverse Heusler structure with
ferrimagnetic ordering to be the lowest energy state, with a saturation
magnetization of 2 $\mu_\mathrm{B}$. $<100>$ is found to be the easy magnetic
axis with considerable magneto-crystalline anisotropy energy. A large positive
Berry flux at/around $\Gamma$ point gives rise to an appreciable anomalous Hall
conductivity ($\sim$-180 S/cm).

###Room-temperature and tunable tunneling magnetoresistance in Fe3GaTe2-based all-2D van der Waals heterojunctions with high spin polarization|Wen Jin,Gaojie Zhang,Hao Wu,Li Yang,Wenfeng Zhang,Haixin Chang###

Room-temperature and tunable tunneling magnetoresistance in Fe3GaTe2-based all-2D van der Waals heterojunctions with high spin polarization. Magnetic tunnel junctions (MTJs) based on all-two dimensional (2D) van der
Waals heterostructures with sharp and clean interfaces in atomic scale are
essential for the application of next-generation spintronics. However, the lack
of room-temperature intrinsic ferromagnetic crystals with perpendicular
magnetic anisotropy has greatly hindered the development of vertical MTJs. The
discovery of room-temperature intrinsic ferromagnetic 2D crystal Fe3GaTe2 has
solved the problem and greatly facilitated the realization of practical
spintronic devices. Here, we demonstrate a room-temperature MTJ based on
Fe3GaTe2/WS2/Fe3GaTe2 heterostructure. The tunnelling magnetoresistance (TMR)
ratio is up to 213% with high spin polarization of 72% at 10 K, the highest
ever reported in Fe3GaTe2-based MTJs up to now. The tunnelling spin-valve
signal robustly exists at room temperature (300 K) with bias current down to 10
nA. Moreover, the spin polarization can be modulated by bias current and the
TMR shows a sign reversal at large bias current. Our work sheds light on the
potential application for low-energy consumption all-2D vdW spintronics and
offers alternative routes for the electronic control of spintronic devices.

###Characteristic time of transition from write error to retention error in voltage-controlled magnetoresistive random-access memory|Hiroko Arai,Hiroshi Imamura###

Characteristic time of transition from write error to retention error in voltage-controlled magnetoresistive random-access memory. Voltage controlled magnetoresistive random access memory (VC MRAM) is a
promising candidate for a future low-power high-density memory. The main causes
of bit errors in VC MRAM are write error and retention error. As the size of
the memory cell decreases, the data retention time decreases, which causes a
transition from the write-error-dominant region to the retention-error-dominant
region at a certain operating time. Here we introduce the characteristic time
of the transition from the write-error-dominant region to the
retention-error-dominant region and analyze how the characteristic time depends
on the effective anisotropy constant, $K_{0}$. The characteristic time is
approximately expressed as $t_{\rm c} = 2\, w\, \tau$, where $w$ is the write
error rate, and $\tau$ is the relaxation time derived by Kalmkov [J. Appl.
Phys. 96, (2004) 1138-1145]. We show that for large $K_{0}$, $t_{\rm c}$
increases with increase of $K_{0}$ similar to $\tau$. The characteristic time
is a key parameter for designing the VC MRAM for the variety of applications
such as machine learning and artificial intelligence.

###Non-Fermi-Liquid Behavior of Superconducting SnH$_4$|Ivan A. Troyan,Dmitrii V. Semenok,Anna G. Ivanova,Andrey V. Sadakov,Di Zhou,Alexander G. Kvashnin,Ivan A. Kruglov,Oleg A. Sobolevskiy,Marianna V. Lyubutina,Dmitry S. Perekalin,Toni Helm,Stanley W. Tozer,Maxim Bykov,Alexander F. Goncharov,Vladimir M. Pudalov,Igor S. Lyubutin###

Non-Fermi-Liquid Behavior of Superconducting SnH$_4$. We studied chemical interaction of Sn with H$_2$ by X-ray diffraction methods
at pressures of 180-210 GPa. A previously unknown tetrahydride SnH$_4$ with a
cubic structure (${fcc}$) exhibiting superconducting properties below ${T}$$_C$
= 72 K was obtained; the formation of a high molecular ${C2/m}$-SnH$_{14}$
superhydride and several lower hydrides, ${fcc}$ SnH$_2$ and
${C2}$-Sn$_{12}$H$_{18}$, was also detected. The temperature dependence of
critical current density ${J}$$_C$(T) in SnH$_4$ yields the superconducting gap
2$\Delta$(0) = 23 meV at 180 GPa. SnH$_4$ has unusual behavior in strong
magnetic fields: ${B,T}$-linear dependences of magnetoresistance and the upper
critical magnetic field ${B}$$_{C2}$(T) $\propto$ (${T}$$_C$ - ${T}$). The
latter contradicts the Wertheimer-Helfand-Hohenberg model developed for
conventional superconductors. Along with this, the temperature dependence of
electrical resistance of ${fcc}$ SnH$_4$ in non-superconducting state exhibits
a deviation from what is expected for phonon-mediated scattering described by
the Bloch-Gr\"uneisen model, and is beyond the framework of the Fermi liquid
theory. Such anomalies occur for many superhydrides, making them much closer to
cuprates than previously believed.

###Superconducting Diode Effect and Large Magnetochiral Anisotropy in T$_d$-MoTe$_2$ Thin Film|Wan-Shun Du,Weipeng Chen,Yangbo Zhou,Tengfei Zhou,Guangjian Liu,Zongteng Zhang,Zichuan Miao,Hao Jia,Song Liu,Yue Zhao,Zhensheng Zhang,Tingyong Chen,Ning Wang,Wen Huang,Zhen-Bing Tan,Jing-Jing Chen,Da-Peng Yu###

Superconducting Diode Effect and Large Magnetochiral Anisotropy in T$_d$-MoTe$_2$ Thin Film. In the absence of time-reversal invariance, metals without inversion symmetry
may exhibit nonreciprocal charge transport -- a magnetochiral anisotropy that
manifests as unequal electrical resistance for opposite current flow
directions. If superconductivity also sets in, the charge transmission may
become dissipationless in one direction while remaining dissipative in the
opposite, thereby realizing a superconducting diode. Through both DC and AC
magnetoresistance measurements, we study the nonreciprocal effects in thin
films of the superconducting noncentrosymmetric type-II Weyl semimetal
T$_d$-MoTe$_2$. We report nonreciprocal superconducting critical currents with
a diode efficiency close to 20\%~, and an extreme magnetochiral anisotropy
coefficient up to \SI{1e9}{\per\tesla\per\ampere}, under weak out-of-plane
magnetic field in the millitesla range. Intriguingly, unlike the finding in
Rashba systems, the strongest in-plane nonreciprocal effect does not occur when
the field is perpendicular to the current flow direction. We develop a
phenomenological theory to demonstrate that this peculiar behavior can be
attributed to the asymmetric structure of spin-orbit coupling in
T$_d$-MoTe$_2$. Our study highlights how the form of spin-orbit coupling, as
dictated by the underlying crystallographic symmetry, critically impacts the
nonreciprocal transport. Our work demonstrates that T$_d$-MoTe$_2$ offers an
accessible material platform for the practical application of superconducting
diodes under a relatively weak magnetic field.

###Enhancing Spin Transfer Torque in Magnetic Tunnel Junction Devices: Exploring the Influence of Capping Layer Materials and Thickness on Device Characteristics|Tahereh Sadat Parvini,Elvira Paz,Tim Böhnert,Alejandro Schulman,Luana Benetti,Felix Oberbauer,Jakob Walowski,Farshad Moradi,Ricardo Ferreira,Markus Münzenberg###

Enhancing Spin Transfer Torque in Magnetic Tunnel Junction Devices: Exploring the Influence of Capping Layer Materials and Thickness on Device Characteristics. We have developed and optimized two categories of spin transfer torque
magnetic tunnel junctions (STT-MTJs) that exhibit a high tunnel
magnetoresistance (TMR) ratio, low critical current, high outputpower in the
micro watt range, and auto-oscillation behavior. These characteristics
demonstrate the potential of STT-MTJs for low-power, high-speed, and reliable
spintronic applications, including magnetic memory, logic, and signal
processing. The only distinguishing factor between the two categories, denoted
as A-MTJs and B-MTJs, is the composition of their free layers, 2 CoFeB/0.21
Ta/6 CoFeSiB for A-MTJs and 2 CoFeB/0.21 Ta/7 NiFe for B-MTJs. Our study
reveals that B-MTJs exhibit lower critical currents for auto-oscillation than
A-MTJs. We found that both stacks have comparable saturation magnetization and
anisotropy field, suggesting that the difference in auto-oscillation behavior
is due to the higher damping of A-MTJs compared to B-MTJs. To verify this
hypothesis, we employed the all-optical time-resolved magneto-optical Kerr
effect (TRMOKE) technique, which confirmed that STT-MTJs with lower damping
exhibited auto-oscillation at lower critical current values. Additionally, our
study aimed to optimize the STT-MTJ performance by investigating the impact of
the capping layer on the device's response to electronic and optical stimuli.

###Weak Antilocalization and topological edge states in PdSn$_4$|N. K. Karn,M. M. Sharma,V. P. S. Awana###

Weak Antilocalization and topological edge states in PdSn$_4$. Here we report, the successful synthesis of single crystals of topological
semimetal (TSM) candidate, PdSn$_4$ using the self-grown route. The synthesized
crystal is well characterized through X-ray diffraction (XRD), field emission
scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy
(XPS). Detailed Rietveld analysis of the powder XRD pattern of PdSn$_4$
confirmed the same to crystallize in the Aea2 space group instead of reported
Ccce. A large magnetoresistance (MR) along with Subnikov-de Haas oscillations
have been observed in magnetotransport measurements at 2K. The presence of a
weak antilocalization (WAL) effect in synthesized PdSn$_4$ crystal is confirmed
and analyzed using Hikami Larkin Nagaoka (HLN) formalism, being applied on
magnetoconductivity of the same at the low magnetic field. An extended Kohler
rule is implemented on MR data, to determine the role of the scattering process
and temperature-dependent carrier density on transport phenomenon in PdSn$_4$.
Further, the non-trivial band topology and presence of edge states are shown
through density functional theory (DFT) based theoretical calculations. All
calculations are performed considering the Aea2 space group symmetry. The
calculated Z2 invariants suggest the presence of weak topological insulating
properties in PdSn$_4$. Clear evidence of topological edge states at the
$\Gamma$ point is visible in calculated edge state spectra. This is the first
report on PdSn$_4$, showing the presence of SdH oscillation in magneto
transport measurement.

###Studies on the proximity effect in Bi-based high-temperature superconductor/manganite heterostructures|V. Gayathri,E. P. Amaladass,A. T. Sathyanarayana,T. Geetha Kumary,R. Pandian,P. Gupta,S. K. Rai,A. Mani###

Studies on the proximity effect in Bi-based high-temperature superconductor/manganite heterostructures. The effect of proximity of the magnetism of the Pr-based manganite
(Pr0.6Sr0.4MnO3) on the superconductivity of Bi-based high-temperature
superconductor (Bi1.75Pb0.25Sr2Ca2Cu3O10+d) was studied based on the results
obtained from the magnetotransport and magnetization measurements. Decrease in
the values of the upper critical field (HC2(0)) and an increase in the width of
the superconducting transition (Delta TC) of Bi1.75Pb0.25Sr2Ca2Cu3O10+d were
observed in proximity with the manganite. The combined effect of magnetic
exchange interaction arising from the manganite, the leakage of Cooper-pairs
from the superconductor into the manganite, and the diffusion and transport of
spin-polarized electrons from the manganite into the superconductor were found
to modify the superconducting properties of Bi1.75Pb0.25Sr2Ca2Cu3O10+d. The
stacking sequence of the individual layers in these heterostructures was found
to dictate the ground state properties of the heterostructure. As a consequence
of the proximity effect, the colossal-magnetoresistance (CMR) ratio as high as
~ 99 % observed in the heterostructure makes the thin film heterostructures
promising candidates for potential technological applications.

###Terahertz probing of anisotropic conductivity and morphology of CuMnAs epitaxial thin films|Peter Kubaščík,Andrej Farkaš,Kamil Olejník,Tinkara Troha,Matěj Hývl,Filip Krizek,Deep C. Joshi,Tomáš Ostatnický,Jiří Jechumtál,Eva Schmoranzerová,Richard P. Campion,Jakub Zázvorka,Vít Novák,Petr Kužel,Tomáš Jungwirth,Petr Němec,Lukáš Nádvorník###

Terahertz probing of anisotropic conductivity and morphology of CuMnAs epitaxial thin films. Antiferromagnetic CuMnAs thin films have attracted attention since the
discovery of the manipulation of their magnetic structure via electrical,
optical, and terahertz pulses of electric fields, enabling convenient
approaches to the switching between magnetoresistive states of the film for the
information storage. However, the magnetic structure and, thus, the efficiency
of the manipulation can be affected by the film morphology and growth defects.
In this study, we investigate the properties of CuMnAs thin films by probing
the defect-related uniaxial anisotropy of electric conductivity by contact-free
terahertz transmission spectroscopy. We show that the terahertz measurements
conveniently detect the conductivity anisotropy, that are consistent with
conventional DC Hall-bar measurements. Moreover, the terahertz technique allows
for considerably finer determination of anisotropy axes and it is less
sensitive to the local film degradation. Thanks to the averaging over a large
detection area, the THz probing also allows for an analysis of strongly
non-uniform thin films. Using scanning near-field terahertz and electron
microscopies, we relate the observed anisotropic conductivity of CuMnAs to the
elongation and orientation of growth defects, which influence the local
microscopic conductivity. We also demonstrate control over the morphology of
defects by using vicinal substrates.

###Angle-dependent Magnetoresistance of an Ordered Bose Glass of Vortices in YBa$_{2}$Cu$_{3}$O$_{7-δ}$ Thin Films with a Periodic Pinning~Lattice|Bernd Aichner,Lucas Backmeister,Max Karrer,Katja Wurster,Reinhold Kleiner,Edward Goldobin,Dieter Koelle,Wolfgang Lang###

Angle-dependent Magnetoresistance of an Ordered Bose Glass of Vortices in YBa$_{2}$Cu$_{3}$O$_{7-δ}$ Thin Films with a Periodic Pinning~Lattice. The competition between intrinsic disorder in superconducting
YBa$_{2}$Cu$_{3}$O$_{7-\delta}$ (YBCO) thin films and an ultradense triangular
lattice of cylindrical pinning centers spaced at 30 nm intervals results in an
ordered Bose glass phase of vortices. The samples were created by scanning the
focused beam of a helium-ion microscope over the surface of the YBCO thin film
to form columns of point defects where superconductivity was locally
suppressed. The voltage-current isotherms reveal critical behavior and scale in
the vicinity of the second-order glass transition. The latter exhibits a
distinct peak in melting temperature ($T_g$) vs. applied magnetic field ($B_a$)
at the magnetic commensurability field, along with a sharp rise in the
lifetimes of glassy fluctuations. Angle-dependent magnetoresistance
measurements in constant-Lorentz-force geometry unveil a strong increase in
anisotropy compared to a pristine reference film where the density of vortices
matches that of the columnar defects. The pinning is therefore, dominated by
the magnetic-field component parallel to the columnar defects, exposing its
one-dimensional character. These results support the idea of an ordered Bose
glass phase.

###Pressure induced color change and evolution of metallic behavior in nitrogen-doped lutetium hydride|Ying-Jie Zhang,Xue Ming,Qing Li,Xiyu Zhu,Bo Zheng,Yuecong Liu,Chengping He,Huan Yang,Hai-Hu Wen###

Pressure induced color change and evolution of metallic behavior in nitrogen-doped lutetium hydride. By applying pressures up to 42 GPa on the nitrogen-doped lutetium hydride
(LuH$_{2\pm\text{x}}$N$_y$), we have found a gradual change of color from
dark-blue to pink-violet in the pressure region of about 12 GPa to 21 GPa. The
temperature dependence of resistivity under pressures up to 50.5 GPa shows
progressively optimized metallic behavior with pressure. Interestingly, in the
pressure region for the color change, a clear decrease of resistivity is
observed with the increase of pressure, which is accompanied by a clear
increase of the residual resistivity ratio (RRR). Fitting to the low
temperature resistivity gives exponents of about 2, suggesting a Fermi liquid
behavior in low temperature region. The general behavior in wide temperature
region suggests that the electron-phonon scattering is still the dominant one.
The magnetoresistance up to 9 tesla in the state under a pressure of 50.5 GPa
shows an almost negligible effect, which suggests that the electric conduction
in the pink-violet state is dominated by a single band. It is highly desired to
have theoretical efforts in understanding the evolution of color and
resistivity in this interesting system.

###Current-Induced Spin Accumulation and Magnetoresistance in Chiral Semimetals|A. A. Burkov,Michael Smith,Alexander Hickey,Ivar Martin###

Current-Induced Spin Accumulation and Magnetoresistance in Chiral Semimetals. Weyl fermions possess the property of spin-momentum locking: the expectation
value of the spin is parallel or antiparallel to the momentum at any given
point in the Brillouin zone in the vicinity of a Weyl node. This is a direct
consequence of the fact that Weyl nodes are monopoles of the Berry curvature,
and in this sense an expression of the nontrivial Weyl electronic structure
topology. Thanks to this property, an isolated Weyl node produces a large spin
accumulation in response to a charge current, $\hbar/2$ per electron, similar
to surface states of time-reversal invariant topological insulators. However,
in bulk Weyl semimetals, the nodes must occur in pairs of opposite chirality
and, when the nodes are at the same energy, the effect cancels out. Here we
show that this cancellation is avoided in chiral semimetals, in which Weyl
nodes of opposite chirality occur at different energies due to broken mirror
symmetry. We find that the spin accumulation is maximized when the Fermi energy
coincides with one of the nodes in a pair and reaches the same value as for an
isolated node in this case. Moreover, we demonstrate the existence of a
distinct magnetoresistance mechanism, closely related to this current-induced
spin accumulation.

###Experimental verification of band convergence in Sr and Na codoped PbTe|Yuya Hattori,Shunsuke Yoshizawa,Keisuke Sagisaka,Yuki Tokumoto,Keiichi Edagawa,Takako Konoike,Shinya Uji,Taichi Terashima###

Experimental verification of band convergence in Sr and Na codoped PbTe. Scanning tunneling microscopy and transport measurements have been performed
to investigate the electronic structure and its temperature dependence in
heavily Sr and Na codoped PbTe, which is recognized as one of the most
promising thermoelectric materials. Our main findings are as follows: (i) Below
T=4.5 K, all carriers are distributed in the first valence band at the L point
(L band), which forms tube-shaped Fermi surfaces with concave curvature. With
Sr and Na doping, the dispersion of the L band changes, and the band gap
increases from 200 meV to 300 meV. (ii) At T=4.5 K, the Fermi energy is located
~100 meV below the edge of the L band for the Sr/Na codoped PbTe. The second
valence band at the Sigma point (Sigma band) is lower than the L band by 150
meV, which is significantly smaller than that of pristine PbTe (200 meV). The
decrease in the band offset, leading to band convergence, provides a desirable
condition for thermoelectric materials.(iii) With increasing temperature, the
carrier distribution to the Sigma band starts at T=100 K and we estimate that
about 50 percent of the total carriers are redistributed in the Sigma band at
T=300 K.Our work demonstrates that scanning tunneling microscopy and angular
dependent magnetoresistance measurements are particularly powerful tools to
determine the electronic structure and carrier distribution. We believe that
they will provide a bird's eye view of the doping strategy towards realizing
high-efficiency thermoelectric materials.

###Emergence of flat bands via orbital-selective electron correlations in Mn-based kagome metal|Subhasis Samanta,Hwiwoo Park,Chanhyeon Lee,Sungmin Jeon,Hengbo Cui,Jungseek Hwang,Kwang-Yong Choi,Heung-Sik Kim###

Emergence of flat bands via orbital-selective electron correlations in Mn-based kagome metal. Kagome lattice has been actively studied for the possible realization of
frustration-induced two-dimensional flat bands and a number of
correlation-induced phases. Currently, the search for kagome systems with a
nearly dispersionless flat band close to the Fermi level is ongoing. Here, by
combining theoretical and experimental tools, we present
Sc$_3$Mn$_3$Al$_7$Si$_5$ as a novel realization of correlation-induced
almost-flat bands in the kagome lattice in the vicinity of the Fermi level. Our
magnetic susceptibility, $^{27}$Al nuclear magnetic resonance, transport, and
optical conductivity measurements provide signatures of a correlated metallic
phase with tantalizing ferromagnetic instability. Our dynamical mean-field
calculations suggest that such ferromagnetic instability observed originates
from the formation of nearly flat dispersions close to the Fermi level, where
electron correlations induce strong orbital-selective renormalization and
manifestation of the kagome-frustrated bands. In addition, a significant
negative magnetoresistance signal is observed, which can be attributed to the
suppression of flat-band-induced ferromagnetic fluctuation, which further
supports the formation of flat bands in this compound. These findings broaden a
new prospect to harness correlated topological phases via multiorbital
correlations in 3$d$-based kagome systems.

###Evidence of magnetoelectronic electromagnon mediated transport in flexoelectronic heterostructures|Anand Katailiha,Paul C. Lou,Ravindra G. Bhardwaj,Ward P. Beyermann,Sandeep Kumar###

Evidence of magnetoelectronic electromagnon mediated transport in flexoelectronic heterostructures. The superposition of atomic vibrations and flexoelectronic effect gives rise
to a cross correlation between free charge carriers and temporal magnetic
moment of phonons in conducting heterostructures under an applied strain
gradient. The resulting dynamical coupling is expected to give rise to
quasiparticle excitations called as magnetoelectronic electromagnon that
carries electronic charge and temporal magnetic moment. Here, we report
experimental evidence of magnetoelectronic electromagnon in the freestanding
degenerately doped p-Si based heterostructure thin film samples. These
quasiparticle excitations give rise to long-distance (>100um) spin transport;
demonstrated using spatially modulated transverse magneto-thermoelectric and
non-local resistance measurements. The magnetoelectronic electromagnons are
non-reciprocal and give rise to large magnetochiral anisotropy (0.352 A-1T-1)
that diminishes at lower temperatures. The superposition of non-reciprocal
magnetoelectronic electromagnons gives rise to longitudinal and transverse
modulations in charge carrier density, spin density and magnetic moment;
demonstrated using the Hall effect and edge dependent magnetoresistance
measurements, which can also be called as inhomogeneous magnetoelectronic
multiferroic effect. These quasiparticle excitations are analogues to photons
where time dependent polarization and temporal magnetic moment replaces
electric and magnetic field, respectively and most likely topological because
it manifests topological Nernst effect. Hence, the magnetoelectronic
electromagnon can potentially give rise to quantum interference and
entanglement effects in conducting solid state system at room temperature in
addition to efficient spin transport.

###Pressure-induced transition from a Mott insulator to a ferromagnetic Weyl metal in La2O3Fe2Se2|Ye Yang,Fanghang Yu,Xikai Wen,Zhigang Gui,Yuqing Zhang,Fangyang Zhan,Rui Wang,Jianjun Ying,Xianhui Chen###

Pressure-induced transition from a Mott insulator to a ferromagnetic Weyl metal in La2O3Fe2Se2. The insulator-metal transition in Mott insulators, known as the Mott
transition, is usually accompanied with various novel quantum phenomena, such
as unconventional superconductivity, non-Fermi liquid behavior and colossal
magnetoresistance. Here, based on high-pressure electrical transport and XRD
measurements, and first-principles calculations, we find that a unique
pressure-induced Mott transition from an antiferromagnetic Mott insulator to a
ferromagnetic Weyl metal in the iron oxychalcogenide La2O3Fe2Se2 occurs around
37 GPa without structural phase transition. Our theoretical calculations reveal
that such an insulator-metal transition is mainly due to the enlarged bandwidth
and diminishing of electron correlation at high pressure, fitting well with the
experimental data. Moreover, the high-pressure ferromagnetic Weyl metallic
phase possesses attractive electronic band structures with six pairs of Weyl
points close to the Fermi level, and its topological property can be easily
manipulated by the magnetic field. The emergence of Weyl fermions in
La2O3Fe2Se2 at high pressure may bridge the gap between nontrivial band
topology and Mott insulating states. Our findings not only realize
ferromagnetic Weyl fermions associated with the Mott transition, but also
suggest pressure as an effective controlling parameter to tune the emergent
phenomena in correlated electron systems.

###Quantum-limit phenomena and bandstructure in the magnetic topological semimetal EuZn2As2|Joanna Blawat,Smita Speer,John Singleton,Weiwei Xie,Rongying Jin###

Quantum-limit phenomena and bandstructure in the magnetic topological semimetal EuZn2As2. We have experimentally investigated the low-temperature (0.6 K) electronic
and magnetic properties of the layered antiferromagnet EuZn2As2 in pulsed
magnetic fields of up to 60 T at a temperature of 0.6 K, giant positive
magnetoresistance (MR) is observed above \mu_{0}H ~ 20 T, a regime in which the
spins are already fully polarized. Both magnetic torque and proximity detector
oscillator (PDO) data show no corresponding anomaly at or close to this field.
By analyzing the quantum oscillations observed in the MR and PDO frequency, we
find that (1) the oscillation frequency F = 46 \pm 6 T for H // c and 42 \pm 2
T for H // ab; (2) the corresponding Berry phase is close to \pi for H // c,
implying a nontrivial topology; and (3) the large linear MR at high fields
corresponds to the quantum limit (i.e., only the last Landau level being
occupied). From these observations we conclude that the linear MR can be
understood by considering diffusing cyclotron centers in the quantum limit. Our
findings help understand the intimate relationship between magnetism and
electronic topology in EuZn2As2 under extremely high fields and suggest reasons
for the emergent behavior in the quantum limit.

###Voltage-tunable giant nonvolatile multiple-state resistance in interlayer-sliding ferroelectric h-BN engineered van der Waals multiferroic tunnel junction|Xinlong Dong,Xuemin Shen,Xiaowen Sun,Yuhao Bai,Zhi Yan,Xiaohong Xu###

Voltage-tunable giant nonvolatile multiple-state resistance in interlayer-sliding ferroelectric h-BN engineered van der Waals multiferroic tunnel junction. Multiferroic tunnel junctions (MFTJs) based on two-dimensional (2D) van der
Waals heterostructures with sharp and clean interfaces at the atomic scale are
crucial for applications in nanoscale multi-resistive logic memory devices. The
recently discovered sliding ferroelectricity in 2D van der Waals materials has
opened new avenues for ferroelectric-based devices. Here, we theoretically
investigate the spin-dependent electronic transport properties of
Fe$_3$GeTe$_2$/graphene/bilayer-$h$-BN/graphene/CrI$_3$ (FGT/Gr-BBN-Gr/CrI)
all-vdW MFTJs by employing the nonequilibrium Green's function combined with
density functional theory. We demonstrate that such FGT/Gr-BBN-Gr/CrI MFTJs
exhibit four non-volatile resistance states associated with different staking
orders of sliding ferroelectric BBN and magnetization alignment of
ferromagnetic free layer CrI$_3$, with a maximum tunnel magnetoresistance
(electroresistance) ratio, i.e., TMR (TER) up to $\sim$$3.36\times10^{4}$\%
($\sim$$6.68\times10^{3}$\%) at a specific bias voltage. Furthermore, the
perfect spin filtering and remarkable negative differential resistance effects
are evident in our MFTJs. We further discover that the TMR, TER, and spin
polarization ratio under an equilibrium state can be enhanced by the
application of in-plane biaxial strain. This work shows that the giant
tunneling resistance ratio, multiple resistance states, and excellent
spin-polarized transport properties of sliding ferroelectric BBN-based MFTJs
indicate its significant potential in nonvolatile memories.

###Non-divergent Chiral Charge Pumping in Weyl Semimetal|Min Ju Park,Suik Cheon,Hyun-Woo Lee###

Non-divergent Chiral Charge Pumping in Weyl Semimetal. Recent studies suggest that the nonlinear transport properties in Weyl
semimetal may be a measurable consequence of its chiral anomaly. Nonlinear
responses in transport are estimated to be substantial, because in real
materials such as TaAs or Bi$_{1-x}$Sb$_x$, the Fermi level resides near the
Weyl nodes where the chiral charge pumping is said to diverge. However, this
work presents semiclassical Boltzmann analysis that indicates that the chiral
charge pumping is non-divergent even at the zero-temperature limit. We
demonstrate that the divergence in common semiclassical calculation scheme is
not a problem of the scheme itself, but occurs because a commonly-used
approximation of the change in particle number breaks down near the Weyl nodes.
Our result suggests the possibility that the nonlinear properties in WSMs can
be overestimated, and provides the validity condition for the conventional
approximation. We also show the distinct Fermi level dependencies of the chiral
magnetic effect and the negative longitudinal magnetoresistance, as a
consequence of non-diverging chiral charge pumping.

###Substantial reduction of write-error rate for voltage-controlled magnetoresistive random access memory by in-plane demagnetizing field and voltage-induced negative out-of-plane anisotropy field|Rie Matsumoto,Shiniji Yuasa,Hiroshi Imamura###

Substantial reduction of write-error rate for voltage-controlled magnetoresistive random access memory by in-plane demagnetizing field and voltage-induced negative out-of-plane anisotropy field. Voltage-controlled magnetoresistive random access memory (VC-MRAM) based on
voltage-induced dynamic switching in magnetic tunnel junctions (MTJs) is a
promising ultimate non-volatile memory with ultralow power consumption.
However, the dynamic switching in a conventional MTJ is accompanied by a
relatively high write error rate (WER), hindering the reliable operation of
VC-MRAM. Here, we propose a reliable writing scheme using the in-plane
demagnetizing field (IDF) and voltage-induced negative out-of-plane anisotropy
field (NOAF). Numerical simulations based on macrospin model demonstrate that
the voltage-induced NOAF modifies the switching dynamics and increases the
torque due to the IDF, thereby reducing the switching time. The IDF and
voltage-induced NOAF also reduce the mean energy difference between the
magnetization direction at the end of the pulse and the equilibrium direction.
As a result, an appropriate combination of the IDF and voltage-induced NOAF
reduces the WER by one order of magnitude compared with that of the dynamic
switching in a conventional MTJ.

###Skyrmion-mediated Nonvolatile Ternary Memory|Md Mahadi Rajib,Namita Bindal,Ravish Kumar Raj,Brajesh Kumar Kaushik,Jayasimha Atulasimha###

Skyrmion-mediated Nonvolatile Ternary Memory. Multistate memory systems have the ability to store and process more data in
the same physical space as binary memory systems, making them a potential
alternative to existing binary memory systems. In the past, it has been
demonstrated that voltage-controlled magnetic anisotropy (VCMA) based writing
is highly energy-efficient compared to other writing methods used in
non-volatile nano-magnetic binary memory systems. In this study, we introduce a
new, VCMA-based and skyrmion-mediated non-volatile ternary memory system using
a perpendicular magnetic tunnel junction (p-MTJ) in the presence of room
temperature thermal perturbation. We have also shown that ternary states {-1,
0, +1} can be implemented with three magnetoresistance values obtained from a
p-MTJ corresponding to ferromagnetic up, down, and skyrmion state, with 99%
switching probability in the presence of room temperature thermal noise in an
energy-efficient way, requiring ~3 fJ energy on an average for each switching
operation. Additionally, we show that our proposed ternary memory demonstrates
an improvement in area and energy by at least 2X and ~60X respectively,
compared to state-of-the-art spin-transfer torque (STT)-based non-volatile
magnetic multistate memories. Furthermore, these three states can be
potentially utilized for energy-efficient, high-density in-memory quantized
deep neural network implementation.

###Field-free all-optical switching and electrical read-out of Tb/Co-based magnetic tunnel junctions|D. Salomoni,Y. Peng,L. Farcis,S. Auffret,M. Hehn,G. Malinowski,S. Mangin,B. Dieny,L. D. Buda-Prejbeanu,R. C. Sousa,I. L. Prejbeanu###

Field-free all-optical switching and electrical read-out of Tb/Co-based magnetic tunnel junctions. Switching of magnetic tunnel junction using femto-second laser enables a
possible path for THz frequency memory operation, which means writing speeds 2
orders of magnitude faster than alternative electrical approaches based on spin
transfer or spin orbit torque. In this work we demonstrate successful
field-free 50fs single laser pulse driven magnetization reversal of [Tb/Co]
based storage layer in a perpendicular magnetic tunnel junction. The
nanofabricated magnetic tunnel junction devices have an optimized bottom
reference electrode and show Tunnel Magnetoresistance Ratio values (TMR) up to
74\% after patterning down to sub-100nm lateral dimensions. Experiments on
continuous films reveal peculiar reversal patterns of concentric rings with
opposite magnetic directions, above certain threshold fluence. These rings have
been correlated to patterned device switching probability as a function of the
applied laser fluence. Moreover, the magnetization reversal is independent on
the duration of the laser pulse. According to our macrospin model, the
underlying magnetization reversal mechanism can be attributed to an in-plane
reorientation of the magnetization due to a fast reduction of the out-of-plane
uniaxial anisotropy. These aspects are of great interest both for the physical
understanding of the switching phenomenon and their consequences for
all-optical-switching memory devices, since they allow for a large fluence
operation window with high resilience to pulse length variability.

###Nonlinear spin dynamics of ferromagnetic ring in the vortex state and its application for spin-transfer nano-oscillator|Vera Uzunova,Boris A. Ivanov###

Nonlinear spin dynamics of ferromagnetic ring in the vortex state and its application for spin-transfer nano-oscillator. We study a nonlinear spin dynamics of a ferromagnetic ring in a vortex state
induced by the spin-polarized current. We also suggest to use the ferromagnetic
ring as a free layer of a coreless vortex spin-transfer nano-oscillator. The
calculated working frequency is about several GHz, that is much higher than the
gyromode frequency of the disk-based vortex oscillator. The response of the
vortex-state ring to the spin-polarized current has hysteretic behavior with
the reasonable values of the thresholds current densities: ignition threshold
is about $10^{8} \text{A}\text{cm}^{-2}$, and elimination current to maintain
the oscillations has much lower values about $10^{6} \text{A} \text{cm}^{-2}$.
The output signal can be extracted by the help of the inverse spin Hall effect
or by the giant magnetoresistance. The output electromotive force averaged over
all sample vanishes, and we suggest to use a ferromagnetic ring or disk in a
vortex state as a GMR analyzer. For an inverse spin Hall analyser we advise to
use two heavy metals with different signs of Spin-Hall angle. The ring-based
STNO is supposed to increase the areas of practical application of the STNOs.

###Constraints on proximity-induced ferromagnetism in a Dirac semimetal (Cd$_3$As$_2$)/ferromagnetic semiconductor (Ga$_{1-x}$Mn$_x$Sb) heterostructure|Arpita Mitra,Run Xiao,Wilson Yanez,Yongxi Ou,Juan Chamorro,Tyrel McQueen,Alexander J. Grutter,Julie A. Borchers,Michael R. Fitzsimmons,Timothy R. Charlton,Nitin Samarth###

Constraints on proximity-induced ferromagnetism in a Dirac semimetal (Cd$_3$As$_2$)/ferromagnetic semiconductor (Ga$_{1-x}$Mn$_x$Sb) heterostructure. Breaking time-reversal symmetry in a Dirac semimetal Cd$_3$As$_2$ through
doping with magnetic ions or by the magnetic proximity effect is expected to
cause a transition to other topological phases (such as a Weyl semimetal). To
this end, we investigate the possibility of proximity-induced ferromagnetic
ordering in epitaxial Dirac semimetal (Cd$_3$As$_2$)/ferromagnetic
semiconductor (Ga$_{1-x}$Mn$_x$Sb) heterostructures grown by molecular beam
epitaxy. We report the comprehensive characterization of these heterostructures
using structural probes (atomic force microscopy, x-ray diffraction, scanning
transmission electron microscopy), angle-resolved photoemission spectroscopy,
electrical magneto-transport, magnetometry, and polarized neutron
reflectometry. Measurements of the magnetoresistance and Hall effect in the
temperature range 2 K - 20 K show signatures that could be consistent with
either a proximity effect or spin-dependent scattering of charge carriers in
the Cd$_3$As$_2$ channel. Polarized neutron reflectometry sets constraints on
the interpretation of the magnetotransport studies by showing that (at least
for temperatures above 6 K) any induced magnetization in the Cd$_3$As$_2$
itself must be relatively small ($<$ 14 emu/cm$^3$).

###Ferromagnetic Superconductivity in Two-dimensional Niobium Diselenide|Tingyu Qu,Shangjian Jin,Fuchen Hou,Deyi Fu,Junye Huang,Darryl Foo Chuan Wei,Xiao Chang,Kenji Watanabe,Takashi Taniguchi,Junhao Lin,Shaffique Adam,Barbaros Özyilmaz###

Ferromagnetic Superconductivity in Two-dimensional Niobium Diselenide. The co-existence of ferromagnetism and superconductivity becomes possible
through unconventional pairing in the superconducting state. Such materials are
exceedingly rare in solid-state systems but are promising platforms to explore
topological phases, such as Majorana bound states. Theoretical investigations
date back to the late 1950s, but only a few systems have so far been
experimentally identified as potential hosts. Here, we show that
atomically-thin niobium diselenide (NbSe$_2$) intercalated with dilute cobalt
atoms spontaneously displays ferromagnetism below the superconducting
transition temperature ($T_c$). We elucidate the origin of this phase by
constructing a magnetic tunnel junction that consists of cobalt and
cobalt-doped niobium diselenide (Co-NbSe$_2$) as the two ferromagnetic
electrodes, with an ultra-thin boron nitride as the tunnelling barrier. At a
temperature well below $T_c$, the tunnelling magnetoresistance shows a bistable
state, suggesting a ferromagnetic order in Co-NbSe$_2$. We propose a RKKY
exchange coupling mechanism based on the spin-triplet superconducting order
parameter to mediate such ferromagnetism. We further perform non-local lateral
spin valve measurements to confirm the origin of the ferromagnetism. The
observation of Hanle precession signals show spin diffusion length up to
micrometres below Tc, demonstrating an intrinsic spin-triplet nature in
superconducting NbSe$_2$. Our discovery of superconductivity-mediated
ferromagnetism opens the door to an alternative design of ferromagnetic
superconductors

###Predictable gate-field control of spin in altermagnets with spin-layer coupling|Run-Wu Zhang,Chaoxi Cui,Runze Li,Jingyi Duan,Lei Li,Zhi-Ming Yu,Yugui Yao###

Predictable gate-field control of spin in altermagnets with spin-layer coupling. Spintronics, a technology harnessing electron spin for information
transmission, offers a promising avenue to surpass the limitations of
conventional electronic devices. While the spin directly interacts with the
magnetic field, its control through the electric field is generally more
practical, and has become a focal point in the field of spintronics. Current
methodologies for generating spin polarization via an electric field generally
necessitate spin-orbit coupling. Here, we propose an innovative mechanism that
accomplishes this task without dependence on spin-orbit coupling. Our method
employs two-dimensional altermagnets with valley-mediated spin-layer coupling
(SLC), in which electronic states display symmetry-protected and
valley-contrasted spin and layer polarization. The SLC facilitates predictable,
continuous, and reversible control of spin polarization using a gate electric
field. Through symmetry analysis and ab initio calculations, we pinpoint
high-quality material candidates that exhibit SLC. We ascertain that applying a
gate field of $0.2$ eV/\AA~ to monolayer Ca(CoN)$_2$ can induce significant
spin splitting up to 123 meV. As a result, perfect and switchable
spin/valley-currents, and substantial tunneling magnetoresistance can be
achieved in these materials using only a gate field. These findings provide new
opportunities for generating predictable spin polarization and designing novel
spintronic devices based on coupled spin, valley and layer physics.

###Orthorhombic distortion drives orbital ordering in an antiferromagnetic 3$d^1$ Mott insulator|Prithwijit Mandal,Shashank Kumar Ojha,Duo Wang,Ranjan Kumar Patel,Siddharth Kumar,Jyotirmay Maity,Zhan Zhang,Hua Zhou,Christoph Klewe,Padraic Shafer,Biplab Sanyal,Srimanta Middey###

Orthorhombic distortion drives orbital ordering in an antiferromagnetic 3$d^1$ Mott insulator. The orbital, which represents the shape of the electron cloud, very often
strongly influences the manifestation of various exotic phenomena, e.g.,
magnetism, metal-insulator transition, colossal magnetoresistance,
unconventional superconductivity etc. in solid-state systems. The observation
of the antiferromagnetism in $RE$TiO$_3$ ($RE$=rare earth) series has been
puzzling since the celebrated Kugel-Khomskii model of spin-orbital super
exchange predicts ferromagnetism in an orbitally degenerate $d^1$ systems.
Further, the existence of the orbitally ordered vs. orbital liquid phase in
both antiferromagnetic and paramagnetic phase have been unsettled issues thus
far. To address these long-standing questions, we investigate single
crystalline film of PrTiO$_3$. Our synchrotron X-ray diffraction measurements
confirm the retention of bulk-like orthorhombic ($D_{2h}$) symmetry in the thin
film geometry. We observe similar X-ray linear dichroism signal in both
paramagnetic and antiferromagnetic phase, which can be accounted by ferro
orbital ordering (FOO). While the presence of $D_{2h}$ crystal field does not
guarantee lifting of orbital degeneracy always, we find it to be strong enough
in these rare-earth titanates, leading to the FOO state. Thus, our work
demonstrates the orthorhombic distortion is the driving force for the orbital
ordering of antiferromagnetic $RE$TiO$_3$.

###General Green's function formalism for transport calculations with spd-Hamiltonians and giant magnetoresistance in Co and Ni based magnetic multilayers|S. Sanvito,C. J. Lambert,J. H. Jefferson,A. M. Bratkovsky###

General Green's function formalism for transport calculations with spd-Hamiltonians and giant magnetoresistance in Co and Ni based magnetic multilayers. A novel, general Green's function technique for elastic spin-dependent
transport calculations is presented, which (i) scales linearly with system size
and (ii) allows straightforward application to general tight-binding
Hamiltonians (spd in the present work). The method is applied to studies of
conductance and giant magnetoresistance (GMR) of magnetic multilayers in CPP
(current perpendicular to planes) geometry in the limit of large coherence
length. The magnetic materials considered are Co and Ni, with various
non-magnetic materials from the 3d, 4d, and 5d transition metal series.
Realistic tight-binding models for them have been constructed with the use of
density functional calculations. We have identified three qualitatively
different cases which depend on whether or not the bands (densities of states)
of a non-magnetic metal (i) form an almost perfect match with one of spin
sub-bands of the magnetic metal (as in Cu/Co spin valves); (ii) have almost
pure sp character at the Fermi level (e.g. Ag); (iii) have almost pure d
character at the Fermi energy (e.g. Pd, Pt). The key parameters which give rise
to a large GMR ratio turn out to be (i) a strong spin polarization of the
magnetic metal, (ii) a large energy offset between the conduction band of the
non-magnetic metal and one of spin sub-bands of the magnetic metal, and (iii)
strong interband scattering in one of spin sub-bands of a magnetic metal. The
present results show that GMR oscillates with variation of the thickness of
either non-magnetic or magnetic layers, as observed experimentally.

###Semiclassical theory of transport in a random magnetic field|F. Evers,A. D. Mirlin,D. G. Polyakov,P. Woelfle###

Semiclassical theory of transport in a random magnetic field. We study the semiclassical kinetics of 2D fermions in a smoothly varying
magnetic field $B({\bf r})$. The nature of the transport depends crucially on
both the strength $B_0$ of the random component of $B({\bf r})$ and its mean
value $\bar{B}$. For $\bar{B}=0$, the governing parameter is $\alpha=d/R_0$,
where $d$ is the correlation length of disorder and $R_0$ is the Larmor radius
in the field $B_0$. While for $\alpha\ll 1$ the Drude theory applies, at
$\alpha\gg 1$ most particles drift adiabatically along closed contours and are
localized in the adiabatic approximation. The conductivity is then determined
by a special class of trajectories, the "snake states", which percolate by
scattering at the saddle points of $B({\bf r})$ where the adiabaticity of their
motion breaks down. The external field also suppresses the diffusion by
creating a percolation network of drifting cyclotron orbits. This kind of
percolation is due only to a weak violation of the adiabaticity of the
cyclotron rotation, yielding an exponential drop of the conductivity at large
$\bar{B}$. In the regime $\alpha\gg 1$ the crossover between the snake-state
percolation and the percolation of the drift orbits with increasing $\bar{B}$
has the character of a phase transition (localization of snake states) smeared
exponentially weakly by non-adiabatic effects. The ac conductivity also
reflects the dynamical properties of particles moving on the fractal
percolation network. In particular, it has a sharp kink at zero frequency and
falls off exponentially at higher frequencies. We also discuss the nature of
the quantum magnetooscillations. Detailed numerical studies confirm the
analytical findings. The shape of the magnetoresistivity at $\alpha\sim 1$ is
in good agreement with experimental data in the FQHE regime near $\nu=1/2$.

###Resonant X-ray Scattering in Manganites - Study of Orbital Degree of Freedom -|Sumio Ishihara,Sadamichi Maekawa###

Resonant X-ray Scattering in Manganites - Study of Orbital Degree of Freedom -. Orbital degree of freedom of electrons and its interplay with spin, charge
and lattice degrees of freedom are one of the central issues in colossal
magnetoresistive manganites. The orbital degree of freedom has until recently
remained hidden, since it does not couple directly to most of experimental
probes. Development of synchrotron light sources has changed the situation; by
the resonant x-ray scattering (RXS) technique the orbital ordering has
successfully been observed . In this article, we review progress in the recent
studies of RXS in manganites. We start with a detailed review of the RXS
experiments applied to the orbital ordered manganites and other correlated
electron systems. We derive the scattering cross section of RXS where the
tensor character of the atomic scattering factor (ASF) with respect to the
x-ray polarization is stressed. Microscopic mechanisms of the anisotropic
tensor character of ASF is introduced and numerical results of ASF and the
scattering intensity are presented. The azimuthal angle scan is a unique
experimental method to identify RXS from the orbital degree of freedom. A
theory of the azimuthal angle and polarization dependence of the RXS intensity
is presented. The theoretical results show good agreement with the experiments
in manganites. Apart from the microscopic description of ASF, a theoretical
framework of RXS to relate directly to the 3d orbital is presented. The
scattering cross section is represented by the correlation function of the
pseudo-spin operator for the orbital degree of freedom. A theory is extended to
the resonant inelastic x-ray scattering and methods to observe excitations of
the orbital degree of freedom are proposed.

###Theoretical Study of Half-Doped Models for Manganites: Fragility of the CE Phase with Disorder, Two Types of Colossal Magnetoresistances, and Charge-Ordered States for Electron-Doped Materials|H. Aliaga,D. Magnoux,A. Moreo,D. Poilblanc,S. Yunoki,E. Dagotto###

Theoretical Study of Half-Doped Models for Manganites: Fragility of the CE Phase with Disorder, Two Types of Colossal Magnetoresistances, and Charge-Ordered States for Electron-Doped Materials. A comprehensive analysis of half-doped manganites is presented using Monte
Carlo simulations applied to the double-exchange model with cooperative
Jahn-Teller lattice distortions in two dimensions. A variety of novel results
are reported: (i) The phase diagram is established in the lambda-J_ AF plane,
with lambda the electron-phonon coupling and J_AF the antiferromagnetic
exchange between classical t_2g spins. The results include standard phases,
such as the CE-insulating and FM-metallic regimes, but they also unveil novel
states, such as a ferromagnetic charge-ordered (CO) orbital-ordered phase
compatible with recent experimental results by Loudon et al. (ii) For realistic
couplings, it was observed that the charge disproportionation delta of the CO
phase is far from the widely accepted extreme limit delta=0.5 of a 3+/4+ charge
separation. A far smaller delta appears more realistic, in agreement with
recent experiments by Garcia et al. and Daoud-Aladine it et al. (iii) Colossal
magnetoresistance (CMR) effects are found in calculations of cluster
resistances using the Landauer formalism. This occurs near the ubiquitous
first-order phase transitions between the insulating and metallic states. (iv)
The CE-state is found to be (very sensitive to disorder) since its long-range
order rapidly disappears when quenched-disorder is introduced, contrary to the
FM state which is more robust. This is also in qualitative agreement with
recent experiments by Akahoshi et al. and Nakajima et al. (v) The phase diagram
in the half-doped (electron doping) regime is briefly discussed as well. A
charge-ordered state is found which is the analog of the x=0.5 CE phase. It
contains a 3+/2+ charge arrangement at large lambda.

###The Dependence of the Superconducting Transition Temperature of Organic Molecular Crystals on Intrinsically Non-Magnetic Disorder: a Signature of either Unconventional Superconductivity or Novel Local Magnetic Moment Formation|B. J. Powell,Ross H. McKenzie###

The Dependence of the Superconducting Transition Temperature of Organic Molecular Crystals on Intrinsically Non-Magnetic Disorder: a Signature of either Unconventional Superconductivity or Novel Local Magnetic Moment Formation. We give a theoretical analysis of published experimental studies of the
effects of impurities and disorder on the superconducting transition
temperature, T_c, of the organic molecular crystals kappa-ET_2X and beta-ET_2X
(where ET is bis(ethylenedithio)tetrathiafulvalene and X is an anion eg I_3).
The Abrikosov-Gorkov (AG) formula describes the suppression of T_c both by
magnetic impurities in singlet superconductors, including s-wave
superconductors and by non-magnetic impurities in a non-s-wave superconductor.
We show that various sources of disorder lead to the suppression of T_c as
described by the AG formula. This is confirmed by the excellent fit to the
data, the fact that these materials are in the clean limit and the excellent
agreement between the value of the interlayer hopping integral, t_perp,
calculated from this fit and the value of t_perp found from angular-dependant
magnetoresistance and quantum oscillation experiments. If the disorder is, as
seems most likely, non-magnetic then the pairing state cannot be s-wave. We
show that the cooling rate dependence of the magnetisation is inconsistent with
paramagnetic impurities. Triplet pairing is ruled out by several experiments.
If the disorder is non-magnetic then this implies that l>=2, in which case
Occam's razor suggests that d-wave pairing is realised. Given the proximity of
these materials to an antiferromagnetic Mott transition, it is possible that
the disorder leads to the formation of local magnetic moments via some novel
mechanism. Thus we conclude that either kappa-ET_2X and beta-ET_2X are d-wave
superconductors or else they display a novel mechanism for the formation of
localised moments. We suggest systematic experiments to differentiate between
these scenarios.

###Magnetoresistance and dephasing in a two-dimensional electron gas at intermediate conductances|G. M. Minkov,A. V. Germanenko,I. V. Gornyi###

Magnetoresistance and dephasing in a two-dimensional electron gas at intermediate conductances. We study, both theoretically and experimentally, the negative
magnetoresistance (MR) of a two-dimensional (2D) electron gas in a weak
transverse magnetic field $B$. The analysis is carried out in a wide range of
zero-$B$ conductances $g$ (measured in units of $e^2/h$), including the range
of intermediate conductances, $g\sim 1$. Interpretation of the experimental
results obtained for a 2D electron gas in GaAs/In$_x$Ga$_{1-x}$As/GaAs single
quantum well structures is based on the theory which takes into account terms
of higher orders in $1/g$, stemming from both the interference contribution and
the mutual effect of weak localization (WL) and Coulomb interaction. We
demonstrate that at intermediate conductances the negative MR is described by
the standard WL "digamma-functions" expression, but with a reduced prefactor
$\alpha$. We also show that at not very high $g$ the second-loop corrections
dominate over the contribution of the interaction in the Cooper channel, and
therefore appear to be the main source of the lowering of the prefactor,
$\alpha\simeq 1-2/\pi g$. We further analyze the regime of a "weak insulator",
when the zero-$B$ conductance is low $g(B=0)<1$ due to the localization at low
$T$, whereas the Drude conductance is high, $g_0>>1.$ In this regime, while the
MR still can be fitted by the digamma-functions formula, the experimentally
obtained value of the dephasing rate has nothing to do with the true one. The
corresponding fitting parameter in the low-$T$ limit is determined by the
localization length and may therefore saturate at $T\to 0$, even though the
true dephasing rate vanishes.

###Magnetization and Magnetotransport of LnBaCo2O5.5 (Ln=Gd, Eu) Single Crystals|Z. X. Zhou,S. McCall,C. S. Alexander,J. E. Crow,P. Schlottmann,S. N. Barilo,S. V. Shiryaev,G. L Bychkov,R. P. Guertin###

Magnetization and Magnetotransport of LnBaCo2O5.5 (Ln=Gd, Eu) Single Crystals. The magnetization, resistivity and magnetoresistance (MR) of single crystals
of GdBaCo2O5.5 and EuBaCo2O5.5 are measured over a wide range of dc magnetic
fields (up to 30 T) and temperature. In LnBaCo2O5.5 (Ln=Gd, Eu), the Co-ions
are trivalent and can exist in three spin states, namely, the S=0 low spin
state (LS), the S= 1 intermediate spin state (IS) and the S=2 high spin state
(HS). We confirm that GdBaCo2O5.5 and EuBaCo2O5.5 have a metal-insulator
transition accompanied by a spin-state transition at TMI >> 365 and 335 K,
respectively. The data suggest an equal ratio of LS (S=0) and IS (S=1) Co3+
ions below TMI, with no indication of additional spin state transitions. The
low field magnetization shows a transition to a highly anisotropic
ferromagnetic phase at 270 K, followed by another magnetic transition to an
antiferromagnetic phase at a slightly lower temperature. The magnetization data
are suggestive of weak correlations between the Gd-spins but no clear signature
of ordering is seen for T > 2 K. Significant anisotropy between the a-b plane
and c axis was observed in magnetic and magnetotransport properties for both
compounds. For GdBaCo2O5.5, the resistivity and MR data imply a strong
correlation between the spin-order and charge carriers. For EuBaCo2O5.5, the
magnetic phase diagram is very similar to its Gd counterpart, but the low-T MR
with current flow in the ab plane is positive rather than negative as for Gd.
The magnitude and the hysteresis of the MR for EuBaCo2O5.5 decrease with
increasing temperature, and at higher T the MR changes sign and becomes
negative. The difference in the behavior of both compounds may arise from a
small valence admixture in the nonmagnetic Eu ions, i.e. a valence slightly
less than 3+.

###Structure, magnetic and transport properties of Ti-substituted La0.7Sr0.3MnO3|M. S. Kim,J. B. Yang,Q. Cai,X. D. Zhou,W. J. James,W. B. Yelon,P. E. Parris,D. Buddhikot,S. K. Malik###

Structure, magnetic and transport properties of Ti-substituted La0.7Sr0.3MnO3. Ti-substituted perovskites, La0.7Sr0.3Mn1-xTixO3, with x between 0 to 0.20,
were investigated by neutron diffraction, magnetization, electric resistivity,
and magnetoresistance (MR) measurements. All samples show a rhombohedral
structure (space group R3c) from 10 K to room temperature. At room temperature,
the cell parameters a, c and the unit cell volume increase with increasing Ti
content. However, at 10 K, the cell parameter a has a maximum value for x =
0.10, and decreases for x greater than 0.10, while the unit cell volume remains
nearly constant for x greater than 0.10. The average (Mn,Ti)-O bond length
increases up to x=0.15, and the (Mn,Ti)-O-(Mn,Ti) bond angle decreases with
increasing Ti content to its minimum value at x=0.15 at room temperature. Below
the Curie temperature T_C, the resistance exhibits metallic behavior for the x
_ 0.05 samples. A metal (semiconductor) to insulator transition is observed for
the x_ 0.10 samples. A peak in resistivity appears below T_C for all samples,
and shifts to a lower temperature as x increases. The substitution of Mn by Ti
decreases the 2p-3d hybridization between O and Mn ions, reduces the bandwidth
W, and increases the electron-phonon coupling. Therefore, the TC shifts to a
lower temperature and the resistivity increases with increasing Ti content. A
field-induced shift of the resistivity maximum occurs at x less than or equal
to 0.10. The maximum MR effect is about 70% for La0.7Sr0.3Mn0.8Ti0.2O3. The
separation of TC and the resistivity maximum temperature Tmax enhances the MR
effect in these compounds due to the weak coupling between the magnetic
ordering and the resistivity as compared with La0.7Sr0.3MnO3.

###Magnetic, electronic and Shubnikov-de Haas investigation of the dense Kondo system CeAgSb2|E. Jobiliong,J. S. Brooks,E. S. Choi,Han-Oh Lee,Z. Fisk###

Magnetic, electronic and Shubnikov-de Haas investigation of the dense Kondo system CeAgSb2. Of the dense Kondo materials in the class CeTSb2 (where T = Au, Ag, Ni, Cu,
or Pd), CeAgSb2 is special due to its complex magnetic ground state, which
exhibits both ferro- and anti-ferromagnetic character below an ordering
temperature TO ~ 9.8 K. To further elucidate a description this magnetic ground
state, we have carried out a systematic study of single crystalline CeAgSb2 by
magnetic, electrical magneto-transport, and Shubnikov-de Haas (SdH) studies
over a broad range of temperature and magnetic field. We have constructed the
magnetic phase diagram based solely on magnetoresistance data. Here, depending
on the orientation of the magnetic field H, either ferromagnetic or
antiferromagnetic ordering occurs below TO. The resistivity of this compound
below TO does not follow a simple Fermi liquid behavior, but requires an
additional contribution from conduction electron scattering from boson
excitations with an energy gap, D. At zero field the temperature dependent
resistivity below TO is most consistent with antiferromagnetic order, based on
the transport theory which includes magnon scattering. Crystal field effect
theory applied to the susceptibility data yields splitting energies from the
ground state to the first and second excited states of 53 K and 137 K,
respectively. Although there is some uncertainty in the Kondo temperature
determination, we estimate TK ~ 23 K from our analysis. In the Fermi surface
studies, the measurements show very small Fermi surface sections, not predicted
by band structure calculations, and the SdH amplitudes are very sensitive to
field direction. Only by considering lens orbits between the main Fermi surface
cylinders can the SdH results be reconciled with the Fermi surface topology
predicted from band structure.

###Poly-MTO, {(CH_3)_{0.92} Re O_3}_\infty, a Conducting Two-Dimensional Organometallic Oxide|R. Miller,E. -W. Scheidt,G. Eickerling,C. Helbig,F. Mayr,R. Herrmann,W. Scherer,H. -A. Krug von Nidda,V. Eyert,P. Schwab###

Poly-MTO, {(CH_3)_{0.92} Re O_3}_\infty, a Conducting Two-Dimensional Organometallic Oxide. Polymeric methyltrioxorhenium, {(CH_{3})_{0.92}ReO_{3}}_{\infty} (poly-MTO),
is the first member of a new class of organometallic hybrids which adopts the
structural pattern and physical properties of classical perovskites in two
dimensions (2D). We demonstrate how the electronic structure of poly-MTO can be
tailored by intercalation of organic donor molecules, such as
tetrathiafulvalene (TTF) or bis-(ethylendithio)-tetrathiafulvalene (BEDT-TTF),
and by the inorganic acceptor SbF$_3$. Integration of donor molecules leads to
a more insulating behavior of poly-MTO, whereas SbF$_3$ insertion does not
cause any significant change in the resistivity. The resistivity data of pure
poly-MTO is remarkably well described by a two-dimensional electron system.
Below 38 K an unusual resistivity behavior, similar to that found in doped
cuprates, is observed: The resistivity initially increases approximately as
$\rho \sim$ ln$(1/T$) before it changes into a $\sqrt{T}$ dependence below 2 K.
As an explanation we suggest a crossover from purely two-dimensional
charge-carrier diffusion within the \{ReO$_2$\}$_{\infty}$ planes at high
temperatures to three-dimensional diffusion at low temperatures in a
disorder-enhanced electron-electron interaction scenario (Altshuler-Aronov
correction). Furthermore, a linear positive magnetoresistance was found in the
insulating regime, which is caused by spatial localization of itinerant
electrons at some of the Re atoms, which formally adopt a $5d^1$ electronic
configuration. X-ray diffraction, IR- and ESR-studies, temperature dependent
magnetization and specific heat measurements in various magnetic fields suggest
that the electronic structure of poly-MTO can safely be approximated by a
purely 2D conductor.

###Oxygen content variation and cation doping dependence of (La)1.4(Sr1-yCay)1.6Mn2O7 (y = 0, 0.25, 0.5) bilayered manganites properties|Lorenzo Malavasi,Maria Cristina Mozzati,Cristina Tealdi,Carlo B. Azzoni,Giorgio Flor###

Oxygen content variation and cation doping dependence of (La)1.4(Sr1-yCay)1.6Mn2O7 (y = 0, 0.25, 0.5) bilayered manganites properties. The results of the synthesis and characterization of the optimally doped
(La)1.4(Sr1-yCay)1.6Mn2O7 solid solution with y=0, 0.25 and 0.5 are reported.
By progressively replacing the Sr with the smaller Ca, while keeping fixed the
hole-concentration due to the divalent dopant, the 'size effect' of the cation
itself on the structural, transport and magnetic properties of the bilayered
manganite has been analysed. Two different annealing treatments of the solid
solution, in pure oxygen and in pure argon, allowed also to study the effect of
the oxygen content variation. Structure and electronic properties of the
samples have been investigated by means of X-ray powder diffraction and X-ray
absorption spectroscopy measurements. Magnetoresistivity and static
magnetization measurements have been carried out to complete the samples
characterization. Oxygen annealing of the solid solution, that showed a limit
for about y=0.5, induces an increase of the Mn average valence state and a
transition of the crystal structure from tetragonal to orthorhombic while the
argon annealing induces an oxygen under-stoichiometry and, in turn, a reduction
of the Mn average valence state. Along with the Ca substitution, the
Jahn-Teller distortion of the MnO6 octahedra is reduced. This has been directly
connected to a general enhancement of the transport properties induced by the
Ca-doping. For the same cation composition, oxygen over-stoichiometry leads to
higher metal-insulator transition temperatures and lower resistivity values.
Curie temperatures (TC) reduce by increasing the Ca-doping. The lower TC for
all the annealed samples with respect to the 'as prepared' ones are connected
to the strong influence on the magnetic interaction of the point defects due to
the oxygen content variation.

###Spin-Diffusion Lengths in Metals and Alloys, and Spin-Flipping at Metal/Metal Interfaces: an Experimentalist's Critical Review|Jack Bass,William P. Pratt Jr###

Spin-Diffusion Lengths in Metals and Alloys, and Spin-Flipping at Metal/Metal Interfaces: an Experimentalist's Critical Review. In magnetoresistive (MR) studies of magnetic multilayers composed of
combinations of ferromagnetic (F) and non-magnetic (N) metals, the magnetic
moment (or related 'spin') of each conduction electron plays a crucial role,
supplementary to that of its charge. While initial analyses of MR in such
multilayers assumed that the direction of the spin of each electron stayed
fixed as the electron transited the multilayer, we now know that this is true
only in a certain limit. Generally, the spins 'flip' in a distance
characteristic of the metal, its purity, and the temperature. They can also
flip at F/N or N1/N2 interfaces. In this review we describe how to measure the
lengths over which electron moments flip in pure metals and alloys, and the
probability of spin-flipping at metallic interfaces. Spin-flipping within
metals is described by a spin-diffusion length,l^M(sf), where the metal M = F
or N. Spin-diffusion lengths are the characteristic lengths in the
current-perpendicular-to-plane (CPP) and lateral non-local (LNL) geometries
that we focus upon in this review. In certain simple cases, l^N(sf) sets the
distance over which the CPP-MR and LNL-MR decrease as the N-layer thickness
(CPP-MR) or N-film length (LNL) increases, and l^F(sf) does the same for
increase of the CPP-MR with increasing F-layer thickness. Spin-flipping at
M1/M2 interfaces can be described by a parameter, delta(M1/M2), which
determines the spin-flipping probability, P = 1 - exp(-delta). Increasing
delta(M1/M2) usually decreases the MR. We list measured values of these
parameters and discuss the limitations on their determinations.

###Probing Spin Accumulation in Ni/Au/Ni Single-Electron Transistors with Efficient Spin Injection and Detection Electrodes|R. S. Liu,H. Pettersson,L. Michalak,C. M. Canali,L. Samuelson###

Probing Spin Accumulation in Ni/Au/Ni Single-Electron Transistors with Efficient Spin Injection and Detection Electrodes. We have investigated spin accumulation in Ni/Au/Ni single-electron
transistors assembled by atomic force microscopy. The fabrication technique is
unique in that unconventional hybrid devices can be realized with unprecedented
control, including real-time tunable tunnel resistances. A grid of Au discs, 30
nm in diameter and 30 nm thick, is prepared on a SiO2 surface by conventional
e-beam writing. Subsequently, 30 nm thick ferromagnetic Ni source, drain and
side-gate electrodes are formed in similar process steps. The width and length
of the source and drain electrodes were different to exhibit different coercive
switching fields. Tunnel barriers of NiO are realized by sequential Ar and O2
plasma treatment. Using an atomic force microscope with specially designed
software, a single non-magnetic Au nanodisc is positioned into the 25 nm gap
between the source and drain electrodes. The resistance of the device is
monitored in real-time while the Au disc is manipulated step-by-step with
Angstrom-level precision. Transport measurements in magnetic field at 1.7 K
reveal no clear spin accumulation in the device, which can be attributed to
fast spin relaxation in the Au disc. From numerical simulations using the
rate-equation approach of orthodox Coulomb blockade theory, we can put an upper
bound of a few ns on the spin-relaxation time for electrons in the Au disc. To
confirm the magnetic switching characteristics and spin injection efficiency of
the Ni electrodes, we fabricated a test structure consisting of a Ni/NiO/Ni
magnetic tunnel junction with asymmetric dimensions of the electrodes similar
to those of the SETs. Magnetoresistance measurements on the test device
exhibited clear signs of magnetic reversal and a maximum TMR of 10%, from which
we deduced a spin-polarization of about 22% in the Ni electrodes.

###Synergy of exchange bias with superconductivity in ferromagnetic-superconducting layered hybrids: the influence of in-plane and out-of-plane magnetic order on superconductivity|D. Stamopoulos,E. Manios,M. Pissas###

Synergy of exchange bias with superconductivity in ferromagnetic-superconducting layered hybrids: the influence of in-plane and out-of-plane magnetic order on superconductivity. It is generally believed that superconductivity and magnetism are two
antagonistic long-range phenomena. However, as it was preliminarily highlighted
in D. Stamopoulos et al. [Phys. Rev. B 75, 014501 (2007)] and extensively
studied in this work under specific circumstances these phenomena instead of
being detrimental to each other may even become cooperative so that their
synergy may promote the superconducting properties of a hybrid structure.
  Here, we have studied systematically the magnetic and transport behavior of
such exchange biased hybrids that are comprised of ferromagnetic (FM) Ni80Fe20
and low-Tc superconducting (SC) Nb for the case where the magnetic field is
applied parallel to the specimens. Two structures have been studied: FM-SC-FM
trilayers (TLs) and FM-SC bilayers (BLs). Detailed magnetization data on the
longitudinal and transverse magnetic components are presented for both the
normal and superconducting states. These data are compared to systematic
transport measurements including I-V characteristics. The comparison of the
exchange biased BLs and TLs that are studied here with the plain ones studied
in D. Stamopoulos et al. [Phys. Rev. B 75, 184504 (2007)] enable us to reveal
an underlying parameter that may falsify the interpretation of the transport
properties of relevant FM-SC-FM TLs and FM-SC BLs investigated in the recent
literature: the underlying mechanism motivating the extreme magnetoresistance
peaks in the TLs relates to the suppression of superconductivity mainly due to
the magnetic coupling of the two FM layers as the out-of-plane rotation of
their magnetizations takes place across the coercive field where stray fields
emerge in their whole surface owing to the multidomain magnetic state that they
acquire.

###Spin transport in nanocontacts and nanowires|David Jacob###

Spin transport in nanocontacts and nanowires. In this thesis we study electron transport through magnetic nanocontacts and
nanowires with ab initio quantum transport calculations. The aim is to gain a
thorough understanding of the interplay between electrical conduction and
magnetism in atomic-size conductors and how it is affected by different aspects
as e.g. the atomic structure and the chemical composition of the conductor. To
this end our ab initio quantum transport program ALACANT which combines the
non-equilibrium Green's function formalism (NEGF) with density functional
theory (DFT) calculations has been extended to describe spin-polarized systems.
We present calculations on nanocontacts made of Ni as a prototypical magnetic
material. We find that atomic disorder in the contact region strongly reduces
the a priori high spin-polarization of the conductance leading to rather
moderate values of the so-called ballistic magnetoresistance (BMR). On the
other hand, we show that the adsorption of oxygen in the contact region could
strongly enhance the spin-polarization of the conduction electrons and thus BMR
by eliminating the spin-unpolarized s-channel. Finally, we show that short
atomic Pt chains suspended between the tips of a nanocontact are magnetic in
contrast to bulk Pt. However, this emergent nanoscale magnetism barely affects
the overall conductance of the nanocontact making it thus difficult to
demonstrate by simple conductance measurements. In conclusion, we find that
spin-transport through atomic-scale conductors is quite sensitive to the actual
atomic structure as well as to the chemical composition of the conductor. This
presents both, opportunities and challenges for the realization of future
nanoscale spintronics devices.

###Electrical and magnetic properties of nano-scale Pi-junctions|Samanta Piano###

Electrical and magnetic properties of nano-scale Pi-junctions. The physics of the "Pi" phase shift in ferromagnetic Josephson junctions
enables a range of applications for spin-electronic devices and quantum
computing. In this respect our research is devoted to the evaluation of the
best materials for the development and the realization of the quantum devices
based on superconductors and at the same point towards the reduction of the
size of the employed heterostructures towards and below nano-scale. In this
chapter we report our investigation of transitions from "0" to "Pi" states in
Nb Josephson junctions with strongly ferromagnetic barriers of Co, Ni,
Ni$_{80}$Fe$_{20}$ (Py) and Fe. We show that it is possible to fabricate
nanostructured Nb/ Ni(Co, Py, Fe)/Nb $\pi$-junctions with a nano-scale magnetic
dead layer and with a high level of control over the ferromagnetic barrier
thickness variation. In agreement with the theoretical model we estimate, from
the oscillations of the critical current as function of the ferromagnetic
barrier thickness, the exchange energy of the ferromagnetic material and we
obtain that it is close to bulk ferromagnetic materials implying that the
ferromagnet is clean and S/F roughness is minimal. We conclude that S/F/S
Josephson junctions are viable structures in the development of
superconductor-based quantum electronic devices; in particular Nb/Co/Nb and
Nb/Fe/Nb multilayers with their low value of the magnetic dead layer and high
value of the exchange energy can readily be used in controllable two-level
quantum information systems. In this respect, we discuss applications of our
nano-junctions to engineering magnetoresistive devices such as programmable
pseudo-spin-valve Josephson structures.

###(Sr_3Sc_2O_5)Fe_2As_2 as a possible parent compound for FeAs-based superconductors|Xiyu Zhu,Fei Han,Gang Mu,Bin Zeng,Peng Cheng,Bing Shen,Hai-Hu Wen###

(Sr_3Sc_2O_5)Fe_2As_2 as a possible parent compound for FeAs-based superconductors. A new compound with the FeAs-layers, namely (Sr_3Sc_2O_5)Fe_2As_2
(abbreviated as FeAs-32522), was successfully fabricated. It has a layered
structure with the space group of I4/mmm, and with the lattice constants a =
4.069 $\AA$ and c = 26.876 $\AA$. The in-plane Fe ions construct a square
lattice which is close to that of other FeAs-based superconductors, such as
REFeAsO (RE = rare earth elements) and (Ba,Sr)Fe_2As_2. However the inter
FeAs-layer spacing in the new compound is greatly enlarged. The temperature
dependence of resistivity exhibits a weak upturn in the low temperature region,
but a metallic behavior was observed above about 60 K. The magnetic
susceptibility shows also a non-monotonic behavior. Interestingly, the
well-known resistivity anomaly which was discovered in all other parent
compounds, such as REFeAsO, (Ba,Sr)Fe_2As_2 and (Sr,Ca,Eu)FeAsF and associated
with the Spin-Density-Wave (SDW)/structural transition has not been found in
the new system either on the resistivity data or the magnetization data. This
could be induced by the large spacing distance between the FeAs-planes,
therefore the antiferromagnetic correlation between the moments of Fe ions in
neighboring FeAs-layers cannot be established. Alternatively it can also be
attributed to the self-doping effect between Fe and Sc ions. The Hall
coefficient R_H is negative but strongly temperature dependent in wide
temperature region, which indicates the dominance of electrical conduction by
electron-like charge carriers and probably a multi-band effect or a spin
related scattering effect. It is found that the magnetoresistance cannot be
described by the Kohler's rule, which gives further support to above arguments.

###Transport theory for disordered multiple-band systems: Anomalous Hall effect and anisotropic magnetoresistance|Alexey A. Kovalev,Yaroslav Tserkovnyak,Karel Vyborny,Jairo Sinova###

Transport theory for disordered multiple-band systems: Anomalous Hall effect and anisotropic magnetoresistance. We present a study of transport in multiple-band non-interacting Fermi
metallic systems based on the Keldysh formalism, taking into account the
effects of Berry curvature due to spin-orbit coupling. We apply this formalism
to a Rashba 2DEG ferromagnet and calculate the anomalous Hall effect (AHE) and
anisotropic magnetoresistance (AMR). The numerical calculations reproduce
analytical results in the metallic regime revealing the crossover between the
skew scattering mechanism dominating in the clean systems and intrinsic
mechanism dominating in the moderately dirty systems. As we increase the
disorder further, the AHE starts to diminish due to the spectral broadening of
the quasiparticles. Although for certain parameters this reduction of the AHE
can be approximated as $\sigma_{xy}\thicksim\sigma_{xx}^{\varphi}$ with
$\varphi$ varying around 1.6, this is found not to be true in general as
$\sigma_{xy}$ can go through a change in sign as a function of disorder
strength in some cases. The reduction region in which the quasiparticle
approximation is meaningful is relatively narrow; therefore, a theory with a
wider range of applicability is called for. By considering the higher order
skew scattering processes, we resolve some discrepancies between the AHE
results obtained by using the Keldysh, Kubo and Boltzmann approaches. We also
show that similar higher order processes are important for the AMR when the
nonvertex and vertex parts cancel each other. We calculate the AMR in
anisotropic systems properly taking into account the anisotropy of the
non-equilibrium distribution function. These calculations confirm recent
findings on the unreliability of common approximations to the Boltzmann
equation.

###Magnetic interactions and electron transport in hole-doped manganite-superconducting cuprate heterostructures|Soumen Mandal###

Magnetic interactions and electron transport in hole-doped manganite-superconducting cuprate heterostructures. This thesis presents a systematic study of magnetotransport and magnetic
ordering in manganite-high T$_c$ cuprate spin valve structures.
YBa$_{2}$Cu$_{3}$O$_{7}$ - La$_{2 / 3}$Sr$_{1 / 3}$MnO$_{3}$ heterostructures
of (110) orientation are grown to allow direct injection of spin polarized
holes from the La$_{2 / 3}$Sr$_{1 / 3}$MnO$_{3}$ (LSMO) into the CuO$_2$
superconducting planes of the YBa$_{2}$Cu$_{3}$O$_{7}$ (YBCO). Galvanomagnetic
studies on the LSMO-YBCO-LSMO trilayers reveal unusually high AMR
($\sim$72000%) on rotating the field in the plane of the heterostructure whose
magnetic ground state is antiferromagnetic (AF). The coupling energy J$_1$ of
the AF state in these trilayers is much higher as compared to energy of (001)
oriented hybrids. First the preparation and measurement of magnetic and
galvanomagnetic properties of (110) and (001) oriented La$_{2 / 3}$Sr$_{1 /
3}$MnO$_{3}$ films are described. The magnetization vector ($\vec{M}$) of the
(001) and (110) type films is pinned along the (110) and (001) directions
respectively at low fields. A magnetization orientation phase transition (MRPT)
which manifests itself as a discontinuity and hysteresis in $R(\psi)$ where
$\psi$ is the angle between $\vec{H}$ and the easy axis for the $\vec{H}$ below
a critical value $\vec{H}^*$ has been established. Further, the relevance of
pair-breaking by exchange and dipolar fields, and by injected spins in a low
carrier density cuprate Y$_{1-x}$Pr$_x$Ba$_2$Cu$_3$O$_7$ sandwiched between two
ferromagnetic LSMO layers is examined. At low external field ($H_{ext}$), the
system shows a giant magnetoresistance(MR), which diverges deep in the
superconducting state.

###Spin-polarized tunneling spectroscopic studies of the intrinsic heterogeneity and pseudogap phenomena in colossal magnetoresistive manganite La_{0.7}Ca_{0.3}MnO_{3}|C. R. Hughes,J. Shi,A. D. Beyer,N. -C. Yeh###

Spin-polarized tunneling spectroscopic studies of the intrinsic heterogeneity and pseudogap phenomena in colossal magnetoresistive manganite La_{0.7}Ca_{0.3}MnO_{3}. Spatially resolved tunneling spectroscopic studies of colossal
magnetoresistive (CMR) manganite $\rm La_{0.7}Ca_{0.3}MnO_3$ (LCMO) epitaxial
films on $\rm (LaAlO_3)_{0.3}(Sr_2AlTaO_6)_{0.7}$ substrate are investigated as
functions of temperature, magnetic field and spin polarization by means of
scanning tunneling spectroscopy. Systematic surveys of the tunneling spectra
taken with Pt/Ir tips reveal spatial variations on the length scale of a few
hundred nanometers in the ferromagnetic state, which may be attributed to the
intrinsic heterogeneity of the manganites due to their tendency towards phase
separation. The electronic heterogeneity is found to decrease either with
increasing field at low temperatures or at temperatures above all magnetic
ordering temperatures. On the other hand, spectra taken with Cr-coated tips are
consistent with convoluted electronic properties of both LCMO and Cr. In
particular, for temperatures below the magnetic ordering temperatures of both
Cr and LCMO, the magnetic-field dependent tunneling spectra may be
quantitatively explained by the scenario of spin-polarized tunneling in a
spin-valve configuration. Moreover, a low-energy insulating energy gap $\sim
0.6$ eV commonly found in the tunneling conductance spectra of bulk metallic
LCMO at $T \to 0$ may be attributed to a surface ferromagnetic insulating (FI)
phase, as evidenced by its spin filtering effect at low temperatures and
vanishing gap value above the Curie temperature. Additionally, temperature
independent pseudogap (PG) phenomena existing primarily along the boundaries of
magnetic domains are observed in the zero-field tunneling spectra. The PG
becomes strongly suppressed by applied magnetic fields at low temperatures when
the tunneling spectra of LCMO become highly homogeneous. These findings suggest
that the occurrence PG is associated with the electronic heterogeneity of the
manganites.

###Electron phenomena in layered conductors|O. V. Kirichenko,Yu. A. Kolesnichenko,V. G. Peschansky###

Electron phenomena in layered conductors. The quasi-two-dimensional nature of the charge carriers energy spectrum in
layered conductors leads to specific effects in an external magnetic field. The
magnetoresistance of layered conductors in a wide range of strong magnetic
fields directed in the plane of the layers can increase proportionally to a
magnetic field value. The electromagnetic impedance and the sound attenuation
rate depend essentially on the polarization of normal to the layers.
Propagation of electromagnetic and acoustic waves in these conductors involves
virtually all charge carriers in the transfer of acoustic pulses and
electromagnetic field spikes to the bulk of the conductor. The orbits of Fermi
electrons in a magnetic field are virtually indistinguishable, which allows the
inclusion of large number of conduction electrons in the formation of peculiar
oscillatory and resonant effects which are absent in the case of ordinary
metals. Investigation of these effects introduce the possibilities for detailed
study of the dissipative processes in electron systems of layered conductors
and the charge carriers energy spectrum. Point contact investigations of
layered metals allow us to obtain the information about electron and phonon
spectra. The electron focusing signal and the point contact spectrum are
extremely sensitive to the orientation of the magnetic field vector $\bs{H}$ in
relation to the layers with a high electrical conductivity. The values of
$\bs{H}$ for which the electron focusing signal has peaks can be used for
determining velocities and extremal diameters for the open Fermi surface. The
dependence of the point contact spectra on the magnitude and the relaxation of
electrons at various types of phonon excitations.

###AC Susceptibility Studies in Fe doped La0.65Ca0.35Mn1-xFexO3: Rare Earth Manganites|Wiqar Hussain Shah,S. K. Hasanain###

AC Susceptibility Studies in Fe doped La0.65Ca0.35Mn1-xFexO3: Rare Earth Manganites. The effect of Fe substitution on Mn sites in the colossal magnetoresistive
compounds La0.65Ca0.35Mn1-xFexO3 with 0.01<x<0.1 have been studied. A careful
study in the magnetic properties has been carried out by the measurement of ac
susceptibility. The temperature range of CMR is greatly broadened with the
addition of Fe. Substitution of Fe induces a gradual transition from a metallic
ferromagnetic with a high Curie temperature (Tc=270 K) to a ferromagnetic
insulator with low Tc=79 K. Increased spin disorder and decrease of Tc with
increasing Fe content are evident. The variations in the critical temperature
Tc and magnetic moment show a rapid change at about 4-5% Fe. The effect of Fe
is seen to be consistent with the disruption of the Mn-Mn exchange possibly due
to the formation of magnetic clusters. An extra-ordinary behavior in the out of
phase part (x") of ac susceptibility, characterized by double bump (shoulder),
was observed around x=0.01 and 0.02. The shoulder in x" disappears at x>0.04 Fe
concentration. With increasing Fe concentration the x" peak shift to T<T1/2
(mid point of the transition temperature) and becomes broader. The x" peak
moves to 8 or 10 K higher temperature on the application of a dc field, for 3 &
4% samples. We also see increasing low temperature dissipation in more strongly
Fe doped samples i.e. increasing the Fe, leads to increased spin disorder and
dissipation at low temperature. The effect of the dc field is discussed in
terms of the suppression of spin fluctuations close to Tc. The same ionic radii
of Fe3+ and Mn3+ cause no structure changes in either series, yet
ferromagnetism has been consistently suppressed by Fe doping. Doping with Fe
bypasses the usually dominant lattice effects, but depopulate the hopping
electrons and thus weakens the double exchange. The results were explained in
terms of the formation of magnetic clusters of Fe ions.

###Spin Transport and Relaxation in Graphene|Wei Han,K. M. McCreary,K. Pi,W. H. Wang,Yan Li,H. Wen,J. R. Chen,R. K. Kawakami###

Spin Transport and Relaxation in Graphene. We review our recent work on spin injection, transport and relaxation in
graphene. The spin injection and transport in single layer graphene (SLG) were
investigated using nonlocal magnetoresistance (MR) measurements. Spin injection
was performed using either transparent contacts (Co/SLG) or tunneling contacts
(Co/MgO/SLG). With tunneling contacts, the nonlocal MR was increased by a
factor of ~1000 and the spin injection/detection efficiency was greatly
enhanced from ~1% (transparent contacts) to ~30%. Spin relaxation was
investigated on graphene spin valves using nonlocal Hanle measurements. For
transparent contacts, the spin lifetime was in the range of 50-100 ps. The
effects of surface chemical doping showed that for spin lifetimes on the order
of 100 ps, impurity scattering (Au) was not the dominant mechanism for spin
relaxation. While using tunneling contacts to suppress the contact-induced spin
relaxation, we observed the spin lifetimes as long as 771 ps at room
temperature, 1.2 ns at 4 K in SLG, and 6.2 ns at 20 K in bilayer graphene
(BLG). Furthermore, contrasting spin relaxation behaviors were observed in SLG
and BLG. We found that Elliot-Yafet spin relaxation dominated in SLG at low
temperatures whereas Dyakonov-Perel spin relaxation dominated in BLG at low
temperatures. Gate tunable spin transport was studied using the SLG property of
gate tunable conductivity and incorporating different types of contacts
(transparent and tunneling contacts). Consistent with theoretical predictions,
the nonlocal MR was proportional to the SLG conductivity for transparent
contacts and varied inversely with the SLG conductivity for tunneling contacts.
Finally, bipolar spin transport in SLG was studied and an electron-hole
asymmetry was observed for SLG spin valves with transparent contacts...

###Thermal and Electrical Properties of Multiwall Carbon Nanotubes|Wei Yi###

Thermal and Electrical Properties of Multiwall Carbon Nanotubes. In this dissertation, thermal and electrical properties of aligned multiwall
carbon nanotubes (MWNTs) prepared by thermal decomposition of hydrocarbons have
been experimentally studied. The thesis consists of six chapters. Ch1 is an
introduction. In Ch2, sample preparation and characterizations are described.
In Ch3, by using a self-heating 3-Omega method, the specific heat, thermal
diffusivity and thermal conductivity of MWNTs are measured. MWNTs of 20-40 nm
diameter show a linear specific heat over a temperature range of 10-300 K,
suggesting that inter-wall coupling in MWNTs is rather weak compared with that
of graphite. The thermal conductivity shows a crossover from linear temperature
dependence to a square law at ~120K, with a rather low room-temperature
amplitude which may have resulted from structural defects. In Ch4, four-wire
tunneling spectroscopy of junctions between MWNTs and a normal metal is
measured. The Coulomb interactions in the MWNTs give rise to a strong zero-bias
suppression of tunneling density of states that can be fitted numerically with
the environmental quantum-fluctuation theory. At low temperatures, an
asymmetric conductance anomaly near zero bias is observed, which is interpreted
as Fano resonance in the strong tunneling regime. In Ch5, the thermoelectric
power (TEP) and longitudinal magnetoresistance (MR) of MWNTs are measured. A
moderate positive TEP with metallic-like linear temperature dependence is
found, suggesting that the electron-hole symmetry in metallic MWNTs is broken.
Periodic oscillations in MR are observed at 20 mK when a longitudinal magnetic
field is applied. The period of oscillation agrees well with the period h/2e of
Altshuler-Aronov-Spivak (AAS) effect if only the outermost graphene wall
contributes to conductance, clearly indicating quantum-interference effects at
low temperatures. Ch6 presents the main conclusions.

###Ferromagnetic Ordering in CeIr2B2: Transport, magnetization, specific heat and NMR studies|A. Prasad,V. K. Anand,U. B. Paramanik,Z. Hossain,R. Sarkar,N. Oeschler,M. Baenitz,C. Geibel###

Ferromagnetic Ordering in CeIr2B2: Transport, magnetization, specific heat and NMR studies. We present a complete characterization of ferromagnetic system CeIr2B2 using
powder x-ray diffraction XRD, magnetic susceptibility chi(T), isothermal
magnetization M(H), specific heat C(T), electrical resistivity rho(T,H), and
thermoelectric power S(T) measurements. Furthermore 11B NMR study was performed
to probe the magnetism on a microscopic scale. The chi(T), C(T) and rho(T) data
confirm bulk ferromagnetic ordering with Tc = 5.1 K. Ce ions in CeIr2B2 are in
stable trivalent state. Our low-temperature C(T) data measured down to 0.4 K
yield Sommerfeld coefficient gamma = 73(4) mJ/molK2 which is much smaller than
the previously reported value of gamma = 180 mJ/molK2 deduced from the specific
heat measurement down to 2.5 K. For LaIr2B2 gamma = 6(1) mJ/molK2 which implies
the density of states at the Fermi level D(EF) = 2.54 states/(eV f.u.) for both
spin directions. The renormalization factor for quasi-particle density of
states and hence for quasi-particle mass due to 4f correlations in CeIr2B2 is
12. The Kondo temperature TK ~ 4 K is estimated from the jump in specific heat
of CeIr2B2 at Tc. Both C(T) and rho(T) data exhibit gapped-magnon behavior in
magnetically ordered state with an energy gap Eg ~ 3.5 K. The rho data as a
function of magnetic field H indicate a large negative magnetoresistance (MR)
which is highest for T = 5 K.While at 5 K the negative MR keeps on increasing
up to 10 T, at 2 K an upturn is observed near H = 3.5 T. On the other hand, the
thermoelectric power data have small absolute values (S ~ 7 {\mu}V/K)
indicating a weak Kondo interaction. A shoulder in S(T) at about 30 K followed
by a minimum at ~ 10 K is attributed to crystal electric field (CEF) effects
and the onset of magnetic ordering. 11B NMR line broadening provides strong
evidence of ferromagnetic correlations below 40 K.

###Ferromagnetic cluster spin-glass behavior in PrRhSn3|V. K. Anand,D. T. Adroja,A. D. Hillier###

Ferromagnetic cluster spin-glass behavior in PrRhSn3. We report the synthesis, structure, and magnetic and transport properties of
a new ternary intermetallic compound PrRhSn3 which crystallizes in LaRuSn3-type
cubic structure (space group Pm-3n). At low applied fields the dc magnetic
susceptibility exhibits a sharp anomaly below 6~K with an irreversible behavior
in zero field cooled (ZFC) and field cooled (FC) susceptibility below 5.5 K.
The ac susceptibility exhibits a frequency dependent anomaly revealing a
spin-glass behavior with a freezing temperature, T_f = 4.3 K. The observation
of spin-glass behavior is further supported by a very slow decay of
thermo-remnant magnetization (mean relaxation time tau = 2149 s). However, a
small jump at very low field in the isothermal magnetization at 2 K and a weak
anomaly in the specific heat near 5.5 K reveal the presence of ferromagnetic
clusters. The frequency dependence of the transition temperature T_f in the ac
susceptibility obeys the Vogel-Fulcher law, nu = nu_0exp[-E_a/k_B(T_f-T_0)]
with activation energy E_a/k_B = 19.1 K. This together with an intermediate
value of the parameter delta T_f = Delta T_f/T_f Delta(log nu) = 0.086 provide
an evidence for the formation of a cluster-glass state in PrRhSn3. The magnetic
contribution of the specific heat reveals a broad Schottky-type anomaly
centered around 10 K and the analysis based on the crystal electric field model
indicates a singlet ground state. Further, below T_f the magnetic part of the
specific heat exhibits a T^{3/2} temperature dependence. The strong influence
of the crystal electric field and a T^{3/2} temperature dependence are also
seen in the electrical resistivity which reveals a metallic character and a
high magnetoresistance. We also obtain a surprisingly large value of
Sommerfeld-Wilson ratio R_W ~ 247$.

###Manipulating Femtosecond Spin--Orbit Torques with Laser Pulse Sequences to Control Magnetic Memory States and Ringing|P. C. Lingos,J. Wang,I. E. Perakis###

Manipulating Femtosecond Spin--Orbit Torques with Laser Pulse Sequences to Control Magnetic Memory States and Ringing. Femtosecond (fs) coherent control of collective order parameters is important
for non--equilibrium phase dynamics in correlated materials. Here we propose a
possible scheme for fs control of a ferromagnetic order parameter based on
non--adiabatic optical manipulation of electron--hole ($e$--$h$)
photoexcitations between spin--orbit--coupled bands that are exchange--split by
magnetic interaction with local spins. We photoexcite fs carrier spin--pulses
with controllable direction and time profile without using
circularly--polarized light, via time--reversal symmetry--breaking by
non--perturbative interplay between spin--orbit and magnetic exchange coupling
of coherent photocarriers. We manipulate photoexcited {\em fs spin--orbit
torques} to control complex switching pathways of the magnetization between
multiple magnetic memory states. We calculate the photoinduced fs magnetic
anisotropy in the time domain by using density matrix equations of motion
rather than the quasi--equilibrium free energy. By comparing to pump--probe
experiments, we identify a "sudden" magnetization canting induced by laser
excitation, which displays magnetic hysteresis absent in static
magneto--optical measurements and agrees with switchings measured by Hall
magnetoresistivity. The fs magnetization canting switches direction with
magnetic state and laser frequency, which distinguishes it from nonlinear
optical and demagnetization longitudinal effects. By shaping two--color
laser--pulse sequences analogous to multi--dimensional Nuclear Magnetic
Resonance (NMR) spectroscopy, we show that sequences of clockwise or
counter--clockwise fs spin--orbit torques can enhance or suppress magnetic
ringing and switching rotation at any desired time. We propose protocols that
can provide controlled access to four magnetic states via consequative 90$^{o}$
switchings.

###Kondo lattice and antiferromagnetic behavior in quaternary CeTAl$_4$Si$_2$ (T~=~Rh, Ir) single crystals|Arvind Maurya,R. Kulkarni,A. Thamizhavel,D. Paudyal,S. K. Dhar###

Kondo lattice and antiferromagnetic behavior in quaternary CeTAl$_4$Si$_2$ (T~=~Rh, Ir) single crystals. We report the synthesis and the magnetic properties of single crystalline
CeRhAl$_4$Si$_2$ and CeIrAl$_4$Si$_2$ and their non magnetic La-analogs. The
single crystals of these quaternary compounds were grown using Al-Si binary
eutectic as flux. The anisotropic magnetic properties of the cerium compounds
were explored in detail by means of magnetic susceptibility, isothermal
magnetization, electrical resistivity, magnetoresistivity and heat capacity
measurements. Both CeRhAl$_4$Si$_2$ and CeIrAl$_4$Si$_2$ undergo two
antiferromagnetic transitions, first from the paramagnetic to an
antiferromagnetic state at $T_{\rm N1}$~=~12.6~K and 15.5~K, followed by a
second transition at lower temperatures $T_{\rm N2}$~=~9.4~K and 13.8~K,
respectively. The paramagnetic susceptibility is highly anisotropic and its
temperature dependence in the magnetically ordered state suggests the $c$-axis
to be the relatively easy axis of magnetization. Concomitantly, isothermal
magnetization at 2~K along the $c$-axis shows a sharp spin-flop transition
accompanied by a sizeable hysteresis, while it varies nearly linearly with
field along the [100] direction up to the highest field 14~T, of our
measurement. The electrical resistivity provides evidence of the Kondo
interaction in both compounds, inferred from its $-lnT$ behavior in the
paramagnetic region. The heat capacity data confirm the bulk nature of the two
magnetic transitions in each compound, and further confirm the presence of
Kondo interaction by a reduced value of the entropy associated with the
magnetic ordering. From the heat capacity data below 1~K, the coefficient of
the linear term in the electronic heat capacity, $\gamma$, is inferred to be
195.6 and 49.4~mJ/mol K$^2$ in CeRhAl$_4$Si$_2$ and CeIrAl$_4$Si$_2$,
respectively classifying these materials as moderate heavy fermion compounds.

###Bulk Fermi-surface of the Weyl type-II semi-metallic candidate MoTe2|D. Rhodes,R. Schönemann,N. Aryal,Q. Zhou,Q. R. Zhang,E. Kampert,Y. -C. Chiu,Y. Lai,Y. Shimura,G. T. McCandless,J. Y. Chan,D. W. Paley,J. Lee,A. D. Finke,J. P. C. Ruff,S. Das,E. Manousakis,L. Balicas###

Bulk Fermi-surface of the Weyl type-II semi-metallic candidate MoTe2. The electronic structure of WTe$_2$ and orthorhombic $\gamma-$MoTe$_2$, are
claimed to contain pairs of Weyl type-II points. A series of ARPES experiments
claim a broad agreement with these predictions. We synthesized single-crystals
of MoTe$_2$ through a Te flux method to validate these predictions through
measurements of its bulk Fermi surface (FS) \emph{via} quantum oscillatory
phenomena. We find that the superconducting transition temperature of
$\gamma-$MoTe$_2$ depends on disorder as quantified by the ratio between the
room- and low-temperature resistivities, suggesting the possibility of an
unconventional superconducting pairing symmetry. Similarly to WTe$_2$, the
magnetoresistivity of $\gamma-$MoTe$_2$ does not saturate at high magnetic
fields and can easily surpass $10^{6}$ \%. Remarkably, the analysis of the de
Haas-van Alphen (dHvA) signal superimposed onto the magnetic torque, indicates
that the geometry of its FS is markedly distinct from the calculated one. The
dHvA signal also reveals that the FS is affected by the Zeeman-effect
precluding the extraction of the Berry-phase. A direct comparison between the
previous ARPES studies and density-functional-theory (DFT) calculations reveals
a disagreement in the position of the valence bands relative to the Fermi level
$\varepsilon_F$. Here, we show that a shift of the DFT valence bands relative
to $\varepsilon_F$, in order to match the ARPES observations, and of the DFT
electron bands to explain some of the observed dHvA frequencies, leads to a
good agreement between the calculations and the angular dependence of the FS
cross-sectional areas observed experimentally. However, this relative
displacement between electron- and hole-bands eliminates their crossings and,
therefore, the Weyl type-II points predicted for $\gamma-$MoTe$_2$.

###Temperature dependence of the electrical resistivity and the anisotropic magnetoresistance (AMR) of electrodeposited Ni Co alloys|B. G. Tóth,L. Péter,Á. Révész,J. Pádár,I. Bakonyi###

Temperature dependence of the electrical resistivity and the anisotropic magnetoresistance (AMR) of electrodeposited Ni Co alloys. The electrical resistivity and the anisotropic magnetoresistance (AMR) was
investigated for Ni Co alloys at and below room temperature. The Ni Co alloy
layers having a thickness of about 2 um were prepared by electrodeposition on
Si wafers with evaporated Cr and Cu underlayers. The alloy composition was
varied in the whole concentration range by varying the ratio of Ni sulfate and
Co sulfate in the electrolyte. The Ni Co alloy deposits were investigated first
in the as deposited state on the substrates and then, by mechanically stripping
them from the substrates, as self supporting layers both without and after
annealing. According to an X ray diffraction study, a strongly textured face
centered cubic (fcc) structure was formed in the as deposited state with an
average grain size of about 10 nm. Upon annealing, the crystal structure was
retained whereas the grain size increased by a factor of 3 to 5, depending on
alloy composition. The zero field resistivity decreased strongly by annealing
due to the increased grain size. The annealing hardly changed the AMR below 50
at.% Co but strongly decreased it above this concentration. The composition
dependence of the resistivity and the AMR of the annealed Ni Co alloy deposits
was in good quantitative agreement with the available literature data both at
13 K and at room temperature. Both transport parameters were found to exhibit a
pronounced maximum in the composition range between 20 and 30 at.% Co and the
data of the Ni Co alloys fit well to the limiting values of the pure component
metals (fcc Ni and fcc Co). The only theoretical calculation reported formerly
on fcc Ni Co alloys yielded at T=0K a resistivity value smaller by a factor of
5 and an AMR value larger by a factor of about 2 than the corresponding low
temperature experimental data, although the theoretical results properly
reproduced the composition dependence of both quantities.

###Controlling many-body states by the electric-field effect in a two-dimensional material|Linjun Li,Eoin C. T. O Farrell,Kianping Loh,Goki Eda,Barbaros Ozyilmaz,Antonio H. Castro Neto###

Controlling many-body states by the electric-field effect in a two-dimensional material. To understand complex physics of a system with strong electron electron
interactions, it is ideal to control and monitor its properties while tuning an
external electric field applied to the system. Indeed, complete electric field
control of many body states in strongly correlated electron systems is
fundamental to the next generation of condensed matter research and devices.
However, the material must be thin enough to avoid shielding of the electric
field in bulk material. Two-dimensional materials do not experience electrical
screening, and their charge carrier density can be controlled by gating. 1T
TiSe2 is a prototypical 2D material that shows charge density wave(CDW) and
superconductivity in its phase diagram, presenting several similarities with
other layered systems such as copper oxides, iron pnictides, crystals of
rare-earth and actinide atoms. By studying 1T TiSe2 single crystals with
thicknesses of 10 nm or less, encapsulated in 2D layers of hexagonal boron
nitride, we achieve unprecedented control over the CDW transition temperature,
tuned from 170 K to 40 K, and over the superconductivity transition
temperature, tuned from a quantum critical point at 0 K up to 3 K. Electrically
driving TiSe2 over different ordered electronic phases allows us to study the
details of the phase transitions between many-body states. Observations of
periodic oscillations of magnetoresistance induced by the Little Parks effect
show that the appearance of superconductivity is directly correlated to the
spatial texturing of the amplitude and phase of the superconductivity order
parameter, corresponding to a 2D matrix of superconductivity. We infer that
this superconductivity matrix is supported by a matrix of incommensurate CDW
states embedded in the commensurate CDW states. Our results show that spatially
modulated electronic states are fundamental to the appearance of 2D
superconductivity.

###Giant magnetoresistance and structure of electrodeposited Co/Cu multilayers: the influence of layer thicknesses and Cu deposition potential|N. Rajasekaran,J. Mani,B. G. Tóth,G. Molnár,S. Mohan,L. Péter,I. Bakonyi###

Giant magnetoresistance and structure of electrodeposited Co/Cu multilayers: the influence of layer thicknesses and Cu deposition potential. The giant magnetoresistance (GMR) and structure was investigated for
electrodeposited Co/Cu multilayers prepared by a conventional
galvanostatic/potentiostatic pulse combination from a pure sulfate electrolyte
with various layer thicknesses, total multilayer thickness and Cu deposition
potential. X-ray diffraction (XRD) measurements revealed superlattice satellite
reflections for many of the multilayers having sufficiently large thickness (at
least 2 nm) of both constituent layers. The bilayer repeats derived from the
positions of the visible superlattice reflections were typically 10-20% higher
than the nominal values.The observed GMR was found to be dominated by the
multilayer-like ferromagnetic (FM) contribution even for multilayers without
visible superlattice satellites. There was always also a modest
superparamagnetic (SPM) contribution to the GMR and this term was the largest
for multilayers with very thin (0.5 nm) magnetic layers containg apparently a
small amount of magnetically decoupled SPM regions. No oscillatory GMR behavior
with spacer thickness was observed at any magnetic layer thickness. The
saturation of the coercivity as measured by the peak position of the MR(H)
curves indicated a complete decoupling of magnetic layers for large spacer
thicknesses. The GMR increased with total multilayer thickness which could be
ascribed to an increasing SPM contribution to the GMR due to an increasing
surface roughness, also indicated by the increasing coercivity. For multilayers
with Cu layers deposited at more and more positive potentials, the GMRFM term
increased and the GMRSPM term decreased. At the same time, a corresponding
reduction of surface roughness measured with atomic force microscopy indicated
an improvement of the multilayer structural quality which was, however, not
accompanied by an increase of the superlattice reflection intensities.

###Quantum-interference transport through surface layers of indium-doped ZnO nanowires|Shao-Pin Chiu,Jia G. Lu,Juhn-Jong Lin###

Quantum-interference transport through surface layers of indium-doped ZnO nanowires. We have fabricated indium-doped ZnO (IZO) nanowires (NWs) and carried out
4-probe electrical-transport measurements at low temperatures. The NWs reveal
charge conduction behavior characteristic of disordered metals. In addition to
the $T$ dependence of resistance $R$, we have measured the magnetoresistances
(MR) in perpendicular and parallel magnetic fields. Our $R(T)$ and MR data in
different $T$ intervals are consistent with the theoretical predictions of the
one- (1D), two- (2D) or three-dimensional (3D) weak-localization (WL) and the
electron-electron interaction (EEI) effects. In particular, a few
dimensionality crossovers in the two effects are observed. These crossover
phenomena are consistent with the model of a "core-shell-like structure" in
individual IZO NWs, where an outer shell of a thickness $t$ ($\simeq$ 15-17 nm)
is responsible for the quantum-interference transport. In the WL effect, as the
electron dephasing length $L_\phi$ gradually decreases with increasing $T$ from
the lowest measurement temperatures, a 1D-to-2D dimensionality crossover takes
place around a characteristic temperature where $L_\phi$ approximately equals
$d$, an effective NW diameter which is slightly smaller than the geometric
diameter. As $T$ further increases, a 2D-to-3D dimensionality crossover occurs
around another characteristic temperature where $L_\phi$ approximately equals
$t$ ($< d$). In the EEI effect, a 2D-to-3D dimensionality crossover takes place
when the thermal diffusion length $L_T$ progressively decreases with increasing
$T$ and approaches $t$. However, a crossover to the 1D EEI effect is not seen
because $L_T < d$ even at $T$ = 1 K in our IZO NWs. Furthermore, we explain the
various inelastic electron scattering processes which govern $L_\phi$. This
work indicates that the surface-related conduction processes are essential to
doped semiconductor nanostructures.

###Strongly suppressed superconducting proximity effect and ferromagnetism in trilayers of $\rm Bi_2Se_3$ / $\rm SrRuO_3$ / underdoped $\rm YBa_2Cu_3O_x$: A possible new platform for Majorana nano-electronics|Gad Koren###

Strongly suppressed superconducting proximity effect and ferromagnetism in trilayers of $\rm Bi_2Se_3$ / $\rm SrRuO_3$ / underdoped $\rm YBa_2Cu_3O_x$: A possible new platform for Majorana nano-electronics. We report properties of topological insulator - ferromagnet - superconductor
trilayers comprised of thin films of 20 nm thick $\rm Bi_2Se_3$ on 10 nm $\rm
SrRuO_3$ on 30 nm $\rm YBa_2Cu_3O_x$. As deposited trilayers are underdoped and
have a superconductive transition with $\rm T_c$ onset at 75 K, zero resistance
at 65 K, $\rm T_{Cueri}$ at 150 K and $\rm T^*$ of about 200 K. Further
reannealing under vacuum yields the 60 K phase of $\rm YBa_2Cu_3O_x$ which
still has zero resistance below about 40 K. Only when $10\times 100$
micro-bridges were patterned in the trilayer, some of the bridges showed
resistive behavior all the way down to low temperatures. Magnetoresistance
versus temperature of the superconductive ones showed the typical peak due to
flux flow against pinning below $\rm T_c$, while the resistive ones showed only
the broad leading edge of such a peak. All this indicates clearly weak-link
superconductivity in the resistive bridges between superconductive $\rm
YBa_2Cu_3O_x$ grains via the topological and ferromagnetic cap layers.
Comparing our results to those of a reference trilayer with the topological
$\rm Bi_2Se_3$ layer substituted by a non-superconducting highly overdoped $\rm
La_{1.65}Sr_{0.35}CuO_4$, indicates that the superconductive proximity effect
as well as ferromagnetism in the topological trilayer are actually strongly
suppressed compared to the non-topological reference trilayer. This strong
suppression is likely to originate in strong proximity induced edge currents in
the SRO/YBCO layer that can lead to Majorana bound states, a possible signature
of which is observed in the present study as zero bias conductance peaks.

###Pure spin currents in magnetically ordered insulator/normal metal heterostructures|Matthias Althammer###

Pure spin currents in magnetically ordered insulator/normal metal heterostructures. Pure spin currents, i.e. the transport of angular momentum without an
accompanying charge current, represent a new, promising avenue in modern
spintronics from both a fundamental and an application point of view. Such pure
spin currents can not only flow in electrical conductors via mobile charge
carriers, but also in magnetically ordered electrical insulators as a flow of
spin excitation quanta. Over the course of the last years remarkable results
have been obtained in heterostructures consisting of magnetically ordered
insulators interfaced with a normal metal, where a pure spin current flows
across the interface. This topical review article deals with the fundamental
principles, experimental findings and recent developments in the field of pure
spin currents in magnetically ordered insulators. We here put our focus onto
four different manifestations of pure spin currents in such heterostructures:
The spin pumping effect, the longitudinal spin Seebeck effect, the spin Hall
magnetoresistance and the all-electrical detection of magnon transport in
non-local device concepts. In this article, we utilize a common theoretical
framework to explain all four effects and explain important material systems
(especially rare-earth iron garnets) used in the experiments. For each effect
we introduce basic measurement techniques and detection schemes and discuss
their application in the experiment. We account for the remarkable progress
achieved in each field by reporting the recent progress in each field and by
discussing research highlights obtained in our group. Finally, we conclude the
review article with an outlook on future challenges and obstacles in the field
of pure spin currents in magnetically ordered insulator / normal metal
heterostructures.

###Theory of Ultrafast Spin--Charge Quantum Dynamics in Strongly Correlated Systems Controlled by Femtosecond Photoexcitation: an Application to Insulating Antiferromagnetic Manganites|P. C. Lingos,M. D. Kapetanakis,M. Mootz,J. Wang,I. E. Perakis###

Theory of Ultrafast Spin--Charge Quantum Dynamics in Strongly Correlated Systems Controlled by Femtosecond Photoexcitation: an Application to Insulating Antiferromagnetic Manganites. We use a non-equilibrium many-body theory that engages the elements of
transient coherence, correlation, and nonlinearity to describe changes in the
magnetic and electronic phases of strongly correlated systems induced by
femtosecond nonlinear photoexcitation. Using a generalized tight--binding mean
field approach based on Hubbard operators and including the coupling of the
laser field, we describe a mechanism for simultaneous insulator--to--metal and
anti-- to ferro--magnetic transition to a transient state triggered by
non-thermal ultrafast spin and charge coupled excitations. We demontrate, in
particular, that photoexcitation of composite fermion quasiparticles induces
quasi-instantaneous spin canting that quenches the energy gap of the
antiferromagnetic insulator and acts as a nonadiabatic "initial condition" that
triggers non-thermal lattice dynamics leading to an insulator to metal and
antiferromagnetic (AFM) to ferromagnetic (FM) transitions. Our theoretical
predictions are consistent with recent ultrafast pump-probe spectroscopy
experiments that revealed a magnetic phase transition during 100fs laser pulse
photoexcitation of the CE--type AFM insulating phase of colossal
magnetoresistive manganites. In particular, experiment observes two distinct
charge relaxation components, fs and ps, with nonlinear threshold dependence at
a pump fluence threshold that coincides with that for femtosecond magnetization
photo excitation. Our theory attributes the correlation between femtosecond
spin and charge nonlinearity leading to transition in the magnetic and
electronic state to spin/charge/lattice coupling and laser-induced quantum spin
canting that accompanies the driven population inversion between two
quasi--particle bands with different properties: a mostly occupied polaronic
band and a mostly empty metallic band, whose dispersion is determined by
quantum spin canting.

###Signature of gate-tunable magnetism in graphene grafted with Pt-porphyrins|Chuan Li,Katsuyoshi Komatsu,G. Clave,S. Campidelli,A. Filoramo,S. Gueron,H. Bouchiat###

Signature of gate-tunable magnetism in graphene grafted with Pt-porphyrins. Inducing magnetism in graphene holds great promises, such as controlling the
exchange interaction with a gate electrode and generating exotic magnetic
phases. Coating graphene with magnetic molecules or atoms has so far mostly
lead to decreased graphene mobility. In the present work, we show that
Pt-porphyrins adsorbed on graphene lead to an enhanced mobility and to
gate-dependent magnetism. We report that porphyrins can be donor or acceptor,
depending on graphene s initial doping. The porphyrins transfer charge and
ionize around the charged impurities on graphene, decreasing the graphene
doping and increasing its mobility. In addition, ionized porphyrins carry a
magnetic moment. Using the sensitivity of mesoscopic transport to magnetism, in
particular the superconducting proximity effect and conductance fluctuations,
we explore the magnetic order induced in graphene by the interacting magnetic
moments of the ionized porphyrins. Among the signatures of magnetism, we find
two-terminal-magnetoresistance fluctuations with an odd component, a tell-tale
sign of time reversal symmetry breaking at zero field, that does not exist in
uncoated graphene sample. When graphene is connected to superconducting
electrodes, the induced magnetism leads to a gate-voltage-dependent suppression
of the supercurrent, modified magnetic interference patterns, and
gate-voltage-dependent magnetic hysteresis. The magnetic signatures are
greatest for long superconductor graphene superconductor junctions and for
samples with the highest initial doping, compatible with a greater number of
ionized and thus magnetic porphyrins. Our findings suggest that long-range
magnetism is induced through graphene by the ionized porphyrins magnetic
moment. This magnetic interaction is controlled by the density of carriers in
graphene, a tunability that could be exploited in spintronic applications.

###Signatures of localization in the effective metallic regime of high mobility Si MOSFETs|S. Das Sarma,E. H. Hwang,K. Kechedzhi,L. A. Tracy###

Signatures of localization in the effective metallic regime of high mobility Si MOSFETs. Combining experimental data, numerical transport calculations, and
theoretical analysis, we study the temperature-dependent resistivity of
high-mobility 2D Si MOSFETs to search for signatures of weak localization
induced quantum corrections in the effective metallic regime above the critical
density of the so-called two-dimensional metal-insulator transition (2D MIT).
The goal is to look for the effect of logarithmic insulating localization
correction to the metallic temperature dependence in the 2D conductivity so as
to distinguish between the 2D MIT being a true quantum phase transition versus
being a finite-temperature crossover. We use the Boltzmann theory of
resistivity including the temperature dependent screening effect on charged
impurities in the system to fit the data. We analyze weak perpendicluar field
magnetoresistance data taken in the vicinity of the transition and show that
they are consistent with weak localization behavior in the strongly disordered
regime $k_F\ell\gtrsim1$. Therefore we supplement the Botzmann transport theory
with a logarithmic in temperature quantum weak localization correction and
analyze the competition of the insulating temperature dependence of this
correction with the metallic temperature dependence of the Boltzmann
conductivity. Using this minimal theoretical model we find that the logarithmic
insulating correction is masked by the metallic temperature dependence of the
Botzmann resistivity and therefore the insulating $\log T$ behavior may be
apparent only at very low temperatures which are often beyond the range of
temperatures accessible experimentally. Analyzing the low-$T$ experimental Si
MOSFET transport data we identify signatures of the putative insulating
behavior at low temperature and density in the effective metallic phase.

###Strong anisotropy in nearly ideal-tetrahedral superconducting FeS single crystals|Christopher K. H. Borg,Xiuquan Zhou,Christopher Eckberg,Daniel J. Campbell,Shanta R. Saha,Johnpierre Paglione,Efrain E. Rodriguez###

Strong anisotropy in nearly ideal-tetrahedral superconducting FeS single crystals. We report the novel preparation of single crystals of tetragonal iron
sulfide, FeS, which exhibits a nearly ideal tetrahedral geometry with S--Fe--S
bond angles of 110.2(2) $^\circ$ and 108.1(2) $^\circ$. Grown via hydrothermal
de-intercalation of K${_x}$Fe${_{2-y}}$S${_2}$ crystals under basic and
reducing conditions, the silver, plate-like crystals of FeS remain stable up to
200 $^\circ$C under air and 250 $^\circ$C under inert conditions, even though
the mineral "mackinawite" (FeS) is known to be metastable. FeS single crystals
exhibit a superconducting state below $T_c=4$ K as determined by electrical
resistivity, magnetic susceptibility, and heat capacity measurements,
confirming the presence of a bulk superconducting state. Normal state
measurements yield an electronic specific heat of 5~mJ/mol-K$^2$, and
paramagnetic, metallic behavior with a low residual resistivity of
250~$\mu\Omega\cdot$cm. Magnetoresistance measurements performed as a function
of magnetic field angle tilted toward both transverse and longitudinal
orientations with respect to the applied current reveal remarkable
two-dimensional behavior. This is paralleled in the superconducting state,
which exhibits the largest known upper critical field $H_{c2}$ anisotropy of
all iron-based superconductors, with $H_{c2}^{||ab}(0) /
H_{c2}^{||c}(0)=$(2.75~T)/(0.275~T)=10. Comparisons to theoretical models for
2D and anisotropic-3D superconductors, however, suggest that FeS is the latter
case with a large effective mass anisotropy. We place FeS in context to other
closely related iron-based superconductors and discuss the role of structural
parameters such as anion height on superconductivity.

###Dynamic magnetic susceptibility and electrical detection of ferromagnetic resonance|Yin Zhang,X. S. Wang,H. Y. Yuan,S. S. Kang,H. W. Zhang,X. R. Wang###

Dynamic magnetic susceptibility and electrical detection of ferromagnetic resonance. The dynamic magnetic susceptibility of magnetic materials near ferromagnetic
resonance (FMR) is very important in interpreting dc-voltage in electrical
detection of FMR. Based on the causality principle and the assumption that the
usual microwave absorption lineshape around FMR is Lorentzian, general forms of
dynamic susceptibility of an arbitrary sample and the corresponding dc-voltage
lineshape are obtained. Our main findings are: 1) The dynamic susceptibility is
not a Polder tensor for material with arbitrary anisotropy. Two off-diagonal
elements are not in general opposite to each other. However, the linear
response coefficient of magnetization to total rf field is a Polder tensor.
This may explain why two off-diagonal elements are always assumed to be
opposite to each other in analyses. 2) The frequency dependence of dynamic
susceptibility near FMR is fully characterized by six numbers while its field
dependence is fully characterized by seven numbers. 3) A recipe of how to
determine these numbers by standard microwave absorption measurements for an
arbitrary sample is proposed. Our results allow one to unambiguously separate
the contribution of the anisotropic magnetoresistance to dc-voltage from that
of the anomalous Hall effect. With these results, one can reliably extract the
information of spin pumping and the inverse spin Hall effect, and determine the
spin-Hall angle. 4) The field-dependence of susceptibility matrix at a fixed
frequency may have several peaks when the effective field is not monotonic of
the applied field. In contrast, the frequency-dependence of susceptibility
matrix at a fixed field has only one peak. Furthermore, in the case that
resonance frequency is not sensitive to the applied field, the field dependence
of susceptibility matrix, as well as dc-voltage, may have another non-resonance
broad peak. Thus, one should be careful in interpreting observed peaks.

###Attractive and repulsive Fermi polarons in two dimensions|Marco Koschorreck,Daniel Pertot,Enrico Vogt,Bernd Fröhlich,Michael Feld,Michael Köhl###

Attractive and repulsive Fermi polarons in two dimensions. The dynamics of a single impurity in an environment is a fundamental problem
in many-body physics. In the solid state, a well-known case is an impurity
coupled to a bosonic bath, for example lattice vibrations. Here the impurity
together with its accompanying lattice distortion form a new entity, a polaron.
This quasiparticle plays an important role in the spectral function of high-Tc
superconductors as well as in colossal-magnetoresistance in manganites. For
impurities in a fermionic bath, the attention so far has been mostly on heavy
or immobile impurities which exhibit Anderson's orthogonality catastrophe and
the Kondo effect. Only recently, mobile impurities have moved into the focus of
research and they have been found to form new quasiparticles, so called Fermi
polarons. The Fermi polaron problem constitutes the extreme, but conceptually
simple, limit of two important quantum many-body problems: the BEC-BCS
crossover with spin-imbalance for attractive interactions and Stoner's
itinerant ferromagnetism for repulsive interactions. It has been proposed that
this and other yet elusive exotic quantum phases might become realizable in
Fermi gases confined to two dimensions. Their stability and observability is
intimately related to the theoretically debated properties of the Fermi polaron
in two dimensional Fermi gas. Here we create and investigate these Fermi
polarons and measure their spectral function using momentum-resolved
photoemission spectroscopy. For attractive interactions we find evidence for
the disputed pairing transition between polarons and tightly bound dimers,
which provides insight into the elementary pairing mechanism of imbalanced,
strongly-coupled two-dimensional Fermi gases. Additionally, for repulsive
interactions we study novel quasiparticles, repulsive polarons, whose lifetime
determine the possibility of stabilizing repulsively interacting Fermi systems.

###On/off switching of bit readout in bias-enhanced tunnel magneto-Seebeck effect|Alexander Boehnke,Marius Milnikel,Marvin Walter,Vladyslav Zbarsky,Christian Franz,Michael Czerner,Karsten Rott,Andy Thomas,Christian Heiliger,Markus Münzenberg,Günter Reiss###

On/off switching of bit readout in bias-enhanced tunnel magneto-Seebeck effect. Thermoelectric effects in magnetic tunnel junctions are currently an
attractive research topic. Here, we demonstrate that the tunnel magneto-Seebeck
effect (TMS) in CoFeB/MgO/CoFeB tunnel junctions can be switched on to a logic
1 state and off to 0 by simply changing the magnetic state of the CoFeB
electrodes. We enable this new functionality of magnetic tunnel junctions by
combining a thermal gradient and an electric field. This new technique unveils
the bias-enhanced tunnel magneto-Seebeck effect, which can serve as the basis
for logic devices or memories in a green information technology with a pure
thermal write and read process. Furthermore, the thermally generated voltages
that are referred to as the Seebeck effect are well known to sensitively depend
on the electronic structure and therefore have been valued in solid-state
physics for nearly one hundred years. Here, we lift Seebeck's historic
discovery from 1821 to a new level of current spintronics. Our results show
that the signal crosses zero and can be adjusted by tuning a bias voltage that
is applied between the electrodes of the junction; hence, the name of the
effect is bias-enhanced tunnel magneto-Seebeck effect (bTMS). Via the spin- and
energy-dependent transmission of electrons in the junction, the bTMS effect can
be configured using the bias voltage with much higher control than the tunnel
magnetoresistance (TMR) and even completely suppressed for only one magnetic
configuration, which is either parallel (P) or anti-parallel (AP). This option
allows a readout contrast for the magnetic information of -3000% at room
temperature while maintaining a large signal for one magnetic orientation. This
contrast is much larger than the value that can be obtained using the TMR
effect. Moreover, our measurements are a step towards the experimental
realization of high TMS ratios, which are predicted for specific Co-Fe
compositions.

###Magnetotransport in Double Quantum Well with Inverted Energy Spectrum: HgTe/CdHgTe|M. V. Yakunin,A. V. Suslov,M. R. Popov,E. G. Novik,S. A. Dvoretsky,N. N. Mikhailov###

Magnetotransport in Double Quantum Well with Inverted Energy Spectrum: HgTe/CdHgTe. We present the first experimental study of the double-quantum-well (DQW)
system made of 2D layers with inverted energy band spectrum: HgTe. The
magnetotransport reveals a considerably larger overlap of the conduction and
valence subbands than in known HgTe single quantum wells (QW), which may be
regulated by an applied gate voltage $V_g$. This large overlap manifests itself
in a much higher critical field $B_c$ separating the range above it where the
quantum peculiarities shift linearly with $V_g$ and the range below with a
complicated behavior. In the latter case the $N$-shaped and double-$N$-shaped
structures in the Hall magnetoresistance $\rho_{xy}(B)$ are observed with their
scale in field pronouncedly enlarged as compared to the pictures observed in an
analogous single QW. The coexisting electrons and holes were found in the whole
investigated range of positive and negative $V_g$ as revealed from fits to the
low-field $N$-shaped $\rho_{xy}(B)$ and from the Fourier analysis of
oscillations in $\rho_{xx}(B)$. A peculiar feature here is that the found
electron density $n$ remains almost constant in the whole range of investigated
$V_g$ while the hole density $p$ drops down from the value a factor of 6 larger
than $n$ at extreme negative $V_g$ to almost zero at extreme positive $V_g$
passing through the charge neutrality point. We show that this difference
between $n$ and $p$ stems from an order of magnitude larger density of states
for holes in the lateral valence band maxima than for electrons in the
conduction band minimum. We interpret the observed reentrant sign-alternating
$\rho_{xy}(B)$ between electronic and hole conductivities and its zero
resistivity state in the quantum Hall range of fields on the basis of a
calculated picture of magnetic levels in a DQW.

###Spectroscopic Evidence of Type II Weyl Semimetal State in WTe2|Chenlu Wang,Yan Zhang,Jianwei Huang,Simin Nie,Guodong Liu,Aiji Liang,Yuxiao Zhang,Bing Shen,Jing Liu,Cheng Hu,Ying Ding,Defa Liu,Yong Hu,Shaolong He,Lin Zhao,Li Yu,Jin Hu,Jiang Wei,Zhiqiang Mao,Youguo Shi,Xiaowen Jia,Fengfeng Zhang,Shenjin Zhang,Feng Yang,Zhimin Wang,Qinjun Peng,Hongming Weng,Xi Dai,Zhong Fang,Zuyan Xu,Chuangtian Chen,X. J. Zhou###

Spectroscopic Evidence of Type II Weyl Semimetal State in WTe2. Quantum topological materials, exemplified by topological insulators,
three-dimensional Dirac semimetals and Weyl semimetals, have attracted much
attention recently because of their unique electronic structure and physical
properties. Very lately it is proposed that the three-dimensional Weyl
semimetals can be further classified into two types. In the type I Weyl
semimetals, a topologically protected linear crossing of two bands, i.e., a
Weyl point, occurs at the Fermi level resulting in a point-like Fermi surface.
In the type II Weyl semimetals, the Weyl point emerges from a contact of an
electron and a hole pocket at the boundary resulting in a highly tilted Weyl
cone. In type II Weyl semimetals, the Lorentz invariance is violated and a
fundamentally new kind of Weyl Fermions is produced that leads to new physical
properties. WTe2 is interesting because it exhibits anomalously large
magnetoresistance. It has ignited a new excitement because it is proposed to be
the first candidate of realizing type II Weyl Fermions. Here we report our
angle-resolved photoemission (ARPES) evidence on identifying the type II Weyl
Fermion state in WTe2. By utilizing our latest generation laser-based ARPES
system with superior energy and momentum resolutions, we have revealed a full
picture on the electronic structure of WTe2. Clear surface state has been
identified and its connection with the bulk electronic states in the momentum
and energy space shows a good agreement with the calculated band structures
with the type II Weyl states. Our results provide spectroscopic evidence on the
observation of type II Weyl states in WTe2. It has laid a foundation for
further exploration of novel phenomena and physical properties in the type II
Weyl semimetals.

###On the search for the chiral anomaly in Weyl semimetals: The negative longitudinal magnetoresistance|R. D. dos Reis,M. O. Ajeesh,N. Kumar,F. Arnold,C. Shekhar,M. Naumann,M. Schmidt,M. Nicklas,E. Hassinger###

On the search for the chiral anomaly in Weyl semimetals: The negative longitudinal magnetoresistance. Recently, the existence of massless chiral (Weyl) fermions has been
postulated in a class of semi-metals with a non-trivial energy dispersion.These
materials are now commonly dubbed Weyl semi-metals (WSM).One predicted property
of Weyl fermions is the chiral or Adler-Bell-Jackiw anomaly, a chirality
imbalance in the presence of parallel magnetic and electric fields. In WSM, it
is expected to induce a negative longitudinal magnetoresistance (NMR), the
chiral magnetic effect.Here, we present experimental evidence that the
observation of the chiral magnetic effect can be hindered by an effect called
"current jetting". This effect also leads to a strong apparent NMR, but it is
characterized by a highly non-uniform current distribution inside the sample.
It appears in materials possessing a large field-induced anisotropy of the
resistivity tensor, such as almost compensated high-mobility semimetals due to
the orbital effect.In case of a non-homogeneous current injection, the
potential distribution is strongly distorted in the sample.As a consequence, an
experimentally measured potential difference is not proportional to the
intrinsic resistance.Our results on the MR of the WSM candidate materials NbP,
NbAs, TaAs, TaP exhibit distinct signatures of an inhomogeneous current
distribution, such as a field-induced "zero resistance' and a strong dependence
of the `measured resistance" on the position, shape, and type of the voltage
and current contacts on the sample. A misalignment between the current and the
magnetic-field directions can even induce a "negative resistance".
Finite-element simulations of the potential distribution inside the sample,
using typical resistance anisotropies, are in good agreement with the
experimental findings. Our study demonstrates that great care must be taken
before interpreting measurements of a NMR as evidence for the chiral anomaly in
putative Weyl semimetals.

###Proximity band structure and spin textures on both sides of topological-insulator/ferromagnetic-metal interface and their transport probes|J. M. Marmolejo-Tejada,K. Dolui,P. Lazic,P. -H. Chang,S. Smidstrup,D. Stradi,K. Stokbro,B. K. Nikolic###

Proximity band structure and spin textures on both sides of topological-insulator/ferromagnetic-metal interface and their transport probes. The control of recently observed spintronic effects in
topological-insulator/ferromagnetic-metal (TI/FM) heterostructures is thwarted
by the lack of understanding of band structure and spin texture around their
interfaces. Here we combine density functional theory with Green's function
techniques to obtain the spectral function at any plane passing through atoms
of Bi$_2$Se$_3$ and Co or Cu layers comprising the interface. In contrast to
widely assumed but thinly tested Dirac cone gapped by the proximity exchange
field, we find that the Rashba ferromagnetic model describes the spectral
function on the surface of Bi$_2$Se$_3$ in contact with Co near the Fermi level
$E_F^0$, where circular and snowflake-like constant energy contours coexist
around which spin locks to momentum. The remnant of the Dirac cone is
hybridized with evanescent wave functions injected by metallic layers and
pushed, due to charge transfer from Co or Cu layers, few tenths of eV below
$E_F^0$ for both Bi$_2$Se$_3$/Co and Bi$_2$Se$_3$/Cu interfaces while hosting
distorted helical spin texture wounding around a single circle. These features
explain recent observation [K. Kondou {\em et al.}, Nat. Phys. {\bf 12}, 1027
(2016)] of sensitivity of spin-to-charge conversion signal at TI/Cu interface
to tuning of $E_F^0$. Interestingly, three monolayers of Co adjacent to
Bi$_2$Se$_3$ host spectral functions very different from the bulk metal, as
well as in-plane spin textures signifying the spin-orbit proximity effect. We
predict that out-of-plane tunneling anisotropic magnetoresistance in vertical
heterostructure Cu/Bi$_2$Se$_3$/Co, where current flowing perpendicular to its
interfaces is modulated by rotating magnetization from parallel to orthogonal
to current flow, can serve as a sensitive probe of spin texture residing at
$E_F^0$.

###Universal response of the type-II Weyl semimetals phase diagram|P. Rüßmann,A. P. Weber,F. Glott,N. Xu,M. Fanciulli,S. Muff,A. Magrez,P. Bugnon,H. Berger,M. Bode,J. H. Dil,S. Blügel,P. Mavropoulos,P. Sessi###

Universal response of the type-II Weyl semimetals phase diagram. The discovery of Weyl semimetals represents a significant advance in
topological band theory. They paradigmatically enlarged the classification of
topological materials to gapless systems while simultaneously providing
experimental evidence for the long-sought Weyl fermions. Beyond fundamental
relevance, their high mobility, strong magnetoresistance, and the possible
existence of even more exotic effects, such as the chiral anomaly, make Weyl
semimetals a promising platform to develop radically new technology. Fully
exploiting their potential requires going beyond the mere identification of
materials and calls for a detailed characterization of their functional
response, which is severely complicated by the coexistence of surface- and
bulk-derived topologically protected quasiparticles, i.e., Fermi arcs and Weyl
points, respectively. Here, we focus on the type-II Weyl semimetal class where
we find a stoichiometry-dependent phase transition from a trivial to a
non-trivial regime. By exploring the two extreme cases of the phase diagram, we
demonstrate the existence of a universal response of both surface and bulk
states to perturbations. We show that quasi-particle interference patterns
originate from scattering events among surface arcs. Analysis reveals that
topologically non-trivial contributions are strongly suppressed by spin
texture. We also show that scattering at localized impurities generate
defect-induced quasiparticles sitting close to the Weyl point energy. These
give rise to strong peaks in the local density of states, which lift the Weyl
node significantly altering the pristine low-energy Weyl spectrum. Visualizing
the microscopic response to scattering has important consequences for
understanding the unusual transport properties of this class of materials.
Overall, our observations provide a unifying picture of the Weyl phase diagram.

###Detailed study on the Fermi surfaces of the type-II Dirac semimetallic candidates PdTe2 and PtTe2|W. Zheng,R. Schönemann,N. Aryal,Q. Zhou,D. Rhodes,Y. -C. Chiu,K. -W. Chen,E. Kampert,T. Förster,T. J. Martin,G. T. McCandless,J. Y. Chan,E. Manousakis,L. Balicas###

Detailed study on the Fermi surfaces of the type-II Dirac semimetallic candidates PdTe2 and PtTe2. We present a detailed quantum oscillatory study on the Dirac type-II
semimetallic candidates PdTe$_{2}$ and PtTe$_{2}$ \emph{via} the temperature
and the angular dependence of the de Haas-van Alphen (dHvA) and Shubnikov-de
Haas (SdH) effects. In high quality single crystals of both compounds, i.e.
displaying carrier mobilities between $10^3$ and $10^4$ cm$^2$/Vs, we observed
a large non-saturating magnetoresistivity (MR) which in PtTe$_2$ at a
temperature $T = 1.3$ K, leads to an increase in the resistivity up to $5
\times 10^{4}$ % under a magnetic field $\mu_0 H = 62$ T. These high mobilities
correlate with their light effective masses in the range of 0.04 to 1 bare
electron mass according to our measurements. For PdTe$_{2}$ the experimentally
determined Fermi surface cross-sectional areas show an excellent agreement with
those resulting from band-structure calculations. Surprisingly, this is not the
case for PtTe$_{2}$ whose agreement between calculations and experiments is
relatively poor even when electronic correlations are included in the
calculations. Therefore, our study provides a strong support for the existence
of a Dirac type-II node in PdTe$_2$ and probably also for PtTe$_2$. Band
structure calculations indicate that the topologically non-trivial bands of
PtTe$_2$ do not cross the Fermi-level ($\varepsilon_F$). In contrast, for
PdTe$_2$ the Dirac type-II cone does intersect $\varepsilon_F$, although our
calculations also indicate that the associated cyclotron orbit on the Fermi
surface is located in a distinct $k_z$ plane with respect to the one of the
Dirac type-II node. Therefore it should yield a trivial Berry-phase.

###Spin-orbit driven band inversion in bilayer graphene by van der Waals proximity effect|J. O. Island,X. Cui,C. Lewandowski,J. Y. Khoo,E. M. Spanton,H. Zhou,D. Rhodes,J. C. Hone,T. Taniguchi,K. Watanabe,L. S. Levitov,M. P. Zaletel,A. F. Young###

Spin-orbit driven band inversion in bilayer graphene by van der Waals proximity effect. Spin orbit coupling (SOC) is the key to realizing time-reversal invariant
topological phases of matter. Famously, SOC was predicted by Kane and Mele to
stabilize a quantum spin Hall insulator; however, the weak intrinsic SOC in
monolayer graphene has precluded experimental observation. Here, we exploit a
layer-selective proximity effect---achieved via van der Waals contact to a
semiconducting transition metal dichalcogenide--to engineer Kane-Mele SOC in
ultra-clean \textit{bilayer} graphene. Using high-resolution capacitance
measurements to probe the bulk electronic compressibility, we find that SOC
leads to the formation of a distinct incompressible, gapped phase at charge
neutrality. The experimental data agrees quantitatively with a simple
theoretical model in which the new phase results from SOC-driven band
inversion. In contrast to Kane-Mele SOC in monolayer graphene, the inverted
phase is not expected to be a time reversal invariant topological insulator,
despite being separated from conventional band insulators by electric field
tuned phase transitions where crystal symmetry mandates that the bulk gap must
close. Electrical transport measurements, conspicuously, reveal that the
inverted phase has a conductivity $\sim e^2/h$, which is suppressed by
exceptionally small in-plane magnetic fields. The high conductivity and
anomalous magnetoresistance are consistent with theoretical models that predict
helical edge states within the inversted phase, that are protected from
backscattering by an emergent spin symmetry that remains robust even for large
Rashba SOC. Our results pave the way for proximity engineering of strong
topological insulators as well as correlated quantum phases in the strong
spin-orbit regime in graphene heterostructures.

###Fascinating interplay between Charge Density Wave Order and magnetic field in Non-magnetic Rare-Earth Tritelluride LaTe$_{3}$|Arnab Pariari,Sudipta Koley,Shubhankar Roy,Ratnadwip Singha,Mukul S. Laad,A. Taraphder,Prabhat Mandal###

Fascinating interplay between Charge Density Wave Order and magnetic field in Non-magnetic Rare-Earth Tritelluride LaTe$_{3}$. Charge density wave (CDW) states in solids bear an intimate connection to
underlying fermiology. Modification of the latter by a suitable perturbation
provides an attractive handle to unearth novel CDW states. Here, we combine
extensive magnetotransport experiments and first-principles electronic
structure calculations on a non-magnetic tritelluride LaTe$_{3}$ single crystal
to uncover phenomena rare in CDW systems: $(i)$ hump-like feature in the
temperature dependence of resistivity at low temperature under application of
magnetic field, which moves to higher temperature with increasing field
strength, $(ii)$ highly anisotropic large transverse magnetoresistance (MR)
upon rotation of magnetic field about current parallel to crystallographic
c-axis, (iii) anomalously large positive MR with spike-like peaks at
characteristic angles when the angle between current and field is varied in the
bc-plane, (iv) extreme sensitivity of the angular variation of MR on field and
temperature. Moreover, our Hall measurement reveals remarkably high carrier
mobility $\sim$ 33000 cm$^{2}$/Vs, which is comparable to that observed in some
topological semimetals. These novel observations find a comprehensive
explication in our density functional theory (DFT) and dynamical mean field
theory (DMFT) calculations that capture field-induced electronic structure
modification in LaTe$_{3}$. The band structure theory together with transport
calculations suggest the possibility of a second field-induced CDW transition
from the field-reconstructed Fermi surface, which qualitatively explains the
hump in temperature dependence of resistivity at low temperature. Thus, our
study exposes the novel manifestations of the interplay between CDW order and
field-induced electronic structure modifications in LaTe$_{3}$, and establishes
a new route to tune CDW states by perturbations like magnetic field.

###Influence of Pr substitution on physical properties of Ce$_{1-x}$Pr$_x$CoGe$_3$ system: A combined experimental and first-principles study|P. Skokowski,K. Synoradzki,M. Werwiński,A. Bajorek,G. Chełkowska,T. Toliński###

Influence of Pr substitution on physical properties of Ce$_{1-x}$Pr$_x$CoGe$_3$ system: A combined experimental and first-principles study. We present the results of our investigations of physical properties for the
novel Ce$_{1-x}$Pr$_x$CoGe$_3$ system performed with a number of experimental
methods: magnetic susceptibility, specific heat, electrical resistivity,
magnetoresistance, and thermoelectric power. Moreover, the electronic structure
was studied by means of photoelectron spectroscopy measurements and
first-principles calculations. All investigated compositions of the
Ce$_{1-x}$Pr$_x$CoGe$_3$ series crystallize in the tetragonal BaNiSn$_3$-type
structure. The lattice parameters and unit cell volumes decrease with
increasing Pr concentration. On the basis of the measurements taken, a
preliminary magnetic phase diagram was created. A continuous suppression of the
long-range magnetic ordering was observed with increase of Pr concentration.
The critical Pr concentration for magnetic moment ordering was determined from
linear extrapolation of the ordering temperature $versus$ $x$ to the lowest
temperatures ($T = 0$ K) and is equal to about 0.66. Based on the
first-principles calculations we show how the substitution of Pr for Ce affects
the electronic structure and magnetic properties of the considered alloys.
Within a single model we take into account the magnetic ordering,
fully-relativistic effects, and Hubbard U repulsion on Ce and Pr. The impact of
Hubbard U on the results of calculations is also discussed. We present the
valence-band analysis, Mulliken electronic population analysis, and calculated
electronic specific heat coefficients. For CeCoGe$_3$ it is found that the
$++--$ configuration of magnetic moments on Ce is slightly more stable than the
$+-+-$ one, and also that the calculated value of total magnetic moment on Ce
(including spin and orbital parts) is in good agreement with the measurements.

###Transport and superconducting properties of Fe-based superconductors: SmFeAs(O1-x Fx) versus Fe1+y (Te1-x, Sex)|M. Tropeano,I. Pallecchi,M. R. Cimberle,C. Ferdeghini,G. Lamura,M. Vignolo,A. Martinelli,A. Palenzona,M. Putti###

Transport and superconducting properties of Fe-based superconductors: SmFeAs(O1-x Fx) versus Fe1+y (Te1-x, Sex). We present transport and superconducting properties - namely resistivity,
magnetoresistivity, Hall effect, Seebeck effect, thermal conductivity, upper
critical field - of two different families of Fe-based superconductors, which
can be viewed in many respects as end members: SmFeAs(O1-xFx) with the largest
Tc and the largest anisotropy and Fe1+y(Te1-x,Sex), with the largest Hc2, the
lowest Tc and the lowest anisotropy. In the case of the SmFeAs(O1-xFx) series,
we find that a single band description allows to extract an approximated
estimation of band parameters such as carrier density and mobility from
experimental data, although the behaviour of Seebeck effect as a function of
doping demonstrates that a multiband description would be more appropriate. On
the contrary, experimental data of the Fe1+y(Te1-x,Sex) series exhibit a
strongly compensated behaviour, which can be described only within a multiband
model. In the Fe1+y(Te1-x,Sex) series, the role of the excess Fe, tuned by Se
stoichiometry, is found to be twofold: it dopes electrons in the system and it
introduces localized magnetic moments, responsible for Kondo like scattering
and likely pair-breaking of Cooper pairs. Hence, excess Fe plays a crucial role
also in determining superconducting properties such as the Tc and the upper
critical field Bc2. The huge Bc2 values of the Fe1+y(Te1-x,Sex) samples are
described by a dirty limit law, opposed to the clean limit behaviour of the
SmFeAs(O1-xFx) samples. Hence, magnetic scattering by excess Fe seems to drive
the system in the dirty regime, but its detrimental pairbreaking role seems not
to be as severe as predicted by theory. This issue has yet to be clarified,
addressing the more fundamental issue of the interplay between magnetism and
superconductivity.

###Kondo effect and absence of quantum interference effects in the charge transport of cobalt doped iron pyrite|S. Guo,D. P. Young,R. T. Macaluso,D. A. Browne,N. L. Henderson,J. Y. Chan,L. L. Henry,J. F. DiTusa###

Kondo effect and absence of quantum interference effects in the charge transport of cobalt doped iron pyrite. The Hall effect and resistivity of the carrier doped magnetic semiconductor
Fe$_{1-x}$Co$_x$S$_2$ were measured for $0\le x \le 0.16$, temperatures between
0.05 and 300 K, and fields of up to 9 T. Our Hall data indicate electron charge
carriers with a density of only 10 to 30% of the Co density of our crystals.
Despite the previous identification of magnetic Griffiths phase formation in
the magnetic and thermodynamic properties of this system for the same range of
$x$, we measure a temperature independent resistivity below 0.5 K indicating
Fermi liquid-like transport. We also observe no indication of quantum
corrections to the conductivity despite the small values of the product of the
Fermi wave vector and the mean-free-path, $1.5 \le k_F\ell \le 15$, over the
range of $x$ investigated. This implies a large inelastic scattering rate such
that the necessary condition for the observation of quantum contributions to
the carrier transport, quantum coherence over times much longer than the
elastic scattering time, is not met in our samples. Above 0.5 K we observe a
temperature and magnetic field dependent resistivity that closely resembles a
Kondo anomaly for $x$ less than that required to form a long range magnetic
state, $x_c$. For $x>x_c$, the resistivity and magnetoresistance resemble that
of a spin glass with a reduction of the resistivity by as much as 35% in 5 T
fields. We also observe an enhancement of the residual resistivity ratio by
almost a factor of 2 for samples with $x\sim x_c$ indicating temperature
dependent scattering mechanisms beyond simple carrier-phonon scattering. We
speculate that this enhancement is due to charge carrier scattering from
magnetic fluctuations which contribute to the resistivity over a wide
temperature range.

###Room-temperature antiferromagnetic memory resistor|X. Marti,I. Fina,C. Frontera,Jian Liu,P. Wadley,Q. He,R. J. Paull,J. D. Clarkson,J. Kudrnovský,I. Turek,J. Kuneš,D. Yi,J. -H. Chu,C. T. Nelson,L. You,E. Arenholz,S. Salahuddin,J. Fontcuberta,T. Jungwirth,R. Ramesh###

Room-temperature antiferromagnetic memory resistor. The bistability of ordered spin states in ferromagnets (FMs) provides the
magnetic memory functionality. Traditionally, the macroscopic moment of ordered
spins in FMs is utilized to write information on magnetic media by a weak
external magnetic field, and the FM stray field is used for reading. However,
the latest generation of magnetic random access memories demonstrates a new
efficient approach in which magnetic fields are replaced by electrical means
for reading and writing. This concept may eventually leave the sensitivity of
FMs to magnetic fields as a mere weakness for retention and the FM stray fields
as a mere obstacle for high-density memory integration. In this paper we report
a room-temperature bistable antiferromagnetic (AFM) memory which produces
negligible stray fields and is inert in strong magnetic fields. We use a
resistor made of an FeRh AFM whose transition to a FM order 100 degrees above
room-temperature, allows us to magnetically set different collective directions
of Fe moments. Upon cooling to room-temperature, the AFM order sets in with the
direction the AFM moments pre-determined by the field and moment direction in
the high temperature FM state. For electrical reading, we use an
antiferromagnetic analogue of the anisotropic magnetoresistance (AMR). We
report microscopic theory modeling which confirms that this archetypical
spintronic effect discovered more than 150 years ago in FMs, can be equally
present in AFMs. Our work demonstrates the feasibility to realize
room-temperature spintronic memories with AFMs which greatly expands the
magnetic materials base for these devices and offers properties which are
unparalleled in FMs.

###Using rf voltage induced ferromagnetic resonance to study the spin-wave density of states and the Gilbert damping in perpendicularly magnetized disks|T. Devolder###

Using rf voltage induced ferromagnetic resonance to study the spin-wave density of states and the Gilbert damping in perpendicularly magnetized disks. We study how the shape of the spinwave resonance lines in rf-voltage induced
FMR can be used to extract the spinwave density of states and the damping
within the precessing layer in nanoscale tunnel junctions that possess
perpendicular anisotropy. We work with a field applied along the easy axis to
preserve the uniaxial symmetry of the system. We describe the set-up to study
the susceptibility contributions of the spin waves in the field-frequency
space. We then identify the maximum device size above which the spinwaves can
no longer be studied in isolation as the linewidths of their responses make
them overlap. The rf-voltage induced signal is the sum of two voltages that
have comparable magnitudes: a first voltage that originates from the transverse
susceptibility and rectification by magnetoresistance and a second voltage that
arises from the non-linear longitudinal susceptibility and the resultant
time-averaged change of the micromagnetic configuration. The transverse and
longitudinal susceptibility signals have different dc bias dependences such
that they can be separated by measuring how the device rectifies the rf voltage
at different dc bias voltages. The transverse and longitudinal susceptibility
signals have different lineshapes; their joint studies can yield the Gilbert
damping of the free layer of the device with a degree of confidence that
compares well with standard FMR. Our method is illustrated on FeCoB-based free
layers in which the individual spin-waves can be sufficiently resolved only for
disk diameters below 200 nm. The resonance line shapes on devices with 90 nm
diameters are consistent with a Gilbert damping of 0.011. This damping of 0.011
exceeds the value of 0.008 measured on the unpatterned films, which indicates
that device-level measurements are needed for a correct evaluation of
dissipation.

###Heterointerface effects in the electro-intercalation of van der Waals heterostructures|D. Kwabena Bediako,Mehdi Rezaee,Hyobin Yoo,Daniel T. Larson,Shu Yang Frank Zhao,Takashi Taniguchi,Kenji Watanabe,Tina L. Brower-Thomas,Efthimios Kaxiras,Philip Kim###

Heterointerface effects in the electro-intercalation of van der Waals heterostructures. Molecular-scale manipulation of electronic/ionic charge accumulation in
materials is a preeminent challenge, particularly in electrochemical energy
storage. Layered van der Waals (vdW) crystals exemplify a diverse family of
materials that permit ions to reversibly associate with a host atomic lattice
by intercalation into interlamellar gaps. Motivated principally by the search
for high-capacity battery anodes, ion intercalation in composite materials is a
subject of intense study. Yet the precise role and ability of heterolayers to
modify intercalation reactions remains elusive. Previous studies of vdW hybrids
represented ensemble measurements at macroscopic films/powders, which do not
permit the isolation and investigation of the chemistry at individual
2-dimensional (2D) interfaces. Here, we demonstrate the intercalation of
lithium at the level of individual atomic interfaces of dissimilar vdW layers.
Electrochemical devices based on vdW heterostructures comprised of
deterministically stacked hexagonal boron nitride, graphene (G) and molybdenum
dichalcogenide (MoX2; X = S, Se) layers are fabricated, enabling the direct
resolution of intermediate stages in the intercalation of discrete
heterointerfaces and the extent of charge transfer to individual layers.
Operando magnetoresistance and optical spectroscopy coupled with
low-temperature quantum magneto-oscillation measurements show that the creation
of intimate vdW heterointerfaces between G and MoX2 engenders over 10-fold
accumulation of charge in MoX2 compared to MoX2/MoX2 homointerfaces, while
enforcing a more negative intercalation potential than that of bulk MoX2 by at
least 0.5 V. Beyond energy storage, our new combined experimental and
computational methodology to manipulate and characterize the electrochemical
behavior of layered systems opens up new pathways to control the charge density
in 2D (opto)electronic devices.

###Growth, electrical, structural, and magnetic properties of half-Heusler CoTi$_{1-x}$Fe$_x$Sb|Sean D. Harrington,Anthony D. Rice,Tobias Brown-Heft,Bastien Bonef,Abhishek Sharan,Anthony P. McFadden,John A. Logan,Mihir Pendharkar,Mayer M. Feldman,Ozge Mercan,Andre G. Petukhov,Anderson Janotti,Leyla Çolakerol Arslan,Chris J. Palmstrøm###

Growth, electrical, structural, and magnetic properties of half-Heusler CoTi$_{1-x}$Fe$_x$Sb. Epitaxial thin films of the substitutionally alloyed half-Heusler series
CoTi$_{1-x}$Fe$_x$Sb were grown by molecular beam epitaxy on InAlAs/InP(001)
substrates for concentrations 0.0$\leq$x$\leq$1.0. The influence of Fe on the
structural, electronic, and magnetic properties was studied and compared to
that expected from density functional theory. The films are epitaxial and
single crystalline, as measured by reflection high-energy electron diffraction
and X-ray diffraction. Using in-situ X-ray photoelectron spectroscopy, only
small changes in the valence band are detected for x$\leq$0.5. For films with
x$\geq$0.05, ferromagnetism is observed in SQUID magnetometry with a saturation
magnetization that scales linearly with Fe content. A dramatic decrease in the
magnetic moment per formula unit occurs when the Fe is substitutionally alloyed
on the Co site indicating a strong dependence on the magnetic moment with site
occupancy. A crossover from both in-plane and out-of-plane magnetic moments to
only in-plane moment occurs for higher concentrations of Fe. Ferromagnetic
resonance indicates a transition from weak to strong interaction with a
reduction in inhomogeneous broadening as Fe content is increased.
Temperature-dependent transport reveals a semiconductor to metal transition
with thermally activated behavior for x$\leq$0.5. Anomalous Hall effect and
large negative magnetoresistance (up to -18.5% at 100 kOe for x=0.3) are
observed for higher Fe content films. Evidence of superparamagnetism for x=0.3
and x=0.2 suggests for moderate levels of Fe, demixing of the
CoTi$_{1-x}$Fe$_x$Sb films into Fe rich and Fe deficient regions may be
present. Atom probe tomography is used to examine the Fe distribution in a
x=0.3 film. Statistical analysis reveals a nonhomogeneous distribution of Fe
atoms throughout the film, which is used to explain the observed magnetic and
electrical behavior.

###SMART: Secure Magnetoelectric AntifeRromagnet-Based Tamper-Proof Non-Volatile Memory|Nikhil Rangarajan,Satwik Patnaik,Johann Knechtel,Ozgur Sinanoglu,Shaloo Rakheja###

SMART: Secure Magnetoelectric AntifeRromagnet-Based Tamper-Proof Non-Volatile Memory. The storage industry is moving toward emerging non-volatile memories (NVMs),
including the spin-transfer torque magnetoresistive random-access memory
(STT-MRAM) and the phase-change memory (PCM), owing to their high density and
low-power operation. In this paper, we demonstrate, for the first time, circuit
models and performance benchmarking for the domain wall (DW) reversal-based
magnetoelectric-antiferromagnetic random access memory (ME-AFMRAM) at
cell-level and at array-level. We also provide perspectives for coherent
rotation-based memory switching with topological insulator-driven anomalous
Hall read-out. In the coherent rotation regime, the ultra-low power
magnetoelectric switching coupled with the terahertz-range antiferromagnetic
dynamics result in substantially lower energy-per-bit and latency metrics for
the ME-AFMRAM compared to other NVMs including STTMRAM and PCM. After
characterizing the novel ME-AFMRAM, we leverage its unique properties to build
a dense, on-chip, secure NVM platform, called SMART: A Secure Magnetoelectric
Antiferromagnet- Based Tamper-Proof Non-Volatile Memory. New NVM technologies
open up challenges and opportunities from a data-security perspective. For
example, their sensitivity to magnetic fields and temperature fluctuations, and
their data remanence after power-down make NVMs vulnerable to data theft and
tampering attacks. The proposed SMART memory is not only resilient against data
confidentiality attacks seeking to leak sensitive information but also ensures
data integrity and prevents Denial-of-Service (DoS) attacks on the memory. It
is impervious to particular power side-channel (PSC) attacks which exploit
asymmetric read/write signatures for 0 and 1 logic levels, and photonic
side-channel attacks which monitor photo-emission signatures from the chip
backside.

###Relativistic Mechanism of Chiral Magnetic Current in Weyl Semimetals with Tilted Dispersion|Zaur Z. Alisultanov###

Relativistic Mechanism of Chiral Magnetic Current in Weyl Semimetals with Tilted Dispersion. The chiral magnetic effect is a one of the exotic bulk transport properties
of the Weyl semimetals. Because of the Nielsen-Ninomiya "no-go theorem", the
total chiral magnetic current is absent in the equilibrium state. One of the
mechanisms for generating this current is the chiral anomaly. This phenomenon
is the anomalous nonconservation of chiral charge for massless relativistic
particles. It can be realized by parallel magnetic and electric fields, and it
leads to such new transport phenomenon as the negative longitudinal
magnetoresistance. Using a simple theory (we consider both linearized and
lattice model), we have shown, that in Weyl metals with tilted dispersion
another mechanism of the chiral magnetic current is possible. It is not
associated with the chiral anomaly. The new transport mechanism is based on the
relativistic effect of electric field on Landau levels. This effect is that an
electric field changes the distance between the Landau levels, and also changes
the effective velocity along magnetic field. At presence of a tilt in the
spectrum, this velocity renormalization is differ for different Weyl points.
This leads to a non-zero resulting drift velocity. As a consequence, an
electrical current arises along the magnetic field. The induced by this
mechanism the electric current is proportional to the pseudoscalar product of
the fields and directed along the magnetic field, that differs it from the Hall
current. At the same time, the conductivity corresponding to this transport
mechanism does not depend on the scattering time like the Hall conductivity.
Thus, we have proposed a new anomalous transport mechanism in the Weyl
semimetal, which is not associated with the chiral anomaly.

###CPP Magnetoresistance of Magnetic Multilayers: A critical review|Jack Bass###

CPP Magnetoresistance of Magnetic Multilayers: A critical review. We present a comprehensive review of data and analysis of Giant (G)
Magnetoresistance (MR) with Current-flow Perpendicular-to-layer-Planes (CPP-MR)
of magnetic multilayers [F/N]n (n = number of repeats) with alternating
nanoscale layers of ferromagnetic (F) and non-magnetic (N) metals. GMR, a large
change in resistance when an applied magnetic field changes the moment ordering
of adjacent F-layers from anti-parallel (AP) to parallel (P), was discovered in
1988 in the Current-flow-in-layer-Planes (CIP) geometry. The CPP-MR has two
advantages over the CIP-MR: (1) it allows more direct access to the underlying
physics; and (2) it is usually larger, which should be advantageous for
devices. When the first CPP-MR data were published in 1991, it was not clear
whether electronic transport in GMR multilayers is fully diffusive or at least
partly ballistic. It was not known whether the properties of layers and
interfaces would vary with layer thickness or number. It was not known if the
CPP-MR would be dominated by scattering within the F-metals or at the F/N
interfaces. Nothing was known about: (1) spin-flipping within F-metals,
characterized by a spin-diffusion length, l(F)sf; (2) interface specific
resistances (AR = area A times resistance R) for N1/N2 interfaces; (3)
interface specific resistances and spin-dependent scattering asymmetry at F/N
and F1/F2 interfaces; and (4) spin-flipping at F/N, F1/F2 and N1/N2 interfaces.
Knowledge of spin-dependent scattering asymmetries in F-metals and F-alloys,
and of spin-flipping in N-metals and N-alloys was limited. We show how CPP-MR
measurements have quantified the scattering and spin-flipping parameters that
determine CPP-MR for a wide range of F- and N-metals and alloys and of F/N
pairs. We also review progress in finding techniques and F-alloys and F/N pairs
to enhance the CPP-MR to make it more competitive for devices.

###Modeling the magnetoresistance vs. field curves of GMR multilayers with antiferromagnetic and/or orthogonal coupling by assuming single-domain state and coherent rotation|Krisztián Szász,Imre Bakonyi###

Modeling the magnetoresistance vs. field curves of GMR multilayers with antiferromagnetic and/or orthogonal coupling by assuming single-domain state and coherent rotation. In order to better understand the role of possible couplings in determining
the giant magnetoresistance (GMR) behavior of multilayers, a knowledge of the
dependence of the $GMR$ on magnetic field $H$ appears to be useful. Since a few
specific cases have only been treated theoretically in the literature, it was
decided to carry out a modeling of the $GMR(H)$ curves of
ferromagnetic/non-magnetic (FM/NM) multilayers with various interlayer
couplings. For simplicity, we focused on a trilayer structure (FM1/NM/FM2)
corresponding fairly well to the case of a large number of FM/NM bilayers. To
carry out the calculations, some fundamental assumptions were made: (i) single
domain FM layer, in plane magnetization; (ii) the magnetization of each layer
is the same; (iii) the magnetization vectors rotate in the plane of the layers
in an external magnetic field. In order to calculate the $GMR(H)$ function, we
need to know the magnetization process in the trilayer, i.e., the $M(H)$
function. Therefore, first we calculate the equilibrium angle $\phi(H)$ between
the two magnetization vectors as a function of the field by minimizing the
total energy of the trilayer. According to most previous theoretical and
experimental works, the angular dependence of the GMR is fairly well described
by the relation $GMR(\phi)\propto (1-\cos\phi)$ and we used this relation to
derive the $GMR(H)$ function. Along this line, the $M(H)$ and $GMR(H)$ curves
were calculated for the following cases: (i) pure AF coupling; (ii) pure
orthogonal coupling; (iii) AF coupling and orthogonal coupling simultaneously
present. As to the calculation of the $GMR(H)$ curves, some of these
configurations have not yet been treated formerly or for some specific
parameter values only. For those cases for which calculations were reported in
the literature for $M(H)$ and $GMR(H)$, our results agree with previous
reports.

###Effect of Cu$^{2+}$ substitution in Spin-Orbit Coupled Sr$_2$Ir$_{1-x}$Cu$_x$O$_4$: Structure, magnetism and electronic properties|Imtiaz Noor Bhatti,R. S. Dhaka,A. K. Pramanik###

Effect of Cu$^{2+}$ substitution in Spin-Orbit Coupled Sr$_2$Ir$_{1-x}$Cu$_x$O$_4$: Structure, magnetism and electronic properties. Sr$_2$IrO$_4$ is an extensively studied spin-orbit coupling induced insulator
with antiferromagnetic ground state. The delicate balance between competing
energy scales plays crucial role for its low temperature phase, and the route
of chemical substitution has often been used to tune these different energy
scales. Here, we report an evolution of structural, magnetic and electronic
properties in doped Sr$_2$Ir$_{1-x}$Cu$_x$O$_4$ ($x$ $\leq$ 0.2). The
substitution of Cu$^{2+}$ (3$d^9$) for Ir$^{4+}$ (5$d^5$) acts for electron
doping, though it tunes the related parameters such as, spin-orbit coupling,
electron correlation and Ir charge state. Moreover, both Ir$^{4+}$ and
Cu$^{2+}$ has single unpaired spin though it occupies different $d$-orbitals.
With Cu substitution, system retains its original structural symmetry but the
structural parameters show systematic changes. X-ray photoemission spectroscopy
measurements show Ir$^{4+}$ equivalently converts to Ir$^{5+}$ and a
significant enhancement in the density of states has been observed at the Fermi
level due to the contribution from the Cu 3$d$ orbitals, which supports the
observed decrease in the resistivity with Cu substitution. While the long-range
magnetic ordering is much weakened and the highest doped sample shows almost
paramagnetic-like behavior the overall system remains insulator. Analysis of
resistivity data shows mode of charge conduction in whole series follows
2-dimensional variable-range-hopping model but the range of validity varies
with temperature. Whole series of samples exhibit negative magnetoresistance at
low temperature which is considered to be a signature of weak localization
effect in spin-orbit coupled system, and its evolution with Cu appears to
follow the variation of resistivity with $x$.

###Landau quantization of nearly degenerate bands, and full symmetry classification of avoided Landau-level crossings|Chong Wang,Wenhui Duan,Leonid Glazman,A. Alexandradinata###

Landau quantization of nearly degenerate bands, and full symmetry classification of avoided Landau-level crossings. Semiclassical quantization rules compactly describe the energy dispersion of
Landau levels, and are predictive of quantum oscillations in transport and
thermodynamic quantities. Such rules -- as formulated by Onsager, Lifshitz and
Roth -- apply when the spin-orbit interaction dominates over the Zeeman
interaction (or vice versa), but does not generally apply when the two
interactions are comparable in strength. In this work, we present a generalized
quantization rule which treats the spin-orbit and Zeeman interactions on equal
footing, and therefore has wider applicability to spin-orbit-coupled materials
lacking a spatial inversion center, or having magnetic order. More generally,
our rule describes the Landau quantization of any number of nearly degenerate
energy bands -- in any symmetry class. The resultant Landau-level spectrum is
generically non-equidistant but may contain spin (or pseudospin) degeneracies.
To tune to such degeneracies in the absence of crystalline point-group
symmetries, three real parameters are needed. We have exhaustively identified
all symmetry classes of cyclotron orbits for which this number is reduced from
three, thus establishing symmetry-enforced 'non-crossing rules' for Landau
levels. In particular, only one parameter is needed in the presence of spatial
rotation or inversion; this single parameter may be the magnitude or
orientation of the field. Signatures of single-parameter tunability include (i)
a smooth crossover between period-doubled and -undoubled quantum oscillations
in the low-temperature Shubnikov-de Haas effect, as well as (ii) 'magic-angle'
magnetoresistance oscillations. We demonstrate the utility of our quantization
rule, as well as the tunability of Landau-level degeneracies, for the
Rashba-Dresselhaus two-dimensional electron gas -- subject to an arbitrarily
oriented magnetic field.

###Hopping conductance and macroscopic quantum tunneling effect in three dimensional Pb$_x$(SiO$_2$)$_{1-x}$ nanogranular films|Xiu-Zhi Duan,Zhi-Hao He,Yang Yang,Zhi-Qing Li###

Hopping conductance and macroscopic quantum tunneling effect in three dimensional Pb$_x$(SiO$_2$)$_{1-x}$ nanogranular films. We have studied the low-temperature electrical transport properties of
Pb$_x$(SiO$_2$)$_{1-x}$ ($x$ being the Pb volume fraction) nanogranular films
with thicknesses of $\sim$1000 nm and $x$ spanning the dielectric,
transitional, and metallic regions. It is found that the percolation threshold
$x_c$ lies between 0.57 and 0.60. For films with $x$$\lesssim$0.50, the
resistivities $\rho$ as functions of temperature $T$ obey
$\rho\propto\exp(\Delta/k_BT)$ relation ($\Delta$ being the local
superconducting gap and the $k_B$ Boltzmann constant) below the superconducting
transition temperature $T_c$ ($\sim$7 K) of Pb granules. The value of the gap
obtained via this expression is almost identical to that by single electron
tunneling spectra measurement. The magnetoresistance is negative below $T_c$
and its absolute value is far larger than that above $T_c$ at a certain field.
These observations indicate that single electron hopping (or tunneling), rather
than Cooper pair hopping (or tunneling) governs the transport processes below
$T_c$. The temperature dependence of resistivities shows reentrant behavior for
the 0.50$<$$x$$<$0.57 films. It is found that single electron hopping (or
tunneling) also dominates the low-temperature transport process for these
films. The reduction of the single electron concentration leads to an
enhancement of the resisivity at sufficiently low temperature. For the
0.60$\lesssim$$x$$\lesssim$0.72 films, the resistivities sharply decrease with
decreasing temperature just below $T_c$, and then show dissipation effect with
further decreasing temperature. Treating the conducting paths composed of Pb
particles as nanowires, we have found that the $R(T)$ data below $T_c$ can be
well explained by a model that includes both thermally activated phase slips
and quantum phase slips.

###Magnetic and electrical transport signatures of uncompensated moments in epitaxial thin films of the non-collinear antiferromagnet Mn$_{3}$Ir|James M. Taylor,Edouard Lesne,Anastasios Markou,Fasil Kidane Dejene,Pranava Keerthi Sivakumar,Simon Pöllath,Kumari Gaurav Rana,Neeraj Kumar,Chen Luo,Hanjo Ryll,Florin Radu,Florian Kronast,Peter Werner,Christian H. Back,Claudia Felser,Stuart S. P. Parkin###

Magnetic and electrical transport signatures of uncompensated moments in epitaxial thin films of the non-collinear antiferromagnet Mn$_{3}$Ir. Non-collinear antiferromagnets, with either an L1$_{2}$ cubic crystal lattice
(e.g. Mn$_{3}$Ir and Mn$_{3}$Pt) or a D0$_{19}$ hexagonal structure (e.g.
Mn$_{3}$Sn and Mn$_{3}$Ge), exhibit a number of novel phenomena of interest to
topological spintronics. Amongst the cubic systems, for example, tetragonally
distorted Mn$_{3}$Pt exhibits an intrinsic anomalous Hall effect (AHE).
However, Mn$_{3}$Pt only enters a non-collinear magnetic phase close to the
stoichiometric composition and at suitably large thicknesses. Therefore, we
turn our attention to Mn$_{3}$Ir, the material of choice for use in exchange
bias heterostructures. In this paper, we investigate the magnetic and
electrical transport properties of epitaxially grown, face-centered-cubic
$\gamma$-Mn$_{3}$Ir thin films with (111) crystal orientation. Relaxed films of
10 nm thickness exhibit an ordinary Hall effect, with a hole-type carrier
concentration of (2.24 $\pm$ 0.08) $\times$ 10$^{23}$ cm$^{-3}$. On the other
hand, TEM characterization demonstrates that ultrathin 3 nm films grow with
significant in-plane tensile strain. This may explain a small remanent moment,
observed at low temperatures, shown by XMCD spectroscopy to arise from
uncompensated Mn spins. Of the order 0.02 $\mu_{B}$ / atom, this dominates
electrical transport behavior, leading to a small AHE and negative
magnetoresistance. These results are discussed in terms of crystal
microstructure and chiral domain behavior, with spatially resolved XML(C)D-PEEM
supporting the conclusion that small antiferromagnetic domains, < 20 nm in
size, of differing chirality account for the absence of observed Berry
curvature driven magnetotransport effects.

###Nonmagnetic substitution in pyrochlore iridate Y$_2$(Ir$_{1-x}$Ti$_{x}$)$_2$O$_7$: Structure, magnetism and electronic properties|Harish Kumar,A. K. Pramanik###

Nonmagnetic substitution in pyrochlore iridate Y$_2$(Ir$_{1-x}$Ti$_{x}$)$_2$O$_7$: Structure, magnetism and electronic properties. Tuning of spin-orbit coupling and electron correlation effects in pyrochlore
iridates is considered for many interesting phenomena. We have investigated the
temperature evolution of structural, magnetic and electronic properties in
doped Y$_2$(Ir$_{1-x}$Ti$_{x}$)$_2$O$_7$ ($x$ = 0.0, 0.02, 0.05, 0.10 and 0.15)
where the substitution of nonmagnetic Ti$^{4+}$ (3$d^0$) for Ir$^{4+}$ (5$d^5$)
amounts to dilution of magnetic network and tuning of these parameters in
opposite way. The system retains its original structural symmetry but local
structural parameters show an evolution with Ti content. While the magnetic
transition temperature is not largely influenced, both magnetic moment and
magnetic frustration decreases with Ti doping. Magnetic relaxation measurement
shows the parent compound Y$_2$Ir$_2$O$_7$ as well as its Ti doped analogues
are in nonequilibrium magnetic state where the magnetic relaxation rate
increases with Ti. Temperature dependent Raman measurements indicate no changes
in structural symmetry, however, across the magnetic transition temperature an
anomaly in A$_{1g}$ Raman mode is observed. Temperature dependent x-ray
diffraction data also support the Raman spectroscopy data, however, an
evolution of lattice parameters with temperature is observed. The electrical
resistivity data of Y$_2$(Ir$_{1-x}$Ti$_{x}$)$_2$O$_7$ series exhibits
insulating behavior throughout the temperature range, however, the resistivity
decreases with Ti doping. The nature of charge conduction is found to follow
power-law behavior in whole series but the validity of this model varies with
temperature. A negative magnetoresistance has been observed at low temperature
in present series which is explained with weak localized mechanism. Similar to
other Ir based oxides, a crossover from negative to positive MR has been
observed in present system.

###Origins Vs. fingerprints of the Jahn-Teller effect in d-electron ABX$_3$ perovskites|Julien Varignon,Manuel Bibes,Alex Zunger###

Origins Vs. fingerprints of the Jahn-Teller effect in d-electron ABX$_3$ perovskites. The Jahn-Teller (JT) distortion that can remove electronic degeneracies in
partially occupied states and results in systematic atomic displacements is a
common underlying feature to many of the intriguing phenomena observed in 3d
perovskites, encompassing magnetism, superconductivity, orbital ordering and
colossal magnetoresistance. Although the seminal Jahn and Teller theorem has
been postulated almost a century ago, the origins of this effect in perovskite
materials are still debated, including propositions such as super exchange,
spin-phonon coupling, sterically induced lattice distortions, and strong
dynamical correlation effects. Here we analyze the driving forces behind the
Jahn-Teller motions and associated electronic fingerprints in a full range of
ABX3 compounds. We identify (i) compounds that are prone to an
electronically-driven instabilities (i.e. a pure JT effect) such as KCrF3,
KCuF3 or LaVO3 and proceed to relax the structures, finding quantitatively the
JTD in excellent agreement with experiment; (ii) compounds such as LaMnO3 or
LaTiO3 that do not show electronically driven JTD despite orbital degeneracies,
because their strongly hybridized B, d-X, p states supply but too weak JT
forces to overcome the needed atomic distortions; (iii) although LaVO3 exhibits
similar B, d-X, p hybridizations as LaTiO3, the former compound exhibits a
robust electronic instability while LaTiO3 has zero stabilization energy, the
reason being that LaVO3 has two electrons t2g2 relative to LaTiO3 with just one
t2g1. (iv) We explain the trends in "orbital ordering" whereby electrons occupy
orbitals that point to orthogonal directions between all nearest-neighbor 3d
atoms. We thereby provide a unified vision to explain octahedra deformations in
perovskites that, at odds with common wisdom, does not require the celebrated
Mott-Hubbard mechanism.

###Comment on "Tuning low-energy scales in YbRh$_2$Si$_2$ by non-isoelectronic substitution and pressure"|Steffen Wirth,Silke Paschen,Qimiao Si,Frank Steglich###

Comment on "Tuning low-energy scales in YbRh$_2$Si$_2$ by non-isoelectronic substitution and pressure". In Ref. 1, Schubert et al. [Phys. Rev. Research 1, 032004 (2019)] reported
measurements of the isothermal magnetoresistance of Fe- and Ni-substituted
YbRh$_2$Si$_2$, based on which they raised questions about the Kondo
destruction description for the magnetic field-induced quantum critical point
(QCP) of pristine YbRh$_2$Si$_2$. Here we make three points. Firstly, as shown
by studies on pristine YbRh$_2$Si$_2$ in Paschen et al. and Friedemann et al.,
isothermal crossed-field and single-field Hall effect measurements are
necessary to ascertain the evolution of the Fermi surface across this QCP.
Because Schubert et al. did not carry out such measurements, their results on
Fe- and Ni-substituted YbRh$_2$Si$_2$ cannot be used to assess the validity of
the Kondo destruction picture neither for substituted nor for pristine
YbRh$_2$Si$_2$. Secondly, when referring to the data of Friedemann et al. on
the isothermal crossover of YbRh$_2$Si$_2$, they did not recognize the
implications of the crossover width, quantified by the full width at half
maximum (FWHM), being linear in temperature, with zero offset, over about $1.5$
decades in temperature, from 30 mK to 1 K. Finally, in claiming deviations of
Hall crossover FWHM data of Friedemann et al. from the above linear-in-$T$
dependence they neglected the error bars of these measurements and discarded
some of the data points. The claims of Schubert et al. are thus not supported
by data, neither previously published nor new (Ref. 1). As such they cannot
invalidate the evidence that has been reported for Kondo destruction quantum
criticality in YbRh$_2$Si$_2$.

###Magnetoresistance and spintronic anisotropy induced by spin excitations along molecular spin chains|K. Katcko,E. Urbain,L. Kandpal,B. Chowrira,F. Schleicher,U. Halisdemir,F. Ngassamnyakam,D. Mertz,B. Leconte,N. Beyer,D. Spor,P. Panissod,A. Boulard,J. Arabski,C. Kieber,E. Sternitsky,V. Da Costa,M. Alouani,M. Hehn,F. Montaigne,A. Bahouka,W. Weber,E. Beaurepaire,D. Lacour,S. Boukari,M. Bowen###

Magnetoresistance and spintronic anisotropy induced by spin excitations along molecular spin chains. Electrically manipulating the quantum properties of nano-objects, such as
atoms or molecules, is typically done using scanning tunnelling microscopes and
lateral junctions. The resulting nanotransport path is well established in
these model devices. Societal applications require transposing this knowledge
to nano-objects embedded within vertical solid-state junctions, which can
advantageously harness spintronics to address these quantum properties thanks
to ferromagnetic electrodes and high-quality interfaces. The challenge here is
to ascertain the device's effective, buried nanotransport path, and to
electrically involve these nano-objects in this path by shrinking the device
area from the macro- to the nano-scale while maintaining high
structural/chemical quality across the heterostructure. We've developed a
low-tech, resist- and solvent-free technological process that can craft
nanopillar devices from entire in-situ grown heterostructures, and use it to
study magnetotransport between two Fe and Co ferromagnetic electrodes across a
functional magnetic CoPc molecular layer. We observe how spin-flip transport
across CoPc molecular spin chains promotes a specific magnetoresistance effect,
and alters the nanojunction's magnetism through spintronic anisotropy. In the
process, we identify three magnetic units along the effective nanotransport
path thanks to a macrospin model of magnetotransport. Our work elegantly
connects the until now loosely associated concepts of spin-flip spectroscopy,
magnetic exchange bias and magnetotransport due to molecular spin chains,
within a solid-state device. We notably measure a 5.9meV energy threshold for
magnetic decoupling between the Fe layer's buried atoms and those in contact
with the CoPc layer forming the so-called 'spinterface'. This provides a first
insight into the experimental energetics of this promising low-power
information encoding unit.

###Multi-GMR sensors controlled by additive dipolar coupling|J. Torrejon,A. Solignac,C. Chopin,J. Moulin,A. Doll,E. Paul,C. Fermon,M. Pannetier-Lecoeur###

Multi-GMR sensors controlled by additive dipolar coupling. Vertical packaging of multiple Giant Magnetoresistance (multi-GMR) stacks is
a very interesting noise reduction strategy for local magnetic sensor
measurements, which has not been reported experimentally so far. Here, we have
fabricated multi-GMR sensors (up to 12 repetitions) keeping good GMR ratio,
linearity and low roughness. From magnetotransport measurements, two different
resistance responses have been observed with a crossover around 5 GMR
repetitions: step-like (N<5) and linear (N>5) behavior, respectively. With the
help of micromagnetic simulations, we have analyzed in detail the two main
magnetic mechanisms: the Neel coupling distribution induced by the roughness
propagation and the additive dipolar coupling between the N free layers.
Furthermore we have correlated the dipolar coupling mechanism, controlled by
the number of GMRs (N) and lateral dimensions (width), to the sensor
performance (sensitivity, noise and detectivity) in good agreement with
analytical theory. The noise roughly decreases in multi-GMRs as 1/\sqrt{N} in
both regimes (low frequency 1/f and thermal noise). The sensitivity is even
stronger reduced, scaling as 1/N, in the strong dipolar regime (narrow devices)
while converges to a constant value in the weak dipolar regime (wide devices).
Very interestingly, they are more robust against undesirable RTN noise than
single GMRs at high voltages and the linearity can be extended towards much
larger magnetic field range without dealing with the size and the reduction of
GMR ratio. Finally, we have identified the optimal conditions for which
multi-GMRs exhibit lower magnetic field detectivity than single GMRs: wide
devices operating in the thermal regime where much higher voltage can be
applied without generating remarkable magnetic noise.

###Unexpected two-fold symmetric superconductivity in few-layer NbSe$_2$|Alex Hamill,Brett Heischmidt,Egon Sohn,Daniel Shaffer,Kan-Ting Tsai,Xi Zhang,Xiaoxiang Xi,Alexey Suslov,Helmuth Berger,László Forró,Fiona J. Burnell,Jie Shan,Kin Fai Mak,Rafael M. Fernandes,Ke Wang,Vlad S. Pribiag###

Unexpected two-fold symmetric superconductivity in few-layer NbSe$_2$. Two-dimensional transition metal dichalcogenides (TMDs) have been attracting
significant interest due to a range of properties, such as layer-dependent
inversion symmetry, valley-contrasted Berry curvatures, and strong spin-orbit
coupling (SOC). Of particular interest is niobium diselenide (NbSe2), whose
superconducting state in few-layer samples is profoundly affected by an unusual
type of SOC called Ising SOC. Combined with the reduced dimensionality, the
latter stabilizes the superconducting state against magnetic fields up to ~35 T
and could lead to other exotic properties such as nodal and crystalline
topological superconductivity. Here, we report transport measurements of
few-layer NbSe$_2$ under in-plane external magnetic fields, revealing an
unexpected two-fold rotational symmetry of the superconducting state. In
contrast to the three-fold symmetry of the lattice, we observe that the
magnetoresistance and critical field exhibit a two-fold oscillation with
respect to an applied in-plane magnetic field. We find similar two-fold
oscillations deep inside the superconducting state in differential conductance
measurements on NbSe$_2$/CrBr$_3$ superconductor-magnet junctions. In both
cases, the anisotropy vanishes in the normal state, demonstrating that it is an
intrinsic property of the superconducting phase. We attribute the behavior to
the mixing between two closely competing pairing instabilities, namely, the
conventional s-wave instability typical of bulk NbSe$_2$ and an unconventional
d- or p-wave channel that emerges in few-layer NbSe2. Our results thus
demonstrate the unconventional character of the pairing interaction in a
few-layer TMD, opening a new avenue to search for exotic superconductivity in
this family of 2D materials.

###Evidence of Ba substitution induced spin-canting in the magnetic Weyl semimetal EuCd$_2$As$_2$|L. D. Sanjeewa,J. Xing,K. M. Taddei,D. Parker,R. Custelcean,D. dela Cruz,A. S. Sefat###

Evidence of Ba substitution induced spin-canting in the magnetic Weyl semimetal EuCd$_2$As$_2$. Recently EuCd$_2$As$_2$ was predicted to be a magnetic Weyl semi-metal with a
lone pair of Weyl nodes generated by A-type antiferromagnetism and protected by
a rotational symmetry. However, it was soon discovered that the actual magnetic
structure broke the rotational symmetry and internal pressure was later
suggested as a route to stabilize the desired magnetic state. In this work we
test this prediction by synthesizing a series of Eu$_{1-x}$Ba$_x$Cd$_2$As$_2$
single crystals and studying their structural, magnetic and transport
properties via both experimental techniques and first-principles calculations.
We find that small concentrations of Ba ($\sim 3-10\% $) lead to a small
out-of-plane canting of the Eu moment. However, for higher concentrations this
effect is suppressed and a nearly in-plane model is recovered. Studying the
transport properties we find that all compositions show evidence of an
Anomalous Hall Effect dominated by the intrinsic mechanism as well as large
negative magnetoresistances in the longitudinal channel. A non-monotonic
evolution of the transport properties is seen across the series which
correlates to the proposed canting suggesting canting may enhance the
topological effects. Careful density functional theory calculations using an
all-electron approach revise prior predictions finding a purely ferromagnetic
ground state with in-plane moments for both the EuCd$_2$As$_2$ and
Eu$_{0.5}$Ba$_{0.5}$Cd$_2$As$_2$ compounds - corroborating our experimental
findings. This work suggests that Ba substitution can tune the magnetic
properties in unexpected ways which correlate to changes in measures of
topological properties, encouraging future work to locate the ideal Ba
concentration for Eu moment canting.

###Transport properties of organic Dirac electron system α-(BEDT-TSeF)$_2$I$_3$|Daigo Ohki,Kazuyoshi Yoshimi,Akito Kobayashi###

Transport properties of organic Dirac electron system α-(BEDT-TSeF)$_2$I$_3$. Motivated by the insulating behavior of $\alpha$-(BEDT-TSeF)$_2$I$_3$ at low
temperatures ($T$'s), we first performed first-principles calculations based on
the crystal structural data at 30 K under ambient pressure, and we constructed
a two-dimensional effective model using maximally localized Wannier functions.
As possible causes of the insulating behavior, we studied the effects of the
on-site Coulomb interaction $U$ and spin-orbit interaction (SOI) by
investigating the electronic state and the transport coefficient using the
Hartree approximation and the $T$-matrix approximation. The calculations at a
finite $T$ demonstrated that a spin-ordered massive Dirac electron (SMD)
appeared due to the on-site Coulomb interaction. We had an interest in the
anomalous competitive effect with $U$ and SOI when the SMD phase is present in
$\alpha$-(BETS)$_2$I$_3$, and we investigated these contributions to the
electronic state and conductivity. The SMD is not a conventional spin order,
but it exhibits the spin-valley Hall effect. Direct current resistivity in the
presence of a spin order gap increased divergently and exhibited negative
magnetoresistance in the low $T$ region with decreasing $T$. The charge density
hardly changed below and above the $T$ at which this insulating behavior
appeared. However, when considering the SOI alone, the state changed to a
topological insulator phase, and the electrical resistivity is saturated by
edge conduction at quite low $T$. When considering both the SMD and the SOI,
the spin order gap was suppressed by the SOI, and gaps with different sizes
opened in the left and right Dirac cones. This phase transition leads to
distinct changes in microwave conductivity, such as a discontinuous jump and a
peak structure.

###Influence of the vicinal substrate miscut on the anisotropic two-dimensional electronic transport in Al2O3-SrTiO3 heterostructures|Karsten Wolff,Roland Schäfer,Daniel Arnold,Rudolf Schneider,Matthieu Le Tacon,Dirk Fuchs###

Influence of the vicinal substrate miscut on the anisotropic two-dimensional electronic transport in Al2O3-SrTiO3 heterostructures. The electrical resistance of the two-dimensional electron system (2DES) which
forms at the interface of SrTiO3 (STO)-based heterostructures displays
anisotropic transport with respect to the direction of current flow at low
temperature. We have investigated the influence of terraces at the surface of
STO substrates from which the 2DES are prepared. Such terraces are always
present in commercially available STO substrates due to the tolerance of
surface preparation which result in small miscut angles of the order of gamma ~
0.1{\deg} with respect to the surface normal. By a controlled increase of the
substrate miscut we could systematically reduce the width of the terraces and
thereby increase the density of substrate surface steps. The in-plane
anisotropy of the electrical resistance was studied as a function of the miscut
angle gamma and found to be mainly related to interfacial scattering arising
from the substrate surface steps. However, the influence of gamma was notably
reduced by the occurrence of step-bunching and lattice-dislocations in the STO
substrate material.
  Magnetoresistance (MR) depends on the current orientation as well, reflecting
the anisotropy of carrier mobility. For gamma >= 2{\deg}, MR is substantially
enhanced and shows the trend towards a linear field dependence which is typical
for inhomogeneous conductors. From weak-antilocalization observed at small
magnetic field we deduce information on inelastic scattering and spin-orbit
coupling. While the field scale associated with a Rashba-type spin-orbit
coupling in 2D weak-localization does not show a pronounced correlation with
gamma, distinct changes of the scale are associated with inelastic scattering.

###Helical magnetic order and Fermi surface nesting in non-centrosymmetric ScFeGe|Sunil K. Karna,D. Tristant,J. K. Hebert,G. Cao,R. Chapai,W. A. Phelan,Q. Zhang,Y. Wu,C. Dhital,Y. Li,H. B. Cao,W. Tian,C. R. Dela Cruz,A. A. Aczel,O. Zaharko,A. Khasanov,M. A. McGuire,A. Roy,W. Xie,D. A. Browne,I. Vekhter,V. Meunier,W. A. Shelton,P. W. Adams,P. T. Sprunger,D. P. Young,R. Jin,J. F. DiTusa###

Helical magnetic order and Fermi surface nesting in non-centrosymmetric ScFeGe. An investigation of the structural, magnetic, thermodynamic, and charge
transport properties of non-centrosymmetric hexagonal ScFeGe reveals it to be
an anisotropic metal with a transition to a weak itinerant incommensurate
helimagnetic state below $T_N = 36$ K. Neutron diffraction measurements
discovered a temperature and field independent helical wavevector
\textbf{\textit{k}} = (0 0 0.193) with magnetic moments of 0.53 $\mu_{B}$ per
formula unit confined to the {\it ab}-plane. Density functional theory
calculations are consistent with these measurements and find several bands that
cross the Fermi level along the {\it c}-axis with a nearly degenerate set of
flat bands just above the Fermi energy. The anisotropy found in the electrical
transport is reflected in the calculated Fermi surface, which consists of
several warped flat sheets along the $c$-axis with two regions of significant
nesting, one of which has a wavevector that closely matches that found in the
neutron diffraction. The electronic structure calculations, along with a strong
anomaly in the {\it c}-axis conductivity at $T_N$, signal a Fermi surface
driven magnetic transition, similar to that found in spin density wave
materials. Magnetic fields applied in the {\it ab}-plane result in a
metamagnetic transition with a threshold field of $\approx$ 6.7 T along with a
sharp, strongly temperature dependent, discontinuity and a change in sign of
the magnetoresistance for in-plane currents. Thus, ScFeGe is an ideal system to
investigate the effect of in-plane magnetic fields on an easy-plane magnetic
system, where the relative strength of the magnetic interactions and
anisotropies determine the topology and magnetic structure.

###Magnetoresistance oscillation study of the half-quantum vortex in doubly connected mesoscopic superconducting cylinders of Sr2RuO4|Xinxin Cai,Brian M. Zakrzewski,Yiqun A. Ying,Hae-Young Kee,Manfred Sigrist,J. Elliott Ortmann,Weifeng Sun,Zhiqiang Mao,Ying Liu###

Magnetoresistance oscillation study of the half-quantum vortex in doubly connected mesoscopic superconducting cylinders of Sr2RuO4. The observation of the highly unusual half-quantum vortex (HQV) in a single
crystalline superconductor excludes unequivocally the spin-singlet symmetry of
the superconducting order parameter. HQVs were observed previously in
mesoscopic samples of Sr2RuO4 in cantilever torque magnetometry measurements,
thus providing direct evidence for spin-triplet pairing in the material. In
addition, it raised important questions on HQV, including its stability and
dynamics. These issues have remained largely unexplored, in particular,
experimentally. We report in this paper the detection of HQVs in mesoscopic,
doubly connected cylinders of single-crystalline Sr2RuO4 of a mesoscopic size
and the examination of the effect of the in-plane magnetic field needed for the
observation of the HQV by magnetoresistance (MR) oscillations measurements.
Several distinct features found in our data, especially a dip and secondary
peaks in the MR oscillations seen only in the presence of a sufficiently large
in-plane magnetic field as well as a large measurement current, are linked to
the formation of the HQV fluxoid state in and crossing of an Abrikosov HQV
through the sample. The conclusion is drawn from the analysis of our data using
a model of thermally activated vortex crossing overcoming a free-energy barrier
which is modulated by the applied magnetic flux enclosed in the cylinder as
well as the measurement current. Evidence for the trapping of an HQV fluxoid
state in the sample was also found. Our observation of the HQV in mesoscopic
Sr2RuO4 provided not only additional evidence for spin-triplet
superconductivity in Sr2RuO4 but also insights into the physics of HQV,
including its spontaneous spin polarization, stability, and dynamics. Our study
also revealed a possible effect of the measurement current on the magnitude of
the spontaneous spin polarization associated with the HQV.

###Systematic study of nonmagnetic resistance changes due to electrical pulsing in single metal layers and metal/antiferromagnet bilayers|B. J. Jacot,G. Krishnaswamy,G. Sala,C. O. Avci,S. Vélez,P. Gambardella,C. -H. Lambert###

Systematic study of nonmagnetic resistance changes due to electrical pulsing in single metal layers and metal/antiferromagnet bilayers. Intense current pulses are often required to operate microelectronic and
spintronic devices. Notably, strong current pulses have been shown to induce
magnetoresistance changes attributed to domain reorientation in
antiferromagnet/heavy metal bilayers and non-centrosymmetric antiferromagnets.
In such cases, nonmagnetic resistivity changes may dominate over signatures of
antiferromagnetic switching. We report systematic measurements of the
current-induced changes of the transverse and longitudinal resistance of Pt and
Pt/NiO layers deposited on insulating substrates, namely Si/SiO$_2$,
Si/Si$_3$N$_4$, and Al$_2$O$_3$. We identify the range of pulse amplitude and
length that can be used without affecting the resistance and show that it
increases with the device size and thermal diffusivity of the substrate. No
significant difference is observed in the resistive response of Pt and NiO/Pt
devices, thus precluding evidence on the switching of antiferromagnetic domains
in NiO. The variation of the transverse resistance is associated to a
thermally-activated process in Pt that decays following a double exponential
law with characteristic timescales of a few minutes to hours. We use a
Wheatstone bridge model to discriminate between positive and negative
resistance changes, highlighting competing annealing and electromigration
effects. Depending on the training of the devices, the transverse resistance
can either increase or decrease between current pulses. Further, we elucidate
the origin of the nonmonotonic resistance baseline, which we attribute to
training effects combined with the asymmetric distribution of the current.
These results provide insight into the origin of current-induced resistance
changes in metal layers and a guide to minimize nonmagnetic artifacts in
switching experiments of antiferromagnets.

###Double Free-Layer Magnetic Tunnel Junctions for Probabilistic Bits|Kerem Y. Camsari,Mustafa Mert Torunbalci,William A. Borders,Hideo Ohno,Shunsuke Fukami###

Double Free-Layer Magnetic Tunnel Junctions for Probabilistic Bits. Naturally random devices that exploit ambient thermal noise have recently
attracted attention as hardware primitives for accelerating probabilistic
computing applications. One such approach is to use a low barrier nanomagnet as
the free layer of a magnetic tunnel junction (MTJ) whose magnetic fluctuations
are converted to resistance fluctuations in the presence of a stable fixed
layer. Here, we propose and theoretically analyze a magnetic tunnel junction
with no fixed layers but two free layers that are circularly shaped disk
magnets. We use an experimentally benchmarked model that accounts for finite
temperature magnetization dynamics, bias-dependent charge and spin-polarized
currents as well as the dipolar coupling between the free layers. We obtain
analytical results for statistical averages of fluctuations that are in good
agreement with the numerical model. We find that the free layers with low
diameters fluctuate to randomize the resistance of the MTJ in an approximately
bias-independent manner. We show how such MTJs can be used to build a binary
stochastic neuron (or a p-bit) in hardware. Unlike earlier stochastic MTJs that
need to operate at a specific bias point to produce random fluctuations, the
proposed design can be random for a wide range of bias values, independent of
spin-transfer-torque pinning. Moreover, in the absence of a carefully optimized
stabled fixed layer, the symmetric double-free layer stack can be manufactured
using present day Magnetoresistive Random Access Memory (MRAM) technology by
minimal changes to the fabrication process. Such devices can be used as
hardware accelerators in energy-efficient computing schemes that require a
large throughput of tunably random bits.

###Electronic transport properties and hydrostatic pressure effect of FeSe$_{0.67}$Te$_{0.33}$ single crystals free of phase separation|Xiangzhuo Xing,Yue Sun,Xiaolei Yi,Meng Li,Jiajia Feng,Yan Meng,Yufeng Zhang,Wenchong Li,Nan Zhou,Xiude He,Jun-Yi Ge,Wei Zhou,Tsuyoshi Tamegai,Zhixiang Shi###

Electronic transport properties and hydrostatic pressure effect of FeSe$_{0.67}$Te$_{0.33}$ single crystals free of phase separation. FeSe$_{1-x}$Te$_{x}$ superconductors manifest some intriguing electronic
properties depending on the value of $x$. In FeSe single crystal, the nematic
phase and Dirac band structure have been observed, while topological surface
superconductivity with the Majorana bound state was found in the crystal of $x
\sim 0.55$. Therefore, the electronic properties of single crystals with $0 < x
\leq 0.5$ are crucial for probing the evolution of those intriguing properties
as well as their relations. However, this study is still left blank due to the
lack of single crystals because of phase separation. Here, we report the
synthesis, magnetization, electronic transport properties, and hydrostatic
pressure effect of FeSe$_{0.67}$Te$_{0.33}$ single crystals free of phase
separation. A structural (nematic) transition is visible at $T_{s} = 39$ K,
below which the resistivity exhibits a Fermi-liquid behavior. Analysis of upper
critical fields suggests that spin-paramagnetic effect should be taken into
account for both $H \parallel c$ axis and $H \parallel ab$ plane. A crossover
from the low-$H$ quadratic to the high-$H$ quasi-linear behavior is observed in
the magnetoresistance, signifying the possible existence of Dirac-cone state.
Besides, the strong temperature dependence of Hall coefficient, violation of
(modified) Kohler's rule, and two-band model analysis indicate the multiband
effects in FeSe$_{0.67}$Te$_{0.33}$ single crystals. Hydrostatic pressure
measurements reveal that $T_{s}$ is quickly suppressed with pressure while
$T_{c}$ is monotonically increased up to 2.31 GPa, indicating the competition
between nematicity and superconductivity. No signature of magnetic order that
has been detected in FeSe$_{1-x}$S$_{x}$ is observed. Our findings fill up the
blank of the knowledge on the basic properties of FeSe$_{1-x}$Te$_{x}$ system
with low-Te concentrations.

###Successive destruction of charge density wave states by pressure in LaAgSb$_2$|Kazuto Akiba,Hiroaki Nishimori,Nobuaki Umeshita,Tatsuo C. Kobayashi###

Successive destruction of charge density wave states by pressure in LaAgSb$_2$. We comprehensively studied the magnetotransport properties of LaAgSb$_2$
under high pressure up to 4 GPa, which showed unique successive charge density
wave (CDW) transitions at $T_{CDW1}\sim 210$ K and $T_{CDW2}\sim 190$ K at
ambient pressure. With the application of pressure, both $T_{CDW1}$ and
$T_{CDW2}$ were suppressed and disappeared at the critical pressures of
$P_{CDW1}=3.0$--3.4 GPa and $P_{CDW2}=1.5$--1.9 GPa, respectively. At
$P_{CDW1}$, the Hall conductivity showed a step-like increase, which is
consistently understood by the emergence of two-dimensional hollow Fermi
surface at $P_{CDW1}$. We also observed a significant negative
magnetoresistance effect when the magnetic field and current were applied
parallel to the $c$ axis. Shubnikov--de Haas (SdH) oscillation measurements
under pressure directly showed the changes in the Fermi surface across the CDW
phase boundaries. In $P<P_{CDW2}$, three major oscillation components,
$\alpha$, $\beta$, and $\gamma$, were identified, whose frequencies were
increased by application of pressure. The increment rate of these frequencies
was considerably larger than that expected from the shrinkage of lattice
constant, indicating the unignorable band modification under pressure. In the
normal metallic phase above $P>P_{CDW1}$, we observed a single frequency of
$\sim 48$ T with a cyclotron effective mass of 0.066 $m_0$, whose cross section
in the reciprocal space corresponded to only 0.22\% of the first Brillouin
zone. Besides, we observed another oscillation component with frequency of
$\sim 9.2$ T, which is significantly enhanced in the limited pressure range of
$P_{CDW2}<P<P_{CDW1}$. The amplitude of this oscillation was anomalously
suppressed in the high-field and low-temperature region, which cannot be
explained by the conventional Lifshitz--Kosevich formula.

###Perpendicular magnetic anisotropy in ultra-thin Cu$_2$Sb-type (Mn-Cr)AlGe films onto thermally oxidized silicon substrates|Takahide Kubota,Keita Ito,Rie Y Umetsu,Koki Takanashi###

Perpendicular magnetic anisotropy in ultra-thin Cu$_2$Sb-type (Mn-Cr)AlGe films onto thermally oxidized silicon substrates. Perpendicularly magnetized films showing small saturation magnetization,
$M_\mathrm{s}$, are essential for spin-transfer-torque writing type
magnetoresistive random access memories, STT-MRAMs. An intermetallic compound,
{(Mn-Cr)AlGe} of the Cu$_2$Sb-type crystal structure was investigated, in this
study, as a material showing the low $M_\mathrm{s}$ ($\sim 300$ kA/m) and
high-perpendicular magnetic anisotropy, $K_\mathrm{u}$. The layer thickness
dependence of $K_\mathrm{u}$ and effects of Mg-insertion layers at top and
bottom (Mn-Cr)AlGe$|$MgO interfaces were studied in film samples fabricated
onto thermally oxidized silicon substrates to realize high-$K_\mathrm{u}$ in
the thickness range of a few nanometer. Optimum Mg-insertion thicknesses were
1.4 and 3.0 nm for the bottom and the top interfaces, respectively, which were
relatively thick compared to results in similar insertion effect investigations
on magnetic tunnel junctions reported in previous studies. The cross-sectional
transmission electron microscope images revealed that the Mg-insertion layers
acted as barriers to interdiffusion of Al-atoms as well as oxidization from the
MgO layers. The values of $K_\mathrm{u}$ were about $7 \times 10^5$ and $2
\times 10^5$ J/m$^3$ at room temperature for 5 and 3 nm-thick (Mn-Cr)AlGe
films, respectively, with the optimum Mg-insertion thicknesses. The
$K_\mathrm{u}$ at a few nanometer thicknesses is comparable or higher than
those reported in perpendicularly magnetized CoFeB films which are
conventionally used in MRAMs, while the $M_\mathrm{s}$ value is one third or
less smaller than those of the CoFeB films. The developed (Mn-Cr)AlGe films are
promising from the viewpoint of not only the magnetic properties, but also the
compatibility to the silicon process in the film fabrication.

###High magnetoresistance of hexagonal boron nitride-graphene heterostructure-based MTJ through excited-electron transmission|Halimah Harfah,Yusuf Wicaksono,Gagus Ketut Sunnardianto,Muhammad Aziz Majidi,Koichi Kusakabea###

High magnetoresistance of hexagonal boron nitride-graphene heterostructure-based MTJ through excited-electron transmission. This work presents an ab-initio study of a few-layers hexagonal boron nitride
(hBN) and hBN-graphene heterostructure sandwiched between Ni(111) layers. The
aim of this study is to understand the electron transmission process through
the interface. Spin-polarized density functional theory calculations and
transmission probability calculations were conducted on Ni(111)/$n$hBN/Ni(111)
with $n$ = 2, 3, 4, and 5 as well as on Ni(111)/hBN-Gr-hBN/Ni(111). Slabs with
magnetic alignment in an anti-parallel configuration (APC) and parallel
configuration (PC) were considered. The pd-hybridizations at both the upper and
lower interfaces between the Ni slabs and hBN were found to stabilize the
system. The Ni/nhBN/Ni magnetic tunnel junction (MTJ) was found to exhibit a
high tunneling magnetoresistance (TMR) ratio at ~0.28 eV for $n$ = 2 and 0.34
eV for $n$ > 2, which are slightly higher than the Fermi energy. The observed
shifting of this high TMR ratio originates from the transmission of electrons
through the surface states of the $d_{z^2}$-orbital of Ni atoms at interfaces
which are hybridized with the $p_z$-orbital of N atoms. In the case of $n$ > 2,
the proximity effect causes an evanescent wave, contributing to decreasing
transmission probability but increasing the TMR ratio. However, TMR ratio, as
well as transmission probability, was found to be increased, by replacing the
unhybridized hBN layer of the Ni/3hBN/Ni MTJ with graphene, thus becoming
Ni/hBN-Gr-hBN/Ni. A TMR ratio as high as ~1200% was observed at an energy of
0.34 eV, which is higher than the Fermi energy. Furthermore, a design is
proposed for a device based on a new reading mechanism using the high TMR
observed just above the Fermi energy level.

###Roadmap of spin-orbit torques|Qiming Shao,Peng Li,Luqiao Liu,Hyunsoo Yang,Shunsuke Fukami,Armin Razavi,Hao Wu,Kang L. Wang,Frank Freimuth,Yuriy Mokrousov,Mark D. Stiles,Satoru Emori,Axel Hoffmann,Johan Åkerman,Kaushik Roy,Jian-Ping Wang,See-Hun Yang,Kevin Garello,Wei Zhang###

Roadmap of spin-orbit torques. Spin-orbit torque (SOT) is an emerging technology that enables the efficient
manipulation of spintronic devices. The initial processes of interest in SOTs
involved electric fields, spin-orbit coupling, conduction electron spins and
magnetization. More recently interest has grown to include a variety of other
processes that include phonons, magnons, or heat. Over the past decade, many
materials have been explored to achieve a larger SOT efficiency. Recently,
holistic design to maximize the performance of SOT devices has extended
material research from a nonmagnetic layer to a magnetic layer. The rapid
development of SOT has spurred a variety of SOT-based applications. In this
Roadmap paper, we first review the theories of SOTs by introducing the various
mechanisms thought to generate or control SOTs, such as the spin Hall effect,
the Rashba-Edelstein effect, the orbital Hall effect, thermal gradients,
magnons, and strain effects. Then, we discuss the materials that enable these
effects, including metals, metallic alloys, topological insulators,
two-dimensional materials, and complex oxides. We also discuss the important
roles in SOT devices of different types of magnetic layers. Afterward, we
discuss device applications utilizing SOTs. We discuss and compare
three-terminal and two-terminal SOT-magnetoresistive random-access memories
(MRAMs); we mention various schemes to eliminate the need for an external
field. We provide technological application considerations for SOT-MRAM and
give perspectives on SOT-based neuromorphic devices and circuits. In addition
to SOT-MRAM, we present SOT-based spintronic terahertz generators,
nano-oscillators, and domain wall and skyrmion racetrack memories. This paper
aims to achieve a comprehensive review of SOT theory, materials, and
applications, guiding future SOT development in both the academic and
industrial sectors.

###Anisotropy and Current Control of Magnetization in SrRuO$_3$ SrTiO$_3$ Heterostructures for Spin-Memristors|A. S. Goossens,M. A. T. Leiviskä,T. Banerjee###

Anisotropy and Current Control of Magnetization in SrRuO$_3$ SrTiO$_3$ Heterostructures for Spin-Memristors. Spintronics-based nonvolatile components in neuromorphic circuits offer the
possibility of realizing novel functionalities at low power. Current-controlled
electrical switching of magnetization is actively researched in this context.
Complex oxide heterostructures with perpendicular magnetic anisotropy (PMA),
consisting of SrRuO$_3$ (SRO) grown on SrTiO$_3$ (STO) are strong material
contenders. Utilizing the crystal orientation, magnetic anisotropy in such
simple heterostructures can be tuned to either exhibit a perfect or slightly
tilted PMA. Here, we investigate current-induced magnetization modulation in
such tailored ferromagnetic layers with a material with strong spin-orbit
coupling (Pt), exploiting the spin Hall effect. We find significant differences
in the magnetic anisotropy between the SRO/STO heterostructures, as manifested
in the first and second harmonic magnetoresistance measurements.
Current-induced magnetization switching can be realized with spin-orbit
torques, but for systems with perfect PMA this switching is probabilistic as a
result of the high symmetry. Slight tilting of the PMA can break this symmetry
and allow the realization of deterministic switching. Control over the magnetic
anisotropy of our heterostructures therefore provides control over the manner
of switching. Based on our findings, we propose a three-terminal spintronic
memristor, with a magnetic tunnel junction design, that shows several resistive
states controlled by electric charge. Non-volatile states can be written
through SOT by applying an in-plane current, and read out as a tunnel current
by applying a small out-of-plane current. Depending on the anisotropy of the
SRO layer, the writing mechanism is either deterministic or probabilistic
allowing for different functionalities to emerge. We envisage that the
probabilistic MTJs could be used as synapses while the deterministic devices
can emulate neurons

###A strange metal in a bosonic system|Chao Yang,Haiwen Liu,Yi Liu,Jiandong Wang,Sishuang Wang,Yang Wang,Qianmei He,Yue Tang,Jian Wang,X. C. Xie,James M. Valles Jr.,Jie Xiong,Yanrong Li###

A strange metal in a bosonic system. Fermi liquid theory forms the basis for our understanding of the majority of
metals, which is manifested in the description of transport properties that the
electrical resistivity goes as temperature squared in the limit of zero
temperature. However, the observations of strange metal states in various
quantum materials, notably high-temperature superconductors, bring this
spectacularly successful theoretical framework into crisis. When electron
scattering rate 1/{\tau} hits its limit, kBT/{\hbar} where {\hbar} is the
reduced Planck's constant, T represents absolute temperature and kB denotes
Boltzmann's constant, Planckian dissipation occurs and lends strange metals a
surprising link to black holes, gravity, and quantum information theory. Here,
we show the characteristic signature of strange metallicity arising
unprecedentedly in a bosonic system. Our nanopatterned YBa2Cu3O7-{\delta}(YBCO)
film arrays reveal T-linear resistance as well as B-linear magnetoresistance
over an extended temperature and magnetic field range in a quantum critical
region in the phase diagram. Moreover, the slope of the T-linear resistance
{\alpha}_cp appears bounded by {\alpha}_cp {\approx} h/2e^2 [1/T]_c^onset where
T_c^onset is the temperature at which Cooper pairs form, intimating a common
scale-invariant transport mechanism corresponding to Planckian dissipation.In
contrast to fermionic systems where the temperature and magnetic field
dependent scattering rates combine in quadrature of {\hbar}/{\tau} {\approx}
{\sqrt} (((k_B T)^2+({\mu}_B B)^2)), both terms linearly combine in the present
bosonic system, i.e. {\hbar}/{\tau} {\approx} (k_B T+[{\gamma}{\mu}]_B B),
where {\gamma} is a constant. By extending the reach of strange metal
phenomenology to a bosonic system, our results suggest that there is a
fundamental principle governing their transport which transcends particle
statistics.

###Unconventional spin Hall effects in nonmagnetic solids|Arunesh Roy,Marcos H. D. Guimarães,Jagoda Sławińska###

Unconventional spin Hall effects in nonmagnetic solids. Direct and inverse spin Hall effects lie at the heart of novel applications
that utilize spins of electrons as information carriers, allowing generation of
spin currents and detecting them via the electric voltage. In the standard
arrangement, applied electric field induces transverse spin current with
perpendicular spin polarization. Although conventional spin Hall effects are
commonly used in spin-orbit torques or spin Hall magnetoresistance experiments,
the possibilities to configure electronic devices according to specific needs
are quite limited. Here, we investigate unconventional spin Hall effects that
have the same origin as conventional ones, but manifest only in low-symmetry
crystals where spin polarization, spin current and charge current are not
enforced to be orthogonal. Based on the symmetry analysis for all 230 space
groups, we have identified crystal structures that could exhibit unusual
configurations of charge-to-spin conversion. The most relevant geometries have
been explored in more detail; in particular, we have analyzed the collinear
components yielding transverse charge and spin current with spin polarization
parallel to one of them, as well as the longitudinal ones, where charge and
spin currents are parallel. In addition, we have demonstrated that
unconventional spin Hall effect can be induced by controllable breaking the
crystal symmetries by an external electric field, which opens a perspective for
external tuning of spin injection and detection by electric fields. The results
have been confirmed by density functional theory calculations performed for
various materials relevant for spintronics. We are convinced that our findings
will stimulate further computational and experimental studies of unconventional
spin Hall effects.

###Materials and possible mechanisms of extremely large magnetoresistance: A review|Rui Niu,W. K. Zhu###

Materials and possible mechanisms of extremely large magnetoresistance: A review. Magnetoresistance (MR) is a characteristic that the resistance of a substance
changes with the external magnetic field, reflecting various physical origins
and microstructures of the substance. A large MR, namely a huge response to a
low external field, has always been a useful functional feature in industrial
technology and a core goal pursued by physicists and materials scientists.
Conventional large MR materials are mainly manganites, whose colossal MR (CMR)
can be as high as -90%. The dominant mechanism is attributed to spin
configuration aligned by the external field, which reduces magnetic scattering
and thus resistance. In recent years, some new systems have shown an extremely
large unsaturated MR (XMR). Unlike ordinary metals, the positive MR of these
systems can reach 103-108% and is persistent under super high magnetic fields.
The XMR materials are mainly metals or semimetals, distributed in high-mobility
topological or non-topological systems, and some are magnetic, which suggests a
wide range of application scenarios. Various mechanisms have been proposed for
the potential physical origin of XMR, including electron-hole compensation,
steep band, ultrahigh mobility, high residual resistance ratio, topological
fermions, etc. It turns out that some mechanisms play a leading role in certain
systems, while more are far from clearly defined. In addition, the researches
on XMR are largely overlapped or closely correlated with other recently rising
physics and materials researches, such as topological matters and
two-dimensional (2D) materials, which makes elucidating the mechanism of XMR
even more important. Moreover, the disclosed novel properties will lay a broad
and solid foundation for the design and development of functional devices. In
this review, we will discuss several aspects in the following order: ...

###Hall anomaly, Quantum Oscillations and Possible Lifshitz Transitions in Kondo Insulator YbB$_{12}$: Evidence for Unconventional Charge Transport|Ziji Xiang,Kuan-Wen Chen,Lu Chen,Tomoya Asaba,Yuki Sato,Nan Zhang,Dechen Zhang,Yuichi Kasahara,Fumitoshi Iga,William A. Coniglio,Yuji Matsuda,John Singleton,Lu Li###

Hall anomaly, Quantum Oscillations and Possible Lifshitz Transitions in Kondo Insulator YbB$_{12}$: Evidence for Unconventional Charge Transport. In correlated electronic systems, strong interactions and the interplay
between different degrees of freedom may give rise to anomalous charge
transport properties, which can be tuned by external parameters like
temperature and magnetic field. Recently, magnetic quantum oscillations and
metallic low-temperature thermal conductivity have been observed in the Kondo
insulator YbB$_{12}$, whose resistivity is a few orders of magnitude higher
than those of conventional metals. As yet, these unusual observations are not
fully understood. Here we present a detailed investigation of the behavior of
YbB$_{12}$ under intense magnetic fields using both transport and torque
magnetometry measurements. A low-field Hall anomaly, reminiscent of the Hall
response associated with "strange-metal" physics, develops at $T < 1.5$ K. At
two characteristic magnetic fields ($\mu_0H_1= 19.6$ T and $\mu_0H_2 \sim 31$
T), signatures appear in the Hall coefficient, magnetic torque, and
magnetoresistance. We suggest that they are likely to be field-induced Lifshitz
transitions. Moreover, above 35 T, the background resistivity displays an
unusual, nonmetallic $T^{\alpha}$-behavior, with $\alpha$ being field-dependent
and varying between -1.5 and -2. By normalizing the Shubnikov-de Haas
oscillation amplitude to this $T^{\alpha}$-dependence, the calculated cyclotron
mass becomes more consistent with that deduced from de Haas-van Alphen
oscillations. Our results support a novel two-fluid scenario in YbB$_{12}$: a
Fermi-liquid-like fluid of charge-neutral quasiparticles coexists with charge
carriers that remain in a nonmetallic state. The former experience successive
Lifshitz transitions and develop Landau quantization in applied magnetic
fields, whilst scattering between both fluids allows the Shubnikov-de Haas
effect to be observed in the electrical transport.

###Magnetotransport studies of the Sb square-net compound LaAgSb$_2$ under high pressure and rotating magnetic fields|Kazuto Akiba,Nobuaki Umeshita,Tatsuo C. Kobayashi###

Magnetotransport studies of the Sb square-net compound LaAgSb$_2$ under high pressure and rotating magnetic fields. Square-net-layered materials have attracted attention as an extended research
platform of Dirac fermions and of exotic magneto-transport phenomena. In this
study, we investigated the magneto-transport properties of LaAgSb$_2$, which
has Sb-square-net layers and shows charge density wave (CDW) transitions at
ambient pressure. The application of pressure suppresses the CDWs, and above a
pressure of 3.2 GPa, a disordered phase with no CDWs is realized. By utilizing
a mechanical rotator combined with a high-pressure cell, we observed the
angular dependence of the Shubnikov-de Haas (SdH) oscillation up to 3.5 GPa and
confirmed the notable two-dimensional nature of the Fermi surface. In the
disordered phase, we also observed a remarkable field-angular-dependent
magnetoresistance (MR), which exhibited a "butterfly-like" polar pattern. To
understand these results, we theoretically calculated the Fermi surface and
conductivity tensor at the disordered phase. We showed that the SdH frequency
and Hall coefficient calculated based on the present Fermi surface model agree
well with the experiment. The transport properties in the disordered phase are
mostly dominated by the anisotropic Dirac band, which has the highest
conductivity owing to linear energy dispersions. We also proposed that
momentum-dependent relaxation time plays an important role in the large
transverse MR and negative longitudinal MR in the disordered phase, which is
experimentally supported by the considerable violation of Kohler's scaling
rule. Although quantitatively complete reproduction was not achieved, the
calculation showed that the elemental features of the butterfly MR could be
reasonably explained as the geometrical effect of the Fermi surface.

###Resonant Precession of Magnetization and Precession -- Induced DC voltages in FeGaB Thin Films|Prabesh Bajracharya,Vinay Sharma,Anthony Johnson,Ramesh C. Budhani###

Resonant Precession of Magnetization and Precession -- Induced DC voltages in FeGaB Thin Films. Measurements of frequency dependent ferromagnetic resonance (FMR) and spin
pumping driven dc voltage (V_{dc}) are reported for amorphous films of
Fe_{78}Ga_{13}B_{9} (FeGaB) alloy to address the phenomenon of self-induced
inverse spin Hall effect (ISHE) in plain films of metallic ferromagnets. The
V_{dc} signal, which is antisymmetric on field reversal, comprises of symmetric
and asymmetric Lorentzians centered around the resonance field. Dominant role
of thin film size effects is seen in setting the magnitude of static
magnetization, V_{dc} and dynamics of magnetization precession in thinner films
(\leq 8 nm). The film thickness dependence of magnetization parameters
indicates the presence of a magnetically disordered region at the
film-substrate interface, which may promote preferential flow of spins
generated by the precessing magnetization towards the substrate. However, the
V_{dc} signal also draws contributions from rectification effects of a \approx
0.4 \% anisotropic magnetoresistance and a large (\approx 54 n\Omega.m)
anomalous Hall resistivity (AHR) of these films which ride over the effect of
spin-orbit coupling driven spin-to-charge conversion near the film-substrate
interface. We have addressed these data in the framework of the existing
theories of electrodynamics of a ferromagnetic film subjected to
radio-frequency field in a coplanar waveguide geometry. Our estimation of the
self-induced ISHE for the sample with 54 n\Omega.m AHR shows that it may
contribute significantly (\approx 90\%) to the measured symmetric voltage. This
study is expected to be very useful for fully understanding the spin pumping
induced dc voltages in metallic ferromagnets with disordered interfaces and
large anomalous Hall effect.

###Magneto-transport and magnetic textures in Ho/FeCoGd/β-W multilayers|Ramesh C. Budhani,Vinay Sharma,Ezana Negusse,Jacob Casey,Arjun K. Pathak,Jerzy T. Sadowski,Brian Kirby###

Magneto-transport and magnetic textures in Ho/FeCoGd/β-W multilayers. The enhancement of interfacial Dzyaloshinskii-Moriya Interaction (DMI) in
magnetic multilayers results in the stabilization of topological spin textures
like chiral domain walls and skyrmions. Here we report on the evaluation of
interface-driven magnetic interactions in a uniquely designed multilayer where
each magnetic layer of two AFM coupled sublattices of 3d and 4f moments is
sandwiched between the layers of \beta-tungsten and holmium whose spin Hall
angles are large but opposite in sign. The atomic and magnetic periodicity of
these multilayers is established by polarized neutron reflectivity measurements
and the presence of a labyrinth domain spin texture of zero remanence with
x-ray photoelectron microscopy. Measurements of the Hall resistivity
(\rho_{xy}(T, H)) together with static magnetization (M(T,H)) over a broad
range of temperature (T) and magnetic field (H) indicate impending compensation
between 3d and 4f sublattices at T>350 K. These multilayers are characterized
by a small (0.04 %) but positive magnetoresistance indicative of interface
enhance scattering and a large (40 n\Omega.m) and negative anomalous
\rho_{xy}(T,H) which results from a parallel alignment of 4f moments with the
external magnetic field. No distinct scaling is seen between \rho_{xy}(T,H),
\rho_{xx}(T, H) and M(T,H) at temperatures above 200K where the magnetization
develops out-of-plane anisotropy. The field scans of \rho_{xy} at T>200K show a
distinct cusp in the vicinity of magnetic saturation. These Hall data have been
analyzed in the framework of a model where a distinct topological contribution
to \rho_{xy} rides over the anomalous Hall resistivities of the 3d and 4f
magnetic sublattices. It is suggested that this apparent topological effect
results from an interfacial DMI and dominates \rho_{xy}(T,H) in the temperature
regime where the 3d and 4f lattices are nearly compensated.

###KCo$_2$As$_2$: A New Portal for the Physics of High-Purity Metals|Abhishek Pandey,Y. Liu,Saroj L. Samal,Yevhen Kushnirenko,A. Kaminski,D. J. Singh,D. C. Johnston###

KCo$_2$As$_2$: A New Portal for the Physics of High-Purity Metals. High-quality single crystals of KCo$_2$As$_2$ with the body-centered
tetragonal ThCr$_2$Si$_2$ structure were grown using KAs self flux. Structural,
magnetic, thermal, and electrical transport were investigated. No clear
evidence for any phase transitions was found in the temperature range 2 to 300
K. The in-plane electrical resistivity $\rho$ versus temperature $T$ is highly
unusual, showing a $T^4$ behavior below 30 K and an anomalous positive
curvature up to 300 K which is different from the linear behavior expected from
the Bloch-Gr\"uneisen theory for electron scattering by acoustic phonons. This
positive curvature has been previously observed in the in-plane resistivity of
high-conductivity layered delafossites such as PdCoO$_2$ and PtCoO$_2$. The
in-plane $\rho(T\to0) = 0.36~\mu\Omega$ cm of KCo$_2$As$_2$ is exceptionally
small for this class of compounds. The material also exhibits a nearly linear
magnetoresistance at low $T$ which attains a value of about 40% at $T=2$K and
magnetic field $H= 80$ kOe. The magnetic susceptibility $\chi$ of KCo$_2$As$_2$
is isotropic and about an order of magnitude smaller than the values for the
related compounds SrCo$_2$As$_2$ and BaCo$_2$As$_2$. The $\chi$ increases above
100 K which is found from our first-principles calculations to arise from a
sharp peak in the electronic density of states just above the Fermi energy
$E_{\rm F}$. Heat capacity $C_{\rm p}(T)$ data at low $T$ yield an electronic
density of states $N(E_{\rm F})$ that is about 36% larger than predicted by the
first-principles theory. The $C_{\rm p}(T)$ data near room temperature suggest
the presence of excited optic vibration modes which may also be the source of
the positive curvature in $\rho(T)$. Our results show that KCo$_2$As$_2$
provides a new avenue for investigating the physics of high-purity metals.

###$Ab$ $Initio$ Study of Magnetic Tunnel Junctions Based on Half-Metallic and Spin-Gapless Semiconducting Heusler Compounds: Reconfigurable Diode and Inverse Tunnel-Magnetoresistance Effect|T. Aull,E. Şaşıoğlu,N. F. Hinsche,I. Mertig###

$Ab$ $Initio$ Study of Magnetic Tunnel Junctions Based on Half-Metallic and Spin-Gapless Semiconducting Heusler Compounds: Reconfigurable Diode and Inverse Tunnel-Magnetoresistance Effect. Magnetic tunnel junctions (MTJs) have attracted strong research interest
within the last decades due to their potential use as nonvolatile memory such
as MRAM as well as for magnetic logic applications. Half-metallic magnets
(HMMs) have been suggested as ideal electrode materials for MTJs to achieve an
extremely large tunnel-magnetoresistance (TMR) effect. Despite their high TMR
ratios, MTJs based on HMMs do not exhibit current rectification, i.e., a diode
effect, which was achieved in a magnetic tunnel junction concept based on HMMs
and type-II spin-gapless semiconductors (SGSs). The proposed concept has
recently been experimentally demonstrated using Heusler compounds. In the
present work, we investigate from first-principles MTJs based on type-II SGS
and HMM quaternary Heusler compounds FeVTaAl, FeVTiSi, MnVTiAl, and CoVTiSb.
Our $ab$ $initio$ quantum transport calculations based on a nonequilibrium
Green's function method have demonstrated that the MTJs under consideration
exhibit current rectification with relatively high on:off ratios. We show that,
in contrast to conventional semiconductor diodes, the rectification bias
voltage window (or breakdown voltage) of the MTJs is limited by the spin gap of
the HMM and SGS Heusler compounds. A unique feature of the present MTJs is that
the diode effect can be configured dynamically, i.e., depending on the relative
orientation of the magnetization of the electrodes, the MTJ allows the
electrical current to pass either in one or the other direction, which leads to
an inverse TMR effect. The combination of nonvolatility, reconfigurable diode
functionality, tunable rectification voltage window, and high Curie temperature
of the electrode materials makes the proposed MTJs very promising for
room-temperature spintronic applications and opens ways to magnetic memory and
logic concepts as well as logic-in-memory computing.

###Probing magnetic anisotropy and spin-reorientation transition in 3D antiferromagnet, Ho$_{0.5}$Dy$_{0.5}$FeO$_{3}\vert$Pt using spin Hall magnetoresistance|Aditya A. Wagh,Priyanka Garg,Arijit Haldar,Kingshuk Mallick,Tirthankar Chakraborty,Suja Elizabeth,P. S. Anil Kumar###

Probing magnetic anisotropy and spin-reorientation transition in 3D antiferromagnet, Ho$_{0.5}$Dy$_{0.5}$FeO$_{3}\vert$Pt using spin Hall magnetoresistance. Orthoferrites ($RE$FeO$_{3}$) containing rare-earth ($RE$) elements are 3D
antiferromagnets (AFM) that exhibit characteristic weak ferromagnetism
originating due to slight canting of the spin moments and display a rich
variety of spin reorientation transitions in the magnetic field
($H$)-temperature ($T$) parameter space. We present spin Hall magnetoresistance
(SMR) studies on a $b$-plate ($ac$-plane) of crystalline
Ho$_{0.5}$Dy$_{0.5}$FeO$_{3}|$Pt (HDFO$|$Pt) hybrid at various $T$ in the
range, 11 to 300 K. In the room temperature $\Gamma_4(G_x, A_y, F_z)$ phase,
the switching between two degenerate domains, $\Gamma_4(+G_x, +F_z)$ and
$\Gamma_4(-G_x, -F_z)$ occurs at fields above a critical value, $H_{\text{c}}
\approx 713$ Oe. Under $H > H_{\text{c}}$, the angular dependence of SMR
($\alpha$-scan) in the $\Gamma_4(G_x, A_y, F_z)$ phase yielded a highly skewed
curve with a sharp change (sign-reversal) along with a rotational hysteresis
around $a$-axis. This hysteresis decreases with an increase in $H$. Notably, at
$H < H_{\text{c}} $, the $\alpha$-scan measurements on the single domain,
$\Gamma_4(\pm G_x, \pm F_z)$ exhibited an anomalous sinusoidal signal of
periodicity 360 deg. Low-$T$ SMR curves ($H$ = 2.4 kOe), showed a systematic
narrowing of the hysteresis (down to 150 K) and a gradual reduction in the
skewness (150 to 52 K), suggesting weakening of the anisotropy possibly due to
the $T$-evolution of Fe-$RE$ exchange coupling. Below 25 K, the SMR modulation
showed an abrupt change around the $c$-axis, marking the presence of
$\Gamma_2(F_x,C_y,G_z)$ phase. We have employed a simple Hamiltonian and
computed SMR to examine the observed skewed SMR modulation. In summary, SMR is
found to be an effective tool to probe magnetic anisotropy as well as a spin
reorientation in HDFO. Our spin-transport study highlights the potential of
HDFO for future AFM spintronic devices.

###Highly tunable spin Hall magnetoresistance in room-temperature magnetoelectric multiferroic, $\text{Sr}_{3}\text{Co}_{2}\text{Fe}_{24}\text{O}_{41}|$Pt hybrids|Aditya A. Wagh,Priyanka Garg,Kingshuk Mallick,Suja Elizabeth,P. S. Anil Kumar###

Highly tunable spin Hall magnetoresistance in room-temperature magnetoelectric multiferroic, $\text{Sr}_{3}\text{Co}_{2}\text{Fe}_{24}\text{O}_{41}|$Pt hybrids. We present spin transport studies on a low-field, room-temperature
magnetoelectric multiferroic polycrystalline
$\text{Sr}_{3}\text{Co}_{2}\text{Fe}_{24}\text{O}_{41}$ (SCFO)|Pt
heterostructure wherein a highly tunable transverse conical magnetic phase is
responsible for static and dynamic magnetoelectric coupling. We measured
angular dependence of spin Hall magnetoresistance (SMR) at constant magnetic
fields ($H$) in the range of 50 to 100 kOe. Application of field below the
critical value (2.5 kOe), yielded negative SMR and the $H$-evolution of
normalized SMR exhibited a negative gradient. Further, an increase in the $H$
resulted in the positive slope of normalized SMR Vs. $H$ and later at higher
$H$ around 14 kOe, a crossover from negative to positive SMR was observed. We
employed a simple model for estimating the equilibrium magnetic configuration
and computed the SMR modulation at various values of $H$. We argue that the
tilting of the cone is dominant and in turn responsible for the observed nature
of SMR below 2.5 kOe while, the closing of the cone-angle is pronounced at
higher fields causing a reversal in sign of the SMR from negative to positive.
Importantly, SMR experiments revealed that a change in the helicity with a
reversal of the magnetic field has no influence on the observed SMR.
Longitudinal spin Seebeck effect (LSSE) signal was measured to be 500 nV at 280
K, under application of thermal gradient, $\Delta T = 23$ K and field, 60 kOe.
The observed LSSE signal, originating from pure magnon spin current, showed a
similar $H$-dependent behavior as that of the magnetization of SCFO. Our
detailed spin transport studies on polycrystalline SCFO|Pt heterostructure
demonstrate high tunability of the amplitude and the sign of the SMR,
highlighting its potential for novel spintronic devices such as SMR-based spin
valves and voltage-controlled spin transport devices.

###Anisotropic magnetotransport properties coupled with spiral spin modulation in a triangular-lattice magnet EuZnGe|Takashi Kurumaji,Masaki Gen,Shunsuke Kitou,Hajime Sagayama,Akihiko Ikeda,Taka-hisa Arima###

Anisotropic magnetotransport properties coupled with spiral spin modulation in a triangular-lattice magnet EuZnGe. We investigate the thermodynamic, magnetic, and electrical transport
properties of a triangular-lattice antiferromagnet EuZnGe using single crystals
grown from Eu-Zn flux in sealed tantalum tubes. Magnetic properties are found
to be isotropic in the paramagnetic state while we observe an enhancement of
in-plane magnetic susceptibility at the temperature near T* =11.3 K, suggesting
an easy-plane anisotropy at low temperatures. Magnetic transition temperature
is lower than T* as specific heat shows a peak at TN =7.6 K. We reveal the
magnetic modulation along the c axis by resonant x-ray scattering at Eu L2
edge, which suggests competing magnetic interaction among Eu triangular-lattice
layers. We observe a double-peak structure in the intensity profile along (0,
0, L) below TN, which is mainly composed of a dominant helical modulation with
q ~ (0, 0, 0.4) coexisting with a secondary contribution from q ~ (0, 0, 0.5).
We reproduce the intensity profile with a random mixture of five- and
four-sublattice helices with spin rotation skipping due to hexagonal in-plane
anisotropy. The metallic conductivity is highly anisotropic with the ratio
rho_zz/rho_xx exceeding 10 over the entire temperature range and additionally
exhibits a sharp enhancement of rho_zz at TN giving rise to rho_zz/rho_xx ~ 50,
suggesting a coupling between out-of-plane electron conduction and the spiral
magnetic modulations. In-plane magnetic field induces a spin-flop like
transition, where the q = 0.4 peak disappears and an incommensurate peak of
approximately qICM ~ 0.47 emerges, while the q = 0.5 modulation retains a
finite intensity. This transition correlates with non-monotonic
magnetoresistance and Hall resistivity, suggesting a significant interplay
between electrons and spin structures through Ruderman-Kittel-Kasuya-Yosida
(RKKY) interaction.

###Electron transport properties of a narrow-bandgap semiconductor Bi$_2$O$_2$Te nanosheet|Xiaobo Li,Haitian Su,H. Q. Xu###

Electron transport properties of a narrow-bandgap semiconductor Bi$_2$O$_2$Te nanosheet. A thin, narrow-bandgap semiconductor Bi$_2$O$_2$Te nanosheet is obtained via
mechanical exfoliation and a Hall-bar device is fabricated from it on a heavily
doped Si/SiO$_2$ substrate and studied at low temperatures. Gate transfer
characteristic measurements show that the transport carriers in the nanosheet
are of $n$-type. The carrier density, mobility, and mean free path in the
nanosheet are determined by measurements of the Hall resistance and the
longitudinal resistance of the Hall-bar device and it is found that the
electron transport in the nanosheet is in a quasi-two-dimensional (2D),
strongly disordered regime. Magnetotransport measurements for the device at
magnetic fields applied perpendicular to the nanosheet plane show dominantly
weak antilocalization (WAL) characteristics at low fields and a linear
magnetoresistance (LMR) behavior at large fields. We attribute the WAL
characteristics to strong spin-orbit interaction (SOI) and the LMR to the
classical origin of strong disorder in the nanosheet. Low-field
magnetoconductivity measurements are also performed and are analyzed based on
the multi-channel Hikami-Larkin-Nagaoka theory with the LMR correction being
taken into account. The phase coherence length, spin relaxation length,
effective 2D conduction channel number and coefficient in the linear term due
to the LMR in the nanosheet are extracted. It is found that the spin relaxation
length in the Bi$_2$O$_2$Te nanosheet is several times smaller than it in its
counterpart Bi$_2$O$_2$Se nanosheet and thus an ultra-strong SOI is present in
the Bi$_2$O$_2$Te nanosheet. Our results reported in this study would greatly
encourage further studies and applications of this emerging narrow-bandgap
semiconductor 2D material.

###The magnetic structure and field dependence of the cycloid phase mediating the spin reorientation transition in Ca$_3$Ru$_2$O$_7$|Q. Faure,C. D. Dashwood,C. V. Colin,R. D. Johnson,E. Ressouche,G. B. G. Stenning,J. Spratt,D. F. McMorrow,R. S. Perry###

The magnetic structure and field dependence of the cycloid phase mediating the spin reorientation transition in Ca$_3$Ru$_2$O$_7$. We report a comprehensive experimental investigation of the magnetic
structure of the cycloidal phase in Ca$_3$Ru$_2$O$_7$, which mediates the spin
reorientation transition, and establishes its magnetic phase diagram. In zero
applied field, single-crystal neutron diffraction data confirms the scenario
deduced from an earlier resonant x-ray scattering study: between $46.7$~K $< T
< 49.0$~K the magnetic moments form a cycloid in the $a-b$ plane with a
propagation wavevector of $(\delta,0,1)$ with $\delta \simeq 0.025$ and an
ordered moment of about 1 $\mu_{\rm{B}}$, with the eccentricity of the cycloid
evolving with temperature. In an applied magnetic field applied parallel to the
$b$-axis, the intensity of the $(\delta,0,1)$ satellite peaks decreases
continuously up to about $\mu_0 H \simeq 5$ T, above which field the system
becomes field polarised. Both the eccentricity of the cycloid and the
wavevector increase with field, the latter suggesting an enhancement of the
anti$-$symmetric Dzyaloshinskii$-$Moriya interaction via magnetostriction
effects. Transitions between the various low-temperature magnetic phases have
been carefully mapped out using magnetometry and resistivity. The resulting
phase diagram reveals that the cycloid phase exists in a temperature window
that expands rapidly with increasing field, before transitioning to a polarised
paramagnetic state at 5 T. High-field magnetoresistance measurements show that
below $T\simeq 70$ K the resistivity increases continuously with decreasing
temperature, indicating the inherent insulating nature at low temperatures of
our high-quality, untwinned, single-crystals. We discuss our results with
reference to previous reports of the magnetic phase diagram of
Ca$_3$Ru$_2$O$_7$ that utilised samples which were more metallic and/or
poly-domain.

###High Temperature Ferromagnetism in Cr$_{1+x}$Pt$_{5-x}$P|Tyler J. Slade,Nao Furukawa,Tanner R. Smith,Juan Schmidt,Ranuri S. Dissanayaka Mudiyanselage,Lin-Lin Wang,Weiwei Xie,Sergey L. Budko,Paul C. Canfield###

High Temperature Ferromagnetism in Cr$_{1+x}$Pt$_{5-x}$P. We present the growth and basic magnetic and transport properties of
Cr$_{1+x}$Pt$_{5-x}$P. We show that single crystals can readily be grown from a
high-temperature solution created by adding dilute quantities of Cr to Pt-P
based melts. Like other 1-5-1 compounds, Cr$_{1+x}$Pt$_{5-x}$P adopts a
tetragonal P4/mmm structure composed face-sharing CrPt$_3$ like slabs that are
broken up along the c-axis by sheets of P atoms. EDS and X-ray diffraction
measurements both suggest Cr$_{1+x}$Pt$_{5-x}$P has mixed occupancy between Cr
and Pt atoms, similar to what is found in the closely related compound
CrPt$_3$, giving real compositions of Cr$_{1.5}$Pt$_{4.5}$P (x = 0.5). We
report that Cr$_{1.5}$Pt$_{4.5}$P orders ferromagnetically at T$_C$ = 464.5 K
with a saturated moment of $\approx$ 2.1 $\mu_{\textit{B}}$/Cr at 1.8 K. Likely
owing to the strong spin-orbit coupling associated with the large quantity of
high Z Pt atoms, Cr$_{1.5}$Pt$_{4.5}$P has exceptionally strong planar
anisotropy with estimated anisotropy fields of 345 kOe and 220 kOe at 1.8 K and
300 K respectively. The resistance of Cr$_{1.5}$Pt$_{4.5}$P has a metallic
temperature dependence with relatively weak magnetoresistance. Electronic band
structure calculations show that CrPt$_5$P has a large peak in the density of
states near the Fermi level which is split into spin majority and minority
bands in the ferromagnetic state. Furthermore, the calculations suggest
substantial hybridization between Cr-3d and Pt-5d states near the Fermi level,
in agreement with the experimentally measured anisotropy.

###Electronic structure, magnetic properties, spin orientation, and doping effect in Mn$_3$Si$_2$Te$_6$|Yang Zhang,Ling-Fang Lin,Adriana Moreo,Elbio Dagotto###

Electronic structure, magnetic properties, spin orientation, and doping effect in Mn$_3$Si$_2$Te$_6$. The layered material Mn$_3$Si$_2$Te$_6$, with alternating stacking honeycomb
and triangular layers, is attracting considerable attention due to its rich
physical properties. Here, using density functional theory and classical Monte
Carlo (MC) methods, we systematically study this system. Near the Fermi level,
the states are mainly contributed by Te $5p$ orbitals hybridized with Mn $3d$
orbitals, resembling a charge transfer system. Furthermore, the spin
orientations of the ferrimagnetic (FiM) ground state display different
conductive behaviors when along the $ab$ plane or out-of-plane directions:
insulating vs. metallic states. The energy difference between the FiM [110]
insulating and FiM [001] metallic phases is very small($ \sim 0.71$ meV/Mn).
Changing the angle $\theta$ of spin orientation from in-plane to out-of-plane
directions, the band gaps of this system are gradually reduced, leading to an
insulator-metal transition, resulting in an enhanced electrical conductivity,
related to the colossal angular magnetoresistance (MR) effect. In addition, we
also constructed the magnetic phase diagram using the classical $XY$ spin model
studied with the MC method. Three magnetic phases were obtained including
antiferromagnetic order, noncollinear spin patterns, and FiM order. Moreover,
we also investigated the Se- and Ge- doping into the Mn$_3$Si$_2$Te$_6$ system:
the FiM state has the lowest energy among the magnetic candidates for both Se-
or Ge- doped cases. The magnetic anisotropy energy (MAE) decreases in the
Se-doped case because the Mn orbital moment is reduced as the doping $x$
increases. Due to the small spin-orbital coupling effect of Se, the
insulator-metal transition caused by the spin orientation disappears in the
Se-doped case, resulting in an insulating phase in the FiM [001] phase. This
causes a reduced colossal angular MR.

###Two-band conduction as a pathway to non-linear Hall effect and unsaturated negative magnetoresistance in the martensitic compound GdPd2Bi|Snehashish Chatterjee,Saurav Giri,Subham Majumdar,Prabir Dutta,Surasree Sadhukhan,Sudipta Kanungo,Souvik Chatterjee,Manju Mishra Patidar,Gunadhor Singh Okram,V. Ganesan,G. Das,V. Rajaji###

Two-band conduction as a pathway to non-linear Hall effect and unsaturated negative magnetoresistance in the martensitic compound GdPd2Bi. The present work aims to address the electronic and magnetic properties of
the intermetallic compound GdPd$_2$Bi through a comprehensive study of the
structural, magnetic, electrical and thermal transport on a polycrystalline
sample, followed by theoretical calculations. Our findings indicate that the
magnetic ground state is antiferromagnetic in nature. Magnetotransport data
present prominent hysteresis loop hinting a structural transition with further
support from specific heat and thermopower measurements, but no such signature
is observed in the magnetization study. Temperature dependent powder x-ray
diffraction measurements confirm martensitic transition from the
high-temperature (HT) cubic Heusler $L2_1$ structure to the low-temperature
(LT) orthorhombic $Pmma$ structure similar to many previously reported shape
memory alloys. The HT to LT phase transition is characterized by a sharp
increase in resistivity associated with prominent thermal hysteresis. Further,
we observe robust Bain distortion between cubic and orthorhombic lattice
parameters related by $a_{orth} = \sqrt{2}a_{cub}$, $b_{orth} = a_{cub}$ and
$c_{orth} = a_{cub}/\sqrt{2}$, that occurs by contraction along $c$-axis and
elongation along $a$-axis respectively. The sample shows an unusual
`non-saturating' $H^2$-dependent negative magnetoresistance for magnetic field
as high as 150 kOe. In addition, non-linear field dependence of Hall
resistivity is observed below about 30 K, which coincides with the sign change
of the Seebeck coefficient. The electronic structure calculations confirm
robust metallic states both in the LT and HT phases. It indicates complex
nature of the Fermi surface along with the existence of both electron and hole
charge carriers. The anomalous transport behaviors can be related to the
presence of both electron and hole pockets.

###Orbital-selective Mott phase and spin nematicity in Ni-substituted FeTe$_{0.65}$Se$_{0.35}$ single crystals|Marta Z. Cieplak,I. Zajcewa,A. Lynnyk,K. M. Kosyl,D. J. Gawryluk###

Orbital-selective Mott phase and spin nematicity in Ni-substituted FeTe$_{0.65}$Se$_{0.35}$ single crystals. The normal state in iron chalcogenides is metallic but highly unusual, with
orbital and spin degrees of freedom partially itinerant or localized depending
on temperature, leading to many unusual features. In this work, we report on
the observations of two of such features, the orbital selective Mott phase
(OSMP) and spin nematicity, evidenced in magnetization and magnetotransport
[resistivity, Hall effect, angular magnetoresistance (AMR)] of Ni-substituted
FeTe$_{0.65}$Se$_{0.35}$ single crystals. Two series of single crystals
Fe$_{1+{\delta}-y}$Ni$_y$Te$_{0.65}$Se$_{0.35}$ were prepared, with $0 < y <
0.2$, and $\delta$ either positive (S crystals) or negative (F crystals),
depending on the crystallization rate. The S crystals, with single, tetragonal
phase exhibit superconducting (SC) properties inferior to F crystals, which
contain Fe vacancy-rich monoclinic inclusions. Substitution of Ni dopes both
types of crystals with electrons, what eliminates some of the hole pockets from
Fermi level, leaving only one, originating from $d_{xy}$ orbital. We show that
electron-dominated transport, observed at low $T$ at large $y$, is replaced by
hole-dominated transport at $T > 180$ K, suggesting direct link with the
appearance of the $d_{z^2}$ hole pockets at X points of the Brillouin zone in
the OSMP phase, as recently reported by angular resolved photoemission
experiments (Commun. Phys. 5, 29 (2022)). The AMR of S crystals shows the $C_4$
rotational symmetry of in-plane magnetocrystalline anisotropy at small $y$,
replaced by $C_2$ symmetry at intermediate $y$, indicating development of Ni
doping-induced spin nematicity. The $C_4$ symmetry is preserved in F crystals
due to microstructural disorder related to vacancy-rich inclusions. The
tendency towards nematicity, induced by Ni doping, appears to be the most
important factor producing inferior superconducting properties of S crystals.

###Accelerating quantum materials development with advances in transmission electron microscopy|Parivash Moradifar,Yin Liu,Jiaojian Shi,Matti Lawton Siukola Thurston,Hendrik Utzat,Tim B. van Driel,Aaron M. Lindenberg,Jennifer A. Dionne###

Accelerating quantum materials development with advances in transmission electron microscopy. Quantum materials are driving a technology revolution in sensing,
communication, and computing, while simultaneously testing many core theories
of the past century. Materials such as topological insulators, complex oxides,
quantum dots, color center hosting semiconductors, and other types of strongly
correlated materials can exhibit exotic properties such as edge conductivity,
multiferroicity, magnetoresistance, single photon emission, and optical-spin
locking. These emergent properties arise and depend strongly on the materials
detailed atomic scale structure, including atomic defects, dopants, and lattice
stacking. In this review, after introduction of different classes of quantum
materials and quantum excitations, we describe how progress in the field of
electron microscopy, including in situ and in operando EM, can accelerate
advances in quantum materials. Our review describes EM methods including: i)
principles and operation modes of EM, ii) EM spectroscopies, such as electron
energy loss spectroscopy, cathodoluminescence, and electron energy gain
spectroscopy, iii) 4D scanning transmission electron microscopy, iv) dynamic
and ultrafast EM, v) complimentary ultrafast spectroscopies, and vi) atomic
electron tomography. We discuss how these methods inform structure function
relations in quantum materials down to the picometer scale and femtosecond time
resolution, and how they enable high resolution manipulation of quantum
materials. Among numerous results, our review highlights how EM has enabled
identification of the 3D structure of quantum defects, measuring reversible and
metastable dynamics of quantum excitations, mapping exciton states and single
photon emission, measuring nanoscale thermal transport and coupled excitation
dynamics, and measuring the internal electric field of quantum
heterointerfaces, all at the quantum materials intrinsic atomic and near
atomic-length scale.

###Unusual magnetotransport and anomalous Hall effect in quasi-two-dimensional van der Waals ferromagnet Fe$_4$GeTe$_2$|Riju Pal,Buddhadeb Pal,Suchanda Mondal,Prabhat Mandal,Atindra Nath Pal###

Unusual magnetotransport and anomalous Hall effect in quasi-two-dimensional van der Waals ferromagnet Fe$_4$GeTe$_2$. Fe$_4$GeTe$_2$, an itinerant vdW ferromagnet (FM) having Curie temperature
(T$_C$) close to room temperature ($\sim 270$ K), exhibits another transition
(T$_{SR}$ $\sim$ 120 K) where the easy axis of magnetization changes from
in-plane to the out-of-plane direction in addition to T$_C$. Here, we have
studied the magnetotransport in a multilayer Hall bar device fabricated on 300
nm Si/SiO$_2$ substrate. Interestingly, the zero field resistivity shows a
negligible change in resistivity near T$_C$ unlike the typical metallic FM,
whereas, it exhibits a dramatic fall below T$_{SR}$. Also, the resistivity
shows a weak anomaly at T $ \sim $ 38 K (T$_Q$), below which the resistivity
shows a quadratic temperature dependence according to the Fermi liquid
behavior. Temperature-dependent Hall data exhibits important consequences. The
ordinary Hall coefficient changes sign near T$_{SR}$ indicating the change in
majority carriers. In a similar manner, the magnetoresistance (MR) data shows
significantly large negative MR near T$_{SR}$ and becomes positive below T$_Q$.
The observations of anomaly in the resistivity, sign-change of the ordinary
Hall coefficient and maximum negative MR near T$_{SR}$, together suggest a
possible Fermi surface reconstruction associated with the spin reorientation
transition. Furthermore, analysis of the Hall data reveals a significant
anomalous Hall conductivity (AHC) from $\sim 123 \Omega^{-1}$ cm$^{-1}$ (at T
$\approx$ 5 K) to the maximum value of $\sim 366 \Omega^{-1}$ cm$^{-1}$ near
T$_{SR}$. While the low-temperature part may originate due to the intrinsic KL
mechanism, our analysis indicates that the temperature-dependent AHC is
primarily appearing due to the side-jump mechanism as a result of the spin-flip
electron-magnon scattering. Our study demonstrates an interplay between
magnetism and band topology and its consequence on electron transport in
Fe$_4$GeTe$_2$.

###Structural and Optoelectronic Properties of Thin Film LaWN$_3$|Rebecca W. Smaha,John S. Mangum,Ian A. Leahy,Julian Calder,Matthew P. Hautzinger,Christopher P. Muzzillo,Craig L. Perkins,Kevin R. Talley,Serena Eley,Prashun Gorai,Sage R. Bauers,Andriy Zakutayev###

Structural and Optoelectronic Properties of Thin Film LaWN$_3$. Nitride perovskites are an emerging class of materials that have been
predicted to display a range of interesting physics and functional properties,
but they are under-explored due to the difficulty of synthesizing oxygen-free
nitrides. LaWN3, recently reported as the first oxygen-free nitride perovskite,
exhibited polar symmetry and a large piezoelectric coefficient. However, the
predicted ferroelectric switching was hindered by large leakage current, which
motivates better understanding of its electronic structure and optical
properties. Here, we study the structure and optoelectronic properties of thin
film LaWN3 in greater detail, employing combinatorial techniques to correlate
these properties with cation stoichiometry. We report a two-step synthesis that
utilizes a more common RF substrate bias instead of a nitrogen plasma source,
yielding nanocrystalline films that are crystallized by ex-situ annealing. We
investigate the structure and composition of these films, finding
polycrystalline La-rich and highly textured W-rich films. The optical
absorption onset and temperature- and magnetic field-dependent resistivity are
consistent with semiconducting behavior and are highly sensitive to cation
stoichiometry, which may be related to amorphous impurities: metallic W or WNx
in W-rich samples and insulating La2O3 in La-rich samples. The fractional
magnetoresistance is linear and small, consistent with defect scattering, and a
W-rich sample has n-type carriers with high densities and low mobilities. We
demonstrate a photoresponse in LaWN3: the resistivity of a La-rich sample is
enhanced by 28% at low temperature, likely due to a defect trapping mechanism.
The physical properties of LaWN3 are highly sensitive to cation stoichiometry,
like many oxide perovskites, which therefore calls for precise composition
control to utilize the interesting properties observed in this nitride
perovskite.

###Order parameter dynamics in Mn$_3$Sn driven by DC and pulsed spin-orbit torques|Ankit Shukla,Siyuan Qian,Shaloo Rakheja###

Order parameter dynamics in Mn$_3$Sn driven by DC and pulsed spin-orbit torques. We numerically investigate and develop analytic models for both the DC and
pulsed spin-orbit-torque (SOT)-driven response of order parameter in
single-domain Mn$_3$Sn, which is a metallic antiferromagnet with an anti-chiral
120$^\circ$ spin structure. We show that DC currents above a critical threshold
can excite oscillatory dynamics of the order parameter in the gigahertz to
terahertz frequency spectrum. Detailed models of the oscillation frequency
versus input current are developed and found to be in excellent agreement with
the numerical simulations of the dynamics. In the case of pulsed excitation,
the magnetization can be switched from one stable state to any of the other
five stable states in the Kagome plane by tuning the duration or the amplitude
of the current pulse. Precise functional forms of the final switched state
versus the input current are derived, offering crucial insights into the
switching dynamics of Mn$_3$Sn. The readout of the magnetic state can be
carried out via either the anomalous Hall effect, or the recently demonstrated
tunneling magnetoresistance in an all-Mn$_3$Sn junction. We also discuss
possible disturbance of the magnetic order due to heating that may occur if the
sample is subject to large currents. Operating the device in pulsed mode or
using low DC currents reduces the peak temperature rise in the sample due to
Joule heating. Our predictive modeling and simulation results can be used by
both theorists and experimentalists to explore the interplay of SOT and the
order dynamics in Mn$_3$Sn, and to further benchmark the device performance.

###Epitaxial thin films of binary Eu-compounds close to a valence transition|Sebastian Kölsch,Alfons Georg Schuck,Michael Huth###

Epitaxial thin films of binary Eu-compounds close to a valence transition. Intermetallic binary compounds of europium reveal a variety of interesting
phenomena due to the interconnection between two different magnetic and 4f
electronic (valence) states, which are particularly close in energy. The
valence states or magnetic properties are thus particularly sensitive to
strain-tuning in these materials. Consequently, we grew epitaxial EuPd$_2$
(magnetic Eu$^{2+}$) and EuPd$_3$ (nonmagnetic Eu$^{3+}$) thin films on
MgO(001) substrates using molecular beam epitaxy. Ambient X-ray diffraction
confirms an epitaxial relationship of cubic Laves-type (C15) EuPd$_2$ with an
(111)-out-of plane orientation, whereby four distinct in-plane crystallographic
domains develop. For simple cubic EuPd$_3$ two different out-of-plane
orientations can be obtained by changing the substrate annealing temperature
under ultra-high vacuum conditions from 600{\deg} C to 1000{\deg} C for one
hour. A small resistance minimum evolves for EuPd$_3$ thin films grown with low
temperature substrate annealing, which was previously found even in single
crystals of EuPd$_3$ and might be attributed to a Kondo or weak localization
effect. Absence of influence of an applied magnetic fields and magnetotransport
measurements suggest always a nonmagnetic ground state for EuPd$_3$ thin films,
i. e., a purely trivalent Eu valence, as previously found in EuPd3 single
crystals. For EuPd$_2$ magnetic ordering below ~72 K is observed, quite similar
to single crystal behaviour. Additional field dependent measurements of the
magnetoresistance and the Hall effect show hysteresis effects below ~0.4 T and
an anomalous Hall effect below ~70 K, which saturates around 1.4 T, thus
proving a ferromagnetic ground state of the divalent Eu.